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

International Nuclear Information System (INIS)

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

1999-01-01

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

Multiaxial fatigue criterion based on parameters from torsion and axial S-N curve

Directory of Open Access Journals (Sweden)

M. Margetin

2016-07-01

Full Text Available Multiaxial high cycle fatigue is a topic that concerns nearly all industrial domains. In recent years, a great deal of recommendations how to address problems with multiaxial fatigue life time estimation have been made and a huge progress in the field has been achieved. Until now, however, no universal criterion for multiaxial fatigue has been proposed. Addressing this situation, this paper offers a design of a new multiaxial criterion for high cycle fatigue. This criterion is based on critical plane search. Damage parameter consists of a combination of normal and shear stresses on a critical plane (which is a plane with maximal shear stress amplitude. Material parameters used in proposed criterion are obtained from torsion and axial S-N curves. Proposed criterion correctly calculates life time for boundary loading condition (pure torsion and pure axial loading. Application of proposed model is demonstrated on biaxial loading and the results are verified with testing program using specimens made from S355 steel. Fatigue material parameters for proposed criterion and multiple sets of data for different combination of axial and torsional loading have been obtained during the experiment.

Low cycle fatigue of irradiated LMFBR materials

International Nuclear Information System (INIS)

Blackburn, L.D.

1976-01-01

A review of low cycle fatigue data on irradiated LMFBR materials was conducted and extensive graphical representations of available data are presented. Representative postirradiation tensile properties of annealed 304 and 316 SS are selected and employed in several predictive methods to estimate irradiated material fatigue curves. Experimental fatigue data confirm the use of predictive methods for establishing conservative design curves over the range of service conditions relevant to such CRBRP components as core former, fixed radial shielding, core barrel, lower inlet module and upper internals structures. New experimental data on fatigue curves and creep-fatigue interaction in irradiated 20 percent cold worked (CW) 316 SS and Alloy 718 would support the design of removable radial shielding and upper internals in CRBRP. New experimental information on notched fatigue behavior and cyclic stress-strain curves of all these materials in the irradiated condition could provide significant design data

Proposal of fatigue crack growth rate curve in air for nickel-base alloys used in BWR

International Nuclear Information System (INIS)

Ogawa, Takuya; Itatani, Masao; Nagase, Hiroshi; Aoike, Satoru; Yoneda, Hideki

2013-01-01

When the defects are detected in the nuclear components in Japan, structural integrity assessment should be performed for the technical judgment on continuous service based on the Rules on Fitness-for-Service for Nuclear Power Plants of the Japan Society of Mechanical Engineers Code (JSME FFS Code). Fatigue crack growth analysis is required when the cyclic loading would be applied for the components. Recently, fatigue crack growth rate curve in air environment for Nickel-base alloys weld metal used in BWR was proposed by the authors and it was adopted as a code case of JSME FFS Code to evaluate the embedded flaw. In this study, fatigue crack growth behavior for heat-affected zone (HAZ) of Nickel-base alloys in air was investigated. And a unified fatigue crack growth rate curve in air for HAZ and weld metal of Nickel-base alloys used in BWR was evaluated. As a result, it was found that the curve for weld metal could be applied as a curve for both HAZ and weld metal since moderately conservative assessment of fatigue crack growth rate of HAZ is possible by the curve for weld metal in the Paris region. And the threshold value of stress intensity far range (ΔK th ) is determined to 3.0 MPa√m based on the fatigue crack growth rate of HAZ. (author)

Two stage S-N curve in corrosion fatigue of extruded magnesium alloy AZ31

Directory of Open Access Journals (Sweden)

Yoshiharu Mutoh

2009-11-01

Full Text Available Tension-compression fatigue tests of extruded AZ31 magnesium alloys were carried out under corrosive environments:(a high humidity environment (80 %RH and (b 5 wt. %NaCl environment. It was found that the reduction rate of fatiguestrength due to corrosive environment was 0.12 under a high humidity and 0.53 under a NaCl environment. It was alsoobserved that under corrosive environments, the S-N curve was not a single curve but a two-stage curve. Above the fatiguelimit under low humidity, the crack nucleation mechanism was due to a localized slip band formation mechanism. Below thefatigue limit under low humidity, the reduction in fatigue strength was attributed to the corrosion pit formation and growth to the critical size for fatigue crack nucleation under the combined effect of cyclic load and the corrosive environment. The critical size was attained when the stress intensity factor range reached the threshold value for crack growth.

Fatigue design 1998

Energy Technology Data Exchange (ETDEWEB)

Marquis, G.; Solin, J. [eds.] [VTT Manufacturing Technology, Espoo (Finland)

1998-12-31

These preprints contain the presentations to be delivered at the Fatigue Design 1998 symposium held on May 26-29, 1998 in Espoo. Fatigue Design 1998 is the tenth in a series of VTT symposia addressing the challenge of fatigue of materials, components and structures. Previous international events were in 1992 and 1995. The key theme of the current meeting is `RELIABILITY`. The two volumes (VTT symposium 181-182) represent 56 contributions by authors representing 26 countries. Emphasis has been given to application oriented research topics that report new technologies, new uses of existing methods and case studies. The objective of the symposium is to bring together researchers and engineers to share experiences and new innovations in designing reliable components to resist alternating loads. (orig.)

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

International Nuclear Information System (INIS)

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

1975-01-01

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

Fatigue data compilation and evaluation of fatigue on design

International Nuclear Information System (INIS)

Nyilas, A.

1985-05-01

The aim of this report is a review of the available fatigue data of various materials necessary for the design of large superconducting magnets for fusion. One of the primary objectives of this work is to present a broad outline of the low temperature fatigue data of relevant materials within the scope of available data. Besides the classical fatigue data of materials the fatigue crack propagation measurements are outlined widely. The existing recommendations for the design of cryogenic structures are described. A brief introduction of fracture mechanics as well as a historical background of the development of our present day understanding of fatigue has been done. (orig.) [de

Creep fatigue assessment for EUROFER components

Energy Technology Data Exchange (ETDEWEB)

Özkan, Furkan, E-mail: oezkan.furkan@partner.kit.edu; Aktaa, Jarir

2015-11-15

Highlights: • Design rules for creep fatigue assessment are developed to EUROFER components. • Creep fatigue assessment tool is developed in FORTRAN code with coupling MAPDL. • Durability of the HCPB-TBM design is discussed under typical fusion reactor loads. - Abstract: Creep-fatigue of test blanket module (TBM) components built from EUROFER is evaluated based on the elastic analysis approach in ASME Boiler Pressure Vessel Code (BPVC). The required allowable number of cycles design fatigue curve and stress-to-rupture curve to estimate the creep-fatigue damage are used from the literature. Local stress, strain and temperature inputs for the analysis of creep-fatigue damage are delivered by the finite element code ANSYS utilizing the Mechanical ANSYS Parametric Design Language (MAPDL). A developed external FORTRAN code used as a post processor is coupled with MAPDL. Influences of different pulse durations (hold-times) and irradiation on creep-fatigue damage for the preliminary design of the Helium Cooled Pebble Bed Test Blanket Module (HCPB-TBM) are discussed for the First Wall component of the TBM box.

High temperature creep-fatigue design

International Nuclear Information System (INIS)

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

2010-01-01

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

High temperature creep-fatigue design

Energy Technology Data Exchange (ETDEWEB)

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

2010-07-01

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

Factors Associated with Visual Fatigue from Curved Monitor Use: A Prospective Study of Healthy Subjects.

Directory of Open Access Journals (Sweden)

Haeng Jin Lee

Full Text Available To investigate the factors associated with visual fatigue using monitors with various radii of curvature.Twenty normal healthy adults (8 men, 12 women; mean age, 26.2 ± 2.5 years prospectively watched five types of monitors including flat, 4000R, 3000R, 2000R, and 1000R curved monitors for 30 min. An experienced examiner measured the ophthalmological factors including near point of accommodation (NPA, near point of convergence (NPC, refraction, parameters during pupil response at light and saccadic movement just before and after the visual tasks. The questionnaires about subjective ocular symptoms were also investigated just before and after the visual tasks.The NPA increased after the visual tasks with a flat monitor compared with the curved monitors, with the 1000R curved monitor showing the smallest change (p = 0.020. The NPC increased for every monitor after the visual tasks; the largest increase occurred with the flat monitor (p = 0.001. There was no difference in refractive error, pupil response, or saccadic movement in the comparison of before and after the visual tasks. Among the nine factors in the questionnaire, the score of "eye pain" was significantly higher for the flat monitor versus the 1000R curved monitor after the visual tasks (p = 0.034.We identified NPA, NPC, and eye pain as factors associated with visual fatigue. Also, the curvature of the monitor was related to the visual fatigue.

Fatigue impact on Mod-1 wind turbine design

Science.gov (United States)

Stahle, C. V., Jr.

1978-01-01

Fatigue is a key consideration in the design of a long-life Wind Turbine Generator (WTG) system. This paper discusses the fatigue aspects of the large Mod-1 horizontal-axis WTG design starting with the characterization of the environment and proceeding through the design. Major sources of fatigue loading are discussed and methods of limiting fatigue loading are described. NASTRAN finite element models are used to determine dynamic loading and internal cyclic stresses. Recent developments in determining the allowable fatigue stress consistent with present construction codes are discussed relative to their application to WTG structural design.

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

International Nuclear Information System (INIS)

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

1994-08-01

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. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves for carbon and low-alloy steels presented in NUREG/CR-5999 is discussed

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

International Nuclear Information System (INIS)

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

1995-03-01

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

Towards the development of mechanistically based design rules for corrosion fatigue in ductile steels

International Nuclear Information System (INIS)

Johnson, R.; McMinn, A.; Tomkins, B.

1980-08-01

Design curves for nuclear pressure vessels and off-shore structures are based on air endurance curves that have had a safety factor applied to account for effects such as corrosive environments, frequency and mean stress. These are supported by a limited number of endurance tests on actual pressure vessels, and on welded joints under service conditions. These data-based rules are limited in their ability to cope with environmental effects and as the time dependencies of fatigue and corrosion processes are so different, no sound basis exists for the extrapolation of data to long component lifetimes. The crack-growth behaviour of materials used in nuclear pressure vessels and off-shore structures is examined with a view to determining how it may be used to re-assess the design curves. Even simple integration of crack-growth laws can be seen to be within reasonable agreement with present design curves; with improved methods of stress analysis, etc. this approach could potentially improve these curves. Mechanistic studies are also seen to offer a means of examining and assessing time-dependent process interactions and so, potentially, to form the basis of new guidelines. Finally the areas where further work would be needed to substantiate any changes in design curves are indicated. (author)

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

DEFF Research Database (Denmark)

Dominguez, Sergio Marquez; Sørensen, John Dalsgaard

2012-01-01

Consequences of failure of offshore wind turbines (OWTs) are in general lower than consequences of failure of, e.g., oil & gas platforms. It is reasonable that lower fatigue design factors can be applied for fatigue design of OWTs when compared to other fixed offshore structures. Calibration...

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

International Nuclear Information System (INIS)

Nam, Hyun Wook

2004-01-01

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

Proof of fatigue strength of nuclear components part II: Numerical fatigue analysis for transient stratification loading considering environmental effects

International Nuclear Information System (INIS)

Krätschmer, D.; Roos, E.; Schuler, X.; Herter, K.-H.

2012-01-01

For the construction, design and operation of nuclear components and systems the appropriate technical codes and standards provide detailed analysis procedures which guarantee a reliable behaviour of the structural components throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. To consider effects of light water reactor coolant environments, new design curves included in report NUREG/CR-6909 for austenitic stainless steels and for low alloy steels have been presented. For the usage of these new design curves an environmental fatigue correction factor for incorporating environmental effects has to be calculated and used. The application of this environmental correction factor to a fatigue analysis of a nozzle with transient stratification loads, derived by in-service monitoring, has been performed. The results are used to compare with calculated usage factors, based on design curves without taking environmental effects particularly into account. - Highlights: ► We model an nozzle for fatigue analysis und mechanical and thermal loading conditions. ► A simplified as well as a general elastic–plastic fatigue analysis considering environmental effects is performed. ► The influence of different factors calculating the environmental factor F en are shown. ► The presented numerical evaluation methodology allows the consideration of all relevant parameters to assess lifetime.

The effect of creep-fatigue damage relationships upon HTGR heat exchanger design

International Nuclear Information System (INIS)

Kozina, M.M.; King, J.H.; Basol, M.

1984-01-01

Materials for heat exchangers in the high temperature gas-cooled reactor (HTGR) are subjected to cyclic loading, extending the necessity to design against fatigue failure into the temperature region where creep processes become significant. Therefore, the fatigue life must be considered in terms of creep-fatigue interaction. In addition, since HTGR heat exchangers are subjected to holds at constant strain levels or constant stress levels in high-temperature environments, the cyclic life is substantially reduced. Of major concern in the design and analysis of HTGR heat exchangers is the accounting for the interaction of creep and fatigue. The accounting is done in conformance to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Code Case N-47, which allows the use of the linear damage criterion for interaction of creep and fatigue. This method separates the damage incurred in the material into two parts: one due to fatigue and one due to creep. The summation of the creep-fatigue damage must be less than 1.0. Recent material test data have indicated that the assumption of creep and fatigue damage equals unity at failure may not always be valid for materials like Alloy 800H, which is used in the higher temperature sections of HTGR steam generators. Therefore, a more conservative creep-fatigue damage relationship was postulated for Alloy 800H. This more conservative bilinear damage relationship consists of a design locus drawn from D F =1.0, D C =0 to D F =0.1, D C =0.1 to D F =0, D C =1.0. D F is the fatigue damage and D C is the creep damage. A more conservative damage relationship for 2-1/4 Cr-1 Mo material consisted of including factors that degrade the fatigue curves. These revised relationships were used in a structural evaluation of the HTGR steam cycle/cogeneration (SC/C) steam generator design. The HTGR-SC/C steam generator, a once-through type, is comprised of an economizer-evaporator-superheater (ESS) helical bundle of 2-1/4 Cr-1

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

International Nuclear Information System (INIS)

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

2003-01-01

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

Creep fatigue design of FBR components

International Nuclear Information System (INIS)

Bhoje, S.B.; Chellapandi, P.

1997-01-01

This paper deals with the characteristic features of Fast Breeder Reactor (FBR) with reference to creep fatigue, current creep fatigue design approach in compliance with RCCMR (1987) design code, material data, effects of weldments and neutron irradiation, material constitutive models employed, structural analysis and further R and D required for achieving maturity in creep fatigue design of FBR components. For the analysis reported in this paper, material constitutive models developed based on ORNIb (Oak Ridge National Laboratory) and Chaboche viscoplastic theories are employed to demonstrate the potential of FBR components for higher plant temperatures and/or longer life. The results are presented for the studies carried out towards life prediction of Prototype Fast Breeder Reactor (PFBR) components. (author). 24 refs, 8 figs, 5 tabs

Evaluation of Strain-Life Fatigue Curve Estimation Methods and Their Application to a Direct-Quenched High-Strength Steel

Science.gov (United States)

Dabiri, M.; Ghafouri, M.; Rohani Raftar, H. R.; Björk, T.

2018-03-01

Methods to estimate the strain-life curve, which were divided into three categories: simple approximations, artificial neural network-based approaches and continuum damage mechanics models, were examined, and their accuracy was assessed in strain-life evaluation of a direct-quenched high-strength steel. All the prediction methods claim to be able to perform low-cycle fatigue analysis using available or easily obtainable material properties, thus eliminating the need for costly and time-consuming fatigue tests. Simple approximations were able to estimate the strain-life curve with satisfactory accuracy using only monotonic properties. The tested neural network-based model, although yielding acceptable results for the material in question, was found to be overly sensitive to the data sets used for training and showed an inconsistency in estimation of the fatigue life and fatigue properties. The studied continuum damage-based model was able to produce a curve detecting early stages of crack initiation. This model requires more experimental data for calibration than approaches using simple approximations. As a result of the different theories underlying the analyzed methods, the different approaches have different strengths and weaknesses. However, it was found that the group of parametric equations categorized as simple approximations are the easiest for practical use, with their applicability having already been verified for a broad range of materials.

On cyclic yield strength in definition of limits for characterisation of fatigue and creep behaviour

Science.gov (United States)

Gorash, Yevgen; MacKenzie, Donald

2017-06-01

This study proposes cyclic yield strength as a potential characteristic of safe design for structures operating under fatigue and creep conditions. Cyclic yield strength is defined on a cyclic stress-strain curve, while monotonic yield strength is defined on a monotonic curve. Both values of strengths are identified using a two-step procedure of the experimental stress-strain curves fitting with application of Ramberg-Osgood and Chaboche material models. A typical S-N curve in stress-life approach for fatigue analysis has a distinctive minimum stress lower bound, the fatigue endurance limit. Comparison of cyclic strength and fatigue limit reveals that they are approximately equal. Thus, safe fatigue design is guaranteed in the purely elastic domain defined by the cyclic yielding. A typical long-term strength curve in time-to-failure approach for creep analysis has two inflections corresponding to the cyclic and monotonic strengths. These inflections separate three domains on the long-term strength curve, which are characterised by different creep fracture modes and creep deformation mechanisms. Therefore, safe creep design is guaranteed in the linear creep domain with brittle failure mode defined by the cyclic yielding. These assumptions are confirmed using three structural steels for normal and high-temperature applications. The advantage of using cyclic yield strength for characterisation of fatigue and creep strength is a relatively quick experimental identification. The total duration of cyclic tests for a cyclic stress-strain curve identification is much less than the typical durations of fatigue and creep rupture tests at the stress levels around the cyclic yield strength.

Proof of fatigue strength of ferritic and austenitic nuclear components

Energy Technology Data Exchange (ETDEWEB)

Roos, E.; Herter, K.H.; Schuler, X.; Weissenberg, T. [Materialpruefungsanstalt, Univ. Stuttgart (Germany)

2009-07-01

For the construction, design and operation of nuclear components and systems the appropriate technical codes and standards provide material data, detailed stress analysis procedures and a design philosophy which guarantees a reliable behaviour of the structural components throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. For the fatigue design curves used as limiting criteria the influence of different factors like e.g., environment, surface finish and temperature must be taken into consideration in an appropriate way. Fatigue tests were performed with low alloy steels as well as with Nb- and Ti-stabilized German austenitic stainless steels in air and simulated high temperature boiling water reactor environment. The experimental results are compared and valuated with the mean data curves in air as well as with mean data curves under high temperature water environment published in the international literature. (orig.)

Creep-fatigue rules in the RCC-MR code

International Nuclear Information System (INIS)

Drubay, B.

1988-01-01

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

Fatigue behavior of porous biomaterials manufactured using selective laser melting.

Science.gov (United States)

Yavari, S Amin; Wauthle, R; van der Stok, J; Riemslag, A C; Janssen, M; Mulier, M; Kruth, J P; Schrooten, J; Weinans, H; Zadpoor, A A

2013-12-01

Porous titanium alloys are considered promising bone-mimicking biomaterials. Additive manufacturing techniques such as selective laser melting allow for manufacturing of porous titanium structures with a precise design of micro-architecture. The mechanical properties of selective laser melted porous titanium alloys with different designs of micro-architecture have been already studied and are shown to be in the range of mechanical properties of bone. However, the fatigue behavior of this biomaterial is not yet well understood. We studied the fatigue behavior of porous structures made of Ti6Al4V ELI powder using selective laser melting. Four different porous structures were manufactured with porosities between 68 and 84% and the fatigue S-N curves of these four porous structures were determined. The three-stage mechanism of fatigue failure of these porous structures is described and studied in detail. It was found that the absolute S-N curves of these four porous structures are very different. In general, given the same absolute stress level, the fatigue life is much shorter for more porous structures. However, the normalized fatigue S-N curves of these four structures were found to be very similar. A power law was fitted to all data points of the normalized S-N curves. It is shown that the measured data points conform to the fitted power law very well, R(2)=0.94. This power law may therefore help in estimating the fatigue life of porous structures for which no fatigue test data is available. It is also observed that the normalized endurance limit of all tested porous structures (<0.2) is lower than that of corresponding solid material (c.a. 0.4). © 2013.

Statistical treatment of fatigue test data

International Nuclear Information System (INIS)

Raske, D.T.

1980-01-01

This report discussed several aspects of fatigue data analysis in order to provide a basis for the development of statistically sound design curves. Included is a discussion on the choice of the dependent variable, the assumptions associated with least squares regression models, the variability of fatigue data, the treatment of data from suspended tests and outlying observations, and various strain-life relations

Fatigue design of steel and composite structures Eurocode 3 : design of steel structures, part 1-9 fatigue ; Eurocode 4 : design of composite steel and concrete structures

CERN Document Server

Nussbaumer, Alain; Davaine, Laurence

2012-01-01

This volume addresses the specific subject of fatigue, a subject not familiar to many engineers, but still relevant for proper and good design of numerous steel structures. It explains all issues related to the subject: Basis of fatigue design, reliability and various verification formats, determination of stresses and stress ranges, fatigue strength, application range and limitations. It contains detailed examples of applications of the concepts, computation methods and verifications.

Probabilistic Fatigue Design of Composite Material for Wind Turbine Blades

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2011-01-01

In the present paper a probabilistic design approach to fatigue design of wind turbine blades is presented. The physical uncertainty on the fatigue strength for composite material is estimated using public available fatigue tests. Further, the model uncertainty on Miner rule for damage accumulation...

Recommendations for fatigue design of welded joints and components

CERN Document Server

Hobbacher, A F

2016-01-01

This book provides a basis for the design and analysis of welded components that are subjected to fluctuating forces, to avoid failure by fatigue. It is also a valuable resource for those on boards or commissions who are establishing fatigue design codes. For maximum benefit, readers should already have a working knowledge of the basics of fatigue and fracture mechanics. The purpose of designing a structure taking into consideration the limit state for fatigue damage is to ensure that the performance is satisfactory during the design life and that the survival probability is acceptable. The latter is achieved by the use of appropriate partial safety factors. This document has been prepared as the result of an initiative by Commissions XIII and XV of the International Institute of Welding (IIW).

Fatigue behaviour and crack growth of ferritic steel under environmental conditions

International Nuclear Information System (INIS)

Herter, K.H.; Schuler, X.; Weissenberg, T.

2012-01-01

The assessment of fatigue and cyclic crack growth behaviour of safety relevant components is of importance for the ageing management with regard to safety and reliability. For cyclic stress evaluation different codes and standards provide fatigue analysis procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. For the fatigue design curves used as a limiting criteria the influence of different factors like e.g. environment, surface finish and temperature must be taken into consideration in an appropriate way. Fatigue tests were performed in the low cycle fatigue (LCF) und high cycle fatigue (HCF) regime with low alloy steels as well as with Nb- and Ti-stabilized German austenitic stainless steels in air and high temperature (HT) boiling water reactor environment to extend the state of knowledge of environmentally assisted fatigue (EAF) as it can occur in boiling water reactor (BWR) plants. Using the reactor pressure vessel (RPV) steel 22NiMoCr3-7 experimental data were developed to verify the influence of BWR coolant environment (high purity water as well as sulphate containing water with 90 ppb SO 4 at a test temperature of 240 C and an oxygen content of 400 ppb) on the fatigue life and to extend the basis for a reliable estimation of the remaining service life of reactor components. Corresponding experiments in air were performed to establish reference data to determine the environmental correction factor F en accounting for the environment. The experimental results are compared with international available mean data curves, the new design curves and on the basis of the environmental factor F en . Furthermore the behaviour of steel 22NiMoCr3-7 in oxygenated high temperature water under transient loading conditions was investigated with respect to crack initiation and cyclic crack growth. In this process the stress state of the specimen and the chemical composition of the high

Fatigue strength degradation of metals in corrosive environments

Science.gov (United States)

Adasooriya, N. D.; Hemmingsen, T.; Pavlou, D.

2017-12-01

Structures exposed to aggressive environmental conditions are often subjected to time-dependent loss of coating and loss of material due to corrosion; this causes reduction in the cross-sectional properties of the members, increased surface roughness, surface irregularities and corrosion pits, and degradation of material strengths. These effects have been identified and simulated in different research studies. However, time and corrosive media dependent fatigue strength curves for materials have not been discussed in the design or assessment guidelines for structures. This paper attempts to review the corrosion degradation process and available approaches/models used to determine the fatigue strength of corroded materials and to interpolate corrosion deterioration data. High cycle fatigue and full range fatigue life formulae for fatigue strength of corroded materials are proposed. The above formulae depend on the endurance limit of corroded material, in addition to the stress-life fatigue curve parameters of the uncorroded material. The endurance limit of corroded material can either be determined by a limited number of tests in the very high-cycle fatigue region or predicted by an analytical approach. Comparison with experimentally measured corrosion fatigue behavior of several materials is provided and discussed.

High cycle fatigue of austenitic stainless steels under random loading

International Nuclear Information System (INIS)

Gauthier, J.P.; Petrequin, P.

1987-08-01

To investigate reactor components, load control random fatigue tests were performed at 300 0 C and 550 0 C, 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

Low cycle fatigue behavior of die cast Mg-Al-Mn-Ce magnesium alloy

Directory of Open Access Journals (Sweden)

Wu Wei

2013-11-01

Full Text Available Fatigue failure is a main failure mode for magnesium and other alloys. It is beneficial for fatigue design and fatigue life improvement to investigate the low cycle fatigue behavior of magnesium alloys. In order to investigate the low cycle fatigue behavior of die cast Mg-Al-Mn-Ce magnesium alloy, the strain controlled fatigue experiments were performed at room temperature and fatigue fracture surfaces of specimens were observed with scanning election microscopy for the alloys under die-cast and aged states. Cyclic stress response curves, strain amplitude versus reversals to failure curve, total strain amplitude versus fatigue life curves and cyclic stress-strain curves of Mg-Al-Mn-Ce alloys were analyzed. The results show that the Mg-Al-Mn-Ce alloys under die-cast (F and aged (T5 states exhibit cyclic strain hardening under the applied total strain amplitudes, and aging treatment could greatly increase the cyclic stress amplitudes of die cast Mg-Al-Mn-Ce alloys. The relationships between the plastic strain amplitude, the elastic strain amplitude and reversals to failure of Mg-Al-Mn-Ce magnesium alloy under different treatment states could be described by Coffin-Manson and Basquin equations, respectively. Observations on the fatigue fracture surface of specimens reveal that the fatigue cracks initiate on the surface of specimens and propagate transgranularly.

Elastic creep-fatigue evaluation for ASME code

International Nuclear Information System (INIS)

Severud, L.K.; Winkel, B.V.

1987-01-01

Experience with applying the ASME Code Case N-47 rules for evaluation of creep-fatigue with elastic analysis results has been problematic. The new elastic evaluation methods are intended to bound the stress level and strain range values needed for use in employing the code inelastic analysis creep-fatigue damage counting procedures. To account for elastic followup effects, ad hoc rules for stress classification, shakedown, and ratcheting are employed. Because elastic followup, inelastic strain concentration, and stress-time effects are accounted for, the design fatigue curves in Case N-47 for inelastic analysis are used instead of the more conservative elastic analysis curves. Creep damage assessments are made using an envelope stress-time history that treats multiple load events and repeated cycles during elevated temperature service life. (orig./GL)

A critical evaluation on the fatigue problem

International Nuclear Information System (INIS)

Rosa, E. da; Costa Machado Leal, L. da

1978-01-01

A review of the different aspects of approaches to the fatigue problems since the Woehler curves till the crack propagation is presented. The interrelationship among each one of the aspects is then carried out as well as the relation of the aspects to the different fatigue phases, since the crack nucleation till the final rupture in an attempt to unify the design procedure. (Author)

Fatigue assessment of the ITER TF coil case based on JJ1 fatigue tests

International Nuclear Information System (INIS)

Hamada, K.; Nakajima, H.; Takano, K.; Kudo, Y.; Tsutsumi, F.; Okuno, K.; Jong, C.

2005-01-01

The material of the TF coil case in the ITER requires to withstand cyclic electromagnetic forces applied up to 3 x 10 4 cycles at 4.2 K. A cryogenic stainless steel, JJ1, is used in high stress region of TF coil case. The fatigue characteristics (S-N curve) of JJ1 base metal and welded joint at 4.2 K has been measured. The fatigue strength of base metal and welded joint at 3 x 10 4 cycles are measured as 1032 and 848 MPa, respectively. The design S-N curve is derived from the measured data taking account of the safety factor of 20 for cycle-to-failure and 2 for fatigue strength, and it indicates that an equivalent alternating stress of the case should be kept less than 516 MPa for the base metal and 424 MPa for the welded joint at 3 x 10 4 cycles. It is demonstrated that the TF coil case has enough margins for the cyclic operation. It is also shown the welded joint should be located in low cyclic stress region because a residual stress affects the fatigue life

Probabilistic Fatigue Damage Program (FATIG)

Science.gov (United States)

Michalopoulos, Constantine

2012-01-01

FATIG computes fatigue damage/fatigue life using the stress rms (root mean square) value, the total number of cycles, and S-N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner's rule. The integration is carried out over all stress amplitudes. This software solves the problem of probabilistic fatigue damage using the integral form of the Palmgren-Miner rule. The software computes fatigue life using an approach involving all stress amplitudes, up to N*sigma, as specified by the user. It can be used in the design of structural components subjected to random dynamic loading, or by any stress analyst with minimal training for fatigue life estimates of structural components.

Evaluation of micro fatigue crack growth under equi-biaxial stress by membranous pressure fatigue test

International Nuclear Information System (INIS)

Iida, Satoshi; Abe, Shigeki; Nakamura, Takao; Kamaya, Masayuki

2014-01-01

For preventing nuclear power plant (NPP) accidents, NPPs are required to ensure system safety in long term safe operation under aging degradation. Now, fatigue accumulation is one of major ageing phenomena and are evaluated to ensure safety by design fatigue curve that are based on the results of uniaxial fatigue tests. On the other hand, thermal stress that occurs in piping of actual components is not uniaxial but equi-biaxial. For accurate evaluation, it is required to conform real circumstance. In this study, membranous pressure fatigue test was conducted to simulated equi-biaxial stress. Crack initiation and crack growth were examined by replica investigation. Calculation result of equivalent stress intensity factor shows crack growth under equi-biaxial stress is faster than under uniaxial stress. It is concluded that equi-biaxial fatigue behavior should be considered in the evaluation of fatigue crack initiation and crack growth. (author)

Influence of combined impact and cyclic loading on the overall fatigue life of forged steel, EA4T

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, A.; Hadidi-Moud, S.; Farhangdoost, Kh [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

2017-03-15

The performance of forged steel, EA4T, used in rail industry, under simulated in service conditions, i.e. combined impact - cyclic loading, was investigated through a comprehensive experimental programme. The standard Paris-Erdogan fatigue design curve parameters, m and C, were calibrated to account for the effect of the impact component of loading. A minimum threshold for impact load component, identified in the experiments, was also incorporated in the proposed empirical model. Comparison with experimental findings indicated that this “modified” Fatigue design curve could predict the fatigue life of pre impact loaded specimens with sufficient accuracy. It was therefore suggested that the modified model may be used as a novel design tool for predicting the overall fatigue life of components made of this material under the specified combined impact and fatigue loading conditions.

Microstructure, Tensile Strength and Probabilistic Fatigue Life Evaluation of Gray Cast Iron

Energy Technology Data Exchange (ETDEWEB)

Sung, Yong Hyeon; Han, Seung-Wook; Choi, Nak-Sam [Hanyang Univ., Seoul (Korea, Republic of)

2017-08-15

High-grade gray cast iron (HCI350) was prepared by adding Cr, Mo and Cu to the gray cast iron (GC300). Their microstructure, mechanical properties and fatigue strength were studied. Cast iron was made from round bar and plate-type castings, and was cut and polished to measure the percentage of each microstructure. The size of flake graphite decreased due to additives, while the structure of high density pearlite increased in volume percentage improving the tensile strength and fatigue strength. Based on the fatigue life data obtained from the fatigue test results, the probability - stress - life (P-S-N) curve was calculated using the 2-parameter Weibull distribution to which the maximum likelihood method was applied. The P-S-N curve showed that the fatigue strength of HCI350 was significantly improved and the dispersion of life data was lower than that of GC300. However, the fatigue life according to fatigue stress alleviation increased further. Data for reliability life design was presented by quantitatively showing the allowable stress value for the required life cycle number using the calculated P-S-N curve.

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

International Nuclear Information System (INIS)

Keisler, J.; Chopra, O.K.

1995-03-01

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

FATIGUE PROPERTIES OF MODIFIED 316LN STAINLESS STEEL AT 4 K FOR HIGH FIELD CABLE-IN-CONDUIT APPLICATIONS

International Nuclear Information System (INIS)

Toplosky, V. J.; Walsh, R. P.; Han, K.

2010-01-01

Cable-In-Conduit-Conductor (CICC) alloys, exposed to Nb 3 Sn reaction heat-treatments, such as modified 316LN require a design specific database. A lack of fatigue life data (S-n curves) that could be applied in the design of the ITER CS and the NHMFL Series Connected Hybrid magnets is the impetus for the research presented here. The modified 316LN is distinguished by a lower carbon content and higher nitrogen content when compared to conventional 316LN. Because the interstitial alloying elements affect the mechanical properties significantly, it is necessary to characterize this alloy in a systematic way. In conjunction, to ensure magnet reliability and performance, several criteria and expectations must be met, including: high fatigue life at the operating stresses, optimal stress management at cryogenic temperatures and thin walled conduit to reduce coil mass. Tension-tension load control axial fatigue tests have good applicability to CICC solenoid magnet design, thus a series of 4 K strength versus fatigue life curves have been generated. In-situ samples of 316LN base metal, seam welded, butt welded and seam plus butt welded are removed directly from the conduit in order to address base and weld material fatigue life variability. The more than 30 fatigue tests show good grouping on the fatigue life curve and allow discretionary 4 K fatigue life predictions for conduit made with modified 316LN.

Development of conventional fatigue database for structure materials of nuclear power plant

International Nuclear Information System (INIS)

Yang Bing

2002-01-01

Management system of the conventional fatigue database for structure materials of nuclear power plant (NPP) is developed. The database included the parameters of design curves, i.e., the stress-life, survival probability-stress-life, strain-life, survival probability-strain-life, stress-strain and survival probability-stress-strain curves, and corresponding information of materials and testing conditions. Two ways, by materials name or by the inter-bounds of material mechanical properties, are constructed to search the database. From the searched information it can be conveniently performed of the conventional fatigue design analysis and reliability assessment of structures

Fatigue strength evaluation of friction stir welded aluminium joints using the nominal and notch stress concepts

International Nuclear Information System (INIS)

Barsoum, Z.; Khurshid, M.; Barsoum, I.

2012-01-01

Highlights: ► Fatigue testing and evaluation of friction stir welded butt and overlap joints. ► Evaluation based on nominal and effective notch stress concept. ► Comparison with different design recommendations and codes. ► Higher fatigue strength and SN-slopes is observed. ► New fatigue design recommendations proposed for FSW joints. -- Abstract: In this study the fatigue strength is investigated for Friction Stir Welded (FSW) overlap and butt welded joints in different thicknesses based on nominal and effective notch stress concepts. The fatigue test results are compared with fatigue strength recommendations according to EN 1999-1-3 and International Institute of Welding (IIW). The results are also compared with available published data and Finite Element Analysis (FEA) is carried out to investigate the effect of plate thickness and nugget size on the fatigue strength of overlap joints. 3–3 mm butt welded joints shows the highest fatigue strength in comparison with 3–5 mm butt welded and overlap joints. Slopes of the SN-curves for two different joint types differ from the slope recommended by IIW. A specific failure trend is observed in overlap FSW joints. However, the slopes of the SN-curves are in close agreement with slopes found in EN 1999-1-3. The slopes of various published results and test results presented in this study are in good agreement with each other. The suggested fatigue design curves for the nominal and effective notch stress concept have a higher slope than given for fusion welds by IIW.

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-07-01

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

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

International Nuclear Information System (INIS)

Fissolo, Antoine; Gourdin, Cedric; Vincent, Ludovic

2009-01-01

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

Stress intensity factors for fatigue loaded details between crossbeams and trapezoidal stringers

NARCIS (Netherlands)

Maljaars, J.; Pijpers, R.J.M.

2013-01-01

A number of orthotropic deck structures of existing bridges are suffering from fatigue cracks. Maintenance of these deck structures may consist of regular inspections and repair of detected cracks. The usual fatigue design life procedure for aswelded structures based on S-N curves is not feasible

Partial Safety Factors for Fatigue Design of Wind Turbine Blades

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2010-01-01

In the present paper calibration of partial safety factors for fatigue design of wind turbine blades is considered. The stochastic models for the physical uncertainties on the material properties are based on constant amplitude fatigue tests and the uncertainty on Miners rule for linear damage...... accumulation is determined from variable amplitude fatigue tests with the Wisper and Wisperx spectra. The statistical uncertainty for the assessment of the fatigue loads is also investigated. The partial safety factors are calibrated for design load case 1.2 in IEC 61400-1. The fatigue loads are determined...... from rainflow-counting of simulated time series for a 5MW reference wind turbine [1]. A possible influence of a complex stress state in the blade is not taken into account and only longitudinal stresses are considered....

Sensitivity of the magnetization curves of different austenitic stainless tube and pipe steels to mechanical fatigue

International Nuclear Information System (INIS)

Niffenegger, M.; Leber, H.J.

2008-01-01

In meta-stable austenitic stainless steels, fatigue is accompanied by a partial strain-induced transformation of paramagnetic austenite to ferromagnetic martensite [G.B. Olsen, M. Cohen, Kinetics of strain induced martensite nucleation, Metall. Trans. 6 (1975) 791-795]. The associated changes of magnetic properties as the eddy current impedance, magnetic permeability or the remanence field may serve as an indication for the degree of fatigue and therefore the remaining lifetime of a component, even though the exact causal relationship between martensite formation and fatigue is not fully understood. However, measuring these properties by magnetic methods may be limited by the low affinity for strain-induced martensite formation. Thus other methods have to be found which are able to detect very small changes of ferromagnetic contents. With this aim the influence of cyclic strain loading on the magnetization curves of the austenitic stainless tube and pipe steels TP 321, 347, 304L and 316L is analysed in the present paper. The measured characteristic magnetic properties, which are the saturation magnetization, residual magnetization, coercive field and the field dependent permeability (AC-magnetization), are sensitive to fatigue and the corresponding material changes (martensitic transformation). In particular, the AC-magnetization was found to be very sensitive to small changes of the amount of strain induced martensite and therefore also to the degree of fatigue. Hence we conclude that applying magnetic minor loops are promising for the non-destructive evaluation of fatigue in austenitic stainless steel, even if a very small amount of strain induced martensite is formed

Designing aluminium friction stir welded joints against multiaxial fatigue

Directory of Open Access Journals (Sweden)

L. Susmel

2016-07-01

Full Text Available The present paper investigates the accuracy of the Modified Wöhler Curve Method (MWCM in estimating multiaxial fatigue strength of aluminium friction stir (FS welded joints. Having developed a bespoke joining technology, circumferentially FS welded tubular specimens of Al 6082-T6 were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out using the experimental results have demonstrated that the MWCM applied in terms of nominal stresses, notch stresses, and also the Point Method is accurate in predicting the fatigue lifetime of the tested FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands.

The Development of Confidence Limits for Fatigue Strength Data

International Nuclear Information System (INIS)

SUTHERLAND, HERBERT J.; VEERS, PAUL S.

1999-01-01

Over the past several years, extensive databases have been developed for the S-N behavior of various materials used in wind turbine blades, primarily fiberglass composites. These data are typically presented both in their raw form and curve fit to define their average properties. For design, confidence limits must be placed on these descriptions. In particular, most designs call for the 95/95 design values; namely, with a 95% level of confidence, the designer is assured that 95% of the material will meet or exceed the design value. For such material properties as the ultimate strength, the procedures for estimating its value at a particular confidence level is well defined if the measured values follow a normal or a log-normal distribution. Namely, based upon the number of sample points and their standard deviation, a commonly-found table may be used to determine the survival percentage at a particular confidence level with respect to its mean value. The same is true for fatigue data at a constant stress level (the number of cycles to failure N at stress level S(sub 1)). However, when the stress level is allowed to vary, as with a typical S-N fatigue curve, the procedures for determining confidence limits are not as well defined. This paper outlines techniques for determining confidence limits of fatigue data. Different approaches to estimating the 95/95 level are compared. Data from the MSU/DOE and the FACT fatigue databases are used to illustrate typical results

Designing Fatigue Warning Systems: The perspective of professional drivers.

Science.gov (United States)

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

2016-03-01

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

Fatigue management considering LWR coolant environments

International Nuclear Information System (INIS)

Park, Heung Bae; Jin, Tae eun

2000-01-01

Design fatigue curve for structural material in the ASME Boiler and Pressure Vessel Code do not explicitly address the effects of reactor coolant environments on fatigue life. Environmentally assisted cracking (EAC) of low-alloy steels in light water reactor (LWR) coolant environments has been a concern ever since the early 1970's. And, recent fatigue test data indicate a significant decrease in fatigue lives of carbon steels, low-alloy steels and austenitic stainless steels in LWR coolant environments. For these reasons, fatigue of major components has been identified as a technical issue remaining to be resolved for life management and license renewal of nuclear power plants. In the present paper, results of recent investigations by many organizations are reviewed to provide technical justification to support the development of utility approach regarding the management of fatigue considering LWR coolant environments for the purpose of life management and license renewal of nuclear power plants. (author)

Uncertainty on Fatigue Damage Accumulation for Composite Materials

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2009-01-01

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

Proposed design procedure for transmission shafting under fatigue loading

Science.gov (United States)

Loewenthal, S. H.

1978-01-01

The B106 American National Standards Committee is currently preparing a new standard for the design of transmission shafting. A design procedure, proposed for use in the new standard, for computing the diameter of rotating solid steel shafts under combined cyclic bending and steady torsion is presented. The formula is based on an elliptical variation of endurance strength with torque exhibited by combined stress fatigue data. Fatigue factors are cited to correct specimen bending endurance strength data for use in the shaft formula. A design example illustrates how the method is to be applied.

Computational predictive methods for fracture and fatigue

Science.gov (United States)

Cordes, J.; Chang, A. T.; Nelson, N.; Kim, Y.

1994-09-01

The damage-tolerant design philosophy as used by aircraft industries enables aircraft components and aircraft structures to operate safely with minor damage, small cracks, and flaws. Maintenance and inspection procedures insure that damages developed during service remain below design values. When damage is found, repairs or design modifications are implemented and flight is resumed. Design and redesign guidelines, such as military specifications MIL-A-83444, have successfully reduced the incidence of damage and cracks. However, fatigue cracks continue to appear in aircraft well before the design life has expired. The F16 airplane, for instance, developed small cracks in the engine mount, wing support, bulk heads, the fuselage upper skin, the fuel shelf joints, and along the upper wings. Some cracks were found after 600 hours of the 8000 hour design service life and design modifications were required. Tests on the F16 plane showed that the design loading conditions were close to the predicted loading conditions. Improvements to analytic methods for predicting fatigue crack growth adjacent to holes, when multiple damage sites are present, and in corrosive environments would result in more cost-effective designs, fewer repairs, and fewer redesigns. The overall objective of the research described in this paper is to develop, verify, and extend the computational efficiency of analysis procedures necessary for damage tolerant design. This paper describes an elastic/plastic fracture method and an associated fatigue analysis method for damage tolerant design. Both methods are unique in that material parameters such as fracture toughness, R-curve data, and fatigue constants are not required. The methods are implemented with a general-purpose finite element package. Several proof-of-concept examples are given. With further development, the methods could be extended for analysis of multi-site damage, creep-fatigue, and corrosion fatigue problems.

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

Science.gov (United States)

Liao, Gaohua; Wu, Jianzhong

2017-07-01

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

Transition curves for highway geometric design

CERN Document Server

Kobryń, Andrzej

2017-01-01

This book provides concise descriptions of the various solutions of transition curves, which can be used in geometric design of roads and highways. It presents mathematical methods and curvature functions for defining transition curves. .

Fatigue Resistant Design Criteria for MD SHA Cantilevered Mast Arm Signal Structure

Science.gov (United States)

2017-12-01

The fatigue design of the mast arm structures and connections vary significantly based on the Category of Importance factor adopted and the load cases for fatigue design loads. Consideration should include the cost and size of the structures for both...

Design rule for fatigue of welded joints in elevated-temperature nuclear components

International Nuclear Information System (INIS)

O'Connor, D.G.; Corum, J.M.

1986-01-01

Elevated-temperature weldment fatigue failures have occurred in several operating liquid-metal reactor plants. Yet, ASME Code Case N-47, which governs the design of such plants in the United States, does not currently address the Code Subgroup on Elevated Temperature Design recently proposed a fatigue strength reduction factor for austenitic and ferritic steel weldments. The factor is based on a variety of weld metal and weldment fatigue data generated in the United States, Europe, and Japan. This paper describes the factor and its bases, and it presents the results of confirmatory fatigue tests conducted at Oak Ridge National Laboratory on 316 stainless steel tubes with axial and circumferential welds of 16-8-2 filler metal. These test results confirm the suitability of the design factor, and they support the premise that the metallurgical notch effect produced by yield strength variations across a weldment is largely responsible for the observed elevated-temperature fatigue strength reduction

Physical and Model Uncertainty for Fatigue Design of Composite Material

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

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

Optimal Fatigue Testing

DEFF Research Database (Denmark)

Faber, Michael Havbro; Sørensen, John Dalsgaard; Kroon, I. B.

1993-01-01

life experiments for the same purpose. The methodology is basedon modern probabilistic concepts amd classical decision theory. The special case where the fatigue life experiments are given in terms of SN curves is considered in Particular. The proposed techniques are illustrated by an example.......This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue...

Methods for predicting isochronous stress-strain curves

International Nuclear Information System (INIS)

Kiyoshige, Masanori; Shimizu, Shigeki; Satoh, Keisuke.

1976-01-01

Isochronous stress-strain curves show the relation between stress and total strain at a certain temperature with time as a parameter, and they are drawn up from the creep test results at various stress levels at a definite temperature. The concept regarding the isochronous stress-strain curves was proposed by McVetty in 1930s, and has been used for the design of aero-engines. Recently the high temperature characteristics of materials are shown as the isochronous stress-strain curves in the design guide for the nuclear energy equipments and structures used in high temperature creep region. It is prescribed that these curves are used as the criteria for determining design stress intensity or the data for analyzing the superposed effects of creep and fatigue. In case of the isochronous stress-strain curves used for the design of nuclear energy equipments with very long service life, it is impractical to determine the curves directly from the results of long time creep test, accordingly the method of predicting long time stress-strain curves from short time creep test results must be established. The method proposed by the authors, for which the creep constitution equations taking the first and second creep stages into account are used, and the method using Larson-Miller parameter were studied, and it was found that both methods were reliable for the prediction. (Kako, I.)

IFMIF - Design Study for in Situ Creep Fatigue Tests

International Nuclear Information System (INIS)

Gordeev, S.; Heinzel, V.; Simakov, St.; Stratmanns, E.; Vladimirov, P.; Moeslang, A.

2006-01-01

While the high flux volume (20-50 dpa/fpy) of the International Fusion Materials Irradiation Facility (IFMIF) is dedicated to the irradiation of ∼ 1100 qualified specimens that will be post irradiation examined after disassembling in dedicated Hot Cells, various in situ experiments are foreseen in the medium flux volume (1-20 dpa/fpy). Of specific importance for structural lifetime assessments of fusion power reactors are instrumented in situ creep-fatigue experiments, as they can simulate realistically a superposition of thermal fatigue or creep fatigue and irradiation with fusion relevant neutrons. Based on former experience with in situ fatigue tests under high energy light ion irradiation, a design study has been performed to evaluate the feasibility of in situ creep fatigue tests in the IFMIF medium flux position. The vertically arranged test module for such experiments consists basically of a frame similar to a universal testing machine, but equipped with three pulling rods, driven by independent step motors, instrumentation systems and specimen cooling systems. Therefore, three creep fatigue specimens may be tested at one time in this apparatus. Each specimen is a hollow tube with coolant flow in the specimen interior to maintain individual specimen temperatures. The recently established IFMIF global 3D geometry model was used together the latest McDeLicious code for the neutral and charged particle transport calculations. These comprehensive neutronics calculations have been performed with a fine special resolution of 0.25 cm 3 , showing among others that the specimens will be irradiated with a homogeneous damage rate of up to 13(∼ 9%) dpa/fpy and a fusion relevant damage to helium ratio of 10-12 appm He/dpa. In addition, damage and gas production rates as well as the heat deposition in structural parts of the test module have been calculated. Despite of the vertical gradients in the nuclear heating, CFD code calculations with STAR-CD revealed very

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-03-15

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

Strength calculation of NPP equipment and pipelines during operation. Low- and high-cycle corrosion fatigue

International Nuclear Information System (INIS)

Filatov, V.M.; Evropin, S.V.

2004-01-01

This paper presents empirical equations and design curves for structural steels employed in nuclear power facilities with light water reactors. These equations allow to take into account the effects of cycle asymmetry, water coolant and ductility decrease during operation. The fatigue curves cover the low-cycle and high-cycle regions (up to 10 12 cycles). The equations include the mechanical characteristics of steels under static tension. The coolant effect on steel fatigue is allowed for using a model developed at the Argonne National Laboratory

Method and data analysis example of fatigue tests

International Nuclear Information System (INIS)

Nogami, Shuhei

2015-01-01

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

Low cycle corrosion fatigue properties of F316Ti in simulated LWR primary environment

International Nuclear Information System (INIS)

Xu Xuelian; Ding Yaping; Katada, Y.; Sato, S.

1998-11-01

Environment effect on fatigue performance of materials used for Pressurized boundary, including fatigue life and crack growth rate, are of importance to nuclear safety. To predict the fatigue life of nuclear materials and to improve the design of nuclear materials, it is necessary to investigated the material fatigue performances in corrosive environment and to get the fatigue data under its environment to be used in. Low cycle corrosion fatigue (CF) performance investigation of domestic F316Ti in simulated BWR and PWR primary environment was carried out. The result shows that the high temperature water environment is one of the most important factors on CF properties. For the same material, the low cycle fatigue life in high temperature air is longer than that in simulated BWR and PWR primary environments. In high temperature water, domestic F316Ti has almost the same low cycle corrosion fatigue performance as F316 (made in Japan). All of the fatigue data are scattered within ASME best-fit curve and ASME design fatigue curve. In high strain range, there is no significant difference of the CF performance for F316Ti in both of BWR and PWR primary environments. With the decrease of strain amplitude, the difference appears gradually. The data is located at the short life side of the fatigue data in simulated BWR primary environment. Titanium is distributed uniformly in F316Ti manufactured in Fushun Steel Factory. Ni, Cr, Mo in this material are located at the high side of the alloy chemical composition range. So, F316Ti has a better CF property in high temperature water

Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

Energy Technology Data Exchange (ETDEWEB)

Haidyrah, Ahmed S., E-mail: ashdz2@mst.edu [Nuclear Engineering, Missouri University of Science & Technology, 301 W. 14th, Rolla, MO 65409 (United States); Nuclear Science Research Institute, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442 (Saudi Arabia); Newkirk, Joseph W. [Materials Science & Engineering, Missouri University of Science & Technology, 1440 N. Bishop Ave, Rolla, MO 65409 (United States); Castaño, Carlos H. [Nuclear Engineering, Missouri University of Science & Technology, 301 W. 14th, Rolla, MO 65409 (United States)

2016-03-15

A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S–N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

International Nuclear Information System (INIS)

Haidyrah, Ahmed S.; Newkirk, Joseph W.; Castaño, Carlos H.

2016-01-01

A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S–N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

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

Directory of Open Access Journals (Sweden)

Changyou Li

2017-03-01

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

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Fatigue and fail-safe design features of the DC-10 airplane

Science.gov (United States)

Stone, M. E.

1972-01-01

The philosophy and methods used in the design of the DC-10 aircraft to assure structural reliability against cracks under repeated service loads are described in detail. The approach consists of three complementary parts: (1) the structure is designed to be fatigue resistant for a crack-free life of 60,000 flight hours; (2) inasmuch as small undetected cracks could develop from other sources, such as material flaws and manufacturing preloads, the structure also is designed to arrest and control cracks within a reasonable service-inspection interval; and (3) a meaningful service-inspection program has been defined on the basis of analysis and test experience from the design development program. This service-inspection program closes the loop to assure the structural integrity of the DC-10 airframe. Selected materials, fasteners, and structural arrangements are used to achieve these design features with minimum structural weight and with economy in manufacturing and maintenance. Extensive analyses and testing were performed to develop and verify the design. The basic design considerations for fatigue-resistant structure are illustrated in terms of material selection, design loads spectra, methods for accurate stress and fatigue damage analysis, and proven concepts for efficient detail design.

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

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-02-15

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

Generic Reliability-Based Inspection Planning for Fatigue Sensitive Details

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard; Straub, Daniel; Faber, Michael Havbro

2005-01-01

of fatigue sensitive details in fixed offshore steel jacket platforms and FPSO ship structures. Inspection and maintenance activities are planned such that code based requirements to the safety of personnel and environment for the considered structure are fulfilled and at the same time such that the overall......The generic approach for planning of in-service NDT inspections is extended to cover the case where the fatigue load is modified during the design lifetime of the structure. Generic reliability-based inspection planning has been developed as a practical approach to perform inspection planning...... expected costs for design, inspections, repairs and failures are minimized. The method is based on the assumption of “no-finds” of cracks during inspections. Each fatigue sensitive detail is categorized according to their type of details (SN curves), FDF values, RSR values, inspection, repair and failure...

Designing the Alluvial Riverbeds in Curved Paths

Science.gov (United States)

Macura, Viliam; Škrinár, Andrej; Štefunková, Zuzana; Muchová, Zlatica; Majorošová, Martina

2017-10-01

The paper presents the method of determining the shape of the riverbed in curves of the watercourse, which is based on the method of Ikeda (1975) developed for a slightly curved path in sandy riverbed. Regulated rivers have essentially slightly and smoothly curved paths; therefore, this methodology provides the appropriate basis for river restoration. Based on the research in the experimental reach of the Holeška Brook and several alluvial mountain streams the methodology was adjusted. The method also takes into account other important characteristics of bottom material - the shape and orientation of the particles, settling velocity and drag coefficients. Thus, the method is mainly meant for the natural sand-gravel material, which is heterogeneous and the particle shape of the bottom material is very different from spherical. The calculation of the river channel in the curved path provides the basis for the design of optimal habitat, but also for the design of foundations of armouring of the bankside of the channel. The input data is adapted to the conditions of design practice.

Prediction of Mean and Design Fatigue Lives of Self Compacting Concrete Beams in Flexure

Science.gov (United States)

Goel, S.; Singh, S. P.; Singh, P.; Kaushik, S. K.

2012-02-01

In this paper, result of an investigation conducted to study the flexural fatigue characteristics of self compacting concrete (SCC) beams in flexure are presented. An experimental programme was planned in which approximately 60 SCC beam specimens of size 100 × 100 × 500 mm were tested under flexural fatigue loading. Approximately 45 static flexural tests were also conducted to facilitate fatigue testing. The flexural fatigue and static flexural strength tests were conducted on a 100 kN servo-controlled actuator. The fatigue life data thus obtained have been used to establish the probability distributions of fatigue life of SCC using two-parameter Weibull distribution. The parameters of the Weibull distribution have been obtained by different methods of analysis. Using the distribution parameters, the mean and design fatigue lives of SCC have been estimated and compared with Normally vibrated concrete (NVC), the data for which have been taken from literature. It has been observed that SCC exhibits higher mean and design fatigue lives compared to NVC.

Improved methods of creep-fatigue life assessment of components

Energy Technology Data Exchange (ETDEWEB)

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

2009-07-01

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

Fatigue Lifetime of ADI from Ultimate Tensile Strength to Permanent Fatigue Limit

Czech Academy of Sciences Publication Activity Database

Zapletal, J.; Věchet, S.; Kohout, J.; Obrtlík, Karel

-, č. 1 (2008), s. 40-43 ISSN 0556-171X. [MSMF /5./. Brno, 27.06.2007-29.06.2007] R&D Projects: GA ČR GA106/03/1265 Institutional research plan: CEZ:AV0Z20410507 Keywords : austempered ductile iron * fatigue behaviour * S N curve Subject RIV: JL - Materials Fatigue , Friction Mechanics

Above-knee prosthesis design based on fatigue life using finite element method and design of experiment.

Science.gov (United States)

Phanphet, Suwattanarwong; Dechjarern, Surangsee; Jomjanyong, Sermkiat

2017-05-01

The main objective of this work is to improve the standard of the existing design of knee prosthesis developed by Thailand's Prostheses Foundation of Her Royal Highness The Princess Mother. The experimental structural tests, based on the ISO 10328, of the existing design showed that a few components failed due to fatigue under normal cyclic loading below the required number of cycles. The finite element (FE) simulations of structural tests on the knee prosthesis were carried out. Fatigue life predictions of knee component materials were modeled based on the Morrow's approach. The fatigue life prediction based on the FE model result was validated with the corresponding structural test and the results agreed well. The new designs of the failed components were studied using the design of experimental approach and finite element analysis of the ISO 10328 structural test of knee prostheses under two separated loading cases. Under ultimate loading, knee prosthesis peak von Mises stress must be less than the yield strength of knee component's material and the total knee deflection must be lower than 2.5mm. The fatigue life prediction of all knee components must be higher than 3,000,000 cycles under normal cyclic loading. The design parameters are the thickness of joint bars, the diameter of lower connector and the thickness of absorber-stopper. The optimized knee prosthesis design meeting all the requirements was recommended. Experimental ISO 10328 structural test of the fabricated knee prosthesis based on the optimized design confirmed the finite element prediction. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Fatigue analysis of HANARO primary cooling system piping

International Nuclear Information System (INIS)

Ryu, Jeong Soo

1998-05-01

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

Study on Fatigue Characteristics of High-Strength Steel Welds

Energy Technology Data Exchange (ETDEWEB)

Chang, Hong Suk; Yoo, Seung Won; Park, Jong Chan [Hyundai Motor Group, Seoul (Korea, Republic of)

2015-03-15

High-strength steel has replaced mild steel as the material of choice for truck decks or frames, owing to the growing demand for lightweight vehicles. Although studies on the weld fatigue characteristics of mild steel are available, studies on high-strength steels have been seldom conducted. In this study, firstly, we surveyed a chosen number of approaches and selected the Radaj method, which uses the notch factor approach, as the one suitable for evaluating the fatigue life of commercial vehicles. Secondly, we obtained the S-N curves of HARDOX and ATOS60 steel welds, and the F-N curves of the T-weld and overlapped-weld structures. Thirdly, we acquired a general S-N curve of welded structures made of high-strength steel from the F-N curve, using the notch factor approach. Fourthly, we extracted the weld fatigue characteristics of high-strength steel and incorporated the results in the database of a commercial fatigue program. Finally, we compared the results of the fatigue test and the CAE prediction of the example case, which demonstrated sufficiently good agreement.

Mean load effect on fatigue of welded joints using structural stress and fracture mechanics approach

International Nuclear Information System (INIS)

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

2006-01-01

In order to ensure the structural integrity of nuclear welded structures during design life, the fatigue life has to be evaluated by fatigue analysis procedures presented in technical codes such as ASME B and PV Code Section III. However, existing fatigue analysis procedures do not explicitly consider the presence of welded joints. A new fatigue analysis procedure based on a structural stress/fracture mechanics approach has been recently developed in order to reduce conservatism by erasing uncertainty in the analysis procedure. A recent review of fatigue crack growth data under various mean loading conditions using the structural stress/fracture mechanics approach, does not consider the mean loading effect, revealed some significant discrepancies in fatigue crack growth curves according to the mean loading conditions. In this paper, we propose the use of the stress intensity factor range ΔK characterized with loading ratio R effects in terms of the structural stress. We demonstrate the effectiveness in characterizing fatigue crack growth and S-N behavior using the well-known data. It was identified that the S-N data under high mean loading could be consolidated in a master S-N curve for welded joints

''Safety rules of fatigue damage for nuclear facilities pressurized equipment at the sizing and the operation stage''

International Nuclear Information System (INIS)

Grandemange, J.M.; Faidy, C.

2001-01-01

This paper presents the method applied in the nuclear industry in the domain of the fatigue risk safety. It recalls the fatigue curves origins and presents the technical requirements implemented during the design and the construction. It also presents the follow-up of transients in service and the periodical examinations. (A.L.B.)

Preliminary tests to determine the fatigue curve of the Ibis ACSR (Aluminum Cable Steel Reinforced) conductor; Ensaios preliminares para determinacao da curva de fadiga do cabo condutor ACSR Ibis

Energy Technology Data Exchange (ETDEWEB)

Rosa, Daniel M. [Universidade de Brasilia (UnB-Gama), DF (Brazil)], E-mail: danielrosa@unb.br; Fadel, Aida A.; Araujo, Jose Alexander; Ferreira, Jorge Luiz A.; Henriques, Antonio Manoel D. [Universidade de Brasilia (EnM/UnB), DF (Brazil). Dept. de Engenharia Mecanica], Emails: aida@unb.br, alex07@unb.br, jorge@unb.br, Henriques@unb.br; Hortencio, Tania M.O.S. [Companhia Energetica de Goias Distribuicao S.A. (CELG D), Goiania, GO (Brazil)], E-mail: tania.hortencio@celg.com.br

2009-07-01

The aim of this work was to present a fretting fatigue experimental rig for overhead conductors and to carry out a set of experiments to obtain life estimative for a standard Ibis ACSR, Aluminium Conductor Steel Reinforced. A preliminary S-N (Wohler) Curve was obtained in the medium high cycle fatigue regime. Experiments considered the occurrence of at least two wire breaks to obtain each point of the S-N curve, which was compared to CIGRE's Safe Border Line (CSBL). The experimental results showed five to ten times large lives than the ones provided by CSBL adoption. (author)

A curved beam test specimen for determining the interlaminar tensile strength of a laminated composite

Science.gov (United States)

Hiel, Clement C.; Sumich, Mark; Chappell, David P.

1991-01-01

A curved beam type of test specimen is evaluated for use in determining the through-the-thickness strength of laminated composites. Two variations of a curved beam specimen configuration (semicircular and elliptical) were tested to failure using static and fatigue loads. The static failure load for the semicircular specimens was found to be highly sensitive to flaw content, with the specimens falling into two distinct groups. This result supports the use of proof testing for structural validation. Static design allowables are derived based on the Weibull distribution. Fatigue data indicates no measured increase in specimen compliance prior to final fracture. All static and fatigue failures at room temperature dry conditions occurred catastrophically. The elliptical specimens demonstrated unusually high failure strengths indicating the presence of phenomena requiring further study. Results are also included for specimens exposed to a wet environment showing a matrix strength degradation due to moisture content. Further testing is underway to evaluate a fatigue methodology for matrix dominated failures based on residual static strength (wearout).

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

International Nuclear Information System (INIS)

Pleune, T.T.

1996-11-01

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

Creep, fatigue and creep-fatigue damage evaluation and estimation of remaining life of SUS 304 austenitic stainless steel at high temperature

International Nuclear Information System (INIS)

Nishino, Seiichi; Sakane, Masao; Ohnami, Masateru

1986-01-01

Experimental study was made on the damage evaluation and estimation of remaining life of SUS 304 stainless steel in creep, low-cycle fatigue and creep-fatigue at 873 K in air. Creep, fatigue and creep-fatigue damage curves were drawn by the method proposed by D.A. Woodford and the relations between these damages and non-destructive parameters, i.e., microvickers hardness and quantities obtained from X-ray diffraction, were discussed. From these tests, the following conclusions were obtained. (1) Constant damage lines in the diagram of remaining lives in creep and fatigue could be drawn by changing load levels during the tests. Constant damage lines in creep-fatigue were also made by a linear damage rule using both static creep and fatigue damage curves, which agree well with the experimental data in creep-fatigue. (2) Microvickers hardness and half-value breadth in X-ray diffraction are appropriate parameters to evaluate creep damage but are not proper to evaluate fatigue damage. Particle size and microstrain obtained by X-ray profile analysis are good parameters to evaluate both creep and fatigue damages. (author)

Fatigue reliability and effective turbulence models in wind farms

DEFF Research Database (Denmark)

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

2007-01-01

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

Individual aircraft life monitoring: An engineering approach for fatigue damage evaluation

Directory of Open Access Journals (Sweden)

Rui JIAO

2018-04-01

Full Text Available Individual aircraft life monitoring is required to ensure safety and economy of aircraft structure, and fatigue damage evaluation based on collected operational data of aircraft is an integral part of it. To improve the accuracy and facilitate the application, this paper proposes an engineering approach to evaluate fatigue damage and predict fatigue life for critical structures in fatigue monitoring. In this approach, traditional nominal stress method is applied to back calculate the S-N curve parameters of the realistic structure details based on full-scale fatigue test data. Then the S-N curve and Miner’s rule are adopted in damage estimation and fatigue life analysis for critical locations under individual load spectra. The relationship between relative small crack length and fatigue life can also be predicted with this approach. Specimens of 7B04-T74 aluminum alloy and TA15M titanium alloy are fatigue tested under two types of load spectra, and there is a good agreement between the experimental results and analysis results. Furthermore, the issue concerning scatter factor in individual aircraft damage estimation is also discussed. Keywords: Fatigue damage, Fatigue monitoring, Fatigue test, Scatter factor, S-N curve

Fatigue criterion for the design of rotating shafts under combined stress

Science.gov (United States)

Loewenthal, S. H.

1977-01-01

A revised approach to the design of transmission shafting which considers the flexure fatigue characteristics of the shaft material under combined cyclic bending and static torsion stress is presented. A fatigue failure relation, corroborated by published combined stress test data, is presented which shows an elliptical variation of reversed bending endurance strength with static torsional stress. From this elliptical failure relations, a design formula for computing the diameter of rotating solid shafts under the most common condition of loading is developed.

A survey of the French creep-fatigue design rules for LMFBR

International Nuclear Information System (INIS)

Tribout, J.; Cordier, G.; Moulin, D.

1987-01-01

The paper provides a survey of the creep-fatigue design rules for the LMFBR in France. These rules are the ones currently implemented in French component manufacturing. The background of each item is discussed and the trends for improvements currently investigated are described. The creep-fatigue rules apply to elastic analysis only. (orig.)

Verification of anti-fatigue effect of anserine by angle fatigue indicator based on median frequency changes of electromyograms

Directory of Open Access Journals (Sweden)

Hirohisa Kishi

2013-10-01

Full Text Available ABSTRACT: Objective: Anserine, which is abundant in avian species and in a wide range of fish such as bonito and tuna, is reported to have anti-fatigue effect. Although chicken soup and bonito soup is traditionally used to recover from physical fatigue, it is generally difficult to verify the effect in humans. This study was to directly demonstrate the anti-fatigue effect of oceanic anserine in humans. Methods: Edible-grade anserine was purified from fish extract with food-grade reagents. Subjects were 17 healthy male volunteers (35.5 ± 5 yr., 75.5 ± 5.0 kg. Each subject performed the isometric exercise tolerance test (ETT on the rectus femoris muscle twice (Ex_1, Ex_2 both for anserine and water conditions on a different day. Median frequency changes (MDF during Functional Foods in Health and Disease 2013; 3(10 389-399 ETTs were calculated and regression curves were calculated over a frequency range of 21-214 Hz. The difference, or angle, between the slopes of Ex_1 and Ex_2 MDF regression curves, which corresponds to the degree of fatigue, was defined as an angle fatigue index and compared between anserine and water intake conditions. Results: MDF decreased during ETTs in most patients and the slopes of regression curves were larger in Ex_2 than in Ex_1. Angle fatigue index for water (control was significantly larger than that for anserine (p<0.01, paired t-test, n=17. The result indicates that anserine have an anti-fatigue effect on skeletal muscle in humans. Conclusions: We proposed the angle fatigue index as a touchstone of the muscle fatigue. The index indicates that anserine is effective to reduce the muscle fatigue in humans.

Fatigue evaluation of the API specification 12F shop welded flat bottom tanks

International Nuclear Information System (INIS)

Rondon, A.; Guzey, S.

2017-01-01

Shop-built storage tanks are widely used in several industries all over the world. These equipment are fabricated with relatively small dimensions and capacities to facilitate their transportation to production fields. Particularly, API 12F shop-welded, flat bottom tanks are a group of standard equipment with specific sizes and capacities that are commonly used in the upstream, exploration, and production segments of oil and gas projects. The extensive utilization of this equipment has raised the need to investigate their behavior under different load cases and determine their service life due to cyclic loading. Throughout this investigation, a fatigue evaluation was performed following the guidelines of the ASME BPVC Section VIII, Division 2, design-by-analysis rules. The thirteen API 12F tanks were separated in three different groups according to their diameters. Also, different thicknesses as well as pressure cycles including internal pressure and vacuum were considered for the evaluation of each group. An elastic stress analysis using finite elements was conducted on shell models, axisymmetric models and solid submodels to determine the stress components and stress tensor range as well as obtain the effective alternating equivalent stress. Moreover, the fatigue penalty factor and a fatigue strength reduction factor were defined in accordance with the ASME code specifications. Hence, the protection against failure from cyclic loading of these equipment was determined using smooth bar design fatigue curves and the permissible number of operational cycles and location of the most critical joint were computed for each API 12F tank. - Highlights: • Stress analysis was performed following the ASME design-by-analysis. • Storage tanks axisymmetric and solid finite element models were developed. • Smooth bar design fatigue curve was obtained to perform the fatigue evaluation. • Clean out juncture is critical for the fatigue life of API 12F tanks. • Smaller

Two micro fatigue test methods for irradiated materials

International Nuclear Information System (INIS)

Nunomura, Shigetomo; Noguchi, Shinji; Okamura, Yuichi; Kumai, Shinji

1993-01-01

This paper demonstrates two miniature fatigue test methods in response to the requirements of the fusion reactor wall materials development program. It is known that the fatigue strength evaluated by the axial loading test is independent of the specimen size, while that evaluated by the bend test or torsion test is dependent upon the size of specimen. The new type of gripping system for the axial, tension-tension, fatigue testing of TEM disk-size specimens that has been developed is described in this paper. An alignment tool assists in gripping the miniature specimen. The miniature tension-tension fatigue test method seems to provide reliable S-N curves for SUS304 and SUS316L stainless steels. An indentation method has also been developed to determine fatigue properties. A hard steel ball or ceramic ball was used for cyclically loading the specimen, and an S-N curve was subsequently obtained. The merit of this method is primarily simple handling. S-N curves obtained from four materials by this indentation method compared well with those obtained from the rotary bend fatigue test employing a standard-size specimen

Fatigue Reliability Analysis of Wind Turbine Cast Components

DEFF Research Database (Denmark)

Rafsanjani, Hesam Mirzaei; Sørensen, John Dalsgaard; Fæster, Søren

2017-01-01

.) and to quantify the relevant uncertainties using available fatigue tests. Illustrative results are presented as obtained by statistical analysis of a large set of fatigue data for casted test components typically used for wind turbines. Furthermore, the SN curves (fatigue life curves based on applied stress......The fatigue life of wind turbine cast components, such as the main shaft in a drivetrain, is generally determined by defects from the casting process. These defects may reduce the fatigue life and they are generally distributed randomly in components. The foundries, cutting facilities and test...... facilities can affect the verification of properties by testing. Hence, it is important to have a tool to identify which foundry, cutting and/or test facility produces components which, based on the relevant uncertainties, have the largest expected fatigue life or, alternatively, have the largest reliability...

Evaluation of conservatisms and environmental effects in ASME Code, Section III, Class 1 fatigue analysis

International Nuclear Information System (INIS)

Deardorff, A.F.; Smith, J.K.

1994-08-01

This report documents the results of a study regarding the conservatisms in ASME Code Section 3, Class 1 component fatigue evaluations and the effects of Light Water Reactor (LWR) water environments on fatigue margins. After review of numerous Class 1 stress reports, it is apparent that there is a substantial amount of conservatism present in many existing component fatigue evaluations. With little effort, existing evaluations could be modified to reduce the overall predicted fatigue usage. Areas of conservatism include design transients considerably more severe than those experienced during service, conservative grouping of transients, conservatisms that have been removed in later editions of Section 3, bounding heat transfer and stress analysis, and use of the ''elastic-plastic penalty factor'' (K 3 ). Environmental effects were evaluated for two typical components that experience severe transient thermal cycling during service, based on both design transients and actual plant data. For all reasonable values of actual operating parameters, environmental effects reduced predicted margins, but fatigue usage was still bounded by the ASME Section 3 fatigue design curves. It was concluded that the potential increase in predicted fatigue usage due to environmental effects should be more than offset by decreases in predicted fatigue usage if re-analysis were conducted to reduce the conservatisms that are present in existing component fatigue evaluations

Fatigue Design and Prevention in Movable Scaffolding Systems

Directory of Open Access Journals (Sweden)

Coelho Hugo

2017-06-01

Full Text Available The Movable Scaffolding System (MSS is a heavy construction equipment used for casting situ of concrete bridge decks. In the past decades, MSSs have become increasingly complex and industrialized, enlarging its span ranges, incorporating auxiliary elevation machinery and increasing productivity. The tendency nowadays is for strong reutilization and the notion of MSS as a disposable or temporary structure is somehow reductive. The main structure of MSSs may be potentially exposed to fatigue, usually characterized by low number of cycles with significant stress amplitude. Fatigue may be prevented through adequate design; judicious selection of materials; demanding quality control and implementation of robust inspection and maintenance plans.

Fatigue Design and Prevention in Movable Scaffolding Systems

Science.gov (United States)

Coelho, Hugo; Torres, Alberto; Pacheco, Pedro; Moreira, Cristiano; Silva, Rute; Soares, José M.; Pinto, Dânia

2017-06-01

The Movable Scaffolding System (MSS) is a heavy construction equipment used for casting situ of concrete bridge decks. In the past decades, MSSs have become increasingly complex and industrialized, enlarging its span ranges, incorporating auxiliary elevation machinery and increasing productivity. The tendency nowadays is for strong reutilization and the notion of MSS as a disposable or temporary structure is somehow reductive. The main structure of MSSs may be potentially exposed to fatigue, usually characterized by low number of cycles with significant stress amplitude. Fatigue may be prevented through adequate design; judicious selection of materials; demanding quality control and implementation of robust inspection and maintenance plans.

Reliability Based Geometric Design of Horizontal Circular Curves

Science.gov (United States)

Rajbongshi, Pabitra; Kalita, Kuldeep

2018-06-01

Geometric design of horizontal circular curve primarily involves with radius of the curve and stopping sight distance at the curve section. Minimum radius is decided based on lateral thrust exerted on the vehicles and the minimum stopping sight distance is provided to maintain the safety in longitudinal direction of vehicles. Available sight distance at site can be regulated by changing the radius and middle ordinate at the curve section. Both radius and sight distance depend on design speed. Speed of vehicles at any road section is a variable parameter and therefore, normally the 98th percentile speed is taken as the design speed. This work presents a probabilistic approach for evaluating stopping sight distance, considering the variability of all input parameters of sight distance. It is observed that the 98th percentile sight distance value is much lower than the sight distance corresponding to 98th percentile speed. The distribution of sight distance parameter is also studied and found to follow a lognormal distribution. Finally, the reliability based design charts are presented for both plain and hill regions, and considering the effect of lateral thrust.

Reliability Based Geometric Design of Horizontal Circular Curves

Science.gov (United States)

Rajbongshi, Pabitra; Kalita, Kuldeep

2018-03-01

Geometric design of horizontal circular curve primarily involves with radius of the curve and stopping sight distance at the curve section. Minimum radius is decided based on lateral thrust exerted on the vehicles and the minimum stopping sight distance is provided to maintain the safety in longitudinal direction of vehicles. Available sight distance at site can be regulated by changing the radius and middle ordinate at the curve section. Both radius and sight distance depend on design speed. Speed of vehicles at any road section is a variable parameter and therefore, normally the 98th percentile speed is taken as the design speed. This work presents a probabilistic approach for evaluating stopping sight distance, considering the variability of all input parameters of sight distance. It is observed that the 98th percentile sight distance value is much lower than the sight distance corresponding to 98th percentile speed. The distribution of sight distance parameter is also studied and found to follow a lognormal distribution. Finally, the reliability based design charts are presented for both plain and hill regions, and considering the effect of lateral thrust.

Fatigue crack growth and endurance data on 9% Cr 1% Mo steels for AGR applications

International Nuclear Information System (INIS)

Priddle, E.K.

1987-01-01

Experimental investigations have been carried out on 9%Cr 1%Mo steels to examine: (1) The significance of carburisation on the fatigue endurance of plain and welded boiler tubes, and tube spacer strip; (2) the high cycle fatigue endurance of spacer strip and spacer weld metal; (3) fatigue crack growth rates in spacer strip and spacer weld metal. This report summarises the results of these investigations and where necessary compares the data to that in current data sheets. The effects of carburisation are variable depending on the structure and type of carburisation. The fatigue endurance properties of spacer strip and spacer weld metal are also similar and need not be considered separately for assessment or design purposes. Fatigue crack growth rates in spacer strip and space weld metal are similar and are influenced by both stress ratio and temperature. A design curve from a fast reactor data sheet may be used as an upper bound to these fatigue crack growth results. (author)

Fatigue and rutting strain analysis of flexible pavements designed ...

African Journals Online (AJOL)

ELO

The study was carried out with the layered elastic analysis software EVERSTRESS. Key words: Layered elastic analysis, fatigue, rutting, strains, design, flexible pavement, CBR. ..... Numerical Computational Stresses and Strains in Multi-Layer ...

Development of a Very High Cycle Fatigue (VHCF multiaxial testing device

Directory of Open Access Journals (Sweden)

M. Vieira

2016-07-01

Full Text Available The very high cycle region of the S-N fatigue curve has been the subject of intensive research on the last years, with special focus on axial, bending, torsional and fretting fatigue tests. Very high cycle fatigue can be achieved using ultrasonic exciters which allow for frequency testing of up to 30 kHz. Still, the multiaxial fatigue analysis is not yet developed for this type of fatigue analyses, mainly due to conceptual limitations of these testing devices. In this paper, a device designed to produce biaxial fatigue testing using a single piezoelectric axial exciter is presented, as well as the preliminary testing of this device. The device is comprised of a horn and a specimen, which are both attached to the piezoelectric exciter. The steps taken towards the final geometry of the device are presented. Preliminary experimental testing of the developed device is made using thermographic imaging, strain measurements and vibration speeds and indicates good behaviour of the tested specimen.

Inconel 718 and UNSM Treated Alloy Study on the Rotary Bending High Temperature Fatigue Characteristics under a Light Concentrating System

Energy Technology Data Exchange (ETDEWEB)

Suh, Chang Min [Kyungpook Nat’l Univ., Daegu (Korea, Republic of); Nahm, Seung Hoon [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Woo, Young Han; Hur, Kwang Ho; Hong, Sang Hwui [Gyeongbuk Hybrid Technology Institute, Daegu (Korea, Republic of); Kim, Jun Hyong; Pyun, Young Sik [Sun Moon Univ., Asan (Korea, Republic of)

2016-11-15

This study investigated the influence of high temperature and UNSM on the fatigue behavior of Inconel 718 alloy at RT, 300, 500, and 600℃. Fatigue properties of Inconel 718 were reduced at high temperatures compared to those at room temperature. However, the endurance limit was similar to that of the room temperature sample at the design stress level. High-temperature fatigue characteristics of the UNSM-treated specimen were significantly improved at the design stress level as compared to the untreated specimens. Specifically, the influence of temperature on the S-N curves at the design stress level of the UNSM-treated specimen showed the tendency of longer fatigue lives than those of untreated ones. Researchers can obtain rotary fatigue test results simply by heating specimens with a halogen lamp to precise temperatures during specific operations.

Fatigue properties of particle reinforced aluminium alloys

International Nuclear Information System (INIS)

Tabernig, B.J.

2000-06-01

In this work the particle reinforced Al-alloys 359 T6 + 20 % SiC and 2124 + 17 % SiC which differ significantly in their production and microstructure are investigated. Standard and in-situ tensile tests show, that in the powder metallurgically produced alloy 2124 reinforcement leads to a higher Young's modulus, yield and ultimate tensile stress where the cast alloy 359 + 20 % SiC exhibit increased stiffness, but low ductility due to cast porosity of some 100 μm. The failure mechanism governed by microstructural parameters is found to play an important role for ductility. The fatigue properties are investigated with specific regard to the influence of the in-service condition (load ratio, temperature, variable amplitude loading) in the foreseen applications in the automobile- and aerospace industry. Standard fatigue tests point out that the endurance limit is improved by reinforcement, but is strongly dependent on the size of given initial defects. The fatigue crack properties are characterised by standard crack growth curves and r(esistance)-curves for the threshold of stress intensity factor range. Both composites exhibit a higher effective threshold than their unreinforced alloys. Furthermore the fatigue resistance described by the R-curve as well as the long crack threshold are improved in the alloy 2124 + 17 % SiC. While in crack growth tests under constant amplitude loading the alloy 2124 + 17 % SiC shows lower crack growth rates than its unreinforced alloy, the opposite case is in the alloy 359 + 20 % SiC at high DK. Periodic overloads lead in the 359 + 20 % SiC to particle fracture at the crack tip and to a steeper increase in the crack growth rate. In the 2124 + 17% SiC the fatigue crack grows predominately in the matrix and a retardation effect due to overloads is observed. In order to describe the fatigue limit of components as a function of initial defect size an analytical concept is developed assuming that the fatigue limit is controlled by the

The hold-time effects on the low cycle fatigue behaviors of 316 SS in PWR primary environment

International Nuclear Information System (INIS)

Lee, Junho; Hong, Jong-Dae; Seo, Myung-Gyu; Jang, Changheui

2015-01-01

The effects of the environments on fatigue life of the structural materials used in nuclear power plants (NPPs) were known to be significant according to the extensive test results. Accordingly, the fatigue analysis procedures and the design fatigue curves were proposed in the ASME Code. However, the implication that the existing ASME design fatigue curves did not sufficiently reflect the effect of the operation conditions of nuclear power plants emerged as an issue to be resolved. One of possible reasons to explain the discrepancy is that the laboratory test conditions do not represent the actual plant transients. Therefore, it is necessary to clarify the effects of light water environments on fatigue life while considering more plant-relevant transient conditions such as hold-time. For this reason, this study will focus on the fatigue life of type 316 stainless steel (SS) in the pressurized water reactor (PWR) environments while incorporating the hold-time during the low cycle fatigue (LCF) test in simulated PWR environments. The objective of this study is to characterize the effects of hold-time on the fatigue life of austenitic stainless steels in PWR environments in comparison with the existing fixed strain rate results. Low cycle fatigue life tests were conducted for the type 316 SS in 310 .deg. C air and simulated PWR environments. To simulate the heat-up and cool-down transient, sub-peak strain holding during the down-hill of strain amplitude was chosen. Currently, LCF tests with 60 seconds holding are in progress. The 0.4, 0.04%/s strain rate condition test results are presented in this study, which shows somewhat longer fatigue life

The hold-time effects on the low cycle fatigue behaviors of 316 SS in PWR primary environment

Energy Technology Data Exchange (ETDEWEB)

Lee, Junho; Hong, Jong-Dae; Seo, Myung-Gyu; Jang, Changheui [KAIST, Daejeon (Korea, Republic of)

2015-05-15

The effects of the environments on fatigue life of the structural materials used in nuclear power plants (NPPs) were known to be significant according to the extensive test results. Accordingly, the fatigue analysis procedures and the design fatigue curves were proposed in the ASME Code. However, the implication that the existing ASME design fatigue curves did not sufficiently reflect the effect of the operation conditions of nuclear power plants emerged as an issue to be resolved. One of possible reasons to explain the discrepancy is that the laboratory test conditions do not represent the actual plant transients. Therefore, it is necessary to clarify the effects of light water environments on fatigue life while considering more plant-relevant transient conditions such as hold-time. For this reason, this study will focus on the fatigue life of type 316 stainless steel (SS) in the pressurized water reactor (PWR) environments while incorporating the hold-time during the low cycle fatigue (LCF) test in simulated PWR environments. The objective of this study is to characterize the effects of hold-time on the fatigue life of austenitic stainless steels in PWR environments in comparison with the existing fixed strain rate results. Low cycle fatigue life tests were conducted for the type 316 SS in 310 .deg. C air and simulated PWR environments. To simulate the heat-up and cool-down transient, sub-peak strain holding during the down-hill of strain amplitude was chosen. Currently, LCF tests with 60 seconds holding are in progress. The 0.4, 0.04%/s strain rate condition test results are presented in this study, which shows somewhat longer fatigue life.

An intriguing design concept to enhance the pulsatile fatigue life of self-expanding stents.

Science.gov (United States)

Hsiao, Hao-Ming; Yin, Ming-Ting

2014-02-01

Intravascular stenting has emerged as the primary treatment for vascular diseases and has received great attention from the medical community since its introduction two decades ago. The endovascular self-expanding stent is used to treat peripheral artery diseases; however, once implanted, these stents suffer from various cyclic motions caused by pulsatile blood pressure and daily activities. Due to this challenging environment, fatigue performance has become a critical issue for stent design. In this paper, a simple yet intriguing concept of stent design aimed at enhancing pulsatile fatigue life is investigated. The concept of this design is to shift the highly concentrated stresses/strains away from the crown and re-distribute them along the stress-free bar arm by tapering its strut width. Finite element models were developed to evaluate the mechanical integrity and pulsatile fatigue resistance of the stent to various loading conditions. Results show that the fatigue safety factor jumped to 2.5-3.0 times that of the standard stent with constant strut width. This is astonishing considering that the stent profile and scaffolding were not compromised. The findings of this paper provide an excellent approach to the optimization of future stent design to greatly improve stent fatigue performance.

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

International Nuclear Information System (INIS)

Steingrimsdottir, Kristin; Dahlberg, Magnus

2011-10-01

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

Solar-cell interconnect design for terrestrial photovoltaic modules

Science.gov (United States)

Mon, G. R.; Moore, D. M.; Ross, R. G., Jr.

1984-01-01

Useful solar cell interconnect reliability design and life prediction algorithms are presented, together with experimental data indicating that the classical strain cycle (fatigue) curve for the interconnect material does not account for the statistical scatter that is required in reliability predictions. This shortcoming is presently addressed by fitting a functional form to experimental cumulative interconnect failure rate data, which thereby yields statistical fatigue curves enabling not only the prediction of cumulative interconnect failures during the design life of an array field, but also the quantitative interpretation of data from accelerated thermal cycling tests. Optimal interconnect cost reliability design algorithms are also derived which may allow the minimization of energy cost over the design life of the array field.

Use of Neuber's rule to estimate the fatigue life of notched specimens of ASME SA 106-B steel piping in 2880C air

International Nuclear Information System (INIS)

Terrell, J.B.

1989-01-01

Fatigue strain-life tests were conducted on notched specimens of ADMESA 106-B piping steel at PWR operating temperatures (288 0 C (550 0 F)), under completely reversed loading. Fatigue limits at 10 7 cycles were estimated for smooth specimens to be 185 M Pa (26.8 ksi) at 24 0 C and 232 MPa (33.7 ksi) at 288 0 C. The higher fatigue strength observed at the PWR temperature is postulated to be caused by dynamic strain aging processes. However, a reduction in fatigue strength in the low cycle fatigue regime was observed in 288 0 C air environment tests, which may indicate that the current ASME Section III design curve for carbon steels is nonconservative in its positioning. Notch strain histories were estimated for the notched specimen tests using various interpretations of Neuber's rule. It was concluded that the use of the fatigue notch concentration factor (K f ) in the Neuber relation in conjunction with the uniaxial cyclic stress-strain curve provided the best correlation of notched specimen fatigue data with results obtained from smooth specimen tests. The notched specimen strain-life results derived from the application of Neuber's rule alone proved to be conservative when compared with smooth specimen test results to such an extent that Neuber-generated notch stresses and strain amplitudes cannot accurately be compared with the mean data curves derived from the ASME Section III fatigue curves for carbon steels which are based on net section stress measurements. (author)

Design of airborne imaging spectrometer based on curved prism

Science.gov (United States)

Nie, Yunfeng; Xiangli, Bin; Zhou, Jinsong; Wei, Xiaoxiao

2011-11-01

A novel moderate-resolution imaging spectrometer spreading from visible wavelength to near infrared wavelength range with a spectral resolution of 10 nm, which combines curved prisms with the Offner configuration, is introduced. Compared to conventional imaging spectrometers based on dispersive prism or diffractive grating, this design possesses characteristics of small size, compact structure, low mass as well as little spectral line curve (smile) and spectral band curve (keystone or frown). Besides, the usage of compound curved prisms with two or more different materials can greatly reduce the nonlinearity inevitably brought by prismatic dispersion. The utilization ratio of light radiation is much higher than imaging spectrometer of the same type based on combination of diffractive grating and concentric optics. In this paper, the Seidel aberration theory of curved prism and the optical principles of Offner configuration are illuminated firstly. Then the optical design layout of the spectrometer is presented, and the performance evaluation of this design, including spot diagram and MTF, is analyzed. To step further, several types of telescope matching this system are provided. This work provides an innovational perspective upon optical system design of airborne spectral imagers; therefore, it can offer theoretic guide for imaging spectrometer of the same kind.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-15

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

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

International Nuclear Information System (INIS)

Shin, Myung Soo; Park, Jun Hyu; Kim, Jung Yup

2016-01-01

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

Device Design and Test of Fatigue Behaviour of Expansion Anchor Subjected to Tensile Loads

Directory of Open Access Journals (Sweden)

Zhang Jinfeng

2016-01-01

Full Text Available In order to study on the fatigue behaviour of expansion anchor (M16, grade 8.8 for overhead contact system in electrification railways, a set of safe, practical loading device is designed and a fatigue test campaign was carried out at structural laboratory of China Academy of Building Research on expansion anchor embedded in concrete block. The mobile frame of the loading device was designed well by finite-element simulation. According to some fatigue performance test of expansion anchor with different size and form, the device have been assessed experimentally its dependability. The results were found that no fatigue damage phenomenon occurred in all specimens after 2×106 cycles tensile fatigue test in this specific series. It shows that in the condition of medium level or slightly lower maximum stress limit and nominal stress range, expansion bolt has good fatigue resistance. The biggest relative displacement and the residual relative displacement after test (Δδ = δ2-δ1 was also strongly lower than the symbol of the fatigue test failure index of this specific series (0.5mm in the high cycle fatigue regime. The ultimate tension failures mode after fatigue tests in all tested samples take place in the concrete anchorage zone. The reduction range of the ultimate tensile strength properties of the anchorage system was not obvious, and the concrete was seen to be the weakest link of the system.

Experimental Method for Plotting S-N Curve with a Small Number of Specimens

Directory of Open Access Journals (Sweden)

Strzelecki Przemysław

2016-12-01

Full Text Available The study presents two approaches to plotting an S-N curve based on the experimental results. The first approach is commonly used by researchers and presented in detail in many studies and standard documents. The model uses a linear regression whose parameters are estimated by using the least squares method. A staircase method is used for an unlimited fatigue life criterion. The second model combines the S-N curve defined as a straight line and the record of random occurrence of the fatigue limit. A maximum likelihood method is used to estimate the S-N curve parameters. Fatigue data for C45+C steel obtained in the torsional bending test were used to compare the estimated S-N curves. For pseudo-random numbers generated by using the Mersenne Twister algorithm, the estimated S-N curve for 10 experimental results plotted by using the second model, estimates the fatigue life in the scatter band of the factor 3. The result gives good approximation, especially regarding the time required to plot the S-N curve.

Designing an ASIP for cryptographic pairings over Barreto-Naehrig curves

NARCIS (Netherlands)

Kammler, D.; Zhang, D.; Schwabe, P.; Scharwaechter, H.; Langenberg, M.; Auras, D.; Ascheid, G.; Mathar, R.; Clavier, C.; Gaj, K.

2009-01-01

This paper presents a design-space exploration of an application-specific instruction-set processor (ASIP) for the computation of various cryptographic pairings over Barreto-Naehrig curves (BN curves). Cryptographic pairings are based on elliptic curves over finite fields—in the case of BN curves a

Probabilistic Calibration of Fatigue Design Factors for Offshore Wind Turbine Support Structures

DEFF Research Database (Denmark)

Ramirez, José Rangel; Sørensen, John Dalsgaard

2010-01-01

for the considered offshore wind turbines in such a way that the specific uncertainties for the fatigue life are accounted in a rational manner. Similar approaches have been used for offshore oil & gas sub-structures, but the required reliability level for offshore wind turbines is generally lower and the fatigue......This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used...

Cumulative fatigue and creep-fatigue damage at 3500C on recrystallized zircaloy 4

International Nuclear Information System (INIS)

Brun, G.; Pelchat, J.; Floze, J.C.; Galimberti, M.

1985-06-01

An experimental programme undertaken by C.E.A., E.D.F. and FRAGEMA with the aim of characterizing the fatigue and creep fatigue behaviour of zircaloy-4 following annealing treatments (recrystallized, stress-delived) is in progress. The results given below concern only recrystallized material. Cyclic properties, low-cycle fatigue curves and creep behaviour laws under stresses have been established. Sequential tests of pure fatigue and creep-fatigue were performed. The cumulative life fractions at fracture depend on the sequence of leading, stress history and number of cycles of prestressing. The MINER's rule appears to be conservative with regard to a low-high loading sequence whereas it is not for the reverse high-low loading sequences. Fatigue and creep damage are not interchangeable. Pre-creep improves the fatigue resistance. Pre-fatigue improves the creep strength as long as the beneficial effect of cyclic hardening overcomes the damaging effect of surface cracking. The introduction of a tension hold time into the fatigue cycle slightly increases cyclic hardening and reduces the number of cycles to failure. For hold times of less than one hour, the sum of fatigue and creep life fractions is closed to one

Ultrathin flexible piezoelectric sensors for monitoring eye fatigue

Science.gov (United States)

Lü, Chaofeng; Wu, Shuang; Lu, Bingwei; Zhang, Yangyang; Du, Yangkun; Feng, Xue

2018-02-01

Eye fatigue is a symptom induced by long-term work of both eyes and brains. Without proper treatment, eye fatigue may incur serious problems. Current studies on detecting eye fatigue mainly focus on computer vision detect technology which can be very unreliable due to occasional bad visual conditions. As a solution, we proposed a wearable conformal in vivo eye fatigue monitoring sensor that contains an array of piezoelectric nanoribbons integrated on an ultrathin flexible substrate. By detecting strains on the skin of eyelid, the sensors may collect information about eye blinking, and, therefore, reveal human’s fatigue state. We first report the design and fabrication of the piezoelectric sensor and experimental characterization of voltage responses of the piezoelectric sensors. Under bending stress, the output voltage curves yield key information about the motion of human eyelid. We also develop a theoretical model to reveal the underlying mechanism of detecting eyelid motion. Both mechanical load test and in vivo test are conducted to convince the working performance of the sensors. With satisfied durability and high sensitivity, this sensor may efficiently detect abnormal eyelid motions, such as overlong closure, high blinking frequency, low closing speed and weak gazing strength, and may hopefully provide feedback for assessing eye fatigue in time so that unexpected situations can be prevented.

Design Optimization and Fatigue Analysis of Laser Stake Welded Connections

National Research Council Canada - National Science Library

Singh, Anshuman; Vel, Senthil S; Caccese, Vincent

2008-01-01

This report summanzes research on the design and fatigue analysis of laser-stake welded connections performed at the University of Maine from January 2006 to December 2007 for the Structural Response...

Placement Design of Changeable Message Signs on Curved Roadways

Directory of Open Access Journals (Sweden)

Zhongren Wang, Ph.D. P.E. T.E.

2015-01-01

Full Text Available This paper presented a fundamental framework for Changeable Message Sign (CMS placement design along roadways with horizontal curves. This analytical framework determines the available distance for motorists to read and react to CMS messages based on CMS character height, driver's cone of vision, CMS pixel's cone of legibility, roadway horizontal curve radius, and CMS lateral and vertical placement. Sample design charts were developed to illustrate how the analytical framework may facilitate CMS placement design.

The Identification of Fatigue Resistant and Fatigue Susceptible Individuals

National Research Council Canada - National Science Library

Harrison, Richard; Chaiken, Scott; Harville, Donald; Fischer, Joseph; Fisher, Dion; Whitmore, Jeff

2008-01-01

The present study was designed to target two specific areas regarding fatigue. The primary purpose was to begin investigations into possible genetic markers linked to fatigue resistance and fatigue susceptibility...

Estimates of thermal fatigue due to beam interruptions for an ALMR-type ATW

International Nuclear Information System (INIS)

Dunn, F. E.; Wade, D. C.

1999-01-01

Thermal fatigue due to beam interruptions has been investigated in a sodium cooled ATW using the Advanced Liquid Metal mod B design as a basis for the subcritical source driven reactor. A k eff of 0.975 was used for the reactor. Temperature response in the primary coolant system was calculated, using the SASSYS- 1 code, for a drop in beam current from full power to zero in 1 microsecond.. Temperature differences were used to calculate thermal stresses. Fatigue curves from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code were used to determine the number of cycles various components should be designed for, based on these thermal stresses

Fatigue limit of Zircaloy-2 under variable one-directional tension and temperature 300 deg C

International Nuclear Information System (INIS)

Spasic, Z.; Simic, G.

1968-11-01

A vacuum chamber wad designed and constructed. It was suitable for study of materials at higher temperatures in vacuum or controlled atmospheres. Zircaloy-2 fatigue at 300 deg C in argon atmosphere was measured. Character of strain is variable one directional (A=1) tension. Obtained results are presented in tables and in the form of Veler's curve. The obtained fatigue limit was σ - 15 kp/mm 2 . The Locati method was allied as well and fatigue limit value obtained was 15,75 kp/mm 2 . Error calculated in reference to the previous value obtained by classical methods was 5% [sr

Fatigue life response of ASME SA 106-B steel in pressurized water reactor environments

International Nuclear Information System (INIS)

Terrell, J.B.

1989-01-01

Fatigue strain-life tests were conducted on ASMESA 106-B piping steel base metal and weld metal specimens in 288 0 C (550 0 F) pressurized water reactor (PWR) environments as a function of strain amplitude, strain ratio, notch acuity, and cyclic frequency. Notched base metal specimens tested at 0.017 Hz in 0.001 part per million (ppm) dissolved oxygen environments nearly completely used up the margins of safety of 2 on stress and 20 on cycles incorporated into the ASMA Section III design curve for carbon steels. Tests conducted with smooth base metal and weld metal specimens at 1.0 Hz showed virtually no degradation in cycles to failure when compared to 288 0 C air test results. In all cases, however, the effect of temperature alone reduced the margin of safety offered by the design curve in the low cycle regime for the test specimens. Comparison between the fatigue life results of smooth and notched specimens suggests that fatigue crack initiation is not significantly affected by 0.001 ppm dissolved oxygen, and that most of the observed degradation may be attributed to crack growth acceleration. These results suggest that the ASMA Section III methodology should be reviewed, taking into account the PWR environment variables which degrade the fatigue life of pressure-retaining components. (author)

Fatigue life response of ASME SA 106-B steel in pressurized water reactor environments

Energy Technology Data Exchange (ETDEWEB)

Terrell, J B [Materials Engineering Associates, Inc., Lanham, MD (USA)

1989-01-01

Fatigue strain-life tests were conducted on ASMESA 106-B piping steel base metal and weld metal specimens in 288{sup 0}C (550{sup 0}F) pressurized water reactor (PWR) environments as a function of strain amplitude, strain ratio, notch acuity, and cyclic frequency. Notched base metal specimens tested at 0.017 Hz in 0.001 part per million (ppm) dissolved oxygen environments nearly completely used up the margins of safety of 2 on stress and 20 on cycles incorporated into the ASMA Section III design curve for carbon steels. Tests conducted with smooth base metal and weld metal specimens at 1.0 Hz showed virtually no degradation in cycles to failure when compared to 288{sup 0}C air test results. In all cases, however, the effect of temperature alone reduced the margin of safety offered by the design curve in the low cycle regime for the test specimens. Comparison between the fatigue life results of smooth and notched specimens suggests that fatigue crack initiation is not significantly affected by 0.001 ppm dissolved oxygen, and that most of the observed degradation may be attributed to crack growth acceleration. These results suggest that the ASMA Section III methodology should be reviewed, taking into account the PWR environment variables which degrade the fatigue life of pressure-retaining components. (author).

Fatigue and damage tolerance scatter models

Science.gov (United States)

Raikher, Veniamin L.

1994-09-01

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

Fatigue properties of type 316LN stainless steel in air and mercury

International Nuclear Information System (INIS)

Strizak, J.P.; Tian, H.; Liaw, P.K.; Mansur, L.K.

2005-01-01

An extensive fatigue testing program on 316LN stainless steel was recently carried out to support the design of the mercury target container for the spallation neutron source (SNS) that is currently under construction at the Oak Ridge National Laboratory in the United States. The major objective was to determine the effects of mercury on fatigue behavior. The S-N fatigue behavior of 316LN stainless steel is characterized by a family of bilinear fatigue curves which are dependent on frequency, environment, mean stress and cold work. Generally, fatigue life increases with decreasing stress and levels off in the high cycle region to an endurance limit below which the material will not fail. For fully reversed loading as well as tensile mean stress loading conditions mercury had no effect on endurance limit. However, at higher stresses a synergistic relationship between mercury and cyclic loading frequency was observed at low frequencies. As expected, fatigue life decreased with decreasing frequency, but the response was more pronounced in mercury compared with air. As a result of liquid metal embrittlement (LME), fracture surfaces of specimens tested in mercury showed widespread brittle intergranular cracking as opposed to typical transgranular cracking for specimens tested in air. For fully reversed loading (zero mean stress) the effect of mercury disappeared as frequency increased to 10 Hz. For mean stress conditions with R-ratios of 0.1 and 0.3, LME was still evident at 10 Hz, but at 700 Hz the effect of mercury had disappeared (R 0.1). Further, for higher R-ratios (0.5 and 0.75) fatigue curves for 10 Hz showed no environmental effect. Finally, cold working (20%) increased tensile strength and hardness, and improved fatigue resistance. Fatigue behavior at 10 and 700 Hz was similar and no environmental effect was observed

Fatigue properties of type 316LN stainless steel in air and mercury

Science.gov (United States)

Strizak, J. P.; Tian, H.; Liaw, P. K.; Mansur, L. K.

2005-08-01

An extensive fatigue testing program on 316LN stainless steel was recently carried out to support the design of the mercury target container for the spallation neutron source (SNS) that is currently under construction at the Oak Ridge National Laboratory in the United States. The major objective was to determine the effects of mercury on fatigue behavior. The S- N fatigue behavior of 316LN stainless steel is characterized by a family of bilinear fatigue curves which are dependent on frequency, environment, mean stress and cold work. Generally, fatigue life increases with decreasing stress and levels off in the high cycle region to an endurance limit below which the material will not fail. For fully reversed loading as well as tensile mean stress loading conditions mercury had no effect on endurance limit. However, at higher stresses a synergistic relationship between mercury and cyclic loading frequency was observed at low frequencies. As expected, fatigue life decreased with decreasing frequency, but the response was more pronounced in mercury compared with air. As a result of liquid metal embrittlement (LME), fracture surfaces of specimens tested in mercury showed widespread brittle intergranular cracking as opposed to typical transgranular cracking for specimens tested in air. For fully reversed loading (zero mean stress) the effect of mercury disappeared as frequency increased to 10 Hz. For mean stress conditions with R-ratios of 0.1 and 0.3, LME was still evident at 10 Hz, but at 700 Hz the effect of mercury had disappeared ( R = 0.1). Further, for higher R-ratios (0.5 and 0.75) fatigue curves for 10 Hz showed no environmental effect. Finally, cold working (20%) increased tensile strength and hardness, and improved fatigue resistance. Fatigue behavior at 10 and 700 Hz was similar and no environmental effect was observed.

Design optimization and fatigue testing of an electronically-driven mechanically-resonant cantilever spring mechanism

International Nuclear Information System (INIS)

Kheng, Lim Boon; Kean, Koay Loke; Gitano-Briggs, Horizon

2010-01-01

A light scanning device consisting of an electronically-driven mechanically-resonant cantilever spring-mirror system has been developed for innovative lighting applications. The repeated flexing of the cantilever spring during operation can lead to premature fatigue failure. A model was created to optimize the spring design. The optimized spring design can reduce stress by approximately one-third from the initial design. Fatigue testing showed that the optimized spring design can operate continuously for over 1 month without failure. Analysis of failures indicates surface cracks near the root of the spring are responsible for the failures.

Load assumption for fatigue design of structures and components counting methods, safety aspects, practical application

CERN Document Server

Köhler, Michael; Pötter, Kurt; Zenner, Harald

2017-01-01

Understanding the fatigue behaviour of structural components under variable load amplitude is an essential prerequisite for safe and reliable light-weight design. For designing and dimensioning, the expected stress (load) is compared with the capacity to withstand loads (fatigue strength). In this process, the safety necessary for each particular application must be ensured. A prerequisite for ensuring the required fatigue strength is a reliable load assumption. The authors describe the transformation of the stress- and load-time functions which have been measured under operational conditions to spectra or matrices with the application of counting methods. The aspects which must be considered for ensuring a reliable load assumption for designing and dimensioning are discussed in detail. Furthermore, the theoretical background for estimating the fatigue life of structural components is explained, and the procedures are discussed for numerous applications in practice. One of the prime intentions of the authors ...

Fatigue Analysis of Load-Carrying Fillet Welds

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard; Tychsen, Jesper; Andersen, Jens Ulfkjær

2006-01-01

that the degree of bending (DOB) has an influence on the fatigue lifetime. The fatigue lifetime decreases significantly when increasing the bending stress. In order to take into account the effect of the bending, a new fatigue stress definition applicable for fillet welds failing through the weld is presented....... Using the test results, it is shown that the new definition of fatigue stress can be used for a wide range of DOB with a low standard deviation of the resulting SN curve....

The Installation for Fatigue and Destruction Tests of Thin Wires

Directory of Open Access Journals (Sweden)

D. V. Prosvirin

2015-01-01

Full Text Available The fatigue strength of high-strength materials such as wire is, essentially, dependent on the surface state, stress concentrators, non-metal inclusions, etc. Multifactorial process of damage accumulation and fracture under cyclic loading makes it difficult to predict the durability of structural materials. So fatigue tests, taking into account the operating conditions of stress exposure as much as possible, are of special importance.A feature of the wire fatigue tests is that it is complicated to secure the samples and create the alternate stresses. Currently, there is no equipment to study the fatigue strength of the wire in accordance with GOST 1579-93. Partly the problem of the wire fatigue tests was solved owing to using the installation developed in IMET RAS and considered as the base case. However, the installation has significant disadvantages, namely: a complicated for implementing in practice method to control stresses in the sample; an imperfect system to count cycles; an incapability to change the engine speed of the motor and thus, the frequency of loading.In developing the new design all the basic blocks of installation were upgraded such as drive unit; unit to control stress in the sample; unit for determining the number of cycles to failure.To change the stresses in the sample the paper offers to use the platform from polymethylmethacrylate with slotted curved channels of different radii. The stresses in the sample are dependent on the channel radius R, the wire diameter d and the modulus of elasticity E of the material and may vary in the range of 200 - 1200 MPa. The use of CNC machines in cutting the channels allows stress adjustment within ± 0,1 MPa.The developed design is used to drive the rotation of the wire and makes it possible to change the frequency of loading in the range of 0 - 100 Hz. It is shown that the use of the closing relay in drive design and the transition to an electronic system of determining the number of

Effects of loading sequences and size of repeated stress block of loads on fatigue life calculated using fatigue functions

International Nuclear Information System (INIS)

Schott, G.

1989-01-01

It is well-known that collective form, stress intensity and loading sequence of individual stresses as well as size of repeated stress blocks can influence fatigue life, significantly. The basic variant of the consecutive Woehler curve concept will permit these effects to be involved into fatigue life computation. The paper presented will demonstrate that fatigue life computations using fatigue functions reflect the loading sequence effect with multilevel loading precisely and provide reliable fatigue life data. Effects of size of repeated stress block and loading sequence on fatigue life as observed with block program tests can be reproduced using the new computation method. (orig.) [de

Deformation Properties and Fatigue of Bituminous Mixtures

Directory of Open Access Journals (Sweden)

Frantisek Schlosser

2013-01-01

Full Text Available Deformation properties and fatigue performance are important characteristics of asphalt bound materials which are used for construction of pavement layers. Viscoelastic asphalt mixtures are better characterized via dynamic tests. This type of tests allows us to collate materials with regard to axle vibrations which lie usually in the range of 6 Hz–25 Hz for standard conditions. Asphalt modified for heat sensitivity in the range from −20°C to +60°C has significant impact on the overall characteristics of the mixture. Deformation properties are used as inputs for empirical mixture design, and fatigue performance of asphalt mixtures reflects the parameters of functional tests. Master curves convey properties of asphalt mixtures for various conditions and allow us to evaluate them without the need of time expensive testing.

Comparative evaluation of cyclic fatigue resistance of D-RaCe and ProTaper retreatment instruments in curved artificial canals.

Science.gov (United States)

Topçuoğlu, H S; Topçuoğlu, G; Aktı, A

2016-06-01

To compare the cyclic fatigue resistance of D-RaCe and ProTaper rotary nickel-titanium (NiTi) retreatment files when used in curved artificial canals. A total of 120 new D-RaCe DR2 and ProTaper D3 retreatment files were tested in stainless steel artificial canals having 45° and 60° angles of curvature. Thirty instruments of each of the file systems were tested in both angles of curvature (n = 30). The retreatment instruments were rotated until fracture to calculate the number of cycles to failure. The length of each fractured fragment was recorded. Data were analysed by independent sample t-test. Fractured surfaces of the instruments were analysed by scanning electron microscopy. In the canal with 45° angle of curvature, no significant difference was observed between the retreatment systems (P > 0.05); on the other hand, in the canal with 60° angle of curvature, D-RaCe DR2 instruments had greater cyclic fatigue resistance than ProTaper D3 (P  0.05). The fracture surfaces of the instruments had morphologic characteristics of ductile fracture. D-RaCe DR2 instrument exhibited greater cyclic fatigue resistance than ProTaper D3 only in root canals with 60° angle of curvature. © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Effect of microstructure on low cycle fatigue properties of ODS steels

Energy Technology Data Exchange (ETDEWEB)

Kubena, Ivo, E-mail: kubena@ipm.cz [IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, Brno (Czech Republic); Fournier, Benjamin [CEA/DEN/DANS/DMN/SRMA, Bat. 453, 91191 Gif-sur-Yvette Cedex (France); Kruml, Tomas [CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, Brno (Czech Republic)

2012-05-15

Highlights: Black-Right-Pointing-Pointer Three various ODS steels are studied and compared. Black-Right-Pointing-Pointer Low cycle fatigue data at RT, 650 Degree-Sign C and 750 Degree-Sign C are given. Black-Right-Pointing-Pointer Microstructural characterization. Black-Right-Pointing-Pointer Detailed discussion of strengthening mechanisms. - Abstract: Low cycle fatigue properties at room temperature, 650 Degree-Sign C and 750 Degree-Sign C of three high chromium steels (9%Cr ferritic-martensitic and two 14%Cr ferritic steels) strengthened by oxide dispersion were studied and compared. Cyclic softening/hardening curves, cyclic deformation curves, S-N curves and Coffin-Manson curves are presented together with microstructural observations. Differences in cyclic response, stress level and fatigue life are attributed to differences in the matrix microstructure. The oxide particles stabilize the cyclic response, even if cyclic softening is detected for some experimental conditions. The strength of these steels is discussed in terms of strengthening mechanisms such as grain size effect, particle-dislocations interaction and dislocation density. Comparing three different ODS steels offers an opportunity to tests the contribution of individual mechanisms to the cyclic strength. The reduction of fatigue life in one of the ferritic steels is explained by the presence of large grains, facilitating the fatigue crack nucleation and the early growth.

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

Science.gov (United States)

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

2016-08-01

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

Effects of LWR coolant environments on fatigue lives of austenitic stainless steels

International Nuclear Information System (INIS)

Chopra, O.K.; Gavenda, D.J.

1997-01-01

The ASME Boiler and Pressure Vessel Code fatigue design 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 life of pressure vessel and piping materials in light water reactor (LWR) environments. Fatigue tests have been conducted on Types 304 and 316NG stainless steel in air and LWR environments to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on fatigue lives of these steels. The results confirm the significant decrease in fatigue life in water. The environmentally assisted decrease in fatigue life depends both on strain rate and DO content in water. A decrease in strain rate from 0.4 to 0.004%/s decreases fatigue life by a factor of ∼ 8. However, unlike carbon and low-alloy steels, environmental effects are more pronounced in low-DO than in high-DO water. At ∼ 0.004%/s strain rate, reduction in fatigue life in water containing <10 ppb D is greater by a factor of ∼ 2 than in water containing ≥ 200 ppb DO. Experimental results have been compared with estimates of fatigue life based on the statistical model. The formation and growth of fatigue cracks in austenitic stainless steels in air and LWR environments are discussed

Fatigue Analysis of Magnesium Alloys Components for Car Industry

Science.gov (United States)

Marsavina, Liviu; Rusu, Lucian; Șerban, Dan Andrei; Negru, Radu Marcel; Cernescu, Anghel

2017-12-01

The use of magnesium alloys in the automotive industry increased in the last decade because of their low weight and relative good mechanical properties. However, the variable loading conditions require a good fatigue behavior. This paper summaries the fatigue properties of magnesium alloys and presents new fatigue curve results for die cast AM50 magnesium alloy.

Low cycle fatigue behavior of Sanicro25 steel at room and at elevated temperature

Energy Technology Data Exchange (ETDEWEB)

Polák, Jaroslav, E-mail: polak@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); CEITEC, Institute of Physics of Materials Academy of Sciences of the Czech Republic, Žižkova 22, Brno (Czech Republic); Petráš, Roman; Heczko, Milan; Kuběna, Ivo [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); Kruml, Tomáš [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); CEITEC, Institute of Physics of Materials Academy of Sciences of the Czech Republic, Žižkova 22, Brno (Czech Republic); Chai, Guocai [Sandvik Materials Technology, SE-811 81 Sandviken (Sweden); Linköping University, Engineering Materials, SE-581 83 Linköping (Sweden)

2014-10-06

Austenitic heat resistant Sanicro 25 steel developed for high temperature applications in power generation industry has been subjected to strain controlled low cycle fatigue tests at ambient and at elevated temperature in a wide interval of strain amplitudes. Fatigue hardening/softening curves, cyclic stress–strain curves and fatigue life curves were evaluated at room temperature and at 700 °C. The internal dislocation structures of the material at room and at elevated temperature were studied using transmission electron microscopy. High resolution surface observations and FIB cuts revealed early damage at room temperature in the form of persistent slip bands and at elevated temperature as oxidized grain boundary cracks. Dislocation arrangement study and surface observations were used to identify the cyclic slip localization and to discuss the fatigue softening/hardening behavior and the temperature dependence of the fatigue life.

Reliability Based Calibration of Fatigue Design Guidelines for Ship Structures

DEFF Research Database (Denmark)

Folsø, Rasmus; Otto, S.; Parmentier, G.

2002-01-01

A simple reliability based framework is applied to calibrate a new set of fatigue design guidelines. This new guideline considers two different approaches for the assessment of both loads, stresses and local stress raising effects, and partial safety factors must be given for any combination...

Next-Generation Intensity-Duration-Frequency Curves for Hydrologic Design in Snow-Dominated Environments

Energy Technology Data Exchange (ETDEWEB)

Yan, Hongxiang [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland Washington United States; Sun, Ning [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland Washington United States; Wigmosta, Mark [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland Washington United States; Distinguished Faculty Fellow, Department of Civil and Environmental Engineering, University of Washington, Seattle Washington United States; Skaggs, Richard [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland Washington United States; Hou, Zhangshuan [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland Washington United States; Leung, Ruby [Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland Washington United States

2018-02-01

There is a renewed focus on the design of infrastructure resilient to extreme hydrometeorological events. While precipitation-based intensity-duration-frequency (IDF) curves are commonly used as part of infrastructure design, a large percentage of peak runoff events in snow-dominated regions are caused by snowmelt, particularly during rain-on-snow (ROS) events. In these regions, precipitation-based IDF curves may lead to substantial over-/under-estimation of design basis events and subsequent over-/under-design of infrastructure. To overcome this deficiency, we proposed next-generation IDF (NG-IDF) curves, which characterize the actual water reaching the land surface. We compared NG-IDF curves to standard precipitation-based IDF curves for estimates of extreme events at 376 Snowpack Telemetry (SNOTEL) stations across the western United States that each had at least 30 years of high-quality records. We found standard precipitation-based IDF curves at 45% of the stations were subject to under-design, many with significant under-estimation of 100-year extreme events, for which the precipitation-based IDF curves can underestimate water potentially available for runoff by as much as 125% due to snowmelt and ROS events. The regions with the greatest potential for under-design were in the Pacific Northwest, the Sierra Nevada Mountains, and the Middle and Southern Rockies. We also found the potential for over-design at 20% of the stations, primarily in the Middle Rockies and Arizona mountains. These results demonstrate the need to consider snow processes in the development of IDF curves, and they suggest use of the more robust NG-IDF curves for hydrologic design in snow-dominated environments.

Review of provisions on corrosion fatigue and stress corrosion in WWER and Western LWR Codes and Standards

International Nuclear Information System (INIS)

Buckthorpe, D.; Filatov, V.; Tashkinov, A.; Evropin, S.V.; Matocha, K.; Guinovart, J.

2003-01-01

Results are presented from a collaborative project performed on behalf of the European Commission, Working Group Codes and Standards. The work covered the contents of current codes and standards, plant experience and R and D results. Current fatigue design rules use S-N curves based on tests in air. Although WWER and LWR design curves are often similar they are derived, presented and used in different ways and it is neither convenient nor appropriate to harmonise them. Similarly the fatigue crack growth laws used in the various design and in-service inspection rules differ significantly with respect to both growth rates in air and the effects of water reactor environments. Harmonised approaches to the effects of WWER and LWR environments are possible based on results from R and D programmes carried out over the last decade. For carbon and low alloy steels a consistent approach to both crack initiation and growth can be formulated based on the superposition of environmentally assisted cracking effects on the fatigue crack development. The approach indicates that effects of the water environment are minimal given appropriate control of the oxygen content of the water and/or the sulphur content of the steel. For austenitic stainless steels a different mechanisms may apply and a harmonised approach is possible at present only for S-N curves. Although substantial progress has been made with respect to corrosion fatigue, more data and a clearer understanding are required in order to write code provisions particularly in the area of high cycle fatigue. Reactor operation experience shows stress corrosion cracking of austenitic steels is the most common cause of failure. These failures are associated with high residual stresses combined with high levels of dissolved oxygen or the presence of contaminants. For primary circuit internals there is a potential threat to integrity from irradiated assisted stress corrosion cracking. Design and in-service inspection rules do not at

Study of the effect of an equi-biaxial loading on the fatigue lifetime of austenitic stainless steel

International Nuclear Information System (INIS)

Bradai, Soumaya

2014-01-01

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures.In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension. The aim of this study is to present the experimental and numerical results obtained with a device 'FABIME2' developed in the LISN in collaboration with EDF and AREVA. The association of the experimental results, obtained on the new experimental fatigue device FABIME2, with the numerical analyses obtained by FEM simulation with Cast3M code, has enabled to define the aggravating effect of the equi-biaxial fatigue loading. However, this effect is covered by the Design fatigue curve defined from the nuclear industry. For the crack propagation, a first simplified approach enables to study the kinetic behavior of crack propagation in equi-biaxial fatigue. (author) [fr

Fatigue resistance of engine-driven rotary nickel-titanium endodontic instruments.

Science.gov (United States)

Chaves Craveiro de Melo, Marta; Guiomar de Azevedo Bahia, Maria; Lopes Buono, Vicente Tadeu

2002-11-01

A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instruments was performed, aiming to access the influence of the cutting flute design and of the size of the files that reach the working length in curved canal shaping. Geometrical conditions similar to those found in practice were used. Series 29 #5 ProFile, together with #6 and #8 Quantec instruments, were tested in artificial canals with a 45-degree angle of curvature and 5-mm radius of curvature. It was observed that the size of the instrument, which determines the maximum strain amplitude during cyclic deformation, is the most important factor controlling fatigue resistance. The effect of heat sterilization on the fatigue resistance of the instruments was also examined. The results obtained indicate that the application of five sterilization procedures in dry heat increases the average number of cycles to failure of unused instruments by approximately 70%.

Update and Improve Subsection NH - Alternative Simplified Creep-Fatigue Design Methods

International Nuclear Information System (INIS)

Asayama, Tai

2009-01-01

This report described the results of investigation on Task 10 of DOE/ASME Materials NGNP/Generation IV Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 10 is to Update and Improve Subsection NH -- Alternative Simplified Creep-Fatigue Design Methods. Five newly proposed promising creep-fatigue evaluation methods were investigated. Those are (1) modified ductility exhaustion method, (2) strain range separation method, (3) approach for pressure vessel application, (4) hybrid method of time fraction and ductility exhaustion, and (5) simplified model test approach. The outlines of those methods are presented first, and predictability of experimental results of these methods is demonstrated using the creep-fatigue data collected in previous Tasks 3 and 5. All the methods (except the simplified model test approach which is not ready for application) predicted experimental results fairly accurately. On the other hand, predicted creep-fatigue life in long-term regions showed considerable differences among the methodologies. These differences come from the concepts each method is based on. All the new methods investigated in this report have advantages over the currently employed time fraction rule and offer technical insights that should be thought much of in the improvement of creep-fatigue evaluation procedures. The main points of the modified ductility exhaustion method, the strain range separation method, the approach for pressure vessel application and the hybrid method can be reflected in the improvement of the current time fraction rule. The simplified mode test approach would offer a whole new advantage including robustness and simplicity which are definitely attractive but this approach is yet to be validated for implementation at this point. Therefore, this report recommends the following two steps as a course of improvement of NH based on newly proposed creep-fatigue evaluation

The Fatigue Life Prediction of Train Wheel Rims Containing Spherical Inclusions

Science.gov (United States)

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

2018-03-01

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

Statistical analysis of fatigue crack propagation data of materials from ancient portuguese metallic bridges

Directory of Open Access Journals (Sweden)

J A F O. Correia

2017-10-01

Full Text Available In Portugal there is a number of old metallic riveted railway and highway bridges that were erected by the end of the 19th century and beginning of the 20th century, and are still in operation, requiring inspections and remediation measures to overcome fatigue damage. Residual fatigue life predictions should be based on actual fatigue data from bridge materials which is scarce due to the material specificities. Fatigue crack propagation data of materials from representative Portuguese riveted bridges, namely the Pinh�o and Luiz I road bridges, the Viana road/railway bridge, the F�o road bridge and the Trez�i railway bridge were considered in this study. The fatigue crack growth rates were correlated using the Pariss law. Also, a statistical analysis of the pure mode I fatigue crack growth (FCG data available for the materials from the ancient riveted metallic bridges is presented. Based on this analysis, design FCG curves are proposed and compared with BS7910 standard proposal, for the Paris region, which is one important fatigue regime concerning the application of the Fracture Mechanics approaches, to predict the remnant fatigue life of structural details

Computer based approach to fatigue analysis and design

International Nuclear Information System (INIS)

Comstock, T.R.; Bernard, T.; Nieb, J.

1979-01-01

An approach is presented which uses a mini-computer based system for data acquisition, analysis and graphic displays relative to fatigue life estimation and design. Procedures are developed for identifying an eliminating damaging events due to overall duty cycle, forced vibration and structural dynamic characteristics. Two case histories, weld failures in heavy vehicles and low cycle fan blade failures, are discussed to illustrate the overall approach. (orig.) 891 RW/orig. 892 RKD [de

Fatigue evaluation of socket welded piping in nuclear power plant

International Nuclear Information System (INIS)

Vecchio, R.S.

1996-01-01

Fatigue failures in piping systems occur, almost without exception, at the welded connections. In nuclear power plant systems, such failures occur predominantly at the socket welds of small diameter piping ad fillet attachment welds under high-cycle vibratory conditions. Nearly all socket weld fatigue failures are identified by leaks which, though not high in volume, generally are costly due to attendant radiological contamination. Such fatigue cracking was recently identified in the 3/4 in. diameter recirculation and relief piping socket welds from the reactor coolant system (RCS) charging pumps at a nuclear power plant. Consequently, a fatigue evaluation was performed to determine the cause of cracking and provide an acceptable repair. Socket weld fatigue life was evaluated using S-N type fatigue life curves for welded structures developed by AASHTO and the assessment of an effective cyclic stress range adjacent to each socket weld. Based on the calculated effective tress ranges and assignment of the socket weld details to the appropriate AASHTO S-N curves, the socket weld fatigue lives were calculated and found to be in excellent agreement with the accumulated cyclic life to-date

Fatigue properties of X80 pipeline steels with ferrite/bainite dual-phase microstructure

Energy Technology Data Exchange (ETDEWEB)

Zhao, Zuo-peng [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China); Qiao, Gui-ying [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China); Key Lab of Applied Chemistry of Hebei Province and School of Environment and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Tang, Lei [Key Lab of Applied Chemistry of Hebei Province and School of Environment and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Zhu, Hong-wei; Liao, Bo [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China); Xiao, Fu-ren, E-mail: frxiao@ysu.edu.cn [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China)

2016-03-07

Fatigue properties are important parameters for the safety design and security evaluation of gas transmission pipelines. In this work, the fatigue life at different stresses of full-thickness X80 pipeline steel plates with a ferrite/bainite dual-phase microstructure was investigated using a MTS servo-hydraulic universal testing machine; the fatigue crack propagation rate was examined with CT specimens by using an INSTRON 8874 testing machine. Results indicate that fatigue life increases as maximum stress decreases; as the maximum stress decreases to the maximum operating stress (440 MPa), the fatigue life is approximately 4.2×10{sup 5} cycles. The fatigue crack of the full-thickness fatigue life specimens is generated at the surface of rolled steel plates and then the crack propagates and grows inward until a fracture is formed. During fatigue crack growth, a transitional turning point appears in the curve of da/dN with ΔK in the Paris region. The transitional turning point that divides the Paris region to two stages is approximately ΔK≅30 MPa m{sup 1/2}. The change in the growth rate (da/dN) is related to the variation of the crack path and in the fracture mode because of the possible microstructural sensitivity of fatigue crack propagation behavior. This study also discussed the effect of duple phase ferrite/bainite microstructure on fatigue crack initiation and propagation.

Fatigue properties of X80 pipeline steels with ferrite/bainite dual-phase microstructure

International Nuclear Information System (INIS)

Zhao, Zuo-peng; Qiao, Gui-ying; Tang, Lei; Zhu, Hong-wei; Liao, Bo; Xiao, Fu-ren

2016-01-01

Fatigue properties are important parameters for the safety design and security evaluation of gas transmission pipelines. In this work, the fatigue life at different stresses of full-thickness X80 pipeline steel plates with a ferrite/bainite dual-phase microstructure was investigated using a MTS servo-hydraulic universal testing machine; the fatigue crack propagation rate was examined with CT specimens by using an INSTRON 8874 testing machine. Results indicate that fatigue life increases as maximum stress decreases; as the maximum stress decreases to the maximum operating stress (440 MPa), the fatigue life is approximately 4.2×10"5 cycles. The fatigue crack of the full-thickness fatigue life specimens is generated at the surface of rolled steel plates and then the crack propagates and grows inward until a fracture is formed. During fatigue crack growth, a transitional turning point appears in the curve of da/dN with ΔK in the Paris region. The transitional turning point that divides the Paris region to two stages is approximately ΔK≅30 MPa m"1"/"2. The change in the growth rate (da/dN) is related to the variation of the crack path and in the fracture mode because of the possible microstructural sensitivity of fatigue crack propagation behavior. This study also discussed the effect of duple phase ferrite/bainite microstructure on fatigue crack initiation and propagation.

Fatigue Reliability of Offshore Wind Turbine Systems

DEFF Research Database (Denmark)

Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

2012-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Reliability Analysis of Fatigue Failure of Cast Components for Wind Turbines

Directory of Open Access Journals (Sweden)

Hesam Mirzaei Rafsanjani

2015-04-01

Full Text Available Fatigue failure is one of the main failure modes for wind turbine drivetrain components made of cast iron. The wind turbine drivetrain consists of a variety of heavily loaded components, like the main shaft, the main bearings, the gearbox and the generator. The failure of each component will lead to substantial economic losses such as cost of lost energy production and cost of repairs. During the design lifetime, the drivetrain components are exposed to variable loads from winds and waves and other sources of loads that are uncertain and have to be modeled as stochastic variables. The types of loads are different for offshore and onshore wind turbines. Moreover, uncertainties about the fatigue strength play an important role in modeling and assessment of the reliability of the components. In this paper, a generic stochastic model for fatigue failure of cast iron components based on fatigue test data and a limit state equation for fatigue failure based on the SN-curve approach and Miner’s rule is presented. The statistical analysis of the fatigue data is performed using the Maximum Likelihood Method which also gives an estimate of the statistical uncertainties. Finally, illustrative examples are presented with reliability analyses depending on various stochastic models and partial safety factors.

Mechanical properties and fatigue strength of high manganese non-magnetic steel/carbon steel welded joints

International Nuclear Information System (INIS)

Nakaji, Eiji; Ikeda, Soichi; Kim, You-Chul; Nakatsuji, Yoshihiro; Horikawa, Kosuke.

1997-01-01

The dissimilar materials welded joints of high manganese non-magnetic steel/carbon steel (hereafter referred to as DMW joints), in which weld defects such as hot crack or blowhole are not found, were the good quality. Tensile strength of DMW joints was 10% higher than that of the base metal of carbon steel. In the bend tests, the DMW joints showed the good ductility without crack. Charpy absorbed energy at 0(degC) of the DMW joints was over 120(J) in the bond where it seems to be the lowest. Large hardening or softening was not detected in the heat affected zone. Fatigue strength of the DMW joints is almost the same with that of the welded joints of carbon steel/carbon steel. As the fatigue strength of the DMW joints exceeds the fatigue design standard curve of JSSC for carbon steel welded joints, the DMW joints can be treated the same as the welded joints of carbon steel/carbon steel of which strength is lower than that of high manganese non-magnetic steel, from the viewpoint of the fatigue design. (author)

Fatigue crack growth threshold as a design criterion - statistical scatter and load ratio in the Kitagawa-Takahashi diagram

International Nuclear Information System (INIS)

Kolitsch, S.; Gänser, H.-P.; Maierhofer, J.; Pippan, R.

2016-01-01

Cracks in components reduce the endurable stress so that the endurance limit obtained from common smooth fatigue specimens cannot be used anymore as a design criterion. In such cases, the Kitagawa-Takahashi diagram can be used to predict the admissible stress range for infinite life, at a given crack length and stress range. This diagram is constructed for a single load ratio R. However, in typical mechanical engineering applications, the load ratio R varies widely due to the applied load spectra and residual stresses. In the present work an extended Kitagawa-Takahashi diagram accounting for crack length, crack extension and load ratio is constructed. To describe the threshold behaviour of short cracks, a master resistance curve valid for a wide range of steels is developed using a statistical approach. (paper)

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

Science.gov (United States)

Irvine, Tom; Larsen, Curtis

2016-01-01

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

The Nature of Fatigue in Chronic Fatigue Syndrome.

Science.gov (United States)

Olson, Karin; Zimka, Oksana; Stein, Eleanor

2015-10-01

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

Multiaxial fatigue of aluminium friction stir welded joints: preliminary results

Directory of Open Access Journals (Sweden)

D. G. Hattingh

2015-07-01

Full Text Available The aim of the present research is to check the accuracy of the Modified Wöhler Curve Method (MWCM in estimating the fatigue strength of friction stir (FS welded tubular joints of Al 6082-T6 subjected to in-phase and out-of-phase multiaxial fatigue loading. The welded samples being investigated were manufactured by equipping an MTS I-STIR process development system with a retracting tool that was specifically designed and optimised for this purpose. These specimens were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out by using the generated experimental results allowed us to prove that the MWCM (applied in terms of nominal stresses is highly accurate in predicting the fatigue strength of the tested FS welded joints, its usage resulting in estimates falling with the uniaxial and torsional calibration scatter bands.

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

Science.gov (United States)

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

2017-12-01

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

Fatigue life of bovine meniscus under longitudinal and transverse tensile loading.

Science.gov (United States)

Creechley, Jaremy J; Krentz, Madison E; Lujan, Trevor J

2017-05-01

The knee meniscus is composed of a fibrous extracellular matrix that is subjected to large and repeated loads. Consequently, the meniscus is frequently torn, and a potential mechanism for failure is fatigue. The objective of this study was to measure the fatigue life of bovine meniscus when applying cyclic tensile loads either longitudinal or transverse to the principal fiber direction. Fatigue experiments consisted of cyclic loads to 60%, 70%, 80% or 90% of the predicted ultimate tensile strength until failure occurred or 20,000 cycles was reached. The fatigue data in each group was fit with a Weibull distribution to generate plots of stress level vs. cycles to failure (S-N curve). Results showed that loading transverse to the principal fiber direction gave a two-fold increase in failure strain, a three-fold increase in creep, and a nearly four-fold increase in cycles to failure (not significant), compared to loading longitudinal to the principal fiber direction. The S-N curves had strong negative correlations between the stress level and the mean cycles to failure for both loading directions, where the slope of the transverse S-N curve was 11% less than the longitudinal S-N curve (longitudinal: S=108-5.9ln(N); transverse: S=112-5.2ln(N)). Collectively, these results suggest that the non-fibrillar matrix is more resistant to fatigue failure than the collagen fibers. Results from this study are relevant to understanding the etiology of atraumatic radial and horizontal meniscal tears, and can be utilized by research groups that are working to develop meniscus implants with fatigue properties that mimic healthy tissue. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental evaluation of torsional fatigue strength of welded bellows and application to design of fusion device

International Nuclear Information System (INIS)

Takatsu, Hideyuki; Yamamoto, Masahiro; Shimizu, Masatsugu; Suzuki, Kazuo; Sonobe, Tadashi; Hayashi, Yuzo; Mizuno, Gen-ichiro.

1984-01-01

Torsional fatigue strength of the welded bellows was evaluated experimentally, aiming the application to a port of a fusion device. The welded bellows revealed elastic torsional buckling and spiral distorsion even under a small angle of torsion. Twisting load never leads the welded bellows to fracture easily so far as the angle of torsion is not excessively large, and the welded bellows has the torsional fatigue strength much larger than that expected so far. Two formulae were proposed to evaluate the stress of the welded bellows under the forced angle of torsion; shearing stress evaluation formula in the case that torsional buckling does not occur and the axial bending stress evaluation formula in the case that torsional buckling occurs. And the results of the torsional fatigue experiments showed that the former is reasonably conservative and simulates the actual behavior of the welded bellows better than the latter in the high cycle fatigue region and vice versa in the low cycle fatigue region from the viewpoint of the mechanical design. The present evaluation method of the torsional fatigue strength was applied to the welded bellows for the port of the JT-60 vacuum vessel and its structural integrity was confirmed under the design load condition. (author)

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

International Nuclear Information System (INIS)

Kuwahara, Kazuo; Nitta, Akihito; Kitamura, Takayuki

1980-01-01

A 2-1/4Cr-1Mo steel is one of principal materials for high temperature equipments in nuclear and thermal power plants. The authors experimentally analyzed the high temperature fatigue strength and creep strength of a 2-1/4 Cr-1Mo steel main steam pipe which had been used in a thermal plant for operation up to 130,000 hours, and pointed out that the strain-range vs. life curves crossed each other due to the difference of temperature-strain phase in thermal fatigue. This suggests that it is difficult to estimate thermal fatigue life of steel materials having been subjected to different temperature-strain phase on the basis of isothermal low-cycle fatigue life at the upper limit temperature of thermal fatigue, and that it is urgently required to establish an appropriate method of evaluating thermal fatigue life. The authors attempted to prove that the strain range partitioning method used for the evaluation of thermal fatigue life in SUS 304 steels is applicable to this 2-1/4Cr-1Mo steel. Consequently, it was found that the thermal fatigue life could be estimated within a factor of 2.5 by the application of this method. (author)

Fatigue life prediction for a cold worked T316 stainless steel

International Nuclear Information System (INIS)

Manjoine, M.J.

1983-01-01

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) [pt

Thermal fatigue loading for a type 304-L stainless steel used for pressure water reactor: investigations on the effect of a nearly perfect biaxial loading, and on the cumulative fatigue life

International Nuclear Information System (INIS)

Fissolo, A.; Gourdin, C.; Bouin, P.; Perez, G.

2010-01-01

Fatigue-life curves are used in order to estimate crack-initiation, and also to prevent water leakage on Pressure Water Reactor pipes. Such curves are built exclusively from push-pull tests performed under constant and uniaxial strain or stress-amplitude. However, thermal fatigue corresponds to a nearly perfect biaxial stress state and severe loading fluctuations are observed in operating conditions. In this frame, these two aspects have been successively investigated in this paper: In order to investigate on potential difference between thermal fatigue and mechanical fatigue, tests have been carried out at CEA using thermal fatigue devices. They show that for an identical level of strain-amplitude, the number of cycles required to achieve crack-initiation is significantly lower under thermal fatigue. This enhanced damage results probably from a perfect biaxial state under thermal fatigue. In this frame, application of the multiaxial Zamrik's criterion seems to be very promising. In order to investigate on cumulative damage effect in fatigue, multi-level strain controlled fatigue tests have been performed. Experimental results show that linear Miner's rule is not verified. A loading sequence effect is clearly evidenced. The double linear damage rule ('DLDR') improves significantly predictions of fatigue-life. (authors)

Areva fatigue concept. Fast fatigue evaluation, a new method for fatigue analysis

International Nuclear Information System (INIS)

Heinz, Benedikt; Bergholz, Steffen; Rudolph, Juergen

2011-01-01

Within the discussions on the long term operation (LTO) of nuclear power plants the ageing management is on the focus of that analysis. The knowledge of the operational thermal cyclic load data on components of the power plants and their evaluation in the fatigue analysis is a central concern. The changes in fatigue requirements (e.g. the consideration of environmentally assisted fatigue - EAF) recently discussed and LTO efforts are a strong motivation for the identification of margins in the existing fatigue analysis approaches. These margins should be considered within new approaches in order to obtain realistic (or more accurate) analysis results. Of course, these new analysis approaches have to be manageable and efficient. The Areva Fatigue Concept (AFC) offers the comprehensive conceptual basis for the consideration of fatigue on different levels and depths. The combination of data logging and automated fatigue evaluation are important modules of the AFC. Besides the established simplified stress based fatigue estimation Areva develops a further automated fatigue analysis method called Fast Fatigue Evaluation (FFE). This method comprises highly automated stress analyses at the fatigue relevant locations of the component. Hence, a component specific course of stress as a function of time is determined based on FAMOS or similar temperature measurement systems. The subsequent application of the rain flow cycle counting algorithm allows for the determination of the usage factor following the rules of the design code requirements. The new FFE approach constitutes a cycle counting method based on the real stresses in the component, and determined as result a rule-conformity cumulative usage factor. (orig.)

IIW guidelines on weld quality in relationship to fatigue strength

CERN Document Server

Jonsson, Bertil; Hobbacher, A F; Kassner, M; Marquis, G

2016-01-01

This book presents guidelines on quantitative and qualitative measures of the geometric features and imperfections of welds to ensure that it meets the fatigue strength requirements laid out in the recommendations of the IIW (International Institute of Welding). Welds that satisfy these quality criteria can be assessed in accordance with existing IIW recommendations based on nominal stress, structural stress, notch stress or linear fracture mechanics. Further, the book defines more restrictive acceptance criteria based on weld geometry features and imperfections with increased fatigue strength. Fatigue strength for these welds is defined as S-N curves expressed in terms of nominal applied stress or hot spot stress. Where appropriate, reference is made to existing quality systems for welds.In addition to the acceptance criteria and fatigue assessment curves, the book also provides guidance on their inspection and quality control. The successful implementation of these methods depends on adequate training for o...

Cement based composites for thin building elements: Fracture and fatigue parameters

Czech Academy of Sciences Publication Activity Database

Seitl, Stanislav; Bílek, V.; Keršner, Z.; Veselý, J.

2010-01-01

Roč. 2, č. 1 (2010), s. 911-916 E-ISSN 1877-7058. [Fatigue 2010. Praha, 06.06.2010-11.06.2010] R&D Projects: GA ČR GA103/08/0963 Institutional research plan: CEZ:AV0Z20410507 Keywords : Cement-based composites * Fatigue concrete * Wöhler curve * Fibers Subject RIV: JL - Materials Fatigue, Friction Mechanics

Fatigue tests and life estimation of Incoloy alloy 908

International Nuclear Information System (INIS)

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

1997-01-01

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

Reliability-based fatigue life estimation of shear riveted connections considering dependency of rivet hole failures

Directory of Open Access Journals (Sweden)

Leonetti* Davide

2018-01-01

Full Text Available Standards and guidelines for the fatigue design of riveted connections make use of a stress range-endurance (S-N curve based on the net section stress range regardless of the number and the position of the rivets. Almost all tests on which S-N curves are based, are performed with a minimum number of rivets. However, the number of rivets in a row is expected to increase the fail-safe behaviour of the connection, whereas the number of rows is supposed to decrease the theoretical stress concentration at the critical locations, and hence these aspects are not considered in the S-N curves. This paper presents a numerical model predicting the fatigue life of riveted connections by performing a system reliability analysis on a double cover plated riveted butt joint. The connection is considered in three geometries, with different number of rivets in a row and different number of rows. The stress state in the connection is evaluated using a finite element model in which the friction coefficient and the clamping force in the rivets are considered in a deterministic manner. The probability of failure is evaluated for the main plate, and fatigue failure is assumed to be originating at the sides of the rivet holes, the critical locations, or hot-spots. The notch stress approach is applied to assess the fatigue life, considered to be a stochastic quantity. Unlike other system reliability models available in the literature, the evaluation of the probability of failure takes into account the stochastic dependence between the failures at each critical location modelled as a parallel system, which means considering the change of the state of stress in the connection when a ligament between two rivets fails. A sensitivity study is performed to evaluate the effect of the pretension in the rivet and the friction coefficient on the fatigue life.

Research for the design of visual fatigue based on the computer visual communication

Science.gov (United States)

Deng, Hu-Bin; Ding, Bao-min

2013-03-01

With the era of rapid development of computer networks. The role of network communication in the social, economic, political, become more and more important and suggested their special role. The computer network communicat ion through the modern media and byway of the visual communication effect the public of the emotional, spiritual, career and other aspects of the life. While its rapid growth also brought some problems, It is that their message across to the public, its design did not pass a relat ively perfect manifestation to express the informat ion. So this not only leads to convey the error message, but also to cause the physical and psychological fatigue for the audiences. It is said that the visual fatigue. In order to reduce the fatigue when people obtain the useful information in using computer. Let the audience in a short time to obtain the most useful informat ion, this article gave a detailed account of its causes, and propose effective solutions and, through the specific examples to explain it, also in the future computer design visual communicat ion applications development prospect.

Materials design data for reduced activation martensitic steel type EUROFER

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A.-A.F. E-mail: tavassoli@cea.fr; Alamo, A.; Bedel, L.; Forest, L.; Gentzbittel, J.-M.; Rensman, J.-W.; Diegele, E.; Lindau, R.; Schirra, M.; Schmitt, R.; Schneider, H.C.; Petersen, C.; Lancha, A.-M.; Fernandez, P.; Filacchioni, G.; Maday, M.F.; Mergia, K.; Boukos, N.; Baluc,; Spaetig, P.; Alves, E.; Lucon, E

2004-08-01

Materials design limits derived so far from the data generated in Europe for the reduced activation ferritic/martensitic (RAFM) steel type Eurofer are presented. These data address the short-term needs of the ITER Test Blanket Modules and a DEMOnstration fusion reactor. Products tested include plates, bars, tubes, TIG and EB welds, as well as powder consolidated blocks and solid-solid HIP joints. Effects of thermal ageing and low dose neutron irradiation are also included. Results are sorted and screened according to design code requirements before being introduced in reference databases. From the physical properties databases, variations of magnetic properties, modulus of elasticity, density, thermal conductivity, thermal diffusivity, specific heat, mean and instantaneous linear coefficients of thermal expansion versus temperature are derived. From the tensile and creep properties databases design allowable stresses are derived. From the instrumented Charpy impact and fracture toughness databases, ductile to brittle transition temperature, toughness and behavior of materials in different fracture modes are evaluated. From the fatigue database, total strain range versus number of cycles to failure curves are plotted and used to derive fatigue design curves. Cyclic curves are also derived and compared with monotonic hardening curves. Finally, irradiated and aged materials data are compared to ensure that the safety margins incorporated in unirradiated design limits are not exceeded.

FATIGUE CRACK PROPAGATION THROUGH AUSTEMPERED DUCTILE IRON MICROSTRUCTURE

Directory of Open Access Journals (Sweden)

Lukáš Bubenko

2010-10-01

Full Text Available Austempered ductile iron (ADI has a wide range of application, particularly for castings used in automotive and earth moving machinery industries. These components are usually subjected to variable dynamic loading that may promote initiation and propagation of fatigue cracks up to final fracture. Thus, it is important to determine the fatigue crack propagation behavior of ADI. Since fatigue crack growth rate (da/dN vs. stress intensity factor K data describe fatigue crack propagation resistance and fatigue durability of structural materials, da/dN vs. Ka curves of ADI 1050 are reported here. The threshold amplitude of stress intensity factor Kath is also determined. Finally, the influence of stress intensity factor amplitude to the character of fatigue crack propagation through the ADI microstructure is described.

Fatigue characteristics of dual-phase steel sheets

Energy Technology Data Exchange (ETDEWEB)

Onn, Irwan Herman; Ahmad, Norhayati; Tamin, Mohd Nasir [Universiti Teknologi Malaysia, Skudai (Malaysia)

2015-01-15

Fatigue characteristics of dual-phase steel sheets, commonly used in automobile body construction were established. For this purpose, a series of fatigue tests, each at constant stress amplitude were conducted on 1.2 mm-thick, dual-phase DP600 steel sheet specimens with two different load ratios of minimum-to-maximum stress, R = 0.1 and -1. The resulting fatigue behavior is expressed in terms of fatigue strength-life (S-N) curves. Fatigue behavior of the steel sheets in the high-cycle fatigue region can be represented by Basquin's equation with coefficient and exponent value of 921.2 and 0.093, respectively. An endurance limit of 255 MPa is observed. In addition, fatigue strengths of the dual-phase steel sheets display lower magnitude than their bulk counterparts. Effect of mean stress on fatigue behavior of the steel sheets is well predicted by Walker's model. Exponential calibration factor is introduced to the models by SWT, Goodman and Morrow with comparable prediction to the Walker's model.

Fatigue Behavior of Inconel 718 TIG Welds

Science.gov (United States)

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

2014-08-01

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

CFD-FEM coupling for accurate prediction of thermal fatigue

International Nuclear Information System (INIS)

Hannink, M.H.C.; Kuczaj, A.K.; Blom, F.J.; Church, J.M.; Komen, E.M.J.

2009-01-01

together with a fatigue curve from a design code. For this assessment, the ASME Boiler and Pressure Vessel Code [2] is used. Previous work concentrated on the development and validation of numerical models for the simulation of turbulent mixing [3, 4]. This work focuses on the coupling between CFD and FEM models, and lifetime prediction by means of code assessment. The analysis tools that were developed are demonstrated on a test case. (orig.)

Evaluation of shot peening on the fatigue strength of anodized Ti-6Al-4V alloy

Directory of Open Access Journals (Sweden)

Costa Midori Yoshikawa Pitanga

2006-01-01

Full Text Available The increasingly design requirements for modern engineering applications resulted in the development of new materials with improved mechanical properties. Low density, combined with excellent weight/strength ratio as well as corrosion resistance, make the titanium attractive for application in landing gears. Fatigue control is a fundamental parameter to be considered in the development of mechanical components. The aim of this research is to analyze the fatigue behavior of anodized Ti-6Al-4V alloy and the influence of shot peening pre treatment on the experimental data. Axial fatigue tests (R = 0.1 were performed, and a significant reduction in the fatigue strength of anodized Ti-6Al-4V was observed. The shot peening superficial treatment, which objective is to create a compressive residual stress field in the surface layers, showed efficiency to increase the fatigue life of anodized material. Experimental data were represented by S-N curves. Scanning electron microscopy technique (SEM was used to observe crack origin sites.

Fatigue assessment of laserbeam welded PM steel components by the notch stress approach

Energy Technology Data Exchange (ETDEWEB)

Waterkotte, R. [Schaeffler Technologies GmbH and Co. KG, Herzogenaurach (Germany); Sonsino, C.M. [Fraunhofer Institute for Structural Durability and System Reliability LBF, Darmstadt (Germany); Baumgartner, J.

2011-10-15

The local fatigue strength of a laserbeam weld of a complex engine component, which joins a PM with a formed sheet component, was assessed by the notch stress concept with the fictitious reference radius of r{sub ref}= 0.05 mm. First, simplified specimens, following the main geometric dimensions of the parts, were manufactured. On these specimens the fatigue strength was identified by tests and the notch stresses calculated by finite element analysis. Based on these results a design SN-curve was derived to assess the fatigue strength of the engine component. The numerical assessment of the welded joint was verified by proof tests with the component. The assessment could be improved by considering statistical and stress gradient dependent size effects according to the concept of the highly stressed volume. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Analysis of fatigue reliability for high temperature and high pressure multi-stage decompression control valve

Science.gov (United States)

Yu, Long; Xu, Juanjuan; Zhang, Lifang; Xu, Xiaogang

2018-03-01

Based on stress-strength interference theory to establish the reliability mathematical model for high temperature and high pressure multi-stage decompression control valve (HMDCV), and introduced to the temperature correction coefficient for revising material fatigue limit at high temperature. Reliability of key dangerous components and fatigue sensitivity curve of each component are calculated and analyzed by the means, which are analyzed the fatigue life of control valve and combined with reliability theory of control valve model. The impact proportion of each component on the control valve system fatigue failure was obtained. The results is shown that temperature correction factor makes the theoretical calculations of reliability more accurate, prediction life expectancy of main pressure parts accords with the technical requirements, and valve body and the sleeve have obvious influence on control system reliability, the stress concentration in key part of control valve can be reduced in the design process by improving structure.

Statistical analysis of elevated-temperature, strain-controlled fatigue data on Type 304 stainless steel

International Nuclear Information System (INIS)

Diercks, D.R.; Raske, D.T.

1976-01-01

The available elevated-temperature, strain-controlled, uniaxial fatigue data on Type 304 stainless steel (435 data points) are summarized, and variables that influence cyclic life are divided into first- and second-order categories. The first-order variables, which include strain range, strain rate, temperature, and tensile hold time, were used in a multivariable regression analysis to describe the observed variation in fatigue life. Goodness of fit with respect to these variables as well as the appropriateness of the transformations employed are discussed. Confidence intervals are estimated, and a comparison with the ASME Boiler and Pressure Vessel Code Case 1592 creep-fatigue design curve is made for a particular set of conditions. The second-order variables include the laboratories at which the data were generated, the different heats from which the test specimens were fabricated, and the heat treatments that preceded testing. These variables were statistically analyzed to determine their effect on fatigue life. The results are discussed, and the heats and heat treatments that are most resistant to fatigue damage under these loading and environmental conditions are identified

Low cycle fatigue strength of austenitic stainless steel under large strain regime

International Nuclear Information System (INIS)

Sakai, Michiya; Saito, Kiyoshi; Matsuura, Shinichi

1998-01-01

In order to establish realistic seismic safety of nuclear power plants, it is necessary to clarify the failure mode of each components and prepare a damage evaluation method. The authors have proposed the damage evaluation method based on the fully numerical approach to evaluate the low cycle fatigue (LCF) failure under seismic loadings. This method has been validated by comparison with the dynamic failure tests of thin elbows which should be the one of the important components of the FBR primary piping system. However, since there exists limited LCF data, fatigue lives under large strain regime have been extrapolated by available fatigue data. In this study, LCF tests have been conducted over a large strain range from 2% to 10% on austenitic stainless steel SUS304. From the results, the regressive LCF curve has been proposed to modify the Wada's best-fit LCF curve under large strain regime. The usage factors calculated by author's numerical approach using proposed LCF curve have been improved to correct the underestimation of the fatigue damage. (author)

Crack Growth Behaviour of P92 Steel Under Creep-fatigue Interaction Conditions

Directory of Open Access Journals (Sweden)

JING Hong-yang

2017-05-01

Full Text Available Creep-fatigue interaction tests of P92 steel at 630℃ under stress-controlled were carried out, and the crack propagation behaviour of P92 steel was studied. The fracture mechanism of crack growth under creep-fatigue interaction and the transition points in a-N curves were analyzed based on the fracture morphology. The results show that the fracture of P92 steel under creep-fatigue interaction is creep ductile fracture and the (Ctavg parameter is employed to demonstrate the crack growth behaviour; in addition, the fracture morphology shows that the crack growth for P92 steel under creep-fatigue interaction is mainly caused by the nucleation and growth of the creep voids and micro-cracks. Furthermore, the transition point of a-lg(Ni/Nf curve corresponds to the turning point of initial crack growth changed into steady crack growth while the transition point of (da/dN-N curve exhibits the turning point of steady creep crack growth changed into the accelerated crack growth.

Evaluation of viewing experiences induced by a curved three-dimensional display

Science.gov (United States)

Mun, Sungchul; Park, Min-Chul; Yano, Sumio

2015-10-01

Despite an increased need for three-dimensional (3-D) functionality in curved displays, comparisons pertinent to human factors between curved and flat panel 3-D displays have rarely been tested. This study compared stereoscopic 3-D viewing experiences induced by a curved display with those of a flat panel display by evaluating subjective and objective measures. Twenty-four participants took part in the experiments and viewed 3-D content with two different displays (flat and curved 3-D display) within a counterbalanced and within-subject design. For the 30-min viewing condition, a paired t-test showed significantly reduced P300 amplitudes, which were caused by engagement rather than cognitive fatigue, in the curved 3-D viewing condition compared to the flat 3-D viewing condition at P3 and P4. No significant differences in P300 amplitudes were observed for 60-min viewing. Subjective ratings of realness and engagement were also significantly higher in the curved 3-D viewing condition than in the flat 3-D viewing condition for 30-min viewing. Our findings support that curved 3-D displays can be effective for enhancing engagement among viewers based on specific viewing times and environments.

Next-Generation Intensity-Duration-Frequency Curves for Hydrologic Design in Snow-Dominated Environments

Science.gov (United States)

Yan, Hongxiang; Sun, Ning; Wigmosta, Mark; Skaggs, Richard; Hou, Zhangshuan; Leung, Ruby

2018-02-01

There is a renewed focus on the design of infrastructure resilient to extreme hydrometeorological events. While precipitation-based intensity-duration-frequency (IDF) curves are commonly used as part of infrastructure design, a large percentage of peak runoff events in snow-dominated regions are caused by snowmelt, particularly during rain-on-snow (ROS) events. In these regions, precipitation-based IDF curves may lead to substantial overestimation/underestimation of design basis events and subsequent overdesign/underdesign of infrastructure. To overcome this deficiency, we proposed next-generation IDF (NG-IDF) curves, which characterize the actual water reaching the land surface. We compared NG-IDF curves to standard precipitation-based IDF curves for estimates of extreme events at 376 Snowpack Telemetry (SNOTEL) stations across the western United States that each had at least 30 years of high-quality records. We found standard precipitation-based IDF curves at 45% of the stations were subject to underdesign, many with significant underestimation of 100 year extreme events, for which the precipitation-based IDF curves can underestimate water potentially available for runoff by as much as 125% due to snowmelt and ROS events. The regions with the greatest potential for underdesign were in the Pacific Northwest, the Sierra Nevada Mountains, and the Middle and Southern Rockies. We also found the potential for overdesign at 20% of the stations, primarily in the Middle Rockies and Arizona mountains. These results demonstrate the need to consider snow processes in the development of IDF curves, and they suggest use of the more robust NG-IDF curves for hydrologic design in snow-dominated environments.

Assessment and propagation of mechanical property uncertainties in fatigue life prediction of composite laminates

DEFF Research Database (Denmark)

Castro, Oscar; Branner, Kim; Dimitrov, Nikolay Krasimirov

2018-01-01

amplitude loading cycles. Fatigue life predictions of unidirectional and multi-directional glass/epoxy laminates are carried out to validate the proposed model against experimental data. The probabilistic fatigue behavior of laminates is analyzed under constant amplitude loading conditions as well as under......A probabilistic model for estimating the fatigue life of laminated composite materials considering the uncertainty in their mechanical properties is developed. The uncertainty in the material properties is determined from fatigue coupon tests. Based on this uncertainty, probabilistic constant life...... diagrams are developed which can efficiently estimate probabilistic É›-N curves at any load level and stress ratio. The probabilistic É›-N curve information is used in a reliability analysis for fatigue limit state proposed for estimating the probability of failure of composite laminates under variable...

Design and Performance Test of Locking Curved-Nut

Energy Technology Data Exchange (ETDEWEB)

Cha, Min Cheol; Kang, Ho Sung; Kim, Do Yeop; Lee, Suk Yong; Lee, Eung Suk [Chungbuk Nat’l Univ., Cheongju (Korea, Republic of); Jeong, Hui Jong [Viblock Company, Cheongwon (Korea, Republic of)

2017-03-15

Many types of locking nut are commercializing in the various industries where has heavy vibration. Because Nut's loosing causes a serious accident. But the most locking nuts are too expensive as the complicate manufacturing process. In this study, we design the new type of locking nut, 'Curved-Nut' that is relatively simple making process. We study a relation between the elastic energy and the nut loosing mechanism. So it is analysed, the elastic energy of Curved-Nut comparing with the locking test. The Curved-Nut was manufactured on the commercial nut using a milling tool with horizontal cutting, one or two time under the nut. As the result, the more elastic energy the more prevent the loosing of the nut. We verified the performance of the loosing nut using the vibration testing equipment (NAS3350).

Standard guide for fretting fatigue testing

CERN Document Server

American Society for Testing and Materials. Philadelphia

2010-01-01

1.1 This guide defines terminology and covers general requirements for conducting fretting fatigue tests and reporting the results. It describes the general types of fretting fatigue tests and provides some suggestions on developing and conducting fretting fatigue test programs. 1.2 Fretting fatigue tests are designed to determine the effects of mechanical and environmental parameters on the fretting fatigue behavior of metallic materials. This guide is not intended to establish preference of one apparatus or specimen design over others, but will establish guidelines for adherence in the design, calibration, and use of fretting fatigue apparatus and recommend the means to collect, record, and reporting of the data. 1.3 The number of cycles to form a fretting fatigue crack is dependent on both the material of the fatigue specimen and fretting pad, the geometry of contact between the two, and the method by which the loading and displacement are imposed. Similar to wear behavior of materials, it is important t...

Aeroelastic analysis of an offshore wind turbine: Design and Fatigue Performance of Large Utility-Scale Wind Turbine Blades

OpenAIRE

Fossum, Peter Kalsaas

2012-01-01

Aeroelastic design and fatigue analysis of large utility-scale wind turbine blades are performed. The applied fatigue model is based on established methods and is incorporated in an iterative numerical design tool for realistic wind turbine blades. All aerodynamic and structural design properties are available in literature. The software tool FAST is used for advanced aero-servo-elastic load calculations and stress-histories are calculated with elementary beam theory.According to wind energy ...

French recent developments in support to rules for creep and creep-fatigue analyses

International Nuclear Information System (INIS)

Touboul, F.; Moulin, D.

1997-01-01

RCC-MR proposes Design rules for creep and creep-fatigue damage evaluation in zones with no geometrical discontinuities. Rules have been developed, based on the σ d concept, in order to consider zones with geometrical discontinuities. Rule for Weld are proposed in the paragraph relative to shell design rules and reduction coefficient due to material properties are given in Appendix A9. For fatigue analysis, last version of RCC-MR (1993) has proposed a reduction factor on fatigue curves (Jf value), derived from preliminary tests performed within European program. Studies have been carried out in order to have a better understanding of the phenomena involved in these fatigue reduction factors. Tests have been performed on large plates, with varying applied displacements, weld geometry, plate thickness, weld direction. It appears that material effect is not the only purpose to be considered but that it is necessary to think about the geometrical effect, linked to the welded zone dimensions, and the elastic follow-up effect between the two materials: base metal and weld metal. As a first approach, simplified calculations have been achieved with precise material characterization. Roche's method and Zarka method's give conservative result in comparison to tests results. (author). 3 refs, 4 tabs

Low cycle fatigue lifetime of HIP bonded Bi-metallic first wall structures of fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Hatano, Toshihisa; Sato, Satoshi; Furuya, Kazuyuki; Kuroda, Toshimasa; Enoeda, Mikio; Takatsu, Hideyuki [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Hashimoto, Toshiyuki; Kitamura, Kazunori

1998-10-01

A HIP bonded bi-metallic panel composed of a dispersion strengthened copper (DSCu) layer and type 316L stainless steel (SS316L) cooling pipes is the reference design of the ITER first wall. To examine the fatigue lifetime of the first wall panel under cyclic mechanical loads, low cycle fatigue tests of HIP bonded bi-metallic specimens made of SS316L and DSCu were conducted with the stress ratio of -1.0 and five nominal strain range conditions ranging from 0.2 to 1.0%. Elasto-plastic analysis has also been conducted to evaluate local strain ranges under the nominal strains applied. Initial cracks were observed at the inner surface of the SS316L cooling pipes for all of the specimens tested, which was confirmed by the elasto-plastic analysis that the maximum strains of the test specimens were developed at the same locations. It was found that the HIP bonded bi-metallic test specimens had a fatigue lifetime longer than that of the SS316L raw material obtained by round bar specimens. Similarly, the fatigue lifetime of the DSCu/SS316L HIP interface was also longer than the round bar test results for the HIP joints. From these results, it has been confirmed that the bi-metallic first wall panel with built-in cooling pipes made by HIP bonding has a sufficient fatigue lifetime in comparison with the raw fatigue data of the materials, which also suggests that the fatigue lifetime evaluation has an adequate margin against fracture if it follows the design fatigue curve based on the material fatigue data. (author)

Design and simulation of Macro-Fiber composite based serrated microflap for wind turbine blade fatigue load reduction

Science.gov (United States)

Sun, Xiao; Dai, Qingli; Bilgen, Onur

2018-05-01

A Macro-Fiber Composite (MFC) based active serrated microflap is designed in this research for wind turbine blades. Its fatigue load reduction potential is evaluated in normal operating conditions. The force and displacement output of the MFC-based actuator are simulated using a bimorph beam model. The work done by the aerodynamic, centripetal and gravitational forces acting on the microflap were calculated to determine the required capacity of the MFC-based actuator. MFC-based actuators with a lever mechanical linkage are designed to achieve the required force and displacement to activate the microflap. A feedback control scheme is designed to control the microflap during operation. Through an aerodynamic-aeroelastic time marching simulation with the designed control scheme, the time responses of the wind turbine blades are obtained. The fatigue analysis shows that the serrated microflap can reduce the standard deviation of the blade root flapwise bending moment and the fatigue damage equivalent loads.

Reduced softening of EUROFER 97 under thermo-mechanical and multiaxial fatigue loading and its impact on the design rules

International Nuclear Information System (INIS)

Aktaa, J.; Weick, M.; Petersen, C.

2007-01-01

Full text of publication follows: Toward test blanket module (TBM) in ITER and DEMO fusion power plants design rules for components built from EUROFER 97 get more and more in the midpoint of interest. One of the specific characteristic of EUROFER 97 as a ferritic-martensitic steel is its cyclic softening yielding to lower stresses under strain controlled fatigue loading and thus longer lifetimes. However our thermo-mechanical and multiaxial fatigue tests showed lifetimes remarkably lower than those expected on the base of isothermal uniaxial fatigue tests. Reduced cyclic softening observed in these experiments is believed as one of the reasons of the shorter fatigue lifetimes. When applying the design rules, derived for EUROFER 97 on the base of isothermal uniaxial data considering the recommendations in the ASME and RCC-MR code, to our thermo-mechanical and multiaxial fatigue tests for verification strong loss in their conservatism has been found. The lifetimes observed in a part of the multiaxial experiments are even lower than the design lifetimes supposed to be sufficiently conservative. To overcome this problem new design rules are proposed among others on the base of damage and lifetime prediction model developed lately for EUROFER 97. In this paper the experimental findings as well as the new design approaches will be presented and discussed. (authors)

In-reactor fatigue crack propagation

International Nuclear Information System (INIS)

Ermi, A.M.; Mervyn, D.A.; Straalsund, J.L.

1979-08-01

An in-reactor fatigue experiment is being designed to determine the effect of dynamic irradiation on the fatigue crack propagation (FCP) behavior of candidate fusion first wall materials. This investigation has been prompted by studies which show gross differences in crack growth characteristics of creep rupture specimens testing by postirradiation versus dynamic in-reactor methods. The experiment utilizes miniature center-cracked-tension specimens developed specifically for in-reactor studies. In the test, a chain of eight specimens, precracked to various initial crack lengths, is stressed during irradiation to determine crack growth rate as a function of stress intensity. Load levels were chosen which result in small crack growth rates encompassing a regime of the crack growth curve not previously investigated during irradiation studies of FCP. The test will be conducted on 20% cold worked 316 stainless steel at a temperature of 425 0 C, in a sodium environment, and at a frequency of 1 cycle/min. Irradiation will occur in the Oak Ridge Research Reactor, resulting in a He/dpa ratio similar to that expected at the first wall in a fusion reactor. Detailed design of the experiment is presented, along with crack growth data obtained from prototypic testing of the experimental apparatus. These results are compared to data obtained under similar conditions generated by conventional test methods

Fatigue Life Prediction of Self-Piercing Rivet Joints Between Magnesium and Aluminum Alloys

Directory of Open Access Journals (Sweden)

Kang Hong-Tae

2018-01-01

Full Text Available Various light materials including aluminum alloys and magnesium alloys are being used to reduce the weight of vehicle structures. Joining of dissimilar materials is always a challenging task to construct a solid structure. Self-piercing rivet (SPR joint is one of various joining methods for dissimilar materials. Front shock tower structures were constructed with magnesium alloy (AM60 joined to aluminum alloy (Al6082 by SPR joints. To evaluate the durability performance of the SPR joints in the structures, fatigue tests of the front shock tower structures were conducted with constant amplitude loadings. Furthermore, this study investigated fatigue life prediction method of SPR joints and compared the fatigue life prediction results with that of experimental results. For fatigue life prediction of the SPR joints in the front shock tower structures, lap-shear and cross-tension specimens of SPR joint were constructed and tested to characterize the fatigue properties of the SPR joint. Then, the SPR joint was represented with area contact method (ACM in finite element (FE models. The load-life curves of the lap-shear and cross-tension specimens were converted to a structural stress-life (S-N curve of the SPR joints. The S-N curve was used to predict fatigue life of SPR joints in the front shock tower structures. The test results and the prediction results were well correlated.

Creep-fatigue damage rules for advanced fast reactor design. Proceedings of a technical committee meeting

International Nuclear Information System (INIS)

1997-03-01

The IAEA, following the recommendations of the International Working Group on Fast Reactors, convened a Technical Committee Meeting on Creep-Fatigue Damage Rules to be used in Fast Reactor Design. The objective of the meeting was to review developments in design rules for creep-fatigue conditions and to identify any areas in which further work would be desirable. The meeting was hosted by AEA Technology, Risley, and held in Manchester, United Kingdom, 11-13 June 1996. It was attended by experts from the European Commission, France, India, Japan, the Republic of Korea, the Russian Federation and the United Kingdom. Refs, figs, tabs

Study on the Mechanical Properties of Stay Cable HDPE Sheathing Fatigue in Dynamic Bridge Environments

Directory of Open Access Journals (Sweden)

Danhui Dan

2015-08-01

Full Text Available As the main force-bearing component of a cable-stayed bridge, a durable stay cable is paramount to the safety and durability of the entire bridge. High-density polyethylene (HDPE sheathing is the main protective component of a stay cable and is the key to insuring cable durability. To address the issue of HDPE sheathing fracture on service, strain level data for in-service, HDPE bridge cable sheathing was used in this study as the basis for HDPE material aging and fatigue testing. A fatigue yield phenomenon with a yield platform on the hysteresis curve of the fatigue cycles is observed by the fatigue test. The parameters to describe this phenomenon are proposed and defined in this paper. A preliminary examination of the relationship between these parameters and the factors, such as the number of cycles, the strain amplitude, and strain rate, are presented. Based on the results obtained, it is suggested that the condition of fatigue yield of HDPE sheathing be defined as the fatigue durability limit state for the purposes of durability design, assessment, and protection of cable-stayed bridges.

Keep fatigue usage low for LTO. Benefits of load monitoring and related fatigue evaluations for long term operation

International Nuclear Information System (INIS)

Rothenhoefer, H.; Koenig, G.

2012-01-01

Design fatigue calculations normally cover a service life of 40 years. Based on design transients with a specified number of cycles the evaluations have to prove that the fatigue usage after 40 years will stay below 1. In 40+ years of operation real loads can differ much from design loads so that premature ageing can occur. For long term operation, monitoring of real loads and detailed fatigue analysis for selected locations can be used to optimize operational modes in order to reduce the loads causing fatigue. As a result fatigue usage can be kept below 1 even for 60+ years. (author)

Collect Available Creep-Fatigue Data and Study Existing Creep-Fatigue Evaluation Procedures for Grade 91 and Hastelloy XR

International Nuclear Information System (INIS)

Asayama, Tai; Tachibana, Yukio

2007-01-01

This report describes the results of investigation on Task 5 of DOE/ASME Materials Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 5 is to collect available creep-fatigue data and study existing creep-fatigue evaluation procedures for Grade 91 steel and Hastelloy XR. Part I of this report is devoted to Grade 91 steel. Existing creep-fatigue data were collected (Appendix A) and analyzed from the viewpoints of establishing a creep-fatigue procedure for VHTR design. A fair amount of creep-fatigue data has been obtained and creep-fatigue phenomena have been clarified to develop design standards mainly for fast breeder reactors. Following this, existing creep-fatigue procedures were studied and it was clarified that the creep-fatigue evaluation procedure of the ASME-NH has a lot of conservatisms and they were analyzed in detail from the viewpoints of the evaluation of creep damage of material. Based on the above studies, suggestions to improve the ASME-NH procedure along with necessary research and development items were presented. Part II of this report is devoted to Hastelloy XR. Existing creep-fatigue data used for development of the high temperature structural design guideline for High Temperature Gas-cooled Reactor (HTGR) were collected. Creep-fatigue evaluation procedure in the design guideline and its application to design of the intermediate heat exchanger (IHX) for High Temperature Engineering Test Reactor (HTTR) was described. Finally, some necessary research and development items in relation to creep-fatigue evaluation for Gen IV and VHTR reactors were presented.

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

International Nuclear Information System (INIS)

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

2009-01-01

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

Fatigue Test Design: Scenarios for Biaxial Fatigue Testing of a 60-Meter Wind Turbine Blade

Energy Technology Data Exchange (ETDEWEB)

Post, Nathan [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2016-07-01

Current practice in commercial certification of wind turbine blades is to perform separate flap and lead-lag fatigue tests. The National Renewable Energy Laboratory has been researching and evaluating biaxial fatigue testing techniques and demonstrating various options, typically on smaller-scale test articles at the National Wind Technology Center. This report evaluates some of these biaxial fatigue options in the context of application to a multimegawatt blade certification test program at the Wind Technology Testing Center in Charlestown, Massachusetts.

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

Science.gov (United States)

2011-09-01

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

Low cycle fatigue of alloy 718 in cryogenic environment

International Nuclear Information System (INIS)

Vergara Aimone, J.

1989-01-01

A specially processed Ni-Fe base superalloy 718 has been selected as a structural material for a critical component in ALCATOR C-MOD, the new fusion experimental facility at the Massachusetts Institute of Technology. Draw bars made out of this material will be subjected to large alternating loads while operating at 77 0 K. Monotonic and cyclic mechanical properties were determined in order to evaluate the reactor's maintenance schedule with special emphasis in developing a Low Cycle Fatigue database for this special alloy. Improved monotonic properties over conventionally heat treated alloy 718 were observed. Partial hardening was observed at 77 0 K at 1% of the fatigue life, while softening was observed at room temperature, both relative to their respective monotonic stress strain curves. The fatigue curves were corrected for non-zero mean stress allowing satisfactory safety margin for the expected alternating stress. (author)

Comparison of cyclic fatigue resistance of three different rotary nickel-titanium instruments designed for retreatment.

Science.gov (United States)

Inan, Ugur; Aydin, Cumhur

2012-01-01

A number of rotary nickel-titanium (NiTi) systems have been developed to provide better, faster, and easier cleaning and shaping of the root canal system, and recently, rotary NiTi systems designed for root canal retreatment have been introduced. Because the main problem with the rotary NiTi files is fracture, the aim of this study was to compare the cyclic fatigue resistance of 3 different rotary NiTi systems designed for root canal retreatment. Total of 60 instruments of 3 different rotary NiTi systems designed for root canal retreatment were used in this study. Twenty R-Endo R3, 20 ProTaper D3, and 20 Mtwo R (Retreatment) 25.05 instruments were tested. Cyclic fatigue testing of instruments was performed by using a device that allowed the instruments to rotate freely inside an artificial canal. Each instrument was rotated until fracture occurred, and the number of cycles to fracture for each instrument was calculated. Representative samples were also evaluated under a scanning electron microscope to confirm the fracture was flexural. Data were analyzed by using 1-way analysis of variance test. R-Endo R3 instruments showed better cyclic fatigue resistance than ProTaper D3 and Mtwo R 25.05 instruments, and the difference was statistically significant (P instruments were more resistant to fatigue failure than ProTaper D3 and Mtwo R 25.05. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Simplified elastoplastic fatigue analysis

International Nuclear Information System (INIS)

Autrusson, B.; Acker, D.; Hoffmann, A.

1987-01-01

Oligocyclic fatigue behaviour is a function of the local strain range. The design codes ASME section III, RCC-M, Code Case N47, RCC-MR, and the Guide issued by PNC propose simplified methods to evaluate the local strain range. After having briefly described these simplified methods, we tested them by comparing the results of experimental strains with those predicted by these rules. The experiments conducted for this study involved perforated plates under tensile stress, notched or reinforced beams under four-point bending stress, grooved specimens under tensile-compressive stress, and embedded grooved beams under bending stress. They display a relative conservatism depending on each case. The evaluation of the strains of rather inaccurate and sometimes lacks conservatism. So far, the proposal is to use the finite element codes with a simple model. The isotropic model with the cyclic consolidation curve offers a good representation of the real equivalent strain. There is obviously no question of representing the cycles and the entire loading history, but merely of calculating the maximum variation in elastoplastic equivalent deformations with a constant-rate loading. The results presented testify to the good prediction of the strains with this model. The maximum equivalent strain will be employed to evaluate fatigue damage

Fatigue properties of high-strength materials used in cold-forging tools

DEFF Research Database (Denmark)

Brøndsted, P.; Skov-Hansen, P.

1998-01-01

In the present work classical analytical models are used to describe the static stress–strain curves, low-cycle fatigue properties and fatigue crack growth behaviour of high-strength materials for use in tools for metal-forming processes such as cold forging and extrusion. The paper describes the...

Principles for designing proteins with cavities formed by curved β sheets

Energy Technology Data Exchange (ETDEWEB)

Marcos, Enrique; Basanta, Benjamin; Chidyausiku, Tamuka M.; Tang, Yuefeng; Oberdorfer, Gustav; Liu, Gaohua; Swapna, G. V. T.; Guan, Rongjin; Silva, Daniel-Adriano; Dou, Jiayi; Pereira, Jose Henrique; Xiao, Rong; Sankaran, Banumathi; Zwart, Peter H.; Montelione, Gaetano T.; Baker, David

2017-01-12

Active sites and ligand-binding cavities in native proteins are often formed by curved β sheets, and the ability to control β-sheet curvature would allow design of binding proteins with cavities customized to specific ligands. Toward this end, we investigated the mechanisms controlling β-sheet curvature by studying the geometry of β sheets in naturally occurring protein structures and folding simulations. The principles emerging from this analysis were used to design, de novo, a series of proteins with curved β sheets topped with α helices. Nuclear magnetic resonance and crystal structures of the designs closely match the computational models, showing that β-sheet curvature can be controlled with atomic-level accuracy. Our approach enables the design of proteins with cavities and provides a route to custom design ligand-binding and catalytic sites.

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

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Hugo A. Rondón-Quintana

2013-11-01

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Creep-fatigue evaluation method for modified 9Cr-1Mo steel

International Nuclear Information System (INIS)

Wada, Y.; Aoto, K.

1997-01-01

As creep-fatigue evaluation methods on normalized and tempered Modified 9Cr-1Mo steel for design use, the time fraction rule and the simplified conventional ductility exhaustion rule are investigated for the prediction of tension strain hold creep-fatigue damage of this material. For the above investigation, stress relaxation behaviour during strain hold has to be analyzed using stress-strain-time relation. The initial value of stress relaxation was determined by cyclic stress-strain curves in continuous cycling fatigue tests. Cyclic stress-strain behaviour of Mod.9Cr-1Mo(NT) steel is different from that of austenitic stainless steels, so this effect was considered. Stress relaxation analysis was performed using static creep strain-time relation and conventional hardening rule. The time fraction by using the above stress relaxation analysis results can give good prediction for creep-fatigue life of Mod.9Cr-1Mo(NT) steel. For design use it is practical to be able to estimate creep damages conservatively by both strain behaviour of cyclic plastic (in continuous cycling fatigue tests) and monotonic creep (in standard creep tests). The life reduction by strain hold at the minimum peak of compressive stress in creep-fatigue tests was examined, and this effects can be evaluated by the relationship between the location of oxidation and the effective deformation at crack tip. In an accelerated oxidation environment, for example in high temperature and high pressure steam, a different approach for life reduction should be developed based on the mechanism of growth of oxide and crack growth with oxidation. However, in the creep damage dominant region, its effect is saturated and the effect of cavity growth along grain boundary becomes dominant for long-term strain hold in the high temperature conditions. (author). 6 refs, 6 figs

Review of fatigue criteria development for HTGR core supports

International Nuclear Information System (INIS)

Ho, F.H.; Vollman, R.E.

1979-10-01

Fatigue criteria for HTGR core support graphite structure are presented. The criteria takes into consideration the brittle nature of the material, and emphasizes the probabilistic approach in the treatment of strength data. The stress analysis is still deterministic. The conventional cumulative damage approach is adopted here. A specified minimum S-N curve is defined as the curve with 99% probability of survival at a 95% confidence level to accommodate random variability of the material strength. A constant life diagram is constructed to reconcile the effect of mean stress. The linear damage rule is assumed to account for the effect of random cycles. An additional factor of safety of three on cycles is recommended. The uniaxial S-N curve is modified in the medium-to-high cycle range (> 2 x 10 3 cycles) for mutiaxial fatigue effects

SI:FatiguePro 4 Advanced Approach for Fatigue Monitoring

International Nuclear Information System (INIS)

Evon, Keith; Gilman, Tim; Carney, Curt

2012-01-01

Many nuclear plants are making commitments to implement fatigue monitoring systems in support of license renewal. Current fatigue monitoring systems use the methodology of ASME Code Subarticle NB-3200, which is a design code intended to compute a bounding cumulative usage factor (CUF). The first generation of fatigue monitoring software utilized a simplified, single stress term assumption and classical stress cycle-counting methods that take order into account such as Rainflow or Ordered Overall Range counting. Recently, the NRC has indicated in Regulatory Issue Summary 2008-30 that any fatigue analyses in support of License Renewal should use ASME Code Section III methodologies considering all six stress components. In addition, fatigue calculations for the license renewal term are required to consider the effects of environment. The implementation of a six stress term NB-3200 fatigue calculation to a Boiling Water Reactor (BWR) feedwater nozzle, including environmental effects, is the topic of this paper. Differences in results between the advanced methodology and the simplified methodology are discussed. (author)

Fatigue behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP)

Science.gov (United States)

Jinghao Li; John F. Hunt; Shaoqin Gong; Zhiyong Cai

2015-01-01

The static and fatigue bending behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP) has been investigated by four-point bending tests. Fatigue panels and weakened panels (wESCP) with an initial interface defect were manufactured for the fatigue tests. Stress σ vs. number of cycles curves (S-N) were recorded under the different stress...

Common Mathematical Model of Fatigue Characteristics

Directory of Open Access Journals (Sweden)

Z. Maléř

2004-01-01

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

Classifying post-stroke fatigue: Optimal cut-off on the Fatigue Assessment Scale.

Science.gov (United States)

Cumming, Toby B; Mead, Gillian

2017-12-01

Post-stroke fatigue is common and has debilitating effects on independence and quality of life. The Fatigue Assessment Scale (FAS) is a valid screening tool for fatigue after stroke, but there is no established cut-off. We sought to identify the optimal cut-off for classifying post-stroke fatigue on the FAS. In retrospective analysis of two independent datasets (the '2015' and '2007' studies), we evaluated the predictive validity of FAS score against a case definition of fatigue (the criterion standard). Area under the curve (AUC) and sensitivity and specificity at the optimal cut-off were established in the larger 2015 dataset (n=126), and then independently validated in the 2007 dataset (n=52). In the 2015 dataset, AUC was 0.78 (95% CI 0.70-0.86), with the optimal ≥24 cut-off giving a sensitivity of 0.82 and specificity of 0.66. The 2007 dataset had an AUC of 0.83 (95% CI 0.71-0.94), and applying the ≥24 cut-off gave a sensitivity of 0.84 and specificity of 0.67. Post-hoc analysis of the 2015 dataset revealed that using only the 3 most predictive FAS items together ('FAS-3') also yielded good validity: AUC 0.81 (95% CI 0.73-0.89), with sensitivity of 0.83 and specificity of 0.75 at the optimal ≥8 cut-off. We propose ≥24 as a cut-off for classifying post-stroke fatigue on the FAS. While further validation work is needed, this is a positive step towards a coherent approach to reporting fatigue prevalence using the FAS. Copyright © 2017 Elsevier Inc. All rights reserved.

Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method

Directory of Open Access Journals (Sweden)

Zhao Fang

2017-01-01

Full Text Available Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely.

Multiaxial creep-fatigue rules

International Nuclear Information System (INIS)

Spindler, M.W.; Hales, R.; Ainsworth, R.A.

1997-01-01

Within the UK, a comprehensive procedure, called R5, is used to assess the high temperature response of structures. One part of R5 deals with creep-fatigue initiation, and in this paper we describe developments in this part of R5 to cover multiaxial stress states. To assess creep-fatigue, damage is written as the linear sum of fatigue and creep components. Fatigue is assessed using Miner's law with the total endurance split into initiation and growth cycles. Initiation is assessed by entering the curve of initiation cycles vs strain range using a Tresca equivalent strain range. Growth is assessed by entering the curve of growth cycles vs strain range using a Rankine equivalent strain range. The number of allowable cycles is obtained by summing the initiation and growth cycles. In this way the problem of defining an equivalent strain range applicable over a range of endurance is avoided. Creep damage is calculated using ductility exhaustion methods. In this paper we address two aspects; first, the nature of stress relaxation and, hence, accumulated creep strain in multiaxial stress fields; secondly, the effect of multiaxial stress on creep ductility. The effect of multiaxial stress state on creep ductility has been examined using experimental data and mechanistic models. Good agreement is demonstrated between an empirical description of test data and a cavity growth model, provided a simple nucleation criterion is included. A simple scaling factor is applied to uniaxial creep ductility, defined as a function of stress state. The factor is independent of the cavity growth mechanisms and yields a value of equivalent strain which can be conveniently used in determining creep damage by ductility exhaustion. (author). 14 refs, 4 figs

Strength behaviour of sintered steel from the view of design-relevant material data

International Nuclear Information System (INIS)

Sonsino, C.M.; Esper, F.J.; Leuze, G.

1982-01-01

A reliable design of sintered components and an aimed material's selection requires the knowledge of designrelevant material data as Cyclic stress-strain-curves, crack propagation and fracture toughness properties as well as statistically evaluated S-N-curves, because conventional material data as tensile strength, monotonic yield strength, elongation, area reduction and impact strength can lead to a false estimation of the material's fatigue behaviour. For this reason the powder metallurgical industry began to determine design-relevant material data on the example of the porous Fe-Cu-C- and Fe-Cu-Ni-alloys. The fatigue tests with notched specimen and different modes of loading show that porous sintered parts having mechanical notches are less sensitive to external notches than wrought steel, because crack-propagation is delayed by pores. The possibility to manufacture cyclic hardening alloys, their relative notch-insensitivity and with wrought steel comparable scatter of fatigue properties show the importance of sintered alloys as alternative materials. (orig.) [de

Fatigue damage monitoring for basalt fiber reinforced polymer composites using acoustic emission technique

Science.gov (United States)

Wang, Wentao; Li, Hui; Qu, Zhi

2012-04-01

Basalt fiber reinforced polymer (BFRP) is a structural material with superior mechanical properties. In this study, unidirectional BFRP laminates with 14 layers are made with the hand lay-up method. Then, the acoustic emission technique (AE) combined with the scanning electronic microscope (SEM) technique is employed to monitor the fatigue damage evolution of the BFRP plates in the fatigue loading tests. Time-frequency analysis using the wavelet transform technique is proposed to analyze the received AE signal instead of the peak frequency method. A comparison between AE signals and SEM images indicates that the multi-frequency peaks picked from the time-frequency curves of AE signals reflect the accumulated fatigue damage evolution and fatigue damage patterns. Furthermore, seven damage patterns, that is, matrix cracking, delamination, fiber fracture and their combinations, are identified from the time-frequency curves of the AE signals.

Obtaining and analysis of results of fatigue and corrosion-fatigue in steel API 5L X60; Obtencao e analise de resultados de fadiga e corrosao-fadiga em aco API 5L X60

Energy Technology Data Exchange (ETDEWEB)

Araujo, Bruno Allison [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Silva, Antonio Almeida; Santos, Fabio Gualberto Chagas [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

2008-07-01

The corrosion process allied to the fatigue, due to repetitive efforts of several natures, is the main responsible for the damages in pipeline and offshore structures that results in the appears of located faults, and by the way can results in leaks and financial and environmental loss. This phenomenon calls corrosion-fatigue, however, it is very complex, and mainly, in what it concerns the form as this it develops in the structure. The objective of this work is to present some results of experimental fatigue tests and corrosion-fatigue accomplished with specimen that the material originated a pipeline steel API 5L X60. The tests developed in a machine which could test until 12 specimens per time. For test of corrosion-fatigue was used a cell-of-corrosion especially projected, in this way simulated an aggressive environmental condition in a corrosion conditions. With the results of tests, was possible estimate the fatigue limits of the specimen when submitted to the repeated flexing, and compare it with evaluate corrosion-fatigue graphs, that as the literature comes moved down of the curve, in relation to the fatigue curve. (author)

Application of viscoelastic continuum damage approach to predict fatigue performance of Binzhou perpetual pavements

Directory of Open Access Journals (Sweden)

Wei Cao

2016-04-01

Full Text Available For this study, the Binzhou perpetual pavement test sections constructed in Shandong Province, China, were simulated for long-term fatigue performance using the layered viscoelastic pavement analysis for critical distresses (LVECD finite element software package. In this framework, asphalt concrete was treated in the context of linear viscoelastic continuum damage theory. A recently developed unified fatigue failure criterion that defined the boundaries of the applicable region of the theory was also incorporated. The mechanistic modeling of the fatigue mechanisms was able to accommodate the complex temperature variations and loading conditions of the field pavements in a rigorous manner. All of the material models were conveniently characterized by dynamic modulus tests and direct tension cyclic fatigue tests in the laboratory using cylindrical specimens. By comparing the obtained damage characteristic curves and failure criteria, it is found that mixtures with small aggregate particle sizes, a dense gradation, and modified asphalt binder tended to exhibit the best fatigue resistance at the material level. The 15-year finite element structural simulation results for all the test sections indicate that fatigue performance has a strong dependence on the thickness of the asphalt pavements. Based on the predicted location and severity of the fatigue damage, it is recommended that Sections 1 and 3 of the Binzhou test sections be employed for perpetual pavement design.

Fatigue testing on samples from Zircaloy-4 tubes type SEU-43

International Nuclear Information System (INIS)

Olaru, V.; Ionescu, V.; Nitu, A.; Ionescu, D.; Voicu, F.

2016-01-01

The paper presents the testing of samples worked from Zicaloy-4 tubes (as-received.. metallurgical state), utilized in the composition of the CANDU SEU-43 fuel bundle. These tests are intended to simulate their behaviour in a power cycling process inside the reactor. The testing process is of low cycle fatigue type, done outside of the reactor, on ''C-ring'' samples, cut along the transversal direction. These samples are tested at 1%, 2% and 3% amplitude deformation, at room temperature. The calibration curves for both types of tube (small and big diameter) are determined by using the finite element analyses with the ANSYS computer code. The cycling test results are in the form of a fatigue life curve (N-e) for zircaloy-4 used in the SEU-43 fuel bundle. The curve is determined by the experimental dependency between the number of cycles to fracture and the deformation amplitude. The low cycle fatigue mechanical tests done at room temperature together with electronic microscopy analyses have reflected the characteristic behaviour of the zircaloy-4 metal in the given environment conditions. (authors)

Time dependent design curves for a high nitrogen grade of 316LN stainless steel for fast reactor applications

Energy Technology Data Exchange (ETDEWEB)

Ganesh Kumar, J.; Ganesan, V.; Laha, K.; Mathew, M.D., E-mail: mathew@igcar.gov.in

2013-12-15

Highlights: • 316LN SS is an important high temperature structural material for sodium cooled fast reactors. • Creep strength of 316LN SS has been increased substantially by increasing the nitrogen content. • Creep design curves based on RCC-MR code procedures have been generated for this new material. • 100,000 h allowable stress at 600 °C increased by more than 40% as a result of doubling the nitrogen content in the steel. - Abstract: Type 316L(N) stainless steel (SS) containing 0.06–0.08 wt.% nitrogen is the major material for reactor assembly components of sodium cooled fast reactors (SFRs). With a view to increase the design life of SFRs to 60 years from the current life of 40 years, studies are being carried out to improve the high temperature creep and low cycle fatigue properties of 316LN SS by increasing the nitrogen content above 0.08 wt.%. In this investigation, the creep properties of a high nitrogen grade of 316LN SS containing 0.14 wt.% nitrogen have been studied. Creep tests were carried out at 550 °C, 600 °C and 650 °C at various stress levels in the range of 140–350 MPa. Creep strength was found to be significantly improved by doubling the nitrogen content in this steel. The maximum rupture life in these tests was 33,000 h. The creep data has been analyzed according to RCC-MR nuclear code procedures in order to generate the creep design curves for the high nitrogen grade of 316LN SS. Allowable stress for 100,000 h at 600 °C increased by more than 38% as a result of doubling the nitrogen content in the steel.

Tuning Low Cycle Fatigue Properties of Cu-Be-Co-Ni Alloy by Precipitation Design

Directory of Open Access Journals (Sweden)

Yanchuan Tang

2018-06-01

Full Text Available As material for key parts applied in the aerospace field, the Cu-Be-Co-Ni alloy sustains cyclic plastic deformation in service, resulting in the low cycle fatigue (LCF failure. The LCF behaviors are closely related to the precipitation states of the alloy, but the specific relevance is still unknown. To provide reasonable regulation of the LCF properties for various service conditions, the effect of precipitation states on the LCF behaviors of the alloy was investigated. It is found that the alloy composed fully of non-shearable γ′ precipitates has higher fatigue crack initiation resistance, resulting in a longer fatigue life under LCF process with low total strain amplitude. The alloy with fine shearable γ′I precipitates presents higher fatigue crack propagation resistance, leading to a longer fatigue life under LCF process with high total strain amplitude. The cyclic stress response behavior of the alloy depends on the competition between the kinematic hardening and isotropic softening. The fine shearable γ′I precipitates retard the decrease of effective stress during cyclic loading, causing cyclic hardening of the alloy. The present work would help to design reasonable precipitation states of the alloy for various cyclic loading conditions to guarantee its safety in service.

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

Science.gov (United States)

Razzaq, Zia

1989-01-01

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

Structural evolution and mechanisms of fatigue in polycrystalline brass

International Nuclear Information System (INIS)

Vejloe Carstensen, J.

1998-03-01

The plastic strain controlled fatigue behaviour of polycrystalline Cu-15%Zn and Cu-30%Zn has been investigated with the aim of studying the effect of slip mode modification by the addition of zinc to copper. It has been clearly demonstrated, that true cyclic saturation does not occur in the plastic strain controlled fatigue of brass. This complicates the contstruction of a cyclic stress-strain (CSS) curve and thus the comparison with copper. A method to overcome this complication has been suggested. Surface observations on fatigued brass specimens show that individual grains tend to deform by Sachs type single slip. This behaviour has been described by the self-consistent Sachs-Eshelby model, which provides estimates of the CSS curve for brass polycrystals. Successive stages of primary hardening, softening and secondary hardening has been observed in the plastic strain controlled fatigue of brass. It has been found that the primary hardening is attributed to an increase of intergranular stresses whereas the secondary hardening apparently is attributed to an increase of friction stresses. Investigations of the structural evolution show that the softening behaviour can be explained by the presence of short-range order (SRO). SRO promote the formation of extended dipole arrays which hardens the material. The formation of intense shear bands destroy the dipole arrays, which explains the cyclic softening. The present results reveal that Cu-30%Zn in a pure planar slip alloy, while Cu-15%Zn displays both planar and wavy slip. The mechanical and structural behaviour observed in brass resembles recent observations in 316L austenitic stainless steels, and the present results reveal that Cu-30%Zn and 316L have approximately the same fatigue life curve. This emphasizes brass as being a convenient model system for the industrially important austenitic steels. (au)

Fatigue behavior of a bolted assembly - a comparison between numerical analysis and experimental analysis

International Nuclear Information System (INIS)

Bosser, M.; Vagner, J.

1987-01-01

The fatigue behavior of a bolted assembly can be analysed, either by fatigue tests, or by computing the stress variations and using a fatigue curve. This paper presents the fatigue analysis of a stud-bolt and stud-flange of a steam generator manway carried out with the two methods. The experimental analysis is performed for various levels of load, according to the recommandations of the ASME code section III appendix II. The numerical analysis of the stresses is based on the results of a finite element analysis performed with the program SYSTUS. The maximum stresses are obtained in the first bolt threads. In using these stresses, the allowable number of cycles for each level of loading analysed, is obtained from fatigue curves, as defined in appendix I section III of the ASME code. The analysis underlines that, for each level of load the purely numerical approach is highly conservative, compared to the experimental approach. (orig.)

Multi-purpose fatigue sensor. Part 1. Uniaxial and multiaxial fatigue

Directory of Open Access Journals (Sweden)

M.V. Karuskevich

2016-10-01

Full Text Available The paper describes the key principles and results of preliminary experiments aimed at the development of new technique for the fatigue life prediction under conditions of biaxial cyclic tension. The foundations of the method were developed early by the numerous tests with monitoring the process of surface deformation relief formation, which is proved to be an indicator of accumulated fatigue damage under uniaxial fatigue. The employed phenomenon was early applied for the development of a family of uniaxial loading fatigue sensors. The formation of strain induced relief has been recently taken into consideration as a part of damage accumulation criteria under biaxial fatigue as well. The home-made testing machine has been designed to implement combined bending and torsion loading that simulates loads experienced by an aircraft wing skin. The experimental evidences on formation and evolution of the deformation relief revealed under conditions of combined loading, supports the proposed concept of biaxial fatigue sensor

New fatigue damage analysis of complex engineering components based on FEM

International Nuclear Information System (INIS)

Ott, W.

1987-05-01

A new type of fatigue damage analysis for multiaxial elastoplastic conditions based on a three-dimensional finite element analysis has been developed. The analysis includes the material model after Mroz. The fatigue life evaluation in the critical areas is based on plastic work at these locations. The proposed damage concept can be applied to arbitrary multiaxial stress-strain paths. For the evaluation of the damage cycles in terms of closed stress-strain hysteresis loops are not required. The damage is determined on the basis of uniaxial material data (stress-strain curve, life to crack iniation curve). (orig./HP) [de

Study of curved glass photovoltaic module and module electrical isolation design requirements

Science.gov (United States)

1980-06-01

The design of a 1.2 by 2.4 m curved glass superstrate and support clip assembly is presented, along with the results of finite element computer analysis and a glass industry survey conducted to assess the technical and economic feasibility of the concept. Installed costs for four curved glass module array configurations are estimated and compared with cost previously reported for comparable flat glass module configurations. Electrical properties of candidate module encapsulation systems are evaluated along with present industry practice for the design and testing of electrical insulation systems. Electric design requirements for module encapsulation systems are also discussed.

Life prediction of l6 steel using strain-life curve and cyclic stress-strain curve by means of low cycle fatigue testing

Science.gov (United States)

Inamdar, Sanket; Ukhande, Manoj; Date, Prashant; Lomate, Dattaprasad; Takale, Shyam; Singh, RKP

2017-05-01

L6 Steel is used as die material in closed die hot forging process. This material is having some unique properties. These properties are due to its composition. Strain softening is the noticeable property of this material. Due to this in spite of cracking at high stress this material gets plastically deformed and encounters loss in time as well as money. Studies of these properties are necessary to nurture this material at fullest extent. In this paper, numerous experiments have been carried on L6 material to evaluate cyclic Stress - strain behavior as swell as strain-life behavior of the material. Low cycle fatigue test is carried out on MTS fatigue test machine at fully reverse loading condition R=-1. Also strain softening effect on forging metal forming process is explained in detail. The failed samples during low cycle fatigue test further investigated metallurgically on scanning electron microscopy. Based on this study, life estimation of hot forging die is carried out and it’s correlation with actual shop floor data is found out. This work also concludes about effect of pre-treatments like nitro-carburizing and surface coating on L6 steel material, to enhance its fatigue life to certain extent.

Creep-fatigue damage evaluation for SS-316LN (ORNL PLATES): - RCC-MR vs. ASME SEC III - NH

International Nuclear Information System (INIS)

Sati, Bhuwan Chandra; Jalaldeen, S.; Velusamy, K.; Selvaraj, P.

2016-01-01

Investigations of high temperature tests done on ORNL plate with deformation control loading, under creep-fatigue damage have been presented. The test results with methodology of RCC-MR and ASME-NH life prediction under creep-fatigue loading have been assessed. The stress relaxation effect in calculating the life using RCC-MR under creep-fatigue damage is found to be significant in presence of secondary stress. RCC-MR: 2007 is more realistic number of cycles (predicts 51 number of cycles) as compared to ASME-NH (predicts 312 number of cycles) which is demonstrated by the experimental work (observed 86 numbers of cycles). Between RCC-MR and experimental work, design code seems to be more conservative for life prediction due to creep-fatigue damage. For fatigue damage, the approaches are same and the difference comes from material properties and the starting stress for applying Neuber's rule. ASME approach has the limitation of stress range magnitude. ASME approach predicts lower elastic plus plastic strain for the cases having S* above the linear stress limit. For creep strain and creep damage evaluation, ASME and RCC-MR have different approaches for calculating the stress at the beginning and during the hold period. The RCC-MR takes account of cyclic hardening or softening effects (hardening in the present case of 316 LN) by means of the cyclic stress-strain curve and the benefit of symmetrization effects which are significant for this material. The ASME code neglects these effects and instead relies on an approach based on the isochronous stress-strain curves. (author)

Fatigue assessments in operating nuclear power plants

International Nuclear Information System (INIS)

Gosselin, S.R.; Deardorff, A.F.; Peltola, D.W.

1994-01-01

In November 1991, the ASME Section XI Task Group on Operating Plant Fatigue Assessment was formed to develop criteria and evaluation methodology for evaluating the effects of cyclic operation in operating nuclear power plants. The objective was to develop guidelines for inclusion in Section XI that could be used by plant operators in evaluating fatigue concerns and their impact on serviceability. This paper discusses the work performed by the Task Group. It explores the concept of ''Fatigue Design Basis'' versus ''Fatigue Operating Basis'' by examining the roles of ASME Section III and ASME Section XI in the design and operation of the nuclear power plants. Guidelines are summarized that may help plant operators perform effective design transient cycle evaluations and optimize cycle counting and fatigue usage tracking. The alternative fatigue evaluation approach using flaw tolerance is also introduced

Fatigue behaviour of X70 steel in crude oil

Czech Academy of Sciences Publication Activity Database

Gajdoš, Lubomír; Šperl, Martin; Bystrianský, J.

2015-01-01

Roč. 49, č. 2 (2015), s. 243-246 ISSN 1580-2949 R&D Projects: GA ČR(CZ) GAP105/10/2052; GA TA ČR(CZ) TE02000162 Institutional support: RVO:68378297 Keywords : corrosion fatigue * S-N curve * X70 steel * crude oil * separated water Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.439, year: 2015 http://mit.imt.si/Revija/izvodi/mit152/gajdos.pdf

Fatigue Behavior of Steel Fiber Reinforced High-Strength Concrete under Different Stress Levels

Science.gov (United States)

Zhang, Chong; Gao, Danying; Gu, Zhiqiang

2017-12-01

The investigation was conducted to study the fatigue behavior of steel fiber reinforced high-strength concrete (SFRHSC) beams. A series of 5 SFRHSC beams was conducted flexural fatigue tests at different stress level S of 0.5, 0.55, 0.6, 0.7 and 0.8 respectively. Static test was conducted to determine the ultimate static capacity prior to fatigue tests. Fatigue modes and S-N curves were analyzed. Besides, two fatige life prediction model were analyzed and compared. It was found that stress level S significantly influenced the fatigue life of SFRHSC beams and the fatigue behavior of SFRHSC beams was mainly determined by the tensile reinforcement.

Flexible hardware design for RSA and Elliptic Curve Cryptosystems

NARCIS (Netherlands)

Batina, L.; Bruin - Muurling, G.; Örs, S.B.; Okamoto, T.

2004-01-01

This paper presents a scalable hardware implementation of both commonly used public key cryptosystems, RSA and Elliptic Curve Cryptosystem (ECC) on the same platform. The introduced hardware accelerator features a design which can be varied from very small (less than 20 Kgates) targeting wireless

On the estimation of durability during thermal fatigue tests

International Nuclear Information System (INIS)

Vashunin, A.I.; Kotov, P.I.

1981-01-01

It is shown that during thermal fatigue tests under conditions of varying loading rigidity the value of stored one-sided deformation in a fracture zone tends to the limit value of material ductility. Holding at Tsub(max) is semicycle of compression increases irreversible deformation on value of Atausub(confer)sup(a), which does not depend on loading rigidity. It is established that the Use of curves of thermal fatigue as basic ones for determination of resistance of non-isothermal low-cycle fatigue is possible only at values of stored quasistatical damage, constituting less than 5% from available ductility [ru

Shoulder girdle muscle activity and fatigue in traditional and improved design carpet weaving workstations.

Science.gov (United States)

Allahyari, Teimour; Mortazavi, Narges; Khalkhali, Hamid Reza; Sanjari, Mohammad Ali

2016-01-01

Work-related musculoskeletal disorders in the neck and shoulder regions are common among carpet weavers. Working for prolonged hours in a static and awkward posture could result in an increased muscle activity and may lead to musculoskeletal disorders. Ergonomic workstation improvements can reduce muscle fatigue and the risk of musculoskeletal disorders. The aim of this study is to assess and to compare upper trapezius and middle deltoid muscle activity in 2 traditional and improved design carpet weaving workstations. These 2 workstations were simulated in a laboratory and 12 women carpet weavers worked for 3 h. Electromyography (EMG) signals were recorded during work in bilateral upper trapezius and bilateral middle deltoid. The root mean square (RMS) and median frequency (MF) values were calculated and used to assess muscle load and fatigue. Repeated measure ANOVA was performed to assess the effect of independent variables on muscular activity and fatigue. The participants were asked to report shoulder region fatigue on the Borg's Category-Ratio scale (Borg CR-10). Root mean square values in workstation A are significantly higher than in workstation B. Furthermore, EMG amplitude was higher in bilateral trapezius than in bilateral deltoid. However, muscle fatigue was not observed in any of the workstations. The results of the study revealed that muscle load in a traditional workstation was high, but fatigue was not observed. Further studies investigating other muscles involved in carpet weaving tasks are recommended. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

A study on damage and fatigue characteristics of plain woven carbon fiber reinforced composite material(I)

International Nuclear Information System (INIS)

Kim, Kwang Soo; Kim, Sang Tae

1993-01-01

The characteristics of damage and fatigue subjected to tensile fatigue loading in plain woven carbon fiber reinforced composite material were studied. Constant amplitude load of 90% stress of notch strength was applied to each specimen, which had different initial notch length, and crack dectectvie compliance curve was determined form load-displacement data. The effective crack length(a eff ) was obtained form this compliance curve and the effective crack growth could be divided to three-steps and explained separately. After cycling the shape of fatigue crack was observed by S.E.M.. Change of elastic modulus(E N ) during fatigue cycle was explained by repeated sudden-death medel. The material constant determined by Jen-Hsu model was more useful to evaluate damage than Wang-Chim model. (Author)

Fatigue Damage Predictions in Aluminium Constructions

DEFF Research Database (Denmark)

Jensen, Jørgen Juncher; Toernqvist, Rikard; Nielsen, Poul Erik

2002-01-01

The paper describes parts of the outcome of a large Danish research project on Large Scale Aluminum Connections. The topic addressed is calculation of fatigue failure in complicated welded aluminum connections. The calculation procedure is based on a S-N curve for the hot-spot stresses at the wel...

A survey of fatigue monitoring in the nuclear power industry

International Nuclear Information System (INIS)

Ware, A.G.

1991-01-01

The original design of nuclear power plants addressed fatigue concerns by including calculations of projected fatigue usage for specific components; the calculations were based on estimates of the number and severity of expected transients over the 40-year design life of the plants. In some cases, the transients occurring in the plants are not as severe as was anticipated in the original design analyses, while in other cases events have occurred that were not anticipated in the design basis documents. Field failures caused by fatigue have identified some of those cases. In response, several organizations in the United States and overseas have developed fatigue monitoring programs to more accurately estimate the fatigue usage. One basic approach consists of reconstructing the fatigue usage to date based on the transients recorded in the operating history instead of those projected in the design documents. Another approach includes monitoring the plant instrumentation to determine actual values for parameters such as temperature and pressure and using the measured values in the fatigue usage calculations instead of the values projected in the design documents. The use of existing plant instrumentation to measure temperature, pressure, flow rate, etc., along with the incorporation of conservative assumptions, had generally proven adequate for estimating fatigue usage; however, in some cases additional instrumentation installed for local monitoring can provide a more accurate estimate, especially where thermal stratification is known to occur. Fatigue monitoring can aid in identifying fatigue concerns not anticipated in the original design and for reducing the excessive conservatism in some of the original design calculations so that the fatigue lives of these components can be justified as they age. Fatigue monitoring can also assist efforts to reduce ongoing fatigue usage through design modifications and operating procedure changes

Metabolomic markers of fatigue: Association between circulating metabolome and fatigue in women with chronic widespread pain.

Science.gov (United States)

Freidin, Maxim B; Wells, Helena R R; Potter, Tilly; Livshits, Gregory; Menni, Cristina; Williams, Frances M K

2018-02-01

Fatigue is a sensation of unbearable tiredness that frequently accompanies chronic widespread musculoskeletal pain (CWP) and inflammatory joint disease. Its mechanisms are poorly understood and there is a lack of effective biomarkers for diagnosis and onset prediction. We studied the circulating metabolome in a population sample characterised for CWP to identify biomarkers showing specificity for fatigue. Untargeted metabolomic profiling was conducted on fasting plasma and serum samples of 1106 females with and without CWP from the TwinsUK cohort. Linear mixed-effects models accounting for covariates were used to determine relationships between fatigue and metabolites. Receiver operating curve (ROC)-analysis was used to determine predictive value of metabolites for fatigue. While no association between fatigue and metabolites was identified in twins without CWP (n=711), in participants with CWP (n=395), levels of eicosapentaenoate (EPA) ω-3 fatty acid were significantly reduced in those with fatigue (β=-0.452±0.116; p=1.2×10 -4 ). A significant association between fatigue and two other metabolites also emerged when BMI was excluded from the model: 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), and C-glycosyltryptophan (p=1.5×10 -4 and p=3.1×10 -4 , respectively). ROC analysis has identified a combination of 15 circulating metabolites with good predictive potential for fatigue in CWP (AUC=75%; 95% CI 69-80%). The results of this agnostic metabolomics screening show that fatigue is metabolically distinct from CWP, and is associated with a decrease in circulating levels of EPA. Our panel of circulating metabolites provides the starting point for a diagnostic test for fatigue in CWP. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Effects of applied stress ratio on the fatigue behavior of additively manufactured porous biomaterials under compressive loading.

Science.gov (United States)

de Krijger, Joep; Rans, Calvin; Van Hooreweder, Brecht; Lietaert, Karel; Pouran, Behdad; Zadpoor, Amir A

2017-06-01

Additively manufactured (AM) porous metallic biomaterials are considered promising candidates for bone substitution. In particular, AM porous titanium can be designed to exhibit mechanical properties similar to bone. There is some experimental data available in the literature regarding the fatigue behavior of AM porous titanium, but the effect of stress ratio on the fatigue behavior of those materials has not been studied before. In this paper, we study the effect of applied stress ratio on the compression-compression fatigue behavior of selective laser melted porous titanium (Ti-6Al-4V) based on the diamond unit cell. The porous titanium biomaterial is treated as a meta-material in the context of this work, meaning that R-ratios are calculated based on the applied stresses acting on a homogenized volume. After morphological characterization using micro computed tomography and quasi-static mechanical testing, the porous structures were tested under cyclic loading using five different stress ratios, i.e. R = 0.1, 0.3, 0.5, 0.7 and 0.8, to determine their S-N curves. Feature tracking algorithms were used for full-field deformation measurements during the fatigue tests. It was observed that the S-N curves of the porous structures shift upwards as the stress ratio increases. The stress amplitude was the most important factor determining the fatigue life. Constant fatigue life diagrams were constructed and compared with similar diagrams for bulk Ti-6Al-4V. Contrary to the bulk material, there was limited dependency of the constant life diagrams to mean stress. The notches present in the AM biomaterials were the sites of crack initiation. This observation and other evidence suggest that the notches created by the AM process cause the insensitivity of the fatigue life diagrams to mean stress. Feature tracking algorithms visualized the deformation during fatigue tests and demonstrated the root cause of inclined (45°) planes of specimen failure. In conclusion, the R

Study of interaction of fatigue damage and ratcheting. Effect of a tensile primary load on torsion fatigue resistance of stainless steel 304 L at ambient temperature

International Nuclear Information System (INIS)

Hakem, N.S.

1987-01-01

Effect of ratcheting on fatigue resistance of a stainless steel 304 L, used for reactor vessels, is studied experimentally. Lifetime of samples is reduced if a static constant tensile load (primary loading) is superimposed to cyclic torsion deformations (secondary loading). An equivalent deformation concept is developed to express a criterion of fatigue rupture under primary loading. No effect is noted on the curve of cyclic strain hardening. This fatigue analysis gives no information on cumulated axial deformation. Progressive elongation, observed during testing, is dependent of primary and secondary loading. Rupture is produced by fatigue because cumulated axial deformation is limited ( 4 cycles at rupture cumulated deformation is [fr

IEA Joint Action. Wind turbine fatigue

Energy Technology Data Exchange (ETDEWEB)

Maribo Pedersen, B [ed.

1996-09-01

Fatigue research on wind turbine blade material has been an important issue over the years in many countries and in the E.U. As a result of the effort the knowledge on fatigue properties of fibre reinforced materials has been expanded enormously. Practical fatigue design properties are available for constant amplitude tests at ambient temperatures. A lack of knowledge can be shown in several other fields, such as variable amplitude and multi-axial testing and the influence of the environment and carbon fibres. Fatigue is seen as dominant for the blade design, improvements in both the load prediction and material fatigue properties should be strove for. In discussions with blade manufacturers and subsidy agencies (E.U. DGXII, NOVEM, ETSU, etc.) on the importance of continuous materials fatigue research the improvement in reliability should be stressed. (au)

Probability of failure prediction for step-stress fatigue under sine or random stress

Science.gov (United States)

Lambert, R. G.

1979-01-01

A previously proposed cumulative fatigue damage law is extended to predict the probability of failure or fatigue life for structural materials with S-N fatigue curves represented as a scatterband of failure points. The proposed law applies to structures subjected to sinusoidal or random stresses and includes the effect of initial crack (i.e., flaw) sizes. The corrected cycle ratio damage function is shown to have physical significance.

Low cycle fatigue design data for India-specific reduced activation ferritic-martensitic (IN-RAFM) steel

Energy Technology Data Exchange (ETDEWEB)

Mariappan, K.; Shankar, Vani, E-mail: vani@igcar.gov.in; Sandhya, R.; Laha, K.

2016-03-15

Highlights: • Generation of first set of experimental data related to LCF performance of the commercial heat of IN-RAFM steel. • Analysis of cyclic behavior from the perspective of both design and material characteristics. • Various correction factors to account for various plastic strain accumulations, change in Poisson’s ratio and asymmetry of loadings. • Low cycle fatigue design parameters and correction factor values were comparable with P91 steel as reported in RCC-MR design code. - Abstract: The objective of the present paper is to provide first hand experimental data and analysis on the low cycle fatigue (LCF) performance of a commercial heat of Indian reduced activation ferritic-martensitic (IN-RAFM) steel. Since this material is not yet codified in RCC-MR, cyclic properties were generated for the design of the structural material of the Test Blanket Modules (TBM) made of RAFM steel. Hence, as a part of the material development program, LCF experiments were conducted on IN-RAFM steel obtained in the normalized and tempered condition. Total axial strain controlled experiments were performed in air by employing strain amplitudes ranging from ±0.25 to ±1.0% and at temperatures of 300, 673, 723, 823, and 873 K and a nominal strain rate, 3 × 10{sup −3} s{sup −1}. In the present work, various cyclic parameters that are useful for the design oriented fatigue analysis are derived as per the systematic procedure given in the RCC-MR design code. The physical significance of each design parameter such as elasto-plastic corrections based on Neuber analysis has been explained and correlated with the material behavior such as the cyclic softening nature of the RAFM steel.

Prodeto, a computer code for probabilistic fatigue design

Energy Technology Data Exchange (ETDEWEB)

Braam, H [ECN-Solar and Wind Energy, Petten (Netherlands); Christensen, C J; Thoegersen, M L [Risoe National Lab., Roskilde (Denmark); Ronold, K O [Det Norske Veritas, Hoevik (Norway)

1999-03-01

A computer code for structural relibility analyses of wind turbine rotor blades subjected to fatigue loading is presented. With pre-processors that can transform measured and theoretically predicted load series to load range distributions by rain-flow counting and with a family of generic distribution models for parametric representation of these distribution this computer program is available for carying through probabilistic fatigue analyses of rotor blades. (au)

Materials design data for fusion reactors

International Nuclear Information System (INIS)

Tavassoli, A.A.F.

1998-01-01

Design data needed for fusion reactors are characterized by the diversity of materials and the complexity of loading situations found in these reactors. In addition, advanced fabrication techniques, such as hot isostatic pressing, envisaged for fabrication of single and multilayered in-vessel components, could significantly change the original materials properties for which the current design rules are written. As a result, additional materials properties have had to be generated for fusion reactors and new structural design rules formulated. This paper recalls some of the materials properties data generated for ITER and DEMO, and gives examples of how these are converted into design criteria. In particular, it gives specific examples for the properties of 316LN-IG and modified 9Cr-1Mo steels, and CuCrZr alloy. These include, determination of tension, creep, isochronous, fatigue, and creep-fatigue curves and their analysis and conversion into design limits. (orig.)

Materials design data for fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A.A.F. [CEA Commissariat a l`Energie Atomique, Gif sur Yvette (France). CEREM

1998-10-01

Design data needed for fusion reactors are characterized by the diversity of materials and the complexity of loading situations found in these reactors. In addition, advanced fabrication techniques, such as hot isostatic pressing, envisaged for fabrication of single and multilayered in-vessel components, could significantly change the original materials properties for which the current design rules are written. As a result, additional materials properties have had to be generated for fusion reactors and new structural design rules formulated. This paper recalls some of the materials properties data generated for ITER and DEMO, and gives examples of how these are converted into design criteria. In particular, it gives specific examples for the properties of 316LN-IG and modified 9Cr-1Mo steels, and CuCrZr alloy. These include, determination of tension, creep, isochronous, fatigue, and creep-fatigue curves and their analysis and conversion into design limits. (orig.) 19 refs.

Investigation into fatigue crack growth and kinetic diagrams of fatigue failure

International Nuclear Information System (INIS)

Yarema, S.Ya.

1977-01-01

Studies on fatigue failure are discussed in terms of fatigue failure kinetic diagrams (FFKD), in which the fatigue crack growth rate is plotted against the stress intensity coefficient (SIC). The physical sense of the crack growth rate and SIC is discussed and their applicability for description of the material in the destruction zone, particularly in presence of various media. Variation of experimental parameters (loading and environment) is followed by a transition period during which the results of the experiment may depend on its history, so that FFKD would remain invariant. Advantages of tests under constant experimental conditions are shown. The ways to stabilize SIC are indicated and requirements to the samples are given. As an example, the tests of disc samples made of plate materials are given, where SIC does not depend on the crack length. The question of controlling the experimental conditions such as asymmetry and shape of the loading cycle, loading frequency, fluctuations of temperature and air composition is considered. The analytical functions describing FFKD are discussed. It is shown, that in appropriate dimensionless coordinates the FFKD of different materials merge into one curve

Development and characterization of fatigue resistant aramid reinforced aluminium laminates (ARALL) for fatigue critical aircraft components

International Nuclear Information System (INIS)

Qaiser, M. H.; Umar, S.; Nauman, S.

2013-01-01

The structural weight of an aircraft has always been a controlling parameter that governs its fuel efficiency and transport capacity. In pursuit of achieving light-weight aircraft structures, high design stress levels have to be adopted and materials with high specific strength such as Aluminum etc. are to be deployed. However, an extensive spectrum of fatigue load exists at the aircraft wings and other aerodynamic components that may cause initiation and propagation of fatigue cracks and concludes in a catastrophic rupture. Fatigue is therefore the limiting design parameter in such cases and materials with high fatigue resistance are then required. A major improvement in the fatigue behavior was observed by laminating Kevlar fibers with Aluminum using epoxy. ARALL (Aramid Reinforced Aluminum Laminates) is a fatigue resistant hybrid composite that consists of layers of thin high strength aluminum alloy sheets surface bonded with aramid fibers. The intact aramid fibers tie up the fatigue cracks, thus reducing the stress intensity factor at the crack tip as a result of which the fatigue properties of can be enhanced with orders of magnitude as compared to monolithic high strength Aluminum alloy sheets. Significant amount of weight savings can be achieved in fatigue critical components in comparison with the traditional materials used in aircraft. (author)

Development and characterization of fatigue resistant Aramid reinforced aluminium laminates (ARALL) for fatigue Critical aircraft components

Science.gov (United States)

Qaiser, M. H.; Umar, S.; Nauman, S.

2014-06-01

The structural weight of an aircraft has always been a controlling parameter that governs its fuel efficiency and transport capacity. In pursuit of achieving light-weight aircraft structures, high design stress levels have to be adopted and materials with high specific strength such as Aluminum etc. are to be deployed. However, an extensive spectrum of fatigue load exists at the aircraft wings and other aerodynamic components that may cause initiation and propagation of fatigue cracks and concludes in a catastrophic rupture. Fatigue is therefore the limiting design parameter in such cases and materials with high fatigue resistance are then required. A major improvement in the fatigue behavior was observed by laminating Kevlar fibers with Aluminum using epoxy. ARALL (Aramid Reinforced ALuminum Laminates) is a fatigue resistant hybrid composite that consists of layers of thin high strength aluminum alloy sheets surface bonded with aramid fibers. The intact aramid fibers tie up the fatigue cracks, thus reducing the stress intensity factor at the crack tip as a result of which the fatigue properties of can be enhanced with orders of magnitude as compared to monolithic high strength Aluminum alloy sheets. Significant amount of weight savings can be achieved in fatigue critical components in comparison with the traditional materials used in aircraft.

Development and characterization of fatigue resistant Aramid reinforced aluminium laminates (ARALL) for fatigue Critical aircraft components

International Nuclear Information System (INIS)

Qaiser, M H; Umar, S; Nauman, S

2014-01-01

The structural weight of an aircraft has always been a controlling parameter that governs its fuel efficiency and transport capacity. In pursuit of achieving light-weight aircraft structures, high design stress levels have to be adopted and materials with high specific strength such as Aluminum etc. are to be deployed. However, an extensive spectrum of fatigue load exists at the aircraft wings and other aerodynamic components that may cause initiation and propagation of fatigue cracks and concludes in a catastrophic rupture. Fatigue is therefore the limiting design parameter in such cases and materials with high fatigue resistance are then required. A major improvement in the fatigue behavior was observed by laminating Kevlar fibers with Aluminum using epoxy. ARALL (Aramid Reinforced ALuminum Laminates) is a fatigue resistant hybrid composite that consists of layers of thin high strength aluminum alloy sheets surface bonded with aramid fibers. The intact aramid fibers tie up the fatigue cracks, thus reducing the stress intensity factor at the crack tip as a result of which the fatigue properties of can be enhanced with orders of magnitude as compared to monolithic high strength Aluminum alloy sheets. Significant amount of weight savings can be achieved in fatigue critical components in comparison with the traditional materials used in aircraft

Towards a unified fatigue life prediction method for marine structures

CERN Document Server

Cui, Weicheng; Wang, Fang

2014-01-01

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

Probabilistic finite elements for fracture and fatigue analysis

Science.gov (United States)

Liu, W. K.; Belytschko, T.; Lawrence, M.; Besterfield, G. H.

1989-01-01

The fusion of the probabilistic finite element method (PFEM) and reliability analysis for probabilistic fracture mechanics (PFM) is presented. A comprehensive method for determining the probability of fatigue failure for curved crack growth was developed. The criterion for failure or performance function is stated as: the fatigue life of a component must exceed the service life of the component; otherwise failure will occur. An enriched element that has the near-crack-tip singular strain field embedded in the element is used to formulate the equilibrium equation and solve for the stress intensity factors at the crack-tip. Performance and accuracy of the method is demonstrated on a classical mode 1 fatigue problem.

Study on high-cycle fatigue behavior of candidate Fe-Cr-Ni alloys for SCWR

International Nuclear Information System (INIS)

Zhao Yuxiang; Liu Guiliang; Tang Rui; Xiong Ru; Qiao Yingjie

2014-01-01

In the design for supercritical water reactor (SCWR), the operating temperature, pressure, burn up and irradiation damage are very high, so it seems vital to make correct choice of structural materials in core and obtain their key application behavior which would beneficial the research and development of SCWR. In this paper, the high cycle fatigue (HCF) tests of commerce austenite alloys including 6XN and 825 were conducted under bending and rotating loads at room temperature (RT) as well as at 550 ℃ in air. The experimental data were analyzed and the S-N curves were processed, the fracture morphology was also observed by SEM. The results indicate that the fatigue limited stresses at RT for the 2 Fe-Cr-Ni alloy were in such order of 825 < 6XN, which consistent with the order of their tensile strength. Elevated temperature would accelerate the oxidation of the specimen and therefore the fatigue life would decrease, among them 6XN was more sensitive to high temperature with the larger decreasing tendency which make the fatigue limited stress of the two alloys more closer at 550 ℃. While 825 is more sensitive to the stress cycles. All the two alloys have good resistance to high cycle fatigue when comparing their experimental data with the calculated value from the empirical formula. The fracture morphology presents areas of crack initiation, crack growth and fracture, the fracture area has much dimples. This work can be applied to the conceptional design for SCWR. (authors)

Fast prediction of the fatigue behavior of short-fiber-reinforced thermoplastics based on heat build-up measurements: application to heterogeneous cases

Science.gov (United States)

Serrano, Leonell; Marco, Yann; Le Saux, Vincent; Robert, Gilles; Charrier, Pierre

2017-09-01

Short-fiber-reinforced thermoplastics components for structural applications are usually very complex parts as stiffeners, ribs and thickness variations are used to compensate the quite low material intrinsic stiffness. These complex geometries induce complex local mechanical fields but also complex microstructures due to the injection process. Accounting for these two aspects is crucial for the design in regard to fatigue of these parts, especially for automotive industry. The aim of this paper is to challenge an energetic approach, defined to evaluate quickly the fatigue lifetime, on three different heterogeneous cases: a classic dog-bone sample with a skin-core microstructure and two structural samples representative of the thickness variations observed for industrial components. First, a method to evaluate dissipated energy fields from thermal measurements is described and is applied to the three samples in order to relate the cyclic loading amplitude to the fields of cyclic dissipated energy. Then, a local analysis is detailed in order to link the energy dissipated at the failure location to the fatigue lifetime and to predict the fatigue curve from the thermomechanical response of one single sample. The predictions obtained for the three cases are compared successfully to the Wöhler curves obtained with classic fatigue tests. Finally, a discussion is proposed to compare results for the three samples in terms of dissipation fields and fatigue lifetime. This comparison illustrates that, if the approach is leading to a very relevant diagnosis on each case, the dissipated energy field is not giving a straightforward access to the lifetime cartography as the relation between fatigue failure and dissipated energy seems to be dependent on the local mechanical and microstructural state.

Evaluation of aluminum drill-pipe material and design

Energy Technology Data Exchange (ETDEWEB)

Placido, Joao C. [PETROBRAS, Rio de Janeiro, RJ (Brazil); Lourenco, Marcelo I.; Netto, Theodoro Antoun [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE)

2008-07-01

Experimental program and numerical analyses were carried out to investigate the fatigue mechanisms of aluminum drill pipes designed and manufactured in compliance with ISO 15546. The main objective is to improve the fatigue performance of these components by selecting the appropriate aluminum alloy and by enhancing the mechanical design of the threaded steel connector. This paper presents the experimental test program and numerical analyses conducted on a drill-pipe of different materials (Al-Cu-Mg and Al-Zn-Mg system aluminum alloys) and geometry. Material mechanical properties, including S-N curve, were determined through small-scale tests on specimens cut from actual drill pipes. Full-scale experiments were also performed in laboratory. A finite element model of the drill pipe, including the tool-joint region, was developed. The model simulates, through different load steps, the tool-joint hot assembly, and then reproduces the physical experiments numerically in order to obtain the actual stress distribution. Good correlation between full-scale and small-scale fatigue tests was obtained by adjusting the strain/stress levels monitored in the full-scale tests in light of the numerical simulations and performing fatigue life calculations via multiaxial fatigue models. The weak points of the current practice design are highlighted for further development. (author)

A Real-time Evaluation Technique of Fatigue Damage in Adhesively Bonded Composite-Metal Joints

International Nuclear Information System (INIS)

Kwon, Oh Yang; Kim, Tae Hyun

1999-01-01

One of the problems for practical use of fiber-reinforced plastics is the performance degradation by fatigue damage in the joints. The study is to develop a nondestructive technique for real-time evaluation of adhesively bonded composite-metal joints. From the prior study we confirmed that the bonding strength can be estimated from the correlation between the qualify of bonded parts and AUP's. We obtained a curve showing the correlation between the degree of fatigue damage and AUP's calculated from signals acquired during fatigue loading of single-lap and double-lap joints of CFRP and Al6061. The curve is an analogy to the one showing stiffness reduction (E/Eo) of polymer matrix composites by fatigue damage. From those facts, it is plausible to predict the degree of fatigue damage in real-time. Amplitude and AUP2 appeared to be optimal parameters to provide more reliable results for single-lap joints whereas Amplitude and AUP2 did for double-lap joints. It is recommended to select optimal parameters for different geometries in the application for real structures

A Real-time Evaluation Technique of Fatigue Damage in Adhesively Bonded Composite-Metal Joints

Energy Technology Data Exchange (ETDEWEB)

Kwon, Oh Yang; Kim, Tae Hyun [Inha University, Incheon (Korea, Republic of)

1999-12-15

One of the problems for practical use of fiber-reinforced plastics is the performance degradation by fatigue damage in the joints. The study is to develop a nondestructive technique for real-time evaluation of adhesively bonded composite-metal joints. From the prior study we confirmed that the bonding strength can be estimated from the correlation between the qualify of bonded parts and AUP's. We obtained a curve showing the correlation between the degree of fatigue damage and AUP's calculated from signals acquired during fatigue loading of single-lap and double-lap joints of CFRP and Al6061. The curve is an analogy to the one showing stiffness reduction (E/Eo) of polymer matrix composites by fatigue damage. From those facts, it is plausible to predict the degree of fatigue damage in real-time. Amplitude and AUP2 appeared to be optimal parameters to provide more reliable results for single-lap joints whereas Amplitude and AUP2 did for double-lap joints. It is recommended to select optimal parameters for different geometries in the application for real structures

Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds.

Science.gov (United States)

Song, Wei; Liu, Xuesong; Berto, Filippo; Razavi, S M J

2018-04-24

The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2⁻1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds

Directory of Open Access Journals (Sweden)

Wei Song

2018-04-01

Full Text Available The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2–1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-01-03

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

A fatigue approach to wind turbine control

International Nuclear Information System (INIS)

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

2007-01-01

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

Prediction of Accurate Mixed Mode Fatigue Crack Growth Curves using the Paris' Law

Science.gov (United States)

Sajith, S.; Krishna Murthy, K. S. R.; Robi, P. S.

2017-12-01

Accurate information regarding crack growth times and structural strength as a function of the crack size is mandatory in damage tolerance analysis. Various equivalent stress intensity factor (SIF) models are available for prediction of mixed mode fatigue life using the Paris' law. In the present investigation these models have been compared to assess their efficacy in prediction of the life close to the experimental findings as there are no guidelines/suggestions available on selection of these models for accurate and/or conservative predictions of fatigue life. Within the limitations of availability of experimental data and currently available numerical simulation techniques, the results of present study attempts to outline models that would provide accurate and conservative life predictions.

Residual stress behaviors induced by laser peening along the edge of curved models

International Nuclear Information System (INIS)

Im, Jong Bin; Grandhi, Ramana V.; Ro, Young Hee

2012-01-01

Laser peening (LP) induces high magnitude compressive residual stresses in a small region of a component. The compressive residual stresses cause plastic deformation that is resistant to fatigue fracture. Fatigue cracks are generally nucleated at critical areas, and LP is applied for those regions so as to delay the crack initiation. Many critical regions are located on the edge of the curved portion of structures because of stress concentration effects. Several investigations that are available for straight components may not give meaningful guidelines for peening curved components. Therefore, in this paper, we investigate residual stress behaviors induced by LP along the edge of curved models. Three curved models that have different curvatures are investigated for peening performance. Two types of peening configurations, which are simultaneous corner shot and sequential corner shots, are considered in order to obtain compressive residual stresses along an edge. LP simulations of multiple shots are performed to identify overlapping effects on the edge portion of a curved model. In addition, the uncertainty calculation of residual stress induced by LP considering laser pulse duration is performed

Computer-aided design of curved surfaces with automatic model generation

Science.gov (United States)

Staley, S. M.; Jerard, R. B.; White, P. R.

1980-01-01

The design and visualization of three-dimensional objects with curved surfaces have always been difficult. The paper given below describes a computer system which facilitates both the design and visualization of such surfaces. The system enhances the design of these surfaces by virtue of various interactive techniques coupled with the application of B-Spline theory. Visualization is facilitated by including a specially built model-making machine which produces three-dimensional foam models. Thus, the system permits the designer to produce an inexpensive model of the object which is suitable for evaluation and presentation.

Muscle Fiber Type Composition and Knee Extension Isometric Strength Fatigue Patterns in Power- and Endurance-Trained Males.

Science.gov (United States)

Kroll, Walter; And Others

1980-01-01

There is a degree of uniqueness in fatigue patterns, particularly between different levels of absolute maximum strength. Caution should be used when analyzing fatigue curves among subjects with unspecified strength levels. (CJ)

Finite-life fatigue constraints in 2D topology optimization of continua

DEFF Research Database (Denmark)

Oest, Jacob; Lund, Erik

2017-01-01

of fatigue damage are estimated using the stress-based Sines fatigue criterion and S − N curves, while the accumulated damage is estimated using Palmgren-Miner’s rule. The method is a natural extension of classical density-based topology optimization with static stress constraints, and thus utilizes many......Topology optimization of 2D continua with the objective of minimizing the mass while considering finite-life fatigue constraint is considered. The structure is subjected to proportional variable-amplitude loading. The topology optimization problem is solved using the density approach. The fractions...

Structural evolution and mechanisms of fatigue in polycrystalline brass

Energy Technology Data Exchange (ETDEWEB)

Vejloe Carstensen, J

1998-03-01

The plastic strain controlled fatigue behaviour of polycrystalline Cu-15%Zn and Cu-30%Zn has been investigated with the aim of studying the effect of slip mode modification by the addition of zinc to copper. It has been clearly demonstrated, that true cyclic saturation does not occur in the plastic strain controlled fatigue of brass. This complicates the contstruction of a cyclic stress-strain (CSS) curve and thus the comparison with copper. A method to overcome this complication has been suggested. Surface observations on fatigued brass specimens show that individual grains tend to deform by Sachs type single slip. This behaviour has been described by the self-consistent Sachs-Eshelby model, which provides estimates of the CSS curve for brass polycrystals. Successive stages of primary hardening, softening and secondary hardening has been observed in the plastic strain controlled fatigue of brass. It has been found that the primary hardening is attributed to an increase of intergranular stresses whereas the secondary hardening apparently is attributed to an increase of friction stresses. Investigations of the structural evolution show that the softening behaviour can be explained by the presence of short-range order (SRO). SRO promote the formation of extended dipole arrays which hardens the material. The formation of intense shear bands destroy the dipole arrays, which explains the cyclic softening. The present results reveal that Cu-30%Zn in a pure planar slip alloy, while Cu-15%Zn displays both planar and wavy slip. The mechanical and structural behaviour observed in brass resembles recent observations in 316L austenitic stainless steels, and the present results reveal that Cu-30%Zn and 316L have approximately the same fatigue life curve. This emphasizes brass as being a convenient model system for the industrially important austenitic steels. (au) 9 tabs., 94 ills., 177 refs.; The thesis is also available as DCAMM-R-S80 and as an electronic document on http://www.risoe.dk/rispubl

Evaluation of upper limb muscle fatigue based on surface electromyography.

Science.gov (United States)

Zhou, Qianxiang; Chen, Yuhong; Ma, Chao; Zheng, Xiaohui

2011-10-01

Fatigue is believed to be a major contributory factor to occupational injuries in machine operators. The development of accurate and usable techniques to measure operator fatigue is therefore important. In this study, we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action. Thirteen young males performed isometric actions with the upper limb at different force levels. sEMG activities of the biceps brachii were recorded during the actions. Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions. sEMG activities were analyzed using the one-third band octave method, and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale. The results showed that the relationship could be expressed by a conic curve, and could be used to evaluate muscle fatigue during machine operation.

Fracture resistance of Zr–Nb alloys under low-cycle fatigue tests

Energy Technology Data Exchange (ETDEWEB)

Nikulin, S.A.; Rozhnov, A.B. [The National University of Science and Technology ‘‘MISIS’’, Leninsky pr. 4, 119049 Moscow (Russian Federation); Gusev, A.Yu. [A.A. Bochvar All-Russia Research Institute of Inorganic Materials (VNIINM), Rogova St. 5a, 123060 Moscow (Russian Federation); Nechaykina, T.A. [The National University of Science and Technology ‘‘MISIS’’, Leninsky pr. 4, 119049 Moscow (Russian Federation); Rogachev, S.O., E-mail: csaap@mail.ru [The National University of Science and Technology ‘‘MISIS’’, Leninsky pr. 4, 119049 Moscow (Russian Federation); Zadorozhnyy, M.Yu. [The National University of Science and Technology ‘‘MISIS’’, Leninsky pr. 4, 119049 Moscow (Russian Federation)

2014-03-15

Highlights: •Low-cycle fatigue tests of Zr–Nb alloys using DMA have been carried out. •The characteristics of low-cycle fatigue of the Zr–Nb alloy at 25/350 °C were determined. •Increasing test temperature up to 350 °C leads to a decrease of fatigue life. •The test temperature doesn’t have an effect on the character of fatigue curves. -- Abstract: Comparative low-cycle fatigue tests of small-scale specimens cut from the cladding tubes of E110, E125, E110opt zirconium alloys at temperatures of 25 and 350 °C using a dynamic mechanical analyzer have been carried out. It is shown that the limited cycles fatigue stress for all alloys is 50% less at temperature of 350 °C comparing to 25 °C. Besides it has been revealed that the limited cycles fatigue stress increases with increasing the strength of zirconium alloy.

Efficacy of Warm Showers on Postpartum Fatigue Among Vaginal-Birth Taiwanese Women: A Quasi-Experimental Design.

Science.gov (United States)

Hsieh, Ching-Hsing; Chen, Chien-Lan; Chung, Feng-Fang; Lin, Su-Ying

2017-05-01

Postpartum fatigue is one of the most common complaints among women following childbirth. As a postpartum ritual practice, Taiwanese women refrain from taking showers while "doing the month." However, warm showers are the systemic application of moist heat, and they maintain physical hygiene, stimulate blood circulation, mitigate discomfort, and provide relaxation. As Taiwanese society becomes increasingly receptive to scientific and contemporary health care practice, more and more women choose to take warm showers after childbirth. The purpose of this study was to evaluate the efficacy of warm showers on postpartum fatigue among vaginal-birth women in Taiwan. This was a two-group quasi-experimental design. Women took showers in warm water with temperatures ranging between 40 °C and 43 °C for approximately 20 minutes. Postpartum women's fatigue is measured using the 10-item Postpartum Fatigue Scale (PFS). The intervention effect was analyzed using a generalized estimating equation (GEE) model. The study population consisted of 358 vaginal-birth postpartum Taiwanese women aged 20-43 years. Postpartum women who took warm showers showed improvements from their pretest to posttest mean scores of postpartum fatigue compared to postpartum women who did not take warm showers. Warm showers helped to reduce postpartum fatigue among vaginal-birth women during the study period. Nurses have the unique opportunity to provide the intervention to Taiwanese women who have vaginal birth to help them relieve postpartum fatigue with warm showers while "doing the month" without the taboo of no-showering customary practices in the early postpartum period.

Fatigue Characterization of Fabricated Ship Details for Design.

Science.gov (United States)

1982-08-01

than the ques- tion of brittle fracture. Such cracking has been found in the forepeak region, bottom amidships, at the bulwark at both ends of the...results of the laboratory studies are presented in the Appendices. 1.3 References 1.1 Vedeler, G. "To What Extent Do Brittle Fracture and Fatigue...Civil Engineering. Appre- ciation is extended to Mr. John R. Williams who prepared the weldments, to Mr. Glen Lafenhagen who assisted in the fatigue

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-07-01

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

Implementation of straight and curved steel girder erection design tools construction : summary.

Science.gov (United States)

2010-11-05

Project 0-5574 Curved Plate Girder Design for Safe and Economical Construction, resulted in the : development of two design tools, UT Lift and UT Bridge. UT Lift is a spreadsheet-based program for analyzing : steel girders during lifting while ...

High-temperature low-cycle fatigue behaviour of HIP treated and untreated superalloy MAR-M247

Czech Academy of Sciences Publication Activity Database

Šulák, Ivo; Obrtlík, Karel; Čelko, L.

2016-01-01

Roč. 54, č. 6 (2016), s. 471-481 ISSN 0023-432X R&D Projects: GA TA ČR(CZ) TA04011525; GA ČR(CZ) GA15-20991S Institutional support: RVO:68081723 Keywords : hot isostatic pressing * high-temperature low cycle fatigue * fatigue life curves * Ni-based superalloy * dislocation structures * planar bands Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.366, year: 2016

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

Science.gov (United States)

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

2015-10-01

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

Fatigue strength ofcomposite wind turbine blade structures

DEFF Research Database (Denmark)

Ardila, Oscar Gerardo Castro

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

Thermo-mechanical fatigue behavior of the intermetallic gamma-TiAl alloy TNB-V5 with different microstructures

International Nuclear Information System (INIS)

Roth, M; Biermann, H

2010-01-01

The cyclic deformation and fatigue behavior of the γ-TiAl alloy TNB-V5 is studied under thermo-mechanical load for the three technically important microstructures Fully-Lamellar (FL), Near-Gamma (NG) and Duplex (DP), respectively. Thus, thermo-mechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400 0 C to 800 0 C and with two different strain ranges. Cyclic deformation curves, stress-strain hysteresis loops and fatigue lives are presented. The type of microstructure shows a surprisingly small influence on the cyclic deformation and fatigue behavior under TMF conditions. For a general life prediction the damage parameter of Smith, Watson and Topper P SWT is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition temperature (approx. 750 0 C). If the maximum temperature is below that temperature, the brittle materials' behavior yields a high scatter of fatigue lives and a low slope of the fatigue life curve and therefore the damage parameter P SWT cannot be applied for the live prediction.

Fatigue analysis through automated cycle counting using ThermAND

International Nuclear Information System (INIS)

Burton, G.R.; Ding, Y.; Scovil, A.; Yetisir, M.

2008-01-01

The potential for fatigue damage due to thermal transients is one of the degradation mechanisms that needs to be managed for plant components. The original design of CANDU stations accounts for projected fatigue usage for specific components over a specified design lifetime. Fatigue design calculations were based on estimates of the number and severity of expected transients for 30 years operation at 80% power. Many CANDU plants are now approaching the end of their design lives and are being considered for extended operation. Industry practice is to have a comprehensive fatigue management program in place for extended operation beyond the original design life. A CANDU-specific framework for fatigue management has recently been developed to identify the options for implementation, and the critical components and locations requiring long-term fatigue monitoring. An essential element of fatigue monitoring is to identify, count and monitor the number of plant transients to ensure that the number assumed in the original design is not exceeded. The number and severity of actual CANDU station thermal transients at key locations in critical systems have been assessed using ThermAND, AECL's health monitor for systems and components, based on archived station operational data. The automated cycle counting has demonstrated that actual transients are generally less numerous than the quantity assumed in the design basis, and are almost always significantly less severe. This paper will discuss the methodology to adapt ThermAND for automated cycle counting of specific system transients, illustrate and test this capability for cycle-based fatigue monitoring using CANDU station data, report the results, and provide data for stress-based fatigue calculations. (author)

Antisideslip and Antirollover Safety Speed Controller Design for Vehicle on Curved Road

Directory of Open Access Journals (Sweden)

Guo Lie

2014-01-01

Full Text Available When the drivers cannot be aware of the existing of forthcoming curved roads and fail to regulate their safety speeds accordingly, sideslip or rollover may occur with high probability. The antisideslip and antirollover control of vehicle on curved road in automatic highway systems is studied. The safety speed warning system is set before entering the curved road firstly. The speed adhesion control is adopted to shorten the braking distance while decelerating and to guarantee the safety speed. The velocity controller when decelerating on the straight path and the posture controller when driving on curved road are designed, respectively, utilizing integral backstepping technology. Simulation results demonstrate that this control system is characterized by quick and precise tracking and global stability. Consequently, it is able to avoid the dangerous operating conditions, such as sideslip and rollover, and guarantee the safety and directional stability when driving on curved road.

Role of intermetallics on the mechanical fatigue behavior of Cu–Al ball bond interfaces

Energy Technology Data Exchange (ETDEWEB)

Lassnig, A., E-mail: alice.lassnig@univie.ac.at [University of Vienna, Faculty of Physics, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Wien (Austria); Pelzer, R. [Infineon Technologies Austria AG, Siemensstrae 2, 9500 Villach (Austria); Gammer, C. [University of Vienna, Faculty of Physics, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Wien (Austria); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Khatibi, G. [Vienna University of Technology, Institute of Chemical Technology and Analytics, Getreidemarkt 9, 1060 Wien (Austria)

2015-10-15

The mechanical fatigue behavior of Cu–Al interfaces occurring in thermosonic ball bonds –typically used in microelectronic packages for automotive applications – is investigated by means of a specially designed fatigue test technique. Fully reversed cyclic shear stresses are induced at the bond interface, leading to subsequent fatigue lift off failure and revealing the weakest site of the bond. A special focus is set on the role of interfacial intermetallic compounds (IMC) on the fatigue performance of such interfaces. Therefore fatigue life curves were obtained for three representative microstructural states: The as-bonded state is compared to two annealed states at 200 °C for 200 h and at 200 °C for 2000 h respectively. In the moderately annealed state two IMC layers (Al{sub 2}Cu, Al{sub 4}Cu{sub 9}) could be identified, whereas in the highly aged state the original pad metallization was almost entirely consumed and AlCu is formed as a third IMC. Finally, the crack path is traced back as a function of interfacial microstructure by means of electron microscopy techniques. Whereas conventional static shear tests reveal no significant decrease of the bond shear force with increased IMC formation the fatigue tests prove a clear degradation in the cyclic mechanical performance. It can be concluded that during cycling the crack deflects easily into the formed intermetallics, leading to early failure of the ball bonds due to their brittle nature. - Highlights: • High cycle fatigue of various miniaturized Cu–Al interfaces is investigated. • Interfacial intermetallic compounds consist of Al2Cu, AlCu and Al4Cu9. • Static shear strength shows minor dependency on interfacial phase formation. • Fatigue tests prove significant degradation with intermetallic compound evolution. • Fatigue fracture surface analysis reveal microstructure dependent crack path.

Role of intermetallics on the mechanical fatigue behavior of Cu–Al ball bond interfaces

International Nuclear Information System (INIS)

Lassnig, A.; Pelzer, R.; Gammer, C.; Khatibi, G.

2015-01-01

The mechanical fatigue behavior of Cu–Al interfaces occurring in thermosonic ball bonds –typically used in microelectronic packages for automotive applications – is investigated by means of a specially designed fatigue test technique. Fully reversed cyclic shear stresses are induced at the bond interface, leading to subsequent fatigue lift off failure and revealing the weakest site of the bond. A special focus is set on the role of interfacial intermetallic compounds (IMC) on the fatigue performance of such interfaces. Therefore fatigue life curves were obtained for three representative microstructural states: The as-bonded state is compared to two annealed states at 200 °C for 200 h and at 200 °C for 2000 h respectively. In the moderately annealed state two IMC layers (Al 2 Cu, Al 4 Cu 9 ) could be identified, whereas in the highly aged state the original pad metallization was almost entirely consumed and AlCu is formed as a third IMC. Finally, the crack path is traced back as a function of interfacial microstructure by means of electron microscopy techniques. Whereas conventional static shear tests reveal no significant decrease of the bond shear force with increased IMC formation the fatigue tests prove a clear degradation in the cyclic mechanical performance. It can be concluded that during cycling the crack deflects easily into the formed intermetallics, leading to early failure of the ball bonds due to their brittle nature. - Highlights: • High cycle fatigue of various miniaturized Cu–Al interfaces is investigated. • Interfacial intermetallic compounds consist of Al2Cu, AlCu and Al4Cu9. • Static shear strength shows minor dependency on interfacial phase formation. • Fatigue tests prove significant degradation with intermetallic compound evolution. • Fatigue fracture surface analysis reveal microstructure dependent crack path

Evaluation of weldment creep and fatigue strength-reduction factors for elevated-temperature design

International Nuclear Information System (INIS)

Corum, J.M.

1989-01-01

New explicit weldment strength criteria in the form of creep and fatigue strength-reduction factors were recently introduced into the American Society of Mechanical Engineers Code Case N-47, which governs the design of elevated-temperature nuclear plants components in the United States. This paper provides some of the background and logic for these factors and their use, and it describes the results of a series of long-term, confirmatory, creep-rupture and fatigue tests of simple welded structures. The structures (welded plates and tubes) were made of 316 stainless steel base metal and 16-8-2 weld filler metal. Overall, the results provide further substantiation of the validity of the strength-reduction factor approach for ensuring adequate life in elevated-temperature nuclear component weldments. 16 refs., 7 figs

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

Directory of Open Access Journals (Sweden)

Leonetti Davide

2018-01-01

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

High speed rails. Fatigue behaviour

International Nuclear Information System (INIS)

Duart, J. M.; Pero-Sanz, J. A.; Verdeja, J. I.

2005-01-01

In recent years, passenger train speed and freight train load have increased to enhance efficiency of rail road transportation. These trends have increased the severity of rail service conditions, calling for rails with greater wear resistance, strength and fatigue behaviour. In the United Stated and Europe, track site weld rails are made entirely by aluminothermic process. This work describes the results of experimental study conducted on bending fatigue strength of plain rails and aluminothermic welded rails with preheating procedures (oxipropane and air-induced propane) approved by railways authorities. Compliance with the required fatigue strength shall be ascertained by 4 point pulsating bending test in accordance with European standards by aluminothermic welding in rails. The locati method, based in the empirical Miner's law about the cumulative damage on a fatigue tested material, allows, once known the Wohler curve of the welding process in use to settle the fatigue tensile limit at 50% with only one test. The values obtained at 2.10''6 cycles for plain rails (S f =353 MPa), oxipropane preheated aluminothermic weld rails (S f =225 MPa), and propane-air induced aluminothermic weld rails (S f =210 MPa) are very similar to those resulting from test method stated in the European Standard. From our point of view and due to its ease, speediness and savings, this is the most suitable test to check the quality and compare the aluminothermic processes in use. (Author) 15 refs

A model for high-cycle fatigue crack propagation

Energy Technology Data Exchange (ETDEWEB)

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

2017-02-01

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

Fatigue behaviour of NiTi shape memory alloy scaffolds produced by SLM, a unit cell design comparison.

Science.gov (United States)

Speirs, M; Van Hooreweder, B; Van Humbeeck, J; Kruth, J-P

2017-06-01

Selective laser melting (SLM) is an additive manufacturing technique able to produce complex functional parts via successively melting layers of metal powder. This process grants the freedom to design highly complex scaffold components to allow bone ingrowth and aid mechanical anchorage. This paper investigates the compression fatigue behaviour of three different unit cells (octahedron, cellular gyroid and sheet gyroid) of SLM nitinol scaffolds. It was found that triply periodic minimal surfaces display superior static mechanical properties in comparison to conventional octahedron beam lattice structures at identical volume fractions. Fatigue resistance was also found to be highly geometry dependent due to the effects of AM processing techniques on the surface topography and notch sensitivity. Geometries minimising nodal points and the staircase effect displayed the greatest fatigue resistance when normalized to yield strength. Furthermore oxygen analysis showed a large oxygen uptake during SLM processing which must be altered to meet ASTM medical grade standards and may significantly reduce fatigue life. These achieved fatigue properties indicate that NiTi scaffolds produced via SLM can provide sufficient mechanical support over an implants lifetime within stress range values experienced in real life. Copyright © 2017 Elsevier Ltd. All rights reserved.

Creep-Fatigue Relationsihps in Electroactive Polymer Systems and Predicted Effects in an Actuator Design

Science.gov (United States)

Vinogradov, Aleksandra M.; Ihlefeld, Curtis M.; Henslee, Issac

2009-01-01

The paper concerns the time-dependent behavior of electroactive polymers (EAP) and their use in advanced intelligent structures for space exploration. Innovative actuator design for low weight and low power valves required in small plants planned for use on the moon for chemical analysis is discussed. It is shown that in-depth understanding of cyclic loading effects observed through accelerated creep rates due to creep-fatigue interaction in polymers is critical in terms of proper functioning of EAP based actuator devices. In the paper, an overview of experimental results concerning the creep properties and cyclic creep response of a thin film piezoelectric polymer polyvinylidene fluoride (PVDF) is presented. The development of a constitutive creep-fatigue interaction model to predict the durability and service life of electroactive polymers is discussed. A novel method is proposed to predict damage accumulation and fatigue life of polymers under oyclic loading conditions in the presence of creep. The study provides a basis for ongoing research initiatives at the NASA Kennedy Space Center in the pursuit of new technologies using EAP as active elements for lunar exploration systems.

Lamb Wave Response of Fatigued Composite Samples

Science.gov (United States)

Seale, Michael; Smith, Barry T.; Prosser, William H.; Masters, John E.

1994-01-01

Composite materials are being more widely used today by aerospace, automotive, sports equipment, and a number of other commercial industries because of their advantages over conventional metals. Composites have a high strength-to-weight ratio and can be constructed to meet specific design needs. Composite structures are already in use in secondary parts of the Douglas MD-11 and are planned to be used in the new MD-12X. Plans also exist for their use in primary and secondary structures on the Boeing 777. Douglas proposed MD-XX may also incorporate composite materials into primary structures such as the wings and tail. Use of composites in these structures offers weight savings, corrosion resistance, and improved aerodynamics. Additionally, composites have been used to repair cracks in many B-1Bs where traditional repair techniques were not very effective. Plans have also been made to reinforce all of the remaining B-1s with composite materials. Verification of the structural integrity of composite components is needed to insure safe operation of these aerospace vehicles. One aspect of the use of these composites is their response to fatigue. To track this progression of fatigue in aerospace structures, a convenient method to nondestructively monitor this damage needs to be developed. Traditional NDE techniques used on metals are not easily adaptable to composites due to the inhomogeneous and anisotropic nature of these materials. Finding an effective means of nondestructively monitoring fatigue damage is extremely important to the safety and reliability of such structures. Lamb waves offer one method of evaluating these composite materials. As a material is fatigued, the modulus degrades. Since the Lamb wave velocity can be related to the modulus of the material, an effective tool can be developed to monitor fatigue damage in composites by measuring the velocity of these waves. In this work, preliminary studies have been conducted which monitor fatigue damage in

Material design data of 2.25Cr-1Mo steel and hastelloy-x for the experimental multi-purpose very-high temperature gas-cooled reactor

International Nuclear Information System (INIS)

Kodaira, Tsuneo; Suzuki, Michiaki; Uga, Takeo

1975-08-01

The preliminary structural design guidelines for the experimental multi-purpose very-high temperature gas-cooled reactor have recently been prepared. The components of the primary system operating at temperatures of creep dominant range are grouped in those of pressure and temperature boundaries respectively. In the material selection, 2 1/4Cr-1Mo steel is chosen for the former and Hastelloy-X for the latter taking into account of material properties at operating temperature. Deriving from the literature in the field, material design data of the alloys are established in design forms such as Sy, So, Sm, St, 100% of minimum stress to rupture, design fatigue curves, isochronous stress-strain curves, creep-fatigue interaction damage factor and so on, which are defined in ASME Code Section III, Code Case 1592. (auth.)

Fatigue in adults with traumatic brain injury

DEFF Research Database (Denmark)

Mollayeva, Tatyana; Kendzerska, Tetyana; Mollayeva, Shirin

2013-01-01

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

Correction for Poisson's effect in an elastic analysis of low cycle fatigue

International Nuclear Information System (INIS)

Roche, R.; Moulin, D.

1984-05-01

Fatigue behaviour is essentially dependent on the real strain range, but the current practice is the use of elastic analysis. In low cycle fatigue conditions where inelastic strains predominate, elastic analysis never gives the real value of the strain range. In order to use these results some corrections are necessary. One of these corrections is due to the Poisson's effect (the Poisson ratio in inelastic behaviour is higher than in elastic behaviour). In this paper a method of correction of this effect is proposed. It consists in multiplying the results of the elastic analysis by a coefficient called Kν. A method to draw curves giving this coefficient Kν as a function of results of elastic analysis is developped. Only simple analytical computations using the unixial cyclic curve are needed to draw these curves. Examples are given. The proposed method is very convenient and low cost effective [fr

Variable amplitude fatigue, modelling and testing

International Nuclear Information System (INIS)

Svensson, Thomas.

1993-01-01

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

Compressive and fatigue behavior of beta-type titanium porous structures fabricated by electron beam melting

International Nuclear Information System (INIS)

Liu, Y.J.; Wang, H.L.; Li, S.J.; Wang, S.G.; Wang, W.J.; Hou, W.T.; Hao, Y.L.; Yang, R.; Zhang, L.C.

2017-01-01

β-type titanium porous structure is a new class of solution for implant because it offers excellent combinations of high strength and low Young's modulus. This work investigated the influence of porosity variation in electron beam melting (EBM)-produced β-type Ti2448 alloy samples on the mechanical properties including super-elastic property, Young's modulus, compressive strength and fatigue properties. The relationship between the misorientation angle of adjacent grains and fatigue crack deflection behaviors was also observed. The super-elastic property is improved as the porosity of samples increases because of increasing tensile/compressive ratio. For the first time, the position of fatigue crack initiation is defined in stress-strain curves based on the variation of the fatigue cyclic loops. The unique manufacturing process of EBM results in the generation of different sizes of grains, and the apparent fatigue crack deflection occurs at the grain boundaries in the columnar grain zone due to substantial misorientation between adjacent grains. Compared with Ti-6Al-4V samples, the Ti2448 porous samples exhibit a higher normalized fatigue strength owing to super-elastic property, greater plastic zone ahead of the fatigue crack tip and the crack deflection behavior. - Highlights: • The super-elastic property is improved with increasing porosity of Ti2448 porous samples. • The position of fatigue crack initiation on the strain curve is defined. • The unique EBM-produced microstructure leads to apparent fatigue crack deflection occurring at columnar grain boundary. • Ti2448 porous samples display only half of the Young's modulus of Ti-6Al-4V porous samples at same fatigue strength level.

Influence of the geometry of curved artificial canals on the fracture of rotary nickel-titanium instruments subjected to cyclic fatigue tests.

Science.gov (United States)

Lopes, Hélio P; Vieira, Márcia V B; Elias, Carlos N; Gonçalves, Lucio S; Siqueira, José F; Moreira, Edson J L; Vieira, Victor T L; Souza, Letícia C

2013-05-01

This study evaluated the influence of different features of canal curvature geometry on the number of cycles to fracture of a rotary nickel-titanium endodontic instrument subjected to a cyclic fatigue test. BioRaCe BR4C instruments (FKG Dentaire, La Chaux-de Fonds, Switzerland) were tested in 4 grooves simulating curved metallic artificial canals, each one measuring 1.5 mm in width, 20 mm in total length, and 3.5 mm in depth with a U-shaped bottom. The parameters of curvature including the radius and arc lengths and the position of the arc differed in the 4 canal designs. Fractured surfaces and helical shafts of the separated instruments were analyzed by scanning electron microscopy. The Student's t test showed that a significantly lower number of cycles to fracture values were observed for instruments tested in canals with the smallest radius, the longest arc, and the arc located in the middle portion of the canal. Scanning electron microscopic analysis of the fracture surfaces revealed morphologic characteristics of ductile fracture. Plastic deformation was not observed in the helical shaft of the fractured instruments. Curvature geometry including the radius and arc lengths and the position of the arc along the root canal influence the number of cycles to fracture of rotary nickel-titanium instruments subjected to flexural load. Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Fracture probability properties of pure and cantilever bending fatigue of STS304 steel

International Nuclear Information System (INIS)

Roh, Sung Kuk; Park, Dae Hyun; Jeong, Soon Uk

2001-01-01

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frequently. Therefore many people are suffering harm of property. The destruction cause of marcaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed

A real time evaluation technique of fatigue damage in adhesively bonded composite metal joints

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Hyun; Kwon Oh Yang [Dept. of Mechanical Engineering, Inje Univesity, Kimhae (Korea, Republic of)

1999-05-15

One of the problems for practical use of fiber-reinforced composite material is performance degradation by fatigue damage in the joints. The study is to develope a nondestructive technique for real-time evaluation of adhesively bonded composite-metal joints. From the prior study we confirmed that the bonding strength can be estimated from the correlation between quality of bonded parts and AUP's. We obtained a curve showing the correlation between AUP's calculated from signals obtained from single-lap and double-lap joints and the degree of fatigue damage at bonding interface during fatigue test. The curve is an analogy to the one showing stiffness reduction(E/E{sub 0}) of polymer matrix composites by fatigue damage. From those facts, it is possible to predict degree of damage in real-time. Amplitude and AUP2 appeared to be optimal parameters to provide more reliable results for single-lap joint whereas amplitude and AUP1 did for double-lap joints. It is recommended to select optimal parameters for different geometries in the real structure.

A real time evaluation technique of fatigue damage in adhesively bonded composite metal joints

International Nuclear Information System (INIS)

Kim, Tae Hyun; Kwon Oh Yang

1999-01-01

One of the problems for practical use of fiber-reinforced composite material is performance degradation by fatigue damage in the joints. The study is to develope a nondestructive technique for real-time evaluation of adhesively bonded composite-metal joints. From the prior study we confirmed that the bonding strength can be estimated from the correlation between quality of bonded parts and AUP's. We obtained a curve showing the correlation between AUP's calculated from signals obtained from single-lap and double-lap joints and the degree of fatigue damage at bonding interface during fatigue test. The curve is an analogy to the one showing stiffness reduction(E/E 0 ) of polymer matrix composites by fatigue damage. From those facts, it is possible to predict degree of damage in real-time. Amplitude and AUP2 appeared to be optimal parameters to provide more reliable results for single-lap joint whereas amplitude and AUP1 did for double-lap joints. It is recommended to select optimal parameters for different geometries in the real structure.

Method to predict fatigue lifetimes of GRP wind turbine blades and comparison with experiments

Energy Technology Data Exchange (ETDEWEB)

Echtermeyer, A.T. [Det Norske Veritas Research AS, Hoevik (Norway); Kensche, C. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Stuttgart (Germany, F.R); Bach, P. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Poppen, M. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Lilholt, H.; Andersen, S.I.; Broendsted, P. [Risoe National Lab., Roskilde (Denmark)

1996-12-01

This paper describes a method to predict fatigue lifetimes of fiber reinforced plastics in wind turbine blades. It is based on extensive testing within the EU-Joule program. The method takes the measured fatigue properties of a material into account so that credit can be given to materials with improved fatigue properties. The large number of test results should also give confidence in the fatigue calculation method for fiber reinforced plastics. The method uses the Palmgren-Miner sum to predict lifetimes and is verified by tests using well defined load sequences. Even though this approach is generally well known in fatigue analysis, many details in the interpretation and extrapolation of the measurements need to be clearly defined, since they can influence the results considerably. The following subjects will be described: Method to measure SN curves and to obtain tolerance bounds, development of a constant lifetime diagram, evaluation of the load sequence, use of Palmgren-Miner sum, requirements for load sequence testing. The fatigue lifetime calculation method has been compared against measured data for simple loading sequences and the more complex WISPERX loading sequence for blade roots. The comparison is based on predicted mean lifetimes, using the same materials to obtain the basic SN curves and to measure laminates under complicated loading sequences. 24 refs, 7 figs, 5 tabs

High Cycle Fatigue Damage Mechanisms of MAR-M 247 Superalloy at High Temperatures

Czech Academy of Sciences Publication Activity Database

Šmíd, Miroslav; Horník, Vít; Hutař, Pavel; Hrbáček, K.; Kunz, Ludvík

2016-01-01

Roč. 69, č. 2 (2016), s. 393-397 ISSN 0972-2815 R&D Projects: GA TA ČR(CZ) TA04011525; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : High cycle fatigue * S-N curves * Fractography * High temperature * EBSD analysis Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.533, year: 2016

Association of sleep and fatigue with decision regret among critical care nurses.

Science.gov (United States)

Scott, Linda D; Arslanian-Engoren, Cynthia; Engoren, Milo C

2014-01-01

The effects of inadequate sleep on clinical decisions may be important for patients in critical care units, who are often more vulnerable than patients in other units. Fatigued nurses are more likely than well-rested nurses to make faulty decisions that lead to decision regret, a negative cognitive emotion that occurs when the actual outcome differs from the desired or expected outcome. To examine the association between selected sleep variables, impairment due to fatigue, and clinical-decision self-efficacy and regret among critical care nurses. Decision regret was the primary outcome variable. Methods A nonexperimental, descriptive design and extant measures were used to obtain data from a random sample of full-time nurses. Binary logistic regression models were used to examine the association between sleep variables, fatigue, and clinical-decision self-efficacy and regret. The discrimination of the models was compared with the C statistic, the area under the receiver operating characteristic curve. A total of 605 nurses returned the questionnaires (17% response rate). Among these, decision regret was reported by 157 of 546 (29%). Nurses with decision regret reported more fatigue, more daytime sleepiness, less intershift recovery, and worse sleep quality than did nurses without decision regret. Being male, working a 12-hour shift, and clinical-decision satisfaction were significantly associated with decision regret (C statistic, 0.719; SE, 0.024). Nurses who experience impairments due to fatigue, loss of sleep, and inability to recover between shifts are more likely than unimpaired nurses to report decision regret.

Condensation of long-term wave climates for the fatigue design of hydrodynamically sensitive offshore wind turbine support structures

DEFF Research Database (Denmark)

Passon, Patrik; Branner, Kim

2016-01-01

important for hydrodynamically sensitive structures since the applied met-ocean parameters have a non-linear influence on calculated fatigue design loads. The present article introduces a new wave lumping method for condensation of the wave climate. The novelty is predominantly based on refined equivalence......Cost-efficient and reliable fatigue designs of offshore wind turbine support structures require an adequate representation of the site-specific wind–wave joint distribution. Establishment of this wind–wave joint distribution for design load calculation purposes requires typically a correlation...... of the marginal wind and wave distribution. This is achieved by condensation of the site-specific wave climate in terms of wave period or wave height lumping, subsequently used as input for a correlation with the corresponding wind climate. The quality of this resulting wind–wave correlation is especially...

Thermo-mechanical fatigue behavior of the intermetallic gamma-TiAl alloy TNB-V5 with different microstructures

Energy Technology Data Exchange (ETDEWEB)

Roth, M [now at IAV GmbH, Kauffahrtei 25, D-09120 Chemnitz (Germany); Biermann, H, E-mail: marcel.roth@iav.d [TU Bergakademie Freiberg, Institute for Materials Engineering, Gustav-Zeuner-Strasse 5, D-09599 Freiberg (Germany)

2010-07-01

The cyclic deformation and fatigue behavior of the {gamma}-TiAl alloy TNB-V5 is studied under thermo-mechanical load for the three technically important microstructures Fully-Lamellar (FL), Near-Gamma (NG) and Duplex (DP), respectively. Thus, thermo-mechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400{sup 0}C to 800{sup 0}C and with two different strain ranges. Cyclic deformation curves, stress-strain hysteresis loops and fatigue lives are presented. The type of microstructure shows a surprisingly small influence on the cyclic deformation and fatigue behavior under TMF conditions. For a general life prediction the damage parameter of Smith, Watson and Topper P{sub SWT} is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition temperature (approx. 750{sup 0}C). If the maximum temperature is below that temperature, the brittle materials' behavior yields a high scatter of fatigue lives and a low slope of the fatigue life curve and therefore the damage parameter P{sub SWT} cannot be applied for the live prediction.

Cyclic and Fatigue Behaviour of Rock Materials: Review, Interpretation and Research Perspectives

Science.gov (United States)

Cerfontaine, B.; Collin, F.

2018-02-01

The purpose of this paper is to provide a comprehensive state of the art of fatigue and cyclic loading of natural rock materials. Papers published in the literature are classified and listed in order to ease bibliographical review, to gather data (sometimes contradictory) on classical experimental results and to analyse the main interpretation concepts. Their advantages and limitations are discussed, and perspectives for further work are highlighted. The first section summarises and defines the different experimental set-ups (type of loading, type of experiment) already applied to cyclic/fatigue investigation of rock materials. The papers are then listed based on these different definitions. Typical results are highlighted in next section. Fatigue/cyclic loading mainly results in accumulation of plastic deformation and/or damage cycle after cycle. A sample cyclically loaded at constant amplitude finally leads to failure even if the peak load is lower than its monotonic strength. This subcritical crack is due to a diffuse microfracturing and decohesion of the rock structure. The third section reviews and comments the concepts used to interpret the results. The fatigue limit and S- N curves are the most common concepts used to describe fatigue experiments. Results published from all papers are gathered into a single figure to highlight the tendency. Predicting the monotonic peak strength of a sample is found to be critical in order to compute accurate S- N curves. Finally, open questions are listed to provide a state of the art of grey areas in the understanding of fatigue mechanisms and challenges for the future.

Bending fatigue tests on SiC-Al tapes under alternating stress at room temperature

Science.gov (United States)

Herzog, J. A.

1981-01-01

The development of a testing method for fatigue tests on SiC-Al tapes containing a small amount of SiC filaments under alternating stress is reported. The fatigue strength curves resulting for this composite are discussed. They permit an estimate of its behavior under continuous stress and in combination with various other matrices, especially metal matrices.

Reliability high cycle fatigue design of gas turbine blading system using probabilistic goodman diagram

Energy Technology Data Exchange (ETDEWEB)

Herman Shen, M.-H. [Ohio State Univ., Columbus, OH (United States). Dept. of Aerospace Engineering and Aviation; Nicholas, T. [MLLN, Wright-Patterson AFB, OH (United States). Air Force Research Lab.

2001-07-01

A framework for the probabilistic analysis of high cycle fatigue is developed. The framework will be useful to U.S. Air Force and aeroengine manufacturers in the design of high cycle fatigue in disk or compressor components fabricated from Ti-6Al-4V under a range of loading conditions that might be encountered during service. The main idea of the framework is to characterize vibratory stresses from random input variables due to uncertainties such as crack location, loading, material properties, and manufacturing variability. The characteristics of such vibratory stresses are portrayed graphically as histograms, or probability density function (PDF). The outcome of the probability measures associated with all the values of a random variable exceeding the material capability is achieved by a failure function g(X) defined by the difference between the vibratory stress and Goodman line or surface such that the probability of HCF failure is P{sub f} =P(g(X<0)). Design can then be based on a go-no go criterion based on an assumed risk. The framework can be used to facilitate the development of design tools for the prediction of inspection schedules and reliability in aeroengine components. Such tools could lead ultimately to improved life extension schemes in aging aircraft, and more reliable methods for the design and inspection of critical components. (orig.)

Fatigue test on aluminium bridges

NARCIS (Netherlands)

Maljaars, J.; Soetens, F.; Straalen, van IJ.J.

2005-01-01

Traffic bridges are subjected to variable loads and should therefore be checked on fatigue. Especially low weight materials, like aluminium, are sensitive to fatigue, because the variable load is a substantial part of the total load. This paper shows the structural design of an aluminium bridge

Evaluation of Mechanical Properties and Fatigue Behavior of STS 304L due to Plastic Working

Energy Technology Data Exchange (ETDEWEB)

Shim, Hyun-Bo [Yeungnam Univ., Daegu (Korea, Republic of); Kim, Young-Kyun [KOGAS Research Institute, Seoul (Korea, Republic of); Suh, Chang-Min [Kyungpook Nat’l Univ., Daegu (Korea, Republic of)

2017-07-15

The purpose of this study is to investigate the influence of the cold reduction rate and an ultrasonic fatigue test (UFT) on the fatigue behaviors of STS 304L. The tensile strength, yield strength, hardness value and fatigue limit in the UFT fatigue test linearly increased as thickness decreased from 1.5 mm to 1.1 mm, as the cold reduction rate of STS 304L increased. As a result of the UFT fatigue test (R = -1) of four specimens, the fatigue limit of the S-N curve formed a knee point in the region of 10{sup 6}, and the 2nd fatigue limit caused by giga cycle fatigue did not appeared. In the case of t = 1.1 mm, the highest fatigue limit was 345 MPa, which was 64.3% higher than the original material (t = 1.5 mm). As a result of the UFT fatigue test of STS 304L, many small surface cracks occurred, grown, coalesced while tearing.

Comparison between FEM and high heat flux thermal fatigue testing results of ITER divertor plasma facing mock-ups

Energy Technology Data Exchange (ETDEWEB)

Crescenzi, F., E-mail: fabio.crescenzi@enea.it; Roccella, S.; Visca, E.; Moriani, A.

2014-10-15

Highlights: • Divertor is an important part of the ITER machine. • Finite element analysis allows designers to explore multiple design options, reducing physical prototypes and optimizing design performance. • The hydraulic thermal-mechanical analysis performed by ANSYS and the test results on small-scale mock-ups manufactured by HRP were compared. • FEA results confirmed many experimental data, then it could be very useful for next design optimization. - Abstract: The divertor is one of the most challenging components of “DEMO” the next step ITER machine, so many tasks regarding modeling and experiments have been made in the past years to assess manufacturing processes, materials and thus the life-time of the components. In this context the finite element analysis (FEA) allows designers to explore multiple design options, to reduce physical prototypes and to optimize design performance. The comparison between the hydraulic thermal-mechanical analysis performed by ANSYS WORKBENCH 14.5 and the test results [1] on small-scale mock-ups manufactured with the Hot Radial Pressing (HRP) [2] technology is presented in this paper. During the thermal fatigue testing in the Efremov TSEFEY facility to assess the heat flux load-carrying capability of the mock-ups, only the surface temperature was measured, so the FEA was important because it allowed to know any other information (temperature inside the materials, local water temperature, local stress, etc.). FEA was performed coupling the thermal-hydraulic analysis, that calculated the temperature distributions on the components and the heat transfer coefficient (HTC) between water and heat sink tube, with the mechanical analysis. The comparison between analysis and testing results was based on the temperature maps of the loaded surface and on number of the cycles supported during the testing and those predicted by the mechanical analysis using the experimental fatigue curves for CuCrZr-IG, that is the structural

Numerical simulation of tearing-fatigue interactions in 316l(N) austenitic stainless steel

International Nuclear Information System (INIS)

Sherry, A.H.; Wilkes, M.A.

2005-01-01

The loading history of engineering components can influence the behaviour of defects in service. This paper presents, the results of a numerical study aimed at using the Gurson ductile damage model, calibrated against J R-curve data, to simulate load-history effects on ductile tearing behaviour in austenitic materials. The work has demonstrated that ductile crack growth resistance is influenced by sub-critical crack growth by an intervening mechanism such as fatigue. Fatigue crack growth under a positive R-ratio leads to increase in subsequent tearing resistance through three main mechanisms: (i) re-sharpening of the crack tip; (ii) crack extension through the fracture process zone; and (iii) cyclic loading effects on void development. The ratio of minimum to maximum stress during fatigue loading (R-ratio) has been shown to influence subsequent tearing resistance, with an R-ratio of 0.2 generally leading to a greater enhancement in tearing resistance than an R-ratio of 0.1. This behaviour is due to the influence of R-ratio on void development ahead of the fatigue crack tip. Finally, relevant experimental data compare favourably with the predicted J R-curves

Jacket Substructure Fatigue Mitigation through Active Control

DEFF Research Database (Denmark)

Hanis, Tomas; Natarajan, Anand

2014-01-01

to the fatigue design loads on the braces of the jacket. Since large wind turbines of 10MW rating have low rotor speeds (p), the modal frequencies of the sub structures approach 3p at low wind speeds, which leads to a modal coupling and resonance. Therefore an active control system is developed which provides...... sufficient structural damping and consequently a fatigue reduction at the substructure. The resulting reduction in fatigue design loads on the jacket structure based on the active control system is presented....

Casting defects and fatigue behaviour of ductile cast iron for wind turbine components: A comprehensive study

Energy Technology Data Exchange (ETDEWEB)

Haerkegaard, G. [Norwegian University of Science and Technology, Dept. of Engineering Design and Materials, Trondheim (Norway); Shirani, M.

2011-12-15

Two types of EN-GJS-400-18-LT ductile cast iron were investigated in this research, clean baseline material in the shape of castings with different thicknesses and also defective material from a rejected wind turbine hub. P-S-N curves for baseline EN-GJS-400-18-LT specimens with different dimensions and from castings with different thicknesses at different load ratios were established. Geometrical size effect, technological size effects and mean stress effect on fatigue strength of baseline EN-GJS-400-18-LT were evaluated. Fatigue strength of baseline EN-GJS-400-18-LT was compared with that of defective material from the rejected hub. The effect of defects type, shape, size and position on fatigue strength of this material was evaluated. The hypothesis that the endurance observed in an S-N test can be predicted based on the analysis of crack growth from casting defects through defect-free 'base' material was tested for the analyzed defective material. 3D X-ray computed tomography was use to detect defects in defective specimens and find the defect size distribution. The obtained defect size distribution for the defective material was used in random defect analysis to establish the scatter of fatigue life for defective specimens. Finally both safe-life design and damage tolerant design of wind turbine castings were analyzed and compared. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

International Nuclear Information System (INIS)

Kamaya, Masayuki; Kawakubo, Masahiro

2012-01-01

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

Strain Rate Effects, Transition Behaviour and Master Curve Concept

Czech Academy of Sciences Publication Activity Database

Dlouhý, Ivo; Pluvinage, G.; Holzmann, Miloslav

č. 8 (2004), s. IV 16-IV 22 ISSN 1291-8199 R&D Projects: GA AV ČR IAA2041003; GA ČR GA106/01/0342 Institutional research plan: CEZ:AV0Z2041904 Keywords : ferritic steel * pressure vessel steel * master curve Subject RIV: JL - Materials Fatigue, Friction Mechanics

Balancing Power Output and Structural Fatigue of Wave Energy Converters by Means of Control Strategies

Directory of Open Access Journals (Sweden)

Francesco Ferri

2014-04-01

Full Text Available In order to reduce the cost of electricity produced by wave energy converters (WECs, the benefit of selling electricity as well as the investment costs of the structure has to be considered. This paper presents a methodology for assessing the control strategy for a WEC with respect to both energy output and structural fatigue loads. Different active and passive control strategies are implemented (proportional (P controller, proportional-integral (PI controller, proportional-integral-derivative with memory compensation (PID controller, model predictive control (MPC and maximum energy controller (MEC, and load time-series resulting from numerical simulations are used to design structural parts based on fatigue analysis using rain-flow counting, Stress-Number (SN curves and Miner’s rule. The objective of the methodology is to obtain a cost-effective WEC with a more comprehensive analysis of a WEC based on a combination of well known control strategies and standardised fatigue methods. The presented method is then applied to a particular case study, the Wavestar WEC, for a specific location in the North Sea. Results, which are based on numerical simulations, show the importance of balancing the gained power against structural fatigue. Based on a simple cost model, the PI controller is shown as a viable solution.

Biaxial fatigue of metals the present understanding

CERN Document Server

Schijve, Jaap

2016-01-01

Problems of fatigue under multiaxial fatigue loads have been addressed in a very large number of research publications. The present publication is primarily a survey of biaxial fatigue under constant amplitude loading on metal specimens. It starts with the physical understanding of the fatigue phenomenon under biaxial fatigue loads. Various types of proportional and non-proportional biaxial fatigue loads and biaxial stress distributions in a material are specified. Attention is paid to the fatigue limit, crack nucleation, initial micro crack growth and subsequent macro-crack in different modes of crack growth. The interference between the upper and lower surfaces of a fatigue crack is discussed. Possibilities for predictions of biaxial fatigue properties are analysed with reference to the similarity concept. The significance of the present understanding for structural design problems is considered. The book is completed with a summary of major observations.

Fatigue strength of a single lap joint SPR-bonded

International Nuclear Information System (INIS)

Di Franco, G.; Fratini, L.; Pasta, A.

2011-01-01

In the last years, hybrid joints, meaning with this the joints which consist in combining a traditional mechanical joint to a layer of adhesive, are gradually attracting the attention of various sectors of the construction of vehicles and transportation industries, for their better performance compared to just mechanical joints (self-piercing riveting SPR, riveting, and so on) or just to bonded joints.The paper investigates the fatigue behavior of a single lap joint self-piercing riveted (SPR) and bonded throughout fatigue tests. The considered geometric configuration allowed the use of two rivets placed longitudinally; an epoxy resin was used as adhesive. In the first part of the work static characterization of the joints was carried out through tensile tests. Then fatigue tests were made with the application of different levels of load. The fatigue curves were also obtained at the varying the distance between the two rivets in order to better assess the joint strength for a given length of overlap.

Importance of fatiguing, overtraining and chronic fatigue in athletes

Directory of Open Access Journals (Sweden)

Adam Piesik

2017-09-01

Full Text Available Each training that requires achieving a higher heart rate limit and/or increased concentration in time may cause fatigue, considered to be a natural defence mechanism of a body. In the case of excessive fatigue and insufficient time designated for rest and regeneration, an overtraining syndrome (OTS may develop. The main symptom of overtraining is increased fatigue that fails to become reversed in normal conditions of regeneration. Although authors are familiar with the overtraining syndrome and associated symptoms, as of today no diagnostic tool has been developed that may form a basis for a final diagnosis, and the diagnosis itself is frequently based on a subjective assessment of the athlete. Possible causes of the band overtraining syndrome are disorders of sodium, inflammatory processes resulting from physical activity and / or disorders of the autonomic nervous system.

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

DEFF Research Database (Denmark)

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

2015-01-01

In this paper, fatigue lifetime prediction of NREL 5MW reference wind turbine is presented. The fatigue response of materials used in selected blade cross sections was obtained by applying macroscopic fatigue approaches and assuming uniaxial stress states. Power production and parked load cases...... suggested by the IEC 61400-1 standard were studied employing different load time intervals and by using two novel fatigue tools called ALBdeS and BECAS+F. The aeroelastic loads were defined thought aeroelastic simulations performed with both FAST and HAWC2 tools. The stress spectra at each layer were...... calculated employing laminated composite theory and beam cross section methods. The Palmgren-Miner linear damage rule was used to calculate the accumulation damage. The theoretical results produced by both fatigue tools proved a prominent effect of analysed design load conditions on the estimated lifetime...

The fatigue behavior of composite laminates under various mean stresses

Science.gov (United States)

Rotem, A.

1991-01-01

A method is developed for predicting the S-N curve of a composite laminate which is subjected to an arbitrary stress ratio, R (minimum stress/maximum stress). The method is based on the measuring of the S-N behavior of two distinct cases, tension-tension and compression-compression fatigue loadings. Using these parameters, expressions are formulated that estimate the fatigue behavior under any stress ratio loading. Experimental results from the testing of graphite/epoxy laminates, with various structures, are compared with the predictions and show good agreement.

Experimental and numerical determination of critical stress intensity factor of aluminum curved thin sheets under tensile stress

Energy Technology Data Exchange (ETDEWEB)

Heidarvand, Majid; Soltani, Naser; Hajializadeh, Farshid [University of Tehran, Tehran (Iran, Islamic Republic of)

2017-05-15

We determined the fracture toughness of aluminum curved thin sheets using tensile stress tests and finite element method. We applied Linear elastic fracture mechanics (LEFM) and Feddersen procedure to evaluate stress intensity factor of the samples with central wire-cut cracks and fatigue cracks with different lengths to investigate the notch radius effect. Special fixture design was utilized to establish uniform stress distribution at the crack zone. Less than 9 % difference was found between the wire-cut and the fatigue cracked samples. Since generating central fatigue crack with different lengths required so much effort, wire-cut cracked samples were used to determine critical stress intensity factor. Finite element analysis was also performed on one-quarter of the specimen using both the singular Borsum elements and the regular isoparametric elements to further investigate fracture toughness of the samples. It was observed that the singular elements presented better results than the isoparametric ones. A slight difference was also found between the results obtained from finite element method using singular elements and the experimental results.

Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock

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Weichao Wang

2016-01-01

Full Text Available The microtest, SEM, was carried out to study the fracture surface of salt rock after the Brazilian splitting test and splitting fatigue test were carried out with a servo-controlled test machine RMT-150B. The results indicate that the deviation of using the tablet splitting method is larger than that of using steel wire splitting method, in Brazilian splitting test of salt rock, when the conventional data processing method is adopted. There are similar deformation features in both the conventional splitting tests and uniaxial compression tests. The stress-strain curves include compaction, elasticity, yielding, and failure stage. Both the vertical deformation and horizontal deformation of splitting fatigue tests under constant average loading can be divided into three stages of “loosening-tightness-loosening.” The failure modes of splitting fatigue tests under the variational average loading are not controlled by the fracturing process curve of the conventional splitting tests. The deformation extent of fatigue tests under variational average loading is even greater than that of conventional splitting test. The tensile strength of salt rock has a relationship with crystallization conditions. Tensile strength of thick crystal salt rock is lower than the bonded strength of fine-grain crystals.

Fatigue Life Prediction of High Modulus Asphalt Concrete Based on the Local Stress-Strain Method

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Mulian Zheng

2017-03-01

Full Text Available Previously published studies have proposed fatigue life prediction models for dense graded asphalt pavement based on flexural fatigue test. This study focused on the fatigue life prediction of High Modulus Asphalt Concrete (HMAC pavement using the local strain-stress method and direct tension fatigue test. First, the direct tension fatigue test at various strain levels was conducted on HMAC prism samples cut from plate specimens. Afterwards, their true stress-strain loop curves were obtained and modified to develop the strain-fatigue life equation. Then the nominal strain of HMAC course determined using finite element method was converted into local strain using the Neuber method. Finally, based on the established fatigue equation and converted local strain, a method to predict the pavement fatigue crack initiation life was proposed and the fatigue life of a typical HMAC overlay pavement which runs a risk of bottom-up cracking was predicted and validated. Results show that the proposed method was able to produce satisfactory crack initiation life.

Study on Standard Fatigue Vehicle Load Model

Science.gov (United States)

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

2018-02-01

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

Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

Science.gov (United States)

Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

2016-03-01

In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

Design data for the 1/4-in. thick alloy 718 in-pile tube

International Nuclear Information System (INIS)

Reuter, W.G.

1977-05-01

Design data applicable to the proposed 0.64-cm (1/4-in.) thick inpile tube (IPT) used in the experimental test loop of the Power Burst Facility (PBF) are reported, together with fracture toughness results which were also desired to complement the design data. These data were required for temperatures ranging from room temperature (RT) to 811 K (1000 0 F). Tests were conducted on transverse-oriented specimens for base metal and longitudinal- and transverse-oriented weld metal specimens. Tensile test results from base metal (Heats 3 and 6) and weld metal (Heat C), for test temperatures ranging from RT to 811 K (1000 0 F), were used to develop curves for ultimate and yield tensile strength. The design fatigue curves for transverse-oriented base metal and longitudinal- and transverse-oriented weld metal specimens were developed using the tensile test results plus an analytical approach. Experimental fatigue data were generated to augment the analytically determined values. The design curves for cycles to failure ranging from 10 1 to 10 6 and for temperatures for RT to 811 K (1000 0 F) are contained in this report. Instrumented precracked-Charpy specimens were tested over a range of temperatures to provide some estimate of the dynamic fracture toughness (K/sub Id/). On the basis of these tests, K/sub Id/ values for the base metal and weldments are quite satisfactory

Fatigue behaviour of coke drum materials under thermal-mechanical cyclic loading

Directory of Open Access Journals (Sweden)

Jie Chen

2014-01-01

Full Text Available Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. There were some studies on the fatigue life estimation for the coke drums, but most of them were based on strain-fatigue life curves at constant temperatures, which do not consider simultaneous cyclic temperature and mechanical loading conditions. In this study, a fatigue testing system is successfully developed to allow performing thermal-mechanical fatigue (TMF test similar to the coke drum loading condition. Two commonly used base and one clad materials of coke drums are then experimentally investigated. In addition, a comparative study between isothermal and TMF lives of these materials is conducted. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums and more accurate prediction of fatigue life of coke drum materials.

Static and Fatigue Behavior Investigation of Artificial Notched Steel Reinforcement

Directory of Open Access Journals (Sweden)

Yafei Ma

2017-05-01

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

Low Cycle Fatigue of Steel in Strain Controled Cyclic Bending

Directory of Open Access Journals (Sweden)

Kulesa Anna

2016-03-01

Full Text Available The paper presents a comparison of the fatigue life curves based on test of 15Mo3 steel under cyclic, pendulum bending and tension-compression. These studies were analyzed in terms of a large and small number of cycles where strain amplitude is dependent on the fatigue life. It has been shown that commonly used Manson-Coffin-Basquin model cannot be used for tests under cyclic bending due to the impossibility of separating elastic and plastic strains. For this purpose, some well-known models of Langer and Kandil and one new model of authors, where strain amplitude is dependent on the number of cycles, were proposed. Comparing the results of bending with tension-compression it was shown that for smaller strain amplitudes the fatigue life for both test methods were similar, for higher strain amplitudes fatigue life for bending tests was greater than for tension-compression.

A methodology to evaluate the fatigue life of flexible pipes

Energy Technology Data Exchange (ETDEWEB)

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

2009-07-01

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

Investigation of magnetic properties of steel in the process of fatigue

International Nuclear Information System (INIS)

Kasimov, G.A.; Pokrovskij, A.D.

1976-01-01

Non-destructive method was developed for the recognition of structural demages of mashine components, which is based on studying the effect of the cyclical loading of constructional steel (brands 10, 20, etc.) upon their magnetic characteristics. Using the experimental installation, we have determined the effect of the degree of fatigue destruction of steel specimens upon the main magnetization curve and the symmetrical cycles of magnetic hysteresis. The obtained results make it possible to choose the conditions of control over the fatigue process

Design parameters of transmission curved crystal spectrometer for hard X-ray diagnoses

International Nuclear Information System (INIS)

Qian Feng; Cao Leifeng; Zhou Weimin; Zhao Zongqing; Gu Yuqiu; Yan Yonghong; Wei Lai; Xiao Shali

2013-01-01

The high resolving measurement of hard X-ray spectra generated in laser-produced plasma is usually performed using a cylindrically curved crystal spectrometer. In this paper, theoretical analysis and numerical simulation are performed to investigate the dependence of the energy range and resolving power on various design parameters, including crystal bending radius, source to crystal standoff distance, source size, location of the detector, etc. The investigation provides a means to design and develop cylindrically transmission curved crystal spectrometer which is used in hard X-ray diagnostics. The results show that crystal bending radius has a great influence on energy range of spectra and resolving power, and the separation between the spectral lines increases with the distance behind the focal circle faster than the line width, resulting in increased resolving power with distance. (authors)

Solar energy captured by a curved collector designed for architectural integration

International Nuclear Information System (INIS)

Rodríguez-Sánchez, D.; Belmonte, J.F.; Izquierdo-Barrientos, M.A.; Molina, A.E.; Rosengarten, G.; Almendros-Ibáñez, J.A.

2014-01-01

Highlights: • We present a new prototype of solar collector for architectural integration. • Equations of the solar radiation on a curved surface. • We compare the energy intercepted by the prototype with the energy intercepted by conventional collectors. • The prototype can be competitive compared with conventional collectors. - Abstract: In this paper we present a prototype for a new type of solar thermal collector designed for architectural integration. In this proposal, the conventional geometry of a flat solar thermal collector is changed to a curved geometry, to improve its visual impact when mounted on a building facade or roof. The mathematical equations for the beam and diffuse solar radiation received by a collector with this geometry are developed for two different orientations, horizontal and vertical. The performance of this curved prototype, in terms of solar radiation received, is compared with a conventional tilted-surface collector for different orientations in Madrid (Spain). The comparison is made for typical clear-sky days in winter and summer as well as for an entire year. The results demonstrate that the curved collector only receives between 12% and 25% less radiation than the conventional tilted-surface collectors when oriented horizontally, depending on the azimuth of the curved surface, although these percentages are reduced to approximately 50% when the collector is oriented vertically

Real-time Alarm Monitoring System for Detecting Driver Fatigue in Wireless Areas

Directory of Open Access Journals (Sweden)

Rongrong Fu

2017-04-01

Full Text Available The purpose of this paper was to develop a real-time alarm monitoring system that can detect the fatigue driving state through wireless communication. The drivers’ electroencephalogram (EEG signals were recorded from occipital electrodes. Seven EEG rhythms with different frequency bands as gamma, hbeta, beta, sigma, alpha, theta and delta waves were extracted. They were simultaneously assessed using relative operating characteristic (ROC curves and grey relational analysis to select one as the fatigue feature. The research results showed that the performance of theta wave was the best one. Therefore, theta wave was used as fatigue feature in the following alarm device. The real-time alarm monitoring system based on the result has been developed, once the threshold was settled by using the data of the first ten minutes driving period. The developed system can detect driver fatigue and give alarm to indicate the onset of fatigue automatically.

Fatigue of wind turbines in the frequency domain

Energy Technology Data Exchange (ETDEWEB)

Bishop, N W.M. [Univ. College London (United Kingdom)

1996-09-01

Fatigue damage is traditionally determined from time signals of loading, usually in the form of stress or strain. However, there are three design scenarios when a spectral form of loading is more appropriate. In this case the loading is defined in terms of its magnitude at different frequencies in the form of a Power Spectral Density (PSD) plot. First, the measurement engineer recording responses from in-service components or structures may be interested in PSD`s because they are a efficient way of defining a random stress or strain time history. Secondly, the test engineer assessing the reliability of prototypes may be interested in spectral tools because such an approach allows the structural condition of the component to be monitored by continuous inspection of the system transfer function. However, the most important benefit of working with PSD`s is relevant to the structural analysis or designer because of the more sophisticated analysis options with which they can be use. For all three of these design scenarios the fatigue designer is presented with a PSD of stress or strain with which to perform his fatigue calculation. There is therefore a requirement for a reliable, accurate and robust spectral fatigue design tool. Such a tool allows the designer to estimate the rainflow range content and hence content and hence fatigue damage from the PSD. (EG)

Estimation of fatigue characteristics of asphaltic mixes using simple tests

NARCIS (Netherlands)

Medani, T.O.; Molenaar, A.A.A.

2000-01-01

A simplified procedure for estimation of fatigue characteristics of asphaltic mixes is presented. The procedure requires the determination of the so-called master curve (Le. the relationship between the mix stiffness, the loading time and the temperature), the asphalt properties and the mix

System Level Design of Reconfigurable Server Farms Using Elliptic Curve Cryptography Processor Engines

Directory of Open Access Journals (Sweden)

Sangook Moon

2014-01-01

Full Text Available As today’s hardware architecture becomes more and more complicated, it is getting harder to modify or improve the microarchitecture of a design in register transfer level (RTL. Consequently, traditional methods we have used to develop a design are not capable of coping with complex designs. In this paper, we suggest a way of designing complex digital logic circuits with a soft and advanced type of SystemVerilog at an electronic system level. We apply the concept of design-and-reuse with a high level of abstraction to implement elliptic curve crypto-processor server farms. With the concept of the superior level of abstraction to the RTL used with the traditional HDL design, we successfully achieved the soft implementation of the crypto-processor server farms as well as robust test bench code with trivial effort in the same simulation environment. Otherwise, it could have required error-prone Verilog simulations for the hardware IPs and other time-consuming jobs such as C/SystemC verification for the software, sacrificing more time and effort. In the design of the elliptic curve cryptography processor engine, we propose a 3X faster GF(2m serial multiplication architecture.

CYCLIC FATIGUE RESISTANCE OF AZ91 MAGNESIUM ALLOY

Directory of Open Access Journals (Sweden)

Aneta Němcová

2009-11-01

Full Text Available The paper deals with determination of principal mechanical properties and the investigation of fatigue behaviour of AZ91 magnesium alloy. The experimental material was made by squeeze casting technique and heat treated to obtain T4 state (solution annealing, when hard, brittle Mg17Al12 intermetallic phase is dissolved. The basic mechanical properties (Young’s modulus, ultimate tensile strength, yield strength, elongation to fracture and reduction of area were determined by static tensile test. Furthermore, fatigue parameters were investigated. The S-N curve on the basis of smooth test bars tested under symmetrical push-pull loading at room temperature was evaluated. The measured data were subsequently used for fitting with suitable regression functions (Kohout & Věchet and Stromeyer for determination of the fatigue parameters. Fatigue limit sigma-c of the studied alloy for 108 cycles is approaching 50 MPa. In addition, the fracture surfaces were observed by scanning electron microscopy. The failure analysis proved that the striations were observed in fatigue crack propagation area and in the area of static fracture was observed the transgranular ductile fracture. The structure of the studied alloy in the basic state and after heat treatment was observed by light and scanning electron microscopy.

Study of fatigue crack propagation in laminated metal composites alluminium 1100/alluminium 2024

International Nuclear Information System (INIS)

Tavares, R.I.

1984-01-01

A study has been made of fatigue crack propagation in laminated metal composites with different volume fraction of constituents. The composites were produced by hot rolling, combining 1100 and 2024 aluminum alloys in crack divider orientation. Mechanical and metallurgical properties of the composites and original alloys sheets have been evaluated. Paris type relationship, corresponding to stage II of fatigue crack propagation curves, has been determined by two different methods, wich have shown to be equivalent. A computer software in FORTRAN language was developed for all the mathematical manipulation of fatigue data including statistical analysis and graphics. (Author) [pt

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Science.gov (United States)

Yang, Shu; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances. PMID:25126606

Dynamic response and optimal design of curved metallic sandwich panels under blast loading.

Science.gov (United States)

Qi, Chang; Yang, Shu; Yang, Li-Jun; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a "soft" outer face and a "hard" inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Directory of Open Access Journals (Sweden)

Chang Qi

2014-01-01

Full Text Available It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

The influence of the martensitic transformation on the fatigue of an AISI type 316 metastable stainless steel

International Nuclear Information System (INIS)

Pacheco, D.J; Sousa e Silva, A.S. de; Monteiro, S.N.

The influence of the martensitic transformation on the process of pulse tension fatigue of a AISI type 316 metastable stainless steel was studied at 25 0 and 196 0 c. The fatigue tests were performed on annealed and cold worked specimens in order to separate the effects of static transformation, dynamic transformation and work hardening. The fatigue limits obtained from the corresponding Wohler curves were compared for the different test conditions. The results showed that the fatigue is not affected by the dynamically induced martensite. On the other hand the static martensite, previously induced, appears to decrease the resistance to fatigue. The reasons for these effects are discussed. (Author) [pt

Materials design data for reduced activation martensitic steel type F82H

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A.-A.F. E-mail: tavassoli@cea.fr; Rensman, J.-W.; Schirra, M.; Shiba, K

2002-11-01

This paper presents materials data for design of ITER test blanket modules with the reduced activation ferritic martensitic steel type F82H as structural material. From the physical properties databases, variations of modulus of elasticity, density, thermal conductivity, thermal diffusivity, specific heat, mean and instantaneous linear coefficients of thermal expansion versus temperature are derived. Also reported are Poisson's ratio and magnetic properties. From the tension test results, nominal and minimum stress values of S{sub y} and S{sub u} are derived and used for calculation of allowable primary membrane stress intensity S{sub m}. Likewise, uniform and total elongations, as well as reduction of area data, are used for calculation of minimum and true ductility at rupture values. From the instrumented Charpy impact and fracture toughness test data, ductile to brittle transition temperature, toughness and behavior of material in different fracture modes are evaluated. The effect of specimen size and geometry are discussed but preference is given to standard size specimens. From the fatigue data, total strain range versus number of cycles to failure curves are plotted and used to derive fatigue design curves, using a reduction factor of 2 on strain and a reduction factor of 20 on number of cycles to failure. Cyclic hardening curves are also derived and compared with monotonic hardening curves. From the creep data, time dependent allowable stresses S{sub r} and S{sub t} are calculated. Combination of tension and creep results are used to deduce S{sub mt} and isochronus curves. Finally, irradiated and aged materials data are compared to insure that the safety margins incorporated in unirradiated design limits are not exceeded.

Fatigue damage mechanism and strength of woven laminates

International Nuclear Information System (INIS)

Xiao, J.; Bathias, C.

1993-01-01

The apparent secant stiffness changes with the cyclic number for both unnotched and notched woven laminated specimens (two orthotropic and one quasi-isotropic) during tensile fatigue test at a fixed ratio of maximum fatigue load to UTS were observed. The observable damage initiation and evolution as a function of the cyclic number were directly measured at the notched specimen surface with a video-camera system. The fatigue strengths of the unnotched and notched specimens were determined. The results show that the normalized apparent secant stiffness change curves as a function of cyclic numbers can be divided into three stages. For the first and the second stages in notched specimens and for total life of unnotched specimens, the damage has not been evidently observed and certainly verified with the traditional experimental methods such as radiography and microscopy although many acoustic emission signals can be obtained. The last stage for the notched specimens (N/Nf>0.4, the secant stiffness decreases fast) corresponds to the initiation and evolution of the observable damages. The fatigue strength of these woven composite laminates is dominated by the third stage during which the observable damage develops along the specimen ligament until fracture. During the third stage, a critical dimension at the specimen ligament and a life threshold can be found beyond which a final catastrophic fracture will immediately occur. The quasi-isotropic laminate is of a fatigue strength lower than the two orthotropic laminates of which the fatigue strengths are approaching to each other. The fatigue life is also influenced by the stacking sequences. (orig.)

Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel

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Josip Brnic

2016-04-01

Full Text Available The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel.

Science.gov (United States)

Brnic, Josip; Turkalj, Goran; Canadija, Marko; Lanc, Domagoj; Krscanski, Sanjin; Brcic, Marino; Li, Qiang; Niu, Jitai

2016-04-20

The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

Treatment of fatigue with methylphenidate, modafinil and amantadine in multiple sclerosis (TRIUMPHANT-MS): Study design for a pragmatic, randomized, double-blind, crossover clinical trial.

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Nourbakhsh, Bardia; Revirajan, Nisha; Waubant, Emmanuelle

2018-01-01

Fatigue is the most common symptom of multiple sclerosis (MS). Amantadine, modafinil and amphetamine-like stimulants are commonly used in clinical practice for treatment of fatigue; however, the evidence supporting their effectiveness is sparse and conflicting. To describe the design of a trial study funded by Patient-Centered Outcome Research Institute (PCORI) that will compare the efficacy of commonly used fatigue medications in patients with MS. The study is a randomized, placebo-controlled, crossover, four-sequence, four-period, double-blind, multicenter trial of three commonly used medications for the treatment of MS-related fatigue (amantadine, modafinil, methylphenidate) versus placebo in fatigued subjects with MS. Adult patients with MS, with an Expanded Disability Status Scale of MS-related fatigue. Clinicaltrials.gov registration number: NCT03185065. Copyright © 2017 Elsevier Inc. All rights reserved.

Formation of stress/strain cycles for analytical assessment of fatigue crack initiation and growth

International Nuclear Information System (INIS)

Tashkinov, A.V.

2005-01-01

This paper discusses standard techniques for setting up cycles of stresses, strains and stress intensity factors (SIF) for use in analysing the fatigue characteristics of crack-free components or the fatigue crack growth if crack-like flaws are present. A number of improved techniques are proposed. An enhanced procedure for analytical description of true metal stress-strain curves, covering plastic effects, is presented. This procedure involves standard physical and mechanical properties of the metal in question, such as ultimate stress, yield stress and elasticity modulus. It is emphasized that the currently practiced rain-flow method of design cycle formation, which is effective for an actual (truly known) cyclic loading history, is not suitable for a projected (anticipated) history, as it leaves out of account possible variations in the sequence of operating conditions. Improved techniques for establishing design stress/strain and SIF cycles are described, which make allowance for the most unfavourable sequence of events in the projected loading history. The paper points to a basic difference in the methods of design cycle formation, employed in assessment of the current condition of a component (with the actual history accounted for) and in estimation of the residual lifetime or life extension (for a projected history). (authors)

Design of Fatigue Resistant Heusler-strengthened PdTi-based Shape Memory Alloys for Biomedical Applications

Science.gov (United States)

Frankel, Dana J.

The development of non-surgical transcatheter aortic valve implantation (TAVI) techniques, which utilize collapsible artificial heart valves with shape memory alloy (SMA)-based frames, pushes performance requirements for biomedical SMAs beyond those for well-established vascular stent applications. Fatigue life for these devices must extend into the ultra-high cycle fatigue (UHCF) regime (>600M cycles) with zero probability of failure predicted at applied strain levels. High rates of Ni-hypersensitivity raise biocompatibility concerns, driving the development of low-Ni and Ni-free SMAs. This work focuses on the development of biocompatible, precipitation-strengthened, fatigue-resistant PdTi-based SMAs for biomedical applications. Functional and structural fatigue are both manifestations of cyclic instability resulting in accumulation of slip and eventual structural damage. While functional fatigue is easily experimentally evaluated, structural fatigue is more difficult to measure without the proper equipment. Therefore, in this work a theoretical approach using a model well validated in steels is utilized to investigate structural fatigue behavior in NiTi in the UHCF regime, while low cycle functional fatigue is evaluated in order to monitor the core phenomena of the cyclic instability. Results from fatigue simulations modeling crack nucleation at non-metallic inclusions in commercial NiTi underscore the importance of increasing yield strength for UHCF performance. Controlled precipitation of nanoscale, low-misfit, L21 Heusler aluminides can provide effective strengthening. Phase relations, precipitation kinetics, transformation temperature, transformation strain, cyclic stability, and mechanical properties are characterized in both Ni-free (Pd,Fe)(Ti,Al) and low-Ni high-strength "hybrid" (Pd,Ni)(Ti,Zr,Al) systems. Atom probe tomography is employed to measure phase compositions and particle sizes used to calibrate LSW models for coarsening kinetics and Gibbs

Tensile and compressive failure modes of laminated composites loaded by fatigue with different mean stress

Science.gov (United States)

Rotem, Assa

1990-01-01

Laminated composite materials tend to fail differently under tensile or compressive load. Under tension, the material accumulates cracks and fiber fractures, while under compression, the material delaminates and buckles. Tensile-compressive fatigue may cause either of these failure modes depending on the specific damage occurring in the laminate. This damage depends on the stress ratio of the fatigue loading. Analysis of the fatigue behavior of the composite laminate under tension-tension, compression-compression, and tension-compression had led to the development of a fatigue envelope presentation of the failure behavior. This envelope indicates the specific failure mode for any stress ratio and number of loading cycles. The construction of the fatigue envelope is based on the applied stress-cycles to failure (S-N) curves of both tensile-tensile and compressive-compressive fatigue. Test results are presented to verify the theoretical analysis.

Miniature specimen technology for postirradiation fatigue crack growth testing

International Nuclear Information System (INIS)

Mervyn, D.A.; Ermi, A.M.

1979-01-01

Current magnetic fusion reactor design concepts require that the fatigue behavior of candidate first wall materials be characterized. Fatigue crack growth may, in fact, be the design limiting factor in these cyclic reactor concepts given the inevitable presence of crack-like flaws in fabricated sheet structures. Miniature specimen technology has been developed to provide the large data base necessary to characterize irradiation effects on the fatigue crack growth behavior. An electrical potential method of measuring crack growth rates is employed on miniature center-cracked-tension specimens (1.27 cm x 2.54 cm x 0.061 cm). Results of a baseline study on 20% cold-worked 316 stainless steel, which was tested in an in-cell prototypic fatigue machine, are presented. The miniature fatigue machine is designed for low cost, on-line, real time testing of irradiated fusion candidate alloys. It will enable large scale characterization and development of candidate first wall alloys

14 CFR 25.907 - Propeller vibration and fatigue.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller vibration and fatigue. 25.907... vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a... propeller to show that failure due to fatigue will be avoided throughout the operational life of the...

Numerical and Experimental Analysis of Aircraft Wing Subjected to Fatigue Loading

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Hatem Rahim Wasmi

2016-10-01

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

Population based study of fatigue and psychological distress.

OpenAIRE

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

1994-01-01

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

Seismic ratchet-fatigue failure of piping systems

International Nuclear Information System (INIS)

Severud, L.K.; Anderson, M.J.; Lindquist, M.R.; Weiner, E.O.

1987-01-01

Failures of piping systems during earthquakes have been rare. Those that have failed were either made of brittle material such as cast iron, were rigid systems between major components where component relative seismic motions tore the pipe out of the component, or were high pressure systems where a ratchet-fatigue fracture followed a local bulging of the pipe diameter. Tests to failure of an unpressurized 3-inch and a pressurized 6-inch diameter carbon steel nuclear pipe systems subjected to high-level shaking have been accomplished. The high-level shaking loads needed to cause failure were much higher than ASME Code rules would permit with present design limits. Failure analyses of these tests are presented and correlated to the test results. It was found that failure of the unpressurized system could be correlated well with standard ASME type fatigue analysis predictions. Moreover, the pressurized system failure occured in significantly less load cycles than predicted by standard fatigue analysis. However, a ratchet-fatigue and ductility exhaustion analysis of the pressurized system did correlate reasonably well. These findings indicate modifications to design analysis methods and the present ASME Code piping design rules to reduce unneeded conservatisms and to cover the ratchet-fatigue failure mode may be appropriate

The direct-stress fatigue strength of 17S-T aluminum alloy throughout the range from 1/2 to 500,000,000 cycles of stress

Science.gov (United States)

Hartmann, E C; Stickley, G W

1942-01-01

Fatigue-test were conducted on six specimens made from 3/4-inch-diameter 17S-T rolled-and-drawn rod for the purpose of obtaining additional data on the fatigue life of the material at stresses up to the static strength. The specimens were tested in direct tension using a stress range from zero to a maximum in tension. A static testing machine was used to apply repeated loads in the case of the first three specimens; the other three specimens were tested in a direct tension-compression fatigue machine. The direct-stress fatigue curve obtained for the material indicates that, in the range of stresses above about two-thirds the tensile strength, the fatigue strength is higher than might be expected by simply extrapolating the ordinary curve of stress plotted against the number of cycles determined at lower stresses.

Thermal fatigue in mixing tees: A step by step simplified procedure

International Nuclear Information System (INIS)

Faidy, Claude

2003-01-01

Following the CIVAUX 1 incident of a leak on RHR system, EDF has developed a step by step procedure to screen and analyse similar locations: mixing tees with long duration at high ΔT between the 2 fluids. The paper present the procedure, the background of the methodology and few R and D work that support this procedure. The procedure is based on: screening criteria on maximum DT and minimum duration. screening criteria without any duration consideration, only DT and material. a simplified and conservative estimation of a usage factor. a detailed analysis of usage factor and crack growth rate, based on specific data collection of operating transients. Around that procedure EDF launched an R and D program on fatigue curves and fatigue reduction factors for high cycle fatigue. The procedure is compared with field experience and recent R and D fatigue tests. (author)

Development of an in situ fatigue sensor.

Science.gov (United States)

2011-01-01

A prototype in situ fatigue sensor has been designed, constructed and evaluated experimentally for its ability to monitor the accumulation of fatigue damage in a cyclically loaded steel structure, e.g., highway bridge. The sensor consists of multiple...

Human cortical neural correlates of visual fatigue during binocular depth perception: An fNIRS study.

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Tingting Cai

Full Text Available Functional near-infrared spectroscopy (fNIRS was adopted to investigate the cortical neural correlates of visual fatigue during binocular depth perception for different disparities (from 0.1° to 1.5°. By using a slow event-related paradigm, the oxyhaemoglobin (HbO responses to fused binocular stimuli presented by the random-dot stereogram (RDS were recorded over the whole visual dorsal area. To extract from an HbO curve the characteristics that are correlated with subjective experiences of stereopsis and visual fatigue, we proposed a novel method to fit the time-course HbO curve with various response functions which could reflect various processes of binocular depth perception. Our results indicate that the parietal-occipital cortices are spatially correlated with binocular depth perception and that the process of depth perception includes two steps, associated with generating and sustaining stereovision. Visual fatigue is caused mainly by generating stereovision, while the amplitude of the haemodynamic response corresponding to sustaining stereovision is correlated with stereopsis. Combining statistical parameter analysis and the fitted time-course analysis, fNIRS could be a promising method to study visual fatigue and possibly other multi-process neural bases.

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

Science.gov (United States)

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

2014-01-01

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

Isothermal and thermal–mechanical fatigue of VVER-440 reactor pressure vessel steels

Energy Technology Data Exchange (ETDEWEB)

Fekete, Balazs, E-mail: fekete.mm.bme@gmail.com [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary); Department of Applied Mechanics, Budapest University of Technology and Economics, Muegyetem 5, Budapest H-1111 (Hungary); Trampus, Peter [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary)

2015-09-15

Highlights: • We aimed to determine the thermomechanical behaviour of VVER reactor steels. • Material tests were developed and performed on GLEEBLE 3800 physical simulator. • Coffin–Manson curves and parameters were derived. • High accuracy of the strain energy based evaluation was found. • The observed dislocation evolution correlates with the mechanical behaviour. - Abstract: The fatigue life of the structural materials 15Ch2MFA (CrMoV-alloyed ferritic steel) and 08Ch18N10T (CrNi-alloyed austenitic steel) of VVER-440 reactor pressure vessel under completely reserved total strain controlled low cycle fatigue tests were investigated. An advanced test facility was developed for GLEEBLE-3800 physical simulator which was able to perform thermomechanical fatigue experiments under in-service conditions of VVER nuclear reactors. The low cycle fatigue results were evaluated with the plastic strain based Coffin–Manson law, and plastic strain energy based model as well. It was shown that both methods are able to predict the fatigue life of reactor pressure vessel steels accurately. Interrupted fatigue tests were also carried out to investigate the kinetic of the fatigue evolution of the materials. On these samples microstructural evaluation by TEM was performed. The investigated low cycle fatigue behavior can provide reference for remaining life assessment and lifetime extension analysis.

Seasonality of cavitation and frost fatigue in Acer mono Maxim.

Science.gov (United States)

Zhang, Wen; Feng, Feng; Tyree, Melvin T

2017-12-08

Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle, whereas frost fatigue was caused by a freeze-thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes. © 2017 John Wiley & Sons Ltd.

Probabilistic Fatigue Model for Reinforced Concrete Onshore Wind Turbine Foundations

DEFF Research Database (Denmark)

Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

2013-01-01

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

Rotary bending fatigue behavior of A356 –T6 aluminum alloys by vacuum pressurizing casting

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