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Sample records for previously developed fatigue

  1. Effect of previous exhaustive exercise on metabolism and fatigue development during intense exercise in humans

    DEFF Research Database (Denmark)

    Iaia, F. M.; Perez-Gomez, J.; Nordsborg, Nikolai

    2010-01-01

    The present study examined how metabolic response and work capacity are affected by previous exhaustive exercise. Seven subjects performed an exhaustive cycle exercise ( approximately 130%-max; EX2) after warm-up (CON) and 2 min after an exhaustive bout at a very high (VH; approximately 30 s), high...... during a repeated high-intensity exercise lasting 1/2-2 min....

  2. Change in knee flexor torque after fatiguing exercise identifies previous hamstring injury in football players.

    Science.gov (United States)

    Lord, C; Ma'ayah, F; Blazevich, A J

    2018-03-01

    Muscular fatigue and interlimb strength asymmetry are factors known to influence hamstring injury risk; however, limb-specific exacerbation of knee flexor (hamstrings) torque production after fatiguing exercise has previously been ignored. To investigate changes in muscular force production before and after sport-specific (repeated-sprint) and non-specific (knee extension-flexion) fatiguing exercise, and explore the sensitivity and specificity of isokinetic endurance (ie, muscle-specific) and single-leg vertical jump (ie, whole limb) tests to identify previous hamstring injury. Twenty Western Australia State League footballers with previous unilateral hamstring injury and 20 players without participated. Peak concentric knee extensor and flexor (180°∙s -1 ) torques were assessed throughout an isokinetic endurance test, which was then repeated alongside a single-leg vertical jump test before and after maximal repeated-sprint exercise. Greater reductions in isokinetic knee flexor torque (-16%) and the concentric hamstring:quadriceps peak torque ratio (-15%) were observed after repeated-sprint running only in the injured (kicking) leg and only in the previously injured subjects. Changes in (1) peak knee flexor torque after repeated-sprint exercise, and (2) the decline in knee flexor torque during the isokinetic endurance test measured after repeated-sprint exercise, correctly identified the injured legs (N = 20) within the cohort (N = 80) with 100% specificity and sensitivity. Decreases in peak knee flexor torque and the knee flexor torque during an isokinetic endurance test after repeated-sprint exercise identified previous hamstring injury with 100% accuracy. Changes in knee flexor torque, but not SLVJ, should be tested to determine its prospective ability to predict hamstring injury in competitive football players. © 2017 The Authors. Scandinavian Journal of Medicine & Science In Sports Published by John Wiley & Sons Ltd.

  3. Developing of impact and fatigue property test database system

    International Nuclear Information System (INIS)

    Park, S. J.; Jun, I.; Kim, D. H.; Ryu, W. S.

    2003-01-01

    The impact and fatigue characteristics database systems were constructed using the data produced from impact and fatigue test and designed to hold in common the data and programs of tensile characteristics database that was constructed on 2001 and others characteristics databases that will be constructed in future. We can easily get the basic data from the impact and fatigue characteristics database systems when we prepare the new experiment and can produce high quality result by compare the previous data. The development part must be analysis and design more specific to construct the database and after that, we can offer the best quality to customers various requirements. In this thesis, we describe the procedure about analysis, design and development of the impact and fatigue characteristics database systems developed by internet method using jsp(Java Server pages) tool

  4. Development of miniature bending fatigue specimens

    International Nuclear Information System (INIS)

    Rao, G.R.; Chin, B.A.; Rowcliffe, A.

    1991-01-01

    Two new miniaturized bending fatigue specimens have been designed and developed to aid in the scoping of materials for fusion first-wall and blanket structural applications. One of these is rectangular in shape with a gauge section 6.35 mm in length, while the other is cut from a 3 mm transmission electron microscopy (TEM) disk and has a gauge length of 1.5 mm. Test rules for unirradiated annealed type 316 stainless steel tested at room temperature, 550deg C and 650deg C are presented. A good correlation between miniature and standard subsize fatigue specimen results was obtained. The miniature specimen results show the same dependence of strain range on cycles to failure as the standard subsize specimens with the miniature-disk specimen results falling below all the other results. The results indicate that these specimens provide reliable data that can be used to scope fatigue properties for fusion applications. (orig.)

  5. Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone.

    Science.gov (United States)

    Whitton, R Christopher; Trope, Gareth D; Ghasem-Zadeh, Ali; Anderson, Garry A; Parkin, Timothy D H; Mackie, Eleanor J; Seeman, Ego

    2010-10-01

    Bone modelling and remodelling reduce the risk of fatigue fractures; the former by adapting bone to its loading circumstances, the latter by replacing fatigued bone. Remodelling transiently increases porosity because of the normal delay in onset of the formation phase of the remodelling sequence. Protracted intense loading suppresses remodelling leaving modelling as the only means of maintaining bone strength. We therefore hypothesized that race horses with fatigue fractures of the distal third metacarpal bone (MC3) will have reduced porosity associated with suppressed remodelling while continued adaptive modelling will result in higher volume fraction (BV/TV) at this site. Using high resolution peripheral quantitative computed tomography (HR-pQCT), we measured the distal aspect of the MC3 obtained at postmortem from 13 thoroughbred race horses with condylar fractures of the MC3 (cases), 8 horses without fractures (training controls), 14 horses with a fracture at another site (fractured controls) and 9 horses resting from training (resting controls). Porosity of the subchondral bone of MC3 was lower in cases than resting controls (12±1.4% vs. 18±1.6%, P=0.017) although areas of focal porosity were observed adjacent to fractures in 6/13 horses. BV/TV of the distal metacarpal epiphysis tended to be higher in horses with condylar fractures (0.79±0.015) than training controls (0.74±0.019, P=0.070), but also higher in controls with a fracture elsewhere (0.79±0.014) than the training controls (0.74±0.019, P=0.040). BV/TV was higher in horses over three years of age than those aged two or three years (0.79±0.01 vs. 0.74±0.01, P=0.016). All metacarpal condylar fractures occurred within focal areas of high BV/TV. We infer that intense training in equine athletes suppresses remodelling of third metacarpal subchondral bone limiting damage repair while modelling increases regional bone volume in an attempt to minimise local stresses but may fail to offset bone

  6. Development of an in situ fatigue sensor.

    Science.gov (United States)

    2011-01-01

    A prototype in situ fatigue sensor has been designed, constructed and evaluated experimentally for its ability to monitor the accumulation of fatigue damage in a cyclically loaded steel structure, e.g., highway bridge. The sensor consists of multiple...

  7. Effects of mental fatigue on the development of physical fatigue: a neuroergonomic approach.

    Science.gov (United States)

    Mehta, Ranjana K; Parasuraman, Raja

    2014-06-01

    The present study used a neuroergonomic approach to examine the interaction of mental and physical fatigue by assessing prefrontal cortex activation during submaximal fatiguing handgrip exercises. Mental fatigue is known to influence muscle function and motor performance, but its contribution to the development of voluntary physical fatigue is not well understood. A total of 12 participants performed separate physical (control) and physical and mental fatigue (concurrent) conditions at 30% of their maximal handgrip strength until exhaustion. Functional near infrared spectroscopy was employed to measure prefrontal cortex activation, whereas electromyography and joint steadiness were used simultaneously to quantify muscular effort. Compared to the control condition, blood oxygenation in the bilateral prefrontal cortex was significantly lower during submaximal fatiguing contractions associated with mental fatigue at exhaustion, despite comparable muscular responses. The findings suggest that interference in the prefrontal cortex may influence motor output during tasks that require both physical and cognitive processing. A neuroergonomic approach involving simultaneous monitoring of brain and body functions can provide critical information on fatigue development that may be overlooked during traditional fatigue assessments.

  8. Development of a Generic Creep-Fatigue Life Prediction Model

    Science.gov (United States)

    Goswami, Tarun

    2002-01-01

    The objective of this research proposal is to further compile creep-fatigue data of steel alloys and superalloys used in military aircraft engines and/or rocket engines and to develop a statistical multivariate equation. The newly derived model will be a probabilistic fit to all the data compiled from various sources. Attempts will be made to procure the creep-fatigue data from NASA Glenn Research Center and other sources to further develop life prediction models for specific alloy groups. In a previous effort [1-3], a bank of creep-fatigue data has been compiled and tabulated under a range of known test parameters. These test parameters are called independent variables, namely; total strain range, strain rate, hold time, and temperature. The present research attempts to use these variables to develop a multivariate equation, which will be a probabilistic equation fitting a large database. The data predicted by the new model will be analyzed using the normal distribution fits, the closer the predicted lives are with the experimental lives (normal line 1 to 1 fit) the better the prediction. This will be evaluated in terms of a coefficient of correlation, R 2 as well. A multivariate equation developed earlier [3] has the following form, where S, R, T, and H have specific meaning discussed later.

  9. Development of a psychological intervention for post-stroke fatigue

    OpenAIRE

    Wu, Simiao

    2016-01-01

    Background Post-stroke fatigue (PSF) is a common and distressing problem after stroke. It impedes patients’ participation in daily activities and is associated with higher risks of institutionalisation and death following stroke. Despite its high prevalence and detrimental consequences, little research has been conducted to develop effective treatments for PSF. Psychological interventions are effective in treating fatigue in other conditions such as cancer and chronic fatigu...

  10. A Development and Application of the Fretting Fatigue Test Apparatus

    Directory of Open Access Journals (Sweden)

    Wang Jun

    2016-01-01

    Full Text Available Fretting fatigue occurs in contacting parts which are subjected to fluctuating loads and very small sliding movements at the same time. Fretting fatigue can significantly reduce the fatigue life of materials. In this investigation, a new device is introduced, which performed using a combination of a servo-hydraulic push-pull fatigue testing machine and a specially designed jig for appropriate positioning of pads. The axial and contact loads are measured by load cells. The functionality of the device is examined by making a comparison between fretting fatigue lives and plain fatigue lives of a number of ZL702A aluminum alloy specimens. The main advantages of the device are its simplicity and cheapness. It can be developed further for high and low temperature tests in future.

  11. Developing a fatigue questionnaire for Chinese civil aviation pilots.

    Science.gov (United States)

    Dai, Jing; Luo, Min; Hu, Wendong; Ma, Jin; Wen, Zhihong

    2018-03-23

    To assess the fatigue risk is an important challenge in improving flight safety in aviation industry. The aim of this study was to develop a comprehensive fatigue risk management indicators system and a fatigue questionnaire for Chinese civil aviation pilots. Participants included 74 (all males) civil aviation pilots. They finished the questionnaire in 20 minutes before a flight mission. The estimation of internal consistency with Cronbach's α and Student's t test as well as Pearson's correlation analysis were the main statistical methods. The results revealed that the fatigue questionnaire had acceptable internal consistency reliability and construct validity; there were significant differences on fatigue scores between international and domestic flight pilots. And some international flight pilots, who had taken medications as a sleep aid, had worse sleep quality than those had not. The long-endurance flight across time zones caused significant differences in circadian rhythm. The fatigue questionnaire can be used to measure Chinese civil aviation pilots' fatigue, which provided a reference for fatigue risk management system to civil aviation pilots.

  12. Analysis of fatigue development during elite male handball matches

    DEFF Research Database (Denmark)

    Póvoas, Susana C A; Ascensão, António A M R; Magalhães, José

    2014-01-01

    This study aimed at describing the physiological demands and fatigue development during elite male handball matches. Our hypothesis was that players perform multiple high-intensity activities during periods of the game and develop temporary and end-match neuromuscular fatigue. Time-motion analyse...... lactate during the match was 3.6±2.1 (1.3-8.6) mM. Plasma FFA, glycerol, glucose and uric acid increased (p...

  13. Development of a patient reported outcome scale for fatigue in multiple sclerosis: The Neurological Fatigue Index (NFI-MS

    Directory of Open Access Journals (Sweden)

    Tennant Alan

    2010-02-01

    Full Text Available Abstract Background Fatigue is a common and debilitating symptom in multiple sclerosis (MS. Best-practice guidelines suggest that health services should repeatedly assess fatigue in persons with MS. Several fatigue scales are available but concern has been expressed about their validity. The objective of this study was to examine the reliability and validity of a new scale for MS fatigue, the Neurological Fatigue Index (NFI-MS. Methods Qualitative analysis of 40 MS patient interviews had previously contributed to a coherent definition of fatigue, and a potential 52 item set representing the salient themes. A draft questionnaire was mailed out to 1223 people with MS, and the resulting data subjected to both factor and Rasch analysis. Results Data from 635 (51.9% response respondents were split randomly into an 'evaluation' and 'validation' sample. Exploratory factor analysis identified four potential subscales: 'physical', 'cognitive', 'relief by diurnal sleep or rest' and 'abnormal nocturnal sleep and sleepiness'. Rasch analysis led to further item reduction and the generation of a Summary scale comprising items from the Physical and Cognitive subscales. The scales were shown to fit Rasch model expectations, across both the evaluation and validation samples. Conclusion A simple 10-item Summary scale, together with scales measuring the physical and cognitive components of fatigue, were validated for MS fatigue.

  14. Muscle fatigue index: reference values in typically developing children and adolescents

    OpenAIRE

    Vanherk, Dorien; Lemmens, Kathelijn

    2016-01-01

    Muscle fatigue index: reference values for typically developing children and adolescents AIM: To obtain reference values of muscle fatigue in grip and pinch strength in typically developing children and adolescents, to enable an adequate comparison with children and adolescents with motor disorders. Determine the influence of actors such as maximal strength, age, gender, physical activity, body weight and height on muscle fatigue.

  15. Design and development of seal components fatigue tester

    OpenAIRE

    P. Czop; D. Sławik; G. Wszołek; M. Związek

    2008-01-01

    Purpose: The aim of the paper is research and development concerning a fatigue tester of shock absorber seal systems.Design/methodology/approach: Analytical approach has been applied to get an understanding of a heat exchange process. The mathematical model has been formulated and validated based on the available measurements. Numerical simulation has been carried out to illustrate a heat exchange process performance.Findings: It is possible to control a seal temperat...

  16. Multidimensional daily diary of fatigue-fibromyalgia-17 items (MDF-fibro-17). part 1: development and content validity.

    Science.gov (United States)

    Morris, S; Li, Y; Smith, J A M; Dube', S; Burbridge, C; Symonds, T

    2017-05-16

    Fibromyalgia (FM), a disorder characterized by chronic widespread pain and tenderness, affects greater than five million individuals in the United States alone. Patients experience multiple symptoms in addition to pain, and among them, fatigue is one of the most bothersome and disabling. There is a growing body of literature suggesting that fatigue is a multidimensional concept. Currently, to our knowledge, no multidimensional Patient Reported Outcome (PRO) measure of FM-related fatigue meets Food and Drug Administration (FDA) requirements to support a product label claim. Therefore, the objective of this research was to evaluate qualitative and quantitative data previously gathered to inform the development of a comprehensive, multidimensional, PRO measure to assess FM-related fatigue in FM clinical trials. Existing qualitative and quantitative data from three previously conducted studies in patients with FM were reviewed to inform the initial development of a multidimensional PRO measure of FM-related fatigue: 1) a concept elicitation study involving in-depth, open-ended interviews with patients with FM in the United States (US) (N = 20), Germany (N = 10), and France (N = 10); 2) a cognitive debriefing and pilot study of a preliminary pool of 23 items (N = 20 US patients with FM); and 3) a methodology study that explored initial psychometrics of the item pool (N = 145 US patients with FM). Five domains were identified that intend to capture the broad experience of FM-related fatigue reported in the qualitative research: the Global Fatigue Experience, Cognitive Fatigue, Physical Fatigue, Motivation, and Impact on Function. Seventeen of the original pool of 23 items were selected to best capture these five dimensions. These 17 items formed the basis of a newly developed multidimensional PRO measure to assess FM-related fatigue in clinical trials: the Multidimensional Daily Diary of Fatigue-Fibromyalgia-17 (MDF-Fibro-17). Qualitative analysis

  17. Development of a psychological intervention for fatigue after stroke

    Science.gov (United States)

    Wu, Simiao; Chalder, Trudie; Anderson, Kirstin E.; Gillespie, David; Macleod, Malcolm R.; Mead, Gillian E.

    2017-01-01

    Background and aim Post-stroke fatigue (PSF) is common and distressing, but there is insufficient evidence to recommend any effective treatment for it. Psychological interventions are effective in treating fatigue in other conditions. This paper describes the development and evaluation of the feasibility of a psychological intervention for PSF. Methods Based on psychological correlates of PSF and evidence-based psychological interventions for fatigue in other medical conditions, we developed a manualised psychological intervention for PSF, with input from stroke clinicians, psychological therapists, and stroke survivors. The intervention was delivered by a clinical psychologist to 12 participants with PSF to test its acceptability and feasibility. According to the feedback from participants and therapists, the intervention was refined for future use. Results The intervention consisted of six individual, face-to-face treatment sessions, and one follow-up, telephone-delivered booster session. It included psycho-education and discussion of strategies to promote physical and social activities and to challenge unhelpful thoughts. Four participants dropped out and the remaining eight participants completed the intervention. These eight participants also completed all assessments and feedback and reported fatigue levels as lower at the end of the study than at the baseline. All participants reported favourable opinions on the intervention and suggested that the last two treatment sessions be combined and the booster session be delivered in person as opposed to telephone. Conclusions This psychological intervention was acceptable to stroke patients and was feasible in the local health service. These findings suggest that a randomised controlled trial to test efficacy is warranted. PMID:28817725

  18. Development of a psychological intervention for fatigue after stroke.

    Directory of Open Access Journals (Sweden)

    Simiao Wu

    Full Text Available Post-stroke fatigue (PSF is common and distressing, but there is insufficient evidence to recommend any effective treatment for it. Psychological interventions are effective in treating fatigue in other conditions. This paper describes the development and evaluation of the feasibility of a psychological intervention for PSF.Based on psychological correlates of PSF and evidence-based psychological interventions for fatigue in other medical conditions, we developed a manualised psychological intervention for PSF, with input from stroke clinicians, psychological therapists, and stroke survivors. The intervention was delivered by a clinical psychologist to 12 participants with PSF to test its acceptability and feasibility. According to the feedback from participants and therapists, the intervention was refined for future use.The intervention consisted of six individual, face-to-face treatment sessions, and one follow-up, telephone-delivered booster session. It included psycho-education and discussion of strategies to promote physical and social activities and to challenge unhelpful thoughts. Four participants dropped out and the remaining eight participants completed the intervention. These eight participants also completed all assessments and feedback and reported fatigue levels as lower at the end of the study than at the baseline. All participants reported favourable opinions on the intervention and suggested that the last two treatment sessions be combined and the booster session be delivered in person as opposed to telephone.This psychological intervention was acceptable to stroke patients and was feasible in the local health service. These findings suggest that a randomised controlled trial to test efficacy is warranted.

  19. The development of a model of fatigue in neuromuscular disorders: a longitudinal study.

    NARCIS (Netherlands)

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

    2007-01-01

    BACKGROUND: Severe fatigue is reported by the majority of patients with three relatively common types of neuromuscular disorders. OBJECTIVE: This study aimed to identify predictors of fatigue in a longitudinal study and to develop a model of fatigue in patients with three neuromuscular disorders.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  1. Fatigue Fracture Analysis and Development of Fundamentals of Predictive NDE of Adhesive Composite Joints

    National Research Council Canada - National Science Library

    Dzenis, Y. A

    2005-01-01

    The objective of this research was a systematic fatigue fracture analysis and development of fundamentals of predictive nondestructive evaluation of adhesive composite joints for aerospace structural applications...

  2. Development of a remote controlled fatigue testing apparatus at elevated temperature in controlled environment

    International Nuclear Information System (INIS)

    Ohmi, Masao; Mimura, Hideaki; Ishii, Toshimitsu

    1996-02-01

    The fatigue characteristics of reactor structural materials at high temperature are necessary to be evaluated for ensuring the safety of the High Temperature engineering Test Reactor (HTTR). Especially, the high temperature test data on safety research such as low cycle fatigue property and crack propagation property for reactor pressure vessel material are important for the development of the HTTR. Responding to these needs, a remote controlled type fatigue testing machine has been developed and installed in a hot cell of JMTR Hot Laboratory to get the fatigue data of irradiated materials. The machine was developed modifying a commercially available electro-hydraulic servo type fatigue testing machine to withstand radiation and be remotely operated, and mainly consists of a testing machine frame, environment chamber, extensometer, actuator and vacuum exhaust system. It has been confirmed that the machine has good performance to obtain low cycle fatigue data through many demonstration tests on unirradiated and irradiated specimens. (author)

  3. Central and peripheral fatigue development in the shoulder muscle with obesity during an isometric endurance task.

    Science.gov (United States)

    Pajoutan, Mojdeh; Ghesmaty Sangachin, Mahboobeh; Cavuoto, Lora A

    2017-07-21

    Fatigue increases the likelihood of developing work-related musculoskeletal disorders and injury. Due to the physiological and neuromuscular changes that accompany obesity, it may alter the fatigue development mechanism and exacerbate injury risk. The upper extremities have the highest incidence rates for work-related musculoskeletal disorders. Therefore, the goals of this study were to investigate the effect of obesity on central vs. peripheral fatigue as well as on the physical signs of fatigue on the middle deltoid muscle. A measure of central activation ratio was used to quantify central fatigue by considering the increment in the torque output by superimposed twitch relative to its corresponding maximum voluntary contraction. For this purpose, electrical stimulation was delivered at the middle deltoid muscles of 22 non-obese (18 fatiguing task at either 30 or 60% of the muscle capacity. Differences in endurance time, torque fluctuation, torque loss, and muscle activity measured by an electromyography sensor were also investigated. A greater reduction of voluntary activation of motor units (p = 0.001) with fatigue was observed for individuals who are obese. Contrary to the effect of obesity on central fatigue, a trend toward reduced peripheral fatigue (p = 0.06) was observed for the obese group compared to the non-obese group. On average, a 14% higher rate of torque loss per second was observed among individuals with obesity in comparison to non-obese participants. The observed greater contribution of central fatigue during the sustained endurance tasks suggests that among young healthy obese individuals, the faster fatigue development with obesity, commonly reported in the literature, is most likely due to the central elements rather than the peripheral factors. This finding has implications for fatigue prevention programs during sustained exertions and can help to develop training, work, and rest schedules considering obesity.

  4. Development of fatigue in trapezius muscle during light manual assembly work

    NARCIS (Netherlands)

    Pikaar, R.N.; Koningsveld, E.A.P.; Settels, P.J.M.; Bosch, T.; Looze, M.P. de; Dieën, J.H. van

    2006-01-01

    Optimisation of the temporal aspects of the task design requires a better understanding of the development of muscle fatigue in the neck and shoulder region over time. Our objective was to investigate the development of muscle fatigue and to determine the relationship between objective and

  5. High-temperature fatigue in metals - A brief review of life prediction methods developed at the Lewis Research Center of NASA

    Science.gov (United States)

    Halford, G. R.

    1983-01-01

    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. Previously announced in STAR as A83-12159

  6. Association between Local Illumination and Visual Fatigue among the Research and Development Staffs of Industry

    Directory of Open Access Journals (Sweden)

    A.R. Mashkoori

    2016-12-01

    Full Text Available Abstract Aims: Work proper lighting means a safe, healthy and comfort conditions for work under a lighting system that includes qualitative and quantitative features. This study aimed to evaluate the surface local lighting of works and eye fatigue among research and development staffs of an automotive industry. Instrument & Methods: In this descriptive study in Research and Development Department of an automotive industry in 2015, 126 official staffs were selected randomly. A demographic questionnaire and the Visual Fatigue Questionnaire (Persian Version were used for data gathering. Hagner EC1 Luxmeter was used to measure the local lighting. Data were analyzed by SPSS 20 software, through descriptive statistics. Findings: The lighting in 382 stations (75.8% was improper and less than standard. The minimum and maximum intensity of light was between 22.4lux in station 2 (inventory department and 581lux in station 4 (systems and methods department. The overall intensity in more than 50% units, except the Systems and Methods Department, were less than the standard (300lux. 40.4% of the participants had severe eye fatigue, 28.6% had moderate visual fatigue, 28.6% had low visual fatigue and only 2.4% had no visual fatigue. The average of visual fatigue was 3.50±1.97. Conclusion: The workplace lighting and the eye fatigue of computer users in the Research and Development Department of the studied automotive industry are not in an acceptable condition.

  7. Development of a Physically-Based Methodology for Predicting Material Variability in Fatigue Crack Initiation and Growth Response

    National Research Council Canada - National Science Library

    Chan, Kwai

    2004-01-01

    ... of aerospace structural alloys. In this three-year program, physics-based fatigue crack initiation and growth models were developed and integrated into a probabilistic micromechanical code for treating fatigue life variability...

  8. Development of the ultrasonic fatigue testing machine due to study on giga-cycle fatigue at elevated temperature. 2001 annual report. Document on collaborative study

    International Nuclear Information System (INIS)

    Hattori, Shuji; Itoh, Takamoto

    2002-03-01

    An ultrasonic fatigue testing machine was developed to obtain the giga-cycle fatigue life at elevated temperature for safety and reliability of structural components in the faster breeder reactor (FBR). This testing machine consists of an amplifier, booster, horn and the equipments such as a system controller and data acquisition. The test specimen is attached at the end of the horn. The electric power generated in the amplifier is transformed into the mechanical vibration in the converter and is magnified in the booster and horn. The vibration was enough to fatigue the specimen. Since the test frequency is set at a resonant frequency, the shape and dimensions of specimen were designed so as to vibrate itself resonantly. However, the maximum amplitudes of stress and strain in the specimen can be calculated easily by measuring the amplitude of displacement at the end of the specimen. The developed ultrasonic fatigue testing machine enables to carry out the fatigue tests at 20 kHz so that it can perform the giga-cycle fatigue test within a very short time as compared with the regular fatigue testing machines such as a hydraulic fatigue testing machine. By clarifying the material strength characteristics in giga-cycle region, the life evaluation, design and examination of components will be more suitable than ever. This study will contribute to improve the safety and reliability of components in FBR. In this technical report, the specification and characteristics of the testing machine were described along with the several experimental results. (author)

  9. Development of a realistic stress analysis for fatigue analysis of notched composite laminates

    Science.gov (United States)

    Humphreys, E. A.; Rosen, B. W.

    1979-01-01

    A finite element stress analysis which consists of a membrane and interlaminar shear spring analysis was developed. This approach was utilized in order to model physically realistic failure mechanisms while maintaining a high degree of computational economy. The accuracy of the stress analysis predictions is verified through comparisons with other solutions to the composite laminate edge effect problem. The stress analysis model was incorporated into an existing fatigue analysis methodology and the entire procedure computerized. A fatigue analysis is performed upon a square laminated composite plate with a circular central hole. A complete description and users guide for the computer code FLAC (Fatigue of Laminated Composites) is included as an appendix.

  10. Dislocation substructures developed in martensitic steels under thermal fatigue

    Science.gov (United States)

    Alvarez-Armas, I.; Armas, A. F.; Petersen, C.

    1992-09-01

    Thermal fatigue tests were carried out on a martensitic steel, DIN denomination W. Nr. 1.4914, commonly named MANET I. The tests were performed in air by allowing the sample to serve as its own heater and converting any longitudinal thermal deformation of the specimen into elastic or inelastic deformation. The low temperature was held constant and equal to 473 K and variable values, 823, 873, 923, 973 K for the high temperature were selected. The effects of different thermal cycling ranges on the mechanical behavior and the accompanying microstructural changes in the specimen were evaluated. A continous softening preceded by a stability period was observed in all thermal fatigue tests. Higher temperature changes produce an accelerated softening process. The original lath structure evolves to a mixed structure of expanded laths and subgrains or a fully subgrain structure depending on the temperature range.

  11. Review of fatigue criteria development for HTGR core supports

    International Nuclear Information System (INIS)

    Ho, F.H.; Vollman, R.E.

    1979-10-01

    Fatigue criteria for HTGR core support graphite structure are presented. The criteria takes into consideration the brittle nature of the material, and emphasizes the probabilistic approach in the treatment of strength data. The stress analysis is still deterministic. The conventional cumulative damage approach is adopted here. A specified minimum S-N curve is defined as the curve with 99% probability of survival at a 95% confidence level to accommodate random variability of the material strength. A constant life diagram is constructed to reconcile the effect of mean stress. The linear damage rule is assumed to account for the effect of random cycles. An additional factor of safety of three on cycles is recommended. The uniaxial S-N curve is modified in the medium-to-high cycle range (> 2 x 10 3 cycles) for mutiaxial fatigue effects

  12. Predictive factors for the development of diabetes in women with previous gestational diabetes mellitus

    DEFF Research Database (Denmark)

    Damm, P.; Kühl, C.; Bertelsen, Aksel

    1992-01-01

    OBJECTIVES: The purpose of this study was to determine the incidence of diabetes in women with previous dietary-treated gestational diabetes mellitus and to identify predictive factors for development of diabetes. STUDY DESIGN: Two to 11 years post partum, glucose tolerance was investigated in 241...... women with previous dietary-treated gestational diabetes mellitus and 57 women without previous gestational diabetes mellitus (control group). RESULTS: Diabetes developed in 42 (17.4%) women with previous gestational diabetes mellitus (3.7% insulin-dependent diabetes mellitus and 13.7% non......-insulin-dependent diabetes mellitus). Diabetes did not develop in any of the controls. Predictive factors for diabetes development were fasting glucose level at diagnosis (high glucose, high risk), preterm delivery, and an oral glucose tolerance test result that showed diabetes 2 months post partum. In a subgroup...

  13. Development of device for grid spring fatigue and a cell-based fuel rod fretting wear tests

    International Nuclear Information System (INIS)

    Kim, Hyung Kyu; Yoon, Kyung Ho; Kang, Heung Seok; Song, Kee Nam

    2001-05-01

    As an activity of experimental research on the cause and the remedy of LWR fuel fretting failure, developed is test equipment for fatigue of grid spring and cell-based fuel rod fretting wear test. The equipment enables to perform the fretting wear test in the case of gap existence between spring and cladding, which has not been possible by the previously developed one (KAERI/TR-1570/2000). It can also provide fatigue test capability with the frequency of more than 10 Hz. Used are a servo-motor, an eccentric cylinder and lever mechanism for driving system as was similarly used for the previous equipment. In fretting wear test, up to 2 span-length of a fuel cladding tube can be accommodated. For fatigue test, on the other hand, a device for clamping the spring fixture is installed additionally. As a feature of the present equipment, the gap or the contacting force between a spring and a tube can be adjusted during the fretting wear test, while an initial spring force can be simulated for the fatigue test. Tests will be conducted in air at room temperature. In this report, every part of the equipment is explained with photographs, which will provide an easy understanding. Test procedure such as specimen installation, sequence of operation and program handling is also given. As a performance test of the present equipment, displacement range is measured when the hinge of the lever locates at its maximum and minimum positions. This will be used as basic information when additional eccentric cylinder is necessary for different displacement ranges

  14. Factors that influence the development of compassion fatigue, burnout, and compassion satisfaction in emergency department nurses.

    Science.gov (United States)

    Hunsaker, Stacie; Chen, Hsiu-Chin; Maughan, Dale; Heaston, Sondra

    2015-03-01

    The purpose of this study was twofold: (a) to determine the prevalence of compassion satisfaction, compassion fatigue, and burnout in emergency department nurses throughout the United States and (b) to examine which demographic and work-related components affect the development of compassion satisfaction, compassion fatigue, and burnout in this nursing specialty. This was a nonexperimental, descriptive, and predictive study using a self-administered survey. Survey packets including a demographic questionnaire and the Professional Quality of Life Scale version 5 (ProQOL 5) were mailed to 1,000 selected emergency nurses throughout the United States. The ProQOL 5 scale was used to measure the prevalence of compassion satisfaction, compassion fatigue, and burnout among emergency department nurses. Multiple regression using stepwise solution was employed to determine which variables of demographics and work-related characteristics predicted the prevalence of compassion satisfaction, compassion fatigue, and burnout. The α level was set at .05 for statistical significance. The results revealed overall low to average levels of compassion fatigue and burnout and generally average to high levels of compassion satisfaction among this group of emergency department nurses. The low level of manager support was a significant predictor of higher levels of burnout and compassion fatigue among emergency department nurses, while a high level of manager support contributed to a higher level of compassion satisfaction. The results may serve to help distinguish elements in emergency department nurses' work and life that are related to compassion satisfaction and may identify factors associated with higher levels of compassion fatigue and burnout. Improving recognition and awareness of compassion satisfaction, compassion fatigue, and burnout among emergency department nurses may prevent emotional exhaustion and help identify interventions that will help nurses remain empathetic and

  15. Development of a fatigue testing setup for dielectric elastomer membrane actuators

    Science.gov (United States)

    Hill, M.; Rizzello, G.; Seelecke, S.

    2017-04-01

    Dielectric elastomers (DE's) represent a transduction technology with high potential in many fields, including industries, due to their low weight, flexibility, and small energy consumption. For industrial applications, it is of fundamental importance to quantify the lifetime of DE technology, in terms of electrical and mechanical fatigue, when operating in realistic environmental conditions. This work contributes toward this direction, by presenting the development of an experimental setup which permits systematic fatigue testing of DE membranes. The setup permits to apply both mechanical and electrical stimuli to several membranes simultaneously, while measuring at the same time their mechanical (force, deformation) and electrical response (capacitance, resistance). In its final state, the setup will allow to test up to 15 DE membranes at the same time for several thousands of cycles. Control of the modules, monitoring of the actuators, and data acquisition are realized on a cRio FPGA-system running with LabVIEW. The setup is located in a climate chamber, in order to investigate the fatigue mechanisms at different environmental conditions, i.e., in terms of temperature and humidity. The setup consists of two main parts, namely a fatigue group and a measurement group. The fatigue group stays permanently in the climate chamber, while the measurement group is assembled to the fatigue group and allows to perform measurements at 20°C.

  16. Influence of blood flow occlusion on the development of peripheral and central fatigue during small muscle mass handgrip exercise.

    Science.gov (United States)

    Broxterman, R M; Craig, J C; Smith, J R; Wilcox, S L; Jia, C; Warren, S; Barstow, T J

    2015-09-01

    Critical power represents an important threshold for neuromuscular fatigue development and may, therefore, dictate intensities for which exercise tolerance is determined by the magnitude of fatigue accrued. Peripheral fatigue appears to be constant across O2 delivery conditions for large muscle mass exercise, but this consistency is equivocal for smaller muscle mass exercise. We sought to determine the influence of blood flow occlusion during handgrip exercise on neuromuscular fatigue development and to examine the relationship between neuromuscular fatigue development and W '. Blood flow occlusion influenced the development of both peripheral and central fatigue, thus providing further evidence that the magnitude of peripheral fatigue is not constant across O2 delivery conditions for small muscle mass exercise. W ' appears to be related to the magnitude of fatigue accrued during exercise, which may explain the reported consistency of intramuscular metabolic perturbations and work performed for severe-intensity exercise. The influence of the muscle metabolic milieu on peripheral and central fatigue is currently unclear. Moreover, the relationships between peripheral and central fatigue and the curvature constant (W ') have not been investigated. Six men (age: 25 ± 4 years, body mass: 82 ± 10 kg, height: 179 ± 4 cm) completed four constant power handgrip tests to exhaustion under conditions of control exercise (Con), blood flow occlusion exercise (Occ), Con with 5 min post-exercise blood flow occlusion (Con + Occ), and Occ with 5 min post-exercise blood flow occlusion (Occ + Occ). Neuromuscular fatigue measurements and W ' were obtained for each subject. Each trial resulted in significant peripheral and central fatigue. Significantly greater peripheral (79.7 ± 5.1% vs. 22.7 ± 6.0%) and central (42.6 ± 3.9% vs. 4.9 ± 2.0%) fatigue occurred for Occ than for Con. In addition, significantly greater peripheral (83.0 ± 4.2% vs. 69.0 ± 6.2%) and central

  17. 78 FR 35263 - Freeport LNG Development, L.P.; Application for Blanket Authorization To Export Previously...

    Science.gov (United States)

    2013-06-12

    ... the LNG at the time of export. The Application was filed under section 3 of the Natural Gas Act (NGA... not prohibited by U.S. law or policy. Current Application The current Application is filed in... Freeport LNG Development, L.P.; Application for Blanket Authorization To Export Previously Imported...

  18. Developing Reading Comprehension through Metacognitive Strategies: A Review of Previous Studies

    Science.gov (United States)

    Channa, Mansoor Ahmed; Nordin, Zaimuariffudin Shukri; Siming, Insaf Ali; Chandio, Ali Asgher; Koondher, Mansoor Ali

    2015-01-01

    This paper has reviewed the previous studies on metacognitive strategies based on planning, monitoring, and evaluating in order to develop reading comprehension. The main purpose of this review in metacognition, and reading domain is to help readers to enhance their capabilities and power reading through these strategies. The researchers reviewed…

  19. Scanning Electron Microscope Mapping System Developed for Detecting Surface Defects in Fatigue Specimens

    Science.gov (United States)

    Bonacuse, Peter J.; Kantzos, Peter T.

    2002-01-01

    An automated two-degree-of-freedom specimen positioning stage has been developed at the NASA Glenn Research Center to map and monitor defects in fatigue specimens. This system expedites the examination of the entire gauge section of fatigue specimens so that defects can be found using scanning electron microscopy (SEM). Translation and rotation stages are driven by microprocessor-based controllers that are, in turn, interfaced to a computer running custom-designed software. This system is currently being used to find and record the location of ceramic inclusions in powder metallurgy materials. The mapped inclusions are periodically examined during interrupted fatigue experiments. The number of cycles to initiate cracks from these inclusions and the rate of growth of initiated cracks can then be quantified. This information is necessary to quantify the effect of this type of defect on the durability of powder metallurgy materials. This system was developed with support of the Ultra Safe program.

  20. A brief fatigue inventory of shoulder health developed by quality function deployment technique.

    Science.gov (United States)

    Liu, Shuo-Fang; Lee, Yannlong; Huang, Yiting

    2009-01-01

    The purpose of this study was to develop a diagnostic outcome instrument that has high reliability and low cost. The scale, called the Shoulder Fatigue Scale-30 Items (SFS-30) risk assessment, was used to determine the severity of patient neck and shoulder discomfort. The quality function deployment (QFD) technique was used in designing and developing a simple medical diagnostic scale with high degree of accuracy. Research data can be used to divide the common causes of neck and shoulder discomfort into 6 core categories: occupation, cumulative, psychologic, diseases, diet, and sleep quality. The SFS-30 was validated by using a group of individuals who had been previously diagnosed with different levels of neck and shoulder symptoms. The SFS-30 assessment determined that 78.57% of the participants experienced a neck and shoulder discomfort level above the SFS-30 risk curve and required immediate medical attention. The QFD technique can improve the accuracy and reliability of an assessment outcome instrument. This is mainly because the QFD technique is effective in prioritizing and assigning weight to the items in the scale. This research successfully developed a reliable risk assessment scale to diagnose neck and shoulder symptoms using QFD technique. This scale was proven to have high accuracy and closely represents reality.

  1. Hormone levels in radiotherapy treatment related fatigue

    International Nuclear Information System (INIS)

    Biswal, B.M.; Mallik, G.S.

    2003-01-01

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

  2. Development of fatigue and discomfort in the upper trapezius muscle during light manual work

    NARCIS (Netherlands)

    Bosch, T.; Looze, M.P. de; Dieën, J.H. van

    2007-01-01

    Optimization of the temporal aspects of task design requires a better understanding of the development of muscle fatigue in the neck and shoulder region over time. The objective of the study was to investigate this in two production companies and to determine the relationship between objective and

  3. Developing a Safety Management System for Fatigue Related Risks in easyJet

    NARCIS (Netherlands)

    Stewart, S.; Koornneef, F.; Akselsson, R.; Turner, C.

    2009-01-01

    Chapter 5: Developing a Safety Management System for Fatigue Related Risks in easyJet The European Commission HILAS project (Human Integration into the Lifecycle of Aviation Systems - a project supported by the European Commission’s 6th Framework between 2005-2009) was focused on using human factors

  4. 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.

  5. Fatigue-enhanced hyperalgesia in response to muscle insult: induction and development occur in a sex-dependent manner

    Science.gov (United States)

    Gregory, N. S.; Gibson-Corley, K.; Frey-Law, L.; Sluka, K. A.

    2014-01-01

    Chronic muscle pain affects 20–50% of the population, is more common in women than men, and is associated with increased pain during physical activity and exercise. Muscle fatigue is common in people with chronic muscle pain, occurs in response to exercise and is associated with release of fatigue metabolites. Fatigue metabolites can sensitize muscle nociceptors which could enhance pain with exercise. Using a mouse model we tested whether fatigue of a single muscle, induced by electrical stimulation, resulted in enhanced muscle hyperalgesia and if the enhanced hyperalgesia was more pronounced in female mice. Muscle fatigue was induced in combination with a sub-threshold muscle insult (2 injections of pH 5.0 saline) in male and female mice. We show that male and female mice, fatigued immediately prior to muscle insult in the same muscle, develop similar muscle hyperalgesia 24h later. However, female mice also develop hyperalgesia when muscle fatigue and muscle insult occur in different muscles, and when muscle insult is administered 24 hours after fatigue in the same muscle. Further, hyperalgesia lasts significantly longer in females. Finally, muscle insult with or without muscle fatigue results in minimal inflammatory changes in the muscle itself, and sex differences are not related to estradiol (ovariectomy) or changes in brainstem activity (pNR1). Thus, the current model mimics muscle fatigue-induced enhancement of pain observed in chronic muscle pain conditions in the human population. Interactions between fatigue and muscle insult may underlie the development of chronic widespread pain with an associated female predominance observed in human subjects. PMID:23906552

  6. Measuring Physical and Cognitive Fatigue in People With Post-Polio Syndrome: Development of the Neurological Fatigue Index for Post-Polio Syndrome (NFI-PP).

    Science.gov (United States)

    Young, Carolyn A; Wong, Samantha M; Quincey, Anne-Marie C; Tennant, Alan

    2018-02-01

    Fatigue in post-polio syndrome (PPS) has been shown to affect quality of life adversely. There is currently no disease-specific measure of fatigue for PPS. To develop a scale to measure fatigue in PPS that meets rigorous psychometric standards. Qualitative followed by validation and test-retest studies. Polio clinic followed by national questionnaire studies. A total of 45 participants from polio clinic for qualitative; 319 participants from clinic or self-referral for validation study, of whom 87 completed the retest questionnaire. Draft questionnaire items on PPS fatigue were derived from transcripts of qualitative interviews. After cognitive debriefing, the draft measure was administered by mail along with comparator questionnaires to a new sample. Draft PPS fatigue measure, Fatigue Severity Scale, and visual analog scale for fatigue. Analysis of 271 of 319 (85%) questionnaires identified a 2-factor solution (RMSEA 0.058). For the physical subscale, a 20-item scale showed good fit (χ 2 P = .189), strict unidimensionality (t-test 5.17%), and reliability 0.91. For the cognitive subscale, a 7-item scale showed excellent fit (χ 2 P = .917), strict unidimensionality (t-test 5.2%), and reliability 0.89. Evidence of a "difficulty factor" emerged also supporting a total score that showed good fit (χ 2 P = .151), strict unidimensionality (t-test 0.4%), and reliability consistent with group use at 0.73. Test-retest correlations for all scales were greater than 0.85. Standard error of measurement on metric ranges was 5.4 for total, 2.9 for physical, and 1.69 for cognitive domains. With the latent estimate of the total score transformed to a 0-100 scale, the mean score was 49.5 (SD 6.9). Spearman correlations with the Fatigue Severity Scale and visual analog scale were 0.60 and 0.55, respectively. A patient-derived Neurological Fatigue Index for PPS, with physical and cognitive subscales and a total score, has demonstrated good reliability, appropriate concurrent

  7. Mentoring to develop research selfefficacy, with particular reference to previously disadvantaged individuals

    OpenAIRE

    S. Schulze

    2010-01-01

    The development of inexperienced researchers is crucial. In response to the lack of research self-efficacy of many previously disadvantaged individuals, the article examines how mentoring can enhance the research self-efficacy of mentees. The study is grounded in the self-efficacy theory (SET) – an aspect of the social cognitive theory (SCT). Insights were gained from an in-depth study of SCT, SET and mentoring, and from a completed mentoring project. This led to the formulation of three basi...

  8. French recent developments in support to rules for creep and creep-fatigue analyses

    International Nuclear Information System (INIS)

    Touboul, F.; Moulin, D.

    1997-01-01

    RCC-MR proposes Design rules for creep and creep-fatigue damage evaluation in zones with no geometrical discontinuities. Rules have been developed, based on the σ d concept, in order to consider zones with geometrical discontinuities. Rule for Weld are proposed in the paragraph relative to shell design rules and reduction coefficient due to material properties are given in Appendix A9. For fatigue analysis, last version of RCC-MR (1993) has proposed a reduction factor on fatigue curves (Jf value), derived from preliminary tests performed within European program. Studies have been carried out in order to have a better understanding of the phenomena involved in these fatigue reduction factors. Tests have been performed on large plates, with varying applied displacements, weld geometry, plate thickness, weld direction. It appears that material effect is not the only purpose to be considered but that it is necessary to think about the geometrical effect, linked to the welded zone dimensions, and the elastic follow-up effect between the two materials: base metal and weld metal. As a first approach, simplified calculations have been achieved with precise material characterization. Roche's method and Zarka method's give conservative result in comparison to tests results. (author). 3 refs, 4 tabs

  9. Impact of Blood Flow Restriction Exercise on Muscle Fatigue Development and Recovery.

    Science.gov (United States)

    Husmann, Florian; Mittlmeier, Thomas; Bruhn, Sven; Zschorlich, Volker; Behrens, Martin

    2018-03-01

    The present study was designed to provide mechanistic insight into the time course and etiology of muscle fatigue development and recovery during and after low-intensity exercise when it is combined with blood flow restriction (BFR). Seventeen resistance-trained males completed four sets of low-intensity isotonic resistance exercise under two experimental conditions: knee extension exercise (i) with BFR and (ii) without BFR (CON). Neuromuscular tests were performed before, during (immediately after each set of knee extension exercise), and 1, 2, 4, and 8 min after each experimental condition. Maximal voluntary torque, quadriceps twitch torque in response to paired electrical stimuli at 10 Hz (PS10) and 100 Hz (PS100), PS10·PS100 ratio as an index of low-frequency fatigue, and voluntary activation were measured under isometric conditions. Perceptual and EMG data were recorded during each exercise condition. After the first set of exercise, BFR induced significantly greater reductions in maximal voluntary torque, PS100, and PS10·PS100 ratio compared with CON. These parameters progressively declined throughout the BFR protocol but recovered substantially within 2 min postexercise when blood flow was restored. Neither a progressive decline in the course of the exercise protocol nor a substantial recovery of these parameters occurred during and after CON. Only at exercise termination, voluntary activation differed significantly between BFR and CON with greater reductions during BFR. At the early stage of exercise, BFR exacerbated the development of muscle fatigue mainly due to a pronounced impairment in contractile function. Despite the high level of muscle fatigue during BFR exercise, the effect of BFR on muscle fatigue was diminished after 2 min of reperfusion, suggesting that BFR has a strong but short-lasting effect on neuromuscular function.

  10. Mentoring to develop research selfefficacy, with particular reference to previously disadvantaged individuals

    Directory of Open Access Journals (Sweden)

    S. Schulze

    2010-07-01

    Full Text Available The development of inexperienced researchers is crucial. In response to the lack of research self-efficacy of many previously disadvantaged individuals, the article examines how mentoring can enhance the research self-efficacy of mentees. The study is grounded in the self-efficacy theory (SET – an aspect of the social cognitive theory (SCT. Insights were gained from an in-depth study of SCT, SET and mentoring, and from a completed mentoring project. This led to the formulation of three basic principles. Firstly, institutions need to provide supportive environmental conditions that facilitate research selfefficacy. This implies a supportive and efficient collective system. The possible effects of performance ratings and reward systems at the institution also need to be considered. Secondly, mentoring needs to create opportunities for young researchers to experience successful learning as a result of appropriate action. To this end, mentees need to be involved in actual research projects in small groups. At the same time the mentor needs to facilitate skills development by coaching and encouragement. Thirdly, mentors need to encourage mentees to believe in their ability to successfully complete research projects. This implies encouraging positive emotional states, stimulating self-reflection and self-comparison with others in the group, giving positive evaluative feedback and being an intentional role model.

  11. Concept development of "compassion fatigue" in clinical nurses: Application of Schwartz-Barcott and Kim's hybrid model

    Directory of Open Access Journals (Sweden)

    Mahdieh Sabery

    2017-06-01

    Full Text Available Compassion fatigue is not a new concept in nursing; yet, it is not well known and there is no fixed clear definition of the term. The ambiguity surrounding how to define compassion fatigue has challenged its measurement and evaluation. Thus, any attempt to determine attributes of this underdeveloped concept and studying it in a new socio-cultural context requires concept development. The purpose of this study is to clarify the concept of compassion fatigue through concept development and to produce a vivid and tentative definition of this concept in clinical practice. Concept development was conducted using a three-step hybrid concept analysis including theoretical, fieldwork, and final analysis phases according to Schwartz-Barcott and Kim's method. We reviewed and analyzed 48 articles that met the inclusion criteria. Following, the first author conducted 13 interviews with clinical nurses followed by an inductive content analysis. Finally, a comprehensive definition of compassion fatigue in nurses was attained. Compassion fatigue in nurses can be explained as a cumulative and progressive process of absorption of the patient’s pain and suffering formed from the sympathetic and caring interactions with the patients and their families. The physical, emotional, intellectual, spiritual, social, and organizational consequences of compassion fatigue are so extensive that they threaten the existential integrity of the nurse. Context-based variables (culture, family, and community such as personality features like devotion behaviors and commitment towards the patient, exposure to multiple stressors, organizational challenges, and lack of self-care are factors associated with an increased risk of compassion fatigue. Concept development of compassion fatigue is the first step in the protection of nurses against the destructive consequences of compassion fatigue and to improve quality of care.

  12. Rate of torque and electromyographic development during anticipated eccentric contraction is lower in previously strained hamstrings.

    Science.gov (United States)

    Opar, David A; Williams, Morgan D; Timmins, Ryan G; Dear, Nuala M; Shield, Anthony J

    2013-01-01

    The effect of prior strain injury on myoelectrical activity of the hamstrings during tasks requiring high rates of torque development has received little attention. To determine if recreational athletes with a history of unilateral hamstring strain injury will exhibit lower levels of myoelectrical activity during eccentric contraction, rate of torque development (RTD), and impulse (IMP) at 30, 50, and 100 milliseconds after the onset of myoelectrical activity or torque development in the previously injured limb compared with the uninjured limb. Case control study; Level of evidence, 3. Twenty-six recreational athletes were recruited. Of these, 13 athletes had a history of unilateral hamstring strain injury (all confined to biceps femoris long head), and 13 had no history of hamstring strain injury. Following familiarization, all athletes undertook isokinetic dynamometry testing and surface electromyography (integrated EMG; iEMG) assessment of the biceps femoris long head and medial hamstrings during eccentric contractions at -60 and -180 deg·s(-1). In the injured limb of the injured group, compared with the contralateral uninjured limb, RTD and IMP was lower during -60 deg·s(-1) eccentric contractions at 50 milliseconds (RTD: injured limb, 312.27 ± 191.78 N·m·s(-1) vs uninjured limb, 518.54 ± 172.81 N·m·s(-1), P = .008; IMP: injured limb, 0.73 ± 0.30 N·m·s vs uninjured limb, 0.97 ± 0.23 N·m·s, P = .005) and 100 milliseconds (RTD: injured limb, 280.03 ± 131.42 N·m·s(-1) vs uninjured limb, 460.54 ± 152.94 N·m·s(-1), P = .001; IMP: injured limb, 2.15 ± 0.89 N·m·s vs uninjured limb, 3.07 ± 0.63 N·m·s, P contraction. Biceps femoris long head muscle activation was lower at 100 milliseconds at both contraction speeds (-60 deg·s(-1), normalized iEMG activity [×1000]: injured limb, 26.25 ± 10.11 vs uninjured limb, 33.57 ± 8.29, P = .009; -180 deg·s(-1), normalized iEMG activity [×1000]: injured limb, 31.16 ± 10.01 vs uninjured limb, 39.64

  13. Shoulder muscle fatigue development in young and older female adults during a repetitive manual task.

    Science.gov (United States)

    Qin, Jin; Lin, Jia-Hua; Buchholz, Bryan; Xu, Xu

    2014-01-01

    Age may modify the association between occupational physical demand and muscle loading, and ultimately increase the risk of musculoskeletal disorders. The goal of this study was to investigate age-related differences in shoulder muscle fatigue development during a repetitive manual task. Twenty participants in two age groups completed an 80-minute simulated low-intensity assembly task. Electromyographic (EMG) manifestation of muscle fatigue was observed in the upper trapezius, deltoid and infraspinatus muscles in both age groups, and coincided with an increase in the subjective ratings of perceived exertions. Compared with the younger group, older group showed a more monotonic decrease in EMG power frequency in the upper trapezius and deltoid muscles. However, the age-related difference in EMG amplitude was less consistent. Relative rest time of the upper trapezius muscle in the older group was less than the young group throughout the task. The observed patterns of EMG measures suggest that older participants may have disadvantages in fatigue resistance in the upper trapezius and posterior deltoid muscles during the simulated repetitive manual task.

  14. Understanding the Association of Fatigue With Other Symptoms of Fibromyalgia: Development of a Cluster Model.

    Science.gov (United States)

    Lukkahatai, Nada; Walitt, Brian; Espina, Alexandra; Gelio, Alves; Saligan, Leorey N

    2016-01-01

    To develop a symptoms cluster model that can describe factors of fibromyalgia syndrome (FMS) associated with fatigue severity as reported by the sample and to explore FMS clinical symptom subclusters based on varying symptom intensities. FMS individuals (n = 120, 82% ages 31-60 years, 90% women, 59% white) diagnosed with the 1990 or 2010 American College of Rheumatology diagnostic criteria were enrolled. Participants completed multiple validated self-report questionnaires to measure fatigue, pain, depression, anxiety, pain catastrophizing, daytime sleepiness, cognitive function, and FMS-related polysymptomatic distress. Cluster analysis using SPSS 19.0 and structural equation modeling using AMOS 17.0 were used. Final structural equation modeling the symptoms cluster model showed good fit and revealed that FMS fatigue was associated with widespread pain, symptoms severity, pain intensity, pain interference, cognitive dysfunction, catastrophizing, anxiety, and depression (χ(2)  = 121.72 (98df), P > 0.05, χ(2) /df = 1.242, comparative fit index = 0.982, root mean square error of approximation = 0.045). Two distinct clinical symptom subclusters emerged: subcluster 1 (78% of total subjects), defined by widespread pain, unrefreshed waking, and somatic symptoms, and subcluster 2 (22% of total subjects), defined by fatigue and cognitive dysfunction with pain being a less severe and less widespread occurrence. Overall, subcluster 1 had more intense symptoms than subcluster 2. FMS symptoms may be categorized into 2 clinical subclusters. These findings have implications for an illness whose diagnosis and management are symptom dependent. A longitudinal study capturing the variability in the symptom experience of FMS subjects is warranted. © 2016, American College of Rheumatology.

  15. Development of a Digital Image Correlation controlled fatigue crack propagation experiment

    Directory of Open Access Journals (Sweden)

    Rethore J.

    2010-06-01

    Full Text Available The present paper exposes the development of a specific Digital Image Correlation (DIC method to ensure a fast calculation of fracture parameters such as stress intensity factors and crack length. This measurement is used to control a fatigue crack propagation using the load shedding method in order to ensure a limited plastic damaged crack. The experimental procedure has the main advantage to be fully automotive. The parameters’ identification is compared with a more sophisticated identification method and shows a good accuracy.

  16. Cyclic stress-strain curve for low cycle fatigue design and development of small specimen technology

    International Nuclear Information System (INIS)

    Nishimura, A.; Nogami, S.; Wakai, Eiichi

    2012-11-01

    A blanket system in DEMO requires a low cycle fatigue design because higher inner pressure will act on a structural wall. An importance of cyclic stress-strain curve is investigated and necessity reason for a precise deformation measurement is discussed. Since a small specimen technique is necessary to investigate neutron irradiation effect, it is desired to establish a test procedure to obtain the stress-strain curve with small specimens. To do this, a new test procedure with nanometer scale resolution was developed and some data were obtained. (author)

  17. Research and development of optic fiber sensitive elements for fatigue gauges

    International Nuclear Information System (INIS)

    Rakhimov, N.R.; Shamirzaev, S.Kh.

    2004-01-01

    In the work a possibility for using the optic fibers as the sensitive element for the fatigue gauge of mechanical construction elements is investigated. The experimental results are presented on investigation of polymer optic fibers subjected to the fatigue loads using the special tools. It was shown that they have a high sensitivity to fatigue damage of construction elements. (author)

  18. Synchronous development of breast cancer and chest wall fibrosarcoma after previous mantle radiation for Hodgkin's disease

    International Nuclear Information System (INIS)

    Patlas, Michael; McCready, David; Kulkarni, Supriya; Dill-Macky, Marcus J.

    2005-01-01

    Survivors of Hodgkin's disease are at increased risk of developing a second malignant neoplasm, including breast carcinoma and sarcoma. We report the first case of synchronous development of chest wall fibrosarcoma and breast carcinoma after mantle radiotherapy for Hodgkin's disease. Mammographic, sonographic and MR features are demonstrated. (orig.)

  19. Reactor cooling water expansion joint bellows: The role of the seam weld in fatigue crack development

    International Nuclear Information System (INIS)

    West, S.L.; Nelson, D.Z.; Louthan, M.R. Jr.

    1992-01-01

    The secondary cooling water system pressure boundary of Savannah River Site reactors includes expansion joints utilizing a thin-wall bellows. While successfully used for over thirty years, an occasional replacement has been required because of the development of small, circumferential fatigue cracks in a bellows convolute. One such crack was recently shown to have initiated from a weld heat-affected zone liquation microcrack. The crack, initially open to the outer surface of the rolled and seam welded cylindrical bellows section, was closed when cold forming of the convolutes placed the outer surface in residual compression. However, the bellows was placed in tension when installed, and the tensile stresses reopened the microcrack. This five to eight grain diameter microcrack was extended by ductile fatigue processes. Initial extension was by relatively rapid propagation through the large-grained weld metal, followed by slower extension through the fine-grained base metal. A significant through-wall crack was not developed until the crack extended into the base metal on both sides of the weld. Leakage of cooling water was subsequently detected and the bellows removed and a replacement installed

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-08-01

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

  1. Sustainable development, tourism and territory. Previous elements towards a systemic approach

    Directory of Open Access Journals (Sweden)

    Pierre TORRENTE

    2009-01-01

    Full Text Available Today, tourism is one of the major challenges for many countries and territories. The balance of payments, an ever-increasing number of visitors and the significant development of the tourism offer clearly illustrate the booming trend in this sector. This macro-economic approach is often used by the organizations in charge of tourism, WTO for instance. Quantitative assessments which consider the satisfaction of customers’ needs as an end in itself have prevailed both in tourism development schemes and in prospective approaches since the sixties.

  2. Fatigue Perceived by Multiple Sclerosis Patients Is Associated With Muscle Fatigue

    NARCIS (Netherlands)

    Steens, Anneke; de Vries, Astrid; Hemmen, Jolien; Heersema, Thea; Heerings, Marco; Maurits, Natasha; Zijdewind, Inge

    Background. Fatigue is a debilitating symptom in multiple sclerosis (MS). Previous studies showed no association between fatigue as perceived by the patient and physiological measures of fatigability. Objective. The authors investigated associations between perceived fatigue and measures of

  3. Development and Applications of a Self-Contained, Non-Invasive EVA Joint Angle and Muscle Fatigue Sensor System

    Science.gov (United States)

    Ranniger, C. U.; Sorenson, E. A.; Akin, D. L.

    1995-01-01

    The University of Maryland Space Systems Laboratory, as a participant in NASA's INSTEP program, is developing a non-invasive, self-contained sensor system which can provide quantitative measurements of joint angles and muscle fatigue in the hand and forearm. The goal of this project is to develop a system with which hand/forearm motion and fatigue metrics can be determined in various terrestrial and zero-G work environments. A preliminary study of the prototype sensor systems and data reduction techniques for the fatigue measurement system are presented. The sensor systems evaluated include fiberoptics, used to measure joint angle, surface electrodes, which measure the electrical signals created in muscle as it contracts; microphones, which measure the noise made by contracting muscle; and accelerometers, which measure the lateral muscle acceleration during contraction. The prototype sensor systems were used to monitor joint motion of the metacarpophalangeal joint and muscle fatigue in flexor digitorum superficialis and flexor carpi ulnaris in subjects performing gripping tasks. Subjects were asked to sustain a 60-second constant-contraction (isometric) exercise and subsequently to perform a repetitive handgripping task to failure. Comparison of the electrical and mechanical signals of the muscles during the different tasks will be used to evaluate the applicability of muscle signal measurement techniques developed for isometric contraction tasks to fatigue prediction in quasi-dynamic exercises. Potential data reduction schemes are presented.

  4. Damage development in woven fabric composites during tension-tension fatigue

    DEFF Research Database (Denmark)

    Hansen, U.

    1999-01-01

    of the operating fatigue damage mechanism(s). Fatigue leads to a degradation of material properties. Consequently, in connection with impact induced local stress raisers, fatigue produces continuously changing non-uniform stress fields because of stress redistribution effects. Other models addressing evolution......Impacted woven fabric composites were tested in tension-tension fatigue. In contrast to results from static testing, the effects of low energy impact damage in a fatigue environment were found to be the critical element leading to failure of the specimen. This difference emphasizes the need...... to identify and understand the fatigue damage mechanism. A relatively new non-destructive inspection technique using infrared thermography was found to be a very useful tool in detecting damage initiation and growth. Furthermore, this technique supplies valuable information to the characterization...

  5. Bending Fatigue of Carburized Steel at Very Long Lives

    Science.gov (United States)

    Nelson, D. V.; Long, Z.

    2016-01-01

    The bending fatigue behavior of two carburized steels is investigated for lives between approximately 105 and 108 cycles. Cracks are observed to start at sub-surface inclusions and develop features on fracture surfaces resembling "fish eyes" in appearance. This type of sub-surface cracking tends to govern fatigue strength at long lives. Previous studies of "fish eye" fatigue in carburized steel have been relatively few and have mainly considered failures originating at depths beneath a carburized case, where compressive residual stresses are minimal and hardness values approach those in the core. This study provides fatigue data for cracks originating within cases at various depths where compressive residual stresses are substantial and hardness is much higher than in the core. Fatigue strength is predicted by a simple model, accounting for the influence of residual stresses and hardness values at the different depths at which cracks started. Predictions of fatigue strength are compared with data generated in this study.

  6. Development of a Cast Iron Fatigue Properties Database for use with Modern Design Methods

    Energy Technology Data Exchange (ETDEWEB)

    DeLa' O, James, D.; Gundlach, Richard, B.; Tartaglia, John, M.

    2003-09-18

    A reliable and comprehensive database of design properties for cast iron is key to full and efficient utilization of this versatile family of high production-volume engineering materials. A database of strain-life fatigue properties and supporting data for a wide range of structural cast irons representing industry standard quality was developed in this program. The database primarily covers ASTM/SAE standard structural grades of ADI, CGI, ductile iron and gray iron as well as an austempered gray iron. Twenty-two carefully chosen materials provided by commercial foundries were tested and fifteen additional datasets were contributed by private industry. The test materials are principally distinguished on the basis of grade designation; most grades were tested in a 25 mm section size and in a single material condition common for the particular grade. Selected grades were tested in multiple sections-sizes and/or material conditions to delineate the properties associated with a range of materials for the given grade. The cyclic properties are presented in terms of the conventional strain-life formalism (e.g., SAE J1099). Additionally, cyclic properties for gray iron and CGI are presented in terms of the Downing Model, which was specifically developed to treat the unique stress-strain response associated with gray iron (and to a lesser extent with CGI). The test materials were fully characterized in terms of alloy composition, microstructure and monotonic properties. The CDROM database presents the data in various levels of detail including property summaries for each material, detailed data analyses for each specimen and raw monotonic and cyclic stress-strain data. The CDROM database has been published by the American Foundry Society (AFS) as an AFS Research Publication entitled ''Development of a Cast Iron Fatigue Properties Database for Use in Modern Design Methods'' (ISDN 0-87433-267-2).

  7. Development of a device to study fatigue life of fixed partial dentures

    Science.gov (United States)

    Gutierrez, S. C.; Meseguer, M. D.; Estal, R.; Folguera, F.; Vidal, V.

    2012-04-01

    Fixed partial dentures can be fabricated by means of different materials and with different manufacturing processes. In order to establish possible differences among them, their behaviour, as fatigue life or cement shear bond strength, have to be evaluated. This article presents a modular, economic and robust device to evaluate fixed partial dentures and dental crowns. A base to support the fixed partial dentures and a device to simulate masticatory loads have been developed. The device has got a simple design. It is based on a pneumatic piston, with a pressure regulator to control masticatory loads. On a first stage, only vertical forces have been taking into account. However, the device will allow simulating tangential masticatory loads on the other axis, studying the behaviour of the fixed partial dentures submerged in a solution similar to saliva, changing masticatory load application, etc. with little modifications.

  8. Recent Developments in Assessing Microstructure-Sensitive Early Stage Fatigue of Polycrystals (Postprint)

    Science.gov (United States)

    2014-04-01

    Disseminated copies will show “//Signature//” stamped or typed above the signature blocks. REPORT DOCUMENTATION PAGE Form Approved OMB No. 074-0188 Public...harmfulness in a cast aluminium alloy. Int J Fatigue 2011;33:1514–25. [33] Caton MJ, Jha SK. Small fatigue crack growth and failure mode transitions in a Ni

  9. Development, dimensions, reliability and validity of the novel Manchester COPD fatigue scale

    DEFF Research Database (Denmark)

    Al-shair, K; Kolsum, U; Berry, P

    2009-01-01

    .97) and test-retest repeatability (r = 0.97, ptested. It had significant convergent validity, correlating with the FACIT (Functional Assessment of Chronic Illness Therapy) fatigue scale and the fatigue in Borg scale at baseline and after a 6 minute walk distance (6MWD) test (r = -0.81, 0.53 and 0...... as well as depressed patients (>or=16 scores in the Center for Epidemiologic Study on Depression (CES-D) scale) had nearly twice as high fatigue scores as those who walked >or=350 m or were not depressed (preliable and valid measurement of total......%, mean age 66 years) completed a pilot fatigue scale covering a pool of 57 items and underwent a range of tests, including indicators of mood and a short general fatigue questionnaire. All patients responded to the 57-item scale and it was readministered to a subset of 30 patients. The pilot scale...

  10. Cross-cultural development of an item list for computer-adaptive testing of fatigue in oncological patients

    DEFF Research Database (Denmark)

    Giesinger, Johannes M.; Petersen, Morten Aa.; Grønvold, Mogens

    2011-01-01

    Within an ongoing project of the EORTC Quality of Life Group, we are developing computerized adaptive test (CAT) measures for the QLQ-C30 scales. These new CAT measures are conceptualised to reflect the same constructs as the QLQ-C30 scales. Accordingly, the Fatigue-CAT is intended to capture phy...

  11. Muscle fatigue during repetitive voluntary contractions: a comparison between children with cerebral palsy, typically developing children and young healthy adults.

    NARCIS (Netherlands)

    Eken, M.M.; Dallmeijer, A.J.; Houdijk, J.H.P.; Doorenbosch, C.A.M.

    2013-01-01

    Aim: To combine peak torque and EMG analyses to investigate the hypothesis that 1) children with cerebral palsy (CP) have lower muscle fatigability than typically developing children (TD) and whether 2) muscle fatigue correlates with muscle strength. Methods: Seven CP children, eight TD children and

  12. Need for recovery from work related fatigue and its role in the development and prediction of subjective health complaints

    NARCIS (Netherlands)

    Sluiter, J.K; de Croon, E.M; Meijman, T.F.; Frings-Dresen, M.H.W.

    Aims: To present the available empirical evidence for the assumed position of the concept of work related fatigue as: (1) short term effect of the working day; and (2) an intermediate variable between work demands and the development of subjective health complaints and sickness absence. Methods:

  13. Fatigue in adolescents with and following a cancer diagnosis: developing an evidence base for practice.

    Science.gov (United States)

    Edwards, J L; Gibson, F; Richardson, A; Sepion, B; Ream, E

    2003-12-01

    Although fatigue has been a focus for research in adult cancer care for some time, the same cannot be said for adolescent oncology practice. This paper summarises the literature concerning fatigue in adolescents with, and following, cancer diagnoses, drawing on data from four empirical studies. Fatigue is multidimensional, multifactorial and highly subjective, but can be managed to enhance self-caring and coping strategies. All of the studies reviewed within indicate that fatigue is a troublesome symptom, which impacts on quality of life. From this review, we set up a research study. This paper provides a brief report of preliminary data from this study drawn from a group of adolescents in late remission from childhood cancer. These data are used to evaluate the utility of focus groups as a method of data collection in exploring the concept of fatigue in adolescents. Concurring with the studies we reviewed, findings from the preliminary data suggest that fatigue is a highly subjective and 'abnormal' phenomenon that holds a variety of implied meanings and associated metaphors connected with past experiences of childhood cancer. The focus group proved to be a viable research method to facilitate mutual disclosure and provoke discussion. Recognition of the research challenges with adolescents, where there is the potential for a range of meanings for the experience of fatigue, is an important finding for future studies.

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

    Science.gov (United States)

    Johnson, W. S.

    1989-01-01

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

  15. Development and Application of a Clinical Microsystem Simulation Methodology for Human Factors-Based Research of Alarm Fatigue.

    Science.gov (United States)

    Kobayashi, Leo; Gosbee, John W; Merck, Derek L

    2017-07-01

    (1) To develop a clinical microsystem simulation methodology for alarm fatigue research with a human factors engineering (HFE) assessment framework and (2) to explore its application to the comparative examination of different approaches to patient monitoring and provider notification. Problems with the design, implementation, and real-world use of patient monitoring systems result in alarm fatigue. A multidisciplinary team is developing an open-source tool kit to promote bedside informatics research and mitigate alarm fatigue. Simulation, HFE, and computer science experts created a novel simulation methodology to study alarm fatigue. Featuring multiple interconnected simulated patient scenarios with scripted timeline, "distractor" patient care tasks, and triggered true and false alarms, the methodology incorporated objective metrics to assess provider and system performance. Developed materials were implemented during institutional review board-approved study sessions that assessed and compared an experimental multiparametric alerting system with a standard monitor telemetry system for subject response, use characteristics, and end-user feedback. A four-patient simulation setup featuring objective metrics for participant task-related performance and response to alarms was developed along with accompanying structured HFE assessment (questionnaire and interview) for monitor systems use testing. Two pilot and four study sessions with individual nurse subjects elicited true alarm and false alarm responses (including diversion from assigned tasks) as well as nonresponses to true alarms. In-simulation observation and subject questionnaires were used to test the experimental system's approach to suppressing false alarms and alerting providers. A novel investigative methodology applied simulation and HFE techniques to replicate and study alarm fatigue in controlled settings for systems assessment and experimental research purposes.

  16. Clinical neurophysiology of fatigue.

    Science.gov (United States)

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

    2008-01-01

    reliability of the psychological and clinical neurophysiological assessment techniques available today allows a multidisciplinary approach to fatigue in neurological patients, which may contribute to the elucidation of the pathophysiological mechanisms of chronic fatigue, with the ultimate goal to develop tailored treatments for fatigue in neurological patients. The present report discusses the different manifestations of fatigue and the available tools to assess peripheral and central fatigue.

  17. Development of a crack monitoring technique for use in a corrosion fatigue study of SA533-B pressure vessel steel

    International Nuclear Information System (INIS)

    Benson, J.M.; Tait, R.B.; Garrett, G.G.

    1981-10-01

    At present there does not exist a realistic crack growth law which will provide a good description of the relationship between the alternating stress intensity factor and the crack growth per cycle of stress. Such a law should be applicable to either the pressurized water reactor environment (PWR) or boiling water reactor environmnt (BWR). This project was formulated with the aim of examining the fatigue crack growth rate of SA533-B steel (a nuclear pressure vessel steel) in the threshold region in a simulated PWR environment. The aim of this report is to develop a crack monitoring technique for use in corrosion fatigue studies. Factors affecting fatigue crack propagation include: frequency, stress range, the effect of irradiation, ageing and environment. The mechanisms of crack propagation that are discussed include: slip dissolution, hydrogen assisted cracking, corrosion potential, and morphology studies. D.C. electrical potential, the compliance technique and the back-faced strain gauge method can be used for crack monitoring. Details are also given on the experimental equipment and programme. The results of the experiment has shown that the potential difference technique for monitoring crack length is a valuable one and is well suited for use in fatigue testing applications

  18. Discerning Primary and Secondary Factors Responsible for Clinical Fatigue in Multisystem Diseases

    Directory of Open Access Journals (Sweden)

    David Maughan

    2014-09-01

    Full Text Available Fatigue is a common symptom of numerous acute and chronic diseases, including myalgic encephalomyelitis/chronic fatigue syndrome, multiple sclerosis, heart failure, cancer, and many others. In these multi-system diseases the physiological determinants of enhanced fatigue encompass a combination of metabolic, neurological, and myofibrillar adaptations. Previous research studies have focused on adaptations specific to skeletal muscle and their role in fatigue. However, most have neglected the contribution of physical inactivity in assessing disease syndromes, which, through deconditioning, likely contributes to symptomatic fatigue. In this commentary, we briefly review disease-related muscle phenotypes in the context of whether they relate to the primary disease or whether they develop secondary to reduced physical activity. Knowledge of the etiology of the skeletal muscle adaptations in these conditions and their contribution to fatigue symptoms is important for understanding the utility of exercise rehabilitation as an intervention to alleviate the physiological precipitants of fatigue.

  19. Fatigue, depressive symptoms, and anxiety from adolescence up to young adulthood: a longitudinal study.

    Science.gov (United States)

    ter Wolbeek, Maike; van Doornen, Lorenz J P; Kavelaars, Annemieke; Tersteeg-Kamperman, Marijke D J; Heijnen, Cobi J

    2011-08-01

    Fatigue is a common complaint among adolescents. We investigated the course of fatigue in females during the transition from adolescence to young adulthood and examined psychological, immunological, and life style risk factors for development of fatigue and chronic fatigue syndrome (CFS)-related symptoms. Six hundred and thirty-three healthy females (age 14.63±1.37 years) filled out questionnaires measuring fatigue severity, depressive symptoms, anxiety, chronic fatigue syndrome (CFS)-related symptoms, sleep features, and life style characteristics at baseline and 4½ years thereafter. Of 64 participants LPS- and CD2CD28-induced cytokine data at baseline were available. The best predictor of fatigue in young adulthood was previous fatigue severity. In participants who were non-fatigued during adolescence and who experienced a notable increase in fatigue, fatigue development was preceded by emotional problems and CFS-related complaints during adolescence. Increases as well as decreases in fatigue severity were accompanied by respectively increase and decrease in depressive symptoms and anxiety, suggesting that these symptoms cluster and co-vary over time. Higher interferon (IFN)-γ, higher IFN-γ/interleukin (IL)-4 ratio, lower tumor necrosis factor-α and lower IL-10 at baseline were related to fatigue severity at follow up. The rise in total number of CFS-related symptoms at follow up was predicted by anxiety and decreased physical activity during adolescence. Sleep and substance use were associated with fatigue severity and anxiety and depression. In conclusion, vulnerability to develop fatigue and associated symptoms in young adulthood can to a certain extent be identified already years before the manifestation of complaints. Copyright © 2011 Elsevier Inc. All rights reserved.

  20. Development of Fatigue Life Improvement Technology of Butt Joints Using Friction Stir Processing

    Directory of Open Access Journals (Sweden)

    Jeong-Ung Park

    2014-03-01

    Full Text Available Burr grinding, tungsten inert gas (TIG dressing, ultrasonic impact treatment, and peening are used to improve fatigue life in steel structures. These methods improve the fatigue life of weld joints by hardening the weld toe, improving the bead shape, or causing compressive residual stress. This study proposes a new postweld treatment method improving the weld bead shape and metal structure at the welding zone using friction stir processing (FSP to enhance fatigue life. For that, a pin-shaped tool and processing condition employing FSP has been established through experiment. Experimental results revealed that fatigue life improves by around 42% compared to as-welded fatigue specimens by reducing the stress concentration at the weld toe and generating a metal structure finer than that of flux-cored arc welding (FCAW. Hot-spot stress, structural stress, and simplified calculation methods cannot predict the accurate stress at the weld toe in case the weld toe has a smooth curvature as in the case of the FSP specimen. On the contrary, a finite element calculation could reasonably predict the stress concentration factor for the FSP specimen because it considers not only the bead profile but also the weld toe profile.

  1. Development of a probabilistic model for the prediction of fatigue life in the very high cycle fatigue (VHCF range based on inclusion population

    Directory of Open Access Journals (Sweden)

    Kolyshkin A.

    2014-06-01

    Full Text Available The VHCF behaviour of metallic materials containing microstructural defects such as non-metallic inclusions is determined by the size and distribution of the damage dominating defects. In the present paper, the size and location of about 60.000 inclusions measured on the longitudinal and transversal cross sections of AISI 304 sheet form a database for the probabilistic determination of failure-relevant inclusion distribution in fatigue specimens and their corresponding fatigue lifes. By applying the method of Murakami et al. the biggest measured inclusions were used in order to predict the size of failure-relevant inclusions in the fatigue specimens. The location of the crack initiating inclusions was defined based on the modeled inclusion population and the stress distribution in the fatigue specimen, using the probabilistic Monte Carlo framework. Reasonable agreement was obtained between modeling and experimental results.

  2. Development of a honey based tonic syrup for cancer-related fatigue

    Directory of Open Access Journals (Sweden)

    R. Norouzian

    2017-11-01

    Full Text Available Background and objectives: Cancer-related fatigue (CRF is the most common and distressing symptom that affects overall quality of life of cancer patients. Due to the multi-factorial etiology, there is currently no “gold standard” for treatment of CRF. Considering the growing importance of national traditional medicines, natural remedies are viewed as playing distinctive role. “Jollab” is a natural syrup prescribed by Iranian traditional medicine (ITM scholars as tonic especially for the cardiovascular system. “Jollab” can consist of several ingredients although almost all traditional recipes include saffron and rose water as well as sugar or honey. The aim of this research was to develop a honey based “Jollab” and evaluate hydroxymethylfurfural (HMF, a product of fructose decomposition, as an indicator of heating effect on honey. Methods: Several “Jollab” formulations with different proportions of honey and rose water were prepared using deslagging procedure through direct or indirect heating. The HMF content of the formulation was measured according to International Honey Commission (IHC method. Results: “Jollab” was formulated with saffron (0.1%, honey (57.1% and rose water (42.8%. Two-thirds of the rose water was evaporated during deslagging procedure through direct heating (up to 95 °C and the remaining was added to the honey at the end of the process. Moreover, the HMF content of the prepared Jollab was 64.47±5.49 mg/kg which meets ICH standards. Conclusion: The developed honey based Jollab could be considered as a safe formulation for further studies in the field of CRF due to the acceptable HMF content.

  3. Fatigue - an underestimated symptom in psoriatic arthritis.

    Science.gov (United States)

    Krajewska-Włodarczyk, Magdalena; Owczarczyk-Saczonek, Agnieszka; Placek, Waldemar

    2017-01-01

    The nature of fatigue is very complex and involves physiological, psychological and social phenomena at the same time, and the mechanisms leading to occurrence and severity of fatigue are still poorly understood. The condition of chronic inflammation associated with psoriatic arthritis can be regarded as a potential factor affecting development of fatigue. Only a few studies so far have focused on the occurrence of fatigue in psoriatic arthritis. The problem of chronic fatigue is underestimated in everyday clinical practice. Identification and analysis of subjective fatigue components in each patient can provide an objective basis for optimal fatigue treatment in daily practice. This review presents a definition of chronic fatigue and describes mechanisms that may be associated with development of fatigue, highlighting the role of chronic inflammation, selected fatigue measurement methods and relations of fatigue occurrence with clinical aspects of psoriatic arthritis.

  4. Development of Activity-Related Muscle Fatigue during Robot-Mediated Upper Limb Rehabilitation Training in Persons with Multiple Sclerosis: A Pilot Trial

    Directory of Open Access Journals (Sweden)

    Johanna Renny Octavia

    2015-01-01

    Full Text Available Robot-assisted rehabilitation facilitates high-intensity training of the impaired upper limb in neurological rehabilitation. It has been clinically observed that persons with Multiple Sclerosis (MS have difficulties in sustaining the training intensity during a session due to the development of activity-related muscle fatigue. An experimental observational pilot study was conducted to examine whether or not the muscle fatigue develops in MS patients during one session of robot-assisted training within a virtual learning environment. Six MS patients with upper limb impairment (motricity index ranging from 50 to 91/100 and six healthy persons completed five training bouts of three minutes each performing lifting tasks, while EMG signals of anterior deltoid and lower trapezius muscles were measured and their subjective perceptions on muscle fatigue were registered. Decreased performance and higher subjective fatigue perception were present in the MS group. Increased mean EMG amplitudes and subjective perception levels on muscle fatigue were observed in both groups. Muscle fatigue development during 15′ training has been demonstrated in the arm of MS patients, which influences the sustainability of training intensity in MS patients. To optimize the training performance, adaptivity based on the detection of MS patient’s muscle fatigue could be provided by means of training program adjustment.

  5. Development and evaluation of an intervention aiming to reduce fatigue in airline pilots: design of a randomised controlled trial.

    Science.gov (United States)

    van Drongelen, Alwin; van der Beek, Allard J; Hlobil, Hynek; Smid, Tjabe; Boot, Cécile R L

    2013-08-26

    A considerable percentage of flight crew reports to be fatigued regularly. This is partly caused by irregular and long working hours and the crossing of time zones. It has been shown that persistent fatigue can lead to health problems, impaired performance during work, and a decreased work-private life balance. It is hypothesized that an intervention consisting of tailored advice regarding exposure to daylight, optimising sleep, physical activity, and nutrition will lead to a reduction of fatigue in airline pilots compared to a control group, which receives a minimal intervention with standard available information. The study population will consist of pilots of a large airline company. All pilots who posses a smartphone or tablet, and who are not on sick leave for more than four weeks at the moment of recruitment, will be eligible for participation.In a two-armed randomised controlled trial, participants will be allocated to an intervention group that will receive the tailored advice to optimise exposure to daylight, sleep, physical activity and nutrition, and a control group that will receive standard available information. The intervention will be applied using a smartphone application and a website, and will be tailored on flight- and participant-specific characteristics. The primary outcome of the study is perceived fatigue. Secondary outcomes are need for recovery, duration and quality of sleep, dietary and physical activity behaviours, work-private life balance, general health, and sickness absence. A process evaluation will be conducted as well. Outcomes will be measured at baseline and at three and six months after baseline. This paper describes the development of an intervention for airline pilots, consisting of tailored advice (on exposure to daylight and sleep-, physical activity, and nutrition) applied into a smartphone application. Further, the paper describes the design of the randomised controlled trial evaluating the effect of the intervention on

  6. The role of personality in the development and perpetuation of chronic fatigue syndrome.

    Science.gov (United States)

    White, C; Schweitzer, R

    2000-06-01

    Qualitative evidence suggests that personality may have special relevance to the predisposition, precipitation and perpetuation of chronic fatigue syndrome (CFS). This study compares three dimensions of personality - perfectionism, self-esteem, and emotional control in the personality profiles of CFS patients (N=44) and a control group (N=44) without a history of CFS, matched for age and gender. Participants were assessed on the MPS [Frost RO, Marten P, Lahart C, Rosenblate R. The dimensions of perfectionism. Cognit Ther Res 1990;14:449-468.]; the Rosenberg Self-Esteem Scale [Rosenberg M. Society and the Adolescent Self-image. Princeton, NJ: Princeton Univ Press, 1965.]; the Courtauld Emotional Scale [Watson M, Greer S. Development of a questionnaire measure of emotional control. J Psychosom Res 1983;27:299-305.] and the Marlowe-Crowne Social Desirability Scale [Crowne DP, Marlowe D. A new scale of social desirability independent of psychopathology. J Consult Psychol 1960;24:349-354.]. Analyses revealed that the CFS group reported higher levels than the control group on the Total Perfectionism score and Doubts about Actions and the Concern over Mistakes subscales. Furthermore, the CFS group also reported lower self-esteem than the control group. No difference between the two groups was found on the dimensions of emotional control and social desirability response bias. A developmental model of CFS, which considers the predisposing, precipitating, and perpetuating factors that may account for the course of the disorder irrespective of etiology, is proposed. In the context of the results, recommendations for practice and future research are discussed.

  7. Developing an Integrative Treatment Program for Cancer-Related Fatigue Using Stakeholder Engagement - A Qualitative Study.

    Science.gov (United States)

    Canella, Claudia; Mikolasek, Michael; Rostock, Matthias; Beyer, Jörg; Guckenberger, Matthias; Jenewein, Josef; Linka, Esther; Six, Claudia; Stoll, Sarah; Stupp, Roger; Witt, Claudia M

    2017-11-01

    Although cancer-related fatigue (CRF) has gained increased attention in the past decade, it remains difficult to treat. An integrative approach combining conventional and complementary medicine interventions seems highly promising. Treatment programs are more likely to be effective if the needs and interests of the people involved are well represented. This can be achieved through stakeholder engagement. The aim of the study was to develop an integrative CRF treatment program using stakeholder engagement and to compare it to an expert version. In a qualitative study, a total of 22 stakeholders (4 oncologists, 1 radiation-oncologist, 1 psycho-oncologist, 5 nurses/nurse experts, 9 patients, 1 patient family member, 1 representative of a local Swiss Cancer League) were interviewed either face-to-face or in a focus group setting. For data analysis, qualitative content analysis was used. With stakeholder engagement, the integrative CRF treatment program was adapted to usual care using a prioritizing approach and allowing more patient choice. Unlike the expert version, in which all intervention options were on the same level, the stakeholder engagement process resulted in a program with 3 different levels. The first level includes mandatory nonpharmacological interventions, the second includes nonpharmacological choice-based interventions, and the third includes pharmacological interventions for severe CRF. The resulting stakeholder based integrative CRF treatment program was implemented as clinical practice guideline at our clinic (Institute for Complementary and Integrative Medicine, University Hospital Zurich). Through the stakeholder engagement approach, we integrated the needs and preferences of people who are directly affected by CRF. This resulted in an integrative CRF treatment program with graded recommendations for interventions and therefore potentially greater sustainability in a usual care setting.

  8. Development and evaluation of a cancer-related fatigue patient education program: protocol of a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Görres Stefan

    2008-07-01

    Full Text Available Abstract Background Cancer-related fatigue (CRF and its impact on patients' quality of life has been an increasing subject of research. However, in Germany there is a lack of evidence-based interventions consistent with the multidimensional character of fatigue. The objective of this study is to develop and evaluate a self-management program for disease-free cancer patients to cope with CRF. Methods Based on evidence extracted from a literature review, a curriculum for the self-management program was elaborated. The curriculum was reviewed and validated by an interdisciplinary expert group and the training-modules will be pretested with a small number of participants and discussed in terms of feasibility and acceptance. To determine the efficacy of the program a randomised controlled trial will be carried out: 300 patients will be recruited from oncological practices in Bremen, Germany, and will be allocated to intervention or control group. The intervention group participates in the program, whereas the control group receives standard care and the opportunity to take part in the program after the end of the follow-up (waiting control group. Primary outcome measure is the level of fatigue, secondary outcome measures are quality of life, depression, anxiety, self-efficacy and physical activity. Data will be collected before randomisation, after intervention, and after a follow-up of 6 months. Discussion Because there are no comparable self-management programs for cancer survivors with fatigue, the development of the curriculum has been complex; therefore, the critical appraisal by the experts was an important step to validate the program and their contributions have been integrated into the curriculum. The experts appreciated the program as filling a gap in outpatient cancer care. If the results of the evaluation prove to be satisfactory, the outpatient care of cancer patients can be broadened and supplemented. Trial Registration Clinical

  9. Recent developments on SMA actuators: predicting the actuation fatigue life for variable loading schemes

    Science.gov (United States)

    Wheeler, Robert W.; Lagoudas, Dimitris C.

    2017-04-01

    Shape memory alloys (SMAs), due to their ability to repeatably recover substantial deformations under applied mechanical loading, have the potential to impact the aerospace, automotive, biomedical, and energy industries as weight and volume saving replacements for conventional actuators. While numerous applications of SMA actuators have been flight tested and can be found in industrial applications, these actuators are generally limited to non-critical components, are not widely implemented and frequently one-off designs, and are generally overdesigned due to a lack of understanding of the effect of the loading path on the fatigue life and the lack of an accurate method for predicting actuator lifetimes. In recent years, multiple research efforts have increased our understanding of the actuation fatigue process of SMAs. These advances can be utilized to predict the fatigue lives and failure loads in SMA actuators. Additionally, these prediction methods can be implemented in order to intelligently design actuators in accordance with their fatigue and failure limits. In the following paper, both simple and complex thermomechanical loading paths have been considered. Experimental data was utilized from two material systems: equiatomic Nickel-Titanium and Nickelrich Nickel-Titanium.

  10. Examination of fatigue development in elite soccer in a hot environment: a multi-experimental approach

    DEFF Research Database (Denmark)

    Mohr, Magni; Mujika, I; Santisteban, J

    2010-01-01

    The study examines fatigue in elite soccer played in hot conditions. High-profile soccer players (n=20) were studied during match play at ~31 °C. Repeated sprint and jump performances were assessed in rested state and after a game and activity profile was examined. Additionally, heart rate (HR), ...

  11. Development of reliable design rules for adhesively bonded joints loaded in fatigue

    NARCIS (Netherlands)

    Straalen, IJ.J. van; Botter, E.

    2005-01-01

    Design rules considering fatigue for practical applications are mostly based on spectra representing the cyclic loading and the so-called SN-curves (Wohler curves). For welded and mechanically fasted joints the reliability of these design ruiles is proved over the years. For adhesive bonded joints

  12. Fatigue data compilation and evaluation of fatigue on design

    International Nuclear Information System (INIS)

    Nyilas, A.

    1985-05-01

    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.) [de

  13. [School phobia and childhood chronic fatigue syndrome (CCFS)].

    Science.gov (United States)

    Tomoda, Akemi

    2007-06-01

    Chronic fatigue occurring in previously healthy children and adolescents is a vexing problem encountered by pediatric practitioners and the impact of fatigue in youngsters should not be underestimated. In its severe form, it is often associated with mood disorders. Findings in children and adolescent cases suggest that severe unexplained fatigue might precede the development of fatigue-related illness, such as childhood chronic fatigue syndrome (CCFS). This is a disabling condition characterized by severe disabling fatigue and a combination of symptoms, the prominent features being self-reported impairments in concentration and short-term memory, sleep disturbances and autonomic symptoms that cannot be explained by medical or psychiatric illness. We have encountered such patients with these complaints; their major symptoms include: general fatigue, fever, headache (not migraine), and memory disturbance. From our clinical experience, we have inferred that patients with CCFS might experience changes in brain function levels, which induce an autonomic imbalance and engender symptoms such as general fatigue, higher-order level cognitive dysfunction, and memory disturbance.

  14. Validation of a Previously Developed Geospatial Model That Predicts the Prevalence of Listeria monocytogenes in New York State Produce Fields.

    Science.gov (United States)

    Weller, Daniel; Shiwakoti, Suvash; Bergholz, Peter; Grohn, Yrjo; Wiedmann, Martin; Strawn, Laura K

    2016-02-01

    Technological advancements, particularly in the field of geographic information systems (GIS), have made it possible to predict the likelihood of foodborne pathogen contamination in produce production environments using geospatial models. Yet, few studies have examined the validity and robustness of such models. This study was performed to test and refine the rules associated with a previously developed geospatial model that predicts the prevalence of Listeria monocytogenes in produce farms in New York State (NYS). Produce fields for each of four enrolled produce farms were categorized into areas of high or low predicted L. monocytogenes prevalence using rules based on a field's available water storage (AWS) and its proximity to water, impervious cover, and pastures. Drag swabs (n = 1,056) were collected from plots assigned to each risk category. Logistic regression, which tested the ability of each rule to accurately predict the prevalence of L. monocytogenes, validated the rules based on water and pasture. Samples collected near water (odds ratio [OR], 3.0) and pasture (OR, 2.9) showed a significantly increased likelihood of L. monocytogenes isolation compared to that for samples collected far from water and pasture. Generalized linear mixed models identified additional land cover factors associated with an increased likelihood of L. monocytogenes isolation, such as proximity to wetlands. These findings validated a subset of previously developed rules that predict L. monocytogenes prevalence in produce production environments. This suggests that GIS and geospatial models can be used to accurately predict L. monocytogenes prevalence on farms and can be used prospectively to minimize the risk of preharvest contamination of produce. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  15. Fatigue modelling for gas nitriding

    Directory of Open Access Journals (Sweden)

    H. Weil

    2016-10-01

    Full Text Available The present study aims to develop an algorithm able to predict the fatigue lifetime of nitrided steels. Linear multi-axial fatigue criteria are used to take into account the gradients of mechanical properties provided by the nitriding process. Simulations on rotating bending fatigue specimens are made in order to test the nitrided surfaces. The fatigue model is applied to the cyclic loading of a gear from a simulation using the finite element software Ansys. Results show the positive contributions of nitriding on the fatigue strength

  16. Muscle Deoxygenation Causes Muscle Fatigue

    Science.gov (United States)

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

    1999-01-01

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

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

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  18. Effect of Withania somnifera (Ashwagandha) on the development of chemotherapy-induced fatigue and quality of life in breast cancer patients.

    Science.gov (United States)

    Biswal, Biswa Mohan; Sulaiman, Siti Amrah; Ismail, Hasanah Che; Zakaria, Hasmat; Musa, Kamarul Imran

    2013-07-01

    Hypothesis. Withania somnifera is an herb with antioxidant, anti-inflammatory, anticancer, antistress, and adaptogenic properties. Previous studies have shown its antistress effects in animals. Traditional Indian medicine has used it for centuries to alleviate fatigue and improve general well-being. This is an open-label prospective nonrandomized comparative trial on 100 patients with breast cancer in all stages undergoing either a combination of chemotherapy with oral Withania somnifera or chemotherapy alone. The chemotherapy regimens were either taxotere, adriamycin, and cyclophosphamide or 5-fluorouracil, epirubicin, and cyclophosphamide. Withania somnifera root extract was administered to patients in the study group at a dose of 2 g every 8 hours, throughout the course of chemotherapy. The quality-of-life and fatigue scores were evaluated before, during, and on the last cycles of chemotherapy using the EORTC QLQ-C30 (Version 3), Piper Fatigue Scale (PFS), and Schwartz Cancer Fatigue Scale (SCFS-6). The median age distributions in the study and control arm were 51 years (range = 36-70) and 50.5 years (range = 32-71), respectively. The majority (77%) of patients had stage II and III disease. Patients in the control arm experienced statistically significant higher estimated marginal means of fatigue score compared with the study group (P Withania somnifera has potential against cancer-related fatigue, in addition to improving the quality of life. However, further study with a larger sample size in a randomized trial is warranted to validate our findings.

  19. [Incidence and clinical risk factors for the development of diabetes mellitus in women with previous gestational diabetes].

    Science.gov (United States)

    Domínguez-Vigo, P; Álvarez-Silvares, E; Alves-Pérez M T; Domínguez-Sánchez, J; González-González, A

    2016-04-01

    Gestational diabetes is considered a variant of diabetes mellitus as they share a common pathophysiological basis: insulin resistance in target and insufficient secretion of it by pancreatic p-cell bodies. Pregnancy is a unique physiological situation provides an opportunity to identify future risk of diabetes mellitus. To determine the long-term incidence of diabetes mellitus in women who have previously been diagnosed with gestational diabetes and identifying clinical risk factors for developing the same. nested case-control cohort study. 671 patients between 1996 and 2009 were diagnosed with gestational diabetes were selected. The incidence of diabetes mellitus was estimated and 2 subgroups were formed: Group A or cases: women who develop diabetes mellitus after diagnosis of gestational diabetes. Group B or control: random sample of 71 women with a history of gestational diabetes in the follow-up period remained normoglycemic. Both groups were studied up to 18 years postpartum. By studying Kaplan Meier survival of the influence of different gestational variables it was obtained in the later development of diabetes mellitus with time parameter and COX models for categorical variables were applied. Significant variables were studied by multivariate Cox analysis. In all analyzes the Hazard ratio was calculated with confidence intervals at 95%. The incidence of diabetes mellitus was 10.3% in patients with a history of gestational diabetes. They were identified as risk factors in the index pregnancy to later development of diabetes mellitus: greater than 35 and younger than 27 years maternal age, BMI greater than 30 kg/m2, hypertensive disorders of pregnancy, insulin therapy, poor metabolic control and more than a complicated pregnancy with gestational diabetes. Clinical factors have been identified in the pregnancy complicated by gestational diabetes that determine a higher probability of progression to diabetes mellitus in the medium and long term.

  20. The effect of brief exercise cessation on pain, fatigue, and mood symptom development in healthy, fit individuals.

    Science.gov (United States)

    Glass, Jennifer M; Lyden, Angela K; Petzke, Frank; Stein, Phyllis; Whalen, Gail; Ambrose, Kirsten; Chrousos, George; Clauw, Daniel J

    2004-10-01

    Abnormalities of the biological stress response (hypothalamic-pituitary-adrenal axis and the autonomic nervous system) have been identified in both fibromyalgia (FM) and chronic fatigue syndrome (CFS). Although these changes have been considered to be partly responsible for symptom expression, we examine an alternative hypothesis that these HPA and autonomic changes can be found in subsets of healthy individuals in the general population who may be at risk of developing these conditions. Exposure to "stressors" (e.g., infections, trauma, etc.) may lead to symptom expression (pain, fatigue, and other somatic symptoms) in part by precipitating lifestyle changes. In particular, we focus on the effect of deprivation of routine aerobic exercise on the development of somatic symptoms. Eighteen regularly exercising (>/=4 h/week) asymptomatic, healthy adults refrained from physical activity for 1 week. We predicted that a subset of these individuals would develop symptoms of FM/CFS with exercise deprivation, and this manuscript focuses on the baseline HPA axis, immune, and autonomic function measures that may predict the development of symptoms. Eight of the subjects reported a 10% increase in one or more symptoms (pain, fatigue, mood) after 1 week of exercise deprivation. These symptomatic subjects had lower HPA axis (baseline cortisol prior to VO2max testing), immune (NK cell responsiveness to venipuncture), and autonomic function (measured by heart rate variability) at baseline (prior to cessation of exercise) when compared to the subjects who did not develop symptoms. A subset of subjects developed symptoms of pain, fatigue, or mood changes after exercise deprivation. This cohort was different from the individuals who did not develop symptoms in baseline measures of HPA axis, immune, and autonomic function. We speculate that a subset of healthy individuals who have hypoactive function of the biological stress response systems unknowingly exercise regularly to augment

  1. Planning policy, sustainability and housebuilder practices: The move into (and out of?) the redevelopment of previously developed land.

    Science.gov (United States)

    Karadimitriou, Nikos

    2013-05-01

    This paper explores the transformations of the housebuilding industry under the policy requirement to build on previously developed land (PDL). This requirement was a key lever in promoting the sustainable urban development agenda of UK governments from the early 1990s to 2010 and has survived albeit somewhat relaxed and permutated in the latest National Planning Policy Framework (NPPF). The paper therefore looks at the way in which the policy push towards densification and mixed use affected housebuilders' business strategy and practices and their ability to cope with the 2007 downturn of the housing market and its aftermath. It also points out the eventual feedback of some of these practices into planning policy. Following the gradual shift of British urban policy focus towards sustainability which started in the early 1990s, new configurations of actors, new skills, strategies and approaches to managing risk emerged in property development and housebuilding. There were at least two ways in which housebuilders could have responded to the requirements of developing long term mixed use high density projects on PDL. One way was to develop new products and to employ practices and combinations of practices involving phasing, a flexible approach to planning applications and innovative production methods. Alternatively, they could approach PDL development as a temporary turn of policy or view mixed use high density schemes as a niche market to be explored without drastically overhauling the business model of the entire firm. These transformations of the UK housebuilding sector were unfolding during a long period of buoyancy in the housing market which came to an end in 2007. Very little is known both about how housebuilder strategies and production practices evolved during the boom years as well as about how these firms coped with the effects of the 2007 market downturn. The paper draws on published data (company annual reports, government statistics) and primary

  2. Planning policy, sustainability and housebuilder practices: The move into (and out of?) the redevelopment of previously developed land

    Science.gov (United States)

    Karadimitriou, Nikos

    2013-01-01

    This paper explores the transformations of the housebuilding industry under the policy requirement to build on previously developed land (PDL). This requirement was a key lever in promoting the sustainable urban development agenda of UK governments from the early 1990s to 2010 and has survived albeit somewhat relaxed and permutated in the latest National Planning Policy Framework (NPPF). The paper therefore looks at the way in which the policy push towards densification and mixed use affected housebuilders’ business strategy and practices and their ability to cope with the 2007 downturn of the housing market and its aftermath. It also points out the eventual feedback of some of these practices into planning policy. Following the gradual shift of British urban policy focus towards sustainability which started in the early 1990s, new configurations of actors, new skills, strategies and approaches to managing risk emerged in property development and housebuilding. There were at least two ways in which housebuilders could have responded to the requirements of developing long term mixed use high density projects on PDL. One way was to develop new products and to employ practices and combinations of practices involving phasing, a flexible approach to planning applications and innovative production methods. Alternatively, they could approach PDL development as a temporary turn of policy or view mixed use high density schemes as a niche market to be explored without drastically overhauling the business model of the entire firm. These transformations of the UK housebuilding sector were unfolding during a long period of buoyancy in the housing market which came to an end in 2007. Very little is known both about how housebuilder strategies and production practices evolved during the boom years as well as about how these firms coped with the effects of the 2007 market downturn. The paper draws on published data (company annual reports, government statistics) and primary

  3. Seafarer fatigue

    DEFF Research Database (Denmark)

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

    2015-01-01

    Background: The consequences of fatigue for the health and safety of seafarers has caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This review gives an overview of the key issues relating...... to seafarer fatigue. Materials and methods: A literature study was conducted aiming to collect publications that address risk factors for fatigue, short-term and long-term consequences for health and safety, and options for fatigue mitigation at sea. Due to the limited number of publications that deals...

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

    Science.gov (United States)

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

    2017-01-01

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

  5. 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...... fatigue design of OWTs is discussed and results for reliability assessment of typical fatigue critical design of offshore steel support structures are presented....

  6. You make me tired: An experimental test of the role of interpersonal operant conditioning in fatigue.

    Science.gov (United States)

    Lenaert, Bert; Jansen, Rebecca; van Heugten, Caroline M

    2018-04-01

    Chronic fatigue is highly prevalent in the general population as well as in multiple chronic diseases and psychiatric disorders. Its etiology however remains poorly understood and cannot be explained by biological factors alone. Occurring in a psychosocial context, the experience and communication of fatigue may be shaped by social interactions. In particular, interpersonal operant conditioning may strengthen and perpetuate fatigue complaints. In this experiment, individuals (N = 44) repeatedly rated their currently experienced fatigue while engaging in cognitive effort (working memory task). Subtle social reward was given when fatigue increased relative to the previous rating; or disapproval when fatigue decreased. In the control condition, only neutral feedback was given. Although all participants became more fatigued during cognitive effort, interpersonal operant conditioning led to increased fatigue reporting relative to neutral feedback. This effect occurred independently of conscious awareness. Interestingly, the experimental condition also performed worse on the working memory task. Results suggest that fatigue complaints (and cognitive performance) may become controlled by their consequences such as social reward, and not exclusively by their antecedents such as effort. Results have implications for treatment development and suggest that interpersonal operant conditioning may contribute to fatigue becoming a chronic symptom. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Influence of body temperature on the development of fatigue during prolonged exercise in the heat

    DEFF Research Database (Denmark)

    Hyldig, Tino Hoffmann

    1999-01-01

    the influence of rate of heat storage (0.10 vs. 0.05°C/min induced by a water-perfused jacket), four cyclists performed two additional exercise bouts, starting with Tes of 37.0°C. Despite different initial temperatures, all subjects fatigued at an identical level of hyperthermia (Tes = 40.1-40.2°C, muscle......, respectively, P stroke volume paralleled the rise in core temperature (36-40°C), with skin blood flow plateauing...

  8. Statistical distribution analysis of rubber fatigue data

    Science.gov (United States)

    DeRudder, J. L.

    1981-10-01

    Average rubber fatigue resistance has previously been related to such factors as elastomer type, cure system, cure temperature, and stress history. This paper extends this treatment to a full statistical analysis of rubber fatigue data. Analyses of laboratory fatigue data are used to predict service life. Particular emphasis is given to the prediction of early tire splice failures, and to adaptations of statistical fatigue analysis for the particular service conditions of the rubber industry.

  9. Development of Novel Pre-alloyed PM Steels for Optimization of Machinability and Fatigue Resistance of PM Components

    Science.gov (United States)

    Mardan, Milad; Blais, Carl

    2016-03-01

    It is well known that a large proportion of ferrous PM components require secondary machining operations for dimensional conformance or for producing geometrical features that cannot be generated during die compaction. Nevertheless, the machining behavior of PM parts is generally characterized as being "difficult" due to the presence of residual porosity that lowers thermal conductivity and induces interrupted cutting. Several admixed additives such as MnS and BN-h can be used to improve the machining behavior of PM steels. Nevertheless, their negative effect on mechanical properties, especially fatigue resistance, makes their utilization uninteresting for the fabrication of high-performance PM steel components. This article summarizes the work carried out to develop a novel PM steel that was especially engineered to form machinability enhancing precipitates. This new material is pre-alloyed with tin (Sn) in order to form Cu-Sn (Cu(α)) precipitates during transient liquid phase sintering. The newly developed material presents machinability improvement of 165% compared to reference material used in the PM industry as well as increases in toughness and fatigue resistance of 100% and 13%, respectively.

  10. Development of Estimating Equation of Machine Operational Skill by Utilizing Eye Movement Measurement and Analysis of Stress and Fatigue

    Directory of Open Access Journals (Sweden)

    Satoshi Suzuki

    2013-01-01

    Full Text Available For an establishment of a skill evaluation method for human support systems, development of an estimating equation of the machine operational skill is presented. Factors of the eye movement such as frequency, velocity, and moving distance of saccade were computed using the developed eye gaze measurement system, and the eye movement features were determined from these factors. The estimating equation was derived through an outlier test (to eliminate nonstandard data and a principal component analysis (to find dominant components. Using a cooperative carrying task (cc-task simulator, the eye movement and operational data of the machine operators were recorded, and effectiveness of the derived estimating equation was investigated. As a result, it was confirmed that the estimating equation was effective strongly against actual simple skill levels (r=0.56–0.84. In addition, effects of internal condition such as fatigue and stress on the estimating equation were analyzed. Using heart rate (HR and coefficient of variation of R-R interval (Cvrri. Correlation analysis between these biosignal indexes and the estimating equation of operational skill found that the equation reflected effects of stress and fatigue, although the equation could estimate the skill level adequately.

  11. Fatigue technology assessment and strategies for fatigue avoidance in marine structures. Appendices

    Science.gov (United States)

    Capanoglu, Cuneyt C.

    This report provides an up-to-date assessment of fatigue technology, directed specifically toward the marine industry. A comprehensive overview of fatigue analysis and design, a global review of fatigue including rules and regulations and current practices, and a fatigue analysis and design criteria are provided as a general guideline to fatigue assessment. A detailed discussion of all fatigue parameters is grouped under three analysis blocks: fatigue stress model, covering environmental forces, structure response and loading, stress response amplitude operations (RAO's) and hot-spot stresses; fatigue stress history model covering long-term distribution of environmental loading; and fatigue resistance of structures and damage assessment methodologies. The analyses and design parameters that affect fatigue assessment are discussed together with uncertainties and research gaps, to provide a basis for developing strategies for fatigue avoidance. Additional in-depth discussions of wave environment, stress concentration factors, etc. are presented in the appendixes. Assessment of fatigue technology, fatigue stress models, fatigue stress history models, fatigue resistance, fatigue parameters, and fatigue avoidance strategies.

  12. Cancer-Related Fatigue in Post-Treatment Cancer Survivors: Theory-Based Development of a Web-Based Intervention.

    Science.gov (United States)

    Corbett, Teresa; Walsh, Jane C; Groarke, AnnMarie; Moss-Morris, Rona; Morrissey, Eimear; McGuire, Brian E

    2017-07-04

    Cancer-related fatigue (CrF) is the most common and disruptive symptom experienced by cancer survivors. We aimed to develop a theory-based, interactive Web-based intervention designed to facilitate self-management and enhance coping with CrF following cancer treatment. The aim of our study was to outline the rationale, decision-making processes, methods, and findings which led to the development of a Web-based intervention to be tested in a feasibility trial. This paper outlines the process and method of development of the intervention. An extensive review of the literature and qualitative research was conducted to establish a therapeutic approach for this intervention, based on theory. The psychological principles used in the development process are outlined, and we also clarify hypothesized causal mechanisms. We describe decision-making processes involved in the development of the content of the intervention, input from the target patient group and stakeholders, the design of the website features, and the initial user testing of the website. The cocreation of the intervention with the experts and service users allowed the design team to ensure that an acceptable intervention was developed. This evidence-based Web-based program is the first intervention of its kind based on self-regulation model theory, with the primary aim of targeting the representations of fatigue and enhancing self-management of CrF, specifically. This research sought to integrate psychological theory, existing evidence of effective interventions, empirically derived principles of Web design, and the views of potential users into the systematic planning and design of the intervention of an easy-to-use website for cancer survivors. ©Teresa Corbett, Jane C Walsh, AnnMarie Groarke, Rona Moss-Morris, Eimear Morrissey, Brian E McGuire. Originally published in JMIR Cancer (http://cancer.jmir.org), 04.07.2017.

  13. Muscle fatigue during repetitive voluntary contractions: a comparison between children with cerebral palsy, typically developing children and young healthy adults.

    Science.gov (United States)

    Eken, M M; Dallmeijer, A J; Houdijk, H; Doorenbosch, C A M

    2013-09-01

    To combine peak torque and EMG analyses to investigate the hypothesis that 1) children with cerebral palsy (CP) have lower muscle fatigability than typically developing children (TD) and whether 2) muscle fatigue correlates with muscle strength. Seven CP children, eight TD children and ten young healthy adults (YHA) performed an all-out fatigue test of 35 maximal concentric knee extension and flexion contractions on an isokinetic dynamometer. Angular velocity was set at 60°/s. Peak torque (PT) was determined per repetition and either normalized to bodyweight or maximum voluntary torque. Surface-EMG of quadriceps and hamstring muscles was measured to obtain changes in median frequency (EMG-mf) and smooth rectified EMG amplitude per contraction. Decline in PT differed between all groups for extensors and flexors, where YHA showed the largest decline and CP children the smallest decline over the course of the test. YHA showed a larger decline in EMG-mf of all quadriceps and hamstrings than TD and CP children, while TD children showed a larger decline in EMG-mf of m.rectus femoris and m.vastus lateralis than CP children. Results confirm that children with CP show lower fatigability than TD children and that the lower fatigability coincides with lower maximal muscle strength. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Fatigue design 1998

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-12-31

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

  15. Assessing Fatigue in Late-Midlife

    DEFF Research Database (Denmark)

    Fieo, Robert A; Mortensen, Erik Lykke; Lund, Rikke

    2014-01-01

    Previous methods examining the Multiple Fatigue Inventory-20 (MFI-20) fatigue questionnaire have been limited to classical test theory, for example, factor analytic approaches. We employed modern test theory to further strengthen the construct validity of the MFI-20 fatigue in a sample of healthy...... late-midlife subjects. Five subdimensions of perceived fatigue were examined in n = 7,233 subjects: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Fatigue burden was compared across age groups (aged 48-52 vs. 57-63) and gender. Mokken item response theory...... was used to investigate dimensionality, monotonicity, and invariant item ordering (IIO). In both age groups, as well as by gender, the Motivation domain presented with weak scalability, suggesting that caution be exercised when interpreting sum scores. For all groupings, the strongest scaling properties...

  16. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-07-01

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

  18. Spectrophotometric determination of uranium with arsenazo previous liquid-liquid extraction and colour development in organic medium

    International Nuclear Information System (INIS)

    Palomares Delgado, F.; Vera Palomino, J.; Petrement Eguiluz, J. C.

    1964-01-01

    The determination of uranium with arsenazo is hindered by a great number of cation which form stable complexes with the reactive and may given rise to serious interferences. By studying the optimum conditions of uranium the extraction be means of tributylphosphate solutions dissolved in methylisobuthylketone, under conditions for previous masking of the interfering cations, an organic extract was obtained containing all the uranium together with small amounts of iron. The possible interference derived from the latter element is avoided by reduction with hydroxylammoniumchlorid followed by complex formation of the Fe(II)-ortophenantroline compound in alcoholic medium. (Author) 17 refs

  19. 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.

  20. 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.

  1. Synchronous development of breast cancer and chest wall fibrosarcoma after previous mantle radiation for Hodgkin's disease

    Energy Technology Data Exchange (ETDEWEB)

    Patlas, Michael [Hamilton General Hospital, Department of Radiology, Hamilton, ON (Canada); McCready, David [University Health Network and Mount Sinai Hospital, Department of Surgery, Toronto, ON (Canada); Kulkarni, Supriya; Dill-Macky, Marcus J. [University Health Network and Mount Sinai Hospital, Department of Medical Imaging, Toronto, ON (Canada)

    2005-09-01

    Survivors of Hodgkin's disease are at increased risk of developing a second malignant neoplasm, including breast carcinoma and sarcoma. We report the first case of synchronous development of chest wall fibrosarcoma and breast carcinoma after mantle radiotherapy for Hodgkin's disease. Mammographic, sonographic and MR features are demonstrated. (orig.)

  2. [Auditory fatigue].

    Science.gov (United States)

    Sanjuán Juaristi, Julio; Sanjuán Martínez-Conde, Mar

    2015-01-01

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

  3. Limitations in intense exercise performance of athletes - effect of speed endurance training on ion handling and fatigue development.

    Science.gov (United States)

    Hostrup, Morten; Bangsbo, Jens

    2017-05-01

    Mechanisms underlying fatigue development and limitations for performance during intense exercise have been intensively studied during the past couple of decades. Fatigue development may involve several interacting factors and depends on type of exercise undertaken and training level of the individual. Intense exercise (½-6 min) causes major ionic perturbations (Ca 2+ , Cl - , H + , K + , lactate - and Na + ) that may reduce sarcolemmal excitability, Ca 2+ release and force production of skeletal muscle. Maintenance of ion homeostasis is thus essential to sustain force production and power output during intense exercise. Regular speed endurance training (SET), i.e. exercise performed at intensities above that corresponding to maximum oxygen consumption (V̇O2, max ), enhances intense exercise performance. However, most of the studies that have provided mechanistic insight into the beneficial effects of SET have been conducted in untrained and recreationally active individuals, making extrapolation towards athletes' performance difficult. Nevertheless, recent studies indicate that only a few weeks of SET enhances intense exercise performance in highly trained individuals. In these studies, the enhanced performance was not associated with changes in V̇O2, max and muscle oxidative capacity, but rather with adaptations in muscle ion handling, including lowered interstitial concentrations of K + during and in recovery from intense exercise, improved lactate - -H + transport and H + regulation, and enhanced Ca 2+ release function. The purpose of this Topical Review is to provide an overview of the effect of SET and to discuss potential mechanisms underlying enhancements in performance induced by SET in already well-trained individuals with special emphasis on ion handling in skeletal muscle. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

  4. Inflatable Antenna for CubeSat: Extension of the Previously Developed S-Band Design to the X-Band

    Science.gov (United States)

    Babuscia, Alessandra; Choi, Thomas; Cheung, Kar-Ming; Thangavelautham, Jekan; Ravichandran, Mithun; Chandra, Aman

    2015-01-01

    The inflatable antenna for CubeSat is a 1 meter antenna reflector designed with one side reflective Mylar, another side clear Mylar with a patch antenna at the focus. The development of this technology responds to the increasing need for more capable communication systems to allow CubeSats to operate autonomously in interplanetary missions. An initial version of the antenna for the S-Band was developed and tested in both anechoic chamber and vacuum chamber. Recent developments in transceivers and amplifiers for CubeSat at X-band motivated the extension from the S-Band to the X-Band. This paper describes the process of extending the design of the antenna to the X-Band focusing on patch antenna redesign, new manufacturing challenges and initial results of experimental tests.

  5. Measuring parent time scarcity and fatigue as barriers to meal planning and preparation: quantitative scale development.

    Science.gov (United States)

    Storfer-Isser, Amy; Musher-Eizenman, Dara

    2013-03-01

    To examine the psychometric properties of 9 quantitative items that assess time scarcity and fatigue as parent barriers to planning and preparing meals for their children. A convenience sample of 342 parents of children aged 2-6 years completed a 20-minute online survey. Exploratory factor analysis was used to examine the factor structure and create summary scales. Internal consistency reliability and measures of construct and concurrent validity were assessed. Two scales were created based on the factor analysis: time and energy for meals and meal planning. Preliminary evidence suggests that both scales are reliable and valid. The time and energy for meals and meal planning scales can be completed quickly by busy and tired parents. As many children do not eat nutritious diets, a better understanding of the barriers that parents face is critical and may help inform interventions tailored to the needs of tired, busy parents. Copyright © 2013 Society for Nutrition Education and Behavior. Published by Elsevier Inc. All rights reserved.

  6. Development of muscle fatigue as assessed by electromyography and mechanomyography during continuous and intermittent low-force contractions: effects of the feedback mode

    DEFF Research Database (Denmark)

    Madeleine, Pascal; Jørgensen, Lars Vincents; Søgaard, Karen

    2002-01-01

    The goal of the present study was to investigate the significance of low-force continuous or intermittent static contraction and feedback mode (visual or proprioceptive) on the development of muscle fatigue as assessed by electromyography (EMG) and mechanomyography (MMG). Visual (force control...... and MPF values versus time were observed with proprioceptive feedback compared with visual feedback. The findings suggest that (1) the EMG and MMG signals give complementary information about localised muscle fatigue at low-level contraction: they responded differently in terms of changes in the time...... and frequency domain during continuous contraction, while they responded in concert in the frequency domain during intermittent contractions, and (2) the different centrally mediated motor control strategies used during fatiguing contraction may be dependent upon the feedback modality....

  7. Development of Fatigue in Cancer Survivors : A Prospective Follow-Up Study From Diagnosis Into the Year After Treatment

    NARCIS (Netherlands)

    Goedendorp, Martine M.; Gielissen, Marieke F. M.; Verhagen, Constans A. H. H. V. M.; Bleijenberg, Gijs

    Context. There is a lack of longitudinal studies investigating fatigue from before cancer treatment to long after successful cancer treatment. Objectives. This prospective follow-up study aimed to determine the prevalence and predictors of persistent fatigue in cancer survivors in the first year

  8. The reliability of the Associate Platinum digital foot scanner in measuring previously developed footprint characteristics: a technical note.

    Science.gov (United States)

    Papuga, M Owen; Burke, Jeanmarie R

    2011-02-01

    An ink pad and paper, pressure-sensitive platforms, and photography have previously been used to collect footprint data used in clinical assessment. Digital scanners have been widely used more recently to collect such data. The purpose of this study was to evaluate the intra- and interrater reliability of a flatbed digital image scanning technology to capture footprint data. This study used a repeated-measures design on 32 (16 male 16 female) healthy subjects. The following measured indices of footprint were recorded from 2-dimensional images of the plantar surface of the foot recorded with an Associate Platinum (Foot Levelers Inc, Roanoke, VA) digital foot scanner: Staheli index, Chippaux-Smirak index, arch angle, and arch index. Intraclass correlation coefficient (ICC) values were calculated to evaluate intrarater, interday, and interclinician reliability. The ICC values for intrarater reliability were greater than or equal to .817, indicating an excellent level of reproducibility in assessing the collected images. Analyses of variance revealed that there were no significant differences between raters for each index (P > .05). The ICC values also indicated excellent reliability (.881-.971) between days and clinicians in all but one of the indices of footprint, arch angle (.689), with good reliability between clinicians. The full-factorial analysis of variance model did not reveal any interaction effects (P > .05), which indicated that indices of footprint were not changing across days and clinicians. Scanning technology used in this study demonstrated good intra- and interrater reliability measurements of footprint indices, as demonstrated by high ICC values. Copyright © 2011 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  9. Mental Fatigue Evaluation

    Directory of Open Access Journals (Sweden)

    Valery V. Rozhentsov

    2013-01-01

    Full Text Available The article offers the method for evaluation of mental fatigue, based on the method of paired light pulses. Ten pre-trained test men with normal vision, aged 18–20 participated in the experiment. Testees were showed subsequent paired light pulses at a 200 ms interval, divided by initial interpulse interval of 70 ms, recurring at the fixed time interval of 1 s. Testees determined the threshold interpulse interval, at which the two pulses in a pair merged into one, three times, using the method of successive approximation. Then testees solved algebraic equations with several unknowns for two hours. The threshold interpulse interval was determined three times every 20 minutes in the course of equations solving. The degree of mental fatigue DMF was calculated, using the formula: DMFi = (TPIi – TPI0 100% / TPIi; i = 1, 2, … , n, where DMFi is the degree of mental fatigue at the i-th measurement; TPIi is average arithmetic duration of threshold interpulse interval at the i-th measurement; TPI0 is average arithmetic duration of threshold interpulse interval before algebraic equations solving; n is the dimension of threshold interpulse interval measurement in the course of algebraic equations solving. After 20 minutes of work, the degree of mental fatigue of one of the testees was 9.5 %, rose to 21 % by the end of the first hour and exceeded 39 % by the end of the second hour. Similar dynamics of mental fatigue was observed in all testees, but its development and the degree of fatigue are individual. To prevent fatigue and ensure high level of efficiency one should set the individual schedule and rest pauses duration during mental activity.

  10. Hemoglobin-Based Oxygen Carrier (HBOC) Development in Trauma: Previous Regulatory Challenges, Lessons Learned, and a Path Forward.

    Science.gov (United States)

    Keipert, Peter E

    2017-01-01

    Historically, hemoglobin-based oxygen carriers (HBOCs) were being developed as "blood substitutes," despite their transient circulatory half-life (~ 24 h) vs. transfused red blood cells (RBCs). More recently, HBOC commercial development focused on "oxygen therapeutic" indications to provide a temporary oxygenation bridge until medical or surgical interventions (including RBC transfusion, if required) can be initiated. This included the early trauma trials with HemAssist ® (BAXTER), Hemopure ® (BIOPURE) and PolyHeme ® (NORTHFIELD) for resuscitating hypotensive shock. These trials all failed due to safety concerns (e.g., cardiac events, mortality) and certain protocol design limitations. In 2008 the Food and Drug Administration (FDA) put all HBOC trials in the US on clinical hold due to the unfavorable benefit:risk profile demonstrated by various HBOCs in different clinical studies in a meta-analysis published by Natanson et al. (2008). During standard resuscitation in trauma, organ dysfunction and failure can occur due to ischemia in critical tissues, which can be detected by the degree of lactic acidosis. SANGART'S Phase 2 trauma program with MP4OX therefore added lactate >5 mmol/L as an inclusion criterion to enroll patients who had lost sufficient blood to cause a tissue oxygen debt. This was key to the successful conduct of their Phase 2 program (ex-US, from 2009 to 2012) to evaluate MP4OX as an adjunct to standard fluid resuscitation and transfusion of RBCs. In 2013, SANGART shared their Phase 2b results with the FDA, and succeeded in getting the FDA to agree that a planned Phase 2c higher dose comparison study of MP4OX in trauma could include clinical sites in the US. Unfortunately, SANGART failed to secure new funding and was forced to terminate development and operations in Dec 2013, even though a regulatory path forward with FDA approval to proceed in trauma had been achieved.

  11. Biologic fatigue in psoriasis.

    Science.gov (United States)

    Levin, Ethan C; Gupta, Rishu; Brown, Gabrielle; Malakouti, Mona; Koo, John

    2014-02-01

    Over the past 15 years, biologic medications have greatly advanced psoriasis therapy. However, these medications may lose their efficacy after long-term use, a concept known as biologic fatigue. We sought to review the available data on biologic fatigue in psoriasis and identify strategies to help clinicians optimally manage patients on biologic medications in order to minimize biologic fatigue. We reviewed phase III clinical trials for the biologic medications used to treat psoriasis and performed a PubMed search for the literature that assessed the loss of response to biologic therapy. In phase III clinical trials of biologic therapies for the treatment of psoriasis, 20-32% of patients lost their PASI-75 response during 0.8-3.9 years of follow-up. A study using infliximab reported the highest percentage of patients who lost their response (32%) over the shortest time-period (0.8 years). Although not consistently reported across all studies, the presence of antidrug antibodies was associated with the loss of response to treatment with infliximab and adalimumab. Biologic fatigue may be most frequent in those patients using infliximab. Further studies are needed to identify risk factors associated with biologic fatigue and to develop meaningful antidrug antibody assays.

  12. Fatigue (PDQ)

    Science.gov (United States)

    ... can lessen the patient's quality of life and self-esteem . Getting help with fatigue may prevent some of ... National Institutes of Health FOLLOW US Facebook Twitter Instagram YouTube Google+ LinkedIn GovDelivery RSS CONTACT INFORMATION Contact ...

  13. Fatigue Countermeasures in Aviation

    Science.gov (United States)

    2009-01-01

    310. 26. Booth-Bourdeau J, Marcil 1, Laurence :M, McCulloch K, Dawson D. Development of fatigue risk management systenls for the Canadian aviation... Warren PSG, Watson B, Drud M. The sleep and performance of shift workers. Hum Factors 1982; 24:629-41. 206. Touitou Y, Bogdan A. Promoting adjustment

  14. Exercise‐induced homeostatic perturbations provoked by singles tennis match play with reference to development of fatigue

    OpenAIRE

    Mendez‐Villanueva, Alberto; Fernandez‐Fernandez, Jaime; Bishop, David

    2007-01-01

    This review addresses metabolic, neural, mechanical and thermal alterations during tennis match play with special focus on associations with fatigue. Several studies have provided a link between fatigue and the impairment of tennis skills proficiency. A tennis player's ability to maintain skilled on‐court performance and/or optimal muscle function during a demanding match can be compromised as a result of several homeostatic perturbations, for example hypoglycaemia, muscle damage and hyperthe...

  15. Interpretation of the influences of irradiation upon fatigue crack propagation in austenitic stainless steels

    International Nuclear Information System (INIS)

    Lloyd, G.J.

    1982-04-01

    An interpretation of the influences of neutron irradiation upon fatigue crack propagation in austenitic stainless steels is given. The approach has been to extend a previously developed rationalisation of the effects of various test and materials variables upon fatigue crack propagation in unirradiated stainless steels to include irradiated stainless steels. Irradiation has diverse influences upon the rate of fatigue crack propagation depending on the exact irradiation and test conditions. It has been shown that by considering the underlying mechanisms of failure, some confidence is established in trends in data in a subject where information is very scarce and difficult to obtain. (author)

  16. Finding the sweet spot: Developing, implementing and evaluating a burn out and compassion fatigue intervention for third year medical trainees.

    Science.gov (United States)

    Tucker, Tara; Bouvette, Maryse; Daly, Shauna; Grassau, Pamela

    2017-12-01

    Medical trainees are at high risk for developing burnout. Introducing trainees to the risks of burnout and supporting identification and proactive responses to their 'warning' signs of compassion fatigue (CF) is critical in building resiliency. The authors developed and evaluated a burnout and CF program for third year trainees at a Canadian Medical School. Of 165 medical trainees who participated in the burnout and CF program, 59 (36%) provided evaluation and feedback of the program and its impact throughout their year. Participation included self-utilization of a validated CF and burnout tool (ProQOL) across three time-points, workshop feedback, and focus group participation. Results highlighted the importance of 1) Recognizing Individual Signs & Symptoms of Stress, CF and Burnout; 2) Normalizing Stress, CF and Burnout for Students and Physicians; 3) Learning to Manage One's Own Stress. A decrease in compassion satisfaction and increase in burnout between beginning and end of third year were found. Further outcomes highlighted the importance of learning, living and surviving CF and burnout in clerkship. Emergent theory reveals the important responsibility educators have to integrate CF and burnout programs into 'the sweet spot' that third year offers, as trainees shift from theoretical to experiential practice as future clinicians. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. A study of classroom acoustics and school teachers' noise exposure, voice load and speaking time during teaching, and the effects on vocal and mental fatigue development.

    Science.gov (United States)

    Kristiansen, Jesper; Lund, Søren Peter; Persson, Roger; Shibuya, Hitomi; Nielsen, Per Møberg; Scholz, Matthias

    2014-11-01

    The study investigated the noise exposure in a group of Danish school teachers. The aims were to investigate if noise posed a risk of impairment of hearing and to study the association between classroom acoustical conditions, noise exposure, vocal symptoms, and cognitive fatigue. Background noise levels, vocal load and speaking time were measured on 35 teachers during actual classroom teaching. The classrooms were characterized acoustically by measurements of reverberation time. Before and after the workday, the teachers answered a questionnaire on fatigue symptoms and carried out two cognitive test tasks sensitive to mental fatigue. The average noise level during the lessons was 72 dB(A), but during indoor sports activities the average noise level increased 6.6 dB(A). Room reverberation time (range 0.39-0.83 s) had no significant effect on the noise level. The teachers were talking with a raised voice in 61% of the time, and the vocal load increased 0.65 dB(A) per dB(A) increase in the average lesson noise level. An increase in voice symptoms during the workday correlated significantly with individual average noise exposure, and a decrease in performance in the two-back test correlated significantly with individual average vocal load. Noise exposure in general classrooms posed no risk of noise-induced hearing impairment in school teachers. However, the results provide evidence for an association between noise exposure and vocal load and development of vocal symptoms and cognitive fatigue after work.

  18. An overview of fatigue

    International Nuclear Information System (INIS)

    Mc Evily, A.J.

    1987-01-01

    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)

  19. Prevalence and predictors of 6-month fatigue in patients with ischemic stroke: a population-based stroke incidence study in Auckland, New Zealand, 2002-2003.

    Science.gov (United States)

    Feigin, Valery L; Barker-Collo, Suzanne; Parag, Varsha; Hackett, Maree L; Kerse, Ngaire; Barber, P Alan; Theadom, Alice; Krishnamurthi, Rita

    2012-10-01

    Although persistent and significant fatigue affects the daily life of stroke survivors, there are no population-based studies examining the prevalence of fatigue in 6-month survivors of ischemic stroke and few studies of predictors of poststroke fatigue. This article examined data from the Auckland Regional Community Stroke study conducted in Auckland, New Zealand, in 2002 to 2003. Presence of fatigue was evaluated at 6 months in 613 patients with ischemic stroke using a Short Form 36 Vitality Score (energy and fatigue) of ≤ 47. Multivariate logistic regression analysis was used to determine predictors of fatigue development 6 months poststroke. The prevalence of fatigue was 30% (28% in men and 33% in women). There was a clear association between increased prevalence of fatigue and advancing age. The only baseline variables independently associated with an increased risk of developing fatigue at 6 months poststroke were prestroke incontinence and being of New Zealand European ethnicity. Being independent and living alone at baseline were associated with significant reduction in the risk of being fatigued at 6 months poststroke. Severe depression at 6 months was significantly and independently associated with being fatigued. The prevalence of fatigue found in our study is at the lower level of range reported in other studies. The prevalence of fatigue increased with advancing age, as found in most previous studies. Because fatigue can have a negative impact on stroke recovery, particular attention needs to be paid to those who are older, incontinent before stroke, and those who report severe symptoms of depression at 6 months after stroke.

  20. Variable amplitude fatigue, modelling and testing

    International Nuclear Information System (INIS)

    Svensson, Thomas.

    1993-01-01

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

  1. Development of methods to control cold temperature and fatigue cracking for asphalt mixtures.

    Science.gov (United States)

    2011-05-01

    Pavement distresses caused by low and intermediate temperatures are a significant source of problems : for highway agencies. While many tests have been developed to address this type of distress, few of : them are considered practical for day to day ...

  2. Interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device – Numerical modelling

    DEFF Research Database (Denmark)

    Martakos, G.; Andreasen, J.H.; Berggreen, Christian

    2017-01-01

    A novel crack arresting device is implemented in foam-cored composite sandwich beams and tested using the Sandwich Tear Test (STT) configuration. A finite element model of the setup is developed, and the predictions are correlated with observations and results from a recently conducted experimental...... fatigue test study. Based on a linear elastic fracture mechanics approach, the developed FE model is utilised to simulate crack propagation and arrest in foam-cored sandwich beam specimens subjected to fatigue loading conditions. The effect of the crack arresters on the fatigue life is analysed......, and the predictive results are subsequently compared with the observations from the previously conducted fatigue tests. The FE model predicts the energy release rate and the mode mixity based on the derived crack surface displacements, utilising algorithms for the prediction of accelerated fatigue crack growth...

  3. Development of testing system for the thermo-mechanical fatigue crack analysis of nuclear power plant pipes

    International Nuclear Information System (INIS)

    Lee, Ho Jin; Kim, Maan Won; Lee, Bong Sang

    2003-12-01

    Fatigue crack growth analysis plays an important role in the structural integrity assessment or the service life calculation of the nuclear power plant pipes. To obtain the material properties as a basic data to achieve an accurate crack growth analysis, a lot of tests and numerical crack growth simulations have been done for decades. The BS 7910 or the ASME Boiler and Pressure Vessel Code Section XI, generally used to evaluate crack growth behavior, were made under the based on simple stress states or at the evaluated isothermal temperature. It is well known that the ASME code could sometimes give so conservative results in some cases of which the cracked components are experiencing with cyclic thermal shock. In this report, we suggested a method for the life assessment of a crack embedded in nuclear power plant pipes under the thermal-mechanical fatigue loads. We here use the numerical method to get the temperature history for thermal- mechanical fatigue crack growth test. And then we can calculate the remaining life time of the pipe by using the fracture mechanics and the test results together. For this purpose, we constructed a thermal-mechanical fatigue crack growth testing system. We also gave a lot of review about recent researches in the experimental field of thermal-mechanical fatigue analysis

  4. Side Effects: Fatigue

    Science.gov (United States)

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

  5. Development of fatigue cracks from mechanically machined scratches on 2024-T351 aluminium alloy - Part II: finite element analysis and prediction method

    OpenAIRE

    Cini, Andrea; Irving, Phil E.

    2016-01-01

    A prediction method to evaluate the effect of scratch geometry on fatigue life of aluminium structures containing scribe marks was developed on the basis of the experimental results described in Part I of this paper. Finite element calculations were performed on scribed samples to investigate the local stress around scribes. Elastic and elastic plastic stress and strain distributions at the scribe root were computed under monotonic and cyclic tensile and bending loads evaluating the driving f...

  6. 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...

  7. Fatigue and Depressive Symptoms in Older People

    DEFF Research Database (Denmark)

    Mänty, Minna; Rantanen, Taina; Era, Pertti

    2014-01-01

    Fatigue is considered an important indicator of aging-related declines in health and functional abilities. Previous studies have indicated strong associations between fatigue and depressive symptoms among younger populations and in patient groups with specific diseases. However, it is not known h...

  8. 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...

  9. Fourier Hull Fatigue Assessment Method’s Proposing and Software Development

    Directory of Open Access Journals (Sweden)

    Jing Chen

    2014-05-01

    Full Text Available In this paper, based on the spectral analysis and the strain energy theory, the systematic errors of Rain-flow Counting Method have been quantitatively analyzed, from which a Fourier Counting Method is put forward. And according to this new method, software has been developed combined with sampling data of the real container ship via rigorous theoretical derivation and compact modular design, which has certain theoretical innovation significance and practical value.

  10. Fatigue management in the workplace.

    Science.gov (United States)

    Sadeghniiat-Haghighi, Khosro; Yazdi, Zohreh

    2015-01-01

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

  11. 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.

  12. Rethinking childhood adversity in chronic fatigue syndrome.

    Science.gov (United States)

    Clark, James E; Davidson, Sean L; Maclachlan, Laura; Newton, Julia L; Watson, Stuart

    2018-01-01

    Background: Previous studies have consistently shown increased rates of childhood adversity in chronic fatigue syndrome (CFS). However, such aetiopathogenic studies of CFS are potentially confounded by co-morbidity and misdiagnosis particularly with depression. Purpose: We examined the relationship between rates of childhood adversity using two complimentary approaches (1) a sample of CFS patients who had no lifetime history of depression and (2) a modelling approach. Methods: Childhood trauma questionnaire (CTQ) administered to a sample of 52 participants with chronic fatigue syndrome and 19 controls who did not meet criteria for a psychiatric disorder (confirmed using the Structured Clinical Interview for DSM-IV). Subsequently, Mediation Analysis (Baye's Rules) was used to establish the risk childhood adversity poses for CFS with and without depression. Results: In a cohort of CFS patients with depression comprehensively excluded, CTQ scores were markedly lower than in all previous studies and, in contrast to these previous studies, not increased compared with healthy controls. Post-hoc analysis showed that CTQ scores correlated with the number of depressive symptoms during the lifetime worst period of low mood. The probability of developing CFS given a history of childhood trauma is 4%, a two-fold increased risk compared to the general population. However, much of this risk is mediated by the concomitant development of major depression. Conclusions: The data suggests that previous studies showing a relationship between childhood adversity and CFS may be attributable to the confounding effects of co-morbid or misdiagnosed depressive disorder. Abbreviations: CFS: Chronic fatigue syndrome; CTQ: Childhood trauma questionnaire; MDD: Major depressive disorder; CA: Childhood adversity; P : Probability.

  13. Inspection Program Development for an Aircraft Fleet and an Airline on the Basis of the Acceptance Fatigue Test Result

    Directory of Open Access Journals (Sweden)

    Paramonov Yuri

    2015-02-01

    Full Text Available An inspection interval planning is considered in order to limit the probability of any fatigue failure (FFP in a fleet of N aircraft (AC and to provide an economical effectiveness of airline (AL under the limitation of fatigue failure rate (FFR. A solution of these two problems is based on the processing of the result of acceptance fatigue test of a new type of aircraft. During this test an estimate of the parameter ϴ, of a fatigue crack growth trajectory has been obtained. If the result of this acceptance test is too bad then this new type of aircraft will not be used in service. A redesign of this project should be done. If the result the acceptance test is pretty good then the reliability of the aircraft fleet and the airline will be provided without inspections. For this strategy there is a maximum of FFP (a maximum of FFR as a function of an unknown parameter ᶿ. This maximum can be limited by the use of the offered here procedure of the choice of the inspection number. The economic effectiveness of the AL operation is considered using the theory of Markov process with rewords.

  14. Helicopter Fatigue Design Guide

    Science.gov (United States)

    1983-11-01

    Utility Tactical Troop Carrying Heavy Lift Air Force: Transport Search and Rescue The sheer scale of the costs of designing and developing a modern...torsion, the latter being related to piano wire and stainless steel 18.8. To my knowledge a 25 % improvement can be ob- tained by shot peening on actual...N testing is not in the test itself, but in the sheer number of tests to be conducted. A modern helicopter may have from 75 to 100 fatigue

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

    Directory of Open Access Journals (Sweden)

    Benjamin ePageaux

    2015-02-01

    Full Text Available 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 (CT were followed by a whole-body endurance task (ET consisting of six minutes 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 CT did not induce any decrease in maximal voluntary contraction (MVC torque (p=0.194. During ET, mentally fatigued subjects reported higher RPE (self-regulation 13.9 ± 3.0, control 13.3 ± 3.2, p=0.044. ET induced a similar decrease in MVC torque (self-regulation -17 ± 15 %, control -15 ± 11 %, p=0.001, maximal voluntary activation level (self-regulation -6 ± 9%, control -6 ± 7%, p=0.013 and resting twitch (self-regulation -30 ± 14%, control -32 ± 10%, P<0.001 in both conditions. These findings reject our hypothesis and confirm previous findings that mental fatigue does not reduce the capacity of the central nervous system to recruit the working muscles. The negative 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

  16. Fatigue crack closure: A review

    Science.gov (United States)

    Kemp, R. M. J.

    1990-09-01

    The phenomenon of fatigue crack closure is now recognized as one of the most influential mechanisms operating during fatigue. This literature survey traces the development of research into fatigue crack closure and has been divided to present the two major approaches. The first part covers early work carried out between 1970 to 1980 which, broadly speaking, adopted a 'continuum' approach. The second part covers the period 1980 to 1988 when a mechanistic approach was widely adopted. The survey has highlighted, firstly, the critical nature of experimental technique in the achievement of a meaningful measurement of crack closure load and secondly, that a diversity of mechanisms may operate to produce closure. Particular attention has been given to crack closure in aluminum alloys and also to work relating crack closure to the corrosion fatigue situation.

  17. 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...

  18. A large-area strain sensing technology for monitoring fatigue cracks in steel bridges

    Science.gov (United States)

    Kong, Xiangxiong; Li, Jian; Collins, William; Bennett, Caroline; Laflamme, Simon; Jo, Hongki

    2017-08-01

    This paper presents a novel large-area strain sensing technology for monitoring fatigue cracks in steel bridges. The technology is based on a soft elastomeric capacitor (SEC), which serves as a flexible and large-area strain gauge. Previous experiments have verified the SEC’s capability to monitor low-cycle fatigue cracks experiencing large plastic deformation and large crack opening. Here an investigation into further extending the SEC’s capability for long-term monitoring of fatigue cracks in steel bridges subject to traffic loading, which experience smaller crack openings. It is proposed that the peak-to-peak amplitude (pk-pk amplitude) of the sensor’s capacitance measurement as the indicator of crack growth to achieve robustness against capacitance drift during long-term monitoring. Then a robust crack monitoring algorithm is developed to reliably identify the level of pk-pk amplitudes through frequency analysis, from which a crack growth index (CGI) is obtained for monitoring fatigue crack growth under various loading conditions. To generate representative fatigue cracks in a laboratory, loading protocols were designed based on constant ranges of stress intensity to limit plastic deformations at the crack tip. A series of small-scale fatigue tests were performed under the designed loading protocols with various stress intensity ratios. Test results under the realistic fatigue crack conditions demonstrated the proposed crack monitoring algorithm can generate robust CGIs which are positively correlated with crack lengths and independent from loading conditions.

  19. Plantar flexor muscle weakness and fatigue in spastic cerebral palsy patients.

    Science.gov (United States)

    Neyroud, Daria; Armand, Stéphane; De Coulon, Geraldo; Sarah R Dias Da Silva; Maffiuletti, Nicola A; Kayser, Bengt; Place, Nicolas

    2017-02-01

    Patients with cerebral palsy develop an important muscle weakness which might affect the aetiology and extent of exercise-induced neuromuscular fatigue. This study evaluated the aetiology and extent of plantar flexor neuromuscular fatigue in patients with cerebral palsy. Ten patients with cerebral palsy and 10 age- and sex-matched healthy individuals (∼20 years old, 6 females) performed four 30-s maximal isometric plantar flexions interspaced by a resting period of 2-3s to elicit a resting twitch. Maximal voluntary contraction force, voluntary activation level and peak twitch were quantified before and immediately after the fatiguing task. Before fatigue, patients with cerebral palsy were weaker than healthy individuals (341±134N vs. 858±151N, pfatiguing task (-10±23%, p>0.05), whereas it decreased by 30±12% (pmuscles of patients with cerebral palsy were weaker than their healthy peers but showed greater fatigue resistance. Cerebral palsy is a widely defined pathology that is known to result in muscle weakness. The extent and origin of muscle weakness were the topic of several previous investigations; however some discrepant results were reported in the literature regarding how it might affect the development of exercise-induced neuromuscular fatigue. Importantly, most of the studies interested in the assessment of fatigue in patients with cerebral palsy did so with general questionnaires and reported increased levels of fatigue. Yet, exercise-induced neuromuscular fatigue was quantified in just a few studies and it was found that young patients with cerebral palsy might be more fatigue resistant that their peers. Thus, it appears that (i) conflicting results exist regarding objectively-evaluated fatigue in patients with cerebral palsy and (ii) the mechanisms underlying this muscle fatigue - in comparison to those of healthy peers - remain poorly understood. The present study adds important knowledge to the field as it shows that when young adults with

  20. PREVIOUS SECOND TRIMESTER ABORTION

    African Journals Online (AJOL)

    PNLC

    PREVIOUS SECOND TRIMESTER ABORTION: A risk factor for third trimester uterine rupture in three ... for accurate diagnosis of uterine rupture. KEY WORDS: Induced second trimester abortion - Previous uterine surgery - Uterine rupture. ..... scarred uterus during second trimester misoprostol- induced labour for a missed ...

  1. Fatigue behavior of 2 1/4 Cr--1 Mo steel in support of steam generator development

    International Nuclear Information System (INIS)

    Brinkman, C.R.; Booker, M.K.; Strizak, J.P.; Weerasooriya, T.

    1978-10-01

    Designers of high-temperature power generation plants, both nuclear and fossil-fired, have made extensive use of 2 1/4 Cr--1 Mo steel for piping, shell, and tubing and as a tubesheet material in steam generators. While this material has been researched as much if not more than any other boiler material, an understanding of the time-dependent fatigue behavior for long-term service applications is still incomplete. Progress is reported in obtaining formulations that can be used for low and high cycle continuous cycle fatigue, time-dependent fatigue, and crack growth behavior. Material variables such as melting practice, heat-to-heat, and heat treatment variations are discussed. The importance of environment is shown by comparing the results of elevated-temperature strain and load-controlled tests of different waveforms conducted in both air and helium. Interim progress is reported in characterizing the crack growth behavior of HAZs adjacent to dissimilar weld joints of this material

  2. Ameloblastic fibroma: a stage in the development of a hamartomatous odontoma or a true neoplasm? Critical analysis of 162 previously reported cases plus 10 new cases.

    Science.gov (United States)

    Buchner, Amos; Vered, Marilena

    2013-11-01

    To analyze neoplastic and hamartomatous variants of ameloblastic fibromas (AFs). Analysis of 172 cases (162 previously reported, 10 new). AF emerged as a lesion primarily of children and adolescents (mean age, 14.9 years), with about 80% diagnosed when odontogenesis is completed (age, 22 years are considered true neoplasms, while those in younger patients may be either true neoplasms or odontomas in early stages of development. Although the histopathology of hamartomatous and neoplastic variants of AF are indistinguishable, clinical and radiologic features can be of some help to distinguish between them. Asymptomatic small unilocular lesions with no or minimal bone expansion in young individuals are likely to be developing odontomas, and large, expansile lesions with extensive bone destruction are neoplasms. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Interpreting "Personality" Taxonomies: Why Previous Models Cannot Capture Individual-Specific Experiencing, Behaviour, Functioning and Development. Major Taxonomic Tasks Still Lay Ahead.

    Science.gov (United States)

    Uher, Jana

    2015-12-01

    As science seeks to make generalisations, a science of individual peculiarities encounters intricate challenges. This article explores these challenges by applying the Transdisciplinary Philosophy-of-Science Paradigm for Research on Individuals (TPS-Paradigm) and by exploring taxonomic "personality" research as an example. Analyses of researchers' interpretations of the taxonomic "personality" models, constructs and data that have been generated in the field reveal widespread erroneous assumptions about the abilities of previous methodologies to appropriately represent individual-specificity in the targeted phenomena. These assumptions, rooted in everyday thinking, fail to consider that individual-specificity and others' minds cannot be directly perceived, that abstract descriptions cannot serve as causal explanations, that between-individual structures cannot be isomorphic to within-individual structures, and that knowledge of compositional structures cannot explain the process structures of their functioning and development. These erroneous assumptions and serious methodological deficiencies in widely used standardised questionnaires have effectively prevented psychologists from establishing taxonomies that can comprehensively model individual-specificity in most of the kinds of phenomena explored as "personality", especially in experiencing and behaviour and in individuals' functioning and development. Contrary to previous assumptions, it is not universal models but rather different kinds of taxonomic models that are required for each of the different kinds of phenomena, variations and structures that are commonly conceived of as "personality". Consequently, to comprehensively explore individual-specificity, researchers have to apply a portfolio of complementary methodologies and develop different kinds of taxonomies, most of which have yet to be developed. Closing, the article derives some meta-desiderata for future research on individuals' "personality".

  4. How do women with lupus manage fatigue?

    DEFF Research Database (Denmark)

    Kier, Anne Ørnholt; Midtgaard, Julie; Hougaard, Karin Sørig

    2016-01-01

    , and learning to accept fatigue) and six sub-themes (i.e., the search for recognition, legitimization, planning and prioritizing, the body’s limits and self-indulgence, adjusting life to comply with resources, and acceptance of dependence). Conclusion: Fatigue is the controlling element in everyday life......Objective: Half of patients with systemic lupus erythematosus (SLE) consider fatigue to be the most disabling disease symptom. To develop and promote strategies to prevent and control fatigue, this study aimed to describe how women with SLE manage the experience of fatigue. Methods: Four focus...... groups were conducted with 27 women with SLE, and data were analyzed by means of framework analysis. Two patient representatives with SLE were part of the investigator team. Results: The analysis revealed three main themes (i.e., learning how to be open about fatigue, learning to listen to the body...

  5. Fatigue and physical performance in children and adolescents receiving chemotherapy.

    Science.gov (United States)

    Hooke, Mary Catherine; Garwick, Ann W; Gross, Cynthia R

    2011-11-01

    To examine the relationship between physical performance and fatigue in child and adolescent cohorts during the first three cycles of chemotherapy. Prospective, observational design. Two pediatric cancer centers in the upper Midwest region of the United States. 16 children and 14 adolescents newly diagnosed with cancer. Standardized instruments were administered during the first and third cycles of chemotherapy. Instruments included physical performance tests (Timed Up and Down Stairs [TUDS] and the 6-Minute Walk Test [6MWT]) and a self-report fatigue scale. Fatigue and physical performance. In the child cohort, physical performance appeared to improve and fatigue diminished from cycle 1 to 3 of chemotherapy. When time on TUDS decreased, fatigue tended to decrease; when 6MWT distance increased, fatigue decreased. In the adolescent cohort, fatigue seemed to decrease but physical performance measures evidenced little change. Correlations between changes in the physical performance variables and fatigue were not significant. Fatigue may decrease early in treatment as disease symptoms resolve. Fatigue in the child cohort was related to physical performance, which is consistent with previous studies that defined fatigue in children as primarily a physical sensation. Findings in the adolescent cohort support research that defined adolescent fatigue as more complex with mental, emotional, and physical components. Knowing how fatigue relates to physical performance in children and adolescents informs the nurse in educating patients and families about symptom management.

  6. An EMG-driven biomechanical model that accounts for the decrease in moment generation capacity during a dynamic fatigued condition.

    Science.gov (United States)

    Rao, Guillaume; Berton, Eric; Amarantini, David; Vigouroux, Laurent; Buchanan, Thomas S

    2010-07-01

    Although it is well known that fatigue can greatly reduce muscle forces, it is not generally included in biomechanical models. The aim of the present study was to develop an electromyographic-driven (EMG-driven) biomechanical model to estimate the contributions of flexor and extensor muscle groups to the net joint moment during a nonisokinetic functional movement (squat exercise) performed in nonfatigued and in fatigued conditions. A methodology that aims at balancing the decreased muscle moment production capacity following fatigue was developed. During an isometric fatigue session, a linear regression was created linking the decrease in force production capacity of the muscle (normalized force/EMG ratio) to the EMG mean frequency. Using the decrease in mean frequency estimated through wavelet transforms between dynamic squats performed before and after the fatigue session as input to the previous linear regression, a coefficient accounting for the presence of fatigue in the quadriceps group was computed. This coefficient was used to constrain the moment production capacity of the fatigued muscle group within an EMG-driven optimization model dedicated to estimate the contributions of the knee flexor and extensor muscle groups to the net joint moment. During squats, our results showed significant increases in the EMG amplitudes with fatigue (+23.27% in average) while the outputs of the EMG-driven model were similar. The modifications of the EMG amplitudes following fatigue were successfully taken into account while estimating the contributions of the flexor and extensor muscle groups to the net joint moment. These results demonstrated that the new procedure was able to estimate the decrease in moment production capacity of the fatigued muscle group.

  7. Multi-purpose fatigue sensor. Part 1. Uniaxial and multiaxial fatigue

    Directory of Open Access Journals (Sweden)

    M.V. Karuskevich

    2016-10-01

    Full Text Available The paper describes the key principles and results of preliminary experiments aimed at the development of new technique for the fatigue life prediction under conditions of biaxial cyclic tension. The foundations of the method were developed early by the numerous tests with monitoring the process of surface deformation relief formation, which is proved to be an indicator of accumulated fatigue damage under uniaxial fatigue. The employed phenomenon was early applied for the development of a family of uniaxial loading fatigue sensors. The formation of strain induced relief has been recently taken into consideration as a part of damage accumulation criteria under biaxial fatigue as well. The home-made testing machine has been designed to implement combined bending and torsion loading that simulates loads experienced by an aircraft wing skin. The experimental evidences on formation and evolution of the deformation relief revealed under conditions of combined loading, supports the proposed concept of biaxial fatigue sensor

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

    International Nuclear Information System (INIS)

    Kim, S.W.; Tanigawa, H.; Hirose, T.; Kohyama, A.

    2007-01-01

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

  9. Multispecimen fatigue crack propagation testing

    International Nuclear Information System (INIS)

    Ermi, A.M.; Bauer, R.E.; Chin, B.A.; Straalsund, J.L.

    1981-01-01

    Chains of miniature center-cracked-tension specimens were tested on a conventional testing machine and on a prototypic in-reactor fatigue machine as part of the fusion reactor materials alloy development program. Annealed and 20 percent cold-worked 316 stainless steel specimens were cycled under various conditions of temperature, frequency, stress ratio and chain length. Crack growth rates determined from multispecimen visual measurements and from an electrical potential technique were consistent with those obtained by conventional test methods. Results demonstrate that multispecimen chain testing is a valid method of obtaining fatigue crack propagation information for alloy development. 8 refs

  10. High temperature fatigue behaviour of intermetallics

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    brittle to ductile transition temperature, mean stress and environment on fatigue behaviour of same γ-TiAl alloys are discussed. Keywords. Nickel aluminides; titanium aluminides; low cycle fatigue; micro- alloying. 1. Introduction. Ordered intermetallic alloys have undergone extensive development over the past two decades.

  11. Statistical treatment of fatigue test data

    International Nuclear Information System (INIS)

    Raske, D.T.

    1980-01-01

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

  12. 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...

  13. A Micromechanics-Based Method for Multiscale Fatigue Prediction

    Science.gov (United States)

    Moore, John Allan

    An estimated 80% of all structural failures are due to mechanical fatigue, often resulting in catastrophic, dangerous and costly failure events. However, an accurate model to predict fatigue remains an elusive goal. One of the major challenges is that fatigue is intrinsically a multiscale process, which is dependent on a structure's geometric design as well as its material's microscale morphology. The following work begins with a microscale study of fatigue nucleation around non- metallic inclusions. Based on this analysis, a novel multiscale method for fatigue predictions is developed. This method simulates macroscale geometries explicitly while concurrently calculating the simplified response of microscale inclusions. Thus, providing adequate detail on multiple scales for accurate fatigue life predictions. The methods herein provide insight into the multiscale nature of fatigue, while also developing a tool to aid in geometric design and material optimization for fatigue critical devices such as biomedical stents and artificial heart valves.

  14. Laparoscopy After Previous Laparotomy

    Directory of Open Access Journals (Sweden)

    Zulfo Godinjak

    2006-11-01

    Full Text Available Following the abdominal surgery, extensive adhesions often occur and they can cause difficulties during laparoscopic operations. However, previous laparotomy is not considered to be a contraindication for laparoscopy. The aim of this study is to present that an insertion of Veres needle in the region of umbilicus is a safe method for creating a pneumoperitoneum for laparoscopic operations after previous laparotomy. In the last three years, we have performed 144 laparoscopic operations in patients that previously underwent one or two laparotomies. Pathology of digestive system, genital organs, Cesarean Section or abdominal war injuries were the most common causes of previouslaparotomy. During those operations or during entering into abdominal cavity we have not experienced any complications, while in 7 patients we performed conversion to laparotomy following the diagnostic laparoscopy. In all patients an insertion of Veres needle and trocar insertion in the umbilical region was performed, namely a technique of closed laparoscopy. Not even in one patient adhesions in the region of umbilicus were found, and no abdominal organs were injured.

  15. Conceptual aspects: analyses law, ethical, human, technical, social factors of development ICT, e-learning and intercultural development in different countries setting out the previous new theoretical model and preliminary findings

    NARCIS (Netherlands)

    Kommers, Petrus A.M.; Smyrnova-Trybulska, Eugenia; Morze, Natalia; Issa, Tomayess; Issa, Theodora

    2015-01-01

    This paper, prepared by an international team of authors focuses on the conceptual aspects: analyses law, ethical, human, technical, social factors of ICT development, e-learning and intercultural development in different countries, setting out the previous and new theoretical model and preliminary

  16. Fatigue in adults with post-infectious fatigue syndrome: a qualitative content analysis.

    Science.gov (United States)

    Stormorken, Eva; Jason, Leonard A; Kirkevold, Marit

    2015-01-01

    Fatigue is a major problem among individuals with post-infectious fatigue syndrome (PIFS), also known as chronic fatigue syndrome or myalgic encephalomyelitis. It is a complex phenomenon that varies across illnesses. From a nursing perspective, knowledge and understanding of fatigue in this illness is limited. Nurses lack confidence in caring for these patients and devalue their professional role. The aim of this study was to explore in-depth the experiences of fatigue among individuals with PIFS. A detailed description of the phenomenon of fatigue is presented. Increased knowledge would likely contribute to more confident nurses and improved nursing care. A qualitative study with open interviews was employed. In-depth interviews with patients were fully transcribed and underwent a qualitative content analysis. A maximum variation sample of 26 affected adults between 26-59 years old was recruited from a population diagnosed at a fatigue outpatient clinic. The fatigue was a post-exertional, multidimensional, fluctuating phenomenon with varying degrees of severity and several distinct characteristics and was accompanied by concomitant symptoms. Fatigue was perceived to be an all-pervasive complex experience that substantially reduced the ability to function personally or professionally. A range of trigger mechanisms evoked or worsened the fatigue, but the affected were not always aware of what triggered it. There was an excessive increase in fatigue in response to even minor activities. An increase in fatigue resulted in the exacerbation of other concomitant symptoms. The term fatigue does not capture the participants' experiences, which are accompanied by a considerable symptom burden that contributes to the illness experience and the severe disability. Although some aspects of the fatigue experience have been reported previously, more were added in our study, such as the dimension of awakening fatigue and the characteristic beyond time, when time passes unnoticed

  17. 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 has on patients' lives. The data obtained informed the development of a conceptual model of fatigue in FM....

  18. Random non-proportional fatigue tests with planar tri-axial fatigue testing machine

    Directory of Open Access Journals (Sweden)

    T. Inoue

    2016-10-01

    Full Text Available Complex stresses, which occur on the mechanical surfaces of transport machinery in service, bring a drastic degradation in fatigue life. However, it is hard to reproduce such complex stress states for evaluating the fatigue life with conventional multiaxial fatigue machines. We have developed a fatigue testing machine that enables reproduction of such complex stresses. The testing machine can reproduce arbitrary in-plane stress states by applying three independent loads to the test specimen using actuators which apply loads in the 0, 45, and 90 degree directions. The reproduction was tested with complex stress data obtained from the actual operation of transport machinery. As a result, it was found that the reproduced stress corresponded to the measured stress with an error range of less than 10 %. Then, we made a comparison between measured fatigue lives under random non-proportional loading conditions and predicted fatigue lives. It was found that predicted fatigue lives with cr, stress on critical plane, were over a factor of 10 against measured fatigue lives. On the other hand, predicted fatigue lives with ma, stress in consideration of a non-proportional level evaluated by using amplitude and direction of principal stress, were within a factor of 3 against measured fatigue lives

  19. Beyond pain in fibromyalgia: insights into the symptom of fatigue.

    Science.gov (United States)

    Vincent, Ann; Benzo, Roberto P; Whipple, Mary O; McAllister, Samantha J; Erwin, Patricia J; Saligan, Leorey N

    2013-01-01

    Fatigue is a disabling, multifaceted symptom that is highly prevalent and stubbornly persistent. Although fatigue is a frequent complaint among patients with fibromyalgia, it has not received the same attention as pain. Reasons for this include lack of standardized nomenclature to communicate about fatigue, lack of evidence-based guidelines for fatigue assessment, and a deficiency in effective treatment strategies. Fatigue does not occur in isolation; rather, it is present concurrently in varying severity with other fibromyalgia symptoms such as chronic widespread pain, unrefreshing sleep, anxiety, depression, cognitive difficulties, and so on. Survey-based and preliminary mechanistic studies indicate that multiple symptoms feed into fatigue and it may be associated with a variety of physiological mechanisms. Therefore, fatigue assessment in clinical and research settings must consider this multi-dimensionality. While no clinical trial to date has specifically targeted fatigue, randomized controlled trials, systematic reviews, and meta-analyses indicate that treatment modalities studied in the context of other fibromyalgia symptoms could also improve fatigue. The Outcome Measures in Rheumatology (OMERACT) Fibromyalgia Working Group and the Patient Reported Outcomes Measurement Information System (PROMIS) have been instrumental in propelling the study of fatigue in fibromyalgia to the forefront. The ongoing efforts by PROMIS to develop a brief fibromyalgia-specific fatigue measure for use in clinical and research settings will help define fatigue, allow for better assessment, and advance our understanding of fatigue.

  20. Beyond pain in fibromyalgia: insights into the symptom of fatigue

    Science.gov (United States)

    2013-01-01

    Fatigue is a disabling, multifaceted symptom that is highly prevalent and stubbornly persistent. Although fatigue is a frequent complaint among patients with fibromyalgia, it has not received the same attention as pain. Reasons for this include lack of standardized nomenclature to communicate about fatigue, lack of evidence-based guidelines for fatigue assessment, and a deficiency in effective treatment strategies. Fatigue does not occur in isolation; rather, it is present concurrently in varying severity with other fibromyalgia symptoms such as chronic widespread pain, unrefreshing sleep, anxiety, depression, cognitive difficulties, and so on. Survey-based and preliminary mechanistic studies indicate that multiple symptoms feed into fatigue and it may be associated with a variety of physiological mechanisms. Therefore, fatigue assessment in clinical and research settings must consider this multi-dimensionality. While no clinical trial to date has specifically targeted fatigue, randomized controlled trials, systematic reviews, and meta-analyses indicate that treatment modalities studied in the context of other fibromyalgia symptoms could also improve fatigue. The Outcome Measures in Rheumatology (OMERACT) Fibromyalgia Working Group and the Patient Reported Outcomes Measurement Information System (PROMIS) have been instrumental in propelling the study of fatigue in fibromyalgia to the forefront. The ongoing efforts by PROMIS to develop a brief fibromyalgia-specific fatigue measure for use in clinical and research settings will help define fatigue, allow for better assessment, and advance our understanding of fatigue. PMID:24289848

  1. Numerical analysis of rolling contact fatigue crack initiation and fatigue life prediction of the railway crossing

    OpenAIRE

    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. Material model accounting for elastic- plastic isotropic and kinematic hardening effects is adopted. The results from FE analysis are combined with J-S fatigue model that is based on critical plan...

  2. Gut inflammation in chronic fatigue syndrome

    OpenAIRE

    Lakhan, Shaheen E; Kirchgessner, Annette

    2010-01-01

    Abstract Chronic fatigue syndrome (CFS) is a debilitating disease characterized by unexplained disabling fatigue and a combination of accompanying symptoms the pathology of which is incompletely understood. Many CFS patients complain of gut dysfunction. In fact, patients with CFS are more likely to report a previous diagnosis of irritable bowel syndrome (IBS), a common functional disorder of the gut, and experience IBS-related symptoms. Recently, evidence for interactions between the intestin...

  3. Anomolous Fatigue Crack Growth Phenomena in High-Strength Steel

    Science.gov (United States)

    Forth, Scott C.; James, Mark A.; Johnston, William M., Jr.; Newman, James C., Jr.

    2004-01-01

    The growth of a fatigue crack through a material is the result of a complex interaction between the applied loading, component geometry, three-dimensional constraint, load history, environment, material microstructure and several other factors. Previous studies have developed experimental and computational methods to relate the fatigue crack growth rate to many of the above conditions, with the intent of discovering some fundamental material response, i.e. crack growth rate as a function of something. Currently, the technical community uses the stress intensity factor solution as a simplistic means to relate fatigue crack growth rate to loading, geometry and all other variables. The stress intensity factor solution is a very simple linear-elastic representation of the continuum mechanics portion of crack growth. In this paper, the authors present fatigue crack growth rate data for two different high strength steel alloys generated using standard methods. The steels exhibit behaviour that appears unexplainable, compared to an aluminium alloy presented as a baseline for comparison, using the stress intensity factor solution.

  4. Multidimensional fatigue in pulmonary hypertension: prevalence, severity and predictors

    Science.gov (United States)

    Tartavoulle, Todd M.; Karpinski, Aryn C.; Aubin, Andrew; Kluger, Benzi M.; Distler, Oliver; Saketkoo, Lesley Ann

    2018-01-01

    Pulmonary hypertension is a potentially fatal disease. Despite pharmacological advances in pulmonary hypertension, fatigue remains common in patients with pulmonary hypertension. A convenience sample of 120 participants at an international patient conference completed the Multidimensional Fatigue Inventory (MFI)-20 scale. Data on New York Heart Association Functional Class, body mass index, oxygen use and medication type/use were also collected. There was a high prevalence of “severe” to “very severe” fatigue for each dimension: General Fatigue (60%), Physical Fatigue (55.8%), Reduced Activity (41.7%), Reduced Motivation (32.5%) and Mental Fatigue (27.5%). The mean±sd overall MFI-20 score was 58±5.1. Dimensions with the highest averaged levels were General Fatigue (13.40±3.61), Physical Fatigue (13.23±3.67) and Reduced Activity (11.33±4.16). Body mass index correlated with higher fatigue scores. Phosphodiesterase inhibitor plus endothelin receptor antagonist combination negatively predicted General Fatigue, Physical Fatigue, Reduced Motivation and Reduced Activity. Triple therapy was a significant predictor of General Fatigue, Physical Fatigue and Reduced Activity. There were no significant predictors of Mental Fatigue. Multidimensional fatigue is common and severe in patients with pulmonary hypertension. Phosphodiesterase inhibitor plus endothelin receptor antagonist combination resulted in lower scores in most fatigue dimensions. Comprehensive assessment of fatigue should be considered in the clinical care of patients with pulmonary hypertension and clinical research to develop formal interventions that target this disabling symptom. PMID:29577043

  5. Cardiorespiratory and neuromuscular deconditioning in fatigued and non-fatigued breast cancer survivors.

    Science.gov (United States)

    Neil, Sarah E; Klika, Riggs J; Garland, S Jayne; McKenzie, Donald C; Campbell, Kristin L

    2013-03-01

    Fatigue is one of the most commonly reported side effects during treatment for breast cancer and can persist following treatment completion. Cancer-related fatigue after treatment is multifactorial in nature, and one hypothesized mechanism is cardiorespiratory and neuromuscular deconditioning. The purpose of this study was to compare cardiorespiratory and neuromuscular function in breast cancer survivors who had completed treatment and met the specified criteria for cancer-related fatigue and a control group of breast cancer survivors without fatigue. Participants in the fatigue (n = 16) and control group (n = 11) performed a maximal exercise test on a cycle ergometer for determination of peak power, power at lactate threshold, and VO(2) peak. Neuromuscular fatigue was induced with a sustained submaximal contraction of the right quadriceps. Central fatigue (failure of voluntary activation) was evaluated using twitch interpolation, and peripheral fatigue was measured with an electrically evoked twitch. Power at lactate threshold was lower in the fatigue group (p = 0.05). There were no differences between groups for power at lactate threshold as percentage of peak power (p = 0.10) or absolute or relative VO(2) peak (p = 0.08 and 0.33, respectively). When adjusted for age, the fatigue group had a lower power at lactate threshold (p = 0.02) and absolute VO(2) peak (p = 0.03). There were no differences between groups in change in any neuromuscular parameters after the muscle-fatiguing protocol. Findings support the hypothesis that cardiorespiratory deconditioning may play a role in the development and persistence of cancer-related fatigue following treatment. Future research into the use of exercise training to reduce cardiorespiratory deconditioning as a treatment for cancer-related fatigue is warranted to confirm these preliminary findings.

  6. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

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

    1996-01-01

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

  7. 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 ...

  8. Recent advances in fatigue crack growth

    International Nuclear Information System (INIS)

    McEvily, A.J.

    2011-01-01

    Many of the recent advances in the understanding of the fatigue crack growth process have resulted from an improved realization of the importance of fatigue crack closure in the crack growth process. Two basic crack closure processes have been identified. One of which is known as plasticity-induced fatigue crack closure (PIFCC), and the other is roughness-induced fatigue crack closure (RIFCC). Both forms occur in all alloys, but PIFCC is a surface-related process which is dominant in aluminum alloys such as 2024-T3, whereas RIFCC is dominant in most steels and titanium alloys. A proposed basic equation governing fatigue crack growth is derived where K/sub max/ is the maximum stress intensity factor in a loading cycle and K/sub op/ is the stress intensity factor at the crack opening level. is the range of the stress intensity factor at the threshold level which is taken to correspond to a crack growth rate of 10-11 m/cycle. The material constant A has units of (MPa)-2, and therefore Eq. 1 is dimensionally correct. Eq.1 has been successfully used in the analysis of both long and short cracks, but in the latter case modification is needed to account for elastic-plastic behavior, the development of crack closure, and the Kitagawa effect which shows that the fatigue strength rather than the threshold level is the controlling factor determining the rate of fatigue crack growth in the very short fatigue crack growth range. Eq. 1 is used to show that The non-propagating cracks observed by Frost and Dugdale resulted from crack closure. The behavior of cracks as short as 10 microns in length can be predicted. Fatigue notch sensitivity is related to crack closure. Very high cycle fatigue (VHCF) behavior is also associated with fatigue crack closure. (author)

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

    Science.gov (United States)

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

    2014-01-01

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

  10. Method to Reduce Muscle Fatigue During Transcutaneous Neuromuscular Electrical Stimulation in Major Knee and Ankle Muscle Groups.

    Science.gov (United States)

    Sayenko, Dimitry G; Nguyen, Robert; Hirabayashi, Tomoyo; Popovic, Milos R; Masani, Kei

    2015-09-01

    A critical limitation with transcutaneous neuromuscular electrical stimulation as a rehabilitative approach is the rapid onset of muscle fatigue during repeated contractions. We have developed a method called spatially distributed sequential stimulation (SDSS) to reduce muscle fatigue by distributing the center of electrical field over a wide area within a single stimulation site, using an array of surface electrodes. To extend the previous findings and to prove feasibility of the method by exploring the fatigue-reducing ability of SDSS for lower limb muscle groups in the able-bodied population, as well as in individuals with spinal cord injury (SCI). SDSS was delivered through 4 active electrodes applied to the knee extensors and flexors, plantarflexors, and dorsiflexors, sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. Isometric ankle torque was measured during fatiguing stimulations using SDSS and conventional single active electrode stimulation lasting 2 minutes. We demonstrated greater fatigue-reducing ability of SDSS compared with the conventional protocol, as revealed by larger values of fatigue index and/or torque peak mean in all muscles except knee flexors of able-bodied individuals, and in all muscles tested in individuals with SCI. Our study has revealed improvements in fatigue tolerance during transcutaneous neuromuscular electrical stimulation using SDSS, a stimulation strategy that alternates activation of subcompartments of muscles. The SDSS protocol can provide greater stimulation times with less decrement in mechanical output compared with the conventional protocol. © The Author(s) 2014.

  11. Assessment of muscle fatigue using electromygraphm sensing

    Science.gov (United States)

    Helmi, Muhammad Hazimin Bin; Ping, Chew Sue; Ishak, Nur Elliza Binti; Saad, Mohd Alimi Bin Mohd; Mokhtar, Anis Shahida Niza Binti

    2017-08-01

    Muscle fatigue is condition of muscle decline in ability after undergoing any physical activity. Observation of the muscle condition of an athlete during training is crucial to prevent or minimize injury and able to achieve optimum performance in actual competition. The aim of this project is to develop a muscle monitoring system to detect muscle fatigue in swimming athlete. This device is capable to measure muscle stress level of the swimmer and at the same time provide indication of muscle fatigue level to trainer. Electromyography signal was recorded from the muscle movement while practicing the front crawl stroke repetitively. The time domain data was processed to frequency spectra in order to study the effect of muscle fatigue. The results show that the recorded EMG signal is able to sense muscle fatigue.

  12. On the Fatigue Analysis of Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Herbert J.

    1999-06-01

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

  13. 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...

  14. Evolution of surface topography in dependence on the grain orientation during surface thermal fatigue of polycrystalline copper

    CERN Document Server

    Aicheler, M; Taborelli, M; Calatroni, S; Neupert, H; Wuensch, W; Sgobba, S

    2011-01-01

    Surface degradation due to cyclic thermal loading plays a major role in the Accelerating Structures (AS) of the future Compact Linear Collider (CLIC) In this article results on surface degradation of thermally cycled polycrystalline copper as a function of the orientation of surface grains are presented Samples with different grain sizes were subjected to thermal fatigue using two different methods and were then characterized using roughness measurements and Orientation Imaging Scanning-Electron-Microscopy (OIM-SEM) Samples fatigued by a pulsed laser show the same trend in the orientation-fatigue damage accumulation as the sample fatigued by pulsed Radio-Frequency-heating (RF) it is clearly shown that 11 1 1] surface grains develop significantly more damage than the surface grains oriented in {[}100] and three reasons for this behaviour are pointed out Based on observations performed near grain boundaries their role in the crack initiation process is discussed The results are in good agreement with previous f...

  15. Fatigue studies of superalloys in Japan

    International Nuclear Information System (INIS)

    Kitagawa, Masaki

    1985-01-01

    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.)

  16. 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

  17. Domain switching of fatigued ferroelectric thin films

    International Nuclear Information System (INIS)

    Tak Lim, Yun; Yeog Son, Jong; Shin, Young-Han

    2014-01-01

    We investigate the domain wall speed of a ferroelectric PbZr 0.48 Ti 0.52 O 3 (PZT) thin film using an atomic force microscope incorporated with a mercury-probe system to control the degree of electrical fatigue. The depolarization field in the PZT thin film decreases with increasing the degree of electrical fatigue. We find that the wide-range activation field previously reported in ferroelectric domains result from the change of the depolarization field caused by the electrical fatigue. Domain wall speed exhibits universal behavior to the effective electric field (defined by an applied electric field minus the depolarization field), regardless of the degree of the electrical fatigue

  18. 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.

  19. Fatigue Characteristics of Selected Light Metal Alloys

    Directory of Open Access Journals (Sweden)

    Cieśla M.

    2016-03-01

    Full Text Available The paper addresses results of fatigue testing of light metal alloys used in the automotive as well as aerospace and aviation industries, among others. The material subject to testing comprised hot-worked rods made of the AZ31 alloy, the Ti-6Al-4V two-phase titanium alloy and the 2017A (T451 aluminium alloy. Both low- and high-cycle fatigue tests were conducted at room temperature on the cycle asymmetry ratio of R=-1. The low-cycle fatigue tests were performed using the MTS-810 machine on two levels of total strain, i.e.Δεc= 1.0% and 1.2%. The high-cycle fatigue tests, on the other hand, were performed using a machine from VEB Werkstoffprufmaschinen-Leipzig under conditions of rotary bending. Based on the results thus obtained, one could develop fatigue life characteristics of the materials examined (expressed as the number of cycles until failure of sample Nf as well as characteristics of cyclic material strain σa=f(N under the conditions of low-cycle fatigue testing. The Ti-6Al-4V titanium alloy was found to be characterised by the highest value of fatigue life Nf, both in lowand high-cycle tests. The lowest fatigue life, on the other hand, was established for the aluminium alloys examined. Under the high-cycle fatigue tests, the life of the 2017A aluminium and the AZ31 magnesium alloy studied was determined by the value of stress amplitude σa. With the stress exceeding 150 MPa, it was the aluminium alloy which displayed higher fatigue life, whereas the magnesium alloy proved better on lower stress.

  20. The fatigue in the nuclear boilers

    International Nuclear Information System (INIS)

    Hutin, J.P.

    2001-01-01

    This paper presents the main conclusions concerning the presentations of the 23 november 2000 conference on fatigue damage of nuclear facilities. The author presents also some propositions of research and development programs. (A.L.B.)

  1. Fatigue strength reduction model: RANDOM3 and RANDOM4 user manual. Appendix 2: Development of advanced methodologies for probabilistic constitutive relationships of material strength models

    Science.gov (United States)

    Boyce, Lola; Lovelace, Thomas B.

    1989-01-01

    FORTRAN programs RANDOM3 and RANDOM4 are documented in the form of a user's manual. Both programs are based on fatigue strength reduction, using a probabilistic constitutive model. The programs predict the random lifetime of an engine component to reach a given fatigue strength. The theoretical backgrounds, input data instructions, and sample problems illustrating the use of the programs are included.

  2. The Identification of Fatigue Resistant and Fatigue Susceptible Individuals

    National Research Council Canada - National Science Library

    Harrison, Richard; Chaiken, Scott; Harville, Donald; Fischer, Joseph; Fisher, Dion; Whitmore, Jeff

    2008-01-01

    The present study was designed to target two specific areas regarding fatigue. The primary purpose was to begin investigations into possible genetic markers linked to fatigue resistance and fatigue susceptibility...

  3. 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...

  4. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

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

    1993-01-01

    life experiments for the same purpose. The methodology is basedon modern probabilistic concepts amd classical decision theory. The special case where the fatigue life experiments are given in terms of SN curves is considered in Particular. The proposed techniques are illustrated by an example.......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...

  5. (Thunb.), Makino on Physical Fatigue

    African Journals Online (AJOL)

    fatigue agent, but there is a need for further research on long-term use in order to show its positive effects on physical fatigue. Key words: polysaccharides from Gynostemma pentaphyllum (Thunb.) Makino; physical fatigue; forced swimming test; ...

  6. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants.

    Science.gov (United States)

    Wiest, Wolfram; Zabler, Simon; Rack, Alexander; Fella, Christian; Balles, Andreas; Nelson, Katja; Schmelzeisen, Rainer; Hanke, Randolf

    2015-11-01

    Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant-abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

  7. A case of cutaneous squamous cell carcinoma associated with small cell carcinoma of lung developing a skin metastasis on previously irradiated area

    International Nuclear Information System (INIS)

    Kohda, Mamoru; Takei, Yoji; Ueki, Hiroaki

    1983-01-01

    Squamous cell carcinoma which occurred in the penis of a 61-year-old male patient was treated surgically and by Linac (a total of 10,400 rad). However, it was not cured. Abnormal shadows in the lung and multiple liver tumor was noted one month before death. Autopsy revealed generalized metastases of pulmonary small-cell carcinoma, and persistent squamous cell carcinoma of the penis with no metastases. Skin metastasis of lung carcinoma occurred only in the area previously irradiated. (Ueda, J.)

  8. Efficacy of an Emotion-Focused Treatment for Prolonged Fatigue

    Science.gov (United States)

    Schutte, Nicola S.; Malouff, John M.; Brown, Rhonda F.

    2008-01-01

    Previous research findings have suggested a relationship between less adaptive emotional functioning and fatigue. The present study used a research design involving multiple baselines across participants to evaluate the efficacy of a new emotion-focused treatment for prolonged fatigue delivered in a cognitive behavioral therapy framework. The 13…

  9. Thermal fatigue cracking of austenitic stainless steels

    International Nuclear Information System (INIS)

    Fissolo, A.

    2001-01-01

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

  10. [Cardiological aspects of fatigue states in athletes].

    Science.gov (United States)

    Bigard, A X; Koulmann, N

    2006-11-01

    The physical load increase during training can lead to the development of clinical patterns of intolerance differing according to their severity, prognosis and reversibility. However, they always include fatigue as a key symptom. The aim of this paper is to review recent data on fatigue states in sportsmen, their clinical presentation and diagnostic orientations. A continuum exists, from acute fatigue states after one or several highly-intensive training sessions, to overreaching, associated to performances alteration which can be easily reversed, and to overtraining, representing a severe clinical pattern which can hardly be reversed. Overreaching and overtraining are characterized by a persisting fatigue state, associated to performances alteration and mood disorders. In an athlete with unexplained alteration of performances associated to physical fatigue, the medical interrogation is critical, in order to check the durable character of sportive performances alteration, to describe the fatigue and identify risk factors of occurrence of overtraining (training program intensity, mental stress, diet factors, hypoxic training, etc.). The use of a validated and adapted questionnaire as the one proposed by the French Society of Sports Medicine is valuable. In majority, in athletes and those doing sports regularly, the cardiological alert signs are rare, and the clinical examination by a specialist is poorly contributive, except for eliminating an organic cause of fatigue.

  11. Chronic fatigue in cancer patients treated with radiotherapy

    International Nuclear Information System (INIS)

    Rucinska, M.; Wojtukiewicz, M.Z.; Tokajuk, P.

    2004-01-01

    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)

  12. Chronic fatigue syndrome

    African Journals Online (AJOL)

    Chronic fatigue syndrome. Committee for Science and Education, Medical. Association of South Africa. Objective. ... Synonyms. Major controversy surrounds the name of the syndrome. In medical circles the preferred term is chronic fatigue .... urine tests using dipsticks. The above investigations should only be pursued when.

  13. Chronic fatigue syndrome

    OpenAIRE

    Reid, Steven F; Chalder, Trudie; Cleare, Anthony; Hotopf, Matthew; Wessely, Simon

    2008-01-01

    Chronic fatigue syndrome (CFS) is characterised by severe, disabling fatigue, and other symptoms including musculoskeletal pain, sleep disturbance, impaired concentration, and headaches. CFS affects between 0.006% and 3% of the population depending on the criteria used, with women being at higher risk than men.

  14. Chronic fatigue syndrome

    OpenAIRE

    Reid, Steven; Chalder, Trudie; Cleare, Anthony; Hotopf, Matthew; Wessely, Simon

    2011-01-01

    Chronic fatigue syndrome is characterised by severe, disabling fatigue, and other symptoms including musculoskeletal pain, sleep disturbance, impaired concentration, and headaches. CFS affects between 0.006% and 3% of the population depending on the criteria used, with women being at higher risk than men.

  15. Chronic fatigue syndrome

    OpenAIRE

    Cleare, Anthony J.; Reid, Steven; Chalder, Trudie; Hotopf, Matthew; Wessely, Simon

    2015-01-01

    Chronic fatigue syndrome (CFS) is characterised by severe, disabling fatigue, and other symptoms, including musculoskeletal pain, sleep disturbance, impaired concentration, and headaches. CFS affects between 0.006% and 3% of the population depending on the criteria used, with women being at higher risk than men.

  16. Perineal neuromuscular fatigue.

    Science.gov (United States)

    Deffieux, X; Hubeaux, K; Damphousse, M; Raibaut, P; Sheikh Ismael, S; Thoumie, P; Amarenco, G; Lapeyre, E; Jousse, M

    2006-07-01

    The physiology of urinary continence during stress is complex and the role of passive and active mechanisms remains unclear. Coughing leads to a contraction of urethral rhabdomyosphincter and pelvic floor muscles leading to a positive urethro-vesical gradient and continence. Neuromuscular fatigue can involve all striated muscles, including rhabdomyosphincter, peri-urethral and pelvic floor muscles. This article reviews results of studies assessing perineal muscular fatigue in urinary incontinence. A systematic review of the literature (Medline, Pascal and Embase) with use of the MESH keywords fatigue, stress, urinary incontinence, pelvic floor, urethra, urethral pressure, and muscle. Animal models have shown that the pelvic muscles (iliococcygeus and pubococcygeous) exhibit more neuromuscular fatigue than classical skeletal striated muscles (i.e. soleus muscle). Although the human external urethral sphincter is considered to be a highly fatigue-resistant muscle with its high proportion of slow muscle fibers, repeated coughing seems to lead to decreased urethral pressure in numerous women affected with stress urinary incontinence. In this case, "urethral fatigue" might be a possibility. Although few studies have focused on perineal muscular fatigue, such increased fatigue in pelvic floor muscles may play a role in the pathophysiologic features of stress urinary incontinence in women.

  17. 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

  18. Fatigue Properties of Plain Concrete under Triaxial Tension-Compression-Compression Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Dongfu Zhao

    2017-01-01

    Full Text Available Fatigue tests were performed on plain concrete under triaxial tension-compression-compression (T-C-C cyclic loading with constant and variable amplitude using a large multiaxial machine. Experimental results show that, under constant amplitude fatigue loads, the development of residual strain in the fatigue loading direction depends mostly on the lateral compressive stress ratio and is nearly independent of stress level. Under variable amplitude fatigue loads, the fatigue residual strain is related to the relative fatigue cycle and lateral compressive stress ratio but has little relationship with the loading process. To model this system, the relative residual strain was defined as the damage variant. Damage evolutions for plain concrete were established. In addition, fatigue damage analysis and predictions of fatigue remaining life were conducted. This work provides a reference for multistage fatigue testing and fatigue damage evaluation of plain concrete under multiaxial loads.

  19. Co-occurrence and associations of pain and fatigue in a community sample of Dutch adults.

    NARCIS (Netherlands)

    Creavin, S.T.; Dunn, K.M.; Mallen, C.D.; Nijrolder, I.; Windt, D.A.W.M. van der

    2010-01-01

    Widespread pain and chronic fatigue are common in the general population. Previous research has demonstrated co-occurrence of syndromes that are associated with pain and fatigue (fibromyalgia and chronic fatigue syndrome), but there is limited existing data on the co-occurrence of these symptoms in

  20. Examining fatigue in COPD

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  1. Application of strain-controlled fatigue concepts to the prediction of weldment fatigue life

    International Nuclear Information System (INIS)

    Lawrence, F.V. Jr.; Mazumdar, P.K.; Illinois Univ., Urbana

    1979-01-01

    The total fatigue life of weldments has been estimated for butt welds using strain controlled fatigue and fatigue crack propagation concepts. Key developments which facilitated these estimates were the assumption of Ksub(f max) conditions (the largest value of Ksub(f) possible for a given weld shape). The total fatigue life was estimated as the sum of a fatigue crack initiation period (cycles to obtain a 0.25 mm fatigue crack) and the fatigue crack propagation period. Mean stress relaxation effects and the fatigue properties of the actual weld zone materials were considered. Influence of welding residual stresses and material strength level were also investigated. The initiation life was found to be very sensitive to changes in Ksub(f) but not too sensitive to strength level. The importance of residual stresses and mean stress varied with material as did the fraction of total life devoted to crack initiation. Mild steels, quenched and tempered high strength low alloy steels, and aluminium alloy welds were considered. (orig.) 891 RW/orig. 892 RKD [de

  2. Assessing fibromyalgia-related fatigue: content validity and psychometric performance of the Fatigue Visual Analog Scale in adult patients with fibromyalgia.

    Science.gov (United States)

    Crawford, B K; Piault, E C; Lai, C; Bennett, R M

    2011-01-01

    To document 1) the content validity and 2) measure improvements in fatigue, using the Fatigue Visual Analogue Scale (VAS) assessment tool in patients with fibromyalgia. The relevance and comprehensiveness of the Fatigue VAS were tested through a qualitative analysis of 20 subjects' verbatim transcripts from semi-structured qualitative interviews. Data from two randomised, controller trials in fibromyalgia (n=1121) were used to conduct correlation analyses with the Fatigue and Tiredness items from the Fibromyalgia Impact Questionnaire (FIQ) and the Short Form-36 Vitality scale. Known-groups and cross classification analyses were conducted to demonstrate the ability to measure improvement in fatigue using the Fatigue VAS. All subjects spontaneously reported that fatigue was an important symptom to capture in fibromyalgia. The Fatigue VAS was well understood by most subjects (n=18/20). High correlations (Pearson r>0.75) and good agreement (k>0.66) were found between the Fatigue VAS and the FIQ tiredness items no. 16 and 17 and SF-36™ Vitality scale. In both clinical trials there was a substantial separation of approximately 20 points on the mean change in the Fatigue VAS score between responders (>30% improvement in pain VAS) and non-responders. Previous studies have confirmed that fatigue is a major component of the fibromyalgia experience. This current study reports that fibromyalgia patients spontaneously rated fatigue as a highly significant feature of their illness, and supports the use of the Fatigue VAS as a valid questionnaire in fibromyalgia clinical trials.

  3. Review on the application of physiological and biomechanical measurement methods in driving fatigue detection

    Directory of Open Access Journals (Sweden)

    Kadek Heri Sanjaya

    2016-07-01

    Full Text Available Previous studies have identified driving fatigue as the main cause of road traffic accidents, therefore, the aim of this literature review is to explore the characteristics of driving fatigue both physically and mentally as well as to explore the technology available to measure the process of fatigue physiologically. We performed e-searching in the field of fatigue detection methods through keywords tracking. The instruments studied have their own strength and weakness, and some are intrusive while the others are non-intrusive. The accuracy and stability of measurements are also varied between those instruments. In order to create more reliable fatigue detection methods, it is necessary to involve more instruments with an inter-disciplinary approach. Our intention is to make this study as a stepping stone for a more comprehensive in-vehicle real-time man-machine interaction study. Such study will not only be useful to prevent traffic accidents but also to bridge man and machine communication in the vehicle control along with developing newer technology in the field of vehicle automation.

  4. Development of system based code for integrity of FBR. Fundamental probabilistic approach, Part 1: Model calculation of creep-fatigue damage (Research report)

    International Nuclear Information System (INIS)

    Kawasaki, Nobuchika; Asayama, Tai

    2001-09-01

    Both reliability and safety have to be further improved for the successful commercialization of FBRs. At the same time, construction and operation costs need to be reduced to a same level of future LWRs. To realize compatibility among reliability, safety and, cost, the Structural Mechanics Research Group in JNC started the development of System Based Code for Integrity of FBR. This code extends the present structural design standard to include the areas of fabrication, installation, plant system design, safety design, operation and maintenance, and so on. A quantitative index is necessary to connect different partial standards in this code. Failure probability is considered as a candidate index. Therefore we decided to make a model calculation using failure probability and judge its applicability. We first investigated other probabilistic standards like ASME Code Case N-578. A probabilistic approach in the structural integrity evaluation was created based on these results, and also an evaluation flow was proposed. According to this flow, a model calculation of creep-fatigue damage was performed. This trial calculation was for a vessel in a sodium-cooled FBR. As the result of this model calculation, a crack initiation probability and a crack penetration probability were found to be effective indices. Last we discussed merits of this System Based Code, which are presented in this report. Furthermore, this report presents future development tasks. (author)

  5. Creep-fatigue damage assessment by subsequent fatigue straining

    International Nuclear Information System (INIS)

    Yaguchi, M.; Nakamura, T.; Ishikawa, A.; Asada, Y.

    1993-01-01

    A series of creep-fatigue tests has been conducted with Modified 9Cr-1Mo steel at 600 deg. C in a high vacuum environment of 0.1mPa to assess an accumulation of creep-fatigue damage. In these tests, each test specimen has been subjected to prior creep-fatigue loading followed by subsequent fatigue loading or prior fatigue loading followed by subsequent creep-fatigue loading. A linear summation of cumulative damage of fatigue and creep life fraction is smaller than unity for the former case, and larger than unity for the latter case. SEM observation was conducted and it was shown that in the case of prior creep-fatigue loading, crack mode transforms from transgranular to intergranular type with the increase of the number of cycles of prior creep-fatigue loading, while crack mode is generally intergranular in the case of prior fatigue loading. (author)

  6. Fatigue Management (La Gestion de la Fatigue)

    Science.gov (United States)

    1991-12-01

    Management Pre’face Etant donne la tenidance de plus en plus marque ~e vets le maintien en service des aironefs au-delak des dates lintites...transport aircraft designed prototype sade its first flight one year about 20 years ago; from the fatigue point later. The results of the flight testing

  7. Effect of loading parameter on fretting fatigue

    Science.gov (United States)

    Kowser, Md. Arefin; Chowdhury, Mohammad Asaduzzaman; Shah, Quazi Md. Zobaer

    2017-06-01

    Fretting fatigue has become one of the major concern in the recent few decades since developed designs both structure's and complex engineering are facing with fatigue accompanied by friction. In this study, load factors as normal and bending forces influence on stress distribution along contact surface as well as fatigue life has been experimented by FEM analysis. Fatigue life is influenced prominently by variable fretting loads than variable tensile loadings. Maximum Von mises Stress and strain shows uniform horizontal straight line is found for maximum loading while for both type of bending, minimum loads yield the same character. It has been observed that stress distribution is more uniform for varying bending loads when variable fretting loads yield stress singularity nearer to the tip of contact between fretting pad and beam.

  8. Ultrasonic fatigue of a high strength steel

    Science.gov (United States)

    Koster, M.; Wagner, G.; Eifler, D.

    2010-07-01

    At the Institute of Materials Science and Engineering at the University of Kaiserslautern an ultrasonic testing system for the fatigue assessment of metallic materials in the very high cycle fatigue (VHCF) regime was developed. The ultrasonic testing system allows to control the test and to measure detailed fatigue data. The achieved results can be used to describe the cyclic deformation behaviour of wheel steels at ultrasonic frequencies. In load increase tests (LIT), the critical stress amplitude can be determined, which leads to a defined change of process parameters like generator power, dissipated energy and specimen temperature. With SEM investigations it was proved that the change of the process parameters correlates with irreversible changes in the microstructure. It can be shown that the stress amplitude, leading to first irreversible changes in the microstructure, strongly depends on the depth position within the original wheel rim. New and basic results on the fatigue mechanisms of high strength steels in the VHCF-regime can be achieved.

  9. Radiotherapy-related fatigue.

    Science.gov (United States)

    Jereczek-Fossa, Barbara Alicja; Marsiglia, Hugo Raul; Orecchia, Roberto

    2002-03-01

    Radiotherapy-induced fatigue is a common early and chronic side-effect of irradiation, reported in up to 80 and 30% of patients during radiation therapy and at follow-up visits, respectively. It is frequently underestimated by medical and nursing staff, only about 50% of patients discuss it with a physician and in one fourth of cases any intervention is proposed to the patient. The patients rarely expect fatigue to be a side-effect of treatment. The etiology of this common symptom, its correlates and prevalence are poorly understood. In numerous studies the level and time course of fatigue was demonstrated to depend on the site of tumor and treatment modalities. For example, psychological mechanisms have been proposed to explain fatigue in women receiving irradiation for early breast cancer, whereas decline in neuromuscular efficiency rather than psychological reasons can lead to the fatigue observed in patients undergoing radiotherapy for prostate cancer. Fatigue can affect global quality of life more than pain, sexual dysfunction and other cancer- or treatment-related symptoms. Several interventions have been tested in the management of radiotherapy-related fatigue and some randomized studies have been recently published. Although an optimal method has not yet been established, some promising results have been reported with relaxation therapy, group psychotherapy, physical exercise and sleep. Further methodologically correct studies are warranted to define better the causes, optimal prevention and management of this symptom.

  10. 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)

  11. Prolonged unexplained fatigue in paediatrics

    NARCIS (Netherlands)

    Bakker, R.J.

    2010-01-01

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

  12. Perceived fatigue following pediatric burns

    NARCIS (Netherlands)

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

    2017-01-01

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

  13. Perceived fatigue following pediatric burns

    NARCIS (Netherlands)

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

    2017-01-01

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

  14. Hyperthermia and fatigue

    DEFF Research Database (Denmark)

    Nybo, Lars

    2008-01-01

    of the cardiovascular function, which eventually reduces arterial oxygen delivery to the exercising muscles. Accordingly, aerobic energy turnover is impaired and anaerobic metabolism provokes peripheral fatigue. In contrast, metabolic disturbances of muscle homeostasis are less important during prolonged exercise...... 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...... and peripheral physiological factors also needs to be considered....

  15. Development of a rapid lateral flow immunoassay test for detection of exosomes previously enriched from cell culture medium and body fluids.

    Science.gov (United States)

    Oliveira-Rodríguez, Myriam; López-Cobo, Sheila; Reyburn, Hugh T; Costa-García, Agustín; López-Martín, Soraya; Yáñez-Mó, María; Cernuda-Morollón, Eva; Paschen, Annette; Valés-Gómez, Mar; Blanco-López, Maria Carmen

    2016-01-01

    Exosomes are cell-secreted nanovesicles (40-200 nm) that represent a rich source of novel biomarkers in the diagnosis and prognosis of certain diseases. Despite the increasingly recognized relevance of these vesicles as biomarkers, their detection has been limited due in part to current technical challenges in the rapid isolation and analysis of exosomes. The complexity of the development of analytical platforms relies on the heterogeneous composition of the exosome membrane. One of the most attractive tests is the inmunochromatographic strips, which allow rapid detection by unskilled operators. We have successfully developed a novel lateral flow immunoassay (LFIA) for the detection of exosomes based on the use of tetraspanins as targets. We have applied this platform for the detection of exosomes purified from different sources: cell culture supernatants, human plasma and urine. As proof of concept, we explored the analytical potential of this LFIA platform to accurately quantify exosomes purified from a human metastatic melanoma cell line. The one-step assay can be completed in 15 min, with a limit of detection of 8.54×10(5) exosomes/µL when a blend of anti-CD9 and anti-CD81 were selected as capture antibodies and anti-CD63 labelled with gold nanoparticles as detection antibody. Based on our results, this platform could be well suited to be used as a rapid exosome quantification tool, with promising diagnostic applications, bearing in mind that the detection of exosomes from different sources may require adaptation of the analytical settings to their specific composition.

  16. Development of a rapid lateral flow immunoassay test for detection of exosomes previously enriched from cell culture medium and body fluids

    Directory of Open Access Journals (Sweden)

    Myriam Oliveira-Rodríguez

    2016-08-01

    Full Text Available Exosomes are cell-secreted nanovesicles (40–200 nm that represent a rich source of novel biomarkers in the diagnosis and prognosis of certain diseases. Despite the increasingly recognized relevance of these vesicles as biomarkers, their detection has been limited due in part to current technical challenges in the rapid isolation and analysis of exosomes. The complexity of the development of analytical platforms relies on the heterogeneous composition of the exosome membrane. One of the most attractive tests is the inmunochromatographic strips, which allow rapid detection by unskilled operators. We have successfully developed a novel lateral flow immunoassay (LFIA for the detection of exosomes based on the use of tetraspanins as targets. We have applied this platform for the detection of exosomes purified from different sources: cell culture supernatants, human plasma and urine. As proof of concept, we explored the analytical potential of this LFIA platform to accurately quantify exosomes purified from a human metastatic melanoma cell line. The one-step assay can be completed in 15 min, with a limit of detection of 8.54×105 exosomes/µL when a blend of anti-CD9 and anti-CD81 were selected as capture antibodies and anti-CD63 labelled with gold nanoparticles as detection antibody. Based on our results, this platform could be well suited to be used as a rapid exosome quantification tool, with promising diagnostic applications, bearing in mind that the detection of exosomes from different sources may require adaptation of the analytical settings to their specific composition.

  17. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    Science.gov (United States)

    Arakere, Nagaraj K.; Swanson, Gregory R.

    2000-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine engines is a pervasive problem affecting a wide range of components and materials. HCF is currently the primary cause of component failures in gas turbine aircraft engines. Turbine blades in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys. Single-crystal Nickel-base superalloys were developed to provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys previously used in the production of turbine blades and vanes. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. PWA1493, identical to PWA1480, but with tighter chemical constituent control, is used in the NASA SSME (Space Shuttle Main Engine) alternate turbopump, a liquid hydrogen fueled rocket engine. Objectives for this paper are motivated by the need for developing failure criteria and fatigue life evaluation procedures for high temperature single crystal components, using available fatigue data and finite element modeling of turbine blades. Using the FE (finite element) stress analysis results and the fatigue life relations developed, the effect of variation of primary and secondary crystal orientations on life is determined, at critical blade locations. The most advantageous crystal orientation for a given blade design is determined. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to optimize blade design by increasing its resistance to fatigue crack growth without adding additional weight or cost.

  18. Fatigue and voluntary utilization of automation in simulated driving.

    Science.gov (United States)

    Neubauer, Catherine; Matthews, Gerald; Langheim, Lisa; Saxby, Dyani

    2012-10-01

    A driving simulator was used to assess the impact on fatigue, stress, and workload of full vehicle automation that was initiated by the driver. Previous studies have shown that mandatory use of full automation induces a state of "passive fatigue" associated with loss of alertness. By contrast, voluntary use of automation may enhance the driver's perceptions of control and ability to manage fatigue. Participants were assigned to one of two experimental conditions, automation optional (AO) and nonautomation (NA), and then performed a 35 min, monotonous simulated drive. In the last 5 min, automation was unavailable and drivers were required to respond to an emergency event. Subjective state and workload were evaluated before and after the drive. Making automation available to the driver failed to alleviate fatigue and stress states induced by driving in monotonous conditions. Drivers who were fatigued prior to the drive were more likely to choose to use automation, but automation use increased distress, especially in fatigue-prone drivers. Drivers in the AO condition were slower to initiate steering responses to the emergency event, suggesting optional automation may be distracting. Optional, driver-controlled automation appears to pose the same dangers to task engagement and alertness as externally initiated automation. Drivers of automated vehicles may be vulnerable to fatigue that persists when normal vehicle control is restored. It is important to evaluate automated systems' impact on driver fatigue, to seek design solutions to the issue of maintaining driver engagement, and to address the vulnerabilities of fatigue-prone drivers.

  19. Developing resources to support the diagnosis and management of Chronic Fatigue Syndrome/Myalgic Encephalitis (CFS/ME in primary care: a qualitative study

    Directory of Open Access Journals (Sweden)

    Hannon Kerin

    2012-09-01

    Full Text Available Abstract Background NICE guidelines emphasise the need for a confident, early diagnosis of Chronic Fatigue Syndrome/ Myalgic Encephalitis (CFS/ME in Primary Care with management tailored to the needs of the patient. Research suggests that GPs are reluctant to make the diagnosis and resources for management are currently inadequate. This study aimed to develop resources for practitioners and patients to support the diagnosis and management of CFS/ME in primary care. Methods Semi structured interviews were conducted with patients, carers, GPs, practice nurses and CFS/ME specialists in North West England. All interviews were audio recorded, transcribed and analysed qualitatively using open explorative thematic coding. Two patient involvement groups were consulted at each stage of the development of resources to ensure that the resources reflect everyday issues faced by people living with CFS/ME. Results Patients and carers stressed the importance of recognising CFS/ME as a legitimate condition, and the need to be believed by health care professionals. GPs and practice nurses stated that they do not always have the knowledge or skills to diagnose and manage the condition. They expressed a preference for an online training package. For patients, information on getting the most out of a consultation and the role of carers was thought to be important. Patients did not want to be overloaded with information at diagnosis, and suggested information should be given in steps. A DVD was suggested, to enable information sharing with carers and family, and also for those whose symptoms act as a barrier to reading. Conclusion Rather than use a top-down approach to the development of training for health care practitioners and information for patients and carers, we have used data from key stakeholders to develop a patient DVD, patient leaflets to guide symptom management and a modular e-learning resource which should equip GPs to diagnose and manage CFS

  20. Experiences of Fatigue at Sea

    DEFF Research Database (Denmark)

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

    2016-01-01

    Fatigue has negative impacts on the general working population as well as on seafarers. In order to study seafarers’ fatigue, a questionnaire-base survey was conducted to gain information about potential risk factors for fatigue and construct indexes indicating fatigue. The study applies T-test t......-test to compare strata of seafarers to analyse work and sleep patterns in global seafaring. Qualitative analysis are also employed to explore the impacts of fatigue on seafarer’s occupational health and safety....

  1. The PROMIS FatigueFM Profile: a self-report measure of fatigue for use in fibromyalgia.

    Science.gov (United States)

    Kratz, Anna L; Schilling, Stephen; Goesling, Jenna; Williams, David A

    2016-07-01

    Fibromyalgia (FM) is characterized by myriad symptoms and problems. Fatigue is one of the most common, distressing, and disabling symptoms in FM. The purpose of this study was to use fatigue item banks that were developed as part of the Patient-Reported Outcomes Measurement Information System (PROMIS) to devise a self-report measure of fatigue for use in individuals with FM. A sample of 532 adults with FM (age range = 18-77, 96.1 % female) completed the PROMIS fatigue item bank. Factor analyses and item response theory analyses were used to identify dimensionality and optimally performing items. These data were used in combination with clinical input to select items for a fatigue self-report measure for use in FM. Factor analyses revealed four distinct factors in the PROMIS fatigue item bank; items for each univariate subscale were identified by selecting four items with high item information values. A 16-item measure, the PROMIS FatigueFM Profile, consisting of four 4-item short forms reflecting fatigue experience ("intensity") and fatigue impact in three subdomains-social, cognitive, and motivation-was created. The new PROMIS FatigueFM Profile short forms showed excellent internal reliability, low ceiling and floor effects, and equivalent or higher test information compared to the standard 4- and 7-item PROMIS fatigue short forms. The newly developed PROMIS FatigueFM Profile, a 16-item measure consisting of four 4-item short forms of self-reported fatigue severity, shows early evidence of good psychometric characteristics, provides the ability to use short forms that assess distinct aspects of fatigue experience and fatigue impact, and demonstrates equivalent or higher levels of test information compared to standard PROMIS fatigue short forms with similar number of items. The PROMIS FatigueFM Profile indicated fatigue experience and impact levels approximately 1.5 standard deviations above the normative sample mean across all short forms. Future work to

  2. Fatigue and its Effect on Performance in Military Environments

    Science.gov (United States)

    2007-01-01

    growth hormone ( HGH ). Evolving over millennia, this circadian pattern is consistent across mammalian species, including humans, and is highly...Fatigue Avoidance Scheduling Tool or FAST ™ Performance Under Stress.indb 240 26/09/2007 17:55:52 Fatigue and its Effect on Performance in Military...Using the Sleep and Fatigue, Task Effectiveness (SAFTE) model developed by Hursh and others, FAST ™ uses the 72 hour sleep history of an individual to

  3. 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’ ... 19004 Phone: (855) 807-6386 email Facebook Twitter Instagram YouTube Contact Us Privacy Policy Site Credits Terms ...

  4. 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...... 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...

  5. 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...

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

    Directory of Open Access Journals (Sweden)

    Mansur A. Kutlubaev

    2013-03-01

    Full Text Available Background: Fatigue is a common and distressing consequence of stroke, and the aetiology of post-stroke fatigue (PSF is poorly understood. It is unclear whether chronic brain changes [cerebral atrophy and white matter lesions (WML], stroke lesion location or certain clinical features are related to its development. The aim of this study was to identify, in patients with acute stroke, whether features in different brain regions on routine CT imaging or routinely collected clinical features predicted PSF at 1 month. Methods: In total, 107 patients (62% male with acute ischaemic or haemorrhagic stroke were assessed for fatigue (Fatigue Assessment Scale, anxiety and depression (Hospital Anxiety and Depression Scale at 1 month. Admission brain CT was rated using a structured scoring system for (i severity of atrophy and (ii severity of WML in different regions of the brain, and (iii site of acute and previous vascular lesions. Results: Cerebral atrophy of mild or greater severity was present in 84 patients (77.5% and WML of mild or greater severity was present in 54 patients (50.5% in at least one of the evaluated brain regions. There was no association between PSF and severity of atrophy or WML, or presence of acute or previous vascular lesions. We used the Oxfordshire Community Stroke Project (OCSP classification to explore the possible influence of lesion location because a minority of the patients (37.4% had visible acute lesions. Fatigue scores were higher in patients with clinically diagnosed posterior strokes (p = 0.046, in females (p = 0.05 and in those with higher depression and anxiety scores (ρ = 0.52; p 2 = 0.254. Stroke subtype (according to the OCSP classification was marginally predictive (β = 0.17; p = 0.05 and sex was not statistically significant (β = 0.15; p = 0.08. Conclusions: Features on routine post-stroke CT do not appear to associate with fatigue at 1 month. However, clinically diagnosed posterior strokes as well as female

  7. A survey of fatigue monitoring in the nuclear power industry

    International Nuclear Information System (INIS)

    Ware, A.G.

    1991-01-01

    The original design of nuclear power plants addressed fatigue concerns by including calculations of projected fatigue usage for specific components; the calculations were based on estimates of the number and severity of expected transients over the 40-year design life of the plants. In some cases, the transients occurring in the plants are not as severe as was anticipated in the original design analyses, while in other cases events have occurred that were not anticipated in the design basis documents. Field failures caused by fatigue have identified some of those cases. In response, several organizations in the United States and overseas have developed fatigue monitoring programs to more accurately estimate the fatigue usage. One basic approach consists of reconstructing the fatigue usage to date based on the transients recorded in the operating history instead of those projected in the design documents. Another approach includes monitoring the plant instrumentation to determine actual values for parameters such as temperature and pressure and using the measured values in the fatigue usage calculations instead of the values projected in the design documents. The use of existing plant instrumentation to measure temperature, pressure, flow rate, etc., along with the incorporation of conservative assumptions, had generally proven adequate for estimating fatigue usage; however, in some cases additional instrumentation installed for local monitoring can provide a more accurate estimate, especially where thermal stratification is known to occur. Fatigue monitoring can aid in identifying fatigue concerns not anticipated in the original design and for reducing the excessive conservatism in some of the original design calculations so that the fatigue lives of these components can be justified as they age. Fatigue monitoring can also assist efforts to reduce ongoing fatigue usage through design modifications and operating procedure changes

  8. The Eukaryotic Microbiome: Origins and Implications for Fetal and Neonatal life note bene: previous titles: The Microbiome in the Development of Terrestrial Life,and,The Origins and Development of the Neonatal Microbiome

    Directory of Open Access Journals (Sweden)

    William B. Miller

    2016-09-01

    Full Text Available All eukaryotic organisms are holobionts representing complex collaborations between the entire microbiome of each eukaryote and its innate cells. These linked constituencies form complex localized and interlocking ecologies in which the specific microbial constituents and their relative abundance differ substantially according to age and environmental exposures. Rapid advances in microbiology and genetic research techniques have uncovered a significant previous underestimate of the extent of that microbial contribution and its metabolic and developmental impact on holobionts. Therefore, a re-calibration of the neonatal period is suggested as a transitional phase in development that includes the acquisition of consequential collaborative microbial life from extensive environmental influences. These co-dependent, symbiotic relationships formed in the fetal and neonatal stages extend into adulthood and even across generations.

  9. Attenuated fatigue in slow twitch skeletal muscle during isotonic exercise in rats with chronic heart failure.

    Directory of Open Access Journals (Sweden)

    Morten Munkvik

    Full Text Available During isometric contractions, slow twitch soleus muscles (SOL from rats with chronic heart failure (chf are more fatigable than those of sham animals. However, a muscle normally shortens during activity and fatigue development is highly task dependent. Therefore, we examined the development of skeletal muscle fatigue during shortening (isotonic contractions in chf and sham-operated rats. Six weeks following coronary artery ligation, infarcted animals were classified as failing (chf if left ventricle end diastolic pressure was >15 mmHg. During isoflurane anaesthesia, SOL with intact blood supply was stimulated (1s on 1s off at 30 Hz for 15 min and allowed to shorten isotonically against a constant afterload. Muscle temperature was maintained at 37°C. In resting muscle, maximum isometric force (F(max and the concentrations of ATP and CrP were not different in the two groups. During stimulation, F(max and the concentrations declined in parallel sham and chf. Fatigue, which was evident as reduced shortening during stimulation, was also not different in the two groups. The isometric force decline was fitted to a bi-exponential decay equation. Both time constants increased transiently and returned to initial values after approximately 200 s of the fatigue protocol. This resulted in a transient rise in baseline tension between stimulations, although this effect which was less prominent in chf than sham. Myosin light chain 2s phosphorylation declined in both groups after 100 s of isotonic contractions, and remained at this level throughout 15 min of stimulation. In spite of higher energy demand during isotonic than isometric contractions, both shortening capacity and rate of isometric force decline were as well or better preserved in fatigued SOL from chf rats than in sham. This observation is in striking contrast to previous reports which have employed isometric contractions to induce fatigue.

  10. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants

    International Nuclear Information System (INIS)

    Wiest, Wolfram; Zabler, Simon; Rack, Alexander; Fella, Christian; Balles, Andreas; Nelson, Katja; Schmelzeisen, Rainer; Hanke, Randolf

    2015-01-01

    Results of a novel in situ microradiography and microtomography setup for the study of fatigue processes are presented. This setup is optimized for the requirements of dental implants and use at synchrotron imaging beamlines. Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant–abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens

  11. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants

    Energy Technology Data Exchange (ETDEWEB)

    Wiest, Wolfram; Zabler, Simon, E-mail: simon.zabler@physik.uni-wuerzburg.de [University of Würzburg (Germany); Rack, Alexander [European Synchrotron Radiation Facility (France); Fella, Christian; Balles, Andreas [University of Würzburg (Germany); Nelson, Katja; Schmelzeisen, Rainer [Medical Centre – University of Freiburg (Germany); Hanke, Randolf [University of Würzburg (Germany); Fraunhofer EZRT, Fürth (Germany)

    2015-10-09

    Results of a novel in situ microradiography and microtomography setup for the study of fatigue processes are presented. This setup is optimized for the requirements of dental implants and use at synchrotron imaging beamlines. Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant–abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

  12. 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.

  13. Multiaxial creep-fatigue rules

    International Nuclear Information System (INIS)

    Spindler, M.W.; Hales, R.; Ainsworth, R.A.

    1997-01-01

    Within the UK, a comprehensive procedure, called R5, is used to assess the high temperature response of structures. One part of R5 deals with creep-fatigue initiation, and in this paper we describe developments in this part of R5 to cover multiaxial stress states. To assess creep-fatigue, damage is written as the linear sum of fatigue and creep components. Fatigue is assessed using Miner's law with the total endurance split into initiation and growth cycles. Initiation is assessed by entering the curve of initiation cycles vs strain range using a Tresca equivalent strain range. Growth is assessed by entering the curve of growth cycles vs strain range using a Rankine equivalent strain range. The number of allowable cycles is obtained by summing the initiation and growth cycles. In this way the problem of defining an equivalent strain range applicable over a range of endurance is avoided. Creep damage is calculated using ductility exhaustion methods. In this paper we address two aspects; first, the nature of stress relaxation and, hence, accumulated creep strain in multiaxial stress fields; secondly, the effect of multiaxial stress on creep ductility. The effect of multiaxial stress state on creep ductility has been examined using experimental data and mechanistic models. Good agreement is demonstrated between an empirical description of test data and a cavity growth model, provided a simple nucleation criterion is included. A simple scaling factor is applied to uniaxial creep ductility, defined as a function of stress state. The factor is independent of the cavity growth mechanisms and yields a value of equivalent strain which can be conveniently used in determining creep damage by ductility exhaustion. (author). 14 refs, 4 figs

  14. Comparison between the Eurocode for fatigue of steel structures, en 1993-1-9, and the Eurocode for fatigue of aluminium structures, en 1999-1-3

    NARCIS (Netherlands)

    Maljaars, J.; Lukić, M.; Soetens, F.

    2013-01-01

    The fatigue behaviour of aluminium shows not only many similarities, but also some differences with the fatigue behaviour of steel. There exist separate Eurocodes for the fatigue design of steel and of aluminium structures, EN1993-1-9 and EN1999-1-3, respectively. The latter standard was developed

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

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A

    2001-07-01

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

  16. Application of fatigue monitoring system in PWR nuclear power plant

    International Nuclear Information System (INIS)

    Piao Lei

    2014-01-01

    Fatigue failure is one form of equipment failure of nuclear power plant, influencing equipment lifetime and lifetime extension. Fatigue monitoring system can track real thermal transient at fatigue sensitive components, establish a basis for fatigue analyses based on realistic operating loads, identify unexpected operational transients, optimize the plant behavior by improved operating modes, provide supporting data for lifetime management, enhance security of plant and reduce economical loss. Fatigue monitoring system has been applied in many plants and is required to be applied in Generation-III nuclear power plant. It is necessary to develop the fatigue monitoring system with independent intellectual property rights and improve the competitiveness of domestic Generation-III nuclear power technology. (author)

  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.

  18. Nonlinear aspects of structural fatigue damage assessment and accumulation

    International Nuclear Information System (INIS)

    Leis, B.N.

    1977-01-01

    The present paper reviews a recently developed concept for structural fatigue analysis which is capable of accounting for nonlinearities in both the above noted transformations. It is shown that, for cases where the local stressing and straining is proportional, the multiplicity of initiation sites and mechanisms observed to dominate structural fatigue resistance can be explained in terms of these additional nonlinearities. The ability of current concepts for structural fatigue analysis which account for nonlinear action to handle situaions where nonproportional stressing occurs in fatigue critical locations is next examined. Limitations in the assumptions made in fatigue analysis are shown to essentially preclude the application of present technology to that class of problems. A new approach whereby the present fatigue analysis procedures based on a deformation-type plasticity analysis can be extended to handle the nonproportional cycling by their application on a 'memory event' by 'memory event' basis is postulated and discussed in the context of a simple component

  19. A State-of-the-Art Review on Fatigue Life Assessment of Steel Bridges

    Directory of Open Access Journals (Sweden)

    X. W. Ye

    2014-01-01

    Full Text Available Fatigue is among the most critical forms of damage potentially occurring in steel bridges, while accurate assessment or prediction of the fatigue damage status as well as the remaining fatigue life of steel bridges is still a challenging and unsolved issue. There have been numerous investigations on the fatigue damage evaluation and life prediction of steel bridges by use of deterministic or probabilistic methods. The purpose of this review is devoted to presenting a summary on the development history and current status of fatigue condition assessment of steel bridges, containing basic aspects of fatigue, classical fatigue analysis methods, data-driven fatigue life assessment, and reliability-based fatigue condition assessment.

  20. Fatigued patients with multiple sclerosis can be discriminated from healthy controls by the recordings of a newly developed measurement system (FAMOS)

    DEFF Research Database (Denmark)

    Yu, Fei; Bilberg, Arne; Dalgas, Ulrik

    2013-01-01

    during the execution of functional (36 m walk test, 5- and 50-repetition sit-to-stand test) and cognitive (short-term memory tests) tests. Furthermore, oxygen saturation (SPO(2)) was measured during the functional and cognitive tests and during rest periods between these tests. RESULTS: Recordings from...... FAMOS indicate that fatigued MS patients have reduced standard deviation (SD) of the heart rate (HR) during the short-term memory test, reduced high frequency (HF) component power spectrum (representing parasympathetic activation) at rest after walk test, and higher ratio of low frequency (LF) to HF (LF....../HF) during 50-repetition sit-to-stand test. CONCLUSIONS: FAMOS recordings can discriminate fatigued MS patients from healthy controls. The data indicate that fatigued MS patients have vagus nerve dysfunction during cognitive tests and disturbed sympathovagal balance during stressful physical tests. [Box: see...

  1. Psychometric evaluation of the EORTC computerized adaptive test (CAT) fatigue item pool

    DEFF Research Database (Denmark)

    Petersen, Morten Aa; Giesinger, Johannes M; Holzner, Bernhard

    2013-01-01

    Fatigue is one of the most common symptoms associated with cancer and its treatment. To obtain a more precise and flexible measure of fatigue, the EORTC Quality of Life Group has developed a computerized adaptive test (CAT) measure of fatigue. This is part of an ongoing project developing a CAT v...

  2. Influence of surface conditions on fatigue strength through the numerical simulation of microstructure; Etude par simulation numerique de la microstructure de l'influence de l'etat de surface sur la resistance a la fatigue d'un acier 304L

    Energy Technology Data Exchange (ETDEWEB)

    Le Pecheur, A.; Clavel, M.; Rey, C.; Bompard, P. [Laboratoire MSSMat, UMR 8579 CNRS, Ecole Centrale Paris (France); Le Pecheur, A.; Curtit, F.; Stephan, J.M. [Departement MMC, EDF RD, Site des Renardieres (France)

    2010-11-15

    A thermal fatigue test (INTHERPOL) was developed by EDF in order to study the initiation of cracks. These tests are carried out on tubular specimens under various thermal loadings and surface finish qualities in order to give an account of these parameters on crack initiation. The main topic of this study is to test the sensitivity of different fatigue criteria to surface conditions using a micro/macro modelling approach. Therefore a 304L polycrystalline aggregate, used for cyclic plasticity based FE modelling, have been considered as a Representative Volume Element located at the surface and subsurface of the test tube. This aggregate has been cyclically strained according to the results issued from FE simulation of INTHERPOL thermal fatigue experiment. Different surface parameters have been numerically simulated: effects of local microstructure and of grains orientation, effects of machining: metallurgical prehardening, residual stress gradient, and surface roughness. Three different fatigue criteria (Manson Coffin, Fatemi Socie and dissipated energy types), previously fitted at a macro-scale for thermal fatigue of 304L, have been computed at a meso scale, in order to show the surface 'hot spots' features and test the sensitivity of these three criteria to different surface conditions. Results show that grain orientation and neighbouring play an important role on the location of hot spots, and also that the positive effect of pre-straining and the negative effect of roughness on fatigue life are not all similarly predicted by these different fatigue criteria. (authors)

  3. Advances in fatigue lifetime predictive techniques; Proceedings of the Symposium, San Francisco, CA, Apr. 24, 1990

    International Nuclear Information System (INIS)

    Mitchell, M.R.; Landgraf, R.W.

    1992-01-01

    Recent progress in the development of methods to predict fatigue performance of materials and structures is reviewed. Attention is given to general approaches to fatigue mechanics, elevated temperature phenomena, spectrum loading, the multiaxial behavior, and applications. Particular attention is given to a fracture-mechanics-based model for cumulative damage assessment, thermo-mechanical fatigue life prediction methods, a probabilistic fracture mechanics approach for structural reliability assessment of space flight systems, a multiaxial fatigue life estimation technique, plasticity and fatigue damage modeling of severely loaded tubing, damage evaluation in composite materials using thermographic stress analysis, and fatigue lifetime monitoring in power plants

  4. Creep-fatigue damage assessment by subsequent fatigue straining

    International Nuclear Information System (INIS)

    Yaguchi, Masatsugu; Nakamura, Toshiya; Ishikawa, Akiyoshi; Asada, Yasuhide

    1993-01-01

    A series of creep-fatigue tests has been conducted with Modified 9Cr-1Mo steel at 600 C in a high vacuum environment of 0.1 mPa to assess an accumulation of creep-fatigue damage. In these tests, each test specimen has been subjected to prior creep-fatigue loading followed by subsequent fatigue loading or prior fatigue loading followed by subsequent creep-fatigue loading. A linear summation of cumulative damage of fatigue and creep life fraction was smaller than unity for the former case, and larger than unity for the latter case. Scanning electron microscopic observation showed that in the case of prior creep-fatigue loading, a crack propagated from inclusions around which cavities were observed and its appearance transformed from transgranular to intergranular type with the increase of the number of cycles of prior creep-fatigue loading, while crack mode was predominantly intergranular in the case of prior fatigue loading. It was suggested that in the case of prior creep-fatigue loading, the fatigue life becomes shorter than that predicted by the linear rule due to early initiation of a crack caused from the cavity creation. In the case of prior fatigue loading, the crack propagates different courses in each loading to lead to the life fraction which is larger than unity

  5. Fatigue monitoring desktop guide

    International Nuclear Information System (INIS)

    Woods, K.; Thomas, K.

    2012-01-01

    The development of a program for managing material aging (MMG) in the nuclear industry requires a new and different perspective. The classical method for MMG is cycle counting, which has been shown to have limited success. The classical method has been successful in satisfying the ductile condition per the America Society of Mechanical Engineers' (ASME) design criteria. However, the defined material failure mechanism has transformed from through-wall cracking and leakage (ASME) to crack initiation (NUREG-6909). This transformation is based on current industry experience with material degradation early in plant life and can be attributed to fabrication issues and environment concerns where cycle counting has been unsuccessful. This new perspective provides a different approach to cycle counting that incorporates all of the information about the material conditions. This approach goes beyond the consideration of a static analysis and includes a dynamic assessment of component health, which is required for operating plants. This health definition should consider fabrication, inspections, transient conditions and industry operating experience. In addition, this collection of information can be transparent to a broader audience that may not have a full understanding of the system design or the potential causes of early material degradation. This paper will present the key points that are needed for a successful fatigue monitoring desktop guide. (authors)

  6. Dangerous intersections? A review of studies of fatigue and distraction in the automated vehicle.

    Science.gov (United States)

    Matthews, Gerald; Neubauer, Catherine; Saxby, Dyani J; Wohleber, Ryan W; Lin, Jinchao

    2018-04-10

    The impacts of fatigue on the vehicle driver may change with technological advancements including automation and the increasing prevalence of potentially distracting in-car systems. This article reviews the authors' simulation studies of how fatigue, automation, and distraction may intersect as threats to safety. Distinguishing between states of active and passive fatigue supports understanding of fatigue and the development of countermeasures. Active fatigue is a stress-like state driven by overload of cognitive capabilities. Passive fatigue is produced by underload and monotony, and is associated with loss of task engagement and alertness. Our studies show that automated driving reliably elicits subjective symptoms of passive fatigue and also loss of alertness that persists following manual takeover. Passive fatigue also impairs attention and automation use in operators of Remotely Piloted Vehicles (RPVs). Use of in-vehicle media has been proposed as a countermeasure to fatigue, but such media may also be distracting. Studies tested whether various forms of phone-based media interacted with automation-induced fatigue, but effects were complex and dependent on task configuration. Selection of fatigue countermeasures should be guided by an understanding of the form of fatigue confronting the operator. System design, regulation of level of automation, managing distraction, and selection of fatigue-resilient personnel are all possible interventions for passive fatigue, but careful evaluation of interventions is necessary prior to deployment. Copyright © 2018. Published by Elsevier Ltd.

  7. Gut inflammation in chronic fatigue syndrome

    Directory of Open Access Journals (Sweden)

    Kirchgessner Annette

    2010-10-01

    Full Text Available Abstract Chronic fatigue syndrome (CFS is a debilitating disease characterized by unexplained disabling fatigue and a combination of accompanying symptoms the pathology of which is incompletely understood. Many CFS patients complain of gut dysfunction. In fact, patients with CFS are more likely to report a previous diagnosis of irritable bowel syndrome (IBS, a common functional disorder of the gut, and experience IBS-related symptoms. Recently, evidence for interactions between the intestinal microbiota, mucosal barrier function, and the immune system have been shown to play a role in the disorder's pathogenesis. Studies examining the microecology of the gastrointestinal (GI tract have identified specific microorganisms whose presence appears related to disease; in CFS, a role for altered intestinal microbiota in the pathogenesis of the disease has recently been suggested. Mucosal barrier dysfunction promoting bacterial translocation has also been observed. Finally, an altered mucosal immune system has been associated with the disease. In this article, we discuss the interplay between these factors in CFS and how they could play a significant role in GI dysfunction by modulating the activity of the enteric nervous system, the intrinsic innervation of the gut. If an altered intestinal microbiota, mucosal barrier dysfunction, and aberrant intestinal immunity contribute to the pathogenesis of CFS, therapeutic efforts to modify gut microbiota could be a means to modulate the development and/or progression of this disorder. For example, the administration of probiotics could alter the gut microbiota, improve mucosal barrier function, decrease pro-inflammatory cytokines, and have the potential to positively influence mood in patients where both emotional symptoms and inflammatory immune signals are elevated. Probiotics also have the potential to improve gut motility, which is dysfunctional in many CFS patients.

  8. Exercise-induced quadriceps muscle fatigue in men and women: effects of arterial oxygen content and respiratory muscle work.

    Science.gov (United States)

    Dominelli, Paolo B; Molgat-Seon, Yannick; Griesdale, Donald E G; Peters, Carli M; Blouin, Jean-Sébastien; Sekhon, Mypinder; Dominelli, Giulio S; Henderson, William R; Foster, Glen E; Romer, Lee M; Koehle, Michael S; Sheel, A William

    2017-08-01

    High work of breathing and exercise-induced arterial hypoxaemia (EIAH) can decrease O 2 delivery and exacerbate exercise-induced quadriceps fatigue in healthy men. Women have a higher work of breathing during exercise, dedicate a greater fraction of whole-body V̇O2 towards their respiratory muscles and develop EIAH. Despite a greater reduction in men's work of breathing, the attenuation of quadriceps fatigue was similar between the sexes. The degree of EIAH was similar between sexes, and regardless of sex, those who developed the greatest hypoxaemia during exercise demonstrated the most attenuation of quadriceps fatigue. Based on our previous finding that women have a greater relative oxygen cost of breathing, women appear to be especially susceptible to work of breathing-related changes in quadriceps muscle fatigue. Reducing the work of breathing or eliminating exercise-induced arterial hypoxaemia (EIAH) during exercise decreases the severity of quadriceps fatigue in men. Women have a greater work of breathing during exercise, dedicate a greater fraction of whole-body V̇O2 towards their respiratory muscles, and demonstrate EIAH, suggesting women may be especially susceptible to quadriceps fatigue. Healthy subjects (8 male, 8 female) completed three constant load exercise tests over 4 days. During the first (control) test, subjects exercised at ∼85% of maximum while arterial blood gases and work of breathing were assessed. Subsequent constant load exercise tests were iso-time and iso-work rate, but with EIAH prevented by inspiring hyperoxic gas or work of breathing reduced via a proportional assist ventilator (PAV). Quadriceps fatigue was assessed by measuring force in response to femoral nerve stimulation. For both sexes, quadriceps force was equally reduced after the control trial (-27 ± 2% baseline) and was attenuated with hyperoxia and PAV (-18 ± 1 and -17 ± 2% baseline, P Physiology © 2017 The Physiological Society.

  9. Effect of torsional loading on compressive fatigue behaviour of trabecular bone.

    Science.gov (United States)

    Fatihhi, S J; Rabiatul, A A R; Harun, M N; Kadir, Mohammed Rafiq Abdul; Kamarul, T; Syahrom, Ardiyansyah

    2016-02-01

    The present study reports the effects of combined torsional and compressive cyclic loading on trabecular bone in order to mimic true physiological conditions and thereby provides improved data that represents clinical and real life conditions. However, only compressive behaviour is evaluated in most previous studies of bone mechanics. From the monotonic evaluation, it is observed that lower stress is needed for the onset of microcrack in the sample under torsional loading, compared to the stress needed in compression. Trabecular bone samples were subjected to a combination of torsion and compression fatigue at different stress levels during which they were compared to compressive axial fatigue. The stress levels were determined by considering the monotonic strength at 25-50% for both compressive and shear stresses. Significant decrease in fatigue lifetime is observed in between samples of pure compression fatigue and those with superpositioned torsional loading (ptorsional stress level. In this case, the failure of the sample is said to be 'torsional dominant'. Fatigue behaviour of bovine trabecular bone begins with plastic deformation, followed by strain accumulation and modulus reduction. As the strain rate increases, more energy dissipates and the sample finally failed. Further, the analysis of fractograph revealed something on the trabeculae by bending in sample with superpositioned torsional loading. In conclusion, torsional loading decreases the quality of the trabecular properties in terms of stiffness, life and structural integrity. It is hoped that results from this study will improve the understanding of the behaviour of trabecular bone under combined fatigue and help to develop future assessments of trabecular failure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Fatigue crack growth model RANDOM2 user manual. Appendix 1: Development of advanced methodologies for probabilistic constitutive relationships of material strength models

    Science.gov (United States)

    Boyce, Lola; Lovelace, Thomas B.

    1989-01-01

    FORTRAN program RANDOM2 is presented in the form of a user's manual. RANDOM2 is based on fracture mechanics using a probabilistic fatigue crack growth model. It predicts the random lifetime of an engine component to reach a given crack size. Details of the theoretical background, input data instructions, and a sample problem illustrating the use of the program are included.

  11. A newly developed floor chair placed on an office chair reduces lumbar muscle fatigue by cyclically changing its lumbar supporting shape.

    Science.gov (United States)

    Matsuda, Tadamitsu; Koyama, Takayuki; Kurihara, Yasushi; Tagami, Miki; Kusumoto, Yasuaki; Nitta, Osamu

    2017-09-01

    [Purpose] This study investigated lumbar muscle fatigue before and after maintaining a seated position for one hour, lumbar and pelvic inclination angle change, in subjects with and without active lumber support. [Subjects and Methods] Fourteen healthy subjects randomized into two groups sat on a floor chair, placed on an office chair, that cyclically changed its lumbar supporting shape to provide active lumbar support (ALS) or no ALS for one hour. Before and after, we measured the frequency of muscle waveforms of the trunk extensor muscles when the subjects lifted an object weighing 10% of their body weight, using both hands while seated. In addition, ROMt (Range of motion test) of trunk rotation, degree of fatigue and muscle stiffness were analyzed. [Results] Muscle frequency while lifting the weight decreased significantly without ALS compared to with ALS. Mean muscle stiffness increased, ROMt decreased in desk work task significantly without ALS compared to with ALS. [Conclusion] These results suggest that the lumbar muscles became fatigued, because low frequencies, increased muscle stiffness, and decreased ROMt without ALS. We suggest lumbar muscle fatigue was maintained low for subjects seated in a chair with ALS.

  12. The Identification of Fatigue Resistant and Fatigue Susceptible Individuals

    Science.gov (United States)

    2008-05-01

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

  13. Fatigue and fibromyalgia syndrome: clinical and neurophysiologic pattern.

    Science.gov (United States)

    Casale, Roberto; Rainoldi, Alberto

    2011-04-01

    The concept of 'fatigue' is strictly related to parameters of the setting in which fatigue is measured. Therefore, it is mandatory to provide a definition of fatigue and the modalities of its use. This is of pivotal importance with regard to the fibromyalgia (FM) syndrome, where fatigue is the most invalidating symptom and where, paradoxically, no clear and widely accepted definition of fatigue is available in the literature as yet. In the clinical setting, fatigue can be measured by different methods of various complexity. The simplest technique to assess fatigue involves the use of a visual analogue scale (VAS); however, a number of scales with differing levels of complexity are available for use. It is, often, difficult to detach the term 'fatigue' from tiredness and task failure, which correspond to two completely distinguished forms of fatigue: one with central origin (tiredness) and another which is localised within the muscle (peripheral muscle fatigue). The former is related to changes in motor-unit-recruitment strategies, whereas the latter is attributed to changes in membrane properties. To extensively assess fatigue and, partially, to avoid confusion among the types of fatigue described above, a number of laboratory tests have been developed; among these, there are multichannel surface electromyography (EMG) recordings. Using this type of an approach, it is possible the estimation of motor unit location within the muscle, the decomposition of the surface EMG (sEMG) interference signal into constituent trains of motor unit action potentials (MUAPs) and the analysis of single unit properties. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Fatigue in Multiple Sclerosis: Misconceptions and Future Research Directions.

    Science.gov (United States)

    Rudroff, Thorsten; Kindred, John H; Ketelhut, Nathaniel B

    2016-01-01

    Fatigue is one of the most disabling side effects in people with multiple sclerosis. While this fact is well known, there has been a remarkable lack of progress in determining the pathophysiological mechanisms behind fatigue and the establishment of effective treatments. The main barrier has been the lack of a unified definition of fatigue that can be objectively tested with validated experimental models. In this "perspective article" we propose the use of the following model and definition of fatigue: the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors. These changes depend on the task being performed, the environmental conditions it is performed in, and the physical and mental capacity of the individual. Our definition and model of fatigue outlines specific causes of fatigue and how it affects task performance. We also outline the strengths and weaknesses of commonly used measures of fatigue and suggest, based on our model and definition, new research strategies, which should include multiple measures. These studies should be mechanistic with validated experimental models to determine changes in central, psychological, and/or peripheral factors that explain fatigue. The proposed new research strategies may lead to the identification of the origins of MS related fatigue and the development of new, more effective treatments.

  15. Fatigue in Multiple Sclerosis: Misconceptions and Future Research Directions

    Directory of Open Access Journals (Sweden)

    Thorsten Rudroff

    2016-08-01

    Full Text Available Fatigue is one of the most disabling side effects in people with multiple sclerosis (PwMS. While this fact is well known, there has been a remarkable lack of progress in determining the pathophysiological mechanisms behind fatigue and the establishment of effective treatments. The main barrier has been the lack of a unified definition of fatigue that can be objectively tested with validated experimental models. In this ‘perspective article’ we propose the use of the following model and definition of fatigue: the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors. These changes depend on the task being performed, the environmental conditions it is performed in, and the physical and mental capacity of the individual. Our definition and model of fatigue outlines specific causes of fatigue and how it affects task performance. We also outline the strengths and weaknesses of commonly used measures of fatigue and suggest, based on our model and definition, new research strategies which should include multiple measures. These studies should be mechanistic with validated experimental models to determine changes in central, psychological, and/or peripheral factors that explain fatigue. The proposed new research strategies may lead to the identification of the origins of MS related fatigue and the development of new, more effective treatments.

  16. Fatigue and multidimensional disease severity in chronic obstructive pulmonary disease

    Directory of Open Access Journals (Sweden)

    Inal-Ince Deniz

    2010-06-01

    Full Text Available Abstract Background and aims Fatigue is associated with longitudinal ratings of health in patients with chronic obstructive pulmonary disease (COPD. Although the degree of airflow obstruction is often used to grade disease severity in patients with COPD, multidimensional grading systems have recently been developed. The aim of this study was to investigate the relationship between perceived and actual fatigue level and multidimensional disease severity in patients with COPD. Materials and methods Twenty-two patients with COPD (aged 52-74 years took part in the study. Multidimensional disease severity was measured using the SAFE and BODE indices. Perceived fatigue was assessed using the Fatigue Severity Scale (FSS and the Fatigue Impact Scale (FIS. Peripheral muscle endurance was evaluated using the number of sit-ups, squats, and modified push-ups that each patient could do. Results Thirteen patients (59% had severe fatigue, and their St George's Respiratory Questionnaire scores were significantly higher (p Conclusions Peripheral muscle endurance and fatigue perception in patients with COPD was related to multidimensional disease severity measured with both the SAFE and BODE indices. Improvements in perceived and actual fatigue levels may positively affect multidimensional disease severity and health status in COPD patients. Further research is needed to investigate the effects of fatigue perception and exercise training on patients with different stages of multidimensional COPD severity.

  17. Fatigue and creep-fatigue behaviour of high-temperature alloys for HTR-application

    International Nuclear Information System (INIS)

    Meurer, H.-P.; Breitling, H.; Grosser, E.D.

    1981-01-01

    The development of High Temperature Gas Cooled Reactors requires the evaluation of the fatigue behaviour of those alloys which have been taken into account for possible use as structural materials. Comparative fatigue tests of six wrought alloys at 850 0 C revealed differences especially at low strain ranges. The influence of the coolant gas on Incoloy 800 H and Inconel 617 resulted in an increased fatigue life and for Incoloy 800 H in changes of the deformation behaviour. Hold times introduced at maximum tensile strain reduced fatigue life considerably. The hold time data have been evaluated following the rules of ASME Code Case N 47 and design curves for inelastic and elastic analysis are suggested. (Auth.)

  18. Adults living with heart failure and fatigue

    DEFF Research Database (Denmark)

    Schjødt, Inge; Sommer, Irene; Bjerrum, Merete

    studies have been performed to develop more coherent and effective interventions to support self-care among heart failure patients experiencing fatigue. The findings of qualitative research should be synthesised to optimise nurses' understanding of fatigue and develop recommendations for practice. Aim....... The Australian Joanna Briggs Institute Qualitative Review Instrument (JBI-QARI) is used to manage, critically appraise, analyse and synthesise findings. Results A total of 255 references were identified and five qualitative research articles met the inclusion criteria and were included after assessment...

  19. 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.

  20. Healing of Early Stage Fatigue Damage in Ionomer/Fe

    NARCIS (Netherlands)

    Post, W.; Bose, R.K.; Garcia Espallargas, Santiago J.; van der Zwaag, S.

    2016-01-01

    This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid) zinc ionomer/Fe3O4 nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue loading.

  1. Evaluating cyclic fatigue of sealants during outdoor testing

    Science.gov (United States)

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

    2009-01-01

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

  2. Structural Fatigue in One-Crack Models with Arbitrary Inspection,

    Science.gov (United States)

    1979-04-01

    Fatigue. Ph.D. Thesis , University of London, April 1967. 2. Ford, D. G. The Development of the Theory of Structural Fatigue. Aeronautical Research...Aircraft Division 178 Military Aircraft Division 179 British Hovercraft Corporation Ltd. (E. Cowes) 180 Short Brothers & Harland 181 Westland

  3. Collect Available Creep-Fatigue Data and Study Existing Creep-Fatigue Evaluation Procedures for Grade 91 and Hastelloy XR

    International Nuclear Information System (INIS)

    Asayama, Tai; Tachibana, Yukio

    2007-01-01

    This report describes the results of investigation on Task 5 of DOE/ASME Materials Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 5 is to collect available creep-fatigue data and study existing creep-fatigue evaluation procedures for Grade 91 steel and Hastelloy XR. Part I of this report is devoted to Grade 91 steel. Existing creep-fatigue data were collected (Appendix A) and analyzed from the viewpoints of establishing a creep-fatigue procedure for VHTR design. A fair amount of creep-fatigue data has been obtained and creep-fatigue phenomena have been clarified to develop design standards mainly for fast breeder reactors. Following this, existing creep-fatigue procedures were studied and it was clarified that the creep-fatigue evaluation procedure of the ASME-NH has a lot of conservatisms and they were analyzed in detail from the viewpoints of the evaluation of creep damage of material. Based on the above studies, suggestions to improve the ASME-NH procedure along with necessary research and development items were presented. Part II of this report is devoted to Hastelloy XR. Existing creep-fatigue data used for development of the high temperature structural design guideline for High Temperature Gas-cooled Reactor (HTGR) were collected. Creep-fatigue evaluation procedure in the design guideline and its application to design of the intermediate heat exchanger (IHX) for High Temperature Engineering Test Reactor (HTTR) was described. Finally, some necessary research and development items in relation to creep-fatigue evaluation for Gen IV and VHTR reactors were presented.

  4. Collect Available Creep-Fatigue Data and Study Existing Creep-Fatigue Evaluation Procedures for Grade 91 and Hastelloy XR

    Energy Technology Data Exchange (ETDEWEB)

    Tai Asayama; Yukio Tachibana

    2007-09-30

    This report describes the results of investigation on Task 5 of DOE/ASME Materials Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 5 is to collect available creep-fatigue data and study existing creep-fatigue evaluation procedures for Grade 91 steel and Hastelloy XR. Part I of this report is devoted to Grade 91 steel. Existing creep-fatigue data were collected (Appendix A) and analyzed from the viewpoints of establishing a creep-fatigue procedure for VHTR design. A fair amount of creep-fatigue data has been obtained and creep-fatigue phenomena have been clarified to develop design standards mainly for fast breeder reactors. Following this, existing creep-fatigue procedures were studied and it was clarified that the creep-fatigue evaluation procedure of the ASME-NH has a lot of conservatisms and they were analyzed in detail from the viewpoints of the evaluation of creep damage of material. Based on the above studies, suggestions to improve the ASME-NH procedure along with necessary research and development items were presented. Part II of this report is devoted to Hastelloy XR. Existing creep-fatigue data used for development of the high temperature structural design guideline for High Temperature Gas-cooled Reactor (HTGR) were collected. Creep-fatigue evaluation procedure in the design guideline and its application to design of the intermediate heat exchanger (IHX) for High Temperature Engineering Test Reactor (HTTR) was described. Finally, some necessary research and development items in relation to creep-fatigue evaluation for Gen IV and VHTR reactors were presented.

  5. Determinants of seafarers’ fatigue

    DEFF Research Database (Denmark)

    Bøggild Dohrmann, Solveig; Leppin, Anja

    2017-01-01

    of the present article was therefore to systematically detect, analyze and assess the quality of this evidence. Methods: Systematic searches in ten databases were performed. Searches considered articles published in scholarly journals from 1980 to April 15, 2016. Nineteen out of 98 eligible studies were included......Purpose: Fatigue jeopardizes seafarer’s health and safety. Thus, knowledge on determinants of fatigue is of great importance to facilitate its prevention. However, a systematic analysis and quality assessment of all empirical evidence specifically for fatigue are still lacking. The aim......: Realistic countermeasures ought to be established, e.g., in terms of shared or split night shifts. As internal as well as external validity of many study findings was limited, the range of factors investigated was insufficient and few studies investigated more complex interactions between different factors...

  6. Fatigue in Cambodia veterans.

    Science.gov (United States)

    de Vries, M; Soetekouw, P M; Van Der Meer, J W; Bleijenberg, G

    2000-05-01

    In 1992 and 1993, Dutch military personnel were deployed in the peace operation UNTAC in Cambodia. Since returning, Cambodia veterans have reported health complaints which they perceive to be related to their service. Their symptoms strikingly resemble health problems reported by Gulf War veterans. Four years post-return, a cross-sectional survey on health symptoms in Cambodia veterans was initiated. Questionnaires were sent to all Cambodia veterans and four comparison groups. Forgetfulness, difficulty concentrating and fatigue were the symptoms most commonly endorsed. An operational case definition was constructed using a validated fatigue severity questionnaire. Cases were not uniquely found in Cambodia veterans (17%). In Rwanda and Bosnia veterans, respectively, 28% and 11% also met our case definition. Fatigue severity level was predicted by pre-mission, during-mission and post-mission variables, of which retrospective recollection of side-effects of vaccines and causal attributions also have been shown to be relevant in studies on Gulf-related illness.

  7. Thermography detection on the fatigue damage

    Science.gov (United States)

    Yang, Bing

    It has always been a great temptation in finding new methods to in-situ "watch" the material fatigue-damage processes so that in-time reparations will be possible, and failures or losses can be minimized to the maximum extent. Realizing that temperature patterns may serve as fingerprints for stress-strain behaviors of materials, a state-of-art infrared (IR) thermography camera has been used to "watch" the temperature evolutions of both crystalline and amorphous materials "cycle by cycle" during fatigue experiments in the current research. The two-dimensional (2D) thermography technique records the surface-temperature evolutions of materials. Since all plastic deformations are related to heat dissipations, thermography provides an innovative method to in-situ monitor the heat-evolution processes, including plastic-deformation, mechanical-damage, and phase-transformation characteristics. With the understanding of the temperature evolutions during fatigue, thermography could provide the direct information and evidence of the stress-strain distribution, crack initiation and propagation, shear-band growth, and plastic-zone evolution, which will open up wide applications in studying the structural integrity of engineering components in service. In the current research, theoretical models combining thermodynamics and heat-conduction theory have been developed. Key issues in fatigue, such as in-situ stress-strain states, cyclic softening and hardening observations, and fatigue-life predictions, have been resolved by simply monitoring the specimen-temperature variation during fatigue. Furthermore, in-situ visulizations as well as qualitative and quantitative analyses of fatigue-damage processes, such as Luders-band evolutions, crack propagation, plastic zones, and final fracture, have been performed by thermography. As a method requiring no special sample preparation or surface contact by sensors, thermography provides an innovative and convenient method to in-situ monitor

  8. 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...

  9. Do cognitive and physical fatigue tasks enhance pain, cognitive fatigue, and physical fatigue in people with fibromyalgia?

    Science.gov (United States)

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

    2015-02-01

    Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue. The primary objective of this study was to determine if pain, perceived cognitive fatigue, and perceived physical fatigue were enhanced in participants with fibromyalgia compared to healthy controls during a cognitive fatigue task, a physical fatigue task, and a dual fatigue task. In total, 24 people with fibromyalgia and 33 healthy controls completed pain, fatigue, and function measures. A cognitive fatigue task (Controlled Oral Word Association Test) and physical fatigue task (Valpar peg test) were done individually and combined for a dual fatigue task. Resting pain, perceived cognitive fatigue, and perceived physical fatigue were assessed during each task using visual analog scales. Function was assessed with shoulder range of motion and grip. People with fibromyalgia had significantly higher increases in pain, cognitive fatigue, and physical fatigue when compared to healthy controls after completion of a cognitive fatigue task, a physical fatigue task, or a dual fatigue task (P fibromyalgia performed equivalently on measures of physical performance and cognitive performance on the physical and cognitive fatigue tasks, respectively. These data show that people with fibromyalgia show larger increases in pain, perceived cognitive fatigue, and perceived physical fatigue to both cognitive and physical fatigue tasks compared to healthy controls. The increases in pain and fatigue during cognitive and physical fatigue tasks could influence subject participation in daily activities and rehabilitation. Copyright © 2015 by the American College of Rheumatology.

  10. Assessment of fatigue in cancer patients and community dwellers: validation study of the Filipino version of the brief fatigue inventory.

    Science.gov (United States)

    Mendoza, Tito R; Laudico, Adriano V; Wang, Xin Shelley; Guo, Hong; Matsuda, Maria Lourdes; Yosuico, Victor D; Fragante, Edilberto P; Cleeland, Charles S

    2010-01-01

    Clinical trials that might identify effective therapies for cancer-related fatigue, one of the most distressing symptoms experienced by patients, require a validated fatigue assessment tool. We developed and validated a Filipino language version of the Brief Fatigue Inventory (BFI-F) for describing the prevalence and severity of fatigue among Filipino patients with cancer. We conducted a cross-sectional study in Manila, Philippines, in 206 patients with cancer and 170 age-matched community-dwelling adults who had never had a diagnosis of cancer. Validity and reliability were evaluated by principal factor analysis and Cronbach's α coefficients. Factor analysis extracted 1 factor, i.e. fatigue severity, with a Cronbach's α of 0.95; this is consistent with the original BFI English version validation study. Approximately 49% of the patients with cancer had mild fatigue, 34% had moderate fatigue, and 17% had severe fatigue. Patients with a poorer performance status had significantly worse fatigue than patients with a better performance status (5.0 ± 2.8 vs. 3.8 ± 2.2; p Filipino cancer patients. Copyright © 2010 S. Karger AG, Basel.

  11. Fatigue 󈨛. Volume 1,

    Science.gov (United States)

    1987-06-01

    Growth of Small Fatigue 261 Cracks in Copper at Room and Cryogenic Temperatures - I.B. KWON , J. WEERTMAN AND M.E. FINE -ehaviour of Short Cracks in a...Cycli Strai Amplitudes. 0 4 . /2 < 0.3 [maximum stress < 60% oy ] Upon cycling, short cracks initiated in the soft (115 HV) precipitate-free...THE INITIATION AND GROWTH OF SMALL FATIGUE CRACKS IN COPPER AT ROOM AND CRYOGENIC TEMPERATURES I. B. Kwon , J. Weertman and M. E. Fine * The

  12. Fatigue Strength of Weathering Steel

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Klusák, Jan

    2012-01-01

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

  13. Residual fatigue life evaluation of rail at squats seeds using 3D explicit finite element analysis

    NARCIS (Netherlands)

    Deng, X.; Naeimi, M.; Li, Z.; Qian, Z.

    2014-01-01

    A modeling procedure to predict the residual fatigue life of rail at squats seeds is developed in this article. Two models are involved: a 3D explicit Finite Element (FE) model to compute the stress and strain at squats in rail, and the J-S fatigue damage model to determine the residual fatigue life

  14. A multidimensional 'path analysis' model of factors explaining fatigue in rheumatoid arthritis

    NARCIS (Netherlands)

    Rongen-van Dartel, Sanne A. A.; Repping-Wuts, Han; Donders, Rogier; van Hoogmoed, Dewy; Knoop, Hans; Bleijenberg, Gijs; van Riel, Piet L. C. M.; Fransen, Jaap

    2016-01-01

    Fatigue is one of the most commonly reported symptoms in rheumatoid arthritis (RA). Many factors may play a causal role on fatigue in RA patients, but their contribution and interplay is barely understood. The objective was to develop a multidimensional model of factors that explain fatigue severity

  15. Assessment of Eye Fatigue Caused by 3D Displays Based on Multimodal Measurements

    Directory of Open Access Journals (Sweden)

    Jae Won Bang

    2014-09-01

    Full Text Available With the development of 3D displays, user’s eye fatigue has been an important issue when viewing these displays. There have been previous studies conducted on eye fatigue related to 3D display use, however, most of these have employed a limited number of modalities for measurements, such as electroencephalograms (EEGs, biomedical signals, and eye responses. In this paper, we propose a new assessment of eye fatigue related to 3D display use based on multimodal measurements. compared to previous works Our research is novel in the following four ways: first, to enhance the accuracy of assessment of eye fatigue, we measure EEG signals, eye blinking rate (BR, facial temperature (FT, and a subjective evaluation (SE score before and after a user watches a 3D display; second, in order to accurately measure BR in a manner that is convenient for the user, we implement a remote gaze-tracking system using a high speed (mega-pixel camera that measures eye blinks of both eyes; thirdly, changes in the FT are measured using a remote thermal camera, which can enhance the measurement of eye fatigue, and fourth, we perform various statistical analyses to evaluate the correlation between the EEG signal, eye BR, FT, and the SE score based on the T-test, correlation matrix, and effect size. Results show that the correlation of the SE with other data (FT, BR, and EEG is the highest, while those of the FT, BR, and EEG with other data are second, third, and fourth highest, respectively.

  16. Placental complications after a previous cesarean section

    OpenAIRE

    Milošević Jelena; Lilić Vekoslav; Tasić Marija; Radović-Janošević Dragana; Stefanović Milan; Antić Vladimir

    2009-01-01

    Introduction The incidence of cesarean section has been rising in the past 50 years. With the increased number of cesarean sections, the number of pregnancies with the previous cesarean section rises as well. The aim of this study was to establish the influence of the previous cesarean section on the development of placental complications: placenta previa, placental abruption and placenta accreta, as well as to determine the influence of the number of previous cesarean sections on the complic...

  17. Clinical, laboratory, and neuroimaging characteristics of fatigue in HIV-infected individuals.

    Science.gov (United States)

    Schifitto, Giovanni; Deng, Lijuan; Yeh, Tzu-Min; Evans, Scott R; Ernst, Thomas; Zhong, Jianhui; Clifford, David

    2011-02-01

    Fatigue is among the most common symptoms reported by HIV-infected individuals. Previous reports suggest that the prevalence of fatigue varies by disease status with rates close to 80% in patients with AIDS. However, most studies have not been conducted in the setting of a controlled trial and have not assessed the association of fatigue with cellular markers of brain activity. Data for this study were derived from baseline and longitudinal evaluations in ACTG A5090, a randomized, double-blind, placebo-controlled trial of the Selegiline Transdermal System for the treatment of HIV-associated cognitive impairment. Fatigue was assessed using the Fatigue Severity Scale with scores of >4 considered "fatigued". Participants in a substudy underwent brain magnetic resonance spectroscopy (MRS) imaging, an in vivo method for assessing brain metabolites associated with neuronal and glia activity. Differences between fatigued and non-fatigued participants were evaluated with respect to demographics and clinical characteristics, plasma and CSF HIV-1 RNA concentration, CD4 counts, and brain metabolites. One hundred and twenty-eight participants were enrolled (88% male, median age = 45 years) and 82 participants (64%, 95% confidence interval 55%, 72%) were fatigued at baseline. MRS was conducted in 62 of the 128 participants. Fatigued participants were significantly younger (p = 0.011), had lower Karnofsky scores (p = 0.032), and had higher levels of depressive symptoms on the Center for Epidemiologic Studies Depression (CES-D) scale (p < 0.001) than non-fatigued participants. Statistically significant differences between fatigued and non-fatigued groups were not detected for plasma and CSF HIV-1RNA concentration, CD4 counts, or on neuropsychological tests. MRS revealed significantly lower levels of the cellular energy marker total creatine (p = 0.002) in the basal ganglia of fatigued participants. Statistically significant differences in other brain

  18. Rescuer fatigue during simulated neonatal cardiopulmonary resuscitation.

    Science.gov (United States)

    Li, E S; Cheung, P-Y; O'Reilly, M; Aziz, K; Schmölzer, G M

    2015-02-01

    To assess development of fatigue during chest compressions (CCs) in simulated neonatal cardiopulmonary resuscitation (CPR). Prospective randomized manikin crossover study. Thirty neonatal healthcare professionals who successfully completed the Neonatal Resuscitation Program performed CPR using (i) 3:1 compression:ventilation (C:V) ratio, (ii) continuous CC with asynchronous ventilation (CCaV) at a rate of 90 CC per min and (iii) CCaV at 120 CC per min for a duration of 10 min on a neonatal manikin. Changes in peak pressure (a surrogate of fatigue) and CC rate were continuously recorded and fatigue among groups was compared. Participants were blinded to pressure tracings and asked to rate their level of comfort and fatigue for each CPR trial. Compared with baseline, a significant decrease in peak pressure was observed after 72, 96 and 156 s in group CCaV-120, CCaV-90 and 3:1 C:V, respectively. CC depth decreased by 50% within the first 3 min during CCaV-120, 30% during CCaV-90 and 20% during 3:1 C:V. Moreover, 3:1 C:V and CCaV were similarly preferred by healthcare professionals. Similarly, 3:1 C:V and CCaV CPR were also fatiguing. We recommend that rescuers should switch after every second cycle of heart rate assessment during neonatal CPR.

  19. Nondestructive characterization of fatigue damage with thermography

    Science.gov (United States)

    Roesner, Henrik; Sathish, Shamachary; Meyendorf, Norbert

    2001-08-01

    A thermal imaging NDE method has been developed for nondestructive characterization of early stages of fatigue damage. The method is based on evaluation of the thermal effects induced in a material by a short-term mechanical loading. The mechanical loading causes in addition to thermoelastic temperature change, an increase due to heat dissipation that depends upon the microstructure of the material in a characteristic manner. The origin of this heat dissipation is the mechanical damping process. Utilizing the initial temperature rise due to a short-term mechanical loading, the dissipated energy per cycle was evaluated as a thermal parameter. This new thermal NDE parameter allows a quantitative characterization of the mechanical hysteresis, without the need for calibration to eliminate influences of thermal boundary conditions. The measurement of the thermal NDE parameters has been performed on Ti-6Al-4V dog-bone specimens, fatigued in low cycle fatigue (LCF) as well as in high cycle fatigue (HCF) experiments. Characteristic dependence of the NDE parameters on the already accumulated fatigue damage has been observed. The advantage of the thermal method is the applicability to components under service conditions because of simplicity, rapid measurements (a few seconds) and the ability of locally resolved evaluations.

  20. Corrosion and corrosion fatigue of airframe aluminum alloys

    Science.gov (United States)

    Chen, G. S.; Gao, M.; Harlow, D. G.; Wei, R. P.

    1994-01-01

    Localized corrosion and corrosion fatigue crack nucleation and growth are recognized as degradation mechanisms that effect the durability and integrity of commercial transport aircraft. Mechanically based understanding is needed to aid the development of effective methodologies for assessing durability and integrity of airframe components. As a part of the methodology development, experiments on pitting corrosion, and on corrosion fatigue crack nucleation and early growth from these pits were conducted. Pitting was found to be associated with constituent particles in the alloys and pit growth often involved coalescence of individual particle-nucleated pits, both laterally and in depth. Fatigue cracks typically nucleated from one of the larger pits that formed by a cluster of particles. The size of pit at which fatigue crack nucleates is a function of stress level and fatigue loading frequency. The experimental results are summarized, and their implications on service performance and life prediction are discussed.

  1. Miniature specimen technology for postirradiation fatigue crack growth testing

    International Nuclear Information System (INIS)

    Mervyn, D.A.; Ermi, A.M.

    1979-01-01

    Current magnetic fusion reactor design concepts require that the fatigue behavior of candidate first wall materials be characterized. Fatigue crack growth may, in fact, be the design limiting factor in these cyclic reactor concepts given the inevitable presence of crack-like flaws in fabricated sheet structures. Miniature specimen technology has been developed to provide the large data base necessary to characterize irradiation effects on the fatigue crack growth behavior. An electrical potential method of measuring crack growth rates is employed on miniature center-cracked-tension specimens (1.27 cm x 2.54 cm x 0.061 cm). Results of a baseline study on 20% cold-worked 316 stainless steel, which was tested in an in-cell prototypic fatigue machine, are presented. The miniature fatigue machine is designed for low cost, on-line, real time testing of irradiated fusion candidate alloys. It will enable large scale characterization and development of candidate first wall alloys

  2. Correlation of Stress Concentration Factors for T-Welded Connections – Finite Element Simulations and Fatigue Behavior

    Directory of Open Access Journals (Sweden)

    Gerardo Terán Méndez

    Full Text Available Abstract The stress concentration factors (SCFs in welded connections usually occur at zones with high stress levels. Stress concentrations reduce the fatigue behavior of welded connections in offshore structures and cracking can develop. By using the grinding technique, cracking can be eliminated. Stress concentration factors are defined as a ratio of maximum stress at the intersection to nominal stress on the brace. Defining the stress concentration factor is an important stage in the fatigue behavior of welded connections. Several approaches have evolved for designing structures with the classical S-N approach for estimating total life. This work correlates to the stress concentration factors of T-welded connections and the fatigue behavior. Stress concentration factors were computed with the finite element employing 3D T-welded connections with intact and grinding depth conditions. Then, T-welded connections were constructed with A36 plate steel and welded with E6013 electrodes to obtain the stress-life (S-N approach. The methodology from previous works was used to compute the SCF and fabricate the T-welded connections. The results indicated that the grinding process could restore the fatigue life of the T-welded connections for SCFs values in the range of 1.29. This value can be considered to be a low SCF value in T-welded connection. However, for higher SCF values, the fatigue life decreased, compromising and reducing the structural integrity of the T-welded connections.

  3. Fatigue after stroke: a systematic review of associations with impaired physical fitness.

    Science.gov (United States)

    Duncan, Fiona; Kutlubaev, Mansur A; Dennis, Martin S; Greig, Carolyn; Mead, Gillian E

    2012-02-01

    Fatigue is a common and distressing post stroke symptom. One important hypothesis is that fatigue after stroke may be triggered by physical deconditioning, which sets up a vicious, self-perpetuating cycle of fatigue, avoidance of physical activity, further deconditioning, and more fatigue. If an association between physical activity and fatigue after stroke could be established, this would provide a rationale for developing a physical activity-based treatment. Systematically review all observational studies, which have measured both fatigue poststroke and one or more measures of physical fitness and/or physical activity at the same time-point and reported the association between fatigue and fitness variables. Publications were identified by systematically searching databases MEDLINE, EMBASE, CINAHL, PsychInfo, and Sportdiscus using keywords 'fatigue', 'stroke', 'fitness', or 'activity' and their associated terms or synonyms. Publications that provided data on associations between fatigue in stroke patients and levels of physical activity, cardiorespiratory fitness and/or muscle strength and mass were included. Twenty-nine potential studies were retrieved after scrutinizing the titles and abstracts, of which only three fulfilled our inclusion criteria. No association between fatigue and any measures of physical activity or fitness were found. One study did find, through structural equation modeling techniques that fatigue indirectly influences exercise through self-efficacy expectations. There is very limited evidence regarding associations between exercise, fitness, and fatigue after stroke. It still remains highly plausible that exercise can have a positive influence on fatigue. Future research should be longitudinal in design.

  4. The prevalence of severe fatigue in rheumatic diseases: an international study.

    Science.gov (United States)

    Overman, Cécile L; Kool, Marianne B; Da Silva, José A P; Geenen, Rinie

    2016-02-01

    Fatigue is a common, disabling, and difficult-to-manage problem in rheumatic diseases. Prevalence estimates of fatigue within rheumatic diseases vary considerably. Data on the prevalence of severe fatigue across multiple rheumatic diseases using a similar instrument is missing. Our aim was to provide an overview of the prevalence of severe fatigue across a broad range of rheumatic diseases and to examine its association with clinical and demographic variables. Online questionnaires were filled out by an international sample of 6120 patients (88 % female, mean age 47) encompassing 30 different rheumatic diseases. Fatigue was measured with the RAND(SF)-36 Vitality scale. A score of ≤35 was taken as representing severe fatigue (90 % sensitivity and 81 % specificity for chronic fatigue syndrome). Severe fatigue was present in 41 to 57 % of patients with a single inflammatory rheumatic disease such as rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, Sjögren's syndrome, psoriatic arthritis, and scleroderma. Severe fatigue was least prevalent in patients with osteoarthritis (35 %) and most prevalent in patients with fibromyalgia (82 %). In logistic regression analysis, severe fatigue was associated with having fibromyalgia, having multiple rheumatic diseases without fibromyalgia, younger age, lower education, and language (French: highest prevalence; Dutch: lowest prevalence). In conclusion, one out of every two patients with a rheumatic disease is severely fatigued. As severe fatigue is detrimental to the patient, the near environment, and society at large, unraveling the underlying mechanisms of fatigue and developing optimal treatment should be top priorities in rheumatologic research and practice.

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

    International Nuclear Information System (INIS)

    Wilhelm, Paul; Rudolph, Juergen; Steinmann, Paul

    2015-01-01

    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.

  6. On a solution to the problem of the poor cyclic fatigue resistance of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Launey, Maximilien E.; Hofmann, Douglas C.; Johnson, William L.; Ritchie, Robert O.

    2009-01-09

    The recent development of metallic glass-matrix composites represents a particular milestone in engineering materials for structural applications owing to their remarkable combinations of strength and toughness. However, metallic glasses are highly susceptible to cyclic fatigue damage and previous attempts to solve this problem have been largely disappointing. Here we propose and demonstrate a microstructural design strategy to overcome this limitation by matching the microstructural length scales (of the second phase) to mechanical crack-length scales. Specifically, semi-solid processing is used to optimize the volume fraction, morphology, and size of second phase dendrites to confine any initial deformation (shear banding) to the glassy regions separating dendrite arms having length scales of {approx} 2 {micro}m, i.e., to less than the critical crack size for failure. Confinement of the damage to such interdendritic regions results in enhancement of fatigue lifetimes and increases the fatigue limit by an order of magnitude making these 'designed' composites as resistant to fatigue damage as high-strength steels and aluminum alloys. These design strategies can be universally applied to any other metallic glass systems.

  7. Examination of the SG tube fatigue cracking at Fessenheim unit no.2 of EDF

    International Nuclear Information System (INIS)

    Boccanfuso, M.; Lorthios, J.; Thebault, Y.; Bruyere, B.; Duisabeau, L.; Herms, E.

    2015-01-01

    In February 2008, a primary-to-secondary leak occurred at Fessenheim Unit No.2 on a steam generator. A circumferential fatigue crack was observed at the upper tube support plate level of the R12C62 tube although the stability ratio evaluation performed to take into account some prior international events, concluded that this tube had no risk of fluid-elastic instability. A new tube pull process was developed and performed by AREVA in 2011 just before the SG replacement. The extraction at the uppermost TSP elevation was a first occurrence in the French EDF PWR. Destructive examinations were carried out in the EDF hot laboratory of CEIDRE/Chinon in order to characterize damage mechanisms at the initiation and propagation stage. The document relates the major results of laboratory examinations leading us to exclude the fluid-elastic instability scenario as previously reported in North-Anna (1987) and Mihama (1991) tube rupture incidents. Results analysis with particular focus on the fracture surface description using Scanning Electron microscopy observations and metallurgical investigations provide new elements concerning the aggravating factors of fatigue damage. Fracture surface investigations reveal that the circumferential crack was due to high cycle fatigue with a very low stress intensity factor. Some aggravating factors like intergranular corrosion appeared to be critical for the fatigue cracking initiation stage. The deterioration was also largely promoted by the lack of tube support at the Anti-Vibration Bars

  8. An analytical model which combines roughness- and plasticity- induced fatigue crack closure

    Science.gov (United States)

    Chen, Nong

    In this study an analytical PICC-RICC Model was developed to describe better the near-threshold fatigue behavior. The PICC-RICC Model was built upon a strip-yield type PICC model originally proposed by Newman and later modified by Hou and Lawrence. A zigzag crack growth path was introduced to simulate surface roughness. The two opposing crack surfaces were considered to be translated and thus mismatched by the mixed-mode displacements occurring near the deflected crack tip. The model is powerful and unique in that it combines the effects of RICC and PICC. Thus, the gradual transition from RICC to PICC dominated crack closure is handled naturally by this model. The influences of the geometrical features of the surface roughness, R-ratio and the cyclic load range on RICC were examined using the PICC-RICC Model. Near-threshold fatigue behavior of various materials was predicted. The effect of microstructure on the RICC level was studied. The predicted results compared favorably with experimental data. The fatigue notch size effect was investigated using the PICC-RICC model. The initial crack length (asb{i}) for propagation was estimated. The predicted notch fatigue strength compared favorably with the Initiation-Propagation (I-P) Model prediction and test data. The existence of a "worst case notch" previously postulated using the I-P Model was confirmed.

  9. Chronic fatigue syndrome

    African Journals Online (AJOL)

    Objective. To acknowledge the dinical syndrome chronic fatigue syndrome (CFS) and outline the diagnostic criteria and reasonable management. Outcomes. Attempt at containment of treatmentcost and improvement of the quality of care of patients with. CFS. Evidence. Delphi-type commentary from 20 expert clinicians and ...

  10. Caffeine, fatigue, and cognition

    NARCIS (Netherlands)

    Lorist, M.M.; Tops, M.

    2003-01-01

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

  11. FATIGUE OF DENTAL CERAMICS

    Science.gov (United States)

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-01-01

    Objectives 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. Data/sources The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Conclusions Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically-assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Clinical significance Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. PMID:24135295

  12. A review of evaluation methods developed for numerical simulation of the temperature fluctuation contributing to thermal fatigue of a T-junction pipe

    International Nuclear Information System (INIS)

    Nakamura, Akira; Utanohara, Yoichi; Miyoshi, Koji; Kasahara, Naoto

    2015-01-01

    This paper reviews the current status of numerical simulation evaluation methods for evaluation of thermal fatigue in a T-junction pipe and identifies future research items to enhance the methods. The influencing factors of numerical simulation methods on the evaluation of temperature fluctuation near a wall are discussed. Then the mechanism of thermal fatigue and the numerical simulation evaluation methods are described, and the influencing factors such as turbulence models, differencing schemes, computational meshes and inlet conditions are discussed. Some recent models LES, SAS, and combined models are examined to assess fluid temperature fluctuation. Differencing schemes and mesh fineness are important to keep the accuracy of calculations. Regarding boundary conditions, the inlet flow conditions, velocity profile and velocity perturbation, influence the temperature fluctuation. (author)

  13. Creep fatigue design of FBR components

    International Nuclear Information System (INIS)

    Bhoje, S.B.; Chellapandi, P.

    1997-01-01

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

  14. The Effect of Porosity on Fatigue of Die Cast AM60

    Science.gov (United States)

    Yang, Zhuofei; Kang, Jidong; Wilkinson, David S.

    2016-07-01

    AM60 high-pressure die castings are known to contain significant porosity which can affect fatigue life. We have studied this using samples drawn from prototype AM60 shock towers by conducting strain-controlled fatigue tests accompanied by X-ray computed tomography analysis. The results show that the machined surface is the preferential location for fatigue crack development, with pores close to these surfaces serving as initiation sites. Fatigue life shows a strong inverse correlation with the size of the fatigue-crack-initiating pore. Pore shape and pore orientation also influence the response. A supplemental study on surface roughness shows that porosity is the dominant factor in fatigue. Tomography enables the link between porosity and fatigue crack initiation to be clearly identified. These data are complemented by SEM observations of the fracture surfaces which are generally flat and full of randomly oriented serration patterns but without long-range fatigue striations.

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

    Science.gov (United States)

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

    2016-03-01

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

  16. Effects of exercise training on fitness, mobility, fatigue, and health-related quality of life among adults with multiple sclerosis: a systematic review to inform guideline development.

    Science.gov (United States)

    Latimer-Cheung, Amy E; Pilutti, Lara A; Hicks, Audrey L; Martin Ginis, Kathleen A; Fenuta, Alyssa M; MacKibbon, K Ann; Motl, Robert W

    2013-09-01

    To conduct a systematic review of evidence surrounding the effects of exercise training on physical fitness, mobility, fatigue, and health-related quality of life in adults with multiple sclerosis (MS). The databases included EMBASE, 1980 to 2011 (wk 12); Ovid MEDLINE and Ovid OLDMEDLINE, 1947 to March (wk 3) 2011; PsycINFO, 1967 to March (wk 4) 2011; CINAHL all-inclusive; SPORTDiscus all-inclusive; Cochrane Library all-inclusive; and Physiotherapy Evidence Database all-inclusive. The review was limited to English-language studies (published before December 2011) of people with MS that evaluated the effects of exercise training on outcomes of physical fitness, mobility, fatigue, and/or health-related quality of life. One research assistant extracted data and rated study quality. A second research assistant verified the extraction and quality assessment. From the 4362 studies identified, 54 studies were included in the review. The extracted data were analyzed using a descriptive approach. There was strong evidence that exercise performed 2 times per week at a moderate intensity increases aerobic capacity and muscular strength. The evidence was not consistent regarding the effects of exercise training on other outcomes. Among those with mild to moderate disability from MS, there is sufficient evidence that exercise training is effective for improving both aerobic capacity and muscular strength. Exercise may improve mobility, fatigue, and health-related quality of life. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  17. Mechanisms of in vivo muscle fatigue in humans: investigating age‐related fatigue resistance with a computational model

    Science.gov (United States)

    Callahan, Damien M.; Umberger, Brian R.

    2016-01-01

    Key points Muscle fatigue can be defined as the transient decrease in maximal force that occurs in response to muscle use. Fatigue develops because of a complex set of changes within the neuromuscular system that are difficult to evaluate simultaneously in humans.The skeletal muscle of older adults fatigues less than that of young adults during static contractions. The potential sources of this difference are multiple and intertwined.To evaluate the individual mechanisms of fatigue, we developed an integrative computational model based on neural, biochemical, morphological and physiological properties of human skeletal muscle.Our results indicate first that the model provides accurate predictions of fatigue and second that the age‐related resistance to fatigue is due largely to a lower reliance on glycolytic metabolism during contraction.This model should prove useful for generating hypotheses for future experimental studies into the mechanisms of muscle fatigue. Abstract During repeated or sustained muscle activation, force‐generating capacity becomes limited in a process referred to as fatigue. Multiple factors, including motor unit activation patterns, muscle fibre contractile properties and bioenergetic function, can impact force‐generating capacity and thus the potential to resist fatigue. Given that neuromuscular fatigue depends on interrelated factors, quantifying their independent effects on force‐generating capacity is not possible in vivo. Computational models can provide insight into complex systems in which multiple inputs determine discrete outputs. However, few computational models to date have investigated neuromuscular fatigue by incorporating the multiple levels of neuromuscular function known to impact human in vivo function. To address this limitation, we present a computational model that predicts neural activation, biomechanical forces, intracellular metabolic perturbations and, ultimately, fatigue during repeated isometric contractions

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

    Science.gov (United States)

    Majd, Hessam

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

  19. Saccadic eye movement metrics reflect surgical residents' fatigue.

    Science.gov (United States)

    Di Stasi, Leandro L; McCamy, Michael B; Macknik, Stephen L; Mankin, James A; Hooft, Nicole; Catena, Andrés; Martinez-Conde, Susana

    2014-04-01

    show, for the first time, that saccadic velocity is a reliable indicator of the subjective fatigue of health care professionals during prolonged time-on-duty. These findings have potential impacts for the development of neuroergonomic tools to detect fatigue among health professionals and in the specifications of future guidelines regarding residents' duty hours.

  20. Numerical analysis of thermomechanical low cycle fatigue

    Science.gov (United States)

    Sulich, Piotr; Egner, Władysław; Egner, Halina

    2018-01-01

    In this paper the numerical analysis of low cycle fatigue behavior of steel in non-isothermal conditions is presented. First the experimental tests are analyzed to recognize different aspects of material behavior. Then the appropriate constitutive model is developed and implemented into numerical procedures. The model parameters are identified on the basis of the available experimental data. Finally some benchmark simulations are performed.

  1. Alexithymia in adolescents with chronic fatigue syndrome

    NARCIS (Netherlands)

    van de Putte, Elise M.; Engelbert, Raoul H. H.; Kuis, Wietse; Kimpen, Jan L. L.; Uiterwaal, Cuno S. P. M.

    2007-01-01

    Alexithymia is postulated as an important factor in the development of medically unexplained physical symptoms. Chronic fatigue syndrome (CFS) is presently medically unexplained. The aim of this study was to investigate whether the prevalence of alexithymia was higher in adolescents with CFS

  2. Fatigue Predictions of Various Joints of Magnesium Alloys

    Science.gov (United States)

    Kang, H.; Kari, K.; Getti, A.; Khosrovaneh, A. K.; Su, X.; Zhang, L.; Lee, Y.-L.

    In this project, a front shock tower of a passenger vehicle is developed with various magnesium alloys and joining methods. To predict the fatigue life of the joints in the structure, fatigue tests of various joint specimens including friction stir linear welding, self-piecing rivet joint with and without adhesive, and friction stir spot welding were conducted. The magnesium alloys used for the specimens are AM60 (cast), AM30 (extrusion), and AZ31 (sheet). Various finite element modeling techniques were attempted for simulating the various joints. Fatigue life prediction method for the joints was performed using the stress-life curve approach. The finite element modeling technique and the fatigue prediction method will be verified with fatigue tests of the actual front shock tower structure subjected to variable amplitude loadings in near future.

  3. A New Static and Fatigue Compression Test Method for Composites

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Goutianos, Stergios; Løgstrup Andersen, Tom

    2011-01-01

    A new test method to determine the compressive properties of composite materials under both static and fatigue loading was developed. The novel fixture is based on the concept of transmitting the load by a fixed ratio of end-to-shear loading. The end-to-shear load ratio is kept fixed during...... the test through a mechanical mechanism, which automatically maintains the gripping pressure. The combined loading method has proven very efficient in static loading and is used in the new fixture which is specially designed for fatigue testing. Optimum gripping (shear loading) and alignment of the test...... coupon are achieved throughout the fatigue life. The fatigue strength obtained is more reliable because bending of the specimen due to poor gripping and alignment is minimised. The application of the new fixture to static and fatigue compression is demonstrated by using unidirectional carbon...

  4. Very high cycle fatigue testing of concrete using ultrasonic cycling

    Energy Technology Data Exchange (ETDEWEB)

    Karr, Ulrike; Schuller, Reinhard; Fitzka, Michael; Mayer, Herwig [Univ. of Natural Resources and Life Sciences, Vienna (Austria). Inst. of Physics and Materials Science; Denk, Andreas; Strauss, Alfred [Univ. of Natural Resources and Life Sciences, Vienna (Austria)

    2017-06-01

    The ultrasonic fatigue testing method has been further developed to perform cyclic compression tests with concrete. Cylindrical specimens vibrate in resonance at a frequency of approximately 20 kHz with superimposed compressive static loads. The high testing frequency allows time-saving investigations in the very high cycle fatigue regime. Fatigue tests were carried out on ''Concrete 1'' (compressive strength f{sub c} = 80 MPa) and ''Concrete 2'' (f{sub c} = 107 MPa) under purely compressive loading conditions. Experiments at maximum compressive stresses of 0.44 f{sub c} (Concrete 1) and 0.38 f{sub c} (Concrete 2) delivered specimen failures above 109 cycles, indicating that no fatigue limit exists for concrete below one billion load cycles. Resonance frequency, power required to resonate the specimen and second order harmonics of the vibration are used to monitor fatigue damage in situ. Specimens were scanned by X-ray computed tomography prior to and after testing. Fatigue cracks were produced by ultrasonic cycling in the very high cycle fatigue regime at interfaces of grains as well as in cement. The possibilities as well as limitations of ultrasonic fatigue testing of concrete are discussed.

  5. Suppression of Fatigue Crack Propagation of Duralumin by Cavitation Peening

    Directory of Open Access Journals (Sweden)

    Hitoshi Soyama

    2015-08-01

    Full Text Available It was demonstrated in the present paper that cavitation peening which is one of the mechanical surface modification technique can suppress fatigue crack propagation in duralumin. The impacts produced when cavitation bubble collapses can be utilised for the mechanical surface modification technique in the same way as laser peening and shot peening, which is called “cavitation peening”. Cavitation peening employing a cavitating jet in water was used to treat the specimen made of duralumin Japanese Industrial Standards JIS A2017-T3. After introducing a notch, fatigue test was conducted by a load-controlled plate bending fatigue tester, which has been originally developed. The fatigue crack propagation behavior was evaluated and the relationship between the fatigue crack propagation rate versus stress intensity factor range was obtained. From the results, the fatigue crack propagation rate was drastically reduced by cavitation peening and the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In addition, the fatigue crack propagation can be suppressed by 88% in the stable crack propagation stage by cavitation peening.

  6. Fatigue Experiences Among OCD Outpatients.

    Science.gov (United States)

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

    2015-12-01

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

  7. Caffeine, fatigue, and cognition.

    Science.gov (United States)

    Lorist, Monicque M; Tops, Mattie

    2003-10-01

    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 the general belief that caffeine acts as a stimulant. Studies using ERP measures indicate that caffeine has an effect on attention, which is independent of specific stimulus characteristics. Behavioural effects on response related processes turned out to be mainly related to more peripheral motor processes. Recent insights in adenosine and dopamine physiology and functionality and their relationships with fatigue point to a possible modulation by caffeine of mechanisms involved in the regulation of behavioural energy expenditure.

  8. Study of fatigue, depression, and associated factors in type 2 diabetes mellitus in industrial workers

    Directory of Open Access Journals (Sweden)

    Akhilesh Jain

    2015-01-01

    Full Text Available Introduction: Type 2 diabetes mellitus is a significant health problem and imposes great physical, financial and psychological burden among the affected population. Among people with diabetes, fatigue is a pervasive and distressing complaint, which is further accentuated by presence of depression. Objective: To assess the prevalence of fatigue and depression and associated clinical and socio demographic correlates in type 2diabetes. Materials and Methods: This cross sectional study included 100 patients of diabetes type 2 and equal number of healthy controls between the ages of 18 to 70 years . A detailed evaluation of socio demographic and clinical parameters was made. Participants were also assessed for presence of depression and fatigue using PHQ-9 and Fatigue Severity Scale(FSSrespectively. Results: Fatigue and depression was found in 68 % and 53 % of diabetic participants. Diabetic patients were 10.37 times and 4.80 times more likely to suffer from fatigue and depression respectively. Both fatigue and depression were found to be significantly associated with duration of illness, fasting and post prandial blood glucose level ,diabetic complications and Body Mass Index (BMI. Fatigue was also strongly correlated with depression in study sample. Conclusions: Fatigue and depression are reasonably correlated with type 2 diabetes. Various clinical parameters of diabetes are strongly associated with both fatigue and depression. Fatigue itself has significant correlation with depression in type 2 diabetes. Regular monitoring of biochemical parameters are paramount to predict the development of fatigue and depression in type 2 diabetes.

  9. A Constitutive Relationship between Fatigue Limit and Microstructure in Nanostructured Bainitic Steels

    Directory of Open Access Journals (Sweden)

    Inga Mueller

    2016-10-01

    Full Text Available The recently developed nanobainitic steels show high strength as well as high ductility. Although this combination seems to be promising for fatigue design, fatigue properties of nanostructured bainitic steels are often surprisingly low. To improve the fatigue behavior, an understanding of the correlation between the nanobainitic microstructure and the fatigue limit is fundamental. Therefore, our hypothesis to predict the fatigue limit was that the main function of the microstructure is not necessarily totally avoiding the initiation of a fatigue crack, but the microstructure has to increase the ability to decelerate or to stop a growing fatigue crack. Thus, the key to understanding the fatigue behavior of nanostructured bainite is to understand the role of the microstructural features that could act as barriers for growing fatigue cracks. To prove this hypothesis, we carried out fatigue tests, crack growth experiments, and correlated these results to the size of microstructural features gained from microstructural analysis by light optical microscope and EBSD-measurements. Finally, we were able to identify microstructural features that influence the fatigue crack growth and the fatigue limit of nanostructured bainitic steels.

  10. Fatigue and creep at variable temperature. Time dependence forecasting

    International Nuclear Information System (INIS)

    Felsen, M.F.; Mottot, M.; Petrequin, P.

    1984-03-01

    Structure materials for nuclear reactors undergo different types of mechanical and thermal stresses for period reaching 300 000 hours. Rapid change of temperature, stress, frequency can occurs in case of accident. Determination of mechanical properties (elongation, creep, fatigue...) of materials for structure dimensioning requires extrapolation of fatigue and creep tests. The comparison of results obtained on steel 316 shows that for creep forecastings agreement is good between the different methods but it is not the case for creep fatigue. For creep in variable conditions, agreement between experiments and calculus is good only in some cases. For fatigue test with samples previously tested for creep, or vice versa, results depend upon the damage evaluation [fr

  11. Occupational therapists' experience of workplace fatigue: Issues and action.

    Science.gov (United States)

    Brown, Cary A; Schell, Jennifer; Pashniak, Lisa M

    2017-01-01

    Occupational therapists (OTs) work in all areas of health and wellbeing. The work is physically and psychologically demanding, but OTs are often not diligent about recognizing and attending to the workplace health and safety issue of fatigue in their own work settings. The purpose of this paper is to determine current issues and the evidence-base as presented in the literature so as to develop awareness and best practice interventions for fatigue reduction and management in occupational therapists' workplace. A comprehensive search strategy was carried out by the medical librarian on the study team and themes were extracted from the relevant literature by the study team. The literature revealed little research directly addressing occupational therapy workplace fatigue and we expanded our review of the evidence-base across all healthcare workers to identify publications of particular relevance to occupational therapists. This background paper is an important first step to raising awareness among OTs, guide key stakeholders regarding contributing factors to, and consequences of, OTs' workplace fatigue, and set research direction. Knowing which factors influencing workplace fatigue are shared across healthcare professionals and which are unique to OTs can also help organizations develop more tailored workplace fatigue risk reduction programs. This review concludes with a list of existing guidelines and tools for developing workplace fatigue risk assessment and management programs relevant to occupational therapists.

  12. Thermal fatigue crack growth in mixing tees nuclear piping - An analytical approach

    International Nuclear Information System (INIS)

    Radu, V.

    2009-01-01

    The assessment of fatigue crack growth due to cyclic thermal loads arising from turbulent mixing presents significant challenges, principally due to the difficulty of establishing the actual loading spectrum. So-called sinusoidal methods represent a simplified approach in which the entire spectrum is replaced by a sine-wave variation of the temperature at the inner pipe surface. The need for multiple calculations in this process has lead to the development of analytical solutions for thermal stresses in a pipe subject to sinusoidal thermal loading, described in previous work performed at JRC IE Petten, The Netherlands, during the author's stage as seconded national expert. Based on these stress distributions solutions, the paper presents a methodology for assessment of thermal fatigue crack growth life in mixing tees nuclear piping. (author)

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

    International Nuclear Information System (INIS)

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

    1995-12-01

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

  14. Interim fatigue design curves for carbon, low-alloy, and austenitic stainless steels in LWR environments

    International Nuclear Information System (INIS)

    Majumdar, S.; Chopra, O.K.; Shack, W.J.

    1993-01-01

    Both temperature and oxygen affect fatigue life; at the very low dissolved-oxygen levels in PWRs and BWRs with hydrogen water chemistry, environmental effects on fatigue life are modest at all temperatures (T) and strain rates. Between 0.1 and 0.2 ppM, the effect of dissolved-oxygen increases rapidly. In oxygenated environments, fatigue life depends strongly on strain rate and T. A fracture mechanics model is developed for predicting fatigue lives, and interim environmentally assisted cracking (EAC)-adjusted fatigue curves are proposed for carbon steels, low-alloy steels, and austenitic stainless steels

  15. Fatigue in the mothers of children with cerebral palsy.

    Science.gov (United States)

    Garip, Yesim; Ozel, Sumru; Tuncer, Ozgul Bozkurt; Kilinc, Gizem; Seckin, Feryal; Arasil, Tansu

    2017-04-01

    To evaluate fatigue in the mothers of children with cerebral palsy (CP), and to determine its associations with clinical parameters of CP, depression and quality of life (QoL). Ninety children (50 girls and 40 boys) with spastic CP and their mothers were included. Control group comprised mothers of healthy children. Gross motor function classification system (GMFCS) was used for determining functional status. Spasticity was evaluated by using modified Ashworth scale. Fatigue symptom inventory (FSI) was used for assessing maternal fatigue, Nottingham health profile (NHP) for maternal QoL, and Beck Depression Scale (BDS) for maternal depression. Mothers of children with CP scored significantly higher in all FSI subgroups (intensity of fatigue, duration of fatigue and interference with QoL), all NHP subgroups and BDS (p  0.05). Our findings indicate that fatigue levels of mothers with CP children are higher than those with healthy children and associated with depression and deterioration in QoL in terms of physical, social and emotional functioning. This should be considered while designing a family centred rehabilitation programme for children with CP. Implications for Rehabilitation Caring for a child with cerebral palsy has psychological, social and financial impacts on familiesand is associated with increased levels of fatigue among mothers. The capacity of current programs and services needs to be strengthened to accommodate theneeds of children with CP and their mothers in order to reduce fatigue of mothers. New programs need to be developed to provide psychosocial support for the mothers andto reduce their fatigue as they continue to care for their children. Provision of assistive technology devices (particularly suitable wheelchairs) will be useful inreduction of fatigue levels of mothers.

  16. 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.

  17. Preventing Fatigue in Patients With Breast Cancer Treated with Chemotherapy

    National Research Council Canada - National Science Library

    Marrow, Gary

    2001-01-01

    ... or alleviate the development of treatment-induced fatigue. We conducted a randomized, double-blind, placebo-controlled clinical trial with 124 breast cancer patients who were studied for up to four successive chemotherapy treatments...

  18. Work-related fatigue among medical personnel in Taiwan

    Directory of Open Access Journals (Sweden)

    Jung-Chun Ho

    2013-10-01

    Conclusion: We identified factors associated with work-related fatigue among hospital workers in Taipei City. These findings can be applied toward on-the-job training and the development of preventive measures for occupational safety in general hospitals.

  19. Enhanced Prediction of Gear Tooth Surface Fatigue Life, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Sentient will develop an enhanced prediction of gear tooth surface fatigue life with rigorous analysis of the tribological phenomena that contribute to pitting...

  20. Measuring fatigue in rheumatoid arthritis: a cross-sectional study to evaluate the Bristol Rheumatoid Arthritis Fatigue Multi-Dimensional questionnaire, visual analog scales, and numerical rating scales.

    Science.gov (United States)

    Nicklin, Joanna; Cramp, Fiona; Kirwan, John; Greenwood, Rosemary; Urban, Marie; Hewlett, Sarah

    2010-11-01

    Current patient-reported outcome measures of fatigue in rheumatoid arthritis (RA) have limitations, providing only a global perspective. This study constructed a questionnaire (the Bristol RA Fatigue Multi-Dimensional Questionnaire [BRAF-MDQ]) from 45 preliminary questions derived from analysis of patient interviews and surveys and explored its structure for fatigue dimensions. The BRAF-MDQ and short BRAF numerical rating scales (NRS) and visual analog scales (VAS) for severity, effect, and ability to cope with fatigue were evaluated for validity. Two hundred twenty-nine RA patients with fatigue (VAS score ≥5 of 10) completed preliminary BRAF and comparator fatigue scales. Iterative analyses informed item removal or retention in the BRAF-MDQ and identification of subscales (using Cronbach's alpha for internal consistency and factor analysis to identify dimensions). The BRAF-MDQ and short scales were tested in relation to potentially associated variables for criterion and construct validity (Spearman's correlation). The 20-item BRAF-MDQ had good internal consistency (Cronbach's α = 0.932), criterion validity (correlation with other fatigue scales: r = 0.643-0.813), and construct validity (correlations with disability, mood, helplessness, and pain: r = 0.340-0.627). Factor analysis showed 4 distinct dimensions (physical fatigue, living with fatigue, cognition fatigue, and emotional fatigue), which correlated well with the RA Multidimensional Assessment of Fatigue scale (r = 0.548-0.834). The BRAF VAS and NRS showed similar criterion and construct validity. The BRAF instruments include standardized NRS and VAS for fatigue severity, effect, and coping, are RA specific, and have evidence to support validity. The BRAF-MDQ uniquely measures 4 separate dimensions, which may facilitate development of individually-tailored fatigue management programs. Copyright © 2010 by the American College of Rheumatology.

  1. Perceived fatigue following pediatric burns.

    Science.gov (United States)

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

    2017-12-01

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

  2. Short-duration fatigue alters neuromuscular coordination of trunk musculature: implications for injury.

    Science.gov (United States)

    Gorelick, M; Brown, J M M; Groeller, H

    2003-07-01

    The aim of this investigation was to determine the effect of muscle fatigue, produced by two different fatigue protocols, on the coordination of trunk and thigh muscles during the performance of a manual-handling task (e.g. a weighted stoop lift). The two fatigue protocols were designed to produce either (a) a non-specific widespread fatigue of trunk and limb muscles (e.g. rowing fatigue protocol), or (b) a specific fatigue of the trunk extensor musculature (e.g. back extension fatigue protocol). Specifically, we wished to determine whether the coordination of trunk muscles during a stoop lift was compromised more, or less, by either of these two fatigue protocols. Ten male subjects (20-24 years) were tested utilising an electromyographic technique which collected electromyograms from trunk flexor and extensor muscles, as well as the Hamstring muscle group, during a pre- and a post-fatigue performance of a weighted stoop lift. The results showed that the back extension fatigue protocol, but not the rowing fatigue protocol, produced significant (pstoop lift. The longer periods of muscle activation seen only after the back extension fatigue protocol, suggested that fatigue of these muscles had required the CNS to alter their periods of activation to a pattern similar to that previously seen in elderly populations. The results also suggested that intense short-duration motor tasks, which may differentially target the back and its musculature, could leave the spine susceptible to increased risk of injury even though worker perceptions of general fatigue are low. Risk assessment guidelines for manual handling should consider not only the weight and frequency of the lift, but lift duration as well to maintain worker safety.

  3. Analysis of Fatigue and Wear Behaviour in Ultrafine Grained Connecting Rods

    Directory of Open Access Journals (Sweden)

    Rodrigo Luri

    2017-07-01

    Full Text Available Over the last few years there has been an increasing interest in the study and development of processes that make it possible to obtain ultra-fine grained materials. Although there exists a large number of published works related to the improvement of the mechanical properties in these materials, there are only a few studies that analyse their in-service behaviour (fatigue and wear. In order to bridge the gap, in this present work, the fatigue and wear results obtained for connecting rods manufactured by using two different aluminium alloys (AA5754 and AA5083 previously deformed by severe plastic deformation (SPD, using Equal Channel Angular Pressing (ECAP, in order to obtain the ultrafine grain size in the processed materials are shown. For both aluminium alloys, two initial states were studied: annealed and ECAPed. The connecting rods were manufactured from the previously processed materials by using isothermal forging. Fatigue and wear experiments were carried out in order to characterize the in-service behaviour of the components. A comparative study of the results was made for both initial states of the materials. Furthermore, Finite Element Modelling (FEM simulations were used in order to compare experimental results with those obtained from simulations. In addition, dimensional wear coefficients were found for each of the aluminium alloys and initial deformation states. This research work aims to progress the knowledge of the behaviour of components manufactured from ultrafine grain materials.

  4. Physiological and psychological indices of fatigue during static contractions.

    Science.gov (United States)

    Kilbom, A; Gamberale, F; Persson, J; Annwall, G

    1983-01-01

    The development of fatigue and the relationship between psychological and physiological indices of fatigue were studied in a group of 18 male subjects during static contractions. Exercise was performed as a static elbow flexion at 25% MVC. Heart rate (HR), intraarterial blood pressure (BP) and surface EMG [mean amplitude (MA) and central frequency (CF)] were studied during contractions sustained until exhaustion. The amount of effort expended (relative to total exhaustion) and the rating of perceived pain were recorded following contractions interrupted after 20, 30 . . . 80, and 100% of endurance time. HR, BP and EMG amplitude responses were similar to those previously recorded. The decline in CF occurred in two phases, possibly related to a change in motor unit recruitment after the initial 70% of endurance time. The subjects overestimated the amount of effort expended and thus underestimated their endurance capacity. The best correlation between perceived effort and physiological responses was obtained using blood pressure data, whereas changes in EMG data did not parallel the psychological responses. It is concluded that the perception of effort during a static contraction is produced through a complex process, in which several influences of peripheral and central origin are integrated.

  5. Quality and fatigue characteristics relation

    Directory of Open Access Journals (Sweden)

    Libor Trško

    2016-03-01

    Full Text Available This paper will explore the mutual correlation of fatigue characteristics ((Kath, σc, ac = f (Rm of five structural steels tested at highfrequency loading based on tests (f ≈ 20 kHz, T = 20 ± 10 °C, R = -1. Different fatigue resistance parameters have different meanings and misunderstanding can lead to significant quality problems in component operation. Consequently, it is necessary to completely understand the relations between the two most important fatigue characteristics which are fatigue limit σc and the threshold value of the stress intensity factor amplitudeKath and how they act with changing of steel ultimate tensile strength.

  6. Creep, fatigue and creep-fatigue interactions in modified 9% Chromium - 1% Molybdenum (P91) steels

    Science.gov (United States)

    Kalyanasundaram, Valliappa

    Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components' life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices. It is also imperative to develop analytical constitutive models that can simulate and predict material response under various long-term in-service conditions using experimental data from short-term laboratory experiments. Consequently, the major objectives of the proposed research are to characterize the creep, fatigue and C-F behavior of grade P91 steels at 625 C and develop robust constitutive models for simulating/predicting their microstructural response under different loading conditions. This work will utilize experimental data from 16 laboratories worldwide that conducted tests (creep, fatigue and C-F) on grade P91 steel at 625°C in a round-robin (RR) program. Along with 7 creep deformation and rupture tests, 32 pure fatigue and 46 C-F tests from the RR are considered in this work. A phenomenological constitutive model formulated in this work needs just five fitting parameters to simulate/predict the monotonic, pure fatigue and C-F behavior of grade P91 at 625 C. A modified version of an existing constitutive model is also presented for particularly simulating its isothermal creep deformation and rupture behavior. Experimental results indicate that specimen C-F lives, as measured by the 2% load drop criterion, seem to decrease with increasing strain ranges and increasing hold times at 625°C. Metallographic assessment of the tested specimens shows that the damage mode in both pure fatigue and 600 seconds hold time cyclic tests is predominantly transgranular fatigue with some presence of

  7. A summary of the fatigue properties of wind turbine materials

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Herbert J. [Sandia National Labs., Wind Energy Technology Dept., Albuquerque, NM (United States)

    2000-07-01

    Modern wind turbines are fatigue-critical machines that are typically used to produce electrical power from the wind. The materials used to construct these machines are subjected to a unique loading spectrum that contains several orders of magnitude more cycles than other fatigue-critical structures, e.g. an aeroplane. To facilitate fatigue designs, a large database of material properties has been generated over the past several years that is specialised to materials typically used in wind turbines. This article reviews the fatigue data that have been developed especially for wind turbines. Major sections are devoted to the properties developed for metals (primarily aluminium), wood and fibreglass. Special emphasis is placed on the fibreglass discussion because this material is currently the material of choice for wind turbine blades. The article focuses on the data developed in the US, but cites European references that provide important insights. (Author)

  8. 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.

  9. Foil system fatigue load environments for commercial hydrofoil operation

    Science.gov (United States)

    Graves, D. L.

    1979-01-01

    The hydrofoil fatigue loads environment in the open sea is examined. The random nature of wave orbital velocities, periods and heights plus boat heading, speed and control system design are considered in the assessment of structural fatigue requirements. Major nonlinear load events such as hull slamming and foil unwetting are included in the fatigue environment. Full scale rough water load tests, field experience plus analytical loads work on the model 929 Jetfoil commercial hydrofoil are discussed. The problem of developing an overall sea environment for design is defined. State of the art analytical approaches are examined.

  10. Validation of Fatigue Modeling Predictions in Aviation Operations

    Science.gov (United States)

    Gregory, Kevin; Martinez, Siera; Flynn-Evans, Erin

    2017-01-01

    Bio-mathematical fatigue models that predict levels of alertness and performance are one potential tool for use within integrated fatigue risk management approaches. A number of models have been developed that provide predictions based on acute and chronic sleep loss, circadian desynchronization, and sleep inertia. Some are publicly available and gaining traction in settings such as commercial aviation as a means of evaluating flight crew schedules for potential fatigue-related risks. Yet, most models have not been rigorously evaluated and independently validated for the operations to which they are being applied and many users are not fully aware of the limitations in which model results should be interpreted and applied.

  11. The influence of the martensitic transformation on the fatigue of an AISI type 316 metastable stainless steel

    International Nuclear Information System (INIS)

    Pacheco, D.J; Sousa e Silva, A.S. de; Monteiro, S.N.

    The influence of the martensitic transformation on the process of pulse tension fatigue of a AISI type 316 metastable stainless steel was studied at 25 0 and 196 0 c. The fatigue tests were performed on annealed and cold worked specimens in order to separate the effects of static transformation, dynamic transformation and work hardening. The fatigue limits obtained from the corresponding Wohler curves were compared for the different test conditions. The results showed that the fatigue is not affected by the dynamically induced martensite. On the other hand the static martensite, previously induced, appears to decrease the resistance to fatigue. The reasons for these effects are discussed. (Author) [pt

  12. Cyclic plasticity and fatigue of metals

    International Nuclear Information System (INIS)

    Mughrabi, H.

    1993-01-01

    This report is a survey of the cyclic deformation and fatigue behaviour of selected engineering steels and alloys. Emphasis is placed on the important roles of the cyclic slip mode and the stability of the microstructure during cyclic stressing and on the conditions of fatigue testing with respect to the failure mechanisms and fatigue life. The examples presented include low-temperature fatigue, high-temperature fatigue in the presence of dynamic strain ageing and thermomechanical fatigue. (orig.)

  13. 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...

  14. Fatigue hardening and softening studies on strain hardened 18-8 austenitic stainless steel

    International Nuclear Information System (INIS)

    Ramakrishna Prasad, C.; Vasudevan, R.

    1976-01-01

    Metals when subjected to fatigue harden or soften depending on their previous mechanical history. Annealed or mildly cold worked metals are known to harden while severely cold worked metals soften when subjected to fatigue loading. In the present work samples of austenitic 18-8 steel cold worked to 11% and 22% reduction in area were mounted in a vertical pulsator and fatigued in axial tension-compression. Clear cut effects were produced and it was noticed that these depended on the extent of cold work, the amplitude as well as the number of cycles of fatigue and mean stress if any. (orig.) [de

  15. Fatigue monitoring program for the Susquehanna Unit 1 reactor pressure vessel

    International Nuclear Information System (INIS)

    Novak, J.; Deardorff, A.

    1990-01-01

    A project was initiated to perform ongoing fatigue evaluation of key reactor vessel components at the Susquehanna Steam Electric Station. This effort has resulted in a program of data collection and evaluation which will assist in assessing the continued safe operation and extending the operating life of this boiling water reactor plant. Initial efforts centered on identification of the key design transient cycles and fatigue sensitive locations in the vessel. Based on these studies a manual system of cycle counting and fatigue usage evaluation was developed. A computer-based fatigue monitoring system (FMS) was chosen for tracking fatigue usage at the most critical locations at the reactor feedwater nozzles and the bottom head control rod drive (CRD) penetrations. With this system, fatigue usage is based on the actual plant operational cycles rather than design basis transient cycles. In this paper lessons learned from the project and key results from the fatigue history evaluation are discussed

  16. A Review of the Fatigue Properties of Additively Manufactured Ti-6Al-4V

    Science.gov (United States)

    Cao, Fei; Zhang, Tiantian; Ryder, Matthew A.; Lados, Diana A.

    2018-03-01

    Various additive manufacturing (AM) technologies have been used to fabricate Ti-6Al-4V. The fatigue performance of Ti-6Al-4V varies from process to process. In this review, fatigue properties of Ti-6Al-4V alloys made by different AM technologies and post-fabrication treatments were compiled and discussed to correlate with the materials' characteristic features, primarily surface roughness and porosity. Microstructure anisotropy and porosity effects on fatigue crack growth and fatigue life are also presented and discussed. A modified Kitagawa-Takahashi diagram developed from current available fatigue data was used to quantify the influence of defects on fatigue strength. This review aims to assist in selecting/optimizing AM processes to achieve high fatigue resistance in Ti-6Al-4V, as well as provide a better understanding of the advantages and limitations of current AM techniques in producing titanium alloys.

  17. The effect of sustained low-intensity contractions on supraspinal fatigue in human elbow flexor muscles

    DEFF Research Database (Denmark)

    Søgaard, Karen; Gandevia, Simon C; Todd, Gabrielle

    2006-01-01

    Subjects quickly fatigue when they perform maximal voluntary contractions (MVCs). Much of the loss of force is from processes within muscle (peripheral fatigue) but some occurs because voluntary activation of the muscle declines (central fatigue). The role of central fatigue during submaximal...... contractions is not clear. This study investigated whether central fatigue developed during prolonged low-force voluntary contractions. Subjects (n=9) held isometric elbow flexions of 15% MVC for 43 min. Voluntary activation was measured during brief MVCs every 3 min. During each MVC, transcranial magnetic...... several minutes while MVC torque only returned to approximately 85% baseline. The resting twitch showed no recovery. Thus, as well as fatigue in the muscle, the prolonged low-force contraction produced progressive central fatigue, and some of this impairment of the subjects' ability to drive the muscle...

  18. Prediction of Fatigue Life of a Continuous Bridge Girder Based on Vehicle Induced Stress History

    Directory of Open Access Journals (Sweden)

    V.G. Rao

    2003-01-01

    Full Text Available The fatigue damage assessment of bridge components by conducting a full scale fatigue testing is often prohibitive. A need, therefore, exists to estimate the fatigue damage in bridge components by a simulation of bridge-vehicle interaction dynamics due to the action of the actual traffic. In the present paper, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials. Vehicle induced time history of maximum flexural stresses has been obtained by Monte Carlo simulation process and utilized to develop the stress range frequency histogram taking into consideration of the annual traffic volume. The linear damage accumulation theory is then applied to calculate cumulative damage index and fatigue life of the bridge. Effect of the bridge span, pavement condition, increase of vehicle operating speed, weight and suspension characteristics on fatigue life of the bridge have been examined.

  19. Reciprocal relationship between acute stress and acute fatigue in everyday life in a sample of university students.

    Science.gov (United States)

    Doerr, Johanna M; Ditzen, Beate; Strahler, Jana; Linnemann, Alexandra; Ziemek, Jannis; Skoluda, Nadine; Hoppmann, Christiane A; Nater, Urs M

    2015-09-01

    We investigated whether stress may influence fatigue, or vice versa, as well as factors mediating this relationship. Fifty healthy participants (31 females, 23.6±3.2 years) completed up to 5 momentary assessments of stress and fatigue during 5 days of preparation for their final examinations (exam condition) and 5 days of a regular semester week (control condition). Sleep quality was measured by self-report at awakening. A sub-group of participants (n=25) also collected saliva samples. Fatigue was associated with concurrent stress, stress reported at the previous measurement point, and previous-day stress. However, momentary stress was also predicted by concurrent fatigue, fatigue at the previous time point, and previous-day fatigue. Sleep quality mediated the association between stress and next-day fatigue. Cortisol and alpha-amylase did not mediate the stress-fatigue relationship. In conclusion, there is a reciprocal stress-fatigue relationship. Both prevention and intervention programs should comprehensively cover how stress and fatigue might influence one another. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Fatigue 󈨛. Volume 3,

    Science.gov (United States)

    1987-06-01

    the University of Virginia, Charlottesville, Virginia. 0 June 28 - July 3, 1987 J 0 EDITORIAL PANEL p...c.. d R.P. Gangloff, R.O. Ritchie, E.A. Starke...8217- rrocee, s hi, ir-.---’atc- % apour prE r ardL heance the rt-4d;ee Kix it tho crac&’ tip cat sos ’ her , qrowtb. rate. in ’ a e oxi-rt-,-tcd -is t t...precursor wire) was typically 0.064 cm. 1334 FATIGUE 87 Fabrication of the precursor wire into panels was done by DWA Composite Specialties, Inc., using the

  1. Fatigue in soccer

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-01-01

    in the game: (1) after short-term intense periods in both halves; (2) in the initial phase of the second half; and (3) towards the end of the game. Temporary fatigue after periods of intense exercise in the game does not appear to be linked directly to muscle glycogen concentration, lactate accumulation......, 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...

  2. A motor unit-based model of muscle fatigue

    Science.gov (United States)

    2017-01-01

    Muscle fatigue is a temporary decline in the force and power capacity of skeletal muscle resulting from muscle activity. Because control of muscle is realized at the level of the motor unit (MU), it seems important to consider the physiological properties of motor units when attempting to understand and predict muscle fatigue. Therefore, we developed a phenomenological model of motor unit fatigue as a tractable means to predict muscle fatigue for a variety of tasks and to illustrate the individual contractile responses of MUs whose collective action determines the trajectory of changes in muscle force capacity during prolonged activity. An existing MU population model was used to simulate MU firing rates and isometric muscle forces and, to that model, we added fatigue-related changes in MU force, contraction time, and firing rate associated with sustained voluntary contractions. The model accurately estimated endurance times for sustained isometric contractions across a wide range of target levels. In addition, simulations were run for situations that have little experimental precedent to demonstrate the potential utility of the model to predict motor unit fatigue for more complicated, real-world applications. Moreover, the model provided insight into the complex orchestration of MU force contributions during fatigue, that would be unattainable with current experimental approaches. PMID:28574981

  3. Corrosion fatigue of biomedical metallic alloys: mechanisms and mitigation.

    Science.gov (United States)

    Antunes, Renato Altobelli; de Oliveira, Mara Cristina Lopes

    2012-03-01

    Cyclic stresses are often related to the premature mechanical failure of metallic biomaterials. The complex interaction between fatigue and corrosion in the physiological environment has been subject of many investigations. In this context, microstructure, heat treatments, plastic deformation, surface finishing and coatings have decisive influence on the mechanisms of fatigue crack nucleation and growth. Furthermore, wear is frequently present and contributes to the process. However, despite all the effort at elucidating the mechanisms that govern corrosion fatigue of biomedical alloys, failures continue to occur. This work reviews the literature on corrosion-fatigue-related phenomena of Ti alloys, surgical stainless steels, Co-Cr-Mo and Mg alloys. The aim was to discuss the correlation between structural and surface aspects of these materials and the onset of fatigue in the highly saline environment of the human body. By understanding such correlation, mitigation of corrosion fatigue failure may be achieved in a reliable scientific-based manner. Different mitigation methods are also reviewed and discussed throughout the text. It is intended that the information condensed in this article should be a valuable tool in the development of increasingly successful designs against the corrosion fatigue of metallic implants. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  4. Fatigue Life Assessment of Orthotropic Steel Deck with UHPC Pavement

    Directory of Open Access Journals (Sweden)

    Xu Jiang

    2017-01-01

    Full Text Available In recent years, a number of large-span bridges with orthotropic steel decks were constructed in China. With increasing traffic volumes and higher wheel loads, many fatigue cracks developed at the welds and the edge of cut-out holes. This paper aims at presenting the numerical analysis on the fatigue performance of the orthotropic steel deck using ultrahigh performance concrete (UHPC overlay as the deck pavement instead of the conventional asphalt concrete pavement. By using finite element method (FEM model, stress distribution at fatigue sensitive locations under the action of wheel loads is characterized and the obtained stress ranges indicate that the UHPC pavement significantly reduces the magnitude of the stress peak valued. A suggested truck stream model based on the weigh-in-motion (WIM data of four bridges in China is employed to calculate the stress variation at specific fatigue details. Furthermore, the fatigue damage accumulation at fatigue details under the UHPC and conventional asphalt concrete pavement is studied based on Miner’s linear cumulative damage rule and the rain-flow method. The results indicate that the UHPC pavement on the orthotropic steel deck can extend the service lives of the concerned regions over 100 years, but the fatigue lives will reduce significantly when the elastic modulus of UHPC decreases to 50% of the original value.

  5. Compassion fatigue in family caregivers: a Wilsonian concept analysis.

    Science.gov (United States)

    Lynch, Susan H; Lobo, Marie L

    2012-09-01

    An analysis of the concept of compassion fatigue in family caregivers. The term 'compassion fatigue' is predominantly used with professional caregivers, such as nurses, doctors and social workers. Secondary traumatic stress, burnout, and other related terms are often cited in the literature in conjunction with compassion fatigue. Although compassion fatigue is linked to professional caregivers as a result of exposure to traumatizing events, minimal knowledge has been developed regarding its presence in family caregivers. Literature published between 1980-2010 from the humanities, nursing and the social sciences, including psychology, sociology, social work, and religion, was reviewed. Data sources included dictionaries, newspapers and multiple academic databases, such as Academic Search Complete, Atla, CINAHL, PsychInfo, and PubMed. Wilson's concept analysis strategy was employed to frame the analysis of compassion fatigue, using model, contrary, related, and borderline cases to illustrate the concept's meaning in relation to family caregivers. Analysis revealed that the concept is predominantly used in relation to healthcare providers. Parallels are drawn between the role of healthcare providers and family caregivers. Compassion fatigue occurs when a care-giving relationship founded on empathy potentially results in a deep psychological response to stress that progresses to physical, psychological, spiritual, and social exhaustion in the family caregiver. This concept analysis clarified the definition and revealed that the concept of compassion fatigue has potential use with family caregivers. Implications for practice and research are identified. © 2012 Blackwell Publishing Ltd.

  6. A motor unit-based model of muscle fatigue.

    Directory of Open Access Journals (Sweden)

    Jim R Potvin

    2017-06-01

    Full Text Available Muscle fatigue is a temporary decline in the force and power capacity of skeletal muscle resulting from muscle activity. Because control of muscle is realized at the level of the motor unit (MU, it seems important to consider the physiological properties of motor units when attempting to understand and predict muscle fatigue. Therefore, we developed a phenomenological model of motor unit fatigue as a tractable means to predict muscle fatigue for a variety of tasks and to illustrate the individual contractile responses of MUs whose collective action determines the trajectory of changes in muscle force capacity during prolonged activity. An existing MU population model was used to simulate MU firing rates and isometric muscle forces and, to that model, we added fatigue-related changes in MU force, contraction time, and firing rate associated with sustained voluntary contractions. The model accurately estimated endurance times for sustained isometric contractions across a wide range of target levels. In addition, simulations were run for situations that have little experimental precedent to demonstrate the potential utility of the model to predict motor unit fatigue for more complicated, real-world applications. Moreover, the model provided insight into the complex orchestration of MU force contributions during fatigue, that would be unattainable with current experimental approaches.

  7. ANSYS Creep-Fatigue Assessment tool for EUROFER97 components

    Directory of Open Access Journals (Sweden)

    M. Mahler

    2016-12-01

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

  8. Quantitative estimation of muscle fatigue using surface electromyography during static muscle contraction.

    Science.gov (United States)

    Soo, Yewguan; Sugi, Masao; Nishino, Masataka; Yokoi, Hiroshi; Arai, Tamio; Kato, Ryu; Nakamura, Tatsuhiro; Ota, Jun

    2009-01-01

    Muscle fatigue is commonly associated with the musculoskeletal disorder problem. Previously, various techniques were proposed to index the muscle fatigue from electromyography signal. However, quantitative measurement is still difficult to achieve. This study aimed at proposing a method to estimate the degree of muscle fatigue quantitatively. A fatigue model was first constructed using handgrip dynamometer by conducting a series of static contraction tasks. Then the degree muscle fatigue can be estimated from electromyography signal with reasonable accuracy. The error of the estimated muscle fatigue was less than 10% MVC and no significant difference was found between the estimated value and the one measured using force sensor. Although the results were promising, there were still some limitations that need to be overcome in future study.

  9. Fatigue assessment by energy approach during tensile tests on AISI 304 steel

    Directory of Open Access Journals (Sweden)

    A. Risitano

    2017-01-01

    Full Text Available Estimation of the fatigue limit for steel ductile materials using non-destructive methods is a topic of great interest to researchers today. In recent years, the method adopted has implemented infrared sensors to detect the surface temperature and correlate it with the fatigue limit. In previous paper, a new energy approach was proposed to investigate the fatigue limit during tensile test. The numerical procedure proposed by Chrysochoos is adopted to clean infrared images and applied to analyse the surface heat sources during tensile test. AISI 304 specimens with rectangular cross-sections are tested. Moreover fatigue tests at increasing loads were carried out on steel by a stepwise succession, applied to the same specimen, for applying the thermographic method. The predictions of the fatigue limit, obtained by the analysis of the energy evolution during the static tests, were compared with the predictions obtained applying the thermographic method during fatigue tests.

  10. Fatigue Damage Estimation and Data-based Control for Wind Turbines

    DEFF Research Database (Denmark)

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

    2015-01-01

    The focus of this work is on fatigue estimation and data-based controller design for wind turbines. The main purpose is to include a model of the fatigue damage of the wind turbine components in the controller design and synthesis process. This study addresses an online fatigue estimation method...... based on hysteresis operators, which can be used in control loops. The authors propose a data-based model predictive control (MPC) strategy that incorporates an online fatigue estimation method through the objective function, where the ultimate goal in mind is to reduce the fatigue damage of the wind...... turbine components. The outcome is an adaptive or self-tuning MPC strategy for wind turbine fatigue damage reduction, which relies on parameter identification on previous measurement data. The results of the proposed strategy are compared with a baseline model predictive controller....

  11. Coexistence of potentiation and fatigue in skeletal muscle

    Directory of Open Access Journals (Sweden)

    D.E. Rassier

    2000-05-01

    Full Text Available Twitch potentiation and fatigue in skeletal muscle are two conditions in which force production is affected by the stimulation history. Twitch potentiation is the increase in the twitch active force observed after a tetanic contraction or during and following low-frequency stimulation. There is evidence that the mechanism responsible for potentiation is phosphorylation of the regulatory light chains of myosin, a Ca2+-dependent process. Fatigue is the force decrease observed after a period of repeated muscle stimulation. Fatigue has also been associated with a Ca2+-related mechanism: decreased peak Ca2+ concentration in the myoplasm is observed during fatigue. This decrease is probably due to an inhibition of Ca2+ release from the sarcoplasmic reticulum. Although potentiation and fatigue have opposing effects on force production in skeletal muscle, these two presumed mechanisms can coexist. When peak myoplasmic Ca2+ concentration is depressed, but myosin light chains are relatively phosphorylated, the force response can be attenuated, not different, or enhanced, relative to previous values. In circumstances where there is interaction between potentiation and fatigue, care must be taken in interpreting the contractile responses.

  12. Fatigue effects on tracking performance

    NARCIS (Netherlands)

    Huysmans, M.A.; Hoozemans, M.; Beek, A.J. van der; Looze, M.P. de; Dieën, J.H. van

    2006-01-01

    The objective of the present study was to test the effect of fatigue on task performance in a tracking task performed with a computer mouse. Participants performed a two-minute tracking task twice before and once immediately after a fatiguing wrist extension protocol. Results indicate that the mean

  13. 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

  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. Brain neurotransmitters in fatigue and overtraining.

    Science.gov (United States)

    Meeusen, Romain; Watson, Philip; Hasegawa, Hiroshi; Roelands, Bart; Piacentini, Maria F

    2007-10-01

    Since the publication of the serotonin hypothesis, numerous theories involving the accumulation or depletion of different substances in the brain have been proposed to explain central fatigue. Although the theoretical rationale for the "serotonin-fatigue hypothesis" is clear, several seemingly well-conducted studies have failed to support a significant role for 5-hydroxytryptamine in the development of fatigue. As brain function appears to be dependent upon the interaction of a number of systems, it is unlikely that a single neurotransmitter system is responsible for central fatigue. Several other mechanisms are involved, with evidence supporting a role for the brain catecholamines. Fatigue is therefore probably an integrated phenomenon, with complex interaction among central and peripheral factors. When prolonged and excessive training happens, concurrent with other stressors and insufficient recovery, performance decrements can result in chronic maladaptations that can lead to the overtraining syndrome (OTS). The mechanism of the OTS could be difficult to examine in detail, perhaps because the stress caused by excessive training load, in combination with other stressors, might trigger different "defence mechanisms" such as the immunological, neuroendocrine, and other physiological systems that all interact and probably therefore cannot be pinpointed as the "sole" cause of the OTS. It might be that, as in other syndromes, the psychoneuroimmunology (study of brain-behavior-immune interrelationships) might shed a light on the possible mechanisms of the OTS, but until there is a definite diagnostic tool, it is of utmost importance to standardize measures that are now thought to provide a good inventory of the training status of the athlete. It is very important to emphasize the need to distinguish the OTS from overreaching and other potential causes of temporary underperformance such as anemia, acute infection, muscle damage, and insufficient carbohydrate intake.

  16. Analysis of Fatigue Crack Growth in Ship Structural Details

    Directory of Open Access Journals (Sweden)

    Leheta Heba W.

    2016-04-01

    Full Text Available Fatigue failure avoidance is a goal that can be achieved only if the fatigue design is an integral part of the original design program. The purpose of fatigue design is to ensure that the structure has adequate fatigue life. Calculated fatigue life can form the basis for meaningful and efficient inspection programs during fabrication and throughout the life of the ship. The main objective of this paper is to develop an add-on program for the analysis of fatigue crack growth in ship structural details. The developed program will be an add-on script in a pre-existing package. A crack propagation in a tanker side connection is analyzed by using the developed program based on linear elastic fracture mechanics (LEFM and finite element method (FEM. The basic idea of the developed application is that a finite element model of this side connection will be first analyzed by using ABAQUS and from the results of this analysis the location of the highest stresses will be revealed. At this location, an initial crack will be introduced to the finite element model and from the results of the new crack model the direction of the crack propagation and the values of the stress intensity factors, will be known. By using the calculated direction of propagation a new segment will be added to the crack and then the model is analyzed again. The last step will be repeated until the calculated stress intensity factors reach the critical value.

  17. Review article Prevalence and clinical specificity of fatigue symptoms in chronic fatigue syndrome, multiple sclerosis, and myasthenia gravis

    Directory of Open Access Journals (Sweden)

    Natalia Treder

    2014-07-01

    Full Text Available This article provides a critical review of the psychological and related literature on fatigue resulting in both mental and physical experiences. On one hand, prolonged severe fatigue is a prominent disabling symptom in various diseases of different aetiology – psychiatric (e.g. depression, somatic (e.g. some infections and neurologic (e.g. multiple sclerosis, myasthenia gravis. For instance, fatigue is a main symptom of myasthenia that leads to pathological skeletal muscle weakness. Furthermore, 40 to 90 per cent of individuals suffering from multiple sclerosis confirm they have experienced fatigue, which impairs their cognitive functioning. In both multiple sclerosis and myasthenia, fatigue has not only a physical but also a psychological dimension. On the other hand, fatigue can be seen as an isolated set of symptoms of unknown origin called the chronic fatigue syndrome (CFS. The development of the concept, diagnostic criteria and some strategies of coping with CFS are presented. Various somatic disorders, as well as subjective cognitive and emotional complaints, are common and well documented in patients with CFS. The most typical include depression, as well as problems with concentration of attention, decision-making and reasoning in complex situations. However, general intellectual abilities and higher order cognitive skills are intact. Directions for future research are outlined.

  18. Simplified elastoplastic fatigue analysis

    International Nuclear Information System (INIS)

    Autrusson, B.; Acker, D.; Hoffmann, A.

    1987-01-01

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

  19. Prevalence of Irritable Bowel Syndrome and Chronic Fatigue 10 Years After Giardia Infection.

    Science.gov (United States)

    Litleskare, Sverre; Rortveit, Guri; Eide, Geir Egil; Hanevik, Kurt; Langeland, Nina; Wensaas, Knut-Arne

    2018-03-06

    Irritable bowel syndrome (IBS) is a complication that can follow gastrointestinal infection, but it is not clear if patients also develop chronic fatigue. We investigated the prevalence and odds ratio of IBS and chronic fatigue 10 years after an outbreak of Giardia lamblia, compared with a control cohort, and changes in prevalence over time. We performed a prospective follow-up study of 1252 laboratory-confirmed cases of giardiasis (exposed), which developed in Bergen, Norway in 2004. Statistics Norway provided us with information from 2504 unexposed individuals from Bergen, matched by age and sex (controls). Questionnaires were mailed to participants 3, 6, and 10 years after the outbreak. Results from the 3- and 6-year follow-up analyses have been published previously. We report the 10-year data and changes in prevalence among time points, determined by logistic regression using generalized estimating equations. The prevalence of IBS 10 years after the outbreak was 43% (n = 248) among 576 exposed individuals and 14% (n = 94) among 685 controls (adjusted odds ratio for development of IBS in exposed individuals, 4.74; 95% CI, 3.61-6.23). At this time point, the prevalence of chronic fatigue was 26% (n = 153) among 587 exposed individuals and 11% (n = 73) among 692 controls (adjusted odds ratio, 3.01; 95% CI, 2.22-4.08). The prevalence of IBS among exposed persons did not change significantly from 6 years after infection (40%) to 10 years after infection (43%; adjusted odds ratio for the change 1.03; 95% CI, 0.87-1.22). However, the prevalence of chronic fatigue decreased from 31% at 6 years after infection to 26% at 10 years after infection (adjusted odds ratio for the change 0.74; 95% CI, 0.61-0.90). The prevalence of IBS did not change significantly from 6 years after an outbreak of Giardia lamblia infection in Norway to 10 years after. However, the prevalence of chronic fatigue decreased significantly from 6 to 10 years afterward. IBS and chronic fatigue were

  20. Modeling of thermo-mechanical fatigue and damage in shape memory alloy axial actuators

    Science.gov (United States)

    Wheeler, Robert W.; Hartl, Darren J.; Chemisky, Yves; Lagoudas, Dimitris C.

    2015-04-01

    The aerospace, automotive, and energy industries have seen the potential benefits of using shape memory alloys (SMAs) as solid state actuators. Thus far, however, these actuators are generally limited to non-critical components or over-designed due to a lack of understanding regarding how SMAs undergo thermomechanical or actuation fatigue and the inability to accurately predict failure in an actuator during use. The purpose of this study was to characterize the actuation fatigue response of Nickel-Titanium-Hafnium (NiTiHf) axial actuators and, in turn, use this characterization to predict failure and monitor damage in dogbone actuators undergoing various thermomechanical loading paths. Calibration data was collected from constant load, full cycle tests ranging from 200-600MPa. Subsequently, actuator lifetimes were predicted for four additional loading paths. These loading paths consisted of linearly varying load with full transformation (300-500MPa) and step loads which transition from zero stress to 300-400MPa at various martensitic volume fractions. Thermal cycling was achieved via resistive heating and convective cooling and was controlled via a state machine developed in LabVIEW. A previously developed fatigue damage model, which is formulated such that the damage accumulation rate is general in terms of its dependence on current and local stress and actuation strain states, was utilized. This form allows the model to be utilized for specimens undergoing complex loading paths. Agreement between experiments and simulations is discussed.

  1. Patient perspective: choosing or developing instruments.

    Science.gov (United States)

    Kirwan, John R; Fries, James F; Hewlett, Sarah; Osborne, Richard H

    2011-08-01

    Previous Outcome Measures in Rheumatology (OMERACT) meetings recognized that patients view outcomes of intervention from a different perspective. This preconference position paper briefly sets out 2 patient-reported outcome (PRO) instrument approaches, the PROMISE computer adaptive testing (CAT) system and development of a rheumatoid arthritis-specific questionnaire to measure fatigue; a tentative proposal for a PRO instrument development pathway is also made.

  2. Changes in the flexion relaxation response induced by lumbar muscle fatigue

    Directory of Open Access Journals (Sweden)

    Cantin Vincent

    2008-01-01

    Full Text Available Abstract Background The flexion relaxation phenomenon (FRP is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task. Methods Twenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1, no fatigue/load (2, fatigue/no load(3, and fatigue/load (4. Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 × 2 repeated-measures ANOVA. Results Onset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition. Conclusion The results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability.

  3. Fatigue During Head-And-Neck Radiotherapy: Prospective Study on 117 Consecutive Patients

    International Nuclear Information System (INIS)

    Jereczek-Fossa, Barbara Alicja; Santoro, Luigi; Alterio, Daniela; Franchi, Benedetta; Fiore, Maria Rosaria; Fossati, Piero; Kowalczyk, Anna; Canino, Paola; Ansarin, Mohssen; Orecchia, Roberto

    2007-01-01

    Purpose: Fatigue is an underevaluated cancer-related and treatment-related symptom. We analyzed fatigue in head and neck cancer patients undergoing radiotherapy (RT). Methods and Materials: A total of 117 patients were enrolled (mean age, 58 years). Radiation therapy (median dose, 66 Gy) was given with either exclusive or postoperative intent in 52 and 65 patients, respectively. Chemotherapy (CT) was added before and/or during RT in 61 patients. The patients completed a 20-item questionnaire (Multidimensional Fatigue Inventory [MFI-20]) before, during (weekly), and after RT. The impact of patient-, tumor-, and treatment-related factors on fatigue was evaluated with unifactorial and multifactorial tests. Results: Fatigue level increased during RT reaching a maximum at Week 6 and then slowly decreased. In multivariate stepwise regression analysis age (inversely related, p < 0.05), psychologic disorders (p < 0.005), and previous head-and-neck surgery (inversely related, p < 0.005) were correlated with higher pre-RT fatigue level. Pre-RT fatigue score (p < 0.0001), induction and/or concomitant CT (p = 0.035), need of cortisone during RT (p = 0.005), and thyroid disorders (p = 0.032) were correlated with higher during-RT fatigue level. Pre-RT fatigue score (p < 0.0001), induction and/or concomitant CT (p < 0.001), and need of cortisone during RT (p < 0.005) were correlated with higher post-RT fatigue level. No impact of gender, performance status, comorbidities other than psychologic and thyroid, tumor stage/site, RT intent, dose, volume, duration, or toxicity was observed. Conclusion: Fatigue affects all patients undergoing RT for head-and-neck cancer, reaches maximum score at the 6th week of RT, and slowly decreases thereafter. Age, thyroid dysfunction, psychologic disorders, pre-RT fatigue score, CT, and cortisone use are correlated with RT-related fatigue levels

  4. What is the best term in Spanish to express the concept of cancer-related fatigue?

    Science.gov (United States)

    Centeno, Carlos; Portela Tejedor, María Angustias; Carvajal, Ana; San Miguel, Maria Teresa; Urdiroz, Julia; Ramos, Luis; De Santiago, Ana

    2009-05-01

    Fatigue is one of the most frequent symptoms in patients with cancer. No adequate term in Spanish has been defined to describe the English concept of fatigue. To identify the most suitable Spanish words that define the concept of fatigue and to check psychometric characteristics. Consensus with professional experts on Spanish words that best suit the English concept of fatigue. A prospective study on oncologic patients was also undertaken, which included an evaluation of the intensity of fatigue through visual numeric scales (VNS) where the words had been previously selected. The fatigue subscale of the Functional Assessment of Cancer Therapy-Fatigue (FACT-F) questionnaire was taken as a reference. The experts highlighted the words cansancio, agotamiento, and debilidad (tiredness, exhaustion, and weakness) as the terms that best defined the concept of fatigue. In the psychometric assessment study, 100 patients were included, of which 61 (61%) presented diagnostic values for cancer-related fatigue in the FACT-F fatigue subscale (score 34/52 or lower). The VNS for the chosen terms obtained a high correlation with the FACT-F fatigue subscale results: cansancio (tiredness) r = -0.71, agotamiento (exhaustion) r = -0.74, debilidad (weakness) r = -0.74, with no statistical differences between them. For the detection of fatigue by means of the VNS, tiredness (cutoff point > or =4/10) gave sensitivity (S) 0.90 and specificity (E) 0.72; exhaustion (cutoff point > or =3/10) S 0.95 and E 0.90 and weakness (cutoff point > or =4/10) S 0.92 and E 0.72. The ROC curve was 0.88 for tiredness, 0.94 for exhaustion, and 0.92 for weakness, with no significant difference between the areas mentioned. The terms cansancio, agotamiento, and debilidad (tiredness, exhaustion, and weakness) are suitable for defining the English concept of fatigue in Spanish, and should be the preferred option for inclusion in evaluation tools.

  5. Bayesian inference model for fatigue life of laminated composites

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Kiureghian, Armen Der; Berggreen, Christian

    2016-01-01

    A probabilistic model for estimating the fatigue life of laminated composite plates is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configurations. Model parameters are estimated by Bayesian inference....... The reference data used consists of constant-amplitude cycle test results for four laminates with different layup configurations. The paper describes the modeling techniques and the parameter estimation procedure, supported by an illustrative application....

  6. Fatigue Crack Propagation Simulation in Plane Stress Constraint

    DEFF Research Database (Denmark)

    Ricardo, Luiz Carlos Hernandes; Spinelli, Dirceu

    2010-01-01

    Nowadays, structural and materials engineers develop structures and materials properties using finite element method. This work presents a numerical determination of fatigue crack opening and closure stress intensity factors of a C(T) specimen. Two different standard variable spectrum loadings...... are utilized, Mini-Falstaff and Wisper. The effects in two-dimensional (2D) small scale yielding models of fatigue crack growth were studied considering plane stress constraint....

  7. Diffraction-based study of fatigue crack initiation and propagation in aerospace aluminum alloys

    Science.gov (United States)

    Gupta, Vipul K.

    crystallographic {111} slip-plane cracking typical of the Stage I crack growth mode observed in single crystals and high purity polycrystals of face centered cubic metals, and which has presently been assumed for the present materials within fatigue crack initiation models. Rather, the facets tend to have near-Mode I spatial orientation, which is another indicator of the importance of environmentally affected fatigue damage. The results provide a physical basis to develop microstructurally-based next generation multi-stage fatigue (MSF) models that should include a new crack decohesion criteria based upon environmental fatigue cracking mechanisms. EBSD study of small-cracks in alloy 7050-T7451, stressed in warm-humid environment, showed that crack-path orientation changes and crack-branching occurred at both low/high-angle grain and subgrain boundaries. Single surface trace analysis suggests that the crack-path differs substantially from crystallographic slip-planes. EBSD-based observations of small-crack propagation through subgrain structure, either formed by cyclic plastic strain accumulation or pre-existing (typical of unrecrystallized grain structure in the present materials), suggest that subgrain structure plays a crucial role in small fatigue crack propagation. As mentioned earlier, local fluctuations in small-crack growth rates appear to be caused by frequent interaction with subgrain boundaries, and multiple occurrences of crack-branching and crack-path orientation changes at low/high-angle grain and subgrain boundaries. The aforementioned deviation from low-index {001}/{101}-planes and the occurrence of high-index cracking planes observed by EBSD/Stereology, in this study and others, are interpreted as trans-subgranular decohesion or inter-subgranular cracking, due to trapped hydrogen. In summary, the results provide a firmer experimental foundation for, and clearer understanding of, the mechanisms of environmental fatigue cracking of aluminum alloys, especially the

  8. Fatigue mitigation effects of en-route napping on commercial airline pilots flying international routes

    Science.gov (United States)

    Baldwin, Jarret Taylor

    The introduction of ultra-long range commercial aircraft and the evolution of the commercial airline industry has provided new opportunities for air carriers to fly longer range international route segments while deregulation, industry consolidation, and the constant drive to reduce costs wherever possible has pressured airline managements to seek more productivity from their pilots. At the same time, advancements in the understanding of human physiology have begun to make their way into flight and duty time regulations and airline scheduling practices. In this complex and ever changing operating environment, there remains an essential need to better understand how these developments, and other daily realities facing commercial airline pilots, are affecting their fatigue management strategies as they go about their rituals of getting to and from their homes to work and performing their flight assignments. Indeed, the need for commercial airline pilots to have access to better and more effective fatigue mitigation tools to combat fatigue and insure that they are well rested and at the top of their game when flying long-range international route segments has never been greater. This study examined to what extent the maximum fatigue states prior to napping, as self-accessed by commercial airline pilots flying international route segments, were affected by a number of other common flight assignment related factors. The study also examined to what extent the availability of scheduled en-route rest opportunities, in an onboard crew rest facility, affected the usage of en-route napping as a fatigue mitigation strategy, and to what extent the duration of such naps affected the perceived benefits of such naps as self-accessed by commercial airline pilots flying international route segments. The study utilized an online survey tool to collect data on crew position, prior flight segments flown in the same duty period, augmentation, commuting, pre-flight rest obtained in the

  9. Hamstring-to-quadriceps fatigue ratio offers new and different muscle function information than the conventional non-fatigued ratio.

    Science.gov (United States)

    Pinto, M D; Blazevich, A J; Andersen, L L; Mil-Homens, P; Pinto, R S

    2018-01-01

    Commonly used injury risk prediction tests such as the hamstring-to-quadriceps (H:Q) strength ratio appear to be poor predictors of non-contact injury. However, these tests are typically performed in a non-fatigued state, despite accumulated fatigue being an important risk factor for both hamstring strain (HS) and anterior cruciate ligament (ACL) injuries in professional soccer players. After the effect of different H:Q calculation methods were compared and contrasted, the influence of neuromuscular fatigue on the H:Q strength ratio and the association between fatigued and non-fatigued ratio scores were examined. Thirty-five professional soccer players performed a 30-repetition isokinetic fatigue test protocol. Peak knee joint moments were computed for each repetition, and the H:Q conventional ratio (H:Q CR ) was calculated using several different, previously published, methods. Knee extensor and flexor moments were statistically decreased by the sixth repetition and continued to decrease until the end of the protocol. However, the H:Q ratio was statistically decreased at the end of the test due to a significant reduction in knee flexor moment (correlation between change in knee flexor moment and change in H:Q, r≈.80; Pratio measurement during a fatiguing test (H:Q F atigue ) provides different outcomes to the traditional H:Q CR . The observed significant hamstring fatigue and the difference, and weak correlation, between H:Q CR and H:Q F atigue indicate that useful information might be obtained with respect to the prediction of HS and ACL injury risk. The potential predictive value of H:Q F atigue warrants validation in future prospective trials. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Multi-analyte profiling and pathway analysis of plasma for proteins associated with cancer-related fatigue syndrome in disease-free breast cancer patients after primary treatment.

    Science.gov (United States)

    Minton, O; Coulton, G R; Stone, P

    2014-12-01

    A significant number of women treated for breast cancer develop long-term fatigue afterwards. Previous research has suggested that fatigue may be due to a prolonged inflammatory response. However, there are conflicting results and the exact nature of the disturbance remains unclear. To identify inflammatory markers associated with fatigue. We recruited women from a breast cancer follow-up clinic and categorised them on the basis of a diagnostic interview as to whether they met the criteria for cancer-related fatigue syndrome (cases) or not (controls). We took plasma samples from each participant to analyse subsequently using a panel of 88 biological markers. 90 samples were analysed in total (45 cases and 45 controls). A factorial analysis of variance (using age as a fixed factor) demonstrated a number of differences in inflammatory cytokines. There were 28 significantly different analytes in total. Granulocyte colony stimulating factor was the most significantly different analyte (pfatigue syndrome is associated with an increased pro-inflammatory immune response. Our findings indicate that these cytokine changes could underpin the subjective symptoms, such as perceived muscle weakness and concentration difficulties, experienced by women who feel fatigued after treatment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  11. Fatigue Crack Prognostics by Optical Quantification of Defect Frequency

    Science.gov (United States)

    Chan, K. S.; Buckner, B. D.; Earthman, J. C.

    2018-01-01

    Defect frequency, a fatigue crack prognostics indicator, is defined as the number of microcracks per second detected using a laser beam that is scanned across a surface at a constant predetermined frequency. In the present article, a mechanistic approach was taken to develop a methodology for deducing crack length and crack growth information from defect frequency data generated from laser scanning measurements made on fatigued surfaces. The method was developed by considering a defect frequency vs fatigue cycle curve that comprised three regions: (i) a crack initiation regime of rising defect frequency, (ii) a plateau region of a relatively constant defect frequency, and (iii) a region of rapid rising defect frequency due to crack growth. Relations between defect frequency and fatigue cycle were developed for each of these three regions and utilized to deduce crack depth information from laser scanning data of 7075-T6 notched specimens. The proposed method was validated using experimental data of crack density and crack length data from the literature for a structural steel. The proposed approach was successful in predicting the length or depth of small fatigue cracks in notched 7075-T6 specimens and in smooth fatigue specimens of a structural steel.

  12. Two micro fatigue test methods for irradiated materials

    International Nuclear Information System (INIS)

    Nunomura, Shigetomo; Noguchi, Shinji; Okamura, Yuichi; Kumai, Shinji

    1993-01-01

    This paper demonstrates two miniature fatigue test methods in response to the requirements of the fusion reactor wall materials development program. It is known that the fatigue strength evaluated by the axial loading test is independent of the specimen size, while that evaluated by the bend test or torsion test is dependent upon the size of specimen. The new type of gripping system for the axial, tension-tension, fatigue testing of TEM disk-size specimens that has been developed is described in this paper. An alignment tool assists in gripping the miniature specimen. The miniature tension-tension fatigue test method seems to provide reliable S-N curves for SUS304 and SUS316L stainless steels. An indentation method has also been developed to determine fatigue properties. A hard steel ball or ceramic ball was used for cyclically loading the specimen, and an S-N curve was subsequently obtained. The merit of this method is primarily simple handling. S-N curves obtained from four materials by this indentation method compared well with those obtained from the rotary bend fatigue test employing a standard-size specimen

  13. Sequential creep-fatigue interaction in austenitic stainless steel type 316L-SPH

    International Nuclear Information System (INIS)

    Tavassoli, A.A.; Mottot, M.; Petrequin, P.

    1986-01-01

    Influence of a prior creep or fatigue exposure on subsequent fatigue or creep properties of stainless steel type 316 L SPH has been investigated. The results obtained are used to verify the validity of time and cycle fraction rule and to obtain information on the effect of very long intermittent hold times on low cycle fatigue properties, as well as on transitory loads occurring during normal service of some structural components of LMFBR reactors. Creep and fatigue tests have been carried out at 600 0 C and under conditions yielding equal or different fatigue saturation and creep stresses. Prior creep damage levels introduced range from primary to tertiary creep, whilst those of fatigue span from 20 to 70 percent of fatigue life. In both creep-fatigue and fatigue-creep sequences in the absence of a permanent prior damage (cavitation or cracking) the subsequent resistance of 316 L-SPH to fatigue or creep is unchanged, if not improved. Thin foils prepared from the specimens confirmed these observations and showed that the dislocation substructure developed during the first mode of testing is quickly replaced by that of the second mode. Grain boundary cavitation does not occur in 316 L-SPH during creep exposures to well beyond the apparent end of secondary stage and as a result prior creep exposures up to approximately 80% of rupture life do not affect fatigue properties. Conversely, significant surface cracks were found in the prior fatigue tested specimens after above about 50% life. In the presence of such cracks the subsequent creep damage was localized at the tip of the main crack and the remaining creep life was found to be usually proportional to the effective specimen cross section. Creep and fatigue sequential damage are not necessarily additive and this type of loadings are in general less severe than the repeated creep-fatigue cycling. 17 refs.

  14. Capturing Uncertainty in Fatigue Life Data

    Science.gov (United States)

    2014-09-18

    to gauge the effectiveness of the transformation. Specific tests have been developed for log-transformed data (Bartlett & Kendall , 1946). This work...techniques have parametric counterparts including two-sample location tests Wilcoxen Rank Sum/ Mann -Whitney U (t- test for difference of means), Kruskal...of time they have spent with me discussing material sciences, fatigue testing , and their modeling efforts. Finally, a considerable amount of thanks

  15. 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.

  16. Fatigue Performance of SFPSC under Hot-Wet Environments and Cyclic Bending Loads

    Directory of Open Access Journals (Sweden)

    Shanshan Luo

    2018-01-01

    Full Text Available A new structural material named “steel fiber polymer structural concrete (SFPSC” with features of both high strength and high toughness was developed by this research group and applied to the bridge superstructures in the hot-wet environments. In order to investigate the fatigue performance and durability of SFPSC under hot-wet environments, the environment and fatigue load uncoupling method and the coupling action of environment and fatigue load were used or developed. Three-point bending fatigue experiments with uncoupling action of environments and cyclic loads were carried out for SFPSC specimens which were pretreated under hot-wet environments, and the experiments with the coupling action of environments and cyclic loads for SFPSC specimens were carried out under hot-wet environments. Then, the effects of hot-wet environments and the experimental methods on the fatigue mechanism of SFPSC material were discussed, and the environmental fatigue equations of SFPSC material under coupling and uncoupling action of hot-wet environments and cyclic bending loads were established. The research results show that the fatigue limits of SFPSC under the coupling action of the environments and cyclic loads were lower about 15%. The proposed fatigue equations could be used to estimate the fatigue lives and fatigue limits of SFPSC material.

  17. Experimental Study on Fatigue Behaviour of BFRP-Concrete Bond Interfaces under Bending Load

    Directory of Open Access Journals (Sweden)

    Jianhe Xie

    2018-01-01

    Full Text Available Basalt fiber reinforced polymer (BFRP composites are increasingly being used to retrofit concrete structures by external bonding. For such strengthened members, the BFRP-concrete interface plays the crucial role of transferring stresses. This study aims to investigate the fatigue behaviour of the interface under bending load. A series of tests were conducted on BFRP-concrete bonded joint, including static, fatigue, and postfatigue loading. The fatigue failure modes, the development of deflection, the evolution of BFRP strains, and the propagation of interfacial cracks were analysed. In addition, the debonding-induced fatigue life of BFRP-concrete bonded joints was studied. Finally, a new model of fatigue life was proposed by defining the effective fatigue bond stress. The results showed that the fatigue experience has a significant effect on the BFRP strength especially near the root of concrete transverse crack and on the bond performance of the adhesive near the interface crack tip. There are two main fatigue failure modes: BFRP rupture and BFRP debonding. The fatigue damage development of the bond interface has three stages: rapid, stable, and unstable growth. The proposed model for the debonding-induced fatigue life is more conservative for the BFRP-concrete bonded joints under pure shear load than for those under bending load.

  18. Disease-Induced Skeletal Muscle Atrophy and Fatigue

    Science.gov (United States)

    Powers, Scott K.; Lynch, Gordon S.; Murphy, Kate T.; Reid, Michael B.; Zijdewind, Inge

    2016-01-01

    Numerous health problems including acute critical illness, cancer, diseases associated with chronic inflammation, and neurological disorders often result in skeletal muscle weakness and fatigue. Disease-related muscle atrophy and fatigue is an important clinical problem because acquired skeletal muscle weakness can increase the duration of hospitalization, result in exercise limitation, and contribute to a poor quality of life. Importantly, skeletal muscle atrophy is also associated with increased morbidity and mortality of patients. Therefore, improving our understanding of the mechanism(s) responsible for skeletal muscle weakness and fatigue in patients is a required first step to develop clinical protocols to prevent these skeletal muscle problems. This review will highlight the consequences and potential mechanisms responsible for skeletal muscle atrophy and fatigue in patients suffering from acute critical illness, cancer, chronic inflammatory diseases, and neurological disorders. PMID:27128663

  19. Standard test method for creep-fatigue testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This test method covers the determination of mechanical properties pertaining to creep-fatigue deformation or crack formation in nominally homogeneous materials, or both by the use of test specimens subjected to uniaxial forces under isothermal conditions. It concerns fatigue testing at strain rates or with cycles involving sufficiently long hold times to be responsible for the cyclic deformation response and cycles to crack formation to be affected by creep (and oxidation). It is intended as a test method for fatigue testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. The cyclic conditions responsible for creep-fatigue deformation and cracking vary with material and with temperature for a given material. 1.2 The use of this test method is limited to specimens and does not cover testing of full-scale components, structures, or consumer products. 1.3 This test method is primarily ...

  20. A metallographic examination of structural degradation during creep-fatigue

    International Nuclear Information System (INIS)

    Hales, R.

    1979-07-01

    A series of specimens of T316 stainless steel, which had been tested under creep-fatigue conditions, has been examined by optical and scanning electron microscopy. The development of cavities which are associated with grain-boundary carbide precipitates has been recorded. These cavities increase in size and number with increasing hold time at peak tensile strain and cause the propagating fatigue crack to follow an intergranular path. At a strain range of +- 0.25% the dominant damage mechanism is due to creep damage when the tensile hold time is greater than one minute. The fatigue crack which causes final failure is nucleated at a stress raiser and it is possible that in a smooth specimen failure may occur without the nucleation of a fatigue crack at all but rather by ductile shearing. (author)

  1. Thermomechanical fatigue, oxidation, and Creep: Part II. Life prediction

    Science.gov (United States)

    Neu, R. W.; Sehitoglu, Huseyin

    1989-09-01

    A life prediction model is developed for crack nucleation and early crack growth based on fatigue, environment (oxidation), and creep damage. The model handles different strain-temperature phasings (i.e., in-phase and out-of-phase thermomechanical fatigue, isothermal fatigue, and others, including nonproportional phasings). Fatigue life predictions compare favorably with experiments in 1070 steel for a wide range of test conditions and strain-temperature phasings. An oxide growth (oxide damage) model is based on the repeated microrupture process of oxide observed from microscopic measurements. A creep damage expression, which is stress-based, is coupled with a unified constitutive equation. A set of interrupted tests was performed to provide valuable damage progression information. Tests were performed in air and in helium atmospheres to isolate creep damage from oxidation damage.

  2. Mental Fatigue Affects Visual Selective Attention

    NARCIS (Netherlands)

    Faber, Leon G.; Maurits, Natasha M.; Lorist, Monicque M.

    2012-01-01

    Mental fatigue is a form of fatigue, induced by continuous task performance. Mentally fatigued people often report having a hard time keeping their attention focussed and being easily distracted. In this study, we examined the relation between mental fatigue, as induced by time on task, and

  3. The role of central and peripheral muscle fatigue in postcancer fatigue: a randomized controlled trial

    NARCIS (Netherlands)

    Prinsen, Hetty; van Dijk, Johannes P.; Zwarts, Machiel J.; Leer, Jan Willem H.; Bleijenberg, Gijs; van Laarhoven, Hanneke W. M.

    2015-01-01

    Postcancer fatigue is a frequently occurring problem, impairing quality of life. Little is known about (neuro)physiological factors determining postcancer fatigue. It may be hypothesized that postcancer fatigue is characterized by low peripheral muscle fatigue and high central muscle fatigue. The

  4. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Unknown

    ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 µm and. 25 µm, and a sintered silicon ... the sintered silicon carbide was found out to be linked to its previous thermal history. Keywords. Indentation fatigue .... This presence of a grain size effect in the RIF behaviour of the ...

  5. Muscular synergy in the shoulder during a fatiguing static contraction.

    Science.gov (United States)

    Nieminen, H; Takala, E-P; Niemi, J; Viikari-Juntura, E

    1995-09-01

    The synergic operation of shoulder muscles during a fatiguing submaximal arm flexion task was studied using both a biomechanical 3-dimensional shoulder model and electromyographic recordings. A new optimization scheme aiming to maximize the task endurance time by constantly regulating the force output of each muscle is utilized in the model. The method can be used to simulate the muscle rotation phenomenon, which has been proposed to occur during an endurance type contraction. The model predictions on the fatigue order of the shoulder muscles were compared to results derived using the median frequencies of the electromyographic signals from nine muscles or muscle parts. In the test performed 10 men held until exhaustion a weight (4 kg) suspended on the wrist with the arm in horizontal flexion. The deltoid, infraspinatus, and supraspinatus muscles were the first to show electromyographic signs of fatigue. The times for detecting electromyographic changes in the trapezius muscle were longer than those in the muscles first showing electromyographic signs of fatigue. The biomechanical model used predicted the upper and lower infraspinatus and the anterior part of the deltoid to be the first to show signs of fatigue during the flexion task. The predictions of the biomechanical model on the order of fatigue of the nine shoulder muscles monitored also using electromyographic recordings corresponded to the electromyographic results. However, the accuracy of this comparison is limited by the fact that the electromyographic recordings did not cover all the muscles used in the model. No clear order was found for the development of electromyographic signs of muscle fatigue. RELEVANCE--:The biomechanical model and the developed optimization methods provide new tools for studying the synergic operation of shoulder muscles during fatiguing contractions. Our results will help in analysing and optimizing shoulder load in problematic functions both of work and leisure activities.

  6. Fatigue Performance under Multiaxial Loading

    Science.gov (United States)

    1990-01-01

    Abramov and H. Nagler. "Investigation of Effect of Welding on the Fatigue Properties of HY-80 Steel," New York Naval Shipyard, Material Laboratory...Project 6160-2, Progress Report 3, July 1961. 4-23.Stern, I., R. Wolfe, H. Nagler and P. Abramov . "Effects of Various Weld Flaws on Fatigue Properties of...V., P. Abramov and E. Lewis. "Investigation of the Effect of Welding on the Fatigue Properties of HY- 80 Steel," New York Naval Shipyard, Material

  7. Microstructure-sensitive extreme value probabilities of fatigue in advanced engineering alloys

    Science.gov (United States)

    Przybyla, Craig P.

    A novel microstructure-sensitive extreme value probabilistic framework is introduced to evaluate material performance/variability for damage evolution processes (e.g., fatigue, fracture, creep). This framework employs newly developed extreme value marked correlation functions (EVMCF) to identify the coupled microstructure attributes (e.g., phase/grain size, grain orientation, grain misorientation) that have the greatest statistical relevance to the extreme value response variables (e.g., stress, elastic/plastic strain) that describe the damage evolution processes of interest. This is an improvement on previous approaches that account for distributed extreme value response variables that describe the damage evolution process of interest based only on the extreme value distributions of a single microstructure attribute; previous approaches have given no consideration of how coupled microstructure attributes affect the distributions of extreme value response. This framework also utilizes computational modeling techniques to identify correlations between microstructure attributes that significantly raise or lower the magnitudes of the damage response variables of interest through the simulation of multiple statistical volume elements (SVE). Each SVE for a given response is constructed to be a statistical sample of the entire microstructure ensemble (i.e., bulk material); therefore, the response of interest in each SVE is not expected to be the same. This is in contrast to computational simulation of a single representative volume element (RVE), which often is untenably large for response variables dependent on the extreme value microstructure attributes. This framework has been demonstrated in the context of characterizing microstructure-sensitive high cycle fatigue (HCF) variability due to the processes of fatigue crack formation (nucleation and microstructurally small crack growth) in polycrystalline metallic alloys. Specifically, the framework is exercised to

  8. Maize sugary enhancer1 (se1) is a presence-absence variant of a previously uncharacterized gene and development of educational videos to raise the profile of plant breeding and improve curricula

    Science.gov (United States)

    Haro von Mogel, Karl J.

    Carbohydrate metabolism is a biologically, economically, and culturally important process in crop plants. Humans have selected many crop species such as maize (Zea mays L.) in ways that have resulted in changes to carbohydrate metabolic pathways, and understanding the underlying genetics of this pathway is therefore exceedingly important. A previously uncharacterized starch metabolic pathway mutant, sugary enhancer1 (se1), is a recessive modifier of sugary1 (su1) sweet corn that increases the sugar content while maintaining an appealing creamy texture. This allele has been incorporated into many sweet corn varieties since its discovery in the 1970s, however, testing for the presence of this allele has been difficult. A genetic stock was developed that allowed the presence of se1 to be visually scored in segregating ears, which were used to genetically map se1 to the deletion of a single gene model located on the distal end of the long arm of chromosome 2. An analysis of homology found that this gene is specific to monocots, and the gene is expressed in the endosperm and developing leaf. The se1 allele increased water soluble polysaccharide (WSP) and decreased amylopectin in maize endosperm, but there was no overall effect on starch content in mature leaves due to se1. This discovery will lead to a greater understanding of starch metabolism, and the marker developed will assist in breeding. There is a present need for increased training for plant breeders to meet the growing needs of the human population. To raise the profile of plant breeding among young students, a series of videos called Fields of Study was developed. These feature interviews with plant breeders who talk about what they do as plant breeders and what they enjoy about their chosen profession. To help broaden the education of students in college biology courses, and assist with the training of plant breeders, a second video series, Pollination Methods was developed. Each video focuses on one or two

  9. Catastrophe models for cognitive workload and fatigue in N-back tasks.

    Science.gov (United States)

    Guastello, Stephen J; Reiter, Katherine; Malon, Matthew; Timm, Paul; Shircel, Anton; Shaline, James

    2015-04-01

    N-back tasks place a heavy load on working memory, and thus make good candidates for studying cognitive workload and fatigue (CWLF). This study extended previous work on CWLF which separated the two phenomena with two cusp catastrophe models. Participants were 113 undergraduates who completed 2-back and 3-back tasks with both auditory and visual stimuli simultaneously. Task data were complemented by several measures hypothesized to be related to cognitive elasticity and compensatory abilities and the NASA TLX ratings of subjective workload. The adjusted R2 was .980 for the workload model, which indicated a highly accurate prediction with six bifurcation (elasticity versus rigidity) effects: algebra flexibility, TLX performance, effort, and frustration; and psychosocial measures of inflexibility and monitoring. There were also two cognitive load effects (asymmetry): 2 vs. 3-back and TLX temporal demands. The adjusted R2 was .454 for the fatigue model, which contained two bifurcation variables indicating the amount of work done, and algebra flexibility as the compensatory ability variable. Both cusp models were stronger than the next best linear alternative model. The study makes an important step forward by uncovering an apparently complete model for workload, finding the role of subjective workload in the context of performance dynamics, and finding CWLF dynamics in yet another type of memory-intensive task. The results were also consistent with the developing notion that performance deficits induced by workload and deficits induced by fatigue result from the impact of the task on the workspace and executive functions of working memory respectively.

  10. Rolling-contact fatigue resistance of hard coatings on bearing steels.

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, A.

    1999-08-18

    Ball- and roller-bearings of the 21st Century are expected to perform better and last longer while operating under more stringent conditions than before. To meet these great expectations, researchers have been constantly exploring new bearing designs or refining existing ones, optimizing microstructure and chemistry of bearing materials, and alternatively, they have been considering the use of thin hard coatings for improved bearing performance and durability. Already, some laboratory tests have demonstrated that hard nitride, carbide (such as TiN, TiC, etc.) and diamondlike carbon (DLC) coatings can be very effective in prolonging the fatigue lives of bearing steels. This paper provides an overview of the recent developments in hard coatings for bearing applications. Previous studies have demonstrated that thin, hard coatings can effectively prolong the fatigue lives of bearing steel substrates. In particular, thinner hard coatings (i.e., 0.2 - 1 {micro}m thick) provide exceptional improvements in the fatigue lives of bearing steel substrates. In contrast, thicker hard coatings suffer micro fracture and delamination when tested under high contact stresses, hence are ineffective and may even have a negative effect on bearing life. Overall, it was concluded that thin hard coatings may offer new possibilities for bearing industry in meeting the performance and durability needs of the 21st Century.

  11. Fatigue and rupture codified rules comparison

    International Nuclear Information System (INIS)

    Faidy, C.

    2004-01-01

    The European Directive on Pressure Equipment requests risk studies and in particular to assure no risk of fatigue and rupture in operation. The answers to these questions are different in the different existing design codes (EN Standards, ASME III and VIII or RCC-M or CODAP-CODETI codes) and corresponding in operation codes (ASME or RSE-M). Design safety factors, material properties, fabrication, refinement in the analysis methods, monitoring in operation, hydro-proof test level... Around these Codes, different rules are under development. A16 in France, R6 in UK or FITNET at the EC level. This paper is concerned by a comparison between 2 different Codes to analyze the risk of fatigue or rupture of pressure equipments and mainly a comparison between RCC-M Code and EN 13445 standard for pressure vessel. Recommendations for future work will be proposed. (authors)

  12. Investigation of fatigue by Australian general practice registrars: a cross-sectional study.

    Science.gov (United States)

    Morgan, Simon; Henderson, Kim M; Tapley, Amanda; Thomson, Allison; Wilson, Jessica; Scott, John; Spike, Neil A; McArthur, Lawrie; van Driel, Mieke L; Magin, Parker J

    2015-06-01

    Fatigue is the most common undifferentiated problem presenting in general practice. Previous studies have shown that this presentation leads to multiple investigations. There is no published literature describing the management of patients with fatigue by general practice (GP) registrars. To document the investigation-ordering behaviour of GP registrars in managing patients with a new diagnosis of unexplained fatigue. This was a cross-sectional analysis of data from Registrar Clinical Encounters in Training (ReCEnT), an ongoing cohort study of GP registrars' consultations. We established the prevalence of new diagnoses of unexplained fatigue and associations with that diagnosis, the rate of test ordering and the number and types of investigations ordered. 644 registrars contributed data from 68 986 encounters. In 0.78% of patient encounters, a new diagnosis of unexplained fatigue was made. Pathology was ordered in 78.4% of these problems (versus 18.1% in non-fatigue problems), at a rate of 488 tests per 100 new fatigue problems. Our study suggests that unexplained fatigue elicits a non-rational approach to test ordering by registrars. These findings contribute to the understanding of GP registrar management of fatigue, and undifferentiated presentations more broadly, and suggest educational approaches to improve practice, including dealing with uncertainty.

  13. Fatigue in Younger and Older Drivers: Effectiveness of an Alertness-Maintaining Task.

    Science.gov (United States)

    Song, Woojin; Woon, Fu L; Doong, Alice; Persad, Carol; Tijerina, Louis; Pandit, Pooja; Cline, Carol; Giordani, Bruno

    2017-09-01

    The aim of this study was to examine the effects of an alertness-maintaining task (AMT) in older, fatigued drivers. Fatigue during driving increases crash risk, and previous research suggests that alertness and driving in younger adults may be improved using a secondary AMT during boring, fatigue-eliciting drives. However, the potential impact of an AMT on driving has not been investigated in older drivers whose ability to complete dual tasks has been shown to decline and therefore may be negatively affected with an AMT in driving. Younger ( n = 29) and older drivers ( n = 39) participated in a 50-minute simulated drive designed to induce fatigue, followed by four 10-minute sessions alternating between driving with and without an AMT. Younger drivers were significantly more affected by fatigue on driving performance than were older drivers but benefitted significantly from the AMT. Older drivers did not demonstrate increased driver errors with fatigue, and driving did not deteriorate significantly during participation in the AMT condition, although their speed was significantly more variable with the AMT. Consistent with earlier research, an AMT applied during fatiguing driving is effective in improving alertness and reducing driving errors in younger drivers. Importantly, older drivers were relatively unaffected by fatigue, and use of an AMT did not detrimentally affect their driving performance. These results support the potential use of an AMT as a new automotive technology to improve fatigue and promote driver safety, though the benefits of such technology may differ between different age groups.

  14. SI:FatiguePro 4 Advanced Approach for Fatigue Monitoring

    International Nuclear Information System (INIS)

    Evon, Keith; Gilman, Tim; Carney, Curt

    2012-01-01

    Many nuclear plants are making commitments to implement fatigue monitoring systems in support of license renewal. Current fatigue monitoring systems use the methodology of ASME Code Subarticle NB-3200, which is a design code intended to compute a bounding cumulative usage factor (CUF). The first generation of fatigue monitoring software utilized a simplified, single stress term assumption and classical stress cycle-counting methods that take order into account such as Rainflow or Ordered Overall Range counting. Recently, the NRC has indicated in Regulatory Issue Summary 2008-30 that any fatigue analyses in support of License Renewal should use ASME Code Section III methodologies considering all six stress components. In addition, fatigue calculations for the license renewal term are required to consider the effects of environment. The implementation of a six stress term NB-3200 fatigue calculation to a Boiling Water Reactor (BWR) feedwater nozzle, including environmental effects, is the topic of this paper. Differences in results between the advanced methodology and the simplified methodology are discussed. (author)

  15. Muscle fatigue: general understanding and treatment

    Science.gov (United States)

    Wan, Jing-jing; Qin, Zhen; Wang, Peng-yuan; Sun, Yang; Liu, Xia

    2017-01-01

    Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments. PMID:28983090

  16. Muscle fatigue: general understanding and treatment

    OpenAIRE

    Wan, Jing-jing; Qin, Zhen; Wang, Peng-yuan; Sun, Yang; Liu, Xia

    2017-01-01

    Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments.

  17. Fatigue Monitoring Tool for Airline Operators (FMT

    Directory of Open Access Journals (Sweden)

    Gislason Sigurdur Hrafn

    2017-12-01

    Full Text Available A Fatigue Monitoring Tool (FMT model was constructed for an operational airline in order to manage the fatigue levels of their crews in accordance with Fatigue Risk Management System (FRMS practices. This article describes the implementation of the Fatigue Monitoring Tool model and the airline’s aims to put the recent scientific findings on aviation fatigue into practical use. The model consists of proxy points allotted to various duties and rest periods.

  18. Lifetime evaluation for thermal fatigue: application at the first wall of a tokamak fusion reactor

    International Nuclear Information System (INIS)

    Merola, M.; Biggio, M.

    1989-01-01

    Thermal fatigue seems to be the most lifetime limiting phenomenon for the first wall of the next generation Tokamak fusion reactors. This work deals with the problem of the thermal fatigue in relation to the lifetime prediction of the fusion reactor first wall. The aim is to compare different lifetime methodologies among them and with experimental results. To fulfil this purpose, it has been necessary to develop a new numerical methodology, called reduced-3D, especially suitable for thermal fatigue problems

  19. Fatigue with HIV/AIDS

    Science.gov (United States)

    ... hormones such as DHEA (see Fact Sheet 724) , cortisol or thyroid can cause similar problems. Hormone levels ... fatigue and a lack of interest in daily activities. There is no blood test ... sexual functioning. Also, some antidepressants interact with some ARVs, ...

  20. Fatigue life prediction in composites

    CSIR Research Space (South Africa)

    Huston, RJ

    1994-01-01

    Full Text Available epoxy were used to test residual strength and residual stiffness models. Further fatigue tests were carried out under spectrum loading so that the results could be correlated with the cumulative damage predicted by the residual strength model....

  1. 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.

  2. [Placental complications after a previous cesarean section].

    Science.gov (United States)

    Milosević, Jelena; Lilić, Vekoslav; Tasić, Marija; Radović-Janosević, Dragana; Stefanović, Milan; Antić, Vladimir

    2009-01-01

    The incidence of cesarean section has been rising in the past 50 years. With the increased number of cesarean sections, the number of pregnancies with the previous cesarean section rises as well. The aim of this study was to establish the influence of the previous cesarean section on the development of placental complications: placenta previa, placental abruption and placenta accreta, as well as to determine the influence of the number of previous cesarean sections on the complication development. The research was conducted at the Clinic of Gynecology and Obstetrics in Nis covering 10-year-period (from 1995 to 2005) with 32358 deliveries, 1280 deliveries after a previous cesarean section, 131 cases of placenta previa and 118 cases of placental abruption. The experimental groups was presented by the cases of placenta previa or placental abruption with prior cesarean section in obstetrics history, opposite to the control group having the same conditions but without a cesarean section in medical history. The incidence of placenta previa in the control group was 0.33%, opposite to the 1.86% incidence after one cesarean section (pcesarean sections and as high as 14.28% after three cesarean sections in obstetric history. Placental abruption was recorded as placental complication in 0.33% pregnancies in the control group, while its incidence was 1.02% after one cesarean section (pcesarean sections. The difference in the incidence of intrapartal hysterectomy between the group with prior cesarean section (0.86%) and without it (0.006%) shows a high statistical significance (pcesarean section is an important risk factor for the development of placental complications.

  3. Testing methodologies for corrosion fatigue

    OpenAIRE

    Delmotte, Edward; Micone, Nahuel; De Waele, Wim

    2015-01-01

    Offshore constructions are subjected to cyclic loading conditions. This situation is combined with the corrosive nature of the surrounding environment. It is of actual concern whether the combined effect is more damaging or not than the superposition of each effect independently. This literature review first introduces the reader to corrosion fatigue. Thereafter a critical comparison of some typical lab-scale fatigue corrosion test setups is given. Special emphasis is devoted to the instru...

  4. Evaluation of upper limb muscle fatigue based on surface electromyography.

    Science.gov (United States)

    Zhou, Qianxiang; Chen, Yuhong; Ma, Chao; Zheng, Xiaohui

    2011-10-01

    Fatigue is believed to be a major contributory factor to occupational injuries in machine operators. The development of accurate and usable techniques to measure operator fatigue is therefore important. In this study, we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action. Thirteen young males performed isometric actions with the upper limb at different force levels. sEMG activities of the biceps brachii were recorded during the actions. Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions. sEMG activities were analyzed using the one-third band octave method, and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale. The results showed that the relationship could be expressed by a conic curve, and could be used to evaluate muscle fatigue during machine operation.

  5. Fatigue behaviour of metals. 2. ed.; Ermuedungsverhalten metallischer Werkstoffe

    Energy Technology Data Exchange (ETDEWEB)

    Christ, H.J. [Siegen Univ. (Gesamthochschule) (Germany). Inst. fuer Werkstofftechnik

    2009-07-01

    The book presents an outline of the fatigue characteristics of metals. Interested students, engineers, scientists and users are provided with a basic understanding of the possible processes, from which they will get a feeling for the processes going on inside materials under fatigue stress which is indispensable for developing and testing modern constructional materials. Subjects: Introduction and outline - Material fatigue and microstructure - Cyclic stress-strain behaviour - Cracking - Electron microscopy - Fundamentals of fracture mechanics - Fatigue crack growth - Cyclic strength of steels - Thermomechanical fatigue - Operating strength of components - Fatigue of welded constructions. [German] In dem vorliegenden Buch wird ein Ueberblick ueber die Ermuedung metallischer Werkstoffe gegeben. Interessierten Studenten, Ingenieuren, Wissenschaftlern und Anwendern wird ein Grundverstaendnis fuer die moeglichen Prozesse vermittelt, aus dem sich ein Gefuehl fuer die Vorgaenge im Werkstoff bei zyklischer Beanspruchung entwickelt - unabdingbar fuer Entwicklung und Pruefung moderner Kontruktionswerkstoffe. Es enthaelt folgende Themen: Einfuehrung und Ueberblick - Materialermuedung und Mikrostruktur - Zyklisches Spannungs-Dehnungsverhalten - Rissbildung - Elektronenmikroskopische Untersuchungen - Grundlagen der Bruchmechanik - Ermuedungsrisswachstum - Schwingfestigkeit von Staehlen - Thermomechanisches Ermuedungsverhalten - Betriebsfestigkeit von Bauteilen - Ermuedung von Schweisskonstruktionen.

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

    Science.gov (United States)

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

    2017-12-08

    Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle, whereas frost fatigue was caused by a freeze-thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes. © 2017 John Wiley & Sons Ltd.

  7. Ultrathin flexible piezoelectric sensors for monitoring eye fatigue

    Science.gov (United States)

    Lü, Chaofeng; Wu, Shuang; Lu, Bingwei; Zhang, Yangyang; Du, Yangkun; Feng, Xue

    2018-02-01

    Eye fatigue is a symptom induced by long-term work of both eyes and brains. Without proper treatment, eye fatigue may incur serious problems. Current studies on detecting eye fatigue mainly focus on computer vision detect technology which can be very unreliable due to occasional bad visual conditions. As a solution, we proposed a wearable conformal in vivo eye fatigue monitoring sensor that contains an array of piezoelectric nanoribbons integrated on an ultrathin flexible substrate. By detecting strains on the skin of eyelid, the sensors may collect information about eye blinking, and, therefore, reveal human’s fatigue state. We first report the design and fabrication of the piezoelectric sensor and experimental characterization of voltage responses of the piezoelectric sensors. Under bending stress, the output voltage curves yield key information about the motion of human eyelid. We also develop a theoretical model to reveal the underlying mechanism of detecting eyelid motion. Both mechanical load test and in vivo test are conducted to convince the working performance of the sensors. With satisfied durability and high sensitivity, this sensor may efficiently detect abnormal eyelid motions, such as overlong closure, high blinking frequency, low closing speed and weak gazing strength, and may hopefully provide feedback for assessing eye fatigue in time so that unexpected situations can be prevented.

  8. Migraine in Gulf War Illness and Chronic Fatigue Syndrome: Prevalence, potential mechanisms, and evaluation

    Directory of Open Access Journals (Sweden)

    Rakib eRayhan

    2013-07-01

    Full Text Available Objective: To assess the prevalence of headache subtypes in Gulf War Illness and Chronic Fatigue Syndrome compared to controls. Background: Migraines are reported in Chronic Fatigue Syndrome (CFS. Approximately, 25% of the military personnel who served in the 1990-1991 Persian Gulf War have developed Gulf War Illness (GWI. Symptoms in GWI share considerable overlap with CFS, including headache complaints. The type and prevalence of headaches in GWI have not been adequately assessed.Methods: 50 GWI, 39 CFS and 45 controls were examined. Participants had structured headache evaluations based on the 2004 International Headache Society criteria. All subjects had history and physical examinations, measurements of systemic hyperalgesia (dolorimetry, assessments for exclusionary indicators, fatigue and symptom related questionnaires. Results: Migraines were detected in 64% of GWI (odds ratio, 11.6, [±95% CI, 4.1 to 32.5] and 82% of CFS subjects (odds ratio, 22.5, [±95% CI, 7.8 to 64.8] compared to only 13% of controls. There was a predominance of females in the CFS compared to GWI and controls. However, gender did not influence migraine status (x2= 2.7; P = 0.101. Measures of fatigue, pain, and other ancillary criteria were comparable between GWI and CFS subjects with and without headache. Conclusion: Results validate previous findings of migraine in CFS and confirms similar increased prevalence in GWI compared to controls. This suggests GWI and CFS subjects share pathophysiological mechanisms that underlie migraine attacks and contribute to the extensive overlap of symptom constructs and disease pathophysiology. The high migraine prevalence warrants the inclusion of a structured headache evaluation that coincides with clinical assessments of GWI and CFS diagnosis.

  9. Fatigue Characterization of Fire Resistant Syntactic Foam Core Material

    Science.gov (United States)

    Hossain, Mohammad Mynul

    Eco-Core is a fire resistant material for sandwich structural application; it was developed at NC A&T State University. The Eco-Core is made of very small amount of phenolic resin and large volume of flyash by a syntactic process. The process development, static mechanical and fracture, fire and toxicity safety and water absorption properties and the design of sandwich structural panels with Eco-Core material was established and published in the literature. One of the important properties that is needed for application in transportation vehicles is the fatigue performance under different stress states. Fatigue data are not available even for general syntactic foams. The objective of this research is to investigate the fatigue performance of Eco-Core under three types of stress states, namely, cyclic compression, shear and flexure, then document failure modes, and develop empherical equations for predicting fatigue life of Eco-Core under three stress states. Compression-Compression fatigue was performed directly on Eco-Core cylindrical specimen, whereas shear and flexure fatigue tests were performed using sandwich beam made of E glass-Vinyl Ester face sheet and Eco-Core material. Compression-compression fatigue test study was conducted at two values of stress ratios (R=10 and 5), for the maximum compression stress (sigmamin) range of 60% to 90% of compression strength (sigmac = 19.6 +/- 0.25 MPa) for R=10 and 95% to 80% of compression strength for R=5. The failure modes were characterized by the material compliance change: On-set (2% compliance change), propagation (5%) and ultimate failure (7%). The number of load cycles correspond to each of these three damages were characterized as on-set, propagation and total lives. A similar approach was used in shear and flexure fatigue tests with stress ratio of R=0.1. The fatigue stress-number of load cycles data followed the standard power law equation for all three stress states. The constant of the equation were

  10. A wireless body measurement system to study fatigue in multiple sclerosis

    DEFF Research Database (Denmark)

    Yu, Fei; Rabotti, Chiara; Bilberg, Arne

    2012-01-01

    Fatigue is reported as the most common symptom by patients with multiple sclerosis (MS). The physiological and functional parameters related to fatigue in MS patients are currently not well established. A new wearable wireless body measurement system, named Fatigue Monitoring System (FAMOS......), was developed to study fatigue in MS. It can continuously measure electrocardiogram, body-skin temperature, electromyogram and motions of feet. The goal of this study is to test the ability of distinguishing fatigued MS patients from healthy subjects by the use of FAMOS. This paper presents the realization...... of the measurement system including the design of both hardware and dedicated signal processing algorithms. Twenty-six participants including 17 MS patients with fatigue and 9 sex- and age-matched healthy controls were included in the study for continuous 24 h monitoring. The preliminary results show significant...

  11. A practical approach for predicting fatigue reliability under random cyclic loading

    International Nuclear Information System (INIS)

    Tang Jun; Zhao Jie

    1995-01-01

    The purpose of this paper is to provide a simple approach for reliability analysis based on fatigue or overstress failure modes of mechanical components, and explain how this integrated method carries out spectral fatigue damage and failure reliability analysis. In exploring the ability to predict spectral fatigue life and assess the reliability under a specified dynamics environment, a methodology for reliability assessment and its corresponding fatigue life prediction of mechanical components using a supply-demand interference approach is developed in this paper. Since the methodology couples dynamics analysis and stochastic analysis for fatigue damage and reliability prediction, the conversion of the duty cycle history for the reliability study of an individual component is also presented. Using the proposed methodology, mechanical component reliability can be predicted according to different mission requirements. For an explanation of this methodology, a probabilistic method of deciding the relationship between the allowable stress or fatigue endurance limit and reliability is also presented

  12. A review of fatigue crack propagation modelling techniques using FEM and XFEM

    Science.gov (United States)

    Rege, K.; Lemu, H. G.

    2017-12-01

    Fatigue is one of the main causes of failures in mechanical and structural systems. Offshore installations, in particular, are susceptible to fatigue failure due to their exposure to the combination of wind loads, wave loads and currents. In order to assess the safety of the components of these installations, the expected lifetime of the component needs to be estimated. The fatigue life is the sum of the number of loading cycles required for a fatigue crack to initiate, and the number of cycles required for the crack to propagate before sudden fracture occurs. Since analytical determination of the fatigue crack propagation life in real geometries is rarely viable, crack propagation problems are normally solved using some computational method. In this review the use of the finite element method (FEM) and the extended finite element method (XFEM) to model fatigue crack propagation is discussed. The basic techniques are presented, together with some of the recent developments.

  13. Study on determination of durability analysis process and fatigue damage parameter for rubber component

    International Nuclear Information System (INIS)

    Moon, Seong In; Cho, Il Je; Woo, Chang Su; Kim, Wan Doo

    2011-01-01

    Rubber components, which have been widely used in the automotive industry as anti-vibration components for many years, are subjected to fluctuating loads, often failing due to the nucleation and growth of defects or cracks. To prevent such failures, it is necessary to understand the fatigue failure mechanism for rubber materials and to evaluate the fatigue life for rubber components. The objective of this study is to develop a durability analysis process for vulcanized rubber components, that can predict fatigue life at the initial product design step. The determination method of nonlinear material constants for FE analysis was proposed. Also, to investigate the applicability of the commonly used damage parameters, fatigue tests and corresponding finite element analyses were carried out and normal and shear strain was proposed as the fatigue damage parameter for rubber components. Fatigue analysis for automotive rubber components was performed and the durability analysis process was reviewed

  14. 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.

  15. Fatigue in engineering structures. A three fold analysis approach

    International Nuclear Information System (INIS)

    Malik, Afzaal M.; Qureshi, Ejaz M.; Dar, Naeem Ullah; Khan, Iqbal

    2007-01-01

    The integrity in most of the engineering structures in influenced by the presence of cracks or crack like defects. These structures fail, even catastrophically if a crack greater than a critically safe size exist. Although most of the optimal designed structures are initially free from critical cracks, sub-critical cracks can lead to failures under cyclic loadings, called fatigue crack growth. It is nearly impractical to prevent sub-critical crack growth in engineering structures particularly in crack sensitive structures like most of the structures in nuclear, aerospace and aeronautical domains. However, it is essential to predict the fatigue crack growth for these structures to preclude the in service failures causing loss of assets. The present research presents an automatic procedure for the prediction of fatigue crack growth in three dimensional engineering structures and the key data for the fracture mechanics based design: the stress intensity factors. Three fold analysis procedures are adopted to investigate the effects of repetitive (cyclic) loadings on the fatigue life of different geometries of aluminum alloy 2219-O. A general purpose Finite Element (FE) Code ANSYS-8.0 is used to predict/estimate the fatigue life of the geometries. Computer codes utilizing the Green's Function are developed to calculate the stress intensity factors. Another code based on superposition technique presented by Shivakumara and Foreman is developed to calculate the fatigue crack growth rate, fatigue life (No. of loading cycles are developed to validate the results and finally full scale laboratory tests are conducted for the comparison of the results. The results showing a close co-relation between the different techniques employed gives the promising feature of the analysis approach for the future work. (author)

  16. Modeling of the mechanical behavior of austenitic stainless steels under pure fatigue and fatigue relaxation loadings

    International Nuclear Information System (INIS)

    Hajjaji-Rachdi, Fatima

    2015-01-01

    Austenitic stainless steels are potential candidates for structural components of sodium-cooled fast neutron reactors. Many of these components will be subjected to cyclic loadings including long hold times (1 month) under creep or relaxation at high temperature. These hold times are unattainable experimentally. The aim of the present study is to propose mechanical models which take into account the involved mechanisms and their interactions during such complex loadings. First, an experimental study of the pure fatigue and fatigue-relaxation behavior of 316L(N) at 500 C has been carried out with very long hold times (10 h and 50 h) compared with the ones studied in literature. Tensile tests at 600 C with different applied strain rates have been undertaken in order to study the dynamic strain ageing phenomenon. Before focusing on more complex loadings, the mean field homogenization approach has been used to predict the mechanical behavior of different FCC metals and alloys under low cycle fatigue at room temperature. Both Hill-Hutchinson and Kroener models have been used. Next, a physically-based model based on dislocation densities has been developed and its parameters measured. The model allows predictions in a qualitative agreement with experimental data for tensile loadings. Finally, this model has been enriched to take into account visco-plasticity, dislocation climb and interaction between dislocations and solute atoms, which are influent during creep-fatigue or fatigue relaxation at high temperature. The proposed model uses three adjustable parameters only and allows rather accurate prediction of the behavior of 316L(N) steel under tensile loading and relaxation. (author) [fr

  17. Comparison of mechanical fatigue with thermal fatigue in ceramics

    International Nuclear Information System (INIS)

    Wilson, B.A.; Case, E.D.

    1993-01-01

    Thermal fatigue studies have shown a saturation of damage accumulation with cycling. Similar damage saturation has been observed for mechanical fatigue. This study compares damage saturation behavior for mechanical fatigue with thermal fatigue in ceramics. Studies of thermal fatigue of ceramics show that the accumulation of thermal shock cycling damage depends on the magnitude of the thermal shock, ΔΤ (where ΔΤ is the temperature change of the specimen from the initial temperature to the temperature of the quenching medium). Three distinct regimes of damage accumulation exist depending on the magnitude of ΔΤ. For the first regime where the thermal shock cycling is below ΔΤ c , a critical thermal shock value, there is no thermal damage detected. In the second regime where ΔΤ is higher than ΔΤ c but lower than ΔΤ 1 , the accumulating microcrack damage initially induces a rapid change in material property P. As the number of cycles increases a steady state value of properties is reached. For the third regime ΔΤ is higher than ΔΤ 1 and rapid crack growth results in fracture of the specimen. Each regime depends on ΔΤ since, for a given specimen and quenching medium, the maximum thermal shock stress is proportional to ΔΤ. So characterization of each regime by ΔΤ is indicative of the maximum stress applied by the thermal shock

  18. The influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination during weightlifting.

    Science.gov (United States)

    Hu, Boyi; Ning, Xiaopeng

    2015-01-01

    Lumbar muscle fatigue is a potential risk factor for the development of low back pain. In this study, we investigated the influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination patterns during weightlifting. Each of the 15 male subjects performed five repetitions of weightlifting tasks both before and after a lumbar extensor muscle fatiguing protocol. Lumbar muscle electromyography was collected to assess fatigue. Trunk kinematics was recorded to calculate lumbar-pelvic continuous relative phase (CRP) and CRP variability. Results showed that fatigue significantly reduced the average lumbar-pelvic CRP value (from 0.33 to 0.29 rad) during weightlifting. The average CRP variability reduced from 0.17 to 0.15 rad, yet this change ws statistically not significant. Further analyses also discovered elevated spinal loading during weightlifting after the development of lumbar extensor muscle fatigue. Our results suggest that frequently experienced lumbar extensor muscle fatigue should be avoided in an occupational environment. Lumbar extensor muscle fatigue generates more in-phase lumbar-pelvic coordination patterns and elevated spinal loading during lifting. Such increase in spinal loading may indicate higher risk of back injury. Our results suggest that frequently experienced lumbar muscle fatigue should be avoided to reduce the risk of LBP.

  19. Time and frequency domain models for multiaxial fatigue life estimation under random loading

    Directory of Open Access Journals (Sweden)

    Andrea Carpinteri

    2015-07-01

    Full Text Available Engineering structures and components are often subjected to random fatigue loading produced, for example, by wind turbulences, marine waves and vibrations. The methods available in the literature for fatigue assessment under random loading are formulated in time domain or, alternatively, in frequency domain. The former methods require the knowledge of the loading time history, and a large number of experimental tests/numerical simulations is needed to obtain statistically reliable results. The latter methods are generally more advantageous with respect to the time domain ones, allowing a rapid fatigue damage evaluation. In the present paper, a multiaxial criterion formulated in the frequency-domain is presented to estimate the fatigue lives of smooth metallic structures subjected to combined bending and torsion random loading. A comparison in terms of fatigue life prediction by employing a time domain methods, previously proposed by the authors, is also performed.

  20. An experimental approach to determining fatigue crack size in polyethylene tibial inserts.

    Science.gov (United States)

    Lockard, Carly A; Sanders, Anthony P; Raeymaekers, Bart

    2016-02-01

    A major limiting factor to the longevity of prosthetic knee joints is fatigue crack damage of the polyethylene tibial insert. Existing methods to quantify fatigue crack damage have several shortcomings, including limited resolution, destructive testing approach, and high cost. We propose an alternative fatigue crack damage visualization and measurement method that addresses the shortcomings of existing methods. This new method is based on trans-illumination and differs from previously described methods in its ability to non-destructively measure subsurface fatigue crack damage while using a simple and cost-effective bench-top set-up. We have evaluated this method to measure fatigue crack damage in two tibial inserts. This new method improves on existing image-based techniques due to its usability for subsurface damage measurement and its decreased reliance on subjective damage identification and measurement. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. An unbiased metagenomic search for infectious agents using monozygotic twins discordant for chronic fatigue

    Directory of Open Access Journals (Sweden)

    Jacks Andreas

    2011-01-01

    Full Text Available Abstract Background Chronic fatigue syndrome is an idiopathic syndrome widely suspected of having an infectious or immune etiology. We applied an unbiased metagenomic approach to try to identify known or novel infectious agents in the serum of 45 cases with chronic fatigue syndrome or idiopathic chronic fatigue. Controls were the unaffected monozygotic co-twins of cases, and serum samples were obtained at the same place and time. Results No novel DNA or RNA viral signatures were confidently identified. Four affected twins and no unaffected twins evidenced viremia with GB virus C (8.9% vs. 0%, p = 0.019, and one affected twin had previously undetected hepatitis C viremia. An excess of GB virus C viremia in cases with chronic fatigue requires confirmation. Conclusions Current, impairing chronic fatigue was not robustly associated with viremia detectable in serum.

  2. Do sleep, stress, and illness explain daily variations in fatigue? A prospective study.

    Science.gov (United States)

    Akerstedt, Torbjörn; Axelsson, John; Lekander, Mats; Orsini, Nicola; Kecklund, Göran

    2014-04-01

    Fatigue is related to a number of serious diseases, as well as to general well-being. It is also a major cause of sickness absence and use of health facilities. Still, the determinants of variations in fatigue are little investigated. The purpose of present study was to investigate the relationships between the daily variations of fatigue with sleep during the previous night, stress or disease symptoms during the same day - across 42 consecutive days of normal life. 50 individuals participated and gave diary reports and used an actigraph across the 42days. The data was analyzed using a multilevel approach with mixed model regression. The analyses showed that the day-to-day variation in fatigue was related to (poor) sleep quality (psleep duration (pstress (psleep (and sleepiness) as well as stress and illness are consistently connected to how fatigue is experienced during normal living conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Thermomechanical and bithermal fatigue behavior of cast B1900 + Hf and wrought Haynes 188

    Science.gov (United States)

    Halford, G. R.; Verrilli, M. J.; Kalluri, S.; Ritzert, F. J.; Duckert, R. E.; Holland, F. A.

    1992-01-01

    A thermomechanical fatigue (TMF) high-temperature life prediction method has been evaluated using the experimental data. Bithermal fatigue (BTF), bithermal creep-fatigue (BTC-F), and TMF experiments were performed using two aerospace structural alloys, cast B1900 + Hf and wrought Haynes 188. The method which is based on the total strain version of strain range partitioning and unified cyclic constitutive modeling requires, as an input, information on the flow and failure behavior of the material of interest. Bithermal temperatures of 483 and 871 C were used for the cast B1900 + Hf nickel-base alloy and 316 and 760 C for the wrought Haynes 188 cobalt-base alloy. Maximum and minimum temperatures were also used in both TMF and BTF tests. Comparisons were made between the results of these tests and isothermal tensile and fatigue test data obtained previously. Qualitative correlations were observed between tensile and isothermal fatigue tests.

  4. Machining of Aircraft Titanium with Abrasive-Waterjets for Fatigue Critical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H. T.; Hovanski, Yuri; Dahl, Michael E.

    2012-02-01

    Laboratory tests were conducted to determine the fatigue performance of abrasive-waterjet- (AWJ-) machined aircraft titanium. Dog-bone specimens machined with AWJs were prepared and tested with and without sanding and dry-grit blasting with Al2O3 as secondary processes. The secondary processes were applied to remove the visual appearance of AWJ-generated striations and to clean up the garnet embedment. The fatigue performance of AWJ-machined specimens was compared with baseline specimens machined with CNC milling. Fatigue test results of the titanium specimens not only confirmed our previous findings in aluminum dog-bone specimens but in comparison also further enhanced the fatigue performance of the titanium. In addition, titanium is known to be difficult to cut, particularly for thick parts, however AWJs cut the material 34% faster han stainless steel. AWJ cutting and dry-grit blasting are shown to be a preferred ombination for processing aircraft titanium that is fatigue critical.

  5. Vibration fatigue using modal decomposition

    Science.gov (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha

    2018-01-01

    Vibration-fatigue analysis deals with the material fatigue of flexible structures operating close to natural frequencies. Based on the uniaxial stress response, calculated in the frequency domain, the high-cycle fatigue model using the S-N curve material data and the Palmgren-Miner hypothesis of damage accumulation is applied. The multiaxial criterion is used to obtain the equivalent uniaxial stress response followed by the spectral moment approach to the cycle-amplitude probability density estimation. The vibration-fatigue analysis relates the fatigue analysis in the frequency domain to the structural dynamics. However, once the stress response within a node is obtained, the physical model of the structure dictating that response is discarded and does not propagate through the fatigue-analysis procedure. The structural model can be used to evaluate how specific dynamic properties (e.g., damping, modal shapes) affect the damage intensity. A new approach based on modal decomposition is presented in this research that directly links the fatigue-damage intensity with the dynamic properties of the system. It thus offers a valuable insight into how different modes of vibration contribute to the total damage to the material. A numerical study was performed showing good agreement between results obtained using the newly presented approach with those obtained using the classical method, especially with regards to the distribution of damage intensity and critical point location. The presented approach also offers orders of magnitude faster calculation in comparison with the conventional procedure. Furthermore, it can be applied in a straightforward way to strain experimental modal analysis results, taking advantage of experimentally measured strains.

  6. Probabilistic and microstructural aspects of fatigue cracks initiation in Inconel 718; Aspects probabilistes et microstructuraux de l'amorcage des fissures de fatigue dans l'alliage INCO 718

    Energy Technology Data Exchange (ETDEWEB)

    Alexandre, F

    2004-03-15

    Thermomechanical treatments have been recently developed to produce Inconel 718DA (Direct Aged). This alloy optimisation leads to an increase of the fatigue life but also the scatter. The aim of this study is on the one hand the understanding of the fatigue crack initiation mechanisms and on the other hand the modelling of the fatigue life and the scatter. An experimental study showed that the fatigue cracks were initiated from carbide particles in fine grain alloy. Interrupted tensile tests show that the particles cracking occurred at the first quarter of the fatigue cycle. Fatigue behaviour tests were also performed on various grain size 718 alloys. The last experimental part was devoted to measurements of the low cycle fatigue crack growth rates using a high focal distance microscope. For these tests, EDM micro-defects were used for the fatigue crack initiation sites. This method was also used to observe the small fatigue crack coalescence. A fatigue life model is proposed. It is based on the three fatigue crack initiation mechanisms competition: particle crack initiation on the surface, internal particle crack initiation and Stade I crack initiation. The particle fatigue crack initiation is supposed instantaneous at a critical stress level. The Tanaka and Mura model is used for analysing the Stage I crack initiation number of cycles. The fatigue crack growth rate was analysed using the Tomkins model identified on the small fatigue crack growth rate measurements. The proposed fatigue life model decomposed in three levels: a deterministic one and two probabilistic with and without crack coalescence. (author)

  7. Technologic Distractions (Part 1): Summary of Approaches to Manage Alert Quantity With Intent to Reduce Alert Fatigue and Suggestions for Alert Fatigue Metrics.

    Science.gov (United States)

    Kane-Gill, Sandra L; O'Connor, Michael F; Rothschild, Jeffrey M; Selby, Nicholas M; McLean, Barbara; Bonafide, Christopher P; Cvach, Maria M; Hu, Xiao; Konkani, Avinash; Pelter, Michele M; Winters, Bradford D

    2017-09-01

    To provide ICU clinicians with evidence-based guidance on tested interventions that reduce or prevent alert fatigue within clinical decision support systems. Systematic review of PubMed, Embase, SCOPUS, and CINAHL for relevant literature from 1966 to February 2017. Focus on critically ill patients and included evaluations in other patient care settings, as well. Identified interventions designed to reduce or prevent alert fatigue within clinical decision support systems. Study selection was based on one primary key question to identify effective interventions that attempted to reduce alert fatigue and three secondary key questions that covered the negative effects of alert fatigue, potential unintended consequences of efforts to reduce alert fatigue, and ideal alert quantity. Data were abstracted by two reviewers independently using a standardized abstraction tool. Surveys, meeting abstracts, "gray" literature, studies not available in English, and studies with non-original data were excluded. For the primary key question, articles were excluded if they did not provide a comparator as key question 1 was designed as a problem, intervention, comparison, and outcome question. We anticipated that reduction in alert fatigue, including the concept of desensitization may not be directly measured and thus considered interventions that reduced alert quantity as a surrogate marker for alert fatigue. Twenty-six articles met the inclusion criteria. Approaches for managing alert fatigue in the ICU are provided as a result of reviewing tested interventions that reduced alert quantity with the anticipated effect of reducing fatigue. Suggested alert management strategies include prioritizing alerts, developing sophisticated alerts, customizing commercially available alerts, and including end user opinion in alert selection. Alert fatigue itself is studied less frequently, as an outcome, and there is a need for more precise evaluation. Standardized metrics for alert fatigue is

  8. Rotor blade full-scale fatigue testing technology and research

    DEFF Research Database (Denmark)

    Nielsen, Per Hørlyk; Berring, Peter; Pavese, Christian

    was started in the beginning of the 1980´s and has been further developed since then. Structures in composite materials are generally difficult and time consuming to test for fatigue resistance. Therefore, several methods for testing of blades have been developed and exist today. These methods......Full scale fatigue test is an important part of the development and design of wind turbine blades. Testing is also needed for the approval of the blades in order for them to be used on large wind turbines. However, usually only one prototype blade is tested. Fatigue test of wind turbine blades...... will be presented in this report giving the blade test facility operator a guide to choose the method that best fit the needs and economic constraints. The state of the art method is currently dual axis mass resonance, where the purpose of the test is to emulate the loads the blades encounter in operation....

  9. Pain, depression, and fatigue: loneliness as a longitudinal risk factor.

    Science.gov (United States)

    Jaremka, Lisa M; Andridge, Rebecca R; Fagundes, Christopher P; Alfano, Catherine M; Povoski, Stephen P; Lipari, Adele M; Agnese, Doreen M; Arnold, Mark W; Farrar, William B; Yee, Lisa D; Carson, William E; Bekaii-Saab, Tanios; Martin, Edward W; Schmidt, Carl R; Kiecolt-Glaser, Janice K

    2014-09-01

    Pain, depression, and fatigue function as a symptom cluster and thus may share common risk factors. Interpersonal relationships clearly influence health, suggesting that loneliness may promote the development of the pain, depression, and fatigue symptom cluster. We hypothesized that loneliness would be related to concurrent symptom cluster levels and increases in symptom cluster levels over time. We utilized two observational studies with distinct longitudinal samples. Study 1 was a sample of cancer survivors and benign controls (N = 115) assessed annually for 2 years. Study 2 was a sample of older adults caring for a spouse with dementia (caregivers) and non-caregiver controls (N = 229) assessed annually for 4 years. Participants completed annual measures assessing loneliness, pain, depression, and fatigue. Across both samples, lonelier participants experienced more concurrent pain, depression, and fatigue and larger increases in symptom cluster levels from one year to the next than less lonely participants. Sleep quality did not mediate the results in either study. All analyses were adjusted for relevant demographic and health variables. Two longitudinal studies with different populations demonstrated that loneliness was a risk factor for the development of the pain, depression, and fatigue symptom cluster over time. The current research helps identify people most at risk for pain, depression, and fatigue, and lays the groundwork for research about their diagnosis and treatment. These data also highlight the health risks of loneliness; pain, depression, and fatigue often accompany serious illness and place people at risk for poor health and mortality. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  10. The Use of Hamstring Fatigue to Reduce Quadriceps Inhibition After Anterior Cruciate Ligament Reconstruction.

    Science.gov (United States)

    Lowe, Timothy; Dong, Xuanliang Neil

    2018-02-01

    Arthrogenic muscle inhibition, an inability to fully activate the quadriceps muscles, has been persistently observed after anterior cruciate ligament reconstruction (ACLr) surgery. Reductions in quadriceps activation may be partly due to the flexion reflex pathway, hamstrings activation, and reciprocal quadriceps inhibition. Since central fatigue has been shown to modify hamstring excitability and change the hamstring reflex response, hamstring fatigue might alleviate quadriceps muscle inhibition by counteracting the flexion reflex. In this study, nine young adult athletes (age: M = 19.9 years, SD = 1.7) with unilateral ACLr and nine control athletes (age: M = 24.0 years, SD = 2.4) with no previous history of knee injury performed tempo squats to induce fatigue. The ACLr group tended to use hamstrings for more hip flexion and trunk forward flexion than the control group. We assessed each participant's quadriceps inhibition through the central activation ratio (CAR), measured by twitch interpolation, before and after the induced fatigue. A mixed analysis of variance was used to examine the effect of fatigue on the CAR between pre- and post-fatigue and for both ACLr and control groups. The ACLr group showed significantly ( p = .010) greater CAR of the quadriceps post-fatigue ( M = 96.0%, SD = 7.6%) than pre-fatigue ( M = 81.2%, SD = 15.8%), while the control group showed no significant ( p = .969) pre-fatigue ( M = 96.9%, SD = 9.6%) and post-fatigue ( M = 97.0%, SD = 17.1%) differences. Thus, fatigue training may be used as a rehabilitation strategy to restore normal quadriceps function at the knee joint following ACL reconstruction by relaxing the hamstrings and overcoming quadriceps inhibition.

  11. Fatiguing exercise intensity influences the relationship between parameters reflecting neuromuscular function and postural control variables.

    Directory of Open Access Journals (Sweden)

    Sébastien Boyas

    Full Text Available The purpose of this study was to investigate the influence of fatiguing exercise intensity on the nature and extent of fatigue-induced changes in neuromuscular function and postural stability in quiet standing. We also explored the contribution of selected neuromuscular mechanisms involved in force production to postural stability impairment observed following fatigue using an approach based on multivariate regressions. Eighteen young subjects performed 30-s postural trials on one leg with their eyes closed. Postural trials were performed before and after fatiguing exercises of different intensities: 25, 50 and 75% of maximal isometric plantarflexor torque. Fatiguing exercises consisted of sustaining a plantarflexor isometric contraction at the target intensity until task failure. Maximal isometric plantarflexor torque, electromyographic activity of plantarflexor and dorsiflexor muscles, activation level (twitch interpolation technique and twitch contractile properties of plantarflexors were used to characterize neuromuscular function. The 25% exercise was associated with greater central fatigue whereas the 50 and 75% exercises involved mostly peripheral fatigue. However, all fatiguing exercises induced similar alterations in postural stability, which was unexpected considering previous literature. Stepwise multiple regression analyses showed that fatigue-related changes in selected parameters related to neuromuscular function could explain more than half (0.51≤R(2≤0.82 of the changes in postural variables for the 25% exercise. On the other hand, regression models were less predictive (0.17≤R(2≤0.73 for the 50 and 75% exercises. This study suggests that fatiguing exercise intensity does not influence the extent of postural stability impairment, but does influence the type of fatigue induced and the neuromuscular function predictors explaining changes in postural variables.

  12. The role of central and peripheral muscle fatigue in postcancer fatigue: a randomized controlled trial.

    Science.gov (United States)

    Prinsen, Hetty; van Dijk, Johannes P; Zwarts, Machiel J; Leer, Jan Willem H; Bleijenberg, Gijs; van Laarhoven, Hanneke W M

    2015-02-01

    Postcancer fatigue is a frequently occurring problem, impairing quality of life. Little is known about (neuro)physiological factors determining postcancer fatigue. It may be hypothesized that postcancer fatigue is characterized by low peripheral muscle fatigue and high central muscle fatigue. The aims of this study were to examine whether central and peripheral muscle fatigue differ between fatigued and non-fatigued cancer survivors and to examine the effect of cognitive behavioral therapy (CBT) on peripheral and central muscle fatigue of fatigued cancer survivors in a randomized controlled trial. Sixteen fatigued patients in the intervention group (CBT) and eight fatigued patients in the waiting list group were successfully assessed at baseline and six months later. Baseline measurements of 20 fatigued patients were compared with 20 non-fatigued patients. A twitch interpolation technique and surface electromyography were applied, respectively, during sustained contraction of the biceps brachii muscle. Muscle fiber conduction velocity (MFCV) and central activation failure (CAF) were not significantly different between fatigued and non-fatigued patients. Change scores of MFCV and CAF were not significantly different between patients in the CBT and waiting list groups. Patients in the CBT group reported a significantly larger decrease in fatigue scores than patients in the waiting list group. Postcancer fatigue is neither characterized by abnormally high central muscle fatigue nor by low peripheral muscle fatigue. These findings suggest a difference in the underlying physiological mechanism of postcancer fatigue vs. other fatigue syndromes. Copyright © 2015 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

  13. Ischemia causes muscle fatigue

    Science.gov (United States)

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

    2001-01-01

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

  14. Analysis of SNL/MSU/DOE Fatigue Database Trends for Wind Turbine Blade Materials 2010-2015.

    Energy Technology Data Exchange (ETDEWEB)

    John F. Mandell; Daniel D. Samborsky; David A. Miller; Pancasatya Agastra; Aaron T. Sears

    2016-02-01

    Wind turbine blades are designed to several major structural conditions, including tip deflection, strength and b uckling during severe loading, as well as very high numbers of fatigue cycles and various service environments. The MSU Database Program has, since 1989, addressed the broad range of properties needed for current and potential blade materials through stati c and fatigue testing and test development in cooperation with Sandia National Laboratories and wind industry and supplier partners. This report is the latest in a series, giving test results and analysis for the period 2010 - 2015. Program data are compiled in a public database [1] and other reports and publications given in the cited references. The report begins with an executive summary and introductory material including background discussion of previous related studies. Section 3 describes experimental methods including processing, test methods, instrumentation and test development. Section 4 provides static tension, compression and shear stress - strain properties in three directions using coupons sectioned from a thick infused unidirectional glass/epoxy laminate. The nonlinear, shear dominated static properties were characterized with loading - u nloading - reloading (LUR) tests in tension and compression to increasing load levels, for +-45O laminates. Section 5 explores the origins of tensile fatigue sensitivity in glass fiber dominated laminates with variations in fabric architecture including speci ally prepared fabrics and aligned strand laminates. Several types of resins are considered, with variations in resin toughness and bonding to fibers, as well as cure cycle variations for an epoxy. Conclusions are drawn as to the limits of tensile fatigue r esistance and the effects of resin type and fabric architecture, including the behavior of a commercial aligned glass strand product. Interactions between cyclic fatigue response and creep are addressed for off - axis (+-45O) glass

  15. Clinically distinct trajectories of fatigue and their longitudinal relationship with the disturbance of personal goals following a cancer diagnosis.

    Science.gov (United States)

    Müller, Fabiola; Tuinman, Marrit A; Janse, Moniek; Almansa, Josué; Sprangers, Mirjam A G; Smink, Ans; Ranchor, Adelita V; Fleer, Joke; Hagedoorn, Mariët

    2017-09-01

    Most studies on fatigue in patients with cancer aggregate its prevalence and severity on a group level, ignoring the possibility that subgroups of patients may differ widely in their development of fatigue. This study aimed to identify subgroups of patients with clinically distinct trajectories of fatigue from diagnosis to 18 months post-diagnosis. As fatigue might trigger goal disturbance, the study also identified trajectories of concrete and abstract goal disturbance and longitudinally examined their co-occurrence with fatigue. Prospective design with quantitative and qualitative method of data collection. Patients with colorectal cancer (n = 183) reported on their levels of fatigue and goal disturbance shortly after diagnosis (T 1 ) and at 7 months (T 2 ) and 18 months (T 3 ) post-diagnosis. Growth mixture model analyses were performed to identify trajectories of fatigue and goal disturbance. Guidelines for the clinical relevance of fatigue were applied. Four clinically distinct trajectories of fatigue were identified as follows: (1) persistent severe fatigue (25.4%), (2) moderate fatigue (56.1%), (3) no fatigue (13.8%), and (4) rapidly improving fatigue (4.7%). The majority of patients with cancer reported high disturbance of their concrete goals, while high disturbance of abstract goals was less evident. Fatigue and concrete goal disturbance co-occurred longitudinally. The fatigue and goal disturbance experienced from diagnosis to 18 months post-diagnosis differ considerably for subgroups of patients with cancer. Fatigue and concrete goal disturbance are persistent burdens in the majority of patients. Investigating symptom burden beyond average trends can guide clinicians to identify patients most in need for treatment. Targeting goal disturbance might benefit the psychological well-being in patients suffering from persistent symptoms. Statement of contribution What is already known on this subject? Fatigue is a common and distressing symptom at all

  16. 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.

  17. High speed rails. Fatigue behaviour

    International Nuclear Information System (INIS)

    Duart, J. M.; Pero-Sanz, J. A.; Verdeja, J. I.

    2005-01-01

    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 (S f =353 MPa), oxipropane preheated aluminothermic weld rails (S f =225 MPa), and propane-air induced aluminothermic weld rails (S f =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

  18. Very high cycle fatigue life of 2.25Cr-1Mo steel at room and high temperatures

    International Nuclear Information System (INIS)

    Itoh, Takamoto; Hattori, Shuji; Fujii, Hiroshi; Wakatsuki, Hayato; Watashi, Katsumi; Hashimoto, Takashi

    2005-01-01

    An ultrasonic fatigue testing machine was developed to obtain the very high cycle fatigue life at elevated temperature for safety and reliability of structural components in the faster breeder reactor (FBR). This testing machine consists of an amplifier, booster, horn and equipments such as system controller and data acquisition. The test specimen is attached at the end of the horn. The electric power generated in the amplifier is transformed into the mechanical vibration in the converter and is magnified in the booster and horn. The developed ultrasonic fatigue testing machine enables to carry out the fatigue test at 20kHz so that it can perform the very high cycle fatigue test within a very shorter time as compared with the regular fatigue testing machines such as a hydraulic fatigue testing machine. This study carried out very high cycle fatigue tests using type STBA 24, the steel for tube in boiler and heat exchanger, at room and elevated (673K) temperatures by the developed testing and conventional hydraulic testing machines, and obtained the fatigue lives. This paper also described the cracks observed on specimen surface of fatigued specimen and discussed the very high cycle fatigue strength properties. It was confirmed that the fatigue data obtained by the ultrasonic fatigue testing machine are continuous and compatible with the results obtained by the hydraulic tension-compression testing machine. Fatigue lives more than 10 6 cycles at room and high temperatures can be predicted conservatively by the best fit design curve employed in the nuclear power plant design. (author)

  19. The effectiveness of nursing education as an intervention to decrease fatigue in Turkish patients receiving chemotherapy.

    Science.gov (United States)

    Yesilbalkan, Oznur Usta; Karadakovan, Ayfer; Göker, Erdem

    2009-07-01

    To determine whether a nurse-led educational intervention decreased the perception of fatigue in patients diagnosed with gastrointestinal (GI) cancers (colon, stomach, liver, rectum, pancreas) who were receiving chemotherapy for the first time. Quasi-experimental, descriptive. Outpatient department in a large university hospital in Izmir, Turkey. 35 patients receiving chemotherapy for GI cancers. Baseline demographic data were collected using a personal information form developed by the researchers. Fatigue and quality of life (QOL) were then assessed using the Brief Fatigue Inventory, the Piper Fatigue Scale, and the European Organisation for Research and Treatment of Cancer Quality of Life (EORTC QLQ C-30) scale before their first cycle of chemotherapy, on the 10th day after (T1), and again 10 days after the second cycle of chemotherapy (T2). Patients received an individual educational intervention at baseline, T1, and T2 based on the results of their fatigue assessment in accordance with the National Comprehensive Cancer Network (NCCN) cancer-related fatigue guidelines. Patients were given an educational booklet on fatigue prior to treatment and symptom specific booklets as required at T1 and T2. Subjective reports of patients' fatigue and QOL. Patients' mean fatigue scores showed a statistically significant decrease and their EORTC QLQC-30 scores were better at T1 and T2 compared with baseline. Nurse-led educational interventions have the potential to reduce fatigue in patients with GI cancer receiving chemotherapy for the first time. The administration of chemotherapy should be preceded by a formal fatigue assessment and the provision of individually tailored educational interventions to reduce the severity of fatigue and improve QOL.

  20. Evaluating Interactive Fatigue Management Workshops for Occupational Health Professionals in the United Kingdom

    Science.gov (United States)

    Ali, Sheila; Chalder, Trudie; Madan, Ira

    2014-01-01

    Background Disabling fatigue is common in the working age population. It is essential that occupational health (OH) professionals are up-to-date with the management of fatigue in order to reduce the impact of fatigue on workplace productivity. Our aim was to evaluate the impact of one-day workshops on OH professionals' knowledge of fatigue and chronic fatigue syndrome (CFS), and their confidence in diagnosing and managing these in a working population. Methods Five interactive problem-based workshops were held in the United Kingdom. These workshops were developed and delivered by experts in the field. Questionnaires were self-administered immediately prior to, immediately after, and 4 months following each workshop. Questionnaires included measures of satisfaction, knowledge of fatigue and CFS, and confidence in diagnosing and managing fatigue. Open-ended questions were used to elicit feedback about the workshops. Results General knowledge of fatigue increased significantly after training (with a 25% increase in the median score). Participants showed significantly higher levels of confidence in diagnosing and managing CFS (with a 62.5% increase in the median score), and high scores were maintained 4 months after the workshops. OH physicians scored higher on knowledge and confidence than nurses. Similarly, thematic analysis revealed that participants had increased knowledge and confidence after attending the workshops. Conclusion Fatigue can lead to severe functional impairment with adverse workplace outcomes. One-day workshops can be effective in training OH professionals in how to diagnose and manage fatigue and CFS. Training may increase general knowledge of fatigue and confidence in fatigue management in an OH setting. PMID:25516811

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

    Directory of Open Access Journals (Sweden)

    Xi-Shu Wang

    2014-05-01

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

  2. Hypoxia Worsens Affective Responses and Feeling of Fatigue During Prolonged Bed Rest

    Directory of Open Access Journals (Sweden)

    Nektarios A. M. Stavrou

    2018-03-01

    Full Text Available Previous research, although limited, suggests that both hypoxia and bed rest influence psychological responses by exaggerating negative psychological responses and attenuating positive emotions. The present study investigated the effect of a 21-day prolonged exposure to normobaric hypoxia and bed rest on affective responses and fatigue. Eleven healthy participants underwent three 21-day interventions using a cross-over design: (1 normobaric hypoxic ambulatory confinement (HAMB, (2 normobaric hypoxic bed rest (HBR and (3 normoxic bed rest (NBR. Affective and fatigue responses were investigated using the Activation Deactivation Adjective Check List, and the Multidimensional Fatigue Inventory, which were completed before (Pre, during (Day 7, Day 14, and Day 21 and after (Post the interventions. The most negative psychological profile appeared during the HBR intervention. Specifically, tiredness, tension, general and physical fatigue significantly increased on days 7, 14, and 21, as well as at Post. After the HBR intervention, general and physical fatigue remained higher compared to Pre values. Additionally, a deterioration of psychological responses was also noted following HAMB and NBR. In particular, both hypoxia and BR per se induced subjective fatigue and negative affective responses. BR seems to exert a moderate negative effect on the sensation of fatigue, whereas exercise attenuates the negative effects of hypoxia as noted during the HAMB condition. In conclusion, our data suggest that the addition of hypoxia to bed rest-induced inactivity significantly worsens affective responses and feeling of fatigue.

  3. Fatigue limit investigation of 6061-T6 aluminum alloy in giga-cycle regime

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Yoshimasa, E-mail: yoshim-t@kansai-u.ac.jp [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680 (Japan); Yoshitake, Hiroaki; Nakamichi, Ryota; Wada, Takuya; Takuma, Masanori [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680 (Japan); Shikama, Takahiro [Kobe Steel Ltd., Aluminum and Copper Business (Chofu Works), 14-1 Chofu Minato-machi, Shimonoseki, Yamaguchi 752-0953 (Japan); Noguchi, Hiroshi [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)

    2014-09-22

    In order to investigate the fatigue limit micro-mechanism of a precipitation-hardened Al–Mg–Si alloy (6061-T6), the alloy was subjected to very-high-cycle fatigue (VHCF) of over 10{sup 9} cycles by an ultrasonic fatigue method. Two kinds of specimens, one with smooth surface and the other with a small artificial hole on the surface, were compared. The smooth specimens showed no distinct fatigue limit. Conversely, the holed specimens showed clear fatigue limit which had been generally deemed to be absent in non-ferrous alloys. In addition to the conventional fatigue crack growth (FCG) observation by replica technique, metallographically critical analyses by electron backscattered diffraction (EBSD) and cross-sectional focused ion beam (FIB) were conducted to reveal the micro-plasticity associated with FCG. It was found that the fatigue life of smooth specimens at low stress amplitude was controlled by an unstoppable FCG mechanism mediated by persistent slip bands (PSBs). On the other hand, the emergence of distinct fatigue limit in holed specimens was attributed to a non-propagating crack having mode I characteristics in essence. No coaxing effect was, however, confirmed for such non-propagating cracks. The above results, which were somewhat different from previous ones obtained by rotating bending under normal frequency, were discussed in terms of both metallurgical and mechanical points of view.

  4. Fatigue limit investigation of 6061-T6 aluminum alloy in giga-cycle regime

    International Nuclear Information System (INIS)

    Takahashi, Yoshimasa; Yoshitake, Hiroaki; Nakamichi, Ryota; Wada, Takuya; Takuma, Masanori; Shikama, Takahiro; Noguchi, Hiroshi

    2014-01-01

    In order to investigate the fatigue limit micro-mechanism of a precipitation-hardened Al–Mg–Si alloy (6061-T6), the alloy was subjected to very-high-cycle fatigue (VHCF) of over 10 9 cycles by an ultrasonic fatigue method. Two kinds of specimens, one with smooth surface and the other with a small artificial hole on the surface, were compared. The smooth specimens showed no distinct fatigue limit. Conversely, the holed specimens showed clear fatigue limit which had been generally deemed to be absent in non-ferrous alloys. In addition to the conventional fatigue crack growth (FCG) observation by replica technique, metallographically critical analyses by electron backscattered diffraction (EBSD) and cross-sectional focused ion beam (FIB) were conducted to reveal the micro-plasticity associated with FCG. It was found that the fatigue life of smooth specimens at low stress amplitude was controlled by an unstoppable FCG mechanism mediated by persistent slip bands (PSBs). On the other hand, the emergence of distinct fatigue limit in holed specimens was attributed to a non-propagating crack having mode I characteristics in essence. No coaxing effect was, however, confirmed for such non-propagating cracks. The above results, which were somewhat different from previous ones obtained by rotating bending under normal frequency, were discussed in terms of both metallurgical and mechanical points of view

  5. Acoustic Correlates of Fatigue in Laryngeal Muscles: Findings for a Criterion-Based Prevention of Acquired Voice Pathologies

    Science.gov (United States)

    Boucher, Victor J.

    2008-01-01

    Purpose: The objective was to identify acoustic correlates of laryngeal muscle fatigue in conditions of vocal effort. Method: In a previous study, a technique of electromyography (EMG) served to define physiological signs of "voice fatigue" in laryngeal muscles involved in voicing. These signs correspond to spectral changes in contraction…

  6. Self-Reported Fatigue and Associated Factors Six Years after Stroke.

    Directory of Open Access Journals (Sweden)

    Marie Elf

    Full Text Available Several studies have found that fatigue is one of the most commonly reported symptoms after stroke and the most difficult to cope with. The present study aimed to investigate the presence and severity of self-reported fatigue six years after stroke onset and associated factors. The cohort "Life After Stroke Phase I" (n = 349 persons was invited at six years to report fatigue (Fatigue Severity Scale 7-item version, perceived impact of stroke and global recovery after stroke (Stroke Impact Scale, anxiety and depression (Hospital Anxiety and Depression Scale, life satisfaction (Life Satisfaction Checklist and participation in everyday social activities (Frenchay Activities Index. At six years 37% of the 102 participants in this cross-sectional study reported fatigue. The results showed that in nearly all SIS domains the odds for post-stroke fatigue were higher in persons with a higher perceived impact. Furthermore, the odds for post-stroke fatigue were higher in those who had experienced a moderate/severe stroke and had signs of depression and anxiety. Fatigue is still present in one-third of persons as long as six years after stroke onset and is perceived to hinder many aspects of functioning in everyday life. There is an urgent need to develop and evaluate interventions to reduce fatigue.

  7. A wireless body measurement system to study fatigue in multiple sclerosis.

    Science.gov (United States)

    Yu, Fei; Bilberg, Arne; Stenager, Egon; Rabotti, Chiara; Zhang, Bin; Mischi, Massimo

    2012-12-01

    Fatigue is reported as the most common symptom by patients with multiple sclerosis (MS). The physiological and functional parameters related to fatigue in MS patients are currently not well established. A new wearable wireless body measurement system, named Fatigue Monitoring System (FAMOS), was developed to study fatigue in MS. It can continuously measure electrocardiogram, body-skin temperature, electromyogram and motions of feet. The goal of this study is to test the ability of distinguishing fatigued MS patients from healthy subjects by the use of FAMOS. This paper presents the realization of the measurement system including the design of both hardware and dedicated signal processing algorithms. Twenty-six participants including 17 MS patients with fatigue and 9 sex- and age-matched healthy controls were included in the study for continuous 24 h monitoring. The preliminary results show significant differences between fatigued MS patients and healthy controls. In conclusion, the FAMOS enables continuous data acquisition and estimation of multiple physiological and functional parameters. It provides a new, flexible and objective approach to study fatigue in MS, which can distinguish between fatigued MS patients and healthy controls. The usability and reliability of the FAMOS should however be further improved and validated through larger clinical trials.

  8. High cycle fatigue test and regression methods of S-N curve

    International Nuclear Information System (INIS)

    Kim, D. W.; Park, J. Y.; Kim, W. G.; Yoon, J. H.

    2011-11-01

    The fatigue design curve in the ASME Boiler and Pressure Vessel Code Section III are based on the assumption that fatigue life is infinite after 106 cycles. This is because standard fatigue testing equipment prior to the past decades was limited in speed to less than 200 cycles per second. Traditional servo-hydraulic machines work at frequency of 50 Hz. Servo-hydraulic machines working at 1000 Hz have been developed after 1997. This machines allow high frequency and displacement of up to ±0.1 mm and dynamic load of ±20 kN are guaranteed. The frequency of resonant fatigue test machine is 50-250 Hz. Various forced vibration-based system works at 500 Hz or 1.8 kHz. Rotating bending machines allow testing frequency at 0.1-200 Hz. The main advantage of ultrasonic fatigue testing at 20 kHz is performing Although S-N curve is determined by experiment, the fatigue strength corresponding to a given fatigue life should be determined by statistical method considering the scatter of fatigue properties. In this report, the statistical methods for evaluation of fatigue test data is investigated

  9. Fatigue Behaviour of Composite T-Joints in Wind Turbine Blade Applications

    Science.gov (United States)

    Wang, Y.; Soutis, C.

    2017-04-01

    This paper presents a study of fatigue performance of composite T-joints used in wind-turbine blades. A T-joint with various fibre reinforcement architectures were selected to investigate its fatigue behaviour. The 3D angle interlock T-joint was found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue performance while the increasing rate in life performance is changed with the number of fatigue cycles. A finite element (FE) model was developed that can determine the stress distribution and the initiation and propagation of a delamination crack. The location for through-thickness reinforcement is very important to improve fatigue performance of composite T-joints. Fatigue performance is significantly improved for the web with through-thickness reinforcement while fatigue performance is decreased if the through-thickness reinforcement is applied to the flange-skin regions. The interlaminar veil significantly increases the ultimate strength under static load but fatigue performance at high stress cycles is increased but not significantly.

  10. A wireless body measurement system to study fatigue in multiple sclerosis

    International Nuclear Information System (INIS)

    Yu, Fei; Bilberg, Arne; Zhang, Bin; Stenager, Egon; Rabotti, Chiara; Mischi, Massimo

    2012-01-01

    Fatigue is reported as the most common symptom by patients with multiple sclerosis (MS). The physiological and functional parameters related to fatigue in MS patients are currently not well established. A new wearable wireless body measurement system, named Fatigue Monitoring System (FAMOS), was developed to study fatigue in MS. It can continuously measure electrocardiogram, body-skin temperature, electromyogram and motions of feet. The goal of this study is to test the ability of distinguishing fatigued MS patients from healthy subjects by the use of FAMOS. This paper presents the realization of the measurement system including the design of both hardware and dedicated signal processing algorithms. Twenty-six participants including 17 MS patients with fatigue and 9 sex- and age-matched healthy controls were included in the study for continuous 24 h monitoring. The preliminary results show significant differences between fatigued MS patients and healthy controls. In conclusion, the FAMOS enables continuous data acquisition and estimation of multiple physiological and functional parameters. It provides a new, flexible and objective approach to study fatigue in MS, which can distinguish between fatigued MS patients and healthy controls. The usability and reliability of the FAMOS should however be further improved and validated through larger clinical trials. (paper)

  11. Cancer-related fatigue management: evaluation of a patient education program with a large-scale randomised controlled trial, the PEPs fatigue study.

    Science.gov (United States)

    Bourmaud, A; Anota, A; Moncharmont, C; Tinquaut, F; Oriol, M; Trillet-Lenoir, V; Bajard, A; Parnalland, S; Rotonda, C; Bonnetain, F; Pérol, D; Chauvin, F

    2017-03-28

    To assess the efficacy of a patient educational program built according to guidelines that aims at reducing cancer-related fatigue (CRF). Randomised controlled trial, multicentre, comparing a patient education program, vs the standard of care. Patients were adult cancer outpatients with any tumour site. The primary outcome was fatigue severity assessed with a visual analogical scale (VAS), between the day of randomisation and week 7. Secondary outcomes were fatigue assessed with other scales, health-related quality of life, anxiety and depression. The time to fatigue severity deterioration was assessed. Analyses were performed in a modified intent-to-treat way, that is, including all patients with at least one baseline and 1 week 7 score. A total of 212 patients were included. Fatigue severity assessment was made on 79 patients in the experimental group and 65 in the control group. Between randomisation and week 7, the fatigue (VAS) improved by 0.96 (2.85) points in the experimental group vs 1.63 (2.63) points in the control group (P=0.15). No differences with the secondary outcomes were highlighted between two groups. No other factors were found to be associated with fatigue severity deterioration. Despite rigorous methodology, this study failed to highlight the program efficacy in fatigue reduction for cancer patients. Other assessment tools should be developed to measure the effect of the program on CRF and behaviour. The implementation of the program should also be explored in order to identify its mechanisms and longer-term impact.

  12. Internet-based therapy for adolescents with chronic fatigue syndrome: long-term follow-up

    NARCIS (Netherlands)

    Nijhof, S.L.; Priesterbach, L.P.; Uiterwaal, C.S.; Bleijenberg, G.; Kimpen, J.L.L.; Putte, E.M. van de

    2013-01-01

    OBJECTIVE: Cognitive behavioral therapy (CBT) is known to be an effective treatment of adolescents with chronic fatigue syndrome (CFS), but its availability is limited. Fatigue in Teenagers on the Internet (FITNET), an Internet-based CBT program for adolescents with CFS, has been developed as an

  13. Manifestations of shoulder fatigue in prolonged activities involving low-force contractions

    NARCIS (Netherlands)

    Looze, M.P. de; Bosch, T.; Dieën, J. van

    2009-01-01

    Shoulder fatigue has been suggested to be a useful risk indicator for shoulder disorders in repetitive, low-force work tasks. In contrast to high-force or purely isometric tasks, it is unclear whether measurable fatigue develops in realistic low-force work. The question addressed in this review was:

  14. Electromyographical manifestations of muscle fatigue during different levels of simulated light manual assembly work

    NARCIS (Netherlands)

    Bosch, T.; Looze, M.P. de; Kingma, I.; Visser, B.; Dieën, J.H. van

    2009-01-01

    The purpose of this study was to determine whether objective electromyographical manifestations of muscle fatigue develop in the upper trapezius muscle in two assembly tasks involving contractions of different low-intensity levels (8% and 12% MVC) and whether these indications of fatigue are

  15. Application of a cycle jump technique for acceleration of fatigue crack growth simulation

    DEFF Research Database (Denmark)

    Moslemian, Ramin; Karlsson, A.M.; Berggreen, Christian

    2010-01-01

    A method for accelerated simulation of fatigue crack growth in a bimaterial interface is proposed. To simulate fatigue crack growth in a bimaterial interface a routine is developed in the commercial finite element code ANSYS and a method to accelerate the simulation is implemented. The proposed...

  16. High strength fibre reinforced concrete : Static and fatigue behaviour in bending

    NARCIS (Netherlands)

    Lappa, E.S.

    2007-01-01

    Recently, a number of high strength and ultra high strength steel fibre concretes have been developed. Since these materials seem very suitable for structures that might be prone to fatigue failure, such as bridge decks, the understanding of the static and fatigue bending behaviour is vital. In

  17. A multidimensional 'path analysis' model of factors explaining fatigue in rheumatoid arthritis

    NARCIS (Netherlands)

    Dartel, S.A.A. van; Repping-Wuts, H.; Donders, R.; Hoogmoed, D. van; Knoop, H.; Bleijenberg, G.; Riel, P.L.C.M. van; Fransen, J.

    2016-01-01

    OBJECTIVES: Fatigue is one of the most commonly reported symptoms in rheumatoid arthritis (RA). Many factors may play a causal role on fatigue in RA patients, but their contribution and interplay is barely understood. The objective was to develop a multidimensional model of factors that explain

  18. Tensile and Fatigue Testing and Material Hardening Model Development for 508 LAS Base Metal and 316 SS Similar Metal Weld under In-air and PWR Primary Loop Water Conditions

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-09-01

    This report provides an update on an assessment of environmentally assisted fatigue for light water reactor components under extended service conditions. This report is a deliverable in September 2015 under the work package for environmentally assisted fatigue under DOE’s Light Water Reactor Sustainability program. In an April 2015 report we presented a baseline mechanistic finite element model of a two-loop pressurized water reactor (PWR) for systemlevel heat transfer analysis and subsequent thermal-mechanical stress analysis and fatigue life estimation under reactor thermal-mechanical cycles. In the present report, we provide tensile and fatigue test data for 508 low-alloy steel (LAS) base metal, 508 LAS heat-affected zone metal in 508 LAS–316 stainless steel (SS) dissimilar metal welds, and 316 SS-316 SS similar metal welds. The test was conducted under different conditions such as in air at room temperature, in air at 300 oC, and under PWR primary loop water conditions. Data are provided on materials properties related to time-independent tensile tests and time-dependent cyclic tests, such as elastic modulus, elastic and offset strain yield limit stress, and linear and nonlinear kinematic hardening model parameters. The overall objective of this report is to provide guidance to estimate tensile/fatigue hardening parameters from test data. Also, the material models and parameters reported here can directly be used in commercially available finite element codes for fatigue and ratcheting evaluation of reactor components under in-air and PWR water conditions.

  19. 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).

  20. Compassion Fatigue in Pediatric Nurses.

    Science.gov (United States)

    Berger, Jill; Polivka, Barbara; Smoot, Elizabeth Ann; Owens, Heather

    2015-01-01

    Compassion fatigue in nursing has been shown to impact the quality of patient care and employee satisfaction and engagement. The aims of this study were to determine the prevalence and severity of compassion fatigue among pediatric nurses and variations in prevalence based on respondent demographics using a cross-sectional survey design. Nurses under 40 years of age, with 6-10 years of experience and/or working in a medical-surgical unit had significantly lower compassion satisfaction and higher levels of burnout. Secondary traumatic stress from caring for children with severe illness or injury or end of life was a key contributor to compassion fatigue. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. 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.

  2. Bone fatigue and its implications for injuries in racehorses.

    Science.gov (United States)

    Martig, S; Chen, W; Lee, P V S; Whitton, R C

    2014-07-01

    Musculoskeletal injuries are a common cause of lost training days and wastage in racehorses. Many bone injuries are a consequence of repeated high loading during fast work, resulting in chronic damage accumulation and material fatigue of bone. The highest joint loads occur in the fetlock, which is also the most common site of subchondral bone injury in racehorses. Microcracks in the subchondral bone at sites where intra-articular fractures and palmar osteochondral disease occur are similar to the fatigue damage detected experimentally after repeated loading of bone. Fatigue is a process that has undergone much study in material science in order to avoid catastrophic failure of engineering structures. The term 'fatigue life' refers to the numbers of cycles of loading that can be sustained before failure occurs. Fatigue life decreases exponentially with increasing load. This is important in horses as loads within the limb increase with increasing speed. Bone adapts to increased loading by modelling to maintain the strains within the bone at a safe level. Bone also repairs fatigued matrix through remodelling. Fatigue injuries develop when microdamage accumulates faster than remodelling can repair. Remodelling of the equine metacarpus is reduced during race training and accelerated during rest periods. The first phase of remodelling is bone resorption, which weakens the bone through increased porosity. A bone that is porous following a rest period may fail earlier than a fully adapted bone. Maximising bone adaptation is an important part of training young racehorses. However, even well-adapted bones accumulate microdamage and require ongoing remodelling. If remodelling inhibition at the extremes of training is unavoidable then the duration of exposure to high-speed work needs to be limited and appropriate rest periods instituted. Further research is warranted to elucidate the effect of fast-speed work and rest on bone damage accumulation and repair. © 2014 EVJ Ltd.

  3. Fatigue damage mechanism and strength of woven laminates

    International Nuclear Information System (INIS)

    Xiao, J.; Bathias, C.

    1993-01-01

    The apparent secant stiffness changes with the cyclic number for both unnotched and notched woven laminated specimens (two orthotropic and one quasi-isotropic) during tensile fatigue test at a fixed ratio of maximum fatigue load to UTS were observed. The observable damage initiation and evolution as a function of the cyclic number were directly measured at the notched specimen surface with a video-camera system. The fatigue strengths of the unnotched and notched specimens were determined. The results show that the normalized apparent secant stiffness change curves as a function of cyclic numbers can be divided into three stages. For the first and the second stages in notched specimens and for total life of unnotched specimens, the damage has not been evidently observed and certainly verified with the traditional experimental methods such as radiography and microscopy although many acoustic emission signals can be obtained. The last stage for the notched specimens (N/Nf>0.4, the secant stiffness decreases fast) corresponds to the initiation and evolution of the observable damages. The fatigue strength of these woven composite laminates is dominated by the third stage during which the observable damage develops along the specimen ligament until fracture. During the third stage, a critical dimension at the specimen ligament and a life threshold can be found beyond which a final catastrophic fracture will immediately occur. The quasi-isotropic laminate is of a fatigue strength lower than the two orthotropic laminates of which the fatigue strengths are approaching to each other. The fatigue life is also influenced by the stacking sequences. (orig.)

  4. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Treatment

    Science.gov (United States)

    ... Search Controls Search Form Controls Cancel Submit Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Note: Javascript is disabled or ... is no cure or approved treatment for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). However, some symptoms ...

  5. Getting the Facts: Cancer-Related Fatigue

    Science.gov (United States)

    ... and depression, that can cause cancer-related fatigue. Cancer treatment such as chemotherapy, radiation therapy, stem cell transplantation, and biologic therapy are often associated with fatigue. Anemia (a ...

  6. Fatigue crack initiation and growth life prediction with statistical consideration

    International Nuclear Information System (INIS)

    Kwon, J.D.; Choi, S.H.; Kwak, S.G.; Chun, K.O.

    1991-01-01

    Life prediction or residual life prediction of structures or machines is one of the most strongly world wide needed problems as requirement in the stage of slowly developing economy which comes after rapidly and highly developing stage. For the purpose of statistical life prediction, fatigue test was conducted under the 3 stress levels, and for each stress level, 20 specimens are used. The statistical properties of the crack growth parameter m and C in the fatigue crack growth law of da/dN = C(ΔK) m , and the relationship between m and C, and the statistical distribution pattern of fatigue crack initiation, growth and fracture lives can be obtained by experimental results

  7. The role of central and peripheral muscle fatigue in postcancer fatigue: a randomized controlled trial

    NARCIS (Netherlands)

    Prinsen, H.; Dijk, J.P. van; Zwarts, M.J.; Leer, J.W.H.; Bleijenberg, G.; Laarhoven, H.W.M. van

    2015-01-01

    CONTEXT: Postcancer fatigue is a frequently occurring problem, impairing quality of life. Little is known about (neuro)physiological factors determining postcancer fatigue. It may be hypothesized that postcancer fatigue is characterized by low peripheral muscle fatigue and high central muscle

  8. Contraintes residuelles et leurs impacts sur l'amorcage de fissures en fatigue de flexion dans des engrenages aeronautiques durcis superficiellement par induction

    Science.gov (United States)

    Savaria, Vincent

    The optimization of gearing for aeronautical engines depends on the development of surface hardening processes to significantly improve in-service durability. Induction heating followed by quenching is a treatment increasingly used in this field to improve the fatigue resistance of critical components such as gears. In this context, this thesis studies the impact of the induction process parameters on residual stresses and the effects of those stresses on the bending fatigue of induction hardened gears. Two existing residual stress measurement techniques, X-ray diffraction and the contour method, were adapted for induction hardened components. The residual stress measurement by X-ray diffraction technique has been significantly improved in this thesis by the consideration of the variation of the X-ray elastic constant at different locations in the hardened layer and the development of a finite element based layer removal correction method that enabled more accurate in-depth residual stress measurements in all sort of geometries. The contour method is clearly a powerful tool for residual stress mapping at the core of parts but proved to be inaccurate for near-surface measurements in the case of thin hardened layers. These methods were used to show the effects of several parameters (initial hardness, preheating, final heating, tempering) with discs and aeronautical spur gears. The results indicate that two induction treatments can sometimes produce two different residual stress distributions (amplitude, severity of gradient in the transition zone, etc.) for a similar hardened depth. The bending fatigue of those gears was studied experimentally with a single tooth bending test rig and numerically with the proposition of a fatigue model for the calculation of the bending endurance limit. The calibration of the model was based on fatigue tests results on traction and torsion specimens. Bending fatigue testing results on gears confirmed the overall accuracy of the

  9. Fatigue life evaluation of 42CrMo4 nitrided steel by local approach: Equivalent strain-life-time

    International Nuclear Information System (INIS)

    Terres, Mohamed Ali; Sidhom, Habib

    2012-01-01

    Highlights: → Ion nitriding treatment of 42CrMo4 steel improves their fatigue strength by 32% as compared with the untreated state. → This improvement is the result of the beneficial effects of the superficial work- hardening and of the stabilized compressive residual stress. → The notch region is found to be the fatigue crack nucleation site resulting from a stress concentration (Kt = 1.6). → The local equivalent strain-fatigue life method was found to be an interesting predictive fatigue life method for nitrided parts. -- Abstract: In this paper, the fatigue resistance of 42CrMo4 steel in his untreated and nitrided state was evaluated, using both experimental and numerical approaches. The experimental assessment was conducted using three points fatigue flexion tests on notched specimens at R = 0.1. Microstructure analysis, micro-Vickers hardness test, and scanning electron microscope observation were carried out for evaluating experiments. In results, the fatigue cracks of nitrided specimens were initiated at the surface. The fatigue life of nitrided specimens was prolonged compared to that of the untreated. The numerical method used in this study to predict the nucleation fatigue life was developed on the basis of a local approach, which took into account the applied stresses and stabilized residual stresses during the cyclic loading and the low cyclic fatigue characteristics. The propagation fatigue life was calculated using fracture mechanics concepts. It was found that the numerical results were well correlated with the experimental ones.

  10. Fatigue Damage and Lifetime of SiC/SiC Ceramic-Matrix Composite under Cyclic Loading at Elevated Temperatures.

    Science.gov (United States)

    Li, Longbiao

    2017-03-31

    In this paper, the fatigue damage and lifetime of 2D SiC/SiC ceramic-matrix composites (CMCs) under cyclic fatigue loading at 750, 1000, 1100, 1200 and 1300 °C in air and in steam atmosphere have been investigated. The damage evolution versus applied cycles of 2D SiC/SiC composites were analyzed using fatigue hysteresis dissipated energy, fatigue hysteresis modulus, fatigue peak strain and interface shear stress. The presence of steam accelerated the damage development inside of SiC/SiC composites, which increased the increasing rate of the fatigue hysteresis dissipated energy and the fatigue peak strain, and the decreasing rate of the fatigue hysteresis modulus and the interface shear stress. The fatigue life stress-cycle (S-N) curves and fatigue limit stresses of 2D SiC/SiC composites at different temperatures in air and in steam condition have been predicted. The fatigue limit stresses approach 67%, 28%, 39% 17% and 28% tensile strength at 750, 1000, 1100, 1200 and 1300 °C in air, and 49%, 10%, 9% and 19% tensile strength at 750, 1000, 1200 and 1300 °C in steam conditions, respectively.

  11. Temperature and grain size effect on the fatigue and creep-fatigue behavior of OFHC copper and CuCrZr for fusion application

    International Nuclear Information System (INIS)

    Pan, X.; Wu, X.; Stubbins, J.

    2007-01-01

    tests at various points in the fatigue life also will be carried out so that the progression of microstructural development could be examined. In order to gain insight into the deformation process operative during creep-fatigue interaction tests, thin foils will be prepared from specimens interrupted at different points and fractured during these tests under different conditions and were examined in a transmission electron microscope (TEM). The variance between pure fatigue and creep-fatigue should be related with the different damage mechanisms (persistent slip bands damage and grain boundary damage) during the cyclic loading process. Crystal orientation and plastic deformation could be discovered by scanning electron microscope (SEM) coupled with electron backscattered diffraction (EBSD). This paper examines the underlying microstructural aspects that control both the stress relaxation process and the changes in fatigue crack initiation. This information is critical for assessing the full impact of cyclic loading with extended hold periods in near term fusion systems design. (authors)

  12. Fatigue assessment of a double submerged arc welded gas pipeline

    Energy Technology Data Exchange (ETDEWEB)

    Fazzini, Pablo; Otegui, Jose Luis [Universidad Nacional Mar del Plata, Mar del Plata (Argentina). Instituto de Ciencia y Tecnologia de Materiales (INTEMA); Teutonico, Mauricio; Manfredi, Carlos [GIE S.A., Mar del Plata (Argentina)

    2005-07-01

    An uncommon blowout in a 24'' diameter, 7 mm thick API 5L X52 gas pipeline was due to fracture at the longitudinal double submerged arc weld. Oddly enough for gas pipelines, it was found that fatigue cracks had propagated from a large embedded weld defect of lack of fusion resulting from severe geometrical mismatch between inner and outer weld passes. What makes this failure particularly interesting is that: previous in line inspections failed to detect any defect, no evidence of third party damage was found, and very few large pressure cycles had been recorded during the last 5 years of service, which were believed to be representative of the entire service life of the pipeline. Fatigue tests were carried out to characterize propagation of fatigue cracks in weld metal, it was found that a large Paris exponent made the few large amplitude cycles most contributing to crack propagation. Crack growth path and striation patterns were studied. Fatigue growth was modelled by integrating experimental results and by extrapolating striation spacing in the fracture surface of the failed pipe. Crack growth path and striation patterns were studied. It was found that microstructure discontinuities govern propagation at low {delta}K, but one striation per cycle was produced at large {delta}K, due to a mostly ductile propagation mode. Fatigue growth was modelled by integrating experimental results and by extrapolating striation spacing in the fracture surface of the failed pipe. It was found that in the early life of the line many more large pressure cycles than expected had occurred. Good correspondence between predicted and actual fatigue lives was in this way obtained (author)

  13. Fatigue behavior of ADI: Some specific features

    Energy Technology Data Exchange (ETDEWEB)

    Svejcar, J.; Vechet, S.; Pokluda, J. [Technical Univ. of Brno (Czech Republic). Faculty of Mechanical Engineering

    1997-12-31

    The paper summarizes the results of fatigue tests on austempered ductile iron. Attention is mainly focused on the effect of graphite on crack propagation and on some irregularities exhibited by ADI and other ductile irons, e.g., some specific features of fatigue fracture (especially the occurrence of fatigue striations on intergranular facets), decrease of fatigue limit with increasing UTS, and anomalous dependence of loading cycle amplitude on mean cycle stress.

  14. Risk Based Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, M.H.; Kroon, I.B.

    1992-01-01

    Optimal fatigue life testing of materials is considered. Based on minimization of the total expected costs of a mechanical component a strategy is suggested to determine the optimal stress range levels for which additional experiments are to be performed together with an optimal value of the maxi......Optimal fatigue life testing of materials is considered. Based on minimization of the total expected costs of a mechanical component a strategy is suggested to determine the optimal stress range levels for which additional experiments are to be performed together with an optimal value...

  15. Muscle glycogen stores and fatigue

    DEFF Research Database (Denmark)

    Ørtenblad, Niels; Westerblad, Håkan; Nielsen, Joachim

    2013-01-01

    function during fatigue is not well understood and a direct cause-and-effect relationship between glycogen and muscle function remains to be established. The use of electron microscopy has revealed that glycogen is not homogeneously distributed in skeletal muscle fibres, but rather localized in distinct...... the sarcoplasmic reticulum (SR). We and others have provided experimental evidence in favour of a direct role of decreased glycogen, localized within the myofibrils, for the reduction in SR Ca2+ release during fatigue. This is consistent with compartmentalized energy turnover and distinctly localized glycogen...

  16. Fatigue data bases in Europe

    International Nuclear Information System (INIS)

    Olivier, R.; Koettgen, V.B.; Seeger, T.; Boller, C.

    1988-01-01

    Based on an inquiry with well-known European fatigue institutions the paper describes existing more or less extensive collections and data bases of S-N and crack growth data, mainly on unwelded and welded steel and aluminium in organizations and countries as follows: CEC, ESA, Federal Republic of Germany, GDR, Italy, Norway, Republic of Ireland, Switzerland, UK. This documentation of the present state is completed by a short survey on available European fatigue standards and design rules, serving as a data base for nominal materials data. Requirements for data base concepts, contents, user interface and data structure are presented in a short overview. (orig./HP)

  17. A new methodology for automating acoustic emission detection of metallic fatigue fractures in highly demanding aerospace environments: An overview

    Science.gov (United States)

    Holford, Karen M.; Eaton, Mark J.; Hensman, James J.; Pullin, Rhys; Evans, Sam L.; Dervilis, Nikolaos; Worden, Keith

    2017-04-01

    The acoustic emission (AE) phenomenon has many attributes that make it desirable as a structural health monitoring or non-destructive testing technique, including the capability to continuously and globally monitor large structures using a sparse sensor array and with no dependency on defect size. However, AE monitoring is yet to fulfil its true potential, due mainly to limitations in location accuracy and signal characterisation that often arise in complex structures with high levels of background noise. Furthermore, the technique has been criticised for a lack of quantitative results and the large amount of operator interpretation required during data analysis. This paper begins by introducing the challenges faced in developing an AE based structural health monitoring system and then gives a review of previous progress made in addresing these challenges. Subsequently an overview of a novel methodology for automatic detection of fatigue fractures in complex geometries and noisy environments is presented, which combines a number of signal processing techniques to address the current limitations of AE monitoring. The technique was developed for monitoring metallic landing gear components during pre-flight certification testing and results are presented from a full-scale steel landing gear component undergoing fatigue loading. Fracture onset was successfully identify automatically at 49,000 fatigue cycles prior to final failure (validated by the use of dye penetrant inspection) and the fracture position was located to within 10 mm of the actual location.

  18. Pilot fatigue survey: exploring fatigue factors in air medical operations.

    Science.gov (United States)

    Gregory, Kevin B; Winn, William; Johnson, Kent; Rosekind, Mark R

    2010-01-01

    Humans confront significant physiological challenges with sleep and alertness when working in 24/7 operations. A web-based national survey of air medical pilots examined issues relevant to fatigue and sleep management. Six hundred ninety-seven responses were received, with a majority of rotor wing pilots working 3/3/7 and 7/7 duty schedules. Over 84% of the pilots reported that fatigue had affected their flight performance; less than 28% reported "nodding off" during flight. More than 90% reported a separate work site "rest" room with a bed available. Over 90% reported no company policies restricting on-duty sleep. Approximately half of the pilots reported getting 4 hours or more sleep during a typical night shift. Approximately half reported that sleep inertia had never compromised flight safety. Over 90% reported that it was better to sleep during the night and overcome sleep inertia if necessary. Survey results reflected practices that can mitigate the degrading effects of fatigue, including the availability of designated work-site sleep rooms. As demands continue to evolve, the need remains for sustained efforts to address fatigue-related risks in the air medical transport industry. This includes further study of sleep inertia issues and the need for alertness management programs. Copyright © 2010 Air Medical Journal Associates. Published by Elsevier Inc. All rights reserved.

  19. [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

  20. [Epidemiology of fatigue in general practice].

    Science.gov (United States)

    Fuhrer, R

    1994-11-01

    The epidemiology of fatigue is not well known in France, and this study reports on factors associated with fatigue in a sample of 3,784 general practice patients. Prevalence rates according to several definitions of fatigue are presented and factors are examined that have been reported to be associated with fatigue. Although 41.2% of the sample report having experienced symptoms of fatigue for at least three days, only 7.6% declare fatigue as a reason for consulting a doctor. Women report more symptoms of fatigue, but they do not consult more often than men for this reason. Age is strongly correlated with fatigue, but this is found only for men. Socioprofessional category bears no relationship to fatigue as a reason for consultation, however, the diagnosis of fatigue is more often attributed to professionals and upper management than it is to office staff or skilled and unskilled workers. We do find a strong relationship between depressive symptomatology as measured by the Center for Epidemiologic Studies (CES-D) and fatigue; nonetheless, fatigue is neither sensitive nor specific to the diagnosis of depression.