Code conforming determination of cumulative usage factors for general elastic-plastic finite element analyses

International Nuclear Information System (INIS)

Rudolph, Juergen; Goetz, Andreas; Hilpert, Roland

2012-01-01

The procedures of fatigue analyses of several relevant nuclear and conventional design codes (ASME, KTA, EN, AD) for power plant components differentiate between an elastic, simplified elastic-plastic and elastic-plastic fatigue check. As a rule, operational load levels will exclude the purely elastic fatigue check. The application of the code procedure of the simplified elastic-plastic fatigue check is common practice. Nevertheless, resulting cumulative usage factors may be overly conservative mainly due to high code based plastification penalty factors Ke. As a consequence, the more complex and still code conforming general elastic-plastic fatigue analysis methodology based on non-linear finite element analysis (FEA) is applied for fatigue design as an alternative. The requirements of the FEA and the material law to be applied have to be clarified in a first step. Current design codes only give rough guidelines on these relevant items. While the procedure for the simplified elastic-plastic fatigue analysis and the associated code passages are based on stress related cycle counting and the determination of pseudo elastic equivalent stress ranges, an adaptation to elastic-plastic strains and strain ranges is required for the elastic-plastic fatigue check. The associated requirements are explained in detail in the paper. If the established and implemented evaluation mechanism (cycle counting according to the peak and valley respectively the rainflow method, calculation of stress ranges from arbitrary load-time histories and determination of cumulative usage factors based on all load events) is to be retained, a conversion of elastic-plastic strains and strain ranges into pseudo elastic stress ranges is required. The algorithm to be applied is described in the paper. It has to be implemented in the sense of an extended post processing operation of FEA e.g. by APDL scripts in ANSYS registered . Variations of principal stress (strain) directions during the loading

Quantification of damage and fatigue life under random loading

Directory of Open Access Journals (Sweden)

Sahnoun ZENGAH

2017-12-01

Full Text Available The fatigue of components and structures under real stress is a very complex process that appears at the grain scale. The present work is to highlight a variable loading fatigue life prediction process using the Rain-flow cycle count method and cumulative damage models. Four damage cumulative models are retained and used to estimate the lifetime and to evaluate the indicator of the damage (D namely: the model Miner, the model of the damaged stress "DSM", the theory unified and finally Henry's law.

Experimental verification of different parameters influencing the fatigue S/N-curve

International Nuclear Information System (INIS)

Roos, E.; Maile, K.; Herter, K.-H.; Schuler, X.

2005-01-01

For the construction, design and operation of nuclear components the appropriate technical codes and standards provide detailed stress analysis procedures, material data and a design philosophy which guarantees a reliable behavior throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various (specified or measured) loading histories which are of mechanical and/or thermal origin and the geometric complexities of the components. In order to fully understand the background of the fatigue analysis included in the codes and standards as well as of the fatigue design curves used as a limiting criteria (to determine the fatigue life usage factor), it is important to understand the history, background as well as the methodologies which are important for the design engineers to get reliable results. The design rules according to the technical codes and standards provide for explicit consideration of cyclic operation, using design fatigue curves of allowable alternating loads (allowable stress or strain amplitudes) vs. number of loading cycles (S/N-curves), specific rules for assessing the cumulative fatigue damage (cumulative fatigue life usage factor) caused by different specified or monitored load cycles. The influence of different factors like welds, environment, surface finish, temperature, mean stress and size must be taken into consideration. In the paper parameters influencing the S/N-curves used within a fatigue analysis, like different type of material, the surface finish, the temperature, the difference between unwelded and welded areas, the strain rate as well as the influences of notches are verified on the basis of experimental results obtained by specimens testing in the LCF regime for high strain amplitudes. Thus safety margins relevant for the assessment of fatigue life depending on the different influencing parameters are

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.

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

International Nuclear Information System (INIS)

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

2016-01-01

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. (paper)

Torsional fatigue model for limitorque type SMB/SB/SBD actuators for motor-operated valves

Energy Technology Data Exchange (ETDEWEB)

Somogyi, D.; Alvarez, P.D.; Kalsi, M.S. [Kalsi Engineering, Inc., Sugar Land, TX (United States)

1996-12-01

Kalsi Engineering, Inc. has recently developed a computer program to predict the torsional fatigue life of Limitorque Type SMB/SB/SBD actuators for motor-operated valves under given loading levels, including those that exceed the ratings. The development effort was an outgrowth of the {open_quote}Thrust Rating Increase{close_quote} test program. The fatigue model computes all pertinent stress components and their variations as a function of the loading ramp. The cumulative damage and fatigue life due to stress cycling is computed by use of a modification of Miner`s rule. Model predictions were validated against actual cyclic loading test results.

Torsional fatigue model for limitorque type SMB/SB/SBD actuators for motor-operated valves

International Nuclear Information System (INIS)

Somogyi, D.; Alvarez, P.D.; Kalsi, M.S.

1996-01-01

Kalsi Engineering, Inc. has recently developed a computer program to predict the torsional fatigue life of Limitorque Type SMB/SB/SBD actuators for motor-operated valves under given loading levels, including those that exceed the ratings. The development effort was an outgrowth of the open-quote Thrust Rating Increase close-quote test program. The fatigue model computes all pertinent stress components and their variations as a function of the loading ramp. The cumulative damage and fatigue life due to stress cycling is computed by use of a modification of Miner's rule. Model predictions were validated against actual cyclic loading test results

Fatigue Analysis of a Mono-Tower Platform

DEFF Research Database (Denmark)

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

In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed thro...... of the natural period, damping ratio, current, stress Spectrum and parameters describing the fatigue strength. Further, soil damping is shown to be significant for the Mono-tower.......In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed...... through linear-elastic fracture mechanics (LEFM). In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability as well as systems reliability is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters...

Seismic fatigue life evaluation of mechanical structures using energy balance equation

International Nuclear Information System (INIS)

Minagawa, Keisuke; Fujita, Satoshi; Kitamura, Seiji; Okamura, Shigeki

2009-01-01

Evaluation of seismic resistant performance for severe earthquakes is required, because of occurrence of earthquakes which exceed the design criteria. Additionally, quantitative evaluation of cumulative damage by earthquake is also required. In this study, the energy balance equation is applied to the evaluation. The energy balance equation expresses integral information of response, so that the energy balance equation is adequate for the evaluation of the influence of cumulative load such as seismic response. At first, vibration experiment that leads experimental model to fatigue failure by continuous vibration disturbance is conducted. As a result of the experiment, relation between fatigue failure and energy balance equation is confirmed. Then the relation is proved from the viewpoint of hysteresis energy, and consistency between energy balance equation and hysteresis energy is confirmed. Finally, we adopted cumulative damage rule to energy balance equation in order to expect the fatigue life under random waves that have various input acceleration. (author)

Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, Mechanical Fatigue, Creep and Thermal Fatigue Effects

Science.gov (United States)

Bast, Callie Corinne Scheidt

1994-01-01

This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

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

/epoxy laminates in Sectio n 6. The nonlinear fatigue and creep stress - strain and cumulative strain response are characterized in tension and compression as a function of stress level, cycles and cumulative time, using square and sinewave loading over a broad range of frequency. The results are analyzed in terms of the cycles and cumulative time under load. A cumulative strain failure criterion is established, and used to construct shear and tension constant life diagrams (CLD's) with data for nine R - values. The effects of a more duc tile urethne resin are also explored. A previous study of thick adhesives testing is extended to mixed mode fracture mechanics testing in Section 7. Mechanisms of static and fatigue crack extension near the laminate adherend interface are reported in deta il. Data are presented for mixed mode adhesive fracture, compared to mixed mode fracture in ply delamination. Fatigue crack growth exponents are also developed for a mixed mode cracked lap shear coupon. The data for fatigue trends and relative failure stra ins and exponents are compared for various blade component materials in Section 8. The effects of temperature and seawater saturation are considered for selected materials of interest for wind and hydrokinetic turbine blades in Section 9. Section 10 gives detailed conclusions for each section. A cknowledgements The research presented in this report was carried out under Sandia National Laboratories purchase orders 1325028 an d 1543945 between 2010 and 2015, with support from the DOE Wind and Water Technologies Office . In addition to the authors listed, significant contributions were made by Patrick Flaherty, Pancastya Agastra, Michael Schuster, and Michael Voth. Industry m aterials suppliers include Vectorply, Saertex, OCV, AGY, Bayer, Ashland, 3M and Nextel. Industry suppliers with significant contributions to the study were Hexion, PPG, Reichhold, Gurit and NEPTCO. Intentionally Left Blank

Dislocation concepts applied to fatigue properties of austenitic stainless steels including time-dependent modes

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A.A.

1986-10-01

Dislocation substructures formed in austenitic stainless steel 304L and 316L, fatigued at 673 K, 823 K and 873 K under total imposed strain ranges of 0.7 to 2.25%, and their correlation with mechanical properties have been investigated. In addition substructures formed at lower strain ranges have been examined using foils prepared from parts of the specimens with larger cross-sections. Investigation has also been extended to include the effect of intermittent hold-times up to 1.8 x 10/sup 4/s and sequential creep-fatigue and fatigue-creep. The experimental results obtained are analysed and their implications for current dislocation concepts and mechanical properties are discussed.

Cycle counting procedure for fatigue failure preditions for complicated multi-axial stress histories

International Nuclear Information System (INIS)

Jones, D.P.; Friedrich, C.M.; Hoppe, R.G.

1977-12-01

A procedure has been developed to determine the cumulative fatigue damage in structures experiencing complicated multi-axial stress histories. The procedure is a generalization of the rainflow method developed by Matsuishi and Endo for one-dimensional situations. It provides a consistent treatment of three-dimensional stress states that is especially suited to computer programming applications for the post-processing of finite element stress data. The procedure includes a unique method to account for the rotation of principal stresses with time during the stress history and for the cumulative fatigue damage resulting from partial stress reversals within a stress cycle. The general procedure and necessary equations for programming are presented. Comparisons are made with life predictions using Section III of the ASME Boiler and Pressure Vessel Code for two hypothetical multi-axial stress histories for which the principal stresses are rotating with time. These comparisons show that the cycle counting method provides a consistent unambiguous interpretation of the fatigue design procedure in the ASME Code for these cases. Finally, the fatigue life of a perforated plate, as analyzed by finite elements, is computed for the combination of several hypothetical stress histories. This example demonstrates the utility of the proposed method when used in conjunction with finite element programs

Fatigue failure by in-line flow-induced vibration and fatigue life evaluation

International Nuclear Information System (INIS)

Odahara, Satoru; Murakami, Yukitaka; Inoue, Masahiro; Sueoka, Atsuo

2004-01-01

The phenomenon of fatigue failure by the In-line flow-induced vibration was studied. A newly water-flow-induced vibration system was made and used to reproduce fatigue failure by flow-induced vibration. A medium carbon steel specimen was fixed to the experimental equipment. A small artificial hole was introduced onto the specimen surface. Fatigue crack initiated from the artificial hole. A small portable strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project of the authors' team was used to acquire the service strain hisogram at a critical point of the specimen and to measure the variation of natural frequency. Cumulative fatigue damage D defined by the Modified Miner Rule was calculated by using the strain histogram at the initial stage of test. The value of D was almost unity in the case of In-line vibration, while the values of D in the case of the Cross-flow vibration ranged from 0.2 to 0.8. (author)

Fatigue Reliability Analysis of a Mono-Tower Platform

DEFF Research Database (Denmark)

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

1991-01-01

In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed thro...... of the natural period, damping ratio, current, stress spectrum and parameters describing the fatigue strength. Further, soil damping is shown to be significant for the Mono-tower.......In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed...... through linear-elastic fracture mechanics (LEFM). In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability, as well as systems reliability, is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters...

Aging Influence on Fatigue Characteristics of RAC Mixtures Containing Warm Asphalt Additives

Directory of Open Access Journals (Sweden)

Feipeng Xiao

2010-01-01

Full Text Available Aging is an important factor to affect the long-term performance of asphalt pavement. The fatigue life of a typical warm mix asphalt (WMA is generally related to various factors of rheological and mechanical properties of the mixture. The study of the fatigue behavior of the specific rubberized WMA is helpful in recycling the scrap tires and saving energy in terms of the conventional laboratory aging process. This study explores the utilization of the conventional fatigue analysis approach in investigating the cumulative dissipated, stiffness, and fatigue life of rubberized asphalt concrete mixtures containing the WMA additive after a long-term aging process. The aged beams were made with one rubber type (−40 mesh ambient crumb rubber, two aggregate sources, two WMA additives (Asphamin and Sasobit, and tested at 5 and 20ºC. A total of 55 aged fatigue beams were tested in this study. The test results indicated that the addition of crumb rubber extends the fatigue resistance of asphalt binder while WMA additive exhibits a negative effect. The study indicated that the WMA additive generally has an important influence on fatigue life. In addition, test temperature and aggregate source play an important role in determining the cumulative dissipated energy, stiffness, and fatigue life of an aged mixture.

Three technical issues in fatigue damage assessment of nuclear power plant components

International Nuclear Information System (INIS)

Ware, A.G.; Shah, V.N.

1991-01-01

This paper addresses three technical issues that affect the fatigue damage assessment of nuclear power plant components: the effect of the environment on the fatigue life, the importance of the loading sequence in calculating the fatigue crack-initiation damage, and the adequacy of current inservice inspection requirements and methods to characterize fatigue cracks. The environmental parameters that affect the fatigue life of carbon and low alloy steel components are the sulphur content in the steel, the temperature, the amount of dissolved oxygen in the coolant, and the presence of oxidizing agents such as copper oxide. The occurrence of large-amplitude stress cycles early in a component's life followed by low-amplitude stress cycles may cause crack initiation at a cumulative usage factor less than 1.0. The current inservice inspection requirements include volumetric inspections of welds but not of some susceptible sites in the base metal. In addition, the conventional ultrasonic testing techniques need to be improved for reliable detection and accurate sizing of fatigue cracks. 28 refs., 4 figs., 1 tab

Best estimate procedures for fatigue evaluation in the framework of German KTA code

Energy Technology Data Exchange (ETDEWEB)

Seichter, Johannes [Siempelkamp Pruef- und Gutachter-Gesellschaft mbH, Dresden (Germany); Reese, Sven H.; Klucke, Dietmar [E.ON Kernkraft GmbH, Hannover (Germany)

2013-07-01

By decreasing the level of conservatism in fatigue analyses it is possible to reduce as well fatigue usage factors calculated for EOL (end of life) as 'actual CUF' (cumulative fatigue usage factor) of NPP components considerably. It is the opinion of the authors, that the mentioned best estimate procedures should be used in the course of fatigue assessment to fulfill e.g. the demands of the KTA code with regard to environmental assisted fatigue. (orig.)

Multiaxial Fatigue Properties of 2A12 Aluminum Alloy Under Different Stress Amplitude Ratio Loadings

Directory of Open Access Journals (Sweden)

CHEN Ya-jun

2017-09-01

Full Text Available The multiaxial fatigue behavior of 2A12 aluminum alloy was studied with SDN100/1000 electro-hydraulic servo tension-torsion fatigue tester under different stress amplitude ratios, the fracture morphology and the fatigue loading curve were observed to study the failure mechanism. The results show that, under the one stage loading condition, the fatigue life prolongs with the stress amplitude ratio increasing. Under pure torsion loading, smooth and even area exists in the fracture surface. As the stress amplitude ratio increases, the number of scratch reduces, the fatigue striation and some special morphology such as the fishbone pattern, scale pattern and honeycomb pattern can be observed; under cumulative paths of different stress amplitude ratios, the variation of multiaxial fatigue life changes with first stage loading cycles; under cumulative paths of high-low stress amplitude ratio, the cycle hardening occurs obviously in the axial direction for the first stage high stress amplitude ratio loading and 2A12 alloy shows training effect.

Docetaxel-related fatigue in men with metastatic prostate cancer: a descriptive analysis.

Science.gov (United States)

Bergin, A R T; Hovey, E; Lloyd, A; Marx, G; Parente, P; Rapke, T; de Souza, P

2017-09-01

Fatigue is a prevalent and debilitating side effect of docetaxel chemotherapy in metastatic prostate cancer. A better understanding of the kinetics and nature of docetaxel-related fatigue may provide a framework for intervention. This secondary analysis was performed using the MOTIF database, from a phase III, randomised, double-blind, placebo-controlled study of modafinil (200 mg/day for 15 days) for docetaxel-related fatigue in men with metastatic prostate cancer [1]. The pattern of fatigue was analysed using the MDASI (MD Anderson Symptom Inventory) score. The impact of modafinil, cumulative docetaxel exposure, age and smoking status on fatigue kinetics were explored. Fatigue-related symptoms were assessed using the SOMA6 (fatigue and related symptoms) subset of the SPHERE (Somatic and Psychological Health Report). Mood was tracked using the short form 36 health survey questionnaire (SF-36). Across four docetaxel cycles, fatigue scores were higher in the first week and decreased over weeks two and three. Whilst men randomised to modafinil had reduced fatigue scores, cumulative docetaxel had little impact. Younger men (55-68 years) had significantly reduced fatigue scores, whereas current and ex-smokers had higher scores. There was no significant change in mood status or haemoglobin across treatment cycles. Men described both 'somnolence' and 'muscle fatigue' contributing significantly to their symptom complex. Assessment and management of docetaxel-related fatigue remains an important challenge. Given the complex, multifactorial nature of fatigue, identification through structured interview and interventions targeted to specific 'at risk' groups may be the most beneficial. Understanding the temporal pattern (kinetics) and nature of fatigue is critical to guide this process.

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)

Fatigue of Composite Materials and Substructures for Wind Turbine Blades; TOPICAL

International Nuclear Information System (INIS)

MANDELL, JOHN F.; SAMBORSKY, DANIEL D.; CAIRNS, DOUGLAS

2002-01-01

This report presents the major findings of the Montana State University Composite Materials Fatigue Program from 1997 to 2001, and is intended to be used in conjunction with the DOE/MSU Composite Materials Fatigue Database. Additions of greatest interest to the database in this time period include environmental and time under load effects for various resin systems; large tow carbon fiber laminates and glass/carbon hybrids; new reinforcement architectures varying from large strands to prepreg with well-dispersed fibers; spectrum loading and cumulative damage laws; giga-cycle testing of strands; tough resins for improved structural integrity; static and fatigue data for interply delamination; and design knockdown factors due to flaws and structural details as well as time under load and environmental conditions. The origins of a transition to increased tensile fatigue sensitivity with increasing fiber content are explored in detail for typical stranded reinforcing fabrics. The second focus of the report is on structural details which are prone to delamination failure, including ply terminations, skin-stiffener intersections, and sandwich panel terminations. Finite element based methodologies for predicting delamination initiation and growth in structural details are developed and validated, and simplified design recommendations are presented

Study of cumulative fatigue damage on an austenitic steel

International Nuclear Information System (INIS)

Baudry, G.; Amzallag, C.; Bernard, J.L.

1984-01-01

The validity of Palmgren-Miner rule is verified for working life between about 500 and 1,000,000 cycles for two damages: one corresponding to complete rupture of smooth test piece and the other corresponding to initiation of a fatigue crack in a high stress area. Material studied is a stainless steel Z3CND17-12 (AISI 316) used in nuclear industry. Validity of the rule is better verified in the case of small cracks than for a smooth sample. (15 references are given) [fr

Study on Determination Method of Fatigue Testing Load for Wind Turbine Blade

Science.gov (United States)

Liao, Gaohua; Wu, Jianzhong

2017-07-01

In this paper, the load calculation method of the fatigue test was studied for the wind turbine blade under uniaxial loading. The characteristics of wind load and blade equivalent load were analyzed. The fatigue property and damage theory of blade material were studied. The fatigue load for 2MW blade was calculated by Bladed, and the stress calculated by ANSYS. Goodman modified exponential function S-N curve and linear cumulative damage rule were used to calculate the fatigue load of wind turbine blades. It lays the foundation for the design and experiment of wind turbine blade fatigue loading system.

Mitigation of Over-conservatism in Fatigue Analysis of the Pressurizer Surge Line

International Nuclear Information System (INIS)

Moon, Chan Kook; Lee, Jang Gon; Kim, Tae Soon; Han, Sung Bong

2007-01-01

The U.S. Nuclear Regulatory Commission (NRC) issued draft regulatory guide DG-1144 in July 2006, entitled 'Guidelines for Evaluating Fatigue Analysis Incorporating the Life Reduction of Metal Components Due to the Effects of the Light-Water Reactor Environment for New Reactors.' This draft guide demands to perform fatigue analysis in accordance with the draft NUREG/CR-6909 report (Effect on Fatigue Life of Reactor material for LWR Coolant Environments) for carbon and low-alloy steels, and austenitic stainless steel materials. In March 2007, NRC formally issued Reg. guide 1.207 which demands to perform fatigue analysis in accordance with the final NUREG/CR-6909 report. Reviewing these documents it is found that in case of austenitic stainless steel and Ni-Cr alloy the new design fatigue curve is much more severe than present curve and will increase the cumulative usage factor (CUF) 4 to 5 times of the present value. In particular, detailed analysis for pressurizer surge line which is made of stainless steel is needed and mitigation of over-conservatism included in present fatigue analysis procedures is absolutely required. In this study, thus, the mitigation method for over conservatism in the present fatigue analysis procedure for the pressurizer surge line is studied

Experimental Study on Fatigue Performance of Foamed Lightweight Soil

Science.gov (United States)

Qiu, Youqiang; Yang, Ping; Li, Yongliang; Zhang, Liujun

2017-12-01

In order to study fatigue performance of foamed lightweight soil and forecast its fatigue life in the supporting project, on the base of preliminary tests, beam fatigue tests on foamed lightweight soil is conducted by using UTM-100 test system. Based on Weibull distribution and lognormal distribution, using the mathematical statistics method, fatigue equations of foamed lightweight soil are obtained. At the same time, according to the traffic load on real road surface of the supporting project, fatigue life of formed lightweight soil is analyzed and compared with the cumulative equivalent axle loads during the design period of the pavement. The results show that even the fatigue life of foamed lightweight soil has discrete property, the linear relationship between logarithmic fatigue life and stress ratio still performs well. Especially, the fatigue life of Weibull distribution is more close to that derived from the lognormal distribution, in the instance of 50% guarantee ratio. In addition, the results demonstrated that foamed lightweight soil as subgrade filler has good anti-fatigue performance, which can be further adopted by other projects in the similar research domain.

Comparative Study of Fatigue Damage Models Using Different Number of Classes Combined with the Rainflow Method

Directory of Open Access Journals (Sweden)

S. Zengah

2013-06-01

Full Text Available Fatigue damage increases with applied load cycles in a cumulative manner. Fatigue damage models play a key role in life prediction of components and structures subjected to random loading. The aim of this paper is the examination of the performance of the “Damaged Stress Model”, proposed and validated, against other fatigue models under random loading before and after reconstruction of the load histories. To achieve this objective, some linear and nonlinear models proposed for fatigue life estimation and a batch of specimens made of 6082T6 aluminum alloy is subjected to random loading. The damage was cumulated by Miner’s rule, Damaged Stress Model (DSM, Henry model and Unified Theory (UT and random cycles were counted with a rain-flow algorithm. Experimental data on high-cycle fatigue by complex loading histories with different mean and amplitude stress values are analyzed for life calculation and model predictions are compared.

Probabilistic assessment of fatigue life including statistical uncertainties in the S-N curve

International Nuclear Information System (INIS)

Sudret, B.; Hornet, P.; Stephan, J.-M.; Guede, Z.; Lemaire, M.

2003-01-01

A probabilistic framework is set up to assess the fatigue life of components of nuclear power plants. It intends to incorporate all kinds of uncertainties such as those appearing in the specimen fatigue life, design sub-factor, mechanical model and applied loading. This paper details the first step, which corresponds to the statistical treatment of the fatigue specimen test data. The specimen fatigue life at stress amplitude S is represented by a lognormal random variable whose mean and standard deviation depend on S. This characterization is then used to compute the random fatigue life of a component submitted to a single kind of cycles. Precisely the mean and coefficient of variation of this quantity are studied, as well as the reliability associated with the (deterministic) design value. (author)

Compassion fatigue: A meta-narrative review of the healthcare literature.

Science.gov (United States)

Sinclair, Shane; Raffin-Bouchal, Shelley; Venturato, Lorraine; Mijovic-Kondejewski, Jane; Smith-MacDonald, Lorraine

2017-04-01

Compassion fatigue describes a work-related stress response in healthcare providers that is considered a 'cost of caring' and a key contributor to the loss of compassion in healthcare. The purpose of this review was to critically examine the construct of compassion fatigue and to determine if it is an accurate descriptor of work-related stress in healthcare providers and a valid target variable for intervention. Meta-narrative review. PubMed, Medline, CINAHL, PsycINFO, and Web of Science databases, Google Scholar, the grey literature, and manual searches of bibliographies. Seminal articles and theoretical and empirical studies on compassion fatigue in the healthcare literature were identified and appraised for their validity and relevance to our review. Sources were mapped according to the following criteria: 1) definitions; 2) conceptual analyses; 3) signs and symptoms; 4) measures; 5) prevalence and associated risk factors; and 6) interventions. A narrative account of included studies that critically examines the concept of compassion fatigue in healthcare was employed, and recommendations for practice, policy and further research were made. 90 studies from the nursing literature and healthcare in general were included in the review. Findings emphasized that the physical, emotional, social and spiritual health of healthcare providers is impaired by cumulative stress related to their work, which can impact the delivery of healthcare services; however, the precise nature of compassion fatigue and that it is predicated on the provision of compassionate care is associated with significant limitations. The conceptualization of compassion fatigue was expropriated from crisis counseling and psychotherapy and focuses on limited facets of compassion. Empirical studies primarily measure compassion fatigue using the Professional Quality of Life Scale, which does not assess any of the elements of compassion. Reported risk factors for compassion fatigue include job

Fatigue Analysis of Tubesheet/Shell Juncture Applying the Mitigation Factor for Over-conservatism

International Nuclear Information System (INIS)

Kang, Deog Ji; Kim, Kyu Hyoung; Lee, Jae Gon

2009-01-01

If the environmental fatigue requirements are applied to the primary components of a nuclear power plant, to which the present ASME Code fatigue curves are applied, some locations with high level CUF (Cumulative Usage Factor) are anticipated not to meet the code criteria. The application of environmental fatigue damage is still particularly controversial for plants with 60-year design lives. Therefore, it is need to develop a detailed fatigue analysis procedure to identify the conservatisms in the procedure and to lower the cumulative usage factor. Several factors are being considered to mitigate the conservatism such as three-dimensional finite element modeling. In the present analysis, actual pressure transient data instead of conservative maximum and minimum pressure data was applied as one of mitigation factors. Unlike in the general method, individual transient events were considered instead of the grouped transient events. The tubesheet/shell juncture in the steam generator assembly is the one of the weak locations and was, therefore, selected as a target to evaluate the mitigation factor in the present analysis

Fatigue analysis of HANARO primary cooling system piping

International Nuclear Information System (INIS)

Ryu, Jeong Soo

1998-05-01

A main form of piping failure which occurring leak before break (LBB) is fatigue failure. The fatigue analysis of HANARO primary cooling system (PCS) piping was performed. The PCS piping had been designed in accordance with ASME Class 3 for service conditions. However fatigue analysis is not required in Class 3. In this study the quantitative fatigue analysis was carried out according to ASME Class 1. The highest stress points which have the largest possibility of ASME class 1. The highest stress points which have the largest possibility of the fatigue were determined from the piping stress analysis for each subsection piping. The fatigue analysis was performed for 3 highest stress points, i.e., branch connection, anchor point and butt welding joint. After calculating the peak stress intensity range the fatigue usage factors were evaluated considering operating cycles and S-N curve. The cumulative usage factors for 3 highest stress points were much less than 1. The results show that the possibility of fatigue failure for PCS piping subjected to thermal expansion and seismic loads is very small. The structural integrity of the HANARO PCS piping for fatigue failure was proved to apply the LBB. (author). 11 tabs., 6 figs

Fatigue life evaluation method of austenitic stainless steel in PWR water

International Nuclear Information System (INIS)

Sakaguchi, Katsumi; Nomura, Yuichiro; Suzuki, Shigeki; Kanasaki, Hiroshi; Higuchi, Makoto

2006-09-01

It is known that the fatigue life in elevated temperature water is substantially reduced compared with that in the air. The fatigue life reduction has been investigated experimentally in EFT project of Japan Nuclear Energy Safety Organization (JNES) to evaluate the environmental effect on fatigue life. Many tests have been done for carbon, low alloy, stainless steels and nickel-based alloy under the various conditions. In this paper, the results of the stainless steel in simulated PWR water environments were reported. Fatigue life tests in simulated PWR environments were carried out and the effect of key parameters on fatigue life reduction was examined. The materials used in this study were base and weld metal of austenitic stainless steel SS316, weld metal of SS304 and the base and aged metal of the duplex stainless steel SCS14A. In order to evaluate the effects of stain amplitude, strain rate, strain ratio, temperature, aging, water flow rate and strain holding time, many fatigue tests were examined. In transient condition in an actual plant, however, such parameters as temperature and strain rate are not constant. In order to evaluate fatigue damage in actual plant on the basis of experimental results under constant temperature and strain rate condition, the modified rate approach method was developed. Various kinds of transient have to be taken into account of in actual plant fatigue evaluation, and stress cycle of several ranges of amplitude has to be considered in assessing damage from fatigue. Generally, cumulative usage factor is applied in this type of evaluation. In this study, in order to confirm the applicability of modified rate approach method together with cumulative usage factor, fatigue tests were carried out by combining stress cycle blocks of different strain amplitude levels, in which strain rate changes in response to temperature in a simulated PWR water environment. Consequently, fatigue life could be evaluated with an accuracy of factor of 3

Creep-fatigue damage in austenitic stainless steels

International Nuclear Information System (INIS)

Rezgui, Brahim.

1980-06-01

This is a study of hold time effects on the low cycle fatigue (L.C.F.) properties of 316L austenitic stainless steel at 600 0 C in air. Results obtained for different plastic strain levels indicate that a tension hold time at peak strain lead to a reduction in fatigue life. The importance of this effect depend on the length of hold period, and also on the strain amplitude. No saturation had been observed. Metallographic and microstructural analysis of failed specimens indicates mechanisms by which failure is produced. For continuous cycling the fractures occurs by the initiation and the propagation of a trans-granular crack. Creep damage in the bulk of material is formed during periods of tensile stress relaxation; it causes a change in the failure mode which became intergranular. It is the interaction between this creep-damage and fatigue cracks which is partly responsable for the reduction in the fatigue life. Predictions based upon linear cumulative damage method indicate that virgin material properties may be irrelevant in creep-fatigue interactions [fr

Fatigue

Science.gov (United States)

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

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

Putting a price on worker fatigue

Energy Technology Data Exchange (ETDEWEB)

Carter, R.A.

2007-03-15

In a round-the-clock industry such as mining, extended work hours may be necessary for production but damaging to the bottom line. A recent report commissioned by the Minerals Council of Australia (MCA) attempts to document the relationship between sleep, working arrangements and fatigue. The study, titled Work Design, Fatigue and Sleep by Dr. Angela Baker and Dr. Sally Ferguson of the Australian Center for Sleep Research at the University of South Australia contains information useful for managing fatigue in the workplace. The publication is available free online at http://www.minerals.org.au. The study offers guidelines for planing work schedules or for chaning shifts. William G. Sirosis, senior vice president and COO of Circadian Technologies Inc., also addressed this topic in a presentation at the recent MineWest 2006 conference. He pointed out that the exact dollar costs of operating with a fatigued workforce was difficult to pinpoint but the cumulative effect can be damaging to a company's production and profitability. He suggested steps to a successful management programme.

Investigation of LWR environmental effect on fatigue lifetime of austenitic stainless steel component

International Nuclear Information System (INIS)

Kim, J. S.; Youm, H. K.; Jin, T. E.

1999-01-01

The fatigue lifetime of principal components in nuclear power plant is evaluated by using the design fatigue curves in ASME B and PV code during design process. However, it is inadequate to evaluate fatigue lifetime considering the LWR environmental effect by these design fatigue curves because these are presented only under atmosphere environment. Therefore, many studies are recently performed for the design fatigue curves considering LWR environmental effect and are presented that the design fatigue curves in ASME B and PV code can be non-conservative. In present paper, the limits and differences of the design fatigue curves considering environmental effect are presented. To investigate the change of fatigue lifetime according to each design fatigue curve, the CUFs for the pressurizer spray nozzle partly composed of austenitic stainless steel are calculated according to each one. Finally, if the evaluation result can not be satisfied with fatigue design requirement, the alternatives to reduce design cumulative usage factor are discussed. (author)

A phenomenological approach for the analysis of combined fatigue and creep

International Nuclear Information System (INIS)

Bui-Quoc, T.; Biron, A.

1982-01-01

An approach is proposed for the life prediction, under cumulative damage conditions, for fatigue and for creep. An interaction effect is introduced to account for a modification in the material behavior due to previous loading. A predictive technique is then developed which is applied to several materials for fatigue and which could potentially be used for creep. With due consideration to the similarity of the formulation for both phenomena, the analysis for the combination of fatigue and creep is then carried out through a straightforward sequential use of the two damage functions. Several patterns are studied without and with an interaction effect. (orig.)

Development of elevated temperature fatigue design information for type 316 stainless steel

International Nuclear Information System (INIS)

Jaske, C.E.; Mindlin, H.; Perrin, J.S.

1975-01-01

To develop material properties information for use in elevated-temperature fatigue design, an extensive study of the fatigue and stress-strain behaviour of Type 316 stainless steel was conducted at temperatures from 21 to 649 0 C. Fatigue life and cyclic stress-strain curves were developed. Creep-fatigue interaction was evaluated by conducting strain hold-time tests at 566 and 649 0 C. Hold periods at peak tensile strain produced a large reduction in cyclic life. It was found that both a linear damage rule and the strain-partitioning method could be used to assess cumulative creep and fatigue damage. Aging for 1000 h at test temperature before testing caused only small or no changes in continuous cycling fatigue resistance at 566 and 649 0 C and in tension hold-time fatigue resistance at 566 0 C. This aging produced a significant increase in tension hold-time fatigue resistance at 649 0 C. (author)

Studies on sleep patterns and fatigue due to shift work and their work adaptability. Kotai sagyo ni yoru suimin dotai to hiro oyobi sono sagyo tekiosei no kenkyu

Energy Technology Data Exchange (ETDEWEB)

Matsuoka, N.; Yokota, A. (Univ. of Occupational and Environmental Health, Kitakyushu (Japan). School of Medicine)

1991-01-01

Studies were made on sleep patterns and fatigue due to shift work and their work adaptability with respect to the following items: (1) With a nurse work system as the object, a survey of rectum temperature, heart rate and rhythm before and after a midnight shift, and sleep at rising in the morning using the OSA survey method; (2) To analyze actual conditions of cumulative fatigue felt by shift workers and fatigue factors, a survey on shift work history, overtime work time, work patterns, symptoms of cumulative fatigue, and and life satisfaction; (3) A survey on daytime sleep record maintained at working places of guards including those of middle or advanced age, and sleep as affected by a nap; (4) A method of improving complains of circadian rhythm disorders because of variations in sleep and emergence rhythms experienced by shift workers, and discussions of usability of light radiation; and (5) Establishment of a technique to indicate effects of psychological burdens and psychogenic stress on visual functions of shift workers using tensions in focal adjustment. 5 figs., 5 tabs.

Fatigue in older adults: An early indicator of the aging process?

DEFF Research Database (Denmark)

Avlund, Kirsten

2010-01-01

The aim of this paper is to give an overview of research on fatigue in older adults, with a focus on fatigue as an early indicator of the aging process. Fatigue is a strong predictor of functional limitations, disability, mortality, and other adverse outcomes in young-old and old-old populations......, between men and women, and in different geographic localities. Several biological, physiological and social explanations are proposed: fatigue may be seen not only as a self-reported indicator of frailty, defined as a physiologic state of increased vulnerability to stressors, which results from decreased...... physiologic reserves and even dysregulation of multiple physiologic systems, but also this state may be accelerated because of the cumulative impact of social, mental and biological factors throughout life....

The Fatigue Life Prediction of Train Wheel Rims Containing Spherical Inclusions

Science.gov (United States)

Li, Yajie; Chen, Huanguo; Cai, Li; Chen, Pei; Qian, Jiacheng; Wu, Jianwei

2018-03-01

It is a common phenomenon that fatigue crack initiation occurs frequently in the inclusions of wheel rims. Research on the fatigue life of wheel rims with spherical inclusions is of great significance on the reliability of wheels. To find the danger point and working condition of a wheel, the stress state of the wheel rim with spherical inclusions was analyzed using the finite element method. Results revealed that curve conditions are dangerous. The critical plane method, based on the cumulative fatigue damage theory, was used to predict the fatigue life of the wheel rim and whether it contained spherical inclusions or not under curve conditions. It was found that the fatigue life of the wheel rim is significantly shorter when the wheel rim contains spherical inclusions. Analysis of the results can provide a theoretical basis and technical support for train operations and maintenance.

Long-Term Fatigue and Its Probability of Failure Applied to Dental Implants

Directory of Open Access Journals (Sweden)

María Prados-Privado

2016-01-01

Full Text Available It is well known that dental implants have a high success rate but even so, there are a lot of factors that can cause dental implants failure. Fatigue is very sensitive to many variables involved in this phenomenon. This paper takes a close look at fatigue analysis and explains a new method to study fatigue from a probabilistic point of view, based on a cumulative damage model and probabilistic finite elements, with the goal of obtaining the expected life and the probability of failure. Two different dental implants were analysed. The model simulated a load of 178 N applied with an angle of 0°, 15°, and 20° and a force of 489 N with the same angles. Von Mises stress distribution was evaluated and once the methodology proposed here was used, the statistic of the fatigue life and the probability cumulative function were obtained. This function allows us to relate each cycle life with its probability of failure. Cylindrical implant has a worst behaviour under the same loading force compared to the conical implant analysed here. Methodology employed in the present study provides very accuracy results because all possible uncertainties have been taken in mind from the beginning.

A fatigue analysis including environmental effects for a pipe system in a Swedish BWR

International Nuclear Information System (INIS)

Steingrimsdottir, Kristin; Dahlberg, Magnus

2011-10-01

A BWR feed water piping system (austenitic steel) has been analyzed with two different fatigue curves and environmental factors. Original fatigue curve from ASME is compared to a new fatigue curve; ANL. The influence of environmental correction factors (Fen) is studied further for the piping system. It is noted that the results apply for this particular system, and general conclusions should be cautiously drawn. Typical for this system is that all dominant loads are within the low-cycle regime. This implies that the change of fatigue curve only leads to limited increases in usage factors. Larger changes can occur if larger number of cycles is within the high-cycle regime

Statistical optimisation techniques in fatigue signal editing problem

International Nuclear Information System (INIS)

Nopiah, Z. M.; Osman, M. H.; Baharin, N.; Abdullah, S.

2015-01-01

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

Statistical optimisation techniques in fatigue signal editing problem

Energy Technology Data Exchange (ETDEWEB)

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

2015-02-03

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

Fatigue Behavior under Multiaxial Stress States Including Notch Effects and Variable Amplitude Loading

Science.gov (United States)

Gates, Nicholas R.

The central objective of the research performed in this study was to be able to better understand and predict fatigue crack initiation and growth from stress concentrations subjected to complex service loading histories. As such, major areas of focus were related to the understanding and modeling of material deformation behavior, fatigue damage quantification, notch effects, cycle counting, damage accumulation, and crack growth behavior under multiaxial nominal loading conditions. To support the analytical work, a wide variety of deformation and fatigue tests were also performed using tubular and plate specimens made from 2024-T3 aluminum alloy, with and without the inclusion of a circular through-thickness hole. However, the analysis procedures implemented were meant to be general in nature, and applicable to a wide variety of materials and component geometries. As a result, experimental data from literature were also used, when appropriate, to supplement the findings of various analyses. Popular approaches currently used for multiaxial fatigue life analysis are based on the idea of computing an equivalent stress/strain quantity through the extension of static yield criteria. This equivalent stress/strain is then considered to be equal, in terms of fatigue damage, to a uniaxial loading of the same magnitude. However, it has often been shown, and was shown again in this study, that although equivalent stress- and strain-based analysis approaches may work well in certain situations, they lack a general robustness and offer little room for improvement. More advanced analysis techniques, on the other hand, provide an opportunity to more accurately account for various aspects of the fatigue failure process under both constant and variable amplitude loading conditions. As a result, such techniques were of primary interest in the investigations performed. By implementing more advanced life prediction methodologies, both the overall accuracy and the correlation of fatigue

Study of Anti-Fatigue Effect in Rats of Ferrous Chelates Including Hairtail Protein Hydrolysates

Directory of Open Access Journals (Sweden)

Saibo Huang

2015-12-01

Full Text Available The ability of ferrous chelates including hairtail protein hydrolysates to prevent and reduce fatigue was studied in rats. After hydrolysis of hairtail surimi with papain, the hairtail protein hydrolysates (HPH were separated into three groups by range of relative molecular weight using ultrafiltration membrane separation. Hairtail proteins were then chelated with ferrous ions, and the antioxidant activity, the amino acid composition and chelation rate of the three kinds of ferrous chelates including hairtail protein hydrolysates (Fe-HPH were determined. Among the three groups, the Fe-HPH chelate showing the best conditions was selected for the anti-fatigue animal experiment. For it, experimental rats were randomly divided into seven groups. Group A was designated as the negative control group given distilled water. Group B, the positive control group, was given glutathione. Groups C, D and E were designated as the Fe-HPH chelate treatment groups and given low, medium, and high doses, respectively. Group F was designated as HPH hydrolysate treatment group, and Group G was designated as FeCl2 treatment group. The different diets were orally administered to rats for 20 days. After that time, rats were subjected to forced swimming training after 1 h of gavage. Rats given Fe-FPH chelate had higher haemoglobin regeneration efficiency (HRE, longer exhaustive swimming time and higher SOD activity. Additionally, Fe-FPH chelate was found to significantly decrease the malondialdehyde content, visibly enhance the GSH-Px activity in liver and reduce blood lactic acid of rats. Fe-HPH chelate revealed an anti-fatigue effect, similar to or better than the positive control substance and superior to HPH or Fe when provided alone.

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

Adaptive strategies for cumulative cultural learning.

Science.gov (United States)

Ehn, Micael; Laland, Kevin

2012-05-21

The demographic and ecological success of our species is frequently attributed to our capacity for cumulative culture. However, it is not yet known how humans combine social and asocial learning to generate effective strategies for learning in a cumulative cultural context. Here we explore how cumulative culture influences the relative merits of various pure and conditional learning strategies, including pure asocial and social learning, critical social learning, conditional social learning and individual refiner strategies. We replicate the Rogers' paradox in the cumulative setting. However, our analysis suggests that strategies that resolved Rogers' paradox in a non-cumulative setting may not necessarily evolve in a cumulative setting, thus different strategies will optimize cumulative and non-cumulative cultural learning. Copyright © 2012 Elsevier Ltd. All rights reserved.

The challenge of cumulative impacts

Energy Technology Data Exchange (ETDEWEB)

Masden, Elisabeth

2011-07-01

Full text: As governments pledge to combat climate change, wind turbines are becoming a common feature of terrestrial and marine environments. Although wind power is a renewable energy source and a means of reducing carbon emissions, there is a need to ensure that the wind farms themselves do not damage the environment. There is particular concern over the impacts of wind farms on bird populations, and with increasing numbers of wind farm proposals, the concern focuses on cumulative impacts. Individually, a wind farm, or indeed any activity/action, may have minor effects on the environment, but collectively these may be significant, potentially greater than the sum of the individual parts acting alone. Cumulative impact assessment is a legislative requirement of environmental impact assessment but such assessments are rarely adequate restricting the acquisition of basic knowledge about the cumulative impacts of wind farms on bird populations. Reasons for this are numerous but a recurring theme is the lack of clear definitions and guidance on how to perform cumulative assessments. Here we present a conceptual framework and include illustrative examples to demonstrate how the framework can be used to improve the planning and execution of cumulative impact assessments. The core concept is that explicit definitions of impacts, actions and scales of assessment are required to reduce uncertainty in the process of assessment and improve communication between stake holders. Only when it is clear what has been included within a cumulative assessment, is it possible to make comparisons between developments. Our framework requires improved legislative guidance on the actions to include in assessments, and advice on the appropriate baselines against which to assess impacts. Cumulative impacts are currently considered on restricted scales (spatial and temporal) relating to individual development assessments. We propose that benefits would be gained from elevating cumulative

Brain Electrodynamic and Hemodynamic Signatures Against Fatigue During Driving

Directory of Open Access Journals (Sweden)

Chun-Hsiang Chuang

2018-03-01

Full Text Available Fatigue is likely to be gradually cumulated in a prolonged and attention-demanding task that may adversely affect task performance. To address the brain dynamics during a driving task, this study recruited 16 subjects to participate in an event-related lane-departure driving experiment. Each subject was instructed to maintain attention and task performance throughout an hour-long driving experiment. The subjects' brain electrodynamics and hemodynamics were simultaneously recorded via 32-channel electroencephalography (EEG and 8-source/16-detector functional near-infrared spectroscopy (fNIRS. The behavior performance demonstrated that all subjects were able to promptly respond to lane-deviation events, even if the sign of fatigue arose in the brain, which suggests that the subjects were fighting fatigue during the driving experiment. The EEG event-related analysis showed strengthening alpha suppression in the occipital cortex, a common brain region of fatigue. Furthermore, we noted increasing oxygenated hemoglobin (HbO of the brain to fight driving fatigue in the frontal cortex, primary motor cortex, parieto-occipital cortex and supplementary motor area. In conclusion, the increasing neural activity and cortical activations were aimed at maintaining driving performance when fatigue emerged. The electrodynamic and hemodynamic signatures of fatigue fighting contribute to our understanding of the brain dynamics of driving fatigue and address driving safety issues through the maintenance of attention and behavioral performance.

Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel; Endommagement et cumul de dommage en fatigue dans le domaine de l'endurance limitee d'un acier inoxydable austenitique 304L

Energy Technology Data Exchange (ETDEWEB)

Lehericy, Y

2007-05-15

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

Prediction of Fatigue Crack Growth in Gas Turbine Engine Blades Using Acoustic Emission.

Science.gov (United States)

Zhang, Zhiheng; Yang, Guoan; Hu, Kun

2018-04-25

Fatigue failure is the main type of failure that occurs in gas turbine engine blades and an online monitoring method for detecting fatigue cracks in blades is urgently needed. Therefore, in this present study, we propose the use of acoustic emission (AE) monitoring for the online identification of the blade status. Experiments on fatigue crack propagation based on the AE monitoring of gas turbine engine blades and TC11 titanium alloy plates were conducted. The relationship between the cumulative AE hits and the fatigue crack length was established, before a method of using the AE parameters to determine the crack propagation stage was proposed. A method for predicting the degree of crack propagation and residual fatigue life based on the AE energy was obtained. The results provide a new method for the online monitoring of cracks in the gas turbine engine blade.

The Nature of Fatigue in Chronic Fatigue Syndrome.

Science.gov (United States)

Olson, Karin; Zimka, Oksana; Stein, Eleanor

2015-10-01

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

The strainrange conversion principle for treating cumulative fatigue damage in the creep range

Science.gov (United States)

Manson, S. S.

1983-01-01

A formula is derived for combining effects of successive hysteresis loops in the creep range of materials when one loop has excess tensile creep, while the other contains excess compressive creep. The resultant effect resembles single loops involving balanced tensile and compressive creep. The attempt to use the Interaction Damage Rule as a tool in combining loops of non-equal size and complex strainrange content has led to important new concepts useful in future studies of creep-fatigue. It turns out that the Interaction Damage Rule is basically an expression of how a set of hysteresis loops involving only single generic strains can combine to produce the same micromechanistic damage as the loop containing the combined strainranges which it analyzes. Making use of the underlying concept of Strainrange Partitioning that only the strainrange content of a hysteresis loop governs fatigue life, not order of introducing strainranges, a rational derivation of the Interaction Damage Rule is provided, showing also how it can effectively be used to synthesize independent loops and determine both damaging and healing effects.

Experimental study on creep-fatigue interaction behavior of GH4133B superalloy

International Nuclear Information System (INIS)

Hu Dianyin; Wang Rongqiao

2009-01-01

The creep-fatigue tests have been conducted with nickel-based superalloy GH4133B at 600 deg. C in three cases of type loading to study the creep-fatigue behavior of the alloy and the loading history effect on the creep-fatigue damage. Since the conventional linear cumulative damage rule failed in evaluating the creep-fatigue life based on experimental data, a continuous non-linear model proposed by Mao et al. was employed to describe the creep-fatigue interaction. The creep-fatigue damage in the cases of continuous cyclic creep loading (CF) and prior fatigue followed by creep loading (F + C) was larger than unity and smaller than unity when the type loading was prior creep followed by fatigue loading (C + F). Scanning electron microscope (SEM) analyses of the fracture surface showed that the cracks initiated from the specimen surface and the fracture modes in different loading history were different. The crack mode at CF loading depended on the cyclic period. In the case of F + C loading, the primary fracture mode was transgranular, and in the condition where the type of waveform was C + F, the fracture mode was of mixed transgranular and intergranular type. In addition, the origin of the history effect on creep-fatigue interaction was explained by the SEM observations.

The Study on Environmental Fatigue Behavior of Low Alloy Steel and Stainless Steel Pipes Using the Simplified Plant Transients

International Nuclear Information System (INIS)

Yoo, One; Song, M. S.; Kim, I. Y.; Park, S. H.; Lee, B. S.

2010-01-01

Nuclear components categorized as ASME Code Class 1 shall be evaluated for the fatigue and satisfy the fatigue acceptance criteria, CUF(cumulative usage factor) < 1 in accordance with ASME Code. However, recent studies have shown the fatigue evaluation procedure may not give conservative results when the components operate in the water environment. NRC issued Regulatory Guide 1.207 which enforces the new fatigue evaluation method or Fen(environmental fatigue correction factor) method to nuclear plants to be newly constructed. This paper describes the characteristics of the behavior of low alloy and austenitic stainless steel straight pipe related to environmental fatigue, which are obtained by using the method suggested by Regulatory Guide 1.207 and simplified plant transients

Behavior of X 6 CrNi 18 11 under sequential testing of creep and fatigue

Energy Technology Data Exchange (ETDEWEB)

Husslage, W [TNO, Apeldoorn (Netherlands); Breitling, H [INTERATOM, Bergisch Gladbach (Germany)

1977-07-01

The behaviour of the austenitic stainless steel X 6 CrNi 18 11 with about 0.05% C, 18% Cr and 11% Ni was investigated under combined creep and cyclic loading at 550 degrees C. Base metal specimens and specimens containing a weld were tested by: prior cyclic loading followed by creep loading to rupture; prior creep loading followed by cyclic loading to rupture; alternating periods of creep and cyclic loading to rupture. The results were evaluated using the linear cumulative fatigue and creep damage rule. The damage factor D determined on basis of the respective behaviour of base material and welds varied between 0.5 and 1.6 if specimens containing a weld defect were not taken into consideration. Weld defects, which had predominantly an influence on fatigue, lowered the damage factor D up to 0.2. Evaluation of the results on welds with the pure creep and fatigue behaviour of base material shows damage factors between 0.4 and 0.9. By the high margins between allowable creep and fatigue life and life measured with specimens, the cumulative damages of base material and welded joints are much better than the allowable values according to CCI 1592 of the ASME Boiler and Pressure Vessel Code. (author)

Microstructure modeling and crystal plasticity simulations for the evaluation of fatigue crack initiation in α-iron specimen including an elliptic defect

Energy Technology Data Exchange (ETDEWEB)

Briffod, Fabien, E-mail: briffod@rme.mm.t.u-tokyo.ac.jp; Shiraiwa, Takayuki; Enoki, Manabu

2017-05-17

In this study, fatigue crack initiation in pure α-iron is investigated through a microstructure-sensitive framework. At first, synthetic microstructures are modeled based on an anisotropic tessellation that accounts for the information of the grains morphology extracted from electron backscatter diffraction (EBSD) analysis. Low-cycle fatigue experiments under strain-controlled conditions are conducted in order to calibrate a crystal plasticity model and a J{sub 2} model including isotropic and kinematic hardening. A critical plane fatigue indicator parameter (FIP) based on the Tanaka-Mura model is then presented to evaluate the location and quantify the driving force for the formation of a crack. The FIP is averaged over several potential crack paths within each grain defined by the intersection between a given slip plane and the plane of the model thus accounting for both the lattice orientation and morphology of the grain. Several fatigue simulations at various stress amplitudes are conducted using a sub-modeling technique for the attribution of boundary conditions on the polycrystalline aggregate models including an elliptic defect. The influence of the microstructure attributes and stress level on the location and amplitude of the FIP are then quantified and discussed.

Order effect of strain applications in low-cycle cumulative fatigue at high temperatures

International Nuclear Information System (INIS)

Bui-Quoc, T.; Biron, A.

1977-01-01

Recent test results on cumulative damage with two strain levels on a stainless steel (AISI 304) at room temperature, 537 and 650 0 C show that the sum of cycle-ratios can be significantly smaller than unity for decreasing levels; the opposite has been noted for increasing levels. As a consequence, the use of the linear damage rule (Miner's law) for life predictions is not conservative in many cases. Since the double linear damage rule (DLDR), originally developed by Manson et al. for room temperature applications, takes the order effect of cyclic loading into consideration, an extension of this rule for high temperature cases may be a potentially useful tool. The present paper is concerned with such an extension. For cumulative damage tests with several levels, according to the DLDR, the summation is applied separately for crack initiation and crack propagation stages, and failure is then assumed to occur when the sum is equal to unity for both stages. Application of the DLDR consists in determining the crack propagation stage Nsub(p) associated with a particular number of cycles at failure N, i.e. Nsub(p)=PNsup(a) where exponent a and coefficient P had been assumed to be equal to 0.6 and 14 respectively for several materials at room temperature. When the DLDR is applied (with a=0.6 and P=14) to predict the remaining life at the second strain level (for two-level cumulative damage) for 304 stainless steel at room temperature 537 0 C and 650 0 C, the results show that the damage due to the first strain level is over-emphasized for decreasing levels when the damaging cycle-ratio is small. For increasing levels, the damage is underestimated and in some testing conditions this damage is simply ignored

Fatigue failure of pb-free electronic packages under random vibration loads

Science.gov (United States)

Saravanan, S.; Prabhu, S.; Muthukumar, R.; Gowtham Raj, S.; Arun Veerabagu, S.

2018-03-01

The electronic equipment are used in several fields like, automotive, aerospace, consumer goods where they are subjected to vibration loads leading to failure of solder joints used in these equipment. This paper presents a methodology to predict the fatigue life of Pb-free surface mounted BGA packages subjected to random vibrations. The dynamic characteristics of the PCB, such as the natural frequencies, mode shapes and damping ratios were determined. Spectrum analysis was used to determine the stress response of the critical solder joint and the cumulative fatigue damage accumulated by the solder joint for a specific duration was determined.

Observations and recommendations for further research regarding environmentally assisted fatigue evaluation methods

Energy Technology Data Exchange (ETDEWEB)

Stevens, G.L.; Tregoning, R.L. [U.S. Nuclear Regulatory Commission (U.S. NRC), Rockville, MD (United States); Chopra, O.K. [Argonne National Laboratory, Argonne, IL (United States)

2014-07-01

The U.S. Nuclear Regulatory Commission (NRC) and Argonne National Laboratory (ANL) have completed research activities on environmentally assisted fatigue (EAF) methods. This work has led to a revision of NUREG/CR-6909 in its entirety, a draft of which is forthcoming for public review and comment. These activities addressed the following areas: - Air and water fatigue curves were re-developed using a much larger fatigue (ε-N) database. The additional data include an expansion in the ε-N data previously used by the NRC and ANL by as much as 50%. - The environmental fatigue multiplier (F{sub en}) expressions for carbon, low-alloy, stainless, and nickel-alloy steels were revised. - The revised F{sub en} expressions address comments from interested stakeholders related to: (a) the constants in previous F{sub en} expressions that results in F{sub en} values of approximately 2.0 even when the strain rate is very high or the temperature is very low, (b) the temperature dependence of the F{sub en} expression for carbon and low-alloy steels, and (c) the dependence of F{sub en} on water chemistry for austenitic stainless steels. - In addition, the appropriateness of a strain threshold and the possible effects of hold periods were evaluated. - The potential effects of dynamic strain aging (DSA) on cyclic deformation and environmental effects were discussed. - The revised F{sub en} expressions proposed were validated to the extent possible by comparing the results of five different experimental data sets obtained from fatigue tests that simulate actual plant conditions to estimates of fatigue usage adjusted for environmental effects using the updated F{sub en} expressions. In the course of performing the foregoing EAF research activities, the NRC and ANL observed several areas where further research could yield reduced conservatism in EAF evaluation. These include more refined, material-specific fatigue (S-N) curves, S-N curves for ferritic materials based on material tensile

Influence of stress change on the fatigue behavior and fatigue life of aluminum oxide-dispersion-strengthening copper alloy at room temperature and 350degC

International Nuclear Information System (INIS)

Kawagoishi, Norio; Kondo, Eiji; Nisitani, Hironobu; Shimamoto, Atsunori; Tashiro, Rieko

2004-01-01

In order to investigate the influence of stress change on the fatigue behavior and fatigue life of an aluminum oxide-dispersion-strengthening copper alloy at elevated temperature, rotating bending fatigue tests were carried out under two-step loading at room temperature and 350degC. Both of static strength and fatigue strength decreased at 350degC. However, at the same relative stress σ a /σ B , fatigue life was longer at 350degC than at room temperature. Although the cumulative ratios Σ(N/N f ) were nearly unity for both the low to high and the high to low block loadings at room temperature, Miner's rule did not hold at 350degC. These results were related to the stress dependence on the log l-N/N f relation. That is, the crack length initiated at the same N/N f was larger in higher stress level at 350degC, whereas there was no stress dependence in the relation at room temperature. The stress dependence on the relation at 350degC was caused by the suppression of crack initiation due to the surface oxidation. (author)

Fatigue behavior of ULTIMETRTM alloy: Experiment and theoretical modeling

Science.gov (United States)

Jiang, Liang

ULTIMETRTM alloy is a commercial Co-26Cr-9Ni (weight percent) superalloy, which possesses excellent resistance to both wear and corrosion. In order to extend the structural applications of this alloy and improve the fundamental understanding of the fatigue damage mechanisms, stress- and strain-controlled fatigue tests were performed at various temperatures and in different environments. The stress- and strain-life data were developed for the structural design and engineering applications of this material. Fractographic studies characterized the crack-initiation and propagation behavior of the alloy. Microstructure evolution during fatigue was revealed by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Specifically, it was found that the metastable face-centered-cubic structure of this alloy in the as-received condition could be transformed into a hexagonal-close-packed structure either under the action of plastic deformation at room temperature, or due to the aging and cyclic deformation at intermediate temperatures. This interesting observation constructed a sound basis for the alloy development. The dominant mechanisms, which control the fatigue behavior of ULTIMET alloy, were characterized. High-speed, high-resolution infrared (IR) thermography, as a non-contact, full-field, and nondestructive technique, was used to characterize the damage during fatigue. The temperature variations during each fatigue cycle, which were due to the thermal-elastic-plastic effect, were observed and related to stress-strain analyses. The temperature evolution during fatigue manifested the cumulative fatigue damage process. A constitutive model was developed to predict thermal and mechanical responses of ULTIMET alloy subjected to cyclic deformation. The predicted cyclic stress-strain responses and temperature variations were found to be in good agreement with the experimental results. In addition, a fatigue life prediction model was developed

Comparison of ASME Code NB-3200 and NB-3600 results for fatigue analysis of B31.1 branch nozzles

International Nuclear Information System (INIS)

Nitzel, M.E.; Ware, A.G.; Morton, D.K.

1996-01-01

Fatigue analyses wre conducted on two reactor coolant system branch nozzles in an operating PWR designed to the B31.1 Code, for which no explicit fatigue analysis was required by the licensing basis. These analyses were performed as part of resolving issues connected with NRC's Fatigue Action Plan to determine if the cumulative usage factor (CUF) for these nozzles, using the 1992 ASME Code and representative PWR transients, were comparable to nozzles designed and analyzed to the ASME Code. Both NB-3200 and NB-3600 ASME Code methods were used. NB-3200 analyses included the development of finite element models for each nozzle. Although detailed thermal transients were not available for the plant analyzed, representative transients from similar PWRs were applied in each method. CUFs calculated using NB-3200 methods were significantly less than using NB-3600. The paper points out differences in analysis methods and highlights difficulties and unknowns in performing more detailed analyses to reduce conservative assumptions

A randomized controlled trial of qigong exercise on fatigue symptoms, functioning, and telomerase activity in persons with chronic fatigue or chronic fatigue syndrome.

Science.gov (United States)

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

2012-10-01

Chronic fatigue is common in the general population. Complementary therapies are often used by patients with chronic fatigue or chronic fatigue syndrome to manage their symptoms. This study aimed to assess the effect of a 4-month qigong intervention program among patients with chronic fatigue or chronic fatigue syndrome. Sixty-four participants were randomly assigned to either an intervention group or a wait list control group. Outcome measures included fatigue symptoms, physical functioning, mental functioning, and telomerase activity. Fatigue symptoms and mental functioning were significantly improved in the qigong group compared to controls. Telomerase activity increased in the qigong group from 0.102 to 0.178 arbitrary units (p chronic fatigue and chronic fatigue syndrome.

Thermal stratification and fatigue stress analysis for pressurizer surge line

International Nuclear Information System (INIS)

Yu Xiaofei; Zhang Yixiong

2011-01-01

Thermal stratification of pressurizer surge line induced by the inside fluid results in the global bending moments, local thermal stresses, unexpected displacements and support loadings of the pipe system. In order to avoid a costly three-dimensional computation, a combined 1D/2D technique has been developed and implemented to analyze the thermal stratification and fatigue stress of pressurize surge line of QINSHAN Phase II Extension Nuclear Power Project in this paper, using the computer codes SYSTUS and ROCOCO. According to the mechanical analysis results of stratification, the maximum stress and cumulative usage factor are obtained. The results indicate that the stress and fatigue intensity considering thermal stratification satisfies RCC-M criterion. (authors)

Development of an integrated fatigue assessment concept for ensuring long term operation

International Nuclear Information System (INIS)

Ilg, U.; Ganswind, J.; Motschiedler, W.; Haelbig, J.

2010-01-01

Demonstrating fatigue resistance of mechanical components will be one of the major tasks for justification of long term operation and life time extension for nuclear power plants in the near future. As the operational periods of several existing plants are already approaching the specified amount of load cycles laid down in the design basis, discussions have raised concerning the reliability of the as so far established fatigue evaluation procedures. For instance the U.S. Nuclear Regulatory Commission addresses this aspect by considering the conservatism of the design fatigue curves in the ASME Boiler and Pressure Vessel Code for nuclear components. Thus, the impact of environmental degradation on the fatigue behaviour of the pressure retaining parts due to light water ambiance is of special concern. The US-NRC has issued a Regulatory Guide providing the acceptance criteria for domestic license application for new power plants appointing the implementation of additional penalty factors accounting for the environmental impact during the ASME fatigue evaluation. Whereas for existing plants the US-NRC encounters due to ''significant conservatism in quantifying other plant-related variables involved in cumulative fatigue life calculations the design of the current fleet of reactors is satisfactory.'' The German Nuclear Safety Standards Commission (KTA) is going to revise the respective rules on the design and analysis for nuclear components, as well. It is intended to define ''Awareness Thresholds'' for the cumulative usage factor demanding additional considerations beyond CUF > 0.2 for austenitic and beyond CUF > 0.4 for ferritic materials underlying approval processes for new components. However, it is expected that these additional requirements will also be augmented to the evaluation of existing components. For that reason VGB intends to set up a programme for investigations in order to prepare an integrated fatigue assessment concept which is entitled to give a

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...... with seafarers, experiences from other populations sharing the same exposures (e.g. shift work) were also included when appropriate. Results: Work at sea involves multiple risk factors for fatigue, which in addition to acute effects (e.g., impaired cognition, accidents) contributes through autonomic, immunologic...

Experimental Investigation on the Fatigue Mechanical Properties of Intermittently Jointed Rock Models Under Cyclic Uniaxial Compression with Different Loading Parameters

Science.gov (United States)

Liu, Yi; Dai, Feng; Dong, Lu; Xu, Nuwen; Feng, Peng

2018-01-01

Intermittently jointed rocks, widely existing in many mining and civil engineering structures, are quite susceptible to cyclic loading. Understanding the fatigue mechanism of jointed rocks is vital to the rational design and the long-term stability analysis of rock structures. In this study, the fatigue mechanical properties of synthetic jointed rock models under different cyclic conditions are systematically investigated in the laboratory, including four loading frequencies, four maximum stresses, and four amplitudes. Our experimental results reveal the influence of the three cyclic loading parameters on the mechanical properties of jointed rock models, regarding the fatigue deformation characteristics, the fatigue energy and damage evolution, and the fatigue failure and progressive failure behavior. Under lower loading frequency or higher maximum stress and amplitude, the jointed specimen is characterized by higher fatigue deformation moduli and higher dissipated hysteresis energy, resulting in higher cumulative damage and lower fatigue life. However, the fatigue failure modes of jointed specimens are independent of cyclic loading parameters; all tested jointed specimens exhibit a prominent tensile splitting failure mode. Three different crack coalescence patterns are classified between two adjacent joints. Furthermore, different from the progressive failure under static monotonic loading, the jointed rock specimens under cyclic compression fail more abruptly without evident preceding signs. The tensile cracks on the front surface of jointed specimens always initiate from the joint tips and then propagate at a certain angle with the joints toward the direction of maximum compression.

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.

Fatigue life of drilling bit bearings under arbitrary random loads

Energy Technology Data Exchange (ETDEWEB)

Talimi, M.; Farshidi, R. [Calgary Univ., AB (Canada)

2009-07-01

A fatigue analysis was conducted in order to estimate the bearing life of a roller cone rock bit under arbitrary random loads. The aim of the study was to reduce bearing failures that can interrupt well operations. Fatigue was considered as the main reason for bearing failure. The expected value of cumulative fatigue damage was used to estimate bearing life. An equation was used to express the relation between bearing life and bearing load when the bearing was subjected to a steady load and constant speed. The Palmgren-Miner hypothesis was used to determine the ultimate tensile strength of the material. The rain flow counting principle was used to determine distinct amplitude cycles. Hertzian equations were used to determine maximum stress loads. Fourier series were used to obtain simple harmonic functions for estimating stress-life relations. It was concluded that the method can be used during the well planning phase to prevent bearing failures. 6 refs.

A hard day's night: a longitudinal study on the relationships among job demands and job control, sleep quality and fatigue.

Science.gov (United States)

de Lange, Annet H; Kompier, Michiel A J; Taris, Toon W; Geurts, Sabine A E; Beckers, Debby G J; Houtman, Irene L D; Bongers, Paulien M

2009-09-01

This prospective four-wave study examined (i) the causal direction of the longitudinal relations among job demands, job control, sleep quality and fatigue; and (ii) the effects of stability and change in demand-control history on the development of sleep quality and fatigue. Based on results of a four-wave complete panel study among 1163 Dutch employees, we found significant effects of job demands and job control on sleep quality and fatigue across a 1-year time lag, supporting the strain hypothesis (Demand-Control model; Karasek and Theorell, Basic Books, New York, 1990). No reversed or reciprocal causal patterns were detected. Furthermore, our results revealed that cumulative exposure to a high-strain work environment (characterized by high job demands and low job control) was associated with elevated levels of sleep-related complaints. Cumulative exposure to a low-strain work environment (i.e. low job demands and high job control) was associated with the highest sleep quality and lowest level of fatigue. Our results revealed further that changes in exposure history were related to changes in reported sleep quality and fatigue across time. As expected, a transition from a non-high-strain towards a high-strain job was associated with a significant increase in sleep-related complaints; conversely, a transition towards a non-high-strain job was not related to an improvement in sleep-related problems.

Fatigue status assessment for reactor pressure vessel based on actual operational transient

International Nuclear Information System (INIS)

Zhu Guangqiang; Liao Changbin; Dai Bing; Gui Chun

2013-01-01

Background: Fatigue is an important aging mechanism in RPV and it must be contained to aging management working range. Purpose: In order to ensure the safety operation of nuclear power plants, as extension of RPV service time, it is necessary to assess the fatigue damage caused by actual operation transient. Methods: Based on monitoring data of actual operation during the past eleven years, refer to design transient, the statistic analysis for types and occurrence times of actual transient is carried out, at the same time, every transients are combined as different operation cycles and the temperature field and stress field of typical components are analyzed by FEM. Results: Based on these information, fatigue analysis and assessment are finished, if later-actual transients are similar with the previous transients, the calculation result shows that the ratio between maximum of cumulative usage factors and design calculation value is 0.4967 the design transients is conservative. Conclusions: Fatigue status of RPV could be assessed and traced quickly through fatigue status assessment method in this paper based on actual operational transient and assessment result would be a good reference for RPV aging management. (authors)

Positron annihilation and electron microscopy study in the early stage of fatigue of polycrystalline copper

International Nuclear Information System (INIS)

Diaz, L.; Pareja, R.; Pedrosa, M.A.; Gonzalez, R.

1985-01-01

Positron annihilation and transmission electron microscopy are used to study the early stage of fatigue in polycrystalline copper cyclically deformed at various temperatures. The concentration of positron traps is correlated to the cumulative plastic strain and to the work done during deformation. The average lifetimes of the trapped positrons are (177 +- 4) and (186 +- 3) ps for samples fatigued at T 15 s -1 for the samples deformed at T <= 293 K. Vacancy clusters like small dislocation loops, are proposed as the main defects responsible for the positron trapping. (author)

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.

Predictors and Trajectories of Morning Fatigue Are Distinct from Evening Fatigue

Science.gov (United States)

Wright, Fay; Melkus, Gail D’Eramo; Hammer, Marilyn; Schmidt, Brian L.; Knobf, M. Tish; Paul, Steven M.; Cartwright, Frances; Mastick, Judy; Cooper, Bruce A.; Chen, Lee-May; Melisko, Michelle; Levine, Jon D.; Kober, Kord; Aouizerat, Bradley E.; Miaskowski, Christine

2015-01-01

Context Fatigue is the most common symptom in oncology patients during chemotherapy (CTX). Little is known about the predictors of interindividual variability in initial levels and trajectories of morning fatigue severity in these patients. Objectives An evaluation was done to determine which demographic, clinical, and symptom characteristics were associated with initial levels as well as the trajectories of morning fatigue and to compare findings with our companion paper on evening fatigue. Methods A sample of outpatients with breast, gastrointestinal, gynecological, and lung cancer (N=586) completed demographic and symptom questionnaires a total of six times over two cycles of CTX. Fatigue severity was evaluated using the Lee Fatigue Scale. Hierarchical linear modeling (HLM) was used to answer the study objectives. Results A large amount of interindividual variability was found in the morning fatigue trajectories. A piecewise model fit the data best. Patients with higher body mass index (BMI), who did not exercise regularly, with a lower functional status, and who had higher levels of state anxiety, sleep disturbance and depressive symptoms, reported higher levels of morning fatigue at enrollment. Variations in the trajectories of morning fatigue were predicted by the patients’ ethnicity and younger age. Conclusion The modifiable risk factors that were associated with only morning fatigue were BMI, exercise, and state anxiety. Modifiable risk factors that were associated with both morning and evening fatigue included functional status, depressive symptoms, and sleep disturbance. Using this information, clinicians can identify patients at higher risk for more severe morning fatigue and evening fatigue, provide individualized patient education, and tailor interventions to address the modifiable risk factors. PMID:25828559

Inclusion of fatigue effects in human reliability analysis

Energy Technology Data Exchange (ETDEWEB)

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

2011-11-15

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

Cumulative stress and autonomic dysregulation in a community sample.

Science.gov (United States)

Lampert, Rachel; Tuit, Keri; Hong, Kwang-Ik; Donovan, Theresa; Lee, Forrester; Sinha, Rajita

2016-05-01

Whether cumulative stress, including both chronic stress and adverse life events, is associated with decreased heart rate variability (HRV), a non-invasive measure of autonomic status which predicts poor cardiovascular outcomes, is unknown. Healthy community dwelling volunteers (N = 157, mean age 29 years) participated in the Cumulative Stress/Adversity Interview (CAI), a 140-item event interview measuring cumulative adversity including major life events, life trauma, recent life events and chronic stressors, and underwent 24-h ambulatory ECG monitoring. HRV was analyzed in the frequency domain and standard deviation of NN intervals (SDNN) calculated. Initial simple regression analyses revealed that total cumulative stress score, chronic stressors and cumulative adverse life events (CALE) were all inversely associated with ultra low-frequency (ULF), very low-frequency (VLF) and low-frequency (LF) power and SDNN (all p accounting for additional appreciable variance. For VLF and LF, both total cumulative stress and chronic stress significantly contributed to the variance alone but were not longer significant after adjusting for race and health behaviors. In summary, total cumulative stress, and its components of adverse life events and chronic stress were associated with decreased cardiac autonomic function as measured by HRV. Findings suggest one potential mechanism by which stress may exert adverse effects on mortality in healthy individuals. Primary preventive strategies including stress management may prove beneficial.

Guide to safe work : fatigue management : an employer's guide to designing and implementing a fatigue management program. 2 ed.

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-02-15

The impacts of fatigue on workplace safety are now commonly recognized. Many employers now wish to include fatigue management as part of their overall health and safety programs. This guide to fatigue management was written to help companies in the petroleum industry design and implement effective fatigue management programs that reduce incidents and injuries among employees. The guide provided information about workplace fatigue and discussed fatigue management issues and strategies. It was suggested that workplace culture can play a significant role in managing fatigue by allowing fatigue factors to be quickly recognized and managed. Employers who wish to build fatigue management programs should involve all levels of employees, and should consider all workplace practices and procedures. Consideration must also be given to the development of employee competency in managing fatigue. The guide included step-by-step recommendations for implementing a fatigue management program. It was concluded that the benefits of fatigue management include reduced worker absence and turnover, as well as avoiding the costs of safety incidents. 1 tab., 1 fig.

Study on fatigue analysis for operational load histories

International Nuclear Information System (INIS)

Wilhelm, Paul; Rudolph, Juergen; Steinmann, Paul

2013-01-01

Some laboratories performed fatigue tests in dissolved oxygen water at elevated temperature to better understand the influence of a long hold-time within cyclic loading. Also, the combined effect of complex waveform and surface finish was examined. The data show a less severe influence compared to the prediction model from Argonne National Laboratory; an increase in fatigue life was noticed and attributed to different effects. To evaluate an operational load history with this experimental data an algorithm is developed, which finds hold-times and the examined complex waveform in a stress-time series. All those cycles, which are either geometrically comparable to the complex loading signal or containing a hold period, are evaluated with the test results and not with the formula from Argonne National Laboratory. The reduction of the cumulative usage factor is calculated. Based on this discussion a realistic test condition is derived for further research activities.

A Preliminary Review of Fatigue Among Rail Staff

Directory of Open Access Journals (Sweden)

Jialin Fan

2018-05-01

Full Text Available Background: Fatigue is a severe problem in the rail industry, which may jeopardize train crew's health and safety. Nonetheless, a preliminary review of all empirical evidence for train crew fatigue is still lacking. The aim of the present paper is, therefore, to provide a preliminary description of occupational fatigue in the rail industry. This paper reviews the literature with the research question examining the risk factors associated with train crew fatigue, covering both papers published in refereed journals and reports from trade organizations and regulators. It assesses the progress of research on railway fatigue, including research on the main risk factors for railway fatigue, the association between fatigue and railway incidents, and how to better manage fatigue in the railway industry.Methods: Systematic searches were performed in both science and industry databases. The searches considered studies published before August 2017. The main exclusion criterion was fatigue not being directly measured through subjective or objective methods.Results: A total of 31 studies were included in the main review. The causes of fatigue included long working hours, heavy workload, early morning or night shifts, and insufficient sleep. Poor working environment, particular job roles, and individual differences also contributed to fatigue.Conclusion: Fatigue in the rail industry includes most of the features of occupational fatigue, and it is also subject to industry-specific factors. The effect of fatigue on well-being and the fatigued population in the railway industry are still not clear. Future studies can consider associations between occupational risk factors and perceived fatigue by examining the prevalence of fatigue and identifying the potential risk factors in staff within the railway industry.

Helping nurses cope with grief and compassion fatigue: an educational intervention.

Science.gov (United States)

Houck, Dereen

2014-08-01

Oncology nurses may experience intense physical and emotional exhaustion, identified in the literature as symptoms of cumulative grief and compassion fatigue, with significant consequences for both nurses and organizations. The first step in preventing these consequences is recognition. Organizations should provide nurses with resources including education, counseling, and opportunities to grieve. Nurses need to learn the importance of work-life balance, self-care strategies, and communication skills. Using recommendations from the literature, an educational intervention was designed with the purpose of providing nurses with knowledge, skills, and resources to practice effective self-care and recognize when assistance is needed. The program's objective was to help nurses develop the coping skills and inner resources necessary to maintain their emotional and physical health.

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...

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

Inclusion of fatigue effects in human reliability analysis

International Nuclear Information System (INIS)

Griffith, Candice D.; Mahadevan, Sankaran

2011-01-01

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

Monitoring and Failure Analysis of Corroded Bridge Cables under Fatigue Loading Using Acoustic Emission Sensors

Directory of Open Access Journals (Sweden)

Hui Li

2012-03-01

Full Text Available Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index.

Monitoring and Failure Analysis of Corroded Bridge Cables under Fatigue Loading Using Acoustic Emission Sensors

Science.gov (United States)

Li, Dongsheng; Ou, Jinping; Lan, Chengming; Li, Hui

2012-01-01

Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE) technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index. PMID:22666009

Taltirelin alleviates fatigue-like behavior in mouse models of cancer-related fatigue.

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Dougherty, John P; Wolff, Brian S; Cullen, Mary J; Saligan, Leorey N; Gershengorn, Marvin C

2017-10-01

Fatigue affects most cancer patients and has numerous potential causes, including cancer itself and cancer treatment. Cancer-related fatigue (CRF) is not relieved by rest, can decrease quality of life, and has no FDA-approved therapy. Thyrotropin-releasing hormone (TRH) has been proposed as a potential novel treatment for CRF, but its efficacy against CRF remains largely untested. Thus, we tested the TRH analog, taltirelin (TAL), in mouse models of CRF. To model fatigue, we used a mouse model of chemotherapy, a mouse model of radiation therapy, and mice bearing colon 26 carcinoma tumors. We used the treadmill fatigue test to assess fatigue-like behavior after treatment with TAL. Additionally, we used wild-type and TRH receptor knockout mice to determine which TRH receptor was necessary for the actions of TAL. Tumor-bearing mice displayed muscle wasting and all models caused fatigue-like behavior, with mice running a shorter distance in the treadmill fatigue test than controls. TAL reversed fatigue-like behavior in all three models and the mouse TRH 1 receptor was necessary for the effects of TAL. These data suggest that TAL may be useful in alleviating fatigue in all cancer patients and provide further support for evaluating TAL as a potential therapy for CRF in humans. Published by Elsevier Ltd.

A full-angle Monte-Carlo scattering technique including cumulative and single-event Rutherford scattering in plasmas

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Higginson, Drew P.

2017-11-01

We describe and justify a full-angle scattering (FAS) method to faithfully reproduce the accumulated differential angular Rutherford scattering probability distribution function (pdf) of particles in a plasma. The FAS method splits the scattering events into two regions. At small angles it is described by cumulative scattering events resulting, via the central limit theorem, in a Gaussian-like pdf; at larger angles it is described by single-event scatters and retains a pdf that follows the form of the Rutherford differential cross-section. The FAS method is verified using discrete Monte-Carlo scattering simulations run at small timesteps to include each individual scattering event. We identify the FAS regime of interest as where the ratio of temporal/spatial scale-of-interest to slowing-down time/length is from 10-3 to 0.3-0.7; the upper limit corresponds to Coulomb logarithm of 20-2, respectively. Two test problems, high-velocity interpenetrating plasma flows and keV-temperature ion equilibration, are used to highlight systems where including FAS is important to capture relevant physics.

Analytical Method to Estimate Fatigue Life Time Duration in Service for Runner Blade Mechanism of Kaplan Turbines

Directory of Open Access Journals (Sweden)

Ana – Maria Budai

2010-10-01

Full Text Available The paper present an analytical method that can be used to determianted fatigue life time duration in service for runner blade mechanism of Kaplan turbines. The study was made for lever button of runer blade mechanism using two analytical relation to calculate the maximum number of stress cycles whereupon the mechanism work without any damage. To estimate fatigue life time duration will be used a formula obtained from one of most comon cumulative damage methodology taking in consideration the real exploatation conditions of a specified Kapaln turbine.

Modified Spectral Fatigue Methods for S-N Curves With MIL-HDBK-5J Coefficients

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Irvine, Tom; Larsen, Curtis

2016-01-01

The rainflow method is used for counting fatigue cycles from a stress response time history, where the fatigue cycles are stress-reversals. The rainflow method allows the application of Palmgren-Miner's rule in order to assess the fatigue life of a structure subject to complex loading. The fatigue damage may also be calculated from a stress response power spectral density (PSD) using the semi-empirical Dirlik, Single Moment, Zhao-Baker and other spectral methods. These methods effectively assume that the PSD has a corresponding time history which is stationary with a normal distribution. This paper shows how the probability density function for rainflow stress cycles can be extracted from each of the spectral methods. This extraction allows for the application of the MIL-HDBK-5J fatigue coefficients in the cumulative damage summation. A numerical example is given in this paper for the stress response of a beam undergoing random base excitation, where the excitation is applied separately by a time history and by its corresponding PSD. The fatigue calculation is performed in the time domain, as well as in the frequency domain via the modified spectral methods. The result comparison shows that the modified spectral methods give comparable results to the time domain rainflow counting method.

Perspectives on cumulative risks and impacts.

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Faust, John B

2010-01-01

Cumulative risks and impacts have taken on different meanings in different regulatory and programmatic contexts at federal and state government levels. Traditional risk assessment methodologies, with considerable limitations, can provide a framework for the evaluation of cumulative risks from chemicals. Under an environmental justice program in California, cumulative impacts are defined to include exposures, public health effects, or environmental effects in a geographic area from the emission or discharge of environmental pollution from all sources, through all media. Furthermore, the evaluation of these effects should take into account sensitive populations and socioeconomic factors where possible and to the extent data are available. Key aspects to this potential approach include the consideration of exposures (versus risk), socioeconomic factors, the geographic or community-level assessment scale, and the inclusion of not only health effects but also environmental effects as contributors to impact. Assessments of this type extend the boundaries of the types of information that toxicologists generally provide for risk management decisions.

Diurnal cortisol rhythms, fatigue and psychosocial factors in five-year survivors of ovarian cancer.

Science.gov (United States)

Cuneo, Michaela G; Schrepf, Andrew; Slavich, George M; Thaker, Premal H; Goodheart, Michael; Bender, David; Cole, Steve W; Sood, Anil K; Lutgendorf, Susan K

2017-10-01

Fatigue is a challenge in ovarian cancer survivorship and greatly impacts quality of life. In other cancer populations, fatigue has been associated with abnormal diurnal cortisol patterns. However, little is known about biological and behavioral factors in 5+-year ovarian cancer survivors and potential mechanisms underlying persistent fatigue have not been investigated in this population. Moreover, relationships between neuroendocrine and psychosocial factors in 5+-year ovarian cancer survivors have not been studied. We addressed these issues by examining relationships between diurnal cortisol rhythms, fatigue, life stress, and social support in 30 survivors of ovarian cancer who were assessed at least 5 years (mean=6.20years) following their primary diagnosis. Flatter diurnal cortisol slopes were associated with higher levels of fatigue, suggesting a role for HPA-axis dysregulation in sustained fatigue experienced by survivors. Moreover, greater cumulative lifetime stressor exposure (p=0.023) and stressor severity (p=0.004) were associated with flatter diurnal cortisol slopes, while higher social attachment (p=0.001) was associated with steeper diurnal cortisol slopes. These findings suggest that ovarian cancer survivors with greater lifetime stress exposure or lower social attachment may be at increased risk for circadian rhythm disruption, which in turn is associated with fatigue. Future research should examine relationships of clinical stage and inflammatory cytokines to cortisol rhythms and fatigue in long-term ovarian cancer survivors, as well as investigating the clinical significance of abnormal diurnal cortisol profiles in this population. Copyright © 2017 Elsevier Ltd. All rights reserved.

Recent developments of continuous damage approaches for the analysis of material behavior under fatigue-creep loading

International Nuclear Information System (INIS)

Bui-Quoc, T.

1982-01-01

A review is presented with an analysis of some recent methods proposed in the literature for predicting failure of materials under a cumulative damage effect due either to fatigue, to creep, or to fatigue-creep combinations. This review is focused on the continuous damage concepts because of their possibilities of application for a wide range of testing conditions. A discussion of the potential of each damage concept is made by examining the correlation between the resulting expressions and available experimental data. The paper also points out particularities encountered in the interpretation of some of the concepts reviewed

AE characteristic for monitoring of fatigue crack in steel bridge members

Science.gov (United States)

Yoon, Dong-Jin; Jung, Juong-Chae; Park, Philip; Lee, Seung-Seok

2000-06-01

Acoustic emission technique was employed for the monitoring of crack activity in both steel bridge members and laboratory specimen. Laboratory experiment was carried out to identify AE characteristics of fatigue cracks for compact tension specimen. The relationship between a stress intensity factor and AE signals activity as well as conventional AE parameter analysis was discussed. A field test was also conducted on a railway bridge, which contain several fatigue cracks. Crack activities were investigated while in service with strain measurement. From the results, in the laboratory tests, the features of three parameters such as the length of crack growth, the AE energy, and the cumulative AE events, showed the almost same trend in their increase as the number of fatigue cycle increased. From the comparisons of peak amplitude and AE energy with stress intensity factor, it was verified that the higher stress intensity factors generated AE signals with higher peak amplitude and a large number of AE counts. In the field test, real crack propagation signals were captured and the crack activity was verified in two cases.

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

Science.gov (United States)

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

2014-01-01

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

Modelling fatigue and the use of fatigue models in work settings.

Science.gov (United States)

Dawson, Drew; Ian Noy, Y; Härmä, Mikko; Akerstedt, Torbjorn; Belenky, Gregory

2011-03-01

In recent years, theoretical models of the sleep and circadian system developed in laboratory settings have been adapted to predict fatigue and, by inference, performance. This is typically done using the timing of prior sleep and waking or working hours as the primary input and the time course of the predicted variables as the primary output. The aim of these models is to provide employers, unions and regulators with quantitative information on the likely average level of fatigue, or risk, associated with a given pattern of work and sleep with the goal of better managing the risk of fatigue-related errors and accidents/incidents. The first part of this review summarises the variables known to influence workplace fatigue and draws attention to the considerable variability attributable to individual and task variables not included in current models. The second part reviews the current fatigue models described in the scientific and technical literature and classifies them according to whether they predict fatigue directly by using the timing of prior sleep and wake (one-step models) or indirectly by using work schedules to infer an average sleep-wake pattern that is then used to predict fatigue (two-step models). The third part of the review looks at the current use of fatigue models in field settings by organizations and regulators. Given their limitations it is suggested that the current generation of models may be appropriate for use as one element in a fatigue risk management system. The final section of the review looks at the future of these models and recommends a standardised approach for their use as an element of the 'defenses-in-depth' approach to fatigue risk management. Copyright © 2010 Elsevier Ltd. All rights reserved.

Exploring nurse leader fatigue: a mixed methods study.

Science.gov (United States)

Steege, Linsey M; Pinekenstein, Barbara J; Arsenault Knudsen, Élise; Rainbow, Jessica G

2017-05-01

To describe hospital nurse leaders' experiences of fatigue. Fatigue is a critical challenge in nursing. Existing literature focuses on staff nurse fatigue, yet nurse leaders are exposed to high demands that may contribute to fatigue and associated risks to patient, nurse and organisational outcomes. A mixed method approach comprising semi-structured interviews and the Occupational Fatigue Exhaustion Recovery scale with 21 nurse administrators (10 nurse managers and 11 nurse executives) from hospitals in a Midwestern state. Most nurse leaders experience fatigue; nurse managers reported higher levels of chronic fatigue. Participants identified multiple sources of fatigue including 24 h accountability and intensity of role expectations, and used a combination of wellness, restorative, social support and boundary setting strategies to cope with fatigue. The consequences of nurse leader fatigue include an impact on decision-making, work-life balance and turnover intent. The high prevalence of nurse leader fatigue could impact the turnover intent of nurse administrators and quality of care. This study highlights the significance and consequences of nurse leader fatigue. As health care organisations continue to raise awareness and establish systems to reduce nurse fatigue, policies and programmes must be adapted to address nurse leader fatigue. © 2017 John Wiley & Sons Ltd.

Markov model of fatigue of a composite material with the poisson process of defect initiation

Science.gov (United States)

Paramonov, Yu.; Chatys, R.; Andersons, J.; Kleinhofs, M.

2012-05-01

As a development of the model where only one weak microvolume (WMV) and only a pulsating cyclic loading are considered, in the current version of the model, we take into account the presence of several weak sites where fatigue damage can accumulate and a loading with an arbitrary (but positive) stress ratio. The Poisson process of initiation of WMVs is considered, whose rate depends on the size of a specimen. The cumulative distribution function (cdf) of the fatigue life of every individual WMV is calculated using the Markov model of fatigue. For the case where this function is approximated by a lognormal distribution, a formula for calculating the cdf of fatigue life of the specimen (modeled as a chain of WMVs) is obtained. Only a pulsating cyclic loading was considered in the previous version of the model. Now, using the modified energy method, a loading cycle with an arbitrary stress ratio is "transformed" into an equivalent cycle with some other stress ratio. In such a way, the entire probabilistic fatigue diagram for any stress ratio with a positive cycle stress can be obtained. Numerical examples are presented.

Damage morphology study of high cycle fatigued as-cast Mg–3.0Nd–0.2Zn–Zr (wt.%) alloy

Energy Technology Data Exchange (ETDEWEB)

Yue, Haiyan; Fu, Penghuai, E-mail: fph112sjtu@sjtu.edu.cn; Peng, Liming; Li, Zhenming; Pan, Jipeng; Ding, Wenjiang

2016-01-15

Laser scanning confocal microscopy (LSCM) and Electron back-scattered diffraction (EBSD) were applied to the study of surface morphology variation of as-cast Mg–3.0Nd–0.2Zn–Zr (NZ30K) (wt.%) alloy under tension-compression fatigue test at room temperature. Two kinds of typical damage morphologies were observed in fatigued NZ30K alloy: One was parallel lines on basal planes led by the cumulation of basal slips, called persistent slip markings (PSMs), and the other was lens shaped, thicker and in less density, led by the formation of twinning. The surface fatigue damage morphology evolution was analyzed in a statistical way. The influences of stress amplitude and grain orientation on fatigue deformation mechanisms were discussed and the non-uniform deformation among grains and the PSMs, within twinning were described quantitatively. - Highlights: • Fatigue morphology evolution was studied by Laser Scanning Confocal Microscopy. • 3D morphology of persistent slip markings and twins was characterized. • Non-uniform deformation among grains, the PSMs and twins were quantified. • Initiations of fatigue crack were clearly investigated.

Clinical neurophysiology of fatigue.

Science.gov (United States)

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

2008-01-01

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

Chronic fatigue in Ehlers-Danlos syndrome-Hypermobile type.

Science.gov (United States)

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

2017-03-01

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

Inflammatory fatigue and sickness behaviour - lessons for the diagnosis and management of chronic fatigue syndrome.

Science.gov (United States)

Arnett, S V; Clark, I A

2012-12-10

Persistent and severe fatigue is a common part of the presentation of a diverse range of disease processes. There is a growing body of evidence indicating a common inflammatory pathophysiology underlying many conditions where fatigue is a primary patient concern, including chronic fatigue syndrome. This review explores current models of how inflammatory mediators act on the central nervous system to produce fatigue and sickness behaviour, and the commonality of these processes in conditions as diverse as surgical trauma, infection, various cancers, inflammatory bowel disease, connective tissue diseases and autoimmune diseases. We also discuss evidence indicating chronic fatigue syndrome may have important pathophysiological similarities with cytokine mediated sickness behaviour, and what lessons can be applied from sickness behaviour to chronic fatigue syndrome with regards to the diagnosis and management. Copyright © 2012 Elsevier B.V. All rights reserved.

Low cycle thermomechanical fatigue of reactor steels: Microstructural and fractographic investigations

Energy Technology Data Exchange (ETDEWEB)

Fekete, Balazs, E-mail: fekete.mm.bme@gmail.com [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary); Department of Applied Mechanics, Budapest University of Technology and Economics, Muegyetem 5, Budapest H-1111 (Hungary); Kasl, Josef; Jandova, Dagmar [Výzkumný a zkušební ústav Plzeň s.r.o., Tylova 1581/46, 316 00 Plzen (Czech Republic); Jóni, Bertalan [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary); Eötvös Loránd University, Egyetem tér 1-3, Budapest H-1053 (Hungary); Misják, Fanni [Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege M. 29-33, Budapest H-1121 (Hungary); Trampus, Peter [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary)

2015-07-29

The fatigue life of the structural materials 15Ch2MFA (CrMoV-alloyed ferritic steel) and 08Ch18N10T (CrNi-alloyed austenitic steel) of a VVER-440 reactor pressure vessel were investigated under fully reversed total strain controlled low cycle fatigue tests. The measurements were carried out in isothermal conditions at 260 °C and with thermal-mechanical conditions in the range 150–270 °C using a GLEEBLE-3800 servo-hydraulic thermal-mechanical simulator. The low cycle fatigue results were evaluated with the Coffin–Manson law, and the parameters of the Ramberg–Osgood stress–strain relation were investigated. Fracture mechanics behavior was observed using scanning electron microscopic analysis of the crack shapes and fracture surfaces. Crack propagation was assessed in relation to the actual crack size and the loading level. Interrupted fatigue tests were also carried out to investigate the kinetics of the fatigue evolution of the materials. Microstructural evaluation of the samples was performed using light, scanning and transmission electron microscopy as well as X-ray diffraction, and measurement of dislocations was completed using TEM and XRD. The course of dislocation density in relation to cumulative usage factor was similar for both steels. However, the nature and distribution of dislocations were different in the individual steels and this resulted in different mechanical behaviors. The nature of the fracture surfaces of both steels appeared similar despite differences in dislocation arrangement. The distances between striation lines initially increased with increasing crack length and then became saturated. The low cycle fatigue behavior investigated can provide a reference for the remaining life assessment and lifetime extension analysis of nuclear power plant components.

Cumulative Poisson Distribution Program

Science.gov (United States)

Bowerman, Paul N.; Scheuer, Ernest M.; Nolty, Robert

1990-01-01

Overflow and underflow in sums prevented. Cumulative Poisson Distribution Program, CUMPOIS, one of two computer programs that make calculations involving cumulative Poisson distributions. Both programs, CUMPOIS (NPO-17714) and NEWTPOIS (NPO-17715), used independently of one another. CUMPOIS determines cumulative Poisson distribution, used to evaluate cumulative distribution function (cdf) for gamma distributions with integer shape parameters and cdf for X (sup2) distributions with even degrees of freedom. Used by statisticians and others concerned with probabilities of independent events occurring over specific units of time, area, or volume. Written in C.

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.

Cumulative Environmental Impacts: Science and Policy to Protect Communities.

Science.gov (United States)

Solomon, Gina M; Morello-Frosch, Rachel; Zeise, Lauren; Faust, John B

2016-01-01

Many communities are located near multiple sources of pollution, including current and former industrial sites, major roadways, and agricultural operations. Populations in such locations are predominantly low-income, with a large percentage of minorities and non-English speakers. These communities face challenges that can affect the health of their residents, including limited access to health care, a shortage of grocery stores, poor housing quality, and a lack of parks and open spaces. Environmental exposures may interact with social stressors, thereby worsening health outcomes. Age, genetic characteristics, and preexisting health conditions increase the risk of adverse health effects from exposure to pollutants. There are existing approaches for characterizing cumulative exposures, cumulative risks, and cumulative health impacts. Although such approaches have merit, they also have significant constraints. New developments in exposure monitoring, mapping, toxicology, and epidemiology, especially when informed by community participation, have the potential to advance the science on cumulative impacts and to improve decision making.

Improving cumulative effects assessment in Alberta: Regional strategic assessment

International Nuclear Information System (INIS)

Johnson, Dallas; Lalonde, Kim; McEachern, Menzie; Kenney, John; Mendoza, Gustavo; Buffin, Andrew; Rich, Kate

2011-01-01

The Government of Alberta, Canada is developing a regulatory framework to better manage cumulative environmental effects from development in the province. A key component of this effort is regional planning, which will lay the primary foundation for cumulative effects management into the future. Alberta Environment has considered the information needs of regional planning and has concluded that Regional Strategic Assessment may offer significant advantages if integrated into the planning process, including the overall improvement of cumulative environmental effects assessment in the province.

Design fatigue curve for Hastelloy-X

International Nuclear Information System (INIS)

Nishiguchi, Isoharu; Muto, Yasushi; Tsuji, Hirokazu

1983-12-01

In the design of components intended for elevated temperature service as the experimental Very High-Temperature gas-cooled Reactor (VHTR), it is essential to prevent fatigue failure and creep-fatigue failure. The evaluation method which uses design fatigue curves is adopted in the design rules. This report discussed several aspects of these design fatigue curves for Hastelloy-X (-XR) which is considered for use as a heat-resistant alloy in the VHTR. Examination of fatigue data gathered by a literature search including unpublished data showed that Brinkman's equation is suitable for the design curve of Hastelloy-X (-XR), where total strain range Δ epsilon sub(t) is used as independent variable and fatigue life Nsub(f) is transformed into log(log Nsub(f)). (author)

EPA Workshop on Epigenetics and Cumulative Risk ...

Science.gov (United States)

Agenda Download the Workshop Agenda (PDF) The workshop included presentations and discussions by scientific experts pertaining to three topics (i.e., epigenetic changes associated with diverse stressors, key science considerations in understanding epigenetic changes, and practical application of epigenetic tools to address cumulative risks from environmental stressors), to address several questions under each topic, and included an opportunity for attendees to participate in break-out groups, provide comments and ask questions. Workshop Goals The workshop seeks to examine the opportunity for use of aggregate epigenetic change as an indicator in cumulative risk assessment for populations exposed to multiple stressors that affect epigenetic status. Epigenetic changes are specific molecular changes around DNA that alter expression of genes. Epigenetic changes include DNA methylation, formation of histone adducts, and changes in micro RNAs. Research today indicates that epigenetic changes are involved in many chronic diseases (cancer, cardiovascular disease, obesity, diabetes, mental health disorders, and asthma). Research has also linked a wide range of stressors including pollution and social factors with occurrence of epigenetic alterations. Epigenetic changes have the potential to reflect impacts of risk factors across multiple stages of life. Only recently receiving attention is the nexus between the factors of cumulative exposure to environmental

Cancer-Related Fatigue in Cancer Survivorship.

Science.gov (United States)

Ebede, Chidinma C; Jang, Yongchang; Escalante, Carmen P

2017-11-01

Cancer-related fatigue (CRF) significantly interferes with usual functioning because of the distressing sense of physical, emotional, and cognitive exhaustion. Assessment of CRF is important and should be performed during the initial cancer diagnosis, throughout cancer treatment, and after treatment using a fatigue scoring scale (mild-severe). The general approach to CRF management applies to cancer survivors at all fatigue levels and includes education, counseling, and other strategies. Nonpharmacologic interventions include psychosocial interventions, exercise, yoga, physically based therapy, dietary management, and sleep therapy. Pharmacologic interventions include psychostimulants. Antidepressants may also benefit when CRF is accompanied by depression. Copyright © 2017 Elsevier Inc. All rights reserved.

Managing regional cumulative effects of oil sands development in Alberta, Canada

International Nuclear Information System (INIS)

Spaling, H.; Zwier, J.

2000-01-01

This paper demonstrates an approach to regional cumulative effects management using the case of oil sands development in Alberta, Canada. The 17 existing, approved, or planned projects, all concentrated in a relatively small region, pose significant challenges for conducting and reviewing cumulative effects assessment (CEA) on a project-by-project basis. In response, stakeholders have initiated a regional cumulative effects management system that is among the first such initiatives anywhere. Advantages of this system include (1) more efficient gathering and sharing of information, including a common regional database, (2) setting acceptable regional environmental thresholds for all projects, (3) collaborative assessment of similar cumulative effects from related projects, (4) co-ordinated regulatory review and approval process for overlapping CEAs, and (5) institutional empowerment from a Regional Sustainable Development Strategy administered by a public authority. This case provides a model for integrating project-based CEA with regional management of cumulative effects. (author)

Stress management skills, neuroimmune processes and fatigue levels in persons with chronic fatigue syndrome.

Science.gov (United States)

Lattie, Emily G; Antoni, Michael H; Fletcher, Mary Ann; Penedo, Frank; Czaja, Sara; Lopez, Corina; Perdomo, Dolores; Sala, Andreina; Nair, Sankaran; Fu, Shih Hua; Klimas, Nancy

2012-08-01

Stressors and emotional distress responses impact chronic fatigue syndrome (CFS) symptoms, including fatigue. Having better stress management skills might mitigate fatigue by decreasing emotional distress. Because CFS patients comprise a heterogeneous population, we hypothesized that the role of stress management skills in decreasing fatigue may be most pronounced in the subgroup manifesting the greatest neuroimmune dysfunction. In total, 117 individuals with CFS provided blood and saliva samples, and self-report measures of emotional distress, perceived stress management skills (PSMS), and fatigue. Plasma interleukin-1-beta (IL-1β, IL-2, IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α), and diurnal salivary cortisol were analyzed. We examined relations among PSMS, emotional distress, and fatigue in CFS patients who did and did not evidence neuroimmune abnormalities. Having greater PSMS related to less fatigue (p=.019) and emotional distress (pfatigue levels most strongly in CFS patients in the top tercile of IL-6, and emotional distress mediated the relationship between PSMS and fatigue most strongly in patients with the greatest circulating levels of IL-6 and a greater inflammatory (IL-6):anti-inflammatory (IL-10) cytokine ratio. CFS patients having greater PSMS show less emotional distress and fatigue, and the influence of stress management skills on distress and fatigue appear greatest among patients who have elevated IL-6 levels. These findings support the need for research examining the impact of stress management interventions in subgroups of CFS patients showing neuroimmune dysfunction. Copyright © 2012 Elsevier Inc. All rights reserved.

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.

Cumulants in perturbation expansions for non-equilibrium field theory

International Nuclear Information System (INIS)

Fauser, R.

1995-11-01

The formulation of perturbation expansions for a quantum field theory of strongly interacting systems in a general non-equilibrium state is discussed. Non-vanishing initial correlations are included in the formulation of the perturbation expansion in terms of cumulants. The cumulants are shown to be the suitable candidate for summing up the perturbation expansion. Also a linked-cluster theorem for the perturbation series with cumulants is presented. Finally a generating functional of the perturbation series with initial correlations is studied. We apply the methods to a simple model of a fermion-boson system. (orig.)

Research on driver fatigue detection

Science.gov (United States)

Zhang, Ting; Chen, Zhong; Ouyang, Chao

2018-03-01

Driver fatigue is one of the main causes of frequent traffic accidents. In this case, driver fatigue detection system has very important significance in avoiding traffic accidents. This paper presents a real-time method based on fusion of multiple facial features, including eye closure, yawn and head movement. The eye state is classified as being open or closed by a linear SVM classifier trained using HOG features of the detected eye. The mouth state is determined according to the width-height ratio of the mouth. The head movement is detected by head pitch angle calculated by facial landmark. The driver's fatigue state can be reasoned by the model trained by above features. According to experimental results, drive fatigue detection obtains an excellent performance. It indicates that the developed method is valuable for the application of avoiding traffic accidents caused by driver's fatigue.

Time-dependent high-temperature low-cycle fatigue behavior of nickel-base heat-resistant alloys for HTGR

International Nuclear Information System (INIS)

Tsuji, Hirokazu; Kondo, Tatsuo

1988-06-01

A series of strain controlled low-cycle fatigue tests at 900 deg C in the simulated HTGR helium environment were conducted on Hastelloy X and its modified version, Hastelloy XR in order to examine time-dependent high-temperature low-cycle fatigue behavior. In the tests with the symmetric triangular strain waveform, decreasing the strain rate led to notable reductions in the fatigue life. In the tests with the trapezoidal strain waveform with different holding types, the fatigue life was found to be reduced most effectively in tensile hold-time experiments. Based on the observations of the crack morphology the strain holding in the compressive side was suggested to play the role of suppressing the initiation and the growth of internal cracks or cavities, and to cause crack branching. When the frequency modified fatigue life method and/or the prediction of life by use of the ductility were applied, both the data obtained with the symmetric triangular strain waveform and those with the tensile hold-time experiments lay on the straight line plots. The data, however, obtained with the compressive and/or both hold-time experiments could not be handled satisfactorily by those methods. When the cumulative damage rule was applied, it was found that the reliability of HTGR components was ensured by limiting the creep-fatigue damage fraction within the value of 1. (author)

Fatigue proofing: The role of protective behaviours in mediating fatigue-related risk in a defence aviation environment.

Science.gov (United States)

Dawson, Drew; Cleggett, Courtney; Thompson, Kirrilly; Thomas, Matthew J W

2017-02-01

In the military or emergency services, operational requirements and/or community expectations often preclude formal prescriptive working time arrangements as a practical means of reducing fatigue-related risk. In these environments, workers sometimes employ adaptive or protective behaviours informally to reduce the risk (i.e. likelihood or consequence) associated with a fatigue-related error. These informal behaviours enable employees to reduce risk while continuing to work while fatigued. In this study, we documented the use of informal protective behaviours in a group of defence aviation personnel including flight crews. Semi-structured interviews were conducted to determine whether and which protective behaviours were used to mitigate fatigue-related error. The 18 participants were from aviation-specific trades and included aircrew (pilots and air-crewman) and aviation maintenance personnel (aeronautical engineers and maintenance personnel). Participants identified 147 ways in which they and/or others act to reduce the likelihood or consequence of a fatigue-related error. These formed seven categories of fatigue-reduction strategies. The two most novel categories are discussed in this paper: task-related and behaviour-based strategies. Broadly speaking, these results indicate that fatigued military flight and maintenance crews use protective 'fatigue-proofing' behaviours to reduce the likelihood and/or consequence of fatigue-related error and were aware of the potential benefits. It is also important to note that these behaviours are not typically part of the formal safety management system. Rather, they have evolved spontaneously as part of the culture around protecting team performance under adverse operating conditions. When compared with previous similar studies, aviation personnel were more readily able to understand the idea of fatigue proofing than those from a fire-fighting background. These differences were thought to reflect different cultural

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

Cumulative radiation exposure in children with cystic fibrosis.

LENUS (Irish Health Repository)

O'Reilly, R

2010-02-01

This retrospective study calculated the cumulative radiation dose for children with cystic fibrosis (CF) attending a tertiary CF centre. Information on 77 children with a mean age of 9.5 years, a follow up time of 658 person years and 1757 studies including 1485 chest radiographs, 215 abdominal radiographs and 57 computed tomography (CT) scans, of which 51 were thoracic CT scans, were analysed. The average cumulative radiation dose was 6.2 (0.04-25) mSv per CF patient. Cumulative radiation dose increased with increasing age and number of CT scans and was greater in children who presented with meconium ileus. No correlation was identified between cumulative radiation dose and either lung function or patient microbiology cultures. Radiation carries a risk of malignancy and children are particularly susceptible. Every effort must be made to avoid unnecessary radiation exposure in these patients whose life expectancy is increasing.

The effects of cumulative practice on mathematics problem solving.

Science.gov (United States)

Mayfield, Kristin H; Chase, Philip N

2002-01-01

This study compared three different methods of teaching five basic algebra rules to college students. All methods used the same procedures to teach the rules and included four 50-question review sessions interspersed among the training of the individual rules. The differences among methods involved the kinds of practice provided during the four review sessions. Participants who received cumulative practice answered 50 questions covering a mix of the rules learned prior to each review session. Participants who received a simple review answered 50 questions on one previously trained rule. Participants who received extra practice answered 50 extra questions on the rule they had just learned. Tests administered after each review included new questions for applying each rule (application items) and problems that required novel combinations of the rules (problem-solving items). On the final test, the cumulative group outscored the other groups on application and problem-solving items. In addition, the cumulative group solved the problem-solving items significantly faster than the other groups. These results suggest that cumulative practice of component skills is an effective method of training problem solving.

High temperature creep-fatigue design

International Nuclear Information System (INIS)

Tavassoli, A. A. F.; Fournier, B.; Sauzay, M.

2010-01-01

Generation IV fission and future fusion reactors envisage development of more efficient high temperature concepts where materials performances are key to their success. This paper examines different types of high temperature creep-fatigue interactions and their implications on design rules for the structural materials retained in both programmes. More precisely, the paper examines current status of design rules for the stainless steel type 316L(N), the conventional Modified 9Cr-1Mo martensitic steel and the low activation Eurofer steel. Results obtained from extensive high temperature creep, fatigue and creep-fatigue tests performed on these materials and their welded joints are presented. These include sequential creep-fatigue and relaxation creep-fatigue tests with hold times in tension, in compression or in both. Effects of larger plastic deformations on fatigue properties are studied through cyclic creep tests or fatigue tests with extended hold time in creep. In most cases, mechanical test results are accompanied with microstructural and fractographic observations. In the case of martensitic steels, the effect of oxidation is examined by performing creep-fatigue tests on identical specimens in vacuum. Results obtained are analyzed and their implications on design allowable and creep-fatigue interaction diagrams are presented. While reasonable confidence is found in predicting creep-fatigue damage through existing code procedures for austenitic stainless steels, effects of cyclic softening and coarsening of microstructure of martensitic steels throughout the fatigue life on materials properties need to be taken into account for more precise damage calculations. In the long-term, development of ferritic/martensitic steels with stable microstructure, such as ODS steels, is proposed. (authors)

High temperature creep-fatigue design

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A. A. F.; Fournier, B.; Sauzay, M. [CEA Saclay, DEN DMN, F-91191 Gif Sur Yvette (France)

2010-07-01

Generation IV fission and future fusion reactors envisage development of more efficient high temperature concepts where materials performances are key to their success. This paper examines different types of high temperature creep-fatigue interactions and their implications on design rules for the structural materials retained in both programmes. More precisely, the paper examines current status of design rules for the stainless steel type 316L(N), the conventional Modified 9Cr-1Mo martensitic steel and the low activation Eurofer steel. Results obtained from extensive high temperature creep, fatigue and creep-fatigue tests performed on these materials and their welded joints are presented. These include sequential creep-fatigue and relaxation creep-fatigue tests with hold times in tension, in compression or in both. Effects of larger plastic deformations on fatigue properties are studied through cyclic creep tests or fatigue tests with extended hold time in creep. In most cases, mechanical test results are accompanied with microstructural and fractographic observations. In the case of martensitic steels, the effect of oxidation is examined by performing creep-fatigue tests on identical specimens in vacuum. Results obtained are analyzed and their implications on design allowable and creep-fatigue interaction diagrams are presented. While reasonable confidence is found in predicting creep-fatigue damage through existing code procedures for austenitic stainless steels, effects of cyclic softening and coarsening of microstructure of martensitic steels throughout the fatigue life on materials properties need to be taken into account for more precise damage calculations. In the long-term, development of ferritic/martensitic steels with stable microstructure, such as ODS steels, is proposed. (authors)

Effect of pressurized water reactor environment on fatigue crack propagation, including hole times

International Nuclear Information System (INIS)

Bamford, W.H.

1976-01-01

Results are presented from an experimental program being conducted to investigate the effects of pressurized water reactor environment on the fatigue crack growth rate of pressure vessel steels. Tests were conducted on precracked WOL type specimens under load controlled conditions. The effects of R ratio, loading rates, and loading wave form are evaluated, and the results are compared for both forging and plate material, as well as weldments

Numerical and Experimental Analysis of Aircraft Wing Subjected to Fatigue Loading

Directory of Open Access Journals (Sweden)

Hatem Rahim Wasmi

2016-10-01

Full Text Available This study deals with the aircraft wing analysis (numerical and experimental which subjected to fatigue loading in order to analyze the aircraft wing numerically by using ANSYS 15.0 software and experimentally by using loading programs which effect on fatigue test specimens at laboratory to estimate life of used metal (aluminum alloy 7075-T651 the wing metal and compare between numerical and experimental work, as well as to formulate an experimental mathematical model which may find safe estimate for metals and most common alloys that are used to build aircraft wing at certain conditions. In experimental work, a (34 specimen of (aluminum alloy 7075-T651 were tested using alternating bending fatigue machine rig. The test results are ; (18 Specimen to establish the (S-N curve and endurance limit and the other specimens used for variable amplitude tests were represented by loading programs which represents actual flight conditions. Also it has been obtained the safe fatigue curves which are described by mathematical formulas. ANSYS results show convergence with experimental results about cumulative fatigue damage (D, a mathematical model is proposed to estimate the life; this model gives good results in case of actual loading programs. Also, Miner and Marsh rules are applied to the specimens and compared with the proposal mathematical model in order to estimate the life of the wing material under actual flight loading conditions, comparing results show that it is possible to depend on present mathematical model than Miner and Marsh theories because the proposal mathematical model shows safe and good results compared with experimental work results.

Risk factors of fatigue status among Chinese adolescents.

Science.gov (United States)

Jin, Yuelong; Peng, Baozhen; Li, Yijun; Song, Lei; He, Lianping; Fu, Rui; Wu, Qianqian; Fan, Qingxiu; Yao, Yingshui

2015-01-01

In recent years, fatigue is common among adolescents. The aim of this study is to evaluate fatigue status and find related factors of fatigue among students ranged from 13-26 years from Wuhu, China. This is a case-control, cross-sectional observational study. The students from six middle schools (high school? 26 years old?) in Wuhu city were recruited, Self-Rating Fatigue Scale (SFS) was used to measure the fatigue status among students ranged from 13-26 years, and some demographic characteristics of students also was determined. A total of 726 students are included in our study. A significant difference was observed between fatigue status and grade, a balanced diet, the partial eclipse, picky for food, lack of sleep, excessive fatigue, drinking (P sleep, drinking; grade while a balanced diet is the protective factor of fatigue. Therefore, the school should pay more attention to the fatigue among students in middle school in China, and take some properly measures to reduce the fatigue.

Childhood Cumulative Risk and Later Allostatic Load

DEFF Research Database (Denmark)

Doan, Stacey N; Dich, Nadya; Evans, Gary W

2014-01-01

State, followed for 8 years (between the ages 9 and 17). Poverty- related stress was computed using the cumulative risk approach, assessing stressors across 9 domains, including environmental, psychosocial, and demographic factors. Allostatic load captured a range of physiological responses, including......Objective: The present study investigated the long-term impact of exposure to poverty-related stressors during childhood on allostatic load, an index of physiological dysregulation, and the potential mediating role of substance use. Method: Participants (n = 162) were rural children from New York...... cardiovascular, hypothalamic pituitary adrenal axis, sympathetic adrenal medullary system, and metabolic activity. Smoking and alcohol/drug use were tested as mediators of the hypothesized childhood risk-adolescent allostatic load relationship. Results: Cumulative risk exposure at age 9 predicted increases...

Roughness Effects on Fretting Fatigue

Science.gov (United States)

Yue, Tongyan; Abdel Wahab, Magd

2017-05-01

Fretting is a small oscillatory relative motion between two normal loaded contact surfaces. It may cause fretting fatigue, fretting wear and/or fretting corrosion damage depending on various fretting couples and working conditions. Fretting fatigue usually occurs at partial slip condition, and results in catastrophic failure at the stress levels below the fatigue limit of the material. Many parameters may affect fretting behaviour, including the applied normal load and displacement, material properties, roughness of the contact surfaces, frequency, etc. Since fretting damage is undesirable due to contacting, the effect of rough contact surfaces on fretting damage has been studied by many researchers. Experimental method on this topic is usually focusing on rough surface effects by finishing treatment and random rough surface effects in order to increase fretting fatigue life. However, most of numerical models on roughness are based on random surface. This paper reviewed both experimental and numerical methodology on the rough surface effects on fretting fatigue.

Complete cumulative index (1963-1983)

International Nuclear Information System (INIS)

1983-01-01

This complete cumulative index covers all regular and special issues and supplements published by Atomic Energy Review (AER) during its lifetime (1963-1983). The complete cumulative index consists of six Indexes: the Index of Abstracts, the Subject Index, the Title Index, the Author Index, the Country Index and the Table of Elements Index. The complete cumulative index supersedes the Cumulative Indexes for Volumes 1-7: 1963-1969 (1970), and for Volumes 1-10: 1963-1972 (1972); this Index also finalizes Atomic Energy Review, the publication of which has recently been terminated by the IAEA

Monitoring and Managing Fatigue in Basketball

Directory of Open Access Journals (Sweden)

Toby Edwards

2018-02-01

Full Text Available The sport of basketball exposes athletes to frequent high intensity movements including sprinting, jumping, accelerations, decelerations and changes of direction during training and competition which can lead to acute and accumulated chronic fatigue. Fatigue may affect the ability of the athlete to perform over the course of a lengthy season. The ability of practitioners to quantify the workload and subsequent fatigue in basketball athletes in order to monitor and manage fatigue levels may be beneficial in maintaining high levels of performance and preventing unfavorable physical and physiological training adaptations. There is currently limited research quantifying training or competition workload outside of time motion analysis in basketball. In addition, systematic research investigating methods to monitor and manage athlete fatigue in basketball throughout a season is scarce. To effectively optimize and maintain peak training and playing performance throughout a basketball season, potential workload and fatigue monitoring strategies need to be discussed.

Session: What do we know about cumulative or population impacts

Energy Technology Data Exchange (ETDEWEB)

Kerlinger, Paul; Manville, Al; Kendall, Bill

2004-09-01

This session at the Wind Energy and Birds/Bats workshop consisted of a panel discussion followed by a discussion/question and answer period. The panelists were Paul Kerlinger, Curry and Kerlinger, LLC, Al Manville, U.S. Fish and Wildlife Service, and Bill Kendall, US Geological Service. The panel addressed the potential cumulative impacts of wind turbines on bird and bat populations over time. Panel members gave brief presentations that touched on what is currently known, what laws apply, and the usefulness of population modeling. Topics addressed included which sources of modeling should be included in cumulative impacts, comparison of impacts from different modes of energy generation, as well as what research is still needed regarding cumulative impacts of wind energy development on bird and bat populations.

Fatigue behaviour of bituminous materials : from binders to mixes

OpenAIRE

SOENEN, H; DE LA ROCHE, C; REDELIUS, P

2003-01-01

Test procedures, aiming at measuring fatigue directly on bituminous binders, are increasingly used. The purpose of this paper is to investigate the relevance of this type of binder fatigue tests and to compare the results with laboratory fatigue properties of the corresponding mixes, using one mix composition for all binders, and similar fatigue tests conditions. Eight binders were selected, derived from two crude sources, including an oxidised and two polymer modified samples. All fatigue te...

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

Population based study of fatigue and psychological distress.

OpenAIRE

Pawlikowska, T.; Chalder, T.; Hirsch, S. R.; Wallace, P.; Wright, D. J.; Wessely, S. C.

1994-01-01

OBJECTIVES--To determine the prevalence of fatigue in the general population and the factors associated with fatigue. DESIGN--Postal survey. SETTING--Six general practices in southern England. SUBJECTS--31,651 men and women aged 18-45 years registered with the practices. MAIN OUTCOME MEASURES--Responses to the 12 item general health questionnaire and a fatigue questionnaire which included self reported measures of duration, severity, and causes of fatigue. RESULTS--15,283 valid questionnaires...

Fatigue in Intensive Care Nurses and Related Factors.

Science.gov (United States)

Çelik, Sevim; Taşdemir, Nurten; Kurt, Aylin; İlgezdi, Ebru; Kubalas, Özge

2017-10-01

Fatigue negatively affects the performance of intensive care nurses. Factors contributing to the fatigue experienced by nurses include lifestyle, psychological status, work organization and sleep problems. To determine the level of fatigue among nurses working in intensive care units and the related factors. This descriptive study was conducted with 102 nurses working in intensive care units in the West Black Sea Region of Turkey. Data were collected between February and May 2014 using a personal information form, the Visual Analogue Scale for Fatigue (VAS-F), the Hospital Anxiety and Depression Scale and the Pittsburg Sleep Quality Index. The intensive care nurses in the study were found to be experiencing fatigue. Significant correlations were observed between scores on the VAS-F Fatigue and anxiety (p=0.01), depression (p=0.002), and sleep quality (pnurses' levels of fatigue. These results can be of benefit in taking measures which may be used to reduce fatigue in nurses, especially the fatigue related to work organization and social life.

Fatigue of Beta Processed and Beta Heat-treated Titanium Alloys

CERN Document Server

Wanhill, Russell

2012-01-01

This publication reviews most of the available literature on the fatigue properties of β annealed Ti-6Al-4V and titanium alloys with similar microstructures. The focus is on β processed and β heat-treated alloys because β annealed Ti-6Al-4V has been selected for highly loaded and fatigue-critical structures, including the main wing-carry-through bulkheads and vertical tail stubs, of advanced high-performance military aircraft.   An important aspect of the review is a concise survey of fatigue life assessment methods and the required types of fatigue data. This survey provides the background to recommendations for further research, especially on the fatigue behaviour of β annealed Ti-6Al-4V under realistic fatigue load histories, including the essential topic of short/small fatigue crack growth. Such research is required for independent fatigue life assessments that conform to the aircraft manufacturer’s design requirements, and also for life reassessments that most probably will have to be made during...

Flexural fatigue life prediction of closed hat-section using materially nonlinear axial fatigue characteristics

Science.gov (United States)

Razzaq, Zia

1989-01-01

Straight or curved hat-section members are often used as structural stiffeners in aircraft. For instance, they are employed as stiffeners for the dorsal skin as well as in the aerial refueling adjacent area structure in F-106 aircraft. The flanges of the hat-section are connected to the aircraft skin. Thus, the portion of the skin closing the hat-section interacts with the section itself when resisting the stresses due to service loads. The flexural fatigue life of such a closed section is estimated using materially nonlinear axial fatigue characteristics. It should be recognized that when a structural shape is subjected to bending, the fatigue life at the neutral axis is infinity since the normal stresses are zero at that location. Conversely, the fatigue life at the extreme fibers where the normal bending stresses are maximum can be expected to be finite. Thus, different fatigue life estimates can be visualized at various distances from the neural axis. The problem becomes compounded further when significant portions away from the neutral axis are stressed into plastic range. A theoretical analysis of the closed hat-section subjected to flexural cyclic loading is first conducted. The axial fatigue characteristics together with the related axial fatigue life formula and its inverted form given by Manson and Muralidharan are adopted for an aluminum alloy used in aircraft construction. A closed-form expression for predicting the flexural fatigue life is then derived for the closed hat-section including materially nonlinear action. A computer program is written to conduct a study of the variables such as the thicknesses of the hat-section and the skin, and the type of alloy used. The study has provided a fundamental understanding of the flexural fatigue life characteristics of a practical structural component used in aircraft when materially nonlinear action is present.

Effects of Accumulating Work Shifts on Performance-Based Fatigue Using Multiple Strength Measurements in Day and Night Shift Nurses and Aides.

Science.gov (United States)

Thompson, Brennan J; Stock, Matt S; Banuelas, Victoria K

2017-05-01

Objective This study aimed to examine the effects of accumulating nursing work on maximal and rapid strength characteristics in female nurses and compare these effects in day versus night shift workers. Background Nurses exhibit among the highest nonfatal injury rates of all occupations, which may be a consequence of long, cumulative work shift schedules. Fatigue may accumulate across multiple shifts and lead to performance impairments, which in turn may be linked to injury risks. Method Thirty-seven nurses and aides performed isometric strength-based performance testing of three muscle groups, including the knee extensors, knee flexors, and wrist flexors (hand grip), as well as countermovement jumps, at baseline and following exposure to three 12-hour work shifts in a four-day period. Variables included peak torque (PT) and rate of torque development (RTD) from isometric strength testing and jump height and power output. Results The rigorous work period resulted in significant decreases (-7.2% to -19.2%) in a large majority (8/9) of the isometric strength-based measurements. No differences were noted for the day versus night shift workers except for the RTD at 200 millisecond variable, for which the night shift had greater work-induced decreases than the day shift workers. No changes were observed for jump height or power output. Conclusions A compressed nursing work schedule resulted in decreases in strength-based performance abilities, being indicative of performance fatigue. Application Compressed work schedules involving long shifts lead to functional declines in nurse performance capacities that may pose risks for both the nurse and patient quality of care. Fatigue management plans are needed to monitor and regulate increased levels of fatigue.

Chronic fatigue syndrome: aetiology, diagnosis and treatment

Science.gov (United States)

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

2009-01-01

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

Muscle injections with lidocaine improve resting fatigue and pain in patients with chronic fatigue syndrome

Directory of Open Access Journals (Sweden)

Staud R

2017-06-01

Full Text Available Roland Staud,1 Taylor Kizer,1 Michael E Robinson2 1Department of Medicine, College of Medicine, 2Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, USA Objective: Patients with chronic fatigue syndrome (CFS complain of long-lasting fatigue and pain which are not relieved by rest and worsened by physical exertion. Previous research has implicated metaboreceptors of muscles to play an important role for chronic fatigue and pain. Therefore, we hypothesized that blocking impulse input from deep tissues with intramuscular lidocaine injections would improve not only the pain but also fatigue of CFS patients. Methods: In a double-blind, placebo-controlled study, 58 CFS patients received 20 mL of 1% lidocaine (200 mg or normal saline once into both trapezius and gluteal muscles. Study outcomes included clinical fatigue and pain, depression, and anxiety. In addition, mechanical and heat hyperalgesia were assessed and serum levels of lidocaine were obtained after the injections. Results: Fatigue ratings of CFS patients decreased significantly more after lidocaine compared to saline injections (p = 0.03. In contrast, muscle injections reduced pain, depression, and anxiety (p < 0.001, but these changes were not statistically different between lidocaine and saline (p > 0.05. Lidocaine injections increased mechanical pain thresholds of CFS patients (p = 0.04 but did not affect their heat hyperalgesia. Importantly, mood changes or lidocaine serum levels did not significantly predict fatigue reductions. Conclusion: These results demonstrate that lidocaine injections reduce clinical fatigue of CFS patients significantly more than placebo, suggesting an important role of peripheral tissues for chronic fatigue. Future investigations will be necessary to evaluate the clinical benefits of such interventions. Keywords: muscle injections, lidocaine, metaboreceptor, chronic fatigue 

Determining the von Mises stress power spectral density for frequency domain fatigue analysis including out-of-phase stress components

Science.gov (United States)

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

2007-04-01

This paper provides a new formula to take into account phase differences in the determination of an equivalent von Mises stress power spectral density (PSD) from multiple random inputs. The obtained von Mises PSD can subsequently be used for fatigue analysis. The formula was derived for use in the commercial vehicle business and was implemented in combination with Finite Element software to predict and analyse fatigue failure in the frequency domain.

Perceived Fatigue Interference and Depressed Mood: Comparison of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis Patients with Fatigued Breast Cancer Survivors.

Science.gov (United States)

Hall, Daniel L; Antoni, Michael H; Lattie, Emily G; Jutagir, Devika R; Czaja, Sara J; Perdomo, Dolores; Lechner, Suzanne C; Stagl, Jamie M; Bouchard, Laura C; Gudenkauf, Lisa M; Traeger, Lara; Fletcher, MaryAnn; Klimas, Nancy G

Persistent fatigue and depressive symptoms are both highly prevalent among patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) as well as breast cancer survivors. This study aimed to assess and directly compare perceptions of fatigue as highly interfering in one's daily functioning in both patient populations to better understand their relationships with depressed mood. Participants were 95 female CFS/ME patients and 67 females who were approximately 5 years post-treatment for stage 0-III breast cancer presenting with clinically elevated fatigue severity. Self-report measures were obtained on participants' fatigue-related interference in daily functioning and fatigue severity as well as depressed mood. Hierarchical regression was used to test effects controlling for relevant demographic, psychosocial, and medical covariates. CFS/ME patients endorsed greater depressed mood and fatigue interference than did fatigued breast cancer survivors, p's fatigued breast cancer survivors (β=.18, p =.19). CFS/ME patients reported elevated fatigue symptoms and depression relative to fatigued breast cancer survivors. In the former group, greater depressed mood was highly and significantly associated with greater fatigue-related inference in daily activities. Potential targets for cognitive behavioral interventions are discussed.

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...

Disease-Induced Skeletal Muscle Atrophy and Fatigue

NARCIS (Netherlands)

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

Prevalence of fatigue and chronic fatigue syndrome in a primary care practice.

Science.gov (United States)

Bates, D W; Schmitt, W; Buchwald, D; Ware, N C; Lee, J; Thoyer, E; Kornish, R J; Komaroff, A L

1993-12-27

Our goals were to determine the prevalence of unusual, debilitating fatigue and the frequency with which it was associated with the chronic fatigue syndrome (CFS) or other physical or psychological illness in an outpatient clinic population. We prospectively evaluated a cohort of 1000 consecutive patients in a primary care clinic in an urban, hospital-based general medicine practice. The study protocol included a detailed history, physical examination, and laboratory and psychiatric testing. Five patients who came because of CFS studies were excluded. Of the remaining 995, 323 reported fatigue, and 271 (27%) complained of at least 6 months of unusual fatigue that interfered with their daily lives. Of the 271, self-report or record review revealed a medical or psychiatric condition that could have explained the fatigue in 186 (69%). Thus, 85 (8.5%) of 995 patients had a debilitating fatigue of at least 6 months' duration, without apparent cause. Of these patients, 48 refused further evaluation, and 11 were unavailable for follow-up; 26 completed the protocol. Three of the 26 were hypothyroid, and one had a major psychiatric disorder. Of the remaining 22 patients, three met Centers for Disease Control and Prevention criteria for CFS, four met British criteria, and 10 met the Australian case definition. The point prevalences of CFS were thus 0.3% (95% confidence interval [CI], 0% to 0.6%), 0.4% (95% CI, 0% to 0.8%), and 1.0% (95% CI, 0.4% to 1.6%) using the Centers for Disease Control and Prevention, British, and Australian case definitions, respectively. These estimates were conservative, because they assumed that none of the patients who refused evaluation or were unavailable for follow-up would meet criteria for CFS. While chronic, debilitating fatigue is common in medical outpatients, CFS is relatively uncommon. Prevalence depends substantially on the case definition used.

Fatigue life determination by damage measuring in SAE 8620 specimens steel subjected to multiaxial experiments in neutral and corrosive environment

International Nuclear Information System (INIS)

Silva, Luiz L. da; Filho, Nelson do N.A.; Gomes, Paulo de T.V.; Rabello, Emerson G.; Mansur, Tanius R.

2013-01-01

Fatigue is the fail phenomenon of a material subjected to cyclic loads. This phenomenon affects any component under loads (forces, temperatures, etc.) that changes in time. When there is a combined load, originating multiaxial fatigue, which is the most of the real loads, worst is the situation. Before the component fail, the fatigue phenomenon produces damages to its material and this is a cumulative process that could not be reduced. In the continuum mechanic context, material damage is defined as a parameter that reduces the component resistance and this could cause its fail. The process of damage measuring by changes in electrical resistance is used in this work, and from experimental results of SAE 8620 steel specimens subjected to multiaxial fatigue in corrosive and neutral environment, the remaining specimen time life could be determined. Each specimen has its initial electrical resistance measured and after a certain number of fatigue cycles stopping points, its electrical resistance was measured again. In order to study multiaxial fatigue in specimens, a machine that induces simultaneously bending and torsional loads in the specimen was developed. Air at the temperature range of 18 deg C and 20 deg C was considered neutral environment. The corrosive environment was a NaCl solution with a concentration of 3,5% in weigh. The experimental results showed that the measuring fatigue damage using the changes in electrical resistance is efficient and that is possible to estimate the effect of a corrosive environment in the fatigue damage. (author)

Gear Fault Detection Effectiveness as Applied to Tooth Surface Pitting Fatigue Damage

Science.gov (United States)

Lewicki, David G.; Dempsey, Paula J.; Heath, Gregory F.; Shanthakumaran, Perumal

2010-01-01

A study was performed to evaluate fault detection effectiveness as applied to gear-tooth-pitting-fatigue damage. Vibration and oil-debris monitoring (ODM) data were gathered from 24 sets of spur pinion and face gears run during a previous endurance evaluation study. Three common condition indicators (RMS, FM4, and NA4 [Ed. 's note: See Appendix A-Definitions D were deduced from the time-averaged vibration data and used with the ODM to evaluate their performance for gear fault detection. The NA4 parameter showed to be a very good condition indicator for the detection of gear tooth surface pitting failures. The FM4 and RMS parameters perfomu:d average to below average in detection of gear tooth surface pitting failures. The ODM sensor was successful in detecting a significant 8lDOunt of debris from all the gear tooth pitting fatigue failures. Excluding outliers, the average cumulative mass at the end of a test was 40 mg.

Fatigue testing of wood composites for aerogenerator blades. Pt. 11: Assessment of fatigue damage accumulation using a fatigue modulus approach

Energy Technology Data Exchange (ETDEWEB)

Hacker, C L; Ansell, M P [Bath Univ. (United Kingdom)

1996-12-31

Stress-strain hysteresis loops have been captured during fatigue tests performed at R=10 (compression-compression) and R=0.1 (tension-tension) on Khaya epoxy wood composites. A fatigue modulus approach, proposed by Hwang and Han in 1989, has been applied to the data and a relationship established between the initial change in fatigue modulus and fatigue life. By following changes in fatigue modulus during the first 100 test cycles it is possible to predict the life of the sample allowing rapid evaluation of the fatigue performance of wood composites. Fatigue modulus values have also been calculated for hysteresis loops captured during complex load - time history tests. Similar trends in change in fatigue modulus suggest that this approach could be used in complex loading conditions to evaluate fatigue damage accumulation and predict fatigue life. (Author)

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...

Risk factors for fatigue in patients with epilepsy.

Science.gov (United States)

Yan, Song; Wu, Yuanbin; Deng, Yanchun; Liu, Yonghong; Zhao, Jingjing; Ma, Lei

2016-11-01

Fatigue is highly prevalent in patients with epilepsy and has a major impact on quality of life, but little data is available on its effects and management in epilepsy. To identify the incidence and risk factors of fatigue in patients with epilepsy, 105 epilepsy patients (45 women and 60 men) were enrolled in our study. Demographic and clinical data were collected and psychological variables including fatigue, sleep quality, excess daytime sleepiness, anxiety, and depression were measured by Fatigue Severity Scale, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and Hospital Anxiety and Depression Scale, respectively. Of 105 patients, 29.5% exhibited fatigue (FSS score ⩾4). We found no correlation between the occurrence of fatigue and any of our demographic or clinical variables. Fatigue is correlated with low sleep quality, anxiety, and depression, but not with excess daytime sleepiness. Thus, we concluded that fatigue is highly prevalent in patients with epilepsy, and that low sleep quality, anxiety, and depression are significantly correlated with fatigue in epileptics, while excess daytime sleepiness not. Copyright © 2016. Published by Elsevier Ltd.

Cumulative effects of wind turbines. A guide to assessing the cumulative effects of wind energy development

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-07-01

This guidance provides advice on how to assess the cumulative effects of wind energy developments in an area and is aimed at developers, planners, and stakeholders interested in the development of wind energy in the UK. The principles of cumulative assessment, wind energy development in the UK, cumulative assessment of wind energy development, and best practice conclusions are discussed. The identification and assessment of the cumulative effects is examined in terms of global environmental sustainability, local environmental quality and socio-economic activity. Supplementary guidance for assessing the principle cumulative effects on the landscape, on birds, and on the visual effect is provided. The consensus building approach behind the preparation of this guidance is outlined in the annexes of the report.

Fatigue crack layer propagation in silicon-iron

Science.gov (United States)

Birol, Y.; Welsch, G.; Chudnovsky, A.

1986-01-01

Fatigue crack propagation in metal is almost always accompanied by plastic deformation unless conditions strongly favor brittle fracture. The analysis of the plastic zone is crucial to the understanding of crack propagation behavior as it governs the crack growth kinetics. This research was undertaken to study the fatigue crack propagation in a silicon iron alloy. Kinetic and plasticity aspects of fatigue crack propagation in the alloy were obtained, including the characterization of damage evolution.

Perceived Fatigue Interference and Depressed Mood: Comparison of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis Patients with Fatigued Breast Cancer Survivors

Science.gov (United States)

Hall, Daniel L.; Antoni, Michael H.; Lattie, Emily G.; Jutagir, Devika R.; Czaja, Sara J.; Perdomo, Dolores; Lechner, Suzanne C.; Stagl, Jamie M.; Bouchard, Laura C.; Gudenkauf, Lisa M.; Traeger, Lara; Fletcher, MaryAnn; Klimas, Nancy G.

2015-01-01

Objective Persistent fatigue and depressive symptoms are both highly prevalent among patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) as well as breast cancer survivors. This study aimed to assess and directly compare perceptions of fatigue as highly interfering in one’s daily functioning in both patient populations to better understand their relationships with depressed mood. Methods Participants were 95 female CFS/ME patients and 67 females who were approximately 5 years post-treatment for stage 0-III breast cancer presenting with clinically elevated fatigue severity. Self-report measures were obtained on participants’ fatigue-related interference in daily functioning and fatigue severity as well as depressed mood. Hierarchical regression was used to test effects controlling for relevant demographic, psychosocial, and medical covariates. Results CFS/ME patients endorsed greater depressed mood and fatigue interference than did fatigued breast cancer survivors, p’sfatigued breast cancer survivors (β=.18, p=.19). Conclusions CFS/ME patients reported elevated fatigue symptoms and depression relative to fatigued breast cancer survivors. In the former group, greater depressed mood was highly and significantly associated with greater fatigue-related inference in daily activities. Potential targets for cognitive behavioral interventions are discussed. PMID:26180660

The influence of cell morphology on the compressive fatigue behavior of Ti-6Al-4V meshes fabricated by electron beam melting.

Science.gov (United States)

Zhao, S; Li, S J; Hou, W T; Hao, Y L; Yang, R; Misra, R D K

2016-06-01

Additive manufacturing technique is a promising approach for fabricating cellular bone substitutes such as trabecular and cortical bones because of the ability to adjust process parameters to fabricate different shapes and inner structures. Considering the long term safe application in human body, the metallic cellular implants are expected to exhibit superior fatigue property. The objective of the study was to study the influence of cell shape on the compressive fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting. The results indicated that the underlying fatigue mechanism for the three kinds of meshes (cubic, G7 and rhombic dodecahedron) is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut. By increasing the buckling deformation on the struts through cell shape design, the cyclic ratcheting rate of the meshes during cyclic deformation was decreased and accordingly, the compressive fatigue strength was increased. With increasing bending deformation of struts, fatigue crack growth in struts contributed more to the fatigue damage of meshes. Rough surface and pores contained in the struts significantly deteriorated the compressive fatigue strength of the struts. By optimizing the buckling and bending deformation through cell shape design, Ti-6Al-4V alloy cellular solids with high fatigue strength and low modulus can be fabricated by the EBM technique. Copyright © 2016 Elsevier Ltd. All rights reserved.

COGNITIVE FATIGUE FACILITATES PROCEDURAL SEQUENCE LEARNING

Directory of Open Access Journals (Sweden)

Guillermo eBorragán

2016-03-01

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

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

Fatigue in adults with traumatic brain injury

DEFF Research Database (Denmark)

Mollayeva, Tatyana; Kendzerska, Tetyana; Mollayeva, Shirin

2013-01-01

BACKGROUND: Despite strong indications that fatigue is the most common and debilitating symptom after traumatic brain injury, little is known about its frequency, natural history, or relation to other factors. The current protocol outlines a strategy for a systematic review that will identify......, assess, and critically appraise studies that assessed predictors for fatigue and the consequences of fatigue on at least two separate time points following traumatic brain injury. METHODS/DESIGN: MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews, CINAHL, and PsycINFO will be systematically...... searched for relevant peer-reviewed studies. Reference lists of eligible papers will also be searched. All English language studies with a longitudinal design that focus on fatigue in adults with primary-impact traumatic brain injury will be included. Studies on fatigue following brain injury due...

Development of a fatigue analysis software system

International Nuclear Information System (INIS)

Choi, B. I.; Lee, H. J.; Han, S. W.; Kim, J. Y.; Hwang, K. H.; Kang, J. Y.

2001-01-01

A general purpose fatigue analysis software to predict fatigue lives of mechanical components and structures was developed. This software has some characteristic features including functions of searching weak regions on the free surface in order to reduce computing time significantly, a database of fatigue properties for various materials, and an expert system which can assist any users to get more proper results. This software can be used in the environment consists of commercial finite element packages. Using the software developed fatigue analyses for a SAE keyhole specimen and an automobile knuckle were carried out. It was observed that the results were agree well with those from commercial packages

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

National Research Council Canada - National Science Library

Underwood, John

2000-01-01

...; overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid...

Usefulness of multiple dimensions of fatigue in fibromyalgia.

Science.gov (United States)

Ericsson, Anna; Bremell, Tomas; Mannerkorpi, Kaisa

2013-07-01

To explore in which contexts ratings of multiple dimensions of fatigue are useful in fibromyalgia, and to compare multidimensional fatigue between women with fibromyalgia and healthy women. A cross-sectional study. The Multidimensional Fatigue Inventory (MFI-20), comprising 5 subscales of fatigue, was compared with the 1-dimensional subscale of fatigue from the Fibromyalgia Impact Questionnaire (FIQ) in 133 women with fibromyalgia (mean age 46 years; standard deviation 8.6), in association with socio-demographic and health-related aspects and analyses of explanatory variables of severe fatigue. The patients were also compared with 158 healthy women (mean age 45 years; standard deviation 9.1) for scores on MFI-20 and FIQ fatigue. The MFI-20 was associated with employment, physical activity and walking capacity (rs = -0.27 to -0.36), while FIQ fatigue was not. MFI-20 and FIQ fatigue were equally associated with pain, sleep, depression and anxiety (rs = 0.32-0.63). Regression analyses showed that the MFI-20 increased the explained variance (R2) for the models of pain intensity, sleep, depression and anxiety, by between 7 and 29 percentage points, compared with if FIQ fatigue alone was included in the models. Women with fibromyalgia rated their fatigue higher than healthy women for all subscales of the MFI-20 and the FIQ fatigue (p fibromyalgia. The patients reported higher levels on all fatigue dimensions in comparison with healthy women.

Capturing the post-exertional exacerbation of fatigue following physical and cognitive challenge in patients with chronic fatigue syndrome.

Science.gov (United States)

Keech, Andrew; Sandler, Carolina X; Vollmer-Conna, Ute; Cvejic, Erin; Lloyd, Andrew R; Barry, Benjamin K

2015-12-01

To design and validate an instrument to capture the characteristic post-exertional exacerbation of fatigue in patients with chronic fatigue syndrome (CFS). Firstly, patients with CFS (N=19) participated in five focus group discussions to jointly explore the nature of fatigue and dynamic changes after activity, and inform development of a self-report instrument - the Fatigue and Energy Scale (FES). The psychometric properties of the FES were then examined in two case-control challenge studies: a physically-demanding challenge (moderate-intensity aerobic exercise; N=10 patients), and a cognitively-demanding challenge (simulated driving; N=11 patients). Finally, ecological validity was evaluated by recording in association with tasks of daily living (N=9). Common descriptors for fatigue included 'exhaustion', 'tiredness', 'drained of energy', 'heaviness in the limbs', and 'foggy in the head'. Based on the qualitative data, fatigue was conceptualised as consisting of 'physical' and 'cognitive' dimensions. Analysis of the psychometric properties of the FES showed good sensitivity to the changing symptoms during a post-exertional exacerbation of fatigue following both physical exercise and driving simulation challenges, as well as tasks of daily living. The 'fatigue' experienced by patients with CFS covers both physical and cognitive components. The FES captured the phenomenon of a post-exertional exacerbation of fatigue commonly reported by patients with CFS. The characteristics of the symptom response to physical and cognitive challenges were similar. Both the FES and the challenge paradigms offer key tools to reliably investigate biological correlates of the dynamic changes in fatigue. Copyright © 2015 Elsevier Inc. All rights reserved.

32 CFR 651.16 - Cumulative impacts.

Science.gov (United States)

2010-07-01

... 32 National Defense 4 2010-07-01 2010-07-01 true Cumulative impacts. 651.16 Section 651.16... § 651.16 Cumulative impacts. (a) NEPA analyses must assess cumulative effects, which are the impact on the environment resulting from the incremental impact of the action when added to other past, present...

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

NARCIS (Netherlands)

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

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

A damage cumulation method for crack initiation prediction under non proportional loading and overloading

International Nuclear Information System (INIS)

Taheri, S.

1992-04-01

For a sequence of constant amplitude cyclic loading containing overloads, we propose a method for damage cumulation in non proportional loading. This method uses as data cyclic stabilized states at non proportional loading and initiation or fatigue curve in uniaxial case. For that, we take into account the dependence of Cyclic Strain Stress Curves (C.S.S.C.) and mean cell size on prehardening and we define a stabilized uniaxial state cyclically equivalent to a non proportional stabilized state through a family of C.S.S.C. Although simple assumptions like linear damage function and linear cumulation is used we obtain a sequence effect for difficult cross slip materials as 316 stainless steel, but the Miner rule for easy cross-slip materials. We show then differences between a load-controlled test and a strain controlled test: for a 316 stainless steel in a load controlled test, the non proportional loading at each cycle is less damaging than the uniaxial one for the same equivalent stress, while the result is opposite in a strain controlled test. We show also that an overloading retards initiation in a load controlled test while it accelerates initiation in a strain controlled test. (author). 26 refs., 8 figs

A review on fatigue life prediction methods for anti-vibration rubber materials

Directory of Open Access Journals (Sweden)

Xiaoli WANG

2016-08-01

Full Text Available Anti-vibration rubber, because of its superior elasticity, plasticity, waterproof and trapping characteristics, is widely used in the automotive industry, national defense, construction and other fields. The theory and technology of predicting fatigue life is of great significance to improve the durability design and manufacturing of anti-vibration rubber products. According to the characteristics of the anti-vibration rubber products in service, the technical difficulties for analyzing fatigue properties of anti-vibration rubber materials are pointed out. The research progress of the fatigue properties of rubber materials is reviewed from three angles including methods of fatigue crack initiation, fatigue crack propagation and fatigue damage accumulation. It is put forward that some nonlinear characteristics of rubber under fatigue loading, including the Mullins effect, permanent deformation and cyclic stress softening, should be considered in the further study of rubber materials. Meanwhile, it is indicated that the fatigue damage accumulation method based on continuum damage mechanics might be more appropriate to solve fatigue damage and life prediction problems for complex rubber materials and structures under fatigue loading.

Differing leukocyte gene expression profiles associated with fatigue in patients with prostate cancer versus chronic fatigue syndrome.

Science.gov (United States)

Light, Kathleen C; Agarwal, Neeraj; Iacob, Eli; White, Andrea T; Kinney, Anita Y; VanHaitsma, Timothy A; Aizad, Hannah; Hughen, Ronald W; Bateman, Lucinda; Light, Alan R

2013-12-01

Androgen deprivation therapy (ADT) often worsens fatigue in patients with prostate cancer, producing symptoms similar to chronic fatigue syndrome (CFS). Comparing expression (mRNA) of many fatigue-related genes in patients with ADT-treated prostate cancer versus with CFS versus healthy controls, and correlating mRNA with fatigue severity may clarify the differing pathways underlying fatigue in these conditions. Quantitative real-time PCR was performed on leukocytes from 30 fatigued, ADT-treated prostate cancer patients (PCF), 39 patients with CFS and 22 controls aged 40-79, together with ratings of fatigue and pain severity. 46 genes from these pathways were included: (1) adrenergic/monoamine/neuropeptides, (2) immune, (3) metabolite-detecting, (4) mitochondrial/energy, (5) transcription factors. PCF patients showed higher expression than controls or CFS of 2 immune transcription genes (NR3C1 and TLR4), chemokine CXCR4, and mitochondrial gene SOD2. They showed lower expression of 2 vasodilation-related genes (ADRB2 and VIPR2), 2 cytokines (TNF and LTA), and 2 metabolite-detecting receptors (ASIC3 and P2RX7). CFS patients showed higher P2RX7 and lower HSPA2 versus controls and PCF. Correlations with fatigue severity were similar in PCF and CFS for only DBI, the GABA-A receptor modulator (r=-0.50, pfatigue and pain severity (r=+0.43 and +0.59, p=0.025 and p=0.001). PCF patients differed from controls and CFS in mean expression of 10 genes from all 5 pathways. Correlations with fatigue severity implicated DBI for both patient groups and P2RY1 for PCF only. These pathways may provide new targets for interventions to reduce fatigue. Copyright © 2013 Elsevier Ltd. All rights reserved.

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.)

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

A Case for Including Atmospheric Thermodynamic Variables in Wind Turbine Fatigue Loading Parameter Identification

International Nuclear Information System (INIS)

Kelley, Neil D.

1999-01-01

This paper makes the case for establishing efficient predictor variables for atmospheric thermodynamics that can be used to statistically correlate the fatigue accumulation seen on wind turbines. Recently, two approaches to this issue have been reported. One uses multiple linear-regression analysis to establish the relative causality between a number of predictors related to the turbulent inflow and turbine loads. The other approach, using many of the same predictors, applies the technique of principal component analysis. An examination of the ensemble of predictor variables revealed that they were all kinematic in nature; i.e., they were only related to the description of the velocity field. Boundary-layer turbulence dynamics depends upon a description of the thermal field and its interaction with the velocity distribution. We used a series of measurements taken within a multi-row wind farm to demonstrate the need to include atmospheric thermodynamic variables as well as velocity-related ones in the search for efficient turbulence loading predictors in various turbine-operating environments. Our results show that a combination of vertical stability and hub-height mean shearing stress variables meet this need over a period of 10 minutes

Supervised exercise reduces cancer-related fatigue: a systematic review

Directory of Open Access Journals (Sweden)

José F Meneses-Echávez

2015-01-01

Full Text Available Question: Does supervised physical activity reduce cancer-related fatigue? Design: Systematic review with meta-analysis of randomised trials. Participants: People diagnosed with any type of cancer, without restriction to a particular stage of diagnosis or treatment. Intervention: Supervised physical activity interventions (eg, aerobic, resistance and stretching exercise, defined as any planned or structured body movement causing an increase in energy expenditure, designed to maintain or enhance health-related outcomes, and performed with systematic frequency, intensity and duration. Outcome measures: The primary outcome measure was fatigue. Secondary outcomes were physical and functional wellbeing assessed using the Functional Assessment of Cancer Therapy Fatigue Scale, European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire, Piper Fatigue Scale, Schwartz Cancer Fatigue Scale and the Multidimensional Fatigue Inventory. Methodological quality, including risk of bias of the studies, was evaluated using the PEDro Scale. Results: Eleven studies involving 1530 participants were included in the review. The assessment of quality showed a mean score of 6.5 (SD 1.1, indicating a low overall risk of bias. The pooled effect on fatigue, calculated as a standardised mean difference (SMD using a random-effects model, was –1.69 (95% CI –2.99 to –0.39. Beneficial reductions in fatigue were also found with combined aerobic and resistance training with supervision (SMD = –0.41, 95% CI –0.70 to –0.13 and with combined aerobic, resistance and stretching training with supervision (SMD = –0.67, 95% CI –1.17 to –0.17. Conclusion: Supervised physical activity interventions reduce cancer-related fatigue. These findings suggest that combined aerobic and resistance exercise regimens with or without stretching should be included as part of rehabilitation programs for people who have been diagnosed with cancer

Cumulative keyboard strokes: a possible risk factor for carpal tunnel syndrome

Directory of Open Access Journals (Sweden)

Eleftheriou Andreas

2012-08-01

Full Text Available Abstract Background Contradictory reports have been published regarding the association of Carpal Tunnel Syndrome (CTS and the use of computer keyboard. Previous studies did not take into account the cumulative exposure to keyboard strokes among computer workers. The aim of the present study was to investigate the association between cumulative keyboard use (keyboard strokes and CTS. Methods Employees (461 from a Governmental data entry & processing unit agreed to participate (response rate: 84.1 % in a cross-sectional study. Α questionnaire was distributed to the participants to obtain information on socio-demographics and risk factors for CTS. The participants were examined for signs and symptoms related to CTS and were asked if they had previous history or surgery for CTS. The cumulative amount of the keyboard strokes per worker per year was calculated by the use of payroll’s registry. Two case definitions for CTS were used. The first included subjects with personal history/surgery for CTS while the second included subjects that belonged to the first case definition plus those participants were identified through clinical examination. Results Multivariate analysis used for both case definitions, indicated that those employees with high cumulative exposure to keyboard strokes were at increased risk of CTS (case definition A: OR = 2.23;95 % CI = 1.09-4.52 and case definition B: OR = 2.41; 95%CI = 1.36-4.25. A dose response pattern between cumulative exposure to keyboard strokes and CTS has been revealed (p  Conclusions The present study indicated a possible association between cumulative exposure to keyboard strokes and development of CTS. Cumulative exposure to key-board strokes would be taken into account as an exposure indicator regarding exposure assessment of computer workers. Further research is needed in order to test the results of the current study and assess causality between cumulative keyboard strokes and

Parental fatigue and parenting practices during early childhood: an Australian community survey.

Science.gov (United States)

Cooklin, A R; Giallo, R; Rose, N

2012-09-01

Parenting behaviours are influenced by a range of factors, including parental functioning. Although common, the influence of parental fatigue on parenting practices is not known. The first aim of this study was to investigate the relationship between fatigue and parenting practices. The second aim was to identify parental psychosocial factors significantly associated with fatigue. A sample of 1276 Australian parents, of at least one child aged 0-5 years, completed a survey. Demographic, psychosocial (social support, coping responses) and parental sleep and self-care information was collected. Hierarchical regression was performed to assess the contribution of fatigue (modified Fatigue Assessment Scale) to parental practices (warmth, irritability and involvement), and parenting experiences (Parenting Stress Index, Parenting Sense of Competence Scale). Hierarchical multiple regression assessed the contribution of a range of parental sleep, psychosocial (social support, coping responses) and self-care variables to fatigue when demographic characteristics were held constant. Higher fatigue was significantly associated with lower parental competence (β=-0.17, P parenting stress (β= 0.21, P parent-child interactions (β= 0.11, P parental fatigue, including inadequate social support, poorer diet, poorer sleep quality and ineffective coping styles including self-blame and behaviour disengagement. Fatigue is common, and results suggest that fatigue contributes to adverse parental practices and experiences. However, possible risk factors for higher fatigue were identified in this study, indicating opportunities for intervention, management and support for parents. © 2011 Blackwell Publishing Ltd.

More on fatigue verification of Class 1 nuclear power piping according to ASME BPV III NB-3600

International Nuclear Information System (INIS)

Zeng, Lingfu; Dahlström, Lars; Jansson, Lennart G.

2011-01-01

In this paper, fatigue verification of Class 1 nuclear power piping according to ASME Boiler and Pressure Vessel Code, Section III, NB-3600, and relevant issues that are often discussed in connection to the power uprate of several Swedish BWR reactors in recent years, are dealt with. Key parameters involved in the fatigue verification, i.e. the alternating stress intensity S alt , the penalty factor K e and the cumulative damage factor U, and relevant computational procedures applicable for the assessment of low-cycle fatigue failure using strain-controlled data, are particularly addressed. A so-called simplified elastic-plastic discontinuity analysis for alternative verification when basic fatigue requirements found unsatisfactory, and the procedures provided in NB-3600 for evaluating the alternating stress intensity S alt , are reviewed in detail. Our emphasis is placed on other procedures alternative to the simplified elastic-plastic discontinuity analysis. A more in-depth discussion is given to an alternative suggested earlier by the authors using nonlinear finite element analyses. This paper is a continuation of our work presented in ICONE16/17/18, which attempted to categorize design rules in the code into linear design rules and non-linear design rules and to clarify corresponding design requirements and finite element analyses, in particular, those non-linear ones. (author)

Cyclic mechanical fatigue in ceramic-ceramic composites: an update

International Nuclear Information System (INIS)

Lewis, D. III

1983-01-01

Attention is given to cyclic mechanical fatigue effects in a number of ceramics and ceramic composites, including several monolithic ceramics in which significant residual stresses should be present as a result of thermal expansion mismatches and anisotropy. Fatigue is also noted in several BN-containing ceramic matrix-particulate composites and in SiC fiber-ceramic matrix composites. These results suggest that fatigue testing is imperative for ceramics and ceramic composites that are to be used in applications subject to cyclic loading. Fatigue process models are proposed which provide a rationale for fatigue effect observations, but do not as yet provide quantitative results. Fiber composite fatigue damage models indicate that design stresses in these materials may have to be maintained below the level at which fiber pullout occurs

Chronic Fatigue Syndrome (CFS) and Cancer Related Fatigue (CRF): two "fatigue" syndromes with overlapping symptoms and possibly related aetiologies.

Science.gov (United States)

Rovigatti, Ugo

2012-12-01

In July 2010, at the Muscle Fatigue Meeting, I presented an overview of Chronic Fatigue Syndrome and Cancer Related Fatigue, emphasizing a critical interpretation of the potential association between Chronic Fatigue Syndrome and Cancer Related Fatigue and a newly discovered retrovirus: Xenotropic Murine Related Virus. Since this association was hotly debated at that time, I suggested at the Meeting that it was wrong and most likely due to the identification of the wrong virus culprit. Today, 20 months after the Meeting, the first part of our prediction has turned out to be correct, as Xenotropic Murine Related Virus was shown to be a laboratory-created artefact. Still, the potential association of fatigue-syndromes with an infection (most likely viral) is sustained by a plethora of evidence and this overview will initially summarize data suggesting prior viral infection(s). The principal hypothesized mechanisms for both peripheral and central Chronic Fatigue Syndrome/Cancer Related Fatigue will be then summarized, also indicating plausible associations and triggering factors. All evidence accrued so far suggests that further research work should be performed in this interesting area and in order to identify an infectious agent for Chronic Fatigue Syndrome/Cancer Related Fatigue. One candidate RNA virus, Micro-Foci inducing Virus, will be described in this overview. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Study on the effect of prior fatigue and creep-fatigue damage on the fatigue and creep characteristics of 316 FR stainless steel. 2nd report. The effect of prior creep-fatigue damage on the creep and fatigue characteristics

International Nuclear Information System (INIS)

Yamauchi, Masafumi; Chuman, Yasuharu; Otani, Tomomi; Takahashi, Yukio

2001-01-01

The effect of prior creep-fatigue damage on the creep and the fatigue characteristics was studied to investigate the creep-fatigue life evaluation procedure of 316FR stainless steel. Creep and fatigue tests were conducted at 550degC by using the specimen exposed to prior creep-fatigue cycles at the same temperature and interrupted at 1/4 Nf, 1/2 Nf and 3/4 Nf cycle. The creep and fatigue strength of the pre-damaged material showed monotonic reduction with the prior creep-fatigue damage compared with the virgin material. The creep ductility also showed monotonic reduction with the prior creep-fatigue damage. These results were evaluated by the stress-based Time Fraction Rule and the strain-based Ductility Exhaustion Method. The result showed that the application of the Ductility Exhaustion Method to the creep-fatigue damage evaluation is more promising than the Time Fraction Rule. (author)

A Review of Non-Chemical Stressors and Their Importance in Cumulative Risk Assessment

Science.gov (United States)

Cumulative exposure/risk assessments need to include non-chemical stressors as well as human activities and chemical data. Multiple stressor research can offer information on the interactions between chemical and non-chemical stressors needed for cumulative risk assessment resea...

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

Divergent Cumulative Cultural Evolution

OpenAIRE

Marriott, Chris; Chebib, Jobran

2016-01-01

Divergent cumulative cultural evolution occurs when the cultural evolutionary trajectory diverges from the biological evolutionary trajectory. We consider the conditions under which divergent cumulative cultural evolution can occur. We hypothesize that two conditions are necessary. First that genetic and cultural information are stored separately in the agent. Second cultural information must be transferred horizontally between agents of different generations. We implement a model with these ...

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

Science.gov (United States)

Bower, Julienne E.

2015-01-01

Fatigue is one of the most common and distressing side effects of cancer and its treatment, and may persist for years after treatment completion in otherwise healthy survivors. Cancer-related fatigue causes disruption in all aspects of quality of life and may be a risk factor for reduced survival. The prevalence and course of fatigue in cancer patients has been well characterized, and there is growing understanding of underlying biological mechanisms. Inflammation has emerged as a key biological pathway for cancer-related fatigue, with studies documenting links between markers of inflammation and fatigue before, during, and particularly after treatment. There is considerable variability in the experience of cancer-related fatigue that is not explained by disease- or treatment-related characteristics, suggesting that host factors may play an important role in the development and persistence of this symptom. Indeed, longitudinal studies have begun to identify genetic, biological, psychosocial, and behavioral risk factors for cancer-related fatigue. Given the multi-factorial nature of cancer-related fatigue, a variety of intervention approaches have been examined in randomized controlled trials, including physical activity, psychosocial, mind-body, and pharmacological treatments. Although there is currently no gold standard for treating fatigue, several of these approaches have shown beneficial effects and can be recommended to patients. This report provides a state of the science review of mechanisms, risk factors, and interventions for cancer-related fatigue, with a focus on recent longitudinal studies and randomized trials that have targeted fatigued patients. PMID:25113839

Cancer-related fatigue--mechanisms, risk factors, and treatments.

Science.gov (United States)

Bower, Julienne E

2014-10-01

Fatigue is one of the most common adverse effects of cancer that might persist for years after treatment completion in otherwise healthy survivors. Cancer-related fatigue causes disruption in all aspects of quality of life and might be a risk factor of reduced survival. The prevalence and course of fatigue in patients with cancer have been well characterized and there is growing understanding of the underlying biological mechanisms. Inflammation seems to have a key role in fatigue before, during, and after cancer-treatment. However, there is a considerable variability in the presentation of cancer-related fatigue, much of which is not explained by disease-related or treatment-related characteristics, suggesting that host factors might be important in the development and persistence of this symptom. Indeed, longitudinal studies have identified genetic, biological, psychosocial, and behavioural risk factors associated with cancer-related fatigue. Although no current gold-standard treatment for fatigue is available, a variety of intervention approaches have shown beneficial effects in randomized controlled trials, including physical activity, psychosocial, mind-body, and pharmacological treatments. This Review describes the mechanisms, risk factors, and possible interventions for cancer-related fatigue, focusing on recent longitudinal studies and randomized trials that have targeted fatigued patients.

Fatigue evaluation including environmental effects for primary circuit components in nuclear power plants

International Nuclear Information System (INIS)

Seichter, Johannes; Reese, Sven H.; Klucke, Dietmar

2013-01-01

The influence of LWR coolant environment to the lifetime of materials in Nuclear Power Plants is in discussion internationally. Environmental phenomena were investigated in laboratory tests and published in recent years. The discussion is mainly focused both on the transition from laboratory to real plant components and on numerical calculation procedures. Since publishing of the NUREG/CR-6909 report in 2007, formulae for calculating the Fen factors have been modified several times. Various calculation procedures like the so called 'Strain-integrated Method' and 'Simplified Approach' have been published while each approach yields to different results. The recent revision of the calculation procedure, proposed by ANL in 2012, is presented and discussed with regard to possible variations in the results depending on the assumptions made. In German KTA Rules the effect of environmentally assisted fatigue (EAF) is taken into account by means of so called attention thresholds. If the threshold value is exceeded, further measures like NDT, in-service inspections including fracture mechanical evaluations or detailed assessment procedures have to be performed. One way to handle those measures is to apply sophisticated procedures and to show that the calculated CUF is below the defined attention thresholds. On the basis of a practical example, methods and approaches will be discussed and recommendations in terms of avoiding over-conservatism and misinterpretation will be presented.

Fatigue evaluation including environmental effects for primary circuit components in nuclear power plants

Energy Technology Data Exchange (ETDEWEB)

Seichter, Johannes [Siempelkamp Pruef- und Gutachter-Gesellschaft mbH, Dresden (Germany); Reese, Sven H.; Klucke, Dietmar [Component Technology Global Unit Generation, E.ON Kernkraft GmbH, Hannover (Germany)

2013-05-15

The influence of LWR coolant environment to the lifetime of materials in Nuclear Power Plants is in discussion internationally. Environmental phenomena were investigated in laboratory tests and published in recent years. The discussion is mainly focused both on the transition from laboratory to real plant components and on numerical calculation procedures. Since publishing of the NUREG/CR-6909 report in 2007, formulae for calculating the Fen factors have been modified several times. Various calculation procedures like the so called 'Strain-integrated Method' and 'Simplified Approach' have been published while each approach yields to different results. The recent revision of the calculation procedure, proposed by ANL in 2012, is presented and discussed with regard to possible variations in the results depending on the assumptions made. In German KTA Rules the effect of environmentally assisted fatigue (EAF) is taken into account by means of so called attention thresholds. If the threshold value is exceeded, further measures like NDT, in-service inspections including fracture mechanical evaluations or detailed assessment procedures have to be performed. One way to handle those measures is to apply sophisticated procedures and to show that the calculated CUF is below the defined attention thresholds. On the basis of a practical example, methods and approaches will be discussed and recommendations in terms of avoiding over-conservatism and misinterpretation will be presented.

An evaluation paradigm for cumulative impact analysis

Science.gov (United States)

Stakhiv, Eugene Z.

1988-09-01

Cumulative impact analysis is examined from a conceptual decision-making perspective, focusing on its implicit and explicit purposes as suggested within the policy and procedures for environmental impact analysis of the National Environmental Policy Act of 1969 (NEPA) and its implementing regulations. In this article it is also linked to different evaluation and decision-making conventions, contrasting a regulatory context with a comprehensive planning framework. The specific problems that make the application of cumulative impact analysis a virtually intractable evaluation requirement are discussed in connection with the federal regulation of wetlands uses. The relatively familiar US Army Corps of Engineers' (the Corps) permit program, in conjunction with the Environmental Protection Agency's (EPA) responsibilities in managing its share of the Section 404 regulatory program requirements, is used throughout as the realistic context for highlighting certain pragmatic evaluation aspects of cumulative impact assessment. To understand the purposes of cumulative impact analysis (CIA), a key distinction must be made between the implied comprehensive and multiobjective evaluation purposes of CIA, promoted through the principles and policies contained in NEPA, and the more commonly conducted and limited assessment of cumulative effects (ACE), which focuses largely on the ecological effects of human actions. Based on current evaluation practices within the Corps' and EPA's permit programs, it is shown that the commonly used screening approach to regulating wetlands uses is not compatible with the purposes of CIA, nor is the environmental impact statement (EIS) an appropriate vehicle for evaluating the variety of objectives and trade-offs needed as part of CIA. A heuristic model that incorporates the basic elements of CIA is developed, including the idea of trade-offs among social, economic, and environmental protection goals carried out within the context of environmental

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

Energy Technology Data Exchange (ETDEWEB)

Herrera Ramirez, J.M.

2004-09-15

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

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.

Corrosion Fatigue in District Heating Water Tanks

DEFF Research Database (Denmark)

Maahn, Ernst Emanuel

1996-01-01

Three candidate materials for construction of buffer tanks for district heating water have been tested for corrosion fatigue properties in a district heating water environment. The investigation included Slow Strain Rate Testing of plain tensile specimens, crack initiation testing by corrosion...... fatigue of plain tensile specimens and crack growth rate determination for Compact Tensile Specimens under corrosion fatigue conditions. The three materials are equal with respect to stress corrosion sensibility and crack initiation. Crack growth rate is increased with a factor of 4-6 relative to an inert...

Validity and everyday clinical applicability of lumbar muscle fatigue assessment methods in patients with chronic non-specific low back pain: a systematic review.

Science.gov (United States)

Villafañe, Jorge H; Gobbo, Massimiliano; Peranzoni, Matteo; Naik, Ganesh; Imperio, Grace; Cleland, Joshua A; Negrini, Stefano

2016-09-01

This systematic literature review aimed at examining the validity and applicability in everyday clinical rehabilitation practise of methods for the assessment of back muscle fatiguability in patients with chronic non-specific low back pain (CNSLBP). Extensive research was performed in MEDLINE, Cumulative Index of Nursing and Allied Health Literature (CINAHL), Embase, Physiotherapy Evidence Database (PEDro) and Cochrane Central Register of Controlled Trials (CENTRAL) databases from their inception to September 2014. Potentially relevant articles were also manually looked for in the reference lists of the identified publications. Studies examining lumbar muscle fatigue in people with CNSLBP were selected. Two reviewers independently selected the articles, carried out the study quality assessment and extracted the results. A modified Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) scale was used to evaluate the scientific rigour of the selected works. Twenty-four studies fulfilled the selection criteria and were included in the systematic review. We found conflicting data regarding the validity of methods used to examine back muscle fatigue. The Biering-Sorensen test, performed in conjunction with surface electromyography spectral analysis, turned out to be the most widely used and comparatively, the most optimal modality currently available to assess objective back muscle fatigue in daily clinical practise, even though critical limitations are discussed. Future research should address the identification of an advanced method for lower back fatigue assessment in patients with CNSLBP which, eventually, might provide physical therapists with an objective and reliable test usable in everyday clinical practise. Implications for Rehabilitation Despite its limitations, the Biering-Sorensen test is currently the most used, convenient and easily available fatiguing test for lumbar muscles. To increase validity and reliability of the Biering

Prevalence of fatigue in a group of airline pilots.

Science.gov (United States)

Reis, Cátia; Mestre, Catarina; Canhão, Helena

2013-08-01

Fatigue is a common phenomenon in airline pilots that can impair alertness and ability of crewmembers to safely operate an aircraft and perform safety related tasks. Fatigue can increase the risk of an incident or even an accident. This study provides the first prevalence values for clinically significant fatigue in Portuguese airline pilots. The hypothesis that medium/short-haul pilots may currently present different levels of fatigue than long-haul pilots was also tested. A survey was conducted by requesting Portuguese airline pilots to complete questionnaires placed in the pilots' personal lockers from 1 April until 15 May 2012. The questionnaire included the self-response Fatigue Severity Scale (FSS) to measure subjective fatigue and some additional questions concerning perception of fatigue by pilots. The prevalence values for total and mental fatigue achieved in the Portuguese airline pilots were: 89.3% (FSS > or = 4) and 94.1% (FSS > or = 4) when splitting the sample in two subsamples, long- and medium/short-haul pilots. Levels of total and mental fatigue were higher for medium/short-haul pilots. The analysis of fatigue levels in each type of aviator showed that medium/short-haul pilots presented the highest levels of total and mental fatigue. This study produced the first prevalence values of total and mental fatigue among Portuguese airline pilots, which represents a great step to understanding and addressing this critical phenomenon.

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.

Myoelectrical manifestation of fatigue less prominent in patients with cancer related fatigue.

Directory of Open Access Journals (Sweden)

Katarzyna Kisiel-Sajewicz

Full Text Available PURPOSE: A lack of fatigue-related muscle contractile property changes at time of perceived physical exhaustion and greater central than peripheral fatigue detected by twitch interpolation technique have recently been reported in cancer survivors with fatigue symptoms. Based on these observations, it was hypothesized that compared to healthy people, myoelectrical manifestation of fatigue in the performing muscles would be less significant in these individuals while sustaining a prolonged motor task to self-perceived exhaustion (SPE since their central fatigue was more prominent. The purpose of this study was to test this hypothesis by examining electromyographic (EMG signal changes during fatiguing muscle performance. METHODS: Twelve individuals who had advanced solid cancer and cancer-related fatigue (CRF, and 12 age- and gender-matched healthy controls performed a sustained elbow flexion at 30% maximal voluntary contraction till SPE. Amplitude and mean power frequency (MPF of EMG signals of the biceps brachii, brachioradialis, and triceps brachii muscles were evaluated when the individuals experienced minimal, moderate, and severe fatigue. RESULTS: CRF patients perceived physical "exhaustion" significantly sooner than the controls. The myoelectrical manifestation of muscular fatigue assessed by EMG amplitude and MPF was less significant in CRF than controls. The lower MPF even at minimal fatigue stage in CRF may indicate pathophysiologic condition of the muscle. CONCLUSIONS: CRF patients experience less myoelectrical manifestation of muscle fatigue than healthy individuals near the time of SPE. The data suggest that central nervous system fatigue plays a more important role in limiting endurance-type of motor performance in patients with CRF.

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

Breast cancer and fatigue: issues for the workplace.

Science.gov (United States)

Mock, V

1998-09-01

1. Women with breast cancer are at high risk for fatigue as a side effect of treatment with surgery, radiation, and chemotherapy. The risk is compounded by the multiple roles of women who return to work during treatment. 2. The fatigue experience includes a physical component of decreased functional status, an affective component of emotional distress, and a cognitive component of difficulty concentrating. These characteristics of fatigue may present significant challenges for employees. 3. The Family Medical Leave Act provides 12 weeks of unpaid leave to receive medical treatment and/or recover from treatment for breast cancer. 4. The nurse in the workplace can assess and monitor the effects of fatigue and teach employees to manage fatigue through energy conservation, effective use of energy, and health promotion activities to restore energy levels.

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

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)

Fatigue with HIV/AIDS

Science.gov (United States)

... 21, 2014 Select a Language: Fact Sheet 551 Fatigue WHAT IS FATIGUE? IS FATIGUE IMPORTANT? HOW DO ... It can be physical or psychological. With physical fatigue , your muscles cannot do things as easily as ...

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

Evidence for sensitized fatigue pathways in patients with chronic fatigue syndrome.

Science.gov (United States)

Staud, Roland; Mokthech, Meriem; Price, Donald D; Robinson, Michael E

2015-04-01

Patients with chronic fatigue syndrome (CFS) frequently demonstrate intolerance to physical exertion that is often reported as increased and long-lasting fatigue. Because no specific metabolic alterations have been identified in CFS patients, we hypothesized that sensitized fatigue pathways become activated during exercise corresponding with increased fatigue. After exhausting handgrip exercise, muscle metabolites were trapped in the forearm tissues of 39 CFS patients and 29 normal control (NC) by sudden occlusion for up to 5 minutes. A nonocclusive condition of similar duration was used as control. Repeated fatigue and pain ratings were obtained before and after exercise. Mechanical and heat hyperalgesia were assessed by quantitative sensory testing. All subjects fulfilled the 1994 Fukuda Criteria for CFS. Normal control and CFS subjects exercised for 6.6 (2.4) and 7.0 (2.7) minutes (P > 0.05). Forearm occlusion lasted for 4.7 (1.3) and 4.9 (1.8) minutes in NC and CFS subjects, respectively (P > 0.05). Although fatigue ratings of CFS subjects increased from 4.8 (2.0) to 5.6 (2.1) visual analogue scale (VAS) units during forearm occlusion, they decreased from 5.0 (1.8) to 4.8 (2.0) VAS units during the control condition without occlusion (P = 0.04). A similar time course of fatigue ratings was observed in NC (P > 0.05), although their ratings were significantly lower than those of CFS subjects (P fatigue in CFS patients consistent with sensitization of fatigue pathways. Future interventions that reduce sensitization of fatigue pathways in CFS patients may be of therapeutic benefit.

A Systematic Review of Fatigue in Radiology: Is It a Problem?

Science.gov (United States)

Stec, Nadia; Arje, Danielle; Moody, Alan R; Krupinski, Elizabeth A; Tyrrell, Pascal N

2018-04-01

The purpose of this study was to review current literature regarding radiologist fatigue. A literature search was performed using PubMed. Key words and Medical Subject Heading terms were used to generate refined queries with inclusion and exclusion criteria, focusing on fatigue and error. Results were selected according to these criteria: examined radiologist fatigue and radiologic error stemming from fatigue; experimental results measured as accuracy, error, or performance; and peer-reviewed publication. The risk of bias was addressed by including both quantitative and qualitative studies. Twenty-seven articles were included, mainly primary research articles. Common outcome measures included subjective self-reports and tests to measure eyestrain. Reaction time was also recorded, accounting for variables such as age and experience. One group recommended that guidelines should be implemented regarding number of hours worked. Most recommended ergonomic interventions, proposing the implementation of tools to measure and standardize fatigue and optimize workflow, in conjunction with considering radiologists individually. Education in appropriate viewing habits and breaks were also suggested. Only one study with seven participants recommended that radiologists should sleep well to improve their performance and overall well-being, despite the undeniable evidence that radiologists are fatigued. Fatigue is present in radiology and affects diagnostic accuracy.

[Factors related to subjective fatigue symptoms of adolescent girls].

Science.gov (United States)

Ikeda, Junko; Fukuda, Sayuri; Murakami, Toshio; Kawamoto, Naoki

2011-09-01

To assess changes in subjective fatigue symptoms of adolescent girls over a 15-year period and investigate factors related to these symptoms. A total of 86 items on physical health (including subjective fatigue symptoms), dietary life, and daily living were investigated and five items on physical activity were measured for approximately 100 female first-year dietetic students at a junior college each October over the 15-year period from 1994 to 2008. A total of 1,547 students (mean age, 19.2 +/- 0.3 years) were studied. Subjects were first divided into two groups using the median subjective fatigue score as the cutoff point, and annual changes in the proportion of students in the high subjective fatigue group were investigated by simple regression analysis. In addition, relationships between the two subjective fatigue groups and each item were investigated. 1) The proportion of students with many subjective fatigue symptoms showed a significantly increasing trend over the 15-year period. 2) Investigation of relationships between subjective fatigue symptoms and each factor revealed significance for many items, including dietary habits, life satisfaction, amount of sleep, and desire for a positive body image. 3) In order to determine which of the items were most strongly related to subjective fatigue symptoms, multiple logistic regression analysis was performed for the 15-year period as well as three 5-year periods into which it was divided. The results showed that the dietary habits score (an indicator of dietary habits) and life satisfaction were related to subjective fatigue symptoms during all four periods. As for other items, relationships were observed for amount of sleep in three, diet and salt intake score in two, and liking for coffee/tea, juice drinks, and oily food, bedtime snack, desire for body image, self-assessment of body type, and health consciousness in one. These findings indicate that perspectives in education for promoting the health of

Fatigue life estimation of MD36 and MD523 bogies based on damage accumulation and random fatigue theory

International Nuclear Information System (INIS)

Younesian, Davood; Solhmirzaei, Ali; Gachloo, Alireza

2009-01-01

Bogies are one of the multifunctional parts of trains which are extremely subjected to random loads. This type of oscillating and random excitation arises from irregularities of the track including rail surface vertical roughness, rail joints, variance in super-elevation, and also wheel imperfections like wheel flats and unbalancy. Since most of the prementioned sources have random nature, a random based theory should be applied for fatigue life estimation of the bogie frame. Two methods of fatigue life estimation are investigated in this paper. The first approach which is being implemented in time domain is based on the damage accumulation (DA) approach. Using Monte-Carlo simulation algorithm, the rail surface roughness is generated. Finite element (FE) model of the bogie is subjected to the generated random excitation in the first approach and the stress time histories are obtained, and consequently the fatigue life is estimated by using the rain-flow algorithm. In the second approach, the fatigue life is estimated in frequency domain. Power spectral density (PSD) of the stress is obtained by using the FE model of the bogie frame and the fatigue life is estimated using Rayleigh technique in random fatigue theory. A comprehensive parametric study is carried out and effects of different parameters like the train speeds and level of the rail surface vertical roughness on the estimated fatigue life are investigated

Oxidative stress and fatigue in systemic lupus erythematosus.

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Segal, B M; Thomas, W; Zhu, X; Diebes, A; McElvain, G; Baechler, E; Gross, M

2012-08-01

The objective of this study is to investigate the relationship of oxidative stress to fatigue in systemic lupus erythematosus (SLE). Patients with a confirmed diagnosis of SLE by ACR criteria and healthy controls completed validated questionnaires to assess depression and fatigue. Fatigue was measured with the Fatigue Severity Scale (FSS) and the Profile of Fatigue (Prof-F). Visual analogue scales (VAS) were also used to assess fatigue and pain. Depression was measured with the Center for Epidemiologic Studies Depression Scale (CES-D). Plasma F(2)-isoprostane was measured with gas chromatography/mass spectroscopy to assess oxidative stress. Evaluation included medical record review, physical exam and calculation of body mass index (BMI), disease activity (SLEDAI) and damage (SLICC) in the SLE patients. Seventy-one SLE patients with low disease activity (mean SLEDAI = 1.62 standard error (SE) 0.37, range 0-8) were compared to 51 controls. Fatigue-limiting physical activity (defined as FSS ≥ 4) was present in 56% of patients and 12% of controls. F(2)-isoprostane was higher in SLE patients with fatigue compared to not-fatigued SLE subjects (p = .0076) who were otherwise similar in ethnicity, disease activity and cardiovascular risk factors. Plasma F(2)-isoprostane was strongly correlated with FSS and Profile of Somatic Fatigue (Prof-S) (p fatigue (p = .005), CES-D (p = .008) and with BMI (p = .0001.) In a multivariate model, F(2)-isoprostane was a significant predictor of FSS after adjustment for age, BMI, pain and depression (p = .0002). Fatigue in SLE patients with low disease activity is associated with increased F(2)-isoprostane. F2-isoprostane could provide a useful biomarker to explore mitochondrial function and the regulation of oxidative pathways in patients with SLE in whom fatigue is a debilitating symptom.

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.

Reduced Electromyographic Fatigue Threshold after Performing a Cognitive Fatiguing Task.

Science.gov (United States)

Ferris, Justine R; Tomlinson, Mary A; Ward, Tayler N; Pepin, Marie E; Malek, Moh H

2018-02-22

Cognitive fatigue tasks performed prior to exercise may reduce exercise capacity. The electromyographic fatigue threshold (EMGFT) is the highest exercise intensity that can be maintained without significant increase in the EMG amplitude versus time relationship. To date, no studies have examined the effect of cognitive fatigue on the estimation of the EMGFT. The purpose of this study, therefore, was to determine whether or not cognitive fatigue prior to performing exercise reduces the estimated EMGFT. Eight healthy college-aged men were recruited from a university student population and visited the laboratory on multiple occasions. In a randomized order, subjects performed either the cognitive fatigue task (AX Continuous Performance Test; AX-CPT) for 60 min on one visit (experimental condition) or watched a video on trains for 60 min on the other visit (control condition). After each condition, subjects performed the incremental single-leg knee-extensor ergometry test while the EMG amplitude was recorded from the rectus femoris muscle and heart rate was monitored throughout. Thereafter, the EMGFT was calculated for each participant for each visit and compared using paired samples t-test. For exercise outcomes, there were no significant mean differences for maximal power output between the two conditions (control: 51 ± 5 vs. fatigue: 50 ± 3 W), but a significant decrease in EMGFT between the two conditions (control: 31 ± 3 vs. fatigue: 24 ± 2 W; p = 0.013). Moreover, maximal heart rate was significantly different between the two conditions (control: 151 ± 5 vs. fatigue: 132 ± 6; p = 0.027). These results suggest that performing the cognitive fatiguing task reduces the EMGFT with a corresponding reduction in maximal heart rate response.

Cumulative risk, cumulative outcome: a 20-year longitudinal study.

Directory of Open Access Journals (Sweden)

Leslie Atkinson

Full Text Available Cumulative risk (CR models provide some of the most robust findings in the developmental literature, predicting numerous and varied outcomes. Typically, however, these outcomes are predicted one at a time, across different samples, using concurrent designs, longitudinal designs of short duration, or retrospective designs. We predicted that a single CR index, applied within a single sample, would prospectively predict diverse outcomes, i.e., depression, intelligence, school dropout, arrest, smoking, and physical disease from childhood to adulthood. Further, we predicted that number of risk factors would predict number of adverse outcomes (cumulative outcome; CO. We also predicted that early CR (assessed at age 5/6 explains variance in CO above and beyond that explained by subsequent risk (assessed at ages 12/13 and 19/20. The sample consisted of 284 individuals, 48% of whom were diagnosed with a speech/language disorder. Cumulative risk, assessed at 5/6-, 12/13-, and 19/20-years-old, predicted aforementioned outcomes at age 25/26 in every instance. Furthermore, number of risk factors was positively associated with number of negative outcomes. Finally, early risk accounted for variance beyond that explained by later risk in the prediction of CO. We discuss these findings in terms of five criteria posed by these data, positing a "mediated net of adversity" model, suggesting that CR may increase some central integrative factor, simultaneously augmenting risk across cognitive, quality of life, psychiatric and physical health outcomes.

A method for gear fatigue life prediction considering the internal flow field of the gear pump

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Shen, Haidong; Li, Zhiqiang; Qi, Lele; Qiao, Liang

2018-01-01

Gear pump is the most widely used volume type hydraulic pump, and it is the main power source of the hydraulic system. Its performance is influenced by many factors, such as working environment, maintenance, fluid pressure and so on. It is different from the gear transmission system, the internal flow field of gear pump has a greater impact on the gear life, therefore it needs to consider the internal hydraulic system when predicting the gear fatigue life. In this paper, a certain aircraft gear pump as the research object, aim at the typical failure forms, gear contact fatigue, of gear pump, proposing the prediction method based on the virtual simulation. The method use CFD (Computational fluid dynamics) software to analyze pressure distribution of internal flow field of the gear pump, and constructed the unidirectional flow-solid coupling model of gear to acquire the contact stress of tooth surface on Ansys workbench software. Finally, employing nominal stress method and Miner cumulative damage theory to calculated the gear contact fatigue life based on modified material P-S-N curve. Engineering practice show that the method is feasible and efficient.

Influence of strain-induced martensitic transformation on fatigue short crack behaviour in an austenitic stainless steel

International Nuclear Information System (INIS)

Baffie, N.; Stolarz, J.; Magnin, Th.

2000-01-01

The influence of martensitic transformation induced by cyclic straining on the mechanisms of low cycle fatigue damage in a metastable austenitic stainless steel with different grain sizes has been investigated using macroscopic measurements and microscopic observations of short crack evolutions. The amount of martensite formed during cyclic straining increases with increasing plastic strain amplitude and cumulative plastic strain but the dominant parameter is the grain size of austenite. The fine microstructure (D = 10 μm) with maximum martensite fraction of about 20% is characterised by a better fatigue resistance than the coarse one (D 40μm and only 2% of martensite) for the same plastic strain amplitude. Martensitic transformation is found to radically modify the cyclic response of the alloy and consequently the damage mechanisms. Indeed, both short crack nucleation and growth take place exclusively in the transformed regions. A mechanism of short crack propagation based on the γ→ α' transformation assisted by stress concentration at the crack tip is proposed. The indirect influence of grain boundaries in the austenite on crack propagation in the martensite is demonstrated. The better fatigue resistance of metastable alloys with fine granular structure can thus be understood. (authors)

Secant cumulants and toric geometry

NARCIS (Netherlands)

Michalek, M.; Oeding, L.; Zwiernik, P.W.

2012-01-01

We study the secant line variety of the Segre product of projective spaces using special cumulant coordinates adapted for secant varieties. We show that the secant variety is covered by open normal toric varieties. We prove that in cumulant coordinates its ideal is generated by binomial quadrics. We

The Nature of Self-Regulatory Fatigue and "Ego Depletion": Lessons From Physical Fatigue.

Science.gov (United States)

Evans, Daniel R; Boggero, Ian A; Segerstrom, Suzanne C

2015-07-30

Self-regulation requires overriding a dominant response and leads to temporary self-regulatory fatigue. Existing theories of the nature and causes of self-regulatory fatigue highlight physiological substrates such as glucose, or psychological processes such as motivation, but these explanations are incomplete on their own. Historically, theories of physical fatigue demonstrate a similar pattern of useful but incomplete explanations, as recent views of physical fatigue emphasize the roles of both physiological and psychological factors. In addition to accounting for multiple inputs, these newer views also explain how fatigue can occur even in the presence of sufficient resources. Examining these newer theories of physical fatigue can serve as a foundation on which to build a more comprehensive understanding of self-regulatory fatigue that integrates possible neurobiological underpinnings of physical and self-regulatory fatigue, and suggests the possible function of self-regulatory fatigue. © 2015 by the Society for Personality and Social Psychology, Inc.

Fatigue-Prone Details in Steel Bridges

Directory of Open Access Journals (Sweden)

Mohsen Heshmati

2012-11-01

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

Cognitive fatigue in patients with myasthenia gravis.

Science.gov (United States)

Jordan, Berit; Schweden, Tabea L K; Mehl, Theresa; Menge, Uwe; Zierz, Stephan

2017-09-01

Cognitive fatigue has frequently been reported in myasthenia gravis (MG). However, objective assessment of cognitive fatigability has never been evaluated. Thirty-three MG patients with stable generalized disease and 17 healthy controls underwent a test battery including repeated testing of attention and concentration (d2-R) and Paced Auditory Serial Addition Test. Fatigability was based on calculation of linear trend (LT) reflecting dynamic performance within subsequent constant time intervals. Additionally, fatigue questionnaires were used. MG patients showed a negative LT in second d2-R testing, indicating cognitive fatigability. This finding significantly differed from stable cognitive performance in controls (P fatigue was significantly higher in MG patients compared with controls (P fatigue is not correlated with objective findings. Muscle Nerve 56: 449-457, 2017. © 2016 Wiley Periodicals, Inc.

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

Science.gov (United States)

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

2016-04-01

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

How Fatigue Is Experienced and Handled by Female Outpatients with Inflammatory Bowel Disease

Directory of Open Access Journals (Sweden)

Anne Beck

2013-01-01

Full Text Available Background. Fatigue is a significant aspect of everyday life for patients with inflammatory bowel disease (IBD, and it influences their health-related quality of life. Little is known about fatigue from the patient’s perspective. Aim. To investigate how female IBD patients experience and handle fatigue. Methods. The study included 11 female outpatients. These patients were 40–59 years old and had IBD ≥ one year and a significantly increased fatigue score. Patients with severe active IBD, anaemia, comorbidity, or pregnancy were excluded. The included patients agreed to participate in a semistructured interview. The interviews were analysed using Malterud’s principles of systematic text condensation. Results. The patients described physical and mental symptoms of fatigue that led to social-, physical-, and work-related limitations with emotional consequences. To handle fatigue, the patients used planning, priority, acceptance, exercise, and support. Two of the eleven patients used exercise on a regular basis. Surprisingly, some patients indicated that they did not need to talk with professionals about their fatigue unless a cure was available. Conclusion. Fatigue in IBD includes physical and mental symptoms that limit the patients’ social-, physical-, and work-related lives. Despite this, some patients expressed that they had chosen to accept their fatigue.

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

Cumulative environmental impacts and integrated coastal management: the case of Xiamen, China.

Science.gov (United States)

Xue, Xiongzhi; Hong, Huasheng; Charles, Anthony T

2004-07-01

This paper examines the assessment of cumulative environmental impacts and the implementation of integrated coastal management within the harbour of Xiamen, China, an urban region in which the coastal zone is under increasing pressure as a result of very rapid economic growth. The first stage of analysis incorporates components of a cumulative effects assessment, including (a) identification of sources of environmental impacts, notably industrial expansion, port development, shipping, waste disposal, aquaculture and coastal construction, (b) selection of a set of valued ecosystem components, focusing on circulation and siltation, water quality, sediment, the benthic community, and mangrove forests, and (c) use of a set of key indicators to examine cumulative impacts arising from the aggregate of human activities. In the second stage of analysis, the paper describes and assesses the development of an institutional framework for integrated coastal management in Xiamen, one that combines policy and planning (including legislative and enforcement mechanisms) with scientific and monitoring mechanisms (including an innovative 'marine functional zoning' system). The paper concludes that the integrated coastal management framework in Xiamen has met all relevant requirements for 'integration' as laid out in the literature, and has explicitly incorporated consideration of cumulative impacts within its management and monitoring processes.

Fatigue and creep-fatigue in sodium of 316 L stainless-steel

International Nuclear Information System (INIS)

Ardellier, A.

1981-03-01

The present paper describes test-facility developed to perform low-cycle fatigue and creep-fatigue interaction in sodium on stainless steel - 316 L . Fatigue life in sodium and in air are compared. A beneficial effect in sodium is noted

Cumulative Culture and Future Thinking: Is Mental Time Travel a Prerequisite to Cumulative Cultural Evolution?

Science.gov (United States)

Vale, G. L.; Flynn, E. G.; Kendal, R. L.

2012-01-01

Cumulative culture denotes the, arguably, human capacity to build on the cultural behaviors of one's predecessors, allowing increases in cultural complexity to occur such that many of our cultural artifacts, products and technologies have progressed beyond what a single individual could invent alone. This process of cumulative cultural evolution…

Crack growth prediction for low-cycle fatigue regime

International Nuclear Information System (INIS)

Kamaya, Masayuki

2017-01-01

The objective of this study is to show a crack growth prediction procedure for the low-cycle fatigue regime. First, fatigue crack growth tests using Type 316 stainless steel specimens at room temperature were reviewed. It was seen that the crack growth rates correlated well with the equivalent stress intensify factor, which was derived using strain range instead of stress range. Furthermore, the effective equivalent stress intensify factor derived using the effective strain range exhibited excellent correlation with the crack growth rates obtained under various specimen geometries and loading conditions including high and low-cycle regimens. The obtained crack growth rates were also compared with the growth rate prescribed in the fitness-for-service code of the Japan Society of Mechanical Engineers (JSME). The test results agreed with the growth rate of JSME code. Finally, the procedure for predicting the low-cycle fatigue crack growth was shown. Although the JSME code is aimed at predicting fatigue crack growth for the so-called small scale yielding condition (high-cycle fatigue regime), the material constants determined for the high-cycle fatigue regime can be used even for the low-cycle fatigue regime. (author)

Computational simulation of acoustic fatigue for hot composite structures

Science.gov (United States)

Singhal, S. N.; Nagpal, V. K.; Murthy, P. L. N.; Chamis, C. C.

1991-01-01

This paper presents predictive methods/codes for computational simulation of acoustic fatigue resistance of hot composite structures subjected to acoustic excitation emanating from an adjacent vibrating component. Select codes developed over the past two decades at the NASA Lewis Research Center are used. The codes include computation of (1) acoustic noise generated from a vibrating component, (2) degradation in material properties of the composite laminate at use temperature, (3) dynamic response of acoustically excited hot multilayered composite structure, (4) degradation in the first-ply strength of the excited structure due to acoustic loading, and (5) acoustic fatigue resistance of the excited structure, including propulsion environment. Effects of the laminate lay-up and environment on the acoustic fatigue life are evaluated. The results show that, by keeping the angled plies on the outer surface of the laminate, a substantial increase in the acoustic fatigue life is obtained. The effect of environment (temperature and moisure) is to relieve the residual stresses leading to an increase in the acoustic fatigue life of the excited panel.

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

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.

The challenges and opportunities in cumulative effects assessment

Energy Technology Data Exchange (ETDEWEB)

Foley, Melissa M., E-mail: mfoley@usgs.gov [U.S. Geological Survey, Pacific Coastal and Marine Science Center, 400 Natural Bridges, Dr., Santa Cruz, CA 95060 (United States); Center for Ocean Solutions, Stanford University, 99 Pacific St., Monterey, CA 93940 (United States); Mease, Lindley A., E-mail: lamease@stanford.edu [Center for Ocean Solutions, Stanford University, 473 Via Ortega, Stanford, CA 94305 (United States); Martone, Rebecca G., E-mail: rmartone@stanford.edu [Center for Ocean Solutions, Stanford University, 99 Pacific St., Monterey, CA 93940 (United States); Prahler, Erin E. [Center for Ocean Solutions, Stanford University, 473 Via Ortega, Stanford, CA 94305 (United States); Morrison, Tiffany H., E-mail: tiffany.morrison@jcu.edu.au [ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, 4811 (Australia); Murray, Cathryn Clarke, E-mail: cmurray@pices.int [WWF-Canada, 409 Granville Street, Suite 1588, Vancouver, BC V6C 1T2 (Canada); Wojcik, Deborah, E-mail: deb.wojcik@duke.edu [Nicholas School for the Environment, Duke University, 9 Circuit Dr., Durham, NC 27708 (United States)

2017-01-15

The cumulative effects of increasing human use of the ocean and coastal zone have contributed to a rapid decline in ocean and coastal resources. As a result, scientists are investigating how multiple, overlapping stressors accumulate in the environment and impact ecosystems. These investigations are the foundation for the development of new tools that account for and predict cumulative effects in order to more adequately prevent or mitigate negative effects. Despite scientific advances, legal requirements, and management guidance, those who conduct assessments—including resource managers, agency staff, and consultants—continue to struggle to thoroughly evaluate cumulative effects, particularly as part of the environmental assessment process. Even though 45 years have passed since the United States National Environmental Policy Act was enacted, which set a precedent for environmental assessment around the world, defining impacts, baseline, scale, and significance are still major challenges associated with assessing cumulative effects. In addition, we know little about how practitioners tackle these challenges or how assessment aligns with current scientific recommendations. To shed more light on these challenges and gaps, we undertook a comparative study on how cumulative effects assessment (CEA) is conducted by practitioners operating under some of the most well-developed environmental laws around the globe: California, USA; British Columbia, Canada; Queensland, Australia; and New Zealand. We found that practitioners used a broad and varied definition of impact for CEA, which led to differences in how baseline, scale, and significance were determined. We also found that practice and science are not closely aligned and, as such, we highlight opportunities for managers, policy makers, practitioners, and scientists to improve environmental assessment.

The challenges and opportunities in cumulative effects assessment

International Nuclear Information System (INIS)

Foley, Melissa M.; Mease, Lindley A.; Martone, Rebecca G.; Prahler, Erin E.; Morrison, Tiffany H.; Murray, Cathryn Clarke; Wojcik, Deborah

2017-01-01

The cumulative effects of increasing human use of the ocean and coastal zone have contributed to a rapid decline in ocean and coastal resources. As a result, scientists are investigating how multiple, overlapping stressors accumulate in the environment and impact ecosystems. These investigations are the foundation for the development of new tools that account for and predict cumulative effects in order to more adequately prevent or mitigate negative effects. Despite scientific advances, legal requirements, and management guidance, those who conduct assessments—including resource managers, agency staff, and consultants—continue to struggle to thoroughly evaluate cumulative effects, particularly as part of the environmental assessment process. Even though 45 years have passed since the United States National Environmental Policy Act was enacted, which set a precedent for environmental assessment around the world, defining impacts, baseline, scale, and significance are still major challenges associated with assessing cumulative effects. In addition, we know little about how practitioners tackle these challenges or how assessment aligns with current scientific recommendations. To shed more light on these challenges and gaps, we undertook a comparative study on how cumulative effects assessment (CEA) is conducted by practitioners operating under some of the most well-developed environmental laws around the globe: California, USA; British Columbia, Canada; Queensland, Australia; and New Zealand. We found that practitioners used a broad and varied definition of impact for CEA, which led to differences in how baseline, scale, and significance were determined. We also found that practice and science are not closely aligned and, as such, we highlight opportunities for managers, policy makers, practitioners, and scientists to improve environmental assessment.

The challenges and opportunities in cumulative effects assessment

Science.gov (United States)

Foley, Melissa M.; Mease, Lindley A; Martone, Rebecca G; Prahler, Erin E; Morrison, Tiffany H; Clarke Murray, Cathryn; Wojcik, Deborah

2016-01-01

The cumulative effects of increasing human use of the ocean and coastal zone have contributed to a rapid decline in ocean and coastal resources. As a result, scientists are investigating how multiple, overlapping stressors accumulate in the environment and impact ecosystems. These investigations are the foundation for the development of new tools that account for and predict cumulative effects in order to more adequately prevent or mitigate negative effects. Despite scientific advances, legal requirements, and management guidance, those who conduct assessments—including resource managers, agency staff, and consultants—continue to struggle to thoroughly evaluate cumulative effects, particularly as part of the environmental assessment process. Even though 45 years have passed since the United States National Environmental Policy Act was enacted, which set a precedent for environmental assessment around the world, defining impacts, baseline, scale, and significance are still major challenges associated with assessing cumulative effects. In addition, we know little about how practitioners tackle these challenges or how assessment aligns with current scientific recommendations. To shed more light on these challenges and gaps, we undertook a comparative study on how cumulative effects assessment (CEA) is conducted by practitioners operating under some of the most well-developed environmental laws around the globe: California, USA; British Columbia, Canada; Queensland, Australia; and New Zealand. We found that practitioners used a broad and varied definition of impact for CEA, which led to differences in how baseline, scale, and significance were determined. We also found that practice and science are not closely aligned and, as such, we highlight opportunities for managers, policy makers, practitioners, and scientists to improve environmental assessment.

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 ...

Fatigue, Work Schedules, and Perceived Performance in Bedside Care Nurses.

Science.gov (United States)

Sagherian, Knar; Clinton, Michael E; Abu-Saad Huijer, Huda; Geiger-Brown, Jeanne

2017-07-01

Hospital nurses are expected to maintain optimal work performance; yet, fatigue can threaten safe practice and result in unfavorable patient outcomes. This descriptive cross-sectional study explored the association between fatigue, work schedules, and perceived work performance among nurses. The study sample included 77 bedside nurses who were mostly female, single, and between 20 and 29 years of age. The majority worked 8-hour shifts and overtime. Nurses who worked during off days reported significantly higher chronic fatigue compared with those nurses who took time off. Nurses who reported feeling refreshed after sleep had significantly less chronic and acute fatigue and more intershift recovery. Nurses with acute and chronic fatigue perceived poorer physical performance. Also, nurses who reported chronic fatigue perceived they were less alert and less able to concentrate when providing patient care. Less effective communication was also associated with acute and chronic fatigue. In conclusion, fatigue has safety implications for nurses' practice that should be monitored by nursing management.

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.

The nature of self-regulatory fatigue and “ego depletion”: Lessons from physical fatigue

Science.gov (United States)

Evans, Daniel R.; Boggero, Ian A.; Segerstrom, Suzanne C.

2016-01-01

Self-regulation requires overriding a dominant response, and leads to temporary self-regulatory fatigue. Existing theories of the nature and causes of self-regulatory fatigue highlight physiological substrates such as glucose or psychological processes such as motivation, but these explanations are incomplete on their own. Historically, theories of physical fatigue demonstrate a similar pattern of useful but incomplete explanations, as recent views of physical fatigue emphasize the roles of both physiological and psychological factors. In addition to accounting for multiple inputs, these newer views also explain how fatigue can occur even in the presence of sufficient resources. Examining these newer theories of physical fatigue can serve as a foundation on which to build a more comprehensive understanding of self-regulatory fatigue that integrates possible neurobiological underpinnings of physical and self-regulatory fatigue, and suggests the possible function of self-regulatory fatigue. PMID:26228914

14 CFR 29.571 - Fatigue evaluation of structure.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Fatigue evaluation of structure. 29.571... § 29.571 Fatigue evaluation of structure. (a) General. An evaluation of the strength of principal... (including tolerance to flaws). The structure must be shown by analysis supported by test evidence and, if...

Tired, weak, or in need of rest: fatigue among general practice attenders.

Science.gov (United States)

David, A; Pelosi, A; McDonald, E; Stephens, D; Ledger, D; Rathbone, R; Mann, A

1990-11-24

To determine the prevalence and associations of symptoms of fatigue. Questionnaire survey. London general practice. 611 General practice attenders. Scores on a fatigue questionnaire and reasons given for fatigue. 10.2% Of men (17/167) and 10.6% of women (47/444) had substantial fatigue for one month or more. Age, occupation, and marital status exerted minor effects. Subjects attributed fatigue equally to physical and non-physical causes. Physical ill health, including viral infection, was associated with more severe fatigue. Women rather than men blamed family responsibilities for their fatigue. The profile of persistent fatigue did not differ from that of short duration. Only one person met criteria for the chronic fatigue syndrome. Fatigue is a common complaint among general practice attenders and can be severe. Patients may attribute this to physical, psychological, and social stress.

The concept of fatigue fracture toughness in fatigue delamination growth behavior

NARCIS (Netherlands)

Yao, L.; Alderliesten, R.C.; Benedictus, R.

2015-01-01

This paper provides a study on mode I fatigue delamination growth in composite laminates using energy principles. Experimental data has been obtained from fatigue tests conducted on Double Cantilever Beam (DCB) specimens at various stress ratios. A concept of fatigue fracture toughness is proposed

System-Reliability Cumulative-Binomial Program

Science.gov (United States)

Scheuer, Ernest M.; Bowerman, Paul N.

1989-01-01

Cumulative-binomial computer program, NEWTONP, one of set of three programs, calculates cumulative binomial probability distributions for arbitrary inputs. NEWTONP, CUMBIN (NPO-17555), and CROSSER (NPO-17557), used independently of one another. Program finds probability required to yield given system reliability. Used by statisticians and users of statistical procedures, test planners, designers, and numerical analysts. Program written in C.

Time-dependent fatigue--phenomenology and life prediction

International Nuclear Information System (INIS)

Coffin, L.F.

1979-01-01

The time-dependent fatigue behavior of materials used or considered for use in present and advanced systems for power generation is outlined. A picture is first presented to show how basic mechanisms and phenomenological information relate to the performance of the component under consideration through the so-called local strain approach. By this means life prediction criteria and design rules can be formulated utilizing laboratory test information which is directly translated to predicting the performance of a component. The body of phenomenological information relative to time-dependent fatigue is reviewed. Included are effects of strain range, strain rate and frequency, environment and wave shape, all of which are shown to be important in developing both an understanding and design base for time dependent fatigue. Using this information, some of the current methods being considered for the life prediction of components are reviewed. These include the current ASME code case, frequency-modified fatigue equations, strain range partitioning, the damage function method, frequency separation and damage rate equations. From this review, it is hoped that a better perspective on future directions for basic material science at high temperature can be achieved

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.......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...

Cumulative human impacts on marine predators.

Science.gov (United States)

Maxwell, Sara M; Hazen, Elliott L; Bograd, Steven J; Halpern, Benjamin S; Breed, Greg A; Nickel, Barry; Teutschel, Nicole M; Crowder, Larry B; Benson, Scott; Dutton, Peter H; Bailey, Helen; Kappes, Michelle A; Kuhn, Carey E; Weise, Michael J; Mate, Bruce; Shaffer, Scott A; Hassrick, Jason L; Henry, Robert W; Irvine, Ladd; McDonald, Birgitte I; Robinson, Patrick W; Block, Barbara A; Costa, Daniel P

2013-01-01

Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact (CUI) on marine predators by combining electronic tracking data of eight protected predator species (n=685 individuals) in the California Current Ecosystem with data on 24 anthropogenic stressors. We show significant variation in CUI with some of the highest impacts within US National Marine Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied in planning the use of marine resources.

A fatigue approach to wind turbine control

International Nuclear Information System (INIS)

Hammerum, K; Brath, P; Poulsen, N K

2007-01-01

Conventional design of wind turbine controllers is focused on speed and produced electric power. As fatigue loads is an important design consideration, the resulting design is evaluated also with respect to the fatigue loads inflicted on the turbine structure. This is normally done by performing simulations using tools like FLEX, HAWC or FAST, followed by rainflow counting in the resulting time series. This procedure constitutes an iterative design procedure involving realisations of the stress processes in order to obtain the time series needed for fatigue estimates. The focus of this paper is the elimination of the need for process realisation. To this end, known techniques for approximative fatigue load assesment based on the spectral moments of the inflicted stress histories are applied. Assuming a linearised system model, we present a novel scheme for efficient computation of these spectral moments. The scheme is applied to obtain rapid evaluation of cost functions including fatigue loads, hereby allowing efficient numerical optimisation of the controller. Three different controller design examples are given, all defined directly in terms of component life times

Effect of Variable Amplitude Blocks' Ordering on the Functional Fatigue of Superelastic NiTi Wires

Science.gov (United States)

Soul, Hugo; Yawny, Alejandro

2017-12-01

Accumulation of superelastic cycles in NiTi uniaxial element generates changes on the stress-strain response. Basically, there is an uneven drop of martensitic transformation stress plateaus and an increase of residual strain. This evolution associated with deterioration of superelastic characteristics is referred to as "functional fatigue" and occurs due to irreversible microstructural changes taking place each time a material domain transforms. Unlike complete cycles, for which straining is continued up to elastic loading of martensite, partial cycles result in a differentiated evolution of those material portions affected by the transformation. It is then expected that the global stress-strain response would reflect the previous cycling history of the specimen. In the present work, the consequences of cycling of NiTi wires using blocks of different strain amplitudes interspersed in different sequences are analyzed. The effect of successive increasing, successive decreasing, and interleaved strain amplitudes on the evolution of the superelastic response is characterized. The feasibility of postulating a functional fatigue criterion similar to the Miner's cumulative damage law used in structural fatigue analysis is discussed. The relation of the observed stress-strain response with the transformational history of the specimen can be rationalized by considering that the stress-induced transformation proceeds via localized propagating fronts.

Cumulative Beam Breakup with Time-Dependent Parameters

CERN Document Server

Delayen, J R

2004-01-01

A general analytical formalism developed recently for cumulative beam breakup (BBU) in linear accelerators with arbitrary beam current profile and misalignments [1] is extended to include time-dependent parameters such as energy chirp or rf focusing in order to reduce BBU-induced instabilities and emittance growth. Analytical results are presented and applied to practical accelerator configurations.

Adrenal Fatigue

Science.gov (United States)

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

Neuromuscular fatigue during exercise: Methodological considerations, etiology and potential role in chronic fatigue.

Science.gov (United States)

Twomey, Rosie; Aboodarda, Saied Jalal; Kruger, Renata; Culos-Reed, Susan Nicole; Temesi, John; Millet, Guillaume Y

2017-04-01

The term fatigue is used to describe a distressing and persistent symptom of physical and/or mental tiredness in certain clinical populations, with distinct but ultimately complex, multifactorial and heterogenous pathophysiology. Chronic fatigue impacts on quality of life, reduces the capacity to perform activities of daily living, and is typically measured using subjective self-report tools. Fatigue also refers to an acute reduction in the ability to produce maximal force or power due to exercise. The classical measurement of exercise-induced fatigue involves neuromuscular assessments before and after a fatiguing task. The limitations and alternatives to this approach are reviewed in this paper in relation to the lower limb and whole-body exercise, given the functional relevance to locomotion, rehabilitation and activities of daily living. It is suggested that under some circumstances, alterations in the central and/or peripheral mechanisms of fatigue during exercise may be related to the sensations of chronic fatigue. As such, the neurophysiological correlates of exercise-induced fatigue are briefly examined in two clinical examples where chronic fatigue is common: cancer survivors and people with multiple sclerosis. This review highlights the relationship between objective measures of fatigability with whole-body exercise and perceptions of fatigue as a priority for future research, given the importance of exercise in relieving symptoms of chronic fatigue and/or overall disease management. As chronic fatigue is likely to be specific to the individual and unlikely to be due to a simple biological or psychosocial explanation, tailored exercise programmes are a potential target for therapeutic intervention. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

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...

Fatigue-Arrestor Bolts

Science.gov (United States)

Onstott, Joseph W.; Gilster, Mark; Rodriguez, Sergio; Larson, John E.; Wickham, Mark D.; Schoonover, Kevin E.

1995-01-01

Bolts that arrest (or, more precisely, retard) onset of fatigue cracking caused by inelastic strains developed. Specifically developed to be installed in flange holes of unrestrained rocket engine nozzle. Fanges sometimes used to bolt nozzle to test stand; however, when rocket engine operated without this restraint, region around bolt holes experience severe inelastic strains causing fatigue cracking. Interference fits introduce compressive preloads that retard fatigue by reducing ranges of strains. Principle of these fatigue-arrestor bolts also applicable to holes in plates made of other materials and/or used for different purposes.

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

Science.gov (United States)

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

2016-08-01

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

Fatigue Fighters in Sjogren's Syndrome

Science.gov (United States)

... your doctor to find a specific cause and treatment for your fatigue. The possibilities may include systemic inflammation, poor sleep, fibromyalgia, depression, hypothyroidism, muscle inflammation or side-effects of medications. Know ...

Fatigue following Acute Q-Fever: A Systematic Literature Review

Science.gov (United States)

Delsing, Corine E.; Bleijenberg, Gijs; Langendam, Miranda; Timen, Aura; Bleeker-Rovers, Chantal P.

2016-01-01

Background Long-term fatigue with detrimental effects on daily functioning often occurs following acute Q-fever. Following the 2007–2010 Q-fever outbreak in the Netherlands with over 4000 notified cases, the emphasis on long-term consequences of Q-fever increased. The aim of this study was to provide an overview of all relevant available literature, and to identify knowledge gaps regarding the definition, diagnosis, background, description, aetiology, prevention, therapy, and prognosis, of fatigue following acute Q-fever. Design A systematic review was conducted through searching Pubmed, Embase, and PsycInfo for relevant literature up to 26th May 2015. References of included articles were hand searched for additional documents, and included articles were quality assessed. Results Fifty-seven articles were included and four documents classified as grey literature. The quality of most studies was low. The studies suggest that although most patients recover from fatigue within 6–12 months after acute Q-fever, approximately 20% remain chronically fatigued. Several names are used indicating fatigue following acute Q-fever, of which Q-fever fatigue syndrome (QFS) is most customary. Although QFS is described to occur frequently in many countries, a uniform definition is lacking. The studies report major health and work-related consequences, and is frequently accompanied by nonspecific complaints. There is no consensus with regard to aetiology, prevention, treatment, and prognosis. Conclusions Long-term fatigue following acute Q-fever, generally referred to as QFS, has major health-related consequences. However, information on aetiology, prevention, treatment, and prognosis of QFS is underrepresented in the international literature. In order to facilitate comparison of findings, and as platform for future studies, a uniform definition and diagnostic work-up and uniform measurement tools for QFS are proposed. PMID:27223465

Fatigue data for polyether ether ketone (PEEK) under fully-reversed cyclic loading.

Science.gov (United States)

Shrestha, Rakish; Simsiriwong, Jutima; Shamsaei, Nima

2016-03-01

In this article, the data obtained from the uniaxial fully-reversed fatigue experiments conducted on polyether ether ketone (PEEK), a semi-crystalline thermoplastic, are presented. The tests were performed in either strain-controlled or load-controlled mode under various levels of loading. The data are categorized into four subsets according to the type of tests, including (1) strain-controlled fatigue tests with adjusted frequency to obtain the nominal temperature rise of the specimen surface, (2) strain-controlled fatigue tests with various frequencies, (3) load-controlled fatigue tests without step loadings, and (4) load-controlled fatigue tests with step loadings. Accompanied data for each test include the fatigue life, the maximum (peak) and minimum (valley) stress-strain responses for each cycle, and the hysteresis stress-strain responses for each collected cycle in a logarithmic increment. A brief description of the experimental method is also given.

Understanding Muscle Dysfunction in Chronic Fatigue Syndrome

Directory of Open Access Journals (Sweden)

Gina Rutherford

2016-01-01

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

CNS fatigue provoked by prolonged exercise in the heat

DEFF Research Database (Denmark)

Nybo, Lars

2010-01-01

to the brain. However, exercise with superimposed hyperthermia is not only a challenge to the brain it also provides an excellent model for studying factors of importance for central fatigue. Excessive heat storage within the brain appears to be the primary cause for the central fatigue during exercise......Exercise-induced hyperthermia is associated with central fatigue as indicated by an impaired ability to sustain maximal motor activation during prolonged voluntary efforts. Therefore, exercise in hot environments challenges not only to the cardiorespiratory and locomotive systems but also...... to aggravate central fatigue and degrade exercise performance. Hyperthermia mediated central fatigue may include other cerebral perturbations such as reduced perfusion of the brain, accumulation of ammonia or depletion of neuronal energy stores, but further research is needed to elucidate their possible...

Stress-based fatigue assessment of major component in NPP using modified Green's function approach

International Nuclear Information System (INIS)

Ko, Han Ok; Jhung, Myung Jo; Choi, Jae Boong

2013-01-01

In this paper, the modified GFA which can consider temperature-dependent material properties is proposed by using a neural network (NN) and weight factor. To verify the modified GFA, thermal stresses by the proposed method are compared with those by FEM. Finally, pros and cons of the new method as well as technical findings from the assessment are discussed to show applicability of them. In this paper, the modified GFA considering temperature-dependent material properties is proposed by using NN and weight factor. To verify the proposed method, thermal stresses by the modified Green's function are compared with those by FEM and the results between two methods show a good agreement. Finally, it is anticipated that more precise fatigue evaluation is performed by using the proposed method. Recently, 434 nuclear reactors are being operated in the world. Among them, about 40% reactors are being operated beyond their design life or will be approaching their life. During the long term operation, various degradation mechanisms are occurred. Fatigue damage caused by alternating operational stresses in terms of temperature or pressure change is the one of important damage mechanisms in the nuclear power plants (NPPs). Although components important to safety were designed to withstand the fatigue damage, cumulative usage factor (CUF) at some locations can exceed the design limit beyond the design life. So, it is necessary to monitor the fatigue damage of major components during the long term operation. Researches on fatigue monitoring system (FMS) have been widely performed. In USA, the FatiguePro was developed by EPRI and was applied to the CE, WEC, B and W and GE type reactors. In Korea, the Kori unit 1 which started commercial operation in 1978 is being operated beyond its design life. At the stage of the license renewal, various plans for degradation mechanisms were established and reviewed. And, in case of fatigue damage, to monitor the fatigue damage of major components

Application of a unified fatigue modelling to some thermomechanical fatigue problems

International Nuclear Information System (INIS)

Dang, K. van; Maitournam, H.; Moumni, Z.

2005-01-01

Fatigue under thermomechanical loadings is an important topic for nuclear industries. For instance, thermal fatigue cracking is observed in the mixing zones of the nuclear reactor. Classical computations using existing methods based on strain amplitude or fracture mechanics are not sufficiently predictive. In this paper an alternative approach is proposed based on a multiscale modelling thanks to shakedown hypothesis. Examples of predictive results are presented. Finally an application to the RHR problem is discussed. Main ideas of the fatigue modelling: Following an idea of Professor D. Drucker who wrote in 1963 'when applied to the microstructure there is a hope that the concept of endurance limit and shakedown are related, and that fatigue failure can be related to energy dissipated in idealized material when shakedown does not occur.' we have developed a theory of fatigue based on this concept which is different from classical fatigue approaches. Many predictive applications have been already done particularly for the automotive industry. Fatigue resistance of structures undergoing thermomechanical loadings in the high cycle regime as well as in the low cycle regime are calculated using this modelling. However, this fatigue theory is until now rarely used in nuclear engineering. After recalling the main points of the theory, we shall present some relevant applications which were done in different industrial sectors. We shall apply this modelling to the prediction of thermal cracking observed in the mixing zones of RHR. (authors)

Common-Reliability Cumulative-Binomial Program

Science.gov (United States)

Scheuer, Ernest, M.; Bowerman, Paul N.

1989-01-01

Cumulative-binomial computer program, CROSSER, one of set of three programs, calculates cumulative binomial probability distributions for arbitrary inputs. CROSSER, CUMBIN (NPO-17555), and NEWTONP (NPO-17556), used independently of one another. Point of equality between reliability of system and common reliability of components found. Used by statisticians and users of statistical procedures, test planners, designers, and numerical analysts. Program written in C.

Cumulative effects assessment: Does scale matter?

International Nuclear Information System (INIS)

Therivel, Riki; Ross, Bill

2007-01-01

Cumulative effects assessment (CEA) is (or should be) an integral part of environmental assessment at both the project and the more strategic level. CEA helps to link the different scales of environmental assessment in that it focuses on how a given receptor is affected by the totality of plans, projects and activities, rather than on the effects of a particular plan or project. This article reviews how CEAs consider, and could consider, scale issues: spatial extent, level of detail, and temporal issues. It is based on an analysis of Canadian project-level CEAs and UK strategic-level CEAs. Based on a review of literature and, especially, case studies with which the authors are familiar, it concludes that scale issues are poorly considered at both levels, with particular problems being unclear or non-existing cumulative effects scoping methodologies; poor consideration of past or likely future human activities beyond the plan or project in question; attempts to apportion 'blame' for cumulative effects; and, at the plan level, limited management of cumulative effects caused particularly by the absence of consent regimes. Scale issues are important in most of these problems. However both strategic-level and project-level CEA have much potential for managing cumulative effects through better siting and phasing of development, demand reduction and other behavioural changes, and particularly through setting development consent rules for projects. The lack of strategic resource-based thresholds constrains the robust management of strategic-level cumulative effects

Cumulative cultural learning: Development and diversity

Science.gov (United States)

2017-01-01

The complexity and variability of human culture is unmatched by any other species. Humans live in culturally constructed niches filled with artifacts, skills, beliefs, and practices that have been inherited, accumulated, and modified over generations. A causal account of the complexity of human culture must explain its distinguishing characteristics: It is cumulative and highly variable within and across populations. I propose that the psychological adaptations supporting cumulative cultural transmission are universal but are sufficiently flexible to support the acquisition of highly variable behavioral repertoires. This paper describes variation in the transmission practices (teaching) and acquisition strategies (imitation) that support cumulative cultural learning in childhood. Examining flexibility and variation in caregiver socialization and children’s learning extends our understanding of evolution in living systems by providing insight into the psychological foundations of cumulative cultural transmission—the cornerstone of human cultural diversity. PMID:28739945

Cumulative cultural learning: Development and diversity.

Science.gov (United States)

Legare, Cristine H

2017-07-24

The complexity and variability of human culture is unmatched by any other species. Humans live in culturally constructed niches filled with artifacts, skills, beliefs, and practices that have been inherited, accumulated, and modified over generations. A causal account of the complexity of human culture must explain its distinguishing characteristics: It is cumulative and highly variable within and across populations. I propose that the psychological adaptations supporting cumulative cultural transmission are universal but are sufficiently flexible to support the acquisition of highly variable behavioral repertoires. This paper describes variation in the transmission practices (teaching) and acquisition strategies (imitation) that support cumulative cultural learning in childhood. Examining flexibility and variation in caregiver socialization and children's learning extends our understanding of evolution in living systems by providing insight into the psychological foundations of cumulative cultural transmission-the cornerstone of human cultural diversity.

Mild traumatic brain injury and fatigue: a prospective longitudinal study.

Science.gov (United States)

Norrie, Joan; Heitger, Marcus; Leathem, Janet; Anderson, Tim; Jones, Richard; Flett, Ross

2010-01-01

To examine fatigue prevalence, severity, predictors and co-variates over 6 months post-mild traumatic brain injury (MTBI). Longitudinal prospective study including 263 adults with MTBI. Participants completed the Fatigue Severity Scale (FSS), Rivermead Post-concussion Symptoms Questionnaire (RPSQ), Hospital Anxiety and Depression Scale (HADS) and the Short Form 36 Health Survey-Version 2 (SF-36v2). Complete data were available for 159 participants. Key measures; prevalence--RPSQ Item 6: severity--FSS. The effect of time on fatigue prevalence and severity was examined using ANOVA. Multiple regression analysis identified statistically significant covariates. Post-MTBI fatigue prevalence was 68%, 38% and 34% at 1 week, 3 and 6 months, respectively. There was a strong effect for time over the first 3 months and moderate-to-high correlations between fatigue prevalence and severity. Early fatigue strongly predicted later fatigue; depression, but not anxiety was a predictor. Fatigue was seen as laziness by family or friends in 30% of cases. Post-MTBI fatigue is a persistent post-concussion symptom, exacerbated by depression but not anxiety. It diminishes in the first 3 months and then becomes relatively stable, suggesting the optimum intervention placement is at 3 months or more post-MTBI.

Influence of Exergaming on the Perception of Cancer-Related Fatigue.

Science.gov (United States)

da Silva Alves, Ricardo; Iunes, Denise Hollanda; Pereira, Isabela Carvalho; Borges, Juliana Bassalobre Carvalho; Nogueira, Denismar Alves; Silva, Andreia Maria; Lobato, Daniel Ferreira Moreira; Carvalho, Leonardo Cesar

2017-04-01

Exercise is recommended for cancer patients to reduce fatigue and improve quality of life. This study's aim is to evaluate the influence of an exergaming protocol on cancer-related fatigue, muscle fatigue, and muscle strength in cancer patients. We conducted a quasi-experimental control study using exergaming in all groups through an Xbox360 Kinect™ console, two to three times per week, for 20 sessions. Three groups were created: cancer patients in chemotherapy and/or radiotherapy group (CRG; n:15), cancer patients after chemotherapy and/or radiotherapy (CAG; n:15), and a control group (CG; n:15). They were assessed for cancer-related fatigue using the fatigue subscale of the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) questionnaire. To assess dorsiflexor and plantar flexor muscle functioning, we used median frequency (MDF) of the surface electromyography and muscle strength using a dynamometer. The assessments were performed preintervention (EV0), after 10 sessions (EV1), and after 20 sessions (EV2). With an exergaming protocol, CRG and CAG showed a reduction in related fatigue compared with CG (P fatigue, including muscle fatigue, and increasing muscle strength in patients' legs.

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

Directory of Open Access Journals (Sweden)

Sergio Márquez-Domínguez

2012-06-01

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

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

International Nuclear Information System (INIS)

Cabet, Celine; Carroll, Laura; Wright, Richard

2013-01-01

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

Fatigue crack growth in an aluminum alloy-fractographic study

Science.gov (United States)

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

2016-08-01

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

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

OpenAIRE

Inoue, T.; Nagao, R.; Takeda, N.

2016-01-01

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 u...

Summary report of a workshop on establishing cumulative effects thresholds : a suggested approach for establishing cumulative effects thresholds in a Yukon context

International Nuclear Information System (INIS)

2003-01-01

Increasingly, thresholds are being used as a land and cumulative effects assessment and management tool. To assist in the management of wildlife species such as woodland caribou, the Department of Indian and Northern Affairs (DIAND) Environment Directorate, Yukon sponsored a workshop to develop and use cumulative thresholds in the Yukon. The approximately 30 participants reviewed recent initiatives in the Yukon and other jurisdictions. The workshop is expected to help formulate a strategic vision for implementing cumulative effects thresholds in the Yukon. The key to success resides in building relationships with Umbrella Final Agreement (UFA) Boards, the Development Assessment Process (DAP), and the Yukon Environmental and Socio-Economic Assessment Act (YESAA). Broad support is required within an integrated resource management framework. The workshop featured discussions on current science and theory of cumulative effects thresholds. Potential data and implementation issues were also discussed. It was concluded that thresholds are useful and scientifically defensible. The threshold research results obtained in Alberta, British Columbia and the Northwest Territories are applicable to the Yukon. One of the best tools for establishing and tracking thresholds is habitat effectiveness. Effects must be monitored and tracked. Biologists must share their information with decision makers. Interagency coordination and assistance should be facilitated through the establishment of working groups. Regional land use plans should include thresholds. 7 refs.

Mediators of the effects on fatigue of pragmatic rehabilitation for chronic fatigue syndrome.

Science.gov (United States)

Wearden, Alison J; Emsley, Richard

2013-10-01

To examine potential mediators of the effect of pragmatic rehabilitation on improvements in fatigue following a randomized controlled trial for patients with chronic fatigue syndrome (CFS/ME) in primary care (IRCTN 74156610). Patients fulfilled the Oxford criteria for CFS. Ninety-five patients were randomized to pragmatic rehabilitation and 100 to general practitioner (GP) treatment as usual. The outcome was the Chalder fatigue scale score (0123 scoring) at end of treatment (20 weeks) and 1-year follow up (70 weeks). First, the effect of treatment on potential mediators was assessed. Then fatigue was regressed on significant mediators, treatment allocation, and baseline measures of fatigue and significant mediators. Reduction in limiting activities at 20 weeks mediated the positive effect of pragmatic rehabilitation on fatigue at 70 weeks (mediated effect size = -2.64, SE = 0.81, p = .001, proportion of effect mediated = 82.0%). Reduction in catastrophizing at 20 weeks mediated the positive effect of pragmatic rehabilitation on fatigue at 70 weeks (mediated effect size = -1.39, SE = 0.61, p = .023, proportion of effect mediated = 43.2%). Reductions in 70-week measures of fear avoidance, embarrassment avoidance, limiting activities, and all-or-nothing behavior all mediated improvement in fatigue at 70 weeks, although the causal direction of these cross-sectional effects cannot be determined. There were no between-group differences on measures of exercise capacity (a timed step test). Improvements in fatigue following pragmatic rehabilitation are related to changes in behavioral responses to and beliefs about fatigue.

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

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......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...... 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....

Effect of tensile holds on the deformation behaviour of a nickel base superalloy subjected to low cycle fatigue

Energy Technology Data Exchange (ETDEWEB)

Zrnik, J.; Semenak, J.; Wangyao, P.; Vrchovinsky, V.; Hornak, P. [Dept. of Materials Science, Technical Univ. of Kosice, Kosice (Slovakia)

2002-07-01

The deformation behaviour of the wrought nickel base superalloy EI698 VD has been investigated in conditions of low cycle fatigue. The tensile hold periods, imposing a constant stress into the fatigue loading, have been introduced at the maximum stress value. The individual hold periods were in the range of 1 minute to 10 hours. The fatigue tests were of tension-tension type defined by a stress ratio R = 0.027 and were conducted at temperature of 650 C. The tests were performed until fracture. The time to failure, the time to failure corresponding to total load at peak amplitude and the number of cycles to failure have been criteria to evaluate the deformation behaviour of the alloy subjected to complex cyclic creep loading. In order to predict lifetime of alloy, regarding the respective types cyclic test, the Kitagawa's modified the linear cumulative damage criterion has been considered. The two regression functions for applied hold period interval were proposed time to calculate the time to failure. The formulae can be used to predict the life of nickel base superalloy considering the specific conditions of low cycle fatigue with tensile hold period introduced at stress amplitude peaks. The failure analysis of fracture surfaces contributed to evaluation of the role of repeatedly reduced stress in damage process. (orig.)

Assessment of corrosion and fatigue damage to light water reactor metal containments

International Nuclear Information System (INIS)

Sinha, U.P.; Shah, V.N.; Smith, S.K.

1991-01-01

This paper presents a generic procedure for estimating aging damage, evaluating structural integrity, and identifying mitigation activities for safe operation of boiling water reactor (BWR) Mark I metal containments and ice-condenser type pressurized water reactor (PWR) cylindrical metal containments. The mechanisms of concern that can cause aging damage to these two types of containments are corrosion and fatigue. Assessment of fatigue damage to bellows is also described. Assessment of corrosion and fatigue damage described in this paper include: containment design features that are relevant to aging assessment, several corrosion and fatigue mechanisms, inspection of corrosion and fatigue damage, and mitigation of damage caused by these mechanisms. In addition, synergistic interaction between corrosion and fatigue is considered. Possible actions for mitigating aging include enhanced inspection methods, maintenance activities based on operating experience, and supplementary surveillance programs. Field experience related to aging of metal containments is reviewed. Finally, conclusions and recommendations are presented

The process of cognitive behaviour therapy for chronic fatigue syndrome: which changes in perpetuating cognitions and behaviour are related to a reduction in fatigue?

Science.gov (United States)

Heins, Marianne J; Knoop, Hans; Burk, William J; Bleijenberg, Gijs

2013-09-01

Cognitive behaviour therapy (CBT) can significantly reduce fatigue in chronic fatigue syndrome (CFS), but little is known about the process of change taking place during CBT. Based on a recent treatment model (Wiborg et al. J Psych Res 2012), we examined how (changes in) cognitions and behaviour are related to the decrease in fatigue. We included 183 patients meeting the US Centers for Disease Control criteria for CFS, aged 18 to 65 years, starting CBT. We measured fatigue and possible process variables before treatment; after 6, 12 and 18 weeks; and after treatment. Possible process variables were sense of control over fatigue, focusing on symptoms, self-reported physical functioning, perceived physical activity and objective (actigraphic) physical activity. We built multiple regression models, explaining levels of fatigue during therapy by (changes in) proposed process variables. We observed large individual variation in the patterns of change in fatigue and process variables during CBT for CFS. Increases in the sense of control over fatigue, perceived activity and self-reported physical functioning, and decreases in focusing on symptoms explained 20 to 46% of the variance in fatigue. An increase in objective activity was not a process variable. A change in cognitive factors seems to be related to the decrease in fatigue during CBT for CFS. The pattern of change varies considerably between patients, but changes in process variables and fatigue occur mostly in the same period. © 2013.

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

Directory of Open Access Journals (Sweden)

Grzegorz SZALA

2014-03-01

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

Calculating Cumulative Binomial-Distribution Probabilities

Science.gov (United States)

Scheuer, Ernest M.; Bowerman, Paul N.

1989-01-01

Cumulative-binomial computer program, CUMBIN, one of set of three programs, calculates cumulative binomial probability distributions for arbitrary inputs. CUMBIN, NEWTONP (NPO-17556), and CROSSER (NPO-17557), used independently of one another. Reliabilities and availabilities of k-out-of-n systems analyzed. Used by statisticians and users of statistical procedures, test planners, designers, and numerical analysts. Used for calculations of reliability and availability. Program written in C.

Some questions regarding the interaction of creep and fatigue

International Nuclear Information System (INIS)

James, L.A.

1975-04-01

Data are presented from fatigue-crack growth tests conducted on Type 304 S.S. in inert environments at elevated temperatures which show that the thermal-activation noted in similar tests run in air environments is not present in the inert environment. Similar observations from the literature are reviewed, including the observation that the time-dependency noted in tests conducted in elevated temperature air environments is also greatly suppressed in inert environments. These findings suggest that an interaction between the fatigue process and the corrosive air environments is responsible for the thermally activated time-dependent behavior often attributed to creep-fatigue interaction. Data are also presented which show that the fatigue-crack growth behavior of Type 304 S.S. subjected to significant creep damage prior to fatigue testing does not differ appreciably from the behavior of material not subjected to prior creep damage, again indicating minimal interaction between creep and fatigue. It is suggested that in the temperature range where pressure vessels and piping are generally designed to operate (i.e. below about one-half the absolute melting temperature of the alloy), the interaction between creep and fatigue is far less significant than once supposed, and that the major parameter interacting with the fatigue process is that of high-temperature corrosion. (39 references, 12 fig) (auth)

Low-cycle fatigue-cracking mechanisms in fcc crystalline materials

Science.gov (United States)

Zhang, P.; Qu, S.; Duan, Q. Q.; Wu, S. D.; Li, S. X.; Wang, Z. G.; Zhang, Z. F.

2011-01-01

The low-cycle fatigue (LCF) cracking behavior in various face-centered-cubic (fcc) crystalline materials, including Cu single crystals, bicrystals and polycrystals, Cu-Al and Cu-Zn alloys, ultrafine-grained (UFG) Al-Cu and Cu-Zn alloys, was systematically investigated and reviewed. In Cu single crystals, fatigue cracking always nucleates along slip bands and deformation bands. The large-angle grain boundary (GB) becomes the preferential site in bicrystals and polycrystals. In addition, fatigue cracking can also nucleate along slip bands and twin boundaries (TBs) in polycrystalline materials. However, shear bands and coarse deformation bands are observed to the preferential sites for fatigue cracking in UFG materials with a large number of GBs. Based on numerous observations on fatigue-cracking behavior, the fatigue-cracking mechanisms along slip bands, GBs, TBs, shear bands and deformation bands were systematically compared and classified into two types, i.e. shear crack and impingement crack. Finally, these fatigue-cracking behaviors are discussed in depth for a better understanding of their physical nature and the transition from intergranular to transgranular cracking in various fcc crystalline materials. These comprehensive results for fatigue damage mechanisms should significantly aid in obtaining the optimum design to further strengthen and toughen metallic materials in practice.

In situ fatigue-crack-propagation experiment

International Nuclear Information System (INIS)

Ermi, A.M.; Chin, B.A.

1981-01-01

An in-reactor fatigue experiment was conducted in the Oak Ridge Research Reactor to determine the effects of dynamic irradiation on fatigue crack propagation. Eight 20% cold-worked 316 stainless steel specimens were precracked to various initial crack lengths, linked together to form a chain, and inserted into a specially designed in-reactor fatigue machine. Test conditions included a maximum temperature of 460 0 C, an environment of sodium, a frequency of 1 cycle/min, and a stress ratio of 0.10. Results indicated that (1) no effects of dynamic irradiation were observed for a fluence of 1.5 x 10 21 n/cm 2 (E > 0.1 MeV); and (2) crack growth rates in elevated temperature sodium were a factor of 3 to 4 lower than in room temperature air

Cumulative human impacts on marine predators

DEFF Research Database (Denmark)

Maxwell, Sara M; Hazen, Elliott L; Bograd, Steven J

2013-01-01

Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact...

High-cycle fatigue properties of small-bore socket-welded pipe joint

International Nuclear Information System (INIS)

Maekawa, Akira; Noda, Michiyasu; Suzuki, Michiaki

2009-01-01

Piping and equipment in nuclear power plants are structures including many welded joints. Reliability of welded joints is one of high-priority issues to improve the safety of nuclear power plants. However, occurrence of fatigue failures in small-bore socket-welded pipe joints by high-cycle vibrations is still reported. In this study, fatigue experiments on a socket-welded joint of austenitic stainless steel pipe was conducted under excitation conditions similar to those in actual plants to investigate vibration characteristics and fatigue strength. It was found that the natural frequency of pipe with socket-welded joint gradually decreased as fatigue damage developed, according to the Miner rule for fatigue life evaluation. The results indicate that the fatigue life of the welded pipe joint could be estimated by monitoring the decreasing ratio of the natural frequency of the pipe. The evaluation of decreasing ratio of the natural frequency in addition to fatigue damage evaluation by the Miner rule could enhance the accuracy of fatigue life evaluation. (author)

Depression and fatigue in patients with multiple sclerosis.

Science.gov (United States)

Greeke, Emily E; Chua, Alicia S; Healy, Brian C; Rintell, David J; Chitnis, Tanuja; Glanz, Bonnie I

2017-09-15

Previous research has examined the components of depression and fatigue in multiple sclerosis (MS), but the findings have been inconsistent. The aim of this study was to explore the associations between overall and subscale scores of the Center for Epidemiologic Studies-Depression Scale (CES-D) and the Modified Fatigue Impact Scale (MFIS) as well as the longitudinal changes in scores in a large cohort of MS patients. MS subjects who completed a battery of patient reported outcome (PRO) measures including the CES-D and MFIS (N=435) were included in our analysis. At the first available MFIS measurement, Pearson's correlation coefficient was used to estimate the association between the CES-D and MFIS in terms of both total scores and subscale scores. In addition, the longitudinal change in each total score and subscale score was estimated using a linear mixed model, and the association between the measures in terms of longitudinal change was estimated using Pearson's correlation coefficient and linear mixed models. At baseline, 15% of subjects were classified as high on both depression and fatigue scales, 16% were classified as high on the fatigue scale only, and 9% were classified as high on the depression scale only. There was a high correlation between CES-D and MFIS total scores (r=0.62). High correlations were also observed between the somatic and retarded activity subscales of the CES-D and each of the MFIS subscales (r≥0.60). In terms of longitudinal change, the change over the first year between the CES-D and MFIS total scores showed a moderate correlation (r=0.49). Subjects with high fatigue scores but low depression scores at baseline were more likely than subjects with low baseline fatigue and depression scores to develop high depression scores at follow-up. Our study demonstrated that depression and fatigue in MS share several features and have a similar longitudinal course. But using cut-off scores to define depression and fatigue, our study also found

Irregular working hours and fatigue of cabin crew.

Science.gov (United States)

Castro, Marta; Carvalhais, José; Teles, Júlia

2015-01-01

Beyond workload and specific environmental factors, flight attendants can be exposed to irregular working hours, conflicting with their circadian rhythms and having a negative impact in sleep, fatigue, health, social and family life, and performance which is critical to both safety and security in flight operations. This study focuses on the irregular schedules of cabin crew as a trigger of fatigue symptoms in a wet lease Portuguese airline. The aim was to analyze: what are the requirements of the cabin crew work; whether the schedules being observed and effective resting timeouts are triggering factors of fatigue; and the existence of fatigue symptoms in the cabin crew. A questionnaire has been adapted and applied to a sample of 73 cabin crew-members (representing 61.9% of the population), 39 females and 34 males, with an average age of 27.68 ± 4.27 years. Our data indicate the presence of fatigue and corresponding health symptoms among the airline cabin crew, despite of the sample favorable characteristics. Senior workers and women are more affected. Countermeasures are required. Recommendations can be made regarding the fatigue risk management, including work organization, education and awareness training programmes and specific countermeasures.

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

Science.gov (United States)

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

2015-10-01

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

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...

Chemotherapy-Induced Fatigue Correlates With Higher Fatigue Scores Before Treatment.

Science.gov (United States)

Araújo, José Klerton Luz; Giglio, Adriana Del; Munhoz, Bruna Antenusse; Fonseca, Fernando Luiz Affonso; Cruz, Felipe Melo; Giglio, Auro Del

2017-06-01

Cancer chemotherapy can induce fatigue in about 20% to 30% of patients. So far, there is very little information as to the predictors of chemotherapy-induced fatigue (CIF). We evaluated potential predictors of CIF in a sample of patients with cancer with several types of solid tumors scheduled to receive chemotherapy according to institutional protocols. Before their first and second chemotherapy cycles, patients answered to the Brief Fatigue Inventory (BFI), Chalder, Mini Nutritional Assessment (MNA), Stress thermometer, and HADS questionnaires as well as provided blood samples for inflammatory markers. We evaluated 52 patients, 37 (71%) were female and mean age was 53 years. The most common tumors were breast cancer 21 (40%) and gastrointestinal tumors 12 (23%). Although 14 (25.2%) patients had an increase in their fatigue BFI scores equal or above 3 points from baseline, we observed no significant overall differences between BFI scores before and after chemotherapy. The only 2 factors associated with an increase of 3 points in the BFI scores after chemotherapy were race and higher baseline BFI levels. By multivariate analysis, overall BFI and Chalder scores after chemotherapy also correlated significantly with their respective baseline scores before treatment. HADS scores before treatment correlated with overall BFI scores postchemotherapy, whereas MNA scores before chemotherapy and female sex correlated with higher Chalder scores after treatment. We conclude that fatigue induced by chemotherapy is common and consistently associated with higher fatigue scores before treatment. Screening for fatigue before chemotherapy may help to identify patients who are prone to develop CIF.

Fatigue analysis of welding seams in automotive structures

International Nuclear Information System (INIS)

Halaszi, C.; Gaier, C.; Dannbauer, H.; Hofwimmer, K.

2006-01-01

For lightweight automotive structures, the stiffness and the fatigue behavior is greatly influenced by the properties of the joints. The joining technology used and the number and locations of the joints are of high importance for both engineers and cost accountants. An overview of common computational procedures including European and national standards is given for the assessments of the fatigue behavior of thin sheet structures with arc welds. The influence of the quality and size of finite shell elements on the fatigue results are investigated and it is shown how this influence can be minimized. (author)

The effect of creep cavitation on the fatigue life under creep-fatigue interaction

International Nuclear Information System (INIS)

Nam, S.W.

1995-01-01

Low cycle fatigue tests have been carried out with three different materials (1Cr-Mo-V steel, 12Cr-Mo-V steel and 304 stainless steel) for the investigation of the effect of surface roughness on the fatigue life. To see the effect systematically, we have chosen those materials which may or may not form grain boundary cavities.Test results show that the continuous fatigue life of 1Cr-Mo-V steel and aged 304 stainless steel with a rough surface is decreased compared with that of the specimens with a smooth surface. These two alloys are found to have no grain boundary cavities formed under creep-fatigue test conditions. On the contrary, the fatigue life of 12Cr-Mo-V steel and solutionized 304 stainless steel in which grain boundary cavities are formed under creep-fatigue test conditions is not influenced by the states of surface roughness.The characteristic test results strongly confirm that the fatigue life of the specimen under creep-fatigue interaction, during which creep cavities are forming, may be controlled by the cavity nucleation and growth processes rather than the process of surface crack initiation. ((orig.))

Understanding the meaning of fatigue at the end of life: an ethnoscience approach.

Science.gov (United States)

Kirshbaum, Marilynne N; Olson, Kärin; Pongthavornkamol, Kanaungnit; Graffigna, Guendalina

2013-04-01

Fatigue is a devastating state of body and mind associated with distress at the end of life. We report the results of the third in a series of papers outlining a novel approach we have developed for understanding the meaning of fatigue by exploring how this meaning is shaped by beliefs and values. The aims of the study were to examine the perception and experiences of fatigue held by patients attending a hospice in England; identify the behavioural patterns that distinguish fatigue from tiredness and exhaustion; provide conceptual definitions of tiredness, fatigue and exhaustion. An Ethnoscience design was selected. The sample comprised nine people who attended a hospice between May and December 2009. Inclusion criteria included: at least 18 years of age, experiencing fatigue, able to provide informed consent and resident in the selected city in northern England for 10 years. Data were collected from two consecutive semi-structured interviews for each participant. We found that tiredness, fatigue and exhaustion are markers of progressive functional decline. Fatigue had two dimensions: 1) Mental Challenge, which included: emotional effects, cognitive realisation of decline and mental tenacity and 2) Physical Challenge, which included: limitations in leisure activities, limitations in functional roles and re-patterning routines. This study provides evidence that symptom experience is socially constructed, which has potential implications for the development of effective interventions. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

Fatigue fracture analysis in medium carbon structural steel and austenitic stainless steel by X-ray fractography

International Nuclear Information System (INIS)

Rao, N.N.; Azmi bin Rahmat

1994-01-01

Apart from the reidual stresses present in the bulk material, a growing fatigue crack may develop its own stress field ahead of the crack tip which in turn could influence the crack propagation behaviour. A fracture surface analysis through measurement of the residual stress of a failed component may provide some additional useful information to that obtained through conventional metallurgical and fracture mechanics investigations. This method of fracture surface analysis using x-ray diffraction technique is known as X -ray Fractography . Residual stress (ρ sub γ) and the full width at half maximum (FWHM) of the x-ray diffraction profile of any reflection are determined at different crack lengths on the fracture surface. These are then corelated to the fracture toughness parameters such as fracture toughness K sub I sub C, the maximum stress intensity factor K sub max and the stress intensity factor range δK. The present investigation aims at detailed x-ray analysis of the fatigue fractured surfaces of the compact tension specimens prepared from ferritic and austenitic stainless steels. The ferritic steel has been subjected to various heat treatments to obtain different microstructures and mechanical properties. The overall observations are analyzed through fatigue (cumulative) damage and material science concepts

Mechanisms of aging and fatigue in ferroelectrics

Energy Technology Data Exchange (ETDEWEB)

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

2015-02-15

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

Mechanisms of aging and fatigue in ferroelectrics

International Nuclear Information System (INIS)

Genenko, Yuri A.; Glaum, Julia; Hoffmann, Michael J.; Albe, Karsten

2015-01-01

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

An analysis of cumulative risks based on biomonitoring data for six phthalates using the Maximum Cumulative Ratio

Science.gov (United States)

The Maximum Cumulative Ratio (MCR) quantifies the degree to which a single chemical drives the cumulative risk of an individual exposed to multiple chemicals. Phthalates are a class of chemicals with ubiquitous exposures in the general population that have the potential to cause ...

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

Science.gov (United States)

Louwerens, Marloes; Appelhof, Bente C; Verloop, Herman; Medici, Marco; Peeters, Robin P; Visser, Theo J; Boelen, Anita; Fliers, Eric; Smit, Johannes W A; Dekkers, Olaf M

2012-12-01

Research on determinants of well-being in patients on thyroid hormone replacement therapy is warranted, as persistent fatigue-related complaints are common in this population. In this study, we evaluated the impact of different states of hypothyroidism on fatigue and fatigue-related symptoms. Furthermore, the relationship between fatigue and the TSH receptor (TSHR)-Asp727Glu polymorphism, a common genetic variant of the TSHR, was analyzed. A cross-sectional study was performed in 278 patients (140 patients treated for differentiated thyroid carcinoma (DTC) and 138 with autoimmune hypothyroidism (AIH)) genotyped for the TSHR-Asp727Glu polymorphism. The multidimensional fatigue inventory (MFI-20) was used to assess fatigue, with higher MFI-20 scores indicating more fatigue-related complaints. MFI-20 scores were related to disease status and Asp727Glu polymorphism status. AIH patients scored significantly higher than DTC patients on all five MFI-20 subscales (P<0.001), independent of clinical and thyroid hormone parameters. The frequency of the TSHR-Glu727 allele was 7.2%. Heterozygous DTC patients had more favorable MFI-20 scores than wild-type DTC patients on four of five subscales. The modest effect of the TSHR-Asp727Glu polymorphism on fatigue was found in DTC patients only. AIH patients had significantly higher levels of fatigue compared with DTC patients, which could not be attributed to clinical or thyroid hormone parameters. The modest effect of the TSHR-Asp727Glu polymorphism on fatigue in DTC patients should be confirmed in other cohorts.

The EPA's human exposure research program for assessing cumulative risk in communities.

Science.gov (United States)

Zartarian, Valerie G; Schultz, Bradley D

2010-06-01

Communities are faced with challenges in identifying and prioritizing environmental issues, taking actions to reduce their exposures, and determining their effectiveness for reducing human health risks. Additional challenges include determining what scientific tools are available and most relevant, and understanding how to use those tools; given these barriers, community groups tend to rely more on risk perception than science. The U.S. Environmental Protection Agency's Office of Research and Development, National Exposure Research Laboratory (NERL) and collaborators are developing and applying tools (models, data, methods) for enhancing cumulative risk assessments. The NERL's "Cumulative Communities Research Program" focuses on key science questions: (1) How to systematically identify and prioritize key chemical stressors within a given community?; (2) How to develop estimates of exposure to multiple stressors for individuals in epidemiologic studies?; and (3) What tools can be used to assess community-level distributions of exposures for the development and evaluation of the effectiveness of risk reduction strategies? This paper provides community partners and scientific researchers with an understanding of the NERL research program and other efforts to address cumulative community risks; and key research needs and opportunities. Some initial findings include the following: (1) Many useful tools exist for components of risk assessment, but need to be developed collaboratively with end users and made more comprehensive and user-friendly for practical application; (2) Tools for quantifying cumulative risks and impact of community risk reduction activities are also needed; (3) More data are needed to assess community- and individual-level exposures, and to link exposure-related information with health effects; and (4) Additional research is needed to incorporate risk-modifying factors ("non-chemical stressors") into cumulative risk assessments. The products of this

Cumulative Environmental Management Association : Wood Buffalo Region

International Nuclear Information System (INIS)

Friesen, B.

2001-01-01

The recently announced oil sands development of the Wood Buffalo Region in Alberta was the focus of this power point presentation. Both mining and in situ development is expected to total $26 billion and 2.6 million barrels per day of bitumen production. This paper described the economic, social and environmental challenges facing the resource development of this region. In addition to the proposed oil sands projects, this region will accommodate the needs of conventional oil and gas production, forestry, building of pipelines and power lines, municipal development, recreation, tourism, mining exploration and open cast mining. The Cumulative Environmental Management Association (CEMA) was inaugurated as a non-profit association in April 2000, and includes 41 members from all sectors. Its major role is to ensure a sustainable ecosystem and to avoid any cumulative impacts on wildlife. Other work underway includes the study of soil and plant species diversity, and the effects of air emissions on human health, wildlife and vegetation. The bioaccumulation of heavy metals and their impacts on surface water and fish is also under consideration to ensure the quality and quantity of surface water and ground water. 3 figs

Cumulative irritation potential of topical retinoid formulations.

Science.gov (United States)

Leyden, James J; Grossman, Rachel; Nighland, Marge

2008-08-01

Localized irritation can limit treatment success with topical retinoids such as tretinoin and adapalene. The factors that influence irritant reactions have been shown to include individual skin sensitivity, the particular retinoid and concentration used, and the vehicle formulation. To compare the cutaneous tolerability of tretinoin 0.04% microsphere gel (TMG) with that of adapalene 0.3% gel and a standard tretinoin 0.025% cream. The results of 2 randomized, investigator-blinded studies of 2 to 3 weeks' duration, which utilized a split-face method to compare cumulative irritation scores induced by topical retinoids in subjects with healthy skin, were combined. Study 1 compared TMG 0.04% with adapalene 0.3% gel over 2 weeks, while study 2 compared TMG 0.04% with tretinoin 0.025% cream over 3 weeks. In study 1, TMG 0.04% was associated with significantly lower cumulative scores for erythema, dryness, and burning/stinging than adapalene 0.3% gel. However, in study 2, there were no significant differences in cumulative irritation scores between TMG 0.04% and tretinoin 0.025% cream. Measurements of erythema by a chromameter showed no significant differences between the test formulations in either study. Cutaneous tolerance of TMG 0.04% on the face was superior to that of adapalene 0.3% gel and similar to that of a standard tretinoin cream containing a lower concentration of the drug (0.025%).

Chapter 19. Cumulative watershed effects and watershed analysis

Science.gov (United States)

Leslie M. Reid

1998-01-01

Cumulative watershed effects are environmental changes that are affected by more than.one land-use activity and that are influenced by.processes involving the generation or transport.of water. Almost all environmental changes are.cumulative effects, and almost all land-use.activities contribute to cumulative effects

Investigations into the fatigue behaviour of nuclear grades of austenitic stainless steel

International Nuclear Information System (INIS)

Mann, J.

2015-01-01

Full text of publication follows. Fatigue is an important problem within the nuclear industry due to the complex combination of thermal and mechanical loading that components experience during the operation of a nuclear reactor. Austenitic stainless steels are widely used within nuclear reactors for a number of applications including piping systems and pressure vessels. A number of studies have shown that austenitic stainless steel components operating within a light water reactor (LWR) environment may experience a significant reduction in fatigue life under certain circumstances, however the precise mechanisms responsible for the reduction are still not fully understood. The effects of environment are included in some fatigue assessment methods, however these are generally considered to be over-conservative and predicted fatigue lifetimes are not reflected well by service experience. This project aims to enhance the understanding of fatigue in both air and LWR environments through the synergistic use of a wide range of different microscopy techniques. It is expected that a better understanding of each of the different stages of fatigue will lead to more accurate fatigue predictions that ultimately result in better and safer lifetime predictions. This paper focuses on introducing the background behind the project, highlighting the current methods for assessing fatigue lifetimes and the motivations for the current research. The results of various initial microscopic investigations are presented, with a focus on a number of novel applications using laser scanning confocal microscopy to perform large scale analyses of fatigue fracture surfaces and test specimen gauge length surfaces. The use of surface replicas in conjunction with laser scanning confocal microscopy is discussed along with its potential applications for the assessment of fatigue damage in in-service components. Initial finite element modelling of crack growth within fatigue test specimens is discussed

Fatigue trajectories during the first 8 months after breast cancer diagnosis

DEFF Research Database (Denmark)

Bødtcher, Hanne; Bidstrup, Pernille Envold; Andersen, Ingelise

2015-01-01

Purpose The objective of this study was to identify distinct groups of fatigue trajectories among women with breast cancer and to evaluate whether age, anxiety symptoms, physical activity, and type of treatment were associated with belonging to the most adverse fatigue group. Methods Women...... scheduled for breast cancer surgery at Copenhagen University Hospital, Denmark, were consecutively invited to participate in the study (n = 424), resulting in 290 women included in the analyses. Semiparametric group-based mixture modeling was used to identify distinct trajectories of fatigue assessed......-fatigue group. Conclusions The results show that one-fifth of women with breast cancer experience continuously high fatigue up to 8 months after surgery and may have been more anxious and physically inactive. This knowledge is important in targeting interventions to women with fatigue throughout their treatment...

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

Science.gov (United States)

Okazaki, Yoshimitsu

2012-01-01

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

An Analysis of Cumulative Risks Indicated by Biomonitoring Data of Six Phthalates Using the Maximum Cumulative Ratio

Science.gov (United States)

The Maximum Cumulative Ratio (MCR) quantifies the degree to which a single component of a chemical mixture drives the cumulative risk of a receptor.1 This study used the MCR, the Hazard Index (HI) and Hazard Quotient (HQ) to evaluate co-exposures to six phthalates using biomonito...

Fatigue Assessment of Nickel-Titanium Peripheral Stents: Comparison of Multi-Axial Fatigue Models

Science.gov (United States)

Allegretti, Dario; Berti, Francesca; Migliavacca, Francesco; Pennati, Giancarlo; Petrini, Lorenza

2018-02-01

Peripheral Nickel-Titanium (NiTi) stents exploit super-elasticity to treat femoropopliteal artery atherosclerosis. The stent is subject to cyclic loads, which may lead to fatigue fracture and treatment failure. The complexity of the loading conditions and device geometry, coupled with the nonlinear material behavior, may induce multi-axial and non-proportional deformation. Finite element analysis can assess the fatigue risk, by comparing the device state of stress with the material fatigue limit. The most suitable fatigue model is not fully understood for NiTi devices, due to its complex thermo-mechanical behavior. This paper assesses the fatigue behavior of NiTi stents through computational models and experimental validation. Four different strain-based models are considered: the von Mises criterion and three critical plane models (Fatemi-Socie, Brown-Miller, and Smith-Watson-Topper models). Two stents, made of the same material with different cell geometries are manufactured, and their fatigue behavior is experimentally characterized. The comparison between experimental and numerical results highlights an overestimation of the failure risk by the von Mises criterion. On the contrary, the selected critical plane models, even if based on different damage mechanisms, give a better fatigue life estimation. Further investigations on crack propagation mechanisms of NiTi stents are required to properly select the most reliable fatigue model.

Fatigue Assessment of Nickel-Titanium Peripheral Stents: Comparison of Multi-Axial Fatigue Models

Science.gov (United States)

Allegretti, Dario; Berti, Francesca; Migliavacca, Francesco; Pennati, Giancarlo; Petrini, Lorenza

2018-03-01

Peripheral Nickel-Titanium (NiTi) stents exploit super-elasticity to treat femoropopliteal artery atherosclerosis. The stent is subject to cyclic loads, which may lead to fatigue fracture and treatment failure. The complexity of the loading conditions and device geometry, coupled with the nonlinear material behavior, may induce multi-axial and non-proportional deformation. Finite element analysis can assess the fatigue risk, by comparing the device state of stress with the material fatigue limit. The most suitable fatigue model is not fully understood for NiTi devices, due to its complex thermo-mechanical behavior. This paper assesses the fatigue behavior of NiTi stents through computational models and experimental validation. Four different strain-based models are considered: the von Mises criterion and three critical plane models (Fatemi-Socie, Brown-Miller, and Smith-Watson-Topper models). Two stents, made of the same material with different cell geometries are manufactured, and their fatigue behavior is experimentally characterized. The comparison between experimental and numerical results highlights an overestimation of the failure risk by the von Mises criterion. On the contrary, the selected critical plane models, even if based on different damage mechanisms, give a better fatigue life estimation. Further investigations on crack propagation mechanisms of NiTi stents are required to properly select the most reliable fatigue model.

Mechanical behavior and fatigue in polymeric composites at low temperatures

International Nuclear Information System (INIS)

Katz, Y.; Bussiba, A.; Mathias, H.

1986-01-01

Advanced fiber reinforced polymeric composite materials are often suggested as structural materials at low temperature. In this study, graphite epoxy and Kevlar-49/epoxy systems were investigated. Fatigue behavior was emphasized after establishing the standard monotonic mechanical properties, including fracture resistance parameters at 77, 190, and 296 K. Tension-tension fatigue crack propagation testing was carried out at nominal constant stress intensity amplitudes using precracked compact tensile specimens. The crack tip damage zone was measured and tracked by an electro-potential device, opening displacement gage, microscopic observation, and acoustic emission activity recording. Fractograhic and metallographic studies were performed with emphasis on fracture morphology and modes, failure processes, and description of sequential events. On the basis of these experimental results, the problem of fatigue resistance, including low temperature effects, is analyzed and discussed. The fundamental concepts of fatigue in composites are assessed, particularly in terms of fracture mechanics methods

Progress in the Research of Fatigue of Weathering Steel after Corrosion

Science.gov (United States)

Jianyu, Liang; Jian, Yao; Youwu, Xu

2017-12-01

Weathering steel has a good corrosion resistance in the atmosphere, and the application of weathering steel in civil structure also reduces the cost of painting and maintenance. It is also possible for the bare weathering steel to bear the fatigue load with a rust layer. This paper summarizes the fatigue researches after corrosion of weathering steel, including the shape of specimens, failure modes of fatigue and the conclusions obtained through experimental investigations. It is also introduced the fatigue model of weathering steel after corrosion, which can be useful for the engineering application or further researches.

[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.

Is Fatigue a Common Crohn's Disease Symptom? What Can Be Done about It?

Science.gov (United States)

... other psychological factors that can impact fatigue, including stress, anxiety and depression. To fight fatigue, it's also helpful to include physical activity in your daily routine, eat healthy foods and get adequate sleep. Be sure to share ...

Development of a screening procedure for vibrational fatigue in small bore piping

International Nuclear Information System (INIS)

Smith, J.K.; Riccardella, P.C.; Gosselin, S.R.

1995-01-01

Approximately 80% of the documented fatigue failures in nuclear power plants are caused by high cycle vibrational fatigue. These failures typically occur in socket welded pipe fittings in small bore piping (2 in. nominal diameter and smaller). These failures have been unexpected, and have caused costly, unscheduled outages in some cases. In order to reduce the number of vibrational fatigue failures in operating nuclear power plants, a vibrational fatigue screening procedure has been developed under Electric Power Research Institute (EPRI) sponsorship. The purpose of this paper is to describe this procedure, and to discuss topics related to vibrational fatigue failures. These topics include sources of vibration in nuclear power plants, the effect of socket welds on vibrational fatigue failures, vibrational fatigue screening criteria for small bore piping systems, and good design practices for reducing the number of vibrational fatigue failures in small bore piping

Fatigue in out-patients with inflammatory bowel disease: Prevalence and predictive factors.

Science.gov (United States)

Villoria, Albert; García, Víctor; Dosal, Angelina; Moreno, Laura; Montserrat, Antònia; Figuerola, Ariadna; Horta, Diana; Calvet, Xavier; Ramírez-Lázaro, María José

2017-01-01

Fatigue is a common and bothersome symptom in inflammatory bowel disease (IBD) patients. The study was aimed to determine the relationship of biological and psychological factors with IBD-related fatigue. Consecutive clinically inactive IBD outpatients receiving immunosuppressants or biological drugs were enrolled between January and December 2013. Patients completed a Fatigue score (FACIT-F), various psychological, quality of life (IBDQ-9), and IBD activity scores. Biological parameters were assessed, including levels of interleukins (IL-5, IL-8 and IL-12) and micronutrients. We prospectively recruited 202 patients (28% ulcerative colitis and 72% Crohn's disease) for the study. Fatigue measured by FACIT-F score was prevalent in the studied population (54%, 96/177) and higher than in the general population. In the univariate analysis no relation was found between IL levels or micronutrient deficiencies and fatigue. Fatigue was significantly related to female sex, Crohn's disease, joint disorders, body mass index (BMI), psychological tests, thiopurine use, and anti-TNF treatment. All these variables were included in the multivariate analysis. Female sex (OR: 4.8), high BMI (OR:1.2) and higher depression rates (OR:1.2) were predictors of increased fatigue. High IBDQ-9 score (OR: 0.82) was significantly related to lower degrees of fatigue. Fatigue was prevalent in quiescent IBD patients with moderate-to-severe disease. It was associated with high levels of depression, low quality of life, and female sex. No association was found with the other biological and psychological factors evaluated.

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

DEFF Research Database (Denmark)

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

2015-01-01

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

Driving fatigue in professional drivers: a survey of truck and taxi drivers.

Science.gov (United States)

Meng, Fanxing; Li, Shuling; Cao, Lingzhi; Li, Musen; Peng, Qijia; Wang, Chunhui; Zhang, Wei

2015-01-01

Fatigue among truck drivers has been studied extensively; however, less is known regarding the fatigue experience of taxi drivers in heavily populated metropolitan areas. This study aimed to compare the differences and similarities between truck and taxi driver fatigue to provide implications for the fatigue management and education of professional drivers. A sample of 274 truck drivers and 286 taxi drivers in Beijing was surveyed via a questionnaire, which included items regarding work characteristics, fatigue experience, accident information, attitude toward fatigue, and methods of counteracting fatigue. Driver fatigue was prevalent among professional drivers, and it was even more serious for taxi drivers. Taxi drivers reported more frequent fatigue experiences and were involved in more accidents. Among the contributing factors to fatigue, prolonged driving time was the most important factor identified by both driver groups. Importantly, the reason for the engagement in prolonged driving was neither due to the lack of awareness concerning the serious outcome of fatigue driving nor because of their poor detection of fatigue. The most probable reason was the optimism bias, as a result of which these professional drivers thought that fatigue was more serious for other drivers than for themselves, and they thought that they were effective in counteracting the effect of fatigue on their driving performance. Moreover, truck drivers tended to employ methods that require stopping to counteract fatigue, whereas taxi drivers preferred methods that were simultaneous with driving. Although both driver groups considered taking a nap as one of the most effective means to address fatigue, this method was not commonly used. Interestingly, these drivers were aware that the methods they frequently used were not the most effective means to counteract fatigue. This study provides knowledge on truck and taxi drivers' characteristics in fatigue experience, fatigue attitude, and

Biologic interventions for fatigue in rheumatoid arthritis

DEFF Research Database (Denmark)

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

2016-01-01

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

Managing cumulative impacts: A key to sustainability?

Energy Technology Data Exchange (ETDEWEB)

Hunsaker, C.T.

1994-12-31

This paper addresses how science can be more effectively used in creating policy to manage cumulative effects on ecosystems. The paper focuses on the scientific techniques that we have to identify and to assess cumulative impacts on ecosystems. The term ``sustainable development`` was brought into common use by the World Commission on Environment and Development (The Brundtland Commission) in 1987. The Brundtland Commission report highlighted the need to simultaneously address developmental and environmental imperatives simultaneously by calling for development that ``meets the needs of the present generation without compromising the needs of future generations.`` We cannot claim to be working toward sustainable development until we can quantitatively assess cumulative impacts on the environment: The two concepts are inextricibally linked in that the elusiveness of cumulative effects likely has the greatest potential of keeping us from achieving sustainability. In this paper, assessment and management frameworks relevant to cumulative impacts are discussed along with recent literature on how to improve such assessments. When possible, examples are given for marine ecosystems.

Serotonergic dysfunctions and abnormal iron metabolism: Relevant to mental fatigue of Parkinson disease.

Science.gov (United States)

Zuo, Li-Jun; Yu, Shu-Yang; Hu, Yang; Wang, Fang; Piao, Ying-Shan; Lian, Teng-Hong; Yu, Qiu-Jin; Wang, Rui-Dan; Li, Li-Xia; Guo, Peng; Du, Yang; Zhu, Rong-Yan; Jin, Zhao; Wang, Ya-Jie; Wang, Xiao-Min; Chan, Piu; Chen, Sheng-Di; Wang, Yong-Jun; Zhang, Wei

2016-12-21

Fatigue is a very common non-motor symptom in Parkinson disease (PD) patients. It included physical fatigue and mental fatigue. The potential mechanisms of mental fatigue involving serotonergic dysfunction and abnormal iron metabolism are still unknown. Therefore, we evaluated the fatigue symptoms, classified PD patients into fatigue group and non-fatigue group, and detected the levels of serotonin, iron and related proteins in CSF and serum. In CSF, 5-HT level is significantly decreased and the levels of iron and transferrin are dramatically increased in fatigue group. In fatigue group, mental fatigue score is negatively correlated with 5-HT level in CSF, and positively correlated with the scores of depression and excessive daytime sleepiness, and disease duration, also, mental fatigue is positively correlated with the levels of iron and transferrin in CSF. Transferrin level is negatively correlated with 5-HT level in CSF. In serum, the levels of 5-HT and transferrin are markedly decreased in fatigue group; mental fatigue score exhibits a negative correlation with 5-HT level. Thus serotonin dysfunction in both central and peripheral systems may be correlated with mental fatigue through abnormal iron metabolism. Depression, excessive daytime sleepiness and disease duration were the risk factors for mental fatigue of PD.

Residual Fatigue Properties of Asphalt Pavement after Long-Term Field Service

Directory of Open Access Journals (Sweden)

Peide Cui

2018-05-01

Full Text Available Asphalt pavement is widely used for expressways due to its advantages of flexibility, low cost, and easy maintenance. However, pavement failures, including cracking, raveling, and potholes, will appear after long-term service. This research evaluated the residual fatigue properties of asphalt pavement after long-term field service. Fatigue behavior of specimens with different pavement failure types, traffic load, service time, and layers were collected and characterized. Results indicate that after long-term field service, surface layer has a longer fatigue life under small stress levels, but shorter fatigue life under large stress levels. Longer service time results in greater sensitivity to loading stress, while heavier traffic results in shorter fatigue life. Surface and underneath layers present very close fatigue trend lines in some areas, indicating that the fatigue behavior of asphalt mixture in surface and underneath layers are aged to the same extent after eight to ten years of field service.

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

Assessment of early onset of driver fatigue using multimodal fatigue measures in a static simulator.

Science.gov (United States)

Jagannath, M; Balasubramanian, Venkatesh

2014-07-01

Driver fatigue is an important contributor to road accidents. This paper reports a study that evaluated driver fatigue using multimodal fatigue measures, i.e., surface electromyography (sEMG), electroencephalography (EEG), seat interface pressure, blood pressure, heart rate and oxygen saturation level. Twenty male participants volunteered in this study by performing 60 min of driving on a static simulator. Results from sEMG showed significant physical fatigue (ρ fatigue. This will help us understand the influence of physical and mental fatigue on driver during monotonous driving. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

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

NARCIS (Netherlands)

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

2012-01-01

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

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

NARCIS (Netherlands)

Louwerens, Marloes; Appelhof, Bente C.; Verloop, Herman; Medici, Marco; Peeters, Robin P.; Visser, Theo J.; Boelen, Anita; Fliers, Eric; Smit, Johannes W. A.; Dekkers, Olaf M.

2012-01-01

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

Fatigue tests and life estimation of Incoloy alloy 908

International Nuclear Information System (INIS)

Feng, J.; Toma, L.S.; Jang, C.H.; Steeves, M.M.

1997-01-01

Incoloy reg-sign alloy 908* is a candidate conduit material for Nb 3 Sn cable-in-conduit superconductors. The conduit is expected to experience cyclic loads at 4 K. Fatigue fracture of the conduit is one possible failure mode. So far, fatigue life has been estimated from fatigue crack growth data, which provide conservative results. The more traditional practice of life estimation using S-N curves has not been done for alloy 908 due to a lack of data at room and cryogenic temperatures. This paper presents a series of fatigue test results in response to this need. Tests were performed in reversed bending, rotating bending, and uniaxial fatigue machines. The test matrix included different heat treatments, two load ratios (R=-1 and 0.1), two temperatures (298 and 77 K), and two orientations (longitudinal and transverse). As expected, there is a semi-log linear relation between the applied stress and fatigue life above an applied stress (e.g., 310 MPa for tests at 298 K and R=-1). Below this stress the curves show an endurance limit. The aged and cold-worked materials have longer fatigue lives and higher endurance limits than the others. Different orientations have no apparent effect on life. Cryogenic temperature results in a much high fatigue life than room temperature. A higher tensile mean stress gives shorter fatigue life. It was also found that the fatigue lives of the reversed bending specimens were of the same order as those of the uniaxial test specimens, but were only half the lives of the rotating bending specimens for given stresses. A sample application of the S-N data is discussed

An Exploratory Study of Fatigue and Physical Activity in Canadian Thyroid Cancer Patients.

Science.gov (United States)

Alhashemi, Ahmad; Jones, Jennifer M; Goldstein, David P; Mina, Daniel Santa; Thabane, Lehana; Sabiston, Catherine M; Chang, Eugene K; Brierley, James D; Sawka, Anna M

2017-09-01

Fatigue is common among cancer survivors, but fatigue in thyroid cancer (TC) survivors may be under-appreciated. This study investigated the severity and prevalence of moderate and severe fatigue in TC survivors. Potential predictive factors, including physical activity, were explored. A cross-sectional, written, self-administered TC patient survey and retrospective chart review were performed in an outpatient academic Endocrinology clinic in Toronto, Canada. The primary outcome measure was the global fatigue score measured by the Brief Fatigue Inventory (BFI). Physical activity was evaluated using the International Physical Activity Questionnaire-7 day (IPAQ-7). Predictors of BFI global fatigue score were explored in univariate analyses and a multivariable linear regression model. The response rate was 63.1% (205/325). Three-quarters of the respondents were women (152/205). The mean age was 52.5 years, and the mean time since first TC surgery was 6.8 years. The mean global BFI score was 3.5 (standard deviation 2.4) out of 10 (10 is worst). The prevalence of moderate-severe fatigue (global BFI score 4.1-10 out of 10) was 41.4% (84/203). Individuals who were unemployed or unable to work due to disability reported significantly higher levels of fatigue compared to the rest of the study population, in uni-and multivariable analyses. Furthermore, increased physical activity was associated with reduced fatigue in uni- and multivariable analyses. Other socio-demographic, disease, or biochemical variables were not significantly associated with fatigue in the multivariable model. Moderate or severe fatigue was reported in about 4/10 TC survivors. Independent predictors of worse fatigue included unemployment and reduced physical activity.

Hyperthermia and fatigue

DEFF Research Database (Denmark)

Nybo, Lars

2008-01-01

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

Cumulative Risk Assessment Toolbox: Methods and Approaches for the Practitioner

Directory of Open Access Journals (Sweden)

Margaret M. MacDonell

2013-01-01

Full Text Available The historical approach to assessing health risks of environmental chemicals has been to evaluate them one at a time. In fact, we are exposed every day to a wide variety of chemicals and are increasingly aware of potential health implications. Although considerable progress has been made in the science underlying risk assessments for real-world exposures, implementation has lagged because many practitioners are unaware of methods and tools available to support these analyses. To address this issue, the US Environmental Protection Agency developed a toolbox of cumulative risk resources for contaminated sites, as part of a resource document that was published in 2007. This paper highlights information for nearly 80 resources from the toolbox and provides selected updates, with practical notes for cumulative risk applications. Resources are organized according to the main elements of the assessment process: (1 planning, scoping, and problem formulation; (2 environmental fate and transport; (3 exposure analysis extending to human factors; (4 toxicity analysis; and (5 risk and uncertainty characterization, including presentation of results. In addition to providing online access, plans for the toolbox include addressing nonchemical stressors and applications beyond contaminated sites and further strengthening resource accessibility to support evolving analyses for cumulative risk and sustainable communities.

Fatigue Crack Topography.

Science.gov (United States)

1984-01-01

alloys (2). [--I Fig. 6. Fatigue fracture in Nitrile- butadien rubber ( NBR ). Fig. 7. The characteristic features of fatigue fracture in press moulded...in plastics and even in rubber . It follows therefore, that fatigue fractures must also occur in the mineral layers of our earth or in the rock on...effective until the weakest point yields and forms a crack. To get a feeling for this process, you can imagine that the stressed article is made of rubber

[Patients with fatigue in family practice: prevalence and treatment].

Science.gov (United States)

Kenter, E G; Okkes, I M

1999-04-10

To gain insight into the prevalence and treatment of severe fatigue in general practice. Secondary data analysis. By means of an episode-oriented morbidity registration by 54 GPs throughout the Netherlands over the period 1985-1994 it was established how often in the course of one year 'fatigue' was listed as the reason for consultation, what diagnoses were then made, how long episodes of care because of 'fatigue' lasted and what interventions took place (n = 93,297). Of the patients with a care episode because of 'fatigue' lasting at least 6 months, age, sex, comorbidity and consumption of care were established; for this purpose use was also made of a file containing data on 4 years in succession (n = 9630). Per annum, 92 per 1000 listed patients consulted the GP because of fatigue. Somatic or psychic diagnoses were made in 27.7 per 1000 patients listed. The episode of care lasted 4 weeks at most in 86% and at least 6 months in approximately 4%. The GPs' management of patients with 'fatigue' included physical examination in 63% and blood testing in 34%, conversation in 35%, prescription of medication in 24% and referral to a specialist in 3%. Of the 97 patients with fatigue lasting longer than 6 months, 61% had a chronic disease or psychic problems. Fatigue is frequently encountered in general practice, but the estimate that one per 1000 listed patients meets the criteria of the chronic fatigue syndrome looks a little high. It appears that GPs, in accordance with recommendations, mostly adopt a policy of wait and see.

Analysis of sensory ratings data with cumulative link models

DEFF Research Database (Denmark)

Christensen, Rune Haubo Bojesen; Brockhoff, Per B.

2013-01-01

Examples of categorical rating scales include discrete preference, liking and hedonic rating scales. Data obtained on these scales are often analyzed with normal linear regression methods or with omnibus Pearson chi2 tests. In this paper we propose to use cumulative link models that allow for reg...

Functional assessment of chronic illness therapy—the fatigue scale exhibits stronger associations with clinical parameters in chronic dialysis patients compared to other fatigue-assessing instruments

Directory of Open Access Journals (Sweden)

Chia-Ter Chao

2016-03-01

Full Text Available Background. Patients with end-stage renal disease (ESRD have a high symptom burden, among which fatigue is highly prevalent. Many fatigue-assessing instruments exist, but comparisons among instruments in this patient population have yet to be investigated. Methods. ESRD patients under chronic hemodialysis were prospectively enrolled and seven types of fatigue instruments were administered: Brief Fatigue Inventory (BFI, Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT-F, Fatigue Severity Scale (FSS, Lee Fatigue Scale (LFS, Fatigue Questionnaire (FQ, Fatigue Symptom Inventory (FSI, and Short-Form 36-Vitality (SF36-V. Using these instruments, we investigated the correlation between fatigue severity and clinical/biochemical parameters, including demographic/comorbidity profile, dialysis-related complications, and frailty severity. We used regression analysis with serum albumin and frailty severity as the dependent variables to investigate the independent correlations. Results. A total of 46 ESRD patients were enrolled (average age of 67 ± 11.6 years, and 50% of them had type 2 diabetes mellitus. Results from the seven tested instruments showed high correlation with each other. We found that the fatigue severity by FACIT-F was significantly associated with age (p = 0.03, serum albumin (p = 0.003 and creatinine (p = 0.02 levels, while SF36-V scores were also significantly associated with age (p = 0.02 and serum creatinine levels (p = 0.04. However, the fatigue severity measured by the FSS, FSI, FQ, BFI, and LFS did not exhibit these associations. Moreover, regression analysis showed that only FACIT-F scores were independently associated with serum albumin levels and frailty severity in ESRD patients. Conclusion. Among the seven fatigue-assessing instruments, only the FACIT-F yielded results that demonstrated significant and independent associations with important outcome-related features in ESRD patients.

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-07-01

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

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

International Nuclear Information System (INIS)

Fissolo, Antoine; Gourdin, Cedric; Vincent, Ludovic

2009-01-01

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

Fatigue evaluation in reactor vessel components

International Nuclear Information System (INIS)

Mattar Neto, Miguel; Miranda, Carlos A. de J.

1994-01-01

This paper presents a sequence of increasing complexity forms of evaluating fatigue damage of nuclear pressure vessel components caused by cycling loadings. Examples are included in order to illustrate such procedures. (author)

Optimal Elbow Angle for Extracting sEMG Signals During Fatiguing Dynamic Contraction

Directory of Open Access Journals (Sweden)

Mohamed R. Al-Mulla

2015-09-01

Full Text Available Surface electromyographic (sEMG activity of the biceps muscle was recorded from 13 subjects. Data was recorded while subjects performed dynamic contraction until fatigue and the signals were segmented into two parts (Non-Fatigue and Fatigue. An evolutionary algorithm was used to determine the elbow angles that best separate (using Davies-Bouldin Index, DBI both Non-Fatigue and Fatigue segments of the sEMG signal. Establishing the optimal elbow angle for feature extraction used in the evolutionary process was based on 70% of the conducted sEMG trials. After completing 26 independent evolution runs, the best run containing the optimal elbow angles for separation (Non-Fatigue and Fatigue was selected and then tested on the remaining 30% of the data to measure the classification performance. Testing the performance of the optimal angle was undertaken on nine features extracted from each of the two classes (Non-Fatigue and Fatigue to quantify the performance. Results showed that the optimal elbow angles can be used for fatigue classification, showing 87.90% highest correct classification for one of the features and on average of all eight features (including worst performing features giving 78.45%.

Implications of applying cumulative risk assessment to the workplace.

Science.gov (United States)

Fox, Mary A; Spicer, Kristen; Chosewood, L Casey; Susi, Pam; Johns, Douglas O; Dotson, G Scott

2018-06-01

Multiple changes are influencing work, workplaces and workers in the US including shifts in the main types of work and the rise of the 'gig' economy. Work and workplace changes have coincided with a decline in unions and associated advocacy for improved safety and health conditions. Risk assessment has been the primary method to inform occupational and environmental health policy and management for many types of hazards. Although often focused on one hazard at a time, risk assessment frameworks and methods have advanced toward cumulative risk assessment recognizing that exposure to a single chemical or non-chemical stressor rarely occurs in isolation. We explore how applying cumulative risk approaches may change the roles of workers and employers as they pursue improved health and safety and elucidate some of the challenges and opportunities that might arise. Application of cumulative risk assessment should result in better understanding of complex exposures and health risks with the potential to inform more effective controls and improved safety and health risk management overall. Roles and responsibilities of both employers and workers are anticipated to change with potential for a greater burden of responsibility on workers to address risk factors both inside and outside the workplace that affect health at work. A range of policies, guidance and training have helped develop cumulative risk assessment for the environmental health field and similar approaches are available to foster the practice in occupational safety and health. Copyright © 2018 Elsevier Ltd. All rights reserved.

Developing measures of fatigue using an alcohol comparison to validate the effects of fatigue on performance.

Science.gov (United States)

Williamson, A M; Feyer, A M; Mattick, R P; Friswell, R; Finlay-Brown, S

2001-05-01

The effects of 28 h of sleep deprivation were compared with varying doses of alcohol up to 0.1% blood alcohol concentration (BAC) in the same subjects. The study was conducted in the laboratory. Twenty long-haul truck drivers and 19 people not employed as professional drivers acted as subjects. Tests were selected that were likely to be affected by fatigue, including simple reaction time, unstable tracking, dual task, Mackworth clock vigilance test, symbol digit coding, visual search, sequential spatial memory and logical reasoning. While performance effects were seen due to alcohol for all tests, sleep deprivation affected performance on most tests, but had no effect on performance on the visual search and logical reasoning tests. Some tests showed evidence of a circadian rhythm effect on performance, in particular, simple reaction time, dual task, Mackworth clock vigilance, and symbol digit coding, but only for response speed and not response accuracy. Drivers were slower but more accurate than controls on the symbol digit test, suggesting that they took a more conservative approach to performance of this test. This study demonstrated which tests are most sensitive to sleep deprivation and fatigue. The study therefore has established a set of tests that can be used in evaluations of fatigue and fatigue countermeasures.

El Carreto o Cumulá - Aspidosperma Dugandii Standl El Carreto o Cumulá - Aspidosperma Dugandii Standl

Directory of Open Access Journals (Sweden)

Dugand Armando

1944-03-01

Full Text Available Nombres vulgares: Carreto (Atlántico, Bolívar, Magdalena; Cumulá, Cumulá (Cundinamarca, ToIima. Según el Dr. Emilio Robledo (Lecciones de Bot. ed. 3, 2: 544. 1939 el nombre Carreto también es empleado en Puerto Berrío (Antioquia. El mismo autor (loc. cit. da el nombre Comulá para una especie indeterminada de Viburnum en Mariquita (Tolima y J. M. Duque, refiriendose a la misma planta y localidad (en Bot. Gen. Colomb. 340, 356. 1943 atribuye este nombre vulgar al Aspidosperma ellipticum Rusby.  Sin embargo, las muestras de madera de Cumulá o Comulá que yo he examinado, procedentes de la región de Mariquita -una de las cuales me fue recientemente enviada por el distinguido ictiólogo Sr. Cecil Miles- pertenecen sin duda alguna al A. Dugandii StandI. Por otra parte, Santiago Cortés (FI. Colomb. 206. 1898; ed, 2: 239. 1912 cita el Cumulá "de Anapoima y otros lugares del (rio Magdalena" diciendo que pertenece a las Leguminosas, pero la brevísima descripción que este autor hace de la madera "naranjada y notable por densidad, dureza y resistencia a la humedad", me induce a creer que se trata del mismo Cumula coleccionado recientemente en Tocaima, ya que esta población esta situada a pocos kilómetros de Anapoima. Nombres vulgares: Carreto (Atlántico, Bolívar, Magdalena; Cumulá, Cumulá (Cundinamarca, ToIima. Según el Dr. Emilio Robledo (Lecciones de Bot. ed. 3, 2: 544. 1939 el nombre Carreto también es empleado en Puerto Berrío (Antioquia. El mismo autor (loc. cit. da el nombre Comulá para una especie indeterminada de Viburnum en Mariquita (Tolima y J. M. Duque, refiriendose a la misma planta y localidad (en Bot. Gen. Colomb. 340, 356. 1943 atribuye este nombre vulgar al Aspidosperma ellipticum Rusby.  Sin embargo, las muestras de madera de Cumulá o Comulá que yo he examinado, procedentes de la región de Mariquita -una de las cuales me fue recientemente enviada por el distinguido ictiólogo Sr. Cecil Miles- pertenecen sin

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)

Structural Damage Identification in Stiffened Plate Fatigue Specimens Using Piezoelectric Active Sensing

Science.gov (United States)

2011-09-01

isolated AO mode first arrival, recorded at PZT 2, is shown at 3 different fatigue levels. Figure 5. The area under the PSD curve, calculated twice...Structural Damage Identification in Stiffened Plate Fatigue Specimens Using Piezoelectric Active Sensing B. L. GRISSO, G. PARK, L. W. SALVINO...with several challenges including limited performance knowledge of the materials, aluminum sensitization, structural fatigue performance, and

Predicting Cumulative Incidence Probability by Direct Binomial Regression

DEFF Research Database (Denmark)

Scheike, Thomas H.; Zhang, Mei-Jie

Binomial modelling; cumulative incidence probability; cause-specific hazards; subdistribution hazard......Binomial modelling; cumulative incidence probability; cause-specific hazards; subdistribution hazard...

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...

7 CFR 42.132 - Determining cumulative sum values.

Science.gov (United States)

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Determining cumulative sum values. 42.132 Section 42... Determining cumulative sum values. (a) The parameters for the on-line cumulative sum sampling plans for AQL's... 3 1 2.5 3 1 2 1 (b) At the beginning of the basic inspection period, the CuSum value is set equal to...

The Algebra of the Cumulative Percent Operation.

Science.gov (United States)

Berry, Andrew J.

2002-01-01

Discusses how to help students avoid some pervasive reasoning errors in solving cumulative percent problems. Discusses the meaning of ."%+b%." the additive inverse of ."%." and other useful applications. Emphasizes the operational aspect of the cumulative percent concept. (KHR)

Translating Fatigue to Human Performance

Science.gov (United States)

Enoka, Roger M.; Duchateau, Jacques

2016-01-01

Despite flourishing interest in the topic of fatigue—as indicated by the many presentations on fatigue at the 2015 annual meeting of the American College of Sports Medicine—surprisingly little is known about its impact on human performance. There are two main reasons for this dilemma: (1) the inability of current terminology to accommodate the scope of the conditions ascribed to fatigue, and (2) a paucity of validated experimental models. In contrast to current practice, a case is made for a unified definition of fatigue to facilitate its management in health and disease. Based on the classic two-domain concept of Mosso, fatigue is defined as a disabling symptom in which physical and cognitive function is limited by interactions between performance fatigability and perceived fatigability. As a symptom, fatigue can only be measured by self-report, quantified as either a trait characteristic or a state variable. One consequence of such a definition is that the word fatigue should not be preceded by an adjective (e.g., central, mental, muscle, peripheral, and supraspinal) to suggest the locus of the changes responsible for an observed level of fatigue. Rather, mechanistic studies should be performed with validated experimental models to identify the changes responsible for the reported fatigue. As indicated by three examples (walking endurance in old adults, time trials by endurance athletes, and fatigue in persons with multiple sclerosis) discussed in the review, however, it has proven challenging to develop valid experimental models of fatigue. The proposed framework provides a foundation to address the many gaps in knowledge of how laboratory measures of fatigue and fatigability impact real-world performance. PMID:27015386

On residual stresses and fatigue of laser hardened steels

International Nuclear Information System (INIS)

Lin, Ru.

1992-01-01

This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10 7 cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au)

On residual stresses and fatigue of laser hardened steels

Energy Technology Data Exchange (ETDEWEB)

Lin, Ru.

1992-01-01

This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10[sup 7] cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au).

Biologic interventions for fatigue in rheumatoid arthritis.

Science.gov (United States)

Almeida, Celia; Choy, Ernest H S; Hewlett, Sarah; Kirwan, John R; Cramp, Fiona; Chalder, Trudie; Pollock, Jon; Christensen, Robin

2016-06-06

Fatigue is a common and potentially distressing symptom for patients with rheumatoid arthritis (RA), with no accepted evidence-based management guidelines. Evidence suggests that biologic interventions improve symptoms and signs in RA as well as reducing joint damage. To evaluate the effect of biologic interventions on fatigue in rheumatoid arthritis. We searched the following electronic databases up to 1 April 2014: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Current Controlled Trials Register, the National Research Register Archive, The UKCRN Portfolio Database, AMED, CINAHL, PsycINFO, Social Science Citation Index, Web of Science, and Dissertation Abstracts International. In addition, we checked the reference lists of articles identified for inclusion for additional studies and contacted key authors. We included randomised controlled trials if they evaluated a biologic intervention in people with rheumatoid arthritis and had self reported fatigue as an outcome measure. Two reviewers selected relevant trials, assessed methodological quality and extracted data. Where appropriate, we pooled data in meta-analyses using a random-effects model. We identified 32 studies for inclusion in this current review. Twenty studies evaluated five anti-tumour necrosis factor (anti-TNF) biologic agents (adalimumab, certolizumab, etanercept, golimumab and infliximab), and 12 studies focused on five non-anti-TNF biologic agents (abatacept, canakinumab, rituximab, tocilizumab and an anti-interferon gamma monoclonal antibody). All but two of the studies were double-blind randomised placebo-controlled trials. In some trials, patients could receive concomitant disease-modifying anti-rheumatic drugs (DMARDs). These studies added either biologics or placebo to DMARDs. Investigators did not change the dose of the latter from baseline. In total, these studies included 9946 participants in the intervention groups and

Ankle and knee biomechanics during normal walking following ankle plantarflexor fatigue.

Science.gov (United States)

Hunt, Michael A; Hatfield, Gillian L

2017-08-01

The purpose of this study was to investigate the immediate effects of unilateral ankle plantarflexor fatigue on bilateral knee and ankle biomechanics during gait. Lower leg kinematics, kinetics, and muscle activation were assessed before and after an ankle plantarflexor fatiguing protocol in 31 healthy individuals. Fatigue (defined as >10% reduction in maximal isometric ankle plantarflexor torque production and a downward shift in the median power frequency of both heads of the gastrocnemius muscle of the fatigued limb) was achieved in 18 individuals, and only their data were used for analysis purposes. Compared to pre-fatigue walking trials, medial gastrocnemius activity was significantly reduced in the study (fatigued) limb. Other main changes following fatigue included significantly more knee flexion during loading, and an associated larger external knee flexion moment in the study limb. At the ankle joint, participants exhibited significantly less peak plantarflexion (occurring at toe-off) with fatigue. No significant differences were observed in the contralateral (non-fatigued) limb. Findings from this study indicate that fatigue of the ankle plantarflexor muscle does not produce widespread changes in gait biomechanics, suggesting that small to moderate changes in maximal ankle plantarflexor force production capacity (either an increase or decrease) will not have a substantial impact on normal lower limb functioning during gait. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Determinants of seafarers’ fatigue

DEFF Research Database (Denmark)

Bøggild Dohrmann, Solveig; Leppin, Anja

2017-01-01

in the review. The main reason for exclusion was fatigue not being the outcome variable. Results: Most evidence was available for work time-related factors suggesting that working nights was most fatiguing, that fatigue levels were higher toward the end of watch or shift, and that the 6-h on–6-h off watch...

Fatiguing effect of multiple take-offs and landings in regional airline operations.

Science.gov (United States)

Honn, Kimberly A; Satterfield, Brieann C; McCauley, Peter; Caldwell, J Lynn; Van Dongen, Hans P A

2016-01-01

Fatigue is a risk factor for flight performance and safety in commercial aviation. In US commercial aviation, to help to curb fatigue, the maximum duration of flight duty periods is regulated based on the scheduled start time and the number of flight segments to be flown. There is scientific support for regulating maximum duty duration based on scheduled start time; fatigue is well established to be modulated by circadian rhythms. However, it has not been established scientifically whether the number of flight segments, per se, affects fatigue. To address this science gap, we conducted a randomized, counterbalanced, cross-over study with 24 active-duty regional airline pilots. Objective and subjective fatigue was compared between a 9-hour duty day with multiple take-offs and landings versus a duty day of equal duration with a single take-off and landing. To standardize experimental conditions and isolate the fatiguing effect of the number of segments flown, the entire duty schedules were carried out in a high-fidelity, moving-base, full-flight, regional jet flight simulator. Steps were taken to maintain operational realism, including simulated airplane inspections and acceptance checks, use of realistic dispatch releases and airport charts, real-world air traffic control interactions, etc. During each of the two duty days, 10 fatigue test bouts were administered, which included a 10-minute Psychomotor Vigilance Test (PVT) assessment of objective fatigue and Samn-Perelli (SP) and Karolinska Sleepiness Scale (KSS) assessments of subjective sleepiness/fatigue. Results showed a greater build-up of objective and subjective fatigue in the multi-segment duty day than in the single-segment duty day. With duty start time and duration and other variables that could impact fatigue levels held constant, the greater build-up of fatigue in the multi-segment duty day was attributable specifically to the difference in the number of flight segments flown. Compared to findings in

How fatigue is experienced and handled by female outpatients with inflammatory bowel disease

DEFF Research Database (Denmark)

Beck, Anne; Bager, Palle; Jensen, Peter Errboe

2013-01-01

fatigue. Methods. The study included 11 female outpatients. These patients were 40–59 years old and had IBD ≥ one year and a significantly increased fatigue score. Patients with severe active IBD, anaemia, comorbidity, or pregnancy were excluded. The included patients agreed to participate...

Are There Any Natural Remedies That Reduce Chronic Fatigue Associated with Chronic Fatigue Syndrome?

Science.gov (United States)

... natural remedies that reduce chronic fatigue associated with chronic fatigue syndrome? Answers from Brent A. Bauer, M.D. Researchers ... a variety of natural products for effectiveness against chronic fatigue syndrome. Most results have been disappointing. A few remedies — ...

Designing Fatigue Warning Systems: The perspective of professional drivers.

Science.gov (United States)

Meng, Fanxing; Li, Shuling; Cao, Lingzhi; Peng, Qijia; Li, Musen; Wang, Chunhui; Zhang, Wei

2016-03-01

Professional drivers have been characterized as experiencing heavy fatigue resulting from long driving time in their daily work. This study aimed to explore the potential demand of Fatigue Warning Systems (FWSs) among professional drivers as a means of reducing the danger of fatigue driving and to examine their opinions regarding the design of FWSs. Six focus groups with 35 participants and a questionnaire survey with 600 respondents were conducted among Chinese truck and taxi drivers to collect qualitative and quantitative data concerning the current situation of fatigue driving and opinions regarding the design of FWSs. The results revealed that both truck and taxi drivers had a positive attitude toward FWSs, and they hoped this system could not only monitor and warn them regarding their fatigue but also somewhat relieve their fatigue before they could stop and rest. As for warning signals, participants preferred auditory warnings, as opposed to visual, vibrotactile or electric stimuli. Interestingly, it was proposed that verbal warnings involving the information regarding consequences of fatigue driving or the wishes of drivers' family members would be more effective. Additionally, different warning patterns, including graded, single and continuous warnings, were discussed in the focus group. Finally, the participants proposed many other suggestions, as well as their concerns regarding FWSs, which will provide valuable information for companies who wish to develop FWSs for professional drivers. Copyright © 2015. Published by Elsevier Ltd.

Fatigue in the shipping industry

NARCIS (Netherlands)

Houtman, I.; Miedema, M.; Jettinghoff, K.; Starren, A.; Heinrich, J.; Gort, J.

2005-01-01

Fatigue is a 'reduction in physical and/or mental capacity as the result of physical, mental, or emotional exertion which may impair nearly all physical abilities including: strength, speed, reaction time, coordination, decision making or balance'. The literature is quite clear on the debilitating

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...

Work-related fatigue and recovery: the contribution of age, domestic responsibilities and shiftwork.

Science.gov (United States)

Winwood, Peter C; Winefield, Antony H; Lushington, Kurt

2006-11-01

This paper reports a study of the relationship between age, domestic responsibilities (being partnered and having dependents), recovery from shiftwork-related fatigue and the evolution of maladaptive health outcomes among full-time working female nurses. Several studies have suggested that full-time working women with family responsibilities are at greater risk of developing work-related fatigue problems than single women without these responsibilities. A questionnaire was distributed in 2004 to 2400 nurses at two hospitals in Australia, and 1280 responses were obtained (response rate 54%). The data from a purposive sample of 846 full-time working nurses are reported here. Domestic responsibilities were not related to differences in fatigue and recovery. Our results suggested that for full-time shiftworking nurses, being part of a family structure, may actually be protective against the development of maladaptive fatigue. The most important factor determining maladaptive fatigue outcome was shift pattern worked, particularly rotation including night duty. The effect of age was equivocal. The youngest age group reported the highest fatigue and poorest recovery compared to the oldest group, who reported the best characteristics. However, this latter group may represent a particularly well-adapted 'survivor cohort'. The relationship between age and fatigue was partly confounded by older, experienced, nurses with greater job responsibilities, working fewer multiple shifts including night duty. In general, increasing age was not associated with poorer recovery or higher maladaptive fatigue. Unpredictable internal shift rotations, including night duty, which are traditional and typical in nursing, are inimical to maintaining nurses' health. More creative approaches to rostering for nurses working multiple shifts are a necessary step towards reducing wastage from the profession due to chronic work-related fatigue. Younger nurses in particular, may need more support than

Research progress of exercise-induced fatigue

Directory of Open Access Journals (Sweden)

Peng-yi DAI

2016-12-01

Full Text Available Exercise-induced fatigue is a comprehensive response to a variety of physiological and biochemical changes in the body, and can affect people's quality of life to different extents. If no timely recovery after occurrence of fatigue, accumulated gradually, it can lead to "burnout", a "overtraining syndrome", "chronic fatigue syndrome", etc., which will cause endocrine disturbance, immune suppression, even physical illness. Exercise-induced fatigue becomes an important factor endangering human health. In recent years, many experts and scholars at home and abroad are committed to the research of exercise-induced fatigue, and have put forward a variety of hypothesis to explain the cause of exercise-induced fatigue. They expect to find out the methods for preventing and eliminating exercise-induced fatigue. This article discusses mainly the pathogenesis, model building, elimination/ relief, etc. of exercise-induced fatigue to point out the research achievements of exercise-induced fatigue and its existing problems. DOI: 10.11855/j.issn.0577-7402.2016.11.14

A model for high-cycle fatigue crack propagation

Energy Technology Data Exchange (ETDEWEB)

Balbi, Marcela Angela [Rosario National Univ. (Argentina); National Council of Scientific Research and Technology (CONICET) (Argentina)

2017-02-01

This paper deals with the prediction of high-cycle fatigue behavior for four different materials (7075-T6 alloy, Ti-6Al-4 V alloy, JIS S10C steel and 0.4 wt.-% C steel) using Chapetti's approach to estimate the fatigue crack propagation curve. In the first part of the paper, a single integral equation for studying the entire propagation process is determined using the recent results of Santus and Taylor, which consider a double regime of propagation (short and long cracks) characterized by the model of El Haddad. The second part of the paper includes a comparison of the crack propagation behavior model proposed by Navarro and de los Rios with the one mentioned in the first half of this work. The results allow us to conclude that the approach presented in this paper is a good and valid estimation of high-cycle fatigue crack propagation using a single equation to describe the entire fatigue crack regime.

Creep-fatigue rules in the RCC-MR code

International Nuclear Information System (INIS)

Drubay, B.

1988-01-01

In 1978, CEA, Electricite de France (EDF) and NOVATOME decided to draw up a complete set of design and construction rules for LMFBR components. This RCC-MR code issued in June 1985 and completed in November 1987 was chosen as a sound basis for the next European Fast Reactor (EFR). The purpose of this paper is to describe the present RCC-MR creep-fatigue design rules to be applied with elastic analysis including the modifications adopted in the first addenda. This method is based on a separate evaluation of a fatigue usage fraction V and creep rupture usage fraction W with the common linear summation rule. The fatigue usage fraction is obtained from continuous fatigue curves (without hold times) and from total strain ranges (elastic + plastic + creep). The creep rupture usage fraction W is obtained from stress to rupture curves and a stress σk evaluating the stress generated during the cycle. (author)

Rhodiola rosea for physical and mental fatigue: a systematic review

Directory of Open Access Journals (Sweden)

Ishaque Sana

2012-05-01

Full Text Available Abstract Background Rhodiola rosea (R. rosea is grown at high altitudes and northern latitudes. Due to its purported adaptogenic properties, it has been studied for its performance-enhancing capabilities in healthy populations and its therapeutic properties in a number of clinical populations. To systematically review evidence of efficacy and safety of R. rosea for physical and mental fatigue. Methods Six electronic databases were searched to identify randomized controlled trials (RCTs and controlled clinical trials (CCTs, evaluating efficacy and safety of R. rosea for physical and mental fatigue. Two reviewers independently screened the identified literature, extracted data and assessed risk of bias for included studies. Results Of 206 articles identified in the search, 11 met inclusion criteria for this review. Ten were described as RCTs and one as a CCT. Two of six trials examining physical fatigue in healthy populations report R. rosea to be effective as did three of five RCTs evaluating R. rosea for mental fatigue. All of the included studies exhibit either a high risk of bias or have reporting flaws that hinder assessment of their true validity (unclear risk of bias. Conclusion Research regarding R. rosea efficacy is contradictory. While some evidence suggests that the herb may be helpful for enhancing physical performance and alleviating mental fatigue, methodological flaws limit accurate assessment of efficacy. A rigorously-designed well reported RCT that minimizes bias is needed to determine true efficacy of R. rosea for fatigue.

Fretting fatigue life estimation using fatigue damage gradient correction factor in various contact configurations

Energy Technology Data Exchange (ETDEWEB)

Hwang, Dong Hyeon; Cho, Sung-San [Hongik University, Seoul (Korea, Republic of)

2017-03-15

A fretting fatigue life estimation method that takes into account the stress gradient effect was developed by the authors [Journal of Mechanical Science and Technology, 28 (2014) 2153-2159]. In the developed method, fatigue damage value at the cracking location is corrected with fatigue damage gradient and the corrected value is compared directly with the plain fatigue data for life estimation. In other words, the correction factor is the ratio of plain fatigue damage to fretting fatigue damage at the same life and a function of fatigue damage gradient. Since reliability of the method was verified only for cylinder-on-flat contact configuration in the previous study, the present study extends application of the method to flat-on-flat contact configurations by developing the correction factor for both the contact configuration. Fretting fatigue experiments were conducted to obtain fatigue life data for various fretting pads. Finite element analyses were conducted to evaluate the Smith-Watson-Topper (SWT) fatigue damage parameter in the cracking region. It is revealed that the SWT parameter in fat-on-flat contact configuration decreases exponentially away from the surface as in cylinder-on-flat contact configuration, and thus the SWT gradient at the surface can be evaluated reliably. Moreover, it is found that decrease in the SWT parameter around the cracking location can be expressed by piecewise exponential curves. If the gradient of SWT at the surface is used as a representative value of SWT gradient, it is impossible to establish functional relationship between the SWT gradient and the correction factor for both the contact configurations although it was possible for cylinder-on-flat contact configuration. However, if weighted average of the SWT gradient values obtained from each exponential curve in the piecewise exponential curve is used as a representative value, the correction factor for both the contact configurations becomes a function of the SWT gradient

Fatigue in soccer

DEFF Research Database (Denmark)

Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

2005-01-01

This review describes when fatigue may develop during soccer games and the potential physiological mechanisms that cause fatigue in soccer. According to time?-?motion analyses and performance measures during match-play, fatigue or reduced performance seems to occur at three different stages......, acidity or the breakdown of creatine phosphate. Instead, it may be related to disturbances in muscle ion homeostasis and an impaired excitation of the sarcolemma. Soccer players' ability to perform maximally is inhibited in the initial phase of the second half, which may be due to lower muscle...... concentrations in a considerable number of individual muscle fibres. In a hot and humid environment, dehydration and a reduced cerebral function may also contribute to the deterioration in performance. In conclusion, fatigue or impaired performance in soccer occurs during various phases in a game, and different...

Fatigue in family caregivers of adult intensive care unit survivors.

Science.gov (United States)

Choi, JiYeon; Tate, Judith A; Hoffman, Leslie A; Schulz, Richard; Ren, Dianxu; Donahoe, Michael P; Given, Barbara A; Sherwood, Paula R

2014-09-01

Family caregivers are a vital resource in the recovery of intensive care unit (ICU) survivors. Of concern, the stress associated with this role can negatively affect caregiver health. Fatigue, an important health indicator, has been identified as a predictor of various illnesses, greater use of health services, and early mortality. Examining the impact of fatigue on caregivers' physical health can assist in identifying critical time points and potential targets for intervention. To describe self-reported fatigue in caregivers of ICU survivors from patients' ICU admission to ≤ 2 weeks, two- and four-months post-ICU discharge. Patient-caregiver pairs were enrolled from a medical ICU. Caregiver fatigue was measured using the Short-Form 36 Health Survey Vitality subscale (SF-36 Vitality). Caregiver psychobehavioral stress responses included depressive symptoms, burden, health risk behaviors, and sleep quality. Patient data included self-reported physical symptoms and disposition (home vs. institution). Forty-seven patient-caregiver pairs were initially enrolled. Clinically significant fatigue (SF-36 Vitality ≤ 45) was reported by 43%-53% of caregivers across the time points, and these caregivers reported worse scores in measures of depressive symptoms, burden, health risk behaviors and sleep quality, and patients' symptom burden. In 26 caregivers with data for all time points (55% of the total sample), SF-36 Vitality scores showed trends of improvement when the patient returned home and greater impairment when institutionalization continued. In caregivers of ICU survivors, fatigue is common and potentially linked with poor psychobehavioral responses. Worsening fatigue was associated with greater symptom distress and long-term patient institutionalization. Copyright © 2014 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

Biopsychosocial risk factors of persistent fatigue after acute infection: A systematic review to inform interventions.

Science.gov (United States)

Hulme, Katrin; Hudson, Joanna L; Rojczyk, Philine; Little, Paul; Moss-Morris, Rona

2017-08-01

Fatigue is a prevalent and debilitating symptom, preceded by an acute infectious episode in some patients. This systematic review aimed to identify risk factors for the development of persistent fatigue after an acute infection, to develop an evidence-based working model of post-infectious fatigue. Electronic databases (Medline, PsycINFO and EMBASE) were searched, from inception to March 2016, for studies which investigated biopsychosocial risk factors of on-going fatigue after an acute infection. Inclusion criteria were: prospective design; biological, psychological or social risk factors; standardised measure of post-infectious fatigue (self-report scales or clinical diagnosis). Studies were excluded if the sample had a pre-existing medical condition, infection was conceptualised as 'vaccination' or they were intervention trials. A narrative synthesis was performed. Eighty-one full texts were screened, of which seventeen were included in the review. Over half included glandular fever populations. Other infections included dengue fever, 'general'/'viral' and Q-fever. Risk factors were summarised under biological, social, behavioural, cognitive and emotional subthemes. Patients' cognitive and behavioural responses to the acute illness, and pre-infection or baseline distress and fatigue were the most consistent risk factors for post-infectious fatigue. An empirical summary model is provided, highlighting the risk factors most consistently associated with persistent fatigue. The components of the model, the possible interaction of risk factors and implications for understanding the fatigue trajectory and informing preventative treatments are discussed. Copyright © 2017. Published by Elsevier Inc.

Cumulative effects in Swedish EIA practice - difficulties and obstacles

International Nuclear Information System (INIS)

Waernbaeck, Antoienette; Hilding-Rydevik, Tuija

2009-01-01

The importance of considering cumulative effects (CE) in the context of environmental assessment is manifested in the EU regulations. The demands on the contents of Environmental Impact Assessment (EIA) and Strategic Environmental Assessment (SEA) documents explicitly ask for CE to be described. In Swedish environmental assessment documents CE are rarely described or included. The aim of this paper is to look into the reasons behind this fact in the Swedish context. The paper describes and analyse how actors implementing the EIA and SEA legislation in Sweden perceive the current situation in relation to the legislative demands and the inclusion of cumulative effects. Through semi-structured interviews the following questions have been explored: Is the phenomenon of CE discussed and included in the EIA/SEA process? What do the actors include in and what is their knowledge of the term and concept of CE? Which difficulties and obstacles do these actors experience and what possibilities for inclusion of CE do they see in the EIA/SEA process? A large number of obstacles and hindrances emerged from the interviews conducted. It can be concluded from the analysis that the will to act does seem to exist. A lack of knowledge in respect of how to include cumulative effects and a lack of clear regulations concerning how this should be done seem to be perceived as the main obstacles. The knowledge of the term and the phenomenon is furthermore quite narrow and not all encompassing. They experience that there is a lack of procedures in place. They also seem to lack knowledge of methods in relation to how to actually work, in practice, with CE and how to include CE in the EIA/SEA process. It can be stated that the existence of this poor picture in relation to practice concerning CE in the context of impact assessment mirrors the existing and so far rather vague demands in respect of the inclusion and assessment of CE in Swedish EIA and SEA legislation, regulations, guidelines and

EXAFS cumulants of CdSe

International Nuclear Information System (INIS)

Diop, D.

1997-04-01

EXAFS functions had been extracted from measurements on the K edge of Se at different temperatures between 20 and 300 K. The analysis of the EXAFS of the filtered first two shells has been done in the wavevector range laying between 2 and 15.5 A -1 in terms of the cumulants of the effective distribution of distances. The cumulants C 3 and C 4 obtained from the phase difference and the amplitude ratio methods have shown the anharmonicity in the vibrations of atoms around their equilibrium position. (author). 13 refs, 3 figs

Characterization of high temperature tensile and creep–fatigue properties of Alloy 800H for intermediate heat exchanger components of (V)HTRs

Energy Technology Data Exchange (ETDEWEB)

Kolluri, M., E-mail: kolluri@nrg.eu; Pierick, P. ten, E-mail: tenpierick@nrg.eu; Bakker, T., E-mail: t.bakker@nrg.eu

2015-04-01

Highlights: • High temperature tensile, creep–fatigue (C–F) properties of Alloy 800H are studied. • Strength and uniform elongation properties at 800 °C are much lower than RT values. • Strong influence of hold time and Δε{sub tot} on low cycle fatigue life was observed. • The total allowable C–F damage (D) at 800 °C decreases with the decreasing Δε{sub tot}. • Synergetic effect of C–F interactions showed stronger effect at lower Δε{sub tot} values. - Abstract: Alloy 800H is considered as a candidate material for intermediate heat exchanger (IHX) components of (very) high temperature reactors (V)HTRs. Qualification of the this alloy for the aforementioned nuclear applications requires understanding of its high temperature tensile, low-cycle fatigue behavior and creep–fatigue interactions because the IHX components suffer from combined creep–fatigue loadings resulting from thermally induced strain cycles associated with start-up and shutdown cycles. To this end, in this paper, the tensile properties of the Alloy 800H base and tungsten inert gas (TIG) welded materials are studied at three different temperatures, room temperature 21, 700 and 800 °C. Low cycle fatigue (LCF) behavior of the base material is investigated at 800 °C with no-hold time (no-HT) and hold time (HT) to study creep–fatigue interactions. The tensile test results showed substantial differences between the strength and ductility properties of the base and weld materials at all 3 temperatures, however, the trends in temperature dependence of tensile properties are similar for both base and weld materials. LCF studies with no-HT and HT showed a strong influence of HT on the low cycle fatigue life of this alloy illustrating the substantial influence of creep mechanisms at 800 °C. Finally, cumulative values of creep versus fatigue damage fractions are plotted in a creep–fatigue interaction diagram and these results are discussed with respect to the existing bi

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

International Nuclear Information System (INIS)

Lehericy, Y.

2007-05-01

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

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.

The role of TRAIL in fatigue induced by repeated stress from radiotherapy.

Science.gov (United States)

Feng, Li Rebekah; Suy, Simeng; Collins, Sean P; Saligan, Leorey N

2017-08-01

Fatigue is one of the most common and debilitating side effects of cancer and cancer treatment, and yet its etiology remains elusive. The goal of this study is to understand the role of chronic inflammation in fatigue following repeated stress from radiotherapy. Fatigue and non-fatigue categories were assessed using ≥ 3-point change in Functional Assessment of Cancer Therapy-Fatigue questionnaire (FACT-F) administered to participants at baseline/before radiotherapy and one year post-radiotherapy. Whole genome microarray and cytokine multiplex panel were used to examine fatigue-related transcriptome and serum cytokine changes, respectively. The study included 86 subjects (discovery phase n = 40, validation phase n = 46). The sample in the discovery phase included men with prostate cancer scheduled to receive external-beam radiotherapy. A panel of 48 cytokines were measured and the significantly changed cytokine found in the discovery phase was validated using sera from a separate cohort of men two years after completing radiotherapy for prostate cancer at a different institution. Effects of the significantly changed cytokine on cell viability was quantified using the MTT assay. During the discovery phase, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and TRAIL decoy receptor, TNFRSF10C (TRAIL-R3), were significantly upregulated in fatigued (≥3-point decrease from baseline to 1yr-post radiotherapy) subjects (n = 15). In the validation phase, TRAIL correlated with fatigue scores 2yrs post-radiotherapy. TRAIL caused selective cytotoxicity in neuronal cells, but not in microglial and muscle cells, in vitro. Late-onset inflammation directed by TRAIL may play a role in fatigue pathogenesis post-repeated stress from irradiation. Published by Elsevier Ltd.

Severe occupational hand eczema, job stress and cumulative sickness absence.

Science.gov (United States)

Böhm, D; Stock Gissendanner, S; Finkeldey, F; John, S M; Werfel, T; Diepgen, T L; Breuer, K

2014-10-01

Stress is known to activate or exacerbate dermatoses, but the relationships between chronic stress, job-related stress and sickness absence among occupational hand eczema (OHE) patients are inadequately understood. To see whether chronic stress or burnout symptoms were associated with cumulative sickness absence in patients with OHE and to determine which factors predicted sickness absence in a model including measures of job-related and chronic stress. We investigated correlations of these factors in employed adult inpatients with a history of sickness absence due to OHE in a retrospective cross-sectional explorative study, which assessed chronic stress (Trier Inventory for the Assessment of Chronic Stress), burnout (Shirom Melamed Burnout Measure), clinical symptom severity (Osnabrück Hand Eczema Severity Index), perceived symptom severity, demographic characteristics and cumulative days of sickness absence. The study group consisted of 122 patients. OHE symptoms were not more severe among patients experiencing greater stress and burnout. Women reported higher levels of chronic stress on some measures. Cumulative days of sickness absence correlated with individual dimensions of job-related stress and, in multiple regression analysis, with an overall measure of chronic stress. Chronic stress is an additional factor predicting cumulative sickness absence among severely affected OHE patients. Other relevant factors for this study sample included the 'cognitive weariness' subscale of the Shirom Melamed Burnout Measure and the physical component summary score of the SF-36, a measure of health-related life quality. Prevention and rehabilitation should take job stress into consideration in multidisciplinary treatment strategies for severely affected OHE patients. © The Author 2014. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Retooling CalEnviroScreen: Cumulative Pollution Burden and Race-Based Environmental Health Vulnerabilities in California

Science.gov (United States)

2018-01-01

The California Community Environmental Health Screening Tool (CalEnviroScreen) advances research and policy pertaining to environmental health vulnerability. However, CalEnviroScreen departs from its historical foundations and comparable screening tools by no longer considering racial status as an indicator of environmental health vulnerability and predictor of cumulative pollution burden. This study used conceptual frameworks and analytical techniques from environmental health and inequality literature to address the limitations of CalEnviroScreen, especially its inattention to race-based environmental health vulnerabilities. It developed an adjusted measure of cumulative pollution burden from the CalEnviroScreen 2.0 data that facilitates multivariate analyses of the effect of neighborhood racial composition on cumulative pollution burden, net of other indicators of population vulnerability, traffic density, industrial zoning, and local and regional clustering of pollution burden. Principal component analyses produced three new measures of population vulnerability, including Latina/o cumulative disadvantage that represents the spatial concentration of Latinas/os, economic disadvantage, limited English-speaking ability, and health vulnerability. Spatial error regression analyses demonstrated that concentrations of Latinas/os, followed by Latina/o cumulative disadvantage, are the strongest demographic determinants of adjusted cumulative pollution burden. Findings have implications for research and policy pertaining to cumulative impacts and race-based environmental health vulnerabilities within and beyond California. PMID:29659481

Retooling CalEnviroScreen: Cumulative Pollution Burden and Race-Based Environmental Health Vulnerabilities in California

Directory of Open Access Journals (Sweden)

Raoul S. Liévanos

2018-04-01

Full Text Available The California Community Environmental Health Screening Tool (CalEnviroScreen advances research and policy pertaining to environmental health vulnerability. However, CalEnviroScreen departs from its historical foundations and comparable screening tools by no longer considering racial status as an indicator of environmental health vulnerability and predictor of cumulative pollution burden. This study used conceptual frameworks and analytical techniques from environmental health and inequality literature to address the limitations of CalEnviroScreen, especially its inattention to race-based environmental health vulnerabilities. It developed an adjusted measure of cumulative pollution burden from the CalEnviroScreen 2.0 data that facilitates multivariate analyses of the effect of neighborhood racial composition on cumulative pollution burden, net of other indicators of population vulnerability, traffic density, industrial zoning, and local and regional clustering of pollution burden. Principal component analyses produced three new measures of population vulnerability, including Latina/o cumulative disadvantage that represents the spatial concentration of Latinas/os, economic disadvantage, limited English-speaking ability, and health vulnerability. Spatial error regression analyses demonstrated that concentrations of Latinas/os, followed by Latina/o cumulative disadvantage, are the strongest demographic determinants of adjusted cumulative pollution burden. Findings have implications for research and policy pertaining to cumulative impacts and race-based environmental health vulnerabilities within and beyond California.

Retooling CalEnviroScreen: Cumulative Pollution Burden and Race-Based Environmental Health Vulnerabilities in California.

Science.gov (United States)

Liévanos, Raoul S

2018-04-16

The California Community Environmental Health Screening Tool (CalEnviroScreen) advances research and policy pertaining to environmental health vulnerability. However, CalEnviroScreen departs from its historical foundations and comparable screening tools by no longer considering racial status as an indicator of environmental health vulnerability and predictor of cumulative pollution burden. This study used conceptual frameworks and analytical techniques from environmental health and inequality literature to address the limitations of CalEnviroScreen, especially its inattention to race-based environmental health vulnerabilities. It developed an adjusted measure of cumulative pollution burden from the CalEnviroScreen 2.0 data that facilitates multivariate analyses of the effect of neighborhood racial composition on cumulative pollution burden, net of other indicators of population vulnerability, traffic density, industrial zoning, and local and regional clustering of pollution burden. Principal component analyses produced three new measures of population vulnerability, including Latina/o cumulative disadvantage that represents the spatial concentration of Latinas/os, economic disadvantage, limited English-speaking ability, and health vulnerability. Spatial error regression analyses demonstrated that concentrations of Latinas/os, followed by Latina/o cumulative disadvantage, are the strongest demographic determinants of adjusted cumulative pollution burden. Findings have implications for research and policy pertaining to cumulative impacts and race-based environmental health vulnerabilities within and beyond California.

Visual perception of fatigued lifting actions.

Science.gov (United States)

Fischer, Steven L; Albert, Wayne J; McGarry, Tim

2012-12-01

Fatigue-related changes in lifting kinematics may expose workers to undue injury risks. Early detection of accumulating fatigue offers the prospect of intervention strategies to mitigate such fatigue-related risks. In a first step towards this objective, this study investigated whether fatigue detection was accessible to visual perception and, if so, what was the key visual information required for successful fatigue discrimination. Eighteen participants were tasked with identifying fatigued lifts when viewing 24 trials presented using both video and point-light representations. Each trial comprised a pair of lifting actions containing a fresh and a fatigued lift from the same individual presented in counter-balanced sequence. Confidence intervals demonstrated that the frequency of correct responses for both sexes exceeded chance expectations (50%) for both video (68%±12%) and point-light representations (67%±10%), demonstrating that fatigued lifting kinematics are open to visual perception. There were no significant differences between sexes or viewing condition, the latter result indicating kinematic dynamics as providing sufficient information for successful fatigue discrimination. Moreover, results from single viewer investigation reported fatigue detection (75%) from point-light information describing only the kinematics of the box lifted. These preliminary findings may have important workplace applications if fatigue discrimination rates can be improved upon through future research. Copyright © 2012 Elsevier B.V. All rights reserved.

Corrosion fatigue of steels

International Nuclear Information System (INIS)

Spaehn, H.; Wagner, G.H.

1976-01-01

Corrosion fatigue phenomena can be classified into two main groups according to the electrochemical state of the metal surface in the presence of electrolytes: the active and the passive state with an important sub-group of corrosion fatigue in the unstable passive state. The allowable stress for structures exposed to the conjoint action of corrosion and fatigue is influenced by many factors: kind of media, number of cycles, frequency, mean stress, size, notches, loading mode, alloy composition and mechanical strength. A critical literature review shows contradictory results if a classification by the electrochemical surface state is not applied. Case histories and counter measures illustrate the practical importance of corrosion fatigue in many branches of industry as well as the urgent need for a better knowledge about the mutual influence of the phenomena to get rules by which the engineer can appraise the risk of corrosion fatigue. (orig.) [de

An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

DEFF Research Database (Denmark)

Ibsø, Jan Behrend; Agerskov, Henning

1996-01-01

test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...... of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied....... determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination...

An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

DEFF Research Database (Denmark)

Ibsø, Jan Behrend; Agerskov, Henning

1996-01-01

test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...... determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination...... of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied....

Static and Fatigue Behavior Investigation of Artificial Notched Steel Reinforcement

Directory of Open Access Journals (Sweden)

Yafei Ma

2017-05-01

Full Text Available Pitting corrosion is one of the most common forms of localized corrosion. Corrosion pit results in a stress concentration and fatigue cracks usually initiate and propagate from these corrosion pits. Aging structures may fracture when the fatigue crack reaches a critical size. This paper experimentally simulates the effects of pitting morphologies on the static and fatigue behavior of steel bars. Four artificial notch shapes are considered: radial ellipse, axial ellipse, triangle and length-variable triangle. Each shape notch includes six sizes to simulate a variety of pitting corrosion morphologies. The stress-strain curves of steel bars with different notch shape and depth are obtained based on static tensile testing, and the stress concentration coefficients for various conditions are determined. It was determined that the triangular notch has the highest stress concentration coefficient, followed by length-variable triangle, radial ellipse and axial ellipse shaped notches. Subsequently, the effects of notch depth and notch aspect ratios on the fatigue life under three stress levels are investigated by fatigue testing, and the equations for stress range-fatigue life-notch depth are obtained. Several conclusions are drawn based on the proposed study. The established relationships provide an experimental reference for evaluating the fatigue life of concrete bridges.

Incorporating cumulative effects into environmental assessments of mariculture: Limitations and failures of current siting methods

International Nuclear Information System (INIS)

King, Sarah C.; Pushchak, Ronald

2008-01-01

Assessing and evaluating the cumulative impacts of multiple marine aquaculture facilities has proved difficult in environmental assessment. A retrospective review of 23 existing mariculture farms in southwestern New Brunswick was conducted to determine whether cumulative interactions would have justified site approvals. Based on current scientific evidence of cumulative effects, six new criteria were added to a set of far-field impacts and other existing criteria were expanded to include regional and cumulative environmental impacts in Hargrave's [Hargrave BT. A traffic light decision system for marine finfish aquaculture siting. Ocean Coast Manag 2002; 45:215-35.] Traffic Light Decision Support System (DSS) presently used in Canadian aquaculture environmental assessments. Before mitigation, 19 of the 23 sites failed the amended set of criteria and after considering mitigation, 8 sites failed. Site and ecosystem indices yielded varying site acceptability scores; however, many sites would not have been approved if siting decisions had been made within a regional management framework and cumulative impact criteria were considered in the site evaluation process

Determining the von Mises stress power spectral density for frequency domain fatigue analysis including out-of-phase stress components

NARCIS (Netherlands)

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

This paper provides a new formula to take into account phase differences in the determination of an equivalent von Mises stress power spectral density (PSD) from multiple random inputs. The obtained von Mises PSD can subsequently be used for fatigue analysis. The formula was derived for use in the

Impact of Fatigue in Rheumatic Diseases in the Work Environment: A Qualitative Study.

LENUS (Irish Health Repository)

Connolly, Deirdre

2015-10-28

Fatigue is a symptom of arthritis that causes difficulty at work. An improved understanding of this symptom could assist its management in the work environment. The aim of this study was to explore people with rheumatic diseases\\' experiences of fatigue in work. A qualitative descriptive design was used with semi-structured interviews and a constant comparative method of data analysis. There were 18 participants, the majority of them female with Rheumatoid Arthritis (RA) and working full-time. Three themes were identified: "Impact of fatigue on work performance" with cognition, mood and physical abilities being the main difficulties reported. In the second theme "Disclosure at Work" participants discussed disclosing their disease to employers but reported a lack of understanding of fatigue from colleagues. The final theme "work-based fatigue management strategies" included cognitive strategies and energy management techniques, which were mainly self-taught. In this study, fatigue was reported to impact on many areas of work performance with limited understanding from colleagues and employers. Interventions from health professionals to assist with development of work-related self-management skills are required to assist with symptom management in the work place. Such interventions should include education to employers and colleagues on the nature of fatigue in Rheumatic diseases.

Impact of Fatigue in Rheumatic Diseases in the Work Environment: A Qualitative Study

Directory of Open Access Journals (Sweden)

Deirdre Connolly

2015-10-01

Full Text Available Fatigue is a symptom of arthritis that causes difficulty at work. An improved understanding of this symptom could assist its management in the work environment. The aim of this study was to explore people with rheumatic diseases’ experiences of fatigue in work. A qualitative descriptive design was used with semi-structured interviews and a constant comparative method of data analysis. There were 18 participants, the majority of them female with Rheumatoid Arthritis (RA and working full-time. Three themes were identified: “Impact of fatigue on work performance” with cognition, mood and physical abilities being the main difficulties reported. In the second theme “Disclosure at Work” participants discussed disclosing their disease to employers but reported a lack of understanding of fatigue from colleagues. The final theme “work-based fatigue management strategies” included cognitive strategies and energy management techniques, which were mainly self-taught. In this study, fatigue was reported to impact on many areas of work performance with limited understanding from colleagues and employers. Interventions from health professionals to assist with development of work-related self-management skills are required to assist with symptom management in the work place. Such interventions should include education to employers and colleagues on the nature of fatigue in Rheumatic diseases.

About the cumulants of periodic signals

Science.gov (United States)

Barrau, Axel; El Badaoui, Mohammed

2018-01-01

This note studies cumulants of time series. These functions originating from the probability theory being commonly used as features of deterministic signals, their classical properties are examined in this modified framework. We show additivity of cumulants, ensured in the case of independent random variables, requires here a different hypothesis. Practical applications are proposed, in particular an analysis of the failure of the JADE algorithm to separate some specific periodic signals.

Fatigue-Damage Estimation and Control for Wind Turbines

DEFF Research Database (Denmark)

Barradas Berglind, Jose de Jesus

How can fatigue-damage for control of wind turbines be represented? Fatigue-damage is indeed a crucial factor in structures such as wind turbines that are exposed to turbulent and rapidly changing wind flow conditions. This is relevant both in their design stage and during the control......, the inclusion of fatigue-damage within feedback control loops is of special interest. Four strategies in total are proposed in this work: three for the wind turbine level and one for the wind farm level. On one hand, the three strategies in the turbine level are based on hysteresis operators and strive......-damage estimation in wind turbine components, to the mixed objective operation of wind energy conversion systems, and to the synthesis of control strategies that include hysteresis operators....

Effect of ratchet strain on fatigue and creep–fatigue strength of Mod.9Cr–1Mo steel

International Nuclear Information System (INIS)

Ando, Masanori; Isobe, Nobuhiro; Kikuchi, Koichi; Enuma, Yasuhiro

2012-01-01

Highlights: ► Uniaxial fatigue and creep–fatigue tests with superimposed strain were performed. ► Variety of superimposed strain were applied as ratchet strain in the tests. ► Effect of superimposed strain on fatigue and creep–fatigue life is negligible. ► A cyclic softening character reducing the effect of superimposed strain. - Abstract: The effect of ratcheting deformation on fatigue and creep–fatigue life in Mod.9Cr–1Mo steel was investigated. Uniaxial fatigue and creep–fatigue testing with superimposed strain were performed to evaluate the effect of ratcheting deformation on the failure cycle. In a series of tests, a specific amount of superimposed strain was accumulated in each cycle. The accumulated strain as ratcheting deformation, cycles to reach the accumulated strain, and test temperatures were varied in the tests. In the fatigue tests with superimposed strain at 550 °C, slight reductions of failure lives were observed. All of the numbers of cycles to failure in the fatigue tests with superimposed strain were within a factor of 1.5 of that of the fatigue test without superimposed strain at 550 °C. The apparent relationship between failure cycles and testing parameters was not observed. In fatigue tests with superimposed strain at 550 °C, maximum mean stress was insignificant and generated in early cycles because Mod.9Cr–1Mo steel exhibits cyclic softening characteristics. It was assumed that suppression of mean stress generation by cyclic softening reduces the effect of ratcheting strain. Conversely, failure lives were increased by accumulated strain in the test conducted at 450 °C because of stress–strain hysteresis loop shrinkage caused by cyclic softening induced by the accumulated strain. In the creep–fatigue tests with superimposed strain, test results indicated that the accumulated stain was negligible. It was concluded that the effect of ratcheting deformation on fatigue and creep–fatigue life is negligible as long

All Fatigue is Not Created Equal: The Association of Fatigue and Its Subtypes on Pain Interference in Orofacial Pain.

Science.gov (United States)

Boggero, Ian A; Rojas-Ramirez, Marcia V; Carlson, Charles R

2017-03-01

Fatigue is known to be a pathway through which depression, psychological distress, pain intensity, and sleep disturbance influence pain interference, but the independent effects of fatigue on pain interference after controlling for these variables remains unknown. In addition, no study to date has tested whether fatigue subtypes of general fatigue, mental fatigue, emotional fatigue, physical fatigue, or vigor differentially predict pain interference. The current study tested these associations using archival medical data of 2133 chronic orofacial pain patients, who completed a battery of psychological questionnaires at the time of their first appointment at an orofacial pain clinic. Hierarchical linear regression analysis revealed that after controlling for depression, psychological distress, sleep disturbance, pain intensity, and demographic variables, fatigue predicted higher pain interference (B=0.70, SE=0.17, Ppain interference after controlling for the aforementioned variables. The findings suggest that fatigue is an important independent predictor of pain interference and not merely a mediator. These findings also suggest that not all fatigue is created equal. Interventions aimed at reducing pain interference should target specific fatigue symptoms of physical fatigue and vigor. Future research investigating the independent associations of fatigue subtypes on pain outcomes may help clarify the nature of the interrelationships between pain and fatigue.

Physical activity buffers fatigue only under low chronic stress.

Science.gov (United States)

Strahler, Jana; Doerr, Johanna M; Ditzen, Beate; Linnemann, Alexandra; Skoluda, Nadine; Nater, Urs M

2016-09-01

Fatigue is one of the most commonly reported complaints in the general population. As physical activity (PA) has been shown to have beneficial effects, we hypothesized that everyday life PA improves fatigue. Thirty-three healthy students (21 women, 22.8 ± 3.3 years, 21.7 ± 2.3 kg/m(2)) completed two ambulatory assessment periods. During five days at the beginning of the semester (control condition) and five days during final examination preparation (examination condition), participants repeatedly reported on general fatigue (awakening, 10 am, 2 pm, 6 pm and 9 pm) by means of an electronic diary, collected saliva samples for the assessment of cortisol and α-amylase immediately after providing information on fatigue and wore a triaxial accelerometer to continuously record PA. Self-perceived chronic stress was assessed as a moderator. Using hierarchical linear modeling, including PA, condition (control vs. examination), sex and chronic stress as predictors, PA level during the 15 min prior to data entry did not predict momentary fatigue level. Furthermore, there was no effect of condition. However, a significant cross-level interaction of perceived chronic stress with PA was observed. In fact, the (negative) relationship between PA and fatigue was stronger in those participants with less chronic stress. Neither cortisol nor α-amylase was significantly related to physical activity or fatigue. Our study showed an immediate short-term buffering effect of everyday life PA on general fatigue, but only when experiencing lower chronic stress. There seems to be no short-term benefit of PA in the face of higher chronic stress. These findings highlight the importance of considering chronic stress when evaluating the effectiveness of PA interventions in different target populations, in particular among chronically stressed and fatigued subjects.

Meta-analysis of the predictive factors of postpartum fatigue.

Science.gov (United States)

Badr, Hanan A; Zauszniewski, Jaclene A

2017-08-01

Nearly 64% of new mothers are affected by fatigue during the postpartum period, making it the most common problem that a woman faces as she adapts to motherhood. Postpartum fatigue can lead to serious negative effects on the mother's health and the newborn's development and interfere with mother-infant interaction. The aim of this meta-analysis was to identify predictive factors of postpartum fatigue and to document the magnitude of their effects using effect sizes. We used two search engines, PubMed and Google Scholar, to identify studies that met three inclusion criteria: (a) the article was written in English, (b) the article studied the predictive factors of postpartum fatigue, and (c) the article included information about the validity and reliability of the instruments used in the research. Nine articles met these inclusion criteria. The direction and strength of correlation coefficients between predictive factors and postpartum fatigue were examined across the studies to determine their effect sizes. Measurement of predictor variables occurred from 3days to 6months postpartum. Correlations reported between predictive factors and postpartum fatigue were as follows: small effect size (r range =0.10 to 0.29) for education level, age, postpartum hemorrhage, infection, and child care difficulties; medium effect size (r range =0.30 to 0.49) for physiological illness, low ferritin level, low hemoglobin level, sleeping problems, stress and anxiety, and breastfeeding problems; and large effect size (r range =0.50+) for depression. Postpartum fatigue is a common condition that can lead to serious health problems for a new mother and her newborn. Therefore, increased knowledge concerning factors that influence the onset of postpartum fatigue is needed for early identification of new mothers who may be at risk. Appropriate treatments, interventions, information, and support can then be initiated to prevent or minimize the postpartum fatigue. Copyright © 2017 Elsevier

Cumulative (DisAdvantage and the Matthew Effect in Life-Course Analysis.

Directory of Open Access Journals (Sweden)

Miia Bask

Full Text Available To foster a deeper understanding of the mechanisms behind inequality in society, it is crucial to work with well-defined concepts associated with such mechanisms. The aim of this paper is to define cumulative (disadvantage and the Matthew effect. We argue that cumulative (disadvantage is an intra-individual micro-level phenomenon, that the Matthew effect is an inter-individual macro-level phenomenon and that an appropriate measure of the Matthew effect focuses on the mechanism or dynamic process that generates inequality. The Matthew mechanism is, therefore, a better name for the phenomenon, where we provide a novel measure of the mechanism, including a proof-of-principle analysis using disposable personal income data. Finally, because socio-economic theory should be able to explain cumulative (disadvantage and the Matthew mechanism when they are detected in data, we discuss the types of models that may explain the phenomena. We argue that interactions-based models in the literature traditions of analytical sociology and statistical mechanics serve this purpose.

Naturally-occurring fatigue and cardiovascular response to a simple memory challenge.

Science.gov (United States)

Mlynski, Christopher; Wright, Rex A; Agtarap, Stephanie D; Rojas, Juan

2017-09-01

Participants first completed a state affect checklist that included a fatigue (energy-tiredness) index and a measure of mental sharpness. They then were presented a simple memory challenge. In the first minute of the two-minute work period, heart rate responses (1) rose with values on the fatigue index, and (2) fell with values on the measure of mental sharpness. In the second minute of the work period, the responses were unrelated to fatigue index and mental sharpness values. Follow-up analysis indicated mental sharpness mediation of fatigue influence on heart rate in Minute 1. First minute findings add substantively to the body of evidence supporting recent suggestions that fatigue can lead people to try harder and experience stronger cardiovascular responses when confronted with simple challenges. They also support the suggestion that fatigue might exert its influence on cardiovascular responses to a mental challenge by diminishing cognitive clarity, that is, by obscuring thought. Second minute findings are contrary to the fatigue suggestions, but could indicate that memorization was accomplished in the first minute. A practical implication of the first minute results is that real-world fatigue could elevate health risk by enhancing CV responses to mundane daily tasks. Copyright © 2017 Elsevier B.V. All rights reserved.

Thermal fatigue strength estimation of 2.25Cr-1Mo steel under creep-fatigue interaction

International Nuclear Information System (INIS)

Kuwahara, Kazuo; Nitta, Akihito; Kitamura, Takayuki