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Sample records for models astm fatigue

  1. The fatigue-crack propagation behavior of ASTM A533-B steel tested in vacuo at LWR operating temperatures

    International Nuclear Information System (INIS)

    James, L.A.

    1987-01-01

    The fatigue-crack propagation (FCP) behavior of ASTM A533-B-1 steel was characterized in vacuo at 288 0 C. Tests were conducted at two stress ratios: R = 0.05 and R = 0.7. Results of these tests were compared with results from previous studies for the same type of steel tested in an air environment, and FCP rates in vacuo were generally lower than those in air. Stress ratio effects in vacuo were not as great as those in air, and both stress ratio effects and environmental effects are discussed from the standpoint of crack closure concepts

  2. Model of ASTM Flammability Test in Microgravity: Iron Rods

    Science.gov (United States)

    Steinberg, Theodore A; Stoltzfus, Joel M.; Fries, Joseph (Technical Monitor)

    2000-01-01

    There is extensive qualitative results from burning metallic materials in a NASA/ASTM flammability test system in normal gravity. However, this data was shown to be inconclusive for applications involving oxygen-enriched atmospheres under microgravity conditions by conducting tests using the 2.2-second Lewis Research Center (LeRC) Drop Tower. Data from neither type of test has been reduced to fundamental kinetic and dynamic systems parameters. This paper reports the initial model analysis for burning iron rods under microgravity conditions using data obtained at the LERC tower and modeling the burning system after ignition. Under the conditions of the test the burning mass regresses up the rod to be detached upon deceleration at the end of the drop. The model describes the burning system as a semi-batch, well-mixed reactor with product accumulation only. This model is consistent with the 2.0-second duration of the test. Transient temperature and pressure measurements are made on the chamber volume. The rod solid-liquid interface melting rate is obtained from film records. The model consists of a set of 17 non-linear, first-order differential equations which are solved using MATLAB. This analysis confirms that a first-order rate, in oxygen concentration, is consistent for the iron-oxygen kinetic reaction. An apparent activation energy of 246.8 kJ/mol is consistent for this model.

  3. Thermal fatigue. Materials modelling

    International Nuclear Information System (INIS)

    Siegele, D.; Fingerhuth, J.; Mrovec, M.

    2012-01-01

    In the framework of the ongoing joint research project 'Thermal Fatigue - Basics of the system-, outflow- and material-characteristics of piping under thermal fatigue' funded by the German Federal Ministry of Education and Research (BMBF) fundamental numerical and experimental investigations on the material behavior under transient thermal-mechanical stress conditions (high cycle fatigue V HCF and low cycle fatigue - LCF) are carried out. The primary objective of the research is the further development of simulation methods applied in safety evaluations of nuclear power plant components. In this context the modeling of crack initiation and growth inside the material structure induced by varying thermal loads are of particular interest. Therefore, three scientific working groups organized in three sub-projects of the joint research project are dealing with numerical modeling and simulation at different levels ranging from atomistic to micromechanics and continuum mechanics, and in addition corresponding experimental data for the validation of the numerical results and identification of the parameters of the associated material models are provided. The present contribution is focused on the development and experimental validation of material models and methods to characterize the damage evolution and the life cycle assessment as a result of thermal cyclic loading. The individual purposes of the subprojects are as following: - Material characterization, Influence of temperature and surface roughness on fatigue endurances, biaxial thermo-mechanical behavior, experiments on structural behavior of cruciform specimens and scatter band analysis (IfW Darmstadt) - Life cycle assessment with micromechanical material models (MPA Stuttgart) - Life cycle assessment with atomistic and damage-mechanical material models associated with material tests under thermal fatigue (Fraunhofer IWM, Freiburg) - Simulation of fatigue crack growth, opening and closure of a short crack under

  4. CCR+: Metadata Based Extended Personal Health Record Data Model Interoperable with the ASTM CCR Standard.

    Science.gov (United States)

    Park, Yu Rang; Yoon, Young Jo; Jang, Tae Hun; Seo, Hwa Jeong; Kim, Ju Han

    2014-01-01

    Extension of the standard model while retaining compliance with it is a challenging issue because there is currently no method for semantically or syntactically verifying an extended data model. A metadata-based extended model, named CCR+, was designed and implemented to achieve interoperability between standard and extended models. Furthermore, a multilayered validation method was devised to validate the standard and extended models. The American Society for Testing and Materials (ASTM) Community Care Record (CCR) standard was selected to evaluate the CCR+ model; two CCR and one CCR+ XML files were evaluated. In total, 188 metadata were extracted from the ASTM CCR standard; these metadata are semantically interconnected and registered in the metadata registry. An extended-data-model-specific validation file was generated from these metadata. This file can be used in a smartphone application (Health Avatar CCR+) as a part of a multilayered validation. The new CCR+ model was successfully evaluated via a patient-centric exchange scenario involving multiple hospitals, with the results supporting both syntactic and semantic interoperability between the standard CCR and extended, CCR+, model. A feasible method for delivering an extended model that complies with the standard model is presented herein. There is a great need to extend static standard models such as the ASTM CCR in various domains: the methods presented here represent an important reference for achieving interoperability between standard and extended models.

  5. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart Andrew; Abe Askari (Boeing)

    2014-10-01

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

  6. Comparing the Methodologies in ASTM G198 Using Combined Hygrothermal-Corrosion Modeling

    Science.gov (United States)

    Samuel L. Zelinka

    2013-01-01

    ASTM G198, “Standard test method for determining the relative corrosion performance of driven fasteners in contact with treated wood,” was accepted by consensus and published in 2011. The method has two different exposure conditions for determining fastener corrosion performance in treated wood. The first method places the wood and embedded fasteners in a...

  7. Fatigue modeling of materials with complex microstructures

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2011-01-01

    with the phenomenological model of fatigue damage growth. As a result, the fatigue lifetime of materials with complex structures can be determined as a function of the parameters of their structures. As an example, the fatigue lifetimes of wood modeled as a cellular material with multilayered, fiber reinforced walls were...

  8. Fatigue and damage tolerance scatter models

    Science.gov (United States)

    Raikher, Veniamin L.

    1994-09-01

    Effective Total Fatigue Life and Crack Growth Scatter Models are proposed. The first of them is based on the power form of the Wohler curve, fatigue scatter dependence on mean life value, cycle stress ratio influence on fatigue scatter, and validated description of the mean stress influence on the mean fatigue life. The second uses in addition are fracture mechanics approach, assumption of initial damage existence, and Paris equation. Simple formulas are derived for configurations of models. A preliminary identification of the parameters of the models is fulfilled on the basis of experimental data. Some new and important results for fatigue and crack growth scatter characteristics are obtained.

  9. Variable amplitude fatigue, modelling and testing

    International Nuclear Information System (INIS)

    Svensson, Thomas.

    1993-01-01

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

  10. Common Mathematical Model of Fatigue Characteristics

    Directory of Open Access Journals (Sweden)

    Z. Maléř

    2004-01-01

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

  11. 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.

  12. Study on Standard Fatigue Vehicle Load Model

    Science.gov (United States)

    Huang, H. Y.; Zhang, J. P.; Li, Y. H.

    2018-02-01

    Based on the measured data of truck from three artery expressways in Guangdong Province, the statistical analysis of truck weight was conducted according to axle number. The standard fatigue vehicle model applied to industrial areas in the middle and late was obtained, which adopted equivalence damage principle, Miner linear accumulation law, water discharge method and damage ratio theory. Compared with the fatigue vehicle model Specified by the current bridge design code, the proposed model has better applicability. It is of certain reference value for the fatigue design of bridge in China.

  13. 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.

  14. 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, ...

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

    Science.gov (United States)

    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.

  16. Individualized Biomathematical Modeling of Fatigue and Performance

    Science.gov (United States)

    2008-05-29

    Interactions and Transitions 53 New Discoveries , Inventions, or Patent Disclosures 56 FA9550-06-1-0055 Individualized Biomathematical Modeling of Fatigue...Old Dominion University, not supported on grant) Daniel J. Mollicone, Ph.D. ( Pulsar Informatics, Inc., not supported on grant) Christopher G...Mott, M.S. ( Pulsar Informatics, Inc., not supported on grant) Erik Olofsen, M.S. (Leiden University, the Netherlands, not supported on grant

  17. Using statistical compatibility to derive advanced probabilistic fatigue models

    Czech Academy of Sciences Publication Activity Database

    Fernández-Canteli, A.; Castillo, E.; López-Aenlle, M.; Seitl, Stanislav

    2010-01-01

    Roč. 2, č. 1 (2010), s. 1131-1140 E-ISSN 1877-7058. [Fatigue 2010. Praha, 06.06.2010-11.06.2010] Institutional research plan: CEZ:AV0Z20410507 Keywords : Fatigue models * Statistical compatibility * Functional equations Subject RIV: JL - Materials Fatigue, Friction Mechanics

  18. Construction Worker Fatigue Prediction Model Based on System Dynamic

    OpenAIRE

    Wahyu Adi Tri Joko; Ayu Ratnawinanda Lila

    2017-01-01

    Construction accident can be caused by internal and external factors such as worker fatigue and unsafe project environment. Tight schedule of construction project forcing construction worker to work overtime in long period. This situation leads to worker fatigue. This paper proposes a model to predict construction worker fatigue based on system dynamic (SD). System dynamic is used to represent correlation among internal and external factors and to simulate level of worker fatigue. To validate...

  19. 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.

  20. 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.

  1. Investigating the effect of coil model losses on computational electromagnetic exposure of an ASTM phantom at 64 MHz MRI.

    Science.gov (United States)

    Kozlov, Mikhail; Horner, Marc; Kainz, Wolfgang; Angelone, Leonardo M

    2017-07-01

    The goal of this work is to investigate the effect of coil losses on the electromagnetic field generated in an ASTM phantom by a birdcage coil. The study was based on different numerical implementations of an RF body coil at 64 MHz, using the same 3D EM and RF circuit co-simulation procedure. The coil quality factor was evaluated with respect to losses due to power feed mismatch and to resistive losses of the coil components. The results of the study showed that the magnetic field at the coil iso-center, normalized to the square root of the whole body specific absorption rate, depends on the coil quality factor.

  2. Construction Worker Fatigue Prediction Model Based on System Dynamic

    Directory of Open Access Journals (Sweden)

    Wahyu Adi Tri Joko

    2017-01-01

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

  3. 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)

  4. Application of Response Surface Methodology for Modeling of Postweld Heat Treatment Process in a Pressure Vessel Steel ASTM A516 Grade 70.

    Science.gov (United States)

    Peasura, Prachya

    2015-01-01

    This research studied the application of the response surface methodology (RSM) and central composite design (CCD) experiment in mathematical model and optimizes postweld heat treatment (PWHT). The material of study is a pressure vessel steel ASTM A516 grade 70 that is used for gas metal arc welding. PWHT parameters examined in this study included PWHT temperatures and time. The resulting materials were examined using CCD experiment and the RSM to determine the resulting material tensile strength test, observed with optical microscopy and scanning electron microscopy. The experimental results show that using a full quadratic model with the proposed mathematical model is YTS = -285.521 + 15.706X1 + 2.514X2 - 0.004X1(2) - 0.001X2(2) - 0.029X1X2. Tensile strength parameters of PWHT were optimized PWHT time of 5.00 hr and PWHT temperature of 645.75°C. The results show that the PWHT time is the dominant mechanism used to modify the tensile strength compared to the PWHT temperatures. This phenomenon could be explained by the fact that pearlite can contribute to higher tensile strength. Pearlite has an intensity, which results in increased material tensile strength. The research described here can be used as material data on PWHT parameters for an ASTM A516 grade 70 weld.

  5. Bayesian inference model for fatigue life of laminated composites

    DEFF Research Database (Denmark)

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

    2016-01-01

    A probabilistic model for estimating the fatigue life of laminated composite plates is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configurations. Model parameters are estimated by Bayesian inference. The ...

  6. Stochastic modeling of thermal fatigue crack growth

    CERN Document Server

    Radu, Vasile

    2015-01-01

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

  7. Physical and Model Uncertainty for Fatigue Design of Composite Material

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    The main aim of the present report is to establish stochastic models for the uncertainties related to fatigue design of composite materials. The uncertainties considered are the physical uncertainty related to the static and fatigue strength and the model uncertainty related to Miners rule...

  8. Influence of Chromium-Cobalt-Molybdenum Alloy (ASTM F75) on Bone Ingrowth in an Experimental Animal Model.

    Science.gov (United States)

    Zuchuat, Jésica; Berli, Marcelo; Maldonado, Ysaí; Decco, Oscar

    2017-12-26

    Cr-Co-Mo (ASTM F75) alloy has been used in the medical environment, but its use as a rigid barrier membrane for supporting bone augmentation therapies has not been extensively investigated. In the present study, Cr-Co-Mo membranes of different heights were placed in New Zealand white, male rabbit tibiae to assess the quality and volume of new bone formation, without the use of additional factors. Animals were euthanized at 20, 30, 40, and 60 days. Bone formation was observed in all of the cases, although the tibiae implanted with the standard membranes reached an augmentation of bone volume that agreed with the density values over the timecourse. In all cases, plasmatic exudate was found under the membrane and in contact with the new bone. Histological analysis indicated the presence of a large number of chondroblasts adjacent to the inner membrane surface in the first stages, and osteoblasts and osteocytes were observed under them. The bone formation was appositional. The Cr-Co-Mo alloy provides a scaffold with an adequate microenvironment for vertical bone volume augmentation, and the physical dimensions and disposition of the membrane itself influence the new bone formation.

  9. Influence of Chromium-Cobalt-Molybdenum Alloy (ASTM F75 on Bone Ingrowth in an Experimental Animal Model

    Directory of Open Access Journals (Sweden)

    Jésica Zuchuat

    2017-12-01

    Full Text Available Cr-Co-Mo (ASTM F75 alloy has been used in the medical environment, but its use as a rigid barrier membrane for supporting bone augmentation therapies has not been extensively investigated. In the present study, Cr-Co-Mo membranes of different heights were placed in New Zealand white, male rabbit tibiae to assess the quality and volume of new bone formation, without the use of additional factors. Animals were euthanized at 20, 30, 40, and 60 days. Bone formation was observed in all of the cases, although the tibiae implanted with the standard membranes reached an augmentation of bone volume that agreed with the density values over the timecourse. In all cases, plasmatic exudate was found under the membrane and in contact with the new bone. Histological analysis indicated the presence of a large number of chondroblasts adjacent to the inner membrane surface in the first stages, and osteoblasts and osteocytes were observed under them. The bone formation was appositional. The Cr-Co-Mo alloy provides a scaffold with an adequate microenvironment for vertical bone volume augmentation, and the physical dimensions and disposition of the membrane itself influence the new bone formation.

  10. Does Implementation of Biomathematical Models Mitigate Fatigue and Fatigue-related Risks in Emergency Medical Services Operations? A Systematic Review

    Science.gov (United States)

    2018-01-11

    Background: Work schedules like those of Emergency Medical Services (EMS) personnel have been associated with increased risk of fatigue-related impairment. Biomathematical modeling is a means of objectively estimating the potential impacts of fatigue...

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

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2013-01-01

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

  12. Fatigue

    Science.gov (United States)

    ... sleep. Fatigue is a lack of energy and motivation. Drowsiness and apathy (a feeling of not caring ... Call your provider right away if you have any of the following: Confusion or dizziness Blurred vision Little or no urine, or recent ...

  13. 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.

  14. 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

  15. Uncertainty analysis of constant amplitude fatigue test data employing the six parameters random fatigue limit model

    Directory of Open Access Journals (Sweden)

    Leonetti Davide

    2018-01-01

    Full Text Available Estimating and reducing uncertainty in fatigue test data analysis is a relevant task in order to assess the reliability of a structural connection with respect to fatigue. Several statistical models have been proposed in the literature with the aim of representing the stress range vs. endurance trend of fatigue test data under constant amplitude loading and the scatter in the finite and infinite life regions. In order to estimate the safety level of the connection also the uncertainty related to the amount of information available need to be estimated using the methods provided by the theory of statistic. The Bayesian analysis is employed to reduce the uncertainty due to the often small amount of test data by introducing prior information related to the parameters of the statistical model. In this work, the inference of fatigue test data belonging to cover plated steel beams is presented. The uncertainty is estimated by making use of Bayesian and frequentist methods. The 5% quantile of the fatigue life is estimated by taking into account the uncertainty related to the sample size for both a dataset containing few samples and one containing more data. The S-N curves resulting from the application of the employed methods are compared and the effect of the reduction of uncertainty in the infinite life region is quantified.

  16. Computational stress and damage modelling for rolling contact fatigue

    DEFF Research Database (Denmark)

    Cerullo, Michele

    Rolling contact fatigue in radial roller bearings is studied by means of a 2D plane strain nite element program. The Dang Van multiaxial fatigue criterion is firstly used, in a macroscopic study modeling the bearing raceway, to investigate the region where fatigue cracks are more likely to nucleate...... and of compressive residual stresses are also analyzed. The stress history of a material point at the depth where the maximum Dang Van damage factor is reached is then recorded and used in a subsequent micro-mechanical analysis. The stress history is applied as periodic boundary conditions in a representative volume...

  17. 47 CFR 90.379 - ASTM E2213-03 DSRC Standard (ASTM-DSRC Standard).

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false ASTM E2213-03 DSRC Standard (ASTM-DSRC Standard... Communications Service (dsrcs) § 90.379 ASTM E2213-03 DSRC Standard (ASTM-DSRC Standard). Roadside Units... incorporated by reference: American Society for Testing and Materials (ASTM) E2213-03, “Standard Specification...

  18. 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

  19. Modelling the fatigue behaviour of a stratified glass-epoxy composite: theoretical and experimental aspects; Modelisation du comportement en fatigue d`un composite stratifie verre-epoxyde: aspects theoriques et experimentaux

    Energy Technology Data Exchange (ETDEWEB)

    Verdiere, N.; Suri, C. [Laboratoire de mecanique appliquee, 25 - Besancon (France)

    1996-01-01

    Composite materials are used in the manufacture of water transport pipework for use in PWR`s. Estimation of their life expectancy relies on long and costly tests (ASTM D2992B standard). It would be extremely advantageous to have another method relying only on short laboratory tests which could be based on a mechanical behaviour and damage model. For several years, the Laboratoire de Mecanique Appliquee de Besancon has been developing a mechanical behaviour model for composite material tubes for different types of multiaxial stresses. However, this model does not take into account the fatigue behaviour. We therefore needed to find out how this type of stress could be incorporated into the model. To this end, research was undertaken in the form of a thesis (by E. Joseph) both to perfect the multiaxial fatigue stress testing machines and to take into account this type of behaviour in the mechanical model. This study covered glass fibre/epoxy resin composite material tubes and allowed their behaviour to be modelled. An important part of the work concerned the instrumentation and adaptation of test machines which hitherto did not exist so that the research could be carried out. For each of the stress axes (traction, internal pressure without vacuum effect ({Sigma}{sup zz}=0) and internal pressure with vacuum effect ({Sigma}{sup zz}=1/2{Sigma}{sup {theta}{theta}})), instantaneous behaviour was studied. Three stress levels and frequency values were used to define the fatigue behaviour. (authors). 23 refs., 41 figs., 5 tabs.

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

    Directory of Open Access Journals (Sweden)

    Humphrey Louise

    2010-09-01

    Full Text Available Abstract Background Fatigue is increasingly recognized as an important symptom in fibromyalgia (FM. Unknown however is how fatigue is experienced by individuals in the context of FM. We conducted qualitative research in order to better understand aspects of fatigue that might be unique to FM as well as the impact it has on patients' lives. The data obtained informed the development of a conceptual model of fatigue in FM. Methods Open-ended interviews were conducted with 40 individuals with FM (US [n = 20], Germany [n = 10] and France [n = 10]. Transcripts were analyzed using qualitative methods based upon grounded theory to identify key themes and concepts. Results Participants were mostly female (70% with a mean age of 48.7 years (range: 25-79. Thirty-one individuals (i.e., 77.5% spontaneously described experiencing tiredness/lack of energy/fatigue due to FM. Participants discussed FM fatigue as being more severe, constant/persistent and unpredictable than normal tiredness. The conceptual model depicts the key elements of fatigue in FM from a patient perspective. This includes: an overwhelming feeling of tiredness (n = 17, 42.5%, not relieved by resting/sleeping (n = 15, 37.5%, not proportional to effort exerted (n = 25, 62.5%, associated with a feeling of weakness/heaviness (n = 20, 50%, interferes with motivation (n = 22, 55%, interferes with desired activities (n = 27, 67.5%, prolongs tasks (n = 15, 37.5%, and makes it difficult to concentrate (n = 21, 52.5%, think clearly (n = 12, 30% or remember things (n = 9, 22.5%. Conclusion The majority of individuals with FM who participated in this study experience fatigue and describe it as more severe than normal tiredness.

  1. The application of an internal state variable model to the viscoplastic behavior of irradiated ASTM 304L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    McAnulty, Michael J., E-mail: mcanulmj@id.doe.gov [Department of Energy, 1955 Fremont Avenue, Idaho Falls, ID 83402 (United States); Potirniche, Gabriel P. [Mechanical Engineering Department, University of Idaho, Moscow, ID 83844 (United States); Tokuhiro, Akira [Mechanical Engineering Department, University of Idaho, Idaho Falls, ID 83402 (United States)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer An internal state variable approach is used to predict the plastic behavior of irradiated metals. Black-Right-Pointing-Pointer The model predicts uniaxial tensile test data for irradiated 304L stainless steel. Black-Right-Pointing-Pointer The model is implemented as a user-defined material subroutine in the finite element code ABAQUS. Black-Right-Pointing-Pointer Results are compared for the unirradiated and irradiated specimens loaded in uniaxial tension. - Abstract: Neutron irradiation of metals results in decreased fracture toughness, decreased ductility, increased yield strength and increased ductile-to-brittle transition temperature. Designers use the most limiting material properties throughout the reactor vessel lifetime to determine acceptable safety margins. To reduce analysis conservatism, a new model is proposed based on an internal state variable approach for the plastic behavior of unirradiated ductile materials to support its use for analyzing irradiated materials. The proposed modeling addresses low temperature irradiation of 304L stainless steel, and predicts uniaxial tensile test data of irradiated experimental specimens. The model was implemented as a user-defined material subroutine (UMAT) in the finite element software ABAQUS. Results are compared between the unirradiated and irradiated specimens subjected to tension tests.

  2. Probabilistic Model for Fatigue Crack Growth in Welded Bridge Details

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard; Yalamas, Thierry

    2013-01-01

    In the present paper a probabilistic model for fatigue crack growth in welded steel details in road bridges is presented. The probabilistic model takes the influence of bending stresses in the joints into account. The bending stresses can either be introduced by e.g. misalignment or redistribution...... of stresses in the structure. The fatigue stress ranges are estimated from traffic measurements and a generic bridge model. Based on the probabilistic models for the resistance and load the reliability is estimated for a typical welded steel detail. The results show that large misalignments in the joints can...

  3. Bayesian inference and model comparison for metallic fatigue data

    KAUST Repository

    Babuška, Ivo

    2016-02-23

    In this work, we present a statistical treatment of stress-life (S-N) data drawn from a collection of records of fatigue experiments that were performed on 75S-T6 aluminum alloys. Our main objective is to predict the fatigue life of materials by providing a systematic approach to model calibration, model selection and model ranking with reference to S-N data. To this purpose, we consider fatigue-limit models and random fatigue-limit models that are specially designed to allow the treatment of the run-outs (right-censored data). We first fit the models to the data by maximum likelihood methods and estimate the quantiles of the life distribution of the alloy specimen. To assess the robustness of the estimation of the quantile functions, we obtain bootstrap confidence bands by stratified resampling with respect to the cycle ratio. We then compare and rank the models by classical measures of fit based on information criteria. We also consider a Bayesian approach that provides, under the prior distribution of the model parameters selected by the user, their simulation-based posterior distributions. We implement and apply Bayesian model comparison methods, such as Bayes factor ranking and predictive information criteria based on cross-validation techniques under various a priori scenarios.

  4. Bayesian inference and model comparison for metallic fatigue data

    KAUST Repository

    Babuška, Ivo; Sawlan, Zaid A; Scavino, Marco; Szabó , Barna; Tempone, Raul

    2016-01-01

    In this work, we present a statistical treatment of stress-life (S-N) data drawn from a collection of records of fatigue experiments that were performed on 75S-T6 aluminum alloys. Our main objective is to predict the fatigue life of materials by providing a systematic approach to model calibration, model selection and model ranking with reference to S-N data. To this purpose, we consider fatigue-limit models and random fatigue-limit models that are specially designed to allow the treatment of the run-outs (right-censored data). We first fit the models to the data by maximum likelihood methods and estimate the quantiles of the life distribution of the alloy specimen. To assess the robustness of the estimation of the quantile functions, we obtain bootstrap confidence bands by stratified resampling with respect to the cycle ratio. We then compare and rank the models by classical measures of fit based on information criteria. We also consider a Bayesian approach that provides, under the prior distribution of the model parameters selected by the user, their simulation-based posterior distributions. We implement and apply Bayesian model comparison methods, such as Bayes factor ranking and predictive information criteria based on cross-validation techniques under various a priori scenarios.

  5. Comparison of ASTM D613 and ASTM D6890

    Science.gov (United States)

    2016-04-01

    cetane values outside of the routine range of traditional CN testing by ASTM D613, this is an important advantage in fuel blending and disposition...Number testing. Particular emphasis was placed on evaluating fuels, and blends thereof, having cetane values outside of the normal range of the...interest covers both petroleum-based and synthetic-based, as well as blends thereof in order to improve the confidence in using DCN as a replacement

  6. Bayesian inference and model comparison for metallic fatigue data

    KAUST Repository

    Babuska, Ivo

    2016-01-06

    In this work, we present a statistical treatment of stress-life (S-N) data drawn from a collection of records of fatigue experiments that were performed on 75S-T6 aluminum alloys. Our main objective is to predict the fatigue life of materials by providing a systematic approach to model calibration, model selection and model ranking with reference to S-N data. To this purpose, we consider fatigue-limit models and random fatigue-limit models that are specially designed to allow the treatment of the run-outs (right-censored data). We first fit the models to the data by maximum likelihood methods and estimate the quantiles of the life distribution of the alloy specimen. We then compare and rank the models by classical measures of fit based on information criteria. We also consider a Bayesian approach that provides, under the prior distribution of the model parameters selected by the user, their simulation-based posterior distributions.

  7. Fatigue reliability and effective turbulence models in wind farms

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Frandsen, Sten Tronæs; Tarp-Johansen, N.J.

    2007-01-01

    behind wind turbines can imply a significant reduction in the fatigue lifetime of wind turbines placed in wakes. In this paper the design code model in the wind turbine code IEC 61400-1 (2005) is evaluated from a probabilistic point of view, including the importance of modeling the SN-curve by linear...

  8. 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.

  9. Convex models and probabilistic approach of nonlinear fatigue failure

    International Nuclear Information System (INIS)

    Qiu Zhiping; Lin Qiang; Wang Xiaojun

    2008-01-01

    This paper is concerned with the nonlinear fatigue failure problem with uncertainties in the structural systems. In the present study, in order to solve the nonlinear problem by convex models, the theory of ellipsoidal algebra with the help of the thought of interval analysis is applied. In terms of the inclusion monotonic property of ellipsoidal functions, the nonlinear fatigue failure problem with uncertainties can be solved. A numerical example of 25-bar truss structures is given to illustrate the efficiency of the presented method in comparison with the probabilistic approach

  10. Hybrid discrete dislocation models for fatigue crack growth

    NARCIS (Netherlands)

    Curtin, W. A.; Deshpande, V. S.; Needleman, A.; Van der Giessen, E.; Wallin, M.

    A framework for accurately modeling fatigue crack growth in ductile crystalline solids is necessarily multiscale The creation of new free surface occurs at the atomistic scale, where the material's cohesive strength is controlled by the local chemistry On the other hand, significant dissipation

  11. Impact evaluation of rolling contact fatigue life models

    International Nuclear Information System (INIS)

    Choi, Young Sik; Yang, Xiaoping

    2012-01-01

    Since the accurate prediction of fatigue life has a significant value, many researchers have attempted to develop a reliable fatigue life model. Recently, rolling contact fatigue life models incorporating machining impact were developed. These models have contributed to a significant improvement in prediction accuracy as compared with earlier models, thus representing a major step forward in the modeling effort. This paper compares the prediction accuracy of these models with that of the prediction method in International Standards. When α is set to 0.25, the observed improvement of prediction accuracy as measured by variance of prediction errors due to these models over that due to prediction method in International Standards is statistically significant. Impact analyses of such improvement are conducted to illustrate its value. It is further noted that while difference was observed between the variance of prediction errors due to the crack initiation life model based on a dislocation model and that due to the crack initiation life model based on a local stress-life curve, the observed difference is not statistically significant

  12. 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.

  13. Efeito da temperatura interpasse na microestrutura, tenacidade ao impacto e propagação de trinca por fadiga de uniões soldadas por GTAW do aço ASTM A743-CA6NM Interpass temperature influence on the microstructure, impact toughness and fatigue crack propagation in ASTM A743-CA6NM GTAW welded joints

    Directory of Open Access Journals (Sweden)

    Ruimar Rubens de Gouveia

    2013-06-01

    in welding procedures development that promotes a better toughness, without post welding heat treatment (PWHT. The mainly objective of this paper is analyze the influence of interpass temperature on the microstructure, impact toughness and fatigue crack propagation in CA6NM martensitic stainless steel multipass welded joints, with AWS410NiMo filler metal, with GTAW (gas tungsten arc welding. It was observed the interpass temperature influence on ferrite δ formation, observing intergranular ferrite d formation on the d+g field in 80 ºC interpass temperature, while the sample welded at 150 ºC the formation of ferrite d occurs mainly in the δ monophase field. Ferrite d formation with the lowest temperature interpass promoted an increase in impact toughness and a decrease in the fatigue crack propagation when compared with 150ºC interpass temperature sample. It was observed that GTAW process can be an excellent alternative for CA6NM hydraulic turbine repair, it was also observed a significant interpass temperature influence.

  14. Method for Estimating Evaporative Potential (IM/CLO) from ASTM Standard Single Wind Velocity Measures

    Science.gov (United States)

    2016-08-10

    IM/CLO) FROM ASTM STANDARD SINGLE WIND VELOCITY MEASURES DISCLAIMER The opinions or assertions contained herein are the private views of the...USARIEM TECHNICAL REPORT T16-14 METHOD FOR ESTIMATING EVAPORATIVE POTENTIAL (IM/CLO) FROM ASTM STANDARD SINGLE WIND VELOCITY... ASTM STANDARD SINGLE WIND VELOCITY MEASURES Adam W. Potter Biophysics and Biomedical Modeling Division U.S. Army Research Institute of Environmental

  15. High-cycle notch sensitivity of alloy steel ASTM A743 CA6NM used in hydrogenator turbine components

    Directory of Open Access Journals (Sweden)

    José Alexander Araújo

    2010-10-01

    Full Text Available The presence of notches and other stress concentrations in turbine blades and other notch hydraulic components is a current problem in engineering. It causes a reduction of endurance limit of material. In that sense, specimens of the ASTM A743 CA6NM alloy steel using in several hydrogenator turbine components was tested. The specimens were tested under uniaxial fatigue loading with a load ratio equal to -1, and the considered stress concentration factors, Kt, values, calculated with respect to net area, were 1.55, 2.04 and 2.42. In order to determine the fatigue limit for such notch type, a reduction data method by Dixon and Mood, Staircase method was used. This approach is based on the assumed target distribution of the fatigue limit. For such geometry at least 8 specimens were tested. In addition, the Peterson and Neuber’s notch fatigue factor were compared through fatigue notch reduction factor, Kf, obtained from experimental data. According to results obtained it was possible to conclude that the tested material is less sensitive to notches than the prediction of the Peterson and Neuber’s empirical models.

  16. 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...

  17. Validating and Verifying Biomathematical Models of Human Fatigue

    Science.gov (United States)

    Martinez, Siera Brooke; Quintero, Luis Ortiz; Flynn-Evans, Erin

    2015-01-01

    Airline pilots experience acute and chronic sleep deprivation, sleep inertia, and circadian desynchrony due to the need to schedule flight operations around the clock. This sleep loss and circadian desynchrony gives rise to cognitive impairments, reduced vigilance and inconsistent performance. Several biomathematical models, based principally on patterns observed in circadian rhythms and homeostatic drive, have been developed to predict a pilots levels of fatigue or alertness. These models allow for the Federal Aviation Administration (FAA) and commercial airlines to make decisions about pilot capabilities and flight schedules. Although these models have been validated in a laboratory setting, they have not been thoroughly tested in operational environments where uncontrolled factors, such as environmental sleep disrupters, caffeine use and napping, may impact actual pilot alertness and performance. We will compare the predictions of three prominent biomathematical fatigue models (McCauley Model, Harvard Model, and the privately-sold SAFTE-FAST Model) to actual measures of alertness and performance. We collected sleep logs, movement and light recordings, psychomotor vigilance task (PVT), and urinary melatonin (a marker of circadian phase) from 44 pilots in a short-haul commercial airline over one month. We will statistically compare with the model predictions to lapses on the PVT and circadian phase. We will calculate the sensitivity and specificity of each model prediction under different scheduling conditions. Our findings will aid operational decision-makers in determining the reliability of each model under real-world scheduling situations.

  18. Fatigue crack propagation: Probabilistic models and experimental evidence

    International Nuclear Information System (INIS)

    Lucia, A.C.; Jovanovic, A.

    1987-01-01

    The central aim of the LWR Primary Circuit Component Life Prediction Project, going on at JRC-Ispra, is to develop and check a 'procedure' (encompassing monitoring and inspection, data collection and analysis, prediction) allowing the quantitatives estimation of the accumulation of structural damage and of the residual lifetime. The ongoing activity matches theoretical development and experimentation, the latter being at present essentially based on a test-rig for room-temperature fatigue cycling of 1:5 scaled models of pressure vessels. During Phase I of fatigue testing of vessel R2, different pieces of information coming from material characterization, non-destructive inspection, continuous monitoring, stress analysis, have been merged and used to infere the future behaviour of the structure. The prediction of residual lifetime (cycles to failure), based on the outcomes of the ultrasonic continuous monitoring and made by means of the COVASTOL code, was in quite good agreement with experimental evidence. (orig./HP)

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

    Science.gov (United States)

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

    2016-03-01

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

  20. 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)

  1. Comparison of two multiaxial fatigue models applied to dental implants

    Directory of Open Access Journals (Sweden)

    JM. Ayllon

    2015-07-01

    Full Text Available This paper presents two multiaxial fatigue life prediction models applied to a commercial dental implant. One model is called Variable Initiation Length Model and takes into account both the crack initiation and propagation phases. The second model combines the Theory of Critical Distance with a critical plane damage model to characterise the initiation and initial propagation of micro/meso cracks in the material. This paper discusses which material properties are necessary for the implementation of these models and how to obtain them in the laboratory from simple test specimens. It also describes the FE models developed for the stress/strain and stress intensity factor characterisation in the implant. The results of applying both life prediction models are compared with experimental results arising from the application of ISO-14801 standard to a commercial dental implant.

  2. Predictive modelling of fatigue failure in concentrated lubricated contacts.

    Science.gov (United States)

    Evans, H P; Snidle, R W; Sharif, K J; Bryant, M J

    2012-01-01

    Reducing frictional losses in response to the energy agenda will require use of less viscous lubricants causing hydrodynamically-lubricated bearings to operate with thinner films leading to "mixed lubrication" conditions in which a degree of direct interaction occurs between surfaces protected only by boundary tribofilms. The paper considers the consequences of thinner films and mixed lubrication for concentrated contacts such as those occurring between the teeth of power transmission gears and in rolling element bearings. Surface fatigue in gears remains a serious problem in demanding applications, and its solution will become more pressing with the tendency towards thinner oils. The particular form of failure examined here is micropitting, which is identified as a fatigue phenomenon occurring at the scale of the surface roughness asperities. It has emerged recently as a systemic difficulty in the operation of large scale wind turbines where it occurs in both power transmission gears and their support bearings. Predictive physical modelling of these contacts requires a transient mixed lubrication analysis for conditions in which the predicted lubricant film thickness is of the same order or significantly less than the height of surface roughness features. Numerical solvers have therefore been developed which are able to deal with situations in which transient solid contacts occur between surface asperity features under realistic engineering conditions. Results of the analysis, which reveal the detailed time-varying behaviour of pressure and film clearance, have been used to predict fatigue and damage accumulation at the scale of surface asperity features with the aim of improving understanding of the micropitting phenomenon. The possible consequences on fatigue of residual stress fields resulting from plastic deformation of surface asperities is also considered.

  3. Modeling Quasi-Static and Fatigue-Driven Delamination Migration

    Science.gov (United States)

    De Carvalho, N. V.; Ratcliffe, J. G.; Chen, B. Y.; Pinho, S. T.; Baiz, P. M.; Tay, T. E.

    2014-01-01

    An approach was proposed and assessed for the high-fidelity modeling of progressive damage and failure in composite materials. It combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. Delamination, matrix cracking, and migration were captured failure and migration criteria based on fracture mechanics. Quasi-static and fatigue loading were modeled within the same overall framework. The methodology proposed was illustrated by simulating the delamination migration test, showing good agreement with the available experimental data.

  4. Development of fatigue crack propagation models for engineering applications at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Tomkins, B.

    1975-05-01

    The value of modelling the fatigue crack propagation process is discussed and current models are examined in the light of increasing knowledge of crack tip deformation. Elevated temperature fatigue is examined in detail as an area in which models could contribute significantly to engineering design. A model is developed which examines the role of time-dependent creep cavitation on the failure process in an interactive creep-fatigue situation. (auth)

  5. Human performance modeling for system of systems analytics :soldier fatigue.

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, Craig R.; Campbell, James E.; Miller, Dwight Peter

    2005-10-01

    The military has identified Human Performance Modeling (HPM) as a significant requirement and challenge of future systems modeling and analysis initiatives as can be seen in the Department of Defense's (DoD) Defense Modeling and Simulation Office's (DMSO) Master Plan (DoD 5000.59-P 1995). To this goal, the military is currently spending millions of dollars on programs devoted to HPM in various military contexts. Examples include the Human Performance Modeling Integration (HPMI) program within the Air Force Research Laboratory, which focuses on integrating HPMs with constructive models of systems (e.g. cockpit simulations) and the Navy's Human Performance Center (HPC) established in September 2003. Nearly all of these initiatives focus on the interface between humans and a single system. This is insufficient in the era of highly complex network centric SoS. This report presents research and development in the area of HPM in a system-of-systems (SoS). Specifically, this report addresses modeling soldier fatigue and the potential impacts soldier fatigue can have on SoS performance.

  6. Effects of fatigue on the chemical and mechanical degradation of model stent sub-units.

    Science.gov (United States)

    Dreher, Maureen L; Nagaraja, Srinidhi; Batchelor, Benjamin

    2016-06-01

    Understanding the fatigue and durability performance of implantable cardiovascular stents is critical for assessing their performance. When the stent is manufactured from an absorbable material, however, this durability assessment is complicated by the transient nature of the device. Methodologies for evaluating the fatigue performance of absorbable stents while accurately simulating the degradation are limited and little is known about the interaction between fatigue and degradation. In this study, we investigated the fatigue behavior and effect of fatigue on the degradation rate for a model absorbable cardiovascular stent. Custom v-shaped stent sub-units manufactured from poly(L-lactide), i.e., PLLA, were subjected to a simultaneous fatigue and degradation study with cycle counts representative of one year of expected in vivo use. Fatigue loading was carried out such that the polymer degraded at a rate that was aligned with a modest degree of fatigue acceleration. Control, un-loaded specimens were also degraded under static immersion conditions representative of simulated degradation without fatigue. The study identified that fatigue loading during degradation significantly increased specimen stiffness and lowered the force at break. Fatigue loading also significantly increased the degree of molecular weight decline highlighting an interaction between mechanical loading and chemical degradation. This study demonstrates that fatigue loading during degradation can affect both the mechanical properties and the chemical degradation rate. The results are important for defining appropriate in vitro degradation conditions for absorbable stent preclinical evaluation. Published by Elsevier Ltd.

  7. 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....

  8. Theoretical modeling and experimental study on fatigue initiation life of 16MnR notched components

    International Nuclear Information System (INIS)

    Wang Xiaogui; Gao Zengliang; Qiu Baoxiang; Jiang Yanrao

    2010-01-01

    In order to investigate the effects of notch geometry and loading conditions on the fatigue initiation life and fatigue fracture life of 16MnR material, fatigue experiments were conducted for both smooth rod specimens and notched rod specimens. The detailed elastic-plastic stress and strain responses were computed by the finite element software (ABAQUS) incorporating a robust cyclic plasticity model via a user subroutine UMAT. The obtained stresses and strains were applied to the multiaxial fatigue damage criterion to compute the fatigue damage induced by a loading cycle on the critical material plane. The fatigue initiation life was then obtained by the proposed theoretical model. The well agreement between the predicted results and the experiment data indicated that the fatigue initiation of notched components in the multiaxial stress state related to all the nonzero stress and strain quantities. (authors)

  9. 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...

  10. A fiber bridging model for fatigue delamination in composite materials

    International Nuclear Information System (INIS)

    Gregory, Jeremy R.; Spearing, S. Mark

    2004-01-01

    A fiber bridging model has been created to examine the effects of bridging on Mode I delamination fatigue fracture in a carbon fiber polymer-matrix composite. The model uses a cohesive zone law that is derived from quasi-static R-curves to determine the bridging energy applied in the bridged region. Timoshenko beam theory and an iterative self-consistent scheme are used to calculate the bridging tractions and displacements. After applying the bridging model to crack propagation data the scatter in the data was significantly reduced and clear trends were observed as a function of temperature that were not apparent previously. This indicated that the model appropriately accounted for the bridging in the experiments. Scanning electron microscopy crack opening displacement measurements were performed to validate the model's predictions. The measurements showed that the predictions were close to the actual bridging levels in the specimen

  11. Study of mathematical models for fatigue crack propagation

    International Nuclear Information System (INIS)

    Yarema, S.Ya.; Mel'nichok, L.S.

    1982-01-01

    Complex composition of mathematical models for description of experimental diagrams of fatigue fracture (EDFF) for different steels and alloys from the view point of their correspondence to experimental data is conducted. 5 simple formulas for EDFF description have been chosen from the known ones. It is revealed that the analytical expression should contain 6 parameters for the main peculiarities of typical EDFF. This conclusion agrees with the fact that the 6-parametric formula provides the best quality of experimental data approximation. It should be also noted that the necessary number of parameters coincides with the number of all the standard characteristics (main and additional) of cyclic crack resistance of materials

  12. Cyclic plasticity models and application in fatigue analysis

    Science.gov (United States)

    Kalev, I.

    1981-01-01

    An analytical procedure for prediction of the cyclic plasticity effects on both the structural fatigue life to crack initiation and the rate of crack growth is presented. The crack initiation criterion is based on the Coffin-Manson formulae extended for multiaxial stress state and for inclusion of the mean stress effect. This criterion is also applied for the accumulated damage ahead of the existing crack tip which is assumed to be related to the crack growth rate. Three cyclic plasticity models, based on the concept of combination of several yield surfaces, are employed for computing the crack growth rate of a crack plane stress panel under several cyclic loading conditions.

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

    DEFF Research Database (Denmark)

    Humphrey, Louise; Arbuckle, Rob; Mease, Philip

    2010-01-01

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

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

    DEFF Research Database (Denmark)

    Humphrey, Louise; Arbuckle, Rob; Mease, Philip

    2010-01-01

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

  15. Analytical modeling of the thermomechanical behavior of ASTM F-1586 high nitrogen austenitic stainless steel used as a biomaterial under multipass deformation.

    Science.gov (United States)

    Bernardes, Fabiano R; Rodrigues, Samuel F; Silva, Eden S; Reis, Gedeon S; Silva, Mariana B R; Junior, Alberto M J; Balancin, Oscar

    2015-06-01

    Precipitation-recrystallization interactions in ASTM F-1586 austenitic stainless steel were studied by means of hot torsion tests with multipass deformation under continuous cooling, simulating an industrial laminating process. Samples were deformed at 0.2 and 0.3 at a strain rate of 1.0s(-1), in a temperature range of 900 to 1200°C and interpass times varying from 5 to 80s. The tests indicate that the stress level depends on deformation temperature and the slope of the equivalent mean stress (EMS) vs. 1/T presents two distinct behaviors, with a transition at around 1100°C, the non-recrystallization temperature (Tnr). Below the Tnr, strain-induced precipitation of Z-phase (NbCrN) occurs in short interpass times (tpass<30s), inhibiting recrystallization and promoting stepwise stress build-up with strong recovery, which is responsible for increasing the Tnr. At interpass times longer than 30s, the coalescence and dissolution of precipitates promote a decrease in the Tnr and favor the formation of recrystallized grains. Based on this evidence, the physical simulation of controlled processing allows for a domain refined grain with better mechanical properties. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Thermomechanical fatigue of Sn-37 wt.% Pb model solder joints

    International Nuclear Information System (INIS)

    Liu, X.W.; Plumbridge, W.J.

    2003-01-01

    The fatigue of Sn-37 wt.% Pb model solder joints has been investigated under thermomechanical and thermal cycling. Based upon an analysis of displacements during thermomechancial cycling, a model solder joint has been designed to simulate actual joints in electronic packages. The strain-stress relationship, characterised by hysteresis loops, was determined during cycling from 30 to 125 deg. C, and the stress-range monitored throughout. The number of cycles to failure, as defined by the fall in stress range, was correlated to strain range and strain energy. The strain hardening exponent, k, varied with the definition of failure and, when a stress-range drop of 50% was used, it was 0.46. Cracks were produced during pure thermal cycling without external strains applied. These arose due to the local strains caused by thermal expansion mismatches between the solder and Cu 6 Sn 5 intermetallic layer, between the phases of solder, and due to the anisotropy of the materials. The fatigue life under thermomechanical cycling was significantly inferior to that obtained in isothermal mechanical cycling. A factor contributing to this inferiority is the internal damage produced during temperature cycling

  17. Analysis of Fatigue Life of PMMA at Different Frequencies Based on a New Damage Mechanics Model

    Directory of Open Access Journals (Sweden)

    Aifeng Huang

    2014-01-01

    Full Text Available Low-cycle fatigue tests at different frequencies and creep tests under different stress levels of Plexiglas Resist 45 were conducted. Correspondingly, the creep fracture time, S-N curves, cyclic creep, and hysteresis loop were obtained. These results showed that the fatigue life increases with frequency at low frequency domain. After analysis, it was found that fatigue life is dependent on the load rate and is affected by the creep damage. In addition, a new continuum damage mechanics (CDM model was established to analyze creep-fatigue life, where the damage increment nonlinear summation rule was proposed and the frequency modification was made on the fatigue damage evolution equation. Differential evolution (DE algorithm was employed to determine the parameters within the model. The proposed model described fatigue life under different frequencies, and the calculated results agreed well with the experimental results.

  18. ASTM reference radiologic digital image standards

    International Nuclear Information System (INIS)

    Wysnewski, R.; Wysnewski, D.

    1996-01-01

    ASTM Reference Radiographs have been essential in defining industry's material defect grade levels for many years. ASTM Reference Radiographs are used extensively as even the American Society for Metals Nondestructive Inspection and Quality Control Metals Handbook, Volume 11, eighth edition refers to ASTM Standard Reference Radiographs. The recently published E 1648 Standard Reference Radiographs for Examination of Aluminum Fusion Welds is a prime example of the on-going need for these references. To date, 14 Standard Reference Radiographs have been published to characterize material defects. Standard Reference Radiographs do not adequately address film-less radiologic methods. There are differences in mediums to content with. On a computer CRT defect indications appear differently when compared to indications viewed in a radiograph on a view box. Industry that uses non-film radiologic methods of inspection can be burdened with additional time and money developing internal standard reference radiologic images. These references may be deemed necessary for grading levels of product defects. Because there are no ASTM Standard Reference Radiologic data files for addressing this need in the industry, the authors of this paper suggested implementing a method for their creation under ASTM supervision. ASTM can assure continuity to those users making the transition from analog radiographic images to digital image data by swiftly addressing the requirements for reference digital image standards. The current status and possible future activities regarding a method to create digital data files is presented in this paper summary

  19. 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.

  20. Fatigue damage modeling in solder interconnects using a cohesive zone approach

    NARCIS (Netherlands)

    Abdul-Baqi, A.J.J.; Schreurs, P.J.G.; Geers, M.G.D.

    2005-01-01

    The objective of this work is to model the fatigue damage process in a solder bump subjected to cyclic loading conditions. Fatigue damage is simulated using the cohesive zone methodology. Damage is assumed to occur at interfaces modeled through cohesive zones in the material, while the bulk material

  1. Probabilistic Modelling of Fatigue Life of Composite Laminates Using Bayesian Inference

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Kiureghian, Armen Der

    2014-01-01

    A probabilistic model for estimating the fatigue life of laminated composite plates subjected to constant-amplitude or variable-amplitude loading is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configuratio...

  2. 46 CFR 163.003-3 - ASTM standard.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 6 2010-10-01 2010-10-01 false ASTM standard. 163.003-3 Section 163.003-3 Shipping...: SPECIFICATIONS AND APPROVAL CONSTRUCTION Pilot Ladder § 163.003-3 ASTM standard. The following standard of the American Society for Testing and Materials (ASTM) is incorporated by reference into this subpart: ASTM D...

  3. Modeling size effects on fatigue life of a zirconium-based bulk metallic glass under bending

    International Nuclear Information System (INIS)

    Yuan Tao; Wang Gongyao; Feng Qingming; Liaw, Peter K.; Yokoyama, Yoshihiko; Inoue, Akihisa

    2013-01-01

    A size effect on the fatigue-life cycles of a Zr 50 Cu 30 Al 10 Ni 10 (at.%) bulk metallic glass has been observed in the four-point-bending fatigue experiment. Under the same bending-stress condition, large-sized samples tend to exhibit longer fatigue lives than small-sized samples. This size effect on the fatigue life cannot be satisfactorily explained by the flaw-based Weibull theories. Based on the experimental results, this study explores possible approaches to modeling the size effects on the bending-fatigue life of bulk metallic glasses, and proposes two fatigue-life models based on the Weibull distribution. The first model assumes, empirically, log-linear effects of the sample thickness on the Weibull parameters. The second model incorporates the mechanistic knowledge of the fatigue behavior of metallic glasses, and assumes that the shear-band density, instead of the flaw density, has significant influence on the bending fatigue-life cycles. Promising predictive results provide evidence of the potential validity of the models and their assumptions.

  4. Bayesian inference and model comparison for metallic fatigue data

    KAUST Repository

    Babuska, Ivo; Sawlan, Zaid A; Scavino, Marco; Szabó , Barma; Tempone, Raul

    2016-01-01

    In this work, we present a statistical treatment of stress-life (S-N) data drawn from a collection of records of fatigue experiments that were performed on 75S-T6 aluminum alloys. Our main objective is to predict the fatigue life of materials

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

    Science.gov (United States)

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

    2010-01-01

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

  6. Applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures

    NARCIS (Netherlands)

    Zou, T.; Kaminski, M.L.

    2016-01-01

    In design and operation of floating offshore structures, one has to avoid fatigue failures caused by action of ocean waves. The aim of this paper is to investigate the applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures. The applicability was investigated

  7. Numerical modeling of thermal fatigue cracks from the viewpoint of eddy current testing

    International Nuclear Information System (INIS)

    Yusa, Noritaka; Hashizume, Hidetoshi; Virkkunen, Iikka; Kemppainen, Mika

    2012-01-01

    This study discusses a suitable numerical modeling of a thermal fatigue crack from the viewpoint of eddy current testing. Five artificial thermal fatigue cracks, introduced into type 304L austenitic stainless steel plates with a thickness of 25 mm, are prepared; and eddy current inspections are carried out to gather signals using an absolute type pancake probe and a differential type plus point probe. Finite element simulations are then carried out to evaluate a proper numerical model of the thermal fatigue cracks. In the finite element simulations, the thermal fatigue cracks are modeled as a semi-elliptic planar region on the basis of the results of the destructive tests. The width and internal conductivity are evaluated by the simulations. The results of the simulations reveal that the thermal fatigue cracks are regarded as almost nonconductive when the internal conductivity is assumed to be uniform inside. (author)

  8. Fatigue of Chinese railway employees and its influential factors: Structural equation modelling.

    Science.gov (United States)

    Tsao, Liuxing; Chang, Jing; Ma, Liang

    2017-07-01

    Fatigue is an identifiable and preventable cause of accidents in transport operations. Regarding the railway sector, incident logs and simulation studies show that employee fatigue leads to lack of alertness, impaired performance, and occurrence of incidents. China has one of the largest rail systems in the world, and Chinese railway employees work under high fatigue risks; therefore, it is important to assess their fatigue level and find the major factors leading to fatigue. We designed a questionnaire that uses Multidimensional Fatigue Instrument (MFI-20), NASA-TLX and subjective rating of work overtime feelings to assess employee fatigue. The contribution of each influential factor of fatigue was analysed using structural equation modelling. In total, 297 employees from the rail maintenance department and 227 employees from the locomotive department returned valid responses. The average scores and standard deviations for the five subscales of MFI-20, namely General Fatigue, Physical Fatigue, Reduced Activity, Reduced Motivation, and Mental Fatigue, were 2.9 (0.8), 2.8 (0.8), 2.5 (0.8), 2.5 (0.7), and 2.4 (0.8) among the rail maintenance employees and 3.5 (0.8), 3.5 (0.7), 3.3 (0.7), 3.0 (0.6), and 3.1 (0.7), respectively, among the locomotive employees. The fatigue of the locomotive employees was influenced by feelings related to working overtime (standardized r = 0.22) and workload (standardized r = 0.27). The work overtime control and physical working environment significantly influenced subjective feelings (standardized r = -0.25 and 0.47, respectively), while improper work/rest rhythms and an adverse physical working environment significantly increased the workload (standardized r = 0.48 and 0.33, respectively). Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Probabilistic Modeling of the Fatigue Crack Growth Rate for Ni-base Alloy X-750

    International Nuclear Information System (INIS)

    Yoon, Jae Young; Nam, Hyo On; Hwang, Il Soon; Tae Hyun Lee

    2012-01-01

    The Bayesian inference was employed to reduce the uncertainties contained in EAC modeling parameters that have been established from experiments with Alloy X-750. Corrosion fatigue crack growth rate model(FCGR) was developed by fitting into Paris' Law of measured data from the several fatigue tests conducted either in constant load or constant ΔK mode. From fitting the data to Paris' Law, the parameters C and m of Paris' Law model were assumed to obey the Gaussian distribution. These parameters characterizing the corrosion fatigue crack growth behavior of X-750 were updated to reduce the uncertainty in the model by using the Bayesian inference method. (author)

  10. A Modified Fatigue Damage Model for High-Cycle Fatigue Life Prediction

    Directory of Open Access Journals (Sweden)

    Meng Wang

    2016-01-01

    Full Text Available Based on the assumption of quasibrittle failure under high-cycle fatigue for the metal material, the damage constitutive equation and the modified damage evolution equation are obtained with continuum damage mechanics. Then, finite element method (FEM is used to describe the failure process of metal material. The increment of specimen’s life and damage state can be researched using damage mechanics-FEM. Finally, the lifetime of the specimen is got at the given stress level. The damage mechanics-FEM is inserted into ABAQUS with subroutine USDFLD and the Python language is used to simulate the fatigue process of titanium alloy specimens. The simulation results have a good agreement with the testing results under constant amplitude loading, which proves the accuracy of the method.

  11. Probabilistic modeling of crack networks in thermal fatigue

    International Nuclear Information System (INIS)

    Malesys, N.

    2007-11-01

    Thermal superficial crack networks have been detected in mixing zone of cooling system in nuclear power plants. Numerous experimental works have already been led to characterize initiation and propagation of these cracks. The random aspect of initiation led to propose a probabilistic model for the formation and propagation of crack networks in thermal fatigue. In a first part, uniaxial mechanical test were performed on smooth and slightly notched specimens in order to characterize the initiation of multiple cracks, their arrest due to obscuration and the coalescence phenomenon by recovery of amplification stress zones. In a second time, the probabilistic model was established under two assumptions: the continuous cracks initiation on surface, described by a Poisson point process law with threshold, and the shielding phenomenon which prohibits the initiation or the propagation of a crack if this one is in the relaxation stress zone of another existing crack. The crack propagation is assumed to follow a Paris' law based on the computation of stress intensity factors at the top and the bottom of crack. The evolution of multiaxial cracks on the surface can be followed thanks to three quantities: the shielding probability, comparable to a damage variable of the structure, the initiated crack density, representing the total number of cracks per unit surface which can be compared to experimental observations, and the propagating crack density, representing the number per unit surface of active cracks in the network. The crack sizes distribution is also computed by the model allowing an easier comparison with experimental results. (author)

  12. Environmentally assisted fatigue evaluation model of alloy 690 steam generator tube in high temperature water

    International Nuclear Information System (INIS)

    Tan Jibo; Wu Xinqiang; Han Enhou; Wang Xiang; Liu Xiaoqiang; Xu Xuelian

    2015-01-01

    Nickel-based alloy 690 has been widely used as steam generator tube in light water reactor (LWR) nuclear power plants, which may suffer from corrosion fatigue during long-term service. Many researches and operating experience indicated that the effect of LWR environment could significantly reduce the fatigue life of structural materials. However. such an environmental degradation effect was not fully addressed in the current ASME code design fatigue curves. Therefore, the Regulatory Guide 1.207 issued by US NRC required a new NPP have to incorporate the environment effects into fatigue analyses. In the last few decades, researchers in USA and Japan systematically investigated the corrosion fatigue behavior of nuclear-grade structural materials in LWR environment. Then, ANL model and JSME model were proposed, which incorporated environmental effects, including temperature, dissolved oxygen (DO) and strain rate for the nickel-based alloys. Due to lack of experiment data on domestic materials, there is no related environmental fatigue design model in China. In the present work, based on the corrosion fatigue tests of a kind of boat-shaped specimen in borated and lithiated high temperature water, the corrosion fatigue behavior and environmentally assisted cracking mechanism of domestic Alloy 690 steam generator tube have been investigate. An IMR model for the nickel-based alloy was proposed. The environmental fatigue life correction factor (F en ) was established, which addressed the environmental factors, including temperature, strain rate and dissolved oxygen. The method to evaluate environmental fatigue damage of structural materials in NPPs was proposed. (authors)

  13. A short summary on finite element modelling of fatigue crack closure

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Konjengbam Darunkumar [Indian Institute of Technology, Guwahati (India); Parry, Matthew Roger [Airbus Operations Ltd, Bristol(United Kingdom); Sinclair, Ian [University of Southampton, Southampton (United Kingdom)

    2011-12-15

    This paper presents a short summary pertaining to the finite element modelling of fatigue crack closure. Several key issues related to finite element modelling of fatigue crack closure are highlighted: element type, mesh refinement, stabilization of crack closure, crack-tip node release scheme, constitutive model, specimen geometry, stress-states (i.e., plane stress, plane strain), crack closure monitoring. Reviews are presented for both straight and deflected cracks.

  14. Influence of dental restorations and mastication loadings on dentine fatigue behaviour: Image-based modelling approach.

    Science.gov (United States)

    Vukicevic, Arso M; Zelic, Ksenija; Jovicic, Gordana; Djuric, Marija; Filipovic, Nenad

    2015-05-01

    The aim of this study was to use Finite Element Analysis (FEA) to estimate the influence of various mastication loads and different tooth treatments (composite restoration and endodontic treatment) on dentine fatigue. The analysis of fatigue behaviour of human dentine in intact and composite restored teeth with root-canal-treatment using FEA and fatigue theory was performed. Dentine fatigue behaviour was analysed in three virtual models: intact, composite-restored and endodontically-treated tooth. Volumetric change during the polymerization of composite was modelled by thermal expansion in a heat transfer analysis. Low and high shrinkage stresses were obtained by varying the linear shrinkage of composite. Mastication forces were applied occlusally with the load of 100, 150 and 200N. Assuming one million cycles, Fatigue Failure Index (FFI) was determined using Goodman's criterion while residual fatigue lifetime assessment was performed using Paris-power law. The analysis of the Goodman diagram gave both maximal allowed crack size and maximal number of cycles for the given stress ratio. The size of cracks was measured on virtual models. For the given conditions, fatigue-failure is not likely to happen neither in the intact tooth nor in treated teeth with low shrinkage stress. In the cases of high shrinkage stress, crack length was much larger than the maximal allowed crack and failure occurred with 150 and 200N loads. The maximal allowed crack size was slightly lower in the tooth with root canal treatment which induced somewhat higher FFI than in the case of tooth with only composite restoration. Main factors that lead to dentine fatigue are levels of occlusal load and polymerization stress. However, root canal treatment has small influence on dentine fatigue. The methodology proposed in this study provides a new insight into the fatigue behaviour of teeth after dental treatments. Furthermore, it estimates maximal allowed crack size and maximal number of cycles for a

  15. ASTM Validates Air Pollution Test Methods

    Science.gov (United States)

    Chemical and Engineering News, 1973

    1973-01-01

    The American Society for Testing and Materials (ASTM) has validated six basic methods for measuring pollutants in ambient air as the first part of its Project Threshold. Aim of the project is to establish nationwide consistency in measuring pollutants; determining precision, accuracy and reproducibility of 35 standard measuring methods. (BL)

  16. Fatigue modelling according to the JCSS Probabilistic model code

    NARCIS (Netherlands)

    Vrouwenvelder, A.C.W.M.

    2007-01-01

    The Joint Committee on Structural Safety is working on a Model Code for full probabilistic design. The code consists out of three major parts: Basis of design, Load Models and Models for Material and Structural Properties. The code is intended as the operational counter part of codes like ISO,

  17. Comparison of the ASME Environmental Fatigue Design Curve with the Leax' Low Bound Model

    International Nuclear Information System (INIS)

    Jeong, Ill Seok; Kim, Wan Jae; Jun, Hyun Ik

    2010-01-01

    Environmental fatigue issue long time argued between industry and regulator. The issues of the debates are about environmental fatigue data only from experiment laboratories, no evidences in fields, and over conservatism. However, NRC issued the requirement to implement it to the construction design prior to industry practical design code. American Society of Mechanical Engineers (ASME) determined to issue non-mandatory code cases of environmental fatigue design. This paper evaluated the conservatism of the ASME proposed environmental fatigue design curve in comparison with the Leax' low bound approach model of environmental fatigue curve. A group of CF8M cast austenitic stainless steel (CASS) produced in KEPCO Research Center was introduced in the evaluation

  18. Modeling the effects of control systems of wind turbine fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, K.G.; Laino, D.J. [Univ. of Utah, Salt Lake City, UT (United States)

    1996-12-31

    In this study we look at the effect on fatigue life of two types of control systems. First, we investigate the Micon 65, an upwind, three bladed turbine with a simple yaw control system. Results indicate that increased fatigue damage to the blade root can be attributed to continuous operation at significant yaw error allowed by the control system. Next, we model a two-bladed teetered rotor turbine using three different control systems to adjust flap deflections. The first two limit peak power output, the third limits peak power and cyclic power output over the entire range of operation. Results for simulations conducted both with and without active control are compared to determine how active control affects fatigue life. Improvement in fatigue lifetimes were seen for all control schemes, with increasing fatigue lifetime corresponding to increased flap deflection activity. 13 refs., 6 figs., 2 tabs.

  19. Contact fatigue of human enamel: Experiments, mechanisms and modeling.

    Science.gov (United States)

    Gao, S S; An, B B; Yahyazadehfar, M; Zhang, D; Arola, D D

    2016-07-01

    Cyclic contact between natural tooth structure and engineered ceramics is increasingly common. Fatigue of the enamel due to cyclic contact is rarely considered. The objectives of this investigation were to evaluate the fatigue behavior of human enamel by cyclic contact, and to assess the extent of damage over clinically relevant conditions. Cyclic contact experiments were conducted using the crowns of caries-free molars obtained from young donors. The cuspal locations were polished flat and subjected to cyclic contact with a spherical indenter of alumina at 2Hz. The progression of damage was monitored through the evolution in contact displacement, changes in the contact hysteresis and characteristics of the fracture pattern. The contact fatigue life diagram exhibited a decrease in cycles to failure with increasing cyclic load magnitude. Two distinct trends were identified, which corresponded to the development and propagation of a combination of cylindrical and radial cracks. Under contact loads of less than 400N, enamel rod decussation resisted the growth of subsurface cracks. However, at greater loads the damage progressed rapidly and accelerated fatigue failure. Overall, cyclic contact between ceramic appliances and natural tooth structure causes fatigue of the enamel. The extent of damage is dependent on the magnitude of cyclic stress and the ability of the decussation to arrest the fatigue damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. 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.

  1. 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

  2. Multi-scale modelling of fatigue microcrack initiation

    International Nuclear Information System (INIS)

    Liu, Jia

    2013-01-01

    The thesis aims to improve the understanding and simulation of microcrack initiation induced by thermal fatigue and the induced crack network formation. The polycrystalline simulations allow the prediction of both macroscopic cyclic behavior and mean grain distributions of stress, plastic strain and number of cycles to microcrack initiation. Various aggregate meshes have been used, from the simplest ones using cubic grains up to a real 3D aggregate built thanks to many re-polishing and EBSD measurement sequences (Institut P', Poitiers). Tension-compression, cyclic shear and equi-biaxial loadings, with and without mean strain, have been considered. All the predictions are in qualitative agreement with many experimental observations obtained at various scales. The single crystal simulations allow us to predict the effect of slip localization in thin persistent slip bands (PSBs). Inside PSBs, vacancies are produced and annihilated because of cyclic dislocation interactions and may diffuse towards the surrounding matrix. This induces extrusion growth at the free surface of PSBs. Microcracking is modelled by cohesive zones located along the PSB - matrix interfaces. The predicted extrusion rates and numbers of cycles to microcrack initiation are in fair agreement with numerous experimental data concerning single and polycrystals, copper and 316L(N), under either air or inert environment. (author) [fr

  3. Two scale damage model and related numerical issues for thermo-mechanical high cycle fatigue

    International Nuclear Information System (INIS)

    Desmorat, R.; Kane, A.; Seyedi, M.; Sermage, J.P.

    2007-01-01

    On the idea that fatigue damage is localized at the microscopic scale, a scale smaller than the mesoscopic one of the Representative Volume Element (RVE), a three-dimensional two scale damage model has been proposed for High Cycle Fatigue applications. It is extended here to aniso-thermal cases and then to thermo-mechanical fatigue. The modeling consists in the micro-mechanics analysis of a weak micro-inclusion subjected to plasticity and damage embedded in an elastic meso-element (the RVE of continuum mechanics). The consideration of plasticity coupled with damage equations at micro-scale, altogether with Eshelby-Kroner localization law, allows to compute the value of microscopic damage up to failure for any kind of loading, 1D or 3D, cyclic or random, isothermal or aniso-thermal, mechanical, thermal or thermo-mechanical. A robust numerical scheme is proposed in order to make the computations fast. A post-processor for damage and fatigue (DAMAGE-2005) has been developed. It applies to complex thermo-mechanical loadings. Examples of the representation by the two scale damage model of physical phenomena related to High Cycle Fatigue are given such as the mean stress effect, the non-linear accumulation of damage. Examples of thermal and thermo-mechanical fatigue as well as complex applications on real size testing structure subjected to thermo-mechanical fatigue are detailed. (authors)

  4. Modelling probabilistic fatigue crack propagation rates for a mild structural steel

    OpenAIRE

    Correia, J.A.F.O.; de Jesus, A.M.P.; Fernández-Canteli, A.

    2014-01-01

    A class of fatigue crack growth models based on elastic–plastic stress–strain histories at the crack tip region and local strain-life damage models have been proposed in literature. The fatigue crack growth is regarded as a process of continuous crack initializations over successive elementary material blocks, which may be governed by smooth strain-life damage data. Some approaches account for the residual stresses developing at the crack tip in the actual crack driving force asse...

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

    NARCIS (Netherlands)

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

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

  6. Toward a comprehensive, theoretical model of compassion fatigue: An integrative literature review.

    Science.gov (United States)

    Coetzee, Siedine K; Laschinger, Heather K S

    2018-03-01

    This study was an integrative literature review in relation to compassion fatigue models, appraising these models, and developing a comprehensive theoretical model of compassion fatigue. A systematic search on PubMed, EbscoHost (Academic Search Premier, E-Journals, Medline, PsycINFO, Health Source Nursing/Academic Edition, CINAHL, MasterFILE Premier and Health Source Consumer Edition), gray literature, and manual searches of included reference lists was conducted in 2016. The studies (n = 11) were analyzed, and the strengths and limitations of the compassion fatigue models identified. We further built on these models through the application of the conservation of resources theory and the social neuroscience of empathy. The compassion fatigue model shows that it is not empathy that puts nurses at risk of developing compassion fatigue, but rather a lack of resources, inadequate positive feedback, and the nurse's response to personal distress. By acting on these three aspects, the risk of developing compassion fatigue can be addressed, which could improve the retention of a compassionate and committed nurse workforce. © 2017 John Wiley & Sons Australia, Ltd.

  7. Comparison of Sleep Models for Score Fatigue Model Integration

    Science.gov (United States)

    2015-04-01

    In order to obtain sleepiness, the Karolinska Sleepiness Scale (KSS) was applied using the following equation. = − ( ∗ ) (8) Where a = 10.3... Karolinska Sleepiness Scale MSE Mean Square Error St Homeostatic sleep pressure TPM Three-Process Model U Ultradian component

  8. Novel Feature Modelling the Prediction and Detection of sEMG Muscle Fatigue towards an Automated Wearable System

    Directory of Open Access Journals (Sweden)

    Mohamed R. Al-Mulla

    2010-05-01

    Full Text Available Surface Electromyography (sEMG activity of the biceps muscle was recorded from ten subjects performing isometric contraction until fatigue. A novel feature (1D spectro_std was used to extract the feature that modeled three classes of fatigue, which enabled the prediction and detection of fatigue. Initial results of class separation were encouraging, discriminating between the three classes of fatigue, a longitudinal classification on Non-Fatigue and Transition-to-Fatigue shows 81.58% correct classification with accuracy 0.74 of correct predictions while the longitudinal classification on Transition-to-Fatigue and Fatigue showed lower average correct classification of 66.51% with a positive classification accuracy 0.73 of correct prediction. Comparison of the 1D spectro_std with other sEMG fatigue features on the same dataset show a significant improvement in classification, where results show a significant 20.58% (p < 0.01 improvement when using the 1D spectro_std to classify Non-Fatigue and Transition-to-Fatigue. In classifying Transition-to-Fatigue and Fatigue results also show a significant improvement over the other features giving 8.14% (p < 0.05 on average of all compared features.

  9. Finite element modelling for fatigue stress analysis of large suspension bridges

    Science.gov (United States)

    Chan, Tommy H. T.; Guo, L.; Li, Z. X.

    2003-03-01

    Fatigue is an important failure mode for large suspension bridges under traffic loadings. However, large suspension bridges have so many attributes that it is difficult to analyze their fatigue damage using experimental measurement methods. Numerical simulation is a feasible method of studying such fatigue damage. In British standards, the finite element method is recommended as a rigorous method for steel bridge fatigue analysis. This paper aims at developing a finite element (FE) model of a large suspension steel bridge for fatigue stress analysis. As a case study, a FE model of the Tsing Ma Bridge is presented. The verification of the model is carried out with the help of the measured bridge modal characteristics and the online data measured by the structural health monitoring system installed on the bridge. The results show that the constructed FE model is efficient for bridge dynamic analysis. Global structural analyses using the developed FE model are presented to determine the components of the nominal stress generated by railway loadings and some typical highway loadings. The critical locations in the bridge main span are also identified with the numerical results of the global FE stress analysis. Local stress analysis of a typical weld connection is carried out to obtain the hot-spot stresses in the region. These results provide a basis for evaluating fatigue damage and predicting the remaining life of the bridge.

  10. An accurate fatigue damage model for welded joints subjected to variable amplitude loading

    Science.gov (United States)

    Aeran, A.; Siriwardane, S. C.; Mikkelsen, O.; Langen, I.

    2017-12-01

    Researchers in the past have proposed several fatigue damage models to overcome the shortcomings of the commonly used Miner’s rule. However, requirements of material parameters or S-N curve modifications restricts their practical applications. Also, application of most of these models under variable amplitude loading conditions have not been found. To overcome these restrictions, a new fatigue damage model is proposed in this paper. The proposed model can be applied by practicing engineers using only the S-N curve given in the standard codes of practice. The model is verified with experimentally derived damage evolution curves for C 45 and 16 Mn and gives better agreement compared to previous models. The model predicted fatigue lives are also in better correlation with experimental results compared to previous models as shown in earlier published work by the authors. The proposed model is applied to welded joints subjected to variable amplitude loadings in this paper. The model given around 8% shorter fatigue lives compared to Eurocode given Miner’s rule. This shows the importance of applying accurate fatigue damage models for welded joints.

  11. Testing of motor unit synchronization model for localized muscle fatigue.

    Science.gov (United States)

    Naik, Ganesh R; Kumar, Dinesh K; Yadav, Vivek; Wheeler, Katherine; Arjunan, Sridhar

    2009-01-01

    Spectral compression of surface electromyogram (sEMG) is associated with onset of localized muscle fatigue. The spectral compression has been explained based on motor unit synchronization theory. According to this theory, motor units are pseudo randomly excited during muscle contraction, and with the onset of muscle fatigue the recruitment pattern changes such that motor unit firings become more synchronized. While this is widely accepted, there is little experimental proof of this phenomenon. This paper has used source dependence measures developed in research related to independent component analysis (ICA) to test this theory.

  12. An Enhanced Random Vibration and Fatigue Model for Printed Circuit Boards

    Directory of Open Access Journals (Sweden)

    Bruno de Castro Braz

    Full Text Available Abstract Aerospace vehicles are mostly exposed to random vibration loads during its operational lifetime. These harsh conditions excites vibration responses in the vehicles printed circuit boards, what can cause failure on mission functionality due to fatigue damage of electronic components. A novel analytical model to evaluate the useful life of embedded electronic components (capacitors, chips, oscillators etc. mounted on Printed Circuit Boards (PCB is presented. The fatigue damage predictions are calculated by the relative displacement between the PCB and the component, the lead stiffness, as well the natural vibration modes of the PCB and the component itself. Statistical methods are used for fatigue cycle counting. The model is applied to experimental fatigue tests of PCBs available on literature. The analytical results are of the same magnitude order of the experimental findings.

  13. On the influence of the environment on modeling the fatigue crack growth process

    International Nuclear Information System (INIS)

    Mc Evily, A.J.

    1987-01-01

    The effect of the environment at room and elevated temperature were considered with respect to the influence exerted on the basic mechanical aspects of the fatigue crack growth process. An experimental assessment of this influence was obtained by conducting fatigue crack growth tests both in air and vacuum and the results of such experiments are given. Topics considered include crack closure, short crack growth in notched and unnotched specimens, Mode II crack growth, and the effects of oxidation at elevated temperatures. It is shown that the basic mechanisms of fatigue crack growth can be greatly altered by the presence of oxide films at the fatigue crack tip. Modeling the mechanical aspects of the crack growth process is by itself a challenging task. In addition, the environmental considerations adds to the complexity of the modeling process. (Author)

  14. Probabilistic multi-scale models and measurements of self-heating under multiaxial high cycle fatigue

    International Nuclear Information System (INIS)

    Poncelet, M.; Hild, F.; Doudard, C.; Calloch, S.; Weber, B.

    2010-01-01

    Different approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as 'self-heating tests'. This paper focuses on two models whose parameters are tuned by resorting to self-heating tests and then used to predict high cycle fatigue properties. The first model is based upon a yield surface approach to account for stress multi-axiality at a microscopic scale, whereas the second one relies on a probabilistic modelling of micro-plasticity at the scale of slip-planes. Both model identifications are cost effective, relying mainly on quickly obtained temperature data in self-heating tests. They both describe the influence of the stress heterogeneity, the volume effect and the hydrostatic stress on fatigue limits. The thermal effects and mean fatigue limit predictions are in good agreement with experimental results for in and out-of phase tension-torsion loadings. In the case of fatigue under non-proportional loading paths, the mean fatigue limit prediction error of the critical shear stress approach is three times less than with the yield surface approach. (authors)

  15. Probabilistic multi-scale models and measurements of self-heating under multiaxial high cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Poncelet, M.; Hild, F. [Univ Paris 11, PRES, Univ Paris 06, LMT Cachan, ENS Cachan, CNRS, F-94235 Cachan (France); Doudard, C.; Calloch, S. [Univ Brest, ENIB, ENSIETA, LBMS EA 4325, F-29806 Brest, (France); Weber, B. [ArcelorMittal Maizieres Res Voie Romaine, F-57283 Maizieres Les Metz (France)

    2010-07-01

    Different approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as 'self-heating tests'. This paper focuses on two models whose parameters are tuned by resorting to self-heating tests and then used to predict high cycle fatigue properties. The first model is based upon a yield surface approach to account for stress multi-axiality at a microscopic scale, whereas the second one relies on a probabilistic modelling of micro-plasticity at the scale of slip-planes. Both model identifications are cost effective, relying mainly on quickly obtained temperature data in self-heating tests. They both describe the influence of the stress heterogeneity, the volume effect and the hydrostatic stress on fatigue limits. The thermal effects and mean fatigue limit predictions are in good agreement with experimental results for in and out-of phase tension-torsion loadings. In the case of fatigue under non-proportional loading paths, the mean fatigue limit prediction error of the critical shear stress approach is three times less than with the yield surface approach. (authors)

  16. Modelling probabilistic fatigue crack propagation rates for a mild structural steel

    Directory of Open Access Journals (Sweden)

    J.A.F.O. Correia

    2015-01-01

    Full Text Available A class of fatigue crack growth models based on elastic–plastic stress–strain histories at the crack tip region and local strain-life damage models have been proposed in literature. The fatigue crack growth is regarded as a process of continuous crack initializations over successive elementary material blocks, which may be governed by smooth strain-life damage data. Some approaches account for the residual stresses developing at the crack tip in the actual crack driving force assessment, allowing mean stresses and loading sequential effects to be modelled. An extension of the fatigue crack propagation model originally proposed by Noroozi et al. (2005 to derive probabilistic fatigue crack propagation data is proposed, in particular concerning the derivation of probabilistic da/dN-ΔK-R fields. The elastic-plastic stresses at the vicinity of the crack tip, computed using simplified formulae, are compared with the stresses computed using an elasticplastic finite element analyses for specimens considered in the experimental program proposed to derive the fatigue crack propagation data. Using probabilistic strain-life data available for the S355 structural mild steel, probabilistic crack propagation fields are generated, for several stress ratios, and compared with experimental fatigue crack propagation data. A satisfactory agreement between the predicted probabilistic fields and experimental data is observed.

  17. Survey on damage mechanics models for fatigue life prediction

    NARCIS (Netherlands)

    Silitonga, S.; Maljaars, J.; Soetens, F.; Snijder, H.H.

    2013-01-01

    Engineering methods to predict the fatigue life of structures have been available since the beginning of the 20th century. However, a practical problem arises from complex loading conditions and a significant concern is the accuracy of the methods under variable amplitude loading. This paper

  18. Creep-fatigue behavior of turbine disc of superalloy GH720Li at 650 °C and probabilistic creep-fatigue modeling

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Dianyin [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China); Ma, Qihang [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Shang, Lihong [Mining and Materials Engineering, McGill University, Montreal, QC H3A 0C5 (Canada); Gao, Ye [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Wang, Rongqiao, E-mail: wangrq@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China)

    2016-07-18

    Creep-fatigue experiments have been conducted in nickel-based superalloy GH720Li at an elevated temperature of 650 °C with a stress ratio of 0.1, based on which, different dwell times at the maximum loading were applied to investigate the effect of dwell time on the creep-fatigue behaviors. The tested specimens were cut from the rim region of an actual turbine disc in the hoop direction. The grain size and precipitates of the GH720Li superalloy were examined through scanning electronic microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses. Experimental data shows creep-fatigue lifetime decreases as the dwell time prolongs. Further, different scattering was observed in the creep-fatigue lifetime at different dwell times. Then a probabilistic model based on the applied mechanical work density (AMWD), with a linear heteroscedastic function that evaluates the non-constant deviation in the creep-fatigue lifetime, was formulated to describe the dependence of creep-fatigue lifetime on the dwell time. Finally, the possible microscopic mechanism of the creep-fatigue behavior has been discussed by SEM with EDS on the fracture surfaces.

  19. Numerical fatigue 3D-FE modeling of indirect composite-restored posterior teeth.

    Science.gov (United States)

    Ausiello, Pietro; Franciosa, Pasquale; Martorelli, Massimo; Watts, David C

    2011-05-01

    In restored teeth, stresses at the tooth-restoration interface during masticatory processes may fracture the teeth or the restoration and cracks may grow and propagate. The aim was to apply numerical methodologies to simulate the behavior of a restored tooth and to evaluate fatigue lifetimes before crack failure. Using a CAD-FEM procedure and fatigue mechanic laws, the fatigue damage of a restored molar was numerically estimated. Tessellated surfaces of enamel and dentin were extracted by applying segmentation and classification algorithms, to sets of 2D image data. A user-friendly GUI, which enables selection and visualization of 3D tessellated surfaces, was developed in a MatLab(®) environment. The tooth-boundary surfaces of enamel and dentin were then created by sweeping operations through cross-sections. A class II MOD cavity preparation was then added into the 3D model and tetrahedral mesh elements were generated. Fatigue simulation was performed by combining a preliminary static FEA simulation with classical fatigue mechanical laws. Regions with the shortest fatigue-life were located around the fillets of the class II MOD cavity, where the static stress was highest. The described method can be successfully adopted to generate detailed 3D-FE models of molar teeth, with different cavities and restorative materials. This method could be quickly implemented for other dental or biomechanical applications. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Experimental evidence and physical models of fatigue crack initiation

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Man, Jiří

    2016-01-01

    Roč. 91, OCT (2016), s. 294-303 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GA13-23652S; GA ČR GA13-32665S; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Crack initiation * Persistent slip band * Point defects * Extrusions * Intrusions Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.899, year: 2016

  1. Fatigue and Model Analysis of the CNC Cylindrical Grinder

    OpenAIRE

    Lin Jui-Chang; Lin Cheng-Jen

    2016-01-01

    The purpose of this study is to lower deviation of workpiece by meeting high stability and rigidity to prevent the resonance in producing procedure of the CNC universal cylindrical grinding machine. Using finite element analysis software ABAQUS in grinder machine tools for numerical simulation of several analyses for the following: structural rigidity analysis, optimized design, vibration frequency analysis and fatigue damage analysis. This work aims on state of the transmission of outer diam...

  2. ASTM International Workshop on Standards & Measurements for Tissue Engineering Scaffolds

    Science.gov (United States)

    Simon, Carl G.; Yaszemski, Michael J.; Ratcliffe, Anthony; Tomlins, Paul; Luginbuehl, Reto; Tesk, John A.

    2016-01-01

    The “Workshop on Standards & Measurements for Tissue Engineering Scaffolds” was held on May 21, 2013 in Indianapolis, IN and was sponsored by the ASTM International (ASTM). The purpose of the workshop was to identify the highest priority items for future standards work for scaffolds used in the development and manufacture of tissue engineered medical products (TEMPs). Eighteen speakers and 78 attendees met to assess current scaffold standards and to prioritize needs for future standards. A key finding was that the ASTM TEMPs subcommittees (F04.41-46) have many active “guide” documents for educational purposes, but that few standard “test methods” or “practices” have been published. Overwhelmingly, the most clearly identified need was standards for measuring the structure of scaffolds, followed by standards for biological characterization, including in vitro testing, animal models and cell-material interactions. The third most pressing need was to develop standards for assessing the mechanical properties of scaffolds. Additional needs included standards for assessing scaffold degradation, clinical outcomes with scaffolds, effects of sterilization on scaffolds, scaffold composition and drug release from scaffolds. Discussions also highlighted the need for additional scaffold reference materials and the need to use them for measurement traceability. Finally, dialogue emphasized the needs to promote the use of standards in scaffold fabrication, characterization, and commercialization and to assess the use and impact of standards in the TEMPs community. Many scaffold standard needs have been identified and focus should now turn to generating these standards to support the use of scaffolds in TEMPs. PMID:25220952

  3. Fatigue and Model Analysis of the CNC Cylindrical Grinder

    Directory of Open Access Journals (Sweden)

    Lin Jui-Chang

    2016-01-01

    Full Text Available The purpose of this study is to lower deviation of workpiece by meeting high stability and rigidity to prevent the resonance in producing procedure of the CNC universal cylindrical grinding machine. Using finite element analysis software ABAQUS in grinder machine tools for numerical simulation of several analyses for the following: structural rigidity analysis, optimized design, vibration frequency analysis and fatigue damage analysis. This work aims on state of the transmission of outer diameter spindle to proceed in stress and fatigue life analysis by FE-SAFE Subroutine. The max values of equivalent stress and average amount of displacement in structural rigidity analysis are 0.67(Mpa and 0.92(µm. Optimization design effectively reducing extreme value of stress, the largest decline of about 5.43%. Modal analysis compared with the experimental, the average error percentage was less than 10% of parts. The whole structure error does not exceed 3%. The fatigue life of approximately 1,193,988 times, estimates into real life time can use more than sixty years, from the viewpoint of structural strength, spindle has a good high breaking strength is designed to be safe.

  4. 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.

  5. The role of neuroticism, perfectionism and depression in chronic fatigue syndrome. A structural equation modeling approach.

    Science.gov (United States)

    Valero, Sergi; Sáez-Francàs, Naia; Calvo, Natalia; Alegre, José; Casas, Miquel

    2013-10-01

    Previous studies have reported consistent associations between Neuroticism, maladaptive perfectionism and depression with severity of fatigue in Chronic Fatigue Syndrome (CFS). Depression has been considered a mediator factor between maladaptive perfectionism and fatigue severity, but no studies have explored the role of neuroticism in a comparable theoretical framework. This study aims to examine for the first time, the role of neuroticism, maladaptive perfectionism and depression on the severity of CFS, analyzing several explanation models. A sample of 229 CFS patients were studied comparing four structural equation models, testing the role of mediation effect of depression severity in the association of Neuroticism and/or Maladaptive perfectionism on fatigue severity. The model considering depression severity as mediator factor between Neuroticism and fatigue severity is the only one of the explored models where all the structural modeling indexes have fitted satisfactorily (Chi square=27.01, p=0.079; RMSE=0.047, CFI=0.994; SRMR=0.033). Neuroticism is associated with CFS by the mediation effect of depression severity. This personality variable constitutes a more consistent factor than maladaptive perfectionism in the conceptualization of CFS severity. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Computational cognitive modeling of the temporal dynamics of fatigue from sleep loss.

    Science.gov (United States)

    Walsh, Matthew M; Gunzelmann, Glenn; Van Dongen, Hans P A

    2017-12-01

    Computational models have become common tools in psychology. They provide quantitative instantiations of theories that seek to explain the functioning of the human mind. In this paper, we focus on identifying deep theoretical similarities between two very different models. Both models are concerned with how fatigue from sleep loss impacts cognitive processing. The first is based on the diffusion model and posits that fatigue decreases the drift rate of the diffusion process. The second is based on the Adaptive Control of Thought - Rational (ACT-R) cognitive architecture and posits that fatigue decreases the utility of candidate actions leading to microlapses in cognitive processing. A biomathematical model of fatigue is used to control drift rate in the first account and utility in the second. We investigated the predicted response time distributions of these two integrated computational cognitive models for performance on a psychomotor vigilance test under conditions of total sleep deprivation, simulated shift work, and sustained sleep restriction. The models generated equivalent predictions of response time distributions with excellent goodness-of-fit to the human data. More importantly, although the accounts involve different modeling approaches and levels of abstraction, they represent the effects of fatigue in a functionally equivalent way: in both, fatigue decreases the signal-to-noise ratio in decision processes and decreases response inhibition. This convergence suggests that sleep loss impairs psychomotor vigilance performance through degradation of the quality of cognitive processing, which provides a foundation for systematic investigation of the effects of sleep loss on other aspects of cognition. Our findings illustrate the value of treating different modeling formalisms as vehicles for discovery.

  7. Curcumin, a polyphenolic antioxidant, attenuates chronic fatigue syndrome in murine water immersion stress model.

    Science.gov (United States)

    Gupta, Amit; Vij, Garima; Sharma, Sameer; Tirkey, Naveen; Rishi, Praveen; Chopra, Kanwaljit

    2009-01-01

    Chronic fatigue syndrome, infection and oxidative stress are interrelated in epidemiological case studies. However, data demonstrating scientific validation of epidemiological claims regarding effectiveness of nutritional supplements for chronic fatigue syndrome are lacking. This study is designed to evaluate the effect of natural polyphenol, curcumin, in a mouse model of immunologically induced fatigue, where purified lipopolysaccharide (LPS) and Brucella abortus (BA) antigens were used as immunogens. The assessment of chronic fatigue syndrome was based on chronic water-immersion stress test for 10 min daily for 19 days and the immobility time was taken as the marker of fatigue. Mice challenged with LPS or BA for 19 days showed significant increase in the immobility time and hyperalgesia on day 19, as well as marked increase in serum tumor necrosis factor-alpha (TNF-alpha) levels. Concurrent treatment with curcumin resulted in significantly decreased immobility time as well as hyperalgesia. There was significant attenuation of oxidative stress as well as TNF-alpha levels. These findings strongly suggest that during immunological activation, there is significant increase in oxidative stress and curcumin can be a valuable option in the treatment of chronic fatigue syndrome.

  8. Model-experiment dialog in low cycle fatigue of stainless steels

    International Nuclear Information System (INIS)

    Aubin, Veronique

    2008-01-01

    In this HDR report (accreditation to supervise research), the author first proposes a synthesis of her research activities in the study of the mechanical behaviour in low cycle fatigue (cyclic hardening, plasticity surfaces), of modelling of the fatigue mechanical behaviour (phenomenological modelling, modelling with scale change), of progressive deformation (experimental analysis, analysis and simulation of plasticity at the microstructure scale). The second part addresses other activities in the field of research (behaviour and damage characterization of an austenitic-ferritic stainless steel), publication and education supervising, teaching

  9. Thermoelastoviscoplastic modeling of RAFM steel JLF-1 using tensile and low cycle fatigue experiments

    Energy Technology Data Exchange (ETDEWEB)

    Msolli, S., E-mail: sabeur.msolli@univ-lorraine.fr

    2014-08-01

    In this paper, a modeling of the elastoviscoplastic behavior of a Reduced Activation Ferritic Martensitic (RAFM) steel JLF-1 is presented. The modeling of this material was based on various Low Cycle Fatigue (LCF) and tensile tests performed in air and vacuum using different imposed strain rates and temperature ranges going from ambient temperature to 873 K. The coupled viscoplastic model is coded in FORTRAN program, implemented into the finite elements code ABAQUS and used to predict the thermomechanical behavior of a fatigue specimen made of RAFM steel JLF-1. Good agreements were found between numerical results and experimental data.

  10. Detection and Alert of muscle fatigue considering a Surface Electromyography Chaotic Model

    International Nuclear Information System (INIS)

    Herrera, V; Romero, J F; Amestegui, M

    2011-01-01

    This work propose a detection and alert algorithm for muscle fatigue in paraplegic patients undergoing electro-therapy sessions. The procedure is based on a mathematical chaotic model emulating physiological signals and Continuous Wavelet Transform (CWT). The chaotic model developed is based on a logistic map that provides suitable data accomplishing some physiological signal class patterns. The CWT was applied to signals generated by the model and the resulting vector was obtained through Total Wavelet Entropy (TWE). In this sense, the presented work propose a viable and practical alert and detection algorithm for muscle fatigue.

  11. Detection and Alert of muscle fatigue considering a Surface Electromyography Chaotic Model

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, V; Romero, J F [Engineering, Modeling and Applied Social Sciences Center, ABC Federal University, Santo Andr - SP (Brazil); Amestegui, M, E-mail: victoria.herrera@ufabc.edu.br [Engineering Faculty, Electronics Engineering, Universidad Mayor de San Andres, La Paz (Bolivia, Plurinational State of)

    2011-03-01

    This work propose a detection and alert algorithm for muscle fatigue in paraplegic patients undergoing electro-therapy sessions. The procedure is based on a mathematical chaotic model emulating physiological signals and Continuous Wavelet Transform (CWT). The chaotic model developed is based on a logistic map that provides suitable data accomplishing some physiological signal class patterns. The CWT was applied to signals generated by the model and the resulting vector was obtained through Total Wavelet Entropy (TWE). In this sense, the presented work propose a viable and practical alert and detection algorithm for muscle fatigue.

  12. Failure Mechanisms and Damage Model of Ductile Cast Iron Under Low-Cycle Fatigue Conditions

    Science.gov (United States)

    Wu, Xijia; Quan, Guangchun; MacNeil, Ryan; Zhang, Zhong; Sloss, Clayton

    2014-10-01

    Strain-controlled low-cycle fatigue (LCF) tests were conducted on ductile cast iron (DCI) at strain rates of 0.02, 0.002, and 0.0002/s in the temperature range from room temperature to 1073 K (800 °C). A constitutive-damage model was developed within the integrated creep-fatigue theory (ICFT) framework on the premise of strain decomposition into rate-independent plasticity and time-dependent creep. Four major damage mechanisms: (i) plasticity-induced fatigue, (ii) intergranular embrittlement (IE), (iii) creep, and (iv) oxidation were considered in a nonlinear creep-fatigue interaction model which represents the overall damage accumulation process consisting of oxidation-assisted fatigue crack nucleation and propagation in coalescence with internally distributed damage ( e.g., IE and creep), leading to final fracture. The model was found to agree with the experimental observations of the complex DCI-LCF phenomena, for which the linear damage summation rule would fail.

  13. A study of probabilistic fatigue crack propagation models in Mg Al Zn alloys under different specimen thickness conditions by using the residual of a random variable

    International Nuclear Information System (INIS)

    Choi, Seon Soon

    2012-01-01

    The primary aim of this paper was to evaluate several probabilistic fatigue crack propagation models using the residual of a random variable, and to present the model fit for probabilistic fatigue behavior in Mg Al Zn alloys. The proposed probabilistic models are the probabilistic Paris Erdogan model, probabilistic Walker model, probabilistic Forman model, and probabilistic modified Forman models. These models were prepared by applying a random variable to the empirical fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models vor describing fatigue crack propagation behavior in Mg Al Zn alloys were generally the probabilistic Paris Erdogan and probabilistic Walker models. The probabilistic Forman model was a good model only for a specimen with a thickness of 9.45mm

  14. Assessment of wrought ASTM F1058 cobalt alloy properties for permanent surgical implants.

    Science.gov (United States)

    Clerc, C O; Jedwab, M R; Mayer, D W; Thompson, P J; Stinson, J S

    1997-01-01

    The behavior of the ASTM F1058 wrought cobalt-chromium-nickel-molybdenum-iron alloy (commonly referred to as Elgiloy or Phynox) is evaluated in terms of mechanical properties, magnetic resonance imaging, corrosion resistance, and biocompatibility. The data found in the literature, the experimental corrosion and biocompatibility results presented in this article, and its long track record as an implant material demonstrate that the cobalt superalloy is an appropriate material for permanent surgical implants that require high yield strength and fatigue resistance combined with high elastic modulus, and that it can be safely imaged with magnetic resonance.

  15. A thick level set interface model for simulating fatigue-drive delamination in composites

    NARCIS (Netherlands)

    Latifi, M.; Van der Meer, F.P.; Sluys, L.J.

    2015-01-01

    This paper presents a new damage model for simulating fatigue-driven delamination in composite laminates. This model is developed based on the Thick Level Set approach (TLS) and provides a favorable link between damage mechanics and fracture mechanics through the non-local evaluation of the energy

  16. Probabilistic model for fatigue crack growth and fracture of welded joints in civil engineering structures

    NARCIS (Netherlands)

    Maljaars, J.; Steenbergen, H.M.G.M.; Vrouwenvelder, A.C.W.M.

    2012-01-01

    This paper presents a probabilistic assessment model for linear elastic fracture mechanics (LEFM). The model allows the determination of the failure probability of a structure subjected to fatigue loading. The distributions of the random variables for civil engineering structures are provided, and

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

    Science.gov (United States)

    Li, Xiaoyan; Sun, Ruifeng; Wang, Yongdong

    2017-09-01

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

  18. The numerical high cycle fatigue damage model of fillet weld joint under weld-induced residual stresses

    Science.gov (United States)

    Nguyen Van Do, Vuong

    2018-04-01

    In this study, a development of nonlinear continuum damage mechanics (CDM) model for multiaxial high cycle fatigue is proposed in which the cyclic plasticity constitutive model has been incorporated in the finite element (FE) framework. T-joint FE simulation of fillet welding is implemented to characterize sequentially coupled three-dimensional (3-D) of thermo-mechanical FE formulation and simulate the welding residual stresses. The high cycle fatigue damage model is then taken account into the fillet weld joints under the various cyclic fatigue load types to calculate the fatigue life considering the residual stresses. The fatigue crack initiation and the propagation in the present model estimated for the total fatigue is compared with the experimental results. The FE results illustrated that the proposed high cycle fatigue damage model in this study could become a powerful tool to effectively predict the fatigue life of the welds. Parametric studies in this work are also demonstrated that the welding residual stresses cannot be ignored in the computation of the fatigue life of welded structures.

  19. Overview (this manuscript is an overview of an ASTM ...

    Science.gov (United States)

    The Symposium on Developing Consensus Standards for Measuring Chemical Emissions from Spray Polyurethane Foam (SPF) Insulation was held on April 30th and May 1, 2015. Sponsored by ASTM Committee D22 on Air Quality, the symposium was held in Anaheim, CA, in conjunction with the standards development meetings of the Committee. ASTM D22.05 is developing tools to answer fundamental questions: what is emitted from SPF, how long do the emissions persist, how does ventilation impact concentrations and potential exposures? How can we model these processes to address the multiplicity of products, applications, and environmental conditions that may impact exposure to emissions over the life cycle of the material? These are complex and interrelated questions that have challenged the indoor environments research community for many years. Objectives of Symposium: Standardized methods are needed to assess the potential impacts of SPF insulation products on indoor air quality, establish re-entry times for trade workers or re-occupancy times for building occupants after product installation and to evaluate post-occupancy ventilation. The objective of the symposium was to provide a forum for the exchange of ideas from SPF manufacturers, regulatory agencies, indoor air quality professionals, testing labs, air quality consultants, instrument vendors and other stakeholders. Following the presentations on the current status of measuring emissions from SPF insulation, participants di

  20. A new model for fatigue damage accumulation of austenitic stainless steel under variable amplitude loading

    International Nuclear Information System (INIS)

    Taheri, S.; Vincent, L.; Le-Roux, J.C.

    2013-01-01

    The application of Miner's rule using a loading issued from a mock-up of a RHR system (removal heat system) of PWR plant, made of 304 steel gives a very important non-conservative fatigue life in strain control when strain fatigue curve is used. This result is due to the absence of sequence effect in Miner's rule. Many non linear damage accumulation models have been proposed to get a sequence effect. Shortcomings of some non linear damage accumulation models are discussed. So Smith-Watson-Topper and Fatemi-Socie criterions with a linear damage accumulation rule are then applied to experimental data. A major issue is the need for an elastic-plastic constitutive law which is difficult to propose in the presence of high cycle secondary hardening observed in austenitic stainless steels. A conservative model for fatigue damage accumulation under variable amplitude loading is then proposed for austenitic stainless steels in strain control, which does not need a constitutive law, but takes into account plasticity through cyclic strain stress curve. The model uses a linear damage accumulation rule. This model is based on the fact that for stainless steels, pre-hardening is detrimental for fatigue life in strain control, while it is beneficial in stress control. In the presence of low mean stress, the model is approved based on a large number of tests. Moreover the model allows to explain the larger detrimental effect of a tension mean stress in strain control tests than in stress control tests. (authors)

  1. Visual fatigue modeling for stereoscopic video shot based on camera motion

    Science.gov (United States)

    Shi, Guozhong; Sang, Xinzhu; Yu, Xunbo; Liu, Yangdong; Liu, Jing

    2014-11-01

    As three-dimensional television (3-DTV) and 3-D movie become popular, the discomfort of visual feeling limits further applications of 3D display technology. The cause of visual discomfort from stereoscopic video conflicts between accommodation and convergence, excessive binocular parallax, fast motion of objects and so on. Here, a novel method for evaluating visual fatigue is demonstrated. Influence factors including spatial structure, motion scale and comfortable zone are analyzed. According to the human visual system (HVS), people only need to converge their eyes to the specific objects for static cameras and background. Relative motion should be considered for different camera conditions determining different factor coefficients and weights. Compared with the traditional visual fatigue prediction model, a novel visual fatigue predicting model is presented. Visual fatigue degree is predicted using multiple linear regression method combining with the subjective evaluation. Consequently, each factor can reflect the characteristics of the scene, and the total visual fatigue score can be indicated according to the proposed algorithm. Compared with conventional algorithms which ignored the status of the camera, our approach exhibits reliable performance in terms of correlation with subjective test results.

  2. Predictive model of muscle fatigue after spinal cord injury in humans.

    Science.gov (United States)

    Shields, Richard K; Chang, Ya-Ju; Dudley-Javoroski, Shauna; Lin, Cheng-Hsiang

    2006-07-01

    The fatigability of paralyzed muscle limits its ability to deliver physiological loads to paralyzed extremities during repetitive electrical stimulation. The purposes of this study were to determine the reliability of measuring paralyzed muscle fatigue and to develop a model to predict the temporal changes in muscle fatigue that occur after spinal cord injury (SCI). Thirty-four subjects underwent soleus fatigue testing with a modified Burke electrical stimulation fatigue protocol. The between-day reliability of this protocol was high (intraclass correlation, 0.96). We fit the fatigue index (FI) data to a quadratic-linear segmental polynomial model. FI declined rapidly (0.3854 per year) for the first 1.7 years, and more slowly (0.01 per year) thereafter. The rapid decline of FI immediately after SCI implies that a "window of opportunity" exists for the clinician if the goal is to prevent these changes. Understanding the timing of change in muscle endurance properties (and, therefore, load-generating capacity) after SCI may assist clinicians when developing therapeutic interventions to maintain musculoskeletal integrity.

  3. Simplified Model for Evaluation of VIV-induced Fatigue Damage of Deepwater Marine Risers

    Institute of Scientific and Technical Information of China (English)

    XUE Hong-xiang; TANG Wen-yong; ZHANG Sheng-kun

    2009-01-01

    A simplified empirical model for fatigue analysis of deepwater marine risers due to vortex-induced vibration (VIV) in non-uniform current is presented. A simplified modal vibration equation is employed according to the characteristics of deepwater top tensioned risers. The response amplitude of each mode is determined by a balance between the energy feeding into the riser over the lock-in regions and the energy dissipated by the fluid damping over the remainder based on the data from self-excited oscillation and forced oscillation experiments of rigid cylinders. Multi-modal VIV fatigue loading is obtained by the square root of the sum of squares approach.Compared with previous works, this model can take fully account of the main intrinsic natures of VIV for low mass ratio structures on lock-in regions, added mass and nonlinear fluid damping. In addition, a closed form solution of fatigue damage is presented for the case of a riser with uniform mass and cross-section oscillating in a uniform flow. Fatigue analysis of a typical deepwater riser operating in Gulf of Mexico and West Africa shows that the current velocity profiles affect the riser's fatigue life significantly and the most dangerous locations of the riser are also pointed out.

  4. Low-cycle fatigue of welded joints: coupled initiation propagation model

    International Nuclear Information System (INIS)

    Madi, Yazid; Recho, Naman; Matheron, Philippe

    2004-01-01

    This paper deals with the low-cycle fatigue (LC) design of welded structures, the aim being the critical analysis of the rule used in the RCC-MR [Design and construction rules for mechanical components of FBR nuclear islands, AFCEN, 1993], for the design and construction of fast breeder reactors. The study takes into account the evolution of the material behavior laws and damage accumulation during the fatigue loading. The adopted model consists of analyzing separately the behavior and the damage evolutions. It allows us to determine the damage ratio corresponding to initiation and propagation of a significant crack in order to determine the life duration. This model suggests the existence of a threshold level of loading, above which micro-cracks initiate. The initiation fatigue life can then be neglected below the threshold level. This work shows also that the RCC-MR rules are valid below this threshold load level

  5. Sensitivity Analysis of Fatigue Crack Growth Model for API Steels in Gaseous Hydrogen.

    Science.gov (United States)

    Amaro, Robert L; Rustagi, Neha; Drexler, Elizabeth S; Slifka, Andrew J

    2014-01-01

    A model to predict fatigue crack growth of API pipeline steels in high pressure gaseous hydrogen has been developed and is presented elsewhere. The model currently has several parameters that must be calibrated for each pipeline steel of interest. This work provides a sensitivity analysis of the model parameters in order to provide (a) insight to the underlying mathematical and mechanistic aspects of the model, and (b) guidance for model calibration of other API steels.

  6. Modeling Creep-Fatigue-Environment Interactions in Steam Turbine Rotor Materials for Advanced Ultra-supercritical Coal Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chen [General Electric Global Research, Niskayuna, NY (United States)

    2014-04-01

    The goal of this project is to model creep-fatigue-environment interactions in steam turbine rotor materials for advanced ultra-supercritical (A-USC) coal power Alloy 282 plants, to develop and demonstrate computational algorithms for alloy property predictions, and to determine and model key mechanisms that contribute to the damages caused by creep-fatigue-environment interactions.

  7. A Combined High and Low Cycle Fatigue Model for Life Prediction of Turbine Blades

    Directory of Open Access Journals (Sweden)

    Shun-Peng Zhu

    2017-06-01

    Full Text Available Combined high and low cycle fatigue (CCF generally induces the failure of aircraft gas turbine attachments. Based on the aero-engine load spectrum, accurate assessment of fatigue damage due to the interaction of high cycle fatigue (HCF resulting from high frequency vibrations and low cycle fatigue (LCF from ground-air-ground engine cycles is of critical importance for ensuring structural integrity of engine components, like turbine blades. In this paper, the influence of combined damage accumulation on the expected CCF life are investigated for turbine blades. The CCF behavior of a turbine blade is usually studied by testing with four load-controlled parameters, including high cycle stress amplitude and frequency, and low cycle stress amplitude and frequency. According to this, a new damage accumulation model is proposed based on Miner’s rule to consider the coupled damage due to HCF-LCF interaction by introducing the four load parameters. Five experimental datasets of turbine blade alloys and turbine blades were introduced for model validation and comparison between the proposed Miner, Manson-Halford, and Trufyakov-Kovalchuk models. Results show that the proposed model provides more accurate predictions than others with lower mean and standard deviation values of model prediction errors.

  8. Modelling of fatigue crack propagation assisted by gaseous hydrogen in metallic materials

    International Nuclear Information System (INIS)

    Moriconi, C.

    2012-01-01

    Experimental studies in a hydrogenous environment indicate that hydrogen created by surface reactions, then drained into the plastic zone, leads to a modification of deformation and damage mechanisms at the fatigue crack tip in metals, resulting in a significant decrease of crack propagation resistance. This study aims at building a model of these complex phenomena in the framework of damage mechanics, and to confront it with the results of fatigue crack propagation tests in high pressure hydrogen on a 15-5PH martensitic stainless steel. To do so, a cohesive zone model was implemented in the finite element code ABAQUS. A specific traction-separation law was developed, which is suitable for cyclic loadings, and whose parameters depend on local hydrogen concentration. Furthermore, hydrogen diffusion in the bulk material takes into account the influence of hydrostatic stress and trapping. The mechanical behaviour of the bulk material is elastic-plastic. It is shown that the model can qualitatively predict crack propagation in hydrogen under monotonous loadings; then, the model with the developed traction-separation law is tested under fatigue loading. In particular, the simulated crack propagation curves without hydrogen are compared to the experimental crack propagation curves for the 15-5PH steel in air. Finally, simulated fatigue crack propagation rates in hydrogen are compared to experimental measurements. The model's ability to assess the respective contributions of the different damage mechanisms (HELP, HEDE) in the degradation of the crack resistance of the 15-5PH steel is discussed. (author)

  9. A phenomenological model of muscle fatigue and the power-endurance relationship.

    Science.gov (United States)

    James, A; Green, S

    2012-11-01

    The relationship between power output and the time that it can be sustained during exercise (i.e., endurance) at high intensities is curvilinear. Although fatigue is implicit in this relationship, there is little evidence pertaining to it. To address this, we developed a phenomenological model that predicts the temporal response of muscle power during submaximal and maximal exercise and which was based on the type, contractile properties (e.g., fatiguability), and recruitment of motor units (MUs) during exercise. The model was first used to predict power outputs during all-out exercise when fatigue is clearly manifest and for several distributions of MU type. The model was then used to predict times that different submaximal power outputs could be sustained for several MU distributions, from which several power-endurance curves were obtained. The model was simultaneously fitted to two sets of human data pertaining to all-out exercise (power-time profile) and submaximal exercise (power-endurance relationship), yielding a high goodness of fit (R(2) = 0.96-0.97). This suggested that this simple model provides an accurate description of human power output during submaximal and maximal exercise and that fatigue-related processes inherent in it account for the curvilinearity of the power-endurance relationship.

  10. Probabilistic Modeling of the Fatigue Crack Growth Rate for Ni-base Alloy X-750

    International Nuclear Information System (INIS)

    Yoon, J.Y.; Nam, H.O.; Hwang, I.S.; Lee, T.H.

    2012-01-01

    Extending the operating life of existing nuclear power plants (NPP's) beyond 60 years. Many aging problems of passive components such as PWSCC, IASCC, FAC and Corrosion Fatigue; Safety analysis: Deterministic analysis + Probabilistic analysis; Many uncertainties of parameters or relationship in general probabilistic analysis such as probabilistic safety assessment (PSA); Bayesian inference: Decreasing uncertainties by updating unknown parameter; Ensuring the reliability of passive components (e.g. pipes) as well as active components (e.g. valve, pump) in NPP's; Developing probabilistic model for failures; Updating the fatigue crack growth rate (FCGR)

  11. Fatigue Characteristics of 3D Printed Acrylonitrile Butadiene Styrene (ABS)

    Science.gov (United States)

    Padzi, M. M.; Bazin, M. M.; Muhamad, W. M. W.

    2017-11-01

    Recently, the use of 3D printer technology has become significant to industries, especially when involving the new product development. 3D printing is a technology, which produces the 3D product or prototype using a layer-by-layer technique. However, there becomes less research on the mechanical performance of the 3D printed component. In the present work, fatigue characteristics of 3D printed specimen have been studied. Acrylonitrile butadiene styrene (ABS) has been chosen as a material research due to its wide applications. Two types of specimen used, which is the 3D printing and moulding specimens. Fused deposition modelling (FDM) technique was used to produce the specimens. The dog bone shape part was produced based on ASTM D638 standard and the tensile test has been carried out to get the mechanical properties. Fatigue test was carried out at 40%, 60% and 80% of the tensile strength. The moulded part shows higher fatigue cycles compared to 3D printed part for all loading percentages. Fatigue lives for 40%, 60% and 80%, were 911, 2645 and 26948 cycles, respectively. The results indicated that 3D printed part has a lower fatigue life, which may not suitable for industrial applications. However, the 3D printed part could be improved by using various parameters and may be introduced in low strength application.

  12. A two-parameter model to predict fatigue life of high-strength steels in a very high cycle fatigue regime

    Science.gov (United States)

    Sun, Chengqi; Liu, Xiaolong; Hong, Youshi

    2015-06-01

    In this paper, ultrasonic (20 kHz) fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue (VHCF) regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area (FGA) centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.

  13. A Critical Plane-energy Model for Multiaxial Fatigue Life Prediction of Homogeneous and Heterogeneous Materials

    Science.gov (United States)

    Wei, Haoyang

    A new critical plane-energy model is proposed in this thesis for multiaxial fatigue life prediction of homogeneous and heterogeneous materials. Brief review of existing methods, especially on the critical plane-based and energy-based methods, are given first. Special focus is on one critical plane approach which has been shown to work for both brittle and ductile metals. The key idea is to automatically change the critical plane orientation with respect to different materials and stress states. One potential drawback of the developed model is that it needs an empirical calibration parameter for non-proportional multiaxial loadings since only the strain terms are used and the out-of-phase hardening cannot be considered. The energy-based model using the critical plane concept is proposed with help of the Mroz-Garud hardening rule to explicitly include the effect of non-proportional hardening under fatigue cyclic loadings. Thus, the empirical calibration for non-proportional loading is not needed since the out-of-phase hardening is naturally included in the stress calculation. The model predictions are compared with experimental data from open literature and it is shown the proposed model can work for both proportional and non-proportional loadings without the empirical calibration. Next, the model is extended for the fatigue analysis of heterogeneous materials integrating with finite element method. Fatigue crack initiation of representative volume of heterogeneous materials is analyzed using the developed critical plane-energy model and special focus is on the microstructure effect on the multiaxial fatigue life predictions. Several conclusions and future work is drawn based on the proposed study.

  14. Health-aware Model Predictive Control of Wind Turbines using Fatigue Prognosis

    DEFF Research Database (Denmark)

    Sardi, Hector Eloy Sanchez; Escobet, Teressa; Puig, Vicenc

    2015-01-01

    management module with the control provides a mechanism for the wind turbine to operate safely and optimize the trade-off between components life and energy production. The research presented in this paper explores the integration of model predictive control (MPC) with fatigue-based prognosis approach...

  15. Experimental and modeling results of creep fatigue life of Inconel 617 and Haynes 230 at 850 C

    International Nuclear Information System (INIS)

    Chen, Xiang; Sokolov, Mikhail A.; Sham, Sam; Erdman, Donald L. III; Busby, Jeremy T.; Mo, Kun; Stubbins, James

    2013-01-01

    Creep fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep fatigue life. The linear damage summation could predict the creep fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep fatigue life prediction results for both materials.

  16. Damage and failure modeling of lotus-type porous material subjected to low-cycle fatigue

    Directory of Open Access Journals (Sweden)

    J. Kramberger

    2016-01-01

    Full Text Available The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications. This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle. Degradation of the elastic stifness was modeled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation.

  17. Implementation of fatigue model for unidirectional laminate based on finite element analysis: theory and practice

    Directory of Open Access Journals (Sweden)

    D. Carrella-Payan

    2016-10-01

    Full Text Available The aim of this study is to deal with the simulation of intralaminar fatigue damage in unidirectional composite under multi-axial and variable amplitude loadings. The variable amplitude and multi-axial loading is accounted for by using the damage hysteresis operator based on Brokate method [6]. The proposed damage model for fatigue is based on stiffness degradation laws from Van Paepegem combined with the ‘damage’ cycle jump approach extended to deal with unidirectional carbon fibres. The parameter identification method is here presented and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the Ladevèze damage model and the permanent shear strain accumulation based on Van Paepegem’s formulation. This approach is implemented into commercial software (Siemens PLM. The validation case is run on a bending test coupon (with arbitrary stacking sequence and load level in order to minimise the risk of inter-laminar damages. This intra-laminar fatigue damage model combined efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level. This work concludes on the next challenges to be addressed (validation tests, multiple-loadings validation, failure criteria, inter-laminar damages….

  18. Annual Book of ASTM Standards, Part 23: Water; Atmospheric Analysis.

    Science.gov (United States)

    American Society for Testing and Materials, Philadelphia, PA.

    Standards for water and atmospheric analysis are compiled in this segment, Part 23, of the American Society for Testing and Materials (ASTM) annual book of standards. It contains all current formally approved ASTM standard and tentative test methods, definitions, recommended practices, proposed methods, classifications, and specifications. One…

  19. 78 FR 1884 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2013-01-09

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on December 12, 2012... seq. (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between...

  20. 76 FR 12370 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2011-03-07

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on February 4, 2011... seq. (``the Act''), ASTM International Standards (``ASTM'') has filed written notifications.... Specifically, ASTM has provided an updated list of current, ongoing ASTM standards activities originating...

  1. 78 FR 35646 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2013-06-13

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on May 10, 2013, pursuant... seq. (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between...

  2. 77 FR 34069 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2012-06-08

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on May 11, 2012, pursuant... seq. (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between...

  3. 77 FR 61786 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2012-10-11

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on September 10, 2012... seq. (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between May...

  4. 78 FR 64248 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2013-10-28

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on September 16, 2013... seq. (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between May...

  5. 76 FR 34252 - Notice Pursuant to the National Cooperative Research and Production Act of 1993; ASTM...

    Science.gov (United States)

    2011-06-13

    ... Production Act of 1993; ASTM International Standards Notice is hereby given that, on May 11, 2011, pursuant... seq. (``the Act''), ASTM International Standards (``ASTM'') has filed written notifications.... Specifically, ASTM has provided an updated list of current, ongoing ASTM standards activities originating...

  6. 78 FR 14836 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2013-03-07

    ... Production Act of 1993--ASTM International Standards Notice is hereby given that, on February 11, 2013... seq. (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between...

  7. Fatigue in isometric contraction in a single muscle fibre: a compartmental calcium ion flow model.

    Science.gov (United States)

    Kothiyal, K P; Ibramsha, M

    1986-01-01

    Fatigue in muscle is a complex biological phenomenon which has so far eluded a definite explanation. Many biochemical and physiological models have been suggested in the literature to account for the decrement in the ability of muscle to sustain a given level of force for a long time. Some of these models have been critically analysed in this paper and are shown to be not able to explain all the experimental observations. A new compartmental model based on the intracellular calcium ion movement in muscle is proposed to study the mechanical responses of a muscle fibre. Computer simulation is performed to obtain model responses in isometric contraction to an impulse and a train of stimuli of long duration. The simulated curves have been compared with experimentally observed mechanical responses of the semitendinosus muscle fibre of Rana pipiens. The comparison of computed and observed responses indicates that the proposed calcium ion model indeed accounts very well for the muscle fatigue.

  8. Modular 3-D solid finite element model for fatigue analyses of a PWR coolant system

    International Nuclear Information System (INIS)

    Garrido, Oriol Costa; Cizelj, Leon; Simonovski, Igor

    2012-01-01

    Highlights: ► A 3-D model of a reactor coolant system for fatigue usage assessment. ► The performed simulations are a heat transfer and stress analyses. ► The main results are the expected ranges of fatigue loadings. - Abstract: The extension of operational licenses of second generation pressurized water reactor (PWR) nuclear power plants depends to a large extent on the analyses of fatigue usage of the reactor coolant pressure boundary. The reliable estimation of the fatigue usage requires detailed thermal and stress analyses of the affected components. Analyses, based upon the in-service transient loads should be compared to the loads analyzed at the design stage. The thermal and stress transients can be efficiently analyzed using the finite element method. This requires that a 3-D solid model of a given system is discretized with finite elements (FE). The FE mesh density is crucial for both the accuracy and the cost of the analysis. The main goal of the paper is to propose a set of computational tools which assist a user in a deployment of modular spatial FE model of main components of a typical reactor coolant system, e.g., pipes, pressure vessels and pumps. The modularity ensures that the components can be analyzed individually or in a system. Also, individual components can be meshed with different mesh densities, as required by the specifics of the particular transient studied. For optimal accuracy, all components are meshed with hexahedral elements with quadratic interpolation. The performance of the model is demonstrated with simulations performed with a complete two-loop PWR coolant system (RCS). Heat transfer analysis and stress analysis for a complete loading and unloading cycle of the RCS are performed. The main results include expected ranges of fatigue loading for the pipe lines and coolant pump components under the given conditions.

  9. Risk factors and visual fatigue of baggage X-ray security screeners: a structural equation modelling analysis.

    Science.gov (United States)

    Yu, Rui-Feng; Yang, Lin-Dong; Wu, Xin

    2017-05-01

    This study identified the risk factors influencing visual fatigue in baggage X-ray security screeners and estimated the strength of correlations between those factors and visual fatigue using structural equation modelling approach. Two hundred and five X-ray security screeners participated in a questionnaire survey. The result showed that satisfaction with the VDT's physical features and the work environment conditions were negatively correlated with the intensity of visual fatigue, whereas job stress and job burnout had direct positive influences. The path coefficient between the image quality of VDT and visual fatigue was not significant. The total effects of job burnout, job stress, the VDT's physical features and the work environment conditions on visual fatigue were 0.471, 0.469, -0.268 and -0.251 respectively. These findings indicated that both extrinsic factors relating to VDT and workplace environment and psychological factors including job burnout and job stress should be considered in the workplace design and work organisation of security screening tasks to reduce screeners' visual fatigue. Practitioner Summary: This study identified the risk factors influencing visual fatigue in baggage X-ray security screeners and estimated the strength of correlations between those factors and visual fatigue. The findings were of great importance to the workplace design and the work organisation of security screening tasks to reduce screeners' visual fatigue.

  10. Characterization of the temperature evolution during high-cycle fatigue of the ULTIMET superalloy: Experiment and theoretical modeling

    Science.gov (United States)

    Jiang, L.; Wang, H.; Liaw, P. K.; Brooks, C. R.; Klarstrom, D. L.

    2001-09-01

    High-speed, high-resolution infrared thermography, as a noncontact, full-field, and nondestructive technique, was used to study the temperature variations of a cobalt-based ULTIMET alloy subjected to high-cycle fatigue. During each fatigue cycle, the temperature oscillations, which were due to the thermal-elastic-plastic effects, were observed and related to stress-strain analyses. A constitutive model was developed for predicting the thermal and mechanical responses of the ULTIMET alloy subjected to cyclic deformation. The model was constructed in light of internal-state variables, which were developed to characterize the inelastic strain of the material during cyclic loading. The predicted stress-strain and temperature responses were found to be in good agreement with the experimental results. In addition, the change of temperature during fatigue was employed to reveal the accumulation of fatigue damage, and the measured temperature was utilized as an index for fatigue-life prediction.

  11. A proposal of parameter determination method in the residual strength degradation model for the prediction of fatigue life (I)

    International Nuclear Information System (INIS)

    Kim, Sang Tae; Jang, Seong Soo

    2001-01-01

    The static and fatigue tests have been carried out to verify the validity of a generalized residual strength degradation model. And a new method of parameter determination in the model is verified experimentally to account for the effect of tension-compression fatigue loading of spheroidal graphite cast iron. It is shown that the correlation between the experimental results and the theoretical prediction on the statistical distribution of fatigue life by using the proposed method is very reasonable. Furthermore, it is found that the correlation between the theoretical prediction and the experimental results of fatigue life in case of tension-tension fatigue data in composite material appears to be reasonable. Therefore, the proposed method is more adjustable in the determination of the parameter than maximum likelihood method and minimization technique

  12. Catastrophe models for cognitive workload and fatigue in N-back tasks.

    Science.gov (United States)

    Guastello, Stephen J; Reiter, Katherine; Malon, Matthew; Timm, Paul; Shircel, Anton; Shaline, James

    2015-04-01

    N-back tasks place a heavy load on working memory, and thus make good candidates for studying cognitive workload and fatigue (CWLF). This study extended previous work on CWLF which separated the two phenomena with two cusp catastrophe models. Participants were 113 undergraduates who completed 2-back and 3-back tasks with both auditory and visual stimuli simultaneously. Task data were complemented by several measures hypothesized to be related to cognitive elasticity and compensatory abilities and the NASA TLX ratings of subjective workload. The adjusted R2 was .980 for the workload model, which indicated a highly accurate prediction with six bifurcation (elasticity versus rigidity) effects: algebra flexibility, TLX performance, effort, and frustration; and psychosocial measures of inflexibility and monitoring. There were also two cognitive load effects (asymmetry): 2 vs. 3-back and TLX temporal demands. The adjusted R2 was .454 for the fatigue model, which contained two bifurcation variables indicating the amount of work done, and algebra flexibility as the compensatory ability variable. Both cusp models were stronger than the next best linear alternative model. The study makes an important step forward by uncovering an apparently complete model for workload, finding the role of subjective workload in the context of performance dynamics, and finding CWLF dynamics in yet another type of memory-intensive task. The results were also consistent with the developing notion that performance deficits induced by workload and deficits induced by fatigue result from the impact of the task on the workspace and executive functions of working memory respectively.

  13. 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.

  14. Modelling of ultrasonic impact treatment (UIT of welded joints and its effect on fatigue strength

    Directory of Open Access Journals (Sweden)

    K.L. Yuan

    2015-10-01

    Full Text Available Ultrasonic impact treatment (UIT is a remarkable post-weld technique applying mechanical impacts in combination with ultrasound into the welded joints. In the present work, a 3D simulation method including welding simulation, numerical modelling of UIT-process and an evaluation of fatigue crack growth has been developed. In the FE model, the actual treatment conditions and local mechanical characteristics due to acoustic softening are set as input parameters. The plastic deformation and compressive stress layer are found to be more pronounced when acoustic softening takes place. The predicted internal residual stress distributions of welded joint before and after UIT are compared with experimental results, showing a fairly good agreement with each other. Finally, simulated results of fatigue crack growth in various residual stress fields are well compared with test results, so that the proposed model may provide an effective tool to simulate UIT-process in engineering structures.

  15. Energy, fatigue, or both? A bifactor modeling approach to the conceptualization and measurement of vitality.

    Science.gov (United States)

    Deng, Nina; Guyer, Rick; Ware, John E

    2015-01-01

    Vitality is an important domain reflecting both the physical and emotional components of health-related quality of life. Because of its complexity, it has been defined and measured both broadly and narrowly. We explored the dimensionality of a very comprehensive item bank hypothesized to measure vitality and its related concepts. Secondary analyses were conducted using the responses of 1,343 adults representative of the US general population to Internet-based surveys including 42 items compiled from multiple scales (e.g., SF-36 Vitality, PROMIS-Fatigue), covering a broad range of vitality-related content areas (energy, fatigue, and their interference with physical, mental, social activities, and quality of life). Exploratory and confirmatory factor models were evaluated independently using split-half samples. Bifactor model was used to assess the essential unidimensionality of the items, in comparison with traditional unidimensional, multidimensional, and hierarchical models. Method effects of a common scale or phrase were modeled via correlating errors. The exploratory factor analysis identified one dominant factor. The confirmatory factor analysis identified a best-fitting (CFI = 0.964, RMSEA = 0.084) bifactor model with one general (vitality) and two group (energy and fatigue) factors, explaining 69, 3, and 4 % of total variance. Correlating errors accounting for the method effects were important in identifying the substantive dimensionality of the items. The bifactor model proved to be useful for evaluating the dimensionality of a complex construct. Results supported conceptualizing and measuring vitality as a unidimensional energy-fatigue construct. We encourage future studies comparing practical implications of measures based on the broader and narrower conceptualizations of vitality.

  16. Usage of Parameterized Fatigue Spectra and Physics-Based Systems Engineering Models for Wind Turbine Component Sizing: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, Taylor; Guo, Yi; Veers, Paul; Dykes, Katherine; Damiani, Rick

    2016-01-26

    Software models that use design-level input variables and physics-based engineering analysis for estimating the mass and geometrical properties of components in large-scale machinery can be very useful for analyzing design trade-offs in complex systems. This study uses DriveSE, an OpenMDAO-based drivetrain model that uses stress and deflection criteria to size drivetrain components within a geared, upwind wind turbine. Because a full lifetime fatigue load spectrum can only be defined using computationally-expensive simulations in programs such as FAST, a parameterized fatigue loads spectrum that depends on wind conditions, rotor diameter, and turbine design life has been implemented. The parameterized fatigue spectrum is only used in this paper to demonstrate the proposed fatigue analysis approach. This paper details a three-part investigation of the parameterized approach and a comparison of the DriveSE model with and without fatigue analysis on the main shaft system. It compares loads from three turbines of varying size and determines if and when fatigue governs drivetrain sizing compared to extreme load-driven design. It also investigates the model's sensitivity to shaft material parameters. The intent of this paper is to demonstrate how fatigue considerations in addition to extreme loads can be brought into a system engineering optimization.

  17. Effect of fibre arrangement on the multiaxial fatigue of fibrous composites: a micromechanical computational model

    Directory of Open Access Journals (Sweden)

    Roberto Brighenti

    2015-10-01

    Full Text Available Structural components made of fibre-reinforced materials are frequently used in engineering applications. Fibre-reinforced composites are multiphase materials, and complex mechanical phenomena take place at limit conditions but also during normal service situations, especially under fatigue loading, causing a progressive deterioration and damage. Under repeated loading, the degradation mainly occurs in the matrix material and at the fibre-matrix interface, and such a degradation has to be quantified for design structural assessment purposes. To this end, damage mechanics and fracture mechanics theories can be suitably applied to examine such a problem. Damage concepts can be applied to the matrix mechanical characteristics and, by adopting a 3-D mixed mode fracture description of the fibre-matrix detachment, fatigue fracture mechanics concepts can be used to determine the progressive fibre debonding responsible for the loss of load bearing capacity of the reinforcing phase. In the present paper, a micromechanical model is used to evaluate the unixial or multiaxial fatigue behaviour of structures with equi-oriented or randomly distributed fibres. The spatial fibre arrangement is taken into account through a statistical description of their orientation angles for which a Gaussian-like distribution is assumed, whereas the mechanical effect of the fibres on the composite is accounted for by a homogenization approach aimed at obtaining the macroscopic elastic constants of the material. The composite material behaves as an isotropic one for randomly distributed fibres, while it is transversally isotropic for unidirectional fibres. The fibre arrangement in the structural component influences the fatigue life with respect to the biaxiality ratio for multiaxial constant amplitude fatigue loading. One representative parametric example is discussed.

  18. Microstructural modeling of fatigue fracture of shape memory alloys at thermomechanical cyclic loading

    Science.gov (United States)

    Belyaev, Fedor S.; Evard, Margarita E.; Volkov, Aleksandr E.

    2018-05-01

    A microstructural model of shape memory alloys (SMA) describing their deformation and fatigue fracture is presented. A new criterion of fracture has been developed which takes into account the effect of hydrostatic pressure, deformation defects and material damage. It is shown that the model can describe the fatigue fracture of SMA under various thermomechanical cycling regimes. Results of calculating the number of cycles to failure at thermocycling under a constant stress, at symmetric two-sided cyclic deformation, at straining-unloading cycles, at cycling in the regime of the thermodynamic cycles of a SMA working body in the hard (strain controlled) and soft (stress controlled) working cycles, is studied. Results of calculating the number of cycles to failure are presented for different parameters of these cycles.

  19. A study on fatigue crack growth model considering high mean loading effects based on structural stress

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Kim, Cheol; Jin, Tae Eun; Dong, P.

    2004-01-01

    The mesh-insensitive structural stress procedure by Dong is modified to apply to the welded joints with local thickness variation and inarguable shear/normal stresses along local discontinuity surface. In order to make use of the structural stress based K solution for fatigue correlation of welded joints, a proper crack growth model needs to be developed. There exist some significant discrepancies in inferring the slope or crack growth exponent in the conventional Paris law regime. Two-stage crack growth model was not considered since its applications are focused upon the fatigue behavior in welded joints in which the load ratio effects are considered negligible. In this paper, a two-stage crack growth law considering high mean loading is proposed and proven to be effective in unifying the so-called anomalous short crack growth data

  20. Comparison of Fatigue crack growth rate of Type 347 stainless steel with ASME and JSME models

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Seokmin; Min, Ki-Deuk; Jeon, Soon-Hyeok; Lee, Bong-Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In this study, the FCGR of 347SS was evaluated in modified PWR high temperature water conditions. The FCGRs of 347SS under modified pressurized-water conditions were measured by using compact-tension (CT) specimens at different levels of dissolved oxygen (DO), and it were compared with other models proposed by ASME and Japanese groups. Corrosion fatigue is main factor of environmental fatigue effect. Increase of DO level in water induced more corrosion damage, and it accelerated FCGR in PWR and FCGR of 347SS in PWR water condition was faster than reference curves in J-PWR and ASME draft code case derived by 304 and 316 stainless steel, but it was slower than J-BWR reference curve. Using J-BWR model for estimating the FCGR of 347SS under PWR might be conservative.

  1. Development of a Fatigue Model for Low Alloy Steels Using a Cycle-Dependent Cohesive Zone Law

    Directory of Open Access Journals (Sweden)

    Kyungmok Kim

    2014-03-01

    Full Text Available A fatigue model for SAE 4130 steels is developed using a cycle-dependent cohesive zone law. Reduction of fracture energy and degradation of stiffness are considered to describe failure resistance after certain number of cycles. The reduction rate of fracture energy is determined with experimental stress (S- number of cycles to failure (N scatter found in the literature. Three-dimensional finite element models containing a cohesive zone are generated with commercial software (ABAQUS. Calculated fatigue lives at different stress ratios are in good agreement with experimental ones. In addition, fatigue behavior of hardened SAE 4130 steels is predicted with that of normalized material.

  2. Damage assessment of low-cycle fatigue by crack growth prediction. Development of growth prediction model and its application

    International Nuclear Information System (INIS)

    Kamaya, Masayuki; Kawakubo, Masahiro

    2012-01-01

    In this study, the fatigue damage was assumed to be equivalent to the crack initiation and its growth, and fatigue life was assessed by predicting the crack growth. First, a low-cycle fatigue test was conducted in air at room temperature under constant cyclic strain range of 1.2%. The crack initiation and change in crack size during the test were examined by replica investigation. It was found that a crack of 41.2 μm length was initiated almost at the beginning of the test. The identified crack growth rate was shown to correlate well with the strain intensity factor, whose physical meaning was discussed in this study. The fatigue life prediction model (equation) under constant strain range was derived by integrating the crack growth equation defined using the strain intensity factor, and the predicted fatigue lives were almost identical to those obtained by low-cycle fatigue tests. The change in crack depth predicted by the equation also agreed well with the experimental results. Based on the crack growth prediction model, it was shown that the crack size would be less than 0.1 mm even when the estimated fatigue damage exceeded the critical value of the design fatigue curve, in which a twenty-fold safety margin was used for the assessment. It was revealed that the effect of component size and surface roughness, which have been investigated empirically by fatigue tests, could be reasonably explained by considering the crack initiation and growth. Furthermore, the environmental effect on the fatigue life was shown to be brought about by the acceleration of crack growth. (author)

  3. Characterization of the Effects of Fatigue on the Central Nervous System (CNS) and Drug Therapies

    National Research Council Canada - National Science Library

    Mery, Laura

    2007-01-01

    .... The model focused on central fatigue. Central fatigue associated with sleep disruption may precede peripheral fatigue, and therefore may predict impaired performance earlier than peripheral fatigue...

  4. 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...

  5. Low Cycle Fatigue Behaviour of DP Steels: Micromechanical Modelling vs. Validation

    Directory of Open Access Journals (Sweden)

    Ghazal Moeini

    2017-07-01

    Full Text Available This study aims to simulate the stabilised stress-strain hysteresis loop of dual phase (DP steel using micromechanical modelling. For this purpose, the investigation was conducted both experimentally and numerically. In the experimental part, the microstructure characterisation, monotonic tensile tests and low cycle fatigue tests were performed. In the numerical part, the representative volume element (RVE was employed to study the effect of the DP steel microstructure of the low cycle fatigue behavior of DP steel. A dislocation-density based model was utilised to identify the tensile behavior of ferrite and martensite. Then, by establishing a correlation between the monotonic and cyclic behavior of ferrite and martensite phases, the cyclic deformation properties of single phases were estimated. Accordingly, Chaboche kinematic hardening parameters were identified from the predicted cyclic curve of individual phases in DP steel. Finally, the predicted hysteresis loop from low cycle fatigue modelling was in very good agreement with the experimental one. The stabilised hysteresis loop of DP steel can be successfully predicted using the developed approach.

  6. Probabilistic Modeling and Simulation of Metal Fatigue Life Prediction

    National Research Council Canada - National Science Library

    Heffern, Thomas

    2002-01-01

    ...% FLE The work of this thesis was to investigate the probability distributions of test data taken for aluminum 7050-T745 1, and to attempt to develop a probability based model from the variation...

  7. Individualized Next-Generation Biomathematical Modeling of Fatigue and Performance

    National Research Council Canada - National Science Library

    Van Dongen, Hans P

    2006-01-01

    .... This project employed a cutting-edge technique called Bayesian forecasting to develop a novel biomathematical performance model to predict responses to sleep loss and circadian displacement for individual subjects...

  8. Simplified rotor load models and fatigue damage estimates for offshore wind turbines.

    Science.gov (United States)

    Muskulus, M

    2015-02-28

    The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  9. Study of cumulative fatigue damage detection for used parts with nonlinear output frequency response functions based on NARMAX modelling

    Science.gov (United States)

    Huang, Honglan; Mao, Hanying; Mao, Hanling; Zheng, Weixue; Huang, Zhenfeng; Li, Xinxin; Wang, Xianghong

    2017-12-01

    Cumulative fatigue damage detection for used parts plays a key role in the process of remanufacturing engineering and is related to the service safety of the remanufactured parts. In light of the nonlinear properties of used parts caused by cumulative fatigue damage, the based nonlinear output frequency response functions detection approach offers a breakthrough to solve this key problem. First, a modified PSO-adaptive lasso algorithm is introduced to improve the accuracy of the NARMAX model under impulse hammer excitation, and then, an effective new algorithm is derived to estimate the nonlinear output frequency response functions under rectangular pulse excitation, and a based nonlinear output frequency response functions index is introduced to detect the cumulative fatigue damage in used parts. Then, a novel damage detection approach that integrates the NARMAX model and the rectangular pulse is proposed for nonlinear output frequency response functions identification and cumulative fatigue damage detection of used parts. Finally, experimental studies of fatigued plate specimens and used connecting rod parts are conducted to verify the validity of the novel approach. The obtained results reveal that the new approach can detect cumulative fatigue damages of used parts effectively and efficiently and that the various values of the based nonlinear output frequency response functions index can be used to detect the different fatigue damages or working time. Since the proposed new approach can extract nonlinear properties of systems by only a single excitation of the inspected system, it shows great promise for use in remanufacturing engineering applications.

  10. A model for life predictions of nickel-base superalloys in high-temperature low cycle fatigue

    Science.gov (United States)

    Romanoski, Glenn R.; Pelloux, Regis M.; Antolovich, Stephen D.

    1988-01-01

    Extensive characterization of low-cycle fatigue damage mechanisms was performed on polycrystalline Rene 80 and IN100 tested in the temperature range from 871 to 1000 C. Low-cycle fatigue life was found to be dominated by propagation of microcracks to a critical size governed by the maximum tensile stress. A model was developed which incorporates a threshold stress for crack extension, a stress-based crack growth expression, and a failure criterion. The mathematical equivalence between this mechanistically based model and the strain-life low-cycle fatigue law was demonstrated using cyclic stress-strain relationships. The model was shown to correlate the high-temperature low-cycle fatigue data of the different nickel-base superalloys considered in this study.

  11. The Fracture Mechanical Markov Chain Fatigue Model Compared with Empirical Data

    DEFF Research Database (Denmark)

    Gansted, L.; Brincker, Rune; Hansen, Lars Pilegaard

    The applicability of the FMF-model (Fracture Mechanical Markov Chain Fatigue Model) introduced in Gansted, L., R. Brincker and L. Pilegaard Hansen (1991) is tested by simulations and compared with empirical data. Two sets of data have been used, the Virkler data (aluminium alloy) and data...... established at the Laboratory of Structural Engineering at Aalborg University, the AUC-data, (mild steel). The model, which is based on the assumption, that the crack propagation process can be described by a discrete Space Markov theory, is applicable to constant as well as random loading. It is shown...

  12. Nonlinear Fatigue Damage Model Based on the Residual Strength Degradation Law

    Science.gov (United States)

    Yongyi, Gao; Zhixiao, Su

    In this paper, a logarithmic expression to describe the residual strength degradation process is developed in order to fatigue test results for normalized carbon steel. The definition and expression of fatigue damage due to symmetrical stress with a constant amplitude are also given. The expression of fatigue damage can also explain the nonlinear properties of fatigue damage. Furthermore, the fatigue damage of structures under random stress is analyzed, and an iterative formula to describe the fatigue damage process is deduced. Finally, an approximate method for evaluating the fatigue life of structures under repeated random stress blocking is presented through various calculation examples.

  13. Evaluation of long-term creep-fatigue life of stainless steel weldment based on a microstructure degradation model

    International Nuclear Information System (INIS)

    Asayama, Tai; Hasebe, Shinichi

    1997-01-01

    This paper describes a newly developed analytical method of evaluation of creep-fatigue strength of stainless weld metals. Based on the observation that creep-fatigue crack initiates adjacent to the interface of sigma-phase/delta-ferrite and matrix, a mechanistic model which allows the evaluation of micro stress/strain concentration adjacent to the interface was developed. Fatigue and creep damage were evaluated using the model which describes the microstructure after exposed to high temperatures for a long time. Thus it was made possible to predict analytically the long-term creep-fatigue life of stainless steel metals whose microstructure is degraded as a result of high temperature service. (author)

  14. Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

    Directory of Open Access Journals (Sweden)

    Dongsheng Wang

    2014-01-01

    Full Text Available Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

  15. Bayesian Model on Fatigue Crack Growth Rate of Type 304 Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sanhae; Yoon, Jae Young; Hwang, Il Soon [Nuclear Materials Laboratory, Seoul National University, Seoul (Korea, Republic of)

    2015-10-15

    The fatigue crack growth rate curve is typically estimated by deterministic methods in accordance with the ASME Boiler and Pressure Vessel Code Sec. XI. The reliability of nuclear materials must also consider the environmental effect. This can be overcome by probabilistic methods that estimate the degradation of materials. In this study, fatigue tests were carried out on Type 304 stainless steel (STS 304) to obtain a fatigue crack growth rate curve and Paris' law constants. Tests were conducted on a constant load and a constant delta K, respectively. The unknown constants of Paris' law were updated probabilistically by Bayesian inference and the method can be used for the probabilistic structural integrity assessment of other nuclear materials. In this paper, Paris' law constants including C and m for Type 304 stainless steel were determined by probabilistic approach with Bayesian Inference. The Bayesian update process is limited in accuracy, because this method should assume initial data distribution. If we select an appropriate distribution, this updating method is powerful enough to get data results considering the environment and materials. Until now, remaining lives of NPPs are estimated by deterministic methods using a priori model to finally assess structural integrity. Bayesian approach can utilize in-service inspection data derived from aged properties.

  16. Bayesian Model on Fatigue Crack Growth Rate of Type 304 Stainless Steel

    International Nuclear Information System (INIS)

    Choi, Sanhae; Yoon, Jae Young; Hwang, Il Soon

    2015-01-01

    The fatigue crack growth rate curve is typically estimated by deterministic methods in accordance with the ASME Boiler and Pressure Vessel Code Sec. XI. The reliability of nuclear materials must also consider the environmental effect. This can be overcome by probabilistic methods that estimate the degradation of materials. In this study, fatigue tests were carried out on Type 304 stainless steel (STS 304) to obtain a fatigue crack growth rate curve and Paris' law constants. Tests were conducted on a constant load and a constant delta K, respectively. The unknown constants of Paris' law were updated probabilistically by Bayesian inference and the method can be used for the probabilistic structural integrity assessment of other nuclear materials. In this paper, Paris' law constants including C and m for Type 304 stainless steel were determined by probabilistic approach with Bayesian Inference. The Bayesian update process is limited in accuracy, because this method should assume initial data distribution. If we select an appropriate distribution, this updating method is powerful enough to get data results considering the environment and materials. Until now, remaining lives of NPPs are estimated by deterministic methods using a priori model to finally assess structural integrity. Bayesian approach can utilize in-service inspection data derived from aged properties

  17. Determination of CTOD C in Fibre Metal Laminates by ASTM and Schwalbe Methods

    Directory of Open Access Journals (Sweden)

    E.M. Castrodeza

    2002-06-01

    Full Text Available Fibre Metal Laminates (FMLs have arisen as a demand of the aeronautical industry to use thin sheets with high resistance to fatigue crack growth, high damage tolerance, corrosion resistance and high specific strength. Considering these requirements, FMLs are an advantageous choice when compared to metal alloys currently used. In order to employ FMLs in aircraft structures, designers must hold a deep knowledge of a wide set of their properties including fracture toughness. The aim of this work was to evaluate the available methodologies to measure fracture toughness at instability (CTOD C in unidirectional fibre metal laminates reinforced with aramid fibres (ARALL®. To achieve this, tests were performed to obtain traditional and Schwalbe CTODs by using experimental ASTM based techniques, especially adapted to these laminates. Results achieved point out that Schwalbe method is more appropriate and also that there are differences between both CTOD parameters.

  18. Modeling of creep-fatigue interaction of zirconium α under cyclic loading at 200 C

    International Nuclear Information System (INIS)

    Vogel, C.

    1996-04-01

    The present work deals with mechanical behaviour of zirconium alpha at 200 deg. C and crack initiation prediction methods, particularly when loading conditions lead to interaction of fatigue and creep phenomena. A classical approach used to study interaction between cyclic effects and constant loading effects does not give easy understanding of experimental results. Therefore, a new approach has been developed, which allow to determine a number of cycles for crack initiation for complex structures under large loading conditions. To study influence of fatigue and creep interaction on crack initiation, a model was chosen, using a scalar variable, giving representation of the material deterioration state. The model uses a non linear cumulating effect between the damage corresponding to cyclic loads and the damage correlated to time influence. The model belongs to uncoupled approaches between damage and behaviour, which is described here by a two inelastic deformations model. This mechanical behaviour model is chosen because it allows distinction between a plastic and a viscous part in inelastic flow. Cyclic damage is function of stress amplitude and mean stress. For the peculiar sensitivity of the material to creep, a special parameter bas been defined to be critical toward creep damage. It is the kinematic term associated to state variables describing this type of hardening in the viscous mechanism. (author)

  19. Fatigue and Serviceability Limit State Model Basis for Assessment of Offshore Wind Energy Converters

    DEFF Research Database (Denmark)

    Thöns, Sebastian; Faber, M. H.; Rücker, W.

    2012-01-01

    , a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted......This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment...... as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide...

  20. Anti-fatigue activity of sea cucumber peptides prepared from Stichopus japonicus in an endurance swimming rat model.

    Science.gov (United States)

    Ye, Jing; Shen, Caihong; Huang, Yayan; Zhang, Xueqin; Xiao, Meitian

    2017-10-01

    Sea cucumber (Stichopus japonicus) is a well-known nutritious and luxurious seafood in Asia which has attracted increasing attention because of its nutrition and bioactivities in recent years. In this study, the anti-fatigue activity of sea cucumber peptides (SCP) prepared from S. japonicus was evaluated in a load-induced endurance swimming model. The SCP prepared in this study was mainly made up of low-molecular-weight peptides (fatigue was significantly improved by SCP treatment. Meanwhile, the remarkable alterations of energy metabolic markers, antioxidant enzymes, antioxidant capacity and oxidative stress biomarkers were normalized. Moreover, administration of SCP could modulate alterations of inflammatory cytokines and downregulate the overexpression of TRL4 and NF-κB. SCP has anti-fatigue activity and it exerted its anti-fatigue effect probably through normalizing energy metabolism as well as alleviating oxidative damage and inflammatory responses. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  1. Model of thermal fatigue of a copper surface under the action of high-power microwaves

    Science.gov (United States)

    Kuzikov, S. V.; Plotkin, M. E.

    2007-10-01

    The accelerating structures of modern supercolliders, as well as the components of high-power microwave electron devices operated in strong cyclic electromagnetic fields should have long lifetimes. Along with the electric breakdown, the surfaces of these microwave components deteriorate and their lifetimes decrease due to thermal strains and subsequent mechanical loads on the surface metal layer. The elementary theory of thermal fatigue was developed in the 1970s. In particular, a model of metal as a continuous medium was considered. Within the framework of this model, thermal fatigue is caused by the strains arising between the hot surface layer and the cold internal layer of the metal. However, this theory does not describe all the currently available experimental data. In particular, the notion of “safe temperature” of the heating, i.e., temperature at which the surface is not destroyed during an arbitrarily long series of pulses, which was proposed in the theoretical model, is in poor agreement with the experiment performed in the Stanford Linear Accelerator Center (SLAC, USA). In this work, the thermal-fatigue theory is developed on the basis of consideration of the copper polycrystalline structure. The necessity to take it into account was demonstrated by the results of the SLAC experiment, in which a change in the mutual orientation of copper grains and the formation of cracks at their boundaries was recorded for the first time. The developed theory makes it possible to use the experimental data to refine the coefficients in the obtained formulas for the lifetime of the metal surface and to predict the number of microwave pulses before its destruction as a function of the radiation power, the surface-temperature increase at the pulse peak, and the pulse duration.

  2. 3D characterization and modeling of low cycle fatigue damage mechanisms at high temperature in a cast aluminum alloy

    International Nuclear Information System (INIS)

    Dezecot, Sebastien; Maurel, Vincent; Buffiere, Jean-Yves; Szmytka, Fabien; Koster, Alain

    2017-01-01

    Synchrotron X-ray tomography was used to monitor damage evolution in three dimensions during in situ Low Cycle Fatigue (LCF) tests at high temperature (250 °C) for an industrial material. The studied material is an AlSi7Cu3Mg aluminum alloy (close to ASTM A319) produced by Lost Foam Casting (LFC), a process which generates coarse microstructures but is nevertheless used for engine parts by the automotive industry. The volume analysis (3D images) has shown that cracks are extremely sensitive to microstructural features: coarse pores and hard particles of the eutectic regions are critical regarding respectively the main crack initiation and the crack growth. Finite Elements (FE) simulations, performed on meshes directly generated from 3D volumes and containing only pores, have revealed that mechanical fields also play a major role on the crack behavior. Initiation sites corresponded to areas of maximum inelastic strain while the crack path was globally correlated to high stress triaxiality and inelastic strain fields.

  3. Spectrophotometric determination of the ASTM color of diesel oil

    Energy Technology Data Exchange (ETDEWEB)

    Douglas Willian Emanuel Alves Santana; Marcelle Prates Sepulveda; Paulo Jorge Sanches Barbeira

    2007-03-15

    One of the parameters analyzed to determine the quality of diesel oil is its ASTM color. Changes in color may be indicative of problems in the production process, contamination, degradation or the oxidation of diesel. The methodology recommended for determining the color of automotive diesel oil samples is the colorimetry according to standard ASTM D1500, in which a sample is introduced into a glass cell and the color of the sample is compared with an optical filter color scale. Although it is very simple, the manual method requires good visual acuity from the operator. This procedure becomes somewhat subjective in some cases since different operators can make distinct evaluations of the same sample. In this way, this work proposes the development of a spectrophotometric analysis methodology to eliminate the subjectiveness in the determination of ASTM color of diesel oil samples by using operator-independent parameters and making quality assay more accurate and precise. Short communication. 7 refs., 2 figs., 2 tabs.

  4. ASTM Standards for Reactor Dosimetry and Pressure Vessel Surveillance

    International Nuclear Information System (INIS)

    GRIFFIN, PATRICK J.

    1999-01-01

    The ASTM standards provide guidance and instruction on how to field and interpret reactor dosimetry. They provide a roadmap towards understanding the current ''state-of-the-art'' in reactor dosimetry, as reflected by the technical community. The consensus basis to the ASTM standards assures the user of an unbiased presentation of technical procedures and interpretations of the measurements. Some insight into the types of standards and the way in which they are organized can assist one in using them in an expeditious manner. Two example are presented to help orient new users to the breadth and interrelationship between the ASTM nuclear metrology standards. One example involves the testing of a new ''widget'' to verify the radiation hardness. The second example involves quantifying the radiation damage at a pressure vessel critical weld location through surveillance dosimetry and calculation

  5. Critical research issues in development of biomathematical models of fatigue and performance.

    Science.gov (United States)

    Dinges, David F

    2004-03-01

    This article reviews the scientific research needed to ensure the continued development, validation, and operational transition of biomathematical models of fatigue and performance. These models originated from the need to ascertain the formal underlying relationships among sleep and circadian dynamics in the control of alertness and neurobehavioral performance capability. Priority should be given to research that further establishes their basic validity, including the accuracy of the core mathematical formulae and parameters that instantiate the interactions of sleep/wake and circadian processes. Since individuals can differ markedly and reliably in their responses to sleep loss and to countermeasures for it, models must incorporate estimates of these inter-individual differences, and research should identify predictors of them. To ensure models accurately predict recovery of function with sleep of varying durations, dose-response curves for recovery of performance as a function of prior sleep homeostatic load and the number of days of recovery are needed. It is also necessary to establish whether the accuracy of models is affected by using work/rest schedules as surrogates for sleep/wake inputs to models. Given the importance of light as both a circadian entraining agent and an alerting agent, research should determine the extent to which light input could incrementally improve model predictions of performance, especially in persons exposed to night work, jet lag, and prolonged work. Models seek to estimate behavioral capability and/or the relative risk of adverse events in a fatigued state. Research is needed on how best to scale and interpret metrics of behavioral capability, and incorporate factors that amplify or diminish the relationship between model predictions of performance and risk outcomes.

  6. Fluoxetine prevents the development of depressive-like behavior in a mouse model of cancer related fatigue.

    Science.gov (United States)

    Norden, Diana M; Devine, Raymond; Bicer, Sabahattin; Jing, Runfeng; Reiser, Peter J; Wold, Loren E; Godbout, Jonathan P; McCarthy, Donna O

    2015-03-01

    Cancer patients frequently suffer from fatigue, a complex syndrome associated with tiredness and depressed mood. Cancer-related fatigue (CRF) can be present at the time of diagnosis, escalates during treatment, and can persist for years after treatment. CRF negatively influences quality of life, limits functional independence, and is associated with decreased survival in patients with incurable disease. We have previously shown that increased pro-inflammatory cytokine expression in the brain contributes to depressive- and fatigue-like behaviors in a mouse model of CRF. Inflammatory cytokines increase the activity of indoleamine 2,3-dioxygenase (IDO) and kynurenine 3-monooxygenase (KMO), which competitively reduce serotonin synthesis. Reduced serotonin availability in the brain and increased production of alternative neuroactive metabolites of tryptophan are thought to contribute to the development of depression and fatigue. The purpose of this study was to determine the effects of fluoxetine, a selective serotonin reuptake inhibitor (SSRI), on brain cytokines and behavioral measures of fatigue and depression in tumor-bearing mice. Here we show that tumor growth increased brain expression of pro-inflammatory cytokines and KMO. Treatment with fluoxetine had no effect on tumor growth, muscle wasting, fatigue behavior, or cytokine expression in the brain. Fluoxetine, however, reduced depressive-like behaviors in tumor bearing mice. In conclusion, our data confirm that increased brain expression of pro-inflammatory cytokines is associated with tumor-induced fatigue- and depressive-like behaviors. However, it is possible to separate the effects of tumor growth on mood and fatigue-like behaviors using SSRIs such as fluoxetine. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Use of ASTM D5304 in assessing unstable diesel fuel

    Energy Technology Data Exchange (ETDEWEB)

    Turner, L.M.; Martin, C.J. [Defense Fuel Supply Center, Alexandria, VA (United States); Beal, E.J.; Hardy, D.R. [Naval Research Lab., Washington, DC (United States)

    1995-05-01

    The storage stability, or the length of time a fuel can be stored, is of great concern to diesel fuel users. This paper reports on the use of the new ASTM accelerated test for storage stability by oxygen overpressure (D5304) to predict future storage life span of 63,000,000 gallons of a diesel fuel for US Naval vessel use. This paper demonstrates the use of ASTM D5304 at storage times of 16, 40 and 96 hours to accurately determine the length of time that this large quantity of diesel fuel could be stored at ambient temperatures before the maximum allowable amount of particulate contamination was reached.

  8. Characterization of ASTM round-robin tungsten-powder samples

    International Nuclear Information System (INIS)

    Slettevold, C.A.; Biermann, A.H.

    1975-01-01

    The Lawrence Livermore Laboratory Particle Characterization Laboratory Group has participated in an industry-wide round-robin investigation on characterization of tungsten powder. sponsored by the ASTM Subcommittee on Refractory-Metal Powders (B-09.3). The analyses performed at the suggestion of the ASTM subcommittee included measurements of tap density, apparent density, true density, average particle size, and surface area. Determinations of particle-weight and size distributions were also performed and particle inspection conducted by microscopy. This report describes the equipment and procedures used and summarizes the results of these analyses. (9 tables, 17 fig) (U.S.)

  9. Impact of turbulence induced loads and wave kinematic models on fatigue reliability estimates of offshore wind turbine monopiles

    DEFF Research Database (Denmark)

    Colone, Lorenzo; Natarajan, Anand; Dimitrov, Nikolay Krasimirov

    2018-01-01

    of fatigue loads. Subsequently, the research focuses on studying the effects of uncertain marine environments on the fatigue load distribution, showing that the latter is insensitive to the random variability of the hydrodynamic coefficients. With respect to the wave kinematic model, a comparison between...... nonlinear and linear waves clearly suggests that hydrodynamic forces depend significantly on the kinematic model adopted and the operational conditions of the turbine. Furthermore, a term is derived to correct the error introduced by Wheeler stretching at finite water depths. The respective model...

  10. Model-Based Fatigue Prognosis of Fiber-Reinforced Laminates Exhibiting Concurrent Damage Mechanisms

    Science.gov (United States)

    Corbetta, M.; Sbarufatti, C.; Saxena, A.; Giglio, M.; Goebel, K.

    2016-01-01

    Prognostics of large composite structures is a topic of increasing interest in the field of structural health monitoring for aerospace, civil, and mechanical systems. Along with recent advancements in real-time structural health data acquisition and processing for damage detection and characterization, model-based stochastic methods for life prediction are showing promising results in the literature. Among various model-based approaches, particle-filtering algorithms are particularly capable in coping with uncertainties associated with the process. These include uncertainties about information on the damage extent and the inherent uncertainties of the damage propagation process. Some efforts have shown successful applications of particle filtering-based frameworks for predicting the matrix crack evolution and structural stiffness degradation caused by repetitive fatigue loads. Effects of other damage modes such as delamination, however, are not incorporated in these works. It is well established that delamination and matrix cracks not only co-exist in most laminate structures during the fatigue degradation process but also affect each other's progression. Furthermore, delamination significantly alters the stress-state in the laminates and accelerates the material degradation leading to catastrophic failure. Therefore, the work presented herein proposes a particle filtering-based framework for predicting a structure's remaining useful life with consideration of multiple co-existing damage-mechanisms. The framework uses an energy-based model from the composite modeling literature. The multiple damage-mode model has been shown to suitably estimate the energy release rate of cross-ply laminates as affected by matrix cracks and delamination modes. The model is also able to estimate the reduction in stiffness of the damaged laminate. This information is then used in the algorithms for life prediction capabilities. First, a brief summary of the energy-based damage model

  11. Modeling of fatigue crack induced nonlinear ultrasonics using a highly parallelized explicit local interaction simulation approach

    Science.gov (United States)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2016-04-01

    This paper presents a parallelized modeling technique for the efficient simulation of nonlinear ultrasonics introduced by the wave interaction with fatigue cracks. The elastodynamic wave equations with contact effects are formulated using an explicit Local Interaction Simulation Approach (LISA). The LISA formulation is extended to capture the contact-impact phenomena during the wave damage interaction based on the penalty method. A Coulomb friction model is integrated into the computation procedure to capture the stick-slip contact shear motion. The LISA procedure is coded using the Compute Unified Device Architecture (CUDA), which enables the highly parallelized supercomputing on powerful graphic cards. Both the explicit contact formulation and the parallel feature facilitates LISA's superb computational efficiency over the conventional finite element method (FEM). The theoretical formulations based on the penalty method is introduced and a guideline for the proper choice of the contact stiffness is given. The convergence behavior of the solution under various contact stiffness values is examined. A numerical benchmark problem is used to investigate the new LISA formulation and results are compared with a conventional contact finite element solution. Various nonlinear ultrasonic phenomena are successfully captured using this contact LISA formulation, including the generation of nonlinear higher harmonic responses. Nonlinear mode conversion of guided waves at fatigue cracks is also studied.

  12. Study of creep-fatigue behavior in a 1000 MW rotor using a phenomenological lifetime model

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nailong; Wang, Weizhe; Jiang, Jishen; Liu, Yingzheng [School of Mechanical Engineering, Shanghai (China)

    2017-02-15

    In this study, the phenomenological lifetime model was applied to part of an ultra-supercritical steam turbine rotor model to predict its lifetime as a post processing of the finite element method. To validate the accuracy and adaptation of the post processing program, stress strain hysteresis loops of a cylinderal model under service-like load cycle conditions in cycle N = 1 and 300 were constructed, and the comparison of the results with experimental data on the same cylinderal specimen showed them to be satisfactory. The temperature and von Mises stress distributions of the rotor during a startup-running-shutdown-natural cool process were numerically studied using ABAQUS and the damage caused by the interaction of creep and fatigue was subsequently computed and discussed. It was found that the maximum damage appeared at the inlet notch zone, with the blade groove areas and the front notch areas also suffering a large damage amplitude.

  13. Psychosocial factors, musculoskeletal disorders and work-related fatigue amongst nurses in Brunei: structural equation model approach.

    Science.gov (United States)

    Abdul Rahman, Hanif; Abdul-Mumin, Khadizah; Naing, Lin

    2017-09-01

    Psychosocial factors, musculoskeletal disorders and work-related fatigue have adverse effects on individual nurses and place a substantial financial burden on health care. Evidence of an association has been reported in the literature, but no theoretical explanation has been published to date. To explore and develop a structural model to provide a theoretical explanation for this relationship. A cross-sectional study using data from 201 valid samples of emergency and critical care nurses across public hospitals in Brunei was performed via self-administered questionnaire. The structural equation model was assessed using partial least squares analysis. A valid and robust structural model was constructed. This revealed that 61.5% of the variance in chronic fatigue could be explained by psychosocial factors and musculoskeletal disorders pathways. Among the psychosocial factors, work-family conflict was identified as a key mediator for progression of musculoskeletal problems and subsequent fatigue through stress and burnout. This report provides a novel theoretical contribution to understanding the relationship between psychosocial factors, musculoskeletal disorders and work-related fatigue. These preliminary results may be useful for future studies on the development of work-related fatigue and musculoskeletal disorders, particularly the central role of work-family conflict. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Numerical simulation of fatigue crack growth rate and crack retardation due to an overload using a cohesive zone model

    NARCIS (Netherlands)

    Silitonga, S.; Maljaars, J.; Soetens, F.; Snijder, H.H.

    2014-01-01

    In this work, a numerical method is pursued based on a cohesive zone model (CZM). The method is aimed at simulating fatigue crack growth as well as crack growth retardation due to an overload. In this cohesive zone model, the degradation of the material strength is represented by a variation of the

  15. Job stress, fatigue, and job dissatisfaction in Dutch lorry drivers: towards an occupation specific model of job demands and control

    NARCIS (Netherlands)

    Croon, E.M. de; Blonk, R.W.B.; Zwart, B.C.H. de; Frings-Dresen, M.H.W.; Broersen, J.P.J.

    2002-01-01

    Building on Karasek's model of job demands and control (JD-C model), this study examined the effects of job control, quantitative workload, and two occupation specific job demands on fatigue and job dissatisfaction in Dutch lorry drivers. From 1181 lorry drivers self reported information was

  16. Job stress, fatigue, and job dissatisfaction in Dutch lorry drivers: towards an occupation specific model of job demands and control

    NARCIS (Netherlands)

    de Croon, E. M.; Blonk, R. W. B.; de Zwart, B. C. H.; Frings-Dresen, M. H. W.; Broersen, J. P. J.

    2002-01-01

    Objectives: Building on Karasek's model of job demands and control (JD-C model), this study examined the effects of job control, quantitative workload, and two occupation specific job demands (physical demands and supervisor demands) on fatigue and job dissatisfaction in Dutch lorry drivers.

  17. HACCP: Integrating Science and Management through ASTM Standards

    Science.gov (United States)

    From a technical perspective, hazard analysis-critical control point (HACCP) evaluation may be considered a risk management tool suited to a wide range of applications. As one outcome of a symposium convened by American Society for Testing and Materials (ASTM) in August, 2005, th...

  18. Modelling of pavement materials on steel decks using the five-point bending test: Thermo mechanical evolution and fatigue damage

    International Nuclear Information System (INIS)

    Arnaud, L; Houel, A

    2010-01-01

    This paper deals with the modelling of wearing courses on steel orthotropic decks such as the Millau viaduct in France. This is of great importance when dealing with durability: due to the softness of such a support, the pavement is subjected to considerable strains that may generate top-down cracks in the layer at right angles of the orthotropic plate stiffeners and shear cracks at the interface between pavement and steel. Therefore, a five-point bending fatigue test was developed and improved since 2003 at the ENTPE laboratory, to test different asphalt concrete mixes. This study aims at modelling the mechanical behavior of the wearing course throughout the fatigue test by a finite element method (Comsol Multiphysics software). Each material - steel, sealing sheet, asphalt concrete layer - is considered and modelled. The modelling of asphalt concrete is complex since it is a heterogeneous material, a viscoelastic medium and it thermosensitive. The actual characteristics of the asphalt concrete (thermo physical parameter and viscoelastic complex modulus) are determined experimentally on cylindrical cores. Moreover, a damage law based on Miner's damage is included in the model. The modelling of the fatigue test leads to encouraging results. Finally, results from the model are compared to the experimental data obtained from the five-point bending fatigue test device. The experimental data are very consistent with the numerical simulation.

  19. Job stress, fatigue, and job dissatisfaction in Dutch lorry drivers: towards an occupation specific model of job demands and control.

    Science.gov (United States)

    de Croon, E M; Blonk, R W B; de Zwart, B C H; Frings-Dresen, M H W; Broersen, J P J

    2002-06-01

    Building on Karasek's model of job demands and control (JD-C model), this study examined the effects of job control, quantitative workload, and two occupation specific job demands (physical demands and supervisor demands) on fatigue and job dissatisfaction in Dutch lorry drivers. From 1181 lorry drivers (adjusted response 63%) self reported information was gathered by questionnaire on the independent variables (job control, quantitative workload, physical demands, and supervisor demands) and the dependent variables (fatigue and job dissatisfaction). Stepwise multiple regression analyses were performed to examine the main effects of job demands and job control and the interaction effect between job control and job demands on fatigue and job dissatisfaction. The inclusion of physical and supervisor demands in the JD-C model explained a significant amount of variance in fatigue (3%) and job dissatisfaction (7%) over and above job control and quantitative workload. Moreover, in accordance with Karasek's interaction hypothesis, job control buffered the positive relation between quantitative workload and job dissatisfaction. Despite methodological limitations, the results suggest that the inclusion of (occupation) specific job control and job demand measures is a fruitful elaboration of the JD-C model. The occupation specific JD-C model gives occupational stress researchers better insight into the relation between the psychosocial work environment and wellbeing. Moreover, the occupation specific JD-C model may give practitioners more concrete and useful information about risk factors in the psychosocial work environment. Therefore, this model may provide points of departure for effective stress reducing interventions at work.

  20. Influence of wave modelling on the prediction of fatigue for offshore wind turbines

    Science.gov (United States)

    Veldkamp, H. F.; van der Tempel, J.

    2005-01-01

    Currently it is standard practice to use Airy linear wave theory combined with Morison's formula for the calculation of fatigue loads for offshore wind turbines. However, offshore wind turbines are typically placed in relatively shallow water depths of 5-25 m where linear wave theory has limited accuracy and where ideally waves generated with the Navier-Stokes approach should be used. This article examines the differences in fatigue for some representative offshore wind turbines that are found if first-order, second-order and fully non-linear waves are used. The offshore wind turbines near Blyth are located in an area where non-linear wave effects are common. Measurements of these waves from the OWTES project are used to compare the different wave models with the real world in spectral form. Some attention is paid to whether the shape of a higher-order wave height spectrum (modified JONSWAP) corresponds to reality for other places in the North Sea, and which values for the drag and inertia coefficients should be used. Copyright

  1. Evaluation of protective effect of Aegle marmelos Corr. in an animal model of chronic fatigue syndrome.

    Science.gov (United States)

    Lalremruta, Vanphawng; Prasanna, Gurunath S

    2012-05-01

    To evaluate ethanolic extract of leaves of Aegle marmelos in an experimental animal model of chronic fatigue syndrome for potential therapeutic benefit. Age/weight-matched female Wistar albino rats were grouped into five groups. (Group I- V) (n = 8). Group I served as naïve control and II served as stress control. Except for group I animals, other group animals were subjected to forced swimming every day for 15 minutes to induce a state of chronic fatigue and simultaneously treated with ethanolic extract of Aegle marmelos (EEAM) 150 and 250 mg/kg b.w. and Imipramine (20 mg.kg b.w.), respectively. Duration of immobility, anxiety level and locomotor activity were assessed on day 1, 7, 14 and 21 followed by biochemical estimation of oxidative biomarkers at the end of the study. Treatment with EEAM (150 and 250 mg/kg b.w.) resulted in a statistically significant and dose dependent reduction (P immobility, reduction in anxiety and increase in locomotor activity. Dose dependent and significant reduction in LPO level and increase in CAT and SOD was observed in extract treated animals. The results are suggestive of potential protective effect of A. marmelos against experimentally induced CFS.

  2. Role of loading direction on cyclic behaviour characteristics of AM30 extrusion and its fatigue damage modelling

    Energy Technology Data Exchange (ETDEWEB)

    Roostaei, Ali A., E-mail: aaroostaei@uwaterloo.ca; Jahed, Hamid, E-mail: hjahed@uwaterloo.ca

    2016-07-18

    Anisotropic fatigue and cyclic behaviour of AM30 Mg alloy extrusion is investigated by performing fully-reversed strain-controlled tension-compression cyclic tests at strain amplitudes between 0.3% and 2.3%, along extrusion (ED) and transverse (TD) directions. The shapes of half-life hysteresis loops suggest the predominance of slip and twinning/de-twinning mechanisms below and above the strain amplitude of 0.5%, respectively. The twinning/de-twinning occurrence is found to be more extensive during straining along ED, which results in higher asymmetry of hysteresis loops, and thereby, higher induced mean stress. This adversely affects the fatigue resistance and yields to less number of cycles before failure in ED. Optical microscopy and texture analysis are employed to validate the findings. In addition, fracture surfaces are studied by scanning electron microscopy to identify the sources of fatigue crack initiation. Persistent slip bands (PSBs) and twin lamellae interfaces are evidenced as crack initiation sites at low and high strain amplitudes, respectively. Cracks emanated from debonded inclusion interface are also observed. Lastly, estimated fatigue life by Smith-Watson-Topper (SWT) and Jahed-Varvani (JV) fatigue models are compared with experimental life obtained through this study as well as the ones reported in the literature. The JV energy model is proven to yield better life predictions.

  3. 75 FR 11196 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM International

    Science.gov (United States)

    2010-03-10

    ... Production Act of 1993--ASTM International Notice is hereby given that, on February 16, 2010, pursuant to.... (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with the..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between May...

  4. 75 FR 65657 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM International

    Science.gov (United States)

    2010-10-26

    ... Production Act of 1993--ASTM International Notice is hereby given that, on September 23, 2010, pursuant to.... (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with the..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between May...

  5. 77 FR 14046 - Amended Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM...

    Science.gov (United States)

    2012-03-08

    ... Research and Production Act of 1993--ASTM International Standards Notice is hereby given that, on February..., 15 U.S.C. 4301 et seq. (``the Act''), ASTM International Standards (``ASTM'') has filed written... circumstances. Specifically, ASTM has provided an updated list of current, ongoing ASTM standards activities...

  6. 76 FR 63658 - Notice Pursuant to the National Cooperative Research and Production Act of 1993; ASTM International

    Science.gov (United States)

    2011-10-13

    ... Production Act of 1993; ASTM International Notice is hereby given that, on August 31, 2011, pursuant to.... (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with the..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between May...

  7. 77 FR 1085 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM International

    Science.gov (United States)

    2012-01-09

    ... Production Act of 1993--ASTM International Notice is hereby given that, on December 5, 2011, pursuant to.... (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with the..., ASTM has provided an updated list of current, ongoing ASTM standards activities originating between...

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

    Science.gov (United States)

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

    2010-10-01

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

  9. Cyclic stress-strain behaviour under thermomechanical fatigue conditions - Modeling by means of an enhanced multi-component model

    Energy Technology Data Exchange (ETDEWEB)

    Christ, H J [Institut fuer Werkstofftechnik, Universitaet Siegen, D-57068 Siegen (Germany); Bauer, V, E-mail: hans-juergen.christ@uni-siegen.d [Wieland Werke AG, Graf-Arco Str. 36, D-89072 Ulm (Germany)

    2010-07-01

    The cyclic stress-strain behaviour of metals and alloys in cyclic saturation can reasonably be described by means of simple multi-component models, such as the model based on a parallel arrangement of elastic-perfectly plastic elements, which was originally proposed by Masing already in 1923. This model concept was applied to thermomechanical fatigue loading of two metallic engineering materials which were found to be rather oppositional with respect to cyclic plastic deformation. One material is an austenitic stainless steel of type AISI304L which shows dynamic strain aging (DSA) and serves as an example for a rather ductile alloy. A dislocation arrangement was found after TMF testing deviating characteristically from the corresponding isothermal microstructures. The second material is a third-generation near-gamma TiAl alloy which is characterized by a very pronounced ductile-to-brittle transition (DBT) within the temperature range of TMF cycling. Isothermal fatigue testing at temperatures below the DBT temperature leads to cyclic hardening, while cyclic softening was found to occur above DBT. The combined effect under TMF leads to a continuously developing mean stress. The experimental observations regarding isothermal and non-isothermal stress-strain behaviour and the correlation to the underlying microstructural processes was used to further develop the TMF multi-composite model in order to accurately predict the TMF stress-strain response by taking the alloy-specific features into account.

  10. Fractal cluster modeling of the fatigue behavior of lead zirconate titanate

    OpenAIRE

    Priya, Shashank; Kim, Hyeoung Woo; Ryu, Jungho; Uchino, Kenji; Viehland, Dwight D.

    2002-01-01

    The fatigue behavior of lead zirconate titanate ceramics (PZT) has been studied under electrical and mechanical drives. Piezoelectric fatigue was studied using a mechanical method. Under ac mechanical drive, hard and soft PZTs showed an increase in the longitudinal piezoelectric constant at short times, reaching a maximum at intermediate times. Systematic investigations were performed to characterize the electrical fatigue behavior. A decrease in the magnitude of the remanent polarization was...

  11. Effect of Fordyce Happiness Model on depression, stress, anxiety, and fatigue in patients with multiple sclerosis.

    Science.gov (United States)

    Khayeri, Fereydoon; Rabiei, Leili; Shamsalinia, Abbas; Masoudi, Reza

    2016-11-01

    This study was conducted to investigate the effect of Fordyce Happiness Model (FHM) on depression, stress, anxiety, and fatigue in MS patients. In this clinical trial, 140 MS patients assigned to experimental and control groups. Depression, anxiety, stress, and fatigue were measured by Depression Anxiety Stress Scale-21 and Piper Standard Scale before and immediately and three months after the implementation of FHM. The data were analyzed by SPSS 18. Independent t-test indicated that total scores of stress, depression, and fatigue of the two groups were not significantly different before the intervention but were significantly different after the intervention (P˂0.05). Moreover, anxiety scores of the two were not significantly different after the intervention (P˃0.05). FHM can assist MS patients to manage their disease and associated problems in life. Besides that, since FHM is efficient and costless, it can be incorporated into the health interventions for MS patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. External anal sphincter fatigue is not improved by N-acetylcysteine in an animal model.

    Science.gov (United States)

    Healy, C F; McMorrow, C; O'Herlihy, C; O'Connell, P R; Jones, J F X

    2008-06-01

    Oxidative stress is associated with skeletal muscle fatigue. This study tests the hypotheses that N-acetylcysteine (NAC) reduces fatigue and accelerates recovery of the rat external anal sphincter (EAS). Fifteen female Wistar rats were killed humanely. The EAS was mounted as a ring preparation and electrically stimulated with 50 Hz trains of 200 ms in duration every 4 s for three and a half minutes. Three groups were analysed: a control group (n = 5), a group pretreated with NAC (10(-4) mol L(-1); n = 5) and a group pretreated with NAC (10(-3) mol L(-1); n = 5). A novel fatigue index was formulated and was compared to a conventional method of expressing fatigue. There was no significant difference at concentrations of NAC (10(-4) mol L(-1); P > 0.05). At high concentrations of NAC (10(-3) mol L(-1)) there was a significant depression in peak twitch amplitude before fatigue (P = 0.04). N-acetylcysteine in both concentrations used, did not alter fatigue or recovery of the rat EAS. There was a significant positive correlation between the two methods of expressing fatigue but the conventional method produced a higher fatigue index (22.4% on average). N-acetylcysteine does not ameliorate fatigue or accelerate recovery of the EAS and may not be a useful medical therapy for faecal incontinence.

  13. A novel approach towards fatigue damage prognostics of composite materials utilizing SHM data and stochastic degradation modeling

    NARCIS (Netherlands)

    Loutas, T.; Eleftheroglou, N.

    2016-01-01

    A prognostic framework is proposed in order to estimate the remaining useful life of composite materials under fatigue loading based on acoustic emission data and a sophisticated Non Homogenous Hidden Semi Markov Model. Bayesian neural networks are also utilized as an alternative machine learning

  14. 76 FR 1459 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM International

    Science.gov (United States)

    2011-01-10

    ... Production Act of 1993-ASTM International Notice is hereby given that, on December 6, 2010, pursuant to.... (``the Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with the...

  15. Systematic Approach to Design Tailor Made Fuel Blends That Meets ASTM Standards

    DEFF Research Database (Denmark)

    Intikhab, S.; Kalakul, Sawitree; H., Choudhury

    2015-01-01

    point, vapor pressure, and heat content were determined using analytical instruments according to their respective American Society for Testing and Materials (ASTM) standards. Most of the properties complied well with the industry standards. However, model gasoline had a comparatively low RVP....... On the other hand, model diesel had a significantly higher cloud point and pour point than what is recommended. This deviation will have an impact on the cold flow properties of the fuels. For both fuels, different additives along with their composition have also been determined using the same computational...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-03

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

  17. 47 CFR 95.1509 - ASTM E2213-03 DSRC Standard.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false ASTM E2213-03 DSRC Standard. 95.1509 Section 95... ASTM E2213-03 DSRC Standard. On-Board Units operating in the 5850-5925 MHz band shall comply with the... Materials (ASTM) E2213-03, Standard Specification for Telecommunications and Information Exchange Between...

  18. Verification of the ASTM G-124 Purge Equation

    Science.gov (United States)

    Robbins, Katherine E.; Davis, Samuel Eddie

    2009-01-01

    ASTM G-124 seeks to evaluate combustion characteristics of metals in high-purity (greater than 99%) oxygen atmospheres. ASTM G-124 provides the following equation to determine the minimum number of purges required to reach this level of purity in a test chamber: n = -4/log10(Pa/Ph), where "n" is the total number of purge cycles required, Ph is the absolute pressure used for the purge on each cycle and Pa is the atmospheric pressure or the vent pressure. The origin of this equation is not known and has been the source of frequent questions as to its accuracy and reliability. This paper shows the derivation of the G-124 purge equation, and experimentally explores the equation to determine if it accurately predicts the number of cycles required.

  19. The representation of inflammatory signals in the brain: A model for subjective fatigue in multiple sclerosis

    NARCIS (Netherlands)

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

    2014-01-01

    In multiple sclerosis (MS) patients, fatigue is rated as one of the most common and disabling symptoms. However, the pathophysiology underlying this fatigue is not yet clear. Several lines of evidence suggest that immunological factors, such as elevated levels of pro-inflammatory cytokines, may

  20. Implementation of creep-fatigue model into finite-element code to assess cooled turbine blade.

    CSIR Research Space (South Africa)

    Dedekind, MO

    1994-01-01

    Full Text Available Turbine blades which are designed with airfoil cooling are subject to thermo-mechanical fatigue as well as creep damage. These problems arise due to thermal cycling and high operating temperatures in service. An implementation of fatigue and creep...

  1. Multi-Scale Modelling of Fatigue of Wind Turbine Rotor Blade Composites

    NARCIS (Netherlands)

    Qian, C.

    2013-01-01

    In this research, extensive fatigue tests were performed on single glass fibres and composite coupons. Comparison of the test results shows that there is a significant difference between the fibre and composite fatigue behaviour. In order to clarify this difference, a multi-scale micro-mechanical

  2. Fatigue life prediction in composites using progressive damage modelling under block and spectrum loading

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Philippidis, T.P.; Brøndsted, Povl

    2010-01-01

    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...

  3. Isothermal Bainite Processing of ASTM A723 Components

    Science.gov (United States)

    1993-09-01

    4 List of Illustrations 1. Photograph of typical cylinders used in the present study ................................. 7 2. CCT diagram for... CCT ) diagram obtained by thermal and magnetic analyses for the high nickel (-3 percent) ASTM A723 steel. The bainite knee for the 2 percent nickel...block. Also shown is the slope giving the average cooling rate in the critical region of the CCT diagram . This average rate happens to approximately

  4. An Automated Safe-to-Mate (ASTM) Tester

    Science.gov (United States)

    Nguyen, Phuc; Scott, Michelle; Leung, Alan; Lin, Michael; Johnson, Thomas

    2013-01-01

    Safe-to-mate testing is a common hardware safety practice where impedance measurements are made on unpowered hardware to verify isolation, continuity, or impedance between pins of an interface connector. A computer-based instrumentation solution has been developed to resolve issues. The ASTM is connected to the circuit under test, and can then quickly, safely, and reliably safe-to-mate the entire connector, or even multiple connectors, at the same time.

  5. The USCG/environment Canada/ASTM standards development program

    International Nuclear Information System (INIS)

    Whittaker, H.

    1992-01-01

    Environment Canada's Emergencies Engineering Division (EED) has been charged, as a result of the Public Review Panel on Tanker Safety and Marine Emergency Response report, with increased R ampersand D in marine oil spills. This activity will, of necessity, include development of standards and guidelines for the testing and/or usage of oil spill cleanup equipment. The United States Coast Guard (USCG) has been charged with implementing the provisions of the Oil Pollution Act of 1990 (OPA-90), as it pertains to marine transportation vessels and facilities. Among the provisions are requirements for vessel and facility owners and operators to develop comprehensive response plans that specifically match response resources to spill removal requirements. Meeting the response plan provisions of OPA-90 requires common standards for testing, selecting and assigning resources to anticipated response needs and objectively evaluating response plans for adequacy. In August of 1991, the USCG OPA-90 office approached ASTM to determine the feasibility of developing standards through that organizations procedures. Meetings were then held between the OPA-90 staff and members of the ASTM Committee F-20 on Hazardous Substances and Oil Spill Response. An agreement was reached to commence standards development in the areas of: Barriers, Skimmers, Treating Agents, Pumps, Beach Clean-up, Sorbents, Bioremediation, In-situ Burning, Temporary Storage Devices, Communications, Remote Sensing. It was recognized that ASTM and other organizational standards existed in several of these areas, but there were those where none were known to exist. Standards development was, therefore, expected to be a complicated and time-consuming process. Both the USCG OPA-90 and EC/EED offices required standards to be developed quickly, without subverting the ASTM process. Mechanical containment and recovery was considered to be the primary area of concern for both groups

  6. Fatigue Model for the Structural Integrity Evaluation Applied to a Wind Turbine Concrete Shaft, Considering Corrosion and Freeze and Thaw Degradation

    DEFF Research Database (Denmark)

    Saucedo-Mora, Luis; Thöns, Sebastian

    2017-01-01

    Fatigue is one of the principal damage mechanisms in a slender concrete structure under cyclic loads. And needs to be calculated locally through all the structure, considering the lading conditions and the particularities of concrete. The model presented here is capable to account for the fatigue...

  7. Comparison of Expandable and Fixed Interbody Cages in a Human Cadaver Corpectomy Model: Fatigue Characteristics.

    Science.gov (United States)

    Pekmezci, Murat; Tang, Jessica A; Cheng, Liu; Modak, Ashin; McClellan, Robert T; Buckley, Jenni M; Ames, Christopher P

    2016-11-01

    In vitro cadaver biomechanics study. The goal of this study is to compare the in situ fatigue life of expandable versus fixed interbody cage designs. Expandable cages are becoming more popular, in large part, due to their versatility; however, subsidence and catastrophic failure remain a concern. This in vitro analysis investigates the fatigue life of expandable and fixed interbody cages in a single level human cadaver corpectomy model by evaluating modes of subsidence of expandable and fixed cages as well as change in stiffness of the constructs with cyclic loading. Nineteen specimens from 10 human thoracolumbar spines (T10-L2, L3-L5) were biomechanically evaluated after a single level corpectomy that was reconstructed with an expandable or fixed cage and anterior dual rod instrumentation. All specimens underwent 98 K cycles to simulate 3 months of postoperative weight bearing. In addition, a third group with hyperlordotic cages was used to simulate catastrophic failure that is observed in clinical practice. Three fixed and 2 expandable cages withstood the cyclic loading despite perfect sagittal and coronal plane fitting of the endcaps. The majority of the constructs settled in after initial subsidence. The catastrophic failures that were observed in clinical practice could not be reproduced with hyperlordotic cages. However, all cages in this group subsided, and 60% resulted in endplate fractures during deployment of the cage. Despite greater surface contact area, expandable cages have a trend for higher subsidence rates when compared with fixed cages. When there is edge loading as in the hyperlordotic cage scenario, there is a higher risk of subsidence and intraoperative fracture during deployment of expandable cages.

  8. Microstructure-sensitive Crystal Viscoplasticity for Ni-base Superalloys Targeting Long-term Creep-Fatigue Interaction Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Neu, Richard W.

    2017-09-30

    The aim of this project is to develop a microstructure-sensitive crystal viscoplasticity (CVP) model for single-crystal Ni-base superalloys to model the behavior of the material and components in the hot gas path sections of industrial gas turbines (IGT). Microstructure degradation associated with aging critical to predicting long-term creep-fatigue interactions will be embedded into the model through the γ' precipitate morphology evolution by coupling the coarsening drivers and kinetics into the constitutive equations of the CVP model. Model parameters will be determined using new experimental protocols that involve systematically artificially aging the alloy under different stress conditions to determine the relationship between the size and morphology g' precipitates on the creep and thermomechanical fatigue response.

  9. Microstructure-sensitive Crystal Viscoelasticity for Ni-base Superalloys Targeting Long-term Creep-Fatigue Interaction Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Neu, Richard W

    2016-09-30

    The aim of this project is to develop a microstructure-sensitive crystal viscoplasticity (CVP) model for single-crystal Ni-base superalloys to model the behavior of the material and components in the hot gas path sections of industrial gas turbines (IGT). Microstructure degradation associated with aging critical to predicting long-term creep-fatigue interactions will be embedded into the model through the γ' precipitate morphology evolution by coupling the coarsening drivers and kinetics into the constitutive equations of the CVP model. Model parameters will be determined using new experimental protocols that involve systematically artificially aging the alloy under different stress conditions to determine the relationship between the size and morphology g' precipitates on the creep and thermomechanical fatigue response.

  10. Probabilistic modeling of fatigue crack growth in Ti-6Al-4V

    International Nuclear Information System (INIS)

    Soboyejo, W.O.; Shen, W.; Soboyejo, A.B.O.

    2001-01-01

    This paper presents the results of a combined experimental and analytical study of the probabilistic nature of fatigue crack growth in Ti-6Al-4V. A simple experimental fracture mechanics framework is presented for the determination of statistical fatigue crack growth parameters from two fatigue tests. The experimental studies show that the variabilities in long fatigue crack growth rate data and the Paris coefficient are well described by the log-normal distributions. The variabilities in the Paris exponent are also shown to be well characterized by a normal distribution. The measured statistical distributions are incorporated into a probabilistic fracture mechanics framework for the estimation of material reliability. The implications of the results are discussed for the probabilistic analysis of fatigue crack growth in engineering components and structures. (orig.)

  11. A study on multi-axial fatigue model based on structural stress

    International Nuclear Information System (INIS)

    Kim, Cheol; Kim, Jong Sung; Jin, Tae Eun; Dong, P.

    2004-01-01

    In nuclear components, cyclic loadings that cause complex states of stress are common. Through a reference review, four sources of the multi-axial fatigue data were collected from LBF, University of Illinois, EPRI, and TWI. All these tests were conducted using tube to flange specimens with a circumferential fillet welds. The loading conditions were mostly bending/ torsion combinations, except that TWI used tension/ torsion combinations. None of fatigue correlation parameters have been demonstrated to be satisfactory in correlating the multi-axial fatigue data outside of their own. In this paper, we proposed the characterizing multi-axial fatigue behavior in terms of the structural stress methods by using some of the well-known multi-axial fatigue data available in the references

  12. Protective effect of epigallocatechin gallate in murine water-immersion stress model of chronic fatigue syndrome.

    Science.gov (United States)

    Sachdeva, Anand Kamal; Kuhad, Anurag; Tiwari, Vinod; Arora, Vipin; Chopra, Kanwaljit

    2010-06-01

    Chronic fatigue syndrome (CFS) is a specific clinical condition that characterizes unexplained disabling fatigue. In the present study, chronic fatigue was produced in mice by subjecting them to forced swim inside a rectangular jar of specific dimensions for 6 min. daily for 15 days. Epigallocatechin gallate (EGCG; 25, 50 and 100 mg/kg, p.o.) was administered daily 30 min. before forced swim session. Immobility period and post-swim fatigue was assessed on alternate days. On the 16th day, after assessment of various behavioural parameters, mice were killed to harvest the brain, spleen and thymus. There was significant increase in oxidative-nitrosative stress and tumour necrosis factor-alpha levels in the brain of mice subjected to water-immersion stress as compared with naive group. These behavioural and biochemical alterations were restored after chronic treatment with EGCG. The present study points out that EGCG could be of therapeutic potential in the treatment of chronic fatigue.

  13. 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 ...

  14. Fatigue Monitoring Tool for Airline Operators (FMT

    Directory of Open Access Journals (Sweden)

    Gislason Sigurdur Hrafn

    2017-12-01

    Full Text Available A Fatigue Monitoring Tool (FMT model was constructed for an operational airline in order to manage the fatigue levels of their crews in accordance with Fatigue Risk Management System (FRMS practices. This article describes the implementation of the Fatigue Monitoring Tool model and the airline’s aims to put the recent scientific findings on aviation fatigue into practical use. The model consists of proxy points allotted to various duties and rest periods.

  15. Effect of additional holes on transient thermal fatigue life of gas turbine casing

    Directory of Open Access Journals (Sweden)

    H. Bazvandi

    2017-10-01

    Full Text Available Gas turbines casings are susceptible to cracking at the edge of eccentric pin hole, which is the most likely position for crack initiation and propagation. This paper describes the improvement of transient thermal fatigue crack propagation life of gas turbines casings through the application of additional holes. The crack position and direction was determined using non-destructive tests. A series of finite element patterns were developed and tested in ASTM-A395 elastic perfectly-plastic ductile cast iron. The effect of arrangement of additional holes on transient thermal fatigue behavior of gas turbines casings containing hole edge cracks was investigated. ABAQUS finite element package and Zencrack fracture mechanics code were used for modeling. The effect of the reduction of transient thermal stress distribution around the eccentric pin hole on the transient thermal fatigue crack propagation life of the gas turbines casings was discussed. The result shows that transient thermal fatigue crack propagation life could be extended by applying additional holes of larger diameter and decreased by increasing the vertical distance, angle, and distance between the eccentric pin hole and the additional holes. The results from the numerical predictions were compared with experimental data.

  16. Application of ASTM E-1559 Apparatus to Study H2O Desorption

    Science.gov (United States)

    Woronowicz, Michael; Perry, Radford, III; Meadows, George A.

    2015-01-01

    The NASA James Webb Space Telescope project identified a need to measure water vapor desorption from cryogenic surfaces in order to validate predictions of spacecraft design performance. A review of available scientific literature indicated no such measurements had been reported below 131 K. Contamination control personnel at NASA Goddard Space Flight Center recognized the possibility they readily possessed the means to collect these measurements at lower temperatures using an existing apparatus commonly employed for making outgassing observations. This presentation will relate how the ASTM E-1559 Molekit apparatus was used without physical modification to measure water vapor sublimation down to 120 K and compare this data to existing equilibrium vapor pressure models.

  17. Infection Elicited Autoimmunity and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: An Explanatory Model

    Science.gov (United States)

    Blomberg, Jonas; Gottfries, Carl-Gerhard; Elfaitouri, Amal; Rizwan, Muhammad; Rosén, Anders

    2018-01-01

    Myalgic encephalomyelitis (ME) often also called chronic fatigue syndrome (ME/CFS) is a common, debilitating, disease of unknown origin. Although a subject of controversy and a considerable scientific literature, we think that a solid understanding of ME/CFS pathogenesis is emerging. In this study, we compiled recent findings and placed them in the context of the clinical picture and natural history of the disease. A pattern emerged, giving rise to an explanatory model. ME/CFS often starts after or during an infection. A logical explanation is that the infection initiates an autoreactive process, which affects several functions, including brain and energy metabolism. According to our model for ME/CFS pathogenesis, patients with a genetic predisposition and dysbiosis experience a gradual development of B cell clones prone to autoreactivity. Under normal circumstances these B cell offsprings would have led to tolerance. Subsequent exogenous microbial exposition (triggering) can lead to comorbidities such as fibromyalgia, thyroid disorder, and orthostatic hypotension. A decisive infectious trigger may then lead to immunization against autoantigens involved in aerobic energy production and/or hormone receptors and ion channel proteins, producing postexertional malaise and ME/CFS, affecting both muscle and brain. In principle, cloning and sequencing of immunoglobulin variable domains could reveal the evolution of pathogenic clones. Although evidence consistent with the model accumulated in recent years, there are several missing links in it. Hopefully, the hypothesis generates testable propositions that can augment the understanding of the pathogenesis of ME/CFS. PMID:29497420

  18. Model calibration for a soft elastomeric capacitor sensor considering slippage under fatigue cracks

    Science.gov (United States)

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

    2016-04-01

    A newly-developed soft elastomeric capacitor (SEC) strain sensor has shown promise in fatigue crack monitoring. The SECs exhibit high levels of ductility and hence do not break under excessive strain when the substrate cracks due to slippage or de-bonding between the sensor and epoxy. The actual strain experienced by a SEC depends on the amount of slippage, which is difficult to simulate numerically, making it challenging to accurately predict the response of a SEC near a crack. In this paper, a two-step approach is proposed to simulate the capacitance response of a SEC. First, a finite element (FE) model of a steel compact tension specimen was analyzed under cyclic loading while the cracking process was simulated based on an element removal technique. Second, a rectangular boundary was defined near the crack region. The SEC outside the boundary was assumed to have perfect bond with the specimen, while that inside the boundary was assumed to deform freely due to slippage. A second FE model was then established to simulate the response of the SEC within the boundary subject to displacements at the boundary from the first FE model. The total simulated capacitance was computed from the model results by combining the computed capacitance inside and outside the boundary. The performance of the simulation incorporating slippage was evaluated by comparing the model results with the experimental data from the test performed on a compact tension specimen. The FE model considering slippage showed results that matched the experimental findings more closely than the FE model that did not consider slippage.

  19. Fatigue crack initiation in nickel-based superalloys studied by microstructure-based FE modeling and scanning electron microscopy

    Directory of Open Access Journals (Sweden)

    Fried M.

    2014-01-01

    Full Text Available In this work stage I crack initiation in polycrystalline nickel-based superalloys is investigated by analyzing anisotropic mechanical properties, local stress concentrations and plastic deformation on the microstructural length scale. The grain structure in the gauge section of fatigue specimens was characterized by EBSD. Based on the measured data, a microstructure-based FE model could be established to simulate the strain and stress distribution in the specimens during the first loading cycle of a fatigue test. The results were in fairly good agreement with experimentally measured local strains. Furthermore, the onset of plastic deformation was predicted by identifying shear stress maxima in the microstructure, presumably leading to activation of slip systems. Measurement of plastic deformation and observation of slip traces in the respective regions of the microstructure confirmed the predicted slip activity. The close relation between micro-plasticity, formation of slip traces and stage I crack initiation was demonstrated by SEM surface analyses of fatigued specimens and an in-situ fatigue test in a large chamber SEM.

  20. Implementation of internal model based control and individual pitch control to reduce fatigue loads and tower vibrations in wind turbines

    Science.gov (United States)

    Mohammadi, Ebrahim; Fadaeinedjad, Roohollah; Moschopoulos, Gerry

    2018-05-01

    Vibration control and fatigue loads reduction are important issues in large-scale wind turbines. Identifying the vibration frequencies and tuning dampers and controllers at these frequencies are major concerns in many control methods. In this paper, an internal model control (IMC) method with an adaptive algorithm is implemented to first identify the vibration frequency of the wind turbine tower and then to cancel the vibration signal. Standard individual pitch control (IPC) is also implemented to compare the performance of the controllers in term of fatigue loads reduction. Finally, the performance of the system when both controllers are implemented together is evaluated. Simulation results demonstrate that using only IMC or IPC alone has advantages and can reduce fatigue loads on specific components. IMC can identify and suppress tower vibrations in both fore-aft and side-to-side directions, whereas, IPC can reduce fatigue loads on blades, shaft and yaw bearings. When both IMC and IPC are implemented together, the advantages of both controllers can be used. The aforementioned analysis and comparisons were not studied in literature and this study fills this gap. FAST, AreoDyn and Simulink are used to simulate the mechanical, aerodynamic and electrical aspects of wind turbine.

  1. Extreme Environment Damage Index and Accumulation Model for CMC Laminate Fatigue Life Prediction, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Materials Research & Design (MR&D) is proposing in the SBIR Phase II an effort to develop a tool for predicting the fatigue life of C/SiC composite...

  2. ASTM international workshop on standards and measurements for tissue engineering scaffolds.

    Science.gov (United States)

    Simon, Carl G; Yaszemski, Michael J; Ratcliffe, Anthony; Tomlins, Paul; Luginbuehl, Reto; Tesk, John A

    2015-07-01

    The "Workshop on Standards & Measurements for Tissue Engineering Scaffolds" was held on May 21, 2013 in Indianapolis, IN, and was sponsored by the ASTM International (ASTM). The purpose of the workshop was to identify the highest priority items for future standards work for scaffolds used in the development and manufacture of tissue engineered medical products (TEMPs). Eighteen speakers and 78 attendees met to assess current scaffold standards and to prioritize needs for future standards. A key finding was that the ASTM TEMPs subcommittees (F04.41-46) have many active "guide" documents for educational purposes, but few standard "test methods" or "practices." Overwhelmingly, the most clearly identified need was standards for measuring the structure of scaffolds, followed by standards for biological characterization, including in vitro testing, animal models and cell-material interactions. The third most pressing need was to develop standards for assessing the mechanical properties of scaffolds. Additional needs included standards for assessing scaffold degradation, clinical outcomes with scaffolds, effects of sterilization on scaffolds, scaffold composition, and drug release from scaffolds. Discussions highlighted the need for additional scaffold reference materials and the need to use them for measurement traceability. Workshop participants emphasized the need to promote the use of standards in scaffold fabrication, characterization, and commercialization. Finally, participants noted that standards would be more broadly accepted if their impact in the TEMPs community could be quantified. Many scaffold standard needs have been identified and focus is turning to generating these standards to support the use of scaffolds in TEMPs. © 2014 Wiley Periodicals, Inc.

  3. ASTM clustering for improving coal analysis by near-infrared spectroscopy.

    Science.gov (United States)

    Andrés, J M; Bona, M T

    2006-11-15

    Multivariate analysis techniques have been applied to near-infrared (NIR) spectra coals to investigate the relationship between nine coal properties (moisture (%), ash (%), volatile matter (%), fixed carbon (%), heating value (kcal/kg), carbon (%), hydrogen (%), nitrogen (%) and sulphur (%)) and the corresponding predictor variables. In this work, a whole set of coal samples was grouped into six more homogeneous clusters following the ASTM reference method for classification prior to the application of calibration methods to each coal set. The results obtained showed a considerable improvement of the error determination compared with the calibration for the whole sample set. For some groups, the established calibrations approached the quality required by the ASTM/ISO norms for laboratory analysis. To predict property values for a new coal sample it is necessary the assignation of that sample to its respective group. Thus, the discrimination and classification ability of coal samples by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) in the NIR range was also studied by applying Soft Independent Modelling of Class Analogy (SIMCA) and Linear Discriminant Analysis (LDA) techniques. Modelling of the groups by SIMCA led to overlapping models that cannot discriminate for unique classification. On the other hand, the application of Linear Discriminant Analysis improved the classification of the samples but not enough to be satisfactory for every group considered.

  4. Carbon nanotube reinforced hybrid composites: Computational modeling of environmental fatigue and usability for wind blades

    DEFF Research Database (Denmark)

    Dai, Gaoming; Mishnaevsky, Leon

    2015-01-01

    The potential of advanced carbon/glass hybrid reinforced composites with secondary carbon nanotube reinforcement for wind energy applications is investigated here with the use of computational experiments. Fatigue behavior of hybrid as well as glass and carbon fiber reinforced composites...... with the secondary CNT reinforcements (especially, aligned tubes) present superior fatigue performances than those without reinforcements, also under combined environmental and cyclic mechanical loading. This effect is stronger for carbon composites, than for hybrid and glass composites....

  5. A neuro-immune model of Myalgic Encephalomyelitis/Chronic fatigue syndrome.

    Science.gov (United States)

    Morris, Gerwyn; Maes, Michael

    2013-12-01

    This paper proposes a neuro-immune model for Myalgic Encephalomyelitis/Chronic fatigue syndrome (ME/CFS). A wide range of immunological and neurological abnormalities have been reported in people suffering from ME/CFS. They include abnormalities in proinflammatory cytokines, raised production of nuclear factor-κB, mitochondrial dysfunctions, autoimmune responses, autonomic disturbances and brain pathology. Raised levels of oxidative and nitrosative stress (O&NS), together with reduced levels of antioxidants are indicative of an immuno-inflammatory pathology. A number of different pathogens have been reported either as triggering or maintaining factors. Our model proposes that initial infection and immune activation caused by a number of possible pathogens leads to a state of chronic peripheral immune activation driven by activated O&NS pathways that lead to progressive damage of self epitopes even when the initial infection has been cleared. Subsequent activation of autoreactive T cells conspiring with O&NS pathways cause further damage and provoke chronic activation of immuno-inflammatory pathways. The subsequent upregulation of proinflammatory compounds may activate microglia via the vagus nerve. Elevated proinflammatory cytokines together with raised O&NS conspire to produce mitochondrial damage. The subsequent ATP deficit together with inflammation and O&NS are responsible for the landmark symptoms of ME/CFS, including post-exertional malaise. Raised levels of O&NS subsequently cause progressive elevation of autoimmune activity facilitated by molecular mimicry, bystander activation or epitope spreading. These processes provoke central nervous system (CNS) activation in an attempt to restore immune homeostatsis. This model proposes that the antagonistic activities of the CNS response to peripheral inflammation, O&NS and chronic immune activation are responsible for the remitting-relapsing nature of ME/CFS. Leads for future research are suggested based on this

  6. Finite Element Modeling of Material Fatigue and Cracking Problems for Steam Power System HP Devices Exposed to Thermal Shocks

    Directory of Open Access Journals (Sweden)

    Pawlicki Jakub

    2016-09-01

    Full Text Available The paper presents a detailed analysis of the material damaging process due to low-cycle fatigue and subsequent crack growth under thermal shocks and high pressure. Finite Element Method (FEM model of a high pressure (HP by-pass valve body and a steam turbine rotor shaft (used in a coal power plant is presented. The main damaging factor in both cases is fatigue due to cycles of rapid temperature changes. The crack initiation, occurring at a relatively low number of load cycles, depends on alternating or alternating-incremental changes in plastic strains. The crack propagation is determined by the classic fracture mechanics, based on finite element models and the most dangerous case of brittle fracture. This example shows the adaptation of the structure to work in the ultimate conditions of high pressure, thermal shocks and cracking.

  7. Lamb wave-based damage quantification and probability of detection modeling for fatigue life assessment of riveted lap joint

    Science.gov (United States)

    He, Jingjing; Wang, Dengjiang; Zhang, Weifang

    2015-03-01

    This study presents an experimental and modeling study for damage detection and quantification in riveted lap joints. Embedded lead zirconate titanate piezoelectric (PZT) ceramic wafer-type sensors are employed to perform in-situ non-destructive testing during fatigue cyclical loading. A multi-feature integration method is developed to quantify the crack size using signal features of correlation coefficient, amplitude change, and phase change. In addition, probability of detection (POD) model is constructed to quantify the reliability of the developed sizing method. Using the developed crack size quantification method and the resulting POD curve, probabilistic fatigue life prediction can be performed to provide comprehensive information for decision-making. The effectiveness of the overall methodology is demonstrated and validated using several aircraft lap joint specimens from different manufactures and under different loading conditions.

  8. ASTM standards for fire debris analysis: a review.

    Science.gov (United States)

    Stauffer, Eric; Lentini, John J

    2003-03-12

    The American Society for Testing and Materials (ASTM) recently updated its standards E 1387 and E 1618 for the analysis of fire debris. The changes in the classification of ignitable liquids are presented in this review. Furthermore, a new standard on extraction of fire debris with solid phase microextraction (SPME) was released. Advantages and drawbacks of this technique are presented and discussed. Also, the standard on cleanup by acid stripping has not been reapproved. Fire debris analysts that use the standards should be aware of these changes.

  9. 75 FR 30440 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-ASTM International

    Science.gov (United States)

    2010-06-01

    ... Production Act of 1993--ASTM International Notice is hereby given that, on May 6, 2010, pursuant to Section 6... Act''), ASTM International (``ASTM'') has filed written notifications simultaneously with the Attorney... recovery of antitrust plaintiffs to actual damages under specified circumstances. Specifically, ASTM has...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

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

    International Nuclear Information System (INIS)

    Wilhelm, Paul; Rudolph, Juergen; Steinmann, Paul

    2015-01-01

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

  12. Fatigue Reliability of Offshore Wind Turbine Systems

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2012-01-01

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

  13. Recommendations for fluorescence instrument qualification: the new ASTM Standard Guide.

    Science.gov (United States)

    DeRose, Paul C; Resch-Genger, Ute

    2010-03-01

    Aimed at improving quality assurance and quantitation for modern fluorescence techniques, ASTM International (ASTM) is about to release a Standard Guide for Fluorescence, reviewed here. The guide's main focus is on steady state fluorometry, for which available standards and instrument characterization procedures are discussed along with their purpose, suitability, and general instructions for use. These include the most relevant instrument properties needing qualification, such as linearity and spectral responsivity of the detection system, spectral irradiance reaching the sample, wavelength accuracy, sensitivity or limit of detection for an analyte, and day-to-day performance verification. With proper consideration of method-inherent requirements and limitations, many of these procedures and standards can be adapted to other fluorescence techniques. In addition, procedures for the determination of other relevant fluorometric quantities including fluorescence quantum yields and fluorescence lifetimes are briefly introduced. The guide is a clear and concise reference geared for users of fluorescence instrumentation at all levels of experience and is intended to aid in the ongoing standardization of fluorescence measurements.

  14. Cancer-related fatigue in breast cancer patients after surgery: a multicomponent model using partial least squares-path modeling.

    Science.gov (United States)

    Bortolon, Catherine; Krikorian, Alicia; Carayol, Marion; Brouillet, Denis; Romieu, Gilles; Ninot, Gregory

    2014-04-01

    The aim of this study is to examine factors contributing to cancer-related fatigue (CRF) in breast cancer patients who have undergone surgery. Sixty women (mean age: 50.0) completed self-rated questionnaires assessing components of CRF, muscular and cognitive functions. Also, physiological and subjective data were gathered. Data were analyzed using partial least squares variance-based structural equation modeling in order to examine factors contributing to CRF after breast surgery. The tested model was robust in terms of its measurement quality (reliability and validity). According to the structural model results, emotional distress (β = 0.59; p accounting for 61% of the explained variance. Also, emotional distress (β = 0.41; p accounted for 41% of the explained variance. However, the relationship between low physical function and CRF was weak and nonsignificant (β = 0.01; p > 0.05). Emotional distress, altered vigilance capacity, and pain are associated with CRF in postsurgical breast cancer. In addition, emotional distress and pain are related to diminished physical function, which, in turn, has no significant impact on CRF. The current model should be examined in subsequent phases of the treatment (chemotherapy and/or radiotherapy) when side effects are more pronounced and may lead to increased intensity of CRF and low physical function. Copyright © 2013 John Wiley & Sons, Ltd.

  15. Melatonin supplementation plus exercise behavior ameliorate insulin resistance, hypertension and fatigue in a rat model of type 2 diabetes mellitus.

    Science.gov (United States)

    Rahman, Md Mahbubur; Kwon, Han-Sol; Kim, Myung-Jin; Go, Hyeon-Kyu; Oak, Min-Ho; Kim, Do-Hyung

    2017-08-01

    The objective was to investigate the effects of melatonin and exercise on insulin resistance (IR), hypertension and fatigue syndrome in a rat model of type 2 diabetes mellitus (T2DM). Rats were divided into 5 groups namely normal control (NC), T2DM control group (DC), diabetes plus exercise (DE), diabetes plus oral melatonin supplement (DM) and diabetes plus melatonin and exercise (DME) groups. Melatonin was administered orally 5mg/kg twice daily and 40min swimming/day 5days/week were regimented after diabetes induction. Blood pressure, fasting blood glucose, insulin, IR, serum leptin, lipid profiles, inflammatory cytokines, lipid peroxidation increased significantly (Phypertension, IR, biochemical alteration induced by diabetes and significantly increased exercise performance (Phypertension and exercise performance or fatigue possibly by improving antioxidative activities, hyperlipidemia, inflammatory cytokines via up-regulation of GLUT4, PGC-1 α and mitochondrial biogenesis in T2DM rats. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  16. Fatigue evaluation algorithms: Review

    Energy Technology Data Exchange (ETDEWEB)

    Passipoularidis, V.A.; Broendsted, P.

    2009-11-15

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

  17. Unified approach for estimating the probabilistic design S-N curves of three commonly used fatigue stress-life models

    International Nuclear Information System (INIS)

    Zhao Yongxiang; Wang Jinnuo; Gao Qing

    2001-01-01

    A unified approach, referred to as general maximum likelihood method, is presented for estimating probabilistic design S-N curves and their confidence bounds of the three commonly used fatigue stress-life models, namely three parameter, Langer and Basquin. The curves are described by a general form of mean and standard deviation S-N curves of the logarithm of fatigue life. Different from existent methods, i.e., the conventional method and the classical maximum likelihood method,present approach considers the statistical characteristics of whole test data. The parameters of the mean curve is firstly estimated by least square method and then, the parameters of the standard deviation curve is evaluated by mathematical programming method to be agreement with the maximum likelihood principle. Fit effects of the curves are assessed by fitted relation coefficient, total fitted standard error and the confidence bounds. Application to the virtual stress amplitude-crack initiation life data of a nuclear engineering material, Chinese 1Cr18Ni9Ti stainless steel pipe-weld metal, has indicated the validity of the approach to the S-N data where both S and N show the character of random variable. Practices to the two states of S-N data of Chinese 45 carbon steel notched specimens (k t = 2.0) have indicated the validity of present approach to the test results obtained respectively from group fatigue test and from maximum likelihood fatigue test. At the practices, it was revealed that in general the fit is best for the three-parameter model,slightly inferior for the Langer relation and poor for the Basquin equation. Relative to the existent methods, present approach has better fit. In addition, the possible non-conservative predictions of the existent methods, which are resulted from the influence of local statistical characteristics of the data, are also overcome by present approach

  18. Stochastic modelling of thermal fatigue crack growth for applying in the structural reliability of nuclear piping

    International Nuclear Information System (INIS)

    Radu, V.

    2016-01-01

    The problem of thermal fatigue in mixing areas arises in nuclear piping where a turbulent mixing or vortices produce rapid fluid temperature fluctuations with random frequencies. The assessment of fatigue crack growth due to cyclic thermal loads arising from turbulent mixing presents significant challenges, principally due to the difficulty of establishing the actual loading spectrum. To apply the Stochastic approach of thermal fatigue, a frequency temperature response function is proposed. For the elastic thermal stresses distribution solutions, the magnitude of the frequency response function is first derived and checked against the prediction by FEA. The connection between SIF.s power spectral density (PSD) and temperature.s PSD is assured with SIF frequency response function modulus. The frequency of the peaks of each magnitude for KI is supposed to be a stationary narrow-band Gaussian process. The probabilities of failure are estimated by means of the Monte Carlo methods considering a limit state function. (authors)

  19. Standard guide for high-resolution gamma-ray spectrometry of soil samples. ASTM standard

    International Nuclear Information System (INIS)

    1998-12-01

    This guide is under the jurisdiction of ASTM Committee C-26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test. The current edition was approved on Jul. 10, 1998. It was published in December 1998. Copyright American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA, 19428, USA. This document is available from NTIS under license from ASTM

  20. Evaluation of Instrumentation for Measuring Undissolved Water in Aviation Turbine Fuels per ASTM D3240

    Science.gov (United States)

    2015-11-05

    Undissolved Water in Aviation Turbine Fuels per ASTM D3240 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Joel Schmitigal... water ) in Aviation Turbine Fuels per ASTM D3240 15. SUBJECT TERMS fuel, JP-8, aviation fuel, contamination, free water , undissolved water , Aqua-Glo 16...Michigan 48397-5000 Evaluation of Instrumentation for Measuring Undissolved Water in Aviation Turbine Fuels per ASTM D3240 Joel Schmitigal Force

  1. Deformation and fatigue of tough 3D printed elastomer scaffolds processed by fused deposition modeling and continuous liquid interface production.

    Science.gov (United States)

    Miller, Andrew T; Safranski, David L; Wood, Catherine; Guldberg, Robert E; Gall, Ken

    2017-11-01

    Polyurethane (PU) based elastomers continue to gain popularity in a variety of biomedical applications as compliant implant materials. In parallel, advancements in additive manufacturing continue to provide new opportunities for biomedical applications by enabling the creation of more complex architectures for tissue scaffolding and patient specific implants. The purpose of this study was to examine the effects of printed architecture on the monotonic and cyclic mechanical behavior of elastomeric PUs and to compare the structure-property relationship across two different printing approaches. We examined the tensile fatigue of notched specimens, 3D crosshatch scaffolds, and two 3D spherical pore architectures in a physically crosslinked polycarbonate urethane (PCU) printed via fused deposition modeling (FDM) as well as a photo-cured, chemically-crosslinked, elastomeric PU printed via continuous liquid interface production (CLIP). Both elastomers were relatively tolerant of 3D geometrical features as compared to stiffer synthetic implant materials such as PEEK and titanium. PCU and crosslinked PU samples with 3D porous structures demonstrated a reduced tensile failure stress as expected without a significant effect on tensile failure strain. PCU crosshatch samples demonstrated similar performance in strain-based tensile fatigue as solid controls; however, when plotted against stress amplitude and adjusted by porosity, it was clear that the architecture had an impact on performance. Square shaped notches or pores in crosslinked PU appeared to have a modest effect on strain-based tensile fatigue while circular shaped notches and pores had little impact relative to smooth samples. When plotted against stress amplitude, any differences in fatigue performance were small or not statistically significant for crosslinked PU samples. Despite the slight difference in local architecture and tolerances, crosslinked PU solid samples were found to perform on par with PCU solid

  2. Modeling time-dependent corrosion fatigue crack propagation in 7000 series aluminum alloys

    Science.gov (United States)

    Mason, Mark E.; Gangloff, Richard P.

    1994-01-01

    Stress corrosion cracking and corrosion fatigue experiments were conducted with the susceptible S-L orientation of AA7075-T651, immersed in acidified and inhibited NaCl solution, to provide a basis for incorporating environmental effects into fatigue crack propagation life prediction codes such as NASA FLAGRO. This environment enhances da/dN by five to ten-fold compared to fatigue in moist air. Time-based crack growth rates from quasi-static load experiments are an order of magnitude too small for accurate linear superposition prediction of da/dN for loading frequencies above 0.001 Hz. Alternate methods of establishing da/dt, based on rising-load or ripple-load-enhanced crack tip strain rate, do not increase da/dt and do not improve linear superposition. Corrosion fatigue is characterized by two regimes of frequency dependence; da/dN is proportional to f(exp -1) below 0.001 Hz and to F(exp 0) to F(exp -0.1) for higher frequencies. Da/dN increases mildly both with increasing hold-time at K(sub max) and with increasing rise-time for a range of loading waveforms. The mild time-dependence is due to cycle-time-dependent corrosion fatigue growth. This behavior is identical for S-L nd L-T crack orientations. The frequency response of environmental fatigue in several 7000 series alloys is variable and depends on undefined compositional or microstructural variables. Speculative explanations are based on the effect of Mg on occluded crack chemistry and embritting hydrogen uptake, or on variable hydrogen diffusion in the crack tip process zone. Cracking in the 7075/NaCl system is adequately described for life prediction by linear superposition for prolonged load-cycle periods, and by a time-dependent upper bound relationship between da/dN and delta K for moderate loading times.

  3. A probabilistic physics-of-failure model for prognostic health management of structures subject to pitting and corrosion-fatigue

    International Nuclear Information System (INIS)

    Chookah, M.; Nuhi, M.; Modarres, M.

    2011-01-01

    A combined probabilistic physics-of-failure-based model for pitting and corrosion-fatigue degradation mechanisms is proposed to estimate the reliability of structures and to perform prognosis and health management. A mechanistic superposition model for corrosion-fatigue mechanism was used as a benchmark model to propose the simple model. The proposed model describes the degradation of the structures as a function of physical and critical environmental stresses, such as amplitude and frequency of mechanical loads (for example caused by the internal piping pressure) and the concentration of corrosive chemical agents. The parameters of the proposed model are represented by the probability density functions and estimated through a Bayesian approach based on the data taken from the experiments performed as part of this research. For demonstrating applications, the proposed model provides prognostic information about the reliability of aging of structures and is helpful in developing inspection and replacement strategies. - Highlights: ► We model an inventory system under static–dynamic uncertainty strategy. ► The demand is stochastic and non-stationary. ► The optimal ordering policy is proven to be a base stock policy. ► A solution algorithm for finding an optimal solution is provided. ► Two heuristics developed produce high quality solutions and scale-up efficiently.

  4. Modification of ASTM Standard E1681 on Environmental Cracking to Include Bolt-Load Specimen Testing

    National Research Council Canada - National Science Library

    Underwood, Jean D. M

    1997-01-01

    Benet Laboratories experience with environmental cracking of cannon components has been combined with the technical expertise of various participants at ASTM technical meetings and symposia to develop...

  5. Exfoliation Corrosion and Pitting Corrosion and Their Role in Fatigue Predictive Modeling: State-of-the-Art Review

    Directory of Open Access Journals (Sweden)

    David W. Hoeppner

    2012-01-01

    Full Text Available Intergranular attack (IG and exfoliation corrosion (EC have a detrimental impact on the structural integrity of aircraft structures of all types. Understanding the mechanisms and methods for dealing with these processes and with corrosion in general has been and is critical to the safety of critical components of aircraft. Discussion of cases where IG attack and exfoliation caused issues in structural integrity in aircraft in operational fleets is presented herein along with a much more detailed presentation of the issues involved in dealing with corrosion of aircraft. Issues of corrosion and fatigue related to the structural integrity of aging aircraft are introduced herein. Mechanisms of pitting nucleation are discussed which include adsorption-induced, ion migration-penetration, and chemicomechanical film breakdown theories. In addition, pitting corrosion (PC fatigue models are presented as well as a critical assessment of their application to aircraft structures and materials. Finally environmental effects on short crack behavior of materials are discussed, and a compilation of definitions related to corrosion and fatigue are presented.

  6. 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...

  7. The traditional drug Gongjin-Dan ameliorates chronic fatigue in a forced-stress mouse exercise model.

    Science.gov (United States)

    Hong, Sung-Shin; Lee, Ji-Young; Lee, Jin-Seok; Lee, Hye-Won; Kim, Hyeong-Geug; Lee, Sam-Keun; Park, Bong-Ki; Son, Chang-Gue

    2015-06-20

    Gongjin-Dan is a representative traditional Oriental medicine herbal drug that has been used to treat chronic fatigue symptoms for several hundred years. We evaluated the anti-fatigue effects of Gongjin-Dan and the underlying mechanisms in a chronic forced exercise mouse model. Balb/C male mice underwent an extreme treadmill-based running stress (1-h, 5 days/week), and daily oral administration of distilled water, Gongjin-Dan (100, 200, or 400 mg/kg), or ascorbic acid (100 mg/kg) for 28 days. The anti-fatigue effects of Gongjin-Dan were evaluated with behavioral tests (exercise tolerance and swimming tests), and the corresponding mechanisms were investigated based on oxidative stress and inflammatory cytokine and stress hormone levels in skeletal muscle, sera, and brain tissue. Gongjin-Dan significantly increased exercise tolerance and latency times but reduced the number of electric shocks and immobilization time on the treadmill running and swimming tests, compared with the control group. Gongjin-Dan also significantly ameliorated alterations in oxidative stress-related biomarkers (reactive oxygen species and malondialdehyde), inflammatory cytokines (tumor necrosis factor-α, interleukin-1 beta, interleukin-6, and interferon-γ) and glycogen and L-lactate levels in skeletal muscle, compared with those in the control group. Moreover, Gongjin-Dan considerably normalized the forced running stress-induced changes in serum corticosterone and adrenaline levels, as well as brain serotonin level. These antioxidant and anti-stress effects of Gongjin-Dan were supported by the results of Western blotting (4-hydroxynonenal and heme oxygenase-1) and the gene expression levels (serotonin receptor and serotonin transporter). These results support the clinical relevance of Gongjin-Dan regarding anti-chronic fatigue properties. The underlying mechanisms involve attenuation of oxidative and inflammatory reactions in muscle and regulation of the stress response through the

  8. Atomistic modeling of nanowires, small-scale fatigue damage in cast magnesium, and materials for MEMS

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, Martin L. [Univ. of Colorado, Boulder, CO (United States); Talmage, Mellisa J. [Univ. of Colorado, Boulder, CO (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); West, Neil [Univ. of Colorado, Boulder, CO (United States); Gullett, Philip Michael [Mississippi State Univ., Mississippi State, MS (United States); Miller, David C. [Univ. of Colorado, Boulder, CO (United States); Spark, Kevin [Univ. of Colorado, Boulder, CO (United States); Diao, Jiankuai [Univ. of Colorado, Boulder, CO (United States); Horstemeyer, Mark F. [Mississippi State Univ., Mississippi State, MS (United States); Zimmerman, Jonathan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gall, K. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2006-10-01

    titled 'Atomistic Modeling of Nanowires, Small-scale Fatigue Damage in Cast Magnesium, and Materials for MEMS'. This project supported a strategic partnership between Sandia National Laboratories and the University of Colorado at Boulder by providing funding for the lead author, Ken Gall, and his students, while he was a member of the University of Colorado faculty.

  9. A new phase field model for material fatigue in an oscillating elastoplastic beam

    Czech Academy of Sciences Publication Activity Database

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

    2015-01-01

    Roč. 35, č. 6 (2015), s. 2465-2495 ISSN 1078-0947 R&D Projects: GA ČR GAP201/10/2315 Institutional support: RVO:67985840 Keywords : hysteresis * fatigue * phase transition Subject RIV: BA - General Mathematics Impact factor: 1.127, year: 2015 http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=10680

  10. Impact of Higher Fidelity Models on Simulation of Active Aerodynamic Load Control For Fatigue Damage Reduction

    NARCIS (Netherlands)

    Resor, B.; Wilson, D.; Berg, D.; Berg, J.; Barlas, T.; Van Wingerden, J.W.; Van Kuik, G.A.M.

    2010-01-01

    Active aerodynamic load control of wind turbine blades is being investigated by the wind energy research community and shows great promise, especially for reduction of turbine fatigue damage in blades and nearby components. For much of this work, full system aeroelastic codes have been used to

  11. An experimentally validated fatigue model for wood subjected to tension perpendicular to the grain

    DEFF Research Database (Denmark)

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

    2009-01-01

    This study presents an experimental investigation of fatigue in wood subjected to tension perpendicular to the grain. The study has been designed with special reference to the influence of the frequency of loading. The investigation reveals an interaction between number of load oscillations and a...... a good basis....

  12. A model for the training effects in swimming demonstrates a strong relationship between parasympathetic activity, performance and index of fatigue.

    Directory of Open Access Journals (Sweden)

    Sébastien Chalencon

    Full Text Available Competitive swimming as a physical activity results in changes to the activity level of the autonomic nervous system (ANS. However, the precise relationship between ANS activity, fatigue and sports performance remains contentious. To address this problem and build a model to support a consistent relationship, data were gathered from national and regional swimmers during two 30 consecutive-week training periods. Nocturnal ANS activity was measured weekly and quantified through wavelet transform analysis of the recorded heart rate variability. Performance was then measured through a subsequent morning 400 meters freestyle time-trial. A model was proposed where indices of fatigue were computed using Banister's two antagonistic component model of fatigue and adaptation applied to both the ANS activity and the performance. This demonstrated that a logarithmic relationship existed between performance and ANS activity for each subject. There was a high degree of model fit between the measured and calculated performance (R(2=0.84±0.14,p<0.01 and the measured and calculated High Frequency (HF power of the ANS activity (R(2=0.79±0.07, p<0.01. During the taper periods, improvements in measured performance and measured HF were strongly related. In the model, variations in performance were related to significant reductions in the level of 'Negative Influences' rather than increases in 'Positive Influences'. Furthermore, the delay needed to return to the initial performance level was highly correlated to the delay required to return to the initial HF power level (p<0.01. The delay required to reach peak performance was highly correlated to the delay required to reach the maximal level of HF power (p=0.02. Building the ANS/performance identity of a subject, including the time to peak HF, may help predict the maximal performance that could be obtained at a given time.

  13. Complex network models reveal correlations among network metrics, exercise intensity and role of body changes in the fatigue process

    Science.gov (United States)

    Pereira, Vanessa Helena; Gama, Maria Carolina Traina; Sousa, Filipe Antônio Barros; Lewis, Theodore Gyle; Gobatto, Claudio Alexandre; Manchado-Gobatto, Fúlvia Barros

    2015-05-01

    The aims of the present study were analyze the fatigue process at distinct intensity efforts and to investigate its occurrence as interactions at distinct body changes during exercise, using complex network models. For this, participants were submitted to four different running intensities until exhaustion, accomplished in a non-motorized treadmill using a tethered system. The intensities were selected according to critical power model. Mechanical (force, peak power, mean power, velocity and work) and physiological related parameters (heart rate, blood lactate, time until peak blood lactate concentration (lactate time), lean mass, anaerobic and aerobic capacities) and IPAQ score were obtained during exercises and it was used to construction of four complex network models. Such models have both, theoretical and mathematical value, and enables us to perceive new insights that go beyond conventional analysis. From these, we ranked the influences of each node at the fatigue process. Our results shows that nodes, links and network metrics are sensibility according to increase of efforts intensities, been the velocity a key factor to exercise maintenance at models/intensities 1 and 2 (higher time efforts) and force and power at models 3 and 4, highlighting mechanical variables in the exhaustion occurrence and even training prescription applications.

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

    Science.gov (United States)

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

    2017-06-01

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

  15. Mobile Robot and Mobile Manipulator Research Towards ASTM Standards Development.

    Science.gov (United States)

    Bostelman, Roger; Hong, Tsai; Legowik, Steven

    2016-01-01

    Performance standards for industrial mobile robots and mobile manipulators (robot arms onboard mobile robots) have only recently begun development. Low cost and standardized measurement techniques are needed to characterize system performance, compare different systems, and to determine if recalibration is required. This paper discusses work at the National Institute of Standards and Technology (NIST) and within the ASTM Committee F45 on Driverless Automatic Guided Industrial Vehicles. This includes standards for both terminology, F45.91, and for navigation performance test methods, F45.02. The paper defines terms that are being considered. Additionally, the paper describes navigation test methods that are near ballot and docking test methods being designed for consideration within F45.02. This includes the use of low cost artifacts that can provide alternatives to using relatively expensive measurement systems.

  16. Interpreting the ASTM 'content standard for digital geospatial metadata'

    Science.gov (United States)

    Nebert, Douglas D.

    1996-01-01

    ASTM and the Federal Geographic Data Committee have developed a content standard for spatial metadata to facilitate documentation, discovery, and retrieval of digital spatial data using vendor-independent terminology. Spatial metadata elements are identifiable quality and content characteristics of a data set that can be tied to a geographic location or area. Several Office of Management and Budget Circulars and initiatives have been issued that specify improved cataloguing of and accessibility to federal data holdings. An Executive Order further requires the use of the metadata content standard to document digital spatial data sets. Collection and reporting of spatial metadata for field investigations performed for the federal government is an anticipated requirement. This paper provides an overview of the draft spatial metadata content standard and a description of how the standard could be applied to investigations collecting spatially-referenced field data.

  17. In vitro fatigue tests and in silico finite element analysis of dental implants with different fixture/abutment joint types using computer-aided design models.

    Science.gov (United States)

    Yamaguchi, Satoshi; Yamanishi, Yasufumi; Machado, Lucas S; Matsumoto, Shuji; Tovar, Nick; Coelho, Paulo G; Thompson, Van P; Imazato, Satoshi

    2018-01-01

    The aim of this study was to evaluate fatigue resistance of dental fixtures with two different fixture-abutment connections by in vitro fatigue testing and in silico three-dimensional finite element analysis (3D FEA) using original computer-aided design (CAD) models. Dental implant fixtures with external connection (EX) or internal connection (IN) abutments were fabricated from original CAD models using grade IV titanium and step-stress accelerated life testing was performed. Fatigue cycles and loads were assessed by Weibull analysis, and fatigue cracking was observed by micro-computed tomography and a stereomicroscope with high dynamic range software. Using the same CAD models, displacement vectors of implant components were also analyzed by 3D FEA. Angles of the fractured line occurring at fixture platforms in vitro and of displacement vectors corresponding to the fractured line in silico were compared by two-way ANOVA. Fatigue testing showed significantly greater reliability for IN than EX (pimplant fixture platforms. FEA demonstrated that crack lines of both implant systems in vitro were observed in the same direction as displacement vectors of the implant fixtures in silico. In silico displacement vectors in the implant fixture are insightful for geometric development of dental implants to reduce complex interactions leading to fatigue failure. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  18. Biaxial fatigue tests and crack paths for AISI 304L stainless steel

    Directory of Open Access Journals (Sweden)

    V. Chaves

    2014-10-01

    Full Text Available AISI 304L stainless steel specimens have been tested in fatigue. The tests were axial, torsional and in-phase biaxial, all of them under load control and R=-1. The S-N curves were built following the ASTM E739 standard and the method of maximum likelihood proposed by Bettinelli. The fatigue limits of the biaxial tests were represented in axes σ-τ. The elliptical quadrant, appropriate for ductile materials, and the elliptical arc, appropriate for fragile materials, were included in the graph. The experimental values were better fitted with an elliptical quadrant, despite the ratio between the pure torsion and tension fatigue limits, τFL/σFL, is 0.91, close to 1, which is a typical value for fragile materials. The crack direction along the surface has been analyzed by using a microscope, with especial attention to the crack initiation zones. The crack direction during the Stage I has been compared with theoretical models.

  19. Uncertainty on Fatigue Damage Accumulation for Composite Materials

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2009-01-01

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

  20. IMPROVEMENT OF FATIGUE STRENGTH OF TIN BABBITT BY REINFORCING WITH NANO ILMENITE

    Directory of Open Access Journals (Sweden)

    M. V. S. BABU

    2017-08-01

    Full Text Available Tin Babbitt is an idle journal bearing material, its fatigue strength limits and its usage. To enhance its fatigue strength, in this paper a Tin Babbitt metal matrix is reinforced with nano Ilmenite. The metal matrix nanocomposite was fabricated by using ultrasonic assisted stir casting technique. ASTM standards in statistical planning for fatigue testing were employed in planning the fatigue tests. Fatigue tests were conducted at three stress levels, i.e., 0.9 UTS, 0.7 UTS and 0.5 UTS. Tests were conducted on a rotating-beam type fatigue testing machine. It was observed that the nano Ilmenite reinforcement enhanced the fatigue strength of Tin Babbitt.

  1. A study on fatigue crack growth in dual phase martensitic steel in air

    Indian Academy of Sciences (India)

    Dual phase (DP) steel was intercritically annealed at different temperatures from fully martensitic state to achieve martensite plus ferrite, microstructures with martensite contents in the range of 32 to 76%. Fatigue crack growth (FCG) and fracture toughness tests were carried out as per ASTM standards E 647 and E 399, ...

  2. Biocompatibility of metal injection molded versus wrought ASTM F562 (MP35N) and ASTM F1537 (CCM) cobalt alloys.

    Science.gov (United States)

    Chen, Hao; Sago, Alan; West, Shari; Farina, Jeff; Eckert, John; Broadley, Mark

    2011-01-01

    We present a comparative analysis between biocompatibility test results of wrought and Metal Injection Molded (MIM) ASTM F562-02 UNS R30035 (MP35N) and F1537 UNS R31538 (CCM) alloy samples that have undergone the same generic orthopedic implant's mechanical, chemical surface pre-treatment, and a designed pre-testing sample preparation method. Because the biocompatibility properties resulting from this new MIM cobalt alloy process are not well understood, we conducted tests to evaluate cytotoxicity (in vitro), hemolysis (in vitro), toxicity effects (in vivo), tissue irritation level (in vivo), and pyrogenicity count (in vitro) on such samples. We show that our developed MIM MP35N and CCM materials and treatment processes are biocompatible, and that both the MIM and wrought samples, although somewhat different in microstructure and surface, do not show significant differences in biocompatibility.

  3. Ductile cast irons: microstructure influence on fatigue crack propagation resistance

    Directory of Open Access Journals (Sweden)

    Mauro Cavallini

    2010-07-01

    Full Text Available Microstructure influence on fatigue crack propagation resistance in five different ductile cast irons (DCI was investigated. Four ferrite/pearlite volume fractions were considered, performing fatigue crack propagation tests according to ASTM E647 standard (R equals to 0.1, 0.5 and 0.75, respectively. Results were compared with an austempered DCI. Damaging micromechanisms were investigated according to the following procedures: - “traditional” Scanning Electron Microscope (SEM fracture surfaces analysis; - SEM fracture surface analysis with 3D quantitative analysis; - SEM longitudinal crack profile analysis - Light Optical Microscope (LOM transversal crack profile analysis;

  4. Developing the (ASTM) voluntary consensus standards required to help implement the National Energy Plan

    International Nuclear Information System (INIS)

    Anon.

    1981-01-01

    The recommended guide is the first American Society for Testing and Materials (ASTM) matrix in a family of such documents that combined, will help manage the development of the ASTM standards considered necessary to implement the current National Plan for Energy Research, Development, and Demonstration. It is expected that the guide will provide a framework for standards development to complement the nation's research and development in support of critical energy needs. The recommended guide identifies the energy-critical areas that are to be developed, the master ASTM recommended guide for developing the standards required to help the National Plan, the section in which each energy-critical area is covered, and the suggested ASTM lead committee responsible for each area (fossil, solar, geothermal, conservation, fusion, and fission reactor development). A comprehensive matrix to identify the areas of need for which ASTM standards will be required to help implement the National Energy Plan is also presented

  5. Fatigue (PDQ)

    Science.gov (United States)

    ... Data Conducting Clinical Trials Statistical Tools and Data Terminology Resources NCI Data Catalog Cryo-EM NCI's Role ... Problems getting enough sleep. Being less active. Other medical conditions. Fatigue is common in people with advanced ...

  6. Monitoring and modeling stress corrosion and corrosion fatigue damage in nuclear reactors

    International Nuclear Information System (INIS)

    Andresen, P.L.; Ford, F.P.; Solomon, H.D.; Taylor, D.F.

    1990-01-01

    Stress corrosion and corrosion fatigue are significant problems in many industries, causing economic penalties from decreased plant availability and component repair or replacement. In nuclear power reactors, environmental cracking occurs in a wide variety of components, including reactor piping and steam generator tubing, bolting materials and pressure vessels. Life assessment for these components is complicated by the belief that cracking is quite irreproducible. Indeed, for conditions which were once viewed as nominally similar, orders of magnitude variability in crack growth rates are observed for stress corrosion and corrosion fatigue of stainless steels and low-alloy steels in 288 degrees C water. This paper shows that design and life prediction approaches are destined to be overly conservative or to risk environmental failure if life is predicted by quantifying only the effects of mechanical parameters and/or simply ignoring or aggregating environmental and material variabilities. Examples include the Nuclear Regulatory Commission (NRC) disposition line for stress-corrosion cracking of stainless steel in boiling water reactor (BWR) water and the American Society of Mechanical Engineers' Section XI lines for corrosion fatigue

  7. Multi-Axial Damage Index and Accumulation Model for Predicting Fatigue Life of CMC Materials, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The fatigue life of CMCs must be well characterized for the safe and reliable use of these materials as integrated TPS components. Existing fatigue life prediction...

  8. Fatigue crack growth in fiber reinforced plastics

    Science.gov (United States)

    Mandell, J. F.

    1979-01-01

    Fatigue crack growth in fiber composites occurs by such complex modes as to frustrate efforts at developing comprehensive theories and models. Under certain loading conditions and with certain types of reinforcement, simpler modes of fatigue crack growth are observed. These modes are more amenable to modeling efforts, and the fatigue crack growth rate can be predicted in some cases. Thus, a formula for prediction of ligamented mode fatigue crack growth rate is available.

  9. Fatigue analysis of aluminum drill pipes

    Directory of Open Access Journals (Sweden)

    João Carlos Ribeiro Plácido

    2005-12-01

    Full Text Available An experimental program was performed to investigate the fundamental fatigue mechanisms of aluminum drill pipes. Initially, the fatigue properties were determined through small-scale tests performed in an optic-mechanical fatigue apparatus. Additionally, full-scale fatigue tests were carried out with three aluminum drill pipe specimens under combined loading of cyclic bending and constant axial tension. Finally, a finite element model was developed to simulate the stress field along the aluminum drill pipe during the fatigue tests and to estimate the stress concentration factors inside the tool joints. By this way, it was possible to estimate the stress values in regions not monitored during the fatigue tests.

  10. Possible role of oxidative stress and immunological activation in mouse model of chronic fatigue syndrome and its attenuation by olive extract.

    Science.gov (United States)

    Gupta, Amit; Vij, Garima; Chopra, Kanwaljit

    2010-09-14

    Various putative theories involved in the development of chronic fatigue syndrome revolve around the role of stress, infection and oxidative stress. Scientific evidence highlighting the protective role of nutritional supplements in chronic fatigue syndrome is lacking. Based on these assumptions, the present study was designed to evaluate the effect of olive extract in a mouse model of immunologically-induced fatigue, wherein purified lipopolysaccharide (LPS) and Brucella abortus (BA) antigen were used as immunogens. The assessment of chronic fatigue syndrome was based on immobility period during chronic water-immersion stress test for 10 min daily. The stress-induced hyperalgesia was measured by tail withdrawal latency. Mice challenged with LPS or BA for 19 days showed significant increase in the immobility time, hyperalgesia and oxidative stress on the 19th day. Serum tumor necrosis factor-alpha (TNF-α) levels were also markedly increased with LPS or BA challenge. Concurrent treatment with olive extract resulted in a significant decrease in the immobility time as well as hyperalgesia. There was significant attenuation of oxidative stress as well as serum TNF-α levels. The results of the present study strongly indicate the role of oxidative stress and immunological activation in the pathophysiology of chronic fatigue syndrome and highlight the valuable role of olive extract in combating chronic fatigue syndrome. Copyright © 2010 Elsevier B.V. All rights reserved.

  11. Application of a Cohesive Zone Model for Simulating Fatigue Crack Growth from Moderate to High ΔK Levels of Inconel 718

    Directory of Open Access Journals (Sweden)

    Huan Li

    2018-01-01

    Full Text Available A cyclic cohesive zone model is applied to characterize the fatigue crack growth behavior of a IN718 superalloy which is frequently used in aerospace components. In order to improve the limitation of fracture mechanics-based models, besides the predictions of the moderate fatigue crack growth rates at the Paris’ regime and the high fatigue crack growth rates at the high stress intensity factor ΔK levels, the present work is also aimed at simulating the material damage uniformly and examining the influence of the cohesive model parameters on fatigue crack growth systematically. The gradual loss of the stress-bearing ability of the material is considered through the degradation of a novel cohesive envelope. The experimental data of cracked specimens are used to validate the simulation result. Based on the reasonable estimation for the model parameters, the fatigue crack growth from moderate to high ΔK levels can be reproduced under the small-scale yielding condition, which is in fair agreement with the experimental results.

  12. Modeling of the fatigue intragranular strain hardening of metals at high temperature with keeping up time; Modelisation de l'ecrouissage intragranulaire en fatigue des metaux a haute temperature avec temps de maintien

    Energy Technology Data Exchange (ETDEWEB)

    Sauzay, M.; Mottot, M.; Noblecourt, M.; Allais, L.; Monnet, I.; Perinet, J. [CEA Saclay, Service de Recherche en Metallurgie Appliquee, DMN/SRMA, 91 - Gif-sur-Yvette (France)

    2003-07-01

    This study aims at foreseeing the behaviour of some alloys during high temperature fatigue-relaxation (creep) conditions when the maximum deformation is maintained during long times (about a month for each cycle). Such experiments can hardly be performed with laboratory tests. A simple modeling of the restoration occurring during the keeping of the conditions of deformation can explain the absence of dislocation microstructures. Abstract only. (J.S.)

  13. Effect of linear and non-linear blade modelling techniques on simulated fatigue and extreme loads using Bladed

    Science.gov (United States)

    Beardsell, Alec; Collier, William; Han, Tao

    2016-09-01

    There is a trend in the wind industry towards ever larger and more flexible turbine blades. Blade tip deflections in modern blades now commonly exceed 10% of blade length. Historically, the dynamic response of wind turbine blades has been analysed using linear models of blade deflection which include the assumption of small deflections. For modern flexible blades, this assumption is becoming less valid. In order to continue to simulate dynamic turbine performance accurately, routine use of non-linear models of blade deflection may be required. This can be achieved by representing the blade as a connected series of individual flexible linear bodies - referred to in this paper as the multi-part approach. In this paper, Bladed is used to compare load predictions using single-part and multi-part blade models for several turbines. The study examines the impact on fatigue and extreme loads and blade deflection through reduced sets of load calculations based on IEC 61400-1 ed. 3. Damage equivalent load changes of up to 16% and extreme load changes of up to 29% are observed at some turbine load locations. It is found that there is no general pattern in the loading differences observed between single-part and multi-part blade models. Rather, changes in fatigue and extreme loads with a multi-part blade model depend on the characteristics of the individual turbine and blade. Key underlying causes of damage equivalent load change are identified as differences in edgewise- torsional coupling between the multi-part and single-part models, and increased edgewise rotor mode damping in the multi-part model. Similarly, a causal link is identified between torsional blade dynamics and changes in ultimate load results.

  14. Effect of Face-to-face Education, Problem-based Learning, and Goldstein Systematic Training Model on Quality of Life and Fatigue among Caregivers of Patients with Diabetes.

    Science.gov (United States)

    Masoudi, Reza; Soleimani, Mohammad Ali; Yaghoobzadeh, Ameneh; Baraz, Shahram; Hakim, Ashrafalsadat; Chan, Yiong H

    2017-01-01

    Education is a fundamental component for patients with diabetes to achieve good glycemic control. In addition, selecting the appropriate method of education is one of the most effective factors in the quality of life. The present study aimed to evaluate the effect of face-to-face education, problem-based learning, and Goldstein systematic training model on the quality of life (QOL) and fatigue among caregivers of patients with diabetes. This randomized clinical trial was conducted in Hajar Hospital (Shahrekord, Iran) in 2012. The study subjects consisted of 105 family caregivers of patients with diabetes. The participants were randomly assigned to three intervention groups (35 caregivers in each group). For each group, 5-h training sessions were held separately. QOL and fatigue were evaluated immediately before and after the intervention, and after 1, 2, 3, and 4 months of intervention. There was a significant increase in QOL for all the three groups. Both the problem-based learning and the Goldstein method showed desirable QOL improvement over time. The desired educational intervention for fatigue reduction during the 4-month post-intervention period was the Goldstein method. A significant reduction was observed in fatigue in all three groups after the intervention ( P problem-based learning and Goldstein systematic training model improve the QOL of caregivers of patients with diabetes. In addition, the Goldstein systematic training model had the greatest effect on the reduction of fatigue within 4 months of the intervention.

  15. SCC and Corrosion Fatigue characterization of a Ti-6Al-4V alloy in a corrosive environment – experiments and numerical models

    Directory of Open Access Journals (Sweden)

    S. Baragetti

    2014-10-01

    Full Text Available In the present article, a review of the complete characterization in different aggressive media of a Ti-6Al-4V titanium alloy, performed by the Structural Mechanics Laboratory of the University of Bergamo, is presented. The light alloy has been investigated in terms of corrosion fatigue, by axial fatigue testing (R = 0.1 of smooth and notched flat dogbone specimens in laboratory air, 3.5% wt. NaCl–water mixture and methanol–water mixture at different concentrations. The first corrosive medium reproduced a marine environment, while the latter was used as a reference aggressive environment. Results showed that a certain corrosion fatigue resistance is found in a salt water medium, while the methanol environment caused a significant drop – from 23% to 55% in terms of limiting stress reduction – of the fatigue resistance of the Ti-6Al-4V alloy, even for a solution containing 5% of methanol. A Stress Corrosion Cracking (SCC experimental campaign at different methanol concentrations has been conducted over slightly notched dog-bone specimens (Kt = 1.18, to characterize the corrosion resistance of the alloy under quasi-static load conditions. Finally, crack propagation models have been implemented to predict the crack propagation rates for smooth specimens, by using Paris, Walker and Kato-Deng-Inoue-Takatsu propagation formulae. The different outcomes from the forecasting numerical models were compared with experimental results, proposing modeling procedures for the numerical simulation of fatigue behavior of a Ti-6Al-4V alloy.

  16. 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

  17. Modeling and Prediction of Corrosion-Fatigue Failures in AF1410 Steel Test Specimens

    Science.gov (United States)

    2009-01-12

    1.73 0.330 4140 Bar 110 0.015 0.381 60 28 2.39 2.14 0.848 110 0.015 0.381 53 26 2.39 2.04 0.770 140 0.025 0.635 72 40 2.11 1.80 0.723 237 0.025...Vol. 41, No. 4, of Nov 1999, pp. 277-290. 18. Socie, D.F. and Marquis, G.B., “Multiaxial Fatigue,” SAE International, 2000, p. 351. 19. Myers

  18. 77 FR 10358 - Acceptance of ASTM F963-11 as a Mandatory Consumer Product Safety Standard

    Science.gov (United States)

    2012-02-22

    ... CONSUMER PRODUCT SAFETY COMMISSION 16 CFR Chapter II Acceptance of ASTM F963-11 as a Mandatory... have accepted the revised ASTM F963-11 standard titled, Standard Consumer Safety Specifications for Toy Safety. Pursuant to section 106 of the Consumer Product Safety Improvement Act of 2008, ASTM F963-11 will...

  19. Sources of Confusion in the Determination of ASTM Repetitive Member Factors for the Allowable Properties of Wood Products

    Science.gov (United States)

    S. Verrill; D. Kretschmann

    2012-01-01

    It is generally accepted that there should be an upward repetitive member allowable property adjustment. ASTM D245 (2011c) and ASTM D1990 (2011b) specify a 1.15 factor for allowable bending stress. This factor is also listed in ASTM D6555 (2011a, Table 1). In this technical note, sources of confusion regarding appropriate repetitive member factors are identified. This...

  20. 76 FR 78614 - Welded ASTM A-312 Stainless Steel Pipe From South Korea and Taiwan: Continuation of Antidumping...

    Science.gov (United States)

    2011-12-19

    ... DEPARTMENT OF COMMERCE International Trade Administration [A-580-810, A-583-815] Welded ASTM A-312... revocation of the antidumping duty orders on welded ASTM A-312 stainless steel pipe from South Korea (Korea... December 30, 1992, the Department published the antidumping duty orders on welded ASTM A-312 stainless...

  1. 76 FR 67673 - Welded ASTM A-312 Stainless Steel Pipe From South Korea and Taiwan: Final Results of Expedited...

    Science.gov (United States)

    2011-11-02

    ... DEPARTMENT OF COMMERCE International Trade Administration [A-580-810, A-583-815] Welded ASTM A-312... the antidumping duty orders on welded ASTM A-312 stainless steel pipe from South Korea and Taiwan... duty orders on welded ASTM A-312 stainless steel pipe from South Korea and Taiwan pursuant to section...

  2. Fatigue Analysis of Large-scale Wind turbine

    Directory of Open Access Journals (Sweden)

    Zhu Yongli

    2017-01-01

    Full Text Available The paper does research on top flange fatigue damage of large-scale wind turbine generator. It establishes finite element model of top flange connection system with finite element analysis software MSC. Marc/Mentat, analyzes its fatigue strain, implements load simulation of flange fatigue working condition with Bladed software, acquires flange fatigue load spectrum with rain-flow counting method, finally, it realizes fatigue analysis of top flange with fatigue analysis software MSC. Fatigue and Palmgren-Miner linear cumulative damage theory. The analysis result indicates that its result provides new thinking for flange fatigue analysis of large-scale wind turbine generator, and possesses some practical engineering value.

  3. 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.

  4. How SEIPS can be used as a model for macroergonomic approach in subunit healthcare (Case study: The nurse perception of fatigue in surgery ward unit)

    Science.gov (United States)

    Iftadi, Irwan; Astuti, Rahmaniyah Dwi; Pristiyana, Ardian Ade

    2017-11-01

    Occupational fatigue in healthcare nurses, which has multifaceted issues, is associated with decreased patient safety and the quality of nursing care. The aim of this study was to investigate the nurses fatigue problem in sub-unit healthcare based on their perceptual experience. Interviews were conducted and analyzed utilizing a direct qualitative content analysis approach using NVivo Software and guided by Model of System Engineering Initiative for Patient Safety (SEIPS). The findings of this research were a steering on what nurses perceive as contributing and preventing to fatigue which are likewise arranged in SEIPS model. It was shown that a macro ergonomic approach is valuable for understanding complexities of work systems, even though it is a small unit organization.

  5. Hydrogen embrittlement of ASTM A 203 D nuclear structural steel

    International Nuclear Information System (INIS)

    Chakravartty, J.K.; Prasad, G.E.; Sinha, T.K.; Asundi, M.K.

    1986-01-01

    The influence of hydrogen on the mechanical properties of ASTM A 203 D nuclear structural steel has been studied by tension, bend and delayed-failure tests at room temperature. While the tension tests of hydrogen charged unnotched specimens reveal no change in ultimate strength and ductility, the effect of hydrogen is manifested in notched specimens (tensile and bend) as a decrease in ultimate strength (maximum load in bend test) and ductility; the effect increases with increasing hydrogen content. It is observed that for a given hydrogen concentration, the decrease in bend ductility is remarkably large compared to that in tensile ductility. Hydrogen charging does not cause any delayed-failure upto 200 h under an applied tensile stress, 0.85 times the notch tensile strength. However delayed failure occurs in hydrogen charged bend samples in less than 10 h under an applied bending load of about 0.80 times of the uncharged maximum load. Fractographs of hydrogen charged unnotched specimens show ductile dimple fracture, while those of notched tension and bend specimens under hydrogen-charged conditions show a mixture of ductile dimple and quasi-cleavage cracking. The proportion of quasi-cleavage cracking increases with increasing hydrogen content and this fracture mode is more predominant in bend specimens. The changes in tensile properties and fracture modes can reasonably be explained by existing theories of hydrogen embrittlement. An attempt is made to explain the significant difference in the embrittlement susceptibility of bend and tensile specimens in the light of difference in triaxiality and plastic zone size near the notch tip. (orig.)

  6. Mode II Interlaminar Fracture Toughness and Fatigue Characterization of a Graphite Epoxy Composite Material

    Science.gov (United States)

    O'Brien, T. Kevin; Johnston, William M.; Toland, Gregory J.

    2010-01-01

    Mode II interlaminar fracture toughness and delamination onset and growth characterization data were generated for IM7/8552 graphite epoxy composite materials from two suppliers for use in fracture mechanics analyses. Both the fracture toughness testing and the fatigue testing were conducted using the End-notched Flexure (ENF) test. The ENF test for mode II fracture toughness is currently under review by ASTM as a potential standard test method. This current draft ASTM protocol was used as a guide to conduct the tests on the IM7/8552 material. This report summarizes the test approach, methods, procedures and results of this characterization effort.

  7. A discrete element model for damage and fracture of geomaterials under fatigue loading

    Science.gov (United States)

    Gao, Xiaofeng; Koval, Georg; Chazallon, Cyrille

    2017-06-01

    Failure processes in geomaterials (concrete, asphalt concrete, masonry, etc.) under fatigue loading (repeated moving loads, cycles of temperature, etc.) are responsible for most of the dysfunctions in pavements, brick structures, etc. In the beginning of the lifetime of a structure, the material presents only inner defects (micro cracks, voids, etc.). Due to the effect of the cyclic loading, these small defects tend to grow in size and quantity which damage the material, reducing its stiffness. With a relatively high number of cycles, these growing micro cracks become large cracks, which characterizes the fracture behavior. From a theoretical point of view, both mechanisms are treated differently. Fracture is usually described locally, with the propagation of cracks defined by the energy release rate at the crack tip; damage is usually associated to non-local approaches. In the present work, damage and fracture mechanics are combined in a local discrete element approach.

  8. Fracture toughness of welded joints of ASTM A543 steel plate

    International Nuclear Information System (INIS)

    Susukida, H.; Uebayashi, T.; Yoshida, K.; Ando, Y.

    1977-01-01

    Fracture toughness and weldability tests have been performed on a high strength steel which is a modification of ASTM A543 Grade B Class 1 steel, with a view to using it for nuclear reactor containment vessels. The results showed that fracture toughness of welded joints of ASTM A543 modified high strength steel is superior and the steel is suitable for manufacturing the containment vessels

  9. Integration of Nanofluids into Commercial Antifreeze Concentrates with ASTM D15 Corrosion Testing

    Science.gov (United States)

    2013-05-01

    Lockwood1 1 Valvoline New Product Development Laboratory, Ashland Consumer Markets , Lexington, Kentucky. 2 Tank Automotive Research, Development...Development Laboratory,Ashland Consumer Markets ,P.O. Box 14000,Lexington,KY,40512 8. PERFORMING ORGANIZATION REPORT NUMBER ; #23826 9. SPONSORING...Technology, Performance, and Life for Light-Duty Applications, Engine Coolant Testing: Fourth Volume, ASTM STP 1335, R.E. Beale ed., ASTM, Philadelphia

  10. 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.

  11. 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.

  12. Modeling of creep-fatigue interaction of zirconium {alpha} under cyclic loading at 200 C; Modelisation du comportement et de l`endommagement en fatigue-fluage du zirconium {alpha} a 200C

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, C.

    1996-04-01

    The present work deals with mechanical behaviour of zirconium alpha at 200 deg. C and crack initiation prediction methods, particularly when loading conditions lead to interaction of fatigue and creep phenomena. A classical approach used to study interaction between cyclic effects and constant loading effects does not give easy understanding of experimental results. Therefore, a new approach has been developed, which allow to determine a number of cycles for crack initiation for complex structures under large loading conditions. To study influence of fatigue and creep interaction on crack initiation, a model was chosen, using a scalar variable, giving representation of the material deterioration state. The model uses a non linear cumulating effect between the damage corresponding to cyclic loads and the damage correlated to time influence. The model belongs to uncoupled approaches between damage and behaviour, which is described here by a two inelastic deformations model. This mechanical behaviour model is chosen because it allows distinction between a plastic and a viscous part in inelastic flow. Cyclic damage is function of stress amplitude and mean stress. For the peculiar sensitivity of the material to creep, a special parameter bas been defined to be critical toward creep damage. It is the kinematic term associated to state variables describing this type of hardening in the viscous mechanism. (author).

  13. Fatigue life prediction in composites

    CSIR Research Space (South Africa)

    Huston, RJ

    1994-01-01

    Full Text Available Because of the relatively large number of possible failure mechanisms in fibre reinforced composite materials, the prediction of fatigue life in a component is not a simple process. Several mathematical and statistical models have been proposed...

  14. Fatigue Strength of Titanium Risers - Defect Sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Babalola, Olusegun Tunde

    2001-07-01

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

  15. A Study of the Protective Effect of Triticum aestivum L. in an Experimental Animal Model of Chronic Fatigue Syndrome.

    Science.gov (United States)

    Borah, Mukundam; Sarma, Phulen; Das, Swarnamoni

    2014-10-01

    Oxidative stress plays a major role in the pathogenesis of chronic fatigue syndrome (CFS). Keeping in view the proven antioxidant activity of Triticum aestivum L., this study has been undertaken to explore the potential therapeutic benefit of this plant in the treatment of CFS. To study the protective effect of the ethanolic extract of the leaves of Triticum aestivum (EETA) in an experimental mice model of CFS. Five groups of albino mice (20-25 g) were selected for the study, with five animals in each group. Group A served as the naïve control and Group B served as the stressed control. Groups C and D received EETA (100 mg/kg and 200 mg/kg b.w.). Group E received imipramine (20 mg/kg b.w.). Except for Group A, mice in each group were forced to swim 6 min each for 7 days to induce a state of chronic fatigue. Duration of immobility was measured on every alternate day. After 7 days, various behavioral tests (mirror chamber and elevated plus maize test for anxiety, open field test for locomotor activity) and biochemical estimations (malondialdehyde [MDA] and catalase activity) in mice brain were performed. Forced swimming in the stressed group resulted in a significant increase in immobility period, decrease in locomotor activity and elevated anxiety level. The brain homogenate showed significantly increased MDA and decreased catalase levels. The extract-treated groups showed significantly (P < 0.05) improved locomotor activity, decreased anxiety level, elevated catalase levels and reduction of MDA. The study confirms the protective effects of EETA in CFS.

  16. Neuromuscular strain as a contributor to cognitive and other symptoms in Chronic Fatigue Syndrome: Hypothesis and conceptual model.

    Directory of Open Access Journals (Sweden)

    Peter C. Rowe

    2013-05-01

    Full Text Available Individuals with chronic fatigue syndrome (CFS have heightened sensitivity and increased symptoms following various physiologic challenges, such as orthostatic stress, physical exercise, and cognitive challenges. Similar heightened sensitivity to the same stressors in fibromyalgia (FM has led investigators to propose that these findings reflect a state of central sensitivity. A large body of evidence supports the concept of central sensitivity in FM. A more modest literature provides partial support for this model in CFS, particularly with regard to pain. Nonetheless, fatigue and cognitive dysfunction have not been explained by the central sensitivity data thus far. Peripheral factors have attracted attention recently as contributors to central sensitivity. Work by Brieg, Sunderland, and others has emphasized the ability of the nervous system to undergo accommodative changes in length in response to the range of limb and trunk movements carried out during daily activity. If that ability to elongate is impaired—due to movement restrictions in tissues adjacent to nerves, or due to swelling or adhesions within the nerve itself—the result is an increase in mechanical tension within the nerve. This adverse neural tension, also termed neurodynamic dysfunction, is thought to contribute to pain and other symptoms through a variety of mechanisms. These include mechanical sensitization and altered nociceptive signaling, altered proprioception, adverse patterns of muscle recruitment and force of muscle contraction, reduced intra-neural blood flow, and release of inflammatory neuropeptides. Because it is not possible to differentiate completely between adverse neural tension and strain in muscles, fascia, and other soft tissues, we use the more general term neuromuscular strain. In our clinical work, we have found that neuromuscular restrictions are common in CFS, and that many symptoms of CFS can be reproduced by selectively adding neuromuscular strain

  17. Gear fatigue damage for a 500 kW wind turbine exposed to increasing turbulence using a flexible multibody model

    Directory of Open Access Journals (Sweden)

    Martin Felix Jørgensen

    2014-04-01

    Full Text Available This paper investigates gear tooth fatigue damage in a 500 kW wind turbine using FLEX5 and own multibody code. FLEX5 provides the physical wind field, rotor and generator torque and the multibody code is used for obtaining gear tooth reaction forces in the planetary gearbox. Different turbulence levels are considered and the accumulated fatigue damage levels are compared. An example where the turbulence/fatigue sensitivity could be important, is in the middle of a big wind farm. Interior wind turbines in large wind farms will always operate in the wake of other wind turbines, causing increased turbulence and therefore increased fatigue damage levels. This article contributes to a better understanding of gear fatigue damage when turbulence is increased (e.g. in the center of large wind farms or at places where turbulence is pronounced.

  18. An overview of fatigue

    International Nuclear Information System (INIS)

    Mc Evily, A.J.

    1987-01-01

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

  19. 3D-FE Modeling of 316 SS under Strain-Controlled Fatigue Loading and CFD Simulation of PWR Surge Line

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish [Argonne National Lab. (ANL), Argonne, IL (United States); Barua, Bipul [Argonne National Lab. (ANL), Argonne, IL (United States); Listwan, Joseph [Argonne National Lab. (ANL), Argonne, IL (United States); Majumdar, Saurin [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, Ken [Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-03-01

    In financial year 2017, we are focusing on developing a mechanistic fatigue model of surge line pipes for pressurized water reactors (PWRs). To that end, we plan to perform the following tasks: (1) conduct stress- and strain-controlled fatigue testing of surge-line base metal such as 316 stainless steel (SS) under constant, variable, and random fatigue loading, (2) develop cyclic plasticity material models of 316 SS, (3) develop one-dimensional (1D) analytical or closed-form model to validate the material models and to understand the mechanics associated with 316 SS cyclic hardening and/or softening, (4) develop three-dimensional (3D) finite element (FE) models with implementation of evolutionary cyclic plasticity, and (5) develop computational fluid dynamics (CFD) model for thermal stratification, thermal-mechanical stress, and fatigue of example reactor components, such as a PWR surge line under plant heat-up, cool-down, and normal operation with/without grid-load-following. This semi-annual progress report presents the work completed on the above tasks for a 316 SS laboratory-scale specimen subjected to strain-controlled cyclic loading with constant, variable, and random amplitude. This is the first time that the accurate 3D-FE modeling of the specimen for its entire fatigue life, including the hardening and softening behavior, has been achieved. We anticipate that this work will pave the way for the development of a fully mechanistic-computer model that can be used for fatigue evaluation of safety-critical metallic components, which are traditionally evaluated by heavy reliance on time-consuming and costly test-based approaches. This basic research will not only help the nuclear reactor industry for fatigue evaluation of reactor components in a cost effective and less time-consuming way, but will also help other safety-related industries, such as aerospace, which is heavily dependent on test-based approaches, where a single full-scale fatigue test can cost

  20. 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.

  1. 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.

  2. ASTM standards associated with PWR and BWR power plant licensing, operation and surveillance

    International Nuclear Information System (INIS)

    McElroy, W.N.; McElroy, R.J.; Gold, R.; Lippincott, E.P.; Lowe, A.L. Jr.

    1994-01-01

    This paper considers ASTM Standards that are available, under revision, and are being considered in support of Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR) Nuclear Power Plant (NPP) licensing, regulation, operation, surveillance and life attainment. The current activities of ASTM Committee E10 and its Subcommittees E10.02 and current activities of ASTM Committee E10 and its Subcommittees E10.02 and E10.05 and their Task Groups (TG) are described. A very important aspect of these efforts is the preparation, revision, and balloting of standards identified in the ASTM E706 Standard on Master Matrix for Light Water Reactor (LWR) Pressure Vessel (PV) Surveillance Standards. The current version (E706-87) of the Master Matrix identifies 21 ASTM LWR physics-dosimetry-metallurgy standards for Reactor Pressure Vessel (RPV) and Support Structure (SS) surveillance programs, whereas, for the next revision 34 standards are identified. The need for national and international coordination of Standards Technology Development, Transfer and Training (STDTT) is considered in this and other Symposium papers that address specific standards related physics-dosimetry-metallurgy issues. 69 refs

  3. Gear fatigue damage for a 500 kW wind turbine exposed to increasing turbulence using a flexible multibody model

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    2014-01-01

    This paper investigates gear tooth fatigue damage in a 500 kW wind turbine using FLEX5 and own multibody code. FLEX5 provides the physical wind eld, rotor and generator torque and the multibody code is used for obtaining gear tooth reaction forces in the planetary gearbox. Dierent turbulence levels...... and therefore increased fatigue damage levels. This article contributes to a better understanding of gear fatigue damage when turbulence is increased (e.g. in the center of large wind farms or at places where turbulence is pronounced)....

  4. A Geometric Approach to Modeling Microstructurally Small Fatigue Crack Formation. 2; Simulation and Prediction of Crack Nucleation in AA 7075-T651

    Science.gov (United States)

    Hochhalter, Jake D.; Littlewood, David J.; Christ, Robert J., Jr.; Veilleux, M. G.; Bozek, J. E.; Ingraffea, A. R.; Maniatty, Antionette M.

    2010-01-01

    The objective of this paper is to develop further a framework for computationally modeling microstructurally small fatigue crack growth in AA 7075-T651 [1]. The focus is on the nucleation event, when a crack extends from within a second-phase particle into a surrounding grain, since this has been observed to be an initiating mechanism for fatigue crack growth in this alloy. It is hypothesized that nucleation can be predicted by computing a non-local nucleation metric near the crack front. The hypothesis is tested by employing a combination of experimentation and nite element modeling in which various slip-based and energy-based nucleation metrics are tested for validity, where each metric is derived from a continuum crystal plasticity formulation. To investigate each metric, a non-local procedure is developed for the calculation of nucleation metrics in the neighborhood of a crack front. Initially, an idealized baseline model consisting of a single grain containing a semi-ellipsoidal surface particle is studied to investigate the dependence of each nucleation metric on lattice orientation, number of load cycles, and non-local regularization method. This is followed by a comparison of experimental observations and computational results for microstructural models constructed by replicating the observed microstructural geometry near second-phase particles in fatigue specimens. It is found that orientation strongly influences the direction of slip localization and, as a result, in uences the nucleation mechanism. Also, the baseline models, replication models, and past experimental observation consistently suggest that a set of particular grain orientations is most likely to nucleate fatigue cracks. It is found that a continuum crystal plasticity model and a non-local nucleation metric can be used to predict the nucleation event in AA 7075-T651. However, nucleation metric threshold values that correspond to various nucleation governing mechanisms must be calibrated.

  5. PMMA-hydroxyapatite composite material retards fatigue failure of augmented bone compared to augmentation with plain PMMA: in vivo study using a sheep model.

    Science.gov (United States)

    Arabmotlagh, Mohammad; Bachmaier, Samuel; Geiger, Florian; Rauschmann, Michael

    2014-11-01

    Polymethylmethacrylate (PMMA) is the most commonly used void filler for augmentation of osteoporotic vertebral fracture, but the differing mechanical features of PMMA and osteoporotic bone result in overload and failure of adjacent bone. The aim of this study was to compare fatigue failure of bone after augmentation with PMMA-nanocrystalline hydroxyapatite (HA) composite material or with plain PMMA in a sheep model. After characterization of the mechanical properties of a composite material consisting of PMMA and defined amounts (10, 20, and 30% volume fraction) of HA, the composite material with 30% volume fraction HA was implanted in one distal femur of sheep; plain PMMA was implanted in the other femur. Native non-augmented bone served as control. Three and 6 months after implantation, the augmented bone samples were exposed to cyclic loading and the evolution of damage was investigated. The fatigue life was highest for the ovine native bone and lowest for bone-PMMA specimens. Bone-composite specimens showed significantly higher fatigue life than the respective bone-PMMA specimens in both 3- and 6-month follow-up groups. These results suggest that modification of mechanical properties of PMMA by addition of HA to approximate those of cancellous bone retards fatigue failure of the surrounding bone compared to augmented bone with plain PMMA. © 2014 Wiley Periodicals, Inc.

  6. An investigation of force components in orthogonal cutting of medical grade cobalt-chromium alloy (ASTM F1537).

    Science.gov (United States)

    Baron, Szymon; Ahearne, Eamonn

    2017-04-01

    An ageing population, increased physical activity and obesity are identified as lifestyle changes that are contributing to the ongoing growth in the use of in-vivo prosthetics for total hip and knee arthroplasty. Cobalt-chromium-molybdenum (Co-Cr-Mo) alloys, due to their mechanical properties and excellent biocompatibility, qualify as a class of materials that meet the stringent functional requirements of these devices. To cost effectively assure the required dimensional and geometric tolerances, manufacturers rely on high-precision machining. However, a comprehensive literature review has shown that there has been limited research into the fundamental mechanisms in mechanical cutting of these alloys. This article reports on the determination of the basic cutting-force coefficients in orthogonal cutting of medical grade Co-Cr-Mo alloy ASTM F1537 over an extended range of cutting speeds ([Formula: see text]) and levels of undeformed chip thickness ([Formula: see text]). A detailed characterisation of the segmented chip morphology over this range is also reported, allowing for an estimation of the shear plane angle and, overall, providing a basis for macro-mechanic modelling of more complex cutting processes. The results are compared with a baseline medical grade titanium alloy, Ti-6Al-4V ASTM F136, and it is shown that the tangential and thrust-force components generated were, respectively, ≈35% and ≈84% higher, depending primarily on undeformed chip thickness but with some influence of the cutting speed.

  7. Experimental and numerical study of a modified ASTM C633 adhesion test for strongly-bonded coatings

    Energy Technology Data Exchange (ETDEWEB)

    Bernardie, Raphaëlle; Berkouch, Reda; Valette, Stéphane; Absi, Joseph; Lefort, Pierre [University of Limoges, Limoges Cedex (France)

    2017-07-15

    When coatings are strongly bonded to their substrates it is often difficult to measure the adhesion values. The proposed method, which is suggested naming “silver print test”, consists in covering the central part of the samples with a thin layer of silver paint, before coating. The process used for testing this new method was the Air plasma spraying (APS), and the materials used were alumina coatings on C35 steel substrates, previously pre-oxidized in CO{sub 2}. The silver painted area was composed of small grains that did not oxidize but that significantly sintered during the APS process. The silver layer reduced the surface where the coating was linked to the substrate, which allowed its debonding, using the classical adhesion test ASTM C633-13, while the direct use of this test (without silver painting) led to ruptures inside the glue used in this test. The numerical modelling, based on the finite element method with the ABAQUS software, provided results in good agreement with the experimental measurements. This concordance validated the used method and allowed accessing to the values of adherence when the experimental test ASTM C633-13 failed, because of ruptures in the glue. After standardization, the “silver print test” might be used for other kinds of deposition methods, such as PVD, CVD, PECVD.

  8. Automated corrosion fatigue crack growth testing in pressurized water environments

    International Nuclear Information System (INIS)

    Ceschini, L.J.; Liaw, P.K.; Rudd, G.E.; Logsdon, W.A.

    1984-01-01

    This paper describes in detail a novel approach to construct a test facility for developing corrosion fatigue crack growth rate (FCGR) properties in aggressive environments. The environment studied is that of a pressurized water reactor (PWR) at 288 0 C (550 0 F) and 13.8 MPa (200 psig). To expedite data generation, each chamber was designed to accommodate two test specimens. A common water recirculation and pressurization system was employed to service two test chambers. Thus, four fatigue crack propagation rate tests could be conducted simultaneously in the pressurized water environment. The data analysis was automated to minimize the typically high labor costs associated with corrosion fatigue crack propagation testing. Verification FCGR tests conducted on an ASTM A469 rotor steel in a room temperature air environment as well as actual PWR environment FCGR tests performed on an ASTM A533 Grade B Class 2 pressure vessel steel demonstrated that the dual specimen test facility is an excellent system for developing the FCGR properties of materials in adverse environments

  9. An Exercise Model to Study Progressive Muscle Fatigue During Constant Work Rate Exercise on a Cycle Ergometer

    National Research Council Canada - National Science Library

    Fulco, Charles

    2003-01-01

    ... of the same muscles during the activity. However, conventional ergometric testing modes such as stationary cycling or treadmill exercise do not readily lend themselves to quantitating the progressive increase in muscle fatigue...

  10. Everyday cognitive failure and depressive symptoms predict fatigue in sarcoidosis : A prospective follow-up study

    NARCIS (Netherlands)

    Hendriks, Celine; Drent, Marjolein; De Kleijn, Willemien; Elfferich, Marjon; Wijnen, Petal; de Vries, J.

    2018-01-01

    Bachground: Fatigue is a major and disabling problem in sarcoidosis. Knowledge concerning correlates of the development of fatigue and possible interrelationships is lacking. Objective: A conceptual model of fatigue was developed and tested. Methods: Sarcoidosis outpatients (n = 292) of Maastricht

  11. [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.

  12. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-08-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of Dc = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times.

  13. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-01-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of D c = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times. (paper)

  14. Combating Wear of ASTM A36 Steel by Surface Modification Using Thermally Sprayed Cermet Coatings

    OpenAIRE

    Shibe, Vineet; Chawla, Vikas

    2016-01-01

    Thermal spray coatings can be applied economically on machine parts to enhance their requisite surface properties like wear, corrosion, erosion resistance, and so forth. Detonation gun (D-Gun) thermal spray coatings can be applied on the surface of carbon steels to improve their wear resistance. In the present study, alloy powder cermet coatings WC-12% Co and Cr3C2-25% NiCr have been deposited on ASTM A36 steel with D-Gun thermal spray technique. Sliding wear behavior of uncoated ASTM A36 ste...

  15. Probabilistic Fatigue Damage Prognosis Using a Surrogate Model Trained Via 3D Finite Element Analysis

    Science.gov (United States)

    Leser, Patrick E.; Hochhalter, Jacob D.; Newman, John A.; Leser, William P.; Warner, James E.; Wawrzynek, Paul A.; Yuan, Fuh-Gwo

    2015-01-01

    Utilizing inverse uncertainty quantification techniques, structural health monitoring can be integrated with damage progression models to form probabilistic predictions of a structure's remaining useful life. However, damage evolution in realistic structures is physically complex. Accurately representing this behavior requires high-fidelity models which are typically computationally prohibitive. In the present work, a high-fidelity finite element model is represented by a surrogate model, reducing computation times. The new approach is used with damage diagnosis data to form a probabilistic prediction of remaining useful life for a test specimen under mixed-mode conditions.

  16. Analytical prediction model for non-symmetric fatigue crack growth in Fibre Metal Laminates

    NARCIS (Netherlands)

    Wang, W.; Rans, C.D.; Benedictus, R.

    2017-01-01

    This paper proposes an analytical model for predicting the non-symmetric crack growth and accompanying delamination growth in FMLs. The general approach of this model applies Linear Elastic Fracture Mechanics, the principle of superposition, and displacement compatibility based on the

  17. Experimental and numerical investigation of strain rate effect on low cycle fatigue behaviour of AA 5754 alloy

    Science.gov (United States)

    Kumar, P.; Singh, A.

    2018-04-01

    The present study deals with evaluation of low cycle fatigue (LCF) behavior of aluminum alloy 5754 (AA 5754) at different strain rates. This alloy has magnesium (Mg) as main alloying element (Al-Mg alloy) which makes this alloy suitable for Marines and Cryogenics applications. The testing procedure and specimen preparation are guided by ASTM E606 standard. The tests are performed at 0.5% strain amplitude with three different strain rates i.e. 0.5×10-3 sec-1, 1×10-3 sec-1 and 2×10-3 sec-1 thus the frequency of tests vary accordingly. The experimental results show that there is significant decrease in the fatigue life with the increase in strain rate. LCF behavior of AA 5754 is also simulated at different strain rates by finite element method. Chaboche kinematic hardening cyclic plasticity model is used for simulating the hardening behavior of the material. Axisymmetric finite element model is created to reduce the computational cost of the simulation. The material coefficients used for “Chaboche Model” are determined by experimentally obtained stabilized hysteresis loop. The results obtained from finite element simulation are compared with those obtained through LCF experiments.

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

    OpenAIRE

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

    2015-01-01

    The procedure for analysing rolling contact fatigue crack initiation and fatigue life prediction of the railway turnout crossing is developed. A three-dimensional finite element (FE) model is used to obtain stress and strain results, considering the dynamic effects of wheel-crossing rolling contact. Material model accounting for elastic- plastic isotropic and kinematic hardening effects is adopted. The results from FE analysis are combined with J-S fatigue model that is based on critical plan...

  19. Modelling the Effects of Surface Residual Stresses on Fatigue Behavior of PM Disk Alloys, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A finite element based model will be developed and validated to capture the evolution of residual stresses and cold work at machined features of compressor and...

  20. A finite element model on effects of impact load and cavitation on fatigue crack propagation in mechanical bileaflet aortic heart valve.

    Science.gov (United States)

    Mohammadi, H; Klassen, R J; Wan, W-K

    2008-10-01

    Pyrolytic carbon mechanical heart valves (MHVs) are widely used to replace dysfunctional and failed heart valves. As the human heart beats around 40 million times per year, fatigue is the prime mechanism of mechanical failure. In this study, a finite element approach is implemented to develop a model for fatigue analysis of MHVs due to the impact force between the leaflet and the stent and cavitation in the aortic position. A two-step method to predict crack propagation in the leaflets of MHVs has been developed. Stress intensity factors (SIFs) are computed at a small initiated crack located on the leaflet edge (the worst case) using the boundary element method (BEM). Static analysis of the crack is performed to analyse the stress distribution around the front crack zone when the crack is opened; this is followed by a dynamic crack analysis to consider crack propagation using the finite element approach. Two factors are taken into account in the calculation of the SIFs: first, the effect of microjet formation due to cavitation in the vicinity of leaflets, resulting in water hammer pressure; second, the effect of the impact force between the leaflet and the stent of the MHVs, both in the closing phase. The critical initial crack length, the SIFs, the water hammer pressure, and the maximum jet velocity due to cavitation have been calculated. With an initial crack length of 35 microm, the fatigue life of the heart valve is greater than 60 years (i.e. about 2.2 x 10(9) cycles) and, with an initial crack length of 170 microm, the fatigue life of the heart valve would be around 2.5 years (i.e. about 9.1 x 10(7) cycles). For an initial crack length greater than 170 microm, there is catastrophic failure and fatigue cracking no longer occurs. A finite element model of fatigue analysis using Patran command language (PCL custom code) in MSC software can be used to evaluate the useful lifespan of MHVs. Similar methodologies can be extended to other medical devices under cyclic

  1. Statistical modelling of compression and fatigue damage of unidirectional fiber reinforced composites

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Brøndsted, Povl

    2009-01-01

    A statistical computational model of strength and damage of unidirectional carbon fiber reinforced composites under compressive and cyclic compressive loading is presented in this paper. The model is developed on the basis of the Budiansky–Fleck fiber kinking condition, continuum damage mechanics...... concept and the Monte-Carlo method. The effects of fiber misalignment variability, fiber clustering, load sharing rules on the damage in composite are studied numerically. It is demonstrated that the clustering of fibers has a negative effect of the damage resistance of a composite. Further, the static...

  2. Fatigue crack propagation in neutron-irradiated ferritic pressure-vessel steels

    International Nuclear Information System (INIS)

    James, L.A.

    1977-01-01

    The results of a number of experiments dealing with fatigue crack propagation in irradiated reactor pressure-vessel steels are reviewed. The steels included ASTM alloys A302B, A533B, A508-2, and A543, as well as weldments in A543 steel. Fluences and irradiation conditions were generally typical of those experienced by most power reactors. In general, the effect of neutron irradiation on the fatigue crack propagation behavior of these steels was neither significantly beneficial nor significantly detrimental

  3. Fatigue of thin walled tubes in copper alloy CuNi10

    DEFF Research Database (Denmark)

    Lambertsen, Søren Heide; Damkilde, Lars; Jepsen, Michael S.

    2016-01-01

    The current work concerns the investigation of the fatigue resistance of CuNi10 tubes, which are frequently used in heat exchangers of large ship engines. The lifetime performances of the exchanger tubes are greatly affected by the environmental conditions, where especially the temperature...... by means of the ASTM E739 guideline and one-sided tolerance limits factor method. The tests show good fatigue resistance and the risk for a failure is low in aspect to the case of a ship heat exchanger....

  4. Comparing the Methodologies in ASTM G198: Is There an Easy Way Out?

    Science.gov (United States)

    Samuel L. Zelinka

    2013-01-01

    ASTM(1) G198, Standard test method for determining the relative corrosion performance of driven fasteners in contact with treated wood, was accepted by consensus and published in 2011. The method has two different exposure conditions for determining fastener corrosion performance in treated wood. The first method places the wood and embedded...

  5. Comparative field permeability measurement of permeable pavements using ASTM C1701 and NCAT permeameter methods.

    Science.gov (United States)

    Li, Hui; Kayhanian, Masoud; Harvey, John T

    2013-03-30

    Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50-90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. The Status of silicosis in the world: Feedback on the ASTM Silica Symposium

    CSIR Research Space (South Africa)

    Pretorius, CJ

    2013-06-01

    Full Text Available The second ASTM Silica Symposium was held in Oct 2012 where speakers reported on the status of silicosis in their respective countries. Speakers reported on findings of research that they carried out on sampling equipment and analytical techniques...

  7. Deriving allowable properties of lumber : a practical guide for interpretation of ASTM standards

    Science.gov (United States)

    Alan Bendtsen; William L. Galligan

    1978-01-01

    The ASTM standards for establishing clear wood mechanical properties and for deriving structural grades and related allowable properties for visually graded lumber can be confusing and difficult for the uninitiated to interpret. This report provides a practical guide to using these standards for individuals not familiar with their application. Sample stress...

  8. Standard specification for tantalum and tantalum alloy plate, sheet, and strip. ASTM standard

    International Nuclear Information System (INIS)

    1998-09-01

    This specification is under the jurisdiction of ASTM Committee B-10 on Reactive and Refractory Metals and Alloys and is the direct responsibility of Subcommittee B10.03 on Niobium and Tantalum. Current edition approved May 10, 1998 and published September 1998. Originally published as B 708-82. Last previous edition was B 708-92

  9. ASTM Committee D-7 : Wood : promoting safety and standardization for 100 years

    Science.gov (United States)

    David W. Green; Robert L. Ethington

    2004-01-01

    In October 2004, Committee D-7 on Wood of the American Society for Testing and Materials (ASTM) is celebrating 100 years of contributions to the safe and efficient use of wood as a building material. Born during a period of rapid social, economic, and technological change, the Committee faced controversial issues and the challenge of a changing forest resource. This...

  10. An evaluation of efforts by nuclear power plants to use ASTM D3803-89

    International Nuclear Information System (INIS)

    Freeman, W.P.

    1995-01-01

    The number of nuclear power plants are now using ASTM D3803-89, open-quotes Standard Test Method for Nuclear-Grade Activated Carbonclose quotes for routine surveillance testing of adsorbents. In order to judge the impact of this change, we have gathered radioiodine removal test results from our data base on a system-by-system basis (i.e. control room, technical support center, and spent fuel pool) and compared test results obtained for the same kind of systems using the new and older test methods. Included in this comparison are systems with and without humidity control. Results are discussed from the standpoint of what to expect if a change to testing using ASTM D3803-89 is contemplated, especially regarding test results in light existing acceptance criteria. Additionally, the results are discussed from the standpoint of the sensitivity of the ASTM test method to detect when the performance of the carbon in air cleaning systems has been compromised (compared to the older methods). Finally, we offer some suggestions for how other plants might upgrade their carbon testing to incorporate testing to ASTM D3803-89

  11. Combating Wear of ASTM A36 Steel by Surface Modification Using Thermally Sprayed Cermet Coatings

    Directory of Open Access Journals (Sweden)

    Vineet Shibe

    2016-01-01

    Full Text Available Thermal spray coatings can be applied economically on machine parts to enhance their requisite surface properties like wear, corrosion, erosion resistance, and so forth. Detonation gun (D-Gun thermal spray coatings can be applied on the surface of carbon steels to improve their wear resistance. In the present study, alloy powder cermet coatings WC-12% Co and Cr3C2-25% NiCr have been deposited on ASTM A36 steel with D-Gun thermal spray technique. Sliding wear behavior of uncoated ASTM A36 steel and D-Gun sprayed WC-12% Co and Cr3C2-25% NiCr coatings on base material is observed on a Pin-On-Disc Wear Tester. Sliding wear performance of WC-12% Co coating is found to be better than the Cr3C2-25% NiCr coating. Wear performance of both these cermet coatings is found to be better than uncoated ASTM A36 steel. Thermally sprayed WC-12% Co and Cr3C2-25% NiCr cermet coatings using D-Gun thermal spray technique is found to be very useful in improving the sliding wear resistance of ASTM A36 steel.

  12. Autogenous shrinkage of Ducorit S5R ASTM C 1698-09 test method

    DEFF Research Database (Denmark)

    Damkilde, Lars

    The report deals with experimental measurement of autogenous shrinkage of Ducorit S5R according to the test method ASTM C 1698-09. This test method measures the bulk strain of a sealed cementitious specimen, at constant temperature and not subjected to external forces, from the time of final...

  13. An evaluation of efforts by nuclear power plants to use ASTM D3803-89

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, W.P.

    1995-02-01

    The number of nuclear power plants are now using ASTM D3803-89, {open_quotes}Standard Test Method for Nuclear-Grade Activated Carbon{close_quotes} for routine surveillance testing of adsorbents. In order to judge the impact of this change, we have gathered radioiodine removal test results from our data base on a system-by-system basis (i.e. control room, technical support center, and spent fuel pool) and compared test results obtained for the same kind of systems using the new and older test methods. Included in this comparison are systems with and without humidity control. Results are discussed from the standpoint of what to expect if a change to testing using ASTM D3803-89 is contemplated, especially regarding test results in light existing acceptance criteria. Additionally, the results are discussed from the standpoint of the sensitivity of the ASTM test method to detect when the performance of the carbon in air cleaning systems has been compromised (compared to the older methods). Finally, we offer some suggestions for how other plants might upgrade their carbon testing to incorporate testing to ASTM D3803-89.

  14. A Simulation Method for High-Cycle Fatigue-Driven Delamination using a Cohesive Zone Model

    DEFF Research Database (Denmark)

    Bak, Brian Lau Verndal; Turon, A.; Lindgaard, Esben

    2016-01-01

    on parameter fitting of any kind. The method has been implemented as a zero-thickness eight-node interface element for Abaqus and as a spring element for a simple finite element model in MATLAB. The method has been validated in simulations of mode I, mode II, and mixed-mode crack loading for both self...

  15. PROPOSED ASTM METHOD FOR THE DETERMINATION OF ASBESTOS IN AIR BY TEM AND INFORMATION ON INTERFERING FIBERS

    Science.gov (United States)

    The draft of the ASTM Test Method for air entitled: "Airborne Asbestos Concentration in Ambient and Indoor Atmospheres as Determined by Transmission Electron Microscopy Direct Transfer (TEM)" (ASTM Z7077Z) is an adaptation of the International Standard, ISO 10312. It is currently...

  16. Standardization work by ASTM and DIN concerning test methods for metallic materials - comparative assessment with regard for practice

    International Nuclear Information System (INIS)

    Gerischer, K.

    1986-01-01

    The article explains the significant role of ASTM and marks out basic elements of the specification system of ASTM standards. Usefulness in practice is taken as the main criterion for the subsequent comparison of ASTM or DIN activities and procedures, and results, for standardization in the field of test methods for metallic materials. The main differences are shown to exist with regard to tropicality of test standards, presentation of useful information and background knowledge, and importance attached to formal questions. ASTM standardization work is shown to be more up-to-date, contain more information, and to be less concerned with formal matters. A closer cooperation between ASTM and DIN is strongly recommended. (orig.) [de

  17. Fatigue strength ofcomposite wind turbine blade structures

    DEFF Research Database (Denmark)

    Ardila, Oscar Gerardo Castro

    Wind turbines are normally designed to withstand 20-30 years of life. During this period, the blades, which are the main rotating structures of a wind turbine, are subjected to high fluctuating load conditions as a result of a combination of gravity, inertia, and aeroelastic forces. For this reason......, fatigue is one of the foremost concerns during the design of these structures. However, current standard fatigue methods used for designing wind turbine blades seem not to be completely appropriate for these structures because they are still based on methods developed for metals and not for composite...... materials from which the blades are made. In this sense, the aim of this work is to develop more accurate and reliable fatigue-life prediction models for composite wind turbine blades. In this project, two types of fatigue models are implemented: fatigue-life models and damage mechanics models. In the first...

  18. A low cycle fatigue model for low carbon manganese steel including the effect of dynamic strain aging

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No.29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle [Université Paris Ouest Nanterre La Défense (France); Wang, Qing Yuan; Khan, Muhammad Kashif [Sichuan University, School of Aeronautics and Astronautics, No.29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean–Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320, Chatillon (France)

    2016-01-27

    Carbon–manganese steel A48 (French standards) is used in steam generator pipes of the nuclear power plant where it is subjected to the cyclic thermal load. The Dynamic Strain Aging (DSA) influences the mechanical behavior of the steel in low cycle fatigue (LCF) at favorable temperature and strain rate. The peak stress of A48 steel experiences hardening–softening–hardening (HSH) evolution at 200 °C and 0.4% s{sup −1} strain rate in fatigue loading. In this study, isotropic and kinematic hardening rules with DSA effect have been modified. The HSH evolution of cyclic stress associated with cumulative plastic deformation has also been estimated.

  19. Beneficial Effect of Brewers' Yeast Extract on Daily Activity in a Murine Model of Chronic Fatigue Syndrome

    Directory of Open Access Journals (Sweden)

    Takashi Takahashi

    2006-01-01

    Full Text Available The aim of this study was to assess the effect of Brewers' yeast extract (BYE on daily activity in a mouse model of chronic fatigue syndrome (CFS. CFS was induced by repeated injection of Brucella abortus (BA antigen every 2 weeks. BYE was orally administered to mice in a dose of 2 g per kg per day for 2 weeks before injecting BA and for 4 weeks thereafter. We evaluated daily running activity in mice receiving BYE as compared with that in untreated mice. Weekly variation of body weight (BW and survival in both groups was monitored during the observation period. Spleen weight (SW, SW/BW ratio, percent splenic follicular area and expression levels of interferon-γ (IFN-γ and interleukin-10 (IL-10 mRNA in spleen were determined in both groups at the time of sacrifice. The daily activity during 2 weeks after the second BA injection was significantly higher in the treated group than in the control. There was no difference in BW between both groups through the experimental course. Two mice in the control died 2 and 7 days after the second injection, whereas no mice in the treated group died. Significantly decreased SW and SW/BW ratio were observed in the treated mice together with elevation of splenic follicular area. There were suppressed IFN-γ and IL-10 mRNA levels in spleens from the treated mice. Our results suggest that BYE might have a protective effect on the marked reduction in activity following repeated BA injection via normalization of host immune responses.

  20. Decay in chest compression quality due to fatigue is rare during prolonged advanced life support in a manikin model

    Directory of Open Access Journals (Sweden)

    Bjørshol Conrad A

    2011-08-01

    Full Text Available Abstract Background The aim of this study was to measure chest compression decay during simulated advanced life support (ALS in a cardiac arrest manikin model. Methods 19 paramedic teams, each consisting of three paramedics, performed ALS for 12 minutes with the same paramedic providing all chest compressions. The patient was a resuscitation manikin found in ventricular fibrillation (VF. The first shock terminated the VF and the patient remained in pulseless electrical activity (PEA throughout the scenario. Average chest compression depth and rate was measured each minute for 12 minutes and divided into three groups based on chest compression quality; good (compression depth ≥ 40 mm, compression rate 100-120/minute for each minute of CPR, bad (initial compression depth 120/minute or decay (change from good to bad during the 12 minutes. Changes in no-flow ratio (NFR, defined as the time without chest compressions divided by the total time of the ALS scenario over time was also measured. Results Based on compression depth, 5 (26%, 9 (47% and 5 (26% were good, bad and with decay, respectively. Only one paramedic experienced decay within the first two minutes. Based on compression rate, 6 (32%, 6 (32% and 7 (37% were good, bad and with decay, respectively. NFR was 22% in both the 1-3 and 4-6 minute periods, respectively, but decreased to 14% in the 7-9 minute period (P = 0.002 and to 10% in the 10-12 minute period (P Conclusions In this simulated cardiac arrest manikin study, only half of the providers achieved guideline recommended compression depth during prolonged ALS. Large inter-individual differences in chest compression quality were already present from the initiation of CPR. Chest compression decay and thereby fatigue within the first two minutes was rare.

  1. Corrosion and Fatigue Behavior of High-Strength Steel Treated with a Zn-Alloy Thermo-diffusion Coating

    Science.gov (United States)

    Mulligan, C. P.; Vigilante, G. N.; Cannon, J. J.

    2017-11-01

    High and low cycle fatigue tests were conducted on high-strength steel using four-point bending. The materials tested were ASTM A723 steel in the as-machined condition, grit-blasted condition, MIL-DTL-16232 heavy manganese phosphate-coated condition, and ASTM A1059 Zn-alloy thermo-diffusion coated (Zn-TDC). The ASTM A723 steel base material exhibits a yield strength of 1000 MPa. The effects of the surface treatments versus uncoated steel were examined. The fatigue life of the Zn-TDC specimens was generally reduced on as-coated specimens versus uncoated or phosphate-coated specimens. Several mechanisms are examined including the role of compressive residual stress relief with the Zn-TDC process as well as fatigue crack initiation from the hardened Zn-Fe alloy surface layer produced in the gas-metal reaction. Additionally, the effects of corrosion pitting on the fatigue life of coated specimens are explored as the Zn-TDC specimens exhibit significantly improved corrosion resistance over phosphate-coated and oiled specimens.

  2. Modeling Fatigue Damage Onset and Progression in Composites Using an Element-Based Virtual Crack Closure Technique Combined With the Floating Node Method

    Science.gov (United States)

    De Carvalho, Nelson V.; Krueger, Ronald

    2016-01-01

    A new methodology is proposed to model the onset and propagation of matrix cracks and delaminations in carbon-epoxy composites subject to fatigue loading. An extended interface element, based on the Floating Node Method, is developed to represent delaminations and matrix cracks explicitly in a mesh independent fashion. Crack propagation is determined using an element-based Virtual Crack Closure Technique approach to determine mixed-mode energy release rates, and the Paris-Law relationship to obtain crack growth rate. Crack onset is determined using a stressbased onset criterion coupled with a stress vs. cycle curve and Palmgren-Miner rule to account for fatigue damage accumulation. The approach is implemented in Abaqus/Standard® via the user subroutine functionality. Verification exercises are performed to assess the accuracy and correct implementation of the approach. Finally, it was demonstrated that this approach captured the differences in failure morphology in fatigue for two laminates of identical stiffness, but with layups containing ?deg plies that were either stacked in a single group, or distributed through the laminate thickness.

  3. Longitudinal and dynamic measurement invariance of the FACIT-Fatigue scale: an application of the measurement model of derivatives to ECOG-ACRIN study E2805.

    Science.gov (United States)

    Estabrook, Ryne; Cella, David; Zhao, Fengmin; Manola, Judith; DiPaola, Robert S; Wagner, Lynne I; Haas, Naomi B

    2018-03-05

    While quality of life measures may be used to assess meaningful change and group differences, their scaling and validation often rely on a single occasion of measurement. Using the 13-item FACIT-Fatigue questionnaire at three timepoints, this study tests whether individual items change together in ways consistent with a general fatigue factor. The measurement model of derivatives (MMOD) is a novel method for measurement evaluation that directly assesses whether a given factor structure accurately describes how individual test items change over time. MMOD transforms item-level longitudinal data into a set of orthogonal change scores, each one representing either a within-person longitudinal mean or a different type of longitudinal change. These change scores are then factor analyzed and tested for invariance. This approach is applied to the FACIT-Fatigue scale in a sample of patients with renal cell carcinoma treated on 'ECOG-ACRIN Cancer Research Group (ECOG-ACRIN) study 2805. Analyses revealed strong evidence of unidimensionality, and apparent factorial invariance using traditional techniques. MMOD revealed a small but statistically significant difference in factor structure ([Formula: see text], [Formula: see text]), where factor loadings were weaker and more variable for measuring longitudinal change. The differences in factor structure were not large enough to substantially affect scale usage in this application, but they do reveal some variability across items in the FACIT-Fatigue in their ability to detect change. Future applications should consider differential sensitivity of individual items in multi-item scales, and perhaps even capitalize upon these differences by selecting items that are more sensitive to change.

  4. The effect of fatigue on the corrosion resistance of common medical alloys.

    Science.gov (United States)

    Di Prima, Matthew; Gutierrez, Erick; Weaver, Jason D

    2017-10-01

    The effect of mechanical fatigue on the corrosion resistance of medical devices has been a concern for devices that experience significant fatigue during their lifespan and devices made from metallic alloys. The Food and Drug Administration had recommended in some instances for corrosion testing to be performed on post-fatigued devices [Non-clinical tests and recommended labeling for intravascular stents and associated delivery systems: guidance for industry and FDA staff. 2005: Food and Drug Administration, Center for Devices and Radiological Health], although the need for this has been debated [Nagaraja S, et al., J Biomed Mater Res Part B: Appl Biomater 2016, 8.] This study seeks to evaluate the effect of fatigue on the corrosion resistance of 5 different materials commonly used in medical devices: 316 LVM stainless steel, MP35N cobalt chromium, electropolished nitinol, mechanically polished nitinol, and black oxide nitinol. Prior to corrosion testing per ASTM F2129, wires of each alloy were split into subgroups and subjected to either nothing (that is, as received); high strain fatigue for less than 8 min; short-term phosphate buffered saline (PBS) soak for less than 8 min; low strain fatigue for 8 days; or long-term PBS soak for 8 days. Results from corrosion testing showed that the rest potential trended to an equilibrium potential with increasing time in PBS and that there was no statistical (p > 0.05) difference in breakdown potential between the fatigued and matching PBS soak groups for 9 out of 10 test conditions. Our results suggest that under these nonfretting conditions, corrosion susceptibility as measured by breakdown potential per ASTM F2129 was unaffected by the fatigue condition. 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2019-2026, 2017. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

  5. 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

  6. 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.

  7. 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

  8. 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 ...

  9. Grazing incidence synchrotron X-ray diffraction and Moessbauer spectroscopy analyses of plasma nitrided ASTM F138 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Danilo Olzon Dionysio de; Ardisson, Jose Domingos, E-mail: dolzon@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Silva, Edilaine Honorio [Studiecentrum voor Kernenergie (Belgium); Olzon-Dionysio, Maristela; Souza, Sylvio Dionysio de; Fabris, Jose Domingos [Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Diamantina, MG (Brazil); Martinez, L.G. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2016-07-01

    Full text: systematic investigation of samples of plasma-nitriding austenitic stainless steels ASTM F138 and AISI 316L is reported. The surface treatment of the steels through plasma-nitriding was used to improve further the hardness, wear and corrosion resistance of these stainless steels. The resulting layered crystallographic structure actually corresponds to several phases with close cell parameters, making their identification and quantification a real experimental challenge. The ASTM F138 and AISI 316L stainless steel disks were plasma nitrided for 4 h at 400 deg C in a 80% H{sub 2} -20% N2 atmosphere at 6 torr, using plasma current frequencies between 6 and 100 kHz. Data of Moessbauer (CEMS and CXMS) and grazing incidence synchrotron X-ray diffraction (XRD-SR) were systematically collected. The nitrided layer thickness were not in general influenced by the plasma frequency, except at 12 kHz, which produced a layer thickness of approximately 8.0 mm, being in average 40% thicker than for the other samples. CXMS and CEMS Moessbauer spectra for this 12 kHz-sample show a much more pronounced magnetic resonance lines than for the other samples. The Fe{sub 4}N phase presents a single magnetic hyperfine interaction; the other two (Fe{sub 2-3}N and the expanded austenite) present both paramagnetic and magnetic components, even though their hyperfine parameters may not be safely separated. We also present the results of XRD-SR that were probed at several depths. The data from these techniques may be consistently correlated and this leads to an improved model to explain the structure of the nitrided layers. (author)

  10. Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

    Energy Technology Data Exchange (ETDEWEB)

    Haidyrah, Ahmed S., E-mail: ashdz2@mst.edu [Nuclear Engineering, Missouri University of Science & Technology, 301 W. 14th, Rolla, MO 65409 (United States); Nuclear Science Research Institute, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442 (Saudi Arabia); Newkirk, Joseph W. [Materials Science & Engineering, Missouri University of Science & Technology, 1440 N. Bishop Ave, Rolla, MO 65409 (United States); Castaño, Carlos H. [Nuclear Engineering, Missouri University of Science & Technology, 301 W. 14th, Rolla, MO 65409 (United States)

    2016-03-15

    A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S–N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

  11. Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

    International Nuclear Information System (INIS)

    Haidyrah, Ahmed S.; Newkirk, Joseph W.; Castaño, Carlos H.

    2016-01-01

    A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S–N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

  12. Mixed-mode fatigue fracture of adhesive joints in harsh environments and nonlinear viscoelastic modeling of the adhesive

    Science.gov (United States)

    Arzoumanidis, Alexis Gerasimos

    A four point bend, mixed-mode, reinforced, cracked lap shear specimen experimentally simulated adhesive joints between load bearing composite parts in automotive components. The experiments accounted for fatigue, solvent and temperature effects on a swirled glass fiber composite adherend/urethane adhesive system. Crack length measurements based on compliance facilitated determination of da/dN curves. A digital image processing technique was also utilized to monitor crack growth from in situ images of the side of the specimen. Linear elastic fracture mechanics and finite elements were used to determine energy release rate and mode-mix as a function of crack length for this specimen. Experiments were conducted in air and in a salt water bath at 10, 26 and 90°C. Joints tested in the solvent were fully saturated. In air, both increasing and decreasing temperature relative to 26°C accelerated crack growth rates. In salt water, crack growth rates increased with increasing temperature. Threshold energy release rate is shown to be the most appropriate design criteria for joints of this system. In addition, path of the crack is discussed and fracture surfaces are examined on three length scales. Three linear viscoelastic properties were measured for the neat urethane adhesive. Dynamic tensile compliance (D*) was found using a novel extensometer and results were considerably more accurate and precise than standard DMTA testing. Dynamic shear compliance (J*) was determined using an Arcan specimen. Dynamic Poisson's ratio (nu*) was extracted from strain gage data analyzed to include gage reinforcement. Experiments spanned three frequency decades and isothermal data was shifted by time-temperature superposition to create master curves spanning thirty decades. Master curves were fit to time domain Prony series. Shear compliance inferred from D* and nu* compared well with measured J*, forming a basis for finding the complete time dependent material property matrix for this

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

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2011-01-01

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

  14. Impact of heat treatment on HSS cutting tool (ASTM A600) and its behaviour during machining of mild steel (ASTM A36)

    Science.gov (United States)

    Afolalu, S. A.; Abioye, O. P.; Salawu, E. Y.; Okokpujie, I. P.; Abioye, A. A.; Omotosho, O. A.; Ajayi., O. O.

    2018-04-01

    Carburization is one the best heat treatment that responded well to hardening with Palm Kernel Shell giving the best hardness value. This work studied the influence of carburization on HSStool(ASTM A600) and its behaviour during machining of mild steel (ASTM A36). Composition of the samples (12 pieces of 180 × 12 × 12 mm) HSS tools were checked using UV-VIS spectrometer and the tools were carburized with PKS at holding temperatures and time of 800, 850, 900, 950 °C and 60,90 120 minutes using muffle furnance. The micro structural analysis, surface and core hardnessof the treated samples gave better results than the untreated samples when checked withsoft driven and optical microscope. It wasalso observed that increase in the feed rate and depth for length of cut of 50 mm significantly reduces the wear progression and thereby gave best machining time at maximum carburizing temperature and time(950 °C / 120 minutes) when it was used to cut mild steelon the lathe machine.

  15. 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

  16. Fatigue and fracture: Overview

    Science.gov (United States)

    Halford, G. R.

    1984-01-01

    A brief overview of the status of the fatigue and fracture programs is given. The programs involve the development of appropriate analytic material behavior models for cyclic stress-strain-temperature-time/cyclic crack initiation, and cyclic crack propagation. The underlying thrust of these programs is the development and verification of workable engineering methods for the calculation, in advance of service, of the local cyclic stress-strain response at the critical life governing location in hot section compounds, and the resultant crack initiation and crack growth lifetimes.

  17. On the ability of some cyclic plasticity models to predict the evolution of stored energy in a type 304L stainless steel submitted to high cycle fatigue

    International Nuclear Information System (INIS)

    Vincent, L.

    2008-01-01

    Fatigue analyses of materials are generally based on a so-called stabilized cycle, on which plastic strain amplitude, plastic energy, maximum shear stress and so on are determined. The part of plastic energy which is dissipated in heat cannot be used to accumulate damage and it should be worthwhile extracting only the part of plastic energy which is stored in material microstructure in order to build a consistent damage model. In this paper, some cyclic plasticity models including a polycrystalline model are reformulated in the thermodynamic framework in order to test their capacity to predict both the stress-strain behaviour and the partition of plastic energy for a high cycle fatigue test on a type 304L stainless steel. For an equivalent description of stress-strain loops, the number of kinematic hardening variables chosen in a model may qualitatively alter the prediction of plastic energy partition due to the modification of the isotropic hardening variable. Measurements of the specimen temperature increase due to plastic dissipation is therefore proposed as a convenient complementary experimental data to identify the constitutive equation of the isotropic hardening variable of a cyclic plasticity model. (author)

  18. Final Report for Project 13-4791: New Mechanistic Models of Creep-Fatigue Crack Growth Interactions for Advanced High Temperature Reactor Components

    Energy Technology Data Exchange (ETDEWEB)

    Kruzic, Jamie J [Oregon State Univ., Corvallis, OR (United States); Siegmund, Thomas [Purdue Univ., West Lafayette, IN (United States); Tomar, Vikas [Purdue Univ., West Lafayette, IN (United States)

    2018-03-20

    This project developed and validated a novel, multi-scale, mechanism-based model to quantitatively predict creep-fatigue crack growth and failure for Ni-based Alloy 617 at 800°C. Alloy 617 is a target material for intermediate heat exchangers in Generation IV very high temperature reactor designs, and it is envisioned that this model will aid in the design of safe, long lasting nuclear power plants. The technical effectiveness of the model was shown by demonstrating that experimentally observed crack growth rates can be predicted under both steady state and overload crack growth conditions. Feasibility was considered by incorporating our model into a commercially available finite element method code, ABAQUS, that is commonly used by design engineers. While the focus of the project was specifically on an alloy targeted for Generation IV nuclear reactors, the benefits to the public are expected to be wide reaching. Indeed, creep-fatigue failure is a design consideration for a wide range of high temperature mechanical systems that rely on Ni-based alloys, including industrial gas power turbines, advanced ultra-super critical steam turbines, and aerospace turbine engines. It is envisioned that this new model can be adapted to a wide range of engineering applications.

  19. Effect of microstructure and environment on the crack growth behaviour on Inconel 718 alloy at 650/sup 0/C under fatigue, creep and combined loading

    Energy Technology Data Exchange (ETDEWEB)

    Pedron, J P; Pineau, A

    1982-11-01

    The crack growth properties of various microstructures developed in one heat of Inconel 718 alloy were investigated at 650/sup 0/C under air and vacuum environments. The microstructures included fine-grained material (ASTM grain sizes 6-8), coarse-grained material (ASTM grain sizes 3-4) and material of a necklace structure (ASTM grain sizes 3-4 and 8-10). The effect of grain boundary ..beta.. (Ni/sub 3/Nb) phase precipitation was also studied. Continuous fatigue, creep and creep-fatigue conditions were examined. For continuous fatigue the influence of frequency was investigated over the range between 5x10/sup -2/ and 20 Hz. For creep-fatigue conditions, hold times of 10 and 300 s were superimposed on a 5x10/sup -2/ Hz triangular wave shape signal. It was shown that the grain boundary microstructure had a very strong effect when the fatigue crack propagation behaviour was essentially time dependent. This effect is associated with the occurrence of brittle intergranular fracture and dramatic increases in crack growth rate. The microstructure had no effect under vacuum testing.

  20. Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete.

    Science.gov (United States)

    Ríos, José D; Cifuentes, Héctor; Yu, Rena C; Ruiz, Gonzalo

    2017-07-07

    The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308-318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter.

  1. Thermal Acoustic Fatigue Apparatus

    Data.gov (United States)

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

  2. Simplified elastoplastic fatigue analysis

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  3. Fretting-corrosion at the modular tapers interface: Inspection of standard ASTM F1875-98.

    Science.gov (United States)

    Bingley, Rachel; Martin, Alan; Manfredi, Olivia; Nejadhamzeeigilani, Mahdiyar; Oladokun, Abimbola; Beadling, Andrew Robert; Siddiqui, Sohail; Anderson, James; Thompson, Jonathan; Neville, Anne; Bryant, Michael

    2018-05-01

    Interest in the degradation mechanisms at the modular tapers interfaces has been renewed due to increased reported cases of adverse reactions to metal debris and the appearance of wear and corrosion at the modular tapers interfaces at revision. Over the past two decades, a lot of research has been expended to understand the degradation mechanisms, with two primary implant loading procedures and orientations used consistently across the literature. ASTM F1875-98 is often used as a guide to understand and benchmark the tribocorrosion processes occurring within the modular tapers interface. This article presents a comparison of the two methods outlined in ASTM F1875-98 as well as a critique of the standard considering the current paradigm in pre-clinical assessment of modular tapers.

  4. A new method to determine J0-integral values (ASTM E 813) without any auxiliary equipment

    International Nuclear Information System (INIS)

    Ullrich, G.; Krompholz, K.

    1987-01-01

    In this contribution the path independent J-integral according to J.R. Rice, respective J.D. Landes and J.A. Begley due to ASTME 813 is calculated by the product J pl = d v J el for 3 point bend type specimen. Here d v is the load point displacement up to the point of the onset of stable crack growth V, which is taken from the load versus load point displacement diagram and J el a value which is equivalent to K 2 /E, where K is the stress intensity factor (ASTME 399) and E is Young's modulus. The advantage of the new procedure is the simplicity of the test arrangement and of the evaluation with the determination of initiation point V without computer or other auxiliary equipment. (orig.) [de

  5. Results of ASTM round robin testing for mode 1 interlaminar fracture toughness of composite materials

    Science.gov (United States)

    Obrien, T. Kevin; Martin, Roderick H.

    1992-01-01

    The results are summarized of several interlaboratory 'round robin' test programs for measuring the mode 1 interlaminar fracture toughness of advanced fiber reinforced composite materials. Double Cantilever Beam (DCB) tests were conducted by participants in ASTM committee D30 on High Modulus Fibers and their Composites and by representatives of the European Group on Fracture (EGF) and the Japanese Industrial Standards Group (JIS). DCB tests were performed on three AS4 carbon fiber reinforced composite materials: AS4/3501-6 with a brittle epoxy matrix; AS4/BP907 with a tough epoxy matrix; and AS4/PEEK with a tough thermoplastic matrix. Difficulties encountered in manufacturing panels, as well as conducting the tests are discussed. Critical issues that developed during the course of the testing are highlighted. Results of the round robin testing used to determine the precision of the ASTM DCB test standard are summarized.

  6. Stuy on Fatigue Life of Aluminum Alloy Considering Fretting

    Science.gov (United States)

    Yang, Maosheng; Zhao, Hongqiang; Wang, Yunxiang; Chen, Xiaofei; Fan, Jiali

    2018-01-01

    To study the influence of fretting on Aluminum Alloy, a global finite element model considering fretting was performed using the commercial code ABAQUS. With which a new model for predicting fretting fatigue life has been presented based on friction work. The rationality and effectiveness of the model were validated according to the contrast of experiment life and predicting life. At last influence factor on fretting fatigue life of aerial aluminum alloy was investigated with the model. The results revealed that fretting fatigue life decreased monotonously with the increasing of normal load and then became constant at higher pressures. At low normal load, fretting fatigue life was found to increase with increase in the pad radius. At high normal load, however, the fretting fatigue life remained almost unchanged with changes in the fretting pad radius. The bulk stress amplitude had the dominant effect on fretting fatigue life. The fretting fatigue life diminished as the bulk stress amplitude increased.

  7. Reactor pressure vessel steels ASTM A533B and A508 Cl.2

    International Nuclear Information System (INIS)

    Pelli, R.; Kemppainen, M.; Toerroenen, K.

    1979-11-01

    This report presents the tensile test results of steels ASTM A533B and A508 Cl.2 obtained in connection with a programme initiated to gather and create information needed for the assessment of the structural integrity of the reactor pressure vessels. The tensile properties were studied between -196 and 300 degC varying austenitizing and tempering temperatures and having two different carbon contents for the heats of A533B. (author)

  8. An Evaluation of a Proposed Revision of the ASTM D 1990 Grouping Procedure

    Science.gov (United States)

    Steve P Verrill; James W. Evans; David E. Kretschmann; Cherilyn A. Hatfield

    2013-01-01

    Lum, Taylor, and Zidek have proposed a revised procedure for wood species grouping in ASTM standard D 1990. We applaud the authors’ recognition of the importance of considering a strength distribution’s variability as well as its fifth percentile. However, we have concerns about their proposed method of incorporating this information into a standard. We detail these...

  9. 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...

  10. Numerical modeling of hydrogen diffusion in structural steels under cathodic overprotection and its effects on fatigue crack propagation

    Energy Technology Data Exchange (ETDEWEB)

    Silva Diniz, D.; Almeida Silva, A. [Federal University of Campina Grande, Campina Grande-PB (Brazil); Andrade Barbosa, J.M. [Federal University of Pernambuco, Recife-PE (Brazil); Palma Carrasco, J.

    2012-05-15

    This paper presents a numerical simulation of the effect of hydrogen atomic diffusion on fatigue crack propagation on structural steels. The simulation was performed with a specimen type CT of API 5CT P110 steel, loaded in the tensile opening mode, in plane strain state and under the effects of a cyclic mechanical load and the hydrogen concentration at the crack tip. As hydrogen source, a cathodic protection system was considered, commonly used in subsea pipelines. The equations of evolution of variables at the crack tip form a non-linear system of ordinary differential equations that was solved by means of the 4th order Runge-Kutta method. The solid-solid diffusion through the lattice ahead of the crack tip was simulated using the finite difference method. The simulations results show that under these conditions, the fatigue crack evolution process is enhanced by the hydrogen presence in the material, and that the start time of the crack propagation decreases as its concentration increases. These results show good correlation and consistency with macroscopic observations, providing a better understanding of hydrogen embrittlement in fatigue crack propagation processes in structural steels. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. 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.

  12. Computer simulation of fatigue under diametrical compression

    OpenAIRE

    Carmona, H. A.; Kun, F.; Andrade Jr., J. S.; Herrmann, H. J.

    2006-01-01

    We study the fatigue fracture of disordered materials by means of computer simulations of a discrete element model. We extend a two-dimensional fracture model to capture the microscopic mechanisms relevant for fatigue, and we simulate the diametric compression of a disc shape specimen under a constant external force. The model allows to follow the development of the fracture process on the macro- and micro-level varying the relative influence of the mechanisms of damage accumulation over the ...

  13. Influence of Casting Section Thickness on Fatigue Strength of Austempered Ductile Iron

    Science.gov (United States)

    Olawale, J. O.; Ibitoye, S. A.

    2017-10-01

    The influence of casting section thickness on fatigue strength of austempered ductile iron was investigated in this study. ASTM A536 65-45-12 grade of ductile iron was produced, machined into round samples of 10, 15, 20 and 25 mm diameter, austenitized at a temperature of 820 °C, quenched into an austempering temperature (TA) of 300 and 375 °C and allowed to be isothermally transformed at these temperatures for a fixed period of 2 h. From the samples, fatigue test specimens were machined to conform to ASTM E-466. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) methods were used to characterize microstructural morphology and phase distribution of heat-treated samples. The fatigue strength decreases as the section thickness increases. The SEM image and XRD patterns show a matrix of acicular ferrite and carbon-stabilized austenite with ferrite coarsening and volume fraction of austenite reducing as the section thickness increases. The study concluded that the higher the value of carbon-stabilized austenite the higher the fatigue strength while it decreases as the ausferrite structure becomes coarse.

  14. 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...

  15. Environmental fatigue in aluminum-lithium alloys

    Science.gov (United States)

    Piascik, Robert S.

    1992-01-01

    Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R and reduced closure, chemical environment effects are pronounced resulting in accelerated near threshold da/dN. The beneficial effects of crack closure are minimized for small cracks resulting in rapid growth rates. Limited data suggest that the 'chemically small crack' effect, observed in other alloy system, is not pronounced in Al-Li alloys. Modeling of environmental fatigue in Al-Li-Cu alloys related accelerated fatigue crack growth in moist air and salt water to hydrogen embrittlement.

  16. Interconnect fatigue design for terrestrial photovoltaic modules

    Science.gov (United States)

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

    1982-03-01

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

  17. Effect of Stress-Strain Behavior on Low-Cycle Fatigue of Alpha-Beta Titanium Alloys.

    Science.gov (United States)

    1980-11-21

    and strain excursion, such a curve would appear to fit much of the high temperature hold-time data compiled by Krempl and Wundt [21]. Thus, it might...34Mechanische Relaxation von Kupfer-Einkristallen," Phys. Stat. Sol. 3, 111-120. 21. Krempl, E. and Wundt , B. M., (1971), Hold-Time Effects in High- Temperature Low-Cycle Fatigue, ASTM STP 489. 26 Low

  18. Ductile fracture toughness of heavy section pressure vessel steel plate. A specimen-size study of ASTM A 533 steels

    International Nuclear Information System (INIS)

    Williams, J.A.

    1979-09-01

    The ductile fracture toughness, J/sub Ic/, of ASTM A 533, Grade B, Class 1 and ASTM A 533, heat treated to simulate irradiation, was determined for 10- to 100-mm thick compact specimens. The toughness at maximum specimen load was also measured to determine the conservatism of J/sub Ic/. The toughness of ASTM A 533, Grade B, Class 1 steel was 349 kJ/m 2 and at the equivalent upper shelf temperature, the heat treated material exhibited 87 kJ/m 2 . The maximum load fracture toughness was found to be linearly proportional to specimen size, and only specimens which failed to meet ASTM size criteria exhibited maximum load toughness less than J/sub Ic/

  19. Fatigue of coated and laser hardened steels

    International Nuclear Information System (INIS)

    La Cruz, P. de.

    1990-01-01

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

  20. Fatigue Assessment of High Strength Steel Welded Joints Under Bending Loading

    International Nuclear Information System (INIS)

    Lee, Myeong-Woo; Kim, Yun-Jae; Park, Jun-Hyub

    2014-01-01

    In this study, a fatigue assessment method for vehicle suspension systems having welded geometries was established under a bending loading condition. For the fatigue life estimation of the actual product s welded joints made of different steels, bending fatigue tests were performed on welded specimens with a simplified shape for obtaining the moment-fatigue-life plot. Further, geometry modeling of the simplified welded specimens was conducted. Results of finite element analysis were used to obtain the stress-fatigue-life plot. The analysis results were also used to calculate the stress concentration factors for notch-factor-based fatigue life estimation. The test results were compared with results of the general notch-factor-based fatigue life estimation for improving fatigue assessment. As a result, it was concluded that both the welded fatigue tests and the notch-factor-based fatigue life estimation are necessary for accurate fatigue assessment

  1. JST Thesaurus Headwords and Synonyms: ASTM [MeCab user dictionary for science technology term[Archive

    Lifescience Database Archive (English)

    Full Text Available MeCab user dictionary for science technology term ASTM 名詞 一般 * * * * 米国材料試験協会 ベイコクザ...イリョウシケンキョウカイ ベイコクザイリョーシケンキョーカイ Thesaurus2015 200906091611619997 C IA02 UNKNOWN_1 ASTM

  2. Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

    Science.gov (United States)

    Sivan, Shiril; Di Prima, Matthew; Weaver, Jason D.

    2017-09-01

    Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties. The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F2129 are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential. However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life. Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials.

  3. Fatigue crack extension in nozzle junctions; comparison of analytical approximations with experimental data

    International Nuclear Information System (INIS)

    Broekhoven, M.J.G.; Ruijtenbeek, M.G. van de

    1975-01-01

    The fracture mechanics based stress intensity factor (K-factor) concept has obtained wide-spread acceptance as a tool for quantitative analysis of both fatigue crack growth and instable fracture. The present study discusses the applicability of various simple analytical approximations by comparing results with experimental data. A semi-analytical procedure has been developed whose main characteristics are: the true stress distribution perpendicular to the crack plane for the uncracked structure is used as input data; an extended version of the Shah and Kobayashi solution for elliptical cracks, loaded on their surfaces by tractions described by fourth order double symmetrical polynomials fit through the data of previous step is used to calculate full K-factor variations along the crack fronts; several corrections, a.o. to correct for free surfaces and for a corner radius are incorporated. The experiments concern careful monitoring crack growth rates (da/dN) under uniaxial fatigue loading of precracked nozzle-on-plate models, a.o. using a closed T.V. circuit. Resulting da/dN versus crack length (a) curves are converted into K versus a curves using da/dN versus ΔK curves for the same material (ASTM A 508 C12) obtained by standard procedures. Comparison of theoretical and experimental data yields the conclusion that: simple analytical approximations as sometimes recommended in literature may largely overestimate or underestimate K-factors for nozzle corner cracks; a computer program based on the semi-analytical procedure yields results within seconds of CPU-time once the input data have been generated. These results compare well with experimental and available finite element data for the range of crack depths of practical concern

  4. 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

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

    NARCIS (Netherlands)

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

    2015-01-01

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

  6. The central governor model of exercise regulation teaches us precious little about the nature of mental fatigue and self-control failure

    Directory of Open Access Journals (Sweden)

    Michael eInzlicht

    2016-05-01

    Full Text Available Self-control is considered broadly important for many domains of life. One of its unfortunate features, however, is that it tends to wane over time, with little agreement about why this is the case. Recently, there has been a push to address this problem by looking to the literature in exercise physiology, specifically the work on the central governor model of physical fatigue. Trying to explain how and why mental performance wanes over time, the central governor model suggests that exertion is throttled by some central nervous system mechanism that receives information about energetic bodily needs and motivational drives to regulate exertion and, ultimately, to prevent homeostatic breakdown, chiefly energy depletion. While we admire the spirit of integration and the attempt to shed light on an important topic in psychology, our concern is that the central governor model is very controversial in exercise physiologists, with increasing calls to abandon it altogether, making it a poor fit for psychology. Our concerns are threefold. First, while we agree that preservation of bodily homeostasis makes for an elegant ultimate account, the fact that such important homeostatic concerns can be regularly overturned with even slight incentives (e.g., a smile renders the ultimate account impotent and points to other ultimate functions for fatigue. Second, despite the central governor being thought to take as input information about the metabolic needs of the body, there is no credible evidence that mental effort actually consumes inordinate amounts of energy that are not already circulating in the brain. Third, recent modifications of the model make the central governor appear like an all-knowing homunculus and unfalsifiable in principle, thus contributing very little to our understanding of why people tend to disengage from effortful tasks over time. We note that the latest models in exercise physiology have actually borrowed concepts and models from

  7. Fatigue impact on Mod-1 wind turbine design

    Science.gov (United States)

    Stahle, C. V., Jr.

    1978-01-01

    Fatigue is a key consideration in the design of a long-life Wind Turbine Generator (WTG) system. This paper discusses the fatigue aspects of the large Mod-1 horizontal-axis WTG design starting with the characterization of the environment and proceeding through the design. Major sources of fatigue loading are discussed and methods of limiting fatigue loading are described. NASTRAN finite element models are used to determine dynamic loading and internal cyclic stresses. Recent developments in determining the allowable fatigue stress consistent with present construction codes are discussed relative to their application to WTG structural design.

  8. Degenerated graphite nodules influence on fatigue crack paths in a ferritic ductile cast iron

    Directory of Open Access Journals (Sweden)

    Francesco Iacoviello

    2015-10-01

    Full Text Available ferritic to a completely pearlitic matrix, and they are widely used for many applications (e.g. wheels, gears, crankshafts in cars, exhaust manifolds, valves, flywheels, boxes bearings, hubs, shafts, valves, flanges, pipelines .... Considering the graphite elements, their morphology can be considered as degenerated when its nodularity is too low and this can be due to different causes (e.g., a partially failed nodularization process or a wrong inoculant. In this work, a ferritic DCI with degenerated nodules was obtained by means of an annealing treatment and the fatigue crack propagation resistance was investigated by means of fatigue crack propagation tests performed according to ASTM E647, focusing on the influence of degenerated graphite nodules on the fatigue crack paths. This analysis was performed both analysing the crack path profile by means of a scanning electron microscope (SEM and by means of a SEM fracture surfaces analysis

  9. Effect of heat-treatment on elevated temperature fatigue-crack growth behavior of two heats of Alloy 718

    International Nuclear Information System (INIS)

    Mills, W.J.; James, L.A.

    1978-05-01

    The room temperature and elevated temperature fatigue-crack growth behavior of two heats of Alloy 718 was characterized within a linear-elastic fracture mechanics framework. Two different heat-treatments were used: the ''conventional'' (ASTM A637) treatment, and a ''modified'' heat-treatment designed to improve the toughness of Alloy 718 base metal and weldments. Heat-to-heat variations in the fatigue-crack propagation behavior were observed in the conventionally-treated material. On the other hand, no heat-to-heat variations were observed in the modified condition. Furthermore, both heats of Alloy 718 exhibited superior fatigue-crack growth resistance when given the modified heat-treatment. Electron fractographic examination of Alloy 718 fatigue fracture surfaces revealed that the operative crack growth mechanisms were dependent on heat-treatment, temperature, and ΔK level

  10. 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

  11. 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...

  12. Perilaku kekuatan fatigue paduan aluminium seri 2014 akibat proses termomekanikal aging

    Directory of Open Access Journals (Sweden)

    Sujita -

    2012-11-01

    Full Text Available Aluminium alloy seri 2014 is material which is often used in industry. Because excellence of mechanic properties. But also have the weakness at properties of strength fatigue. Though fatigue strength is important parameter in desain, especially if application at condition of dinamic loading, so that need the treatment to improve it. Fatigue strength go together the micro structure and mode of failure of failure of effect of stress concentration. Aging treatment ordinary done not yet given the influence which even on the contrary. Inconsistence of fatigue strength alluminium alloy show the phenomenon which must be research instructing at repair of fatigue strength , so that need the advanced treatment in the form of termomechanical aging. The research conducted by using alluminium alloy series 2014 formed by specimen fatigue test of the size diameter 8 mm and long 87 mm relate at standart (ASTM E 513, continued treatment of termomechanical aging, tested the fatigue, and monitoring microstructure of change. By structure micro, the treatmentTMA have the effect which sicnificant to improvement of Alluminium alloy series 2104 fatigue strength. Generally entire process TMA improve of limit fatigue from specimen at condition early of limit fatigue 48.3 N / mm2 (48.3 MPA, mounting to become 50 until MPA, or mount 3.4 % until 44.9%. With the process of termomechanical aging TMA I, happened the increasing of cycle number equal to, 26.3 %, at treatment of TMA II go up equal to 62 % and 89.8% at process of TMA III, at maximal loading (180 Mpa.

  13. ASTM STANDARD GUIDE FOR EVALUATING DISPOSAL OPTIONS FOR REUSE OF CONCRETE FROM NUCLEAR FACILITY DECOMMISSIONING

    International Nuclear Information System (INIS)

    Phillips, Ann Marie; Meservey, Richard H.

    2003-01-01

    Within the nuclear industry, many contaminated facilities that require decommissioning contain huge volumes of concrete. This concrete is generally disposed of as low-level waste at a high cost. Much of the concrete is lightly contaminated and could be reused as roadbed, fill material, or aggregate for new concrete, thus saving millions of dollars. However, because of the possibility of volumetric contamination and the lack of a method to evaluate the risks and costs of reusing concrete, reuse is rarely considered. To address this problem, Argonne National Laboratory-East (ANL-E) and the Idaho National Engineering and Environmental Laboratory teamed to write a ''concrete protocol'' to help evaluate the ramifications of reusing concrete within the U.S. Department of Energy (DOE). This document, titled the Protocol for Development of Authorized Release Limits for Concrete at U.S. Department of Energy Site (1) is based on ANL-E's previously developed scrap metal recycle protocols; on the 10-step method outlined in DOE's draft handbook, Controlling Release for Reuse or Recycle of Property Containing Residual Radioactive Material (2); and on DOE Order 4500.5, Radiation Protection of the Public and the Environment (3). The DOE concrete protocol was the basis for the ASTM Standard Guide for Evaluating Disposal Options for Concrete from Nuclear Facility Decommissioning, which was written to make the information available to a wider audience outside DOE. The resulting ASTM Standard Guide is a more concise version that can be used by the nuclear industry worldwide to evaluate the risks and costs of reusing concrete from nuclear facility decommissioning. The bulk of the ASTM Standard Guide focuses on evaluating the dose and cost for each disposal option. The user calculates these from the detailed formulas and tabulated data provided, then compares the dose and cost for each disposal option to select the best option that meets regulatory requirements. With this information

  14. Impact of ASTM Standard E722 update on radiation damage metrics

    Energy Technology Data Exchange (ETDEWEB)

    DePriest, Kendall Russell [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-06-01

    The impact of recent changes to the ASTM Standard E722 is investigated. The methodological changes in the production of the displacement kerma factors for silicon has significant impact for some energy regions of the 1-MeV(Si) equivalent fluence response function. When evaluating the integral over all neutrons energies in various spectra important to the SNL electronics testing community, the change in the response results in an increase in the total 1-MeV(Si) equivalent fluence of 2 7%. Response functions have been produced and are available for users of both the NuGET and MCNP codes.

  15. Glove powder's carrying capacity for latex protein: analysis using the ASTM ELISA test.

    Science.gov (United States)

    Beezhold, D; Horton, K; Hickey, V; Daddona, J; Kostyal, D

    2003-01-01

    Glove donning powders carry latex proteins and disperse them into the workplace environment. We have used the ASTM D6499 ELISA to quantify the amount of latex antigen bound to and carried by glove powders. We could differentiate between a small amount of protein actually bound to the powders and a larger amount carried by the powder. Enhanced binding of a major allergen, Hev b 5, to the starch powders was demonstrated by Western blot. The D6499 ELISA is able to measure total latex antigen, soluble and powder bound, simultaneously without the need to centrifuge the samples.

  16. Data development for ASTM E24.06.02 round robin program on instability prediction

    Science.gov (United States)

    Mccabe, D. E.

    1979-01-01

    Basis data for use in an ASTM E24.06.02 task group round robin activity was developed. Compact specimens were made of 2024-T351, 7075-T651 aluminum alloys, and 304 stainless steel. All were 12.7 mm thick and planar dimension variables incorporated were for 1T, 2T and 4T sizes. Representative raw data for each material and specimen size are contained herein. R-curves plotted in terms of delta a physical and delta a effective are plotted for each material.

  17. Mechanical behaviour of Astm A 297 grade Hp joints welded using different processes

    International Nuclear Information System (INIS)

    Emygdio, Paulo Roberto Oliveira; Zeemann, Annelise; Almeida, Luiz Henrique de

    1996-01-01

    The influence of different arc welding processes on mechanical behaviour was studied for cast heat resistant stainless steel welded joints, in the as welded conditions. ASTM A 297 grade HP with niobium and niobium/titanium additions were welded following three different welding procedures, using shielded metal arc welding gas tungsten arc welding and plasma arc welding, in six welded joints. The welded joint mechanical behaviour was evaluated by ambient temperature and 870 deg C tensile tests; and creep tests at 900 deg C and 50 MPa. Mechanical test results showed that the welding procedure qualification following welding codes is not suitable for high temperature service applications. (author)

  18. 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

  19. Fatigue 󈨛. Volume 2,

    Science.gov (United States)

    1987-06-01

    ROLAND STICKLER Absolute Fatigue Thresholds in Metallic 801 Materials - J.A. LEWIS Thermometrical Investigations on the Near 809 Threshold Fatigue...impurities reported by Semi- Alloys Inc. totaled less than 0.1%. Specimens were cast in a flat open aluminum mold. Each specimen was 6 mm thick and 12...and 2024-T351 Aluminum Alloy", in "Fatigue Crack Growth Threshold Concepts", D.L. Davidson, S. Suresh, editors, TMS-AIME. 1984, pp. 63-82. (2) Bailon

  20. Statistical aspects of fatigue crack growth life of base metal, weld metal and heat affected zone in FSWed 7075-T651aluminum alloy

    International Nuclear Information System (INIS)

    Sohn, Hye Jeong; Haryadi, Gunawan Dwi; Kim, Seon Jin

    2014-01-01

    The statistical aspects of fatigue crack growth life of base metal (BM), weld metal (WM) and heat affected zone (HAZ) in friction stir welded (FSWed) 7075-T651 aluminum alloy has been studied by Weibull statistical analysis. The fatigue crack growth tests were performed at room temperature on ASTM standard CT specimens under three different constant stress intensity factor range controls. The main objective of this paper is to investigate the effects of statistical aspects of fatigue crack growth life on stress intensity factor ranges and material properties, namely BM, WM and HAZ specimens. In this work, the Weibull distribution was employed to estimate the statistical aspects of fatigue crack growth life. The shape parameter of Weibull distribution for fatigue crack growth life was significantly affected by material properties and the stress intensity factor range. The scale parameter of WM specimen exhibited the lowest value at all stress intensity factor ranges.

  1. 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...

  2. 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.

  3. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

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

    1999-01-01

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

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

    NARCIS (Netherlands)

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

    2014-01-01

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

  5. 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

  6. Identification of distinct fatigue trajectories in patients with breast cancer undergoing adjuvant chemotherapy.

    Science.gov (United States)

    Junghaenel, Doerte U; Cohen, Jules; Schneider, Stefan; Neerukonda, Anu R; Broderick, Joan E

    2015-09-01

    The goal of this study was to characterize changes in daily fatigue in women undergoing chemotherapy for breast cancer. We examined whether there are subgroups of patients with distinct fatigue trajectories and explored potential psychosocial and biomedical predictors of these subgroups. Participants were 77 women with breast cancer receiving adjuvant chemotherapy with AC-T (2-week cycle) and TC or TCH (3-week cycle) regimens. They completed 28 daily ratings online using an adapted version of the Patient-Reported Outcomes Measurement Information System (PROMIS®) fatigue instrument. Both regimens followed an "inverted-U-shaped" fatigue pattern over approximately 2 weeks. Growth mixture modeling identified three patient subgroups with distinct trajectories. Fatigue scores in the "low fatigue" group (23 %) increased following the infusion and quickly abated. The "transient fatigue" (27 %) group had a very pronounced increase. Patients in the "high fatigue" (50 %) group reported consistently elevated fatigue with a relatively small increase. Demographic and medical variables were not associated with fatigue trajectory. Patients in the "high fatigue" group reported significantly poorer physical, emotional, and social functioning, poorer general health, and more depressed mood than patients in the "low fatigue" group. The "transient fatigue" group reported significantly better physical and social functioning than the "high fatigue" group, but emotional distress and depression similar to the "high fatigue" group. The identification of patient subgroups with distinct fatigue trajectories during chemotherapy is an essential step for developing preventative strategies and tailored interventions. Our results suggest that different trajectories are associated with patients' psychosocial and general health.

  7. Application of MCDM based hybrid optimization tool during turning of ASTM A588

    Directory of Open Access Journals (Sweden)

    Himadri Majumder

    2017-07-01

    Full Text Available Multi-criteria decision making approach is one of the most troublesome tools for solving the tangled optimization problems in the machining area due to its capability of solving the complex optimization problems in the production process. Turning is widely used in the manufacturing processes as it offers enormous advantages like good quality product, customer satisfaction, economical and relatively easy to apply. A contemporary approach, MOORA coupled with PCA, was used to ascertain an optimal combination of input parameters (spindle speed, depth of cut and feed rate for the given output parameters (power consumption, average surface roughness and frequency of tool vibration using L27 orthogonal array for turning on ASTM A588 mild steel. Comparison between MOORA-PCA and TOPSIS-PCA shows the effectiveness of MOORA over TOPSIS method. The optimum parameter combination for multi-performance characteristics has been established for ASTM A588 mild steel are spindle speed 160 rpm, depth of cut 0.1 mm and feed rate 0.08 mm/rev. Therefore, this study focuses on the application of the hybrid MCDM approach as a vital selection making tool to deal with multi objective optimization problems.

  8. A Knowledge- Based Computer System for UO2 Characterization According to ASTM Requirements

    International Nuclear Information System (INIS)

    Afifi, Y.K.; El-Hakim, E.

    2000-01-01

    The uranium dioxde (UO 2 ) powder properties and the pellets fabrication processes determine the characteristics of the sintered UO 2 pellets. The powder properties include chemical and physical characteristics. The physical and chemical properties of UO 2 powder are normally checked to ensure consistency and reproducibility of the sintered UO 2 pellets. Powder characteristics are known to influence the subsequent manufacturing performance or the fuel properties. The aim of this paper is to provide the nuclear industry with a program dealing with the processes and the related requirements to determine the specifications of UO 2 powder according to the American Standards for Testing and Materials (ASTM). This program covers the physical and chemical characteristics of UO 2 powder. A group of logic flow charts dealing with the data and information available in the ASTM for each step in the characterization of UO 2 powder process and the technical assistance are constructed. These logic flow charts are collected to form a module of the software to qualify the UO 2 powder. The program contains 8 modules, each one deals with one object. This program saves time, is also considered as a collective schema for all the required UO 2 powder characterization and the related processes, and could be used as a training tool for less skilled personnel involved in UO 2 powder characterization laboratories

  9. Relation between the national handbook of recommended methods for water data acquisition and ASTM standards

    Science.gov (United States)

    Glysson, G. Douglas; Skinner, John V.

    1991-01-01

    In the late 1950's, intense demands for water and growing concerns about declines in the quality of water generated the need for more water-resources data. About thirty Federal agencies, hundreds of State, county and local agencies, and many private organizations had been collecting water data. However, because of differences in procedures and equipment, many of the data bases were incompatible. In 1964, as a step toward establishing more uniformity, the Bureau of the Budget (now the Office of Management and Budget, OMB) issued 'Circular A-67' which presented guidelines for collecting water data and also served as a catalyst for creating the Office of Water Data Coordination (OWDC) within the U.S. Geological Survey. This paper discusses past, present, and future aspects of the relation between methods in the National Handbook and standards published by ASTM (American Society for Testing and Materials) Committee D-19 on Water's Subcommittee D-19.07 on Sediment, Geomorphology, and Open Channel Flow. The discussion also covers historical aspects of standards - development work jointly conducted by OWDC and ASTM.

  10. Improved ASTM G72 Test Method for Ensuring Adequate Fuel-to-Oxidizer Ratios

    Science.gov (United States)

    Juarez, Alfredo; Harper, Susana Tapia

    2016-01-01

    The ASTM G72/G72M-15 Standard Test Method for Autogenous Ignition Temperature of Liquids and Solids in a High-Pressure Oxygen-Enriched Environment is currently used to evaluate materials for the ignition susceptibility driven by exposure to external heat in an enriched oxygen environment. Testing performed on highly volatile liquids such as cleaning solvents has proven problematic due to inconsistent test results (non-ignitions). Non-ignition results can be misinterpreted as favorable oxygen compatibility, although they are more likely associated with inadequate fuel-to-oxidizer ratios. Forced evaporation during purging and inadequate sample size were identified as two potential causes for inadequate available sample material during testing. In an effort to maintain adequate fuel-to-oxidizer ratios within the reaction vessel during test, several parameters were considered, including sample size, pretest sample chilling, pretest purging, and test pressure. Tests on a variety of solvents exhibiting a range of volatilities are presented in this paper. A proposed improvement to the standard test protocol as a result of this evaluation is also presented. Execution of the final proposed improved test protocol outlines an incremental step method of determining optimal conditions using increased sample sizes while considering test system safety limits. The proposed improved test method increases confidence in results obtained by utilizing the ASTM G72 autogenous ignition temperature test method and can aid in the oxygen compatibility assessment of highly volatile liquids and other conditions that may lead to false non-ignition results.

  11. Cavitation erosion - corrosion behaviour of ASTM A27 runner steel in natural river water

    International Nuclear Information System (INIS)

    Tôn-Thât, L

    2014-01-01

    Cavitation erosion is still one of the most important degradation modes in hydraulic turbine runners. Part of researches in this field focuses on finding new materials, coatings and surface treatments to improve the resistance properties of runners to this phenomenon. However, only few studies are focused on the deleterious effect of the environment. Actually, in some cases a synergistic effect between cavitation erosion mechanisms and corrosion kinetics can establish and increase erosion rate. In the present study, the cavitation erosion-corrosion behaviour of ASTM A27 steel in natural river water is investigated. This paper state the approach which has been used to enlighten the synergy between both phenomena. For this, a 20 kHz vibratory test according ASTM G32 standard is coupled to an electrochemical cell to be able to follow the different corrosion parameters during the tests to get evidence of the damaging mechanism. Moreover, mass losses have been followed during the exposure time. The classical degradation parameters (cumulative weight loss and erosion rate) are determined. Furthermore, a particular effort has been implemented to determine the evolution of surface damages in terms of pitting, surface cracking, material removal and surface corrosion. For this, scanning electron microscopy has been used to link the microstructure to the material removal mechanisms

  12. Weldability examination of ASTM A 240 S41500 martensitic stainless steel by thermal cycles simulation testings

    Directory of Open Access Journals (Sweden)

    Alberto Velázquez-del Rosario

    2015-07-01

    Full Text Available The weldability assets of ASTM A 240 S41500 (ASTM A 240/A 240M martensitic stainless steel are presented through the study of the effects of single and double thermal weld cycles on mechanical properties and microstructure of base metal (BM and the artificial heat affected zone (HAZ created by thermal weld simulations. For single cycles, separate peak temperatures of 1000 ºC/12 s and 1350 ºC/12 s (cooling times: 12 s in both cases were evaluated, whilst two combinations of peak temperatures: (1350 ºC/5 s + 1000 ºC/5 s ºC and (1350 ºC/12 s + 1000 ºC/12 s ºC (cooling times: 5 s and 12 s, were applied for double cycles. Post weld heat treatment (PWHT with short and long holding times were applied and Vickers hardness, impact toughness and metallographic examinations were used in order to assess mechanical and metallographic properties in the as-simulated (no heat treated and postweld heat treated conditions. Best properties of the welded joint for double thermal weld cycles with long holding times were reached, which reveals the good weldability and applicability of the tested material in post weld heat treated conditions.

  13. Chronic ankle pain and fibrosis successfully treated with a new noninvasive augmented soft tissue mobilization technique (ASTM): a case report.

    Science.gov (United States)

    Melham, T J; Sevier, T L; Malnofski, M J; Wilson, J K; Helfst, R H

    1998-06-01

    This clinical case report demonstrates the clinical effectiveness of a new form of soft tissue mobilization in the treatment of excessive connective tissue fibrosis (scar tissue) around an athlete's injured ankle. The scar tissue was causing the athlete to have pain with activity, pain on palpation of the ankle, decreased range of motion, and loss of function. Surgery and several months of conventional physical therapy failed to alleviate the athlete's symptoms. As a final resort, augmented soft tissue mobilization (ASTM) was administered. ASTM is an alternative nonsurgical treatment modality that is being researched at Performance Dynamics (Muncip, IN). ASTM is a process that uses ergonomically designed instruments that assist therapists in the rapid localization and effective treatment of areas exhibiting excessive soft tissue fibrosis. This is followed by a stretching and strengthening program. Upon the completion of 6 wk of ASTM therapy, the athlete had no pain and had regained full range of motion and function. This case report is an example of how a noninvasive augmented form of soft tissue mobilization (ASTM) demonstrated impressive clinical results in treating a condition caused by connective tissue fibrosis.

  14. The role of the American Society for Testing and Materials (ASTM) in providing standards to support reliability technology for nuclear power plants

    International Nuclear Information System (INIS)

    Steele, L.E.

    1978-01-01

    ASTM is an international society for managing the development of standards on characteristics and performance of materials, products, systems and services and the promotion of related knowledge. This paper provides on overview of ASTM, emphasizing its contribution to nuclear systems reliability. In so doing, the author, from his perspective as chairman of ASTM committee E 10 on ''Nuclear Applications and the Measurement of Radiation Effects and the Committee on Standards'', illustrates ASTM contributions to the understanding and control of radiation embrittlement of light-water reactor pressure vessels. Four major related taks are summarized and pertinent standards identified. These include: (1) surveillance practice (5 standards), (2) neutron dosimetry (8 standards), (3) specification for steels for nuclear service (7 standards) and (4) basic guidelines for thermal annealing to correct radiation embrittlement (1 standard). This illustration, a specific accomplishment using ASTM standards, is cited within the context of the broader nuclear-related activities of ASTM. (author)

  15. Microstructural and Material Quality Effects on Rolling Contact Fatigue of Highly Elastic Intermetallic Ball Bearings

    Science.gov (United States)

    DellaCorte, Christopher; Howard, S. Adam; Thomas, Fransua; Stanford, Malcolm K.

    2016-01-01

    Rolling element bearings made from highly-elastic intermetallic materials (HIM)s, such as 60NiTi, are under development for applications that require superior corrosion and shock resistance. Compared to steel, intermetallics have been shown to have much lower rolling contact fatigue (RCF) stress capability in simplified 3-ball on rod (ASTM STP 771) fatigue tests. In the 3-ball tests, poor material quality and microstructural flaws negatively affect fatigue life but such relationships have not been established for full-scale 60NiTi bearings. In this paper, 3-ball-on-rod fatigue behavior of two quality grades of 60NiTi are compared to the fatigue life of full-scale 50mm bore ball bearings made from the same materials. 60NiTi RCF rods with material or microstructural flaws suffered from infant mortality failures at all tested stress levels while high quality 60NiTi rods exhibited no failures at lower stress levels. Similarly, tests of full-scale bearings made from flawed materials exhibited early surface fatigue and through crack type failures while bearings made from high quality material did not fail even in long-term tests. Though the full-scale bearing test data is yet preliminary, the results suggest that the simplified RCF test is a good qualitative predictor of bearing performance. These results provide guidance for materials development and to establish minimum quality levels required for successful bearing operation and life.

  16. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Brøndsted, Povl

    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...

  17. Clinical neurophysiology of fatigue.

    NARCIS (Netherlands)

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

    2008-01-01

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

  18. Metabolomic markers of fatigue: Association between circulating metabolome and fatigue in women with chronic widespread pain.

    Science.gov (United States)

    Freidin, Maxim B; Wells, Helena R R; Potter, Tilly; Livshits, Gregory; Menni, Cristina; Williams, Frances M K

    2018-02-01

    Fatigue is a sensation of unbearable tiredness that frequently accompanies chronic widespread musculoskeletal pain (CWP) and inflammatory joint disease. Its mechanisms are poorly understood and there is a lack of effective biomarkers for diagnosis and onset prediction. We studied the circulating metabolome in a population sample characterised for CWP to identify biomarkers showing specificity for fatigue. Untargeted metabolomic profiling was conducted on fasting plasma and serum samples of 1106 females with and without CWP from the TwinsUK cohort. Linear mixed-effects models accounting for covariates were used to determine relationships between fatigue and metabolites. Receiver operating curve (ROC)-analysis was used to determine predictive value of metabolites for fatigue. While no association between fatigue and metabolites was identified in twins without CWP (n=711), in participants with CWP (n=395), levels of eicosapentaenoate (EPA) ω-3 fatty acid were significantly reduced in those with fatigue (β=-0.452±0.116; p=1.2×10 -4 ). A significant association between fatigue and two other metabolites also emerged when BMI was excluded from the model: 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), and C-glycosyltryptophan (p=1.5×10 -4 and p=3.1×10 -4 , respectively). ROC analysis has identified a combination of 15 circulating metabolites with good predictive potential for fatigue in CWP (AUC=75%; 95% CI 69-80%). The results of this agnostic metabolomics screening show that fatigue is metabolically distinct from CWP, and is associated with a decrease in circulating levels of EPA. Our panel of circulating metabolites provides the starting point for a diagnostic test for fatigue in CWP. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  19. 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

  20. Examining fatigue in COPD

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  1. Using endogenous saccades to characterize fatigue in multiple sclerosis.

    Science.gov (United States)

    Ferreira, Marisa; Pereira, Paulo A; Parreira, Marta; Sousa, Inês; Figueiredo, José; Cerqueira, João J; Macedo, Antonio F

    2017-05-01

    Multiple Sclerosis (MS) is likely to cause dysfunction of neural circuits between brain regions increasing brain working load or a subjective overestimation of such working load leading to fatigue symptoms. The aim of this study was to investigate if saccades can reveal the effect of fatigue in patients with MS. Patients diagnosed with MS (EDSSendogenous generated saccade paradigm (valid and invalid trials). The fatigue severity scale (FSS) was used to assess the severity of fatigue. FSS scores were used to define two subgroups, the MS fatigue group (score above normal range) and the MS non-fatigue. Differences between groups were tested using linear mixed models. Thirty-one MS patients and equal number of controls participated in this study. FSS scores were above the normal range in 11 patients. Differences in saccade latency were found according to group (p<0.001) and trial validity (p=0.023). Differences were 16.9ms, between MS fatigue and MS non-fatigue, 15.5ms between MS fatigue and control. The mean difference between valid and invalid trials was 7.5ms. Differences in saccade peak velocity were found according to group (p<0.001), the difference between MS fatigue and control was 22.3°/s and between MS fatigue and non-fatigue was 12.3°/s. Group was a statistically significant predictor for amplitude (p<0.001). FSS scores were correlated with peak velocity (p=0.028) and amplitude (p=0.019). Consistent with the initial hypothesis, our study revealed altered saccade latency, peak velocity and amplitude in patients with fatigue symptoms. Eye movement testing can complement the standard inventories when investigating fatigue because they do not share similar limitations. Our findings contribute to the understanding of functional changes induced by MS and might be useful for clinical trials and treatment decisions. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. 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...

  3. 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...

  4. Rutin, a flavonoid and principal component of saussurea involucrata, attenuates physical fatigue in a forced swimming mouse model.

    Science.gov (United States)

    Su, Kang-Yi; Yu, Chao Yuan; Chen, Yue-Wen; Huang, Yi-Tsau; Chen, Chun-Ting; Wu, Hsueh-Fu; Chen, Yi-Lin Sophia

    2014-01-01

    This study investigated the antifatigue effects of rutin, a flavonoid extracted from the ethyl acetate extract of S. involucrata. Mice were subjected to a weight-loaded forced swim test (WFST) on alternate days for 3 wk. Rutin was administered orally to the mice for 7 days in dosages of 15, 30, and 60 mg/kg body weight, and several biomarkers of physical fatigue were evaluated: swimming time, change in body weight, lipid peroxidation, lactic acid (LA), glycogen, and the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx). On Day 7, the rutin-treated mice had a 3-fold longer exhaustive swimming time than the control mice, as well as significantly reduced blood LA concentrations. The 15, 30, and 60 mg/kg body weight rutin-supplemented groups displayed 11.2%, 22.5%, and 37.7% reduced malondialdehyde (MDA) concentrations, respectively, in brain and muscle tissues compared with the control exercised group. Our results indicated that the administration of rutin protected the mice against the depletion of SOD and GPx activities significantly. Following 7 days of rutin treatment, we sacrificed the mice and analyzed their soleus muscle and brain for peroxisome proliferator-activated receptor-α coactivator (PGC-1α) and sirtuin 1 (SIRT1) mRNA expression. We observed that rutin treatment increased PGC-1α and SIRT1 mRNA and protein expression. The changes in these markers of mitochondrial biogenesis were associated with increased maximal endurance capacity. The application of 2D gel electrophoresis to analyze the rutin-responsive protein profiles in the WFST mouse brain further revealed the upregulation of the CB1 cannabinoid receptor-interacting protein 1, myelin basic protein, Rho GDP dissociation inhibitor (GDI) alpha, and TPI, indicating that rutin might inhibit anxiety through the upregulation of the expression of anxiety-associated proteins. Western blot analysis of MAPK expression further confirmed the antianxiety effects

  5. Modeling of the fatigue damage accumulation processes in the material of NPP design units under thermomechanical unstationary effects. Estimation of spent life and forecast of residual life

    International Nuclear Information System (INIS)

    Kiriushin, A.I.; Korotkikh, Yu.G.; Gorodov, G.F.

    2002-01-01

    Full text: The estimation problems of spent life and forecast of residual life of NPP equipment design units, operated at unstationary thermal force loads are considered. These loads are, as a rule, unregular and cause rotation of main stress tensor platforms of the most loaded zones of structural elements and viscoelastic plastic deformation of material in the places of stresses concentrations. The existing engineering approaches to the damages accumulation processes calculation in the material of structural units, their advantages and disadvantages are analyzed. For the processes of fatigue damages accumulation a model is proposed, which allows to take into account the unregular pattern of deformation multiaxiality of stressed state, rotation of main platforms, non-linear summation of damages at the loading mode change. The model in based on the equations of damaged medium mechanics, including the equations of viscoplastic deformation of the material and evolutionary equations of damages accumulation. The algorithms of spent life estimation and residual life forecast of the controlled equipment and systems zones are made on the bases of the given model by the known real history of loading, which is determined by real model of NPP operation. The results of numerical experiments on the basis of given model for various processes of thermal force loads and their comparison with experimental results are presented. (author)

  6. Computed tomographic imaging of subchondral fatigue cracks in the distal end of the third metacarpal bone in the thoroughbred racehorse can predict crack micromotion in an ex-vivo model.

    Directory of Open Access Journals (Sweden)

    Marie-Soleil Dubois

    Full Text Available Articular stress fracture arising from the distal end of the third metacarpal bone (MC3 is a common serious injury in Thoroughbred racehorses. Currently, there is no method for predicting fracture risk clinically. We describe an ex-vivo biomechanical model in which we measured subchondral crack micromotion under compressive loading that modeled high speed running. Using this model, we determined the relationship between subchondral crack dimensions measured using computed tomography (CT and crack micromotion. Thoracic limbs from 40 Thoroughbred racehorses that had sustained a catastrophic injury were studied. Limbs were radiographed and examined using CT. Parasagittal subchondral fatigue crack dimensions were measured on CT images using image analysis software. MC3 bones with fatigue cracks were tested using five cycles of compressive loading at -7,500N (38 condyles, 18 horses. Crack motion was recorded using an extensometer. Mechanical testing was validated using bones with 3 mm and 5 mm deep parasagittal subchondral slots that modeled naturally occurring fatigue cracks. After testing, subchondral crack density was determined histologically. Creation of parasagittal subchondral slots induced significant micromotion during loading (p<0.001. In our biomechanical model, we found a significant positive correlation between extensometer micromotion and parasagittal crack area derived from reconstructed CT images (SR = 0.32, p<0.05. Correlations with transverse and frontal plane crack lengths were not significant. Histologic fatigue damage was not significantly correlated with crack dimensions determined by CT or extensometer micromotion. Bones with parasagittal crack area measurements above 30 mm2 may have a high risk of crack propagation and condylar fracture in vivo because of crack micromotion. In conclusion, our results suggest that CT could be used to quantify subchondral fatigue crack dimensions in racing Thoroughbred horses in-vivo to

  7. Summary: Update to ASTM guide E 1523 to charge control and charge referencing techniques in x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Baer, D.R.

    2005-01-01

    An updated version of the American Society for Testing and Materials (ASTM) guide E 1523 to the methods to charge control and charge referencing techniques in x-ray photoelectron spectroscopy has been released by ASTM [Annual Book of ASTM Standards Surface Analysis (American Society for Testing and Materials, West Conshohocken, PA, 2004), Vol. 03.06]. The guide is meant to acquaint x-ray photoelectron spectroscopy (XPS) users with the various charge control and charge referencing techniques that are and have been used in the acquisition and interpretation of XPS data from surfaces of insulating specimens. The current guide has been expanded to include new references as well as recommendations for reporting information on charge control and charge referencing. The previous version of the document had been published in 1997 [D. R. Baer and K. D. Bomben, J. Vac. Sci. Technol. A 16, 754 (1998)

  8. Probabilistic Analysis for Comparing Fatigue Data Based on Johnson-Weibull Parameters

    Science.gov (United States)

    Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.

    2013-01-01

    Leonard Johnson published a methodology for establishing the confidence that two populations of data are different. Johnson's methodology is dependent on limited combinations of test parameters (Weibull slope, mean life ratio, and degrees of freedom) and a set of complex mathematical equations. In this report, a simplified algebraic equation for confidence numbers is derived based on the original work of Johnson. The confidence numbers calculated with this equation are compared to those obtained graphically by Johnson. Using the ratios of mean life, the resultant values of confidence numbers at the 99 percent level deviate less than 1 percent from those of Johnson. At a 90 percent confidence level, the calculated values differ between +2 and 4 percent. The simplified equation is used to rank the experimental lives of three aluminum alloys (AL 2024, AL 6061, and AL 7075), each tested at three stress levels in rotating beam fatigue, analyzed using the Johnson- Weibull method, and compared to the ASTM Standard (E739 91) method of comparison. The ASTM Standard did not statistically distinguish between AL 6061 and AL 7075. However, it is possible to rank the fatigue lives of different materials with a reasonable degree of statistical certainty based on combined confidence numbers using the Johnson- Weibull analysis. AL 2024 was found to have the longest fatigue life, followed by AL 7075, and then AL 6061. The ASTM Standard and the Johnson-Weibull analysis result in the same stress-life exponent p for each of the three aluminum alloys at the median, or L(sub 50), lives

  9. Nanoscale and submicron fatigue crack growth in nickel microbeams

    International Nuclear Information System (INIS)

    Yang, Y.; Yao, N.; Imasogie, B.; Soboyejo, W.O.

    2007-01-01

    This paper presents a novel edge-notched microbeam technique for the study of short fatigue crack growth. The technique is used to study submicron and nanoscale fatigue in LIGA Ni thin films with columnar microstructures. The edge-notched microbeams were fabricated within LIGA Ni thin films, using focused ion beam (FIB) techniques. The microbeams were then cyclically deformed to failure at a stress ratio of 0.1. Different slip-band structures were observed below the nanoscale notches. Cyclic deformation resulted in the formation of primary slip bands below the notch. Subsequent crack growth then occurred by the unzipping of fatigue cracks along intersecting slip bands. The effects of the primary slip bands were idealized using dislocation-based models. These were used to estimate the intrinsic fatigue threshold and the fatigue endurance limit. The estimates from the model are shown to be consistent with experimental data from prior stress-life experiments and current/prior fatigue threshold estimates

  10. 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

  11. White Paper Summary of 2nd ASTM International Workshop on Hydrides in Zirconium Alloy Cladding

    Energy Technology Data Exchange (ETDEWEB)

    Sindelar, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Louthan, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); PNNL, B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-05-29

    This white paper recommends that ASTM International develop standards to address the potential impact of hydrides on the long term performance of irradiated zirconium alloys. The need for such standards was apparent during the 2nd ASTM International Workshop on Hydrides in Zirconium Alloy Cladding and Assembly Components, sponsored by ASTM International Committee C26.13 and held on June 10-12, 2014, in Jackson, Wyoming. The potentially adverse impacts of hydrogen and hydrides on the long term performance of irradiated zirconium-alloy cladding on used fuel were shown to depend on multiple factors such as alloy chemistry and processing, irradiation and post irradiation history, residual and applied stresses and stress states, and the service environment. These factors determine the hydrogen content and hydride morphology in the alloy, which, in turn, influence the response of the alloy to the thermo-mechanical conditions imposed (and anticipated) during storage, transport and disposal of used nuclear fuel. Workshop presentations and discussions showed that although hydrogen/hydride induced degradation of zirconium alloys may be of concern, the potential for occurrence and the extent of anticipated degradation vary throughout the nuclear industry because of the variations in hydrogen content, hydride morphology, alloy chemistry and irradiation conditions. The tools and techniques used to characterize hydrides and hydride morphologies and their impacts on material performance also vary. Such variations make site-to-site comparisons of test results and observations difficult. There is no consensus that a single material or system characteristic (e.g., reactor type, burnup, hydrogen content, end-of life stress, alloy type, drying temperature, etc.) is an effective predictor of material response during long term storage or of performance after long term storage. Multi-variable correlations made for one alloy may not represent the behavior of another alloy exposed to

  12. 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

  13. Development of a Conceptual Etiological Model of Treatment Regimen Fatigue Among Patients Engaged in HIV Care: A Qualitative Study.

    Science.gov (United States)

    Claborn, Kasey; Miller, Mary Beth; Meier, Ellen; Carbone, Sofia

    Treatment regimen fatigue (TRF) is a decreased desire and motivation to maintain vigilance in adhering to treatment, and little is known about TRF in people living with HIV. We aimed to develop a conceptual framework of TRF. Five focus groups were conducted in 2014. Eligible participants were (a) HIV infected, (b) at least 18 years of age, (c) prescribed antiretroviral therapy, and (d) fluent in English. Data were analyzed using thematic analysis. Analyses revealed these themes: patient experiences of TRF; etiological factors at the systems, provider, and patient levels; strategies to manage TRF; consequences of TRF; and protective factors that prevent the occurrence of TRF. The results provided a conceptual framework for future investigations to build on in an effort to improve adherence and retention in HIV care. Study results indicate avenues for intervention at multiple levels (systems, provider, and patient) to reduce treatment burden and improve patient resources and capacity. Copyright © 2017 Association of Nurses in AIDS Care. Published by Elsevier Inc. All rights reserved.

  14. Mesoscopic scale thermal fatigue damage

    International Nuclear Information System (INIS)

    Robertson, C.; Fissolo, A.; Fivel, M.

    2001-01-01

    In an attempt to better understand damage accumulation mechanisms in thermal fatigue, dislocation substructures forming in 316L steel during one specific test were examined and simulated. Hence, thin foils taken out of massive, tested specimens were first observed in transmission electron microscopy (TEM). These observations help in determining one initial dislocation configuration to be implemented in a 3-D model combining 3D discrete dislocation dynamics simulation (DDD) and finite element method computations (FEM). It was found that the simulated mechanical behaviour of the DDD microstructure is compatible with FEM and experimental data. The numerically generated dislocation microstructure is similar to ladder-like dislocation arrangements as found in many fatigued f.c.c. materials. Distinct mechanical behaviour for the two active slip systems was shown and deformation mechanisms were proposed. (authors)

  15. Mesoscopic scale thermal fatigue damage

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, C.; Fissolo, A. [CEA Saclay, Dept. des Materiaux pour le Nucleaire, DMN, 91 - Gif sur Yvette (France); Fivel, M. [Centre National de la Recherche Scientifique, CNRS-GPM2, 38 - Saint Martin d' Heres (France)

    2001-07-01

    In an attempt to better understand damage accumulation mechanisms in thermal fatigue, dislocation substructures forming in 316L steel during one specific test were examined and simulated. Hence, thin foils taken out of massive, tested specimens were first observed in transmission electron microscopy (TEM). These observations help in determining one initial dislocation configuration to be implemented in a 3-D model combining 3D discrete dislocation dynamics simulation (DDD) and finite element method computations (FEM). It was found that the simulated mechanical behaviour of the DDD microstructure is compatible with FEM and experimental data. The numerically generated dislocation microstructure is similar to ladder-like dislocation arrangements as found in many fatigued f.c.c. materials. Distinct mechanical behaviour for the two active slip systems was shown and deformation mechanisms were proposed. (authors)

  16. 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

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

    Directory of Open Access Journals (Sweden)

    Sergio Márquez-Domínguez

    2012-06-01

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

  18. Hardness optimization of boride diffusion layer on Astm F-75 alloy using response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Arguelles O, J. L.; Corona R, M. A. [Universidad Autonoma de San Luis Potosi, Doctorado Institucional en Ingenieria y Ciencia de Materiales, San Luis Potosi 78000, SLP (Mexico); Marquez H, A.; Saldana R, A. L.; Saldana R, A. [Universidad de Guanajuato, Ingenieria Mecanica Agricola DICIVA, Irapuato, Guanajuato 36500 (Mexico); Moreno P, J., E-mail: amarquez@ugto.mx [Universidad de Guanajuato, Departamento de Minas, Metalurgia y Geologia, Ex-Hacienda San Matias s/n, Guanajuato, Guanajuato 36020 (Mexico)

    2017-11-01

    In this study, the Response Surface Methodology (Rsm) and Central Composite Design (Ccd) were used to optimize the hardness of boride diffusion layer on Astm F-75 alloy (also called Haynes alloy). A boronizing thermochemical treatment was carried out at different temperatures and for different time periods. Hardness tests were conducted. The boride diffusion layer was verified by the X-ray diffraction (XRD) analysis indicating the formation of Co B, Co{sub 2}B, Cr B and Mo{sub 2}B phases. An optimal hardness of 3139.7 Hv was obtained for the samples subjected to the boriding process for a duration of 6.86 h at 802.4 degrees Celsius. (Author)

  19. Corrosion resistance and microstructure of alloy 625 weld overlay on ASTM A516 grade 70

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Mohammad J. [Amirkabir Univ. of Technology, Tehran (Iran, Islamic Republic of). Petroleum Engineering Dept.; Ketabchi, Mostafa [Amirkabir Univ. of Technology, Tehran (Iran, Islamic Republic of). Mining and Metallurgical Engineering Dept.

    2016-02-01

    Nickel-based alloys are a crucial class of materials because of their excellent corrosion resistance. In the present study, single layer and two layers alloy 625 weld overlays were deposited by GTAW process on A516 grade 70 carbon steel. The dilution in terms of Fe, Ni, Mo and Nb content was calculated in 30 points of weld overlay. Microstructure observations showed that alloy 625 had austenitic structure with two types of Laves and NbC secondary phases. The uniform and pitting corrosion resistance of alloy 625 weld overlay as casted and as forged were evaluated in accordance with ASTM G48-2011 standard at different temperatures to determine the weight loss and critical pitting temperature. For achieving a better comparison, samples from alloy 625 as casted and as forged were tested under the same conditions. The results point out that single layer alloy 625 weld overlay is not suitable for chloride containing environments, two layers alloy 625 weld overlay and alloy 625 as casted have acceptable corrosion resistance and almost the same critical pitting temperature. Alloy 625 as forged has the best corrosion resistance and the highest critical pitting temperature among all test specimens. Also, the corrosion behavior was evaluated in accordance with ASTM G28 standard. The corrosion rate of single layer weld overlay was unacceptable. The average corrosion rate of two layers weld overlay and in casted condition were 35.82 and 33.01 mpy, respectively. [German] Nickellegierungen sind aufgrund ihres exzellenten Korrosionswiderstandes eine bedeutende Werkstoffklasse. In der diesem Beitrag zugrunde liegenden Studie wurden mittels WIG-Schweissens ein- und zweilagige Schweissplattierungen auf den Kohlenstoffstahl A516 (Grade 70) aufgebracht. Die Vermischung in Form des Fe-, Ni-, Mo- und Nb-Gehaltes wurde an 30 Punkten der Schweissplattierungen berechnet. Die mikrostrukturellen Untersuchungen ergaben, dass die Legierung 625 eine austenitische Struktur mit zwei Arten von

  20. Comparisons of ASTM standards cited in the NRC standard review plan, NUREG-0800 and related documents

    International Nuclear Information System (INIS)

    Ankrum, A.R.; Bohlander, K.L.; Gilbert, E.R.; Pawlowski, R.A.; Spiesman, J.B.

    1995-10-01

    This report provides the results of comparisons of the cited and latest versions of ASTM standards cited in the NRC Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants (NUREG 0800) and related documents. The comparisons were performed by Battelle Pacific Northwest Laboratories in support of the NRC's Standard Review Plan Update and Development Program. Significant changes to the standards, from the cited version to the latest version, are described and discussed in a tabular format for each standard. Recommendations for updating each citation in the Standard Review Plan are presented. Technical considerations and suggested changes are included for related regulatory documents (i.e., Regulatory Guides and the Code of Federal Regulations) citing the standard. The results and recommendations presented in this document have not been subjected to NRC staff review

  1. Comparative study between EDXRF and ASTM E572 methods using two-way ANOVA

    Science.gov (United States)

    Krummenauer, A.; Veit, H. M.; Zoppas-Ferreira, J.

    2018-03-01

    Comparison with reference method is one of the necessary requirements for the validation of non-standard methods. This comparison was made using the experiment planning technique with two-way ANOVA. In ANOVA, the results obtained using the EDXRF method, to be validated, were compared with the results obtained using the ASTM E572-13 standard test method. Fisher's tests (F-test) were used to comparative study between of the elements: molybdenum, niobium, copper, nickel, manganese, chromium and vanadium. All F-tests of the elements indicate that the null hypothesis (Ho) has not been rejected. As a result, there is no significant difference between the methods compared. Therefore, according to this study, it is concluded that the EDXRF method was approved in this method comparison requirement.

  2. ASTM and VAMAS activities in titanium matrix composites test methods development

    Science.gov (United States)

    Johnson, W. S.; Harmon, D. M.; Bartolotta, P. A.; Russ, S. M.

    1994-01-01

    Titanium matrix composites (TMC's) are being considered for a number of aerospace applications ranging from high performance engine components to airframe structures in areas that require high stiffness to weight ratios at temperatures up to 400 C. TMC's exhibit unique mechanical behavior due to fiber-matrix interface failures, matrix cracks bridged by fibers, thermo-viscoplastic behavior of the matrix at elevated temperatures, and the development of significant thermal residual stresses in the composite due to fabrication. Standard testing methodology must be developed to reflect the uniqueness of this type of material systems. The purpose of this paper is to review the current activities in ASTM and Versailles Project on Advanced Materials and Standards (VAMAS) that are directed toward the development of standard test methodology for titanium matrix composites.

  3. Heat treatment evaluation of steel ASTM A-131 grade A by X-Ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira Junior, Francisco; Feio, Luciana Gaspar; Costa, Ednelson Silva; Rodrigues, Lino Alberto Soares; Braga, Eduardo Magalhaes, E-mail: juniorferrer93@gmail.com [Universidade Federal do Pará (UFPA), Belém, PA (Brazil)

    2016-07-01

    Full text: This study evaluates the residual stress of naval steel ASTM A-131 grade A before and after heat treatment. Residual stresses were determined by the technique of X-ray diffraction (XRD). Before heat treatment the residual stress measurements were made at 36 (thirty six) points distributed in a specimen with dimensions of 400 mm long, 200 mm wide and 95 mm thick, then the plate under analysis was brought to the oven for the implementation of heat treatment. To check the performance of the heat treatment, the plate was again subjected to XRD measurements of the same points previously measured in order to compare the residual stresses. As result, there was a reduction of residual stresses with the application of heat treatment. References: [1] COLPAERT, H. Metalografia dos Produtos Siderurgicos Comuns. 4 Edição. Editora Blucher. Saõ Paulo, SP, 2008. [2] HILL, R. Princípios de Metalurgia Física, 1992. (author)

  4. Designing cathodic protection systems for marine structures and vehicles. ASTM special technical publication 1370

    Energy Technology Data Exchange (ETDEWEB)

    Hack, H.P. [ed.

    1999-07-01

    Cathodic protection is an important method of protecting structures and ships from the corrosive effects of seawater. Poor designs can be far more costly to implement than optimal designs, Improper design can cause overprotection, with resulting paint blistering and accelerated corrosion of some alloys, underprotection, with resultant structure corrosion, or stray current corrosion of nearby structures. The first ASTM symposium specifically aimed at cathodic protection in seawater was intended to compile all the criteria and philosophy for designing both sacrificial and impressed current cathodic protection systems for structures and vehicles in seawater. The papers which are included in this STP are significant in that they summarize the major seawater cathodic protection system design philosophies. Papers have been processed separately for inclusion on the database.

  5. Phases Evolution of an ASTM 335 steel under continuous cooling P91

    International Nuclear Information System (INIS)

    Carrizo, D.A; Danon, C.A; Ramos, C.P

    2012-01-01

    This paper studies the influence of the cooling rate on phase transformations and the resulting microstructure in continuous cooling cycles for an ASTM A335 P91 steel, under fixed austenization conditions. The CCT (Continuous Cooling Transformation) diagram of this material is reported in the literature, so the main phase fields are known. The final structure of the samples depends on the austenitic grain size and the cooling rate. The studied samples were austenized at 1050 o C for 30 minutes and then cooled at different rates between 50 o C/h and 300 o C/h. The identification and characterization of the phases was carried out by using Scanning Electron Microscopy, X-ray Diffraction and Moessbauer Spectroscopy. From the results so obtained, additions to the CCT diagram of the material are proposed, providing new information to it

  6. Corrosion resistant properties and weldabilities of ASTM Grade 12 titanium alloy

    International Nuclear Information System (INIS)

    Tsumori, Yoshikatsu; Itoh, Hideo

    1988-01-01

    Plates, sheets, bars, wires and thinner seam-welded tubings were manufactured from large-scaled ingot of ASTM Grade 12 alloy (Ti-0.8Ni-0.3Mo). The processability of G-12 alloy has proved almost similar to that of conventional commercially pure titanium grades. It has been clarified that the G-12 alloy showed several advantageous features: Chlorides-Crevice corrosion resistance of the alloy was almost equals to G-7 and Pd0/TiO 2 coated titanium, and the maximum allowable stress was able to be designed higher than that of commercially pure titanium. This alloy has been in applications also offers where such environments as seawater, brines and moist chlorine, various oil refinery and chemical industries, and others. (author)

  7. Effects of heat treatment to the sound velocity and microstructural changes of ASTM A516 steels

    International Nuclear Information System (INIS)

    Norasiah Abdul Kasim; Azali Muhammad; Amry Amin Abas; Zaiton Selamat

    2010-01-01

    Full-text: The used of ultrasonic testing as a thickness measurement for structural components (pipeline and pressure vessel) is among the popular inspection tool widely use in the industrial power plant such as at petrochemical and nuclear power plant. Currently, there are cases where the thickness grows and the result will affect the reliability of the test. There are many factors that can affect the reliability of measurement. One of it is the material under test itself. In the Malaysian Nuclear Agency, initial efforts are underway to study the understanding on the effects of heat treatment to the sound velocity and microstructure changes of ASTM A516 steel. Few samples of thin square shaped prepared were heat treated under the following conditions: austenitization at 9800 degree Celsius - 2 hours, quenching; tempering at various temperature 4000, 5000, 6000 and 7000 degree Celsius. The results show that the microstructure changes and samples exhibit different sound velocity at different heat treatment. (author)

  8. Microstructure evolution of ASTM 335 P91 steel, subjected to continuous cooling

    International Nuclear Information System (INIS)

    Carrizo, D.A; Danon, C.A; Ramos, C.P

    2012-01-01

    This paper studies the influence of the cooling rate on an isothermal phase transformations in ASTM A335 P91 steel, by the analysis of the resulting microstructure after several continuous cooling cycles under fixed austenization conditions. The CCT (Continuous Cooling Transformation) diagram of this material has already been reported in the literature, so the main phase fields are known, and they depend on the austenitic grain size and the cooling rate. Five samples were tested in a dilatometer, they were austenized and then cooled at different rates between 50 o C/h and 300 o C/h. The identification and characterization of the resulting phases was carried out by using Scanning Electron Microscopy, X-ray Diffraction and Mossbauer Spectroscopy. The obtained results allowed to add information about the presence of retained austenite and (Fe,Cr) 3 C - type carbides to the CCT diagram of the material (author)

  9. Multiaxial creep-fatigue rules

    International Nuclear Information System (INIS)

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

    1997-01-01

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

  10. Determination of ASTM 1016 structural welded joints fracture toughness through J integral

    International Nuclear Information System (INIS)

    Martins, Geraldo de Paula; Villela, Jefferson Jose; Terra, Jose Lucio; Rabello, Emerson Giovani; Martins, Geraldo Antonio Scoralick; Carneiro, Jose Rubens Goncalves

    2009-01-01

    Fracture toughness is an important parameter for studies of materials behavior in nuclear and conventional industry. Crack propagation resistance is, in general, evaluate using one of the fracture mechanics parameters K IC , for the case of the materials that exhibits a linear elastic behavior, the CTOD (crack tip opening displacement) and J IC , the critical value of J Integral, for the case of materials with elastic-plastic behavior. On this work the fracture mechanics parameters of the ASTM 1016 structural steel welded joints were obtained, using the J Integral. Charpy V tests at several temperatures were also obtained, with the purpose to obtain the curves of ductile-brittle of the regions of the welded joints: Base Metal, (MB), and Melted Zone (MZ). The joints were welded by Gas Metal Arc Welding (GMAW) with V bevel for evaluation the MZ toughness properties. The tests were accomplished at temperatures varying from -100 deg C to 100 deg C using the technical of compliance variation for J IC determination, the critical value that defines the initial stable crack growth, that applies to brittle and ductile materials. The J Integral alternative specimens has square cross section 10mmX10mm, according ASTM E 1820, with notch localized respectively at the BM and MZ. After the tests, the specimens fractured were analyzed in a scanning microscopic electronic (SME) for verification of the fracture surface. The fractography of the specimens at elevated temperatures presented dimples at the region of stable crack growth, characteristic of ductile fracture. The results of J Integral and Charpy V presented a good correlation between these two parameters. From these correlations it can be concluded that in some applications, the use Charpy V energy to infer fracture toughness can be substitute the Integral J tests. (author)

  11. Probabilistic fatigue life prediction methodology for notched components based on simple smooth fatigue tests

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. R.; Li, Z. X. [Dept.of Engineering Mechanics, Jiangsu Key Laboratory of Engineering Mechanics, Southeast University, Nanjing (China); Hu, X. T.; Xin, P. P.; Song, Y. D. [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing (China)

    2017-01-15

    The methodology of probabilistic fatigue life prediction for notched components based on smooth specimens is presented. Weakestlink theory incorporating Walker strain model has been utilized in this approach. The effects of stress ratio and stress gradient have been considered. Weibull distribution and median rank estimator are used to describe fatigue statistics. Fatigue tests under different stress ratios were conducted on smooth and notched specimens of titanium alloy TC-1-1. The proposed procedures were checked against the test data of TC-1-1 notched specimens. Prediction results of 50 % survival rate are all within a factor of two scatter band of the test results.

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

    International Nuclear Information System (INIS)

    Kawasaki, Nobuchika; Asayama, Tai

    2001-09-01

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

  13. 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.

  14. Oxidative stress and fatigue in systemic lupus erythematosus.

    Science.gov (United States)

    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.

  15. Fatigue Performance of Fiber Reinforced Concrete

    DEFF Research Database (Denmark)

    Jun, Zhang; Stang, Henrik

    1996-01-01

    The objective of the present study is to obtain basic data of fibre reinforced concrete under fatigue load and to set up a theoretical model based on micromechanics. In this study, the bridging stress in fiber reinforced concrete under cyclic tensile load was investigted in details. The damage...... mechanism of the interface between fiber and matrix was proposed and a rational model given. Finally, the response of a steel fiber reinforced concrete beam under fatigue loading was predicted based on this model and compared with experimental results....

  16. Insomnia and Fatigue

    Science.gov (United States)

    ... week at work or a busy day of hiking or chasing a toddler. Fatigue related to cancer ... Coworkers About Your Diagnosis Work Accommodations and Disability Benefits Offsetting the “Hidden Costs” of Breast Cancer Getting ...

  17. Brain Tumors and Fatigue

    Science.gov (United States)

    ... Subscribe for e-updates Please leave this field empty Fatigue SHARE Home > Treatment and Care > Side Effects ... take-out food tends to be high in calories, fat and sodium and low in energy-boosting ...

  18. 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...

  19. 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...

  20. Predicting Performance during Chronic Sleep Loss: Identification of Factors Sensitive to Individual Fatigue Resistance

    Science.gov (United States)

    2015-03-18

    fatigue-related performance impairments for a given schedule. However, these models fail to account for individual differences in fatigue susceptibility...Tool, FAST ™ ), yet these models fail to take into account important individual differences in fatigue states and susceptibility to fatigue. However...Venkatraman et al., 2007) and confusion ( Drury et al., 2012). However, sustained or continuous operations in high tempo, wartime operations often