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Sample records for vessel steel fatigue

  1. Fatigue crack propagation in steels for reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Klesnil, M.; Lukas, P.; Kunz, L. (Ceskoslovenska Akademie Ved, Brno. Ustav Fyzikalni Metalurgie); Troshchenko, V.T.; Pokrovskij, V.V.; Yasnij, P.V.; Skorenko, Y.S. (AN Ukrainskoj SSR, Kiev. Inst. Problem Prochnosti)

    1983-01-01

    Fatigue crack propagation data were measured on 15Kh2NMFA steel of Czechoslovak and Soviet makes. The results obtained by two laboratories were compared with other available data regarding materials for pressure vessels of nuclear power plants. Crack propagation curves were measured at temperatures -60, 20 and 350 degC and the corresponding parameters of crack growth equation were found. Threshold values of stress intensity factor amplitude, Ksub(apz), and the influence of stress ratio R in the range of small crack rates were determined experimentally. Fractography revealed either transgranular or mixed transgranular and interaranular fracture modes depending on stress intensity amplitude Ksub(a) and the environment.

  2. Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

    Science.gov (United States)

    Liaw, P. K.; Logsdon, W. A.; Begley, J. A.

    1989-10-01

    The fatigue crack growth rate (FCGR) properties of SA508 C1 2a and SA533 Gr A C1 2 pressure vessel steels and the corresponding automatic submerged are weldments were developed in a high-temperature pressurized water (HPW) environment at 288 °C (550°F) and 7.2 MPa (1044 psi) at load ratios of 0.02 and 0.50. The HPW enviromment FCGR properties of these pressure vessel steels and submerged arc weldments were generally conservative, compared with the approrpriate American Society of Mechanical Engineers (ASME) Section XI water environmental reference curve. The growth rate of fatigue cracks in the base materials, however, was considerably faster in the HPW environment than in a corresponding 288°C (550°F) base line air environment. The growth rate of fatigue cracks in the two submerged are weldments was also accelerated in the HPW environment but to a significantly lesser degree than that demonstrated by the corresponding base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials, as compared with the weldments, was attributed to a different sulfide composition and morphology.

  3. Fatigue crack growth rates in a pressure vessel steel under various conditions of loading and the environment

    Science.gov (United States)

    Hicks, P. D.; Robinson, F. P. A.

    1986-10-01

    Corrosion fatigue (CF) tests have been carried out on SA508 Cl 3 pressure vessel steel, in simulated P.W.R. environments. The test variables investigated included air and P.W.R. water environments, frequency variation over the range 1 Hz to 10 Hz, transverse and longitudinal crack growth directions, temperatures of 20 °C and 50 °C, and R-ratios of 0.2 and 0.7. It was found that decreasing the test frequency increased fatigue crack growth rates (FCGR) in P.W.R. environments, P.W.R. environment testing gave enhanced crack growth (vs air tests), FCGRs were greater for cracks growing in the longitudinal direction, slight increases in temperature gave noticeable accelerations in FCGR, and several air tests gave FCGR greater than those predicted by the existing ASME codes. Fractographic evidence indicates that FCGRs were accelerated by a hydrogen embrittlement mechanism. The presence of elongated MnS inclusions aided both mechanical fatigue and hydrogen embrittlement processes, thus producing synergistically fast FCGRs. Both anodic dissolution and hydrogen embrittlement mechanisms have been proposed for the environmental enhancement of crack growth rates. Electrochemical potential measurements and potentiostatic tests have shown that sample isolation of the test specimens from the clevises in the apparatus is not essential during low temperature corrosion fatigue testing.

  4. Residual Stress Estimation and Fatigue Life Prediction of an Autofrettaged Pressure Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Song, Kyung Jin; Kim, Eun Kyum; Koh, Seung Kee [Kunsan Nat’l Univ., Kunsan (Korea, Republic of)

    2017-09-15

    Fatigue failure of an autofrettaged pressure vessel with a groove at the outside surface occurs owing to the fatigue crack initiation and propagation at the groove root. In order to predict the fatigue life of the autofrettaged pressure vessel, residual stresses in the autofrettaged pressure vessel were evaluated using the finite element method, and the fatigue properties of the pressure vessel steel were obtained from the fatigue tests. Fatigue life of a pressure vessel obtained through summation of the crack initiation and propagation lives was calculated to be 2,598 cycles for an 80% autofrettaged pressure vessel subjected to a pulsating internal pressure of 424 MPa.

  5. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    1999-01-01

    Fatigue damage accumulation in steel structures under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series have been carried through on various...... types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel with a yield stress of ~ 360-410 MPa or high-strength steel with a yield stress of ~ 810-1010 MPa. The fatigue tests and the fracture mechanics analyses...... test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from Miner's rule will depend...

  6. Fatigue strength tests of layered steel

    Directory of Open Access Journals (Sweden)

    Michal Černý

    2013-01-01

    Full Text Available The work deals with original measurement of fatigue properties of formed layered steel material – damask steel. This is a material that exhibits a fine micro-structure as well as a regular composition of many material layers with complementary properties. The article experimentally verifies high-cycle fatigue properties of layered steel and evaluates them from the point of view of fatigue tests of conventional steel materials and a parallel application of a non-destructive – acoustic emission – testing. Finally, it discusses the influence of production on fatigue strength and the possibilities of using multi-layered steel materials in technological practice. A serious result of this pilot experiment is the fact documented no only by the fractographic observation, but mainly by the AE records that the fatigue service life of this material is high if it its not stressed by tension approximating the yield point Re. However, such stress is not common in practical use of tools made of damask steel and thus under common bending stress an exceptionally long service life of tools made of this type of material is demonstrable. The fact that damask steel behaves like a homogeneous material is mainly confirmed by the records of the AE signal at lower values of stress σa. When stressed by higher amplitudes of tension σa damask responds in AE records similarly to a laminate material that is stressed by bending.

  7. Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Energy Technology

    2002-08-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify 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. Existing fatigue strain-vs.-life ({var_epsilon}-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This report provides an overview of fatigue crack initiation in austenitic stainless steels in LWR coolant environments. The existing fatigue {var_epsilon}-N data have been evaluated to establish the effects of key material, loading, and environmental parameters (such as steel type, strain range, strain rate, temperature, dissolved-oxygen level in water, and flow rate) on the fatigue lives of these steels. Statistical models are presented for estimating the fatigue {var_epsilon}-N curves for austenitic stainless steels as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are presented. The influence of reactor environments on the mechanism of fatigue crack initiation in these steels is also discussed.

  8. Fatigue damage of steel components

    DEFF Research Database (Denmark)

    Fæster, Søren; Zhang, Xiaodan; Huang, Xiaoxu

    2014-01-01

    Railway rails and the inner ring in roller bearings in wind turbines are both experiencing steel-to-steel contact in small areas with huge loads resulting in extremely high stresses in the base materials......Railway rails and the inner ring in roller bearings in wind turbines are both experiencing steel-to-steel contact in small areas with huge loads resulting in extremely high stresses in the base materials...

  9. Tensile and Fatigue Behavior of ASS304 for Cold Stretching Pressure Vessels at Cryogenic Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hoon Seok [The 5th R and D Institute, Agency for Defense Development, Daejeon (Korea, Republic of); Kim, Jae Hoon; Na, Seong Hyun [Chungnam National Univ., Daejon (Korea, Republic of); Lee, Youn Hyung [Korean Gas Safety Corporation, Chungju (Korea, Republic of); Kim, Sung Hun [Daechang Solution Co. Ltd, Busan (Korea, Republic of); Kim, Young Kyun; Kim, Ki Dong [Korean Gas Corporation, R and D Division, Ansan (Korea, Republic of)

    2016-05-15

    Cold stretching(CS) pressure vessels from ASS304 (austenitic stainless steel 304) are used for the transportation and storage of liquefied natural gas(LNG). CS pressure vessels are manufactured by pressurizing the finished vessels to a specific pressure to produce the required stress σk. After CS, there is some degree of plastic deformation. Therefore, CS vessels have a higher strength and lighter weight compared to conventional vessels. In this study, we investigate the tensile and fatigue behavior of ASS304 sampled by CS pressure vessels in accordance with the ASME code at cryogenic temperature. From the fatigue test results, we show S-N curves using a statistical method recommended by JSEM-S002. We carried out the fractography of fractured specimens using scanning electron microscopy (SEM)

  10. Fatigue-Prone Details in Steel Bridges

    Directory of Open Access Journals (Sweden)

    Mohsen Heshmati

    2012-11-01

    Full Text Available This paper reviews the results of a comprehensive investigation including more than 100 fatigue damage cases, reported for steel and composite bridges. The damage cases are categorized according to types of detail. The mechanisms behind fatigue damage in each category are identified and studied. It was found that more than 90% of all reported damage cases are of deformation-induced type and generated by some kind of unintentional or otherwise overlooked interaction between different load-carrying members or systems in the bridge. Poor detailing, with unstiffened gaps and abrupt changes in stiffness at the connections between different members were also found to contribute to fatigue cracking in many details.

  11. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2009-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...... of the investigation, fatigue test series with a total of 540 fatigue tests have been carried through on various types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel or high-strength steel. The fatigue tests...... and variable amplitude fatigue test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner’s rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from...

  12. Effect of material heat treatment on fatigue crack initiation in austenitic stainless steels in LWR environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Alexandreanu, B.; Shack, W. J.; Energy Technology

    2005-07-31

    The ASME Boiler and Pressure Vessel Code provides rules for the design of Class 1 components of nuclear power plants. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify design curves for applicable structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. The existing fatigue strain-vs.-life ({var_epsilon}-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. Under certain environmental and loading conditions, fatigue lives of austenitic stainless steels (SSs) can be a factor of 20 lower in water than in air. This report presents experimental data on the effect of heat treatment on fatigue crack initiation in austenitic Type 304 SS in LWR coolant environments. A detailed metallographic examination of fatigue test specimens was performed to characterize the crack morphology and fracture morphology. The key material, loading, and environmental parameters and their effect on the fatigue life of these steels are also described. Statistical models are presented for estimating the fatigue {var_epsilon}-N curves for austenitic SSs as a function of material, loading, and environmental parameters. Two methods for incorporating the effects of LWR coolant environments into the ASME Code fatigue evaluations are presented.

  13. Fatigue crack growth and fracture behavior of bainitic rail steels.

    Science.gov (United States)

    2011-09-01

    "The microstructuremechanical properties relationships, fracture toughness, fatigue crack growth and fracture surface morphology of J6 bainitic, manganese, and pearlitic rail steels were studied. Microstructuremechanical properties correlation ...

  14. Fatigue crack growth and fracture behavior of bainitic rail steels.

    Science.gov (United States)

    2011-08-01

    "The microstructuremechanical properties relationships, fracture toughness, fatigue crack growth and fracture surface morphology of J6 bainitic, manganese, and pearlitic rail steels were studied. Microstructuremechanical properties correlation ...

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

    DEFF Research Database (Denmark)

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

    1996-01-01

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

  16. Modal Based Fatigue Monitoring of Steel Structures

    DEFF Research Database (Denmark)

    Graugaard-Jensen, J.; Brincker, Rune; Hjelm, H. P.

    2005-01-01

    In this paper it is shown how the accumulated fatigue in steel structures can be estimated with high accuracy by continuously measuring the accelerations in a few points of the structure. First step is to obtain a good estimate of the mode shapes by performing a natural input modal analysis. The so...... by applying the mode shapes of the calibrated Finite Element model and strains are obtained using the shape functions for the actual elements. The technique has been applied on a model frame structure in the laboratory and on a wind loaded lattice pylon structure. In both cases the estimated stresses has been...

  17. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, Jette Andkjær

    1999-01-01

    Fatigue damage accumulation in steel highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test specimens...... have been carried through. The materials that have been used are either conventional structural steel with a yield stress of f(y) similar to 400-410 MPa or high-strength steel with a yield stress of f(y) similar to 810-840 MPa. The fatigue tests have been carried out using load histories, which...

  18. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, J.A.; Vejrum, Tina

    1997-01-01

    In the present investigation, fatigue damage accumulation in steel highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis.In the experimental part of the investigation, fatigue test series...... on welded plate test specimens have been carried through. The materials that have been used are either conventional structural steel with a yield stress of ~ 400-410 MPa or high-strength steel with a yield stress of ~ 810-840 MPa.The fatigue tests have been carried out using load histories, which correspond...

  19. A preliminary bending fatigue spectrum for steel monostrand cables

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2011-01-01

    This paper presents the results of the experimental study on the bending fatigue resistance of high-strength steel monostrand cables. From the conducted fatigue tests in the high-stress, low-cycle region, a preliminary bending fatigue spectrum is derived for the estimation of monostrand cable...... service life expectancy. The presented preliminary bending fatigue spectrum of high-strength monostrands is currently unavailable in the published literature. The presented results provide relevant information on the bending mechanism and fatigue characteristics of monostrand steel cables in tension...

  20. Review of environmental effects on fatigue crack growth of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Shack, W.J.; Kassner, T.F. [Argonne National Lab., IL (United States)

    1994-05-01

    Fatigue and environmentally assisted cracking of piping, pressure vessel cladding, and core components in light water reactors are potential concerns to the nuclear industry and regulatory agencies. The degradation processes include intergranular stress corrosion cracking of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or stress corrosion cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Crack growth data for wrought and cast austenitic SSs in simulated BWR water, developed at Argonne National Laboratory under US Nuclear Regulatory Commission sponsorship over the past 10 years, have been compiled into a data base along with similar data obtained from the open literature. The data were analyzed to develop corrosion-fatigue curves for austenitic SSs in aqueous environments corresponding to normal BWR water chemistries, for BWRs that add hydrogen to the feedwater, and for pressurized water reactor primary-system-coolant chemistry.

  1. Effects of LWR coolant environments on fatigue design curves of carbon and low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1998-03-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the code specify fatigue design curves for structural materials. While effects of reactor coolant environments are not explicitly addressed by the design curves, test data indicate that the Code fatigue curves may not always be adequate in coolant environments. This report summarizes work performed by Argonne National Laboratory on fatigue of carbon and low-alloy steels in light water reactor (LWR) environments. The existing fatigue S-N data have been evaluated to establish the effects of various material and loading variables such as steel type, dissolved oxygen level, strain range, strain rate, temperature, orientation, and sulfur content on the fatigue life of these steels. Statistical models have been developed for estimating the fatigue S-N curves as a function of material, loading, and environmental variables. The results have been used to estimate the probability of fatigue cracking of reactor components. The different methods for incorporating the effects of LWR coolant environments on the ASME Code fatigue design curves are presented.

  2. High Cycle Fatigue Behavior of Shot-Peened Steels

    Science.gov (United States)

    Mirzazadeh, M. M.; Plumtree, A.

    2012-08-01

    The uniaxial fully reversed (R = -1) long life fatigue behavior of four shot-peened engineering steels with approximately the same hardness was investigated. Shot-peening, air-cooled forged AISI 1141 and crackable AISI 1070 steels had little effect on their fatigue limits (+2.5 and -2.0 pct, respectively). In the case of a powder forged 0.5 pct C steel, an increase in the fatigue limit of 10.4 pct was observed, albeit with a large standard deviation. Shot-peening quench and tempered AISI 1151 steel decreased its fatigue limit 12.0 pct, as a result of cyclic softening. In general, the beneficial effects of shot-peening these smooth specimens were relatively small. Neither cyclic softening nor hardening occurred in the non-shot-peened steels cycled under the same conditions.

  3. 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.

  4. Corrosion fatigue crack growth behaviour of austenitic stainless steels under light water reactor conditions

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.P., E-mail: hans-peter.seifert@psi.ch [Paul Scherrer Institute (PSI), Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen PSI (Switzerland); Ritter, S.; Leber, H.J. [Paul Scherrer Institute (PSI), Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen PSI (Switzerland)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Corrosion fatigue in austenitic stainless steels under light water reactor conditions. Black-Right-Pointing-Pointer Identification of major parameters of influence. Black-Right-Pointing-Pointer Critical system conditions for environmental acceleration of fatigue crack growth. Black-Right-Pointing-Pointer Proposal for new code fatigue curves, which consider environmental effects. - Abstract: The corrosion fatigue crack growth behaviour of different wrought low-carbon and stabilised austenitic stainless steels was characterised under simulated boiling water and primary pressurised water reactor conditions by cyclic fatigue tests with pre-cracked fracture mechanics specimens in the temperature range from 70 to 320 Degree-Sign C. The major parameter effects and critical conjoint threshold conditions, which result in relevant environmental acceleration of fatigue crack growth are discussed and summarised. Furthermore, the observed corrosion fatigue behaviour is compared with the corresponding (corrosion) fatigue curves in the ASME and JSME boiler and pressure vessel code or open literature and conclusions with regard to their adequacy and conservatism are given.

  5. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2008-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...... of the investigation, fatigue test series with a total of 540 fatigue tests have been carried through on various types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel or high-strength steel. The fatigue tests...... and the fracture mechanics analyses have been carried out using load histories, which are realistic in relation to the types of structures studied, i.e. primarily bridges, offshore structures and chimneys. In general, the test series carried through show a significant difference between constant amplitude...

  6. Renovation techniques for fatigue cracked orthotropic steel bridge decks

    NARCIS (Netherlands)

    de Jong, F.B.P.

    2007-01-01

    This dissertation presents the research into renovation techniques for orthotropic steel bridge decks. These techniques are needed to solve fatigue problems in the decks of these bridges, as several fatigue cracks have been detected in the deck structure of these bridges the last decade. A

  7. Fatigue classification of welded joints in orthotropic steel bridge decks

    NARCIS (Netherlands)

    Kolstein, M.H.

    2007-01-01

    This dissertation presents the research into fatigue classifications of welded joints in orthotropic steel bridge decks. These classifications are needed to calculate the fatigue life of these joints and should be included in the design codes. For years bridge design was mainly based on static

  8. Fatigue crack Behaviour in a High Strength Tool Steel

    DEFF Research Database (Denmark)

    Højerslev, Christian; Carstensen, Jesper V.; Brøndsted, Povl

    2002-01-01

    The influence of microstructure on fatigue crack initiation and crack growth of a hardened and tempered high speed steel was investigated. The evolution of fatigue cracks was followed in four point bending at room temperature. It was found that a carbide damage zone exists above a threshold load...... value of maximally 80% of the yield strength of the steel. The size of this carbide damage zone increases with increasing load amplitude, and the zone is apparently associated with crack nucleation. On fatigue crack propagation plastic deformation of the matrix occurs in a radius of approximately 4...

  9. QUANTITATIVE ANALYSIS OF FATIGUE FRACTURE SURFACE IN THE DUPLEX STEEL

    OpenAIRE

    Maria Sozańska; Francesco Iacoviello; Jan Cwajna; Michel Jerome; Jaroslav Sojka; Jacques Galland

    2011-01-01

    We present a quantitative and qualitative analysis of the fatigue surface of Z2CND2205 duplex steel. Both the ferritic and austenitic phases of this duplex steel are investigated. The observed brittleness of the steel is here due to the presence of hydrogen. The hydrogen influence is complex in that the two phases are altered by hydrogen in different ways. Quantitative parameters describing striations spacing in each phase are measured.

  10. QUANTITATIVE ANALYSIS OF FATIGUE FRACTURE SURFACE IN THE DUPLEX STEEL

    Directory of Open Access Journals (Sweden)

    Maria Sozańska

    2011-05-01

    Full Text Available We present a quantitative and qualitative analysis of the fatigue surface of Z2CND2205 duplex steel. Both the ferritic and austenitic phases of this duplex steel are investigated. The observed brittleness of the steel is here due to the presence of hydrogen. The hydrogen influence is complex in that the two phases are altered by hydrogen in different ways. Quantitative parameters describing striations spacing in each phase are measured.

  11. Thermomechanical fatigue and damage mechanisms in Sanicro 25 steel

    Energy Technology Data Exchange (ETDEWEB)

    Petráš, R. [CEITEC IPM, Institute of Physics of Materials ASCR, Žižkova 22, 616 62 Brno (Czech Republic); Institute of Physics of Materials ASCR, Žižkova 22, 616 62 Brno (Czech Republic); Škorík, V. [Institute of Physics of Materials ASCR, Žižkova 22, 616 62 Brno (Czech Republic); Polák, J., E-mail: polak@ipm.cz [CEITEC IPM, Institute of Physics of Materials ASCR, Žižkova 22, 616 62 Brno (Czech Republic); Institute of Physics of Materials ASCR, Žižkova 22, 616 62 Brno (Czech Republic)

    2016-01-05

    Heat resistant austenitic Sanicro 25 steel was subjected to in-phase and out-of-phase thermomechanical fatigue (TMF) loading conditions with different amplitudes of mechanical strain in a wide interval of temperatures (250–700 °C). Cyclic hardening/softening curves, cyclic stress-strain curves and fatigue life curves were evaluated for both type of loadings. Scanning electron microscopy combined with FIB cutting and EBSD imaging in longitudinal sections containing cracks revealed the mechanisms responsible for fatigue crack initiation and growth. Fatigue cracks developed rapidly in oxidized grain boundaries during in-phase loading and intergranular crack growth resulted in short fatigue life. Multiple cracks in out-of-phase loading perpendicular to the stress axis have arisen only afterwards oxide layer was formed. The delayed initiation and transgranular growth led to longer fatigue life. The effect of grain boundary oxidation and surface oxide cracking on fatigue life was discussed.

  12. Analysis of Fatigue Crack Paths in Cold Drawn Pearlitic Steel

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2015-11-01

    Full Text Available In this paper, a fracto-metallographic analysis was performed on the cracked specimens of cold drawn pearlitic steel subjected to fatigue tests. Fatigue cracks are transcollonial and exhibit a preference for fracturing pearlitic lamellae, with non-uniform crack opening displacement values, micro-discontinuities, branchings, bifurcations and frequent local deflections that create microstructural roughness. At the micro-level, the cold drawn pearlitic steel exhibits higher micro-roughness than the hot rolled bar (this is a consequence of the manufacturing process by cold drawing, so that the actual fractured surface in the cold drawn wire is greater than that in the hot rolled bar, due to the fact that the crack deflection events are more frequent and with higher angle in the former (the heavily drawn prestressing steel wire. These findings show the relevant role on the manufacturing process by cold drawing in the fatigue crack propagation in pearlitic steel.

  13. Low cycle thermomechanical fatigue of reactor steels: Microstructural and fractographic investigations

    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); Kasl, Josef; Jandova, Dagmar [Výzkumný a zkušební ústav Plzeň s.r.o., Tylova 1581/46, 316 00 Plzen (Czech Republic); Jóni, Bertalan [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary); Eötvös Loránd University, Egyetem tér 1-3, Budapest H-1053 (Hungary); Misják, Fanni [Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege M. 29-33, Budapest H-1121 (Hungary); Trampus, Peter [College of Dunaujvaros, Tancsics 1A, Dunaujvaros H-2400 (Hungary)

    2015-07-29

    The fatigue life of the structural materials 15Ch2MFA (CrMoV-alloyed ferritic steel) and 08Ch18N10T (CrNi-alloyed austenitic steel) of a VVER-440 reactor pressure vessel were investigated under fully reversed total strain controlled low cycle fatigue tests. The measurements were carried out in isothermal conditions at 260 °C and with thermal-mechanical conditions in the range 150–270 °C using a GLEEBLE-3800 servo-hydraulic thermal-mechanical simulator. The low cycle fatigue results were evaluated with the Coffin–Manson law, and the parameters of the Ramberg–Osgood stress–strain relation were investigated. Fracture mechanics behavior was observed using scanning electron microscopic analysis of the crack shapes and fracture surfaces. Crack propagation was assessed in relation to the actual crack size and the loading level. Interrupted fatigue tests were also carried out to investigate the kinetics of the fatigue evolution of the materials. Microstructural evaluation of the samples was performed using light, scanning and transmission electron microscopy as well as X-ray diffraction, and measurement of dislocations was completed using TEM and XRD. The course of dislocation density in relation to cumulative usage factor was similar for both steels. However, the nature and distribution of dislocations were different in the individual steels and this resulted in different mechanical behaviors. The nature of the fracture surfaces of both steels appeared similar despite differences in dislocation arrangement. The distances between striation lines initially increased with increasing crack length and then became saturated. The low cycle fatigue behavior investigated can provide a reference for the remaining life assessment and lifetime extension analysis of nuclear power plant components.

  14. Fatigue crack initiation in carbon and low-alloy steels in light water reactor environments : mechanism and prediction.

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-01-27

    Section 111 of the ASME Boiler and Pressure Vessel Code specifies fatigue design curves for structural materials. The effects of reactor coolant environments are not explicitly addressed by the Code design curves. Recent test data illustrate potentially significant effects of light water reactor (LWR) coolant environments on the fatigue resistance of carbon and low-alloy steels. Under certain loading and environmental conditions, fatigue lives of test specimens may be shorter than those in air by a factor of {approx}70. The crack initiation and crack growth characteristics of carbon and low-alloy steels in LWR environments are presented. Decreases in fatigue life of these steels in high-dissolved-oxygen water are caused primarily by the effect of environment on growth of short cracks < 100 {micro}m in depth. The material and loading parameters that influence fatigue life in LWR environments are defined. Fatigue life is decreased significantly when five conditions are satisfied simultaneously, viz., applied strain range, service temperature, dissolved oxygen in water, and S content in steel are above a threshold level, and loading strain rate is below a threshold value. Statistical models have been developed for estimating the fatigue life of these steels in LWR environments. The significance of the effect of environment on the current Code design curve is evaluated.

  15. Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    National Research Council Canada - National Science Library

    TOYODA, Shunsuke; ISHIGURO, Yasuhide; KAWABATA, Yoshikazu; SAKATA, Kei; SATO, Akio; SAKAI, Jun'ichi

    2009-01-01

    The microstructural influence of martensitic carbon steel on torsional fatigue endurance was investigated, taking into consideration the application of high strength steel electric resistance welded (ERW...

  16. Fatigue Life Assessment of Orthotropic Steel Deck with UHPC Pavement

    Directory of Open Access Journals (Sweden)

    Xu Jiang

    2017-01-01

    Full Text Available In recent years, a number of large-span bridges with orthotropic steel decks were constructed in China. With increasing traffic volumes and higher wheel loads, many fatigue cracks developed at the welds and the edge of cut-out holes. This paper aims at presenting the numerical analysis on the fatigue performance of the orthotropic steel deck using ultrahigh performance concrete (UHPC overlay as the deck pavement instead of the conventional asphalt concrete pavement. By using finite element method (FEM model, stress distribution at fatigue sensitive locations under the action of wheel loads is characterized and the obtained stress ranges indicate that the UHPC pavement significantly reduces the magnitude of the stress peak valued. A suggested truck stream model based on the weigh-in-motion (WIM data of four bridges in China is employed to calculate the stress variation at specific fatigue details. Furthermore, the fatigue damage accumulation at fatigue details under the UHPC and conventional asphalt concrete pavement is studied based on Miner’s linear cumulative damage rule and the rain-flow method. The results indicate that the UHPC pavement on the orthotropic steel deck can extend the service lives of the concerned regions over 100 years, but the fatigue lives will reduce significantly when the elastic modulus of UHPC decreases to 50% of the original value.

  17. Fatigue tests results of blade steels with modified surface

    Science.gov (United States)

    Kachalin, G. V.; Mednikov, A. F.; Tkhabisimov, A. B.; Lebedeva, A. I.

    2017-11-01

    The paper presents the results of metallographic studies and fatigue tests of blade steel 12kH13 and EI961samples with modified nearsurface layer. Fatigue tests and studies of the samples with the modified layer were carried out using the research equipment URI (unique research installation) “Hydroshock rig Erosion-M” of NRU “MPEI”. The surface modification is found to increase the fatigue strength of blade steel up to 50%. Sample surface after modifications features a cell structure with the characteristic cell size ranging from 1÷2 μm to 4÷8 μm total thickness of the modified layer for steel samples 12kH13 and EI961 was about 40 μm.

  18. Specimen edge effects on bending fatigue of carburized steel

    Science.gov (United States)

    Cohen, R. E.; Matlock, D. K.; Krauss, G.

    1992-10-01

    The effects of specimen geometry on the fatigue behavior of SAE 4320 steel carburized at 927 °C were evaluated with two sets of cantilever bend specimens, one set machined with square edges and one set machined with round edges. The specimens with square edges exhibited a 13% lower fatigue limit. In comparison to the rounded samples, the lower fatigue limit in the square-edged samples was attributed to the presence of a higher volume fraction of retained austenite in the sample corners and a lower surface residual compressive stress. As a result of the differences in residual stress, preferential crack initiation sites existed in the square-edged samples at a location approximately 200 to 900 ώm from the square edge. The implications of this study on laboratory analyses of the bending fatigue performance of carburized gear steels are discussed.

  19. Balance Fatigue Design of Cast Steel Nodes in Tubular Steel Structures

    Directory of Open Access Journals (Sweden)

    Libin Wang

    2013-01-01

    Full Text Available Cast steel nodes are being increasingly popular in steel structure joint application as their advanced mechanical performances and flexible forms. This kind of joints improves the structural antifatigue capability observably and is expected to be widely used in the structures with fatigue loadings. Cast steel node joint consists of two parts: casting itself and the welds between the node and the steel member. The fatigue resistances of these two parts are very different; the experiment results showed very clearly that the fatigue behavior was governed by the welds in all tested configurations. This paper focuses on the balance fatigue design of these two parts in a cast steel node joint using fracture mechanics and FEM. The defects in castings are simulated by cracks conservatively. The final crack size is decided by the minimum of 90% of the wall thickness and the value deduced by fracture toughness. The allowable initial crack size could be obtained through the integral of Paris equation when the crack propagation life is considered equal to the weld fatigue life; therefore, the two parts in a cast steel node joint will have a balance fatigue life.

  20. Review of environmental effects on fatigue crack growth of austenitic stainless steels.

    Energy Technology Data Exchange (ETDEWEB)

    Shack, W. J.; Kassner, T. F.; Energy Technology

    1994-07-11

    Fatigue and environmentally assisted cracking of piping, pressure vessel cladding, and core components in light water reactors are potential concerns to the nuclear industry and regulatory agencies. The degradation processes include intergranular stress corrosion cracking of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or stress corrosion cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Crack growth data for wrought and cast austenitic SSs in simulated BWR water, developed at Argonne National Laboratory under US Nuclear Regulatory Commission sponsorship over the past 10 years, have been compiled into a data base along with similar data obtained from the open literature. The data were analyzed to develop corrosion-fatigue curves for austenitic SSs in aqueous environments corresponding to normal BWR water chemistries, for BWRs that add hydrogen to the feedwater, and for pressurized water reactor primary-system-coolant chemistry. The corrosion-fatigue data and curves in water were compared with the air line in Section XI of the ASME Code.

  1. Thermomechanical fatigue and damage mechanisms in Sanicro 25 steel

    Czech Academy of Sciences Publication Activity Database

    Petráš, Roman; Škorík, Viktor; Polák, Jaroslav

    2016-01-01

    Roč. 650, JAN (2016), s. 52-62 ISSN 0921-5093 R&D Projects: GA MŠk(CZ) EE2.3.30.0063; GA ČR(CZ) GA13-23652S Institutional support: RVO:68081723 Keywords : thermomechanical fatigue * Sanicro 25 steel * damage mechanism * FIB cutting * localized oxidation-cracking Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 3.094, year: 2016

  2. Threshold Corrosion Fatigue of Welded Shipbuilding Steels.

    Science.gov (United States)

    1992-01-01

    8. J. C. Walter, E. Olbjorn, 0. Allstad and G. Elde, "Safety Against Corrosion Fatigue Offshore," Publication No. 94, Det Norske Ventas , Horik...Offshore. Publication No;. 94;, Det Norske Ventas , Horik, Norway, April 1976. 18. C. E. Jaske, D. Broek, J. E. Slater, W. E. Anderson. Corrosion Fatigue

  3. Crack initiation in smooth fatigue specimens of austenitic stainless steel in light water reactor environments.

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-04-08

    The fatigue design curves for structural materials specified in Section III of the ASME Boiler and Pressure Vessel Code are based on tests of smooth polished specimens at room temperature in air. The effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves; however, recent test data illustrate the detrimental effects of LWR coolant environments on the fatigue resistance of austenitic stainless steels (SSs). Certain loading and environmental conditions have led to test specimen fatigue lives that are significantly shorter than those obtained in air. Results of fatigue tests that examine the influence of reactor environments on crack initiation and crack growth of austenitic SSs are presented. Block loading was used to mark the fracture surface to determine crack length as a function of fatigue cycles in water environments, Crack lengths were measured by scanning electron microscopy. The mechanism for decreased fatigue life in LWR environments is discussed, and crack growth rates in the smooth fatigue specimens are compared with existing data from studies of crack growth rates.

  4. 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.

  5. Static and Fatigue Behavior Investigation of Artificial Notched Steel Reinforcement.

    Science.gov (United States)

    Ma, Yafei; Wang, Qiang; Guo, Zhongzhao; Wang, Guodong; Wang, Lei; Zhang, Jianren

    2017-05-14

    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.

  6. The Vibration Based Fatigue Damage Assessment of Steel and Steel Fiber Reinforced Concrete (SFRC Composite Girder

    Directory of Open Access Journals (Sweden)

    Xu Chen

    2015-01-01

    Full Text Available The steel-concrete composite girder has been usually applied in the bridge and building structures, mostly consisting of concrete slab, steel girder, and shear connector. The current fatigue damage assessment for the composite girder is largely based on the strain values and concrete crack features, which is time consuming and not stable. Hence the vibration-based fatigue damage assessment has been considered in this study. In detail, a steel-steel fiber reinforced concrete (SFRC composite girder was tested. The steel fiber reinforced concrete is usually considered for dealing with the concrete cracks in engineering practice. The composite girder was 3.3m long and 0.45m high. The fatigue load and impact excitation were applied on the specimen sequentially. According to the test results, the concrete crack development and global stiffness degradation during the fatigue test were relatively slow due to the favourable performance of SFRC in tension. But on the other hand, the vibration features varied significantly during the fatigue damage development. Generally, it confirmed the feasibility of executing fatigue damage assessment of composite bridge based on vibration method.

  7. ESTIMATION OF IRREVERSIBLE DAMAGEABILITY AT FATIGUE OF CARBON STEEL

    Directory of Open Access Journals (Sweden)

    I. O. Vakulenko

    2014-04-01

    Full Text Available Purpose. Damageability estimation of carbon steel in the conditions of cyclic loading. Methodology. The steel fragments of railway wheel rim and rail head served as material for research with chemical composition 0.65 % С, 0.67 % Mn, 0.3 % Si, 0.027 % P, 0.028 % S и 0.7 % C, 0.82 % Mn, 0.56 % Si, 0.025 % P, 0.029 % S accordingly. The microstructure of tested steels corresponded to the state of metal after a hot plastic deformation. The fatigue research was conducted in the conditions of symmetric bend using the proof-of-concept machine of type «Saturn-10». Full Wohler diagrams and the lines corresponding to forming of sub-and micro cracks were constructed. The distribution analysis of internal stresses in the metal under cyclic loading was carried out using the microhardness tester of PMT-3 type.Findings. On the basis of fatigue curves for high-carbon steels analysis the positions of borders dividing the areas of convertible and irreversible damages were determined. The article shows that with the growth of carbon concentration in the steel at invariability of the structural state an increase of fatigue limit is observed. At the same time the acceleration of processes, which determine transition terms from the stage of forming of submicrocracks to the microcracks occurs. The research of microhardness distribution in the metal after destruction confirmed the nature of carbon amount influence on the carbon steel characteristics. Originality. Regardless on the stages of breakdown site forming the carbon steels behavior at a fatigue is determined by the ration between the processes of strengthening and softening. At a cyclic loading the heterogeneity of internal stresses distribution decreases with the increase of distance from the destruction surface. Analysis of metal internal restructuring processes at fatigue loading made it possible to determine that at the stages prior to incubation period in the metal microvolumes the cells are already

  8. 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.

  9. Low Temperature Irradiation Embrittlement of Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-08-01

    The embrittlement trend curve development project for HFIR reactor pressure vessel (RPV) steels was carried out with three major tasks. Which are (1) data collection to match that used in HFIR steel embrittlement trend published in 1994 Journal Nuclear Material by Remec et. al, (2) new embrittlement data of A212B steel that are not included in earlier HFIR RPV trend curve, and (3) the adjustment of nil-ductility-transition temperature (NDTT) shift data with the consideration of the irradiation temperature effect. An updated HFIR RPV steel embrittlement trend curve was developed, as described below. NDTT( C) = 23.85 log(x) + 203.3 log (x) + 434.7, with 2- uncertainty of 34.6 C, where parameter x is referred to total dpa. The developed update HFIR RPV embrittlement trend curve has higher embrittlement rate compared to that of the trend curve developed in 1994.

  10. Microstructure influence on fatigue behaviour of austenitic stainless steels with high molybdenum content; Influencia de la microestructura en el comportamiento a fatiga de aceros inoxidables austeniticos con alto contenido en molibdeno

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J.; Gamboa, R.; Ranninger, C.

    2006-07-01

    Austenitic stainless steels with molybdenum present high mechanical properties and corrosion resistance to aggressive environments. These steels have been used to tank and vessel components for high liquids as phosphoric, nitric and sulphuric acids. These materials with low carbon and nitrogen addition have been proposed candidates as structural materials for the international thermonuclear experimental reactor (ITER) in-vessel components. Molybdenum addition in austenitic stainless steel improves mechanical and corrosion properties, but with it can produce the presence of nitrogen microstructure modifications by presence or precipitation of second phases. This paper summarises the fatigue and corrosion fatigue behaviour of two 317LN stainless steels with different microstructure. Fully austenitic steel microstructure show better fatigue, corrosion fatigue resistance and better ductility than austenitic steel with delta ferrite microstructure, mainly at low stresses. (Author)

  11. Biaxial fatigue behavior of a powder metallurgical TRIP steel

    Directory of Open Access Journals (Sweden)

    S. Ackermann

    2015-10-01

    Full Text Available Multiaxial fatigue behavior is an important topic in critical structural components. In the present study the biaxial-planar fatigue behavior of a powder metallurgical TRIP steel (Transformation Induced Plasticity was studied by taking into account martensitic phase transformation and crack growth behavior. Biaxial cyclic deformation tests were carried out on a servo hydraulic biaxial tension-compression test rig using cruciform specimens. Different states of strain were studied by varying the strain ratio between the axial strain amplitudes in the range of -1 (shear loading to 1 (equibiaxial loading. The investigated loading conditions were proportional due to fixed directions of principal strains. The studied TRIP steel exhibits martensitic phase transformation from -austenite via ε-martensite into α‘- martensite which causes pronounced cyclic hardening. The α‘-martensite formation increased with increasing plastic strain amplitude. Shear loading promoted martensite formation and caused the highest α‘-martensite volume fractions at fatigue failure in comparison to uniaxial and other biaxial states of strain. Moreover, the fatigue lives of shear tests were higher than those of uniaxial and other biaxial tests. The von Mises equivalent strain hypothesis was found to be appropriate for uniaxial and biaxial fatigue, but too conservative for shear fatigue, according to literature for torsional fatigue. The COD strain amplitude which is based on crack opening displacement gave a better correlation of the investigated fatigue lives, especially those for shear loading. Different types of major cracks were observed on the sample surfaces after biaxial cyclic deformation by using electron monitoring in an electron beam universal system and scanning electron microscopy (SEM. Specimens with strain ratios of 1, 0.5, -0.1 and -0.5 showed mode I major cracks (perpendicular to the axis of maximum principal strain. Major cracks after shear fatigue

  12. Fatigue behavior of welded austenitic stainless steel in different environments

    Directory of Open Access Journals (Sweden)

    D.S. Yawas

    2014-01-01

    Full Text Available The fatigue behavior of welded austenitic stainless steel in 0.5 M hydrochloric acid and wet steam corrosive media has been investigated. The immersion time in the corrosive media was 30 days to simulate the effect on stainless steel structures/equipment in offshore and food processing applications and thereafter annealing heat treatment was carried out on the samples. The findings from the fatigue tests show that seawater specimens have a lower fatigue stress of 0.5 × 10−5 N/mm2 for the heat treated sample and 0.1 × 10−5 N/mm2 for the unheat-treated sample compared to the corresponding hydrochloric acid and steam samples. The post-welding heat treatment was found to increase the mechanical properties of the austenitic stainless steel especially tensile strength but it reduces the transformation and thermal stresses of the samples. These findings were further corroborated by the microstructural examination of the stainless steel specimen.

  13. Fretting fatigue in AISI 1015 steel

    Indian Academy of Sciences (India)

    A small osillatory movement between two contacting surfaces is termed as fretting and on many occasions it acts as the crack initiation site leading to catastrophic failure of the overall structure. The occurrence of fretting is observed in many engineering structures such as shaft flanges, gas turbines, steel ropes etc.

  14. Interfacial fatigue stress in PVD TiN coated tool steels under rolling contact fatigue conditions

    NARCIS (Netherlands)

    Carvalho, N.J.M.; Huis in ’t Veld, A.J.; Hosson, J.Th. De

    1998-01-01

    Titanium–nitrogen (TiN) films were Physical Vapour Deposited (PVD) on tool steel substrates with different hardness and surface roughness, in a Bai 640R unit using a triode ion plating (e-gun) with a high plasma density. The coated substrates were submitted to a rolling contact fatigue test

  15. Interfacial fatigue stress in PVD TiN coated tool steels under rolling contact fatigue conditions

    NARCIS (Netherlands)

    Carvalho, N.J.M.; Huis in 't Veld, A.J.; Hosson, J.T. de

    1998-01-01

    Titanium-nitrogen (TiN) films were Physical Vapour Deposited (PVD) on tool steel substrates with different hardness and surface roughness, in a Bai 640R unit using a triode ion plating (e-gun) with a high plasma density. The coated substrates were submitted to a rolling contact fatigue test

  16. Progress in the Research of Fatigue of Weathering Steel after Corrosion

    Science.gov (United States)

    Jianyu, Liang; Jian, Yao; Youwu, Xu

    2017-12-01

    Weathering steel has a good corrosion resistance in the atmosphere, and the application of weathering steel in civil structure also reduces the cost of painting and maintenance. It is also possible for the bare weathering steel to bear the fatigue load with a rust layer. This paper summarizes the fatigue researches after corrosion of weathering steel, including the shape of specimens, failure modes of fatigue and the conclusions obtained through experimental investigations. It is also introduced the fatigue model of weathering steel after corrosion, which can be useful for the engineering application or further researches.

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

    Directory of Open Access Journals (Sweden)

    X. W. Ye

    2014-01-01

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

  18. Fatigue Strength and Crack Initiation Mechanism of Very-High-Cycle Fatigue for Low Alloy Steels

    Science.gov (United States)

    Hong, Youshi; Zhao, Aiguo; Qian, Guian; Zhou, Chengen

    2012-08-01

    The fatigue strength and crack initiation mechanisms of very-high-cycle fatigue (VHCF) for two low alloy steels were investigated. Rotary bending tests at 52.5 Hz with hour-glass type specimens were carried out to obtain the fatigue propensity of the test steels, for which the failure occurred up to the VHCF regime of 108 cycles with the S-N curves of stepwise tendency. Fractography observations show that the crack initiation of VHCF is at subsurface inclusion with "fish-eye" pattern. The fish-eye is of equiaxed shape and tends to tangent the specimen surface. The size of the fish-eye becomes large with the increasing depth of related inclusion from the surface. The fish-eye crack grows faster outward to the specimen surface than inward. The values of the stress intensity factor ( K I ) at different regions of fracture surface were calculated, indicating that the K I value of fish-eye crack is close to the value of relevant fatigue threshold (Δ K th ). A new parameter was proposed to interpret the competition mechanism of fatigue crack initiation at the specimen surface or at the subsurface. The simulation results indicate that large inclusion size, small grain size, and high strength of material will promote fatigue crack initiation at the specimen subsurface, which are in agreement with experimental observations.

  19. Behavior of Steel Branch Connections during Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Sládek A.

    2017-09-01

    Full Text Available Fatigue behavior of the branch connection made of low-alloyed steel with yield stress of 355 MPa during low-cycle bending test is investigated in the article. Numerical prediction of the stress and strain distribution are described and experimentally verified by fatigue test of the branch connection sample. Experimental verification is based on low-cycle bending testing of the steel pipes welded by manual metal arc process and loaded by external force in the appropriate distance. Stresses and displacement of the samples induced by bending moment were measured by unidirectional strain gauges and displacement transducers. Samples were loaded in different testing levels according to required stress for 2.106 cycles. Increase of the stress value was applied until the crack formation and growth was observed. Results showed a high agreement of numerical and experimental results of stress and displacement.

  20. Continuous Cooling Transformations in Nuclear Pressure Vessel Steels

    Science.gov (United States)

    Pous-Romero, Hector; Bhadeshia, Harry K. D. H.

    2014-10-01

    A class of low-alloy steels often referred to as SA508 represent key materials for the manufacture of nuclear reactor pressure vessels. The alloys have good properties, but the scatter in properties is of prime interest in safe design. Such scatter can arise from microstructural variations but most studies conclude that large components made from such steels are, following heat treatment, fully bainitic. In the present work, we demonstrate with the help of a variety of experimental techniques that the microstructures of three SA508 Gr.3 alloys are far from homogeneous when considered in the context of the cooling rates encountered in practice. In particular, allotriomorphic ferrite that is expected to lead to a deterioration in toughness, is found in the microstructure for realistic combinations of austenite grain size and the cooling rate combination. Parameters are established to identify the domains in which SA508 Gr.3 steels transform only into the fine bainitic microstructures.

  1. Detection of localized fatigue damage in steel by thermography

    Science.gov (United States)

    Medgenberg, Justus; Ummenhofer, Thomas

    2007-04-01

    Fatigue damage of unalloyed steels in the high cycle regime is governed by localized cyclic plastic deformations and subsequent crack initiation. The extent of early microplastic deformations depends on the applied stress level, stress concentration at macroscopic notches, surface treatment, residual stresses etc. The onset of a nonlinear material response can be regarded as an early indicator of fatigue damage. During fatigue loading thermoelastic coupling and thermoplastic dissipation cause characteristic temperature variations in tested specimens which have been assessed by a highly sensitive infrared camera. A specialized data processing method in the time domain has been developed which allows to separate the different contributions to the measured temperature signal. In contrast to other methods - as e.g. measuring the rise of mean temperature during fatigue loading - the proposed methodology is based on measurements during the stabilized temperature regimen and offers very high spatial resolution of localized phenomena. Investigations have been made on mildly notched cylindrical and also on welded specimens. The results confirm the close relation between the local temperature signal and typical fatigue phenomena. The new methodology allows for a much better localization and quantification of effects as cyclic plasticity, crack initiation, crack growth etc. The following paper presents considerations and experimental results of an application of thermography to the local assessment of fatigue damage.

  2. Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.P.; Ritter, S

    2002-02-01

    The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

  3. Localized bending fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2012-01-01

    of the strain distribution in the strand and helps in identifying potential failure mechanisms along the strand and at the wedge location. Initial analysis of the deformations shows that the bending fatigue behavior of the monostrand may be controlled either by local bending deformations or by relative......In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement...... displacement (opening/closing and sliding) of the helically wound wires. Moreover, the results are a step towards understanding the bending fatigue damage mechanisms of monostrand cables....

  4. Creep, fatigue and creep-fatigue interactions in modified 9% Chromium - 1% Molybdenum (P91) steels

    Science.gov (United States)

    Kalyanasundaram, Valliappa

    Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components' life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices. It is also imperative to develop analytical constitutive models that can simulate and predict material response under various long-term in-service conditions using experimental data from short-term laboratory experiments. Consequently, the major objectives of the proposed research are to characterize the creep, fatigue and C-F behavior of grade P91 steels at 625 C and develop robust constitutive models for simulating/predicting their microstructural response under different loading conditions. This work will utilize experimental data from 16 laboratories worldwide that conducted tests (creep, fatigue and C-F) on grade P91 steel at 625°C in a round-robin (RR) program. Along with 7 creep deformation and rupture tests, 32 pure fatigue and 46 C-F tests from the RR are considered in this work. A phenomenological constitutive model formulated in this work needs just five fitting parameters to simulate/predict the monotonic, pure fatigue and C-F behavior of grade P91 at 625 C. A modified version of an existing constitutive model is also presented for particularly simulating its isothermal creep deformation and rupture behavior. Experimental results indicate that specimen C-F lives, as measured by the 2% load drop criterion, seem to decrease with increasing strain ranges and increasing hold times at 625°C. Metallographic assessment of the tested specimens shows that the damage mode in both pure fatigue and 600 seconds hold time cyclic tests is predominantly transgranular fatigue with some presence of

  5. Creep-fatigue modelling in structural steels using empirical and constitutive creep methods implemented in a strip-yield model

    Science.gov (United States)

    Andrews, Benjamin J.

    The phenomena of creep and fatigue have each been thoroughly studied. More recently, attempts have been made to predict the damage evolution in engineering materials due to combined creep and fatigue loading, but these formulations have been strictly empirical and have not been used successfully outside of a narrow set of conditions. This work proposes a new creep-fatigue crack growth model based on constitutive creep equations (adjusted to experimental data) and Paris law fatigue crack growth. Predictions from this model are compared to experimental data in two steels: modified 9Cr-1Mo steel and AISI 316L stainless steel. Modified 9Cr-1Mo steel is a high-strength steel used in the construction of pressure vessels and piping for nuclear and conventional power plants, especially for high temperature applications. Creep-fatigue and pure creep experimental data from the literature are compared to model predictions, and they show good agreement. Material constants for the constitutive creep model are obtained for AISI 316L stainless steel, an alloy steel widely used for temperature and corrosion resistance for such components as exhaust manifolds, furnace parts, heat exchangers and jet engine parts. Model predictions are compared to pure creep experimental data, with satisfactory results. Assumptions and constraints inherent in the implementation of the present model are examined. They include: spatial discretization, similitude, plane stress constraint and linear elasticity. It is shown that the implementation of the present model had a non-trivial impact on the model solutions in 316L stainless steel, especially the spatial discretization. Based on these studies, the following conclusions are drawn: 1. The constitutive creep model consistently performs better than the Nikbin, Smith and Webster (NSW) model for predicting creep and creep-fatigue crack extension. 2. Given a database of uniaxial creep test data, a constitutive material model such as the one developed for

  6. A Review on Strengthening Steel Beams Using FRP under Fatigue

    Directory of Open Access Journals (Sweden)

    Mohamed Kamruzzaman

    2014-01-01

    Full Text Available In recent decades, the application of fibre-reinforced polymer (FRP composites for strengthening structural elements has become an efficient option to meet the increased cyclic loads or repair due to corrosion or fatigue cracking. Hence, the objective of this study is to explore the existing FRP reinforcing techniques to care for fatigue damaged structural steel elements. This study covers the surface treatment techniques, adhesive curing, and support conditions under cyclic loading including fatigue performance, crack propagation, and failure modes with finite element (FE simulation of the steel bridge girders and structural elements. FRP strengthening composites delay initial cracking, reduce the crack growth rate, extend the fatigue life, and decrease the stiffness decay with residual deflection. Prestressed carbon fibre-reinforced polymer (CFRP is the best strengthening option. End anchorage prevents debonding of the CRRP strips at the beam ends by reducing the local interfacial shear and peel stresses. Hybrid-joint, nanoadhesive, and carbon-flex can also be attractive for strengthening systems.

  7. A Review on Strengthening Steel Beams Using FRP under Fatigue

    Science.gov (United States)

    Jumaat, Mohd Zamin; Ramli Sulong, N. H.

    2014-01-01

    In recent decades, the application of fibre-reinforced polymer (FRP) composites for strengthening structural elements has become an efficient option to meet the increased cyclic loads or repair due to corrosion or fatigue cracking. Hence, the objective of this study is to explore the existing FRP reinforcing techniques to care for fatigue damaged structural steel elements. This study covers the surface treatment techniques, adhesive curing, and support conditions under cyclic loading including fatigue performance, crack propagation, and failure modes with finite element (FE) simulation of the steel bridge girders and structural elements. FRP strengthening composites delay initial cracking, reduce the crack growth rate, extend the fatigue life, and decrease the stiffness decay with residual deflection. Prestressed carbon fibre-reinforced polymer (CFRP) is the best strengthening option. End anchorage prevents debonding of the CRRP strips at the beam ends by reducing the local interfacial shear and peel stresses. Hybrid-joint, nanoadhesive, and carbon-flex can also be attractive for strengthening systems. PMID:25243221

  8. A review on strengthening steel beams using FRP under fatigue.

    Science.gov (United States)

    Kamruzzaman, Mohamed; Jumaat, Mohd Zamin; Sulong, N H Ramli; Islam, A B M Saiful

    2014-01-01

    In recent decades, the application of fibre-reinforced polymer (FRP) composites for strengthening structural elements has become an efficient option to meet the increased cyclic loads or repair due to corrosion or fatigue cracking. Hence, the objective of this study is to explore the existing FRP reinforcing techniques to care for fatigue damaged structural steel elements. This study covers the surface treatment techniques, adhesive curing, and support conditions under cyclic loading including fatigue performance, crack propagation, and failure modes with finite element (FE) simulation of the steel bridge girders and structural elements. FRP strengthening composites delay initial cracking, reduce the crack growth rate, extend the fatigue life, and decrease the stiffness decay with residual deflection. Prestressed carbon fibre-reinforced polymer (CFRP) is the best strengthening option. End anchorage prevents debonding of the CRRP strips at the beam ends by reducing the local interfacial shear and peel stresses. Hybrid-joint, nanoadhesive, and carbon-flex can also be attractive for strengthening systems.

  9. Creep of A508/533 Pressure Vessel Steel

    Energy Technology Data Exchange (ETDEWEB)

    Richard Wright

    2014-08-01

    ABSTRACT Evaluation of potential Reactor Pressure Vessel (RPV) steels has been carried out as part of the pre-conceptual Very High Temperature Reactor (VHTR) design studies. These design studies have generally focused on American Society of Mechanical Engineers (ASME) Code status of the steels, temperature limits, and allowable stresses. Initially, three candidate materials were identified by this process: conventional light water reactor (LWR) RPV steels A508 and A533, 2¼Cr-1Mo in the annealed condition, and Grade 91 steel. The low strength of 2¼Cr-1Mo at elevated temperature has eliminated this steel from serious consideration as the VHTR RPV candidate material. Discussions with the very few vendors that can potentially produce large forgings for nuclear pressure vessels indicate a strong preference for conventional LWR steels. This preference is based in part on extensive experience with forging these steels for nuclear components. It is also based on the inability to cast large ingots of the Grade 91 steel due to segregation during ingot solidification, thus restricting the possible mass of forging components and increasing the amount of welding required for completion of the RPV. Grade 91 steel is also prone to weld cracking and must be post-weld heat treated to ensure adequate high-temperature strength. There are also questions about the ability to produce, and very importantly, verify the through thickness properties of thick sections of Grade 91 material. The availability of large components, ease of fabrication, and nuclear service experience with the A508 and A533 steels strongly favor their use in the RPV for the VHTR. Lowering the gas outlet temperature for the VHTR to 750°C from 950 to 1000°C, proposed in early concept studies, further strengthens the justification for this material selection. This steel is allowed in the ASME Boiler and Pressure Vessel Code for nuclear service up to 371°C (700°F); certain excursions above that temperature are

  10. Quantitative acoustic emission monitoring of fatigue cracks in fracture critical steel bridges.

    Science.gov (United States)

    2014-01-01

    The objective of this research is to evaluate the feasibility to employ quantitative acoustic : emission (AE) techniques for monitoring of fatigue crack initiation and propagation in steel : bridge members. Three A36 compact tension steel specimens w...

  11. Effects of LWR coolant environments on fatigue S-N curves for carbon and low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-06-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figure I-90 of Appendix I to Section III of the Code specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Recent test data indicate significant decreases in fatigue lives of carbon and low-alloy steels in LWR environments when five conditions are satisfied simultaneously: applied strain range, temperature, dissolved oxygen in the water, and S content of the steel are above minimum threshold levels, and loading strain rate is below a threshold value. Only moderate decrease in fatigue life is observed when any one of these conditions is not satisfied. This paper presents several methods that have been proposed for evaluating the effects of LWR coolant environments on fatigue S-N curves for carbon and low-alloy steels. Estimations of fatigue lives under actual loading histories are discussed.

  12. Steel Containment Vessel Model Test: Results and Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Costello, J.F.; Hashimote, T.; Hessheimer, M.F.; Luk, V.K.

    1999-03-01

    A high pressure test of the steel containment vessel (SCV) model was conducted on December 11-12, 1996 at Sandia National Laboratories, Albuquerque, NM, USA. The test model is a mixed-scaled model (1:10 in geometry and 1:4 in shell thickness) of an improved Mark II boiling water reactor (BWR) containment. A concentric steel contact structure (CS), installed over the SCV model and separated at a nominally uniform distance from it, provided a simplified representation of a reactor shield building in the actual plant. The SCV model and contact structure were instrumented with strain gages and displacement transducers to record the deformation behavior of the SCV model during the high pressure test. This paper summarizes the conduct and the results of the high pressure test and discusses the posttest metallurgical evaluation results on specimens removed from the SCV model.

  13. Preliminary results of steel containment vessel model test

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, T.; Komine, K.; Arai, S. [Nuclear Power Engineering Corp., Tokyo (Japan)] [and others

    1997-04-01

    A high pressure test of a mixed-scaled model (1:10 in geometry and 1:4 in shell thickness) of a steel containment vessel (SCV), representing an improved boiling water reactor (BWR) Mark II containment, was conducted on December 11-12, 1996 at Sandia National Laboratories. This paper describes the preliminary results of the high pressure test. In addition, the preliminary post-test measurement data and the preliminary comparison of test data with pretest analysis predictions are also presented.

  14. Preliminary results of steel containment vessel model test

    Energy Technology Data Exchange (ETDEWEB)

    Luk, V.K.; Hessheimer, M.F. [Sandia National Labs., Albuquerque, NM (United States); Matsumoto, T.; Komine, K.; Arai, S. [Nuclear Power Engineering Corp., Tokyo (Japan); Costello, J.F. [Nuclear Regulatory Commission, Washington, DC (United States)

    1998-04-01

    A high pressure test of a mixed-scaled model (1:10 in geometry and 1:4 in shell thickness) of a steel containment vessel (SCV), representing an improved boiling water reactor (BWR) Mark II containment, was conducted on December 11--12, 1996 at Sandia National Laboratories. This paper describes the preliminary results of the high pressure test. In addition, the preliminary post-test measurement data and the preliminary comparison of test data with pretest analysis predictions are also presented.

  15. Fatigue in Welded High-Strength Steel Plate Elements under Stochastic Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1999-01-01

    The present project is a part of an investigation on fatigue in offshore structures in high-strength steel. The fatigue life of plate elements with welded attachments is studied. The material used has a yield stress of ~ 810-840 MPa, and high weldability and toughness properties. Fatigue test...... series with constant amplitude loading and with various types of stochastic loading have been carried through on test specimens in high-strength steel, and - for a comparison - on test specimens in conventional offshore structural steel with a yield stress of ~ 400-410 MPa.A comparison between constant...... amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those...

  16. Manufacturing Cost Analysis of Novel Steel/Concrete Composite Vessel for Stationary Storage of High-Pressure Hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhili [ORNL; Zhang, Wei [ORNL; Wang, Jy-An John [ORNL; Ren, Fei [ORNL

    2012-09-01

    A novel, low-cost, high-pressure, steel/concrete composite vessel (SCCV) technology for stationary storage of compressed gaseous hydrogen (CGH2) is currently under development at Oak Ridge National Laboratory (ORNL) sponsored by DOE s Fuel Cell Technologies (FCT) Program. The SCCV technology uses commodity materials including structural steels and concretes for achieving cost, durability and safety requirements. In particular, the hydrogen embrittlement of high-strength low-alloy steels, a major safety and durability issue for current industry-standard pressure vessel technology, is mitigated through the use of a unique layered steel shell structure. This report presents the cost analysis results of the novel SCCV technology. A high-fidelity cost analysis tool is developed, based on a detailed, bottom-up approach which takes into account the material and labor costs involved in each of the vessel manufacturing steps. A thorough cost study is performed to understand the SCCV cost as a function of the key vessel design parameters, including hydrogen pressure, vessel dimensions, and load-carrying ratio. The major conclusions include: The SCCV technology can meet the technical/cost targets set forth by DOE s FCT Program for FY2015 and FY2020 for all three pressure levels (i.e., 160, 430 and 860 bar) relevant to the hydrogen production and delivery infrastructure. Further vessel cost reduction can benefit from the development of advanced vessel fabrication technologies such as the highly automated friction stir welding (FSW). The ORNL-patented multi-layer, multi-pass FSW can not only reduce the amount of labor needed for assembling and welding the layered steel vessel, but also make it possible to use even higher strength steels for further cost reductions and improvement of vessel structural integrity. It is noted the cost analysis results demonstrate the significant cost advantage attainable by the SCCV technology for different pressure levels when compared to the

  17. High cycle fatigue properties of CLAM steel at 723 K and 823 K

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yanyun; Zhai, Xiangwei; Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn; Li, Chunjing; Huang, Qunying

    2015-11-15

    Highlights: • High cycle fatigue properties of CLAM steel were investigated at 723 K and 823 K. • The condition fatigue limit at N = 10{sup 7} were 275 MPa and 235 MPa at 723 K and 823 K. • Fatigue strength decreased when stress and temperature increased at 723 K and 823 K. • Dislocation density decrease and subgrain coarsening during the test process were the possible reasons for fatigue limit decrease. - Abstract: This paper highlights the results of a study on the high cycle fatigue strength and fracture mechanism of China Low Activation Martensitic (CLAM) steel. The high cycle fatigue test results showed that the fatigue strength of CLAM steel decreased with the temperature, and the condition fatigue strengths (N = 10{sup 7}) were 275 MPa and 235 MPa at 723 K and 823 K, respectively. The fractograph results indicated that the fractures were mainly initiated from the surface of the specimen.

  18. Fatigue behaviors and damage mechanism of a Cr-Mn-N austenitic steel

    DEFF Research Database (Denmark)

    Lv, Z.; Cai, P.; Yu, Tianbo

    2017-01-01

    Four-point bending fatigue tests were conducted on a Cr-Mn-N austenitic steel at room temperature, at frequency of 20 Hz and the stress ratio of R = 0.1, in air. The fatigue strength of this Cr-Mn-N austenitic steel was measured to be 503 MPa in the maximum stress from the S-N curve obtained...

  19. Structural health monitoring in end-of-life prediction for steel bridges subjected to fatigue cracking

    NARCIS (Netherlands)

    Attema, T.; Courage, W.M.G.; Maljaars, J.; Meerveld, H. van; Paulissen, J.H.; Pijpers, R.J.M.; Slobbe, A.T.

    2015-01-01

    This paper presents a monitoring and modelling methodology to assess the current and future conditions of steel bridges subjected to fatigue cracking. Steel bridges are subjected to fatigue cracking as a result of fluctuating stresses caused by the crossing of heavy vehicles. Specifically for

  20. Estimation of early fatigue damage in heat treated En-8 grade steel

    Science.gov (United States)

    Talukdar, P.; Sen, S. K.; Ghosh, A. K.

    1998-08-01

    Generally, the failure of major machinery parts is due to fatigue damage. Because of the structural inhomogeneity of metals, fatigue damage may sometimes occur significantly below the yield strength of the material due to microplastic deformation at low stress levels. Commercial En-8 grade steel (widely used for making secondary metalworking products) was used to estimate the fatigue damage response during cyclic loading nearer to the fatigue endurance limit. Estimation of fatigue damage was carried out with the aid of a nondestructive testing (NDT) method, that is, Elastosonic measurement of fatigue damping coefficient and slope of fatigue damping curves. Results indicate that fatigue damage increases in annealed En-8 steel with an increase in peak stress and with an increase in the number of cycles. However, for hardened and tempered En-8 steel, experimental results may not provide a true indication of fatigue damage during fatigue loading nearer to the endurance limit, most likely due to the more homogeneous structure. Generally, fatigue failure occurs in this grade of steel due to microcrack generation in the cementite of the pearlite phase of annealed steel.

  1. High cycle torsional fatigue properties of 17-4PH stainless steel

    Directory of Open Access Journals (Sweden)

    K. Yanase

    2016-07-01

    Full Text Available Sensitivity to small defects under torsional fatigue loading condition is examined in the high cycle fatigue regime. Fatigue crack initiation and small crack growth behaviors were observed during fatigue testing and fractographic investigations were performed. The results are compared to the data obtained in the uniaxial fatigue tests, which allows the effect of biaxial stresses on the surface of material to be discussed. Finally, an approach for predicting the fatigue limit of 17-4PH stainless steel under torsional and tension-compression fatigue loadings is presented.

  2. Strain-rate dependent fatigue behavior of 316LN stainless steel in high-temperature water

    Science.gov (United States)

    Tan, Jibo; Wu, Xinqiang; Han, En-Hou; Ke, Wei; Wang, Xiang; Sun, Haitao

    2017-06-01

    Low cycle fatigue behavior of forged 316LN stainless steel was investigated in high-temperature water. It was found that the fatigue life of 316LN stainless steel decreased with decreasing strain rate from 0.4 to 0.004 %s-1 in 300 °C water. The stress amplitude increased with decreasing strain rate during fatigue tests, which was a typical characteristic of dynamic strain aging. The fatigue cracks mainly initiated at pits and slip bands. The interactive effect between dynamic strain aging and electrochemical factors on fatigue crack initiation is discussed.

  3. An Investigation on Fatigue in High-Strength Steel Offshore Structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Lopez Martinez, L.

    1997-01-01

    In the present investigation, the fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa, and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading....... In the experimental part of the investigation, fatigue test series have been carried through on both full-scale tubular joints and smaller welded plate test specimens, in high-strength steel as well as in conventional offshore structural steel. The present document gives a summary of the main results presented in two......, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  4. Fatigue-damage localization in steel catenary risers

    Directory of Open Access Journals (Sweden)

    Hernández Víctor F.

    2014-06-01

    Full Text Available Risers used to transport crude oil require Structural Integrity Management plans and programs to allow proper functioning during its design life. Cyclic loading may cause fatigue damage during operation of the riser. Structural Health Monitoring (SHM is usually applied to detect damages ahead, and be confirmed by non- destructive inspection using remotely operated vehicles. With the information obtained the riser is assessed and if required mitigating measures can be implemented to prevent failure and disasters such as environmental pollution, and human and economic losses. This paper presents a study to locate fatigue damages using signals of the dynamic response. Numerical study cases were defined for a Steel Catenary Riser (SCR installed in 2000 m water depth. A damage case was considered, decreasing the stiffness value at a specific location of the structure. Dynamic analyses were performed using a commercial software that incorporates nonlinear behavior. The Modal Slope Difference, Modal Slope Difference and Damage Index methods (with two variations were applied to locate damage. Based on results the MSlD yielded the smallest error values in damage location followed by the Damage Index Method for severity values greater than 6%. Results demonstrate the effectiveness of the proposed methodology to locate fatigue damages in deep-water SCRs.

  5. Steel bridge fatigue crack detection with piezoelectric wafer active sensors

    Science.gov (United States)

    Yu, Lingyu; Giurgiutiu, Victor; Ziehl, Paul; Ozevin, Didem; Pollock, Patrick

    2010-04-01

    Piezoelectric wafer active sensors (PWAS) are well known for its dual capabilities in structural health monitoring, acting as either actuators or sensors. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In our research, our use of the PWAS based sensing has the novelty of implementing both passive (as acoustic emission) and active (as ultrasonic transducers) sensing with a single PWAS network. The combined schematic is using acoustic emission to detect the presence of fatigue cracks in steel bridges in their early stage since methods such as ultrasonics are unable to quantify the initial condition of crack growth since most of the fatigue life for these details is consumed while the fatigue crack is too small to be detected. Hence, combing acoustic emission with ultrasonic active sensing will strengthen the damage detection process. The integration of passive acoustic emission detection with active sensing will be a technological leap forward from the current practice of periodic and subjective visual inspection, and bridge management based primarily on history of past performance. In this study, extensive laboratory investigation is performed supported by theoretical modeling analysis. A demonstration system will be presented to show how piezoelectric wafer active sensor is used for acoustic emission. Specimens representing complex structures are tested. The results will also be compared with traditional acoustic emission transducers to identify the application barriers.

  6. 46 CFR 42.09-30 - Additional survey requirements for steel-hull vessels.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Additional survey requirements for steel-hull vessels...-30 Additional survey requirements for steel-hull vessels. (a) In addition to the requirements in § 42..., peaks, bilges, machinery spaces, and bunkers shall be examined to determine the condition of the framing...

  7. Macrosegregation and Microstructural Evolution in a Pressure-Vessel Steel

    Science.gov (United States)

    Pickering, E. J.; Bhadeshia, H. K. D. H.

    2014-06-01

    This work assesses the consequences of macrosegregation on microstructural evolution during solid-state transformations in a continuously cooled pressure-vessel steel (SA508 Grade 3). Stark spatial variations in microstructure are observed following a simulated quench from the austenitization temperature, which are found to deliver significant variations in hardness. Partial-transformation experiments are used to show the development of microstructure in segregated material. Evidence is presented which indicates the bulk microstructure is not one of upper bainite, as it has been described in the past, but one comprised of Widmanstätten ferrite and pockets of lower bainite. Segregation is observed on three different length scales, and the origins of each type are proposed. Suggestions are put forward for how the segregation might be minimized, and its detrimental effects suppressed by heat treatments.

  8. Interfacial fatigue stress in PVD TiN coated tool steels under rolling contact fatigue conditions

    OpenAIRE

    Carvalho, N.J.M.; Huis in ’t Veld, A.J.; Hosson, J.Th. De

    1998-01-01

    Titanium–nitrogen (TiN) films were Physical Vapour Deposited (PVD) on tool steel substrates with different hardness and surface roughness, in a Bai 640R unit using a triode ion plating (e-gun) with a high plasma density. The coated substrates were submitted to a rolling contact fatigue test technique (modified pin-on-ring test) to obtain some clarifications of the mechanism of interfacial failure. Tests were run using PVD-coated rings finished by polishing or grinding to produce different sur...

  9. Fatigue performance and cyclic softening of F82H, a ferritic martensic steel

    Energy Technology Data Exchange (ETDEWEB)

    Stubbins, J.F. [Univ. of Illinois, Urbana, IL (United States); Gelles, D.S. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1996-04-01

    The room temperature fatigue performance of F82H has been examined. The fatigue life was determined in a series of strain-controlled tests where the stress level was monitored as a function of the number of accrued cycles. Fatigue lives in the range of 10{sup 3} to 10{sup 6} cycles to failure were examined. The fatigue performance was found to be controlled primarily by the elastic strain range over most of the range of fatigue lives examined. Only at low fatigue lives did the plastic strain range contribute to the response. However, when the significant plastic strain did contribute, the material showed a tendency to cyclically soften. That is the load carrying capability of the material degrades with accumulated fatigue cycles. The overall fatigue performance of the F82H alloy was found to be similiar to other advanced martensitic steels, but lower than more common low alloy steels which possess lower yield strengths.

  10. Fatigue Damage Monitoring in 304L Steel Specimens by an Acoustic Emission Method

    Directory of Open Access Journals (Sweden)

    Ould-Amer Ammar

    2014-06-01

    Full Text Available The aim of this work was to clarify fatigue crack initiation and propagation mechanisms in 304L austenitic stainless steel under different total-strain-amplitudes. A complete process from crack initiation and propagation was recorded by using the acoustic emission method in one hand, and replica method in another hand. The effect of strain amplitude on fatigue crack growth was investigated and a new representation of various fatigue curves associated to various levels of fatigue damage is proposed.

  11. A Constitutive Relationship between Fatigue Limit and Microstructure in Nanostructured Bainitic Steels

    Directory of Open Access Journals (Sweden)

    Inga Mueller

    2016-10-01

    Full Text Available The recently developed nanobainitic steels show high strength as well as high ductility. Although this combination seems to be promising for fatigue design, fatigue properties of nanostructured bainitic steels are often surprisingly low. To improve the fatigue behavior, an understanding of the correlation between the nanobainitic microstructure and the fatigue limit is fundamental. Therefore, our hypothesis to predict the fatigue limit was that the main function of the microstructure is not necessarily totally avoiding the initiation of a fatigue crack, but the microstructure has to increase the ability to decelerate or to stop a growing fatigue crack. Thus, the key to understanding the fatigue behavior of nanostructured bainite is to understand the role of the microstructural features that could act as barriers for growing fatigue cracks. To prove this hypothesis, we carried out fatigue tests, crack growth experiments, and correlated these results to the size of microstructural features gained from microstructural analysis by light optical microscope and EBSD-measurements. Finally, we were able to identify microstructural features that influence the fatigue crack growth and the fatigue limit of nanostructured bainitic steels.

  12. An investigation on fatigue in high-strength steel offshore structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1998-01-01

    The fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading. In the experimental part...... of the investigation, fatigue test series were carried out on both full scale tubular joints and smaller welded plate test specimens in high-strength steel as well as in conventional offshore structural steel. This paper gives a summary of the main results presented in two recent research reports [15, 16], from...... specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  13. Effect of Silicon Content on Carbide Precipitation and Low-Temperature Toughness of Pressure Vessel Steels

    Science.gov (United States)

    Ruan, L. H.; Wu, K. M.; Qiu, J. A.; Shirzadi, A. A.; Rodionova, I. G.

    2017-05-01

    Cr - Mn - Mo - Ni pressure vessel steels containing 0.54 and 1.55% Si are studied. Metallographic and fractographic analyses of the steels after tempering at 650 and 700°C are performed. The impact toughness at - 30°C and the hardness of the steels are determined. The mass fraction of the carbide phase in the steels is computed with the help of the J-MatPro 4.0 software.

  14. Effect of Fe ion concentration on fatigue life of carbon steel in aqueous CO2 environment

    DEFF Research Database (Denmark)

    Rogowska, Magdalena; Gudme, J.; Rubin, A.

    2016-01-01

    In this work, the corrosion fatigue behaviour of steel armours used in the flexible pipes, in aqueous solutions initially containing different concentrations of Fe2+, was investigated by four-point bending testing under saturated 1 bar CO2 condition. Corrosion fatigue results were supported with ......, fatigue samples experienced the same corrosion rate as samples that were not subjected to dynamic loading.......In this work, the corrosion fatigue behaviour of steel armours used in the flexible pipes, in aqueous solutions initially containing different concentrations of Fe2+, was investigated by four-point bending testing under saturated 1 bar CO2 condition. Corrosion fatigue results were supported with ex...... situ measurements of Fe2+ and pH. Characterisation of the corrosion scales and crack formations was performed using microscopic and diffraction techniques. Fatigue results showed two times better fatigue life, at the stress ranges of 250 MPa, for samples tested in solutions containing the concentration...

  15. Dynamic strain aging in the high-temperature low-cycle fatigue of SA508 Cl. 3 forging steel

    Science.gov (United States)

    Lee, Byung Ho; Kim, In Sup

    1995-10-01

    The effect of dynamic strain aging on cyclic stress response and fatigue resistance of ASME SA508 Cl.3 forging steel for nuclear reactor pressure vessels has been evaluated in the temperature range of room temperature to 500°C. Total strain ranges and strain rates were varied from 0.7 to 2.0% and from 4 × 10 -4 to 1 × 10 -2 s -1, respectively. The cyclic stress response depended on the testing temperature, strain rate, and range. Generally, the initial cyclic hardening was immediately followed by cyclic softening at all strain rates. However, at 300°C, the operating temperature of nuclear reactor pressure vessels, the variation of cyclic stress amplitude showed the primary and secondary hardening stages dependent on the strain rate and strain range. Dynamic strain aging was manifested by enhanced cyclic hardening, distinguished secondary hardening, and negative strain rate sensitivity. A modified cell shutting model was described for the onset of the secondary hardening due to the dynamic strain aging and it was in good agreement with the experimental results. Fatigue life increased in strain rate at all testing temperatures. Specifically the fatigue life was longer at the dynamic strain aging temperature. Further, the dynamic strain aging was easy to initiate the crack, while crack propagation was retarded by crack branching and suppression of plastic zone, hence the dynamic strain aging caused the improvement of fatigue resistance.

  16. Effects of Thermal Aging on Type 316H Stainless Steel for Reactor Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ji Hyun; Hong, Seok Min; Lee, Bong Sang; Koo, Gyeong Hoi [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    Type 316H stainless steel is a prime candidate for reactor vessel material of sodium-cooled fast reactor (SFR) which has been developed as one of the Gen IV nuclear reactors in Korea. The reactor vessel steel will be exposed to higher temperature for an extended design life time. It is known that austenitic stainless steel such as Type 316H stainless steel shows excellent toughness and adequate strength at a moderate temperature. However, the previous researches reported the mechanical properties of Type 316H stainless weld would be deteriorated by the aging at the elevated temperature range.

  17. Fatigue corrosion of pressure vessel steel 16 MND 5 exposed to primary PWR coolant: effect of passivation-depassivation phenomena at the tip of a crack. Fatigue-corrosion de l'acier de cuve 16 MND 5 en milieu primaire de REP: role des phenomenes de depassivation-repassivation en pointe de fissure

    Energy Technology Data Exchange (ETDEWEB)

    Combrade, P.; Foucault, M. (Institut de Recherches de la Siderurgie Francaise (IRSID), 78 - Saint-Germain-en-Laye (France))

    1992-10-01

    Kinetics of crack propagation under the coating of some PWR vats. The corrosive atmosphere acts more strongly on steels with high sulfur content. The role of sulfur in the cracking process of steel 16 MND 5 in primary cooling is explained. (Author). 7 refs., 3 figs.

  18. Current Status of Development of High Nickel Low Alloy Steels for Commercial Reactor Pressure Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Chul; Lee, B. S.; Park, S. G.; Lee, K. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-12-15

    SA508 Gr.3 Mn-Mo-Ni low alloy steels have been used for nuclear reactor pressure vessel steels up to now. Currently, the design goal of nuclear power plant is focusing at larger capacity and longer lifetime. Requirements of much bigger pressure vessels may cause critical problems in the manufacturing stage as well as for the welding stage. Application of higher strength steel may be required to overcome the technical problems. It is known that a higher strength and fracture toughness of low alloy steels such as SA508 Gr.4N low alloy steel could be achieved by increasing the Ni and Cr contents. Therefore, SA508 Gr.4N low alloy steel is very attractive as eligible RPV steel for the next generation PWR systems. In this report, we propose the possibility of SA508 Gr.4N low alloy steel for an application of next generation commercial RPV, based on the literature research result about development history of the RPV steels and SA508 specification. In addition, we have surveyed the research result of HSLA(High Strength Low Alloy steel), which has similar chemical compositions with SA508 Gr.4N, to understand the problems and the way of improvement of SA508 Gr.4N low alloy steel. And also, we have investigated eastern RPV steel(WWER-1000), which has higher Ni contents compared to western RPV steel.

  19. Environmental Assisted Fatigue Evaluation of Direct Vessel Injection Piping Considering Thermal Stratification

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taesoon; Lee, Dohwan [KHNP CRI, Daejeon (Korea, Republic of)

    2016-10-15

    As the environmentally assisted fatigue (EAF) due to the primary water conditions is to be a critical issue, the fatigue evaluation for the components and pipes exposed to light water reactor coolant conditions has become increasingly important. Therefore, many studies to evaluate the fatigue life of the components and pipes in LWR coolant environments on fatigue life of materials have been conducted. Among many components and pipes of nuclear power plants, the direct vessel injection piping is known to one of the most vulnerable pipe systems because of thermal stratification occurred in that systems. Thermal stratification occurs because the density of water changes significantly with temperature. In this study, fatigue analysis for DVI piping using finite element analysis has been conducted and those results showed that the results met design conditions related with the environmental fatigue evaluation of safety class 1 pipes in nuclear power plants. Structural and fatigue integrity for the DVI piping system that thermal stratification occurred during the plant operation has conducted. First of all, thermal distribution of the piping system is calculated by computational fluid dynamic analysis to analyze the structural integrity of that piping system. And the fatigue life evaluation considering environmental effects was carried out. Our results showed that the DVI piping system had enough structural integrity and fatigue life during the design lifetime of 60 years.

  20. Acoustic Emission Technique for Characterizing Deformation and Fatigue Crack Growth in Austenitic Stainless Steels

    Science.gov (United States)

    Raj, Baldev; Mukhopadhyay, C. K.; Jayakumar, T.

    2003-03-01

    Acoustic emission (AE) during tensile deformation and fatigue crack growth (FCG) of austenitic stainless steels has been studied. In AISI type 316 stainless steel (SS), AE has been used to detect micro plastic yielding occurring during macroscopic plastic deformation. In AISI type 304 SS, relation of AE with stress intensity factor and plastic zone size has been studied. In AISI type 316 SS, fatigue crack growth has been characterised using acoustic emission.

  1. Assessment of Steel Bearing Structures - Estimation of the Remaining Fatigue Life

    Science.gov (United States)

    Omishore, Abayomi

    2017-10-01

    A significant number of steel bridges exist in operation worldwide. The budget for new infrastructure projects is tight, so the importance of inspection, maintenance and assessment of the existing bridges increases. A new fatigue assessment guideline for the estimation of the remaining fatigue life of steel bridges should be developed soon. This paper presents (i) a discussion based on the state-of-the-art review and (ii) new possibilities of applications of probabilistic methods for the time dependent reliability assessment of the lifetime of steel bridges. The probabilistic fatigue assessment procedure can be applied to existing steel bridges under cyclic loading. The guideline concentrates on the existing traffic infrastructure made from old steel due to its public importance. The essential general methods for these calculations are provided using structural and fracture mechanics and the reliability theory used in a probabilistic framework.

  2. Study on fatigue property of a new 2.8 GPa grade maraging steel

    Energy Technology Data Exchange (ETDEWEB)

    Wang Wei [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Graduate University of Chinese Academy of Sciences, Beijing 10049 (China); Yan Wei [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Duan, Qiqiang [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Shan Yiyin [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang Zhefeng [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Yang Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2010-05-25

    A new 2.8 GPa grade maraging steel was developed in the present work and the tension-tension fatigue property of the steel was studied after peak-aging treatment. The results showed that the steel could reach an ultimate tensile strength of 2760 MPa, a fracture toughness of 31.6 MPa m{sup 1/2}, and a fatigue limit of 1150 MPa at stress ratio of 0.1. It was revealed that the fatigue crack initiation of the steel mainly originated from the surface at high stress level but from the interior inclusions at low stress level. From the observations by transmission electron microscope (TEM) and fatigue crack propagation curves, it was proposed that the cyclic softening occurred, which was induced by the resolution as well as the growth of precipitates, and the poor fatigue crack growth resistance and high fatigue crack propagation rate might be the main reason for the relatively low fatigue limit of the steel.

  3. Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth

    Science.gov (United States)

    Kruml, T.; Hutař, P.; Náhlík, L.; Seitl, S.; Polák, J.

    2011-05-01

    The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 μm was followed in symmetrical cycling with constant strain amplitude ( R ɛ = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.

  4. Experimental Investigation and Stochastic Modelling of the Fatigue Behaviour of Welded Steel Joints

    DEFF Research Database (Denmark)

    Lassen, Tom

    The present report describes the fatigue behaviour of surface cracks in welded steel joints. Emphasis is laid on fracture mechanics modelling and the stochastic nature of the fatigue process. Various sources which may contribute to the observed scatter in time to crack initiation and time spent...

  5. Influence of asphalt on fatigue crack monitoring in steel bridge decks using guided waves

    NARCIS (Netherlands)

    Pahlavan, P.L.; De Soares Silva e Melo Mota, M.; Blacquière, G.

    2016-01-01

    Asphalt materials generally exhibit temperature-dependent properties, which can influence the performance of fatigue crack inspection and monitoring systems for bridge deck structures. For a non-intrusive fatigue crack sizing methodology applied to steel decks using ultrasonic guided waves, the

  6. Fatigue strength of repaired cracks in welded connections made of very high strength steels

    NARCIS (Netherlands)

    Akyel, A.

    2017-01-01

    For cyclically loaded structures, fatigue design becomes one of the important design criteria. The state of art shows that with modification of the conventional structural design methodology, the use of very high strength steels may have a positive effect on fatigue strength of welded connections.

  7. The effect of low temperatures on the fatigue of high-strength structural grade steels

    NARCIS (Netherlands)

    Walters, C.L.

    2014-01-01

    It is well-known that for fracture, ferritic steels undergo a sudden transition from ductile behavior at higher temperatures to brittle cleavage failure at lower temperatures. However, this phenomenon has not received much attention in the literature on fatigue. The so-called Fatigue Ductile-Brittle

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

    DEFF Research Database (Denmark)

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

    2002-01-01

    Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 × 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained...... scanning electron microscopy. Fatigue cracks initiate at the surface and no significant influence from frequency or from loading modes on fatigue crack initiation and growth is visible....

  9. Fatigue Properties of the Ultra-High Strength Steel TM210A.

    Science.gov (United States)

    Yin, Guang-Qiang; Kang, Xia; Zhao, Gui-Ping

    2017-09-09

    This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = -1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 10⁷ cycles. A double weighted least square method was then used to fit the stress-life (S-N) curve. The S-N curves of the two sets of specimens were obtained and the morphologies of the fractures of the two sets of specimens were observed with scanning electron microscopy (SEM). The results showed that the fatigue limit of the smooth specimen for rotating bending fatigue was 615 MPa; the ratio of the fatigue limit to tensile strength was 0.29, and the cracks initiated at the surface of the smooth specimen; while the fatigue limit of the notched specimen for rotating bending fatigue was 363 MPa, and the cracks initiated at the edge of the notch. The fatigue notch sensitivity index of the ultra-high strength maraging steel TM210A was 0.69.

  10. Influence of shear cutting parameters on the fatigue behavior of a dual-phase steel

    Science.gov (United States)

    Paetzold, I.; Dittmann, F.; Feistle, M.; Golle, R.; Haefele, P.; Hoffmann, H.; Volk, W.

    2017-09-01

    The influence of the edge condition of car body and chassis components made of steel sheet on fatigue behavior under dynamic loading presents a major challenge for automotive manufacturers and suppliers. The calculated lifetime is based on material data determined by the fatigue testing of specimens with polished edges. Prototype components are often manufactured by milling or laser cutting, whereby in practice, the series components are produced by shear cutting due to its cost-efficiency. Since the fatigue crack in such components usually starts from a shear cut edge, the calculated and experimental determined lifetime will vary due to the different conditions at the shear cut edges. Therefore, the material data determined with polished edges can result in a non-conservative component design. The aim of this study is to understand the relationship between the shear cutting process and the fatigue behavior of a dual-phase steel sheet. The geometry of the shear cut edge as well as the depth and degree of work hardening in the shear affected zone can be adjusted by using specific shear cutting parameters, such as die clearance and cutting edge radius. Stress-controlled fatigue tests of unnotched specimens were carried out to compare the fatigue behavior of different edge conditions. By evaluating the results of the fatigue experiments, influential shear cutting parameters on fatigue behavior were identified. It was possible to assess investigated shear cutting strategies regarding the fatigue behavior of a high-strength steel DP800.

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

    Science.gov (United States)

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

    2012-04-01

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

  12. Laboratory Investigation of Fatigue Characteristics of Asphalt Mixtures with Steel Slag Aggregates

    Directory of Open Access Journals (Sweden)

    Hassan Ziari

    2015-01-01

    Full Text Available There are many steel-manufacturing factories in Iran. All of their byproducts, steel slag, are dumped randomly in open areas, causing many environmentally hazardous problems. This research is intended to study the effectiveness of using steel slag aggregate (SSA in improving the engineering properties, especially fatigue life of Asphalt Concrete (AC produced with steel slag. The research started by evaluating the physical properties of the steel slag aggregate. Then the 13 types of mixes which contain steel slag in portion of fine aggregates or in portion of coarse aggregates or in all portions of aggregates were tested. The effectiveness of the SSA was judged by the improvement in Marshall stability, indirect tensile strength, resilient modulus, and fatigue life of the AC samples. It was found that replacing the 50% of the limestone coarse or fine aggregate by SSA improved the mechanical properties of the AC mixes.

  13. Fatigue strength improvement of the AISI 316Ti austenitic stainless steel by shot peening

    Directory of Open Access Journals (Sweden)

    František Nový

    2014-10-01

    Full Text Available Stainless steels are structural materials used for a wide range of applications. One of the fields of application of these highly corrosion resistant materials is for various medical applications. Different methods of mechanical property improvement have been studied in recent years to increase the durability of components manufactured from these materials. The main goal of this study was an analysis of fatigue strength improvement of the AISI 316Ti austenitic stainless steel by shot peening. A significant improvement of surface hardness, yield strength and fatigue limit by shot peening was observed in this study. This is despite increasing the surface roughness which usually degrades material’s fatigue strength.

  14. EVALUATION OF METHODS FOR ESTIMATING FATIGUE PROPERTIES APPLIED TO STAINLESS STEELS AND ALUMINUM ALLOYS

    Directory of Open Access Journals (Sweden)

    Taylor Mac Intyer Fonseca Junior

    2013-12-01

    Full Text Available This work evaluate seven estimation methods of fatigue properties applied to stainless steels and aluminum alloys. Experimental strain-life curves are compared to the estimations obtained by each method. After applying seven different estimation methods at 14 material conditions, it was found that fatigue life can be estimated with good accuracy only by the Bäumel-Seeger method for the martensitic stainless steel tempered between 300°C and 500°C. The differences between mechanical behavior during monotonic and cyclic loading are probably the reason for the absence of a reliable method for estimation of fatigue behavior from monotonic properties for a group of materials.

  15. The research of axial corrosion fatigue on 10Ni3CrMoV steel

    Science.gov (United States)

    Xie, Xing; Yi, Hong; Xu, Jian; Xie, Kun

    2017-09-01

    Fatigue life had been studied with 10CrNi3MoV steel at different load ratios and in different environmental medias. The microstructure and micro-topography had been observed and analyzed by means of SEM, EDS and TEM. Our findings indicated that, the fatigue life of 10Ni3CrMoV steel in seawater was shorter than in air, the difference in longevity was larger with the decreasing of axis stress. Corrosion pits had a great influence on corrosion fatigue life.

  16. Initiation and Growth of Corrosion Pit and Its Effect on Corrosion Fatigue Strength in 12Cr Stainless Steel

    National Research Council Canada - National Science Library

    HAYASHI, Makoto; AMANO, Kazuo; UEYAMA, Yoshiharu

    2017-01-01

    .... The corrosion fatigue cracks often initiate from the pits. In order to prevent the corrosion fatigue failure, 12Cr stainless steel is employed for the components used in the corrosive environments...

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

    Science.gov (United States)

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

    2014-01-01

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

  18. Influence of laser cutting on the fatigue limit of two high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Mateo, Antonio; Fargas, Gemma; Calvo, Jessica; Roa, Joan Josep [Univ. Politecnica de Catalunya, Barcelona (Spain). Dept. of Materials Science and Metallurgical Engineering

    2015-02-01

    Laser cutting is widely used in the metal industry, particularly when components of high strength steel sheets are produced. However, the roughness of cut edges produced by laser differs from that obtained by other methods, such as mechanical blanking, and this fact influences the fatigue performance. In the present investigation, specimens of two grades of high strength austenitic steels, i.e. AISI 301LN and TWIP17Mn, were cut by laser and tested in the high cycle fatigue regime to determine their corresponding fatigue limits. A series of fatigue specimens were tested without polishing and other series after a careful polishing of the cut edges, in order to assess the influence of the cut edges condition. Results indicate a significant influence of the edge roughness, more distinctive for AISI 301LN than for TWIP steel.

  19. Corrosion fatigue behaviour of 317LN austenitic stainless steel in phosphoric acid

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J. [Ingenieria y Ciencia de los Materiales, ETSI Industriales, Universidad Politecnica de Madrid, c/Jose Gutierrez Abascal, 2, 28006 Madrid (Spain)], E-mail: javier.onoro@upm.es

    2009-10-15

    The corrosion fatigue crack-growth behaviour of AISI 317LN stainless steel was evaluated in air and in 85% phosphoric acid at 20 deg. C. Austenitic stainless steels with high molybdenum content have high corrosion resistance and good mechanical properties. However, this increase in the molybdenum content and other elements such as nitrogen can also modify the microstructure. This leads to a modification of its mechanical properties. The corrosion fatigue crack-growth rate was higher in phosphoric acid immersion than in air. Austenitic stainless steels with a fully austenitic microstructure were more ductile, tough, and behave better against corrosion fatigue. The higher resistance to corrosion fatigue was directly associated to its higher resistance to corrosion.

  20. Fatigue behavior of functionally graded steel produced by electro-slag remelting

    Energy Technology Data Exchange (ETDEWEB)

    Salehi, M., E-mail: m-salehi@aut.ac.ir [Department of Mechanical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Alizadeh Vaghasloo, Y., E-mail: alizadeh@aut.ac.ir [Department of Mechanical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Naderi, M., E-mail: mnaderi@aut.ac.ir [Department of Mining and Metallurgical Engineering Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Ramezani Movaffagh, M., E-mail: m68rm@aut.ac.ir [Department of Mining and Metallurgical Engineering Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Varmaziar, A., E-mail: varmaziar@aut.ac.ir [Department of Mining and Metallurgical Engineering Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2013-11-01

    The present study attempts to investigate the fatigue behavior of functionally graded steel (FGS) produced through electroslag remelting (ESR) process. To produce FGSs, two different slices of plain carbon steel and austenitic stainless steel were welded and used as ESR's electrode. Some of alloying elements in austenitic stainless steel, such as Nickel and Chromium, as well as carbon in plain carbon steel may be replaced during remelting stage; graded layers (austenite and martensite layers) may also be fabricated. Vickers micro-hardness test and scanning electron microscopy (SEM) of FGS were performed and variations in hardness and microstructure were observed. SEM images exhibited multi-phase graded steel. The rotating bending fatigue test was performed on specimens. The fatigue test results showed improvement in fatigue limit of FGS in comparison with that of its ingredients. SEM's images of fatigue fracture surfaces in FGS showed deviation and branching in crack propagation when crack propagates from graded austenite to graded martensite phase.

  1. 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.

  2. Fatigue damage in 20% cold-worked type 316L stainless steel under deuteron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, R. (CEC, Joint Research Centre, 21020, Ispra (Vatican City State, Holy See) (Italy))

    1994-09-01

    Type 316L stainless steel samples in 20% cold-worked conditions were exposed to fully reversed fatigue cycling in torsion at 400 C during an irradiation with 19 MeV deuterons. Fatigue tests were performed in the high cycle fatigue (HCF) range under continuous cycling and in the low cycle fatigue (LCF) range by imposing a hold-time at the minimum strain value. In comparison with tests under thermal conditions, an increase in the number of cycles to failure N[sub f] by a factor of 6 is observed for the HCF tests and a decrease in N[sub f], by more than an order of magnitude, for the LCF tests. The data are analyzed using a fatigue damage model: a fatigue damage parameter is defined and the change in this parameter caused by the different irradiation or loading conditions shows directly the effect of changed experimental conditions on the fatigue life. ((orig.))

  3. Bending Fretting Fatigue Characteristics of 18CrNiMo7-6 Alloy Steel

    Directory of Open Access Journals (Sweden)

    SHEN Yan-tuan

    2017-07-01

    Full Text Available A series of bending fretting fatigue tests of 18CrNiMo7-6 alloy steel were carried out, the bending fretting fatigue S-N curve was built up, and an analysis was made on the test results. The results show that, the S-N curve of 18CrNiMo7-6 alloy steel presents a shape of "ε" curve, which is different from the medium carbon steel, and also different from the plain bending fatigue. With the increase of the bending fatigue stress, the fretting regime transforms from partial slip regime to mixed regime and slip regime. The wear mechanisms of fretting damage zones mainly are delaminated, abrasive wear and oxidative wear. In the mixed regime, the cracks are easy to initiate and propagate, and the cracks all originate from the subsurface of contact zone. Due to the different influence levels of the contact stress and bending fatigue stress, the initiation and propagation of the bending fretting fatigue cracks can be divided into three stages. Firstly, the cracks initiate from subsurface under the control of contact stress; then propagate to a larger angle direction under the joint control of contact stress and bending fatigue stress; lastly the cracks propagate vertically to contact surface until fracture failure under the control of bending fatigue stress.

  4. Microstructural Characterization Of Laser Heat Treated AISI 4140 Steel With Improved Fatigue Behavior

    Directory of Open Access Journals (Sweden)

    Oh M.C.

    2015-06-01

    Full Text Available The influence of surface heat treatment using laser radiation on the fatigue strength and corresponding microstructural evolution of AISI 4140 alloy steel was investigated in this research. The AISI 4140 alloy steel was radiated by a diode laser to give surface temperatures in the range between 600 and 800°C, and subsequently underwent vibration peening. The fatigue behavior of surface-treated specimens was examined using a giga-cycle ultrasonic fatigue test, and it was compared with that of non-treated and only-peened specimens. Fatigue fractured surfaces and microstructural evolution with respect to the laser treatment temperatures were investigated using an optical microscope. Hardness distribution was measured using Vickers micro-hardness. Higher laser temperature resulted in higher fatigue strength, attributed to the phase transformation.

  5. Fatigue cracks in Eurofer 97 steel: Part I. Nucleation and small crack growth kinetics

    Science.gov (United States)

    Kruml, T.; Polák, J.

    2011-05-01

    Fatigue crack nucleation and growth were studied in the Eurofer 97 ferritic-martensitic steel at room temperature. Cylindrical specimens with a shallow notch and no artificial crack starters were used. The constant strain amplitude cycling was adopted. First fatigue cracks nucleate at about 5% of the fatigue life along the surface slip bands. If a crack overcome the barrier of the first high angle boundary, its growth is regular and an exponential growth law is observed. This law may be used for the residual fatigue life prediction based on the small crack growth kinetics.

  6. Microstructural changes induced near crack tip during corrosion fatigue tests in austenitic-ferritic steel.

    Science.gov (United States)

    Gołebiowski, B; Swiatnicki, W A; Gaspérini, M

    2010-03-01

    Microstructural changes occurring during fatigue tests of austenitic-ferritic duplex stainless steel (DSS) in air and in hydrogen-generating environment have been investigated. Hydrogen charging of steel samples during fatigue crack growth (FCG) tests was performed by cathodic polarization of specimens in 0.1M H(2)SO(4) aqueous solution. Microstructural investigations of specimens after FCG tests were carried out using transmission electron microscopy to reveal the density and arrangement of dislocations formed near crack tip. To determine the way of crack propagation in the microstructure, electron backscatter diffraction investigations were performed on fatigue-tested samples in both kinds of environment. To reveal hydrogen-induced phase transformations the atomic force microscopy was used. The above investigations allowed us to define the character of fatigue crack propagation and microstructural changes near the crack tip. It was found that crack propagation after fatigue tests in air is accompanied with plastic deformation; a high density of dislocations is observed at large distance from the crack. After fatigue tests performed during hydrogen charging the deformed zone containing high density of dislocations is narrow compared to that after fatigue tests in air. It means that hydrogenation leads to brittle character of fatigue crack propagation. In air, fatigue cracks propagate mostly transgranularly, whereas in hydrogen-generating environment the cracks have mixed transgranular/interfacial character.

  7. Thermal fatigue cracking of austenitic stainless steels; Fissuration en fatigue thermique des aciers inoxydables austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A

    2001-07-01

    This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N{sub i} is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50{mu}m to 150{open_square}m long crack is observed. Additional SPLASH tests were performed for N >> N{sub i}, with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the

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

    Directory of Open Access Journals (Sweden)

    Libor Trško

    2014-06-01

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

  9. 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.

  10. Experimental Study on Fatigue Behaviour of Shot-Peened Open-Hole Steel Plates.

    Science.gov (United States)

    Wang, Zhi-Yu; Wang, Qing-Yuan; Cao, Mengqin

    2017-08-25

    This paper presents an experimental study on the fatigue behaviour of shot-peened open-hole plates with Q345 steel. The beneficial effects induced by shot peening on the fatigue life improvement are highlighted. The characteristic fatigue crack initiation and propagation modes of open-hole details under fatigue loading are revealed. The surface hardening effect brought by the shot peening is analyzed from the aspects of in-depth micro-hardness and compressive residual stress. The fatigue life results are evaluated and related design suggestions are made as a comparison with codified detail categories. In particular, a fracture mechanics theory-based method is proposed and demonstrated its validity in predicting the fatigue life of studied shot-peened open-hole details.

  11. Research on Fatigue Damage of Compressor Blade Steel KMN-I Using Nonlinear Ultrasonic Testing

    Directory of Open Access Journals (Sweden)

    Pengfei Wang

    2017-01-01

    Full Text Available The fatigue damage of compressor blade steel KMN-I was investigated using nonlinear ultrasonic testing and the relation curve between the material nonlinearity parameter β and the fatigue life was obtained. The results showed that the nonlinearity parameter increased first and then decreased with the increase of the fatigue cycles. The microstructures were observed by scanning electron microscopy (SEM. It was found that some small defects like holes and pits appeared in the material matrix with the increase of the fatigue cycles, and the nonlinearity parameter increased correspondingly. The nonlinearity parameter reached the peak value when the microcracks initiated, and the nonlinearity parameter began to decrease when the microcracks further propagated to macrocracks. Therefore, it is proved that the nonlinearity parameter can be used to characterize the initiation of microcracks at the early stage of fatigue, and a method of evaluating the fatigue life of materials by nonlinear ultrasonic testing is proposed.

  12. Comparison of Post Weld Treatment of High Strength Steel Welded Joints in Medium Cycle Fatigue

    DEFF Research Database (Denmark)

    Pedersen, Mikkel Melters; Mouritsen, Ole Ø.; Hansen, Michael Rygaard

    2010-01-01

    the stress range can exceed the yield-strength of ordinary structural steel, especially when considering positive stress ratios (R > 0). Fatigue experiments and qualitative evaluation of the different post-weld treatments leads to the selection of TIG dressing. The process of implementing TIG dressing......This paper presents a comparison of three post-weld treatments for fatigue life improvement of welded joints. The objective is to determine the most suitable post-weld treatment for implementation in mass production of certain crane components manufactured from very high-strength steel....... The processes investigated are: burr grinding, TIG dressing and ultrasonic impact treatment. The focus of this investigation is on the so-called medium cycle area, i.e. 10 000-500 000 cycles and very high stress ranges. In this area of fatigue design, the use of very high strength steel becomes necessary, since...

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

    Directory of Open Access Journals (Sweden)

    C. Gourdin

    2016-10-01

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

  14. Analysis of bearing steel exposed to rolling contact fatigue

    DEFF Research Database (Denmark)

    Hansen, K. T.; Fæster, Søren; Natarajan, Anand

    2017-01-01

    The objective of this work is to characterize fatigue damage in roller bearings under conditions of high load and slippage. A test rig constructed for rolling contact fatigue tests of rings is described, and test results are presented for rings taken from two spherical roller bearings. The prepar......The objective of this work is to characterize fatigue damage in roller bearings under conditions of high load and slippage. A test rig constructed for rolling contact fatigue tests of rings is described, and test results are presented for rings taken from two spherical roller bearings...

  15. Effect of laser shock processing on fatigue life of 2205 duplex stainless steel notched specimens

    Science.gov (United States)

    Vázquez Jiménez, César A.; Gómez Rosas, Gilberto; Rubio González, Carlos; Granados Alejo, Vignaud; Hereñú, Silvina

    2017-12-01

    The effect laser shock processing (LSP) on high cycle fatigue behavior of 2205 duplex stainless steel (DSS) notched samples was investigated. The swept direction parallel (LSP 1) and perpendicular (LSP 2) to rolling were used in order to examine the sensitivity of LSP to manufacturing process since this steel present significantly anisotropy. The Nd:YAG pulsed laser operating at 10 Hz frequency and 1064 nm wavelength was utilized. The LSP configuration was the water jet mode without protective coating. Notched specimens 4 mm thick were treated on both sides, and then fatigue loading was applied with R = 0.1. The results showed that the LSP 2 condition induces higher compressive residual stresses as well as a higher fatigue life than the LSP 1 condition. By applying LSP 2 condition, an enhancement of fatigue life up to 402% is reported. In addition, the microhardness profiles showed different depths of hardening layer for each direction, according to the anisotropy observed.

  16. Fatigue cracking behaviour of epoxy-based marine coatings on steel substrate under cyclic tension

    OpenAIRE

    Wu, Tongyu; Irving, Phil E.; Ayre, David; Jackson, P.; Zhao, F.

    2017-01-01

    Strain controlled fatigue tests have been performed on two types of heavily filled epoxy corrosion protection coating sprayed onto a 6 mm steel substrate. Fatigue cycling was performed at R ratios of 0 and −1. The two coatings differed in their formulation and the major differences in mechanical performance were in their static strain to first crack development and their fracture toughness, where Coating A was significantly tougher than coating B. During strain cycling coating crack developme...

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

    Energy Technology Data Exchange (ETDEWEB)

    Raske, D.T.

    1980-01-01

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

  18. The Effect of Phosphate Coatings on Fatigue Crack Initiation in Quenched and Tempered Low Alloy Steel

    Science.gov (United States)

    1990-12-01

    zinc and manganese phosphate on fatigue life to crack initiation was determined at two levels of applied stress, selected to... manganese phosphate or zinc phosphate which is then given a supplementary coating such as oil or solid film lubricant. The manganese phosphate is typically...surface with phosphate ( zinc or manganese ) has on the initiation of fatigue cracks in a representative high strength cannon steel. This report descries

  19. Gigacycle Fatigue Properties of Hydrogen-Charged JIS-SCM440 Low-Alloy Steel Under Ultrasonic Fatigue Testing

    Science.gov (United States)

    Furuya, Yoshiyuki; Hirukawa, Hisashi; Hayakawa, Masao

    2010-09-01

    Gigacycle fatigue tests were conducted on hydrogen-charged low-alloy steel. In this study, high- and low-strength specimens were prepared to investigate the effects of hydrogen on internal and surface fractures, respectively. The fatigue tests were conducted mainly by ultrasonic fatigue testing at 20 kHz and additionally by conventional servohydraulic fatigue testing at 50 Hz. All high-strength specimens revealed internal fractures. The fatigue strength of the hydrogen-charged specimens was much lower than that of the uncharged specimens. In the low-strength specimens, the uncharged specimens revealed surface fractures in the short-life regions in addition to internal fractures in the long-life regions. However, the hydrogen-charged specimens revealed internal fractures only that were combined with a much lower fatigue strength. The difference in fracture surfaces was small between the hydrogen-charged and the uncharged specimens, whereas the optically dark areas of the hydrogen-charged specimens seemed smaller than those of the uncharged specimens.

  20. Fatigue Isotropy in Cross-Rolled, Hardened Isotropic-Quality Steel

    Science.gov (United States)

    Temmel, C.; Karlsson, B.; Ingesten, N.-G.

    2008-05-01

    Deformation and forging operations often introduce microstructural orientation and, therewith, mechanical anisotropy to steel. Flattened manganese sulfide inclusions are held responsible for a great part of fatigue anisotropy. Isotropic-quality (IQ) steel maintains the mechanical isotropy of the material, even after a deformation operation. Isotropic material generally contains little S and, therewith, few manganese sulfides. Further, the IQ steels used in this investigation were Ca treated. The Ca treatment improves the shape stability of the sulfides, even during a hot-working deformation. Two commercial materials were compared for their fatigue response, a standard medium-carbon steel with 0.04 wt pct S and a low-sulfur variant that underwent IQ treatment. The two batches were cross-rolled to plates with a deformation ratio of 4.5, leading to in-plane isotropy. Tension-compression fatigue testing was performed in longitudinal and short transversal directions relative to the rolling plane. The results showed strong anisotropy of the fatigue behavior for the standard material. The performance in the short transverse direction, with the principal stress perpendicular to the flattened inclusions, was inferior. The IQ material with nearly spherical inclusions was almost perfectly isotropic, with only slightly worse fatigue response in the short transverse direction.

  1. Quantitative Acoustic Emission Fatigue Crack Characterization in Structural Steel and Weld

    Directory of Open Access Journals (Sweden)

    Adutwum Marfo

    2013-01-01

    Full Text Available The fatigue crack growth characteristics of structural steel and weld connections are analyzed using quantitative acoustic emission (AE technique. This was experimentally investigated by three-point bending testing of specimens under low cycle constant amplitude loading using the wavelet packet analysis. The crack growth sequence, that is, initiation, crack propagation, and fracture, is extracted from their corresponding frequency feature bands, respectively. The results obtained proved to be superior to qualitative AE analysis and the traditional linear elastic fracture mechanics for fatigue crack characterization in structural steel and welds.

  2. Fatigue-crack growth behavior of Type 347 stainless steels under simulated PWR water conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Seokmin; Min, Ki-Deuk; Yoon, Ji-Hyun; Kim, Min-Chul; Lee, Bong-Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    Fatigue crack growth rate (FCGR) curve of stainless steel exists in ASME code section XI, but it is still not considering the environmental effects. The longer time nuclear power plant is operated, the more the environmental degradation issues of materials pop up. There are some researches on fatigue crack growth rate of S304 and S316, but researches of FCGR of S347 used in Korea nuclear power plant are insufficient. In this study, the FCGR of S347 stainless steel was evaluated in the PWR high temperature water conditions. The FCGRs of S347 stainless steel under pressurized-water conditions were measured by using compact-tension (CT) specimens at different levels of dissolved oxygen (DO) and frequency. 1. FCGRs of SS347 were slower than that in ASME XI and environmental effect did not occur when frequency was higher than 1Hz. 2. Fatigue crack growth is accelerated by corrosion fatigue and it is more severe when frequency is slower than 0.1Hz. 3. Increase of crack tip opening time increased corrosion fatigue and it deteriorated environmental fatigue properties.

  3. Statistical model of water environment effects on the fatigue behavior of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-01

    Many studies on the effects of elevated temperature environments on the cycle fatigue performance of austenitic stainless steels typically used for boiling and light water reactor components have been performed. The key parameters (e. g. strain rate, and temperature) that influence the fatigue life were identified and the range of these key parameters where environmental effects become pronounced were defined. The two major efforts to characterize environmentally assisted fatigue (EAF) are by Argonne National Laboratory (U. S.) and EFD (Japan). Since each nation considers only domestic fatigue data, the widely applied titanium and niobium stabilized austenitic stainless steels in Germany are not included by any data points in these models. Based on a review of past and current research reports about EAF a database for wrought Types 304, 304L, 316, 316NG, 321, 347, and 348 stainless steels was compiled. Only specimen tests under strain control with a fully reversed uniaxial loading were included. The modified Langer equation was used to develop the room temperature in air curve to the collected data, which serves as the basis for the discussion of the EAF database. Besides the key variables that influence fatigue life in light and boiling water reactor environments additional parameters like, for example, the strain amplitude, which pronounces environmental effects more at low than at high strain amplitudes, can reduce the fatigue life by a factor of about two and should not be neglected in the current fatigue approach. A statistical model is evolved to address EAF in fatigue usage calculation by a fatigue life correction factor (F{sub en}), which is defined as the ratio of life in air at room temperature to that in water at elevated temperature. Compared to the current ANL statistical prediction model, a different functional form is used and additional variables are considered, too.

  4. Joining dissimilar stainless steels for pressure vessel components

    Science.gov (United States)

    Sun, Zheng; Han, Huai-Yue

    1994-03-01

    A series of studies was carried out to examine the weldability and properties of dissimilar steel joints between martensitic and austenitic stainless steels - F6NM (OCr13Ni4Mo) and AISI 347, respectively. Such joints are important parts in, e.g. the primary circuit of a pressurized water reactor (PWR). This kind of joint requires both good mechanical properties, corrosion resistance and a stable magnetic permeability besides good weldability. The weldability tests included weld thermal simulation of the martensitic steel for investigating the influence of weld thermal cycles and post-weld heat treatment (PWHT) on the mechanical properties of the heat-affected zone (HAZ); implant testing for examining the tendency for cold cracking of martensitic steel; rigid restraint testing for determining hot crack susceptibility of the multi-pass dissimilar steel joints. The joints were subjected to various mechanical tests including a tensile test, bending test and impact test at various temperatures, as well as slow strain-rate test for examining the stress corrosion cracking tendency in the simulated environment of a primary circuit of a PWR. The results of various tests indicated that the quality of the tube/tube joints is satisfactory for meeting all the design requirements.

  5. Biaxial fatigue tests of notched specimens for AISI 304L stainless steel

    Directory of Open Access Journals (Sweden)

    G. Beretta

    2016-07-01

    Full Text Available High cycle fatigue tests were conducted for stainless steel AISI 304L. The geometry was a thin walled tube with a passing through hole. The tests were axial, torsional and in-phase axial-torsional, all of them under load control with R = −1. The S-N curves were constructed following the ASTM E739 standard and the fatigues limits were calculated following the method of maximum likelihood proposed by Bettinelli. The crack direction along the surface was analysed, with especial attention to the crack initiation zones. The notch fatigue limits for different hole diameters were compared with the predictions done with a microstructural fracture mechanics model.

  6. Effects of irradiation on low cycle fatigue properties for reduced activation ferritic/martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.W. [Kyoto Univ., Graduate School of Energy Science (Japan); Tanigawa, H. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Kohyama, A. [Kyoto Univ., lnstitute of Advanced Energy (Japan)

    2007-07-01

    Full text of publication follows: In materials life decision for a commercial blanket, thermal fatigue property of materials is a particularly important. The loading of structural materials in fusion reactor is, besides the plasma surface interactions, a combined effect of high heat fluxes and neutron irradiation. Depending on the pulse lengths, the operating conditions, and the thermal conductivity, these oscillating temperature gradients will cause elastic and elastic-plastic cyclic deformation giving rise to (creep-) fatigue in structural first wall and blanket components. Especially, investigation of the fatigue property in Reduced Activation Ferritic/Martensitic (RAF/M) steel and establishment of the evaluation technology are demanded in particular immediately for design/manufacturing of ITER-TBM. And also, fatigue testing after irradiation will be carried out in hot cells with remote control system. Considering limited ability of specimen manipulation in the cells, the specimen and the test method need to be simple for operation. The existing data bases of RAF/M steel provide baseline data set including post-irradiation fatigue data. However, to perform the accurate fatigue lifetime assessment for ITER-TBM and beyond utilizing the existing data base, the mechanical understanding of fatigue fracture is mandatory. It has been previously reported by co-authors that dislocation cell structure was developed on low cycle fatigued RAF/M steel, and led the fatigue crack to develop along prior austenitic grain boundary. In this work, the effects of nuclear irradiation on low cycle fatigue properties for RAF/M steels and its fracture mechanisms were examined based on the flow stress analysis and detailed microstructure analysis. Fracture surfaces and crack initiation site were investigated by scanning electron microscope (SEM). Transmission electron microscopy (TEM) was also applied to clarify the microstructural features of fatigue behavior. It is also important to

  7. A study on the fatigue strength characteristics of ship structural steel with gusset welds

    Directory of Open Access Journals (Sweden)

    Sung-Jo Park

    2012-06-01

    Full Text Available This study aims to assess fatigue property by the static overload and average load in the fillet welded joints which is on the ship structural steel having gusset welds. To this end, a small specimen was made, to which the same welding condition for the actual ship structure was applied, to perform fatigue tests. In this study, a method to simply assess changes in welding residual stress according to different static overload was suggested. By measuring actual strain at the weld toe, the weld stress concentration factor and property which is determined by recrystallization in the process of welding were estimated to investigate the relation between overload and fatigue strength.

  8. A study on the fatigue strength characteristics of ship structural steel with gusset welds

    Science.gov (United States)

    Park, Sung-Jo; Lee, Hyun-Woo

    2012-06-01

    This study aims to assess fatigue property by the static overload and average load in the fillet welded joints which is on the ship structural steel having gusset welds. To this end, a small specimen was made, to which the same welding condition for the actual ship structure was applied, to perform fatigue tests. In this study, a method to simply assess changes in welding residual stress according to different static overload was suggested. By measuring actual strain at the weld toe, the weld stress concentration factor and property which is determined by recrystallization in the process of welding were estimated to investigate the relation between overload and fatigue strength.

  9. Pressure vessels design methods using the codes, fracture mechanics and multiaxial fatigue

    Directory of Open Access Journals (Sweden)

    Fatima Majid

    2016-10-01

    Full Text Available This paper gives a highlight about pressure vessel (PV methods of design to initiate new engineers and new researchers to understand the basics and to have a summary about the knowhow of PV design. This understanding will contribute to enhance their knowledge in the selection of the appropriate method. There are several types of tanks distinguished by the operating pressure, temperature and the safety system to predict. The selection of one or the other of these tanks depends on environmental regulations, the geographic location and the used materials. The design theory of PVs is very detailed in various codes and standards API, such as ASME, CODAP ... as well as the standards of material selection such as EN 10025 or EN 10028. While designing a PV, we must design the fatigue of its material through the different methods and theories, we can find in the literature, and specific codes. In this work, a focus on the fatigue lifetime calculation through fracture mechanics theory and the different methods found in the ASME VIII DIV 2, the API 579-1 and EN 13445-3, Annex B, will be detailed by giving a comparison between these methods. In many articles in the literature the uniaxial fatigue has been very detailed. Meanwhile, the multiaxial effect has not been considered as it must be. In this paper we will lead a discussion about the biaxial fatigue due to cyclic pressure in thick-walled PV. Besides, an overview of multiaxial fatigue in PVs is detailed

  10. A Novel Ni-Containing Powder Metallurgy Steel with Ultrahigh Impact, Fatigue, and Tensile Properties

    Science.gov (United States)

    Wu, Ming-Wei; Shu, Guo-Jiun; Chang, Shih-Ying; Lin, Bing-Hao

    2014-08-01

    The impact toughness of powder metallurgy (PM) steel is typically inferior, and it is further impaired when the microstructure is strengthened. To formulate a versatile PM steel with superior impact, fatigue, and tensile properties, the influences of various microstructures, including ferrite, pearlite, bainite, and Ni-rich areas, were identified. The correlations between impact toughness with other mechanical properties were also studied. The results demonstrated that ferrite provides more resistance to impact loading than Ni-rich martensite, followed by bainite and pearlite. However, Ni-rich martensite presents the highest transverse rupture strength (TRS), fatigue strength, tensile strength, and hardness, followed by bainite, pearlite, and ferrite. With 74 pct Ni-rich martensite and 14 pct bainite, Fe-3Cr-0.5Mo-4Ni-0.5C steel achieves the optimal combination of impact energy (39 J), TRS (2170 MPa), bending fatigue strength at 2 × 106 cycles (770 MPa), tensile strength (1323 MPa), and apparent hardness (38 HRC). The impact energy of Fe-3Cr-0.5Mo-4Ni-0.5C steel is twice as high as those of the ordinary high-strength PM steels. These findings demonstrate that a high-strength PM steel with high-toughness can be produced by optimized alloy design and microstructure.

  11. Short fatigue cracks nucleation and growth in lean duplex stainless steel LDX 2101

    Energy Technology Data Exchange (ETDEWEB)

    Strubbia, R., E-mail: strubbia@ifir-conicet.gov.ar [Instituto de Física Rosario – CONICET, Universidad Nacional de Rosario (Argentina); Hereñú, S.; Alvarez-Armas, I. [Instituto de Física Rosario – CONICET, Universidad Nacional de Rosario (Argentina); Krupp, U. [Faculty of Engineering and Computer Science, University of Applied Sciences Osnabrück (Germany)

    2014-10-06

    This work is focused on the fatigue damage of lean duplex stainless steels (LDSSs) LDX 2101. Special interest is placed on analyzing short fatigue crack behavior. In this sense, short crack initiation and growth during low cycle fatigue (LCF) and short crack nucleation during high cycle fatigue (HCF) of this LDSS have been studied. The active slip systems and their associated Schmid factors (SF) are determined using electron backscattered diffraction (EBSD). Additionally, the dislocation structure developed during cycling is observed by transmission electron microscopy (TEM). Regardless of the fatigue regime, LCF and HCF, short cracks nucleate along intrusion/extrusions in ferritic grains. Moreover, during the LCF phase boundaries decelerate short crack propagation. These results are rationalized by the hardness of the constitutive phases and the dependence of screw dislocation mobility in the ferrite phase on strain rate and stress amplitude.

  12. Fatigue Crack Growth Behavior of Stainless Steel Coated with TiN Film

    Science.gov (United States)

    Fukui, Satoshi; Yonekura, Daisuke; Murakami, Ri-Ichi

    In our previous study, we examined the influence of the fatigue properties of the stainless steel coated with TiN film and clarified the influence of TiN coating and the surface roughness on the fatigue property. In this study, the four point bending fatigue crack growth tests were carried out for martensitic stainless steel coated with TiN film deposited by arc ion plating method in order to investigate the effect of surface finishing on the fatigue crack behavior for film coated material. The fatigue crack growth behavior was evaluated using the replica method. As a result, the crack propagation rate of mirror polished specimens were lower than that of rough surface specimens. The crack propagation rate was especially decreased for TiN coatings deposited on the mirror polished substrate. The surface roughness near the crack initiation site increased after fatigue test. It concludes that the surface roughness of substrate influences crack propagation rate and the deposition of TiN film affected influenced crack propagation rate and fatigue strength when the surface roughness of substrate is small enough.

  13. Magnetic non-destructive evaluation of hardening of cold rolled reactor pressure vessel steel

    Science.gov (United States)

    Wang, Xuejiao; Qiang, Wenjiang; Shu, Guogang

    2017-08-01

    Non-destructive test (NDT) of reactor pressure vessel (RPV) steel is urgently required due to the life extension program of nuclear power plant. Here magnetic NDT of cold rolled RPV steel is studied. The strength, hardness and coercivity increase with the increasing deformation, and a good linear correlation between the increment of coercivity, hardness and yield strength is found, which may be helpful to develop magnetic NDT of degradation of RPV steel. It is also found that besides dislocation density, the distribution of dislocations may affect coercivity as well.

  14. Fatigue crack growth retardation in spot heated mild steel sheet

    Indian Academy of Sciences (India)

    Unknown

    Department of Applied Mechanics and Hydraulics, Regional Engineering. College, Rourkela 769 008, India. MS received 29 November 2001; revised 24 June 2002. Abstract. A fatigue crack can be effectively retarded by heating a spot near the crack ...

  15. Fretting fatigue behavior of high-strength steel monostrands under bending load

    DEFF Research Database (Denmark)

    Winkler, Jan; Georgakis, Christos T.; Fischer, Gregor

    2015-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. To measure the local deformations on the strands, a novel method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires...

  16. Fatigue fracture surface analysis in C45 steel specimens using X-Ray fractography

    NARCIS (Netherlands)

    Rajanna, K.; Kolster, B.H.; Pathiraj, B.

    1991-01-01

    X-Ray fractography is a useful technique to analyse the mechanisms operating in fracture and involves an examination of the fracture surface. In the present investigation, this technique has been employed to study the fatigue fracture behaviour of a medium carbon steel of C45 grade in different heat

  17. Application of carbon FRP for fatigue strengthening of old steel structures

    Science.gov (United States)

    Vůjtěch, J.; Ryjáček, P.; Vovesný, M.

    2017-02-01

    The traffic requirements on the existing infrastructure are rising still. This coupled with its age puts a strain on it. This is especially problematic for old steel bridges. Higher and more frequent loads will lead to development of fatigue damage to those structures. This causes an issue for the infrastructure owners as the existing methods of repair are difficult, time consuming and expensive. So there is a need to find some easier alternatives. One of such can be the use of carbon fibre reinforced polymers (CFRP). They are being successfully used for repairs and strengthening of concrete structures however their use with steel is still relatively new. The purpose of this work is to establish how does a deteriorated steel reinforced with CFRP behave under fatigue loading. To test this a series of experiments was designed. With the help of a preliminary numerical study the dimensions of the specimens and the applied loading was established. There are two sets of specimens. With both we are using mild steel and each set has different level of surface deterioration (corrosion pits or corrosion holes). The specimens are reinforced using hand laid wet layup composites. They are subjected to fatigue loading and the difference between the fatigue life reinforced and unreinforced specimens is observed. Based on the preliminary study, it is expected, that the reinforcement will prolong the life expectancy by half.

  18. Fatigue strength of truss girders made of very high strength steel

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.

    2010-01-01

    An effective application of Very High Strength Steel (VHSS) in civil engineering structures is expected in stiff, truss like structures, typically made of Circular Hollow Sections (CHS). Use of castings in combination with CHS could be promising for the design of highly fatigue resistant joints.

  19. The Influence of Laser Surface Alloying on the Thermal Fatigue Resistance of Hot Work Tool Steels

    Directory of Open Access Journals (Sweden)

    Jonda E.

    2016-09-01

    Full Text Available The paper presents results of the effect of laser surface remelting and alloying by carbides powders of NbC, TaC, TiC, VC and WC on the structure and thermal fatigue resistance of the surface layer of hot work tool steels X40CrMoV5-1 and 32CrMoV12-28. The laser surface alloying and remelting treatments was performed using a high power diode laser (HPDL ROFIN SINAR DL 020. In order to investigate the effect of applied laser treatments and used alloying powders on the microstructure and thermal fatigue resistance of processed surface layer of hot work tool steels, the microstructure evaluation by light microscopy, hardness test, and dedicated thermal fatigue resistance test were performed. The best results regarding fatigue cracks inhibition was obtained when the surface of hot work tool steels was alloyed with TiC and VC carbides at the laser beam power of 2.0 and 2.3 kW. The grain refinement effect of laser remelting has a lower impact on the thermal crack inhibition, than a strong strengthening effect of matrix saturation in alloying elements and precipitation of fine carbides in the steel matrix.

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

    Indian Academy of Sciences (India)

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

  1. Effect of Tantalum content on the low cycle fatigue properties of CLAM steel at 823 K

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Xiangwei [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); University of Science and Technology of China, Hefei, Anhui, 230027 (China); Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Zhao, Yanyun; Wang, Kun [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China)

    2017-01-15

    Highlights: • The fatigue life initially decreased and then increased as the Ta content was increased from 0.027 wt% to 0.18 wt%. • The softening rate had declined with Ta content increased and the reduced softening rate was attributed to the increased number of Ta-rich MX particles. • The grain size and M{sub 23}C{sub 6} were closely associated with the Ta content. • The crack distribution was quite sensitive to the Ta content. - Abstract: The effect of tantalum (Ta) content on the low cycle fatigue (LCF) properties of CLAM steel at 823 K was investigated in this paper. Low cycle fatigue tests were carried out on four ingots of CLAM steel with Ta contents of 0.027 wt%, 0.078 wt%, 0.15 wt% and 0.18 wt%, respectively. The results showed that the fatigue life and softening behavior of CLAM steel were influenced by Ta content. The fatigue life initially decreased and then increased as the Ta content was increased from 0.027 wt% to 0.18 wt%. The softening rate had declined with Ta content increased and the reduced softening rate was attributed to the increased number of Ta-rich MX particles.

  2. Effect of Microstructure on Fatigue Crack Propagation and S-N Fatigue Behaviors of TMCP Steels with Yield Strengths of Approximately 450 MPa

    Science.gov (United States)

    Kim, Youngju; Kwon, Jaeki; Lee, Hyunjung; Jang, Wookil; Choi, Jongkyo; Kim, Sangshik

    2011-04-01

    In the present study, stress (S) - number of cycles to failure (N) (S-N) fatigue and fatigue crack propagation behaviors of three thermomechanical control process steels with different microstructures but similar yield strengths of approximately 450 MPa were investigated. The P + F steel was predominately pearlite plus ferrite, whereas B1 and B2 steels were both bainitic steels with martensite-austenite and pearlitic islands. Despite the significant difference in microstructural features, the resulting fatigue crack propagation rates and near-threshold Δ K values were comparable with each other. The hard phases, such as pearlite colonies in the P + F specimen, tended to affect fatigue crack propagation behavior in a similar manner, and severe crack branching was observed in intermediate and high Δ K regimes. Despite similar fatigue crack propagation rates and near-threshold Δ K values, the resistance to S-N fatigue was substantially different for each steel specimen. Depending on fatigue crack initiators, such as the ferrite/pearlite phase boundaries for the P + F specimens and the cracked martensite-austenite and/or small pearlitic islands for the bainitic specimens, the cycles for crack initiation varied greatly.

  3. EFFECT OF SHOT PEENING ON FATIGUE PROPERTIES OF STEEL IN DIFFERENT STRUCTURAL STATES

    Directory of Open Access Journals (Sweden)

    Gejza Rosenberg

    2011-07-01

    Full Text Available The aim of this paper is to evaluate the effect of shot peening on fatigue properties of dual-phase steels DP 600 in received condition, as well as in condition after different regimes of heat treatment. In the work, there are presented results of tests on smooth samples as well as on samples with stress concentrator (a drilling hole, size d = 4mm. The expectations, that shot peening of flat steel samples improves resistance to fatigue failure, were approved by all tested structural states. The tests on samples with the drilled hole showed, that effect of shot peening on fatigue properties may be negative, if the hole was drilled after shot peening of surface of samples.

  4. Influence of Residual Stress on Fatigue Design of AISI 304 Stainless Steel

    Directory of Open Access Journals (Sweden)

    L. Singh

    2011-06-01

    Full Text Available Austenitic stainless steel cannot be hardened by any form of heat treatment, in fact, quenching from 10000C merely softens them. They are usually cold worked to increase the hardness. Shot peening is a cold working process that changes micro-structure as well as residual stress in the surface layer. In the present work, the compressive residual stress and fatigue strength of AISI 304 austenitic stainless steel have been evaluated at various shot peening conditions. The improvement in various mechanical properties such as hardness, damping factors and fatigue strength was noticed. Compressive residual stress induced by shot peening varies with cyclic loading due to relaxation of compressive residual stress field. The consideration of relaxed compressive residual stress field instead of original compressive residual stress field provides reliable fatigue design of components. In this paper, the exact reductions in weight and control of mechanical properties due to shot peening process are discussed.

  5. Damage-Coupled Constitutive Model for Uniaxial Ratcheting and Fatigue Failure of 304 Stainless Steel

    Science.gov (United States)

    Kang, Guozheng; Ding, Jun; Liu, Yujie

    Based on the existed experimental results of 304 stainless steel, the evolution of fatigue damage during the stress-controlled cyclic loading was discussed first. Then, a damage-coupled visco-plastic cyclic constitutive model was proposed in the framework of unified visco-plasticity and continuum damage mechanics to simulate the whole-life ratcheting and predict the fatigue failure life of the material presented during the uniaxial stress-controlled cyclic loading with non-zero mean stress. In the proposed model, the whole life ratcheting was described by employing a non-linear kinematic hardening rule, i.e., the Armstrong-Frederick model combined with the Ohno-Wang model I, and considering the effect of fatigue damage. The damage threshold was employed to determine the failure life of the material. The simulated whole-life ratcheting and predicted failure lives are in a fairly good agreement with the experimental ones of 304 stainless steel.

  6. Effect of hot dip galvanization on the fatigue strength of steel bolted connections

    Directory of Open Access Journals (Sweden)

    S.M.J. Razavi

    2017-07-01

    Full Text Available Hot dip galvanized steel bolted joints has been tested under fatigue loading to evaluate the effect of galvanizing coating on the fatigue strength of S355 structural steel. The experimental results showed that the decrease of the fatigue life of coated specimens in comparison with that of uncoated joints is very limited and the results are in good agreement with Eurocode detail category, without substantial reductions. The procedure for coating and preparation of the bolted joints is described in detail in this paper providing a useful tool for engineers involved in similar practical applications. The experimental results are compared with the previously published data on central hole notched galvanized and not treated specimens characterized by the same geometry.

  7. Thermal Embrittlement of Reactor Pressure Vessel Steel due to Aging

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Soo; Park, Duck Gun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    Thermal SS sets are located above the nuclear core where a fast neutron flux is negligible and temperature is 320 .deg. C (as opposed to 290 .deg. C in locations of high-irradiated SS). These SS allow monitoring of continuous operation temperature exposure effect on mechanical characteristics of the steels. Although transgranular cleavage is the predominant mode of brittle fracture in RPV steels, solute (e.g. phosphorus) segregation to grain boundaries can result in another type of brittle fracture known as intergranular (grain boundary) fracture. Figures 1 a) and b) show examples of transgranular and intergranular (IG) fracture, respectively, as viewed in a scanning electron microscope. The investigators have interpreted the intergranular cracking occurs as a result of segregation of sulfur and/or phosphorus at grain boundary. The IG cracking is a kind of symptom of embrittlement. It is reported that the IG cracking occurs in inert (Ar) environment under slow strain rate test. 1. The lath grain size in SA508 RPV steel increases slightly due to thermal aging at 350, 420, and 420 .deg. C for 2,250H. 2. The decrease in toughness appeared 4-25% and the lattice contraction appeared to be +0.004% - -0.022% due to thermal aging at 350, 420, and 420 .deg. C for 2,250H. 3. The amount of decrease in Charpy impact energy due to thermal aging is correlated well with the magnitude of lattice contraction.

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

    Directory of Open Access Journals (Sweden)

    Ghazal Moeini

    2017-07-01

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

  9. Effect of laser shock peening on bending fatigue performance of AISI 9310 steel spur gear

    Science.gov (United States)

    Peng, Chong; Xiao, Yuzhe; Wang, Yanzhong; Guo, Wei

    2017-09-01

    The effect of laser shock peening (LSP) on bending fatigue performance of AISI 9310 steel spur gear has been investigated in this study. To help to explain bending fatigue test results, residual stress distribution induced by LSP is studied by means of finite element modelling, results of which are verified by X-ray diffraction analysis. It is found that a compressive layer of desirable depth can be induced on the gear root fillet after LSP, and both magnitude and depth of compressive stress increase with laser energy. The bending fatigue test is conducted using the single-tooth bending method to compare fatigue performance of laser peened teeth and non-peened teeth, which is followed by relevant statistical analysis. S-N curves acquired from the fatigue test reveal that bending fatigue lives of gear teeth has been significantly improved after LSP in comparison with those non-peened teeth, and the bending fatigue limit is enhanced correspondingly. It is noticeable that higher laser energy does not necessarily lead to much better fatigue performance of test gears.

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

    Directory of Open Access Journals (Sweden)

    Qasim Bader

    2014-04-01

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

  11. 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.

  12. High-cycle fatigue characteristics of weldable steel for light-water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Klesnil, M.; Polak, J.; Obrtlik, K. (Ceskoslovenska Akademie Ved, Brno. Ustav Fyzikalni Metalurgie); Troshchenko, V.T.; Mishchenko, Yu.I.; Khamaza, L.A. (AN Ukrainskoj SSR, Kiev. Inst. Problem Prochnosti)

    1982-11-01

    Czechoslovak and Soviet 15Kh2NMFA steel was used for running fatigue tests at temperatures of 20, 350 and 400 degC in the high-cycle range with various loading regimes. The results show that at the given temperatures in this type of steel a cyclic softening occurs. The fatigue characteristics were measured with great dispersion of results, but within this dispersion they are almost identical for various steels at the same temperature. Increased temperature results in the decrease in the amplitude of cyclic deformation stress and in the increase in the amplitude of plastic deformation. The diversity in the values of cyclic plasticity and stress response measured in the given mode may be explained by the lower level of softening and the non-homogeneous cyclic plastic deformation of material under the given constant conditions.

  13. Lessons Learned From Developing Reactor Pressure Vessel Steel Embrittlement Database

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL

    2010-08-01

    Materials behaviors caused by neutron irradiation under fission and/or fusion environments can be little understood without practical examination. Easily accessible material information system with large material database using effective computers is necessary for design of nuclear materials and analyses or simulations of the phenomena. The developed Embrittlement Data Base (EDB) at ORNL is this comprehensive collection of data. EDB database contains power reactor pressure vessel surveillance data, the material test reactor data, foreign reactor data (through bilateral agreements authorized by NRC), and the fracture toughness data. The lessons learned from building EDB program and the associated database management activity regarding Material Database Design Methodology, Architecture and the Embedded QA Protocol are described in this report. The development of IAEA International Database on Reactor Pressure Vessel Materials (IDRPVM) and the comparison of EDB database and IAEA IDRPVM database are provided in the report. The recommended database QA protocol and database infrastructure are also stated in the report.

  14. Application of high strength MnMoNi steel to pressure vessels for nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, K.; Kurihara, I.; Sasaki, T.; Koyama, Y.; Tanaka, Y. [The Japan Steel Works, Ltd. (Japan)

    1999-07-01

    Recent increase in output of nuclear power plant has been attained by enlargement of major components such as pressure vessels. Such large components have almost reached limit of size from the points of manufacturing capacity and cost in both forgemasters and fabricaters. In order to solve this problem, it must be beneficial to apply design by use of material of higher strength which brings reduction of pressure vessel thickness and weight. The Japan Steel Works, Ltd. (JSW) has many manufacturing experiences of large integrated forgings made from high strength MnMoNi steel with tensile strength level of 620MPa for steam generator (SG) pressure vessel, and has made confirmation tests of its material properties. This paper describes the confirmation test results such as tensile and impact properties, nil-ductility transition temperature (NDT-T), static and dynamic fracture toughness weldability including under clad cracking (UCC) sensitivity and metallurgical factors which influence on such material properties. (orig.)

  15. Application of high strength MnMoNi steel to pressure vessels for nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, K. E-mail: koumei_suzuki@jsw.co.jp; Kurihara, I.; Sasaki, T.; Koyoma, Y.; Tanaka, Y

    2001-06-01

    Recent increase in output of nuclear power plant has been attained by enlargement of major components such as pressure vessels. Such large components have almost reached a size limit from the points of manufacturing capacity and cost in both forgemasters and fabricaters. In order to solve this problem, it must be beneficial to apply design by use of material of higher strength, which brings reduction of pressure vessel thickness and weight. The Japan Steel Works Ltd. (JSW) has many manufacturing experiences of large integrated forgings made from high strength MnMoNi steel with tensile strength level of 620 MPa for steam generator (SG) pressure vessel, and has performed confirmation tests of its material properties. This paper describes the confirmation test results such as tensile and impact properties, nil-ductility transition temperature (NDT-T), static and dynamic fracture toughness, weldability including under-clad cracking (UCC) sensitivity, as well as metallurgical factors which influence on such material properties.

  16. Analysis of bearing steel exposed to rolling contact fatigue

    Science.gov (United States)

    Hansen, K. T.; Fæster, S.; Natarajan, A.; Mishin, O. V.; Danielsen, H. K.; Jensen, D. Juul; Klit, P.

    2017-07-01

    The objective of this work is to characterize fatigue damage in roller bearings under conditions of high load and slippage. A test rig constructed for rolling contact fatigue tests of rings is described, and test results are presented for rings taken from two spherical roller bearings. The preparation of the rings and the loading situation are explained. Test conditions are chosen with the aim of achieving pitting formation at the contacting surfaces. During testing the contact pressure, torque and the rotational speed are monitored and recorded. After testing the tested rings have been characterized using X-ray tomography and scanning electron microscopy. The observations confirm that rolling contact fatigue testing at high loads leads to pitting failure at the contacting surfaces. The pitting mostly appears on one side of the contact, attributed to a non-uniform contact pressure in the axial direction.

  17. Hydrogen Cracking and Stress Corrosion of Pressure Vessel Steel ASTM A543

    Science.gov (United States)

    AlShawaf, Ali Hamad

    The purpose of conducting this research is to develop fundamental understanding of the weldability of the modern Quenched and Tempered High Strength Low Alloy (Q&T HSLA) steel, regarding the cracking behavior and susceptibility to environmental cracking in the base metal and in the heat affected zone (HAZ) when welded. A number of leaking cracks developed in the girth welds of the pressure vessel after a short time of upgrading the material from plain carbon steel to Q&T HSLA steel. The new vessels were constructed to increase the production of the plant and also to save weight for the larger pressure vessel. The results of this research study will be used to identify safe welding procedure and design more weldable material. A standardized weldability test known as implant test was constructed and used to study the susceptibility of the Q&T HSLA steel to hydrogen cracking. The charged hydrogen content for each weld was recorded against the applied load during weldability testing. The lack of understanding in detail of the interaction between hydrogen and each HAZ subzone in implant testing led to the need of developing the test to obtain more data about the weldability. The HAZ subzones were produced using two techniques: standard furnace and GleebleRTM machine. These produced subzones were pre-charged with hydrogen to different levels of concentration. The hydrogen charging on the samples simulates prior exposure of the material to high humidity environment during welding process. Fractographical and microstructural characterization of the HAZ subzones were conducted using techniques such as SEM (Scanning Electron Microscopy). A modified implant test using the mechanical tensile machine was also used to observe the effects of the hydrogen on the cracking behavior of each HAZ subzone. All the experimental weldability works were simulated and validated using a commercial computational software, SYSWELD. The computational simulation of implant testing of Q&T HSLA

  18. Investigation of fatigue properties of shot peened and plasma nitrocarburized P/M FC0205 steel

    Energy Technology Data Exchange (ETDEWEB)

    Basaran, Ali [Institute of Aerospace Technology, Air Force Academy, Istanbul (Turkmenistan); Kurgan, Naci [Karabuk University, Karabuk (Turkmenistan); Varol, Remzi [Suleyman Demirel University, Isparta (Turkmenistan)

    2013-08-15

    One of the widely used powder metal materials in automotive industry, which is copper steel FC 0205 (Fe + 2% Cu + 0.5% C), was used in this study. The pressed samples has been prepared at the compression pressure of 680 MPa and sintered in conventional furnace at 1120 .deg. C for 30 minutes. The samples with 7 Mg/m{sup 3} densities were used as fatigue and shot peening processes. Shot peening were applied with 20A and 32A and the others were not peened. Plasma nitrocarburizing process was performed at 555 .deg. C for 2 hours under 600-900 Pa pressure. Fatigue tests were conducted at room temperature on a rotating bending type fatigue test device. It was determined that shot peening should be used where increased fatigue strength is needed, and plasma nitrocarburizing should be preferred where surface hardness is required, and plasma nitrocarburizing after shot peening process is much more useful.

  19. Limit to corrosion fatigue strength evaluation of SAE1020 steel in acidic environment

    Directory of Open Access Journals (Sweden)

    William Mauricio Sanabria Becerra

    2015-01-01

    Full Text Available This paper shows the results of the research in terms of the evaluation of corrosion fatigue resistance of SAE1020 steel in acidic conditions, using as corrosive substance: acetate buffer with pH 2, 4 and 6. The fatigue tests were performed according to the model of cantilever rotating bending. The results were compared with the limit of fatigue resistance of the material tested in air. It was observed a significantly reduced limit with increasing acidity of the substance. Likewise, localized corrosion type filiform corrosion was observed on the surface material, caused by the effect of the specimen aerated to be partially submerged in rotation. Limits fatigue strength determined using staircase method recommended by standard ISO1143 and ISO12107, with confidence level of 50 % and a probability of failure of 10 %.Finally, the surfaces were analyzed to find multiple origins of fracture and crack propagation lengths related to the acidity of the medium.

  20. Effect of Fe ion concentration on fatigue life of carbon steel in aqueous CO2 environment

    DEFF Research Database (Denmark)

    Rogowska, Magdalena; Gudme, J.; Rubin, A.

    2016-01-01

    In this work, the corrosion fatigue behaviour of steel armours used in the flexible pipes, in aqueous solutions initially containing different concentrations of Fe2+, was investigated by four-point bending testing under saturated 1 bar CO2 condition. Corrosion fatigue results were supported with ex...... situ measurements of Fe2+ and pH. Characterisation of the corrosion scales and crack formations was performed using microscopic and diffraction techniques. Fatigue results showed two times better fatigue life, at the stress ranges of 250 MPa, for samples tested in solutions containing the concentration...... of Fe2+ marginally above the solubility limit of FeCO3 compared to the samples tested in highly supersaturated solution of Fe2+. Results revealed that the impact of the alternating stresses on the corrosion behaviour of samples reduces with lowering the applied stresses. At the stress range of 100 MPa...

  1. Fatigue crack growth retardation in spot heated mild steel sheet

    Indian Academy of Sciences (India)

    A fatigue crack can be effectively retarded by heating a spot near the crack tip under nil remote stress condition. The subcritical spot heating at a proper position modifies the crack growth behaviour in a way, more or less, similar to specimen subjected to overload spike. It is observed that the extent of crack growth retardation ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-10-15

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

  3. Thermal fatigue crack nucleation in ferritic-martensitic steels before and after neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Belyaeva, L.A.; Zisman, A.A.; Petersen, C. E-mail: claus.petersen@imf.fzk.de; Potapova, V.A.; Rybin, V.V

    2000-12-01

    Thermal fatigue behaviour of the ferritic-martensitic steels MANET-II, 12Cr-1.5NiMo and F82H-mod. have been investigated in the temperature range from 50 deg. C to 350 deg. C and total strain range {<=}0.33%. Crack appearance has been checked after 3x10{sup 3}, 6x10{sup 3} and 10{sup 4} cycles and has been successively detected in these steels. The thermal fatigue cracks have a transgranular character; sometimes, intergranular cracks are observed in the F82H-mod. steel. A certain correlation of grain size and ferrite content with the thermal fatigue crack peculiarities has been noted. Specimens of MANET-II and 12Cr-1.5NiMo have been irradiated in a WWR-M reactor with a fluence of 1x10{sup 25} n m{sup -2} at a temperature of 300 deg. C and then subjected to thermocyclic loading. It has been established that the neutron irradiation does not significantly affect fatigue crack nucleation in both materials.

  4. Fatigue Reliability Assessment for Orthotropic Steel Decks Based on Long-Term Strain Monitoring.

    Science.gov (United States)

    Deng, Yang; Li, Aiqun; Feng, Dongming

    2018-01-10

    A time-dependent fatigue reliability assessment approach is proposed for welded details of orthotropic steel decks (OSDs) using long-term strain monitoring data. The fatigue reliability limit function of the welded details is established based on the Eurocode specifications. Depending on the distribution characteristics of the measured daily equivalent stress range, either the lognormal distribution or Gaussian mixture model (GMM) is selected to quantify its uncertainty. Subsequently, the fatigue reliability can be calculated using either an explicit formula or the Monte Carlo method. This proposed approach is applied for the fatigue reliability evaluation of two rib-to-deck and two rib-to-rib welded fatigue details of an in-service suspension bridge. The results show that the reliability indices decrease significantly with bridge's service life. Except for a rib-to-deck detail, all other three welded details cannot meet the target fatigue reliability during this bridge's 100-year service life. The proposed approach can help bridge owners and operators make informed decisions regarding maintenance and repair of potential fatigue cracks.

  5. Fatigue assessment of an existing steel bridge by finite element modelling and field measurements

    Science.gov (United States)

    Kwad, J.; Alencar, G.; Correia, J.; Jesus, A.; Calçada, R.; Kripakaran, P.

    2017-05-01

    The evaluation of fatigue life of structural details in metallic bridges is a major challenge for bridge engineers. A reliable and cost-effective approach is essential to ensure appropriate maintenance and management of these structures. Typically, local stresses predicted by a finite element model of the bridge are employed to assess the fatigue life of fatigue-prone details. This paper illustrates an approach for fatigue assessment based on measured data for a connection in an old bascule steel bridge located in Exeter (UK). A finite element model is first developed from the design information. The finite element model of the bridge is calibrated using measured responses from an ambient vibration test. The stress time histories are calculated through dynamic analysis of the updated finite element model. Stress cycles are computed through the rainflow counting algorithm, and the fatigue prone details are evaluated using the standard SN curves approach and the Miner’s rule. Results show that the proposed approach can estimate the fatigue damage of a fatigue prone detail in a structure using measured strain data.

  6. Correlation between radiation damage and magnetic properties in reactor vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Kempf, R.A., E-mail: kempf@cnea.gov.ar [División Caracterización, GCCN, CAC-CNEA (Argentina); Sacanell, J. [Departamento Física de la Materia Condensada, GIyA, CAC-CNEA, CONICET (Argentina); Milano, J. [División Resonancias Magnéticas, CAB-CNEA, CONICET (Argentina); Guerra Méndez, N. [Departamento Física de la Materia Condensada, GIyA, CAC-CNEA, CONICET (Argentina); Winkler, E.; Butera, A. [División Resonancias Magnéticas, CAB-CNEA, CONICET (Argentina); Troiani, H. [División Física de Metales, CAB-CNEA and Instituto Balseiro (UNCU), CONICET (Argentina); Saleta, M.E. [División Resonancias Magnéticas, CAB-CNEA, CONICET (Argentina); Fortis, A.M. [Departamento Estructura y Comportamiento. Gerencia Materiales-GAEN, CAC-CNEA (Argentina)

    2014-02-01

    Since reactor pressure vessel steels are ferromagnetic, provide a convenient means to monitor changes in the mechanical properties of the material upon irradiation with high energy particles, by measuring their magnetic properties. Here, we discuss the correlation between mechanical and magnetic properties and microstructure, by studying the flux effect on the nuclear pressure vessel steel used in reactors currently under construction in Argentina. Charpy-V notched specimens of this steel were irradiated in the RA1 experimental reactor at 275 °C with two lead factors (LFs), 93 and 183. The magnetic properties were studied by means of DC magnetometry and ferromagnetic resonance. The results show that the coercive field and magnetic anisotropy spatial distribution are sensitive to the LF and can be explained by taking into account the evolution of the microstructure with this parameter. The saturation magnetization shows a dominant dependence on the accumulated damage. Consequently, the mentioned techniques are suitable to estimate the degradation of the reactor vessel steel.

  7. Influence of the mechanical fatigue progress on the magnetic properties of electrical steel sheets

    Directory of Open Access Journals (Sweden)

    Karthaus Jan

    2017-06-01

    Full Text Available The purpose of this paper is to study the variation of the magnetic properties of non-oriented electrical steel sheets with the fatigue state during cyclic mechanical loading. The obtained results are central to the design of variable drives such as traction drives in electric vehicles in which varying mechanical loads, e.g. in the rotor core (centrifugal forces, alter the magnetic properties. Specimens of non-oriented electrical steel are subject to a cyclically varying mechanical tensile stress with different stress amplitudes and number of cycles. The specimens are characterised magnetically at different fatigue states for different magnetic flux densities and magnetising frequencies. The measurements show a variation in magnetic properties depending on the number of cycles and stress magnitude which can be explained by changes in the material structure due to a beginning mechanical fatigue process. The studied effect is critical for the estimation of the impact of mechanical material fatigue on the operational behaviour of electrical machines. Particularly in electrical machines with a higher speed where the rotor is stressed by high centrifugal forces, material fatigue occurs and can lead to deterioration of the rotor’s stack lamination.

  8. Fatigue assessment for selected connections of structural steel bridge components using the finite elements method

    Science.gov (United States)

    Śledziewski, Krzysztof

    2018-01-01

    Material fatigue it is one of the most frequent causes of steel bridge failures, particularly the bridges already existing. Thus, the procedure of fatigue life assessment is one of the most relevant procedures in a comprehensive assessment of load-carrying capacity and service life of the structure. A reliable assessment of the fatigue life is predominantly decisive for estimation of the remaining service life. Hitherto, calculation methods of welded joints took into account only stresses occurring in cross sections of whole elements and did not take into account stress concentration occurring in the vicinity of the weld, caused by geometrical aspects of the detail. At present, use of the Finite Element Analysis, makes possible looking for more accurate approach to the fatigue design of steel structures. The method of geometrical stresses is just such approach which is based on definition of stresses which take into account geometry of the detail. The study presents fatigue assessment of a representative type of welded joint in welded bridge structures. The testing covered longitudinal attachments. The main analyses were carried out on the basis of FEM and the method of local stresses, so-called "hot-spot" stresses. The obtained values of stresses were compared with the values obtained in accordance with the method of nominal stress.

  9. Low cycle notched fatigue behavior and life predictions of A723 high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Troiano, E.; Underwood, J.H.; Crayon, D. [Army Armament Research, Development and Engineering Center, Watervliet, NY (United States). Benet Labs.

    1995-12-31

    Two types of ASTM A723 steels have been investigated for their low cycle fatigue behavior. Specimens were tested in four-point bending, both with and without notches, and the measured fatigue lives were compared with those predicted by Neubers notch analysis, and standard fracture mechanics life prediction techniques. Comparison of measured and predicted lives indicate that the elastic/plastic Neuber analysis under predicts the measured fatigue life by as much as 67% at large strains, and becomes a better predictor of life as the applied strains decrease. The elastic Neubers analysis also under predicts the measured fatigue lives by 45% at large applied strains, but seems to accurately predict lives at reversals to failure greater than 100. The fracture mechanics approach assumes elastic stresses at the crack tip, and predicts lives within 30% over the full range of strains investigated. The results show that the Neuber notch analysis is not as good an indicator of the low cycle fatigue behavior of A723 steels as is the fracture mechanics life prediction techniques. As the life cycles to failure decreases, the Neubers analysis predicts lives that are two to three times more conservative than those experimentally measured.

  10. Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    Science.gov (United States)

    Toyoda, Shunsuke; Ishiguro, Yasuhide; Kawabata, Yoshikazu; Sakata, Kei; Sato, Akio; Sakai, Jun'ichi

    The microstructural influence of martensitic carbon steel on torsional fatigue endurance was investigated, taking into consideration the application of high strength steel electric resistance welded (ERW) tubes to automotive structural parts. The chemical composition of the base steel alloy was 0.1-0.2%C-0.2-1.5%Si-1.3-1.9%Mn-0.01%P-0.001%S-(Cr, Mo, Ti, Nb, B). Laboratory vacuum-fused ingots were hot-rolled, heated to 1023 or 1223 K in a salt bath, and then water-quenched and tempered at 473 K. Consequently, three types of microstructure, martensite (M), martensite and ferrite (M+F), and ferrite and pearlite (F+P), were prepared. Fully reversed torsional fatigue testing was conducted with 6 mm diameter round bar specimens. Torsional fatigue endurance was found to monotonously increase with increases in the tensile strength of the specimen from 540 to 1380 MPa. The martensitic single structure and the M+F dual-phase structure showed a similar level of fatigue endurance at a tensile strength of approximately 950 MPa. However, fatigue micro-crack morphology varied slightly between them. At the surface of the M+F specimen, many small cracks were observed in addition to the main crack. Conversely, in the martensitic specimen, these small cracks were rarely observed. ΔK decreasing/increasing crack growth testing with compact tension (CT)-type specimens was also conducted. Based on these experimental results, the effect of microstructure and stress level on the initiation/propagation cycle ratio is discussed. In addition to fatigue properties, some practical properties, such as low-temperature toughness and hydrogen embrittlement resistance, were also evaluated in view of actual applications for automotive structural parts.

  11. Detection of Fatigue Damage in a Steel Member

    DEFF Research Database (Denmark)

    Rytter, A.; Brincker, Rune; Hansen, Lars Pilegaard

    In this paper the posibilities of detection of crack extension in a steel beam by observation of changes in the dynamical response are investigated. System changes are observed by frequency domain and time domain techniques. The position and the size of the crack by finite element calculations. T...

  12. Detection of Fatigue Damage in a Steel Member

    DEFF Research Database (Denmark)

    Rytter, Anders; Brincker, Rune; Hansen, Lars Pilegaard

    1991-01-01

    In this paper the possibilities of detection of crack extension in a steel beam by observation of changes in the dynamical response are investigated. System changes are observed by frequency domain and the time domain techniques. The position and the size of the crack are found by finite element ...

  13. Fatigue experiments on connections made of very high strength steels

    NARCIS (Netherlands)

    Pijpers, R.; Kolstein, H.; Bijlaard, F.

    2013-01-01

    An effective application of Very High Strength Steels (VHSS) can be expected in truss-like structures, typically made of hollow sections. Improved design of VHSS truss structures could incorporate the application of cast joints, since an appropriate design of cast joints limits the stress

  14. Fatigue testing structural steel as a factor of safety of technical facilities maintenance

    Directory of Open Access Journals (Sweden)

    Robert Ulewicz

    2013-04-01

    Full Text Available Guarantee of quality and safety exploitation of machines and equipment is a significant factor in the design and manufacture of these components. This paper presents an analysis of fatigue test results of samples in the bending load on the rotation in the range from 104 to 107 ,the number of cycles of applied load, with a frequency of 40 Hz. Whöler curve shows the results of the fatigue properties of steel S355J2 which is used in the construction of vehicles. There was also carried out a fractographic analysis.

  15. Hydrogen-enhanced fatigue crack growth in steels and its frequency dependence

    Science.gov (United States)

    Matsunaga, Hisao; Takakuwa, Osamu; Yamabe, Junichiro; Matsuoka, Saburo

    2017-06-01

    In the context of the fatigue life design of components, particularly those destined for use in hydrogen refuelling stations and fuel cell vehicles, it is important to understand the hydrogen-induced, fatigue crack growth (FCG) acceleration in steels. As such, the mechanisms for acceleration and its influencing factors are reviewed and discussed in this paper, with a special focus on the peculiar frequency dependence of the hydrogen-induced FCG acceleration. Further, this frequency dependence is debated by introducing some potentially responsible elements, along with new experimental data obtained by the authors. This article is part of the themed issue 'The challenges of hydrogen and metals'.

  16. Fatigue of micromachined stainless steel structural materials for vibrational energy harvesting

    Science.gov (United States)

    Shimizu, Y.; Van Minh, L.; Kitayoshi, H.; Kuwano, H.

    2016-11-01

    This work presents fatigue measurement for micromachined stainless steel (SUS304) structural substrate using resonant bending mode. Micromachined specimens for fatigue test had a cantilever structure with a proof mass. They were fabricated by FeCl3 wet etching and wire-discharged cutting. The SUS specimens had Young's modulus of 198 GPa on average. The endurance limit of micromachined specimens was 213 MPa on average after 108 cycles under our fracture definition. The large SUS specimens had the endurance limit of 229 MPa after 107 cycles.

  17. Effect of welding processes and consumables on fatigue crack growth behaviour of armour grade quenched and tempered steel joints

    Directory of Open Access Journals (Sweden)

    G. Magudeeswaran

    2014-03-01

    Full Text Available Quenched and Tempered (Q&T steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking (HIC in the heat affected zone (HAZ after welding. The use of austenitic stainless steel (ASS consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel (LHF consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. The use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. This microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&T steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&T Steel joints. Shielded metal arc welding (SMAW and Flux cored arc welding (FCAW were used for fabrication of joints using ASS and LHF consumables. The joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.

  18. Development of heavy steel plate for Mayflower Resolution, special purpose vessel for erection of offshore wind towers

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, W.; Schroeter, F.

    2005-05-15

    Special problems necessitate special solutions. Installation vessels for the erection of offshore wind towers are subject to extremely demanding design and structural specifications. Such projects are made possible only by the use of high strength, fine grained structural steels possessing good toughness properties even at extremely low temperatures; in addition, such steels must also offer good workability. Such steel plate material exhibits mechanical properties greatly superior to those possessed by conventional shipbuilding plate. This article focuses on the material for such an installation vessel and the underlying steel development work performed at AG der Dillinger Huettenwerke. (author)

  19. FATIGUE BEHAVIOR OF HOT-ROLLED STEEL INTENDED FOR COLD FORMING

    Directory of Open Access Journals (Sweden)

    Gejza Rosenberg

    2011-07-01

    Full Text Available In the work, there are presented measured tension and fatigue properties of eight low-carbon steels moulded in form of 20 kg ingots that were processed by controlled regime of rolling /cooling and then exposed to simulated effect of two coiling temperatures. The experimental results presented in the work show, that steels with ferrite-martensite or ferrite-bainitic microstructure have in comparison to ferrite-pearlitic or ferrite-carbidic microstructure better strength-plastic properties, but worse resistance to cyclic loading.

  20. Stress Corrosion-Cracking and Corrosion Fatigue Impact of IZ-C17+ Zinc Nickel on 4340 Steel

    Science.gov (United States)

    2017-05-17

    REPORT NO: NAWCADPAX/TIM-2016/189 STRESS CORROSION-CRACKING AND CORROSION FATIGUE IMPACT OF IZ-C17+ ZINC-NICKEL ON 4340 STEEL by...DEPARTMENT OF THE NAVY NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION PATUXENT RIVER, MARYLAND NAWCADPAX/TIM-2016/189 STRESS ...5a. CONTRACT NUMBER STRESS CORROSION-CRACKING AND CORROSION FATIGUE IMPACT OF IZ-C17+ ZINC-NICKEL ON 4340 STEEL 5b. GRANT NUMBER 5c. PROGRAM

  1. A numerical method for predicting the bending fatigue life of NiTi and stainless steel root canal instruments.

    Science.gov (United States)

    Cheung, G S P; Zhang, E W; Zheng, Y F

    2011-04-01

    To evaluate the bending fatigue lifetime of nickel-titanium alloy (NiTi) and stainless steel (SS) endodontic files using finite element analysis. The strain-life approach was adopted and two theoretical geometry profiles, the triangular (TR) and the square cross-sections, were considered. Both low-cycle fatigue (LCF) lifetime and high-cycle fatigue (HCF) lifetime were evaluated. The bending fatigue behaviour was affected by the material property and the cross-sectional configuration of the instrument. Both the cross-section factor and material property had a substantial impact on fatigue lifetime. The NiTi material and TR geometry profiles were associated with better fatigue resistance than that of SS and square cross-sections. Within the limitations of this study, finite element models were established for endodontic files to prejudge their fatigue lifetime, a tool that would be useful for dentist to prevent premature fatigue fracture of endodontic files. © 2010 International Endodontic Journal.

  2. IAEA international studies on irradiation embrittlement of reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Brumovsky, M. [Nuclear Research Institute Rez plc (Czech Republic); Steele, L.E. [Chief Scientific Investigator of the Programme, Springfield, VA (United States)

    1997-02-01

    In last 25 years, three phases a Co-operative Research Programme on Irradiation Embrittlement of Reactor Pressure Vessel Steels has been organized by the International Atomic Energy Agency. This programme started with eight countries in 1971 and finally 16 countries took part in phase III of the Programme in 1983. Several main efforts were put into preparation of the programme, but the principal task was concentrated on an international comparison of radiation damage characterization by different laboratories for steels of {open_quotes}old{close_quotes} (with high impurity contents) and {open_quotes}advanced{close_quotes} (with low impurity contents) types as well as on development of small scale fracture mechanics procedures applicable to reactor pressure vessel surveillance programmes. This year, a new programme has been opened, concentrated mostly on small scale fracture mechanics testing.

  3. Effect of shot peening coverage on fatigue limit in round bar of annealed medium carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Junji; Lee, Yong Sung; Seong Kyun [Seoul National Univ., Seoul (Korea, Republic of)

    2014-09-15

    Shot peening is an effective and economical technique for improving the fatigue strength of metallic components by inducing compressive residual stress and hardening the layer near the surface. The effect is generally evaluated by main two parameters: coverage and peening intensity. However, the valuable coverage for improving the fatigue strength depends on the shape of the target material. In this study, the effect of coverage on fatigue limit in round bar of annealed medium carbon steel was experimentally studied. The fatigue limits for shot peened round bar specimens with 140-2300% coverage increased 14-25% by comparing those for non-peened round bar specimens. The valuable range of coverage was 280-560% in the used material and shot peening condition for improving the fatigue limit in short time. The result indicates that the valuable coverage of the round bar material is higher than full coverage to improve the fatigue limit of the material due to the effect of incident angle on round bar, even though the degree depends on the materials and shot peening conditions.

  4. Embrittlement recovery due to annealing of reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Eason, E.D.; Wright, J.E.; Nelson, E.E. [Modeling and Computing Services, Boulder, CO (United States); Odette, G.R.; Mader, E.V. [Univ. of California, Santa Barbara, CA (United States)

    1996-03-01

    Embrittlement of reactor pressure vessels (RPVs) can be reduced by thermal annealing at temperatures higher than the normal operating conditions. Although such an annealing process has not been applied to any commercial plants in the United States, one US Army reactor, the BR3 plant in Belgium, and several plants in eastern Europe have been successfully annealed. All available Charpy annealing data were collected and analyzed in this project to develop quantitative models for estimating the recovery in 30 ft-lb (41 J) Charpy transition temperature and Charpy upper shelf energy over a range of potential annealing conditions. Pattern recognition, transformation analysis, residual studies, and the current understanding of the mechanisms involved in the annealing process were used to guide the selection of the most sensitive variables and correlating parameters and to determine the optimal functional forms for fitting the data. The resulting models were fitted by nonlinear least squares. The use of advanced tools, the larger data base now available, and insight from surrogate hardness data produced improved models for quantitative evaluation of the effects of annealing. The quality of models fitted in this project was evaluated by considering both the Charpy annealing data used for fitting and the surrogate hardness data base. The standard errors of the resulting recovery models relative to calibration data are comparable to the uncertainty in unirradiated Charpy data. This work also demonstrates that microhardness recovery is a good surrogate for transition temperature shift recovery and that there is a high level of consistency between the observed annealing trends and fundamental models of embrittlement and recovery processes.

  5. Flexural fatigue characteristics of steel fiber reinforced recycled aggregate concrete (SFRRAC)

    OpenAIRE

    Heeralal M.; Kumar Rathish P.; Rao Y.V.

    2009-01-01

    This research work is aimed at investigating the flexural fatigue behavior of Steel Fiber Reinforced Recycled Aggregate Concrete (SFRRAC). This study gains importance in view of the wide potential for demolished concrete to serve as a source of quality aggregate feed stock in a variety of structural and non-structural applications. This is a continuation of a series of investigations being conducted aimed at optimizing the utilization of recycled aggregate concrete in rigid pavements. A total...

  6. Evaluation of fatigue damage in steels using Preisach model analysis of magnetic hysteresis measurements

    Science.gov (United States)

    Lo, C. C. H.; Melikhov, Y. Y.; Kadlecová, J.; Perevertov, O. V.; Tomáš, I.; Ring, A. P.; Jiles, D. C.

    2001-04-01

    The Preisach model analysis of magnetic hysteresis measurements has been applied to evaluate the microstructural changes in steels subjected to cyclic loading. Families of hysteresis loops were measured to obtain the Preisach-like functions. Barkhausen effect signals were also measured. The Preisach representation was found to be more sensitive to the increase in the number of stress cycles during the stable fatigue stage than the traditional hysteresis loop properties and Barkhausen effect signals.

  7. Distribution of Corrosion Fatigue Crack Lengths in Carbon Steel : 1st Report, The Cracks Which Grow Individually

    OpenAIRE

    Ishihara, Sotomi; Shiozawa, Kazuaki; Miyao, Kazyu

    1985-01-01

    It has been known that very small distributed cracks can be observed on the surface of a smooth specimen subjected to corrosion fatigue. The fracture process can be characterized by the interaction and coalescence of these small distributed cracks. In order to analize this corrosion fatigue fracture process, high cycle fatigue tests were performed on carbon steel sheet specimens under completely reversed plane bending stresses in salt water (3.0%NaCl). Initiation and growth of cracks on the s...

  8. Normalizing effect on fatigue crack propagation at the heat-affected zone of AISI 4140 steel shielded metal arc weldings

    OpenAIRE

    B. Vargas-Arista; J. Teran-Guillen; Solis, J.; García-Cerecero,G.; Martínez-Madrid,M.

    2013-01-01

    The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ) of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughne...

  9. Nonlinear Lamb waves for fatigue damage identification in FRP-reinforced steel plates.

    Science.gov (United States)

    Wang, Yikuan; Guan, Ruiqi; Lu, Ye

    2017-09-01

    A nonlinear Lamb-wave-based method for fatigue crack detection in steel plates with and without carbon fibre reinforcement polymer (CFRP) reinforcement is presented in this study. Both numerical simulation and experimental evaluation were performed for Lamb wave propagation and its interaction with a fatigue crack on these two steel plate types. With the generation of the second harmonic, the damage-induced wave nonlinearities were identified by surface-bonded piezoelectric sensors. Numerical simulation revealed that the damage-induced wave component at the second harmonic was slightly affected by the existence of CFRP laminate, although the total wave energy was decreased because of wave leakage into the CFRP laminate. Due to unavoidable nonlinearity from the experimental environments, it was impractical to directly extract the time-of-flight of the second harmonic for locating the crack. To this end, the correlation coefficient of benchmark and signal with damage at double frequency in the time domain was calculated, based on which an imaging method was introduced to locate the fatigue crack in steel plates with and without CFRP laminates. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Rolling-contact fatigue resistance of hard coatings on bearing steels.

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, A.

    1999-08-18

    Ball- and roller-bearings of the 21st Century are expected to perform better and last longer while operating under more stringent conditions than before. To meet these great expectations, researchers have been constantly exploring new bearing designs or refining existing ones, optimizing microstructure and chemistry of bearing materials, and alternatively, they have been considering the use of thin hard coatings for improved bearing performance and durability. Already, some laboratory tests have demonstrated that hard nitride, carbide (such as TiN, TiC, etc.) and diamondlike carbon (DLC) coatings can be very effective in prolonging the fatigue lives of bearing steels. This paper provides an overview of the recent developments in hard coatings for bearing applications. Previous studies have demonstrated that thin, hard coatings can effectively prolong the fatigue lives of bearing steel substrates. In particular, thinner hard coatings (i.e., 0.2 - 1 {micro}m thick) provide exceptional improvements in the fatigue lives of bearing steel substrates. In contrast, thicker hard coatings suffer micro fracture and delamination when tested under high contact stresses, hence are ineffective and may even have a negative effect on bearing life. Overall, it was concluded that thin hard coatings may offer new possibilities for bearing industry in meeting the performance and durability needs of the 21st Century.

  11. Three-dimensional observations of magnetic flux density around fatigue crack tips of bearing steels

    Science.gov (United States)

    Kida, Katsuyuki; Santos, Edson C.; Honda, Takashi; Tanabe, Hirotaka

    2010-03-01

    Fatigue failure of steel occurs when small cracks form in a component and then continue to grow to a size large enough to cause failure. In order to understand the strength of steel components it is important to find these cracks. However, at present, it is not easy to distinguish the cracks that will grow fast and cause failure. We developed a three-dimensional scanning Hall probe microscope (3D-SHPM) and observed fatigue cracks at room temperature while they were growing. Four-point-bending fatigue tests were carried out using pre-cracked specimens (JIS-SUJ2, bearing steel). We observed the two-dimensional magnetic flux density distributions around the crack tips and found that there is a strong correlation between the changes in the magnetic flux densities and the crack growth. In order to understand this, we looked into all the three components of the magnetic flux densities, and found that they shape an arched bridge around a crack. We also found that the magnetic flux density moves in front of the crack tip along the crack growth direction.

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

    Directory of Open Access Journals (Sweden)

    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.

  13. Creep-fatigue damage characteristics for a welded cylindrical structure of austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeo Yeon; Kim, Jong Bum; Kim, Seok Hoon; Joo, Young Sang; Lee, Jae Han [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2004-07-01

    In the design and assessment of a high temperature structure, it is important to ensure the structural integrity for the welded joint subjected to a creep-fatigue load because a statistical investigation shows that 29 events out of 46 leaks in liquid metal reactors were caused at the welded joints. As for the structural integrity due to thermal ratchet load at the welded joint, KAERI has performed the test and analysis work for a cylindrical structure with welded joints. As a continuation of the study on welded joints at a high temperature structure, a creep-fatigue structural test and analysis work is now on-going and this paper present the interim findings for the structural test and analysis work. Recently the structural and analysis work for the Y-piece made of a 316L stainless steel structure has been carried out. The objectives of the present structural creep-fatigue test with the welded cylindrical specimen are to compare the creep-fatigue damage mechanisms for the 304 and 316L stainless steels, to compare the different behavior of the welding methods in a high temperature austenitic structures and to quantify the conservatism of the design guidelines for a high temperature structure.

  14. Fatigue and fracture assessment of cracks in steel elements using acoustic emission

    Science.gov (United States)

    Nemati, Navid; Metrovich, Brian; Nanni, Antonio

    2011-04-01

    Single edge notches provide a very well defined load and fatigue crack size and shape environment for estimation of the stress intensity factor K, which is not found in welded elements. ASTM SE(T) specimens do not appear to provide ideal boundary conditions for proper recording of acoustic wave propagation and crack growth behavior observed in steel bridges, but do provide standard fatigue crack growth rate data. A modified versions of the SE(T) specimen has been examined to provide small scale specimens with improved acoustic emission(AE) characteristics while still maintaining accuracy of fatigue crack growth rate (da/dN) versus stress intensity factor (ΔK). The specimens intend to represent a steel beam flange subjected to pure tension, with a surface crack growing transverse to a uniform stress field. Fatigue test is conducted at low R ratio. Analytical and numerical studies of stress intensity factor are developed for single edge notch test specimens consistent with the experimental program. ABAQUS finite element software is utilized for stress analysis of crack tips. Analytical, experimental and numerical analysis were compared to assess the abilities of AE to capture a growing crack.

  15. Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel

    Science.gov (United States)

    Krantz, Timothy; Tufts, Brian

    2007-01-01

    The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.

  16. Development of High Strength and High Toughness Steels for Reactor Vessel and Surgeline Pipe

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. S.; Kim, M. C.; Yoon, J. H.; Kim, K. B.; Choi, K. J.; Cho, H. D.

    2010-07-15

    In addition to evaluating the effects of alloying elements, heat treatment conditions, weldability and neutron irradiation behavior were evaluated with 15 types of SA508 Gr.4N model alloys for reactor pressure vessel. The maximum yield strength of 630MPa were obtained by controlling chemical compositions and heat treatment conditions. Model alloys also showed excellent impact toughness and fracture toughness. The microstructure and mechanical properties of weld heat affected zone were evaluated by using simulated specimens and the effects of post weld heat treatment conditions were also investigated. Neutron irradiation behavior at high fluence level were characterized and then compared with commercial reactor pressure vessel steel. The value of transition temperature shift(TTS) was 22 .deg. C at 6.4x10{sup 19} n/cm{sup 2} which is similar to commercial RPV steel. However, its toughness after irradiation is much better than that of unirradiated commercial RPV steel due to the superior initial toughness. Leak-before-break(LBB) properties of type 316 stainless steel model alloys and their welds for surge line were evaluated as well as microstructure and mechanical properties. Tensile tests and J-R fracture resistance tests were carried out at RT and 316 .deg. C. The model alloys showed good tensile strength over standard value, except type 316L which has lower C/N. In the LBB safety analysis result, all of type 316 model alloys have higher allowable load than that of OPR1000 surge line

  17. Effect of Welding Consumables on Fatigue Performance of Shielded Metal Arc Welded High Strength, Q&T Steel Joints

    Science.gov (United States)

    Magudeeswaran, G.; Balasubramanian, V.; Madhusudhan Reddy, G.

    2009-02-01

    Quenched and Tempered (Q&T) steels are widely used in the construction of military vehicles due to their high strength-to-weight ratio and high hardness. These steels are prone to hydrogen-induced cracking in the heat affected zone (HAZ) after welding. The use of austenitic stainless steel consumables to weld the above steel was the only remedy because of higher solubility for hydrogen in austenitic phase. Recent studies proved that high nickel steel and low hydrogen ferritic steel consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. In this investigation an attempt has been made to study the effect of welding consumables on high cycle fatigue properties of high strength, Q&T steel joints. Three different consumables namely (i) austenitic stainless steel, (ii) low hydrogen ferritic steel, and (iii) high nickel steel have been used to fabricate the joints by shielded metal arc (SMAW) welding process. The joints fabricated using low hydrogen ferritic steel electrodes showed superior fatigue properties than other joints.

  18. On the role of microstructure in governing the fatigue behaviour of nanostructured bainitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Rementeria, Rosalia, E-mail: rosalia.rementeria@cenim.csic.es [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain); Morales-Rivas, Lucia, E-mail: lucia.morales@cenim.csic.es [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain); Kuntz, Matthias, E-mail: matthias.kuntz2@de.bosch.com [Robert Bosch GmbH, Materials and Processing Department, Renningen, 70465 Stuttgart (Germany); Garcia-Mateo, Carlos, E-mail: cgm@cenim.csic.es [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain); Kerscher, Eberhard, E-mail: kerscher@mv.uni-kl.de [University of Kaiserslautern, Materials Testing, Gottlieb-Damiler-Straße, 67663 Kaiserslautern (Germany); Sourmail, Thomas, E-mail: thomas.sourmail@ascometal.com [Ascometal-CREAS (Research Centre) Metallurgy, BP 70045, Hagondange Cedex 57301 (France); Caballero, Francisca G., E-mail: fgc@cenim.csic.es [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain)

    2015-04-10

    Nanostructured bainite is not a novel laboratory-scale steel anymore and the interest on the commercial production of these microstructures by steelmakers and end-users is now conceivable. These microstructures are achieved through the isothermal transformation of high-carbon high-silicon steels at low temperature, leading to nanoscale plates of ferrite with thickness of 20–40 nm and retained austenite. Nanostructured bainitic steels present the highest strength/toughness combinations ever recorded in bainitic steels (2.2 GPa/40 MPa m{sup 1/2}) and the potential for engineering components is alluring. However, fatigue properties, responsible of the durability of a component, remain to be examined. In order to understand the role of the microstructure during the fatigue crack propagation, the crack path in three nanoscale bainitic structures has been analysed on the basis of the relationships between grain misorientations and grain boundaries by Electron Backscatter Diffraction. Active slip systems in bainitic ferrite and crack deflection at grain boundaries have been identified, while retained austenite is cast doubt on its role.

  19. Nondestructive characterization of embrittlement in reactor pressure vessel steels -- A feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    McHenry, H.I.; Alers, G.A. [National Inst. of Standards and Technology, Boulder, CO (United States). Materials Reliability Div.

    1998-03-01

    The Nuclear Regulatory Commission recently initiated a study by NIST to assess the feasibility of using physical-property measurements for evaluating radiation embrittlement in reactor pressure vessel (RPV) steels. Ultrasonic and magnetic measurements provide the most promising approaches for nondestructive characterization of RPV steels because elastic waves and magnetic fields can sense the microstructural changes that embrittle materials. The microstructural changes of particular interest are copper precipitation hardening, which is the likely cause of radiation embrittlement in RPV steels, and the loss of dislocation mobility that is an attribute of the ductile-to-brittle transition. Measurements were made on a 1% copper steel, ASTM grade A710, in the annealed, peak-aged and overaged conditions, and on an RPV steel, ASTM grade A533B. Nonlinear ultrasonic and micromagnetic techniques were the most promising measures of precipitation hardening. Ultrasonic velocity measurements and the magnetic properties associated with hysteresis-loop measurements were not particularly sensitive to either precipitation hardening or the ductile-to-brittle transition. Measurements of internal friction using trapped ultrasonic resonance modes detected energy losses due to the motion of pinned dislocations; however, the ultrasonic attenuation associated with these measurements was small compared to the attenuation caused by beam spreading that would occur in conventional ultrasonic testing of RPVs.

  20. Fatigue Properties of SUS304 Stainless Steel after Ultrasonic Nanocrystal Surface Modification (unsm)

    Science.gov (United States)

    Zhang, K. Y.; Pyoun, Y. S.; Cao, X. J.; Wu, B.; Murakami, R.

    The changing of materials surface properties method always was taken into improving the fatigue strength. In this paper, an ultrasonic nanocrystal surface modification(UNSM) technique was used on the SUS 304 stainless steel to form a nanostructured surface layer with different static load(70N, 90N, 110N, 130N) and the vibration strike number was about 20,000times/mm2. The untreated and different condition specimens fatigue strength was all tested by a dual-spindle rotating bending fatigue test machine. SPring-8(a large synchrotron radiation facility) was used to test the surface nanocrystallization components. The X-ray diffraction (XRD), the scanning electron microscopy (SEM), optical microscope and a micro-Vickers hardness tester (MVK-E3, Akashi) were separately used to get the surface residual stresses, fracture surface after fatigue testing, metallographic structure and the microhardness of the nanostructured surface layer. The result showed that martensite transformation took place on the surface of specimens, the surface residual stresses had only a small increase and some cracks occurred between the martensite layer and the austenite layer, but the fatigue strength of 90N improved 81%.

  1. Simultaneous life extension and crack monitoring of fatigue-damaged steel members using multifunctional carbon nanotube based composites

    Science.gov (United States)

    Ahmed, Shafique; Schumacher, Thomas; Thostenson, Erik T.; McConnell, Jennifer

    2017-04-01

    Steel structures including bridges are susceptible to cracking, particularly due to fatigue-sensitive details found in older designs. Therefore, one of the major challenges to keep those steel bridges in service is to rehabilitate existing and potential fatigue damage. There are several conventional approaches to extend the fatigue-life of damaged steel members, e.g., drilling a crack stop-hole to reduce the stress concentration at the crack tip as well as welding and bolting of steel plates or adhesive-bonding of fiber-reinforced polymers (FRP) to reduce the overall stresses. Improvement in material properties of FRP and adhesives make them a viable candidate to apply for extending the fatigue-life of steel members. However, drawbacks include the potential for debonding of the adhesive layer and/or interfaces between adhesive and adherents as well as difficulty in monitoring fatigue crack growth after rehabilitation. In this research, a holistic approach is proposed and evaluated for simultaneous extension of fatigue-life and monitoring by integrating a carbon nanotube (CNT)-based sensing layer with an adhesively-bonded FRP reinforcement. CNT-based sensing layers have a nerve-like electric resistance network, which enables distributed sensing capabilities to monitor stress levels, crack growth, and damage progression. Using laboratory-scale experiments, the simultaneous fatigue-life extension and crack monitoring capability of multifunctional CNT-based composites was evaluated. This paper introduces the fundamental concept of integrated fatigue-rehabilitation and monitoring of steel members, presents a laboratory-scale experiment to demonstrate the feasibility and effectiveness, and discusses challenges for implementation in real structures.

  2. Effect of orientation of small defects on fatigue limit of steels

    Directory of Open Access Journals (Sweden)

    Lorenzino Pablo

    2014-06-01

    Full Text Available In order to clarify the effect of defect orientation on the fatigue limit of three types of steels; JIS-S15C, JIS-S45C and JIS-SNCM439, a small semi-circular slit was introduced into the surface of a round specimen. The slits were tilted at 0∘, 30∘ or 60∘ with respect to the plane normal to the loading axis, but all of them had the same defect size, \\vec{area} See Formula in PDF = 188 μm, where the area denotes the area of the domain defined by projecting the defect on a plane normal to the loading axis. In all the combinations of the materials and tilting angles, a non-propagating crack was found at the fatigue limit, i.e. the fatigue limit was determined by the non-propagation condition of crack initiated from the defect. In JIS-S15C and JIS-S45C, the fatigue limit was nearly independent of the tilting angle, which was in good agreement with the predicted value by the \\vec{area} See Formula in PDF parameter model. On the other hand, in JIS-SNCM439, the fatigue limit was also in agreement with the prediction at the tilting angle of 0∘, but it increased with an increase in the tilting angle. These results indicated that the \\vec{area} See Formula in PDF parameter model can predict a conservative fatigue limit for the tilted defects. In this paper, the mechanistic reason for the effect of the tilting angle on the fatigue limit will be discussed by paying special attention to the crack path and length of non-propagating crack.

  3. Microstructure and Fatigue Properties of Laser Welded DP590 Dual-Phase Steel Joints

    Science.gov (United States)

    Xie, Chaojie; Yang, Shanglei; Liu, Haobo; Zhang, Qi; Cao, Yaming; Wang, Yuan

    2017-08-01

    In this paper, cold-rolled DP590 dual-phase steel sheets with 1.5 mm thickness were butt-welded by a fiber laser, and the evolution and effect on microhardness, tensile property and fatigue property of the welded joint microstructure were studied. The results showed that the base metal is composed of ferrite and martensite, with the martensite dispersed in the ferrite matrix in an island manner. The microstructure of the weld zone was lath-shaped martensite that can be refined further by increasing the welding speed, while the heat-affected zone was composed of ferrite and tempered martensite. The microhardness increased with increasing welding speed, and the hardness reached its highest value—393.8 HV—when the welding speed was 5 m/min. Static tensile fracture of the welded joints always occurred in the base metal, and the elongation at break was more than 16%. The conditional fatigue limits of the base metal and the weld joints were 354.2 and 233.6 MPa, respectively, under tension-tension fatigue tests with a stress rate of 0.1. After observation of the fatigue fracture morphology, it was evident that the fatigue crack of the base metal had sprouted into the surface pits and that its expansion would be accelerated under the action of a secondary crack. The fatigue source of the welded joint was generated in the weld zone and expanded along the martensite, forming a large number of fatigue striations. Transient breaking, which occurred in the heat-affected zone of the joint as a result of the formation of a large number of dimples, reflected the obvious characteristics of ductile fracture.

  4. Effect of corrosion and sandblasting on the high cycle fatigue behavior of reinforcing B500C steel bars

    Directory of Open Access Journals (Sweden)

    Marina C. Vasco

    2017-10-01

    Full Text Available In a series of applications, steel reinforced concrete structures are subjected to fatigue loads during their service life, what in most cases happens in corrosive environments. Surface treatments have been proved to represent proper processes in order to improve both fatigue and corrosion resistances. In this work, the effect of corrosion and sandblasting on the high cycle fatigue behavior reinforcing steel bars is investigated. The investigated material is the reinforcing steel bar of technical class B500C, of nominal diameter of 12 mm. Steel bars specimens were first exposed to corrosion in alternate salt spray environment for 30 and 60 days and subjected to both tensile and fatigue tests. Then, a series of specimens were subjected to common sandblasting, corroded and mechanically tested. Metallographic investigation and corrosion damage evaluation regarding mass loss and martensitic area reduction were performed. Tensile tests were conducted after each corrosion exposure period prior to the fatigue tests. Fatigue tests were performed at a stress ratio, R, of 0.1 and loading frequency of 20 Hz. All fatigue tests series as well as tensile test were also performed for as received steel bars to obtain the reference behavior. The results have shown that sandblasting hardly affects the tensile behavior of the uncorroded material. The effect of sandblasting on the tensile behavior of pre-corroded specimens seems to be also limited. On the other hand, fatigue results indicate an improved fatigue behavior for the sandblasted material after 60 days of corrosion exposure. Martensitic area reductions, mass loss and depth of the pits were significantly smaller for the case of sandblasted materials, which confirms an increased corrosion resistance

  5. Weldability and toughness evaluation of pressure vessel quality steel using the shielded metal arc welding (SMAW) process

    Science.gov (United States)

    Datta, R.; Mukerjee, D.; Mishra, S.

    1998-12-01

    The present study was carried out to assess the weldability properties of ASTM A 537 Cl. 1 pressure-vessel quality steel using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were conducted under different welding conditions to determine the cold cracking susceptibility of the steel. The static fatigue limit values determined for the implant test indicate adequate resistance to cold cracking even with unbaked electrodes. The ERC test, however, established the necessity to rebake the electrodes before use. Lamellar tearing tests carried out using full-thickness plates under three welding conditions showed no incidence of lamellar tearing upon visual examination, ultrasonic inspection, and four-section macroexamination. Lamellar tearing tests were repeated using machined plates, such that the central segregated band located at the midthickness of the plate corresponded to the heat-affected zone (HAZ) of the weld. Only in one (no rebake, heat input: 14.2 kj cm-1, weld restraint load: 42 kg mm-2) of the eight samples tested was lamellar tearing observed. This was probably accentuated due to the combined effects of the presence of localized pockets of a hard phase (bainite) and a high hydrogen level (unbaked electrodes) in the weld joint. Optimal welding conditions were formulated based on the above tests. The weld joint was subjected to extensive tests and found to exhibit excellent strength (tensile strength: 56.8 kg mm-2, or 557 MPa), and low temperature impact toughness (7.4 and 4.5 kg-m at-20 °C for weld metal, WM, and HAZ) properties. Crack tip opening displacement tests carried out for the WM and HAZ resulted in δm values 0.36 and 0.27 mm, respectively, which indicates adequate resistance to brittle fracture.

  6. Fatigue behavior of superferritic stainless steel laser shock treated without protective coating

    Science.gov (United States)

    Spadaro, L.; Gomez-Rosas, G.; Rubio-González, C.; Bolmaro, R.; Chavez-Chavez, A.; Hereñú, S.

    2017-08-01

    The laser shock peening (LSP) is a new technique that improves the fatigue life of metallic components by inducing deep compressive residual stresses through the surface. However, the beneficial effects of LSP depend on the persistence and stability of such residual stress fields under cyclic loading and temperature. Moreover, if no absorbent coating is used in LSP operation, thermal effects can occur on the metallic substrate. The purpose of this work is to study the influence of LSP, without protective coating and with different pulse densities, on the low cyclic fatigue behavior of a superferritic stainless steel UNS S 44600. These results are correlated with observations performed by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with electron diffraction spectroscopy (EDS). The hole-drilling method is used to measure residual stresses. The micro-hardness and roughness profiles are also presented. This paper shows that LSP without coating produces beneficial compression residual stresses. However, in the first 10 μm beneath the surface, thermal effects occur that induce intergranular corrosion. This intergranular corrosion deteriorates the fatigue properties of a superferritic stainless steel UNS S 44600.

  7. Small fatigue crack propagation in Y2O3 strengthened steels

    Science.gov (United States)

    Hutař, P.; Kuběna, I.; Ševčík, M.; Šmíd, M.; Kruml, T.; Náhlík, L.

    2014-09-01

    This paper is focused on two type of Y2O3 strengthened steels (Fe-14Cr ODS and ODS-EUROFER). Small fatigue crack propagation was experimentally measured using special small cylindrical specimens (diameter 2 and 2.6 mm) with shallow notch grinded in the gauge length. In the middle of this notch, a pre-crack of length of 50 μm was fabricated using a focused ion beam technique. Fatigue crack growth rate was measured for different applied total strain amplitudes and described using plastic part of the J-integral. Obtained results were compared with published data of EUROFER 97. The effect of the oxide dispersion on small fatigue crack propagation was found rather insignificant. Ferritic Fe-14Cr ODS steel shows more brittle behaviour, i.e. for the same cyclic plasticity, characterised by the plastic part of the J-integral, the small cracks grow faster. A new methodology for residual lifetime prediction of structures containing physically small cracks, based on plastic part of the J-integral, is presented.

  8. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part II. Fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, B., E-mail: margolinbz@yandex.ru; Minkin, A.; Smirnov, V.; Sorokin, A.; Shvetsova, V.; Potapova, V.

    2016-11-15

    The experimental data on the fatigue crack growth rate (FCGR) have been obtained for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various radiation swelling. The performed study of the fracture mechanisms for cracked specimens under cyclic loading has explained why radiation swelling affects weakly FCGR unlike its effect on fracture toughness. Mechanical modeling of fatigue crack growth has been carried out and the dependencies for prediction of FCGR in irradiated austenitic steel with and with no swelling are proposed and verified with the obtained experimental results. As input data for these dependencies, FCGR for unirradiated steel and the tensile mechanical properties for unirradiated and irradiated steels are used.

  9. Low cycle fatigue properties of CLAM steel at 450 °C and 550 °C

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yanyun; Zhai, Xiangwei; Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn

    2016-11-15

    Highlights: • Low cycle fatigue properties of CLAM steel were investigated at 450 °C and 550 °C. • CLAM steel showed the continuous softening up to fail failure under cyclic loading. The degree of softening increased with increasing temperature. • Dislocation density decrease and subgrain coarsening during the test process were the possible reasons for the cyclic softening of the CLAM steel. - Abstract: The low cycle fatigue behavior of China Low Activation Martensitic (CLAM) steel has been studied using a constant strain rate of 8 × 10{sup −3}/s with the strain amplitudes ranging from 0.3% to 0.8% at 450 °C and 550 °C. Cyclic stress response showed a gradual softening until complete failure. The fatigue life decreased with increasing test temperature, and the effect of temperature on fatigue life was more pronounced at lower strain amplitudes. The cyclic deformation behavior at different temperatures has been analyzed according to the hysteresis loop, and the mechanism of cyclic softening was interpreted in view of the changes taking place in dislocation density and lath structures. Evaluation of low cycle fatigue properties of CLAM steel at 450 °C and 550 °C can help in design of the Chinese Test Blanket Module (TBM) for the International Thermonuclear Experimental Reactor (ITER) and a future fusion power plant.

  10. Material Characterization of Fatigue Specimens made from Meta-stable Austenitic Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Niffenegger, M.; Grosse, M.; Kalkhof, D.; Leber, H. [Paul Scherrer Institut Villigen (Switzerland); Vincent, A.; Pasco, L.; Morin, M. [Insa de Lyon (France)

    2003-07-01

    The main objective of the EU-project CRETE (Contract No.: FIS5-1999-00280) was to assess the capability and the reliability of innovative NDT-inspection techniques for the detection of material degradation, induced by thermal fatigue and neutron irradiation, of metastable austenitic and ferritic low-alloy steel. Several project partners tested aged or irradiated samples, using various techniques (acoustic, magnetic and thermoelectric). However, these indirect methods require a careful interpretation of the measured signal in terms of micro-structural evolutions due to ageing of the material. Therefore the material had to be characterized in its undamaged, as well as in its damaged state. The present report summarises only the material characterization of the fatigue specimens. It is issued simultaneously as an PSI Bericht and the CRETE work package 3 (WP3) report. Each partner according to their own specifications purchased three materials under investigation, namely AISI 347, AISI 321 and AISI 304L. After sending the material to PSI, all fatigue specimens were manufactured by the same Swiss company. Each partner was responsible for his fatigue tests which are documented in the report WP1, written by FANP. In order to characterize the material in its unfatigued as well as in its fatigued state and to consider microstructural changes related to fatigue damage the methods listed below were employed either by PSI or by INSA de Lyon: (1) Inductive Coupled Plasma Emission Photometry (ICP-OES) was applied to determine the chemical composition, (2) Scanning electron microscopy (SEM) for observing cracks, slip bands between grain and twin boundaries, - Ferromaster for measuring the magnetic permeability, (3) Physical Properties Measuring System (PPMS) for measuring magnetization characteristics, (4) Neutron- and advanced X-ray diffraction methods for the quantitative determination of martensite, - Transmission electron microscopy (TEM) for the observation of crystalline

  11. Characterisation of creep cavitation damage in a stainless steel pressure vessel using small angle neutron scattering

    CERN Document Server

    Bouchard, P J; Treimer, W

    2002-01-01

    Grain-boundary cavitation is the dominant failure mode associated with initiation of reheat cracking, which has been widely observed in austenitic stainless steel pressure vessels operating at temperatures within the creep range (>450 C). Small angle neutron scattering (SANS) experiments at the LLB PAXE instrument (Saclay) and the V12 double-crystal diffractometer of the HMI-BENSC facility (Berlin) are used to characterise cavitation damage (in the size range R=10-2000 nm) in a variety of creep specimens extracted from ex-service plant. Factors that affect the evolution of cavities and the cavity-size distribution are discussed. The results demonstrate that SANS techniques have the potential to quantify the development of creep damage in type-316H stainless steel, and thereby link microstructural damage with ductility-exhaustion models of reheat cracking. (orig.)

  12. Welding simulation and fatigue assessment of tubular K-joints in high-strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Zamiri Akhlaghi, F.

    2014-07-01

    Application of newly developed high strength steel hollow sections is increasing in construction industry – especially for bridge structures – due to their satisfactory material properties and fabrication advantages. These sections allow for longer spans, more slender structures. Savings in weight and volume of material compared to traditional steel grades increase sustainability of construction and compensate for part of higher unit cost of material. Nevertheless, use of high strength steels cannot be promoted unless potential fatigue issues are properly addressed. Two fabrication methods are currently available for the planar Warren trusses made of circular hollow sections (CHS): welding the tubes together, or using cast steel nodes and connecting truss members to them by girth welds. Previous research on tubular bridge trusses indicates that the problematic fatigue cracking sites for the first fabrication method are located at weld toes in the gap region of the truss joints. For the second method, cracking occurs at the root of CHS–cast butt welds. Fatigue performance of these two methods were investigated by constant amplitude fatigue testing of two full scale trusses made of steel grade S690QH and with a geometry similar to previous S355J2H investigation. Fatigue lives of K-joints were in agreement with current recommended code values. For CHS–cast welded connections, no visible cracking was observed up to 2£10{sup 6} cycles. Due to the effect of residual stresses, fatigue cracking was observed in compressive joints as well as tensile joints. Indeed, tensile welding residual stresses keep the crack open during all or part of the compressive load cycle. Their distribution and impact on fatigue life of tubular joints has not been fully investigated before for a complex detail such as Tubular K-joint made of high strength steel. Experimental and numerical methods were utilized for assessment of welding residual stresses. Neutron diffraction experiments

  13. Current understanding on the neutron irradiation embrittlement of BWR reactor pressure vessel steels in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Asano, K.; Nishiyama, T. [TEPCO (Japan); Soneda, N.; Dohi, K.; Nishida, K.; Nomoto, A. [CRIEPI (Japan); Ohta, T. [Japan Atomic Power Co. (Japan); Ishimaru, Y. [Chugoku EPCO (Japan); Yoneda, H. [Hokuriku EPCO (Japan); Lida, J. [Tohoku EPCO (Japan); Yuya, H. [Chubu EPCO (Japan)

    2011-07-01

    Neutron irradiation embrittlement of reactor pressure vessel (RPV) steels has been of concern primarily for the pressurized water reactors (PWRs). After long operation experiences, we are now becoming aware of the situation that the neutron irradiation embrittlement is also of concern for some of the boiling water reactors (BWRs) particularly with Cu-containing RPV steels. The surveillance data of Cu-containing BWR RPV steels show relatively larger shift in ductile-to-brittle transition temperature of fracture toughness than predicted by the embrittlement correlation method developed in late eighties and early nineties. Accurate evaluation of the amount of embrittlement is now very important for long-term operation of BWRs. In this paper, we will describe the neutron irradiation embrittlement of BWR RPVs in Japan. Some of the materials that show relatively large transition temperature shifts are investigated to understand the causes of embrittlement using state-of-the-art microstructural characterization techniques. Furthermore, some archive materials of such RPVs are irradiated in a material testing reactor with high neutron flux to understand the effect of flux on transition temperature shifts and corresponding microstructural changes. Microstructural evolution under irradiation, solute clustering in particular could explain the differences in transition temperature shift of the analyzed specimens. Larger BWR RPVs, which have larger water gaps, receive less neutron irradiation and harmful impurities in steels such as copper are well controlled since 1980 so irradiation embrittlement in BWR vessels can now be considered a concern only in old and small plants. All the new information obtained through these activities was considered in the development of new embrittlement correlation that is now adopted in JEAC 4201- 2007 of Japan Electric Association

  14. Corrosion fatigue studies on F82H mod. martensitic steel in reducing water coolant environments

    Energy Technology Data Exchange (ETDEWEB)

    Maday, M.F.; Masci, A. [ENEA, Casaccia (Italy). Centro Ricerche Energia

    1998-03-01

    Load-controlled low cycle fatigue tests have been carried out on F82H martensitic steel in 240degC oxygen-free water with and without dissolved hydrogen, in order to simulate realistic coolant boundary conditions to be approached in DEMO. It was found that water independently of its hydrogen content, determined the same fatigue life reduction compared to the base-line air results. Water cracks exhibited in their first propagation stages similar fracture morphologies which were completely missing on the air cracks, and were attributed to the action of an environment related component. Lowering frequency gave rise to an increase in F82H fatigue lifetimes without any change in cracking mode in air, and to fatigue life reduction by microvoid coalescence alone in water. The data were discussed in terms of (i) frequency dependent concurrent processes for crack initiation and (ii) frequency-dependent competitive mechanisms for crack propagation induced by cathodic hydrogen from F82H corrosion. (author)

  15. Hydrogen Assisted Cracking in Pearlitic Steel Rods: The Role of Residual Stresses Generated by Fatigue Precracking

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2017-05-01

    Full Text Available Stress corrosion cracking (SCC of metals is an issue of major concern in engineering since this phenomenon causes many catastrophic failures of structural components in aggressive environments. SCC is even more harmful under cathodic conditions promoting the phenomenon known as hydrogen assisted cracking (HAC, hydrogen assisted fracture (HAF or hydrogen embrittlement (HE. A common way to assess the susceptibility of a given material to HAC, HAF or HE is to subject a cracked rod to a constant extension rate tension (CERT test until it fractures in this harsh environment. This paper analyzes the influence of a residual stress field generated by fatigue precracking on the sample’s posterior susceptibility to HAC. To achieve this goal, numerical simulations were carried out of hydrogen diffusion assisted by the stress field. Firstly, a mechanical simulation of the fatigue precracking was developed for revealing the residual stress field after diverse cyclic loading scenarios and posterior stress field evolution during CERT loading. Afterwards, a simulation of hydrogen diffusion assisted by stress was carried out considering the residual stresses after fatigue and the superposed rising stresses caused by CERT loading. Results reveal the key role of the residual stress field after fatigue precracking in the HAC phenomena in cracked steel rods as well as the beneficial effect of compressive residual stress.

  16. Hydrogen Assisted Cracking in Pearlitic Steel Rods: The Role of Residual Stresses Generated by Fatigue Precracking.

    Science.gov (United States)

    Toribio, Jesús; Aguado, Leticia; Lorenzo, Miguel; Kharin, Viktor

    2017-05-02

    Stress corrosion cracking (SCC) of metals is an issue of major concern in engineering since this phenomenon causes many catastrophic failures of structural components in aggressive environments. SCC is even more harmful under cathodic conditions promoting the phenomenon known as hydrogen assisted cracking (HAC), hydrogen assisted fracture (HAF) or hydrogen embrittlement (HE). A common way to assess the susceptibility of a given material to HAC, HAF or HE is to subject a cracked rod to a constant extension rate tension (CERT) test until it fractures in this harsh environment. This paper analyzes the influence of a residual stress field generated by fatigue precracking on the sample's posterior susceptibility to HAC. To achieve this goal, numerical simulations were carried out of hydrogen diffusion assisted by the stress field. Firstly, a mechanical simulation of the fatigue precracking was developed for revealing the residual stress field after diverse cyclic loading scenarios and posterior stress field evolution during CERT loading. Afterwards, a simulation of hydrogen diffusion assisted by stress was carried out considering the residual stresses after fatigue and the superposed rising stresses caused by CERT loading. Results reveal the key role of the residual stress field after fatigue precracking in the HAC phenomena in cracked steel rods as well as the beneficial effect of compressive residual stress.

  17. Influence of Residual Stress Field on the Fatigue Crack Propagation in Prestressing Steel Wires

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2015-11-01

    Full Text Available This paper deals with the effect of several residual stress profiles on the fatigue crack propagation in prestressing steel wires subjected to tension loading or bending moment. To this end, a computer program was developed to evaluate the crack front evolution on the basis of the Walker law. Results demonstrate that the absence of residual stresses makes the crack propagate towards a preferential crack path. When surface residual stresses are tensile and, correspondingly, core residual stresses are compressive, the fatigue crack fronts rapidly converge towards a quasi-straight shape. When surface residual stresses are compressive, with their corresponding tensile stresses in the core area, a preferential crack path also appears.

  18. Fatigue damage accumulation and lifetime prediction of defective C35 steel subjected to block loading

    Directory of Open Access Journals (Sweden)

    Sallem Haifa

    2014-06-01

    Full Text Available This paper deals with the influence of both defect and loading sequence on fatigue damage accumulation of C35 steel containing artificial defects. Tests were carried out using fatigue samples with artificial spherical defects introduced at the surface. Tests were performed using two blocks loading under increasing and decreasing magnitude. The experimental results were compared to the damage calculated by the Miner rule. In the case of defective material; it is shown in both cases a minor influence of sequence’s effect. A lifetime prediction method is then developed to assess the residual lifetime of damaged defective material. The method is based on a multiaxial endurance criterion used to calculate the equivalent local stress distribution around the defect and to inject it in an uniaxial damage cumulative rule. Finally a comparison between experimental and theoretical results is performed. It is observed that the Mesmacque sequential law gives the most accurate lifetime prediction of defective specimens.

  19. Lower Length Scale Model Development for Embrittlement of Reactor Presure Vessel Steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schwen, Daniel [Idaho National Lab. (INL), Idaho Falls, ID (United States); Chakraborty, Pritam [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bai, Xianming [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-09-01

    This report summarizes the lower-length-scale effort during FY 2016 in developing mesoscale capabilities for microstructure evolution, plasticity and fracture in reactor pressure vessel steels. During operation, reactor pressure vessels are subject to hardening and embrittlement caused by irradiation induced defect accumulation and irradiation enhanced solute precipitation. Both defect production and solute precipitation start from the atomic scale, and manifest their eventual effects as degradation in engineering scale properties. To predict the property degradation, multiscale modeling and simulation are needed to deal with the microstructure evolution, and to link the microstructure feature to material properties. In this report, the development of mesoscale capabilities for defect accumulation and solute precipitation are summarized. A crystal plasticity model to capture defect-dislocation interaction and a damage model for cleavage micro-crack propagation is also provided.

  20. Creep crack growth in a reactor pressure vessel steel at 360 deg C

    Energy Technology Data Exchange (ETDEWEB)

    Rui Wu; Seitisleam, F.; Sandstroem, R. [Swedish Institute for Metals Research, Stockholm (Sweden)

    1998-12-31

    Plain creep (PC) and creep crack growth (CCG) tests at 360 deg C and post metallography were carried out on a low alloy reactor pressure vessel steel (ASTM A508 class 2) with different microstructures. Lives for the CCG tests were shorter than those for the PC tests and this is more pronounced for simulated heat affected zone microstructure than for the parent metal at longer lives. For the CCG tests, after initiation, the cracks grew constantly and intergranularly before they accelerated to approach rupture. The creep crack growth rate is well described by C*. The relations between reference stress, failure time and steady crack growth rate are presented for the CCG tests. It is demonstrated that the failure stress due to CCG is considerably lower than the yield stress at 360 deg C. Consequently, the CCG will control the static strength of a reactor vessel. (orig.) 17 refs.

  1. Low cycle fatigue of 2.25Cr1Mo steel with tensile and compressed hold loading at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Junfeng; Yu, Dunji; Zhao, Zizhen; Zhang, Zhe; Chen, Gang; Chen, Xu, E-mail: xchen@tju.edu.cn

    2016-06-14

    A series of uniaxial strain-controlled fatigue and creep-fatigue tests of the bainitic 2.25Cr1Mo steel forging were performed at 455 °C in air. Three different hold periods (30 s, 120 s, 300 s) were employed at maximum tensile strain and compressive strain under fully reversed strain cycling. Both tensile and compressive holds significantly reduce the fatigue life. Fatigue life with tensile hold is shorter than that with compressive hold. A close relationship is found between the reduction of fatigue life and the amount of stress relaxation. Microstructural examination by scanning electron microscope reveals that strain hold introduces more crack sources, which can be probably ascribed to the intensified oxidation and the peeling-off of oxide layers. A modified plastic strain energy approach considering stress relaxation effect is proposed to predict the creep-fatigue life, and the predicted lives are in superior agreement with the experimental results.

  2. Fatigue Property of Open-Hole Steel Plates Influenced by Bolted Clamp-up and Hole Fabrication Methods

    Directory of Open Access Journals (Sweden)

    Zhi-Yu Wang

    2016-08-01

    Full Text Available Steel plates with open holes are commonly used in structural assemblies. The fatigue properties of such details are influenced by bolted clamp-up and hole fabrication methods. The fracture surface, stiffness degradation and fatigue life of test specimens are investigated in detail and compared with the contemporary test data. The analysis results show that the presence of draglines greatly influences the fatigue crack initiation at the open-hole cut by laser. The bolted clamp-up condition greatly enhances the stiffness and the fatigue life of the open-hole details. A discussion is also made from a comparison with the referred fatigue life of hole fabrication details, such as the influence of plate thickness and plasma cutting, drilling and oxy-fuel gas cutting, with the details studied herein. This work could enhance the understanding of the fatigue property and design of such details.

  3. Standard practice for examination of seamless, gas-filled, steel pressure vessels using angle beam ultrasonics

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice describes a contact angle-beam shear wave ultrasonic technique to detect and locate the circumferential position of longitudinally oriented discontinuities and to compare the amplitude of the indication from such discontinuities to that of a specified reference notch. This practice does not address examination of the vessel ends. The basic principles of contact angle-beam examination can be found in Practice E 587. Application to pipe and tubing, including the use of notches for standardization, is described in Practice E 213. 1.2 This practice is appropriate for the ultrasonic examination of cylindrical sections of gas-filled, seamless, steel pressure vessels such as those used for the storage and transportation of pressurized gasses. It is applicable to both isolated vessels and those in assemblies. 1.3 The practice is intended to be used following an Acoustic Emission (AE) examination of stacked seamless gaseous pressure vessels (with limited surface scanning area) described in Test Met...

  4. Effect on property of HIC-Resistance of vessel steel of PWHT

    Science.gov (United States)

    Zhao, Xinyu; Zou, Yang; Qin, Liye; Lv, Yanchun

    2017-09-01

    Post-Welding Heat Treatment (PWHT) is usually taken after welding and joining of vessel steel, which effects the mechanical and Hydrogen Induced Cracking (HIC) resistance property of vessel plates. Simulating PWHT experiment was taken to research on the effect on mechanical property and HIC-resistance of PWHT of vessel plates. Some conclusions can be summarized as following. Comparing with the normalizing samples, the tensile strength of the samples after PWHT with holding time of 2h, 6h and 20h decreases by 27MPa, 44MPa and 47MPa. Ductile Brittle Transition Temperature (DBTT) of the normalizing samples was almost close to those of the samples after PWHT. But the impact energy of samples at 0°C increased with rise of PWHT holding time. And the hardness of samples decreases with rise of PWHT holding time. As shown in morphology structure, the precipitation of carbonide increases with the rise of holding time of PWHT, which decreases the strength and hardness of samples and raises the impact energy. But PWHT has a little effect on HIC-Resistance, which means PWHT don't deteriorate property of HIC-Resistance of vessel plates severely.

  5. Experimental evaluation of the fretting fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2013-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. A method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires along the length of the monostrand. The experimental data...... indicate that the interwire movement due to transverse deformations is highest at the neutral axis of the monostrand. The results showthat the midspan and the anchorage of the monostrand are the two locationswhere the combination of tensile strains and the interwire friction is the most unfavorable...

  6. Fatigue and fracture of three austenitic stainless steels at cryogenic temperatures

    Science.gov (United States)

    McRae, D. M.; Balachandran, S.; Walsh, R. P.

    2017-12-01

    For the past couple decades, 316LN stainless steel has remained the “go-to” alloy for structural components intended for cryogenic temperature service, partially because of its favorable mechanical properties, but also because of the data available in the literature for T = 4 K. In recent years, some interest has arisen to investigate and develop stronger and tougher alloys for cryogenic structural components, particularly for magnet systems like ITER. This study presents new 4 K fatigue crack growth rate (FCGR) and fracture toughness data for Nitronic® 50 and JK2LB stainless steels, compiles existing data for these alloys, and compares them with 316LN data found in literature. This study intends to further expand the existing cryogenic data set for these alloys, clarify key differences between them to better facilitate mechanical design, and potentially bolster further alloy development.

  7. Effect of composition and processing on the thermal fatigue and toughness of high performance die steels. Year 1 report

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, J.F.; Wang, Yumin; Schwam, D.

    1996-06-01

    The goal of this project is to extend the lifetime of dies for die casting by 20%. Since the die contributes about 10% to the cost of die cast parts, such an improvement in lifetime would result in annual savings of over $200 Million dollars. This is based on the estimated annual die production of one Billion dollars in the US. The major tasks of this two year project are: (1) Evaluate NEW DIE STEEL COMPOSITIONS that have been developed for demanding applications and compare them to Premium Grade H-13 die steel. (2) Optimize the AUSTENITIZING TREATMENT of the new composition. Assess the effects of fast, medium and slow COOLING RATES DURING HEAT TREATMENT, on the thermal fatigue resistance and toughness of the die steel. (3) Determine the effect of ELECTRO-DISCHARGE MACHINING (EDM) on the thermal fatigue resistance and impact properties of the steel. (4) Select demanding components and conduct IN-PLANT TESTING by using the new steel. Compare the performance of the new steel with identical components made of Premium Grade H-13. The immersion thermal fatigue specimen developed at CWRU is being used to determine resistance to heat checking, and the Charpy V-notch test for evaluating the toughness. The overall result of this project will be identification of the best steel available on the market and the best processing methods for aluminum die casting dies. This is an interim report for year 1 of the project.

  8. The thermal fatigue behaviour of creep-resistant Ni-Cr cast steel

    Directory of Open Access Journals (Sweden)

    B. Piekarski

    2007-12-01

    Full Text Available The study gives a summary of the results of industrial and laboratory investigations regarding an assessment of the thermal fatigue behaviour of creep-resistant austenitic cast steel. The first part of the study was devoted to the problem of textural stresses forming in castings during service, indicating them as a cause of crack formation and propagation. Stresses are forming in carbides and in matrix surrounding these carbides due to considerable differences in the values of the coefficients of thermal expansion of these phases. The second part of the study shows the results of investigations carried out to assess the effect of carbon, chromium and nickel on crack resistance of austenitic cast steel. As a criterion of assessment the amount and propagation rate of cracks forming in the specimens as a result of rapid heating followed by cooling in running water was adopted. Tests were carried out on specimens made from 11 alloys. The chemical composition of these alloys was comprised in a range of the following values: (wt-%: 18-40 %Ni, 17-30 %Cr, 1.2-1.6%Si and 0.05-0.6 %C. The specimens were subjected to 75 cycles of heating to a temperature of 900oC followed by cooling in running water. After every 15 cycles the number of the cracks was counted and their length was measured. The results of the measurements were mathematically processed. It has been proved that the main factor responsible for an increase in the number of cracks is carbon content in the alloy. In general assessment of the results of investigations, the predominant role of carbon and of chromium in the next place in shaping the crack behaviour of creep-resistant austenitic cast steel should be stressed. Attention was also drawn to the effect of high-temperature corrosion as a factor definitely deteriorating the cast steel resistance to thermal fatigue.

  9. Influence of Carbon Content on Fatigue Strength of Drawn Steel Tubes for Small Once-Through Boiler

    Science.gov (United States)

    Yonekura, Daisuke; Fujie, Yuta; Murakami, Ri-Ichi; Tokunaga, Yukihiro

    Tension-tension fatigue tests were performed to examine the influence of carbon content on the fatigue properties of drawn specific steel tube (STB340) with/without post heat treatment for small once-through boiler. Two different carbon content steel tubes, C=0.06 and 0.12% were prepared. The as-received, as-drawn and post drawing heat treated series for each carbon content tube were prepared for fatigue test. The hardness, grain size and residual stress were measured for each series. As a result, the fatigue strength of as-received and as-drawn series showed a small difference between C=0.06 and 0.12% specimens. However, the post drawing heat treatment series showed obvious difference in the fatigue strength. The fatigue strength of higher carbon content tubes significantly decreased by the post drawing heat treatment, whereas the decrease of fatigue strength was little for lower carbon content heat treated tubes. The difference of fatigue strength was mainly caused by the degree of relaxation of work hardening by post heat treatment.

  10. Fatigue

    Science.gov (United States)

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-04-01

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

  12. Exploratory Study of Irradiation, Annealing, and Reirradiation Effects on American and Russian Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Chernobaeva, A.A., Kryukov, A.M., Nikolaev, Y.A., Korolev, Y.N. [Russian Research Centre Kurchatov Inst., Moscow (Russian Federation)], Sokolov, M.A., Nanstad, R.K. [Oak Ridge National Lab., TN (United States)

    1997-12-31

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPVS) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. even though a postirradiation anneal may be deemed successful, a critical aspect of continued RPV operation is the rate of embrittlement upon reirradiation. There are insufficient data available to allow for verification models of reirradiation embrittlement or for the development of a reliable predictive methodology. This is especially true in the case of fracture toughness data. Under the U.S.-Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS), Working Group 3 on Radiation Embrittlement, Structural Integrity, and Life Extension of Reactor Vessels and Supports agreed to conduct a comparative study of annealing and reirradiation effects on RPV steels. The working group agreed that each side would irradiate, anneal, reirradiate (if feasible), and test two materials of the other; so far, only charpy impact and tensile specimens have been included. Oak Ridge National Laboratory (ornl) conducted such a program (irradiation and annealing) with two weld metals representative of VVER-440 AND VVER-1000 RPVS, while the Russian Research Center-Kurchatov Institute (RRC-KI) conducted a program (irradiation,annealing, reirradiation, and reannealing) with Heavy-Section Steel Technology (HSST) program plate 02 and Heavy-Section Steel Irradiation (HSSI) program weld 73w. The results for each material from each laboratory are compared with those from the other laboratory. the ORNL experiments with the VVER welds included irradiation to about 1 x 10 (exp 19) N/SQ CM ({gt}1 MeV), while the RRC-KI experiments with the U.S. materials included irradiations from about 2 to 18 X 10 (exp 19) N/SQ CM ({gt}1 MeV).

  13. Irradiation, Annealing, and Reirradiation Effects on American and Russian Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Chernobaeva, A.A.; Korolev, Y.N.; Nanstad, R.K.; Nikolaev, Y.A.; Sokolov, M.A.

    1998-06-16

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPVs) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. Even though a postirradiation anneal may be deemed successful, a critical aspect of continued RPV operation is the rate of embrittlement upon reirradiation. There are insufficient data available to allow for verification of available models of reirradiation embrittlement or for the development of a reliable predictive methodology. This is especially true in the case of fracture toughness data. Under the U.S.-Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS), Working Group 3 on Radiation Embrittlement, Structural Integrity, and Life Extension of Reactor Vessels and Supports agreed to conduct a comparative study of annealing and reirradiation effects on RPV steels. The Working Group agreed that each side would irradiate, anneal, reirradiate (if feasible ), and test two materials of the other. Charpy V-notch (CVN) and tensile specimens were included. Oak Ridge National Laboratory (ORNL) conducted such a program (irradiation and annealing, including static fracture toughness) with two weld metals representative of VVER-440 and VVER-1000 RPVs, while the Russian Research Center-Kurchatov Institute (RRC-KI) conducted a program (irradiation, annealing, reirradiation, and reannealing) with Heavy-Section Steel Technology (HSST) Program Plate 02 and Heavy-Section Steel Irradiation (HSSI) Program Weld 73W. The results for each material from each laboratory are compared with those from the other laboratory. The ORNL experiments with the VVER welds included irradiation to about 1 x 10{sup 19} n/cm{sup 2} (>1 MeV), while the RRC-KI experiments with the U.S. materials included irradiations from about 2 to 18 x 10{sup 19} n/cm{sup 2} (>l MeV). In both cases, irradiations were conducted at {approximately}290 C and annealing treatments were conducted

  14. An investigation of rolling-sliding contact fatigue damage of carburized gear steels

    Science.gov (United States)

    Kramer, Patrick C.

    The goal of this study was to evaluate the differences in RSCF performance between vacuum and gas carburized steels as well as to investigate the evolution of damage (wear and microstructure changes) leading to pitting. Vacuum and gas carburizing was performed on two gear steels (4120 and 4320) at 1010°C. The carburized specimens were tested in the as-carburized condition using a RSCF machine designed and built at the Colorado School of Mines. The tests were conducted at 3.2 GPa nominal Hertzian contact stress, based on pure rolling, 100°C, and using a negative twenty percent slide ratio. Tests were conducted to pitting failure for each condition for a comparison of the average fatigue lives. Pure rolling tests were also conducted, and were suspended at the same number of cycles as the average RSCF life for a comparison of fatigue damage developed by RCF and RSCF. Incremental tests were suspended at 1,000, 10,000, 100,000, and 200,000 cycles for the vacuum carburized steels to evaluate the wear and damage developed during the initial cycles of RSCF testing and to relate the wear and damage to pitting resistance. Incremental damage was not investigated for gas carburizing due to the limited number of available specimens. The vacuum carburized samples showed a decreased pitting fatigue resistance over the gas carburized samples, possibly due to the presence of bainite in the vacuum carburized cases. Pitting was observed to initiate from surface micropitting and microcracking. A microstructural change induced by contact fatigue, butterflies, was shown to contribute to micropitting and microcracking. Incremental testing revealed that the formation of a microcrack preceded and was necessary for the formation of the butterfly features, and that the butterfly features developed between 10,000 and 100,000 cycles. The orientation and depth of butterfly formation was shown to be dependent upon the application of traction stresses from sliding. RSCF butterflies formed

  15. Effect of unit size on thermal fatigue behavior of hot work steel repaired by a biomimetic laser remelting process

    Science.gov (United States)

    Cong, Dalong; Li, Zhongsheng; He, Qingbing; Chen, Dajun; Chen, Hanbin; Yang, Jiuzhou; Zhang, Peng; Zhou, Hong

    2018-01-01

    AISI H13 hot work steel with fatigue cracks was repaired by a biomimetic laser remelting (BLR) process in the form of lattice units with different sizes. Detailed microstructural studies and microhardness tests were carried out on the units. Studies revealed a mixed microstructure containing martensite, retained austenite and carbide particles with ultrafine grain size in units. BLR samples with defect-free units exhibited superior thermal fatigue resistance due to microstructure strengthening, and mechanisms of crack tip blunting and blocking. In addition, effects of unit size on thermal fatigue resistance of BLR samples were discussed.

  16. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Keisler, J.; Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1995-08-01

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

  17. Measurement of fatigue accumulation in high-strength steels by microstructural examination

    Science.gov (United States)

    Nakagawa, Y. G.; Yoshizawa, H.; Lapides, M. E.

    1990-07-01

    Fatigue test bars fabricated from an SA508 class 3 low-carbon steel plate were cyclically deformed at 300 °C (constant low-cycle fatigue, total strain range Δɛ = 0.78 pct and 0.48 pct) to crack initiation (100 pct cumulative damage, CD) and to the factors 75, 50, and 25 pct CD. The test bars were cut perpendicular to the stress axis at the center of the gage length. The X-ray diffraction line-broadening (XRD) was performed on the cross sections created by the cuts. Thin foils (˜0.1-μm thick) were prepared from each cross section and used for the transmission electron microscope (TEM) and selected area diffraction (SAD) study. The half-value line breadth change measured by the XRD increased with the CD increase up to 50 pct, beyond which a significant reduction was observed for the 75 and 100 pct CD sample regardless of the incident X-ray beam angle. By the TEM, the undamaged material (0 pct CD) was characterized by high-angle boundaries, small carbide precipitates, and dislocation cell networks in grains. These characteristics did not show any appreciable changes in all of the samples with fatigue damage of the respective levels. Micro-orientation changes of the dislocation cells studied by the SAD of the foils and a statistical data analysis clearly demonstrated that the mean orientation difference in the cells and its standard deviation increased gradually as the CD increased.

  18. Phosphorus and carbon segregation: Effects on fatigue and fracture of gas-carburized modified 4320 steel

    Science.gov (United States)

    Hyde, R. S.; Krauss, G.; Matlock, D. K.

    1994-06-01

    Phosphorus and carbon segregation to austenite grain boundaries and its effects on fatigue and fracture were studied in carburized modified 4320 steel with systematic variations, 0.005, 0.017, and 0.031 wt pct, in alloy phosphorus concentration. Specimens subjected to bending fatigue were characterized by light metallography, X-ray analyses for retained austenite and residual stress measurements, and scanning electron microscopy (SEM) of fracture surfaces. Scanning Auger electron spectroscopy (AES) was used to determine intergranular concentrations of phosphorus and carbon. The degree of phosphorus segregation is directly dependent on alloy phosphorus and carbon content. The degree of carbon segregation, in the form of cementite, at austenite grain boundaries was found to be a function of alloy phosphorus concentration. The endurance limit and fracture toughness decreased slightly when alloy phosphorus concentration was increased from 0.005 to 0.017 wt pct. Between 0.017 and 0.031 wt pct phosphorus, the endurance limit and fracture toughness decreased substantially. Other effects related to increasing alloy phosphorus concentration include increased case carbon concentration, decreased case retained austenite, increased case compressive residual stresses, and increased case hardness. All of these results are consistent with the phosphorus-enhanced formation of intergranular cementite and a decrease in carbon solubility in intragranular austenite with increasing phosphorus concentration. Differences in fatigue and fracture correlate with the degree of cementite coverage on the austenite grain boundaries and the buildup of phosphorus at cementite/matrix interfaces because of the insolubility of phosphorus in cementite.

  19. Mechanism-Based Modeling for Low Cycle Fatigue of Cast Austenitic Steel

    Science.gov (United States)

    Wu, Xijia; Quan, Guangchun; Sloss, Clayton

    2017-09-01

    A mechanism-based approach—the integrated creep-fatigue theory (ICFT)—is used to model low cycle fatigue behavior of 1.4848 cast austenitic steel over the temperature range from room temperature (RT) to 1173 K (900 °C) and the strain rate range from of 2 × 10-4 to 2 × 10-2 s-1. The ICFT formulates the material's constitutive equation based on the physical strain decomposition into mechanism strains, and the associated damage accumulation consisting of crack nucleation and propagation in coalescence with internally distributed damage. At room temperature, the material behavior is controlled by plasticity, resulting in a rate-independent and cyclically stable behavior. The material exhibits significant cyclic hardening at intermediate temperatures, 673 K to 873 K (400 °C to 600 °C), with negative strain rate sensitivity, due to dynamic strain aging. At high temperatures >1073 K (800 °C), time-dependent deformation is manifested with positive rate sensitivity as commonly seen in metallic materials at high temperature. The ICFT quantitatively delineates the contribution of each mechanism in damage accumulation, and predicts the fatigue life as a result of synergistic interaction of the above identified mechanisms. The model descriptions agree well with the experimental and fractographic observations.

  20. Detection of Steel Fatigue Cracks with Strain Sensing Sheets Based on Large Area Electronics

    Directory of Open Access Journals (Sweden)

    Yao Yao

    2015-04-01

    Full Text Available Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with sensors of high spatial resolution. Technologies based on Large Area Electronics (LAE can enable direct sensing and can be scaled to the level required for Structural Health Monitoring (SHM of civil structures and infrastructure. Sensing sheets based on LAE contain dense arrangements of thin-film strain sensors, associated electronics and various control circuits deposited and integrated on a flexible polyimide substrate that can cover large areas of structures. This paper presents the development stage of a prototype strain sensing sheet based on LAE for crack detection and localization. Two types of sensing-sheet arrangements with size 6 × 6 inch (152 × 152 mm were designed and manufactured, one with a very dense arrangement of sensors and the other with a less dense arrangement of sensors. The sensing sheets were bonded to steel plates, which had a notch on the boundary, so the fatigue cracks could be generated under cyclic loading. The sensors within the sensing sheet that were close to the notch tip successfully detected the initialization of fatigue crack and localized the damage on the plate. The sensors that were away from the crack successfully detected the propagation of fatigue cracks based on the time history of the measured strain. The results of the tests have validated the general principles of the proposed sensing sheets for crack detection and identified advantages and challenges of the two tested designs.

  1. Low Cycle Fatigue behavior of SMAW welded Alloy28 superaustenitic stainless steel at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kchaou, Y., E-mail: yacinekchaou@yahoo.fr [Institut Pprime, Département Physique et Mécanique des Matériaux, UPR 3346 CNRS ISAE-ENSMA Université de Poitiers, Téléport 2, 1, avenue Clément Ader, BP 40109, F – 86961 Futuroscope Chasseneuil Cedex (France); Laboratoire de Génie des Matériaux et Environnement (LGME), ENIS, BPW 1173, Sfax (Tunisia); Pelosin, V.; Hénaff, G. [Institut Pprime, Département Physique et Mécanique des Matériaux, UPR 3346 CNRS ISAE-ENSMA Université de Poitiers, Téléport 2, 1, avenue Clément Ader, BP 40109, F – 86961 Futuroscope Chasseneuil Cedex (France); Haddar, N.; Elleuch, K. [Laboratoire de Génie des Matériaux et Environnement (LGME), ENIS, BPW 1173, Sfax (Tunisia)

    2016-01-10

    This paper focused on the study of Low Cycle Fatigue of welded joints of superaustenitic (Alloy28) stainless steels. Chemical composition and microstructure investigation of Base Metal (BM) and Weld Metal (WM) were identified. The results showed that both of composition is fully austenitic with a dendritic microstructure in the WM. Low cycle fatigue tests at different strain levels were performed on Base Metal (BM) and Welded Joint (WJ) specimens with a strain ratio R{sub ε}=−1. The results indicated that the fatigue life of welded joints is lower than the base metal. This is mainly due to the low ductility of the Welded Metal (WM) and the presence of welding defects. Simultaneously, Scanning Electron Microscope (SEM) observations of fractured specimens show that WJ have brittle behavior compared to BM with the presence of several welding defects especially in the crack initiation site. An estimation of the crack growth rate during LCF tests of BM and WJ was performed using distance between striations. The results showed that the crack initiation stage is shorter in the case of WJ compared to BM because of the presence of welding defects in WJ specimens.

  2. Fatigue crack initiation from small defects under low stress ratios in SAE52100 bearing steel

    Science.gov (United States)

    Hino, Y.; Matsunaga, H.

    2010-03-01

    Axial-loading fatigue tests were carried out under low stress ratios, R = -∞ ~ -5.33, by use of a cylindrical specimen of SAE52100 bearing steel having drill holes of 50 ~ 200 μm in diameter. The maximum stresses, σmax = 0 ~ 300 MPa were combined with the minimum stresses, σmin of -1600 or -1800 MPa. Even at σmax = 0, fatigue cracks were initiated at hole edges by cyclic compressive stress of σmin = -1800 MPa, and the cracks finally became non-propagating. When σmax was positive, fatigue cracks were initiated even at σmin = -1600 MPa and they also became non-propagating. The length of non-propagating cracks increased with an increase in σmax. Those phenomena were considered to be related to the tensile residual stress that was induced by the plastic deformation in the vicinity of hole edges. The relationship between the length of non-propagating crack and the residual stress field was investigated in terms of elastic-plastic finite element analysis.

  3. Structure-property relations for monotonic and fatigue loading conditions for a powder metal steel

    Science.gov (United States)

    Allison, Paul Galon

    Developing a multi-scale math-based model for powder metallurgy (PM) component design and performance prediction requires experimental calibration and validation. Monotonic tension, compression and torsion tests were performed at various porosity and temperatures to obtain the set of plasticity and damage constants required for model calibration. Uniaxial fatigue experiments were performed to determine the constants required for capturing the low cycle and high cycle fatigue characteristics of a PM steel. Optical microscopy of the material was performed prior to testing to quantify the initial state microstrucutral characteristics of each specimen. Tension tests on two different Bridgman notched specimens were undertaken to study the damage-triaxiality dependence for model validation. Validation of the model was further performed by monotonic component testing using PM bearing caps. Fracture surface analysis was performed using Scanning Electron Microscopy (SEM) to quantify the void nucleation and void sizes of the different specimens. The developed model will be used for optimizing component performance and design for PM parts. Key words: Powder Metallurgy, FC-0205, Mechanical Testing, Fatigue

  4. Effects of irradiation at lower temperature on the microstructure of Cr-Mo-V-alloyed reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Grosse, M.; Boehmert, J.; Gilles, R. [Hahn-Meitner-Institut Berlin GmbH (Germany)

    1998-10-01

    The microstructural damage process due to neutron irradiation [1] proceeds in two stages: - formation of displacement cascades - evolution of the microstructure by defect reactions. Continuing our systematic investigation about the microstructural changes of Russian reactor pressure vessel steel due to neutron irradiation the microstructure of two laboratory heats of the VVER 440-type reactor pressure vessel steel after irradiation at 60 C was studied by small angle neutron scattering (SANS). 60 C-irradiation differently changes the irradiation-induced microstructure in comparison with irradiation at reactor operation temperature and can, thus, provide new insights into the mechanisms of the irradiation damage. (orig.)

  5. Normalizing effect on fatigue crack propagation at the heat-affected zone of AISI 4140 steel shielded metal arc weldings

    Directory of Open Access Journals (Sweden)

    B. Vargas-Arista

    2013-01-01

    Full Text Available The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughness and critical crack length, and a transgranular brittle final fracture with an area fraction of dimple zones connecting cleavage facets. A fractographic analysis proved that as the normalizing time increased the crack length decreased. The increase in the river patterns on the fatigue crack propagation in zone II was also evidenced and final brittle fracture because of transgranular quasicleavage was observed. Larger grains induced a deterioration of the fatigue resistance of the HAZ.

  6. 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.

  7. Fretting fatigue behaviour of Ni-free high-nitrogen stainless steel in a simulated body fluid

    Directory of Open Access Journals (Sweden)

    Norio Maruyama, Sachiko Hiromoto, Eiji Akiyama and Morihiko Nakamura

    2013-01-01

    Full Text Available Fretting fatigue behaviour of Ni-free high-nitrogen steel (HNS with a yield strength of about 800 MPa, which was prepared by nitrogen gas pressurized electroslag remelting, was studied in air and in phosphate-buffered saline (PBS(-. For comparison, fretting fatigue behaviour of cold-rolled SUS316L steel (SUS316L(CR with similar yield strength was examined. The plain fatigue limit of HNS was slightly lower than that of SUS316L(CR although the former had a higher tensile strength than the latter. The fretting fatigue limit of HNS was higher than that of SUS316L(CR both in air and in PBS(-. A decrease in fatigue limit of HNS by fretting was significantly smaller than that of SUS316L(CR in both environments, indicating that HNS has better fretting fatigue resistance than SUS316L(CR. The decrease in fatigue limit by fretting is discussed taking into account the effect of friction stress due to fretting and the additional influences of wear, tribocorrosion and plastic deformation in the fretted area.

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

    Science.gov (United States)

    Sun, Chengqi; Liu, Xiaolong; Hong, Youshi

    2015-06-01

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

  9. Synchrotron 3D characterization of arrested fatigue cracks initiated from small tilted notches in steel

    Directory of Open Access Journals (Sweden)

    P. Lorenzino

    2015-07-01

    Full Text Available High resolution synchrotron X-ray tomography has been used to obtain 3D images of arrested cracks initiated at small artificial defects located on the surface of cylindrical steel specimens subjected to mode I fatigue loading. These defects consist in small semi-circular slits tilted at 0°, 30° or 60° with respect to the plane normal to the loading axis; all of them had the same defect size, area = 188 μm, where the area denotes the area of the domain defined by projecting the defect on a plane normal to the loading axis. Arrested cracks initiated from the notch were observed for all tilt angles at the surface of samples cycled at the fatigue limit (stress amplitude at which the specimen does not fail after 1×107 cycles. High resolution synchrotron X-ray tomography has been used to obtain 3D images of those small defects and non-propagating cracks (NPC. Despite the fact that steel is a highly attenuating material for X rays, high resolution 3D images of the cracks and of the initiating defects were obtained (0.65 m voxel size. The values of surface crack length measured by tomography are the same as those obtained by optical microscope measurements. The area values present the same tendency as the surface length of NPC, i.e. larger non-propagating cracks areas were observed in the softer steel. In the extreme case of 60º tilted defect, the crack fronts appear much more discontinuous with several cracks propagating in mode I until arrest.

  10. Visualization of Hydrogen Diffusion in a Hydrogen-Enhanced Fatigue Crack Growth in Type 304 Stainless Steel

    Science.gov (United States)

    Matsunaga, Hisao; Noda, Hiroshi

    2011-09-01

    To study the influence of hydrogen on the fatigue strength of AISI type 304 metastable austenitic stainless steel, specimens were cathodically charged with hydrogen. Using tension-compression fatigue tests, the behavior of fatigue crack growth from a small drill hole in the hydrogen-charged specimen was compared with that of noncharged specimen. Hydrogen charging led to a marked increase in the crack growth rate. Typical characteristics of hydrogen effect were observed in the slip band morphology and fatigue striation. To elucidate the behavior of hydrogen diffusion microscopically in the fatigue process, the hydrogen emission from the specimens was visualized using the hydrogen microprint technique (HMT). In the hydrogen-charged specimen, hydrogen emissions were mainly observed in the vicinity of the fatigue crack. Comparison between the HMT image and the etched microstructure image revealed that the slip bands worked as a pathway for hydrogen to move preferentially. Hydrogen-charging resulted in a significant change in the phase transformation behavior in the fatigue process. In the noncharged specimen, a massive type α' martensite was observed in the vicinity of the fatigue crack. On the other hand, in the hydrogen-charged specimen, large amounts of ɛ martensite and a smaller amount of α' martensite were observed along the slip bands. The results indicated that solute hydrogen facilitated the ɛ martensitic transformation in the fatigue process. Comparison between the results of HMT and EBSD inferred that martensitic transformations as well as plastic deformation itself can enhance the mobility of hydrogen.

  11. Forecasting Low-Cycle Fatigue Performance of Twinning-Induced Plasticity Steels: Difficulty and Attempt

    Science.gov (United States)

    Shao, C. W.; Zhang, P.; Zhang, Z. J.; Liu, R.; Zhang, Z. F.

    2017-10-01

    We find the existing empirical relations based on monotonic tensile properties and/or hardness cannot satisfactorily predict the low-cycle fatigue (LCF) performance of materials, especially for twinning-induced plasticity (TWIP) steels. Given this, we first identified the different deformation mechanisms under monotonic and cyclic deformation after a comprehensive study of stress-strain behaviors and microstructure evolutions for Fe-Mn-C alloys during tension and LCF, respectively. It is found that the good tensile properties of TWIP steel mainly originate from the large activation of multiple twinning systems, which may be attributed to the grain rotation during tensile deformation; while its LCF performance depends more on the dislocation slip mode, in addition to its strength and plasticity. Based on this, we further investigate the essential relations between microscopic damage mechanism (dislocation-dislocation interaction) and cyclic stress response, and propose a hysteresis loop model based on dislocation annihilation theory, trying to quickly assess the LCF resistance of Fe-Mn-C steels as well as other engineering materials. It is suggested that the hysteresis loop and its evolution can provide significant information on cyclic deformation behavior, e.g., (point) defect multiplication and vacancy aggregation, which may help estimate the LCF properties.

  12. Forecasting Low-Cycle Fatigue Performance of Twinning-Induced Plasticity Steels: Difficulty and Attempt

    Science.gov (United States)

    Shao, C. W.; Zhang, P.; Zhang, Z. J.; Liu, R.; Zhang, Z. F.

    2017-12-01

    We find the existing empirical relations based on monotonic tensile properties and/or hardness cannot satisfactorily predict the low-cycle fatigue (LCF) performance of materials, especially for twinning-induced plasticity (TWIP) steels. Given this, we first identified the different deformation mechanisms under monotonic and cyclic deformation after a comprehensive study of stress-strain behaviors and microstructure evolutions for Fe-Mn-C alloys during tension and LCF, respectively. It is found that the good tensile properties of TWIP steel mainly originate from the large activation of multiple twinning systems, which may be attributed to the grain rotation during tensile deformation; while its LCF performance depends more on the dislocation slip mode, in addition to its strength and plasticity. Based on this, we further investigate the essential relations between microscopic damage mechanism (dislocation-dislocation interaction) and cyclic stress response, and propose a hysteresis loop model based on dislocation annihilation theory, trying to quickly assess the LCF resistance of Fe-Mn-C steels as well as other engineering materials. It is suggested that the hysteresis loop and its evolution can provide significant information on cyclic deformation behavior, e.g., (point) defect multiplication and vacancy aggregation, which may help estimate the LCF properties.

  13. Characteristics of Modified 9Cr-1Mo Steel for Reactor Pressure Vessel of Very High Temperature Gas Cooled Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Ho; Ryu, W. S.; Han, Chang Hee; Yoon, J. H.; Chang, Jong Hwa

    2004-11-15

    Many researches and developments have been progressed for the construction of VHTR by 2020 in Korea. Modified 9Cr-1Mo steel has been receiving attention for the application to the reactor pressure vessel material of VHTR. We collected and analyzed the research data for modified 9Cr-1Mo steel in order to understand the characteristics of modified 9Cr-1Mo steel. The modified 9Cr-1Mo steel is a modified alloy system similar to conventional 9Cr-1Mo grade ferritic steel. Modifications include additions of vanadium, niobium, and nitrogen, as well as lower carbon content. In this report, we summarized the change of microstructure and mechanical properties after tempering, thermal aging, and irradiation. Modified 9Cr-1Mo steel has high strength and thermal conductivity, low thermal expansion, and good resistance to corrosion. But the irradiation embrittlement behavior of modified 9Cr-1Mo steel should be evaluated and the evaluation methodology also should be developed. At the same time, the characteristics of weldment which is the weak part in pressure vessel should be evaluated.

  14. CFRP-Strengthening and Long-Term Performance of Fatigue Critical Welds of a Steel Box Girder

    Directory of Open Access Journals (Sweden)

    Roland E. Koller

    2014-02-01

    Full Text Available Empa’s research efforts in the 1990s provided evidence that a considerable increase of the fatigue strength of welded aluminum beams can be achieved by externally bonding pultruded carbon fiber reinforced polymer (CFRP laminates using rubber-toughened epoxies over the fatigue-weak welding zone on their tensile flange. The reinforcing effect obtained is determined by the stiffness of the unidirectional CFRP laminate which has twice the elastic modulus of aluminum. One can therefore easily follow that an unstressed CFRP laminate reinforcement of welded beams made of steel will not lead to a substantial increase in fatigue strength of the steel structure. This consideration led to the idea of prestressing an external reinforcement of the welded zone. The present investigation describes experimental studies to identify the adhesive system suitable for achieving high creep and fatigue strength of the prestressed CFRP patch. Experimental results (Wöhler-fields of shear-lap-specimens and welded steel beams reinforced with prestressed CFRP laminates are presented. The paper concludes by presenting a field application, the reinforcement of a steel pendulum by adhesively bonded prestressed CFRP laminates to the tensile flanges of the welded box girder. Inspections carried out periodically on this structure revealed neither prestress losses nor crack initiation after nine years of service.

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

    Science.gov (United States)

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

    2017-09-01

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

  16. Consideration on fatigue strength of corroded steel plates; Fushoku suimo koban no hiro kyodo ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, M.; Yajima, H.; Yamamoto, M.; Saito, T. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1996-10-01

    Discussions were given on fatigue strength of corroded steel plates taken from a hull of a ship seventeen years old after construction. The steel plates have had their original thickness of 13 mm reduced to 5.3 to 8.3 mm. After having been cut by a machine, the steel plates were used for tests as ground plates after going through grinding and as corroded plates with rust remaining on them. The fatigue test was performed in artificially made sea water at a temperature of 25{degree}C and in air with axial power pulsating tensile load and at iterative loading velocities of 3 to 5 Hz. The corroded material test verified that corrosion pits exist innumerably on the test piece surface and fatigue cracks have been developed and grown from bottoms of the pits. The stress concentration coefficient of the corrosion pits was about 1.9. Good agreement with the test result was found in the S-N chart in which the number of iteration of fracture was regarded as the number of iteratively generated cracks, and notch coefficient was estimated as 1.9. These results proved that the fatigue strength assessing method for virgin materials can be applied also to steel plates which have been exposed to corrosive environment for extended periods of time. 5 refs., 7 figs., 1 tab.

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

    Science.gov (United States)

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

    2017-11-01

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

  18. Effect of Stress Ratio and Loading Frequency on the Corrosion Fatigue Behavior of Smooth Steel Wire in Different Solutions

    Directory of Open Access Journals (Sweden)

    Songquan Wang

    2016-09-01

    Full Text Available In this work, the effects of loading condition and corrosion solution on the corrosion fatigue behavior of smooth steel wire were discussed. The results of polarization curves and weight loss curves showed that the corrosion of steel wire in acid solution was more severe than that in neutral and alkaline solutions. With the extension of immersion time in acid solution, the cathodic reaction of steel wire gradually changed from the reduction of hydrogen ion to the reduction of oxygen, but was always the reduction of hydrogen ion in neutral and alkaline solutions. The corrosion kinetic parameters and equivalent circuits of steel wires were also obtained by simulating the Nyquist diagrams. In corrosion fatigue test, the effect of stress ratio and loading frequency on the crack initiation mechanism was emphasized. The strong corrosivity of acid solution could accelerate the nucleation of crack tip. The initiation mechanism of crack under different conditions was summarized according to the side and fracture surface morphologies. For the crack initiation mechanism of anodic dissolution, the stronger the corrosivity of solution was, the more easily the fatigue crack source formed, while, for the crack initiation mechanism of deformation activation, the lower stress ratio and higher frequency would accelerate the generation of corrosion fatigue crack source.

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

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-10-01

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

  20. Assessment of the microstructure and torsional fatigue performance of an induction hardened vanadium microalloyed medium-carbon steel

    Science.gov (United States)

    Rothleutner, Lee M.

    Vanadium microalloying of medium-carbon bar steels is a common practice in industry for a number of hot rolled as well as forged and controlled-cooled components. However, use of vanadium microalloyed steels has expanded into applications beyond their originally designed controlled-cooled processing scheme. Applications such as transmission shafts often require additional heat-treatments such as quench and tempering and/or induction hardening to meet packaging or performance requirements. As a result, there is uncertainty regarding the influence of vanadium on the properties of heat-treated components, specifically the effect of rapid heat-treating such as induction hardening. In the current study, the microstructural evolution and torsional fatigue behavior of induction hardened 1045 and 10V45 (0.08 wt pct V) steels were examined. Torsional fatigue specimens specifically designed for this research were machined from the as-received, hot rolled bars and induction hardened using both scanning (96 kHz/72 kW) and single-shot (31 kHz/128 kW) methods. Four conditions were evaluated, three scan hardened to 25, 32, and 44 pct nominal effective case depths and one single-shot hardened to 44 pct. Torsional fatigue tests were conducted at a stress ratio of 0.1 and shear stress amplitudes of 550, 600, and 650 MPa. Physical simulations using the thermal profiles from select induction hardened conditions were conducted in the GleebleRTM 3500 to augment microstructural analysis of torsional fatigue specimens. Thermal profiles were calculated by a collaborating private company using electro-thermal finite element analysis. Residual stresses were evaluated for all conditions using a strain gage hole drilling technique. The results showed that vanadium microalloying has an influence on the microstructure in the highest hardness region of the induction-hardened case as well as the total case region. Vanadium microalloyed conditions consistently exhibited a greater amount of non

  1. Study of a neutron irradiated reactor pressure vessel steel by X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cammelli, S. [LWV, NES, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)], E-mail: sebastiano.cammelli@psi.ch; Degueldre, C.; Kuri, G.; Bertsch, J. [LWV, NES, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)

    2008-11-15

    Reactor pressure vessel (RPV) reference steel samples submitted to neutron irradiations followed by thermal annealing were investigated by X-ray absorption fine structure (XAFS) spectroscopy. Several studies revealed that Cu and Ni impurities can form nanoclusters. In the unirradiated sample and in the only-irradiated sample no significant clustering is detected. In all irradiated and subsequently annealed samples increases of Cu and Ni atom densities are recorded around the absorber. Furthermore, the density of Cu and Ni atoms determined in the first and second shells around the absorber is found to be affected by the irradiation and annealing treatment. The comparison of the XAFS data at Cu and Ni K-edges shows that these elements reside in arrangements similar to bcc Fe. However, the local irradiation damage yields vacancy fractions which were determined from the analysis of XAFS data with a precision of {approx}5%.

  2. Mechanical spectroscopy of reactor-pressure-vessel steel embrittlement: a progress report

    Energy Technology Data Exchange (ETDEWEB)

    Van Ouytsel, K

    1998-08-01

    An enhanced surveillance strategy for testing the fracture toughness of reactor-pressure-vessel steel embrittlement is described. Microstructural investigation in support of damage modelling is an essential element in this enhanced strategy. Temperature-dependent experiments are very sensitive to differences in chemical composition and to effects of neutron irradiation as well as thermal ageing. Amplitude-dependent experiments can be related to tensile test results and correspond to a model for the yield stress. A full range of experiments were carried out on base and weld metal from the Doel-I-II power plants. The results have indicated that internal friction yields information which cannot always be detected by means of standard testing techniques. An inverted torsion pendulum for measuring internal friction has been constructed.

  3. Evaluation Of Fatigue In Yazd Steel Industry Workers And Its Relation with Some Demographic Variables in 2014

    Directory of Open Access Journals (Sweden)

    P Azad

    2016-03-01

    Full Text Available Introduction: Fatigue phenomenon, as an important and unique of living creatures, is certainly experienced by the majority of human in their life. It may cause bad effect on the expected occupational performance of workers including weakness in judgment and decision making, forgetting the details, causes indifference to the essential items and loss of performance. This study was performed to investigate the prevalence of fatigue and its relationship with some demographic variables.  Methods: This present study, as a descriptive cross-sectional, was carried out in 2014, among the workers in the Yazd steel.  A sample of 388 workers was selected by random cluster sampling method. A multi-part questionnaire including demographic characteristics and Occupational Fatigue Exhaustion/Recovery Scale were applied.  Data were analyzed by SPSS19.  Results: The result of this study showed that most of the subjects have experienced the moderate severity of chronic fatigue but in the intensity of acute fatigue was higher than chronic one. The prevalence of severe acute and chronic fatigue was 30.49% and 55.4%, respectively. There was significant relationship between the fatigue with job history and education level (PV=0.019. Conclusion: The results of this study indicate the high incidence of fatigue in workers.

  4. Experimental and Numerical Investigations of Fretting Fatigue Behavior for Steel Q235 Single-Lap Bolted Joints

    Directory of Open Access Journals (Sweden)

    Yazhou Xu

    2016-01-01

    Full Text Available This work aims to investigate the fretting fatigue life and failure mode of steel Q235B plates in single-lap bolted joints. Ten specimens were prepared and tested to fit the S-N curve. SEM (scanning electron microscope was then employed to observe fatigue crack surfaces and identify crack initiation, crack propagation, and transient fracture zones. Moreover, a FEM model was established to simulate the stress and displacement fields. The normal contact stress, tangential contact stress, and relative slipping displacement at the critical fretting zone were used to calculate FFD values and assess fretting fatigue crack initiation sites, which were in good agreement with SEM observations. Experimental results confirmed the fretting fatigue failure mode for these specimens. It was found that the crack initiation resulted from wear regions at the contact surfaces between plates, and fretting fatigue cracks occurred at a certain distance away from hole edges. The proposed FFD-N relationship is an alternative approach to evaluate fretting fatigue life of steel plates in bolted joints.

  5. Plasma immersion ion implantation on 15-5PH stainless steel: influence on fatigue strength and wear resistance

    Science.gov (United States)

    Bonora, R.; Cioffi, M. O. H.; Voorwald, H. J. C.

    2017-05-01

    Surface improvement in steels is of great interest for applications in industry. The aim of this investigation is to study the effect of nitrogen ion implantation on the axial fatigue strength and wear resistance of 15-5 PH stainless steel. It is well know that electroplated coatings, which are used to improve abrasive wear and corrosion properties, affects negatively the fatigue strength. It is also important to consider requirements to reduce the use of coated materials with electroplated chromium and cadmium, that produce waste, which is harmful to health and environment. The HVOF (High velocity oxygen fuel) process provides hardness, wear strength and higher fatigue resistance in comparison to electroplated chromium. Plasma immersion ion implantation has been used to enhance the hardness, wear, fatigue and corrosion properties of metals and alloys. In the present research the fatigue life increased twice for 15-5 PH three hours PIII treated in comparison to base material. From the abrasive wear tests a lower pin mass reduction was observed, associated to the superficial treatments. The improvement of fatigue and mechanical performance is attributed to a combination of nitrides phase structure and compressive residual stresses during the PIII treatment.

  6. Effects of thermal annealing and reirradiation on toughness of reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Nanstad, R.K.; Iskander, S.K.; Sokolov, M.A. [Oak Ridge National Lab., TN (United States)] [and others

    1997-02-01

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPV) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. This paper summarizes recent experimental results from work performed at the Oak Ridge National Laboratory (ORNL) to study the annealing response, or {open_quotes}recovery,{close_quotes} of several irradiated RPV steels; it also includes recent results from both ORNL and the Russian Research Center-Kurchatov Institute (RRC-KI) on a cooperative program of irradiation, annealing and reirradiation of both U.S. and Russian RPV steels. The cooperative program was conducted under the auspices of Working Group 3, U.S./Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS). The materials investigated are an RPV plate and various submerged-arc welds, with tensile, Charpy impact toughness, and fracture toughness results variously determined. Experimental results are compared with applicable prediction guidelines, while observed differences in annealing responses and reirradiation rates are discussed.

  7. Influence of fluence rate on radiation-induced mechanical property changes in reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Hawthorne, J.R.; Hiser, A.L. (Materials Engineering Associates, Inc., Lanham, MD (USA))

    1990-03-01

    This report describes a set of experiments undertaken using a 2 MW test reactor, the UBR, to qualify the significance of fluence rate to the extent of embrittlement produced in reactor pressure vessel steels at their service temperature. The test materials included two reference plates (A 302-B, A 533-B steel) and two submerged arc weld deposits (Linde 80, Linde 0091 welding fluxes). Charpy-V (C{sub v}), tension and 0.5T-CT compact specimens were employed for notch ductility, strength and fracture toughness (J-R curve) determinations, respectively. Target fluence rates were 8 {times} 10{sup 10}, 6 {times} 10{sup 11} and 9 {times} 10{sup 12} n/cm{sup 2} {minus}s{sup {minus}1}. Specimen fluences ranged from 0.5 to 3.8 {times} 10{sup 19} n/cm{sup 2}, E > 1 MeV. The data describe a fluence-rate effect which may extend to power reactor surveillance as well as test reactor facilities now in use. The dependence of embrittlement sensitivity on fluence rate appears to differ for plate and weld deposit materials. Relatively good agreement in fluence-rate effects definition was observed among the three test methods. 52 figs., 4 tabs.

  8. Microstructure and mechanical characteristics of a laser welded joint in SA508 nuclear pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wei, E-mail: wei.guo-2@manchester.ac.uk [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom); Dong, Shiyun [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom); Institute of Laser Engineering, Beijing University of Technology, Beijing 100124 (China); Guo, Wei; Francis, John A.; Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom)

    2015-02-11

    SA508 steels are typically used in civil nuclear reactors for critical components such as the reactor pressure vessel. Nuclear components are commonly joined using arc welding processes, but with design lives for prospective new build projects exceeding 60 years, new welding technologies are being sought. In this exploratory study, for the first time, autogenous laser welding was carried out on 6 mm thick SA508 Cl.3 steel sheets using a 16 kW fiber laser system operating at a power of 4 kW. The microstructure and mechanical properties (including microhardness, tensile strength, elongation, and Charpy impact toughness) were characterized and the microstructures were compared with those produced through arc welding. A three-dimensional transient model based on a moving volumetric heat source model was also developed to simulate the laser welding thermal cycles in order to estimate the cooling rates included by the process. Preliminary results suggest that the laser welding process can produce welds that are free of macroscopic defects, while the strength and toughness of the laser welded joint in this study matched the values that were obtained for the parent material in the as-welded condition.

  9. DIC-aided biaxial fatigue tests of a 304L steel

    Science.gov (United States)

    Poncelet, M.; Barbier, G.; Raka, B.; Courtin, S.; Desmorat, R.; Le-Roux, J. C.; Vincent, L.

    2010-06-01

    Several biaxial fatigue tests are conducted up to 106 cycles at room temperature in the context of a collaboration LMT-Cachan / EDF / AREVA / SNECMA / CEA. Malteses cross specimens of 304L steel, designed to initiate crack in the bulk, are loaded by a triaxial testing machine. A Digital Image Correlation technique is used to measure strain during loading and detect crack initiation early. A special optical assembly and a stroboscopic sampling method are set up in this purpose. Several types of loadings are performed: equibiaxial with a loading ratio R = 0.1, equibiaxial with loading ratio R = -1, pseudo uniaxial (cyclic loading at R= 0.1 in one direction and constant loading in the other). First results are commented.

  10. DIC-aided biaxial fatigue tests of a 304L steel

    Directory of Open Access Journals (Sweden)

    Le-Roux J.C.

    2010-06-01

    Full Text Available Several biaxial fatigue tests are conducted up to 106 cycles at room temperature in the context of a collaboration LMT-Cachan / EDF / AREVA / SNECMA / CEA. Malteses cross specimens of 304L steel, designed to initiate crack in the bulk, are loaded by a triaxial testing machine. A Digital Image Correlation technique is used to measure strain during loading and detect crack initiation early. A special optical assembly and a stroboscopic sampling method are set up in this purpose. Several types of loadings are performed: equibiaxial with a loading ratio R = 0.1, equibiaxial with loading ratio R = –1, pseudo uniaxial (cyclic loading at R= 0.1 in one direction and constant loading in the other. First results are commented.

  11. Effect of defect length on rolling contact fatigue crack propagation in high strength steel

    Directory of Open Access Journals (Sweden)

    T. Makino

    2015-10-01

    Full Text Available The objective of the present paper is to clarify the effect of defect length in depth direction on rolling contact fatigue (RCF crack propagation in high strength steel. RCF test and synchrotron radiation micro computed tomography (SR micro CT imaging were conducted. In the case of the defect with the 15 m diameter, flaking life decreased with increasing defect length. In a comparison of the CT image and the SEM view, the shapes of defects and the locations of the horizontal cracks were almost the same respectively. The mechanism of RCF crack propagation was discussed by finite element (FE analysis. Defects led to higher tensile residual stress than that without defects in the region where the defect exists. The shear stress range at 0.1 mm in depth on the middle line of the defect and the range of mode II stress intensity factor at the bottom of a vertical crack increased with increasing defect length.

  12. Effect of Macrosegregation on the Microstructure and Mechanical Properties of a Pressure-Vessel Steel

    Science.gov (United States)

    Yan, Guanghua; Han, Lizhan; Li, Chuanwei; Luo, Xiaomeng; Gu, Jianfeng

    2017-07-01

    Macrosegregation refers to the chemical segregation, which occurs quite commonly in the large forgings such as nuclear reactor pressure vessel. This work assesses the effect of macrosegregation and homogenization treatment on the mechanical properties of a pressure-vessel steel (SA508 Gr.3). It was found that the primary reason for the inhomogeneity of the microstructure was the segregation of Mn, Mo, and Ni. Martensite, and coarse upper bainite with M-A (martensite-austenite) islands have been obtained, respectively, in the positive and negative segregation zone during a simulated quenching process. During tempering, the carbon-rich M-A islands decomposed into a mixture of ferrite and numerous carbides which deteriorated the toughness of the material. The segregation has been substantially minimized by a homogenizing treatment. The results indicate that the material homogenized has a higher impact toughness than the material with segregation, due to the reduction in M-A island in the negative segregation zone. It can be concluded that the microstructure and mechanical properties have been improved remarkably by means of homogenization treatment.

  13. The influence of fire exposure on austenitic stainless steel for pressure vessel fitness-for-service assessment: Experimental research

    Science.gov (United States)

    Li, Bo; Shu, Wenhua; Zuo, Yantian

    2017-04-01

    The austenitic stainless steels are widely applied to pressure vessel manufacturing. The fire accident risk exists in almost all the industrial chemical plants. It is necessary to make safety evaluation on the chemical equipment including pressure vessels after fire. Therefore, the present research was conducted on the influences of fire exposure testing under different thermal conditions on the mechanical performance evolution of S30408 austenitic stainless steel for pressure vessel equipment. The metallurgical analysis described typical appearances in micro-structure observed in the material suffered by fire exposure. Moreover, the quantitative degradation of mechanical properties was investigated. The material thermal degradation mechanism and fitness-for-service assessment process of fire damage were further discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lehericy, Y

    2007-05-15

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

  15. THE INFLUENCE MECHANISM OF FERRITE GRAIN SIZE ON STRENGTH STRESS AT THE FATIGUE OF LOW-CARBON STEEL

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2014-01-01

    Full Text Available Purpose. Explanation of the influence mechanism of ferrite grain size on the fatigue strength of low-carbon steel. Methodology. Material for research is the low-carbon steel with 0.1% of carbon contnent. The different size of ferrite grain was obtained due to varying the degree of cold plastic deformation and temperature of annealing. The estimation of grain size was conducted using methodologies of quantitative metallography. The microstructure of metal was investigated under a light microscope with increase up to 1500 times. As a fatigue response the fatigue strength of metal – a maximal value of load amplitude with endless endurance limit of specimen was used. Fatigue tests were carried out using the test machine «Saturn-10», at the symmetric cycle of alternating bend loading. Findings. On the basis of research the dependence for fatigue strength of low-carbon steel, which is based on an additive contribution from hardening of solid solution by the atoms of carbon, boundary of the ferrite grain and amount of mobile dislocations was obtained. It was established that as the grainy structure of low-carbon steel enlarges, the influence of grain size on the fatigue strength level is reduced. For the sizes of grains more than 100 mcm, basic influence on fatigue strength begins to pass to the solid solution hardening, which is determined by the state of solid solution of introduction. Originality. From the analysis of the obtained dependences it ensues that with the increase of ferrite grain size the required amount of mobile dislocations for maintenance of conditions for spreading plastic deformation becomes less dependent from the scheme of metal loading. Practical value. The obtained results present certain practical interest when developing of recommendations, directed on the increase of resource of products work from low-carbon steels in the conditions of cyclic loading. Estimation of separate contribution of the studied processes of

  16. Effect of postweld treatment on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel

    Science.gov (United States)

    Wang, Chien-Chun; Chang, Yih

    1996-10-01

    This article studies the effect of in-chamber electron beam and ex-chamber furnace postweld treatments on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel. Mechanical properties of the weldment are evaluated by tensile testing, while the fatigue properties are investigated by a fatigue crack propagation method. Microstructural examination shows that both postweld treatments temper the weldment by the appropriate control of beam pattern width, input beam energy, and furnace temperature. In addition, the ductility, strength, and microhardness of the weldment also reflect this tempering effect. The fatigue crack growth rate is decreased after both postweld treatments. This is mainly caused by the existence of a toughened microstructure and relief of the residual stress due to the fact that (1) the residual stress becomes more compressive as more beam energy is delivered into the samples and (2) postweld furnace tempering effectively releases the tensile stress into a compressive stress state.

  17. Very high cycle fatigue strength and crack growth of thin steel sheets

    Directory of Open Access Journals (Sweden)

    Mohand Ouarabi

    2016-03-01

    Full Text Available For basic observations or for industrial applications it is of interest to use flat specimens at very high frequency in the gigacycle regime. In this work, thin flat sheet, with 1.2 mm thickness of a complex phase ferrite-martensitic steels were considered for carrying out fatigue tests at high frequency (20 kHz up to the gigacycle regime (>109 cycles. The crack initiation tests were carried out with water cooling, while the crack growth test were carried out in laboratory air at room temperature. All the tests were carried out under loading ratio R=-1. To do that, special designs of specimens were made and computed using FEM for defining the stress amplitude for endurance tests. Special attachments for specimens to the ultrasonic system’s horn were enhanced. A particular FEM computing of the stress intensity range on crack growth specimens was carried out for determining the specimen dimensions and an equation that defines the stress intensity range as a function of the harmonic displacement amplitude, dynamic Young’s modulus, material density and crack length. Detailed procedures and fatigue results are presented in this paper.

  18. Impact of choice of stabilized hysteresis loop on the end result of investigation of high-strength low-alloy (HSLA steel on low cycle fatigue

    Directory of Open Access Journals (Sweden)

    S. Bulatović

    2014-10-01

    Full Text Available High strength low-alloy steel under low cycle fatigue at a certain level of strain controlled achieve stabilized condition. During the fatigue loading stabilized hysteresis loop is determined, which typical cycle of stabilization is calculated as half number of cycles to failure. Stabilized hysteresis loop is a representative of all hysteresis and it’s used to determine all of the parameters for the assessment of low cycle fatigue. This paper shows comparison of complete strain-life curves of low cycle fatigue for two chosen stabilized hysteresis loop cycles of base metal HSLA steel marked as Nionikral 70.

  19. Fatigue crack sizing in rail steel using crack closure-induced acoustic emission waves

    Science.gov (United States)

    Li, Dan; Kuang, Kevin Sze Chiang; Ghee Koh, Chan

    2017-06-01

    The acoustic emission (AE) technique is a promising approach for detecting and locating fatigue cracks in metallic structures such as rail tracks. However, it is still a challenge to quantify the crack size accurately using this technique. AE waves can be generated by either crack propagation (CP) or crack closure (CC) processes and classification of these two types of AE waves is necessary to obtain more reliable crack sizing results. As the pre-processing step, an index based on wavelet power (WP) of AE signal is initially established in this paper in order to distinguish between the CC-induced AE waves and their CP-induced counterparts. Here, information embedded within the AE signal was used to perform the AE wave classification, which is preferred to the use of real-time load information, typically adopted in other studies. With the proposed approach, it renders the AE technique more amenable to practical implementation. Following the AE wave classification, a novel method to quantify the fatigue crack length was developed by taking advantage of the CC-induced AE waves, the count rate of which was observed to be positively correlated with the crack length. The crack length was subsequently determined using an empirical model derived from the AE data acquired during the fatigue tests of the rail steel specimens. The performance of the proposed method was validated by experimental data and compared with that of the traditional crack sizing method, which is based on CP-induced AE waves. As a significant advantage over other AE crack sizing methods, the proposed novel method is able to estimate the crack length without prior knowledge of the initial crack length, integration of AE data or real-time load amplitude. It is thus applicable to the health monitoring of both new and existing structures.

  20. Evaluation of Fatigue Strength Improvement by CFRP Laminates and Shot Peening onto the Tension Flanges Joining Corrugated SteelWebs

    Directory of Open Access Journals (Sweden)

    Zhi-Yu Wang

    2015-08-01

    Full Text Available Corrugated steel web with inherent high out-of-plane stiffness has a promising application in configuring large span highway bridge girders. Due to the irregularity of the configuration details, the local stress concentration poses a major fatigue problem for the welded flange plates of high strength low alloy structural steels. In this work, the methods of applying CFRP laminate and shot peening onto the surfaces of the tension flanges were employed with the purpose of improving the fatigue strength of such configuration details. The effectiveness of this method in the improvement of fatigue strength has been examined experimentally. Test results show that the shot peening significantly increases hardness and roughness in contrast to these without treatment. Also, it has beneficial effects on the fatigue strength enhancement when compared against the test data of the joints with CFRP strengthening. The stiffness degradation during the loading progress is compared with each treatment. Incorporating the stress acting on the constituent parts of the CFRP laminates, a discussion is made regarding the mechanism of the retrofit and related influencing factors such as corrosion and economic cost. This work could enhance the understanding of the CFRP and shot peening in repairing such welded details and shed light on the reinforcement design of welded joints between corrugated steel webs and flange plates.

  1. A fracture mechanics approach for estimating fatigue crack initiation in carbon and low-alloy steels in LWR coolant environments

    Energy Technology Data Exchange (ETDEWEB)

    Park, H. B.; Chopra, O. K.

    2000-04-10

    A fracture mechanics approach for elastic-plastic materials has been used to evaluate the effects of light water reactor (LWR) coolant environments on the fatigue lives of carbon and low-alloy steels. The fatigue life of such steel, defined as the number of cycles required to form an engineering-size crack, i.e., 3-mm deep, is considered to be composed of the growth of (a) microstructurally small cracks and (b) mechanically small cracks. The growth of the latter was characterized in terms of {Delta}J and crack growth rate (da/dN) data in air and LWR environments; in water, the growth rates from long crack tests had to be decreased to match the rates from fatigue S-N data. The growth of microstructurally small cracks was expressed by a modified Hobson relationship in air and by a slip dissolution/oxidation model in water. The crack length for transition from a microstructurally small crack to a mechanically small crack was based on studies on small crack growth. The estimated fatigue S-N curves show good agreement with the experimental data for these steels in air and water environments. At low strain amplitudes, the predicted lives in water can be significantly lower than the experimental values.

  2. Analysis of the Mechanical Behavior, Creep Resistance and Uniaxial Fatigue Strength of Martensitic Steel X46Cr13.

    Science.gov (United States)

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

    2017-04-06

    The article deals with the analysis of the mechanical behavior at different temperatures, uniaxial creep and uniaxial fatigue of martensitic steel X46Cr13 (1.4034, AISI 420). For the purpose of considering the aforementioned mechanical behavior, as well as determining the appropriate resistance to creep and fatigue strength levels, numerous uniaxial tests were carried out. Tests related to mechanical properties performed at different temperatures are presented in the form of engineering stress-strain diagrams. Short-time creep tests performed at different temperatures and different stress levels are presented in the form of creep curves. Fatigue tests carried out at stress ratios R = 0.25 and R = - 1 are shown in the form of S-N (fatigue) diagrams. The finite fatigue regime for each of the mentioned stress ratios is modeled by an inclined log line, while the infinite fatigue regime is modeled by a horizontal line, which represents the fatigue limit of the material and previously was calculated by the modified staircase method. Finally, the fracture toughness has been calculated based on the Charpy V-notch impact energy.

  3. Analysis of the Mechanical Behavior, Creep Resistance and Uniaxial Fatigue Strength of Martensitic Steel X46Cr13

    Directory of Open Access Journals (Sweden)

    Josip Brnic

    2017-04-01

    Full Text Available The article deals with the analysis of the mechanical behavior at different temperatures, uniaxial creep and uniaxial fatigue of martensitic steel X46Cr13 (1.4034, AISI 420. For the purpose of considering the aforementioned mechanical behavior, as well as determining the appropriate resistance to creep and fatigue strength levels, numerous uniaxial tests were carried out. Tests related to mechanical properties performed at different temperatures are presented in the form of engineering stress-strain diagrams. Short-time creep tests performed at different temperatures and different stress levels are presented in the form of creep curves. Fatigue tests carried out at stress ratios R = 0.25 and R = − 1 are shown in the form of S–N (fatigue diagrams. The finite fatigue regime for each of the mentioned stress ratios is modeled by an inclined log line, while the infinite fatigue regime is modeled by a horizontal line, which represents the fatigue limit of the material and previously was calculated by the modified staircase method. Finally, the fracture toughness has been calculated based on the Charpy V-notch impact energy.

  4. Effect of ion implantation on fatigue strength of martensitic stainless steel and surface hardness evaluation by ultra micro hardness tester

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Tsuneshichi [Ritsumeikan Univ., Kyoto (Japan). Faculty of Science and Engineering; Nakayama, Hideaki; Kato, Masahiko

    1995-02-01

    The effect of surface modification by ion implantation on the fatigue strength of 13Cr martensitic stainless steel was first described. Then the relationship between the fatigue performance and the surface microhardness of the material was dealt with. N{sup +} ions were implanted into the specimen surface with doses in the range of 5x10{sup 13} ions/cm{sup 2} - 5x10{sup 17} ions/cm{sup 2} with energy level of 350 keV. The results of out-of-plane bending fatigue tests revealed that the fatigue strength was improved by the ion implantation with implantation doses more than 2x10{sup 17} ions/cm{sup 2}, and that the further increase of fatigue strength was attained by the post heat treatment following the ion implantation. The microhardness of ultra-thin surface layer of submicron order was evaluated by the method previously proposed by the authors. The results indicated that the surface layer was hardened by the ion implantation and the hardness was increased by the post heat treatment. A remarkable increase in hardness was observed at the surface layer after the fatigue test, and this increase of the microhardness well coincides with the improvement of fatigue strength by ion implantation and post heat treatment. (author).

  5. Effect of W and Ta on creep–fatigue interaction behavior of reduced activation ferritic–martensitic (RAFM) steels

    Energy Technology Data Exchange (ETDEWEB)

    Shankar, Vani, E-mail: vani@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Institute for Plasma Research, Ahmedabad 382428 (India); Mariappan, K.; Sandhya, R.; Laha, K.; Jayakumar, T.; Kumar, E. Rajendra [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Institute for Plasma Research, Ahmedabad 382428 (India)

    2015-11-15

    Highlights: • SR correlated with deformation under CFI in RAFM steels. • Stress relaxation directly related to plastic strain accumulated, inversely to CFI life. • Optimum combination of W and Ta best for CFI life. • RAFM steels demonstrated compressive dwell sensitivity. • SR tends toward constant value at long hold. - Abstract: The aim of this work is to understand the effect of varying tungsten and tantalum contents on creep–fatigue interaction (CFI) behavior of reduced activation ferritic–martensitic (RAFM) steels. Increase in W improved CFI life. Effect of changing Ta and W upon the resultant CFI life seems to be interrelated and an optimum combination of both W and Ta works out to be the best for CFI life. Stress relaxation obtained during application of hold can be a useful parameter to relate deformation and damage in the RAFM steels.

  6. Effect of microstructure on fatigue behavior of advanced high strength steels produced by quenching and partitioning and the role of retained austenite

    Energy Technology Data Exchange (ETDEWEB)

    Diego-Calderón, I. de, E-mail: irenedediego.calderon@imdea.org [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Rodriguez-Calvillo, P. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Lara, A. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Molina-Aldareguia, J.M. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Petrov, R.H. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Department of Materials Science and Engineering, Delft University of Technology, 2628 CD Delft (Netherlands); De Knijf, D. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Sabirov, I. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain)

    2015-08-12

    Despite the significant body of research on mechanical properties of quenched and partitioned (Q&P) steels, their fatigue behavior has not been investigated. This work focuses on the effect of microstructure on high cycle fatigue of Q&P steels and microstructural evolution during cyclic loading. It is demonstrated that increased content of retained austenite (RA) improves fatigue limit of Q&P steels that is related to delay of crack propagation due to austenite–martensite phase transformation. Increasing stress amplitude promotes austenite–martensite phase transformation during cycling loading. It is shown that size and crystallographic orientation of RA are the main factors determining its stability, whereas its shape and spatial distribution do not seem to affect it significantly. Fatigue crack initiation during fatigue testing with high stress amplitudes occurs by intergranular cracking, whereas transgranular cracking controls fatigue crack initiation during cycling loading with lower stress amplitudes. Transgranular crack propagation dominates in the second stage of fatigue at all stress amplitudes. The final stage of fatigue is also not affected by the stress amplitude. It is suggested that fatigue life of Q&P steels can be enhanced via improvement of strength of grain/interphase boundaries.

  7. Combined Effect of Hydrogen and Dynamic Strain Aging on Low Cycle Fatigue Behaviors of SA508 Gr.1a Low Alloy Steels in 310 .deg. C Deoxygenated Water

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Hun; Kim, Jeong Hyeon; Jang, Chang Heui [KAIST, Daejeon (Korea, Republic of); Kim, Tae Soon [Korea Hydro and Nuclear Power Co., Daejeon (Korea, Republic of)

    2011-05-15

    Significant reduction of fatigue life of structural materials in nuclear power plants is one of the issues of considerable significance to maintain superior integrity throughout their service life. From extensive studies, hydrogen induced cracking (HIC) is widely accepted mechanisms for reduction of fatigue life of low alloy steels (LAS) used as structural materials. Some of authors reported that hydrogen content in reactor pressure vessel could reach 2 {approx} 5 ppm during reactor operation. Hydrogen was resulted from corrosion reaction at the metal surface or crack tip in water. In addition, it has been reported that LAS is susceptible material for dynamic strain aging (DSA) in PWR environment at specific strain rate. Therefore, it is possible that the synergism between DSA and hydrogen might induce more significant LCF damage in PWR environment. In this regard, combined effect of DSA and hydrogen was investigated in this study. For that, LCF tests of SA508 Gr.1a LAS in various environments and tensile tests of hydrogen charged (H charged) samples in DSA range were conducted

  8. Low-cycle fatigue behavior of 316 stainless steel at FBR temperature. Effects of strain rate and strain wave form

    Energy Technology Data Exchange (ETDEWEB)

    Nonaka, Isamu; Kitagawa, Masaki; Ohtomo, Akira (Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan))

    1983-07-01

    The effects of strain rate and strain wave form on the low-cycle fatigue behavior of 316 stainless steel at FBR temperature were studied in order to clarify the controlling factor of fatigue strength and fracture mechanism. The following major results are obtained. (1) Under symmetrical and asymmetrical straining (slow-fast and fast-slow wave) with the strain rate between 10/sup 0/%/sec to 10/sup -3/%/sec, the fatigue life decreases with a decrease of strain rate in tension going period. The fatigue life is affected only by the strain rate in tension going period, and is not affected by the strain rate in compression going period. Slow-fast wave is most damaging, but the effect of saw-tooth wave is not significant. (2) The dependence of fatigue life on the strain rate in tension going period may not be due to the creep effect but due to the dynamic strain aging effect proper to FBR temperature (500/sup 0/C to 600/sup 0/C) (3) The fracture mode changes from transgranular cracking to intergranular cracking with a decrease of strain rate in tension going period. Slow-fast wave enhances the intergranular cracking, whereas fast-slow wave enhances the transgranular cracking. (4) Thermal aging increases the fatigue life under symmetrical and asymmetrical straining, and the life reduction with the strain rate reduction in tension going period is not so significant for the thermally aged condition.

  9. Elucidating the Relations Between Monotonic and Fatigue Properties of Laser Powder Bed Fusion Stainless Steel 316L

    Science.gov (United States)

    Zhang, Meng; Sun, Chen-Nan; Zhang, Xiang; Goh, Phoi Chin; Wei, Jun; Li, Hua; Hardacre, David

    2017-11-01

    The laser powder bed fusion (L-PBF) technique builds parts with higher static strength than the conventional manufacturing processes through the formation of ultrafine grains. However, its fatigue endurance strength σ f does not match the increased monotonic tensile strength σ b. This work examines the monotonic and fatigue properties of as-built and heat-treated L-PBF stainless steel 316L. It was found that the general linear relation σ f = mσ b for describing conventional ferrous materials is not applicable to L-PBF parts because of the influence of porosity. Instead, the ductility parameter correlated linearly with fatigue strength and was proposed as the new fatigue assessment criterion for porous L-PBF parts. Annealed parts conformed to the strength-ductility trade-off. Fatigue resistance was reduced at short lives, but the effect was partially offset by the higher ductility such that comparing with an as-built part of equivalent monotonic strength, the heat-treated parts were more fatigue resistant.

  10. Appropriate welding conditions of temper bead weld repair for SQV2A pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, R.; Matsuda, F. [NDE Center, Japan Power Engineering and Inspection Corp. (Japan); Brziak, P. [Welding Research Inst. - Industrial Inst. of Slovak Republic (Slovakia); Lomozik, M. [Inst. of Welding (Poland)

    2004-07-01

    Temper bead welding technique is one of the most important repair welding methods for large structures for which it is difficult to perform the specified post weld heat treatment. In this study, appropriate temper bead welding conditions to improve the characteristics of heat affected zone (HAZ) are studied using pressure vessel steel SQV2A corresponding to ASTM A533 Type B Class 1. Thermal/mechanical simulator is employed to give specimens welding thermal cycles from single to quadruple cycle. Charpy absorbed energy and hardness of simulated CGHAZ by first cycle were degraded as compared with base metal. Improvability of these degradations by subsequent cycles is discussed and appropriate temper bead thermal cycles are clarified. When the peak temperature lower than Ac1 and near Ac1 in the second thermal cycle is applied to CGAHZ by first thermal cycle, the characteristics of CGHAZ improve enough. When the other peak temperatures (that is, higher than Ac1) in the second thermal cycle are applied to the CGHAZ, third or more thermal cycle temper bead process should be applied to improve the properties. Appropriate weld condition ranges are selected based on the above results. The validity of the selected ranges is verified by the temper bead welding test. (orig.)

  11. Fatigue crack monitoring in train track steel structures using plastic optical fiber sensor

    Science.gov (United States)

    Yang, D.; Li, D.; Kuang, K. S. C.

    2017-10-01

    Plastic optical fiber (POF) sensors have shown excellent potential for damage detection and structural health monitoring in a variety of engineering structures. This paper discusses the feasibility of using POF sensors in conjunction with a signal-processing algorithm capable of detecting and monitoring fatigue-induced cracks in train track steel structures in real time. The POF sensor, which was modified from an existing design to increase the signal sensitivity, allows for accurate detection of a fatigue crack developed in a specimen, and was found to compare well to the reference acoustic emission (AE) sensors and crack opening displacement (COD) gauge attached to the specimen. The crack-detection technique, which relies on capturing the intensity variation of the POF sensor, was not susceptible to any signal fluctuations commonly associated with intensity-based optical fiber sensors. The results show that the technique has potential for use in detecting the initiation and propagation of specific segments of a structure vulnerable to cracking due to external cyclic loading, e.g. at welded joints in train tracks under train loads or offshore structures subject to wave loads. The POF sensor system is composed of inexpensive parts (LED light source, photodetectors, and data acquisition units) and can easily be installed to the host structure. To validate the proposed damage-detection technique, the instrumented specimens are subjected to cyclic loading in order to induce stable crack propagation in the specimen. A COD gauge and AE were used for the purpose of calibration and comparison. The results show remarkable resemblance in terms of crack initiation and propagation identification exhibited by all three types of sensors, highlighting the potential of the proposed sensor for crack initiation detection and subsequent monitoring of crack propagation.

  12. Comparison of SA508 Gr.3 and SA508 Gr.4N Low Alloy Steels for Reactor Pressure Vessel Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Chul; Lee, B. S

    2009-12-15

    The microstructural characteristics and mechanical properties of SA508 Gr.3 Mn-Mo-Ni low alloy steel and SA508 Gr.4N Ni-Mo-Cr low alloy steel were investigated. The differences in the stable phases between these two low alloy steels were evaluated by means of a thermodynamic calculation using ThermoCalc. They were then compared to microstructural features and correlated with mechanical properties. Mn-Mo-Ni low alloy steel shows the upper bainite structure which has the coarse cementite in the lath boundaries. However, Ni-Mo-Cr low alloy steel shows the mixture of lower bainite and tempered martensite structure that homogeneously precipitates the small carbides such as M{sub 23}C{sub 6} and M{sub 7}C{sub 3} due to an increase of hardenability and Cr addition. In the mechanical properties, Ni-Mo-Cr low alloy steel has higher strength and toughness than Mn-Mo-Ni low alloy steel. Ni and Cr additions increase the strength by solid solution hardening. Besides, microstructural changes from upper bainite to tempered martensite improve the strength of the low alloy steel by grain refining effect. And the changes in the precipitation behavior by Cr addition improve the ductile-brittle transition behavior along with a toughening effect of Ni addition.

  13. Fatigue-creep of martensitic steels containing 9-12% Cr: behaviour and damage; Fatigue-fluage des aciers martensitiques a 9-12% Cr: comportement et endommagement

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, B

    2007-09-15

    It is in the framework of the research programs on nuclear reactors (generation IV) that the martensitic steels containing 9-12% Cr are studied by the CEA. Most of the structures for which they are considered will be solicited in fatigue-creep at high temperature (550 C). The aim of this work is to understand and model the cyclic behaviour and the damage of these materials. The proposed modelling are based on detailed observations studies (SEM, TEM, EBSD...). The cyclic softening is attributed to the growth of the microstructure. A micro-mechanical model based on the physical parameters is proposed and leads to encouraging results. The damage results of interactions between fatigue, creep and oxidation. Two main types of damage are revealed. A model of anticipation of service time is proposed and gives very satisfying results. The possible extrapolations are discussed. (O.M.)

  14. ROLLING CONTACT FATIGUE AND WEAR OF CrL AND CrM MODE POWDER METALLURGY STEELS

    Directory of Open Access Journals (Sweden)

    Dušan Rodziňák

    2010-03-01

    Full Text Available Contact fatigue properties of sintered steels type CrM and CrL with addition of 0,3-0,7 %C were examined on the device type „pin on disc“ and confronted with wear tests on the same principle. Achieved outcomes are better for CrM material; the higher carbon content the better they are. Fatigue strength ranges from 925 - 1410 MPa and is consistent with the value of hardness. Dry wear tests show that the wear is dependent on the hardness of carbide particles (microhardness and not on macrohardness of material. These causes wear of indentor. Between values obtained from tests of contact fatigue and wear testing is not possible to find relevant compliance. Both rupture mechanisms are based on breaches of other principles, particularly the PM materials are in the mode of wear that is not sufficiently explored.

  15. Environmental influence on the near-threshold fatigue crack propagation behaviour of a high-strength steel

    Science.gov (United States)

    Henaff, G.; Petit, J.; Bouchet, B.

    1992-07-01

    The near-threshold fatigue crack propagation behavior of a high-strength low-alloy steel has been investigated in ambient air and in vacuum so as to determine the role of the environment precisely. The analysis of the results is conducted by taking crack closure effects into account. It is concluded that fatigue crack growth rates measured in ambient air depend upon three processes: intrinsic fatigue crack propagation as observed in vacuum, adsorption of water vapor molecules on freshly created rupture surfaces, which enhances crack propagation, and a subsequent step of hydrogen-assisted cracking. The appearance of intergranular ruptures and oxide layers on rupture surfaces in ambient air is also discussed.

  16. Study on Dynamic Strain Aging and Low-Cycle Fatigue of Stainless Steel in Ultra-Supercritical Unit

    Science.gov (United States)

    Hongwei, Zhou; Yizhu, He; Jizu, Lv; Sixian, Rao

    Dynamic strain aging (DSA) and low-cycle fatigue (LCF) behavior of TP347H stainless steel in ultra-supercritical unit were investigated at 550-650 °C. All the LCF tests were carried out under a fully-reversed, total axial strain control mode at the total strain amplitude from ±0.2% to ±1.0%. The effects of DSA in cyclic stress response, microstructure evolution and fatigue fracture surfaces and fatigue life were investigated in detail. The results show that DSA occurs during tensile, which is manifested as serrated flow in tensile stress-strain curves. The apparent activation energy for appearing of serrations in tensile stress-strain curves was 270 kJ/mol. Pipe diffusion of substitutional solutes such as Cr and Nb along the dislocation core, and strong interactions between segregated solutes and dislocations are considered as the mechanism of DSA. DSA partly restricts dislocation cross-slip, and dislocation cross-slip and planar-slip happen simultaneously during LCF. A lot of planar structures form, which is due to dislocation gliding on the special plane. This localized deformation structures result in many crack initiation sites. Meanwhile, DSA hardening increases cyclic stress response, accelerating crack propagation, which reduces high temperature strain fatigue life of steel.

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

    Science.gov (United States)

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

    2001-01-01

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

  18. Studies of fragileness in steels of vessels of BWR reactors; Estudios de fragilizacion en aceros de vasija de reactores BWR

    Energy Technology Data Exchange (ETDEWEB)

    Robles, E.F.; Balcazar, M.; Alpizar, A.M.; Calderon, B.E. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2003-07-01

    The structural materials with those that are manufactured the pressure vessels of the BWR reactors, suffer degradation in its mechanical properties mainly to the damage taken place by the fast neutrons (E > 1 MeV) coming from the reactor core. Its are experimentally studied those mechanisms of neutron damage in this material type, by means of the irradiation of steel vessel in experimental reactors to age them quickly. Alternatively it is simulated the neutron damage by means of irradiation of steel with heavy ions. In this work those are shown first results of the damage induced by irradiation from a similar steel to the vessel of a BWR reactor. The irradiation was carried out with fast neutrons (E > 1 MeV, fluence of 1.45 x 10{sup 18} n/cm{sup 2}) in the TRIGA MARK lll reactor and separately with Ni{sup +3} ions in a Tandetrom accelerator, E = 4.8 MeV and range of the ionic flow of 0.1 to 53 iones/A{sup 2}. (Author)

  19. Corrosion fatigue initiation behaviour of wrought austenitic stainless pipe steels under simulated BWR/HWC and PWR conditions

    Energy Technology Data Exchange (ETDEWEB)

    Leber, H.J.; Ritter, S.; Seifert, H.P [Paul Scherrer Institute, Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen PSI (Switzerland)

    2011-07-01

    The corrosion fatigue (CF) initiation and short crack growth behavior of different low-carbon and stabilized austenitic stainless steels was characterized under simulated BWR and primary PWR conditions by cyclic fatigue tests with sharply notched fracture mechanics specimens in the temperature range from 70 to 320 C. Environmental reduction of fatigue initiation life was observed in all stainless steels at strain rates {<=} 0.1 %/s in BWR and PWR environment. The stationary short crack CF crack growth rates after crack advances of 50 to 300 {mu}m from the notch-root were in the typical range of corresponding results from tests with long cracks (pre-cracked specimens) and also showed the same system parameter response. The effect of environment on the initiation process ({Delta}a = 10 {mu}m) was relevantly stronger than on the subsequent stationary short crack growth. Both, under BWR/HWC and PWR conditions, a relevant environmental reduction of fatigue initiation life occurred for the combination of temperatures {>=} 100 C, notch strain rates {<=} 0.1 %/s and notch strain amplitudes {>=} 0.3 %. If these conjoint threshold conditions were simultaneously satisfied, the environmental enhancement increased with decreasing strain rate and increasing temperature. Material and water chemistry parameters usually only had a little effect. Sensitization affected the CF behavior under highly oxidizing BWR/NWC conditions only. Preliminary block loading experiments did not reveal significant static load hold period effects on the technical corrosion fatigue initiation life. If the critical requirements were satisfied, the BWR/HWC and PWR environments usually resulted in acceleration of short fatigue crack growth by a factor of 5 to 20 with respect to air. Solution annealed steels showed slightly shorter CF initiation lives, but also lower stationary short CF crack growth rates under BWR/HWC and PWR conditions with low ECPs than under highly oxidizing BWR/NWC conditions. A very

  20. Effect of notch location on fatigue crack growth behavior of strength-mismatched high-strength low-alloy steel weldments

    Science.gov (United States)

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

    2004-12-01

    Welding of high-strength low-alloy (HSLA) steels involves the use of low-strength, equal-strength, and high-strength filler materials (electrodes) compared with the parent material, depending on the application of the welded structures and the availability of filler material. In the present investigation, the fatigue crack growth behavior of weld metal (WM) and the heat-affected zone (HAZ) of undermatched (UM), equally matched (EM), and overmatched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) has been used to fabricate the butt joints. A center-cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behavior of welded joints, utilizing a servo-hydraulic-controlled fatigue-testing machine at constant amplitude loading (R=0). The effect of notch location on the fatigue crack growth behavior of strength mismatched HSLA steel weldments also has been analyzed.

  1. Fatigue

    Science.gov (United States)

    ... as systemic lupus erythematosus Cancer Heart failure Diabetes Fibromyalgia Infection, especially one that takes a long time ... Bennett RM. Fibromyalgia, chronic fatigue syndrome, and ... Schafer AI, eds. Goldman-Cecil Medicine . 25th ed. Philadelphia, ...

  2. Effects of the cryogenic cooling on the fatigue strength of the AISI 304 stainless steel ground components

    Science.gov (United States)

    Ben Fredj, Nabil; Sidhom, Habib

    2006-06-01

    For environmental considerations, the substitution of the conventionally used oil-based grinding fluids has nowadays become strongly recommended. Although several alternatives have been proposed, cryogenic cooling by liquid nitrogen is the non-polluting coolant that has been given relatively more attention because of its very low temperature. In this investigation, in order to contribute to developing this promising cooling mode, its beneficial effects on the ground surface integrity of the AISI 304 stainless steel and their consequences on the fatigue lifetime are explored. Results of this investigation show that grinding under cryogenic cooling mode generates surfaces with lower roughness, less defects, higher work hardening and less tensile residual stresses than those obtained on surfaces ground under oil-based grinding fluid. These surface enhancements result into substantial improvements in the fatigue behaviour of components ground under this cooling mode. An increasing rate of almost 15% of the endurance limit at 2 × 10 6 cycles could be realized. SEM analyses of the fatigue fracture surfaces have shown that the fatigue cracks observed on the specimens ground under cryogenic cooling are shorter (i.e., 30-50 μm) than those generated under oil-based cooling mode (i.e., 150-200 μm). The realized improvements in the surface integrity and in the fatigue behaviour are thought to be related to the reduction of the grinding zone temperature observed under cryogenic cooling, as no significant differences between the grinding force components for both cooling modes have been observed.

  3. Effect of tempering temperature on the microstructure and mechanical properties of a reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Li, C.W.; Han, L.Z.; Luo, X.M.; Liu, Q.D.; Gu, J.F., E-mail: gujf@sjtu.edu.cn

    2016-08-15

    The microstructure and mechanical properties of reactor pressure vessel (RPV) steel were investigated after tempering at different temperatures ranging from 580 to 700 °C for 5 h. With increasing tempering temperature, the impact toughness, which is qualified by Charpy V-notch total absorbed energy, initially increases from 142 to 252 J, and then decreases to 47 J, with a maximum value at 650 °C, while the ultimate tensile strength varies in exactly the opposite direction. Comparing the microstructure and fracture surfaces of different specimens, the variations in toughness and strength with the tempering temperature were generally attributed to the softening of the bainitic ferrite, the agminated Fe{sub 3}C carbides that resulted from decomposition of martensite/austenite (M/A) constituents, the precipitation of Mo{sub 2}C carbides, and the newly formed M/A constituents at the grain boundaries. Finally, the correlation between the impact toughness and the volume fraction of the M/A constituents was established, and the fracture mechanisms for the different tempering conditions are explained. - Highlights: • The dependence of the deterioration of impact toughness on tempering temperature has been analysed. • The instrumented Charpy V-notch impact test has been employed to study the fracture mechanism. • The influence of M/A constituents on different fracture mechanisms based on the hinge model has been demonstrated. • A correlation between the mechanical properties and the amount of M/A constituents has been established.

  4. Prediction and Monitoring Systems of Creep-Fracture Behavior of 9Cr-1Mo Steels for Teactor Pressure Vessels

    Energy Technology Data Exchange (ETDEWEB)

    Potirniche, Gabriel [Univ. of Idaho, Moscow, ID (United States); Barlow, Fred D. [Univ. of Idaho, Moscow, ID (United States); Charit, Indrajit [Univ. of Idaho, Moscow, ID (United States); Rink, Karl [Univ. of Idaho, Moscow, ID (United States)

    2013-11-26

    A recent workshop on next-generation nuclear plant (NGNP) topics underscored the need for research studies on the creep fracture behavior of two materials under consideration for reactor pressure vessel (RPV) applications: 9Cr-1Mo and SA-5XX steels. This research project will provide a fundamental understanding of creep fracture behavior of modified 9Cr-1Mo steel welds for through modeling and experimentation and will recommend a design for an RPV structural health monitoring system. Following are the specific objectives of this research project: Characterize metallurgical degradation in welded modified 9Cr-1Mo steel resulting from aging processes and creep service conditions; Perform creep tests and characterize the mechanisms of creep fracture process; Quantify how the microstructure degradation controls the creep strength of welded steel specimens; Perform finite element (FE) simulations using polycrystal plasticity to understand how grain texture affects the creep fracture properties of welds; Develop a microstructure-based creep fracture model to estimate RPVs service life; Manufacture small, prototypic, cylindrical pressure vessels, subject them to degradation by aging, and measure their leak rates; Simulate damage evolution in creep specimens by FE analyses; Develop a model that correlates gas leak rates from welded pressure vessels with the amount of microstructural damage; Perform large-scale FE simulations with a realistic microstructure to evaluate RPV performance at elevated temperatures and creep strength; Develop a fracture model for the structural integrity of RPVs subjected to creep loads; and Develop a plan for a non-destructive structural health monitoring technique and damage detection device for RPVs.

  5. 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.)

  6. Rotary Bending Fatigue Characteristics According to Optimal Friction Welding of SF45 to SM45C Steel Bars

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Yu Sik; Park, Young Whan [Pukyong Nat’l Univ., Busan (Korea, Republic of)

    2017-03-15

    A study on dissimilar friction-welded joints was performed for cam shaft applications using solid bar samples, 20mm in diameter, of forging steel(SF45) and carbon steel(SM45C). The main parameters of friction welding such as tensile tests, Vickers hardness surveys of the bond of area, the heat affected zone (HAZ), and the observation of microstructure were investigated to ensure a good quality of friction welding through visual observations. The specimens were tested as-welded and post weld heat treatment(PWHT). This paper deals with optimizing the welding conditions and analyzing various rotary bending fatigue test(RBFT) properties about heat-treated base metal(BM), as-welded and PWHT. Consequently, two materials for friction welding are strongly mixed with a well-combined structure of micro-particles without any molten material, particle growth, or any defect. Moreover, the fatigue limit of BM(SF45) and PWHT for the RBFT were observed as 180MPa and 250MPa, respectively. It was confirmed that the PWHT causes approximately 40% improvement in the fatigue limit when compared to the BM(SF45).

  7. FATIGUE LIFE PREDICTION BASED ON MACROSCOPIC PLASTIC ZONE ON FRACTURE SURFACE OF AISI-SAE 1018 STEEL

    Directory of Open Access Journals (Sweden)

    G.M. Domínguez Almaraz

    2010-06-01

    Full Text Available This paper deals with rotating bending fatigue tests at high speed (150 Hz carried out on AISI-SAE 1018 steel with a high content of impurities (non metallic inclusions, for which the high experimental stress inside the specimen is close to the elastic limit of the material. Simulations of rotating loading are obtained by Visual NASTRAN software in order to determine the numerical stresse and strain distributions inside a hypothetical homogeneous specimen; later, this information is used for the experimental set up. A general description of experimental test machine and experimental conditions are developed and then, the experimental results are presented and discussed according the observed failure origin related to the non metallic inclusions and the associated high stress zones. Finally, a simple model is proposed to predict the fatigue life for this non homogeneous steel under high speed rotating bending fatigue tests close to the elastic limit, based on the rate between the visual macro-plastic deformation zone at fracture surface and the total fracture surface, together with the crack initiation inclusion (or inclusions located at this zone.

  8. A new method for detection of fatigue cracking in steel bridge girders using self-powered wireless sensors

    Science.gov (United States)

    Hasni, Hassene; Alavi, Amir H.; Jiao, Pengcheng; Lajnef, Nizar

    2017-04-01

    Development of fatigue cracking is affecting the structural performance of many of welded steel bridges in the United States. This paper presents a support vector machine (SVM) method for the detection of distortion-induced fatigue cracking in steel bridge girders based on the data provided by self-powered wireless sensors (SWS). The sensors have a series of memory gates that can cumulatively record the duration of the applied strain at a specific threshold level. Each sensor output has been characterized by a Gaussian cumulative density function. For the analysis, extensive finite element simulations were carried out to obtain the structural response of an existing highway steel bridge girder (I-96/M- 52) in Webberville, Michigan. The damage states were defined based on the length of the crack. Initial damage indicator features were extracted from the sensor output distribution at different data acquisition nodes. Subsequently, the SVM classifier was developed to identify multiple damage states. A data fusion model was proposed to increase the classification performance. The results indicate that the models have acceptable detection performance, specific ally for cracks larger than 10 mm. The best classification performance was obtained using the information from a group of sensors located near the damage zone.

  9. Development of Novel Pre-alloyed PM Steels for Optimization of Machinability and Fatigue Resistance of PM Components

    Science.gov (United States)

    Mardan, Milad; Blais, Carl

    2016-03-01

    It is well known that a large proportion of ferrous PM components require secondary machining operations for dimensional conformance or for producing geometrical features that cannot be generated during die compaction. Nevertheless, the machining behavior of PM parts is generally characterized as being "difficult" due to the presence of residual porosity that lowers thermal conductivity and induces interrupted cutting. Several admixed additives such as MnS and BN-h can be used to improve the machining behavior of PM steels. Nevertheless, their negative effect on mechanical properties, especially fatigue resistance, makes their utilization uninteresting for the fabrication of high-performance PM steel components. This article summarizes the work carried out to develop a novel PM steel that was especially engineered to form machinability enhancing precipitates. This new material is pre-alloyed with tin (Sn) in order to form Cu-Sn (Cu(α)) precipitates during transient liquid phase sintering. The newly developed material presents machinability improvement of 165% compared to reference material used in the PM industry as well as increases in toughness and fatigue resistance of 100% and 13%, respectively.

  10. Separation of surface, subsurface and volume fatigue damage effects in AISI 348 steel for power plant applications

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Martin; Nowak, David; Walther, Frank [Technical Univ. Dortmund (Germany). Dept. of Materials Test Engineering (WPT); Starke, Peter [Saarland Univ., Saarbruecken (Germany). Chair of Non-Destructive Testing and Quality Assurance; Boller, Christian [Saarland Univ., Saarbruecken (Germany). Chair of Non-Destructive Testing and Quality Assurance; Fraunhofer IZFP, Saarbruecken (Germany)

    2016-08-01

    A wide range of industries including energy, chemistry, pharmacy, textiles, food and drink, pulp and paper, etc. is using stainless steels. Metastable austenitic steels such as used in power plants and chemical industry are subjected to cyclic mechanical and thermal loading in air as well as under the influence of corrosive media. This paper provides an overview on different nondestructive and electrochemical measurement techniques, which allow differentiating fatigue damage effects in total strain controlled multiple and constant amplitude tests with respect to damage appearance on surface, in subsurface area as well as in volume of specimens or components microstructure. In addition to conventional mechanical stress-strain hysteresis curves, electrical resistance, magnetic and open circuit potential measurements have been applied to characterize the cyclic deformation behavior of the metastable austenitic steel AISI 348 (X10CrNiNb18-9) in laboratory air and in distilled water. Based on these results obtained, the paper provides an outlook on the possibility for an efficient (remaining) fatigue life evaluation approach, which is adapted to the needs of the application areas.

  11. J-Integral characterization of the nozzle steels from intermediate test vessels IV-5 and IV-9

    Energy Technology Data Exchange (ETDEWEB)

    Auten, T.A.; Macdonald, B.D.; Scavone, D.W.; Bozik, D.

    1994-10-01

    Reported here are the results of elastic-plastic fracture toughness tests performed on low alloy steels from the nozzles of the intermediate test vessels IV-5 and IV-9 from the Heavy Steel Section Technology Program at Oak Ridge National Laboratory. These vessels had been given prototypic nozzle corner flaw tests prior to the development of the ASTM E-813 standard test procedure for J-integral testing. The objective of this work is to provide J-integral material test support for future elastic-plastic fracture mechanics analysis of the nozzles. J-integral tests at 88{degrees}C (190{degrees}F) of the IV-5 nozzle material produced stable ductile tearing. The tearing resistance data are expected to support analysis of the observed similar stable tearing response of the nozzle corner flaw. J-integral tests at 24{degrees}C (75{degrees}F) of the IV-9 nozzle produced elastic-plastic fracture instability preceded by stable tearing. A similar response was observed in the IV-9 nozzle corner flaw test. It will be a major and important challenge to develop a fracture mechanics rationale that reconciles these small specimen and nozzle corner flaw test results. These test results are being made available to allow their use by a wide variety of organizations in developing such a rationale, which would be a significant contribution to quantifying the flaw tolerance of reactor pressure vessels.

  12. Temperature effect on corrosion fatigue strength of coated ship structural steel; Zosen`yoko tosozai no fushoku hiro kyodo ni okeru ondo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Takanashi, M.; Fuji, A.; Kojima, M.; Kitagawa, M. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan); Kobayashi, Y. [Ship Research Inst., Tokyo (Japan); Kumakura, Y.

    1997-08-01

    The corrosion fatigue life was obtained using uncoated and tar epoxy resin specimens to clarify the temperature effect. The life curve for corrosion fatigue of machined and uncoated steel in the air and sea was obtained. The fatigue strength of uncoated steel largely decreases in the sea and breaks even in the nominal stress range of less than 1/2 of the fatigue limit in the air. The effect of temperature on the coated steel is represented by a corrosion coefficient. The steel coated at 25{degree}C is 1/1.03 to 1/1.13 at 40 to 60{degree}C. This showed that the fatigue strength decreases when the temperature exceeds 25{degree}C. However, it has not such tendency and significance that are represented quantitatively. There is a slight difference in the short-life area between the crack generation life and breaking life. However, the long-life area has no significance that influences the whole evaluation. In the long-life corrosion fatigue, the crack occurs from the corrosion pit due to the exposure below the coated film and progresses in the base material before the coated film is destroyed. The effect of the corrosion pit remarkably appears at a low-stress level. 14 refs., 14 figs., 4 tabs.

  13. The influence of inclusions on the low cycle fatigue properties of reduced activation ferritic/martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.H.; Kima, S.W. [Kyoto Univ., Graduate School of Energy Science (Japan); Tanigawa, H. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Kohyama, A. [Kyoto Univ., lnstitute of Advanced Energy (Japan)

    2007-07-01

    Full text of publication follows: Reduced activation ferritic/martensitic (RAFM) steels, such as F82H, are the primary near-term candidate for the blanket structural material of nuclear fusion reactors. During operation, blanket structural materials will be subjected to cyclic loading caused by start-up and shut-down procedure or plasma disruption. Therefore, investigation of fatigue property is essential to reactor design. It is considered that fatigue properties depend on the material factor such as the inclusion distribution, surface morphology and so on. Especially, many experimental results show that inclusions become the fracture origin in a given volume of material subjected to cyclic stress, and fracture failure is most likely to initiate at the largest inclusion in the volume. Therefore, the prediction of the size of maximum inclusion and its impact on fatigue properties would be essential to the fusion reactor materials development and application. This paper examines the possible relation between fatigue life and inclusion parameters such as size, shape, distribution and composition. The low cycle fatigue behavior of F82H steel at room temperature in air condition under fully reversed push-pull triangular wave was studied using miniaturized hourglass-type specimens with 1.25 mm in diameter. Total strain range is selected from 0.8% to 2.4%, and the strain rate was 0.04%/s. To examine the size and composition of the inclusions, fracture surfaces and crack initiation region were investigated by a scanning electron microscope (SEM) and EDS. The inclusions such as TaO{sub x}, TaO{sub x}- Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3} with the size below 10 {mu}m are observed on specimen surface. The surface observation of the specimen which discontinued testing at 20 and 500 cycle tested at the strain range of 1.4% revealed that fatigue loading induced separation of inclusions from the matrix in initial stage, then micro-crack induced around the inclusions

  14. High-Cycle Fatigue of High-Strength Low Alloy Steel Q345 Subjected to Immersion Corrosion for Mining Wheel Applications

    Science.gov (United States)

    Dicecco, Sante; Altenhof, William; Hu, Henry; Banting, Richard

    2017-04-01

    In an effort to better understand the impact of material degradation on the fatigue life of mining wheels made of a high-strength low alloy carbon steel (Q345), this study seeks to evaluate the effect of surface corrosion on the high-cycle fatigue behavior of the Q345 alloy. The fatigue behavior of the polished and corroded alloy was investigated. Following exposure to a 3.5 wt.% NaCl saltwater solution, polished and corroded fatigue specimens were tested using an R.R. Moore rotating-bending fatigue apparatus. Microstructural analyses via both optical microscopy and scanning electron microscopy (SEM) revealed that one major phase, α-iron phase, ferrite, and one minor phase, colony pearlite, existed in the extracted Q345 alloy. The results of the fatigue testing showed that the polished and corroded specimens had an endurance strength of approximately 295 and 222 MPa, respectively, at 5,000,000 cycles. The corroded surface condition resulted in a decrease in the fatigue strength of the Q345 alloy by 24.6%. Scanning electron microscope fractography indicated that failure modes for polished and corroded fatigue specimens were consistent in the high-cycle low loading fatigue regime. Conversely, SEM fractography of low-cycle high-loading fatigue specimens found considerable differences in fracture surfaces between the corroded and polished fatigue specimens.

  15. Effect of Fillet Rolling Load on the Fatigue Performance of a Micro-Alloy Steel Diesel Engine Crankshaft

    Science.gov (United States)

    Çevik, Gül; Gürbüz, Rıza

    2017-05-01

    Fillet rolling process is an effective method used to improve the fatigue performance of crankshafts by hardening the fillet region and inducing compressive residual stresses. This paper summarizes the work conducted to investigate the effect of rolling load on fatigue behaviour of a micro-alloy steel crankshaft used in diesel engine applications. Based on the staircase test methodology, component-scale resonant bending fatigue tests were conducted to obtain stress versus number of cycles curves and to evaluate the fatigue endurance limits of the crankshaft at un-rolled condition and fillet-rolled conditions at three different loads. Test data was analysed by Dixon-Mood method to calculate the endurance limits. Results showed that the endurance limit increased significantly with fillet rolling process in comparison to un-rolled condition. Endurance limit further increased with the increasing rolling load however with a limited extent above which excessive hardening deteriorates the fillet region; that is the workability limit. The outcomes of this study has shed light on the fillet rolling process to select the optimum rolling load for the used design and material conditions.

  16. Effects of External Hydrogen on Hydrogen Transportation and Distribution Around the Fatigue Crack Tip in Type 304 Stainless Steel

    Science.gov (United States)

    Chen, Xingyang; Zhou, Chengshuang; Cai, Xiao; Zheng, Jinyang; Zhang, Lin

    2017-10-01

    The effects of external hydrogen on hydrogen transportation and distribution around the fatigue crack tip in type 304 stainless steel were investigated by using hydrogen microprint technique (HMT) and thermal desorption spectrometry. HMT results show that some silver particles induced by hydrogen release are located near the fatigue crack and more silver particles are concentrated around the crack tip, which indicates that hydrogen accumulates in the vicinity of the crack tip during the crack growth in hydrogen gas environment. Along with the crack propagation, strain-induced α' martensite forms around the crack tip and promotes hydrogen invasion into the matrix, which will cause the crack initiation and propagation at the austenite/ α' martensite interface. In addition, the hydrogen content in the vicinity of the crack tip is higher than that at the crack edge far away from the crack tip, which is related to the stress state and strain-induced α' martensite.

  17. Study on the welding continuous cooling transformation and weldability of SA508Gr4 steel for nuclear pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Qingwei; Ma, Yonglin; Xing, Shuqing; Chen, Zhongyi [Inner Mongolia Univ. of Science and Technology, Baotou (China). School of Material and Metallurgy; Kang, Xiaolan [Baotou Vocational and Technical College (China)

    2017-02-15

    SA508Gr4 is a newly developed high-strength steel for nuclear reactor pressure vessels. Its welding characteristics remain largely unexplored. In this work, the simulated heat affected zone continuous cooling transformation (SH-CCT) diagram of SA508Gr4 steel was constructed and the high-temperature cooling phase compositions and the properties of the heat affected zone (HAZ) were characterized using dilatometry and microscopic tests. The results show that the phase transformation in the HAZ was divided into bainite and martensite transformation stages. When 4.6 ≤ t{sub 8/5} (the HAZ cooling time from 800 C to 500 C) ≤ 15 s, lath-shaped martensite was fully developed, resulting in extensive hardening and cold cracking in the HAZ, while the cooling time required to form the bainite completely exceeds 1 200 s. Thus, to improve weld quality, preheating to 196 C or higher is recommended.

  18. Embrittlement and annealing of reactor pressure vessel steels: comparison of BR3 surveillance and vessel plates to the surrogate plates representative of the Yankee Rowe vessel

    Energy Technology Data Exchange (ETDEWEB)

    Fabry, A.; Chaouadi, T.; Puzzolante, J.L.; Van de Velde, J. [Centre de l``Etude de l``Energie Nucleaire, Mol (Belgium); Biemiller, E.C. [Yankee Atomic Electric Company, Bolton (United States); Rossinski, S.T.; Carter, R.G. [Electric Power Research Institute, Charlotte (United States)

    1996-07-01

    The sister pressure vessels at the BR3 and Rowe Yankee PWR plants were operated at a lower-than-usual temperature (260 degrees Celsius) and their plates were austenitized at higher-than-usual temperature (970 degrees Celsius). A heat tratemement leading to a coarser microstructure than typical for the fine grain plates that are considered in development of USNRC Regulatory guide 1.99. This material displayed outlier behaviour charackterized by a 41J CVN-shift significantly larger than predicted by Regulatory Guide 1.99. Because lower radiation temperature and nickell alloying are generally considered detrimental to irradiation sensitivity, there was a major concern that the nickel-modified lower Rowe plate and the nickel-modified BR3 plate may become too embrittled to satisfy the toughness requirements enbodied in the PTS screening criterion. This paper compares three complementary studies undertaken to clarify these uncertainties: 1) the accelerated irradiation and test program launched in 1990 by Yankee Atomic Electric Company using typical vessel plate materials containing 0.24% copper at two nickel levels: YA1, 0.63% (A533-B) and YA9, 0.19% (A302-B). These were heat-treated to produce the coarse and fine grain microstructures representative of the Yankee/BR3 and the Regulatory Guide plates, respectively, 2) the BR3 surveillance and vessel testing program: this vessel was wet-annealed in 1984, relicensed for operation till the plant shutdown in 1987, ANCL was trepanned in early 1995, 3) the accelerated irradiations in the Belgian BR2 test reactor of the Yankee coarse grain plates YA1 and YA9 together with BR3 vessel specimens extracted at nozzle elevation, a location with negligible radiation exposure. It is shown that the PTS screening criterion was never attained by the BR3 and Rowe plates, and that the BR3 vessel anneal was neither necessary nor sufficient. Finally, the sensitivity of embrittlement, annealing and post-annealing reembrittlement to irradiation

  19. Mechanical properties of type 316L stainless steel welded joint for ITER vacuum vessel (1). Experiment of unirradiated welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Shigeru; Fukaya, Kiyoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ishiyama, Shintaro [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Takahashi, Hiroyuki; Koizumi, Kouichi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    2001-01-01

    In design activity of ITER, the vacuum vessel (VV) is ranked as one of the most important components in core reactor from the view point of first barrier to tritium release from the reactor. The VV of ITER is designed as double walled structure so that some parts of them are not qualified in the conventional design standards. So it is necessary to prepare the new design standards to be applied them. JAERI has executed the preparation activity of the new design standards and the technical data to support them. In this study, the results of metallographic observation and mechanical properties of unirradiated type 316L stainless steel welded joint were reported. (author)

  20. A study on the radiation damage and recovery of neutron irradiated vessel steel using magnetic Barkhausen noise

    Science.gov (United States)

    Park, Duck-Gun; Jeong, Hee-Tae; Hong, Jun-Hwa

    1999-04-01

    The radiation damage and thermal recovery characteristic of neutron irradiated SA508-3 reactor pressure vessel steel specimens have been investigated. Two recovery stages were identified from the results of hardness measurements during isochronal annealing and the mechanism responsible for the two stages was explained by using the results of Barkhausen noise measurement on the basis of the interaction between radiation induced defects and the magnetic domain wall. The coercivity was not changed by neutron irradiation, whereas the maximum magnetic induction increased. Barkhausen noise parameters associated with the domain wall motion were decreased by neutron irradiation and recovered with subsequent heat treatments.

  1. The effect of microstructural changes on magnetic barkhausen noise in Mn-Mo-Ni pressure vessel steel

    CERN Document Server

    Jeong, H T; Hong, J H; Ahn, Y S; Kim, G M

    1999-01-01

    The effect of microstructural changes on magnetic Barkhausen noise (BN) has been investigated in Mn-Mo-Ni pressure-vessel steel with various microstructures. The BN energy was strongly influenced by the microstructural features, such as the dislocation density, the residual stress, and the carbide morphology. The measured differences in BN signals are discussed on the basis of the domain wall dynamics associated with the microstructural states. The microstructures were observed by using atomic force microscopy(AFM), and the AFM results compared with the scanning electron microscopy observations.

  2. Identification and analysis of slip systems activated during low-cycle fatigue in a duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    El Bartali, A.; Aubin, V.; Sabatier, L. [Laboratoire de Mecanique de Lille, LML, UMR CNRS 8107, Ecole Centrale de Lille, BP 48, 59651 Villeneuve d' Ascq Cedex (France); Villechaise, P. [Laboratoire de Mecanique et de Physique des Materiaux, LMPM, UMR CNRS 6617, Ecole Nationale Superieure de Mecanique et Aerotechnique, Teleport 2, 1 Avenue C. Ader, BP 40109, 86961 Futuroscope, Chasseneuil Cedex (France); Degallaix-Moreuil, S. [Laboratoire de Mecanique de Lille, LML, UMR CNRS 8107, Ecole Centrale de Lille, BP 48, 59651 Villeneuve d' Ascq Cedex (France)], E-mail: suzanne.degallaix@ec-lille.fr

    2008-12-15

    This paper focuses on the identification of activated slip systems in low-cycle fatigue ({delta}{epsilon}{sub t}/2 = 5 x 10{sup -3}) in a duplex stainless steel. From electron backscattered diffraction measurements and scanning electron microscopy observations, the slip systems and their associated Schmid factor are analyzed in both constitutive phases. In austenitic grains, one or two slip systems are activated with Schmid factors greater than 0.25. While in the ferritic grains, several slip systems are activated, with a variety of Schmid factors.

  3. Influence of Exposure to an Aggressive Environment on Cyclic Fatigue Response and Life of an Alloy Steel

    Directory of Open Access Journals (Sweden)

    Tirumalai Srivatsan

    2017-06-01

    Full Text Available Corrosion or environment-induced degradation often occurs in structural steel as an electrochemical process which leads to gradual loss in mass over a period when subjected to prolonged exposure to an aggressive environment. Immediate effects of this environment-induced degradation, also referred to in industry circles as corrosion, includes a progressive reduction of the cross section, which in turn has a detrimental influence on stiffness and load carrying capacity of the components in a structure, such as a bridge, a stiffened panel or a building. Due to its high strength, low alloy A572 Grade 50 steel is a potentially viable candidate for a wide range of applications in the construction industry. However, like in other high strength alloy steels, A572 is vulnerable to the effects of degradation-induced by the environment owing to its chemical composition. This paper discusses the details of tests conducted to determine the fatigue properties of A572 steel after inducing uniform environment-induced degradation or corrosion.  Flat (rectangular dog-bone shaped specimens, conforming to specifications detailed in ASTM E8 standard, were used in this study.  A technique that was developed by the ASTM and General Motors Corporation (GM [called GMW14872] for a controlled corrosion process based on use of the spray technique was used to induce accelerated corrosion on selected test specimens in an environment chamber.  Stress-controlled high cycle fatigue tests were conducted on the corroded test specimens and compared with the as-new, uncorroded counterpart.

  4. Microstructure and dislocation arrangements in Sanicro 25 steel fatigued at ambient and elevated temperatures

    Czech Academy of Sciences Publication Activity Database

    Heczko, Milan; Polák, Jaroslav; Kruml, Tomáš

    2017-01-01

    Roč. 680, JAN (2017), s. 168-181 ISSN 0921-5093 R&D Projects: GA MŠk LM2015069; GA MŠk(CZ) LQ1601; GA ČR(CZ) GA13-23652S Institutional support: RVO:68081723 Keywords : Sanicro 25 * Z-phase * Low cycle fatigue * Low cycle fatigue * Transmission Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 3.094, year: 2016

  5. Effects of carbon content on high-temperature mechanical and thermal fatigue properties of high-boron austenitic steels

    Directory of Open Access Journals (Sweden)

    Xiang Chen

    2016-01-01

    Full Text Available High-temperature mechanical properties of high-boron austenitic steels (HBASs were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239 (0.19wt.% C to 302 (0.29wt.% C and 312 HV (0.37wt.% C; the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests (performed for 300 cycles from room temperature to 800 °C indicate that the degree of thermal fatigue of the HBAS with 0.29wt.% C (rating of 2–3 is superior to those of the alloys with 0.19wt.% (rating of 4–5 and 0.37wt.% (rating of 3–4 carbon. The main cause of this difference is the ready precipitation of M23(C,B6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.

  6. Neutron radiation embrittlement studies in support of continued operation, and validation by sampling of Magnox reactor steel pressure vessels and components

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R.B.; Bolton, C.J. [Magnox Electric plc, Berkeley Centre, Glos (United Kingdom)

    1997-02-01

    Magnox steel reactor pressure vessels differ significantly from US LWR vessels in terms of the type of steel used, as well as their operating environment (dose level, exposure temperature range, and neutron spectra). The large diameter ferritic steel vessels are constructed from C-Mn steel plates and forgings joined together with manual metal and submerged-arc welds which are stress-relieved. All Magnox vessels are now at least thirty years old and their continued operation is being vigorously pursued. Vessel surveillance and other programmes are summarized which support this objective. The current understanding of the roles of matrix irradiation damage, irradiation-enhanced copper impurity precipitation and intergranular embrittlement effects is described in so far as these influence the form of the embrittlement and hardening trend curves for each material. An update is given on the influence of high temperature exposure, and on the role of differing neutron spectra. Finally, the validation offered by the results of an initial vessel sampling exercise is summarized together with the objectives of a more extensive future sampling programme.

  7. Data demonstrating the effects of build orientation and heat treatment on fatigue behavior of selective laser melted 17–4 PH stainless steel

    OpenAIRE

    Yadollahi, Aref; Simsiriwong, Jutima; Thompson, Scott M.; Shamsaei, Nima

    2016-01-01

    Axial fully-reversed strain-controlled ( R = ? 1 ) fatigue experiments were performed to obtain data demonstrating the effects of building orientation (i.e. vertical versus horizontal) and heat treatment on the fatigue behavior of 17?4 PH stainless steel (SS) fabricated via Selective Laser Melting (SLM) (Yadollahi et al., submitted for publication [1]). This data article provides detailed experimental data including cyclic stress-strain responses, variations of peak stresses during cyclic def...

  8. Application of strainrange partitioning to the prediction of MPC creep-fatigue data for 2 1/4 Cr-1Mo steel

    Science.gov (United States)

    Saltsman, J. F.; Halford, G. R.

    1976-01-01

    Strainrange partitioning is used to predict the long time cyclic lives of the metal properties council (MPC) creep-fatigue interspersion and cyclic creep-rupture tests conducted with annealed 2 1/4 Cr-1Mo steel. Observed lives agree with predicted lives within factors of two. The strainrange partitioning life relations used for the long time predictions were established from short time creep-fatigue data generated at NASA-Lewis on the same heat of material.

  9. Creep-Fatigue Damage Evaluation of a Model Reactor Vessel and Reactor Internals of Sodium Test Facility according to ASME-NH and RCC-MRx Codes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dong-Won; Lee, Hyeong-Yeon; Eoh, Jae-Hyuk; Son, Seok-Kwon; Kim, Jong-Bum; Jeong, Ji-Young [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    The objective of the STELLA-2 is to support the specific design approval for PGSFR by synthetic reviews of key safety issues and code validations through the integral effect tests. Due to its high temperature operation in SFRs (and in a testing facility) up to 550 °C, thermally induced creep-fatigue damage is very likely in components including a reactor vessel, reactor internals (interior structures), heat exchangers, pipelines, etc. In this study, structural integrity of the components such as reactor vessel and internals in STELLA-2 has been evaluated against creep-fatigue failures at a concept-design step. As 2D analysis yields far conservative results, a realistic 3D simulation is performed by a commercial software. A design integrity guarding against a creep-fatigue damage failure operating at high temperature was evaluated for the reactor vessel with its internal structure of the STELLA-2. Both the high temperature design codes were used for the evaluation, and results were compared. All the results showed the vessel as a whole is safely designed at the given operating conditions, while the ASME-NH gives a conservative evaluation.

  10. An Experimental Study on the Low Cycle Fatigue Behaviors of Domestic IP Rotor Steel for 1000MW Ultra-Supercritical Turbine

    Science.gov (United States)

    Wang, Yanfeng; Lin, Fusheng; Zhao, Shuangqun

    Due to the good combination of high temperature strength and manufacturing performance, 10%Cr steel has been widely used as the material of 1000MW ultra-supercritical turbine HP/IP rotors in China. In addition to creep strength, good low cycle fatigue resistance is needed for rotor's design and service safety because high cyclic stresses are often produced during start-stop and variable load operations of turbine. In this paper, low cycle fatigue experiments of 12Cr10Mo1W1NiVNbN steel, which is a domestic IP rotor steel used in ultra-supercritical turbines, were carried out under constant strain condition at room temperature and 873K. The cyclic stress-strain relationship and strain-life curve were established using Ramberg-Osgood and Manson-Coffin equations, respectively. The transition fatigue life of the material was also obtained, over which the elastic strain dominates the fatigue life and under which the plastic strain does. Finally, the low cycle fatigue property of the current steel is compared with that of the German rotor materials reported in the literatures.

  11. Effect of load ratio and saltwater corrosive environment on the initiation life of fatigue of 10Ni5CrMoV steel

    Science.gov (United States)

    Xie, Xing; Yi, Hong; Xu, Jian; Gen, Liming; Chen, Luyun

    2017-09-01

    Fatigue initiation life has been studied with 10CrNi5MoV steel for use in ocean engineering at different load ratios and in different environmental media. The microstructure and micro-topography have been observed and analyzed by means of SEM, EDS and EBSD. Our findings indicate that, the initiation life of 10Ni5CrMoV steel in seawater is shorter than that in air, and the difference in longevity is larger with the increasing of load ratio. Corrosion pits had a great influence on initial corrosion fatigue life.

  12. Fatigue crack initiation and propagation in steels exposed to inert and corrosive environments. Final report, May 1, 1977--December 31, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Youseffi, K.; Finnie, I.

    1978-02-01

    The fatigue crack initiation life of AISI 1018 steel was investigated using compact tension specimens having sharp notch root radii. The data were analyzed using two methods for predicting initiation in strain cycling experiments. Also, another approach in which initiation is related to the stress intensity factor was developed. The next phase, that of propagation, was studied using AISI 1018 steel and a new high strength steel HY-180. The crack propagation data obtained for both steels tested in air can be described accurately by the power law first suggested by Paris, da/dN = C(..delta..K)/sup n/, where a is the crack length, N the number of cycles, and C and n are material constants. However, the exponent n was found to be two times larger for AISI 1018 steel than HY-180 steel.

  13. Digital image correlation and infrared measurements to determine the influence of a uniaxial pre-strain on fatigue properties of a dual phase steel.

    Directory of Open Access Journals (Sweden)

    Calloch S.

    2010-06-01

    Full Text Available The high cycle fatigue (HCF is a major element for a great design of automotive parts. A wide part of the steel sheets for the automotive industry are stamped, sometimes deeply. During this operation, the steel is plastically strained in different directions, so that a good prediction of the fatigue behavior requires the determination of the fatigue properties of the pre-strained material. Nowadays, the evolution of HCF properties is often neglected, because of prohibitive time dedicated to traditional fatigue campaigns. To reduce the characterization time, self-heating measurements are used. This approach permits to identify the influence of homogeneous pre-strain on fatigue properties. The aim of this paper is to develop an original experimental test to identify this influence for a wide range of pre-strain with only one specimen. The study of a particular case of specimen with a constant gradient of pre-strain is presented. Digital image correlation is a way to determine the heterogeneity of the plastic pre-strain on the specimen and infrared measurements with a ”1D” approach allows the determination of the influence of a plastic pre-strain on the fatigue properties of the studied steel.

  14. Disclosure of the oscillations in kinetics of the reactor pressure vessel steel damage at fast neutron intensity decreasing

    Science.gov (United States)

    Krasikov, E.; Nikolaenko, V.

    2017-01-01

    Fast neutron intensity influence on reactor materials radiation damage is a critically important question in the problem of the correct use of the accelerated irradiation tests data for substantiation of the materials workability in real irradiation conditions that is low neutron intensity. Investigations of the fast neutron intensity (flux) influence on radiation damage and experimental data scattering reveal the existence of non-monotonous sections in kinetics of the reactor pressure vessels (RPV) steel damage. Discovery of the oscillations as indicator of the self-organization processes presence give reasons for new ways searching on reactor pressure vessel (RPV) steel radiation stability increasing and attempt of the self-restoring metal elaboration. Revealing of the wavelike process in the form of non monotonous parts of the kinetics of radiation embrittlement testifies that periodic transformation of the structure take place. This fact actualizes the problem of more precise definition of the RPV materials radiation embrittlement mechanisms and gives reasons for search of the ways to manage the radiation stability (nanostructuring and so on to stimulate the radiation defects annihilation), development of the means for creating of more stableness self recovering smart materials.

  15. Stress Corrosion Cracking and Fatigue Crack Growth Studies Pertinent to Spacecraft and Booster Pressure Vessels

    Science.gov (United States)

    Hall, L. R.; Finger, R. W.

    1972-01-01

    This experimental program was divided into two parts. The first part evaluated stress corrosion cracking in 2219-T87 aluminum and 5Al-2.5Sn (ELI) titanium alloy plate and weld metal. Both uniform height double cantilever beam and surface flawed specimens were tested in environments normally encountered during the fabrication and operation of pressure vessels in spacecraft and booster systems. The second part studied compatibility of material-environment combinations suitable for high energy upper stage propulsion systems. Surface flawed specimens having thicknesses representative of minimum gage fuel and oxidizer tanks were tested. Titanium alloys 5Al-2.5Sn (ELI), 6Al-4V annealed, and 6Al-4V STA were tested in both liquid and gaseous methane. Aluminum alloy 2219 in the T87 and T6E46 condition was tested in fluorine, a fluorine-oxygen mixture, and methane. Results were evaluated using modified linear elastic fracture mechanics parameters.

  16. A study on the irradiation embrittlement and recovery characteristics of light water reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Se Hwan; Hong, Jun Hwa; Lee, Bong Sang; Oh, Jong Myung; Song, Sook Hyang; Milan, Brumovsky [NRI Czech (Czech Republic)

    1999-03-01

    The neutron irradiation embrittlement phenomenon of light water RPV steels greatly affects the life span for safe operation of a reactor. Reliable evaluation and prediction of the embrittlement of RPV steels, especially of aged reactors, are of importance to the safe operation of a reactor. In addition, the thermal recovery of embrittled RPV has been recognized as an option for life extension. This study aimed to tracer/refine available technologies for embrittlement characterization and prediction, to prepare relevant materials for several domestic RPV steels of the embrittlement and recovery, and to find out possible remedy for steel property betterment. Small specimen test techniques, magnetic measurement techniques, and the Meechan and Brinkmann's recovery curve analysis method were examined/applied as the evaluation techniques. Results revealed a high irradiation sensitivity in YG 3 RPV steel. Further extended study may be urgently needed. Both the small specimen test technique for the direct determination of fracture toughness, and the magnetic measurement technique for embrittlement evaluation appeared to be continued for the technical improvement and data base preparation. Manufacturing process relevant to the heat treatment appeared to be improved in lowering the irradiation sensitivity of the steel. Further study is needed especially in applying the present techniques to the new structural materials under new irradiation environment of advanced reactors. (author)

  17. Multiple Fatigue Failure Behaviors and Long-Life Prediction Approach of Carburized Cr-Ni Steel with Variable Stress Ratio.

    Science.gov (United States)

    Deng, Hailong; Li, Wei; Zhao, Hongqiao; Sakai, Tatsuo

    2017-09-14

    Axial loading tests with stress ratios R of -1, 0 and 0.3 were performed to examine the fatigue failure behavior of a carburized Cr-Ni steel in the long-life regime from 10⁴ to 10⁸ cycles. Results show that this steel represents continuously descending S-N characteristics with interior inclusion-induced failure under R = -1, whereas it shows duplex S-N characteristics with surface defect-induced failure and interior inclusion-induced failure under R = 0 and 0.3. The increasing tension eliminates the effect of compressive residual stress and promotes crack initiation from the surface or interior defects in the carburized layer. The FGA (fine granular area) formation greatly depends on the number of loading cycles, but can be inhibited by decreasing the compressive stress. Based on the evaluation of the stress intensity factor at the crack tip, the surface and interior failures in the short life regime can be characterized by the crack growth process, while the interior failure with the FGA in the long life regime can be characterized by the crack initiation process. In view of the good agreement between predicted and experimental results, the proposed approach can be well utilized to predict fatigue lives associated with interior inclusion-FGA-fisheye induced failure, interior inclusion-fisheye induced failure, and surface defect induced failure.

  18. Conditioning monitoring by microstructural evaluation of cumulative fatigue damage

    Science.gov (United States)

    Fukuoka, C.; Nakagawa, Y. G.; Lance, J. J.; Pangborn, R. N.

    1996-12-01

    The objective of this work is to evaluate the damage induced below and above the fatigue limit (Δ σ t =360 MPa) in pressure vessel steels, such as SA508. Fatigue damage was induced in samples taken from an SA508 steel plate by various loading histories in order to examine the influence of prior cyclic loading below the fatigue limit. Cell-to-cell misorientation differences were measured by the selected area diffraction (SAD) method. Surface cracking was also studied by the replication method. Small cracks were observed after precycling both below and above the fatigue limit. It was, however, found that fatigue test bars had a longer lifetime after precycling below the fatigue limit, while precycling above the fatigue limit caused other specimens to fail even when subsequently cycled below the fatigue limit. Cell-to-cell misorientation usually increases with accumulation of fatigue damage, but it was found that the misorientations measured after precycling below the fatigue limit decreased again at the beginning of the subsequent cycling above the fatigue limit. It should be noted that the misorientation at failure was always about 4 to 5 deg, regardless of loading histories. Misorientation showed good correlation with the fatigue lifetime of the samples.

  19. Specific Features of Structural-Phase State and Properties of Reactor Pressure Vessel Steel at Elevated Irradiation Temperature

    Directory of Open Access Journals (Sweden)

    E. A. Kuleshova

    2017-01-01

    Full Text Available This paper considers influence of elevated irradiation temperature on structure and properties of 15Kh2NMFAA reactor pressure vessel (RPV steel. The steel is investigated after accelerated irradiation at 300°C (operating temperature of VVER-1000-type RPV and 400°C supposed to be the operating temperature of advanced RPVs. Irradiation at 300°C leads to formation of radiation-induced precipitates and radiation defects-dislocation loops, while no carbide phase transformation is observed. Irradiation at a higher temperature (400°C neither causes formation of radiation-induced precipitates nor provides formation of dislocation loops, but it does increase the number density of the main initial hardening phase—of the carbonitrides. Increase of phosphorus concentration in grain boundaries is more pronounced for irradiation at 400°C as compared to irradiation at 300°C due to influence of thermally enhanced diffusion at a higher temperature. The structural-phase changes determine the changes of mechanical properties: at both irradiation temperatures irradiation embrittlement is mainly due to the hardening mechanism with some contribution of the nonhardening one for irradiation at 400°C. Lack of formation of radiation-induced precipitates at T = 400°C provides a small ΔTK shift (17°C. The obtained results demonstrate that the investigated 15Kh2NMFAA steel may be a promising material for advanced reactors with an elevated operating temperature.

  20. Effects of Hydrogen on Fatigue Crack Growth and Stretch Zone of 0.08mass%C Low Carbon Steel Pipe

    OpenAIRE

    松岡,三郎; 堤, 紀子; 村上, 敬宜

    2008-01-01

    In order to investigate the influence of hydrogen and test frequency on fatigue crack growth rate, fatigue crack growth tests (R=0) were conducted on hydrogen charged and uncharged specimens of a 0.08mass%C low carbon steel pipe at test frequency 0.001-10Hz. Following the fatigue crack growth tests, the test for producing a stretch zone was carried out. Observing the morphologies of the striation and stretch zone on the fracture surface and slip bands on the specimen surface, it was revealed ...

  1. Study of the fatigue behaviour and damage of a aged duplex stainless steel; Etude du comportement et de l'endommagement en fatigue d'un acier inoxydable austeno-ferritique moule vieilli

    Energy Technology Data Exchange (ETDEWEB)

    Le Roux, J.Ch

    2000-07-01

    Cast duplex stainless steels are commonly used in components of pressurized water reactors primary circuit. When submitted to in-service temperatures embrittlement occurs because of the nucleation and growth of a harder phase in the ferrite by spinodal composition. Macrostructure of this steel (ferritic primary grain size is about 4-5 mm) and embrittlement of ferrite due to aging lead to a very high scattering of mechanical properties for monotonous loadings. We showed that, in spite of this macrostructure, the cyclic behaviour of aged duplex stainless steels fits usual Manson-Coffin law while initial hardening is followed by softening, in part because of the demodulation of the composition. The fatigue crack propagation rate of material follows a Paris law. While crack initiation mainly appears next to the millimetric cast defects, fatigue crack propagation remains a continuous mechanism. Ferritic and austenitic elements break successively (ferrite first breaks by cleavage, then austenite breaks by ductile fatigue). In spite of the fact that the aged ferrite is embrittled, cleavage microcracks, for load levels examined, seldom appear in ferrite at the crack tip and on both sides of the main crack. Effects of cast defects and crystallographic ferrite orientation were also studied. Propagation fatigue crack behaviour was modeled assuming that the crack tip material behaves as if it was submitted to low cycle fatigue loadings. If we consider a homogeneous material, results are in good agreement with experiments. (authors)

  2. Mechanical properties of a modified 2 1/4 Cr-1 Mo steel for pressure vessel applications. [V-Ti-B-modified

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Swindeman, R.W.

    1983-12-01

    Tensile and creep properties were determined on a V-Ti-B-modified 2 1/4 Cr-1 Mo steel considered to be a candidate alloy for pressure vessel aplications for coal liquefaction. The modified 2 1/4 Cr-1 Mo steel had about 0.2% V added for improved elevated-temperature strength and 0.02% Ti for grain refinement. Boron was added to improve the hardenability, thus allowing thicker sections to be quenched and normalized to completely bainitic microstructures. Lower carbon and silicon concentrations were used (approx. 0.1% C and 0.02% Si) than in standard 2 1/4 Cr-1 Mo steel. The mechanical properties determined on the modified steel after a heat treatment typical for SA-387, grade 22, class 2, indicated high toughness and excellent elecated-temperature tensile and creep strength. The modified steel had substantially better stress-rupture properties than did a standard 2 1/4 Cr-1 Mo steel (both with bainitic microstructures) with equivalent tensile properties - especially at the lowest stresses and highest temperatures. The modified steel had toughness properties superior to those of the standard 2 1/4 Cr-1 Mo steel. Comparative transmission electron microscopy studies of the standard and modified 2 1/4 Cr-1 Mo steels indicated that the differences involve the carbide precipitates and the dislocation substructures present in the steels.

  3. The Influence of Hydrogen on the Evolving Microstructure During Fatigue Crack Growth in Metastable and Stable Austenitic Stainless Steels

    Science.gov (United States)

    Nygren, Kelly Elizabeth

    The effect of high levels of internal hydrogen on the microstructure evolving during stage II fatigue crack growth was investigated through a series of tensile and fatigue studies in metastable (304) and stable (316, 316L) stainless steels. The first, a tensile study in 304 stainless steel, identified the underlying microstructure which resulted in the flat and quasi-cleavage features on the fracture surface of a hydrogen-charged tensile bar. The second study utilized single-edge notched tensile specimens loaded in fatigue, and compared the evolving microstructure ahead of a fatigue crack for cases of an uncharged, 10 wppm hydrogen-charged, and 104 wppm hydrogen-charged 304 and 316L alloy. The final fatigue study, a small fatigue crack growth study in round bars of 304 and 316, provided a contextual comparison of microstructures to previous results in literature. In the metastable 304 stainless steel, hydrogen is found to change the nature of the martensitic transformation and subsequent fracture path. This transformation is attributed to enhanced plasticity and hydrogen-dislocation interactions stabilizing the austenitic matrix and confining slip to particular close-packed planes. The martensite acts as a fast diffusion pathway for hydrogen, leading to final fracture along martensitic laths or cleavage planes. In 316L, the material deforms via slip and twinning and hydrogen does not induce a change in deformation mechanisms. Instead, the enhanced plasticity and hydrogen-dislocation interactions increase the degree of plasticity, leading to smaller dislocation cell sizes with thicker walls before the onset of twinning. The crack interacts with a heavily twinned structure superimposed on dislocation cells, resulting in a curvature of one twin-variant in the direction of crack growth and the formation of a refined region at the fracture surface. These structures are localized to the crack surface and limited in rotation in the presence of hydrogen. The presence of a

  4. Fatigue experiments on very high strength steel base material and transverse butt welds

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2009-01-01

    Very High Strength Steels (VHSS) with nominal strengths up to 1100 MPa have been available on the market for many years. However, the use of these steels in the civil engineering industry is still uncommon, due to lack of design and fabrication knowledge and therefore limited inclusion in codes.

  5. Failure and fatigue life assessment of steel railway bridges with brittle material

    NARCIS (Netherlands)

    Maljaars, J.

    2014-01-01

    Some existing steel bridges have been constructed from steels with a toughness that does not fulfil the requirements in modern standards. In such a case, standards for bridges do not provide an alternative assessment route. Yet such bridges may still be fit for purpose. This paper presents an

  6. High strength reinforcing steel bars : low-cycle fatigue behavior : final report - part B.

    Science.gov (United States)

    2017-03-01

    High-strength steel (HSS) reinforcing steel, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) reinfor...

  7. High strength reinforcing steel bars : low cycle fatigue behavior : final report - part B.

    Science.gov (United States)

    2017-03-01

    High-strength steel (HSS) reinforcing steel, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) reinfor...

  8. INFLUENCE OF SHOCK VOLTAGE FROM THE ELECTRIC DISCHARGE ON THE FATIGUE ENDURANCE OF CARBON STEEL IN WATER

    Directory of Open Access Journals (Sweden)

    I. O. Vakulenko

    2015-09-01

    Full Text Available Purpose. The research supposes the explanation of influence of stress impulses from an electrical discharge in water on the level of the limited endurance at a cyclic loading of the thermally work-hardened carbon steel. Methodology. Material for research was steel 45 (0,45 % carbon with сoncentration of chemical elements within the limits of steel composition. Specimens for tests are made as plates in 1 thick, width 15 and length 120-180 mm. The structural state of steel corresponded to quenching on a martensite from the normal temperatures of annealing and tempering at 300C, duration of 1 h. Microstructure was investigated with the use of electronic microscopy, the density of dislocations was estimated on the methods of X-ray analysis. Hardness was measured on the method of Rockwell (scale of «C». A cyclic loading was carried out in the conditions of symmetric bend on a tester «Saturn-10» at a temperature +20C. The treatment by shock voltage from the electrical discharge was carried out in water on setting of bath type «Iskra-23», used for cleaning of castings manufactures. Electric impulses were formed at 15-18 kV with energy of 10-12 kJ and amplitude of 1-2 GPа. Findings. As a result of processing pulses of a pressure wave of heat-strengthened steel 45 found the increase of endurance under the cyclic loading corresponds to an increased amount of accumulated dislocations on the fracture surface. The use of Coffin–Manson Equation allowed finding the decrease of deformation per cycle of loading as a result of arising stress from an electrical discharge in water. On the fracture surface (after pulse exposure was found the increased number of dislocations, located in different crystallographic systems, that is a testament to the rather complicated development of dislocation transformations in the structure of steel, which provide an increase of endurance at a fatigue. The increase of the limited endurance became as a result of impulsive

  9. Development of High Strength Low Alloy Steel for Nuclear Reactor Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. S.; Kim, M. C.; Yoon, J. H; Choi, K. J.; Kim, J. M.; Hong, J. H.

    2013-11-15

    SA508 Gr. 4N Ni-Cr-Mo low alloy steel has an improved strength and fracture toughness, compared to commercial low alloy steels such as SA508 Gr. 3 Mn-Mo-Ni low alloy steel. In this study, the microstructural observation and baseline test were carried out using SA508 Gr. 4N model alloy of 1 ton scale. Thermal embrittlement and neutron irradiation embrittlement behaviors of SA508 Gr. 4N model alloy were also evaluated. The yield strength of 540MPa, Charpy transition temperature, T{sub 41J} of -132 .deg. C, Reference temperature, T{sub 0} of -146 .deg. C, and RT{sub NDT} of -105 .deg. C were obtained from large scale SA508 Gr. 3 low alloy steel. Effect of alloy elements on thermal embrittlement was carefully evaluated and embrittlement mechanism was characterized using small scale model alloys with various alloy composition. Neutron irradiation behavior at high fluence level up to 1.5x10{sup 20} n/cm{sup 2} corresponding over 80 years operation of RPV were investigated using irradiated samples from research reactor 'HANARO'. The irradiation embrittlement behavior of SA508 Gr. 4N model alloy was similar to that of commercial RPV steel. However, after neutron irradiation up to 1.3x10{sup 20} n/cm{sup 2}, SA508 Gr. 4N model alloy shows lower transition temperature(T{sub 41J} = -63 .deg. C) than unirradiated commercial RPV steel because it has a superior initial toughness.

  10. Hot Deformation Behavior of SA508Gr.4N Steel for Reactor Pressure Vessels

    OpenAIRE

    Yang, Zhi-Qiang; Liu, Zheng-Dong; HE Xi-kou; Liu, Ning

    2017-01-01

    The high-temperature plastic deformation and dynamic recrystallization behavior of SA508Gr.4N steel were investigated through hot deformation tests in a Gleeble1500D thermal mechanical simulator. The compression tests were performed in the temperature range of 1050-1250℃ and the strain rate range of 0.001-0.1s-1 with true strain of 0.16. The results show that from the high-temperature true stress-strain curves of the SA508Gr.4N steel, the main feature is dynamic recrystallization,and the peak...

  11. 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)

  12. A comparison of tensile, fracture and fatigue mechanical behaviour of structural reinforcing bars made with different steels

    Directory of Open Access Journals (Sweden)

    Rodríguez, C.

    2013-09-01

    Full Text Available The use of austenitic stainless steels as rebar is an option increasingly used in reinforced concrete structures exposed to aggressive environments and especially those that have to work in marine environments. The same is true for duplex stainless steel rebars, although nowadays they have a lower use, mainly due to the fact that their inclusion in the reinforced concrete standards was delayed 10 years compared to austenitic stainless steel ones, and consequently their in-service behavior is not as well known. A study of the mechanical properties, including fracture toughness, fatigue behaviour and corrosion resistance in saline alkaline environments of austenitic (AISI 304LN and 316LN and duplex (D2205 stainless steel reinforcing bars was performed in this work. Bars made on a high ductility carbon steel (B500SD that are normally used to reinforce concrete were also characterized and used as a comparison. Stainless steel reinforcing bars show mechanical properties at least similar but usually higher than one of the best carbon steel re-bars (B500SD, along with a significantly higher ductility and, of course, much better corrosion behaviour in saline alkaline environments.El uso de aceros inoxidables austeníticos como armaduras de refuerzo es una opción cada vez más utilizada en estructuras de hormigón armado expuestas a ambientes agresivos y especialmente en las que han de trabajar en ambientes marinos. Lo mismo cabe decir de las armaduras de acero inoxidable dúplex, si bien su uso es menor, debido sobre todo a que su inclusión en la normativa aplicable al armado de hormigón se retrasó 10 años con respecto a los inoxidables austeníticos y, consecuentemente, su comportamiento en servicio es menos conocido. En este trabajo se analiza el comportamiento mecánico, incluyendo fractura y fatiga, así como la resistencia a la corrosión en medios que simulan un hormigón contaminado de cloruros, de armaduras fabricadas tanto con

  13. A procedure to identify and to assess risk parameters in a SCR (Steel Catenary Riser) due to the fatigue failure

    Energy Technology Data Exchange (ETDEWEB)

    Stefane, Wania [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Faculdade de Engenharia Mecanica; Morooka, Celso K. [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Dept. de Engenharia de Petroleo. Centro de Estudos de Petroleo; Pezzi Filho, Mario [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). E and P. ENGP/IPMI/ES; Matt, Cyntia G.C.; Franciss, Ricardo [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)

    2009-12-19

    The discovery of offshore fields in ultra deep water and the presence of reservoirs located in great depths below the seabed requires innovative solutions for offshore oil production systems. Many riser configurations have emerged as economically viable technological solutions for these scenarios. Therefore the study and the development of methodologies applied to riser design and procedures to calculate and to dimension production risers, taken into account the effects of mete ocean conditions, such as waves, current and platform motion in the fatigue failure is fundamental. The random nature of these conditions as well as the mechanical characteristics of the riser components are critical to a probabilistic treatment to ensure the greatest reliability for risers and minimum risks associated to different aspects of the operation like the safety of the installation, economical concerns and the environment. The current work presents a procedure of the identification and the assessment of main parameters of risk when considering fatigue failure. Static and dynamic behavior of Steel Catenary Riser (SCR) under the effects of mete ocean conditions and uncertainties related to total cumulative damage (Miner-Palmgren's rule) are taken into account. The methodology adopted is probabilistic and the approach is analytical. The procedure is based on the First Order Reliability Method (FORM) which usually presents low computational effort and acceptable accuracy. The procedure suggested is applied for two practical cases, one using data available from the literature and the second with data collected from an actual Brazilian offshore field operation. For both cases, results of the probability of failure due to fatigue were obtained for different locations along the SCR length connected to a semi-submersible platform. From these results, the sensitivity of the probability of failure due to fatigue for a SCR could be verified, and the most effective parameter could also be

  14. Fatigue Assessment of Underwater CFRP-Repaired Steel Panels using Finite Element Analysis

    Science.gov (United States)

    2014-09-01

    U.S. Army Corps of Engineers. Maruyama, K. 1997. JCI Activities on Continuous Fibre Reinforced Concrete , Non- Metallic (FRP) Reinforcement for...Symposium on Fatigue Design, Fatigue Design and Reliability. Benmokrane, B., and H. Rahman. 1998. Durability of Fibre Reinforced Polymer (FRP...Triantafillou, T. C. 1998. Shear Strengthening of Reinforced Concrete Beams Using Epoxy Bonded FRP Composites. ACI Structural Journal, 95(2): 107-115

  15. Review of the margins for ASME code fatigue design curve - effects of surface roughness and material variability.

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-10-03

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. 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. Existing fatigue strain-vs.-life ({var_epsilon}-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This report provides an overview of the existing fatigue {var_epsilon}-N data for carbon and low-alloy steels and wrought and cast austenitic SSs to define the effects of key material, loading, and environmental parameters on the fatigue lives of the steels. Experimental data are presented on the effects of surface roughness on the fatigue life of these steels in air and LWR environments. Statistical models are presented for estimating the fatigue {var_epsilon}-N curves as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are discussed. Data available in the literature have been reviewed to evaluate the conservatism in the existing ASME Code fatigue evaluations. A critical review of the margins for ASME Code fatigue design curves is presented.

  16. Fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro

    NARCIS (Netherlands)

    Foek, Dave Lie Sam; Yetkiner, Enver; Ozcan, Mutlu

    Objective: To analyze the fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro. Methods: Roots of human mandibular central incisors were covered with silicone, mimicking the

  17. Observations of the effect of varying Hoop stress on fatigue failure and the formation of white etching areas in hydrogen infused 100Cr6 steel rings

    DEFF Research Database (Denmark)

    Janakiraman, Shravan; West, Ole; Klit, Peder

    2015-01-01

    White etching cracks (WECs) in wind turbine gearbox bearings have been studied previously. Rolling contact fatigue (RCF) tests are conducted on 100Cr6 bearing steel rings, in this study, to generate WECs like those found in wind turbine bearings. This research studies the effect of two different...

  18. Hot Deformation Behavior of SA508Gr.4N Steel for Reactor Pressure Vessels

    Directory of Open Access Journals (Sweden)

    YANG Zhi-qiang

    2017-08-01

    Full Text Available The high-temperature plastic deformation and dynamic recrystallization behavior of SA508Gr.4N steel were investigated through hot deformation tests in a Gleeble1500D thermal mechanical simulator. The compression tests were performed in the temperature range of 1050-1250℃ and the strain rate range of 0.001-0.1s-1 with true strain of 0.16. The results show that from the high-temperature true stress-strain curves of the SA508Gr.4N steel, the main feature is dynamic recrystallization,and the peak stress increases with the decrease of deformation temperature or the increase of strain rate, indicating the experimental steel is temperature and strain rate sensitive material. The constitutive equation for SA508Gr.4N steel is established on the basis of the true stress-strain curves, and exhibits the characteristics of the high-temperature flow behavior quite well, while the activation energy of the steel is determined to be 383.862kJ/mol. Furthermore, an inflection point is found in the θ-σ curve, while the -dθ/dσ-σ curve shows a minimum value. The critical strain increases with increasing strain rate and decreasing deformation temperature. A linear relationship between critical strain (εc and peak strain (εp is found and could be expressed as εc/εp=0.517. The predicted model of critical strain could be described as εc=8.57×10-4Z0.148.

  19. Ductile-Brittle Transition Behavior in Tempered Martensitic SA508 Gr. 4N Ni-Mo-Cr Low Alloy Steels for Reactor Pressure Vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-05-15

    Reactor pressure vessels (RPVs) operate under severe conditions of elevated temperature, high pressure, and irradiation. Therefore, a combination of sufficient strength, toughness, good weldability, and high irradiation resistance are required for RPV materials. SA508 Gr.4N low alloy steel, which has higher Ni and Cr contents than those of commercial RPV steel, Gr.3 steel, is considered as a candidate material due to its excellent mechanical properties from tempered martensitic microstructure. The ferritic steels such as Gr.3 and Gr.4N low alloy steels reveal a ductile-brittle transition and large scatters in the fracture toughness within a small temperature range. Recently, there are some observations of the steeper transition behavior in the tempered martensitic steels, such as Eurofer97 than the transition behavior of commercial RPV steels. It was also reported that the fracture toughness increased discontinuously when the phase fraction of the tempered martensite was over a critical fraction in the heat affected zones of SA508 Gr.3. Therefore, it may be necessary to evaluate the changes of transition behavior with a microstructure for the tempered martensitic SA508 Gr.4N low alloy steel. In this study, the fracture toughness for SA508 Gr.4N low alloy steels was evaluated from a view point of the temperature dependency with phase fraction of tempered martensite controlled by cooling rate. Additionally, a possible modification of the fracture toughness master curve was proposed and discussed

  20. Electrochemical investigation of crack initiation during corrosion fatigue of stainless steels in the passive state. Elektrochemische Untersuchung der Rissbildung bei Schwingungsrisskorrosion im stabil-passiven Werkstoffzustand

    Energy Technology Data Exchange (ETDEWEB)

    Spaehn, R. (Technische Hochschule Darmstadt (Germany, F.R.))

    1991-03-01

    The corrosion fatigue behaviour of three stainless steels - ferritic (12% Cr), austenitic (type 316 Ti) and austenitic-ferritic (type 31803; Duplex stainless steel) - was studied under rotating bending moments in aqueous sulphuric acid of 30deg C. An instrumental set-up for recording the transient currents of specimens during potentiostatically controlled corrosion fatigue is described. Based on this transient current signal technique, three stages on the corrosion fatigue process can be discerned. In the incubation period, small stochastic current transients are caused by the response of the passive layer to alternating stresses and environmental conditions. The appearance of sinusoidal current signals indicates crack initiation whereas the phase angle between a fixed marker - i.e. a light barrier signal -, and the anodic amplitude represents the site of initiating cracks. Finally, the crack growth period is characterized by an increasing cell current and steadily growing sinusoidal current signals caused by the interplay of microplastic and repassivation processes at the crack tip. (orig.).

  1. Mechanical property evaluations of an amorphous metallic/ceramic multilayer and its role in improving fatigue properties of 316L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Cheng-Min [Nano Technology Center, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Jeng, R.J.; Yu, Chia-Chi; Chang, Chia-Hao [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Li, Chia-Lin [Department of Materials Science and Engineering and Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chu, Jinn P., E-mail: jpchu@mail.ntust.edu.tw [Nano Technology Center, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2016-08-01

    We have used nanoindentation to investigate mechanical properties of 200-nm-thick amorphous multilayer consisting of alternating layers of Zr-based thin film metallic glass (TFMG) and holmium scandium oxide (HSO). Nanoindentation results show that TFMG/HSO multilayer exhibits the high hardness and Young's modulus. Owing to its high hardness, smooth surface, and good adhesion properties, TFMG/HSO multilayer is then employed as a protective coating to improve the four-point bending fatigue properties of 316L stainless steel. With coating, the fatigue life is increased from 2.4×10{sup 5} to 4.9×10{sup 6} cycles, at the stress of 700 MPa. A crack retardation mechanism has been proposed to explain the role of TFMG/HSO multilayer in improving fatigue properties of 316L stainless steel substrate.

  2. Effect of NaCl Solution Spraying on Fatigue Lives of Smooth and Slit Specimens of 0.37% Carbon Steel

    Science.gov (United States)

    Makabe, Chobin; Ferdous, Md. Shafiul; Shimabukuro, Akimichi; Murdani, Anggit

    2017-07-01

    The fatigue crack initiation life and growth rate are affected by experimental conditions. A corrosive environment can be created in a laboratory by means of dropping salt water onto the specimen surface, spraying chloride mist into the experimental chamber, etc. In the case of smooth specimens of some metals, fatigue life is shortened and the fatigue limit disappears under such corrosive experimental conditions. In this study, the effects of intermittent spraying of 3% NaCl solution-mist on corrosion fatigue behavior were investigated. The material used was 0.37% carbon steel. This is called JIS S35C in Japan. Spraying of 3% NaCl solution-mist attacked the surface layer of the specimen. It is well known that the pitting, oxidation-reduction reaction, etc. affect the fatigue strength of metals in a corrosive environment. We carried out corrosion fatigue tests with smooth specimens, holed specimens and slit specimens. Then the effects of such specimen geometry on the fatigue strength were investigated when the NaCl solution-mist was sprayed onto the specimen surface. In the case of lower stress amplitude application in slit specimens, the fatigue life in a corrosive atmosphere was longer than that in the open air. It is discussed that the behavior is related to the crack closure which happens when the oxide builds up and clogs the crack or slit.

  3. The specific heat loss combined with the thermoelastic effect for an experimental analysis of the mean stress influence on axial fatigue of stainless steel plain specimens

    Directory of Open Access Journals (Sweden)

    G. Meneghetti

    2014-10-01

    Full Text Available The energy dissipated to the surroundings as heat in a unit volume of material per cycle, Q, was recently proposed by the authors as fatigue damage index and it was successfully applied to correlate fatigue data obtained by carrying out fully reversed stress- and strain-controlled fatigue tests on AISI 304L stainless steel plain and notched specimens. The use of the Q parameter to analyse the experimental results led to the definition of a scatter band having constant slope from the low- to the high-cycle fatigue regime. In this paper the energy approach is extended to analyse the influence of mean stress on the axial fatigue behaviour of unnotched cold drawn AISI 304L stainless steel bars. In view of this, stress controlled fatigue tests on plain specimens at different load ratios R (R=-1; R=0.1; R=0.5 were carried out. A new energy parameter is defined to account for the mean stress effect, which combines the specific heat loss Q and the relative temperature variation due to the thermoelastic effect corresponding to the achievement of the maximum stress level of the stress cycle. The new two-parameter approach was able to rationalise the mean stress effect observed experimentally. It is worth noting that the results found in the present contribution are meant to be specific for the material and testing condition investigated here.

  4. Using DOProC method in reliability assessment of steel elements exposed to fatigue

    Directory of Open Access Journals (Sweden)

    Krejsa Martin

    2017-01-01

    Full Text Available Fatigue crack damage depends on a number of stress range cycles. This is a time factor in the course of reliability for the entire designed service life. Three sizes are important for the characteristics of the propagation of fatigue cracks - initial size, detectable size and acceptable size. The theoretical model of fatigue crack progression can be based on a linear fracture mechanic. Depending on location of an initial crack, the crack may propagate in structural element e.g. from the edge or from the surface. When determining the required degree of reliability, it is possible to specify the time of the first inspection of the construction which will focus on the fatigue damage. Using a conditional probability and Bayesian approach, times for subsequent inspections can be determined. For probabilistic modelling of fatigue crack progression was used the original and new probabilistic method - the Direct Optimized Probabilistic Calculation (“DOProC”, which uses a purely numerical approach without any simulation techniques or approximation approach based on optimized numerical integration.

  5. On high-cycle fatigue of 316L stents.

    Science.gov (United States)

    Barrera, Olga; Makradi, Ahmed; Abbadi, Mohammed; Azaouzi, Mohamed; Belouettar, Salim

    2014-01-01

    This paper deals with fatigue life prediction of 316L stainless steel cardiac stents. Stents are biomedical devices used to reopen narrowed vessels. Fatigue life is dominated by the cyclic loading due to the systolic and diastolic pressure and the design against premature mechanical failure is of extreme importance. Here, a life assessment approach based on the Dang Van high cycle fatigue criterion and on finite element analysis is applied to explore the fatigue reliability of 316L stents subjected to multiaxial fatigue loading. A finite element analysis of the stent vessel subjected to cyclic pressure is performed to carry out fluctuating stresses and strain at some critical elements of the stent where cracks or complete fracture may occur. The obtained results show that the loading path of the analysed stent subjected to a pulsatile load pressure is located in the safe region concerning infinite lifetime.

  6. Modeling flow stress constitutive behavior of SA508-3 steel for nuclear reactor pressure vessels

    Science.gov (United States)

    Sun, Mingyue; Hao, Luhan; Li, Shijian; Li, Dianzhong; Li, Yiyi

    2011-11-01

    Based on the measured stress-strain curves under different temperatures and strain rates, a series of flow stress constitutive equations for SA508-3 steel were firstly established through the classical theories on work hardening and softening. The comparison between the experimental and modeling results has confirmed that the established constitutive equations can correctly describe the mechanical responses and microstructural evolutions of the steel under various hot deformation conditions. We further represented a successful industrial application of this model to simulate a forging process for a large conical shell used in a nuclear steam generator, which evidences its practical and promising perspective of our model with an aim of widely promoting the hot plasticity processing for heavy nuclear components of fission reactors.

  7. Master curve analysis of the SA508 Gr. 4N Ni-Mo-Cr low alloy steels for reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-10-15

    Low alloy steels used as Reactor Pressure Vessels (RPVs) materials directly relate to the safety margin and the life span of reactors. Currently, SA508 Gr.3 low alloy steel is generally used for RPV material. But, for larger capacity and long-term durability of RPV, materials that have better properties including strength and toughness are needed. Therefore, tempered martensitic SA508 Gr.4N low alloy steel is considered as a candidate material due to excellent mechanical properties. The fracture toughness loss caused by irradiation embrittlement during reactor operation is one of the important issues for ferritic RPV steels, because the decrease of fracture toughness is directly related to the integrity of RPVs. One reliable and efficient concept to evaluate the fracture toughness of ferritic steels is master curve method. In ASTM E1921, it is clearly mentioned the universal shape of the median toughness-temperature curve for ferritic steels including tempered martensitic steels. However, currently, concerns have arisen regarding the appropriateness of the universal shape in ASTM for the tempered martensitic steels such as Eurofer97. Therefore, it may be necessary to assess the master curve applicability for the tempered martensitic SA508 Gr.4N low alloy steel. In this study, the fracture toughness behavior with temperature of the tempered martensitic SA508 Gr.4N low alloy steels was evaluated using the ASTM E1921 master curve method. And the results were compared with those of the bainitic SA508 Gr.3 low alloy steel. Furthermore, the way to define the fracture toughness behavior of Gr.4N steels well is discussed.

  8. Fatigue fracture of cutter blade made of high-speed steel

    Directory of Open Access Journals (Sweden)

    Beata Letkowska

    2015-04-01

    Full Text Available The quality of the surface of cyclically loaded components is very important. Many observations confirm that the root cause of the micro cracks (causing the fatigue fracture are primarily a surface's defects appearing during production process. These surface defects can be also caused by engraving processes used to perform identification marks. This paper presents the failure analysis of broken blade of the cutter Ku 500VX. The blade was subject of standard metallographic examination, hardness measurements, fractography analysis and metallographic studies using stereoscopic, light and scanning electron microscopes. The damage of the blade was caused by changes of the structure (formation of the brittle micro dendritic structure that occurred during manual electric engraving process when the material was heated till its melting point. As a result the stresses occurred in surface what provided to micro cracking and to propagate the fatigue fracture. The origin of this fatigue fracture was in the place where the inscription was made.

  9. Application of strainrange partitioning to the prediction of creep-fatigue lives of AISI types 304 and 316 stainless steel

    Science.gov (United States)

    Saltsman, J. F.; Halford, G. R.

    1976-01-01

    As a demonstration of the predictive capabilities of the method of Strainrange Partitioning, published high-temperature, low cycle, creep-fatigue test results on AISI Types 304 and 316 stainless steel were analyzed and calculated, cyclic lives compared with observed lives. Predicted lives agreed with observed lives within factors of two for 76 percent, factors of three for 93 percent, and factors of four for 98 percent of the laboratory tests analyzed. Agreement between observed and predicted lives is judged satisfactory considering that the data are associated with a number of variables (two alloys, several heats and heat treatments, a range of temperatures, different testing techniques, etc.) that are not directly accounted for in the calculations.

  10. Effect of a Shot Peening Pre Treatment on the Fatigue Behaviour of Hard Chromium on Electroless Nickel Interlayer Coated AISI 4340 Aeronautical Steel

    Directory of Open Access Journals (Sweden)

    Nascimento Marcelino P.

    2002-01-01

    Full Text Available Multiple layer systems of coatings are considered to have larger resistance to crack propagation in comparison to coatings with simple layer. With regard to fatigue, it is possible to improve the resistance of a component with the application of shot peening treatment, whose compressive residual stresses delay or eliminate the initiation and propagation of fatigue cracks. The aim of this study is to analyse the effects on rotating bending fatigue behaviour of hard chromium fraction three-quarters electroless nickel multilayer system coated AISI 4340 high strength steel submitted to shot peening pre treatment. Results indicated that the interaction between the shot peening process with the multilayer system was not satisfactory, resulting in intense delamination. Fracture surface analysis by SEM was performed toward to identify the fatigue crack origin, as well as the coating-substrate delamination process.

  11. Effect of strain wave shape on low-cycle fatigue crack propagation of SUS 304 stainless steel at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Okazaki, M.; Hattori, I.; Koizwmi, T.; Shiraiwa, F.

    1983-08-01

    Effect of strain wave shape on strain-controlled low-cycle fatigue crack propagation of SUS 304 stainless steel was investigated at 600 and 700/sup 0/C. It was found that the rate of crack propagation in a cycle-dependent region was successfully correlated with the range of cyclic J-integral, ..delta..J /SUB f/, regardless of the strain wave shape, frequency, and test temperature. It was also shown that the rate of crack propagation gradually increased from cycle-dependent curve to time-dependent one with decreasing frequency and slow-fast strain wave shape, and that one of the factors governing the rate of crack propagation in such a region was the ratio of the range of creep J-integral to that of total J-integral, ..delta..J /SUB c/ /..delta..J /SUB T/. Based on the results thus obtained, an interaction damage rule proposed semi-empirically was interpreted, with regard to crack propagation. Furthermore, fatigue crack initiation mechanism in slow-fast strain wave shape was studied, and it was shown that grain boundary sliding took an important role in it.

  12. Microstructure and embrittlement of VVER 440 reactor pressure vessel steels; Microstructure et fragilisation des aciers de cuve des reacteurs nucleaires VVER 440

    Energy Technology Data Exchange (ETDEWEB)

    Hennion, A

    1999-03-15

    27 VVER 440 pressurised water reactors operate in former Soviet Union and in Eastern Europe. The pressure vessel, is made of Cr-Mo-V steel. It contains a circumferential arc weld in front of the nuclear core. This weld undergoes a high neutron flux and contains large amounts of copper and phosphorus, elements well known for their embrittlement potency under irradiation. The embrittlement kinetic of the steel is accelerated, reducing the lifetime of the reactor. In order to get informations on the microstructure and mechanical properties of these steels, base metals, HAZ, and weld metals have been characterized. The high amount of phosphorus in weld metals promotes the reverse temper embrittlement that occurs during post-weld heat treatment. The radiation damage structure has been identified by small angle neutron scattering, atomic probe, and transmission electron microscopy. Nanometer-sized clusters of solute atoms, rich in copper with almost the same characteristics as in western pressure vessels steels, and an evolution of the size distribution of vanadium carbides, which are present on dislocation structure, are observed. These defects disappear during post-irradiation tempering. As in western steels, the embrittlement is due to both hardening and reduction of interphase cohesion. The radiation damage specificity of VVER steels arises from their high amount of phosphorus and from their significant density of fine vanadium carbides. (author)

  13. Dynamic strain ageing evidences during low cycle fatigue deformation in ferritic martensitic stainless steels

    Science.gov (United States)

    Armas, A. F.; Avalos, M.; Alvarez-Armas, I.; Petersen, C.; Schmitt, R.

    1998-10-01

    The influence of dynamic strain ageing (DSA) on the strain cyclic behaviour of ferrite-martensite stainless steels was investigated at temperatures ranging from room temperature to 823 K. For fully annealed AISI 420 initial hardening followed by a saturation stage was observed at each test temperature. This steel was found to be susceptible to DSA as evidenced by the temperature independent stress saturation observed between 523 and 723 K. Normalized and tempered MANET II and F82H mod. softens during cyclic loading at all temperatures. In this steel DSA manifestations were observed on plotting the peak tensile stress difference between hysteresis loops obtained at different strain rates. Strongly abnormal behaviour with higher peak tensile stresses corresponding to slower strain rates was observed in the temperature range between 500 and 700 K. It is proposed that DSA mechanisms caused by the drag of solution carbon atoms is responsible for this unusual behaviour.

  14. Microstructure variation and local plastic response of chrome molybdenum alloy steel after quasi rolling contact fatigue testing

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Lechun, E-mail: lechunxie@yahoo.com [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240 (China); Zhou, Qinghua [School of Aeronautics and Astronautics, Sichuan University, Chengdu 610065 (China); Wen, Yan [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing, Jiangsu 210044 (China); Wang, Liqiang; Lu, Weijie [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240 (China)

    2016-04-06

    This work presented the microstructure variation and local plastic response of chrome molybdenum alloy steel under quasi rolling contact fatigue (quasi-RCF) testing. The quasi-RCF testing means using the similar method of actual RCF to introduce obviously local plastic deformation and microstructure variation on surface layers of materials. After quasi-RCF testing, the microstructure were observed using optical microscope and scanning electron microscope (SEM) from both the top surface and cross section. Based on microstructure analysis, the deformation volume of materials after quasi-RCF testing were calculated. The local plastic response was demonstrated by the unique local strain-stress curve and strain hardening exponent obtained via experimental measurements and simulation prediction. One hand, the increase in the hardness of plastic zones due to quasi-RCF testing was measured by a Vickers indenter. The other hand, based on the virgin hardness and elastic modulus, some possible local stress-strain curves were obtained. Then according to the possible local stress-strain curves, finite element analysis was introduced to predict the increased hardness. Comparing the increased hardness obtained by experiments and prediction, the unique local strain-stress curve and strain hardening exponent of chrome molybdenum alloy steel were determined. All results were discussed in detail.

  15. Modeling of Late Blooming Phases and Precipitation Kinetics in Aging Reactor Pressure Vessel (RPV) Steels

    Energy Technology Data Exchange (ETDEWEB)

    Yongfeng Zhang; Pritam Chakraborty; S. Bulent Biner

    2013-09-01

    The principle work at the atomic scale is to develop a predictive quantitative model for the microstructure evolution of RPV steels under thermal aging and neutron radiation. We have developed an AKMC method for the precipitation kinetics in bcc-Fe, with Cu, Ni, Mn and Si being the alloying elements. In addition, we used MD simulations to provide input parameters (if not available in literature). MMC simulations were also carried out to explore the possible segregation/precipitation morphologies at the lattice defects. First we briefly describe each of the simulation algorithms, then will present our results.

  16. Hydrogen Absorption Induced Slow Crack Growth in Austenitic Stainless Steels for Petrochemical Pressure Vessel Industries

    Directory of Open Access Journals (Sweden)

    Ronnie Rusli

    2011-05-01

    Full Text Available Type 304Land type 309 austenitic stainless steels were tested either by exposed to gaseous hydrogen or undergoing polarized cathodic charging. Slow crack growth by straining was observed in type 304L, and the formation of α‘ martensite was indicated to be precursor for such cracking. Gross plastic deformation was observed at the tip of the notch, and a single crack grew slowly from this region in a direction approximately perpendicular to the tensile axis. Martensite formation is not a necessary condition for hydrogen embrittlement in the austenitic phase.

  17. The Effect of the Production Process and Heat Processing Parameters on the Fatigue Strength of High-Grade Medium-Carbon Steel

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2012-04-01

    Full Text Available The experimental material consisted of semi-finished products of high-grade, medium-carbon constructional steel with: manganese, chromium, nickel, molybdenum and boron. The experimental material consisted of steel products obtained in three metallurgical processes: electric and desulfurized (E, electric and desulfurized with argon-refined (EA and oxygen converter with vacuum degassed of steel (KP. The production process involved two melting technologies: in a 140-ton basic arc furnace with desulphurisation and argon refining variants, and in a 100-ton oxygen converter. Billet samples were collected to analyze: relative volume of impurities, microstructure and fatigue tests. The samples were quenched and austenitized at a temperature of 880oC for 30 minutes. They were then cooled in water and tempered by holding the sections at a temperature of 200, 300, 400, 500 and 600oC for 120 minutes and air-cooled. Fatigue tests were performed with the use of a rotary bending machine at a frequency of 6000 cpm. The results were statistical processed and presented in graphic form. This paper discusses the results of microstructural analyses, the distribution of the relative volume of impurities in different size ranges, the fatigue strength characteristics of different production processes, the average number of sample- damaging cycles and the average values of the fatigue strength coefficient for various heat processing options.

  18. Development of structural steels for nuclear application

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jun Hwa; Chi, S. H.; Ryu, W. S.; Lee, B. S.; Kim, D. H.; Kim, J. H.; Oh, Y. J.; Byun, T. S.; Yoon, J. H.; Park, D. K.; Oh, J. M.; Cho, H. D.; Kim, H.; Kim, H. D.; Kang, S. S.; Kim, J. W.; Ahn, S. B.

    1997-08-01

    To established the bases of nuclear structural material technologies, this study was focused on the localization and improvement of nuclear structural steels, the production of material property data, and technology developments for integrity evaluation. The important test and analysis technologies for material integrity assessment were developed, and the materials properties of the pressure vessel steels were evaluated systematically on the basis of those technologies, they are microstructural characteristics, tensile and indentation deformation properties, impact properties, and static and dynamic fracture toughness, fatigue and corrosion fatigue etc. Irradiation tests in the research reactors were prepared or completed to obtain the mechanical properties of irradiated materials. The improvement of low alloy steel was also attempted through the comparative study on the manufacturing processes, computer assisted alloy and process design, and application of the inter critical heat treatment. On the other hand, type 304 stainless steels for reactor internals were developed and tested successfully. High strength type 316LN stainless steels for reactor internals were developed and the microstructural characteristics, corrosion resistance, mechanical properties at high temperatures, low cycle fatigue property etc. were tested and analyzed in the view point of the effect of nitrogen. Type 347 stainless steels with high corrosion resistance and toughness for pipings and tubes and low-activated Cr-Mn steels were also developed and their basic properties were evaluated. Finally, the martensitic stainless steels for turbine blade were developed and tests. (author). 242 refs., 100 tabs., 304 figs.

  19. Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes

    Science.gov (United States)

    Ahiale, Godwin Kwame; Oh, Yong-Jun; Choi, Won-Doo; Lee, Kwang-Bok; Jung, Jae-Gyu; Nam, Soo Woo

    2013-09-01

    This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen's resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope.

  20. Plastic deformation and fracture behaviour of 21/4 Cr-1 Mo pressure-vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Holzmann, M.; Vlach, B.; Man, J.; Bilek, Z.

    1989-01-01

    During the heat treatment of steel plates and forgings of large thicknesses, microstructures with various volume fractions of ferrite appear. Plastic properties and fracture behaviour of these mixed microstructures are a function of ferrite content. The influence of ferrite content in the range from 0% to 54% in the bainitic-ferritic microstructure on mechanical properties and fracture behaviour of 21/4 Cr-1 Mo steel was examined. The yield stress was found to decrease linearly with the volume fraction of ferrite. The tensile strength was independent of ferrite content up to 25%, after which the tensile strength decreased. Using the Charpy test it has been found that the critical ferrite content-25%-exists in a mixed microstructure, at which the propagation and initiation transition temperatures attain the highest values. The fracture toughness tests gave the same results. Increasing the volume fraction of ferrite, the cleavage fracture toughness/temperature curves were shifted to higher temperatures. Simultaneously, the ductile-brittle fracture toughness transition temperature was raised reaching the highest value for the critical ferrite content. The fracture behaviour could be tentatively explained through the influence of ferrite volume fraction on both the cleavage fracture stress and the stress level at the crack tip.

  1. Irradiation embrittlement of reactor pressure vessel steel at very high neutron fluence

    Science.gov (United States)

    Kryukov, A.; Debarberis, L.; von Estorff, U.; Gillemot, F.; Oszvald, F.

    2012-03-01

    For the prediction of radiation embrittlement of RPV materials beyond the NPP design time the analysis of research data and extended surveillance data up to a fluence ˜23 × 1020 cm-2 (E > 0.5 MeV) has been carried out. The experimental data used for the analysis are extracted from the International Database of RPV materials. Key irradiation embrittlement mechanisms, direct matrix damage, precipitation and element segregation have been considered. The essential part of the analysis concerns the assessment of irradiation embrittlement of WWER-440 steel irradiated with very high neutron fluence. The analysis of several surveillance sets irradiated at a fluence up to 23 × 1020 cm-2 (E > 0.5 MeV) has been performed. The effect of the main influencing chemical elements phosphorus and copper has been verified up to a fluence of 4.6 × 1020 cm-2 (E > 0.5 MeV). The data are indicating good radiation stability, in terms of the Charpy transition temperature shift and yield strength increase for steels with relatively low concentrations of copper and phosphorus. The linear dependence between ΔTk and ΔRp0.2 can be an evidence of strengthening mechanisms of irradiation embrittlement and absence of non-hardening embrittlement even at very high neutron fluence.

  2. Influence of different combined severe shot peening and laser surface melting treatments on the fatigue performance of 20CrMnTi steel gear

    Energy Technology Data Exchange (ETDEWEB)

    Lv, You, E-mail: llvvyou@163.com.cn; Lei, Liqun; Sun, Lina

    2016-03-21

    In this paper, the effect of severe shot peening combined with laser melting (LSMSSP for short) on the fatigue resistance of 20CrMiTi steel gears is investigated in comparison with the effect of traditional shot peening on the fatigue resistance of the laser surface melted (LSMTSP for short) 20CrMiTi steel gear. The surface characteristics of the gear have been analyzed by a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). The Forschungsstelle für Zahnräder und Getriebebau (FZG) back-to-back spur gear test rig was used for fatigue experiments. Experimental results showed that the residual stresses, full width at half maximum (FWHM), microhardness and retained austenite of the LSMSSP gears and LSMTSP gear were entirely different. Although the LSMSSP gears had higher surface roughness than the LSMTSP gear, the LSMSSP gears still had better fatigue resistance than the LSMTSP gear and laser surface melted gear. The nanocrystallized surface layer on the gear tooth flank created by severe shot peening might be a very important factor for improving the fatigue property of the LSMSSP gears.

  3. Effects of shot peening on fatigue behavior in high speed steel and cast iron with spheroidal vanadium carbides dispersed within martensitic-matrix microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Uematsu, Y., E-mail: yuematsu@gifu-u.ac.jp [Department of Mechanical and Systems Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193 (Japan); Kakiuchi, T.; Tokaji, K. [Department of Mechanical and Systems Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193 (Japan); Nishigaki, K. [Okamoto Co. Ltd., 5 Nawate-cho, Gifu 500-8743 (Japan); Ogasawara, M. [MEIRA Co. Ltd., 17-15 Tsubaki-cho, Nakamura-ku, Nagoya City, Aichi 453-0015 (Japan)

    2013-01-20

    Four-point bending fatigue tests had been performed using high speed steel and cast iron with vanadium carbides (VCs) dispersed within the martensitic-matrix microstructure. Shot peening or shot blast was applied to both the materials and the effect of surface treatments on fatigue behavior was investigated. The fatigue strengths of the high speed steel were improved by both shot peening and shot blast processes due to the high hardness near the specimen surface and residual compressive stress. Although the hardness of cast iron was enhanced by both treatments, the fatigue strengths were not improved by the shot blast because of the existence of large casting defects. Shot peening with higher shot energy could induce the transition of crack initiation mechanism of cast iron, where crack initiated from the cluster of VCs. However the shot peening had small effect on the fatigue strengths of the cast iron because large casting defects were not removed by the shot peening due to the high hardness of the martensitic matrix.

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

    Indian Academy of Sciences (India)

    Unknown

    intensity ranges (∆K) were determined to obtain the threshold value of stress intensity range (∆Kth). Crack path morphology was ... Scanning electron fractography of DP steel in the near threshold region revealed transgranular .... to an apparent 2% increment in crack extension was esta- blished. From this value of PQ, ...

  5. Data demonstrating the effects of build orientation and heat treatment on fatigue behavior of selective laser melted 17–4 PH stainless steel

    Directory of Open Access Journals (Sweden)

    Aref Yadollahi

    2016-06-01

    Full Text Available Axial fully-reversed strain-controlled (R=−1 fatigue experiments were performed to obtain data demonstrating the effects of building orientation (i.e. vertical versus horizontal and heat treatment on the fatigue behavior of 17–4 PH stainless steel (SS fabricated via Selective Laser Melting (SLM (Yadollahi et al., submitted for publication [1]. This data article provides detailed experimental data including cyclic stress-strain responses, variations of peak stresses during cyclic deformation, and fractography of post-mortem specimens for SLM 17–4 PH SS.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kibitkin, Vladimir V., E-mail: vvk@ispms.tsc.ru; Solodushkin, Andrey I., E-mail: s.ai@sibmail.com; Pleshanov, Vasily S., E-mail: vsp@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

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

  7. Use of ultrasonic back-reflection intensity for predicting the onset of crack growth due to low-cycle fatigue in stainless steel under block loading.

    Science.gov (United States)

    Islam, Md Nurul; Arai, Yoshio; Araki, Wakako

    2015-02-01

    The present study proposes the use of ultrasonic back-reflected waves for evaluating low cycle fatigue crack growth from persistent slip bands (PSBs) of stainless steel under block loading. Fatigue under high-low block loading changes the back-reflected intensity of the ultrasonic wave that emanates from the surface. Measuring the change in ultrasonic intensity can predict the start of crack growth with reasonable accuracy. The present study also proposes a modified constant cumulative plastic strain method and a PSB damage evolution model to predict the onset of crack growth under block loads. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Estimation of lower-bound K{sub Jc} on pressure vessel steels from invalid data

    Energy Technology Data Exchange (ETDEWEB)

    McCable, D.E.; Merkle, J.G.

    1996-10-01

    Statistical methods are currently being introduced into the transition temperature characterization of ferritic steels. Objective is to replace imprecise correlations between empirical impact test methods and universal K{sub Ic} or K{sub Ia} lower-bound curves with direct use of material-specific fracture mechanics data. This paper introduces a computational procedure that couples order statistics, weakest-link statistical theory, and a constraint model to arrive at estimates of lower-bound K{sub Jc} values. All of the above concepts have been used before to meet various objectives. In the present case, scheme is to make a best estimate of lower-bound fracture toughness when resource K{sub Jc} data are too few to use conventional statistical analyses. Utility of the procedure is of greatest value in the middle-to-high toughness part of the transition range where specimen constraint loss and elevated lower-bound toughness interfere with conventional statistical analysis methods.

  9. Thermal fatigue of a 304L austenitic stainless steel: simulation of the initiation and of the propagation of the short cracks in isothermal and aniso-thermal fatigue; Fatigue thermique d'un acier inoxydable austenitique 304L: simulation de l'amorcage et de la croissance des fissures courtes en fatigue isotherme et anisotherme

    Energy Technology Data Exchange (ETDEWEB)

    Haddar, N

    2003-04-01

    The elbow pipes of thermal plants cooling systems are submitted to thermal variations of short range and of variable frequency. These variations bound to temperature changes of the fluids present a risk of cracks and leakages. In order to solve this problem, EDF has started the 'CRECO RNE 808' plan: 'thermal fatigue of 304L austenitic stainless steels' to study experimentally on a volume part, the initiation and the beginning of the propagation of cracks in thermal fatigue on austenitic stainless steels. The aim of this study is more particularly to compare the behaviour and the damage of the material in mechanic-thermal fatigue (cycling in temperature and cycling in deformation) and in isothermal fatigue (the utmost conditions have been determined by EDF for the metal: Tmax = 165 degrees C and Tmin = 90 degrees C; the frequency of the thermal variations can reach a Hertz). A lot of experimental results are given. A model of lifetime is introduced and validated. (O.M.)

  10. Nanostructure evolution under irradiation of Fe(C)MnNi model alloys for reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Chiapetto, M., E-mail: mchiapet@sckcen.be [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, B-2400 Mol (Belgium); Unité Matériaux Et Transformations (UMET), UMR 8207, Université de Lille 1, ENSCL, F-59600 Villeneuve d’Ascq Cedex (France); Becquart, C.S. [Unité Matériaux Et Transformations (UMET), UMR 8207, Université de Lille 1, ENSCL, F-59600 Villeneuve d’Ascq Cedex (France); Laboratoire commun EDF-CNRS Etude et Modélisation des Microstructures pour le Vieillissement des Matériaux (EM2VM) (France); Domain, C. [EDF R& D, Département Matériaux et Mécanique des Composants, Les Renardières, F-77250 Moret sur Loing (France); Laboratoire commun EDF-CNRS Etude et Modélisation des Microstructures pour le Vieillissement des Matériaux (EM2VM) (France); Malerba, L. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, B-2400 Mol (Belgium)

    2015-06-01

    Radiation-induced embrittlement of bainitic steels is one of the most important lifetime limiting factors of existing nuclear light water reactor pressure vessels. The primary mechanism of embrittlement is the obstruction of dislocation motion produced by nanometric defect structures that develop in the bulk of the material due to irradiation. The development of models that describe, based on physical mechanisms, the nanostructural changes in these types of materials due to neutron irradiation are expected to help to better understand which features are mainly responsible for embrittlement. The chemical elements that are thought to influence most the response under irradiation of low-Cu RPV steels, especially at high fluence, are Ni and Mn, hence there is an interest in modelling the nanostructure evolution in irradiated FeMnNi alloys. As a first step in this direction, we developed sets of parameters for object kinetic Monte Carlo (OKMC) simulations that allow this to be done, under simplifying assumptions, using a “grey alloy” approach that extends the already existing OKMC model for neutron irradiated Fe–C binary alloys [1]. Our model proved to be able to describe the trend in the buildup of irradiation defect populations at the operational temperature of LWR (∼300 °C), in terms of both density and size distribution of the defect cluster populations, in FeMnNi model alloys as compared to Fe–C. In particular, the reduction of the mobility of point-defect clusters as a consequence of the presence of solutes proves to be key to explain the experimentally observed disappearance of detectable point-defect clusters with increasing solute content.

  11. Evaluation of defects induced by neutron radiation in reactor pressure vessels steels; Evaluacion de los defectos inducidos por la radiacion neutronica en los aceros de vasijas

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Jimenez, J.

    1978-07-01

    We have developed a method for calculating the production of neutron induced defects (depleted zone and crowdions) in ferritic pressure vessel steels for different neutron spectra. They have been analysed both the recoil primary atoms produced by elastic and inelastic collisions with fast neutrons and the ones produced by gamma-ray emission by thermal neutron absorption. Theoretical modelling of increasing in the ductile-brittle transition temperature of ferritic steels has been correlated with experimental data at irradiation temperature up to 400 degree centigree (Author) 15 refs.

  12. Fatigue Crack Growth Behavior of a New Type of 10% Cr Martensitic Steel Welded Joints with Ni-Based Weld Metal

    Science.gov (United States)

    Zhang, Qunbing; Zhang, Jianxun

    2017-08-01

    In the present work, the fatigue crack growth (FCG) behavior of a new type of 10% Cr martensitic steel welded joints with Ni-based weld metal was comparatively studied for different regions including base metal (BM), heat-affected zone (HAZ) and weld metal (WM). FCG results indicated that the tempered lath martensite BM has a higher fatigue crack growth resistance than the tempered granular martensite HAZ that without a typical lath structure. In comparison, the austenitic WM has the highest fatigue crack growth threshold. Meanwhile, due to the microstructural and chemical compositional differences between BM and WM, a clear interface existed in the welded joints. At the region of the interface, the microstructures were physically connected and an element transition layer was formed. Although the starter notch was positioned at the region of interface, the fatigue crack gradually deviated from the interface and ultimately propagated along the inter-critically heat-affected zone. The difference in microstructure is considered as the primary factor that resulted in the different fatigue crack growth behaviors of the welded joints. In addition, the continuous microstructure connection and composition transition at the interface contributed to the good fatigue resistance at this region.

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

    DEFF Research Database (Denmark)

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

    2013-01-01

    of specimens are used, two of these are non-welded and the third is welded with a transverse welding (T-Joint). The 13 laser welded specimens are cut out with a milling cutter. The non-welded specimens are divided in 13 specimens cut out with a milling cutter and 10 specimens cut out by a plasma cutter......In this paper the fatigue behavior of laser welded T-joints of stainless steel AISI304 is investigated experimentally. In the fatigue experiments 36 specimens with a sheet thickness of 1 mm are exposed to one-dimensional cyclic loading. Three different types of specimens are adopted. Three groups....... The non-welded specimens are used to study the influence of heat and surface effects on the fatigue life. The fatigue life from the experiments is compared to fatigue life calculated from the guidelines in the standards DNV-RP-C203 and EUROCODE 3 EN-1993-1-9. Insignificant differences in fatigue life...

  14. Effect of Prior Fatigue-Stressing on the Impact Resistance of Chromium-Molybdenum Aircraft Steel

    Science.gov (United States)

    1943-03-01

    corrosion , erosion, and abrasiqn, Any of th~~~ irregularities may result in concentrations of stress for which it iS difticult to make ample allow...the study of fatigu’s i’n aircraf’t ‘mat~rials in tlia pr=– cra ~lr stags~” Kins and Quick (r~f~ranc~ 16) found no loss in notch~d- bar impact resistanc...ovidont that with th~ coarser polish large nul~bers mf cra ,cks formod only wh=r~ som6 plastic deformation ficcurrpd during fatigu-. If the mean t~nsil

  15. A new criterion for predicting rolling-element fatigue lives of through-hardened steels.

    Science.gov (United States)

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

    1972-01-01

    A carbide factor was derived based upon a statistical analysis which related rolling-element fatigue life to the total number of residual carbide particles per unit area, median residual carbide size, and percent residual carbide area. An equation was empirically determined which predicts material hardness as a function of temperature. The limiting temperatures of all of the materials studied were dependent on initial room temperature hardness and tempering temperature. An equation was derived combining the effects of material hardness, carbide factor, and bearing temperature to predict rolling-element bearing life.

  16. Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel Part II: Plate bending test and proposal of a simplified evaluation method

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Masanori, E-mail: ando.masanori@jaea.go.jp; Takaya, Shigeru, E-mail: takaya.shigeru@jaea.go.jp

    2016-12-15

    Highlights: • Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel is proposed. • A simplified evaluation method is also proposed for the codification. • Both proposed evaluation method was validated by the plate bending test. • For codification, the local stress and strain behavior was analyzed. - Abstract: In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for evaluating the creep-fatigue life of Mod.9Cr-1Mo steel weld joints was proposed based on finite element analysis (FEA) and a series of cyclic plate bending tests of longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and the failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. Inelastic FEA models consisting of the base metal, heat-affected zone and weld metal were employed to estimate the elastic follow-up behavior caused by the metallurgical discontinuities. The elastic follow-up factors determined by comparing the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints. The creep-fatigue life obtained using the plate bending test was compared to those estimated from the results of inelastic FEA and by a simplified evaluation method.

  17. Reporting the Fatigue Life of 316L Stainless Steel Locking Compression Plate Implants: The Role of the Femoral and Tibial Biomechanics During the Gait.

    Science.gov (United States)

    Rice, Devyn; Shaat, Mohamed

    2017-10-01

    In this study, the fatigue characteristics of femoral and tibial locking compression plate (LCP) implants are determined accounting for the knee biomechanics during the gait. A biomechanical model for the kinematics and kinetics of the knee joint during the complete gait cycle is proposed. The rotations of the femur, tibia, and patella about the knee joint during the gait are determined. Moreover, the patellar-tendon force (PT), quadriceps-tendon force (QT), the tibiofemoral joint force (TFJ), and the patellofemoral joint force (PFJ) through the standard gait cycle are obtained as functions of the body weight (BW). On the basis of the derived biomechanics of the knee joint, the fatigue factors of safety along with the fatigue life of 316L stainless steel femoral and tibial LCP implants are reported as functions of the BW and bone fracture location, for the first time. The reported results reveal that 316L stainless steel LCP implants for femoral surgeries are preferred for conditions in which the bone fracture is close to the knee joint and the BW is less than 80 kg. For tibial surgeries, 316L stainless steel LCP implants can be used for conditions in which the bone fracture is close to the knee joint and the BW is less than 100 kg. This study presents a critical guide for the determination of the fatigue characteristics of LCP implants. The obtained results reveal that the fatigue analyses should be performed on the basis of the body biomechanics to guarantee accurate designs of LCP implants for femoral and tibial orthopedic surgeries.

  18. Microstructural changes of a thermally aged stainless steel submerged arc weld overlay cladding of nuclear reactor pressure vessels

    Science.gov (United States)

    Takeuchi, T.; Kameda, J.; Nagai, Y.; Toyama, T.; Matsukawa, Y.; Nishiyama, Y.; Onizawa, K.

    2012-06-01

    The effect of thermal aging on microstructural changes in stainless steel submerged arc weld-overlay cladding of reactor pressure vessels was investigated using atom probe tomography (APT). In as-received materials subjected to post-welding heat treatments (PWHTs), with a subsequent furnace cooling, a slight fluctuation of the Cr concentration was observed due to spinodal decomposition in the δ-ferrite phase but not in the austenitic phase. Thermal aging at 400 °C for 10,000 h caused not only an increase in the amplitude of spinodal decomposition but also the precipitation of G phases with composition ratios of Ni:Si:Mn = 16:7:6 in the δ-ferrite phase. The degree of the spinodal decomposition in the submerged arc weld sample was similar to that in the electroslag weld one reported previously. We also observed a carbide on the γ-austenite and δ-ferrite interface. There were no Cr depleted zones around the carbide.

  19. Effect of Heavy Ion Irradiation Dosage on the Hardness of SA508-IV Reactor Pressure Vessel Steel

    Directory of Open Access Journals (Sweden)

    Xue Bai

    2017-01-01

    Full Text Available Specimens of the SA508-IV reactor pressure vessel (RPV steel, containing 3.26 wt. % Ni and just 0.041 wt. % Cu, were irradiated at 290 °C to different displacement per atom (dpa with 3.5 MeV Fe ions (Fe2+. Microstructure observation and nano-indentation hardness measurements were carried out. The Continuous Stiffness Measurement (CSM of nano-indentation was used to obtain the indentation depth profile of nano-hardness. The curves showed a maximum nano-hardness and a plateau damage near the surface of the irradiated samples, attributed to different hardening mechanisms. The Nix-Gao model was employed to analyze the nano-indentation test results. It was found that the curves of nano-hardness versus the reciprocal of indentation depth are bilinear. The nano-hardness value corresponding to the inflection point of the bilinear curve may be used as a parameter to describe the ion irradiation effect. The obvious entanglement of the dislocations was observed in the 30 dpa sample. The maximum nano-hardness values show a good linear relationship with the square root of the dpa.

  20. Effects of neutron irradiation on microstructures and hardness of stainless steel weld-overlay cladding of nuclear reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, T., E-mail: takeuchi.tomoaki@jaea.go.jp [Oarai Research and Development Center, Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan); Kakubo, Y.; Matsukawa, Y.; Nozawa, Y.; Toyama, T.; Nagai, Y. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nishiyama, Y.; Katsuyama, J.; Yamaguchi, Y.; Onizawa, K. [Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

    2014-06-01

    The microstructures and the hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to neutron irradiation at a dose of 7.2 × 10{sup 19} n cm{sup −2} (E > 1 MeV) and a flux of 1.1 × 10{sup 13} n cm{sup −2} s{sup −1} at 290 °C were investigated by atom probe tomography and by a nanoindentation technique. To isolate the effects of the neutron irradiation, we compared the results of the measurements of the neutron-irradiated samples with those from a sample aged at 300 °C for a duration equivalent to that of the irradiation. The Cr concentration fluctuation was enhanced in the δ-ferrite phase of the irradiated sample. In addition, enhancement of the concentration fluctuation of Si, which was not observed in the aged sample, was observed. The hardening in the δ-ferrite phase occurred due to both irradiation and aging; however, the hardening of the irradiated sample was more than that expected from the Cr concentration fluctuation, which suggested that the Si concentration fluctuation and irradiation-induced defects were possible origins of the additional hardening.

  1. Effects of thermal aging on microstructure and hardness of stainless steel weld-overlay claddings of nuclear reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, T., E-mail: takeuchi.tomoaki@jaea.go.jp [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan); Kakubo, Y.; Matsukawa, Y.; Nozawa, Y.; Toyama, T.; Nagai, Y. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nishiyama, Y.; Katsuyama, J.; Yamaguchi, Y.; Onizawa, K. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Suzuki, M. [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan)

    2014-09-15

    The effects of thermal aging of stainless steel weld-overlay claddings of nuclear reactor pressure vessels on the microstructure and hardness of the claddings were investigated using atom probe tomography and nanoindentation testing. The claddings were aged at 400 °C for periods of 100–10,000 h. The fluctuation in Cr concentration in the δ-ferrite phase, which was caused by spinodal decomposition, progressed rapidly after aging for 100 h, and gradually for aging durations greater than 1000 h. On the other hand, NiSiMn clusters, initially formed after aging for less than 1000 h, had the highest number density after aging for 2000 h, and coarsened after aging for 10,000 h. The hardness of the δ-ferrite phase also increased rapidly for short period of aging, and saturated after aging for longer than 1000 h. This trend was similar to the observed Cr fluctuation concentration, but different from the trend seen in the formation of the NiSiMn clusters. These results strongly suggest that the primary factor responsible for the hardening of the δ-ferrite phase owing to thermal aging is Cr spinodal decomposition.

  2. Post irradiation tensile and fatigue behavior of austenitic PCA stainless steels irradiated in HFIR

    Science.gov (United States)

    Tanaka, M. P.; Hamada, S.; Hishinuma, A.; Grossbeck, M. L.

    1988-07-01

    Mechanical properties were determined on solution annealed (SA) and cold worked (CW) JPCA (Ti-modified austenitic stainless steel) irradiated in the High Flux Isotope Reactor (HFIR) at temperatures ranging from 300 to 600°C. The irradiation produced damage levels from 16 to 56 dpa and helium concentration from 1020 to 4100 appm. The improved stability of MC precipitates which formed in the matrix during irradiation prevent loss of ductility at 500°C and below. Application of solution annealed JPCA is recommended for structural components of fusion reactors to be operated at 500°C and below.

  3. 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.

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

    Directory of Open Access Journals (Sweden)

    Hailong Deng

    2015-12-01

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

  5. In-air and pressurized water reactor environment fatigue experiments of 316 stainless steel to study the effect of environment on cyclic hardening

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish, E-mail: smohanty@anl.gov; Soppet, William K., E-mail: soppet@anl.gov; Majumdar, Saurindranath, E-mail: majumdar@anl.gov; Natesan, Krishnamurti, E-mail: natesan@anl.gov

    2016-05-15

    Argonne National Laboratory (ANL), under the sponsorship of Department of Energy's Light Water Reactor Sustainability (LWRS) program, is trying to develop a mechanistic approach for more accurate life estimation of LWR components. In this context, ANL has conducted many fatigue experiments under different test and environment conditions on type 316 stainless steel (316 SS) material which is widely used in the US reactors. Contrary to the conventional S ∼ N curve based empirical fatigue life estimation approach, the aim of the present DOE sponsored work is to develop an understanding of the material ageing issues more mechanistically (e.g. time dependent hardening and softening) under different test and environmental conditions. Better mechanistic understanding will help develop computer-based advanced modeling tools to better extrapolate stress-strain evolution of reactor components under multi-axial stress states and hence help predict their fatigue life more accurately. Mechanics-based modeling of fatigue such as by using finite element (FE) tools requires the time/cycle dependent material hardening properties. Presently such time-dependent material hardening properties are hardly available in fatigue modeling literature even under in-air conditions. Getting those material properties under PWR environment, are even harder. Through this work we made preliminary attempt to generate time/cycle dependent stress-strain data both under in-air and PWR water conditions for further study such as for possible development of material models and constitutive relations for FE model implementation. Although, there are open-ended possibility to further improve the discussed test methods and related material estimation techniques we anticipate that the data presented in this paper will help the metal fatigue research community particularly, the researchers who are dealing with mechanistic modeling of metal fatigue such as using FE tools. In this paper the fatigue

  6. Evaluation of Thermodynamic Stable Phase and Microstructure of SA508 Gr.4N Model Alloys for Reactor Pressure Vessel Steel with Variation of Alloying Elements

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Mim Chul; Lee, B. S

    2009-12-15

    In order to increase the strength and the fracture toughness of RPV(reactor pressure vessel) steels, an effective way is the change of material specification from Mn-Mo-Ni low alloy steel(SA508 Gr.3) into Ni-Mo-Cr low alloy steel(SA508 Gr.4N). In this study, we evaluate the effects of alloying elements on microstructural characteristics in Ni-Mo-Cr low alloy steel. The changes in stable phase of SA508 Gr.4N low alloy steel with alloying elements were evaluated using a thermodynamic calculation by ThermoCalc software, and then compared with its microstructural observation results. From the calculation of Ni-Mo-Cr low alloy steels, ferrite formation temperature were decreased with increasing Ni and Mn contents due to austenite stabilization effect. Consequently, in the microscopic observation, the microstructure became finer with increasing Ni and Mn contents. However, they does not affects the carbide phase such as M{sub 23}C{sub 6} and M{sub 7}C{sub 3}. When the content of Cr is decreased, carbide phases became unstable and carbide coarsening is observed. With increase of Mo content, M{sub 2}C phase become stable instead of M{sub 7}C{sub 3} and it also observed in the TEM.

  7. Models for embrittlement recovery due to annealing of reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Eason, E.D.; Wright, J.E.; Nelson, E.E. [Modeling and Computing Services, Boulder, CO (United States); Odette, G.R.; Mader, E.V. [California Univ., Santa Barbara, CA (United States)

    1995-05-01

    The reactor pressure vessel (RPV) surrounding the core of a commercial nuclear power plant is subject to embrittlement due to exposure to high energy neutrons. The effects of irradiation embrittlement can be reduced by thermal annealing at temperatures higher than the normal operating conditions. However, a means of quantitatively assessing the effectiveness of annealing for embrittlement recovery is needed. The objective of this work was to analyze the pertinent data on this issue and develop quantitative models for estimating the recovery in 30 ft-lb (41 J) Charpy transition temperature and Charpy upper shelf energy due to annealing. Data were gathered from the Test Reactor Embrittlement Data Base and from various annealing reports. An analysis data base was developed, reviewed for completeness and accuracy, and documented as part of this work. Independent variables considered in the analysis included material chemistries, annealing time and temperature, irradiation time and temperature, fluence, and flux. To identify important variables and functional forms for predicting embrittlement recovery, advanced statistical techniques, including pattern recognition and transformation analysis, were applied together with current understanding of the mechanisms governing embrittlement and recovery. Models were calibrated using multivariable surface-fitting techniques. Several iterations of model calibration, evaluation with respect to mechanistic and statistical considerations, and comparison with the trends in hardness data produced correlation models for estimating Charpy upper shelf energy and transition temperature after irradiation and annealing. This work provides a clear demonstration that (1) microhardness recovery is generally a very good surrogate for shift recovery, and (2) there is a high level of consistency between the observed annealing trends and fundamental models of embrittlement and recovery processes.

  8. On the role of sulfur on the dissolution of pressure vessel steels at the tip of a propagating crack in PWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Combrade, P.; Foucault, M. (UNIREC 42- Firminy (FR)); Marcus, P. (Ecole Nationale Superieure de Chimie 75 - Paris (FR)); Slama, G. (Societe Franco-Americaine de Constructions Atomiques (Framatome), 92 - Courbevoie (FR))

    1990-03-01

    Different aspects of the effect of sulfur on the dissolution and film repair on pressure vessel steel exposed to PWR environment at 300{sup 0}C were examined. A monolayer of sulfur adsorbed on a bare surface was shown to inhibit the nucleation of a magnetite film. The comparison of this result with dissolution measurements performed by using CERT under controlled potential lead to the assumption that mechanical rupture steps are involved in the environmental effect on the crack propagation rate. 27 refs.

  9. Effect of heterogeneities on the thermoelectric power of pressure vessel steel; Effet des heterogeneites sur le pouvoir thermoelectrique de l'acier de cuve

    Energy Technology Data Exchange (ETDEWEB)

    Simonet, L

    2006-12-15

    In service working conditions, the vessel of the Pressurized Water Reactors (PWR) undergoes an ageing due to irradiation. In order to follow the evolution of the mechanical characteristics of the steel in service, EDF launched a surveillance program which consists to carry out mechanical tests on samples aged in reactor. However, the results of these tests have the disadvantage to be affected by the presence of heterogeneities within the steel. Indeed, because of its manufacturing process, the steel contains segregated areas. Thus, EDF launched Thermoelectric Power Measurements (TEP) on the resilience samples of the surveillance program, to complete the mechanical tests and to help with their interpretation. However, these measurements are today difficult to analyse because they include at the same time the effect of the irradiation and the effect of the metallurgical heterogeneities. The aim of this work consisted in evaluating the effect of the heterogeneities on the TEP of the non-irradiated vessel steel. For that, a numerical model was developed which allows to calculate the TEP of a composite structure. We have shown that the model is pertinent to highlight the effect of the heterogeneities on the TEP of the vessel steel, which is considered like a 'matrix'/'segregation' composite. The model allowed us to put emphasis on the influence of different parameters on the TEP measurement. We have thus showed that the measurements conditions have an important effect on the obtained TEP value (influence of the applied pressure, the position of the sample on the device, the site of the metallurgical heterogeneities,...). (author)

  10. Influence of the stress gradient on the fatigue life calculation of a martensitic high strength steel

    Directory of Open Access Journals (Sweden)

    I. Milo�evic

    2017-10-01

    Full Text Available Nowadays lifetime calculation in the high cycle fatigue region is commonly based on S/N curves which are modified by different influences to ensure accurate results. Especially the application of these models is important when small components with complex stress distributions are used. The influence of the stress distribution was considered by the stress gradient approach which is implemented in the lifetime tool FEMFAT. Specimens with diameters of D4mm and D7.5mm were used to examine the effect of the calculation modified by the stress gradient. On the one hand regarding different types of this approach it can be shown that the results fit very well compared to the testing results but on the other hand a big difference was observed when the gradient increases by smaller specimen sizes.

  11. Application of cyclic J-integral to low cycle fatigue crack growth of Japanese carbon steel pipe

    Energy Technology Data Exchange (ETDEWEB)

    Miura, N.; Fujioka, T.; Kashima, K. [and others

    1997-04-01

    Piping for LWR power plants is required to satisfy the LBB concept for postulated (not actual) defects. With this in mind, research has so far been conducted on the fatigue crack growth under cyclic loading, and on the ductile crack growth under excessive loading. It is important, however, for the evaluation of the piping structural integrity under seismic loading condition, to understand the fracture behavior under dynamic and cyclic loading conditions, that accompanies large-scale yielding. CRIEPI together with Hitachi have started a collaborative research program on dynamic and/or cyclic fracture of Japanese carbon steel (STS410) pipes in 1991. Fundamental tensile property tests were conducted to examine the effect of strain rate on tensile properties. Cracked pipe fracture tests under some loading conditions were also performed to investigate the effect of dynamic and/or cyclic loading on fracture behavior. Based on the analytical considerations for the above tests, the method to evaluate the failure life for a cracked pipe under cyclic loading was developed and verified. Cyclic J-integral was introduced to predict cyclic crack growth up to failure. This report presents the results of tensile property tests, cracked pipe fracture tests, and failure life analysis. The proposed method was applied to the cracked pipe fracture tests. The effect of dynamic and/or cyclic loading on pipe fracture was also investigated.

  12. Assessment of Negligible Creep, Off-Normal Welding and Heat Treatment of Gr91 Steel for Nuclear Reactor Pressure Vessel Application

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Weiju [ORNL; Terry, Totemeier [Idaho National Laboratory (INL)

    2006-10-01

    Two different topics of Grade 91 steel are investigated for Gen IV nuclear reactor pressure vessel application. On the first topic, negligible creep of Grade 91 is investigated with the motivation to design the reactor pressure vessel in negligible creep regime and eliminate costly surveillance programs during the reactor operation. Available negligible creep criteria and creep strain laws are reviewed, and new data needs are evaluated. It is concluded that modifications of the existing criteria and laws, together with their associated parameters, are needed before they can be reliably applied to Grade 91 for negligible creep prediction and reactor pressure vessel design. On the second topic, effects of off-normal welding and heat treatment on creep behavior of Grade 91 are studied with the motivation to better define the control over the parameters in welding and heat treatment procedures. The study is focused on off-normal austenitizing temperatures and improper cooling after welding but prior to post-weld heat treatment.

  13. Fatigue cracking of a bare steel first wall in an inertial confinement fusion chamber

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, R. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Abbott, R. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Havstad, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dunne, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-06-01

    Inertial confinement fusion power plants will deposit high energy X-rays onto the outer surfaces of the first wall many times a second for the lifetime of the plant. These X-rays create brief temperature spikes in the first few microns of the wall, which cause an associated highly compressive stress response on the surface of the material. The periodicity of this stress pulse is a concern due to the possibility of fatigue cracking of the wall. We have used finite element analyses to simulate the conditions present on the first wall in order to evaluate the driving force of crack propagation on fusion-facing surface cracks. Analysis results indicate that the X-ray induced plastic compressive stress creates a region of residual tension on the surface between pulses. This tension film will likely result in surface cracking upon repeated cycling. Additionally, the compressive pulse may induce plasticity ahead of the crack tip, leaving residual tension in its wake. However, the stress amplitude decreases dramatically for depths greater than 80–100 μm into the fusion-facing surface. Crack propagation models as well as stress-life estimates agree that even though small cracks may form on the surface of the wall, they are unlikely to propagate further than 100 μm without assistance from creep or grain erosion phenomena.

  14. The crystallography of fatigue crack initiation in Incoloy-908 and A-286 steel

    Energy Technology Data Exchange (ETDEWEB)

    Krenn, C.R. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering]|[Lawrence Berkeley National Lab., CA (United States)

    1996-12-01

    Fatigue crack initiation in the austenitic Fe-Ni superalloys Incoloy-908 and A-286 is examined using local crystallographic orientation measurements. Results are consistent with sharp transgranular initiation and propagation occurring almost exclusively on {l_brace}111{r_brace} planes in Incoloy-908 but on a variety of low index planes in A-286. This difference is attributed to the influence of the semicoherent grain boundary {eta} phase in A-286. Initiation in each alloy occurred both intergranularly and transgranularly and was often associated with blocky surface oxide and carbide inclusions. Taylor factor and resolved shear stress and strain crack initiation hypotheses were tested, but despite an inconclusive suggestion of a minimum required {l_brace}111{r_brace} shear stress, none of the hypotheses were found to convincingly describe preferred initiation sites, even within the subsets of transgranular cracks apparently free from the influence of surface inclusions. Subsurface inclusions are thought to play a significant role in crack initiation. These materials have applications for use in structural conduit for high field superconducting magnets designed for fusion energy use.

  15. Influence of non-metallic second phases on fatigue behaviour of high strength steel components; Efecto de segundas fases no metalicas sobre el comportamiento a fatiga de componentes de acero con elevadas solicitaciones

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, L.; Elvira, R.; Garcia de Andoin, A.; Pizarro, R.; Bertrand, C.

    2005-07-01

    To assess the real effect of the inclusion type on fatigue life of ultra clean high strength steels mechanical components made of 100Cr6 steel were fatigue tested and fracture surfaces analysed to determine the origin of fatigue cracks.Two heats proceedings from different steelmaking routes were taken for the tests. The material were forged into ring shape components which were fatigue tested under compression-compression loads. Failures were analysed by SFEM (Scanning field Emission Microscopy), proving that most of failures at high loads were originated by manganese sulphides of small size (10-70 micros), while less than 40% of all fatigue cracks due to inclusions were caused by titanium carbonitrides and hard oxides. It has been demonstrated that once number and size of hard inclusions have been reduced, the hazardous effect of oxides and carbonitrides on the fatigue life decreases also. However, softer inclusions as manganese sulphides, currently considered as less hazardous, play a more relevant role as direct cause of fatigue failure and they should be taken into account in a deeper way in order to balance both machinability and fatigue life requirements in high strength steel components. (Author) 11 refs.

  16. The propagation of short fatigue crack effect in 304L stainless steel: closure and plasticity effect; Propagation par fatigue des fissures physiquement courtes dans un acier inoxydable de type 304L: role de la fermeture et de la plasticite

    Energy Technology Data Exchange (ETDEWEB)

    Lesur, N

    2005-12-15

    The behaviour of 2D physically short cracks has been studied for an austenitic stainless steel type A304L. Experimental fatigue tests have shown an increase of the threshold fatigue range when the crack length is increasing from 0.1 to 0.8 mm. This effect is explained in term of crack closure variation. The numerical simulation by mean of finite elements supports such an effect of crack closure when computing is performed in plane stress at R=0.1 and R=0.7. Such behaviour is typical for a material characterized by an isotropic and cinematic constitutive cyclic hardening law. The local plasticity effect is shown to control the crack growth rate and has been related to an effective plastic intensity factor range. (author)

  17. Microscopic analysis of the influence of ratcheting on the evolution of dislocation structures observed in AISI 316L stainless steel during low cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Facheris, G., E-mail: giacomo.facheris@psi.ch [Laboratory for Nuclear Materials, Nuclear Energy and Safety Research Department, Paul Scherrer Institute, Villigen PSI (Switzerland); Pham, M.-S. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); High Temperature Integrity Group, Mechanics for Modelling and Simulation, Swiss Federal Laboratories for Materials Science and Technology, EMPA, Dübendorf (Switzerland); Janssens, K.G.F., E-mail: koen.janssens@psi.ch [Laboratory for Nuclear Materials, Nuclear Energy and Safety Research Department, Paul Scherrer Institute, Villigen PSI (Switzerland); Holdsworth, S.R. [High Temperature Integrity Group, Mechanics for Modelling and Simulation, Swiss Federal Laboratories for Materials Science and Technology, EMPA, Dübendorf (Switzerland)

    2013-12-10

    When subjected to controlled cyclic deformation, the response of austenitic stainless steel typically involves primary hardening followed by softening, and eventually cyclic stabilization with or without secondary hardening. If a continuously drifting mean strain is superposed to an alternating strain path (i.e. strain controlled ratcheting), the response in terms of mean stress and strain amplitude is significantly different. A series of low cycle fatigue and ratcheting experiments are performed at room temperature on round specimens extracted from a batch of AISI 316L hot rolled plate. The experiments are interrupted at cycle numbers selected to correspond with the different strain controlled cycle response stages. The as-received material and the fatigued specimens are analyzed by means of transmission electron microscopy to characterize the microstructure and its evolution with cyclic loading. The low cycle fatigue experiments, performed to establish a reference point for the zero mean strain loading condition, are in line with observations reported for AISI 316L stainless steel by other authors. The continuously increasing mean strain is found to induce higher dislocation densities in the channels of the evolving microstructure, being responsible for the macroscopically observed additional hardening. The observed polarized dislocation walls at least partially accommodate the continuously drifting mean strain and play a role in the non-zero mean stress response.

  18. Improved fatigue behavior of low-carbon steel 20GL by applying ultrasonic impact treatment combined with the electric discharge surface alloying

    Energy Technology Data Exchange (ETDEWEB)

    Mordyuk, B.N., E-mail: mordyuk@imp.kiev.ua [Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky blvd., UA-03142, Kyiv (Ukraine); Prokopenko, G.I.; Volosevich, P.Yu. [Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky blvd., UA-03142, Kyiv (Ukraine); Matokhnyuk, L.E.; Byalonovich, A.V. [Pisarenko Institute for Strength of Materials, NAS of Ukraine, 2 Timiryazevs’ka str., UA-01014, Kyiv (Ukraine); Popova, T.V. [Ukrainian Research Institute Rail carriage building, 33 Prikhodko str., UA-39621, Kremenchuk (Ukraine)

    2016-04-06

    The effects of severe plastic deformation induced by ultrasonic impact treatment (UIT) and the electric discharge surface alloying (EDSA) with chromium on the stress-controlled fatigue response of low-carbon steel 20GL are studied. The surface microrelief and integrity were analyzed using light microscopy and scanning electron microscopy (SEM). The structural formations in the sub-surface layers were characterized by means of X-ray diffraction analysis and transmission electron microscopy (TEM). The steel specimens underwent UIT, and complex UIT+EDSA and UIT+EDSA+UIT processes demonstrate the fatigue strength magnitudes increased respectively by ~15, ~5 and ~30% on the base of 10{sup 7} cycles in comparison with that for the pristine specimen. SEM analysis of fracture surfaces reveals the subsurface crack nucleation in the UIT-processed specimens instead of superficial crack initiation observed in the pristine and EDSA-processed ones. TEM studies demonstrate that a dislocation-cell structure forms in ferrite grains and partial dissolution of cementite occurs in pearlite grains both at the surface after UIT and in the layer at a depth of 15–25 µm after the UIT+EDSA+UIT process. The enhanced fatigue strength and prolonged lifetime of the low-carbon steel specimens after UIT and UIT+EDSA+UIT processes are concluded to be associated with the subsurface crack nucleation achieved by the following factors: (i) minimized surface roughness and improved integrity of the modified layer; (ii) compressive residual stresses; and (iii) surface hardening coupled with the alloying by chromium and with the formation of the dislocation-cell structure containing the cell walls impenetrable to moving dislocations at cyclic loading.

  19. Effects of frequency and temperature- and strain-wave form on thermal fatigue strength of type 316 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Tsunenari, Toshiyasu; Horikawa, Takeshi; Okada, Tomonobu; Take, Koji; Miyashita, Takuya (Kawasaki Heavy Industries Ltd., Akashi, Hyogo (Japan). Technical Inst.)

    1983-06-01

    The effects of frequency and temperature- and strain-wave form on thermal fatigue strength were examined by conducting out-of-phase and in-phase thermal fatigue tests with three kinds of temperature-wave forms (fast heating and fast cooling, slow heating and slow cooling, slow heating and fast cooling) under temperature cycling between 350 - 650/sup 0/C and by isothermal low-cycle fatigue tests at 650/sup 0/C under cyclic frequencies of 0.5 -- 0.039 cpm. The following results were obtained. (1) The effect of frequency on fatigue life in out-of-phase thermal fatigue was as small as in isothermal low-cycle fatigue, whereas in in-phase thermal fatigue it was much greater and the fatigue life reduction was more remarkable in low frequency. (2) The effect of temperature- and strain-wave form on thermal fatigue life was still smaller than the effect of frequency on out-of-phase thermal fatigue life. (3) The fracture mode of out-of-phase thermal fatigue was the transgranular type even at the lowest frequency tested, but that of in-phase thermal fatigue changed to the intergranular type at low frequency. (4) Out-of-phase and in-phase thermal fatigue data obtained at the test condition of such an extremely low frequency as 0.039 cpm were found to coincide well with ..delta..epsilon sub(PC) - N sub(PC) and ..delta..epsilon sub(CP) - N sub(CP) relations, respectively.

  20. The changes of the structural, magnetic, and mechanical properties in a reactor pressure vessel steel neutron-irradiated at 70 .deg. C

    CERN Document Server

    Park, D G; Jang, K S; Jung, M M; Kim, G M

    1999-01-01

    The irradiation embrittlement of reactor-pressure-vessel steel has been one of the main safety concerns in nuclear power plants. In the present study, an SA508-3 RPV steel was irradiated by neutrons with various fluences up to 10 sup 1 sup 8 n/cm sup 2 (E>=1MeV) at a temperature of approximately 70 .deg. C. The irradiation responses of the structural, the magnetic, and the mechanical properties of the steel were investigated by means of X-ray diffraction, Moessbauer spectroscopy, magnetic Barkhausen noise, and micro-Vickers hardness measurements. The transitions of all of these parameters occurred above a neutron does of 10 sup 1 sup 6 n/cm sup 2. The results of the X-ray and the Moessbauer experiments revealed that neutron irradiation led to the possibility of partial amorphization in the investigated RPV steel. The changes of the physical and the mechanical properties were discussed in terms of irradiation-induced cascade damage of crystalline materials.

  1. Main results of study on the interaction between the corium melt and steel in the VVER-1000 reactor vessel during a severe accident performed under the MASCA project

    Science.gov (United States)

    Asmolov, V. G.; Zagryazkin, V. N.; Tsurikov, D. F.; Vishnevsky, V. Yu.; D'Yakov, Ye. K.; Kotov, A. Yu.; Repnikov, V. M.

    2010-12-01

    The interactions that take place in the corium melt in the reactor vessel in the case of a severe accident at a nuclear power plant were investigated in accordance with the MASCA international program. Results of the interaction between the oxide melt and iron (steel), partition of the main components [U, Zr, Fe (stainless steel)] between the oxide and the metal phases of the melt, partition of low-volatile simulators of fission products between the phases of the stratified core melt pool, and impact of the oxidizing atmosphere on the melt stratification are presented. The results obtained were used for prediction of thermodynamic properties of the melts belonging to the U-Zr-Fe-O system.

  2. The role of water chemistry for environmentally assisted cracking in low-alloy reactor pressure vessel and piping steels under boiling reactor conditions

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.-P.; Ritter, S

    2005-07-01

    The environmentally assisted initiation and propagation of cracks in structural materials is one of the most important degradation and ageing mechanisms in light water reactors (LWR) and may seriously affect plant availability and economics. In the first part of this paper a short general introduction on environmentally assisted cracking (EAC) and its significance for LWR is given. Then the important role of water chemistry control in reducing the EAC risk in LWR is illustrated by current research results about the effect of chloride transients and hydrogen water chemistry on the EAC crack growth behaviour of low-alloy reactor pressure vessel and piping steels under boiling water reactor conditions. (author)

  3. PREDICTION OF LONG-TERM CREEP-FATIGUE LIFE OF STAINLESS STEEL WELDMENT BASED ON MICROSTRUCTURE DEGRADATION

    OpenAIRE

    Tai, ASAYAMA; Shinichi, HASEBE; Oarai Engineering Center, Power Reactor and Nuclear Fuel Development Corporation

    1997-01-01

    This paper describes a newly developed analytical method for the evaluation of creep-fatigue strength for stainless weld metal. Based on the observation that creep-fatigue crack initiated adjacent to the interface of σ-phase/δ-ferrite and matrix, a mechanical model, which allowed the evaluation of micro stress/strain concentration adjacent to the interface, was developed. Fatigue and creep damages were evaluated, using the model which described the microstructure after long time exposure to h...

  4. Distribution of Corrosion Fatigue Crack Lengths in Carbon Steel : 2nd Report, The Distributed Cracks which Interact and Coalesce

    OpenAIRE

    Ishihara, Sotomi; Shiozawa, Kazuaki; Miyao, Kazyu

    1985-01-01

    It has been known that very small distributed cracks can be observed on the surface of smooth specimen subjected to corrosion fatigue, and the fatigue crack growth rate is accelerated by the interaction and coalescence of them. In this report, following the previous report of the authors, the interaction and coalescence behaviour of the distributed cracks on the specimen surface were observed in detail. Based on the experimental results, distribution of corrosion fatigue crack lengths after a...

  5. Metal magnetic memory technique used to predict the fatigue crack propagation behavior of 0.45%C steel

    Energy Technology Data Exchange (ETDEWEB)

    Chongchong, Li [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); National Key Lab for Remanufacturing, Academy of Armored Forces Engineering, Beijing 100072 (China); Lihong, Dong, E-mail: lihong.dong@126.com [National Key Lab for Remanufacturing, Academy of Armored Forces Engineering, Beijing 100072 (China); Haidou, Wang [National Key Lab for Remanufacturing, Academy of Armored Forces Engineering, Beijing 100072 (China); Guolu, Li [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Binshi, Xu [National Key Lab for Remanufacturing, Academy of Armored Forces Engineering, Beijing 100072 (China)

    2016-05-01

    Monitoring fatigue crack propagation behavior of ferromagnetic components is very important. In this paper, the tension–tension fatigue tests of center cracked tension (CCT) specimens were carried out; the variation regularity of both tangential and normal components of magnetic signals during fatigue process were investigated. The results showed that the initial abnormal signals which appeared at the notch were reversed after cyclic loading. The abnormal magnetic signals became more significant with the increase of fatigue cycles and reversed again after failure. The characteristic parameters, i.e., the peak value of tangential component, B{sub tp}, and maximum gradient value of normal component, K{sub m}, showed similar variation trends during the fatigue process, which can be divided into three different stages. An approximate linear relationship was found between the characteristic parameters and fatigue crack length 2a. The feasibility of predicting the fatigue crack propagation using the abnormal magnetic signals was discussed. What's more, the variation and distribution of the magnetic signals were also analyzed based on the theory of magnetic charge. - Highlights: • A novel and passive NDT method, i.e. MMMT method, is proposed. • Both tangential and normal components of magnetic signals were investigated. • The prediction of crack propagation by abnormal magnetic signals was discussed. • A linear relationship was found between the parameters and fatigue crack length 2a. • The parameters can be potentially used to evaluate the crack propagation state.

  6. The Influence of Lath, Block and Prior Austenite Grain (PAG Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel

    Directory of Open Access Journals (Sweden)

    Thomas Simm

    2017-06-01

    Full Text Available The influence of martensitic microstructure and prior austenite grain (PAG size on the mechanical properties of novel maraging steel was studied. This was achieved by looking at two different martensitic structures with PAG sizes of approximately 40 µm and 80 µm, produced by hot rolling to different reductions. Two ageing heat-treatments were considered: both heat-treatments consisted of austenisation at 960 °C, then aging at 560 °C for 5 h, but while one was rapidly cooled the other was slow cooled and then extended aged at 480 °C for 64 h. It is shown that for the shorter ageing treatment the smaller PAG size resulted in significant improvements in strength (increase of more than 150 MPa, ductility (four times increase, creep life (almost four times increase in creep life and fatigue life (almost doubled. Whereas, the extended aged sample showed similar changes in the fatigue life, elongation and hardness it displayed yet showed no difference in tensile strength and creep. These results display the complexity of microstructural contributions to mechanical properties in maraging steels.

  7. The Influence of Lath, Block and Prior Austenite Grain (PAG) Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel.

    Science.gov (United States)

    Simm, Thomas; Sun, Lin; McAdam, Steven; Hill, Paul; Rawson, Martin; Perkins, Karen

    2017-06-30

    The influence of martensitic microstructure and prior austenite grain (PAG) size on the mechanical properties of novel maraging steel was studied. This was achieved by looking at two different martensitic structures with PAG sizes of approximately 40 µm and 80 µm, produced by hot rolling to different reductions. Two ageing heat-treatments were considered: both heat-treatments consisted of austenisation at 960 °C, then aging at 560 °C for 5 h, but while one was rapidly cooled the other was slow cooled and then extended aged at 480 °C for 64 h. It is shown that for the shorter ageing treatment the smaller PAG size resulted in significant improvements in strength (increase of more than 150 MPa), ductility (four times increase), creep life (almost four times increase in creep life) and fatigue life (almost doubled). Whereas, the extended aged sample showed similar changes in the fatigue life, elongation and hardness it displayed yet showed no difference in tensile strength and creep. These results display the complexity of microstructural contributions to mechanical properties in maraging steels.

  8. Investigation of the Effects of Submerged Arc Welding Process Parameters on the Mechanical Properties of Pressure Vessel Steel ASTM A283 Grade A

    Directory of Open Access Journals (Sweden)

    Prachya Peasura

    2017-01-01

    Full Text Available The pressure vessel steel is used in boilers and pressure vessel structure applications. This research studied the effects of submerged arc welding (SAW process parameters on the mechanical properties of this steel. The weld sample originated from ASTM A283 grade A sheet of 6.00-millimeter thickness. The welding sample was treated using SAW with the variation of three process factors. For the first factor, welding currents of 260, 270, and 280 amperes were investigated. The second factor assessed the travel speed, which was tested at both 10 and 11 millimeters/second. The third factor examined the voltage parameter, which was varied between 28 and 33 volts. Each welding condition was conducted randomly, and each condition was tested a total of three times, using full factorial design. The resulting materials were examined using tensile strength and hardness tests and were observed with optical microscopy (OM and scanning electron microscopy (SEM. The results showed that the welding current, voltage, and travel speed significantly affected the tensile strength and hardness (P value < 0.05. The optimum SAW parameters were 270 amperes, 33 volts, and 10 millimeters/second travel speed. High density and fine pearlite were discovered and resulted in increased material tensile strength and hardness.

  9. Magnetic flux gradient observation during fatigue crack propagation: A case study of SAE 1045 carbon steel used for automotive transmission parts

    Directory of Open Access Journals (Sweden)

    Ahmad S.R.

    2017-01-01

    Full Text Available The objective of this study is to evaluate the application of the metal magnetic memory (MMM technique for investigations on fatigue crack propagation in a ferromagnetic material. Fatigue failure caused by stress concentration is serious in practical engineering. However, early fatigue damages cannot be detected by using traditional nondestructive testing (NDT methods. Therefore this paper study about NDT method called metal magnetic memory (MMM that has potentials for evaluating the fatigue damage at the early damage and critical fracture stages. While its capacity to evaluate the distribution of self-magnetic leakage field signals on the component’s surface is well-established, there remains a need to scrutinize the physical mechanism and quantitative analysis aspects of this method. To begin with, a fatigue test involving a loading of 7kN was conducted on a SAE 1045 carbon steel specimen. This material is frequently used in the manufacturing of automotive transmission components that include the axle and spline shaft. MMM signals were measured along a scanning distance of 100 mm and analysed during the propagation stage. Other than revealing that the value of the magnetic flux gradient signals dH(y/dx increased in tandem with the crack length, the results also led to the detection of the crack growth location. It was anticipated that the dH(y/dx value will also exhibit an upward trend with a rise in the fatigue growth rate of da/dN. A modified Paris equation was utilized to correlate dH(y/dx with da/dn through the replacement of the stress intensity factor range ΔK. This resulted in the log-log plot of da/dN versus dH(y/dx portraying an inclination similar to the log-log plot of da/dN versus ΔK. A linear relationship was established between dH(y/dx and ΔK with the R2 value as 0.96. Players in the automotive industry can benefit from the disclosure that dH(y/dx can effectively replace ΔK for the monitoring of fatigue crack growth

  10. Effect of inclusion size on the high cycle fatigue strength and failure mode of a high V alloyed powder metallurgy tool steel

    Science.gov (United States)

    Yao, Jun; Qu, Xuan-hui; He, Xin-bo; Zhang, Lin

    2012-07-01

    The fatigue strength of a high V alloyed powder metallurgy tool steel with two different inclusion size levels, tempered at different temperatures, was investigated by a series of high cycle fatigue tests. It was shown that brittle inclusions with large sizes above 30 μm prompted the occurrence of subsurface crack initiation and the reduction in fatigue strength. The fracture toughness and the stress amplitude both exerted a significant influence on the fish-eye size. A larger fish-eye area would form in the sample with a higher fracture toughness subjected to a lower stress amplitude. The stress intensity factor of the inclusion was found to lie above a typical value of the threshold stress intensity factor of 4 MPa·m1/2. The fracture toughness of the sample with a hardness above HRC 56 could be estimated by the mean value of the stress intensity factor of the fish-eye. According to fractographic evaluation, the critical inclusion size can be calculated by linear fracture mechanics.

  11. Analysis of the micro-structural damages by neutronic irradiation of the steel of reactor vessels of the nuclear power plant of Laguna Verde. Characterization of the design steel; Analisis de los danos micro-estructurales por irradiacion neutronica del acero de la vasija de los reactores de la Central Nuclear de Laguna Verde. Caracterizacion del acero de diseno

    Energy Technology Data Exchange (ETDEWEB)

    Moranchel y Rodriguez, M.; Garcia B, A. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Fisica, Av. Luis Enrique Erro s/n, Unidad Profesional Adolfo Lopez Mateos, Col. Lindavista, 07738 Mexico D. F. (Mexico); Longoria G, L. C., E-mail: mmoranchel@ipn.m [ININ, Direccion de Investigacion Cientifica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2010-09-15

    The vessel of a nuclear reactor is one of the safety barriers more important in the design, construction and operation of the reactor. If the vessel results affected to the grade of to have fracture and/or cracks it is very probable the conclusion of their useful life in order to guarantee the nuclear safety and the radiological protection of the exposure occupational personnel, of the public and the environment avoiding the exposition to radioactive sources. The materials of the vessel of a nuclear reactor are exposed continually to the neutronic irradiation that generates the same nuclear reactor. The neutrons that impact to the vessel have the sufficient energy to penetrate certain depth in function of the energy of the incident neutron until reaching the repose or to be absorbed by some nucleus. In the course of their penetration, the neutrons interact with the nuclei, atoms, molecules and with the same crystalline nets of the vessel material producing vacuums, interstitial, precipitate and segregations among other defects that can modify the mechanical properties of the steel. The steel A533-B is the material with which is manufactured the vessel of the nuclear reactors of nuclear power plant of Laguna Verde, is an alloy that, among other components, it contains atoms of Ni that if they are segregated by the neutrons impact this would favor to the cracking of the same vessel. This work is part of an investigation to analyze the micro-structural damages of the reactor vessels of the nuclear power plant of Laguna Verde due to the neutronic irradiation which is exposed in a continuous way. We will show the characterization of the design steel of the vessel, what offers a comprehension about their chemical composition, the superficial topography and the crystalline nets of the steel A533-B. It will also allow analyze the existence of precipitates, segregates, the type of crystalline net and the distances inter-plains of the design steel of the vessel. (Author)

  12. Evaluation of fatigue vessel in the Sta. M Garona NPP : real transients and design transients; Evaluacion de la fatiga en la vasija de CN Santa M de Garona: transitorios reales frente a transitorios de diseno

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J.; Gorrochategui, I.

    2005-07-01

    The number of transient that control the fatigue of its reactor pressure vessel is included in the Sta. M Garona NPP Technical Specifications, being the different transients described in the design specification of the corresponding component. In this work, on the one hand, the description of the design transients with their corresponding real ones is compared and, on the other hand, the number of occurrences and the number of transients originally estimated is also compared. In both cases the influence of the difference between design and reality in the fatigue usage is discussed. (Author)

  13. Study of the damage processes induced by thermal fatigue in stainless steels F17TNb and R20-12 for automobile application; Etude de l'endommagement en fatigue thermique des aciers inoxydables F17TNb et R20-12 pour application automobile

    Energy Technology Data Exchange (ETDEWEB)

    Bucher, L.

    2004-12-15

    Thermal cycling is the main cause of fatigue failure in automobile exhaust manifolds for which the use of stainless steel now rivals that of cast iron which has been traditionally used. An original fatigue test has been developed by Ugine and ALZ, a stainless steel producer, so as to be able to compare different grades of stainless steel alloys. This test is representative of the thermal conditions encountered in the critical zones of exhaust manifolds. However, it has revealed significant differences in damage processes in the ferritic and austenitic grades tested. The subject of this thesis is the damage processes induced by thermal fatigue in stainless steels used for automotive exhaust manifolds. Two stainless steels were studied: a ferritic grade, F17TNb (17%Cr and stabilized with Ti and Nb), and an austenitic grade, R20-12, containing 20% Cr and 12% Ni. The first objective was to understand the different damage processes induced by thermal fatigue in the ferritic and austenitic grades. The second was to develop a numerical design tool of the thermally tested structures. (author)

  14. Mitigation of FOD and Corrosion Fatigue Damage in 17-4 PH Stainless Steel Compressor Blades With Surface Treatment

    National Research Council Canada - National Science Library

    Prevey, Paul S; Jayaraman, N; Ravindranath, Ravi

    2004-01-01

    ... the geometrical conditions of thick section and blade leading edges of compressor blades. The FOD tolerance and corrosion fatigue performance of 17-4PH prepared by low plasticity burnishing (LPB), shot peening (SP...

  15. Estimation of the resistance to the initiation of fatigue cracks in the welded joints of steel constructions

    Science.gov (United States)

    Odesskii, P. D.; Shuvalov, A. N.; Emel'yanov, O. V.

    2017-04-01

    The problem of choosing an effective approach to determining the fatigue strength of welded butt joints at the stage of crack nucleation is solved. The results of the calculations performed according to the existing building code from the specified strength characteristics and the calculations that take into account local elastoplastic deformation in stress concentration zones are compared. Full-scale specimens of the welded joints of pair angles are tested in the low-cycle fatigue region at a constant load. The kinetics of the state of stress in the zones of terminating flange welded joints is studied by a tensometric method. It is shown that the stage of fatigue crack nucleation is best described using the deformation criterion of fracture: a comparison of the results of calculating the number of cycles to the nucleation of a fatigue crack with experimental data demonstrates good agreement.

  16. On the microstructural basis of creep strength and creep-fatigue interaction in 9-12 % Cr steels for application in power plants

    Energy Technology Data Exchange (ETDEWEB)

    Chilukuru, H.

    2007-03-06

    As part of the efforts of preserving the environment it is necessary to reduce of the CO2 emissions from power plants. This can be done by increasing the plant efficiency. Research groups around the world are engaged in developing new steels capable of sustaining higher stresses and temperatures envisaged for high-efficiency power plants. Research carried out in Europe is organized within the COST Programme (Co-Operation in Science and Technology) aiming at replacing the conventional steels of type X20CrMoV121 by the new class of 9-12% Cr-steels with modified composition. The resistance of materials against deformation at elevated temperatures depends on their microstructure. Frequently in 9-12% Cr-steels improved short-term creep properties do not persist in the long-term service [1, 2, 3, 4, 5, 6]. This is related with insufficient microstructural stability. Hardening contributions in 9-12% Cr-steels come from solute atoms of the ferritic matrix, from dislocations, and from precipitates of foreign phases within the matrix. The term ''carbide stabilized substructure hardening'' of 9-12% Cr steels [7, 8] indicates that the hardening contributions are interdependent. The dislocations are the carriers of plastic deformation. They interact with each other, with solute atoms and with precipitates. The dislocation-dislocation interaction leads to formation of planar dislocation networks constituting low-angle boundaries. They form a subgrain structure within the grains. At present, a full and detailed understanding of the effects exerted by the different components of microstructure on creep strength is still lacking. The present work makes a contribution to the efforts of understanding the microstructural basis of creep strength and of creep-fatigue interaction by transmission electron microscopic structure investigations coupled with creep tests. Investigations by transmission electron microscopy (TEM) were carried out with regard to hardening by

  17. Influence of plasma nitro carburization on fatigue properties in a 4340 steel with different microstructure; Infuencia da nitrocarbonetacao a plasma nas propriedades de fadiga de um aco 4340 com diferentes microestruturas

    Energy Technology Data Exchange (ETDEWEB)

    Ranieri, A.; Hashimoto, T.M. [UNESP, Guaratingueta, SP (Brazil). Faculdade de Engenharia (FEG); Baggio-Scheid, V.H.; Abdalla, A.J., E-mail: abdalla@ieav.cta.b [Departamento de Ciencia e Tecnologia Aeroespacial (IEAv/DCTA), Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados

    2010-07-01

    Three different routes of heat treatments were applied in samples of 4340 steel in order to modify the microstructures and mechanical properties. After this initial treatment was applied a plasma nitrocarburizing thermochemical treatment in a part of the samples, forming a layer of nitride (Fe{sub 4}N and Fe{sub 3}N{sub 2}) of about 10{mu}m, with high hardness, in order to improve the surface characteristics. The layer and microstructure were characterized with X-ray analysis, optical microscopy, confocal laser scanning and hardness test by microindentation. Tensile and fatigue tests show the influence of microstructure formed on the mechanical properties, the microstructure predominantly bainitic phase showed a better combination of ductility, toughness and fatigue life. After treatment nitrocarburizing was observed the effect of tempering, with a reduction in hardness of substrate and tensile strength. In steel with martensitic microstructure the fatigue life decreases. (author)

  18. The Assessment and Validation of Mini-Compact Tension Test Specimen Geometry and Progress in Establishing Technique for Fracture Toughness Master Curves for Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, Mikhail A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nanstad, Randy K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-01

    Small specimens are playing the key role in evaluating properties of irradiated materials. The use of small specimens provides several advantages. Typically, only a small volume of material can be irradiated in a reactor at desirable conditions in terms of temperature, neutron flux, and neutron dose. A small volume of irradiated material may also allow for easier handling of specimens. Smaller specimens reduce the amount of radioactive material, minimizing personnel exposures and waste disposal. However, use of small specimens imposes a variety of challenges as well. These challenges are associated with proper accounting for size effects and transferability of small specimen data to the real structures of interest. Any fracture toughness specimen that can be made out of the broken halves of standard Charpy specimens may have exceptional utility for evaluation of reactor pressure vessels (RPVs) since it would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs. Assessment and validation of mini-CT specimen geometry has been performed on previously well characterized HSST Plate 13B, an A533B class 1 steel. It was shown that the fracture toughness transition temperature measured by these Mini-CT specimens is within the range of To values that were derived from various large fracture toughness specimens. Moreover, the scatter of the fracture toughness values measured by Mini-CT specimens perfectly follows the Weibull distribution function providing additional proof for validation of this geometry for the Master Curve evaluation of rector pressure vessel steels. Moreover, the International collaborative program has been developed to extend the assessment and validation efforts to irradiated weld metal. The program is underway and involves ORNL, CRIEPI, and EPRI.

  19. Laboratory Simulation of Rolling Contact Fatigue Cracks in Wind Turbine Bearings Using Hydrogen Infused 100Cr6 Bearing Steel

    DEFF Research Database (Denmark)

    Janakiraman, Shravan; West, Ole; Klit, Peder

    Premature fatigue failure is observed in rolling element bearings used in wind turbine components. It is believed that decomposed hydrogen from the lubricant diffuses into the surface of the bearing inner ring making it susceptible to failure. An attempt is made to simulate the formation of these......Premature fatigue failure is observed in rolling element bearings used in wind turbine components. It is believed that decomposed hydrogen from the lubricant diffuses into the surface of the bearing inner ring making it susceptible to failure. An attempt is made to simulate the formation...

  20. A FIB/TEM study of butterfly crack formation and white etching area (WEA) microstructural changes under rolling contact fatigue in 100Cr6 bearing steel

    Energy Technology Data Exchange (ETDEWEB)

    Evans, M.-H., E-mail: martin.evans@soton.ac.uk [National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ (United Kingdom); Walker, J.C.; Ma, C.; Wang, L.; Wood, R.J.K. [National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ (United Kingdom)

    2013-05-15

    Butterflies are microscopic damage features forming at subsurface material imperfections induced during rolling contact fatigue (RCF) in rolling element bearings. Butterflies can lead to degradation of the load bearing capacity of the material by their associated cracks causing premature spalling failures. Recently, butterfly formation has been cited to be related to a premature failure mode in wind turbine gearbox bearings; white structure flaking (WSF). Butterflies consist of cracks with surrounding microstructural change called ‘white etching area’ (WEA) forming wings that revolve around their initiators. The formation mechanisms of butterflies in bearing steels have been studied over the last 50 years, but are still not fully understood. This paper presents a detailed microstructural analysis of a butterfly that has initiated from a void in standard 100Cr6 bearing steel under rolling contact fatigue on a laboratory two-roller test rig under transient operating conditions. Analysis was conducted using focused ion beam (FIB) tomography, 3D reconstruction and transmission electron microscopy (STEM/TEM) methods. FIB tomography revealed an extensive presence of voids/cavities immediately adjacent to the main crack on the non-WEA side and at the crack tip. This provides evidence for a void/cavity coalescence mechanism for the butterfly cracks formation. Spherical M{sub 3}C carbide deformation and dissolution as part of the microstructural change in WEA were observed in both FIB and STEM/TEM analyses, where TEM analyses also revealed the formation of superfine nano-grains (3–15 nm diameter) intersecting a dissolving spherical M{sub 3}C carbide. This is evidence of the early formation of nano-grains associated with the WEA formation mechanism.

  1. Contributions of Cu-rich clusters, dislocation loops and nanovoids to the irradiation-induced hardening of Cu-bearing low-Ni reactor pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Bergner, F., E-mail: f.bergner@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); Gillemot, F. [Centre for Energy Research of the Hungarian Academy of Sciences, 29-33 Konkoly-Thege street, 1121 Budapest XII (Hungary); Hernández-Mayoral, M.; Serrano, M. [Division of Materials, CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Török, G. [Wigner Research Center for Physics of the Hungarian Academy of Sciences, 29-33 Konkoly-Thege street, 1121 Budapest XII (Hungary); Ulbricht, A.; Altstadt, E. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany)

    2015-06-15

    Highlights: • TEM and SANS were applied to estimate mean size and number density of loops, nanovoids and Cu-rich clusters. • A three-feature dispersed-barrier hardening model was applied to estimate the yield stress increase. • The values and errors of the dimensionless obstacle strength were estimated in a consistent way. • Nanovoids are stronger obstacles for dislocation glide than dislocation loops, loops are stronger than Cu-rich clusters. • For reactor-relevant conditions, Cu-rich clusters contribute most to hardening due to their high number density. - Abstract: Dislocation loops, nanovoids and Cu-rich clusters (CRPs) are known to represent obstacles for dislocation glide in neutron-irradiated reactor pressure vessel (RPV) steels, but a consistent experimental determination of the respective obstacle strengths is still missing. A set of Cu-bearing low-Ni RPV steels and model alloys was characterized by means of SANS and TEM in order to specify mean size and number density of loops, nanovoids and CRPs. The obstacle strengths of these families were estimated by solving an over-determined set of linear equations. We have found that nanovoids are stronger than loops and loops are stronger than CRPs. Nevertheless, CRPs contribute most to irradiation hardening because of their high number density. Nanovoids were only observed for neutron fluences beyond typical end-of-life conditions of RPVs. The estimates of the obstacle strength are critically compared with reported literature data.

  2. A Review of the Application of Rate Theory to Simulate Vacancy Cluster Formation and Interstitial Defect Formation in Reactor Pressure Vessel Steel

    Directory of Open Access Journals (Sweden)

    Fallon Laliberte

    2015-10-01

    Full Text Available The beltline region of the reactor pressure vessel (RPV is subject to an extreme radiation, temperature, and pressure environment over several decades of operation; therefore it is necessary to understand the mechanisms through which radiation damage occurs and how it affects the mechanical and chemical properties of the RPV steel. Chemical rate theory is a mean field rate theory simulation model which applies chemistry to the evaluation of irradiation-induced embrittlement. It presents one method of analysis that may be coupled to other distinct methods, in order to analyze defect formation, ultimately providing useful information on strength, ductility, toughness and dimensional stability changes for effects such as embrittlement, reduction in ductility and toughness, void swelling, hardening, irradiation creep, stress corrosion cracking, etc. over time as materials are subjected to reactor operational irradiation. This paper serves as a brief review of rate theory fundamentals and presents several examples of research that exemplify the application and importance of rate theory in examining the effects of radiation damage on RPV steel.

  3. Corrosion Fatigue Crack Propagation Rate Characteristics for Weldable Ship and Offshore Steels with Regard to the Influence of Loading Frequency and Saltwater Temperature

    Directory of Open Access Journals (Sweden)

    Jakubowski Marek

    2017-03-01

    Full Text Available After Vosikovsky (1975, the corrosion fatigue crack growth rate (CFCGR characteristics have been divided into three regions. The region-III rates are very close to mechanical fatigue crack growth rates. CFCGR formulae, including the long-crack length effect (in region I only, the loading frequency effect (in region II only, and the saltwater temperature effect, have been proposed. It has been assumed that CFCGR is proportional to f-k, where f is the loading frequency and k is a constant. The averaged k-value for all steels of yield stress (YS below 500 MPa, usually with ferrite-pearlite microstructures, is higher than that for YS > 500 MPa, usually with quenched and tempered microstructures. The temperature effect does not appear in region I below room temperature. In the remaining cases, that is, in region I for elevated temperatures and in region II for both low and elevated temperatures, the CFCGR increases with increasing temperature. Under a potential of -0.8 V, a long-crack-length effect, qualitatively similar to analogous effect for free corrosion conditions, appears.

  4. Effect of oxidation on the fatigue crack propagation behavior of Z3CN20.09M dyplex stainless steel in high temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huan Chun; Yang, Bin [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing (China); Chen, Yue Feng; Chen, Xu Dong [Collaborative Innovation Center of Steel Technology, Beijing (China)

    2017-06-15

    The fatigue crack propagation behaviors of Z3CN20.09M duplex stainless steel (DSS) were investigated by studying oxide films of specimens tested in 290°C water and air. The results indicate that a full oxide film that consisted of oxides and hydroxides was formed in 290°C water. By contrast, only a half-baked oxide film consisting of oxides was formed in 290°C air. Both environments are able to deteriorate the elastic modulus and hardness of the oxide films, especially the 290°C water. The fatigue lives of the specimens tested in 290°C air were about twice of those tested in 290°C water at all strain amplitudes. Moreover, the crack propagation rates of the specimen tested in 290°C water were confirmed to be faster than those tested in 290°C air, which was thought to be due to the deteriorative strength of the oxide films induced by the mutual promotion of oxidation and crack propagation at the crack tip. It is noteworthy that the crack propagation can be postponed by the ferrite phase in the DSS, especially when the specimens were tested in 290°C water.

  5. Finite element analysis to estimate burst pressure of mild steel pressure vessel using Ramberg–Osgood model

    OpenAIRE

    Deolia, Puneet; Firoz A. Shaikh

    2016-01-01

    Burst pressure is the pressure at which vessel burst/crack and internal fluid leaks. An accurate prediction of burst pressure is necessary in chemical, medical and aviation industry. Burst pressure is a design safety limit, which should not be exceeded. If this pressure is exceeded it may lead to the mechanical breach and permanent loss of pressure containment. So burst pressure calculation is necessary for all the critical applications. To numerically calculate burst pressure material curve ...

  6. A study on material degradation in SB 410 carbon steel plates for boilers and other pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Baek, U. B.; Park, J. S. [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Nam, K. W.; Kim, H. Y. [Korea Energy Management Corp., Yongin (Korea, Republic of)

    2005-07-01

    In spite of frequent defect in industrial boilers, life assessment or diagnostic method for them has not been studied. In this research, SB410 carbon steel used in industrial boilers is simulated with artificial aging heat treatment. To do qualitative life assessment, differences in micro-structures and hardness of SB410 by the degradation time are studied. In addition, variation in material properties by aging was observed with the tensile test at room temperature and 179 .deg. C and changes in ductile to brittle transition temperature was observed with the charpy impact test performed at several test temperature.

  7. Developing Fatigue Pre-crack Procedure to Evaluate Fracture Toughness of Pipeline Steels Using Spiral Notch Torsion Test

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL; Tan, Ting [ORNL; Jiang, Hao [ORNL; Zhang, Wei [ORNL; Feng, Zhili [ORNL

    2012-10-01

    The spiral notch torsion test (SNTT) has been utilized to investigate the crack growth behavior of X52 steel base and welded materials used for hydrogen infrastructures. The X52 steel materials are received from a welded pipe using friction stir welding techniques. Finite element models were established to study the crack growth behavior of steel SNTT steel samples, which were assumed to be isotropic material. A series SNTT models were set up to cover various crack penetration cases, of which the ratios between crack depth to diameter (a/D ratio) ranging from 0.10 to 0.45. The evolution of compliance and energy release rates in the SNTT method have been investigated with different cases, including different geometries and materials. Indices of characteristic compliance and energy release rates have been proposed. Good agreement has been achieved between predictions from different cases in the same trend. These work shed lights on a successful protocol for SNTT application in wide range of structural materials. The further effort needed for compliance function development is to extend the current developed compliance function to the deep crack penetration arena, in the range of 0.55 to 0.85 to effectively determine fracture toughness for extremely tough materials.

  8. 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)

  9. Integral Steel Casting of Full Spade Rudder Trunk Carrier Housing for Supersized Container Vessels through Casting Process Engineering (Sekjin E&T

    Directory of Open Access Journals (Sweden)

    Tae Won Kim

    2015-04-01

    Full Text Available In casting steel for offshore construction, integral casted structures are superior to welded structures in terms of preventing fatigue cracks in the stress raisers. In this study, mold design and casting analysis were conducted for integral carrier housing. Casting simulation was used for predicting molten metal flow and solidification during carrier housing casting, as well as the hot spots and porosity of the designed runner, risers, riser laggings, and the chiller. These predictions were used for deriving the final carrier housing casting plan, and a prototype was fabricated accordingly. A chemical composition analysis was conducted using a specimen sampled from a section of the prototype; the analytically obtained chemical composition agreed with the chemical composition of the existing carrier housing. Tensile and Charpy impact tests were conducted for determining the mechanical material properties. Carrier housing product after normalizing (920 °C/4.5 h, air-cooling has 371 MPa of yield strength, 582 MPa of tensile strength, 33.4% of elongation as well as 64 J (0 °C of impact energy.

  10. J-R Fracture Resistance of SA533 Gr.B-Cl.1 Steel for Reactor Pressure Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ji-Hyun; Hong, Seokmin; Lee, Bong-Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    A rolled plate might show different mechanical behaviors from a forging, even though they contain same chemical compositions. Furthermore, it is known that the fracture behavior of a rolled plate is very sensitive to material orientation comparing to a forging. In this study, the J-R fracture resistances of SA533 Gr.B-Cl.1 plate were measured at reactor operating temperature and the material orientation sensitivity was discussed. The decrease of fracture resistance of this kind of low alloy steel at an elevated temperature is known as the effect of dynamic strain aging (DSA). It was attributed to that the carbides and grains elongated to primary rolling direction, so that the aspect ratio of carbides and grains in the specimen with T-L orientation is larger. Generally, the hard second phase could take a roll of trigger point of unstable fracture. It is needed that the fracture surfaces of the tested specimens to be examined profoundly.

  11. Rolling Contact Fatigue and Wear Behavior of High-Performance Railway Wheel Steels Under Various Rolling-Sliding Contact Conditions

    Science.gov (United States)

    Faccoli, Michela; Petrogalli, Candida; Lancini, Matteo; Ghidini, Andrea; Mazzù, Angelo

    2017-07-01

    An experimental investigation was carried out to study and compare the response to cyclic loading of the high-performance railway wheel steels ER8 EN13262 and SUPERLOS®. Rolling contact tests were performed with the same contact pressure, rolling speed and sliding/rolling ratio, varying the lubrication regime to simulate different climatic conditions. The samples, machined out of wheel rims at two depths within the reprofiling layer, were coupled with UIC 900A rail steel samples. The wear rates, friction coefficients and hardness were correlated with the deformation beneath the contact surface. The crack morphology was studied, and the damage mechanisms were identified. The distribution of crack length and depth at the end of the dry tests was analyzed to quantify the damage. The main difference between the steels lies in the response of the external samples to dry contact: SUPERLOS® is subjected to a higher wear and lower friction coefficient than ER8, and this reduces the density of surface cracks that can propagate under wet contact conditions. The analysis of feedback data from in-service wheels confirmed the experimental results.

  12. Effect of high-temperature water and hydrogen on the fracture behavior of a low-alloy reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Roychowdhury, S., E-mail: sroy27@gmail.com [Paul Scherrer Institut, Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen, PSI (Switzerland); Materials Processing & Corrosion Engineering Division, Mod-Lab, D-Block, Bhabha Atomic Research Centre, Mumbai 400085 (India); Seifert, H.-P.; Spätig, P.; Que, Z. [Paul Scherrer Institut, Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen, PSI (Switzerland)

    2016-09-15

    Structural integrity of reactor pressure vessels (RPV) is critical for safety and lifetime. Possible degradation of fracture resistance of RPV steel due to exposure to coolant and hydrogen is a concern. In this study tensile and elastic-plastic fracture mechanics (EPFM) tests in air (hydrogen pre-charged) and EFPM tests in hydrogenated/oxygenated high-temperature water (HTW) was done, using a low-alloy RPV steel. 2–5 wppm hydrogen caused embrittlement in air tensile tests at room temperature (25 °C) and at 288 °C, effects being more significant at 25 °C and in simulated weld coarse grain heat affected zone material. Embrittlement at 288 °C is strain rate dependent and is due to localized plastic deformation. Hydrogen pre-charging/HTW exposure did not deteriorate the fracture resistance at 288 °C in base metal, for investigated loading rate range. Clear change in fracture morphology and deformation structures was observed, similar to that after air tests with hydrogen. - Highlights: • Hydrogen content, microstructure of LAS, and strain rate affects tensile properties at 288 °C. • Strength affects hydrogen embrittlement susceptibility to a greater extent than grain size. • Hydrogen in LAS leads to strain localization and restricts cross-slip at 288 °C. • Possible hydrogen pickup due to exposure to 288 °C water alters fracture surface appearance without affecting fracture toughness in bainitic base material. • Simulated weld heat affected zone microstructure shows unstable crack propagation in 288 °C water.

  13. Qualification of phased array ultrasonic examination on T-joint weld of austenitic stainless steel for ITER vacuum vessel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, G.H. [ITER Korea, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Park, C.K., E-mail: love879@hanmail.net [ITER Korea, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Jin, S.W.; Kim, H.S.; Hong, K.H.; Lee, Y.J.; Ahn, H.J.; Chung, W. [ITER Korea, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Jung, Y.H.; Roh, B.R. [Hyundai Heavy Industries Co. Ltd., Ulsan 682-792 (Korea, Republic of); Sa, J.W.; Choi, C.H. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France)

    2016-11-01

    Highlights: • PAUT techniques has been developed by Hyundai Heavy Industries Co., LTD (HHI) and Korea Domestic Agency (KODA) to verify and settle down instrument calibration, test procedures, image processing, and so on. As the first step of development for PAUT technique, Several dozens of qualification blocks with artificial defects, which are parallel side drilled hole, embedded lack of fusion, embedded repair weld notch, and so on, have been designed and fabricated to simulate all potential defects during welding process. Real UT qualification group-1 for T-joint weld was successfully conducted in front of ANB inspector. • In this paper, remarkable progresses of UT qualification are presented for ITER vacuum vessel. - Abstract: Full penetration welding and 100% volumetric examination are required for all welds of pressure retaining parts of the ITER Vacuum Vessel (VV) according to RCC-MR Code and French Order of Nuclear Pressure Equipment (ESPN). The NDE requirement is one of important technical issues because radiographic examination (RT) is not applicable to many welding joints. Therefore the ultrasonic examination (UT) has been selected as an alternative method. Generally the UT on the austenitic welds is regarded as a great challenge due to the high attenuation and dispersion of the ultrasonic signal. In this paper, Phased array ultrasonic examination (PAUT) has been introduced on double sided T-shape austenitic welds of the ITER VV as a major NDE method as well as RT. Several dozens of qualification blocks with artificial defects, which are parallel side drilled hole, embedded lack of fusion, embedded repair weld notch, embedded parallel vertical notch, and so on, have been designed and fabricated to simulate all potential defects during welding process. PAUT techniques on the thick austenitic welds have been developed taking into account the acceptance criteria. Test procedure including calibration of equipment is derived and qualified through

  14. Tensile and fatigue data for irradiated and unirradiated AISI 310 stainless steel and titanium - 5 percent aluminum - 2.5 percent tin: Application of the method of universal slopes

    Science.gov (United States)

    Debogdan, C. E.

    1973-01-01

    Irradiated and unirradiated tensile and fatigue specimens of AISI 310 stainless steel and Ti-5Al-2.5Sn were tested in the range of 100 to 10,000 cycles to failure to determine the applicability of the method of universal slopes to irradiated materials. Tensile data for both materials showed a decrease in ductility and increase in ultimate tensile strength due to irradiation. Irradiation caused a maximum change in fatigue life of only 15 to 20 percent for both materials. The method of universal slopes predicted all the fatigue data for the 310 SS (irradiated as well as unirradiated) within a life factor of 2. For the titanium alloy, 95 percent of the data was predicted within a life factor of 3.

  15. Fatigue-Crack Growth in D6AC Steel Heat-Treated to Different Values of Fracture Toughness,

    Science.gov (United States)

    1979-04-01

    with a cyclic Kmx of - 15 MPa.m * applied for 5 to 10 x 104 cycles. 2.4.2 Test Atmospere A constant environment was preserved by maintaining a flow of...Director 59 C.S. I. R.O. Materials Science Division. Director 60 Qantas , Library 61 Trans Australia Airlines. Library 62 Gas and Fuel Corporation of...204 Calspan Corporation, Professor H. Johnson 205 Rockwell International , Dr H. L. Marcus 206 U.S. Steel Applied Research Labs, J. M. Barsom 207 U.S

  16. Finite element analysis to estimate burst pressure of mild steel pressure vessel using Ramberg–Osgood model

    Directory of Open Access Journals (Sweden)

    Puneet Deolia

    2016-09-01

    Full Text Available Burst pressure is the pressure at which vessel burst/crack and internal fluid leaks. An accurate prediction of burst pressure is necessary in chemical, medical and aviation industry. Burst pressure is a design safety limit, which should not be exceeded. If this pressure is exceeded it may lead to the mechanical breach and permanent loss of pressure containment. So burst pressure calculation is necessary for all the critical applications. To numerically calculate burst pressure material curve is essential. There are various material models which are used to define material curve, amongst them Ramberg–Osgood is very popular. Ramberg–Osgood accurately capture material curve in strain hardening region. This approach is applicable for different material grades. In this paper a finite element method is used to predict burst pressure using Ramberg–Osgood equation. These results are then compared with results obtained from elasto-plastic curve and true stress strain curve. Results obtained by finite element analysis are validated with experimental data which is considered from open literature.

  17. Analysis of the master curve approach on the fracture toughness properties of SA508 Gr.4N Ni-Mo-Cr low alloy steels for reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung, E-mail: shirimp@kaist.ac.kr [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Kim, Min-Chul; Lee, Bong-Sang [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-06-15

    This study aims at assessing the fracture toughness behavior of tempered martensitic Ni-Mo-Cr low alloy steels for reactor pressure vessels in a transition temperature region using a master curve approach. The fracture toughness tests for model alloys with various chemical compositions were carried out following ASTM E1921-08. The microstructures, tensile properties, and Charpy impact toughness were also evaluated. Alloying elements such as Ni, Cr, and Mo affected the mechanical properties of alloys from changes in the phase fraction and precipitation behavior. In the fracture toughness test results, the data sets showed a deviation from the median curve and a smaller scatter than that of the prediction of the ASTM standard, especially in the lower transition region. The exponential parameter of the master curve equation was adjusted by an exponential fitting to data sets for expressing well the temperature dependency of the fracture toughness. The adjusted parameter provided good agreement for data distribution and the independence of T{sub 0} from test temperatures through an overall temperature range in contrast with the results from the standard master curve.

  18. Annealing for plant life management: hardness, tensile and Charpy toughness properties of irradiated, annealed and re-irradiated mock-up low alloy nuclear pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Tipping, Philip; Cripps, Robin (Paul Scherrer Inst. (PSI), Villigen (Switzerland))

    1994-01-01

    Hardness, tensile and Charpy properties of an irradiated (I) and irradiated-annealed-reirradiated (IAR) mock-up pressure vessel steel are presented. Spectrum tailored pressurized light water reactor (PWR) irradiation at 290[sup o]C by fast neutrons up to nominal fluences of 5 x 10[sup 19]/cm[sup 2] (E [>=] 1 MeV) in a swimming pool type reactor caused the hardness, tensile yield stress and tensile strength to increase. Embrittlement also occurred as indicated by Charpy toughness tests. The optimum annealing heat treatment for the main program was determined using isochronal and isothermal runs on the material and measuring the Vickers microhardness. The response to an intermediate annealing treatment (460[sup o]C for 18 h), when 50% of the target fluence has been reached and then irradiating to the required end fluence (IAR condition) was then monitored further by Charpy and tensile mechanical properties. Annealing was beneficial in mitigating overall hardening or embrittlement effects. The rate of re-embrittlement after annealing and re-irradiating was no faster than when no annealing had been performed. Annealing temperatures below 440[sup o]C were indicated as requiring relatively long times, i.e. [>=] 168 h to achieve some reduction in radiation induced hardness for example. (Author).

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

    Science.gov (United States)

    Peasura, Prachya

    2015-01-01

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

  20. Investigation of the deformation of in-vessel components of a nuclear fusion experiment using optical strain sensors

    Energy Technology Data Exchange (ETDEWEB)

    Vorpahl, Christian Georg

    2013-05-03

    A fibre-optic, EM-insensitive measurement for the deformation of in-vessel components has successfully been installed and operated at the nuclear fusion experiment ASDEX Upgrade. The sensors were tested for their neutron tolerance and vacuum compatibility. Installation was done by copper-steel laser beam welding. Measurements of in-service oscillations due to all three existing types of load cases show good agreement with theory and simulations. A fatigue lifetime assessment was performed.

  1. Steel plate reinforcement of orthotropic bridge decks

    NARCIS (Netherlands)

    Teixeira de Freitas, S.

    2012-01-01

    The PhD research is focused on the reinforcement of fatigue cracked orthotropic steel bridge decks (OBD) by adding a second steel plate to the existing deck. The main idea is to stiffen the existing deck plate, which will reduce the stresses at the fatigue sensitive details and extend the fatigue

  2. Development of Mini-Compact Tension Test Method for Determining Fracture Toughness Master Curves for Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, Mikhail A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-01

    Small specimens are playing the key role in evaluating properties of irradiated materials. The use of small specimens provides several advantages. Typically, only a small volume of material can be irradiated in a reactor at desirable conditions in terms of temperature, neutron flux, and neutron dose. A small volume of irradiated material may also allow for easier handling of specimens. Smaller specimens reduce the amount of radioactive material, minimizing personnel exposures and waste disposal. However, use of small specimens imposes a variety of challenges as well. These challenges are associated with proper accounting for size effects and transferability of small specimen data to the real structures of interest. Any fracture toughness specimen that can be made out of the broken halves of standard Charpy specimens may have exceptional utility for evaluation of reactor pressure vessels (RPVs) since it would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs. Validation of the mini compact tension specimen (mini-CT) geometry has been performed on previously well characterized Midland beltline Linde 80 (WF-70) weld in the unirradiated condition. It was shown that the fracture toughness transition temperature, To, measured by these Mini-CT specimens is almost the same as To value that was derived from various larger fracture toughness specimens. Moreover, an International collaborative program has been established to extend the assessment and validation efforts to irradiated Linde 80 weld metal. The program is underway and involves the Oak Ridge National Laboratory (ORNL), Central Research Institute for Electrical Power Industry (CRIEPI), and Electric Power Research Institute (EPRI). The irradiated Mini-CT specimens from broken halves of previously tested Charpy

  3. Investigation of fatigue assessments accuracy for beam weldments considering material data input and FE-mode type

    Science.gov (United States)

    Gorash, Yevgen; Comlekci, Tugrul; MacKenzie, Donald

    2017-05-01

    This study investigates the effects of fatigue material data and finite element types on accuracy of residual life assessments under high cycle fatigue. The bending of cross-beam connections is simulated in ANSYS Workbench for different combinations of structural member shapes made of a typical structural steel. The stress analysis of weldments with specific dimensions and loading applied is implemented using solid and shell elements. The stress results are transferred to the fatigue code nCode DesignLife for the residual life prediction. Considering the effects of mean stress using FKM approach, bending and thickness according to BS 7608:2014, fatigue life is predicted using the Volvo method and stress integration rules from ASME Boiler & Pressure Vessel Code. Three different pairs of S-N curves are considered in this work including generic seam weld curves and curves for the equivalent Japanese steel JIS G3106-SM490B. The S-N curve parameters for the steel are identified using the experimental data available from NIMS fatigue data sheets employing least square method and considering thickness and mean stress corrections. The numerical predictions are compared to the available experimental results indicating the most preferable fatigue data input, range of applicability and FE-model formulation to achieve the best accuracy.

  4. Optimal, Generic Planning of Maintenance and Inspection of Steel Bridges

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, Michael Havbro

    2002-01-01

    Fatigue damage is an important deterioration mechanism for steel bridges. This paper describes a simplified and generic approach for reliability and risk based inspection planning of fatigue sensitive structural details. Fatigue sensitive details are categorized according to their loading charact...

  5. Continuous steel production and apparatus

    Science.gov (United States)

    Peaslee, Kent D [Rolla, MO; Peter, Jorg J [McMinnville, OR; Robertson, David G. C. [Rolla, MO; Thomas, Brian G [Champaign, IL; Zhang, Lifeng [Trondheim, NO

    2009-11-17

    A process for continuous refining of steel via multiple distinct reaction vessels for melting, oxidation, reduction, and refining for delivery of steel continuously to, for example, a tundish of a continuous caster system, and associated apparatus.

  6. Thermal-Fatigue Analysis of W-coated Ferritic-Martensitic Steel Mockup for Fusion Reactor Components

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Won; Kim, Suk Kwon; Park, Seong Dae; Kim, Dong Jun [KAERI, Daejeon (Korea, Republic of); Moon, Se Yeon; Hong, Bong Guen [Chonbuk University, Jeonju (Korea, Republic of)

    2016-05-15

    In this study, commercial ANSYS-CFX for thermalhydraulic analysis and ANSYS-mechanical for the thermo-mechanical analysis are used to evaluate the thermal-lifetime of the mockup to determine the test conditions. Also, the Korea Heat Load Test facility with an Electron Beam (KoHLT-EB) will be used and its water cooling system is considered to perform the thermal-hydraulic analysis especially for considering the two-phase analysis with a higher heat flux conditions. Through the ITER blanket first wall (BFW) development project in Korea, the joining methods were developed with a beryllium (Be) layer as a plasma-facing material, a copper alloy (CuCrZr) layer as a heat sink, and type 316L austenitic stainless steel (SS316L) as a structural material. And joining methods were developed such as Be as an armor and FMS as a structural material, or W as an armor and FMS as a structural material were developed through the test blanket module (TBM) program. As a candidate of PFC for DEMO, a new W/FMS joining methods, W coating with plasma torch, have been developed. The HHF test conditions are found by performing a thermal-hydraulic and thermo-mechanical analysis with the conventional codes such as ANSYSCFX and .mechanical especially for considering the two-phase condition in cooling tube.

  7. Mechanical Behavior of Lithium-Ion Batteries and Fatigue Behavior of Ultrasonic Weld-Bonded Lap-Shear Specimens of Dissimilar Magnesium and Steel Sheets

    Science.gov (United States)

    Lai, Wei-Jen

    The mechanical behaviors of LiFePO4 battery cell and module specimens under in-plane constrained compression were investigated for simulations of battery cells, modules and packs under crush conditions. The experimental stress-strain curves were correlated to the deformation patterns of battery cell and module specimens. Analytical solutions were developed to estimate the buckling stresses and to provide a theoretical basis for future design of representative volume element cell and module specimens. A physical kinematics model for formation of kinks and shear bands in battery cells was developed to explain the deformation mechanism for layered battery cells under in-plane constrained compression. A small-scale module constrained punch indentation test was also conducted to benchmark the computational results. The computational results indicate that macro homogenized material models can be used to simulate battery modules under crush conditions. Fatigue behavior and failure modes of ultrasonic spot welds in lap-shear specimens of magnesium and steel sheets with and without adhesive were investigated. For ultrasonic spot welded lap-shear specimens, the failure mode changes from the partial nugget pullout mode under low-cycle loading conditions to the kinked crack failure mode under high-cycle loading conditions. For adhesive-bonded and weld-bonded lap-shear specimens, the test results show the near interface cohesive failure mode and the kinked crack failure mode under low-cycle and high-cycle loading conditions, respectively. Next, the analytical effective stress intensity factor solutions for main cracks in lap-shear specimens of three dissimilar sheets under plane strain conditions were developed and the solutions agreed well with the computational results. The analytical effective stress intensity factor solutions for kinked cracks were compared with the computational results at small kink lengths. The results indicate that the computational results approach to

  8. Crack propagation during fatigue in cast duplex stainless steels: influence of the microstructure, of the aging and of the test temperature; Propagation de fissure par fatigue dans les aciers austeno-ferritiques moules: influence de la microstructure, du vieillissement et de la temperature d'essai

    Energy Technology Data Exchange (ETDEWEB)

    Calonne, V

    2001-07-15

    Duplex stainless steels are used as cast components in nuclear power plants. At the service temperature of about 320 C, the ferrite phase is thermally aged and embrittled. This induces a significant decrease in fracture properties of these materials. The aim of this work consists in studying Fatigue Crack Growth Rates (FCGR) and Fatigue Crack Growth Mechanisms (FCGM) as a function of thermal ageing and test temperature (20 C/320 C). Two cast duplex stainless steels (30% ferrite) are tested. In order to better understand the influence of the crystallographic orientation of the phases on the FCGM, the solidification structure of the material is studied by Electron Back-Scatter Diffraction (EBSD) and by Unidirectional Solidification Quenching. Fatigue crack growth tests are also performed in equiaxed and basaltic structures. Microstructure, fatigue crack growth mechanical properties and mechanisms are thus studied in relation to each other. In the studied range of delta K, the crack propagates without any preferential path by successive ruptures of phase laths. The macroscopic crack propagation plane, as determined by EBSD, depends on the crystallographic orientation of the ferrite grain. So, according to the solidification structure, secondary cracks can appear, which in turn influences the FCGR. Fatigue crack closure, which has to be determined to estimate the intrinsic FCGR, decreases with increasing ageing. This can be explained by a decrease in the kinematic cyclic hardening. The Paris exponent as determined from intrinsic FCGR increases with ageing. Intrinsic FCGR can then be separated in two ranges: one with lower FCGR in aged materials than in un-aged and one with the reversed tendency. (author)

  9. 2014 New Trends in Fatigue and Fracture Conference

    CERN Document Server

    Milovic, Ljubica

    2017-01-01

    This book is a compilation of selected papers from the 2014 New Trends in Fatigue and Fracture (NT2F14) Conference, which was held in Belgrade, Serbia. This prestigious conference brought together delegates from around the globe to discuss how to characterize, predict and analyze the fatigue and fracture of engineering materials, components, and structures using theoretical, experimental, numerical and practical approaches. It highlights some important new trends in fracture mechanics presented at the conference, such as: • two-parameter fracture mechanics, arising from the coupling of fracture toughness and stress constraints • high-performance steel for gas and oil transportation and production (pressure vessels and boilers) • safety and reliability of welded joints This book includes 12 contributions from well-known international scientists and a special tribute dedicated to the scientific contributions of Stojan Sedmark, who passed away in 2014.

  10. Atom probe study of the microstructural evolution induced by irradiation in Fe-Cu ferritic alloys and pressure vessel steels; Etude a la sonde atomique de l`evolution microstructurale sous irradiation d`alliages ferritiques Fe-Cu et d`aciers de cuve REP

    Energy Technology Data Exchange (ETDEWEB)

    Pareige, P.

    1996-04-01

    Pressure vessel steels used in pressurized water reactors are low alloyed ferritic steels. They may be prone to hardening and embrittlement under neutron irradiation. The changes in mechanical properties are generally supposed to result from the formation of point defects, dislocation loops, voids and/or copper rich clusters. However, the real nature of the irradiation induced-damage in these steels has not been clearly identified yet. In order to improve our vision of this damage, we have characterized the microstructure of several steels and model alloys irradiated with electrons and neutrons. The study was performed with conventional and tomographic atom probes. The well known importance of the effects of copper upon pressure vessel steel embrittlement has led us to study Fe-Cu binary alloys. We have considered chemical aging as well as aging under electron and neutron irradiations. The resulting effects depend on whether electron or neutron irradiations ar used for thus. We carried out both kinds of irradiation concurrently so as to compare their effects. We have more particularly considered alloys with a low copper supersaturation representative of that met with the French vessel alloys (0.1% Cu). Then, we have examined steels used on French nuclear reactor pressure vessels. To characterize the microstructure of CHOOZ A steel and its evolution when exposed to neutrons, we have studied samples from the reactor surveillance program. The results achieved, especially the characterization of neutron-induced defects have been compared with those for another steel from the surveillance program of Dampierre 2. All the experiment results obtained on model and industrial steels have allowed us to consider an explanation of the way how the defects appear and grow, and to propose reasons for their influence upon steel embrittlement. (author). 3 appends.

  11. Estimate of radiation-induced steel embrittlement in the BWR core shroud and vessel wall from reactor-grade MOX/UOX fuel for the nuclear power plant at Laguna Verde, Veracruz, Mexico

    Science.gov (United States)

    Vickers, Lisa Rene

    The government of Mexico has expressed interest to utilize the Laguna Verde boiling water reactor (BWR) nuclear power plant for the disposition of reprocessed spent uranium oxide (UOX) fuel in the form of reactor-grade mixed-oxide (MOX) fuel. MOX fuel would replace spent UOX fuel as a fraction in the core from 18--30% depending on the fuel loading cycle. MOX fuel is expected to increase the neutron fluence, flux, fuel centerline temperature, reactor core pressure, and yield higher energy neutrons. There is concern that a core with a fraction of MOX fuel (i.e., increased 239Pu wt%) would increase the radiation-induced steel embrittlement within the core shroud and vessel wall as compared to only conventional, enriched UOX fuel in the core. The evaluation of radiation-induced steel embrittlement within the core shroud and vessel wall is a concern because of the potentially adverse affect to plant and public safety, environment, and operating life of the reactor. This dissertation provides computational results of the neutron fluence, flux, energy spectrum, and radiation damage displacements per atom per second (dpa-s-1) in steel within the core shroud and vessel wall of the Laguna Verde Unit 1 BWR. The results were computed using the nuclear data processing code NJOY99 and the continuous energy Monte Carlo Neutral Particle transport code MCNP4B. The MCNP4B model of the reactor core was for maximum core loading fractions of ⅓ MOX and ⅔ UOX reactor-grade fuel in an equilibrium core. The primary conclusion of this dissertation was that the addition of the maximum fraction of ⅓ MOX fuel to the LV1 BWR core did significantly accelerate the radiation-induced steel embrittlement such that without mitigation of steel embrittlement by periodic thermal annealing or reduction in operating parameters such as, neutron fluence, core temperature and pressure, it posed a potentially adverse affect to the plant and public safety, environment, and operating life of the reactor.

  12. Creep strength of N9 and N10 material (steel)

    Energy Technology Data Exchange (ETDEWEB)

    1943-02-17

    This letter was a response to the receipt of tables of information from the materials-testing laboratory at Ludwigshafen. The tables dealt with various properties of N9 and N10 steels for production of high-pressure hydrogenation vessels. The letter expressed questions about some of the information, especially about the methods of tempering the test steels and about certain figures for contraction of N9. The letter gave Leuna's values for creep strength (long-time rupture strength) after 20,000 hours of operation as 11 to 15 kg/mm/sup 2/ for N9 versus 26 to 30 kg/mm/sup 2/ for N10, and said that similar relationships existed in values for continuous creep strength (fatigue strength for an infinite time) between the steels. It had generally been Leuna's experience in high-temperature ruptures of pipes, though, that long before brittleness and contraction had set in very much, the physical action of hydrogen on the steel had led to ruptures. Because of this hydrogen activity, it was the aim of current work to increase the stability of N10 against hydrogen. One reason for the effort was to avoid being forced to rely on austenitic steels alone for the future development of the best steels for pressure vessels, since the resulting large demands on chromium and manganese might not always be able to be supplied. It was known that stability against hydrogen could be increased by addition of titanium to the steel, but it was not known to what extent creep strength in a hydrogen atmosphere could be improved thereby. Addition of titanium could also allow a corresponding reduction in the usage of vanadium or tungsten. Further discussions with steel suppliers were recommended.

  13. Vessel Operating Units (Vessels)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains data for vessels that are greater than five net tons and have a current US Coast Guard documentation number. Beginning in1979, the NMFS...

  14. Present Situation of the Anti-Fatigue Processing of High-Strength Steel Internal Thread Based on Cold Extrusion Technology: A Review

    Science.gov (United States)

    Miao, Hong; Jiang, Cheng; Liu, Sixing; Zhang, Shanwen; Zhang, Yanjun

    2017-03-01

    The adoption of cold-extrusion forming for internal thread net forming becomes an important component of anti-fatigue processing with the development of internal thread processing towards high performance, low cost and low energy consumption. It has vast application foreground in the field of aviation, spaceflight, high speed train and etc. The internal thread processing and anti-fatigue manufacture technology are summarized. In terms of the perspective of processing quality and fatigue serving life, the advantages and disadvantages of the processing methods from are compared. The internal thread cold-extrusion processing technology is investigated for the purpose of improving the anti-fatigue serving life of internal thread. The superiorities of the plastic deformation law and surface integrity of the metal layer in the course of cold extrusion for improving its stability and economy are summed up. The proposed research forecasts the development tendency of the internal thread anti-fatigue manufacturing technology.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

  16. Fatigue life of AISI 316L stainless steel welded joints, obtained by GMAW; Vida a la fatiga de juntas soldadas del acero inoxidable AISI 316L obtenidas mediante el proceso GMAW

    Energy Technology Data Exchange (ETDEWEB)

    Puchi-Cabrera, E. S.; Saya-Gamboa, R. A.; Barbera-Sosa, J. G. la; Staia, M. H.; Ignoto-Cardinale, V.; Berrios-Ortiz, J. A.; Mesmacque, G.

    2007-07-01

    An investigation has been conducted in order to determine the effect of both the metallic transfer mode (pulsed arc or short circuit) and the O{sub 2} content in the Ar/O{sub 2} gas mixture, of the gas-metal arc welding process (GMAW), on the fatigue life under uniaxial conditions of welded joints of 316L stainless. it has been concluded that the mixture of the protective gases employed in the process could have an important influence on the fatigue life of the welded joints of such steel in two different ways. firstly, through the modification of the radius of curvature at the joint between the welding tow and the base metal and, secondly, through a more pronounced degree of oxidation of the alloying elements induced by a higher O{sub 2} content in the mixture. As far as the metallic transfer mode is concerned, it has been determined that the welded joints obtained under a pulsed arc mode show a greater fatigue life in comparison with the joints obtained under short circuit for both gas mixtures. (Author) 25 refs.

  17. Comparison on Mechanical Properties of SA508 Gr.3 Cl.1, Cl.2, and Gr.4N Low Alloy Steels for Pressure Vessels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Chul; Park, Sang-Gyu; Lee, Bong-Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Ki-Hyoung [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2014-10-15

    In this study, microstructure and mechanical properties of SA508 Gr.3 Cl. 1, Cl.2, and Gr.4N low alloy steels are characterized to compare their properties. To evaluate the fracture toughness in the transition region, the master curve method according to ASTM E1921 was adopted in the cleavage transition region. Tensile tests and Charpy impact tests were also performed to evaluate the mechanical properties, and a microstructural investigation was carried out. The microstructure and mechanical properties of SA508 Gr.3 Cl.1, Cl2 and Gr.4N low alloy steels were characterized.. The predominant microstructure of SA508 Gr.4N model alloy is tempered martensite, while SA508 Gr.3 Cl.1 and Cl.2 steels show a typical tempered upper bainitic structure. SA508 Gr. 4N model alloy shows the best strength and transition behavior among the three SA508 steels. SA508 Gr.3 Cl.2 steel also has quite good strength, but there is a loss of toughness.

  18. Fatigue Crack Growth Characteristics of Cold Stretched STS 304 Welded Joint

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Won; Na, Seong Hyeon; Yoon, Dong Hyun; Kim, Jae Hoon [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Kim, Young Kyun; Kim, Ki Dong [Korea Gas Coporation R& D Division, Daejeon (Korea, Republic of)

    2017-09-15

    STS 304 steel is used as pressure vessel material, and although it exhibits excellent mechanical characteristics at a low temperature, it is heavier than other materials. To address this issue, a method using cold-stretching techniques for STS 304 can be applied. In this study, a cold-stretching part and welded joint specimen were directly obtained from a cold-stretching pressure vessel manufactured according to ASME code. Fatigue crack propagation tests were carried out at room temperature and -170℃ using the compliance method for stress ratios of 0.1 and 0.5. The results indicate that crack growth rate of the welded joint is higher than that of the cold-stretching part within the same stress intensity factor range. The outcome of this work is expected to serve as a basis for the development of a cold-stretched STS 304 pressure vessel.

  19. Structural integrity of nuclear reactor pressure vessels

    Science.gov (United States)

    Knott, John F.

    2013-09-01

    The paper starts from concerns expressed by Sir Alan Cottrell, in the early 1970s, related to the safety of the pressurized water reactor (PWR) proposed at that time for the next phase of electrical power generation. It proceeds to describe the design and operation of nuclear generation plant and gives details of the manufacture of PWR reactor pressure vessels (RPVs). Attention is paid to stress-relief cracking and under-clad cracking, experienced with early RPVs, explaining the mechanisms for these forms of cracking and the means taken to avoid them. Particular note is made of the contribution of non-destructive inspection to structural integrity. Factors affecting brittle fracture in RPV steels are described: in particular, effects of neutron irradiation. The use of fracture mechanics to assess defect tolerance is explained, together with the failure assessment diagram embodied in the R6 procedure. There is discussion of the Master Curve and how it incorporates effects of irradiation on fracture toughness. Dangers associated with extrapolation of data to low probabilities are illustrated. The treatment of fatigue-crack growth is described, in the context of transients that may be experienced in the operation of PWR plant. Detailed attention is paid to the thermal shock associated with a large loss-of-coolant accident. The final section reviews the arguments advanced to justify 'Incredibility of Failure' and how these are incorporated in assessments of the integrity of existing plant and proposed 'new build' PWR pressure vessels.

  20. Generic Inspection Planning for Steel Structures

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, Michael H.

    2002-01-01

    This paper presents a simplified and practically applicable approach for risk based inspection planning of fatigue sensitive structural details in steel structures. The basic idea is that the fatigue sensitive details are categorized according to their Fatigue Design Factor (FDF) and SN curve. When...