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1

Very high cycle fatigue life of 2.25Cr-1Mo steel at room and high temperatures  

International Nuclear Information System (INIS)

An ultrasonic fatigue testing machine was developed to obtain the very high cycle fatigue life at elevated temperature for safety and reliability of structural components in the faster breeder reactor (FBR). This testing machine consists of an amplifier, booster, horn and equipments such as system controller and data acquisition. The test specimen is attached at the end of the horn. The electric power generated in the amplifier is transformed into the mechanical vibration in the converter and is magnified in the booster and horn. The developed ultrasonic fatigue testing machine enables to carry out the fatigue test at 20kHz so that it can perform the very high cycle fatigue test within a very shorter time as compared with the regular fatigue testing machines such as a hydraulic fatigue testing machine. This study carried out very high cycle fatigue tests using type STBA 24, the steel for tube in boiler and heat exchanger, at room and elevated (673K) temperatures by the developed testing and conventional hydraulic testing machines, and obtained the fatigue lives. This paper also described the cracks observed on specimen surface of fatigued specimen and discussed the very high cycle fatigue strength properties. It was confirmed that the fatigue data obtained by the ultrasonic fatigue testing machine are continuous and compatible with the results obtained by the hydraulic tension-compression testing machine. Fatigue lives more than 106 cycles at room and high temperatures can be predicted conservatively by the best fit design curve employed in the nuclear power plant design. (author)

2005-01-01

2

High-cycle and long-life fatigue of 25CrMo4 under multiaxial load conditions by three alternating stresses  

International Nuclear Information System (INIS)

Statistically verified experimental results from high-cycle and long-life fatigue tests (HCF and LLF) with altogether 537 unnotched solid cylindrical and thin-walled hollow specimen are demonstrating the fatigue behaviour (S-N-characteritics, scatterband) of 25CrMo4 under uniaxial loading with superimposed static stresses (consideration of the mean stress effect) and under biaxial loadings in variation of phase differences between the three combined normal and torsional stresses ?x, ?y, ?xy. The fatigue strength is commonly decreasing with life time in the high-cycle regime until reaching the fatigue endurance limit in the transition range to infinite life. The 'ductility level' ?W/?W and the 'mean stress sensibility' p=p (?W, ?zSch, Rm) are relatively independent of the intensity by stress amplitudes and fatigue life to failure. In comparison with the specific case of biaxial combined loading with synchroneous amplitudes, the fatigue resistance characteristics are detrimentally influenced by out-of-phase normal stresses ?x, ?y; a phase difference of 180deg between the normal stress amplitudes is the most critical state of combination, especially in the lower cycle regime caused by a greater slope coefficient (probability of survival Ps=50%). On the contrary is there in the high-cycle regime as well as in the long-life range no significant influence to the fatigue strength by biaxial load conditions of simultaneously normal stresses with out-of-phase torsional stress ?xy. (orig.).

1991-01-01

3

Effects of mean tensile stresses on high-cycle fatigue life and strain accumulation in some reactor materials  

International Nuclear Information System (INIS)

An assessment has been made of the effects of mean tensile stresses on the high-cycle fatigue behavior of solution-treated Type 304 stainless steel, normalized and tempered 21/4Cr-1Mo steel, Incoloy-800H, and low-carbon Incoloy-800. Mean stresses are usually detrimental to fatigue strength, especially at high temperatures and stress levels, where significant creep can occur during fatigue cycling. Depending on the magnitudes of the alternating and mean stresses, failure may be creep or fatigue controlled. Strain accumulation is also affected by these stress levels and possibly, also, by the cyclic work-hardening characteristics of the material. It is shown that the Goodman Law for estimating mean stress effects is inadequate, since it does not account for time-dependent deformation. An alternative expression not having such a limitation was, therefore, derived and this relates the alternating and mean stresses to the time to failure. Based on limited metallographic observations of fatigue striations in the 21/4Cr-1Mo steel an estimate was made of the crack propagation rate. It was found that a crack of critical size could, under certain conditions, propagate through most of the specimen diameter in a matter of seconds. This presents a more significant safety problem than the case for a crack extending under low-cycle conditions since preventative measures probably could not be implemented before the crack had grown to a large size

1977-01-01

4

High-cycle and long-life fatigue of 25CrMo4 under multiaxial load conditions by three alternating stresses. Langzeit- und Dauerschwingfestigkeit des Verguetungsstahls 25CrMo4 bei mehrachsiger Beanspruchung durch drei schwingende Lastspannungen  

Energy Technology Data Exchange (ETDEWEB)

Statistically verified experimental results from high-cycle and long-life fatigue tests (HCF and LLF) with altogether 537 unnotched solid cylindrical and thin-walled hollow specimen are demonstrating the fatigue behaviour (S-N-characteritics, scatterband) of 25CrMo4 under uniaxial loading with superimposed static stresses (consideration of the mean stress effect) and under biaxial loadings in variation of phase differences between the three combined normal and torsional stresses {sigma}{sub x}, {sigma}{sub y}, tau{sub xy}. The fatigue strength is commonly decreasing with life time in the high-cycle regime until reaching the fatigue endurance limit in the transition range to infinite life. The 'ductility level' tau{sub W}/{sigma}{sub W} and the 'mean stress sensibility' p=p ({sigma}{sub W}, {sigma}{sub zSch}, R{sub m}) are relatively independent of the intensity by stress amplitudes and fatigue life to failure. In comparison with the specific case of biaxial combined loading with synchroneous amplitudes, the fatigue resistance characteristics are detrimentally influenced by out-of-phase normal stresses {sigma}{sub x}, {sigma}{sub y}; a phase difference of 180deg between the normal stress amplitudes is the most critical state of combination, especially in the lower cycle regime caused by a greater slope coefficient (probability of survival P{sub s}=50%). On the contrary is there in the high-cycle regime as well as in the long-life range no significant influence to the fatigue strength by biaxial load conditions of simultaneously normal stresses with out-of-phase torsional stress tau{sub xy}. (orig.).

Gruen, P.; Troost, A.; Akin, O.; Klubberg, F. (Technische Hochschule Aachen (Germany, F.R.). Lehrstuhl fuer Werkstoffkunde A und Inst. fuer Werkstoffkunde)

1991-03-01

5

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)

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.

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

6

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

Directory of Open Access Journals (Sweden)

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.

Mirco D. Chapetti

2002-01-01

7

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

International Nuclear Information System (INIS)

[en] 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

1994-01-01

8

High-cycle fatigue behavior of type 316 stainless steel at 593/sup 0/C  

Energy Technology Data Exchange (ETDEWEB)

The available low- and high-cycle fatigue data on Type 316 stainless steel at 593 to 600/sup 0/C have been combined and analyzed to provide a preliminary strain-life correlation. This correlation was then reduced by the appropriate safety factors to a design curve and compared with the ASME T-1420-1B curve. The comparison indicates that significant increases in allowable fatigue cycles should be realized when the present study is concluded.

Raske, D.T.

1980-01-01

9

Effects of HTGR helium on the high cycle fatigue of structural materials  

International Nuclear Information System (INIS)

High cycle fatigue tests have been conducted on Incoloy 800H and Hastelloy X in air and in HTGR helium environments containing low and high levels of moisture. For the helium environments, a higher mositure level usually gives a lower fatigue strength. For air, however, the strength is usually much lower than those for helium. For long test times at higher test temperatures, the fatigue strengths for Incoloy 800H often show a large decrease, and the fatigue limits are much lower than those anticipated from low cycle tests. Optical and scanning electron microscope observations were made to correlate fatigue life with surface and bulk microstructural changes in the material during test. Oxide scale cracking and spallation, surface recrystallization and intergranular attack appear to contribute to losses in fatigue strength

1982-01-01

10

A multi-temporal scale approach to high cycle fatigue simulation  

Science.gov (United States)

High cycle fatigue (HCF) is a failure mechanism that dominates the life of many engineering components and structures. Time scale associated with HCF loading is a main challenge for developing a simulation based life prediction framework using conventional FEM approach. Motivated by these challenges, the extended space-time method (XTFEM) based on the time discontinuous Galerkin formulation is proposed. For HCF life prediction, XTFEM is coupled with a two-scale continuum damage mechanics model for evaluating the fatigue damage accumulation. Direct numerical simulations of HCF are performed using the proposed methodology on a notched specimen of AISI 304L steel. It is shown the total fatigue life can be accurately predicted using the proposed simulation approach based on XTFEM. The presented computational framework can be extended for predicting the service and the residual life of structural components.

Bhamare, Sagar; Eason, Thomas; Spottswood, Stephen; Mannava, Seetha R.; Vasudevan, Vijay K.; Qian, Dong

2013-08-01

11

High cycle fatigue of Type 422 stainless steel  

International Nuclear Information System (INIS)

High cycle fatigue testing has been carried out on Type 422 stainless steel to determine the performance of cyclically stressed disks and blades in the main and auxiliary HTGR helium circulators. Tests were performed at 316, 482, and 5380C (600, 900, and 10000F) in air for the fully reversible and mean load conditions. Goodman's analysis is shown to be valid in predicting failure at 3160C (6000F), marginally valid at 4820C (9000F), and probably invalid at 5380C (10000F). Metallographic analyses were conducted to characterize the nature of failure for the temperatures and loading conditions investigated

1978-11-25

12

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 device. The results obtained were compared to those of the conventional torsional fatigue test machine operated at 35 Hz to observe any discrepancy in results due to frequency effects between two experiments.Findings: All the fatigue tests were done up to 1010 cycles at room temperature. Damage mechanisms in torsional fatigues such as crack initiation and propagation in different modes were studied by imaging the samples in a Scanning Electron Microscope (SEM). The results of the two kinds of material show that the stress vs. number of cycle curves (S-N curves) display a considerable decrease in fatigue strength beyond 107 cycles.Research limitations/implications: Each test, the strain of specimen in the gage length must be calibrated with a strain gage bonded to the gage section. This is a critical point of this study. The results are very sensitive to the calibration system. Control of the displacement and the output of the power supply are made continuously by computer and recorded the magnitude of the strain in the specimen.Practical implications: torsional fatigue tests has been investigated in the very high cycle fatigue (VHCF) range for two kinds of alloys used very largely in automotive engine components. Based on the test results and analyses presented in this paper, practical applications are being actually carried out in the automotive industry essentially in France.Originality/value: Ultrasonic fatigue damage (VHCF >109) in VHCF is originally different from classical fatigue (up to 106) by typical internal fish eye formation. Additionally, fatigue crack of all the fractured specimens for the 2-AS5U3G-Y35 specimens initiated at the surface of the specimens. Fatigue fracture surfaces of AISI52100 steel specimens show a typical “scorpion-shaped” formation, which was considerably different from the fatigue fracture specimen subjected to axial cyclic loading, which exhibited the “fish-eye” formation.

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

2010-01-01

13

High cycle-number fatigue of Zirconium 702: fatigue life and crack propagation - relation with microstructure; Fatigue a grand nombre de cycles du zirconium 702: limites d`endurance et propagation des fissures - relation avec la microstructure  

Energy Technology Data Exchange (ETDEWEB)

The influence of various metallurgical states and parameters such as temperature, mean stress, etc. on the fatigue strength (crack initiation in the domain of high number of cycles, crack propagation) of zirconium 702, is experimentally studied. Results concern high-number of cycles fatigue tests with cylindrical or tubular specimens (base metal and related welds) and measurements of crack propagation rate on CT type specimens. 7 refs.

Gauhier, J.P.; Fauxinstier, J.; Bouchet, F.; Espinas, J.J. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Direction des Technologies Avancees

1996-12-31

14

Fatigue crack initiation life prediction of railroad  

International Nuclear Information System (INIS)

[en] Study of multiaxial high-cycle fatigue initiation life prediction for railroad is done in this paper. Using ANSYS 11.0 software three dimensional elasto-plastic finite element model of rail/wheel contact is constructed and fine mesh technique in contact region is used to achieve both computational efficiency and accuracy. Stress analysis is performed and fatigue damage in railroad is evaluated numerically using multiaxial fatigue crack initiation model. Using the stress history during one loading cycle and fatigue damage model, the effects of vertical loading, material hardness material fatigue properties and wheel/rail contact situation on fatigue crack initiation life are investigated.

2009-08-01

15

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)

2007-01-01

16

The significance of crack initiation stage in very high cycle fatigue of steels  

Energy Technology Data Exchange (ETDEWEB)

Different stages of the Very High Cycle Fatigue (VHCF) crack evolution in tool steels have been explored using a 20 kHz ultrasonic fatigue testing equipment. Extensive experimental data is presented describing VHCF behaviour, strength and crack initiating defects in an AISI H11 tool steel. Striation measurements are used to estimate fatigue crack growth rate, between 10{sup -8} and 10{sup -6} m/cycle, and the number of load cycles required for a crack to grow to critical dimensions. The growth of small fatigue cracks within the ''fish-eye'' is shown to be distinctively different from the crack propagation behaviour of larger cracks. More importantly, the crack initiation stage is shown to determine the total fatigue life, which emphasizes the inherent difficulty to detect VHCF cracks prior to failure. Several mechanisms for initiation and early crack growth are possible. Some of them are discussed here: crack development by local accumulation of fatigue damage at the inclusion - matrix interface, hydrogen assisted crack growth and crack initiation by decohesion of carbides from the matrix. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Bergstroem, J. [Department of Materials Engineering, Karlstad University (Sweden); Burman, C.; Kazymyrovych, V.

2010-04-15

17

Numerical analysis of thermal striping induced high cycle thermal fatigue in a mixing tee  

International Nuclear Information System (INIS)

Thermal striping, characterized by turbulent mixing of two flow streams of different temperatures that result in temperature fluctuations of coolant near the pipe wall, is one of the main causes of thermal fatigue failure. Coolant temperature oscillations due to thermal striping are on the order of several Hz. Thermal striping high-cycle thermal fatigue that occurs at tee junctions is one of the topics that should be addressed for the life management of light water reactor (LWR) piping systems. This study focuses on numerical analyses of the temperature fluctuations and structural response of coolant piping at a mixing tee. The coolant temperature fluctuations are obtained from Large Eddy Simulations that are validated by experimental data. For the thermal stress fatigue analysis, a model is developed to identify the relative importance of various parameters affecting fatigue-cracking failure. This study shows that the temperature difference between the hot and cold fluids of a tee junction and the enhanced heat transfer coefficient due to turbulent mixing are the dominant factors of thermal fatigue failure of a tee junction.

2009-01-01

18

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

Energy Technology Data Exchange (ETDEWEB)

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.

Ren Weiju; Nicholas, Theodore

2003-09-25

19

The high-cycle fatigue and fracture behavior of a copper-niobium microcomposite  

Energy Technology Data Exchange (ETDEWEB)

Niobium particle-reinforced dispersion strengthened copper composite has shown the promise of being the candidate material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. In this paper, the results of a study on the high-cycle fatigue and final fracture behavior of a microcomposite based on an oxide dispersion strengthened copper matrix is presented and discussed. Specimens of both the composite and the unreinforced counterpart were cyclically deformed, over a range of stress amplitudes, at both ambient and elevated temperatures. Increase in test temperature was found to have a detrimental influence on the cyclic fatigue life of the copper-niobium microcomposite. Temperature was found to have little influence on the cyclic fatigue life of the unreinforced dispersion strengthened microstructure. For both the unreinforced and reinforced materials macroscopic fracture was reminiscent of brittle fracture over the entire range of stress amplitudes. However, on a microscopic scale cyclic fracture revealed features reminiscent of locally brittle and ductile mechanisms. The cyclic fatigue and final fracture behavior of the composite are discussed in light of the mutually interactive influences of intrinsic composite microstructural effects, stress amplitude and test temperature.

Srivatsan, T.S.; Singh, K.P.D. [Univ. of Akron, OH (United States). Dept. of Mechanical Engineering; Troxell, J.D. [OGM Americas, Research Triangle Park, NC (United States)

1997-12-31

20

Statistical Analysis of High-Cycle Fatigue Behavior of Friction Stir Welded AA5083-H321  

Science.gov (United States)

A review of the literature revealed that high-cycle fatigue data associated with friction stir-welded (FSW) joints of AA5083-H321 (a solid-solution-strengthened and strain-hardened/stabilized Al-Mg-Mn alloy) are characterized by a relatively large statistical scatter. This scatter is closely related to the intrinsic variability of the FSW process and to the stochastic nature of the workpiece material microstructure/properties as well as to the surface condition of the weld. Consequently, the use of statistical methods and tools in the analysis of FSW joints is highly critical. A three-step FSW-joint fatigue-strength/life statistical-analysis procedure is proposed in this study. Within the first step, the type of the most appropriate probability distribution function is identified. The parameters of the selected probability distribution function, along with their confidence limits, are computed in the second step. In the third step, a procedure is developed for assessment of the statistical significance of the effect of the FSW process parameters and fatigue specimen surface conditions. The procedure is then applied to a set of stress-amplitude versus number of cycles to failure experimental data in which the tool translational speed was varied over four levels, while the fatigue specimen surface condition was varied over two levels. The results obtained showed that a two-parameter weibull distribution function with its scale factor being dependent on the stress amplitude is the most appropriate choice for the probability distribution function. In addition, it is found that, while the tool translational speed has a first-order effect on the AA5083-H321 FSW-joint fatigue strength/life, the effect of the fatigue specimen surface condition is less pronounced.

Grujicic, M.; Arakere, G.; Pandurangan, B.; Hariharan, A.; Yen, C.-F.; Cheeseman, B. A.; Fountzoulas, C.

2011-08-01

 
 
 
 
21

Effects of high mean stress on the high-cycle fatigue behavior of PWA 1480  

International Nuclear Information System (INIS)

PWA 1480 is a potential candidate material for use in the high-pressure fuel turbine blade of the Space Shuttle Main Engine. As an engine material it will be subjected to high-cycle fatigue loading superimposed on a high mean stress due to combined centrifugal and thermal loadings. This paper describes results obtained in an ongoing program to determine the effects of a high mean stress on the high-cycle fatigue behavior of this material

1985-01-01

22

Damage estimates for European and US sites using the US high-cycle fatigue data base  

Energy Technology Data Exchange (ETDEWEB)

This paper uses two high-cycle fatigue data bases, US blade materials and one for European materials the service lifetime of a wind turbine blade sit WISPER load spectrum for northern European sit 19921 and the WISPER protocol load spectrum farm sites. The US data base, developed by Mandell, et al. (1995), 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 US wind farm site; i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a US wind farm site. Further, the analyses demonstrate that the European and the US 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 US data base predicting significantly shorter service lifetimes than the European data base.

Sutherland, H.J.

1996-02-01

23

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

24

Comparative study to evaluate remaining life in steel SAE 8620 under high cycle fatigue; Estudo comparativo para avaliar vida restante em aco SAE 8620, quando submetido a fadiga de alto-ciclo  

Energy Technology Data Exchange (ETDEWEB)

Life of metallic structures is often governed by processes of fatigue, caused by either vibration or by the application of cyclic, periodic or not, load. Most of the life is related to a sequence of processes during which slip bands, localized strain, damages and begin and they grow until the nucleation of some macroscopic crack. To evaluate the life of structural components (from now on refereed as components) related to fatigue, several proposed models some linear and others not. This paper presents a comparison among some of them, for the steel SAE 8620. (author)

Mansur, Tanius Rodrigues; Pinto, Joao Mario Andrade [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil); Palma, Ernani Sales; Alvarenga Junior, Alvaro [Pontificia Univ. Catolica de Minas Gerais, MG (Brazil); Colosimo, Enrico A. [Minas Gerais Univ., Belo Horizonte, MG (Brazil)

2002-07-01

25

High cycle fatigue of austenitic stainless steels under random loading  

International Nuclear Information System (INIS)

[en] 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

1987-01-01

26

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1995-12-01

27

High cycle fatigue properties of irradiated and unirradiated stainless steel DIN 1.4948 plate at 823 K  

International Nuclear Information System (INIS)

[en] High cycle fatigue experiments have been carried out on stainless steel DIN X 6 CrNi 1811 (Werkst. 1.4948, similar to AISI 304) in irradiated and reference condition. Specimens were irradiated at 823 K up to a fast fluence (E > 0.1 MeV) of 5x1024n.m-2 and a thermal fluence of 1.6x1024n.m-2. The nominal test temperature was 823 K; deviations from this nominal value were kept smaller than 3 K by avoiding too high test frequencies. The results indicate a slight increase of the fatigue limit after irradiation from 152.5 MPa to 162.5 MPa. For both conditions the fatigue curve has a horizontal part for Nsub(f) > 8x104 cycles. Striation counts indicate that a major part of the fatigue life is consumed by initiation. As a consequence fatigue life and possibly the fatigue limit are dependent on factors which influence the initiation stage of fatigue, like surface roughness, residual stresses and defects

28

Analysis of methods for determining high cycle fatigue strength of a material with investigation of titanium-aluminum-vanadium gigacycle fatigue behavior  

Science.gov (United States)

Today, aerospace engineers still grapple with the qualitative and quantitative understanding of fatigue behavior in the design and testing of turbine-driven jet engines. The Department of Defense has taken a very active role in addressing this problem with the formation of the National High Cycle Fatigue Science & Technology Program in 1994. The primary goal of this program is to further the understanding of high cycle fatigue (HCF) behavior and develop methods in order to mitigate the negative impact of HCF on aerospace operations. This research supports this program by addressing the fatigue strength testing guidance currently provided by the DoD to engine manufacturers, with the primary goal to investigate current methods and recommend a test strategy to characterize the fatigue strength of a material at a specified number of cycles, such as the 109 design goal specified by MIL-HDBK-1783B, or range of cycles. The research utilized the benefits of numerical simulation to initially investigate the staircase method for use in fatigue strength testing. The staircase method is a commonly used fatigue strength test, but its ability to characterize fatigue strength variability is extremely suspect. A modified staircase approach was developed and shown to significantly reduce bias and scatter in estimates for fatigue strength variance. Experimental validation of this proposed test strategy was accomplished using a dual-phase Ti-6Al-4V alloy. The HCF behavior of a second material with a very different microstructure (beta annealed Ti-6Al-4V) was also investigated. The random fatigue limit (RFL) model, a recently developed analysis tool, was investigated to characterize stress-life behavior but found to have difficulty representing fatigue life curves with sharp transitions. Two alternative models (bilinear and hyperbolic) were developed based on maximum likelihood methods to better characterize the Ti-6Al-4V fatigue life behavior. These models provided a good fit to the experimental data for the dual-phase Ti-6Al-4V and were applied to the beta annealed variant in order to estimate stress-life behavior using a small-sample approach. Based on this research, designers should be better able to make reliable estimates of fatigue strength parameters using small-sample testing.

Pollak, Randall D.

29

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)

2007-01-01

30

Robust high-cycle fatigue stress threshold optimization under uncertain loadings  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english This paper proposes a strategy to achieve robust optimization of structures against high-cycle fatigue when a potentially large number of uncertain load cases are considered. The strategy is heavily based on a convexity property of some of the most commonly used high-cycle design criteria. The convexity property is rigorously proven for the Crossland fatigue criterion. The proof uses a perturbation technique and involves the principal stress components and analytical expr (more) essions for the applicable fatigue criteria. The multiplicity of load cases is treated using load ratios which are bounded but are otherwise free to vary within certain limits. The strategy is applied to a notched plate subject to traditional normal and shear loadings that possess uncertain or unspecified components.

Faria, Alfredo R. de; Frota Jr., Roberto T. C.

2012-10-01

31

Effects of laser peening treatment on high cycle fatigue and crack propagation behaviors in austenitic stainless steel  

International Nuclear Information System (INIS)

Laser peening without protective coating (LPwC) treatment is one of surface enhancement techniques using an impact wave of high pressure plasma induced by laser pulse irradiation. High compressive residual stress was induced by the LPwC treatment on the surface of low-carbon type austenitic stainless steel SUS316L. The affected depth reached about 1mm from the surface. High cycle fatigue tests with four-points rotating bending loading were carried out to confirm the effects of the LPwC treatment on fatigue strength and surface fatigue crack propagation behaviors. The fatigue strength was remarkably improved by the LPwC treatment over the whole regime of fatigue life up to 108 cycles. Specimens with a pre-crack from a small artificial hole due to fatigue loading were used for the quantitative study on the effect of the LPwC treatment. The fracture mechanics investigation on the pre-cracked specimens showed that the LPwC treatment restrained the further propagation of the pre-crack if the stress intensity factor range ?K on the crack tip was less than 7.6 MPa?m. Surface cracks preferentially propagated into the depth direction as predicted through ?K analysis on the crack by taking account of the compressive residual stresses due to the LPwC treatment. (author)

2010-01-01

32

The effect of low cycle fatigue cracks and loading history on high cycle fatigue threshold  

Science.gov (United States)

High cycle fatigue (HCF) has been of great concern of late in light of the many HCF gas turbine engine failures experienced by the U.S. Air Force. Due to the high frequency, failures occur rapidly when components sustain damage from other sources. Low cycle fatigue (LCF) can initiate cracks that produce such damage. This study investigates the HCF threshold of Ti-6A1-4V when naturally initiated small surface cracks (2a = 25 mum--600 mum) are present. Small surface cracks are initiated in notched specimens using two different LCF loading histories at room temperature and 10 Hz. Direct current potential difference (DCPD) is used to detect crack initiation. Surface crack measurements are made using a scanning electron microscope prior to HCF testing. Heat tinting prior to HCF testing is used to mark the crack front to allow for post fracture crack measurements. HCF thresholds at R = 0.1 and R = 0.5 are determined for each specimen using step loading at room temperature and 600 Hz. Additionally, the HCF threshold is measured at R = 0.1 for specimens with small cracks that have been stress relief annealed to eliminate residual stresses and load history. Long crack thresholds are determined using a similar step loading procedure at R = 0.1 and R = 0.5 for specimens which have been precracked using a range of Kmax. Long crack threshold measurements are also determined for specimens which have been precracked using a range of Kmax, but stress relief annealed prior to testing. Comparisons show that HCF threshold measurements, when naturally initiated small cracks are present, are dependent on the load histories that are used to initiate the cracks. Further comparisons show that the measured small crack thresholds follow similar trends for load history effects which occur in the long crack threshold data. Additionally, it is found that thresholds can be measured free of load history effects by using a stress relief annealing process after the precracking and prior to the threshold testing.

Moshier, Monty Allen

33

Experimental study on properties of high cycle thermal fatigue. Outline and test plan of high cycle fatigue test equipment on sodium  

International Nuclear Information System (INIS)

[en] At a nuclear power plant, where fluids of high and low temperature flow into each other, it is necessary to prevent structural failure damage caused by high cycle thermal fatigue (thermal striping phenomenon). High cycle fatigue test equipment on thermal can be develop by modifying the thermal transient test facility for structure (TTS) in order to clarify the effect of temperature fluctuation induced by the thermal striping phenomenon on crack initiation and their propagation behavior. The test equipment has the following characteristic. (1) Fluid is controlled by a circulation pump, and by continuously changing the flow quantity ratio of high and low temperature Sodium, sinusoidal temperature fluctuations at various period of the test samples can be taken. (2) Mixing is done by the jet flow mix, thus it can generate axisymmetric temperature fluctuations by accelerating the mixing process of high and low temperature Sodium. (3) It can also control the temperature fluctuation, in which short and long term changes are superimposed. (4) Because the test sample cylinder is hollow, analysis of thermal stress and data from crack initiation to crack propagation can easily be obtained. Sinusoidal temperature fluctuations, random temperature fluctuations, and strength testing of the weld zone by test samples made of stainless steel are planned in the next stage. (author)

2003-01-01

34

High Cycle Fatigue of Cast Mg-3Nd-0.2Zn Magnesium Alloys  

Science.gov (United States)

This paper investigates the high cycle fatigue properties of a recently developed high-strength cast magnesium alloy [Mg-3Nd-0.2Zn (all compositions in wt pct except when otherwise stated)] with varied Zr contents for grain refinement (NZ30K) and the influence of heat treatment conditions. The NZ30K alloy containing 0.45Zr and heat treated to the peak-aged T6 condition [14 hours at 473 K (200 °C)] shows the highest fatigue strength, about 100 MPa, which is about 25 pct higher than that of commercial AZ91D-T6 alloy. In the absence of casting flaws, the high cycle fatigue properties of the NZ30K alloy strongly depend on its grain size and heat treatment conditions. The dependency of fatigue strength on grain sizes follows the Hall-Petch relationship. The NZ30K alloy also shows a significant response to heat treatments. The fatigue strength increases in a near linear fashion with increasing yield strength of the material through heat treatment.

Li, Zhenming; Wang, Qigui; Luo, Alan A.; Fu, Penghuai; Peng, Liming; Wang, Yingxin; Wu, Guohua

2013-06-01

35

Study of crack initiation or damage in very high cycle fatigue using ultrasonic fatigue test and microstructure analysis.  

UK PubMed Central (United Kingdom)

Fatigue damage behaviors of four metal materials in the very high cycle fatigue (VHCF) regime have been studied using ultrasonic fatigue test and microstructure analysis. The results show that the fatigue crack initiation in VHCF regime could occur at subsurface non-defect fatigue crack origin (SNDFCO), where the accumulated cyclic strains or damage in the specimens were highly localized, especially in the materials with some softer phase, where the local maximum strain can be eight times higher than the average strain value in the specimen. This high strain localization can cause a local plasticity exhaustion that leads to a stress concentration and consequently fatigue crack initiation, and finally the formation of SNDFCO. For pure single phase austenitic material, strain localization can also occur due to dislocation accumulation at or near grain boundaries, which can become fatigue crack initiation origin in the VHCF regime. The results in this study show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.

Chai G; Zhou N

2013-12-01

36

Study of crack initiation or damage in very high cycle fatigue using ultrasonic fatigue test and microstructure analysis.  

Science.gov (United States)

Fatigue damage behaviors of four metal materials in the very high cycle fatigue (VHCF) regime have been studied using ultrasonic fatigue test and microstructure analysis. The results show that the fatigue crack initiation in VHCF regime could occur at subsurface non-defect fatigue crack origin (SNDFCO), where the accumulated cyclic strains or damage in the specimens were highly localized, especially in the materials with some softer phase, where the local maximum strain can be eight times higher than the average strain value in the specimen. This high strain localization can cause a local plasticity exhaustion that leads to a stress concentration and consequently fatigue crack initiation, and finally the formation of SNDFCO. For pure single phase austenitic material, strain localization can also occur due to dislocation accumulation at or near grain boundaries, which can become fatigue crack initiation origin in the VHCF regime. The results in this study show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion. PMID:23850182

Chai, Guocai; Zhou, Nian

2013-05-30

37

High-cycle fatigue crack initiation and propagation in laser melting deposited TC18 titanium alloy  

Science.gov (United States)

This article examines fatigue crack nucleation and propagation in laser deposited TC18 titanium alloy. The Widmanstätten structure was obtained by double-annealing treatment. High-cycle fatigue (HCF) tests were conducted at room temperature with the stress ratio of 0.1 and the notch concentration factor K t = 1. Fatigue cracks initiated preferentially at micropores, which had great effect on the HCF properties. The effect decreased with the decrease of pore size and the increase of distance from the pore location to the specimen surface. The crack initiation region was characterized by the cleavage facets of ? lamella and the tearing of ? matrix. The soft ? precipitated-free zone formed along grain boundaries accelerated the crack propagation. Subsurface observation indicated that the crack preferred to propagate along the grain boundary ? or border of ? lamella or vertical to ? lamella.

Wang, Yang; Zhang, Shu-quan; Tian, Xiang-jun; Wang, Hua-ming

2013-07-01

38

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

39

The high cycle thermal fatigue cracking, a problem bond to the structure; Le faiencage thermique a grand nombre de cycles, un phenomene lie a la structure  

Energy Technology Data Exchange (ETDEWEB)

High cycle thermal fatigue cracking is explained through the arrest of cracks initiated at surface, in the thickness of the component. On some components of nuclear power plants the configuration of crack network is explained through the sign of weld residual stress. We show also that local residual stresses are dependent on second derivative of temperature field. Far from the weld we explain the presence of crack network under high compressive stress for stainless steels by detrimental effect of pre-hardening on fatigue life in strain control and we conclude that shot peening may be detrimental in thermal fatigue. (author)

Said Taheri [LaMSID UMR EDF-CNRS 2832, 1 Av. General de Gaulle 92141 Clamart Cedex (France)

2005-07-01

40

High cycle fatigue test and regression methods of S-N curve  

International Nuclear Information System (INIS)

[en] The fatigue design curve in the ASME Boiler and Pressure Vessel Code Section III are based on the assumption that fatigue life is infinite after 106 cycles. This is because standard fatigue testing equipment prior to the past decades was limited in speed to less than 200 cycles per second. Traditional servo-hydraulic machines work at frequency of 50 Hz. Servo-hydraulic machines working at 1000 Hz have been developed after 1997. This machines allow high frequency and displacement of up to ±0.1 mm and dynamic load of ±20 kN are guaranteed. The frequency of resonant fatigue test machine is 50-250 Hz. Various forced vibration-based system works at 500 Hz or 1.8 kHz. Rotating bending machines allow testing frequency at 0.1-200 Hz. The main advantage of ultrasonic fatigue testing at 20 kHz is performing Although S-N curve is determined by experiment, the fatigue strength corresponding to a given fatigue life should be determined by statistical method considering the scatter of fatigue properties. In this report, the statistical methods for evaluation of fatigue test data is investigated

2011-01-01

 
 
 
 
41

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1996-09-01

42

Aspects of high-cycle fatigue performance in a Ti-6Al-4V alloy  

Energy Technology Data Exchange (ETDEWEB)

Determination of critical levels of microstructural damage that can lead to fatigue crack propagation under high-cycle fatigue loading conditions is a major concern for the aircraft industry regarding structural integrity of turbine engine components. The cyclic frequencies characteristic of service loading spectra are extremely high and appear to require a damage-tolerant design approach. One idea for such an approach is to attempt to define a practical, appropriate crack-propagation threshold, {Delta}K{sub TH}. The present study identifies a practical lower-bound large-crack threshold under high-cycle fatigue conditions in a Ti-6 Al-4V blade alloy (with {approximately}60% primary {alpha} in a matrix of lamellar {alpha}+{beta}). The authors suggest that lower-bound thresholds can be determined by modifying standard large-crack propagation tests to simulate small-crack behavior. Modification techniques include high load-ratio testing under both constant-R and constant-K{sub max} conditions, performed at cyclic loading frequencies up to 1 kHz and R ratios up to 0.95. The results of these tests are compared to the near-threshold behavior of naturally-initiated small cracks, and to the crack initiation and early growth behavior of small cracks emanating from sites of simulated foreign object damage.

Boyce, B.L.; Campbell, J.P.; Roder, O.; Thompson, A.W.; Ritchie, R.O.

1999-07-01

43

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

CERN Multimedia

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...

Heikkinen, Samuli; Wuensch, Walter

2010-01-01

44

High cycle fatigue behavior of gas-carburized medium carbon Cr-Mo steel  

Energy Technology Data Exchange (ETDEWEB)

High cycle fatigue properties of gas-carburized 4140 steel were assessed to compare with those of 8620 steel which is widely used as a carburizing steel. Fatigue limit was evaluated associated with microstructure, case depth, and distribution of retained austenite and compressive residual stress near the surface. Test results indicated that the reheat quenching method of 4140 and 8620 steels produced a reduction in grain size, retained austenite level, and compressive residual stress at the surface and an increase in fatigue limit. The fatigue limit of direct-quenched 4140 steel shows substantially lower value than that of direct-quenched 8620 steel due to larger grain size of direct-quenched 4140 steel. However, the fatigue limit of reheat-quenches 4140 steel is greatly improved and is comparable to the reheat-quenched 8620 steel. This is attributed to the larger reduction ratio in grain size and deeper case depth of reheat-quenched 4140 steel as compared to direct-quenched and reheat-quenched 8620 steels.

Kim, H.J.; Kweon, Y.G. [Research Inst. of Industrial Science and Technology, Pohang (Korea, Republic of). Steel Products Div.

1996-09-01

45

High cycle fatigue behavior of gas-carburized medium carbon Cr-Mo steel  

Science.gov (United States)

High cycle fatigue properties of gas-carburized 4140 steel were assessed to compare with those of 8620 steel which is widely used as a carburizing steel. Fatigue limit was evaluated associated with microstructure, case depth, and distribution of retained austenite and compressive residual stress near the surface. Test results indicated that the reheat quenching method of 4140 and 8620 steels produced a reduction in grain size, retained austenite level, and compressive residual stress at the surface and an increase in fatigue limit. The fatigue limit of direct-quenched 4140 steel shows substantially lower value than that of direct-quenched 8620 steel due to larger grain size of direct-quenched 4140 steel. However, the fatigue limit of reheat-quenched 4140 steel is greatly improved and is comparable to the reheat-quenched 8620 steel. This is attributed to the larger reduction ratio in grain size and deeper case depth of reheat-quenched 4140 steel as compared to direct-quenched and reheat-quenched 8620 steels.

Kim, Hyung-Jun; Kweon, Young-Gak

1996-09-01

46

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

Energy Technology Data Exchange (ETDEWEB)

In nuclear power plants, it is very important to foresee occurring events with in-operation -inspection (IOI) since the foreseeing makes plant maintenance more speedy and reliable. Moreover, information on plant condition under operating would make period of in-service inspection (ISI) shorter because maintenance plan can be made effectively using the information. In this study, a high cycle fatigue diagnostic system is being developed applying to especially pipe branches with small diameter under in-operating condition, which are in the radioactive areas of PWR plants and hard to access. This paper presents a concept of the in-operating diagnostic system and current status of developing sensing systems. (author)

Doi, So-myo; Nekomoto, Yoshitsugu; Takeishi, Masayuki [Mitsubishi Heavy Industries Ltd., Tokyo (Japan); Miyoshi, Toshiaki; O' shima, Eiji

1999-07-01

47

Shot-Peening Effect on High Cycling Fatigue of Al-Cu Alloy  

Science.gov (United States)

The present work was aimed at evaluating the effects of shot-peening on the high cycle fatigue performance of the age-hardening aircraft alloy Al 2024 at different almen intensities. Shot-peening to full coverage (100 pct) was performed using spherically conditioned cut wire (SCCW 14) with an average shot size of 0.36 mm and at almen intensities of 0.1, 0.2, and 0.3 mmA. After applying the various mechanical surface treatments, the changes in the surface and near-surface layer properties such as microhardness, residual stress-depth profiles, and surface roughness were determined. The microhardness, surface roughness, and the residual stresses increased proportionally with the almen intensity. Electropolitically polished conditions were used as reference in the mechanically surface treated specimens. A significant improvement was seen in the fatigue performance of the 0.1 mmA.

Fouad, Yasser; Metwally, Mostafa El

2013-07-01

48

Prediction method of metal surface temperature fluctuation for evaluation of high cycle thermal fatigue  

International Nuclear Information System (INIS)

[en] Nuclear reactor plants often cause high-cycle thermal fatigue damages (thermal striping) due to turbulent temperature fluctuations resulting from the mixing of hot and cold fluid. The boundary layer attenuation effects for fluid temperature fluctuation have been greatly desired to be studied in order to improve the evaluation accuracy high-cycle thermal fatigue damages. This paper describes the strict derivation of the power spectrum method to evaluate effective heat transfer coefficients required to predict the surface temperature fluctuation from the measured fluid temperature. Two prediction methods of metal surface temperature fluctuation: 'Improved Time Range Method' and 'Frequency Range Method' were proposed using the effective heat transfer coefficient predicted by the power spectrum method and fluid temperature fluctuation data. The prediction errors of these methods were investigated using parallel impinging jet test data. It was found that the metal temperature fluctuations predicted by the two methods agreed with the corresponding experimental data and the validity of the methods were demonstrated. Metal surface temperature fluctuation was predicted by the two methods. The predicted results appeared to be in good agreement each other and no marked difference in prediction accuracy were found between the Time Range Method and the Frequency Range Method. (author)

2003-01-01

49

On fatigue process and life  

International Nuclear Information System (INIS)

[en] It is estimated that about 80 -90 % mechanical failures are due to fatigue loading. The failures might be avoided by applying heavy safety factors or by adopting over-conservating lifing techniques e.g. safe-life approach. However, this would result in inefficient and un-economical use of materials and components. Therefore, it is important to predict fatigue life as accurately as possible so that a good balance between safety and economy could be achieved. For macro-scale analysis, the fatigue life (and behavior) is generally divided into four regions: crack initiation, small fatigue crack propagation, long fatigue crack propagation and rapid crack propagation. In real designing the first two, crack initiation and small fatigue crack propagation, are the most important; and unfortunately in literature the life estimation for both is not very accurate. The first one, crack initiation, is not even very well defined. In this paper, a tentative division into seven small zones for micro-scale response is suggested. Our aim is to propose a shifting from the classical macro-scale analysis to a new concept, the suggested seven small zones, in order to comprehensively define the fatigue process and definitively improve the estimate of total fatigue life as a final outcome. (author)

2003-01-01

50

Long life fatigue of type 304 stainless steel  

International Nuclear Information System (INIS)

Fully reversed axial strain-controlled and load-controlled fatigue experiments have been conducted on type 304 stainless steel in air at 6000C and long-life or high cycle (more than 104 cycles to failure) fatigue properties have been obtained. Under strain-controlled conditions, the well-known Manson-Coffin relationship has not been observed. It was also found that softening occurred at the end of the primary hardening, followed by secondary hardening with further strain cycling. Under load-controlled conditions, fatigue life was shown to be significantly sensitive to the cyclic frequency. Strain-controlled fatigue life is compared with load-controlled fatigue life based on the strain range coverted from controlled stress range using the cyclic stress-strain relations. (orig.).

1985-01-01

51

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

International Nuclear Information System (INIS)

[en] In nuclear power plants, it is very important to foresee occurring events with in-operation -inspection (IOI) since the foreseeing makes plant maintenance more speedy and reliable. Moreover, information on plant condition under operating would make period of in-service inspection (ISI) shorter because maintenance plan can be made effectively using the information. In this study, a high cycle fatigue diagnostic system is being developed applying to especially pipe branches with small diameter under in-operating condition, which are in the radioactive areas of PWR plants and hard to access. This paper presents a concept of the in-operating diagnostic system and current status of developing sensing systems. (author)

1999-01-01

52

Study of the influence of microstructure on fatigue crack propagation in the high cycle fatigue regime in 316L steel  

International Nuclear Information System (INIS)

Full text of publication follows: In the High cycle fatigue regime, about 80 percent of the fatigue live of austenitic stainless steel specimens consists in the propagation of short cracks whose length is comparable to the size of few grains. This high sensitivity of crack propagation to microstructure can explain partly the dispersion that is observed in this regime. At very low load level close to the fatigue limit, this dispersion can reach a factor 100 which complicates predictions of fatigue lives of large structures in service. As a consequence, to assess and predict this dispersion, it is necessary to understand better how microstructure influences locally crack propagation, i.e., the development of cyclic plasticity at the crack tip. In this aim, we propose to describe the influence of crystallographic orientation on the cyclic behavior of the grains of 316L stainless steel using crystal plasticity theory. In a first step, the stress strain response of the 316L grains is simulated using elastic-plastic constitutive equations that have been implemented in the three dimensional finite element code Cast3m of the CEA. The evolution of the resolved shear stress on each slip system is described with a non linear kinematics hardening law. This law is identified using cyclic stress strain curves obtained on austenitic stainless steel monocrystal. In a second step, the crack tip opening displacement (CTOD) will be calculated for different crystallographic orientation in order to quantify the influence of the crystallographic orientation of the grain at the crack tip on crack propagation. A statistic treatment of the CTOD values obtained from the finite element simulations performed at the local scale of the grain can help to understand the dispersion observed at the macroscopic scale. (authors)

2007-01-01

53

Comparison of the very high cycle fatigue behaviors of INCONEL 718 with different loading frequencies  

Science.gov (United States)

In order to clarify the differences of very high cycle fatigue (VHCF) behavior of nickel based superalloy IN718 with different loading frequencies, stress-controlled fatigue tests were carried out by using ultrasonic testing method (20 KHz) and rotary bending testing method (52.5 Hz), both at room temperatures, to establish stress versus cycles to failure (S-N) relationships. Results disclosed that cycles to failure at a given stress level increased with an increase of the applied frequency, i.e., the higher frequency produced an upper shift of the S-N curves. Fractographic analysis suggested that crack initiation and propagation behaviors had large differences: cracks in low-frequency tests preferentially initiated from multiple sources on the specimen surface, while in high-frequency tests, cracks mostly originated from a unique source of subsurface inclusions. Subsequently, frequency-involved modeling was proposed, based on the damage accumulation theory, which could well illustrate qualitatively those comparisons due to different loading frequencies.

Zhang, YangYang; Duan, Zheng; Shi, HuiJi

2013-03-01

54

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

Directory of Open Access Journals (Sweden)

Full Text Available 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, with 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.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 elementos 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.

Pedro P. Camanho; Albert Turon; Josep Costa

2008-01-01

55

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese 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 elementos 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, with 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 load (more) ed 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.

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

2008-01-01

56

The Effect of Nitriding Treatment Variables on the Fatigue Limit of Alloy Steel (34crnimo6) Under High Cycle Fatigue  

International Nuclear Information System (INIS)

The aim of this research is to improve the fatigue limit for alloy steel (34CrNiMo6) by salt bath nitriding process. This property is more effective to increase the fatigue life for parts which are used in continuous cyclic loading. All the fatigue tests were implemented before and after nitriding process under rotating bending. Constant and variable capacity stresses were applied before and after nitriding processes. The nitriding process were implemented in salt bath component at three different times (1, 2, 3) hr when temperature was constant at (555 degree centigrade). The depth of the nitride layer reached (0.24, 0.37, 0.5) mm. The nitriding process repeated of another specimens at the same times but the temperature was (600 degree centigrade), the layer depth reached (0.28, 0.41, 0.55) mm. The formation of a high nitrogen iron phases were detected with a layer of the hard chrome nitrides on the surface. The nitriding process is forming the barriers on the surface that resist the initiation and propagation of cracks, as well as generating the compressive residual stresses which delay the progress of fatigue crack. This research deduced that the nitriding processes increased the fatigue limit and this limit is proportional to the time of the nitriding process. When the time increased, the depth of nitride layer is increased, but decreased when the temperature increased to (600 degree centigrade) because of the formation of brittle phase,in spite of the increase in layer depth. (author)

2009-01-01

57

Correlation of low-cycle and high-cycle fatigue data for solution-annealed Incoloy 800  

International Nuclear Information System (INIS)

It is shown that load-controlled high-cycle fatigue test data for Incoloy 800 may be correlated successfully with strain-controlled low-cycle results, provided stress-to-strain conversions and strain-to-stress conversions are made with the aid of cyclic stress-strain curves which must take into consideration steady state, or average, behavior during test. The differences in the initial stress-strain response for load- and strain-control procedures do not appear to significantly influence the correlation. In addition, the strain rate differences for the low- and high-cycle data given do not appear to be important. (Auth.)

1978-03-16

58

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)

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.)

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

2008-08-15

59

Application of in situ thermography for evaluating the high-cycle and very high-cycle fatigue behaviour of cast aluminium alloy AlSi7Mg (T6).  

UK PubMed Central (United Kingdom)

The present paper illustrates the application of infrared thermal measurements for the investigation of crack initiation point and crack propagation in the high-cycle and the very high-cycle fatigue range of cast AlSi7Mg alloy (A356). The influence of casting defects, their location, size and amount was studied both by fractography and thermography. Besides internal and surface fatigue crack initiation as a further crack initiation type multiple fatigue crack initiation was observed via in situ thermography which can be well correlated with the results from fractography obtained by SEM investigations. In addition, crack propagation was studied by the development of the temperature measured via thermography. Moreover, the frequency influence on high-cycle fatigue behaviour was investigated. The presented results demonstrate well that the combination of fractography and thermography can give a significant contribution to the knowledge of crack initiation and propagation in the VHCF regime.

Krewerth D; Weidner A; Biermann H

2013-12-01

60

Evaluation of high cycle thermal fatigue caused by mixing flow at RHR system  

Energy Technology Data Exchange (ETDEWEB)

In case of nuclear power plant, it is still room to bring pipe and instrument thermal fatigue because of carrying with changing temperature both under operation and in shutdown. Therefore pipe and instrument are designed not to exceed fatigue limit by material until close. However local part of pipe and instrument is damaged by thermal fatigue out of design. Now it is slowly known to local thermal fatigue mechanism. So in this paper, it is evaluated that how fluid's temperature change in pipe from mixing hot water with cold water, one of local thermal fatigue mechanism, is relation to pipe integrity.

Lee, S. K.; Lee, W. R.; Lee, H. H.; Kim, T. R. [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Lee, B. W.; Shin, S. D. [Korea Hydraulic and Nuclear Power Company, Taejon (Korea, Republic of)

2004-07-01

 
 
 
 
61

High cycle thermal fatigue crack initiation and growth behavior in simulated BWR environment  

International Nuclear Information System (INIS)

At a tee junction point of piping system, hot water and cold water is mixed with each other in a whirl. The vibrating mixing boundary between the hot and cold water causes a temperature fluctuation on an inside surface of the pipe just after the connection point. The temperature fluctuation yields a cyclic thermal stress near the pipe surface and results in the crack initiation. In this study the thermal fatigue tests using disk specimens in simulated BWR environment were performed and the thermal fatigue crack initiation strength was compared with the mechanical fatigue strength. Furthermore the thermal fatigue crack arrest depth was analyzed using the linear fracture mechanics, and the arrest depth was found to be in proportion to the reciprocal root of the frequency of temperature fluctuation, and the experimental results agreed well with the analytical ones. (author)

2003-01-01

62

On the nature and crystallographic orientation of subsurface cracks in high cycle fatigue of Ti-6Al-4V  

Science.gov (United States)

Subsurface fatigue damage, in the form of cracking of the ? phase, was observed in Ti-6A1-4V during high cycle fatigue of total hip prostheses tested in a simulated physiological test geometry and environment. The subsurface cracking was found only in the region of highest fatigue stresses and was present in a zone between 50 and 700 ?m beneath the surface. The density of these cracks appeared to depend on the fabrication process used to form the part, where the direction of forging deformation strongly influenced the texture and grain morphology of the near-? bimodal microstructure. A novel scanning electron microscopy (SEM) technique, using selected area channeling patterns (SACPs) and electron channeling contrast imaging (ECCI), is described and was used to determine the crystallographic orientation of the fracture plane in the a phase. The texture resulting from the forming operation appeared to be such that the basal pole of the hcp lattice became oriented in the direction of flow. Also, the deformation substructure (in the form of dislocation subcells) influenced the formation of the subsurface cracks. Observations based on four independent fractured grains, using the channeling analysis techniques, indicated that the fracture plane for these subsurface fatigue cracks is the pyramidal plane of the hcp lattice.

Gilbert, Jeremy L.; Piehler, Henry R.

1993-03-01

63

High cycle fatigue behavior of a nanostructured composite produced via extrusion of amorphous Al89Gd7Ni3Fe1 alloy powders  

International Nuclear Information System (INIS)

[en] A nanostructured composite Al89Gd7Ni3Fe1 alloy was created by extruding atomized amorphous Al89Gd7Ni3Fe1 powders at different extrusion ratios (ER = 5:1, 10:1, 20:1). The microstructures and mechanical properties produced were examined with special attention given to the high cycle fatigue properties. High cycle fatigue tests were conducted at room temperature under three-point bending at a stress ratio R = 0.1. Increasing the extrusion ratio (ER) improved the hardness, bend strength, and fatigue behavior, with alloys extruded at higher ER exhibiting bend strengths exceeding 1000 MPa and high cycle fatigue behavior well in excess of conventional aluminum alloys. The results obtained are compared to conventional aluminum alloys and particulate reinforced composites.

1151-01-00

64

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)

2008-01-01

65

Thermal mixing in T-junction piping system related to high-cycle thermal fatigue in structure  

International Nuclear Information System (INIS)

The numerical simulation code 'MUGTHES' has been developed by the authors to investigate thermal striping phenomena caused by turbulence mixing of fluids at different temperatures and to utilize with an evaluation method for high-cycle thermal fatigue. MUGTHES employs the large eddy simulation (LES) approach to predict unsteady thermal mixing phenomena and the boundary fitted coordinate (BFC) system to fit complex boundary shapes in a reactor. In this paper, thermal striping phenomena in a T-junction piping system (T-pipe) are numerically simulated as a code validation study and the simulation results are used to investigate temperature fluctuation generation mechanism in the T-pipe. The boundary conditions for the simulation are chosen from the WATLON experiment which was a water experiment conducted at JAEA using the T-pipe. In the simulation, the standard Smagorinsky model is employed as a turbulence eddy viscosity model with the model coefficient of 0.14 (=Cs). Numerical results of MUGTHES are compared with experimental velocity and temperature profiles. Applicability of MUGTHES to the thermal striping phenomena is confirmed through the numerical simulation in the T-pipe and the characteristic large-scale vortex structure which dominates thermal mixing and may cause high-cycle thermal fatigue is revealed. (author)

2010-01-01

66

High-cycle fatigue crack growth in the Paris- and threshold regime at ultrasonic frequencies  

Energy Technology Data Exchange (ETDEWEB)

Fatigue crack growth and {Delta}K{sub th} measurements can be performed at ultrasonic frequencies within very short testing times. The main features of ultrasonic fracture mechanical testing and various experimental possibilities are described. Testing is possible at different positive and negative mean loads. Likewise static shear loads may be superimposed to the 20 kHz axial fatigue loads. Also torsional loading at ultrasonic frequency has been developed. In addition, not only constant, but also multi-step or random loading can be performed with computerized devices. Results are reported and compared with measurements at conventional frequencies.

Stanzl-Tschegg, S. [Univ. of Agricultural Sciences, Vienna (Austria)

1997-12-31

67

Simulation of damage evolution in a uni-directional titanium matrix composite subjected to high cycle fatigue  

Energy Technology Data Exchange (ETDEWEB)

Among the advanced material systems under consideration for use in gas turbine engines special consideration is given to the family of metal matrix composites especially the Titanium matrix composites. This is attributed mainly to the superior stiffness to weight ratio as compared to other conventional materials. The lack of appropriate material models capable of simulating the material behavior realistically is a major drawback in the success of this material system. In the current research the results of numerical simulations for the damage evolution in a unidirectional Titanium matrix composite subjected to high cycle fatigue loading are presented. The employed micro-mechanical fatigue damage model has been developed previously by the authors. Results obtained from the numerical simulations include those from parametric studies on the influence of various model parameters as well as those for damage evolution in the constituents during the material lifetime. Comparison of the final results for the number of cycles to failure for room temperature fatigue with those obtained from experimental investigations show good agreement. (author)

Echle, R. [HILTI Servicegesellschaft GbR, Kaufering (Germany); Voyiadjis, G.Z. [Louisiana State University, Baton Rouge, LA (United States). Dept. of Civil and Environmental Engineering

1999-10-01

68

High cycle thermal fatigue crack initiation and growth behavior in the semi-infinite plate model  

International Nuclear Information System (INIS)

[en] At a T-junction in piping systems, hot and cold water mixes in a whirl. The vibrating mixing boundary between the hot and cold water causes a temperature fluctuation on the inner surface of the pipe just after the connection point at T-junction, and this temperature fluctuation yields a cyclic thermal stress near the pipe surface, resulting in crack initiation. In this study the thermal stress distribution was analyzed for a semi-infinite plate model and the fatigue crack growth behavior was examined. The thermal fatigue cracks are arrested and the arrested crack depth is found to be in proportion to the reciprocal root of the frequency of temperature fluctuation

1994-01-01

69

Influence of Microstructural Inhomogeneity and Residual Stress on Very High Cycle Fatigue Property of Clean Spring Steel  

Science.gov (United States)

The present study investigated the very high cycle fatigue (VHCF) properties of a spring steel SUP7-T386 under the conditions of surface grinding and electro-polishing by performing the axial loading test at a stress ratio of -1. The influence of the microstructural inhomogeneity (MI) generated in the process of heat treatment and the residual stress induced by surface grinding on the VHCF properties was discussed. This steel with surface grinding exhibits the continuously descending S-N characteristics, corresponding to the surface flaw-induced failure at high stress level and the interior flaw-induced failure at low stress level. Otherwise, with surface electro-polishing, it exhibits continuously descending S-N characteristics with lower fatigue strength, but only corresponding to the surface flaw-induced failure even at low stress level. Compared with the evaluated maximum inclusion size of about 11.5 ?m, the larger MI size and the compressive residual stress play a key role in determining fatigue failure mechanism of this steel under axial loading in the VHCF regime. From the viewpoint of fracture mechanics, MI-induced crack growth behavior belongs to the category of small crack growth, and threshold stress intensity factors controlling surface and interior crack growth are evaluated to be 2.85 and 2.51 MPa m1/2, respectively. The predicted maximum MI size of about 27.6 ?m can be well used to evaluate surface and interior fatigue limit of this steel under axial loading in the VHCF regime, combined with the correction of residual stress.

Li, Wei; Sakai, Tatsuo; Wang, Ping

2013-09-01

70

Multiple matrix cracking in a fiber-reinforced titanium matrix composite under high-cycle fatigue  

International Nuclear Information System (INIS)

An experimental study of multiple matrix cracking in a fiber-reinforced titanium alloy has been conducted. The focus has been on the effects of stress amplitude on the saturation crack density and the effects of crack density on hysteresis behavior. Comparisons have been made with predictions based on unit cell models, assuming the sliding resistance of the interface to be characterized by a constant interfacial shear stress. In addition, independent measurements of the sliding stress have been made using fiber pushout tests on both pristine and fatigues specimens.

1996-01-01

71

Tensile and high cycle fatigue properties of Zirconium alloy at elevated temperature  

International Nuclear Information System (INIS)

[en] Zirconium (Zr) alloys have been extensively used as cladding materials for fuel elements in nuclear reactor systems due to their low thermal neutron absorption cross-section, excellent corrosion resistance and good mechanical properties at high temperatures. Zirconium alloy containing 1.0 wt% Sn and small amounts of Fe and Cr is widely used as a spacer grid. In the present study, tensile tests were carried out for Zirconium alloy sheet-type specimens with different orientation and temperature conditions. In addition tention-tention fatigue test (stress ratio R=0.1) was studied at room temperature. The specimen surface was observed through scanning electron microscopy (SEM), and fracture mechanisms of the specimens were evaluated

2010-01-01

72

High-cycle metal fatigue under multiaxial loading damage accumulation models applied to an industrial structure  

International Nuclear Information System (INIS)

Some components in French nuclear power plants are submitted to thermo-mechanical loadings during their lifetime. Thermal fatigue cracking (striping) is observed in the mixing zones of the reactor in some areas of the residual heat removal system (RHR). Edge cracks located on the internal surface of the pipe are observed essentially near weld tips but also far from the weld. Crack initiation has been related in a qualitative way to the thermal fluctuation and to the detrimental effects of residual weld stress and surface finishing. The aim is to simulate the damage accumulation for two industrial structures : a mock-up of a RHR and the RHR itself. For that we used two endurance limit criteria for multiaxial loading : MATAKE and DANG VAN both based on the concept of critical plane. We extend these models to damage accumulation and constant or variable amplitude loading. Furthermore, in these models we have introduced a new parameter to take into account an initial hardening. These criteria have been implemented in Code-Aster the structural analysis finite element code of EDF [http://www.code-aster.org]. Finite Element simulations are carried out on a RHR structure and an experimental T-piece, denoted FATHER, in which cold water and hot water are mixed. In our computations the thermal loading used results from a thermo-hydraulic calculation realized at EDF R and D [1,2]. For the moment there is no guaranty about the validity of thermal loading, but we consider that it is sufficiently realistic to be employed. From the comparison of the numerical results we conclude that the damage is at least three times more important with models extended to variable amplitude than with those extended to constant amplitude. Furthermore when we compare the largest fatigue damage obtained with a variable amplitude criterion in which the pre-hardening coefficient is equal to 1.25, with a constant amplitude criterion the ratio is about ten. (authors)

2005-01-01

73

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)

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)

Lehericy, Y

2007-05-15

74

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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, ad (more) dressing 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.

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

2012-01-01

75

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. Final report  

Energy Technology Data Exchange (ETDEWEB)

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.

Bast, C.C.; Boyce, L.

1995-11-01

76

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. Final technical report, June 1992-January 1995  

Energy Technology Data Exchange (ETDEWEB)

This report presents the results of both the fifth and sixth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA). The research included on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model`s empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for five variables, namely, high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using an updated version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of high-cycle mechanical fatigue, creep and thermal fatigue was performed. Then using the current version of PROMISS, entitled PROMISS94, a second sensitivity study including the effect of low-cycle mechanical fatigue, as well as, the three previous effects was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect.

Bast, C.C.; Boyce, L.

1995-01-01

77

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)

2009-01-01

78

Aluminum/boron composite - fatigue life prediction  

International Nuclear Information System (INIS)

[en] The fatigue behaviour of a 6061-0 aluminum alloy reinforce with 0.25 volume fraction undirectional boron fibres of 100 ?m diameter has been investigated. The specimens were tested under constant stress amplitude using a stress ratio (minimum/maximum stress) of 0.2 with the fibres oriented at an angle to the loading direction in order to study the matrix dominated fatigue behaviour. Two sets of data were obtained for unidirectional specimens tested with fibre to load axis angles of 200 and 450 A third set of data was obtained with V 45 angle-ply specimens. It is shown that a microstress/strain analysis in conjunction with a multiaxial fatigue parameter can be applied to successfully predict the fatigue lives of these boron reinforced aluminum alloy composites. The multiaxial parameter enables a generalized strain-life relationship to be determined using limited experimental data. Once this generalized relationship is known, the life of the composite cycled under different loads and load-fibre angles can be predicted. (author)

2002-01-01

79

Aluminum/boron composite - fatigue life prediction  

Energy Technology Data Exchange (ETDEWEB)

The fatigue behaviour of a 6061-0 aluminum alloy reinforce with 0.25 volume fraction undirectional boron fibres of 100 {mu}m diameter has been investigated. The specimens were tested under constant stress amplitude using a stress ratio (minimum/maximum stress) of 0.2 with the fibres oriented at an angle to the loading direction in order to study the matrix dominated fatigue behaviour. Two sets of data were obtained for unidirectional specimens tested with fibre to load axis angles of 200 and 450 A third set of data was obtained with V 45 angle-ply specimens. It is shown that a microstress/strain analysis in conjunction with a multiaxial fatigue parameter can be applied to successfully predict the fatigue lives of these boron reinforced aluminum alloy composites. The multiaxial parameter enables a generalized strain-life relationship to be determined using limited experimental data. Once this generalized relationship is known, the life of the composite cycled under different loads and load-fibre angles can be predicted. (author)

Plumtree, A.; Glinka, G. [Univ. of Waterloo, Dept. of Mechanical Engineering, Waterloo, Ontario (Canada)]. E-mail: plumtree@uwaterloo.ca

2002-07-01

80

Fatigue life prediction of shot peened components  

Directory of Open Access Journals (Sweden)

Full Text Available Shot peening is one of the most effective surface treatments in order to prevent crack initiation and early crack propagation. Part of the studies to determine the fatigue performance of shot peening are based on experimental tests. Almost no work is published related with the prediction of shot peening behaviour. The present paper evaluates the ability of the current methodologies, used to predict fatigue life, on components treated with shot peening. The Finite Element Method was used to determine the stress, strain and strain energy due to shot peening of some specimens tested experimentally. These results were used to apply methods to predict the total fatigue life. A final discussion is presented about the ability of the methods used, to predict the fatigue life of the specimens tested experimentally.A grenalhagem é um dos tratamentos mais eficientes na prevenção da iniciação de fendas por fadiga e na fase inicial de propagação. Grande parte dos estudos sobre o feito da grenalhagem no comportamento à fadiga são experimentais. Praticamente não existem trabalhos publicados relativos ao estudo de previsão do comportamento da grenalhagem. Neste trabalho são usados modelos tradicionais, de determinação da vida à fadiga, em componentes grenalhados. O método dos elementos finitos é usado para determinar a tensão, extensão e energia de deformação de provetes grenalhados que foram testados experimentalmente. Estes resultados são usados em modelos de previsão da vida total à fadiga. É apresentada uma discussão sobre a capacidade dos modelos usados na previsão de vida à fadiga de provetes que foram testados experimentalmente.

R.A. Cláudio; J.M. Silva; C.M. Branco; J. Byrne

2008-01-01

 
 
 
 
81

Effects of conventional machining on high cycle fatigue behavior of the intermetallic alloy Ti-47Al-2Nb-2Cr (at percent)  

Science.gov (United States)

The purpose of this work was to test the hypothesis that surface alteration by conventional machining processes will have a strong influence on the high cycle fatigue (HCF) behavior of brittle intermetallic alloys. The near-gamma titanium aluminide alloy Ti-47Al-2Nb-2Cr (at%) was selected as a model for this class of alloys. Grinding and turning under production conditions doubled the near-surface hardness, and turning hardened the alloy to a depth of 180mum. The heavily deformed outer 20mum of turned samples recrystallized in less than 1 hour when heated to the anticipated service temperature of 760sp°C. Step loaded axial fatigue tests comparing turned samples to an electropolished control group were performed at 23 and 760sp°C. The initial maximum stress level was 75% of the yield strength, and was increased 20 MPa after every million cycles until failure. Miner's Rule analyses of the step loaded test histories confirmed that the last two stress levels are most damaging. Fatigue behavior was defined by three parameters: the highest stress at which the sample survived a 10sp6 cycle block (10sp6 cycle endurance strength, Ssb{e}), the maximum stress at failure (fatigue strength, Ssb{f}), and the number of cycles at the final stress level (Nsb{f}). (Because of the step loaded test method, Ssb{e} is 20 MPa less than Ssb{f}.) No effect of machining on fatigue strength or initiation sites was found at 23sp°C. At 760sp°C, turning improved average strength by 5% and average Nsb{f} by about 1.5 orders of magnitude. This improvement was attributed to fine recrystallized grains in the outer 10-30mum which suppressed surface crack initiation. Air exposure at 760sp°C for 24 hours prior to 23sp°C testing reduced fatigue strength compared to the as-manufactured condition. In all cases, cracks initiated at stress intensities below the long crack thresholds. Stress intensity threshold values were independent of surface condition and test temperature. These results indicate that surface deformation from conventional machining will not have a strong effect on fatigue strength at low temperatures. However, thermal stability of the deformed layer and environmental effects can be significant variables in fatigue behavior of brittle intermetallic alloys.

Jones, Peggy Ellis

82

Control technique of high-cycle thermal fatigue at a mixing tee with a 90-degree bend upstream by changing its location  

International Nuclear Information System (INIS)

In nuclear and various power plants, there are many mixing tees at which different temperature fluids are mixed. At this kind of mixing tee, temperature fluctuation in fluids due to the unstable mixing is transported to the surrounding wall, which leads to high-cycle thermal fatigue of structural materials. Depending on the amplitude and frequency of the temperature fluctuation, it could induce cracks on the pipe surface and in the worst case lead to coolant leakage. For pipe maintainability and its reliability improvement in the future power plans, therefore, it becomes important to control the high-cycle thermal fatigue. Particularly in the case of the mixing tee with a 90-degree bend upstream, an unsteady secondary flow arises in the 90-degree bend, and then strongly affects the fluid mixing. Furthermore, the unsteady secondary flow has the tendency to change its velocity distribution after the bend outlet. Therefore, the location of the mixing tee is one of the important parameters to characterize the mixing structure and the temperature fluctuation near the wall. In this study, the temperature fluctuation and its intensity, including frequency analysis, and the fluid mixing structure above the mixing tee are investigated experimentally in different cases of location of the mixing tee from the 90-degree bend outlet. In case of closer location of the mixing tee from the 90-degree bend, the fluid mixing area tends to shift to the inward side of the bended pipe. As a result, the temperature fluctuation intensity becomes lower and decays faster in the streamwise direction. This result means that the location of the mixing tee strongly affects the fluid mixing and the temperature fluctuation near the wall. Experimental results suggest that changing the location of the mixing tee closer to the 90-degree bend could be an effective control technique for the higher-cycle thermal fatigue. (author)

2007-01-01

83

Experimental study on prevention of high cycle thermal fatigue in a compact reactor vessel of advanced sodium cooled reactor. Thermal striping phenomena at bottom of upper internal structure  

International Nuclear Information System (INIS)

Japan sodium-cooled fast reactor, JSFR, has been investigated in the frame work of Fast Reactor Cycle Technology Development Project (FaCT). As the temperature difference between the control rod channels and the core fuel subassemblies is around 100degC, temperature fluctuation due to the fluid mixing at the core outlet may cause high cycle thermal fatigue at the bottom of Upper Internal Structure (UIS). Then, a water experiment was conducted using a 1/3 scale 60 degree sector model. Temperature and its fluctuation intensity distributions around the control rod were measured and an effect of the improved structure against the thermal fatigue was examined. The objectives of the experiment are as follows; (1) to grasp the flow pattern around the control rod(CR) channel outlet, (2) to grasp the amplitude and the frequency characteristics of the temperature fluctuation, (3) to confirm the effect of a countermeasure for the high cycle thermal fatigue. As a result, thermal striping phenomena in the region between the fuel subassembly outlet and the bottom of the UIS were grasped. The geometry of the UIS bottom and the handling head of the primary CR channel was modified so as to suppress the cold jets exiting from the CR channels. The comparison of measured temperature fluctuations around the CR channels revealed that the modified geometry was effective to decrease the temperature fluctuation intensity and amplitude in the sensitive frequency band to the stress in the structures. Temperature fluctuation intensity distributions at the boundary between blanket subassemblies and core fuel subassemblies were also grasped. (author)

2012-01-01

84

Effects of conventional machining on the high cycle fatigue strength and crack initiation sites of the gamma titanium aluminide alloy Ti-47Al-2Nb-2Cr (at%) at 23 and 760 C  

Energy Technology Data Exchange (ETDEWEB)

Effects of a deformed surface layer, created by conventional machining, on the high cycle fatigue strength (10e6 cycles) and fatigue initiation sites of Ti-48Al-2Nb-2Cr (at%) were examined above and below the ductile-to-brittle transition temperature. All samples were tested to failure under the same step loading profile. Comparisons were made between samples having the same load history. At room temperature, fatigue strength and initiation sites were equivalent for turned and electropolished surface conditions. At the anticipated service temperature, 760 C, the work hardened layer created by turning quickly recrystallized. This fine recrystallized surface enhanced the fatigue crack initiation resistance of turned specimens when compared to coarse grained electropolished samples which did not recrystallize during the test. The severe surface deformation resulting from conventional machining did not impair the high cycle fatigue behavior of this intermetallic alloy under the conditions evaluated.

Jones, P.E.; Eylon, D.

1999-07-01

85

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.

2010-01-01

86

Fatigue Life Investigation of PZT Ceramics by MSP Method  

Directory of Open Access Journals (Sweden)

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.

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

2012-01-01

87

Leakage from CVCS pipe of regenerative heat exchanger induced by high-cycle thermal fatigue at Tsuruga Nuclear Power Station Unit 2  

International Nuclear Information System (INIS)

[en] On July 12, 1999 while Tsuruga-2, PWR 4-loop plant, was operating at full power (1,160 MWe), unidentified leakage inside the primary containment vessel was detected. As the leakage was identified, the plant promptly started to proceed to cold shutdown. Visual inspection after an isolation of the CVCS (Chemical and Volume Control System) revealed that the leakage was from a connecting pipe between the middle and lower stages in the CVCS regenerative heat exchanger. The CVCS regenerative heat exchanger has three shells, i.e. the upper shell, the middle shell and the lower shell. Each heat exchanger shell has an inner cylinder containing a heat exchanger tube bundle. Reactor coolant is cooled inside the inner cylinder, however, the temperature of the coolant which flows outside the inner cylinder keeps high. These two coolant flows are mixed around the outlet of the inner cylinder. Thermal hydraulic mock-up tests simulating internal flows in the heat exchanger were conducted along with thermal and structural analyses to investigate a high-cycle thermal fatigue mechanism. As a result of the investigation, the cause of the leakage from the connecting pipe was considered to be as follows; (1) Flow out of the lower temperature bypass flow region occurred repeatedly at the lower part of the shell which yielded a cyclic deformation of the shell due to thermal expansion and shrinkage. (2) This cyclic deformation caused a cyclic change of the gap between the inner cylinder support ring and shell, and consequently the cyclic change of the flow pattern at the region where the bypass flow and main flow mixed. (3) Superposition of lower frequent temperature change due to the change of flow pattern and higher frequent temperature fluctuation due the mixture of the bypass flow and main flow caused high-cycle thermal fatigue cracking. (author)

2000-01-01

88

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)

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.)

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

89

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

2007-01-01

90

Mixed-Mode, High-Cycle Fatigue-Crack Growth Thresholds in Ti-6Al-4V: A Comparison of Large and Small Crack Behavior  

UK PubMed Central (United Kingdom)

: There are few experimental results to date describing the crack-propagationthreshold behavior of short fatigue cracks under multiaxial loading conditions. To address thisneed, in the present study, the variation in mixed-mode, high-cycle fatigue-crack growththresholds with crack size and shape are reported for a Ti-6Al-4V turbine blade alloy, heattreated to two widely different microstructural conditions, namely fine-grained bimodal andcoarser fully lamellar microstructures. Specifically, fatigue thresholds are examined forthrough-thickness large cracks (as compared to the microstructural dimensions), throughthicknessshort cracks (< 200 m in length), and small, semi-elliptical surface cracks(comparable with microstructural dimensions), under the effect of combined mode I and modeII loading for load ratios (ratio of minimum to maximum load) ranging from 0.1 to 0.8. For arange of mode-mixities, large crack, mode I thresholds, #K I,TH , were found to be decreasesubstantially with increasing phase angle. However, by characterizing in terms of the range instrain energy release rate, #G TH , incorporating both mode I and mode II contributions, it wasobserved that the pure mode I threshold could be regarded as a "worst case" large crackthreshold under mixed-mode loading in this alloy. An estimation of the shielding-corrected,crack-driving forces actually experienced at the crack tip was also performed. For such neartip(shielding-corrected) thresholds, the influence of mode-mixity was dramatically reduced.Corresponding thresholds for through-thickness short cracks and small surface cracks, wherethe effect of such shielding is minimized, were also substantially less sensitive to mode-mixityand corresponded in magnitude to the shielding-corrected large crack...

R. K. Nalla; J. P. Campbell; R. O. Ritchie

91

Analysis of fatigue properties and failure mechanisms of Ti6Al4V in the very high cycle fatigue regime using ultrasonic technology and 3D laser scanning vibrometry.  

UK PubMed Central (United Kingdom)

Accelerated fatigue tests with Ti6Al4V were carried out using a 20kHz ultrasonic testing facility to investigate the cyclic deformation behavior in the Very High Cycle Fatigue (VHCF) regime in detail. Beside parameters like the ultrasonic generator power and the displacement of the specimen, a 3D laser scanning vibrometer was used to characterize the oscillation and fatigue behavior of the Ti-alloy. The course of the S-Nf curve at the stress ratio R=-1 shows a significant decrease of the bearable stress amplitude and a change from surface to subsurface failures in the VHCF regime for more than 10(7) cycles. Microscopic investigations of the distribution of the ?- and ?-phase of Ti6Al4V indicate that inhomogeneities in the phase distribution are reasons for the internal crack initiation. High resolution vibrometry was used to visualize the eigenmode of the designed VHCF-specimen at 20kHz in the initial state and to indicate local changes in the eigenmodes as a result of progressing fatigue damage. Non-contact strain measurements were realized and used to determine the stress amplitude. The determined stress amplitudes were correlated with strain gauge measurements and finite element analysis.

Heinz S; Balle F; Wagner G; Eifler D

2013-12-01

92

Life prediction of creep fatigue at very high temperatures  

Energy Technology Data Exchange (ETDEWEB)

Life prediction methods of creep fatigue were investigated to consider applications to Hastelloy XRs at very high temperatures where materials would be damaged severely by creep deformation. The ductility exhaustion rule, coupled with a creep constitutive equation consisting of primary and secondary stages, showed a good prediction of creep-fatigue life as well as the damage-rate equations. The strain range partitioning method was also discussed regarding its possibility for life prediction. The results of these methods were compared with the time fraction rule in conjunction with the Miner's rule. In these experiments, creep tests were done under constant stress condition in air, and low-cycle fatigue tests were carried out with and without a dwell period in vacuum. Creep-fatigue damage was evaluated in the life of low-cycle fatigue tests with a dwell period. All specimens were fabricated from the same hot-rolled plates to reduce scatter in different heat treatments. (author).

Kikuchi, Kenji; Kaji, Yoshiyuki; Muto, Yasushi (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment); Kitade, Shoji

1993-01-01

93

Strain rate dependence of the growth rate of grain boundary cavities during the high cycle high temperature fatigue of copper  

Energy Technology Data Exchange (ETDEWEB)

High temperature fully reversed fatigue tests of high purity copper were made as a function of stress amplitude. A mean cavity volume V{sub p} and corresponding number density of cavities N{sub p} were determined from the total cavity volume fraction V{sub v} obtained from precision density measurements (PDM) and the total cavity surface area S{sub v} calculated from small angle neutron scattering (SANS) measurements. Under the range of stress amplitudes tested, the plastic strain rate d{epsilon}{sub p}/dt was found to cover three orders of magnitude. The results of these tests of the influence of stress amplitude on cavity growth were combined with previous results in which the frequency of cycling was varied. It was found that the cavity growth rate correlates well with the measured plastic strain and stress amplitude through the relation dV{sub p}/dt {proportional{underscore}to} (d{epsilon}{sub p}/dt){sup 0.45} {proportional{underscore}to} {Delta}{sigma}{sup 2}.

Barker, J.G.; Weertman, J.R.; Pedersen, J.S.

1999-07-01

94

Influence of static magnetic field on fatigue life  

Energy Technology Data Exchange (ETDEWEB)

The crack growth rate in a central notched carbon steel plate was not affected by static magnetic field under cyclic tension fatigue, but under reversed torsional fatigue some decrease of fatigue life was clearly observed in a static magnetic field for carbon steel bar. The decrease of fatigue life changed with specimen configuration, temperature, shear stress amplitude, specimen support condition. The additional tensile stress which gave almost same decrease of torsional fatigue life in the magnetic field was confirmed experimentally to be 20-50 MPa. The magnetostriction of tested steel was shrinkage in the longitudinal direction and elongation in the circumferential direction, and the volume magnetostriction was zero in this experimental condition. Some shift of fracture appearance to that of higher stress level were observed in a magnetic field: it would suggest a shear stress increase by the magnetic moment due to the Wertheim effect in which a circumferential magnetic field appears in a longitudinally magnetized bar when twisted. (author).

Misumi, Masaaki; Ohkubo, Masafumi [Seikei Univ., Musashino, Tokyo (Japan)

1993-12-31

95

Influence of static magnetic field on fatigue life  

International Nuclear Information System (INIS)

[en] The crack growth rate in a central notched carbon steel plate was not affected by static magnetic field under cyclic tension fatigue, but under reversed torsional fatigue some decrease of fatigue life was clearly observed in a static magnetic field for carbon steel bar. The decrease of fatigue life changed with specimen configuration, temperature, shear stress amplitude, specimen support condition. The additional tensile stress which gave almost same decrease of torsional fatigue life in the magnetic field was confirmed experimentally to be 20-50 MPa. The magnetostriction of tested steel was shrinkage in the longitudinal direction and elongation in the circumferential direction, and the volume magnetostriction was zero in this experimental condition. Some shift of fracture appearance to that of higher stress level were observed in a magnetic field: it would suggest a shear stress increase by the magnetic moment due to the Wertheim effect in which a circumferential magnetic field appears in a longitudinally magnetized bar when twisted. (author)

1993-01-01

96

Fatigue tests and life estimation of Incoloy alloy 908  

International Nuclear Information System (INIS)

Incoloy reg-sign alloy 908* is a candidate conduit material for Nb3Sn cable-in-conduit superconductors. The conduit is expected to experience cyclic loads at 4 K. Fatigue fracture of the conduit is one possible failure mode. So far, fatigue life has been estimated from fatigue crack growth data, which provide conservative results. The more traditional practice of life estimation using S-N curves has not been done for alloy 908 due to a lack of data at room and cryogenic temperatures. This paper presents a series of fatigue test results in response to this need. Tests were performed in reversed bending, rotating bending, and uniaxial fatigue machines. The test matrix included different heat treatments, two load ratios (R=-1 and 0.1), two temperatures (298 and 77 K), and two orientations (longitudinal and transverse). As expected, there is a semi-log linear relation between the applied stress and fatigue life above an applied stress (e.g., 310 MPa for tests at 298 K and R=-1). Below this stress the curves show an endurance limit. The aged and cold-worked materials have longer fatigue lives and higher endurance limits than the others. Different orientations have no apparent effect on life. Cryogenic temperature results in a much high fatigue life than room temperature. A higher tensile mean stress gives shorter fatigue life. It was also found that the fatigue lives of the reversed bending specimens were of the same order as those of the uniaxial test specimens, but were only half the lives of the rotating bending specimens for given stresses. A sample application of the S-N data is discussed.

1997-01-01

97

A predictive fatigue life model for anodized 7050 aluminium alloy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study is to predict fatigue life of anodized 7050 aluminum alloy specimens. In the case of anodized 7050-T7451 alloy, fractographic observations of fatigue tested specimens showed that pickling pits were the predominant sites for crack nucleation and subsequent failure. It has ...

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

98

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 specimens 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.

Søren Heide Lambertsen; Lars Damkilde; Anders Schmidt Kristensen; Ronnie Refstrup Pedersen

2013-01-01

99

Predicting mooring system fatigue life by probabilistic methods  

Energy Technology Data Exchange (ETDEWEB)

Failure of moored structures from accumulated fatigue damage in shackles, connecting links, chain and wire rope components is common. When systems will be deployed for long periods, it is especially important to determine at the design, inspection and maintenance stages the fatigue damage. Since slack moored structures behave in a highly nonlinear manner, commonly used fatigue analysis procedures are normally inadequate. This paper reviews present probablistic fatigue analysis methods, and provides a means for incorporating nonlinear mooring behavior into analysis and design to predict accumulated damage and remaining service life. The procedures presented are general, and they are also applicable to ship and buoy moorings, offshore terminals, and guyed and tension leg platforms.

Saders, D.R.; Dominguez, R.F.; Ho, K.C.; Lai, N.W.

1983-05-01

100

An investigation on fatigue life of borided AISI 1010 steel  

Directory of Open Access Journals (Sweden)

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.

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

2009-01-01

 
 
 
 
101

Probabilistic fatigue life prediction of metallic and composite materials  

Science.gov (United States)

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Xiang, Yibing

102

Fatigue life prediction in woven carbon fabric polyester composites  

International Nuclear Information System (INIS)

An analytical model, based on stiffness degradation during fatigue loading, which has been used for fatigue life predictions in the Fiber Reinforced Plastics (FRP), is employed to examine its validity to the fatigue life predictions in the Woven Fabric Reinforced Plastics. The rate of stiffness degradation (dE/dN) has been obtained from the constant amplitude fatigue testing of 8-ply coupons made from prepreg plain-weave woven carbon-carbon fabric having a polyester resin as the matrix material. The test coupons had three different ply stacking sequences, namely, the unidirectional (0)8,and two off axis plied (0,0,+45,-45)s, and (+45,-45,0,0)s orientations. The estimated fatigue lives obtained from the damage rate function dD/dN, which in turn was a function of the stiffness degradation rate dE/dN, were compared with the experimentally observed fatigue life data. It is shown that the stiffness degradation model provides reasonably good correlation between the analytically determined fatigue lives and the experimentally observed fatigue for the plain-weave woven Carbon-Carbon Fabric Reinforced Plastic Composites. (author)

1999-01-01

103

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

Science.gov (United States)

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.

Qi, Huan; Azer, Magdi; Deal, Andrew

2012-11-01

104

Temperature evolution and life prediction in fatigue of superalloys  

Science.gov (United States)

Low-cycle fatigue behavior of two superalloys, ULTIMET® alloy, Co-26 pct Cr-9 pct Ni (wt pct), and HAYNES® HR-120® alloy, Ni-33 pct Fe-25 pct Cr, was studied at room temperature. An infrared thermography system was employed to monitor the temperature evolution of fatigue processes for both superalloys. Temperature changes during fatigue were related to the hysteresis effect, and were successfully predicted, based on the consideration of the hysteresis effect and heat conduction. The temperature increase of a specimen from the initial to the equilibrium stages was used as an index to predict the fatigue life of the two superalloys. It was found that the fatigue-life predictions using the present model were in good agreement with the experimental results.

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

2004-03-01

105

Estimation of fatigue life of wind turbine`s blades  

Energy Technology Data Exchange (ETDEWEB)

We estimated the fatigue life-time of a wind turbine`s blade by modified Goodman`s rule counting by the Rain-Flow procedure each values and numbers of stresses measured at TAPPI Wind Park where it is very mountainous and very rough terrain. It was concluded that the fatigue life-time of a blade at our site would be 12 years. (author)

Tsuchiya, K.; Inomata, N. [Tohoku Electric Power Co., Inc., Research and Development Center, Sendai (Japan)

1996-12-31

106

Prestraining and its influence on subsequent fatigue life  

Energy Technology Data Exchange (ETDEWEB)

An experimental program was conducted to study the damaging effects of tensile and compressive prestrains on the fatigue life of nickel-base, Inconel 718 superalloy at room temperature. To establish baseline fatigue behavior, virgin specimens with a solid uniform gage section were fatigued to failure under fully reversed strain control. Additional specimens were prestrained to 2, 5, and 10% (engineering strains) in the tensile direction and to 2% (engineering strain) in the compressive direction under stroke control and were subsequently fatigued to failure under fully reversed strain control. Experimental results are compared with estimates of remaining fatigue lives (after prestraining) using three life prediction approaches: (1) the linear damage rule (LDR), (2) the linear strain and life fraction rule (LSLFR), and (3) the nonlinear damage curve approach (DCA). The Smith-Watson-Topper parameter was used to estimate fatigue lives in the presence of mean stresses. Among the cumulative damage rules investigated, the best remaining fatigue life predictions were obtained with the nonlinear damage curve approach.

Kalluri, S. [NYMA, Inc., Cleveland, OH (United States). NASA Lewis Research Center; Halford, G.R.; McGaw, M.A. [NASA Lewis Research Center, Cleveland, OH (United States)

1996-12-31

107

FATIGUE LIFE EVALUATION OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE  

Directory of Open Access Journals (Sweden)

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.

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

2012-01-01

108

APPLICATION OF MULTIBODY SIMULATION FOR FATIGUE LIFE ESTIMATION  

Directory of Open Access Journals (Sweden)

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

M. Kamal; M.M. Rahman; M.S.M. Sani

2013-01-01

109

Improved methods of creep-fatigue life assessment of components  

Energy Technology Data Exchange (ETDEWEB)

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.)

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

2009-07-01

110

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

Science.gov (United States)

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.

Neu, R. W.; Sehitoglu, Huseyin

1989-09-01

111

A fatigue life analysis of small fragment screws.  

UK PubMed Central (United Kingdom)

OBJECTIVES: To conduct a comparative fatigue analysis of several commonly used small fragment screws. DESIGN: Biomechanical laboratory study. SETTING: Research laboratory. MAIN OUTCOME MEASUREMENTS: A fatigue life analysis of seven different types of small fragment screws was conducted using a Wohler fatigue-testing machine. Four different types of 3.5-millimeter cortical screws were subjected to fatigue analysis. These included solid stainless steel screws from Synthes Ltd. (core diameter 2.4 millimeters), Zimmer Inc. (core diameter 2.4 millimeter), and Smith and Nephew Richards Inc. (core diameter 2.4 millimeters) and cannulated stainless steel screws from Synthes Ltd. (core diameter 2.5 millimeters). In addition, three types of 4.0-millimeter cancellous screws were tested. These included stainless steel screws from Synthes Ltd. (core diameter 1.9 millimeters), titanium screws from Synthes Ltd. (core diameter 2.0 millimeters), and titanium alloy screws from DePuy-Ace (core diameter 2.8 millimeters). Fatigue lives, as reflected by mean cycles to failure, were compared. RESULTS: The four types of cortical screws had longer fatigue lives than the Synthes cancellous screws did ( p < 0.001) but shorter fatigue lives than the DePuy-Ace cancellous screws did ( p < 0.0001). Among the cortical screws, the cannulated and solid Synthes screws and the solid Zimmer screws did not differ statistically. The Smith and Nephew Richards cortical screws failed at statistically fewer cycles than the Synthes solid and cannulated cortical screws did ( p < 0.003) but did not statistically differ from the Zimmer screws. The DePuy-Ace titanium alloy cancellous screw had the longest fatigue life of the tested implants by a large margin ( p < 0.0001). The Synthes pure titanium and stainless steel cancellous screws did not significantly differ. CONCLUSIONS: This analysis supports core diameter as the principal factor determining fatigue life as the results paralleled implant geometry. This design modification to improve bending and fatigue strength may come at a price to pullout strength, however, because of a decreased major-to-minor diameter and increased pitch. Cortical screws differed in fatigue performance despite identical dimensions, presumably highlighting the importance of implant processing and machining. Cannulated cortical screws performed well relative to solid screws, thereby supporting their clinical use. Pure titanium and stainless steel cancellous screws performed similarly in fatigue despite differing material properties, presumably because of geometric design differences. This report highlights some of the differences in the in vitro fatigue performance among several commonly used small fragment screws.

Merk BR; Stern SH; Cordes S; Lautenschlager EP

2001-09-01

112

Fatigue life assessment under multiaxial variable amplitude loading  

Energy Technology Data Exchange (ETDEWEB)

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.

Morilhat, P. [Electricite de France (EDF), 93 - Saint-Denis (France); Kenmeugne, B.; Vidal-Salle, E.; Robert, J.L. [Institut National des Sciences Appliquees (INSA), 69 - Villeurbanne (France)

1996-06-01

113

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

1996-01-01

114

Fatigue crack initiation and growth life prediction with statistical consideration  

International Nuclear Information System (INIS)

Life prediction or residual life prediction of structures or machines is one of the most strongly world wide needed problems as requirement in the stage of slowly developing economy which comes after rapidly and highly developing stage. For the purpose of statistical life prediction, fatigue test was conducted under the 3 stress levels, and for each stress level, 20 specimens are used. The statistical properties of the crack growth parameter m and C in the fatigue crack growth law of da/dN = C(?K)m, and the relationship between m and C, and the statistical distribution pattern of fatigue crack initiation, growth and fracture lives can be obtained by experimental results.

1991-01-01

115

Fracture Mechanics Prediction of Fatigue Life of Aluminium Highway Bridges  

DEFF Research Database (Denmark)

Fatigue damage accumulation in aluminium highway bridges under random loading is studied. The fatigue life of welded joints has been determined both from fracture mechanics analyses and from experimental investigations. The fatigue life of welded plate specimens has been investigated. The material that has been used has a 0.2% proof strength of 310 MPa and an ultimate tensile strength of 327 MPa. 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 in the present investigation show a significant difference between constant amplitude and variable amplitude results. Both the fracture mechanics analyses and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in aluminium bridges, may give results which are unconservative. The validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression.

Rom, SØren; Agerskov, Henning

2012-01-01

116

Finite element reliability analysis of fatigue life  

International Nuclear Information System (INIS)

[en] Fatigue reliability is addressed by the first-order reliability method combined with a finite element method. Two-dimensional finite element models of components with cracks in mode I are considered with crack growth treated by the Paris law. Probability density functions of the variables affecting fatigue are proposed to reflect a setting where nondestructive evaluation is used, and the Rosenblatt transformation is employed to treat non-Gaussian random variables. Comparisons of the first-order reliability results and Monte Carlo simulations suggest that the accuracy of the first-order reliability method is quite good in this setting. Results show that the upper portion of the initial crack length probability density function is crucial to reliability, which suggests that if nondestructive evaluation is used, the probability of detection curve plays a key role in reliability. (orig.)

1992-01-01

117

Prediction of fatigue life of flawed pipe under vibration and fatigue loading  

International Nuclear Information System (INIS)

A systematic experimental and analytical study has been carried out to predict the fatigue life of a flawed pipe under vibration loading with cyclic loading. Three Point Bend (TPB) specimens machined from the actual pipe have been used for evaluation of Paris constants by carrying out experiments under vibration loading followed by cyclic loading and cyclic loading only as per ASTM standard E-647. These constants were used for predicting the fatigue life of the pipe having part through flaw of a/t=0.25 and aspect ratio (2c/a) of 10. Predicted results show that the life of the notched pipe subjected to vibration loading followed by cyclic loading has been reduced by 50% compared to that of cyclic loading only. Predicted results have been validated by carrying out full-scale pipe tests. Experimental results of fullscale pipe tests under vibration followed by cyclic loading showed the reduction in fatigue life by 70% compared to that of cyclic loading only. The analytical prediction for the crack initiation life and the crack growth behavior were carried out and the results were compared with that of experiments. Fatigue crack growth was confirmed by examine and measuring the striation spacing on fracture surface. ASME O and M design code calls for qualification of piping system subjected to the vibration. The deflection and velocity measurement have been taken on the pipe specimen and compared with the ASME criterion. (author)

2011-01-01

118

Prediction of fatigue life using extreme statistics analysis  

International Nuclear Information System (INIS)

Fatigue fracture in machine components is produced by surface micro-crack from stress concentration area such as notch and material defect. It is difficult to predict the remaining fatigue life of mechanical components because the surface micro-crack on critical area initiates and grows with statistical distribution. Plane bending fatigue tests were carried out on the plain specimen of Al 2024-T3 and the initiation and growth behavior of surface micro cracks were observed. The statistical distribution of surface length of multiple micro cracks and their maximum length were investigated. The maximum surface crack length distributions were analyzed on the basis of the statistics of extremes in order to examine the prediction of remaining life.

2002-01-01

119

Prediction of corrosion fatigue life using DCPD method  

Energy Technology Data Exchange (ETDEWEB)

In order to develop a method of corrosion fatigue design and estimate reliability of TMCP steel using as the material of heavy industries and plants, its corrosion susceptibilities and corrosion fatigue life considering corrosion degradation were investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. The potential difference due to the crack growth behavior in 25 deg. C, 3.5wt.% NaCl solution is very susceptible. And it was found that stress amplitude has a linear relationship with the critical potential. Therefore, it is expected that the corrosion fatigue life of TMCP steel can be nondestructively predicted using the DCPD method.

Bae, Dong Ho [Sungkyunkwan Univ., Seoul (Korea, Republic of); Park, Jin Hyung [Samsung Heavy Industries Co., Ltd., Seoul (Korea, Republic of)

2003-07-01

120

Prediction of corrosion fatigue life using DCPD method  

International Nuclear Information System (INIS)

[en] In order to develop a method of corrosion fatigue design and estimate reliability of TMCP steel using as the material of heavy industries and plants, its corrosion susceptibilities and corrosion fatigue life considering corrosion degradation were investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. The potential difference due to the crack growth behavior in 25 deg. C, 3.5wt.% NaCl solution is very susceptible. And it was found that stress amplitude has a linear relationship with the critical potential. Therefore, it is expected that the corrosion fatigue life of TMCP steel can be nondestructively predicted using the DCPD method

2003-01-01

 
 
 
 
121

Fatigue life assessment of free spanning pipelines containing corrosion defects  

Energy Technology Data Exchange (ETDEWEB)

The free spanning pipelines assessment is a highlighted issue to be considered during the project and maintenance of the submarine pipelines. It is required to evaluate the fatigue life and the maximum stress due to VIV (Vortex Induced Vibration) as well as wave forces when applicable in case of shallow water. The code DNV-RP-F105 (2006) presents a methodology to calculate the fatigue life for free spanning pipelines. Such methodology however considers the pipe with no kind of defects. Nevertheless, sometimes corrosion defects are detected in periodic inspections and therefore their effects need to be taken into account in the fatigue life evaluation. The purpose of this paper thus is to present a procedure to assess the influence of the corrosion defects in the fatigue life of free spanning pipelines. Some FE analyses were performed to determine the stress concentrate factor (SCF) of the corrosion defects, which were used as input in the methodology presented in the code DNV-RP-F105 (2006). Curves of damage and so lifetime have been generated as function of the span length and water depth. As a practical application, this methodology was applied to a sub sea pipeline with several corrosion defects, localized in shallow water offshore Brazil. (author)

Lopes, Rita de Kassia D.; Campello, Georga C.; Matt, Cyntia G. da Costa; Benjamin, Adilson C.; Franciss, Ricardo [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)

2009-12-19

122

Evaluation of Environmental Effects on Fatigue Life of Piping  

Energy Technology Data Exchange (ETDEWEB)

This paper calculates the expected probabilities of fatigue failures and associated core damage frequencies at a 40-year and 60-year plant life for a sample of components from five PWR and BWR plants. These calculations were made possible by the development of an enhanced version of the pc-PRAISE probabilistic fracture mechanics code.

Simonen, Fredric A.; Khaleel, Mohammad A.; Phan, Hanh K.; Harris, David O.; Dedhia, D. D.; Kalinousky, D. N.; Shaukat, S. K.

2000-03-01

123

Evaluation of Environmental Effects on Fatigue Life of Piping  

International Nuclear Information System (INIS)

This paper calculates the expected probabilities of fatigue failures and associated core damage frequencies at a 40-year and 60-year plant life for a sample of components from five PWR and BWR plants. These calculations were made possible by the development of an enhanced version of the pc-PRAISE probabilistic fracture mechanics code.

2000-01-01

124

In Situ Imaging of High Cycle Fatigue Crack Growth in Single Crystal Nickel-Base Superalloys by Synchrotron X-Radiation  

Energy Technology Data Exchange (ETDEWEB)

A novel X-ray synchrotron radiation approach is described for real-time imaging of the initiation and growth of fatigue cracks during ultrasonic fatigue (f=20 kHz). We report here on new insights on single crystal nickel-base superalloys gained with this approach. A portable ultrasonic fatigue instrument has been designed that can be installed at a high-brilliance X-ray beamline. With a load line and fatigue specimen configuration, this instrument produces stable fatigue crack propagation for specimens as thin as 150 {mu}m. The in situ cyclic loading/imaging system has been used initially to image real-time crystallographic fatigue and crack growth under positive mean axial stress in the turbine blade alloy CMSX-4.

Liu, Liu; Husseini, Naji S.; Torbet, Christopher J.; Kumah, Divine P.; Clarke, Roy; Pollock, Tresa M.; Jones, J.Wayne (Michigan)

2008-05-01

125

Study on the fatigue crack initiation life under spherical contact  

Energy Technology Data Exchange (ETDEWEB)

In case of contact fatigue, the accurate calculation of surface tractions and subsurface stress is essential to the prediction of crack initiation life. Surface tractions influencing shear stress amplitude have been obtained by contact analysis based on influence function. Subsurface stress has been obtained by using rectangular patch solutions. In this study, to simulate asperity contact under sliding condition, the tip of asperity was simulated by sphere and to calculate crack initiation life in the substrate, dislocation pileup theory was used.

Cho, Yong Joo; Kim, Tae Wan [Busan National Univ., Busan (Korea, Republic of); Lee, Mun Ju [Samsung Electronics Co., Ltd., Suwon (Korea, Republic of)

2001-08-01

126

Fatigue Life and Strain Hardening Behavior of JLF-1 Steel  

International Nuclear Information System (INIS)

Full text of publication follows: Development of reactor materials and blankets is a critical issue for early realization of fusion energy. A reduced activation ferritic/martensitic steel, JLF-I, is considered as one of the candidate alloys for the first wall application of fusion reactor. In this paper, the low cycle fatigue (LCF) properties of JLF-1 steel were studied from room temperature (RT) to 873 K in a vacuum condition using engineering size cylinder specimens with 8 mm in diameter. The fatigue life at elevated temperature was almost as same as that at RT when the life was plotted against the total strain range. But when the life was plotted against the plastic strain range, the fatigue life curves for RT, 673 K and 873 K of JLF-1 were on different lines, which is not in agreement with the Coffin's model. The TEM images showed that dislocation structure is dependent on temperature. At RT, dislocation rearrangements forming cell structure and keeping high density. At 673 K, dislocation decrease to medium level, dislocation cell was observed at 10. cycle. However the cell structure did not remain during the following fatigue and were not observed at the TEM images at 500. cycle and the final failure at 673 K. At 873 K, the cell structure was not observed, dislocation density decrease to low level. Loss of dislocation pile up will result in reduction of strain hardening at high temperature. So, the loss of strain hardening will be responsible for the increase of fatigue life at high temperature when plotted against the plastic strain range. (authors)

2007-01-01

127

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

Directory of Open Access Journals (Sweden)

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.

M. Maj

2013-01-01

128

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.

2010-01-01

129

Life prediction for bridged fatigue cracks  

Energy Technology Data Exchange (ETDEWEB)

One of the more promising classes of composites touted for high temperature applications, and certainly the most available, is that of relatively brittle matrices, either ceramic or intermetallic, reinforced by strong, aligned, continuous fibers. Under cyclic loading in the fiber direction, these materials develop matrix cracks that often run perpendicular to the fibers, while the fibers remain intact in the crack wake, supplying bridging tractions across the fracture surfaces. The bridging tractions shield the crack tip from the applied load, dramatically reducing the crack velocity from that expected in an unreinforced material subjected to the same value, {Delta}K{sub a}, of the cyclic applied stress intensity factor. An important issue in reliability is the prediction of the growth rates of the bridged cracks. The growth rates of matrix fatigue cracks bridged by sliding fibers are now commonly predicted by models based on the micromechanics of frictional interfaces. However, there exist many reasons, both theoretical and experimental, for suspecting that the most popular micromechanical models are probably wrong in detail in the context of fatigue cracks. Furthermore, a review of crack growth data reveals that the validity of the micromechanics-based predictive model has never been tested and may never be tested. In this paper, two alternative approaches are suggested to the engineering problem of predicting the growth rates of bridged cracks without explicit recourse to micromechanics. Instead, it is shown that the material properties required to analyze bridging effects can be deduced directly from crack growth data. Some experiments are proposed to test the validity of the proposals.

Cox, B.N.

1994-08-01

130

Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations  

UK PubMed Central (United Kingdom)

A methodology is presented for determining the fatigue life of bonded compositeskin/stringer structures based on delamination fatigue characterization data andgeometric nonlinear finite element analyses. Results were compared to fatigue tests onstringer flange/skin specimens to verify the approach.INTRODUCTION.Many composite components in aerospace structures are made of flat or curvedpanels with co-cured or adhesively bonded frames and stiffeners. Testing of stiffenedpanels designed for pressurized aircraft fuselage has shown that bond failure at the tipof the frame flange is an important and very likely failure mode. Comparatively simplespecimens consisting of a stringer flange bonded onto a skin were developed [1-3].The failure that initiates at the tip of the flange in these specimens is identical to thefailure observed in the full-scale panels and the frame pull-off specimens.The first objective of this work was to investigate the damage mechanisms inbonded compo...

T. Kevin O'brien; Ronald Krueger; Isabelle L. Paris

131

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

Directory of Open Access Journals (Sweden)

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.

Soyuer, F.; Mirza, M.; Öztürk, A.

2005-01-01

132

Multiaxial plasticity and fatigue life prediction in coiled tubing  

Energy Technology Data Exchange (ETDEWEB)

Coiled tubing is being used increasingly in the oil well drilling and servicing industry. Continuous steel tubing of structural dimensions (up to 89 mm or 3.5 in. in diameter) is wound onto a large-diameter reel for repeated deployment into and out of a well bore. The bending strain range associated with each wrap-unwrap cycle can exceed 3% with lives well below 100 cycles. During constant internal pressure fatigue testing, tubing has been observed to grow in diameter by as much as 30%. This paper describes an analytical model to predict the fatigue behavior of coiled tubing subjected to variable pressure service conditions. The approach utilizes standard low-cycle fatigue data but requires additional experimental results from constant pressure fatigue testing. The algorithm is based on estimates of biaxial ratcheting from an incremental plasticity model using a hybrid associated flow rule, a modified kinematic hardening rule with multiple von Mises yield surfaces, and a specialized limit surface concept. An empirical damage parameter was formulated based on constant pressure fatigue data using mean and fluctuating von Mises equivalent strain components occurring throughout the life of a section of tubing. This parameters is used with the Palmgren-Miner definition of cumulative damage to track damage that is accumulating nonlinearly under constant or variable pressure histories. Modifications to standard incremental plasticity components and implementation assumptions used to apply the model are presented and discussed. The predictive capability of the model is demonstrated relative to data generated under constant and variable pressure histories.

Tipton, S.M. [Univ. of Tulsa, OK (United States). Mechanical Engineering Dept.

1996-12-31

133

Evaluation of environmental effects on fatigue life of piping  

Energy Technology Data Exchange (ETDEWEB)

Recent data indicate that the effects of light water reactor environments can significantly reduce the fatigue resistance of materials, and show that design fatigue curves may not be conservative for reactor coolant environments. Using revised fatigue curves developed by Argonne National Laboratory (ANL), the work of this paper calculates the expected probabilities of fatigue failures and associated core damage frequencies at a 40-year and 60-year plant life for a sample of components from five PWR and two BWR plants. These calculations were made possible by the development of an enhanced version of the pc-PRAISE probabilistic fracture mechanics code that has the ability to simulate the initiation of fatigue cracks followed by the linking of these cracks. Results of interim calculations subject to review are presented. Components with the highest probabilities of failure can have predicted frequencies of through-wall cracks in the order of about 5x10{sup -2} per year. The corresponding maximum contributions to core damage frequencies are in the order of 10{sup -6} per year. Components with the very high failure rates show essentially no increase in calculated core damage frequency from 40 to 60 years.

Simonen, F.A. E-mail: fredric.simonen@pnl.gov; Khaleel, M.A.; Phan, H.K.; Harris, D.O.; Dedhia, D.D.; Kalinousky, D.N.; Shaukat, S.K

2001-09-01

134

Evaluation of environmental effects on fatigue life of piping  

International Nuclear Information System (INIS)

Recent data indicate that the effects of light water reactor environments can significantly reduce the fatigue resistance of materials, and show that design fatigue curves may not be conservative for reactor coolant environments. Using revised fatigue curves developed by Argonne National Laboratory (ANL), the work of this paper calculates the expected probabilities of fatigue failures and associated core damage frequencies at a 40-year and 60-year plant life for a sample of components from five PWR and two BWR plants. These calculations were made possible by the development of an enhanced version of the pc-PRAISE probabilistic fracture mechanics code that has the ability to simulate the initiation of fatigue cracks followed by the linking of these cracks. Results of interim calculations subject to review are presented. Components with the highest probabilities of failure can have predicted frequencies of through-wall cracks in the order of about 5x10-2 per year. The corresponding maximum contributions to core damage frequencies are in the order of 10-6 per year. Components with the very high failure rates show essentially no increase in calculated core damage frequency from 40 to 60 years.

2001-09-01

135

Fatigue mediates the relationship between physical fitness and quality of life in cancer survivors.  

UK PubMed Central (United Kingdom)

OBJECTIVES: This study aims to investigate whether fatigue mediates the association between physical fitness and quality of life. DESIGN: Uncontrolled pre-post intervention design. METHODS: Pre- and post-intervention measurements were conducted in 119 patients who completed chemotherapy treatment for various types of cancer. The intervention was an 18-week exercise programme consisting of high-intensity resistance and interval training. We assessed physical fitness - peak oxygen uptake and peak power output - self-reported fatigue (Multidimensional Fatigue Inventory - subscales general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue-, and fatigue symptom scale of EORTC QLQ-C30) and quality of life (EORTC QLQ-C30, subscale global quality of life). Linear regression analyses were conducted on the residual change scores of the variables. The mediated effect of fatigue on the association between physical fitness and quality of life was examined using the products of coefficient method. Bootstrapping was used to calculate the confidence intervals. RESULTS: We found significant associations between changes in physical fitness and global quality of life, between physical fitness and fatigue, and between fatigue and global quality of life. General fatigue mediated the positive association between peak power output and global quality of life, accounting for 82% of the total association. Physical fatigue, reduced activity, reduced motivation, and fatigue symptom were also mediators of this association. The mediation effects accounted for 91%, 76%, 38% and 71% of the total association, respectively. Reduced activity and reduced motivation mediated the association between peak oxygen uptake and global quality of life. Multiple mediation analyses showed that physical aspects of fatigue were stronger mediators than mental aspects. CONCLUSIONS: General fatigue and physical aspects of fatigue mediate the relationship between physical fitness and quality of life in cancer survivors. We found no mediating effect of mental fatigue.

Buffart LM; De Backer IC; Schep G; Vreugdenhil A; Brug J; Chinapaw MJ

2013-03-01

136

The LIFE computer code: Fatigue life prediction for vertical axis wind turbine components  

Science.gov (United States)

The LIFE computer code was originally written by Veers to analyze the fatigue life of a vertical axis wind turbine (VAWT) blade. The basic assumptions built into this analysis tool are: the fatigue life of a blade component is independent of the mean stress; the frequency distribution of the vibratory stresses may be described adequately by a Rayleigh probability density function; and damage accumulates linearly (Miner's Rule). Further, the yearly distribution of wind is assumed to follow a Rayleigh distribution. The original program has been updated to run in an interactive mode on a personal computer with a BASIC interpreter and 256K RAM. Additional capabilities included in this update include: the generalization of the Rayleigh function for the wind speed distribution to a Weibull function; the addition of two constitutive rules for the evaluation of the effects of mean stress on fatigue life; interactive data input; and the inclusion of a stress concentration factor into the analysis.

Sutherland, H. J.; Ashwill, T. D.; Slack, N.

1987-08-01

137

Estimation of fatigue life for I-beam structure of wind turbine blade  

International Nuclear Information System (INIS)

The research of fatigue analysis is based on the purpose that prevents the fatigue failure as estimate the material strength and structure stability. In this paper, the fatigue life is analyzed for I-beam which used as spar part in the wind turbine blade. To estimate the fatigue life, I-beam structure is modeled by MSC.Patran and the static analysis is performed by MSC.Nastran. All of the geometric information and conditions are based on DOE/MSU data base to compare the fatigue life between the proposed fatigue analysis method and the test result. The proposed fatigue analysis is used least square method to get regression curve form the S-N data. Moreover, the coefficient of determination method is used to ensure how accuracy it has. In addition, the Goodman method is used to consider the mean stress effect for evaluating more accuracy fatigue life. The proposed analysis program is accomplished by Fortran code.

2009-01-01

138

Bending Fatigue Initiation Life Estimation of Disposable Spur Gears  

Directory of Open Access Journals (Sweden)

Full Text Available A method to estimate the bending fatigue initiation life of disposable gears is proposed in this study. Disposable gears used in disposable aeronautics and space equipment undertake much higher loads than general gears. The main damage type for disposable gears is low-cycle bending fatigue failure. In the study, the finite element method is used to analyze the stress-strain state of disposable gears. The moving load model is established to simulate the real load acting on the teeth. For the purpose of analyzing the multi-axial stress state of teeth roots, the crack initiation life is calculated based on the critical plane theory. As the basis parameter of the critical plane theory, the orientation of critical plane is determined by using maximum variance method. The comparison of the simulation results and the experiment data shows that it is security to predict the bending fatigue crack initiation life of disposable gears using the method provided in the study.

Yuefeng Li; Xudong Pan; Guanglin Wang

2013-01-01

139

A comparison of two total fatigue life prediction methods  

Energy Technology Data Exchange (ETDEWEB)

A 2-D analytical model which is termed the PICC-RICC model combines the effects of plasticity-induced crack closure (PICC) and roughness-induced crack closure (RICC). The PICC-RICC model handles naturally the gradual transition from RICC to PICC dominated crack growth. In this study, the PICC-RICC model is combined with a crack nucleation model to predict the total fatigue life of a notched component. This modified PICC-RICC model will be used to examine several controversial aspects of an earlier, computationally simpler total-life model known as the IP model.

Chen, N.; Lawrence, F.V.

1999-07-01

140

Corrosion fatigue behavior and life prediction method under changing temperature condition  

International Nuclear Information System (INIS)

[en] Axially strain controlled low cycle fatigue tests of a carbon steel in oxygenated high temperature water were carried out under changing temperature conditions. Two patterns of triangular wave were selected for temperature cycling. One was in-phase pattern synchronizing with strain cycling and the other was an out-of-phase pattern in which temperature was changed in anti-phase to the strain cycling. The fatigue life under changing temperature condition was in the range of the fatigue life under various constant temperature within the range of the changing temperature. The fatigue life of in-phase pattern was equivalent to that of out-of-phase pattern. The corrosion fatigue life prediction method was proposed for changing temperature condition, and was based on the assumption that the fatigue damage increased in linear proportion to increment of strain during cycling. The fatigue life predicted by this method was in good agreement with the test results

1997-01-01

 
 
 
 
141

Fatigue life behaviour of nanocomposite coated carbon steel  

Energy Technology Data Exchange (ETDEWEB)

Recently, nano-materials have received increasingly more attention for their potential applications as structural and functional materials. The unique mechanical properties of CNTs, their high strength and stiffness and the enormous aspect ratio provide potentials for the improvement of the mechanical properties of structural materials. The aim of this research is to investigate experimentally the effect of nanocomposite coating on the fatigue life of carbon steel AISI 1045 specimens with different surface finishes. Nanoadhesives of epoxy resin are synthesized and evaluated. They are originally modified by multiwalled carbon nanotubes (MWCNT) with 0.5 wt.-% as reinforcement. Fatigue tests are conducted on the respective specimens by a rotating bending machine of the cantilever type. Comparing the results for specimens coated with 0.5 wt.-% MWCNT-epoxy composition with the base materials it is found that fatigue life increased five times for a roughness of 0.3 {mu}m and three times for an average specimen roughness of 0.8, 1.6 and 2.5 {mu}m, respectively. (orig.)

Hedia, Hassan S.; Aldousari, S.M. [King Abdulaziz Univ., Jeddah (Saudi Arabia); Khairy, A. [King Abdulaziz Univ., Jeddah (Saudi Arabia). Faculty of Engineering; Aljabarti, Ezat [Saudi Electricity Company, Jeddah (Saudi Arabia). Mechanical Maintenance Dept.

2012-07-01

142

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

1993-01-01

143

The Effect of Geometry on Fatigue Life for Bellows  

Science.gov (United States)

A bellows is a component installed in the automobile exhaust system to reduce or prevent the impact from engine. Generally, the specifications on the bellows are determined in the system design process of exhaust system and the component design is carried out to meet the specifications such as stiffness. Consideration of fatigue is generally an important aspect of design on metallic bellows expansion joints. These components are subject to displacement loading which frequently results in cyclic strains. This study has been investigated to analyze the effect of geometry on fatigue life for automotive bellows. 8 node shell element and non-linear method is employed for the analysis. The optimized shapes of the bellows are expected to give good guidelines to the practical designs.

Kim, Jinbong

144

Constituent damage mechanisms in metal matrix composites under fatigue loading, and their effects on fatigue life  

Energy Technology Data Exchange (ETDEWEB)

Load controlled fatigue experiments were performed on 8-ply unidirectional ([0]{sub 8}) SCS-6-Ti-15-3 metal matrix composites (MMCs) at different temperatures, and the results were interpreted in terms of the overall three-regime framework of fatigue. The emphasis was on understanding the mechanisms and mechanics of constituent damage evolution, and their effects on fatigue life. Most tests were performed at an R-ratio of 0.1, but limited fully-reversed (R=-1) tests were conducted. In regime 1, damage was fiber failure dominated, but the exact mechanisms were different at room and elevated temperatures. In regime 2, observation of matrix cracks and persistent slip bands provided convincing evidence of matrix dominated damage. Weak fiber-matrix interfaces contributed to crack bridging. However, fiber fracture also played an important role in regime 2; tension-tension and tension-compression tests showed similar lives on a maximum fiber stress basis, although the strain range, which primarily controls matrix crack growth, was almost double for R=-1 compared with R=0 or 0.1. Good agreement was obtained from the different R-ratio tests, between the MMC and matrix data, and data at room and elevated temperatures, when compared based on the strain range in the tension part of a cycle. Analyses and observations of fiber pull-out lengths and fiber fractures in the matrix crack wake provided evidence of fiber damage; the analyses also helped to explain increased fiber bridging with fiber volume fraction. Issues of fatigue life prediction are briefly discussed. (orig.)

Majumdar, B.S. [UES, Inc., Dayton, OH (United States); Newaz, G.M. [Battelle, Columbus, OH (United States)

1995-09-01

145

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)

1983-12-01

146

Effects of temperature change on fatigue life of carbon steel in high temperature water  

International Nuclear Information System (INIS)

Strain controlled fatigue tests of a carbon steel in oxygenated high temperature water were carried out under the condition of combined and synchronized mechanical and thermal strain cycling. The effects of temperature change on environmental fatigue life were investigated, showing basic conceptual data to evaluate the fatigue damage under the condition of transient temperature change of actual plant components

1995-01-01

147

Effects of temperature change on fatigue life of carbon steel in high temperature water  

Energy Technology Data Exchange (ETDEWEB)

Strain controlled fatigue tests of a carbon steel in oxygenated high temperature water were carried out under the condition of combined and synchronized mechanical and thermal strain cycling. The effects of temperature change on environmental fatigue life were investigated, showing basic conceptual data to evaluate the fatigue damage under the condition of transient temperature change of actual plant components.

Kanasaki, Hiroshi [Mitsubishi Heavy Industries, Ltd., Takasago, Hyogo (Japan). Takasago Research and Development Center; Hayashi, Makoto [Hitachi Ltd., Ibaraki (Japan). Mechanical Engineering Research Lab.; Iida, Kunihiro [Shibaura Inst. of Technology, Tokyo (Japan). Dept. of Mechanical Engineering; Asada, Yasuhide [Univ. of Tokyo (Japan). Dept. of Mechanical Engineering

1995-12-31

148

Fatigue life prediction of oil ducts under service loads  

Energy Technology Data Exchange (ETDEWEB)

A methodology to calculate the residual initiation and propagation lives of fatigue cracks in oil pipelines with corrosion-like defects is proposed and applied to predict the residual life of an old duct made of API 5L Gr. B steel, in service for more than 40 years. Since its inauguration, this pipeline has carried several heated products under variable temperatures and pressures. The calculated (nominal) service stresses are very high, due to thermal loads that induce significant bending in curved parts of the duct, with peaks close to the yield strength of the steel. The elastic- plastic fatigue damage at a notch or a corrosion pit root is calculated using the {epsilon}N method, and the effects of surface semi-elliptical cracks in its internal (or external) wall is studied considering appropriate stress intensity factor expressions and the actual service loads. In the presence of surface flaws associated to stress concentration factors of the order of three, a fatigue crack likely will initiate in the pipeline. However, if these surface cracks are small compared to the duct wall thickness, their predicted propagation rates are very low. (author)

Meggiolaro, Marco A.; Castro, Jaime T.P. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil)

2003-07-01

149

Fatigue Life Analyze Due To Corrosive Environment Stresses  

International Nuclear Information System (INIS)

Fatigue life analyze is necessary to know the material toughness especially against stress in the corrosive environment. Base on design calculation of the specimen thick, engineering drawing and requirement designs were done. Bend test method in the corrosive media is chosen as base of testing. Load handle component, static load place, cycle load motor, corrosive media basin, roller and fixture of bend test specimen are components of the test equipment. Test specimen and test equipment is made base on the design results. Integration process of the components have give the test equipment for prolonged research

2001-03-29

150

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

Directory of Open Access Journals (Sweden)

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

Yan Yifei; Shao Bing; Liu Jinkun; Cheng Lufeng

2013-01-01

151

Structural health monitoring of wind towers: residual fatigue life estimation  

Science.gov (United States)

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

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

2013-04-01

152

Estimate the thermomechanical fatigue life of two flip chip packages  

International Nuclear Information System (INIS)

[en] The continuing demand towards high density and low profile integrated circuit packaging has accelerated the development of flip chip structures as used in direct chip attach (DCA) technology, ball grid array (BOA) and chip scale package (CSP). In such structures the most widely used flip chip interconnects are solder joints. The reliability of flip chip structures largely depends on the reliability of solder joints. In this work solder joint fatigue life prediction for two chip scale packages is carried out. Elasto-plastic deformation behavior of the solder was simulated using ANSYS. Two dimensional plain strain finite element models were developed for each package to numerically compute the stress and total strain of the solder joints under temperature cycling. These stress and strain values are then used to predict the solder joint lifetime through modified Coffin Manson equation. The effect of solder joint's distance from edge of silicon die on life of the package is explored. The solder joint fatigue response is modeled for a typical temperature cycling of -60 to 140 degree C. (author)

2005-01-01

153

Blade fatigue life assessment with application to VAWTs  

Science.gov (United States)

The possibility of satisfactory modeling of the vibratory stress level history of a vertical axis wind turbine (VAWT) is considered. Fatigue life prediction is expressed as a function of the vibratory stress level, the wind speed, and the wind speed distribution on-site. A statistical distribution of stress levels is asserted to more accurately simulate the stress level than determination of the stress levels at each wind speed. Miner's cumulative damage rule is examined as a tool to generate a vibratory stress level distribution in terms of peak vibrations in a narrow-band Gaussian process. Examples are given for 30-40 sec intervals on the 17 m VAWT at Sandia Laboratories. A threshold was set beneath which no vibrations were recorded, yielding a Rayleigh distribution at the 0.5 significance level. It is concluded that a Rayleigh distribution from test data produces a cycle to failure versus wind speed curve which is superior to constant amplitude fatigue life data such as appropriate to Miner's Rule.

Veers, P. S.

1982-05-01

154

Residual life evaluation method for transmission line conductors subjected to fatigue damage  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to develop a method for evaluating the status of electrical conductors subjected to fatigue damage and to estimate their residual life. The proposed method is based on the correlation between the loss of ductility of the material subjected to cyclic loading and the fatigue-consumed life fraction. The approach put forward to confirm this correlation comprises four consecutive steps: Determination of the tensile ductility of the conductor strands before the damage occurs; establishment of the fatigue curve of the strand; fatigue tests on the strands at different fractions of fatigue life; and determination of the residual tensile ductility of the tested strands. This paper presents the results of the study test program, performed on steel and aluminum strands of an ACSR 26/7 conductor. The end product of the study is a diagram containing all the necessary elements for estimating the residual life of conductors stressed by fatigue loading.

NONE

1995-12-31

155

Estimation of fatigue strain-life curves for austenitic stainless steels in light water reactor environments.  

Energy Technology Data Exchange (ETDEWEB)

The ASME Boiler and Pressure Vessel Code design fatigue curves for structural materials do not explicitly address the effects of reactor coolant environments on fatigue life. Recent test data indicate a significant decrease in fatigue lives of austenitic stainless steels (SSs) in light water reactor (LWR) environments. Unlike those of carbon and low-alloy steels, environmental effects on fatigue lives of SSs are more pronounced in low-dissolved-oxygen (low-DO) water than in high-DO water, This paper summarizes available fatigue strain vs. life data on the effects of various material and loading variables such as steel type, DO level, strain range, and strain rate on the fatigue lives of wrought and cast austenitic SSs. Statistical models for estimating the fatigue lives of these steels in LWR environments have been updated with a larger data base. The significance of the effect of environment on the current Code design curve has been evaluated.

Chopra, O. K.; Smith, J. L.

1998-02-12

156

An approach for long-term NSSS fatigue life assessment/validation  

International Nuclear Information System (INIS)

The prevention of metal fatigue due to mechanical and thermal loading cycles is an integral part of the design of nuclear power plants. Since fatigue is a cumulative process which increases with the number and severity of cycles experienced by plant components, metal fatigue should be addressed in plant life extension evaluations. The history of fatigue considerations for nuclear power plants is discussed. It is concluded that fatigue is generally not a concern at locations considered in the original plant design. Based on a number of considerations, an integrated program of fatigue monitoring focused inspection, and the associated technical justification is outlined as an approach for addressing the few fatigue-sensitive locations which should be included in nuclear plant life extension programs.

1988-08-03

157

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

International Nuclear Information System (INIS)

[en] 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)

1990-01-01

158

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

Directory of Open Access Journals (Sweden)

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.

Shahrum Abdullah; Choi Jae-Chil; John R. Yates; Joseph A. Giacomin

2008-01-01

159

Effects of stress concentrations on the fatigue life of a gamma-based titanium aluminide  

Energy Technology Data Exchange (ETDEWEB)

S-N curves for a gamma-based titanium aluminide alloy of nominal chemistry Ti-48Al-2Mn-2Nb (at.%)+2TiB{sub 2} (wt.%) have been used to define the fatigue life. The microstructure, residual stress and surface roughness have been observed to influence the fatigue life. Fully lamellar microstructures show an increased life when compared with near-lamellar microstructures. Residual tensile stresses and microcracking are introduced by electrodischarge machining and the fatigue life is reduced compared with polished samples. Notch fatigue tests show a significant notch strengthening effect which increases with increasing stress concentration factors. The fracture surfaces reveal fully brittle failure mechanisms and no evidence of stable crack growth is observed. Thus the fatigue life is determined predominantly by the number of cycles to crack initiation. Probable sites for crack initiation are addressed. ((orig.))

Trail, S.J. [School of Metallurgy and Materials/IRC in Materials for High Performance Applications, University of Birmingham, Elms Road, North Campus, Edgbaston, Birmingham, B15 2TT (United Kingdom); Bowen, P. [School of Metallurgy and Materials/IRC in Materials for High Performance Applications, University of Birmingham, Elms Road, North Campus, Edgbaston, Birmingham, B15 2TT (United Kingdom)

1995-02-15

160

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

Science.gov (United States)

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.

Rahman, M. M.; Ariffin, A. K.; Jamaludin, N.; Abdullah, S.; Noor, M. M.

 
 
 
 
161

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

Directory of Open Access Journals (Sweden)

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.

M.M. Rahman; A.K. Ariffin; N. Jamaludin; S. Abdullah; M.M. Noor

2008-01-01

162

The effect of residual stresses induced by prestraining on fatigue life of notched specimens  

Science.gov (United States)

The effect of tensile prestraining-induced residual stress on the fatigue life of notched steel parts was investigated. The study was performed on AISI 4140 steel. Rotating bending fatigue tests were carried out on semicircular notched specimens with different notch radii in the as-quenched and tempered conditions. Metallography of the specimens was performed by means of light optical microscopy. The finite-element method was used to evaluate the residual stress distribution near the notch region. Fatigue tests revealed fatigue life improvement for notched specimens, which changes depending on the notch radii and applied stress. Scanning electron microscopy was used to examine the fracture surfaces of the specimens.

Sadeler, R.; Ozel, A.; Kaymaz, I.; Totik, Y.

2005-06-01

163

A study of fatigue life prediction for automotive spot weldment using local strain approach  

International Nuclear Information System (INIS)

[en] The fatigue crack initiation life is studied on automotive spot weldment made from cold rolled carbon steel(SPC) sheet by using DCPDM and local strain approach. It can be found that the fatigue crack initiation behavior in spot weldment can be definitely detected by DCPDM system. The local stresses and strains are estimated by elastic-plastic FEM analysis and the alternative approximate method based on Neuber's rule were applied to predict the fatigue life of spot weldment. A satisfactory correlation between the predicted life and experimental life can be found in spot weldment within a factor of 4

2000-01-01

164

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

International Nuclear Information System (INIS)

[en] 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)

2003-01-01

165

Study on fatigue life evaluation of structural component based on crack growth criterion  

International Nuclear Information System (INIS)

[en] As one of the practical application of fracture mechanics, fatigue life evaluation method based on crack growth criterion has been diffusing in various field of technology in order to determine the rational and reliable life of structural components. The fatigue life by this method is evaluated based on the fatigue crack growth analysis from defects, while many problems, such as the influence of residual stress on the crack growth behavior, the effect of overloading, and evaluation method for multiple surface cracks, are not sufficiently solved yet. In this paper, the above problems are treated, and based on some exprimental data some simple mehtods for fatigue life evaluation are proposed regarding the above problems. Verification of the proposed methods are shown in the paper by comparing with some experimental results, and the applicability of the proposed method is also examined by the fatigue test of pipes with cracks in the inner surface. (author)

1984-01-01

166

FATIGUE LIFE PREDICTION BY THE STRUCTURALLY SENSITIVE DAMAGE INDICATOR ????????????? ??????? ????????????? ?? ????????? ??????????-????????? ?????????? ???????????  

Directory of Open Access Journals (Sweden)

Full Text Available The investigations of the new fatigue sensor that was carried out at the wide range of cyclicloads conditions show the ability of the indicator application in Structural Health Monitoringsystems of planes, bridges, vessels, and other structures. Accumulated fatigue damage may byestimated by the intensity of deformation relief, i.e. by its extrusion/intrusion and persistent slipbands structures on the indicator surface.Keywords: alelad aluminum alloys, deformation relief, fatigue, fatigue indicator.?????????? ?????????? ??????????? ?????? ?????????? ?????, ?????????? ? ????????????????? ??????? ?????????? ??????????????. ???????? ?????????? ???????????? ?????????? ????????? ???????? ?????????? ????? ???????, ??????, ???????? ?? ????? ???????????.?????????? ?????? ??????????? ????????? ?? ????????????? ?????????????? ???????????????, ???? ???????? ?????????, ???????? ? ????? ????? ???????? ?? ???????? ??????????.??????? ?????: ?????, ????????????? ??????, ????????? ?????, ?????????? ????????????????.?????????? ?????????? ??????????? ?????? ?????????? ?????,  ?????????? ? ????????????????? ??????? ?????????? ??????????????. ???????? ?????????? ???????????? ?????????? ????????? ???????? ?????????? ????? ???????,  ??????,  ???????? ?? ????? ???????????. ?????????? ?????? ??????????? ????????? ?? ????????????? ?????????????? ???????????????, ???? ???????? ?????????, ???????? ? ????? ????? ???????? ?? ???????? ??????????.

Mikhail Karuskevich

2012-01-01

167

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

UK PubMed Central (United Kingdom)

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

Chen K; Fan Y; Hu R; Yang T; Li K

2013-04-01

168

Locking buttons increase fatigue life of locking plates in a segmental bone defect model.  

UK PubMed Central (United Kingdom)

BACKGROUND : Durability of plate fixation is important in delayed union. Although locking plates result in stronger constructs, it is not known if locking affects the fatigue life of a plate. Two locking screws on either side of the nonunion could decrease working length and increase strain in the plate. However, the reinforcing effect of the locking head on the plate may compensate, so that it is unclear whether locking reduces fatigue life. QUESTIONS/PURPOSES : We determined whether locking screws, compression screws, and locking buttons reduce or increase the fatigue life of a plate. METHODS : We tested fatigue life of four constructs using an eight-hole locking plate in a segmental defect model: (1) all locking screws (Locked; n = 5); (2) all compression screws (Unlocked; n = 5); (3) six compression screws with two locking buttons in the central holes (Button; n = 6); and (4) six compression screws with two open central holes (Open; n = 6). RESULTS : The Button group had the longest fatigue life (1.3 million cycles). There was no difference between the Locked and Unlocked groups. All of the constructs failed by fracture of the plates through a screw hole adjacent to the defect. CONCLUSIONS : Locking screws did not improve fatigue life, however a locking button increased the fatigue life of a locking plate in a segmental bone defect model. CLINICAL RELEVANCE : Locking buttons in holes adjacent to a defect may improve durability, which is important when delayed union is a possibility.

Tompkins M; Paller DJ; Moore DC; Crisco JJ; Terek RM

2013-03-01

169

Residual life evaluations method for transmission line conductors subjected to fatigue damage  

Energy Technology Data Exchange (ETDEWEB)

A study undertaken to develop a method for evaluating the status of electrical conductors subjected to fatigue damage, and to estimate their residual life was described. It was proposed to establish the correlation between the loss of ductility of the material submitted to cyclic loading and the fatigue-consumed life fraction. The approach taken to do this had four steps: (1) determination of the tensile ductility of the conductor strands before the damage occurs, (2) establishment of the fatigue S-N curve of the strand, (3) fatigue tests on the strands at different fractions of fatigue life, and (4) determination of the residual tensile ductility of the tested strands. Testing was performed on steel and aluminum ACST 26/7 conductor strands. Scatter in tensile and fatigue tests on conductor material was noted and explained. It was concluded that a standardized tensile testing method applied to the conductor strands would improve the reliability and reproducibility of the testing process. Residual tensile ductility-fatigue-consumed life fraction diagram could be used directly to evaluate residual life of conductors that have suffered cumulative fatigue damage merely by performing tensile tests on samples of conductor strands. 10 refs., 6 figs, 3 tabs.

Nguyen-Duy, P.; Boisvert, S.; Corriveau, R.; Bacon, I. [Ontario Hydro, Toronto, ON (Canada)

1995-12-31

170

Effects of strain rate change on fatigue life of carbon steel in high temperature water  

Energy Technology Data Exchange (ETDEWEB)

Strain controlled fatigue tests of carbon steels in oxygenated high temperature water were carried out with various wave shapes of strain, e.g. triangle, slow/fast saw tooth, fast/slow saw tooth, stepwise changed and continuously changed sine waves. The effects of strain rate change on environmental fatigue life were investigated, showing basic conceptual data to evaluate the fatigue damage under the condition of transient strain change of actual plant components.

Higuchi, Makoto [Ishikawajima-Harima Heavy Industries, Yokohama (Japan); Iida, Kunihiro [Shibaura Inst. of Technology, Tokyo (Japan). Dept. of Mechanical Engineering; Asada, Yasuhide [Univ. of Tokyo (Japan). Dept. of Mechanical Engineering

1995-12-31

171

Effects of strain rate change on fatigue life of carbon steel in high temperature water  

International Nuclear Information System (INIS)

Strain controlled fatigue tests of carbon steels in oxygenated high temperature water were carried out with various wave shapes of strain, e.g. triangle, slow/fast saw tooth, fast/slow saw tooth, stepwise changed and continuously changed sine waves. The effects of strain rate change on environmental fatigue life were investigated, showing basic conceptual data to evaluate the fatigue damage under the condition of transient strain change of actual plant components.

1995-01-01

172

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

Science.gov (United States)

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.

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

2013-02-01

173

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

International Nuclear Information System (INIS)

[en] 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.

2009-01-01

174

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

175

Effects of stress concentrations on the fatigue life of a gamma based titanium aluminide  

International Nuclear Information System (INIS)

S-N curves for a gamma based titanium aluminide alloy of composition Ti-47.2Al-2.1Mn-1.9Nb(at.%)+2TiB2(wt.%) have been used to define fatigue life. Effects of residual stress, stressed volume, loading ratio, loading mode, elevated temperature and surface roughness have been considered. Residual tensile stresses and micro-cracking are introduced by Electro Discharge Machining and the fatigue life is reduced slightly compared with polished samples. Notched fatigue tests show a significant notch strengthening effect which increases with increasing stress concentration factor. The fracture surfaces of specimens tested at room temperature reveal fully brittle failure mechanisms and no evidence of stable crack growth is observed. The fatigue life appears, therefore, to be determined predominantly by the number of cycles to crack initiation. At the elevated temperature of 830 C, evidence for some stable fatigue crack growth has been found. Probable sites for crack initiation are addressed

1995-01-01

176

Statistical analysis of fatigue strain-life data for carbon and low-alloy steels  

Energy Technology Data Exchange (ETDEWEB)

The existing fatigue strain vs life (S-N) data, foreign and domestic, for carbon and low-alloy steels used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. A statistical model has been developed for estimating the effects of the various test conditions on fatigue life. 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 applying design margins for size, geometry, and surface finish to crack initiation curves estimated from the model.

Keisler, J.; Chopra, O.K.

1995-03-01

177

Thermal fatigue life prediction of Ni base alloy ceramic composite coating  

Energy Technology Data Exchange (ETDEWEB)

Ni base alloy ceramic grain composite coating is used mostly in high temperature condition, so thermal fatigue failure will be easy. If the thermal expansion coefficients and elastic modulus of Ni base alloy and ceramic grain are different, there will be thermal stresses between grain and matrix in thermosyphon. The thermal stress will arouse the initiation and growth of thermal fatigue crack. We use Eshebly-Mori-Tanaka method to study the thermal stress field in matrix and grain. It can be shown that the more difference of thermal expansion coefficients between Ni base alloy and ceramic grain is, the bigger the thermal stress is. The thermal stress relates to volume fractions and elastic constants of Ni base alloy and ceramic grain. Based on low-cycle fatigue crack growth rate formation, the thermal fatigue life was computed. The bigger thermal stress is, the smaller thermal fatigue life is. Thermal life is an exponential function of crack initiation length and critical length. (orig.)

Liu Xiequan; Ni Xinhua; Wang Junying [Mechanical Engineering Coll., Shijiazhuang, HEB (China)

2005-07-01

178

Low-cycle fatigue life of steel P92 under gradual loading  

Science.gov (United States)

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.

Cie?la, M.; Junak, G.

2012-05-01

179

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.

2012-05-02

180

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

Directory of Open Access Journals (Sweden)

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.

Ghasem Salehpoor; S. Mousa Kafi; Sajjad Rezaei; Mozaffar Hosseininezhad; Iraj Salehi

2012-01-01

 
 
 
 
181

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 th...

M.M. Rahman; A.K. Ariffin; N. Jamaludin; S. Abdullah; M.M. Noor

182

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

Directory of Open Access Journals (Sweden)

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.

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

2008-01-01

183

Effects of LWR environments on fatigue life of carbon and low-alloy steels  

International Nuclear Information System (INIS)

SME Boiler and Pressure Vessel Code provides construction of nuclear power plant components. Figure I-90 Appendix I to Section III of the Code specifies fatigue design curves for structural materials. While effects of environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A 106-Gr B carbon steel and A533-Gr B low-alloy steel in water.

1995-01-01

184

Effects of LWR environments on fatigue life of carbon and low-alloy steels  

Energy Technology Data Exchange (ETDEWEB)

SME Boiler and Pressure Vessel Code provides construction of nuclear power plant components. Figure I-90 Appendix I to Section III of the Code specifies fatigue design curves for structural materials. While effects of environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A 106-Gr B carbon steel and A533-Gr B low-alloy steel in water.

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

1995-03-01

185

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

Directory of Open Access Journals (Sweden)

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 (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),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.

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

2010-01-01

186

Applying a Physics-Based Description of Fatigue Variability Behavior to Probabilistic Life Prediction (Preprint).  

Science.gov (United States)

We describe fatigue lifetime variability as the separation/overlap of a crack-growth-controlled life-limiting mechanism and a mean-lifetime dominating behavior. We implement this description through a bimodal probability density representing the superposi...

A. H. Rosenberger J. M. Larsen S. K. Jha

2007-01-01

187

Modeling the effects of control systems of wind turbine fatigue life  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1996-12-31

188

Factors influencing quality of life in cancer patients: anemia and fatigue.  

UK PubMed Central (United Kingdom)

Anemia is a multi-symptom syndrome involving both physical and emotional problems that can be evaluated for their impact on quality of life. Fatigue is the cardinal symptom of anemia, reported by three of four cancer patients using the general version of the Functional Assessment of Cancer Therapy (FACT-G) questionnaire. A subscale of the FACT-G, consisting of the FACT-Fatigue (FACT-F) and the FACT-Anemia (FACT-An), has been developed to specifically address this problem. The FACT-F is comprised of the FACT-G plus 13 questions related to fatigue, while the FACT-An is comprised of the FACT-F plus an additional set of seven miscellaneous (non-fatigue) questions relevant to anemia in cancer patients. The FACT-An subscale was initially validated in a cohort of 50 cancer patients. Tests of internal consistency and stability confirmed the reliability of the fatigue component, as well as that of the FACT-G (27 items), the FACT-F (FACT-G plus 13 fatigue items), and the FACT-An (FACT-G plus 20 anemia subscale items) measurement systems. Quality of life scores on these FACT scales significantly decline as patient performance status worsens, and the scales correlate well with other questionnaires (Profile of Mood States and Piper Fatigue Scale) purported to measure the same thing. The scores on the FACT-An subscale also clearly differentiate between patients with low and high hemoglobin levels. Low hemoglobin levels are associated with greater fatigue, poorer overall quality of life, and decreased ability to work (beyond that related directly to fatigue). Interventions that reverse fatigue and other anemia-related symptoms should have a positive effect on quality of life.

Cella D

1998-06-01

189

Nanosize Carbides Formation and Fatigue Life Increase of Stainless Steel by Electron Beam Treatment  

Directory of Open Access Journals (Sweden)

Full Text Available Electron – beam treatment with 20 J/cm2 energy density of Fe-0.20C-23Cr-18Ni stainless steel increases fatigue life up to 2.1 times. Fracture surface investigations have been carried out by the methods of scanning and transmission diffraction electron microscopy and layer-by-layer analysis of structural phase states and defect substructure of steel subjected to the multicyclic fatigue tests, has been made as well. Nanosize (Cr,Fe)23C6 carbides formation and physical reasons of steel fatigue life increase by electron – beam treatment have been found out.

Gromov V.E.; Sizov V.V.; Vorobyov S.V.; Ivanov Yu.F.; Myasnikova V.I.; Konovalov S.V.

2012-01-01

190

Assessment of concepts for fatigue crack initiation and propagation life prediction  

Energy Technology Data Exchange (ETDEWEB)

A great variety of fatigue life prediction concepts has evolved during the last decades. Nevertheless, there is a lack of satisfying fundamental theories for the evaluation of fatigue damage under variable amplitude loading; progress has been made, however, in the development of numerical prediction concepts which are backed up by experimental work and are, therefore, used as relative concepts. In the paper, some basic requirements concerning the assessment of fatigue life prediction methods are discussed. A survey on different concepts is given and capabilities and limitations are elucidated by typical results selected from the literature.

Heuler, P.; Schuetz, W.

1986-11-01

191

Low-Cycle Fatigue Life Prediction in GTD-111 Superalloy at Elevated Temperatures  

International Nuclear Information System (INIS)

The Ni-base super-heat-resistant alloy, GTD-111, is employed in gas turbines because of its high temperature strength and oxidation resistance. It is important to predict the fatigue life of this superalloy in order to improve the efficiency of gas turbines. In this study, low-cycle fatigue tests are performed as variables of total strain range and temperature. The relationship between the strain energy density and number of cycles to failure is examined in order to predict the low-cycle fatigue life of the GTD-111 superalloy. The fatigue life predicted by using the strain-energy methods is found to coincide with that obtained from the experimental data and from the Coffin-Manson method

2011-01-01

192

Application of artificial neural network for predicting fatigue crack propagation life of aluminum alloys  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: In this work, fatigue crack propagation life of 7020 T7 and 2024 T3 aluminum alloys under the influence of load ratio was predicted by using artificial neural network (ANN).Design/methodology/approach: Numerous phenomenological models have been proposed for predicting fatigue life of the components under the influence of load ratio to take into account the mean load effect.Findings: In current research, an automatic prediction methodology has been adopted to estimate the constant amplitude loading fatigue life under the above condition by applying artificial neural network (ANN).Practical implications: ANNs show great potential for predicting fatigue crack growth rate especially by interpolation within the tested range. However, its benefit is lost when the model is needed to extrapolate the available experimental data.Originality/value: The predicted results are found to be in good agreement with the experimental findings when tested on two aluminum alloys 7020 T7 and 2024 T3 respectively.

J.R. Mohanty; B.B. Verma; D.R.K. Parhi; P.K. Ray

2009-01-01

193

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

DEFF Research Database (Denmark)

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

SØrensen, Eigil V.

2011-01-01

194

Thermal fatigue life and failure mode in high-temperature component materials for power plant  

International Nuclear Information System (INIS)

[en] The thermal fatigue life characteristics of various materials is described for high-temperature components in power plants, including low-alloy steels, austenitic stainless steels and superalloys, were summarized. As a result, the characteristics were found to be basically classified into four types associated with a difference in failure mode. A discussion was also made on thermal fatigue life prediction methods based on other mechanical properties such as tensile and isothermal failure properties. It was found that the good or safe prediction, excepting a case showing the great effect of creep-fatique interaction, could be made by applying the total-strain-range-based relations, particularly the total strain range vs. life relation in isothermal fatigue at the maximum temperature in thermal fatigue. (author)

1984-01-01

195

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.

1975-09-07

196

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

International Nuclear Information System (INIS)

[en] 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

1992-01-01

197

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-10-01

198

Study on durability of welded bellows. Fatigue life of bellows with crack in welded bead  

International Nuclear Information System (INIS)

Reports of study for welded bellows with cracks have apparently not been published to date. The purpose of this investigation is to understand the relationship between the state of stress of welded bellows with micro cracks and the fatigue life. Stresses of welded bellows with cracks were calculated for several different crack lengths by finite element method (FEM), and lives of bellows with cracks were examined by fatigue test. The fatigue life, i.e. the number of cycles to failure was arranged against the remaining wall thickness measured after test instead of the crack length. As a result, it was found that there is a regular relationship between the stress amplitude of peak stress calculated by FEM and the fatigue life of bellows. And then, it was shown that the life of bellows becomes longer than the life estimated using a theoretical S-N curve calculated by Manson's method. Stress intensity factor range (?K) and crack propagation rate (da/dN) were also calculated using the results of stress analysis by FEM and fatigue test. The relationship between ?K and da/dN obtained was almost coincident with the earlier result of fatigue crack growth test of Inconel 718 in the region of da/dN > 1.5x10-6 mm/cycle, and the propriety of the present results was confirmed. (author).

1994-01-01

199

Study on durability of welded bellows. Fatigue life of bellows with crack in welded bead  

Energy Technology Data Exchange (ETDEWEB)

Reports of study for welded bellows with cracks have apparently not been published to date. The purpose of this investigation is to understand the relationship between the state of stress of welded bellows with micro cracks and the fatigue life. Stresses of welded bellows with cracks were calculated for several different crack lengths by finite element method (FEM), and lives of bellows with cracks were examined by fatigue test. The fatigue life, i.e. the number of cycles to failure was arranged against the remaining wall thickness measured after test instead of the crack length. As a result, it was found that there is a regular relationship between the stress amplitude of peak stress calculated by FEM and the fatigue life of bellows. And then, it was shown that the life of bellows becomes longer than the life estimated using a theoretical S-N curve calculated by Manson`s method. Stress intensity factor range ({Delta}K) and crack propagation rate (da/dN) were also calculated using the results of stress analysis by FEM and fatigue test. The relationship between {Delta}K and da/dN obtained was almost coincident with the earlier result of fatigue crack growth test of Inconel 718 in the region of da/dN > 1.5x10{sup -6} mm/cycle, and the propriety of the present results was confirmed. (author).

Hirata, Osamu; Okada, Ken; Yanagisawa, Takasi [Eagle Industry Co. Ltd., Tokyo (Japan); Nakajima, Akira

1994-11-01

200

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Fatigue life of metal treated by magnetic field  

Science.gov (United States)

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

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

2009-03-01

 
 
 
 
201

Fatigue, quality of life, and mood states during chemotherapy in Italian cancer patients.  

UK PubMed Central (United Kingdom)

AIMS AND BACKGROUND: In cancer patients, fatigue interferes with the individual's functioning and quality of life (QoL). We investigated the association between fatigue and the main QoL dimensions and mood states as well as the main sociodemographic and clinical variables. METHODS: A total of 105 inpatients undergoing chemotherapy were administered the Revised Piper Fatigue Scale and the EORTC QLQ-C30 and POMS questionnaires, along with a form for collecting personal and clinical data. RESULTS: Compared with patients reporting lower fatigue levels, patients with higher levels showed worse functioning (P <0.001) in every QoL domain (i.e., physical, role, emotional, social, cognitive functioning, pain, and general health) as well as in the assessed mood states (depression-dejection, tension-anxiety, confusion-bewilderment). Moreover, both QoL and mood states in the subgroup reporting intermediate fatigue levels were worse than those of the subgroup with lower fatigue levels (P <0.02), except for emotional functioning, general health and QoL, and tension-anxiety. In addition, fatigue was significantly associated with gender, age, education, performance status, but not with marital status, survival rate of cancer type, and current chemotherapy cycle. CONCLUSIONS: The associations observed between fatigue, the main QoL domains, and negative mood states call for further active interventions to prevent and reduce fatigue.

Annunziata MA; Muzzatti B; Mella S; Bidoli E

2013-01-01

202

Increasing fatigue life of weld repaired rotating elements  

Energy Technology Data Exchange (ETDEWEB)

The paper discusses the use of controlled shot peening to regain the fatigue strength lost on rotating elements due to welding during original manufacture, welding used for salvaging expensive components due to mishaps during final machining, and weld repair after years of successful service. Weld repair of rotating components is becoming more popular due to improved welding techniques and non-destructive testing capabilities. Confidence in weld repair has further been heightened by the ability to regain the fatigue strength lost by welding and actually raise the fatigue strength close to that of the original homogeneous metal.

Welsch, W.

1998-07-01

203

An improved method for estimating fatigue life under combined stress  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with a complicated problem of estimating fatigue lives of machine parts exposed to various kinds of dynamic loading. An origin of the presented method can be found 25 years ago when a simple algorithm of strain energy density cumulation was applied for evaluation of uniaxial harmonic and random fatigue tests. Recently, the method has been adopted for multiaxial loading. Unfortunately, results of its application have shown rather big variance. This paper presents the improved method, which yields much lower scattering of estimated fatigue lives compared with earlier approaches.

Balda M.; Svoboda J.; Frohlich V.

2007-01-01

204

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

International Nuclear Information System (INIS)

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

2011-01-01

205

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-15

206

Analysis of Impact Fatigue Life for Valve Leaves in Small Hermetic Reciprocating Compressors  

Directory of Open Access Journals (Sweden)

Full Text Available Impact fatigue life of valve leaves has great influence on energy saving performance and lifetime of small hermetic reciprocating compressors. This paper presented a test system that intended to analysis and evaluate of impact fatigue life of valve leaves used in small hermetic reciprocating compressors. Firstly, an incentive system was designed to simulate real work condition for valve leaf. Then, a data acquisition system was built to collect the sound signal while valve leaf was being under test. Simultaneously, the system could control the working state of incentive system so that test could be terminated automatically once fatigue was detected. Finally, fatigue detection system was designed to detect fatigue of valve leaf. Fatigue detection was the key point of this test system. Fast Fourier Transform (FFT) and Wavelet Packet Transform (WPT) were applied to analyze sound signal, both of which were effective in detecting the damage through analyzing. Facts showed that the test system provided a feasible approach to evaluate impact fatigue life for valve leaf manufacturing.

Dong Zhang; Ming Xu; Jiang-Ping Gu; Yue-Jin Huang; Xi Shen

2013-01-01

207

Crack initiation life prediction method of thermal creep-fatigue  

International Nuclear Information System (INIS)

[en] Experimental and analytical results are presented of different surface roughness SUS304 tapered cylinders subjected to thermal creep-fatigue in liquid sodium. An experimental formula was developed to determine crack initiation cycles and subsequent propagation behaviors under repeated temperature gradient loads in a wall. A failure criterion of 'unity in creep-fatigue damage' roughly agreed with the occurrance of experimental 1 mm deep cracks. Surface roughness had no effect on crack initiation cycles and subsequent propagation behavior. (orig.)

1992-06-05

208

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

International Nuclear Information System (INIS)

[en] 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)

2011-01-01

209

A life evaluation under creep-fatigue-environment interaction of Ni-base wrought alloys  

International Nuclear Information System (INIS)

[en] In order to determine a failure criteria under cyclic loading and affective environment for HTGR systems, a series of strain controlled low-cycle fatigue tests were carried out at HTGR maximum gas temperatures in air, in vacuum and in HTGR helium environments on two nickel-base wrought alloys, namely Inconel 617 and Hastelloy XR. This paper first describes the creep-fatigue-environment properties of these alloys followed by a proposal of an evaluation method of creep-fatigue-environment interaction based on the experimental data to define the more reasonable design criteria, which is a modification of the linear damage summation rule. Second, the creep-fatigue properties of Hastelloy XR at 900 deg C and the result evaluated by this proposed method are shown. This criterion is successfully applied to the life prediction at 900 deg C. In addition, the creep-fatigue properties of Hastelloy XR-II are discussed. (author)

1986-01-01

210

Near-terminal creep damage does not substantially influence fatigue life under physiological loading.  

UK PubMed Central (United Kingdom)

Cortical bone specimens were damaged using repeated blocks of tensile creep loading until a near-terminal amount of creep damage was generated (corresponding to a reduction in elastic modulus of 15%). One group of cortical bone specimens was submitted to the near-terminal damage protocol and subsequently underwent fatigue loading in tension with a maximum strain of 2000 ?? (Damage Fatigue, n=5). A second group was submitted to cyclic fatigue loading but was not pre-damaged (Control Fatigue, n=5). All but one specimen (a damaged specimen) reached run-out (10 million cycles, 7.7 days). No significant differences in microscopic cracks or other tissue damage were observed between the two groups or between either group and additional, completely unloaded specimens. Our results suggest that damage in cortical bone allograft that is not obvious or associated with a stress riser may not substantially affect its fatigue life under physiologic loading.

Stern LC; Brinkman JG; Furmanski J; Rimnac CM; Hernandez CJ

2011-07-01

211

Near-terminal creep damage does not substantially influence fatigue life under physiological loading.  

Science.gov (United States)

Cortical bone specimens were damaged using repeated blocks of tensile creep loading until a near-terminal amount of creep damage was generated (corresponding to a reduction in elastic modulus of 15%). One group of cortical bone specimens was submitted to the near-terminal damage protocol and subsequently underwent fatigue loading in tension with a maximum strain of 2000 ?? (Damage Fatigue, n=5). A second group was submitted to cyclic fatigue loading but was not pre-damaged (Control Fatigue, n=5). All but one specimen (a damaged specimen) reached run-out (10 million cycles, 7.7 days). No significant differences in microscopic cracks or other tissue damage were observed between the two groups or between either group and additional, completely unloaded specimens. Our results suggest that damage in cortical bone allograft that is not obvious or associated with a stress riser may not substantially affect its fatigue life under physiologic loading. PMID:21592481

Stern, Lorraine C; Brinkman, Jennifer G; Furmanski, Jevan; Rimnac, Clare M; Hernandez, Christopher J

2011-05-18

212

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

Science.gov (United States)

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

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

2013-07-01

213

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.

2011-01-01

214

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

Directory of Open Access Journals (Sweden)

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.

?abuz-Roszak, Beata; Kubicka-B?czyk, Katarzyna; Pierzcha?a, Krystyna; Horyniecki, Maciej; Machowska-Majchrzak, Agnieszka; Augusty?ska-Mutryn, Daria; Kosa?ka, Konrad; Michalski, Krzysztof; Pyszak, Dominika; Wach, Joanna

2013-01-01

215

[Quality of life in multiple sclerosis--association with clinical features, fatigue and depressive syndrome].  

UK PubMed Central (United Kingdom)

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.

?abuz-Roszak B; Kubicka-Baczyk K; Pierzcha?a K; Horyniecki M; Machowska-Majchrzak A; Augusty?ska-Mutryn D; Kosa?ka K; Michalski K; Pyszak D; Wach J

2013-05-01

216

Damage due to low-cycle fatigue of type 316 stainless steel. Fatigue life under variable loading and influence of internal cracks  

International Nuclear Information System (INIS)

To reasonably predict of fatigue life under variable loading, it is important to understand the damaging process. In this study, the damage process of low-cycle fatigue was investigated for Type 316 stainless steel. Fully-reversed axial fatigue tests were conducted in the ambient air at a room temperature by controlling strain amplitude, which was 6% at the maximum. Two-step strain tests were also conducted in order to assess the effect of loading history on fatigue life. The fatigue life was shown to be not always longer than that estimated using a linear damage accumulation rule. Furthermore, in order to evaluate the effect of initiation and growth of surface cracks on the fatigue life, the surface layer of specimens was removed after the first step. The fatigue life was extended by surface removal, although it was not recovered completely. Many internal cracks were observed on the fractured surface of the surface-removed specimens, and in some cases the specimens were fractured by these internal cracks. It was concluded that the low-cycle fatigue damage of Type 316 stainless steel consisted of three factors: surface cracking, internal cracking, and strain accumulation. (author)

2010-01-01

217

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-12-19

218

Prediction of corrosion fatigue life of TMCP steel using the DCPD method  

Energy Technology Data Exchange (ETDEWEB)

In order to nondestructively evaluate the degradation characteristics by corrosion fatigue and reliability of TMCP steel using as a material of heavy industries and plants, its electro-chemical corrosion susceptibilities and corrosion fatigue life were investigated. From the results, the corrosion characteristics of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its corrosion susceptibility linearly increases with solution temperature increase. In particular, the DC potential difference due to the crack growth behavior in 25 C, 3.5wt.% NaCl solution is very susceptible. And the stress amplitude applied in the corrosion fatigue tests has a linear relationship with the critical potential. It is expected that corrosion fatigue life of TMCP steel can be nondestructively predicted using the DCPD method. (orig.)

Bae, D.H. [School of Mechanical Engineering, Sungkyunkwan Univ., Kyunggi-do (Korea); Park, J.H. [Samsung Heavy Industries Co., Kyungnam (Korea)

2004-07-01

219

FATIGUE LIFE PREDICTION OF COMMERCIALLY PURE TITANIUM AFTER NITROGEN ION IMPLANTATION  

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

220

Ratcheting and low cycle fatigue behavior of SA333 steel and their life prediction  

International Nuclear Information System (INIS)

[en] Ratcheting and low cycle fatigue (LCF) experiments have been conducted at 25 oC temperature in laboratory environment under different loading conditions. SA333 steel exhibits cyclic hardening throughout its life during LCF. It is found that ratcheting strain increases with both increasing mean stress and stress amplitude. It has also been noticed that plastic strain amplitude and plastic strain energy decrease with increase in mean stress at constant stress amplitude. Ratcheting and LCF life in the range of 102-105 cycles have been predicted with the help of a mean stress-based fatigue lifing equation.

2010-01-01

 
 
 
 
221

Ratcheting and low cycle fatigue behavior of SA333 steel and their life prediction  

Energy Technology Data Exchange (ETDEWEB)

Ratcheting and low cycle fatigue (LCF) experiments have been conducted at 25 {sup o}C temperature in laboratory environment under different loading conditions. SA333 steel exhibits cyclic hardening throughout its life during LCF. It is found that ratcheting strain increases with both increasing mean stress and stress amplitude. It has also been noticed that plastic strain amplitude and plastic strain energy decrease with increase in mean stress at constant stress amplitude. Ratcheting and LCF life in the range of 10{sup 2}-10{sup 5} cycles have been predicted with the help of a mean stress-based fatigue lifing equation.

Paul, Surajit Kumar, E-mail: paulsurajit@yahoo.co.i [Materials Science and Technology Division, National Metallurgical Laboratory (Council of Scientific and Industrial Research), Jamshedpur 831 007 (India); Sivaprasad, S. [Materials Science and Technology Division, National Metallurgical Laboratory (Council of Scientific and Industrial Research), Jamshedpur 831 007 (India); Dhar, S. [Department of Mechanical Engineering, Jadavpur University, Kolkata 700 032 (India); Tarafder, S. [Materials Science and Technology Division, National Metallurgical Laboratory (Council of Scientific and Industrial Research), Jamshedpur 831 007 (India)

2010-06-15

222

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

DEFF Research Database (Denmark)

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.

Hansen, Jens Zangenberg

2013-01-01

223

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

DEFF Research Database (Denmark)

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.

Passipoularidis, Vaggelis; Philippidis, T.P.

2010-01-01

224

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

Directory of Open Access Journals (Sweden)

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.

Jessie M. Huisinga, PhD; Mary L. Filipi, PhD; Nicholas Stergiou, PhD

2011-01-01

225

A way of a life, fatigue and disease of students of pedagogical colleges  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents information about how the life, frequency of morbidity for the year and the nature of fatigue students teacher training colleges. The study used data questionnaire 1238 students' 1-4 courses three teacher training colleges. Found similar results in various colleges of the Western region of Ukraine. Bad habits in the student team of pedagogical higher education institutions are more widespread than technical. Nearly half of students at the end of the day feel considerable fatigue. Every third student revealed complains about the fatigue of general nature.

Romanchyshyn O.N.; Sydorko O.U.; Martyn P.M.

2010-01-01

226

Roller-burnishing to improve fatigue life in beta-titanium alloys  

Energy Technology Data Exchange (ETDEWEB)

The possibilities for using roller-burnishing to improve fatigue behavior in the beta titanium alloys Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) and Ti-10V-2Fe-3Al (10-2-3) are examined. While roller burnishing does not significantly increase the endurance limit in Beta C, fatigue lifetimes at high cyclic stresses can be increased by up to one order of magnitude. In 10-2-3, the endurance limit can be increased by roughly 100 MPa, while fatigue life at high cyclic stresses is only marginally improved.

Berg, A.; Drechsler, A.; Wagner, L.

1999-07-01

227

Fatigue life prediction of ZE41A magnesium alloy using Weibull distribution  

Energy Technology Data Exchange (ETDEWEB)

In this investigation, the fatigue life prediction of ZE41A magnesium alloy has been statistically analyzed by Weibull distribution. The mechanical fatigue tests are conducted under R = 0.1 axial tension condition on specimen machined at as cast and welded materials. The micro structural investigations performed shows strong influence of precipitation on the fatigue failure of material. The curve for maximum stress and cycles to failure has been constructed for above stated materials. Using Weibull, the probability distribution according to which the material will fail is obtained. The fracture surface of the specimens is studied using scanning electron microscope.

Sivapragash, M. [Department of Mechanical Engineering, Jayamatha Engineering College, Aralvaimozhi, Tamil Nadu (India)], E-mail: mspragash@rediffmail.com; Lakshminarayanan, P.R.; Karthikeyan, R.; Raghukandan, K. [Department of Manufacturing Engineering, Annamalai University, Chidambaram, Tamil Nadu (India); Hanumantha, M. [Foundry and Forging Division, HAL, Bangalore, Karnataka (India)

2008-07-01

228

Fatigue life prediction of ZE41A magnesium alloy using Weibull distribution  

International Nuclear Information System (INIS)

In this investigation, the fatigue life prediction of ZE41A magnesium alloy has been statistically analyzed by Weibull distribution. The mechanical fatigue tests are conducted under R = 0.1 axial tension condition on specimen machined at as cast and welded materials. The micro structural investigations performed shows strong influence of precipitation on the fatigue failure of material. The curve for maximum stress and cycles to failure has been constructed for above stated materials. Using Weibull, the probability distribution according to which the material will fail is obtained. The fracture surface of the specimens is studied using scanning electron microscope

2008-01-01

229

Fracture-mechanics concept offers models to help calculate fatigue life in drillpipe  

Energy Technology Data Exchange (ETDEWEB)

This paper is the second of two articles on drillpipe fatigue analysis, and discusses the use of concepts set forth in part 1 to address the problem of calculating fatigue life of drillpipe under known operating conditions. The study tacitly accepts the presence of crack-like defects of various types in the pipe even in the as-received condition. The paper attempts to characterize the most severe surface cracks in terms of their dimensions and location by non-destructive examination.

Kral, E.; Newlin, L.; Quan, S.S.; Sengupta, P.K.

1984-08-13

230

Theoretical analysis of the fatigue life of fixture screws in osseointegrated dental implants.  

UK PubMed Central (United Kingdom)

Metal fatigue failure of the gold screw used to retain a fixed prosthesis to Brånemark osseointegrated fixtures/abutments has been analyzed theoretically. Mechanical engineering principles show the importance of appropriate preload being applied through the gold screw to the gold cylinder and abutment. The significance of the screw design and necessity of applying the correct torque to achieve a long fatigue life for the screw are also described. The consequence of misalignment of a gold cylinder to an abutment is discussed.

Patterson EA; Johns RB

1992-01-01

231

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

Science.gov (United States)

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

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

2013-05-01

232

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

Directory of Open Access Journals (Sweden)

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.

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

2009-01-01

233

The relationship between cancer-related fatigue and patient satisfaction with quality of life in cancer.  

Science.gov (United States)

Fatigue affects a majority of patients undergoing cancer-related therapies. We conducted a study of 954 adult cancer patients presenting for treatment at our hospital between April 2001 and November 2004 to quantify the relationship between fatigue and patient satisfaction with quality of life (QoL). Fatigue was measured using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire fatigue subscale. Patient satisfaction with QoL was measured using the Ferrans and Powers Quality of Life Index (QLI). The relationship between fatigue and QLI was evaluated using univariate and multivariate linear regression after controlling for the effects of clinical and demographic factors. Of the 954 patients, 579 were females and 375 males, with a median age at presentation of 56 years (range 20-90 years). Sixty-six percent had failed prior treatment. The most common cancers were breast (26%), colorectal (19%), and lung (16%) cancers. After controlling for the effects of age and prior treatment history, every 10-unit increase in fatigue was statistically significantly associated with 1.5-, 0.22-, 0.77-, 0.27-, and 0.85-unit declines in QLI health and physical, social and economic, psychological and spiritual, family, and global function scores, respectively. Consequently, a 30-point increase in fatigue score correlates with a 4.5-point decline in QLI health functioning-a clinically significant decline. In our study, we found that fatigue is strongly associated with patient satisfaction with QoL independent of the effects of age and prior treatment history. PMID:17532179

Gupta, Digant; Lis, Christopher G; Grutsch, James F

2007-05-25

234

The relationship between cancer-related fatigue and patient satisfaction with quality of life in cancer.  

UK PubMed Central (United Kingdom)

Fatigue affects a majority of patients undergoing cancer-related therapies. We conducted a study of 954 adult cancer patients presenting for treatment at our hospital between April 2001 and November 2004 to quantify the relationship between fatigue and patient satisfaction with quality of life (QoL). Fatigue was measured using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire fatigue subscale. Patient satisfaction with QoL was measured using the Ferrans and Powers Quality of Life Index (QLI). The relationship between fatigue and QLI was evaluated using univariate and multivariate linear regression after controlling for the effects of clinical and demographic factors. Of the 954 patients, 579 were females and 375 males, with a median age at presentation of 56 years (range 20-90 years). Sixty-six percent had failed prior treatment. The most common cancers were breast (26%), colorectal (19%), and lung (16%) cancers. After controlling for the effects of age and prior treatment history, every 10-unit increase in fatigue was statistically significantly associated with 1.5-, 0.22-, 0.77-, 0.27-, and 0.85-unit declines in QLI health and physical, social and economic, psychological and spiritual, family, and global function scores, respectively. Consequently, a 30-point increase in fatigue score correlates with a 4.5-point decline in QLI health functioning-a clinically significant decline. In our study, we found that fatigue is strongly associated with patient satisfaction with QoL independent of the effects of age and prior treatment history.

Gupta D; Lis CG; Grutsch JF

2007-07-01

235

Practical methodology to evaluate the fatigue life of seam welded joints  

Directory of Open Access Journals (Sweden)

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.

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

2011-01-01

236

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)

2004-01-01

237

Comparison of different damage laws for creep fatigue life assessment  

International Nuclear Information System (INIS)

The structures of fast breeder reactors are submitted to cyclic loading at high temperature. Consequently, they must be designed relatively to creep fatigue. Creep fatigue damage models already exist in the design codes, ASME and RCCMR propose models which provide separate estimation of fatigue damage and creep damage and then recombine them by means of an interaction diagram, with creep damage being assessed as a function of the stresses. The LASG procedure developed in Great Britain is similar in its principle but different as concerns the manner of assessing creep damage which is, in this case, based on the exhausting of the material's ductility. These models have already been widely used for the design of structures and have already formed the subject of benchmarch allowing their comparison with experimental results (reference 1). Other damage models have been developed, in France in particular, by ONERA and EMP (Ecole des Mines de Paris). These models are based on different considerations than those mentioned above. After presentation of the equations and principles of these models, the results of validations with respect to uniaxial fatigue relaxation tests are shown. Their utilization is then extended to the prediction of multiaxial tests on mock-ups tested in sodium

1993-01-01

238

Fatigue Life Investigation of PZT Ceramics by MSP Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Th...

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

239

Fatigue life prediction of fiber reinforced concrete under flexural load  

DEFF Research Database (Denmark)

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.

Zhang, Jun; Stang, Henrik

1999-01-01

240

Fatigue life analysis of unexpected failure in a lamellar TiAl alloy  

Energy Technology Data Exchange (ETDEWEB)

Unexpected catastrophic failure occurred in specimens of a lamellar TiAl alloy tested by axial fatigue. The failure initiated at locations away from artificial defects introduced to the specimens as crack starters. Fractographic examination of the fracture surface revealed the presence of featureless, low-energy facets that suggested the catastrophic crack may have initiated in one or more large grains that cleaved on a cleavage plane or an interface. A crack growth analysis of fatigue life of the test specimens suggested that the catastrophic crack propagated at stress intensity levels below the large crack threshold. Furthermore, the catastrophic crack propagated at rates that were higher than the average rates exhibited by small cracks, as well as by the large crack under equivalent stress intensity ranges. Because of this, the conventional life prediction approach based on the large crack growth data grossly overpredicted the fatigue life.

Chan, K.S.

1999-07-01

 
 
 
 
241

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

1991-01-01

242

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

Energy Technology Data Exchange (ETDEWEB)

The provisions of ASME B 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.

Blass, J.J.; Battiste, R.L.; O' Connor, D.G.

1991-01-01

243

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

Directory of Open Access Journals (Sweden)

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.

Mileti? Svetlana; Ton?ev Gordana; Jev?i? Jasna; Jovanovi? B.; Canovi? D.

2011-01-01

244

A simplified method for creep-fatigue life prediction for structures subjected to thermal loadings  

International Nuclear Information System (INIS)

[en] A simplified creep-fatigue failure prevention-life prediction method (TTSDS) for pressure vessels and pipings subjected to thermal expansion-thermal transient loadings is presented. The method was constructed based on numerous SUS304 material-structure test data, and incorporates a linear cumulative damage rule with an instrinsic life reduction factor. When the TTSDS method was applied using no safety factors, good life predictions for piping elements-components subjected to cyclic thermal transient loads were achieved. ((orig.))

1995-01-01

245

Fatigue life of Ti-50 at.% Ni and Ti-40Ni-10Cu (at.%) shape memory alloy wires  

International Nuclear Information System (INIS)

Fatigue lives of Ti-Ni and Ti-Ni-10Cu alloys were measured using a rotary bending fatigue tester. The fatigue tests were carried out at 308, 323, 338, 368, and 398 K, respectively, under a constant strain amplitude condition. The Af points of Ti-Ni and Ti-Ni-10Cu alloys, which were annealed at 673 K for 3.6 ks, were 351 and 331 K, respectively. Two types of strain amplitude vs fatigue life curves were observed, one composed of two straight lines with one turning point whereas the other composed of three straight lines with two turning points. The upper turning point coincided with the elastic limit strain and the lower one with the proportional limit strain. The single turning point was observed in a fatigue test condition under which both the limit strains are almost the same. The fatigue life decreased with increasing test temperature in general. However, it became less sensitive to test temperature both in higher and lower temperature regions. Deformation mode and applied stress during fatigue testing are factors affecting fatigue life. However, the fatigue life of the Ti-50.0 at.% Ni is always longer than that of the Ti-40Ni-10Cu (at.%) if the fatigue life is plotted as a function of temperature difference between test temperature and Ms. (orig.)

1999-12-15

246

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

International Nuclear Information System (INIS)

[en] 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)

1992-01-01

247

Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.  

UK PubMed Central (United Kingdom)

BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse. This cross-sectional study examined sleep and fatigue in relation to depression and quality of life (QoL) after treatment for childhood ALL. PROCEDURE: Sleep, fatigue, depression, and QoL were evaluated by parent proxy and/or child self-reports of the Children's Sleep Habits Questionnaire, the PedsQL™ multidimensional fatigue scale, the Children's Depression Inventory and the Child Health Questionnaire. All total scores were compared to Dutch norm references. RESULTS: Sixty-two children were included, being 36 (interquartile range 22-62) months after finishing treatment. Parents rated the ALL survivors as having more disturbed sleep, more fatigue and poorer physical QoL compared to the Dutch norm. ALL survivors themselves reported less sleep problems, less depressive symptoms, and better psychosocial QoL than the Dutch norm. More sleep disturbances and fatigue correlated with more symptoms of depression and a worse QoL. CONCLUSIONS: Differences in parental and self-reports, including worse parental ratings, might be explained by worried parents and/or the adaptive style of the children. Impaired sleep and fatigue correlated with more depressive symptoms and a worse QoL.

Gordijn MS; van Litsenburg RR; Gemke RJ; Huisman J; Bierings MB; Hoogerbrugge PM; Kaspers GJ

2013-03-01

248

Fatigue  

Science.gov (United States)

... 20-40% in the short term. Trials using modafinil in MS fatigue have involved small numbers and ... studies are recommended to ascertain the effect of modafinil in the longer term and the appropriate dose. ...

249

Fatigue life estimation of ball screw in control element drive mechanism of SMART  

Energy Technology Data Exchange (ETDEWEB)

Various kinds of mechanisms are applied or studied for the driving control elements in reactors. One of these mechanisms is a ball screw type drive mechanism, which has advantages in precise operation and high stiffness. So this system is one of the candidate control element drive mechanism of SMART. The fatigue lifes of ball bearing and ball screws are generally limited by flaking at normal operation and are estimated by statistical method. A method to estimate the fatigue life of the ball screw on a control element drive mechanism is presented, and the suitability of ball screw type mechanism is discussed in this paper.

Lee, J. S.; Kim, J. H.; Kim, J. I. [KAERI, Taejon (Korea, Republic of)

2001-10-01

250

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.)

1993-01-01

251

Predicting the Fatigue Life in Steel and Glass Fiber Reinforced Plastics Using Damage Models  

Directory of Open Access Journals (Sweden)

Full Text Available Three cumulative damage models are examined for the case of cyclic loading of AISI 6150 steel, S2 glass fibre/epoxy and E glass fibre/epoxy composites. The Palmgren-Miner, Broutman-Sahu and Hashin-Rotem models are compared to determine which of the three gives the most accurate estimation of the fatigue life of the materials tested. In addition, comparison of the fatigue life of the materials shows the superiority of AISI 6150 steel and S2 glass fibre/epoxy at lower mean stresses, and that of steel to the composites at higher mean stresses.

Roselita Fragoudakis; Anil Saigal

2011-01-01

252

Experimental and modeling results of creep-fatigue life of Inconel 617 and Haynes 230 at 850 °C  

Science.gov (United States)

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

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

2013-01-01

253

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-07-01

254

Influence of cyclic thermal loading on residual fatigue life of materials damaged by simulated plasma disruption  

International Nuclear Information System (INIS)

Surface damage of type 304 stainless steel, which is one of the candidates for the first-wall structural material in a fusion reactor, at cyclic plasma disruption loadings is simulated by a high heat flux Neutron Beam Injection. Influences of the cyclic thermal loads on the residual fatigue life are studied. The results obtained are summarized as follows. (1) The maximum tensile residual stresses near the damaged surface increased with increasing thermal loading cycles from 1 to 5. (2) The fatigue strength and the fatigue limit of the specimen subjected to 5 cycles of thermal loading and those for 1 cycle are the same. (3) A critical crack length, 2be to vanish from sight caused by thermal loading is important for the evaluation of the residual fatigue life. If the defect length, 2be, residual life after the second thermal loading and that before thermal loading are the same. If 2b>2be, fatigue crack growth occurs due to the cyclic thermal load. (author).

1995-01-01

255

Effects of stress concentrations on the fatigue life of a gamma based titanium aluminide  

Energy Technology Data Exchange (ETDEWEB)

S-N curves for a gamma based titanium aluminide alloy of composition Ti-47.2Al-2.1Mn-1.9Nb(at.%)+2TiB{sub 2}(wt.%) have been used to define fatigue life. Effects of residual stress, stressed volume, loading ratio, loading mode, elevated temperature and surface roughness have been considered. Residual tensile stresses and micro-cracking are introduced by Electro Discharge Machining and the fatigue life is reduced slightly compared with polished samples. Notched fatigue tests show a significant notch strengthening effect which increases with increasing stress concentration factor. The fracture surfaces of specimens tested at room temperature reveal fully brittle failure mechanisms and no evidence of stable crack growth is observed. The fatigue life appears, therefore, to be determined predominantly by the number of cycles to crack initiation. At the elevated temperature of 830 C, evidence for some stable fatigue crack growth has been found. Probable sites for crack initiation are addressed.

Trail, S.J.; Bowen, P. [Univ. of Birmingham (United Kingdom)

1995-12-31

256

Fatigue life of the plasma-facing components in PULSAR  

International Nuclear Information System (INIS)

The PULSAR project is a multi-institutional effort to determine the advantages that can be gained by building a tokamak without current drive. This machine would reduce the capital and operating costs of the machine by avoiding the need for complex current drive hardware but it must compensate for this with an energy storage scheme and with increased structural requirements due to cyclic fatigue. This paper presents the results of the fatigue analysis for the plasma-facing components of PULSAR. The structural analysis is carried out using two-dimensional finite element models and a variety of boundary conditions to account for the third dimension. In some cases the temperature distribution is modified to simulate behaviors which cannot normally be modeled with two-dimensional finite element models. PULSAR features two major engineering designs: a liquid metal-cooled vanadium design and a helium-cooled SiC/SiC design. Results are given for each. It is shown that the superior thermal and strength properties of the vanadium alloy simplify the component design process significantly. The SiC composite properties cause significantly more difficulty for the designer and, in particular, no credible design is found for a divertor fabricated solely from the SiC composite. This conclusion is based on current data for the thermophysical properties and fatigue strength of SiC fiber composites, so developments in these areas could allow the fabrication of a SiC/SiC divertor for a pulsed tokamak.

1994-07-01

257

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

International Nuclear Information System (INIS)

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

2005-01-01

258

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-07-01

259

Evaluation of extrapolation for creep-fatigue life by hysteresis energy  

International Nuclear Information System (INIS)

The creep-fatigue life has been evaluated by the hysteresis energy in 316FR stainless steel with low carbon and medium nitrogen, which is a candidate for structural material in Fast Breeder Reactor (FBR) plant with the design life of 60 years. The creep-fatigue is a main damage mode to prevent. The hysteresis energy rate is considered as the parameter to predict the life time. It is clear that the relationship between this parameter and the time to failure can be approximately expressed by the power-law function. The function depends on the ratio of plastic strain to total strain. Total fracture energy for creep-fatigue loading intends to be independent of the ratio of plastic strain to total strain in long-term test condition. The value is related to grain boundary strength for creep-fatigue loading because fracture mode in long-term test condition is intergranular fracture. The life could be predicted by the function in the case of no significant change of fracture energy. Coarse precipitation, for example sigma phase, might be considered as a factor to change the fracture energy. It is important to predict the precipitation formation. The result of life prediction by the hysteresis energy rate is compared with that of the time fraction rule based on 'Demonstration Reactor Design Standard (Draft)'. The predicted lives by both methods for long-term region are comparable and independent of the ratio of plastic strain to total strain. (author)

2011-01-01

260

Fatigue life prediction of Ni-base thermal solar receiver tubes  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-07-01

 
 
 
 
261

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

Science.gov (United States)

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

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

2011-03-01

262

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

UK PubMed Central (United Kingdom)

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.

Al-Bayaa NJ; Clark RK; Juszczyk AS; Radford DR

2011-03-01

263

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

Energy Technology Data Exchange (ETDEWEB)

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.

Wong, F.M.G.

1990-06-01

264

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

International Nuclear Information System (INIS)

[en] 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

1990-01-01

265

Effects of hard-shot peening on high cycle fatigue properties and material properties on SUS316L steel; HSP shori ni yoru SUS316 ko no zaishitsu henka to ko cycle hiro tokusei  

Energy Technology Data Exchange (ETDEWEB)

The effects of normal shot-peening (SP) and hard shot-peening (HSP) on the fatigue properties and material properties of SUS316L austenite stainless steel were investigated. The rotating bending fatigue tests at 50Hz in air and under water cooling conditions were carried out on the SP and HSP treated and the non-shotted SUS316L specimens. In air condition, the fatigue strength of the SP and HSP treated materials were improved, but the specimens became heated because of internal friction. The fatigue strength under water cooling condition was improved on the SP and HSP treated SUS316L. The fatigue limit of 10{sup 8} and the fatigue strength in all lives of the HSP treated materials were highest in comparing with the SP and the non-shotted materials. X-ray diffraction measurement and hardness tests were also carried out on the SP and HSP treated SUS316L. The results showed that there existed the hardening layer caused by plastic deformation and the high compressive residual stress in the surface layers of the SP and HSP treated materials. Fatigue crack origins were transferred from the surface to the subsurface by the surface hardening and by the compressive residual stress. For the fatigue strength improvement the HSP treatment of austenite stainless steel was very successful. 20 refs., 12 figs., 5 tabs.

Masaki, K.; Ochi, Y.; Ishii, A. [University of Electro Communications, Tokyo (Japan)

1997-10-15

266

A study on fretting fatigue life in elevated temperature for Inconel 600 alloy  

Energy Technology Data Exchange (ETDEWEB)

The safety needs in the operation of nuclear power plant facilities have been increased due to the high temperature and pressure operation conditions within these facilities. Several reports exist on the fretting occurring in the materials of steam generator tubes used in nuclear power plants, which leads to a lower service life. The Inconel 600 alloy, used in steam generator tubes, is a type of nickel-chromium based heat resistant alloy. However, it is necessary to establish a systematic database to guarantee its integrity because there are few data indicating fretting fatigue behaviors at both room and high temperature conditions for the Inconel 600 alloy. Thus, this study analyzed the change in the fatigue characteristics of the Inconel 600 alloy under fretting fatigue by applying plain and fretting fatigue tests at 320 .deg. C, which is the room and actual operating temperature applied to the materials of steam generator tubes. In addition, this study measured the change in the friction force for repetitive cycles in fretting fatigue tests and analyzed the mechanism of fretting fatigue by observing the fracture surfaces.

Park, D. K. [Korea Textile Machinery Research Institute, Kyongsan (Korea, Republic of); Woo, S. W.; Yoon, D. H.; Jeung, H. K.; Chung, I. S.; Kwon, J. D. [Yeunganm University, Kyongsan (Korea, Republic of)

2009-07-01

267

A study on fretting fatigue life in elevated temperature for Inconel 600 alloy  

International Nuclear Information System (INIS)

[en] The safety needs in the operation of nuclear power plant facilities have been increased due to the high temperature and pressure operation conditions within these facilities. Several reports exist on the fretting occurring in the materials of steam generator tubes used in nuclear power plants, which leads to a lower service life. The Inconel 600 alloy, used in steam generator tubes, is a type of nickel-chromium based heat resistant alloy. However, it is necessary to establish a systematic database to guarantee its integrity because there are few data indicating fretting fatigue behaviors at both room and high temperature conditions for the Inconel 600 alloy. Thus, this study analyzed the change in the fatigue characteristics of the Inconel 600 alloy under fretting fatigue by applying plain and fretting fatigue tests at 320 .deg. C, which is the room and actual operating temperature applied to the materials of steam generator tubes. In addition, this study measured the change in the friction force for repetitive cycles in fretting fatigue tests and analyzed the mechanism of fretting fatigue by observing the fracture surfaces.

2009-01-01

268

ARRANGING THICKNESSES AND SPANS OF ORTHOTROPIC DECK FOR DESIRED FATIGUE LIFE AND DESIGN CATEGORY  

Directory of Open Access Journals (Sweden)

Full Text Available Orthotropic steel highway bridges are subject to variable traffic loads, which differ in type and magnitude. Most of these bridges were built in 1960’s under design traffic load, which reflects the traffic conditions of those times. However, the number and weight of vehicles in traffic have increased since then too much in comparison to today. As a result these bridges are loaded more than their designed traffic loads and hence bridges' fatigue lives are shorten. As a remedy for this issue, thicknesses of fatigue sensitive structural parts of bridge shall be determined under today' s valid wheel loads and design category for desired fatigue life. In the scope of this study the traditional steel orthotropic highway bridge is analyzed using a FE- model, which encompasses bridge' s entire geometry. The traffic load is selected so conservatively, that it is composed of static wheel loads and wheel load area, which comply with the wheels of vehicles used today in traffic. Subsequently, fatigue lives of four fatigue sensitive structural parts of bridge are calculated. These are critical section in web of cross girder due to cut outs, weld connecting deck plate to trapezoidal rib, continuous longitudinal stringer and deck plate. Finally, required thicknesses and spans of these structural parts depending on their fatigue lives and design categories are given.

Abdullah Fettahoglu

2013-01-01

269

Analysis of thermal stress and cyclic fatigue life for nuclear steam turbine H.P.rotor  

International Nuclear Information System (INIS)

In order to know the starting and load changing performance of nuclear steam turbine, the thermal stress calculation at different operation conditions and cyclic fatigue life analysis for H.P. rotor of 310 MW nuclear steam turbine are described. In addition, the results from different thermal stress calculation methods are discussed.

1993-01-01

270

Effect of Persistent Slip Band (PSB) Parameters on Fatigue Life. (Reannouncement with New Availability Information).  

Science.gov (United States)

An examination of PSB data pertaining to the effects of an air-excluding environment and electric current on the fatigue life of polycrystalline Cu and 316 stainless steel in rotating bending reveals that the spacing and width of the PSBs are smaller thro...

W. D. Cao H. Conrad

1992-01-01

271

Multiaxial creep-fatigue life analysis using strainrange partitioning  

International Nuclear Information System (INIS)

[en] 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

1976-11-29

272

Fatigue life prediction of components under variable amplitude loading  

Energy Technology Data Exchange (ETDEWEB)

The fundamentals for the calculation and experimental determination of the fatigue lives of components subjected to irregular loading are developed and so-called cumulated damage hypotheses are described. Hereby the Miner rule and the Paris and Forman equations were chosen as starting points and compared with the measured stress collectives. Stress-time functions (load histories) have been measured during operation and statistically evaluated in so-called service-durability experiments so that an operating-conditions-like simulation of loading becomes possible.

Schuetz, W.

1983-01-01

273

The effects of sheet spacing on the fatigue life of spot­welded joints  

Directory of Open Access Journals (Sweden)

Full Text Available While investigating the fatigue strength of spot-welded joints, the effects of sheet spacing or gap amounts between sheet joints may be considered as one of the most important parameters on the fatigue life duration of the joints. The main goal of the present work is to study the influence of sheet spacing on the fatigue life of 5083-O aluminium alloy spot welded tensile-shear joints. The amounts of sheet spacing are the average values over three measurements of photograph observation of the cut-off surfaces from the nugget centre of the spot-welded joints. The amounts of gap distances between spot weld sheet joints for three different electrode clamping force levels were 0.09mm, 0.11mm and 0.13mm, respectively. The values of notch strength reduction factors have been obtained at all levels of applied loads based on volumetric approach. The fatigue lives of spot welded joints have been obtained according to the volumetric method using the notch strength reduction factors and the available smooth S-N curve of 5083-O aluminium alloy sheets. The results based on the volumetric approach have been compared with the experimental fatigue test data and there is good agreement between numerical predictions and experimental results.

Hassanifard S.; Zehsaz M.; Esmaeili F.

2010-01-01

274

Fatigue and quality of life in citrin deficiency during adaptation and compensation stage.  

UK PubMed Central (United Kingdom)

Citrin-deficient children and adolescents between adult-onset type II citrullinemia and neonatal intrahepatic cholestasis by citrin deficiency do not have clear clinical features except for unusual diet of high-fat, high-protein, and low-carbohydrate food. The aims of the present study are to characterize fatigue and quality of life (QOL) in citrin-deficient patients during adaptation and compensation stage, and to define the relationship between fatigue and QOL. The study subjects were 55 citrin-deficient patients aged 1-22years (29 males) and 54 guardians. Fatigue was evaluated by self-reports and proxy-reports of the PedsQL Multidimensional Fatigue Scale. QOL was evaluated by the PedsQL Generic Core Scales. Both scale scores were significantly lower in child self-reports (p<0.01 and p<0.05, respectively) and parent proxy-reports (p<0.01 and p<0.01, respectively) than those of healthy children. Citrin-deficient patients with scores of 50 percentile or less of healthy children constituted 67.5% of the sample for the Fatigue Scale and 68.4% for the Generic Core Scales. The PedsQL Fatigue Scale correlated with the Generic Core Scales for both the patients (r=0.56) and parents reports (r=0.71). Assessments by the patients and their parents showed moderate agreement. Parents assessed the condition of children more favorably than their children. The study identified severe fatigue and impaired QOL in citrin-deficient patients during the silent period, and that such children perceive worse fatigue and poorer QOL than those estimated by their parents. The results stress the need for active involvement of parents and medical staff in the management of citrin-deficient patients during the silent period.

Okano Y; Kobayashi K; Ihara K; Ito T; Yoshino M; Watanabe Y; Kaji S; Ohura T; Nagao M; Noguchi A; Mushiake S; Hohashi N; Hashimoto-Tamaoki T

2013-05-01

275

Prediction of low cycle fatigue life for Inconel 617 using strain energy method  

International Nuclear Information System (INIS)

The relation between strain energy density and numbers of cycles to failure is examined in order to predict the low cycle fatigue life of Inconel 617. The life predicted by the strain energy method is found to coincide with experimental data and results obtained from the Coffin-Manson method. Also the cyclic behavior of Inconel 617 is characterized by cyclic hardening with increasing number of cycle at room temperature.

2004-01-01

276

Effects of the crack propagation direction on the propagation rate by high cycle fatigue of the API 5L-X70 and ASTM A516-GR65 class rolled steels; Efeito da orientacao da trinca na taxa de propagacao por fadiga de alto ciclo nos acos laminados da classe API 5L-X70 e ASTM A516-Gr65  

Energy Technology Data Exchange (ETDEWEB)

The influence of the crack propagation direction generated by high cycle fatigue on the behaviour of two different steels is investigated, by evaluation of API 5L-X70 and ASTM A516-Gr65 steel for pipelines, used in pressure vessels. The first one is controlled rolling steel and the second one is obtained by conventional rolling. The longitudinal `TL` and short transverse `SL` directions were investigated. Compact tensions samples were used and the crack displacement monitored by a travel microscope 4 refs., 8 figs., 2 tabs.

Farias, M.A.; Santos, M.A. dos [Paraiba Univ., Campina Grande, PB (Brazil). Dept. de Engenharia Mecanica

1995-12-31

277

Fatigue Life of Reciproc and Mtwo instruments subjected to static and dynamic tests.  

UK PubMed Central (United Kingdom)

INTRODUCTION: This study evaluated the influence of flexibility and reciprocating movement on the fatigue life of endodontic instruments subjected to static and dynamic tests. METHODS: The rotary nickel-titanium instruments used in this study were Reciproc and Mtwo. The instruments were initially subjected to a cantilever-bending test and then to static and dynamic fatigue tests. Reciproc instruments were operated in reciprocating movement, whereas Mtwo instruments were worked in continuous rotation. RESULTS: The means of bending resistance (maximum load in grams) of the instruments were 274.9 for Reciproc and 429 for Mtwo. The mean times (in seconds) to fracture of the instruments subjected to static and dynamic tests were 214.5 (static) and 286.3 (dynamic) for Reciproc and 38.9 (static) and 99 (dynamic) for Mtwo. The Student's t test revealed significant differences in all tests (P < .05). CONCLUSIONS: The results of the present study showed longer fatigue life for instruments with higher flexibility, driven by reciprocating movement, and in the dynamic testing model. These findings reinforce the assumption that use of reciprocating movement is a means to prolong the fatigue life of rotary nickel-titanium endodontic instruments during instrumentation of curved canals.

Lopes HP; Elias CN; Vieira MV; Siqueira JF Jr; Mangelli M; Lopes WS; Vieira VT; Alves FR; Oliveira JC; Soares TG

2013-05-01

278

Thermal fatigue life prediction based on crack propagation behaviors in high-temperature materials for power plant components  

International Nuclear Information System (INIS)

[en] For reducing an electric power supply cost, it is desired to extend the life of thermal power plant being still supplying the greater part of electric power in Japan. It is, therefore, becoming more and more important for the remaining life control of long-operated thermal power plants to exactly estimate the thermal fatigue damage accumulating in high temperature components. In this report, a discussion was made on thermal fatigue life laws derived from the crack propagation laws. As a result, the life laws were found to be effective for the evaluation of thermal fatigue life as well as isothermal fatigue life. Based on the concept of the life laws, the thermal and isothermal fatigue lives were also predicted as a propagation period of a crack with initial length equal to grain size from the characteristics of high temperature fatigue crack propagation. In addition to them, the rapid straining method was found to be required for more accurate estimation of creep strain in in-phase thermal fatigue. (author)

1986-01-01

279

Unstimulated cortisol secretory activity in everyday life and its relationship with fatigue and chronic fatigue syndrome: A systematic review and subset meta-analysis.  

UK PubMed Central (United Kingdom)

The hypothalamic-pituitary-adrenal (HPA) axis is a psychoneuroendocrine regulator of the stress response and immune system, and dysfunctions have been associated with outcomes in several physical health conditions. Its end product, cortisol, is relevant to fatigue due to its role in energy metabolism. The systematic review examined the relationship between different markers of unstimulated salivary cortisol activity in everyday life in chronic fatigue syndrome (CFS) and fatigue assessed in other clinical and general populations. Search terms for the review related to salivary cortisol assessments, everyday life contexts, and fatigue. All eligible studies (n=19) were reviewed narratively in terms of associations between fatigue and assessed cortisol markers, including the cortisol awakening response (CAR), circadian profile (CP) output, and diurnal cortisol slope (DCS). Subset meta-analyses were conducted of case-control CFS studies examining group differences in three cortisol outcomes: CAR output; CAR increase; and CP output. Meta-analyses revealed an attenuation of the CAR increase within CFS compared to controls (d=-.34) but no statistically significant differences between groups for other markers. In the narrative review, total cortisol output (CAR or CP) was rarely associated with fatigue in any population; CAR increase and DCS were most relevant. Outcomes reflecting within-day change in cortisol levels (CAR increase; DCS) may be the most relevant to fatigue experience, and future research in this area should report at least one such marker. Results should be considered with caution due to heterogeneity in one meta-analysis and the small number of studies.

Powell DJ; Liossi C; Moss-Morris R; Schlotz W

2013-08-01

280

Friction grip enclosure: a means for increasing the fatigue life of fuel rod end welds. LWBR Development Program  

International Nuclear Information System (INIS)

A friction grip enclosure was developed to increase the fatigue life of end welds in the LWBR fuel rods. This report describes the friction grip enclosure design concept and provides a sample analysis to illustrate the design application procedure. A cyclic proof test, performed to verify the fatigue performance of the friction grip enclosure, is also described. Adequate fatigue performance was demonstrated for the LWBR end welds when subjected to the maximum expected cyclic loads during LWBR operation

1983-01-01

 
 
 
 
281

Fatigue life evaluation under out-of-phase push-pull and torsion. Iso sa wo yusuru hippari asshuku-nejiri no kumiawase oryoku ka ni okeru hiro jumyo hyoka ni tsuite  

Energy Technology Data Exchange (ETDEWEB)

Fatigue tests are performed on a low carbon steel under combined push-pull and completely reversed torsion at room temperature, and the stress based evaluation parameters for the life in comparatively wide intermediate to high cycle region including fatigue threshold are investigated basing on the result of the tests. Under combined loadings, fatigue life becomes longer with the increase in phase difference. The equivalent stress including out-of-phase loadings, which is an extended Gough{prime}s equation, is simple and can be applied if the time strength ratio for each single stress is given, but the life is slightly overestimated. The equivalent stress which is a modified Lee criterion can make a comparatively accurate evaluation of the life under combined stress. The equivalent stress which is a Bronw-Miller{prime}s theory extended to the out-of-phase case can standardize the result of this test for the entire region of life. 23 refs., 14 figs., 1 tab.

Okawa, I.; Takahashi, H. (Hosei Univ., Tokyo (Japan). Faculty of Engineering); Tomaru, T. (Hosei Univ., Tokyo (Japan). Graduate School); Misumi, M. (Seikei Univ., Tokyo (Japan). Faculty of Engineering)

1991-11-15

282

Fatigue life prediction for wind turbines: A case study on loading spectra and parameter sensitivity  

Science.gov (United States)

Wind turbines are fatigue-critical machines used to produce electrical energy from the wind. These rotating machines are subjected to environmental loadings that are highly irregular in nature. Historical examples of fatigue problems in both research and commercial wind turbine development are presented. Some example data on wind turbine environments, loadings and material properties are also shown. Before a description of how the authors have chosen to attack the cumulative damage assessment, questions are presented for the reader's reflection. The solution technique used by the authors is then presented, followed by a case study applying the procedures to an actual wind turbine blade joint. The wind turbine is the 34-meter diameter vertical axis wind turbine (VAWT) erected by Sandia National Laboratories near Bushland, Texas. The case study examines parameter sensitivities for realistic uncertainties in inputs defining the turbine environment, stress response and material properties. The fatigue lifetimes are calculated using a fatigue analysis program, called LIFE2, which was developed at Sandia. The LIFE2 code, described in some detail in an appendix, is a PC-based, menu-driven package that leads the user through the steps required to characterize the loading and material properties, then uses Miner's rule or a linear crack propagation rule to numerically calculate the time to failure. Only S-n based cumulative damage applications are illustrated here. The LIFE2 code is available to educational institutions for use as a case study in describing complicated loading histories and for use by students in examining, hands on, parameter sensitivity of fatigue life analysis.

Sutherland, H. J.; Veers, P. S.; Ashwill, T. D.

283

The relationships between fatigue, quality of life, and family impact among children with special health care needs.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To examine the relationships among pediatric fatigue, health-related quality of life (HRQOL), and family impact among children with special health care needs (CSHCNs), specifically whether HRQOL mediates the influence of fatigue on family impact. METHODS: 266 caregivers of CSHCNs were studied. The Pediatric Quality of Life Inventory Multidimensional Fatigue Scale, Pediatric Quality of Life Inventory Generic Scale, and Impact on Family Scale were used to measure fatigue, HRQOL, and family impact, respectively. Linear regressions were used to analyze the designated relationships; path analyses were performed to quantify the mediating effects of HRQOL on fatigue-family impact relationship. RESULTS: Although greater fatigue was associated with family impact (p < .05), the association was not significant after accounting for HRQOL. Path analyses indicated the direct effect of fatigue on family impact was not significant (p > .05), whereas physical and emotional functioning significantly mediated the fatigue-family impact relationship (p < .001). CONCLUSION: Fatigue is related to family impact among CSHCNs, acting through the impairment in HRQOL.

Huang IC; Anderson M; Gandhi P; Tuli S; Krull K; Lai JS; Nackashi J; Shenkman E

2013-08-01

284

Fatigue life prediction for high-heat-load components made of GlidCop by elastic-plastic analysis.  

Science.gov (United States)

A procedure to predict the fatigue fracture life of high-heat-load components made of GlidCop has been successfully established. This method is based upon the Manson-Coffin equation with a cumulative linear damage law. This prediction was achieved by consolidating the results of experiments and analyses, and considered the effects of environment and creep. A low-cycle-fatigue test for GlidCop was conducted so that environment-dependent Delta(t)-N(f) diagrams for any temperature could be prepared. A special test piece was designed to concentrate the strain in a central area locally, resulting in the low-cycle-fatigue fracture. The experiments were carried out by repeatedly irradiating a test piece with an electron beam. The results of the experiment confirmed that the observed fatigue life was within a factor of two when compared with the predicted fatigue life, yet located on the safer side. PMID:18296780

Takahashi, Sunao; Sano, Mutsumi; Mochizuki, Tetsuro; Watanabe, Atsuo; Kitamura, Hideo

2008-02-19

285

Fatigue life prediction for high-heat-load components made of GlidCop by elastic-plastic analysis.  

UK PubMed Central (United Kingdom)

A procedure to predict the fatigue fracture life of high-heat-load components made of GlidCop has been successfully established. This method is based upon the Manson-Coffin equation with a cumulative linear damage law. This prediction was achieved by consolidating the results of experiments and analyses, and considered the effects of environment and creep. A low-cycle-fatigue test for GlidCop was conducted so that environment-dependent Delta(t)-N(f) diagrams for any temperature could be prepared. A special test piece was designed to concentrate the strain in a central area locally, resulting in the low-cycle-fatigue fracture. The experiments were carried out by repeatedly irradiating a test piece with an electron beam. The results of the experiment confirmed that the observed fatigue life was within a factor of two when compared with the predicted fatigue life, yet located on the safer side.

Takahashi S; Sano M; Mochizuki T; Watanabe A; Kitamura H

2008-03-01

286

Fatigue and quality of life in citrin deficiency during adaptation and compensation stage.  

Science.gov (United States)

Citrin-deficient children and adolescents between adult-onset type II citrullinemia and neonatal intrahepatic cholestasis by citrin deficiency do not have clear clinical features except for unusual diet of high-fat, high-protein, and low-carbohydrate food. The aims of the present study are to characterize fatigue and quality of life (QOL) in citrin-deficient patients during adaptation and compensation stage, and to define the relationship between fatigue and QOL. The study subjects were 55 citrin-deficient patients aged 1-22years (29 males) and 54 guardians. Fatigue was evaluated by self-reports and proxy-reports of the PedsQL Multidimensional Fatigue Scale. QOL was evaluated by the PedsQL Generic Core Scales. Both scale scores were significantly lower in child self-reports (psilent period, and that such children perceive worse fatigue and poorer QOL than those estimated by their parents. The results stress the need for active involvement of parents and medical staff in the management of citrin-deficient patients during the silent period. PMID:23453692

Okano, Yoshiyuki; Kobayashi, Kyoko; Ihara, Kenji; Ito, Tetsuya; Yoshino, Makoto; Watanabe, Yoriko; Kaji, Shunsaku; Ohura, Toshihiro; Nagao, Masayoshi; Noguchi, Atsuko; Mushiake, Sotaro; Hohashi, Naohiro; Hashimoto-Tamaoki, Tomoko

2013-02-09

287

Mean load effects on the fatigue life of offshore wind turbine monopile foundations  

DEFF Research Database (Denmark)

This paper discusses the importance of mean load effects on the estimation of the fatigue damage in offshore wind turbine monopile foundations. The mud line bending moment time series are generated using a fully coupled aero-hydro-elastic model accounting for non-linear water waves and sea current. The fatigue damage is analysed in terms of the lifetime fatigue damage equivalent bending moment. Three different mean value correction techniques are considered, namely, Goodman, Walker, and mean sensitivity factor. An increase in the lifetime fatigue damage equivalent bending moment between 6% (mean sensitivity factor) and 33% (Goodman) is observed when mean load corrections are considered. The lifetime damage equivalent bending moment is further increased by approximately 7% when considering sea current forces. The results indicate that mean load correction techniques should be employed in the analysis of the fatigue life of offshore wind turbine monopile foundations. Moreover, it is shown that a nonlinear hydrodynamic model is required in order to correctly account for the effect of the current.

Blasques, José Pedro Albergaria Amaral; Natarajan, Anand

2013-01-01

288

Creep-fatigue life property of FBR high-temperature structural materials under tension-torsion loading and life evaluation method  

International Nuclear Information System (INIS)

Creep-fatigue damage in high temperature structural components in a FBR progress under multiaxial stress condition depending on their operating conditions and configuration. Therefore, multiaxial stress effects on creep-fatigue damage evolution must be clarified to make precise creep-fatigue damage evaluation of these components. In this study, creep-fatigue tests in FBR high temperature materials such as SUS304, 316FR stainless steels and a modified 9Cr steel were conducted under biaxial stress subjecting tension-compression and torsion loading, in order to examine biaxial stress effects on failure mechanism and life property, and to discuss creep-fatigue life evaluation methods under biaxial stress. Main results obtained in this study are summarized as follows: 1. The main cracks under cyclic torsion loading propagated by shear mode in three materials. But intergranular failure was occurred in SUS304 and 316FR, and transgranular failure was observed in Mod.9Cr steel. 2. Nonlinear damage accumulation model proposed based on uniaxial creep-fatigue test results was extended to apply for creep-fatigue damage evaluation under biaxial stress state by considering the biaxial stress effects on fatigue and creep damage evolution. 3. It was confirmed that creep-fatigue life under biaxial stress could be predicted by the extended evaluation method with higher accuracy than existing methods. (author).

1994-01-01

289

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

Directory of Open Access Journals (Sweden)

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.

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

2009-01-01

290

Natalizumab treatment reduces fatigue in multiple sclerosis. Results from the TYNERGY trial; a study in the real life setting.  

UK PubMed Central (United Kingdom)

UNLABELLED: 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<0.0001). Walking speed as measured by the six-minute walk-test also increased at month 12 (p = 0.0016). All patients were aware of the nature of the treatment agent, and of the study outcomes. CONCLUSION: Natalizumab, as used in a real-life setting, might improve MS-related fatigue based on the results from this one-armed un-controlled stud. Also other parameters related to patients' quality of life seemed to improve with natalizumab treatment. TRIAL REGISTRATION: ClinicalTrials.gov NCT00884481.

Svenningsson A; Falk E; Celius EG; Fuchs S; Schreiber K; Berkö S; Sun J; Penner IK

2013-01-01

291

Effects of material and loading variables on fatigue life of carbon and low-alloy steels in LWR environments  

International Nuclear Information System (INIS)

[en] This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A106-Gr B carbon steel and A533-Gr B low-alloy steel in water. (author). 22 refs., 10 figs., 1 tab

1995-01-01

292

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-10-09

293

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

International Nuclear Information System (INIS)

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

2007-12-15

294

Load type influences on the high-temperature creep-fatigue behaviour of the titanium alloy IMI 834 and creep-fatigue life prediction  

Energy Technology Data Exchange (ETDEWEB)

In the present investigation which especially considers the engineering application of the Ti-alloy IMI 834 for high-temperature components the influence of balanced and unbalanced creep-fatigue cycles and of stress-hold strain range partitioning (SRP) cycles on crack initiation and crack propagation was systematically investigated at 600 C. It was found that not only the creep or the inelastic strain portion of complex creep-fatigue cycles and their frequencies have a significant influence on crack propagation and on crack initiation life but also in which way the creep and fatigue portions are superimposed in the cycles. A slow increase of load into the tension direction led to the shortest crack initiation life and to the fastest crack propagation per cycle. The propagation behaviour of short and long fatigue cracks (which is important, for example, for the damage tolerance design of aeroengine components) could be well represented on the basis of {Delta}J{sub eff}. Based on the experimental results and on observations of the microscopical damage mechanisms life prediction methods for creep-fatigue conditions (Frequency Modification Approach and Strain Range Partitioning (SRP) Method) were evaluated and further developed. This led to predictions within a scatterband of +/-1.5 of the actual life. (orig.) 24 refs.

Kordisch, T.; Nowack, H. [Duisburg Univ. (Gesamthochschule) (Germany). Fachbereich 7 - Maschinenbau

1999-10-01

295

Effects of material and loading variables on fatigue life of carbon and low-alloy steels in LWR environments  

Energy Technology Data Exchange (ETDEWEB)

The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Section III of the Code specifies fatigue design curves for structural materials. While effects of reactor coolant environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A106-Gr B carbon steel and A533-Gr B low-alloy steel in water.

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

1995-03-01

296

Effects of material and loading variables on fatigue life of carbon and low-alloy steels in LWR environments  

International Nuclear Information System (INIS)

[en] The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Section III of the Code specifies fatigue design curves for structural materials. While effects of reactor coolant environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A106-Gr B carbon steel and A533-Gr B low-alloy steel in water

1995-01-01

297

Influence of the height of the external hexagon and surface treatment on fatigue life of commercially pure titanium dental implants.  

UK PubMed Central (United Kingdom)

PURPOSE: This study evaluated the effect of external hexagon height and commonly applied surface treatments on the fatigue life of titanium dental implants. MATERIALS AND METHODS: Electropolished commercially pure titanium dental implants (seven implants per group) with three different external hexagon heights (0.6, 1.2, and 1.8 mm) and implants with the highest external hexagon height (1.8 mm) and different surface treatments (electropolishing, grit blasting with aluminium oxide, and acid etching with sulfuric acid) were tested to evaluate their mechanical fatigue life. To do so, 10-Hz triangular flexural load cycles were applied at 37 degrees C in artificial saliva, and the number of load cycles until implant fracture was determined. Tolerances of the hexagon/abutment fit and implant surface roughness were analyzed by scanning electron microscopy and light interferometry. Transmission electron microscopy and electron diffraction analyses of titanium hydrides were performed. RESULTS: First, the fatigue life of implants with the highest hexagon (8,683 +/- 978 load cycles) was more than double that of the implants with the shortest hexagons (3,654 +/- 789 load cycles) (P < .02). Second, the grit-blasted implants had the longest fatigue life of the tested materials (21,393 +/- 2,356 load cycles), which was significantly greater than that of the other surfaces (P < .001). The compressive surface residual stresses induced when blasting titanium are responsible for this superior mechanical response. Third, precipitation of titanium hydrides in grain boundaries of titanium caused by hydrogen adsorption from the acid solution deteriorates the fatigue life of acid-etched titanium dental implants. These implants had the shortest fatigue life (P < .05). CONCLUSIONS: The fatigue life of threaded root-form dental implants varies with the height of the external hexagon and/or the surface treatment of the implant. An external hexagon height of 1.8 mm and/or a blasting treatment appear to significantly increase fatigue life of dental implants.

Gil FJ; Aparicio C; Manero JM; Padros A

2009-07-01

298

Correlation of Fatigue with Clinical Parameters and Quality of Life in Rheumatoid Arthritis  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: We aimed to investigate fatigue and its relationship with disease activity, radiological findings and quality of life in patients with rheumatoid arthritis (RA).Materials and Methods: 41 patients who were diagnosed as RA according to criteria of ACR and 38 healthy controls were enrolled to this study. Patients were asked to record the severity of rest pain (Visual Analog Scale) and duration of morning stiffness. Fatigue was evaluated by the Multidimensional Assessment of Fatigue (MAF) test. Disease activity and quality of life were assessed respectively with DAS-28 and Short Form-36 (SF-36). Radiologic involvement was evaluated according to modified Larsen’s grading system. Results: The mean age of patient and control groups were 50.9±13.4 years and 50±10.1 years, respectively. Two groups were similar with respect age (p=0.744). The median MAF total score was higher in patients with RA (38.5, min-max: 4-50) than in control subjects (22.5, min-max: 0-42) (p<0.001). There were significant correlations between MAF and DAS-28 scores (r=0.478, p=0.004), rest pain (r=0.491, p=0.001), ACR functional scale (r=0.563, p<0.001) and four dimensions of SF36; physical role (r=-0.504, p=0.014), bodily pain (r=-0.416, p=0.048), vitality (r=-0.522, p=0.011), emotional role (r=-0.523, p=0.011). Conclusion: Fatigue symptom may be quite disabling for patients with rheumatoid arthritis. It is affected by disease activity and pain but not by disease duration and radiologic score. Therefore, it is concluded that fatigue is essentially related with disease activity rather than the chronic inflammatory process in RA.

Yasemin Turan; Zehra Kocaa?a; Hikmet Koçyi?it; Alev Gürgan; Korhan Bar?? Bayram; Serdar ?pek

2010-01-01

299

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

Directory of Open Access Journals (Sweden)

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.

Ghaem Haleh; Haghighi Afshin

2008-01-01

300

Utilization of random process spectral properties for the calculation of fatigue life under combined loading  

Directory of Open Access Journals (Sweden)

Full Text Available The contribution includes the results of experimental works aiming to find a new methodology for the calculation of fatigue life of structures subjected to operational loading from a combination of forces and moments of random character. Considering the fracture mechanics theory, then the damaging of material is both in the micro- and macro-plastic area connected with the rise of plastic deformation and hence with the plastic transformation rate which depends on the amount of supplied energy. The power spectral density (PSD) indicating the power at individual frequencies in the monitored frequency band yields information about the supplied amount of energy. Therefore, it can be assumed that there is a dependence between the PSD shape and the size of damage and that the supplied power which is proportional to the value of dispersion s^2 under the PSD curve could be a new criterion for the calculation of fatigue life under combined loading. The searching for links between the spectral properties of the loading process and the fatigue life of structure under load is dealt with by new Grant GA No. 101/09/0904 of the Czech Technical University in Prague and the Institute of Thermomechanics of the Academy of Sciences of the Czech Republic, v.v.i.

Svoboda J.; Balda M.; Fröhlich V.

2009-01-01

 
 
 
 
301

Vibration-induced fatigue life estimation of ball grid array packaging  

Science.gov (United States)

Vibration loading has become very important in the reliability assessment of modern electronic systems. The objective of this paper is to develop a rapid assessment methodology that can determine the solder joint fatigue life of ball grid array (BGA) and chip scale packages (CSP) under vibration loading. The current challenge is how to execute the vibration fatigue life analysis rapidly and accurately. The approach in this paper will involve global (entire printed wiring board (PWB)) and local (particular component of interest) modeling approaches. In the global model approach, the vibration response of the PWB will be determined. This global model will give us the response of the PWB at specific component locations of interest. This response is then fed into a local stress analysis for accurate assessment of the critical stresses in the solder joints of interest. The stresses are then fed into a fatigue damage model to predict the life. The goal is to retain as much accuracy and physical insight as possible while retaining computation efficiency.

Wu, Mei-Ling

2009-06-01

302

??????????????????????????? Investigation of Fatigue Life of Solder Bumps in a Thermally Enhanced FC-PBGA Assembly  

Directory of Open Access Journals (Sweden)

Full Text Available ??????????ANSYS??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????,????????????????????????????????????????????Von-Mise?????????Coffin-Manson????????????????????????????????????????????????????,??????????????????????????????In this paper, three-dimensional finite element analysis using the commercial ANSYS software is performed to study solder bump fatigue life for a thermally enhanced FC-PBGA (Flip-Chip Plastic Ball Grid Array) assembly subjected to temperature cycling. The thermally enhanced FC-PBGA assembly is a basic FC-PBGA package that is overmolded with molding compound, after which an aluminum heat spreader is adhered to the top of the molding compound and subsequently mounted on a PCB (Printed Circuit Board). In the simulation, all the solder bumps and the solder balls are modeled with nonlinear viscoplastic time and temperature dependent material properties based on Anand’s constitutive equation. Solder bump fatigue life is estimated by the widely accepted modified Coffin-Manson equation. The thermo-mechanical behavior of the solder bumps is presented. Solder bump fatigue life is analyzed by considering various design parameters of the polymer-based materials and the thermal enhancement components.

???; ???; ???; ???

2012-01-01

303

A Probabilistic Approach to Predict Thermal Fatigue Life for Ball Grid Array Solder Joints  

Science.gov (United States)

Numerous studies of the reliability of solder joints have been performed. Most life prediction models are limited to a deterministic approach. However, manufacturing induces uncertainty in the geometry parameters of solder joints, and the environmental temperature varies widely due to end-user diversity, creating uncertainties in the reliability of solder joints. In this study, a methodology for accounting for variation in the lifetime prediction for lead-free solder joints of ball grid array packages (PBGA) is demonstrated. The key aspects of the solder joint parameters and the cyclic temperature range related to reliability are involved. Probabilistic solutions of the inelastic strain range and thermal fatigue life based on the Engelmaier model are developed to determine the probability of solder joint failure. The results indicate that the standard deviation increases significantly when more random variations are involved. Using the probabilistic method, the influence of each variable on the thermal fatigue life is quantified. This information can be used to optimize product design and process validation acceptance criteria. The probabilistic approach creates the opportunity to identify the root causes of failed samples from product fatigue tests and field returns. The method can be applied to better understand how variation affects parameters of interest in an electronic package design with area array interconnections.

Wei, Helin; Wang, Kuisheng

2011-11-01

304

Quality of life, fatigue, and activity in Australians with chronic kidney disease: A longitudinal study.  

UK PubMed Central (United Kingdom)

In this study we investigated the relationship between health-related quality of life, fatigue, and activity levels of people with anemia secondary to chronic kidney disease over a 12 month period following the introduction of an erythropoietin-stimulating agent. Using a longitudinal repeated-measure design, 28 people with chronic kidney disease completed the Short Form-36 Health Survey, Human Activity Profile and Fatigue Severity Scale at the commencement of an erythropoietin-stimulating agent, and then at 3, 6, and 12 months. Over a 12 month period, a significant change was found for health-related quality of life in relation to role-physical, vitality, mental health/emotional well-being, and overall mental health. However, activity levels did not significantly improve during that time. Renal nurses in dialysis units and chronic kidney disease outpatient clinics have repeated and frequent contact with people with chronic kidney disease over long periods of time, and are in an ideal position to routinely assess fatigue and activity levels and to institute timely interventions to optimize health-related quality of life and independent activity.

Bonner A; Caltabiano M; Berlund L

2013-09-01

305

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.

2009-01-01

306

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

Science.gov (United States)

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

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

2013-01-01

307

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

Directory of Open Access Journals (Sweden)

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.

Stroud Nicole M; Minahan Clare L

2009-01-01

308

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-10-10

309

A continuum damage mechanics model on low cycle fatigue life assessment of steam turbine rotor  

Energy Technology Data Exchange (ETDEWEB)

A nonlinear Continuum Damage Mechanics model (CDM) is proposed to assess the low cycle fatigue life of a steam turbine rotor, in which the effects of mean stress are taken into account and the damage is accumulated nonlinearly. The model is applied to a 200 MW steam turbine under cold start and sliding parameter stop. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison results show that the nonlinear CDM model describes the accumulation and development of damage better than the linear accumulation theory. (author)

Jian Ping Jing; Yi Sun [Harbin Inst. of Technology (China). Dept. of Astronautics and Mechanics; Song Bo Xia; Guo Tai Feng [Harbin Inst. of Technology (China). School of Energy Science and Engineering

2001-01-01

310

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

International Nuclear Information System (INIS)

[en] 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

1998-05-19

311

A generalized fitting technique for the LIFE2 fatigue analysis code  

Energy Technology Data Exchange (ETDEWEB)

The analysis of component fatigue lifetime for a wind energy conversion system (WECS) requires that the component load spectrum be formulated in terms of stress cycles. Typically, these stress cycles are obtained from time series data using a cycle identification scheme. As discussed by many authors, the matrix or matrices of cycle counts that describe the stresses on a turbine are constructed from relatively short, representative samples of time series data. The ability to correctly represent the long-term behavior of the distribution of stress cycles from these representative samples is critical to the analysis of service lifetimes. Several techniques are currently used to convert representative samples to the lifetime cyclic loads on the turbine. There has been recently developed a set of fitting algorithms that is particularly useful for matching the body of the distribution of fatigue stress cycles on a turbine component. Fitting techniques are now incorporated into the LIFE2 fatigue/fracture analysis code for wind turbines. In this paper, the authors provide an overview of the fitting algorithms and describe the pre- and post-count algorithms developed to permit their use in the LIFE2 code. Typical case studies are used to illustrate the use of the technique.

Sutherland, H.J. [Sandia National Labs., Albuquerque, NM (United States). Wind Energy Research Dept.; Wilson, T. [Univ. of New Mexico, Albuquerque, NM (United States). New Mexico Engineering Research Inst.

1996-08-01

312

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

Directory of Open Access Journals (Sweden)

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.

A. Marek; G. Junak; J. Okrajni

2009-01-01

313

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)

[en] 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.)[de] Das Ziel der Arbeit ist es, die verschiedenen Einfluesse von Zyklusform und Zyklusdauer auf die Ermuedungsschaedigung und damit auf die zyklische Lebensdauer am Beispiel zweier nicht oder nur wenig aushaertbarer Hochtemperatur-Legierungen vom Typ 800H und 617 nachzuweisen und naeher zu diskutieren. (orig.)

1989-01-01

314

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

DEFF Research Database (Denmark)

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.

Li, M.; Singh, B.N.

2004-01-01

315

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.

1994-01-01

316

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 (more) 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.

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

2013-05-01

317

Further refinement of a methodology for fatigue life estimation in resistance spot weld connections  

Energy Technology Data Exchange (ETDEWEB)

The overall objective of this research is to develop a general model of fatigue crack propagation in resistance spot-welded joints. An important feature of this development is that the model and accompanying methodology should be accessible to designers evaluating fatigue response of structures containing multiple welds. This objective is achieved by examining the stress state around a resistance spot weld. A general expression for the structural stress around the weld is formulated that is dependent only on the loading immediately surrounding the weld; as such, it is specimen independent. In the current work, the methodology developed in Ref 2 for estimating propagation life is extended by explicitly considering the effects of axial loading and of load ratio on life estimates. In addition, issues related to creating an appropriate finite element model are addressed, and a number of modeling guidelines are established. Total life estimations are made and compare favorably with experimentally measured lives of welds in mild steels in a variety of specimen configurations.

Sheppard, S.D. [Stanford Univ., CA (United States)

1996-12-31

318

Ion bombardment effects on the fatigue life of stainless steel under simulated fusion first wall conditions  

International Nuclear Information System (INIS)

Pressurized tube specimens have been exposed to simultaneous multi-energy surface ion bombardment, fast neutron irradiation and stress and temperature cycling, in a simulation of a possible fusion reactor first wall environment. After ion bombardments equivalent to months-years of reactor operation and up to 30,000 cycles, no detrimental effects on post-irradiation fatigue life were found. The ion damage is found to enhance surface cracking, but this effect is limited to the several micron surface layer in which the ions are implanted

1983-01-01

319

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 device works in a power cycle that consists of being switched ON and OFF. To accurately predict the fatigue life cycle of a device, then, the evaluation should take account of this important aspect of the power cycle. To verify the utility of the evaluation method presented in this study, the results for a power cycle based on the combined use of electrical analysis, heat analysis, and stress analysis are compared to the results based on the thermal cycle, as found in the literature. Our conclusion is that the fatigue life cycle as estimated by the thermal cycle test is higher than that estimated by the power cycle.

Kazunori Shinohara; Qiang Yu

2010-01-01

320

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

Science.gov (United States)

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.

Lim, Yee Yan; Kiong Soh, Chee

2011-12-01

 
 
 
 
321

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

International Nuclear Information System (INIS)

[en] 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.

2012-06-30

322

Gender differences in sleep disruption and fatigue on quality of life among persons with ostomies.  

UK PubMed Central (United Kingdom)

STUDY OBJECTIVES: The aim of this study is to examine differences in sleep disruption and fatigue of men and women colorectal cancer (CRC) survivors with intestinal ostomies and associated health-related quality of life (HR-QOL). METHODS: Participants in this cross-sectional study of long-term (> 5 years) CRC survivors received care at Kaiser Permanente. Measures included the City of Hope QOL Ostomy questionnaire with narrative comments for ostomy-related "greatest challenges." The Short Form-36 Version 2 (SF-36v2) health survey provided physical (PCS) and mental composite scale (MCS) scores to examine generic HR-QOL. The "sleep disruption" and "fatigue" items from the ostomy questionnaire (scale from 0 to 10 with higher scores indicating better HR-QOL) were dependent variables, while independent variables included age, ethnicity, education, partnered status, body mass index, and time since surgery. Data were analyzed using chi-square for nominal variables, Student t-tests for continuous variables, and logistic regression with significance set at p < 0.05. RESULTS: On the ostomy-specific measure, women (n = 118) compared to men (n = 168) reported more sleep disruption (p < 0.01), adjusted for age, and greater levels of fatigue (p < 0.01), adjusted for time since surgery. Women's PCS and MCS scores indicated poorer HR-QOL compared to men, and differences were clinically meaningful. Qualitative narrative comments suggested that sleep disruption could stem from ostomy-associated fear of or actual leakage during sleep. CONCLUSION: Although women CRC survivors with ostomies report more sleep disruption and fatigue, which is reflected in their reduced physical and mental health scores on the SF-36v2 compared to men with ostomies, their stated reasons for disrupted sleep are similar to their male counterparts. These findings can provide a foundation for gender-relevant ostomy interventions to improve sleep and HR-QOL in this patient population.

Baldwin CM; Grant M; Wendel C; Hornbrook MC; Herrinton LJ; McMullen C; Krouse RS

2009-08-01

323

Fatigue behavior of reactor pressure vessel steels  

Energy Technology Data Exchange (ETDEWEB)

High-cycle fatigue tests have been conducted on reactor pressure vessel steels, SA533-B1, with four levels of sulfur contents at room temperature. The applied stress versus fatigue life cycle (S-N) curves were developed at load ratios, R, of 0.2 and 0.8. At a load ratio of 0.2, the fatigue limit for SA533-B1 steels with sulfur contents less than 0.015 wt % is around 650 MPa, which is slightly higher than that with sulfur contents higher than 0.027 wt %. At a load ratio of 0.8, there were no fatigue indications on the fracture surface. In some fatigue-tested specimens, specifically those with higher sulfur content levels, fatigue cracks were observed to initiate around the inclusions. A digital video camera was used to record the entire fatigue process, and the results demonstrated that the crack initiation period dominated more than 80% of the total fatigue life. The fatigue-tested specimen surface had been thoroughly examined using optical and scanning electron microscopy. Apparent distinctions were observed between the neighborhood of the crack initiation site and the rest of the specimen surface. A great number of precipitates were found distributed along the sub-grain boundary using transmission electron microscopy. There is no or little change of the morphology of precipitates before and after fatigue tests. The mis-orientation between two neighboring sub-grains ranges from 1 to 5{degree}. The effects of the applied maximum stress, precipitate distribution, and fatigue cycle on the mis-orientation of the sub-grain boundary will be discussed in this paper.

Huang, J.Y.; Chen, C.Y.; Chien, K.F.; Kuo, R.C.; Liaw, P.K.; Huang, J.G.

1999-07-01

324

Prediction of fatigue life of high-heat-load components made of oxygen-free copper by comparing with Glidcop.  

Science.gov (United States)

Following a successful study on the prediction of fatigue life of high-heat-load components made of Glidcop, the thermal limitation of oxygen-free copper (OFC), which is used more commonly than Glidcop, has been studied. In addition to its general mechanical properties, the low-cycle-fatigue (LCF) and creep properties of OFC were investigated in detail and compared with those of Glidcop. The breaking mode of OFC, which was observed to be completely different from that of Glidcop in a fatigue fracture experiment, clarified the importance of considering the creep-fatigue interaction. An additional LCF test with compressive strain holding was conducted so that the creep-fatigue life diagram for out-of-phase thermal fatigue could be obtained on the basis of the strain-range partitioning method. The life predicted from elasto-plastic creep analysis agreed well with that determined from the void ratio estimated in the fatigue fracture experiment. PMID:23254657

Takahashi, Sunao; Sano, Mutsumi; Watanabe, Atsuo; Kitamura, Hideo

2012-11-10

325

Prediction of fatigue life of high-heat-load components made of oxygen-free copper by comparing with Glidcop.  

UK PubMed Central (United Kingdom)

Following a successful study on the prediction of fatigue life of high-heat-load components made of Glidcop, the thermal limitation of oxygen-free copper (OFC), which is used more commonly than Glidcop, has been studied. In addition to its general mechanical properties, the low-cycle-fatigue (LCF) and creep properties of OFC were investigated in detail and compared with those of Glidcop. The breaking mode of OFC, which was observed to be completely different from that of Glidcop in a fatigue fracture experiment, clarified the importance of considering the creep-fatigue interaction. An additional LCF test with compressive strain holding was conducted so that the creep-fatigue life diagram for out-of-phase thermal fatigue could be obtained on the basis of the strain-range partitioning method. The life predicted from elasto-plastic creep analysis agreed well with that determined from the void ratio estimated in the fatigue fracture experiment.

Takahashi S; Sano M; Watanabe A; Kitamura H

2013-01-01

326

Thermal fatigue life prediction. Verification of Coffin-Mansons's law in the phase transformation range of ferrite matrix ductile cast iron  

Energy Technology Data Exchange (ETDEWEB)

For clarifying the behavior of thermal fatigue and verifying the role of Coffin-Manson's law in thermal fatigue, out-of-phase type thermal fatigue tests were carried out on ferritic ductile cast iron. As a result of the tests, the dependence of thermal fatigue life and the plastic strain produced in each cycle on cyclic peak temperature and the dependence of thermal fatigue life on cyclic plastic strain were made clear. Particularly, the exponent and the coefficient in the latter relationship, i.e. Coffin-Manson's law, are kept constant over all ranges, including the phase transformation range. And it shows that the thermal fatigue life can be predicted by the tensile the properties of specimens at room temperature. By the way, the microstructure and the fracture surface of failed specimens were observed and the mechanism of thermal fatigue is discussed here. (orig.)

Hayashi Morihito

2004-07-01

327

The impact of fatigue and psychosocial variables on quality of life for patients with motor neuron disease.  

UK PubMed Central (United Kingdom)

Our objective was to evaluate the direct and indirect relationships between psychosocial variables, fatigue and quality of life for patients with motor neuron disease (MND). A cross-sectional sample of 147 MND patients was recruited from five neurological care centres in England. Variables included anxiety, coping, depression, fatigue, functional status, social withdrawal and quality of life. Direct and indirect relationships between study variables were assessed using structural equation modelling (SEM), using linear values derived from Rasch analyses of study questionnaires. Following some modification, Rasch analysis confirmed the suitability of all measures for use in this population. The final SEM model consisting of anxiety, coping, depression, fatigue, social withdrawal and quality of life showed excellent fit to the data. The model accounted for 59% of the variance in quality of life and 50% of the variance in depression. In conclusion, our data support a model that explains a large degree of the variance in quality of life for MND patients. Coping was most strongly related to quality of life, with the largest proportion of its influence mediated by anxiety and depression. Significant direct effects upon quality of life were exhibited by depression, fatigue and social withdrawal.

Gibbons C; Thornton E; Ealing J; Shaw P; Talbot K; Tennant A; Young C

2013-05-01

328

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

DEFF Research Database (Denmark)

Occurrence of voltage sags due to electrical grid faults and other network disturbances generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system and may also have a detrimental effect on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries (Spain and Germany) with high wind energy penetration it is mandatory or under bonus to retrofit these fixed speed wind turbines and provide ride through capability. An electro-mechanical model is built to simulate the grid disturbances that easily excite the asynchronous generators poorly damped by the stator flux oscillations which cause high transients of the generator electromagnetic torque. This paper focuses in estimating the resulting significant stresses transients due to the electromagnetic torque transients, which transmits to the wind turbine mechanical system that may have a detrimental effect on the fatigue life of drivetrain components. The capability to simulate these phenomena is a novel aspect in the present effort.

Veluri, Badrinath; Santos-Martin, David

2011-01-01

329

Fatigue life of pipelines with dents and gouges subjected to cyclic internal pressure  

Energy Technology Data Exchange (ETDEWEB)

Research has been conducted to study the effects of dents, gouges, and weld seams on pipelines under cyclic internal pressure loading. The work has involved pipes experimentally with D/t ratios from 18 to 94 and theoretically via finite element analysis with D/t ratios from 18 to 100. According to both the experimental and theoretical work, plain smooth dents whose diameter is less than 5% of the pipe diameter should not be a problem, assuming that the cyclic pressure loading is not extreme. The experimental work indicated that gouge depth was an important factor in reducing the pipeline fatigue life; however, grinding was found to be a suitable form of repair for this defect. Categorizing gouges based on depth to wall thickness (d/t) was proven to be an effective means of classification. An analytical method was developed to predict the fatigue life of pipes subjected to cyclic internal pressure. The values are then compared to the experimentally obtained values.

Fowler, J.R.; Alexander, C.R.; Kovach, P.J.; Connelly, L.M. [Stress Engineering Services, Inc., Houston, TX (United States)

1995-12-31

330

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

Directory of Open Access Journals (Sweden)

Full Text Available Occurrence of voltage sags due to electrical grid faults and other network disturbances generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system and may also have a detrimental effect on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries (Spain and Germany) with high wind energy penetration it is mandatory or under bonus to retrofit these fixed speed wind turbines and provide ride through capability. An electro-mechanical model is built to simulate the grid disturbances that easily excite the asynchronous generators poorly damped by the stator flux oscillations which cause high transients of the generator electromagnetic torque. This paper focuses in estimating the resulting significant stresses transients due to the electromagnetic torque transients, which transmits to the wind turbine mechanical system that may have a detrimental effect on the fatigue life of drivetrain components. The capability to simulate these phenomena is a novel aspect in the present effort.

Badrinath Veluri; David Santos Martin; Henrik Myhre Jensen

2011-01-01

331

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

Science.gov (United States)

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).

Jin, J. F.; Xiao, W. L.; Chen, H. B.

2010-05-01

332

Fatigue Life Assessment of Structures Using Electro-Mechanical Impedance Technique  

International Nuclear Information System (INIS)

This paper describes a new experimental approach for fatigue life assessment of structures based on the equivalent stiffness determined by surface bonded piezo-impedance transducers through the electro-mechanical impedance (EMI) technique. The remaining life of the component (in terms of the cycles of loading that can be sustained) is non-dimensionally correlated with the equivalent identified stiffness. The proposed approach circumvents the determination of the absolute stiffness of the joint and employs the admittance signature of the surface-bonded piezo-transducers directly. The second part of the paper briefly describes the recent advances made in the field of impedance based structural health monitoring (SHM) in terms of low-cost hardware system and improved damage diagnosis through the integration of global dynamic and EMI techniques using the same set of piezo-sensors. Other recent applications such as bio-sensors and traffic sensors pioneered at the Smart Structures and Dynamics Laboratory (SSDL) are also briefly covered.

2012-05-28

333

Fatigue of metallic microdevices and the role of fatigue-induced surface oxides  

International Nuclear Information System (INIS)

A new method for fatigue testing of metallic micro-electro-mechanical systems has been developed and applied to characterize the high-cycle fatigue behavior of nickel microspecimens formed by the LIGA process. Cantilever microbeams with a cross-section of 26 x 250 ?m were tested under fully reversed loading conditions at 20 Hz. The observed stress-life curve and fatigue limit was similar to what has typically been reported for conventional bulk nickel. SEM inspection of the fatigue surface revealed that failure initiated in zones of localized extrusions and intrusions associated with persistent slip bands (PSBs). Focused ion beam machining was used to extract a cross-sectional TEM foil from the deformation zone, revealing an unexpected thick (up to 400 nm) oxide on the surface of the PSBs. This PSB oxide thickening mechanism appears to be the source of crack initiation.

2004-04-05

334

Statistical analysis of bending fatigue life data using Weibull distribution in glass-fiber reinforced polyester composites  

International Nuclear Information System (INIS)

[en] The bending fatigue behaviors were investigated in glass fiber-reinforced polyester composite plates, made from woven-roving with four different weights, 800, 500, 300, and 200 g/m2, random distributed glass-mat with two different weights 225, and 450 g/m2 and polyester resin. The plates which have fiber volume ratio Vf ? 44% and obtained by using resin transfer moulding (RTM) method were cut down in directions of [0/90 deg.] and [±45 deg.]. Thus, eight different fiber-glass structures were obtained. These samples were tested in a computer aided fatigue apparatus which have fixed stress control and fatigue stress ratio [R = -1]. Two-parameter Weibull distribution function was used to analysis statistically the fatigue life results of composite samples. Weibull graphics were plotted for each sample using fatigue data. Then, S-N curves were drawn for different reliability levels (R = 0.99, R = 0.50, R = 0.368, R = 0.10) using these data. These S-N curves were introduced for the identification of the first failure time as reliability and safety limits for the benefit of designers. The probabilities of survival graphics were obtained for several stress and fatigue life levels. Besides, it was occurred that RTM conditions like fiber direction, resin permeability and full infiltration of fibers are very important when composites (GFRP) have been used for along time under dynamic loads by looking at test results in this study

2008-01-01

335

Comparison of fatigue life prediction based on local strains and nominal stresses respectively  

International Nuclear Information System (INIS)

Fatigue life predictions based on local strains and nominal stresses respectively have been performed for notched cylindrical bending test specimens (Ksub(t)=1.4, 2.2, 3.3) made of steel 42 Cr Mo 4, Ck 45 and 49 Mn CS 3 under random loading. The results of calculation are compared with relevant test results. The accuracy of the life prediction based on local strains increases the more informations of the notched specimen (e. g. endurance limit, S-N-curve etc.) will be taken into consideration for the life calculation. In the main the accuracy of life prediction based on nominal stresses is dependent on the slope of the S-N-curve assumed to be valid below the endurance limit. By application of relative Miner's rule life prediction can be improved if relevant test results are available. The comparison of the two prediction methods investigated reveals no favour for one of them. Hence, the decision which method should be applied depends on the special problems to be solved. (orig.)

1983-01-01

336

Quantitative description of the fatigue life with the four-parameter Weibull distribution. Ermuedungslebensdauer mit der vierparametrigen Weibullverteilung quantitativ beschreiben  

Energy Technology Data Exchange (ETDEWEB)

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.)

Tittes, E.

1993-07-01

337

An effective continuum damage mechanics model for creep-fatigue life assessment of a steam turbine rotor  

International Nuclear Information System (INIS)

A nonlinear Continuum Damage Mechanics model is proposed to assess the creep-fatigue life of a steam turbine rotor, in which the effects of complex multiaxial stress and the coupling of fatigue and creep are taken into account. The nonlinear evolution of damage is also considered. The model is applied to a 600 MW steam turbine under a practical start-stop operation. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison show that the nonlinear continuum damage mechanics model describes the accumulation and development of damage better than the linear accumulation theory.

2003-01-01

338

An effective continuum damage mechanics model for creep-fatigue life assessment of a steam turbine rotor  

Energy Technology Data Exchange (ETDEWEB)

A nonlinear Continuum Damage Mechanics model is proposed to assess the creep-fatigue life of a steam turbine rotor, in which the effects of complex multiaxial stress and the coupling of fatigue and creep are taken into account. The nonlinear evolution of damage is also considered. The model is applied to a 600 MW steam turbine under a practical start-stop operation. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison show that the nonlinear continuum damage mechanics model describes the accumulation and development of damage better than the linear accumulation theory.

JianPing, Jing; Guang, Meng; Yi, Sun; SongBo, Xia

2003-06-01

339

An effective continuum damage mechanics model for creep-fatigue life assessment of a steam turbine rotor  

Energy Technology Data Exchange (ETDEWEB)

A nonlinear Continuum Damage Mechanics model is proposed to assess the creep-fatigue life of a steam turbine rotor, in which the effects of complex multiaxial stress and the coupling of fatigue and creep are taken into account. The nonlinear evolution of damage is also considered. The model is applied to a 600 MW steam turbine under a practical start-stop operation. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison show that the nonlinear continuum damage mechanics model describes the accumulation and development of damage better than the linear accumulation theory. (Author)

Jing Jianping; Meng Guang [Shanghai JiaoTong Univ., State Key Lab. of Vibration, Shock and Noise, Shanghai (China); Sun Yi; Xia Songbo [Harbin Inst. of Technology, School of Energy Science and Engineering, Harbin (China)

2003-06-01

340

Evaluation of effects of LWR coolant environments on fatigue life of carbon and low-alloy steels  

Energy Technology Data Exchange (ETDEWEB)

The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figure I-90 of Appendix I to Section III of the Code specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Recent test data indicate a significant decrease in fatigue life of carbon and low-alloy steels in LWR environments when five conditions are satisfied simultaneously, viz., applied strain range, temperature, dissolved oxygen in the water, and sulfur content of the steel are above a minimum threshold level, and the loading strain rate is below a threshold value. Only a moderate decrease in fatigue life is observed when any one of these conditions is not satisfied. This paper summarizes available data on the effects of various material and loading variables such as steel type, dissolved oxygen level, strain range, strain rate, and sulfur content on the fatigue life of carbon and low-alloy steels. The data have been analyzed to define the threshold values of the five critical parameters. Methods for estimating fatigue lives under actual loading histories are discussed.

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

1996-02-01

 
 
 
 
341

Evaluation of effects of LWR coolant environments on fatigue life of carbon and low-alloy steels  

International Nuclear Information System (INIS)

[en] The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figure I-90 of Appendix I to Section III of the Code specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Recent test data indicate a significant decrease in fatigue life of carbon and low-alloy steels in LWR environments when five conditions are satisfied simultaneously, viz., applied strain range, temperature, dissolved oxygen in the water, and sulfur content of the steel are above a minimum threshold level, and the loading strain rate is below a threshold value. Only a moderate decrease in fatigue life is observed when any one of these conditions is not satisfied. This paper summarizes available data on the effects of various material and loading variables such as steel type, dissolved oxygen level, strain range, strain rate, and sulfur content on the fatigue life of carbon and low-alloy steels. The data have been analyzed to define the threshold values of the five critical parameters. Methods for estimating fatigue lives under actual loading histories are discussed

1996-01-01

342

Method for fatigue life evaluation of solder for electronic equipments. Denshikikiyo handa zairyo no hiro jumyo hyokaho  

Energy Technology Data Exchange (ETDEWEB)

In this paper, concerning the raw material for solder (60Sn-40Pb), in order to obtain the effect of repetition rate under a uniform shearing stress, a torsion fatigue test has been conducted using thin-walled cylindrical specimens and based upon its result, an evaluation method of fatigue life has been studied. Part of the obtained result is as follows; when the repetition number becomes about 10% of the fatigue life N [sub f] (the repetition number at the time when the range of the shearing stress is lowered by about 20% at 0.5N [sub f]), skidding has been observed in a lattice form with the interval of several-20 [mu] m on the surface of the specimen. In general, as the repetition rate becomes smaller, the life becomes shorter, but contrary to the above, in the high strain region at which the range of inelastic strain surpasses about 1.4%, the life becomes longer. It is considered that this is due to the creep effect. Between the plastic strain range, which was obtained by separating from the inelastic strain range by the strain range partitioning using the half cycle quick deformation insection method, and the fatigue life, the Coffin-Manson rule has been established for each repetition rate. 11 refs., 17 figs., 4 tabs.

Taneda, M.; Kaminishi, K. (Yamaguchi Univ., Yamaguchi (Japan). Faculty of Engineering); Oku, Y. (Ube Industries Ltd., Yamaguchi (Japan))

1992-07-15

343

Health-related quality of life and fatigue in patients with adrenal incidentaloma.  

UK PubMed Central (United Kingdom)

The objective of the present study was to examine several dimensions of quality of life (QoL) and fatigue in patients with adrenal incidentaloma. This was a case-control study designed to analyze patient outcomes using three validated generic QoL questionnaires, EQ-5D, SF-36, and MFI-20, the results of which were compared to those obtained for age- and sex-matched controls. The study population comprised 139 consecutive patients with nonfunctioning adrenal masses (104 females, 35 males; age 59.1 ± 10.8) and 139 age- and sex-matched controls. Reduced QoL was found in patients with adrenal incidentaloma as compared to controls. Dimensions of QoL that were notably affected included mobility (P = 0.03), performance of usual activities (P = 0.002), and anxiety/depression (P = 0.04) as evaluated using the EQ-5D; physical functioning (P < 0.001), physical role (P < 0.001), general health (P < 0.001), vitality (P = 0.001), social functioning (P = 0.001), and emotional role (P < 0.001) as evaluated using the SF-36; and physical fatigue (P = 0.04) as assessed using the MFI-20 questionnaire. In addition, perceived health on a visual analogue scale was also significantly lower in patients than in controls (64.8 ± 19.2 vs. 77.1 ± 15.1; P < 0.001). Patients with adrenal incidentaloma reported reduced QoL and a higher level of physical fatigue compared to age- and sex-matched controls. This subject will benefit from further studies comparing QoL outcomes of laparoscopic adrenalectomy versus no treatment in patients with adrenal incidentaloma.

Kastelan D; Dzubur F; Dusek T; Poljicanin T; Crncevic-Orlic Z; Kraljevic I; Solak M; Bencevic T; Aganovic I; Knezevic N; Kastelan Z; Korsic M

2011-08-01

344

The effects of group exercise on fatigue and quality of life during cancer treatment.  

UK PubMed Central (United Kingdom)

PURPOSE/OBJECTIVES: To determine the feasibility of participating in a structured group exercise program (SGEP) for adult patients receiving cancer treatment and to test the impact of an SGEP on reducing cancer-related fatigue (CRF) and improving quality of life (QOL). DESIGN: One-group, prospective, pre- and post-test design. SETTING: Two community outpatient infusion centers. SAMPLE: Convenience sample of 12 adults with varying cancer diagnoses receiving cancer treatment. METHODS: Nine of 12 subjects participated in SGEP twice weekly for six weeks. Exercises focused on strengthening proximal muscle groups and improving functional ability. All subjects completed the Fatigue Symptom Inventory and the Short Form-36 version 2 (SF-36v2) Health Survey at baseline and six weeks. MAIN RESEARCH VARIABLES: Feasibility of the intervention, CRF, and QOL. FINDINGS: No difference in reported fatigue was found. The SF-36v2 subscale score for bodily pain showed a significant decrease in this symptom. Subscale scores for physical role, vitality, and social function increased but did not yield statistical significance. Social interactions resulted in strong group cohesiveness. A postprogram questionnaire identified themes of support, learning from shared information, and the usefulness of having an exercise program that also serves as an informal support group. CONCLUSIONS: SGEP is feasible, safe, and well tolerated by adult patients with cancer and may have positive effects on CRF and QOL. IMPLICATIONS FOR NURSING: The benefits of exercise for patients with cancer receiving treatment are well documented. Using a multidisciplinary approach, oncology nurses, working with an exercise physiologist, can safely create an SGEP, combining the power of group interactions with the appeal of a wellness-promoting behavior, and provide an additional tool to assist in the management of physiologic and psychosocial effects of cancer treatment.

Losito J; Murphy S; Thomas M

2006-07-01

345

Effect of nanocomposite coating with different concentrations on the fatigue life of stainless steel316 with different surface roughness  

Energy Technology Data Exchange (ETDEWEB)

Many experimental researches succeeded to improve fatigue properties of materials by treating their surfaces. In this study, the benefits of nanocomposite material are used to investigate the fatigue life of stainless steel specimens with different surface roughness. Nanocomposite coating was prepared with different concentrations (0.3 %, 0.5 %, and 0.7 %) of multi wall carbon nano tubes MWCNT. This coating was applied on stainless steel test specimens with four different values of the surface roughness (0.3, 0.8, 1.6, and 2.5). It turned out that fatigue life increased more than four times compared to the original material when using 0.5 % and 0.7 % MWCNT concentration in coating composition with the 0.3 surface roughness, while no significant difference was detected at another roughness. (orig.)

Hedia, Hassan S.; Aldousari, S.M.; Abdellatif, Ahmed K. [King Abdulaziz Univ., Jeddah (Saudi Arabia). Faculty of Engineering; Gadhi, Raed Hasan M. [King Abdulaziz Univ., Jeddah (Saudi Arabia). Faculty of Engineering; Saudi Electricity Company, Jeddah (Saudi Arabia). GTS Dept.

2012-07-01

346

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

CERN Multimedia

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.

American Society for Testing and Materials. Philadelphia

2010-01-01

347

Health-related quality of life and fatigue in patients with adrenal incidentaloma.  

Science.gov (United States)

The objective of the present study was to examine several dimensions of quality of life (QoL) and fatigue in patients with adrenal incidentaloma. This was a case-control study designed to analyze patient outcomes using three validated generic QoL questionnaires, EQ-5D, SF-36, and MFI-20, the results of which were compared to those obtained for age- and sex-matched controls. The study population comprised 139 consecutive patients with nonfunctioning adrenal masses (104 females, 35 males; age 59.1 ± 10.8) and 139 age- and sex-matched controls. Reduced QoL was found in patients with adrenal incidentaloma as compared to controls. Dimensions of QoL that were notably affected included mobility (P = 0.03), performance of usual activities (P = 0.002), and anxiety/depression (P = 0.04) as evaluated using the EQ-5D; physical functioning (P adrenal incidentaloma reported reduced QoL and a higher level of physical fatigue compared to age- and sex-matched controls. This subject will benefit from further studies comparing QoL outcomes of laparoscopic adrenalectomy versus no treatment in patients with adrenal incidentaloma. PMID:21442381

Kastelan, Darko; Dzubur, Fedja; Dusek, Tina; Poljicanin, Tamara; Crncevic-Orlic, Zeljka; Kraljevic, Ivana; Solak, Mirsala; Bencevic, Tanja; Aganovic, Izet; Knezevic, Nikola; Kastelan, Zeljko; Korsic, Mirko

2011-03-26

348

Fatigue life calculation of desuperheater for solving pipe cracking issue using finite element method (FEM) software  

Science.gov (United States)

Desuperheater assembly experiences thermal cycling in operation by design. During power plant's start up, load change and shut down, thermal gradient is highest. Desuperheater should be able to handle rapid ramp up or ramp down of temperature in these operations. With "hump style" two nozzle desuperheater, cracks were appearing in the pipe after only few cycles of operation. From the field data, it was clear that desuperheater is not able to handle disproportionate thermal expansion happening in the assembly during temperature ramp up and ramp down in operation and leading to cracks appearing in the piping. Growth of thermal fatigue crack is influenced by several factors including geometry, severity of thermal stress and applied mechanical load. This paper seeks to determine cause of failure of two nozzle "hump style" desuperheater using Finite Element Method (FEM) simulation technique. Thermal stress simulation and fatigue life calculation were performed using commercial FEA software "ANSYS" [from Ansys Inc, USA]. Simulation result showed that very high thermal stress is developing in the region where cracks are seen in the field. From simulation results, it is also clear that variable thermal expansion of two nozzle studs is creating high stress at the water manifold junction. A simple and viable solution is suggested by increasing the length of the manifold which solved the cracking issues in the pipe.

Kumar, Aravinda; Singh, Jeetendra Kumar; Mohan, K.

2012-06-01

349

Fatigue life prediction for finite ratchetting of bellows at cryogenic temperatures  

International Nuclear Information System (INIS)

The expansion bellows, used in the magnet interconnections of the Large Hadron Collider (LHC), are designed for severe service conditions (cryogenic temperatures, high internal pressure, large cyclic deflections). According to the results of the material research, a stainless steel of grade AISI 316 exhibits a high ductility at cryogenic temperatures. This results in the development of the plastic strain fields in the bellows wall, subjected to cyclic loadings, and to failure after a comparatively low number of cycles. In the present work the progressive deformation (ratchetting) of bellows subjected to a sustained load (internal pressure) and to a superimposed cyclic deflection programme at cryogenic temperatures is examined. In order to estimate the number of cycles to failure a generalized Manson-Coffin equation was developed. The model is based on two parameters: the ratchetting induced mean plastic strain and the plastic strain amplitude. The material model is based on the bilinear elastic-plastic response with kinematic hardening. The cyclic hardening and the evolution of the material model parameters (yield strength and hardening modulus) are accounted for. The finite element simulation of the initial 20 cycles leads to an estimation of the accumulated plastic strains and enables the calculation of the fatigue life of the bellows. An experimental stand for cryogenic fatigue tests is also presented and the first verification tests are reported.

1997-01-01

350

Artificial neural networks and the effects of loading conditions on fatigue life of carbon and low-alloy steels  

Energy Technology Data Exchange (ETDEWEB)

The ASME Boiler and Pressure Vessel Code contains rules for the construction of nuclear power plant components. Figure 1-90 of Appendix I to Section III of the Code specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Recent test data indicate significant decreases in the fatigue lives of carbon and low-alloy steels in LWR environments when five conditions are satisfied simultaneously. When applied strain range, temperature, dissolved oxygen in the water, and sulfur content of the steel are above a minimum threshold level, and the loading strain rate is below a threshold value, environmentally assisted fatigue occurs. For this study, a data base of 1036 fatigue tests was used to train an artificial neural network (ANN). Once the optimal ANN was designed, ANN were trained and used to predict fatigue life for specified sets of loading and environmental conditions. By finding patterns and trends in the data, the ANN can find the fatigue lifetime for any set of conditions. Artificial neural networks show great potential for predicting environmentally assisted corrosion. Their main benefits are that the fit of the data is based purely on data and not on preconceptions and that the network can interpolate effects by learning trends and patterns when data are not available.

Pleune, T.T. [Argonne National Lab., IL (United States)]|[Massachusetts Institute of Technology, Cambridge, MA (United States). Nuclear Engineering Dept.; Chopra, O.K. [Argonne National Lab., IL (United States)

1996-11-01

351

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

UK PubMed Central (United Kingdom)

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

Kim YH; Kim HJ; Ahn SD; Seo YJ; Kim SH

2013-08-01

352

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

CERN Multimedia

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

American Society for Testing and Materials. Philadelphia

2003-01-01

353

Estimation of fatigue life of third dimensional piping system deteriorated with age  

International Nuclear Information System (INIS)

The vibration test of locally thinned three-dimensional (3D) piping system was carried out. The dynamic analysis reproduced the deformation of piping system and the static analysis reproduced the elliptic deformation and ratchet deformation using the above results. The damaged parts by the low-cycle fatigue life estimation were agreed with the experimental results. The seismic loading until fracture of piping was able to be estimated. The tests, dynamic and static analyses, and comparison between the results of experiments and analyses are reported. The elastic-plastic analysis of 3D piping system, stress-strain curve, and the effects of eigenfrequency, attenuation and yield stress on the response are reported. (S.Y.)

2006-01-01

354

The life estimation of turbine rotor through fracture mechanics and fatigue analysis  

International Nuclear Information System (INIS)

[en] Stress analysis for High Pressure Turbine Rotor of Korea Nuclear Power Unit 9/10 was carried out by finite element method. And, using the greatest value of stress output, the maximum allowable non-metallic inclusion size and the operating cycle limit at bore surface were calculated through linear elastic fracture mechnics and low cycle fatigue theory respectively; the inclusion smaller than 14.3mm in length was safe from brittle fracture regardless of its existing position and crack initiating life was 3886 cycles under the most severe starting condition. FEM program TDROTOR(Temperature Distribution of was developed to calculate temperature distribution of Rotor by heat transfer from hot steam, and centrifugal, thermal and total stress components were calculated by SAROTOR(Stress Analysis of ROTOR). Both FEM codes used axi-symmetric, quadrilateral element, and plasticity was not considered. (Author)

1987-01-01

355

User`s guide for the frequency domain algorithms in the LIFE2 fatigue analysis code  

Energy Technology Data Exchange (ETDEWEB)

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.

Sutherland, H.J. [Sandia National Labs., Albuquerque, NM (United States); Linker, R.L. [New Mexico Engineering Research Inst., Albuquerque, NM (United States)

1993-10-01

356

Fatigue, depression, and health-related quality of life in patients with multiple sclerosis in Isfahan, Iran.  

UK PubMed Central (United Kingdom)

BACKGROUND AND PURPOSE: Quality of life (QoL) of patients with multiple sclerosis (MS) is worse than that of other chronic diseases. There is a need to examine the impact of fatigue and depression on the QoL independent of level of physical disability in MS. The aim of this study is to explore physical, psychological, and social aspects of health-related QoL (HRQoL) of MS patients in association with physical disability, fatigue, and depression. METHODS: In a cross-sectional study, 281 (63.4% women, 36.6% men) patients with MS participated in the study. The HRQoL was assessed by the Persian version of the multiple sclerosis quality of life (MSQoL-54) questionnaires. Other covariates included in the study were disease type, physical disability, fatigue, disease impact, and depression. RESULTS: In univariate analysis disease type, physical disability, fatigue, disease impact, and depression were significantly associated with both physical and mental health composite summaries of MSQoL-54. In multivariate regression analysis, patients' physical disability remained significantly associated with both components of MSQoL-54, whilst fatigue and depression were associated with physical and mental composite summaries, respectively. CONCLUSIONS: Our findings suggest that MS-related physical disability, fatigue, and depression affect the HRQoL of MS patients, independently of each other and other potential confounding factors. Effective interventions that target fatigue and depression may help improve the QoL of patients, regardless of their disease type and level of disability.

Kargarfard M; Eetemadifar M; Mehrabi M; Maghzi AH; Hayatbakhsh MR

2012-03-01

357

Thermal fatigue of NPP components: potential multiaxial, environmental and small cycle effects  

International Nuclear Information System (INIS)

[en] Current fatigue design curves for NPP components are based largely on strain controlled tests of small specimens tested in air at room temperature. Reduction factors of 2 for strain or 20 for fatigue life are applied to the mean data and are intended to account for material, environment, surface finish and loading uncertainties. Pipe failures in recent years have been attributed to high cycle thermomechanical fatigue and have prompted re-evaluation of the fatigue design curves. Research has focused especially on environmental effects and load sources. Some data also suggests that multiaxial loading and small stress cycles as part of a spectrum may cause significantly more fatigue damage than what is predicted. This paper examines some of these potential sources of fatigue damage. (orig.)

2001-01-01

358

Creep-fatigue life analysis of fuel-cell reformer tube by finite element method  

Energy Technology Data Exchange (ETDEWEB)

The stress-strain behavior of a reformer tube was analyzed using a finite element method to study a typical fuel cell reformer. Also, the strain-range partitioning method was applied to the above results to estimate the life of tubes made of two materials HP-BST-M and low-C-HP-Nb. The findings are as follows: (1) In the specimen reformer tube, the plastic strain is very low, and most inelastic strain is creep strain. (2) When the creep constitutive equation is varied, the resulting total strain range remains almost unchanged. (3) HP-BST-M has a higher creep strength than low-C-HP-Nb, so has a lower inelastic strain range and a lower ratchet strain. In addition, HP-BST-M has good creep-fatigue characteristics and has a high creep-rupture strength; therefore, the life estimated by the strain range partitioning method is considerably long. It is expected that the life of HP-BST-M is two to three times longer than 25Cr-20Ni HK40. 3 refs., 10 figs., 3 tabs.

Yokomaku, Toshinori; Saori, Mitsuru; Nohara, Akira (Kobe Steel Ltd. (Japan))

1989-02-15

359

Self-regulatory fatigue in hematologic malignancies: impact on quality of life, coping, and adherence to medical recommendations.  

UK PubMed Central (United Kingdom)

BACKGROUND: Hematopoietic stem cell transplantation (HSCT) is an intensive cancer therapy entailing numerous physical, emotional, cognitive, and practical challenges. Patients' ability to adjust and cope with such challenges may depend on their ability to exert control over cognitive, emotional, and behavioral processes, that is, ability to self-regulate. Self-regulatory capacity is a limited resource that can be depleted or fatigued (i.e., "self-regulatory fatigue"), particularly in the context of stressful life events such as cancer diagnosis and treatment. PURPOSE: This is one of the first studies to examine self-regulatory fatigue in a cancer population. The current study aimed to (1) extract items for a specific scale of self-regulatory capacity and (2) examine the impact of such capacity on adaptation in patients with hematologic malignancies preparing for HSCT. METHODS: Factor analysis of four existing scales gauging psychological adjustment and well-being in 314 patients preparing for HSCT (63% male and 89% Caucasian) identified 23 items (??=?0.85) related to self-regulatory control or fatigue. This measure was then examined using existing clinical data obtained from 178 patients (57% male and 91% Caucasian) undergoing treatment for hematologic malignancies in relationship to quality of life, coping, and self-reported adherence to physicians' recommendations. RESULTS: Controlling for pain severity, physical fatigue, and depression, self-regulatory fatigue scores were incrementally associated with decreased quality of life, use of avoidance coping strategies, and decreased adherence to physicians' recommendations. CONCLUSION: These results emphasize the potential role of self-regulatory capacity in coping with and adjusting to hematologic cancers and future research is warranted.

Solberg Nes L; Ehlers SL; Patten CA; Gastineau DA

2013-03-01

360

Influence of grain orientation on evolution of surface features in fatigued polycrystalline copper: a comparison of thermal and uniaxial mechanical fatigue results  

CERN Document Server

Surface state plays a major role in the crack nucleation process of pure metals in the High-Cycle-Fatigue (HCF) as well as in the Ultra-High-Cycle-Fatigue (UHCF) regime. Therefore, in studies dealing with HCF or UHCF, special attention is paid to the evolution of surface degradation during fatigue life. The accelerating structures of the future Compact Linear Collider (CLIC) under study at CERN will be submitted to a high number of thermal-mechanical fatigue cycles, arising from Radio Frequency (RF) induced eddy currents, causing local superficial cyclic heating. The number of cycles during the foreseen lifetime of CLIC reaches 2x10(11). Fatigue may limit the lifetime of CLIC structures. In order to assess the effects of superficial fatigue, specific tests are defined and performed on polycrystalline Oxygen Free Electronic (OFE) grade Copper, a candidate material for the structures. Surface degradation depends on the orientation of near-surface grains. Copper samples thermally fatigued in two different fatigu...

Aicheler, M

2010-01-01

 
 
 
 
361

Effect of irradiation creep, swelling, wall erosion and embrittlement on the fatigue life of a tokamak first wall  

International Nuclear Information System (INIS)

A lifetime methodology has been developed which couples the long-term stress history for a generic first wall element to a two-dimensional fatigue crack growth calculation, while including, in a self-consistent manner, the detrimental effects of radiation damage. The reduction in fracture toughness due to embrittlement can reduce lifetimes by as much as a factor of 10 by accelerating stage II fatigue crack growth and enhancing the potential for brittle fracture. Swelling and irradiation creep appear not to be life-limiting, and a certain amount of wall erosion is found to enhance first wall lifetimes

1981-01-01

362

Influence of Solid-State Diffusion during Equilibration on Microstructure and Fatigue Life of Superalloy Wide-Gap Brazements  

Science.gov (United States)

The influence of solid-state diffusion-controlled solute-loss into additive powder particles (APPs), as determined by particles size, during the equilibration stage of wide-gap brazing, on microstructure and fatigue behavior of a brazed aerospace superalloy was studied. The results, which experimentally confirm previously reported numerical model simulation results, show that, in order to avoid degradation of fatigue life of wide-gap brazement, adequate solute-loss into the APPs, which is necessary to prevent their complete melting, but has not been generally considered, is imperative.

Osoba, L. O.; Ojo, O. A.

2013-09-01

363

Improvement of Fatigue Life of a Holed Specimen of Aluminum-Alloy 2024-T3 by Indentation and Hole Expansion  

Science.gov (United States)

A method of improving the fatigue life and crack growth behavior of a center holed specimen was investigated. Local plastic deformation was applied around the hole by indentation to achieve the purpose. A series of fatigue tests was conducted on aluminum-alloy 2024-T3. Push-pull tests were performed under a stress ratio of R= -1 and a frequency of 10Hz. The observations of the crack initiation and growth were performed with a microscope, and hardness around the hole was measured by Vickers hardness testing machine. In the present study, the longest fatigue life was observed in the case of an indentation specimen with the highest load. The indentation was performed on both sides of the hole edges. The crack growth rate was decreased by indentation or expansion of the material around the hole. From the experimental results, it is found that the fatigue life and crack growth behavior of a holed or notched specimen can be improved by a simple technical method that is related to the local plastic working.

Shafiul Ferdous, Md.; Makabe, Chobin; Miyazaki, Tatsujiro; Hattori, Nobusuke

364

Emerging technology for component life assessment  

International Nuclear Information System (INIS)

Operating plant component damage and failure experience is reviewed. Loading conditions such as thermal stratification and striping, turbulent flow and flow-induced vibrations are often found to limit useful life, even though such loadings were typically not considered when the components were designed. High cycle thermal and mechanical fatigue are identified as important damage mechanisms. A new method of correlating fatigue data and extrapolating to the very high cycle regime is described. The results of environmental degradation testing during the past fifteen years have shown that such effects ar much more deleterious than previously assumed. Therefore environmental and aging effects must be taken into account in evaluating the reliability and dependability of components for extended period of operation. Since most of the available data on environmental effects focus on measured crack growth rates, methods of developing improved fatigue life evaluation methods which include environmental effects on crack growth rates are now being developed. (Author)

1992-01-01

365

Effect of twinning, slip, and inclusions on the fatigue anisotropy of extrusion-textured AZ61 magnesium alloy  

International Nuclear Information System (INIS)

Highlights: ? Twinning and detwinning was observed in the hysteresis loops of the AZ61 mg alloy. ? Fatigue cracks incubated from fractured intermetallic particles in the AZ61 mg alloy. ? Inclusions were more important in determining fatigue life than microstructure. ? The model predicted the different fatigue lives in the two orientations tested. - Abstract: In this study, experiments were conducted to quantify structure-property relations with respect to fatigue of an extruded AZ61 magnesium alloy using a MultiStage Fatigue (MSF) model. Experiments were conducted in the extruded and transverse directions under low and high cycle strain control fatigue conditions. The cyclic behavior of this alloy displayed varying degrees of twinning and slip depending on the strain amplitude as observed in the hysteresis loops of both directions. Under low cyclic conditions, asymmetrical stress strain response was observed for both orientations. However, systematic stabilization of the hysteresis occurred by half-life due to subsequent twinning and detwinning mechanisms. In addition, under high cycle fatigue, pseudo-elasticity was observed at the first and at half-life cycles. Structure-property relations were quantified by examining the fracture surfaces of the fatigued specimens using a scanning electron microscope. In terms of crack incubation, fatigue cracks were found to initiate from intermetallic particles (inclusions) that were typically larger than the mean size. Quantified sources of fatigue crack incubation, microstructurally small cracks, and cyclic stress-strain behavior were correlated to the MSF model. Based on the specific material parameters, the MSF model was able to predict the difference in the strain-life results of the AZ61 magnesium alloy in the extruded and extruded transverse directions including the scatter of the experimental results. Finally, the MSF model revealed that the inclusion size was more important in determining the fatigue life than the anisotropic effects from the texture, yield, and work hardening.

2011-08-25

366

Effect of twinning, slip, and inclusions on the fatigue anisotropy of extrusion-textured AZ61 magnesium alloy  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} Twinning and detwinning was observed in the hysteresis loops of the AZ61 mg alloy. {yields} Fatigue cracks incubated from fractured intermetallic particles in the AZ61 mg alloy. {yields} Inclusions were more important in determining fatigue life than microstructure. {yields} The model predicted the different fatigue lives in the two orientations tested. - Abstract: In this study, experiments were conducted to quantify structure-property relations with respect to fatigue of an extruded AZ61 magnesium alloy using a MultiStage Fatigue (MSF) model. Experiments were conducted in the extruded and transverse directions under low and high cycle strain control fatigue conditions. The cyclic behavior of this alloy displayed varying degrees of twinning and slip depending on the strain amplitude as observed in the hysteresis loops of both directions. Under low cyclic conditions, asymmetrical stress strain response was observed for both orientations. However, systematic stabilization of the hysteresis occurred by half-life due to subsequent twinning and detwinning mechanisms. In addition, under high cycle fatigue, pseudo-elasticity was observed at the first and at half-life cycles. Structure-property relations were quantified by examining the fracture surfaces of the fatigued specimens using a scanning electron microscope. In terms of crack incubation, fatigue cracks were found to initiate from intermetallic particles (inclusions) that were typically larger than the mean size. Quantified sources of fatigue crack incubation, microstructurally small cracks, and cyclic stress-strain behavior were correlated to the MSF model. Based on the specific material parameters, the MSF model was able to predict the difference in the strain-life results of the AZ61 magnesium alloy in the extruded and extruded transverse directions including the scatter of the experimental results. Finally, the MSF model revealed that the inclusion size was more important in determining the fatigue life than the anisotropic effects from the texture, yield, and work hardening.

Jordon, J.B., E-mail: bjordon@eng.ua.edu [Department of Mechanical Engineering, University of Alabama, Tuscaloosa, AL 35487 (United States); Gibson, J.B. [Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Mississippi State, MS 39762 (United States); Horstemeyer, M.F.; Kadiri, H. El [Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Mississippi State, MS 39762 (United States); Department of Mechanical Engineering, Mississippi State University, Mississippi State, MS 39762 (United States); Baird, J.C. [Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Mississippi State, MS 39762 (United States); Luo, A.A. [General Motors Research and Development Center, Warren, MI 48090 (United States)

2011-08-25

367

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)

1986-01-01

368

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

International Nuclear Information System (INIS)

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

1982-01-28

369

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

Energy Technology Data Exchange (ETDEWEB)

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

Booker, M.K.; Majumdar, S.

1982-01-01

370

A study on fretting fatigue life for INCONEL 600 and 690 alloy  

International Nuclear Information System (INIS)

[en] The fretting fatigue occurs at lower stress amplitude and at lower cycles of cyclic loading then plain fatigue. INCNEL 600 and 690 alloy are high-chromium nickel alloy having excellent resistance to many corrosive aqueous media and high-temperature atmospheres. In this paper, the effect of fretting damage on fatigue behavior for INCNEL 600 and 690 alloy were studied. Also, various kinds of mechanical tests such as hardness, tension and plain fatigue tests are per formed. Through these experiments, it is found that the fretting fatigue strength decreased about 40 ? 70% compared to the plain fatigue strength in two materials. In fretting fatigue, the wear debris is observed on the contact surface and the oblique micro-cracks at on earlier stage are initiated

2005-01-01

371

Relationship of health-related quality of life with fatigue and exercise capacity in patients with coronary artery disease.  

UK PubMed Central (United Kingdom)

Objective:The study objective was to evaluate the relationship of health-related quality of life (HRQoL) with fatigue and exercise capacity in coronary artery disease (CAD) patients.Methods:A total of 1072 consecutive CAD patients on admission to a cardiac rehabilitation program were evaluated for HRQoL (36-item Short Form Medical Outcome Questionnaire; SF-36), body mass index, clinical characteristics (New York Heart Association (NYHA) class, angina pectoris class, coronary interventions, treatment with beta blockers, hypertension and diabetes), symptoms of depression and anxiety (Hospital Anxiety and Depression Scale), fatigue (Multidimensional Fatigue Inventory-20; MFI-20), and exercise capacity (bicycle ergometer test).Results:In univariate regression analyses lower scores on all SF-36 domains were associated with greater scores on all MFI-20 subscales. Exercise capacity was associated with all SF-36 domains, except for social functioning and mental health domains. In multivariate regression analyses, after adjusting for age, gender, body mass index, NYHA class, angina pectoris class, hypertension, diabetes, coronary interventions, treatment with betablockers, and symptoms of depression and anxiety, greater limitation due to physical and due to emotional problems, poor social functioning, decreased energy/vitality, worse general health perception, reduced mental component summary and lower global SF-36 score were independently associated with higher MFI-20 general fatigue score. Reduced physical functioning, greater pain, and reduced physical component summary SF-36 scores were associated with greater MFI-20 physical fatigue score. Lower SF-36 mental health score was associated, with greater MFI-20 mental fatigue score.Conclusion:In CAD patients undergoing rehabilitation, poor HRQoL is associated with greater fatigue and decreased exercise capacity independently from mental distress and CAD severity score.

Staniute M; Bunevicius A; Brozaitiene J; Bunevicius R

2013-07-01

372

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

Directory of Open Access Journals (Sweden)

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.

D. I. Chernousov; Vl. P. Podolsky; E. V. Trufanov; B. A. Bondarev

2011-01-01

373

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

International Nuclear Information System (INIS)

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

1995-01-01

374

Structural investigation of composite wind turbine blade considering various load cases and fatigue life  

International Nuclear Information System (INIS)

[en] This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass/epoxy for a 750 kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure various loads such as aerodynamic loads and loads due to accumulation of ice, hygro-thermal and mechanical loads, was proposed. To evaluate the proposed composite wind turbine blade, structural analysis was performed by using the finite element method. Parametric studies were carried out to determine an acceptable blade structural design, and the most dominant design parameters were confirmed. In this study, the proposed blade structure was confirmed to be safe and stable under various load conditions, including the extreme load conditions. Moreover, the blade adapted a new blade root joint with insert bolts, and its safety was verified at design loads including fatigue loads. The fatigue life of a blade that has to endure for more than 20 years was estimated by using the well-known S-N linear damage theory, the service load spectrum, and the Spera's empirical equations. With the results obtained from all the structural design and analysis, prototype composite blades were manufactured. A specific construction process including the lay-up molding method was applied to manufacturing blades. Full-scale static structural test was performed with the simulated aerodynamic loads. From the experimental results, it was found that the designed blade had structural integrity. In addition, the measured results of deflections, strains, mass, and radial center of gravity agreed well with the analytical results. The prototype blade was successfully certified by an international certification institute, GL (Germanisher Lloyd) in Germany

2005-01-01

375

Statistical analysis of bending fatigue life data using Weibull distribution in glass-fiber reinforced polyester composites  

Energy Technology Data Exchange (ETDEWEB)

The bending fatigue behaviors were investigated in glass fiber-reinforced polyester composite plates, made from woven-roving with four different weights, 800, 500, 300, and 200 g/m{sup 2}, random distributed glass-mat with two different weights 225, and 450 g/m{sup 2} and polyester resin. The plates which have fiber volume ratio V{sub f} {approx_equal} 44% and obtained by using resin transfer moulding (RTM) method were cut down in directions of [0/90 deg.] and [{+-}45 deg.]. Thus, eight different fiber-glass structures were obtained. These samples were tested in a computer aided fatigue apparatus which have fixed stress control and fatigue stress ratio [R = -1]. Two-parameter Weibull distribution function was used to analysis statistically the fatigue life results of composite samples. Weibull graphics were plotted for each sample using fatigue data. Then, S-N curves were drawn for different reliability levels (R = 0.99, R = 0.50, R = 0.368, R = 0.10) using these data. These S-N curves were introduced for the identification of the first failure time as reliability and safety limits for the benefit of designers. The probabilities of survival graphics were obtained for several stress and fatigue life levels. Besides, it was occurred that RTM conditions like fiber direction, resin permeability and full infiltration of fibers are very important when composites (GFRP) have been used for along time under dynamic loads by looking at test results in this study.

Sakin, Raif [Edremit Technical Vocational School of Higher Education, Balikesir University, Edremit (Turkey); Ay, Irfan [Department of Mechanical Engineering, Engineering and Architecture Faculty, Balikesir University, 10145 Balikesir (Turkey)], E-mail: ay@balikesir.edu.tr

2008-07-01

376

Effect of loading frequency on fatigue life and dissipated energy of structural plywood under panel shear load  

UK PubMed Central (United Kingdom)

Wood-based panels are subjected to cyclic panel shear load caused by wind and seismic forces in such an application as the sheathing of bearing walls. The fatigue behavior of structural plywood under panel shear load with two different loading frequencies was examined. Pulsating panel shear load with a triangular waveform and loading frequency of 0.5 or 5 Hz was applied to the plywood specimens. Stress-strain hysteresis loops were measured throughout the fatigue tests. Fatigue life was highly dependent on loading frequency at more than 0.5 stress level. The deterioration of mechanical property and damage accumulation in plywood specimen was observed to be slower at higher loading frequency at more than 0.5 stress level. Analyses based on energy loss suggest that panel shear load with higher loading frequency causes less damage to the plywood specimen during one loading cycle at higher stress level, and that the fatigue damage accumulation causing failure might be dependent on stress level although it seems to be unaffected by loading frequency. Based on these results, a new fatigue failure model for plywood specimen was qualitatively developed by combining Weibull's weakest link model and Daniels' fiber bundle model.

Sugimoto T; Sasaki Y

2006-08-01

377

An approach for low cycle fatigue life prediction of various metallic materials subjected to non-proportional multiaxial loading  

International Nuclear Information System (INIS)

The safety and durability of structures is an important issue because the sudden failure of complex system such as nuclear power plants, automobiles, aircraft and pressure vessels may cause many injuries, much financial loss and even environmental damage. Since many of these systems are subjected to repeated multiaxial loading, evaluation of low-cycle fatigue (LCF) becomes one of the major considerations in the design structures. An approach for estimating the multiaxial low cycle fatigue life under non-proportional loading using the non-proportional parameter by Itoh, Sakane, Ohnami and Socie has been developed. The non-proportional parameter includes the maximum principal strain range, non-proportional factor (it's a function of only strain path) and has a material constant which is defined as the sensitivity of the material to the non-proportional loading. The paper proposes the different versions of the non-proportional parameter and reports an investigation on the applicability of these versions to LCF life prediction. The proposed parameter, which includes Pisarenko-Lebedev's equivalent strain (or equivalent strain of Coulomb-More type), has shown a very good correlation of multiaxial low-cycle fatigue lives for various non-proportional loading paths with di