WorldWideScience

Sample records for high-cycle fatigue life

  1. 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.

  2. Crack propagation mechanism and life prediction for very-high-cycle fatigue of a structural steel in different environmental medias

    Directory of Open Access Journals (Sweden)

    Guian Qian

    2013-07-01

    Full Text Available The influence of environmental medias on crack propagation of a structural steel at high and very-high-cycle fatigue (VHCF regimes is investigated based on the fatigue tests performed in air, water and 3.5% NaCl aqueous solution. Crack propagation mechanisms due to different crack driving forces are investigated in terms of fracture mechanics. A model is proposed to study the relationship between fatigue life, applied stress and material property in different environmental medias, which reflects the variation of fatigue life with the applied stress, grain size, inclusion size and material yield stress in high cycle and VHCF regimes. The model prediction is in good agreement with experimental observations.

  3. Fatigue characteristics of bearing steel in very high cycle fatigue

    International Nuclear Information System (INIS)

    Very high cycle fatigue (VHCF) tests were carried out to find the fatigue characteristics of a super-long life range by using a cantilever type rotational bending fatigue test machine on three kinds of specimens in bearing steel which were quenched and tempered in air (A: non-shot peened and B: shot peened after heat treatment) and under vacuum environment(C: non-shot peened) in this study. S-N curves obtained from the VHCF tests of the B and C specimens tend to come down again in the super-long life (109 cycles) range due to fish-eye type cracking, while most of the A and B specimens were fractured by surface defects such as scratches and slip lines. This duplex S-N behavior of bearing steel has to be reviewed by the change of the fracture modes

  4. Very High Cycle Fatigue Failure Analysis and Life Prediction of Cr-Ni-W Gear Steel Based on Crack Initiation and Growth Behaviors

    Directory of Open Access Journals (Sweden)

    Hailong Deng

    2015-12-01

    Full Text Available The unexpected failures of structural materials in very high cycle fatigue (VHCF regime have been a critical issue in modern engineering design. In this study, the VHCF property of a Cr-Ni-W gear steel was experimentally investigated under axial loading with the stress ratio of R = ?1, and a life prediction model associated with crack initiation and growth behaviors was proposed. Results show that the Cr-Ni-W gear steel exhibits the constantly decreasing S-N property without traditional fatigue limit, and the fatigue strength corresponding to 109 cycles is around 485 MPa. The inclusion-fine granular area (FGA-fisheye induced failure becomes the main failure mechanism in the VHCF regime, and the local stress around the inclusion play a key role. By using the finite element analysis of representative volume element, the local stress tends to increase with the increase of elastic modulus difference between inclusion and matrix. The predicted crack initiation life occupies the majority of total fatigue life, while the predicted crack growth life is only accounts for a tiny fraction. In view of the good agreement between the predicted and experimental results, the proposed VHCF life prediction model involving crack initiation and growth can be acceptable for inclusion-FGA-fisheye induced failure.

  5. Study on dominant mechanism of high-cycle fatigue life in 6061-T6 aluminum alloy through microanalyses of microstructurally small cracks

    International Nuclear Information System (INIS)

    The mechanism controlling the fatigue life of a precipitation-hardened Al–Mg–Si alloy (6061-T6) at a high-cycle fatigue (HCF) regime of over 107 cycles was investigated in detail. It was found that over 90% of the total fatigue life was occupied by the growth process of a microstructurally small crack at relatively low stress amplitude. The small crack was often found to be arrested and halted for a long period (more than 106 cycles) before it began to grow again, which resulted in a significantly slow growth process. The small crack was then analyzed not only by the conventional fractography but also by the cross-sectional observation of the crack tip region using a focused ion beam and transmission electron microscopy. These observations, supplemented also by a grain orientation analysis using electron backscattered diffraction, explicitly revealed the following points: (i) the small crack growth observed on the specimen surface is primarily related to facet-type cracking that occurs exclusively at the specimen surface; (ii) the growth direction of the small crack has strong anisotropy (i.e. surface-induced growth); (iii) the facet-type cracking is related to the formation of persistent fine slip bands that accompany no structural change of the matrix. On the basis of these results, the micromechanism of small crack growth and its relation to the concept of fatigue limit at the HCF regime is discussed in detail.

  6. Torsional fatigue behaviour and damage mechanisms in the very high cycle regime

    OpenAIRE

    E. Bayraktar; Xue, H.; F. Ayari; C. Bathias

    2010-01-01

    Purpose: of this paper: Many engineering components operate under combined torsion and axial cyclic loading conditions, which can result in fatigue fracture after a very long life regime of fatigue. This fatigue regime were carried out beyond 109 loading cycles called very high cycle fatigue (VHCF) to understand the fatigue properties and damage mechanisms of materials.Design/methodology/approach: Torsional fatigue tests were conducted using a 20 kHz frequency ultrasonic fatigue testing devic...

  7. 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.

  8. High-cycle fatigue properties of structural materials for FBR (2). High-cycle fatigue tests of 316FR steel at elevated temperature. Interim report

    International Nuclear Information System (INIS)

    In liquid metal cooled Fast Reactors (LMFBRs), thermal fluctuation due to fluid mixing induces high-cycle fatigue damages on structural materials. Such a cyclic thermal stress is estimated to repeat approximately from 108 to 109 cycles during a plant service period. Therefore, it is essential to investigate the fatigue property in a very-high cycle region. In this study, high-cycle fatigue tests at 550degC, 600degC, and 650degC under strain controlled conditions were carried out for the 316FR steel. The following results are obtained until now. (1) Adopting experimental techniques using laser level meter, high-cycle fatigue tests were performed at elevated temperature in the repetition frequency of 10-60 Hz, and the high cycle fatigue fracture data up to 107 cycle regions were obtained. (2) The number of cycles to failure observed in the high-cycle fatigue tests up to 107 cycle regions was larger than that calculated from simple extrapolation of average fatigue failure formula given in the material strength standard (DDS) for a design. Moreover, these lives were also conservative in comparison with those estimated from the high-cycle fatigue failure formula given by KOM-MSS WG. (3) The influence of frequency on fatigue life was not almost significant in the range from 0.1 to 60Hz. In contrast, the influence of temperature on fatigue life was observed. (4) The fisheye fracture was observed in the high-cycle fatigue test specimens failure in 107 cycle regions. (author)

  9. High cycle fatigue of austenitic stainless steels

    International Nuclear Information System (INIS)

    This study concerns the evaluation of material data to be used in LMFBR design codes. High cycle fatigue properties of three austenitic stainless steels are evaluated: type AISI 316 (UKAEA tests), type AISI 316L (CEA tests) and type AISI 304 (Interatom tests). The data on these steels comprised some 550 data points from 14 casts. This data set covered a wide range of testing parameters: temperature from 20-6250C, frequency from 1-20 000 Hz, constant amplitude and random fatigue loading, with and without mean stress, etc. However, the testing conditions chosen by the three partners differed considerably because they had been fixed independently and not harmonized prior to the tests. This created considerable difficulties for the evaluations. Experimental procedures and statistical treatments used for the three subsets of data are described and discussed. Results are presented in tables and graphs. Although it is often difficult to single out the influence of each parameter due to the different testing conditions, several interesting conclusions can be drawn: The HCF properties of the three steels are consistent with the 0.2% proof stress, the fatigue limit being larger than the latter at temperatures above 5500C. The type 304 steel has lower tensile properties than the two other steels and hence also lower HCF properties. Parameters which clearly have a significant effect of HCF behaviour are mean stress or R-ratio (less in the non-endurance region than in the endurance region), temperature, cast or product. Other parameters have probably a weak or no effect but it is difficult to conclude due to insufficient data: environment, specimen orientation, frequency, specimen geometry

  10. Effects of a high mean stress on the high cycle fatigue life of PWA 1480 and correlation of data by linear elastic fracture mechanics

    Science.gov (United States)

    Majumdar, S.; Kwasny, R.

    1985-01-01

    High-cycle fatigue tests using 5-mm-diameter smooth specimens were performed on the single crystal alloy PWA 1480 (001 axis) at 70F (room temperature) in air and at 100F (538C) in vacuum (10 to the -6 power torr). Tests were conducted at zero mean stress as well as at high tensile mean stress. The results indicate that, although a tensile mean stress, in general, reduces life, the reduction in fatigue strength, for a given mean stress at a life of one million cycles, is much less than what is predicted by the usual linear Goodman plot. Further, the material appears to be significantly more resistant to mean stress effects at 1000F than at 70F. Metallographic examinations of failed specimens indicate that failures in all cases are initiated from micropores of sizes of the order of 30 to 40 microns. Since the macroscopic stress-strain response in all cases was observed to be linear elastic, linear elastic fracture mechanics (LEFM) analyses were carried out to determine the crack growth curves of the material assuming that crack initiation from a micropore (a sub o = 40 microns) occurs very early in life. The results indicate that the calculated crack growth rates at an R (defined as the ratio between minimum stress to maximum stress) value of zero are approximately the same at 70F as at 1000F. However, the calculated crack growth rates at other R ratios, both positive and negative, tend to be higher at 70F than at 1000F. Calculated threshold effects at large R values tend to be independent of temperature in the temperature regime studied. They are relatively constant with increasing R ratio up to a value of about 0.6, beyond which the calculated threshold stress intensity factor range decreases rapidly with increasing R ratios.

  11. High cycle fatigue behaviour of extruded Magnesium alloys containing Neodymium

    OpenAIRE

    Nascimento Silva Ferri, Ligia

    2014-01-01

    In the present work the high cycle fatigue behaviour and quasi-static mechanical properties of extruded profiles of newly designed magnesium alloys containing rare earth element, Nd were investigated. The study mainly concerned the damage mechanisms under dynamic loading in the high cycle fatigue regime. The different damage mechanisms, interactions among them as well as their association with microstructural features (i.e. crystallographic texture, precipitates and grain size), which have a ...

  12. High-cycle Fatigue Properties of Alloy718 Base Metal and Electron Beam Welded Joint

    Science.gov (United States)

    Ono, Yoshinori; Yuri, Tetsumi; Nagashima, Nobuo; Sumiyoshi, Hideshi; Ogata, Toshio; Nagao, Naoki

    High-cycle fatigue properties of Alloy 718 plate and its electron beam (EB) welded joint were investigated at 293 K and 77 K under uniaxial loading. At 293 K, the high-cycle fatigue strength of the EB welded joint with the post heat treatment exhibited somewhat lower values than that of the base metal. The fatigue strengths of both samples basically increased at 77 K. However, in longer life region, the EB welded joint fractured from a blow hole formed in the welded zone, resulting in almost the same fatigue strength at 107 cycles as that at 293 K.

  13. 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.

  14. Estimation of the Plain High-Cycle Fatigue Propagation Resistance in Steels

    Directory of Open Access Journals (Sweden)

    Mirco D. Chapetti

    2002-06-01

    Full Text Available In this work a method to estimate the high cyclic fatigue propagation life of steel specimens under constant loading is presented. This method is based in experimental evidence that the fatigue limit represents the threshold stress for the propagation of nucleated cracks, so that both the fatigue limit and the fatigue resistance depend on the effective resistance of the microstructural barriers that have to be overcome by the nucleated cracks. It is proposed also, that in those cases where the number of cycles that is necessary for the nucleation of the cracks can be neglected, the fatigue crack propagation life can be taken as an estimation of the total fatigue life. The high cycle fatigue propagation life of a structural steel of the type JIS 10C is estimated.

  15. Estimation of the Plain High-Cycle Fatigue Propagation Resistance in Steels

    Scientific Electronic Library Online (English)

    Mirco D., Chapetti.

    2002-06-01

    Full Text Available In this work a method to estimate the high cyclic fatigue propagation life of steel specimens under constant loading is presented. This method is based in experimental evidence that the fatigue limit represents the threshold stress for the propagation of nucleated cracks, so that both the fatigue li [...] mit and the fatigue resistance depend on the effective resistance of the microstructural barriers that have to be overcome by the nucleated cracks. It is proposed also, that in those cases where the number of cycles that is necessary for the nucleation of the cracks can be neglected, the fatigue crack propagation life can be taken as an estimation of the total fatigue life. The high cycle fatigue propagation life of a structural steel of the type JIS 10C is estimated.

  16. High cycle thermal fatigue crack initiation behavior of type 304 stainless steel in pure water

    International Nuclear Information System (INIS)

    In order to maintain the integrity of engineering plants, it is necessary to evaluate the thermal fatigue life of certain structures. While low cycle thermal fatigue behavior has been widely studied in the past, high cycle thermal fatigue behavior has not been studied due to some difficulties with experiment. In this paper, an apparatus for performing high cycle thermal fatigue tests in pure water is described. High and low temperature water is continuously supplied into each passage in an autoclave, so that the surface of a revolving cylindrical specimen in the autoclave suffers from revolution synchronized thermal fatigue. The beat transfer coefficients between the water and the metal surface were considerably high. These were 50,000--70,OOOW/m 2K for the thermal cycle frequency less than 5Hz and 70,000--120,000W/m2K for the thermal cycle frequency higher than 5Hz. A high stress amplitude can therefore be obtained at a high thermal cycle frequency by the high heat transfer coefficient. Thermal fatigue cracks were observed in specimens under the testing conditions of fictitious stress amplitudes over 290MPa in Type 304 stainless steel. The thermal fatigue limit is therefore considered to be around 290MPa. The number of cycles to crack initiation agreed with that for the mechanical fatigue when the fictitious stress amplitudes were identical. It is considered that the thermal fatigue crack initiation life can be predicted from the mechanical fatigue crack initiation life

  17. A New Multiaxial High-Cycle Fatigue Criterion Based on the Critical Plane for Ductile and Brittle Materials

    Science.gov (United States)

    Wang, Cong; Shang, De-Guang; Wang, Xiao-Wei

    2015-02-01

    An improved high-cycle multiaxial fatigue criterion based on the critical plane was proposed in this paper. The critical plane was defined as the plane of maximum shear stress (MSS) in the proposed multiaxial fatigue criterion, which is different from the traditional critical plane based on the MSS amplitude. The proposed criterion was extended as a fatigue life prediction model that can be applicable for ductile and brittle materials. The fatigue life prediction model based on the proposed high-cycle multiaxial fatigue criterion was validated with experimental results obtained from the test of 7075-T651 aluminum alloy and some references.

  18. High-cycle fatigue strength of a pultruded composite material

    Directory of Open Access Journals (Sweden)

    L. Vergani

    2009-01-01

    Full Text Available Dealing with composites in polymeric matrix, the pultruded ones are among the more suitable for large production rates and volumes. For this reason, their use is increasing also in structural applications in civil and mechanical engineering. However, their use is still limited by the partial knowledge of their fatigue behaviour; in many applications it is, indeed, required a duration of many millions of cycles, while most of the data that can be found in literature refer to a maximum number of cycles equal to 3 millions. In this paper a pultruded composite used for manufacturing structural beams is considered and its mechanical behaviour characterized by means of static and high-cycle fatigue tests. The results allowed to determine the S-N curve of the material and to assess the existence of a fatigue limit. Observations at the scanning electronic microscope (SEM allowed to evaluate the damage mechanisms involved in the static and fatigue failure of the material.

  19. High-cycle fatigue of IN 713LC.

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Mintách, Rastislav; Kone?ná, R.

    Brno : VUTIUM Brno, 2008 - (Pokluda, J.; Lukáš, P.; Šandera, P.; Dlouhý, I.), s. 945-951 ISBN 978-80-214-3692-3. [ECF17 - European Conference on Fracture /17./. Brno (CZ), 02.09.2008-05.09.2008] R&D Projects: GA MPO FT-TA4/023 Institutional research plan: CEZ:AV0Z20410507 Keywords : Inconel 713LC * high cycle fatigue * casting defects * largest extreme value statistic Subject RIV: JG - Metallurgy

  20. Competition between microstructure and defect in multiaxial high cycle fatigue

    Directory of Open Access Journals (Sweden)

    F. Morel

    2015-07-01

    Full Text Available This study aims at providing a better understanding of the effects of both microstructure and defect on the high cycle fatigue behavior of metallic alloys using finite element simulations of polycrystalline aggregates. It is well known that the microstructure strongly affects the average fatigue strength and when the cyclic stress level is close to the fatigue limit, it is often seen as the main source of the huge scatter generally observed in this fatigue regime. The presence of geometrical defects in a material can also strongly alter the fatigue behavior. Nonetheless, when the defect size is small enough, i.e. under a critical value, the fatigue strength is no more affected by the defect. The so-called Kitagawa effect can be interpreted as a competition between the crack initiation mechanisms governed either by the microstructure or by the defect. Surprisingly, only few studies have been done to date to explain the Kitagawa effect from the point of view of this competition, even though this effect has been extensively investigated in the literature. The primary focus of this paper is hence on the use of both FE simulations and explicit descriptions of the microstructure to get insight into how the competition between defect and microstructure operates in HCF. In order to account for the variability of the microstructure in the predictions of the macroscopic fatigue limits, several configurations of crystalline orientations, crystal aggregates and defects are studied. The results of each individual FE simulation are used to assess the response at the macroscopic scale thanks to a probabilistic fatigue criterion proposed by the authors in previous works. The ability of this criterion to predict the influence of defects on the average and the scatter of macroscopic fatigue limits is evaluated. In this paper, particular emphasis is also placed on the effect of different loading modes (pure tension, pure torsion and combined tension and torsion on the experimental and predicted fatigue strength of a 316 stainless steel containing artificial defect.

  1. High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels

    International Nuclear Information System (INIS)

    High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 106 cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

  2. High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S. [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P., E-mail: pentti.karjalainen@oulu.fi [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland)

    2010-08-20

    High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 10{sup 6} cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

  3. High cycle fatigue of 2.25Cr-1Mo steel at elevated temperatures

    International Nuclear Information System (INIS)

    Information on the elevated temperature, long life (> 105 cycles to failure) fatigue resistance of pressure vessel and piping alloys is needed to properly design structural components subjected to low amplitude cyclic loadings at high temperatures. The high cycle fatigue resistance of annealed 2 1/4 Cr-1Mo steel has been evaluated in air at temperatures up to 5380C. A design fatigue curve has been developed for temperatures 0C, and a design fatigue curve has been developed for 5380C maximum temperature. These curves are for strain rates >= 4 x 10-3 sec-1, more long life fatigue data are needed for applications at lower strain rates. The effect of tensile mean stress on fatigue life has been evaluated. Design fatigue curve corrections for maximum effect of mean stress appear to be adequate at 0C, but they may not be satisfactory at higher temperatures. The present experimental work was limited to constant amplitude cycling and a crack initiation failure criterion. (author)

  4. Fatigue behaviour and failure analysis of IN 713LC in high-cycle fatigue region.

    Czech Academy of Sciences Publication Activity Database

    Mintách, R.; Kunz, Ludvík; Bok?vka, O.

    2009-01-01

    Ro?. 16, 3a (2009), s. 37-40. ISSN 1335-0803 R&D Projects: GA MPO FT-TA4/023 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ni base superalloy * casting defect * high-cycle fatigue Subject RIV: JG - Metallurgy

  5. Fatigue behaviour of ultrafine-grained copper in very high cycle fatigue regime.

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Bok?vka, O.

    2008-01-01

    Ro?. 15, ?. 4 (2008), s. 1-5. ISSN 1335-0803 R&D Projects: GA MŠk(CZ) 1P05ME804 Institutional research plan : CEZ:AV0Z20410507 Keywords : very high cycle fatigue * ultrafine-grained structure * ECAP * Copper Subject RIV: JG - Metallurgy

  6. Al-Li alloy AA2198's very high cycle fatigue crack initiation mechanism and its fatigue thermal effect

    Science.gov (United States)

    Xu, Luopeng; Cao, Xiaojian; Chen, Yu; Wang, Qingyuan

    2015-10-01

    AA2198 alloy is one of the third generation Al-Li alloys which have low density, high elastic modulus, high specific strength and specific stiffness. Compared With the previous two generation Al-Li alloys, the third generation alloys have much improved in alloys strength, corrosion resistance and weldable characteristic. For these advantages, the third generation Al-Li alloys are used as aircraft structures, such as C919 aviation airplane manufactured by China and Russia next generation aviation airplane--MS-21. As we know, the aircraft structures are usually subjected to more than 108 cycles fatigue life during 20-30 years of service, however, there is few reported paper about the third generation Al-Li alloys' very high cycle fatigue(VHCF) which is more than 108 cycles fatigue. The VHCF experiment of AA2198 have been carried out. The two different initiation mechanisms of fatigue fracture have been found in VHCF. The cracks can initiate from the interior of the testing material with lower stress amplitude and more than 108 cycles fatigue life, or from the surface or subsurface of material which is the dominant reason of fatigue failures. During the experiment, the infrared technology is used to monitor the VHCF thermal effect. With the increase of the stress, the temperature of sample is also rising up, increasing about 15 °C for every 10Mpa. The theoretical thermal analysis is also carried out.

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

    International Nuclear Information System (INIS)

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

  8. Effects of loading condition on very-high-cycle fatigue behaviour and dominant variable analysis

    Science.gov (United States)

    Lei, ZhengQiang; Xie, JiJia; Sun, ChengQi; Hong, YouShi

    2014-01-01

    The specimens of a high carbon chromium steel were quenched and tempered at 150°C, 180°C and 300°C. Such specimens were tested via rotating bending and a push-pull type of axial loading to investigate the influences of loading condition on the behaviour of very-high-cycle fatigue (VHCF). Experimental results show the different influences of inclusion size on the fatigue life for the two loading conditions. Predominant factors and mechanism for the fine-granular-area (FGA) of crack origin were discussed. In addition, a reliability analysis based on a modified Tanaka-Mura model was carried out to evaluate the sensitivity of inclusion size, stress, and ? K FGA to the life of VHCF crack initiation.

  9. Notch size effects on high cycle fatigue limit stress of Udimet 720

    International Nuclear Information System (INIS)

    Notch size effects on the high cycle fatigue (HCF) limit stress of Ni-base superalloy Udimet 720 were investigated on cylindrical specimens with three notch sizes of the same stress concentration factor Kt=2.74. The HCF limit stress corresponding to a life of 106 cycles was experimentally determined at a stress ratio of 0.1 and a frequency of 25 Hz at room temperature. The stresses were calculated using finite element analysis (FEA) and the specimens analyzed using scanning electron microscopy (SEM). Test results show that at the same Kt value, notch size can slightly affect the HCF limit stress of U720 when notch root plasticity occurs. FEA and SEM results reveal that the notch size effects are influenced by a complicated combination of the stress and plastic strain fields at the notch tip, the nominal stress, and the effects of prior plastic deformation on fatigue crack initiation

  10. Notch size effects on high cycle fatigue limit stress of Udimet 720

    Energy Technology Data Exchange (ETDEWEB)

    Ren Weiju; Nicholas, Theodore

    2003-09-25

    Notch size effects on the high cycle fatigue (HCF) limit stress of Ni-base superalloy Udimet 720 were investigated on cylindrical specimens with three notch sizes of the same stress concentration factor K{sub t}=2.74. The HCF limit stress corresponding to a life of 10{sup 6} cycles was experimentally determined at a stress ratio of 0.1 and a frequency of 25 Hz at room temperature. The stresses were calculated using finite element analysis (FEA) and the specimens analyzed using scanning electron microscopy (SEM). Test results show that at the same K{sub t} value, notch size can slightly affect the HCF limit stress of U720 when notch root plasticity occurs. FEA and SEM results reveal that the notch size effects are influenced by a complicated combination of the stress and plastic strain fields at the notch tip, the nominal stress, and the effects of prior plastic deformation on fatigue crack initiation.

  11. Development of a high cycle vibration fatigue diagnostic system with non-contact vibration sensing

    Energy Technology Data Exchange (ETDEWEB)

    Yoshitsugu, Nekomoto; Satoshi, Kiriyama; Moritatsu, Nishimura [Mitsubishi Heavy Industries Ltd., Tokyo (Japan); Kenji, Matsumoto [Japan Power Engineering and Inspection Corporation (Japan); Eiji, O' shima [Tokyo Institute of Technology (Japan)

    2001-07-01

    Nuclear power plants have a large number of pipes. Of these small-diameter pipe branches in particular are often damaged due to high-cycle fatigue. In order to ensure the reliability of a plant it is important to detect the fatigues in pipe branches at an early stage and to develop the technology to predict and diagnose the advancement of fatigue. Further, in order to carry out the diagnosis of the piping system effectively during operation, non-contact evaluation is useful. Hence, we have developed a 'high-cycle fatigue diagnostic system with non-contact vibration sensing', where the vibration of the pipe branch is measured using a non-contact sensor. Since the contents of the developed sensor technology has already been reported, this paper mainly describes the newly developed high-cycle fatigue diagnostic system. (authors)

  12. Fatigue behavior of titanium Ti-4Al-2V rods under high cycle loading

    International Nuclear Information System (INIS)

    The high cycle fatigue behavior of titanium alloy Ti-4Al-2V rods at room temperature was evaluated. The common high cycle fatigue (HCF) tests with group specimen and the up-and-down tests were performed under bending and rotating loadings at room temperature in air environment. The experimental data were analyzed and the S-N curve and P-S-N curve were plotted, and the fracture morphology is analyzed by SEM. The results show that Ti-4Al-2V rods have good resistance to high cycle fatigue and the value of ?-1(107) is about the same with that of the corresponding equation. The fracture morphology of Ti-4Al-2V specimen after fatigue failure presents typical characteristics with three areas of fatigue crack initiation,growth and rupture. (authors)

  13. Conducting High Cycle Fatigue Strength Step Tests on Gamma TiAl

    Science.gov (United States)

    Lerch, Brad; Draper, Sue; Pereira, J. Mike

    2002-01-01

    High cycle fatigue strength testing of gamma TiAl by the step test method is investigated. A design of experiments was implemented to determine if the coaxing effect occurred during testing. Since coaxing was not observed, step testing was deemed a suitable method to define the fatigue strength at 106 cycles.

  14. Microstructural aspects of duplex steel during high cycle and very high cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Knobbe, H; Koester, P; Christ, H-J [Institut fuer Werkstofftechnik, Universitaet Siegen, Paul-Bonatz-Strasse 9-11, D-57068 Siegen (Germany); Krupp, U [Fakultaet Ingenieurwissenschaften und Informatik, Fachhochschule Osnabrueck, Albrechtstrasse 30, D-49076 Osnabrueck (Germany); Fritzen, C-P, E-mail: helge.knobbe@uni-siegen.d [Institut fuer Mechanik und Regelungstechnik - Mechatronik, Universitaet Siegen, Paul-Bonatz-Strasse 9-11, D-57068 Siegen (Germany)

    2010-07-01

    Fatigue experiments were conducted up to N=10{sup 8} cycles on a duplex stainless steel. The investigations revealed important information: (i) most of the slip markings on {l_brace}111{r_brace}-slip planes form during the early stage of fatigue ({approx}10{sup 4}), although many grains stay active in developing more and/or longer slip bands (investigations with SEM/EBSD). It was found that the damage in these grains often has its origin at grain or phase boundaries, growing into the interior of the grains; (ii) in most of the recrystallisation twins slip markings are present in all parts of the grain leading to the assumption that just tilted grain boundaries are not very effective as microstructural barriers. In cases where the twin grain boundary is favorably oriented, it even can promote microcrack initiation; (iii) phase boundaries are most effective in restricting dislocation movement to the softer austenite, since no evidence of growing fatigue damage was found in ferritic grains. These findings lead to the conclusion that for the material studied an endurance limit exists despite occurring plastic deformation. This behaviour is a consequence of the barrier effect induced by phase boundaries against short crack propagation and holds true as long as no inclusions are present.

  15. Microstructural aspects of duplex steel during high cycle and very high cycle fatigue

    International Nuclear Information System (INIS)

    Fatigue experiments were conducted up to N=108 cycles on a duplex stainless steel. The investigations revealed important information: (i) most of the slip markings on {111}-slip planes form during the early stage of fatigue (?104), although many grains stay active in developing more and/or longer slip bands (investigations with SEM/EBSD). It was found that the damage in these grains often has its origin at grain or phase boundaries, growing into the interior of the grains; (ii) in most of the recrystallisation twins slip markings are present in all parts of the grain leading to the assumption that just tilted grain boundaries are not very effective as microstructural barriers. In cases where the twin grain boundary is favorably oriented, it even can promote microcrack initiation; (iii) phase boundaries are most effective in restricting dislocation movement to the softer austenite, since no evidence of growing fatigue damage was found in ferritic grains. These findings lead to the conclusion that for the material studied an endurance limit exists despite occurring plastic deformation. This behaviour is a consequence of the barrier effect induced by phase boundaries against short crack propagation and holds true as long as no inclusions are present.

  16. Effect of rare earth elements on high cycle fatigue behavior of AZ91 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Mokhtarishirazabad, M., E-mail: mehdi-mokhtari@hotmail.com [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Boutorabi, S.M.A. [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Azadi, M.; Nikravan, M. [Irankhodro Powertrain Company (IPCO), Tehran (Iran, Islamic Republic of)

    2013-12-10

    This article investigates effects of adding rare earth elements (RE) into a magnesium–aluminum–zinc alloy (the AZ91 alloy) on its high cycle fatigue (HCF) behavior. For this purpose, AZ91 and AZ91+1% RE (AZE911) alloys were gravity casted in a metallic die. RE elements were added to the AZ91 alloy in the form of mischmetals. Microscopic evaluations with the scanning electron microscopy (SEM) and mechanical tests include tensile, hardness and HCF behaviors, were performed on prepared samples. Rotary bending fatigue tests were carried out at a stress ratio (R) of ?1 and a frequency of 125 Hz, at the room temperature, in the air. The microscopic investigation demonstrates that the addition of 1% RE elements leads to the formation of Al{sub 11}RE{sub 3} intermetallic particles which is associated to the reduction of ?-(Mg{sub 17}Al{sub 12}) phases. Results of mechanical experiments suggest a negligible effect of adding 1% RE elements on mechanical properties of the AZ91 alloy. Curves of stress-life (S–N) shows an increase in the fatigue strength at 10{sup 5} cycles, from 100±10 MPa to 135±10 MPa, when RE elements were added to the AZ91 alloy.

  17. Effectiveness of the modified fatigue criteria for biaxial loading of notched specimen in high-cycle region.

    Czech Academy of Sciences Publication Activity Database

    Major, Št?pán; Hubálovský, Š.; Kocour, Vladimír; Valach, Jaroslav

    Vol. 732. Zürich : Trans Tech Publications, 2015 - (Polach, P.), s. 63-70 ISBN 978-3-03835-413-0. ISSN 1660-9336. [EAN 2014. Conference on experimental stress analysis. /52./. Mariánské Lázn? (CZ), 02.06.2014-05.06.2014] Institutional support: RVO:68378297 Keywords : notched specimen * multiaxial criteria * biaxial loading * fatigue life * bending-torsion loading * high-cycle loading Subject RIV: JM - Building Engineering http://www.scientific.net/AMM.732.63

  18. High cycle fatigue of austenitic stainless steels under random loading

    International Nuclear Information System (INIS)

    To investigate reactor components, load control random fatigue tests were performed at 3000C and 5500C, on specimens from austenitic stainless steels plates in the transverse orientation. Random solicitations are produced on closed loop servo-hydraulic machines by a mini computer which generates random load sequence by the use of reduced Markovian matrix. The method has the advantage of taking into account the mean load for each cycle. The solicitations generated are those of a stationary gaussian process. Fatigue tests have been mainly performed in the endurance region of fatigue curve, with scattering determination using stair case method. Experimental results have been analysed aiming at determining design curves for components calculations, depending on irregularity factor and temperature. Analysis in term of mean square root fatigue limit calculation, shows that random loading gives more damage than constant amplitude loading. Damage calculations following Miner rule have been made using the probability density function for the case where the irregularity factor is nearest to 100 %. The Miner rule is too conservative for our results. A method using design curves including random loading effects with irregularity factor as an indexing parameter is proposed

  19. Application of the U.S. high cycle fatigue data base to wind turbine blade lifetime predictions

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, H.J. [Sandia National Labs., Albuquerque, NM (United States); Mandell, J.F. [Montana State Univ., Bozeman, MT (United States)

    1995-12-01

    This paper demonstrates a methodology for predicting the service lifetime of wind turbine blades using the high-cycle fatigue data base for typical U.S. blade materials developed by Mandell, et al. (1995). The first step in the analysis is to normalize the data base (composed primarily of data obtained from specialized, relatively small coupons) with fatigue data from typical industrial laminates to obtain a Goodman Diagram that is suitable for analyzing wind turbine blades. The LIFE2 fatigue analysis code for wind turbines is then used for the fatigue analysis of a typical turbine blade with a known load spectrum. In the analysis, a linear damage model, Miner`s Rule, is used to demonstrate the prediction of the service lifetime for a typical wind turbine blade under assumed operating strain ranges and stress concentration factors. In contrast to typical European data, the asymmetry in this data base predicts failures under typical loads to be compressive.

  20. High cycle fatigue crack propagation resistance and fracture toughness in ship steels (Short Communication

    Directory of Open Access Journals (Sweden)

    R.S. Tripathi

    2001-04-01

    Full Text Available In this paper, two grades of steel, viz., plain carbon steel and low alloy steel used in naval ships have been selected for studies on high cycle fatigue, crack propagation, stress intensity and crack opening displacement (COD. Specimen for high cycle fatigue was prepared as per IS: 1608. High cycle fatigue was carried out up to 50,000 cycles at 1000 kgfto 2000 kgfloads. Up to 2000 kgfloads, both the materials were observed within elastic zones. A number of paran1eters, including stress, strain and strain range, which indicate elastic behaviour of steels, have been considered. Low alloy steel specimen was prepared as per ASTM standard: E-399 and subjected to 5,00,000 cycles. Crack propagation, COD, stress intensity, load-cycle variations, load-COD relation, and other related paran1eters have been studied using a modem universal testing machine with state-of-the-art technology

  1. High-cycle fatigue of Ni-base superalloy Inconel 713LC.

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Kone?ná, R.

    2010-01-01

    Ro?. 32, ?. 6 (2010), s. 908-913. ISSN 0142-1123 R&D Projects: GA MPO FT-TA4/023; GA MŠk MEB080812 Institutional research plan: CEZ:AV0Z20410507 Keywords : IN 713LC * High-cycle fatigue * Effect of mean stress * Fractography * Casting defetcts * Extreme value statistics Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.799, year: 2010

  2. The role of high cycle fatigue (HCF) onset in Francis runner reliability

    International Nuclear Information System (INIS)

    High Cycle Fatigue (HCF) plays an important role in Francis runner reliability. This paper presents a model in which reliability is defined as the probability of not exceeding a threshold above which HCF contributes to crack propagation. In the context of combined Low Cycle Fatigue (LCF) and HCF loading, the Kitagawa diagram is used as the limit state threshold for reliability. The reliability problem is solved using First-Order Reliability Methods (FORM). A study case is proposed using in situ measured strains and operational data. All the parameters of the reliability problem are based either on observed data or on typical design specifications. From the results obtained, we observed that the uncertainty around the defect size and the HCF stress range play an important role in reliability. At the same time, we observed that expected values for the LCF stress range and the number of LCF cycles have a significant influence on life assessment, but the uncertainty around these values could be neglected in the reliability assessment.

  3. High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718

    Science.gov (United States)

    Ono, Y.; Yuri, T.; Sumiyoshi, H.; Takeuchi, E.; Matsuoka, S.; Ogata, T.

    2006-03-01

    High-cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged-INCONEL 718 nickel-based superalloy with a mean gamma (?) grain size of 25 ?m. In the present material, plate-like delta phase precipitated at ? grain boundaries and niobium (Nb)-enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High-cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn't appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb-enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds of distinctive crack initiation behavior seem to lower the high-cycle fatigue strength below room temperature in the present material.

  4. High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718

    International Nuclear Information System (INIS)

    High-cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged-INCONEL 718 nickel-based superalloy with a mean gamma (?) grain size of 25 ?m. In the present material, plate-like delta phase precipitated at ? grain boundaries and niobium (Nb)-enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High-cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn't appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb-enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds of distinctive crack initiation behavior seem to lower the high-cycle fatigue strength below room temperature in the present material

  5. High cycle fatigue of nickel-based superalloy MAR-M 247 at high temperatures.

    Czech Academy of Sciences Publication Activity Database

    Šmíd, Miroslav; Kunz, Ludvík; Huta?, Pavel; Hrbá?ek, K.

    Amsterdam : Elsevier, 2014 - (Gulagliano, M.; Vergani, L.), s. 329-332 ISSN 1877-7058. - (Procedia Engineering. 74). [ICMFM 2014 International Colloquium on Mechanical Fatigue of Metals /17./. Verbania (IT), 25.06.2014-27.06.2014] R&D Projects: GA MPO FR-TI4/030; GA MŠk(CZ) EE2.3.20.0214 Institutional support: RVO:68081723 Keywords : High cycle fatigue * Superalloy * MAR-M 247 * High temperature * Fracture surface * S-N curve Subject RIV: JL - Materials Fatigue , Friction Mechanics

  6. High-Cycle Fatigue Resistance of Si-Mo Ductile Cast Iron as Affected by Temperature and Strain Rate

    Science.gov (United States)

    Matteis, Paolo; Scavino, Giorgio; Castello, Alessandro; Firrao, Donato

    2015-09-01

    Silicon-molybdenum ductile cast irons are used to fabricate exhaust manifolds of internal combustion engines of large series cars, where the maximum pointwise temperature at full engine load may be higher than 973 K (700 °C). In this application, high-temperature oxidation and thermo-mechanical fatigue (the latter being caused by the engine start and stop and by the variation of its power output) have been the subject of several studies and are well known, whereas little attention has been devoted to the high-cycle fatigue, arising from the engine vibration. Therefore, the mechanical behavior of Si-Mo cast iron is studied here by means of stress-life fatigue tests up to 10 million cycles, at temperatures gradually increasing up to 973 K (700 °C). The mechanical characterization is completed by tensile and compressive tests and ensuing fractographic examinations; the mechanical test results are correlated with the cast iron microstructure and heat treatment.

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

    International Nuclear Information System (INIS)

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

  8. Biaxial high cycle fatigue: experimental investigation and two-scale damage model

    International Nuclear Information System (INIS)

    This research thesis first describes the multi-axial fatigue phenomenon in the cases of mechanical and complex loadings, discusses multi-axial fatigue criteria, and presents the approach of fatigue by incremental damage mechanics. Then, it reports an experimental investigation of fatigue crack initiation under biaxial polycyclic fatigue in 304L austenitic stainless steel and in titanium alloy. The author presents a probabilistic two-scale damage model, and then reports the assessment of multi-axial fatigue life by means of this model

  9. Effects of load ratio, R, and test temperature on high cycle fatigue behavior of nano-structured Al–4Y–4Ni–X alloy composites

    International Nuclear Information System (INIS)

    Nanostructured Al–4Y–4Ni–X composites created by extruding atomized amorphous powders at different extrusion ratios were tested under high cycle bending fatigue at load ratios, R=0.1, 0.33 and ?1 at room temperature, 149 °C and 260 °C. Increasing the extrusion ratio generally improved the fatigue life and the fatigue limits were well in excess of that obtained on conventional aluminum alloys at all temperatures tested. The fatigue limits obtained in this work were also compared to previously reported values for a nanostructured composite Al–Gd–Ni–Fe alloy produced via similar means.

  10. Estimation of High Cycle Thermal Fatigue Caused by Mixing Flow at RHR System (II)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sun-ki; Lee, Sang-kook [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

    2006-07-01

    In the case of nuclear power plant, thermal fatigue occurs in the piping system because of temperature change accompanied with plant operations. Therefore pipe and instrument are designed not to exceed fatigue limit. But damage is happening in piping system by thermal fatigue that is not considered at design (for example, abnormal movement at surge line of Torjan, crack at safety injection line of Farley unit 2 and Tihange unit 1, crack at RHR system of Genkai unit 1 and Civaux unit 1 etc). Root cause of these damages is explained by the thermal stratification and thermal cycling, thermal striping phenomena. In this paper, integrity assessment of high cycle thermal fatigue were carried out about the heat exchange out let of residual heat removal system (RHR system) of operating domestic PWR nuclear power plants, which is the high temperature coolant mixing region.

  11. Influence of defects on the very high cycle fatigue behaviour of forged aeronautic titanium alloy

    Directory of Open Access Journals (Sweden)

    Nikitin Alexander

    2014-06-01

    Full Text Available This paper is focused on fatigue failure of forged aeronautic titanium alloy Ti-6Al-4Mo under VHCF loading. Continuous fatigue tests were carried out in gigacycle fatigue regime (up to on 1010 cycles on specimens machined from real aircraft compressor disk produced by forging. It has been shown, that crack initiation site shifts from surface to subsurface location with stress amplitude decreasing and fatigue life increasing. Microstructural inhomogeneities so that “hard” alpha particles, borders of large alpha lamella clusters and TiN particles are the cause of fatigue crack nucleation in forged Ti-6Al-4Mo titanium alloy under VHCF loading.

  12. Avoiding thermal striping damage: Experimentally-based design procedures for high-cycle thermal fatigue

    International Nuclear Information System (INIS)

    In the coolant circuits of a liquid metal cooled reactor (LMR), where there is turbulent mixing of coolant streams at different temperatures, there are temperature fluctuations in the fluid. If an item of the reactor structure is immersed in this fluid it will, because of the good heat transfer from the flowing liquid metal, experience surface temperature fluctuations which will induce dynamic surface strains. It is necessary to design the reactor so that these temperature fluctuations do not, over the life of the plant, cause damage. The purpose of this paper is to describe design procedures to prevent damage of this type. Two such procedures are given, one to prevent the initiation of defects in a nominally defect-free structure or to allow initiation only at the end of the component life, and the other to prevent significant growth of undetectable pre-existing defects of the order of 0.2 to 0.4 mm in depth. Experimental validation of these procedures is described, and the way they can be applied in practice is indicated. To set the scene the paper starts with a brief summary of cases in which damage of this type, or the need to avoid such damage, have had important effects on reactor operation. Structural damage caused by high-cycle thermal fatigue has had a significant adverse influence on the operation of LMRs on several occasions. It is necessary to eliminate the risk of such damage at the design stage. In the absence of detailed knowledge of the temperature history to which it will be subject, an LMR structure can be designed so that, if it is initially free of defects more than 0.1 mm deep, no such defects will be initiated by high-cycle fatigue. This can be done by ensuring that the maximum source temperature difference in the liquid metal is less than a limiting value, which depends on temperature. The limit is very low, however, and likely to be restrictive. This method, by virtue of its safety margin, takes into account pre-existing surface crack-like defects up to 0.1 mm deep. If the surface temperature-time history for points on the component is known, the procedure allows the calculation of allowable surface temperature amplitudes such that crack initiation will not occur before the end of the component life. This imposes a less restrictive limit, but it still might be 65 K for a life of 300,000 hours. It is also dependent on the nature of the surface temperature fluctuations, in particular the infrequent large fluctuations. In practice it is difficult to ensure that a structure as built is free from defects greater than 0.1 mm deep, and it has to be recognised that such defects may grow under the imposed thermal loading. A procedure based on limited crack growth and arrest at a depth of about 0.5 mm has been developed. It requires a knowledge of the maximum surface temperature amplitude and the frequency spectrum if the fluctuations, as well as the stress state of the component and the postulated crack shape. For a nominally unstressed structure this procedure is less restrictive and can give allowable amplitudes (though a design safety factor is not included). Detailed information on the temperature fluctuations can in principle be obtained from measurements on the plant or in a liquid metal rig, but it has been shown that if the modelling is correct an air model can provide reliable and conservative information, and can provide it more quickly and economically

  13. Effective Fatigue Stress and Criterion for High-Cycle Multi-axial Fatigue

    Science.gov (United States)

    Cai, Xiaojing; Xu, Jinquan

    2015-01-01

    Multi-axial fatigue criterion corresponding to the limiting condition of complicated multi-axial stress state is very important in application. Stresses and deformations are usually elastic if cyclic loadings are near to the limiting condition. A definition of effective fatigue stress has been proposed. Adopting the effective fatigue stress, a multi-axial fatigue criterion has been proposed by considering the equivalence of multi-axial stresses to a uni-axial problem. To clarify the fatigue criterion for a uni-axial problem with arbitrary mean stress, a quantitative relationship between fatigue limit and mean stress has also been proposed and examined. To verify the multi-axial fatigue criterion, examinations have been carried out for the cases of pure shear, shear and axial, and two-axial fatigue by experimental results. It is found that the criterion agrees well with experimental results, even for the cases with various multi-axial mean stresses and phase differences. It is also found that the shear fatigue limit is not an independent material property in common metals.

  14. Study of high cycle fatigue of PVD surface-modified austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Feng, H.P.; Lee, S.C.; Hsu, C.H.; Ho, J.M. [Tatung Inst. of Technol., Taipei (Taiwan, Province of China). Dept. of Mater. Eng.

    1999-05-25

    Austempered ductile iron (ADI) is made from ductile iron by an austempering treatment, and its main microstructure is ausferrite that is composed of acicular ferrite and high carbon austenite. The purpose of this experiment is to investigate the influence of different coating layers and the size of casting (mass effect) on the high-cycle fatigue properties of ADI. Specimens in two casting sizes of the same chemical composition were subjected to a high-toughness austempering treatment, then coated with TiN or TiCN hard films by a physical vapor deposition (PVD) process. The results showed that the fatigue limit of the small casting size ADI is 292 MPa for ADI coated with TiN and 306 MPa for ADI coated with TiCN, which are 16% and 22%, respectively, higher than that of the ADI without coating (251 MPa). For the large casting size ADI, the fatigue limits are 200, 214 and 217 MPa for ADI without coating, ADI coated with TiN and ADI coated with TiCN, respectively. ADI coated with TiN and with TiCN are 7% and 9% better than the uncoated. Thus, it is concluded that TiN and TiCN coatings by PVD can improve the high-cycle fatigue strength of ADI. This is due to the high surface hardness and possibly the ADI surface compressive residual stress as well. For the small casting size ADI, TiCN-coated specimens have a bit higher fatigue strengths and this might be attributed to the higher hardness of TiCN than TiN films. As to the effect of mass, it is found that the small casting size has better fatigue properties and benefits more from the coating films. This could have stemmed from the higher nodule count and its associated benefits in thinner castings. (orig.) 24 refs.

  15. Fatigue damage of ultrafine-grain copper in very-high cycle fatigue region.

    Czech Academy of Sciences Publication Activity Database

    Lukáš, Petr; Kunz, Ludvík; Navrátilová, Lucie; Bok?vka, O.

    2011-01-01

    Ro?. 528, - (2011), s. 7036-7040. ISSN 0921-5093 R&D Projects: GA ?R GAP108/10/2001 Institutional research plan: CEZ:AV0Z20410507 Keywords : ultrafine- grain ed microstructure * ultrasonic fatigue * crack initiation * copper Subject RIV: JL - Materials Fatigue , Friction Mechanics Impact factor: 2.003, year: 2011

  16. Damage estimates for European and U.S.sites using the U.S. high-cycle fatigue data base

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, H.J. [Wind Energy Technology, Sandia National Lab., Albuquerque, NM (United States)

    1996-09-01

    This paper uses two high-cycle fatigue data bases, one for typical U.S. blade materials and one for European materials, to analyze the service lifetime of a wind turbine blade subjected to the WISPER load spectrum for northern European sites and the WISPER protocol load spectrum for U.S. wind farm sites. The U.S. data base contains over 2200 data points that were obtained using coupon testing procedures. These data are used to construct a Goodman diagram that is suitable for analyzing wind turbine blades. This result is compared to the Goodman diagram derived from the European fatigue data base FACT. The LIFE2 fatigue analysis code for wind turbines is then used to predict the service lifetime of a turbine blade subjected to the two loading histories. The results of this study indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a U.S. wind farm site, i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a U.S. wind farm site. Further, the analysis demonstrate that the European and the U.S. fatigue material data bases are in general agreement for the prediction of tensile failures. However, for compressive failures, the two data bases are significantly different, with the U.S. data base predicting significantly shorter service lifetimes than the European data base. (au) 14 refs.

  17. Thermally Induced Ultra High Cycle Fatigue of Copper Alloys of the High Gradient Accelerating Structures

    CERN Document Server

    Heikkinen, Samuli; Wuensch, Walter

    2010-01-01

    In order to keep the overall length of the compact linear collider (CLIC), currently being studied at the European Organization for Nuclear Research (CERN), within reasonable limits, i.e. less than 50 km, an accelerating gradient above 100 MV/m is required. This imposes considerable demands on the materials of the accelerating structures. The internal surfaces of these core components of a linear accelerator are exposed to pulsed radio frequency (RF) currents resulting in cyclic thermal stresses expected to cause surface damage by fatigue. The designed lifetime of CLIC is 20 years, which results in a number of thermal stress cycles of the order of 2.33•1010. Since no fatigue data existed in the literature for CLIC parameter space, a set of three complementary experiments were initiated: ultra high cycle mechanical fatigue by ultrasound, low cycle fatigue by pulsed laser irradiation and low cycle thermal fatigue by high power microwaves, each test representing a subset of the original problem. High conductiv...

  18. Very high cycle regime fatigue of thin walled tubes made from austenitic stainless steel

    DEFF Research Database (Denmark)

    Carstensen, J.V.; Mayer, H.

    2002-01-01

    Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 × 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained in conventional rotating bending at 160 and 200 Hz and in ultrasonic axial loading at 20 kHz. Above 5 × 106 cycles the fatigue lifetimes found with both methods were comparable. The results show that the slope of the S–N curve significantly decreases beyond 108 cycles. Fracture surfaces were examined using scanning electron microscopy. Fatigue cracks initiate at the surface and no significant influence from frequency or from loading modes on fatigue crack initiation and growth is visible.

  19. Very high cycle regime fatigue of thin walled tubes made from austenitic stainless steel

    DEFF Research Database (Denmark)

    Carstensen, J.V.; Mayer, H.; Brøndsted, P.

    2002-01-01

    Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 × 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained in conventional rotating bending at 160 and 200 Hz and in ultrasonic axial loading at 20 kHz. Above 5 × 106 cycles the fatigue lifetimes found with both methods were comparable. The results show that the slope ...

  20. Additive manufactured AlSi10Mg samples using Selective Laser Melting (SLM): Microstructure, high cycle fatigue, and fracture behavior

    OpenAIRE

    Brandl, E.; Heckenberger, U.; Holzinger, V.; Buchbinder, D.

    2012-01-01

    In order to produce serial parts via additive layer manufacturing, the fatigue performance can be a critical attribute. In this paper, the microstructure, high cycle fatigue (HCF), and fracture behavior of additive manufactured AlSi10Mg samples are investigated. The samples were manufactured by a particular powder-bed process called Selective Laser Melting (SLM) and machined afterwards. 91 samples were manufactured without (30°C) and with heating (300°C) of the building platform and in differ...

  1. Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested

    Science.gov (United States)

    Zhu, Dong-Ming; Fox, Dennis S.; Miller, Robert A.

    2001-01-01

    Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high-cycle thermal fatigue behavior has been investigated on a flat Haynes 188 alloy specimen, under the test condition of 30-Hz cycle frequency (33-msec pulse period and 10-msec pulse width including a 0.2-msec pulse spike; ref. 4). Temperature distributions were calculated with one-dimensional finite difference models. The calculations show that that the 0.2-msec pulse spike can cause an additional 40 C temperature fluctuation with an interaction depth of 0.08 mm near the specimen surface region. This temperature swing will be superimposed onto the temperature swing of 80 C that is induced by the 10-msec laser pulse near the 0.53-mm-deep surface interaction region.

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

    Science.gov (United States)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

  3. Simulation of delamination growth under high cycle fatigue using cohesive zone models

    Scientific Electronic Library Online (English)

    Pedro P., Camanho; Albert, Turon; Josep, Costa.

    2008-01-01

    Full Text Available Este artigo apresenta um modelo coesivo para simular a delaminagem de materiais compósitos sob fadiga de altos ciclos. O modelo constitutivo proposto relaciona a evolução da variável de dano, d, com a velocidade de crescimento da delaminagem, da/dN. O modelo coesivo é implementado no código de eleme [...] ntos finitos ABAQUS e é utilizado na simulação de provetes fabricados em carbono-epoxy carregados ciclicamente em modo I, modo II e modo misto I e II. O modelo é validado comparando as suas previsões com resultados experimentais. Abstract in english A cohesive zone model is proposed for the simulation of delamination growth in composite materials under high-cycle fatigue loading. The basis for the formulation is an interfacial constitutive law that links fracture mechanics and damage mechanics relating the evolution of the damage variable, d, w [...] ith the crack growth rate, da/dN. The cohesive zone model is implemented in ABAQUS finite element code and used in the simulation of carbon-epoxy test specimens cyclically loaded in mode I, mode II and mixed-mode I and II. The accuracy of the model is assessed by comparing the predictions with experimental data.

  4. Manifestations of ''high-cycle fatigue'' in the nickel based alloy Inconel 792; Erscheinungsformen von ''High-Cycle-Fatigue'' in der Nickel-Basis Legierung Inconel 792

    Energy Technology Data Exchange (ETDEWEB)

    Wanzek, H.; Gartner, T.; Fruhner, A. [Lufthansa Technik, Hamburg (Germany)

    2008-08-15

    A cluster of turbine rotor blade breakages caused substantial damage to the APU generators used to generate electrical power for aircraft, eventually causing the APU to fail. The APU is located in the tail cone area of all large aircraft directly under the vertical tail. The examination of the damage to the turbine rotor blades revealed the unusual occurrence of the smooth facets which are typical of ''Stage I'' of a high-cycle fatigue fracture. The cracks had propagated from just under the surface of the strain-hardened marginal zone; the repair work being carried out made it difficult to detect the cracks. This presentation demonstrates the distinctive signs of high-cycle fatigue as well as pinpointing the problems associated with identifying these cracks in time during repair work. (orig.)

  5. Micro-scale testing and micromechanical modelling for high cycle fatigue of CoCr stent material.

    Science.gov (United States)

    Sweeney, C A; O'Brien, B; Dunne, F P E; McHugh, P E; Leen, S B

    2015-06-01

    This paper presents a framework of experimental testing and crystal plasticity micromechanics for high cycle fatigue (HCF) of micro-scale L605 CoCr stent material. Micro-scale specimens, representative of stent struts, are manufactured via laser micro-machining and electro-polishing from biomedical grade CoCr alloy foil. Crystal plasticity models of the micro-specimens are developed using a length scale-dependent, strain-gradient constitutive model and a phenomenological (power-law) constitutive model, calibrated from monotonic and cyclic plasticity test data. Experimental microstructural characterisation of the grain morphology and precipitate distributions is used as input for the polycrystalline finite element (FE) morphologies. Two microstructure-sensitive fatigue indicator parameters are applied, using local and non-local (grain-averaged) implementations, for the phenomenological and length scale-dependent models, respectively, to predict fatigue crack initiation (FCI) in the HCF experiments. PMID:25817609

  6. The Effect of Ballistic Impacts on the High Cycle Fatigue Properties of Ti-48Al-2Nb-2Cr (at.%)

    Science.gov (United States)

    Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Austin, C. M.; Erdman, O.

    2000-01-01

    The ability of gamma - TiAl to withstand potential foreign and/or domestic object damage is a technical risk to the implementation of gamma - TiAl in low pressure turbine (LPT) blade applications. The overall purpose of the present study was to determine the influence of ballistic impact damage on the high cycle fatigue strength of gamma - TiAl simulated LPT blades. Impact and specimen variables included ballistic impact energy, projectile hardness, impact temperature, impact location, and leading edge thickness. The level of damage induced by the ballistic impacting was studied and quantified on both the impact (front) and backside of the specimens. Multiple linear regression was used to model the cracking and fatigue response as a function of the impact variables. Of the impact variables studied, impact energy had the largest influence on the response of gamma - TiAl to ballistic impacting. Backside crack length was the best predictor of remnant fatigue strength for low energy impacts (gamma - TiAl samples displayed a classical mean stress dependence on the fatigue strength. For the fatigue design stresses of a 6th stage LPT blade in a GE90 engine, a Ti-48Al-2Nb-2Cr LPT blade would survive an impact of normal service conditions.

  7. High cycle fatigue and threshold behaviour of powder metallurgical Mo and Mo-alloys

    International Nuclear Information System (INIS)

    A detailed characterization of the room temperature fatigue properties of powder metallurgical Mo, Mo-W and Ti-Zr-Mo (TZM) alloys is presented. In particular the factors affecting fatigue crack nucleation and growth behaviour are described. Fatigue tests were carried out by conventional rotating-bending and compared with results from a time-saving 20 kHz resonance push-pull test method. Fatigue strength data were determined by a statistical evaluation of test results from a sufficiently large number of specimens. The results show an increase in fatigue strength with alloying additions. Fatigue cracks were observed nucleating at highly localized slip bands at the specimen surface with the fatigue crack zones comprising only a small fraction of the total specimen cross-section. Fatigue crack growth rates at low stress intensities and threshold stress intensity values for crack growth were determined for a stress ratio of R = -1 using a 20 kHz resonance test method. These latter values were found to be sensitively dependent on microstructure, composition and processing history. (author)

  8. High cycle thermal fatigue: benchmark at a Te junction piping system of the nuclear power plant Phenix

    International Nuclear Information System (INIS)

    This paper presents the studies of the benchmark concerning a high cycle thermal fatigue problem. This benchmark is based on an industrial case, a Te junction piping system of the french FBR Phenix. The main objectives were the comparison of the different methods used by the participants and the analysis of the damage evaluation methods capacity compared to the observed phenomena. This study took place in an international framework with the United Kingdom, Italy, Japan, Korea, Russia, India and France. (A.L.B.)

  9. High cycle fatigue behavior of Fe-Cr-Mn-C and Ni-Mo-Al aligned eutectics

    Energy Technology Data Exchange (ETDEWEB)

    Miyahara, Y. (Komatsu Ltd., Osaka (Japan)); Stoloff, N.S. (Materials Engineering Dept., Rensselaer Polytechnic Inst., Troy, NY (United States))

    1991-12-30

    High cycle fatigue tests were conducted on an Fe-Cr-Mn-C eutectic alloy at 500, 650 and 800degC and on an Ni-Al-Mo eutectic (AG-170) at 500 and 650degC. Fractographic observations were also conducted on fractured samples. The fatigue strength of the Fe-Cr-Mn-C eutectic decreased with increasing temperature while that of AG-170 exhibited almost no perceivable difference with temperature change. A remarkably high value of {Delta}{sigma}{sub 10}{sup 7}/{sigma}{sub UTS} was obtained for AG-170 (UTS, ultimate tensile strength). Crack initiation sites were found to be prior broken fibers for the Fe-Cr-Mn-C eutectic and an unidentified faceted particle for AG-170. (orig.).

  10. Thermal mixing in T-junction piping system concerned with high-cycle thermal fatigue in structure

    International Nuclear Information System (INIS)

    In Japan Atomic Energy Agency (JAEA), a numerical simulation code 'MUGTHES' has been developed to investigate thermal striping phenomena caused by turbulence mixing of fluids in different temperature and to provide transient data for an evaluation method of high-cycle thermal fatigue. MUGTHES adopts Large Eddy Simulation (LES) approach to predict unsteady phenomena in thermal mixing and employs boundary fitted coordinate system to be applied to complex geometry in a power reactor. Numerical simulation of thermal striping phenomena in a T-junction piping system (T-pipe) is conducted. Boundary condition for the simulation is chosen from an existing water experiment in JAEA, named as WATLON experiment. In the numerical simulation, standard Smagorinsky model is employed as eddy viscosity model with the model coefficient of 0.14 (=Cs). Numerical results of MUGTHES are verified by the comparisons with experimental results of velocity and temperature. Through the numerical simulation in the T-pipe, applicability of MUGTHES to the thermal striping phenomena is confirmed and the characteristic large-scale eddy structure which dominates thermal mixing and may cause high-cycle thermal fatigue is revealed. (author)

  11. Study on high cycle thermal fatigue in mixing tee. Evaluation of transfer characteristics of temperature fluctuation from fluid to structure

    International Nuclear Information System (INIS)

    Thermal striping is observed at a point where hot and cold fluids are mixing. Evaluation of high cycle thermal fatigue on structural components is a significant issue for the reactor safety design. Japan Atomic Energy Agency (JAEA) has conducted experimental and numerical investigations to establish a quantitative evaluation method of high cycle thermal fatigue in a sodium-cooled fast reactor, based on the nature of the phenomena. A water experiment WATLON (as Water Experiment of Fluid Mixing in T-pipe with Long Cycle Fluctuation) has been conducted to clarify the thermal striping phenomena in a mixing tee area. In this study, water experiments WATLON were carried out to clarify the unsteady behavior of heat transfer under wall jet condition. In experiments, heat transfer coefficients between fluid and wall in the mixing region were obtained from temperature measurements using thermocouples (movable tree type in fluid and embedded type in wall). To clarify the relation between the local velocity and the wall temperature, those were measured simultaneously by the Particle Image Velocimetry (PIV) and the thermocouple measurement, respectively. Sampling time of the velocity by the PIV and the temperature by the thermocouple were synchronized in the measurement. The experimental results showed that the heat transfer coefficient was 2?6 time larger than the reference value predicted by the Dittus-Boelter correlation in straight pipes and was increased as the local velocity near the wall. A CD-ROM is attached as an appendix. (J.P.N.)

  12. Nitinol Fatigue Life for Variable Strain Amplitude Fatigue

    Science.gov (United States)

    Lin, Z.; Pike, K.; Schlun, M.; Zipse, A.; Draper, J.

    2012-12-01

    Nitinol fatigue testing results are presented for variable strain amplitude cycling. The results indicate that cycles smaller than the constant amplitude fatigue limit may contribute to significant fatigue damage when they occur in a repeating sequence of large and small amplitude cycles. The testing utilized two specimen types: stent-like diamond specimens and Z-shaped wire specimens. The diamond specimens were made from nitinol tubing with stent-like manufacturing processes and the Z-shaped wire specimens were made from heat set nitinol wire. The study explored the hypothesis that duty cycling can have an effect on nitinol fatigue life. Stent-like structures were subjected to different in vivo loadings in order to create more complex strain amplitudes. The main focus in this study was to determine whether a combination of small and large amplitudes causes additional damage that alters the fatigue life of a component.

  13. Influence of surface finish on the high cycle fatigue behavior of a 304L austenitic stainless steel

    International Nuclear Information System (INIS)

    This work has dealt with the influence of surface finish on the high cycle fatigue behavior of a 304L. The role played by roughness, surface hardening and residual stresses has been particularly described. First part of this study has consisted of the production of several surface finishes. These latter were obtained by turning, grinding, mechanical polishing and sandblasting. The obtained surfaces were then characterised in terms of roughness, hardening, microstructure and residual stresses. Fatigue tests were finally conducted under various stress ratios or mean stresses at two temperatures (25 C and 300 C). Results clearly evidenced an effect of the surface integrity on the fatigue resistance of the 304L. This influence is nevertheless more pronounced at ambient temperature and for a positive mean stress. For all explored testing conditions, the lowest endurance limit was obtained for ground specimens whereas polished samples exhibited the best fatigue strength. Results also cleared out a detrimental influence of a positive mean stress in the case of specimens having surface defaults of a great acuity. The study of the relative effect of each of the surface parameter, under a positive stress ratio and at the ambient temperature, showed that roughness profile and surface hardening are the two more influential factors. The role of the residual stresses remains negligible due to their rapid relaxation during the application of the first cycles of fatigue. The estimation of the initiation and propagation periods showed that mechanisms differed as a function of the applied stress ratio. Crack propagation is governed by the parameter DK at a positive stress ratio and by Dep/2 in the case of tension-compression tests. (author)

  14. Deformation behaviour and fracture of Ni-base single crystals at simultaneous action of high-cycle fatigue and creep.

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr

    2007-01-01

    Ro?. 14, ?. 2 (2007), s. 15-20. ISSN 1335-0803 R&D Projects: GA ?R GA106/05/2112 Institutional research plan: CEZ:AV0Z20410507 Keywords : CMSX-4 * CM186LC * Fatigue life * Constant lifetime diagram Subject RIV: JG - Metallurgy

  15. Deformation mechanisms induced under high cycle fatigue tests in a metastable austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Roa, J.J., E-mail: joan.josep.roa@upc.edu [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Campus Diagonal Sud, Edificio C’, Universitat Politècnica de Catalunya, C/ Pascual i Vila 15, 08028 Barcelona (Spain); Fargas, G. [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); Jiménez-Piqué, E. [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Campus Diagonal Sud, Edificio C’, Universitat Politècnica de Catalunya, C/ Pascual i Vila 15, 08028 Barcelona (Spain); Mateo, A. [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain)

    2014-03-01

    Advanced techniques were used to study the deformation mechanisms induced by fatigue tests in a metastable austenitic stainless steel AISI 301LN. Observations by Atomic Force Microscopy were carried out to study the evolution of a pre-existing martensite platelet at increasing number of cycles. The sub-superficial deformation mechanisms of the austenitic grains were studied considering the cross-section microstructure obtained by Focused Ion Beam and analysed by Scanning Electron Microscopy and Transmission Electron Microscopy. The results revealed no deformation surrounding the pre-existing martensitic platelet during fatigue tests, only the growth on height was observed. Martensite formation was associated with shear bands on austenite, mainly in the {111} plane, and with the activation of the other intersecting austenite {111}?110? slip system. Furthermore, transmission electron microscopy results showed that the nucleation of ?-martensite follows a two stages phase transformation (?{sub fcc}??{sub hcp}??'{sub bcc})

  16. Deformation mechanisms induced under high cycle fatigue tests in a metastable austenitic stainless steel

    International Nuclear Information System (INIS)

    Advanced techniques were used to study the deformation mechanisms induced by fatigue tests in a metastable austenitic stainless steel AISI 301LN. Observations by Atomic Force Microscopy were carried out to study the evolution of a pre-existing martensite platelet at increasing number of cycles. The sub-superficial deformation mechanisms of the austenitic grains were studied considering the cross-section microstructure obtained by Focused Ion Beam and analysed by Scanning Electron Microscopy and Transmission Electron Microscopy. The results revealed no deformation surrounding the pre-existing martensitic platelet during fatigue tests, only the growth on height was observed. Martensite formation was associated with shear bands on austenite, mainly in the {111} plane, and with the activation of the other intersecting austenite {111}?110? slip system. Furthermore, transmission electron microscopy results showed that the nucleation of ?-martensite follows a two stages phase transformation (?fcc??hcp??'bcc)

  17. Effect of secondary flow generated in 90-degree bend upon high-cycle thermal fatigue in a mixing tee

    International Nuclear Information System (INIS)

    In nuclear power plants, there are many T-junctions at which different temperature fluids are mixed. When the fluids with different temperature are mixed, temperature fluctuation in fluids reachs wall and high-cycle heat fatigue occurs. Depending on amplitude and frequency of temperature fluctuation, it could lead to pipe rupture accident at worst. In addition, in case of the T-junction with 90-degree bend at upstream, there is higher risk for pipe rupture accident due to secondary flow which arises in the 90-degree bend. In this study, the effects of temperature fluctuation above the T-junction in case of different distance of 90-degree bend outlet to the T-junction are investigated. (author)

  18. Prediction of fatigue life in notched bodies.

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Kruml, Tomáš; Petrenec, Martin; Obrtlík, Karel; Kotecký, Ond?ej; Degallaix, S.

    Lancaster : DEStech Publications, 2008 - (Fan, J.; Chen, H.), s. 1189-1192 ISBN 978-1-932078-80-0. [International Conference on Heterogeneous Material Mechanics /2./. Huangshan (CN), 03.06.2008-08.06.2008] R&D Projects: GA ?R GA101/07/1500 Institutional research plan: CEZ:AV0Z20410507 Keywords : fatigue life * notch * fatigue crack * prediction Subject RIV: JL - Materials Fatigue, Friction Mechanics

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

    Energy Technology Data Exchange (ETDEWEB)

    Lehericy, Y

    2007-05-15

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

  20. Multiscale Fatigue Life Prediction for Composite Panels

    Science.gov (United States)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Arnold, Steven M.

    2012-01-01

    Fatigue life prediction capabilities have been incorporated into the HyperSizer Composite Analysis and Structural Sizing Software. The fatigue damage model is introduced at the fiber/matrix constituent scale through HyperSizer s coupling with NASA s MAC/GMC micromechanics software. This enables prediction of the micro scale damage progression throughout stiffened and sandwich panels as a function of cycles leading ultimately to simulated panel failure. The fatigue model implementation uses a cycle jumping technique such that, rather than applying a specified number of additional cycles, a specified local damage increment is specified and the number of additional cycles to reach this damage increment is calculated. In this way, the effect of stress redistribution due to damage-induced stiffness change is captured, but the fatigue simulations remain computationally efficient. The model is compared to experimental fatigue life data for two composite facesheet/foam core sandwich panels, demonstrating very good agreement.

  1. A constitutive high cycle fatigue damage model - based on the interaction between microplasticity and local damage

    Energy Technology Data Exchange (ETDEWEB)

    Flaceliere, L. [Futurscope (France); Morel, F.; Dragon, A.

    2006-07-01

    This paper presents a new model that accounts, on a local scale, for the coupling between plasticity due to gliding in shear bands and damage occurring when the accumulated plastic strain has reached a threshold value. The irreversible thermodynamics with internal state variables is employed to keep a middle way between extensive description of plastic and damage flow and application of accessibility requirements. Plasticity and damage are governed by their proper complementary rules (yield functions and potentials). At the same time, a coupling occurs between the damage variable and the hardening parameters. A large experimental database relative to the fatigue behavior of a mild steel C36 submitted to different loading modes (tension, torsion, combined proportional tension and torsion) proves the efficiency of such a model. The prediciton of Woehler curves for cyclic complex stress states can be readily done, but the main feature of this approach is to ensure a clear link between mesoscopic parameters like the hardening behavior of individual grains and the subsequent local damage.

  2. Fatigue life prediction for 316 stainless steel. Case of superimposed and repeated two-step stress

    International Nuclear Information System (INIS)

    In this study, applicability of linear-cumulative damage rule was investigated for variable loading of high-cycle fatigue for Type 316 stainless steel. Push-pull fatigue tests were conducted in ambient air and room temperature by controlling stress amplitude. Two types variable loading were tested. Repeated two-step tests were conducted in order to assess the effect of loading history by crack on fatigue life. And superimposed tests were also conducted to investigate applicability for linear-cumulative damage rule. As a result, effect of loading history by crack was not confirmed in repeated two-step test. However, fatigue life for superimposed wave decreased by change of crack opening range. It was concluded that considering safety factor, a linear-cumulative damage rule almost applicable to thermal fatigue. (author)

  3. Generation of stationary Gaussian processes and extreme value distributions for high-cycle fatigue models - application to tidal stream Turbines

    Scientific Electronic Library Online (English)

    M., Suptille; E., Pagnacco; L., Khalij; J. E. Souza de, Cursi; J., Brossard.

    Full Text Available The operating environment of tidal stream turbines is random due to the variability of the sea flow (turbulence, wake, tide, streams, among others). This yields complex time-varying random loadings, making it necessary to deal with high cycle multiaxial fatigue when designing such structures. It is [...] thus required to apprehend extreme value distributions of stress states, assuming they are stationary multivariate Gaussian processes. This work focus on such distributions, addressing their numerical simulation with an analytical description. For that, we first focused on generating one-dimensional Gaussian processes, considering a band-limited white noise in both the narrow-band and the wide-band cases. We then fitted the resulting extreme value distributions with GEV distributions. We secondly extended the generation method to the correlated two-dimensional case, in which the joint extreme value distribution can be obtained from the associated margins. Finally, an example of application related to tidal stream turbines introduces a Bretschneider spectrum, whose shape is commonly encountered in the field of hydrology. Comparing the empirical calculations with the GEV fits for the extreme value distributions shows a very well agreement between the results.

  4. On the effect of deep-rolling and laser-peening on the stress-controlled low- and high-cycle fatigue behavior of Ti-6Al-4V at elevated temperatures up to 550?C

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, IAltenberger, RKNalla, YSano LWagner, RO

    2012-04-01

    The effect of surface treatment on the stress/life fatigue behavior of a titanium Ti-6Al-4V turbine fan blade alloy is investigated in the regime of 102 to 106 cycles to failure under fully reversed stress-controlled isothermal push-pull loading between 25? and 550?C at a frequency of 5 Hz. Specifically, the fatigue behavior was examined in specimens in the deep-rolled and laser-shock peened surface conditions, and compared to results on samples in the untreated (machined and stress annealed) condition. Although the fatigue resistance of the Ti-6Al-4V alloy declined with increasing test temperature regardless of surface condition, deep-rolling and laser-shock peening surface treatments were found to extend the fatigue lives by factors of more than 30 and 5-10, respectively, in the high-cycle and low-cycle fatigue regimes at temperatures as high as 550?C. At these temperatures, compressive residual stresses are essentially relaxed; however, it is the presence of near-surface work hardened layers, with a nanocystalline structure in the case of deep-rolling and dense dislocation tangles in the case of laser-shock peening, which remain fairly stable even after cycling at 450?-550?C, that provide the basis for the beneficial role of mechanical surface treatments on the fatigue strength of Ti-6Al-4V at elevated temperatures.

  5. Experimental study of cyclic creep and high-cycle fatigue of welded joints of St3 steel by the DIC technique

    Science.gov (United States)

    Kibitkin, Vladimir V.; Solodushkin, Andrey I.; Pleshanov, Vasily S.

    2015-10-01

    In the paper the mechanisms of plastic deformation and fracture of welded joints of steel St3 were investigated at high-cycle fatigue and cyclic creep by the digital image correlation (DIC) technique. The evolution of strain rate is studied for the following regions: base metal, HAZ, and fusion zone. This strain rate evolution can be considered as a mechanical response of material. Three stages of deformation evolution are shown: deformation hardening (I), fatigue crack initiation (II), and the last stage is related to main crack (III). Two criteria are offered to evaluate the current mechanical state of welded joints.

  6. Effect of different distribution condition of fatigue loads on fatigue life

    International Nuclear Information System (INIS)

    In this article, 3 distribution styles, i.e, normal distribution, log-normal distribution and Gamma distribution, are used to simulate the variety of fatigue loads S. Same average value of fatigue loads variety S and different coefficient of variation C are adopted in every distribution style, and corresponding fatigue life Nrand and the average fatigue life Navg in the condition of S=S are calculated. By comparing the fatigue life Nrand and Navg, a rule can be found that when the average value of fatigue loads variety is small, the fatigue life will first increase and decrease later with the increasing of the coefficient of variation, and when the average value of the fatigue loads variety is large, the fatigue life will always decrease while the coefficient of variation increases. (authors)

  7. Fatigue maps and multistage life prediction methods

    Energy Technology Data Exchange (ETDEWEB)

    Pratesi, F.; Zonfrillo, G.; Del Puglia, A. (Dipt. di Meccanica e Tecnologie Industriali, Univ. Florence (Italy))

    1992-04-01

    Various methods have been recently developed for life prediction under creep-fatigue conditions. This study is concerned with continuous damage models. In particular, a model developed at ONERA, which evaluates the creep and fatigue contributions separately and which sums the corresponding differential damage, has been used for fitting the high-temperature experimental data for IN 738 test bars. The data were taken both from the literature and from our own tests. In addition, it was found that the model can also be used to derive schematic fatigue maps. Following the introduction of Ashby maps for creep, several other maps have been proposed for fatigue. However, the task for fatigue maps is more difficult to define. This work presents a discussion of the whole problem, a review of existing proposals, and some indicative maps that have been obtained for IN 100. Even though the approach appears to be promising for outlining approximate fatigue maps, metallographic observations are still a necessary complement for mapping single domains where given microstructural mechanisms are predominant. (orig.).

  8. Fatigue maps and multistage life prediction methods

    International Nuclear Information System (INIS)

    Various methods have been recently developed for life prediction under creep-fatigue conditions. This study is concerned with continuous damage models. In particular, a model developed at ONERA, which evaluates the creep and fatigue contributions separately and which sums the corresponding differential damage, has been used for fitting the high-temperature experimental data for IN 738 test bars. The data were taken both from the literature and from our own tests. In addition, it was found that the model can also be used to derive schematic fatigue maps. Following the introduction of Ashby maps for creep, several other maps have been proposed for fatigue. However, the task for fatigue maps is more difficult to define. This work presents a discussion of the whole problem, a review of existing proposals, and some indicative maps that have been obtained for IN 100. Even though the approach appears to be promising for outlining approximate fatigue maps, metallographic observations are still a necessary complement for mapping single domains where given microstructural mechanisms are predominant. (orig.)

  9. Simulation of irreversible damage accumulation in the very high cycle fatigue (VHCF) regime using the boundary element method

    International Nuclear Information System (INIS)

    Many components have to withstand a very high number of loading cycles due to high frequency or long product life. In this regime, the period of fatigue crack initiation and thus the localization of plastic deformation play an important role. Metastable austenitic stainless steel (AISI304) that is investigated in this study shows localization of plastic deformation in bands of intense slip. In order to provide a physically-based understanding of the relevant damage mechanisms under VHCF condition, simulation of irreversible damage accumulation in slip bands is performed. For this purpose, a microstructural simulation model is proposed which accounts for the damage mechanisms in slip bands documented by experimental results. The model describes the damage accumulation through formation of slip bands, sliding and multiplication of dislocations and the amount of irreversibility of such mechanisms in case of VHCF relevant loading conditions. The implementation of the simulation model into a numerical method allows the investigation of the damage accumulation in a real microstructure simulated on the basis of metallographic analysis. The numerical method used in this study is the two-dimensional (2-D) boundary element method which is based on two integral equations: the displacement and the stress boundary integral equation. Fundamental solutions within these integral equations represent anisotropic elastic behavior. By using this method, a 2-D microstructure can be reproduced that considers orientations as well as individual anisotropic elastic properties in each grain. Contours of shear stresses along most critical slip systems are compared with images of slip band formation at the surface of fatigued specimens provided by scanning electron microscopy (SEM). Results show that simulation of slip bands is in good agreement with experimental observations and that plastic deformation in slip bands has a high impact on shear stresses at grain boundaries acting as possible crack origin in the fully austenitic material condition. In contrast to most other publications in the field of fatigue simulation the present paper tackles the problem of modeling cyclic slip irreversibility and gives an insight into its effect on the microstructural damage evolution

  10. Simulation of irreversible damage accumulation in the very high cycle fatigue (VHCF) regime using the boundary element method

    Energy Technology Data Exchange (ETDEWEB)

    Hilgendorff, P.-M., E-mail: philipp.hilgendorff@uni-siegen.de [Institut für Mechanik und Regelungstechnik—Mechatronik, Universität Siegen, Siegen 57068 (Germany); Grigorescu, A. [Institut für Werkstofftechnik, Universität Siegen, Siegen 57068 (Germany); Zimmermann, M. [Institut für Werkstoffwissenschaft, Technische Universität Dresden, 01062 Dresden (Germany); Fritzen, C.-P. [Institut für Mechanik und Regelungstechnik—Mechatronik, Universität Siegen, Siegen 57068 (Germany); Christ, H.-J. [Institut für Werkstofftechnik, Universität Siegen, Siegen 57068 (Germany)

    2013-07-15

    Many components have to withstand a very high number of loading cycles due to high frequency or long product life. In this regime, the period of fatigue crack initiation and thus the localization of plastic deformation play an important role. Metastable austenitic stainless steel (AISI304) that is investigated in this study shows localization of plastic deformation in bands of intense slip. In order to provide a physically-based understanding of the relevant damage mechanisms under VHCF condition, simulation of irreversible damage accumulation in slip bands is performed. For this purpose, a microstructural simulation model is proposed which accounts for the damage mechanisms in slip bands documented by experimental results. The model describes the damage accumulation through formation of slip bands, sliding and multiplication of dislocations and the amount of irreversibility of such mechanisms in case of VHCF relevant loading conditions. The implementation of the simulation model into a numerical method allows the investigation of the damage accumulation in a real microstructure simulated on the basis of metallographic analysis. The numerical method used in this study is the two-dimensional (2-D) boundary element method which is based on two integral equations: the displacement and the stress boundary integral equation. Fundamental solutions within these integral equations represent anisotropic elastic behavior. By using this method, a 2-D microstructure can be reproduced that considers orientations as well as individual anisotropic elastic properties in each grain. Contours of shear stresses along most critical slip systems are compared with images of slip band formation at the surface of fatigued specimens provided by scanning electron microscopy (SEM). Results show that simulation of slip bands is in good agreement with experimental observations and that plastic deformation in slip bands has a high impact on shear stresses at grain boundaries acting as possible crack origin in the fully austenitic material condition. In contrast to most other publications in the field of fatigue simulation the present paper tackles the problem of modeling cyclic slip irreversibility and gives an insight into its effect on the microstructural damage evolution.

  11. High-Strength Bolt Corrosion Fatigue Life Model and Application

    OpenAIRE

    Wang Hui-li; Qin Si-feng

    2014-01-01

    The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture...

  12. 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 fatigue life of welded plate specimens has been investigated. Both the fracture mechanics analyses and the fatigue tests have been carried out using load histories, which correspond to one week's traffic loa...

  13. A study on the role of grain boundary engineering in promoting high-cycle fatigue resistance and improving reliability in nickel base superalloys for propulsion systems

    Science.gov (United States)

    Gao, Yong

    High-cycle fatigue, involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency (vibratory) loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain boundary engineering has been used to obtain significant improvements in intergranular corrosion and cracking, creep and cavitation behavior, toughness and plasticity, cold-work embrittlement, and weldability, only very limited, but positive, results exist for fatigue. Accordingly, using a commercial polycrystalline nickel base gamma/gamma' superalloy, ME3, as a typical engine disk material, sequential thermomechanical processing, involving alternate cycles of strain and annealing, is used to (i) modify the proportion of special grain boundaries, and (ii) interrupt the connectivity of the random boundaries in the grain boundary network. The processed microstructures are then subjected to fracture-mechanics based high cycle fatigue testing to evaluate how the crack initiation and small- and large-crack growth properties are affected and to examine how the altered grain boundary population and connectivity can influence growth rates and overall lifetimes. The effect of such grain-boundary engineering on the fatigue-crack-propagation behavior of large (˜8 to 20 mm), through-thickness cracks at 25, 700, and 800°C was examined. Although there was little influence of an increased special boundary fraction at ambient temperatures, the resistance to near-threshold crack growth was definitively improved at elevated temperatures, with fatigue threshold-stress intensities some 10 to 20% higher than at 25°C, concomitant with a lower proportion (˜20%) of intergranular cracking. This work demonstrated that for cracks large compared to the scale of the microstructure, the principal role of an increased fraction of "special" grain boundaries is to enhance resistance only to intergranular cracking. Microstructurally small fatigue cracks exhibit considerably scattered growth rates at ambient temperatures and there is little discernible overall effect of an increased fraction of special boundaries on the growth rates of small cracks due to scattering. Crystallographic cracking shows deflection at grain boundaries, preferably along {111}. The analysis on the crack growth perturbation and crack deflection indicates that grain boundaries with higher misorientation angles, particularly twin boundaries (Sigma3), may be more effective in locally retarding small crack propagation.

  14. 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...

  15. 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 ...

  16. Fatigue life of automotive rubber jounce bumper

    International Nuclear Information System (INIS)

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

  17. Fatigue life of automotive rubber jounce bumper

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-05-15

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

  18. Fatigue Life Investigation of PZT Ceramics by MSP Method

    Directory of Open Access Journals (Sweden)

    DENG Qi-Huang, WANG Lian-Jun, XU Hong-Jie, WANG Hong-Zhi, JIANG Wan

    2012-10-01

    Full Text Available The cycle fatigue of PZT ceramic under different stress was investigated by modified small punch (MSP tests. The research results show that residual strength and piezoelectric constant decrease with increasing cycle stress, which is attributed to crack propagation during cyclic stress process. The value of fatigue crack propagation (n is calculated to be 395 according to the relationship between maximum stress and fatigue life. The fatigue life under series cycle maximum stress can be induce by fatigue crack propagation. Below the maximum strength of 79.1 MPa, the PZT ceramics can be used over 5 years.

  19. Fatigue life and damage evolution of martensitic steels for low-pressure steam turbine blades in the VHCF regime

    International Nuclear Information System (INIS)

    Low-pressure steam turbine blades are usually made of martensitic steels with Cr contents between 9 and 12%, which combine good corrosion resistance, high mechanical strength and sufficient ductility. The inhomogeneous flow field behind the vanes generates high-frequency oscillations above 1 kHz. In addition, the blades with lengths up to 1.5 m are operated at rotational speeds up to 3000 rpm, resulting in large centrifugal forces leading to the superposition of extremely high mean stresses. Also resonance oscillations during start-up and shutdown cannot be completely excluded. Currently, the components are designed using high safety factors against S-N curves with an assumed asymptotic fatigue limit above 107 load cycles. Nevertheless, fatigue cracks are observed even at high number of cycles, starting from the blade root without pre-damage by erosion or steam droplet impingement. While fatigue failure usually occurs at the surface, fatigue cracks at very high number of cycles (> 108) initiate at oxides or intermetallic inclusions below the surface. This transition between both failure mechanisms in the Very High-Cycle Fatigue (VHCF) regime is in the focus of numerous current research activities, because numbers of cycles above 108 can be attained in a viable period of time using the recently developed high-frequency testing techniques operated at 20 kHz. Also for wind turbines, gas turbines, bearings, springs, etc. VHCF issues become increasingly important. Within this work, the fatigue life and damage behavior of a martensitic Cr-steel during fatigue loading with and without high mean stresses at number of cycles to failure above 108 was analyzed. On the one hand, the studies gave insights into the relation between fatigue life and fatigue damage evolution of the investigated group of high-strength steels in the very high cycle fatigue regime (up to 2·109). In particular, the influence of high mean stresses on the VHCF behavior (fracture origin, crack growth, fatigue life) which was not investigated in detail before is studied and the crack initiation and propagation mechanisms are analyzed by electron microscopy (SEM, TEM / FIB). With this, the work contributes to the reliable design of future low-pressure steam turbines. The results show that in particular non-metallic inclusions in the steel cause fracture by fatigue cracks initiated in the volume under very high cycle fatigue conditions. This fatigue behavior can be described very well by means of fracture mechanics approaches over a wide range of load ratios.

  20. A study at understanding the mechanisms governing the high cycle fatigue and final fracture behavior of the titanium alloy: Ti-4Al-2.5V

    International Nuclear Information System (INIS)

    In this research paper, the cyclic stress amplitude-controlled high cycle fatigue properties and fracture behavior of a titanium alloy are presented and discussed. The material chosen for this study is a Ti-Al-V-Fe-O2 alloy that is marketed under the trade name ATI 425TM. This alloy was initially developed and put forth for use as a ballistic material but through the last few years it gained in stature for use in other areas due to a healthy combination of physical and mechanical properties. Test specimens were prepared, in conformance with the ASTM E-8 standard, from the as-received sheet stock, which was cold rolled and mill annealed, with the rolling direction both parallel (longitudinal) and perpendicular (transverse) to the length of the sheet. The test specimens were cyclically deformed at three different load ratios (R = 0.1, R = 0.3 and R = 0.033) and the cycles-to-failure (Nf) was recorded. The fatigue fracture surfaces were examined in a scanning electron microscope to examine the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of magnitude of applied stress-microstructural feature interactions in governing failure.

  1. 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 initiated from surface inclusions in nearly all wires. Compressive pre-strain-induced damage may accelerate such crack initiation, thereby reducing fatigue life. The results of the present study indicate that large compressive pre-strains are detrimental to the fatigue properties of Nitinol, and, taken together, the findings underscore the importance of accounting for thermo-mechanical history in the design and testing of wire-based percutaneous implants. PMID:25625888

  2. High cycle thermal fatigue: benchmark at a Te junction piping system of the nuclear power plant Phenix; Fatigue a grand nombre de cycles: benchmark d'un te de tuyauterie de la centrale Phenix

    Energy Technology Data Exchange (ETDEWEB)

    Gelineau, O.; Simoneau, J.P. [NOVATOME, a Div. of Framatome, 69 - Lyon (France); Roubin, P. [CEA Cadarache, DER, 13 - Saint-Paul-lez-Durance (France)

    2001-07-01

    This paper presents the studies of the benchmark concerning a high cycle thermal fatigue problem. This benchmark is based on an industrial case, a Te junction piping system of the french FBR Phenix. The main objectives were the comparison of the different methods used by the participants and the analysis of the damage evaluation methods capacity compared to the observed phenomena. This study took place in an international framework with the United Kingdom, Italy, Japan, Korea, Russia, India and France. (A.L.B.)

  3. High-cycle fatigue of nickel-base superalloy Rene 104 (ME3): Interaction of microstructurally small cracks with grain boundaries of known character

    International Nuclear Information System (INIS)

    High-cycle fatigue (HCF), involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency cyclic loading, has been identified as one of the leading causes of turbine engine failures in aircraft. In this work, we consider the feasibility of using grain-boundary engineering to improve the HCF properties of a polycrystalline nickel-base superalloy, Rene 104 (also known as ME3), through systematic modification of the grain-boundary distribution. In particular, we investigate the growth of microstructurally small fatigue cracks at ambient temperature in microstructures with varying proportions of 'special' vs. 'random' boundaries, as defined by coincident-site lattice theory. Specifically, we examine the interaction of propagating small (?10-900 ?m) surface cracks with grain boundaries of known character, with respect both to any deflection in crack trajectory that occurs at or near the boundary, and more importantly to any local changes in crack-growth rates. In addition, finite-element calculations are performed to evaluate the effective driving force and plastic-zone profile for such small-crack propagation, incorporating information from both the local microstructure (from electron backscattering diffraction scans) and the surface crack-path profile

  4. Fatigue and quality of life in pediatric multiple sclerosis.

    Science.gov (United States)

    MacAllister, William S; Christodoulou, Christopher; Troxell, Regina; Milazzo, Maria; Block, Pamela; Preston, Thomas E; Bender, Heidi A; Belman, Anita; Krupp, Lauren B

    2009-12-01

    Fatigue and quality of life are significant concerns in adult multiple sclerosis (MS) but little is known about these factors in pediatric MS. The present investigation evaluates fatigue and quality of life in 51 pediatric MS patients to determine the rate of fatigue and reduced quality of life and assesses the relations between these variables and clinical factors. Fatigue and quality of life were assessed by self- and parent-report via the PedsQL Multidimensional Fatigue Scale and the PedsQL Quality of Life Scale. One-sample t-tests determined if scores were below published data for healthy individuals. Moreover, scores falling one standard deviation from norms were considered mildly affected, with severe difficulties being defined as scores falling two or more standard deviations from norms. Associations between self- and parent-reported difficulties and clinical factors were examined via Pearson correlation analyses. In comparison with healthy samples, pediatric MS patients reported greater difficulties with respect to fatigue, sleep, cognition, physical limitations, and academics. In addition to significant difficulties on these factors, parents reported problems with respect to emotional functioning, and tended to report greater fatigue, sleep, and cognitive difficulties than were self-reported. Expanded Disability Status Scale score was the only neurologic variable significantly related to fatigue or quality of life scores. Fatigue was significantly correlated with reports of sleep difficulties, cognitive problems, and quality of life variables. These findings suggest that fatigue and poorer quality of life is a clear concern in pediatric MS, and is related to overall physical disability. PMID:19965517

  5. On line fatigue life monitoring methodology for power plant components

    International Nuclear Information System (INIS)

    Fatigue is one of the most important ageing effects of power plant components. Information about fatigue helps in assessing structural degradation of the components and so assists in planning in-service inspection and maintenance. It may also support the future life extension programme of a power plant. In the present paper, the development of a methodology for on line fatigue life monitoring using available plant instrumentation is presented. The Green's function technique is used to convert plant data to stress-time data. Using a rainflow cycle counting method, stress-time data are analysed and the fatigue usage factor is computed from the material fatigue curve. Various codes are developed to generate Green's functions, to convert plant data to stress-time data, to find the fatigue usage factor and to display fatigue information. Using the developed codes, information about the fatigue life of various components of a power plant can be updated, stored and displayed interactively by plant operators. Three different case studies are reported in the present paper. These are the fatigue analyses of a thick pipe, of a nozzle connected to a pressure vessel and of a reducer connecting a heat exchanger to its piping system. (Author)

  6. Fatigue life prediction under service load considering strengthening effect of loads below fatigue limit

    Science.gov (United States)

    Zhao, Lihui; Zheng, Songlin; Feng, Jinzhi

    2014-11-01

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

  7. Carbide factor predicts rolling-element bearing fatigue life

    Science.gov (United States)

    Chevalier, J. L.; Zaretsky, E. V.

    1973-01-01

    Analysis was made to determine correlation between number and size of carbide particles and rolling-element fatigue. Correlation was established, and carbide factor was derived that can be used to predict fatigue life more effectively than such variables as heat treatment, chemical composition, and hardening mechanism.

  8. Fatigue life prediction of pedicle screw for spinal surgery.

    Czech Academy of Sciences Publication Activity Database

    Major, Št?pán; Kocour, Vladimír

    Ferrara : University of Ferrara, 2015. s. 94 ISBN N. [International Conference on Crack Paths (CP 2015) /5./. 16.08.2015-18.08.2015, Ferrara] Institutional support: RVO:68378297 Keywords : pedicle-screw * titan alloy * fatigue life * finite element analysis Subject RIV: JL - Materials Fatigue, Friction Mechanics http://www.gruppofrattura.it/events/CP2015/index.html#682

  9. Application of multistage life prediction methods to fretting fatigue interactions

    International Nuclear Information System (INIS)

    This paper reports the application field of the multistage prediction model extended to fretting- fatigue interaction. The model was used to achieve a preliminary evaluation of the reduction in fatigue life induced by fretting conditions in a case-hardening steel. Satisfactory agreement with experimental data was found without considering any effects on the propagation stage

  10. 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

    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 of specimens are used, two of these are non-welded and the third is welded with a transverse welding (T-Joint). The 13 laser welded specimens are cut out with a milling cutter. The non-welded specimens are divided in 13 specimens cut out with a milling cutter and 10 specimens cut out by a plasma cutter. 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 conclude that the fatigue life assessment according to the mentioned standards is not satisfactory and reliable.

  11. An investigation on fatigue life of borided AISI 1010 steel

    Directory of Open Access Journals (Sweden)

    O.N. Celik

    2009-01-01

    Full Text Available Purpose: This study aims to investigate the fatigue life of box borided AISI 1010 steel materials.Design/methodology/approach: Fatigue specimens firstly have been prepared according to ASTM E466-96 standard and normalized. Then their surfaces have been cleaned by polishing. Boriding heat treatment has been applied in solid media with the help of Ekabor2 powder. Specimens have been borided at 1173-1223-1273 and 1323 K temperatures for 2-4 and 6 hours respectively. Fatigue tests have been made in rotating-bend test device. Separate S-N diagram has been formed for each boriding condition and then their results were compared with the results of the specimens on which any heat treatment has not been made.Findings: As a result it has been seen that boriding has no positive effect on fatigue life of AISI 1010 steel materials. And also it has been determined that fatigue life of the materials on which boriding heat treatment applied, decreases in between 14 %-55 %.Research limitations/implications: It can be noted that the reasons of short fatigue life determination are the boride layer’s much higher hardness than the substrate material’s, and the micro cracks existed between boride phases formed onto the surface.Originality/value: The investigations on fatigue life of borided AISI 1010 steel were made.

  12. Numerical life prediction of mechanical fatigue for hot forging tools

    OpenAIRE

    Mocellin, Katia; Ferraro, Matthieu; Velay, Vincent; Logé, Roland E.; Rezai-Aria, Farhad

    2009-01-01

    In the forging industry, tools represent an important part in term of production and costs. Enhancing their life cycle is then a challenging issue. Several mechanical and thermal mechanisms are responsible for hot forging tools damage such as wear, thermal and mechanical fatigue. This work will be focused only on the mechanical fatigue life prediction for hot forging tools. Both experimental data analysis and numerical simulation will be discussed in this paper. The aim is to perform qualitat...

  13. The role of microtexture on the faceted fracture morphology in Ti-6Al-4V subjected to high-cycle fatigue

    International Nuclear Information System (INIS)

    Microtextured regions (or macrozones) are commonly reported in titanium alloys and are believed to be related to fatigue life. Here, fractographic investigations are conducted on bimodal Ti-6Al-4V plate, including transmission electron microscopy to determine the mechanism of fatigue facet formation and electron backscattered diffraction to examine the underlying macrozone structures. It is found that macrozones oriented with their c-axis close to the loading direction are responsible for facet formation, and that the facets are associated with basal slip. Microtextured regions with c-axis orientations near-perpendicular to the loading direction are believed to act as barriers to faceted crack growth, based on the change in crack morphology as the crack crosses a macrozone boundary. The variant selection occurring during the transformation of the retained beta appears to favour a common orientation with the surrounding primary alpha grains, contributing to the size of the macrozones and therefore to the extent of the observed faceted regions.

  14. Fatigue life and microstructure of ODS steels.

    Czech Academy of Sciences Publication Activity Database

    Kub?na, Ivo; Kruml, Tomáš

    2013-01-01

    Ro?. 103, SI (2013), s. 39-47. ISSN 0013-7944 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA ?R(CZ) GA106/09/1954 Institutional support: RVO:68081723 Keywords : ODS steels * Fatigue * Surface evolution * Crack nucleation mechanisms Subject RIV: JL - Materials Fatigue , Friction Mechanics Impact factor: 1.662, year: 2013

  15. 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.

  16. Studies of Microtexture and Its Effect on Tensile and High-Cycle Fatigue Properties of Laser-Powder-Deposited INCONEL 718

    Science.gov (United States)

    Qi, Huan; Azer, Magdi; Deal, Andrew

    2012-11-01

    The current work studies the microstructure, texture, and mechanical properties of INCONEL 718 alloy (IN718) produced by laser direct metal deposition. The grain microstructure exhibits an alternative distribution of banded fine and coarse grain zones as a result of the rastering scanning pattern. The effects of the anisotropic crystallographic texture on the tensile and high-cycle fatigue (HCF) properties at room temperature are investigated. Tensile test results showed that the tensile strength of laser-deposited IN718 after direct aging or solution heat treatment is equivalent to the minimum-forged IN718 properties. The transverse direction (relative to the laser scanning direction) produces >10 pct stiffer modulus of elasticity but 3 to 6 pct less tensile strength compared to the longitudinal direction due to the preferential alignment of grains having and directions parallel to the tensile loading direction. Laser-deposited IN718 with good metallurgical integrity showed equivalent HCF properties compared to the direct-aged wrought IN718, which can be attributed to the banded grain size variation and cyclic change of inclining grain orientations resulted from alternating rastering deposition path.

  17. Improved methods of creep-fatigue life assessment of components

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Alfred; Berger, Christina [Inst. fuer Werkstoffkunde (IfW), Technische Univ. Darmstadt (Germany)

    2009-07-01

    The improvement of life assessment methods contributes to a reduction of efforts at design and an effective long term operation of high temperature components, reduces technical risk and increases high economical advantages. Creep-fatigue at multi-stage loading, covering cold start, warm start and hot start cycles in typical loading sequences e.g. for medium loaded power plants, was investigated here. At hold times creep and stress relaxation, respectively, lead to an acceleration of crack initiation. Creep fatigue life time can be calculated by a modified damage accumulation rule, which considers the fatigue fraction rule for fatigue damage and the life fraction rule for creep damage. Mean stress effects, internal stress and interaction effects of creep and fatigue are considered. Along with the generation of advanced creep data, fatigue data and creep fatigue data as well scatter band analyses are necessary in order to generate design curves and lower bound properties inclusive. Besides, in order to improve lifing methods the enhancement of modelling activities for deformation and life time are important. For verification purposes, complex experiments at variable creep conditions as well as at creep fatigue interaction under multi-stage loading are of interest. Generally, the development of methods to transfer uniaxial material properties to multiaxial loading situations is a current challenge. For specific design purposes, a constitutive material model is introduced which is implemented as an user subroutine for Finite Element applications due to start-up and shut-down phases of components. Identification of material parameters have been performed by Neural Networks. (orig.)

  18. Thermomechanical fatigue, oxidation, and Creep: Part II. Life prediction

    Science.gov (United States)

    Neu, R. W.; Sehitoglu, Huseyin

    1989-09-01

    A life prediction model is developed for crack nucleation and early crack growth based on fatigue, environment (oxidation), and creep damage. The model handles different strain-temperature phasings (i.e., in-phase and out-of-phase thermomechanical fatigue, isothermal fatigue, and others, including nonproportional phasings). Fatigue life predictions compare favorably with experiments in 1070 steel for a wide range of test conditions and strain-temperature phasings. An oxide growth (oxide damage) model is based on the repeated microrupture process of oxide observed from microscopic measurements. A creep damage expression, which is stress-based, is coupled with a unified constitutive equation. A set of interrupted tests was performed to provide valuable damage progression information. Tests were performed in air and in helium atmospheres to isolate creep damage from oxidation damage.

  19. Fatigue Life Prediction of Composite Under Two Block Loading

    Directory of Open Access Journals (Sweden)

    M. Bendouba

    2014-02-01

    Full Text Available The damage evolution mechanism is one of the important focuses of fatigue behaviour investigation of composite materials and also the foundation to predict fatigue life of composite structures for engineering applications. This paper is dedicated to damage investigation of composite materials under two block loading cycle fatigue conditions. The loading sequence effect and the influence of the cycle ratio of the first stage on the cumulative fatigue life are studied. Two loading sequences, i.e., high-to-low and low-to-high cases are considered. The proposed damage indicator is connected cycle by cycle to the S-N curve and the experimental results are in agreement with model expectations. Previous experimental research is employed for validation.

  20. Deformation heterogeneities and their role in life-limiting fatigue failures in a two-phase titanium alloy

    International Nuclear Information System (INIS)

    Fatigue crack-initiation sites in Ti–6Al–2Sn–4Zr–6Mo (Ti–6–2–4–6), an ? + ? titanium alloy used in turbine engine applications, were characterized with emphasis on distinguishing the microstructural neighborhoods and mechanisms that produce the life-limiting failures vs. those that promote the mean-lifetime behavior. The characterization methods included quantitative tilt fractography, focused ion beam milling across crack-initiation facets, and electron backscattered diffraction analysis. The motivation for discerning between the life-limiting and the mean-dominating crack-initiation microstructural neighborhoods stemmed from the previously developed understanding that the mean and the life-limiting behaviors respond differently to stress level (and many other variables), leading to an increasing separation between the two subpopulations as the stress level is decreased, thereby increasing the variability in lifetime. The different rates of response of the two behaviors was found to arise because the life-limiting mechanism was dominated by the crack-growth lifetime, with microstructural-scale crack-initiation occurring within the first few fatigue cycles, whereas the mean behavior was increasingly dominated by the crack-initiation lifetime as the stress level was decreased. Representative specimens for 2-D characterization of crack-initiation neighborhoods were selected from life-limiting and mean-dominating populations generated by fatigue tests on a duplex ? + ? phase microstructure of Ti–6–2–4–6 under a narrow range of applied stress amplitudes. A compilation of data on the crack-initiation facet and the neighborhood of the faceted grain from multiple specimens pointed to at least four categories of critical microstructural configurations, each representing a set of necessary (but perhaps not sufficient) conditions for crack-initiation in this alloy. Based on this characterization, a hypothesis for the life-limiting fatigue behavior is presented. The hypothesis invokes the concept of hierarchy of fatigue deformation heterogeneities, which is suggested to develop within the first few fatigue cycles. The deformation heterogeneity is suggested to be linked to the underlying randomness and hierarchy in the microstructural arrangements. This hypothesis appears to explain the occurrence of crack-growth-lifetime-dominated, life-limiting failures in the regime of high-cycle fatigue, as shown in this study, and suggests a probability of occurrence of such failures even in the very-high-cycle fatigue regime, although with diminishing probability as the stress level is decreased

  1. An investigation on fatigue life of borided AISI 1010 steel

    OpenAIRE

    O.N. Celik; H. Gasan; M. Ulutan; M. Saygin

    2009-01-01

    Purpose: This study aims to investigate the fatigue life of box borided AISI 1010 steel materials.Design/methodology/approach: Fatigue specimens firstly have been prepared according to ASTM E466-96 standard and normalized. Then their surfaces have been cleaned by polishing. Boriding heat treatment has been applied in solid media with the help of Ekabor2 powder. Specimens have been borided at 1173-1223-1273 and 1323 K temperatures for 2-4 and 6 hours respectively. Fatigue tests have been made ...

  2. Fatigue-Life Computational Analysis for the Self-Expanding Endovascular Nitinol Stents

    Science.gov (United States)

    Grujicic, M.; Pandurangan, B.; Arakere, A.; Snipes, J. S.

    2012-11-01

    Self-expanding endovascular stents made of Nitinol (a Ni-Ti intermetallic compound possessing superelastic and shape-memory properties) are being widely used to treat a common circulatory problem in which narrowed arteries, primarily due to fatty deposits, hamper blood flow to the extremities (the problem commonly referred to as "peripheral artery disease"). The stents of this type unfortunately occasionally fail structurally (and, in turn, functionally) rendering the stenting procedure ineffective. The failure is most often attributed to the fatigue-induced damage since over its expected ten-year life span, the stent will normally experience 370-400 million pulsating-blood flow-induced loading cycles. Redesign/redevelopment of the stents using the conventional make-and-test approaches is quite expensive and time consuming and therefore is being increasingly complemented by computational engineering methods and tools. In the present study, advanced structural and fluid-structure interaction finite element computational methods are combined with the advanced fatigue-based durability analysis techniques to further enhance the use of the computational engineering analysis tools in the development of vascular stents with improved high-cycle fatigue life.

  3. Fatigue life and initiation mechanisms in wrought Inconel 718 DA for different microstructures

    OpenAIRE

    Abikchi, Meriem; Billot, Thomas; Crépin, Jérome; Longuet, Arnaud; Mary, Caroline; Morgeneyer, Thilo F.; Pineau, André

    2013-01-01

    Wrought Inconel 718 DA superalloy disk zones present a wide range of behavior in fatigue life due to the variability of the microstructure. In order to link the effect of the forging conditions and achieved microstructure to the fatigue life, two microstructures have been tested in fatigue. Fatigue tests under strain control were performed at 450°C. Grain size distributions and phase distributions were characterized in the specimens and related to fatigue failure initiation modes. Fatigue cra...

  4. Fatigue life assessment under multiaxial variable amplitude loading

    International Nuclear Information System (INIS)

    A variable amplitude multiaxial fatigue life prediction method is presented in this paper. It is based on a stress as input data are the stress tensor histories which may be calculated by FEM analysis or measured directly on the structure during the service loading. The different steps of he method are first presented then its experimental validation is realized for log and finite fatigue lives through biaxial variable amplitude loading tests using cruciform steel samples. (authors). 9 refs., 7 figs

  5. An improved method for estimating fatigue life under combined stress.

    Czech Academy of Sciences Publication Activity Database

    Balda, Miroslav; Svoboda, Jaroslav; Fröhlich, Vladislav

    2007-01-01

    Ro?. 1, ?. 1 (2007), s. 1-10. ISSN 1802-680X. [Applied and Computational Mechanics 2007. Ne?tiny, 05.11.2007 - 07.11.2007] R&D Projects: GA ?R GA101/05/0199 Institutional research plan: CEZ:AV0Z20760514 Keywords : multiaxial fatigue * life- time estimation * nonlinear least squares Subject RIV: JL - Materials Fatigue, Friction Mechanics

  6. 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 fatigue life of welded plate specimens has been investigated. Both the fracture mechanics analyses and the fatigue tests have been carried out using load histories, which correspond to one week's traffic loading, determined by means of strain gauge measurements on the deck structure of the Farø Bridges in Denmark. The results obtained from the fracture mechanics analyses show a significant difference between constant amplitude and variable amplitude results. Both the fracture mechanics analyses and the results of the fatigue tests carried out indicate that Miner's rule, which is normally used in the design 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.

  7. Fatigue life prediction modeling for turbine hot section materials

    Science.gov (United States)

    Halford, G. R.; Meyer, T. G.; Nelson, R. S.; Nissley, D. M.; Swanson, G. A.

    1989-01-01

    A major objective of the fatigue and fracture efforts under the NASA Hot Section Technology (HOST) program was to significantly improve the analytic life prediction tools used by the aeronautical gas turbine engine industry. This was achieved in the areas of high-temperature thermal and mechanical fatigue of bare and coated high-temperature superalloys. The cyclic crack initiation and propagation resistance of nominally isotropic polycrystalline and highly anisotropic single crystal alloys were addressed. Life prediction modeling efforts were devoted to creep-fatigue interaction, oxidation, coatings interactions, multiaxiality of stress-strain states, mean stress effects, cumulative damage, and thermomechanical fatigue. The fatigue crack initiation life models developed to date include the Cyclic Damage Accumulation (CDA) and the Total Strain Version of Strainrange Partitioning (TS-SRP) for nominally isotropic materials, and the Tensile Hysteretic Energy Model for anisotropic superalloys. A fatigue model is being developed based upon the concepts of Path-Independent Integrals (PII) for describing cyclic crack growth under complex nonlinear response at the crack tip due to thermomechanical loading conditions. A micromechanistic oxidation crack extension model was derived. The models are described and discussed.

  8. 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)

  9. Fatigue Life of Extended Hollobolt Connection in Concrete Filled Tube

    Directory of Open Access Journals (Sweden)

    Norashidah Abd Rahman

    2013-12-01

    Full Text Available Studies on the performance of blind bolt connections have been carried out by many researchers. A number of recent studies of new blind bolted connection system have been proposed. The system uses the so called Extended Hollobolt fastener to connect the concrete filled tubular columns. The strength performance of this system has been investigated under both monotonic and cyclic loading. However, the performance of such connections under fatigue loading is still unknown.  Therefore, a study to investigate the fatigue performance of Extended Hollobolt was proposed. The main objective of this study is to provide a better understanding of the fatigue life of the proposed blind bolt, consequently provides the design guidance for Extended Hollobolt connection in concrete filled tube. A number of tests were conducted to determine the effect of the frequency and the level of stress range loading on the behaviour of the Extended Hollobolt. The tests were used grade 8.8 bolts subjected to tension. Results show that the frequencies between 0.2 Hz to 5 Hz does affect fatigue life and the stress-range versus fatigue life behaviour of Extended Hollobolt follows the expected pattern of behaviour of standard bolts. The test results of Extended Hollobolt under different stress range then further compared to the normative regulation Eurocode 3. The fatigue life or behaviour of Extended Hollobolt is found to be higher than the theoretical curve of Eurocode 3. Meanwhile, the failure mode of Extended Hollobolt is similar to the standard bolt which is a very positive outcome for blind bolt. However, fatigue life for standard bolt appears to be higher.

  10. Fatigue life of the casting-magnesium alloy AZ91

    International Nuclear Information System (INIS)

    The cyclic deformation behaviour of the die-casting magnesium alloy AZ91 was investigated at constant total strain amplitudes between 1.4 x 10-3 and 2 x 10-2 at room temperature (20 C) and at 130 C. At low total strain amplitudes, a weak cyclic softening at the beginning of the fatigue tests is followed by cyclic hardening, whereas at high total strain amplitudes a strong cyclic hardening occurs throughout. The fatigue lives at 130 C are slightly longer at high strain amplitudes but shorter at low strain amplitudes than at room temperature. The fatigue life data for both temperatures can be described well by the laws of Manson-Coffin and Basquin. The microstructural investigations performed show the strong influence of several microstructural features on the initiation and propagation of fatigue cracks. In order to understand the fatigue crack propagation behaviour, fatigue tests were interrupted at certain numbers of cycles in order to make replicas of the surface of the samples. It could be verified that crack propagation occurs mainly by the coalescence of smaller cracks. Furthermore, unloading tests, performed within a closed cycle, were carried out in order to capture the changes of stiffness (compliance) during a closed cycle with the aim to ascertain the damage evolution occurring during the fatigue tests and to determine the stresses at which the cracks open and close. Finally, two-step fatigue tests were carried out with the objective to quantify deviations from the linear damage rule (LDR) of Palmgren and Miner. The results obtained in this study will be used to formulate a microstructurally based life-prediction concept for single-step as well as for two-step fatigue loading. (orig.)

  11. Fatigue of vanadium--hydrogen alloys

    International Nuclear Information System (INIS)

    The fatigue behavior of unalloyed V, a V-H solid solution, and alloys containing H in excess of the room temperature solubility limit was investigated. It was found that hydrogen contents near and above the room temperature solubility limit increase the high cycle fatigue life, but decrease low cycle life of polycrystalline vanadium. Changes in endurance limit with hydrides may be a consequence of decreased cyclic strain hardening coefficient, n'. 132 ppM hydrogen in solution has only a slightly beneficial effect on stress controlled fatigue life and essentially no effect on low cycle fatigue life. Unalloyed vanadium exhibits profuse striations, while hydrides produce cleavage cracks in fatigued samples

  12. Practical methodology to evaluate the fatigue life of seam welded joints

    OpenAIRE

    K.C.Goes; G.F. Batalha; M.V. Pereira; A.F. Camarao

    2011-01-01

    Purpose: of this paper is to present a practical and robust methodology developed to evaluate the fatigue life of seam welded joints under combined cyclic loading.Design/methodology/approach: Fatigue analysis was conducted in virtual environment. The finite element stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life) method. A tube-to-plate specimen was submitted to a combined cyclic loadi...

  13. Effects of pre-working and dynamic strain aging on high cycle fatigue fracture of a stainless steel SUS316NG at 300degC

    International Nuclear Information System (INIS)

    In order to obtain information about relationships between fatigue strength of a SUS316NG austenitic stainless steel and hardening behavior due to dynamic strain aging during fatigue tests, rotating bending fatigue tests were carried out at 300degC for notched specimens for stress concentration factors being less than 2.0 and for burnished hourglass type specimens. As for the notched specimens, fatigue fracture occurred before the specimens hardened enough during fatigue tests and the fatigue strengths did not reach the expected values from fatigue strengths of notched specimens for stress concentration factor being greater than 2.0. As for the burnished specimens, the specimen surfaces hardened enough previously to fatigue test but the fatigue strength also did not reach the expected value. Internal fracture occurred for burnished specimens and fish-eye patterns were observed on the fracture surfaces. (author)

  14. Study the Effect of Cooling Rate on Fatigue Strength and Fatigue Life of Heated Carbon Steel Bars

    OpenAIRE

    Ali S. Yasir

    2013-01-01

    The fatigue failure is the reason of (90%) of mechanical failures. This work tries improving the fatigue strength and increasing the fatigue life for steel bars that used in concrete reinforcing. Tensile test were done to find the mechanical properties of steel bar. The heating over critical temperature (AC3) and cooling by different cooling rates were done for steel bars, and tested this samples by tensile and fatigue tests. The tensile test results show increasing in yield and tensile stren...

  15. Development of generic creep-fatigue life prediction models

    International Nuclear Information System (INIS)

    This paper presents a data bank that was compiled from published and unpublished sources. Using these data, low cycle fatigue curves were generated under a range of test conditions showing the effect of test parameters on the Coffin-Manson behavior of steel alloys. Phenomenological methods of creep-fatigue life prediction are summarized in a table showing number of material parameters required by each method and type of tests needed to generate such parameters. Applicability of viscosity method was assessed with creep-fatigue data on 1Cr-Mo-V, 2.25Cr-Mo and 9Cr-1Mo steels. Generic equations have been developed in this paper to predict the creep-fatigue life of high temperature materials. Several new multivariate equations were developed to predict the creep-fatigue life of following alloy groups; (1) Cr-Mo steels, (2) stainless steels and (3) generic materials involving the materials from the following alloy groups, solder, copper, steels, titanium, tantalum and nickel-based alloys. Statistical analyses were performed in terms of coefficient of correlation (R2) and normal distribution plots and recommended these methods in the design of components operating at high temperatures

  16. 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...

  17. 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...

  18. 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.

  19. Finite Element Analysis of the Fatigue Life for the Connecting Rod Remanufacturing

    Directory of Open Access Journals (Sweden)

    Cheng Gang

    2013-01-01

    Full Text Available One important technical issue is whether the residual fatigue life of products meeting the needs of its next life cycle.This study analyzes the failure mechanism of the connecting rod, establishes its three dimensional model, uses dynamic simulation software ADAMS to calculate its time-load spectrum of the connecting rod; uses finite element analysis software ANSYS to get local stress-strain distribution; uses the traditional anti-fatigue methods to calculate the condition limited fatigue strength and then based on Miner fatigue damage theory and the stress of the connecting rod to make analysis, finally, uses Goodman fatigue theory to get fatigue strength and to estimate its total fatigue life, combined with its historical service time to predict its residual fatigue life. Provide reliable data to support how to calculate the residual fatigue life of these parts.

  20. Simulation work of fatigue life prediction of rubber automotive components

    Science.gov (United States)

    Samad, M. S. A.; Ali, Aidy

    2010-05-01

    The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behaviour which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

  1. Simulation work of fatigue life prediction of rubber automotive components

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-05-15

    The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behaviour which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

  2. Simulation work of fatigue life prediction of rubber automotive components

    International Nuclear Information System (INIS)

    The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behaviour which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

  3. Fatigue life prediction of autofrettage tubes using actual material behaviour

    International Nuclear Information System (INIS)

    There is a profound Bauschinger effect in the behaviour of high-strength steels used in autofrettaged tubes. This has led to development of methods capable of considering experimentally obtained (actual) material behaviour in residual stress calculations. The extension of these methods to life calculations is presented here. To estimate the life of autofrettaged tubes with a longitudinal surface crack emanating from the bore more accurately, instead of using idealized models, the experimental loading-unloading stress-strain behaviour is employed. The resulting stresses are then used to calculate stress intensity factors by the weight function method as input to fatigue life determination. Fatigue lives obtained using the actual material behaviour are then compared with the results of frequently used ideal models including those considering Bauschinger effect factors and strain hardening in unloading. Using standard fatigue crack growth relationships, life of the vessel is then calculated based on recommended initial and final crack length. It is shown that the life gain due to autofrettage above 70% overstrain is considerable

  4. Fatigue life prediction of autofrettage tubes using actual material behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Jahed, Hamid [Mechanical Engineering Department, University of Waterloo, 200 University Ave West, Waterloo, Ont., N2L 3G1 (Canada)]. E-mail: hjahedmo@uwaterloo.ca; Farshi, Behrooz [Mechanical Engineering Department, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of); Hosseini, Mohammad [Mechanical Engineering Department, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)

    2006-10-15

    There is a profound Bauschinger effect in the behaviour of high-strength steels used in autofrettaged tubes. This has led to development of methods capable of considering experimentally obtained (actual) material behaviour in residual stress calculations. The extension of these methods to life calculations is presented here. To estimate the life of autofrettaged tubes with a longitudinal surface crack emanating from the bore more accurately, instead of using idealized models, the experimental loading-unloading stress-strain behaviour is employed. The resulting stresses are then used to calculate stress intensity factors by the weight function method as input to fatigue life determination. Fatigue lives obtained using the actual material behaviour are then compared with the results of frequently used ideal models including those considering Bauschinger effect factors and strain hardening in unloading. Using standard fatigue crack growth relationships, life of the vessel is then calculated based on recommended initial and final crack length. It is shown that the life gain due to autofrettage above 70% overstrain is considerable.

  5. Numerical calculation of bending fatigue life of thin-rim spur gears

    OpenAIRE

    Kramberger, Janez; Šraml, Matjaž; Potr?, Iztok; Flašker, Jože

    2012-01-01

    Mechanical elements subjected to cyclic loading have to be designed against fatigue. The main goal of the presented analysis was to determine the the bending fatigue life prediction of thin rim spur gears. The service life is divided into the initiation phase of the damage accumulation and the crack growth, resprcitively. The analysis has been performed usig FEM and BEM. The continuum mechanics approach is used for the prediction of the fatigue life initiation phase, where the basic fatigue m...

  6. Fatigue Life Prediction of the Keel Structure of A Tsunami Buoy Using Spectral Fatigue Analysis Method

    Directory of Open Access Journals (Sweden)

    Angga Yustiawan

    2013-04-01

    Full Text Available One of the components of the Indonesia Tsunami Early Warning System (InaTEWS is a surface buoy. The surface buoy is exposed to dynamic and random loadings while operating at sea, particularly due to waves. Because of the cyclic nature of the wave load, this may result in a fatigue damage of the keel structure, which connects the mooringline with the buoy hull. The operating location of the buoy is off the Java South Coast at the coordinate (10.3998 S, 108.3417 E. To determine the stress transfer function, model tests were performed, measuring the buoy motions and the stress at the mooring line. A spectral fatigue analysis method is applied for the purpose of estimating the fatigue life of the keel structure. Utilizing the model-test results, the S-N curve obtained in a previous study and the wave data at the buoy location, it is found that the fatigue life of the keel structure is approximately 11 years.

  7. Impact of Fatigue and Disability on Quality of Life in Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Öztürk, A.

    2005-01-01

    Full Text Available Purpose: To investigate the impact of fatigue and disability on the quality of life in 70 multiple sclerosis (MS patients. Material and Methods: Quality of Life was assessed using the Functional Assessment of MS (FAMS. Disability was assessed using the Kurtzke’s expanded disability status scale (EDSS and fatigue was quantified using the fatigue severity scale (FSS. Results: Fatigue groups (MSF had more impaired scores than nonfatigue groups (MSNF (p<0,05. Fatigue and disability were significantly associated with FAMS total and subgroups (p<0,05. Conclusion: Fatigue and disability have an effect on the quality of life.

  8. Time-dependent fatigue--phenomenology and life prediction

    International Nuclear Information System (INIS)

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

  9. Thermomechanical Fatigue of Ductile Cast Iron and Its Life Prediction

    Science.gov (United States)

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

    2015-06-01

    Thermomechanical fatigue (TMF) behaviors of ductile cast iron (DCI) were investigated under out-of-phase (OP), in-phase (IP), and constrained strain-control conditions with temperature hold in various temperature ranges: 573 K to 1073 K, 723 K to 1073 K, and 433 K to 873 K (300 °C to 800 °C, 450 °C to 800 °C, and 160 °C to 600 °C). The integrated creep-fatigue theory (ICFT) model was incorporated into the finite element method to simulate the hysteresis behavior and predict the TMF life of DCI under those test conditions. With the consideration of four deformation/damage mechanisms: (i) plasticity-induced fatigue, (ii) intergranular embrittlement, (iii) creep, and (iv) oxidation, as revealed from the previous study on low cycle fatigue of the material, the model delineates the contributions of these physical mechanisms in the asymmetrical hysteresis behavior and the damage accumulation process leading to final TMF failure. This study shows that the ICFT model can simulate the stress-strain response and life of DCI under complex TMF loading profiles (OP and IP, and constrained with temperature hold).

  10. A study on the material properties and fatigue life prediction of natural rubber component

    International Nuclear Information System (INIS)

    Fatigue life prediction and evaluation are very important in design procedure to assure the safety and reliability of the rubber components. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test. Finite element analysis of rubber component was performed based on a hyper-elastic material model determined from material test. The Green-Lagrange strain at the critical location determined from the finite element method was used to evaluate the fatigue damage parameter of the natural rubber. Fatigue life of rubber components was predicted by using the fatigue damage parameter at the critical location. Predicted fatigue life of the rubber component agreed fairly well with the experimental fatigue lives

  11. 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...

  12. Comparison between tensile, stiffness and fatigue life tests results

    OpenAIRE

    Silva, Hugo Manuel Ribeiro Dias da; Pais, Jorge C.; Pereira, Paulo A. A.

    2003-01-01

    A laboratory mechanical test is being implemented in the University of Minho to evaluate the asphalt-aggregate interaction. This test measures the tensile properties of the bituminous mixture in the interface between the asphalt and the aggregates. By using the tensile test it is intended to observe how the asphalt-aggregate interaction influences the mechanical properties of the bituminous mixtures, namely, stiffness modulus and fatigue life. The tensile test results must have a good correla...

  13. Fatigue life of layered metallic and ceramic plasma sprayed coatings.

    Czech Academy of Sciences Publication Activity Database

    Ková?ík, O.; Haušild, P.; Siegl, J.; Mat?jí?ek, Ji?í; Davydov, V.

    2014-01-01

    Ro?. 3, July (2014), s. 586-591. ISSN 2211-8128. [European Conference on Fracture (ECF20)/20./. Trondheim, 30.06.2014-04.07.2014] R&D Projects: GA ?R(CZ) GAP108/12/1872 Institutional support: RVO:61389021 Keywords : functionally graded materials * fatigue life * neutron diffraction * grit blasting Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://www.sciencedirect.com/science/article/pii/S2211812814000984#

  14. 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 evalu...

  15. Cyclic behaviour and fatigue life prediction in welded aluminium joints

    International Nuclear Information System (INIS)

    The paper gives an overall state-of-the-art view of international attempts to find a solution, describes cyclic stress-strain behavior for the different zones of aluminium weldments, as stated above, states results from a recent research program of the Versuchsanstalt Stahl, Holz, und Steine in Karlsruhe and gives a step by step model for the calculation procedure of fatigue life. (orig.) 891 RW/orig. 892 RKD

  16. Casting defects and high temperature fatigue life of IN 713LC superalloy.

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Kone?ná, R.; Fintová, S.

    2012-01-01

    Ro?. 41, AUG (2012), s. 47-51. ISSN 0142-1123 R&D Projects: GA MPO(CZ) FR-TI3/055; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : IN 713LC * High-cycle fatigue * casting defects * hot isostatic pressing * extreme value statistics Subject RIV: JL - Materials Fatigue , Friction Mechanics Impact factor: 1.976, year: 2012

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

    International Nuclear Information System (INIS)

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

  18. High cycles fatigue damage of CFRP plates clamped by bolts for axial coupling joint with off-set angle during rotation

    Science.gov (United States)

    Ooka, Kazuaki; Okubo, Kazuya; Fujii, Toru; Umeda, Shinichi; Fujii, Masayuki; Sugiyama, Tetsuya

    2014-03-01

    This study discussed the change of residual fracture torque and the fatigue damage process of thin CFRP plates clamped by bolts for axial coupling joint, in which flexible deformation was allowed in the direction of off-set angle by the deflection of the CFRP plates while effective stiffness was obtained in rotational direction. Mechanically laminated 4 layers of the CFRP plates were repeatedly deflected during the rotation of axial coupling, when two axes were jointed with 3 degree of off-set angle, in which number of revolution was 1,800 rpm (30Hz of loading frequency). At first, the fracture morphology of specimen and the residual fracture torque was investigated after 1.0×107 cycles of repeated revolutions. The reduction ratio of spring constant was also determined by simple bending test after the fatigue. The residual fracture torque of the joint was determined on the rotational test machine after 1.0×107 cycles of fatigue. After rotations of cyclic fatigue, fiber breaking and wear of matrix were observed around the fixed parts compressed by washers for setting bolts. The reduction of spring constant of the CFRP plates was caused by the initiation of cyclic fatigue damages around the fixed parts, when the axial coupling joint was rotated with off-set angle. It was found that residual fracture torque of the joint was related with the specific fatigue damage of the CFRP observed in this study.

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

    DEFF Research Database (Denmark)

    Dalgas, U; Stenager, E; Jakobsen, J; Petersen, T; Hansen, H J; Knudsen, C; Overgaard, K; Ingemann-Hansen, T

    2010-01-01

    Fatigue occurs in the majority of multiple sclerosis patients and therapeutic possibilities are few. Fatigue, mood and quality of life were studied in patients with multiple sclerosis following progressive resistance training leading to improvement of muscular strength and functional capacity. 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 r...

  20. Service life determination for a fatigue-limited Class 1 piping component

    International Nuclear Information System (INIS)

    The design fatigue life assessment of an ASME Class 1 piping component typically has a significant safety margin. Methods containing varying degrees of detail may be used to develop the component's fatigue usage factor. This paper presents the technical bases used to establish a more realistic fatigue life for a piping component which was nearing its calculated design fatigue limit. The original design basis methodology was superseded by a more detailed inelastic evaluation to demonstrate structural integrity and determine the revised component fatigue life. An effective design cycle curve was developed to assess future fatigue damage, and for tracking ongoing fatigue accumulation. In addition, the existing transient tracking procedure was updated to take into account the actual transient severity for all future fatigue-significant events

  1. Life extension of components with high cumulative fatigue usage

    International Nuclear Information System (INIS)

    The current ASME Boiler and Pressure Vessel Code fatigue design approach has significant margins of safety as evidenced by fatigue data from full-scale vessels. In order to extend the qualification (life) of components which have reached the Code design usage limit of unity, improved criteria are needed which address crack initiation and propagation separately such that safe operation of these components is assured. The fatigue crack initiation phase is composed of two processes: initial microcracking of internal particles or accumulation of local strain (cyclic slip) creating discontinuities which form microcracks, and the growth of the microcracks, and the growth of the microcracks in a noncontinuum manner. The microcracks which initiate will eventually grow to a size in which continuum mechanics apply, and fracture mechanics concepts can be employed. The later propagation to failure of a component is also composed of two parts, continuum crack growth in a stable manner and eventual unstable fracture of the remaining ligament of material. This paper reviews the current status of technology in assessing initiation and propagation relative to the current design Code and suggests areas of improvement to cover extended life of high usage factor components

  2. A real time neural net estimator of fatigue life

    Science.gov (United States)

    Troudet, T.; Merrill, W.

    1990-01-01

    A neural network architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopumps blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high-frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines.

  3. A review of the effects of coolant environments on the fatigue life of LWR structural materials

    International Nuclear Information System (INIS)

    The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code specifies design curves for the fatigue life of structural materials in nuclear power plants. However, the effects of light water reactor (LWR) coolant environments were not explicitly considered in the development of the design curves. The existing fatigue-strain-versus-life ((varepsilon)-N) data indicate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. Under certain environmental and loading conditions, fatigue lives in water relative to those in air can be a factor of 15 lower for austenitic stainless steels and a factor of ?30 lower for carbon and low-alloy steels. This paper reviews the current technical basis for the understanding of the fatigue of piping and pressure vessel steels in LWR environments. The existing fatigue (varepsilon)-N data have been evaluated to identify the various material, environmental, and loading parameters that influence fatigue crack initiation and to establish the effects of key parameters on the fatigue life of these steels. Statistical models are presented for estimating fatigue life as a function of material, loading, and environmental conditions. An environmental fatigue correction factor for incorporating the effects of LWR environments into ASME Code fatigue evaluations is described. This paper also presents a critical review of the ASME Code fatigue design margins of 2 on stress (or strain) and 20 on life and assesses the possible conservatism in the current choice of design margins.

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

    OpenAIRE

    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 fatigue behaviour. A life prediction contains different, partly independent, elements: · the counting method, used for describing variable amplitude signals as a collection of constant amplitu...

  5. Fatigue life prediction for a cold worked T316 stainless steel

    International Nuclear Information System (INIS)

    Permanent damage curves of initiation-life and propagation-life which predict the fatigue life of specimens of a cold-worked type 316 stainless steel under complex strain-range histories were generated by a limited test program. Analysis of the test data showed that fatigue damage is not linear throughout life and that propagation life is longer than initiation-life at high strain ranges but is shorter at low strain ranges. If permanent damage has been initiated by prior history and/or fabrication, propagation to a given life can occur at a lower strain range than that estimated from the fatigue curves for constant CSR. (author)

  6. Life extension of components with high cumulative fatigue usage

    International Nuclear Information System (INIS)

    The current ASME Boiler and Pressure Vessel Code fatigue design approach has significant margins of safety as evidenced by fatigue data on full-scale vessels. In order to extend qualification (life) of components which have reached the Code design usage limit of unity, improved criteria are needed which address crack initiation and propagation separately such that safe operation of these components is ensured. The fatigue initiation phase is composed of two processes: initial microcracking of internal particles or accumulation of local strain (cyclic slip) creating discontinuities which form microcracks, and the growth of the microcracks in a noncontinuum manner. The microcracks which initiate will eventually grow to a size in which continuum mechanics apply, and fracture mechanics concepts have been employed. The later propagation to failure of a component is also composed of two parts, continuum crack growth in a stable manner and eventual unstable fracture of the remaining ligament of material. This paper reviews the current status of technology in assessing initiation and propagation relative to the current design Code and suggests areas of improvement to cover extended life of high usage factor components. To illustrate some of these considerations, a case study for a small manufacturing defect was reviewed. A realistic component was analyzed to investigate the interrelationship between the ASME Code Section III design life and crack propagation behavior of a small manufacturing defect. A pressurized water reactor (PWR) primary coolant system was used in the analysis, and the terminal end of the hot-leg pipe at the safe end weld was selected since usage factors as high as 0.95 had been reported. The particular plant chosen was Zion-1 because the necessary information on loading, including thermal transients, was available in the open literature. 11 refs., 1 fig., 1 tab

  7. 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 obtai...

  8. Fatigue Life Analysis of Thrust Ball Bearing Using ANSYS

    OpenAIRE

    Prabhat Singh,; , Prof Upendra Kumar Joshi2

    2014-01-01

    This paper compares the total deformation of thrust ball bearing & contact stress b/w ball & raceways & its effect on fatigue life of thrust ball bearing. The 3-Dimensional Modeling has been done through modeling software Pro-e wildfire-5.0. The parts assembly is also done in Pro-e wildfire-5.0 & analysis has been done through ANSYS- 14. An analylitical method is good, less expensive and gives the best results. Analytical results give good agreement with the experimental data. ...

  9. Fatigue life and damage evolution of martensitic steels for low-pressure steam turbine blades in the VHCF regime; Lebensdauer und Schaedigungsentwicklung martensitischer Staehle fuer Niederdruck-Dampfturbinenschaufeln bei Ermuedungsbeanspruchung im VHCF-Bereich

    Energy Technology Data Exchange (ETDEWEB)

    Kovacs, Stephan

    2014-07-01

    Low-pressure steam turbine blades are usually made of martensitic steels with Cr contents between 9 and 12%, which combine good corrosion resistance, high mechanical strength and sufficient ductility. The inhomogeneous flow field behind the vanes generates high-frequency oscillations above 1 kHz. In addition, the blades with lengths up to 1.5 m are operated at rotational speeds up to 3000 rpm, resulting in large centrifugal forces leading to the superposition of extremely high mean stresses. Also resonance oscillations during start-up and shutdown cannot be completely excluded. Currently, the components are designed using high safety factors against S-N curves with an assumed asymptotic fatigue limit above 107 load cycles. Nevertheless, fatigue cracks are observed even at high number of cycles, starting from the blade root without pre-damage by erosion or steam droplet impingement. While fatigue failure usually occurs at the surface, fatigue cracks at very high number of cycles (> 108) initiate at oxides or intermetallic inclusions below the surface. This transition between both failure mechanisms in the Very High-Cycle Fatigue (VHCF) regime is in the focus of numerous current research activities, because numbers of cycles above 108 can be attained in a viable period of time using the recently developed high-frequency testing techniques operated at 20 kHz. Also for wind turbines, gas turbines, bearings, springs, etc. VHCF issues become increasingly important. Within this work, the fatigue life and damage behavior of a martensitic Cr-steel during fatigue loading with and without high mean stresses at number of cycles to failure above 108 was analyzed. On the one hand, the studies gave insights into the relation between fatigue life and fatigue damage evolution of the investigated group of high-strength steels in the very high cycle fatigue regime (up to 2·109). In particular, the influence of high mean stresses on the VHCF behavior (fracture origin, crack growth, fatigue life) which was not investigated in detail before is studied and the crack initiation and propagation mechanisms are analyzed by electron microscopy (SEM, TEM / FIB). With this, the work contributes to the reliable design of future low-pressure steam turbines. The results show that in particular non-metallic inclusions in the steel cause fracture by fatigue cracks initiated in the volume under very high cycle fatigue conditions. This fatigue behavior can be described very well by means of fracture mechanics approaches over a wide range of load ratios.

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

    OpenAIRE

    Winnie K.W. SO; Gene Marsh; W.M. Ling

    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 de...

  11. Childhood Adversity and Cumulative Life Stress: Risk Factors for Cancer-Related Fatigue

    OpenAIRE

    Julienne E. Bower; Crosswell, Alexandra D.; Slavich, George M

    2014-01-01

    Fatigue is a common symptom in healthy and clinical populations, including cancer survivors. However, risk factors for cancer-related fatigue have not been identified. On the basis of research linking stress with other fatigue-related disorders, we tested the hypothesis that stress exposure during childhood and throughout the life span would be associated with fatigue in breast cancer survivors. Stress exposure was assessed using the Stress and Adversity Inventory, a novel computer-based inst...

  12. Finite Element Based Fatigue Life Prediction of Cylinder Head for Two-Stroke Linear Engine Using Stress-Life Approach

    OpenAIRE

    M.M.Rahman; A.K.Ariffin; S. Abdullah; Noor, M. M.; R.A. Bakar; Maleque, M.A.

    2008-01-01

    This study describes the finite element based fatigue life prediction of cylinder head for a two-stroke free piston linear engine subjected to variable amplitude loading, applicable to electric power generation. A set of aluminum alloys, cast iron and forged steel for cylinder head are considered in this study. The finite element modeling and analysis were performed utilizing the finite element analysis codes. The fatigue life analysis was carried out using finite element based fatigue ...

  13. 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 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.

  14. 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; Fæster, Søren; Sturlason, Asger

    2014-01-01

    Wind turbine components experience heavily variable loads during its lifetime and fatigue failure is a main failure mode of casted components during their design working life. The fatigue life is highly dependent on the microstructure (grain size and graphite form and size), number, type, location 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 ...

  15. Creep-fatigue life prediction method using Diercks equation for Cr-Mo steel

    International Nuclear Information System (INIS)

    For dealing with the situation that creep-fatigue life properties of materials do not exist, a development of the simple method to predict creep-fatigue life properties is necessary. A method to predict the creep-fatigue life properties of Cr-Mo steels is proposed on the basis of D. Diercks equation which correlates the creep-fatigue lifes of SUS 304 steels under various temperatures, strain ranges, strain rates and hold times. The accuracy of the proposed method was compared with that of the existing methods. The following results were obtained. (1) Fatigue strength and creep rupture strength of Cr-Mo steel are different from those of SUS 304 steel. Therefore in order to apply Diercks equation to creep-fatigue prediction for Cr-Mo steel, the difference of fatigue strength was found to be corrected by fatigue life ratio of both steels and the difference of creep rupture strength was found to be corrected by the equivalent temperature corresponding to equal strength of both steels. (2) Creep-fatigue life can be predicted by the modified Diercks equation within a factor of 2 which is nearly as precise as the accuracy of strain range partitioning method. Required test and analysis procedure of this method are not so complicated as strain range partitioning method. (author)

  16. Use of Strain-life Models with Wavelet Bump Extraction (WBE fro Prediction Fatigue Damage

    Directory of Open Access Journals (Sweden)

    John R. Yates

    2008-08-01

    Full Text Available This paper presents the use of strain-life fatigue damage models to observe the cycle sequence effects in the wavelet-based fatigue data editing algorithm. This algorithm is called Wavelet Bump Extraction (WBE, which was developed to produce a shortened signal by extracting fatigue damaging events from the original signal with the retention of the original cycle sequences. Current industrial practice uses the Plamgren-Miner linear damage rule to predict the fatigue life or fatigue damage under variable amplitude(VA loadings. Using VA loadings, however, this rule does not have load interaction accountability in the analysis. Thus, a more suitable approach has been identified for predicting fatigue damage od VA loadings, i.e. the Effective Strain Damage (ESD model. In this study, the cycle sequence effect observation was implemented in both analytical and experimental works using the WBE extracted VA loadings. The study includes the comparison between the experimental and the anlytical (using four strain-life fatigue damage models: Coffin-Manson, Morrow, Smith-Watson-Topper and ESD fatigue damage. The smallest average in the fatigue damage difference was found when using the ESD strain-life model, suggesting the suitability of the model for analysing VA fatigue technique.

  17. Finite Element Based Fatigue Life Prediction of a New Free Piston Engine Mounting

    Directory of Open Access Journals (Sweden)

    M.M. Rahman

    2008-01-01

    Full Text Available This study presents the finite element based fatigue life prediction of a new free piston linear generator engine mounting. The objective of this research is to assess the critical fatigue locations on the component due to loading conditions. The effects of mean stress and probabilistic nature on the fatigue life are also investigated. Materials SAE 1045-450-QT and SAE 1045-595-QT are considered in this study. The finite element modeling and analysis was performed using computer-aided design and finite element analysis codes. In addition, the fatigue life prediction was carried out utilizing the finite element based fatigue code. Total-life approach and crack initiation approach were applied to predict the fatigue life of the free piston linear engine mounting. The results show the contour plots of fatigue life and damage histogram at the most damaging case. The comparison between the total-life approach and crack initiation approach were investigated. From the results, it can be concluded that Morrow mean stress correction method gives the most conservative (less life results for crack initiation method. It can be seen that SAE 1045-595-QT material gives consistently higher life than SAE 1045-450-QT material for all loading conditions for both methods.

  18. 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; Pechlivanoglou, George; Nayeri, Christian; Paschereit, Christian Oliver

    2015-01-01

    In this paper, fatigue lifetime prediction of NREL 5MW reference wind turbine is presented. The fatigue response of materials used in selected blade cross sections was obtained by applying macroscopic fatigue approaches and assuming uniaxial stress states. Power production and parked load cases 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 aeroel...

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

    International Nuclear Information System (INIS)

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

  20. Uncertainty Analysis in Fatigue Life Prediction of Gas Turbine Blades Using Bayesian Inference

    Science.gov (United States)

    Li, Yan-Feng; Zhu, Shun-Peng; Li, Jing; Peng, Weiwen; Huang, Hong-Zhong

    2015-12-01

    This paper investigates Bayesian model selection for fatigue life estimation of gas turbine blades considering model uncertainty and parameter uncertainty. Fatigue life estimation of gas turbine blades is a critical issue for the operation and health management of modern aircraft engines. Since lots of life prediction models have been presented to predict the fatigue life of gas turbine blades, model uncertainty and model selection among these models have consequently become an important issue in the lifecycle management of turbine blades. In this paper, fatigue life estimation is carried out by considering model uncertainty and parameter uncertainty simultaneously. It is formulated as the joint posterior distribution of a fatigue life prediction model and its model parameters using Bayesian inference method. Bayes factor is incorporated to implement the model selection with the quantified model uncertainty. Markov Chain Monte Carlo method is used to facilitate the calculation. A pictorial framework and a step-by-step procedure of the Bayesian inference method for fatigue life estimation considering model uncertainty are presented. Fatigue life estimation of a gas turbine blade is implemented to demonstrate the proposed method.

  1. 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.

  2. Fatigue, Physical Function and Quality of Life in Relation to Disease Activity in Established Rheumatoid Arthritis

    OpenAIRE

    Barman A; Chatterjee A.; Das KM; Mandal PK; Ghosh A; Ballav A

    2010-01-01

    Objectives: This study was intended to find out therelationship of fatigue, functional disability and Health-Related Quality Of Life (HRQOL) with disease activityin adult patients with active rheumatoid arthritis (RA)and to observe the effect of rehabilitation programme onthese parameters.Material and Methods: 106 patients participated and 96completed the study. Disease Activity Score-28 (DAS-28), visual analogue scale for pain and fatigue,Multidimensional Assessment of Fatigue Scale (MAF),He...

  3. Development of a methodology for on line fatigue life monitoring of nuclear power plant components

    International Nuclear Information System (INIS)

    A methodology has been developed for on line fatigue life monitoring of nuclear power plant components. Green's function technique is used to convert plant data to stress time data. Rainflow cycle counting method is used to compute the fatigue usage factor from stress time history by using material fatigue data. An interactive user friendly graphics code has been developed for updating the stored data and also for retrieving relevant informations by plant operators. (author)

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

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Berggreen, Christian

    2015-01-01

    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 perf...

  5. Room temperature creep-fatigue response of selected copper alloys for high heat flux applications

    DEFF Research Database (Denmark)

    Li, M.; Singh, B.N.; Stubbins, J.F.

    2004-01-01

    Two copper alloys, dispersion-strengthened CuAl25 and precipitation-hardened CuCrZr, were examined under fatigue and fatigue with hold time loading conditions. Tests were carried out at room temperature and hold times were imposed at maximum tensile and maximum compressive strains. It was found that hold times could be damaging even at room temperature, well below temperatures typically associated with creep. Hold times resulted in shorter fatigue lives in the high cycle fatigue, long life regim...

  6. Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants

    Science.gov (United States)

    Chan, Kwai S.; Koike, Marie; Mason, Robert L.; Okabe, Toru

    2013-02-01

    Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.

  7. 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 that spinel appears when the Al content is lowered below 2 w/o in the bond coat. Here it was shown that a faster growing oxide, rich in Ni, Cr and Co forms at the interface. Al depletion is also linked to BC phases. Initially the bond coat is a {gamma}/{beta}-material possibly with very fine dispersed {gamma}. Simultaneously with Al-depletion the {beta}-phase is found to disappear. This occurs simultaneously with the formation of spinel. However, oxidation is not only a disadvantage. Low cycle fatigue tests reveal that oxide streaks within the bond coat will slow down crack growth due to crack deflection and crack branching. Therefore benefit of or damage from oxide growth on crack initiation and propagation is dependent on crack mode, spalling of the ceramic TC or growth of 'classic' cracks perpendicular to the surface. From the observations conclusions are drawn regarding fatigue behaviour of TBC systems. The basic idea is that all cracks leading to failure initiate in the thermally grown oxide. Following the initiation, they can, however, grow to form either delamination cracks leading to top coat spallation or cracks transverse to the surface leading to component failure.

  8. 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. PMID:25050406

  9. Residual stress evaluation and fatigue life prediction in the welded joint by X-ray diffraction

    International Nuclear Information System (INIS)

    In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture or occurs the stress corrosion cracking and fatigue fracture. The residual stress of the welded part in the recently constructed power plants has been the cause of a variety of accidents. The objective of this study is measurement of the residual stress by X-ray diffraction method and to estimate the feasibility of this application for fatigue life assessment of the high-temperature pipeline. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The test results were analyzed by the distributed characteristics of residual stresses and the Full Width at Half Maximum intensity (FWHM) in x-ray diffraction intensity curve. Also, X-ray diffraction tests using specimens simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the ratio of the FWHM due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationships, it was suggested that direct expectation of the life consumption rate was feasible.

  10. Residual stress evaluation and fatigue life prediction in the welded joint by X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Keun Bong [Korea Electric Power Research Institute, Daejeon (Korea, Republic of); Kim, Jae Hoon [Chungnam National University, Daejeon (Korea, Republic of)

    2009-07-01

    In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture or occurs the stress corrosion cracking and fatigue fracture. The residual stress of the welded part in the recently constructed power plants has been the cause of a variety of accidents. The objective of this study is measurement of the residual stress by X-ray diffraction method and to estimate the feasibility of this application for fatigue life assessment of the high-temperature pipeline. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The test results were analyzed by the distributed characteristics of residual stresses and the Full Width at Half Maximum intensity (FWHM) in x-ray diffraction intensity curve. Also, X-ray diffraction tests using specimens simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the ratio of the FWHM due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationships, it was suggested that direct expectation of the life consumption rate was feasible.

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

    DEFF Research Database (Denmark)

    Ardila, Oscar Gerardo Castro; Lennie, Matthew

    2015-01-01

    In this paper, fatigue lifetime prediction of NREL 5MW reference wind turbine is presented. The fatigue response of materials used in selected blade cross sections was obtained by applying macroscopic fatigue approaches and assuming uniaxial stress states. Power production and parked load cases 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 calculated employing laminated composite theory and beam cross section methods. The Palmgren-Miner linear damage rule was used to calculate the accumulation damage. The theoretical results produced by both fatigue tools proved a prominent effect of analysed design load conditions on the estimated lifetime of the wind turbine blades and are good starting points for future fatigue analysis using other methods.

  12. Low-cycle fatigue life of steel P92 under gradual loading

    International Nuclear Information System (INIS)

    The aim of the study was to determine low-cycle fatigue life characteristics of P92 steel used in the power unit components that work under the highest effort. Steel service life was determined in the tests for total fixed strain ??t ranges from 0.6 to 1.2 % and with application of two-stage sequence loading. Low-cycle fatigue tests were conducted at room temperature and at 550 °C on MTS-810 testing machine. The tests under sequence loading were carried out for two strain ranges: ??t = 0.6 and 1.2 %. Sinusoidal load cycles of a coefficient R = ?1 were used. Low-cycle fatigue life characteristics were developed with consideration of loading sequence impact. It was found out the fatigue life of an element under sequence loading is strictly correlated with its history of strain, which determines the degree of material microstructure damage. Higher degree of steel damage was found in two-stage tests, in which the larger range of strain ??t = 1.2 % was used as the first one. Fractography analyses of scrap revealed the patterns of fatigue lines and bands typical for this process as well as numerous secondary cracks occurred to the boundaries of former austenite grains. Analytic method of predicting low-cycle fatigue life of an element under two-stage sequence loading is presented. For this purpose, an energy criterion for the material life developed for tests carried out in conditions of low-cycle fatigue was used.

  13. The Relation between Fatigue Severity with Psychological Symptoms and Quality of Life in Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Ghasem Salehpoor

    2012-09-01

    Full Text Available Background: Fatigue is one of the most common and disabling symptoms of multiple sclerosis (MS disease. Since fatigue can cause a great deal of problems it create can cause a variety of psychological symptoms particularly depression, anxiety and stress as well, that quality of daily lives, endanger. Thus, the objective of this study was to determine the relation between fatigue severity and psychological symptoms and quality of life in patients with MS.Materials and Methods: In this descriptive-correlational study, 76 patients with MS with a mean age of 34.02±9.42 (16-58 year, a member of Guilan province MS association, were selected consecutively. At first, all patients completed the questionnaire of demographic information, and then they were evaluated by the Fatigue Severity Scale (Fatigue Severity Scale, depression, anxiety, Stress Scale (depression, anxiety, stress scale-21 and Quality of Life questionnaire (Short Form-36. Results: Correlational analyses indicated a significant association between fatigue severity and patient's age, depression, anxiety and stress (p<0.05 and quality of life (p<0.01, While there were no significant relations between fatigue severity and duration of MS. The results of multiple stepwise regression analysis showed that only the factor of quality of life as a selected variable in final model could explain 27% of the shared variance of fatigue severity results (p=0.002.Conclusion: The findings showed that regardless of other variables, the levels of quality of life are predictor of fatigue severity in patients with MS. Therefore it is suggested in these patients psychotherapy based on improvement of quality of life for decrease of the levels of fatigue be set as the central aim of psychological interventions.

  14. Cyclic plastic response and fatigue life in superduplex 2507 stainless steel.

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Petrenec, Martin; Kruml, Tomáš

    2010-01-01

    Ro?. 32, ?. 2 (2010), s. 279-287. ISSN 0142-1123 R&D Projects: GA AV ?R IAA100480704; GA ?R GA101/07/1500 Institutional research plan: CEZ:AV0Z20410507 Keywords : Cyclic plasticity * Hysteresis loop * Fatigue life * Superduplex steel Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.799, year: 2010

  15. Cyclic plastic response and fatigue life in symmetric and asymmetric cyclic loading.

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Petrenec, Martin; Kruml, Tomáš; Chlupová, Alice

    10 2011, - (2011), 568–577. ISSN 1877-7058. [11th International Conference on the Mechanical Behavior of Materials. Lake Como, 06.06.2001-09.06.2011] R&D Projects: GA ?R GAP108/10/2371 Institutional research plan: CEZ:AV0Z20410507 Keywords : hysteresis loop * mean stress * fatigue life Subject RIV: JL - Materials Fatigue, Friction Mechanics

  16. MS quality of life, depression, and fatigue improve after mindfulness training: A randomized trial

    OpenAIRE

    Grossman, P.; Kappos, L; Gensicke, H.; D'Souza, M.; Mohr, D C; Penner, I K; Steiner, C.

    2010-01-01

    Objective: Health-related quality of life (HRQOL) is often much reduced among individuals with multiple sclerosis (MS), and incidences of depression, fatigue, and anxiety are high. We examined effects of a mindfulness-based intervention (MBI) compared to usual care (UC) upon HRQOL, depression, and fatigue among adults with relapsing-remitting or secondary progressive MS.

  17. Evaluation of creep-fatigue life prediction methods for low-carbon/nitrogen-added SUS316

    International Nuclear Information System (INIS)

    Low-carbon/medium nitrogen 316 stainless steel called 316FR is a principal candidate for the high-temperature structural materials of a demonstration fast reactor plant. Because creep-fatigue damage is a dominant failure mechanism of the high-temperature materials subjected to thermal cycles, it is important to establish a reliable creep-fatigue life prediction method for this steel. Long-term creep tests and strain-controlled creep-fatigue tests have been conducted at various conditions for two different heats of the steel. In the constant load creep tests, both materials showed similar creep rupture strength but different ductility. The material with lower ductility exhibited shorter life under creep-fatigue loading conditions and correlation of creep-fatigue life with rupture ductility, rather than rupture strength, was made clear. Two kinds of creep-fatigue life prediction methods, i.e. time fraction rule and ductility exhaustion method were applied to predict the creep-fatigue life. Accurate description of stress relaxation behavior was achieved by an addition of 'viscous' strain to conventional creep strain and only the latter of which was assumed to contribute to creep damage in the application of ductility exhaustion method. The current version of the ductility exhaustion method was found to have very good accuracy in creep-fatigue life prediction, while the time fraction rule overpredicted creep-fatigue life as large as a factor of 30. To make a reliable estimation of the creep damage in actual components, use of ductility exhaustion method is strongly recommended. (author)

  18. Tensile, Fracture, Fatigue Life, and Fatigue Crack Growth Rate Behavior of Structural Materials for the ITER Magnets: The European Contribution

    Science.gov (United States)

    Nyilas, A.; Nikbin, K.; Portone, A.; Sborchia, C.

    2004-06-01

    Fatigue crack growth rates (FCGR) are determined for R ratios between 0.1 - 0.7 at 7 K for three full-size Mock-up Models of the ITER Toroidal Field coil case produced by modified Type 316LN alloys. A representative forged block of Model 3 is additionally manufactured to determine its improved spatial tensile properties and compare it to former Model 3 data. From the new candidate jacket materials, developed for the ITER Central Solenoid coil, a batch is investigated to assess the fatigue life behavior at 7 K. Furthermore, the 4 K test facility, a 630 kN load capacity hydraulic machine has been used to allow fatigue life investigations under four point bending of the full-size jackets with artificial surface flaws. Cyclic life results have been assessed for the heat affected zone, weld, and base metal. The results are used in the fatigue analysis of the coil. Residual stresses resulting from jacket welding have been determined using two different techniques. First by distortion measurements of sliced pieces of the weld section and secondly by neutron diffraction measurements. In addition, tensile and fracture tests have been performed at 7 K with Al 7075, a candidate alloy for the pre-compression system of the CS coil.

  19. Tensile, Fracture, Fatigue Life, and Fatigue Crack Growth Rate Behavior of Structural Materials for the ITER Magnets: The European Contribution

    International Nuclear Information System (INIS)

    Fatigue crack growth rates (FCGR) are determined for R ratios between 0.1 - 0.7 at 7 K for three full-size Mock-up Models of the ITER Toroidal Field coil case produced by modified Type 316LN alloys. A representative forged block of Model 3 is additionally manufactured to determine its improved spatial tensile properties and compare it to former Model 3 data. From the new candidate jacket materials, developed for the ITER Central Solenoid coil, a batch is investigated to assess the fatigue life behavior at 7 K. Furthermore, the 4 K test facility, a 630 kN load capacity hydraulic machine has been used to allow fatigue life investigations under four point bending of the full-size jackets with artificial surface flaws. Cyclic life results have been assessed for the heat affected zone, weld, and base metal. The results are used in the fatigue analysis of the coil. Residual stresses resulting from jacket welding have been determined using two different techniques. First by distortion measurements of sliced pieces of the weld section and secondly by neutron diffraction measurements. In addition, tensile and fracture tests have been performed at 7 K with Al 7075, a candidate alloy for the pre-compression system of the CS coil

  20. Fatigue, Physical Function and Quality of Life in Relation to Disease Activity in Established Rheumatoid Arthritis

    Directory of Open Access Journals (Sweden)

    Barman A

    2010-04-01

    Full Text Available Objectives: This study was intended to find out therelationship of fatigue, functional disability and Health-Related Quality Of Life (HRQOL with disease activityin adult patients with active rheumatoid arthritis (RAand to observe the effect of rehabilitation programme onthese parameters.Material and Methods: 106 patients participated and 96completed the study. Disease Activity Score-28 (DAS-28, visual analogue scale for pain and fatigue,Multidimensional Assessment of Fatigue Scale (MAF,Health Assessment Questionnaire (HAQ, AmericanCollege of Rheumatology revised criteria for functionalstatus classification, World Health Organization QualityOf Life instrument (WHOQOL-BREF wereadministered. A comprehensive rehabilitation programmecomprising pharmacologic and non-pharmacologic therapywas continued for 6 months.Results: Mean VAS fatigue, DAS28 & HAQ scores were45.68, 5.14 and 1.16 respectively. Significant correlation(Pearson’s r =0.82, p<0.05; r=0.75, p<0.05; r=0.85,p=<0.05 between the disease activity and the value ofthe VAS Fatigue, Global Fatigue (MAF and HAQ scorerespectively and inverse co-relation between quality oflife (QOL domain scores and disease activity wereobserved. Similar results were also found in the final visit.Comprehensive rehabilitation reduced the disease activity,fatigue, functional disability and improved QOL.Conclusion: High fatigue level, disability, pain anddecreased QOL characterized RA disease activity.Reduction of DAS, Fatigue, HAQ scores with treatmentimproved QOL.

  1. Finite Element Based Fatigue Life Prediction of Cylinder Head for Two-Stroke Linear Engine Using Stress-Life Approach

    Directory of Open Access Journals (Sweden)

    M.M. Rahman

    2008-01-01

    Full Text Available This study describes the finite element based fatigue life prediction of cylinder head for a two-stroke free piston linear engine subjected to variable amplitude loading, applicable to electric power generation. A set of aluminum alloys, cast iron and forged steel for cylinder head are considered in this study. The finite element modeling and analysis were performed utilizing the finite element analysis codes. The fatigue life analysis was carried out using finite element based fatigue analysis commercial codes. Fatigue stress-life approach was used when the piston is subjected to variable amplitude at different loading conditions. The effects of mean stress and sensitivity analysis on fatigue life are discussed. From the results, it was shown that the Goodman mean stress correction method is predicted more conservative (minimum life results. It was found to differ significantly the compressive and tensile mean stresses. The compressive mean stress are beneficial however tensile mean stress detrimental to the fatigue life. The effect of materials and components S-N was also investigated and not found to give any large advantages, however the effect of certainty of survival was found to give noticeable advantages and it concluded that the 99.9% are fond to be design criteria. The proposed technique is capable of determining premature products failure phenomena.

  2. Fatigue life analysis of die forged railway axle manufactured from C30 steel

    Directory of Open Access Journals (Sweden)

    Libor Trško

    2014-06-01

    Full Text Available With respect to the manufacturing process, different parts of one structural component can have different fatigue properties. In this study, the fatigue life of a railway axle manufactured from C30 steel by die forging is evaluated in the part of the axle bolster and axle body. According to the fatigue test results obtained at high frequency tension - compression fatigue tests (f ? 20 kHz, R = -1, T = 20 ± 5 °C, due to the higher level of work hardening of the axle bolster, the fatigue strength of material in this part is significantly higher than in the axle body. Different fatigue strength of these parts were observed despite the fact, that results of static tensile tests did not proved any important differences in the ultimate tensile strength, yield point and elongation. 

  3. Fatigue life prediction of magnetorheological elastomers subjected to dynamic equi-biaxial cyclic loading

    International Nuclear Information System (INIS)

    Prediction of fatigue life is of great significance in ensuring that dynamically loaded rubber components exhibit safety and reliability in service. In this text, the dynamic equi-biaxial fatigue behaviour of magnetorheological elastomer (MREs) using a bubble inflation method is described. Wöhler (S–N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range of stress amplitudes (?a) between 0.75 MPa and 1.4 MPa. Changes in physical properties, including variation in stress–strain relations and complex modulus (E*) during the fatigue process were analysed. It was found that the complex modulus of MRE samples decreased throughout the entire fatigue test and failure took place at a limiting value of approximately 1.228MPa ± 4.38% for isotropic MREs and 1.295 ± 10.33% for anisotropic MREs. It was also determined that a dynamic stored energy criterion can be used as a plausible predictor in determining the fatigue life of MREs. - Highlights: • The first Wöhler curves for MREs subjected to equi-biaxial loading were presented. • Anisotropic MREs exhibited higher fatigue resistance than isotropic MREs. • There is a limiting value of complex modulus (E*) at which fatigue failure will occur. • The dynamic stored energy criterion can be used as a fatigue life predictor

  4. Fatigue life prediction of magnetorheological elastomers subjected to dynamic equi-biaxial cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yanfen, E-mail: yanfen.zhou@mydit.ie [Centre for Elastomer Research, Focas Research Institute, Dublin Institute of Technology, Dublin 8 (Ireland); Jerrams, Stephen [Centre for Elastomer Research, Focas Research Institute, Dublin Institute of Technology, Dublin 8 (Ireland); Betts, Anthony [Applied Electrochemistry Group, Focas Research Institute, Dublin Institute of Technology, Dublin 8 (Ireland); Chen, Lin [Beijing Aeronautical Science and Technology Research Institute, Commercial Aircraft Corporation of China (China)

    2014-08-01

    Prediction of fatigue life is of great significance in ensuring that dynamically loaded rubber components exhibit safety and reliability in service. In this text, the dynamic equi-biaxial fatigue behaviour of magnetorheological elastomer (MREs) using a bubble inflation method is described. Wöhler (S–N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range of stress amplitudes (?{sub a}) between 0.75 MPa and 1.4 MPa. Changes in physical properties, including variation in stress–strain relations and complex modulus (E*) during the fatigue process were analysed. It was found that the complex modulus of MRE samples decreased throughout the entire fatigue test and failure took place at a limiting value of approximately 1.228MPa ± 4.38% for isotropic MREs and 1.295 ± 10.33% for anisotropic MREs. It was also determined that a dynamic stored energy criterion can be used as a plausible predictor in determining the fatigue life of MREs. - Highlights: • The first Wöhler curves for MREs subjected to equi-biaxial loading were presented. • Anisotropic MREs exhibited higher fatigue resistance than isotropic MREs. • There is a limiting value of complex modulus (E*) at which fatigue failure will occur. • The dynamic stored energy criterion can be used as a fatigue life predictor.

  5. Residual stress evaluation and fatigue life prediction in the welded joint by x-ray diffraction

    Science.gov (United States)

    Yoo, Keun Bong; Hwang, Kwon Tae; Chang, Jung Chel; Kim, Jae Hoon

    2009-07-01

    In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture. The residual stress of the welded part in the recently constructed power plants has been the cause of a variety of accidents. The objective of this study is measurement of the residual stress and the full width at half maximum intensity (FWHM) by X-ray diffraction method and to estimate the feasibility of this application for fatigue life assessment of the high-temperature pipeline. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The test results were analyzed by the distributed characteristics of residual stresses and FWHM in x-ray diffraction intensity curve. Also, X-ray diffraction tests using specimens simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the ratio of the FWHM due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationship, it was suggested that direct expectation of the life consumption rate was feasible.

  6. 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 improve the design. A new improved slot for the longitudinal intersection in the web plate is found on the basis of a shape optimization of the conventional slot. The new slot has an unique shape (tongue form) resulting in a stress relaxation around the slot. Both the conventional and the new slot structure were analyzed by FEM followed by fatigue life calculations and subsequently compared. The overall expected fatigue life for the shape optimized slot will increase by approximately 12 %. The results were compared with an another study concerning a slot for a T-longitudinal.

  7. 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.

  8. The influence of secondary bending on fatigue life improvement in bolted joints

    Science.gov (United States)

    Evans, R. L.

    1993-08-01

    Secondary bending often occurs in structural joints, and to assess its influence on the fatigue life enhancement technique of hole cold-expansion, an experimental program has been undertaken. The results indicate that the effect of cold working is substantially reduced in specimens with secondary bending. For any marked extension in fatigue life, additional treatments, for example, the combination of cold expansion and interference fit, are required.

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

    DEFF Research Database (Denmark)

    Hansen, Jens Zangenberg; Østergaard, Rasmus

    2013-01-01

    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 un...

  10. Fatigue

    Science.gov (United States)

    ... little energy, followed by poor sleep and more fatigue. Mental or physical stimulation leads to activity, which uses ... suited to their child’s level of strength and endurance, use adaptive equipment ... may lead to fatigue. It’s not surprising that the heart is affected ...

  11. Fatigue life prediction under variable amplitude axial–torsion loading using maximum damage parameter range method

    International Nuclear Information System (INIS)

    This article deals with the problem of multiaxial fatigue life assessment under variable amplitude axial–torsion loading. A maximum damage parameter range (MDPR) reversal counting method is proposed to predict fatigue life under variable amplitude multiaxial loading. First, a multiaxial fatigue damage parameter is selected for a given multiaxial loading time history. Then, a damage parameter range time history can be calculated. Finally, based on the MDPR method, fatigue life can be predicted by correlating with multiaxial fatigue damage model and the Miner–Palmgren damage rule. The proposed method is evaluated with experimental data of the 7050-T7451 aluminum alloy and En15R steel under variable amplitude multiaxial loading. The results demonstrated that the proposed method can provide satisfactory prediction. -- Highlights: • A maximum damage parameter range (MDPR) reversal counting method is proposed. • Fatigue damage parameter will be directly defined as cycle counting parameter. • Based on MDPR method, a fatigue life prediction procedure is proposed. • The detailed algorithm is proposed. • The proposed method can provide satisfactory prediction

  12. Fatigue failure by in-line flow-induced vibration. Fatigue crack detection and fatigue life evaluation

    International Nuclear Information System (INIS)

    The phenomenon of fatigue failure due to In-line flow-induced vibration has been investigated. In the experimental program an induced-vibration experimental set-up involving water flow was developed. This apparatus was used to produce fatigue failure resulting from In-line flow-induced vibration. The fatigue test cylinders were made of medium carbon steel. A small hole was drilled onto the test cylinder surface to localize the fatigue cracking process. A strain histogram recorder was used to acquire the service strain histogram and also to detect any variation in natural frequency. The cumulative fatigue damage, D, as defined by the Modified Miner Rule, was determined by using the strain histogram of the early portion of the test record. The value of D was close to unity in the case of In-line vibration. In contrast, the value of D obtained in a previous investigation for the case of the Cross-flow vibration ranged approximately from 0.2 to 0.8. (author)

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

    DEFF Research Database (Denmark)

    Rafsanjani, Hesam Mirzaei; SØrensen, John Dalsgaard

    2015-01-01

    The reliability of the component of a wind turbine is often highly dependent on defects introduced during the manufacturing process. In this paper a stochastic model is proposed for modeling these defects and the influence on the fatigue life is considered. Basically the defects assumed distributed 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 by stochastic models. In this paper, the Poisson distribution for modeling of defects of component are considered and the surface and sub-surface defects categorized. Furthermore, a model to estimate the probability of failure by fatigue due to the defects is proposed. Moreover, the relation between defect distribution and fatigue life of component explained.

  14. A methodology for on line fatigue life monitoring : rainflow cycle counting method

    International Nuclear Information System (INIS)

    Green's function technique is used in on line fatigue life monitoring to convert plant data to stress versus time data. This technique converts plant data most efficiently to stress versus time data. To compute the fatigue usage factor the actual number of cycles experienced by the component is to be found out from stress versus time data. Using material fatigue properties the fatigue usage factor is to be computed from the number of cycles. Generally the stress response is very irregular in nature. To convert an irregular stress history to stress frequency spectra rainflow cycle counting method is used. This method is proved to be superior to other counting methods and yields best fatigue estimates. A code has been developed which computes the number of cycles experienced by the component from stress time history using rainflow cycle counting method. This postprocessor also computes the accumulated fatigue usage factor from material fatigue properties. The present report describes the development of a code to compute fatigue usage factor using rainflow cycle counting technique and presents a real life case study. (author). 10 refs., 10 figs

  15. Low cycle fatigue life of two nickel-base casting alloys in a hydrogen environment

    International Nuclear Information System (INIS)

    Results of low cycle fatigue tests on alloy Mar-M-246 and Inconel 713 are presented. Based on the limited data, it was concluded that the Mar-M-246 material had a cyclic life in hydrogen that averaged three times higher than the alloy 713LC material for similar strain ranges. The hydrogen environment reduced life for both materials. The life reduction was more than an order of magnitude for the 713LC material. Porosity content of the cast specimens was as expected and was an important factor governing low cycle fatigue life

  16. The Effect of Hole Quality on the Fatigue Life of 2024-T3 Aluminum Alloy Sheet

    Science.gov (United States)

    Everett, Richard A., Jr.

    2004-01-01

    This paper presents the results of a study whose main objective was to determine which type of fabrication process would least affect the fatigue life of an open-hole structural detail. Since the open-hole detail is often the fundamental building block for determining the stress concentration of built-up structural parts, it is important to understand any factor that can affect the fatigue life of an open hole. A test program of constant-amplitude fatigue tests was conducted on five different sets of test specimens each made using a different hole fabrication process. Three of the sets used different mechanical drilling procedures while a fourth and fifth set were mechanically drilled and then chemically polished. Two sets of specimens were also tested under spectrum loading to aid in understanding the effects of residual compressive stresses on fatigue life. Three conclusions were made from this study. One, the residual compressive stresses caused by the hole-drilling process increased the fatigue life by two to three times over specimens that were chemically polished after the holes were drilled. Second, the chemical polishing process does not appear to adversely affect the fatigue life. Third, the chemical polishing process will produce a stress-state adjacent to the hole that has insignificant machining residual stresses.

  17. Effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK).

    Science.gov (United States)

    Simsiriwong, Jutima; Shrestha, Rakish; Shamsaei, Nima; Lugo, Marcos; Moser, Robert D

    2015-11-01

    In this study, the effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK) was investigated. Due to the versatility of its material properties, the semi-crystralline PEEK polymer has been increasingly adopted in a wide range of applications particularly as a biomaterial for orthopedic, trauma, and spinal implants. To obtain the cyclic behavior of PEEK, uniaxial fully-reversed strain-controlled fatigue tests were conducted at ambient temperature and at 0.02 mm/mm to 0.04 mm/mm strain amplitudes. The microstructure of PEEK was obtained using the optical and the scanning electron microscope (SEM) to determine the microstructural inclusion properties in PEEK specimen such as inclusion size, type, and nearest neighbor distance. SEM analysis was also conducted on the fracture surface of fatigue specimens to observe microstructural inclusions that served as the crack incubation sites. Based on the experimental strain-life results and the observed microstructure of fatigue specimens, a microstructure-sensitive fatigue model was used to predict the fatigue life of PEEK that includes both crack incubation and small crack growth regimes. Results show that the employed model is applicable to capture microstructural effects on fatigue behavior of PEEK. PMID:26301567

  18. Fatigue

    Science.gov (United States)

    ... can be a normal and important response to physical activity, emotional stress, boredom, or lack of sleep. Fatigue is a common symptom, and it is usually not due to a serious disease. But it can be a sign of a ...

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

    OpenAIRE

    A.G.A. Rahman; M.M.Rahman; M Kamal

    2012-01-01

    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...

  20. 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.

  1. A numerical investigation of creep-fatigue life prediction utilizing hysteresis energy as a damage parameter

    International Nuclear Information System (INIS)

    This paper explores the hypothesis that there exists an intrinsic material property, hysteresis damage energy at failure, which could be used as a creep-fatigue life prediction parameter. The connection between hysteresis energy and fatigue damage was introduced in the 1920's by Inglis, but the use of hysteresis energy as a measure of damage was first presented by Morrow and Halford. Hysteresis energy shows promise in bridging the gaps associated with life prediction when the combination of both creep and fatigue scenarios are present. Numerical simulations which replicate experimental test configurations with 9Cr-1Mo steel were performed from which the hysteresis energy failure density (HEFD) could be calculated for each experiment. Taking the average of the HEFD values calculated for all of the experimental data as the parameter for failure (EIntrinsic), creep-fatigue life predictions were made using a simplistic hysteresis energy based method as well as the time fraction/cycle fraction method endorsed by ASME Code and compared to experimental results. A good correlation with experimental results was obtained for life predictions using hysteresis energy density as a damage parameter. An investigation of the interaction between creep damage and fatigue damage based on the hysteresis energy method was also performed and compared with the damage interaction diagram utilized by the ASME and RCC-MR design codes. The hysteresis energy based method proved easy to implement and gave improved accuracy over the time fraction/cycle fraction method for low cycle creep-fatigue loading.

  2. A methodology for on-line fatigue life monitoring of Indian nuclear power plant components

    International Nuclear Information System (INIS)

    Fatigue is one of the most important aging effects of nuclear power plant components. Information about accumulation of fatigue helps in assessing structural degradation of the components. This assists in-service inspection and maintenance and may also support future life extension program of a plant. In the present report a methodology is being proposed for monitoring on line fatigue life of nuclear power plant components using available plant instrumentations. Major factors affecting fatigue life of a nuclear power plant components are the fluctuations of temperature, pressure and flow rate. Green's function technique is used in on line fatigue monitoring as computation time is much less than finite element method. A code has been developed which computes temperature and stress Green's functions in 2-D and axisymmetric structure by finite element method due to unit change in various fluid parameters. A post processor has also been developed which computes the temperature and stress responses using corresponding Green's functions and actual fluctuation in fluid parameters. In this post processor, the multiple site problem is solved by superimposing single site Green's function technique. It is also shown that Green's function technique is best suited for on line fatigue life monitoring of nuclear power plant components. (author). 6 refs., 43 figs

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

    International Nuclear Information System (INIS)

    The phenomenon of fatigue failure due to In-line flow-induced vibration has been investigated. In the experimental program an induced-vibration experimental set-up involving water flow was developed. This apparatus was used to produce fatigue failure resulting from In-line flow-induced vibration. The fatigue specimens were made of a medium carbon steel. A small hole was drilled into the specimen surface to localize the fatigue cracking process. A strain histogram recorder (Mini Rainflow Corder, MRC) was used to acquire the service strain histogram and also to detect any variations in natural frequency. The cumulative fatigue damage, D, as defined by the Modified Miner Rule, was determined by using the strain histogram of the early portion of the test record. The value of D was almost unity in the case of In-line vibration. In contrast, the value of D obtained in a previous investigation for the case of the Cross-flow vibration ranged approximately from 0.2 to 0.8. (author)

  4. Quality of life in multiple sclerosis – association with clinical features, fatigue and depressive syndrome

    Directory of Open Access Journals (Sweden)

    ?abuz-Roszak, Beata

    2013-06-01

    Full Text Available Introduction. The aim of the study was to assess the health related quality of life in patients suffering from multiple sclerosis (MS in association with clinical features, fatigue and depressive symptoms. Methods. The examined group consisted of 61 patients (45 women and 16 men in the mean age of 38.6±11.4. The mean duration of disease was 7.1±6.1 years. The control group consisted of 30 healthy volunteers. The following questionnaires were used: EuroQol (EQ5D with visual scale EuroQol-VAS, Modified Impact Fatigue Scale (MIFS and Beck Depression Inventory (BDI. Results. The quality of life in the examined group of MS patients was significantly lower in comparison to the control group. Results of EQ-5D and EQ-VAS were influenced by age, disease course, level of disability and carried treatment. Statistically significant association was also found between results of the questionnaires assessing quality of life and either fatigue or depressive symptoms. Conclusion. The used questionnaires confirmed that quality of life in patients with MS is significantly worse, especially in the older people with secondary progressive course of the disease, more disable and not treated. Presence of fatigue and depressive symptoms influenced the self-assessment of quality of life. Complex care of MS patient should consider diagnosis and treatment of fatigue and depression which could improve their quality of life.

  5. Evaluation of Fatigue Life of Semiconductor Power Device by Power Cycle Test and Thermal Cycle Test Using Finite Element Analysis

    OpenAIRE

    Kazunori Shinohara; Qiang Yu

    2010-01-01

    To accurately predict the fatigue life of a power device, a fatigue life evaluation method that is based on the power cycle is presented in terms of an algorithm based on a combination of electrical analysis, heat analysis, and stress analysis. In literature, the fatigue life of power devices has been evaluated on the basis of the thermal cycle. This cycle is alternately repeated within a range from a high temperature to a low temperature. In an actual operating environment, however, a power ...

  6. Fatigue life estimates for a notched member in a corrosive environment

    International Nuclear Information System (INIS)

    It is often assumed that the effects of an aggressive environment can be included in fatigue life estimation procedures by determining the material properties in the environment and at the frequency of interest. An analytical and experimental program was conducted to confirm or refute this assumption. Automotive grade aluminum alloy, 5454-H32, in 3 percent NaCl solution and laboratory environment was selected for this study. A simple model where the total fatigue life is the summation of the portion where fatigue damage is best described by the notch strain field, and the portion where nominal stress and crack length dominate damage assessment, was used to estimate fatigue lives for center notched plates. Smooth cylindrical specimens were employed to determine the material properties for initiation

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

    DEFF Research Database (Denmark)

    Hansen, Jens Zangenberg

    2013-01-01

    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 fibre radii distribution ensures optimum mechanical properties, damage tolerance, and fatigue performance. The experimental fatigue results and analyses identify and explain the onset of tension fatigue failure. It is documented that improvements of the fibre architecture and specimen design are needed in order to provide next generation of fatigue resistant composite materials for wind turbine rotor blades.

  8. Elliptical exercise improves fatigue ratings and quality of life in patients with multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Jessie M. Huisinga, PhD

    2011-08-01

    Full Text Available Fatigue, reduced quality of life (QOL, and lower physical activity levels are commonly reported in patients with multiple sclerosis (MS. This study evaluated the effects of elliptical exercise on fatigue and QOL reports in patients with MS. Patients with MS (n = 26 completed the Fatigue Severity Scale (FSS, the Modified Fatigue Impact Scale (MFIS, and the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36 before and after completing 15 elliptical exercise training sessions. Changes in fatigue and QOL were assessed based on any changes in the fatigue and SF-36 questionnaires, and correlations between changes in each of the scales were made to determine whether a relationship was present between the fatigue and QOL measures. Results showed significant improvement in FSS, MFIS, and five SF-36 subscales as a result of elliptical exercise. The change in FSS correlated with change in two of the SF-36 subscales. Elliptical exercise for patients with MS results in significant improvements in both fatigue and QOL. These findings indicate that regular elliptical exercise could be a part of inpatient and outpatient MS rehabilitation programs.

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

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Philippidis, T.P.

    2010-01-01

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

  10. Fatigue Life and Crack Growth Behavior in Annealed and Normalized 0.83% Carbon Steel

    Science.gov (United States)

    Makabe, Chobin; Yamazaki, Shinya; Miyazaki, Tatsujiro; Fujikawa, Masaki

    2015-09-01

    The variations of fatigue limit and fatigue life of a plain specimen of annealed and normalized 0.83% carbon steel were investigated. This material is used for cutting tools and the original microstructure includes a spherical microstructure. After heat treatment under some conditions, the microstructure changed to a lamellar microstructure. However, the fatigue lives of the plain specimens of this material showed almost the same tendency even after heat treatment under some conditions. In those cases, the initial crack length in the fatigue process is related to the size of the crystal structure and related to the distribution of ferrite. In the present study, the relationship between the distribution of hardness and the fatigue limit was investigated. Also, it was discussed that the fatigue limit of heat-treated 0.83% carbon steel could be evaluated by a relationship in which the parameters are the hardness and initial crack length. Finally, the tendencies of fatigue life of heat-treated 0.83% carbon steel were discussed based on the observations of crack growth behavior.

  11. Effects of variable loading on residual fatigue life of the railway wheelset.

    Czech Academy of Sciences Publication Activity Database

    Pokorný, Pavel; Náhlík, Luboš; Šev?ík, Martin; Huta?, Pavel

    Zurich : Trans Tech Publications, 2014 - (Milazzo, A.; Aliabadi, M.), s. 121-124 ISBN 978-3-03785-830-1. ISSN 1013-9826. - (Key Engineering Materials. 577-578). [FDM 2013 - International Conference on Fracture and Damage Mechanics /12./. Sardinia (IT), 17.09.2013-19.09.2013] R&D Projects: GA MŠk(CZ) EE2.3.20.0214 Grant ostatní: VUT(CZ) FSIJ- 13-2046 Institutional support: RVO:68081723 Keywords : variable amplitude loading * residual fatigue life * generalized Willenborg model * fatigue crack * railway wheelset Subject RIV: JL - Materials Fatigue, Friction Mechanics

  12. 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 configurations. Model parameters are estimated by Bayesian inference. The reference data used consists of constant-amplitude fatigue test results for a multi-directional laminate subjected to seven different load ratios. The paper describes the modelling techniques and the parameter estimation procedure, supported by an illustrative application and result assessment.

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

    OpenAIRE

    Nurdin Ali; M.S. Mustapa; M.I. Ghazali; T. Sujitno; M.Ridha

    2013-01-01

    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...

  14. Assessment of existing steel structures. A guideline for estimation of the remaining fatigue life

    OpenAIRE

    Helmerich, Rosemarie; Kühn, Bertram; Nussbaumer, Alain

    2007-01-01

    In many countries and regions, traffic infrastructure projects suffer from low funding. The budget is tight for new infrastructure building and, thus, the importance of inspection, maintenance and assessment of the existing traffic infrastructure increases. A new fatigue assessment guideline for the estimation of the remaining fatigue life of steel bridges has been written by technical committee 6 from ECCS. It will be a useful tool for the complementation of bridge management systems, used c...

  15. The impact of hysteresis shape on failure mechanisms and the endurance fatigue life of ductile materials subject to high-temperature fatigue stressing

    International Nuclear Information System (INIS)

    The paper discusses the various effects of load cycle shape and load cycle duration on the fatigue damage and thus on the endurance fatigue life of a material. The author illustrates his point by explaining experiments with two high-temperature alloys 800H and 617, which cannot be age-hardened or only slightly. (orig.)

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

    Science.gov (United States)

    Zehsaz, M.; Hassanifard, S.; Esmaeili, F.

    2010-06-01

    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.

  17. 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 .

  18. 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.

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

    International Nuclear Information System (INIS)

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

  20. Application of the strain energy for fatigue life prediction (LCF) of metals by the energy-based criterion

    International Nuclear Information System (INIS)

    Full text: In this study, the plastic strain energy under multiaxial fatigue condition has been calculated in the cyclic plasticity models by the stress-strain hysteresis loops. Then, using the results of these models, the fatigue lives in energy-based fatigue model is predicted and compared to experimental data. Moreover, a weighting factor on shear plastic work is presented to decrease the life factors in the model fatigue. (author)

  1. 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.

  2. Deformation history and load sequence effects on cumulative fatigue damage and life predictions

    Science.gov (United States)

    Colin, Julie

    Fatigue loading seldom involves constant amplitude loading. This is especially true in the cooling systems of nuclear power plants, typically made of stainless steel, where thermal fluctuations and water turbulent flow create variable amplitude loads, with presence of mean stresses and overloads. These complex loading sequences lead to the formation of networks of microcracks (crazing) that can propagate. As stainless steel is a material with strong deformation history effects and phase transformation resulting from plastic straining, such load sequence and variable amplitude loading effects are significant to its fatigue behavior and life predictions. The goal of this study was to investigate the effects of cyclic deformation on fatigue behavior of stainless steel 304L as a deformation history sensitive material and determine how to quantify and accumulate fatigue damage to enable life predictions under variable amplitude loading conditions for such materials. A comprehensive experimental program including testing under fully-reversed, as well as mean stress and/or mean strain conditions, with initial or periodic overloads, along with step testing and random loading histories was conducted on two grades of stainless steel 304L, under both strain-controlled and load-controlled conditions. To facilitate comparisons with a material without deformation history effects, similar tests were also carried out on aluminum 7075-T6. Experimental results are discussed, including peculiarities observed with stainless steel behavior, such as a phenomenon, referred to as secondary hardening characterized by a continuous increase in the stress response in a strain-controlled test and often leading to runout fatigue life. Possible mechanisms for secondary hardening observed in some tests are also discussed. The behavior of aluminum is shown not to be affected by preloading, whereas the behavior of stainless steel is greatly influenced by prior loading. Mean stress relaxation in strain control and ratcheting in load control and their influence on fatigue life are discussed. Some unusual mean strain test results are presented for stainless steel 304L, where in spite of mean stress relaxation fatigue lives were significantly longer than fully-reversed tests. Prestraining indicated no effect on either deformation or fatigue behavior of aluminum, while it induced considerable hardening in stainless steel 304L and led to different results on fatigue life, depending on the test control mode. In step tests for stainless steel 304L, strong hardening induced by the first step of a high-low sequence significantly affects the fatigue behavior, depending on the test control mode used. For periodic overload tests of stainless steel 340L, hardening due to the overloads was progressive throughout life and more significant than in high-low step tests. For aluminum, no effect on deformation behavior was observed due to periodic overloads. However, the direction of the overloads was found to affect fatigue life, as tensile overloads led to longer lives, while compressive overloads led to shorter lives. Deformation and fatigue behaviors under random loading conditions are also presented and discussed for the two materials. The applicability of a common cumulative damage rule, the linear damage rule, is assessed for the two types of material, and for various loading conditions. While the linear damage rule associated with a strain-life or stress-life curve is shown to be fairly accurate for life predictions for aluminum, it is shown to poorly represent the behavior of stainless steel, especially in prestrained and high-low step tests, in load control. In order to account for prior deformation effects and achieve accurate fatigue life predictions for stainless steel, parameters including both stress and strain terms are required. The Smith-Watson-Topper and Fatemi-Socie approaches, as such parameters, are shown to correlate most test data fairly accurately. For damage accumulation under variable amplitude loading, the linear damage rule associated with strain

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

    Directory of Open Access Journals (Sweden)

    Winnie K.W.So

    2009-06-01

    Full Text Available 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 a ff ect the fi ve 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 suff ered 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.

  4. 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

    2013-01-01

    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. PMID:24250159

  5. 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.

  6. Practical methodology to evaluate the fatigue life of seam welded joints

    Directory of Open Access Journals (Sweden)

    K.C.Goes

    2011-11-01

    Full Text Available Purpose: of this paper is to present a practical and robust methodology developed to evaluate the fatigue life of seam welded joints under combined cyclic loading.Design/methodology/approach: Fatigue analysis was conducted in virtual environment. The finite element stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life method. A tube-to-plate specimen was submitted to a combined cyclic loading (bending and torsion with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.Findings: The finite element model was validated due to laboratory results. The analytical stress result presented upper value due to the approach used that considered the fillet weld supported all work. The model presented a good representation of failure and load correlation.Research limitations/implications: The measurement or modelling of the residual stresses resulting from the welding process was not included in this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly with regard to the corrections performed in the fatigue curves obtained from the investigated samples.Practical implications: Integrating fatigue analysis and finite elements, it is possible to analyse several welded joint configurations in the design phase, providing development time and cost reduction, increasing the project reliability.Originality/value: This methodology will permit, in further studies, the modelling of both stresses, in-service and residual stresses, acting together, which seem like an advantage to engineers and researchers who work in design and evaluation of structural components against fatigue failures.

  7. Fatigue

    Science.gov (United States)

    ... See Fact Sheet 554 on diarrhea, 800 on nutrition, and 801 on vitamins . If possible, meet with a dietitian who knows ... to discuss your eating habits. For some people, vitamin B12 supplements or better nutrition can eliminate fatigue. Anemia (see Fact Sheet 552). ...

  8. Fatigue life prediction of fiber reinforced concrete under flexural load

    DEFF Research Database (Denmark)

    Zhang, Jun; Stang, Henrik; Li, Victor

    1999-01-01

    This paper presents a semi-analytical method to predict fatigue behavior in flexure of fiber reinforced concrete (FRC) based on the equilibrium of force in the critical cracked section. The model relies on the cyclic bridging law, the so-called stress-crack width relationship under cyclic tensile load as the fundamental consitutive relationship in tension.

  9. On fatigue life prediction of composites in automotive engineering; Zur Lebensdauerberechnung faserverstaerkter Kunststoffe im Automobilbau

    Energy Technology Data Exchange (ETDEWEB)

    Oppermann, Helge [BMW AG, Muenchen (Germany). Forschungszentrum

    2012-07-01

    Fibre reinforced composites are a major aspect in terms of lightweight design, sustainability and costs. Therefore they are currently in the focus of all major automobile manufacturers. Methodological approaches already exist for individual facets of fatigue life prediction of such material systems. However in most cases these are insufficiently validated or the application corridor is very narrow. Therefore such methodologies are not integrable into the development process of automotive engineering. Due to the complexity of influencing factors (interlaminar stresses, viscoelasticity, ageing etc.) and the lack of comprehensive material models, high expenditures are to be expected for the fatigue life calculation of composites. It is essential to take into account this aspect during development of methods for fatigue life calculation i.e. the experimental expenditure for the determination of material data for the calculation shall not be exceed an acceptable level. (orig.)

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

    DEFF Research Database (Denmark)

    Rafsanjani, Hesam Mirzaei; SØrensen, John Dalsgaard

    2014-01-01

    Wind turbine components experience heavily variable loads during its lifetime and fatigue failure is a main failure mode of casted components during their design working life. The fatigue life is highly dependent on the microstructure (grain size and graphite form and size), number, type, location 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 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 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 the reliability of a representative component in an offshore wind turbine.

  11. Reduction factors for creep strength and fatigue life of modified 9 Cr-1 Mo steel weldments

    International Nuclear Information System (INIS)

    The provisions of ASME B ampersand PV Code Case N-47 currently include reduction factors for creep strength and fatigue life of weldments. To provide experimental confirmation of such factors for modified 9 Cr-1 Mo steel, tests of tubular specimens were conducted at 538 degree C (1000 degree F). Three creep-rupture specimens with longitudinal welds were tested in tension; and, of three with circumferential welds, two were tested in tension and one in torsion. In each specimen with a circumferential weld, a nonuniform axial distribution of strain was easily visible. The test results were compared to an existing empirical model of creep-rupture life. For the torsion test, the comparison was based on a definition of equivalent normal stress recently adopted in Code Case N-47. Some 27 fatigue specimens, with longitudinal, circumferential, or no welds, were tested under axial or torsional strain control. In specimens with welds, fatigue cracking initiated at fusion lines. In axial tests cracks grew in the circumferential direction, and in torsional tests cracks grew along fusion lines. The test results were compared to empirical models of fatigue life based on two definition of equivalent normal strain range. The results have provided some needed confirmation of the reduction factors for creep strength and fatigue life of modified 9 Cr-1 Mo steel weldments currently under consideration by ASME Code committees. 8 refs., 5 figs

  12. Effects of High Temperature Exposures on Fatigue Life of Disk Superalloys

    Science.gov (United States)

    Gabb, Tim P.; Telesman, Jack; Kantzos, Pete T.; Smith, James W.; Browning, Paul F.

    2004-01-01

    The effects on fatigue life of high temperature exposures simulating service conditions were considered for two disk superalloys. Powder metallurgy processed, supersolvus heat treated Udimet (trademark) 720 and ME3 fatigue specimens were exposed in air at temperatures of 650 to 704 C, for times of 100 h to over 1000 h. They were then tested using conventional fatigue tests at 650 and 704 C, to determine the effects of exposure on fatigue resistance. Cyclic dwell verification tests were also performed to contrast the effects of intermixed exposures and fatigue cycles. The prior exposures reduced life by up to 70% and increased the scatter in life, compared to unexposed levels. Cyclic dwell tests reduced lives even more. Fractographic evaluations indicated the failure mode was shifted by the exposures and cyclic dwells from predominantly internal to often surface crack initiations. The increased scatter in life was related to the competition between internal crack initiations at inclusions or large grains producing longer lives, and surface crack initiations at an environmentally affected surface layer producing shorter lives.

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

    Directory of Open Access Journals (Sweden)

    Mileti? 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.

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

    DEFF Research Database (Denmark)

    Dalgas, U; Stenager, E

    2010-01-01

    Fatigue occurs in the majority of multiple sclerosis patients and therapeutic possibilities are few. Fatigue, mood and quality of life were studied in patients with multiple sclerosis following progressive resistance training leading to improvement of muscular strength and functional capacity. 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 improved during exercise by -0.6 (95% confidence interval (CI) -1.4 to 0.4) a.u. vs. 0.1 (95% CI -0.4 to 0.6) a.u. in controls (p = 0.04), mood improved by -2.4 (95% CI -4.1 to 0.7) a.u. vs. 1.1 (-1.2 to 3.4) a.u. in controls (p = 0.01) and quality of life (PCS-SF36) improved by 3.5 (95% CI 1.4-5.7) a.u. vs. -1.0 (95% CI -3.4-1.4) a.u. in controls (p = 0.01). The beneficial effect of progressive resistance training on all scores was maintained at follow-up after further 12 weeks. Fatigue, mood and quality of life all improved following progressive resistance training, the beneficial effect being maintained for at least 12 weeks after end of intervention.

  15. Proposal of life prediction method based on long-term creep-fatigue test results of 304 stainless steel

    International Nuclear Information System (INIS)

    Failure induced by creep-fatigue damage during operation, is an important failure mode to be avoided in high temperature structural components of thermal and nuclear power plants. Prediction of failure mechanism under creep-fatigue conditions in actual plants, and evaluation of the validity of creep-fatigue life prediction methods need to be done on the basis of long-term creep-fatigue test results. In this study, long-term creep-fatigue tests with up to 10 hours strain peak dwell were conducted using 304 stainless steel and the subsequent failure mechanism and creep-fatigue life prediction method were discussed. From the detailed observations of the failure specimens using a scanning electron microscope, many creep cavities and microcracks at grain boundaries were observed inside specimens. It was indicated that the main crack initiated on the specimen surface and propagated favorably on the cavitated grain boundaries under long-term creep-fatigue conditions with a tension hold period of over 30 min. A creep-fatigue life evaluation method was proposed considering the interaction between fatigue and creep damage based on the failure observation. The experimental data of long-term creep-fatigue life in this study and existing literatures were compared with the predicted life by the proposed method and it showed good agreement. (author)

  16. Cancer-related fatigue: impact on patient quality of life and management approaches

    Directory of Open Access Journals (Sweden)

    Yeo TP

    2015-07-01

    Full Text Available Theresa Pluth Yeo,1,2 Shawnna Cannaday1 1Thomas Jefferson University Hospital, Department of Surgery Thomas Jefferson University, 2Jefferson College of Nursing, Philadelphia, PA, USA Abstract: Cancer-related fatigue is a common and distressing symptom that is present in the majority of cancer patients at some point during the disease course. Cancer-related fatigue has a profound influence on patients, affecting functional performance, mood, and one's overall quality of life. The etiology of cancer-related fatigue is multifactorial, involving a complex interplay of biological and body system factors. All cancer patients should be screened for fatigue, as it often coexists with other symptoms and its side effects may be underdiagnosed. Treatment modalities for cancer-related fatigue are still evolving. Current recommendations for management from national and international cancer experts and societies focus on patient and family education regarding cancer-related fatigue, exercise and physical activity, and psychosocial interventions. Pharmacologic interventions are less effective but may be helpful in a selected subset of affected individuals. Keywords: evidence based practice, CRF, disease management, quality of life, exercise 

  17. Early Life Stress and Inflammatory Mechanisms of Fatigue in the Coronary Artery Risk Development in Young Adults (CARDIA) Study

    OpenAIRE

    Cho, Hyong Jin; Bower, Julienne E.; Kiefe, Catarina I; Seeman, Teresa E.; Irwin, Michael R.

    2012-01-01

    Fatigue is highly prevalent and causes serious disruption in quality of life. Although cross-sectional studies suggest childhood adversity is associated with adulthood fatigue, longitudinal evidence of this relationship and its specific biological mechanisms have not been established. This longitudinal study examined the association between early life stress and adulthood fatigue and tested whether this association was mediated by low-grade systemic inflammation as indexed by circulating C-re...

  18. Statistical analysis of the effect of machining parameters on fatigue life of aerospace grade aluminum alloy (Al 6082T6)

    OpenAIRE

    Jamshaid, Muhammad; Jaffery, Husain; Ali, Liaqat; Khan, Mushtaq; Alam, Khurshid; Ahmed, Riaz; Rehman, Masood

    2013-01-01

    In this research work, aerospace grade aluminium alloy (Al 6082-T6) was analysed for the effect of cutting parameters on the fatigue life of the machined samples and optimization of cutting parameters for response factor. Different combinations of machining parameters were selected according to the ISO 3685 for sample preparation. Fatigue life of the samples was the response variable under investigation. Specimens for the rotating bending fatigue test were prepared according to the BS ISO 114...

  19. Quantitative description of the fatigue life with the four-parameter Weibull distribution

    International Nuclear Information System (INIS)

    Frequently, statistical distributions of service life which are observed with ageing and fatigue processes do not obey to Weibull's distribution function. In those cases, the introduction of a third parameter into the distribution function permits to restore, quite phenomenologically, the straight line in the service life network that is advantageous for the evaluation. The article briefly discusses basic doubts about this approach. A procedure is described which avoids grave drawbacks of the three-parameter approach and is suitable for being used on a PC. The basic idea of this procedure is in unisson with recent results from research concerning the fatigue of metals. (orig.)

  20. 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

    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. The TYNERGY study aimed to further evaluate the effects of natalizumab treatment on MS-related fatigue. In this one-armed clinical trial including 195 MS patients, natalizumab was prescribed in a real-life setting, and a validated questionnaire, the Fatigue Scale for Motor and Cognitive functions (FSMC), was used both before and after 12 months of treatment to evaluate a possible change in the fatigue experienced by the patients. In the treated cohort all measured variables, that is, fatigue score, quality of life, sleepiness, depression, cognition, and disability progression were improved from baseline (all p values

  1. Fatigue life assessment of components damaged by pitting corrosion.

    Czech Academy of Sciences Publication Activity Database

    Gajdoš, Lubomír; Šperl, Martin

    Zagreb : Studio HRG Zagreb, 2004 - (Jeci?, S.; Semenski, D.), s. 282-283 ISBN 953-96243-6-3. [DANUBIA-ADRIA Symposium on Experimental Methods in Solid Mechanics /21./. Brijuni - Pula (HR), 29.09.2004-02.10.2004] R&D Projects: GA AV ?R IAA2811201 Institutional research plan: CEZ:AV0Z2071913 Keywords : pipeline * fatigue * corrosion Subject RIV: JM - Building Engineering

  2. Fatigue life improvement of an autofrettage thick-walled pressure vessel with an external groove

    Science.gov (United States)

    Koh, Seung K.; Stephens, Ralph I.

    1992-01-01

    This report presents an investigation into a fatigue life improvement of an autofrettaged thick-walled pressure vessel with an external groove subjected to pulsating internal pressure, along with mean strain and mean stress effects on strain-controlled low cycle fatigue behavior. Linear elastic stress analysis of an autofrettaged thick-walled pressure vessel with an external groove is done using a finite element method. Autofrettage loading is performed using a thermal loading analogy. Change of external groove geometry is made using a quasi-optimization technique and finite element method to achieve longer fatigue life by relieving the stress concentration at the groove root. Surface treatment using shot peening is employed to produce compressive residual stresses at the vulnerable surface of the groove root to counteract the high tensile stresses. An evaluation of the fatigue life of an autofrettaged thick-walled pressure vessel with an external groove is done through a series of simulation fatigue tests using C-shaped specimens taken from the thick-walled pressure vessel.

  3. Perkiraan Fatigue Life pada Bracket Kapal Tanker Berdasarkan Common Structural Rules

    Directory of Open Access Journals (Sweden)

    Dita septiana

    2012-09-01

    Full Text Available Umur kelelahan (fatigue life dari struktur kapal dianalisis dengan menggunakan standar pada Common Structural Rules for Double Hull Oil Tanker. Kapal tanker single hull direncanakan akan dikonversi menjadi FPSO sehingga perlu diketahui sisa fatigue life konstruksinya. Dalam penelitian ini, fokus analisis dilakukan pada konstruksi bracket karena bracket sebagai salah satu penopang yang esensial pada kapal ini. Oleh karena itu, perlu diketahui letak bracket dengan tegangan paling besar dan besar fatigue lifenya. Kapal tersebut dimodelkan menggunakan softwareMSC Pastran sebagai pre-processor dan MSC Nastran sebagai processor. Bagian kapal yang dimodelkan adalah 3 ruang muat pada midship. Ruang muat pada bagian tengah dari ketiga ruang muat tersebut adalah ruang muat yang paling besar. Fatigue life yang dianalisa merupakan pengaruh dari beban lingkungan (beban gelombang air laut dan beban internal (beban tangki. Kondisi pembebanan yang dilakukan ada 6 macam load cases sesuai dengan ketentuan CSR. Tegangan pada bracket yang didapat dari pemodelan diambil tegangan yang paling besar untuk dianalisa fatigue lifenya. Hasil perhitungan menunjukkan bahwa bracket dengan tegangan paling besar terjadi pada web frame 7 pada ruang muat tengah dan pada kondisi pembebanan A2 didapat umur kapal yang paling rendah yaitu sebesar 26 tahun.

  4. 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.

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

    International Nuclear Information System (INIS)

    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

  6. Enhancing fatigue life of cylinder-crown integrated structure by optimizing dimension

    Science.gov (United States)

    Zhang, Weiwei; Wang, Xiaosong; Wang, Zhongren; Yuan, Shijian

    2015-03-01

    Cylinder-crown integrated hydraulic press (CCIHP) is a new press structure. The hemispherical hydraulic cylinder also functions as a main portion of crown, which has lower weight and higher section modulus compared with the conventional hydraulic cylinder and press crown. As a result, the material strength capacity is better utilized. During the engineering design of cylinder-crown integrated structure, in order to increase the fatigue life, structural optimization on the basis of the adaptive macro genetic algorithms (AMGA) is first conducted to both reduce weight and decrease peak stress. It is shown that the magnitude of the maximum principal stress is decreased by 28.6%, and simultaneously the total weight is reduced by 4.4%. Subsequently, strain-controlled fatigue test is carried out, and the stress-strain hysteresis loops and cyclic hardening curve are obtained. Based on linear fit, the fatigue properties are calculated and used for the fatigue life prediction. It is shown that the predicted fatigue life is significantly increased from 157000 to 1070000 cycles after structural optimization. Finally, according to the optimization design, a 6300 kN CCIHP has been manufactured, and priority application has been also suggested.

  7. Low Cycle Fatigue Life Prediction of Notched Specimens Under Proportional and Non-proportional Multiaxial Loadings

    Science.gov (United States)

    Itoh, Takamoto; Ozaki, Tomohiko

    This study discusses multiaxial low cycle fatigue life of notched specimens under proportional and non-proportional loadings at room temperature. Strain controlled multiaxial low cycle fatigue tests were carried out using smooth and circumferentially notched round-bar specimens of two types of steels, SUS316 and SGV410. Two kinds of shallow notched specimens were employed of which elastic stress concentration factors, Kt, are 1.5 and 2.5. The strain paths include proportional and non-proportional loadings. The former employed a push-pull straining or a reversed torsion straining. The latter was achieved by strain path where axial and shear strains had 90 degree phase difference but their amplitudes were the same based on von Mises' criterion. The notch dependency of multiaxial low cycle fatigue life and the life predictability were discussed. The lives for both steels depend on both Kt and strain path. The data correlations also showed the different trend between the steels. The strain parameter for the life prediction was discussed with the non-proportional strain parameter proposed by one of the authors with introducing Kt. The proposed parameter gave a satisfactory correlation with multiaxial low cycle fatigue life of notched specimens for two steels under proportional and non-proportional loadings.

  8. Deformation behaviour and fatigue life of the alloy PE 16 under creep stress

    International Nuclear Information System (INIS)

    The service life of components subject to combined creep and fatigue stress in general is shorter than that of components affected only by one or the other. In the presence of both types of stress, their interactive effects lead to creep fatigue, which has to be taken into account in assessing the service life of turbine blades or turbine disks in a power plant or aircraft. The investigations reported in the paper have shown that the mechanisms of interaction between dislocations and precipitations have an effect on the stress curve in case of low-cycle fatigue stress. Introducing a holding time in case of LCF stress induces an additional solidification and shortens the service life of the material. This additional solidification is caused by a rearrangement of the distribution of dislocations. The reduction of service life observed at the smallest strain amplitude is mainly due to grain boundary damage. At larger strain amplitudes, fatigue damage seems to also contribute to the shortening of the material's service life. (orig./RHM)

  9. Implementation of on-line fatigue monitoring methodology in Heavy Water Plant, Kota for remnant life assessment programme

    International Nuclear Information System (INIS)

    Fatigue, creep and creep-fatigue interaction phenomena are important in the design and operation of components used in nuclear industry, thermal power plant and chemical process plant. Extension of life of the existing plants is a major concern to plant management. Recently, a methodology has been developed to predict the aging degradation of various components subjected to severe fluctuating loading conditions. This methodology converts the plant transients to responses on the structure using Green's function technique. The stresses on the structure due to combined thermal and mechanical loading is transformed into stress frequency spectrum using Rainflow cycle counting algorithm. Using material fatigue data, fatigue usage factor is computed. There is a proposal to implement this on-line fatigue life monitoring system to estimate the fatigue degradation of components at Heavy Water Plant, Kota. This present paper describes the implementation of this methodology for remnant life assessment of components. (author). 3 refs., 3 figs

  10. An analytical method on evaluation of creep-fatigue life with long-time strain hold

    International Nuclear Information System (INIS)

    Evaluation of creep-fatigue life with long-time strain hold is a very important problem for structural design of FBR. But, these creep-fatigue tests are very difficult because of test techniques and costs. Therefore, the life prediction for long-time must be based on analytical approach by which the extrapolation to the range of longer hold time effect can be evaluated and justified. In this paper, an analytical method is proposed, which is based on generalized relaxation analysis, creep damage analysis, total damage evaluation per cycle and the diagram of creep-fatigue interaction effect. By this method, it is expected that the prediction is simplified and the evaluation is conservative. (author)

  11. 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 < 0.001). Consequently, the technique may not be appropriate for repairing cobalt chromium clasps on removable partial dentures. Scanning electron microscopy indicated the presence of cracks, pores and constriction of the outer surface in the welded specimens despite 70% penetration of the weld. PMID:21528682

  12. Fatigue, fracture, and life prediction criteria for composite materials in magnets

    International Nuclear Information System (INIS)

    An explosively-bonded copper/Inconel 718/copper laminate conductor was proposed to withstand the severe face compression stresses in the central core of the Alcator C-MOD tokamak toroidal field (TF) magnet. Due to the severe duty of the TF magnet, it is critical that an accurate estimate of useful life be determined. As part of the effort to formulate an appropriate life prediction, fatigue crack growth experiments were performed on the laminate as well as its components. Metallographic evaluation of the laminate interface revealed many shear bands in the Inconel 718. Shear bands and shear band cracks were produced in the Inconel 718 as a result of the explosion bonding process. These shear bands were shown to have a detrimental effect on the crack growth behavior of the laminate, by significantly reducing the load carrying capability of the reinforcement layer and providing for easy crack propagation paths. Fatigue crack growth rate was found not only to be dependent on temperature but also on orientation. Fatigue cracks grew faster in directions which contained shear bands in the plane of the propagating crack. Fractography showed crack advancement by fatigue cracking in the Inconel 718 and ductile tearing of the copper at the interface. However, further away from the interfaces, the copper exhibited fatigue striations indicating that cracks were now propagating by fatigue. Laminate life prediction results showed a strong dependence on shear band orientation, and exhibited little variation between room temperature and 77 degree K. Predicted life of this laminate was lower when the crack propagation was along a shear band than when crack propagation was across the shear bands. Shear bands appear to have a dominating effect on crack growth behavior

  13. A numerical investigation of creep-fatigue life prediction utilizing hysteresis energy as a damage parameter

    Energy Technology Data Exchange (ETDEWEB)

    Oldham, Joseph, E-mail: josephwoldham@gmail.com [Bradley University, 106 Jobst Hall, 1501 W. Bradley Ave., Peoria, IL 61615 (United States); Abou-Hanna, Jeries, E-mail: jannah@bradley.edu [Bradley University, 106 Jobst Hall, 1501 W. Bradley Ave., Peoria, IL 61615 (United States)

    2011-04-15

    This paper explores the hypothesis that there exists an intrinsic material property, hysteresis damage energy at failure, which could be used as a creep-fatigue life prediction parameter. The connection between hysteresis energy and fatigue damage was introduced in the 1920's by Inglis, but the use of hysteresis energy as a measure of damage was first presented by Morrow and Halford. Hysteresis energy shows promise in bridging the gaps associated with life prediction when the combination of both creep and fatigue scenarios are present. Numerical simulations which replicate experimental test configurations with 9Cr-1Mo steel were performed from which the hysteresis energy failure density (HEFD) could be calculated for each experiment. Taking the average of the HEFD values calculated for all of the experimental data as the parameter for failure (E{sub Intrinsic}), creep-fatigue life predictions were made using a simplistic hysteresis energy based method as well as the time fraction/cycle fraction method endorsed by ASME Code and compared to experimental results. A good correlation with experimental results was obtained for life predictions using hysteresis energy density as a damage parameter. An investigation of the interaction between creep damage and fatigue damage based on the hysteresis energy method was also performed and compared with the damage interaction diagram utilized by the ASME and RCC-MR design codes. The hysteresis energy based method proved easy to implement and gave improved accuracy over the time fraction/cycle fraction method for low cycle creep-fatigue loading.

  14. Thermal fatigue. Materials modelling

    International Nuclear Information System (INIS)

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

  15. 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 ?tting. 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 in?uence 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.

  16. The effect of holes quality on fatigue life of open hole

    International Nuclear Information System (INIS)

    In this paper, a series of study were conducted on the effect of hole quality on the fatigue life of open holes in 2A12-T4 aircraft quality aluminum alloy. Four metrics that can define holes quality are analyzed. They are roughness, verticality, cylindricity and roundness. Firstly, open holes with different roughness were fatigue tested under constant amplitude remote tensile load and post-failure investigations were performed by scanning electron microscope. Further, the effects of another three metrics on the stress distributions around the holes have been studied by the finite element method (FEM). The fatigue lives are determined based on the stress distributions by the method of nominal stress approach. The results show that the fatigue lives of open holes are dependent on the holes quality. For these four metrics, the fatigue lives decrease with the increasing of the values of the tolerance of these metrics. At last, empirical equations that relate these four metrics to fatigue lives were established by linear regression method

  17. Multiaxial creep-fatigue life analysis using strainrange partitioning

    Energy Technology Data Exchange (ETDEWEB)

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

    1976-01-01

    Strain-Range Partitioning is a recently developed method for treating creep-fatigue interaction at elevated temperature. Most of the work to date has been on uniaxially loaded specimens, whereas practical applications often involve load multiaxiality. This paper shows how the method can be extended to treat multiaxiality through a set of rules for combining the strain components in the three principal directions. Closed hysteresis loops, as well as plastic and creep strain ratcheting, are included. An application to hold-time tests in torsion is used to illustrate the approach.

  18. Study on the tensile test behavior and fatigue life rate of the bolted joint in elastic region tightening and bolted joint in plastic region tightening of the SCM435H; SCM435H dansei iki teiketsu boruto to sosei iki teiketsu boruto no hippari shiken kyodo to hiro jumyo hi ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Kyochul; Son, Seungyo

    1996-07-25

    There are an excess and a short case of bolt axial power in elastic region tightening due to differences of tightening nut area and surface state, bolt outer diameter, nut in-face state, and so on. In order to overcome such problem and obtain a given axial power, a plastic region bolt is used. The plastic region bolt is used for tightening in plastic region when beyond elastic region, and showed 15 - 20% larger axial power than when using elastic region bolt. As the plastic region tightening can make the most of material ability sufficiently and can obtain high tightening power in comparison with the elastic region tightening, application to strength efficiently of the bolt in plastic region tightening is effective. A lot of studies on fatigue life in low cycle fatigue are conducted and fatigue data, analytical method and mathematical model are also proposed. In this study, S-N curves of the elastic region tightening bolt and the plastic region tightening bolt using static fatigue life equation and fatigue life equation for high cycle fatigue were described and effectiveness of this equation was investigated after comparing fatigue life ratio with experimental value. 8 refs., 12 figs., 5 tabs.

  19. A method of calculating the safe fatigue life of compact, highly-stressed components

    Science.gov (United States)

    Cardick, Arthur W.; Pike, Vera J.

    1994-01-01

    This paper describes a method which has been developed for estimating the safe fatigue life of compact, highly-stressed and inaccessible components for aeroplanes and helicopters of the Royal Air Force. It is explained why the Design Requirements for British Military Aircraft do not favor the use of a damage-tolerance approach in these circumstances.

  20. Cyclic plastic response and fatigue life of duplex and superduplex stainless steel.

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav

    43 2005, ?. 4 (2005), s. 280-289. ISSN 0023-432X R&D Projects: GA ?R(CZ) GA106/02/0584 Institutional research plan: CEZ:AV0Z20410507 Keywords : duplex steel * fatigue life * cyclic plasticity Subject RIV: JG - Metallurgy Impact factor: 0.973, year: 2005

  1. Fatigue life of carburized steel specimens under push-pull loading.

    Czech Academy of Sciences Publication Activity Database

    Major, Št?pán; Hubálovský, Š.; Šedivý, J.; Bryscejn, Jan

    2014-01-01

    Ro?. 1, ?. 1 (2014), s. 99-104. ISSN 2313-0555 Institutional support: RVO:68378297 Keywords : carburizing * fatigue life * sub-surface crack * highstrength steel * push-pull loading Subject RIV: JM - Building Engineering http://www.naun.org/cms.action?id=7631

  2. Improvement of fatigue life of steel orthotropic desks with carbon fibre reinforcement composites.

    Czech Academy of Sciences Publication Activity Database

    Urushadze, Shota; Frýba, Ladislav; Pirner, Miroš

    Brno : Czech society for mechanics, 2011 - (Návrat, T.; Fuis, V.; Houfek, L.; Vlk, M.), s. 403-410 ISBN 978-80-214-4275-7. [EAN 2011. Znojmo (CZ), 06.06.2011-09.06.2011] Institutional research plan: CEZ:AV0Z20710524 Keywords : orthotropic deck * fatigue * prolonged life Subject RIV: JM - Building Engineering

  3. The Relationship between Qi Deficiency, Cancer-related Fatigue and Quality of Life in Cancer Patients

    OpenAIRE

    Hsu, Chung-Hua; Lee, Chia-Jung; Chien, Tsai-Ju; Lin, Che-Pin; Chen, Chien-Hung; Yuen, Mei-Jen; Lai, Yuen-Liang

    2012-01-01

    Background: Qi (? qì) refers to the vital energy of the body in Traditional Chinese medicines (TCM). Qi deficiency (?? qì x?) is the most common symptom in cancer patients according to the concept of TCM. We hypothesized that cancer patients with Qi deficiency suffer from poor quality of life (QOL) and fatigue.

  4. 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 ?=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. ? is a principal stress ratio and is defined as ?=?II/?I, where ?I and ?II are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at ?=0 is a uniaxial loading test and that at ?=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 ? 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.

  5. Effect of low temperature on fatigue life and cyclic stress-strain response of UFG copper.

    Czech Academy of Sciences Publication Activity Database

    Lukáš, Petr; Kunz, Ludvík; Svoboda, Milan

    2007-01-01

    Ro?. 38, ?. 9 (2007), s. 1910-1915. ISSN 1073-5623 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ultrafine-grained copper * Low temperature * Fatigue life Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.278, year: 2007

  6. 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,…

  7. Effects of High-Temperature Exposures on the Fatigue Life of Disk Superalloys Examined

    Science.gov (United States)

    Gabb, Timothy P.; Telesman, Jack; Kantzos, Pete T.; Smith, James W.

    2005-01-01

    Tests used to characterize the low-cycle-fatigue resistance of disk superalloys are usually performed at cyclic frequencies of 0.33 Hz or faster. However, service conditions for disks in some aerospace and land-based gas turbine engines can produce major cycle periods extending from minutes to hours and days. Over a service life, this can produce total service times near the maximum temperature that exceed 100 hr for aerospace applications and 100,000 hr for land-based applications. Such time-dependent effects of realistic mission cycles on fatigue resistance can be significant in superalloy disks, and need to be considered for accurate disk life prediction. The purpose of this study at the NASA Glenn Research Center was to examine the effects of extended exposures and extended cycle periods on the fatigue resistance of two disk superalloys. Current alloy Udimet 720 (Special Metals Corporation, Huntington, WV) disk material was provided by Solar Turbines/Caterpillar Co., and advanced alloy ME3 was provided by the NASA Ultra-Efficient Engine Technologies (UEET) Project, in powder-metallurgy-processed, supersolvus heat-treated form. Fatigue specimens were fully machined and exposed in air at temperatures of 650 to 704 C for extended times. Then, they were tested using conventional fatigue tests with a total strain range of 0.70 percent and a minimum-to-maximum strain ratio of zero to determine the effects of prior exposure on fatigue resistance. Subsequent tests with extended dwells at minimum strain in each fatigue cycle were performed to determine cyclic exposure effects.

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

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Berggreen, Christian

    2015-01-01

    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 shearproperties, for both static strength and fatigue failure, is higher than the variance normallyobserved in the properties for fiber-reinforced polymer composite laminates. This could be attributed to the fact that end-grain balsa wood is the product of a naturally occurringgrowth process, which cannot 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-reinforced laminates.

  9. Fatigue life assessment of cast nodular iron disc brakes for railway vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Sonsino, C.M.; Hanselka, H. [Fraunhofer-Institut fuer Betriebsfestigkeit (LBF), Darmstadt (Germany); Technical Univ. Darmstadt (Germany)

    2008-07-01

    Disc brakes, not only for railway applications but generally in all vehicle applications count as safety components. Therefore, their reliability during service is essential. A disc brake is submitted to different loadings: braking, including emergency braking; horizontal and vertical wheel forces and forces on driving over switches; mass forces acting in the attachment of the disc brakes to the wheels due to relative displacements and centrifugal forces during rolling of the wheel at higher speeds. In the present work, only the influence of thermal strains/stresses caused by braking on the fatigue life will be discussed. For the disc brake of the cast nodular iron EN-GJS-400-15 considered in this study, the other loadings were proved to be not critical. Because of the continuous distortions of a disc brake after each brake operation due to heating, calculated local strains had to be verified experimentally by strain and temperature measurements. The experiments were carried out in a special test rig of the manufacturer where a spectrum of braking operations from the speeds 200, 160 and 90 km/h were investigated. With the preliminary design, the required fatigue life could not be achieved but the fatigue critical areas were recognized. After the redesign of the discs, fatigue failures were prevented. This study is a re-evaluation of a former analysis on the fatigue behaviour of railway disc brakes. (orig.)

  10. Study on creep-fatigue life improvement and life evaluation of 316FR stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Kazuo; Yamaguchi, Koji; Yamazaki, Masayoshi; Hongo, Hiromichi [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan); Nakazawa, Takanori [Gunma Univ., Kiryu (Japan). Faculty of Technology; Kaguchi, Hitoshi; Kurome, Kazuya [Mitsubishi Heavy Industries Ltd., Kobe Shipyard and Machinery Works, Hyogo (Japan); Date, Shingo [Mitsubishi Heavy Industries Ltd., Takasago Works, Hyogo (Japan); Tendo, Masayuki [Nippon Steel Corp., Chiba (Japan)

    2000-01-01

    Creep rupture and creep-fatigue interaction tests were conducted at 550deg C for modified 316FR austenitic stainless steels in order to improve the creep-fatigue lives. Reducing the carbon contents from 0.01% to 0.002 or 0.003% and finning the grain size were effective for increasing the creep-fatigue lives and the creep rupture ductilities. From these results, an estimation method of the creep-fatigue lives by using the creep rupture ductilities in the modified 316FR steels was proposed. (author)

  11. Study on creep-fatigue life improvement and life evaluation of 316FR stainless steels

    International Nuclear Information System (INIS)

    Creep rupture and creep-fatigue interaction tests were conducted at 550deg C for modified 316FR austenitic stainless steels in order to improve the creep-fatigue lives. Reducing the carbon contents from 0.01% to 0.002 or 0.003% and finning the grain size were effective for increasing the creep-fatigue lives and the creep rupture ductilities. From these results, an estimation method of the creep-fatigue lives by using the creep rupture ductilities in the modified 316FR steels was proposed. (author)

  12. Complex System Models used in the Automobile Clutch Release Bearing Fatigue Life Studies

    Directory of Open Access Journals (Sweden)

    Guoliang Chen

    2013-01-01

    Full Text Available According to the system engineering point of view, any kind of technical product, regardless of the size and complexity of its structure are how a system should achieve the intended technical process and in this process relies on the input and output into contact with the outside world. Any mechanical system\\should be achieved economically task book the required technical capabilities and maintain the safety of people and the environment as part of its general goal to pursue. Regardless of economic feasibility, technical capabilities alone to achieve the target will lose mechanical practical value. In the automotive power transmission process, the role of the clutch release bearing by means of the axial displacement of the bearing to connect or disconnect the power transmission between the transmission and the engine, thus completing the smooth start the car, suspended and transform operations such gear. Automobile clutch release bearings are vital parts clutch parts of the merits of its performance, the car's handling performance vehicle has great influence. Release bearing fatigue life analysis is based on the bearing rings or rolling fatigue spalling began to appear, a phenomenon with exposure to cyclic stress related. Rolling elastic contact between components belong, the contact stress analysis methods used in the past experience or simple analytical method. In this study, bearing materials, lubricants, sealing structure, fatigue life test and simulate working conditions failure data processing methods have raised new research content, by establishing a new release bearing fatigue life model for complex systems, the introduction of the smelting process, the surface defect, roughness, residual stress, EHL oil film, environmental cleanliness, temperature, variable load characteristics And other factors that affect the fatigue life. The results showed that: release bearing new life prediction model is closer to the actual condition clutch for further study a new generation of high- speed heavy automobile clutch release bearings provide a theoretical support.

  13. Investigations on the evaluation of the residual fatigue life-time in austenitic stainless steels

    International Nuclear Information System (INIS)

    In view of plant life extension of nuclear power plants, many efforts are taken to assess the structural integrity of components affected by service, such as the components of the primary circuit, but also the auxiliary and safety systems. Frequently damage in components during operation is caused by cyclic loading, due to mechanical or thermal fatigue. Fatigue damage often involves loads, which were not taken into account in the design e.g. temperature cycling arising from unforeseen stratification flow conditions. Therefore lifetime calculations should be supported by non-destructive measurements on the components during the operation life to guarantee their integrity, by monitoring of the changes in the microstructure, and the related mechanical and physical material properties, which are due to fatigue damage. Those changes of the microstructure appear in a period before crack initiation, which covers a considerable part of the fatigue life. To gain information on the changes in the microstructure during fatigue loading, samples of the stainless steel materials 1.4541 and 1.4550, which are the representative materials for the majority of auxiliary and safety systems, were strained under static and dynamic conditions at different temperature between RT and 300 deg. C in order to correlate the fatigue loading conditions and residual lifetime with the microstructural phenomena. In particular the formation of deformation induced martensite was analysed, which is accompanied by pronounced changes in the magnetic properties. Non-destructive testing methods (NDT), based on eddy current techniques, are of use to detect these changes in the magnetic properties. The results lead to an assessment scheme for the evaluation of the residual lifetime of components

  14. Robust design and thermal fatigue life prediction of anisotropic conductive film flip chip package

    International Nuclear Information System (INIS)

    The use of flip-chip technology has many advantages over other approaches for high-density electronic packaging. ACF(Anisotropic Conductive Film) is one of the major flip-chip technologies, which has short chip-to-chip interconnection length, high productivity, and miniaturization of package. In this study, thermal fatigue life of ACF bonding flip-chip package has been predicted. Elastic and thermal properties of ACF were measured by using DMA and TMA. Temperature dependent nonlinear bi-thermal analysis was conducted and the result was compared with Moire interferometer experiment. Calculated displacement field was well matched with experimental result. Thermal fatigue analysis was also conducted. The maximum shear strain occurs at the outmost located bump. Shear stress-strain curve was obtained to calculate fatigue life. Fatigue model for electronic adhesives was used to predict thermal fatigue life of ACF bonding flip-chip packaging. DOE (Design Of Experiment) technique was used to find important design factors. The results show that PCB CTE (Coefficient of Thermal Expansion) and elastic modulus of ACF material are important material parameters. And as important design parameters, chip width, bump pitch and bump width were chose. 2nd DOE was conducted to obtain RSM equation for the choose 3 design parameter. The coefficient of determination (R2) for the calculated RSM equation is 0.99934. Optimum design is conducted using the RSM equation. MMFD (Modified Method for Feasible Direction) algorithm is used to optimum design. The optimum value for chip width, bump pitch and bump width were 7.87mm, 430?m, and 78?m, respectively. Approximately, 1400 cycles have been expected under optimum conditions. Reliability analysis was conducted to find out guideline for control range of design parameter. Sigma value was calculated with changing standard deviation of design variable. To acquire 6 sigma level thermal fatigue reliability, the Std. Deviation of design parameter should be controlled within 3% of average value

  15. 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.

  16. Deterioration of fatigue life of 316L stainless steel due to TEXTOR exposure

    International Nuclear Information System (INIS)

    Fatigue tests in vacuum and air were carried out on solution-annealed 316L stainless steel specimens (NET reference material) in push-pull type, load-controlled experiments at 20, 150 and 425deg C. Reference specimens were compared to specimens which had been exposed to the plasma of the TEXTOR tokamak prior to testing. It is found that the surface modifications caused by the TEXTOR exposure lead to fatigue life deterioration by factors between 2 (at 20deg C) and 6 (at 425deg C). Possible reasons for this degradation are discussed. (orig.)

  17. Evaluation of creep–fatigue life based on fracture energy for modified 9Cr–1Mo steel

    International Nuclear Information System (INIS)

    Preventing creep–fatigue damage is a major consideration in nuclear power plants, which operate at high temperatures. Energy absorbed during creep–fatigue loading is focused on for predicting long-term creep–fatigue life for modified 9Cr–1Mo steel. Fracture energy decreases with time owing to creep deformation localization. Change in fracture energy is described by a power law function of hysteresis energy density rate and time to fracture. Hysteresis energy density is approximately expressed as a function of the total strain range. Then, hysteresis energy density rate is determined by dividing hysteresis energy density by time per cycle. The function gives a good fit of data for creep–fatigue and low strain-rate fatigue. The creep–fatigue life can be predicted using the power law function. According to microstructure observation, change in fracture energy is due to annihilation of block and packet boundary.

  18. Split mandrel versus split sleeve coldworking: Dual methods for extending the fatigue life of metal structures

    Science.gov (United States)

    Rodman, Geoffrey A.; Creager, Matthew

    1994-01-01

    It is common practice to use split sleeve coldworking of fastener holes as a means of extending the fatigue life of metal structures. In search of lower manufacturing costs, the aerospace industry is examining the split mandrel (sleeveless) coldworking process as an alternative method of coldworking fastener holes in metal structures. The split mandrel process (SpM) significantly extends the fatigue life of metal structures through the introduction of a residual compressive stress in a manner that is very similar to the split sleeve system (SpSl). Since the split mandrel process is significantly less expensive than the split sleeve process and more adaptable to robotic automation, it will have a notable influence upon other new manufacture of metal structures which require coldworking a significant number of holes, provided the aerospace community recognizes that the resulting residual stress distributions and fatigue life improvement are the same for both processes. Considerable testing has validated the correctness of that conclusion. The findings presented in this paper represent the results of an extensive research and development program, comprising data collected from over 400 specimens fabricated from 2024-T3 and 7075-T651 aluminum alloys in varied configurations, which quantify the benefits (fatigue enhancement and cost savings) of automating a sleeveless coldworking system.

  19. Fatigue life prediction of a cable harness in an industrial robot using dynamic simulation

    International Nuclear Information System (INIS)

    The cable which transfers the signal and power in an industrial robot has a problem of fatigue fracture like steel components. Since the cable is very flexible compared to other components of the system, it is difficult to estimate its motion numerically. Some studies have been done on a large deformation problem, especially in a cable, and a few attempts have been made to apply the absolute nodal coordinate formulation (ANCF), which can simulate a large deformation. Only researches about the fatigue life of structural cables or comparative studies of FEM and ANCF simulations can be found. This paper presents a method to simulate the behavior of the cable harness using the ANCF and to predict the fatigue life while computing the strain time history of the point of interest. Rigid body dynamics is applied for the robot system, while ANCF is used for the cable harness. The simulation is performed by using the dynamic analysis process. The material property of the cable is obtained by a test. A simplified model is prepared. With these data, the behavior of the cable is simulated and the fatigue life is predicted

  20. Fatigue life prediction of a cable harness in an industrial robot using dynamic simulation

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ji Won; Park, Tae Won [Ajou University, Suwon (Korea, Republic of); Yim, Hong Jae [Kookmin University, Seoul (Korea, Republic of)

    2008-03-15

    The cable which transfers the signal and power in an industrial robot has a problem of fatigue fracture like steel components. Since the cable is very flexible compared to other components of the system, it is difficult to estimate its motion numerically. Some studies have been done on a large deformation problem, especially in a cable, and a few attempts have been made to apply the absolute nodal coordinate formulation (ANCF), which can simulate a large deformation. Only researches about the fatigue life of structural cables or comparative studies of FEM and ANCF simulations can be found. This paper presents a method to simulate the behavior of the cable harness using the ANCF and to predict the fatigue life while computing the strain time history of the point of interest. Rigid body dynamics is applied for the robot system, while ANCF is used for the cable harness. The simulation is performed by using the dynamic analysis process. The material property of the cable is obtained by a test. A simplified model is prepared. With these data, the behavior of the cable is simulated and the fatigue life is predicted

  1. Split mandrel versus split sleeve coldworking: Dual methods for extending the fatigue life of metal structures

    Science.gov (United States)

    Rodman, Geoffrey A.; Creager, Matthew

    1994-09-01

    It is common practice to use split sleeve coldworking of fastener holes as a means of extending the fatigue life of metal structures. In search of lower manufacturing costs, the aerospace industry is examining the split mandrel (sleeveless) coldworking process as an alternative method of coldworking fastener holes in metal structures. The split mandrel process (SpM) significantly extends the fatigue life of metal structures through the introduction of a residual compressive stress in a manner that is very similar to the split sleeve system (SpSl). Since the split mandrel process is significantly less expensive than the split sleeve process and more adaptable to robotic automation, it will have a notable influence upon other new manufacture of metal structures which require coldworking a significant number of holes, provided the aerospace community recognizes that the resulting residual stress distributions and fatigue life improvement are the same for both processes. Considerable testing has validated the correctness of that conclusion. The findings presented in this paper represent the results of an extensive research and development program, comprising data collected from over 400 specimens fabricated from 2024-T3 and 7075-T651 aluminum alloys in varied configurations, which quantify the benefits (fatigue enhancement and cost savings) of automating a sleeveless coldworking system.

  2. 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. PMID:26479993

  3. Influences of cyclic deformation on creep property and creep-fatigue life prediction considering them

    International Nuclear Information System (INIS)

    Evaluation of creep-fatigue is essential in design and life management of high-temperature components in power generation plants. Cyclic deformation may alter creep property of the materials and its consideration may improve predictability of creep-fatigue failure life. To understand them, creep tests were conducted for the materials subjected to cyclic loading and their creep rupture and deformation behaviors were compared with those of as-received materials. Both 316FR and modified 9Cr-1Mo steel were tested. (1) Creep rupture time and elongation generally tend to decrease with cyclic loading in both materials, and especially elongation of 316FR drastically decreases by being cyclically deformed. (2) Amount of primary creep deformation decreases by cyclic loading and the ways to improve its predictability were developed. (3) Use of creep rupture ductility after cyclic deformation, instead of that of as-received material, brought about clear improvement of life prediction in a modified ductility exhaustion approach. (author)

  4. Seismic fatigue life evaluation of mechanical structures using energy balance equation

    International Nuclear Information System (INIS)

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

  5. Estimation of fatigue life for aluminium welded joints with the application of artificial neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Karakas, Oe.

    2011-10-15

    The aim of this investigation was determining the fatigue behaviour of welded aluminium joints and so the appertaining SN-lines by application of Artificial Neural Network (ANN) architectures. For this, fatigue data obtained with aluminium welded joints subjected to constant amplitude loading were used. The main benefit of ANN is the good description of the effects of different factors on fatigue life. The results determined by the ANN method for four aluminium alloys are displayed in scatter bands of SN-lines. It is observed that the trained results are in good agreement with the tested data and enable the estimation of SN-lines. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. 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

  7. Inclusions Size-based Fatigue Life Prediction Model of NiTi Alloy for Biomedical Applications

    Science.gov (United States)

    Urbano, Marco Fabrizio; Cadelli, Andrea; Sczerzenie, Frank; Luccarelli, Pietro; Beretta, Stefano; Coda, Alberto

    2015-06-01

    Current standards consider the size and distribution of inclusions in semi-finished material, but do not place requirements on final biomedical devices made of NiTi shape memory alloys. In this paper, we analyze this by comparing the fatigue performances of NiTi superelastic wires obtained by different processes through a simple bilinear model of fatigue response in terms of strain life. The fracture surfaces of failed wires are analyzed through SEM microscopy and data regarding the presence of particles, and their morphology is recorded and analyzed using Type-I extreme value distribution. The results show a strong correlation between the fatigue limit of wires (in terms of strain) and the predicted extreme values of inclusions at fracture origin. Then, following the concept of treating the inclusions as `small cracks,' a simple relationship between fatigue limit strain range and inclusion size is proposed based on ?Kth data from the literature. The model is compared with the fatigue data obtained from the tested wires.

  8. Influence of Graphite Nodules Geometrical Features on Fatigue Life of High-Strength Nodular Cast Iron

    Science.gov (United States)

    Costa, Nuno; Machado, Nuno; Silva, Filipe Samuel

    2008-06-01

    This paper is concerned with the evaluation of different fatigue strength theories to predict the fatigue life of high-strength nodular cast iron. There have been some studies on the effects of the shape and size of graphite nodules, and of microstructure, on the fatigue strength of nodular cast iron. However, there is not a consensus on how to correlate the fatigue limit with material intrinsic properties or with external features such as considering graphite nodules as defects. Some researchers found good correlations between fatigue strength, ?w0, and the geometrical aspects of the graphite nodules, considering it as internal material defects. It will be shown in this study that geometrical features such as shape, size, and relative position seem to be adequate to be included in those predictions. In this article, a high-strength cast iron, with rupture strength of about 1300 MPa and Young’s modulus of about 160 GPa, has been used. Correlations both with intrinsic properties as well as with other geometrical effects have been made. A comparison of different theories has also been carried out.

  9. Assessment of Surface Treatment on Fatigue Life of Cylinder Block for Linear Engine using Frequency Response Approach

    Directory of Open Access Journals (Sweden)

    M. M. Rahman

    2009-01-01

    Full Text Available Objectives: This study was focused on the finite element techniques to investigate the effect of surface treatment on the fatigue life of the vibrating cylinder block for new two-stroke free piston engine using random loading conditions. Motivation: An understanding of the effects related to the random loading is necessary to improve the ability of designers to accurately predict the fatigue behavior of the components in service. An internal combustion engine cylinder block is a high volume production component subjected to random loading. Problem statement: Proper optimization of this component that is critical to the engine fuel efficiency and more robustly pursued by the automotive industry in recent years. A detailed understanding of the applied loads and resulting stresses under in-service conditions is demanded. Approach: The finite element modeling and analysis were performed utilizing the computer aided design and finite element analysis codes respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis code. Aluminum alloys were considered as typical materials in this study. Results: The frequency response approach was applied to predict the fatigue life of cylinder block using different load histories. Based on the finite element results, it was observed that the fatigue life was significantly influenced for the nitriding treatment. The obtained results were indicated that the nitrided treatment produces longest life for all loading conditions. Conclusion: The nitriding process is one of the promising surface treatments to increase the fatigue life for aluminum alloys linear engine cylinder block.

  10. Effect of mean stress on short crack growth and fatigue life in austenitic-ferritic duplex steel.

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Obrtlík, Karel; Petrenec, Martin

    Ottawa : NRCan - CANMET, 2009, s. 1-10. ISBN N. [International Conference on Fracture /12./. Ottawa (CA), 12.07.2009-17.07.2009] R&D Projects: GA ?R GA101/07/1500 Institutional research plan: CEZ:AV0Z20410507 Keywords : short crack * mean stress * fatigue life Subject RIV: JL - Materials Fatigue, Friction Mechanics

  11. Method and data analysis example of fatigue tests

    International Nuclear Information System (INIS)

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

  12. Load Identification of Offshore Platform for Fatigue Life Estimation

    DEFF Research Database (Denmark)

    Perisic, Nevena; Kirkegaard, Poul Henning

    2014-01-01

    The lifetime of an offshore platform is typically governed by accumulated fatigue damage. Thus, the load time history is an essential parameter for prediction of the lifetime of the structure and its components. Consequently, monitoring of structural loads is of special importance in relation to re-assessment of offshore platforms. Structural monitoring systems (SMSs) on offshore structures typically consist of a set of sensors such as strain gauges, accelerometers, wave radars and GPSs, however direct measuring of the actual loading is usually not feasible. One approach is to measure the loads indirectly by monitoring of the available dynamic responses of the structure. This work investigates the possibility for using an economically beneficial, model-based load estimation algorithm for indirect measuring of the loading forces acting on the offshore structure. The algorithm is based on the reduced order model of the structure and the discrete Kalman filter which recursively estimates unknown states of the system in real time. As a test-case, the algorithm is designed to estimate the equivalent total loading forces of the structure. The loads are estimated from noised displacement measurements of a single location on the topside of the offshore structure. The method is validated using simulated data for two wave loading cases: regular and irregular wave loadings.

  13. Adaptive active vibration control to improve the fatigue life of a carbon-epoxy smart structure

    Science.gov (United States)

    Ripamonti, Francesco; Cazzulani, Gabriele; Cinquemani, Simone; Resta, Ferruccio; Torti, Alessandro

    2015-04-01

    Active vibration controls are helpful in improving fatigue life of structures through limitation of absolute displacements. However, control algorithms are usually designed without explicitly taking into account the fatigue phenomenon. In this paper, an adaptive vibration controller is proposed to increase the fatigue life of a smart structure made of composite material and actuated with piezoelectric patches. The main innovation with respect to the most common solutions is that the control laws are directly linked to a damage driving force, which is correlated to a fatigue damage model for the specific material. The control logic is different depending on the damage state of the structure. If no significant damage affects the structure, the controller decreases the crack nucleation probability by limiting the driving forces in the overall structure. On the contrary, if initiated cracks are present, their further propagation is prevented by controlling the damage driving forces in the already damaged areas. The structural diagnostics is performed through a vibration-based health monitoring technique, while periodical adaptation of the controller is adopted to consider damage-induced changes on the structure state-space model and to give emphasis to the most excited modes. The control algorithm has been numerically validated on the finite element model of a cantilever plate.

  14. Optimal Shot Peening Treatments to Maximize the Fatigue Life of Quenched and Tempered Steels

    Science.gov (United States)

    Llaneza, V.; Belzunce, F. J.

    2015-07-01

    The search for the optimal Almen intensity to use in shot peening treatments to maximize the fatigue life of industrial steel components involves many different variables and physical phenomena. In this paper, the optimal peening intensity of different steel grades obtained from an AISI 4340 steel through heat treatments has been determined. Six different steel grades were subjected to shot peening treatments, which were performed under full coverage, but employing diverse Almen intensities, shot sizes and air pressures. The role of the mechanical properties of the treated steel and the applied Almen intensity on the shot peening effects were studied to understand the results obtained by means of rotating bending fatigue tests. Each steel has a specific Almen intensity value able to optimize its fatigue life, thereby allowing an optimal balance between the positive and negative effects induced by shot peening. This value, or range of values, is dependent on the mechanical properties of the treated steel, increasing with increasing steel properties up to a certain point and then decreasing for stronger steels. In these cases, over peening treatments produce sufficiently large surface defects to induce relaxation of the surface residual stress and facilitate the initiation of surface fatigue cracks.

  15. On the fatigue life of M50 NiL rolling bearings

    Science.gov (United States)

    Harris, T. A.; Skiller, John; Spitzer, Ronald F.

    1992-10-01

    The fatigue life of rolling bearings made of M50 NiL (a nickel-low carbon variant of M50 tool steel) was investigated using data from a battery of 15 R2 endurance test rigs specially modified to accommodate the aircraft application test conditions. Results indicate that bearings manufactured from case-hardened M50 NiL steel can provide significantly greater rolling contact fatigue life than bearings made from through-hardened M50 steel. In addition, it was found that M50 NiL bearings endurance-tested under conditions of heavy tensile hoop stresses showed no tendency toward raceway spalling or cracking through, unlike M50 bearings, which exhibited both tendencies.

  16. Random thermal stress oscillations and fatigue life estimation for steam generator tubes

    International Nuclear Information System (INIS)

    A one-dimensional computation model was used to determine the temperature and stress fields under conditions corresponding to those found in once-through steam generator tubes. The random oscillatory nature of the water/steam convective boundary conditions in the transition boiling zone was simulated by postulating random variations in heat transfer coefficients for flow temperatures. Statistical parameters describing the tube temperatures and thermal stress oscillatory history are determined allowing appropriate fatigue life estimations to be made. The results indicate that the tube wall temperature oscillation parameter provides a strong influence on thermal stress and the predicted fatigue life. In contrast, Biot number variations provide only a relatively small effect. An improved method of determining the allowable thermal stress limitations due to certain wall temperature oscillations is proposed

  17. Prediction of fatigue crack initiation life of circumferentially notched steel bars under cyclic torsion

    International Nuclear Information System (INIS)

    Torsional fatigue tests were conducted for smooth solid bars, smooth hollow cylinders, and circumferentially notched bars of carbon steel (JIS SGV410) and austenitic stainless steel (JIS SUS316L) under completely reversed cyclic torsion. The cyclic stress strain relation was first determined for two steels. The yield stress and the flow stress were higher for SUS316L than for SGV410. The torsional fatigue life of smooth solid bars was longer than that of hollow cylinders when compared at the same nominal stress amplitude. The true strain amplitude on the surface of solid bars under torsion was calculated by the elastic-plastic analysis by the finite element method (FEM). The relation between the strain amplitude on the specimen surface calculated by FEM and the fatigue life was nearly equal to the relation obtained for hollow cylinders. The crack initiation life for notched specimens was determined by the direct electrical potential method. When compared at the same nominal stress amplitude, the crack initiation life got shorter as the notches became sharper. The distribution of the amplitude of equivalent strain near the root of circumferential notches under torsion was calculated by the elastic-plastic analysis of FEM. The crack initiation life got slightly longer for sharper notches when the life was correlated to the strain amplitude at the notch root. The relation between the crack initiation life and the strain amplitude at 0.1 mm distant from the notch root was nearly unique independent of the notch shapes and was equivalent to the relation obtained for smooth specimens. (author)

  18. Technique for Exterior Expansion Measurement During Autofrettaging for Constant Fatigue Life

    Directory of Open Access Journals (Sweden)

    Rajeev M. Bhatnagar

    2014-07-01

    Full Text Available In an autofrettage process a given thick cylinder is subjected to such a pressure which gives a specified depth of elasto-plastic boundary. The outside diameter expansion during autofrettage process is a function of depth of autofrettage. To obtain a specified depth of elastic-plastic interface, the applied autofrettage pressure increases in direct proportion to the proof stress of the pressure vessel material. Although this increases the load bearing capacity of the barrel, resulting in enhanced factor of safety, this increases the maintenance cost of a hydraulic autofrettage plant. To assure quality, product safety and manufacturing economy, an optimal autofrettage pressure is defined. The paper proposes that the minimum autoftrettage pressure is the pressure at which the pressure exterior expansion curve intersects line of constant factor of safety. At higher values of 0.2 per cent proof stress of tube material autofrettaging based on line of constant factor of safety will result in a reduction in fatigue life. The point of intersection of exterior expansion curve with line of constant fatigue life has been defined as the optimal pressure because the specifications of factor of safety and fatigue life are simultaneously achieved. The proposed process design based on above concept has been validated using finite element simulation and empirical post-autofrettage measurements. The verification of the shakedown condition for reverse yielding due to the Bauschinger effect (Huang’s model and fatigue life has also been satisfied. Defence Science Journal, Vol. 64, No. 4, July 2014, pp. 385-392, DOI:http://dx.doi.org/10.14429/dsj.64.3886  

  19. 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.

  20. Fatigue life evaluation of A356 aluminum alloy used for engine cylinder head

    OpenAIRE

    Angeloni, Mauricio

    2011-01-01

    The studied material is an A356 Al alloy, used to produce engine cylinder heads for the automotive industry by die casting process. The material displays a quite coarse dendritic microstructure in a eutectic matrix, with a mean grains size of 25 microns, intemetallic precipitates and porosities. The tensile properties are strongly affected by testing temperature, with a quite sensitive drop of the Young's modulus, the Yield stress as the temperature was raised. The isothermal fatigue life dro...

  1. Effect of carburizing on fatigue life of highstrength steel specimen under push-pull loading.

    Czech Academy of Sciences Publication Activity Database

    Major, Št?pán; Jakl, V.; Hubálovský, Š.

    Santorini : WSEAS Press, 2014 - (Pshikhopov, V.; Foti, D.), s. 143-146 ISBN 978-1-61804-241-5. [International conference on materials: MATERIALS 2014. Santorini (GR), 17.07. 2014-21.07.2014] Institutional support: RVO:68378297 Keywords : carburizing * fatigue life * sub-surface crack * highstrength steel * push-pull * bending-torsion Subject RIV: JM - Building Engineering http://www.europment.org/library/2014/santorini/bypaper/MECHANICS/MECHANICS-00.pdf

  2. Short-Time Procedure for the Determination of Woehler and Fatigue Life Curves Using Mechanical, Thermal and Electrical Data

    Science.gov (United States)

    Walther, Frank; Eifler, Dietmar

    Mechanical stress-strain hysteresis, temperature and electrical resistance measurements were performed to characterize the fatigue behavior and to calculate the lifetime of metals under constant amplitude loading and random loading. Constant amplitude sequences were periodically inserted in random load tests to measure the plastic strain amplitude as well as the deformation-induced changes in specimen temperature and electrical resistance. These data are plotted versus the number of cycles for the fatigue assessment under random loading, similar as commonly practiced under constant amplitude loading. On the basis of Morrow and Basquin equations in generalized formulations, to be applicable for mechanical, thermal and electrical measurement techniques, a physically based fatigue life calculation method “PHYBAL” was developed. This new short-time procedure requires data of only three fatigue tests for a rapid and nevertheless precise determination of Woehler curves for constant amplitude loading or fatigue life curves for random loading.

  3. Fatigue Behavior of Inconel 718 TIG Welds

    Science.gov (United States)

    Alexopoulos, Nikolaos D.; Argyriou, Nikolaos; Stergiou, Vasillis; Kourkoulis, Stavros K.

    2014-08-01

    Mechanical behavior of reference and TIG-welded Inconel 718 specimens was examined in the present work. Tensile, constant amplitude fatigue, and fracture toughness tests were performed in ambient temperature for both, reference and welded specimens. Microstructure revealed the presence of coarse and fine-grained heat-affected zones. It has been shown that without any post-weld heat treatment, welded specimens maintained their tensile strength properties while their ductility decreased by more than 40%. It was found that the welded specimens had lower fatigue life and this decrease was a function of the applied fatigue maximum stress. A 30% fatigue life decrease was noticed in the high cycle fatigue regime for the welded specimens while this decrease exceeded 50% in the low cycle fatigue regime. Cyclic stress-strain curves showed that Inconel 718 experiences a short period of hardening followed by softening for all fatigue lives. Cyclic fatigue response of welded specimens' exhibited cyclically stable behavior. Finally, a marginal decrease was noticed in the Mode I fracture toughness of the welded specimens.

  4. The impact of regular physical activity on fatigue, depression and quality of life in persons with multiple sclerosis

    OpenAIRE

    Minahan Clare L; Stroud Nicole M

    2009-01-01

    Abstract Background The purpose of this study was to compare fatigue, depression and quality of life scores in persons with multiple sclerosis who do (Exercisers) and do not (Non-exercisers) regularly participate in physical activity. Methods A cross-sectional questionnaire study of 121 patients with MS (age 25–65 yr) living in Queensland, Australia was conducted. Physical activity level, depression, fatigue and quality of life were assessed using the International Physical Activity Questionn...

  5. 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 quality of mental score and covariates ( P < 0.001. Discussion and Conclusion: In conclusion, it may be said that MS patients had poor and moderate quality of mental and physical health. The quality of life was impaired as seen by PSQI, EDSS, and FSS. It is our suggestion that these patients require the attention of health care professionals, to be observed for the need of possible psychological support.

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

    Science.gov (United States)

    Ghaem, Haleh; Haghighi, Afshin Borhani

    2008-01-01

    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 ? 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 quality of mental score and covariates (P<0.001). Discussion and Conclusion: In conclusion, it may be said that MS patients had poor and moderate quality of mental and physical health. The quality of life was impaired as seen by PSQI, EDSS, and FSS. It is our suggestion that these patients require the attention of health care professionals, to be observed for the need of possible psychological support. PMID:19893680

  7. Shot-peening process for fatigue-life delay effect of laser welding

    International Nuclear Information System (INIS)

    At present, welding technology is not only emphasized in the development of manufacturing technology but also application is expanding. In these systems, application of SUS as high-temperature material which is used for special purposes is attempted, and improvement of manufacturing technologies bear watching together with increase of using rate. Specifically, Wings with surface of three-dimensional shape usually applied to Fastener with purpose of light weight. However, due to development of welding technology, methods of existing assembly tend to be replaced by welding, recently. Specifically, if laser welding techniques is applied, it minimizes heat-affected zone than other welding techniques. However, in the case of these special welding, residual stress is raised, and it fatally affects fatigue life. In order to remove residual stress and delay effect of fatigue life, shot-peening is executed; it executes shot-peening and verifies delayed effects of fatigue life. The intention of this study is to obtain the optimal conditions of shot-peening.

  8. Prediction of creep-fatigue life by use of creep rupture ductility

    International Nuclear Information System (INIS)

    It was clarified that tension strain hold reduced creep-fatigue life of many engineering materials in different degrees depending on material, temperature and test duration. However the reduction in the life due to holding for various durations could be correlated to the fraction of intergranular facets on fracture surfaces which was considered to be an index of the damage introduced during strain hold. This fraction of intergranular facets by creep-fatigue failure exhibited a direct relation to the creep rupture ductility of the material tested at the same temperature and for the same creep-fatigue life-time. From these results an empirical equation has been derived as follow; (? sub(epsilonsub(i)))/Dsub(c).(N sub(h sup(?))) = C, where ? sub(epsilonsub(i)) is inelastic strain range, Dsub(c) is the creep rupture ductility for the same duration as creep-fatigue life time, Nsub(h) is the creep-fatigue life under tension strain hold conditions, and ? and C are constants depending on the material and testing temperature. From the equation the life prediction is possible for a given inelastic strain range ? sub(epsilonsub(i)) if the constants ? and C, and Dsub(c) are known. The value of ? was found to be 0.62 and 0.74 for various austenitic stainless steels and NCF800 at 600 0C and 700 0C, respectively, and 0.69 for 1 1/4Cr-1/2Mo steel at 600 0C. The value of C was found to be 0.50 and 0.59 for various austenitic stainless steels and NCF800 at 600 0C and 700 0C, respectively, and 0.49 for 1 1/4Cr-1/2Mo steel at 600 0C. The creep rupture ductility Dsub(c) is available in the NRIM Creep Data Sheets up to 105 h for multi-heats of many kinds of heat resistant alloys. (author)

  9. 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.

  10. The impact of regular physical activity on fatigue, depression and quality of life in persons with multiple sclerosis

    Science.gov (United States)

    Stroud, Nicole M; Minahan, Clare L

    2009-01-01

    Background The purpose of this study was to compare fatigue, depression and quality of life scores in persons with multiple sclerosis who do (Exercisers) and do not (Non-exercisers) regularly participate in physical activity. Methods A cross-sectional questionnaire study of 121 patients with MS (age 25–65 yr) living in Queensland, Australia was conducted. Physical activity level, depression, fatigue and quality of life were assessed using the International Physical Activity Questionnaire, Health Status Questionnaire Short Form 36, Becks Depression Inventory and Modified Fatigue Impact Scale. Results 52 participants performed at least two 30-min exercise sessions·wk-1 (Exercisers) and 69 did not participate in regular physical activity (Non-exercisers). Exercisers reported favourable fatigue, depression and quality of life scores when compared to Non-exercisers. Significant weak correlations were found between both leisure-time and overall reported physical activity levels and some subscales of the quality of life and fatigue questionnaires. Additionally, some quality of life subscale scores indicated that regular physical activity had a greater benefit in subjects with moderate MS. Conclusion Favourable fatigue, depression and quality of life scores were reported by persons with MS who regularly participated in physical activity, when compared to persons with MS who were classified as Non-exercisers. PMID:19619337

  11. The impact of regular physical activity on fatigue, depression and quality of life in persons with multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Minahan Clare L

    2009-07-01

    Full Text Available Abstract Background The purpose of this study was to compare fatigue, depression and quality of life scores in persons with multiple sclerosis who do (Exercisers and do not (Non-exercisers regularly participate in physical activity. Methods A cross-sectional questionnaire study of 121 patients with MS (age 25–65 yr living in Queensland, Australia was conducted. Physical activity level, depression, fatigue and quality of life were assessed using the International Physical Activity Questionnaire, Health Status Questionnaire Short Form 36, Becks Depression Inventory and Modified Fatigue Impact Scale. Results 52 participants performed at least two 30-min exercise sessions·wk-1 (Exercisers and 69 did not participate in regular physical activity (Non-exercisers. Exercisers reported favourable fatigue, depression and quality of life scores when compared to Non-exercisers. Significant weak correlations were found between both leisure-time and overall reported physical activity levels and some subscales of the quality of life and fatigue questionnaires. Additionally, some quality of life subscale scores indicated that regular physical activity had a greater benefit in subjects with moderate MS. Conclusion Favourable fatigue, depression and quality of life scores were reported by persons with MS who regularly participated in physical activity, when compared to persons with MS who were classified as Non-exercisers.

  12. A work-life perspective on sleep and fatigue-looking beyond shift workers.

    Science.gov (United States)

    Skinner, Natalie; Dorrian, Jill

    2015-10-01

    This study examines sleep and fatigue through a work-life lens. Whilst most often thought of as an issue for shift workers, this study observed that self-reported insufficient sleep and fatigue were prevalent for workers on standard daytime schedules. Using a representative sample of 573 daytime workers (51.3% men; 70.7% aged 25-54?yr) from one Australian state, it was observed that 26.4% of daytime workers never or rarely get the seven hours of sleep a night that is recommended for good health. Those with parenting responsibilites (29.4%) or working long (45+) hours (37.4%) were most likely to report insufficient sleep. Whereas mothers in full-time work were most likely to report frequent fatigue (42.5%). This study highlights the common experience of insufficient sleep and fatigue in a daytime workforce, with significant implications for health and safety at work and outside of work. Stronger and more effective legislation addressing safe and 'decent' working time is clearly needed, along with greater awareness and acceptance within workplace cultures of the need to support reasonable workloads and working hours. PMID:26027709

  13. Loading Analysis of Composite Wind Turbine Blade for Fatigue Life Prediction of Adhesively Bonded Root Joint

    Science.gov (United States)

    Salimi-Majd, Davood; Azimzadeh, Vahid; Mohammadi, Bijan

    2015-06-01

    Nowadays wind energy is widely used as a non-polluting cost-effective renewable energy resource. During the lifetime of a composite wind turbine which is about 20 years, the rotor blades are subjected to different cyclic loads such as aerodynamics, centrifugal and gravitational forces. These loading conditions, cause to fatigue failure of the blade at the adhesively bonded root joint, where the highest bending moments will occur and consequently, is the most critical zone of the blade. So it is important to estimate the fatigue life of the root joint. The cohesive zone model is one of the best methods for prediction of initiation and propagation of debonding at the root joint. The advantage of this method is the possibility of modeling the debonding without any requirement to the remeshing. However in order to use this approach, it is necessary to analyze the cyclic loading condition at the root joint. For this purpose after implementing a cohesive interface element in the Ansys finite element software, one blade of a horizontal axis wind turbine with 46 m rotor diameter was modelled in full scale. Then after applying loads on the blade under different condition of the blade in a full rotation, the critical condition of the blade is obtained based on the delamination index and also the load ratio on the root joint in fatigue cycles is calculated. These data are the inputs for fatigue damage growth analysis of the root joint by using CZM approach that will be investigated in future work.

  14. Ti–6Al–4V welded joints via electron beam welding: Microstructure, fatigue properties, and fracture behavior

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoguang [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Co-Innovation Center for Advanced Aero-Engine, Beijing 100191 (China); Li, Shaolin [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Qi, Hongyu, E-mail: qhy@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Co-Innovation Center for Advanced Aero-Engine, Beijing 100191 (China)

    2014-03-01

    The effect of microstructural characteristics on the fatigue properties of electron beam-welded joints of forged Ti–6Al–4V and its fracture behavior were investigated. Tensile tests and fatigue tests were conducted at room temperature in air atmosphere. The test data were analyzed in relation to microstructure, high-cycle fatigue properties, low-cycle fatigue properties, and fatigue crack propagation properties. The high-cycle fatigue test results indicated that the fatigue strength of the joint welded via electron beam welding was higher than that of the base metal because the former had a high yield strength and all high-cycle fatigue specimens were fractured in the base metal. Although the joint specimens had a lower low-cycle fatigue life than the base metal, they mainly ruptured at the fusion zone of the joint specimen and their crack initiation mechanism is load-dependent. The fatigue crack propagation test results show that the joint had a slower crack propagation rate than the base metal, which can be attributed to the larger grain in the fusion zone.

  15. Ti–6Al–4V welded joints via electron beam welding: Microstructure, fatigue properties, and fracture behavior

    International Nuclear Information System (INIS)

    The effect of microstructural characteristics on the fatigue properties of electron beam-welded joints of forged Ti–6Al–4V and its fracture behavior were investigated. Tensile tests and fatigue tests were conducted at room temperature in air atmosphere. The test data were analyzed in relation to microstructure, high-cycle fatigue properties, low-cycle fatigue properties, and fatigue crack propagation properties. The high-cycle fatigue test results indicated that the fatigue strength of the joint welded via electron beam welding was higher than that of the base metal because the former had a high yield strength and all high-cycle fatigue specimens were fractured in the base metal. Although the joint specimens had a lower low-cycle fatigue life than the base metal, they mainly ruptured at the fusion zone of the joint specimen and their crack initiation mechanism is load-dependent. The fatigue crack propagation test results show that the joint had a slower crack propagation rate than the base metal, which can be attributed to the larger grain in the fusion zone

  16. Effects of High-Temperature Exposures on the Fatigue Life of Superalloy Udimet(Registered Trademark) 720

    Science.gov (United States)

    Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Sweeney, Joseph W.; Browning, Paul F.

    2002-01-01

    The purpose of this study was to examine the effects of extended exposures on the near-surface fatigue resistance of a disk superalloy. Powder metallurgy processed, supersolvus heat-treated Udimet 720 (U720) fatigue specimens were exposed in air at temperatures from 650 to 705 C for 100 hr to over 1000 hr. They were then tested using conventional fatigue tests at 650 C to determine the effects of exposure on fatigue resistance. The exposures reduced life by up to 70% and increased the scatter in life, compared to unexposed levels. Fractographic evaluations indicated the failure mode was shifted by the exposures from internal to surface crack initiations. The increased scatter in life was related to the competition between internal crack initiations at inclusions or large grains producing longer lives, and surface crack initiations at an environmentally affected surface layer producing shorter lives.

  17. One-Year Longitudinal Study of Fatigue, Cognitive Functions, and Quality of Life After Adjuvant Radiotherapy for Breast Cancer

    International Nuclear Information System (INIS)

    Purpose: Most patients with localized breast cancer (LBC) who take adjuvant chemotherapy (CT) complain of fatigue and a decrease in quality of life during or after radiotherapy (RT). The aim of this longitudinal study was to compare the impact of RT alone with that occurring after previous CT on quality of life. Methods and Materials: Fatigue (the main endpoint) and cognitive impairment were assessed in 161 CT-RT and 141 RT patients during RT and 1 year later. Fatigue was assessed with Functional Assessment of Cancer Therapy-General questionnaires, including breast and fatigue modules. Results: At baseline, 60% of the CT-RT patients expressed fatigue vs. 33% of the RT patients (p <0.001). Corresponding values at the end of RT were statistically similar (61% and 53%), and fatigue was still reported at 1 year by more than 40% of patients in both groups. Risk factors for long-term fatigue included depression (odds ratio [OR] = 6), which was less frequent in the RT group at baseline (16% vs. 28 %, respectively, p = 0.01) but reached a similar value at the end of RT (25% in both groups). Initial mild cognitive impairments were reported by RT (34 %) patients and CT-RT (24 %) patients and were persistent at 1 year for half of them. No biological disorders were associated with fatigue or cognitive impairment. Conclusions: Fatigue was the main symptom in LBC patients treated with RT, whether they received CT previously or not. The correlation of persistent fatigue with initial depressive status favors administering medical and psychological programs for LBC patients treated with CT and/or RT, to identify and manage this main quality-of-life-related symptom.

  18. Service Life Of Main Piping Component Due To Low Thermal Stresses.Fatigue

    International Nuclear Information System (INIS)

    The paper deals with estimating the service life of the power station Main piping component and describing the repair process for extending of its service life. After a long period of service, several circular fatigue cracks have been discovered at the bottom of the Main piping component chamber. Finite element analyses of transient thermal stresses, caused by power station startup, are carried out in the paper. The calculation results show good agreement between the theoretical locations of the maximum stresses and the actual locations of the cracks. There is a good agreement between theoretical evaluation and actual service life, as well. The possibility of machining out the cracks in order to prevent their growing is examined here. The machining enables us to extend the power station component's life service

  19. Fatigue life of creep resisting steels under conditions of cyclic mechanical and thermal interactions

    Directory of Open Access Journals (Sweden)

    A. Marek

    2009-11-01

    Full Text Available urpose: This study sets out to determine the characteristics of high-temperature creep resisting steels under conditions of thermo-mechanical fatigue with the use of a method proposed in the Code-of-Practice under the EU TMF-Standard project.Design/methodology/approach: The thermo-mechanical fatigue (TMF tests were carried out in the conditions where the value of complete strain and the temperature were under control. Two methods of investigating samples in TMF tests were applied: OP (out-of-phase and IP (in-phase.Findings: Based on the tests, the characteristics of TMF life was determined and it was found that X20CrMoV12.1 steel shows lower life in comparison with new steels: X10CrMoVNb9-1 (T/P91 and X10CrWMoVNb9-2 (T/P92. The results of the OP tests made for X10CrMoVNb9-1 (T/P91 steel are an exception here. Tests of thermo-mechanical fatigue have shown that in a majority of cases in fatigue tests, the X20CrM0V12.1 steel has lower TMF life when compared to X10CrMoVNb9-1 (T/P91 and X10CrWMoVNb9-2 (T/P92 steels, despite its better strength properties, as a measure of which, the range of stress was adopted.Research limitations/implications: At the present stage of the research, two types of tests (IP and PO were performed. Due to a limited number of experiments connected with the application of selected types of tests and their number, the conclusions resulting from the research may, at the present stage, serve as guidelines for its continuation only.Practical implications: The test results may also be used to compare the properties of creep resisting steels used in the power engineering industry and represent a contribution to widening the knowledge of the behaviour of materials under thermo-mechanical fatigue conditions.Originality/value: This study is one of the first attempts to determine the TMF life characteristics of the steels used in the Polish power engineering industry.

  20. Room temperature creep-fatigue response of selected copper alloys for high heat flux applications

    DEFF Research Database (Denmark)

    Li, M.; Singh, B.N.

    2004-01-01

    Two copper alloys, dispersion-strengthened CuAl25 and precipitation-hardened CuCrZr, were examined under fatigue and fatigue with hold time loading conditions. Tests were carried out at room temperature and hold times were imposed at maximum tensile and maximum compressive strains. It was found that hold times could be damaging even at room temperature, well below temperatures typically associated with creep. Hold times resulted in shorter fatigue lives in the high cycle fatigue, long life regime (i.e., at low strain amplitudes) than those of materials tested under the same conditions without hold times. The influence of hold times on fatigue life in the low cycle fatigue, short life regime (i.e., at high strain amplitudes) was minimal. When hold time effects were observed, fatigue lives were reduced with hold times as short as two seconds. Appreciable stress relaxation was observed during the hold period at all applied strain levels in both tension and compression. In all cases, stresses relaxed quickly within the first few seconds of the hold period and much more gradually thereafter. The CuAl25 alloy showed a larger effect of hold time on reduction of high cycle fatigue life than did the CuCrZr alloy.

  1. A combined approach to buffet response analyses and fatigue life prediction

    Science.gov (United States)

    Jacobs, J. H.; Perez, R.

    1994-03-01

    Experimental measurement and neural network based prediction of wind tunnel model empennage random pressures are discussed. Artificially generated neural network power spectral densities of surface pressures are used to augment existing data and then load an elastic finite element model to obtain response spectra. Details on the use of actual response spectra from flight test data are also discussed. A random spectra fatigue method is described which effectively combines buffet and maneuver loads into a time series based on aircraft usage data. A peak-valley damage analysis procedure is employed to compute the aggregate fatigue life of the structure based on five combined load time series information. Applications of the method as a continual learning tool for buffet response spectra is elaborated.

  2. Effect of Buckling Modes on the Fatigue Life and Damage Tolerance of Stiffened Structures

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara; Rose, Cheryl A.

    2015-01-01

    The postbuckling response and the collapse of composite specimens with a co-cured hat stringer are investigated experimentally and numerically. These specimens are designed to evaluate the postbuckling response and the effect of an embedded defect on the collapse load and the mode of failure. Tests performed using controlled conditions and detailed instrumentation demonstrate that the damage tolerance, fatigue life, and collapse loads are closely tied with the mode of the postbuckling deformation, which can be different between two nominally identical specimens. Modes that tend to open skin/stringer defects are the most damaging to the structure. However, skin/stringer bond defects can also propagate under shearing modes. In the proposed paper, the effects of initial shape imperfections on the postbuckling modes and the interaction between different postbuckling deformations and the propagation of skin/stringer bond defects under quasi-static or fatigue loads will be examined.

  3. Fatigue life of silumin irradiated by high intensity pulsed electron beam

    Science.gov (United States)

    Konovalov, S. V.; Alsaraeva, K. V.; Gromov, V. E.; Ivanov, Yu F.

    2015-09-01

    The electron-beam processing of silumin, leading to the evolution of structure-phase state of its surface is carried out. It has been shown that this alloy is a multiphase material and contains, except an aluminum-based phase, the particles of intermetallic compounds of Al-Si- Fe-Mn. It is shown that electron beam treatment of the eutectic silumin surface increases the fatigue service life more than in 3.5 times. The analysis of structure-phase states modification of silumin subjected to electron beam treatment with the following fatigue loading up to the failure is carried out by methods of optical and scanning electron diffraction microscopy. Analysis of the surface layer structure revealed the sources of nucleation of submicrocracks. It is revealed that the large silicon plates located on the surface and in the subsurface layer are the most dangerous stress concentrators.

  4. High-temperature fatigue life of type 316 stainless steel containing irradiation induced helium

    International Nuclear Information System (INIS)

    Specimens of 20%-cold-worked AISI type 316 stainless steel were irradiated in the High Flux Isotope Reactor (HFIR) at 5500C to a maximum damage level of 15 dpa and a transmutation produced helium level of 820 at. ppM. Fully reversed strain controlled fatigue tests were performed in a vacuum at 5500C. No significant effect of the irradiation on low-cycle fatigue life was observed; however, the strain range of the 107 cycle endurance limit decreased from 0.35 to 0.30%. The relation between total strain range and number of cycles to failure was found to be ?epsilon/sub T/ = 0.02N/sub f/-012 + N/sub f/-06 for N/sub f/ 7 cycles

  5. 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.

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

    International Nuclear Information System (INIS)

    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)

  7. Evaluation of corrosion fatigue life of steam turbine (Monte Carlo simulation of pitting initiation and crack propagation)

    International Nuclear Information System (INIS)

    For simulating corrosion fatigue fracture of blades and rotors in wet steam environment at the low-pressure stages of steam turbines, Monte Carlo method is developed. The corrosion fatigue, which seriously affects the life of low-temperature sections of steam turbine units, is an extremely complex phenomenon, and involves many factors that can not be predicted by deterministic analysis. Paying attention to the fact that the process of corrosion fatigue is a stochastic (random) process, this study enabled such complex phenomenon to be analyzed by visual simulation

  8. Assessment of Surface Treatment on Fatigue Life of Cylinder Block for Linear Engine using Frequency Response Approach

    OpenAIRE

    M.M.Rahman; A.K.Ariffin; S. Abdullah; Noor, M. M.; Rosli A. Bakar; Maleque, M.A.

    2009-01-01

    Objectives: This study was focused on the finite element techniques to investigate the effect of surface treatment on the fatigue life of the vibrating cylinder block for new two-stroke free piston engine using random loading conditions. Motivation: An understanding of the effects related to the random loading is necessary to improve the ability of designers to accurately predict the fatigue behavior of the components in service. An internal combustion engine cylinder block is a high volume p...

  9. Influence of Hold Times on Fatigue Life and Fracture Behavior of Cast Superalloy INCONEL 713LC at 700°C.

    Czech Academy of Sciences Publication Activity Database

    Obrtlík, Karel; Man, Ji?í; Petrenec, Martin; Polák, Jaroslav; Podrábský, T.

    Ottawa : NRCan - CANMET, 2009, s. 1-9. ISBN N. [International Conference on Fracture /12./. Ottawa (CA), 12.07.2009-17.07.2009] R&D Projects: GA AV ?R 1QS200410502; GA ?R GA106/08/1631; GA ?R GA106/07/1507 Institutional research plan: CEZ:AV0Z20410507 Keywords : Fatigue life * Hold times * High temperature * Inconel 713LC Subject RIV: JL - Materials Fatigue, Friction Mechanics http://www.icf12.org/

  10. Fatigue analysis and life prediction of composite highway bridge decks under traffic loading

    Scientific Electronic Library Online (English)

    Fernando N., Leitão; José Guilherme S. da, Silva; Sebastião A. L. de, Andrade.

    2013-05-01

    Full Text Available Steel and composite (steel-concrete) highway bridges are currently subjected to dynamic actions of variable magnitude due to convoy of vehicles crossing on the deck pavement. These dynamic actions can generate the nucleation of fractures or even their propagation on the bridge deck structure. Proper [...] consideration of all of the aspects mentioned pointed our team to develop an analysis methodology with emphasis to evaluate the stresses through a dynamic analysis of highway bridge decks including the action of vehicles. The design codes recommend the application of the curves S-N associated to the Miner's damage rule to evaluate the fatigue and service life of steel and composite (steel-concrete) bridges. In this work, the developed computational model adopted the usual mesh refinement techniques present in finite element method simulations implemented in the ANSYS program. The investigated highway bridge is constituted by four longitudinal composite girders and a concrete deck, spanning 40.0m by 13.5m. The analysis methodology and procedures presented in the design codes were applied to evaluate the fatigue of the bridge determining the service life of the structure. The main conclusions of this investigation focused on alerting structural engineers to the possible distortions, associated to the steel and composite bridge's service life when subjected to vehicle's dynamic actions.

  11. Class I review of LOFT steam generator stress and fatigue life analysis report

    International Nuclear Information System (INIS)

    Review of the LOFT steam generator stress and fatigue life analysis report is presented. Deficiencies were found which will require evaluation and in some areas reanalysis. The effects of these deficiencies upon the steam generator will include: to further reduce the allowable ?P across the tubesheet for the abnormal design case of pressure on primary; and to reduce the allowable number of LOCE transients at some locations of the steam generator from the numbers listed in the stress report and to increase them at other locations

  12. Long-life fatigue test results for two nickel-base structural alloys

    International Nuclear Information System (INIS)

    The results are reported of fatigue tests on two nickel--base alloys, hot-cold-worked and stress-relieved nickel--chrome--iron Alloy 600 and mill-annealed nickel--chrome--moly--iron Alloy 625 in which S-N data were obtained in the life range of 106 to 1010 cycles. The tests were conducted in air at 6000F, in the reversed membrane loading mode, at a frequency of approx. 1850 Hz. An electromagnetic, closed loop servo-controlled machine was built to perform the tests. A description of the machine is given

  13. Fatigue life estimation of a 1D aluminum beam under mode-I loading using the electromechanical impedance technique

    Science.gov (United States)

    Lim, Yee Yan; Kiong Soh, Chee

    2011-12-01

    Structures in service are often subjected to fatigue loads. Cracks would develop and lead to failure if left unnoticed after a large number of cyclic loadings. Monitoring the process of fatigue crack propagation as well as estimating the remaining useful life of a structure is thus essential to prevent catastrophe while minimizing earlier-than-required replacement. The advent of smart materials such as piezo-impedance transducers (lead zirconate titanate, PZT) has ushered in a new era of structural health monitoring (SHM) based on non-destructive evaluation (NDE). This paper presents a series of investigative studies to evaluate the feasibility of fatigue crack monitoring and estimation of remaining useful life using the electromechanical impedance (EMI) technique employing a PZT transducer. Experimental tests were conducted to study the ability of the EMI technique in monitoring fatigue crack in 1D lab-sized aluminum beams. The experimental results prove that the EMI technique is very sensitive to fatigue crack propagation. A proof-of-concept semi-analytical damage model for fatigue life estimation has been developed by incorporating the linear elastic fracture mechanics (LEFM) theory into the finite element (FE) model. The prediction of the model matches closely with the experiment, suggesting the possibility of replacing costly experiments in future.

  14. Fatigue life estimation of a 1D aluminum beam under mode-I loading using the electromechanical impedance technique

    International Nuclear Information System (INIS)

    Structures in service are often subjected to fatigue loads. Cracks would develop and lead to failure if left unnoticed after a large number of cyclic loadings. Monitoring the process of fatigue crack propagation as well as estimating the remaining useful life of a structure is thus essential to prevent catastrophe while minimizing earlier-than-required replacement. The advent of smart materials such as piezo-impedance transducers (lead zirconate titanate, PZT) has ushered in a new era of structural health monitoring (SHM) based on non-destructive evaluation (NDE). This paper presents a series of investigative studies to evaluate the feasibility of fatigue crack monitoring and estimation of remaining useful life using the electromechanical impedance (EMI) technique employing a PZT transducer. Experimental tests were conducted to study the ability of the EMI technique in monitoring fatigue crack in 1D lab-sized aluminum beams. The experimental results prove that the EMI technique is very sensitive to fatigue crack propagation. A proof-of-concept semi-analytical damage model for fatigue life estimation has been developed by incorporating the linear elastic fracture mechanics (LEFM) theory into the finite element (FE) model. The prediction of the model matches closely with the experiment, suggesting the possibility of replacing costly experiments in future

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

    International Nuclear Information System (INIS)

    Highlights: ? Effect of laser peen intensity on local residual stress fields in 2024 aluminium. ? Peening induces significant changes in surface topography and local hardness. ? Residual stress at peen spot centre in tension, spot overlap in compression. ? Notched fatigue lives increased; crack morphology correlated to residual stress field. ? 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 ?m deep scribes, and slight improvement for samples with 150 ?m scribes. Use of the residual stress intensity Kresid 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.

  16. 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 sleep disturbances did not (p > 0.05). The stage of IPD and levodopa-entacapone treatment had independent effects on HRQoL too (p < 0.05). Fatigue was found as the most important factor which affects HRQoL among all investigated NMS. So, it is important to ask about fatigue in routine controls of IPD patients and try to treat it for improving life quality. PMID:26198763

  17. Approach to Fatigue Life Management for Primary Components in APR1400 Nuclear Power Plants Considering LWR Environments

    International Nuclear Information System (INIS)

    Full text: APR1400, the advanced power reactor with an electric capacity of 1450 MWe, is designed to the requirements of enhanced plant safety, availability and performance criteria for a 60 year design life. Currently, eight reactors of the APR1400 model are under construction and four reactors are being planned to construct in Korea and abroad. Of those, the first two reactors are planned to begin their commercial operations in 2013 and 2014, respectively. Effects of light water reactor (LWR) environments on fatigue behavior in reactor coolant system (RCS) structural materials have been an issue for several decades among nuclear industries and safety regulators, particulary for the design of long-life nuclear power plants including APR1400. In 2007, Nuclear Regulatory Commission (NRC) of the United States issued Regulatory Guide (RG) 1.207 for use in the design analyses of new reactors, incorporating the fatigue life reduction of pressure boundary components due to the effects of the LWR environment [1]. The environmental fatigue has also been a license renewal (LR) issue for operating reactors. The issue (Generic Safety Issue 190) was closed out in 1999, concluding that the environmental effects would have a negligible impact on core damage frequency. However, reactor coolant environmental fatigue effects would result in an increased frequency of pipe leakage. License renewal applicants must address the environmental effects on fatigue usage of components. The environmental fatigue is not considered as a safety issue but a quality standard issue for new plant design. ASME Boiler and Pressure Vessel (BPV) Standards Committee has implemented Environmental Fatigue Action Plan following USNRC RG 1.207 to incorporate environmental fatigue in the ASME BPV Code. The action plan includes development of a Non-mandatory Appendix that is a handbook on addressing environmental fatigue, and of individual Code Cases for the sections of the proposed Appendix, including Code Case N-792 for use in fatigue evaluations including environmental effects [2]. Based on the previous studies, it has been tentatively concluded that the back-fitting of the environmental fatigue to comply with RG 1.207 is not feasible without removing conservatisms inherent in the Code design and analyses [3]. More researches and Code developments are needed to bridge gap between the required and the available technologies in order to explicitly consider the environmental effects as design-basis requirements. This paper presents an alternative method to comply with the regulatory requirements of the environmental fatigue for the new reactors, including the following approaches: 2 - Environment assisted fatigue (EAF) evaluations for Code Class 1 components are performed in accordance with the requirements of RG 1.207 and applicable ASME Code Cases and, based on results of EAF evaluations, critical parts of components and piping selected for fatigue monitoring. - Ageing management programs, fatigue monitoring and enhanced inservice inspection (ISI), are applied to manage fatigue lives of susceptive components considering real operation transients occurred during the plant lifetime. - Fatigue monitoring program starts from the beginning of plant lifetime and includes cycle counting of operation transients, real transient-based fatigue and fatigue crack growth monitoring for critical components considering effects of LWR environment. (author)

  18. 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.

  19. Improvements in the microstructure and fatigue behavior of pure copper using equal channel angular extrusion

    Science.gov (United States)

    Nemati, J.; Majzoobi, G. H.; Sulaiman, S.; Baharudin, B. T. H. T.; Azmah Hanim, M. A.

    2014-06-01

    In this study, annealed pure copper was extruded using equal channel angular extrusion (ECAE) for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applied stresses using fatigue tests, fractography, and metallography. The mechanical properties of the extruded material were obtained at a tensile test velocity of 0.5 mm/min. It was found that the maximum increase in strength occurred after the 2nd pass. The total increase in ultimate strength after eight passes was 94%. The results of fatigue tests indicated that a significant improvement in fatigue life occurred after the 2nd pass. In subsequent passes, the fatigue life continued to improve but at a considerably lower rate. The improved fatigue life was dependent on the number of passes and applied stresses. For low stresses (or high-cycle fatigue), a maximum increase in fatigue resistance of approximately 500% was observed for the extruded material after eight passes, whereas a maximum fatigue resistance of 5000% was obtained for high-applied stresses (or low-cycle fatigue). Optical microscopic examinations revealed grain refinements in the range of 32 to 4 ?m. A maximum increase in impact energy absorption of 100% was achieved after eight passes. Consistent results were obtained from fractography and metallography examinations of the extruded material during fatigue tests.

  20. Fatigue life of the casting-magnesium alloy AZ91; Ermuedungslebensdauer der Magnesium-Gusslegierung AZ91

    Energy Technology Data Exchange (ETDEWEB)

    Eisenmeier, G.; Mughrabi, H.; Holzwarth, B.; Hoeppel, H.W.; Ding, H.Z. [Erlangen-Nuernberg Univ., Erlangen (Germany). Inst. fuer Werkstoffwissenschaften

    2000-07-01

    The cyclic deformation behaviour of the die-casting magnesium alloy AZ91 was investigated at constant total strain amplitudes between 1.4 x 10{sup -3} and 2 x 10{sup -2} at room temperature (20 C) and at 130 C. At low total strain amplitudes, a weak cyclic softening at the beginning of the fatigue tests is followed by cyclic hardening, whereas at high total strain amplitudes a strong cyclic hardening occurs throughout. The fatigue lives at 130 C are slightly longer at high strain amplitudes but shorter at low strain amplitudes than at room temperature. The fatigue life data for both temperatures can be described well by the laws of Manson-Coffin and Basquin. The microstructural investigations performed show the strong influence of several microstructural features on the initiation and propagation of fatigue cracks. In order to understand the fatigue crack propagation behaviour, fatigue tests were interrupted at certain numbers of cycles in order to make replicas of the surface of the samples. It could be verified that crack propagation occurs mainly by the coalescence of smaller cracks. Furthermore, unloading tests, performed within a closed cycle, were carried out in order to capture the changes of stiffness (compliance) during a closed cycle with the aim to ascertain the damage evolution occurring during the fatigue tests and to determine the stresses at which the cracks open and close. Finally, two-step fatigue tests were carried out with the objective to quantify deviations from the linear damage rule (LDR) of Palmgren and Miner. The results obtained in this study will be used to formulate a microstructurally based life-prediction concept for single-step as well as for two-step fatigue loading. (orig.)

  1. A Comparison of Fatigue Properties of Austempered Versus Quenched and Tempered 4340 Steel

    Science.gov (United States)

    Tartaglia, John M.; Hayrynen, Kathy L.

    2012-06-01

    This study was conducted to determine if austempered 4340 steel had different fatigue resistance compared to quench and tempered (Q&T) 4340 steel with an identical hardness of nominally 45 HRC and an identical yield strength of nominally 1340 MPa (194 ksi). Strain-life and stress-life fatigue testing was conducted at room temperature under identical test conditions. The standard array of strain-life and stress-life regression constants was obtained. The two heat treatments produced virtually identical total strain-life curves and fatigue limits at 5 million cycles. However, the two materials exhibited different trends in the elastic and plastic strain regimes. The austempered steel exhibited greater high cycle fatigue (finite) lives than the Q&T samples at comparable elastic strain amplitudes in strain-life fatigue testing and at comparable stress amplitudes in stress-life fatigue testing. However, the Q&T samples exhibited greater low cycle fatigue lives than the austempered samples at comparable plastic strain amplitudes in strain-life testing. Although both materials generally exhibited similar fatigue fracture characteristics, the overload regions of the Q&T samples were composed entirely of dimple rupture, whereas the austempered samples exhibited both dimple rupture and quasicleavage.

  2. Overview of the fatigue/fracture/life working group program at the Lewis Research Center

    Science.gov (United States)

    Mcgaw, Michael A.

    1989-01-01

    Constitutive and life prediction models are developed and verified for materials typically used in hot gas path components of reusable space propulsion systems over the range of relevant operating environments. The efforts were centered on the development of crack initiation life prediction methods, while the efforts of a counterpart group were centered on the development of cyclic crack propagation life prediction methods. The complexion of the active tasks are presented. A significant new task started this year will incorporate the various material constitutive and life prediction models developed in this program into a comprehensive creep-fatigue damage analysis and life assessment computer code. The program will function as a postprocessor to general structural analysis programs (such as finite element or boundary element codes) using the output of such analyses (stress, strain, and temperature fields as functions of time) as the input to the damage analysis and life assessment code. The code will be designed to execute on engineering/scientific workstations and will feature a windowing, mouse-driven user interface. Current plans call for the code to be finished and made available for use in mid 1991.

  3. Effects of exercise on angiogenesis and apoptosis-related molecules, quality of life, fatigue and depression in breast cancer patients.

    Science.gov (United States)

    Ergun, M; Eyigor, S; Karaca, B; Kisim, A; Uslu, R

    2013-09-01

    The aim of this study was to explore the effects of exercise on angiogenesis and apoptosis-related molecules, quality of life, fatigue and depression in patients who completed breast cancer treatment. Sixty breast cancer patients were randomised into three groups, as supervised exercise group, home exercise group and education group. Angiogenesis and apoptosis-related cytokine levels and quality of life (EORTC QOL-C30: European Organisation for Research and Treatment of Cancer Quality of Life C30), fatigue (Brief Fatigue Inventory) and depression (BDI: Beck Depression Inventory) scores were compared before and after a 12-week exercise programme. After the exercise programme, statistically significant decreases were found in interleukin-8 and neutrophil activating protein-78 levels in the home exercise group (P depression in breast cancer patients whose treatments are complete. PMID:23731173

  4. Uncertainties in fatigue life prediction and a rational definition of safety factors

    International Nuclear Information System (INIS)

    To cope with uncertainties in mechanical and structural design, engineers exercise their judgement through the use of safety factors based on service experience and laboratory data on relevant design parameters. Using the problem of fatigue life prediction as a vehicle, the relationship between the size of a safety factor and the associated risk and cost-benefit estimates of the engineering judgement based on new technical information, is demonstrated. The subtle influence of the choice of a distribution function for a given set of data is exhibited by comparing the gaussian with the three-parameter Weibull fits of a set of fatigue life data on 6061-T6 aluminium. A system of ranking the importance of different sources of uncertainties based on an analysis of service data is proposed along with an example to ''refine'' the system using up-to-date laboratory and field measurements. The concept of a rational definition of safety factors as a tool for engineers who design under uncertainty is discussed. (Auth.)

  5. Thermal Fatigue Life of Glidcop Al-15 High-Heat-Load Components

    International Nuclear Information System (INIS)

    Shanghai Synchrotron Radiation Facility (SSRF) is a third-generation of synchrotron radiation light source and is presently under construction as a large scale national scientific project in China. Depending on the outstanding thermal and mechanical performance, Glidcop Al-15, a dispersion strengthened copper alloy, is chosen to serve for the high-heat-load components at beam line front end in SSRF. Present study is to investigate the thermal fatigue lives of critical SSRF components. A nonlinear finite element method (FEM) is used to simulate the nonlinear three dimensional stress-strain fields of the critical component-Mask2 at SSRF beam line. The method consists of transient temperature analyses followed by elastic-plastic stress analyses. Then, a critical plane approach is used to predict the thermal fatigue life of mask2. The critical plane approach is appropriate for estimating service life of critical SSRF components since the results are in good consistent with the experimental ones taken at the Advanced Photon Source (APS).

  6. Fatigue Life of Lead Free Solder BGA Joints Against Vibration Stress under High Temperature Circumstance

    Science.gov (United States)

    Matsushima, Michiya; Furusawa, Takeshi; Fukuda, Kyohei; Egusa, Minoru; Yasuda, Kiyokazu; Fujimoto, Kozo

    Recently, the wave of car computerizing is surging such as electronic control unit, car navigation system, electronic toll collection system, car to car communication system, etc. The use environment of in-car devices is under combined environmental stresses such as thermal stress, vibration, and humidity. In general, the reliability of the joints of the devices is individually tested by the evaluation methods for each stress. Our main purpose of this study is to construct the evaluation method for the damages of solder joints under multiple environmental stresses. We investigated the relationship between the plastic strain caused by one cycle vibration stress calculated with FEM analysis considering the temperature dependency of the elasto-plasticity and the fatigue life obtained by the vibration experiment. We indicated the adequacy of the analysis by the correspondence of the resonance frequency of the BGA package mounting board with the experimental result. We also showed that the plastic strain concentrating position corresponded to the crack position. We clarified that the creep strain rate in the total strain was less than 1 percent. We demonstrated that we could apply the power-law equation to predict the fatigue life of the vibration stress from plastic strain rate under 80°C and 125°C as well as the room temperature.

  7. Application of fracture mechanics and half-cycle method to the prediction of fatigue life of B-52 aircraft pylon components

    Science.gov (United States)

    Ko, W. L.; Carter, A. L.; Totton, W. W.; Ficke, J. M.

    1989-01-01

    Stress intensity levels at various parts of the NASA B-52 carrier aircraft pylon were examined for the case when the pylon store was the space shuttle solid rocket booster drop test vehicle. Eight critical stress points were selected for the pylon fatigue analysis. Using fracture mechanics and the half-cycle theory (directly or indirectly) for the calculations of fatigue-crack growth ,the remaining fatigue life (number of flights left) was estimated for each critical part. It was found that the two rear hooks had relatively short fatigue life and that the front hook had the shortest fatigue life of all the parts analyzed. The rest of the pylon parts were found to be noncritical because of their extremely long fatigue life associated with the low operational stress levels.

  8. Investigation of Bearing Fatigue Damage Life Prediction Using Oil Debris Monitoring

    Science.gov (United States)

    Dempsey, Paula J.; Bolander, Nathan; Haynes, Chris; Toms, Allison M.

    2011-01-01

    Research was performed to determine if a diagnostic tool for detecting fatigue damage of helicopter tapered roller bearings can be used to determine remaining useful life (RUL). The taper roller bearings under study were installed on the tail gearbox (TGB) output shaft of UH- 60M helicopters, removed from the helicopters and subsequently installed in a bearing spall propagation test rig. The diagnostic tool was developed and evaluated experimentally by collecting oil debris data during spall progression tests on four bearings. During each test, data from an on-line, in-line, inductance type oil debris sensor was monitored and recorded for the occurrence of pitting damage. Results from the four bearings tested indicate that measuring the debris generated when a bearing outer race begins to spall can be used to indicate bearing damage progression and remaining bearing life.

  9. 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.

  10. Effect of substrate surface roughening and cold spray coating on the fatigue life of AA2024 specimens

    International Nuclear Information System (INIS)

    Highlights: • Investigated effect of CP-Al coatings cold sprayed onto roughened Al2024 substrate. • CP-Al coating improved rotating-bend fatigue strength up to 50% on average. • CP-Al coating diminished stress raisers caused by the surface roughening. • Glass-bead blasting plus coating offered most significant fatigue life improvement. - Abstract: The effects of cold spray coating and substrate surface preparation on crack initiation under cyclic loading have been studied on Al2024 alloy specimens. Commercially pure (CP) aluminum feedstock powder has been deposited on Al2024-T351 samples using a cold-spray coating technique known as high velocity particle consolidation. Substrate specimens were prepared by surface grit blasting or shot peening prior to coating. The fatigue behavior of both coated and uncoated specimens was then tested under rotating bend conditions at two stress levels, 180 MPa and 210 MPa. Scanning electron microscopy was used to analyze failure surfaces and identify failure mechanisms. The results indicate that the fatigue strength was significantly improved on average, up to 50% at 180 MPa and up to 38% at 210 MPa, by the deposition of the cold-sprayed CP-Al coatings. Coated specimens first prepared by glass bead grit blasting experienced the largest average increase in fatigue life over bare specimens. The results display a strong dependency of the fatigue strength on the surface preparation and cold spray parameters

  11. 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.

  12. 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.

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

    Scientific Electronic Library Online (English)

    Bendouba, Mostefa; Aid, Abdelkrim; Benhamena, Ali; Benguediab, Mohamed.

    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 w [...] ere 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.

  14. 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.

  15. Creep-Fatigue Life Design with Various Stress and Temperature Conditions on the Basis of Lethargy Coefficient

    International Nuclear Information System (INIS)

    High temperature and stress are encounted in power plants and vehicle engines. Therefore, determination of the creep-fatigue life of a material is necessary prior to fabricating equipment. In this study, life design was determined on the basis of the lethargy coefficient for different temperatures, stress and rupture times. SP-Creep test data was compared with computed data. The SP-Creep test was performed to obtain the rupture time for X20CrMoV121 steel. The integration life equation was considered for three cases with various load, temperature and load-temperature. First, the lethargy coefficient was calculated by using the obtained rupture stress and the rupture time that were determined by carrying out the SP-Creep test. Next, life was predicted on the basis of the temperature condition. Finally, it was observed that life decreases considerably due to the coupling effect that results when fatigue and creep occur simultaneously

  16. 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 the overall accuracy of unidirectional and laminated composite deformation and fatigue response.

  17. Fatigue life assessment of reactor coolant system components by using transfer functions of integrated FE model

    International Nuclear Information System (INIS)

    Recently, efficient operation and practical management of power plants have become important issues in the nuclear industry. In particular, typical aging parameters such as stress and cumulative usage factor should be determined accurately for continued operation of a nuclear power plant beyond design life. However, most of the major components have been designed via conservative codes based on a 2-D concept, which do not take into account exact boundary conditions and asymmetric geometries. The present paper aims to suggest an effective fatigue evaluation methodology that uses a prototype of the integrated model and its transfer functions. The validity of the integrated 3-D Finite Element (FE) model was proven by comparing the analysis results of individual FE models. Also, mechanical and thermal transfer functions, known as Green's functions, were developed for the integrated model with the standard step input. Finally, the stresses estimated from the transfer functions were compared with those obtained from detailed 3-D FE analyses results at critical locations of the major components. The usefulness of the proposed fatigue evaluation methodology can be maximized by combining it with an on-line monitoring system, and this combination, will enhance the continued operations of old nuclear power plants

  18. Literature Review on Design, Analysis and Fatigue Life of a Mechanical Spring

    Directory of Open Access Journals (Sweden)

    Supriya Burgul

    2014-07-01

    Full Text Available In this paper there is reviewed some papers on the design and analysis spring performance and fatigue life prediction of spring. There is also the analysis of failure in spring. The aim of this review paper is to represent a general study on the analysis of spring. Compression springs are commonly used in the I.C. Engine valves,2 wheeler horn & many more and are subjected to number of stress cycles leading to fatigue failure. A lot of research has been done for improving the performance of spring. Now the automobile industry has shown interest in the replacement of steel spring with composite spring. In general, it is found that fiberglass material has better strength characteristic and lighter in weight as compare to steel for spring. We can reduce product development cost and time while improving the safety, comfort, and durability of the vehicles produce. The CAE tool has where much of the design verification is now done using computer simulation rather than physical prototype testing.

  19. Stochastic Analysis of the Influence of Tower Shadow on Fatigue Life of Wind Turbine Blade

    DEFF Research Database (Denmark)

    Pedersen, Ronnie; Nielsen, SØren R.K.

    2012-01-01

    Fatigue damage accumulation in upwind turbine blades is primarily influenced by turbulence in the inflow. However, the stress reversals during blade passages through the stagnating and deflected mean wind field in front of the tower also contributes significantly. In the paper the lower order statistical moments of the fatigue life of a blade are estimated and compared for a turbine with a tripod tower and a standard mono-tower, respectively. The stagnation zones for each of the legs of the tripod are narrower than for the mono-tower, and hence the stress reversals will be comparable smaller. The blade stresses are calculated from a dynamic mechanical model based on a two dynamic degree of freedom with quasi-static correction for higher modes. The self-induced aero-elastic loading and the turbulence loading are modeled by means of a quasi-static model linearized around the operational point, ignoring any memory effects on the load coefficients. However, such memory effects are taken into consideration at the calculation of the aero-dynamic load during tower passage by the use of a rational approximation to the relevant indicial function. Based on Monte Carlo simulations it is demonstrated that the expected damage accumulation per unit of time in the turbine blades are reduced significantly for the tripod when compared to the damage in a comparable mono-tower design.

  20. Initial Assessment of the Effects of Nonmetallic Inclusions on Fatigue Life of Powder-Metallurgy-Processed Udimet(TM) 720

    Science.gov (United States)

    Gabb, T. P.; Telesman, J.; Kantzos, P. T.; Bonacuse, P. J.; Barrie, R. L.

    2002-01-01

    The fatigue lives of modern powder metallurgy (PM) disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary due to the different steps of materials/component processing and machining. One of these variables, the presence of nonmetallic inclusions, has been shown to significantly degrade low-cycle fatigue (LCF) life. Nonmetallic inclusions are inherent defects in powder alloys that are a by-product of powder-processing techniques. Contamination of the powder can occur in the melt, during powder atomization, or during any of the various handling processes through consolidation. In modern nickel disk powder processing facilities, the levels of inclusion contamination have been reduced to less than 1 part per million by weight. Despite the efforts of manufacturers to ensure the cleanliness of their powder production processes, the presence of inclusions remains a source of great concern for the designer. the objective of this study was to investigate the effects on fatigue life of these inclusions. Since natural inclusions occur so infrequently, elevated levels of inclusions were carefully introduced in a nickel-based disk superalloy, Udimet 720 (registered trademark of Special Metals Corporation), produced using PM processing. Multiple strain-controlled fatigue tests were then performed on this material at 650 C. Analyses were performed to compare the LCF lives and failure initiation sites as functions of inclusion content and fatigue conditions. A large majority of the failures in specimens with introduced inclusions occurred at cracks initiating from inclusions at the specimen surface. The inclusions could reduce fatigue life by up to 100 times. These effects were found to be dependent on strain range and strain ratio. Tests at lower strain ranges and higher strain ratios produced larger effects of inclusions on life.

  1. Standard practice for statistical analysis of linear or linearized stress-life (S-N) and strain-life (?-N) fatigue data

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice covers only S-N and ?-N relationships that may be reasonably approximated by a straight line (on appropriate coordinates) for a specific interval of stress or strain. It presents elementary procedures that presently reflect good practice in modeling and analysis. However, because the actual S-N or ?-N relationship is approximated by a straight line only within a specific interval of stress or strain, and because the actual fatigue life distribution is unknown, it is not recommended that (a) the S-N or ?-N curve be extrapolated outside the interval of testing, or (b) the fatigue life at a specific stress or strain amplitude be estimated below approximately the fifth percentile (P ? 0.05). As alternative fatigue models and statistical analyses are continually being developed, later revisions of this practice may subsequently present analyses that permit more complete interpretation of S-N and ?-N data.

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

    Science.gov (United States)

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

    2012-04-01

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

  3. User's guide for the frequency domain algorithms in the LIFE2 fatigue analysis code

    Science.gov (United States)

    Sutherland, H. J.; Linker, R. L.

    1993-10-01

    The LIFE2 computer code is a fatigue/fracture analysis code that is specialized to the analysis of wind turbine components. The numerical formulation of the code uses a series of cycle count matrices to describe the cyclic stress states imposed upon the turbine. However, many structural analysis techniques yield frequency-domain stress spectra and a large body of experimental loads (stress) data is reported in the frequency domain. To permit the analysis of this class of data, a Fourier analysis is used to transform a frequency-domain spectrum to an equivalent time series suitable for rainflow counting by other modules in the code. This paper describes the algorithms incorporated into the code and their numerical implementation. Example problems are used to illustrate typical inputs and outputs.

  4. Experimental observations on uniaxial whole-life transformation ratchetting and low-cycle stress fatigue of super-elastic NiTi shape memory alloy micro-tubes

    Science.gov (United States)

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

    2015-07-01

    In this work, the low-cycle fatigue failure of super-elastic NiTi shape memory alloy micro-tubes with a wall thickness of 150 ?m is investigated by uniaxial stress-controlled cyclic tests at human body temperature 310 K. The effects of mean stress, peak stress, and stress amplitude on the uniaxial whole-life transformation ratchetting and fatigue failure of the NiTi alloy are observed. It is concluded that the fatigue life depends significantly on the stress levels, and the extent of martensite transformation and its reverse play an important role in determining the fatigue life. High peak stress or complete martensite transformation shortens the fatigue life.

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. Fatigue Damage Simulator (FADAS) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Puck, to model the degradation caused by failure events in ply level. Residual strength is incorporated as fatigue damage accumulation metric. Once the typical fatigue and static properties of the constitu...

  6. 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.

  7. Effect of grit blasting surface treatment on high temperature low cycle fatigue life of Inconel 713LC.

    Czech Academy of Sciences Publication Activity Database

    Šulák, Ivo; Obrtlík, Karel; ?elko, L.; Gejdoš, P.

    Brno : Brno University of Technology, 2015 - (Dlouhý, I.; Vít, J.; Maca, K.; Válka, L.), s. 139-144 ISBN 978-80-214-5146-9. [Multi Scale Design of Advanced Materials. Velké Bílovice (CZ), 28.05.2015-29.05.2015] R&D Projects: GA MŠk(CZ) EE2.3.20.0214; GA ?R(CZ) GA15-20991S Institutional support: RVO:68081723 Keywords : Grit blasting * Surface relief * Surface microhardnes * High temperature fatigue life * Inocel 713LC Subject RIV: JL - Materials Fatigue, Friction Mechanics

  8. Effect of Cryorolling and Aging on Fatigue Behavior of Ultrafine-grained Al6061

    Science.gov (United States)

    Yadollahpour, M.; Hosseini-Toudeshky, H.; Karimzadeh, F.

    2015-11-01

    The effects of cryorolling (rolling at liquid nitrogen temperature) and heat treatment on tensile and high-cycle fatigue properties and fatigue crack growth rate of Al6061 alloy have been investigated in the present work. First, the solid solution-treated bulk Al6061 alloy was subjected to cryorolling with 90% total thickness reduction and subsequent short annealing at 205°C for 5 min and peak aging at 148°C for 39 h to achieve grain refinement and simultaneous improvement of the strength and ductility. Then, hardness measurements, tensile tests, fatigue life, and fatigue crack growth rate tests including fractography analyses using scanning electron microscopy were performed on bulk Al6061 alloy, cryorolled (CR), and cryorolled material followed by peak aging (PA). The PA specimen showed improved yield strength by 24%, ultimate tensile strength by 20%, and ductility by 12% as compared with the bulk Al6061 alloy. It is shown that the fatigue strength of both CR and PA specimens under a high-cycle fatigue regime are larger than that of the bulk Al6061 alloy. Also, fatigue crack growth rates of the CR and PA specimens show significant enhancement in fatigue crack growth resistances as compared with the bulk Al6061 alloy, as a result of grain refinement.

  9. A study on creep-fatigue life analysis using a unified constitutive equation and a continuous damage law

    International Nuclear Information System (INIS)

    A newly developed type of life analysis is introduced using a unified constitutive equation and a continuous damage law on 2 1/4Cr - 1Mo steel at 600 deg C. the viscoplasticity theory based on total strain and overstress used for the rate effect at room temperature is extended for application to the inelastic analysis at elevated temperature, and the extended uniaxial model is shown to reproduce the inelastic stress and strain behavior with a strain rate change observed in the experiment. The incremental life prediction law is employed and its coupling with the viscoplasticity model produces both an inelastic stress-strain response and the damage accumulation, simultaneously and continuously. The life prediction for creep, fatigue and creep-fatigue loading shows good correspondence with the experimental data. (author)

  10. Multi-scale analysis of behavior and fatigue life of 304L stainless under cyclic loading with pre-hardening

    International Nuclear Information System (INIS)

    This study investigates the effects of loading history on the cyclic stress-strain curve and fatigue behavior of 304L stainless steel at room temperature. Tension-compression tests were performed on the same specimen under controlled strain, using several loading sequences of increasing or decreasing amplitude. The results showed that fatigue life is significantly reduced by the previous loading history. A previously developed method for determining the effect of prehardening was evaluated. Microstructural analyses were also performed; the microstructures after pre-loading and their evolution during the fatigue cycles were characterized by TEM. The results of these analyses improve our understanding of the macroscopic properties of 304L stainless steel and can help us identify the causes of failure and lifetime reduction. (author)

  11. 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 life experiments for the same purpose. The methodology is basedon modern probabilistic concepts amd classical decision theory. The special case where the fatigue life experiments are given in terms of SN...

  12. Effects of hydrogen on fatigue of vanadium and niobium. Annual report

    International Nuclear Information System (INIS)

    The fatigue behavior of unalloyed vanadium and niobium as well as their alloys with hydrogen is described. The response of vanadium-hydrogen alloys to cyclic loading is shown to depend markedly upon the presence or absence of notches, the hydrogen level, method of test, and frequency. In general, hydrides improve high cycle life of unnotched alloys, but are detrimental in the presence of a notch. Low test frequencies also lead to reduced fatigue lives. Stress-assisted hydride growth in previously hydrided alloys has been noted both in fatigue and in delayed failure experiments. Unalloyed vanadium and solid solution vanadium-hydrogen alloys do not undergo delayed failure. Preliminary tests on unalloyed niobium and several niobium-vanadium alloys reveal improvements in stress-controlled fatigue life and decreased low cycle life, in agreement with previous observations on vanadium-hydrogen alloys

  13. A STUDY OF FATIGUE LIFE OF ASPHALT CONCRETE BASED ON SHUNGITE MINERAL POWDER

    Directory of Open Access Journals (Sweden)

    D. I. Chernousov

    2011-11-01

    Full Text Available 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 modulus of elasticity and tensile bending strength. To forecast operating properties ofasphalt concrete, 4×4×16 cm beams were tested on vibrostand ?? 70/100, which enables one toobtain frequency and amplitude of oscillations continuously adjustable during operation. The techniqueuses analytical relationships which allow one to determine durability of operating period undersimulation of axis load of 6 and 10 tons. Comparison of the relationships obtained shows thatmodulus of elasticity, bending and comparison strength of involved asphalt concrete mixes markedlydecrease. However, this decrease is more pronounced with reference asphalt concretes.Conclusions. The use of shungite mineral powder provides for increasing fatigue life of asphaltconcrete, which can be related to higher adhesion activity of shungite powder compared with limestonepowder.

  14. High fatigue life and tensile strength characteristics of low activation ferritic steel(JLF-1) by TIG welding

    International Nuclear Information System (INIS)

    JLF-1 steel (Fe-9Cr-2W-V-Ta), low activation ferritic steel, is one of the promising candidate materials for fusion reactor applications. High temperature fatigue life and tensile strength of JLF-1 steel and its TIG welded joints were investigated at the room temperature and 400 .deg. C. The strength of base metal (JLF-1) is in between those of weld metal and the HAZ. When the test temperature was increase from room temperature to 400 deg. C, both strength and ductility decreased for base metal, weld metal and the HAZ. The longitudinal specimens of base metal showed similar strength and ductility compared with those of the transverse specimens at room temperature and 400 .deg. C. Little anisotropy was observed in the JLF-1 steel base metal in terms of rolling direction. Fatigue limit of weld metal which was obtained from cross-weld specimen is 495MPa. Thus, the weld metal showed the higher fatigue limit than those of base metal at both room temperature and 400 deg. C. Little anisotropy of fatigue properties was observed for JLF-1 base metal in terms of rolling direction. When the test temperature was increased from room temperature to 400 .deg. C, the fatigue limit of both base metal and weld metal decreased substantially

  15. Characterisation of the fatigue life, dynamic creep and modes of damage accumulation within mitral valve chordae tendineae.

    Science.gov (United States)

    Gunning, Gillian M; Murphy, Bruce P

    2015-09-01

    Mitral valve prolapse is often caused by either elongated or ruptured chordae tendineae (CT). In many cases, rupture is spontaneous, meaning there is no underlying cause. We hypothesised that spontaneous rupture may be due to mechanical fatigue. To investigate this hypothesis, we tested porcine marginal CT: in uniaxial tension, and in fatigue at a range of peak stresses (n=12 at 15, 10 and 7.5MPa respectively, n=6 at 5MPa). The rupture surfaces of failed CT were observed histologically, under polarised light microscopy, and SEM. The cycles to failure for 15, 10, 7.5 and 5 MPa peak stresses were: (average±SD): 5077±4366, 49513±56414, 99927±108908, 197099±69103. A Weibull plot was constructed and from this, the number of cycles at 50% probability of failure was established in order to approximate the fatigue life, which was found to be 2.43MPa at 10 million cycles. The rate of creep increases exponentially with increasing peak stress. Under histological examination it was observed that CT which have been fatigued at low stress partially lose their organised collagen structure and can sustain micro-cracks that can be linked to increases in the creep rate. Furthermore our SEM images closely matched descriptions from the literature of spontaneous in vivo rupture. In conclusion, we believe that the mechanical test results we present strongly suggest that spontaneous chordal rupture and chordal elongation in vivo can be caused by mechanical fatigue. PMID:26087111

  16. Influence of temperature and carbon content on the cyclic deformation and fatigue behavior of {alpha}-iron. Part 2: Crack initiation and fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, C.; Mughrabi, H.; Lochner, D. [Univ. Erlangen-Nuernberg, Erlangen (Germany). Inst. fuer Werkstoffwissenschaften

    1998-03-02

    The crack initiation mechanisms and the fatigue life of {alpha}-iron polycrystals have been characterized in plastic-strain-controlled tests with small to intermediate plastic strain ranges {Delta}{epsilon}{sub pl} in the temperature range from 220 to 400 K. The fatigue life of pure decarburized {alpha}-iron cannot be described generally by means of a Manson-Coffin law, except under conditions under which distinct cyclic hardening occurs. A Basquin law is found to be valid, when the effective stress component {sigma}{sup *} dominates (i.e. at low temperatures and small {delta}{epsilon}{sub pl}). At low temperatures and up to room temperature, intergranular crack initiation is observed. At higher temperatures, mostly transgranular cracks develop in decarburized {alpha}-iron in the valleys of the surface rumpling, while in {alpha}-iron with small carbon contents persistent slip bands form which then act as sites of transgranular crack initiation. Crack initiation rates and crack growth rates are evaluated in a semi-quantitative manner from crack depth distributions.

  17. Prediction of fatigue life of reinforced concrete bridges using Fracture Mechanics

    OpenAIRE

    Biondini, Fabio; Frangopol, Dan; Rocha, Marina; Brühwiler, Eugen

    2012-01-01

    With the occurrence of higher and more frequent axle loads, bridges are more solicited by fatigue loading. Bridge elements like deck slabs are subjected to a high number of stress cycles at relatively small stress magnitudes. The application of Fracture Mechanics as a useful tool for the analysis of fatigue crack growth in steel elements was demonstrated by Paris et al. in the early 1960s. With respect to reinforced concrete, the fatigue strength of the steel reinforcement is determinant. The...

  18. Life prediction and mechanisms for the initiation and growth of short cracks under fretting fatigue loading

    OpenAIRE

    Cadario, Alessandro

    2006-01-01

    Fretting fatigue is a damage process that may arise in engineering applications where small cyclic relative displacements develop inside contacts leading to detrimental effects on the material fatigue properties. Fretting is located in regions not easily accessible, which makes it a dangerous phenomenon. It is therefore important to be able to make reliable predictions of the fretting fatigue lives. The work presented in this thesis has its focus on different aspects related to fretting fatig...

  19. Fatigue after stroke

    DEFF Research Database (Denmark)

    Kirkevold, Marit; Christensen, Doris; Andersen, Grethe; Johnsen, Søren Paaske; Harder, Ingegerd

    2011-01-01

    Purpose: To describe how fatigue is experienced by stroke survivors, how they understand and deal with fatigue and how fatigue impacts their daily life. Method: A qualitative interview study was carried out as part of a larger longitudinal study investigating the prevalence, characteristics and contributing factors to post-stroke fatigue. Thirty-two participants (15 men and 17 women) were strategically sampled to explore the experiences of fatigue. Participants were interviewed at 6 months, 1 ye...

  20. 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 %.

  1. 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.

  2. 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.

  3. 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

    International Nuclear Information System (INIS)

    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

  4. Fatigue characterization of flowformed A356-T6

    Directory of Open Access Journals (Sweden)

    Roy Matthew J.

    2014-06-01

    Full Text Available Flowforming is an incremental rotary forming technology consisting of deforming a cylindrical workpiece through contact between a roller and a rotating mandrel. This process delivers significant local compressive plastic strain to the workpiece. The effects on fatigue resilience of a common aluminum foundry alloy (A356 processed in this manner at an elevated temperature has been shown to improve post heat treatment. Fatigue properties of material processed with a standard heat treatment following casting is compared to material which has been cast and flowformed to varying degrees and then heat treated. Flowformed material with varying degrees of rotary deformation have been tested. Endurance limits have been found to be generally governed by porosity and maximum principal stress for high cycle fatigue on undeformed material. Fatigue properties have been quantified employing stress-life relationships derived from uniaxial fatigue tests. A 30% increase in the high-cycle endurance limits of flowformed compared to non-deformed material has been observed and is linked to the extent of deformation. Fractographic examination shows that this increase in endurance limit can be attributed primarily to the mitigation of porosity. Microstructural changes due to processing appear to be a secondary factor.

  5. The effect of allergic rhinitis on the degree of stress, fatigue and quality of life in OSA patients.

    Science.gov (United States)

    Park, Cheol Eon; Shin, Seung Youp; Lee, Kun Hee; Cho, Joong Saeng; Kim, Sung Wan

    2012-09-01

    Both allergic rhinitis (AR) and obstructive sleep apnea (OSA) are known to increase stress and fatigue, but the result of their coexistence has not been studied. The objective of this study was to evaluate the amount of stress and fatigue when AR is combined with OSA. One hundred and twelve patients diagnosed with OSA by polysomnography were enrolled. Among them, 37 patients were diagnosed with AR by a skin prick test and symptoms (OSA-AR group) and 75 patients were classified into the OSA group since they tested negative for allergies. We evaluated the Epworth sleepiness scale (ESS), stress score, fatigue score, ability to cope with stress, and rhinosinusitis quality of life questionnaire (RQLQ) with questionnaires and statistically compared the scores of both groups. There were no significant differences in BMI and sleep parameters such as LSAT, AHI, and RERA between the two groups. However, the OSA-AR group showed a significantly higher ESS score compared to the OSA group (13.7 ± 4.7 vs. 9.3 ± 4.8). Fatigue scores were also significantly higher in the OSA-AR group than in the OSA group (39.8 ± 11.0 vs. 30.6 ± 5.4). The OSA-AR group had a significantly higher stress score (60.4 ± 18.6 vs. 51.2 ± 10.4). The ability to cope with stress was higher in the OSA group, although this difference was not statistically significant. RQLQ scores were higher in the OSA-AR group (60.2 ± 16.7 compared to 25.1 ± 13.9). In conclusion, management of allergic rhinitis is very important in treating OSA patients in order to eliminate stress and fatigue and to minimize daytime sleepiness and quality of life. PMID:22207526

  6. Service life prediction. Development of models for predicting the service life of power plant components subject to thermomechanical creep fatigue; Lebensdauervorhersage. Entwicklung von Modellen zur Lebensdauervorhersage von Kraftwerksbauteilen unter thermisch-mechanischer Kriechermuedungsbeanspruchung. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Cui, L.; Scholz, A. [Technische Univ. Darmstadt (Germany). Institut fuer Werkstoffkunde; Hartrott, P. von; Schlesinger, M. [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany)

    2009-07-01

    Extensive use is made of massive components of heat resistant and highly heat resistant materials in installations of the power and heating industry. These components are exposed to varying thermomechanical stress as a result of ramping-up and down processes. In this research project two computer-assisted methods of predicting service life until crack initiation were extended to include cases of thermomechanical multi-axis stress conducive to creep fatigue and of superposition of high-cycle stress on power plant components. Investigations were limited to rotor steel of type X12CrMoWVNbN10-1-1. Complex thermomechanical multi-axis experiments were performed on round, notched and cruciform test specimens of close-to-life dimensions in order to demonstrate by experiment the validity of these models. The results of these calculations showed an acceptable degree of agreement between experiment and simulation for both models. Calculations on earlier TMF experiments performed at IfW on hollow specimens of 1%CrMoNiV showed good predictability for both the SARA and the ThoMat programme. Calculations on experiments performed at MPA Stuttgart on model bodies consisting of the same 1%CrMoNiV showed a predictability of acceptable variability considering the complexity of the stresses involved. A further outcome of this project is that the use of SARA appears universally suitable for the construction of new plants and in the service area, while the use of ThoMat appears suited for detail optimisation in the development process.

  7. Influence of composition and distribution of the reinforcing particles on fatigue properties of metal matrix composites

    International Nuclear Information System (INIS)

    Fatigue-life-time behaviour has been examined of extruded 6061 aluminium alloy composites reinforced with 15 vol.% SiC and 10 vol.% Al2O3 particles. The peak particle sizes are at about 4.5 and 6 ?m. Within measured S-N curves the fatigue life-time at given stress amplitudes of SiCp/AA6061 is superiour to that of Al2O3p/AA6061 in the low-cycle fatigue region as well as in the high-cycle fatigue region. The discussion of these results has been done by means of theoretical evaluated crack propagation curves. Interfacial bonding has been studied by means of TEM investigations. (orig.)

  8. Improvement of Fatigue Life of Welded Structural Components of a Large Two-Stroke Diesel Engine by Grinding

    DEFF Research Database (Denmark)

    Agerskov, Henning; Hansen, Anders V.; Bjørnbak-Hansen, Jørgen; Olesen, John Forbes

    2004-01-01

    The crankshaft housings of large two-stroke diesel engines are welded structures subjected to constant amplitude loading and designed for infinite life at full design load. A new design of the so-called frame box has been introduced in the engine using butt weld joints of thick plates, welded from one side only, with no access to the root side. Various investigations on the fatigue life of the structural components of this new design have been carried out. The present investigation concentrates ...

  9. Low cycle fatigue life prediction of 316 L(N) stainless steel based on cyclic elasto-plastic response

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Samir Chandra [Metallurgical and Material Engineering, Jadavpur University, Kolkata 700 032 (India); Goyal, Sunil, E-mail: goyal@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Sandhya, R. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Ray, S.K. [Metallurgical and Material Engineering, Jadavpur University, Kolkata 700 032 (India)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer Low cycle fatigue tests were carried out on 316 L(N) stainless steel. Black-Right-Pointing-Pointer The stable hysteresis loops showed non-Masing behavior. Black-Right-Pointing-Pointer The elasto-plastic response of the material under cyclic loading was evaluated. Black-Right-Pointing-Pointer Hysteresis loops and life were predicted by isotropic and kinematic hardening models. - Abstract: Low cycle fatigue (LCF) tests were carried out on 316 L(N) stainless steel at room temperature employing strain amplitudes ranging from {+-}0.3% to {+-}1.0% and a strain rate of 3 Multiplication-Sign 10{sup -3} s{sup -1}. The material showed initial hardening for a few cycles followed by prolonged softening, saturation and final failure. The fatigue life was found to decrease with increase in strain amplitude. The analysis of the stable hysteresis loops under the tested conditions showed Masing behavior at lower strain amplitudes but non-Masing behavior at higher strain amplitudes. The elasto-plastic response of the material under cyclic loading was characterized taking into account isotropic and kinematic hardening occurring during cyclic loading. The material parameters required for characterization of cyclic behavior were obtained from the experimental hysteresis loops and cyclic stress response of the material. Finite element (FE) analysis of elasto-plastic deformation was carried out to obtain the hysteresis loop and cyclic stress response of the material. The predicted hysteresis loops from simulation showed good agreement with experimental results. The low cycle fatigue life prediction carried out based on plastic strain energy dissipation with cycling showed good correlation with experimental results.

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

    International Nuclear Information System (INIS)

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

  11. 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 improve the design. A new improved slot for the longitudinal intersection in the web plate is found on the basis of a shape optimization of the conventional slot. The new slot has an unique shape (tongue ...

  12. Fatigue and creep-fatigue behavior of irradiated and unirradiated type 308 stainless steel weld metal at elevated temperatures

    International Nuclear Information System (INIS)

    Results from elevated temperature, strain controlled fatigue tests with and without hold periods at peak tensile strain on specimens cut from Type 304 stainless steel plates welded using Type 308 stainless weld wire with controlled residual elements (CRE) are reported. Specimens were irradiated to fluences of 0.1 to 1.1 x 1022 neutrons (n)/cm2, E > 0.1 MeV at 450 and 6000C, while the postirradiation test temperature was 482 and 5930C respectively. Irradiation reduced the fatigue life of the weld metal at 5930C by about one half in the low cycle region (10,000 cycles to fail). At 4820C and at the lower fluence, the fatigue behavior of the irradiated specimens was almost equivalent in the low cycle region and superior in the high cycle region. Introducing tensile hold periods at the peak strain of each fatigue cycle of the 5930C tests resulted in reductions in the fatigue life but at a much lesser rate than the base (parent) metal. Irradiation further reduced the life of the hold time tests. Hold periods had no significant effect at 4820C. Orientation effects were seen in all weld metal tests with the parallel orientation (specimen axis parallel to the weld seam) showing a superiority in cyclic life over those taken transverse to the welding direction

  13. Effect of salt-water fog on fatigue crack nucleation of Al and Al-Li alloys

    Scientific Electronic Library Online (English)

    O. C., Gamboni; J. A., Moreto; L. H. C., Bonazzi; C. O. F. T., Ruchert; W. W., Bose Filho.

    2014-02-01

    Full Text Available Fatigue and corrosion-fatigue tests were performed to quantify the fatigue properties of AA2524-T3 and AA2198-T851 Al alloys. High cycle axial fatigue tests were carried out under air and salt-water fog conditions. In air, the specimens were fatigue tested at a frequency of 50 Hz, using specimens wi [...] th and without preconditioning in a salt spray chamber, and for the corrosion fatigue condition, the tests took place at a frequency of 30 Hz in a salt-water fog condition. In all cases it was used a sinusoidal waveform and a stress ratio (R) of 0.1. The results indicate that the saline environment had a deleterious effect on the fatigue life of the two aluminum alloys. AA2524-T3 exhibited a better fatigue strength than AA2198-T851 when fatigue tested in air. However, considering the corrosion fatigue test in a saline fog environment an inverse behavior was observed with the AA2198-T851 exhibiting higher fatigue strength.

  14. Influence of test specimen fabrication method and cross-section configuration on tension-tension fatigue life of PMMA bone cement.

    Science.gov (United States)

    Sheafi, E M; Tanner, K E

    2015-11-01

    Different cyclic loading modes have been used in in vitro fatigue studies of PMMA bone cement. It is unclear which loading mode is most appropriate from the perspective of the in vivo loading experienced by the cement in a cemented arthroplasty. Also, in different in vitro fatigue studies, different test specimen configurations have been used. The present work considers the influence of test specimen fabrication method (direct moulding vs moulding followed by machining) and cross-section shape (rectangular vs circular) on the tension-tension fatigue performance of two bone cement brands (SmartSet GHV and CMW1), under force control conditions. Two trends were consistent: 1) for each of the cements, for moulded specimens, a longer fatigue life was obtained with circular cross-sectioned specimens and, 2) for either rectangular or circular CMW1 specimens, a longer fatigue life was obtained using machined specimens. A comparison of the present results to those reported in our previous work on fully-reversed tension-compression loading under force control showed that, regardless of the test specimen fabrication method or cross-section configuration used, the fatigue life was considerably shorter under tension-compression than tension-tension loading. This finding highlights the fact that the presence of the compression portion in the loading cycle accelerates fatigue failure. PMID:26295451

  15. Application of fracture mechanics and half-cycle theory to the prediction of fatigue life of aerospace structural components

    Science.gov (United States)

    Ko, William L.

    1989-01-01

    The service life of aircraft structural components undergoing random stress cycling was analyzed by the application of fracture mechanics. The initial crack sizes at the critical stress points for the fatigue crack growth analysis were established through proof load tests. The fatigue crack growth rates for random stress cycles were calculated using the half-cycle method. A new equation was developed for calculating the number of remaining flights for the structural components. The number of remaining flights predicted by the new equation is much lower than that predicted by the conventional equation. This report describes the application of fracture mechanics and the half-cycle method to calculate the number of remaining flights for aircraft structural components.

  16. Fatigue life of creep resisting steels under conditions of cyclic mechanical and thermal interactions

    OpenAIRE

    Marek, A; G. Junak; J. Okrajni

    2009-01-01

    urpose: This study sets out to determine the characteristics of high-temperature creep resisting steels under conditions of thermo-mechanical fatigue with the use of a method proposed in the Code-of-Practice under the EU TMF-Standard project.Design/methodology/approach: The thermo-mechanical fatigue (TMF) tests were carried out in the conditions where the value of complete strain and the temperature were under control. Two methods of investigating samples in T...

  17. Damage mechanics and Paris regime in fatigue life assessment of metals

    International Nuclear Information System (INIS)

    The fatigue assessment of structural components under uniaxial or multiaxial stress histories can be performed by employing damage mechanics concepts and a physics-based approach. A model for fatigue damage evaluation for an arbitrary loading (uniaxial or multiaxial, cyclic or random) has recently been proposed by the authors using an endurance function which quantifies the damage accumulation in the material up to the final failure. On the other hand, the approach based on the Paris law interprets fatigue failure as the result of the crack propagation inside the material up to the final collapse. In the context of damage mechanics, the structure collapse is assumed to occur when a scalar damage parameter (evaluated by using a proper damage accumulation law depending on the material parameters) is equal to the unity, whereas the final failure according to the Paris law is assumed to occur when the growing crack reaches the ‘critical size’ which depends on the mechanical properties of the material. In the present paper, these two fatigue assessment methods (damage model and Paris approach) are compared in order to determine both a damage value according to the Paris law and the crack length corresponding to a given damage. Such two methods are shown to be different formulations of the same physics-based approach to fatigue. -- Highlights: ? Both damage mechanics and the Paris law can be used to analyse fatigue problems. ? The proposed damage model examines the fatigue effects through damage increments. ? The damage approach is compared with the Paris approach. ? The two methods are shown to be different formulations of the fatigue problem. ? Applications to uniaxial cyclic and variable amplitude loading are presented

  18. Fatigue life of drawn filled niti-ag wires for medical applications.

    Czech Academy of Sciences Publication Activity Database

    Major, Št?pán; Hubalovský, Š.; Šedivý, J.; Hanuš, J.

    Sliema : WSEAS Press, 2012 - (Marques, V.; Dmitriev, A.; Pop, E.; Barbu, C.), s. 249-253 ISBN 978-1-61804-118-0. [International conference WSEAS /5./. Sliema (MT), 07.09.2012-09.09.2012] Institutional support: RVO:68378297 Keywords : nitinol * fatigue crack growth * drawn filled wires * fatigue crack initiation. Subject RIV: JI - Composite Materials http://www.wseas.us/e-library/conferences/2012/sliema/dnmat/dnmat-00.pdf

  19. Cyclic response and fatigue life of TiAl alloys at high temperatures.

    Czech Academy of Sciences Publication Activity Database

    Kruml, Tomáš; Obrtlík, Karel; Petrenec, Martin; Polák, Jaroslav

    2010-01-01

    Ro?. 417 - 418, - (2010), s. 585-588. ISSN 1013-9826. [8th International Conference on Fracture and Damage Mechanics. St. Georges Bay, 08.09.2009-10.09.2010] R&D Projects: GA ?R GA106/07/0762; GA ?R GA106/08/1631 Institutional research plan: CEZ:AV0Z20410507 Keywords : TiAl * lamellar microstructure * low cycle fatigue * transmission electron microscopy Subject RIV: JL - Materials Fatigue, Friction Mechanics

  20. Fatigue life prediction for broad-band multiaxial loading with various PSD curve shapes.

    Czech Academy of Sciences Publication Activity Database

    Nieslony, A.; R?ži?ka, M.; Papuga, J.; Hodr, A.; Balda, Miroslav; Svoboda, Jaroslav

    2012-01-01

    Ro?. 44, NOV 2012 (2012), s. 74-88. ISSN 0142-1123 R&D Projects: GA ?R(CZ) GA101/09/0904 Institutional research plan: CEZ:AV0Z20760514 Keywords : random loading * spectral method * power spectral density * fatigue damage Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.976, year: 2012 http://www.sciencedirect.com/science/article/pii/S0142112312001971#

  1. Quality of Life, Fatigue and Balance Improvements after Home-Based Exercise Program in Multiple Sclerosis Patients

    Directory of Open Access Journals (Sweden)

    Özge Ertekin

    2012-03-01

    Full Text Available Objectives: To determine the effects of home-based exercise program (HEP on aspects of disability, quality of life (QoL, fatigue and balance in multiple sclerosis (MS patients. Method: 40 MS patients were enrolled in the study. Demographic, socioeconomic and medical statuses were recorded. Disability [Expanded Disability Status Scale (EDSS], functional balance [Berg Balance Scale (BBS], perceived level of balance confidence in everyday tasks [Activities-specific Balance Confidence (ABC Scale], fatigue [Fatigue Impact Scale (FIS], and QoL [Multiple Sclerosis International Quality of Life (MusiQoL questionnaire] were assessed at baseline and 3 months later. All participants received standardized 12-weeks HEP from an experienced physiotherapist. Results: There were no statistically significant differences in EDSS scores before and after treatment (p=0.41. All patients showed significant improvement in BBS, ABC scale, and MusiQoL scores (p<0.001, and in the cognitive, physical and social components of FIS from baseline to three months (p=0.002, p=0.001, p=0.002, respectively. A statistically significant difference was not found in FIS-total scores (p=0.060. A positive significant correlation was found between MusiQoL and FIS-total scores (p<0.001, cognitive (p=0.004, physical and social (p<0.001 subscores; as well as negative correlation between QoL and ABC scale scores (p<0.001. Discussion: Home-based exercise program resulted in improvements in QoL, fatigue and balance functions in MS individuals. Therefore, neurological rehabilitation professionals, who are specialized on this area, have to consider the benefits of exercise and physical activity for MS patients and encourage them to take part in an exercise program. (Arc­hi­ves of Neu­ropsy­chi­atry 2012;49: 33-8

  2. 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.

  3. Numerical simulation of the fatigue behavior of additive manufactured titanium porous lattice structures.

    Science.gov (United States)

    Zargarian, A; Esfahanian, M; Kadkhodapour, J; Ziaei-Rad, S

    2016-03-01

    In this paper, the effects of cell geometry and relative density on the high-cycle fatigue behavior of Titanium scaffolds produced by selective laser melting and electron beam melting techniques were numerically investigated by finite element analysis. The regular titanium lattice samples with three different unit cell geometries, namely, diamond, rhombic dodecahedron and truncated cuboctahedron, and the relative density range of 0.1-0.3 were analyzed under uniaxial cyclic compressive loading. A failure event based algorithm was employed to simulate fatigue failure in the cellular material. Stress-life approach was used to model fatigue failure of both bulk (struts) and cellular material. The predicted fatigue life and the damage pattern of all three structures were found to be in good agreement with the experimental fatigue investigations published in the literature. The results also showed that the relationship between fatigue strength and cycles to failure obeyed the power law. The coefficient of power function was shown to depend on relative density, geometry and fatigue properties of the bulk material while the exponent was only dependent on the fatigue behavior of the bulk material. The results also indicated the failure surface at an angle of 45° to the loading direction. PMID:26706539

  4. Evolution of a laser shock peened residual stress field locally with foreign object damage and subsequent fatigue crack growth

    International Nuclear Information System (INIS)

    Foreign object damage (FOD) can seriously shorten the fatigue lives of components. On the other hand, laser shock peening improves fatigue life by introducing deep compressive residual stress into components. In this paper we examine how the non-uniform steep residual stress profile arising from FOD of laser peened aerofoil leading edges varies as a function of fatigue crack growth under high cycle fatigue and mixed high and low cycle fatigue conditions. The ballistic FOD impacts were introduced by impacting a cube edge head-on (at an angle of 0°) to the leading edge. The residual stress distributions have been mapped by synchrotron X-ray diffraction prior to cracking and subsequent to short (?1 mm) and long (up to 6 mm) crack growth. The results suggest that the local residual stress field is highly stable even to the growth of relatively long cracks

  5. Validation of the fatigue life of thermo mechanical stressed cast iron cylinder heads; Lebensdauerbewertung von thermo-mechanisch belasteten Gusseisen-Zylinderkoepfen

    Energy Technology Data Exchange (ETDEWEB)

    Leidenfrost, Marc; Werner, Ewald [TU Muenchen, Garching (Germany). Lehrstuhl fuer Werkstoffkunde; Meyer, Dietrich [MAN Truck und Bus AG (Germany)

    2011-07-01

    Mechanical and thermal loads increased considerably in modern diesel engines. This demands a detailed analysis of the ''hightemperature'' parts, for example the cylinder heads. Depending on the used material the higher thermo mechanical fatigue (TMF) limits the life-time dramatically. Besides time and cost intensive thermo-shock engine tests the numerical simulation (finite-element-method) is preferentially applied for the life-time evaluation. To achieve quantitative statements about the fatigue life a comparison must be made between numerical simulation and test results. The present article describes the proceeding in the numerical simulation to represent realistically the test. Also, the employed mathematical models for the description of the material and the fatigue life in numerical simulation are briefly introduced. Finally the results of the test and of the numerical simulation are compared and discussed. (orig.)

  6. Effect of rare earth Ce on the fatigue life of SnAgCu solder joints in WLCSP device using FEM and experiments

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liang, E-mail: zhangliangjsnu@126.com [School of Mechanical and Electrical Engineering, Jiangsu Normal University, Xuzhou 221116 (China); Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Han, Ji-guang; Guo, Yong-huan; He, Cheng-wen [School of Mechanical and Electrical Engineering, Jiangsu Normal University, Xuzhou 221116 (China)

    2014-03-01

    With the addition of 0.03 wt% rare earth Ce, in our previous works, the properties of SnAgCu solder were enhanced obviously. Based on the Garofalo–Arrhenius creep constitutive model, finite element method was used to simulate the stress–strain response during thermal cycle loading, and combined with the fatigue life prediction models, the fatigue life of SnAgCu/SnAgCuCe solder joints was calculated respectively, which can demonstrate the effect of the rare earth Ce on the fatigue life of SnAgCu solder joints. The results indicated that the maximum stress–strain can be found on the top surface of the corner solder joint, and the warpage of the PCB substrate occurred during thermal cycle loading. The trends obtained from modeling results have a good agreement with the experimental data reported in the literature for WLCSP devices. In addition, the stress–strain of SnAgCuCe solder joints is lower than that of SnAgCu solder joints. The thermal fatigue lives of solder joints calculated based on the creep model and creep strain energy density model show that the fatigue life of SnAgCuCe solder joints is higher than the SnAgCu solder joints. The fatigue life of SnAgCuCe solder joints can be enhanced significantly with the addition of Ce, is 30.2% higher than that of SnAgCu solder joints, which can be attributed to the CeSn{sub 3} particles formed resisting the motion of dislocation; moreover, the refinement of microstructure and the IMC sizes also contribute to the enhancement of fatigue life, which elucidates that SnAgCuCe solder can be utilized in electronic industry with high reliability replacing the SnAgCu solder.

  7. Influence of phosphorus content and quenching/tempering temperatures on fracture toughness and fatigue life of SAE 5160 steel

    Scientific Electronic Library Online (English)

    Danilo Borges Villarino de, Castro; Jaime Milan, Ventura; Cassius Olivio Figueiredo Terra, Ruckert; Dirceu, Spinelli; Waldek Wladimir, Bose Filho.

    2010-12-01

    Full Text Available This study investigates the influence of quenching/tempering temperatures on the fracture toughness and fatigue life of SAE 5160 steel, considering different phosphorus contents. Quenching and tempering treatments were applied to samples removed from different bars of commercial SAE 5160 steel with [...] different P content. Three different austenitizing temperatures for quenching: 850, 900 and 1000 ºC and a constant holding time of 15 minutes were used. The oil temperature for quenching was kept at 66 ºC and the tempering conditions were 470, 500 and 530 ºC with the necessary time for a final hardness of 45 ± 3 HRC. Therefore, the heat treatments cycles were applied to specimens containing low (0.012 wt. (%)), medium (0.017 wt. (%)) and high (above 0.025 wt. (%)) phosphorus contents, in order to observe the effects of this element on the susceptibility of these steels to enhance quench and tempering embrittlements. The Charpy tests results showed that the phosphorus content analyzed in this work has caused embrittlement, even in the bars with the lowest P content, leading to intergranular fracture. However, if the nucleation life is taken into consideration, this embrittlement has no effect on the nucleation fatigue life of the component.

  8. 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

    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 when the waves are large and nonlinear and most notably for small wind speeds. In case of strong velocities and turbulent wind, the excitation is damped out. In the monopile no excitation of the force is seen, but even for turbulent strong wind the wave affects the forces in the pile significantly. The analysis indicates that the nonlinearity of the waves can change the fatigue damage level significantly in particular when the wave and wind direction is misaligned.

  9. Effect of machining damage on low cycle fatigue crack initiation life in drilled holes in UdimetRTM 720

    Science.gov (United States)

    Magadanz, Christine M.

    White layer is a generic term for a light etching surface layer on metal alloys that can result under extreme deformation conditions in wear, sliding or machining. While there has been some characterization of white layer due to abusive machining, the specific effect on fatigue crack initiation life has not been well documented. This study aimed to establish a relationship between the presence of white layer due to abusive machining and fatigue crack initiation life in a wrought nickel based superalloy (Udimet ® 720). Low cycle fatigue testing was conducted on large specimens containing through holes drilled with parameters aimed at creating holes with and without white layer. Initially, Acoustic Emission monitoring technologies were used to monitor for acoustic events associated with crack initiation, however, this technology was deemed unreliable for this testing. Instead, cycles to crack initiation was determined using striation density measurements on each fracture surface to estimate the number of cycles of crack propagation, which was subtracted from the total number of cycles for the specimen. A total of sixteen specimens were tested in this manner. The results suggested that the crack initiation lives of holes machined with good machining parameters were statistically longer than crack initiation lives of holes machined with poor machining parameters. The mean initiation life of the poorly machined specimens was a factor of approximately 2 times shorter than the mean initiation life of the well machined specimens. The holes machined with good machining parameters exhibited subsurface initiations which suggested that no anomalies affected crack initiation for these specimens. It was also shown that some of the poorly machined holes exhibited subsurface initiations rather than initiations at white layer damage. These holes had better surface finish than the poorly machined specimens that did fail at white layer. The mean initiation life of the poorly machined holes with subsurface initiation was 7 times longer than the mean initiation life of the holes that exhibited white layer at the crack origins. Lastly, no apparent correlation between white layer thickness and initiation life was demonstrated in this study.

  10. Applications of a new magnetic monitoring technique to in situ evaluation of fatigue damage in ferrous components

    International Nuclear Information System (INIS)

    This project consisted of research into the use of magnetic inspection methods for the estimation of fatigue life of nuclear pressure vessel steel. Estimating the mechanical and magnetic properties of ferromagnetic materials are closely interrelated, therefore, measurements of magnetic properties could be used to monitor the evolution of fatigue damage in specimens subjected to cyclic loading. Results have shown that is possible to monitor the fatigue damage nondestructively by magnetic techniques. For example, in load-controlled high-cycle fatigue tests, it has been found that the plastic strain and coercivity accumulate logarithmically during the fatigue process. Thus a quantitative relationship between coercivity and the number of fatigue cycles could be established based on two empirical coefficients, which can be determined from the test conditions and material properties. Also it was found that prediction of the onset of fatigue failure in steels was possible under certain conditions. In strain-controlled low cycle fatigue, critical changes in Barkhausen emissions, coercivity and hysteresis loss occurred in the last ten to twenty percent of fatigue life

  11. Ion-bombardment effects on the fatigue life of stainless steel under simulated fusion first-wall conditions

    International Nuclear Information System (INIS)

    An experiment which uses the MITR-II 5 MW research reactor to simulate several aspects of the anticipated environment of a fusion reactor first wall is described. Pressurized tube specimens are subjected simultaneously to stress and temperature cycling, surface bombardment by energetic helium and lithium ions and bulk irradiation by high-energy neutrons. Analysis of the samples is aimed primarily at determining the behavior of the ion bombarded surface layer, which has a depth of 2.5 ?m, with particular reference to possible effects on the fatigue life of the material

  12. Life Management Technique of Thermal Fatigue for SMST Boiler Tube at Different Heating Zone Using Smithy Furnace

    Directory of Open Access Journals (Sweden)

    Shekhar Pal,

    2014-06-01

    Full Text Available This paper highlights on the evaluation of thermal fatigue failure for SMST (Salzgitter Mannesmann strain less boiler tube DMV 304 HCu boiler tube using life management technique by using of smithy furnace. Boiler tubes are highly affected by operating conditions like, high temperature and high pressure. So it needs periodic checking for the purpose of safety and health assessment of the plant. So using this technique we can identify the degradation of tubes at microstructure level, So that one create the current situation of the component and give respective result.

  13. The Health-Related Quality of Life for Patients with Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS)

    DEFF Research Database (Denmark)

    Falk Hvidberg, Michael; Brinth, Louise Schouborg; Olesen, Anne V; Petersen, Karin D; Ehlers, Lars

    2015-01-01

    INTRODUCTION: Myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) is a common, severe condition affecting 0.2 to 0.4 per cent of the population. Even so, no recent international EQ-5D based health-related quality of life (HRQoL) estimates exist for ME/CFS patients. The main purpose of this study was to estimate HRQoL scores using the EQ-5D-3L with Danish time trade-off tariffs. Secondary, the aims were to explore whether the results are not influenced by other conditions using regressi...

  14. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    International Nuclear Information System (INIS)

    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

  15. The impact of physical activity on fatigue and quality of life in lung cancer patients: a randomised controlled trial protocol

    Directory of Open Access Journals (Sweden)

    Dhillon Haryana M

    2012-12-01

    Full Text Available Abstract Background People with lung cancer have substantial symptom burden and more unmet needs than the general cancer population. Physical activity (PA has been shown to positively influence quality of life (QOL, fatigue and daily functioning in the curative treatment of people with breast and colorectal cancers and lung diseases, as well as in palliative settings. A randomised controlled trial (RCT is needed to determine if lung cancer patients benefit from structured PA intervention. The Physical Activity in Lung Cancer (PAL trial is designed to evaluate the impact of a 2-month PA intervention on fatigue and QOL in patients with non-resectable lung cancer. Biological mechanisms will also be studied. Methods/design A multi-centre RCT with patients randomised to usual care or a 2-month PA programme, involving supervised PA sessions including a behavioural change component and home-based PA. QOL questionnaires, disease and functional status and body composition will be assessed at baseline, 2, 4 and 6 months follow-up. The primary endpoint is comparative levels of fatigue between the 2 arms. Secondary endpoints include: QOL, functional abilities and physical function. Exploratory endpoints include: anxiety, depression, distress, dyspnoea, PA behaviour, fitness, hospitalisations, survival, cytokines and insulin-like growth factor levels. Discussion This study will provide high-level evidence of the effect of PA programmes on cancer-related fatigue and QOL in patients with advanced lung cancer. If positive, the study has the potential to change care for people with cancer using a simple, inexpensive intervention to improve their QOL and help them maintain independent function for as long as possible. Trial registration Australian New Zealand Clinical Trials Registry No. ACTRN12609000971235

  16. The fatigue life of steel plate girders subjected to repeated loading.

    Czech Academy of Sciences Publication Activity Database

    Škaloud, Miroslav; Zörnerová, Marie

    Praha : ?eské Vysoké U?ení v Praze, 2003 - (Studni?ka, J.), s. 403 -408 ISBN 80-01-02747-3. [?esko-slovenská konference s mezinárodní ú?astí - Ocelové konstrukce a mosty /20./. Praha (CZ), 17.09.2003-20.09.2003] R&D Projects: GA ?R GA103/03/0003; GA ?R GA103/02/0008 Institutional research plan: CEZ:AV0Z2071913 Keywords : web breathing * fatigue crack * fatigue limit state Subject RIV: JM - Building Engineering

  17. Approach to a Method of Integrated Evaluation of Thermal Fatigue and its Validation Using SPECTRA

    Science.gov (United States)

    Oumaya, Toru; Nakamura, Akira; Takenaka, Nobuyuki

    Thermal fatigue may initiate at a T-junction or a branched off line where high and low temperature fluids mix. These are common piping elements in nuclear power plants. To ensure structural integrity against thermal fatigue during the design phase, it is important to estimate thermal load from such design specifications as flow rate, temperature difference, pipe diameter, etc. IMAT-F, an evaluation method integrating thermal hydraulic and structural analysis, was developed in this study to precisely determine thermal load excluding safety margins or conservative engineering judgment. The method was validated by numerical flow simulations of high-cycle thermal fatigue experiment SPECTRA, conducted by Japan Atomic Energy Agency. Results confirmed that IMAT-F can accurately simulate fluid and pipe wall temperature fluctuation using fluid-structure coupled analysis. Thermal stress fluctuation resulting from distribution of temperature fluctuation in the pipe wall was then calculated. Fluctuation fatigue life was also estimated for comparison with the experimental results.

  18. Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models

    Science.gov (United States)

    Gangloff, Richard P.; Kim, Sang-Shik

    1993-01-01

    This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on 'stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

  19. Short crack growth and fatigue life in plasma nitrided 316L stainless steel.

    Czech Academy of Sciences Publication Activity Database

    Obrtlík, Karel; Polák, Jaroslav

    Vol. 2. Amsterdam : Elsevier, 2000 - (Miannay, D.; Costa, P.; François, D.; Pineau , A.), s. 1119-1124 ISBN 0-08-042815-0. [Euromat 2000. Tours (FR), 07.11.2000-09.11.2000] R&D Projects: GA ?R GA106/97/1034; GA AV ?R IBS2041001 Subject RIV: JL - Materials Fatigue, Friction Mechanics

  20. Short crack growth and fatigue life in austenitic-ferritic duplex stainless steel.

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Zezulka, Petr

    28 2005, ?. 10 (2005), s. 923-935. ISSN 8756-758X R&D Projects: GA ?R(CZ) GA106/01/0376 Institutional research plan: CEZ:AV0Z20410507 Keywords : crack growth * crack initiation * duplex steel Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.673, year: 2004

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-12-01

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

  3. Calculation of crack growth in welded specimens under seawater conditions in order to predict fatigue life of offshore components

    International Nuclear Information System (INIS)

    Welded components in the offshore field generally are designed that no cracks should occur. Under cyclic loading cracks must be taken in account, yet. In the research work described a suitable calculation method had to be proved to predict the crack growth behaviour of offshore components in seawater and under service-like conditions. Using Paris' law the crack growth behaviour of specimens which are similar to the component (welded V-shape specimens) may be predicted quite well in air, free corrosion, under cathodic protection (-860 mV Ag/AgCl) and under a variable load sequence. The use of Wheeler's model including crack retardation yielded in a significant higher crack propagation life and therefore unconservative predictions of fatigue life. (orig.)

  4. Characterization of IMC layer and its effect on thermomechanical fatigue life of Sn–3.8Ag–0.7Cu solder joints

    International Nuclear Information System (INIS)

    Highlights: ? The IMC microstructure and growth were studied under thermal aging conditions. ? The Young’s modulus and hardness were determined for CuSn and CuNiSn IMC. ? Simulation results show that the thick IMC layer results in a lower fatigue life. ? The IMC layer with higher modulus results in a lower solder joint fatigue life. - Abstract: Intermetallic compound (IMC) growth was investigated under isothermal aging condition at 125 °C for up to 500 h. The evolution in the IMC morphology and microstructure were observed at four aging time conditions for 0, 120, 260 and 500 h, respectively. Solid state IMC growth thickness measurements were determined from scanning electron microscope (SEM) observations for Cu–Sn and Cu–Ni–Sn IMC systems. The Young’s modulus and hardness of the IMCs were determined by nanoindentation tests. A finite element analysis (FEA) was carried out to model the effect of the IMC layer on the solder joint thermal fatigue life. The nanoindentation mechanical properties of Cu6Sn5 and CuNiSn IMCs were modeled with different IMC thicknesses in the FEA simulation to study the effect of the IMC growth on the fatigue life of the solder joint. It was shown that the IMC layer reduces the fatigue life of the solder joints and thick IMC layer results in a lower fatigue life. In addition, thermal cycling test and analysis for plastic ball grid array (PBGA) package with Sn–3.8Ag–0.7Cu Pb-free solder joints was performed. The mean-time-to-failure (MTTF) for the PBGA solder joints was determined, which was used for validating the FEA simulation results.

  5. 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 two points, high response at 3 months, and this improvement was sustained until 12 months. Remaining subjects (n=9, low responders either showed inconsistent or less than one point decrease in average FSS scores in the 12 months. Energy and general health scores of RAND 36-item Health Survey (Short Form-36 increased during the study (P<0.05. Decrease in FSS scores during the 12 months was associated with shorter disease duration (r=0.511, P=0.011, and lower baseline Patient Determined Disease Steps score (rs=0.563, P=0.005 and EDSS scores (rs=0.501, P=0.012. Compared to low responders, high responders had lower level of physical disability (P<0.05 and lower intake of gluten, dairy products, and eggs (P=0.036 at baseline. High responders undertook longer duration of massage and stretches per muscle (P<0.05 in 12 months. Conclusion: A multimodal intervention may reduce fatigue and improve quality of life of subjects with progressive MS. Larger randomized controlled trials with blinded raters are needed to prove efficacy of this intervention on MS-related fatigue. Keywords: modified Paleolithic diet, exercise, neuromuscular electrical stimulation, stress management, lifestyle changes, vitamins, supplements

  6. Impurity levels and fatigue lives of pseudoelastic NiTi shape memory alloys

    International Nuclear Information System (INIS)

    In the present work we show how different oxygen (O) and carbon (C) levels affect fatigue lives of pseudoelastic NiTi shape memory alloys. We compare three alloys, one with an ultrahigh purity and two which contain the maximum accepted levels of C and O. We use bending rotation fatigue (up to cycle numbers >108) and scanning electron microscopy (for investigating microstructural details of crack initiation and growth) to study fatigue behavior. High cycle fatigue (HCF) life is governed by the number of cycles required for crack initiation. In the low cycle fatigue (LCF) regime, the high-purity alloy outperforms the materials with higher number densities of carbides and oxides. In the HCF regime, on the other hand, the high-purity and C-containing alloys show higher fatigue lives than the alloy with oxide particles. There is high experimental scatter in the HCF regime where fatigue cracks preferentially nucleate at particle/void assemblies (PVAs) which form during processing. Cyclic crack growth follows the Paris law and does not depend on impurity levels. The results presented in the present work contribute to a better understanding of structural fatigue of pseudoelastic NiTi shape memory alloys

  7. Fatigue crack initiation life prediction in high strength structural steel welded joints

    Science.gov (United States)

    Tricoteaux, A.; Fardoun, F.; Degallaix, S.; Sauvage, F.

    1995-02-01

    The local approach method is used to calculate the fatigue crack initiation/early crack growth lives (N(i)) in high strength structural steel weldments. Weld-toe geometries, welding residual stresses and HAZ (heat affected zone) cyclic mechanical properties are taken into account in the N(i) estimation procedure. Fatigue crack initiation lives are calculated from either a Basquin type or a Manson-Coffin type equation. The local (HAZ) stress and strain amplitudes and the local mean stress are determined from an analysis based on the Neuber rule and the Molski-Glinka energy approach. The accuracy of the different methods is evaluated and discussed. Finally the previous methods are used with HAZ cyclic mechanical properties estimated from hardness measurements.

  8. Residual fatigue life of a pipe wall with a network of surface cracks.

    Czech Academy of Sciences Publication Activity Database

    Šperl, Martin; Gajdoš, Lubomír

    Zagreb : Studio HRG Zagreb, 2004 - (Jeci?, S.; Semenski, D.), s. 272-273 ISBN 953-96243-6-3. [DANUBIA-ADRIA Symposium on Experimental Methods in Solid Mechanics /21./. Brijuni - Pula (HR), 29.09.2004-02.10.2004] R&D Projects: GA AV ?R IAA2811201 Institutional research plan: CEZ:AV0Z2071913 Keywords : pipeline * crack * residual fatigue Subject RIV: JM - Building Engineering

  9. Evaluation of thermal stratification and primary water environment effects on fatigue life of austenitic piping

    International Nuclear Information System (INIS)

    During the last two decades, lots of efforts have been devoted to resolve thermal stratification phenomenon and primary water environment issues. While several effective methods were proposed especially in related to thermally stratified flow analyses and corrosive material resistance experiments, however, lack of details on specific stress and fatigue evaluation make it difficult to quantify structural behaviors. In the present work, effects of the thermal stratification and primary water are numerically examined from a structural integrity point of view. First, a representative austenitic nuclear piping is selected and its stress components at critical locations are calculated in use of four stratified temperature inputs and eight transient conditions. Subsequently, both metal and environmental fatigue usage factors of the piping are determined by manipulating the stress components in accordance with NUREG/CR-5704 as well as ASME B and PV Codes. Key findings from the fatigue evaluation with applicability of pipe and three-dimensional solid finite elements are fully discussed and a recommendation for realistic evaluation is suggested

  10. An improvement of fatigue lifetime estimation by taking into account the life ratio of spectrum vs. constant amplitude loading; Verbesserung der Lebensdauerabschaetzung durch Beruecksichtigung des Lebensdauervielfachen

    Energy Technology Data Exchange (ETDEWEB)

    Esderts, A.; Zenner, H. [Institut fuer Maschinelle Anlagentechnik und Betriebsfestigkeit, Technische Universitaet Clausthal, Clausthal-Zellerfeld (Germany); Hinkelmann, K.

    2012-10-15

    Fatigue life assessments of parts are frequently undertaken using the nominal stress concept. The main element in the process is the linear damage accumulation concept according Palmgren and Miner. Statistical analyses show the calculated fatigue life to commonly be on the unsafe side and the accuracy to be low. A higher accuracy would be advantageous, as the present use of effective damage sums is only an adaption. Improvements of the original Palmgren-Miner rule made use of in practical calculations have mainly been achieved by taking into account amplitudes below the fatigue limit as further damage. The method described in the following utilises a different approach. The influence of the spectrum shape and the inclination of the S-N curve under constant amplitude loading on the progression of the S-N curve under variable amplitude loading, easily made visible in statistical comparisons of calculated and experimental fatigue lives, shall be included in a new correction function. The verification of the improvement of the fatigue life estimation can be undertaken using existing experimental data of steel specimens. Furthermore calculations are carried out to find optimized parameters of two Palmgren-Miner modifications (Haibach, Liu/Zenner). (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Fatigue life evaluation based on welding residual stress relaxation and notch strain approach for cruciform welded joint

    International Nuclear Information System (INIS)

    The fatigue strength of welded joint is influenced by the welding residual stress which is relaxed depending on local stress distributed in vicinity of stress raisers, eg. under cut, overlap and blow hole. To evaluate its fatigue life the geometry of the stress raisers and the welding residual stress should be taken into account. The several methods based on notch strain approach have been proposed in order to consider the two factors above mentioned. These methods, however, have shown considerable differences between analytical and experimental results. It is due to the fact that the amount of the relaxed welding residual stress evaluated by the cyclic stress-strain relationship do not correspond with that occurred in reality. In this paper the residual stress relaxation model based on experimental results was used in order to reduce the discrepancy of the estimated amount of the relaxed welding residual stress. Under an assumption of the superimposition of the relaxed welding residual stress and the local stress, a modified notch strain approach was proposed and verified to the cruciform welded joint

  12. Fatigue of stainless steel

    International Nuclear Information System (INIS)

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

  13. 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

    Full Text Available Plastics belong to the most complex and probably least understood engineering materials of today. Combining the best aspects of design, mechanical properties and manufacturing, the structural integrity of plastics is on par with aluminium and can in some cases even rival those of steels. One of the most important aspects of plastics is the ability to tailor-drive their material properties for a specific purpose or towards a specific strength value. The morphology of plastics is directly dependent on the manufacturing process, e.g. injection moulding, extruding and casting. Plastics contain multiple phases (crystalline, amorphous, oriented, and are in no sense at all isotropic, although integrally deduced mechanical properties may appear to claim the opposite. As such, it becomes obvious that attempting to analyse such materials using conventional material models and explanations of mechanics is an inherently complex task. The static situation alone requires concepts such as creep, relaxation and rate effects to be incorporated on a numerical level. If the load situation changes, such that cyclic loading is acting on the continuum, with the morphology taken into account (without considering the actual geometrical shape, then the result is that of a complex multiaxial fatigue case. Classical theories used for treating fatigue such as SN or eN analysis have proven much less successful for plastics than they have for metals. Fatigue crack propagation using fracture mechanics has seen some success in application, although appropriate crack initiation criteria still need to be established. The physical facts are more than intriguing. For injection moulded parts (being the most common manufacturing process in place, fracture is in most cases seen to initiate from inside the material, unless the surface has been mechanically compromised. This appears to hold true regardless of the load case. In this review, we have scrutinised physically useful methods 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

  14. Overview of the fatigue/fracture/life prediction working group program at the Lewis Research Center

    Science.gov (United States)

    Mcgaw, Michael A.

    1991-01-01

    The objective is to develop and verify constitutive and life prediction models for materials typically used in hot gas path components of reusable space propulsion systems over the range of relevant operative environments. The efforts were concentrated on the development of crack initiation life prediction methods and on the development of cyclic crack propagation and fracture life prediction methods.

  15. Relation between constraint and fatigue crack growth rate.

    Czech Academy of Sciences Publication Activity Database

    Huta?, Pavel; Knésl, Zden?k

    Atlanta : Elsevier, 2006, s. 1-9. [Fatigue 2006. Atlanta (US), 14.05.2006-19.05.2006] R&D Projects: GA ?R GA101/03/0331; GA ?R GP106/06/P239 Institutional research plan: CEZ:AV0Z20410507 Keywords : constraint * T- stress * high cycle fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics

  16. Experimental characterisation and modelling of crack initiation and short crack propagation for fatigue life prediction of a ?-titanium alloy

    International Nuclear Information System (INIS)

    Up to 90% of the life time of cyclically loaded components is determined by short crack initiation and propagation. This stage of the fatigue damage process is strongly influenced by microstructural features, e.g. grain boundaries and crystallographic grain orientation. Therefore LEFM can not be applied in a reasonable manner explaining the demand for a mechanism-related modelling method. The present study deals with mechanical testing and microstructural examinations applied to the relatively new ?-titanium alloy LCB. The results are used as data base to develop a new short crack model that is based on the model of Navarro and de los Rios. By using various techniques such as electron back-scattered diffraction and finite-element calculations the origin of crack initiation is revealed and the characteristics of crack propagation is determined. (orig.)

  17. Response Surface Approximation for Fatigue Life Prediction and Its Application to Multi-Criteria Optimization With a Priori Preference Information

    International Nuclear Information System (INIS)

    In this paper, a versatile multi-criteria optimization concept for fatigue life prediction is introduced. Multi-criteria decision making in engineering design refers to obtaining a preferred optimal solution in the context of conflicting design objectives. Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a response surface model, the compromise decision support problem, which is a multi-objective formulation based on goal programming. Examples illustrate the concepts and demonstrate their applicability

  18. Application of a thermal fatigue life prediction model to high-temperature aerospace alloys B1900 + Hf and Haynes 188

    Science.gov (United States)

    Halford, G. R.; Salisman, J. F.; Verrilli, M. J.; Arya, V.

    1992-01-01

    The results of the application of a newly proposed thermomechanical fatigue (TMF) life prediction method to a series of laboratory TMF results on two high-temperature aerospace engine alloys are presented. The method, referred to as TMF/TS-SRP, is based on three relatively recent developments: the total strain version of the method of Strain Range Partitioning (TS-SRP), the bithermal testing technique for characterizing TMF behavior, and advanced viscoplastic constitutive models. The high-temperature data reported in a companion publication are used to evaluate the constants in the model and to provide the TMF verification data to check its accuracy. Predicted lives are in agreement with the experimental lives to within a factor of approximately 2.

  19. Plane strain crack growth models for fatigue crack growth life predictions

    International Nuclear Information System (INIS)

    This paper discusses the development of a crack closure expression for the 4-point bend specimen using numerical results obtained from a modified strip-yield model. Data from tests of eight 4-point bend specimens were used to estimate the specimen constraint factor (stress triaxiality effect). The constraint factor was then used in the estimation of the crack opening stresses for each of the bend tests. The numerically estimated crack opening stresses were used to develop an effective stress intensity factor range, ?Keff. The resulting crack growth rate data when plotted versus ?Keff resulted in a material fatigue crack growth rate property curve independent of test specimen type, stress level, and R-ratio. Fatigue crack growth rate data from center cracked panels using Newman's crack closure model, from compact specimens using Eason's R-ratio expression, and from bend specimens using the model discussed in this paper are all shown to fall along the same straight line (on log-log paper) when plotted versus ?Keff even though crack closure differs for each specimen type

  20. Study on creep-fatigue evaluation procedures for high-chromium steels-Part I: Test results and life prediction based on measured stress relaxation

    International Nuclear Information System (INIS)

    Strong demand for improving thermal efficiency of power generation plants promoted the use of high-chromium steels, which have high creep strength and corrosion resistance. Aiming at cost reduction for future nuclear power plants, these materials are also regarded as candidates for structural materials, being favoured for lower thermal expansion rate compared with austenitic stainless steels. In structural design and life management of these plants, failure due to the combination of fatigue and creep damages has been considered as an important phenomenon to be evaluated, in addition to simple creep failure under sustained loading such as inner pressure. The author has been conducting a series of creep-fatigue tests for three types of high-chromium steels used in fossil power plants and the applicability of life prediction methods has been studied. It was found that the time fraction rule gives a relatively small amount of creep damage and overpredicts the failure life, whereas a simple ductility exhaustion method provides very large creep damage which leads to too conservative prediction of failure lives. A modified ductility exhaustion method developed on the re-definition of creep damage as a ductility consumer gave a moderate amount of creep damage and provided reasonable life predictability. Moreover, an empirical formula was derived which can represent the life reduction in compressive hold tests as a function of pure fatigue life and hold time

  1. 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

    International Nuclear Information System (INIS)

    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. 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. 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 trajectory. NKCA was also similar between therapy groups but additional post hoc analysis revealed that better quality of life significantly predicted higher NKCA regardless of therapy. Compared to WBRT, PBRT results in more rapid recovery from cancer-related fatigue with improved restoration of quality of life after radiation therapy. Additionally, better quality of life predicts higher NKCA against tumor targets, emphasizing the importance of fostering quality of life for women undergoing adjuvant radiation therapy

  2. Developments in new aircraft tire tread materials. [fatigue life of elastomeric materials

    Science.gov (United States)

    Yager, T. J.; Mccarty, J. L.; Riccitiello, S. R.; Golub, M. A.

    1976-01-01

    Comparative laboratory and field tests were conducted on experimental and state-of-the-art aircraft tire tread materials in a program aimed at seeking new elastomeric materials which would provide improved aircraft tire tread wear, traction, and blowout resistance in the interests of operational safety and economy. The experimental stock was formulated of natural rubber and amorphous vinyl polybutadiene to provide high thermal-oxidative resistance, a characteristic pursued on the premise that thermal oxidation is involved both in the normal abrasion or wear of tire treads and probably in the chain of events leading to blowout failures. Results from the tests demonstrate that the experimental stock provided better heat buildup (hysteresis) and fatigue properties, at least equal wet and dry traction, and greater wear resistance than the state-of-the-art stock.

  3. Micromechanical study of the effect of inclusions on fatigue failure in a roller bearing

    DEFF Research Database (Denmark)

    Cerullo, Michele; Tvergaard, Viggo

    2015-01-01

    Purpose - The purpose of this paper is to carry out a set of micromechanical analyses to study the effect of small inclusions on fatigue life of wind turbine bearings. Design/methodology/approach - The local stress concentrations around an inclusion are determined from a characteristic unit cell model containing a single inclusion, using the approximation of a 2D plane strain numerical analysis. The Dang Van multiaxial fatigue criterion is used for the local stresses in the matrix material, to ensure that the stresses remain within the fatigue limit. The matrix material is taken to be one of the most commonly used bearing steels, AISI 52100, and two different types of inclusions are considered. The macroscopic stress histories applied correspond to either a Hertzian or an elastohydrodynamic (EHL) contact pressure distribution under the rollers. Findings - The paper shows that sub-surface fatigue failure due to rolling contact is more likely to develop close to the inclusion-matrix interface, at particular angles that depend on the material and on the inclusion orientation. Originality/value - Inclusions represent an important issue in the design of wind turbine bearings, that are supposed to work in the very high cycle regime (N>109 cycles). This paper develops a micromechanical study that provides a deeper understanding on effect of inclusions on the fatigue life, according to one of the most used multiaxial fatigue criteria.

  4. Review of fatigue criteria development for HTGR core supports

    International Nuclear Information System (INIS)

    Fatigue criteria for HTGR core support graphite structure are presented. The criteria takes into consideration the brittle nature of the material, and emphasizes the probabilistic approach in the treatment of strength data. The stress analysis is still deterministic. The conventional cumulative damage approach is adopted here. A specified minimum S-N curve is defined as the curve with 99% probability of survival at a 95% confidence level to accommodate random variability of the material strength. A constant life diagram is constructed to reconcile the effect of mean stress. The linear damage rule is assumed to account for the effect of random cycles. An additional factor of safety of three on cycles is recommended. The uniaxial S-N curve is modified in the medium-to-high cycle range (> 2 x 103 cycles) for mutiaxial fatigue effects

  5. 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

    2014-01-01

    Background: 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. Materials and Methods: 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. Results: 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 < 0.01). Hierarchical regression analysis indicated that among the predictor variables in the final step, fatigue, depression, and anxiety were identified as the physical component summary predictor variables. Anxiety was found to be the most powerful predictor variable amongst all (? = ?0.46, P < 0.001). Furthermore, results have shown depression as the only significant mental component summary predictor variable (? = ?0.39, P < 0.001). Conclusions: This study has highlighted the role of anxiety, fatigue, and depression in physical dimensions and the role of depression in psychological dimensions of the lives of 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. PMID:25558256

  6. The effect of anodic oxide coating on the fatigue behaviour of AA6082 with an ultrafine-grained microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, L.; Haendel, M.; Halle, T.; Nickel, D.; Alisch, G.; Lampke, T. [Technische Universitaet Chemnitz, Institut fuer Werkstoffwissenschaft und Werkstofftechnik, Chemnitz (Germany); Hockauf, K.

    2011-07-15

    In this work, the high-cycle fatigue behaviour of the precipitation hardening aluminium wrought alloy AA6082 was investigated for a conventionally-grained and an ultrafine-grained substrate condition, with each a hard and a soft electrolytic anodic oxide (EAO) coating. The investigations were focused on the susceptibility of the coatings to anodising- and fatigue-induced cracking of the coatings and its impact on the fatigue life. For both substrate materials, the fatigue strength of the coated specimens was significantly reduced compared to the uncoated materials. Considering the resistance to crack initiation in the coating, the soft-anodised coatings were found to be superior compared to the hard-anodised ones. Moreover, the coatings on the ultrafine-grained substrate showed an enhanced resistance to anodising-induced as well as fatigue-induced cracking. However, it is supposed that the lower resistance to crack transition from the coating into the substrate is one of the most important factors which strongly limits the fatigue life of the EAO-coated specimens. This might be the reason why the fatigue strength of the ultrafine-grained substrates is relatively low, despite their higher resistance to crack initiation. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Work capacity and health-related quality of life among individuals with multiple sclerosis reduced by fatigue: a cross-sectional study

    Science.gov (United States)

    2013-01-01

    Background Among individuals diagnosed with the chronic neurologic disease, multiple sclerosis (MS), a majority suffers from fatigue, which strongly influences their every-day-life. The aim of this study was to investigate work capacity and health-related quality of life (HRQoL) in a group of MS patients and also to investigate if work capacity and HRQoL could be predicted by background factors, fatigue, heat sensitivity, cognitive dysfunction, emotional distress or degree of disability. Methods A descriptive, cross-sectional, designed survey was undertaken A questionnaire was sent to 323 individuals diagnosed with MS, aged between 20 and 65 years, with physical disability on the expanded disability status score (EDSS) in the interval 0???EDSS???6.5, living in Östergötland county in eastern Sweden. Questions on background factors, occupation and work, together with the health-related quality of life short form instrument (SF-36), the fatigue severity scale (FSS), the perceived deficit questionnaire (PDQ) and the hospital anxiety depression scale (HAD) were posed. Associations between variables were analyzed using Pearson’s and Spearman’s correlations. Differences between groups were tested using the Chi-square test, the Mann Whitney U-test, and the Student’s t-test. Predictive factors were analyzed using multiple linear and multiple logistic regression analysis. Results Of those who completed the questionnaire (n?=?257, 79.6%), 59.8% were working. Work capacity was found significantly more among men (p?fatigue (p?fatigue, higher level of education, male sex and lower age. Those with work capacity showed significantly higher HRQoL than those who had no work capacity (p?fatigue, cognition and emotional distress were found to be major contributing factors for HRQoL. Conclusions Work capacity and HRQoL among individuals diagnosed with MS are highly influenced by fatigue which can be considered as a key symptom. Work capacity was influenced by heat-sensitivity, cognitive difficulties and emotional distress and significant predictive factors besides fatigue, were physical disability (EDSS), age, sex, and level of education. Remaining at work also gives a better HRQoL. PMID:23497281

  8. Half-cycle slip activity of persistent slip bands at different stages of fatigue life of polycrystalline nickel

    International Nuclear Information System (INIS)

    The slip activity of persistent slip bands (PSBs) in polycrystalline nickel was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The half-cycle slip activity as well as the local shear strain amplitudes was investigated after half-cycle deformation at different numbers of cycles in the domain of stress saturation. Moreover, the fraction of grains containing cumulated PSBs and the accumulated volume fraction of PSBs was estimated depending on the number of cycles during fatigue life. The volume fraction of active PSBs during half-cycle deformation is significantly lower than the cumulated PSB volume and decreases with increasing number of cycles. Additionally, an increasing localization of cyclic plastic strain within the PSBs was observed. However, with increasing number of cycles the average local shear strain amplitude remains almost unchanged. Thus, PSBs in polycrystals are subjected to a life history which is characterized by active and inactive periods of their half-cycle slip activity during cyclic deformation at different stages of the saturation state

  9. Effect of Porosity on the Fatigue Life of Cast AC4C-T6 Alloy for Lcd Glass Transfer Robot

    Science.gov (United States)

    Shim, Hee-Jin; Kim, Jung-Kyu

    Aluminium has good corrosion properties and a high strength to weight reduction which makes it favourable in many applications. The increased use of aluminium casting in the automotive industry does also imply that the need for design data for aluminium increases. Especially for castings, the influences of casting defects are always an issue. For this reason fatigue properties for as-cast sand and permanent mould specimens with different contents of porosity have been studied. The cast aluminium specimens of two different porosities were fatigue tested in cyclic axial test at R=-1. Prior to fatigue test specimens were examined by CT-scan and sorted into two quality groups depending on the porosity level. The aim of this work was to investigate the fatigue life for cast AC4C-T6 alloy with different amounts of inherent porosity. An additional aim was to predict the durability for cast components with defect constrained in a specified volume of components, by using a commercial program MSC. Fatigue.

  10. Fatigue behaviour of fiberglass wind turbine blade material under variable amplitude loading

    Energy Technology Data Exchange (ETDEWEB)

    Delft, D.R.V. Van; Winkel, G.D. de [Delft Univ. of Technology, STEVIN Lab., Delft (Netherlands); Joosse, P.A. [Stork Product Engineering b.v., Amsterdam (Netherlands)

    1996-09-01

    In the work presented here fatigue tests with the WISPER and WISPERX load sequence have been carried out and analysed. The test programme includes tests at low stress levels which results in fatigue lives of 50 millions of cycles. The results are compared with constant amplitude tests in the very high cycle range, carried out in a previous programme. The results are also compared with ECN results in the lower cycle range (on identical specimens). It appeared, that the difference between the fatigue life of the specimens tested with the WISPER and the WISPERX load sequence is larger than can be expected from the theoretical damage rates. Moreover, the slope of the S-N data differs from theoretical values obtained by using commonly applied design rules. (au)

  11. Near threshold fatigue testing

    International Nuclear Information System (INIS)

    Measurement of the near-threshold fatigue crack growth rate (FCGR) behavior provides a basis for the design and evaluation of components subjected to high cycle fatigue. Typically, the near-threshold fatigue regime describes crack growth rates below approximately 10-5 mm/cycle (4x10-7 inch/cycle). One such evaluation was recently performed by the authors for the binary alloy U-6Nb. The procedures developed for this evaluation are described in detail here to provide a general test method for near-threshold FCGR testing. In particular, we describe techniques for high-resolution measurements of crack length performed in-situ through a direct current, potential drop (DCPD) apparatus, and a method which eliminates crack closure effects through the use of loading cycles with constant maximum stress intensity

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

    Science.gov (United States)

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

    2015-09-01

    We investigated whether stress may influence fatigue, or vice versa, as well as factors mediating this relationship. Fifty healthy participants (31 females, 23.6±3.2 years) completed up to 5 momentary assessments of stress and fatigue during 5 days of preparation for their final examinations (exam condition) and 5 days of a regular semester week (control condition). Sleep quality was measured by self-report at awakening. A sub-group of participants (n=25) also collected saliva samples. Fatigue was associated with concurrent stress, stress reported at the previous measurement point, and previous-day stress. However, momentary stress was also predicted by concurrent fatigue, fatigue at the previous time point, and previous-day fatigue. Sleep quality mediated the association between stress and next-day fatigue. Cortisol and alpha-amylase did not mediate the stress-fatigue relationship. In conclusion, there is a reciprocal stress-fatigue relationship. Both prevention and intervention programs should comprehensively cover how stress and fatigue might influence one another. PMID:26143479

  13. 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%, paboriginal (20% versus 3%, phousing (19% versus 1%, p<0.001) at the time they completed the survey. Co-infected patients reported more symptoms consistent with depression, increased fatigue and poorer quality of life. 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 primarily related to socio-economic issues rather than HCV infection. PMID:16036236

  14. Multi-stage fatigue life monitoring on quasi-isotropic carbon fibre reinforced polymers enhanced with multi-wall carbon nanotubes: parallel use of electrical resistance, acoustic emission, and acousto-ultrasonic techniques

    Science.gov (United States)

    Kostopoulos, V.; Vavouliotis, A.; Loutas, T.; Karapappas, P.

    2009-03-01

    In this study, CNTs were used as modifiers of the epoxy matrix of quasi-isotropic carbon fibre reinforced laminates. The prepared laminates were subjected to tensile loading and tension-tension fatigue and, the changes in the longitudinal resistance were monitored via a digital multimeter. In addition, Acoustic Emission and Acousto-Ultrasonic techniques were used for monitoring the fatigue process of the laminates. The nano-enhanced laminates on the one hand exhibited superior fatigue properties and on the other hand they demonstrated the full-potential of the material to be used as an integrated sensor to monitor the fatigue life.

  15. Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures

    OpenAIRE

    Barsoum, Zuheir

    2008-01-01

    This doctoral thesis is concerned with fatigue life of welded structures. Several topics related to fatigue of welded structures are treated such as; weld defects and their influence on fatigue performance of welded structures, fatigue life prediction using LEFM (Linear Elastic Fracture Mechanics), fatigue testing, welding simulation, residual stress prediction and measurement and their influence on fatigue life. The work that is reported in this doctoral thesis is part results of the Nordic ...

  16. Identification of acoustic emission sources in early stages of fatigue process of Inconel 713LC

    Energy Technology Data Exchange (ETDEWEB)

    Bartkova, Denisa; Vlasic, Frantisek; Mazal, Pavel [Brno Univ. of Technology, Brno (Czech Republic). Faculty of Mechanical Engineering

    2014-11-01

    Inconel 713LC is low carbon variant of Inconel 713 nickel-based cast alloy. The biggest advantage of these alloys is their ability to resist a wide variety of operating conditions (corrosive environment, high temperature, high stresses). Main area of applications is aircraft, energetic, chemical and petrochemical industry etc. In many applications, components undergo cyclic stresses. This study presents results of acoustic emission response of Inconel 713LC during high-cycle fatigue testing. In comparison with low-cycle fatigue, stage of initiation of micro cracks is in high-cycle region much more significant and can take several tens of percent of whole fatigue life. This work is focused on comparison of selected parameters of acoustic emission signal in pre-initiation and initiation stage of fatigue crack creation. Signal data were specified by linear location technique, hence only signal from shallow notch was analysed. Acoustic emission signal was correlated with frequency of load reversals which is a function of specimen's rigidity (modulus). Acoustic emission hits with higher stress were detected in pre-initiation stage whereas initiation stage hits exhibited low stress. Acoustic emission signal measurements are supplemented by fractographic and metallographic analysis.

  17. Identification of acoustic emission sources in early stages of fatigue process of Inconel 713LC

    International Nuclear Information System (INIS)

    Inconel 713LC is low carbon variant of Inconel 713 nickel-based cast alloy. The biggest advantage of these alloys is their ability to resist a wide variety of operating conditions (corrosive environment, high temperature, high stresses). Main area of applications is aircraft, energetic, chemical and petrochemical industry etc. In many applications, components undergo cyclic stresses. This study presents results of acoustic emission response of Inconel 713LC during high-cycle fatigue testing. In comparison with low-cycle fatigue, stage of initiation of micro cracks is in high-cycle region much more significant and can take several tens of percent of whole fatigue life. This work is focused on comparison of selected parameters of acoustic emission signal in pre-initiation and initiation stage of fatigue crack creation. Signal data were specified by linear location technique, hence only signal from shallow notch was analysed. Acoustic emission signal was correlated with frequency of load reversals which is a function of specimen's rigidity (modulus). Acoustic emission hits with higher stress were detected in pre-initiation stage whereas initiation stage hits exhibited low stress. Acoustic emission signal measurements are supplemented by fractographic and metallographic analysis.

  18. Fatigue Strength of Weathering Steel

    OpenAIRE

    Klusák, Jan; Petr LUKÁŠ; Ludvík KUNZ

    2012-01-01

    Fatigue behaviour of Atmofix 52 steel (comparable to COR-TENâ steel) exposed to atmospheric corrosion for 20 years was investigated. S-N curves for load symmetrical cycling and cycling with stress ratio R = 0 were determined on specimens detracted from a failed transmission tower. The data were compared with those on material without a rust layer. The fracture surfaces and, in particular, the sites of fatigue crack initiation were analyzed. Substantial decrease of fatigue life and fatigue lim...

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

    OpenAIRE

    Redik Sabine; Tauscher Markus; Grün Florian

    2014-01-01

    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 sour...

  20. Effects of resistance exercise on fatigue and quality of life in breast cancer patients undergoing adjuvant chemotherapy: A randomized controlled trial.

    Science.gov (United States)

    Schmidt, Martina E; Wiskemann, Joachim; Armbrust, Petra; Schneeweiss, Andreas; Ulrich, Cornelia M; Steindorf, Karen

    2015-07-15

    Multiple exercise interventions have shown beneficial effects on fatigue and quality of life (QoL) in cancer patients, but various psychosocial interventions as well. It is unclear to what extent the observed effects of exercise interventions are based on physical adaptations or rather on psychosocial factors associated with supervised, group-based programs. It needs to be determined which aspects of exercise programs are truly effective. Therefore, we aimed to investigate whether resistance exercise during chemotherapy provides benefits on fatigue and QoL beyond potential psychosocial effects of group-based interventions. One-hundred-one breast cancer patients starting chemotherapy were randomly assigned to resistance exercise (EX) or a relaxation control (RC) group. Both interventions were supervised, group-based, 2/week over 12 weeks. The primary endpoint fatigue was assessed with a 20-item multidimensional questionnaire, QoL with the EORTC QLQ-C30/BR23. Analyses of covariance for individual changes from baseline to Week 13 were calculated. In RC, total and physical fatigue worsened during chemotherapy, whereas EX showed no such impairments (between-group p?=?0.098 and 0.052 overall, and p?=?0.038 and 0.034 among patients without severe baseline depression). Differences regarding affective or cognitive fatigue were not significant. Benefits of EX were also seen to affect role and social function. Effect sizes were between 0.43 and 0.48. Explorative analyses indicated significant effect modification by thyroxin use (p-interaction?=?0.044). In conclusion, resistance exercise appeared to mitigate physical fatigue and maintain QoL during chemotherapy beyond psychosocial effects inherent to supervised group-based settings. Thus, resistance exercise could be an integral part of supportive care for breast cancer patients undergoing chemotherapy. PMID:25484317

  1. 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. PMID:24036849

  2. 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

    OpenAIRE

    Rahmani, Soheila; Talepasand, Siavash

    2015-01-01

    Background: 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.

  3. Physical activity and quality of life in multiple sclerosis: Intermediary roles of disability, fatigue, mood, pain, self-efficacy and social support

    OpenAIRE

    Motl, Robert W.; McAuley, Edward; Snook, Erin M.; Gliottoni, Rachael C.

    2009-01-01

    Physical activity has been associated with a small improvement in quality of life (QOL) among those with multiple sclerosis (MS). This relationship may be indirect and operate through factors such as disability, fatigue, mood, pain, self-efficacy and social support. The present study examined variables that might account for the relationship between physical activity and QOL in a sample (N = 292) of individuals with a definite diagnosis of MS. The participants wore an accelerometer for 7 days...

  4. Investigation of technological size effects of welding on the residual stresses and fatigue life of tubular joints made of structural steels S355 and S690

    OpenAIRE

    Zamiri Akhlaghi, Farshid; Acevedo, Claire; Nussbaumer, Alain; Krummenacker, Janna

    2011-01-01

    The fabrication procedure changes when changing the size of the structural components. For the weldments, the change of the welding procedure leads to the change in residual stresses which consequently affects the fatigue life of the structure. The weld size and number of welding passes are important factors which have considerable impact on the values and distribution of the welding residual stresses. This technological size effect is investigated in this study by simulating the welding proc...

  5. A supervised versus home-based program effects on liver transplanted familial amyloidotic polyneuropathy patients: walking, fatigue and quality of life

    OpenAIRE

    Tomás, Mª Teresa; Santa-Clara, Helena; Monteiro, Estela; Gil, João; Bruno, Paula Marta; Barroso, Eduardo; Sardinha, Luís

    2011-01-01

    Purpose: To evaluate the effects of a six months exercise training program on walking capacity, fatigue and health related quality of life (HRQL). Relevance: Familial amyloidotic polyneuropathy disease (FAP) is an autossomic neurodegenerative disease, related with systemic deposition of amyloidal fibre mainly on peripheral nervous system and mainly produced in the liver. FAP often results in severe functional limitations. Liver transplantation is used as the only therapy so far, that stop the...

  6. 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...

  7. Fatigue life of cast Inconel 713LC with/without protective diffusion coating under bending, torsion and their combination.

    Czech Academy of Sciences Publication Activity Database

    Sláme?ka, K.; Pokluda, J.; Kianicová, M.; Horníková, J.; Obrtlík, Karel

    2013-01-01

    Ro?. 110, SEP (2013), s. 459-467. ISSN 0013-7944 Institutional support: RVO:68081723 Keywords : nickel-based superalloys * diffusion coating * bending * torsion * multiaxial fatigue Subject RIV: JL - Materials Fatigue , Friction Mechanics Impact factor: 1.662, year: 2013

  8. Comparison of the Fatigue Performance of Commercially Produced Nitinol Samples versus Sputter-Deposited Nitinol

    Science.gov (United States)

    Siekmeyer, Gerd; Schüßler, Andreas; de Miranda, Rodrigo Lima; Quandt, Eckhard

    2014-07-01

    Self-expanding vascular implants are typically manufactured from Nitinol tubing, using laser cutting, shape setting, and electropolishing processes. The mechanical and fatigue behavior of those devices are affected by the raw material and its processing such as the melting process and subsequent warm and cold forming processes. Current trends focus on the use of raw material with fewer inclusions to improve the fatigue performance. Further device miniaturization and higher fatigue life requirements will drive the need toward smaller inclusions and new manufacturing methods. As published previously, the high-cycle fatigue region of medical devices from standard processed Nitinol is usually about 0.4-0.5% half-alternating strain. However, these results highly depend on the ingot and semi-finished materials, the applied manufacturing processes, the final dimensions of test samples, and applied test methods. Fabrication by sputter deposition is favorable, because it allows the manufacturing of micro-patterned Nitinol thin-film devices without small burrs, heat-affected zones, microcracks, or any contamination with carbides, as well as the fabrication of complex components e.g., 3D geometries. Today, however, there is limited data available on the fatigue behavior for real stent devices based on such sputter-deposited Nitinol. A detailed study (e.g., using metallographic methods, corrosion, tensile, and fatigue testing) was conducted for the first time in order to characterize the micro-patterned Nitinol thin-film material.

  9. Fatigue and quality of life in breast cancer survivors: a comparative study / Fadiga e qualidade de vida em pacientes sobreviventes de câncer de mama: um estudo comparativo

    Scientific Electronic Library Online (English)

    Ana Claudia Garabeli Cavalli, Kluthcovsky; Almir Antonio, Urbanetz.

    2015-03-01

    Full Text Available OBJETIVO: Avaliar a fadiga e a qualidade de vida de sobreviventes de câncer de mama, livres da doença, em relação a uma amostra de mulheres da mesma idade, sem histórico de câncer, e explorar a relação entre fadiga e qualidade de vida. MÉTODOS: Estudo transversal realizado com uma amostra consecuti [...] va de 202 pacientes brasileiras, sobreviventes de câncer de mama e livres da doença, que haviam completado o tratamento em 2 grandes hospitais. As pacientes foram comparadas com mulheres da mesma idade, sem história de câncer, acompanhadas em uma Unidade Básica de Saúde. A Escala de Fadiga de Piper-Revisada e o World Health Organization Quality of Life Instrument (WHOQOL-BREF) foram usados para avaliar a fadiga e a qualidade de vida, respectivamente. Dados sociodemográficos e clínicos também foram obtidos. O teste do ?2, modelo linear generalizado e coeficiente de correlação de Spearman foram utilizados para fins estatísticos. Foi adotado o nível de significância de 5%. RESULTADOS: As sobreviventes de câncer de mama apresentaram significativamente maiores escores de fadiga total e das subescalas do que o grupo controle (todos os valores de p Abstract in english PURPOSE: To assess fatigue and quality of life in disease-free breast cancer survivors in relation to a sample of age-matched women with no cancer history and to explore the relationship between fatigue and quality of life. METHODS: A cross-sectional study was conducted in a sample of 202 consecuti [...] ve disease-free Brazilian breast cancer survivors, all of whom had completed treatment, treated at 2 large hospitals. The patients were compared to age-matched women with no cancer history attending a primary health care center. The Piper Fatigue Scale-Revised and the World Health Organization Quality of Life Instrument (WHOQOL-BREF) were used to measure the fatigue and quality of life, respectively. Socio-demographic and clinical variables were also obtained. The ?2 test, generalized linear model, and Spearman correlation coefficient were used for statistical purposes. The adopted level of significance was 5%. RESULTS: Breast cancer survivors experienced significantly greater total and subscale fatigue scores than comparison group (all p-values

  10. The Nature of Fatigue in Chronic Fatigue Syndrome.

    Science.gov (United States)

    Olson, Karin; Zimka, Oksana; Stein, Eleanor

    2015-10-01

    In this article, we report the findings of our study on the nature of fatigue in patients diagnosed with chronic fatigue syndrome. Using ethnoscience as a design, we conducted a series of unstructured interviews and card sorts to learn more about how people with chronic fatigue syndrome describe fatigue. Participants (N = 14) described three distinct domains: tiredness, fatigue, and exhaustion. Most participants experienced tiredness prior to diagnosis, fatigue during daily life, and exhaustion after overexertion. We also discuss participants' ability to adapt to a variety of stressors and prevent shifts to exhaustion, and relate our findings to stress theory and other current research. Primary strategies that promoted adaptation to stressors included pacing and extended rest periods. These findings can aid health care professionals in detecting impending shifts between tiredness, fatigue, and exhaustion and in improving adaptive strategies, thereby improving quality of life. PMID:25721719

  11. Influence of microstructure and load ratio on cyclic fatigue and final fracture behavior of two high strength steels

    International Nuclear Information System (INIS)

    Highlights: • The study was aimed at understanding effects of load ratios on fatigue properties. • The steels have better mechanical properties in comparison with rest in this category. • The steels were cyclically deformed at two different load ratios. • SEM was used to characterize the intrinsic features on the fracture surface. - Abstract: The results of a recent study aimed at understanding the conjoint influence of load ratio and microstructure on the high cycle fatigue properties and resultant fracture behavior of two high strength alloy steels is presented and discussed. Both the chosen alloy steels, i.e., AerMet® 100 and PremoMet™ 290 have much better strength and ductility properties to offer in comparison with the other competing high strength steels having near similar chemical composition. Test specimens were precision machined from the as-provided stock of each steel. The machined specimens were deformed in both uniaxial tension and cyclic fatigue under conditions of stress control. The test specimens of each alloy steel were cyclically deformed over a range of maximum stress at two different load ratios and the number of cycles to failure recorded. The specific influence of load ratio on cyclic fatigue life is presented and discussed keeping in mind the maximum stress used during cyclic deformation. The fatigue fracture surfaces were examined in a scanning electron microscope to establish the macroscopic mode and to concurrently characterize the intrinsic features on the fracture surface. The conjoint influence of nature of loading, maximum stress and microstructure on cyclic fatigue life is discussed

  12. Fatigue life enhancement of high reliability metallic components by laser shock processing

    Science.gov (United States)

    Ocaña, J. L.; Porro, J. A.; Díaz, M.; Ruiz de Lara, L.; Correa, C.; Peral, D.

    2015-03-01

    Laser shock processing (LSP) is increasingly applied as an effective technology for the improvement of metallic materials mechanical properties in different types of components as a means of enhancement of their mechanical behavior. As reported in the literature, a main effect resulting from the application of the LSP technique consists on the generation of relatively deep compression residual stresses field into metallic alloy pieces allowing the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Additional results accomplished by the authors in the line of practical development of the LSP technique at an experimental level (aiming its integral assessment from an interrelated theoretical and experimental point of view) are presented in this paper. Concretely, experimental results on the residual stress profiles and associated mechanical properties modification successfully reached in typical materials under different LSP irradiation conditions are presented along with a practical correlated analysis on the protective character of the residual stress profiles obtained under different irradiation strategies. In this case, the specific behavior of a widely used material in high reliability components (especially in nuclear and biomedical applications) as AISI 316L is analyzed, the effect of possible "in-service" thermal conditions on the relaxation of the LSP effects being specifically characterized.

  13. Life time evaluation of spectrum loaded machine parts

    Energy Technology Data Exchange (ETDEWEB)

    Rabb, R. [Waertsilae NSD Corporation, Vaasa (Finland)

    1998-12-31

    In a medium speed diesel engine there are some important components, such as the cylinder head, the piston and the cylinder liner, which are subjected to a specific load spectrum consisting of mainly two distinct parts. One is the low cycle part which is due to the temperature field that builds up after that the engine has been started. This low cycle part causes a big stress amplitude but consists of only a couple of thousand cycles during the engine life time. The other part of the load spectrum is the high cycle part due to the firing pressure. The high cycle part has a smaller amplitude but consists of billions of cycles during the engine life time. The cylinder head and the cylinder liner are made of cast iron. In this investigation the true extension into the high cycle domain of the S-N curve for grey cast iron grade 300/ISO 185 was established through fatigue tests with a load spectrum resembling the existing one. This testing resulted in much new and improved knowledge about the fatigue properties of grey cast iron and it was even possible to generalize the outcome of the spectrum fatigue tests into a simple design curve. (orig.) 11 refs.

  14. Physical activity and quality of life in multiple sclerosis: Intermediary roles of disability, fatigue, mood, pain, self-efficacy and social support

    Science.gov (United States)

    Motl, Robert W.; McAuley, Edward; Snook, Erin M.; Gliottoni, Rachael C.

    2009-01-01

    Physical activity has been associated with a small improvement in quality of life (QOL) among those with multiple sclerosis (MS). This relationship may be indirect and operate through factors such as disability, fatigue, mood, pain, self-efficacy and social support. The present study examined variables that might account for the relationship between physical activity and QOL in a sample (N = 292) of individuals with a definite diagnosis of MS. The participants wore an accelerometer for 7 days and then completed self-report measures of physical activity, QOL, disability, fatigue, mood, pain, self-efficacy and social support. The data were analysed using covariance modelling in Mplus 3.0. The model provided an excellent fit for the data (?2 = 51.33, df = 18, p < 0.001, standardised root mean squared residual = 0.03, comparative fit index = 0.98). Those who were more physically active reported lower levels of disability (? = -0.50), depression (? = -0.31), fatigue (? = -0.46) and pain (? = -0.19) and higher levels of social support (? = 0.20), self-efficacy for managing MS (? = 0.41), and self-efficacy for regular physical activity (? = 0.49). In turn, those who reported lower levels of depression (? = -0.37), anxiety (? = -0.15), fatigue (? = -0.16) and pain (? = -0.08) and higher levels of social support (? = 0.26) and self-efficacy for controlling MS (? = 0.17) reported higher levels of QOL. The observed pattern of relationships supports the possibility that physical activity is indirectly associated with improved QOL in individuals with MS via depression, fatigue, pain, social support and self-efficacy for managing MS. PMID:19085318

  15. Lifing the thermo-mechanical fatigue (TMF) behaviour of the polycrystalline nickel-based superalloy RR1000

    OpenAIRE

    Jones Jonathan; Whittaker Mark; Lancaster Robert; Williams Stephen

    2014-01-01

    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...

  16. Fatigue life and fracture of cast gamma TiAl intermetallic alloy at room and elevated temperatures.

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Šmíd, Miroslav; Polák, Jaroslav

    Ostrava : Tanger s.r.o., 2011, s. 969-974. ISBN 978-80-87294-24-6. [METAL 2011 /20./. Brno (CZ), 18.05.2011-20.05.2011] R&D Projects: GA ?R(CZ) GAP107/11/0704 Institutional research plan: CEZ:AV0Z20410507 Keywords : low cycle fatigue * cast gamma TiAl alloy * fracture surfaces * PSMs * elevated temperature Subject RIV: JL - Materials Fatigue, Friction Mechanics

  17. Fatigue Strength of Titanium Risers - Defect Sensitivity

    OpenAIRE

    Babalola, Olusegun Tunde

    2001-01-01

    This study is centered on assessment of the fatigue strength of titanium fusion welds for deep-water riser’s applications. Deep-water risers are subjected to significant fatigue loading.

    Relevant fatigue data for titanium fusion welds are very scarce. Hence there is a need for fatigue data and life prediction models for such weldments.

    The study has covered three topics: Fatigue testing, Fractography and defect assessment, and Fracture Mechani...

  18. Chronic Fatigue Syndrome (CFS): Childhood Adversity

    Science.gov (United States)

    ... message, please visit this page: About CDC.gov . Chronic Fatigue Syndrome (CFS) Share Compartir Early Life Stress and Adult ... reported in studies of survivors of childhood abuse. Chronic fatigue syndrome (CFS) is a debilitating illness that can sometimes ...

  19. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre

    1996-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Fatigue failure is found to depend both on the total time under load and on the number of cycles.Recent accelerated fatigue research on wood is reviewed, and a discrepancy between failure explanation under fatigue and static load conditions is observed. In the present study small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation between stiffness reduction and accumulated creep is observed. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and attempted explained at a microstructural level. The outline of a model explaining the interaction of the effect of load duration and the effect of the loading sequences is presented.

  20. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; BrØndsted, Povl

    2010-01-01

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