WorldWideScience

Sample records for fatigue life methodology

  1. A comparison of fatigue life prediction methodologies for rotorcraft

    Science.gov (United States)

    Everett, R. A., Jr.

    1990-01-01

    Because of the current U.S. Army requirement that all new rotorcraft be designed to a 'six nines' reliability on fatigue life, this study was undertaken to assess the accuracy of the current safe life philosophy using the nominal stress Palmgrem-Miner linear cumulative damage rule to predict the fatigue life of rotorcraft dynamic components. It has been shown that this methodology can predict fatigue lives that differ from test lives by more than two orders of magnitude. A further objective of this work was to compare the accuracy of this methodology to another safe life method called the local strain approach as well as to a method which predicts fatigue life based solely on crack growth data. Spectrum fatigue tests were run on notched (k(sub t) = 3.2) specimens made of 4340 steel using the Felix/28 tests fairly well, being slightly on the unconservative side of the test data. The crack growth method, which is based on 'small crack' crack growth data and a crack-closure model, also predicted the fatigue lives very well with the predicted lives being slightly longer that the mean test lives but within the experimental scatter band. The crack growth model was also able to predict the change in test lives produced by the rainflow reconstructed spectra.

  2. A methodology to evaluate the fatigue life of flexible pipes

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, Fernando J.M. de; Sousa, Jose Renato M. de; Siqueira, Marcos Q. de; Sagrilo, Luis V.S. [Coordenacao dos Programas de Pos-graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Lemos, Carlos Alberto D. de [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

    2009-07-01

    This paper focus on a methodology to perform the fatigue analysis of flexible pipes. This methodology employs functions that convert forces and moments obtained in global analyses into stresses. The stresses are then processed by well-known cycle counting methods, and S-N curves evaluate the damage at several points in the pipe cross-section. Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A parametric study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers in the results, the importance of evaluating the fatigue life in various points of the pipe cross-section and the effect of different mean stress levels. The obtained results suggest that the consideration of friction effects strongly influences the fatigue life of flexible risers and these effects have to be accounted both in the global and local analyses of the riser. Moreover, mean stress effects are also significant and at least 8 equally spaced wires in each analyzed section of the riser must be considered in fatigue analyses. (author)

  3. Fatigue in high-speed aluminium craft: A design methodology for predicting the fatigue life

    NARCIS (Netherlands)

    Tuitman, J.T.; Hoogendoorn, D.

    2013-01-01

    Within the VOMAS project, a methodology has been developed to predict the fatigue life of high-speed aluminium crafts. This paper describes this methodology and its implementation into a computational tool. This methodology computes the seakeeping and resulting pressure at the structure for all cond

  4. Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams

    Science.gov (United States)

    urri, Gretchen B.; Schaff, Jeffery R.

    2006-01-01

    Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.

  5. Fatigue in high speed aluminium craft: Evaluating a design methodology for estimating the fatigue life using large scale tests and full scale trials

    NARCIS (Netherlands)

    Drummen, I.; Schiere, M.; Tuitman, J.T.

    2013-01-01

    Within the VOMAS project, a methodology has been developed to estimate the fatigue life of high-speed aluminium crafts. This paper presents the large scale test and full scale trials which were done to acquire data for evaluating the developed methodology and presents results of this evaluation. Dur

  6. A Methodology to Predict Uniform Material Fatigue Life of Cast Iron: Law for Cast Iron%A Methodology to Predict Uniform Material Fatigue Life of Cast Iron: Law for Cast Iron

    Institute of Scientific and Technical Information of China (English)

    Sinan Korkmaz

    2011-01-01

    Mechanical, physical and manufacturing properties of east iron make it attractive for many fields of application, such as cranks and cylinder holds. As in design of all metals, fatigue life prediction is an intrinsic part of the design process of structural sections that are made of cast iron. A methodology to predict high-cycle fatigue life of cast iron is proposed. Stress amplitude-strain amplitude, strain amplitude-number of loading cycles relationships of cast iron are investigated. Also, fatigue life prediction in terms of Smith, Watson and Topper parameter is carried out using the proposed method. Results indicate that the analytical outcomes of the proposed methodology are in good accordance with the experimental data for the two studied types of cast iron: EN-GJS-400 and EN-GJS-600.

  7. Life prediction methodology for thermal-mechanical fatigue and elevated temperature creep design

    Science.gov (United States)

    Annigeri, Ravindra

    Nickel-based superalloys are used for hot section components of gas turbine engines. Life prediction techniques are necessary to assess service damage in superalloy components resulting from thermal-mechanical fatigue (TMF) and elevated temperature creep. A new TMF life model based on continuum damage mechanics has been developed and applied to IN 738 LC substrate material with and without coating. The model also characterizes TMF failure in bulk NiCoCrAlY overlay and NiAl aluminide coatings. The inputs to the TMF life model are mechanical strain range, hold time, peak cycle temperatures and maximum stress measured from the stabilized or mid-life hysteresis loops. A viscoplastic model is used to predict the stress-strain hysteresis loops. A flow rule used in the viscoplastic model characterizes the inelastic strain rate as a function of the applied stress and a set of three internal stress variables known as back stress, drag stress and limit stress. Test results show that the viscoplastic model can reasonably predict time-dependent stress-strain response of the coated material and stress relaxation during hold times. In addition to the TMF life prediction methodology, a model has been developed to characterize the uniaxial and multiaxial creep behavior. An effective stress defined as the applied stress minus the back stress is used to characterize the creep recovery and primary creep behavior. The back stress has terms representing strain hardening, dynamic recovery and thermal recovery. Whenever the back stress is greater than the applied stress, the model predicts a negative creep rate observed during multiple stress and multiple temperature cyclic tests. The model also predicted the rupture time and the remaining life that are important for life assessment. The model has been applied to IN 738 LC, Mar-M247, bulk NiCoCrAlY overlay coating and 316 austenitic stainless steel. The proposed model predicts creep response with a reasonable accuracy for wide range of

  8. Fatigue life extension

    Science.gov (United States)

    Matejczyk, D. E.; Lin, J.

    1985-01-01

    Potential fatigue rejuvenation processes were carried out on fatigue-damaged material both with and without observable surface-connected fatigue cracks. The fatigue life of fatigue-damaged MAR-M246(Hf)(DS), a directionally solidified nickel-base superalloy used in turbine airfoils, was extended by reheat treatment. The fatigue life of fatigue-cracked Inconel 718, a wrought nickel-base superalloy used in a wide variety of advanced rocket engine components, was extended by electron-beam welding to close off the surface-connected crack, followed by hot isostatic pressing and reheat treatment.

  9. An all-in-one numerical methodology for fretting wear and fatigue life assessment

    Directory of Open Access Journals (Sweden)

    I. Llavori

    2016-07-01

    Full Text Available Many mechanical components such as, bearing housings, flexible couplings and spines or orthopedic devices are simultaneously subjected to a fretting wear and fatigue damage. For this reason, the combined study on a single model of wear, crack initiation and propagation is of great interest. This paper presents an all-in-one 2D cylinder on flat numerical model for life assessment on coupled fretting wear and fatigue phenomena. In the literature, two stages are usually distinguished: crack nucleation and its subsequent growth. The method combines the Archard wear model, a critical-plane implementation of the Smith-Watson- Topper (SWT multiaxial fatigue criterion coupled with the Miner-Palmgren accumulation damage rule for crack initiation prediction. Then, the Linear Elastic Fracture Mechanics (LEFM via eXtended Finite Element Method (X-FEM embedded into the commercial finite element code Abaqus FEA has been employed to determine the crack propagation stage. Therefore, the sum of the two stages gives a total life prediction. Finally, the numerical model was validated with experimental data reported in the literature and a good agreement was obtained.

  10. PROBABILISTIC METHODOLOGY OF LOW CYCLE FATIGUE ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    Jin Hui; Wang Jinnuo; Wang Libin

    2003-01-01

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

  11. Probabilistic fatigue methodology and wind turbine reliability

    Energy Technology Data Exchange (ETDEWEB)

    Lange, C.H. [Stanford Univ., CA (United States)

    1996-05-01

    Wind turbines subjected to highly irregular loadings due to wind, gravity, and gyroscopic effects are especially vulnerable to fatigue damage. The objective of this study is to develop and illustrate methods for the probabilistic analysis and design of fatigue-sensitive wind turbine components. A computer program (CYCLES) that estimates fatigue reliability of structural and mechanical components has been developed. A FORM/SORM analysis is used to compute failure probabilities and importance factors of the random variables. The limit state equation includes uncertainty in environmental loading, gross structural response, and local fatigue properties. Several techniques are shown to better study fatigue loads data. Common one-parameter models, such as the Rayleigh and exponential models are shown to produce dramatically different estimates of load distributions and fatigue damage. Improved fits may be achieved with the two-parameter Weibull model. High b values require better modeling of relatively large stress ranges; this is effectively done by matching at least two moments (Weibull) and better by matching still higher moments. For this purpose, a new, four-moment {open_quotes}generalized Weibull{close_quotes} model is introduced. Load and resistance factor design (LRFD) methodology for design against fatigue is proposed and demonstrated using data from two horizontal-axis wind turbines. To estimate fatigue damage, wind turbine blade loads have been represented by their first three statistical moments across a range of wind conditions. Based on the moments {mu}{sub 1}{hor_ellipsis}{mu}{sub 3}, new {open_quotes}quadratic Weibull{close_quotes} load distribution models are introduced. The fatigue reliability is found to be notably affected by the choice of load distribution model.

  12. 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.

  13. In-situ fatigue life prognosis for composite laminates based on stiffness degradation

    Data.gov (United States)

    National Aeronautics and Space Administration — In this paper, a real-time composite fatigue life prognosis framework is proposed. The proposed methodology combines Bayesian inference, piezoelectric sensor...

  14. ENDOFEM INTEGRATED METHODOLOGY FOR FATIGUE CRACK GROWTH

    Institute of Scientific and Technical Information of China (English)

    C.F.Lee; L.T.Hsiao

    2002-01-01

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

  15. FATIGUE LIFE PREDICTION THEORY OF COMPOSITE LAMINATES AND EXPERIMENTAL VERIFICATION

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    According to traditional phenomenological fatigue methodology and modern continuum damage mechanics theory, dual fatigue cumulative damage rules to predict fatigue damage formation and propagation lives of the notched composite laminates are presented.A 3-dimensional damage constitutive equation of anisotropic composites is also established.Damage strain energy release rate is interpreted as a driving force of the fatigue delamination damage propagation.A new damage evolution equation and a damage propagation (a-(m-N( surface (stress amplitude-mean stress-life surface) are derived.Hence, using the method above, the fatigue life of composite components can be predicted.Finally, theoretically predicted results are compared with experimental data.It is found that the deviation of theoretic prediction from experimental results is about 22%.

  16. Fatigue life prediction in composites

    CSIR Research Space (South Africa)

    Huston, RJ

    1994-01-01

    Full Text Available as the modulus is measured accurately. Its main disadvantage is that it can be applied only to constant amplitude fatigue loadings. REFERENCES 1. Mandell, J. F., Huang, D. D. & McGarry, F. J., Tensile fatigue performance...

  17. LIFE PREDICTION APPROACH FOR RANDOM MULTIAXIAL FATIGUE

    Institute of Scientific and Technical Information of China (English)

    Wang Lei; Wang Dejun

    2005-01-01

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

  18. The Effect of Structural Quality on Fatigue Life in 319 Aluminum Alloy Castings

    Science.gov (United States)

    Özdeş, Hüseyin; Tiryakioğlu, Murat

    2016-12-01

    Tensile and fatigue life data for 319 aluminum alloy from seventeen datasets reported in four independent studies from the literature have been reanalyzed. Analysis of fatigue life data involved mean stress correction for different R ratios used in fatigue testing, inclusion of survival (runout) data along with failure data, as well as volumetric correction for Weibull distributions for different specimen sizes used in these studies. Tensile data have been transformed into the structural quality index, Q T, which is used as a measure of the structural quality of castings. A distinct relationship has been observed between the expected fatigue life and mean quality index. Moreover, fatigue strengths at 104 and 106 cycles have been found increase with quality index, providing further evidence about the relationship observed between structural quality and fatigue performance. Empirical equations between Basquin parameters and structural quality index have been developed. The use of the comprehensive methodology to estimate fatigue life is demonstrated with an example.

  19. The Effect of Structural Quality on Fatigue Life in 319 Aluminum Alloy Castings

    Science.gov (United States)

    Özdeş, Hüseyin; Tiryakioğlu, Murat

    2017-02-01

    Tensile and fatigue life data for 319 aluminum alloy from seventeen datasets reported in four independent studies from the literature have been reanalyzed. Analysis of fatigue life data involved mean stress correction for different R ratios used in fatigue testing, inclusion of survival (runout) data along with failure data, as well as volumetric correction for Weibull distributions for different specimen sizes used in these studies. Tensile data have been transformed into the structural quality index, Q T, which is used as a measure of the structural quality of castings. A distinct relationship has been observed between the expected fatigue life and mean quality index. Moreover, fatigue strengths at 104 and 106 cycles have been found increase with quality index, providing further evidence about the relationship observed between structural quality and fatigue performance. Empirical equations between Basquin parameters and structural quality index have been developed. The use of the comprehensive methodology to estimate fatigue life is demonstrated with an example.

  20. The probability distribution of fatigue damage and the statistical moment of fatigue life

    Institute of Scientific and Technical Information of China (English)

    熊峻江; 高镇同

    1997-01-01

    The randomization of deterministic fatigue damage equation leads to the stochastic differential equation and the Fokker-Planck equation affected by random fluctuation. By means of the solution of equation, the probability distribution of fatigue damage with the change of time is obtained. Then the statistical moment of fatigue life in consideration of the stationary random fluctuation is derived. Finally, the damage probability distributions during the fatigue crack initiation and fatigue crack growth are given

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

    Institute of Scientific and Technical Information of China (English)

    LI Shouju; LIU Yingxi; SUN Huiling

    2004-01-01

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

  2. Low-Cycle Fatigue Life and Fatigue Crack Propagation of Sintered Ag Nanoparticles

    Science.gov (United States)

    Shioda, Ryutaro; Kariya, Yoshiharu; Mizumura, Noritsuka; Sasaki, Koji

    2017-02-01

    The low-cycle fatigue life and fatigue crack propagation behavior of sintered silver nanoparticles were investigated using miniature specimens sintered at two different temperatures. The fatigue crack initiation life and fatigue crack propagation rate of sintered Ag nanoparticles were extremely sensitive to changes in the range of inelastic energy density and the cyclic J integral, exhibiting brittle characteristics, in contrast to tin-based lead-free solder alloys. With increasing sintering temperature, the fatigue crack propagation rate decreased. On the other hand, the effect of sintering temperature on the fatigue crack initiation life differed depending on the use of either a smooth specimen (low-cycle fatigue test) or notched specimen (fatigue crack propagation test). For the notched specimens, the probability of grain boundaries around the notch decreased due to increased sintering temperature. Therefore, the fatigue crack initiation life was increased with an increase in sintering temperature in the fatigue crack propagation test. In the smooth specimen, however, the fatigue life decreased with an increase in sintering temperature, as the elastic modulus of the specimen increased with increasing sintering temperature. In the low-cycle fatigue test, the specimen sintered with high internal stress started to develop crack initiation early, causing a decrease in the crack initiation life.

  3. A predictive fatigue life model for anodized 7050 aluminium alloy

    OpenAIRE

    Chaussumier, Michel; Mabru, Catherine; Shahzad, Majid; Chieragatti, Rémy; Rezaï-Aria, Farhad

    2013-01-01

    International audience; The objective of this study is to predict fatigue life of anodized 7050 aluminum alloy specimens. In the case of anodized 7050-T7451 alloy, fractographic observations of fatigue tested specimens showed that pickling pits were the predominant sites for crack nucleation and subsequent failure. It has been shown that fatigue failure was favored by the presence of multiple cracks. From these experimental results, a fatigue life predictive model has been developed including...

  4. Fatigue life of metal treated by magnetic field

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  5. MULTIAXIAL CREEP-FATIGUE LIFE EVALUATION UNDER PROPORTIONAL LOADING

    Institute of Scientific and Technical Information of China (English)

    Y.Noguchi; M.Miyahara

    2004-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    张怀亮; 邱显焱; 谭冠军

    2001-01-01

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

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

    CERN Document Server

    Cui, Weicheng; Wang, Fang

    2014-01-01

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

  8. Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life

    Science.gov (United States)

    Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

    2012-01-01

    Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

  9. Conductor fatigue-life research. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Ramey, G.E.

    1981-07-01

    This is the final report of Research Project RP 1278-1 sponsored by the Electric Power Research Institute and carried out at the Civil Engineering Department of Auburn University (Auburn, Alabama). The objective of this study was to evaluate the effects of reducing vibration amplitudes of ACSR conductors which had been minimally damaged by aeolian vibration. The aeolian vibration was simulated by mechanical means in a controlled laboratory situation and the reduction in vibration amplitudes was a simulation of the addition of amplitude limiting devices (dampers). Conductors were vibrated at high amplitudes until a predetermined number of strand breaks occurred, after which the vibration was continued at reduced amplitudes. Three different ACSB conductors were tested: 795 KCM 26/7, 795 KCM 45/7, and 397.5 KCM 26/7. These conductors were chosen to establish the effects of conductor size and stranding on the amplitude reduction tests. Two different amplitude reductions were used to establish a threshold value for a maximum reduced amplitude. Previous preliminary research by others indicated that amplitude reductions extended the working life of conductors. This research expanded the amplitude reduction values and conductor sizes and strandings tested. For each set of parameters, four duplicative tests were performed to give statistical credence to the data. The results of the investigation indicated that amplitude reductions arrested fatigue strand breakage in each case. Electric utilities can utilize the results of this EPRI project in assessing the fatigue life of minimally damaged transmisson lines and in evaluating techniques for mitigating fatigue damage.

  10. Mobile Technology Use by People Experiencing Multiple Sclerosis Fatigue: Survey Methodology

    Science.gov (United States)

    Reay, Nicholas

    2017-01-01

    Background Fatigue is one of the most commonly reported symptoms of multiple sclerosis (MS). It has a profound impact on all spheres of life, for people with MS and their relatives. It is one of the key precipitants of early retirement. Individual, group, and Internet cognitive behavioral therapy–based approaches to supporting people with MS to manage their fatigue have been shown to be effective. Objective The aim of this project was to (1) survey the types of mobile devices and level of Internet access people with MS use or would consider using for a health intervention and (2) characterize the levels of fatigue severity and their impact experienced by the people in our sample to provide an estimate of fatigue severity of people with MS in New Zealand. The ultimate goal of this work was to support the future development of a mobile intervention for the management of fatigue for people with MS. Methods Survey methodology using an online questionnaire was used to assess people with MS. A total of 51 people with MS participated. The average age was 48.5 years, and the large majority of the sample (77%) was female. Results Participants reported significant levels of fatigue as measured with the summary score of the Neurological Fatigue Index (mean 31.4 [SD 5.3]). Most (84%) respondents scored on average more than 3 on the fatigue severity questions, reflecting significant fatigue. Mobile phone usage was high with 86% of respondents reporting having a mobile phone; apps were used by 75% of respondents. Most participants (92%) accessed the Internet from home. Conclusions New Zealand respondents with MS experienced high levels of both fatigue severity and fatigue impact. The majority of participants have a mobile device and access to the Internet. These findings, along with limited access to face-to-face cognitive behavioral therapy–based interventions, create an opportunity to develop a mobile technology platform for delivering a cognitive behavioral therapy

  11. What roles do team climate, roster control, and work life conflict play in shiftworkers' fatigue longitudinally?

    Science.gov (United States)

    Pisarski, Anne; Barbour, Jennifer P

    2014-05-01

    The study aimed to examine shiftworkers fatigue and the longitudinal relationships that impact on fatigue such as team climate, work life conflict, control of shifts and shift type in shift working nurses. We used a quantitative survey methodology and analysed data with a moderated hierarchical multiple regression. After matching across two time periods 18 months apart, the sample consisted of 166 nurses from one Australian hospital. Of these nurses, 61 worked two rotating day shifts (morning & afternoon/evening) and 105 were rotating shiftworkers who worked three shifts (morning afternoon/evening and nights). The findings suggest that control over shift scheduling can have significant effects on fatigue for both two-shift and three-shift workers. A significant negative relationship between positive team climate and fatigue was moderated by shift type. At both Time 1 and Time 2, work life conflict was the strongest predictor of concurrent fatigue, but over time it was not.

  12. Calculation of the fatigue life distribution of a composite laminate

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, IA.A.; Limonov, V.A. (AN LSSR, Institut Mekhaniki Polimerov, Riga, Latvian (USSR))

    1991-02-01

    A method based on a probabilistic interpretation of the Hashin criterion is proposed for calculating the fatigue life distributions of a unidirectional composite under conditions of a plane stressed state from test results obtained for simple loading schemes. By using the linear damage accumulation law, an estimate is obtained of the scatter of the composite fatigue life related to the scatter of the material fatigue strength. A procedure is then presented for estimating the fatigue life distribution of a composite laminate in the plane stressed state based on layer-by-layer fracture analysis using the linear damage summation law and the determining layer concept. 26 refs.

  13. An Integrated Health Monitoring Method for Structural Fatigue Life Evaluation Using Limited Sensor Data

    Directory of Open Access Journals (Sweden)

    Jingjing He

    2016-11-01

    Full Text Available A general framework for structural fatigue life evaluation under fatigue cyclic loading using limited sensor data is proposed in this paper. First, limited sensor data are measured from various sensors which are preset on the complex structure. Then the strain data at remote spots are used to obtain the strain responses at critical spots by the strain/stress reconstruction method based on empirical mode decomposition (REMD method. All the computations in this paper are directly performed in the time domain. After the local stress responses at critical spots are determined, fatigue life evaluation can be performed for structural health management and risk assessment. Fatigue life evaluation using the reconstructed stresses from remote strain gauge measurement data is also demonstrated with detailed error analysis. Following this, the proposed methodology is demonstrated using a three-dimensional frame structure and a simplified airfoil structure. Finally, several conclusions and future work are drawn based on the proposed study.

  14. A method for calculation of finite fatigue life under multiaxial loading in high-cycle domain

    Directory of Open Access Journals (Sweden)

    M. Malnati

    2014-04-01

    Full Text Available A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made.

  15. Fatigue life characterization for piezoelectric macrofiber composites

    Science.gov (United States)

    Henslee, Isaac A.; Miller, David A.; Tempero, Tyler

    2012-10-01

    In an effort to aid the investigation into lightweight and reliable materials for actuator design, a study was developed to characterize the temperature-dependent lifetime performance of a piezoelectric macrofiber composite (MFC). MFCs are thin rectangular patches of polyimide film, epoxy and a single layer of rectangular lead zirconium titanate (PZT) fibers. In this study, the useful life of the MFC is characterized to determine the effect of temperature on the performance of the composite as it is fatigued by cyclic piezoelectric excitation. The test specimen consists of the MFC laminated to a cantilevered stainless steel beam. Beam strain and tip displacement measurements are used as a basis for determining the performance of the MFC as it is cyclically actuated under various operating temperatures. The temperature of the beam laminate is held constant and then cycled to failure, or 250 million cycles, in order to determine the useful life of the MFC over a temperature range from - 15 to 145 °C. The results of the experiments show a strong temperature dependence of the operational life for the MFC. Damage inside the composite was identified through in situ visual inspection and during post-test microstructural observation; however, no degradation in operational performance was identified as it was cyclically actuated up to the point of failure, regardless of temperature or actuation cycle number.

  16. How surface damage removal affects fatigue life

    Science.gov (United States)

    Jeelani, S.; Scott, M. A.

    1988-01-01

    The effect of the removal of work hardened surface layers from specimens of 2024-T4 aluminum alloy and AISI-4130 steel on their fatigue lives has been investigated. Specimens were fatigued at selected stress levels for a given number of cycles, and the surface layer was removed followed by subsequent fatigue cycling. Results confirm that when a material is subjected to fatigue loading, damage accumulates in the surface layers in the form of work hardening. Removal of the surface layer brings the specimen back to its pre-fatigued condition.

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

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

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

  18. Equi-biaxial loading effect on austenitic stainless steel fatigue life

    Directory of Open Access Journals (Sweden)

    C. Gourdin

    2016-10-01

    Full Text Available Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equibiaxial tension. Two calibration tests (with strain gauges and image correlation were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship. Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to -1. The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent. These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components

  19. A comparison of some methods to estimate the fatigue life of plain dents

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Ricardo R.; Noronha Junior, Dauro B. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2009-12-19

    This paper describes a method under development at PETROBRAS R and D Center (CENPES) to estimate the fatigue life of plain dents. This method uses the API Publication 1156 as a base to estimate the fatigue life of dome shaped plain dents and the Pipeline Defect Assessment Manual (PDAM) approach to take into account the uncertainty inherent in the fatigue phenomenon. CENPES method, an empirical and a semi-empirical method available in the literature were employed to estimate the fatigue lives of 10 plain dents specimens of Year 1 of an ongoing test program carried out by BMT Fleet Technology Limited, with the support of the Pipeline Research Council International (PRCI). The results obtained with the different methods are presented and compared. Furthermore some details are given on the numerical methodology proposed by PETROBRAS that have been used to describe the behavior of plain dents. (author)

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

    Science.gov (United States)

    Razzaq, Zia

    1989-01-01

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

  1. 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...

  2. Reducing Uncertainty in Fatigue Life Limits of Turbine Engine Alloys

    Science.gov (United States)

    2014-03-01

    this behavior in turbine engine alloys , we have developed a physically- based approach for describing fatigue var- iability, and this approach has been...of competing mechanisms in the fatigue life variability of a nearly fully-lamellar c-TiAl based alloy . Acta Mater 2005;53:1293–304. [50] Buchanan DJ...Burns JT, Larsen JM, Gangloff RP. Driving forces for localized corrosion -to- fatigue crack transition in Al–Zn– Mg –Cu. Fatigue Fract Eng Mater Struct

  3. Fatigue Life of High-Strength Steel Offshore Tubular Joints

    DEFF Research Database (Denmark)

    Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

    1996-01-01

    In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high-strength...... steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated...... amplitude fatigue test results showed shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, the fatigue tests on high-strength steel tubular joints showed slightly longer fatigue lives than those obtained...

  4. Fatigue Life Analysis of Cantilever Probe on Wafer Test

    Directory of Open Access Journals (Sweden)

    Hsiao Te-Ching

    2016-01-01

    Full Text Available This research utilizes the finite element analysis software (ANSYS to stimulate the different probe material quality (tungsten, SUS304 stainless steel, SUS316L stainless steel and SKD11 tool steel, respectively during wafer tests. Under a room temperature of (25°C, the stress and fatigue life (cycles of probing test of the cantilever probe were measured with an OverDriver (OD of 20µm, 40µm, 50µm, 60µm and 80µm, respectively. First, to obtain the magnitude of pinpoint shift of the probe under wafer test and the OverDriver is 50µm. And, calculate the fatigue life of the probe. Then, a probe model with the same characteristics as the experiment is created and the probe fatigue life analyzed with the ANSYS. After the reliability of the model is ascertained, the wafer tests of different probe materials are stimulated under different OverDriver circumstances to calculate its stress and fatigue life. The results indicate that the greatest stress measured during the wafer test of the tungsten, SUS304 stainless steel, SUS316L stainless steel and SKD11 tool steel cantilever probe are all smaller than the yield strength, and the fatigue life could reach over one hundred K cycles. When catalogued by the cantilever probe fatigue life during one hundred K cycles, the life span, in order, is tungsten < SUS316L stainless steel < SUS304 stainless steel < SKD11 tool steel.

  5. Enhanced Prediction of Gear Tooth Surface Fatigue Life Project

    Data.gov (United States)

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

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

    Institute of Scientific and Technical Information of China (English)

    熊峻江; 武哲; 高镇同

    2002-01-01

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

  7. FATIGUE LIFE EVALUATION OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE

    Directory of Open Access Journals (Sweden)

    A.G.A. Rahman

    2012-12-01

    Full Text Available Suspension is part of automotive systems, providing both vehicle control and passenger comfort. The knuckle is an important part within the suspension system, constantly encountering the cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using multibody simulation (MBS techniques. Load time history extracted from the MBS is used for stress analysis. An actual road profile of road bumps was used as the input to MBS. The stress fluctuations for fatigue simulations are considered with the road profile. The strain-life method is utilized to assess the fatigue life. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. Mesh sensitivity analysis has been performed. The results show that the steering link in the knuckle is found to be the most susceptible region for fatigue failure. The number of times the knuckle can manage a road bump at 40 km/hr is determined to be approximately 371 times with a 50% certainty of survival. The proposed method of using the loading time history extracted from MBS simulation for fatigue life estimation is found to be very promising for the accurate evaluation of the performance of suspension system components.

  8. APPLICATION OF MULTIBODY SIMULATION FOR FATIGUE LIFE ESTIMATION

    Directory of Open Access Journals (Sweden)

    M. Kamal

    2013-06-01

    Full Text Available In automobile design, the safety of passengers is of prime concern to the manufacturers. Suspension is one of the safety-related automotive systems which is responsible for maintaining traction between the road and tires, and offers a comfortable ride experience to the passengers by absorbing disturbances. One of the critical components of the suspension system is the knuckle, which constantly faces cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using a gravel road profile acquired using a data acquisition system and standard SAE profiles for the suspension (SAESUS, bracket (SAEBRAKT and transmission (SAETRN. The gravel road profile was applied as the input to a multi body simulation (MBS, and the load history for various mounting points of the knuckle is extracted. Fatigue life is predicted using the strain-life method. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. From the results, the strut connection is found to be the critical region for fatigue failure. The fatigue life from loading extracted from gravel road MBS agreed well with the life prediction when standard SAE profiles were used. This close agreement shows the effectiveness of the load extraction technique from MBS. This method can also be effectively used for more complex loading conditions that occur during real driving environments.

  9. Dramatic increase in fatigue life in hierarchical graphene composites.

    Science.gov (United States)

    Yavari, F; Rafiee, M A; Rafiee, J; Yu, Z-Z; Koratkar, N

    2010-10-01

    We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ∼0.2% (with respect to the epoxy resin weight and ∼0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ∼3-5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ∼1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries.

  10. Life prediction of thermal-mechanical fatigue using strainrange partitioning

    Science.gov (United States)

    Halford, G. R.; Manson, S. S.

    1975-01-01

    This paper describes the applicability of the method of Strainrange Partitioning to the life prediction of thermal-mechanical strain-cycling fatigue. An in-phase test on 316 stainless steel is analyzed as an illustrative example. The observed life is in excellent agreement with the life predicted by the method using the recently proposed Step-Stress Method of experimental partitioning, the Interaction Damage Rule, and the life relationships determined at an isothermal temperature of 705 C. Implications of the present study are discussed relative to the general thermal fatigue problem.

  11. The effects of fibre architecture on fatigue life-time of composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Zangenberg Hansen, J.

    2013-09-15

    Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation methodologies in order to be assessed. Furthermore, numerical evaluation and predictions of the fatigue damage evolution are decisive in order to make future improvements. The present work is focused around two central themes: fibre architecture and fatigue failure. The fibre architecture is characterised using real material samples and numerical simulations. Experimental fatigue tests identify, quantify, and analyse the cause of failure. Different configurations of the fibre architecture are investigated in order to determine and understand the tension-tension fatigue failure mechanisms. A numerical study is used to examine the onset of fatigue failure. Topics treated include: experimental fatigue investigations, scanning electron microscopy, numerical simulations, advanced measurements techniques (micro computed tomography and thermovision), design of test specimens and preforms, and advanced materials characterisation. The results of the present work show that the fibre radii distribution has limited effect on the fibre architecture. This raises the question of which

  12. a Study on the Fretting Fatigue Life of Zircaloy Alloys

    Science.gov (United States)

    Kwon, Jae-Do; Park, Dae-Kyu; Woo, Seung-Wan; Chai, Young-Suck

    Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr, and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

  13. Rolling contact fatigue life of ion-implanted GCr15

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Presents an experimental research into the rooling contact fatigue life of GCr15 steel with Tix N, TiX N + Ag and Tix N + DLC layers ion-implanted using the plasma ion-implantation technology on a ball-rod style high-speed con tact fatigue tester, and concludes with test results that the fatigue life increases to varying degrees with Tix N, Tix N + Ag, and Tix N + DLC layers implanted, and increases 1.8 times with Tix N + Ag layer implanted, hairline cracks grow continuously into fatigue pits under the action of shear stress in the superficial layer of material, and ion-implantation acts to prevent initiation of cracks and slow down propagation of cracks.

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

    Institute of Scientific and Technical Information of China (English)

    ukasz Pejkowski; Dariusz Skibicki

    2016-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

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

  16. Economic evaluation of LIFE methodology

    OpenAIRE

    2007-01-01

    Background: The LIFE project (Lifecycle Information For E-Literature) was carried out during 2004-2006 by a consortium consisting of The British Library and University College London Library Services . The project was joint venture funded by JISC under the programme area Institutional Management Support and Collaboration. The project has received favourable feedback, for instance during a workshop organised at the end of it, and JISC has agreed to fund a second phase during...

  17. Methodological triangulation in work life research

    DEFF Research Database (Denmark)

    Warring, Niels

    Based on examples from two research projects on preschool teachers' work, the paper will discuss potentials and challenges in methodological triangulation in work life research. Analysis of ethnographic and phenomenological inspired observations of everyday life in day care centers formed the basis...

  18. On Fatigue Life Under Stationary Gaussian Random Loads (A)

    DEFF Research Database (Denmark)

    Talreja, R.

    1973-01-01

    Power spectra are taken to represent stationary Gaussian random loads. Location, scale, and shape parameters are defined for power spectra and proposed as a convenient set of load parameters for random loads. The center frequency of a power spectrum, defined as its weighted average frequency......, is proposed as a measure of fatigue life. A servohydraulic closed loop testing machine is used to load specimens of carbon steel under six different power spectral shapes. Test results are utilized to evaluate a fatigue life function formulated in terms of the load parameters. The concept of a shape operator...

  19. Fatigue life prediction of crankshaft repaired by twin arc spraying

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guo-qing; WANG Cheng-tao; PU Geng-qiang

    2005-01-01

    This paper used Baumel Jr. and Seeger's approach estimating fatigue parameters of 48MnV with 3Cr13coatings. The fatigue life of the crankshaft of a six-cylinder engine, repaired by twin arc spraying 3cr13 deposits, is respectively calculated using different damage model such as S-N method, normal strain approaches, SWT-Bannantine approaches, shear strain approaches, and fatemi-Socie method based on dynamical simulation and FE analysis of crankshaft. The results indicate that the traditional calculation is conservative and that the life of crankshaft repaired by arc spraying is sufficient.

  20. Fatigue life of ablation-cast 6061-T6 components

    Energy Technology Data Exchange (ETDEWEB)

    Tiryakioglu, Murat, E-mail: m.tiryakioglu@unf.edu [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Eason, Paul D. [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Campbell, John [Department of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT (United Kingdom)

    2013-01-01

    The fatigue life of 6061-T6 alloy, normally used in its wrought form, was investigated in this study in cast form from parts produced by the new ablation casting process. All specimens were excised from military castings. Unidirectional tensile test results yielded elongation values comparable to forgings and extrusions. A total of 39 fatigue specimens were tested by the rotating cantilever beam technique at five maximum stress levels. Moreover nine specimens excised from a forging were also tested for comparison. Results revealed that the fatigue life of ablation-cast 6061-T6 (i) follows a three-parameter Weibull distribution, and (ii) is comparable to data from the 6061 forging and is superior to conventionally cast Al-7% Si-Mg alloy castings published in the literature. Analysis of the fracture surfaces of ablation-cast 6061-T6 via scanning electron microscopy showed the existence of fracture surface facets and multiple cracks propagating in different directions.

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

    Directory of Open Access Journals (Sweden)

    M. Maj

    2013-01-01

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

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

    Science.gov (United States)

    Berkovits, A.; Nadiv, S.

    1988-01-01

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

  3. Multi-Axial Damage Index and Accumulation Model for Predicting Fatigue Life of CMC Materials Project

    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...

  4. 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 provide

  5. Fatigue Life Analysis of Rolling Bearings Based on Quasistatic Modeling

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2015-01-01

    Full Text Available Rolling bearings are widely used in aeroengine, machine tool spindles, locomotive wheelset, and so forth. Rolling bearings are usually the weakest components that influence the remaining life of the whole machine. In this paper, a fatigue life prediction method is proposed based on quasistatic modeling of rolling bearings. With consideration of radial centrifugal expansion and thermal deformations on the geometric displacement in the bearings, the Jones’ bearing model is updated, which can predict the contact angle, deformation, and load between rolling elements and bearing raceways more accurately. Based on Hertz contact theory and contact mechanics, the contact stress field between rolling elements and raceways is calculated. A coupling model of fatigue life and damage for rolling bearings is given and verified through accelerated life test. Afterwards, the variation of bearing life is investigated under different working conditions, that is, axial load, radial load, and rotational speed. The results suggested that the working condition had a great influence on fatigue life of bearing parts and the order in which the damage appears on bearing parts.

  6. Fatigue in cold-forging dies: Tool life analysis

    DEFF Research Database (Denmark)

    Skov-Hansen, P.; Bay, Niels; Grønbæk, J.;

    1999-01-01

    In the present investigation it is shown how the tool life of heavily loaded cold-forging dies can be predicted. Low-cycle fatigue and fatigue crack growth testing of the tool materials are used in combination with finite element modelling to obtain predictions of tool lives. In the models...... the number of forming cycles is calculated first to crack initiation and then during crack growth to fatal failure. An investigation of a critical die insert in an industrial cold-forging tool as regards the influence of notch radius, the amount and method of pre-stressing and the selected tool material...

  7. Fatigue Life of Postbuckled Structures with Indentation Damages

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of each stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 32 millimeters to 56 millimeters were tested quasi-statically and in fatigue, and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  8. Fatigue Life of Postbuckled Structures with Indentation Damage

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of the stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 37 millimeters to 56 millimeters were tested in fatigue and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  9. 10 CFR 436.12 - Life cycle cost methodology.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Life cycle cost methodology. 436.12 Section 436.12 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION FEDERAL ENERGY MANAGEMENT AND PLANNING PROGRAMS Methodology and Procedures for Life Cycle Cost Analyses § 436.12 Life cycle cost methodology. The life cycle cost methodology...

  10. Blade Group Fatigue Life Calculation under Resonant Stresses

    Directory of Open Access Journals (Sweden)

    Zlatko Petreski

    2017-02-01

    Full Text Available The results of the simulations of the blade group resonant stresses in a FE environment and fatigue life calculation are presented in this paper. Numerical calculation for determination of natural frequencies, mode shapes and dynamic stresses, based on FEM and NISA package is used. Analyses are made on the blade group with three blades with rectangular cross section and typical turbine blades with taper, pretwist and asymmetric airfoil as well. The influence of the position of the lacing wire on the resonant stresses is analyzed. Three-dimensional finite element models of the blade group are made by using twenty node isoparametric solid elements. The number of degrees of freedom is different for each model (more than 30000 DOF. The fatigue life and consequent life prediction according the stress load history of the blades is made. The results of the investigation are given in tables and graphics.

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

    Directory of Open Access Journals (Sweden)

    X. W. Ye

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Ana – Maria Budai

    2010-10-01

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

  13. The Study on Fatigue Experiment and Reliability Life of Submarine Pipeline Steel

    OpenAIRE

    Yan Yifei; Shao Bing; Liu Jinkun; Cheng Lufeng

    2013-01-01

    The aim of the fatigue experiment study is to solve the fatigue fracture problem of X70 submarine tubing when it is under the scouring effect of offshore current. The multilevel fatigue experiments are carried out following the internation (GB4337-84) recommended method. The standard round bar fatigue specimen was made by the material of submarine pipeline steel. The fatigue life of submarine pipeline steel in different survival probability and P-S-N curve were achieved. According to reliabil...

  14. A Sensitivity Analysis on Component Reliability from Fatigue Life Computations

    Science.gov (United States)

    1992-02-01

    AD-A247 430 MTL TR 92-5 AD A SENSITIVITY ANALYSIS ON COMPONENT RELIABILITY FROM FATIGUE LIFE COMPUTATIONS DONALD M. NEAL, WILLIAM T. MATTHEWS, MARK G...HAGI OR GHANI NUMBI:H(s) Donald M. Neal, William T. Matthews, Mark G. Vangel, and Trevor Rudalevige 9. PERFORMING ORGANIZATION NAME AND ADDRESS lU...Technical Information Center, Cameron Station, Building 5, 5010 Duke Street, Alexandria, VA 22304-6145 2 ATTN: DTIC-FDAC I MIAC/ CINDAS , Purdue

  15. Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading

    Institute of Scientific and Technical Information of China (English)

    RAHMAN M.M.; ARIFFIN A.K.; JAMALUDIN N.; HARON C.H.C.

    2006-01-01

    This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine's components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.

  16. 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

    Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate...... 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...

  17. Fatigue Life Estimation of Medium-Carbon Steel with Different Surface Roughness

    Directory of Open Access Journals (Sweden)

    Changyou Li

    2017-03-01

    Full Text Available Medium-carbon steel is commonly used for the rail, wire ropes, tire cord, cold heading, forging steels, cold finished steel bars, machinable steel and so on. Its fatigue behavior analysis and fatigue life estimation play an important role in the machinery industry. In this paper, the estimation of fatigue life of medium-carbon steel with different surface roughness using established S-N and P-S-N curves is presented. To estimate the fatigue life, the effect of the average surface roughness on the fatigue life of medium-carbon steel has been investigated using 75 fatigue tests in three groups with average surface roughness (Ra: 0.4 μm, 0.8 μm, and 1.6 μm, respectively. S-N curves and P-S-N curves have been established based on the fatigue tests. The fatigue life of medium-carbon steel is then estimated based on Tanaka-Mura crack initiation life model, the crack propagation life model using Paris law, and material constants of the S-N curves. Six more fatigue tests have been conducted to validate the presented fatigue life estimation formulation. The experimental results have shown that the presented model could estimate well the mean fatigue life of medium-carbon steel with different surface roughness.

  18. 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.

  19. CARES/Life Ceramics Durability Evaluation Software Enhanced for Cyclic Fatigue

    Science.gov (United States)

    Nemeth, Noel N.; Powers, Lynn M.; Janosik, Lesley A.

    1999-01-01

    The CARES/Life computer program predicts the probability of a monolithic ceramic component's failure as a function of time in service. The program has many features and options for materials evaluation and component design. It couples commercial finite element programs--which resolve a component's temperature and stress distribution--to reliability evaluation and fracture mechanics routines for modeling strength-limiting defects. The capability, flexibility, and uniqueness of CARES/Life have attracted many users representing a broad range of interests and has resulted in numerous awards for technological achievements and technology transfer. Recent work with CARES/Life was directed at enhancing the program s capabilities with regards to cyclic fatigue. Only in the last few years have ceramics been recognized to be susceptible to enhanced degradation from cyclic loading. To account for cyclic loads, researchers at the NASA Lewis Research Center developed a crack growth model that combines the Power Law (time-dependent) and the Walker Law (cycle-dependent) crack growth models. This combined model has the characteristics of Power Law behavior (decreased damage) at high R ratios (minimum load/maximum load) and of Walker law behavior (increased damage) at low R ratios. In addition, a parameter estimation methodology for constant-amplitude, steady-state cyclic fatigue experiments was developed using nonlinear least squares and a modified Levenberg-Marquardt algorithm. This methodology is used to give best estimates of parameter values from cyclic fatigue specimen rupture data (usually tensile or flexure bar specimens) for a relatively small number of specimens. Methodology to account for runout data (unfailed specimens over the duration of the experiment) was also included.

  20. 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

    Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate...... 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....

  1. Methodologies for Social Life Cycle Assessment

    DEFF Research Database (Denmark)

    Jørgensen, Andreas; Le Bocq, Agathe; Nazakina, Liudmila

    2008-01-01

    Goal, Scope and Background. In recent years several different approaches towards Social Life Cycle Assessment (SLCA) have been developed. The purpose of this review is to compare these approaches in order to highlight methodological differences and general shortcomings. SLCA has several...... stage in the product life cycle. Another very important difference among the proposals is their position towards the use of generic data. Several of the proposals argue that social impacts are connected to the conduct of the company leading to the conclusion that each individual company in the product...... and formulation of indicators. The indicators address a wide variety of issues; some approaches focus on impacts created in the very close proximity of the processes included in the product system, whereas others focus on the more remote societal consequences. Only very little focus has been given to the use...

  2. Evaluation of corrosion fatigue and life prediction of lower arm for automotive suspension component

    Science.gov (United States)

    Kim, Yong-Sang; Kim, Jung-Gu

    2017-01-01

    Lower arm is one of the suspension components of automobile. It is suffered from driving vibration and corrosive environment, namely corrosion fatigue. In this study, corrosion fatigue property of lower arm was investigated, and a modified model based on Palmgren-Miner rule was developed to predict the lifetimes of corrosion fatigue. The corrosion fatigue life of lower arm was about 1/6 times shorter than fatigue life. Based on the results of corrosion fatigue tests and meteorological data in Seoul and Halifax, the corrosion fatigue life of lower arm was predicted. The satisfaction of 10-year and 300,000 km warranty was dominated by the climate of automobile driving. This prediction indicates that the weather condition or driving condition influences the life of automotive parts. Therefore, to determine the warranty of automotive parts, the driving condition has to be carefully considered.

  3. Study on effect of mean stress on fatigue life prediction of thin film structure

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Myung Soo [Ahtti Co., Seongnam (Korea, Republic of); Park, Jun Hyu [Tongmyong University, Busan (Korea, Republic of); Kim, Jung Yup [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2016-04-15

    This paper describes the effect of mean stress on fatigue life prediction of structure made with thin film. It is well known that the mean stress influences fatigue life prediction of mechanical structure. We investigated a reasonable method for considering mean stress when fatigue strength assessment of micro structure of thin film should be performed. Fatigue tests of smooth specimen of beryllium-copper (BeCu) thin film were performed in ambient air at R = 0.1 with 5 Hz. A micro probe was designed and made with BeCu thin film by the precision press process. Fatigue tests of micro structure were performed with 5 Hz frequency, in ambient air to verify the fatigue life predicted by computer simulation through FE analysis. The fatigue life predicted by the Sa -N curve modified by Goodman method with principal stress through FE analysis shows a more reasonable result than other methods.

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

    Science.gov (United States)

    Goswami, Tarun

    2002-01-01

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

  5. Slow Crack Growth and Fatigue Life Prediction of Ceramic Components Subjected to Variable Load History

    Science.gov (United States)

    Jadaan, Osama

    2001-01-01

    Present capabilities of the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth (SCG) type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, while for cyclic fatigue applications various types of repetitive constant amplitude loads can be accounted for. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as, for example, engine start up, shut down, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that takes into account the change in material response with time. In this paper, the dominant delayed failure mechanism is assumed to be SCG. This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code, which has also been modified to have the ability of interfacing with commercially available FEA codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program.

  6. An equivalent strain/Coffin-Manson approach to multiaxial fatigue and life prediction in superelastic Nitinol medical devices.

    Science.gov (United States)

    Runciman, Amanda; Xu, David; Pelton, Alan R; Ritchie, Robert O

    2011-08-01

    Medical devices, particularly endovascular stents, manufactured from superelastic Nitinol, a near-equiatomic alloy of Ni and Ti, are subjected to complex mixed-mode loading conditions in vivo, including axial tension and compression, radial compression, pulsatile, bending and torsion. Fatigue lifetime prediction methodologies for Nitinol, however, are invariably based on uniaxial loading and thus fall short of accurately predicting the safe lifetime of stents under the complex multiaxial loading conditions experienced physiologically. While there is a considerable body of research documented on the cyclic fatigue of Nitinol in uniaxial tension or bending, there remains an almost total lack of comprehensive fatigue lifetime data for other loading conditions, such as torsion and tension/torsion. In this work, thin-walled Nitinol tubes were cycled in torsion at various mean and alternating strains to investigate the fatigue life behavior of Nitinol and results compared to equivalent fatigue data collected under uniaxial tensile/bending loads. Using these strain-life results for various loading modes and an equivalent referential (Lagrangian) strain approach, a strategy for normalizing these data is presented. Based on this strategy, a fatigue lifetime prediction model for the multiaxial loading of Nitinol is presented utilizing a modified Coffin-Manson approach where the number of cycles to failure is related to the equivalent alternating transformation strain.

  7. Statistical Distribution of Fatigue Life for Cast TiAl Alloy

    Directory of Open Access Journals (Sweden)

    WAN Wenjuan

    2016-08-01

    Full Text Available Statistic distribution of fatigue life data and its controls of cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr (atom fraction/% alloy were investigated. Fatigue tests were operated by means of load-controlled rotating bending fatigue tests (R=-1 performed at a frequency of 100 Hz at 750 ℃ in air. The fracture mechanism was analyzed by observing the fracture surface morphologies through scanning electron microscope,and the achieved fatigue life data were analyzed by Weibull statistics. The results show that the fatigue life data present a remarkable scatter ranging from 103 to 106 cycles, and distribute mainly in short and long life regime. The reason for this phenomenon is that the fatigue crack initiators are different with different specimens. The crack initiators for short-life specimens are caused by shrinkage porosity, and for long-life ones are caused by bridged porosity interface and soft-oriented lamellar interface. Based on the observation results of fracture surface, two-parameter Weibull distribution model for fatigue life data can be used for the prediction of fatigue life at a certain failure probability. It has also shown that the shrinkage porosity causes the most detrimental effect to fatigue life.

  8. The Study on Fatigue Experiment and Reliability Life of Submarine Pipeline Steel

    Directory of Open Access Journals (Sweden)

    Yan Yifei

    2013-02-01

    Full Text Available The aim of the fatigue experiment study is to solve the fatigue fracture problem of X70 submarine tubing when it is under the scouring effect of offshore current. The multilevel fatigue experiments are carried out following the internation (GB4337-84 recommended method. The standard round bar fatigue specimen was made by the material of submarine pipeline steel. The fatigue life of submarine pipeline steel in different survival probability and P-S-N curve were achieved. According to reliability numerical analysis method, the reliability fatigue life of pipeline steel in different stress level is got. The results show that the fatigue life of X70 submarine pipeline steel obeys the normal distribution. The detection of submarine pipeline scouring condation should be enhanced and the pipeline zone which was scoured seriously should be repaired and controlled effectively in order to reduce the scouring effect of ocean current.

  9. Structural health monitoring of wind towers: residual fatigue life estimation

    Science.gov (United States)

    Benedetti, M.; Fontanari, V.; Battisti, L.

    2013-04-01

    In a recent paper (Benedetti et al 2011 Smart Mater. Struct. 20 055009), the authors investigated the possibility of detecting cracks in critical sites of onshore wind towers using a radial arrangement of strain sensors around the tower periphery in the vicinity of the base welded joint. Specifically, the strain difference between adjacent strain sensors is used as a damage indicator. The number of sensors to be installed is determined by the minimum crack size to be detected, which in turn depends on the expected extreme wind conditions and programmed inspection/repair schedule. In this companion paper, we address these issues by investigating possible strategies for residual fatigue life assessment and management of onshore wind towers once the crack has been detected. For this purpose, fracture mechanics tests are carried out using welded samples to quantify the resistance to fatigue crack growth as well as the elastic-plastic fracture toughness of the welded joint at the tower base. These material strength characteristics are used to estimate (i) the critical crack size for structural integrity on the basis of fracture toughness tests, elastoplastic finite element analyses and loading spectra under extreme wind conditions, (ii) the residual life before structural collapse, applying a frequency-domain method to typical in-service wind actions and wind directionality.

  10. Fatigue life of organic fiber/epoxy pressure vessels

    Science.gov (United States)

    Hamstad, M. A.; Chiao, T. T.; Patterson, R. G.

    1975-01-01

    The cyclic fatigue life of 10.2-cm-diam cylindrical pressure vessels has been studied. The vessels were made of an organic fiber/epoxy composite. To determine the typical strength distribution of the vessels, 25 of them were internally pressurized until they burst. Twenty-five vessels were then tested under sinusoidal cycling at 1 Hz between 4% and 91% of the mean burst strength. An additional twenty-five vessels were tested between 4% and 91% with a rectangular pressure pulse at 1/3 Hz. A limited number of vessels were tested for stress rupture at the 91% level. Cyclic life was found to depend on time at peak load as well as the number of stress cycles.

  11. A Model of the Fatigue Life Distribution of Composite Laminates Based on Their Static Strength Distribution

    Institute of Scientific and Technical Information of China (English)

    Wu Fuqiang; Yao Weixing

    2008-01-01

    The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article.It is concluded that the inner original defects,which derived from the manufacturing process of composite laminates,are the common and major reason of causing the random distributions of the static strength and the fatigue life.And there is a correlative relation between the two distributions.With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material,the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained.And then the model which is used to describe the distributions of fatigue life of composites,based on their distributions of static strength,is set up.This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates.The experimental data of three kinds of composite laminates are employed to verify this model,and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.

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

    Directory of Open Access Journals (Sweden)

    V.G. Rao

    2003-01-01

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

  13. Fatigue life prediction and strength degradation of wind turbine rotor blade composites

    NARCIS (Netherlands)

    Nijssen, R.P.L.

    2006-01-01

    Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fat

  14. Influence of Working Environment on Fatigue Life Time Duration for Runner Blades of Kaplan Turbines

    Directory of Open Access Journals (Sweden)

    Ana-Maria Budai

    2010-10-01

    Full Text Available The paper present an analytical analyzes refer to influence of working environment on life time duration in service of runner blades of Kaplan turbines. The study are made using only analytical method, the entry dates being obtained from measurements made in situ for a Kaplan turbine. To calculate the maximum number of stress cycles whereupon the runner blades work without any damage it was used an analytical relation known in specialized literatures under the name of Morrow’s relation. To estimate fatigue life time duration will be used a formula obtained from one of most common cumulative damage methodology taking in consideration the real exploitation conditions of a specified Kaplan turbine.

  15. 10 CFR 455.64 - Life-cycle cost methodology.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Life-cycle cost methodology. 455.64 Section 455.64 Energy..., Hospitals, Units of Local Government, and Public Care Institutions § 455.64 Life-cycle cost methodology. (a) The life-cycle cost methodology under § 455.63(b) of this part is a systematic comparison of the...

  16. Effect of higher strain range cycling on near fatigue-limit fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Fukuoka, Chie; Nakagawa, Y.G. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan). Research Inst; Rosinski, S.T.

    1999-04-01

    The objective of this study is to clarify the effects of pre-cycling above the fatigue limit on near the fatigue-limit fatigue behaviors of SA508, low alloy steel for nuclear pressure vessels, correlating fatigue lifetime with microstructural changes in the bulk. It has been observed that dislocation cell structure is well developed in an as-received SA508 sample and the misorientation among cells increases with fatigue accumulation during fatigue tests. The cell to cell misorientation was measured and statistically quantified by the Selected Area electron beam Diffraction (SAD). It was shown that a fatigue crack started growing abruptly when the SAD value (the mean misorientation among cells) exceeded a critical angle, 4-5 degrees. Fatigue tests were performed for SA508 samples, first at a high total strain range (0.62%) to 10, 100, and 6000 cycles followed by cycling at near the fatigue-limit strain range (0.40%). The sample with pre-cycling for 100 and 6000 cycles failed while ones with pre-cycling for 10 cycles and without pre-cycling did not rupture till about 10{sup 6} cycles where the tests were terminated. Small surface cracks were found all samples pre-cycled at the high strain range but the cracks were arrested for a long time at the near fatigue limit cycling followed by an abrupt growth at the failure. It was found by the SAD that samples failed at the fatigue limit when the average misorientation among cells exceeds the critical angle regardless of pre-cycling histories. The SAD value changed even during cycling below the fatigue limit, and the change in SAD value was strongly influenced by the number of pre-cycling above the fatigue limit. These changes well agreed with fatigue lifetime of the samples. (author)

  17. The application of strain field intensity method in the steel bridge fatigue life evaluation

    Science.gov (United States)

    Zhao, Xuefeng; Wang, Yanhong; Cui, Yanjun; Cao, Kaisheng

    2012-04-01

    Asce's survey shows that 80%--90% bridge damage were associated with fatigue and fracture problems. With the operation of vehicle weight and traffic volume increases constantly, the fatigue of welded steel bridge is becoming more and more serious in recent years. A large number of studies show that most prone to fatigue damage of steel bridge is part of the welding position. Thus, it's important to find a more precise method to assess the fatigue life of steel bridge. Three kinds of fatigue analysis method is commonly used in engineering practice, such as nominal stress method, the local stress strain method and field intensity method. The first two methods frequently used for fatigue life assessment of steel bridge, but field intensity method uses less ,and it widely used in fatigue life assessment of aerospace and mechanical. Nominal stress method and the local stress strain method in engineering has been widely applied, but not considering stress gradient and multiaxial stress effects, the accuracy of calculation stability is relatively poor, so it's difficult to fully explain the fatigue damage mechanism. Therefore, it used strain field intensity method to evaluate the fatigue life of steel bridge. The fatigue life research of the steel bridge based on the strain field method and the fatigue life of the I-section plate girder was analyzed. Using Ansys on the elastoplastic finite element analysis determined the dangerous part of the structure and got the stress-strain history of the dangerous point. At the same time, in order to divide the unit more elaborate introduced the sub-structure technology. Finally, it applies K.N. Smith damage equation to calculate the fatigue life of the dangerous point. In order to better simulating the actual welding defects, it dug a small hole in the welding parts. It dug different holds from different view in the welding parts and plused the same load to calculate its fatigue life. Comparing the results found that the welding

  18. Prediction of multiaxial fatigue life for notched specimens of titanium alloy TC4

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. R.; Li, Z. X. [Southeast University, Nanjing (China); Hu, X. T.; Song, Y. D. [Nanjing University, Nanjing (China)

    2016-05-15

    Both the proportional and nonproportional multiaxial fatigue tests were conducted on two kinds of notched specimens of titanium alloy TC4. The multiaxial fatigue critical area of notched specimen is considered as the location experiencing the maximum damage. It is unsatisfactory to predict the multiaxial fatigue life with the local stress and strain in the fatigue critical area. The critical distance concepts are employed in the multiaxial life prediction method for notched specimens. The proposed method was checked by the test data of TC4 notched specimens. The prediction results are almost within a factor of three scatter band of the test results.

  19. Study on Contact Fatigue Life and Failure Mechanism of Subquenched 42CrMo Steel

    Institute of Scientific and Technical Information of China (English)

    HE Bo-lin; YU Ying-xia; SHAO Er-yu

    2004-01-01

    The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.

  20. Influence of Asymmetrical Waveform on Low-Cycle Fatigue Life of Micro Solder Joint

    Science.gov (United States)

    Kanda, Yoshihiko; Kariya, Yoshiharu

    2010-02-01

    The effects of waveform symmetry on the low-cycle fatigue life of the Sn-3.0Ag-0.5Cu alloy have been investigated, using micro solder joint specimens with approximately the same volume of solder as is used in actual products. Focusing on crack initiation life, fatigue tests on Sn-Ag-Cu micro solder joints using asymmetrical triangular waveforms revealed no significant reduction in fatigue life. A slight reduction in fatigue life at low strain ranges caused by an increase in the fatigue ductility exponent, which is the result of a weakening microstructure due to loads applied at high temperature for long testing time, was observed. This was due to the fact that grain boundary damage, which has been reported in large-size specimens subjected to asymmetrical triangular waveforms, does not occur in Sn-Ag-Cu micro size solder joints with only a small number of crystal grain boundaries.

  1. Impact of depression, fatigue and disability on quality of life in Chinese patients with multiple sclerosis.

    Science.gov (United States)

    Chen, Kelong; Fan, Yongping; Hu, Rui; Yang, Tao; Li, Kangning

    2013-04-01

    The aim of this work is to investigate and analyze the main factors that influence the quality of life (QOL) of multiple sclerosis (MS) patients. The QOL (multiple sclerosis impact scale), disability (expanded disability status scale), fatigue (modified fatigue impact scale) and depression (Beck Depression Inventory) were assessed in 100 MS patients. Correlation analysis shows that QOL is positively correlated with disability status, fatigue and depression, i.e., the more severe the disability, fatigue and depression, the worse the QOL. Multiple linear regression analysis indicated that Expanded Disability Status Scale grade and fatigue have important predictive value on the somatic QOL of MS patients. On the other hand, depression and fatigue have important predictive value on the mental QOL of MS patients. The QOL of MS patients is influenced by various factors, nursing care that focuses on patient disability, fatigue and depression should be strengthened. Copyright © 2012 John Wiley & Sons, Ltd.

  2. Verification of recursive probabilistic integration (RPI) method for fatigue life management using non-destructive inspections

    Science.gov (United States)

    Chen, Tzikang J.; Shiao, Michael

    2016-04-01

    This paper verified a generic and efficient assessment concept for probabilistic fatigue life management. The concept is developed based on an integration of damage tolerance methodology, simulations methods1, 2, and a probabilistic algorithm RPI (recursive probability integration)3-9 considering maintenance for damage tolerance and risk-based fatigue life management. RPI is an efficient semi-analytical probabilistic method for risk assessment subjected to various uncertainties such as the variability in material properties including crack growth rate, initial flaw size, repair quality, random process modeling of flight loads for failure analysis, and inspection reliability represented by probability of detection (POD). In addition, unlike traditional Monte Carlo simulations (MCS) which requires a rerun of MCS when maintenance plan is changed, RPI can repeatedly use a small set of baseline random crack growth histories excluding maintenance related parameters from a single MCS for various maintenance plans. In order to fully appreciate the RPI method, a verification procedure was performed. In this study, MC simulations in the orders of several hundred billions were conducted for various flight conditions, material properties, and inspection scheduling, POD and repair/replacement strategies. Since the MC simulations are time-consuming methods, the simulations were conducted parallelly on DoD High Performance Computers (HPC) using a specialized random number generator for parallel computing. The study has shown that RPI method is several orders of magnitude more efficient than traditional Monte Carlo simulations.

  3. Evaluation of Pressurization Fatigue Life of 1441 Al-li Fuselage Panel

    Science.gov (United States)

    Bird, R. Keith; Dicus, Dennis I.; Fridlyander, Joseph; Davydov, Valentin

    1999-01-01

    A study was conducted to evaluate the pressurization fatigue life of fuselage panels with skins fabricated from 1441 Al-Li, an attractive new Russian alloy. The study indicated that 1441 Al-Li has several advantages over conventional aluminum fuselage skin alloy with respect to fatigue behavior. Smooth 1441 Al-Li sheet specimens exhibited a fatigue endurance limit similar to that for 1163 Al (Russian version of 2024 Al) sheet. Notched 1441 Al-Li sheet specimens exhibited greater fatigue strength and longer fatigue life than 1163 Al. In addition, Tu-204 fuselage panels fabricated by Tupolev Design Bureau using Al-Li skin and ring frames with riveted 7000-series aluminum stiffeners had longer pressurization fatigue lives than did panels constructed from conventional aluminum alloys. Taking into account the lower density of this alloy, the results suggest that 1441 Al-Li has the potential to improve fuselage performance while decreasing structural weight.

  4. Aspects of fatigue life in thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Brodin, H.

    2001-08-01

    Thermal barrier coatings (TBC) are applied on hot components in airborne and land based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment. Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO{sub 2} + 6-8% Y{sub 2}O{sub 3}. Below the top coat there is a metallic bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% Yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions, have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal barrier coatings fail. As a final outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's. In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the bond coat due to inter-diffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed

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

    Directory of Open Access Journals (Sweden)

    Xiaoli WANG

    2016-08-01

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

  6. An Energy-Critical Plane Based Fatigue Damage Approach for the Life Prediction of Metal Alloys

    Science.gov (United States)

    Pitatzis, N.; Savaidis, G.

    2016-11-01

    This paper presents a new energy-critical plane based fatigue damage approach for the assessment of the fatigue life under uniaxial and multiaxial proportional and non-proportional fatigue loading. The proposed approximate method, based on Farahani's multiaxial fatigue damage model, takes into account the critical plane orientations during a loading cycle and the values of the respective damage parameters on them. The uniqueness of the proposed method lies on the fact that it considers a weighted contribution of each critical plane orientation to the material damage. The relative weighting factors depend on the declination of each critical plane with respect to the critical plane, where the damage parameters exhibit their maximum values during a fatigue loading cycle. Herein, several low, mid and high-cycle fatigue loading cases are being investigated. The induced elastic-plastic stress-strain states are approximated by means of respective finite element analyses (FEA). Several experimental fatigue data derived from uniaxial and multiaxial fatigue tests on StE460 steel alloy thin-walled hourglass-type specimens have been used to verify the model's calculation accuracy. Comparison of experimental and calculated fatigue lives confirm remarkable fatigue life calculation accuracy in all cases examined.

  7. Factors Affecting Quality of Life and Fatigue in Gynaecologic Cancer Patients

    Directory of Open Access Journals (Sweden)

    Güngör İ

    2017-06-01

    Full Text Available Background: Cancer-related fatigue (CRF is the most commonly reported and most distressing symptom in cancer patients. Health-related quality of life (QOL is an important outcome in cancer management, the authors sought to better understand its determinants. Aim: This study aims to identify quality of life and fatigue levels and the affecting factors in gynaecologic cancer patients. Method: This descriptive and cross-sectional study was conducted with 154 volunteer women with gynaecologic cancer. The data were collected through the interview form, functional assessment of cancer therapy-general (FACT-G Quality of Life Scale, and Piper Fatigue Scale. Results: The mean score of total quality of life in gynaecologic cancer patients was low, 53.4 ± 15.4. Physical and emotional states were found to be the mostly affected states in the quality of life. According to the Piper Fatigue Scale, the total fatigue score was mild, 3.5 ± 2.4. Total fatigue scores were found to be high in metastatic cancers. Multivariate analyses indicate that the most important factor affecting the quality of life is economic condition, and the most important variables affecting fatigue are the level of activity and use of medicine. Conclusion: This study found that quality of life dimensions in women with gynaecologic cancer was affected by factors such as cancer type, time of diagnosis, and stage and spread of the cancer.

  8. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

    Directory of Open Access Journals (Sweden)

    Nuha Salim Mashaan

    2014-01-01

    Full Text Available Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test, dynamic creep (repeated load creep, and fatigue test (indirect tensile fatigue test at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa. Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

  9. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

    Science.gov (United States)

    Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati

    2014-01-01

    Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture. PMID:25050406

  10. Evaluation of fatigue life of CRM-reinforced SMA and its relationship to dynamic stiffness.

    Science.gov (United States)

    Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati; Koting, Suhana

    2014-01-01

    Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

  11. Advanced High Cycle Fatigue (HCF) Life Assurance Methodologies

    Science.gov (United States)

    2004-07-01

    Kk Rcaa σπ σπ (K5) Note that ao and co depend on the assumed aspect ratio of a vanishing small initiated crack through the dependence of the...constant/,0,0()( 1,/ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =→→∆ ∆ = ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =→→∆ ∆ = iRcie th io iRaie th io RfcacafR K Rcac RfcacafR K Rcaa σπ σπ (K6) It is clear from

  12. Reduction in alert fatigue in an assisted electronic prescribing system, through the Lean Six Sigma methodology

    Directory of Open Access Journals (Sweden)

    Mª Jesús Cuéllar Monreal

    2017-01-01

    Full Text Available Objective: To reduce the alert fatigue in our Assisted Electronic Prescribing System (AEPS, through the Lean Six Sigma (LSS methodology. Method: An observational (transversal and retrospective study, in a general hospital with 850 beds and AEPS. The LSS methodology was followed in order to evaluate the alert fatigue situation in the AEPS system, to implement improvements, and to assess outcomes. The alerts generated during two trimesters studied (before and after the intervention were analyzed. In order to measure the qualitative indicators, the most frequent alert types were analyzed, as well as the molecules responsible for over 50% of each type of alert. The action by the prescriber was analyzed in a sample of 496 prescriptions that generated such alerts. For each type of alert and molecule, there was a prioritization of the improvements to be implemented according to the alert generated and its quality. A second survey evaluated the pharmacist action for the alerts most highly valued by physicians. Results: The problem, the objective, the work team and the project schedule were defined. A survey was designed in order to understand the opinion of the client about the alert system in the program. Based on the surveys collected (n = 136, the critical characteristics and the quanti/qualitative indicators were defined. Sixty (60 fields in the alert system were modified, corresponding to 32 molecules, and this led to a 28% reduction in the total number of alerts. Regarding quality indicators, false po sitive results were reduced by 25% (p < 0.05, 100% of those alerts ignored with justification were sustained, and there were no significant differences in user adherence to the system. The project improvements and outcomes were reviewed by the work team. Conclusions: LSS methodology has demonstrated being a valid tool for the quantitative and qualitative improvement of the alert system in an Assisted Electronic Prescription Program, thus reducing

  13. Laser Shock Peening of Aluminum Alloy 7050 for Fatigue Life Improvement

    Institute of Scientific and Technical Information of China (English)

    Qian; Ming; Lian; Ying; Zou; Shikun; Gong; Shuili

    2007-01-01

    The effects of laser shock peening (LSP) on improving fatigue life of aluminum alloy 7050 are investigated.Surface hardness is increased corresponding to a high dislocation density induced by LSP.The X-ray diffraction stress measurement shows that LSP results in prominent increase of surface compressive stress,quasi-symmetrically distributed in the laser peened region.The fatigue life of the alloy 7050 in rivet fastener hole structure is notably improved owing to LSP.The sequence of LSP and fastener hole preparation also influence the fatigue cycle life of the alloy.

  14. Modeling of fatigue life of materials and structures under low-cycle loading

    Science.gov (United States)

    Volkov, I. A.; Korotkikh, Yu. G.

    2014-05-01

    A damaged medium model (DMM) consisting of three interconnected components (relations determining the cyclic elastoplastic behavior of the material, kinetic damage accumulation equations, and the strength criterion for the damaged material) was developed to estimate the stress strain state and the fatigue life of important engineering objects. The fatigue life of a strip with a cut under cyclic loading was estimated to obtain qualitative and quantitative estimates of the DMM constitutive relations under low-cycle loading. It was shown that the considered version of the constitutive relations reliably describes the main effects of elastoplastic deformation and the fatigue life processes of materials and structures.

  15. Relation between Shot Peening Process and Fatigue Life in the Case of Hardening Steels

    Institute of Scientific and Technical Information of China (English)

    SHIGEYOSHI HAGA; HARUSHIGE TSUBAKINO; YASUNORI HARADA

    2004-01-01

    Nowadays, in the auto industry, the need for improvement of fuel efficiency is getting increased more and more in terms of the global warming, as well as the need of light-weighting of gears, transmission parts. Hence, we've studied the relation between the shot peening working conditions and factors for improvement of gear's fatigue life, and also the relation between the factors for improvement and the fatigue life, applying shot peening to a gear of SNCM220. Also, we examined the relation between the fatigue life and arc height that is utilized as a substitute characteristic for shot peening working conditions, adding its observation here.

  16. A Simple Fatigue Life Prediction Algorithm Using the Modified NASGRO Equation

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2016-01-01

    Full Text Available A simple fatigue life prediction algorithm using the modified NASGRO equation is proposed in this paper. The NASGRO equation is modified by introducing the concept of intrinsic effective threshold stress intensity factor (SIF range ΔKeffth. One advantage of the proposed method is that the complex growth behavior analysis of small cracks can be avoided, and then the fatigue life can be calculated by directly integrating the crack growth model from the initial defect size to the critical crack size. The fatigue limit and the intrinsic effective threshold SIF range ΔKeffth are used to calculate the initial defect size or initial flaw size. The value of ΔKeffth is determined by extrapolating the crack propagation rate curves. Instead of using the fatigue limit determined by the fatigue strength at the specific fatigue life, the fatigue limit is selected based on the horizontal tendency of the S-N curve. The calculated fatigue lives are compared to the experimental data of two different alloys. The predicted S-N curves agree with the test data well. Besides, the prediction results are compared with that calculated using the FASTRAN code. Results indicate that the proposed life prediction algorithm is simple and efficient.

  17. Fatigue and quality of life in breast cancer survivors: temporal courses and long-term pattern

    NARCIS (Netherlands)

    Schmidt, M.E.; Chang-Claude, J.; Vrieling, A.; Heinz, J.; Flesch-Janys, D.; Steindorf, K.

    2012-01-01

    INTRODUCTION: Fatigue is a frequent problem during and after cancer treatment. We investigated different courses of fatigue from pre-diagnosis, through therapy, to long-term survivorship and evaluated potential implications on long-term quality of life (QoL). METHODS: Breast cancer patients diagnose

  18. Impact of fatigue on quality of life in patients with Parkinson's disease

    NARCIS (Netherlands)

    Havlikova, E.; Rosenberger, J.; Nagyova, I.; Middel, B.; Dubayova, T.; Gdovinova, Z.; van Dijk, J. P.; Groothoff, J. W.

    2008-01-01

    Background and purpose: Fatigue is frequent and important in the lives of Parkinson's disease (PD) patients. It is multidimensional, with physical and mental aspects. The aim of our study was to explore the impact of fatigue on quality of life (QoL) for PD patients. Methods: The sample consisted of

  19. 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...

  20. Fatigue Life Prediction of Metallic Materials Based on the Combined Nonlinear Ultrasonic Parameter

    Science.gov (United States)

    Zhang, Yuhua; Li, Xinxin; Wu, Zhenyong; Huang, Zhenfeng; Mao, Hanling

    2017-07-01

    The fatigue life prediction of metallic materials is always a tough problem that needs to be solved in the mechanical engineering field because it is very important for the secure service of mechanical components. In this paper, a combined nonlinear ultrasonic parameter based on the collinear wave mixing technique is applied for fatigue life prediction of a metallic material. Sweep experiments are first conducted to explore the influence of driving frequency on the interaction of two driving signals and the fatigue damage of specimens, and the amplitudes of sidebands at the difference frequency and sum frequency are tracked when the driving frequency changes. Then, collinear wave mixing tests are carried out on a pair of cylindrically notched specimens with different fatigue damage to explore the relationship between the fatigue damage and the relative nonlinear parameters. The experimental results show when the fatigue degree is below 65% the relative nonlinear parameter increases quickly, and the growth rate is approximately 130%. If the fatigue degree is above 65%, the increase in the relative nonlinear parameter is slow, which has a close relationship with the microstructure evolution of specimens. A combined nonlinear ultrasonic parameter is proposed to highlight the relationship of the relative nonlinear parameter and fatigue degree of specimens; the fatigue life prediction model is built based on the relationship, and the prediction error is below 3%, which is below the prediction error based on the relative nonlinear parameters at the difference and sum frequencies. Therefore, the combined nonlinear ultrasonic parameter using the collinear wave mixing method can effectively estimate the fatigue degree of specimens, which provides a fast and convenient method for fatigue life prediction.

  1. Fatigue Life Prediction of Metallic Materials Based on the Combined Nonlinear Ultrasonic Parameter

    Science.gov (United States)

    Zhang, Yuhua; Li, Xinxin; Wu, Zhenyong; Huang, Zhenfeng; Mao, Hanling

    2017-08-01

    The fatigue life prediction of metallic materials is always a tough problem that needs to be solved in the mechanical engineering field because it is very important for the secure service of mechanical components. In this paper, a combined nonlinear ultrasonic parameter based on the collinear wave mixing technique is applied for fatigue life prediction of a metallic material. Sweep experiments are first conducted to explore the influence of driving frequency on the interaction of two driving signals and the fatigue damage of specimens, and the amplitudes of sidebands at the difference frequency and sum frequency are tracked when the driving frequency changes. Then, collinear wave mixing tests are carried out on a pair of cylindrically notched specimens with different fatigue damage to explore the relationship between the fatigue damage and the relative nonlinear parameters. The experimental results show when the fatigue degree is below 65% the relative nonlinear parameter increases quickly, and the growth rate is approximately 130%. If the fatigue degree is above 65%, the increase in the relative nonlinear parameter is slow, which has a close relationship with the microstructure evolution of specimens. A combined nonlinear ultrasonic parameter is proposed to highlight the relationship of the relative nonlinear parameter and fatigue degree of specimens; the fatigue life prediction model is built based on the relationship, and the prediction error is below 3%, which is below the prediction error based on the relative nonlinear parameters at the difference and sum frequencies. Therefore, the combined nonlinear ultrasonic parameter using the collinear wave mixing method can effectively estimate the fatigue degree of specimens, which provides a fast and convenient method for fatigue life prediction.

  2. Fatigue, mood and quality of life improve in MS patients after progressive resistance training

    DEFF Research Database (Denmark)

    Dalgas, U; Stenager, E; Petersen, T

    2010-01-01

    . Fatigue (Fatigue Severity Scale, FSS), mood (Major Depression Inventory, MDI) and quality of life (physical and mental component scores, PCS and MCS, of SF36) were scored at start, end and follow-up of a randomized controlled clinical trial of 12 weeks of progressive resistance training in moderately...... disabled (Expanded Disability Status Scale, EDSS: 3-5.5) multiple sclerosis patients including a Control group (n = 15) and an Exercise group (n = 16). Fatigue (FSS > 4) was present in all patients. Scores of FSS, MDI, PCS-SF36 and MCS-SF36 were comparable at start of study in the two groups. Fatigue...

  3. Fatigue Life Analysis of Tapered Hybrid Composite Flexbeams

    Science.gov (United States)

    Murri, Gretchen B.; Schaff, Jeffery R.; Dobyns, Alan L.

    2002-01-01

    Nonlinear-tapered flexbeam laminates from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. The two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) obtained from the above codes using the virtual crack closure technique (VCCT) at a resin crack location in the flexbeams are presented for both hybrid material types. These results compare well with each other and suggest that the initial delamination growth from the resin crack toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves and compared with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared reasonably well with the test results.

  4. Fatigue life of high strength steel for cold forming

    Directory of Open Access Journals (Sweden)

    R. Ulewicz

    2017-01-01

    Full Text Available The article presents the results of fatigue tests carried out on STRENX-type high-strength cold forming steel. For high-cycle fatigue tests carried out using low cycle loading frequencies of around 30 Hz, a ROTOFLEX machine was used. For ultra high-cycle tests, a KAUP-ZU testing machine was employed, which enables fatigue tests to be performed with symetric specimen loading (R = -1 and at a frequency of f ≈ 20 kHz. The relationships σa = f(N were determined experimentally in the high and ultra high-cycle region for STRENX high-strength steel. To determine the fatigue crack initiation mechanism, the fractographic analysis of fatigue fractures was made.

  5. Fatigue life prediction method for contact wire using maximum local stress

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean [Sungkyunkwan University, Suwon (Korea, Republic of); Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)

    2015-01-15

    Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.

  6. Fatigue Life Prediction of Horizontal Press Frame Based on Statistical Probability and Its Redesign

    Institute of Scientific and Technical Information of China (English)

    WeiWei Zhang; XiaoSon Wang; Bo Yang; Shi-Jian Yuan

    2014-01-01

    Horizontal press as an important part of hydro-forming machine is used to output the horizontal force to keep the high internal pressure during tube hydro-forming. However, the horizontal press frame is usually mounted on the press bed and not pre-stressed. Meanwhile it will be subjected to the reaction force caused by liquid pressure. Stresses are concentrated severely on the assemble region due to deformation, and total fatigue life will decrease. In order to predict the total fatigue life of the frame, the simulations are used firstly to determine to stress concentration region, and then strain gauge measurements are carried out under different loads. Next, the methods of statistical probability are conducted to calculate the fatigue life based on long-term load history. Finally a structure with the considerable longer fatigue life is redesigned.

  7. Extreme Environment Damage Index and Accumulation Model for CMC Laminate Fatigue Life Prediction Project

    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...

  8. Effect of various drilling procedures on the fatigue life of rivet holes ...

    African Journals Online (AJOL)

    Synthèse: Revue des Sciences et de la Technologie ... In addition, the machining process used for drilling can increase or decrease the fatigue life of materials. ... and surface quality observed using a scanning electron microscopy (SEM).

  9. Fatigue life prediction of casing welded pipes by using the extended finite element method

    National Research Council Canada - National Science Library

    Ljubica Lazi; Aleksandar Raji; Aleksandar Grbovi; Aleksandar Sedmak; e Sarko

    2016-01-01

      The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life...

  10. 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.

  11. Voltage sag influence on fatigue life of the drivetrain of fixed speed wind turbines

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2011-01-01

    on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries...... effect on the fatigue life of drivetrain components. The capability to simulate these phenomena is a novel aspect in the present effort....

  12. The prediction technology study of fatigue life for key parts of a tracked vehicle's suspension system

    Institute of Scientific and Technical Information of China (English)

    WANG Hongyan; RUI Qiang; HE Xiaojun

    2007-01-01

    In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software-ADAMS. Node force and stress results of the torsion bar from last step simu- lation were acquired; taking into account the material charac- teristics and influential factors, fatigue life of the flexible body. of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.

  13. The fatigue life of a cobalt-chromium alloy after laser welding.

    Science.gov (United States)

    Al-Bayaa, Nabil Jalal Ahmad; Clark, Robert K F; Juszczyk, Andrzej S; Radford, David R

    2011-03-01

    The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p welded specimens despite 70% penetration of the weld.

  14. Estimation of the Residual Fatigue Life of Laminated Composites Under a Multistage Cyclic Loading

    Science.gov (United States)

    Strizhius, V.

    2016-11-01

    Problems on estimation of the residual fatigue life of laminated composites under a multistage regular cyclic loading (with a constant amplitude at each loading stage) are among the most frequently ones encountered in the practice of fatigue life estimations of laminated composites. There are several methods for solving these problems, but their use not always gives results of acceptable accuracy. To improve the accuracy of such estimations for the type of cyclic loading mentioned, a special model of nonlinear accumulation of fatigue damage is proposed.

  15. Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.

    2011-01-01

    the fatigue life of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens at varying levels of cyclic frequency and load. The fatigue tests were performed in two series, one with the specimens tested in air and one with the specimens submerged in water during...... the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when tested in water than when tested in air, particularly at low frequency....

  16. Fatigue Life of Stainless Steel in PWR Environments with Strain Holding

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taesoon; Kim, Kyuhyung [KHNP CRI, Daejeon (Korea, Republic of); Seo, Myeonggyu; Jang, Changheui [KAIST, Daejeon (Korea, Republic of)

    2016-10-15

    Many components and structures of nuclear power plants are exposed to the water chemistry conditions during the operation. Recently, as design life of nuclear power plant is expanded over 60 years, the environmentally assisted fatigue (EAF) due to these water chemistry conditions has been considered as one of the important damage mechanisms of the safety class 1 components. Therefore, many studies to evaluate the effect of light water reactor (LWR) coolant environments on fatigue life of materials have been conducted. Many EAF test results including Argonne National Laboratory’s consistently indicated the substantial reduction of fatigue life in the light water reactor environments. However, there is a discrepancy between laboratory test data and plant operating experience regarding the effects of environment on fatigue: while laboratory test data suggest huge accumulation of fatigue damage, very limited experience of cracking caused by the low cycle fatigue in light water reactor. These hold-time effect tests are preformed to characterize the effects of strain holding on the fatigue life of austenitic stainless steels in PWR environments in comparison with the existing fixed strain rate results. Low cycle fatigue life tests were conducted for the type 316 stainless steel in 310℃ air and PWR environments with triangular strain. In agreement with the previous reports, the LCF life was reduced in PWR environments. Also for the slower strain rate, the reduction of LCF life was greater than the faster strain rate. The LCF test conditions for the hold-time effects were determined by the references and consideration of actual plant transient. To simulate the heat-up and cooldown transient, sub-peak strain holding during the down-hill of strain amplitude was chosen instead of peak strain holding which used in the previous researches.

  17. Development of a Novel Approach for Fatigue Life Prediction of Structural Materials

    Science.gov (United States)

    2008-12-01

    11] for Inconel 718 under a similar loading condition. A kink around a fatigue life of 3xl05 cycles was noticed in the shear strain-life curve from...observed on AISI 304 stainless steel [10], Inconel 718 [11], 1045 steel [12], and an aluminum alloy [13]. However, no kink in the strain-life curves

  18. Consideration on corrosion fatigue crack life assessment; Fushoku hiro kiretsu hassei jumyo hyoka ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yajima, H.; Yamamoto, M.; Saito, T. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Morita, K. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

    1996-10-01

    Discussions were given on corrosion fatigue crack life by using corrosion fatigue crack initiation test and analysis. The test used 13Cr-based stainless steel as a test material, and aquamarine at 60{degree}C as a corrosion environment. The fatigue test was performed under a tension loading condition with a stress ratio of 0.1 and an iterative velocity of 1.7 Hz by using a 10-tonf fatigue testing machine. In the corrosion fatigue crack initiation test, a pit has been generated on a boundary of an exposed part and a painted part for masking, hence direct observation was impossible on pit growth behavior. Therefore, an intrinsic crack model was introduced from pit dimensions as observed from a fracture face, and analysis was made on corrosion fatigue crack growth by using the linear fracture dynamics, wherein clarification was made on a phenomenon occurring after the crack growth passes the pit growth until the test piece is fractured. A proposal was made to define the time when fatigue crack initiates and grows from the bottom of a pit as a result of surpassing the growth of corrosion pit as the corrosion fatigue crack life. 4 refs., 7 figs., 1 tab.

  19. Fatigue life on a full scale test rig: Forged versus cast wind turbine rotor shafts

    Science.gov (United States)

    Herrmann, J.; Rauert, T.; Dalhoff, P.; Sander, M.

    2016-09-01

    To reduce uncertainties associated with the fatigue life of the highly safety relevant rotor shaft and also to review today's design practice, the fatigue behaviour will be tested on a full scale test rig. Until now tests on full scale wind turbine parts are not common. Therefore, a general lack of experience on how to perform accelerated life time tests for those components exists. To clarify how to transfer real conditions to the test environment, the arrangements and deviations for the upcoming experimental test are discussed in detail. In order to complete investigations of weight saving potentials, next to getting a better comprehension of the fatigue behaviour by executing a full scale test, a further outcome are suggestions for the usage of cast and forged materials regarding the fatigue and the remaining life of the rotor shaft. It is shown, that it is worthwhile to think about a material exchange for the forged rotor shaft.

  20. Fatigue life of stainless steel 304 enhancement by addition of multi-walled carbon nanotubes (MWCNTs)

    Energy Technology Data Exchange (ETDEWEB)

    Syed, Rizwanulhaque; Jiang, Wei; Wang, Cunshan [Dalian University of Technology, Dalian (China); Sabir, M. Iqbal [Xiao Zhang County, Tianjin (China)

    2015-01-15

    Stainless steel is among the most widely used industrial materials. In particular, stainless steel 304 (304SS) is the most used material grade. To increase the utilization of any industrial material, its fatigue life should be optimized. In this work, the fatigue life of 304SS was enhanced by the addition of multi-walled carbon nanotubes (MWCNTs). Moreover, the incorporation of a small amount of MWCNTs increased the fatigue life of 304SS. Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction (XRD) results showed that the suppression of fatigue crack growth rate was caused by CNT deposition at the crack tip. CNTs were entangled with each other, thereby resulting in finer grain size. The XRD diffractograms of the 304SS treated area peak showed that the microstructure consisted of austenite and carbon.

  1. Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.

    2011-01-01

    The cementitious material in grouted connections of offshore monopile wind turbine structures is subjected to very high oscillating service stresses. The fatigue capacity of the grout therefore becomes essential to the performance and service life of the grouted connection. In the present work...... the fatigue life of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens at varying levels of cyclic frequency and load. The fatigue tests were performed in two series, one with the specimens tested in air and one with the specimens submerged in water during...... the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when tested in water than when tested in air, particularly at low frequency....

  2. The ROF+ methodology for grease life testing

    NARCIS (Netherlands)

    Lugt, Pieter Martin; van den Kommer, A.; Lindgren, H.; Deinhofer, L.

    2013-01-01

    Very often, the service life of grease lubricated rolling bearings is determined by the so called “grease life”. This can be tested on R0F test rigs, which have been available for this since more than 40 years. Recently, this technology has been updated and is now called R0F+. The R0F+ can be used a

  3. Multiaxial Fatigue Life Prediction for Steels Based on Some Simple Approximations

    Science.gov (United States)

    Li, Jing; Yao, Zhi-feng; Zhang, Zhong-ping

    2015-01-01

    The Roessle-Fatemi's hardness method (HM) and Muralidharan-Manson's modified universal slopes method (MUSM) were employed to determine the uniaxial fatigue properties of steels from easily obtained tensile properties. Both methods give good life predictions, while the Roessle-Fatemi's HM is somewhat better. Furthermore, for predicting multiaxial fatigue lives of steels in the absence of any fatigue data, the Li's modified Wang-Brown model (MWB) was used in combination with the HM method (MWB-HM) as well as the MUSM method (MWB-MUSM), respectively. Correlation between the yield strength and the Brinell hardness was also developed to estimate the multiaxial fatigue lives of steels based only on hardness and elasticity modulus. It is shown that multiaxial fatigue lives were predicted fairly well by all the methods, and the MWB-MUSM method is slightly more accurate. In addition, a computer-based procedure for multiaxial fatigue life assessment incorporating MWB-MUSM approach was proposed and implemented to predict the fatigue life of an intermediate compressor casing. The predicted results are promising.

  4. Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

    Science.gov (United States)

    Sivan, Shiril; Di Prima, Matthew; Weaver, Jason D.

    2017-06-01

    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.

  5. Life prediction of thermal-mechanical fatigue using strain-range partitioning

    Science.gov (United States)

    Halford, G. R.; Manson, S. S.

    1975-01-01

    The applicability is described of the method of Strainrange Partitioning to the life prediction of thermal-mechanical strain-cycling fatigue. An in-phase test on 316 stainless steel is analyzed as an illustrative example. The observed life is in excellent agreement with the life predicted by the method using the recently proposed Step-Stress Method of experimental partitioning, the Interation Damage Rule, and the life relationships determined at an isothermal temperature of 705 C. Implications of the study are discussed relative to the general thermal fatigue problem.

  6. Effect of vibration loading on the fatigue life of part-through notched pipe

    Energy Technology Data Exchange (ETDEWEB)

    Mittal, Rahul [Nuclear Power Corporation of India Limited, Mumbai (India); Singh, P.K., E-mail: singh_pawank@yahoo.com [Bhabha Atomic Research Centre, Mumbai (India); Pukazhendi, D.M. [Structural Engineering research Centre, Chennai (India); Bhasin, V.; Vaze, K.K.; Ghosh, A.K. [Bhabha Atomic Research Centre, Mumbai (India)

    2011-10-15

    A systematic experimental and analytical study has been carried out to investigate the effect of vibration loading on the fatigue life of the piping components. Three Point bend (TPB) specimens machined from the actual pipe have been used for the evaluation of Paris constants by carrying out the experiments under vibration + cyclic and cyclic loading as per the ASTM Standard E647. These constants have been used for the prediction of the fatigue life of the pipe having part-through notch of a/t = 0.25 and aspect ratio (2c/a) of 10. Predicted results have shown the reduction in fatigue life of the notched pipe subjected to vibration + cyclic loading by 50% compared to that of cyclic loading. Predicted results have been validated by carrying out the full-scale pipe (with part-through notch) tests. Notched pipes were subjected to loading conditions such that the initial stress-intensity factor remains same as that of TPB specimen. Experimental results of the full-scale pipe tests under vibration + cyclic loading has shown the reduction in fatigue life by 70% compared to that of cyclic loading. Fractographic examination of the fracture surface of the tested specimens subjected to vibration + cyclic loading have shown higher presence of brittle phases such as martensite (in the form of isolated planar facets) and secondary micro cracks. This could be the reason for the reduction of fatigue life in pipe subjected to vibration + cyclic loading. - Highlights: > Vibration loading affects fatigue crack growth rate. > Crack initiation life depends on crack tip radius. > Crack initiation life depends on the characteristic distance. > Characteristic distance depends on the loading conditions. > Vibration + cyclic load gives lower fatigue life.

  7. Time and frequency domain models for multiaxial fatigue life estimation under random loading

    Directory of Open Access Journals (Sweden)

    Andrea Carpinteri

    2015-07-01

    Full Text Available Engineering structures and components are often subjected to random fatigue loading produced, for example, by wind turbulences, marine waves and vibrations. The methods available in the literature for fatigue assessment under random loading are formulated in time domain or, alternatively, in frequency domain. The former methods require the knowledge of the loading time history, and a large number of experimental tests/numerical simulations is needed to obtain statistically reliable results. The latter methods are generally more advantageous with respect to the time domain ones, allowing a rapid fatigue damage evaluation. In the present paper, a multiaxial criterion formulated in the frequency-domain is presented to estimate the fatigue lives of smooth metallic structures subjected to combined bending and torsion random loading. A comparison in terms of fatigue life prediction by employing a time domain methods, previously proposed by the authors, is also performed.

  8. Methodologies for defining quality of life

    Energy Technology Data Exchange (ETDEWEB)

    Glicken, J. [Ecological Planning and Toxicology, Inc., Albuquerque, NM (United States); Engi, D. [Sandia National Labs., Albuquerque, NM (United States)

    1996-10-10

    Quality of life as a concept has been used in many ways in the public policy arena. It can be used in summative evaluations to assess the impacts of policies or programs. Alternatively, it can be applied to formative evaluations to provide input to the formation of new policies. In short, it provides the context for the understanding needed to evaluate the results of choices that have been made in the public policy arena, or the potential of choices yet to be made. In either case, the public policy question revolves around the positive or negative impact the choice will have on quality of life, and the magnitude of that impact. This discussion will develop a conceptual framework that proposes that an assessment of quality of life is based on a comparison of expectations with experience. The framework defines four basic components from which these expectations arise: natural conditions, social conditions, the body, and the mind. Each one of these components is generally described, and associated with a general policy or rhetorical category which gives it its policy vocabulary--environmental quality, economic well-being, human health, and self-fulfillment.

  9. An Integrated Approach to Fatigue Life Prediction of Whole System for Offshore Platforms

    Institute of Scientific and Technical Information of China (English)

    方华灿; 段梦兰; 许发彦; 吴永宁; 樊晓东

    2001-01-01

    The failure of one or even more components usually does not lead to the collapse of the whole structure. Most of theanalysis of fatigue is centered on only a single component which the researchers are interested in or much attentionshould be paid to. However, the collapse of a structure is the result of failure of a series of components in a specific orderor path. This paper proposes an integrated approach to fatigue life prediction of whole structural system for offshoreplatforms, mainly describing the basic principles and prediction method. A method is presented for determining the fail-ure path of the whole structure system and calculating the fatigue life in the determined failure path. The correspondingfinal collapse criteria for the whole structure system are discussed. A simple method of equivalent fatigue stress range cal-culation and a mathematical model of structural component fatigue life estimation in consideration of sea wave and seaice loads are provided. As an application of the proposed approach, a fixed production platform Bohai No. 8 is chosenfor the predication of fatigue life of the whole structure system by means of the software OSFAC developed based on thepresent methods.

  10. Effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy

    Institute of Scientific and Technical Information of China (English)

    何晓; 岳俊; 沈保罗; 曹建玲; 邱绍宇; 邹红

    2003-01-01

    Four hydrogen contents were employed to investigate the effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy by means of section-varied samples. Results reveal that the fatigue life of the materials with (116~280)×10-6 hydrogen is higher than that of natural hydrogen material provided that the fatigue load Δσ is over 550MPa. At higher Δσ, the content of hydrogen has small effects on fatigue life within (116-280)×10-6 hydrogen. For material containing 280×10-6 hydrogen, fatigue cracks tend to initiate at sample edges at higher load, in contrast, to initiate at sites of hydrides at lower load. The interstitial hydrogen atoms softening the persistent slip bands(PSB) and hydrides separating from the body become the cause of decrease in fatigue life. Hydrides resolved into the body is observed at lower Δσ for material with 280×10-6 hydrogen, which is the result of concentration of hydrogen atoms at crack tips and stress-induced re-precipitation of hydrides.

  11. Numerical fatigue life assessment of cardiovascular stents: A two-scale plasticity-damage model

    Science.gov (United States)

    Santos, H. A. F. A.; Auricchio, F.; Conti, M.

    2013-07-01

    Cardiovascular disease has become a major global health care problem in the last decades. To tackle this problem, the use of cardiovascular stents has been considered a promising and effective approach. Numerical simulations to evaluate the in vivo behavior of stents are becoming more and more important to assess potential failures. As the material failure of a stent device has been often associated with fatigue issues, numerical approaches for fatigue life assessment of stents have gained special interest in the engineering community. Numerical fatigue life predictions can be used to modify the design and prevent failure without making and testing numerous physical devices, thus preventing from undesired fatigue failures. We present a numerical fatigue life model for the analysis of cardiovascular balloon-expandable stainless steel stents that can hopefully provide useful information either to be used for product improvement or for clinicians to make life-saving decisions. This model incorporates a two-scale continuum damage mechanics model and the so-called Soderberg fatigue failure criterion. We provide numerical results for both Palmaz-Schatz and Cypher stent designs and demonstrate that a good agreement is found between the numerical and the available experimental results.

  12. Fatigue life estimation procedures for the endurance of a cardiac valve prosthesis: stress/life and damage-tolerant analyses.

    Science.gov (United States)

    Ritchie, R O; Lubock, P

    1986-05-01

    Projected fatigue life analyses are performed to estimate the endurance of a cardiac valve prosthesis under physiological environmental and mechanical conditions. The analyses are conducted using both the classical stress-strain/life and the fracture mechanics-based damage-tolerant approaches, and provide estimates of expected life in terms of initial flaw sizes which may pre-exist in the metal prior to the valve entering service. The damage-tolerant analysis further is supplemented by consideration of the question of "short cracks," which represents a developing area in metal fatigue research, not commonly applied to data in standard engineering design practice.

  13. Fatigue in patients with neuromyelitis optica spectrum disorder and its impact on quality of life.

    Science.gov (United States)

    Seok, Jin Myoung; Choi, Misong; Cho, Eun Bin; Lee, Hye Lim; Kim, Byoung Joon; Lee, Kwang Ho; Song, Pamela; Joo, Eun Yeon; Min, Ju-Hong

    2017-01-01

    Fatigue is a prevalent symptom and major burden in neuroimmunological diseases. In neuromyelitis optica spectrum disorder (NMOSD), a severe autoimmune central nervous system (CNS) inflammatory disease with autoantibodies reactive to aquaporin-4, there are few reports about fatigue and quality of life (QOL). We aimed to evaluate the severity of fatigue and its relationship with QOL in patients with NMOSD. We prospectively studied patients with NMOSD who were in remission and seropositive for anti-aquaporin-4 antibody, and they were divided into 2 groups based on the presence of fatigue assessed using the Functional Assessment of Chronic Illness Therapy-fatigue score. Sleep quality, depression, pain, and QOL were also evaluated. A total of 35 patients were enrolled (mean age, 46.5 ± 14.1 years; female: male = 29:6), and the median Expanded Disability Status Scale (EDSS) score was 2.0 (range, 0 to 8.0). The patients with fatigue (N = 25, 71.4%) had poorer sleep quality and more severe depression than those without fatigue (p = 0.009 and p = 0.001). Both the physical and mental QOL scores were lower in patients with fatigue than in those without fatigue (p = 0.033 and p = 0.004). Multiple linear regression analyses showed that the degree of fatigue with EDSS score and pain were independent predictors of physical aspects of QOL (B = 0.382, p = 0.001), whereas depression was the only predictor of the mental components of QOL (B = -0.845, p = <0.001). Fatigue is a common symptom and an important predictor of QOL in patients with NMOSD.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    suggested by the IEC 61400-1 standard were studied employing different load time intervals and by using two novel fatigue tools called ALBdeS and BECAS+F. The aeroelastic loads were defined thought aeroelastic simulations performed with both FAST and HAWC2 tools. The stress spectra at each layer were...

  15. Experimental Investigation on the Fatigue Life of Ti-6Al-4V Treated by Vibratory Stress Relief

    Directory of Open Access Journals (Sweden)

    Han-Jun Gao

    2017-05-01

    Full Text Available Vibratory stress relief (VSR is a highly efficient and low-energy consumption method to relieve and homogenize residual stresses in materials. Thus, the effect of VSR on the fatigue life should be determined. Standard fatigue specimens are fabricated to investigate the fatigue life of Ti-6Al-4V titanium alloy treated by VSR. The dynamic stresses generated under different VSR amplitudes are measured, and then the relationship between the dynamic stress and vibration amplitude is obtained. Different specimen groups are subjected to VSRs with different amplitudes and annealing treatment with typical process parameters. Residual stresses are measured to evaluate the stress relieving effects. Finally, the fatigue behavior under different states is determined by uniaxial tension–compression fatigue experiments. Results show that VSR and annealing treatment have negative effects on the fatigue life of Ti-6Al-4V. The fatigue life is decreased with the increase in VSR amplitude. When the VSR amplitude is less than 0.1 mm, the decrease in fatigue limit is less than 2%. Compared with specimens without VSR or annealing treatment, the fatigue limit of the specimens treated by VSR with 0.2 mm amplitude and annealing treatment decreases by 10.60% and 8.52%, respectively. Although the stress relieving effect is better, high amplitude VSR will lead to the decrease of Ti-6Al-4V fatigue life due to the defects generated during vibration. Low amplitude VSR can effectively relieve the stress with little decrease in fatigue life.

  16. Quality of life, fatigue, depression and cognitive impairment in Lyme neuroborreliosis.

    Science.gov (United States)

    Dersch, Rick; Sarnes, Antonia A; Maul, Monika; Hottenrott, Tilman; Baumgartner, Annette; Rauer, Sebastian; Stich, Oliver

    2015-11-01

    The prognosis and impact of residual symptoms on quality of life in patients with Lyme neuroborreliosis (LNB) is subject to debate. The aim of this study was to assess quality of life, fatigue, depression, cognitive impairment and verbal learning in patients with definite LNB and healthy controls in a case-control study. We retrospectively identified all patients diagnosed with definite LNB between 2003 and 2014 in our tertiary care center. Healthy controls were recruited from the same area. Patients and healthy controls were assessed for quality of life [Short Form (36) with subscores for physical and mental components (PCS, MCS)], fatigue (fatigue severity scale), depression (Beck depression inventory), verbal memory and learning and cognitive impairment (mini-mental state examination). 53 patients with definite LNB could be identified, of which 30 partook in the follow-up assessment. Estimates for quality of life, fatigue, depression, verbal memory and cognitive impairment did not differ statistically significantly between 30 patients with LNB and 35 healthy controls. Patients with residual symptoms had lower scores for quality of life (PCS) compared to patients without residual symptoms. Our results do not support the hypothesis that a considerable proportion of patients with antibiotically treated LNB develop a 'post Lyme syndrome' consisting of debilitating fatigue or cognitive impairment or have severe limitations of quality of life. However, some patients experience residual symptoms of LNB.

  17. Development of Probabilistic Life Prediction Methodologies and Testing Strategies for MEMS

    Science.gov (United States)

    Jadaan, Osama M.

    2003-01-01

    This effort is to investigate probabilistic life prediction methodologies for MicroElectroMechanical Systems (MEMS) and to analyze designs that determine stochastic properties of MEMS. This includes completion of a literature survey regarding Weibull size effect in MEMS and strength testing techniques. Also of interest is the design of a proper test for the Weibull size effect in tensile specimens. The Weibull size effect is a consequence of a stochastic strength response predicted from the Weibull distribution. Confirming that MEMS strength is controlled by the Weibull distribution will enable the development of a probabilistic design methodology for MEMS - similar to the GRC developed CARES/Life program for bulk ceramics. Another potential item of interest is analysis and modeling of material interfaces for strength as well as developing a strategy to handle stress singularities at sharp corners, filets, and material interfaces. The ultimate objective of this effort is to further develop and verify the ability of the Ceramics Analysis and Reliability Evaluation of Structuredlife (CARES/Life) code to predict the time-dependent reliability of MEMS structures subjected to multiple transient loads. Along these lines work may also be performed on transient fatigue life prediction methodologies.

  18. FATIGUE LIFE PREDICTION OF COMMERCIALLY PURE TITANIUM AFTER NITROGEN ION IMPLANTATION

    Directory of Open Access Journals (Sweden)

    Nurdin Ali

    2013-06-01

    Full Text Available Prediction of fatigue life has become an interesting issue in biomaterial engineering and design for reliability and quality purposes, particularly for biometallic material with modified surfaces. Commercially pure titanium (Cp-Ti implanted with nitrogen ions is a potential metallic biomaterial of the future. The effect of nitrogen ion implantation on fatigue behavior of Cp-Ti was investigated by means of axial loading conditions. The as-received and nitrogen-ion implanted specimens with the energy of 100 keV and dose of 2 × 1017 ions cm-2, were used to determine the fatigue properties and to predict the life cycle of the specimens. The effect of nitrogen ion implantation indicated revealed improved the tensile strength due to the formation of nitride phases, TiN and Ti2N. The fatigue strength of Cp-Ti and Nii-Ti was 250 and 260 MPa, respectively. The analytical results show good agreement with experimental results.

  19. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

    Institute of Scientific and Technical Information of China (English)

    WANG Qingyuan (王清远); N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI

    2003-01-01

    Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials,loading,and environmental conditions.A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (i.e.the pit nucleation and growth,pit-crack transition,short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size,corrosion pitting current,and material properties due to the scatter found in the experimental data.Monte Carlo simulations were performed to define the failure probability distribution.Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data.

  20. The effects of fibre architecture on fatigue life-time of composite materials

    DEFF Research Database (Denmark)

    Hansen, Jens Zangenberg; Østergaard, Rasmus

    Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre...... reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last...... decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation...

  1. Comparing Guidelines Concerning Construction of the S-N Curve within Limited Fatigue Life Range

    Directory of Open Access Journals (Sweden)

    Strzelecki Przemysław

    2015-09-01

    Full Text Available The article collates guidelines concerning experimental construction of the S-N fatigue curves within a limited fatigue life range. An attempt is made to compare these guidelines, based on experimental data recorded during rotating bending of a notched specimen made of 42CrMo4. The recorded differences in fatigue life values between the constructed curves reach the maximum of 12.2%. According to the above guidelines, the number of tests in particular test series varies from 6 to 28. Based on the performed analysis a conclusion was made that the increase in the number of tests leads to the increase of accuracy but, on the other hand, remarkably increases the time of the experiment and, consequently, its cost. In this context, it is the research worker who, taking into account a possible future use of the fatigue curve, should individually decide about its accuracy.

  2. Mathematical Model of Load Pass and Prediction of Fatigue Life on Bolt Threads with Reduced Lead

    Science.gov (United States)

    Asayama, Yukiteru

    A mathematical model is proposed in order to elucidate the mechanism that the fatigue strength of external threads increases by reducing the lead on a thread system such as a bolt and nut. The model is constructed from the concept that a local strain proportional to the reducing degree of the lead, although the local strain is at first produced in the bolt thread farthest from the bearing surface of the nut, is induced in each thread root with an increase of applied load. The fatigue life predicted from the mathematical model shows good agreement with the experimental fatigue life of cadmium-plated external threads with the reduced lead on the material having strength as high as 1270MPa. The model can provide useful suggestions for the design of fasteners for aerospace, which are required to satisfy severe requirements of fatigue strengths and dimensions.

  3. Probabilistic fatigue life of balsa cored sandwich composites subjected to transverse shear

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Berggreen, Christian

    2015-01-01

    be controlled to the same extent as an industrial manufacturing processes. The large variance in the probabilistic model for fatigue life is reflected in the corresponding calibrated partial safety factors, which are higher thanthe factors usually associated with synthetic materials such as fiber......A probabilistic fatigue life model for end-grain balsa cored sandwich composites subjectedto transverse shear is proposed. The model is calibrated to measured three-pointbending constant-amplitude fatigue test data using the maximum likelihood method. Some possible applications of the probabilistic...... model are obtaining characteristic S–Ncurves corresponding to a given survival probability, and calibrating partial safety factorsfor material fatigue. The latter is demonstrated by a calibration performed using reliability analysis with the first-order reliability method. The measured variance in balsa...

  4. The effects of fibre architecture on fatigue life-time of composite materials

    DEFF Research Database (Denmark)

    Hansen, Jens Zangenberg; Østergaard, Rasmus

    Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre...... reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last...... decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation...

  5. High-cycle Fatigue Life Extension of Glass Fiber/Polymer Composites with Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Christopher S Grimmer; C K H Dharan

    2009-01-01

    The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) to the matrix results in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture of nanotubes bridging across nano-scale cracks and from nanotube pull-out from the matrix are mechanisms that can improve the fatigue life. An energy-based model was proposed to estimate the additional strain energy absorbed in fatigue. The distributed nanotubes in the matrix appear to both distribute damage as well as inhibit damage propagation resulting in an overall improvement in the fatigue strength of glass fiber composites.

  6. Fatigue Reliability Assessment of Steel Member Using Probabilistic Stress-Life Method

    Directory of Open Access Journals (Sweden)

    Dae-Hung Kang

    2012-01-01

    Full Text Available The fatigue reliability of a steel member in a bridge is estimated by using the probabilistic stress-life method. The stress history of a member is defined as the loading block when a truck passes over a bridge, and the stress range frequency distribution of the stress history is obtained by a stress range frequency analysis. A probabilistic method is applied to the stress range frequency distribution, and the parameters of the probability distribution for the stress range frequency distribution are used in a numerical simulation. To obtain the probability of failure of a member under a loading block, Monte Carlo simulation is performed in conjunction with Miner's rule, the modified Miner's rule, and Haibach's rule for fatigue damage evaluation. Through these analyses procedures, we obtain an evaluation method for fatigue reliability that can predict the block number of the failure load and residual fatigue life.

  7. Probabilistic Fatigue Life Prediction of Bridge Cables Based on Multiscaling and Mesoscopic Fracture Mechanics

    Directory of Open Access Journals (Sweden)

    Zhongxiang Liu

    2016-04-01

    Full Text Available Fatigue fracture of bridge stay-cables is usually a multiscale process as the crack grows from micro-scale to macro-scale. Such a process, however, is highly uncertain. In order to make a rational prediction of the residual life of bridge cables, a probabilistic fatigue approach is proposed, based on a comprehensive vehicle load model, finite element analysis and multiscaling and mesoscopic fracture mechanics. Uncertainties in both material properties and external loads are considered. The proposed method is demonstrated through the fatigue life prediction of cables of the Runyang Cable-Stayed Bridge in China, and it is found that cables along the bridge spans may have significantly different fatigue lives, and due to the variability, some of them may have shorter lives than those as expected from the design.

  8. Structural strength analysis and fatigue life prediction of traction converter box in high-speed EMU

    Science.gov (United States)

    Tan, Qin; Li, Qiang

    2017-01-01

    The method of building the FEA model of traction converter box in high-speed EMU and analyzing the static strength and fatigue strength of traction converter box based on IEC 61373-2010 and EN 12663 standards is presented in this paper. The load-stress correlation coefficients of weak points is obtained by FEA model, applied to transfer the load history of traction converter box to stress history of each point. The fatigue damage is calculated based on Miner's rule and the fatigue life of traction converter box is predicted. According to study, the structural strength of traction converter box meets design requirements.

  9. Fatigue Life of High Performance Grout for Wind Turbine Grouted Connection in Wet or Dry Environment

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.; Westhof, Luc; Yde, Elo;

    Grouted connections of monopile supported offshore wind turbine structures are subjected to loads leading to very high oscillating service stresses in the grout material. The fatigue capacity of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens...... at varying levels of cyclic frequency and load. The fatigue tests were performed in two series: one with the specimens in air and one with the specimens submerged in water during the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when...... tested in water than when tested in air....

  10. High compressive pre-strains reduce the bending fatigue life of nitinol wire.

    Science.gov (United States)

    Gupta, Shikha; Pelton, Alan R; Weaver, Jason D; Gong, Xiao-Yan; Nagaraja, Srinidhi

    2015-04-01

    Prior to implantation, Nitinol-based transcatheter endovascular devices are subject to a complex thermo-mechanical pre-strain associated with constraint onto a delivery catheter, device sterilization, and final deployment. Though such large thermo-mechanical excursions are known to impact the microstructural and mechanical properties of Nitinol, their effect on fatigue properties is still not well understood. The present study investigated the effects of large thermo-mechanical pre-strains on the fatigue of pseudoelastic Nitinol wire using fully reversed rotary bend fatigue (RBF) experiments. Electropolished Nitinol wires were subjected to a 0%, 8% or 10% bending pre-strain and RBF testing at 0.3-1.5% strain amplitudes for up to 10(8) cycles. The imposition of 8% or 10% bending pre-strain resulted in residual set in the wire. Large pre-strains also significantly reduced the fatigue life of Nitinol wires below 0.8% strain amplitude. While 0% and 8% pre-strain wires exhibited distinct low-cycle and high-cycle fatigue regions, reaching run out at 10(8) cycles at 0.6% and 0.4% strain amplitude, respectively, 10% pre-strain wires continued to fracture at less than 10(5) cycles, even at 0.3% strain amplitude. Furthermore, over 70% fatigue cracks were found to initiate on the compressive pre-strain surface in pre-strained wires. In light of the texture-dependent tension-compression asymmetry in Nitinol, this reduction in fatigue life and preferential crack initiation in pre-strained wires is thought to be attributed to compressive pre-strain-induced plasticity and tensile residual stresses as well as the formation of martensite variants. Despite differences in fatigue life, SEM revealed that the size, shape and morphology of the fatigue fracture surfaces were comparable across the pre-strain levels. Further, the mechanisms underlying fatigue were found to be similar; despite large differences in cycles to failure across strain amplitudes and pre-strain levels, cracks

  11. Mechanical strength, fatigue life, and failure analysis of two prototypes and five conventional tibial locking screws.

    Science.gov (United States)

    Hou, Sheng-Mou; Wang, Jaw-Lin; Lin, Jinn

    2002-01-01

    To investigate the effects of the design and microstructure on the mechanical strength of tibial locking devices. The mechanical strength of two prototypes of specially developed locking devices (a both-ends-threaded screw and an unthreaded bolt) was tested and compared with that of five types of commercially available tibial locking screws (Synthes, Howmedica, Richards, Osteo AG, and Zimmer) with similar dimensions. The devices were inserted into a polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three-point bending test. Single-loading yielding strength and cyclic-loading fatigue life were then measured. Failure analysis of the fractured screws was performed to investigate the microstructure and potential causes of the fatigue fracture. Test results showed that both yielding strength and fatigue life were closely related to the section modulus of the inner diameter of screws. Among the threaded screws, the both-ends-threaded screws had a higher yielding strength and longer fatigue life than the Osteo AG, Howmedica, Richards, and Zimmer screws. The unthreaded bolts had a lower yielding strength than Synthes screws, but they demonstrated the longest fatigue life among all. In failure analysis of broken screws, no metallurgical or manufacturing defects were found except for surface microimperfections. The implants investigated in this study are manufactured with high-quality materials and manufacturing processes. The main cause of hardware failure was mechanical overloading. The five commercially used tibial locking screws had a relatively short fatigue life under high loading. Removing the screw threads might substantially increase the fatigue life of the locking devices. In unthreaded bolts, this increase might be tenfold to a hundredfold.

  12. Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure

    OpenAIRE

    Hualiang Wan; Qizhi Wang; Zheng Zhang

    2016-01-01

    New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing fu...

  13. Evaluation of creep-fatigue life-prediction models for the solar central receiver

    Science.gov (United States)

    Hyzak, J. M.; Hughes, D. A.

    1981-09-01

    The applicability of several creep fatigue models to life prediction of boiler tubes in a solar central receiver (SCR) was evaluated. The SCR boiler tubes will experience compressive strain dwell loading with hold times up to 6 to 8 hours at temperatures where time dependent deformation will occur. The evaluation criteria include the ability of the model to account for mean stress effects and to be practical in the long life, small strain range regime. A correlation between maximum tensile stress and fatigue life is presented. Using this correlation, compressive dwell behavior is predicted based on continuous cycling data. The limits of this predictive scheme are addressed.

  14. FATIGUE LIFE PREDICTION OF CRANKSHAFT MADE OF MATERIAL 48MnV BASED ON FATIGUE TESTS,DYNAMIC SIMULATION AND FEA

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guoqing; PU Gengqiang; WANG Chengtao

    2006-01-01

    S-N curve and fatigue parameters of 48MnV are obtained using small sample tests and staircase or up and down method, which paves the way for predicting fatigue life of crankshaft made of 48MnV. The fatigue life of the crankshaft of a six-cylinder engine is calculated using different damage models such as S-N method, normal strain approach, Smoth-Watson-Topper (SWT)-Bannantine approach, shear strain approach, and Fatemi-Socie method based on dynamic simulation and finite element analysis (FEA) of crankshaft. The results indicate that the traditional calculation is conservative and the residual fatigue life of crankshaft is sufficient to maintain next life cycle if the crankshaft is remanufactured after its end of life.

  15. Probabilistic Fatigue Life Prediction of Turbine Disc Considering Model Parameter Uncertainty

    Science.gov (United States)

    He, Liping; Yu, Le; Zhu, Shun-Peng; Ding, Liangliang; Huang, Hong-Zhong

    2016-06-01

    Aiming to improve the predictive ability of Walker model for fatigue life prediction and taking the turbine disc alloy GH4133 as the application example, this paper investigates a new approach for probabilistic fatigue life prediction when considering parameter uncertainty inherent in the life prediction model. Firstly, experimental data are used to update the model parameters using Bayes' theorem, so as to obtain the posterior probability distribution functions of two parameters of the Walker model, as well to achieve the probabilistic life prediction model for turbine disc. During the updating process, Markov Chain Monte Carlo (MCMC) technique is used to generate samples of the given distribution and estimating the parameters distinctly. After that, the turbine disc life is predicted using the probabilistic Walker model based on Monte Carlo simulation technique. The experimental results indicate that: (1) after using the small sample test data obtained from turbine disc, parameter uncertainty of the Walker model can be quantified and the corresponding probabilistic model for fatigue life prediction can be established using Bayes' theorem; (2) there exists obvious dispersion of life data for turbine disc when predicting fatigue life in practical engineering application.

  16. The Prediction of Fatigue Life Based on Four Point Bending Test

    NARCIS (Netherlands)

    Pramesti, F.P.; Molenaar, A.A.A.; Van de Ven, M.F.C.

    2013-01-01

    To be able to devise optimum strategies for maintenance and rehabilitation, it is essential to formulate an accurate prediction of pavement life and its maintenance needs. One of the pavement life prediction methods is based on the pavement's capability to sustain fatigue. If it were possible to hav

  17. Detection and Influence of Shrinkage Pores and Nonmetallic Inclusions on Fatigue Life of Cast Aluminum Alloys

    Science.gov (United States)

    Tijani, Yakub; Heinrietz, André; Stets, Wolfram; Voigt, Patrick

    2013-12-01

    In the current study, test bars of cast aluminum alloys EN AC-AlSi8Cu3 and EN AC-AlSi7Mg0.3 were produced with a defined amounts of shrinkage pores and oxides. For this purpose, a permanent mold with heating and cooling devices for the generation of pores was constructed. The oxides were produced by contaminating the melt. The specimens and their corresponding defect distributions were examined and quantified by X-ray computer tomography (CT) and quantitative metallography, respectively. A special test algorithm for the simultaneous image analyses of pores and oxides was developed. Fatigue tests were conducted on the defective samples. It was found that the presence of shrinkage pores lowers the fatigue strength, and only few oxide inclusions were found to initiate fatigue cracks when shrinkage pores are present. The results show that the pore volume is not sufficient to characterize the influence of shrinkage pores on fatigue life. A parametric model for the calculation of fatigue life based on the pore parameters obtained from CT scans was implemented. The model accounts for the combined impact of pore location, size, and shape on fatigue life reduction.

  18. Effect of V Notch Shape on Fatigue Life in Steel Beam Made of AISI 1037

    Directory of Open Access Journals (Sweden)

    Qasim Bader

    2014-04-01

    Full Text Available The present work encompasses effect of V notch shape with various geometries and dimensions on fatigue life behavior in steel beam made of Medium Carbon Steel AISI 1037 which has a wide application in industry. Fatigue life of notched specimens is calculated using the fatigue life obtained from the experiments for smooth specimens (reference and by use Numerical method (FEA.The fatigue experiments were carried out at room temperature, applying a fully reversed cyclic load with the frequency of (50Hz and mean stress equal to zero (R= -1, on a cantilever rotating-bending fatigue testing machine. The stress ratio was kept constant throughout the experiment. Different instruments have been used in this investigation like Chemical composition analyzer type (Spectromax ,Tensile universal testing machine type (WDW-100E ,Hardness tester type (HSV- 1000 , Fatigue testing machine model Gunt WP 140, Optical Light Microscope (OLM and Scanning Electron Microscope (SEM were employed to examine the fracture features . The results show that there is acceptable error between experimental and numerical works .

  19. Fatigue life estimation for different notched specimens based on the volumetric approach

    Directory of Open Access Journals (Sweden)

    Esmaeili F.

    2010-06-01

    Full Text Available In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

  20. Evaluation of Fatigue Life Reliability of Steering Knuckle Using Pearson Parametric Distribution Model

    Directory of Open Access Journals (Sweden)

    E. A. Azrulhisham

    2010-01-01

    Full Text Available Steering module is a part of automotive suspension system which provides a means for an accurate vehicle placement and stability control. Components such as steering knuckle are subjected to fatigue failures due to cyclic loads arising from various driving conditions. This paper intends to give a description of a method used in the fatigue life reliability evaluation of the knuckle used in a passenger car steering system. An accurate representation of Belgian pave service loads in terms of response-time history signal was obtained from accredited test track using road load data acquisition. The acquired service load data was replicated on durability test rig and the SN method was used to estimate the fatigue life. A Pearson system was developed to evaluate the predicted fatigue life reliability by considering the variations in material properties. Considering random loads experiences by the steering knuckle, it is found that shortest life appears to be in the vertical load direction with the lowest fatigue life reliability between 14000–16000 cycles. Taking into account the inconsistency of the material properties, the proposed method is capable of providing the probability of failure of mass-produced parts.

  1. Prevalence of fatigue in patients with multiple sclerosis and its effect on the quality of life

    Directory of Open Access Journals (Sweden)

    Karthik Nagaraj

    2013-01-01

    Full Text Available Objective: This prospective study was carried out to observe the prevalence of fatigue in patients with multiple sclerosis (MS and its effect on quality-of-life (QoL. Study Design and Setting: Prospective observational study in a University Tertiary Research Hospital in India. Patients and Methods: A total of 31 patients (25 females with definite MS according to McDonald′s criteria presented in out-patient/admitted in the Department of Neurology (between February 2010 and December 2011 were included in the study. Disease severity was evaluated using the Kurtzke′s expanded disability status scale (EDSS. Fatigue was assessed using Krupp′s fatigue severity scale (FSS. QoL was assessed by the World Health Organization QoL-BREF questionnaire. Results: The mean age of patients was 30.1 ± 9.1 years. The mean age at first symptom was 25.23 ± 6.4 years. The mean number of relapses was 4.7 ± 3.6 in the patients. The mean duration of illness was 4.9 ± 4.4 years. The mean EDSS score was 3.5 ± 2.2. Mean fatigue score was 38.7 ± 18.5 (cut-off value 36 in FSS. The prevalence of fatigue in patients with MS was 58.1% (18/31. MS patients with fatigue were significantly more impaired (P < 0.05 on all QoL domains (i.e., physical, psychosocial, social, and environment than MS patients without fatigue. Conclusion: Prevalence of fatigue was found to be high in the MS patients in the study. All four domains of QoL were significantly more impaired in the group with fatigue than in those without fatigue.

  2. Fatigue and Quality of Life of Women Undergoing Chemotherapy or Radiotherapy for Breast Cancer

    Institute of Scientific and Technical Information of China (English)

    Winnie K.W.So; Gene Marsh; W.M.Ling; F.E Leung; Joe C.K.Lo; Maggie Yeung; George K.H.Li

    2009-01-01

    OBJECTIVE To examine fatigue and quality of life (QOL) in breast cancer patients undergoing chemotherapy or radiotherapy.METHODS A self-report survey derived from the Chinese version of Brief Fatigue Inventory, the Functional Assessment of Chronic Illness Therapy for Breast Cancer, and the Medical Outcomes Study Social Support Survey. Descriptive statistics was used to examine the intensity of fatigue and the prevalence of severe fatigue. Multivariate analysis of variance was used to determine factors that affect the five domains of QOL among the participants.RESULTS The majority of the participants (n = 261) perceived a mild level of fatigue, but 35.6% of them suffered severe fatigue. Fatigue had a significantly negative association with all domains of QOL except social/family wellbeing. The participants who were receiving chemotherapy, undergoing curative treatment and having inadequate social support were more likely to have poorer QOL in all five domains (after adjustment for age).CONCLUSION Although the majority of the participants experienced a mild level of fatigue, there was a substantial group of breast cancer patients who perceived their fatigue as severe. The findings of this study showed that fatigue had a detrimental effect on the various aspects of the participants'QOL. Demographic and clinical characteristics of breast cancer patients who were at risk of getting poorer QOL were identified. The results of the study demonstrate that we should enhance healthcare professionals' awareness of the importance of symptom assessment, and provide them with information for planning effective symptom-management strategies among this study population.

  3. Prevalence of fatigue in patients with multiple sclerosis and its effect on the quality of life.

    Science.gov (United States)

    Nagaraj, Karthik; Taly, Arun B; Gupta, Anupam; Prasad, Chandrajit; Christopher, Rita

    2013-07-01

    This prospective study was carried out to observe the prevalence of fatigue in patients with multiple sclerosis (MS) and its effect on quality-of-life (QoL). Prospective observational study in a University Tertiary Research Hospital in India. A total of 31 patients (25 females) with definite MS according to McDonald's criteria presented in out-patient/admitted in the Department of Neurology (between February 2010 and December 2011) were included in the study. Disease severity was evaluated using the Kurtzke's expanded disability status scale (EDSS). Fatigue was assessed using Krupp's fatigue severity scale (FSS). QoL was assessed by the World Health Organization QoL-BREF questionnaire. The mean age of patients was 30.1 ± 9.1 years. The mean age at first symptom was 25.23 ± 6.4 years. The mean number of relapses was 4.7 ± 3.6 in the patients. The mean duration of illness was 4.9 ± 4.4 years. The mean EDSS score was 3.5 ± 2.2. Mean fatigue score was 38.7 ± 18.5 (cut-off value 36 in FSS). The prevalence of fatigue in patients with MS was 58.1% (18/31). MS patients with fatigue were significantly more impaired (P QoL domains (i.e., physical, psychosocial, social, and environment) than MS patients without fatigue. Prevalence of fatigue was found to be high in the MS patients in the study. All four domains of QoL were significantly more impaired in the group with fatigue than in those without fatigue.

  4. An Experimental Investigation of the Effects of Vacuum Environment on the Fatigue Life, Fatigue-Crack-Growth Behavior, and Fracture Toughness of 7075-T6 Aluminum Alloy. Ph.D. Thesis - North Carolina State Univ.

    Science.gov (United States)

    Hudson, C. M.

    1972-01-01

    Axial load fatigue life, fatigue-crack propagation, and fracture toughness tests were conducted on 0.090-inch thick specimens made of 7075-T6 aluminum alloy. The fatigue life and fatigue-crack propagation experiments were conducted at a stress ratio of 0.02. Maximum stresses ranged from 33 to 60 ksi in the fatigue life experiments, and from 10 to 40 ksi in the fatigue-crack propagation experiments, and fatigue life experiments were conducted at gas pressures of 760, 0.5, 0.05, and 0.00000005 torr. Fatigue-crack-growth and fracture toughness experiments were conducted at gas pressures of 760 and 5 x 10 to the minus 8th power torr. Residual stress measurements were made on selected fatigue life specimens to determine the effect of such stresses on fatigue life. Analysis of the results from the fatigue life experiments indicated that fatigue life progressively increased as the gas pressure decreased. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue crack growth rates were approximately twice as high in air as in vacuum. Fracture toughness data showed there was essentially no difference in the fracture toughness of 7075-T6 in vacuum and in air.

  5. Life Cycle Engineering – from methodology to enterprise culture

    DEFF Research Database (Denmark)

    Hauschild, Michael Zwicky; Alting, Leo; Poll, Christian

    2003-01-01

    As part of a sustainable development, the environmental efficiency of industry must increase by a factor four to ten. This engenders attention to the environmental impact of products and technical systems over their entire life cycle. The last decade has seen the development of a number...... of methodologies and tools for life cycle assessment and development of more eco-efficient products, from complex to simplified, catering to the needs of especially small and medium-sized enterprizes. The tools and data are in place, but dissemination lacks behind. Propagation of life cycle thinking and life cycle...

  6. Fatigue in Patients With Advanced Terminal Cancer Correlates With Inflammation, Poor Quality of Life and Sleep, and Anxiety/Depression.

    Science.gov (United States)

    Rodrigues, Alex Rua; Trufelli, Damila Cristina; Fonseca, Fernando; de Paula, Larissa Carvalho; Giglio, Auro Del

    2016-12-01

    To assess which laboratory and clinical factors are associated with fatigue in patients with terminal cancer. We evaluated 51 patients with advanced incurable solid tumors using the Chalder Fatigue Questionnaire (CFQ) and the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scale for fatigue; the Pittsburgh Sleep Quality Index (PSQI-BR) for sleep quality; the Hospital Anxiety and Depression Scale (HADS) for anxiety and depression; the European Organization for Research and Treatment of Cancer (EORTC) Core Quality of Life Questionnaire, Version 3.0 (QLQ C-30); and Functional Assessment of Cancer Therapy (FACT) for quality of life. We also analyzed several inflammatory markers and the modified Glasgow prognostic score (mGPS). We observed severe fatigue in 19 (38%) patients (FACIT-F score >36). There was a significant correlation between fatigue as evaluated by the CFQ and quality of sleep and between the CFQ mental fatigue subscale scores and TNF-α level. When fatigue was evaluated using the FACIT-F scale, we observed a significant association between fatigue and anxiety/depression, quality of sleep, mGPS, and hemoglobin levels. Fatigue measured both with the CFQ and FACIT-F scale correlated with poor quality of life according to the EORTC QLQ C-30. In patients with advanced cancer, fatigue is a common symptom associated with the presence of inflammation, poor quality of sleep, depression/anxiety, and poor quality of life. © The Author(s) 2015.

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

    Directory of Open Access Journals (Sweden)

    Jeong-Ung Park

    2014-03-01

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

  8. Fatigue and depression in multiple sclerosis: Correlation with quality of life

    Directory of Open Access Journals (Sweden)

    Miletić Svetlana

    2011-01-01

    Full Text Available The aim of this work was to examine the relationship between fatigue and depression, common features of multiple sclerosis (MS, and the quality of life (QOL. The study was comprised of 120 patients with clinical manifestations of definite MS. Relapsing-remitting MS was present in 76.7% patients and secondary progressive MS was present in 23.3% patients. Mean disease duration was 8.1 ± 5.6 years and the mean Expanded Disability Status Score (EDSS was 3.5 ± 1.8 (range 1-8. Fatigue was measured with the Fatigue Severity Scale (FSS, depression was measured by the Beck Depression Inventory (BDI and QOL was assessed using the health-related quality of life questionnaire SF-36. We observed that the global FSS score was 4.6 ± 1.8 (range 1-7 and BDI was 10.7 ± 10.3 (range 0-39. The FSS significantly and positively correlated with the BDI scores (r = 0.572; p = 0.000. The severity of fatigue had a significant impact on the quality of life (r = -0.743; p = 0.000, in particular on mental health (r = -0.749; p = 0.000. We observed a significant correlation between the severity of depression and impaired quality of life (r = -0.684; p = 0.000. This study shows that fatigue and depression are associated with impaired QOL in MS.

  9. SOURCES OF DIFFERENCES IN CALCULATIONS AND EXPERIMENTAL TEST RESULTS OF FATIGUE LIFE OF STRUCTURAL ELEMENTS

    Directory of Open Access Journals (Sweden)

    Józef SZALA

    2014-06-01

    Full Text Available Calculation results are the base for evaluation of fatigue life of structural elements during machine design processes. It results from the fact that there are no material objects in the phase of existence of a product. Reliability of tests results is an essential element in the calculation fatigue life evaluation method and it can be evaluated by comparison of the results with experimental ones. In the paper there was performed an analysis of the chosen factors essentially influencing conformity of calculation results and experimental test ones connected with basic elements of a calculation algorithm including: - elaboration and analysis of service loadings of a structural element, - determination and analysis of cyclic properties of structural elements, - selection of fatigue damage accumulation hypothesis being a description of fatigue life processes. The mentioned analysis was illustrated with examples of fatigue life tests performed in the Machine Design Department of the University of Technology and Agriculture within the research grant no. 2221/B/T02/2010/39 financed by The Ministry of Science and Higher Education and National Science Centre.

  10. Self-reported fatigue and physical function in late mid-life

    DEFF Research Database (Denmark)

    Boter, Han; Mänty, Minna; Hansen, Åse Marie

    2014-01-01

    population cohort (n = 4,964; age 49-63 years). Methods: Self-reported fatigue was measured using the MFI-20 comprising: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Handgrip strength and chair rise tests were used as measures of physical function. Multiple.......001), general fatigue (adjusted OR 0.72 (0.62-0.84); p ≤ 0.001), reduced activity (adjusted OR 0.79 (0.70-0.90); p ≤ 0.001) and reduced motivation (adjusted OR 0.84 (0.74-0.95); p ≤ 0.01), but not with mental fatigue. Subgroup analyses for sex did not show statistically significant different associations......Objective: To determine the association between the 5 subscales of the Multidimensional Fatigue Inventory (MFI-20) and physical function in late mid-life. Design: Cross-sectional study. Subjects: A population-based sample of adults who participated in the Copenhagen Aging and Midlife Biobank...

  11. Uphill both ways: Fatigue and quality of life in valley fever.

    Science.gov (United States)

    Garrett, Ashley L; Chang, Yu-Hui H; Ganley, Kathleen; Blair, Janis E

    2016-03-01

    Primary pulmonary coccidioidomycosis is characterized by prolonged respiratory and systemic symptoms and fatigue. We prospectively administered the fatigue severity scale (FSS) and Short Form-36 Health Status Questionnaire (SF-36) to patients with proven or probable primary pulmonary coccidioidomycosis to quantify disease effect on quality of life (QOL). The 24-week observational study did not specify whether antifungal treatment would be provided; the treating physician made treatment decisions. FSS and SF-36 were completed at 4-week intervals. Thirty-six patients participated, of whom 20 received antifungal treatment. At onset of coccidioidal illness, mean FSS score was higher (ie, more fatigue) in the treatment group. However, in early illness, both groups had higher fatigue levels than reference populations with other diseases (eg, multiple sclerosis). FSS scores gradually improved, and scores in each group were below the severe fatigue level at week 12 and week 16 in the nontreatment and treatment groups, respectively. By week 24, mean FSS score of the nontreatment group equaled the general population. SF-36 component and profile scores were lower (with more symptoms) in the treatment group at each time point than the nontreatment group; both groups showed similar improvement. Mental and emotional health SF-36 scores were not as severely affected as physical scores. Most patients reached a physical functioning level similar to the general population at week 12. Pulmonary coccidioidomycosis causes severe fatigue and substantially affects physical abilities. Fatigue was found to be prolonged, with gradual improvement in QOL, regardless of antifungal administration.

  12. Effects of sodium tartrate anodizing on fatigue life of TA15 titanium alloy

    Directory of Open Access Journals (Sweden)

    Fu Chunjuan

    2015-08-01

    Full Text Available Anodizing is always used as an effective surface modification method to improve the corrosion resistance and wear resistance of titanium alloy. The sodium tartrate anodizing is a new kind of environmental anodizing method. In this work, the effects of sodium tartrate anodizing on mechanical property were studied. The oxide film was performed on the TA15 titanium alloy using sodium tartrate as the film former. The effects of this anodizing and the traditional acid anodizing on the fatigue life of TA15 alloy were compared. The results show that the sodium tartrate anodizing just caused a slight increase of hydrogen content in the alloy, and had a slight effect on the fatigue life. While, the traditional acid anodizing caused a significant increase of hydrogen content in the substrate and reduced the fatigue life of the alloy significantly.

  13. Fatigue assessment and its impact in the quality of life of patients with ankylosing spondylitis.

    Science.gov (United States)

    Schneeberger, Emilce Edith; Marengo, María Florencia; Dal Pra, Fernando; Maldonado Cocco, José Antonio; Citera, Gustavo

    2015-03-01

    The most frequently reported symptoms by patients with ankylosing spondylitis (AS) are pain, stiffness, and fatigue. Previous studies have estimated a 63% prevalence of fatigue in AS, with a low correlation of fatigue with pain and functional capacity. The objective of this study is to assess fatigue prevalence in AS patients and establish the main associated factors. A case-control study including AS patients according to New York modified criteria was carried out. The control group included individuals of the general population without rheumatic conditions, matched by gender, age, and socioeconomic level. Disease-related variables were recorded. Functional capacity, disease activity, and quality of life were assessed using Bath Ankylosing Spondylitis Funcional Index (BASFI), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and ankylosing spondylitis quality of life (ASQoL). CES-D questionnaire was used to evaluate depression and fatigue severity scale (FSS) to evaluate fatigue. Sixty-four consecutive AS patients and 95 controls were included. Patients' median age was 44 years (interquartile range (IQR), 33.25-53), 89.1% were male, and had a median disease duration of 17 years (IQR, 10.3-25). Fatigue prevalence in AS was 73.4% compared to 30.5% in the control group (p < 0.001; OR, 2.08 (95% CI, 1.53-2.83)). Furthermore, fatigue in AS correlated with ASQoL (r = 0.65), BASFI (r = 0.52), BASDAI (r = 0.52), and depression (r = 0.51), whereas no correlation with age or disease duration was found. In the linear regression analysis using fatigue as the dependent variable, depression was the only associated variable (p = 0.01). No association with age, gender, disease duration, BASDAI, BASFI, or presence of comorbidities was found. Finally, BASDAI fatigue question correlated with the FSS (r = 0.55). Fatigue was significantly more prevalent in AS than in healthy controls. The main determinant factor of fatigue was the presence of

  14. PSYCHOMETRIC PROPERTY OF FATIGUE SEVERITY SCALE AND CORRELATION WITH DEPRESSION AND QUALITY OF LIFE IN CIRRHOTICS

    Directory of Open Access Journals (Sweden)

    Danusa ROSSI

    2017-10-01

    Full Text Available ABSTRACT BACKGROUND: Fatigue is a common complaint in cirrhotic patients and may be considered a debilitating symptom with negative impact on quality of life. Research on its etiology and treatment has been hampered by the lack of relevant and reproducible measures of fatigue. OBJECTIVE: To evaluate the psychometric properties of the Fatigue Severity Scale (FSS in cirrhotic patients and to correlate with depressive symptomatology and quality of life. METHODS: Cross-sectional study with a convenience sample of 106 cirrhotic patients, aged between 18 and 70 years, both genders, literate, pre and post liver transplantation in outpatient follow-up. Internal consistency, reproducibility, discriminant validity, criterion validity, construct validity, responsiveness criterion, depressive symptomatology and quality of life were evaluated through questionnaires between January and October 2015. RESULTS: The mean age was 54.75±9.9 years, 65.1% male and 32.1% of the sample had cirrhosis due to hepatitis C virus. The mean FSS score was 4.74±1.64. Cronbach’s alpha was 0.93, and the Intraclass Correlation Coefficient was 0.905 (95% CI: 0.813-0.952. For discriminant validity, FSS differentiated scores from different groups (P=0.009 and presented a correlation with the Modified Fatigue Impact Scale (r=0.606, P=0.002. FSS correlated significantly and positively with depressive symptomatology and correlated negatively with the SF-36 domains for construct validity. For responsiveness, no significant changes were observed in the fatigue scores in the pre and post-liver transplantation periods (P=0.327. CONCLUSION: FSS showed good psychometric performance in the evaluation of fatigue in patients with cirrhosis. Fatigue presented a strong correlation with depressive symptomatology and quality of life.

  15. Effect of electric discharge machining on the fatigue life of Inconel 718

    Science.gov (United States)

    Jeelani, S.; Collins, M. R.

    1988-01-01

    The effect of electric discharge machining on the fatigue life of Inconel 718 alloy at room temperature was investigated. Data were generated in the uniaxial tension fatigue mode at ambient temperature using flat 3.175 mm thick specimens. The specimens were machined on a wire-cut electric discharge machine at cutting speeds ranging from 0.5 to 2 mm per minute. The specimens were fatigued at a selected stress, and the resulting fatigue lives compared with that of the virgin material. The surfaces of the fatigued specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard profilometer. From the results of the investigation, it was concluded that the fatigue life of the specimens machined using EDM decreased slightly as compared with that of the virgin material, but remained unchanged as the cutting speed was changed. The results are explained using data produced employing microhardness measurements, profilometry, and optical and scanning microscopy.

  16. Influences of size and position of defects on the fatigue life of electron beam welded-aluminum alloy joints

    Institute of Scientific and Technical Information of China (English)

    LU Li; ZHAO Haiyan; CAI Zhipeng; CUI Xiaofang

    2007-01-01

    Defects such as pores influence the fatigue life of electron beam-welded aluminum alloy joints. In this paper,the influences of pore size and position on the fatigue life of aluminum overlap joint are studied. A finite element model (FEM), combined with experimental data, is established to evaluate the fatigue life of overlap joints. By employing this FE model, the effects of pore size and position on fatigue lives of overlap joints are investigated and discussed. From the present study, when pore position is closer to the weld bead tip or the faying surface, the fatigue life decreases. Also, there is a critical size for the pore; when the pore size is larger than the critical value, the fatigue strength decreases sharply.

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

    Science.gov (United States)

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

    2017-07-01

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

  18. Fatigue Life Prediction of Ductile Iron Based on DE-SVM Algorithm

    Science.gov (United States)

    Yiqun, Ma; Xiaoping, Wang; lun, An

    the model, predicting fatigue life of ductile iron, based on SVM (Support Vector Machine, SVM) has been established. For it is easy to fall into local optimum during parameter optimization of SVM, DE (Differential Evolution algorithm, DE) algorithm was adopted to optimize to improve prediction precision. Fatigue life of ductile iron is predicted combining with concrete examples, and simulation experiment to optimize SVM is conducted adopting GA (Genetic Algorithm), ACO (Ant Colony Optimization) and POS (Partial Swarm Optimization). Results reveal that DE-SVM algorithm is of a better prediction performance.

  19. Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications

    Science.gov (United States)

    Prevey, Paul S.; Shepard, Michael; Ravindranath, Ravi A.; Gabb, Timothy

    2003-01-01

    Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The X-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including: * The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing fatigue benefit of thermal stability at engine temperatures. * An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. * Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. * Corrosion fatigue mitigation with LPB in Carpenter 450 steel. *Damage tolerance improvement in 17-4PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine

  20. Measurement of quality of life I. A methodological framework

    DEFF Research Database (Denmark)

    Ventegodt, Søren; Hilden, Jørgen; Merrick, Joav

    2003-01-01

    meet to provide a sound basis for investigation by questionnaire. The seven criteria or desiderata are: (1) an explicit definition of quality of life; (2) a coherent philosophy of human life from which the definition is derived; (3) a theory that operationalizes the philosophy by specifying unambiguous......Despite the widespread acceptance of quality of life (QOL) as the ideal guideline in healthcare and clinical research, serious conceptual and methodological problems continue to plague this area. In an attempt to remedy this situation, we propose seven criteria that a quality-of-life concept must...... guided the design of a validated 5-item generic, global quality-of-life questionnaire (QOL5), and a validated 317-item generic, global quality-of-life questionnaire (SEQOL), administered to a well-documented birth cohort of 7,400 Danes born in 1959-1961, as well as to a reference sample of 2,500 Danes...

  1. A computational approach for thermomechanical fatigue life prediction of dissimilarly welded superheater tubes

    Energy Technology Data Exchange (ETDEWEB)

    Krishnasamy, Ram-Kumar; Seifert, Thomas; Siegele, Dieter [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany)

    2010-07-01

    In this paper a computational approach for fatigue life prediction of dissimilarly welded superheater tubes is presented and applied to a dissimilar weld between tubes made of the nickel base alloy Alloy617 tube and the 12% chromium steel VM12. The approach comprises the calculation of the residual stresses in the welded tubes with a multi-pass dissimilar welding simulation, the relaxation of the residual stresses in a post weld heat treatment (PWHT) simulation and the fatigue life prediction using the remaining residual stresses as initial condition. A cyclic fiscoplasticity model is used to calculate the transient stresses and strains under thermocyclic service loadings. The fatigue life is predicted with a damage parameter which is based on fracture mechanics. The adjustable parameters of the model are determined based on LCF and TMF experiments. The simulations show, that the residual stresses that remain after PWHT further relax in the first loading cycles. The predicted fatigue lives depend on the residual stresses and, thus, on the choice of the loading cycle in which the damage parameter is evaluated. It the first loading cycle, where residual stresses are still present, is considered, lower fatigue lives are predicted compared to predictions considering loading cycles with relaxed residual stresses. (orig.)

  2. Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, W., E-mail: wyman.zhuang@dsto.defence.gov.au [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Liu, Q.; Djugum, R.; Sharp, P.K. [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Paradowska, A. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2232 (Australia)

    2014-11-30

    Highlights: • Deep surface rolling as a post-repair enhancement technology was applied to the laser cladded 7075-T651 aluminium alloy specimens that simulated corrosion damage blend-out repair. • The residual stresses induced by the deep surface rolling process were measured. • The deep surface rolling process can introduce deep and high magnitude compressive residual stresses beyond the laser clad and substrate interface. • Spectrum fatigue test showed the fatigue life was significantly increased by deep surface rolling. - Abstract: Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface.

  3. Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle

    Directory of Open Access Journals (Sweden)

    V.K.Aher

    2012-06-01

    Full Text Available The Leaf spring is widely used in automobiles and one of the components of suspension system. It needs to have high fatigue life. As a general rule, the leaf spring is regarded as a safety component as failure could lead to severe accidents. The purpose of this paper is to predict the fatigue life of steel leaf spring along with analytical stress and deflection calculations. This present work describes static and fatigue analysis of a steel leaf spring of a light commercial vehicle (LCV. The dimensions of the leaf spring of a LCV are taken and are verified by design calculations. The non-linear static analysis of 2D model of the leaf spring is performed using NASTRAN solver and compared with analytical results. The preprocessing of the model is done by using HYPERMESH software. The stiffness of the leaf spring is studied by plotting load versus deflection curve for various load applications. The simulation results are compared with analytical results. The fatigue life of the leaf spring is predicted using MSC Fatigue software.

  4. Estimation of Fatigue-life of Electronic Packages Subjected to Random Vibration Load

    Directory of Open Access Journals (Sweden)

    M.I. Sakri

    2009-01-01

    Full Text Available Random vibration is being specified for acceptance tests, screening tests, and qualification tests by manufacturers of electronic equipment meant for military applications, because it has been shown that random vibration more closely represents the true environment in which the electronic equipment must operate. In this paper, the methodology of testing an electronic package subjected to random vibration load is illustrated using Joint Electronic Device Engineering Council’s (JEDEC JESD22-B103B standard. The electronic package mounted at the centre of the printed circuit board was subjected to vibration, variable frequency condition ‘D’ of JEDEC standard for 30 min. After 30 min of random vibration test, the component lead-wires, solderjoints, and PCB were thoroughly inspected for failure. From the observations, it was found that no failure occurred during the test period. The fatigue life of the component, estimated using analytical method, was found to be 96.48 hours.Defence Science Journal, 2009, 59(1, pp.58-62, DOI:http://dx.doi.org/10.14429/dsj.59.1486

  5. Effect of pre-deformation on the fatigue crack initiation life of X60 pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, M. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)]. E-mail: mszheng@mail.xjtu.edu.cn; Luo, J.H. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center, CNPC, Xi' an 710065 (China); Zhao, X.W. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center, CNPC, Xi' an 710065 (China); Bai, Z.Q. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center, CNPC, Xi' an 710065 (China); Wang, R. [School of Mechanical Engineering, Xi' an Petroleum University, Xi' an 710065 (China)

    2005-07-01

    It is impossible to keep petroleum and natural gas transmission pipelines free from defects in the manufacturing, installation and servicing processes. The damage might endanger the safety of pipelines and even shorten their service life; gas or petroleum release due to defects may jeopardise the surrounding ecological environments with associated economic and life costs. Pre-tensile deformation of X60 steel is employed to experimentally simulate the influence of dents on the fatigue crack initiation life. The investigation indicates that the fatigue crack initiation life of pre-deformed X60 pipeline steel can be assessed by a previously proposed energetic approach. The threshold for crack initiation increases with the pre-deformation due to a strain hardening effect, while the fatigue resistant factor exhibits a maximum with pre-deformation owing to its special dependence on fracture strain and fracture strength. The result is expected to be beneficial to the understanding of the effect of damage on the safety of pipelines and fatigue life prediction.

  6. A study on the fatigue life prediction of the various gas-welded joints using a probabilistic statistics technique

    Science.gov (United States)

    Baek, Seung Yeb; Bae, Dong Ho

    2011-02-01

    Gas welding is a very important and useful technology in the fabrication of railroad cars and commercial vehicle structures. However, since the fatigue strength of gas-welded joints is considerably lower than that of the base of material due to stress concentration at the weld, the fatigue strength assessment of gas-welded joints is very important for the reliability and durability of railroad cars and establishment of criteria for long-life fatigue design. In this study, after evaluating the fatigue strength using a simulated specimen that satisfies not only the structural characteristics but also the mechanical condition of the actual structure, the fatigue design criteria are determined and applied to the fatigue design of the gas welded body structure. To save time and cost for the fatigue design, we investigated an accelerated life-prediction using a probabilistic statistics technique based on the theory of statistical reliability. The (Δσ a )R-Nf relationship was obtained from actual fatigue test data, including welding residual stress. On the basis of these results, the (Δσa)R-(Nf)ALP relationship that was derived from statistical probability analysis was compared with the actual fatigue test data. Therefore, it is expected that the accelerated life prediction will provide a useful method of determining the criteria for fatigue design and predicting a specific target life.

  7. Evaluation of fatigue life via stress and strain damage criterions

    Science.gov (United States)

    Savkin, A. N.; Sedov, A. A.; Badikov, K. A.

    2016-11-01

    Attempts to describe the effect of the variable amplitude loading character on fatigue damage accumulation are made for a structural steel element. We show the possibility of durability prediction of steel taking into account stress and strain parameters of stationary cyclic loading and parameters that describe the range of random loading. It is proposed to quantify the influence of the loading character on durability by a damage model with the nonstationarity factor and spectrum fullness factor. The accuracy of the model is analyzed on the basis of steel 40Cr tests. The experimental evidence and analytical results of the proposed model are correlated.

  8. Statistical analysis of manufacturing defects on fatigue life of wind turbine casted Component

    DEFF Research Database (Denmark)

    Rafsanjani, Hesam Mirzaei; Sørensen, John Dalsgaard; Mukherjee, Krishnendu;

    2014-01-01

    and size of defects in the casted components and is therefore rather uncertain and needs to be described by stochastic models. Uncertainties related to such defects influence prediction of the fatigue strengths and are therefore important in modelling and assessment of the reliability of wind turbine...... for the fatigue life, namely LogNormal and Weibull distributions. The statistical analyses are performed using the Maximum Likelihood Method and the statistical uncertainty is estimated. Further, stochastic models for the fatigue life obtained from the statistical analyses are used for illustration to assess...... components. The defect distribution is usually affected by the manufacturing process. In this paper, two methods of casting, sand casting and chill casting are considered. These are compared in statistical analyses of a large number of representative test samples using two basic stochastic models...

  9. Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure

    Directory of Open Access Journals (Sweden)

    Hualiang Wan

    2016-01-01

    Full Text Available New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing further development on the ANSYS platform, the anisotropic elastoplastic damage mechanics-finite element method is developed. The fatigue crack propagation life of satellite structure is predicted using the present method and the computational results comply with the experimental data very well.

  10. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

    Institute of Scientific and Technical Information of China (English)

    王清远; N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI

    2003-01-01

    Corrosion and fatigue properties of aircraft materials axe known to have a considerablescatter due to the random nature of materials, loading, and environmental conditions. A probabilisticapproach for predicting the pitting corrosion fatigue life has been investigated which captures the effectof the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigueprocess (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pittingcurrent, and material properties due to the scatter found in the experimental data. Monte Carlo simu-lations were performed to define the failure probability distribution. Predicted cumulative distributionfunctions of fatigue life agreed reasonably well with the existing experimental data.

  11. Influence of fibre volume fraction and temperature on fatigue life of glass fibre reinforced plastics

    Directory of Open Access Journals (Sweden)

    Konrad Wegener

    2016-07-01

    Full Text Available The influence of fibre volume fraction and temperature on fatigue life of continuous glass fibre reinforced plastics is investigated in detail. The physical causes of the two effects on the slope of the S-N-curve in fibre direction at R = 0.1 are researched and can be explained with help of micrographs. A new phenomenological approach is presented to model both effects in fibre dominated laminates with different stacking sequences using only the static ultimate strength as an input. Static and fatigue tests of different layups and fibre volume fractions are performed at different temperatures to validate the fatigue life predictions. Additionally it is derived that there is an optimal fibre volume fraction regarding a minimum damage sum. This fibre volume fraction is dependent on a given loading spectra and can be calculated using the phenomenological model.

  12. Noncontact monitoring of surface-wave nonlinearity for predicting the remaining life of fatigued steels

    Science.gov (United States)

    Ogi, Hirotsugu; Hirao, Masahiko; Aoki, Shinji

    2001-07-01

    A nonlinear acoustic measurement is studied for fatigue damage monitoring. An electromagnetic acoustic transducer (EMAT) magnetostrictively couples to a surface-shear-wave resonance along the circumference of a rod specimen during rotating bending fatigue of carbon steels. Excitation of the EMAT at half of the resonance frequency caused the standing wave to contain only the second-harmonic component, which was received by the same EMAT to determine the second-harmonic amplitude. Thus measured surface-wave nonlinearity always showed two distinct peaks at 60% and 85% of the total life. We attribute the earlier peak to crack nucleation and growth, and the later peak to an increase of free dislocations associated with crack extension in the final stage. This noncontact resonance-EMAT measurement can monitor the evolution of the surface-shear-wave nonlinearity throughout the metal's fatigue life and detect the pertinent precursors of the eventual failure.

  13. Fatigue life prediction of Ni-base thermal solar receiver tubes

    Energy Technology Data Exchange (ETDEWEB)

    Hartrott, Philipp von; Schlesinger, Michael [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany); Uhlig, Ralf; Jedamski, Jens [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Stuttgart (Germany)

    2010-07-01

    Solar receivers for tower type Solar Thermal Power Plants are subjected to complex thermo-mechanical loads including fast and severe thermo-mechanical cycles. The material temperatures can reach more than 800 C and fall to room temperature very quickly. In order to predict the fatigue life of a receiver design, receiver tubes made of Alloy 625 with a wall thickness of 0.5 mm were tested in isothermal and thermo-cyclic experiments. The number of cycles to failure was in the range of 100 to 100,000. A thermo-mechanical fatigue life prediction model was set up. The model is based on the cyclic deformation of the material and the damage caused by the growth of fatigue micro cracks. The model reasonably predicts the experimental results. (orig.)

  14. Bi-variable damage model for fatigue life prediction of metal components

    Institute of Scientific and Technical Information of China (English)

    Miao Zhang; Qing-Chun Meng; Xing Zhang; Wei-Ping Hu

    2011-01-01

    Based on the theory of continuum damage mechanics, a bi-variable damage mechanics model is developed, which, according to thermodynamics, is accessible to derivation of damage driving force, damage evolution equation and damage evolution criteria. Furthermore, damage evolution equations of time rate are established by the generalized Drucker's postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations, and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise, for notched specimens under the repeated loading with constant strain amplitude, the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus, the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1, 2 and 3.

  15. A new Cumulative Damage Model for Fatigue Life Prediction under Shot Peening Treatment

    Directory of Open Access Journals (Sweden)

    Abdul-Jabar H. Ali

    2015-07-01

    Full Text Available In this paper, fatigue damage accumulation were studied using many methods i.e.Corton-Dalon (CD,Corton-Dalon-Marsh(CDM, new non-linear model and experimental method. The prediction of fatigue lifetimes based on the two classical methods, Corton-Dalon (CDandCorton-Dalon-Marsh (CDM, are uneconomic and non-conservative respectively. However satisfactory predictions were obtained by applying the proposed non-linear model (present model for medium carbon steel compared with experimental work. Many shortcomings of the two classical methods are related to their inability to take into account the surface treatment effect as shot peening. It is clear that the new model shows that a much better and conservative prediction of fatigue life in comparison with CD and CDM methods. The prediction of the present model gave slightly below the experimental data while the CDM gave overestimate prediction and CD showed strongly underestimates the life of specimens.

  16. Thermomechanical fatigue – Damage mechanisms and mechanism-based life prediction methods

    Indian Academy of Sciences (India)

    H-J Christ; A Jung; H J Maier; R Teteruk

    2003-02-01

    An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy IMI 834 and dispersoidstrengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinforced conditions was used to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these concepts were, then adjusted by using data from independent experiments in order to avoid any sort of fitting. It is shown that the cyclic -integral ($\\Delta J_{\\text{eff}}$ concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep–fatigue damage parameter $\\Delta_{C\\ F}$ introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating influence of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law. Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account.

  17. Initiation and propagation life distributions of fatigue cracks and the life evaluation in high cycle fatigue of ADI; ADI zai no ko cycle hiro kiretsu hassei shinten jumyo bunpu tokusei to jumyo hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Y.; Ishii, A. [University of Electro Communications, Tokyo (Japan); Ogata, T. [Hitachi Metals, Ltd., Tokyo (Japan); Kubota, M. [Kyushu University, Fukuoka (Japan). Faculty of Engineering

    1997-10-15

    Rotating bending fatigue tests were carried out on austempered ductile cast iron (ADI) in order to investigate the statistical properties of life distributions of crack initiation and propagation, and also the evaluation of fatigue life. The results are summarized as follows: (1) The size of crack initiation sites of the material was represented by a Weibull distribution without regarding to the kinds of crack initiation sites such as microshrinkage and graphite grain. The crack initiation life scattered widely, but the scatter became much smaller as soon as the cracks grew. (2) The crack propagation life Nac which was defined as the minimum crack propagation rate showed lower scatter than the crack initation life. (3) The fatigue life of the material was evaluated well by Nac and the propagation rate after Nac. It was clear that the fatigue life of ductile cast iron was goverened by the scatter of Nac. 8 refs., 13 figs., 4 tabs.

  18. Effect of creep and oxidation on reduced fatigue life of Ni-based alloy 617 at 850 °C

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang, E-mail: chenx@ornl.gov [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States); Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Yang, Zhiqing [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Sokolov, Mikhail A.; Erdman, Donald L. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Mo, Kun; Stubbins, James F. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

    2014-01-15

    Low cycle fatigue (LCF) and creep–fatigue testing of Ni-based alloy 617 was carried out at 850 °C. Compared with its LCF life, the material’s creep–fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep–fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material’s fatigue life.

  19. Effect of Creep and Oxidation on Reduced Creep-Fatigue life of Ni-based Alloy 617 at 850 C

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang [ORNL; Yang, Zhiqing [ORNL; Sokolov, Mikhail A [ORNL; ERDMAN III, DONALD L [ORNL; Mo, Kun [ORNL; Stubbins, James [ORNL

    2014-01-01

    Low cycle fatigue (LCF) and creep fatigue testing of Ni-based alloy 617 was carried out at 850 C. Compared with its LCF life, the material s creep fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material s fatigue life.

  20. Measurement of Quality of Life I. A Methodological Framework

    Directory of Open Access Journals (Sweden)

    Soren Ventegodt

    2003-01-01

    Full Text Available Despite the widespread acceptance of quality of life (QOL as the ideal guideline in healthcare and clinical research, serious conceptual and methodological problems continue to plague this area. In an attempt to remedy this situation, we propose seven criteria that a quality-of-life concept must meet to provide a sound basis for investigation by questionnaire. The seven criteria or desiderata are: (1 an explicit definition of quality of life; (2 a coherent philosophy of human life from which the definition is derived; (3 a theory that operationalizes the philosophy by specifying unambiguous, nonoverlapping, and jointly exhaustive questionnaire items; (4 response alternatives that permit a fraction-scale interpretation; (5 technical checks of reproducibility; (6 meaningfulness to investigators, respondents, and users; and (7 an overall aesthetic appeal of the questionnaire. These criteria have guided the design of a validated 5-item generic, global quality-of-life questionnaire (QOL5, and a validated 317-item generic, global quality-of-life questionnaire (SEQOL, administered to a well-documented birth cohort of 7,400 Danes born in 1959�1961, as well as to a reference sample of 2,500 Danes. Presented in outline, the underlying integrative quality-of-life (IQOL theory is a meta-theory. To illustrate the seven criteria at work, we show the extent to which they are satisfied by one of the eight component theories. Next, two sample results of our investigation are presented: satisfaction with one's sex life has the expected covariation with one's quality of life, and so does mother's smoking during pregnancy, albeit to a much smaller extent. It is concluded that the methodological framework presented has proved helpful in designing a questionnaire that is capable of yielding acceptably valid and reliable measurements of global and generic quality of life.

  1. SHM-Based Probabilistic Fatigue Life Prediction for Bridges Based on FE Model Updating.

    Science.gov (United States)

    Lee, Young-Joo; Cho, Soojin

    2016-03-02

    Fatigue life prediction for a bridge should be based on the current condition of the bridge, and various sources of uncertainty, such as material properties, anticipated vehicle loads and environmental conditions, make the prediction very challenging. This paper presents a new approach for probabilistic fatigue life prediction for bridges using finite element (FE) model updating based on structural health monitoring (SHM) data. Recently, various types of SHM systems have been used to monitor and evaluate the long-term structural performance of bridges. For example, SHM data can be used to estimate the degradation of an in-service bridge, which makes it possible to update the initial FE model. The proposed method consists of three steps: (1) identifying the modal properties of a bridge, such as mode shapes and natural frequencies, based on the ambient vibration under passing vehicles; (2) updating the structural parameters of an initial FE model using the identified modal properties; and (3) predicting the probabilistic fatigue life using the updated FE model. The proposed method is demonstrated by application to a numerical model of a bridge, and the impact of FE model updating on the bridge fatigue life is discussed.

  2. Compassion Fatigue, Compassion Satisfaction, and Burnout: Factors Impacting a Professional's Quality of Life

    Science.gov (United States)

    Sprang, Ginny; Whitt-Woosley, Adrienne; Clark, James J.

    2007-01-01

    This study examined the relationship between three variables, compassion fatigue (CF), compassion satisfaction (CS), and burnout, and provider and setting characteristics in a sample of 1,121 mental health providers in a rural southern state. Respondents completed the Professional Quality of Life Scale as part of a larger survey of provider…

  3. Effect of Defects Distribution on Fatigue Life of Wind Turbine Components

    DEFF Research Database (Denmark)

    Rafsanjani, Hesam Mirzaei; Sørensen, John Dalsgaard

    2015-01-01

    by a Poisson process / field where the defects form clusters that consist of a parent defect and related defects around the parent defect. The fatigue life is dependent on the number, type, location and size of the defects in the component and is therefore quite uncertain and needs to be described...

  4. Quality of Life in Patients with Multiple Sclerosis: The Impact of Depression, Fatigue, and Disability

    Science.gov (United States)

    Goksel Karatepe, Altlnay; Kaya, Taciser; Gunaydn, Rezzan; Demirhan, Aylin; Ce, Plnar; Gedizlioglu, Muhtesem

    2011-01-01

    Aim: The aim of this study was to assess the quality of life (QoL) in patients with multiple sclerosis (MS), and to evaluate its association with disability and psychosocial factors especially depression and fatigue. Methods: Demographic characteristics, education level, disease severity, and disease duration were documented for each patient. QoL,…

  5. Crack mode and life of Ti-6Al-4V under multiaxial low cycle fatigue

    Directory of Open Access Journals (Sweden)

    Takamoto Itoh

    2015-10-01

    Full Text Available This paper studies multiaxial low cycle fatigue crack mode and failure life of Ti-6Al-4V. Stress controlled fatigue tests were carried out using a hollow cylinder specimen under multiaxial loadings of λ=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. λ is a principal stress ratio and is defined as λ=II/I, where I and II are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at λ=0 is a uniaxial loading test and that at λ=1 an equi-biaxial loading test. A testing machine employed is a newly developed multiaxial fatigue testing machine which can apply push-pull and reversed torsion loadings with inner pressure onto the hollow cylinder specimen. Based on the obtained results, this study discusses evaluation of the biaxial low cycle fatigue life and crack mode. Failure life is reduced with increasing λ induced by cyclic ratcheting. The crack mode is affected by the surface condition of cut-machining and the failure life depends on the crack mode in the multiaxial loading largely.

  6. Structural fatigue life assessment and sustainment implications for a New Class of US Coast Guard Cutters

    NARCIS (Netherlands)

    Stambaugh, K.; Drummen, I.; Cleary, C.; Sheinberg, R.; Kaminski, M.L.

    2014-01-01

    This paper presents an overview of the US Coast Guard’s Fatigue Life Assessment Project (FLAP) and the application of the results in hull structure lifecycle management of the National Security Cutter class. One of the key measurements of the FLAP instrumentation included a radar based wave data

  7. Evaluation of health-related quality of life, fatigue and depression in neuromyelitis optica.

    Science.gov (United States)

    Chanson, J-B; Zéphir, H; Collongues, N; Outteryck, O; Blanc, F; Fleury, M; Vermersch, P; de Seze, J

    2011-06-01

    The burden of multiple sclerosis (MS) includes fatigue, depression and worsening of health-related quality of life (HRQOL). These changes have not been yet measured in neuromyelitis optica (NMO). Our aim was to assess the HRQOL, fatigue and depression in NMO. We administered French validated self-questionnaires on HRQOL (SEP-59), fatigue (EMIF-SEP) and depression (EHD) to 40 patients followed up in two centres. We assessed the relationship of these parameters with gender, age, disability, disease duration, visual acuity and NMO-antibody status and also compared our results with equivalent data in MS and normal subjects derived from previous studies. Health-related quality of life scores were lower (P < 0.01) in patients with NMO when compared to normal subjects. No significant difference was noted between patients with NMO and MS for most scores, the exceptions being HRQOL related to cognitive function (better in NMO than in MS), HRQOL related to sphincter dysfunction (worse in NMO than in MS) and the psychological dimension of fatigue (milder in NMO than in MS). Disability was the main predictive factor of an unfavourable evolution. This study reveals the strong impact of NMO on HRQOL, fatigue and depression and the importance of screening patients, especially the more disabled, so as to initiate suitable treatment. © 2010 The Author(s). European Journal of Neurology © 2010 EFNS.

  8. Cyclic fatigue damage characteristics observed for simple loadings extended to multiaxial life prediction

    Science.gov (United States)

    Jones, David J.; Kurath, Peter

    1988-01-01

    Fully reversed uniaxial strain controlled fatigue tests were performed on smooth cylindrical specimens made of 304 stainless steel. Fatigue life data and cracking observations for uniaxial tests were compared with life data and cracking behavior observed in fully reversed torsional tests. It was determined that the product of maximum principle strain amplitude and maximum principle stress provided the best correlation of fatigue lives for these two loading conditions. Implementation of this parameter is in agreement with observed physical damage and it accounts for the variation of stress-strain response, which is unique to specific loading conditions. Biaxial fatigue tests were conducted on tubular specimens employing both in-phase and out-of-phase tension torsion cyclic strain paths. Cracking observations indicated that the physical damage which occurred in the biaxial tests was similar to the damage observed in uniaxial and torsional tests. The Smith, Watson, and Topper parameter was then extended to predict the fatigue lives resulting from the more complex loading conditions.

  9. Novel Electrochemical Test Bench for Evaluating the Functional Fatigue Life of Biomedical Alloys

    Science.gov (United States)

    Ijaz, M. F.; Dubinskiy, S.; Zhukova, Y.; Korobkova, A.; Pustov, Y.; Brailovski, V.; Prokoshkin, S.

    2017-08-01

    The aim of the present work was first to develop and validate a test bench that simulates the in vitro conditions to which the biomedical implants will be actually subjected in vivo. For the preliminary application assessments, the strain-controlled fatigue tests of biomedically pure Ti and Ti-Nb-Zr alloy in simulated body fluid were undertaken. The in situ open-circuit potential measurements from the test bench demonstrated a strong dependence on the dynamic cycling and kind of material under testing. The results showed that during fatigue cycling, the passive oxide film formed on the surface of Ti-Nb-Zr alloy was more resistant to fatigue degradation when compared with pure Ti. The Ti-Nb-Zr alloy exhibited prolonged fatigue life when compared with pure Ti. The fractographic features of both materials were also characterized using scanning electron microscopy. The electrochemical results and the fractographic evidence confirmed that the prolonged functional fatigue life of the Ti-Nb-Zr alloy is apparently ascribable to the reversible martensitic phase transformation.

  10. A Multiaxial Low Cycle Fatigue Life Prediction Model for Both Proportional and Non-proportional Loading Conditions

    Science.gov (United States)

    Paul, Surajit Kumar

    2014-09-01

    This paper has presented a life prediction model in the field of multiaxial low-cycle fatigue. The proposed model is generally applied for constant amplitude multiaxial proportional and non-proportional loading. Depending upon applied strain path the equivalent strain varies within a cycle. Equivalent average strain amplitude is considered as fatigue damage parameter in the proposed model. The model has requirement of only two material constants and no other tuning parameters. The model is examined by the proportional and non-proportional low-cycle fatigue life experimental data for eight different types of materials. The model is successfully correlated with multiaxial fatigue lives of eight different materials.

  11. The origin of life and its methodological challenge.

    Science.gov (United States)

    Wächtershäuser, G

    1997-08-21

    The problem of the origin of life is discussed from a methodological point of view as an encounter between the teleological thinking of the historian and the mechanistic thinking of the chemist; and as the Kantian task of replacing teleology by mechanism. It is shown how the Popperian situational logic of historic understanding and the Popperian principle of explanatory power of scientific theories, when jointly applied to biochemistry, lead to a methodology of biochemical retrodiction, whereby common precursor functions are constructed for disparate successor functions. This methodology is exemplified by central tenets of the theory of the chemo-autotrophic origin of life: the proposal of a surface metabolism with a two-dimensional order; the basic polarity of life with negatively charged constituents on positively charged mineral surfaces; the surface-metabolic origin of phosphorylated sugar metabolism and nucleic acids; the origin of membrane lipids and of chemi-osmosis on pyrite surfaces; and the principles of the origin of the genetic machinery. The theory presents the early evolution of life as a process that begins with chemical necessity and winds up in genetic chance.

  12. Fatigue Life Improving of Drill Rod by Inclusion Control

    Science.gov (United States)

    Wang, Linzhu; Yang, Shufeng; Li, Jingshe; Liu, Wei; Zhou, Yinghao

    2016-08-01

    Large and hard inclusions often deteriorate the service performance and reduce the fatigue lifetime of drill rods. In this paper, the main reasons of the rupture of drill rods were analyzed by the examination of their fracture and it is found that the large inclusions were the main reason of breakage of rod drill. The inclusions were high of Ca content or Al2O3 rich. Smaller and better deformability inclusions were obtained by the optimization of refining slag, calcium treatment process and the flow control devices of tundish. Results of industrial experiment after optimization show that total oxygen content of drill rods decreased by more than 50%, macro-inclusions weight fraction decreased from about 4 mg/10 kg to about 0.3 mg/10 kg and the micro-inclusions average size decreased from 6 to 3.6 μm. The average using times of drill rods after optimization were increased by about 60%.

  13. Prediction of Fatigue Life of Boom Nose End Casting Using Linear Elastic Fracture Mechanics

    OpenAIRE

    Nitin D.Ghongade; Rajesh.M. Metkar

    2014-01-01

    The main objective of this study is to get the life estimation of Boom nose end casting using theoretical approach and compaired it with finite element method. Therefore, this study consists of three major sections : (1) dynamic load analysis (2) FEM and stress analysis (3) prediction of fatigue life for Boom nose end casting. In this study a dynamic loads were obtained from cyclic loading at different time. Finite element analysis was performed to obtain the variation of stress...

  14. Fatigue Life of Cast Titanium Alloys Under Simulated Denture Framework Displacements

    Science.gov (United States)

    Koike, Mari; Chan, Kwai S.; Hummel, Susan K.; Mason, Robert L.; Okabe, Toru

    2013-02-01

    The objective of the study was to evaluate the hypothesis that the mechanical properties and fatigue behavior of removable partial dentures (RPD) made from cast titanium alloys can be improved by alloying with low-cost, low-melting elements such as Cu, Al, and Fe using commercially pure Ti (CP-Ti) and Ti-6Al-4V as controls. RPD specimens in the form of rest-shaped, clasp, rectangular-shaped specimens and round-bar tensile specimens were cast using an experimental Ti-5Al-5Cu alloy, Ti-5Al-1Fe, and Ti-1Fe in an Al2O3-based investment with a centrifugal-casting machine. The mechanical properties of the alloys were determined by performing tensile tests under a controlled displacement rate. The fatigue life of the RPD specimens was tested by the three-point bending in an MTS testing machine under a cyclic displacement of 0.5 mm. Fatigue tests were performed at 10 Hz at ambient temperature until the specimens failed into two pieces. The tensile data were statistically analyzed using one-way ANOVA (α = 0.05) and the fatigue life data were analyzed using the Kaplan-Meier survival analysis (α = 0.05). The experimental Ti-5Al-5Cu alloy showed a significantly higher average fatigue life than that of either CP-Ti or Ti-5Al-1Fe alloy ( p casting pores. Among the alloys tested, the Ti-5Al-5Cu alloy exhibited favorable results in fabricating dental appliances with an excellent fatigue behavior compared with other commercial alloys.

  15. Fatigue Life Prediction of 2D Woven Ceramic-Matrix Composites at Room and Elevated Temperatures

    Science.gov (United States)

    Longbiao, Li

    2017-02-01

    In this paper, the fatigue life of 2D woven ceramic-matrix composites, i.e., SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate, at room and elevated temperatures has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the microstress field of the damaged composite considering fibers failure. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress and fibers strength degradation model and oxidation region propagation model have been adopted to analyze the fatigue and oxidation effects on fatigue life of the composite, which is controlled by interface frictional slip and diffusion of oxygen gas through matrix multicrackings. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composites fatigue fractures. The fatigue life S-N curves of 2D SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate composites at room temperature and 800, 1000 and 1200 °C in air and steam have been predicted.

  16. Mechanisms of fatigue-crack initiation and their impact on fatigue life of AlSi7 die-cast components

    Directory of Open Access Journals (Sweden)

    Redik Sabine

    2014-06-01

    Full Text Available In the course of the present study, in-situ observations of crack initiation and crack growth of naturally induced cracks in cyclically loaded specimens along with conventional fatigue tests and fracture surface analyses were performed. The specimens used were taken from different sampling positions of standard and HIPed aluminum-die-cast engine blocks, with different cooling conditions. In one sampling position within the standard engine block microporosity was able to form, acting as a source for fatigue-crack initiation. While in the absence of microporosity, as observed in specimens taken from HIPed components, crack initiation occured via slip band mechanism. If material defects such as pores were present, premature crack initiation reduced the fatigue life yielding a lower fatigue life and fatigue strength than specimens where cracks formed by slip band mechanism. For cracks formed at pores, the pore size is the determining factor for fatigue behavior. While for cracks initiated via slip band mechanism fatigue strength is a function of the local material strength.

  17. Application of Mathematica Software for Estimate the Fatigue Life Time Duration of Mechanical System

    Directory of Open Access Journals (Sweden)

    Petru Florin Minda

    2010-10-01

    Full Text Available The paper present how we can use Mathematica to solve the equations types usually used to determinate the maximum stress cycles that can be support by a mechanical system until he will be out of use. To illustrate the type of equations used in specialized literature to estimate fatigue life time duration was chosen a specific case of mechanical structure applied to fatigue. It is about lever button of runner blade mechanism of Kaplan turbine, that in function support a very intensive alternative strain.

  18. Life Cycle Engineering – from methodology to enterprise culture

    DEFF Research Database (Denmark)

    Hauschild, Michael Zwicky; Alting, Leo; Poll, Christian

    2003-01-01

    of methodologies and tools for life cycle assessment and development of more eco-efficient products, from complex to simplified, catering to the needs of especially small and medium-sized enterprizes. The tools and data are in place, but dissemination lacks behind. Propagation of life cycle thinking and life cycle......As part of a sustainable development, the environmental efficiency of industry must increase by a factor four to ten. This engenders attention to the environmental impact of products and technical systems over their entire life cycle. The last decade has seen the development of a number...... engineering to larger parts of industry is attempted by strengthening the market pull through integrated product policy measures, and at the same time pushing through information activities, training and dissemination of tools. Experience hitherto shows that these forces are insufficient and that stronger...

  19. Influence of Subgrade and Unbound Granular Layers Stiffness on Fatigue Life of Hot Mix Asphalts - HMA

    Directory of Open Access Journals (Sweden)

    Hugo A. Rondón-Quintana

    2013-11-01

    Full Text Available The mainly factors studied to predict fatigue life of hot mix asphalt-HMA in flexible pavements are the loading effect, type of test, compaction methods, design parameters of HMA (e.g., particle size and size distribution curve, fine content, type of bitumen and the variables associated with the environment (mainly moisture, temperature, aging. This study evaluated through a computer simulation, the influence of the granular layers and subgrade on the fatigue life of asphalt layers in flexible pavement structures. Mechanics parameters of granular layers of subgrade, base and subbase were obtained using the mathematical equations currently used for this purpose in the world. The emphasis of the study was the city of Bogotá, where the average annual temperature is 14°C and soils predominantly clay, generally experience CBR magnitudes between 1% and 4%. General conclusion: stiffness of the granular layers and subgrade significantly affect the fatigue resistance of HMA mixtures. Likewise, the use of different equations reported in reference literature in order to characterize granular layers may vary the fatigue life between 4.6 and 48.5 times, varying the thickness of the pavement layers in the design.

  20. Bayesian techniques for fatigue life prediction and for inference in linear time dependent PDEs

    KAUST Repository

    Scavino, Marco

    2016-01-08

    In this talk we introduce first the main characteristics of a systematic statistical approach to model calibration, model selection and model ranking when stress-life data are drawn from a collection of records of fatigue experiments. Focusing on Bayesian prediction assessment, we consider fatigue-limit models and random fatigue-limit models under different a priori assumptions. In the second part of the talk, we present a hierarchical Bayesian technique for the inference of the coefficients of time dependent linear PDEs, under the assumption that noisy measurements are available in both the interior of a domain of interest and from boundary conditions. We present a computational technique based on the marginalization of the contribution of the boundary parameters and apply it to inverse heat conduction problems.

  1. Method to calculate fatigue fracture life of control fissure in perilous rock

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong-kai; TANG Hong-mei

    2007-01-01

    Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰ and model-Ⅱ stress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris's fatigue equation. Further, parameters(C and m)of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.

  2. Effect of test frequency on the in vitro fatigue life of acrylic bone cement.

    Science.gov (United States)

    Lewis, Gladius; Janna, Si; Carroll, Michael

    2003-03-01

    The goal of the present work was to test the hypothesis that test frequency, f, does not have a statistically significant effect on the in vitro fatigue life of an acrylic bone cement. Uniaxial constant-amplitude tension-compression fatigue tests were conducted on 12 sets of cements, covering three formulations with three very different viscosities, two different methods of mixing the cement constituents, and two values of f (1 and 10 Hz). The test results (number of fatigue stress cycles, N(f)) were analyzed using the linearized form of the three-parameter Weibull equation, allowing the values of the Weibull mean (N(WM)) to be determined for each set. Statistical analysis of the lnN(f) data, together with an examination of the N(WM) estimates, showed support for the hypothesis over the range of f used. The principal use and explanation of the present finding are presented.

  3. Fatigue Behaviour and Life Assessment of Jute-epoxy Composites under Tension-Tension Loading

    Science.gov (United States)

    Padmaraj, N. H.; Chethan, K. N.; Pavan; Onkar, Anand

    2017-08-01

    The present study involves fabrication and fatigue life assessment of multi-layered, woven jute fibres with epoxy matrix composites. Jute fabric were treated with 1N sodium hydroxidesolution for a duration of 6 hours. Alkali treatment was done to modify internal structure as well as surface properties of fibre. Laminates were fabricated by laying up multi layered woven jute fabric at varying angle [0-900/ (±450)2/0-900]. Vacuum bagging method was used to reduce the void content and thus increase the quality of composites. Tension-Tension fatigue tests were performed with a constant fatigue stress ratio (R=0.1) and results obtained from the tests were used to plot S-N Curve. A model based on power law equation was used for curve fitting.

  4. Probabilistic Fatigue Life Updating for Railway Bridges Based on Local Inspection and Repair

    Science.gov (United States)

    Lee, Young-Joo; Kim, Robin E.; Suh, Wonho; Park, Kiwon

    2017-01-01

    Railway bridges are exposed to repeated train loads, which may cause fatigue failure. As critical links in a transportation network, railway bridges are expected to survive for a target period of time, but sometimes they fail earlier than expected. To guarantee the target bridge life, bridge maintenance activities such as local inspection and repair should be undertaken properly. However, this is a challenging task because there are various sources of uncertainty associated with aging bridges, train loads, environmental conditions, and maintenance work. Therefore, to perform optimal risk-based maintenance of railway bridges, it is essential to estimate the probabilistic fatigue life of a railway bridge and update the life information based on the results of local inspections and repair. Recently, a system reliability approach was proposed to evaluate the fatigue failure risk of structural systems and update the prior risk information in various inspection scenarios. However, this approach can handle only a constant-amplitude load and has limitations in considering a cyclic load with varying amplitude levels, which is the major loading pattern generated by train traffic. In addition, it is not feasible to update the prior risk information after bridges are repaired. In this research, the system reliability approach is further developed so that it can handle a varying-amplitude load and update the system-level risk of fatigue failure for railway bridges after inspection and repair. The proposed method is applied to a numerical example of an in-service railway bridge, and the effects of inspection and repair on the probabilistic fatigue life are discussed. PMID:28441768

  5. Probabilistic Fatigue Life Updating for Railway Bridges Based on Local Inspection and Repair.

    Science.gov (United States)

    Lee, Young-Joo; Kim, Robin E; Suh, Wonho; Park, Kiwon

    2017-04-24

    Railway bridges are exposed to repeated train loads, which may cause fatigue failure. As critical links in a transportation network, railway bridges are expected to survive for a target period of time, but sometimes they fail earlier than expected. To guarantee the target bridge life, bridge maintenance activities such as local inspection and repair should be undertaken properly. However, this is a challenging task because there are various sources of uncertainty associated with aging bridges, train loads, environmental conditions, and maintenance work. Therefore, to perform optimal risk-based maintenance of railway bridges, it is essential to estimate the probabilistic fatigue life of a railway bridge and update the life information based on the results of local inspections and repair. Recently, a system reliability approach was proposed to evaluate the fatigue failure risk of structural systems and update the prior risk information in various inspection scenarios. However, this approach can handle only a constant-amplitude load and has limitations in considering a cyclic load with varying amplitude levels, which is the major loading pattern generated by train traffic. In addition, it is not feasible to update the prior risk information after bridges are repaired. In this research, the system reliability approach is further developed so that it can handle a varying-amplitude load and update the system-level risk of fatigue failure for railway bridges after inspection and repair. The proposed method is applied to a numerical example of an in-service railway bridge, and the effects of inspection and repair on the probabilistic fatigue life are discussed.

  6. Prediction of Fatigue Life of Gear Subjected to Varying Loads

    Directory of Open Access Journals (Sweden)

    D. Hanumanna

    1998-07-01

    Full Text Available Structural members and components of a vehicle during service are subjected to varying loads which are random in nature. For structural members subjected to loads of constant amplitude, it is possible to describe the load with explicit mathematical relationship, and thereby, the life span can be estimated. Whereas, for structural members subjected to varying loads with time, there is no satisfactory method to estimate their life span. This paper describes a method for the estimation of life span of a gear in the gear box of a fighting vehicle subjected to fluctuating loads. For this purpose, it is assumed that the load spectrum corresponds to Gaussian (normal distribution, and the life has been worked out by applying linear cumulative damage theory.

  7. Fatigue in Children With Sickle Cell Disease: Association With Neurocognitive and Social-Emotional Functioning and Quality of Life.

    Science.gov (United States)

    Anderson, Lindsay M; Allen, Taryn M; Thornburg, Courtney D; Bonner, Melanie J

    2015-11-01

    Children with sickle cell disease (SCD) report fatigue in addition to acute and chronic pain, which can decrease overall health-related quality of life (HRQL). The primary objective of the current study was to investigate the relationship between fatigue and HRQL. Given limited prior research, secondary objectives included investigation of associations between fatigue and functional outcomes, including child neurocognitive and social-emotional functioning. Children aged 8 to 16 years (N=32) and a caregiver completed measures of fatigue, HRQL, pain, and neurocognitive and social-emotional functioning. Controlling for pain and number of SCD-related hospitalizations, hierarchical linear regression models were used to determine the impact of child-reported and parent-reported fatigue on child HRQL. Correlational analyses were used to explore the relationship between fatigue and additional child outcomes. Data indicated that children with SCD experience clinically relevant levels of fatigue, which independently predicts lower HRQL. Fatigue was also associated with lower working memory, executive functioning, and higher levels of internalizing symptoms. Given its observed impact on HRQL and relationship to functional outcomes, fatigue may be an important target of clinical, home, or school interventions. This practice may attenuate the burden of fatigue in these patients, and in turn, help improve the quality of life of children living with SCD.

  8. Fatigue, Sleep Quality, and Disability in Relation to Quality of Life in Multiple Sclerosis.

    Science.gov (United States)

    Tabrizi, Fatemeh Moghaddam; Radfar, Moloud

    2015-01-01

    Quality of life (QOL) is impaired in multiple sclerosis (MS) in part due to physical disability. MS-associated fatigue and poor sleep are common and treatable features of MS that affect QOL. We assessed the association between fatigue, sleep quality, and QOL in people with MS. Cross-sectional data were collected from 217 patients with MS. Health-related QOL (MS Quality of Life-54), fatigue (Fatigue Severity Scale [FSS]), and sleep quality (Pittsburgh Sleep Quality Inventory [PSQI]) were assessed. Expanded Disability Status Scale scores were also provided by a qualified neurologist. The mean ± SD age of the 217 patients was 32.6 ± 8.6 years, and 79% were female. One hundred fifty-two patients (70.0%) were classified as poor sleepers based on PSQI scores; 122 (56.2%) had significant fatigue based on FSS results. The mean ± SE physical (PCS) and mental (MCS) health composite scores of the MSQOL-54 were 40.12 ± 1.27 and 43.81 ± 1.61, respectively. There was a strong statistically significant positive correlation between PCS scores and MCS (r = 0.58), FSS (r = 0.49), and PSQI (r = 0.52) scores. MCS scores were strongly correlated with FSS (r = 0.53) and PSQI (r = 0.35) scores. Age exhibited statistically significant negative correlations with PCS (r = -0.21) and MCS (r = -0.58) scores, and was statistically significantly correlated with FSS (r = 0.23) and PSQI (r = 0.21) scores. Expanded Disability Status Scale scores were strongly correlated with FSS scores. These findings support screening of fatigue severity and sleep quality and their effects on QOL.

  9. Fatigue, Sleep Quality, and Disability in Relation to Quality of Life in Multiple Sclerosis

    Science.gov (United States)

    Radfar, Moloud

    2015-01-01

    Background: Quality of life (QOL) is impaired in multiple sclerosis (MS) in part due to physical disability. MS-associated fatigue and poor sleep are common and treatable features of MS that affect QOL. We assessed the association between fatigue, sleep quality, and QOL in people with MS. Methods: Cross-sectional data were collected from 217 patients with MS. Health-related QOL (MS Quality of Life-54), fatigue (Fatigue Severity Scale [FSS]), and sleep quality (Pittsburgh Sleep Quality Inventory [PSQI]) were assessed. Expanded Disability Status Scale scores were also provided by a qualified neurologist. Results: The mean ± SD age of the 217 patients was 32.6 ± 8.6 years, and 79% were female. One hundred fifty-two patients (70.0%) were classified as poor sleepers based on PSQI scores; 122 (56.2%) had significant fatigue based on FSS results. The mean ± SE physical (PCS) and mental (MCS) health composite scores of the MSQOL-54 were 40.12 ± 1.27 and 43.81 ± 1.61, respectively. There was a strong statistically significant positive correlation between PCS scores and MCS (r = 0.58), FSS (r = 0.49), and PSQI (r = 0.52) scores. MCS scores were strongly correlated with FSS (r = 0.53) and PSQI (r = 0.35) scores. Age exhibited statistically significant negative correlations with PCS (r = −0.21) and MCS (r = −0.58) scores, and was statistically significantly correlated with FSS (r = 0.23) and PSQI (r = 0.21) scores. Expanded Disability Status Scale scores were strongly correlated with FSS scores. Conclusions: These findings support screening of fatigue severity and sleep quality and their effects on QOL. PMID:26664332

  10. Quality of life in patients with multiple sclerosis in Turkey: relationship to depression and fatigue.

    Science.gov (United States)

    Tanriverdi, Derya; Okanli, Ayşe; Sezgin, Serap; Ekinci, Mine

    2010-10-01

    The purposes of this study were to assess the self-reported quality of life (QOL) in a group of Turkish patients with multiple sclerosis (MS) and to analyze whether the QOL was associated with fatigue and depression. The study used a descriptive design. A number of evaluation scales were administered to a study sample comprising 47 outpatients. The Short Form 36 for QOL, the Beck Depression Inventory for Depression, and the Visual Analogue Scale for Fatigue were used. The mean score for general QOL was 34.8 and indicated low QOL in MS patients. The results of our study have also shown that fatigue and depression strongly influence QOL in Turkish MS patients. Our findings may have important implications for the overall care of MS patients. The QOL of MS patients was affected negatively. Both fatigue and depression are common and treatable manifestations of MS, and these symptoms should be screened carefully in all MS patients. Care of MS patients requires the collaboration of all team members. Nurses have a key role as part of this team through the continuity of the care they provide and interaction with patients. Awareness of depression and fatigue can contribute to the nurses' ability to provide psychological support and enhance the QOL in MS patients.

  11. Effect of Notch Location on Fatigue Life Prediction of Strength Mismatched HSLA Steel Weldments

    Institute of Scientific and Technical Information of China (English)

    S. Ravi; V. Balasubramanian; S. Nemat Nasser

    2004-01-01

    Welding of high strength low alloy steels (HSLA) involves usage of Iow, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the filler material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM)joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0). A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.

  12. Relation Between Residual and Hoop Stresses and Rolling Bearing Fatigue Life

    Science.gov (United States)

    Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

    2015-01-01

    Rolling-element bearings operated at high speed or high vibration may require a tight interference fit between the bore of the bearing and shaft to prevent rotation of the bearing bore around the shaft and fretting damage at the interfaces. Previous work showed that the hoop stresses resulting from tight interference fits can reduce bearing lives by as much as 65 percent. Where tight interference fits are required, case-carburized steel such as AISI 9310 or M50 NiL is often used because the compressive residual stresses inhibit subsurface crack formation and the ductile core inhibits inner-ring fracture. The presence of compressive residual stress and its combination with hoop stress also modifies the Hertz stress-life relation. This paper analyzes the beneficial effect of residual stresses on rolling-element bearing fatigue life in the presence of high hoop stresses for three bearing steels. These additional stresses were superimposed on Hertzian principal stresses to calculate the inner-race maximum shearing stress and the resulting fatigue life of the bearing. The load-life exponent p and Hertz stress-life exponent n increase in the presence of compressive residual stress, which yields increased life, particularly at lower stress levels. The Zaretsky life equation is described and is shown to predict longer bearing lives and greater load- and stress-life exponents, which better predicts observed life of bearings made from vacuum-processed steel.

  13. Probability of Occurrence of Life-Limiting Fatigue Mechanism in P/M Nickel-Based Alloys (Postprint)

    Science.gov (United States)

    2016-03-30

    AFRL-RX-WP-JA-2017-0146 PROBABILITY OF OCCURRENCE OF LIFE-LIMITING FATIGUE MECHANISM IN P/M NICKEL-BASED ALLOYS (POSTPRINT) M.J...February 2016 4. TITLE AND SUBTITLE PROBABILITY OF OCCURRENCE OF LIFE-LIMITING FATIGUE MECHANISM IN P/M NICKEL-BASED ALLOYS (POSTPRINT) 5a...paper, a micro structure-based model of the probability of occurrence of the minimum-lifetime, or the life-limiting, mechanism in powder processed Ni

  14. Influence of specimen type and reinforcement on measured tension-tension fatigue life of unidirectional GFRP laminates

    DEFF Research Database (Denmark)

    Korkiakoski, Samuli; Brøndsted, Povl; Sarlin, Essi

    2016-01-01

    It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test...... specimen that fails in the gauge section. The second objective was to compare fatigue performance of two laminates, one having a newly developed UD powder-bound fabric as a reinforcement and the other having a quasi-UD stitched non-crimp fabric as a reinforcement. In the first phase, a rectangular specimen...... a significant effect on the failure mode and measured fatigue life of the laminates. A significantly higher fatigue life was measured for the laminate with the powder-bound fabric reinforcement when compared to the laminate with the stitched reinforcement....

  15. Effect of beam oscillation on fatigue life of Ti-6Al-4V electron beam weldments

    Energy Technology Data Exchange (ETDEWEB)

    Babu, N. Kishore [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai (India); Raman, S. Ganesh Sundara [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai (India)], E-mail: ganesh@iitm.ac.in; Murthy, C. V. Srinivasa [Defence Research and Development Laboratory, Hyderabad (India); Reddy, G. Madhusudhan [Defence Metallurgical Research Laboratory, Hyderabad (India)

    2007-12-15

    The present study deals with the effect of beam oscillation technique using elliptical waveform on fatigue life of Ti-6Al-4V electron beam weldments. Autogenous full penetration bead-on-plate electron beam welds were made with and without beam oscillation. Some welds were subjected to post-weld heat treatment (PWHT) at two different temperatures (700 and 900 deg. C). Room temperature hardness, tensile properties and fatigue life of the weldments in the as-welded and PWHT conditions were studied and correlated with the microstructure. The beam oscillated weldments exhibited lower strength (hardness) compared to those made without beam oscillation. This was attributed to wider diffusional {alpha} plates in the beam oscillated welds due to lower cooling rates. The beam oscillated weldments exhibited inferior fatigue lives compared with unoscillated weldments owing to the presence of wider {alpha} platelets in the former. As the width of {alpha} platelets in the weldments subjected to PWHT at 700 deg. C was smaller than that in the weldments subjected to PWHT at 900 deg. C, they exhibited longer fatigue lives.

  16. Substrate Creep on The Fatigue Life of A Model Dental Multilayer Structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J; Huang, M; Niu, X; soboyejo, W

    2006-10-09

    In this paper, we investigated the effects of substrate creep on the fatigue behavior of a model dental multilayer structure, in which a top glass layer was bonded to a polycarbonate substrate through a dental adhesive. The top glass layers were ground using 120 grit or 600 grit sand papers before bonding to create different sub-surface crack sizes and morphologies. The multilayer structures were tested under cyclic Hertzian contact loading to study crack growth and obtain fatigue life curves. The experiment results showed that the fatigue lives of the multilayer structures were impaired by increasing crack sizes in the sub-surfaces. They were also significantly reduced by the substrate creep when tested at relatively low load levels i.e. P{sub m} < 60 N (Pm is the maximum magnitude of cyclic load). But at relatively high load levels i.e. P{sub m} > 65 N, slow crack growth (SCG) was the major failure mechanisms. A modeling study was then carried out to explore the possible failure mechanisms over a range of load levels. It is found that fatigue life at relatively low load levels can be better estimated by considering the substrate creep effect (SCE).

  17. Effects of prolonged fasting on fatigue and quality of life in patients with multiple sclerosis.

    Science.gov (United States)

    Etemadifar, Masoud; Sayahi, Farnaz; Alroughani, Raed; Toghianifar, Nafiseh; Akbari, Mojtaba; Nasr, Zahra

    2016-06-01

    Fasting is one of the recommended worships of several great religions in the world. During the month of Ramadan, circadian rhythm and pattern of eating changes result in physiological, biochemical and hormonal changes in the body. Many Muslims with medical conditions ask their physicians about the feasibility and safety of fasting during Ramadan. In this study, we aim to assess the effect of Ramadan fasting on the quality of life and fatigue in multiple sclerosis (MS) patients. Relapsing-remitting MS (RRMS) patients according to McDonald's criteria who had mild disability (EDSS score ≤3) were included in this study. Fatigue and quality of life were were assessed using the validated Persian versions of modified fatigue impact scale (MFIS) and multiple sclerosis quality of life-54 (MSQOL-54) questionnaires, respectively. 218 patients (150 females and 68 males) were enrolled in our study. There was no statistically significant difference between the mean total score of MSIF before and after fasting (25.50 ± 13.81 versus 26.94 ± 16.65; p = 0.58). The mean physical health and mental health composites of quality of life increased significantly after fasting (p = 0.008 and p = 0.003 respectively). Despite the observed lack of favorable effects on fatigue, our results showed increased quality of life of MS patients once Ramadan has ended. Whether this is specifically related to Ramadan-related fasting deserves further testing in appropriately designed larger prospective clinical studies.

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

    Directory of Open Access Journals (Sweden)

    Kolyshkin A.

    2014-06-01

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

  19. Environmental sustainability modeling with exergy methodology for building life cycle

    Institute of Scientific and Technical Information of China (English)

    刘猛; 姚润明

    2009-01-01

    As an important human activity,the building industry has created comfortable space for living and work,and at the same time brought considerable pollution and huge consumption of energy and recourses. From 1990s after the first building environmental assessment model-BREEAM was released in the UK,a number of assessment models were formulated as analytical and practical in methodology respectively. This paper aims to introduce a generic model of exergy assessment on environmental impact of building life cycle,taking into consideration of previous models and focusing on natural environment as well as building life cycle,and three environmental impacts will be analyzed,namely energy embodied exergy,resource chemical exergy and abatement exergy on energy consumption,resource consumption and pollutant discharge respectively. The model of exergy assessment on environmental impact of building life cycle thus formulated contains two sub-models,one from the aspect of building energy utilization,and the other from building materials use. Combining theories by ecologists such as Odum,building environmental sustainability modeling with exergy methodology is put forward with the index of exergy footprint of building environmental impacts.

  20. Associations Between Fatigue and Disability, Functional Mobility, Depression, and Quality of Life in People with Multiple Sclerosis

    Science.gov (United States)

    Bush, Steffani; Gappmaier, Eduard

    2016-01-01

    Background: Fatigue is a common symptom in people with multiple sclerosis (MS), but its associations with disability, functional mobility, depression, and quality of life (QOL) remain unclear. We aimed to determine the associations between different levels of fatigue and disability, functional mobility, depression, and physical and mental QOL in people with MS. Methods: Eighty-nine individuals with MS (mean [SD] disease duration = 13.6 [9.8] years, mean [SD] Expanded Disability Status Scale [EDSS] score = 5.3 [1.5]) and no concurrent relapses were retrospectively analyzed. Participants were divided into two groups based on five-item Modified Fatigue Impact Scale (MFIS-5) scores: group LF (n = 32, MFIS-5 score ≤10 [low levels of fatigue]) and group HF (n = 57, MFIS-5 score >10 [high levels of fatigue]). Results: Sixty-four percent of the sample reported high levels of fatigue. Compared with group LF, group HF demonstrated significantly (P scale, and 12-item Multiple Sclerosis Walking Scale scores; depression; and QOL but not in the EDSS scores, which were not significantly different between groups. Conclusions: Fatigue was found to be a predominant symptom in the study participants. Individuals reporting higher levels of fatigue concomitantly exhibited greater impairments in functional mobility, depression, and physical and mental QOL. Disability was not found to be related to level of fatigue. These findings can be important for appropriate assessment and management of individuals with MS with fatigue. PMID:27134580

  1. The Effect of Drive Signal Limiting on High Cycle Fatigue Life Analysis

    Science.gov (United States)

    Kihm, Frederic; Rizzi, Stephen A.

    2014-01-01

    It is common practice to assume a Gaussian distribution of both the input acceleration and the response when modeling random vibration tests. In the laboratory, however, shaker controllers often limit the drive signal to prevent high amplitude peaks. The high amplitudes may either be truncated at a given level (socalled brick wall limiting or abrupt clipping), or compressed (soft limiting), resulting in drive signals which are no longer Gaussian. The paper first introduces several methods for limiting a drive signal, including brick wall limiting and compression. The limited signal is then passed through a linear time-invariant system representing a device under test. High cycle fatigue life predictions are subsequently made using spectral fatigue and rainflow cycle counting schemes. The life predictions are compared with those obtained from unclipped input signals. Some guidelines are provided to help the test engineer decide how clipping should be applied under different test scenarios.

  2. Fatigue life prediction of casing welded pipes by using the extended finite element method

    Directory of Open Access Journals (Sweden)

    Ljubica Lazić Vulićević

    2016-03-01

    Full Text Available The extended finite element (XFEM method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to verify numerical results with the experimental ones. After successful verification, the XFEM was used to simulate fatigue crack growth, position axially in the pipe, and estimate its remaining life.

  3. Random Amplitude Fatigue Life of Electroformed Nickel Micro-Channel Heat Exchanger Coupons

    Directory of Open Access Journals (Sweden)

    Larry Byrd

    1998-01-01

    Full Text Available The use of micro-channel heat exchangers (MCHEX with coolant flow passage diameters less than 1 mm has been proposed for heat flux, weight, or volume limited environments. This paper presents room temperature, random amplitude, ε − N (strain versus number of cycles to failure curves for MCHEX coupons formed by electroplating nickel on a suitable form. These coupons are unique in two aspects; the microstructure formed by electroplating and the presence of holes as an integral part of the structure. The hole diameters range from approximately 10% to 50% to the specimen thickness. The fatigue life of electroformed nickel can be estimated from constant amplitude data using the formulation presented. The heat exchangers with channels parallel to the coupon direction have a lower fatigue life than the solid material.

  4. Space Shuttle Rudder Speed Brake Actuator-A Case Study Probabilistic Fatigue Life and Reliability Analysis

    Science.gov (United States)

    Oswald, Fred B.; Savage, Michael; Zaretsky, Erwin V.

    2015-01-01

    The U.S. Space Shuttle fleet was originally intended to have a life of 100 flights for each vehicle, lasting over a 10-year period, with minimal scheduled maintenance or inspection. The first space shuttle flight was that of the Space Shuttle Columbia (OV-102), launched April 12, 1981. The disaster that destroyed Columbia occurred on its 28th flight, February 1, 2003, nearly 22 years after its first launch. In order to minimize risk of losing another Space Shuttle, a probabilistic life and reliability analysis was conducted for the Space Shuttle rudder/speed brake actuators to determine the number of flights the actuators could sustain. A life and reliability assessment of the actuator gears was performed in two stages: a contact stress fatigue model and a gear tooth bending fatigue model. For the contact stress analysis, the Lundberg-Palmgren bearing life theory was expanded to include gear-surface pitting for the actuator as a system. The mission spectrum of the Space Shuttle rudder/speed brake actuator was combined into equivalent effective hinge moment loads including an actuator input preload for the contact stress fatigue and tooth bending fatigue models. Gear system reliabilities are reported for both models and their combination. Reliability of the actuator bearings was analyzed separately, based on data provided by the actuator manufacturer. As a result of the analysis, the reliability of one half of a single actuator was calculated to be 98.6 percent for 12 flights. Accordingly, each actuator was subsequently limited to 12 flights before removal from service in the Space Shuttle.

  5. 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.

  6. The impact of disability, fatigue and sleep quality on the quality of life in multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Ghaem Haleh

    2008-01-01

    Full Text Available Background: Only few papers have investigated the impact of multiple sclerosis (MS, especially MS-related fatigue and the impact of the quality of sleep on the quality of life (QoL in MS patients. Objective: The objective of this study was to measure the quality of life in MS patients and the impact of disability, fatigue and sleep quality, using statistical modeling. Materials and Methods: A cross-sectional study was conducted and data was collected from 141 MS patients, who were referred to the Mottahari Clinic, Shiraz, Iran, in 2005. Data on health-related quality of life (MSQoL-54, fatigue severity scale (FSS, and Pittsburgh sleep quality Index (PSQI were obtained in the case of all the patients. Epidemiology data concerning MS type, MS functional system score, expanded disability status scale (EDSS etc. were also provided by a qualified neurologist. Spearman a coefficient, Mann-Whitney U test, and linear regression model were used to analyze the data. Results : The mean ±SD age of 141 MS patients was 32.6±9.6 year. Thirty five (24.8% of them were male and the others were female. Eighty two (58.1% of the patients had EDSS score of ≤ 2, 36 (25.5% between 2.5 and 4.5, and 23 (16.3% ≥ 5. As per PSQI scores, two (1.4% of the patients had good sleep, 16 (11.3% had moderate sleep and 123 (87.2% had poor sleep. There was a significant high positive correlation between the quality of mental and physical health composite scores (r = 0.791, P < 0.001. There was a significant negative correlation between the quality of physical score and age (r = -0.88, P < 0.001, fatigue score (r = -0.640, P < 0.001, EDSS score (r = -0.476, P < 0.001 and PSQI (sleep quality r = -0.514, P < 0.000. Linear regression analysis showed that PSQI score, EDSS, and fatigue score were predictors in the model between the quality of physical score and covariates ( P < 0.001. Linear regression model showed that fatigue score and PSQI were predictors in the model between the

  7. A New Energy-Critical Plane Damage Parameter for Multiaxial Fatigue Life Prediction of Turbine Blades

    Directory of Open Access Journals (Sweden)

    Zheng-Yong Yu

    2017-05-01

    Full Text Available As one of fracture critical components of an aircraft engine, accurate life prediction of a turbine blade to disk attachment is significant for ensuring the engine structural integrity and reliability. Fatigue failure of a turbine blade is often caused under multiaxial cyclic loadings at high temperatures. In this paper, considering different failure types, a new energy-critical plane damage parameter is proposed for multiaxial fatigue life prediction, and no extra fitted material constants will be needed for practical applications. Moreover, three multiaxial models with maximum damage parameters on the critical plane are evaluated under tension-compression and tension-torsion loadings. Experimental data of GH4169 under proportional and non-proportional fatigue loadings and a case study of a turbine disk-blade contact system are introduced for model validation. Results show that model predictions by Wang-Brown (WB and Fatemi-Socie (FS models with maximum damage parameters are conservative and acceptable. For the turbine disk-blade contact system, both of the proposed damage parameters and Smith-Watson-Topper (SWT model show reasonably acceptable correlations with its field number of flight cycles. However, life estimations of the turbine blade reveal that the definition of the maximum damage parameter is not reasonable for the WB model but effective for both the FS and SWT models.

  8. Influences of fine pitch solder joint shape parameters on fatigue life under thermal cycle

    Institute of Scientific and Technical Information of China (English)

    HUANG Chun-yue; WU Zhao-hua; HUANG Hong-yan; ZHOU De-jian

    2005-01-01

    The solder joint reliability of a 0. 5 mm lead pitch, 240-pin quad flat package(QFP) was studied by nonlinear finite element analysis(FEA). The stress/strain distributions within the solder joints and the maximum plastic strain range of the solder joints were determined. Based on the calculated maximum plastic strain range the thermal fatigue life of the solder joints was calculated using Coffin-Manson equation. The influences of shape parameters including volume of solder joint, pad size and stand-off on the thermal fatigue life of the solder joints were also studied. The results show that the stress and strain distribution in the solder joint are not uniform; the interface between the lead and the solder joint is the high stress and strain region; the maximum stress and stain occur at the topmost point where the solder joint intersects with the inner side of the lead. The solder joint cracks should occur firstly at this point and propagate along the interface between the solder and the lead. The solder joint with the pad size of 1.25 mm× 0.35 mm, the stand-off of 0.02 mm and the solder volume of 0. 026 mm3 has longer fatigue life than that of any others. These optimal parameters have been applied in practice to assemble the 240-pin, 0.5 mm pitch QFP.

  9. Fatigue criterion to system design, life and reliability: A primer

    Science.gov (United States)

    Zaretsky, Erwin V.

    1992-01-01

    A method for estimating a component's design survivability by incorporating finite element analysis and probabilistic material properties was developed. The method evaluates design parameters through direct comparisons of component survivability expressed in terms of Weibull parameters. The analysis was applied to a rotating disk with mounting bolt holes. The highest probability of failure occurred at, or near, the maximum shear stress region of the bolt holes. Distribution of material failure as a function of Weibull slope affects the probability of survival. Where Weibull parameters are unknown for a rotating disk, it may be permissible to assume Weibull parameters, as well as the stress-life exponent, in order to determine the qualitative effect of disk speed on the probability of survival.

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

    Science.gov (United States)

    Wheeler, Robert W.; Lagoudas, Dimitris C.

    2017-04-01

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

  11. Experimental examination of fatigue life of welded joint with stress concentration

    Directory of Open Access Journals (Sweden)

    Miodrag Arsic

    2016-03-01

    Full Text Available This paper presents results of experimental examinations of stress concentration influence to fatigue life of butt welded joints with K-groove, produced from the most frequently used structural steel S355J2+N. One group of experiments comprised examinations carried out on the K-groove specimens with stress concentrators of edged notch type. Specimens with short cracks (limited length of initial crack, defined on the basis of the experience from fracture mechanics by the three points bending examinations, have been examined according to standard for the determination of S-N curve, and aimed to determine fatigue strengths for different lengths of initial crack and Relationship between fatigue strength and crack length. Other group of experiments comprised examinations of specimens with edge notch, prepared in accordance with ASTM E 399 for three points bending, in order to establish regularity between crack growth and range of exerted stress intensity factor aimed to determine resistance of welded joint to initial crack growth, namely fatigue threshold (ΔKth.

  12. Effect of Intermittent Overload Cycles on Thermomechanical Fatigue Life of NiTi Shape Memory Alloy Wire

    Science.gov (United States)

    Saikrishna, C. N.; Ramaiah, K. V.; Vidyashankar, B.; Bhaumik, S. K.

    2013-01-01

    Effect of intermittent overload cycles on fatigue behavior of NiTi shape memory alloy wire during thermomechanical cycling (TMC) has been evaluated. Results showed that fatigue life of NiTi is enhanced when the intermittent overload is above certain minimum level. An enhancement in fatigue life by ~50 pct is observed when the overload ratio is 2.0. Accumulation of plastic strain in the material under such TMC condition is found to be relatively high compared to that of TMC with no overload cycles.

  13. Laser Peening and Shot Peening Effects on Fatigue Life and Surface Roughness of Friction Stir Welded 7075-T7351 Aluminum

    Science.gov (United States)

    Hatamleh, Omar; Lyons, Jed; Forman, Royce

    2006-01-01

    The effects of laser peening, shot peening, and a combination of both on the fatigue life of Friction Stir Welds (FSW) was investigated. The fatigue samples consisted of dog bone specimens and the loading was applied in a direction perpendicular to the weld direction. Several laser peening conditions with different intensities, durations, and peening order were tested to obtain the optimum peening parameters. The surface roughness resulting from various peening techniques was assessed and characterized. The results indicate a significant increase in fatigue life using laser peening compared to shot peened versus their native welded specimens.

  14. Research of weld joint fatigue life of the AlMgSi07.F25 aluminium alloy under bending-torsion cyclic loading

    Directory of Open Access Journals (Sweden)

    M. Vaško

    2017-01-01

    Full Text Available The contribution deals with a research into the fatigue life of weld joints of AlMgSi07.F25 aluminium alloy. The paper will present unique biaxial testing equipment, process of preparation of specimen rods for fatigue tests, and the results of fatigue life assessment for the aluminium alloy during cyclic bending-torsion loading. Fatigue tests under constant amplitude loading were performed on a special electromechanical machine with a suitable clamping system. The obtained fatigue curves were compared with the most widely-known fatigue criteria such as LIU, F-S and B-M.

  15. The effect of coating residual stress on the fatigue life of thermal spray-coated steel and aluminum

    Energy Technology Data Exchange (ETDEWEB)

    McGrann, R.T.R.; Greving, D.J.; Shadley, J.R.; Rybicki, E.F. [Tulsa Univ., OK (United States). Mechanical Engineering Dept.; Kruecke, T.L.; Bodger, B.E. [Southwest Aeroservice, Inc., Tulsa, OK (United States)

    1998-10-10

    The acceptance of thermal spray coatings in many applications depends on the effect of the coating on the fatigue performance of the coated part. One of the factors that influences the fatigue life of thermal spray-coated components is the residual stress in the coating. This study investigates the fatigue performance of tungsten carbide-cobalt (WC-Co) thermal spray coating systems. Bending fatigue tests of specimens with WC-Co coatings on both 4130 steel substrates and 6061 aluminum substrates were conducted. The through-thickness residual stress level in the thermal spray coatings was determined using the modified layer removal method. The effect of the residual stresses on the fatigue life of the coated specimens was analyzed. It was found that there is a direct relation between the residual stress in the coating and the fatigue life of the coated part. Fatigue life can be changed by a factor of ten due to the level of compressive residual stress in the coating. (orig.) 7 refs.

  16. A new methodology for automating acoustic emission detection of metallic fatigue fractures in highly demanding aerospace environments: An overview

    Science.gov (United States)

    Holford, Karen M.; Eaton, Mark J.; Hensman, James J.; Pullin, Rhys; Evans, Sam L.; Dervilis, Nikolaos; Worden, Keith

    2017-04-01

    The acoustic emission (AE) phenomenon has many attributes that make it desirable as a structural health monitoring or non-destructive testing technique, including the capability to continuously and globally monitor large structures using a sparse sensor array and with no dependency on defect size. However, AE monitoring is yet to fulfil its true potential, due mainly to limitations in location accuracy and signal characterisation that often arise in complex structures with high levels of background noise. Furthermore, the technique has been criticised for a lack of quantitative results and the large amount of operator interpretation required during data analysis. This paper begins by introducing the challenges faced in developing an AE based structural health monitoring system and then gives a review of previous progress made in addresing these challenges. Subsequently an overview of a novel methodology for automatic detection of fatigue fractures in complex geometries and noisy environments is presented, which combines a number of signal processing techniques to address the current limitations of AE monitoring. The technique was developed for monitoring metallic landing gear components during pre-flight certification testing and results are presented from a full-scale steel landing gear component undergoing fatigue loading. Fracture onset was successfully identify automatically at 49,000 fatigue cycles prior to final failure (validated by the use of dye penetrant inspection) and the fracture position was located to within 10 mm of the actual location.

  17. Life cycle methodology for copper : allocation and recycling approaches

    Energy Technology Data Exchange (ETDEWEB)

    Gobling-Reisemann, S. [Bremen Univ., Bremen (Germany). Faculty of Production Engineering; Tikana, L.; Sievers, H.; Klassert, A. [Deutsches Kupferinstitut, Dusseldorf (Germany). Life Cycle Centre

    2007-07-01

    This paper provided an overview of different methodologies available for recycling and assessing the life cycles of copper ores. Approaches towards allocation in life cycle assessments (LCA) included detailed modelling; system expansion; physical allocation; economic allocation; and subsequent-use allocation. Approaches towards recycling included system expansion, cut-off approaches, open loop approach; value corrected substitution; and the cascade approach. Sulphuric acid and steam are produced as by-products during copper production, and most copper ores contain molybdenum, gold, silver, and nickel. The environmental impacts of copper by-products must be considered when conducting LCAs. Existing standards allow different implementation methods for recycling and allocation into metal LCAs, and the selection of a methodology can significantly influence the ecological profile of copper and copper products. Allocation is needed when processes with more than 1 function are investigated. ISO standards recommend avoiding allocation problems by using detailed system modelling. Allocation factors should be chosen that reflect the physical relationship between the functional units produced and their associated environmental burdens. Case studies were presented to demonstrate allocations of co- and byproducts and recycling in copper production. 19 refs., 2 tabs., 4 figs.

  18. Effect of stress ratio on long life fatigue behavior of Ti-Al alloy under flexural loading

    Institute of Scientific and Technical Information of China (English)

    XUE Hong-qian; TAO Hua; SHAO Ren-ping; B.CLAUDE

    2008-01-01

    A new ultrasonic three-point bending fatigue test device was introduced to investigate fatigue life ranging up to 1010 cycles and associated fracture behavior of Ti-Al alloy. Tests were performed at a frequency of 20kHz with stress ratio R=0.5 and R=0.7 at ambient temperature in air. Three groups of specimens with different surface roughness were applied to investigate the effect of surface roughness on fatigue life. Furthermore, optical microscopy (OM) and scanning electron microscopy (SEM) were used for microstructure characteristic and fracture surface analysis. The S-N curves obtained show that fatigue failure occurs in the range of 105-1010 cycles, and the asymptote of S-N curve inclines slightly in very high cycle regime, but is not horizontal for R=0.5. Fatigue limit appears after 108 cycles for R=0.7. Surface roughness (the maximum roughness is no more than 3μm) has no influence on the fatigue properties in the high cycle regime. A detailed investigation on fatigue fracture surface shows that the Ti-Al alloy studied here is a binary alloy in the microstructure composed of α2-Ti3Al and γ-Ti-Al with fully lamellar microstructure. Fractography shows that fatigue failures are mostly initiated on the surface of specimens, also, in very high cycle regime, subsurface fatigue crack initiation can be found. Interlamellar fatigue crack initiation is predominant in the Ti-Al alloy with fully lamellar structure. Fatigue crack growth is mainly in transgranular mode.

  19. Methodological Principles of Ethnic Minority Life Conditions Assessment

    Directory of Open Access Journals (Sweden)

    Konstantin KLOKOV

    2015-06-01

    Full Text Available The transition to the post-industrial society is connected with revaluation of non-material values which become cultural resources acquiring their social and economic measurement. The purpose of the research has been to find new methodological approach for better evaluation of positive and negative results of rapid social changes in local communities of small-numbered ethnic groups in remote areas of Siberia. Up to the present many of these communities have been keeping very specific subsistence economy connected with nomadic pastoralism, hunting and gathering. Now, their traditional values and way of life are endangered by rapid social changes caused mostly by industrial encroachment. The transdisciplinary research made a synthesis of social, economic and ecological approaches and was based on several case-studies. The new methodology for assessment of traditional ethnic groups’ life conditions takes into account that their living space emerged on the intersection of several semiotic systems routed in different value perspectives. The first one is a commonly used value system which includes income level, availability of the community services and other common living-standard criteria. The second one is a traditional value system based on internal ethnic criteria. Assessment of living conditions from external and internal standpoints may differ greatly. Author suggest to assess indigenous minorities life conditions using two scales simultaneously, one of which corresponds to universal assessment criteria, and the other – to ethno-specific criteria characteristic of a specific traditional culture. The new approach advocates for cautious decision making in regional politics and helps to reinforce active cultural security of indigenous minorities, i.e. to raise the ability of the cultural system itself to oppose different kinds of arising challenges.

  20. The effect of ply folds as manufacturing defect on the fatigue life of CFRP materials

    Directory of Open Access Journals (Sweden)

    S. Hörrmann

    2016-10-01

    Full Text Available Manufacturing defects are inherent to any manufacturing process. However, in composite materials they might be unavoidable, e.g. ply waviness or even folds of plies are present in complex shaped parts during high pressure resin transfer molding of carbon fiber reinforced polymers. In this work, the effect of the ply folds on the fatigue life of the composite material is investigated. Folds along fiber direction (as they commonly appear during manufacturing were artificially introduced in unidirectional non crimp fabric plies. The target of this study is the prediction of damage initiation due to this particular type of manufacturing defect. The folds locally increase the fiber volume fraction and also introduce resin rich areas. Fatigue tests in fiber direction and transverse to fiber direction are performed at different load ratios under constant amplitude loading. The influence of the defect geometry on damage initiation and progression is investigated at different scales by non-destructive methods before testing, continuous strain measurement and monitoring the damage progression during testing and fractography analysis after final failure. Most of the time, the first damage was observed at the location of the introduced fold for all considered load cases. However, it was also found, that the folds lead to no significant reduction in fatigue life

  1. The influence of applied heat-treatment on in 718 fatigue life at three point flexural bending

    Directory of Open Access Journals (Sweden)

    J. Belan

    2017-01-01

    Full Text Available The Inconel alloy 718 is an iron-nickel based superalloy with a working temperature up to 650 °C. Presented phases such as γ'' (Ni3Nb, γ' (Ni3Al, and δ (delta – Ni3Nb are responsible for the alloy's unique properties. The δ – delta phase is profitable when situated at grain boundaries in small quantities due to increasing fatigue life. However, at temperatures close to 650 °C the γ'' transforms to δ – delta and causes a decrease in fatigue life. Heat-treatment (800°C/ for 72 hours and its influence on fatigue life are discussed in this paper. Fatigue tests were carried out at room temperature. After the tests we plotted the S-N curves for both stages. SEM (Scanning Electron Microscopy fractography was carried out as well.

  2. Cryogenic Tensile Strength and Fatigue Life of Carbon Nanotube Multi-Yarn.

    Science.gov (United States)

    Misak, H E; Mall, S

    2016-03-01

    Carbon nanotube (CNT) multi-yarns, consisting of 30 yarns, were tested under monotonic tensile load and fatigue at the room temperature (298 K) and two cryogenic temperatures (232 and 123 K). Tensile stiffness increased with the decrease of temperature. The average ultimate tensile strength was higher at 123 K when compared to the higher temperatures (232 and 298 K). Failure mechanism changed from a combination of classical variant and independent fiber breakage at the two higher temperatures to mostly classical variant failure mechanism at the lower temperature. The CNT-yarn's fatigue life also increased with decreasing temperature. CNT-yarns have been shown to function well at lower temperatures making them usable for applications requiring operation at cryogenic temperatures, such as in satellites and high altitude aircraft.

  3. Factors affecting the corrosion fatigue life in nickel based superalloys for disc applications

    Directory of Open Access Journals (Sweden)

    Rosier Hollie

    2014-01-01

    Full Text Available The nickel based superalloy 720Li is employed in the gas turbine due to its mechanical performance at elevated temperature. A comprehensive assessment of the materials behaviour under representative service conditions is reported to address the drive for ever increasing temperatures and more arduous environmental exposure. Fatigue experiments have been performed in an air and air/SOx environment at 700 ∘C containing a mixed salt as a contaminant. There is an intimate relationship between local salt level (flux, stress level and stress state, i.e. static or cyclic. The interaction with these variables with the work hardened layer present on the surface of all tested specimens as a result of the shot peening process directly affects the crack initiation process. If specific conditions of environment and stress are achieved, a significant reduction in fatigue life is observed.

  4. Reconstruction of probabilistic S-N curves under fatigue life following lognormal distribution with given confidence

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yong-xiang; YANG Bing; PENG Jia-chun

    2007-01-01

    When the historic probabilistic S-N curves are given under special survival probability and confidence levels and there is no possible to re-test, fatigue reliability analysis at other levels can not be done except for the special levels. Therefore, the wide applied curves are expected. Monte Carlo reconstruction methods of the test data and the curves are investigated under fatigue life following lognormal distribution. To overcome the non-conservative assessment of existent man-made enlarging the sample size up to thousands, a simulation policy is employed to address the true production where the sample size is controlled less than 20 for material specimens, 10 for structural component specimens and the errors matching the statistical parameters are less than 5 percent. Availability and feasibility of the present methods have been indicated by the reconstruction practice of the test data and curves for 60Si2Mn high strength spring steel of railway industry.

  5. Influence of the Inclusion Shape on the Rolling Contact Fatigue Life of Carburized Steels

    Science.gov (United States)

    Neishi, Yutaka; Makino, Taizo; Matsui, Naoki; Matsumoto, Hitoshi; Higashida, Masashi; Ambai, Hidetaka

    2013-05-01

    It has been well known that the flaking failure in rolling contact fatigue (RCF) originates from nonmetallic inclusions in steels, and their apparent size is one of the important factors affecting RCF life. However, the influence of inclusion shape on the RCF life has not been fully clarified. In this study, attention was paid to the influence of the inclusion shape on the RCF life. This was evaluated by using carburized JIS-SCM420 (SAE4320) steels that contained two different shapes of MnS—stringer type and spheroidized type—as inclusions. Sectional observations were made to investigate the relation between the occurrence of shear crack in the subsurface and the shape of MnS. It was found that the RCF life was well correlated with the length of MnS projected to the load axis, and the initiation of shear crack in subsurface was accelerated as the length of MnS increased.

  6. Recent Methodologies for Creep Deformation Analysis and Its Life Prediction

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo-Gon; Park, Jae-Young; Iung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    To design the high-temperature creeping materials, various creep data are needed for codification, as follows: i) stress vs. creep rupture time for base metals and weldments (average and minimum), ii) stress vs. time to 1% total strain (average), iii) stress vs. time to onset of tertiary creep (minimum), and iv) constitutive eqns. for conducting time- and temperature- dependent stress-strain (average), and v) isochronous stress-strain curves (average). Also, elevated temperature components such as those used in modern power generation plant are designed using allowable stress under creep conditions. The allowable stress is usually estimated on the basis of up to 10{sup 5} h creep rupture strength at the operating temperature. The master curve of the “sinh” function was found to have a wider acceptance with good flexibility in the low stress ranges beyond the experimental data. The proposed multi-C method in the LM parameter revealed better life prediction than a single-C method. These improved methodologies can be utilized to accurately predict the long-term creep life or strength of Gen-IV nuclear materials which are designed for life span of 60 years.

  7. Effects of zinc supplementation on fatigue and quality of life in patients with colorectal cancer.

    Science.gov (United States)

    Ribeiro, Sofia Miranda de Figueiredo; Braga, Camila Bitu Moreno; Peria, Fernanda Maris; Martinez, Edson Zangiacomi; Rocha, José Joaquim Ribeiro da; Cunha, Selma Freire Carvalho

    2017-01-01

    To investigate the effects of oral zinc supplementation on fatigue intensity and quality of life of patients during chemotherapy for colorectal cancer. A prospective, randomized, double-blinded, placebo-controlled study was conducted with 24 patients on chemotherapy for colorectal adenocarcinoma in a tertiary care public hospital. The study patients received zinc capsules 35mg (Zinc Group, n=10) or placebo (Placebo Group, n=14) orally, twice daily (70mg/day), for 16 weeks, from the immediate postoperative period to the fourth chemotherapy cycle. Approximately 45 days after surgical resection of the tumor, all patients received a chemotherapeutic regimen. Before each of the four cycles of chemotherapy, the Functional Assessment of Chronic Illness Therapy-Fatigue scale was completed. We used a linear mixed model for longitudinal data for statistical analysis. The scores of quality of life and fatigue questionnaires were similar between the groups during the chemotherapy cycles. The Placebo Group presented worsening of quality of life and increased fatigue between the first and fourth cycles of chemotherapy, but there were no changes in the scores of quality of life or fatigue in the Zinc Group. Zinc supplementation prevented fatigue and maintained quality of life of patients with colorectal cancer on chemotherapy. Investigar os efeitos da suplementação oral de zinco sobre a intensidade da fadiga e a qualidade de vida de pacientes durante a quimioterapia para neoplasia colorretal. Estudo prospectivo, randomizado, controlado e duplo-cego conduzido em um hospital universitário público terciário, com 24 pacientes em regime quimioterápico para adenocarcinoma colorretal. Os pacientes receberam cápsulas de zinco 35mg (Grupo Zinco, n=10) ou placebo (Grupo Placebo, n=14) por via oral, duas vezes ao dia (70mg/dia), durante 16 semanas, desde o período pós-operatório imediato até o quarto ciclo de quimioterapia. Todos os pacientes receberam quimioterapia por

  8. Development of a Nonlinear Cumulative Fatigue Damage Methodology for Aircraft Engine Components under Multiaxial Loadings

    Science.gov (United States)

    2007-04-01

    fatigue damage accumulation under a variety of loading conditions. These models are, for the most part, empirical approaches that have relied little on...elastic-plastic stresses listed in this table represent the surface stresses at maximum and minimum loads as determined by an elastic-plastic finite...Torsion,Load Control • R=-1 .Torsion.Strain Control © R-0,Torsion,Strain Control ■ Proportional • R=-1 .Torsion,Load Control A Runout ■ \\ n 0 X

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

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Luiz L. da; Filho, Nelson do N.A.; Gomes, Paulo de T.V.; Rabello, Emerson G.; Mansur, Tanius R., E-mail: silvall@cdtn.br, E-mail: nnaf@cdtn.br, E-mail: ptvg@cdtn.br, E-mail: egr@cdtn.br, E-mail: tanius@cdtn.br [Centro de Desenvolvimento da Tencologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2013-07-01

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

  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. A critical analysis of the Mises stress criterion used in frequency domain fatigue life prediction

    Directory of Open Access Journals (Sweden)

    Adam Niesłony

    2016-10-01

    Full Text Available Multiaxial fatigue failure criteria are formulated in time and frequency domain. The number of frequency domain criteria is rather small and the most popular one is the equivalent von Mises stress criterion. This criterion was elaborated by Preumont and Piefort on the basis of well-known von Mises stress concept, first proposed by Huber in 1907, and well accepted by the scientific community and engineers. It is important to know, that the criterion was developed to determine the yield stress and material effort under static load. Therefore the direct use of equivalent von Mises stress criterion for fatigue life prediction can lead to some incorrectness of theoretical and practical nature. In the present study four aspects were discussed: influence of the value of fatigue strength of tension and torsion, lack of parallelism of the SN curves, abnormal behaviour of the criterion under biaxial tensioncompression and influence of phase shift between particular stress state components. Information contained in this article will help to prevent improper use of this criterion and contributes to its better understanding

  12. Fatigue (PDQ)

    Science.gov (United States)

    ... of daily living . Better quality of life . More satisfaction with life. A greater sense of well-being. ... and decrease fatigue. The importance of eating enough food and drinking enough fluids. Physical therapy for patients ...

  13. Strength and fatigue life evaluation of composite laminate with embedded sensors

    Science.gov (United States)

    Rathod, Vivek T.; Hiremath, S. R.; Roy Mahapatra, D.

    2014-04-01

    Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

  14. An inverse method for online stress monitoring and fatigue life analysis of boiler drums

    Institute of Scientific and Technical Information of China (English)

    HU Wen-sen; LI Bin; CAO Zi-dong; YANG Dong; LI Ya-chao

    2009-01-01

    A method based on solution of the inverse heat conduction problem was presented for online stress monitoring and fatigue life analysis of boiler drums. The mathematical model of the drum temperature distribution is based on the assumptions that the difference of temperature along the longitudinal axis of the boiler drum is negligible with changes only in the radial direction and the circumferential direction, and that the outer surface of drum is thermally insulated. Combining this model with the control-volume method provides temperatures at different points on a eross-section of the drum. With the temperature data, the stresses and the life expectancy of the boiler drum are derived according to the ASME code. Applying this method to the cold start-up process of a 300 MW boiler demonswated the absence of errors caused by the boundary condition assumptions on the inner surface of the drum and testified that the method is an applicable technique for the online stress monitoring and fatigue life analysis of boiler drums.

  15. Fatigue life assessment of cardiovascular balloon-expandable stents: a two-scale plasticity-damage model approach.

    Science.gov (United States)

    Argente dos Santos, H A F; Auricchio, F; Conti, M

    2012-11-01

    Cardiovascular disease has become a major global health care problem in the present decade. To tackle this problem, the use of cardiovascular stents has been considered a promising and effective approach. Numerical simulations to evaluate the in vivo behavior of stents are becoming more and more important to assess potential failures. As the material failure of a stent device has been often associated with fatigue issues, as a result of the high number of cyclic loads these devices are subjected to in vivo, numerical approaches for fatigue life assessment of stents has gained special interest in the engineering community. Numerical fatigue predictions can be used to modify the design and prevent failure, without making and testing numerous physical devices, thus preventing from undesired fatigue failures. This work presents a fatigue life numerical method for the analysis of cardiovascular balloon-expandable stainless steel stents. The method is based on a two-scale continuum damage mechanics model in which both plasticity and damage mechanisms are assumed to take place at a scale smaller than the scale of the representative volume element. The fatigue failure criterion is based on the Soderberg relation. The method is applied to the fatigue life assessment of both PalmazShatz and Cypher stent designs. Validation of the method is performed through comparison of the obtained numerical results with some experimental results available for the PalmazShatz stent design. The present study gives also possible directions for future research developments in the framework of the numerical fatigue life assessment of real balloon-expandable stents.

  16. Fatigue life prediction of casing welded pipes by using the extended finite element method

    OpenAIRE

    2016-01-01

    The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to...

  17. Reducing Uncertainty in Fatigue Life Limits of Turbine Engine Alloys (Preprint)

    Science.gov (United States)

    2012-08-01

    Calcaterra, M.L. Dent, M.M. Derriso , W.J. Hardman, J.W. Jones, S.M. Russ, Materials Damage Prognosis - Proceedings of a Symposium of the Materials Science and... Derriso , W.J. Hardman, J. Wayne Jones, S.M. Rusa (Eds.), New Orleans, LA, 2005, pp. 343-350. [24] S.K. Jha, M.J. Caton, J.M. Larsen, Mean vs. life...ultrasonic fatigue, in: J.M. Larsen, L. Christodoulou, J.R. Calcaterra, M.L. Dent, M.M. Derriso , W.J. Hardman, J. Wayne Jones, S.M. Rusa (Eds.), New

  18. Advanced Failure Determination Measurement Techniques Used in Thermal Fatigue Life Testing of Electronic Packaging

    Science.gov (United States)

    Wallace, A. P.; Cornford, S. L.; Gross, M. A.

    1996-01-01

    Thermal fatigue life testing of various electronic packaging technologies is being performed by the Reliability Technology Group at the Jet Propulsion Laboratory. These testing efforts are in progress to improve uderstanding of the reliability issues associated with low volume packaging technologies for space applications and to develop qualification and acceptance approaches for these technologies. The work described here outlines the electrical failure detection techniques used during testing by documenting the circuits and components used to make these measurements, the sensitivity of the measurements, and the applicability of each specific measurement.

  19. Low Cycle Fatigue Behavior of 316LN Stainless Steel Alloyed with Varying Nitrogen Content. Part II: Fatigue Life and Fracture Behavior

    Science.gov (United States)

    Prasad Reddy, G. V.; Sandhya, R.; Sankaran, S.; Mathew, M. D.

    2014-10-01

    Influence of nitrogen content on low cycle fatigue life and fracture behavior of 316LN stainless steel (SS) alloyed with 0.07 to 0.22 wt pct nitrogen is presented in this paper over a range of total strain amplitudes ( ±0.25 to 1.0 pct) in the temperature range from 773 K to 873 K (500 °C to 600 °C). The combined effect of nitrogen and strain amplitude on fatigue life is observed to be complex i.e., fatigue life either decreases/increases with increase in nitrogen content or saturates/peaks at 0.14 wt pct N depending on strain amplitude and temperature. Coffin-Manson plots (CMPs) revealed both single-slope and dual-slope strain-life curves depending on the test temperature and nitrogen content. 316LN SS containing 0.07 and 0.22 wt pct N showed nearly single-slope CMP at all test temperatures, while 316LN SS with 0.11 and 0.14 wt pct N exhibited marked dual-slope behavior at 773 K (500 °C) that changes to single-slope behavior at 873 K (600 °C). The changes in slope of CMP are found to be in good correlation with deformation substructural changes.

  20. Effect of Progressive Muscle Relaxation on the Fatigue and Quality of Life Among Iranian Aging Persons.

    Science.gov (United States)

    Hassanpour-Dehkordi, Ali; Jalali, Amir

    2016-07-01

    Since the elderly population is increasing rapidly in developing countries which may decrease the physical activity and exercise and in turn could affect the elderly's quality of life, this study aimed to investigate the effect of progressive muscle relaxation on the elderly's quality of life in Iran. In a randomized clinical trial, participants were randomly divided into intervention and control groups. For the intervention group, muscular progressive relaxation was run three days per week for three months (totally 36 sessions). In relaxation, a patient contract a group of his/her muscles in each step and relaxes them after five seconds and finally loosens all muscles and takes five deep breaths. Each session lasts for 45 minutes. The instrument of data gathering consisted of questionnaires on individual's demographic data and quality of life SF-36. After intervention, quality of life increased significantly in the patients undergoing muscular progressive relaxation and fatigue severity decreased significantly in the intervention group compared to prior to intervention. In addition, there was a statistically significant difference in mean score of physical performance, restricted activity after physical problem, energy, socially function, physical pain, overall hygiene, and quality of life between intervention and control groups. By implementing regular and continuous progressive muscle relaxation, quality of life could be increased in different dimensions in the elderly and the context could be provided to age healthily and enjoy higher health and autonomy. Therefore, all of the therapeutic staffs are recommended to implement this plan to promote the elderly's quality of life.

  1. Modelling the Strength and Fatigue Life of a Unidirectional Fibrous Composite by Using Daniels' Sequence and Markov Chains

    Science.gov (United States)

    Paramonov, Yu.; Cimanis, V.; Varickis, S.; Kleinhofs, M.

    2013-11-01

    A review of the previous works of the authors dedicated to the use of Daniels' sequence (DS) for analyzing the relation between the distribution of the static strength of components of a unidirectional fibrous composite (UFC) and the distribution of its fatigue life is presented. A generalization of the DS which can be used to analyze the association of distribution of the static strength of composite components with distribution of the static strength of the UFC itself is given. In analyzing the fatigue life of a UFC, unlike in Daniels' model, the loading rate and randomness of the number of still workable components in the weak microvolume in which the destruction process takes place are taken into account. By analyzing the fatigue life, it is possible to explain the existence of the random fatigue strength and to calculate the maximum load at which the probability of absence of fatigue failure is great enough when the number of cycles of fatigue loading tends to infinity. Numerical examples of processing of experimental data are presented, and estimates for parameters of the corresponding nonlinear regression model, which can be interpreted as the strength parameters of UFC, are obtained.

  2. Surface fatigue life and failure characteristics of EX-53, CBS 1000M, and AISI 9310 gear materials

    Science.gov (United States)

    Townsend, D. P.

    1985-01-01

    Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.

  3. Averaged strain energy density-based synthesis of crack initiation life in notched steel bars under torsional fatigue

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-10-01

    Full Text Available The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the crack nucleation life was reduced with increasing stress concentration, on the other hand the crack propagation life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue crack propagation phase, such as sliding contact and/or friction between fracture surfaces, crack initiation life has been considered in the present work. In the original paper, initiation life was defined in correspondence of a 0.1÷0.4-mm-deep crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and cracked specimens at NA = 2 million loading cycles

  4. QUICK ASSESSMENT METHODOLOGY FOR RELIABILITY OF SOLDER JOINTS IN BALL GRID ARRAY (BGA) ASSEMBLY——PART Ⅰ: CREEP CONSTITUTIVE RELATION AND FATIGUE MODEL

    Institute of Scientific and Technical Information of China (English)

    史训清; 王志平; John HL Pang; 张学仁; 聂景旭

    2002-01-01

    In this study, a new unified creep constitutive relation and a modified energy-based fatigue model have been established respectively to describe the creep flow and predict the fatigue life of Sn-Pb solders. It is found that the relation successfully elucidates the creep mechanism related to current constitutive relations.The model can be used to describe the temperature and frequency dependent low cycle fatigue behavior of the solder. The relation and the model are further employed in part Ⅱ to develop the numerical simulation approach for the long-term reliability assessment of the plastic ball grid array (BGA) assembly.

  5. The effect of plasma electrolytic oxidation on the mean stress sensitivity of the fatigue life of the 6082 aluminum alloy

    Science.gov (United States)

    Winter, L.; Morgenstern, R.; Hockauf, K.; Lampke, T.

    2016-03-01

    In this work the mean stress influence on the high cycle fatigue behavior of the plasma electrolytic oxidized (PEO) 6082 aluminum alloy (AlSi1MgMn) is investigated. The present study is focused on the fatigue life time and the susceptibility of fatigue-induced cracking of the oxide coating and their dependence on the applied mean stress. Systematic work is done comparing conditions with and without PEO treatment, which have been tested using three different load ratios. For the uncoated substrate the cycles to failure show a significant dependence on the mean stress, which is typical for aluminum alloys. With increased load ratio and therefore increased mean stress, the fatigue strength decreases. The investigation confirms the well-known effect of PEO treatment on the fatigue life: The fatigue strength is significantly reduced by the PEO process, compared to the uncoated substrate. However, also the mean stress sensitivity of the fatigue performance is reduced. The fatigue limit is not influenced by an increasing mean stress for the PEO treated conditions. This effect is firstly shown in these findings and no explanation for this effect can be found in literature. Supposedly the internal compressive stresses and the micro-cracks in the oxide film have a direct influence on the crack initiation and growth from the oxide film through the interface and in the substrate. Contrary to these findings, the susceptibility of fatigue-induced cracking of the oxide coating is influenced by the load ratio. At tension-tension loading a large number of cracks, which grow partially just in the aluminum substrate, are present. With decreasing load ratio to alternating tension-compression stresses, the crack number and length increases and shattering of the oxide film is more pronounced due to the additional effective compressive part of the load cycle.

  6. Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

    Science.gov (United States)

    Sudbrack, Chantal K.; Draper, Susan L.; Gorman, Timothy T.; Telesman, Jack; Gab, Timothy P.; Hull, David R.

    2012-01-01

    Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 C, 760 C, and 815 C was consistent with other chromia forming nickel-based superalloys: a TiO2-Cr2O3 external oxide formed with a branched Al2O3 internal subscale that extended into a recrystallized - dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and dissolution layers followed a cubic rate law, while Al2O3 subscales followed a parabolic rate law. Cr- rich M23C6 carbides at the grain boundaries dissolved to help sustain Cr2O3 growth to depths about 12 times thicker than the scale. The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 m thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M23C6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M23C6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M23C6 carbide dissolution layer led to nearly full recovery of life, with a

  7. International Psychometric Validation of an EORTC Quality of Life Module Measuring Cancer Related Fatigue (EORTC QLQ-FA12).

    Science.gov (United States)

    Weis, Joachim; Tomaszewski, Krzysztof A; Hammerlid, Eva; Ignacio Arraras, Juan; Conroy, Thierry; Lanceley, Anne; Schmidt, Heike; Wirtz, Markus; Singer, Susanne; Pinto, Monica; Alm El-Din, Mohamed; Compter, Inge; Holzner, Bernhard; Hofmeister, Dirk; Chie, Wei-Chu; Czeladzki, Marek; Harle, Amelie; Jones, Louise; Ritter, Sabrina; Flechtner, Hans-Henning; Bottomley, Andrew

    2017-05-01

    The European Organisation for Research and Treatment of Cancer (EORTC) Group has developed a new multidimensional instrument measuring cancer-related fatigue to be used in conjunction with the quality of life core questionnaire (EORTC QLQ-C30). The module EORTC QLQ-FA13 assesses physical, cognitive, and emotional aspects of cancer-related fatigue. The methodology follows the EORTC guidelines for phase IV validation of modules. This paper focuses on the results of the psychometric validation of the factorial structure of the module. For validation and cross-validation confirmatory factor analysis (maximum likelihood estimation), intraclass correlation and Cronbach alpha for internal consistency were employed. The study involved an international multicenter collaboration of 11 European and non-European countries. A total of 946 patients with various tumor diagnoses were enrolled. Based on the confirmatory factor analysis, we could approve the three-dimensional structure of the module. Removing one item and reassigning the factorial mapping of another item resulted in the EORTC QLQ-FA12. For the revised scale, we found evidence supporting good local (indicator reliability ≥ 0.60, factor reliability ≥ 0.82) and global model fit (GFI t1|t2 = 0.965/0.957, CFI t1|t2 = 0.976/0.972, RMSEA t1|t2 = 0.060/0.069) for both measurement points. For each scale, test-retest reliability proved to be very good (intraclass correlation: R t1-t2 = 0.905-0.921) and internal consistency proved to be good to high (Cronbach alpha = .79-.90). Based on the former phase III module, the multidimensional structure was revised as a phase IV module (EORTC FA12) with an improved scale structure. For a comprehensive validation of the EORTC FA12, further aspects of convergent and divergent validity as well as sensitivity to change should be determined.

  8. Evaluation method of multiaxial low cycle fatigue life for cubic single crystal material

    Institute of Scientific and Technical Information of China (English)

    CHEN Jiping; DING Zhiping

    2007-01-01

    The coupling effect of normal stress and shear stress on orthotropic materials happens when applied loading deflects from the directions of the principal axes of the material coordinate system.By taking account of the coupling effects,formulas of equivalent stress and strain for cubic single crystal materials are cited.Using the equivalent strain and equivalent stress for such material and a variable k,which is introduced to express the effect of asymmetrical cyclic loading on fatigue life,a low cycle fatigue (LCF) life prediction model for such material in multiaxial stress starts is proposed.On the basis of the yield criterion and constitutive model of cubic single crystal materials,a subroutine to calculate the thermo elastic-plastic stress-strain of the material on an ANSYS platform was developed.The cyclic stress-strain of DD3 notched specimens under asymmetrical loading at 680℃ was analyzed.Low cycle fatigue test data of the single crystal nickel-based superalloy are used to fit the different parameters of the power law with multiple linear regression analysis.The equivalent stress and strain for a cubic single crystal material as failure parameters have the largest correlation coefficient.A power law exists between k and the failure cycle.The model was validated with LCF test data of CMSX-2 and DD3 single crystal nickel-based superalloys.All the test data fall into the factor of 2.5 for CMSX-2 hollow cylinder specimens and 2.0 scatter band for DD3 notched specimens,respectively.

  9. Bending Resistance and Cyclic Fatigue Life of Reciproc, Unicone, and WaveOne Reciprocating Instruments.

    Science.gov (United States)

    Silva, Emmanuel João Nogueira Leal; Villarino, Laise Silva; Vieira, Victor Talarico Leal; Accorsi-Mendonça, Thais; Antunes, Henrique Dos Santos; De-Deus, Gustavo; Lopes, Hélio Pereira

    2016-12-01

    This study evaluated the bending resistance and cyclic fatigue life of a new single-file reciprocating instrument (Unicone; Medin, Nové Město na Moravě, Czech Republic). Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer) instruments were used as references for comparison. Flexibility was determined by 45° bending tests using a universal testing machine. The cyclic fatigue test was performed using a custom-made device. For this test, an artificial canal with a 60° angle and a 5-mm radius of curvature was used. Scanning electron microscopic analysis was performed to determine the mode of fracture and possible deformations at the helical shaft. Statistical analysis for the bending resistance test was performed using parametric methods (ie, 1-way analysis of variance). Post hoc pair-wise comparisons were performed using the Tukey test for multiple comparisons (P bending resistance than the other tested systems (P  .05). When mean life was compared among the brands, Reciproc lasted longer than WaveOne with a probability of 99.9%, longer than Unicone in the "RECIPROC ALL" mode with a probability of 99.9%, and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.9% (all statistically significant). Moreover, WaveOne lasted longer than Unicone in the "RECIPROC ALL" mode with a probability of 98.5% and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.8% (all statistically significant). Finally, Unicone in the "RECIPROC ALL" mode lasted longer than Unicone in the "WAVEONE ALL" mode with a probability of 95.3% (statistically significant). The new reciprocating instrument Unicone showed lower cyclic fatigue resistance compared with Reciproc R25 and WaveOne Primary files. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  10. Dynamic additional loads influencing the fatigue life of gears in an electric vehicle transmission

    Directory of Open Access Journals (Sweden)

    G.Belingardi

    2014-10-01

    Full Text Available In recent years the implementation of the electric engine in the automotive industries has been increasingly marked. The speed of the electric motors is much higher than the combustion engine ones, bringing transmission gears to be subjected to high dynamic loads. For this reason the dynamic effects on fatigue life of these components have be taken into account in a more careful way respect to what is done with the usual gears. In the present work the overload effects due to both speed and meshing in a gear couple of an electric vehicle transmission have been analyzed. The electric vehicle is designed for urban people mobility and presents all the requirements to be certified as M1 vehicle (a weight less than 600 kg and a maximum speed more than 90 Km/h. To investigate the overload effects of teeth in contact, the reference gear design Standards (ISO 6336 introduce a specific multiplicative factor to the applied load called Internal Dynamic Factor (Kv. Aim of this work is to evaluate how dynamic overloads may influence the fatigue life of the above quoted gears in term of durability. To this goal, Kv values have been calculated by means of the analytical equations (ISO 6336 Methods B and C and then they have been compared with the results coming from multibody simulations, involving full rigid and rigid-flexible models.

  11. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

    Science.gov (United States)

    Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

    2016-09-01

    A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

  12. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

    Science.gov (United States)

    Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

    2016-11-01

    A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

  13. Uniaxial and Multiaxial Fatigue Life Prediction of the Trabecular Bone Based on Physiological Loading: A Comparative Study.

    Science.gov (United States)

    Fatihhi, S J; Harun, M N; Abdul Kadir, Mohammed Rafiq; Abdullah, Jaafar; Kamarul, T; Öchsner, Andreas; Syahrom, Ardiyansyah

    2015-10-01

    Fatigue assessment of the trabecular bone has been developed to give a better understanding of bone properties. While most fatigue studies are relying on uniaxial compressive load as the method of assessment, in various cases details are missing, or the uniaxial results are not very realistic. In this paper, the effect of three different load histories from physiological loading applied on the trabecular bone were studied in order to predict the first failure surface and the fatigue lifetime. The fatigue behaviour of the trabecular bone under uniaxial load was compared to that of multiaxial load using a finite element simulation. The plastic strain was found localized at the trabecular structure under multiaxial load. On average, applying multiaxial loads reduced more than five times the fatigue life of the trabecular bone. The results provide evidence that multiaxial loading is dominated in the low cycle fatigue in contrast to the uniaxial one. Both bone volume fraction and structural model index were best predictors of failure (p < 0.05) in fatigue for both types of loading, whilst uniaxial loading has indicated better values in most cases.

  14. The effect of lubricating oils on bearing fatigue-life using the Evonik RohMax pitting test procedure

    Energy Technology Data Exchange (ETDEWEB)

    Bartels, Thorsten [Evonik RohMax Additives GmbH, Darmstadt (Germany)

    2009-07-01

    A major requirement for modern driveline lubricants is the need to reduce churning losses and friction in order to deliver continual improvements in fuel efficiency. In trying to achieve this oil formulators target lower and lower viscosities, testing the limits of what is acceptable Churning loss reductions are being made by reducing the viscosity of the lubricating oil. Reduced oil viscosities can lead to reduced oil film thicknesses, especially at high operating temperatures. Thinner oil films can lead to an increase in friction, and a decrease in the fatigue-life capacity in lubricated contacts of bearings and gears in several driveline applications. Extensive fluid testing is required. Current test procedures are subject to extremely high variability, and large numbers of experiments are required to develop high confidence in the test conclusions. This publication introduces a new fatigue-life test method, which in our hands provides a clear improvement in test time, cost, and reproducibility. The test's results enable an estimation of the effect of lubricating oils on bearing fatigue-life. This is done by comparing the results to those obtained with reference oils which have also been tested in the standardized bearing tests for lubricating oils. The effects of operating parameters on test accuracy and repeatability have been studied. The parameters studied are oil temperature, contact pressure, speed and the test specimen batch. In addition to the measurement of bearing fatigue-life, the new test may also be used to study gear fatigue-life. We have used this test to investigate the lubrication oils' influence on fatigue-life in bearings and in gears. In order to extend the comparisons to gear performance the reference fluids were evaluated in standard industry test procedures used for determining gear performance, in particular the FZG test rig, thus establishing an extra insight in the fluids' performance by comparing gear test performance

  15. Effects of a home-based exercise program on quality of life, fatigue, and depression in patients with ankylosing spondylitis.

    Science.gov (United States)

    Durmus, Dilek; Alayli, Gamze; Cil, Erhan; Canturk, Ferhan

    2009-04-01

    The aim of this trial was to investigate the effects of a 12-week home-based exercise program (HEP) on quality of life (QOL) and fatigue in patients with Ankylosing Spondylitis (AS). Forty-three patients with AS were included in this study. Group 1 was given a HEP; Group 2 served as the control group. The functional capacity (Bath Ankylosing Spondylitis Functional Index), disease activity (Bath Ankylosing Spondylitis Disease Assessment Index), fatigue (Multidimensional Assessment of Fatigue Scale), depression (Beck Depression Inventory scores), and QOL (Short Form 36) of all participants were evaluated. There were significant improvements for all the parameters in two groups after the treatment. The improvements for all the parameters were better in the exercise group than in the control group. Home-based exercise programs are very effective in improving QOL and reducing fatigue. Because of these advantages, HEP should be advised for the management program in AS in addition to medical treatments.

  16. Microstructures and fatigue life of SnAgCu solder joints bearing Nano-Al particles in QFP devices

    Science.gov (United States)

    Zhang, Liang; Fan, Xi-ying; Guo, Yong-huan; He, Cheng-wen

    2014-05-01

    Microstructures and fatigue life of SnAgCu and SnAgCu bearing nano-Al particles in QFP (Quad flat package) devices were investigated, respectively. Results show that the addition of nano-Al particles into SnAgCu solder can refine the microstructures of matrix microstructure. Moreover, the nano-Al particles present in the solder matrix, act as obstacles which can create a back stress, resisting the motion of dislocations. In QFP device, it is found that the addition of nano-Al particles can increase the fatigue life by 32% compared with the SnAgCu solder joints during thermal cycling loading.

  17. Microstructural Influence on Deformation and Fatigue Life of Composites Using the Generalized Method of Cells

    Science.gov (United States)

    Arnold, S. M.; Murthy, P.; Bednarcyk, B. A.; Pineda, E. J.

    2015-01-01

    A fully coupled deformation and damage approach to modeling the response of composite materials and composite laminates is presented. It is based on the semi-­-analytical generalized method of cells (GMC) micromechanics model as well as its higher fidelity counterpart, HFGMC, both of which provide closed-form constitutive equations for composite materials as well as the micro scale stress and strain fields in the composite phases. The provided constitutive equations allow GMC and HFGMC to function within a higher scale structural analysis (e.g., finite element analysis or lamination theory) to represent a composite material point, while the availability of the micro fields allow the incorporation of lower scale sub­-models to represent local phenomena in the fiber and matrix. Further, GMC's formulation performs averaging when applying certain governing equations such that some degree of microscale field accuracy is surrendered in favor of extreme computational efficiency, rendering the method quite attractive as the centerpiece in a integrated computational material engineering (ICME) structural analysis; whereas HFGMC retains this microscale field accuracy, but at the price of significantly slower computational speed. Herein, the sensitivity of deformation and the fatigue life of graphite/epoxy PMC composites, with both ordered and disordered microstructures, has been investigated using this coupled deformation and damage micromechanics based approach. The local effects of fiber breakage and fatigue damage are included as sub-models that operate on the microscale for the individual composite phases. For analysis of laminates, classical lamination theory is employed as the global or structural scale model, while GMC/HFGMC is embedded to operate on the microscale to simulate the behavior of the composite material within each laminate layer. A key outcome of this study is the statistical influence of microstructure and micromechanics idealization (GMC or HFGMC) on

  18. Small Crack Growth and Fatigue Life Predictions for High-Strength Aluminium Alloys. Part 1; Experimental and Fracture Mechanics Analysis

    Science.gov (United States)

    Wu, X. R.; Newman, J. C.; Zhao, W.; Swain, M. H.; Ding, C. F.; Phillips, E. P.

    1998-01-01

    The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests A,ere conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and A weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plastisity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions, Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminum alloys was developed and demonstrated using the crack-closure model.

  19. Exercise Interventions to Reduce Cancer-Related Fatigue and Improve Health-Related Quality of Life in Cancer Patients.

    Science.gov (United States)

    Scott, Kelly; Posmontier, Bobbie

    Cancer-related fatigue (CRF) is the most common and debilitating side effect of patients receiving treatment of cancer. It is reported that 60% to 100% of patients will develop CRF as a result of the treatment or the cancer itself. The effects last for years posttreatment and lower overall quality of life. The purpose of this integrative review was to determine whether exercise interventions could reduce CRF and improve overall health-related quality of life (HRQOL) among selected cancer patients. Clinical Key, ProQuest Nursing and Allied Health Source, Cochrane Library, Mosby's Nursing Consult, and MEDLINE (Ovid) were the databases searched. Key terms searched were fatigue, exercise, cancer fatigue, holistic, spiritual, quality of life, and prevention. Findings from most studies suggest that exercise can decrease the effects of CRF among cancer patients, leading to an overall improved HRQOL. No negative results on the effects of exercise on CRF were reported. Nurses can be instrumental in developing holistic multidisciplinary exercise programs to assist in the management of CRF and improve HRQOL among cancer patients during and after cancer treatment. Recommendations for future research include the need for larger study sample sizes, a universal definition of fatigue, determination of the best exercise regimens, more consistent fatigue measures to facilitate better comparison across studies, and specifically assess patient improvements in overall mental and spiritual well-being within a holistic framework.

  20. Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6

    Directory of Open Access Journals (Sweden)

    Bendouba Mostefa

    2012-12-01

    Full Text Available Hole cold expansion (HCE is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue damage accumulation of cold expanded hole in aluminum alloy which is widely used in transportation and in aeronautics was analyzed. Experimental tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. These tests were performed by using two and four blocks under uniaxial constant amplitude loading. The increasing and decreasing loading were carried. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the 'damaged stress model', which takes into account the loading history, yields a good estimation according to the experimental results. Moreover, the error is minimized in comparison to the Miner's model.

  1. Pre-crack fatigue life assessment of relevant aircraft materials using fractal analysis of eddy current test data

    Science.gov (United States)

    Schreiber, Jürgen; Cikalova, Ulana; Hillmann, Susanne; Meyendorf, Norbert; Hoffmann, Jochen

    2013-01-01

    Successful determination of residual fatigue life requires a comprehensive understanding of the fatigue related material deformation mechanism. Neither macroscopic continuum mechanics nor micromechanic observations provide sufficient data to explain subsequent deformation structures occurring during the fatigue life of a metallic structure. Instead mesomechanic deformation on different scaling levels can be studied by applying fractal analysis of various means of nondestructive inspection measurements. The resulting fractal dimension data can be correlated to the actual material damage states, providing an estimation of the remaining residual fatigue life before macroscopic fracture develops. Recent efforts were aimed to apply the fractal concept to aerospace relevant materials AA7075-T6 and Ti-6Al-4V. Proven and newly developed fractal analysis methods were applied to eddy current (EC) measurements of fatigued specimens, with the potential to transition this approach to an aircraft for an in-situ nondestructive inspection. The occurrence of mesomechanic deformation at the material surface of both AA7075-T6 and Ti-6Al-4V specimens could be established via topography images using confocal microscopy (CM). Furthermore, a pulsed eddy current (PEC) approach was developed, combined with a sophisticated new fractal analysis algorithm based on short pulse excitation and evaluation of EC relaxation behavior. This paper presents concept, experimental realization, fractal analysis procedures, and results of this effort.

  2. Analysis and Evaluation Methodology of Effect of Light Water Reactor Coolant Environment on Fatigue Life of Class 1 Components%轻水堆冷却剂环境对核一级部件疲劳寿命影响的分析与评价方法

    Institute of Scientific and Technical Information of China (English)

    房永刚; 王庆; 初起宝; 张跃; 孙造占; 王臣

    2013-01-01

    It is required that the fatigue analysis should be done for nuclear reactor class 1 components composing of the reactor pressure boundary .Based on worldwide resear-ches ,it is found that the fatigue design curves currently used in the analysis have no enough margins considering the coolant environmental effect ,and the regulatory bodies in the world have paid high attention to it .General information related to the research background was introduced ,and the NRC method and the related ASME activities were discussed .Possible ways are recommended to deal with the potential issues that may arise .%反应堆压力边界的核一级部件在设计中要求进行疲劳分析。当前国际上的研究结果表明,目前分析中使用的规范疲劳设计曲线在考虑冷却剂环境条件下并不保守,并引起了各国核电监管机构对此的广泛关注。文中介绍了各主要核电国家对冷却剂环境疲劳的研究情况,讨论了N RC关于冷却剂环境的疲劳分析方法以及ASM E规范的后续进展。针对考虑环境疲劳后可能带来的一系列问题,提出了建议的解决方法。

  3. Analysis of Fatigue Crack Growth in Longitudinals of Ship Hull and Fatigue Life%船体纵骨疲劳裂纹扩展及寿命分析

    Institute of Scientific and Technical Information of China (English)

    何文涛; 刘敬喜; 解德

    2015-01-01

    Based on ABAQUS in python scripting language, and combined with virtual crack closure technique, a program (FCG-System) is developed to simulate the growth of fatigue crack. The crack in a typical longitudinal connection of an oil tanker is simulated. Crack growth path and fatigue life is discussed under lateral pressure load and axial tension load respectively. Results indicate that crack growth paths are different under these two load conditions and the fatigue lives before the fractures of face-plate occupy a large proportion in total life.%基于有限元软件 ABAQUS,结合虚拟裂纹闭合法、裂纹扩展判据及子结构技术,应用脚本语言 Python开发了模拟疲劳裂纹扩展的程序(FCG-System)。对含初始裂纹的油船纵骨节点疲劳裂纹扩展进行数值模拟,并探讨侧向压力和轴向拉力这两种载荷对疲劳裂纹扩展路径和疲劳寿命的影响。结果表明,两种加载方式下裂纹扩展路径不同,且面板断裂前的疲劳寿命在总寿命中占据很大的成分。

  4. Investigation of Cumulative Fatigue Damage Through Sequential Low Cycle Fatigue and High Cycle Fatigue Cycling at High Temperature for a Type 316LN Stainless Steel: Life-Prediction Techniques and Associated Mechanisms

    Science.gov (United States)

    Sarkar, Aritra; Nagesha, A.; Parameswaran, P.; Sandhya, R.; Laha, K.; Okazaki, M.

    2017-01-01

    Cumulative fatigue damage under sequential low cycle fatigue (LCF) and high cycle fatigue (HCF) cycling was investigated at 923 K (650 °C) by conducting HCF tests on specimens subjected to prior LCF cycling at various strain amplitudes. Remnant HCF lives were found to decrease drastically with increase in prior fatigue exposure as a result of strong LCF-HCF interactions. The rate of decrease in remnant lives varied as a function of the applied strain amplitude. A threshold damage in terms of prior LCF life-fraction was found, below which no significant LCF-HCF interaction takes place. Similarly, a critical damage during the LCF pre-cycling marking the highest degree of LCF-HCF interaction was identified which was found to depend on the applied strain amplitude. In view of the non-linear damage accumulation behavior, Miner's linear damage rule proved to be highly non-conservative. Manson's damage curve approach, suitably modified, was found to be a better alternative for predicting the remnant HCF life. The single constant (β) employed in the model, which reflects the damage accumulation of the material under two/multi-level loading conditions is derived from the regression analysis of the experimental results and validated further.

  5. Effect of Progressive Muscle Relaxation on the Fatigue and Quality of Life Among Iranian Aging Persons

    Directory of Open Access Journals (Sweden)

    Ali Hassanpour-Dehkordi

    2016-07-01

    Full Text Available Since the elderly population is increasing rapidly in developing countries which may decrease the physical activity and exercise and in turn could affect the elderly’s quality of life, this study aimed to investigate the effect of progressive muscle relaxation on the elderly’s quality of life in Iran. In a randomized clinical trial, participants were randomly divided into intervention and control groups. For the intervention group, muscular progressive relaxation was run three days per week for three months (totally 36 sessions. In relaxation, a patient contract a group of his/her muscles in each step and relaxes them after five seconds and finally loosens all muscles and takes five deep breaths. Each session lasts for 45 minutes. The instrument of data gathering consisted of questionnaires on individual’s demographic data and quality of life SF-36. After intervention, quality of life increased significantly in the patients undergoing muscular progressive relaxation and fatigue severity decreased significantly in the intervention group compared to prior to intervention. In addition, there was a statistically significant difference in mean score of physical performance, restricted activity after physical problem, energy, socially function, physical pain, overall hygiene, and quality of life between intervention and control groups. By implementing regular and continuous progressive muscle relaxation, quality of life could be increased in different dimensions in the elderly and the context could be provided to age healthily and enjoy higher health and autonomy. Therefore, all of the therapeutic staffs are recommended to implement this plan to promote the elderly’s quality of life.

  6. A case study on relation between roughness, lubrication and fatigue life of rolling bearings

    Science.gov (United States)

    Balan, M. R.; Tufescu, A.; Cretu, S. S.

    2016-08-01

    A spherical roller bearing under high radial loading, constant speed and imposed roughness for the contacting surfaces was chosen as case study. Different lubrication regimes were obtained by varying oil viscosity through the operating temperature. For bearings with especially machined contacting surfaces, λ-ratio is firstly determined and its value is used to estimate the particular value of the lubrication parameter κ. Using the λ-ratio approach the paper reveals the relationship between roughness amplitude and the modified rating life of rolling bearings. The roughness values corresponding to good manufacturing practice are possible to be determined for each particular case. Three groups of random Gaussian roughness were generated with the same values for the Ra parameter as used in the modified lives investigations. For medium and especially high radial loads, the contacts between rough surfaces develop, inside the shallow layer, von Mises equivalent stresses higher than the fatigue limit stress. For condition of lack of lubricant or starved lubrication, these findings explain the initiation of the rolling contact fatigue in the shallow layer, close to contacting surfaces.

  7. EFFECTS OF MODIFICATION OF THE CARBIDE CHARACTERISTICS THROUGH GRAIN BOUNDARY SERRATION ON CREEP-FATIGUE LIFE IN AUSTENITIC STAINLESS STEELS

    Institute of Scientific and Technical Information of China (English)

    K.J.Kim; H.U.Hong; K.S.Min; S.W.Nam

    2004-01-01

    Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundaries while planar carbides vere observed at the serrated grain boundaries. The serrated grain boundary energy is observed to be much lower than that of the straight one. Therefore, the carbide morphology is found to be changed from triangular to planar along the serrated boundary to reduce the interfacial energy between the carbide and the matrix. The creep-fatigue properties of these steels at 873K have been investigated. The creep-fatigue life of the sample vith planar carbide at the serrated grain boundary was found to be much longer than that with triangular carbide at the straight one. These results imply that the planar carbides with lower interfacial energy have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life.

  8. The Effects of Shot and Laser Peening on Fatigue Life and Crack Growth in 2024 Aluminum Alloy and 4340 Steel

    Science.gov (United States)

    Everett, R. A., Jr.; Matthews, W. T.; Prabhakaran, R.; Newman, J. C., Jr.; Dubberly, M. J.

    2001-01-01

    Fatigue and crack growth tests have been conducted on 4340 steel and 2024-T3 aluminum alloy, respectively, to assess the effects of shot peening on fatigue life and the effects of shot and laser peening on crack growth. Two current programs involving fixed and rotary-wing aircraft will not be using shot peened structures. Since the shot peening compressive residual stress depth is usually less than the 0.05-inch initial damage tolerance crack size, it is believed by some that shot peening should have no beneficial effects toward retarding crack growth. In this study cracks were initiated from an electronic-discharged machining flaw which was cycled to produce a fatigue crack of approximately 0.05-inches in length and then the specimens were peened. Test results showed that after peening the crack growth rates were noticeably slower when the cracks were fairly short for both the shot and laser peened specimens resulting in a crack growth life that was a factor of 2 to 4 times greater than the results of the average unpeened test. Once the cracks reached a length of approximately 0.1-inches the growth rates were about the same for the peened and unpeened specimens. Fatigue tests on 4340 steel showed that the endurance limit of a test specimen with a 0.002-inch-deep machining-like scratch was reduced by approximately 40 percent. However, if the "scratched" specimen was shot peened after inserting the scratch, the fatigue life returned to almost 100 percent of the unflawed specimens original fatigue life.

  9. Surface fatigue life of CBN and vitreous ground carburized and hardened AISI 9310 spur gears

    Science.gov (United States)

    Townsend, Dennis P.; Patel, P. R.

    1988-01-01

    Spur gear surface endurance tests were conducted to investigate CBN ground AISI 9310 spur gears for use in aircraft applications, to determine their endurance characteristics and to compare the results with the endurance of standard vitreous ground AISI 9310 spur gears. Tests were conducted with VIM-VAR AISI 9310 carburized and hardened gears that were finish ground with either CBN or vitreous grinding methods. Test conditions were an inlet oil temeprature of 320 K (116 F), an outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. The CBN ground gears exhibited a surface fatigue life that was slightly better than the vitreous ground gears. The subsurface residual stress of the CBN ground gears was approximately the same as that for the standard vitreous ground gears for the CBN grinding method used.

  10. Standard test method for ambient temperature fatigue life of metallic bonded resistance strain gages

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2003-01-01

    1.1 This test method covers a uniform procedure for the determination of strain gage fatigue life at ambient temperature. A suggested testing equipment design is included. 1.2 This test method does not apply to force transducers or extensometers that use bonded resistance strain gages as sensing elements. 1.3 Strain gages are part of a complex system that includes structure, adhesive, gage, leadwires, instrumentation, and (often) environmental protection. As a result, many things affect the performance of strain gages, including user technique. A further complication is that strain gages, once installed, normally cannot be reinstalled in another location. Therefore, it is not possible to calibrate individual strain gages; performance characteristics are normally presented on a statistical basis. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices ...

  11. Impact of restless legs syndrome in patients with inflammatory bowel disease on sleep, fatigue, and quality of life.

    Science.gov (United States)

    Schindlbeck, Katharina A; Becker, Janek; Berger, Felix; Mehl, Arne; Rewitzer, Charlotte; Geffe, Sarah; Koch, Peter M; Preiß, Jan C; Siegmund, Britta; Maul, Jochen; Marzinzik, Frank

    2017-01-01

    Inflammatory bowel disease has been associated with neurological symptoms including restless legs syndrome. Here, we investigated the impact of restless legs syndrome in patients with inflammatory bowel disease on sleep, fatigue, mood, cognition, and quality of life. Two groups of inflammatory bowel disease patients, with and without restless legs syndrome, were prospectively evaluated for sleep disorders, fatigue, daytime sleepiness, depression, anxiety, and health-related quality of life. Furthermore, global cognitive function, executive function, attention, and concentration were assessed in both groups. Disease activity and duration of inflammatory bowel disease as well as current medication were assessed by interview. Inflammatory bowel disease patients with and without restless legs syndrome were matched for age, education, severity, and duration of their inflammatory bowel disease. Patients with inflammatory bowel disease and clinically relevant restless leg syndrome suffered significantly more frequent from sleep disturbances including sleep latency and duration, more fatigue, and worse health-related quality of life as compared to inflammatory bowel disease patients without restless legs syndrome. Affect and cognitive function including cognitive flexibility, attention, and concentration showed no significant differences among groups, indicating to be not related to restless legs syndrome. Sleep disorders including longer sleep latency, shorter sleep duration, and fatigue are characteristic symptoms of restless legs syndrome in inflammatory bowel disease patients, resulting in worse health-related quality of life. Therefore, clinicians treating patients with inflammatory bowel disease should be alert for restless legs syndrome.

  12. Effects of meditation on anxiety, depression, fatigue, and quality of life of women undergoing radiation therapy for breast cancer.

    Science.gov (United States)

    Kim, Yeon Hee; Kim, Hwa Jung; Ahn, Seung Do; Seo, Yun Jeong; Kim, So Hee

    2013-08-01

    To investigate the effects of meditation on anxiety, depression, fatigue, and quality of life in women who are receiving radiation therapy for breast cancer. Randomized, non-program controlled, parallel intervention clinical trial. The ASAN Cancer Center located in Seoul, Korea. The subjects of this study included 102 female breast cancer patients who had undergone breast-conserving surgery; these female patients were randomized into equally assigned meditation control groups, with each group consisting of 51 patients. The test group received a total of 12 meditation therapy sessions during their 6-week radiation therapy period, and the control group underwent only a conventional radiation therapy. The tools used to evaluate the effects of meditation were Hospital Anxiety and Depression scale, Revised Piper Fatigue scale, and European Organization for Research and Treatment of Cancer-Quality of Life Core-30. The results were analyzed based on the principles of intention-to-treat analysis, and, as a corollary analysis, per-protocol analysis was conducted. The breast cancer patients who received meditation therapy compared with the non-intervention group saw improvements in reduction of anxiety (p=.032), fatigue (p=.030), and improvement in global quality of life (p=.028). Based on the results of this study, an affirmation can be made that meditation can be used as a non-invasive intervention treatment for improving fatigue, anxiety, quality of life, and emotional faculties of women with breast cancer. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Stress and fatigue in sound engineers: the effect of broadcasting in a life show and shift work.

    Science.gov (United States)

    Vangelova, Katia K

    2008-06-01

    The aim was to study the time-of-day variations of cortisol, fatigue and sleep disturbances in sound engineers in relation to job task and shift work. The concentration of saliva cortisol and feeling of stress, sleepiness and fatigue were followed at three hour intervals in 21 sound engineers: 13 sound engineers, aged 45.1 +/- 7.3 years, broadcasting in a life show during fast forward rotating shifts and 8 sound engineers, aged 47.1 +/- 9.8 years, making records in a studio during fast rotating day shifts. Cortisol concentration was assessed in saliva with radioimmunological kits. The participants reported for stress symptoms during the shifts and filled sleep diary. The data were analyzed by tests of between-subjects effects (SPSS). A trend for higher cortisol was found with the group broadcasting in a life show. The sound engineers broadcasting in a life show reported higher scores of stress, sleepiness and fatigue, but no significant differences concerning the sleep disturbances between the groups were found. In conclusion our data show moderate level of stress and fatigue with the studied sound engineers, higher with the subjects broadcasting in a life show. The quality of sleep showed no significant differences between the studied groups, an indication that the sound engineers were able to tolerate the fast forward rotating shifts.

  14. A Comparative Study on Fatigue Life Optimization of the Intersection between a Longitudinal and a Webframe

    DEFF Research Database (Denmark)

    Birk-Sørensen, Martin

    1996-01-01

    The connection between longitudinals and transverse web frames, is a weak point in the fatigue strength of a ship structure. Moreover it is very expensive to repair fatigue damages in these intersections, and a fatigue analysis for a specific detail was therefore carried out in order to seek to i...

  15. An influence of static load on fatigue life of parts under combined stress

    Directory of Open Access Journals (Sweden)

    Svoboda J.

    2008-11-01

    Full Text Available The paper deals with a special case of multiaxial fatigue in a plain stress possessing one component static and the other dynamic. Exponents of Haigs' limit curves were obtained experimentally both for tensile fatigue test and combined tensile/torgue tests. Errors of estimated fatigue lives are less than 20 %.

  16. STRESS-STRAIN FINITE ELEMENT ANALYSIS AND FATIGUE LIFE PREDICTION FOR BOLTED CONNECTIONS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A cyclic plasticity model is used into finite element (FE) method to obtain the details of elastic-plastic stress-strain in the bolts under cyclic axial loading. Two criteria in multiaxial fatigue are employed to predict fatigue lives of bolts. The predicted fatigue lives are in favorable agreement with the experimental results for machined bolts.

  17. Simulation of Voltage Dip Event in Fixed-Speed Wind Turbines: Fatigue Evaluation

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2012-01-01

    transients affecting the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method was developed to evaluate the fatigue life of the mechanical system. The methodology analyses the stress history and estimates the mean and amplitudes of the counted cycles, and time of duration...

  18. Fatigue in adolescents and young adults with sickle cell disease: biological and behavioral correlates and health-related quality of life.

    Science.gov (United States)

    Ameringer, Suzanne; Elswick, R K; Smith, Wally

    2014-01-01

    This descriptive, correlational study examined fatigue and potential biological and behavioral correlates in adolescents and young adults with sickle cell disease. Sixty adolescents and young adults with sickle cell disease completed the Brief Fatigue Inventory, Multidimensional Fatigue Symptom Inventory-Short Form, Patient Reported Outcomes Measurement Information System (PROMIS) fatigue short form and measures of pain, sleep quality, anxiety, depressive mood, stress, disease severity, and quality of life. Blood samples were obtained for hemoglobin and cytokines. Fatigue scores were mostly moderate in severity. Fatigue interfered to a moderate degree with daily activities and correlated significantly with pain, sleep quality, state and trait anxiety, depressive mood, stress, and quality of life. Fatigue was correlated with hemoglobin on the PROMIS measure. Fatigue was not correlated with cytokines or age, nor differed by disease severity. Fatigue was common in these adolescents and young adults, interfered with daily activities such as school, work and exercise, and significantly correlated with several potentially modifiable factors. As life expectancy increases in sickle cell disease, research is needed to test interventions to reduce fatigue.

  19. Comparison of cyclic fatigue life of nickel-titanium files: an examination using high-speed camera

    Directory of Open Access Journals (Sweden)

    Taha Özyürek

    2017-08-01

    Full Text Available Objectives To determine the actual revolutions per minute (rpm values and compare the cyclic fatigue life of Reciproc (RPC, VDW GmbH, WaveOne (WO, Dentsply Maillefer, and TF Adaptive (TFA, Axis/SybronEndo nickel-titanium (NiTi file systems using high-speed camera. Materials and Methods Twenty RPC R25 (25/0.08, 20 WO Primary (25/0.08, and 20 TFA ML 1 (25/0.08 files were employed in the present study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which has an artificial stainless steel canal with a 60° angle of curvature and a 5-mm radius of curvature. The files were divided into 3 groups (group 1, RPC R25 [RPC]; group 2, WO Primary [WO]; group 3, TF Adaptive ML 1 [TFA]. All the instruments were rotated until fracture during the cyclic fatigue test and slow-motion videos were captured using high-speed camera. The number of cycles to failure (NCF was calculated. The data were analyzed statistically using one-way analysis of variance (ANOVA, p < 0.05. Results The slow-motion videos were indicated that rpm values of the RPC, WO, and TFA groups were 180, 210, and 425, respectively. RPC (3,464.45 ± 487.58 and WO (3,257.63 ± 556.39 groups had significantly longer cyclic fatigue life compared with TFA (1,634.46 ± 300.03 group (p < 0.05. There was no significant difference in the mean length of the fractured fragments. Conclusions Within the limitation of the present study, RPC and WO NiTi files showed significantly longer cyclic fatigue life than TFA NiTi file.

  20. Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects

    Energy Technology Data Exchange (ETDEWEB)

    Dorman, M. [Department of Aerospace Engineering, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Toparli, M.B. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Smyth, N.; Cini, A. [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Fitzpatrick, M.E. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Irving, P.E., E-mail: p.e.irving@cranfield.ac.uk [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom)

    2012-06-30

    Highlights: Black-Right-Pointing-Pointer Effect of laser peen intensity on local residual stress fields in 2024 aluminium. Black-Right-Pointing-Pointer Peening induces significant changes in surface topography and local hardness. Black-Right-Pointing-Pointer Residual stress at peen spot centre in tension, spot overlap in compression. Black-Right-Pointing-Pointer Notched fatigue lives increased; crack morphology correlated to residual stress field. Black-Right-Pointing-Pointer Large peening power densities can cause fatigue life reduction in notched samples. - Abstract: Laser peening at a range of power densities has been applied to 2 mm-thick sheets of 2024 T351 aluminium. The induced residual stress field was measured using incremental hole drilling and synchrotron X-ray diffraction techniques. Fatigue samples were subjected to identical laser peening treatments followed by scribing at the peen location to introduce stress concentrations, after which they were fatigue tested. The residual stresses were found to be non-biaxial: orthogonal to the peen line they were tensile at the surface, moving into the desired compression with increased depth. Regions of peen spot overlap were associated with large compression strains; the centre of the peen spot remaining tensile. Fatigue lives showed moderate improvement over the life of unpeened samples for 50 {mu}m deep scribes, and slight improvement for samples with 150 {mu}m scribes. Use of the residual stress intensity K{sub resid} approach to calculate fatigue life improvement arising from peening was unsuccessful at predicting the relative effects of the different peening treatments. Possible reasons for this are explored.

  1. Effects from fully nonlinear irregular wave forcing on the fatigue life of an offshore wind turbine and its monopile foundation

    DEFF Research Database (Denmark)

    Schløer, Signe; Bredmose, Henrik; Bingham, Harry B.;

    2013-01-01

    The effect from fully nonlinear irregular wave forcing on the fatigue life of the foundation and tower of an offshore wind turbine is investigated through aeroelastic calculations. Five representative sea states with increasing significant wave height are considered in a water depth of 40 m....... The waves are both linear and fully nonlinear irregular 2D waves. The wind turbine is the NREL 5-MW reference wind turbine. Fatigue analysis is performed in relation to analysis of the sectional forces in the tower and monopile. Impulsive excitation of the sectional force at the bottom of the tower is seen...

  2. Predictions for fatigue crack growth life of cracked pipes and pipe welds using RMS SIF approach and experimental validation

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Punit, E-mail: punit@barc.gov.in [Bhabha Atomic Research Centre, Department of Atomic Energy, Maharashtra, Mumbai 400 085 (India); Singh, P.K.; Bhasin, Vivek; Vaze, K.K.; Ghosh, A.K. [Bhabha Atomic Research Centre, Department of Atomic Energy, Maharashtra, Mumbai 400 085 (India); Pukazhendhi, D.M.; Gandhi, P.; Raghava, G. [Structural Engineering Research Centre, Chennai 600 113 (India)

    2011-10-15

    The objective of the present study is to understand the fatigue crack growth behavior in austenitic stainless steel pipes and pipe welds by carrying out analysis/predictions and experiments. The Paris law has been used for the prediction of fatigue crack growth life. To carry out the analysis, Paris constants have been determined for pipe (base) and pipe weld materials by using Compact Tension (CT) specimens machined from the actual pipe/pipe weld. Analyses have been carried out to predict the fatigue crack growth life of the austenitic stainless steel pipes/pipes welds having part through cracks on the outer surface. In the analyses, Stress Intensity Factors (K) have been evaluated through two different schemes. The first scheme considers the 'K' evaluations at two points of the crack front i.e. maximum crack depth and crack tip at the outer surface. The second scheme accounts for the area averaged root mean square stress intensity factor (K{sub RMS}) at deepest and surface points. Crack growth and the crack shape with loading cycles have been evaluated. In order to validate the analytical procedure/results, experiments have been carried out on full scale pipe and pipe welds with part through circumferential crack. Fatigue crack growth life evaluated using both schemes have been compared with experimental results. Use of stress intensity factor (K{sub RMS}) evaluated using second scheme gives better fatigue crack growth life prediction compared to that of first scheme. Fatigue crack growth in pipe weld (Gas Tungsten Arc Welding) can be predicted well using Paris constants of base material but prediction is non-conservative for pipe weld (Shielded Metal Arc Welding). Further, predictions using fatigue crack growth rate curve of ASME produces conservative results for pipe and GTAW pipe welds and comparable results for SMAW pipe welds. - Highlights: > Predicting fatigue crack growth of Austenitic Stainless Steel pipes and pipe welds. > Use of RMS-SIF and

  3. Fatigue Life and Microstructure after Multiple Remelting of A359 Matrix Composites Reinforced with SiC Particles

    Directory of Open Access Journals (Sweden)

    Klasik A.

    2016-12-01

    Full Text Available The article presents the results of fatigue life tests and microstructure examinations of A359 alloy matrix composites (F3S.10S and F3S.30S containing 10 and 30wt% of SiC particles, subjected to multiple remelting by conventional gravity casting. Mechanical characteristics were determined in a modified low cycle fatigue (MLCF test, enabling rapid estimation of fatigue life and other mechanical parameters in practice of any material. Qualitative and quantitative metallographic examinations were also carried out. The quantitative evaluation of microstructure was performed by computer image analysis. A set of geometrical parameters of the reinforcing particles, pores and eutectic precipitates present in the metal matrix was determined. The relationships between the mechanical parameters, structural characteristics and the number of remelting operations were presented. It was found that up to the fourth remelting, the mechanical characteristics, including fatigue life, are slightly deteriorated but decrease gradually in the subsequent operations of remelting. The observed effect is mainly due to the shrinkage porosity occurring as a result of gravity casting. To eliminate this defect, the use of squeeze casting process was recommended. It has also been shown that multiple remelting can be an easy and economically well-founded alternative to other more expensive recycling methods.

  4. Independent effect of fatigue on health-related quality of life in patients with idiopathic Parkinson's disease.

    Science.gov (United States)

    Dogan, Vasfiye Burcu; Koksal, Ayhan; Dirican, Ayten; Baybas, Sevim; Dirican, Ahmet; Dogan, Gulsum Buse

    2015-12-01

    Nonmotor symptoms (NMS) of idiopathic Parkinson's disease (IPD), specifically fatigue, depression and sleep disturbances, are important contributors for worse quality of life and poor patient outcomes. The aim of this research is to determine the relationship between fatigue and other NMS and the independent effect of fatigue on health-related quality of life (HRQoL) in patients with IPD. 86 IPD patients and 85 healthy individuals were included in our study. Participants were evaluated by their answers to the Beck Depression Inventory, Fatigue Severity Scale, Epworth Sleepiness Scale and Parkinson's Disease Questionnaire-39. Hoehn-Yahr stage, disease duration, medications and demographical characteristics were also noted. ROC analysis was used to determine the cutoff point for HRQoL. Nonparametric Spearman correlation analysis was used for determining the relationship between variables. Independent factors which affect HRQoL were detected by multiple forward stepwise logistic regression analysis. NMS were associated with each other and with HRQoL when they act concomitantly (p 0.05). The stage of IPD and levodopa-entacapone treatment had independent effects on HRQoL too (p life quality.

  5. Synergistic Effects of Frequency and Temperature on Damage Evolution and Life Prediction of Cross-Ply Ceramic Matrix Composites under Tension-Tension Fatigue Loading

    Science.gov (United States)

    Longbiao, Li

    2016-12-01

    In this paper, the synergistic effects of loading frequency and testing temperature on the fatigue damage evolution and life prediction of cross-ply SiC/MAS ceramic-matrix composite have been investigated. The damage parameters of the fatigue hysteresis modulus, fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of SiC/MAS composite. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/MAS composite under the loading frequency of 1 and 10 Hz at 566 °C and 1093 °C in air condition have been predicted. The synergistic effects of the loading frequency and testing temperature on the degradation rate of fatigue hysteresis dissipated energy and the interface shear stress have been analyzed.

  6. Review of time-dependent fatigue behavior and life prediction for 2 1/4 Cr-1 Mo steel. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Booker, M.K.; Majumdar, S.

    1982-01-01

    Available data on creep-fatigue life and fracture behavior of 2 1/4 Cr-1 Mo steel are reviewed. Whereas creep-fatigue interaction is important for Type 304 stainless steel, oxidation effects appear to dominate the time-dependent fatigue behavior of 2 1/4 Cr-1 Mo steel. Four of the currently available predictive methods - the Linear Damage Rule, Frequency Separation Equation, Strain Range Partitioning Equation, and Damage Rate Equation - are evaluated for their predictive capability. Variations in the parameters for the various predictive methods with temperature, heat of material, heat treatment, and environment are investigated. Relative trends in the lives predicted by the various methods as functions of test duration, waveshape, etc., are discussed. The predictive methods will need modification in order to account for oxidation and aging effects in the 2 1/4 Cr-1 Mo steel. Future tests that will emphasize the difference between the various predictive methods are proposed.

  7. An estimation of fatigue life for a carbon fibre/poly ether ether ketone hip joint prosthesis.

    Science.gov (United States)

    Akay, M; Aslan, N

    1995-01-01

    A fracture mechanics approach was applied to estimate the life of a prosthesis injection moulded from short carbon fibre reinforced poly ether ether ketone. Flexural modulus and strength, fracture toughness, fatigue endurance limit, fatigue crack growth rate and threshold stress intensity factor were determined. The dimensions of the test pieces were selected to yield fibre orientation and fibre length distributions similar to those obtained in the prosthesis. Stress levels generated in the prosthesis under different activities were estimated by conducting three-dimensional finite element analysis. It was shown by a fracture mechanics approach that a fatigue failure due to the propagation of an embedded elliptical slit, under these stresses, would be unlikely for a crack length smaller than 1.85 mm. However, the cement would fail under the same conditions, irrespective of the type of the prosthesis employed.

  8. Finite element analysis of sucker rod couplings with guidelines for improving fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, E.L. [Sandia National Labs., Albuquerque, NM (United States). Engineering and Structural Mechanics Div.

    1997-09-01

    The response of a variety of sucker rod couplings to an applied axial load was simulated using axisymmetric finite element models. The calculations investigated three sucker rod sizes and various combinations of the slimhole, Spiralock, and Flexbar modifications to the coupling. In addition, the effect of various make-ups (assembly tightness) on the performance of coupling was investigated. An axial load was applied to the sucker rod ranging from {minus}5 ksi to 40 ksi, encompassing three load cycles identified on a modified Goodman diagram as acceptable for indefinite service life of the sucker rods. The simulations of the various coupling geometries and make-ups were evaluated with respect to how well they accomplish the two primary objectives of preloading threaded couplings: (1) to lock the threaded coupling together so that it will not loosen and eventually uncouple, and (2) to improve the fatigue resistance of the threaded connection by reducing the stress amplitude in the coupling when subjected to cyclic loading. Perhaps the most significant finding in this study was the characterization of the coupling parameters which affect two stress measures. The mean hydrostatic stress, which determines the permissible effective alternating stress, is a function of the coupling make-up. Whereas, the alternating effective stress is a function of the relative stiffnesses of the pin and box sections of the coupling and, as long as the coupling does not separate, is unaffected by the amount of circumferential displacement applied during make-up. The results of this study suggest approaches for improving the fatigue resistance of sucker rod couplings.

  9. Estimation of Fatigue Life of Laser Welded AISI304 Stainless Steel T-Joint Based on Experiments and Recommendations in Design Codes

    DEFF Research Database (Denmark)

    Lambertsen, Søren Heide; Damkilde, Lars; Kristensen, Anders Schmidt;

    2013-01-01

    In this paper the fatigue behavior of laser welded T-joints of stainless steel AISI304 is investigated experimentally. In the fatigue experiments 36 specimens with a sheet thickness of 1 mm are exposed to one-dimensional cyclic loading. Three different types of specimens are adopted. Three groups....... The non-welded specimens are used to study the influence of heat and surface effects on the fatigue life. The fatigue life from the experiments is compared to fatigue life calculated from the guidelines in the standards DNV-RP-C203 and EUROCODE 3 EN-1993-1-9. Insignificant differences in fatigue life...... of the welded and non-welded specimens are observed in the experiments and the largest difference is found in the High Cycle Fatigue (HCF) area. The specimens show a lower fatigue life compared to DNV-RP-C203 and EUROCODE 3 EN-1993-1-9 when the spe-cimens are exposed to less than 4.0 1E06 cycles. Therefore, we...

  10. Life distribution of thermal fatigue crack propagation under random temperature fluctuation with wide-band spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Toyoda, Michiko; Tanaka, Hiroaki [Kyoto Univ. (Japan)

    1995-05-01

    Thermal fatigue crack propagation under random temperature fluctuation is theoretically investigated from a probabilistic view point by the use of a Markov approximation method, under the condition that the temporary variation of the inner surface temperature of plate is modeled as a wide-band stationary Gaussian process. First, a crack growth equation is formulated on the basis of the Paris law under the assumption that the stress intensity factor range {Delta}K can be approximated by the local expectation of a relative maximum of the stress intensity factor K. Next it is extended to a random differential equation, where the randomness in crack propagation resistance is taken into account. The Markov approximation method is then applied to derive a residual life distribution function as well as a probability distribution function of the crack length. Finally, numerical examples are shown to examine the quantitative behavior of the residual life distribution, whose results indicate that the present model is applicable even if the spectrum of temperature is of narrow-band type. (author).

  11. Report on an Assessment of the Application of EPP Results from the Strain Limit Evaluation Procedure to the Prediction of Cyclic Life Based on the SMT Methodology

    Energy Technology Data Exchange (ETDEWEB)

    Jetter, R. I. [R. I. Jetter Consulting, Pebble Beach, CA (United States); Messner, M. C. [Argonne National Lab. (ANL), Argonne, IL (United States); Sham, T. -L. [Argonne National Lab. (ANL), Argonne, IL (United States); Wang, Y. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    The goal of the proposed integrated Elastic Perfectly-Plastic (EPP) and Simplified Model Test (SMT) methodology is to incorporate an SMT data based approach for creep-fatigue damage evaluation into the EPP methodology to avoid the separate evaluation of creep and fatigue damage and eliminate the requirement for stress classification in current methods; thus greatly simplifying evaluation of elevated temperature cyclic service. This methodology should minimize over-conservatism while properly accounting for localized defects and stress risers. To support the implementation of the proposed methodology and to verify the applicability of the code rules, analytical studies and evaluation of thermomechanical test results continued in FY17. This report presents the results of those studies. An EPP strain limits methodology assessment was based on recent two-bar thermal ratcheting test results on 316H stainless steel in the temperature range of 405 to 7050C. Strain range predictions from the EPP evaluation of the two-bar tests were also evaluated and compared with the experimental results. The role of sustained primary loading on cyclic life was assessed using the results of pressurized SMT data from tests on Alloy 617 at 9500C. A viscoplastic material model was used in an analytic simulation of two-bar tests to compare with EPP strain limits assessments using isochronous stress strain curves that are consistent with the viscoplastic material model. A finite element model of a prior 304H stainless steel Oak Ridge National Laboratory (ORNL) nozzle-to-sphere test was developed and used for an EPP strain limits and creep-fatigue code case damage evaluations. A theoretical treatment of a recurring issue with convergence criteria for plastic shakedown illustrated the role of computer machine precision in EPP calculations.

  12. Interior Fracture Mechanism Analysis and Fatigue Life Prediction of Surface-Hardened Gear Steel under Axial Loading

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-10-01

    Full Text Available The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles characteristics without conventional fatigue limit related to 107 cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 105 cycles, whereas the inclusion induced fracture with fine granular area (FGA and fisheye occurs in the long life region beyond 106 cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results.

  13. Interior Fracture Mechanism Analysis and Fatigue Life Prediction of Surface-Hardened Gear Steel under Axial Loading.

    Science.gov (United States)

    Li, Wei; Deng, Hailong; Liu, Pengfei

    2016-10-18

    The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles) characteristics without conventional fatigue limit related to 10⁷ cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 10⁵ cycles, whereas the inclusion induced fracture with fine granular area (FGA) and fisheye occurs in the long life region beyond 10⁶ cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results.

  14. Improvement of the fatigue life of titanium alloys for biomedical devices through microstructural control.

    Science.gov (United States)

    Niinomi, Mitsuo; Akahori, Toshikazu

    2010-07-01

    A limited number of reports exist regarding the systematic investigation or comparison of the fatigue strength of titanium alloys for medical devices, including plain, fretting and notch fatigue, for improvement through various treatments and processes, with respect to related microstructures. This article focuses on the changes and improvements in fatigue strength of newly developed beta-type and practically used alpha + beta-titanium alloys for medical devices through heat treatments, thermomechanical treatments and surface modifications.

  15. 悬架下摆臂的疲劳寿命分析%Fatigue Life Analysis of Lower Suspension Arm

    Institute of Scientific and Technical Information of China (English)

    史建鹏; 管欣

    2013-01-01

    根据汽车悬架下摆臂所受的极限静载工况下的结构应力分析、道路载荷作用下的疲劳损伤分析和常用行驶工况下的疲劳寿命等分析,采用CAE与台架和道路试验相结合的方法,从多体动力学得到载荷值,应用“惯性释放法”获得不同工况下,下摆臂的应力分布特征;据此确定易出现疲劳损伤的部位,为下摆臂探索出一种一体化疲劳寿命分析方法;采用该方法对某型汽车下摆臂进行分析的结果表明,受到的应力下降1OMPa时,疲劳寿命约能提高1倍.%Based on the analyses on the structural stress of static loads in extreme condition, the fatigue damage under road loads and the fatigue life in normal driving conditions for lower suspension arm and combining CAE technique with road test, the load values are obtained with multi-body dynamics, and by applying inertia relief method the stress distribution features of lower suspension arm are acquired, and based on which the locations are i-dentified where fatigue damages are easy to occur. Thus an integrated fatigue life analysis technique for lower suspension arm is explored, using which the analysis on the lower suspension arm of a real vehicle is conducted with a result showing that for this specific situation a reduction of stress by 10 MPa can lead to nearly a doubling in fatigue life.

  16. Mean load effects on the fatigue life of offshore wind turbine monopile foundations

    DEFF Research Database (Denmark)

    Blasques, José Pedro Albergaria Amaral; Natarajan, Anand

    2013-01-01

    This paper discusses the importance of mean load effects on the estimation of the fatigue damage in offshore wind turbine monopile foundations. The mud line bending moment time series are generated using a fully coupled aero-hydro-elastic model accounting for non-linear water waves and sea current....... The fatigue damage is analysed in terms of the lifetime fatigue damage equivalent bending moment. Three different mean value correction techniques are considered, namely, Goodman, Walker, and mean sensitivity factor. An increase in the lifetime fatigue damage equivalent bending moment between 6% (mean...

  17. Experimental Modeling and Optimization of Fatigue Life and Hardness of Carbon Steel CK35 under Dynamic Buckling

    Directory of Open Access Journals (Sweden)

    Ahmed Naif Al-Khazraji

    2014-12-01

    Full Text Available The aim of this paper is to model and optimize the fatigue life and hardness of medium carbon steel CK35 subjected to dynamic buckling. Different ranges of shot peening time (STP and critical points of slenderness ratio which is between the long and intermediate columns, as input factors, were used to obtain their influences on the fatigue life and hardness, as main responses. Experimental measurements of shot peening time and buckling were taken and analyzed using (DESIGN EXPERT 8 experimental design software which was used for modeling and optimization purposes. Mathematical models of responses were obtained and analyzed by ANOVA variance to verify the adequacy of the models. The resultant quadratic models were obtained. A good agreement was found between the results of these models and optimization with the experimental ones with confidence level of 95 %.

  18. Lifing the thermo-mechanical fatigue (TMF behaviour of the polycrystalline nickel-based superalloy RR1000

    Directory of Open Access Journals (Sweden)

    Jones Jonathan

    2014-01-01

    Full Text Available Microstructural damage and subsequent failures resulting from thermo-mechanical fatigue (TMF loading within the temperature range 300–700 ∘C are investigated for the polycrystalline nickel superalloy, RR1000. Strain controlled TMF experiments were conducted over various mechanical strain ranges, encompassing assorted phase angles, using hollow cylindrical test pieces. The paper explores two scenarios; the first where the mechanical strain range is held constant and comparisons of the fatigue life are made for different phase angle tests, and secondly, the difference between the behaviour of In-phase (IP and − 180 ∘ Out-Of-Phase (OOP tests over a variety of applied strain ranges. It is shown that different lifing approaches are currently required for the two scenarios, with a mean stress based approach being more applicable in the first case, whereas a Basquin-type model proves more appropriate in the second.

  19. Perception of fatigue and quality of life in patients with COPD

    NARCIS (Netherlands)

    Breslin, E; van der Schans, C; Breukink, S; Meek, P; Mercer, K; Volz, W; Louie, S

    1998-01-01

    Introduction: Although dyspnea is considered the primary activity-limiting symptom in patients with COPD, other symptoms, such as fatigue, are frequently reported, The purpose of this study was to determine the relationship between fatigue and pulmonary function, exercise tolerance, depression, and

  20. A pilot study to test psychophonetics methodology for self-care and empathy in compassion fatigue, burnout and secondary traumatic stress

    Directory of Open Access Journals (Sweden)

    Katherine J. Train

    2013-01-01

    Full Text Available Background: Home-based care is recognised as being a stressful occupation. Practitioners working with patients experiencing high levels of trauma may be susceptible to compassion fatigue, with the sustained need to remain empathic being a contributing factor.Objectives: The aim of this research was to evaluate psychophonetics methodology for self-care and empathy skills as an intervention for compassion fatigue. Objectives were to measure levels of compassion fatigue pre-intervention, then to apply the intervention and retest levels one month and six months post-intervention.Method: The research applied a pilot test of a developed intervention as a quasi-experiment.The study sample comprised home-based carers working with HIV-positive patients at a hospice in Grabouw, a settlement in the Western Cape facing socioeconomic challenge.Results: The result of the pilot study showed a statistically-significant improvement in secondary traumatic stress, a component of compassion fatigue, measured with the ProQOL v5 instrument post-intervention.Conclusion: The results gave adequate indication for the implementation of a larger study in order to apply and test the intervention. The study highlights a dire need for further research in this field.

  1. Development of Probabilistic Life Prediction Methodologies and Testing Strategies for MEMS and CMC's

    Science.gov (United States)

    Jadaan, Osama

    2003-01-01

    This effort is to investigate probabilistic life prediction methodologies for ceramic matrix composites and MicroElectroMechanical Systems (MEMS) and to analyze designs that determine stochastic properties of MEMS. For CMC's this includes a brief literature survey regarding lifing methodologies. Also of interest for MEMS is the design of a proper test for the Weibull size effect in thin film (bulge test) specimens. The Weibull size effect is a consequence of a stochastic strength response predicted from the Weibull distribution. Confirming that MEMS strength is controlled by the Weibull distribution will enable the development of a probabilistic design methodology for MEMS - similar to the GRC developed CARES/Life program for bulk ceramics. A main objective of this effort is to further develop and verify the ability of the Ceramics Analysis and Reliability Evaluation of Structures/Life (CARES/Life) code to predict the time-dependent reliability of MEMS structures subjected to multiple transient loads. A second set of objectives is to determine the applicability/suitability of the CARES/Life methodology for CMC analysis, what changes would be needed to the methodology and software, and if feasible, run a demonstration problem. Also important is an evaluation of CARES/Life coupled to the ANSYS Probabilistic Design System (PDS) and the potential of coupling transient reliability analysis to the ANSYS PDS.

  2. Demonstrating the Effect of Particle Impact Dampers on the Random Vibration Response and Fatigue Life of Printed Wiring Assemblies

    Science.gov (United States)

    Knight, Brent; Montgomery, Randall; Geist, David; Hunt, Ron; LaVerde, Bruce; Towner, Robert

    2013-01-01

    In a recent experimental study, small Particle Impact Dampers (PID) were bonded directly to the surface of printed circuit board (PCB) or printed wiring assemblies (PWA), reducing the random vibration response and increasing the fatigue life. This study provides data verifying practicality of this approach. The measured peak strain and acceleration response of the fundamental out of plane bending mode was significantly attenuated by adding a PID device. Attenuation of this mode is most relevant to the fatigue life of a PWA because the local relative displacements between the board and the supported components, which ultimately cause fatigue failures of the electrical leads of the board-mounted components are dominated by this mode. Applying PID damping at the board-level of assembly provides mitigation with a very small mass impact, especially as compared to isolation at an avionics box or shelf level of assembly. When compared with other mitigation techniques at the PWA level (board thickness, stiffeners, constrained layer damping), a compact PID device has the additional advantage of not needing to be an integral part of the design. A PID can simply be bonded to heritage or commercial off the shelf (COTS) hardware to facilitate its use in environments beyond which it was originally qualified. Finite element analysis and test results show that the beneficial effect is not localized and that the attenuation is not due to the simple addition of mass. No significant, detrimental reduction in frequency was observed. Side-by-side life testing of damped and un-damped boards at two different thicknesses (0.070" and 0.090") has shown that the addition of a PID was much more significant to the fatigue life than increasing the thickness. High speed video, accelerometer, and strain measurements have been collected to correlate with analytical results.

  3. Sleep, Fatigue and Quality of Life: A Comparative Analysis among Night Shift Workers with and without Children

    Science.gov (United States)

    Fernandes-Junior, Silvio Araújo; Ruiz, Francieli Silva; Antonietti, Leandro Stetner; Tufik, Sergio; Túlio de Mello, Marco

    2016-01-01

    Introduction The reversal of the natural cycle of wakefulness and sleep may cause damage to the health of workers. However, there are few studies evaluating sleep, fatigue and quality of life of night shift workers considering the influence of small children on these variables. Aims Evaluate the sleep time, fatigue and quality of life of night shift workers and verify the relationship between these variables with the presence or absence of children in different age groups. Methods Were evaluated 78 mens shiftworkers, with or without children. Group 1, workers without children (G1-NC), group 2, workers with children pré-school age (G2-PS) and group 3, workers with children school age (G3-S). The sleep time (ST), sleep efficiency (SE), sleep latency (SL) and maximum time awake (MTA) were recorded by actigraphy. The risk of being fatigued at work was estimated by risk index for fatigue (RIF). Results The G1-NC showed a longer ST on working days and when evaluated only the first nights shift, after day off (p<0,005). This sample, the age of the children did not influence the sleep time these workers. The MTA on day off was lower in the workers from G2-PS. The RIF was lower on G1-NC in the first nights shift compared to the other groups. Conclusion In this research, workers without children had higher sleep time during the working days. These workers also were less likely to feel fatigued during night work than workers with children, regardless of age these children. PMID:27391478

  4. The effect of SiC powder mixing electrical discharge machining on white layer thickness, heat flux and fatigue life of AISI D2 die steel

    Directory of Open Access Journals (Sweden)

    Ahmed Al-Khazraji

    2016-09-01

    Full Text Available This paper deals with studying the effect of powder mixing electrical discharge machining (PMEDM parameters using copper and graphite electrodes on the white layer thickness (WLT, the total heat flux generated and the fatigue life. Response surface methodology (RSM was used to plan and design the experimental work matrices for two groups of experiments: for the first EDM group, kerosene dielectric was used alone, whereas the second was treated by adding the SiC micro powders mixing to dielectric fluid (PMEDM. The total heat flux generated and fatigue lives after EDM and PMEDM models were developed by FEM using ANSYS 15.0 software. The graphite electrodes gave a total heat flux higher than copper electrodes by 82.4%, while using the SiC powder and graphite electrodes gave a higher total heat flux than copper electrodes by 91.5%. The lowest WLT values of 5.0 µm and 5.57 µm are reached at a high current and low current with low pulse on time using the copper and graphite electrodes and the SiC powder, respectively. This means that there is an improvement in WLT by 134% and 110%, respectively, when compared with the use of same electrodes and kerosene dielectric alone. The graphite electrodes with PMEDM and SiC powder improved the experimental fatigue safety factor by 7.30% compared with the use of copper electrodes and by 14.61% and 18.61% compared with results using the kerosene dielectric alone with copper and graphite electrodes, respectively.

  5. Cyclic softening as a parameter for prediction of remnant creep rupture life of a Indian reduced activation ferritic–martensitic (IN-RAFM) steel subjected to fatigue exposures

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Aritra, E-mail: aritra@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Vijayanand, V.D.; Shankar, Vani; Parameswaran, P.; Sandhya, R.; Laha, K.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Rajendrakumar, E. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India)

    2014-12-15

    Sequential fatigue-creep tests were conducted on Indian reduced activation ferritic–martensitic steel at 823 K leading to sharp decrease in residual creep life with increase in prior fatigue exposures. Extensive recovery of martensitic-lath structure taking place during fatigue deformation, manifested as cyclic softening in the cyclic stress response, shortens the residual creep life. Based on the experimental results, cyclic softening occurring during fatigue stage can be correlated with residual creep life, evolving in an empirical model which predicts residual creep life as a function of cyclic softening. Predicted creep lives for specimens pre-cycled at various strain amplitudes are explained on the basis of mechanism of cyclic softening.

  6. Comparison of warm laser shock peening and laser shock peening techniques in lengthening the fatigue life of welded joints made of aluminum alloy

    Science.gov (United States)

    Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Sheng, Jie

    2017-07-01

    Welded joints made of 6061-T6 Al alloy were studied to evaluate warm laser shock peening (WLSP) and laser shock peening (LSP) processes. The estimation model of laser-induced surface residual stress was examined by means of experiments and numerical analysis. The high-cycle fatigue lives of welded joint specimens treated with WLSP and LSP were estimated by conducting tensile fatigue tests. The fatigue fracture mechanisms of these specimens are studied by surface integrity and fracture surface tests. Experimental results and analysis indicated that the fatigue life of the specimens processed by WLSP was higher than that with LSP. The large increase in fatigue life appeared to be the result of the larger residual stress, more uniform microstructure refinement and the lower surface roughness of the WLSP specimens.

  7. Relationship between fatigue life of asphalt concrete and polypropylene/polyester fibers using artificial neural network and genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    Morteza Vadood; Majid Safar Johari; Ali Reza Rahai

    2015-01-01

    While various kinds of fibers are used to improve the hot mix asphalt (HMA) performance, a few works have been undertaken on the hybrid fiber-reinforced HMA. Therefore, the fatigue life of modified HMA samples using polypropylene and polyester fibers was evaluated and two models namely regression and artificial neural network (ANN) were used to predict the fatigue life based on the fibers parameters. As ANN contains many parameters such as the number of hidden layers which directly influence the prediction accuracy, genetic algorithm (GA) was used to solve optimization problem for ANN. Moreover, the trial and error method was used to optimize the GA parameters such as the population size. The comparison of the results obtained from regression and optimized ANN with GA shows that the two-hidden-layer ANN with two and five neurons in the first and second hidden layers, respectively, can predict the fatigue life of fiber-reinforced HMA with high accuracy (correlation coefficient of 0.96).

  8. A gender-based analysis of work patterns, fatigue, and work/life balance among physicians in postgraduate training.

    Science.gov (United States)

    Gander, Philippa; Briar, Celia; Garden, Alexander; Purnell, Heather; Woodward, Alistair

    2010-09-01

    To document fatigue in New Zealand junior doctors in hospital-based clinical training positions and identify work patterns associated with work/life balance difficulties. This workforce has had a duty limitation of 72 hours/week since 1985. The authors chose a gender-based analytical approach because of the increasing proportion of female medical graduates. The authors mailed a confidential questionnaire to all 2,154 eligible junior doctors in 2003. The 1,412 respondents were working > or = 40 hours/week (complete questionnaires from 1,366: response rate: 63%; 49% women). For each participant, the authors calculated a multidimensional fatigue risk score based on sleep and work patterns. Women were more likely to report never/rarely getting enough sleep (P work/life balance and for part-time work, particularly in relation to parenthood. Limitation of duty hours alone is insufficient to manage fatigue risk and difficulties in maintaining work/life balance. These findings have implications for schedule design, professional training, and workforce planning.

  9. Methodological Validation of Quality of Life Questionnaire for Coal Mining Groups-Indian Scenario

    Science.gov (United States)

    Sen, Sayanti; Sen, Goutam; Tewary, B. K.

    2012-01-01

    Maslow's hierarchy-of-needs theory has been used to predict development of Quality of Life (QOL) in countries over time. In this paper an attempt has been taken to derive a methodological validation of quality of life questionnaire which have been prepared for the study area. The objective of the study is to standardize a questionnaire tool to…

  10. Methodological Validation of Quality of Life Questionnaire for Coal Mining Groups-Indian Scenario

    Science.gov (United States)

    Sen, Sayanti; Sen, Goutam; Tewary, B. K.

    2012-01-01

    Maslow's hierarchy-of-needs theory has been used to predict development of Quality of Life (QOL) in countries over time. In this paper an attempt has been taken to derive a methodological validation of quality of life questionnaire which have been prepared for the study area. The objective of the study is to standardize a questionnaire tool to…

  11. Proposition of Improved Methodology in Creep Life Extrapolation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Gon; Park, Jae Young; Jang, Jin Sung [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    To design SFRs for a 60-year operation, it is desirable to have the experimental creep-rupture data for Gr. 91 steel close to 20 y, or at least rupture lives significantly higher than 10{sup 5} h. This requirement arises from the fact that, for the creep design, a factor of 3 times for extrapolation is considered to be appropriate. However, obtaining experimental data close to 20 y would be expensive and also take considerable time. Therefore, reliable creep life extrapolation techniques become necessary for a safe design life of 60 y. In addition, it is appropriate to obtain experimental longterm creep-rupture data in the range 10{sup 5} ∼ 2x10{sup 5} h to improve the reliability of extrapolation. In the present investigation, a new function of a hyperbolic sine ('sinh') form for a master curve in time-temperature parameter (TTP) methods, was proposed to accurately extrapolate the long-term creep rupture stress of Gr. 91 steel. Constant values used for each parametric equation were optimized on the basis of the creep rupture data. Average stress values predicted for up to 60 y were evaluated and compared with those of French Nuclear Design Code, RCC-MRx. The results showed that the master curve of the 'sinh' function was a wider acceptance with good flexibility in the low stress ranges beyond the experimental data. It was clarified clarified that the 'sinh' function was reasonable in creep life extrapolation compared with polynomial forms, which have been used conventionally until now.

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

    Science.gov (United States)

    Halford, G. R.

    1983-01-01

    The presentation focuses primarily on the progress we at NASA Lewis Research Center have made. The understanding of the phenomenological processes of high temperature fatigue of metals for the purpose of calculating lives of turbine engine hot section components is discussed. Improved understanding resulted in the development of accurate and physically correct life prediction methods such as Strain-Range partitioning for calculating creep fatigue interactions and the Double Linear Damage Rule for predicting potentially severe interactions between high and low cycle fatigue. Examples of other life prediction methods are also discussed. Previously announced in STAR as A83-12159

  13. Above-knee prosthesis design based on fatigue life using finite element method and design of experiment.

    Science.gov (United States)

    Phanphet, Suwattanarwong; Dechjarern, Surangsee; Jomjanyong, Sermkiat

    2017-05-01

    The main objective of this work is to improve the standard of the existing design of knee prosthesis developed by Thailand's Prostheses Foundation of Her Royal Highness The Princess Mother. The experimental structural tests, based on the ISO 10328, of the existing design showed that a few components failed due to fatigue under normal cyclic loading below the required number of cycles. The finite element (FE) simulations of structural tests on the knee prosthesis were carried out. Fatigue life predictions of knee component materials were modeled based on the Morrow's approach. The fatigue life prediction based on the FE model result was validated with the corresponding structural test and the results agreed well. The new designs of the failed components were studied using the design of experimental approach and finite element analysis of the ISO 10328 structural test of knee prostheses under two separated loading cases. Under ultimate loading, knee prosthesis peak von Mises stress must be less than the yield strength of knee component's material and the total knee deflection must be lower than 2.5mm. The fatigue life prediction of all knee components must be higher than 3,000,000 cycles under normal cyclic loading. The design parameters are the thickness of joint bars, the diameter of lower connector and the thickness of absorber-stopper. The optimized knee prosthesis design meeting all the requirements was recommended. Experimental ISO 10328 structural test of the fabricated knee prosthesis based on the optimized design confirmed the finite element prediction. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  14. Life Cycle Assessment and Risk Assessment: A Methodological Comparison

    DEFF Research Database (Denmark)

    Olsen, Stig Irving; Christensen, Frans Møller; Hauschild, Michael Zwicky

    2001-01-01

    Life Cycle Assessment and Risk Assessment are two different tools in environmental management. The paper identifies harmonies, discrepancies and relations between the two tools exemplified by the risk assessment principles of the European Commission (EC) and the LCA method ‘EDIP’ (En-vironmental...... conditions. It is concluded that the conceptual background and the purpose of the tools are different but that there are overlaps where they may benefit from each other and they do complement each other in an overall environmental effort....... Design of Industrial Products) developed in Denmark, respectively. A very important feature of LCA is the relative assessment due to the use of a functional unit. Risk assessment on the other hand is an absolute assessment, which may require very specific and detailed information on e.g. the exposure...

  15. Fatigue life prediction and experiment research for composite laminates with circular hole

    Institute of Scientific and Technical Information of China (English)

    齐红宇; 温卫东; 孙联文

    2004-01-01

    Based on the fatigue prediction model of exponential function and Whitney-Nuismer(WN) criterion of static strength for the composite material laminate with a circular hole, the stress correct factor (β) was put forward and a new fatigue prediction model for composite material laminate was set up. T300/KH304, which is recently studied and is a high capability composite material, was used as the raw material. In order to gain the factorβ, the fatigue experiments of the laminates with holes in different diameters and the same ratio of width to diameter were conducted. The fatigue analysis and tests of the laminates with a hole 5 mm in diameter are carried out at different stress levels, and the results meet the engineering requirement. The simple, prompt and practical method is provided for the prediction of S-N curve of composite laminate with a circular hole.

  16. Study of the Fatigue Life and Weight Optimization of an Automobile Aluminium Alloy Part under Random Road Excitation

    Directory of Open Access Journals (Sweden)

    A. Saoudi

    2010-01-01

    Full Text Available Weight optimization of aluminium alloy automobile parts reduces their weight while maintaining their natural frequency away from the frequency range of the power spectral density (PSD that describes the roadway profile. We present our algorithm developed to optimize the weight of an aluminium alloy sample relative to its fatigue life. This new method reduces calculation time; It takes into account the multipoint excitation signal shifted in time, giving a tangle of the constraint signals of the material mesh elements; It also reduces programming costs. We model an aluminium alloy lower vehicle suspension arm under real conditions. The natural frequencies of the part are inversely proportional to the mass and proportional to flexural stiffness, and assumed to be invariable during the process of optimization. The objective function developed in this study is linked directly to the notion of fatigue. The method identifies elements that have less than 10% of the fatigue life of the part's critical element. We achieved a weight loss of 5 to 11% by removing the identified elements following the first iteration.

  17. Predicting quality of life in multiple sclerosis: accounting for physical disability, fatigue, cognition, mood disorder, personality, and behavior change.

    Science.gov (United States)

    Benedict, Ralph H B; Wahlig, Elizabeth; Bakshi, Rohit; Fishman, Inna; Munschauer, Frederick; Zivadinov, Robert; Weinstock-Guttman, Bianca

    2005-04-15

    Health-related quality of life (HQOL) is poor in multiple sclerosis (MS) but the clinical precipitants of the problem are not well understood. Previous correlative studies demonstrated relationships between various clinical parameters and diminished HQOL in MS. Unfortunately, these studies failed to account for multiple predictors in the same analysis. We endeavored to determine what clinical parameters account for most variance in predicting HQOL, and employability, while accounting for disease course, physical disability, fatigue, cognition, mood disorder, personality, and behavior disorder. In 120 MS patients, we measured HQOL (MS Quality of Life-54) and vocational status (employed vs. disabled) and then conducted detailed clinical testing. Data were analyzed by linear and logistic regression methods. MS patients reported lower HQOL (pPhysical HQOL was predicted by fatigue, depression, and physical disability. Mental HQOL was associated with only depression and fatigue. In contrast, vocational status was predicted by three cognitive tests, conscientiousness, and disease duration (p<0.05). Thus, for the first time, we predicted HQOL in MS while accounting for measures from these many clinical domains. We conclude that self-report HQOL indices are most strongly predicted by measures of depression, whereas vocational status is predicted primarily by objective measures of cognitive function. The findings highlight core clinical problems that merit early identification and further research regarding the development of effective treatment.

  18. Rolling Contact Fatigue Life of Steel Rollers Treated by Cavitation Peening and Shot Peening

    Science.gov (United States)

    Seki, Masanori; Soyama, Hitoshi; Kobayashi, Yuji; Gowa, Daisuke; Fujii, Masahiro

    The purpose of this study is to investigate the influence of peening on the rolling contact fatigue (RCF) life of steel rollers. First, steel rollers were treated by three types of peenings to ensure the same surface roughness of peened rollers. One is the cavitation peening (CP) used a cavitating jet in water with an injection pressure of 30 MPa, and the others are the fine particle peening (FPP) with a shot diameter of 0.1 mm and the normal shot peening (NSP) with a shot diameter of 0.3 mm. The surface hardness and the surface compressive residual stress of the steel rollers were increased by all the peenings. In particular, they were most increased by the FPP. On the other hand, the work-hardened depth due to the CP and the NSP was larger than that due to the FPP. As a result of the RCF tests, the RCF lives of the steel rollers were improved by all the peenings, and they were most improved by the NSP. Judging from the pmax - N curves and the [A(σy/√3 HV)]max - N curves, the improvement in RCF lives due to the FPP depended heavily on the increase in surface hardness due to that, and the effects of the CP and the NSP on the RCF were equivalent under the same surface roughness and the same surface hardness. It follows from these that the surface treatment condition should be selected according to the rolling contact conditions and the failure modes of machine elements.

  19. DETERMINATION OF VEHICLE COMPONENTS FATIGUE LIFE BASED ON FEA METHOD AND EXPERIMENTAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Arif Senol SENER

    2012-01-01

    Full Text Available In this study, construction and standardization of a track for performing fatigue and reliability test of light commercial vehicles is described. For the design and process verification of the company’s vehicles one test track is defined. A questionnaire was used to determine the average usage of light commercial vehicles in Turkey. Fatigue characteristics of Turkish roads were determined by analyzing fifty different roads and this article focuses on defining the load spectrum and equivalent fatigue damage of the leaf spring resulting from the accelerated test route. Fatigue analysis and estimated lifespan of the part were calculated using Finite Element Analyses and verified by the Palmgren-Miner rule. When the customer profile is taken into consideration; Turkish customer automotive usage profile, the aim of usage of this kind of vehicle (LCV, fatigue characteristics of Turkish roads for this vehicle were determined and around Bursa one accelerated test tracks were formed for the reliability and fatigue test for the related company, linear analysis executed on the FEA of the spring was more convenient were obtained.

  20. On the development of life prediction methodologies for the failure of human teeth

    Energy Technology Data Exchange (ETDEWEB)

    Nalla, R.K.; Imbeni, V.; Kinney, J.H.; Marshall, S.J.; Ritchie, R.O.

    2002-09-18

    Human dentin is known to be susceptible to failure under cyclic loading. Surprisingly, there are few reports that quantify the effect of such loading, considering the fact that a typical tooth experiences a million or so loading cycles annually. In the present study, a systematic investigation is described of the effects of prolonged cyclic loading on human dentin in a simulated physiological environment. In vitro stress-life (S/N) data are discussed in the context of possible mechanisms of fatigue damage and failure.

  1. Bending resistance and dynamic and static cyclic fatigue life of Reciproc and WaveOne large instruments.

    Science.gov (United States)

    De-Deus, Gustavo; Leal Vieira, Victor Talarico; Nogueira da Silva, Emmanuel João; Lopes, Helio; Elias, Carlos Nelson; Moreira, Edson Jorge

    2014-04-01

    The aim of the present study was to evaluate the bending resistance and the dynamic and static cyclic fatigue life of Reciproc R40 and WaveOne large instruments. A sample of 68 nickel-titanium instruments (25 mm in length) for use under reciprocation movement (Reciproc and WaveOne) from 3 different lots was tested. Reciproc R40 and WaveOne Large files, both of which had a nominal size of 0.40 mm at D0, were selected. The bending resistance was performed in 10 instruments of each system by using a universal testing machine. Dynamic and static models for cyclic fatigue testing were performed by using a custom-made device. For these tests, an artificial canal measuring 1.4 mm in diameter and 19 mm total length was fabricated from a stainless steel tube. Scanning electron microscopy analysis was performed to determine the mode of fracture. Statistical analysis was performed by using parametric methods, 1-way analysis of variance. Post hoc pair-wise comparisons were performed by using Tukey test for multiple comparisons. WaveOne instruments presented significantly higher bending resistance than Reciproc (P < .05). Moreover, Reciproc revealed a significantly longer cyclic fatigue life (P < .05) in both static and dynamic tests (P < .05). Reciproc R40 instruments resisted dynamic and static cyclic fatigue significantly more than WaveOne Large instruments. Furthermore, WaveOne instruments presented significantly less flexibility than Reciproc. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  2. Comparison of Fatigue Life Between C/SiC and SiC/SiC Ceramic-Matrix Composites at Room and Elevated Temperatures

    Science.gov (United States)

    Longbiao, Li

    2016-10-01

    In this paper, the comparison of fatigue life between C/SiC and SiC/SiC ceramic-matrix composites (CMCs) at room and elevated temperatures has been investigated. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface wear model and fibers statistical failure model at room temperature, and interface/fibers oxidation model, interface wear model and fibers statistical failure model at elevated temperatures in the oxidative environments. When the broken fibers fraction approaches to the critical value, the composites fatigue fracture. The fatigue life S-N curves and fatigue limits of cross-ply, 2D and 3D C/SiC and SiC/SiC composites at room temperature, 550 °C in air, 750 °C in dry and humid condition, 800 °C in air, 1000 °C in argon and air, 1100 °C, 1300 °C and 1500 °C in vacuum, have been predicted. At room temperature, the fatigue limit of 2D C/SiC composite with ECFL of 20 % lies between 0.78 and 0.8 tensile strength; and the fatigue limit of 2D SiC/SiC composite with ECFL of 20 % lies between 0.75 and 0.85 tensile strength. The fatigue limit of 2D C/SiC composite increases to 0.83 tensile strength with ECFL increasing from 20 to 22.5 %, and the fatigue limit of 3D C/SiC composite is 0.85 tensile strength with ECFL of 37 %. The fatigue performance of 2D SiC/SiC composite is better than that of 2D C/SiC composite at elevated temperatures in oxidative environment.

  3. Disease-free ovarian cancer patients report severe pain and fatigue over time: prospective quality of life assessment in a consecutive series.

    Science.gov (United States)

    Shinde, S; Wanger, T; Novotny, P; Grudem, M; Jatoi, A

    2015-01-01

    objective: Among ovarian cancer patients, cancer treatment is aggressive and yet survival is often so limited; hence, this study sought to measure quality of life with the ultimate goal of identifying ways of improving it over the duration of these patients' lives. The medical records of all ovarian cancer patients who received some/all of their initial chemotherapy at the Mayo Clinic in Rochester, Minnesota from late 2010 through 2012 were reviewed. Patient-reported quality of life was derived from the following ten-point linear analogue scale questions which had been administered to all patients: 1) How would you describe your degree of pain, on average? 2) How would you describe your level of fatigue, on average? 3) How would you describe your overall quality of life? Quality of life data were censored upon cancer recurrence. Among 59 eligible patients, the median cumulative interval during which quality of life was serially assessed was 1.15 years (range: three months, 3.2 years). Area under the curve for pain, fatigue, and global quality of life showed no statistically significant differences between patients treated with dose-dense chemotherapy with carboplatin/paclitaxel (n = 10) versus three-week chemotherapy with carboplatin/paclitaxel (n = 36) versus other (n = 13). Although pain, fatigue, and global quality of life improved over time, 35 of 59 (59%) patients reported grade 4 or worse pain during follow up, and 47 of 59 (80%) reported grade 4 or worse fatigue (higher scores denote worse pain or fatigue). After completion of cancer treatment, 30 (51%) described grade 4 or worse pain or fatigue. The most common pain site was the abdomen/pelvis, followed by the back, followed by the hands, feet, fingers, and toes. In ovarian cancer patients who remain cancer-free, severe pain and fatigue occur years after cancer treatment. Further research should focus on how best to address these symptoms.

  4. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Faber, M. H.; Sørensen, John Dalsgaard; Kroon, I. B.

    1993-01-01

    This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue ...

  5. Prediction of low-cycle fatigue-life by acoustic emission—1: 2024-T3 aluminum alloy, and —2: 7075-T6 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Baram, J. [Ben-Gurion Univ. of the Negev, Beer Sheva (Israel). Materials Engineering Division; Rosen, M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials and Molecular Research Division

    1981-01-01

    1: In this paper, low-cycle fatigue tests were conducted by tension-tension until rupture, on a 2024-T3 aluminum alloy sheet. Initial crack sizes and orientations in the fatigue specimens were found to be randomly distributed. Acoustic emission was continuously monitored during the tests. Every few hundred cycles, the acoustic signal having the highest peak-amplitude, was recorded as an extremal event for the elapsed period. This high peak-amplitude is related to a fast crack propagation rate through a phenomenological relationship. The extremal peak amplitudes are shown by an ordered statistics treatment, to be extremally distributed. The statistical treatment enables the prediction of the number of cycles left until failure. Predictions performed a posteriori based on results gained early in each fatigue test are in good agreement with actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress appears to be a promising nondestructive method of predicting fatigue life. 2: In this paper, low cycle high stress fatigue tests were conducted by tension-tension on an Alclad 7075-T6 aluminum sheet alloy, until rupture. Initial crack sizes and orientations in the fatigue specimens were randomly distributed. Acoustic emission was continuously monitored during the tests. Extremal peak-amplitudes, equivalent to extremal crack-propagation rates, are shown to be extremally Weibull distributed. The prediction of the number of cycles left until failure is made possible, using an ordered statistics treatment and an experimental equipment parameter obtained in previous experiments (Part 1). The predicted life-times are in good agreement with the actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress has been proven to be a feasible nondestructive method of predicting fatigue life.

  6. Associations of Midlife to Late Life Fatigue With Physical Performance and Strength in Early Old Age

    DEFF Research Database (Denmark)

    Mänty, Minna Regina; Kuh, Diana; Cooper, Rachel

    2015-01-01

    objective measures: grip strength, standing balance, chair rising, and timed get-up-and-go (TUG) tests. RESULTS: There were associations between reports of frequent fatigue at both ages and poorer grip strength, chair rise, and TUG performance at 60 to 64 years. Furthermore, individuals reporting frequent...... fatigue at both ages had weaker grip strength (β = -4.09 kg, 95% confidence interval [CI] = -6.71 to -1.48) and slower chair rise (β = -4.65 repetitions/min, 95% CI = -6.65 to -2.64) and TUG (β = -4.22 cm/s, 95% CI = -12.16 to -2.28) speeds when compared with those who reported no fatigue at both time...

  7. Fatigue in Rheumatoid Arthritis.

    Science.gov (United States)

    Katz, Patricia

    2017-05-01

    The purpose of this study was to review the current information on fatigue in rheumatoid arthritis (RA). Severe fatigue is common among individuals with RA and has a significant impact on quality of life (QOL). RA-related factors (e.g., inflammation, pain) are associated with greater fatigue, but other factors, such as obesity, physical inactivity, sleep disturbance, and depression, explain the majority of variation in fatigue. Medications targeting RA have little effect on fatigue. Instead, the most effective interventions seem to address non-RA-specific factors such as physical inactivity or use cognitive behavioral approaches. No recommendations have been made for tools to measure fatigue in RA, leading to potential difficulty comparing studies. Although fatigue has great impact on patients' QOL, effective interventions that are feasible for broad dissemination remain elusive. Additional multi-faceted research is needed to identify modifiable sources of fatigue. Such research would be enhanced by harmonization of fatigue measurement across studies.

  8. Semiempirical Methodology for Estimating the Service Life of Concrete Deck Panels Strengthened with Fiber-Reinforced Polymer

    Directory of Open Access Journals (Sweden)

    Eon-Kyoung Kim

    2014-01-01

    Full Text Available Deterioration of concrete bridge decks affects their durability, safety, and function. It is therefore necessary to conduct structural rehabilitation of damaged concrete decks by strengthening them with fiber-reinforced polymer. Of the recent studies on the strengthened structures, most have focused on static behavior; only a few studies have investigated fatigue behavior. Accurate analysis of fatigue in concrete deck performance requires a more realistic simulated moving load. This study developed a theoretical live-load model to reflect the effect of moving vehicle loads, based on a statistical approach to the measurement of real traffic loads over various time periods in Korea. It assessed the fatigue life and strengthening effect of bridge decks strengthened with either carbon fiber sheets or grid carbon fiber polymer plastic using probabilistic and reliability analyses. It used extrapolations and simulations to derive maximum load effects for time periods ranging from 1 day to 75 years. Limited fatigue tests were conducted and probabilistic and reliability analyses were carried out on the strengthened concrete bridge deck specimens to predict the extended fatigue life. Analysis results indicated that strengthened concrete decks provide sufficient resistance against increasing truck loads during the service life of a bridge.

  9. Synergistic Effects of Temperature, Oxidation and Multicracking Modes on Damage Evolution and Life Prediction of 2D Woven Ceramic-Matrix Composites under Tension-Tension Fatigue Loading

    Science.gov (United States)

    Longbiao, Li

    2017-08-01

    In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed.

  10. Fatigue Life Prediction of Fiber-Reinforced Ceramic-Matrix Composites with Different Fiber Preforms at Room and Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Longbiao Li

    2016-03-01

    Full Text Available In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional, 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL was introduced to describe the fiber architecture of preforms. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Under cyclic fatigue loading, the fiber broken fraction was determined by combining the interface wear model and fiber statistical failure model at room temperature, and interface/fiber oxidation model, interface wear model and fiber statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfies the Global Load Sharing (GLS criterion. When the broken fiber fraction approaches the critical value, the composites fatigue fracture.

  11. Fatigue life prediction in a unidirectional glass-epoxy composite material subjected to off-axis cyclic loads

    Directory of Open Access Journals (Sweden)

    Revuelta, D.

    2005-03-01

    Full Text Available Most of today s fatigue analysis and design methods for composite laminates were developed primarily on the basis of experience with homogeneous metals. Such methods are subject to serious drawbacks, however, because the failure the modes of failure observed in metals. A theoretical model for predicting the fatigue life of continuous glass-fibre/epoxy composite materials under general loading conditions has been developed on the basis of fundamental fatigue failure modes and local failure criteria.

    La mayoría de los actuales métodos de cálculo y diseño a fatiga de estructuras de materiales compuestos se han desarrollado principalmente a partir de la experiencia previa en materiales metálicos homogéneos. Sin embargo, estos métodos presentan serios inconvenientes debido a que la heterogeneidad y micro estructura orientada características de los materiales compuestos laminados provocan modos de fallo diferentes a los de los metales. Basándose en los modos fundamentales de rotura por fatiga y en criterios de rotura local, se desarrolla un modelo teórico de vida a fatiga para materiales compuestos de matriz epoxi reforzados con fibra de vidrio bajo condiciones generales de carga

  12. [Effects of Lifestyle Intervention on Fatigue, Nutritional Status and Quality of Life in Patients with Gynecologic Cancer].

    Science.gov (United States)

    An, Hyunjin; Nho, Ju Hee; Yoo, Sunyoung; Kim, Hyunmin; Nho, Minji; Yoo, Hojeong

    2015-12-01

    The purpose of this study was to examine the effect of lifestyle intervention on the development of fatigue, nutritional status and quality of life of patients with gynecologic cancer. A nonequivalent control group quasi-experimental design was used. Participants were 49 patients with gynecologic cancer. They were assigned to the experiment group (n=24) or the control group (n=25). The lifestyle intervention for this study consisted of physical activity, nutritional education, telephone call counseling, health counseling, monitoring for lifestyle, and affective support based on Cox's Interaction Model of Client Health Behavior and was implemented for six weeks. Significant group differences were found for fatigue (p =.037), nutritional status (p =.034) and social/family well-being (p =.035) in these patients with gynecologic cancer. Results indicate that this lifestyle intervention is effective in lessening fatigue, and improving nutritional status and social/family well-being. Therefore, nurses in hospitals should develop strategies to expand and provide lifestyle interventions for patients with cancer.

  13. FATIGUE LIFE PREDICTION BASED ON MACROSCOPIC PLASTIC ZONE ON FRACTURE SURFACE OF AISI-SAE 1018 STEEL

    Directory of Open Access Journals (Sweden)

    G.M. Domínguez Almaraz

    2010-06-01

    Full Text Available This paper deals with rotating bending fatigue tests at high speed (150 Hz carried out on AISI-SAE 1018 steel with a high content of impurities (non metallic inclusions, for which the high experimental stress inside the specimen is close to the elastic limit of the material. Simulations of rotating loading are obtained by Visual NASTRAN software in order to determine the numerical stresse and strain distributions inside a hypothetical homogeneous specimen; later, this information is used for the experimental set up. A general description of experimental test machine and experimental conditions are developed and then, the experimental results are presented and discussed according the observed failure origin related to the non metallic inclusions and the associated high stress zones. Finally, a simple model is proposed to predict the fatigue life for this non homogeneous steel under high speed rotating bending fatigue tests close to the elastic limit, based on the rate between the visual macro-plastic deformation zone at fracture surface and the total fracture surface, together with the crack initiation inclusion (or inclusions located at this zone.

  14. Effect of Application of Short and Long Holds on Fatigue Life of Modified 9Cr-1Mo Steel Weld Joint

    Science.gov (United States)

    Shankar, Vani; Mariappan, K.; Sandhya, R.; Mathew, M. D.; Jayakumar, T.

    2013-11-01

    Modified 9Cr-1Mo steel is a heat-treatable steel and hence the microstructure is temperature sensitive. During welding, the weld joint (WJ) is exposed to various temperatures resulting in a complex heterogeneous microstructure across the weld joint, such as the weld metal, heat-affected zone (HAZ) (consisting of coarse-grained HAZ, fine-grained HAZ, and intercritical HAZ), and the unaffected base metal of varying mechanical properties. The overall creep-fatigue interaction (CFI) response of the WJ is hence due to a complex interplay between various factors such as surface oxides and stress relaxation (SR) occurring in each microstructural zone. It has been demonstrated that SR occurring during application of hold in a CFI cycle is an important parameter that controls fatigue life. Creep-fatigue damage in a cavitation-resistant material such as modified 9Cr-1Mo steel base metal is accommodated in the form of microstructural degradation. However, due to the complex heterogeneous microstructure across the weld joint, SR will be different in different microstructural zones. Hence, the damage is accommodated in the form of preferential coarsening of the substructure, cavity formation around the coarsened carbides, and new surface formation such as cracks in the soft heat-affected zone.

  15. Fatigue life analysis of cracked gas receiver of emergency cut-off system in gas gathering station

    Science.gov (United States)

    Hu, Junzhi; Zhou, Jiyong; Li, Siyuan

    2017-06-01

    Small-scale air compressor and gas receiver are used as the driving gas of the emergency cut-off system in gas gathering station. Operation of block valve is ensured by starting and stopping compressor automatically. The frequent start-stop of compressor and the pressure fluctuation pose a threat to the service life of gas receiver, and then affect normal operation of the emergency cut-off system and security of gas gathering station. In this paper, the fatigue life of a pressure vessel with axial semi-elliptical surface crack in the inner wall is analyzed under the varying pressure by means of the theory of fracture mechanics. The influences of the amplitude of pressure fluctuation and the initial crack size on the residual life of gas receiver are discussed. It provides a basis for setting the working parameters of gas receiver of emergency cut-off system and determining the maintenance cycle.

  16. Effect of Fe ion concentration on fatigue life of carbon steel in aqueous CO2 environment

    DEFF Research Database (Denmark)

    Rogowska, Magdalena; Gudme, J.; Rubin, A.

    2016-01-01

    In this work, the corrosion fatigue behaviour of steel armours used in the flexible pipes, in aqueous solutions initially containing different concentrations of Fe2+, was investigated by four-point bending testing under saturated 1 bar CO2 condition. Corrosion fatigue results were supported with ex...... of Fe2+ marginally above the solubility limit of FeCO3 compared to the samples tested in highly supersaturated solution of Fe2+. Results revealed that the impact of the alternating stresses on the corrosion behaviour of samples reduces with lowering the applied stresses. At the stress range of 100 MPa...

  17. Methodology for establishing life curves based on condition monitoring data and expert judgements

    Energy Technology Data Exchange (ETDEWEB)

    Eggen, Arnt Ove; Welte, Thomas; Susa, Dejan

    2010-04-15

    Remaining lifetime and probability of failure of components in the power system are important issues for planning of maintenance and refurbishment. The concept of life curves provides an approach to utilize information about the technical condition (condition states) for modelling component degradation and for calculation of remaining lifetime and failure probability. This technical report describes methodologies for establishing life curves based on condition monitoring data and/or expert judgement. The methodologies presented in this report can be applied for different types of components and failure mechanisms. Thus, life curves provide a generic approach for degradation and lifetime modelling. The report describes methodologies that can be used to established life curves based on different sources of information, such as judgements provided by one or several experts, or condition monitoring data. Furthermore, establishing life curves using a combination of expert judgments and condition monitoring data is also described. Because different failure mechanisms and components are assessed separately by the life curve approach, the report also shows how analysis results can be aggregated. In addition, references are given to tools and software prototypes that can be used to establish the life curves, to calculate failure probability and remaining lifetime, and to aggregate the results. The report also presents a number of examples of life curves for selected components and failure mechanisms. The examples include different components of power transformers and circuit breakers. Furthermore, a study on water tree degraded XLPE cables and case study on wood poles are presented. These examples show the use of the life curve approach and can be used as basis for an own analysis. A file is attached to this report where some of the life curve examples are collected. (Author)

  18. Estimation method for random sonic fatigue life of thin-walled structure of a combustor liner based on stress probability distribution%Estimation method for random sonic fatigue life of thin-walled structure of a combustor liner based on stress probability distribution

    Institute of Scientific and Technical Information of China (English)

    SHA Yun-dong; GUO Xiao-peng; LIAO Lian-fang; XIE Li-juan

    2011-01-01

    As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings, an effective method for predicting the fatigue life of a structure under random loadings was studied. Firstly, the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied, analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution. The formula for calculating Weibull parameters were given. Based on the Miner linear theory, the method for predicting the random sonic fatigue life based on the stress probability density was developed, and the model for fatigue life prediction was constructed. As an example, an aero-engine combustor liner structure was considered. The power spectrum density (PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM (finite element method/boundary element method) model, the fatigue life was estimated by using the constructed model. And considering the influence of the wide frequency band, the calculated results were modified. Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend. The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.

  19. Effect of load ratio and saltwater corrosive environment on the initiation life of fatigue of 10Ni5CrMoV steel

    Science.gov (United States)

    Xie, Xing; Yi, Hong; Xu, Jian; Gen, Liming; Chen, Luyun

    2017-09-01

    Fatigue initiation life has been studied with 10CrNi5MoV steel for use in ocean engineering at different load ratios and in different environmental media. The microstructure and micro-topography have been observed and analyzed by means of SEM, EDS and EBSD. Our findings indicate that, the initiation life of 10Ni5CrMoV steel in seawater is shorter than that in air, and the difference in longevity is larger with the increasing of load ratio. Corrosion pits had a great influence on initial corrosion fatigue life.

  20. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Keisler, J.; Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1995-08-01

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

  1. The effect of music and progressive muscle relaxation on anxiety, fatigue, and quality of life in family caregivers of hospice patients.

    Science.gov (United States)

    Choi, Yoon Kyung

    2010-01-01

    The purpose of this study was to examine the effects of music, progressive muscle relaxation (PMR), and music combined with progressive muscle relaxation on the reduction of anxiety, fatigue, and improvement of quality of life in family hospice caregivers. Subjects (N = 32) were divided randomly into 4 groups: control, music only, progressive muscle relaxation only, and music combined with progressive muscle relaxation and were tested twice a week for a duration of 2 weeks. A pre and posttest measuring anxiety and fatigue was administered each session. Quality of life was measured only on the first and last session. Results of three-way mixed design ANOVA indicated no significant main effect for group. However, results revealed a significant main effect for pretest and posttest on anxiety F(1, 28) = 51.82, p fatigue, F(1, 28) = 32.86, p fatigue F(3, 84) = 5.21, p fatigue (r(32) = .55, p fatigue and quality of life (r(32) = -.53, p < .01).

  2. Translating Oral Health-Related Quality of Life Measures: Are There Alternative Methodologies?

    Science.gov (United States)

    Brondani, Mario; He, Sarah

    2013-01-01

    Translating existing sociodental indicators to another language involves a rigorous methodology, which can be costly. Free-of-charge online translator tools are available, but have not been evaluated in the context of research involving quality of life measures. To explore the value of using online translator tools to develop oral health-related…

  3. Translating Oral Health-Related Quality of Life Measures: Are There Alternative Methodologies?

    Science.gov (United States)

    Brondani, Mario; He, Sarah

    2013-01-01

    Translating existing sociodental indicators to another language involves a rigorous methodology, which can be costly. Free-of-charge online translator tools are available, but have not been evaluated in the context of research involving quality of life measures. To explore the value of using online translator tools to develop oral health-related…

  4. A New Paradigm of Fatigue Variability Behavior and Implications for Life Prediction (Preprint)

    Science.gov (United States)

    2006-06-01

    31] S. Suresh, Fatigue of Materials, Cambridge University Press, 1991. [32] A. S. Beranger, X. Feaugas, and M. Clavel , Mater. Sci. Eng., Vol...A172, p. 31, 1993. [33] X. Feaugas and M. Clavel , Acta Materialia, Vol. 45, p. 2685, 1997. [34] D. L. McDowell, K. Gall, M. F. Horstememyer, and J. Fan

  5. Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

    NARCIS (Netherlands)

    Gordijn, M.S.; Litsenburg, R.R. van; Gemke, R.J.; Huisman, J.; Bierings, M.B.; Hoogerbrugge, P.M.; Kaspers, G.J.L.

    2013-01-01

    BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse. Th

  6. Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

    NARCIS (Netherlands)

    Gordijn, M.S.; Litsenburg, R.R. van; Gemke, R.J.; Huisman, J.; Bierings, M.B.; Hoogerbrugge, P.M.; Kaspers, G.J.L.

    2013-01-01

    BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse.

  7. Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

    NARCIS (Netherlands)

    Gordijn, M.S.; Litsenburg, R.R. van; Gemke, R.J.; Huisman, J.; Bierings, M.B.; Hoogerbrugge, P.M.; Kaspers, G.J.L.

    2013-01-01

    BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse. Th

  8. Further Investigations to Improve the Fatigue Life of the Mirage IIID Wing Main Spar.

    Science.gov (United States)

    1985-01-01

    Airworthiness Division Canberra, Mr. C. Torkington Statutory & State Authorities and Industry Trans-Australia Airlines, Library Qantas Airways Limited ...t No limitations 13. b CQiti toi ath pu rp ot( cin,’ annaarwIr; mwy be twMwcf U’~TtI?’ ciedjoJ a tot 13 14 .onW 16. COSATI Group 2 Fatigue (materials

  9. Research on the Fatigue Property of HFW Pipe Welded Seam and Fatigue Life Forecast Method%HFW钢管焊缝疲劳特性与疲劳寿命预测方法研究

    Institute of Scientific and Technical Information of China (English)

    韩军; 高惠临; 韩新利

    2011-01-01

    受停输启用和供需变动的影响,油气管道的输送压力会发生周期性的变化,疲劳失效问题异常突出.特别是对于含有裂纹缺陷的管道,在疲劳载荷的作用下,若管道的应力强度因子幅超过疲劳裂纹扩展门槛值,裂纹就会发生疲劳扩展.当裂纹扩展到一定程度,超过管道运行压力下所能承受的临界缺陷极限尺寸,管道就会发生疲劳失效,从而影响到管道的使用寿命.采用高频疲劳试验机测试了X80钢级HFW焊管焊缝的疲劳裂纹扩展门槛值与疲劳裂纹扩展速率,结合API 579《适用性评价规范》中推荐的失效评估图技术(FAD)和Miner线性疲劳损伤积累理论,考虑了多种应力比对管道疲劳寿命的影响,建立了双参数HFW管道的疲劳寿命预测方法.%The transportation pressure of oil and gas pipeline can change periodically because of restart and supply change, so the fatigue failure problems stand out exceptionally. Especially for pipeline with crack defect, when the value of stress intensity factor exceeds fatigue crack expansion threshold value under fatigue load, the crack will expand; when crack expansion exceed critical defect extreme dimension under pipeline operation pressure, the fatigue failure of pipeline will happen, this will affect useful life of pipeline. In this article, the fatigue crack expansion threshold value of X80 HFW pipe welded seam and fatigue crack propagation rate were tested by using high-frequency fatigue testing machine, combined with the failure assessment diagram (FAD) recommended in API 579 Fitness-for-service Specification and the Miner's linear cumulative damage theory, considering the effect of combined stress ratio on pipeline fatigue life, the fatigue life forecast method for two-parameter HFW pipeline was established.

  10. Life cycle sustainability of solid oxide fuel cells: From methodological aspects to system implications

    Science.gov (United States)

    Mehmeti, Andi; McPhail, Stephen J.; Pumiglia, Davide; Carlini, Maurizio

    2016-09-01

    This study reviews the status of life cycle assessment (LCA) of Solid Oxide Fuel Cells (SOFCs) and methodological aspects, communicates SOFC environmental performance, and compares the environmental performance with competing power production technologies using a life cycle perspective. Results indicate that power generation using SOFCs can make a significant contribution to the aspired-to greener energy future. Despite superior environmental performance, empirical studies indicate that economic performance is predominantly the highest-ranked criterion in the decision making process. Future LCA studies should attempt to employ comprehensive dynamic multi-criteria environmental impact analysis coupled with economic aspects, to allow a robust comparison of results. A methodology framework is proposed to achieve simultaneously ambitious socio-economic and environmental objectives considering all life cycle stages and their impacts.

  11. The Effect of Group Mindfulness-based Stress Reduction and Consciousness Yoga Program on Quality of Life and Fatigue Severity in Patients with MS

    Directory of Open Access Journals (Sweden)

    Somayeh Nejati

    2016-12-01

    Full Text Available Introduction: The chronic nature of Multiple Sclerosis (MS, have can leave devastating effects on quality of life and fatigue. The present research aimed to study the effect of group Mindfulness-based Stress Reduction (MBSR and conscious yoga program on the quality of life and fatigue severity among patients with MS. Methods: This study was quasi-experimental with intervention and control groups. The statistical population included all members to MS Society of Tehran Province, 24 of whom diagnosed with MS were selected as the sample based on the inclusion criteria. The subjects were randomly assigned into the test group (12 patients and the control group (12 patients. MS Quality of Life-54 (MSQOL-54 and Fatigue Severity Scale (FSS were used for data collection. Subjects in the test group underwent a MBSR and conscious yoga program in 8 two-hour sessions. The data were analyzed using the SPSS ver.13 software. Results: The study findings showed that there was a significant difference between subjects in the experimental and control groups in terms of mean score of some subscales of quality of life including physical health, role limitations due to physical and emotional problems, energy, emotional well-being, health distress, health perception, and satisfaction with sexual function, overall quality of life, and fatigue severity. Conclusion: The results show that the program is effective in reduction of fatigue severity and improving some subscales of quality of life in MS patients. Hence, this supportive method can be used as an effective way for improving quality of life and relieving fatigue in MS patients.

  12. The Effect of Group Mindfulness-based Stress Reduction and Consciousness Yoga Program on Quality of Life and Fatigue Severity in Patients with MS.

    Science.gov (United States)

    Nejati, Somayeh; Rajezi Esfahani, Sepideh; Rahmani, Soheila; Afrookhteh, Gita; Hoveida, Shahrzad

    2016-12-01

    Introduction: The chronic nature of Multiple Sclerosis (MS), have can leave devastating effects on quality of life and fatigue. The present research aimed to study the effect of group Mindfulness-based Stress Reduction (MBSR) and conscious yoga program on the quality of life and fatigue severity among patients with MS. Methods: This study was quasi-experimental with intervention and control groups. The statistical population included all members to MS Society of Tehran Province, 24 of whom diagnosed with MS were selected as the sample based on the inclusion criteria. The subjects were randomly assigned into the test group (12 patients) and the control group (12 patients). MS Quality of Life-54 (MSQOL-54) and Fatigue Severity Scale (FSS) were used for data collection. Subjects in the test group underwent a MBSR and conscious yoga program in 8 two-hour sessions. The data were analyzed using the SPSS ver.13 software. Results: The study findings showed that there was a significant difference between subjects in the experimental and control groups in terms of mean score of some subscales of quality of life including physical health, role limitations due to physical and emotional problems, energy, emotional well-being, health distress, health perception, and satisfaction with sexual function, overall quality of life, and fatigue severity. Conclusion: The results show that the program is effective in reduction of fatigue severity and improving some subscales of quality of life in MS patients. Hence, this supportive method can be used as an effective way for improving quality of life and relieving fatigue in MS patients.

  13. The Effect of Group Mindfulness-based Stress Reduction and Consciousness Yoga Program on Quality of Life and Fatigue Severity in Patients with MS

    Science.gov (United States)

    Nejati, Somayeh; Rajezi Esfahani, Sepideh; Rahmani, Soheila; Afrookhteh, Gita; Hoveida, Shahrzad

    2016-01-01

    Introduction: The chronic nature of Multiple Sclerosis (MS), have can leave devastating effects on quality of life and fatigue. The present research aimed to study the effect of group Mindfulness-based Stress Reduction (MBSR) and conscious yoga program on the quality of life and fatigue severity among patients with MS. Methods: This study was quasi-experimental with intervention and control groups. The statistical population included all members to MS Society of Tehran Province, 24 of whom diagnosed with MS were selected as the sample based on the inclusion criteria. The subjects were randomly assigned into the test group (12 patients) and the control group (12 patients). MS Quality of Life-54 (MSQOL-54) and Fatigue Severity Scale (FSS) were used for data collection. Subjects in the test group underwent a MBSR and conscious yoga program in 8 two-hour sessions. The data were analyzed using the SPSS ver.13 software. Results: The study findings showed that there was a significant difference between subjects in the experimental and control groups in terms of mean score of some subscales of quality of life including physical health, role limitations due to physical and emotional problems, energy, emotional well-being, health distress, health perception, and satisfaction with sexual function, overall quality of life, and fatigue severity. Conclusion: The results show that the program is effective in reduction of fatigue severity and improving some subscales of quality of life in MS patients. Hence, this supportive method can be used as an effective way for improving quality of life and relieving fatigue in MS patients. PMID:28032077

  14. Perceived Quality of Work Life and Risk for Compassion Fatigue Among Oncology Nurses: A Mixed-Methods Study.

    Science.gov (United States)

    Denigris, Jami; Fisher, Kathleen; Maley, MaryKay; Nolan, Elizabeth

    2016-05-01

    To examine factors that influenced the nurse's perceived quality of work life and risk for compassion fatigue (CF). The specific aims of the study were to describe the (a) relationship among nurse characteristics and perceived quality of work life, (b) relationship between personal life stress and perceived quality of work life, and (c) the nurse's beliefs about his or her risk for CF.
. A descriptive, mixed-methods study.
. A hematology-oncology unit in a large urban teaching hospital in Pennsylvania.
. 20 oncology nurses. 
. Descriptive study using questionnaires and in-depth interviews. The variables were nurse characteristics, personal life stress, and quality of work life. Data were analyzed descriptively and thematically. Scores on the self-report questionnaires were compared to themes.
. Personal life stressors, measured by combining the Impact of Events Scale and Life Events Scale, identified powerful or severe impacts on well-being for 30% of nurse respondents in this study, theoretically placing them at risk for CF. However, qualitative data did not complement the results of the Life Events Scale, and 55% of the nurses described their overall work experiences as "life-affirming and rewarding." The participants provided multiple sources of their work-related stress, including subcategories of communication breakdown, work environment/institution, and care-driven factors. 
. Overall, oncology nurses experienced positive reinforcement at work and they had little concern about individual or organizational effectiveness. Positive experiences offset the negative and balanced out the risk for CF.
. The identification of personal and social contributors, as well as solutions to work-related stress, supports the philosophical premises (i.e., conceptual model) that the circumstances that place a nurse at risk for CF are socially constructed. Nurses can achieve greater empathy through self-understanding and translate this learning to patient care.

  15. Stress Analysis and Fatigue Analysis of Front Axle of Heavy-Duty Truck using ANSYS Ncode Design Life for Different Loading Cases

    Directory of Open Access Journals (Sweden)

    Hemant L. Aghav

    2016-06-01

    Full Text Available Front axle of heavy duty truck is the important component of vehicle and needs good design under the various loading conditions of the complete vehicle. Aim of the project is to stress analysis and predict the life of front axle for vertical, and vertical and braking loading case. The fatigue life of front axle is generally estimated by stress life approach and strain life approach method. Front axle beam assembly was modeled in the NX cad software. Meshing and Stress analysis is performed by ANSYS workbench and fatigue analysis is performed by NCODE design life ANSYS tool under different loading cases. Fatigue life of axle obtained by FEA method is more than 2 x 105 cycles, which is considered as safe for vertical loading case. Similarly, Fatigue life of axle obtained is more than 4 x 103 cycles, which is considered as safe for vertical and braking loading case. The max stress region is below spring pad of axle for vertical loading and in the goose neck of axle for vertical and braking loading case

  16. Challenges in implementing a Planetary Boundaries based Life-Cycle Impact Assessment methodology

    DEFF Research Database (Denmark)

    Ryberg, Morten; Owsianiak, Mikolaj; Richardson, Katherine

    2016-01-01

    of resolving the challenges and developing such methodology is discussed. The challenges are related to technical issues, i.e., modelling and including the Earth System processes and their control variables as impact categories in Life-Cycle Impact Assessment and to theoretical considerations with respect...... to the interpretation and use of Life-Cycle Assessment results in accordance with the Planetary Boundary framework. The identified challenges require additional research before a Planetary Boundaries based Life-Cycle Impact Assessment method can be developed. Research on modelling the impacts on Earth System processes......, for a number of processes which are essential for maintaining the Earth System in its present state. Life-Cycle Assessment was identified as a suitable tool for linking human activities to the Planetary Boundaries. However, to facilitate proper use of Life-Cycle Assessment for non-global environmental...

  17. Reliability analysis for aeroengine turbine disc fatigue life with multiple random variables based on distributed collaborative response surface method

    Institute of Scientific and Technical Information of China (English)

    高海峰; 白广忱; 高阳; 鲍天未

    2015-01-01

    The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables, such as applied load, working temperature, geometrical dimensions and material properties. In order to ameliorate reliability analysis efficiency without loss of reliability, the distributed collaborative response surface method (DCRSM) was proposed, and its basic theories were established in this work. Considering the failure dependency among the failure modes, the distributed response surface was constructed to establish the relationship between the failure mode and the relevant random variables. Then, the failure modes were considered as the random variables of system response to obtain the distributed collaborative response surface model based on structure failure criterion. Finally, the given turbine disc structure was employed to illustrate the feasibility and validity of the presented method. Through the comparison of DCRSM, Monte Carlo method (MCM) and the traditional response surface method (RSM), the results show that the computational precision for DCRSM is more consistent with MCM than RSM, while DCRSM needs far less computing time than MCM and RSM under the same simulation conditions. Thus, DCRSM is demonstrated to be a feasible and valid approach for improving the computational efficiency of reliability analysis for aeroengine turbine disc fatigue life with multiple random variables, and has great potential value for the complicated mechanical structure with multi-component and multi-failure mode.

  18. Indentation hardness: A simple test that correlates with the dissipated-energy predictor for fatigue-life in bovine pericardium membranes for bioprosthetic heart valves.

    Science.gov (United States)

    Tobaruela, Almudena; Rojo, Francisco Javier; García Paez, José María; Bourges, Jean Yves; Herrero, Eduardo Jorge; Millán, Isabel; Alvarez, Lourdes; Cordon, Ángeles; Guinea, Gustavo V

    2016-08-01

    The aim of this study was to evaluate the variation of hardness with fatigue in calf pericardium, a biomaterial commonly used in bioprosthetic heart valves, and its relationship with the energy dissipated during the first fatigue cycle that has been shown to be a predictor of fatigue-life (García Páez et al., 2006, 2007; Rojo et al., 2010). Fatigue tests were performed in vitro on 24 pericardium specimens cut in a root-to-apex direction. The specimens were subjected to a maximum stress of 1MPa in blocks of 10, 25, 50, 100, 250, 500, 1000 and 1500 cycles. By means of a modified Shore A hardness test procedure, the hardness of the specimen was measured before and after fatigue tests. Results showed a significant correlation of such hardness with fatigue performance and with the energy dissipated in the first cycle of fatigue, a predictor of pericardium durability. The study showed indentation hardness as a simple and reliable indicator of mechanical performance, one which could be easily implemented in improving tissue selection.

  19. A Study on the Effects on Low Cycle Fatigue Life of a High Pressure Turbine Nozzle due to the Perturbation of Crystal Orientation of Grain of DS Materials

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Korea Aerospace Research Institute, Daejeon (Korea, Republic of)

    2016-07-15

    High pressure components of a gas turbine engine are generally made of nickel-base superalloys, using precision casting process due to complicated geometries with intricate channels and cooling holes. Turbine components manufactured from directionally solidified and single crystal materials have columnar grains; however, it is found that the crystals do not grow in its preferred direction, although the orientation can be controlled. This anisotropy can lead to the variations of elastic and Hill's parameters in constitutive equations, and they alter stress distributions and the low cycle fatigue life. We aims to evaluate the effects of perturbed crystal orientations on the structural integrity of a directionally solidified nozzle using low cycle fatigue life. We also attempt to show the necessity for the control of allowed manufacturing errors and stochastic analysis. Our approaches included conjugate heat transfer and structural analysis, along with low cycle fatigue life assessment.

  20. Multimodal intervention improves fatigue and quality of life in subjects with progressive multiple sclerosis: a pilot study

    Directory of Open Access Journals (Sweden)

    Bisht B

    2015-02-01

    Full Text Available Babita Bisht,1 Warren G Darling,2 E Torage Shivapour,3 Susan K Lutgendorf,4–6 Linda G Snetselaar,7 Catherine A Chenard,1 Terry L Wahls1,8 1Department of Internal Medicine, Carver College of Medicine, University of Iowa, 2Department of Health and Human Physiology, College of Liberal Arts and Sciences, University of Iowa, 3Department of Neurology, Carver College of Medicine, University of Iowa, 4Department of Psychology, College of Liberal Arts and Sciences, University of Iowa, 5Department of Obstetrics and Gynecology, Carver College of Medicine, University of Iowa, 6Department of Urology, Carver College of Medicine, University of Iowa, 7Department of Epidemiology, College of Public Health, University of Iowa, 8Department of Internal Medicine, VA Medical Center, Iowa City, IA, USA Background: Fatigue is a disabling symptom of multiple sclerosis (MS and reduces quality of life. The aim of this study was to investigate the effects of a multimodal intervention, including a modified Paleolithic diet, nutritional supplements, stretching, strengthening exercises with electrical stimulation of trunk and lower limb muscles, and stress management on perceived fatigue and quality of life of persons with progressive MS. Methods: Twenty subjects with progressive MS and average Expanded Disability Status Scale (EDSS score of 6.2 (range: 3.5–8.0 participated in the 12-month phase of the study. Assessments were completed at baseline and at 3 months, 6 months, 9 months, and 12 months. Safety analyses were based on monthly side effects questionnaires and blood analyses at 1 month, 3 months, 6 months, 9 months, and 12 months. Results: Subjects showed good adherence (assessed from subjects' daily logs with this intervention and did not report any serious side effects. Fatigue Severity Scale (FSS and Performance Scales-fatigue subscale scores decreased in 12 months (P<0.0005. Average FSS scores of eleven subjects showed clinically significant reduction (more than

  1. Beyond integrating social sciences: Reflecting on the place of life sciences in empirical bioethics methodologies.

    Science.gov (United States)

    Mertz, Marcel; Schildmann, Jan

    2017-07-21

    Empirical bioethics is commonly understood as integrating empirical research with normative-ethical research in order to address an ethical issue. Methodological analyses in empirical bioethics mainly focus on the integration of socio-empirical sciences (e.g. sociology or psychology) and normative ethics. But while there are numerous multidisciplinary research projects combining life sciences and normative ethics, there is few explicit methodological reflection on how to integrate both fields, or about the goals and rationales of such interdisciplinary cooperation. In this paper we will review some drivers for the tendency of empirical bioethics methodologies to focus on the collaboration of normative ethics with particularly social sciences. Subsequently, we argue that the ends of empirical bioethics, not the empirical methods, are decisive for the question of which empirical disciplines can contribute to empirical bioethics in a meaningful way. Using already existing types of research integration as a springboard, five possible types of research which encompass life sciences and normative analysis will illustrate how such cooperation can be conceptualized from a methodological perspective within empirical bioethics. We will conclude with a reflection on the limitations and challenges of empirical bioethics research that integrates life sciences.

  2. Effect of interaction of embedded crack and free surface on remaining fatigue life

    Directory of Open Access Journals (Sweden)

    Genshichiro Katsumata

    2016-12-01

    Full Text Available Embedded crack located near free surface of a component interacts with the free surface. When the distance between the free surface and the embedded crack is short, stress at the crack tip ligament is higher than that at the other area of the cracked section. It can be easily expected that fatigue crack growth is fast, when the embedded crack locates near the free surface. To avoid catastrophic failures caused by fast fatigue crack growth at the crack tip ligament, fitness-for-service (FFS codes provide crack-to-surface proximity rules. The proximity rules are used to determine whether the cracks should be treated as embedded cracks as-is, or transformed to surface cracks. Although the concepts of the proximity rules are the same, the specific criteria and the rules to transform embedded cracks into surface cracks differ amongst FFS codes. This paper focuses on the interaction between an embedded crack and a free surface of a component as well as on its effects on the remaining fatigue lives of embedded cracks using the proximity rules provided by the FFS codes. It is shown that the remaining fatigue lives for the embedded cracks strongly depend on the crack aspect ratio and location from the component free surface. In addition, it can be said that the proximity criteria defined by the API and RSE-M codes give overly conservative remaining lives. On the contrary, the WES and AME codes always give long remaining lives and non-conservative estimations. When the crack aspect ratio is small, ASME code gives non-conservative estimation.

  3. The Influence of Secondary Bending on Fatigue Life Improvement in Bolted Joints

    Science.gov (United States)

    1993-08-01

    Canberra) ASTA Engineering, Document Control Office Ansett Airlines of Australia, Library Qantas Airways Limit»! . Hawker de Havilland Aast Pty Ltd...320 MPa. The four non-bending specimens were tested at a net-area stress level of 350 MPa only. SPATE (Stress Pattern Analysis by measurement of...Lives A two-way analysis of variance of the fatigue data from the secondary-bending specimens (Table 4) indicated that cold expansion provides a

  4. Factors affecting the corrosion fatigue life in nickel based superalloys for disc applications

    OpenAIRE

    Rosier Hollie; Perkins Karen; Girling Andrew; Leggett Jonathan; Gibson Grant

    2014-01-01

    The nickel based superalloy 720Li is employed in the gas turbine due to its mechanical performance at elevated temperature. A comprehensive assessment of the materials behaviour under representative service conditions is reported to address the drive for ever increasing temperatures and more arduous environmental exposure. Fatigue experiments have been performed in an air and air/SOx environment at 700 ∘C containing a mixed salt as a contaminant. There is an intimate relationship between loca...

  5. The Effect of Residual Stress State in the Notch Root Region Caused by the Hold Period of the Overload to the Fatigue Life

    OpenAIRE

    Anindito Purnowidodo; Ari Wahyudi; Rudy Soenoko; Khairul Anam

    2015-01-01

    In the present study, the effect of the overload together with the hold period of the overload to the fatigue life associating with the crack emerging from the notch root region is investigated because the region is vulnerable to the plastic deformation. The result of the study shows that the fatigue life is affected by the residual stress state in front of the notch root, and the state of the residual stress depends on the constant amplitude load condition following of the overload. The resi...

  6. Analysis of the link between a definition of sustainability and the life cycle methodologies

    DEFF Research Database (Denmark)

    Jørgensen, Andreas; Herrmann, Ivan Tengbjerg; Bjørn, Anders

    2013-01-01

    , is presented and detailed to a level enabling an analysis of the relation to the impact categories at midpoint level considered in life cycle (LC) methodologies.The interpretation of the definition of sustainability as outlined in Our Common Future (WCED 1987) suggests that the assessment of a product......'s sustainability is about addressing the extent to which product life cycles affect poverty levels among the current generation, as well as changes in the level of natural, human and produced and social capital available for the future population. It is shown that the extent to which product life cycles affect...... poverty to some extent is covered by impact categories included in existing SLCA approaches. It is also found that the extent to which product life cycles affect natural capital is well covered by LCA, and human capital is covered by both LCA and SLCA but in different ways. Produced capital is not to any...

  7. Typology of end-of-life priorities in Saudi females: averaging analysis and Q-methodology

    Directory of Open Access Journals (Sweden)

    Hammami MM

    2016-05-01

    Full Text Available Muhammad M Hammami,1,2 Safa Hammami,1 Hala A Amer,1 Nesrine A Khodr1 1Clinical Studies and Empirical Ethics Department, King Faisal Specialist Hospital and Research Centre, 2College of Medicine, Alfaisal University, Riyadh, Saudi Arabia Background: Understanding culture-and sex-related end-of-life preferences is essential to provide quality end-of-life care. We have previously explored end-of-life choices in Saudi males and found important culture-related differences and that Q-methodology is useful in identifying intraculture, opinion-based groups. Here, we explore Saudi females’ end-of-life choices.Methods: A volunteer sample of 68 females rank-ordered 47 opinion statements on end-of-life issues into a nine-category symmetrical distribution. The ranking scores of the statements were analyzed by averaging analysis and Q-methodology.Results: The mean age of the females in the sample was 30.3 years (range, 19–55 years. Among them, 51% reported average religiosity, 78% reported very good health, 79% reported very good life quality, and 100% reported high-school education or more. The extreme five overall priorities were to be able to say the statement of faith, be at peace with God, die without having the body exposed, maintain dignity, and resolve all conflicts. The extreme five overall dis-priorities were to die in the hospital, die well dressed, be informed about impending death by family/friends rather than doctor, die at peak of life, and not know if one has a fatal illness. Q-methodology identified five opinion-based groups with qualitatively different characteristics: “physical and emotional privacy concerned, family caring” (younger, lower religiosity, “whole person” (higher religiosity, “pain and informational privacy concerned” (lower life quality, “decisional privacy concerned” (older, higher life quality, and “life quantity concerned, family dependent” (high life quality, low life satisfaction. Out of the

  8. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

    Science.gov (United States)

    Avery, Katherine R.

    Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

  9. Consequences of variations in spatial turbulence characteristics for fatigue life time of wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, G.C.

    1998-09-01

    The fatigue loading of turbines situated in complex terrain is investigated in order to determine the crucial parameters in the spatial structure of the turbulence in such situations. The parameter study is performed by means of numerical calculations, and it embraces three different wind turbine types, representing a pitch controlled concept, a stall controlled concept, and a stall controlled concept with an extremely flexible tower. For each of the turbine concepts, the fatigue load sensibility to the selected turbulence characteristics are investigated for three different mean wind speeds at hub height. The selected mean wind speeds represent the linear-, the stall-, and the post stall aerodynamic region for the stall controlled turbines and analogously the unregulated-, the partly regulated-, and the fully regulated regime for the pitch controlled turbine. Denoting the turbulence component in the mean wind direction by u, the lateral turbulence component by v, and the vertical turbulence component by w, the selected turbulence characteristics comprise the u-turbulence length scale, the ratio between the v- and w-turbulence intensities and the u-turbulence intensity, the uu-coherence decay factor, and finally the u-v and u-w cross-correlations. The turbulence length scale in the mean wind direction gives rise to significant modification of the fatigue loading on all the investigated wind turbine concepts, but for the other selected parameter variations, large individual differences exists between the turbines. With respect to sensitivity to the performed parameter variations, the Vestas V39 wind turbine is the most robust of the investigated turbines. The Nordtank 500/37 turbine, equipped with the (artificial) soft tower, is by far the most sensitive of the investigated turbine concepts - also much more sensitive than the conventional Nordtank 500/37 turbine equipped with a traditional tower. (au) 2 tabs., 43 ills., 7 refs.

  10. The effect of group mindfulness - based stress reduction program and conscious yoga on the fatigue severity and global and specific life quality in women with breast cancer.

    Science.gov (United States)

    Rahmani, Soheila; Talepasand, Siavash

    2015-01-01

    Cancer is not merely an event with a certain end, but it is a permanent and vague situation that is determined by delayed effects due to the disease, its treatment and its related psychological issues. The aim of this study was to examine the effectiveness of the mindfulness-based stress reduction program and conscious yoga on the mental fatigue severity and life quality of women with breast cancer. This was a quasi-experimental study with a pre-test, post-test and control group. In this study, 24 patients with the diagnosis of breast cancer were selected among the patients who referred to the Division of Oncology and Radiotherapy of Imam Hossein hospital in Tehran using available sampling method, and were randomly assigned into the experimental and control groups. All the participants completed the Fatigue Severity Scale, Global Life Quality of Cancer Patient and Specific Life Quality of Cancer Patient questionnaires. Data were analyzed by multivariate repeated measurement variance analysis model. Findings revealed that the mindfulness-based stress reduction treatment significantly improved the overall quality of life, role, cognitive, emotion, social functions and pain and fatigue symptoms in global life quality in the experimental group. It also significantly improved the body image, future functions and therapy side effects in specific life quality of the experimental group compared to the control group. In addition, fatigue severity caused by cancer was reduced significantly. The results showed that the mindfulness - based stress reduction treatment can be effective in improving global and specific life quality and fatigue severity in women with breast cancer.

  11. Long-Term Fatigue Life Expenditure of Turbine Shafts Owing to Noncharacteristic Harmonics Produced by Slip Energy Recovery Induction Motor Drives

    Science.gov (United States)

    Tsai, Jong-Ian

    In this paper, the long-term effect of noncharacteristic harmonics resulting from a slip energy recovery induction motor drive (SERIMD) on the fatigue life expenditure of turbine-generator shafts is analyzed. A feed-water pump (FP) in power plants is one of the most essential pieces of auxiliary equipment and consumes considerably large quantities of energy. An SERIMD has many advantages and is an adequate candidate for the purpose of variable speed control. However, it gives rise to sustainable variable frequency subharmonics which induce electromechanical subsynchronous oscillations in turbine shafts through proposed deductions. Accordingly, the author has determined that the long-term effect of these subharmonics is a cause of fatigue damage on turbine shafts even under normal operating conditions through fatigue life estimation.

  12. Fatigue Performance and Fatigue Life Prediction of Aluminum Resistance Spot Welded Tensile Shear Specimen%铝合金点焊拉剪接头疲劳性能及寿命分析

    Institute of Scientific and Technical Information of China (English)

    石燕栋; 郭海丁

    2014-01-01

    Fatigue performance of spot welds of aluminum alloy AA5754 was investigated experi-mentally herein .Fatigue failure mode of spot welded tensile shear specimen was discussed and fatigue crack growth path was also explored .Theoretical crack growth angle was determined for tensile shear specimen ,which was under mix mode I/II loading ,and results were verified by measured angles of failed specimens .Local stress intensity factor at nugget circumference was derived ,modified by actual fatigue crack length in sheet thickness and treated as a fatigue parameter K(i) in fatigue data correla-tion .The proposed fatigue delete parameter is proven efficient in correlating fatigue data and can be used for fatigue life prediction of aluminum resistance spot welds .%研究了铝合金A A 5754点焊拉剪接头的疲劳性能,获得了不同厚度试件的载荷寿命曲线。研究了铝合金焊点的疲劳失效模式,讨论了焊点疲劳裂纹的扩展形式,并测量了裂纹扩展路径与点焊熔核界面之间的角度。分析了点焊拉剪试件在同时承受I型和II型载荷时,疲劳裂纹的扩展方向,并与测量值进行了比较。利用疲劳破坏后沿铝板厚度方向的实际裂纹长度修正了裂纹尖端的局部应力强度因子,提出了评价焊点寿命的疲劳参量 K (i),并对试验数据进行了分析比较。结果证明 K (i)可以有效关联试件尺寸效应和焊点疲劳寿命,能够用于预测焊点疲劳寿命。

  13. Motor, psychiatric and fatigue features associated with nutritional status and its effects on quality of life in Parkinson's disease patients.

    Directory of Open Access Journals (Sweden)

    Seyed-Mohammad Fereshtehnejad

    Full Text Available OBJECTIVES: Parkinson's disease (PD patients are more likely to develop impaired nutritional status because of the symptoms, medications and complications of the disease. However, little is known about the determinants and consequences of malnutrition in PD. This study aimed to investigate the association of motor, psychiatric and fatigue features with nutritional status as well as the effects of malnutrition on different aspects of quality of life (QoL in PD patients. METHODS: One hundred and fifty patients with idiopathic PD (IPD were recruited in this study. A demographic checklist, the Unified Parkinson's Disease Rating Scale (UPDRS, the Hospital Anxiety and Depression Scale (HADS and the Fatigue Severity Scale (FSS were completed through face-to-face interviews and clinical examinations. The health-related QoL (HRQoL was also evaluated by means of the Parkinson's Disease Questionnaire (PDQ-39. For evaluation of nutritional status, the Mini Nutritional Assessment (MNA questionnaire was applied together with anthropometric measurements. RESULTS: Thirty seven (25.3% patients were at risk of malnutrition and another 3 (2.1% were malnourished. The total score of the UPDRS scale (r =  -0.613, P<0.001 and PD duration (r =  -0.284, P = 0.002 had a significant inverse correlation with the total MNA score. The median score of the Hoehn and Yahr stage was significantly higher in PD patients with abnormal nutritional status [2.5 vs. 2.0; P<0.001]. More severe anxiety [8.8 vs. 5.9; P = 0.002], depression [9.0 vs. 3.6; P<0.001] and fatigue [5.4 vs. 4.2; P<0.001] were observed in PD patients with abnormal nutritional status. Except for stigma, all other domains of the PDQ-39 were significantly correlated with the total score of the MNA. CONCLUSION: Our study demonstrates that disease duration, severity of motor and psychiatric symptoms (depression, anxiety and fatigue are associated with nutritional status in PD. Different aspects of the HRQoL were

  14. A critical review of fracture mechanics as a tool for multiaxial fatigue life prediction of plastics1

    Directory of Open Access Journals (Sweden)

    Anders Winkler

    2015-07-01

    of crack initiation, as well as the use of fracture mechanics for multiaxial fatigue life prediction of injectionmoulded plastics. Numerical tools have been utilised alongside experimental experience and public domain data to offer what we hope will be a contemporary overview, and offer an outlook for future research into the matter

  15. TiNi-based films for elastocaloric microcooling— Fatigue life and device performance

    Science.gov (United States)

    Ossmer, H.; Chluba, C.; Kauffmann-Weiss, S.; Quandt, E.; Kohl, M.

    2016-06-01

    The global trend of miniaturization and concomitant increase of functionality in microelectronics, microoptics, and various other fields in microtechnology leads to an emerging demand for temperature control at small scales. In this realm, elastocaloric cooling is an interesting alternative to thermoelectrics due to the large latent heat and good down-scaling behavior. Here, we investigate the elastocaloric effect due to a stress-induced phase transformation in binary TiNi and quaternary TiNiCuCo films of 20 μm thickness produced by DC magnetron sputtering. The mesoscale mechanical and thermal performance, as well as the fatigue behavior are studied by uniaxial tensile tests combined with infrared thermography and digital image correlation measurements. Binary films exhibit strong features of fatigue, involving a transition from Lüders-like to homogeneous transformation behavior within three superelastic cycles. Quaternary films, in contrast, show stable Lüders-like transformation without any signs of degradation. The elastocaloric temperature change under adiabatic conditions is -15 K and -12 K for TiNi and TiNiCuCo films, respectively. First-of-its-kind heat pump demonstrators are developed that make use of out-of-plane deflection of film bridges. Owing to their large surface-to-volume ratio, the demonstrators reveal rapid heat transfer. The TiNiCuCo-based devices, for instance, generate a temperature difference of 3.5 K within 13 s. The coefficients of performance of the demonstrators are about 3.

  16. Development of a life time assessment method for power plant components subjected to complex multiaxial fatigue loadings; Entwicklung einer Methode zur Lebensdauerbewertung von Kraftwerkskomponenten bei komplexer mehrachsiger Schwingbeanspruchung

    Energy Technology Data Exchange (ETDEWEB)

    Fesich, Thomas M. [Stuttgart Univ. (Germany). Inst. fuer Materialpruefung, Werkstoffkunde und Festigkeitslehre

    2012-11-01

    Technical components are loaded by forces and moments that can be constant or dynamic. Therefore multi-axial loadings can develop dependent on load and/or geometry of the component. The evaluation of multi-axial loadings is still not solved, mainly because the time dependent stresses can cause in complex loading states. Since in contrary to static failures no significant changes of material characteristics are observable in case of fatigue failures a sufficiently accurate lifetime assessment is of main importance. In nuclear engineering the components are mostly individual constructions that need the demonstration of fatigue resistance in the frame of a local fatigue analysis. For the materials side the Woehler curve is sufficient since representative component test would not be economic. The national standards include guidelines for the determination of reference values for complex fatigue loadings that are very conservative or only applicable for definite tasks. The presented of an advanced integrated multi-axial fatigue life concept is an experimentally verified technique that allows a realistic evaluation of the multi-axial loading of components and lifetime assessment based on the so called fatigue damage parameter.

  17. Interval Solution for Nonlinear Programming of Maximizing the Fatigue Life of V-Belt under Polymorphic Uncertain Environment

    Directory of Open Access Journals (Sweden)

    Zhong Wan

    2013-01-01

    Full Text Available In accord with the practical engineering design conditions, a nonlinear programming model is constructed for maximizing the fatigue life of V-belt drive in which some polymorphic uncertainties are incorporated. For a given satisfaction level and a confidence level, an equivalent formulation of this uncertain optimization model is obtained where only interval parameters are involved. Based on the concepts of maximal and minimal range inequalities for describing interval inequality, the interval parameter model is decomposed into two standard nonlinear programming problems, and an algorithm, called two-step based sampling algorithm, is developed to find an interval optimal solution for the original problem. Case study is employed to demonstrate the validity and practicability of the constructed model and the algorithm.

  18. Regionalized life cycle assessment: computational methodology and application to inventory databases.

    Science.gov (United States)

    Mutel, Christopher L; Hellweg, Stefanie

    2009-08-01

    Life cycle assessment (LCA) studies have shown that site-dependent impact assessment for categories like acidification and eutrophication give more accurate and realistic results than site-generic assessments. To date, existing geography-specific, or regionalized, impact assessment factors have not been applied to LCA databases and software tools. We describe a simple, generic methodology to couple existing regionalized characterization factors with large life cycle inventory databases. This approach allows for detailed geographic life cycle impact assessment results. Case-study results for European country-specific electricity mixes are calculated using the Ecoinvent 2.01 database and the EDIP 2003 and Accumulated Exceedance impact assessment methods and CASES project external energy cost characterization factors. In most cases, regionalization shows different total scores, different processes of high importance, and varying geographic distributions of environmental impacts. As the methodology requires no additional input other than the geographic information already in existing LCA databases, it can be used routinely. Better and more consistent geographic information in life cycle inventory databases and impact assessment methods, tailored to the specific spatial range of all environmental effects considered, would be beneficial.

  19. Pain in People with Multiple Sclerosis: Associations with Modifiable Lifestyle Factors, Fatigue, Depression, Anxiety, and Mental Health Quality of Life

    Directory of Open Access Journals (Sweden)

    Claudia H. Marck

    2017-09-01

    Full Text Available BackgroundPeople with multiple sclerosis (MS often experience pain, which can interfere with mobility, employment, and quality of life (QOL.MethodsThis cross-sectional study explored associations between pain, demographic, disease, and modifiable lifestyle factors in an international sample of people with MS recruited online.ResultsSubstantial pain, of moderate/severe intensity and interfering at least moderately with work/household or enjoyment of life in the past 4 weeks, was reported by 682/2,362 (28.9%. Substantial pain was associated with fatigue (odds ratio (OR: 6.7, 95% confidence interval (CI: 4.9,9.3, depression (OR:4.0, 95% CI:3.2,5.1, anxiety (OR:2.4, 95% CI:1.9,2.9, and lower mental health QOL (Mean Difference: −14.7, 95% CI:−16.6,−12.8. Regression analyses showed that smoking (OR: 2.0, 95% CI:1.35,2.87 and obesity (OR:2.1, 95% CI: 1.5,2.8, moderate alcohol use (OR: 0.7, 95% CI:0.5,0.9, moderate (OR 0.7, 95% CI: 0.55,0.98 or high (OR 0.6, 95% CI: 0.4,0.8 physical activity level, and healthy diet (OR 0.8, 95% CI: 0.75,0.95, per 10 points were associated with substantial pain.ConclusionOur results show clear associations with modifiable lifestyle factors and substantial pain in MS. These factors are already considered in the prevention and management of pain in other populations but have not previously been considered in MS. Conversely, pain and associated common MS comorbidities, such as depression, anxiety, and fatigue, may hamper efforts to start or maintain healthy behaviors. Strategies to overcome these barriers need to be considered. Further research should clarify the direction of these associations.

  20. Associations between nausea, vomiting, fatigue and health-related quality of life of women in early pregnancy: The generation r study

    NARCIS (Netherlands)

    G. Bai (Guannan); I.J. Korfage (Ida); E.H.D. Hafkamp-De Groen (Esther); V.W.V. Jaddoe (Vincent); Mautner, E. (Eva); H. Raat (Hein)

    2016-01-01

    textabstractThe objective of this study was to evaluate the independent associations between nausea, vomiting, fatigue and health-related quality of life of women in early pregnancy in the Generation R study, which is a prospective mother and child cohort. Analyses were based on 5079 women in early

  1. Androgen deficiency in male patients diagnosed with ANCA-associated vasculitis : A cause of fatigue and reduced health-related quality of life?

    NARCIS (Netherlands)

    Tuin, Janneke; Sanders, Jan-Stephan F.; Buhl, Birgit M.; van Beek, Andre P.; Stegeman, Coen A.

    2013-01-01

    Introduction: Low testosterone levels in men are associated with fatigue, limited physical performance and reduced health-related quality of life (HRQOL); however, this relationship has never been assessed in patients with anti-neutrophil cytoplasmic antibodies (ANCA) -associated vasculitides (AAV).

  2. Investigating epigenetic consequences of early-life adversity: some methodological considerations

    Directory of Open Access Journals (Sweden)

    Laura M. Fiori

    2016-11-01

    Full Text Available Stressful and traumatic events occurring during early childhood have been consistently associated with the development of psychiatric disorders later in life. This relationship may be mediated in part by epigenetic mechanisms, such as DNA methylation, which are influenced by the early-life environment. Epigenetic patterns can have lifelong effects on gene expression and on the functioning of biological processes relevant to stress reactivity and psychopathology. Optimization of epigenetic research activity necessitates a discussion surrounding the methodologies used for DNA methylation analysis, selection of tissue sources, and timing of psychological and biological assessments. Recent studies related to early-life adversity and methylation, including both candidate gene and epigenome-wide association studies, have drawn from the variety of available techniques to generate interesting data in the field. Further discussion is warranted to address the limitations inherent to this field of research, along with future directions for epigenetic studies of adversity-related psychopathology.

  3. Optimization Parameters of tool life Model Using the Taguchi Approach and Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Kompan Chomsamutr

    2012-01-01

    Full Text Available The objective of this research is to compare the cutting parameters of turning operation the work pieces of medium carbon steel (AISI 1045 by finding the longest tool life by Taguchi methods and Response Surface Methodology: RSM. This research is to test the collecting data by Taguchi method. The analyses of the impact among the factors are the depth of cut, cutting speed and feed rate. This research found that the most suitable response value; and tool life methods give the same suitable values, i.e. feed rate at 0.10 mm/rev, cutting speed at 150 m/min, and depth of cut at 0.5 mm, which is the value of longest tool life at 670.170 min, while the average error is by RSM at the percentage of 0.07 as relative to the testing value.

  4. Natalizumab treatment reduces fatigue in multiple sclerosis. Results from the TYNERGY trial; a study in the real life setting

    DEFF Research Database (Denmark)

    Svenningsson, Anders; Falk, Eva; Celius, Elisabeth G;

    2013-01-01

    Fatigue is a significant symptom in multiple sclerosis (MS) patients. First-generation disease modifying therapies (DMTs) are at best moderately effective to improve fatigue. Observations from small cohorts have indicated that natalizumab, an antibody targeting VLA-4, may reduce MS-related fatigue...

  5. Experimental Damage Criterion for Static and Fatigue Life Assessment of Commercial Aluminum Alloy Die Castings

    Science.gov (United States)

    Battaglia, Eleonora; Bonollo, Franco; Ferro, Paolo

    2017-05-01

    Defects, particularly porosity and oxides, in high-pressure die casting can seriously compromise the in-service behavior and durability of products subjected to static or cyclic loadings. In this study, the influence of dimension, orientation, and position of casting defects on the mechanical properties of an AlSi12(b) (EN-AC 44100) aluminum alloy commercial component has been studied. A finite element model has been carried out in order to calculate the stress distribution induced by service loads and identify the crack initiation zones. Castings were qualitatively classified on the basis of porosities distribution detected by X-ray technique and oxides observed on fracture surfaces of specimens coming from fatigue and tensile tests. A damage criterion has been formulated which considers the influence of defects position and orientation on the mechanical strength of the components. Using the proposed damage criterion, it was possible to describe the mechanical behavior of the castings with good accuracy.

  6. A demand-centered, hybrid life-cycle methodology for city-scale greenhouse gas inventories.

    Science.gov (United States)

    Ramaswami, Anu; Hillman, Tim; Janson, Bruce; Reiner, Mark; Thomas, Gregg

    2008-09-01

    Greenhouse gas (GHG) accounting for individual cities is confounded by spatial scale and boundary effects that impact the allocation of regional material and energy flows. This paper develops a demand-centered, hybrid life-cycle-based methodology for conducting city-scale GHG inventories that incorporates (1) spatial allocation of surface and airline travel across colocated cities in larger metropolitan regions, and, (2) life-cycle assessment (LCA) to quantify the embodied energy of key urban materials--food, water, fuel, and concrete. The hybrid methodology enables cities to separately report the GHG impact associated with direct end-use of energy by cities (consistent with EPA and IPCC methods), as well as the impact of extra-boundary activities such as air travel and production of key urban materials (consistent with Scope 3 protocols recommended by the World Resources Institute). Application of this hybrid methodology to Denver, Colorado, yielded a more holistic GHG inventory that approaches a GHG footprint computation, with consistency of inclusions across spatial scale as well as convergence of city-scale per capita GHG emissions (approximately 25 mt CO2e/person/year) with state and national data. The method is shown to have significant policy impacts, and also demonstrates the utility of benchmarks in understanding energy use in various city sectors.

  7. Life prediction methodology for ceramic components of advanced vehicular heat engines: Volume 1. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Khandelwal, P.K.; Provenzano, N.J.; Schneider, W.E. [Allison Engine Co., Indianapolis, IN (United States)

    1996-02-01

    One of the major challenges involved in the use of ceramic materials is ensuring adequate strength and durability. This activity has developed methodology which can be used during the design phase to predict the structural behavior of ceramic components. The effort involved the characterization of injection molded and hot isostatic pressed (HIPed) PY-6 silicon nitride, the development of nondestructive evaluation (NDE) technology, and the development of analytical life prediction methodology. Four failure modes are addressed: fast fracture, slow crack growth, creep, and oxidation. The techniques deal with failures initiating at the surface as well as internal to the component. The life prediction methodology for fast fracture and slow crack growth have been verified using a variety of confirmatory tests. The verification tests were conducted at room and elevated temperatures up to a maximum of 1371 {degrees}C. The tests involved (1) flat circular disks subjected to bending stresses and (2) high speed rotating spin disks. Reasonable correlation was achieved for a variety of test conditions and failure mechanisms. The predictions associated with surface failures proved to be optimistic, requiring re-evaluation of the components` initial fast fracture strengths. Correlation was achieved for the spin disks which failed in fast fracture from internal flaws. Time dependent elevated temperature slow crack growth spin disk failures were also successfully predicted.

  8. Quality of life, depression and fatigue among persons co-infected with HIV and hepatitis C: outcomes from a population-based cohort.

    Science.gov (United States)

    Braitstein, P; Montessori, V; Chan, K; Montaner, J S G; Schechter, M T; O'Shaughnessy, M V; Hogg, R S

    2005-05-01

    The objective of the study was to describe the additional burden generated by hepatitis C (HCV) infection among HIV-infected individuals as measured by self-reported quality of life, depression and fatigue. The provincial HIV/AIDS Drug Treatment Program (DTP) distributes all antiretroviral medication in the province of British Columbia. Eligibility for accessing antiretrovirals is based on published guidelines commensurate with the International AIDS Society. Each participant is asked to complete a self-administered mailed questionnaire that includes patient sociodemographic information, quality of life measures (Medical Outcomes Study-Short Form (MOS-SF), mental health issues (Centre for Epidemiological Studies Depression scale (CESD) and fatigue information. HIV-HCV co-infected individuals were compared to HIV mono-infected individuals using parametric and nonparametric methods. Multivariate logistic regression was used to examine the impact of hepatitis C on quality of life, depression and fatigue, after controlling for sociodemographics and HIV-specific clinical characteristics. Of the 4,134 individuals who were sent a HIV/AIDS DTP survey in 1999, 2000 or 2001, 484 participants both returned one and had an HCV-antibody test result on file. Of the 484 participants eligible for this analysis, 105 (22%) were HCV-positive. In comparison to the 379 (78%) patients testing negative for HCV, a larger proportion of co-infected patients were female (18% versus 3%, plife. However, using multivariate modeling, it was determined that the impact of HCV on quality of life, depression and fatigue was better explained by the sociodemographic factors related to poverty and injection drug use, than by HCV itself. In conclusion, individuals co-infected with HIV and HCV represent a patient population with significant physical and mental health challenges. Although these patients experience poorer quality of life, increased depression and fatigue, this experience appears to be

  9. SPENVIS Implementation of End-of-Life Solar Cell Calculations Using the Displacement Damage Dose Methodology

    Science.gov (United States)

    Walters, Robert; Summers, Geoffrey P.; Warmer. Keffreu J/; Messenger, Scott; Lorentzen, Justin R.; Morton, Thomas; Taylor, Stephen J.; Evans, Hugh; Heynderickx, Daniel; Lei, Fan

    2007-01-01

    This paper presents a method for using the SPENVIS on-line computational suite to implement the displacement damage dose (D(sub d)) methodology for calculating end-of-life (EOL) solar cell performance for a specific space mission. This paper builds on our previous work that has validated the D(sub d) methodology against both measured space data [1,2] and calculations performed using the equivalent fluence methodology developed by NASA JPL [3]. For several years, the space solar community has considered general implementation of the D(sub d) method, but no computer program exists to enable this implementation. In a collaborative effort, NRL, NASA and OAI have produced the Solar Array Verification and Analysis Tool (SAVANT) under NASA funding, but this program has not progressed beyond the beta-stage [4]. The SPENVIS suite with the Multi Layered Shielding Simulation Software (MULASSIS) contains all of the necessary components to implement the Dd methodology in a format complementary to that of SAVANT [5]. NRL is currently working with ESA and BIRA to include the Dd method of solar cell EOL calculations as an integral part of SPENVIS. This paper describes how this can be accomplished.

  10. Fatigue Life Prediction for 45 Steel with Given Survivability%给定存活率下45钢的疲劳寿命估算

    Institute of Scientific and Technical Information of China (English)

    刘嘉; 李静; 杨友社; 李强; 张忠平

    2011-01-01

    基于临界损伤原理,在以损伤应变范围作为金属材料疲劳裂纹萌生寿命控制参量的基础上,推导了一个新的疲劳裂纹萌生寿命(Fatigue Crack Initation Life,FCIL)估算模型,并给出了模型中始裂抗力系数和始裂门槛值与金属拉伸性能参数之间的关系.与郑氏公式不同,新的FCIL估算模型中疲劳延性指数不恒等于-0.5,而是一个材料常数,用以反映材料抵抗疲劳破坏的能力.以新的FCIL估算模型为基础,建立了含缺口45钢具有给定存活率的疲劳寿命预测公式(PSN曲线公式).与基于郑氏公式的PSN公式相比,新的PSN曲线公式可以更为准确地预测45钢具有给定存活率的疲劳寿命.%Based on the critical damage principle, a new prediction model for fatigue crack initiation life (FCIL) is developed through taking the cyclic damage strain range as the damage parameter. Correlations between the mono-tonic tensile data and two of the material constants (the stress fatigue - resisting coefficient and the theoretical fatigue threshold) in the proposed FCIL prediction model are founded as well. In contrast to Zhengs model, the fatigue ductility exponent contained in the proposed FCIL prediction model is a material constant which doesn't identically equal to the constant value -0.5. Besides, the fatigue ductility exponent shows the damage resistance ability of the material. The expressions of fatigue life curves with given survivability ( PSN curves) for 45 steel notched specimen are developed on the basis of the proposed FCIL predication model. In comparison with the Zhengs model - based PSN curves, the new PSN curves can be used to predict the fatigue life with given survivability of 45 steel better.

  11. Structural health monitoring for fatigue life prediction of orthotropic brdige decks

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Pahlavan, P.L.; Paulissen, J.H.; Hakkesteegt, H.C.; Jansen, T.H.

    2013-01-01

    Infrastructure asset owners are more and more confronted with structures reaching the end of their structural life. Structural Health Monitoring (SHM) systems should provide up-to-date information about the actual condition, as well predict the structural life and required maintenance of the assets

  12. Effect of Thermal Shock Process in Accelerated Environment Spectrum on the Fatigue Life of 7B04-T6 Aluminum Alloy

    Institute of Scientific and Technical Information of China (English)

    CUI Tengfei; LIU Daoxin; ZHANG Xiaohua; YU Shouming

    2016-01-01

    The effect of thermal shock, in an accelerated-corrosion environment spectrum, on the fatigue and corrosion behavior of 7B04-T6 aluminum alloy, was determined. The environment spectrum consists of two modules, namely: salt-spray corrosion and thermal shock. The effect of thermal shock on the mechanical properties was determined via tensile tests; SEM, DCS, and XRD were used to determine the effect of thermal shock on the corrosion products. In addition, the corrosion resistance of the products was ascertained through electrochemical testing. The results show that the mechanical properties and fatigue life of the aluminum alloy will decline with prolonged thermal shock time. The thermal shock process may result in denser surface corrosion products than those formed on the no thermal shock specimens, and transformation of some Al (OH)3 into AlOOH. AlOOH may have resulted in improved corrosion resistance and hence a lower decrease in the fatigue life after corrosion, compared with that of the no thermal shock specimen. Repeated corrosion/thermal shock may have delayed further decease in the fatigue life. Therefore, selection of an appropriate equivalent thermal shock temperature and time was essential for designing the environmental spectrum.

  13. FATIGUE LIFE, MORPHOLOGICAL STUDIES, AND THERMAL AGING OF RATTAN POWDER-FILLED NATURAL RUBBER COMPOSITES AS A FUNCTION OF FILLER LOADING AND A SILANE COUPLING AGENT

    Directory of Open Access Journals (Sweden)

    Hanafi Ismail,

    2012-01-01

    Full Text Available Fatigue life, morphological studies, and thermal aging properties of rattan powder-filled natural rubber (NR composites were investigated as a function of filler loading and a silane coupling agent. NR composites were prepared by the incorporation of rattan powder in the range of 0 to 30 phr into a NR matrix with a laboratory size two roll mill. Thermal aging was carried out for 7 and 14 days at a temperature of 70 °C, and tensile testing was performed in order to determine the aging properties. The results indicated that the fatigue life of rattan powder-filled NR composites decreased with increasing rattan powder loading. Tensile strength and elongation at break decreased whilst tensile modulus, stress at 100% elongation (M100, and stress at 300% elongation (M300 increased after aging. Nevertheless, the addition of the silane coupling agent improved both fatigue life and the aging properties of NR composites due to better adhesion between the rubber matrix and the rattan filler which was confirmed by FTIR studies of composites and SEM studies of fatigue fractured surfaces.

  14. Research on Analysis Method of Gear Fatigue Life and Reliability%齿轮弯曲疲劳寿命及可靠性分析研究

    Institute of Scientific and Technical Information of China (English)

    侯凤国

    2012-01-01

    Gears are the key components in Transmission system and cheir fatigue life and reliability is very important. In this paper, the gear fatigue life estimation and its reliability are studied by the nominal load method. The metal gear material is defined as structural steel materials, and given the gear load spectrum the study of the gear fatigue life is completed based on the fatigue damage theory Miner.%齿轮是传动系统中的关键部件,对其疲劳寿命及可靠性研究非常重要.采用了名义载荷法完成齿轮疲劳寿命的估算并对其可靠性进行研究.将齿轮材料属性定义为结构钢,给定齿轮工作载荷谱,并基于疲劳损伤理论Miner,完成时齿轮疲劳寿命的研究.

  15. Impact of partial versus whole breast radiation therapy on fatigue, perceived stress, quality of life and natural killer cell activity in women with breast cancer

    Directory of Open Access Journals (Sweden)

    Albuquerque Kevin

    2012-06-01

    Full Text Available Abstract Introduction This pilot study used a prospective longitudinal design to compare the effect of adjuvant whole breast radiation therapy (WBRT versus partial breast radiation therapy (PBRT on fatigue, perceived stress, quality of life and natural killer cell activity (NKCA in women receiving radiation after breast cancer surgery. Methods Women (N = 30 with early-stage breast cancer received either PBRT, Mammosite brachytherapy at dose of 34 Gy 10 fractions/5 days, (N = 15 or WBRT, 3-D conformal techniques at dose of 50 Gy +10 Gy Boost/30 fractions, (N = 15. Treatment was determined by the attending oncologist after discussion with the patient and the choice was based on tumor stage and clinical need. Women were assessed prior to initiation of radiation therapy and twice after completion of radiation therapy. At each assessment, blood was obtained for determination of NKCA and the following instruments were administered: Perceived Stress Scale (PSS, Functional Assessment of Cancer Therapy-Fatigue (FACT-F, and Functional Assessment of Cancer Therapy-General (FACT-G. Hierarchical linear modeling (HLM was used to evaluate group differences in initial outcomes and change in outcomes over time. Results Fatigue (FACT-F levels, which were similar prior to radiation therapy, demonstrated a significant difference in trajectory. Women who received PBRT reported progressively lower fatigue; conversely fatigue worsened over time for women who received WBRT. No difference in perceived stress was observed between women who received PBRT or WBRT. Both groups of women reported similar levels of quality of life (FACT-G prior to initiation of radiation therapy. However, HLM analysis revealed significant group differences in the trajectory of quality of life, such that women receiving PBRT exhibited a linear increase in quality of life over time after completion of radiation therapy; whereas women receiving WBRT showed a decreasing

  16. New Methodology in Life Cycle Impact Assessment (LCIA) of waste water treatment

    DEFF Research Database (Denmark)

    Larsen, Henrik Fred; Wenzel, Henrik; Hauschild, Michael

    chose among different waste water treatments? Which ones are most beneficial in a holistic perspective? Here, the life cycle assessment (LCA) approach as a decision supporting tool may help because its goal is to allow quantification and direct comparison of characteristics as diverse as energy...... EU research project "NEPTUNE" focusing on nutrient recycling, micro-pollutants and ecotoxicity removal, energy production, and reuse of sludge and of its resources, this paper will present the first results of the development of a new methodology for assessing advances in wastewater treatment...

  17. STATE INSPECTION METHODOLOGY OF ENVIRONMENTAL REGULATORY ACTIVITY FOCUSED ON THE LIFE CYCLE PROCESSESES

    Directory of Open Access Journals (Sweden)

    Yuniey Quiala Armenteros

    2016-10-01

    Full Text Available The Cuban Environmental Regulatory Activity has on the Environmental State Inspection an instrument for control and monitoring of compliance of current legal standards regarding environmental protection and rational use of natural resources. In this research, a design methodology for effective implementation of environmental regulatory activity in Cuba directed to processes is proposed; based on the life cycle assessment and the applicable environmental management standards, including new performance indicators, which form a new tool based on scientific criterions for the Center of Environmental Inspection and Control.

  18. 航空航天轴承接触疲劳寿命分析%Analysis on Contact Fatigue Life of Aerospace Bearing

    Institute of Scientific and Technical Information of China (English)

    张明; 李志勇; 崔帅; 冯蕴雯

    2012-01-01

    A method of analyzing and calculating contact fatigue life of aerospace bearing under arbitrary application load is presented in this paper. The input load data is transformed into stress according to the line-contact stress formula and fatigue equation of constantife. Bringing the stress into the commonly used empirical formula of high cycle fatigue, the amended contact fatigue life under arbitrary application load is obtained. Taking the bearing series MS21438 of the roller wheel track applied in wing flap mechanism as an example, its contact fatigue life is calculaed under its working load. Furthermore, we obtain the conclusion that the service life is prolonged obviously as the model number of bearings increases. The result could provide helpful reference for choosing aerospace bearing designation and confirming bearing 's repair cycle.%提出一种航空航天轴承在任意使用载荷下接触疲劳寿命的分析方法。利用线接触应力公式和等寿命转化公式对载荷输入数据进行转化,之后将载荷数据代入到描述高周疲劳的常用经验公式中,经修正得到任意使用载荷下的接触疲劳寿命。以航空航天轴承中的MS21438轴承系列用做襟翼滚轮滑轨运动机构上的滚轮为例,得到此轴承系列在使用载荷下的飞行架次寿命,随轴承选用型号的增大,轴承可使用的飞行架次显著增大。

  19. Fatigue behavior of thin-walled grade 2 titanium samples processed by selective laser melting. Application to life prediction of porous titanium implants.

    Science.gov (United States)

    Lipinski, P; Barbas, A; Bonnet, A-S

    2013-12-01

    Because of its biocompatibility and high mechanical properties, the commercially pure grade 2 titanium (CPG2Ti) is largely used for fabrication of patient specific implants or hard tissue substitutes with complex shape. To avoid the stress-shielding and help their colonization by bone, prostheses with a controlled porosity are designed. The selective laser melting (SLM) is well adapted to manufacture such geometrically complicated structures constituted by struts with rough surfaces and relatively small diameters. Few studies were dedicated to characterize the fatigue properties of SLM processed samples and bulk parts. They followed conventional or standard protocols. The fatigue behavior of standard samples is very different from the one of porous raw structures. In this study, the SLM made "as built" (AB) and "heat treated" (HT) tubular samples were tested in fatigue. Wöhler curves were determined in both cases. The obtained endurance limits were equal to σD(AB)=74.5MPa and σD(HT)=65.7MPa, respectively. The heat treatment worsened the endurance limit by relaxation of negative residual stresses measured on the external surface of the samples. Modified Goodman diagram was established for raw specimens. Porous samples, based on the pattern developed by Barbas et al. (2012), were manufactured by SLM. Fatigue tests and finite element simulations performed on these samples enabled the determination of a simple rule of fatigue assessment. The method based on the stress gradient appeared as the best approach to take into account the notch influence on the fatigue life of CPG2Ti structures with a controlled porosity. The direction dependent apparent fatigue strength was found. A criterion based on the effective, or global, nominal stress was proposed taking into account the anisotropy of the porous structures. Thanks to this criterion, the usual calculation methods can be used to design bone substitutes, without a precise modelling of their internal fine porosity.

  20. Fatigue Life Prediction of Mooring Chains for a Floating Tidal Current Power Station

    Institute of Scientific and Technical Information of China (English)

    Fengmei Jing; Liang Zhang; Zhong Yang

    2012-01-01

    As a kind of clean and renewable energy,tidal current energy is becoming increasingly popular all over the world with the shortage of energy and environmental problems becoming more and more severe.A floating tidal current power station is a typical type of tidal current power transformers which can sustain the loads of wind,waves,and current,and even the extreme situation of a typhoon.Therefore,the mooring system must be reliable enough to keep the station operating normally and to survive in extreme situations.The power station examined in this paper was installed at a depth of 40 m.A 44 mm-diameter R4-RQ4 chain was chosen,with a 2 147 kN minimum break strength and 50 kN pretension.Common studless link chain was used in this paper.Based on the Miner fatigue cumulative damage rule,S-N curves of chains,and MOSES software,a highly reliable mooring system was designed and analyzed.The calculation results show that the mooring system designed is reliable throughout a 10-year period.It can completely meet the design requirements of American Petroleum institution (API).Therefore,the presented research is significant for advancing the design of this kind of power station.

  1. Social Life Cycle Assessment as a Management Tool: Methodology for Application in Tourism

    Directory of Open Access Journals (Sweden)

    Roberto Merli

    2013-08-01

    Full Text Available As is widely known, sustainability is an important factor in competition, increasing the added value of a company in terms of image and credibility. However, it is important that sustainability assessments are effectively addressed in a global perspective. Therefore, life cycle tools are adopted to evaluate environmental and social impacts. Among these, and of particular significance, appears the Social Life Cycle Assessment (SLCA, which, although in its early stage of development, seems to have extremely promising methodological features. For this reason, it seemed interesting to propose a first application to the tourism sector, which could be better than other methods, studied in terms of social sustainability data. The particular characteristics of service delivery lend themselves more to the development of data related to social sustainability than other sectors. In this paper the results of a case study carried out using social accounting and business management tools are shown.

  2. Quality of life in multiple sclerosis (MS) and role of fatigue, depression, anxiety, and stress: A bicenter study from north of Iran.

    Science.gov (United States)

    Salehpoor, Ghasem; Rezaei, Sajjad; Hosseininezhad, Mozaffar

    2014-11-01

    Although studies have demonstrated significant negative relationships between quality of life (QOL), fatigue, and the most common psychological symptoms (depression, anxiety, stress), the main ambiguity of previous studies on QOL is in the relative importance of these predictors. Also, there is lack of adequate knowledge about the actual contribution of each of them in the prediction of QOL dimensions. Thus, the main objective of this study is to assess the role of fatigue, depression, anxiety, and stress in relation to QOL of multiple sclerosis (MS) patients. One hundred and sixty-two MS patients completed the questionnaire on demographic variables, and then they were evaluated by the Persian versions of Short-Form Health Survey Questionnaire (SF-36), Fatigue Survey Scale (FSS), and Depression, Anxiety, Stress Scale-21 (DASS-21). Data were analyzed by Pearson correlation coefficient and hierarchical regression. Correlation analysis showed a significant relationship between QOL elements in SF-36 (physical component summary and mental component summary) and depression, fatigue, stress, and anxiety (P MS patients. In addition, the findings of this study indirectly suggest that psychological interventions for reducing fatigue, depression, and anxiety can lead to improved QOL of MS patients.

  3. Small punch creep test: A promising methodology for high temperature plant components life evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Tettamanti, S. [CISE SpA, Milan (Italy); Crudeli, R. [ENEL SpA, Milan (Italy)

    1998-12-31

    CISE and ENEL are involved for years in a miniaturization creep methodology project to obtain similar non-destructive test with the same standard creep test reliability. The goal can be reached with `Small punch creep test` that collect all the requested characteristics; quasi nondestructive disk specimens extracted both on external or internal side of components, than accurately machined and tested on little and cheap apparatus. CISE has developed complete creep small punch procedure that involved peculiar test facility and correlation`s law comparable with the more diffused isostress methodology for residual life evaluation on ex-serviced high temperature plant components. The aim of this work is to obtain a simple and immediately applicable relationship useful for plant maintenance managing. More added work is need to validate the Small Punch methodology and for relationship calibration on most diffusion high temperature structural materials. First obtained results on a comparative work on ASTM A355 P12 ex-serviced pipe material are presented joint with a description of the Small Punch apparatus realized in CISE. (orig.) 6 refs.

  4. Chemical footprint: a methodological framework for bridging life cycle assessment and planetary boundaries for chemical pollution.

    Science.gov (United States)

    Sala, Serenella; Goralczyk, Malgorzata

    2013-10-01

    The development and use of footprint methodologies for environmental assessment are increasingly important for both the scientific and political communities. Starting from the ecological footprint, developed at the beginning of the 1990s, several other footprints were defined, e.g., carbon and water footprint. These footprints-even though based on a different meaning of "footprint"-integrate life cycle thinking, and focus on some challenging environmental impacts including resource consumption, CO2 emission leading to climate change, and water consumption. However, they usually neglect relevant sources of impacts, as those related to the production and use of chemicals. This article presents and discusses the need and relevance of developing a methodology for assessing the chemical footprint, coupling a life cycle-based approach with methodologies developed in other contexts, such as ERA and sustainability science. Furthermore, different concepts underpin existing footprint and this could be the case also of chemical footprint. At least 2 different approaches and steps to chemical footprint could be envisaged, applicable at the micro- as well as at the meso- and macroscale. The first step (step 1) is related to the account of chemicals use and emissions along the life cycle of a product, sector, or entire economy, to assess potential impacts on ecosystems and human health. The second step (step 2) aims at assessing to which extent actual emission of chemicals harm the ecosystems above their capability to recover (carrying capacity of the system). The latter step might contribute to the wide discussion on planetary boundaries for chemical pollution: the thresholds that should not be surpassed to guarantee a sustainable use of chemicals from an environmental safety perspective. The definition of what the planetary boundaries for chemical pollution are and how the boundaries should be identified is an on-going scientific challenge for ecotoxicology and ecology. In

  5. Compassion fatigue in nurses.

    Science.gov (United States)

    Yoder, Elizabeth A

    2010-11-01

    Compassion fatigue, trigger situations, and coping strategies were investigated in hospital and home care nurses. The Professional Quality of Life Scale measured compassion fatigue, compassion satisfaction, and burnout. Narrative questions elicited trigger situations and coping strategies. Compassion fatigue scores were significantly different between nurses who worked 8- or 12-hour shifts. Fifteen percent of the participants had scores indicating risk of the compassion fatigue. There were significant differences in compassion satisfaction, depending on the unit worked and time as a nurse. The most common category of trigger situations was caring for the patient. Work-related and personal coping strategies were identified. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. Methodological issues in life cycle assessment of mixed-culture polyhydroxyalkanoate production utilising waste as feedstock.

    Science.gov (United States)

    Heimersson, Sara; Morgan-Sagastume, Fernando; Peters, Gregory M; Werker, Alan; Svanström, Magdalena

    2014-06-25

    Assessing the environmental performance of emerging technologies using life cycle assessment (LCA) can be challenging due to a lack of data in relation to technologies, application areas or other life cycle considerations, or a lack of LCA methodology that address the specific concerns. Nevertheless, LCA can be a valuable tool in the environmental optimisation in the technology development phase. One emerging technology is the mixed-culture production of polyhydroxyalkanoates (PHAs). PHA production by pure microbial cultures has been developed and assessed in several LCAs during the previous decade. Recent developments within mixed-culture PHA production call for environmental assessment to guide in technology development. Mixed-culture PHA production can use the organic content in wastewater as a feedstock; the production may then be integrated with wastewater treatment (WWT) processes. This means that mixed-culture PHA is produced as a by-product from services in the WWT. This article explores different methodological challenges for LCA of mixed-culture PHA production using organic material in wastewater as feedstock. LCAs of both pure- and mixed-culture PHA production were reviewed. Challenges, similarities and differences when assessing PHA production by mixed- or pure-cultures were identified and the resulting implications for methodological choices in LCA were evaluated and illustrated, using a case study with mixed- and pure-culture PHA model production systems, based on literature data. Environmental impacts of processes producing multiple products or services need to be allocated between the different products or services. Such situations occur both in feedstock production and when the studied system is providing multiple functions. The selection of allocation method is shown to determine the LCA results. The type of data used, for electricity in the energy system, is shown to be important for the results, which indicates, a strong regional dependency of

  7. Improvement in Fatigue, Sleepiness, and Health-Related Quality of Life with Bright Light Treatment in Persons with Seasonal Affective Disorder and Subsyndromal SAD

    Directory of Open Access Journals (Sweden)

    Cecilia Rastad

    2011-01-01

    Full Text Available Objective. To investigate the effects of bright light treatment for secondary outcome measures and to explore and validate empirically derived subgroups and treatment effects in subgroups. Methods. A descriptive design. A sample of forty-nine persons (mean age of 45.8 with clinically assessed seasonal affective disorder (SAD or subsyndromal SAD (S-SAD participated in a two-group clinical trial evaluating the effects of treatment with bright light therapy. A person-oriented cluster analysis was applied to study treatment effects in subgroups. Results. For the merged group, sleepiness (Epworth Sleepiness Scale, fatigue (fatigue questionnaire, and health-related quality of life (SF-36 were improved at posttreatment, and results were maintained at the one-month followup. Three distinct subgroups had a high level of fatigue in common, while the level of excessive daytime sleepiness and depressed mood differed between the subgroups. Over time, all subgroups improved following ten days treatment in a light room. Conclusion. Fatigue, excessive daytime sleepiness, and health-related quality of life improve in a similar way as depressed mood following treatment with bright light. The treatment was effective irrespective of the severity of the disorder, that is, for persons with SAD and subsyndromal SAD.

  8. Crack initiation life in notched Ti-6Al-4V titanium bars under uniaxial and multiaxial fatigue: synthesis based on the averaged strain energy density approach

    Directory of Open Access Journals (Sweden)

    Giovanni Meneghetti

    2017-07-01

    Full Text Available The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD technique. Based on the results obtained from the potential drop technique, the crack initiation life has been defined in correspondence of a relative potential drop increase V/V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the crack initiation life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests

  9. 空冷风机桥架疲劳寿命分析%Analysis of fatigue life for air-cooling fan bridges

    Institute of Scientific and Technical Information of China (English)

    徐亚洲; 白国良

    2013-01-01

    Based on the in-situ tested vibration responses of an air-cooling fan bridge,the dynamic analysis is performed with modulation amplitude disturbing force model of draught fans.Rainflow method is used to count stress cycles and the fatigue load spectrum of air-cooling fan bridges is then programmed combined with investigation results of running frequencies of different operation modes per year.Fatigue damage to the air-cooling fan bridge is calculated in terms of Miner' s cumulative damage rule and design p-S-N curve.After giving the damage threshold corresponding to fatigue failure,the predicted fatigue life of the fan bridge is longer than the designed service life.Furthermore,the fatigue life slightly decreases as effects of mean stress are taken into consideration by Goodman' s,Gerber' s and Soderberg' s models.%基于现场实测风机桥架振动响应,采用风机调幅扰力模型进行结构动力响应分析.根据不同工况下疲劳危险点的名义应力时程,采用雨流计数法和各工况年运行频次调查结果编制疲劳载荷谱.通过Miner损伤累积准则和p-S-N关系对风机桥架进行疲劳损伤分析,给定疲劳破坏的损伤阈值,所得疲劳寿命满足设计使用年限的要求.采用Goodman、Gerber和Soderberg模型考虑平均应力影响时的疲劳寿命略有降低.

  10. Surface fatigue life of carburized and hardened M50NiL and AISI 9310 spur gears and rolling-contact test bars

    Science.gov (United States)

    Townsend, Dennis P.; Bamberger, Eric N.

    1989-01-01

    Spur gear endurance tests and rolling-element surface tests were conducted to investigate vacuum-induction-melted, vacuum-arc-melted (VIM-VAR) M50NiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIM-VAR AISI 9310 gear material. Tests were conducted with spur gears and rolling-contact bars manufactured from VIM-VAR M50NiL and VAR and VIM-VAR AISI 9310. The gear pitch diameter was 8.9 cm (3.5 in.). Gear test conditions were an inlet oil temperature of 320 K (116 F), and outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench rolling-element fatigue tests were conducted at ambient temperatures with a bar speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPA (700 ksi). The VIM-VAR M50NiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR M50NiL rolling-contact bars was 13.2 and 21.6 times that for the VIM-VAR and VAR AISI 9310, respectively. The VIM-VAR M50NiL material was shown to have good resistance to fracture through a fatigue spall and to have fatigue life far superior to that of both VIM-VAR and VAR AISI 9310 gears and rolling-contact bars.

  11. Effect of corrosion on the fatigue service-life on steel and reinforced concrete beams

    NARCIS (Netherlands)

    Veerman, R.P.; van Breugel, K.; Koenders, E.A.B.

    2015-01-01

    Chloride-induced corrosion is a point of big concern in reinforced concrete (RC) structures. To monitor the actual health and to predict the remaining service-life of structures, it is important to understand the structural behaviour and the failure mechanism of structures exposed to chlorides under

  12. Effect of corrosion on the fatigue service-life on steel and reinforced concrete beams

    NARCIS (Netherlands)

    Veerman, R.P.; van Breugel, K.; Koenders, E.A.B.

    2015-01-01

    Chloride-induced corrosion is a point of big concern in reinforced concrete (RC) structures. To monitor the actual health and to predict the remaining service-life of structures, it is important to understand the structural behaviour and the failure mechanism of structures exposed to chlorides under

  13. Quality of life, fatigue and mental health in patients with the m.3243A > G mutation and its correlates with genetic characteristics and disease manifestation.

    Science.gov (United States)

    Verhaak, Christianne; de Laat, Paul; Koene, Saskia; Tibosch, Marijke; Rodenburg, Richard; de Groot, Imelda; Knoop, Hans; Janssen, Mirian; Smeitink, Jan

    2016-03-18

    Mitochondrial disorders belong to the most prevalent inherited metabolic diseases with the m.3243A > G mutation reflecting being one of the most common mutations in mitochondrial DNA. Previous studies showed little relationship between mitochondrial genetics and disease manifestation. Relationship between genotype and disease manifestation with patient reported quality of life and other patient reported outcomes is still unexplored. Seventy-two out of the 122 invited adult patients with m.3243A > G mutation completed online standardized questionnaires on quality of life, functional impairment, fatigue and mental health as assessed by the RAND-SF36, the Sickness Impact Profile (SIP), the Checklist Individual Strength (CIS) and the Hospital Anxiety and Depression scale (HADS). Data were related to clinical manifestation reflected by the Newcastle Mitochondrial Disease Adult Scale (NMDAS) score and heteroplasmy levels of the mutation in urine epithelial cells. Patients reported impaired quality of life. Sixty percent showed severe levels of fatigue, and 37% showed clinical relevant mental health problems, which was significantly more than healthy norms. These patient reported health outcomes showed negligible relationship with levels of heteroplasmy (r = life, fatigue and mental health problems, are only partly reflected by clinical assessments. In order to support patients more effectively, integration of patient reported outcomes, alongside symptoms of their disease, in clinical practice is warranted.

  14. Fatigue case study and loading spectra for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, H.J.

    1994-05-01

    The paper discusses two aspects of Sandia`s Wind Energy Program. The first section of the paper presents a case study of fatigue in wind turbines. This case study was prepared for the American Society of Testing Material`s (ASTM) Standard Technical Publication (STP) on fatigue education. Using the LIFE2 code, the student is lead through the process of cumulative damage summation for wind turbines and typical data are used to demonstrate the range of life estimates that will result from typical parameter variations. The second section summarizes the results from a workshop held by Sandia and the National Renewable Energy Laboratory (NREL) to discuss fatigue life prediction methodologies. This section summarizes the workshop discussions on the use of statistical modeling to deduce the shape and magnitude of the low-probability-of-occurrence, high-stress tail of the load distribution on a wind turbine during normal operation.

  15. Boiler-turbine life extension

    Energy Technology Data Exchange (ETDEWEB)

    Natzkov, S. [TOTEMA, Ltd., Sofia (Bulgaria); Nikolov, M. [CERB, Sofia (Bulgaria)

    1995-12-01

    The design life of the main power equipment-boilers and turbines is about 105 working hours. The possibilities for life extension are after normatively regulated control tests. The diagnostics and methodology for Boilers and Turbines Elements Remaining Life Assessment using up to date computer programs, destructive and nondestructive control of metal of key elements of units equipment, metal creep and low cycle fatigue calculations. As well as data for most common damages and some technical decisions for elements life extension are presented.

  16. 40 CFR Appendix A to Part 132 - Great Lakes Water Quality Initiative Methodologies for Development of Aquatic Life Criteria and...

    Science.gov (United States)

    2010-07-01

    ... demonstrating that the alternative values will protect the aquatic life uses of the water. Appropriate... 40 Protection of Environment 21 2010-07-01 2010-07-01 false Great Lakes Water Quality Initiative Methodologies for Development of Aquatic Life Criteria and Values A Appendix A to Part 132 Protection of...

  17. A STUDY OF FATIGUE LIFE OF ASPHALT CONCRETE BASED ON SHUNGITE MINERAL POWDER

    OpenAIRE

    D. I. Chernousov; Vl. P. Podolsky; E. V. Trufanov; B. A. Bondarev

    2011-01-01

    Problem statement. Shortage of mineral powder stimulates seeking of new materials and technologiesby which traditional ones can be replaced without deterioration of their operating properties. Thatis why a study of mineral powder from shungite and development of new technologies of arrangementof high quality and durable asphalt concrete pavement based on shungite is an actual problem.Results. Bearing capacity and service life of asphalt concrete pavement is most completely characterizedby mod...

  18. Endurance training in MS: short-term immune responses and their relation to cardiorespiratory fitness, health-related quality of life, and fatigue.

    Science.gov (United States)

    Bansi, J; Bloch, W; Gamper, U; Riedel, S; Kesselring, J

    2013-12-01

    The influences of exercise on cytokine response, health-related quality of life (HR-QoL), and fatigue are important aspects of MS rehabilitation. Physical exercises performed within these programs are often practiced in water, but the effects of immersion have not been investigated. To investigate the influences of short-term immune responses and cardiorespiratory fitness on HR-QoL and fatigue during 3 weeks endurance training conducted on a cycle-ergometer or an aquatic-bike. Randomized controlled clinical trial in 60 MS patients. HR-QoL, fatigue, cardiorespiratory fitness, and short-term immune changes (serum concentrations in response to cardiopulmonary exercise test) of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), interleukin-6, and the soluble receptor of IL-6 (sIL-6R) were determined at the beginning and end of 3 weeks of training intervention. Subjects performed daily 30 min training at 60 % of their VO2peak. SF-36 total (p = 0.031), physical (p = 0.004), and mental health (p = 0.057) scores show time effects within both groups. Between-group effects were shown for FSMC total (p = 0.040) and motor function score (p = 0.041). MFIS physical fatigue showed time effects (p = 0.008) for both groups. Linear regression models showed relationships between short-term immune responses and cardiorespiratory fitness with HR-QoL and fatigue after the intervention. This study indicates beneficial effects of endurance training independent of the training setting. Short-term immune adaptations and cardiorespiratory fitness have the potential to influence HR-QoL and fatigue in persons with MS. The specific immune responses of immersion to exercise need further clarification.

  19. THE ADVERSE EFFECT OF STEEL PARTICLE CONTAMINANTS ON FATIGUE LIFE OF GREASE LUBRICATED BALL BEARINGS

    Directory of Open Access Journals (Sweden)

    A. Stathis

    2014-01-01

    Full Text Available The rating life of ball bearings is reduced when hard particle contaminants are present in the lubricant. Usually, this life reduction is taken into account in the calculation of modified rating life by using the contamination factor through a general characterization of the lubrication conditions. However, the impact of contaminant’s variables such as size, hardness and concentration level has to be specified in detail. This need is resolved by the present work, where greases contaminated with hard steel particles of different sizes are tested with the purpose of finding a pattern in the relationship between steel particle sizes and the progress of wear inside the bearings. A laboratory rig is utilized for these tests and vibration analysis is performed to estimate the condition and the residual life of the bearings. After the tests, optical inspections performed in a stereoscope verify the predictions of vibration analyses. It was found that large contaminating particles, after their initial deformation, produce high stresses and therefore higher wear of the bearings and that the wear mechanism is closely related to the interruption of the lubricating film in such a way that local overheating caused point melting and adhesion of the particles adhered on the raceways. In case of grease contaminated with steel particles, vibration analysis can indicate the severity of wear and monitor its progress. From the conducted tests of the present work it is proved that the size of the contaminant particles affect strongly the wear process in such a way that the larger steel particle contaminants cause greater damage to the bearing. The vibration levels were higher and the damage was greater as particle size increased. It is difficult to establish an equation that describes and quantifies the wear progress involving all the parameters of size and concentration levels of the steel contaminant particles due to the stochastic nature of the wear mechanisms

  20. Nonlinear cumulative damage model for multiaxial fatigue

    Institute of Scientific and Technical Information of China (English)

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

    2006-01-01

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

  1. Estrogenic botanical supplements, health-related quality of life, fatigue, and hormone-related symptoms in breast cancer survivors: a HEAL study report

    Directory of Open Access Journals (Sweden)

    Ma Huiyan

    2011-11-01

    Full Text Available Abstract Background It remains unclear whether estrogenic botanical supplement (EBS use influences breast cancer survivors' health-related outcomes. Methods We examined the associations of EBS use with health-related quality of life (HRQOL, with fatigue, and with 15 hormone-related symptoms such as hot flashes and night sweats among 767 breast cancer survivors participating in the Health, Eating, Activity, and Lifestyle (HEAL Study. HRQOL was measured by the Medical Outcomes Study short form-36 physical and mental component scale summary score. Fatigue was measured by the Revised-Piper Fatigue Scale score. Results Neither overall EBS use nor the number of EBS types used was associated with HRQOL, fatigue, or hormone-related symptoms. However, comparisons of those using each specific type of EBS with non-EBS users revealed the following associations. Soy supplements users were more likely to have a better physical health summary score (odds ratio [OR] = 1.66, 95% confidence interval [CI] = 1.02-2.70. Flaxseed oil users were more likely to have a better mental health summary score (OR = 1.76, 95% CI = 1.05-2.94. Ginseng users were more likely to report severe fatigue and several hormone-related symptoms (all ORs ≥ 1.7 and all 95% CIs exclude 1. Red clover users were less likely to report weight gain, night sweats, and difficulty concentrating (all OR approximately 0.4 and all 95% CIs exclude 1. Alfalfa users were less likely to experience sleep interruption (OR = 0.28, 95% CI = 0.12-0.68. Dehydroepiandrosterone users were less likely to have hot flashes (OR = 0.33, 95% CI = 0.14-0.82. Conclusions Our findings indicate that several specific types of EBS might have important influences on a woman's various aspects of quality of life, but further verification is necessary.

  2. Damage Evolution and Life Prediction of Cross-Ply C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading at Room Temperature and 800 °C in Air

    Directory of Open Access Journals (Sweden)

    Longbiao Li

    2015-12-01

    Full Text Available The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss energy. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy degrade with increasing applied cycles attributed to transverse cracks in the 90° plies, matrix cracks and fiber/matrix interface debonding in the 0° plies, interface wear at room temperature, and interface and carbon fibers oxidation at 800 °C in air. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus and fatigue hysteresis loss energy have been established. Comparing experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface shear stress corresponding to different cycle numbers has been estimated. It was found that the degradation rate at 800 °C in air is much faster than that at room temperature due to serious oxidation in the pyrolytic carbon (PyC interphase and carbon fibers. Combining the fiber fracture model with the interface shear stress degradation model and the fibers strength degradation model, the fraction of broken fibers versus the cycle number can be determined for different fatigue peak stresses. The fatigue life S-N curves of cross-ply C/SiC composite at room temperature and 800 °C in air have been predicted.

  3. The Recognition Of Fatigue

    DEFF Research Database (Denmark)

    Elsass, Peter; Jensen, Bodil; Mørup, Rikke;

    2007-01-01

    Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87......Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87...

  4. Advances in Fatigue Life Prediction and Accelerated Test of Rubber Vibration Isolator%橡胶隔振器寿命预测及加速试验研究进展

    Institute of Scientific and Technical Information of China (English)

    孙伟星; 刘山尖; 欧阳昕; 董兴建

    2013-01-01

    The failure modes of rubber vibration isolator and the factors influencing its fatigue life were introduced.The fatigue life prediction method for rubber materials based on fracture energy and S-N curve approaches were summarized.The recent research on fatigue life accelerated test for rubber vibration isolator was presented and the current development trends in rubber fatigue life prediction were prospected.%介绍了橡胶材料的疲劳失效形式及影响橡胶材料抗疲劳性能的因素,总结了基于撕裂能和基于S-N曲线的橡胶材料疲劳寿命预测方法,阐明了橡胶隔振器加速试验研究的现状,展望了未来值得研究的方向.

  5. Contact Stress Analysis and Fatigue Life Prediction of a Turbine Fan Disc

    Science.gov (United States)

    Yang, Liang; Zhu, Shun-Peng; Lv, Zhiqiang; Zuo, Fang-Jun; Huang, Hong-Zhong

    2016-06-01

    Fan discs are critical components of an aero engine. In this paper, contact stress and life prediction of a turbine fan disc were investigated. A simplified pin/disc model was conducted to simulate the practical working condition under applied loads using finite element (FE) analysis. This study is devoted to examining the effects of interface condition of pin/disc such as gap and coefficient upon the maximum stress. The FE model indicated that the maximum stress occurs at the top right corner in the second pin hole, and larger gap or friction coefficient has a significant effect on the maximum stress. In addition, FE analysis without considering friction is also conducted. The results show that the dangerous point is similar to the result which considers friction and the stress state is relatively larger than that of considering friction. Finally, based on FE analysis result, life prediction for the fan disc is conducted to combine the material S-N curve, mean stress effects and concentration stress factor obtained by means of FE method.

  6. A New Perspective on Fatigue Performance of Advanced High- Strength Steels (AHSS) GMAW Joints

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhili [ORNL; Chiang, Dr. John [Ford Motor Company; Kuo, Dr. Min [MIttal Steel; Jiang, Cindy [AET Integration, Inc; Sang, Yan [AET Integration, Inc

    2008-01-01

    Weld fatigue performance is a critical aspect for application of advanced high-strength steels (AHSS) in automotive body structures. A comparative study has been conducted to evaluate the fatigue life of AHSS welds. The material studied included seven AHSS of various strength levels - DP 600, DP 780, DP 980, M130, M220, solution annealed boron and fully hardened boron steels. Two conventional steels, HSLA 590 and DR 210, were also included for baseline comparison. Lap fillet welds were made on 2-mm nominal thick sheets by the gas metal arc welding process (GMAW). Fatigue test was conducted under a number of stress levels to obtain the S/N curves of the weld joints. It was found that, unlike in the static and impact loading conditions, the fatigue performance of AHSS is not influenced by the HAZ softening in AHSS. There are appreciable differences in the fatigue lives among different AHSS. Changes in weld parameters can influence the fatigue life of the weld joints, particularly of these of higher strength AHSS. A model is developed to predict the fatigue performance of AHSS welds. The validity of the model is benchmarked with the experimental results. This model is capable to capture the effects of weld geometry and weld microstructure and strength on the fatigue performance experimentally observed. The theoretical basis and application of the newly developed fatigue modeling methodology will be discussed.

  7. Thermo-fatigue life study on LCCC electronic packaging structure%LCCC电子封装结构的热疲劳寿命分析

    Institute of Scientific and Technical Information of China (English)

    侯传涛; 童军; 荣克林

    2014-01-01

    以典型LCCC电子封装结构为研究对象,分别基于有限元仿真分析方法和工程算法开展电子封装结构在温循载荷作用下的疲劳寿命分析,分析结果表明,有限元仿真分析方法和工程算法所预测的结构疲劳寿命一致性较好。所探索的有限元方法和工程估算方法在解决电子封装结构的热疲劳寿命问题时具有很好地推广性。%Basing on the FEM and theory methods, Thermo-fatigue life of LCCC electronic packaging structure is investigated. The analysis outcomes show that the Fatigue life predicated by FEM is associated with the result of the theory method. The techniques explored by this paper are extended conveniently to evaluate thermo-fatigue life for other electronic packaging structures.

  8. The Potential United Kingdom Energy Gap and Creep Life Prediction Methodologies

    Science.gov (United States)

    Evans, Mark

    2013-01-01

    The United Kingdom faces a looming energy gap with around 20 pct of its generating capacity due for closure in the next 10 to 15 years as a result of plant age and new European legislation on environmental protection and safety at work. A number of solutions exist for this problem including the use of new materials so that new plants can operate at higher temperatures, new technologies related to carbon capture and gasification, development of renewable resources, and less obviously the use of accurate models for predicting creep life. This article reviews, with illustrations, some of the more applicable and successful creep prediction methodologies used by academics and industrialists and highlights how these techniques can help alleviate the looming energy gap. The role that these approaches can play in solving the energy gap is highlighted throughout.

  9. New Methodology in Life Cycle Impact Assessment (LCIA) of waste water treatment

    DEFF Research Database (Denmark)

    Larsen, Henrik Fred; Wenzel, Henrik; Hauschild, Michael

    chose among different waste water treatments? Which ones are most beneficial in a holistic perspective? Here, the life cycle assessment (LCA) approach as a decision supporting tool may help because its goal is to allow quantification and direct comparison of characteristics as diverse as energy......Reducing environmental problems related to wastewater effluents containing micro-pollutants requires resources in terms of energy, chemicals, infrastructure, installations for wastewater treatment, thus, involves advantages as well as disadvantages to the environment and society. But how does one...... EU research project "NEPTUNE" focusing on nutrient recycling, micro-pollutants and ecotoxicity removal, energy production, and reuse of sludge and of its resources, this paper will present the first results of the development of a new methodology for assessing advances in wastewater treatment...

  10. Life cycle assessment in green chemistry: overview of key parameters and methodological concerns

    DEFF Research Database (Denmark)

    Tufvesson, Linda M.; Tufvesson, Pär; Woodley, John

    2013-01-01

    Several articles within the area of green chemistry often promote new techniques or products as ‘green’ or ‘more environmentally benign’ than their conventional counterpart although these articles often do not quantitatively assess the environmental performance. In order to do this, life cycle...... with the purpose to reduce the time-consuming steps in LCA.In this review, several LCAs of so-called ‘green chemicals’ are analysed and key parameters and methodological concerns are identified. Further, some conclusions on the environmental performance of chemicals were drawn.For fossil-based platform chemicals...... several LCAs exists but for chemicals produced with industrial biotechnology or from renewable resources the number of LCAs is limited, with the exception of biofuels, for which a large number of studies are made. In the review, a significant difference in the environmental performance of bulk and fine...

  11. 挤压AZ31B镁合金多轴疲劳寿命预测%MULTIAXIAL FATIGUE LIFE PREDICTION FOR EXTRUDED AZ31B MAGNESIUM ALLOY

    Institute of Scientific and Technical Information of China (English)

    熊缨; 程利霞

    2012-01-01

    采用挤压AZ31B镁合金薄壁圆筒试样,分别进行了单轴和多轴加载下的对称应变控制疲劳实验,研究了不同加载路径对疲劳寿命的影响.单轴加载包括对称拉压和扭转路径,多轴加载包括45°比例加载和90°非比例加载路径.结果表明,在加载的等效应变幅值为0.3% 0.55%附近,4种加载路径下的应变-寿命曲线均出现了不连续的拐点;比例加载路径在等效应变幅大于0.45%时疲劳寿命最高,拉压路径在等效应变幅小于0.45%时疲劳寿命最高;非比例加载路径的疲劳寿命最低.使用基于临界平面法的多轴疲劳模型FS,SWT以及修正SWT分别预测了各个路径加载下的疲劳寿命.预测结果表明,SWT模型对于拉压和循环扭转加载下寿命预测结果误差较大;FS模型与修正SWT模型可以较好地预测挤压AZ31B镁合金各个路径加载下的疲劳寿命.%Magnesium alloy components were widely used in automobile and aircraft industries, due to their light weight, high specific strength, stiffness, damping capacity, machinability, and recyclability. Engineering components subjected cyclic loading inevitably and led to fatigue failure. Most studies on magnesium alloy were focus on uniaxial fatigue, very limited work has been done of magnesium alloys under multiaxial loading. In this study, strain-controlled multiaxial fatigue experiments were conducted on extruded AZ31B magnesium alloy using thin-walled tubular specimens in ambient air. Four loading paths, including fully reversed tension-compression, cyclic torsion, 45° in-phase axial-torsion and 90° out-of-phase axial-torsion, were adopted in the fatigue experiments. It is observed that the strain-life curve displays a distinguishable kink under each loading path at the equivalent strain amplitude around 0.3% to 0.55%. The fatigue life -under the proportional loading path is the highest when equivalent strain amplitudes higher than 0.45%, and the fatigue

  12. 'Setting a principled boundary'? Euthanasia as a response to 'life fatigue'.

    Science.gov (United States)

    Huxtable, Richard; Möller, Maaike

    2007-03-01

    The Dutch case of Brongersma presents novel challenges to the definition and evaluation of voluntary euthanasia since it involved a doctor assisting the suicide of an individual who was (merely?) 'tired of life'. Legal officials had called on the courts to 'set a principled boundary', excluding such cases from the scope of permissible voluntary euthanasia, but they arguably failed. This failure is explicable, however, since the case seems justifiable by reference to the two major principles in favour of that practice, respect for autonomy and beneficence. Ultimately, it will be argued that those proponents of voluntary euthanasia who are wary of its use in such circumstances may need to draw upon 'practical' objections, in order to erect an otherwise arbitrary perimeter. Furthermore, it will be suggested that the issues raised by the case are not peculiarly Dutch in nature and that, therefore, there are lessons here for other jurisdictions too.

  13. Study on the Fatigue Life of Steel Crane Structures in Service%在役钢结构吊车梁疲劳寿命研究

    Institute of Scientific and Technical Information of China (English)

    张琳

    2012-01-01

    In recent years, according to the survey of industrial plant, most of the crane steel crane beam with large tonnage, heavy grade level or overweight duty prematurely appeared different degree of fatigue crack under the action of repeated load, and endanger the safety in production. So the fatigue life of crane beam structure is usually considered as the major indexes of the safety control. The evaluation parameters and index of fatigue life is great different from the practical load, and the structure form, stress state, production process of crane beam are the main factors that influence the fatigue life. At present, the technology personnel has done further research to the basic theory of the fatigue life of steel crane beam and has put forward a variety of evaluation methods. But we can see that each evaluation method has some limitations, and there is no better assessment method. Therefore, to seek a more reasonable evaluation method so as to more accurately calculate the fatigue life of crane beam is very necessary. This paper mainly uses the details fatigue rating method (DFR method) to calculate the fatigue life of steel crane beam.%近年来,对工业厂房的调查结果显示,大吨位、重级或超重级工作制起重机的钢吊车梁在反复荷载的作用下,大部分均过早地出现了不同程度的疲劳裂缝,危害生产安全.因此通常将吊车梁结构的疲劳寿命作为控制安全性的主要指标.疲劳寿命的评估参数及指标和实际的荷载存在较大的差异,还有吊车梁的结构形式、受力状态、制作工艺都是影响疲劳寿命的主要因素.目前已有技术人员对钢结构吊车梁疲劳寿命的基本理论进行了深入的研究且提出了多种评估方法,但每种评估方法都有一定的局限性,而且目前尚缺乏较好的评估方法.因此,寻求一个更加合理的评估方法以期能较准确地计算吊车梁的疲劳寿命就显得十分必要.本文主要采用细节疲劳

  14. Fatigue Life Simulation Design and Research of the Taper Leaf Spring on Automobile%汽车少片变截面板簧的疲劳寿命仿真设计

    Institute of Scientific and Technical Information of China (English)

    朱剑宝; 陈建宏; 林平

    2011-01-01

    利用基于非线性有限元仿真分析的疲劳设计方法,对少片变截面板簧进行了疲劳寿命试验仿真分析,确定出板簧的疲劳破坏发生区域,然后基于材料的S-N曲线,利用ANSYS疲劳分析模块进行板簧的疲劳寿命设计计算.该疲劳寿命分析方法可以较准确地得出板簧产品的疲劳寿命,节约了疲劳试验成本.%By using the fatigue life prediction method based on the non-linear finite element model, fatigue life test simulation analysis of the designed taper leaf spring in the paper are performed, then based on the S-N curve of material, detect the fatigue dangerous area and predict fatigue life of the structure in critical location with the help of ANSYS’ Fatigue module, it is feasible to predict fatigue life of leafspring product, reduce fatigue test costs, provide practical significance in engineering.

  15. Life cycle analysis of mitigation methodologies for railway rolling noise and groundbourne vibration.

    Science.gov (United States)

    Tuler, Mariana Valente; Kaewunruen, Sakdirat

    2017-04-15

    Negative outcomes such as noise and vibration generated by railways have become a challenge for both industry and academia in order to guarantee that the railway system can accomplish its purposes and at the same time provide comfort for users and people living in the neighbourhood along the railway corridor. The research interest on this field has been increasing and the advancement in noise and vibration mitigation methodologies can be observed using various engineering techniques that are constantly put into test to solve such effects. In contrast, the life cycle analysis of the mitigation measures has not been thoroughly carried out. There is also a lack of detailed evaluation in the efficiency of various mechanisms for controlling rolling noise and ground-borne vibration. This research is thus focussed on the evaluation of materials used, the total cost associated with the maintenance of such the measures and the carbon footprint left for each type of mechanism. The insight into carbon footprint together with life cycle cost will benefit decision making process for the industry in the selection of optimal and suitable mechanism since the environmental impact is a growing concern around the world. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. A grey-based group decision-making methodology for the selection of hydrogen technologiess in Life Cycle Sustainability perspective

    DEFF Research Database (Denmark)

    Manzardo, Alessandro; Ren, Jingzheng; Mazzi, Anna

    2012-01-01

    The objective of this research is to develop a grey-based group decision-making methodology for the selection of the best renewable energy technology (including hydrogen) using a life cycle sustainability perspective. The traditional grey relational analysis has been modified to better address...... using the proposed methodology, electrolysis of water technology by hydropower has been considered to be the best technology for hydrogen production according to the decision-making group....

  17. 核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的研究%Study on Crack Propagation Life under Low Cycle Fatigue and High Cycle Fatigue of Nuclear Steam Turbine Rotors

    Institute of Scientific and Technical Information of China (English)

    史进渊

    2015-01-01

    The calculation and assessment methods for the crack propagation life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors is presented. The low high fatigue cycle stress amplitude and stress range as well as the crack propagation life calculation methods for low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are introduced. The calculation and assessment methods for the crack propagation calendar life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are given together with an application example for calculation and improvement of the fatigue crack propagation calendar life of a low pressure welded rotor for 1 000 MW nuclear steam turbines. The example results indicate that effect of the high cycle fatigue on the fatigue crack propagation calendar life of nuclear steam turbine rotors is bigger, it is necessary that assessment for the crack propagation life under low cycle fatigue and high cycle fatigue of rotors in the rotor structure design of new development for nuclear steam turbine and the rotor safety assessment for operation steam turbine for nuclear power plants.%提出核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的计算与评定方法.介绍核电汽轮机转子的低周疲劳与高周疲劳的应力幅与应力范围、低周疲劳裂纹扩展寿命与高周疲劳扩展寿命的计算方法.给出了核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展日历寿命的计算与评定方法,以及1 000 MW级核电汽轮机焊接低压转子疲劳裂纹扩展日历寿命的计算与改进的应用实例.结果表明,高周疲劳对汽轮机转子疲劳裂纹扩展日历寿命有比较大的影响,新研制核电汽轮机的转子结构设计和在役核电汽轮机的转子安全性评定,需要评估转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命.

  18. Mo(ve)ment methodology – Researching conflictual meanings, double-binds and change in extreme life situations

    DEFF Research Database (Denmark)

    Mørck, Line Lerche

    2015-01-01

    The social practice theoretical moment-movement methodology explores significant moments in depth, such as moments of frustration, anger, engagement and (be)longing. The moments are conceptualized as part of broader conflictual struggles and processes (movements), which include both continuity...... and change in conduct of life. This moment-movement methodology is developed in close collaboration with a former biker-gang member - involved as a research apprentice. Together we are developing the methodology, while researching concrete processes of change from biker gang member towards becoming...

  19. 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.

  20. 基于数值模拟的多圈QFN封装热疲劳可靠性试验设计方法%Design of Experiment Methodology for Thermal Fatigue Reliability of Multi-row QFN Packages Based on Numerical Simulations

    Institute of Scientific and Technical Information of China (English)

    秦飞; 夏国峰; 高察; 安彤; 朱文辉

    2014-01-01

    A design of experiment (DOE) methodology based on numerical simulation is presented to improve thermal fatigue reliability of multi-row quad flat non-lead (QFN) packages. The influences of material properties, structural geometries and temperature cycling profiles on thermal fatigue life are evaluated. Anand constitutive model is adopted to describe the viscoplastic behavior of lead-free solder Sn3.0Ag0.5Cu. The stress and strain in solder joints under temperature cycling are studied by 3D finite element model. Coffin-Manson model is employed to predict the fatigue life. A L27(38) orthogonal array is built based on Taguchi method to figure out optimized factor combination design for improving thermal fatigue reliability. The optimized factor combination design derived from DOE methodology is verified by finite element analysis. Results indicate that the coefficients of thermal expansion (CTE) of printed circuit board (PCB), the height of solder joints and CTE of epoxy molding compound (EMC) have critical influence on thermal fatigue life. The fatigue life of multi-row QFN package with original design is 767 cycles, which can be substantially improved by 5.43 times to 4 165 cycles after the optimized factor combination design based on the presented method.%提出一种基于数值模拟的试验设计方法,研究材料属性和几何结构对多圈四边扁平无引脚(Quad flat no-lead,QFN)封装热疲劳寿命的影响,并进行最优因子的组合设计,以提升热疲劳可靠性。采用 Anand 黏塑性本构模型描述无铅钎料Sn3.0Ag0.5Cu的力学行为,建立三维有限元模型分析焊点在温度循环过程中的应力应变,采用Coffin-Manson寿命预测模型计算多圈QFN封装的热疲劳寿命。采用Taguchi试验设计(Design of experiment,DOE)方法建立L27(38)正交试验表进行最优因子的组合设计。采用有限元分析方法对最优因子组合设计结果进行验证。结