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Sample records for low-cycle-fatigue lcf testing

  1. Synthesis of low cycle fatigue test results

    International Nuclear Information System (INIS)

    Andrews, R.M.

    1990-01-01

    Axial strain controlled cycle fatigue tests were carried out on type 316 stainless steel parent metal, vacuum and non-vacuum electron beams welds, submerged arc welds and gas shielded metal arc welds. Testing covered total strains in the range 0.6% to 2%, and was at room temperature and 550 0 C. Parent metal and the electron beam welds showed rapid cyclic hardening, while arc welds showed little hardening. The weld metal cyclic stress-strain response was above that obtained for the parent metal, although below data obtained by other workers for similar parent materials. Weld metal endurances were above the ASME N47 continuous cycling design line at both temperatures, and comparable with parent metal data. However, the weld metal data approached the design line at low strain ranges (around 0.5%). Endurances were predicted from crack growth rates estimated from striation spacings, giving acceptable results except for the gas shielded metal arc weldments. (author)

  2. Challenges in high temperature low cycle fatigue testing of metallic materials

    International Nuclear Information System (INIS)

    Sandhya, R.; Valsan, M.; Bhanu Sankara Rao, K.

    2007-01-01

    The evaluation of the high strain Low Cycle Fatigue properties of structural materials is an involved and complicated procedure requiring skill and diligence from the experimentalist. This presentation describes the various testing methods to evaluate the LCF properties of structural materials, the complexities involved and some solutions to exacting requirements, not covered by the testing procedure standards. The basic components of servo-hydraulic fatigue testing machines is described, as are the calibration and maintenance procedures. Results of LCF tests conducted at the authors' laboratory on AISI 316L(N) stainless steel and Mod.9Cr-1Mo ferritic steel are described. The complications in total strain controlled testing of weld joints is brought out and soft zone development in Mod. 9Cr-1Mo ferritic steel is described. The special requirements for testing in environmental chambers is a challenging task. In-house chambers, designed to carry out testing in dynamic sodium environment is highlighted. These chambers have provision to accommodate extensometers for strain measurements, and also house all the safety instrumentation needed to carry out to mechanical testing in dynamic sodium environment. The variation of LCF results as a function of specimen geometry is examined. The various failure criteria adopted by laboratories in different countries are also touched upon. (author)

  3. Results from low cycle fatigue testing of 316L plate and weld material

    International Nuclear Information System (INIS)

    Kaellstroem, R.; Josefsson, B.; Haag, Y.

    1993-01-01

    Specimens for low cycle fatigue testing from the second heat of the CEC reference 316L plate and from Tungsten Inert Gas (TIG) weld material have been neutron irradiated near room temperature to a displacement dose of approximately 0.3 dpa. The low cycle fatigue testing of both irradiated and unirradiated specimens was performed at 75, 250 and 450 degrees C, and with strain ranges of 0.75, 1.0 and 1.5%. There is no clear effect of the irradiation on low cycle fatigue properties. For the weld material the endurance is shorter than for plate, and the dependences on temperature and strain range are not clear

  4. Low cycle fatigue testing in flowing sodium at elevated temperatures

    International Nuclear Information System (INIS)

    Flagella, P.N.; Kahrs, J.R.

    1976-01-01

    The paper describes equipment developed to obtain low cycle strain-controlled fatigue data in flowing sodium at elevated temperatures. Operation and interaction of the major components of the system are discussed, including the calibration technique using remote strain measurement and control. Confirmation of in-air results using the special technique is demonstrated, with data presented for Type 316 stainless steel tested in high purity flowing sodium at 593 0 C. The fatigue life of the material in sodium is essentially the same as that obtained in air for delta epsilon/sub t/= 1 percent. On the other hand, sodium pre-exposure at 650 0 C for 5000 hours increased the fatigue life in-sodium by a factor of two, and sodium pre-exposure at 718 0 C for 5000 hours increased the fatigue life in-sodium by a factor of three

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-15

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

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

    Directory of Open Access Journals (Sweden)

    M. Maj

    2013-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Maj M.

    2013-03-01

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

  8. Identification of low cycle fatigue parameters

    Directory of Open Access Journals (Sweden)

    Balda M.

    2009-12-01

    Full Text Available The article describes a new approach to the processing of experimental data coming from low-cycle fatigue (LCF tests. The data may be either tables from the standard tests, or a time series of loading processes and corresponding numbers of cycles to damage. A new method and a program for the evaluation of material parameters governing the material behavior under a low cycle loading have been developed. They exploit a minimization procedure for an appropriate criterion function based on differences of measured and evaluated damages.

  9. Prediction of residual life of low-cycle fatigue in austenitic stainless steel based on indentation test

    International Nuclear Information System (INIS)

    Yonezu, Akio; Touda, Yuya; Kim, HakGui; Yoneda, Keishi; Sakihara, Masayuki; Minoshima; Kohji

    2011-01-01

    In this study, a method to predict residual life of low-cycle fatigue in austenitic stainless steel (SUS316NG) was proposed based on indentation test. Low-cycle fatigue tests for SUS316NG were first conducted based on uniaxial tensile-compressive loading under the control of true strain range. Applied strain ranges were varied from about 3 to 12%. Their hysteresis loops of stress and strain were monitored during the fatigue tests. Plastic deformation range in hysteresis loop at each cycle could be roughly expressed by bi-linear hardening rule, whose plastic properties involve yield stress and work-hardening coefficient. The cyclic plastic properties were found to be dependent on the number of cycles and applied strain range, due to work-hardening. We experimentally investigated the empirical relationship between the plastic properties and number of cycles for each applied strain range. It is found that the relationship quantitatively predicts the applied strain range and number of cycles, when the plastic properties, or yield stress and work-hardening coefficient were known. Indentation tests were applied to the samples subjected to low cycle fatigue test, in order to quantitatively determine the plastic properties. The estimated properties were assigned to the proposed relationship, yielding the applied strain range and the cycle numbers. The proposed method was applied to the several stainless steel samples subjected to low cycle fatigue tests, suggesting that their residual lives could be reasonably predicted. Our method is thus useful for predicting the residual life of low-cycle fatigue in austenitic stainless steel. (author)

  10. Simulation and analysis of data for enhancing low cycle fatigue test procedures

    Energy Technology Data Exchange (ETDEWEB)

    Sarajaervi, U.; Cronvall, O. [VTT Technical Research Centre of Finland (Finland)

    2006-04-15

    The simulation and analysis of data for enhancing low cycle fatigue test procedures is discussed in this report. The analysed materials are an austenitic stainless piping steel and an austenitic weld material. This project continues the work performed in 2003 and 2004. The fatigue test data treatment application developed within the project in 2004 for the preparation of the fatigue data has been developed further. Also, more fatigue test data has been analysed with the application than in 2004. In addition to this numerical fatigue simulations were performed with FEM code ABAQUS. With the fatigue test data treatment application one can e.g. both calculate cyclically certain relevant characteristic values, e.g. elastic range, and form a set of certain cyclical parameter values needed as a part of ABAQUS analysis input files. The hardening properties of metals were modelled with both isotropic and kinematic hardening models. The further development of the application included trimming of the analysed data, and consequently trimming of resulting hardening parameters. The need for the trimming arose from the fact that the analysed fatigue test data presents some scatter caused by the limited accuracy of the test equipment and the sampling rate. The hardening parameters obtained from the application analysis results were used in the subsequent ABAQUS analyses, and then the fatigue test data were compared with the ABAQUS simulation results. After finding a procedure to trim result data to get smooth curves for cyclic hardening, hardening and softening could be reproduced in ABAQUS analysis with a reasonable accuracy. The modelling of the fatigue induced initiation and growth of cracks was not considered in this study. On the other hand, a considerable part of the fatigue life of nuclear power plant (NPP) piping components is spent in the phase preceding the initiation and growth of cracks. (au)

  11. Simulation and analysis of data for enhancing low cycle fatigue test procedures

    International Nuclear Information System (INIS)

    Sarajaervi, U.; Cronvall, O.

    2006-04-01

    The simulation and analysis of data for enhancing low cycle fatigue test procedures is discussed in this report. The analysed materials are an austenitic stainless piping steel and an austenitic weld material. This project continues the work performed in 2003 and 2004. The fatigue test data treatment application developed within the project in 2004 for the preparation of the fatigue data has been developed further. Also, more fatigue test data has been analysed with the application than in 2004. In addition to this numerical fatigue simulations were performed with FEM code ABAQUS. With the fatigue test data treatment application one can e.g. both calculate cyclically certain relevant characteristic values, e.g. elastic range, and form a set of certain cyclical parameter values needed as a part of ABAQUS analysis input files. The hardening properties of metals were modelled with both isotropic and kinematic hardening models. The further development of the application included trimming of the analysed data, and consequently trimming of resulting hardening parameters. The need for the trimming arose from the fact that the analysed fatigue test data presents some scatter caused by the limited accuracy of the test equipment and the sampling rate. The hardening parameters obtained from the application analysis results were used in the subsequent ABAQUS analyses, and then the fatigue test data were compared with the ABAQUS simulation results. After finding a procedure to trim result data to get smooth curves for cyclic hardening, hardening and softening could be reproduced in ABAQUS analysis with a reasonable accuracy. The modelling of the fatigue induced initiation and growth of cracks was not considered in this study. On the other hand, a considerable part of the fatigue life of nuclear power plant (NPP) piping components is spent in the phase preceding the initiation and growth of cracks. (au)

  12. Low cycle fatigue characteristics of duplex stainless steel with degradation under pure torsional load

    International Nuclear Information System (INIS)

    Kwon, Jae Do; Park, Joong Cheul

    2002-01-01

    Monotonic torsional and pure torsional low cycle fatigue (LCF) test with artificial degradation were performed on duplex stainless steel (CF8M). CF8M is used in pipes and valves in nuclear reactor coolant system. It was aged at 430 degree C for 3600hrs. Through the monotonic and LCF test, it is found that mechanical properties (i.e., yield strength, strain hardening exponent, strength coefficient etc.) increase and fatigue life (N f ) decreases with degradation of material. The relationship between shear strain amplitude (γ α ) and N f was proposed

  13. Low Cycle Fatigue of Composite Materials in Army Structural Applications: A Review of Literature and Recommendations for Research

    National Research Council Canada - National Science Library

    Harik, Vasyl Michael

    2000-01-01

    Low cycle fatigue (LCF) of laminate composite structures used in Army applications is assessed to identify the key physical phenomena occurring during LCF processes and to determine their main characteristics...

  14. Low Cycle Fatigue of Single Crystal Nickel-based Superalloy DD6 at 1100℃

    Directory of Open Access Journals (Sweden)

    ZHANG Shichao

    2018-02-01

    Full Text Available The total strain-controlled low cycle fatigue(LCF behaviors of a single crystal superalloy DD6 at 1100℃ for R=-1 and 0.05 were investigated. The results of LCF tests indicated that the cyclic hardening/softening behavior of the alloy not only has the relationship with the microstructure of the material, but also the loading status. The mean stress relaxation occurred under asymmetric straining. The rate of mean stress relaxation increased with the increasing of strain amplitude; when R=-1, the alloy shows tension-compression asymmetry behavior. All the LCF data obtain under various ratios were well correlated by three models for lifetime prediction, the precision rates predicted are fallen into the factor of±2 times scatter band.

  15. 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.

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

    International Nuclear Information System (INIS)

    Sakai, Michiya; Saito, Kiyoshi; Matsuura, Shinichi

    1998-01-01

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

  17. Dynamic strain ageing in Inconel® Alloy 783 under tension and low cycle fatigue

    International Nuclear Information System (INIS)

    Nagesha, A.; Goyal, Sunil; Nandagopal, M.; Parameswaran, P.; Sandhya, R.; Mathew, M.D.; Mannan, Sarwan K.

    2012-01-01

    Highlights: ► Low cycle fatigue (LCF) and tensile tests were performed on Inconel ® Alloy 783. ► A stable cyclic stress response followed by continuous softening was noted under LCF. ► Material exhibited DSA in the temperature range, 573–723 K. ► Occurrence of DSA reduced the extent of cycling softening in LCF. ► Both interstitial and substitutional atoms were found to be responsible for DSA. - Abstract: Low cycle fatigue (LCF) tests were performed on Inconel ® Alloy 783 at a strain rate of 3 × 10 −3 s −1 and a strain amplitude of ±0.6%, employing various temperatures in the range 300–923 K. A continuous reduction in the LCF life was observed with increase in the test temperature. The material generally showed a stable stress response followed by a region of continuous softening up to failure. However, in the temperature range of 573–723 K, the alloy was seen to exhibit dynamic strain ageing (DSA) which was observed to reduce the extent of cyclic softening. With a view to identifying the operative mechanisms responsible for DSA, tensile tests were conducted at temperatures in the range, 473–798 K with strain rates varying from 3 × 10 −5 s −1 to 3 × 10 −3 s −1 . Interaction of dislocations with interstitial (C) and substitutional (Cr) atoms respectively, in the lower and higher temperature regimes was found to be responsible for DSA. Further, the friction stress, as determined using the stabilised stress–strain hysteresis loops, was seen to show a more prominent peak in the DSA range, compared to the maximum tensile stress.

  18. Low cycle fatigue behavior of hot-bent 347 stainless steel in a simulated PWR water environment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Ho; Seo, Myung Gyu; Jang, Chang Heui [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Hong, Jong Tae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Tae Soon [Central Research InstituteKorea Hydro and Nuclear Power Co., Ltd., Daejeon (Korea, Republic of)

    2016-11-15

    The effect of hot bending on the Low cycle fatigue (LCF) behavior of 347 SS was evaluated in Room temperature (RT) air and simulated Pressurized water reactor (PWR) water environments. The LCF life of 347 SS in PWR water was shorter than that in RT air for the as-received and hot-bent conditions. The LCF life of hot-bent 347 SS was relatively longer than that of the as-received condition in both RT air and PWR water. Microstructure analysis indicated development of dislocation structure near niobium carbide particles and increase in dislocation density for the hot-bent 347 SS. Such microstructure acted as barriers to dislocation movement during the LCF test, resulting in minimal hardening for the hot-bent 347 SS in RT air.

  19. Thermoelastoviscoplastic modeling of RAFM steel JLF-1 using tensile and low cycle fatigue experiments

    Energy Technology Data Exchange (ETDEWEB)

    Msolli, S., E-mail: sabeur.msolli@univ-lorraine.fr

    2014-08-01

    In this paper, a modeling of the elastoviscoplastic behavior of a Reduced Activation Ferritic Martensitic (RAFM) steel JLF-1 is presented. The modeling of this material was based on various Low Cycle Fatigue (LCF) and tensile tests performed in air and vacuum using different imposed strain rates and temperature ranges going from ambient temperature to 873 K. The coupled viscoplastic model is coded in FORTRAN program, implemented into the finite elements code ABAQUS and used to predict the thermomechanical behavior of a fatigue specimen made of RAFM steel JLF-1. Good agreements were found between numerical results and experimental data.

  20. Low cycle fatigue properties of CLAM steel at 823 K

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xue [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049 (China); Huang, Lixin [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Yan, Wei; Wang, Wei [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Sha, Wei [School of Planning, Architecture and Civil Engineering, Queen' s University Belfast, Belfast BT9 5AG (United Kingdom); Shan, Yiyin, E-mail: yyshan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2014-09-08

    China Low Activation Martensitic (CLAM) steel is considered to be the main candidate material for the first wall components of future fusion reactors in China. In this paper, the low cycle fatigue (LCF) behavior of CLAM steel is studied under fully reversed tension–compression loading at 823 K in air. Total strain amplitude was controlled from 0.14% to 1.8% with a constant strain rate of 2.4×10{sup −3} s{sup −1}. The corresponding plastic strain amplitude ranged from 0.023% to 1.613%. The CLAM steel displayed continuous softening to failure at 823 K. The relationship between strain, stress and fatigue life was obtained using the parameters obtained from fatigue tests. The LCF properties of CLAM steel at 823 K followed Coffin–Manson relationship. Furthermore, irregular serration was observed on the stress–strain hysteresis loops of CLAM steel tested with the total strain amplitude of 0.45–1.8%, which was attributed to the dynamic strain aging (DSA) effect. During continuous cyclic deformation, the microstructure and precipitate distribution of CLAM steel changed gradually. Many tempered martensitic laths were decomposed into subgrains, and the size and number of M{sub 23}C{sub 6} carbide and MX carbonitride precipitates decreased with the increase of total strain amplitude. The response cyclic stress promoted the recovery of martensitic lath, while the thermal activation mainly played an important role on the growth of precipitates in CLAM steel at 823 K. In order to have a better understanding of high-temperature LCF behavior, the potential mechanisms controlling stress–strain response, DSA phenomenon and microstructure changes have also been evaluated.

  1. Low cycle fatigue behavior of titanium carbide coated molybdenum

    International Nuclear Information System (INIS)

    Nishi, Hiroshi; Oku, Tatsuo; Kodaira, Tsuneo; Kikuyama, Toshihiko

    1985-09-01

    Sintered molybdenum coated by TiC is used for the first wall such as a troidal fixed limiter and a magnetic limiter plate in JT-60, that is being operated at JAERI presently. This report describes the low cycle fatigue behavior of sintered molybdenum and the influence of TiC coating on fatigue strength. The low cycle fatigue test was conducted at room temperature and 500 0 C. The test results was also analyzed by fractographic observation, metallography and element analysis using EPMA. The low cycle fatigue strength of the molybdenum coated by TiC at 500 0 C is decreased compared with the one at room temperature. (author)

  2. Low cycle fatigue behavior of a ferritic reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Apu, E-mail: asarkar@barc.gov.in; Kumawat, Bhupendra K.; Chakravartty, J.K.

    2015-07-15

    The cyclic stress–strain response and the low cycle fatigue (LCF) behavior of 20MnMoNi55 pressure vessel steel were studied. Tensile strength and LCF properties were examined at room temperature (RT) using specimens cut from rolling direction of a rolled block. The fully reversed strain-controlled LCF tests were conducted at a constant total strain rate with different axial strain amplitude levels. The cyclic strain–stress relationships and the strain–life relationships were obtained through the test results, and related LCF parameters of the steel were calculated. The studied steel exhibits cyclic softening behavior. Furthermore, analysis of stabilized hysteresis loops showed that the steel exhibits non-Masing behavior. Complementary scanning electron microscopy examinations were also carried out on fracture surfaces to reveal dominant damage mechanisms during crack initiation, propagation and fracture. Multiple crack initiation sites were observed on the fracture surface. The investigated LCF behavior can provide reference for pressure vessel life assessment and fracture mechanisms analysis.

  3. The Effects of Hot Bending on the Low Cycle Fatigue Behaviors of 347 SS in PWR Primary Environment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ho-Sub; Hong, Jong-Dae; Lee, Junho; Jang, Changheui [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-10-15

    Fatigue damage could be significant for some locations, especially the welds and bends where stress concentration is typically high. As a possible solution, a large radius hot-bending method has been suggested to eliminate some weld joints and all tight bends. However, for the hot-bending process which involves a high temperature thermal cycle, there is a concern about changes in mechanical properties including low cycle fatigue behaviors. In APR1400, Type 347 SS have been used as surge line pipes. Therefore, to verify the applicability of hot-bending on 347 SS surge line pipes, an environmental fatigue test program was initiated. In this paper, the preliminary results of the on-going test program are introduced. Also, the low cycle fatigue behaviors of 347 SS are compared with those of other grade of stainless steels. The effects of hot bending on the low cycle fatigue behavior of 347 SS were quantitatively evaluated. The fatigue life was compared with the estimated values per NUREG 6909 rev. 1. There are no distinct differences between NUREG 6909 and LCF tests. According to fractography and cross section analysis in progress, basically, the reduction of LCF life of 347 SS in PWR water was caused by operation of HIC mechanism. The cyclic stress responses shows that there is no secondary hardening in 330 .deg.C air and PWR water.

  4. A Combined High and Low Cycle Fatigue Model for Life Prediction of Turbine Blades

    Directory of Open Access Journals (Sweden)

    Shun-Peng Zhu

    2017-06-01

    Full Text Available Combined high and low cycle fatigue (CCF generally induces the failure of aircraft gas turbine attachments. Based on the aero-engine load spectrum, accurate assessment of fatigue damage due to the interaction of high cycle fatigue (HCF resulting from high frequency vibrations and low cycle fatigue (LCF from ground-air-ground engine cycles is of critical importance for ensuring structural integrity of engine components, like turbine blades. In this paper, the influence of combined damage accumulation on the expected CCF life are investigated for turbine blades. The CCF behavior of a turbine blade is usually studied by testing with four load-controlled parameters, including high cycle stress amplitude and frequency, and low cycle stress amplitude and frequency. According to this, a new damage accumulation model is proposed based on Miner’s rule to consider the coupled damage due to HCF-LCF interaction by introducing the four load parameters. Five experimental datasets of turbine blade alloys and turbine blades were introduced for model validation and comparison between the proposed Miner, Manson-Halford, and Trufyakov-Kovalchuk models. Results show that the proposed model provides more accurate predictions than others with lower mean and standard deviation values of model prediction errors.

  5. Low cycle fatigue of PM/HIP astroloy

    Energy Technology Data Exchange (ETDEWEB)

    Choe, S.J.; Stoloff, N.S.; Duquette, D.J. (Rensselaer Polytechnic Institute, Troy, NY (USA))

    Low cycle fatigue and creep-fatigue-environment interactions of PM/HIP Astrology were studied at 650 C and 725 C. Total strain range was varied from 1.5% to 2.7% at a frequency of 0.3Hz. Creep-fatigue tests were performed with 2 min. or 5 min. tensile hold times. All tests were run in high purity argon in an attempt to minimize environmental effects. Employing a tensile hold was more damaging than raising temperature by 75 C. Slopes of Coffin-Manson plots were nearly independent of temperature and hold time. Raising temperature from 650 C to 725 C did not change the transgranular (TG) crack propagation mode, whereas employing hold times caused TG+IG propagation. All samples displayed multiple fracture origins associated with inclusions located at the specimen surface; pre-existing pores did not affect fatigue crack initiation. Examination of secondary cracks showed no apparent creep damage. Oxidation in high purity argon appeared to be the major factor in LCF life degradation due to hold times.

  6. Statistical investigation of the crack initiation lives of piping structural welded joint in low cycle fatigue test of 240 degree C

    International Nuclear Information System (INIS)

    Zhao Yongxiang; Gao Qing; Cai Lixun

    1999-01-01

    A statistical investigation into the fitting of four possible fatigue assumed distributions (three parameter Weibull, two parameter Weibull, lognormal and extreme maximum value distributions) for the crack initiation lives of piping structural welded joint in low cycle fatigue test of 240 degree C is performed by linear regression and least squares methods. The results reveal that the three parameters Weibull distribution may give misleading results in fatigue reliability analysis because the shape parameter is often less than 1. This means that the failure rate decreases with fatigue cycling which is contrary to the general understanding of the behaviour of welded joint. Reliability analyses may also affected by the slightly nonconservative evaluations in tail regions of this distribution. The other three distributions are slightly poor in the total fit effects, but they can be safety assumed in reliability analyses due to the non-conservative evaluations in tail regions mostly and the consistency with the fatigue physics of the structural behaviour of welded joint in the range of engineering practice. In addition, the extreme maximum value distribution is in good consists with the general physical understanding of the structural behaviour of welded joint

  7. Low cycle fatigue behaviour of Ti-6Al-5Zr-0.5Mo-0.25Si alloy at room temperature

    International Nuclear Information System (INIS)

    Nag, Anil Kumar; Praveen, K.V.U.; Singh, Vakil

    2006-01-01

    Low cycle fatigue (LCF) behaviour of the near α titanium alloy, Ti-6Al-5Zr-0.5Mo-0.25Si (LT26A), was investigated in the (α+ β) as well as β treated conditions at room temperature. LCF tests were carried out under total strain controlled mode in the range of Δε t /2: from ± 0.60% to ± 1.40%. The alloy shows cyclic softening in both the conditions. Also it exhibits dual slope Coffin-Manson (C-M) relationship in both the treated conditions. (author)

  8. 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.

  9. Characterization of coatings and the low cycle fatigue behaviour of 316L

    International Nuclear Information System (INIS)

    Groot, P.; Horsten, M.G.; Tjoa, G.L.

    1993-03-01

    In the framework of the European Fusion Technology Programme ECN participates in a NET task PSM-8 'Coatings and Surface Effects on Stainless Steel 316L'. High emissivity coatings were developed for enhanced heat transfer from graphite tiles to a Stainless Steel First Wall. Four candidate materials, Cr 2 O 3 , Black Cr, Al 2 O 3 /TiO 2 and TiC were tested as candidate high emissivity coatings. These coatings were manufactured by atmospheric and vacuum plasma spraying technique and the Black Chromium coatings were manufactured by a galvanic coating technique. The tests included total emissivity measurements and Low Cycle Fatigue (LCF) experiments. The total emissivity of two TiC coatings at 525 K appeared to be 0.62 and 0.64. The total emissivity of the TiC and 5 wt% TiO 2 /Al 2 O 3 coating was about 0.7. (orig.)

  10. Effect of tungsten and tantalum on the low cycle fatigue behavior of reduced activation ferritic/martensitic 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); Mariappan, K.; Nagesha, A.; Prasad Reddy, G.V.; Sandhya, R.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Effect of tungsten and tantalum on low cycle fatigue behavior of RAFM steels. Black-Right-Pointing-Pointer Both alloying elements W and Ta improved fatigue life. Black-Right-Pointing-Pointer Increase in Ta content improved fatigue life more than W. Black-Right-Pointing-Pointer Optimization of W content at 1.4 wt.%. Black-Right-Pointing-Pointer Softening behavior closely related to W and Ta content. - Abstract: Reduced activation ferritic/martensitic (RAFM) steels are candidate materials for the test blanket modules of International Thermonuclear Experimental Reactor (ITER). Several degradation mechanisms such as thermal fatigue, low cycle fatigue, creep fatigue interaction, creep, irradiation hardening, swelling and phase instability associated irradiation embrittlement must be understood in order to estimate the component lifetime and issues concerning the structural integrity of components. The current work focuses on the effect of tungsten and tantalum on the low cycle fatigue (LCF) behavior of RAFM steels. Both alloying elements tungsten and tantalum improved the fatigue life. Influence of Ta on increasing fatigue life was an order of magnitude higher than the influence of W on improving the fatigue life. Based on the present study, the W content was optimized at 1.4 wt.%. Softening behavior of RAFM steels showed a strong dependence on W and Ta content in RAFM steels.

  11. 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.

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

    International Nuclear Information System (INIS)

    Paul, Surajit Kumar; Sivaprasad, S.; Dhar, S.; Tarafder, S.

    2010-01-01

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

  13. Microstructural study of multiaxial low cycle fatigue

    Directory of Open Access Journals (Sweden)

    Masao Sakane

    2015-07-01

    Full Text Available This paper discusses the relationship between the stress response and the microstructure under tension-torsion multiaxial proportional and nonproportional loadings. Firstly, this paper discusses the material dependency of additional hardening of FCC materials in relation with the stacking fault energy of the materials. The FCC materials studied were Type 304 stainless steel, pure copper, pure nickel, pure aluminum and 6061 aluminum alloy. The material with lower stacking fault energy showed stronger additional hardening, which was discussed in relation with slip morphology and dislocation structures. This paper, next, discusses dislocation structures of Type 304 stainless steel under proportional and nonproportional loadings at high temperature. The relationship between the microstructure and the hardening behavior whether isotropic or anisotropic was discussed. The re-arrangeability of dislocation structure was discussed in loading mode change tests. Microstructures of the steel was discussed in more extensively programmed multiaxial low cycle fatigue tests at room temperature, where three microstructures, dislocation bundle, stacking fault and cells, which were discussed in relation with the stress response. Finally, temperature dependence of the microstructure was discussed under proportional and nonproportional loadings, by comparing the microstructures observed at room and high temperatures.

  14. HCF + LCF Interactions at Elevated Temperature

    National Research Council Canada - National Science Library

    Byrne, James; Hall, R. F; Ding, J

    2005-01-01

    ...) crack propagation in Ti- 6Al-4V will be studied under combined HCF/low cycle fatigue (LCF) loading conditions at elevated temperatures up to 350 deg C where creep stress ratcheting and environmental effects may arise...

  15. Crack initiation and propagation in welded joints of turbine and boiler steels during low cycle fatigue

    International Nuclear Information System (INIS)

    Lindblom, J.; Sandstroem, R.; Linde, L.; Henderson, P.

    1990-01-01

    Low cycle fatigue (LCF) tests have been performed at 300 and 565 degrees C on welded joints and on microstructures to be found in or near welded joints in a low alloy ferritic steel 0.5 Cr, 0.5 Mo, 0.25 V. The difference in lifetimes between the 300 degrees C and 565 degrees C tests was small comparing the same microstructures and strain ranges, although the stress amplitude was greater at 300 degrees C. Under constant stress conditions the fatigue life depended on the fatigue life of the parent metal but under constant strain conditions the lifetime was governed by that of the bainitic structures. Strain controlled LCF tests have been performed at 750 degrees C on welded joints in the austenitic steel AISI 316 and on different parent and weld metals used in these joints. In continuously cycled samples all cracks were transgranular and initiated at the surface; hold-time samples displayed internally initiated intergranular cracking in the weld metal. Under constant strain conditions the 316 parent and weld metals exhibited similar lifetimes. When considering a constant stress situation the strength of the microsturctures decreased in the following order: Sanicro weld metal, cold deformed parent metal, undeformed parent metal and weld metal (K.A.E.)

  16. Experimental study of microstructure changes due to low cycle fatigue of a steel nanocrystallised by Surface Mechanical Attrition Treatment (SMAT)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Z. [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); Retraint, D., E-mail: delphine.retraint@utt.fr [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); Baudin, T.; Helbert, A.L.; Brisset, F. [ICMMO, Univ Paris-Sud, Université Paris-Saclay, UMR CNRS 8182, 91405 Orsay Cedex (France); Chemkhi, M.; Zhou, J. [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); Kanouté, P. [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); ONERA, The French Aerospace Lab, 29 avenue de la Division Leclerc, 92322 Chatillon Cedex (France)

    2017-02-15

    Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. - Highlights: •LCF tests are carried out on specimens processed by SMAT. •EBSD is used to investigate microstructural changes induced by LCF. •A grain size gradient is generated by SMAT from surface to the bulk of the fatigue samples. •New slip systems are activated by LCF and GOS is increased in plastically deformed region. •However, these phenomena are not observed in the top surface ultra-fine grain area.

  17. Experimental study of microstructure changes due to low cycle fatigue of a steel nanocrystallised by Surface Mechanical Attrition Treatment (SMAT)

    International Nuclear Information System (INIS)

    Sun, Z.; Retraint, D.; Baudin, T.; Helbert, A.L.; Brisset, F.; Chemkhi, M.; Zhou, J.; Kanouté, P.

    2017-01-01

    Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. - Highlights: •LCF tests are carried out on specimens processed by SMAT. •EBSD is used to investigate microstructural changes induced by LCF. •A grain size gradient is generated by SMAT from surface to the bulk of the fatigue samples. •New slip systems are activated by LCF and GOS is increased in plastically deformed region. •However, these phenomena are not observed in the top surface ultra-fine grain area.

  18. Failure Mechanisms and Damage Model of Ductile Cast Iron Under Low-Cycle Fatigue Conditions

    Science.gov (United States)

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

    2014-10-01

    Strain-controlled low-cycle fatigue (LCF) tests were conducted on ductile cast iron (DCI) at strain rates of 0.02, 0.002, and 0.0002/s in the temperature range from room temperature to 1073 K (800 °C). A constitutive-damage model was developed within the integrated creep-fatigue theory (ICFT) framework on the premise of strain decomposition into rate-independent plasticity and time-dependent creep. Four major damage mechanisms: (i) plasticity-induced fatigue, (ii) intergranular embrittlement (IE), (iii) creep, and (iv) oxidation were considered in a nonlinear creep-fatigue interaction model which represents the overall damage accumulation process consisting of oxidation-assisted fatigue crack nucleation and propagation in coalescence with internally distributed damage ( e.g., IE and creep), leading to final fracture. The model was found to agree with the experimental observations of the complex DCI-LCF phenomena, for which the linear damage summation rule would fail.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-15

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

  20. Crack growth prediction for low-cycle fatigue regime

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2017-01-01

    The objective of this study is to show a crack growth prediction procedure for the low-cycle fatigue regime. First, fatigue crack growth tests using Type 316 stainless steel specimens at room temperature were reviewed. It was seen that the crack growth rates correlated well with the equivalent stress intensify factor, which was derived using strain range instead of stress range. Furthermore, the effective equivalent stress intensify factor derived using the effective strain range exhibited excellent correlation with the crack growth rates obtained under various specimen geometries and loading conditions including high and low-cycle regimens. The obtained crack growth rates were also compared with the growth rate prescribed in the fitness-for-service code of the Japan Society of Mechanical Engineers (JSME). The test results agreed with the growth rate of JSME code. Finally, the procedure for predicting the low-cycle fatigue crack growth was shown. Although the JSME code is aimed at predicting fatigue crack growth for the so-called small scale yielding condition (high-cycle fatigue regime), the material constants determined for the high-cycle fatigue regime can be used even for the low-cycle fatigue regime. (author)

  1. LCF- and LCF/HCF-behaviour of the superalloy MAR-M247LC

    Energy Technology Data Exchange (ETDEWEB)

    Gelmedin, Domnin; Lang, Karl-Heinz [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). Inst. fuer Werkstoffkunde I

    2010-07-01

    The fatigue behaviour of the Nickel-base superalloy Mar-M247LC was investigated at 650 C in air environment under total strain control. Pure low cycle fatigue (LCF) loading, pure high cycle fatigue (HCF) loading and superimposed LCF/HCF loading were realised. In LCF tests with a strain ratio of zero and a hold time of 60 seconds the cyclic deformation and the lifetime behaviour was investigated. The dependence of the fatigue limit on the mean strain was estimated in HCF tests at a frequency of 60 Hz using an ultimate number of cycles of ten million. Finally the influence of superimposed HCF and LCF loadings was examined. At high total strain ranges of the HCF loading the lifetime of the superalloy as reduced about more than one magnitude compared to the lifetime under pure LCF loading. With decreasing HCF loadings the reduction of the lifetime decreases. This life time reduction can be explained by the interaction of the LCF and the superimposed HCF loading. Crack initiation and first crack propagation is predominantly induced by the LCF loading. After reaching an adequate long fatigue crack length the superimposed HCF loading contributes considerably to the crack growth. This contribution can be determined evaluating the distance between the LCF marking lines which form on the fracture surface. The higher the superimposed HCF loading was the longer the distance between the LCF marking lines and the lower the crack length were when first LCF marking lines could be recognized. On the basis of this cognition the life time under superimposed LCF/HCF loading was modelled using a model basing on fracture mechanics. (orig.)

  2. Experimental and numerical investigation of strain rate effect on low cycle fatigue behaviour of AA 5754 alloy

    Science.gov (United States)

    Kumar, P.; Singh, A.

    2018-04-01

    The present study deals with evaluation of low cycle fatigue (LCF) behavior of aluminum alloy 5754 (AA 5754) at different strain rates. This alloy has magnesium (Mg) as main alloying element (Al-Mg alloy) which makes this alloy suitable for Marines and Cryogenics applications. The testing procedure and specimen preparation are guided by ASTM E606 standard. The tests are performed at 0.5% strain amplitude with three different strain rates i.e. 0.5×10-3 sec-1, 1×10-3 sec-1 and 2×10-3 sec-1 thus the frequency of tests vary accordingly. The experimental results show that there is significant decrease in the fatigue life with the increase in strain rate. LCF behavior of AA 5754 is also simulated at different strain rates by finite element method. Chaboche kinematic hardening cyclic plasticity model is used for simulating the hardening behavior of the material. Axisymmetric finite element model is created to reduce the computational cost of the simulation. The material coefficients used for “Chaboche Model” are determined by experimentally obtained stabilized hysteresis loop. The results obtained from finite element simulation are compared with those obtained through LCF experiments.

  3. Macro and Microscopic Investigation on Fracture Specimen of Alloy 617 Base Metal and Weldment in Low Cycle Fatigue Regime

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seon Jin; Dewa, Rando Tungga [Pukyung National Univ., Busan (Korea, Republic of); Kim, Won Gon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-06-15

    This paper investigates macro- and microscopic fractography performed on fracture specimens from low cycle fatigue (LCF) testings through an Alloy 617 base metal and weldments. The weldment specimens were taken from gas tungsten arc welding (GTAW) pad of Alloy 617. The aim of the present study is to investigate the macro- and microscopic aspects of the low cycle fatigue fracture mode and mechanism of Alloy 617 base metal and GTAWed weldment specimens. Fully axial total strain controlled fatigue tests were conducted at room temperature with total strain ranges of 0.6, 0.9, 1.2 and 1.5%. Macroscopic fracture surfaces of Alloy 617 base metal specimens showed a flat type normal to the fatigue loading direction, whereas the GTAWed weldment specimens were of a shear/star type. The fracture surfaces of both the base metal and weldment specimens revealed obvious fatigue striations at the crack propagation regime. In addition, the fatigue crack mechanism of the base metal showed a transgranular normal to fatigue loading direction; however, the GTAWed weldment specimens showed a transgranular at approximately 45° to the fatigue loading direction.

  4. Macro and Microscopic Investigation on Fracture Specimen of Alloy 617 Base Metal and Weldment in Low Cycle Fatigue Regime

    International Nuclear Information System (INIS)

    Kim, Seon Jin; Dewa, Rando Tungga; Kim, Won Gon

    2016-01-01

    This paper investigates macro- and microscopic fractography performed on fracture specimens from low cycle fatigue (LCF) testings through an Alloy 617 base metal and weldments. The weldment specimens were taken from gas tungsten arc welding (GTAW) pad of Alloy 617. The aim of the present study is to investigate the macro- and microscopic aspects of the low cycle fatigue fracture mode and mechanism of Alloy 617 base metal and GTAWed weldment specimens. Fully axial total strain controlled fatigue tests were conducted at room temperature with total strain ranges of 0.6, 0.9, 1.2 and 1.5%. Macroscopic fracture surfaces of Alloy 617 base metal specimens showed a flat type normal to the fatigue loading direction, whereas the GTAWed weldment specimens were of a shear/star type. The fracture surfaces of both the base metal and weldment specimens revealed obvious fatigue striations at the crack propagation regime. In addition, the fatigue crack mechanism of the base metal showed a transgranular normal to fatigue loading direction; however, the GTAWed weldment specimens showed a transgranular at approximately 45° to the fatigue loading direction

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-15

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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  7. Influence of Thermal Aging on Tensile and Low Cycle Fatigue Behavior of Type 316LN Austenitic Stainless Steel Weld Joint

    Science.gov (United States)

    Suresh Kumar, T.; Nagesha, A.; Ganesh Kumar, J.; Parameswaran, P.; Sandhya, R.

    2018-05-01

    Influence of short-term thermal aging on the low-cycle fatigue (LCF) behavior of 316LN austenitic stainless steel weld joint with 0.07 wt pct N has been investigated. Prior thermal exposure was found to improve the fatigue life compared with the as-welded condition. Besides, the treatment also imparted a softening effect on the weld metal, leading to an increase in the ductility of the weld joint which had a bearing on the cyclic stress response. The degree of cyclic hardening was seen to increase after aging. Automated ball-indentation (ABI) technique was employed toward understanding the mechanical properties of individual zones across the weld joint. It was observed that the base metal takes most of the applied cyclic strain during LCF deformation in the as-welded condition. In the aged condition, however, the weld also participates in the cyclic deformation. The beneficial effect of thermal aging on cyclic life is attributed to a reduction in the severity of the metallurgical notch leading to a restoration of ductility of the weld region. The transformation of δ-ferrite to σ-phase during the aging treatment was found to influence the location of crack initiation. Fatigue cracks were found to initiate in the base metal region of the joint in most of the testing conditions. However, embrittlement in the weld metal caused a shift in the point of crack initiation with increasing strain amplitude under LCF.

  8. Low cycle fatigue and creep-fatigue interaction behavior of nickel-base superalloy GH4169 at elevated temperature of 650 °C

    Energy Technology Data Exchange (ETDEWEB)

    Chen, G., E-mail: agang@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Zhang, Y. [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Xu, D.K. [Environmental Corrosion Center, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Lin, Y.C. [School of Mechanical and Electrical Engineering, Central South University, Changsha 410083 (China); Chen, X. [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2016-02-08

    Total strain-controlled low cycle fatigue (LCF) tests of a nickel based superalloy were performed at 650 °C. Various hold times were introduced at the peak tensile strain to investigate the high-temperature creep-fatigue interaction (CFI) effects under the same temperature. A substantial decrease in fatigue life occurred as the total strain amplitude increased. Moreover, tensile strain holding further reduced fatigue life. The saturation phenomenon of holding effect was found when the holding period reached 120 s. Cyclic softening occurred during the LCF and CFI process and it was related to the total strain amplitude and the holding period. The relationship between life-time and total strain amplitude was obtained by combining Basquin equation and Coffin-Manson equation. The surface and fracture section of the fatigued specimens were observed via scanning electronic microscope (SEM) to determine the failure mechanism.

  9. The influence of temperature on low cycle fatigue behavior of prior cold worked 316L stainless steel (II) : life prediction and failure mechanism

    International Nuclear Information System (INIS)

    Hong, Seong Gu; Yoon, Sam Son; Lee, Soon Bok

    2003-01-01

    Tensile and low cycle fatigue tests on prior cold worked 316L stainless steel were carried out at various temperatures from room temperature to 650 deg. C. Fatigue resistance was decreased with increasing temperature and decreasing strain rate. Cyclic plastic deformation, creep, oxidation and interactions with each other are thought to be responsible for the reduction in fatigue resistance. Currently favored life prediction models were examined and it was found that it is important to select a proper life prediction parameter since stress-strain relation strongly depends on temperature. A phenomenological life prediction model was proposed to account for the influence of temperature on fatigue life and assessed by comparing with experimental result. LCF failure mechanism was investigated by observing fracture surfaces of LCF failed specimens with SEM

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

    International Nuclear Information System (INIS)

    Lehericy, Y.

    2007-05-01

    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)

  11. High temperature low cycle fatigue behavior of a directionally solidified Ni-base superalloy DZ951

    International Nuclear Information System (INIS)

    Chu Zhaokuang; Yu Jinjiang; Sun Xiaofeng; Guan Hengrong; Hu Zhuangqi

    2008-01-01

    Total strain-controlled low cycle fatigue (LCF) tests were performed at a temperature range from 700 to 900 deg. C in ambient air condition on a directionally solidified Ni-base superalloy DZ951. The fatigue life of DZ951 alloy does not monotonously decrease with increasing temperature, but exhibits a strong dependence on the total strain range. The dislocation characteristics and failed surface observation were evaluated through transmission electron microscopy and scanning electron microscopy. The alloy exhibits cyclic hardening, softening or cyclic stability as a whole, which is dependent on the testing temperature and total strain range. At 700 deg. C, the cyclic plastic deformation process is the main cause of fatigue failure. At 900 deg. C, the failure mostly results from combined fatigue and creep damage under total strain range from 0.6 to 1.2% and the reduction in fatigue life can be taken as the cause of oxidation, creep and cyclic plastic deformation under total strain range of 0.5%

  12. Low cycle fatigue of irradiated LMFBR materials

    International Nuclear Information System (INIS)

    Blackburn, L.D.

    1976-01-01

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

  13. Experimental investigation on low cycle fatigue and creep-fatigue interaction of DZ125 in different dwell time at elevated temperatures

    International Nuclear Information System (INIS)

    Shi Duoqi; Liu Jinlong; Yang Xiaoguang; Qi Hongyu; Wang Jingke

    2010-01-01

    Research highlights: → This paper has researched creep-fatigue interaction of directionally solidified superalloy DZ125 with different dwell time at high temperature combined with micro-mechanism by experiment. → The results indicated that the life of creep-fatigue decreases as dwell time increases, but the life of this alloy was almost unchanged when dwell time exceeds a critical value at 850 deg. C. - Abstract: The low cycle fatigue (LCF) and creep-fatigue tests have been conducted with directionally solidified nickel-based superalloy DZ125 at 850 and 980 deg. C to study the creep-fatigue interaction behavior of alloy with different dwell time. On the average, the life of creep-fatigue tests are about 70% less than the life of LCF tests under the same strain range at 850 deg. C. The life of creep-fatigue decreases as dwell time increases, but the life of this alloy was almost unchanged when dwell time exceeds a critical value at 850 deg. C. Scanning electron microscope (SEM) analyses of the fracture revealed that the fracture modes were influenced by different way of loading. In case of LCF, the primary fracture mode was transgranular, while in case of creep-fatigue, the primary fracture mode was mixed with transgranular and intergranular. There were also obvious different morphologies of surface crack between LCF and creep-fatigue.

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

    Directory of Open Access Journals (Sweden)

    Yanchuan Tang

    2018-06-01

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

  15. Low cycle fatigue behavior of ITER-like divertor target under DEMO-relevant operation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Muyuan; Werner, Ewald [Lehrstuhl für Werkstoffkunde und Werkstoffmechanik, Technische Universität München, Boltzmannstr. 15, 85748 Garching (Germany); You, Jeong-Ha, E-mail: you@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)

    2015-01-15

    Highlights: • LCF behavior of the cooling tube and the interlayer of an ITER-like divertor target is studied. • For the cooling tube, LCF failure will not be an issue under an HHF load of up to 18 MW/m{sup 2}. • Plastic strain in the interlayer is concentrated at the free surface edge of the bond interface. • The predicted LCF lifetime of the interlayer may not meet the design requirement. - Abstract: In this work the low cycle fatigue (LCF) behavior of the copper alloy cooling tube and the copper interlayer of an ITER-like divertor target is reported for nine different combinations of loading and cooling conditions relevant to DEMO divertor operation. The LCF lifetime is presented as a function of loading and cooling conditions considered here by means of cyclic plasticity simulation and using LCF data of materials relevant for ITER. The numerical predictions indicate, that fatigue failure will not be an issue for the copper alloy tube under a high heat flux (HHF) load of up to 18 MW/m{sup 2} as long as it preserves its initial strength. In contrast, the copper interlayer exhibits significant plastic dissipation at the free surface edge of the bond interface adjacent to the cooling tube, where the LCF lifetime is predicted to be below 3000 load cycles for HHF loads higher than 15 MW/m{sup 2}. Most of the bulk region of the copper interlayer away from the free surface edge does not experience severe plastic fatigue and hence does not pose any critical concern as the LCF lifetime is predicted to be at least 7000 load cycles. LCF lifetime decreases as HHF load is increased or coolant temperature is decreased.

  16. Influence of PbBi environment on the low-cycle fatigue behavior of SNS target container materials

    International Nuclear Information System (INIS)

    Kalkhof, D.; Grosse, M.

    2003-01-01

    The low-cycle fatigue (LCF) behavior of the stainless steel 316L and the 10.5Cr-steel Manet-II was investigated at 260 deg. C in air and in stagnant lead-bismuth (PbBi). At low-strain levels, the fatigue lives for 316L in PbBi and air were comparable. At total strain amplitudes of 0.50% and higher a weak influence of PbBi was observed. In contrast to 316L, the results of LCF tests for Manet-II in PbBi showed a significant reduction of lifetime for all applied strain amplitudes. In the worst case the cycle number to crack initiation was reduced by a factor of ∼7 compared with the comparable test in air. For the low-strain amplitude of 0.30%, fatigue tests conducted at a frequency of 0.1 Hz had shorter fatigue lives than at a frequency of 1.0 Hz. For Manet-II the crack propagation in PbBi was much faster than in air, and failure immediate followed the formation of the first macroscopic crack

  17. 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.

  18. Influences of overload on low cycle fatigue behaviors of elbow pipe with local wall thinning

    International Nuclear Information System (INIS)

    Sato, Kyohei; Ogino, Kanako; Takahashi, Koji; Ando, Kotoji; Urabe, Yoshio

    2011-01-01

    Low cycle fatigue tests were conducted using 100A elbow pipe specimens with or without local wall thinning. Local wall thinning was machined on the inside of the extrados of test elbows to simulate metal loss due to flow-accelerated corrosion or liquid droplet impingement erosion. Low cycle fatigue tests were carried out under displacement control with an inner pressure of 9 MPa. To simulate seismic events, low cycle fatigue tests were carried out on elbow pipe subjected to cyclic overloads. Regardless of local wall thinning, fatigue life of overload pipe was not so different from that of the non-overload pipe in appearance. Miner's rule can be applied to evaluate fatigue life of the elbow pipes with and without wall thinning, even if overload is applied. (author)

  19. LCF life prediction for waspaloy in the creep-fatigue interaction regime

    International Nuclear Information System (INIS)

    Yeom, Jong Taek; Park, Nho Kwang

    2001-01-01

    This paper describes the empirical rule of strain rate modified linear accumulation of creep damage(SRM rule) for Low-Cycle Fatigue(LCF) life prediction of Waspaloy in the creep-fatigue interaction regime and Chaboche type unified viscoplastic model predicting the stress-strain response in various cyclic loading conditions. The comparison of the experimental data and the predictions for strain controlled LCF tests carried out for various strain ranges at 600 .deg. C and 650 .deg. C was made. Chaboche type unified viscoplastic model described efficiently the inelastic deformation behavior during LCF tests. Crack-initiation lifting method to predict the material life was investigated with Strain Rate Modification(SRM) rule. The application of SRM rule to LCF tests on Waspaloy indicated a good agreement between measured and predicted cycles to failure

  20. Low-cycle fatigue and damage of an uncoated and coated single crystal nickel-base superalloy SCB

    International Nuclear Information System (INIS)

    Stekovic, S.; Ericsson, T.

    2007-01-01

    This paper presents low-cycle fatigue (LCF) behaviour and damage mechanisms of uncoated and coated specimens of a single crystal nickel-base superalloy SCB tested at 500 C and 900 C. Four coatings were deposited on the base material, an overlay coating AMDRY997, a platinum-modified aluminide diffusion coating RT22 and two innovative coatings called IC1 and IC3 with a NiW diffusion barrier in the interface. AMDRY997 and RT22 were used as reference coatings. The LCF tests were performed at three strain amplitudes, 1.0, 1.2 and 1.4%, with R = -1, in laboratory air and without any dwell time. The LCF life of the specimens is determined by crack initiation and propagation. Crack data are presented for different classes of crack size in the form of crack density, that is, the number of cracks normalised to the investigated interface length. Micrographs of damage of the coatings are also shown. The effect of the coatings on the LCF life of the superalloy was dependent on the test temperature and deposited coating. At 500 C all coatings had a detrimental effect on the LCF life of the superalloy. At 900 C both AMDRY997 and IC1 prolonged the fatigue life of the superalloy by factors ranging between 1.5 and 4 while RT22 and IC3 shortened the life of the coating-substrate system. Specimens coated with RT22 exhibited generally more damage than other tested coatings at 900 C. Most of the cracks observed initiated at the coating surface and a majority were arrested in the interdiffusion zone between the base material and the coating. No topologically close-packed phases were found. Delamination was only found in AMDRY997 at higher strains. Surface roughness or rumpling was found in the overlay coating AMDRY997 with some cracks initiating from the rumples. The failure morphology at 900 C reflected the role of oxidation in the fatigue life, the crack initiation and propagation of the coated specimens. The wake of the cracks grown into the substrate was severely oxidised leading to

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

    International Nuclear Information System (INIS)

    Cooper, R.A.

    1976-01-01

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

  2. Influence of martensitic transformation on the low-cycle fatigue behaviour of 316LN stainless steel at 77 K

    International Nuclear Information System (INIS)

    Botshekan, M.; Degallaix, S.; Desplanques, Y.

    1997-01-01

    Tensile and low-cycle fatigue tests were performed on a 316LN austenitic stainless steel at 300 and 77 K. The tensile and low-cycle fatigue properties were obtained and analysed in terms of influence of temperature on the plastic deformation process, and particularly on the strain-induced martensite formation. The martensite content was measured by a magnetic-at-saturation method. No martensite was detected at 300 K. On the contrary, strain-induced martensite transformation is responsible for the higher tensile elongation at 77 K and for the secondary hardening observed on softening-hardening curves in low-cycle fatigue at 77 K. The induced martensite content in tensile tests is a function of the strain according to Angel's model, and in low-cycle fatigue it is a function of the strain level and of the accumulated plastic strain. (orig.)

  3. A model for life predictions of nickel-base superalloys in high-temperature low cycle fatigue

    Science.gov (United States)

    Romanoski, Glenn R.; Pelloux, Regis M.; Antolovich, Stephen D.

    1988-01-01

    Extensive characterization of low-cycle fatigue damage mechanisms was performed on polycrystalline Rene 80 and IN100 tested in the temperature range from 871 to 1000 C. Low-cycle fatigue life was found to be dominated by propagation of microcracks to a critical size governed by the maximum tensile stress. A model was developed which incorporates a threshold stress for crack extension, a stress-based crack growth expression, and a failure criterion. The mathematical equivalence between this mechanistically based model and the strain-life low-cycle fatigue law was demonstrated using cyclic stress-strain relationships. The model was shown to correlate the high-temperature low-cycle fatigue data of the different nickel-base superalloys considered in this study.

  4. Energy based study of quasi-static delamination as a low cycle fatigue process

    NARCIS (Netherlands)

    Amaral, L.; Yao, L.; Alderliesten, R.C.; Benedictus, R.

    2015-01-01

    This work proposes to treat quasi-static mode I delamination growth of CFRP as a low-cycle fatigue process. To this end, mode I quasi-static and fatigue delamination tests were performed. An average physical Strain Energy Release Rate (SERR), derived from an energy balance, is used to characterize

  5. Effects of warm laser peening at elevated temperature on the low-cycle fatigue behavior of Ti6Al4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J.Z.; Meng, X.K., E-mail: mengdetiankong10@126.com; Huang, S.; Sheng, J.; Lu, J.Z.; Yang, Z.R.; Su, C.

    2015-09-03

    This study focused on the effects of warm laser peening (WLP) on the fatigue behavior of Ti6Al4V titanium alloy during low-cycle fatigue (LCF) tests. The Ti6Al4V specimens were treated by laser peening at room temperature (RT-LP) and WLP at elevated temperatures from 100 °C to 400 °C. The residual stress relaxation (RSR) tests and LCF tests were conducted subsequently. In addition, the microstructure analysis of fracture surfaces was performed using scanning electron microscope (SEM). Finally, the fracture mechanism of the untreated, RT-LPed and 300 °C-WLPed samples during LCF was revealed. It is found that although the compressive residual stress (CRS) induced by WLP decreases at elevated temperatures, the depth and stability of CRS increase with the increasing treatment temperature, which help to retard the early fatigue crack initiation. Moreover, for the 300 °C-WLPed specimens, the growth rate of effective cracks is decreased and the lengths of crack growth paths are increased by the induced high angle boundaries (HABs) and nano-precipitates. Therefore, specimens treated by WLP at 300 °C are found to have a significantly extended fatigue life when subjected to low-cycle loads. This extended fatigue life is attributed to the great depth and stability of introduced CRS, as well as the enhanced fracture toughness. It can be concluded that 300 °C is the optimal temperature for WLP of Ti6Al4V titanium alloy from the perspective of LCF improvement.

  6. Low cycle fatigue properties of neutron irradiated solid HIP 316L(N). ITER Task T214, NET deliverable GB6 ECN-5

    International Nuclear Information System (INIS)

    Rensman, J.; Van Osch, E.V.; Tjoa, G.L.; Boskeljon, J.; Van Hoepen, J.

    1998-05-01

    The Low Cycle Fatigue (LCF) properties of neutron irradiated Hot Isostatically Pressed (HIP) joints of type 316L(N) stainless steel (heat PM-130) have been measured, as well as the LCF properties of reference 316L(N)-ERHII. Cylindrical LCF test specimens of 3 mm diameter were irradiated in the High Flux Reactor (HFR) in Petten, The Netherlands, simulating the first wall conditions of future fusion reactors by a combination of high displacement damage with proportional amounts of helium. The solid HIP specimens were irradiated up to a target dose level of 5 dpa at a temperature of 550K. The damage levels realised range from 3.0 to 4.4 dpa, with helium contents up to 41 appm. Testing temperature was equal to the irradiation temperature: 550K. The report contains the experimental conditions and summarises the results, which are given in terms of first cycle stress, the peak stress, the number of cycles where the peak stress is reached, the stress at half life and the plastic strain at half life, and the total number of cycles to failure, N f . The main conclusions are that the unirradiated solid-HIP materials has the same LCF properties as unirradiated 316L(N)-ERHII plate material. The neutron irradiation induces both hardening and reduction of fatigue life. The bond does not seem to have any effect on the fatigue properties for the unirradiated solid HIP 316L(N), whereas a combined effect of irradiation and the bond cannot be established. No failures related to debonding of the joint were observed for the tests. 7 refs

  7. In pile AISI 316L. Low cycle fatigue. Final report

    International Nuclear Information System (INIS)

    Van Nieuwenhove, R.; Moons, F.

    1994-12-01

    In pile testing of the effect of neutron irradiation on the fatigue life of the reference material AISI 316L was performed in the framework of the European fusion technology program. The overall programme, carried out at SCK CEN (Mol,Belgium), exists of two instrumented rigs for low cycle fatigue testing, which were consecutively loaded in the BR-2 reactor during periods Jan (94) June (94) and Aug (94)-Dec(94). In each experiment, two identical samples were loaded by means of a pneumatically driven system. The samples were instrumented with thermocouples, strain gages, linear variable displacement transducers, and activation monitors. The experimental conditions are given. Type of fatigue test: load controlled, symmetric, uniaxial, triangular wave shape; stress range: about 580 MPa; sample shape: hourglass, diameter 3.2 mm, radius 12.5 mm; environment: NaK (peritectic); temperature: 250 C; maximum dpa value up to fracture: 1.7. Two of four samples were broken (one in each experiment) after having experienced 17 419 respectively 11 870 stress cycles. These new data points confirm earlier results from pile fatigue tests: irradiation causes no degradation of fatigue life of AISI 316L steel, at least for the parameters corresponding to these experiments

  8. Microstructural characterization of EUROFER 97 during low-cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Giordana, M.F., E-mail: giordana@ifir-conicet.gov.ar [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 bis, 2000 Rosario (Argentina); Alvarez-Armas, I., E-mail: alvarez@ifir-conicet.gov.ar [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 bis, 2000 Rosario (Argentina); Armas, A., E-mail: armas@ifir-conicet.gov.ar [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 bis, 2000 Rosario (Argentina)

    2012-05-15

    The quenched and tempered reduced-activation ferritic/martensitic steel EUROFER 97 is one of the candidates for structural components of Generation IV nuclear power plants. The cyclic behaviour of this steel during isothermal plastic strain-controlled tests was investigated at room temperature and at 550 Degree-Sign C. Under low-cycle fatigue test this steel shows, after the first few cycles, a pronounced cyclic softening accompanied by microstructural changes such as the decrease of the free dislocation density inside the subgrain. The rate of softening increases with temperature being very pronounced at temperatures above 500 Degree-Sign C. The evolution of the flow stress during cycling was studied by analyzing the so-called 'back' and 'friction' stresses obtained from the hysteresis loops measured along the entire test. From the analysis of the hysteresis loops and corroborated by electron microscopy observations, it can be concluded that the strong cyclic softening observed is produced by the decrease exhibited by the friction stress. The Taylor coefficient was calculated measuring the evolution of the free dislocation density.

  9. Microstructural characterization of EUROFER 97 during low-cycle fatigue

    International Nuclear Information System (INIS)

    Giordana, M.F.; Alvarez-Armas, I.; Armas, A.

    2012-01-01

    The quenched and tempered reduced-activation ferritic/martensitic steel EUROFER 97 is one of the candidates for structural components of Generation IV nuclear power plants. The cyclic behaviour of this steel during isothermal plastic strain-controlled tests was investigated at room temperature and at 550 °C. Under low-cycle fatigue test this steel shows, after the first few cycles, a pronounced cyclic softening accompanied by microstructural changes such as the decrease of the free dislocation density inside the subgrain. The rate of softening increases with temperature being very pronounced at temperatures above 500 °C. The evolution of the flow stress during cycling was studied by analyzing the so-called “back” and “friction” stresses obtained from the hysteresis loops measured along the entire test. From the analysis of the hysteresis loops and corroborated by electron microscopy observations, it can be concluded that the strong cyclic softening observed is produced by the decrease exhibited by the friction stress. The Taylor coefficient was calculated measuring the evolution of the free dislocation density.

  10. 3D characterization and modeling of low cycle fatigue damage mechanisms at high temperature in a cast aluminum alloy

    International Nuclear Information System (INIS)

    Dezecot, Sebastien; Maurel, Vincent; Buffiere, Jean-Yves; Szmytka, Fabien; Koster, Alain

    2017-01-01

    Synchrotron X-ray tomography was used to monitor damage evolution in three dimensions during in situ Low Cycle Fatigue (LCF) tests at high temperature (250 °C) for an industrial material. The studied material is an AlSi7Cu3Mg aluminum alloy (close to ASTM A319) produced by Lost Foam Casting (LFC), a process which generates coarse microstructures but is nevertheless used for engine parts by the automotive industry. The volume analysis (3D images) has shown that cracks are extremely sensitive to microstructural features: coarse pores and hard particles of the eutectic regions are critical regarding respectively the main crack initiation and the crack growth. Finite Elements (FE) simulations, performed on meshes directly generated from 3D volumes and containing only pores, have revealed that mechanical fields also play a major role on the crack behavior. Initiation sites corresponded to areas of maximum inelastic strain while the crack path was globally correlated to high stress triaxiality and inelastic strain fields.

  11. A low cycle fatigue model for low carbon manganese steel including the effect of dynamic strain aging

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No.29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle [Université Paris Ouest Nanterre La Défense (France); Wang, Qing Yuan; Khan, Muhammad Kashif [Sichuan University, School of Aeronautics and Astronautics, No.29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean–Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320, Chatillon (France)

    2016-01-27

    Carbon–manganese steel A48 (French standards) is used in steam generator pipes of the nuclear power plant where it is subjected to the cyclic thermal load. The Dynamic Strain Aging (DSA) influences the mechanical behavior of the steel in low cycle fatigue (LCF) at favorable temperature and strain rate. The peak stress of A48 steel experiences hardening–softening–hardening (HSH) evolution at 200 °C and 0.4% s{sup −1} strain rate in fatigue loading. In this study, isotropic and kinematic hardening rules with DSA effect have been modified. The HSH evolution of cyclic stress associated with cumulative plastic deformation has also been estimated.

  12. Role of butter layer in low-cycle fatigue behavior of modified 9Cr and CrMoV dissimilar rotor welded joint

    International Nuclear Information System (INIS)

    Wu, Qingjun; Lu, Fenggui; Cui, Haichao; Liu, Xia; Wang, Peng; Tang, Xinhua

    2014-01-01

    Highlights: • Modified 9Cr–CrMoV dissimilar turbine rotor was successfully welded by NG-SAW. • LCF properties of both welded joints were approximate at smaller strain amplitude. • Tempered martensite with amounts of carbides in HAZ contributed to weakest zones. • Matched BL determined LCF properties of whole joint for dissimilar welded rotor. - Abstract: The present work aims at studying the role of butter layer (BL) in low-cycle fatigue (LCF) behavior of modified 9Cr steel and CrMoV steel dissimilar welded joint. The significant difference of the chemical composition of base metals (BMs) makes it a challenge to achieve sound welded joint. Therefore, buttering was considered to obtain a transition layer between the dissimilar steels. The LCF tests of two kinds of specimens without and with butter layer were performed applying strain-controlled cyclic load with different axial strain amplitudes. The test results indicated that the number of cycles at higher strain amplitudes of welded joint without butter layer was greatly higher than that of the joint with butter layer, while the fatigue lifetime to crack initiation (2N f ) became closer to each other at low and middle strain amplitudes. The failure was in the tempered heat affected zone (HAZ) at the CrMoV side for specimens without BL, while the fracture occurred at the tempered HAZ in the BL for specimens with BL. The microstructure details of BM, BL, HAZ and weld metals (WMs) were revealed by optical microscopy (OM). It was found that the tempered martensite was major microstructure for welded joint and much more carbides were observed in tempered HAZ than other parts due to the repeated tempering. Microhardness test indicated a softest zone existing tempered HAZ of BL and also there was a softer zone in tempered HAZ at the CrMoV side due to repeated tempering during welding and post weld heat treatment (PWHT). And scanning electron microscopy (SEM) was applied to observe the fractography. It was

  13. Effect of the Machining Processes on Low Cycle Fatigue Behavior of a Powder Metallurgy Disk

    Science.gov (United States)

    Telesman, J.; Kantzos, P.; Gabb, T. P.; Ghosn, L. J.

    2010-01-01

    A study has been performed to investigate the effect of various machining processes on fatigue life of configured low cycle fatigue specimens machined out of a NASA developed LSHR P/M nickel based disk alloy. Two types of configured specimen geometries were employed in the study. To evaluate a broach machining processes a double notch geometry was used with both notches machined using broach tooling. EDM machined notched specimens of the same configuration were tested for comparison purposes. Honing finishing process was evaluated by using a center hole specimen geometry. Comparison testing was again done using EDM machined specimens of the same geometry. The effect of these machining processes on the resulting surface roughness, residual stress distribution and microstructural damage were characterized and used in attempt to explain the low cycle fatigue results.

  14. Fatigue Life Analysis and Prediction of 316L Stainless Steel Under Low Cycle Fatigue Loading

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Hyeong; Myung, NohJun; Choi, Nak-Sam [Hanyang Univ., Seoul (Korea, Republic of)

    2016-12-15

    In this study, a strain-controlled fatigue test of widely-used 316L stainless steel with excellent corrosion resistance and mechanical properties was conducted, in order to assess its fatigue life. Low cycle fatigue behaviors were analyzed at room temperature, as a function of the strain amplitude and strain ratio. The material was hardened during the initial few cycles, and then was softened during the long post period, until failure occurred. The fatigue life decreased with increasing strain amplitude. Masing behavior in the hysteresis loop was shown under the low strain amplitude, whereas the high strain amplitude caused non-Masing behavior and reduced the mean stress. Low cycle fatigue life prediction based on the cyclic plastic energy dissipation theory, considering Masing and non-Masing effects, showed a good correlation with the experimental results.

  15. Effect of cyclic pre-strain on low cycle fatigue life at middle high temperature

    International Nuclear Information System (INIS)

    Nakane, Motoki; Kanno, Satoshi; Takagi, Yoshio

    2011-01-01

    This study examined the effect of cyclic plastic pre-strain on low cycle fatigue life at middle high temperature to evaluate the structural integrity of the nuclear components introduced plastic strain to the local portion by the large seismic load. The materials selected in this study were austenitic steel (SUS316NG) and ferritic steel (SFVQ1A, STS410: JIS (Japanese Industrial Standards). The low cycle fatigue tests at RT and middle high temperature (300 degrees C) were carried out using cyclic plastic pre-strained materials. The results obtained here show that the damage by the cyclic plastic pre-strain, which is equivalent to usage factor UF=0.2, does not affect the fatigue lives of the materials. In addition, it is confirmed that the estimation based on the usage factor UF can also be useful for the life prediction at 300 degrees C as well as RT. (author)

  16. Monitoring Low-Cycle Fatigue Material-Degradation by Ultrasonic Methods

    Directory of Open Access Journals (Sweden)

    R. Himawan

    2010-08-01

    Full Text Available Any system consisting of structural material often undergoes fatigue, which is caused by dynamic load cycle. As a structural system, nuclear power plant is very likely to have low-cycle fatigue at many of its components. Taking into account the importance of monitoring low-cycle fatigue on structural components to prevent them from getting failure, the authors have conducted a work to monitor material degradation caused by low-cycle fatigue by using ultrasonic method. An alloy of Cu-40Zn was used as a test specimen. Ultrasonic water immersion procedure was employed in this ultrasonic test. The probe used is a focusing type and has frequency as high as 15 MHz. The specimen area tested is in the middle part divided into 14 points × 23 points. The results, which were frequency spectrums, were analyzed using two parameters: frequency spectrum peak intensity and attenuation function gradient. The analysis indicates that peak intensity increases at the beginning of load cycle and then decreases. Meanwhile, gradient of attenuation function is lower at the beginning of fatigue process, and then consistently gets higher. It concludes that low-fatigue material degradation can be monitored by using ultrasonic method.

  17. Effect of grain size on high temperature low-cycle fatigue properties of inconel 617

    International Nuclear Information System (INIS)

    Hattori, Hiroshi; Kitagawa, Masaki; Ohtomo, Akira

    1982-01-01

    The effect of grain size on the high temperature low-cycle fatigue behavior and other material strength properties of Inconel 617 was studied at 1 273 K in air. The strain controlled low-cycle fatigue tests were conducted with a symmetrical (FF type) and an asymmetrical (SF type) strain wave forms. The latter wave form was used for the evaluation of creep-fatigue interaction. The main results obtained in this study are as follows: 1) The tensile strength slightly increased with the increase of the grain diameter. On the other hand, the tensile ductility remarkabley decreased with the increase of the grain diameter. 2) The creep rupture life remarkabley increased with the increase of the grain diameter, especially at the lower stress levels. The effect of grain size on creep ductility has not detailed. 3) The low-cycle fatigue life remarkably decreased with the increase of the grain diameter, especially at the lower strain ranges. 4) The creep-fatigue life was less sensitive to the grain diameter than the fatigue life, because the grain size effects on creep and on fatigue were contrary. It is seemed that the creep-fatigue life is determined by the proportion of the creep and fatigue contribution. 5) The fatigue and creep-fatigue test results have good relations with the tensile and creep ductilities at the test temperature. (author)

  18. Multiaxial low cycle fatigue life under non-proportional loading

    International Nuclear Information System (INIS)

    Itoh, Takamoto; Sakane, Masao; Ohsuga, Kazuki

    2013-01-01

    A simple and clear method of evaluating stress and strain ranges under non-proportional multiaxial loading where principal directions of stress and strain are changed during a cycle is needed for assessing multiaxial fatigue. This paper proposes a simple method of determining the principal stress and strain ranges and the severity of non-proportional loading with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. This study also discusses properties of multiaxial low cycle fatigue lives for various materials fatigued under non-proportional loadings and shows an applicability of a parameter proposed by author for multiaxial low cycle fatigue life evaluation

  19. 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.

  20. The low cycle fatigue factor in the construction of sodium-cooled fast reactors

    International Nuclear Information System (INIS)

    Petrequin, Pierre; Mottot, Michel; Valibus, Louis; Grattier, Georges

    1976-01-01

    The working conditions of fast neutron reactors are such that it is essential to know the resistance of the component steels to low cycle fatigue. The behavior of Z2CND17-13 type austenitic stainless steels and of welds was studied in three laboratories. The steels offer an excellent resistance to low cycle fatigue, in keeping with their good ductility and very strong aptitude for cyclic strain hardening. Increasing the testing temperature from 20 to 600 deg C reduces the resistance to some extent (about an order of magnitude on the number of cycles to failure). Steels possessing improved mechanical properties without loss of ductility show greater fatigue resistance. Welds characterized by an austenitic ferritic structure and a slightly cold-hardened state are less ductile than laminated steels. Their resistance to low cycle fatigue is lower at strong deformations. At high temperature (600 deg C) a reduced test frequency or a pause at each cycle leads to a considerable drop in the number of cycles to failure and the appearance of intergranular cracking [fr

  1. The effect of shot peening on notched low cycle fatigue

    International Nuclear Information System (INIS)

    Soady, K.A.; Mellor, B.G.; Shackleton, J.; Morris, A.; Reed, P.A.S.

    2011-01-01

    Highlights: → Shot peening improves notched component three point bend low cycle fatigue life. → Notch shape does not affect the efficacy of the peening process. → Strain hardening and residual stress effects need separate consideration. → Loading direction residual stresses do not relax under bend load. - Abstract: The improvement in low cycle fatigue life created by shot peening ferritic heat resistant steel was investigated in components of varying geometries based on those found in conventional power station steam turbine blades. It was found that the shape of the component did not affect the efficacy of the shot peening process, which was found to be beneficial even under the high stress amplitude three point bend loads applied. Furthermore, by varying the shot peening process parameters and considering fatigue life it has been shown that the three surface effects of shot peening; roughening, strain hardening and the generation of a compressive residual stress field must be included in remnant life models as physically separate entities. The compressive residual stress field during plane bending low cycle fatigue has been experimentally determined using X-ray diffraction at varying life fractions and found to be retained in a direction parallel to that of loading and to only relax to 80% of its original magnitude in a direction orthogonal to loading. This result, which contributes to the retention of fatigue life improvement in low cycle fatigue conditions, has been discussed in light of the specific stress distribution applied to the components. The ultimate aim of the research is to apply these results in a life assessment methodology which can be used to justify a reduction in the length of scheduled plant overhauls. This will result in significant cost savings for the generating utility.

  2. Identification of low cycle fatigue parameters of high strength low-alloy (HSLA steel at room temperature

    Directory of Open Access Journals (Sweden)

    S. Bulatović

    2014-10-01

    Full Text Available Low cycle fatigue test was performed in ambient atmosphere at room temperature. Cycle loading of material, in case of High strength low-alloy steel, entails modifications of its properties and in this paper is therefore shown behavior of fatigue life using low cycle fatigue parameters. More precisely, crack initiation life of tested specimens was computed using theory of Coffin-Manson relation during the fatigue loading. The geometry of the stabilized hysteresis loop of welded joint HSLA steel, marked as Nionikral 70, is also analyzed. This stabilized hysteresis loop is very important for determination of materials properties.

  3. Effect of temperature on low cycle fatigue behavior of annealed Cu-Cr-Zr-Ti alloy in argon atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Sudarshan Rao, G., E-mail: srgundi@yahoo.co.in [Materials and Mechanical Entity, Vikram Sarabhai Space Center, Trivandrum (India); Srinath, J. [Materials and Mechanical Entity, Vikram Sarabhai Space Center, Trivandrum (India); Ganesh Sundara Raman, S. [Dept of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai (India); Sharma, V.M.J.; Narayana Murthy, S.V.S.; Narayanan, P. Ramesh [Materials and Mechanical Entity, Vikram Sarabhai Space Center, Trivandrum (India); Tharian, K. Thomas [Materials and Manufacturing Entity, Liquid Propulsion Systems Center, Valiamala, Trivandrum (India); Kumar, P. Ram; Venkita Krishnan, P.V. [Materials and Mechanical Entity, Vikram Sarabhai Space Center, Trivandrum (India)

    2017-04-24

    Isothermal low cycle fatigue (LCF) properties of Cu-Cr-Zr-Ti alloy were evaluated at different temperatures (300 °C, 450 °C and 600 °C) in high purity argon atmosphere. The cyclic stress response (CSR) was highly dependent on the test temperature. CSR at 300 °C showed primary hardening and secondary hardening at lower strain amplitudes from 0.25% to 0.8% and primary hardening followed by continuous softening at 1.2% strain amplitude. At 450 °C, the alloy exhibited a higher degree of primary hardening followed by saturation of stress. Transmission electron microscopic observations made on the samples tested upto different number of cycles indicate that precipitation of fine Cr precipitates was the main reason for the secondary hardening at 300 °C and extensive primary hardening at 450 °C. Even though precipitation was assisted by mechanical working during cycling, it is observed that the secondary hardening occurred almost at the same time irrespective of the strain amplitude used in the tests. At 450 °C and higher strain amplitudes, precipitates nucleated at the dislocations within a few initial cycles causing pinning of the dislocations thereby increasing the stress response. CSR at 600 °C showed continuous softening without any hardening. It is found that the precipitates nucleated during heating and soaking at the test temperature itself before the start of the strain cycling and coarsening of precipitates as well as loss of coherency with the matrix caused continuous softening at 600 °C. With an increase in test temperature, a reduction in fatigue life is observed and the life reduction is significant at higher strain amplitudes. Microstructural observations and fractographic studies indicated that cracks initiated predominantly at surface and propagated inward. Intergranular cracking was observed at higher strain amplitudes at all temperatures.

  4. Risk estimation for LCF crack initiation

    OpenAIRE

    Schmitz, Sebastian; Rollmann, Georg; Gottschalk, Hanno; Krause, Rolf

    2013-01-01

    An accurate risk assessment for fatigue damage is of vital importance for the design and service of today's turbomachinery components. We present an approach for quantifying the probability of crack initiation due to surface driven low-cycle fatigue (LCF). This approach is based on the theory of failure-time processes and takes inhomogeneous stress fields and size effects into account. The method has been implemented as a finite-element postprocessor which uses quadrature formulae of higher o...

  5. Effect of high pressure hydrogen on low-cycle fatigue

    International Nuclear Information System (INIS)

    Rie, K.T.; Kohler, W.

    1979-01-01

    It has been shown that the fatigue life can be influenced in low-cycle range by high pressure hydrogen while the effect of high pressure hydrogen on high-cycle fatigue will not be as significant. The paper reports the details and the results of the investigations of the effect of high pressure hydrogen on the low-cycle endurance of commercially pure titanium. The results of this study indicate that: 1. The degradation of the fatigue life in low-cycle region for commercially pure titanium under high pressure hydrogen can be described by Nsub(cr)sup(α x Δepsilon)sub(pl)sup(=c) 2. The fatigue life decreases with decreasing strain rate. 3. The fatigue life decreases with increasing hydrogen pressure. It was found that the semilogarithmic plot of the fatigue life versus the hydrogen pressure gives a linear relationship. The Sievert's law does not hold in low-cycle fatigue region. 4. HAC in titanium in low-cycle fatigue region is the result of the disolution of hydrogen at the crack tip and of the strain-induced hybride formation. (orig.) 891 RW/orig. 892 RKD [de

  6. Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

    International Nuclear Information System (INIS)

    Huang, Zhi Yong; Chaboche, Jean-Louis; Wang, Qing Yuan; Wagner, Danièle; Bathias, Claude

    2014-01-01

    Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C

  7. Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean-Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320 Chatillon (France); Wang, Qing Yuan [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle; Bathias, Claude [Université ParisOuest Nanterre La Défense (France)

    2014-01-01

    Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C.

  8. Low Cycle Fatigue Behavior of Alloy 617 Base Metal and Welded Joints at Room Temperature and 850 .deg. C for VHTR Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seon Jin; Dew, Rando T. [Pukyong National Univ., Busan (Korea, Republic of); Kim, Woo Gon; Kim, Min Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    Low cycle fatigue (LCF) is an important design consideration for high temperature IHX components. Moreover, some of the components are joined by welding techniques and therefore the welded joints are unavoidable in the construction of mechanical structures. Since Alloy 617 was introduced in early 1970s, many attempts have been made in the past two decades to evaluate the LCF and creep-fatigue behavior in Alloy 617 base metal at room temperature and high temperature. However, little research has focused on the evaluation and characterization of the Alloy 617 welded joints. butt-welded joint specimens was performed at room temperature and 850 .deg. C. Fatigue lives of GTAW welded joint specimens were lower than those of base metal specimens. LCF cracking and failure in welded specimens initiated in the weld metal zone and followed transgranluar dendritic paths for both at RT and 850 .deg. C.

  9. Low-cycle fatigue-cracking mechanisms in fcc crystalline materials

    Science.gov (United States)

    Zhang, P.; Qu, S.; Duan, Q. Q.; Wu, S. D.; Li, S. X.; Wang, Z. G.; Zhang, Z. F.

    2011-01-01

    The low-cycle fatigue (LCF) cracking behavior in various face-centered-cubic (fcc) crystalline materials, including Cu single crystals, bicrystals and polycrystals, Cu-Al and Cu-Zn alloys, ultrafine-grained (UFG) Al-Cu and Cu-Zn alloys, was systematically investigated and reviewed. In Cu single crystals, fatigue cracking always nucleates along slip bands and deformation bands. The large-angle grain boundary (GB) becomes the preferential site in bicrystals and polycrystals. In addition, fatigue cracking can also nucleate along slip bands and twin boundaries (TBs) in polycrystalline materials. However, shear bands and coarse deformation bands are observed to the preferential sites for fatigue cracking in UFG materials with a large number of GBs. Based on numerous observations on fatigue-cracking behavior, the fatigue-cracking mechanisms along slip bands, GBs, TBs, shear bands and deformation bands were systematically compared and classified into two types, i.e. shear crack and impingement crack. Finally, these fatigue-cracking behaviors are discussed in depth for a better understanding of their physical nature and the transition from intergranular to transgranular cracking in various fcc crystalline materials. These comprehensive results for fatigue damage mechanisms should significantly aid in obtaining the optimum design to further strengthen and toughen metallic materials in practice.

  10. Low-cycle fatigue of welded joints of alloy AMg5

    International Nuclear Information System (INIS)

    Modestova, R.V.; Borisenko, V.A.; Parfenova, I.N.; Stepanov, S.V.

    1986-01-01

    The authors study the low-cycle fatigue of welded joints of aluminum alloy AMg5 in order to determine the cyclic strength coefficient of welded seams. Tests were carried out on cylindrical specimens of the parent metal, welded specimens, and models of welded vessels. The average values of mechanical properties of the specimens and the parent metal are shown. It is shown that when designing welded vessels of aluminum alloy AMg5, the permissible amplitudes of conventional compressive stresses are recommended to be determined as the lower of the two values calculated using the equations presented

  11. Preliminary tension effect on low-cycle fatigue of 40Kh13 steel in gaseous hydrogen

    International Nuclear Information System (INIS)

    Romaniv, A.N.

    1984-01-01

    Comparative bending tests of specimens deformed by tension at 65, 18 and 30% in hydrogen and vacuum were accomplished to reveal the effect of preliminary tension on low-cycle fatigue strength of 40Kh13 martensitic steel. It was found that small amounts of preliminary strains induced a considerable decrease in low-cycle durability in vacuum and hydrogen which was connected with developing defects arising at the early stages of plastic deformation. A rather high degree of preliminary tension promoted steel homogenization, hydrogen embrittlement decrease and service behaviour improvement

  12. Low-cycle fatigue of sheet elements with ''soft'' surface layer

    International Nuclear Information System (INIS)

    Luk'yanov, V.F.; Kharchenko, V.Ya.; Berezutskij, V.I.; Ovsyannikov, V.G.

    1978-01-01

    Investigated are regularities of low-cycle fatigue of bimetallic sheet constructions made of chrome-nickel-molybdenum steel, plated with a low-alloyed steel with a reduced yield limit. Static repeated bending tests have been carried out using two-layer samples. The surface layer has been shown to increase resistance to nucleation and propagation of cracks under pulsating load if stresses are not more than 2 times higher than the yield limit. Increase in stresses leads to elastoplastic deformation and reduces durability. The positive effect of the surface layer is advisable to be used when welding-up surface defects and strengthening welded joints of high-strength steels

  13. Low cycle fatigue of alloy 718 in cryogenic environment

    International Nuclear Information System (INIS)

    Vergara Aimone, J.

    1989-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Takamoto Itoh

    2015-10-01

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

  15. Modification of creep and low cycle fatigue behaviour induced by welding

    Directory of Open Access Journals (Sweden)

    A. Carofalo

    2014-10-01

    Full Text Available In this work, the mechanical properties of Waspaloy superalloy have been evaluated in case of welded repaired material and compared to base material. Test program considered flat specimens on base and TIG welded material subjected to static, low-cycle fatigue and creep test at different temperatures. Results of uniaxial tensile tests showed that the presence of welded material in the gage length specimen does not have a relevant influence on yield strength and UTS. However, elongation at failure of TIG material was reduced with respect to the base material. Moreover, low-cycle fatigue properties have been determined carrying out tests at different temperature (room temperature RT and 538°C in both base and TIG welded material. Welded material showed an increase of the data scatter and lower fatigue strength, which was anyway not excessive in comparison with base material. During test, all the hysteresis cycles were recorded in order to evaluate the trend of elastic modulus and hysteresis area against the number of cycles. A clear correlation between hysteresis and fatigue life was found. Finally, creep test carried out on a limited number of specimens allowed establishing some changes about the creep rate and time to failure of base and welded material. TIG welded specimen showed a lower time to reach a fixed strain or failure when a low stress level is applied. In all cases, creep behaviour of welded material is characterized by the absence of the tertiary creep.

  16. Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy

    Science.gov (United States)

    Telesman, J.; Gabb, T. P.; Yamada, Y.; Ghosn, L. J.; Jayaraman, N.

    2012-01-01

    A study was conducted to determine the processes which govern dwell notch low cycle fatigue (NLCF) behavior of a powder metallurgy (P/M) ME3 disk superalloy. The emphasis was placed on the environmentally driven mechanisms which may embrittle the highly stressed notch surface regions and reduce NLCF life. In conjunction with the environmentally driven notch surface degradation processes, the visco-plastic driven mechanisms which can significantly change the notch root stresses were also considered. Dwell notch low cycle fatigue testing was performed in air and vacuum on a ME3 P/M disk alloy specimens heat treated using either a fast or a slow cooling rate from the solutioning treatment. It was shown that dwells at the minimum stress typically produced a greater life debit than the dwells applied at the maximum stress, especially for the slow cooled heat treatment. Two different environmentally driven failure mechanisms were identified as the root cause of early crack initiation in the min dwell tests. Both of these failure mechanisms produced mostly a transgranular crack initiation failure mode and yet still resulted in low NLCF fatigue lives. The lack of stress relaxation during the min dwell tests produced higher notch root stresses which caused early crack initiation and premature failure when combined with the environmentally driven surface degradation mechanisms. The importance of environmental degradation mechanisms was further highlighted by vacuum dwell NLCF tests which resulted in considerably longer NLCF lives, especially for the min dwell tests.

  17. Low cycle fatigue of Alloy 690 and welds in a simulated PWR primary water environment

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jongdae; Cho, Pyungyeon; Jang, Changheui [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Cho, Pyungyeon [Khalifa Univ., Abu Dhabi (United Arab Emirates); Kim, Tae Soon; Lee, Yong Sung [Korea Hydro and Nuclear Power Co., Daejeon (Korea, Republic of)

    2013-05-15

    In this study, environmental fatigue tests for these materials were performed and the new prediction model of fatigue life of Alloy 690 and weld in primary water condition was proposed. To evaluate the fatigue life of Alloy 690 and 52M in a PWR environment, low cycle fatigue tests were performed and revised fatigue life prediction models and environmental factor were proposed. With the revised Fen model for Alloy 690 and 52M, the reliability of the fatigue life prediction has been improved. The reduction of low cycle fatigue life of metallic materials in the primary coolant water environments has been the subject of debate between the utility and regulator since 1980s. It became the significant licensing problem since the issue of RG-1.207 by U. S. NRC. The statistical model for the environmental factor, Fen, specified in RG-1.207 was based on the extensive test results accumulated by the ANL and Japanese national program. Of the materials, the limited fatigue life data of Ni-Cr-Fe alloys were used to develop the Fen for the alloys. Furthermore, test data for Alloy 690 and its weld are limited. Considering that Alloy 690 will be extensively used in the new nuclear power plants, additional effort to validate or improve current Fen model is required.

  18. Low cycle fatigue analysis of a last stage steam turbine blade

    Directory of Open Access Journals (Sweden)

    Měšťánek P.

    2008-11-01

    Full Text Available The present paper deals with the low cycle fatigue analysis of the low pressure (LP steam turbine blade. The blade is cyclically loaded by the centrifugal force because of the repeated startups of the turbine. The goal of the research is to develop a technique to assess fatigue life of the blade and to determine the number of startups to the crack initiation. Two approaches were employed. First approach is based on the elastic finite element analysis. Fictive 'elastic' results are recalculated using Neuber's rule and the equivalent energy method. Triaxial state of stress is reduced using von Mises theory. Strain amplitude is calculated employing the cyclic deformation curve. Second approach is based on elastic-plastic FE analysis. Strain amplitude is determined directly from the FE analysis by reducing the triaxial state of strain. Fatigue life was assessed using uniaxial damage parameters. Both approaches are compared and their applicability is discussed. Factors that can influence the fatigue life are introduced. Experimental low cycle fatigue testing is shortly described.

  19. Effect of microstructure on low cycle fatigue properties of ODS steels

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-05-15

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

  20. Life Prediction of Low Cycle Fatigue for Ni-base Superalloy GTD111 DS at Elevated Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Yeol; Yoon, Dong Hyun; Kim, Jae Hoon [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Bae, Si Yeon; Chang, Sung Yong; Chang, Sung Ho [KEPCO Research Institute, Daejeon (Korea, Republic of)

    2017-08-15

    GTD111 DS of nickel base superalloy has been used for gas turbine blades. In this study, low cycle fatigue test was conducted on the GTD111 DS alloy by setting conditions similar to the real operating environment. The low cycle fatigue tests were conducted at room temperature, 760 °C, 870 °C, and various strain amplitudes. Test results showed that fatigue life decreased with increasing total strain amplitude. Cyclic hardening response was observed at room temperature and 760 °C; however, tests conducted at 870 °C showed cyclic softening response. Stress relaxation was observed at 870 °C because creep effects occurred from holding time. A relationship between fatigue life and total strain range was obtained from the Coffin-Manson method. The fratography using a SEM was carried out at the crack initiation and propagation regions.

  1. Low cycle fatigue studies on a type 304 stainless steel

    International Nuclear Information System (INIS)

    Bhanu Sankara Rao, K.; Valsan, M.; Sandhya, R.; Ray, S.K.; Rodriguez, P.

    The effects of temperature and strain rate on the low cycle fatigue behaviour were investigated for an AISI 304 stainless steel under total axial strain control mode at 823 and 923 K. The fatigue life was strongly dependent on cyclic deformation rate for this material at these temperatures, decreasing markedly with decreasing strain rate. The cyclic stress-strain response recorded in the form of hysterisis loops exhibited serrations at low strain rates at 823 and 923 K. Cyclic stress-strain response at 823 K has shown an increase in saturation stress and decrease in plastic strain range whereas there is an increase in plastic strain range without marked variation in saturation stress level at 923 K with decreasing strain rate. It has been observed that there are three simultaneous effects namely environment, creep and cyclic strain ageing which contribute to the observed degradation in fatigue life at low strain rates. At 823 K, where the creep damage as well as environmental damage is relatively small, the fatigue life is considered mainly to be affected by dynamic strain ageing effect which depends on strain rate. At 923 K, on the other hand, the strain rate dependence of fatigue life is considered to be determined by the combination of creep and environmental effects. Deformation and fracture studies have also confirmed that the wedge type crack propagation is accelerated by oxidation effect. (author)

  2. Low cycle fatigue behaviour of zirconium alloys at 3000C

    International Nuclear Information System (INIS)

    Hosbons, R.R.

    1975-01-01

    The low cycle fatigue lives of two zirconium alloys, zirconium-2.5 wt% niobium and zirconium-1.1 wt% chronium-0.1 wt% iron, have been determined at 300 0 C. Both annealed material and cold-worked and stress-relieved material have similar fatigue lives to annealed Zircaloy-2 but β-quenched zirconium-niobium and zirconium-chromium-iron have lower fatigue lives than annealed Zircaloy-2. An atmosphere containing a concentration of iodine lower than that required for stress corrosion cracking still significantly lowers the fatigue life. A mathematical relationship between fatigue life and short-term tensile properties was used to estimate the fatigue life of zirconium alloy fuel sheaths and it was estimated that for a strain cycle of 0.1 per cent a cyclic frequency exceeding 0.116 Hz (10 000 cycles/day) would be required to cause fatigue failure of the sheath before its design life is realized. (author)

  3. Low cycle fatigue behaviour of zirconium alloys at 3000C

    International Nuclear Information System (INIS)

    Hosbons, R.R.

    1975-01-01

    The low cycle fatigue lives of two zirconium alloys, zirconium--2.5 wt percent niobium and zirconium--1.1 wt percent chromium--0.1 wt percent iron, have been determined at 300 0 C. Both annealed material and cold-worked and stress-relieved material have similar fatigue lives to annealed Zircaloy-2 but β-quenched zirconium--niobium and zirconium--chromium--iron have lower fatigue lives than annealed Zircaloy-2. An atmosphere containing a concentration of iodine lower than that required for stress corrosion cracking still significantly lowers the fatigue life. A mathematical relationship between fatigue life and short-term tensile properties was used to estimate the fatigue life of zirconium alloy fuel sheaths and it was estimated that for a strain cycle of 0.1 percent a cyclic frequency exceeding 0.116 Hz (10,000 cycles/ day) would be required to cause fatigue failure of the sheath before its design life is realized

  4. Cyclic mechanical behavior of 316L: Uniaxial LCF and strain-controlled ratcheting tests

    International Nuclear Information System (INIS)

    Facheris, G.; Janssens, K.G.F.

    2013-01-01

    Highlights: ► Characterization of cyclic plastic deformation behavior of plate and tubular 316L. ► Strain-controlled ratcheting response between room temperature and 200 °C. ► Isotropic cyclic hardening is dependent on the yield criterion used. ► Ratcheting induced hardening mostly affects the kinematic hardening component. ► Ratcheting induced hardening is related to the mean strain and the ratcheting rate. -- Abstract: With the purpose of analyzing the fatigue behavior under loading conditions relevant for the primary cooling circuit of a light water nuclear reactor, a set of uniaxial low cycle fatigue and strain-controlled ratcheting tests (also named ‘cyclic tension tests’) has been performed at room temperature and at 200 °C on specimens manufactured from two different batches of stainless steel grade 316L. The experiments have been repeated varying strain amplitude, cyclic ratcheting rate and ratcheting direction in order to investigate the influence on the cyclic deformation behavior. In strain-controlled ratcheting tests, the stress response is found to be a superposition of two hardening mechanisms: the first one due to the zero mean strain cycling and the second one linked with the monotonic drifting of mean plastic strain. An approach is proposed to distinguish the effect of each mechanism and the influence of the test parameters on the hardening mechanisms is discussed

  5. Frequency interpretation of hold-time experiments on high temperature low-cycle fatigue of steels for LMFBR

    International Nuclear Information System (INIS)

    Udoguchi, T.; Asada, Y.; Ichino, I.

    1975-01-01

    The effect of frequency or hold-time on the low-cycle fatigue strength of AISI 316 stainless steel and SCM 3 Cr--Mo steel for fuel cladding, piping, and other structural members of LMFBR is investigated under high temperature conditions. Push-pull fatigue tests are conducted in air under conditions of fully reversed axial strain-control with a tensile strain hold-time ranging fromm 0 to 120 min for AISI 316, and with a tensile and an equal compressive strain hold-time ranging from 0 to 995 s for SCM 3. In these tests, a decrease of fatigue life is observed as the hold-time is increased. An empirical formula is presented which can predict well the effect of hold-time on high temperature low-cycle fatigue life in terms of frequency. The formula is a little different from those in the literature

  6. A frequency interpretation of hold-time experiments on high temperature low-cycle fatigue of steels for LMFBR

    International Nuclear Information System (INIS)

    Udoguchi, T.; Asada, Y.; Ichino, I.

    1975-01-01

    The effect of frequency or hold-time on the low-cycle fatigue strength of AISI 316 stainless steel and SCM 3 Cr-Mo steel for fuel cladding, piping and other structural members of LMFBR is investigated under high temperature conditions. Push-pull fatigue tests are conducted in air under conditions of fully reversed axial strain-control with a tensile strain hold-time ranging from 0 to 120 min for AISI 316, and with a tensile and an equal compressive strain hold-time ranging from 0 to 995 s for SCM 3. In these tests, a considerable decrease of fatigue life is observed as the hold-time is increased. An empirical formula is presented which can predict well the effect of hold-time on high temperature low-cycle fatigue life in terms of frequency. The formula is a little different from those in the literature. (author)

  7. A new lease of life for turbine rotors subject to low-cycle fatigue at elevated temperature

    International Nuclear Information System (INIS)

    Coulon, P.A.; Knosp, B.; Saisse, H.

    1989-01-01

    The purpose of the study was to determine the depth of the zone damaged during fatigue crack initiation at the notch root in a Cr Mo V ferritic steel used for the manufacture of steam turbine rotors. Low cycle fatigue tests were conducted at 500 and 550 0 C (932 0 F and 1022 0 F) and the Manson - Coffin curves have been plotted. The results showed firstly that for Na * = 10,000 cycles (Number of cycles for crack initiation Na = 12,500 cycles) the damaged zone in the test-pieces the authors used corresponded to h ≅0.4 mm, and secondly that this zone had the same order of magnitude as the cyclic plastic zone determined according to the mechanical properties of the material studied. Conclusion is clear: if the turbine rotors are remachined over a depth h greater than ≅0.4 mm, their initial low cycle fatigue properties are considered as largely restored

  8. Texture, microstructure, and fractal features of the low-cycle fatigue failure of the metal in pipeline welded joints

    Science.gov (United States)

    Usov, V. V.; Gopkalo, E. E.; Shkatulyak, N. M.; Gopkalo, A. P.; Cherneva, T. S.

    2015-09-01

    Crystallographic texture and fracture features are studied after low-cycle fatigue tests of laboratory specimens cut from the base metal and the characteristic zones of a welded joint in a pipeline after its longterm operation. The fractal dimensions of fracture surfaces are determined. The fractal dimension is shown to increase during the transition from ductile to quasi-brittle fracture, and a relation between the fractal dimension of a fracture surface and the fatigue life of the specimen is found.

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

    International Nuclear Information System (INIS)

    Kim, S.W.; Tanigawa, H.; Hirose, T.; Kohyama, A.

    2007-01-01

    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

  10. A structural strain method for low-cycle fatigue evaluation of welded components

    International Nuclear Information System (INIS)

    Dong, P.; Pei, X.; Xing, S.; Kim, M.H.

    2014-01-01

    In this paper, a new structural strain method is presented to extend the early structural stress based master S–N curve method to low cycle fatigue regime in which plastic deformation can be significant while an elastic core is still present. The method is formulated by taking advantage of elastically calculated mesh-insensitive structural stresses based on nodal forces available from finite element solutions. The structural strain definition is consistent with classical plate and shell theory in which a linear through-thickness deformation field is assumed a priori in both elastic or elastic–plastic regimes. With considerations of both yield and equilibrium conditions, the resulting structural strains are analytically solved if assuming elastic and perfectly plastic material behavior. The formulation can be readily extended to strain-hardening materials for which structural strains can be numerically calculated with ease. The method is shown effective in correlating low-cycle fatigue test data of various sources documented in the literature into a single narrow scatter band which is remarkable consistent with the scatter band of the existing master S–N curve adopted ASME B and PV Code since 2007. With this new method, some of the inconsistencies of the pseudo-elastic structural stress procedure in 2007 ASME Div 2 Code can now be eliminated, such as its use of Neuber's rule in approximating structural strain beyond yield. More importantly, both low cycle and high cycle fatigue behaviors can now be treated in a unified manner. The earlier mesh-insensitive structural stress based master S–N curve method can now be viewed as an application of the structural strain method in high cycle regime, in which structural strains are linearly related to traction-based structural stresses according to Hooke's law. In low-cycle regime, the structural strain method characterizes fatigue damage directly in terms of structural strains that satisfy linear through

  11. 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

  12. Low cycle fatigue behavior of electron beam and friction welded joints of an α-β titanium alloy

    International Nuclear Information System (INIS)

    Mohandas, T.; Varma, V.K.; Banerjee, D.; Kutumbarao, V.V.

    1996-01-01

    Fusion welds in titanium alloys, with intermediate β stabilizing additions, show poor mechanical properties due to large fusion zone grain size coupled with a brittle plate martensitic microstructure and hydrogen induced microporosity. These problems, associated with fusion welding, have been reported to be overcome by friction welding. The alloy used in this study is a Soviet composition (VT9) of the α-β class with the nominal chemical composition Ti-6.5Al-3.3Mo-1.6Zr-0.3 Si (in weight percent), intended to be used as discs and blades in compressor stages of gas turbine engine where low cycle fatigue (LCF) loading is experienced. Electron beam welding of the alloy was largely unsuccessful for the reasons described above. Fatigue properties of such welds had large scatter due to the presence of microporosity. A continuous drive friction welding technique was investigated to overcome this problem These welds showed encouraging results in that microporosity, a problem in the electron beam welding, was not observed and the mechanical properties were at par or better than those of the base metal. This paper deals with the study of stress controlled LCF behavior of friction welds and electron beam welds of the α-β titanium alloy at ambient temperature and the results are compared with those of base metal

  13. 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.

  14. Influence of the crystalline orientations on microcrack initiation in low-cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Mu, P. [Univ Lille Nord de France, F-59000 Lille (France); ECLille, LML, F-59650 Villeneuve d’Ascq (France); CNRS, UMR 8107, UMR 8579 (France); Aubin, V., E-mail: veronique.aubin@ecp.fr [ECP, MSSMat, F-92295 Châtenay-Malabry (France); CNRS, UMR 8107, UMR 8579 (France); Alvarez-Armas, I.; Armas, A. [IFIR, CONICET, Universidad Nacional de Rosario (Argentina)

    2013-06-20

    Present study aims at analyzing the crack initiation in an austenitic stainless steel in low-cycle fatigue. A fatigue test was carried out using a polished specimen. The surface of the specimen was observed in situ during the fatigue test, in order to establish the time of slip activity or crack initiation. After a number of cycles sufficient to initiate small cracks, the test was stopped and the surface observed by scanning electron microscopy. The electron backscattered diffraction technique (EBSD) was used to identify the orientations of surface grains in the central zone of the fatigue specimen. Crack-initiation sites and slip systems associated to the initiated microcracks were identified. The criterion of the maximum Schmid factor explains two-thirds of the cracks initiated in slip systems; however if the favorably oriented slip band with respect to this criterion makes an angle of around 45° to the loading direction, a crack may initiate in another slip system.

  15. Benefits of high gradient solidification for creep and low cycle fatigue of AM1 single crystal superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Steuer, S., E-mail: Susanne.Steuer@ensma.fr [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Villechaise, P. [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Pollock, T.M. [Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106-5050 (United States); Cormier, J. [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France)

    2015-10-01

    The influence of high thermal gradient processing on the creep and low cycle fatigue properties of the AM1 Ni-based single crystal superalloy has been studied. Isothermal creep (from 750 °C up to 1200 °C) and low cycle fatigue (750 °C and 950 °C) experiments were performed for AM1 alloy solidified with a conventional radiation cooled (Bridgman) and higher thermal gradient liquid-metal cooled (LMC) casting process to produce coarse and finer-scaled dendritic structures, respectively. There was no significant effect of the casting technique on creep properties, due to the very similar microstructures (γ′-size and γ-channel width) established after full heat treatment of both Bridgman and LMC samples. For low cycle fatigue properties, the benefit of the higher gradient LMC process was dependent on the testing temperature. At 750 °C, cracks primarily initiated at pores created by solidification shrinkage in both Bridgman and LMC samples. Samples produced by the LMC technique demonstrated fatigue lives up to 4 times longer, compared to the Bridgman samples, due to refined porosity. At 950 °C the low cycle fatigue properties of the LMC and conventionally solidified material were not distinguishable due to a shift of crack initiation sites from internal pores to oxidized surface layers or near-surface pores. The benefit of the LMC approach was, however, apparent in fatigue at 950 °C when testing in a vacuum environment. Based on these results, a crack initiation model based on the local slip activity close to casting defect is proposed.

  16. Low Cycle Fatigue Behavior of Alloy617 Weldment at 850°C

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Jeong Jun; Kim, Seon Jin [Pukyong Nat’l Univ., Busan (Korea, Republic of); Kim, Woo Gon; Kim, Eung-Seon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-03-15

    Alloy 617 is one of the primary candidate materials to be used in a very high temperature reactor (VHTR) system as an intermediate heat exchanger (IHX). To investigate the low cycle fatigue behavior of Alloy 617 weldments at a high temperature of 850℃, fully reversed strain-controlled fatigue tests were conducted with the total strain values ranging from 0.6~1.5%. The weldment specimens were machined using the weld pads fabricated with a single V-grove configuration by gas tungsten arc welding (GTAW) process. The fatigue life is reduced as the total strain range increases. For all testing conditions, the cyclic stress response behavior of the Alloy 617 weldments exhibited the initial cyclic strain hardening phenomenon during the initial small number of cycles. Furthermore, the overall fatigue cracking and the propagation or cracks showed a transgranular failure mode.

  17. High temperature low cycle fatigue behavior of Ni-base superalloy M963

    International Nuclear Information System (INIS)

    He, L.Z.; Zheng, Q.; Sun, X.F.; Guan, H.R.; Hu, Z.Q.; Tieu, A.K.; Lu, C.; Zhu, H.T.

    2005-01-01

    The cyclic stress-strain response and the low cycle fatigue life behavior of solution treated Ni-base superalloy M963 were studied. Fully reversed strain-controlled tests were performed at temperature range from 700 to 950 deg. C in air at a constant total strain rate. The dislocation characteristics and failed surface observation were evaluated through scanning electron microscopy and transmission electron microscopy, respectively. The alloy exhibited the cyclic hardening, softening, or stable cyclic stress response, which was dependent on the temperature and total strain range. The fracture surface observation revealed that fatigue crack initiation was transgranular and closely related to the total strain range; however, fatigue crack propagation exhibited a strong dependence on testing temperature. The dramatic reduction in fatigue life and intergranular cracking observed at 900 and 950 deg. C were attributed to oxidation

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-06

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

  19. Sensitivity Variation on Low Cycle Fatigue Cracks Using Level 4/Method B Penetrant

    Energy Technology Data Exchange (ETDEWEB)

    FULWOOD,HARRY; MOORE,DAVID G.

    1999-09-02

    The Federal Aviation Administration's Airworthiness Assurance NDI Validation Center (AANC) is currently conducting experiments with Level 4, Method B penetrant on low cycle fatigue specimens. The main focus of these experiments is to document the affect on penetrant brightness readings by varying inspection parameters. This paper discusses the results of changing drying temperature, drying time, and dwell time of both penetrant and emulsifier on low cycle fatigue specimens.

  20. Microstructural aspects of crack formation and propagation in the austenitic steel X6CrNiNb18-10 under low cycle fatigue loading

    International Nuclear Information System (INIS)

    Soppa, E.; Kohler, C.; Roos, E.; Schuler, X.

    2012-01-01

    The understanding of the crack initiation mechanisms and crack growth in apparently monolithic materials like X6CrNiNb18-10 stainless steel under cyclic loading requires the explicit analysis of the phenomena underlying fatigue on both atomistic and microscopic levels. The permanent delivery of mechanical energy through cyclic loading evokes changes in the microstructure that can lead to a martensitic transformation. The transformation of a metastable cubic face centered austenite and formation of a cubic body centered α'-martensite under cyclic loading at room temperature was found, both, in the experiment and in molecular dynamics simulations. The martensite nucleates prevalently at grain boundaries, triple points and at the specimen free surface and forms small (∝ 1 μm) differently oriented grains, also in the same parent austenitic grain. By a combination of interrupted low cycle fatigue tests (LCF) and electron backscatter diffraction (EBSD) measurements the martensitic transformation and subsequent fatigue crack formation were observed at the same area in the microstructure at different stages of the specimen lifetime. The EBSD measurements showed the following crack initiation scenarios: Cracks started (a) at the phase boundary between austenite and α'-martensite, (b) inside fully martensitic areas in the matrix, (c) at broken or debonded coarse NbCs. It is obvious that formation of a hard α'-martensite in a ductile and soft austenite and forming two-phase material causes a heterogeneous stress and strain distribution on the microscopic level. α'-martensite enhances locally the stress amplitude whereas in a soft austenite the plastic strain amplitude increases. Strain concentration in the austenite along the phase boundary is connected with a stress increase along the interface and can initiate fatigue crack there. Also at the crack tip, a permanent martensitic transformation occurs, so that the growth of the fatigue cracks at room temperature seems

  1. Microstructural aspects of crack formation and propagation in the austenitic steel X6CrNiNb18-10 under low cycle fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Soppa, E.; Kohler, C.; Roos, E.; Schuler, X. [Stuttgart Univ. (Germany). MPA

    2012-07-01

    The understanding of the crack initiation mechanisms and crack growth in apparently monolithic materials like X6CrNiNb18-10 stainless steel under cyclic loading requires the explicit analysis of the phenomena underlying fatigue on both atomistic and microscopic levels. The permanent delivery of mechanical energy through cyclic loading evokes changes in the microstructure that can lead to a martensitic transformation. The transformation of a metastable cubic face centered austenite and formation of a cubic body centered α'-martensite under cyclic loading at room temperature was found, both, in the experiment and in molecular dynamics simulations. The martensite nucleates prevalently at grain boundaries, triple points and at the specimen free surface and forms small (∝ 1 μm) differently oriented grains, also in the same parent austenitic grain. By a combination of interrupted low cycle fatigue tests (LCF) and electron backscatter diffraction (EBSD) measurements the martensitic transformation and subsequent fatigue crack formation were observed at the same area in the microstructure at different stages of the specimen lifetime. The EBSD measurements showed the following crack initiation scenarios: Cracks started (a) at the phase boundary between austenite and α'-martensite, (b) inside fully martensitic areas in the matrix, (c) at broken or debonded coarse NbCs. It is obvious that formation of a hard α'-martensite in a ductile and soft austenite and forming two-phase material causes a heterogeneous stress and strain distribution on the microscopic level. α'-martensite enhances locally the stress amplitude whereas in a soft austenite the plastic strain amplitude increases. Strain concentration in the austenite along the phase boundary is connected with a stress increase along the interface and can initiate fatigue crack there. Also at the crack tip, a permanent martensitic transformation occurs, so that the growth of the fatigue cracks at room

  2. The Effects of LCF Loadings on HCF Crack Growth

    National Research Council Canada - National Science Library

    Hall, R

    1999-01-01

    .... In this phase, the contractor will begin by collating and reviewing all data relating to threshold values and combined high and low cycle fatigue testing on forged material previously developed...

  3. Strain-controlled low cycle fatigue properties of a rare-earth containing ME20 magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Mirza, F.A., E-mail: f4mirza@ryerson.ca [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Wang, K.; Bhole, S.D.; Friedman, J.; Chen, D.L. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Ni, D.R.; Xiao, B.L. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Ma, Z.Y., E-mail: zyma@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2016-04-20

    The present study was aimed to evaluate the strain-controlled cyclic deformation characteristics and low cycle fatigue (LCF) life of a low (~0.3 wt%) Ce-containing ME20-H112 magnesium alloy. The alloy contained equiaxed grains with ellipsoidal particles containing Mg and Ce (Mg{sub 12}Ce), and exhibited a relatively weak basal texture. Unlike the high rare earth (RE)-containing magnesium alloy, the ME20M-H112 alloy exhibited asymmetrical hysteresis loops somewhat similar to the RE-free extruded Mg alloys due to the presence of twinning-detwinning activities during cyclic deformation. While cyclic stabilization was barely achieved even at the lower strain amplitudes, cyclic softening was the predominant characteristics at most strain amplitudes. The ME20M-H112 alloy showed basically an equivalent fatigue life to that of the RE-free extruded Mg alloys, which could be described by the Coffin-Manson law and Basquin's equation. Fatigue crack was observed to initiate from the near-surface imperfections, and in contrast to the typical fatigue striations, the present alloy showed some shallow dimples along with some fractions of quasi-cleavage features in the crack propagation area.

  4. 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)

  5. Effect of weld metal toughness on fracture behavior under ultra-low cycle fatigue loading (earthquake)

    Energy Technology Data Exchange (ETDEWEB)

    Kermajani, M. [School of Materials Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Ghaini, F. Malek, E-mail: Fmalek@modares.ac.ir [School of Materials Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Miresmaeili, R. [School of Materials Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Aghakouchak, A.A. [School of Civil Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Shadmand, M. [Department of Research and Development, MAPNA Electric and Control (MECO) Company, Karaj (Iran, Islamic Republic of)

    2016-06-21

    Results from 12 ultra-low cycle fatigue tests performed on the weld metals of both toughness and non-toughness rated grades are presented. Fracture resistance under these loadings seemed to be dependent on materials' toughness, displacement amplitude, and stress state triaxiality, while the toughness effect was more highlighted at high stress levels and concentrations. To study the effect of microstructures on these failures, supporting ancillary tests including all-weld tension coupons, Charpy V-notched impact tests, and optical and scanning electron microscope analyses were performed. The favored microstructures appeared to be those which absorbed energy by plastic deformation and, hence, hindered void formation and/or could avoid crack propagation by deflection. Considering the response of the tested materials to cyclic loadings and the requirements of the materials specified in AISC341 Provisions could question the adequacy of these requirements for weld metals. However, the role of microstructural features like inclusions would be the same in both the Charpy impact tests and ultra-low cycle loadings.

  6. Study on low cycle fatigue behavior of two titanium alloy materials with elevated temperature effects

    International Nuclear Information System (INIS)

    Cai Lixun; Sun Yafang; Wang Li; Huang Shuzhen

    2000-01-01

    A serial of tensional and low cycle fatigue tests for two titanium alloy materials:T42NG and T225NG under room temperature and 350 degree C elevated temperature are carried out. Based on the test results, four monotonic constitutive relationships between stress and strain and four relationships between life Nf and strain amplitude controlled are given. By three ratio λ σ , λ Δσ and λ Nf of the materials related to the elevated temperature, systematical investigations about the influence of the elevated temperature on monotonic tensional intensity, cyclic intensity and fatigue life are performed. According to the important rule opened out that it exists a linearity relationship between the ratio λ Nf and strain amplitude Δε/2, the author present a λ-M-C model for predicting the fatigue life of a exponential material under R= -1 and an elevated temperature. To get the λ-M-C model, the authors give available discussion about the method simplified test and regression. The authors know from test results that T42NG steel has better fatigue and tensional behaviors than those of T225NG steel

  7. Effect of alloying composition on low-cycle fatigue properties and microstructure of Fe–30Mn–(6−x)Si–xAl TRIP/TWIP alloys

    Energy Technology Data Exchange (ETDEWEB)

    Nikulin, Ilya, E-mail: nikulin.i.a@gmail.com [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Belgorod State University, Pobeda 85, Belgorod 308015 (Russian Federation); Sawaguchi, Takahiro [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Tsuzaki, Kaneaki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)

    2013-12-10

    The change in low-cycle fatigue (LCF) properties and deformation microstructure due to the alteration of aluminum and silicon contents was studied in relation with the tensile properties in Fe–30Mn–(6−x)Si–xAl (x=0, 1, 2, 3, 4, 5, 6 wt%) alloys, which are high-Mn austenitic TRIP/TWIP alloys. Austenite to ε-martensite transformation took place during LCF deformation in the TRIP alloys with x≤2 while mechanical twinning was not observed by electron-backscattering diffraction (EBSD) analysis in the TWIP alloys with x>2 after LCF deformation. The fatigue resistance of the alloys was shown to be correlated with the tensile proof strength and the hardening rate. Superior fatigue life of 8×10{sup 3} cycles at a total strain range Δε=2% was found in the Fe–30Mn–4Si–2Al TRIP alloy with a low fraction of ε-martensite, high tensile proof strength and low hardening rate at both tensile and fatigue deformations. On the other hand, a considerable decrease in the fatigue properties was observed in the alloys with decreasing proof strength and increasing hardening rate. Proof strength provided by the solid solution of Al and Si, represents the hampering of plastic deformation, and the hardening rate reflects the strain reversibility affected by the stacking fault energy (SFE) through the rate of austenite to martensite transformation in the TRIP alloys and the substructure formation in the TWIP alloys.

  8. Effects of environment on the low-cycle fatigue behavior of Type 304 stainless steel

    International Nuclear Information System (INIS)

    Maiya, P.S.; Burke, W.F.

    1979-12-01

    The low-cycle fatigue behavior of Type 304 stainless steel has been investigated at 593 0 C in a dynamic vacuum of better than 1.3 x 10 -6 Pa (10 -8 torr). The results concerning the effects of strain range, strain rate and tensile hold time on fatigue life are presented and compared with results of similar tests performed in air and sodium environments. Under continuous symmetrical cycling, fatigue life is significantly longer in vacuum than in air; in the low strain range regime, the effect of sodium on fatigue life appears to be similar to that of vacuum. Strain rate (or frequency) strongly influences fatigue life in both air and vacuum. In compressive hold-time tests, the effect of environment on life is similar to that in a continuous-cycling test. However, tensile hold times are nearly as damaging in vacuum as in air. Thus, at least for austenitic stainless steels, the influence of the environment of fatigue life appears to depend on the loading waveshape

  9. Low-cycle fatigue behavior of HT-9 alloy in a flowing-lithium environment

    International Nuclear Information System (INIS)

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

    1983-06-01

    Low-cycle fatigue data have been obtained on normalized/tempered or lithium-preexposed HT-9 alloy at 755 K in flowing lithium of controlled purity. The results show that the fatigue life of this material decreases with an increase in nitrogen content in lithium. A reduction in strain rate also decreases the fatigue life in high-nitrogen lithium. However, in the range from approx. 4 x 10 - 4 to 4 x 10 - 2 s - 1 , the strain rate has no effect on fatigue life in lithium containing <200 wppM nitrogen. The fatigue life of the HT-9 alloy in low-nitrogen lithium is significantly greater than the fatigue life of Fe-9Cr-1Mo steel or Type 403 martensitic steel in air. Furthermore, a 4.0-Ms preexposure to low-nitrogen lithium has no influence on fatigue life. The reduction in fatigue life in high-nitrogen lithium is attributed to internal corrosive attack of the material. The specimens tested in high-nitrogen lithium show internal corrosion along grain and martensitic lathe boundaries and intergranular fracture. This behavior is not observed in specimens tested in low-nitrogen lithium. Results for a constant-load corrosion test in flowing lithium are also presented

  10. New aspects about reduced LCF-life time of spherical ductile cast iron due to dynamic strain aging at intermediate temperatures

    International Nuclear Information System (INIS)

    Mouri, Hayato; Wunderlich, Wilfried; Hayashi, Morihito

    2009-01-01

    Spherical ductile cast iron (FCD400) is widely used as container material in nuclear energy processing line due to its superior mechanical properties and low price. Fatigue properties in low cycle fatigue (LCF) can be described well by the Manson-Coffin-Basquin's rule. However, at intermediate temperature range between 453 and 723 K the elongation-temperature-diagram shows a significantly 20-10% reduced elongation and an increase in yield stress in tensile test experiments. These non-linear deviations and the phenomenon of less ductility at intermediate temperatures are known for a long time [K. Chijiiwa, M. Hayashi, Mechanical properties of ductile cast iron at temperature in the region of room temperature to liquid, Imono 51 (7) (2004) 395-400]. But the following explanation is presented for the first time. In the same temperature range as the reduced fatigue life time dynamic strain ageing (DSA) also known as Portevin-le-Chartelier effect with the formation of visible serrations occurs. Both phenomena are explained by interaction effects between carbon diffusion and dislocation velocity which have at this temperature the same order of magnitude. However, this phenomenon shows interesting behavior at intermediate temperature range. During the low cycle fatigue test, DSA phenomenon disappeared, but mechanical properties show clear evidence of DSA phenomenon. Therefore, the purpose of this paper is to study the correlation of DSA occurrence, LCF and mechanical properties.

  11. Effects of microstructures on low cycle fatigue behavior in Al-Si-Mg cast alloys

    International Nuclear Information System (INIS)

    Han, Sang Won; Kim, Sug Won

    2002-01-01

    Low cycle fatigue tests were carried out using four kinds of Al-7%Si-0.4Mg cast alloys, i.e., two kinds of sand mold casts, permanent mold cast and semi-solid die cast. They were heat-treated in the condition of under aging and over aging to investigate effects of precipitates on fatigue. All tests were conducted under axial plastic strain amplitude control. Stress level of cyclic hardening curves increased sensitively with needle like eutectic Si particle, refine grain size and dendrite arm spacing (DAS). In particular, the refined grain structure of under aged matrix was more effective encourager for cyclic hardening compared with DAS and eutectic Si particle size. After rapid increase in cyclic hardening during several number of cycles, the stress amplitude kept increasing steadily until fracture in under aged alloys strengthened by shearable G.P. zone. On the other hand, over aged alloys strengthened by non-shearable β ' precipitates generated more drastic initial hardening and the stress amplitude reached the saturation state in quite early stage of the fatigue

  12. Effect of cyclic plastic pre-strain on low cycle fatigue life

    International Nuclear Information System (INIS)

    Kanno, Satoshi; Nakane, Motoki; Yorikawa, Morio; Takagi, Yoshio

    2010-01-01

    In order to evaluate structural integrity of nuclear components subjected large seismic load which produce locally plastic strain, low cycle fatigue life was examined using cyclic plastic pre-strained materials of austenitic steel (SUS316, SUS316L, SUS304TP: JIS (Japanese Industrial Standards)) and ferritic steel (SFVQ1A, STS480, STPT410, SFVC2B, SS400: JIS). It was not found that cyclic plastic pre-strain up to range of 16%, 2.5 times affected on low cycle fatigue life. The validity of existing procedure of fatigue life estimation based on usage factor was confirmed when large seismic load brought nuclear materials cyclic plastic strain. (author)

  13. Low-cycle fatigue deformation characteristics of Haynes {reg{underscore}sign} HR-120{reg{underscore}sign} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, P.K.; He, Y.H.; Miller, L.; Huang, M.; Brooks, C.R.; Seeley, R.R.; Klarstrom, D.L.

    1999-07-01

    Low-cycle fatigue deformation characteristics of HAYNES HR-120 alloy at room and high temperatures were studied under axial strain control. Test results show that there is a significant effect of test temperature on the low-cycle fatigue behavior of HAYNES HR-120 alloy. It was found that the alloy could cyclically harden at moderately high temperatures (649 C and 871 C), but generally cyclically soften at room temperature (24 C) and high temperature (982 C). However, the variation of the stress amplitude with cycles at the temperatures of 24 C and 982 C depended on the total strain range. The significant cyclic hardening of the alloy occurred at the high total strain ranges of 1.5% and 2.0% during the beginning state of the test at both 24C and 982 C. Microstructural analyses indicated that the cyclic hardening behavior of the alloy at the test temperature of 649 C could be related to the formation of a number of deformation bands. Nevertheless, increasing the test temperature to 871 C, cyclic hardening was attributed to the precipitation of secondary-phase particles. Furthermore, it was also found that the coarsening of secondary-phase particles brought about cyclic softening of the alloy at the high temperature of 982 C. Coffin-Manson equations and Holloman equations were given for HAYNES HR-120 alloy at different temperatures.

  14. In situ observation of high temperature tensile deformation and low cycle fatigue response in a nickel-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xudong, E-mail: lxdong0700@hotmail.com; Du, Jinhui; Deng, Qun

    2013-12-20

    High temperature tension and low cycle fatigue experiments of IN718 alloy have been performed in the electro-hydraulic servo system with scanning electron microscope at 455 °C. Fatigue crack initiation and propagation process are investigated in situ. Results show that the carbide and twin grain are the crack source of the low cycle fatigue of IN718 alloy, and the low cycle fatigue life of the alloy increases with the decrease in grain size.

  15. Low cycle fatigue behavior in a medium-carbon carbide-free bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kang, J. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, F.C., E-mail: zfc@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Long, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Lv, B. [College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2016-06-01

    In the paper, different morphologies of bainite were obtained through isothermal quenching at 320 °C and 395 °C in a medium-carbon carbide-free bainitic steel. The cyclic deformation mechanism was explored by using low cycle fatigue testing. The volume fraction of retained austenite was measured by X-ray diffraction and the space partitioning of the solute atoms was constructed by three-dimensional atom probe. Results showed that the fatigue life at 320 °C was always higher than that at 395 °C under low and high total strain amplitude. The cyclic softening at the early fatigue stage increased the plastic strain of the sample which was responsible for the reduction of the fatigue life at 395 °C. Strain-induced retained austenite to martensite contributed to initial cyclic hardening, but almost having no effect on the subsequent cyclic stable/softening behaviors. The finer bainitic ferrite sheaves obtained at 320 °C changed the small fatigue crack propagation direction and delayed the crack propagation rate, which was beneficial for the fatigue properties. In addition, the substitutional atoms did not redistribute between the retained austenite and bainitic ferrite before and after cyclic deformation.

  16. Influence of temperature on a low-cycle fatigue behavior of a ferritic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, S. M. Humayun [Chittagong University of Engineering and Technology, Chittagong (Bangladesh); Yeo, Tae in [University of Ulsan, Ulsan (Korea, Republic of)

    2014-07-15

    The main objective of this study is to reveal the effect of dynamic strain ageing (DSA) on a ferritic stainless steel with detail relation to monotonic and cyclic responses over a wide range of temperatures. For assessing the effect of strain rate on mechanical properties, tensile test results are studied at two different strain rates of 2X10{sup -3} /s and 2X10{sup -4} /s. Typical responses of this material are compared with other alloy in literatures that exhibits DSA. Serrations in monotonic stress-strain curves and anomalous dependence of tensile properties with temperatures are attributed to the DSA effect. The low cycle fatigue curves exhibit prominent hardening and negative temperature dependence of half-life plastic strain amplitude in temperatures between 300 .deg. C - 500 .deg. C which can be explained by DSA phenomenon. The regime for dependence of marked cyclic hardening lies within the DSA regime of anomalous dependence of flow stress and dynamic strain hardening stress with temperature and negative strain rate sensitivity regime of monotonic response. It is believed that shortened fatigue life observed in the intermediate temperature is mainly due to the adverse effect of DSA. An empirical life prediction model is addressed for as-received material to consider the effect of temperature on fatigue life. The numbers of load reversals obtained from experiment and predicted from fatigue parameter are compared and found to be in good agreement.

  17. Evaluation of notch effects in low cycle fatigue of alloy 718 using critical distances

    Directory of Open Access Journals (Sweden)

    Eriksson Robert

    2018-01-01

    Full Text Available Gas turbine disks contain many notch-like features acting as stress raisers. The fatigue life based on the notch root stress may be overly conservative as the steep stress gradient in front of the notch may give rise to so-called notch support. In the current work, the theory of critical distances was applied to the prediction of the total fatigue life of low cycle fatigued, notched specimens made from alloy 718. The fatigue tests were performed at 450 °C and 550 °C. It was found that, for lives shorter than 5000–10000 cycles, the notched specimens had longer lives than would have been expected based on the notch root strain. For lives longer than 5000–10000 cycles, there were no notch support. The life prediction for notched specimens could be significantly improved by basing the prediction on the strain chosen some distance from the notch (the critical distance. An expression for calculating the critical distance based on the notch root strain was suggested.

  18. Environmental degradation of 316 stainless steel in high temperature low cycle fatigue

    Science.gov (United States)

    Kalluri, Sreeramesh; Manson, S. Stanford; Halford, Gary R.

    1987-01-01

    Procedures based on modification of the conventional Strainrange Partitioning method are proposed to characterize the time-dependent degradation of engineering alloys in high-temperature, low-cycle fatigue. Creep-fatigue experiments were conducted in air using different waveforms of loading on 316 stainless steel at 816 C (1500 F) to determine the effect of exposure time on cyclic life. Reductions in the partitioned cyclic lives were observed with an increase in the time of exposure (or with the corresponding decrease in the steady-state creep rate) for all the waveforms involving creep strain. Excellent correlations of the experimental data were obtained by modifying the Conventional Strainrange Partitioning life relationships involving creep strain using a power-law term of either: (1) time of exposure, or (2) steady-state creep rate of the creep-fatigue test. Environmental degradation due to oxidation, material degradation due to the precipitation of carbides along the grain boundaries and detrimental deformation modes associated with the prolonged periods of creep were observed to be the main mechanisms responsible for life reductions at long exposure times.

  19. Influence of temperature on a low-cycle fatigue behavior of a ferritic stainless steel

    International Nuclear Information System (INIS)

    Kabir, S. M. Humayun; Yeo, Tae in

    2014-01-01

    The main objective of this study is to reveal the effect of dynamic strain ageing (DSA) on a ferritic stainless steel with detail relation to monotonic and cyclic responses over a wide range of temperatures. For assessing the effect of strain rate on mechanical properties, tensile test results are studied at two different strain rates of 2X10"-"3 /s and 2X10"-"4 /s. Typical responses of this material are compared with other alloy in literatures that exhibits DSA. Serrations in monotonic stress-strain curves and anomalous dependence of tensile properties with temperatures are attributed to the DSA effect. The low cycle fatigue curves exhibit prominent hardening and negative temperature dependence of half-life plastic strain amplitude in temperatures between 300 .deg. C - 500 .deg. C which can be explained by DSA phenomenon. The regime for dependence of marked cyclic hardening lies within the DSA regime of anomalous dependence of flow stress and dynamic strain hardening stress with temperature and negative strain rate sensitivity regime of monotonic response. It is believed that shortened fatigue life observed in the intermediate temperature is mainly due to the adverse effect of DSA. An empirical life prediction model is addressed for as-received material to consider the effect of temperature on fatigue life. The numbers of load reversals obtained from experiment and predicted from fatigue parameter are compared and found to be in good agreement.

  20. Effect of HIP temperature on microstructure and low cycle fatigue strength of CuCrZr alloy

    Science.gov (United States)

    Nishi, Hiroshi; Enoeda, Mikio

    2011-10-01

    In order to investigate the effect of the HIP cycle temperatures on the metallurgic degradation and the mechanical properties of CuCrZr alloy, assessments of the microstructure, tensile test, Charpy impact test and low cycle fatigue test are performed for various heat treated CuCrZr alloys, which were solution-annealed followed by water-quenched and aged state of CuCrZr with simulated HIP cycle at temperatures of 980 and 1045 °C. Grain growth occurred on 1045 °C HIP CuCrZr, though slightly on 980 °C HIP CuCrZr. Metallurgic degradation such as voids was not found by optical and SEM observations. There were coarse precipitates in all the CuCrZr and the precipitates did not easily dissolve at 980 °C. The low cycle fatigue strength of 1045 °C HIP CuCrZr was lower than that of other CuCrZr because of the metallurgic degradation caused by the heat cycle, while that of other CuCrZr was corresponding to the best fit curve of ITER MPH.

  1. Effect of HIP temperature on microstructure and low cycle fatigue strength of CuCrZr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nishi, Hiroshi, E-mail: nishi.hiroshi88@jaea.go.jp [Japan Atomic Energy Agency, Naka-shi, Ibaraki-ken 311-0193 (Japan); Enoeda, Mikio [Japan Atomic Energy Agency, Naka-shi, Ibaraki-ken 311-0193 (Japan)

    2011-10-01

    In order to investigate the effect of the HIP cycle temperatures on the metallurgic degradation and the mechanical properties of CuCrZr alloy, assessments of the microstructure, tensile test, Charpy impact test and low cycle fatigue test are performed for various heat treated CuCrZr alloys, which were solution-annealed followed by water-quenched and aged state of CuCrZr with simulated HIP cycle at temperatures of 980 and 1045 deg. C. Grain growth occurred on 1045 deg. C HIP CuCrZr, though slightly on 980 deg. C HIP CuCrZr. Metallurgic degradation such as voids was not found by optical and SEM observations. There were coarse precipitates in all the CuCrZr and the precipitates did not easily dissolve at 980 deg. C. The low cycle fatigue strength of 1045 deg. C HIP CuCrZr was lower than that of other CuCrZr because of the metallurgic degradation caused by the heat cycle, while that of other CuCrZr was corresponding to the best fit curve of ITER MPH.

  2. Effect of HIP temperature on microstructure and low cycle fatigue strength of CuCrZr alloy

    International Nuclear Information System (INIS)

    Nishi, Hiroshi; Enoeda, Mikio

    2011-01-01

    In order to investigate the effect of the HIP cycle temperatures on the metallurgic degradation and the mechanical properties of CuCrZr alloy, assessments of the microstructure, tensile test, Charpy impact test and low cycle fatigue test are performed for various heat treated CuCrZr alloys, which were solution-annealed followed by water-quenched and aged state of CuCrZr with simulated HIP cycle at temperatures of 980 and 1045 deg. C. Grain growth occurred on 1045 deg. C HIP CuCrZr, though slightly on 980 deg. C HIP CuCrZr. Metallurgic degradation such as voids was not found by optical and SEM observations. There were coarse precipitates in all the CuCrZr and the precipitates did not easily dissolve at 980 deg. C. The low cycle fatigue strength of 1045 deg. C HIP CuCrZr was lower than that of other CuCrZr because of the metallurgic degradation caused by the heat cycle, while that of other CuCrZr was corresponding to the best fit curve of ITER MPH.

  3. Effect of tensile holds on the deformation behaviour of a nickel base superalloy subjected to low cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Zrnik, J.; Semenak, J.; Wangyao, P.; Vrchovinsky, V.; Hornak, P. [Dept. of Materials Science, Technical Univ. of Kosice, Kosice (Slovakia)

    2002-07-01

    The deformation behaviour of the wrought nickel base superalloy EI698 VD has been investigated in conditions of low cycle fatigue. The tensile hold periods, imposing a constant stress into the fatigue loading, have been introduced at the maximum stress value. The individual hold periods were in the range of 1 minute to 10 hours. The fatigue tests were of tension-tension type defined by a stress ratio R = 0.027 and were conducted at temperature of 650 C. The tests were performed until fracture. The time to failure, the time to failure corresponding to total load at peak amplitude and the number of cycles to failure have been criteria to evaluate the deformation behaviour of the alloy subjected to complex cyclic creep loading. In order to predict lifetime of alloy, regarding the respective types cyclic test, the Kitagawa's modified the linear cumulative damage criterion has been considered. The two regression functions for applied hold period interval were proposed time to calculate the time to failure. The formulae can be used to predict the life of nickel base superalloy considering the specific conditions of low cycle fatigue with tensile hold period introduced at stress amplitude peaks. The failure analysis of fracture surfaces contributed to evaluation of the role of repeatedly reduced stress in damage process. (orig.)

  4. Low-cycle fatigue and cyclic deformation behavior of Type 16-8-2 weld metal at elevated temperature

    International Nuclear Information System (INIS)

    Raske, D.T.

    1977-01-01

    The low-cycle fatigue behavior of Type 16-8-2 stainless steel ASA weld metal at 593 0 C was investigated, and the results are compared with existing data for Type 316 stainless steel base metal. Tests were conducted under axial strain control and at a constant axial strain rate of 4 x 10 -3 s -1 for continuous cyclic loadings as well as hold times at peak tensile strain. Uniform-gauge specimens were machined longitudinally from the surface and root areas of 25.4-mm-thick welded plate and tested in the as-welded condition. Results indicate that the low-cycle fatigue resistance of this weld metal is somewhat better than that of the base metal for continuous-cycling conditions and significantly better for tension hold-time tests. This is attributed to the fine duplex delta ferrite-austenite microstructure in the weld metal. The initial monotonic tensile properties and the cyclic stress-strain behavior of this material were also determined. Because the cyclic changes in mechanical properties are strain-history dependent, a unique cyclic stress-strain curve does not exist for this material

  5. Uniaxial low cycle fatigue behavior for pre-corroded 16MND5 bainitic steel in simulated pressurized water reactor environment

    Science.gov (United States)

    Chen, Xu; Ren, Bin; Yu, Dunji; Xu, Bin; Zhang, Zhe; Chen, Gang

    2018-06-01

    The effects of uniaxial tension properties and low cycle fatigue behavior of 16MND5 bainitic steel cylinder pre-corroded in simulated pressurized water reactor (PWR) were investigated by fatigue at room temperature in air and immersion test system, scanning electron microscopy (SEM), energy disperse spectroscopy (EDS). The experimental results indicated that the corrosion fatigue lives of 16MND5 specimen were significantly affected by the strain amplitude and simulated PWR environments. The compositions of corrosion products were complexly formed in simulated PWR environments. The porous corrosion surface of pre-corroded materials tended to generate pits as a result of promoting contact area to the fresh metal, which promoted crack initiation. For original materials, the fatigue cracks initiated at inclusions imbedded in the micro-cracks. Moreover, the simulated PWR environments degraded the mechanical properties and low cycle fatigue behavior of 16MND5 specimens remarkably. Pre-corrosion of 16MND5 specimen mainly affected the plastic term of the Coffin-Manson equation.

  6. Life prediction for high temperature low cycle fatigue of two kinds of titanium alloys based on exponential function

    Science.gov (United States)

    Mu, G. Y.; Mi, X. Z.; Wang, F.

    2018-01-01

    The high temperature low cycle fatigue tests of TC4 titanium alloy and TC11 titanium alloy are carried out under strain controlled. The relationships between cyclic stress-life and strain-life are analyzed. The high temperature low cycle fatigue life prediction model of two kinds of titanium alloys is established by using Manson-Coffin method. The relationship between failure inverse number and plastic strain range presents nonlinear in the double logarithmic coordinates. Manson-Coffin method assumes that they have linear relation. Therefore, there is bound to be a certain prediction error by using the Manson-Coffin method. In order to solve this problem, a new method based on exponential function is proposed. The results show that the fatigue life of the two kinds of titanium alloys can be predicted accurately and effectively by using these two methods. Prediction accuracy is within ±1.83 times scatter zone. The life prediction capability of new methods based on exponential function proves more effective and accurate than Manson-Coffin method for two kinds of titanium alloys. The new method based on exponential function can give better fatigue life prediction results with the smaller standard deviation and scatter zone than Manson-Coffin method. The life prediction results of two methods for TC4 titanium alloy prove better than TC11 titanium alloy.

  7. Damage and failure modeling of lotus-type porous material subjected to low-cycle fatigue

    Directory of Open Access Journals (Sweden)

    J. Kramberger

    2016-01-01

    Full Text Available The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications. This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle. Degradation of the elastic stifness was modeled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation.

  8. Low Cycle Fatigue of Steel in Strain Controled Cyclic Bending

    Directory of Open Access Journals (Sweden)

    Kulesa Anna

    2016-03-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-10-01

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

  10. Low cycle fatigue behaviors of low alloy steels in 310 .deg. C deoxygenated water

    International Nuclear Information System (INIS)

    Jang, Hun

    2008-02-01

    After low cycle fatigue tests of SA508 Gr.1a low alloy steel in 310 .deg. C deoxygenated water, the fatigue surface and the sectioned area of specimens were observed to understand the effect of the cyclic strain rate on the environmentally assisted cracking behaviors. From the fatigue crack morphologies of the specimen tested at a strain rate of 0.008 %/s, unclear ductile striations and blunt crack tip were observed. So, metal dissolution could be the main cracking mechanism of the material at the strain rate. On the other hand, on the fatigue surface of the specimen tested at strain rates of 0.04 and 0.4 %/s, the brittle cracks and the flat facets, which are the evidence of the hydrogen induced cracking, were observed. Also, the tendency of linkage between the main crack and micro-cracks was observed on the sectioned area. Therefore, the main cracking mechanism at the strain rates of 0.04 and 0.4 %/s could be the hydrogen induced cracking. Additionally, the evidence of the dissolved MnS inclusions was observed on the fatigue surface from energy dispersive x-ray spectrometer analyses. So, despite of the low sulfur content of the test material, the sulfides seem to contribute to environmentally assisted cracking of SA508 Gr.1a low alloy steel in 310 .deg. C deoxygenated water. Additionally, our experimental fatigue life data of SA508 Gr.1a low alloy steel (heat A) showed a consistent difference with statistical model produced in argon national laboratory. So, additional low cycle fatigue tests of other heat SA508 Gr.1a (heat B) and SA508 Gr.3 low alloy steels were performed to investigate the effect of material variability on fatigue behaviors of low alloy steels in 310 .deg. C deoxygenated water. In results, the fatigue lives of three low alloy steels were increased following order: SA508 Gr.1a low alloy steel - heat A, SA508 Gr.3 low alloy steel, and SA508 Gr.1a low alloy steel - heat B. From microstructure observation, the fatigue surface of SA508 Gr.1a low alloy

  11. Study of crack initiation in low-cycle fatigue of an austenitic stainless steel

    International Nuclear Information System (INIS)

    Mu, P.

    2011-03-01

    The material studied is an austenitic stainless steel, that is widely used in nuclear equipment for its very high corrosion resistance combined to good mechanical properties. Although crack initiation is proved to play an important role in fatigue, its mechanisms have not been fully understood. Some crack initiation criteria based on physical mechanisms of plastic deformation have been defined. However, these criteria are not easy to use and valid, as they need local variables at the grain scale. The present study aims at establishing a crack initiation criterion in low-cycle fatigue, which should be usable under variable amplitude loading conditions. Tension-compression fatigue tests were first carried out to characterize the mechanical behavior of the stainless steel AISI 316L. The mechanical behavior was simulated using a self-consistent model using a crystalline plastic law based on dislocation densities. The evolution of surface damage was observed during a fatigue test using an in situ optical microscopic device. Cracks were analyzed after 2000 cycles and their crystallographic characteristics calculated. As surface grains exhibit larger strain because they are less constraint by neighbor grains, a specific numerical frame is necessary to determine stress state in surface grains. A localization law specific to surface grains under cyclic loading was identified from finite element simulations. The proposed form needs an intergranular accommodation variable, on the pattern of the localization law of Cailletaud-Pilvin. Stress-strain state in surface grains was simulated. Potential indicators for crack initiation were then compared on a same experimental data base. Indicators based on the equivalent plastic strain were found to be suitable indicators of fatigue damage. (author)

  12. Oxide-assisted crack growth in hold-time low-cycle-fatigue of single-crystal superalloys

    Directory of Open Access Journals (Sweden)

    Suzuki Akane

    2014-01-01

    Full Text Available Compressive hold-time low-cycle fatigue is one of the important damage modes in Ni-based superalloy hot-gas path components. In strain controlled LCF, the compressive hold typically degrades fatigue life significantly due to creep relaxation and the resultant generation of tensile stress upon returning to zero strain. Crack initiation typically occurs on the surface, and therefore, the cracks are covered with layers of oxides. Recent finite element modeling based on experimental observations has indicated that the in-plane compressive stress in the alumina layer formed on the surface of the bond coat assists rumpling and, eventually, leads to initiation of cracks. The stress in the oxide layer continues to assist crack extension by pushing the alumina layer along the crack front during the compressive hold. In-situ measurements of the growth strains of alumina were performed using high energy synchrotron X-rays at Argonne National Lab. Specimens of single-crystal superalloys with and without aluminide coatings were statically pre-oxidized to form a layer of alumina at 1093 and 982 ∘C. For the in-situ synchrotron measurements, the specimens were heated up to the pre-oxidation temperatures with a heater. The alumina layers on both bare and coated specimens show compressive in-plane strains at both temperatures. The oxide strains on the superalloys showed dependency on temperature; on the other hand, the oxide strains in the aluminide coatings were insensitive to temperature. The magnitude of the compressive strains was larger on the superalloys than the ones on the aluminide coatings.

  13. Low-cycle fatigue of dissimilar friction stir welded aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, R.I. [The University of Alabama, Department of Mechanical Engineering, Tuscaloosa, AL 35487 (United States); Jordon, J.B., E-mail: bjordon@eng.ua.edu [The University of Alabama, Department of Mechanical Engineering, Tuscaloosa, AL 35487 (United States); Allison, P.G. [The University of Alabama, Department of Mechanical Engineering, Tuscaloosa, AL 35487 (United States); Rushing, T.; Garcia, L. [Engineering Research and Development Center, Army Corps of Engineers, Vicksburg, MS 39180 (United States)

    2016-01-27

    In this work, experiments were conducted to quantify structure-property relations of low-cycle fatigue behavior of dissimilar friction stir welding (FSW) of AA6061-to-AA7050 high strength aluminum alloys. In addition, a microstructure-sensitive fatigue model is employed to further elucidate cause-effect relationships. Experimental strain-controlled fatigue testing revealed an increase in the cyclic strain hardening and the number-of cycles to failure as the tool rotational speed was increased. At higher applied strain amplitudes (>0.3%), the corresponding stress amplitude increased and the plastic strain amplitude decreased, as the number of cycles increased. However, at 0.2% strain amplitude, the plastic strain decreased until it was almost negligible. Inspection of the hysteresis loops demonstrated that at low strain amplitudes, there was an initial stage of strain hardening that increased until it reached a maximum strain hardening level, afterwards a nearly perfect elastic behavior was observed. Under fully-reversed fatigue loading, all samples failed at the region between the heat-affected and thermomechanically-affected zones. Inspection of the fractured surfaces under scanning electron microscopy revealed that the cracks initiated at either the crown or the root surface of the weld, and from secondary intermetallic particles located near the free surface of the weld. Lastly, a microstructure-sensitive multistage fatigue model was employed to correlate the fatigue life of the dissimilar FSW of AA6061-to-AA7050 considering microstructural features such as grain size, intermetallic particles and mechanical properties.

  14. Effect of microstructure on elevated temperature LCF behaviour of nimonic PE16 superalloy

    International Nuclear Information System (INIS)

    Valsan, M.; Bhanu Sankara Rao, K.; Mannan, S.L.

    1989-01-01

    The influence of microstructure on elevated temperature low cycle fatigue (LCF) behaviour of Nimonic PE16 superalloy has been studied. Samples with the following three different prior microstructures were chosen for testing: (A) a fine grain structure, free from carbides and γ'(1313K/4h); (B) microstructure with intra and intergranular M 23 C 6 and uniform distribution of spherical and peak aged γ' of 18 nm diameter (1313K/4h + 1073K/2h + 973K/16h); and (C) microstructure with predominantly intergranular MC and uniform distribution of coarse γ' of 35 nm diameter (1313K/4h+1173K/1h+1023K/8h). Total strain controlled LCF tests were carried out on all the three microstructures at 823 and 923K and at a constant strain rate of 3.2x10 -3 s -1 over strain amplitudes ranging from ±0.25 ±1.00 per cent. (author). 54 refs., 17 figs., 3 tabs

  15. High-temperature low cycle fatigue behavior of a gray cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Fan, K.L., E-mail: 12klfan@tongji.edu.cn; He, G.Q.; She, M.; Liu, X.S.; Lu, Q.; Yang, Y.; Tian, D.D.; Shen, Y.

    2014-12-15

    The strain controlled low cycle fatigue properties of the studied gray cast iron for engine cylinder blocks were investigated. At the same total strain amplitude, the low cycle fatigue life of the studied material at 523 K was higher than that at 423 K. The fatigue behavior of the studied material was characterized as cyclic softening at any given total strain amplitude (0.12%–0.24%), which was attributed to fatigue crack initiation and propagation. Moreover, this material exhibited asymmetric hysteresis loops due to the presence of the graphite lamellas. Transmission electron microscopy analysis suggested that cyclic softening was also caused by the interactions of dislocations at 423 K, such as cell structure in ferrite, whereas cyclic softening was related to subgrain boundaries and dislocation climbing at 523 K. Micro-analysis of specimen fracture appearance was conducted in order to obtain the fracture characteristics and crack paths for different strain amplitudes. It showed that the higher the temperature, the rougher the crack face of the examined gray cast iron at the same total strain amplitude. Additionally, the microcracks were readily blunted during growth inside the pearlite matrix at 423 K, whereas the microcracks could easily pass through pearlite matrix along with deflection at 523 K. The results of fatigue experiments consistently showed that fatigue damage for the studied material at 423 K was lower than that at 523 K under any given total strain amplitude. - Highlights: • The low cycle fatigue behavior of the HT250 for engine cylinder blocks was investigated. • TEM investigations were conducted to explain the cyclic deformation response. • The low cycle fatigue cracks of HT250 GCI were studied by SEM. • The fatigue life of the examined material at 523 K is higher than that at 423 K.

  16. Effect of microstructure on low cycle fatigue properties of ODS steels

    Czech Academy of Sciences Publication Activity Database

    Kuběna, Ivo; Fournier, B.; Kruml, Tomáš

    2012-01-01

    Roč. 424, 1-3 (2012), s. 101-108 ISSN 0022-3115 R&D Projects: GA ČR GA106/09/1954; GA MŠk(CZ) ED1.1.00/02.0068 Institutional research plan: CEZ:AV0Z20410507 Keywords : ODS steels * low cycle fatigue * fusion energy Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.211, year: 2012

  17. Comparison of low cycle fatigue of ductile cast irons with different matrix alloyed with nickel

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Tesařová, H.; Beran, Přemysl; Šmíd, Miroslav; Roupcová, Pavla

    2010-01-01

    Roč. 2, č. 1 (2010), s. 2307-2316 E-ISSN 1877-7058. [ Fatigue 2010. Praha, 06.06.2010-11.06.2010] R&D Projects: GA ČR GAP108/10/2371 Institutional research plan: CEZ:AV0Z20410507; CEZ:AV0Z10480505 Keywords : Low cycle fatigue * ferritic ductile cast iron * ADI * nickel alloying * neutron diffraction Subject RIV: JL - Materials Fatigue , Friction Mechanics

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

    International Nuclear Information System (INIS)

    Kamaya, Masayuki; Kawakubo, Masahiro

    2012-01-01

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

  19. Low-cycle fatigue behaviors of pre-hardening Hadfield steel

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chen [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Lv, Bo [College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Wang, Fei [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, Fucheng, E-mail: zfc@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004 (China)

    2017-05-17

    Low-cycle fatigue behaviors of the pre-hardening (PH) and the water-quenching (WQ) Hadfield steel were studied using optical microscopy, transmission electron microscopy, and electron backscatter diffraction technique. The effect of the PH treatment on low-cycle fatigue behavior of the Hadfield steel was analyzed through comparing the cyclic hardening/softening behaviors and the changing regulations of stress amplitude, internal stress, and effective stress at different total strain amplitudes. Results showed obvious differences in fatigue behaviors between the PH (with a cold rolling deformation degree of 40%) and the WQ Hadfield steels. Transient hardening followed by cyclic stability behavior occurred in the PH Hadfield steel under cyclic loading, whereas cyclic softening behavior was barely observed. The fatigue life of the PH Hadfield steel was higher than that of the WQ Hadfield steel at relatively low strain amplitudes, while a contrary result was obtained at relatively high strain amplitudes. At low strain amplitudes, the deformation twins induced in the PH Hadfield steel could enhance the multiplication and slip process of dislocations, which actually improved the deformation uniformity. The long-range motion of dislocations was intensified at high strain amplitudes. However, the dislocation motion was also blocked by twin boundaries. As a result, the interactions between dislocations and deformation twins enhanced, finally causing severe dislocation accumulation. These two effects of deformation twins on dislocation motion eventually resulted in different low-cycle fatigue behaviors of the PH Hadfield steel.

  20. Low-cycle fatigue properties of SUS304 stainless steel in high-temperature sodium

    International Nuclear Information System (INIS)

    Hirano, M.; Komine, R.; Kitao, K.; Nihei, I.; Yoshitoshi, A.

    Low-cycle fatigue tests in sodium and in air have been performed to investigate the influence of a high-temperature sodium environment on the strain-controlled fatigue behaviour for SUS304 stainless steel. The oxygen concentration in sodium was 2.4 ppm at the cold trap temperature of 145 deg. C. Tests in both environments were conducted at 450 deg. C, 550 deg. C and 650 deg. C at a constant strain rate of 1x10 -3 /sec with a fully-reversed triangular waveform and a zero mean strain. The fatigue life of SUS304 stainless steel in sodium at 450 deg. C, 550 deg. C and 650 deg. C was greater than those in air at the same temperature except at higher strain range (>0.8%) at 650 deg. C, and this difference had a tendency to increase as the total strain range decreases. At the higher total strain range at 650 deg. C, there was no marked difference between both environments. As the temperature increased, the fatigue life in sodium and in air decreased, and the Nsub(f sodium)/Nsub(f air) ratio also decreased. Microscopic examination of specimens tested in sodium and in air at 450 deg. C, 550 deg. C and 650 deg. C revealed no difference in the microstructure, but few surface cracks were observed on specimens tested in sodium than in those tested in air. Fractography of specimens tested in air at 450 deg. C, 550 deg. C and 650 deg. C revealed well-defined striations. But, in sodium, striations on specimens tested at 450 deg. C and 550 deg. C showed obscure configuration and it was difficult to find out, whereas, at 650 deg. C in sodium intergranular fracture was observed. The specimens tested in sodium had a longer fatigue life than those tested in air because the latter are subjected to considerable oxidation, while the former are free of such chemical action. Accordingly, it is concluded that crack initiation and propagation are more likely to occur in air than in sodium. (author)

  1. Low cycle fatigue behavior of polycrystalline NiAl at 300 and 1000 K

    Science.gov (United States)

    Lerch, Bradley A.; Noebe, Ronald D.

    1993-01-01

    The low cycle fatigue behavior of polycrystalline NiAl was determined at 300 and 1000 K - temperatures below and above the brittle- to-ductile transition temperature (BDTT). Fully reversed, plastic strain-controlled fatigue tests were conducted on two differently fabricated alloy samples: hot isostatically pressed (HIP'ed) prealloyed powder and hot extruded castings. HIP'ed powder (HP) samples were tested only at 1000 K, whereas the more ductile cast-and-extruded (C+E) NiAl samples were tested at both 1000 and 300 K. Plastic strain ranges of 0.06 to 0.2 percent were used. The C+E NiAl cyclically hardened until fracture, reaching stress levels approximately 60 percent greater than the ultimate tensile strength of the alloy. Compared on a strain basis, NiAl had a much longer fatigue life than other B2 ordered compounds in which fracture initiated at processing-related defects. These defects controlled fatigue life at 300 K, with fracture occurring rapidly once a critical stress level was reached. At 1000 K, above the BDTT, both the C+E and HP samples cyclically softened during most of the fatigue tests in air and were insensitive to processing defects. The processing method did not have a major effect on fatigue life; the lives of the HP samples were about a factor of three shorter than the C+E NiAl, but this was attributed to the lower stress response of the C+E material. The C+E NiAl underwent dynamic grain growth, whereas the HP material maintained a constant grain size during testing. In both materials, fatigue life was controlled by intergranular cavitation and creep processes, which led to fatigue crack growth that was primarily intergranular in nature. Final fracture by overload was transgranular in nature. Also, HP samples tested in vacuum had a life three times longer than their counterparts tested in air and, in contrast to those tested in air, hardened continuously over half of the sample life, thereby indicating an environmentally assisted fatigue damage

  2. Experimental study on kinematic hardening of 1Cr18Ni9Ti stainless steel under low cycle fatigue

    International Nuclear Information System (INIS)

    Shao Er; Yang Xianjie; Mao Jianghui; Sun Yafang

    2006-01-01

    To study the effect of the monotonic loading on subsequent cyclic plastic hardening and flow properties of 1Cr18Ni9Ti steel, an experimental study of the low cycle fatigue tests with mean strains for 1Cr18Ni9Ti stainless steel was carried out. An analysis on the evolutions of the yield surface radius and the back stresses under symmetric and asymmetric cyclic strain loading with different strain amplitudes was made. The dependence of the evolutions of the material kinematic hardening and isotropic hardening on the strain amplitude and mean strain was observed. These results provide the experimental foundation for the constitutive model of the material under combined monotonic and cyclic complicated loads. (authors)

  3. Low cycle fatigue numerical estimation of a high pressure turbine disc for the AL-31F jet engine

    Directory of Open Access Journals (Sweden)

    Spodniak Miroslav

    2017-01-01

    Full Text Available This article deals with the description of an approximate numerical estimation approach of a low cycle fatigue of a high pressure turbine disc for the AL-31F turbofan jet engine. The numerical estimation is based on the finite element method carried out in the SolidWorks software. The low cycle fatigue assessment of a high pressure turbine disc was carried out on the basis of dimensional, shape and material disc characteristics, which are available for the particular high pressure engine turbine. The method described here enables relatively fast setting of economically feasible low cycle fatigue of the assessed high pressure turbine disc using a commercially available software. The numerical estimation of accuracy of a low cycle fatigue depends on the accuracy of required input data for the particular investigated object.

  4. Environmental aspects on LCF-life of Ni-base superalloys during long term operation; Miljoeinverkan paa LCF-egenskaper vid laanga drifttider hos superlegeringar

    Energy Technology Data Exchange (ETDEWEB)

    Moverare, Johan; Leijon, Gunnar; Palmert, Frans

    2012-02-15

    The applicability of fine grain polycrystalline nickel base superalloys in gas or steam turbine applications is often limited by their susceptibility to fast intergranular cracking during fatigue in combination with extended hold times at high temperatures and high tensile stresses. This effect is further enhanced in corrosive environments even at moderate temperatures such as 400-600 deg In this study the negative effect of SO{sub 2} + water vapour on the low cycle fatigue resistance of three different nickel based superalloys (Nimonic 901, Inconel 718 and 718 plus) has been studied at 450 deg and 550 deg. A negative effect was found on both the crack initiation and crack propagation process. The effect increases with increasing temperature and is likely to be influenced by both the chemical composition and the grain size of the material. The negative effect of water vapour + SO{sub 2} is manifested by a decreased resistance to cyclic plastic deformation and a transition from transcrystalline to intercrystalline fracture behaviour. In Nimonic 901 this negative effect increases with the degree of plastic deformation. For lower mechanical strain amplitudes where the number of cycles and the total exposure time is increased the environmental impact is reduced. Similar trends can also be noticed for the other alloys. The surface corrosion in air and in SO{sub 2} + water vapour are found to be rather similar in this study and it is therefore concluded that the surface scale can remain adherent and protective if the strains on the oxide scale are low. However, for LCF tests with higher strain ranges, the oxide scale will rupture preferably at the grain boundaries and intergranular microcracks will initiate which promotes inward diffusion of embritteling elements such as oxygen and sulphur. Inconel 718 seems to be more sensitive to SO{sub 2} + water vapour than Nimonic 901 when tested at 450. The overall resistance to LCF is however still higher in Inconel 718 for the

  5. Model-experiment dialog in low cycle fatigue of stainless steels

    International Nuclear Information System (INIS)

    Aubin, Veronique

    2008-01-01

    In this HDR report (accreditation to supervise research), the author first proposes a synthesis of her research activities in the study of the mechanical behaviour in low cycle fatigue (cyclic hardening, plasticity surfaces), of modelling of the fatigue mechanical behaviour (phenomenological modelling, modelling with scale change), of progressive deformation (experimental analysis, analysis and simulation of plasticity at the microstructure scale). The second part addresses other activities in the field of research (behaviour and damage characterization of an austenitic-ferritic stainless steel), publication and education supervising, teaching

  6. Life estimation of low-cycle fatigue of pipe elbows. Proposed criteria of low-cycle fatigue life under the multi-axial stress field

    International Nuclear Information System (INIS)

    Ando, Kotoji; Takahashi, Koji; Matsuo, Kazuya; Urabe, Yoshio

    2013-01-01

    Pipe elbows were important parts frequently used in the pipelines of nuclear power, thermal power and chemical plants, and their integrity needed to be assured under seismic loads and thermal stresses considering local wall thinning or complex stress distribution due to special configuration different from straight pipe. This article investigated in details elastic-plastic stress-strain state of pipe elbow using finite element analysis and clarified there existed high bi-axial stress field at side inner surface of pipe elbow axial cracks initiated. Bi-axial stress factor was around 0.6 for sound elbow and up to 0.95 for local wall thinning at crown. Fracture strain of 1.15 was reduced to around 0.15 for bi-axial stress factor from 0.6 to 0.9. Normalized fatigue life for bi-axial stress field (0.6 - 0.8) was largely reduced to around 15, 19 and 10% of fatigue life of uni-axial state dependent on material strength level. Proposed revised universal slopes taking account of multi-axial stress factor could explain qualitatively effects of strain range, internal pressure and ratchet strain (pre-strain) on low-cycle fatigue life of pipe elbow. (T. Tanaka)

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

    Directory of Open Access Journals (Sweden)

    Wu Wei

    2013-11-01

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

  8. Current state of low-cycle fatigue research based on multiaxial stress intensity and its challenges. Part 1. Focusing on low-cycle fatigue strength evaluation method of elbow piping subjected to in-plane cyclic bending displacement load

    International Nuclear Information System (INIS)

    Urabe, Yoshio

    2017-01-01

    The R and D of fatigue strength at multiaxial stress intensity is recognized to become extremely important in the future in terms of the elaboration of low-cycle fatigue evaluation of various structures including piping systems and reflection on those standards. This paper focuses on the evaluation method developed by the author, namely cumulative damage rule in consideration of multiaxial stress intensity, and explains the concept and the results of verification and evaluation. It also discusses the engineering problems of the current low cycle fatigue assessment technology that were clarified in the process of developing low-cycle fatigue assessment method based on multiaxial stress intensity. The conservative lifespan and somewhat more conservative actual lifetime of elbow piping can be estimated by the conventional 'revised universal slope method' and 'advanced revised universal slope method.' However, these are empirical rules, and the theoretical basis is not clear. From 'cumulative damage rule in consideration of multiaxial stress intensity,' the author calculated furthermore 'low cycle fatigue evaluation formula based on cumulative damage rule in consideration of multi-axial stress intensity,' and examined it. As a result, an evaluation formula that can reasonably assume the equivalent thermoplastic strain range could be obtained at half of the repeat count as targeted. Furthermore, at the stage where future high precision FEM analysis can be used, direct low-cycle fatigue life curve can be established. (A.O.)

  9. Influence of sodium on the low-cycle fatigue behavior of types 304 and 316 stainless steel

    International Nuclear Information System (INIS)

    Smith, D.L.; Zeman, G.J.; Natesan, K.; Kassner, T.F.

    1976-01-01

    Fatigue tests in sodium were conducted to investigate the influence of a high-temperature sodium environment on the low-cycle fatigue behavior of Types 304 and 316 stainless steel. The effects of testing in a sodium environment as well as long-term sodium exposure were investigated. The fatigue tests were conducted at 600 and 700 0 C in sodium of controlled purity, viz., approximately 1 ppM oxygen and 0.4 ppM carbon, at a strain rate of 4 x 10 -3 s -1 . The fatigue life of annealed Type 316 stainless steel is substantially greater in sodium than when tested in air; however, the fatigue life of annealed Type 304 stainless steel is altered much less when tested in sodium. A 1512-h preexposure to sodium had no significant effect on the fatigue life of Type 316 stainless steel tested in sodium. However, a similar exposure substantially increased the fatigue life of Type 304 stainless steel in sodium. 10 fig

  10. The role of crystallographic texture on load reversal and low cycle fatigue performance of commercially pure titanium

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Subhasis; Gurao, N.P., E-mail: npgurao@iitk.ac.in

    2017-04-13

    Microstructural and textural design of hexagonal close packed titanium is of paramount importance for in-service applications comprising of monotonic and cyclic loading. The effect of initial texture on load reversal and low cycle fatigue behaviour of commercially pure titanium was investigated using servohydraulic testing, electron back scatter diffraction (EBSD) and in situ experiments. Uniaxial tensile test on sample A with prismatic texture along the tensile axis showed lower yield strength but higher ductility and twin activity with multiple variants compared to orientation B with basal texture along the tensile axis. Tension-compression load reversal tests show distinct Bauschinger co-efficient for samples A and B at different strain while displacement control cyclic tests yield higher fatigue life for sample B. Higher extent of detwinning in sample B during load reversal in cyclic test releases the backstress and contributes to higher cyclic ductility. In situ EBSD experiments provide evidence of partial reversibility of twinned microstructure in titanium, which explains the formation of thin, small twins during cyclic deformation and rationalizes the difference in monotonic and cyclic ductility. Thus multiple twin variants with intersecting twins contribute to higher strain hardening and ductility in monotonic tension but cyclic life depends on the extent of detwinning.

  11. A procedure to generate input data of cyclic softening and hardening for FEM analysis from constant strain amplitude fatigue tests in LCF regime

    International Nuclear Information System (INIS)

    Sarajaervi, U.; Cronvall, O.

    2007-03-01

    Fatigue is produced by cyclic application of stresses by mechanical or thermal loading. The metal subjected to fluctuating stress will fail at stresses much lower than those required to cause fracture in a single application of load. The key parameters are the range of stress variation and the number of its occurrences. Low-cycle fatigue, usually induced by mechanical and thermal loads, is distinguished from high-cycle fatigue, mainly associated with vibration or high number of small thermal fluctuations. Numerical models describing fatigue behaviour of austenitic stainless piping steels under cyclic loading and their applicability for modelling of low-cycle-fatigue are discussed in this report. In order to describe the cyclic behaviour of the material for analysis with finite element method (FEM) based analysis code ABAQUS, the test data, i.e. stress-strain curves, have to be processed. A code to process the data all through the test duration was developed within this study. A description of this code is given also in this report. Input data for ABAQUS was obtained to describe both kinematic and isotropic hardening properties. Further, by combining the result data for various strain amplitudes a mathematic expression was be created which allows defining a parameter surface for cyclic (i.e. isotropic) hardening. Input data for any strain amplitude within the range of minimum and maximum strain amplitudes of the test data can be assessed with the help of the developed 3D stress-strain surface presentation. The modelling of the fatigue induced initiation and growth of cracks was not considered in this study. On the other hand, a considerable part of the fatigue life of nuclear power plant (NPP) piping components is spent in the phase preceding the initiation and growth of cracks. (au)

  12. A procedure to generate input data of cyclic softening and hardening for FEM analysis from constant strain amplitude fatigue tests in LCF regime

    Energy Technology Data Exchange (ETDEWEB)

    Sarajaervi, U.; Cronvall, O. [VTT (Finland)

    2007-03-15

    Fatigue is produced by cyclic application of stresses by mechanical or thermal loading. The metal subjected to fluctuating stress will fail at stresses much lower than those required to cause fracture in a single application of load. The key parameters are the range of stress variation and the number of its occurrences. Low-cycle fatigue, usually induced by mechanical and thermal loads, is distinguished from high-cycle fatigue, mainly associated with vibration or high number of small thermal fluctuations. Numerical models describing fatigue behaviour of austenitic stainless piping steels under cyclic loading and their applicability for modelling of low-cycle-fatigue are discussed in this report. In order to describe the cyclic behaviour of the material for analysis with finite element method (FEM) based analysis code ABAQUS, the test data, i.e. stress-strain curves, have to be processed. A code to process the data all through the test duration was developed within this study. A description of this code is given also in this report. Input data for ABAQUS was obtained to describe both kinematic and isotropic hardening properties. Further, by combining the result data for various strain amplitudes a mathematic expression was be created which allows defining a parameter surface for cyclic (i.e. isotropic) hardening. Input data for any strain amplitude within the range of minimum and maximum strain amplitudes of the test data can be assessed with the help of the developed 3D stress-strain surface presentation. The modelling of the fatigue induced initiation and growth of cracks was not considered in this study. On the other hand, a considerable part of the fatigue life of nuclear power plant (NPP) piping components is spent in the phase preceding the initiation and growth of cracks. (au)

  13. Effect of pre-strain history on small crack growth under low cycle fatigue for JIS SFVQ1A steel

    International Nuclear Information System (INIS)

    Hasunuma, Shota; Miyata, Yohei; Sakaue, Kenichi; Ogawa, Takeshi

    2011-01-01

    Low cycle fatigue tests were performed for a low alloy steel, JIS SFVQ1A, used for pressure vessels of nuclear power plants. The effect of pre-strain history on the small crack initiation and growth was investigated in detail using cellulose acetate replicas. Under the tests in which the total strain range, Δε, is constant, surface crack length, 2c, was smaller for the tests with larger Δε due to the different numbers of small crack initiation and coalescence. The pre-strain histories were applied at Δε of 8 or 16% with its fatigue usage factor, UF, of less than 0.2, followed by fatigue loading at Δε=2% until fracture. In these tests, the relationships between 2c and UF agreed with each other unless crack coalescence occurred. The scatter in fatigue life was attributed to the coalescences of small cracks. Fracture mechanics approach was applied to predict the fatigue lives and to characterize the growth behavior of small fatigue cracks. (author)

  14. Low-cycle fatigue of welded joints: coupled initiation propagation model

    International Nuclear Information System (INIS)

    Madi, Yazid; Recho, Naman; Matheron, Philippe

    2004-01-01

    This paper deals with the low-cycle fatigue (LC) design of welded structures, the aim being the critical analysis of the rule used in the RCC-MR [Design and construction rules for mechanical components of FBR nuclear islands, AFCEN, 1993], for the design and construction of fast breeder reactors. The study takes into account the evolution of the material behavior laws and damage accumulation during the fatigue loading. The adopted model consists of analyzing separately the behavior and the damage evolutions. It allows us to determine the damage ratio corresponding to initiation and propagation of a significant crack in order to determine the life duration. This model suggests the existence of a threshold level of loading, above which micro-cracks initiate. The initiation fatigue life can then be neglected below the threshold level. This work shows also that the RCC-MR rules are valid below this threshold load level

  15. Thermal and isothermal low cycle fatigue of MANET I and II

    International Nuclear Information System (INIS)

    Petersen, C.; Schmitt, R.; Garnier, D.

    1996-01-01

    Structural components of a DEMO-blanket are subjected during service to alternating thermal and mechanical stresses as a consequence of the pulsed reactor operation. Of particular concern is the fatigue endurance of martensitic steels like MANET under cyclic strains and stresses produced by these temperature changes. In order to design such structures, operating under combined mechanical and thermal cycling, fatigue life has to be calculated with reasonable accuracy. This paper proposes a description of thermal and isothermal mechanical low-cycle fatigue of MANET I and II steels using a single damage model, including plastic strain, temperature and strain rate as variables. This model presents notable advantages for the designer. As it corresponds to a single and continuous 'fatigue strength surface', it enables a reliable interpolation to be made throughout the studied domain of strains and temperatures, and allows for a reasonable extrapolation out of this domain, provided that no different metallurgical phenomena occur. (orig.)

  16. Effect of the structure on the low-cycle fatigue behaviour of alloy 800

    International Nuclear Information System (INIS)

    Robert, G.; Mathiot, A.; Regnard, C.; Dessus, J.; Claret, J.

    1982-04-01

    Alloy 800 (grade I) is used for making the steam generators of liquid metal fast breeder reactors. At working temperature (525 0 C) alloy 800 is strengthned by γ' (Ni 3 (Ti,Al)) precipitation which occurs during thermal aging. The mechanical properties of this alloy depend on the parameters which define the γ' precipitation and obviously on the structural characteristics due to the thermomechanical treatments which govern the manufacture of the product. For one cast of alloy 800 this work aims to analyse the influence, on low cycle fatigue behaviour at 550 0 C, of structural and microstructural variations originating either in different elaboration procedures or in γ' precipitation obtained by a thermal aging of 3000h at 550 0 C with or without a preceeding cold working of 10% [fr

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

    International Nuclear Information System (INIS)

    Roche, R.; Moulin, D.

    1984-05-01

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

  18. A simple approximative procedure for taking into account low cycle fatigue loads

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, G; Thomsen, K

    1996-09-01

    In this paper a simple approximative algorithm for taking into account low cycle fatigue loads is presented. Traditionally, the fatigue life consumption of a wind turbine is estimated by considering a number of (independent) load cases and performing a rainflow counting analysis on each of those. These results are then subsequently synthesized into a total load spectrum by performing a weighed sum of the number of individual load case ranges. The fatigue life consumption is thus obtained by applying the Palmgren-Miner rule on the total load spectrum. However, due to the assumption of isolated basic load cases, the above procedure fail to represent the low-frequency contributions related to the transition between those load cases. The procedure to be described in the following aims at taking the fatigue contribution, related to the transitions between the defined load cases, into account in an approximative manner. (au)

  19. Low-cycle fatigue of heat-resistant alloys in high-temperature gas-cooled reactor helium

    International Nuclear Information System (INIS)

    Tsuji, H.; Kondo, T.

    1984-01-01

    Strain controlled low-cycle fatigue tests were conducted on four nickel-base heat-resistant alloys at 900 0 C in simulated high-temperature gas-cooled reactor (HTGR) environments and high vacuums of about 10 -6 Pa. The observed behaviors of the materials were different and divided into two groups when tests were made in simulated HTGR helium, while all materials behaved similarly in vacuums. The materials that have relatively high ductility and compatibility with impure helium at test temperature showed considerable resistance to the fatigue damage in impure helium. On the other hand, the alloys qualified with their high creep strength were seen to suffer from the adverse effects of impure helium and the trend of intergranular cracking as well. The results were analyzed in terms of their susceptibility to the environmentenhanced fatigue damage by examining the ratios of the performance in impure helium to in vacuum. The materials that showed rather unsatisfactory resistance were considered to be characterized by their limited ductility partly due to their coarse grain structure and susceptibility to intergranular oxidation. Moderate carburization was commonly noted in all materials, particularly at the cracked portions, indicating that carbon intrusion had occurred during the crack growth stage

  20. Calculation of low-cycle fatigue in accordance with the national standard and strength codes

    Science.gov (United States)

    Kontorovich, T. S.; Radin, Yu. A.

    2017-08-01

    Over the most recent 15 years, the Russian power industry has largely relied on imported equipment manufactured in compliance with foreign standards and procedures. This inevitably necessitates their harmonization with the regulatory documents of the Russian Federation, which include calculations of strength, low cycle fatigue, and assessment of the equipment service life. An important regulatory document providing the engineering foundation for cyclic strength and life assessment for high-load components of the boiler and steamline of a water/steam circuit is RD 10-249-98:2000: Standard Method of Strength Estimation in Stationary Boilers and Steam and Water Piping. In January 2015, the National Standard of the Russian Federation 12952-3:2001 was introduced regulating the issues of design and calculation of the pressure parts of water-tube boilers and auxiliary installations. Thus, there appeared to be two documents simultaneously valid in the same energy field and using different methods for calculating the low-cycle fatigue strength, which leads to different results. In this connection, the current situation can lead to incorrect ideas about the cyclic strength and the service life of high-temperature boiler parts. The article shows that the results of calculations performed in accordance with GOST R 55682.3-2013/EN 12952-3: 2001 are less conservative than the results of the standard RD 10-249-98. Since the calculation of the expected service life of boiler parts should use GOST R 55682.3-2013/EN 12952-3: 2001, it becomes necessary to establish the applicability scope of each of the above documents.

  1. Estimation of Low Cycle Fatigue Response of 316 LN Stainless Steel in the Presence of Notch

    Science.gov (United States)

    Agrawal, Richa; Veerababu, J.; Goyal, Sunil; Sandhya, R.; Uddanwadiker, Rashmi; Padole, Pramod

    2018-02-01

    Notches introduced in the plain specimen result in the multiaxial state of stress that exists in the actual components due to the presence of flaws and defects. In the present work, low cycle fatigue life estimation of plain and notched specimens of 316 LN stainless steel is carried out at room temperature and 823 K. The plain and notched specimens with different notch radii were subjected to varying strain amplitudes ranging from ± 0.25 to ± 1.0% at a strain rate of 3 × 10-3 s-1. The fatigue life decreased in the presence of notch for all strain amplitudes at both the temperatures. The decrease in fatigue life was found to be more at room temperature than at 823 K. The fatigue life of the notched specimen decreased by approximately 94.2% compared to plain specimen at room temperature. However, at 823 K the decrease in fatigue life for notched specimen was approximately 84.6%. Low cycle fatigue life of the plain and notched specimens was estimated by Neuber's rule and finite element analysis approach. Neuber's rule overestimated the fatigue life by maximum factor of 2.6 for specimens at room temperature and by maximum factor of 5 for specimens at 823 K. However, it gives closer approximation at higher strain amplitudes at 823 K. Life estimation by finite element analysis at room temperature was within a factor of 1.5 as compared to experimental life, whereas it underestimated the fatigue life within a factor of 6 at high temperature.

  2. Strain ratio effects on low-cycle fatigue behavior and deformation microstructure of 2124-T851 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Hong, E-mail: 10928008@zju.edu.cn [Institute for Process Equipment, Zhejiang University, Hangzhou 310027 (China); School of Environment and Safety, Taiyuan University of Science and Technology, Taiyuan 030024 (China); Ye, Duyi, E-mail: duyi_ye@zju.edu.cn [Institute for Process Equipment, Zhejiang University, Hangzhou 310027 (China); Chen, Chuanyong [Institute for Process Equipment, Zhejiang University, Hangzhou 310027 (China)

    2014-05-01

    The low-cycle fatigue tests of 2124-T851 aluminum alloy with strain ratios of −1, −0.06, 0.06 and 0.5 were conducted under constant amplitude at room temperature. Microstructural and fractographic examinations of the material after fatigue tests were performed by optical microscopy (OM) and scanning electron microscopy (SEM), respectively. Firstly, the results showed that the material exhibited cyclic softening characteristic as a whole. The degree of softening decreased linearly with the increasing strain amplitude and the decreasing strain ratio. The lower fatigue life and ductility of the material corresponded to the larger strain ratios. Secondly, microstructure observations revealed that the density and length of slip bands increased with the increasing strain ratio at the given strain amplitude, and so did the volume fraction and size of coarse constituents, which were responsible for the reduction of fatigue life and ductility of the material. Finally, the SEM micrographs revealed that multiple crack initiation sites took place on the fracture surfaces at different strain ratios. The reduction of stable crack growth area with the increasing strain ratio was observed. Unstable crack growth region was only observed under R≠−1.

  3. Assessment of Low Cycle Fatigue Behavior of Powder Metallurgy Alloy U720

    Science.gov (United States)

    Gabb, Tomothy P.; Bonacuse, Peter J.; Ghosn, Louis J.; Sweeney, Joseph W.; Chatterjee, Amit; Green, Kenneth A.

    2000-01-01

    The fatigue lives of modem powder metallurgy disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary as functions of variables the different steps of materials/component processing: powder atomization, consolidation, extrusion, forging, heat treating, and machining. It is important to understand the relationship between the statistical variations in life and these variables, as well as the change in life distribution due to changes in fatigue loading conditions. The objective of this study was to investigate these relationships in a nickel-base disk superalloy, U720, produced using powder metallurgy processing. Multiple strain-controlled fatigue tests were performed at 538 C (1000 F) at limited sets of test conditions. Analyses were performed to: (1) assess variations of microstructure, mechanical properties, and LCF failure initiation sites as functions of disk processing and loading conditions; and (2) compare mean and minimum fatigue life predictions using different approaches for modeling the data from assorted test conditions. Significant variations in life were observed as functions of the disk processing variables evaluated. However, the lives of all specimens could still be combined and modeled together. The failure initiation sites for tests performed at a strain ratio R(sub epsilon) = epsilon(sub min)/epsilon(sub max) of 0 were different from those in tests at a strain ratio of -1. An approach could still be applied to account for the differences in mean and maximum stresses and strains. This allowed the data in tests of various conditions to be combined for more robust statistical estimates of mean and minimum lives.

  4. Effect of temperature on the rate of fatigue crack propagation in some steels during low cycle fatigue

    International Nuclear Information System (INIS)

    Taira, S.; Fujino, M.; Maruyama, S.

    Temperature dependence of the rate of fatigue crack propagation in steels was examined, and compared with the temperature dependence of tensile ductility. Microcracks initiate and affect the propagation behavior of the main crack at elevated temperatures. Factors found to be elucidated include initiation rate of microcracks, reduction of ductility of the material in the vicinity of the main crack tip, and relaxation of concentrated strain by multi-cracks. It was found that during a strain controlled low cycle fatigue test at 1 cpm, the rate of crack propagation is largest at the blue-brittleness temperature range (200 to 300 0 C) in a low carbon steel. On the other hand, it is largest at above 700 0 C in austenite stainless steels. The temperature dependence of the rate of fatigue crack propagation is opposite to that of tensile ductility. Microcracks formed in the vicinity of the main crack tip were calculated, by considering the strain concentration and strain cycles imposed. Then, the local fracture strain was evaluated. Good correlation was found between the rate of crack propagation and the local fracture strain. (U.S.)

  5. Time-dependent high-temperature low-cycle fatigue behavior of nickel-base heat-resistant alloys for HTGR

    International Nuclear Information System (INIS)

    Tsuji, Hirokazu; Kondo, Tatsuo

    1988-06-01

    A series of strain controlled low-cycle fatigue tests at 900 deg C in the simulated HTGR helium environment were conducted on Hastelloy X and its modified version, Hastelloy XR in order to examine time-dependent high-temperature low-cycle fatigue behavior. In the tests with the symmetric triangular strain waveform, decreasing the strain rate led to notable reductions in the fatigue life. In the tests with the trapezoidal strain waveform with different holding types, the fatigue life was found to be reduced most effectively in tensile hold-time experiments. Based on the observations of the crack morphology the strain holding in the compressive side was suggested to play the role of suppressing the initiation and the growth of internal cracks or cavities, and to cause crack branching. When the frequency modified fatigue life method and/or the prediction of life by use of the ductility were applied, both the data obtained with the symmetric triangular strain waveform and those with the tensile hold-time experiments lay on the straight line plots. The data, however, obtained with the compressive and/or both hold-time experiments could not be handled satisfactorily by those methods. When the cumulative damage rule was applied, it was found that the reliability of HTGR components was ensured by limiting the creep-fatigue damage fraction within the value of 1. (author)

  6. Low-Cycle Fatigue Behaviour of AISI 18Ni300 Maraging Steel Produced by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Ricardo Branco

    2018-01-01

    Full Text Available Selective laser melting has received a great deal of attention in recent years. Nevertheless, research has been mainly focused on the technical issues and their relationship with the final microstructure and monotonic properties. Fatigue behaviour has rarely been addressed, and the emphasis has been placed on high-cycle regimes. The aim of this paper is, therefore, to study, in a systematic manner, the cyclic plastic behaviour of AISI 18Ni300 maraging steel manufactured by selective laser melting. For this purpose, low-cycle fatigue tests, under fully-reversed strain-controlled conditions, with strain amplitudes ranging from 0.3% to 1.0%, were performed. After testing, fracture surfaces were examined by scanning electron microscopy to identify the main fatigue damage mechanisms. The analysis of results showed a non-Masing material, with a slight strain-softening behaviour, and non-linear response in both the elastic and plastic regimes. In addition, this steel exhibited a very low transition life of about 35 reversals, far below the values of conventional materials with equivalent monotonic mechanical properties, which can be attributed to the combination of high strength and low ductility. The total strain energy density, irrespective of strain amplitude, revealed itself to be a quite stable parameter throughout the lifetime. Finally, the SEM analysis showed for almost all the tested samples cracks initiated from the surface and inner defects which propagated through the rest of the cross section. A ductile/brittle fracture, with a predominance of brittle fracture, was observed in the samples, owing to the presence of defects which make it easier to spread the microcracks.

  7. Non local approach in crystalline plasticity: study of mechanical behaviour of AISI 316LN stainless steel during low cycle fatigue

    International Nuclear Information System (INIS)

    Schwartz, J.

    2011-01-01

    If fatigue crack initiation is currently quite well understood for pure single crystals, its comprehension and prediction in cases of polycrystal alloys such as AISI 316LN stainless steel remain complicated. Experimentally our study focuses on the characterisation of the mechanical behaviour and on the study at different scales of the phenomenon leading to low cycle fatigue crack initiation in 316LN stainless steel. For straining amplitudes of?e/2 = 0,3 and 0,5%, the cyclic softening observed during testing has been related to the organisation of dislocations in band structures. These bands, formed due to the activation of slip systems having the greatest Schmid's factor, carry the most part of the deformation. Their emergence at free surfaces leads to the formation of intrusions and extrusions which help cracks initiate and spread. Numerically we worked on the mesoscopic scale, proposing a new model of crystalline plasticity. This model integrates geometrically necessary dislocations (GND) directly computed from the lattice curvature. Implemented in the finite element code Abaqus TM and Cast3m TM , it is based on single crystal finite deformations laws proposed by Peirce et al. (1983) and Teodosiu et al. (1993). Extended for polycrystals by Hoc (2001) and Erieau (2003), it has been improved by the introduction of GND (Acharya and Bassani, 2000). The simulations performed on different types of aggregates (2D/3D) have shown that taking GND into account enables:- the prediction of the grain size effect on a macroscopic and on a local scale,- a finer computation of local stress field.The influence of the elasticity and interaction matrices on the values and the evolution of the isotropic and kinematic mean stresses has been shown. The importance of boundary conditions on computed mechanical fields could also be pointed out. (author)

  8. Influence of microstructure on low cycle fatigue in some single phase and biphasic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Stolarz, J. [Ecole Nationale Superieure des Mines, Centre SMS, URA CNRS 1884, Saint-Etienne (France)

    2004-07-01

    This overview deals with the effects of microstructural parameters in different single phase and biphasic stainless steels on short crack behaviour and on fatigue life in the low cycle regime. The effect of the grain size is investigated in a single phase austenitic stainless steel. Under plastic strain control, the fatigue life increases when the grain size decreases. The results are discussed by analysing the distributions of crack depths as a function of the grain size. The second type of material is a metastable austenitic steel which partially transforms into martensite during LCF at temperatures between -50 C and +120 C. The grain size of the initially single phase austenitic microstructure has a combined influence on the volume fraction of martensite produced during fatigue and on the fatigue life. In this case, the grain size effect is still considerable but totally indirect because all fatigue cracks grow exclusively in the martensite. The cyclic behaviour analysis in biphasic alloys in which two phases undergo plastic deformation during LCF is considerably more complex because the conventional concept of microstructural barriers cannot be applied. The possible damage patterns in a pair of grains with different mechanical properties are discussed on the example of a solution treated and aged superduplex austenitic-ferritic stainless steel (SDSS). The hardening of one phase (ferrite) through ageing at 475 C changes the cyclic behaviour of the initial ''quasi single phase'' microstructure. Consequently, the fatigue life under plastic strain control decreases compared with the solution treated SDSS. The discussion is focussed on LCF damage mechanisms at the microstructure size scale with a particular accent put on the propagation of short cracks in the bulk. All the microstructures exhibit some common features with respect to the behaviour of short cracks. In particular a strong effect of microstructural barriers in the bulk and the

  9. ANOVA parameters influence in LCF experimental data and simulation results

    Directory of Open Access Journals (Sweden)

    Vercelli A.

    2010-06-01

    Full Text Available The virtual design of components undergoing thermo mechanical fatigue (TMF and plastic strains is usually run in many phases. The numerical finite element method gives a useful instrument which becomes increasingly effective as the geometrical and numerical modelling gets more accurate. The constitutive model definition plays an important role in the effectiveness of the numerical simulation [1, 2] as, for example, shown in Figure 1. In this picture it is shown how a good cyclic plasticity constitutive model can simulate a cyclic load experiment. The component life estimation is the subsequent phase and it needs complex damage and life estimation models [3-5] which take into account of several parameters and phenomena contributing to damage and life duration. The calibration of these constitutive and damage models requires an accurate testing activity. In the present paper the main topic of the research activity is to investigate whether the parameters, which result to be influent in the experimental activity, influence the numerical simulations, thus defining the effectiveness of the models in taking into account of all the phenomena actually influencing the life of the component. To obtain this aim a procedure to tune the parameters needed to estimate the life of mechanical components undergoing TMF and plastic strains is presented for commercial steel. This procedure aims to be easy and to allow calibrating both material constitutive model (for the numerical structural simulation and the damage and life model (for life assessment. The procedure has been applied to specimens. The experimental activity has been developed on three sets of tests run at several temperatures: static tests, high cycle fatigue (HCF tests, low cycle fatigue (LCF tests. The numerical structural FEM simulations have been run on a commercial non linear solver, ABAQUS®6.8. The simulations replied the experimental tests. The stress, strain, thermal results from the thermo

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

    Czech Academy of Sciences Publication Activity Database

    Šulák, Ivo; Obrtlík, Karel; Čelko, L.

    2016-01-01

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

  11. Effect of Stress-Strain Behavior on Low-Cycle Fatigue of Alpha-Beta Titanium Alloys.

    Science.gov (United States)

    1980-11-21

    and strain excursion, such a curve would appear to fit much of the high temperature hold-time data compiled by Krempl and Wundt [21]. Thus, it might...34Mechanische Relaxation von Kupfer-Einkristallen," Phys. Stat. Sol. 3, 111-120. 21. Krempl, E. and Wundt , B. M., (1971), Hold-Time Effects in High- Temperature Low-Cycle Fatigue, ASTM STP 489. 26 Low

  12. An advanced revised universal slope method for low cycle fatigue evaluation of elbow piping subjected to in-plane cyclic bending displacement

    International Nuclear Information System (INIS)

    Urabe, Yoshio

    2015-01-01

    In order to rationalize the low cycle fatigue evaluation of elbow piping subjected to in-plane cyclic bending displacement, an advanced revised universal slope method is proposed. In the proposed method, the coefficient of the first term of the fatigue life equation which resembles Manson's equation is expressed by parameters of the multi-axial degree, the tensile strength and the fracture strength. Also, the coefficient of the second term is expressed by the multi-axial degree, the fracture ductility and the minimum fracture ductility under the maximum multi-axial degree. Here equivalent strain range is used for the fatigue life estimation. The previously carried out pipe elbow test data were reanalyzed using the proposed method. As the result, the experimentally obtained fatigue lives had considerably good coincidences with the predicted fatigue lives by the proposed method. Application of the proposed method is also discussed. (author)

  13. 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.

  14. Influence of microstructure of different stainless steels on their low cycle fatigue damage mechanisms

    International Nuclear Information System (INIS)

    Baffie, Natacha

    2002-01-01

    The present study is focused on understanding low cycle fatigue damage mechanisms in three different kind of stainless steels. In all structures, crack propagation is conditioned by microstructural barriers. In single phase austenitic alloys, short cracks initiation and growth are crystallographic. Cracks are arrested by grain and twin boundaries both at surface and in the bulk. Grain size refinement improve the fatigue life at applied Δε p . The second barrier in the bulk is shown to be very efficient because of the important number of misoriented grains. In the metastable austenitic alloy, the martensitic transformation induced by cyclic straining leads to significant modifications of damage mechanisms. The fatigue behaviour has been investigated between -50 deg. C and 120 deg. C. The γ→α' transformation takes place at the surface, in the bulk (except at 120 deg. C) and locally at the crack tip. At all temperatures, the amount of martensite formed and the fatigue life increase as the grain size decreases, even if at the same Δε p , the maximal stresses are considerably higher than in a stable γ. Short cracks growth takes place in transformed regions, γ→α' transformation being assisted by strain concentrations at the crack tip. This mechanism consumes a part of plastic deformation, which would have been available for crack propagation. Such a dynamic barrier can decrease crack propagation rate. The austenite grain size is shown to have a decisive influence both on the amount of martensite formed and on the fatigue resistance through the effect of γ grain boundaries as indirect barriers to the crack propagation. The fatigue life of the 475 deg. C aged α/γ alloy decreases sharply at high applied Δε p compared to the solution annealed one. This behaviour is explained by the modification of short cracks nucleation sites. Indeed, cleavage occurs in the hard and brittle α phase, even if plastic deformation is concentrated in γ phase. Then, easy

  15. Prediction of fatigue crack growth behaviour of an α-β titanium alloy in Paris-regime using LCF properties

    International Nuclear Information System (INIS)

    Varma, V.K.; Saxena, V.K.; Srinivas, M.

    1993-01-01

    A model has been developed in the recent past to predict fatigue crack growth (FCG) behaviour in the Paris-regime of various steels by employing low cycle fatigue (LCF) properties. The model forms its basis on the assumption that the cyclic damage process immediately ahead of a crack-tip, restricted in a small zone termed as process zone, is identical to those experienced in the LCF loading of a smooth specimen. Within the process zone, fatigue damage has been assumed in terms of product of stress and plastic strain which is analogous to the plastic strain energy density of the smooth specimen under fatigue loading. In this paper the model developed by Kujawski and Ellyin has been used to predict the FCG behaviour of an α-β titanium alloy in the Paris-regime by employing the experimentally obtained LCF properties. The FCG behaviour thus theoretically predicted was compared with the experimentally determined FCG behaviour

  16. 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

  17. Low cycle fatigue of austempered ductile cast iron alloyed with nickel at room and at depressed temperature

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Beran, Přemysl; Šmíd, Miroslav; Roupcová, Pavla; Tesařová, H.

    2009-01-01

    Roč. 16, 3a (2009), s. 1-6 ISSN 1335-0803. [Degradácia konštrukčných materiálov 2009. Tatranská Lomnica, 02.09.2009-04.09.2009] R&D Projects: GA AV ČR 1QS200410502 Institutional research plan: CEZ:AV0Z20410507; CEZ:AV0Z10480505 Keywords : Low cycle fatigue * ADI with nickel alloying * Neutron diffraction * Fatigue crack initiation * Depressed temperature Subject RIV: JL - Materials Fatigue , Friction Mechanics

  18. Multiaxial Cycle Deformation and Low-Cycle Fatigue Behavior of Mild Carbon Steel and Related Welded-Metal Specimen

    Directory of Open Access Journals (Sweden)

    Weilian Qu

    2017-01-01

    Full Text Available The low-cycle fatigue experiments of mild carbon Q235B steel and its related welded-metal specimens are performed under uniaxial, in-phase, and 90° out-of-phase loading conditions. Significant additional cyclic hardening for 90° out-of-phase loading conditions is observed for both base metal and its related weldment. Besides, welding process produces extra additional hardening under the same loading conditions compared with the base metal. Multiaxial low-cycle fatigue strength under 90° out-of-phase loading conditions is significantly reduced for both base-metal and welded-metal specimens. The weldment has lower fatigue life than the base metal under the given loading conditions, and the fatigue life reduction of weldment increases with the increasing strain amplitude. The KBM, FS, and MKBM critical plane parameters are evaluated for the fatigue data obtained. The FS and MKBM parameters are found to show better correlation with fatigue lives for both base-metal and welded-metal specimens.

  19. Influence of specimen size and grain orientation to the life of a polycrystalline Ni-base alloy at LCF stress; Einfluss der Probengroesse und der Kornorientierung auf die Lebensdauer einer polykristallinen Ni-Basislegierung bei LCF-Beanspruchung

    Energy Technology Data Exchange (ETDEWEB)

    Seibel, Thomas

    2014-07-01

    In the present work the LCF (Low Cycle Fatigue) crack initiation life of the conventionally cast Ni-base alloy RENE 80 was analyzed as a function of specimen size and grain orientation. Five specimen geometries with distinctly different gauge sections were used: 3 geometries with cylindrical gauge section (G1-G3) and two notched geometries with a stress concentration factor of α{sub 1} = 1,62 (KG1) and α{sub 2} = 2,60 (KG2), resulting in a maximum difference of the damage relevant surface area up to a factor of approximately 72. Correction factors were determined by FEM calculations for all specimen geometries with highly reduced gauge sections where direct strain measurement was not possible. Additionally a uniform failure criterion with a relatively small crack size of 0,962 mm{sup 2} was defined. Totally, 116 isothermal LCF tests were carried out at the different specimen types at a temperature of 850 C in total strain control with a load ratio (minimum strain / maximum strain) of R{sub ε} = -1. The load cycles were applied with triangular waveform at a frequency of 0.1 Hz for high strain amplitudes and 1 Hz for low strain amplitudes, respectively. After the LCF-Tests the fracture surfaces of all samples were analyzed in more detail by SEM to identify the crack initiation mechanisms as well as the crack initiation sites. In this context it could be shown, that fatigue cracks were generally initiated at slip bands in surface grains. Accordingly, the grain orientations at the crack initiation sites were measured by electron back scatter diffraction (EBSD) and the maximum shear stresses in the respective principal slip system (111) <110> was calculated using the Schmid approach. For this, longitudinal sections were be prepared exactly at the crack initiation sites of samples loaded with low strain amplitudes where clearly defined single crack initiation sites were observed. Afterwards the maximum shear stress in the principal slip system at the crack initiation

  20. Influence of specimen size and grain orientation to the life of a polycrystalline Ni-base alloy at LCF stress

    International Nuclear Information System (INIS)

    Seibel, Thomas

    2014-01-01

    In the present work the LCF (Low Cycle Fatigue) crack initiation life of the conventionally cast Ni-base alloy RENE 80 was analyzed as a function of specimen size and grain orientation. Five specimen geometries with distinctly different gauge sections were used: 3 geometries with cylindrical gauge section (G1-G3) and two notched geometries with a stress concentration factor of α 1 = 1,62 (KG1) and α 2 = 2,60 (KG2), resulting in a maximum difference of the damage relevant surface area up to a factor of approximately 72. Correction factors were determined by FEM calculations for all specimen geometries with highly reduced gauge sections where direct strain measurement was not possible. Additionally a uniform failure criterion with a relatively small crack size of 0,962 mm 2 was defined. Totally, 116 isothermal LCF tests were carried out at the different specimen types at a temperature of 850 C in total strain control with a load ratio (minimum strain / maximum strain) of R ε = -1. The load cycles were applied with triangular waveform at a frequency of 0.1 Hz for high strain amplitudes and 1 Hz for low strain amplitudes, respectively. After the LCF-Tests the fracture surfaces of all samples were analyzed in more detail by SEM to identify the crack initiation mechanisms as well as the crack initiation sites. In this context it could be shown, that fatigue cracks were generally initiated at slip bands in surface grains. Accordingly, the grain orientations at the crack initiation sites were measured by electron back scatter diffraction (EBSD) and the maximum shear stresses in the respective principal slip system (111) <110> was calculated using the Schmid approach. For this, longitudinal sections were be prepared exactly at the crack initiation sites of samples loaded with low strain amplitudes where clearly defined single crack initiation sites were observed. Afterwards the maximum shear stress in the principal slip system at the crack initiation site was correlated

  1. Low cycle fatigue of the European type 316L reference steel for the NET first wall and blanket

    International Nuclear Information System (INIS)

    Schaaf, B. van der; Hoepen, J. van.

    1992-12-01

    This report gives a comprehensive overview of the experiments performed on Type 316L steel at the Netherlands Energy Research Foundation in Petten. It is observed that the effects of neutron irradiation, resulting in 3-4 dpa and 30-40 appm helium are limited. The strain rate dependence of low cycle fatigue endurance is not negligible for material in the three conditions considered: irradiated, as-received and thermal control condition. All fatigue cracks propagated in a ductile manner in the parameter range were investigated. Both fatigue strain rate effects and crack initiation effects should be taken into account for the NET/ITER design. (author). 24 refs., 18 figs., 13 tabs

  2. A Study on the Effects on Low Cycle Fatigue Life of a High Pressure Turbine Nozzle due to the Perturbation of Crystal Orientation of Grain of DS Materials

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Korea Aerospace Research Institute, Daejeon (Korea, Republic of)

    2016-07-15

    High pressure components of a gas turbine engine are generally made of nickel-base superalloys, using precision casting process due to complicated geometries with intricate channels and cooling holes. Turbine components manufactured from directionally solidified and single crystal materials have columnar grains; however, it is found that the crystals do not grow in its preferred direction, although the orientation can be controlled. This anisotropy can lead to the variations of elastic and Hill's parameters in constitutive equations, and they alter stress distributions and the low cycle fatigue life. We aims to evaluate the effects of perturbed crystal orientations on the structural integrity of a directionally solidified nozzle using low cycle fatigue life. We also attempt to show the necessity for the control of allowed manufacturing errors and stochastic analysis. Our approaches included conjugate heat transfer and structural analysis, along with low cycle fatigue life assessment.

  3. Effect of sodium environment on the creep-rupture and low-cycle fatigue behavior of austenitic stainless steels

    International Nuclear Information System (INIS)

    Natesan, K.; Chopra, D.K.; Zeman, G.J.; Smith, D.L.; Kassner, T.F.

    1977-01-01

    Austenitic stainless steels used for in-core structural components, piping, valves, and the intermediate heat exchanger in Liquid-Metal Fast-Breeder Reactors (LMFBRs) are subjected to sodium at elevated temperatures and to complex stress conditions. As a result, the materials can undergo compositional and microstructural changes as well as mechanical deformation by creep and cyclic fatigue processes. In the present paper, information is presented on the creep-rupture and low-cycle fatigue behavior of Types 304 and 316 stainless steel in the solution-annealed condition and after long-term exposure to flowing sodium. The nonmetallic impurity-element concentrations in the sodium were controlled at levels similar to those in EBR-II primary sodium. Strain-time relationships developed from the experimental creep data were used to generate isochronous stress-creep strain curves as functions of sodium-exposure time and temperature. The low-cycle fatigue data were used to obtain relationships between plastic strain range and cycles-to-failure based on the Coffin-Manson formalism and a damage-rate approach developed at ANL. An analysis of the cyclic stress-strain behavior of the materials showed that the strain-hardening rates for the sodium-exposed steels were larger than those for the annealed material. However, the sodium-exposed specimens showed significant softening, as evidenced by the lower stress at half the fatigue life. Microstructural information obtained from the different specimens suggests that crack initiation is more difficult in the long-term sodium-exposed specimens when compared with the solution-annealed material. Based on the expected carbon concentrations in LMFBR primary system sodium, moderate carburization of the austenitic stainless steels will not degrade the mechanical properties to a significant extent, and therefore, will not limit the performance of out-of-core components. (author)

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

    Science.gov (United States)

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

    2018-04-24

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

  5. Investigation of endurance limit- and low-cycle fatigue strength of St E 47 and STE 70 in the welded and unwelded state

    International Nuclear Information System (INIS)

    Jaenicke, B.; Helms, R.; Florian, W.; Lipp, H.J.; Seidl, W.; Kaiser, B.

    1979-01-01

    To clarify clear the effect of the welding conditions and the heat treatment, alternating load tests were carried out in the endurance limit- and low-cycle-fatigue strength range on specimens of St E 47 and St E 70. Grounded basic material flat specimens cleared from their rolling skins and welded flat specimens with a butt weld of special quality were used. The welds were produced by the metal arc manual welding method with bar electrodes (low heat introduction) and with the submerged-arc welding method (high heat introduction). Part of the specimens were tempered free from stress after welding. The tests were carried out force-controlled at tension-repeated loading (S=0) and strain controlled at tension-compression alternating loading (S approx. -1). In the range of N = 5 x 10 4 ...1,5 x 10 6 cycles a small effect of the welding (special quality) for St E 47 with subsequence tempering on the endurance limit was proofed, which in comparison with the unwelded basic material (grounded surface) was characterized by broad range at nearly the same endurance limit. For St E 70, a clear decrease of the endurance limit of welded, tempered specimens (special quality) was found as compared with the basic material (grounded surface). (orig./RW) 891 RW/orig.- 892 RKD [de

  6. Effect of Solder-Joint Geometry on the Low-Cycle Fatigue Behavior of Sn- xAg-0.7Cu

    Science.gov (United States)

    Lee, Hwa-Teng; Huang, Kuo-Chen

    2016-12-01

    Low-cycle fatigue tests of Sn-Ag-Cu (SAC) Pb-free solder joints under fixed displacement were performed to evaluate the influence of Ag content (0-3 wt.%) and solder-joint geometry (barrel and hourglass types) on solder-joint fatigue behavior and reliability. The solder joints were composed of fine particles of Ag3Sn and Cu6Sn5, which aggregated as an eutectic constituent at grain boundaries of the primary β-Sn phase and formed a dense network structure. A decrease in the Ag content resulted in coarsening of the β-Sn and eutectic phases, which, in turn, decreased the strength of the joint and caused earlier failure. Solder joints in the hourglass form exhibited better fatigue performance with longer life than barrel-type joints. The sharp contact angle formed between the solder and the Cu substrate by the barrel-type joints concentrated stress, which compromised fatigue reliability. The addition of Ag to the solder, however, enhanced fatigue performance because of strengthening caused by Ag3Sn formation. The cracks of the barrel-type SAC solder joints originated mostly at the contact corner and propagated along the interfacial layer between the interfacial intermetallic compound (IMC) and solder matrix. Hourglass-type solder joints, however, demonstrated both crack initiation and propagation in the solder matrix (solder mode). The addition of 1.5-2.0 wt.% Ag to SAC solder appears to enhance the fatigue performance of solder joints while maintaining sufficient strength.

  7. A comparative study on low cycle fatigue behaviour of nano and micro Al2O3 reinforced AA2014 particulate hybrid composites

    Directory of Open Access Journals (Sweden)

    R. Senthilkumar

    2015-01-01

    Full Text Available Aluminium based metal matrix composites have drawn more attraction due to their improved properties in structural applications for the past two decades. The fatigue behaviour of composite materials needs to be studied for their structural applications. In this work, powder metallurgy based aluminium (AA2014 alloy reinforced with micro and nano-sized alumina particles were fabricated and consolidated with the hot extrusion process. The evaluation of mechanical properties in the extruded composite was carried out. This composite was subjected to low cycle fatigue test with a constant strain rate. Scanning Electron Microscope (SEM and Transmission Electron Microscope (TEM images were used to evaluate the fatigue behaviour of aluminium-nano composite samples. Enhanced mechanical properties were exhibited by the nano alumina reinforced aluminium composites, when compared to the micron sized alumina reinforced composites. The failure cycle is observed to be higher for the nano alumina reinforced composites when compared with micron sized alumina composites due to a lower order of induced plastic strain.

  8. High-temperature, low-cycle fatigue of advanced copper-base alloys for rocket nozzles. Part II: NASA 1.1, Glidcop, and sputtered copper alloys. Contractor report, Mar.--Sep. 1974

    International Nuclear Information System (INIS)

    Conway, J.B.; Stentz, R.H.; Berling, J.T.

    1974-11-01

    Short-term tensile and low-cycle fatigue data are reported for five advance Cu-base alloys: Sputtered Zr--Cu as received, sputtered Zr--Cu heat-treated, Glidcop AL-10, and alloys 1-1A and 1-1B. Tensile tests were performed in argon at 538 0 C using an axial strain rate of 0.002/s. Yield strength and ultimate tensile strength data are reported along with reduction in area values. Axial strain controlled low-cycle fatigue tests were performed in argon at 538 0 C using an axial strain rate of 0.002/s to define the fatigue life over the range from 100 to 3000 cycles for the five materials studied. Fatigue characteristics of the NASA 1-1A and NASA 1-1B compositions are identical and represent fatigue life values which are much greater than those for the other materials tested. The effect of temperature on NASA 1-1B alloy at a strain rate of 0.002/s and effect of strain rates of 0.0004 and 0.01/s at 538 0 C were evaluated. Hold-time data are reported for the NASA 1-1B alloy at 538 0 C using 5 minute hold periods in tension only and compression only at two different strain range values. (U.S.)

  9. Development of India-specific RAFM steel through optimization of tungsten and tantalum contents for better combination of impact, tensile, low cycle fatigue and creep properties

    Energy Technology Data Exchange (ETDEWEB)

    Laha, K., E-mail: laha@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Saroja, S.; Moitra, A.; Sandhya, R.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Rajendra Kumar, E. [Institute for Plasma Research, Bhat, Gandhinagar 382 428, Gujarat (India)

    2013-08-15

    Effects of tungsten and tantalum contents on impact, tensile, low cycle fatigue and creep properties of Reduced Activation Ferritic–Martensitic (RAFM) steel were studied to develop India-specific RAFM steel. Four heats of the steel have been melted with tungsten and tantalum contents in the ranges 1–2 wt.% and 0.06–0.14 wt.% respectively. Increase in tungsten content increased the ductile-to-brittle transition temperature (DBTT), low cycle fatigue and creep strength of the steel, whereas the tensile strength was not changed significantly. Increase in tantalum content increased the DBTT and low cycle fatigue strength of the steel whereas the tensile and creep strength decreased. Detailed TEM investigations revealed enhanced microstructural stability of the steel against creep exposure on tungsten addition. The RAFM steel having 1.4 wt.% tungsten with 0.06 wt.% tantalum was found to possess optimum combination of impact, tensile, low cycle fatigue and creep properties and is considered for Indian-specific RAFM steel.

  10. Seismic Capacity Estimation of Steel Piping Elbow under Low-cycle Fatigue Loading

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Bub Gyu; Kim, Sung Wan; Choi, Hyoung Suk; Kim, Nam Sik [Pusan National University, Busan (Korea, Republic of); Hahm, Dae Gi [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In some cases, this large relative displacement can increase seismic risk of the isolated facility. Especially, a inelastic behavior of crossover piping system to connect base isolated building and fixed base building can caused by a large relative displacement. Therefore, seismic capacity estimation for isolated piping system is needed to increase safety of nuclear power plant under seismic condition. Dynamic behavior analysis of piping system under seismic condition using shake table tests was performed by Touboul et al in 1995. In accordance with their study, plastic behavior could be occurred at pipe elbow under seismic condition. Experimental researches for dynamic behavior of typical piping system in nuclear power plant have been performed for several years by JNES(Japan Nuclear Energy Safety Organization) and NUPEC(Nuclear Power Engineering Corporation). A low cycle ratcheting fatigue test was performed with scaled model of elbow which is a weakest component in piping system by Mizuno et al. In-plane cyclic loading tests under internal pressure condition were performed to evaluate the seismic capacity of the steel piping elbow. Leakage phenomenon occurred on and near the crown in piping elbow. Those cracks grew up in axial direction. The fatigue curve was estimated from test results. In the fatigue curve, loading amplitude exponentially decreased as the number of cycles increased. A FEM model of piping elbow was modified with test results. The relationships between displacement and force from tests and numerical analysis was well matched.

  11. Low cycle fatigue strength of some austenitic stainless steels at room temperature and elevated temperatures

    International Nuclear Information System (INIS)

    Type 304, 316, and 316L stainless steels were tested from room temperature to 650 0 C using two kinds of bending test specimens. Particularly, Type 304 was tested at several cyclic rates and 550 0 and 650 0 C, and the effect of cyclic rate on its fatigue strength was investigated. Test results are summarized as follows: (1) The bending fatigue strength at room temperature test shows good agreement with the axial fatigue one, (2) Manson--Coffin's fatigue equation can be applied to the results, (3) the ratio of crack initiation to failure life becomes larger at higher stress level, and (4) the relation between crack propagation life and total strain range or elastic strain range are linear in log-log scale. This relation also agrees with the equations which were derived from some crack propagation laws. It was also observed at the elevated temperature test: (1) The reduction of fatigue strength is not noticeable below 500 0 C, but it is noted at higher temperature. (2) The cycle rate does not affect on fatigue strength in faster cyclic rate than 20 cpm and below 100,000 cycles life range. (3) Type 316 stainless steel shows better fatigue property than type 304 and 316L stainless steels. 30 figures

  12. Radiation effects on low cycle fatigue properties of reduced activation ferritic/martensitic steels

    International Nuclear Information System (INIS)

    Hirose, T.; Tanigawa, H.; Ando, M.; Kohyama, A.; Katoh, Y.; Narui, M.

    2002-01-01

    The reduced activation ferritic/martensitic steel, RAFs F82H IEA heat has been fatigue-tested at ambient temperature under diametral strain controlled conditions. In order to evaluate the effects of radiation damage and transmutation damage on fatigue characteristics, post-neutron irradiation and post-helium ion implantation fatigue tests were carried out. Fracture surfaces and fatigue crack initiation on the specimen surface were observed by SEM. Low-temperature irradiation caused an increase in stress amplitude and a reduction in fatigue lifetime corresponding to radiation hardening and loss of ductility. Neutron irradiated samples showed brittle fracture surface, and it was significant for large strain tests. On the other hand, helium implantation caused delay of cyclic softening. However, brittle crack initiation and propagation did not depend on the helium concentration profiles

  13. Reactor thread-joint metal with corrosion resistant coating material low cycle fatigue

    International Nuclear Information System (INIS)

    Gorynin, V.I.; Kondratyev, S.Yu.

    1991-01-01

    The results of test carried out show that the Ni-P plating which was thermally treated in inert medium, provide the dependence of the reactor equipment studs in the high-concentrated medium of leakage for a period of up to 3000 hours. The Al and aluminized platings of the studs made of steel 38 KhN 3 MFA don't provide their corrosion dependence in the reactor medium. Cr plating provides the dependence during 500 hours. The reported test allows to recommend Ni-P plating to depend the studs in the conditions of the effect of the high-concentrated leakage medium, containing KOH, H 3 BO 3 and NaCl. (author)

  14. Properties of high temperature low cycle fatigue in austenitic stainless steel

    International Nuclear Information System (INIS)

    Kim, D. H.; Han, C. H.; Ryu, W. S.

    2002-01-01

    Tensile and fatigue tests were conducted at R. T. and 300 .deg. C for type 304 and 316 stainless steel. Tensile strength and elongation decreased and fatigue life increased with temperature for both type 304 and 316 stainless steel. Dislocation structures were mixed with cell and planar at R. T. and 300 .deg. C for both type 304 and 316 stainless steel. Strain induced martensite of type 316 stainless steel was less than that of type 304 stainless steel and decreased with temperature. It is considered that strain induced martensite is an important factor to increase fatigue life at 300 .deg. C

  15. Comparison of low-cycle fatigue data of 2 1/4 % CrMo steels

    International Nuclear Information System (INIS)

    Sanderson, S.J.; Petrequin, P.; Nieuwland, H.C.D.; Breuer, H.J.

    1983-01-01

    Data files have been produced on international strain-controlled fatigue information available for 2 1/4 %CrMo steels. The available data have been considered generally in terms of total strain range vs. cycles to failure (Nsub(f)), tensile stress at Nsub(f)/2 vs. cycles to failure and time to failure vs. cycles to failure. Where possible the continuous cycling data been statistically analysed in terms of the elastic and plastic strain components and cycles to failure to yield best-fit equations over defined temperature (T) regime viz: T 0 C, 427 0 C 0 C and 550 0 C 0 C. Increasing test temperatures result in a progressive decrease in continuous cycling fatigue endurance and sustainable stress range

  16. Low cycle fatigue and creep fatigue behavior of alloy 617 at high temperature

    International Nuclear Information System (INIS)

    Cabet, Celine; Carroll, Laura; Wright, Richard

    2013-01-01

    Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) application of the very high temperature nuclear reactor (VHTR), expected to have an outlet temperature as high as 950 C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Initial creep-fatigue work on Alloy 617 suggests a more dominant role of environment with increasing temperature and/or hold times evidenced through changes in creep-fatigue crack growth mechanisms and failure life. Continuous cycle fatigue and creep-fatigue testing of Alloy 617 was conducted at 950 C and 0.3% and 0.6% total strain in air to simulate damage modes expected in a VHTR application. Continuous cycle fatigue specimens exhibited transgranular cracking. Intergranular cracking was observed in the creep-fatigue specimens and the addition of a hold time at peak tensile strain degraded the cycle life. This suggests that creep-fatigue interaction occurs and that the environment may be partially responsible for accelerating failure. (authors)

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

    Directory of Open Access Journals (Sweden)

    Wei Song

    2018-04-01

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

  18. A study on variations of the low cycle fatigue life of a high pressure turbine nozzle caused by inlet temperature profiles and installation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Aero-propulsion Research Office, Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Seo, Do Young [School of Mechanical and Aerospace Engineering, Pusan National University, Busan (Korea, Republic of)

    2015-11-15

    High pressure components of a gas turbine engine must operate for a long life under severe conditions in order to maximize the performance and minimize the maintenance cost. Enhanced cooling design, thermal barrier coating techniques, and nickel-base superalloys have been applied for overcoming them and furthermore, material modeling, finite element analysis, statistical techniques, and etc. in design stage have been utilized widely. This article aims to evaluate the effects on the low cycle fatigue life of the high pressure turbine nozzle caused by different turbine inlet temperature profiles and installation conditions and to investigate the most favorable operating condition to the turbine nozzle. To achieve it, the structural analysis, which utilized the results of conjugate heat transfer analysis as loading boundary conditions, was performed and its results were the input for the assessment of low cycle fatigue life at several critical zones.

  19. A Study on Variations of the Low Cycle Fatigue Life of a High Pressure Turbine Nozzle Caused by Inlet Temperature Profiles and Installation Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hur, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Seo, Do Young [Pusan National Univ., Busan (Korea, Republic of)

    2015-11-15

    High pressure components of a gas turbine engine must operate for a long life under severe conditions in order to maximize the performance and minimize the maintenance cost. Enhanced cooling design, thermal barrier coating techniques, and nickel-base superalloys have been applied for overcoming them and furthermore, material modeling, finite element analysis, statistical techniques, and etc. in design stage have been utilized widely. This article aims to evaluate the effects on the low cycle fatigue life of the high pressure turbine nozzle caused by different turbine inlet temperature profiles and installation conditions and to investigate the most favorable operating condition to the turbine nozzle. To achieve it, the structural analysis, which utilized the results of conjugate heat transfer analysis as loading boundary conditions, was performed and its results were the input for the assessment of low cycle fatigue life at several critical zones.

  20. Improving High-Temperature Tensile and Low-Cycle Fatigue Behavior of Al-Si-Cu-Mg Alloys Through Micro-additions of Ti, V, and Zr

    Science.gov (United States)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2015-07-01

    High-temperature tensile and low-cycle fatigue tests were performed to assess the influence of micro-additions of Ti, V, and Zr on the improvement of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in the as-cast condition. Addition of transition metals led to modification of microstructure where in addition to conventional phases present in the Al-7Si-1Cu-0.5Mg base, new thermally stable micro-sized Zr-Ti-V-rich phases Al21.4Si4.1Ti3.5VZr3.9, Al6.7Si1.2TiZr1.8, Al2.8Si3.8V1.6Zr, and Al5.1Si35.4Ti1.6Zr5.7Fe were formed. The tensile tests showed that with increasing test temperature from 298 K to 673 K (25 °C to 400 °C), the yield stress and tensile strength of the present studied alloy decreased from 161 to 84 MPa and from 261 to 102 MPa, respectively. Also, the studied alloy exhibited 18, 12, and 5 pct higher tensile strength than the alloy A356, 354 and existing Al-Si-Cu-Mg alloy modified with additions of Zr, Ti, and Ni, respectively. The fatigue life of the studied alloy was substantially longer than those of the reference alloys A356 and the same Al-7Si-1Cu-0.5Mg base with minor additions of V, Zr, and Ti in the T6 condition. Fractographic analysis after tensile tests revealed that at the lower temperature up to 473 K (200 °C), the cleavage-type brittle fracture for the precipitates and ductile fracture for the matrix were dominant while at higher temperature fully ductile-type fracture with debonding and pull-out of cracked particles was identified. It is believed that the intermetallic precipitates containing Zr, Ti, and V improve the alloy performance at increased temperatures.

  1. Effect of tensile dwell on high-temperature low-cycle fatigue and fracture behaviour of cast superalloy MAR-M247

    Czech Academy of Sciences Publication Activity Database

    Šulák, Ivo; Obrtlík, Karel

    2017-01-01

    Roč. 185, NOV (2017), s. 92-100 ISSN 0013-7944. [ICMFM 2016 - International Colloquium on Mechanical Fatigue of Metals /18./. Gijón, 05.09.2016-07.09.2016] R&D Projects: GA ČR(CZ) GA15-20991S Institutional support: RVO:68081723 Keywords : Nickel-based superalloy * High-temperature low-cycle fatigue * Tensile dwell * Fatigue life * Damage mechanisms Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering , reliability analysis Impact factor: 2.151, year: 2016

  2. 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.

  3. T55-L-714 Engine Development and Qualification. Engine M11 Low Cycle Fatigue Test Report. (0213-005-87),

    Science.gov (United States)

    1987-12-01

    Adjust nozzle/cylinder to obtain best runouts at cylinder, also check 2nd nozzle pVc’ first nozzle. Notify engineering of results before safety wiring and...installation of ir " GP wheel . 2.6 Complete GP assembly using reworked nozzle 2-121-100-R72 SN 37. 2.7 Measure and record all firs and , assembly

  4. Temperature dependence of liquid metal embrittlement susceptibility of a modified 9Cr–1Mo steel under low cycle fatigue in lead–bismuth eutectic at 160–450 °C

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Xing, E-mail: gongxingzfl@hotmail.com [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, B-2400 Mol (Belgium); KU Leuven, Department of Materials Engineering (MTM), Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium); Marmy, Pierre, E-mail: pmarmy@sckcen.be [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, B-2400 Mol (Belgium); Qin, Ling; Verlinden, Bert; Wevers, Martine [KU Leuven, Department of Materials Engineering (MTM), Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium); Seefeldt, Marc, E-mail: Marc.Seefeldt@mtm.kuleuven.be [KU Leuven, Department of Materials Engineering (MTM), Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium)

    2016-01-15

    Low cycle fatigue properties of a 9Cr–1Mo ferritic-martensitic steel (T91) have been tested in a low oxygen concentration (LOC) lead–bismuth eutectic (LBE) environment and in vacuum at 160–450 °C. The results show a clear fatigue endurance “trough” in LOC LBE, while no such a strong temperature dependence of the fatigue endurance is observed when the steel is tested in vacuum. The fractographic observations by means of scanning electron microscopy (SEM) show that ductile microdimples are prevalent on the fracture surfaces of the specimens tested in vacuum, whereas the fracture surfaces produced in LOC LBE at all the temperatures are characterized by quasi-cleavage. Interestingly, using electron backscatter diffraction (EBSD), martensitic laths close to the fatigue crack walls or to the fracture surfaces of the specimens tested in vacuum are found to have transformed into very fine equiaxed subgrains. Nevertheless, such microstructural modifications do not happen to the specimens tested in LOC LBE at 160–450 °C. These interesting microstructural distinctions indicate that liquid metal embrittlement (LME) is able to occur throughout the fatigue crack propagation phase in the full range of the temperatures investigated, i.e. LME is not very sensitive to temperature during the fatigue crack propagation.

  5. Temperature dependence of liquid metal embrittlement susceptibility of a modified 9Cr-1Mo steel under low cycle fatigue in lead-bismuth eutectic at 160-450 °C

    Science.gov (United States)

    Gong, Xing; Marmy, Pierre; Qin, Ling; Verlinden, Bert; Wevers, Martine; Seefeldt, Marc

    2016-01-01

    Low cycle fatigue properties of a 9Cr-1Mo ferritic-martensitic steel (T91) have been tested in a low oxygen concentration (LOC) lead-bismuth eutectic (LBE) environment and in vacuum at 160-450 °C. The results show a clear fatigue endurance "trough" in LOC LBE, while no such a strong temperature dependence of the fatigue endurance is observed when the steel is tested in vacuum. The fractographic observations by means of scanning electron microscopy (SEM) show that ductile microdimples are prevalent on the fracture surfaces of the specimens tested in vacuum, whereas the fracture surfaces produced in LOC LBE at all the temperatures are characterized by quasi-cleavage. Interestingly, using electron backscatter diffraction (EBSD), martensitic laths close to the fatigue crack walls or to the fracture surfaces of the specimens tested in vacuum are found to have transformed into very fine equiaxed subgrains. Nevertheless, such microstructural modifications do not happen to the specimens tested in LOC LBE at 160-450 °C. These interesting microstructural distinctions indicate that liquid metal embrittlement (LME) is able to occur throughout the fatigue crack propagation phase in the full range of the temperatures investigated, i.e. LME is not very sensitive to temperature during the fatigue crack propagation.

  6. Simulation Research on Adaptive Control of a Six-degree-of-freedom Material-testing Machine

    Directory of Open Access Journals (Sweden)

    Dan Wang

    2014-02-01

    Full Text Available This paper presents an adaptive controller equipped with a stiffness estimation method for a novel material-testing machine, in order to alleviate the performance depression caused by the stiffness variance of the tested specimen. The dynamic model of the proposed machine is built using the Kane method, and kinematic model is established with a closed-form solution. The stiffness estimation method is developed based on the recursive least-squares method and the proposed stiffness equivalent matrix. Control performances of the adaptive controller are simulated in detail. The simulation results illustrate that the proposed controller can greatly improve the control performance of the target material-testing machine by online stiffness estimation and adaptive parameter tuning, especially in low-cycle fatigue (LCF and high-cycle fatigue (HCF tests.

  7. Generalization of Coffin-Manson relation in connection with the low-cycle fatigue in the temperature range 20-300 o C

    International Nuclear Information System (INIS)

    Radu, V.

    1992-01-01

    The low-cycle fatigue phenomenon in the framework of plastic deformation is studied considering the temperature parameter. The experimental results obtained for the plastic strain Δε p (1-7%), in the temperature range 20-300 o C are examined. The conclusion is that the lifetime, expressed by the number of stress cycles, N f , is given by the relation N f = C exp(-A/T)(Δε p ) β+αΔT , where T is the absolute temperature, Δε p is double of plastic deformation amplitude, and C, A, β, and α are material constants. This relation can be interpreted as being the generalization of a relation, known in literature as the 'Coffin-Manson relation', but which does not include the temperature parameter. The validation of this relation can be done either on the results presented in this paper or an those published in literature. (Author)

  8. Investigation of in-plane biaxial low cycle fatigued austenitic stainless steel AISI 321. II. Neutron diffraction stress analysis at the IBR-2 pulsed nuclear reactor

    International Nuclear Information System (INIS)

    Taran, Yu.V.; Balagurov, A.M.; Sheverev, S.G.; ); Schreiber, J.; Bomas, H.; Korsunsky, A.M.

    2007-01-01

    The in-plane biaxial low cycle fatigued sample of the cruciform geometry from austenitic stainless steel AISI 321 was investigated on the time-of-flight neutron Fourier stress-diffractometer. The lattice parameters in the austenite matrix and the martensite inclusions created during the fatigue cycling as well as the martensite volume fraction were measured along two mutually perpendicular planar axes of the sample of the cruciform geometry by using the strain neutron scanner. The phase total residual strain components were calculated using the stress equilibrium relations. The separation of the residual stresses into macro- and microstresses was performed using the mixture rule. The measurements of the applied load-phase elastic strain responses were carried out on a uniaxial load machine. The strong difference between the phase elastic moduli was found out

  9. Effect of thermal aging on the low cycle fatigue behavior of Z3CN20.09M cast duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weifeng [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Xue, Fei [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Tian, Yang [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Yu, Dunji, E-mail: djyu@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Yu, Weiwei [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Chen, Xu [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2015-10-14

    Nuclear grade Z3CN20.09M cast duplex stainless steel exhibits enhanced cyclic stress response and prolonged low cycle fatigue life at room temperature after thermal aging at 400 °C for up to 6000 h. The threshold strain amplitude for the onset of secondary hardening is shifted to a lower value after thermal aging. Microstructural observations reveal that fatigue cracks tend to initiate from phase boundaries in virgin specimens, but to initiate in the ferrite phase in aged ones. Denser fatigue striations are found on the fracture surface of fatigued specimen subjected to longer thermal aging duration. These observations are explained in the context of thermal aging induced embrittlement of the ferrite phase and deformation induced martensitic phase transformation in the austenite phase.

  10. Theoretical and experimental analysis of cyclic stresses in gas turbine rotor blades, taking thermal fatigue into account (low cycle fatigue). Theoretische und experimentelle Analyse der zyklischen Beanspruchung von Gasturbinenlaufschaufeln unter besonderer Beruecksichtigung der thermischen Ermuedung (low cycle fatigue)

    Energy Technology Data Exchange (ETDEWEB)

    Hoelscher, R.

    1982-08-01

    The author is concerned with determining the life of highly stressed hot components of gas turbines. The main point of the experimental and theoretical investigations is the analysis of the cyclic stresses of an uncooled turbine rotor blade of an aircraft gas turbine ATAR 101. Apart from simulating cyclic load changes of turbine blades on a model test rig, models of service life predictions are prepared and tested. (HAG).

  11. Creep and low cycles fatigue behaviour of inconel 617 and alloy 800H in the temperature range 1073-1223

    International Nuclear Information System (INIS)

    Yun, H.M.

    1984-01-01

    The creep rupture properties of high temperature alloys are being determined as part of the materials programme for the development of the high temperature, gas-cooled reactor (HTGR) as a source of nuclear process heat, especially for the gasification of lignite and coal. INCOLOY 800H AND INCONEL 617 have been tested in the temperature range from 1073 K to 1223 K in air as well as in helium with HTGR specific impurities. The static and dynamic creep behaviour of INCONEL 617 have been determined in constant load creep tests, relaxation tests and stress reduction tests. The results have been interpreted using the internal stress on the applied stress and test temperature was determined. In a few experiments the influence of cold deformation prior to the creep test on the magnitude of the internal stress was also investigated. (Author)

  12. 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.

  13. Appendix BB: long coring facility (LCF)

    International Nuclear Information System (INIS)

    Driscoll, A.H.; Silva, A.J.

    1981-01-01

    During the 1979 performance period the Engineering Design of the Long Coring Facility has addressed a variety of tasks relating to the establishment of a series of operating parameters for a conceptual 50 meter long coring system. The results of these efforts have indicated that an operational system capable of the recovery of 50 meter long cores, from oceanic depths in sediments of 400 gm cm 2 is wholly possible given existing technology. Specific tasks included in the 1979 Engineering Design are as follows: (1) Hydrodynamic Stability; (2) Corer Structural Stability; (3) Corer Penetration Mechanics; (4) Anticipated Corer Pullout forces; (5) LCF Cable Dynamics; and (6) Core Head Instrumentation. Within the realm of Subseabed Disposal Programs Master Plan the LCF, as a part of the Instrumentation Development activity, is currently on schedule. Delays in receiving funding during 1979 have reduced, some what, the latitude enjoyed by the LCF project and have limited our progress to a point where any future delay can result in the LCF's falling behind the program schedule. However, at this time the LCF is considered to be on schedule, but lacking in flexibility to respond to any major contingency that may arise in the future

  14. Study of Mechanical Features for Low Cycle Fatigue Samples of Metastable Austenitic Steel AISI 321 by Neutron Stress Analysis under Applied Load

    CERN Document Server

    Taran, Yu V; Eifler, D; Nebel, Th; Schreiber, J

    2002-01-01

    The elastoplastic properties of the austenitic matrix and martensitic volume areas induced during cyclic tensile-compressive loading of low carbon metastable austenitic stainless steel were studied in an in situ neutron diffraction stress rig experiment on the ENGIN instrument at the ISIS pulsed neutron facility. Samples prepared from the steel AISI 321 annealed at 1050 ^{\\circ}C and quenched in water were subjected to low-cycle fatigue under total-strain control with an amplitude of 1 % at a frequency of 0.5 Hz. Subsequent applied stress?elastic strain responses of the austenitic and martensitic phases were obtained by Rietveld and Le Bail refinements of the neutron diffraction spectra, and were used to determine the elastic constants of the phases as a function of fatigue level. The results of modified refinements accounting for the elastic anisotropy in polycrystalline materials under load are also presented. The residual strains in the austenitic matrix were determined as a function of fatigue cycling, us...

  15. Correlation between residual stress and plastic strain amplitude during low cycle fatigue of mechanically surface treated austenitic stainless steel AISI 304 and ferritic-pearlitic steel SAE 1045

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, I. [Institute of Materials Engineering, University of Kassel, 34125 Kassel, Hessen (Germany)], E-mail: Ivan.Nikitin@infineon.com; Besel, M. [Institute of Materials Engineering, University of Kassel, 34125 Kassel, Hessen (Germany)

    2008-09-15

    Mechanical surface treatments such as deep rolling are known to affect the near-surface microstructure and induce, e.g. residual stresses and/or increase the surface hardness. It is well known that, e.g. compressive residual stress states usually increase the lifetime under fatigue loading. The stress relaxation behaviour and the stability of the residual stress during fatigue loading depend on the mechanical surface treatment method. In this paper three different surface treatments are used and their effects on the low cycle fatigue behaviour of austenitic stainless steel (AISI 304) and ferritic-pearlitic steel (SAE 1045) are investigated. X-ray diffraction is applied for the non-destructive evaluation of the stress state and the microstructure. It is found that consecutive deep rolling and annealing as well as high temperature deep rolling produce more stable near-surface stress states than conventional deep rolling at room temperature. The plastic strain amplitudes during fatigue loading are measured and it is shown that they correlate well with the induced residual stress and its relaxation, respectively. Furthermore, Coffin-Manson plots are presented which clearly show the correlation between the plastic strain amplitude and the fatigue lifetime.

  16. Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

    The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth did not depend on the heat transfer coefficient and only slightly depended on the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

  17. Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

    The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth was almost the same regardless of the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

  18. Low-cycle fatigue behavior of oxygen-free high-conductivity copper at 3000C in high vacuum

    International Nuclear Information System (INIS)

    Liu, K.C.; Loring, C.M. Jr.

    1983-01-01

    In-vacuum fatigue tests were performed on commercially-pure OFHC copper and 35% Au-65% Cu brazing filler metal at 300 0 C. Excessive recrystallization due to exposure in the 1025 0 C brazing temperature cycle was detrimental to the fatigue life of the base metal; cold work was beneficial to the fatigue resistance. Triple-point cracking and grain boundary sliding were the prevailing modes of fatigue failure observed in the full-size specimens. However, a mixed morphology of ductile and cleavage-like fracture was observed on the fracture surface of the subsize specimen in which the grain structure appeared to have undergone a change because of the presence of surface cold work. The braze has superior fatigue resistance, but to exploit the maximum strength, the brazed joint must be devoid of defects such as cavities and cracks

  19. 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.

  20. Contribution of the low cycle fatigue on ultra high purity Ni-Cr-Fe alloys and on Ni monocrystals to the understanding of the hydrogen role in stress corrosion cracking for the alloys 600 and 690

    International Nuclear Information System (INIS)

    Renaudot, N.

    1999-06-01

    We discuss the role of hydrogen in cracking of Ni base alloys used for pressurised water reactor (PWR) primary tubes (alloy 600 and 690). Cracking can be explained by a Stress Corrosion Cracking (SCC) phenomenon. For this purpose, Low cycle fatigue (R = - 1) under cathodic charging at room temperature is conducted to study hydrogen effects on propagation of cracks mechanically initiated by the formation of Persistent Slip Bands (PSB). Low cycle fatigue on Ultra High Purity specimens (Ni, alloy 600 and 690) reveals the very important hydrogen effect on crack propagation rate, whatever the Cr content in the Ni base alloy. If Cr seems to have an effect over-hydrogen penetration in specimens (by a protective film formation), it have no beneficial effect when hydrogen have diffused ahead of a crack tip. Propagation rates (transgranular or intergranular) are highly increased, no matter of the absence of impurities like sulphur. Then, in PWR, the difference in the behaviour of alloy 600 and 690 could be due to a slower microcrack propagation rate for alloy 690. Protective films could play an important role in this difference, which is to study. Low cycle fatigue on Ni single crystals oriented for single slip shows, for the first time on bulk specimen, a macroscopic softening which can be explained. by hydrogen-dislocation interactions. Moreover, a simple quantitative model based on these interactions results in the same softening as the one observed experimentally. These results allow to validate experimentally one of the most important steps in the 'Corrosion Enhanced Plasticity (CEP) model', i.e. the softening ahead of a stress corrosion crack tip by hydrogen dislocation interactions. This is of importance because this model can explain cracking in numerous FCC materials-environment couple. (author)

  1. High temperature fatigue behaviour of intermetallics

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    The effect of processing route on strain-controlled low cycle fatigue (LCF) life of binary ..... the once regarding close control of composition, control and reproduction of ... inverse effect of temperature on fatigue life seen in tests conducted in air.

  2. The application of the finite element method for the low-cycle fatigue calculation of the elementsof the pipelines’ fixed support construction for the areas of above-ground routing of the oil pipeline «Zapolyarye — NPS „Pur-Pe“»

    Directory of Open Access Journals (Sweden)

    Surikov Vitaliy Ivanovich

    2014-02-01

    Full Text Available The present article studies the order of performing low-cycle fatigue strength calculation of the elements of the full-scale specimen construction of the fixed support DN 1000 of the above-ground oil pipeline “Zapolyarye — Purpe” during rig-testing. The calculation is performed with the aim of optimizing the quantity of testing and, accordingly, cost cutting for expensive experiments. The order of performing the calculation consists of two stages. At the first stage the calculation is performed by the finite element method of the full-scale specimen construction’s stressed-deformed state in the calculation complex ANSYS. Thearticle describes the main creation stages of the finite element calculation model for the full-scale specimen in ANSYS. The calculation model is developed in accordance with a three-dimensional model of the full-scale specimen, adapted for rig-testing by cyclic loads. The article provides the description of the full-scale specimen construction of the support and loading modes in rig-testing. Cyclic loads are accepted as calculation ones, which influence the support for the 50 years of the oil pipeline operation and simulate the composite impact in the process of the loads’ operation connected to the changes in the pumping pressure, operational bending moment. They also simulate preloading in the case of sagging of the neighboring free support. For the determination of the unobservable for the diagnostic devices defects impact on the reliability of the fixed support and welding joints of the fixed support with the oil pipeline by analogy with the full-scale specimen, artificial defects were embedded in the calculation model. The defects were performed in the form of cuts of the definite form, located in a special way in the spool and welding joints. At the second stage of calculation for low-cycle fatigue strength, the evaluation of the cyclic strength of the full-scale specimen construction’s elements of the

  3. Investigation of in-plane biaxial low cycle fatigued austenitic stainless steel AISI 321. I. Mechanical testing on the planar biaxial load machine

    International Nuclear Information System (INIS)

    Taran, Yu.V.; Balagurov, A.M.; Kuznetsov, A.N.; Schreiber, J.; Bomas, H.; Stoeberl, Ch.; Rathjen, P.; Vorster, W.J.J.; Korsunsky, A.M.

    2007-01-01

    During fatigue loading of structural materials such as stainless steel, changes in the microstructure which affect the mechanical and physical properties occur. Experimental simulation of the loading conditions that induce the changes can be performed by mechanical loading, usually in the form of uniaxial tension-compression cycling. However, real machines and structures are subjected to more complex multiaxial stresses. Fatigue and fracture under multiaxial stresses are one of the most important current topics aimed at ensuring improved reliability of industrial components. The first step towards better understanding of this problem is to subject the materials to biaxial loading. The material examined was low austenitic stainless steel AISI 321 H. A set of the four samples of cruciform geometry was subjected to the biaxial tension-compression fatigue cycling with the frequency of 0.5 Hz at the applied load of 10-17 kN. The samples are intended for the neutron diffraction measurements of the residual stresses and the mechanical characterizations on a dedicated stress-diffractometer

  4. Tensile and low cycle fatigue properties of EUROFER97-steel after 16.3 dpa neutron irradiation at 523, 623 and 723 K

    Energy Technology Data Exchange (ETDEWEB)

    Materna-Morris, E., E-mail: edeltraud.materna-morris@kit.edu; Möslang, A., E-mail: anton.moeslang@kit.edu; Schneider, H.-C., E-mail: hans-christian.schneider@kit.edu

    2013-11-15

    Neutron-irradiated specimens of the reduced-activation tempered martensitic steel EUROFER97 were tested by tensile and low cycle conditions to detect the impact of irradiation on strength and lifetime. The irradiation temperature ranged from 523 to 723 K with an accumulated dose of up to 16.3 dpa. Tensile tests revealed a significant irradiation-induced hardening below 673 K with a peak of ∼430 MPa at 573 K but none was seen at 723 K, as expected. Despite the significant irradiation-induced reduction of uniform elongation, the total elongation is only reduced by about 50% below 673 K. Post-irradiation strain-controlled fatigue tests have been carried out at T{sub irrad} = T{sub test} = 523, 623 and 723 K. Pronounced cyclic softening was observed in all specimens. At 623 and 723 K, neutron irradiation had no effect on fatigue life within the data scatter. A significant lifetime increase has been observed at T{sub irrad} = T{sub test} = 523 K that advances with decreasing stress amplitude Δε (1% → 0.5%) up to a factor of ten. Scanning electron microscopy (SEM) analysis revealed ductile fracture and fatigue striations on the fracture surfaces. After push–pull fatigue testing, transmission electron microscopy (TEM) investigations showed the typical sub-cell formation, even at T{sub irrad} = T{sub test} = 523 K.

  5. A study on the notch effect on the low cycle fatigue of metals in creep-fatigue interacting conditions at elevated temperature

    International Nuclear Information System (INIS)

    Sakane, M.; Oknami, M.

    1983-01-01

    Frequency and hold-time effects on fatigue lives of cylindrical notched specimens of SUS 316 stainless steel were studied at 600 0 C in air. From the tests, the following conclusions were obtained: Neuber's rule, as used in the ASME N-47 Code, predicts very conservatively the life of notched specimens in tests without a hold-time. But it gives a nonconservative estimate for the reduction in the life of the material by the introduction of a hold-time. An empirical formula of a ''frequency-elastic stress concentration factor modified equation'' was obtained by analysing the experimental data. It predicts accurately the life of the notched specimen tested at different frequencies

  6. Correlation of microstructure and low cycle fatigue properties for 13.5Cr1.1W0.3Ti ODS steel

    Energy Technology Data Exchange (ETDEWEB)

    He, P., E-mail: pei.he@kit.edu; Klimenkov, M.; Möslang, A.; Lindau, R.; Seifert, H.J.

    2014-12-15

    Reduced activation oxide dispersion strengthened (ODS) steels are prospective structural materials for the blanket system and first wall components in Tokamak-type fusion reactors. Under the pulsed operation, these components will be predominantly subjected to cyclic thermal–mechanical loading which leads to inevitable fatigue damage. In this work, strain controlled isothermal fatigue tests were conducted for 13.5Cr1.1W0.3Ti ODS steel at 550 °C. The total strain range varied from 0.54% to 0.9%. After thermomechanical processing, 13.5CrWTi–ODS steel exhibits a remarkable lifetime extension with a factor of 10–20 for strain ranges Δε ⩽ 0.7%. 13.5Cr ODS steel shows no cyclic softening at all during the whole testing process irrespective of the strain range. TEM observations reveal ultrastable grain structure and constant dislocation densities around 10{sup 14} m{sup −2}, independent of the number of cycles or the applied strain amplitude. The presence of the stabilized ultrafine Y–Ti–O dispersoids enhances the microstructural stability and therefore leads to outstanding fatigue resistance for 13.5Cr1.1W0.3Ti–ODS steel.

  7. Correlation of microstructure and low cycle fatigue properties for 13.5Cr1.1W0.3Ti ODS steel

    International Nuclear Information System (INIS)

    He, P.; Klimenkov, M.; Möslang, A.; Lindau, R.; Seifert, H.J.

    2014-01-01

    Reduced activation oxide dispersion strengthened (ODS) steels are prospective structural materials for the blanket system and first wall components in Tokamak-type fusion reactors. Under the pulsed operation, these components will be predominantly subjected to cyclic thermal–mechanical loading which leads to inevitable fatigue damage. In this work, strain controlled isothermal fatigue tests were conducted for 13.5Cr1.1W0.3Ti ODS steel at 550 °C. The total strain range varied from 0.54% to 0.9%. After thermomechanical processing, 13.5CrWTi–ODS steel exhibits a remarkable lifetime extension with a factor of 10–20 for strain ranges Δε ⩽ 0.7%. 13.5Cr ODS steel shows no cyclic softening at all during the whole testing process irrespective of the strain range. TEM observations reveal ultrastable grain structure and constant dislocation densities around 10 14 m −2 , independent of the number of cycles or the applied strain amplitude. The presence of the stabilized ultrafine Y–Ti–O dispersoids enhances the microstructural stability and therefore leads to outstanding fatigue resistance for 13.5Cr1.1W0.3Ti–ODS steel

  8. Metallurgical characterization of M-Wire nickel-titanium shape memory alloy used for endodontic rotary instruments during low-cycle fatigue.

    Science.gov (United States)

    Ye, Jia; Gao, Yong

    2012-01-01

    Rotary instruments made of a new nickel-titanium (NiTi) alloy (M-Wire) have shown improved cyclic fatigue resistance and mechanical properties compared with those made of conventional superelastic NiTi wires. The objective of this study was to characterize microstructural changes of M-Wire throughout the cyclic fatigue process under controlled strain amplitude. The average fatigue life was calculated from 30 M-Wire samples that were subjected to a strain-controlled (≈ 4%) rotating bend fatigue test at room temperature and rotational speed of 300 rpm. Microstructural evolution of M-Wire has been investigated by different metallurgical characterization techniques, including differential scanning calorimetry, Vickers microhardness, and transmission electron microscopy at 4 different stages (as-received state, 30%, 60%, and 90% of average fatigue life). During rotating bend fatigue test, no statistically significant difference (P > .05) was found on austenite finish temperatures between as-received M-Wire and fatigued samples. However, significant differences (P Wire are expected to have higher strength and wear resistance than similar instruments made of conventional superelastic NiTi wires because of its unique nano-crystalline martensitic microstructure. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  9. Preliminary results of effect of environment on the low cycle fatigue behaviour of type 316 stainless steel and 9% Cr ferritic steel

    International Nuclear Information System (INIS)

    Wood, D.S.; Slattery, G.F.; Wynn, J.; Connaughton, M.D.; Lambert, M.E.

    1976-06-01

    Strain controlled fatigue tests on Type 316 steel at 625 0 C and 9% Cr steel at 525 0 C have been performed in air and in helium containing 200 μ atm H 2 and 1 μ atm H 2 O. In rapid cycling the endurance of Type 316 steel in this helium mixture was found to be about five times longer than in air. When a hold time was introduced into the tension part of the cycle however the endurance in the two environments was found to be virtually identical. Fractomicrographic examinations have been performed which have helped to explain some of these findings which are attributed to differences in oxidation behaviour at the crack tip. In the case of the 90% Cr steel the endurance in the helium mixture was found to be only slightly better than in air. The implications of these results are considered in relation to thermal shock effects on sodium cooled fast reactor components. (author)

  10. Low cycle fatigue behaviour of neutron irradiated copper alloys at 250 and 350 deg. C. (ITER R and D Task no. T213)

    International Nuclear Information System (INIS)

    Singh, B.N.; Stubbins, J.F.; Toft, P.

    2000-03-01

    The fatigue behaviour of a dispersion strengthened and a precipitation hardened copper alloys was investigated with and without irradiation exposure. Fatigue specimens of these alloys were irradiated with fission neutrons in the DR-3 reactor at Risoe with a flux of ∼2.5 x 10 17 n/m 2 s (E> 1 MeV) to influence levels of 1.0 - 1.5 x 10 24 n/m 2 (E> 1 MeV) at 250 and 350 deg. C. These irradiations were carried out in temperature controlled rigs where the irradiation temperature was monitored and controlled continuously throughout the whole irradiation experiment. Both unirradiated and irradiated specimens were fatigue tested in vacuum at the irradiation temperatures of 250 and 350 deg. C in a strain controlled mode with a loading frequency of 0.5Hz. Post-fatigue microstructures were examined using transmission electron microscopy and the fracture surfaces were investigated using scanning electron microscope. The present investigations demonstrated that the fatigue life decreases with increasing temperature and that the exposure to neutron irradiation causes further degradation in fatigue life at both temperatures. These results are discussed in terms of the observed post-fatigue microstructures and the fracture surface morphology. Finally, the main conclusions and their implications are summarised. (au)

  11. Effect of liquid metal embrittlement on low cycle fatigue properties and fatigue crack propagation behavior of a modified 9Cr–1Mo ferritic–martensitic steel in an oxygen-controlled lead–bismuth eutectic environment at 350 °C

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Xing, E-mail: gongxingzfl@hotmail.com [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, B-2400 Mol (Belgium); KU Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium); Marmy, Pierre, E-mail: pierre.marmy@sckcen.be [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, B-2400 Mol (Belgium); Qin, Ling, E-mail: Ling.Qin@mtm.kuleuven.be [KU Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium); Verlinden, Bert, E-mail: Bert.Verlinden@mtm.kuleuven.be [KU Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium); Wevers, Martine, E-mail: Martine.Wevers@mtm.kuleuven.be [KU Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium); Seefeldt, Marc, E-mail: Marc.Seefeldt@mtm.kuleuven.be [KU Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44, Box 2450, B-3001 Heverlee (Belgium)

    2014-11-17

    The low cycle fatigue properties of a modified 9Cr–1Mo ferritic–martensitic steel (T91) have been tested in stagnant liquid lead–bismuth eutectic (LBE) with oxygen concentrations ranging from 1.16×10{sup −6} to 6.0×10{sup −10} wt% at 350 °C. The effect of liquid metal embrittlement (LME) on fatigue endurance, fatigue crack propagation modes and secondary cracking has been studied. The results showed that the fatigue lives of T91 steel in a low oxygen concentration LBE were drastically reduced compared to those in vacuum due to the presence of LME. The microstructural observations on the fatigue crack propagation modes revealed that fatigue cracks in LBE mainly propagate across prior-austenite grain boundaries and then cut through martensitic lath boundaries, simultaneously leaving a few plastic flow traces and characteristic brittle features. Intergranular and interlath cracking occurred occasionally and their occurrence depended on the orientation of the boundaries relative to the stress axis. The complexity of the LME-induced fracture features can be attributed to a mixture of the multiple failure modes. No obvious plastic shear strain localization was present around the crack tips when LME occurred. However, using a high resolution electron backscatter diffraction (EBSD) technique, highly localized plastic shear strain was observed in the vicinity of the crack tips in vacuum, manifested by the presence of very fine subgrains along the crack walls. A qualitative mechanism was proposed to account for the LME phenomenon in the T91/LBE system. In addition, the secondary cracking at fatigue striations was different in the presence of LBE compared to vacuum. This phenomenon was elucidated by taking into account the influence of the LME on the fatigue crack propagation rate.

  12. Fatigue crack nucleation of type 316LN stainless steel

    International Nuclear Information System (INIS)

    Kim, Dae Whan; Kim, Woo Gon; Hong, Jun Hwa; Ryu, Woo Seog

    2000-01-01

    Low Cycle Fatigue (LCF) life decreases drastically with increasing temperature but increases with the addition of nitrogen at room and high temperatures. The effect of nitrogen on LCF life may be related to crack nucleation at high temperatures in austenitic stainless steel because the fraction of crack nucleation in LCF life is about 40%. The influence of nitrogen on the crack nucleation of LCF in type 316LN stainless steel is investigated by observations of crack population and crack depth after testing at 40% of fatigue life. Nitrogen increases the number of cycles to nucleate microcracks of 100 μm but decreases the crack population

  13. 78 FR 47235 - Airworthiness Directives; General Electric Company Turbofan Engines

    Science.gov (United States)

    2013-08-05

    ... cycle counts of those LLPs to account for the additional low cycle fatigue (LCF) life consumed during... Boeing 747-8 flight tests had consumed more cyclic life than they would have in revenue flight cycles... Company Turbofan Engines AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed...

  14. Contribution of the low cycle fatigue on ultra high purity Ni-Cr-Fe alloys and on Ni monocrystals to the understanding of the hydrogen role in stress corrosion cracking for the alloys 600 and 690; Apport de la fatigue oligocyclique sur alliages Ni-Cr-Fe d'ultra haute purete et sur monocristaux de Ni a la comprehension sous contrainte des alliages 600 et 69O

    Energy Technology Data Exchange (ETDEWEB)

    Renaudot, N

    1999-06-01

    We discuss the role of hydrogen in cracking of Ni base alloys used for pressurised water reactor (PWR) primary tubes (alloy 600 and 690). Cracking can be explained by a Stress Corrosion Cracking (SCC) phenomenon. For this purpose, Low cycle fatigue (R = - 1) under cathodic charging at room temperature is conducted to study hydrogen effects on propagation of cracks mechanically initiated by the formation of Persistent Slip Bands (PSB). Low cycle fatigue on Ultra High Purity specimens (Ni, alloy 600 and 690) reveals the very important hydrogen effect on crack propagation rate, whatever the Cr content in the Ni base alloy. If Cr seems to have an effect over-hydrogen penetration in specimens (by a protective film formation), it have no beneficial effect when hydrogen have diffused ahead of a crack tip. Propagation rates (transgranular or intergranular) are highly increased, no matter of the absence of impurities like sulphur. Then, in PWR, the difference in the behaviour of alloy 600 and 690 could be due to a slower microcrack propagation rate for alloy 690. Protective films could play an important role in this difference, which is to study. Low cycle fatigue on Ni single crystals oriented for single slip shows, for the first time on bulk specimen, a macroscopic softening which can be explained. by hydrogen-dislocation interactions. Moreover, a simple quantitative model based on these interactions results in the same softening as the one observed experimentally. These results allow to validate experimentally one of the most important steps in the 'Corrosion Enhanced Plasticity (CEP) model', i.e. the softening ahead of a stress corrosion crack tip by hydrogen dislocation interactions. This is of importance because this model can explain cracking in numerous FCC materials-environment couple. (author)

  15. Effect of aging and cold working on the high-temperature low-cycle fatigue behavior of alloy 800H. Part I. The effect of hardening processes on the initial stress--strain curve

    International Nuclear Information System (INIS)

    Villagrana, R.E.; Kaae, J.L.; Ellis, J.R.; Gantzel, P.K.

    1978-01-01

    The individual and combined effects of cold working (5 and 10%) and aging (4000 and 8000 h at 538 to 760 0 C) on the microstructure and high-temperature yield strength of alloy 800H have been investigated. The specimens were tested at the aging temperatures. During testing some of the specimens showed the phenomenon of serrated yielding. In order of importance, the principal hardening agents observed in this work were: cold work, the precipitation of Cr 23 C 6 at the grain boundaries, and, in some cases, the precipitation of a Perovskite-type γ' phase in the grain interiors

  16. Mechanisms of Recovering Low Cycle Fatigue Damage in Incoloy 901.

    Science.gov (United States)

    1979-01-01

    ZAP. 0665 0374 19A% DATA : 19AE MPS 15 0666 2375 F2e4 JMP .IDF r e667 e376 9 110 LSI ZAP 668 e377 E2?E LOX F,12 ASSURE X- PEG !0SITIVE FOR LSI 0669 0378...NC(MC) 0( 3350 PRIN4T 22,N4TDELTELC(M),DLTPLC(MC,SIGC(MC)o , 03360 A~1~𔃾C..,TP(M.T~4l~lC) -003370 230 22 VORMAT (12, IT1,F6.5,T2,F6.5,T30,F7.2,T42

  17. On low cycle fatigue in metal matrix composites

    DEFF Research Database (Denmark)

    Pedersen, Thomas Ø; Tvergaard, Viggo

    2000-01-01

    A numerical cell model analysis is used to study the development of fatigue damage in aluminium reinforced by aligned, short SiC fibres. The material is subjected to cyclic loading with either stress control or strain control, and the matrix material is represented by a cyclic plasticity model......, in which continuum damage mechanics is incorporated to model fatigue damage evolution. This material model uses a superposition of kinematic and isotropic hardening, and is able to account for the Bauschinger effect as well as ratchetting, mean stress relaxation, and cyclic hardening or softening. The cell...... model represents a material with transversely staggered fibres. With focus on low cyclic fatigue, the effect of different fibre aspect ratios, different triaxial stress states, and balanced as well as unbalanced cyclic loading is studied....

  18. Numerical Studies of Low Cycle Fatigue in Forward Extrusion Dies

    DEFF Research Database (Denmark)

    Pedersen, Thomas Ø

    2000-01-01

    of describing the elastic-plastic material behaviour under cyclic loadings is used to study the effects of different pre-stressing concepts on the accumulation of plastic strain and the development of fatigue damage. The results show, that the accumulation of plastic strain in the critical region can......Forward extrusion dies typically fail due to transverse fatigue cracks or wear. Fatigue cracks are initiated in regions where the material is subjected to repeated plastic deformations, e.g. the transition radius in a forward extrusion die, in the present work, a material model capable...... be controlled by means of the pre-stressing system or the geometry of the die insert. (C) 2000 Elsevier Science B.V. All rights reserved....

  19. Crack propagation under conditions of low cycle fatigue

    International Nuclear Information System (INIS)

    Hellmann, D.

    1988-01-01

    A literature review is given of convenient concepts describing the mechanical behaviour of a cracked body under cyclic loading. Only the range of high growth rates is considered. However, caused by large scale yielding in this range, the application of linear elastic fracture mechanics is no longer possible. Mechanical parameters which control fatigue crack growth are a modified stress intensity factor, the J-integral, the crack tip opening displacement and a suitable strain amplitude. (orig.) With 20 figs [de

  20. LCF behavior of Zr-4 alloy at elevated temperature

    International Nuclear Information System (INIS)

    Ye Yuming; Cai Lixun

    2006-01-01

    A series of strain fatigue tests were carried out on small bugle-like slice-specimens of Zr-4 alloy at room temperature and 400 degree C. According to Elastic and Plastic Finite Element Analysis and assumption of local damage equivalence, a strain conversion equation was given to transform the transverse strain of the specimen to the axial strain. Based on the test results of the alloy and the strain conversion equation, fatigue life estimation equations of Zr-4alloy, or M-C (Manson-Coffin) models, were obtained. The results showed that, Zr-4 alloy had obvious cyclic hardening character during high amplitude strain at different temperatures, but showed reverse character during low amplitude strain. Elevated temperature lowered seriously the fatigue life of Zr-4 alloys, ann as the increasing of amplitude strain, temperature effect impaired gradually. Analysis showed that the prediction life by using M-C model based on the traditional strain conversion equation was quite conservative when axial strain amplitude was less than 5000 micro-strain. (authors)

  1. Possible in-lattice confinement fusion (LCF). Dynamic application of atomic and nuclear data

    International Nuclear Information System (INIS)

    Kawarasaki, Yuuki

    1995-01-01

    New scheme of a nuclear fusion reactor system is proposed, the basic concept of which comes from ingenious combination of hitherto developed techniques and verified facts; 1) so-called cold fusion (CF), 2) plasma of both magnetic confinement fusion (MCF) and inertial confinement fusion (ICF), and 3) accelerator-based D-T(D) neutron source. Details of the LCF reactor physics require dynamics of atomic data as well as nuclear data; interaction of ions with matters in solid and the problems of radiation damage. (author)

  2. Development of a remote controlled fatigue testing apparatus at elevated temperature in controlled environment

    International Nuclear Information System (INIS)

    Ohmi, Masao; Mimura, Hideaki; Ishii, Toshimitsu

    1996-02-01

    The fatigue characteristics of reactor structural materials at high temperature are necessary to be evaluated for ensuring the safety of the High Temperature engineering Test Reactor (HTTR). Especially, the high temperature test data on safety research such as low cycle fatigue property and crack propagation property for reactor pressure vessel material are important for the development of the HTTR. Responding to these needs, a remote controlled type fatigue testing machine has been developed and installed in a hot cell of JMTR Hot Laboratory to get the fatigue data of irradiated materials. The machine was developed modifying a commercially available electro-hydraulic servo type fatigue testing machine to withstand radiation and be remotely operated, and mainly consists of a testing machine frame, environment chamber, extensometer, actuator and vacuum exhaust system. It has been confirmed that the machine has good performance to obtain low cycle fatigue data through many demonstration tests on unirradiated and irradiated specimens. (author)

  3. Numerical and experimental investigations into life assessment of blade-disc connections of gas turbines

    International Nuclear Information System (INIS)

    Issler, Stephan; Roos, Eberhard

    2003-01-01

    The positively engaged connection between blade and disc of a gas turbine s highly stressed by fatigue and creep fatigue loadings. For this purpose, a ew calculating method based on inelastic finite element analyses considering he main influences on damage was developed at MPA Stuttgart. Low cycle fatigue (LCF) tests with component-like specimens have been conducted for verification. Experimental data and life assessment results based on the Smith, Watson and Topper parameters were compared well

  4. Stress-strain time-dependent behavior of A356.0 aluminum alloy subjected to cyclic thermal and mechanical loadings

    Science.gov (United States)

    Farrahi, G. H.; Ghodrati, M.; Azadi, M.; Rezvani Rad, M.

    2014-08-01

    This article presents the cyclic behavior of the A356.0 aluminum alloy under low-cycle fatigue (or isothermal) and thermo-mechanical fatigue loadings. Since the thermo-mechanical fatigue (TMF) test is time consuming and has high costs in comparison to low-cycle fatigue (LCF) tests, the purpose of this research is to use LCF test results to predict the TMF behavior of the material. A time-independent model, considering the combined nonlinear isotropic/kinematic hardening law, was used to predict the TMF behavior of the material. Material constants of this model were calibrated based on room-temperature and high-temperature low-cycle fatigue tests. The nonlinear isotropic/kinematic hardening law could accurately estimate the stress-strain hysteresis loop for the LCF condition; however, for the out-of-phase TMF, the condition could not predict properly the stress value due to the strain rate effect. Therefore, a two-layer visco-plastic model and also the Johnson-Cook law were applied to improve the estimation of the stress-strain hysteresis loop. Related finite element results based on the two-layer visco-plastic model demonstrated a good agreement with experimental TMF data of the A356.0 alloy.

  5. Toward enhanced hydrogen generation from water using oxygen permeating LCF membranes

    KAUST Repository

    Wu, Xiao-Yu

    2015-01-01

    © the Owner Societies. Hydrogen production from water thermolysis can be enhanced by the use of perovskite-type mixed ionic and electronic conducting (MIEC) membranes, through which oxygen permeation is driven by a chemical potential gradient. In this work, water thermolysis experiments were performed using 0.9 mm thick La0.9Ca0.1FeO3-δ (LCF-91) perovskite membranes at 990 °C in a lab-scale button-cell reactor. We examined the effects of the operating conditions such as the gas species concentrations and flow rates on the feed and sweep sides on the water thermolysis rate and oxygen flux. A single step reaction mechanism is proposed for surface reactions, and three-resistance permeation models are derived. Results show that water thermolysis is facilitated by the LCF-91 membrane especially when a fuel is added to the sweep gas. Increasing the gas flow rate and water concentration on the feed side or the hydrogen concentration on the sweep side enhances the hydrogen production rate. In this work, hydrogen is used as the fuel by construction, so that a single-step surface reaction mechanism can be developed and water thermolysis rate parameters can be derived. Both surface reaction rate parameters for oxygen incorporation/dissociation and hydrogen-oxygen reactions are fitted at 990 °C. We compare the oxygen fluxes in water thermolysis and air separation experiments, and identify different limiting steps in the processes involving various oxygen sources and sweep gases for this 0.9 mm thick LCF-91 membrane. In the air feed-inert sweep case, the bulk diffusion and sweep side surface reaction are the two limiting steps. In the water feed-inert sweep case, surface reaction on the feed side dominates the oxygen permeation process. Yet in the water feed-fuel sweep case, surface reactions on both the feed and sweep sides are rate determining when hydrogen concentration in the sweep side is in the range of 1-5 vol%. Furthermore, long term studies show that the surface

  6. Investigation of thermal fatigue behavior of thermal barrier coating systems

    International Nuclear Information System (INIS)

    Zhu Dongming; Miller, R.A.

    1997-01-01

    In the present study, the mechanisms of fatigue crack initiation and propagation, and of coating failure under thermal loads that simulate those in diesel engines are investigated. Surface cracks initiate early and grow continuously under thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) stresses. It is found that, in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures. Significant LCF and HCF interactions have been observed in the thermal fatigue tests. The fatigue crack growth rate in the ceramic coating strongly depends on the characteristic HCF cycle number, N* HCF which is defined as the number of HCF cycles per LCF cycle. The crack growth rate is increased from 0.36 μm/LCF cycle for a pure LCF test to 2.8 μm/LCF cycle for a combined LCF and HCF test at N* HCF about 20 000. A surface wedging model has been proposed to account for the HCF crack growth in the coating systems. This mechanism predicts that the HCF damage effect increases with heat flux and thus with increasing surface temperature swing, thermal expansion coefficient and elastic modulus of the ceramic coating, as well as with the HCF interacting depth. Good correlation has been found between the analysis and experimental evidence. (orig.)

  7. Cyclic Deformation and Fatigue Behaviors of Alloy 617 Base Metal and Weldments at 900℃ for VHTR Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seon Jin; Kim, Byung Tak; Dewa, Rando T.; Hwang, Jeong Jun; Kim, Tae Su [Pukyong National Univ., Busan (Korea, Republic of); Kim, Woo Gon; Kim, Eung Seon [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    An analysis of cyclic deformation can contribute to a deeper understanding of the fatigue fracture mechanisms as well as to improvements in the design and application of VHTR system. However, the studies associated with cyclic deformation and low cycle fatigue (LCF) properties of Alloy 617 have focused mainly on the base metal, with little attention given to the weldments. Totemeier studied on high-temperature creep-fatigue of Alloy 617 base metal and weldments. Current research activities at PKNU and KAERI focus on the study of cyclic deformation and LCF behaviors of Alloy 617 base metal (BM) and weldments (WM) specimens were machined from GTAW buttwelded plates at very high-temperature of 900℃. In this work, the cyclic deformation characteristics and fatigue behaviors of Alloy 617 BM and WM are studied and discussed with respect to LCF. In this paper, cyclic deformation and low cycle fatigue behaviors of Alloy 617 base metal and weldments was evaluated using strain-controlled LCF tests at 900℃for 0.6% total strain range. Results of the current experiments can be concluded; The WM specimen has shown a higher cyclic stress response than the BM specimen. The fatigue life of WM specimen was reduced relative to that of BM specimen.

  8. Environmental fatigue behaviors of wrought and cast stainless steels in 310degC deoxygenated water

    International Nuclear Information System (INIS)

    Cho, Pyung-Yeon; Jang, Hun; Jang, Changheui; Jeong, Ill-Seok; Lee, Jae-Gon

    2009-01-01

    Environmental fatigue behaviors of wrought type 316LN stainless steel and cast CF8M stainless steel were investigated. Low cycle fatigue tests were performed in a 310degC deoxygenated water environment at a strain rate of 0.04%/s with various strain amplitudes. It was shown that the low cycle fatigue life of CF8M was slightly longer than that of 316LN. To understand the causes of the difference, fracture surface was observed and material factors like microstructure, mechanical properties, and chemical compositions of both materials were analyzed. In a duplex microstructure of CF8M, the fatigue crack growth was affected by barrier role of ferrite phase and acceleration role of microvoids in ferrite phase. Test results indicate that the former is greater than the latter, resulting in slower fatigue crack growth rate, or longer LCF lives in CF8M than in 316LN. (author)

  9. On the estimation of durability during thermal fatigue tests

    International Nuclear Information System (INIS)

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

    1981-01-01

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

  10. FBR structural material test facility in flowing sodium environment

    International Nuclear Information System (INIS)

    Shanmugasundaram, M.; Kumar, Hemant; Ravi, S.

    2016-01-01

    In Fast Breeder Reactor (FBR), components such as Control and Safety Rod Drive Mechanism (CSRDM), Diverse Safety Rod Drive Mechanism (DSRDM), Transfer arm and primary sodium pumps etc., are experiencing friction and wear between the moving parts in contact with liquid sodium at high temperature. Hence, it is essential to evaluate the friction and wear behaviour to validate the design of components. In addition, the above core structural reactor components such as core cover plate, control plugs etc., undergoes thermal striping which is random thermal cycling induced by flow stream resulting from the mixing of non isothermal jets near that component. This leads to development of surface cracks and assist in crack growth which in turn may lead to failure of the structural component. Further, high temperature components are often subjected to low cycle fatigue due to temperature gradient induced cyclic thermal stresses caused by start-ups, shutdowns and transients. Also steady state operation at elevated temperature introduces creep and the combination of creep and fatigue leads to creep-fatigue interactions. Therefore, resistance to low cycle fatigue, creep and creep-fatigue are important considerations in the design of FBR components. Liquid sodium is used as coolant and hence the study of the above properties in dynamic sodium are equally important. In view of the above, facility for materials testing in sodium (INSOT) has been constructed and in operation for conducting the experiments such as tribology, thermal stripping, low cycle fatigue, creep and creep-fatigue interaction etc. The salient features of the operation and maintenance of creep and fatigue loops of INSOT facility are discussed in detail. (author)

  11. Modeling of uniaxial ratchetting behavior of SA333 carbon manganese steel

    International Nuclear Information System (INIS)

    Shit, J.; Dhar, S.; Acharyya, S.K.; Goyal, S.

    2012-01-01

    The paper deals with uniaxial ratcheting phenomenon of cyclic plasticity behavior of the materials SA333 carbon Manganese steel. A mechanistic model for the ratcheting phenomenon has been proposed. It is observed that von Mises yield criterion together with Chaboche’s kinematic hardening rules are not sufficient to model ratcheting phenomenon. Other associated phenomena like plastic strain memory surface, back stress memory points and over all the extra hardening behavior have to be incorporated to get a complete material model for ratcheting. The proposed model assembled all these ideas together with von Mises yield criterion and Chabache’s kinematic hardening rule. Low cycle fatigue tests and uniaxial ratcheting tests have been conducted for the materials. The material constants are identified and derived from experimental results. The ratcheting coefficients have been properly calibrated with these material constants. The material model, as mentioned above, for the ratcheting phenomenon has been implemented in an elastic plastic finite element code. The ratcheting results for different stress controlled ratcheting loads have been computed. The good feature of this model is that it reduces to symmetric low cycle fatigue model when loop closes. - Highlights: ► A common material model to simulate symmetric LCF and ratcheting. ► Extra hardening to take care the shift of plastic strain centre. ► Material parameters from tensile and LCF tests. ► Saturated loop in LCF and ratcheting strain rate is compared with experiment. ► Consideration of loading path, memory path and their directions.

  12. Evaluation of combined hardening parameters for type 304LN stainless steel under strain-controlled cyclic loading

    International Nuclear Information System (INIS)

    Kumar, Abhishek; Vishnuvardhan, S.; Raghava, G.

    2016-01-01

    Low cycle fatigue (LCF) is the primary degradation mechanism affecting coolant piping of pressurized water reactor (PWR) caused by combination of pressure and transient mechanical or thermal loads. In the case of LCF, stresses are high enough for plastic deformation to occur and the fatigue life is correlated with the cyclic plastic strain. Modelling cyclic plastic deformation of a material requires hardening parameters, which have to be obtained from LCF test results. It is customary in low cycle fatigue tests that the strain ranges are kept constant and the stresses are allowed to vary which typically leads to a hysteresis loop that consists of linear and nonlinear parts. In this paper, numerical studies on mechanical behaviour of Type 304LN stainless steel under fully reversed strain-controlled cyclic loading have been carried out. A linear combination of the two hardening types, isotropic and kinematic, governed by a scalar parameter, β (0 ≤β ≤ 1) is used. A value of β=1 indicates a pure isotropic hardening while a value of β=0 indicates pure kinematic hardening. The details of the combined isotropic-kinematic hardening model are also presented. Constitutive relations for the classical von Mises theory along with a bilinear hardening theory have been used. The model is implemented in finite element software ABAQUS using a user subroutine written in FORTRAN, UMAT. An iterative method is adopted to arrive at the model's hardening parameters and the value of β. (author)

  13. Low cycle fatigue of pressurized pipes with circumferential flaws under cyclic bending moment

    International Nuclear Information System (INIS)

    Stoppler, W.; Sturm, D.

    1993-01-01

    Pipes of 706 mm inner diameter, 47 mm wall thickness and about 5,000 mm in length were provided with circumferential surface cracks and loaded by internal pressure of 15 MPa whilst being simultaneously subjected to an alternating external bending moment. Usually a load ratio R of -1 (M min /M max ), in one case R = 0.1, was applied. The pipes were fabricated of two types of ferritic steel: one, grade 20 MnMoNi 5 5, with a high upper shelf impact energy of about 200 J and one, MnMoNiV-special melt, with a low upper shelf impact energy of about 60 J. Deformation and crack growth in the wall thickness and circumferential direction were determined and compared with calculated values. 9 refs., 13 figs

  14. Reliability Assessment of a Turbogenerator Coil Retaining Ring Based on Low Cycle Fatigue Data

    Directory of Open Access Journals (Sweden)

    Olmi Giorgio

    2014-03-01

    Full Text Available Pierscienie ustalajace cewek turbogeneratora sa pasowane skurczowo na wirniku wokół cerek by zabezpieczyc je przed działaniem sił odsrodkowych. W typowych warunkach, sa one poddane narazeniom zmeczeniowym o malej liczbie cykli, przy czym kazdy cykl rozpoczyna sie od startu maszyny, a konczy przy jej zatrzymaniu. Przedmiotem artykułu jest wyznaczenie prawdopodobienstwa awarii pierscienia ustalajacego cewki. Rozwazanym uszkodzeniem jest pekniecie pierscienia spowodowane puchnieciem materiału pod wpływem naprezen wywołanych sila odsrodkowa. Ocena niezawodnosci przeprowadzona w tej pracy wykorzystuje dane wejsciowe wpływajace na obciazenie zmeczeniowe przy małej liczbie cykli i ich rozkłady stochastyczne. Dla rozwiazania problemu wyznaczono eksperymentalnie charakterystyki statyczne i krzywe cykli zmeczeniowych stosowanego materiału i zastosowano model statystyczny dla wyliczenia odpowiednich parametrów i ich odchylen standardowych. Na podstawie wyznaczonych rozkładów zmiennych estymuje sie prawdopodobienstwo uszkodzenia w formie dystrybuanty rozkładu. Wykorzystanyalgorytm obliczeniowy o duzej skutecznosci wykorzystuje metode ”zaawansowanej sredniej” (Advanced Mean Value. Uzyskane wyniki daja informacje o odpowiedzi materiału i stanie lokalnych naprezen i odkształcen w najbardziej obciazonych obszarach pierscienia ustalajacego cewki. Prawdopodobienstwo uszkodzenia, wyznaczone na koniec okresu eksploatacji maszyny, wynosi 10-12 i jest porównywalne z wartosciami referencyjnymi dla innych konstrukcji mechanicznych i lotniczych narazonych na zmeczenie.

  15. Influence of impacts on static and low-cycle fatigue characteristics of composite specimens (Draft)

    NARCIS (Netherlands)

    Walters, C.L.

    2012-01-01

    This paper describes the effect of impacts on the possible reduction of the structural characteristics and damage growth of graphite-epoxy specimens. The considered specimens are undamaged specimens and specimens impacted with two different energy levels. In particular, barely visible impact damage

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

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Petráš, Roman; Heczko, Milan; Kuběna, Ivo; Kruml, Tomáš; Chai, G.

    2014-01-01

    Roč. 615, OKT (2014), s. 175-182 ISSN 0921-5093 R&D Projects: GA ČR(CZ) GA13-23652S Institutional support: RVO:68081723 Keywords : Sanicro 25 steel * Cyclic plasticity * Dislocation structure * Fatigue life * Effect of temperature Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.567, year: 2014

  17. On the cyclic stress-strain behavior and low cycle fatigue of aerospace materials

    Science.gov (United States)

    Burbach, J.

    1972-01-01

    The elastic-plastic deformation behavior under cyclic stress of a number of different engineering materials was experimentally investigated with the aid of high-precision methods of measuring, some of which had been newly developed. Experiments made with a variety of steels, the titanium alloy Ti-A16-V4, a cobalt (tungsten) alloy, the high-temperature material Nimonic 90 and Dural (A1-Cu) are reported. The theory given in an attempt to explain these experiments is aimed at finding general formulas for the cyclic stress-strain behavior materials.

  18. Comparison of materials resistance to rupture for low-cycle fatigue under isothermal and nonisothermal conditions

    International Nuclear Information System (INIS)

    Sobolev, N.D.; Egorov, V.I.

    1979-01-01

    Proposed is the following conception of damage at cyclic change of deformation and temperature allowing for two effects: 1) material damage occurs mainly in the stretching semicycle and the higher the temperature and the greater the ageing time, the greater the material damage; 2) the healing effect may take place in the compression semicycle and the higher the temperature and the greater the ageing time, the greater the effect. Comparison in durability of some loading conditions is carried out for the 304 stainless steel to confirm the above conception. It is shown that it is necessary to take into account separately damages is stretching and compression semicycles with allowance for temperature and durability of active loading and holdings

  19. Resistance of heat resisting steels and alloys to thermal and mechanical low-cycle fatigue

    International Nuclear Information System (INIS)

    Tulyakov, G.A.

    1980-01-01

    Carried out is a comparative evalUation of resistance of different materials to thermocyclic deformation and fracture on the base of the experimental data on thermal and mechanical low-cycle fatigUe. Considered are peculiarities of thermal fatigue resistance depending on strength and ductility of the material. It is shown, that in the range of the cycle small numbers before the fracture preference is given to the high-ductility cyclically strengthening austenitic steels of 18Cr-10Ni type with slight relation of yield strength to the σsub(0.2)/σsub(B) tensile strength Highly alloyed strength chromium-nickel steels, as well as cyclically destrengthening perlitic and ferritic steels with stronger σsub(0.2)/σsub(B) relation as compared with simple austenitic steels turn to be more long-lived in the range of the cycle great numbers berore fracture. Perlitic steels are stated to have the lowest parameter values of the K crack growth intensity under the similar limiting conditions of the experiment, while steels and alloys with austenite structure-higher values of the K parameter

  20. Comparison of low-cycle fatigue data of 2 1/4%CrMo steels

    International Nuclear Information System (INIS)

    Sanderson, S.J.; Petrequin, P.; Nieuwland, H.C.D.

    Data files have been produced on international strain-controlled fatigue information available for 2 1/4%CrMo steels; data assessment from these files is treated in three categories viz: annealed and isothermally annealed 2 1/4%Cr1%Mo steel; normalised and tempered and quenched and tempered 2 1/4%Cr1%Mo steel; and 2 1/4%CrMo variants. The available data have been considered generally in terms of total strain range vs. cycles to failure (Nsub(f)), tensile stress at Nsub(f)/2 vs. cycles to failure and time to failure vs. cycles to failure. Where possible the continuous cycling data have been statistically analysed in terms of the elastic and plastic strain components and cycles to failure to yield best-fit equations over defined temperature (T) regimes viz: T <= 427 deg. C, 427 deg. C < T <= 550 deg. C. and 550 deg. C < T <= 600 deg. C. The behaviour of the steels within the various classifications is discussed. (author)

  1. Crack growth through low-cycle fatigue loading of material ARMOX 500T

    Directory of Open Access Journals (Sweden)

    V. Pepel

    2016-10-01

    Full Text Available This paper presents microstructure analysis of the creation and growth of cracks in uniaxial load. Analyse were done for steel Armox 500T (armour sheet. Results show that cracks are present quit early in steel lifetime. First micro cracks occur before the 200th cycles, whereby crack growth is progressive during further loading. Also it can be seen that after a certain number of cycles there are more longer cracks then shorter ones.

  2. Low cycle fatigue behaviour of neutron irradiated copper alloys at 250 and 350 deg. C

    DEFF Research Database (Denmark)

    Singh, B.N.; Stubbins, J.F.; Toft, P.

    2000-01-01

    V) to influence levels of 1.0 - 1.5 x 1024 n/m2 (E> 1 MeV) at 250 and 350 deg. C. These irradiations were carried out in temperature controlled rigs where the irradiation temperature was monitored and controlledcontinuously throughout the whole irradiation experiment. Both unirradiated and irradiated speciments...

  3. Study on low-cycle fatigue property of candidate stainless steels for SCWR

    International Nuclear Information System (INIS)

    Chen Le; Tang Rui; Liang Bo; Zhang Qiang; Liu Hong

    2013-01-01

    Low cyclic fatigue property of three austenitic stainless steels (316Ti, 347 and HR3C) as candidate materials for SCWR was investigated at room temperature (RT) and 650℃ under a strain amplitude of ± 0.5%, and fracture morphology of all the samples was observed by scanning electron microscope (SEM). The results showed that, at both temperatures the fatigue life of 347 was best and 316Ti worst. For each material, the area of hysteresis was nearly the same in the two temperatures. The elastic deformation was 0.1% - 0.15% both at RT and 650℃ for the three materials with different fatigue lives, indicating it had no direct connection with fatigue life. There was different cyclic hardening/saturation behavior for each material. The maximum/minimum stress of either HR3C or 347 was quite different at the two temperatures, while of 316Ti was almost the same. The cyclic hardening behavior was more remarkable in 316Ti compared with 347 at 650℃. SEM observation found that the fatigue striation width was only 1.87 μm for 347, but up to 4.67 μm and 3.0 μm for 316Ti and HR3C respectively, which further demonstrated that 347 had the best fatigue property at 650℃. (authors)

  4. Method and data analysis example of fatigue tests

    International Nuclear Information System (INIS)

    Nogami, Shuhei

    2015-01-01

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

  5. Coatings for Oxidation and Hot Corrosion Protection of Disk Alloys

    Science.gov (United States)

    Nesbitt, Jim; Gabb, Tim; Draper, Sue; Miller, Bob; Locci, Ivan; Sudbrack, Chantal

    2017-01-01

    Increasing temperatures in aero gas turbines is resulting in oxidation and hot corrosion attack of turbine disks. Since disks are sensitive to low cycle fatigue (LCF), any environmental attack, and especially hot corrosion pitting, can potentially seriously degrade the life of the disk. Application of metallic coatings are one means of protecting disk alloys from this environmental attack. However, simply the presence of a metallic coating, even without environmental exposure, can degrade the LCF life of a disk alloy. Therefore, coatings must be designed which are not only resistant to oxidation and corrosion attack, but must not significantly degrade the LCF life of the alloy. Three different Ni-Cr coating compositions (29, 35.5, 45wt. Cr) were applied at two thicknesses by Plasma Enhanced Magnetron Sputtering (PEMS) to two similar Ni-based disk alloys. One coating also received a thin ZrO2 overcoat. The coated samples were also given a short oxidation exposure in a low PO2 environment to encourage chromia scale formation. Without further environmental exposure, the LCF life of the coated samples, evaluated at 760C, was less than that of uncoated samples. Hence, application of the coating alone degraded the LCF life of the disk alloy. Since shot peening is commonly employed to improve LCF life, the effect of shot peening the coated and uncoated surface was also evaluated. For all cases, shot peening improved the LCF life of the coated samples. Coated and uncoated samples were shot peened and given environmental exposures consisting of 500 hrs of oxidation followed by 50 hrs of hot corrosion, both at 760C). The high-Cr coating showed the best LCF life after the environmental exposures. Results of the LCF testing and post-test characterization of the various coatings will be presented and future research directions discussed.

  6. MODELS OF FATIGUE LIFE CURVES IN FATIGUE LIFE CALCULATIONS OF MACHINE ELEMENTS – EXAMPLES OF RESEARCH

    Directory of Open Access Journals (Sweden)

    Grzegorz SZALA

    2014-03-01

    Full Text Available In the paper there was attempted to analyse models of fatigue life curves possible to apply in calculations of fatigue life of machine elements. The analysis was limited to fatigue life curves in stress approach enabling cyclic stresses from the range of low cycle fatigue (LCF, high cycle fatigue (HCF, fatigue limit (FL and giga cycle fatigue (GCF appearing in the loading spectrum at the same time. Chosen models of the analysed fatigue live curves will be illustrated with test results of steel and aluminium alloys.

  7. Local strain in front of cracks in the case of creep fatigue

    International Nuclear Information System (INIS)

    Rie Kyongtschong; Olfe, J.

    1993-01-01

    In-situ measurements of strain fields in front of cracks were performed for high temperature Low Cycle Fatigue (LCF) with different hold times by means of a grid method. The tests were carried out on the austenitic stainless steel 304 L and the ferritic steel X22 CrMoV 12 1. Simultaneous observation of crack growth leads to a correlation between crack growth and local strain. The interaction of creep and fatigue related to strain concentration at the crackk tip and crack growth was discussed. A model is proposed which is based on the formation of cavities on grain boundaries. (orig.) [de

  8. Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Thibault, Denis, E-mail: thibault.denis@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Bocher, Philippe, E-mail: philippe.bocher@etsmtl.ca [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Thomas, Marc, E-mail: marc.thomas@etsmtl.ca [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Lanteigne, Jacques, E-mail: lanteigne.jacques@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Hovington, Pierre, E-mail: hovington.pierre@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Robichaud, Patrice, E-mail: patrice.robichaud@riotinto.com [Centre de recherche et de developpement Arvida (CRDA), 1955, boul. Mellon, Jonquiere, Quebec, G7S 4K8 (Canada)

    2011-08-15

    Highlights: {yields} Reformed austenite in 13%Cr-4%Ni stainless steel transforms during fatigue crack growth. {yields} Low cycle fatigue tests showed that this transformation to martensite is gradual. {yields} XRD spectrums obtained on the fracture surface and have been correlated to LCF results. - Abstract: In the as-quenched state, 13%Cr-4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

  9. Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

    International Nuclear Information System (INIS)

    Thibault, Denis; Bocher, Philippe; Thomas, Marc; Lanteigne, Jacques; Hovington, Pierre; Robichaud, Patrice

    2011-01-01

    Highlights: → Reformed austenite in 13%Cr-4%Ni stainless steel transforms during fatigue crack growth. → Low cycle fatigue tests showed that this transformation to martensite is gradual. → XRD spectrums obtained on the fracture surface and have been correlated to LCF results. - Abstract: In the as-quenched state, 13%Cr-4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  11. Verication of an LCF-Style First-Order Prover with Equality

    DEFF Research Database (Denmark)

    Jensen, Alexander Birch; Schlichtkrull, Anders; Villadsen, Jørgen

    2016-01-01

    as a verified kernel. By doing this we also obtain verified components such as derived rules, a tableau prover, tactics, and a small declarative interactive theorem prover. We test that the kernel and the components give the same results as Harrison’s original on all the examples from his book...

  12. Environmental Fatigue of Metallic Materials in Nuclear Power Plants - A Review of Korean Test Programs

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Changheul; Jang, Hun; Hong, Jongdae [KAIST, Daejeon (Korea, Republic of); Cho, Hyunchul [Doosan Heavy Industry and Construction, Changwon (Korea, Republic of); Kim, Tae Soon; Lee, Jaegon [KHNP, Daejeon (Korea, Republic of)

    2013-12-15

    Environmental fatigue of the metallic components in light water reactors has been the subject of extensive research and regulatory interest in Korea and abroad. Especially, it was one of the key domestic issues for the license renewal of operating reactors and licensing of advanced reactors during the early 2000s. To deal with the environmental fatigue issue domestically, a systematic test program has been initiated and is still underway. The materials tested were SA508 Gr.1a low alloy steels, 316LN stainless steels, cast stainless steels, and an Alloy 690 and 52M weld. Through tests and subsequent analysis, the mechanisms of reduced low cycle fatigue life have been investigated for those alloys. In addition, the effects of temperature, dissolved oxygen level, and dissolved hydrogen level on low cycle fatigue behaviors have been investigated. In this paper, the test results and key analysis results are briefly summarized. Finally, an on-going test program for hot-bending of 347 stainless steel is introduced.

  13. The influence of microstructure and operating temperature on the fatigue endurance of hot forged Inconel{sup ®} 718 components

    Energy Technology Data Exchange (ETDEWEB)

    Maderbacher, H., E-mail: hermann.maderbacher@unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Oberwinkler, B., E-mail: bernd.oberwinkler@bohler-forging.com [Böhler Schmiedetechnik GmbH and Co KG, Mariazellerstraße 25, 8605 Kapfenberg (Austria); Gänser, H.-P., E-mail: hans-peter.gaenser@mcl.at [Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben (Austria); Tan, W., E-mail: wen.tan@unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Rollett, M., E-mail: mathias.rollett@stud.unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Stoschka, M., E-mail: michael.stoschka@stud.unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria)

    2013-11-15

    The dependence of the fatigue behavior of hot-forged Inconel{sup ®} 718 aircraft components on the operating temperature and the material microstructure is investigated. To this purpose, possible correlations between a variety of tested microstructural parameters and the results from low-cycle fatigue (LCF) testing are analyzed using statistical methods. To identify the prevailing damage mechanisms, failure analyses are carried out on specimens tested at different temperatures. Optical and scanning electron microscopy are used for the inspection of surface crack networks and of the final fracture surface. In addition, energy dispersive X-ray (EDX) analyses are performed at the crack initiation sites to track down possible accumulations of alloying elements. The results are critically reviewed and used to propose a temperature and microstructure dependent fatigue model for predicting LCF ε⧸N-curves.

  14. Influence of steel-making process and heat-treatment temperature on the fatigue and fracture properties of pressure vessel steels

    International Nuclear Information System (INIS)

    Koh, S. K.; Na, E. G.; Baek, T. H.; Won, S. Y.; Park, S. J.; Lee, S. W.

    2001-01-01

    In this paper, high strength pressure vessel steels having the same chemical compositions were manufactured by the two different steel-making processes, such as Vacuum Degassing(VD) and Electro-Slag Remelting(ESR) methods. After the steel-making process, they were normalized at 955 deg. C, quenched at 843 .deg. C, and finally tempered at 550 .deg. C or 450 deg. C, resulting in tempered martensitic microstructures with different yielding strengths depending on the tempering conditions. Low-Cycle Fatigue(LCF) tests, Fatigue Crack Growth Rate(FCGR) tests, and fracture toughness tests were performed to investigate the fatigue and fracture behaviors of the pressure vessel steels. In contrast to very similar monotonic, LCF, and FCGR behaviors between VD and ESR steels, a quite difference was noticed in the fracture toughness. Fracture toughness of ESR steel was higher than that of VD steel, being attributed to the removal of impurities in steel-making process

  15. Life time calculations for LCF loading combined with tensional hold periods

    International Nuclear Information System (INIS)

    Bocek, M.; Armas, A.; Piel, D.

    1983-01-01

    The life time in high amplitude strain cycling with tensional hold periods is analysed presuming that creep failure damage is life determining. The life fraction rule (LFR) is used to calculate the life time consumpted during the dwell period in strain controlled tests as well as during tensional hold time stress cycles. It follows from the present investigation that stress relaxation occurring during the strain hold periods plays the dominant influence upon the relationship between life and dwell time. For strong stress relaxation (e.g. high temperature) less damage is accumulated as compared to suppressed relaxation (low temperature). The damage in stress relaxation is calculated by means of the LFR and the results are compared to experiments conducted on Zircaloy-4 and the austenitic stainless stell Type AISI 304. From the very good agreement between both it is concluded that under the loading conditions considered, creep failure damage is the main life determining damage contribution. (orig.)

  16. Investigation of bending fatigue-life of aluminum sheets based on rolling direction

    Directory of Open Access Journals (Sweden)

    Raif Sakin

    2018-03-01

    Full Text Available High-cycle fatigue (HCF and low-cycle fatigue (LCF fatigue lives of rolled AA1100 and AA1050 aluminum sheets along different directions were evaluated at room temperature. Four types of samples denoted as longitudinal (L and transverse (T to the rolling direction were compared because the samples along the two typical directions show an obvious anisotropy. A cantilever plane-bending and multi-type fatigue testing machine was specially designed for this purpose. Deflection-controlled fatigue tests were conducted under fully reversed loading. The longest fatigue lives in the LCF region were obtained for AA1050 (L while AA1100 (L samples had the longest fatigue lives in the HCF region. Keywords: AA1100, AA1050, Aluminum sheet, Bending fatigue life, Rolling direction

  17. An investigation on high temperature fatigue properties of tempered nuclear-grade deposited weld metals

    Science.gov (United States)

    Cao, X. Y.; Zhu, P.; Yong, Q.; Liu, T. G.; Lu, Y. H.; Zhao, J. C.; Jiang, Y.; Shoji, T.

    2018-02-01

    Effect of tempering on low cycle fatigue (LCF) behaviors of nuclear-grade deposited weld metal was investigated, and The LCF tests were performed at 350 °C with strain amplitudes ranging from 0.2% to 0.6%. The results showed that at a low strain amplitude, deposited weld metal tempered for 1 h had a high fatigue resistance due to high yield strength, while at a high strain amplitude, the one tempered for 24 h had a superior fatigue resistance due to high ductility. Deposited weld metal tempered for 1 h exhibited cyclic hardening at the tested strain amplitudes. Deposited weld metal tempered for 24 h exhibited cyclic hardening at a low strain amplitude but cyclic softening at a high strain amplitude. Existence and decomposition of martensite-austenite (M-A) islands as well as dislocations activities contributed to fatigue property discrepancy among the two tempered deposited weld metal.

  18. Microstructure evolution during cyclic tests on EUROFER 97 at room temperature. TEM observation and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Giordana, M.F., E-mail: giordana@ifir-conicet.gov.ar [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 Bis, 2000 Rosario (Argentina); Giroux, P.-F. [Commissariat a l' Energie Atomique, DEN/DANS/DMN/SRMA, 91191 Gif-sur-Yvette Cedex (France); Alvarez-Armas, I. [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 Bis, 2000 Rosario (Argentina); Sauzay, M. [Commissariat a l' Energie Atomique, DEN/DANS/DMN/SRMA, 91191 Gif-sur-Yvette Cedex (France); Armas, A. [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 Bis, 2000 Rosario (Argentina); Kruml, T. [CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, Brno, 616 62 (Czech Republic)

    2012-07-30

    Highlights: Black-Right-Pointing-Pointer Low cycle fatigue test are carried out on EUROFER 97 at room temperature. Black-Right-Pointing-Pointer EUROFER 97 shows a pronounced cyclic softening accompanied by microstructural changes. Black-Right-Pointing-Pointer Cycling induces a decrement in dislocation density and subgrain growth. Black-Right-Pointing-Pointer A simple mean-field model based on crystalline plasticity is proposed. Black-Right-Pointing-Pointer The mean subgrain size evolution is predicted by modelling. - Abstract: The 9% Cr quenched and tempered reduced-activation ferritic/martensitic steel EUROFER 97 is one of the candidates for structural components of fusion reactors. Isothermal, plastic strain-controlled, low-cycle fatigue tests are performed. Tested at room temperature, this steel suffers a cyclic softening effect linked to microstructural changes observed by transmission electron microscopy, such as the decrease of dislocation density inside subgrains or the growth of subgrain size. From the assumed mechanisms of softening a simple mean-field model based on crystalline plasticity is proposed to predict these microstructure evolutions during cycling and monotonic deformation.

  19. Data processing codes for fatigue and tensile tests

    International Nuclear Information System (INIS)

    Sanchez Sarmiento, Gustavo; Iorio, A.F.; Crespi, J.C.

    1981-01-01

    The processing of fatigue and tensile tests data in order to obtain several parameters of engineering interest requires a considerable effort of numerical calculus. In order to reduce the time spent in this work and to establish standard data processing from a set of similar type tests, it is very advantageous to have a calculation code for running in a computer. Two codes have been developed in FORTRAN language; one of them predicts cyclic properties of materials from the monotonic and incremental or multiple cyclic step tests (ENSPRED CODE), and the other one reduces data coming from strain controlled low cycle fatigue tests (ENSDET CODE). Two examples are included using Zircaloy-4 material from different manufacturers. (author) [es

  20. Out-of-pile fatigue tests on Zircaloy CANDU sheaths

    International Nuclear Information System (INIS)

    Roth, Maria; Ciocanescu, Marin; Gheorghiu, Constantin; Pitigoi, Vasile; Ducu, Catalin; Malinovschi, Viorel

    2005-01-01

    The paper outlines the achievements in the nuclear research field of cooperation on Nuclear Fuel performed as part of the collaboration under the Memorandum of Understanding, settled between Atomic Energy of Canada Limited (AECL) and Institute for Nuclear Research (ICN), The sheath behavior was simulated using out-of-pile fatigue tests, in conditions identical with those met during the operation in power cycling of CANDU reactor, except for irradiation. A special test rig, designed and carried-out at ICN ensured the experimental requirements according to the Canadian testing procedure. The description of the experimental setup and monitoring of testing parameters were also done. The fatigue life time, expressed as number of cycles to rupture (N), was measured as a function of the total strain amplitude (e) induced in the Zircaloy-4 sheath samples. Strain-Life time fatigue dependence (e-N) under low cycle fatigue conditions was also verified using the Coffin-Manson correlation. (authors)

  1. Thermo-mechanical Fatigue Failure of Thermal Barrier Coated Superalloy Specimen

    Science.gov (United States)

    Subramanian, Rajivgandhi; Mori, Yuzuru; Yamagishi, Satoshi; Okazaki, Masakazu

    2015-09-01

    Failure behavior of thermal barrier coated (TBC) Ni-based superalloy specimens were studied from the aspect of the effect of bond coat material behavior on low cycle fatigue (LCF) and thermo-mechanical fatigue (TMF) at various temperatures and under various loading conditions. Initially, monotonic tensile tests were carried out on a MCrAlY alloy bond coat material in the temperature range of 298 K to 1273 K (25 °C to 1000 °C). Special attention was paid to understand the ductile to brittle transition temperature (DBTT). Next, LCF and TMF tests were carried out on the thermal barrier coated Ni-based alloy IN738 specimen. After these tests, the specimens were sectioned to understand their failure mechanisms on the basis of DBTT of the bond coat material. Experimental results demonstrated that the LCF and TMF lives of the TBC specimen were closely related to the DBTT of the bond coat material, and also the TMF lives were different from those of LCF tests. It has also been observed that the crack density in the bond coat in the TBC specimen was significantly dependent on the test conditions. More importantly, not only the number of cracks but also the crack penetration probability into substrate were shown to be sensitive to the DBTT.

  2. Some new fatigue tests in high temperature water and liquid sodium environment

    International Nuclear Information System (INIS)

    Hattori, Takahiro; Yamauchi, Takayoshi; Kanasaki, Hiroshi; Kondo, Yoshiyuki; Endo, Tadayoshi.

    1987-01-01

    To evaluate the fatigue strength of structural materials for PWR or FBR plants, fatigue test data must be obtained in an environment of simulated primary and secondary water for PWR or of high temperature liquid sodium for FBR. Generally, such tests make it necessary to prepare expensive facilities, so when large amount of fatigue data are required, it is necessary to rationalize and simplify the fatigue tests while maintaining high accuracy. At the Takasago Research Development Center, efforts to rationalize facilities and maintain accuracy in fatigue tests have been made by developing new test methods and improving conventional techniques. This paper introduces a new method of low cycle fatigue test in high temperature water, techniques for automatic measurement of crack initiation and propagation in high temperature water environment and a multiple type fatigue testing machine for high temperature liquid sodium. (author)

  3. 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.

  4. Early detection of fatigue cracks by means of nondestructive testing, NDT; Tidig detektering av utmattningssprickor genom ofoerstoerande provning, OFP

    Energy Technology Data Exchange (ETDEWEB)

    Broddegaard, Mattias [Siemens Industrial Turbines, Finspaang (Sweden)

    2004-12-01

    Components in gas turbines, steam turbines and boilers are subjected to both high and low cycle fatigue. The lifetime of components is established by calculations based on conservative assumptions and safety factors, which means that most components will have a real life far exceeding the calculated. Conventional nondestructive testing is aimed at detecting macroscopic defects, such as cracks, inclusions and other discontinuities in the material. By having the possibility of detecting damage at a microscopic level, the risk of fractures in components subjected to fatigue can be reduced and the interval between testing occasions can be extended. The project goal has been to establish knowledge about possibilities and limitations for early detection of low and high cycle fatigue damage, by a literature survey and by practical experiments on low cycle fatigue specimens in 12% Cr-steel, for the following nondestructive testing methods: MWM (Meandering Winding Magnetometer) eddy current testing; and Nonlinear ultrasonics, both classical (second harmonic) and non-classical (crack closure). The project started with a literature survey. This resulted in a proposal for specimen design and selection of testing techniques and project partners. Manufacturing of specimens in 12% Cr-steel, designation X22CrMoV12-1, and low cycle fatigue testing at 300 deg C testing temperature was carried out at Siemens Industrial Turbines in Finspaang. Specimens with 0, 25, 50, 75 and 100% consumed life, based on the number of cycles to presence of macroscopic cracks, were produced. MWM eddy current testing was carried out by Jentek Sensors Inc. in the USA. Measurements with nonlinear ultrasonics were carried out by Siemens Corporate Technology in Munich and at Blekinge Univ. The specimens were finally examined in SEM and light optical microscope in Finspaang. In the literature, results showing that early detection of fatigue damage by nondestructive testing is possible, can be found. By

  5. Test report on experimental stress analysis of a 24 inch diameter tee (ORNL T-12)

    International Nuclear Information System (INIS)

    Henley, D.R.

    1975-04-01

    The experimental stress analysis and low cycle fatigue test of one 24'' x 24'' x 10'' schedule 40 carbon steel, ANSI B16.9 tee performed by Combustion Engineering, Inc. is described. The tee was instrumented with 230 rectangular strain gage rosettes. Elastic data was obtained for 12 loading conditions consisting of internal pressure and orthogonal pure moments and orthogonal direct forces applied individually to the free branch and run ends of the tee. One of the run ends of the tee was ''built in'' throughout the test. All loads were applied through pipe extensions welded to the tee. The tee was tested to failure in a low cycle pressure fatigue test with a cyclic internal pressure between 0 psi and 1800 psi. A through-the-wall fatigue crack occurred at 76620 cycles. Significant test results are summarized and compared with design values tabulated in the ASME Boiler and Pressure Vessel Code, Section III, 1971. (U.S.)

  6. Characterization of high temperature tensile and creep–fatigue properties of Alloy 800H for intermediate heat exchanger components of (V)HTRs

    Energy Technology Data Exchange (ETDEWEB)

    Kolluri, M., E-mail: kolluri@nrg.eu; Pierick, P. ten, E-mail: tenpierick@nrg.eu; Bakker, T., E-mail: t.bakker@nrg.eu

    2015-04-01

    Highlights: • High temperature tensile, creep–fatigue (C–F) properties of Alloy 800H are studied. • Strength and uniform elongation properties at 800 °C are much lower than RT values. • Strong influence of hold time and Δε{sub tot} on low cycle fatigue life was observed. • The total allowable C–F damage (D) at 800 °C decreases with the decreasing Δε{sub tot}. • Synergetic effect of C–F interactions showed stronger effect at lower Δε{sub tot} values. - Abstract: Alloy 800H is considered as a candidate material for intermediate heat exchanger (IHX) components of (very) high temperature reactors (V)HTRs. Qualification of the this alloy for the aforementioned nuclear applications requires understanding of its high temperature tensile, low-cycle fatigue behavior and creep–fatigue interactions because the IHX components suffer from combined creep–fatigue loadings resulting from thermally induced strain cycles associated with start-up and shutdown cycles. To this end, in this paper, the tensile properties of the Alloy 800H base and tungsten inert gas (TIG) welded materials are studied at three different temperatures, room temperature 21, 700 and 800 °C. Low cycle fatigue (LCF) behavior of the base material is investigated at 800 °C with no-hold time (no-HT) and hold time (HT) to study creep–fatigue interactions. The tensile test results showed substantial differences between the strength and ductility properties of the base and weld materials at all 3 temperatures, however, the trends in temperature dependence of tensile properties are similar for both base and weld materials. LCF studies with no-HT and HT showed a strong influence of HT on the low cycle fatigue life of this alloy illustrating the substantial influence of creep mechanisms at 800 °C. Finally, cumulative values of creep versus fatigue damage fractions are plotted in a creep–fatigue interaction diagram and these results are discussed with respect to the existing bi

  7. Test of large-scale specimens and models as applied to NPP equipment materials

    International Nuclear Information System (INIS)

    Timofeev, B.T.; Karzov, G.P.

    1993-01-01

    The paper presents the test results on low-cycle fatigue, crack growth rate and fracture toughness of large-scale specimens and structures, manufactured from steel, widely applied in power engineering industry and used for the production of NPP equipment with VVER-440 and VVER-1000 reactors. The obtained results are compared with available test results of standard specimens and calculation relations, accepted in open-quotes Calculation Norms on Strength.close quotes At the fatigue crack initiation stage the experiments were performed on large-scale specimens of various geometry and configuration, which permitted to define 15X2MFA steel fracture initiation resistance by elastic-plastic deformation of large material volume by homogeneous and inhomogeneous state. Besides the above mentioned specimen tests in the regime of low-cycle loading, the test of models with nozzles were performed and a good correlation of the results on fatigue crack initiation criterium was obtained both with calculated data and standard low-cycle fatigue tests. It was noted that on the Paris part of the fatigue fracture diagram a specimen thickness increase does not influence fatigue crack growth resistance by tests in air both at 20 and 350 degrees C. The estimation of the comparability of the results, obtained on specimens and models was also carried out for this stage of fracture. At the stage of unstable crack growth by static loading the experiments were conducted on specimens of various thickness for 15X2MFA and 15X2NMFA steels and their welded joints, produced by submerged arc welding, in as-produced state (the beginning of service) and after embrittling heat treatment, simulating neutron fluence attack (the end of service). The obtained results give evidence of the possibility of the reliable prediction of structure elements brittle fracture using fracture toughness test results on relatively small standard specimens. 35 refs., 23 figs

  8. Joined application of a multiaxial critical plane criterion and a strain energy density criterion in low-cycle fatigue

    Directory of Open Access Journals (Sweden)

    Andrea Carpinteri

    2017-07-01

    Full Text Available In the present paper, the multiaxial fatigue life assessment of notched structural components is performed by employing a strain-based multiaxial fatigue criterion. Such a criterion, depending on the critical plane concept, is extended by implementing the control volume concept reated to the Strain Energy Density (SED approach: a material point located at a certain distance from the notch tip is assumed to be the verification point where to perform the above assessment. Such a distance, measured along the notch bisector, is a function of both the biaxiality ratio (defined as the ratio between the applied shear stress amplitude and the normal stress amplitude and the control volume radii under Mode I and Mode III. Once the position of the verification point is determined, the fatigue lifetime is assessed through an equivalent strain amplitude, acting on the critical plane, together with a unique material reference curve (i.e. the Manson-Coffin curve. Some uniaxial and multiaxial fatigue data related to V-notched round bars made of titanium grade 5 alloy (Ti-6Al-4V are examined to validate the present criterion.

  9. Low cycle fatigue behaviour of Ti–6Al–5Zr–0⋅5Mo–0⋅25Si alloy at ...

    Indian Academy of Sciences (India)

    Unknown

    condition as compared to the β treated one is in conformity with the higher degree of softening in the former one, as indicated by the stress-response curves in figures 3a and b. Some investigators have reported cross over in the cyclic and monotonic stress–strain curves above 1⋅5% of total strain in the near-α titanium alloy, ...

  10. Effect of Forging Parameters on Low Cycle Fatigue Behaviour of Al/Basalt Short Fiber Metal Matrix Composites

    Directory of Open Access Journals (Sweden)

    R. Karthigeyan

    2013-01-01

    Full Text Available This paper deals with metal matrix composites (MMCs of Al 7075 alloy containing different weight percentage (2.5, 5, 7.5, and 10 basalt short fiber reinforcement and unreinforced matrix alloy. The samples were produced by the permanent stir casting technique. The casting ingots were cut into blanks to be forged in single stage and double stage, using MN press and graphite-based lubricant. The microstructures and fatigue properties of the matrix alloy and MMC samples were investigated in the as cast state and in the single and double stage forging operations. The microstructure results showed that the forged sample had a uniform distribution of the basalt short fiber throughout the specimens. Evaluation of the fatigue properties showed that the forged samples had higher values than those of the as cast counterparts. After forging, the enhancement of the fatigue strength of the matrix alloy was so significant and high in the case of 2.5 and 5.0 wt. percentage basalt short fiber reinforced MMC, and there was no enhancement in 7.5 and 10 weight percentages short fiber reinforced MMCs. The fracture damage was mainly due to decohesion at the matrix-fiber interface.

  11. Effect of forging parameters on low cycle fatigue behaviour of Al/basalt short fiber metal matrix composites.

    Science.gov (United States)

    Karthigeyan, R; Ranganath, G

    2013-01-01

    This paper deals with metal matrix composites (MMCs) of Al 7075 alloy containing different weight percentage (2.5, 5, 7.5, and 10) basalt short fiber reinforcement and unreinforced matrix alloy. The samples were produced by the permanent stir casting technique. The casting ingots were cut into blanks to be forged in single stage and double stage, using MN press and graphite-based lubricant. The microstructures and fatigue properties of the matrix alloy and MMC samples were investigated in the as cast state and in the single and double stage forging operations. The microstructure results showed that the forged sample had a uniform distribution of the basalt short fiber throughout the specimens. Evaluation of the fatigue properties showed that the forged samples had higher values than those of the as cast counterparts. After forging, the enhancement of the fatigue strength of the matrix alloy was so significant and high in the case of 2.5 and 5.0 wt. percentage basalt short fiber reinforced MMC, and there was no enhancement in 7.5 and 10 weight percentages short fiber reinforced MMCs. The fracture damage was mainly due to decohesion at the matrix-fiber interface.

  12. Potential drop crack growth monitoring in high temperature biaxial fatigue tests

    International Nuclear Information System (INIS)

    Fitzgerald, B.P.; Krempl, E.

    1993-01-01

    The present work describes a procedure for monitoring crack growth in high temperature, biaxial, low cycle fatigue tests. The reversing DC potential drop equipment monitors smooth, tubular type 304 stainless steel specimens during fatigue testing. Electrical interference from an induction heater is filtered out by an analog filter and by using a long integration time. A Fourier smoothing algorithm and two spline interpolations process the large data set. The experimentally determined electrical potential drop is compared with the theoretical electrostatic potential that is found by solving Laplace's equation for an elliptical crack in a semi-infinite conducting medium. Since agreement between theory and experiment is good, the method can be used to measure crack growth to failure from the threshold of detectability

  13. 78 FR 44052 - Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Model Helicopters

    Science.gov (United States)

    2013-07-23

    ..., which proposed establishing new fatigue life limits for certain GE engine gas generator turbine (GGT... limits need to be based on low cycle fatigue (LCF) events instead of hours time-in- service. This action would retain the previously proposed requirements but correct the life limit formula for a certain GGT...

  14. Gelcast AS800 Materials Characterization for Rocket Engine Applications

    National Research Council Canada - National Science Library

    Khoshbin, Simin

    2000-01-01

    .... The testing results summarized in this paper include tensile, flexural strength, compressive strength, interrupted stress rupture, thermal cycle, fracture toughness, low cycle fatigue, and elastic moduli determinations...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-15

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

  16. Fatigue and fracture behavior of low alloy ferritic forged steels

    International Nuclear Information System (INIS)

    Chaudhry, V.; Sharma, A.K.; Muktibodh, U.C.; Borwankar, Neeraj; Singh, D.K.; Srinivasan, K.N.; Kulkarni, R.G.

    2016-01-01

    Low alloy ferritic steels are widely used in nuclear industry for the construction of pressure vessels. Pressure vessel forged low alloy steels 20MnMoNi55 (modified) have been developed indigenously. Experiments have been carried out to study the Low Cycle Fatigue (LCF) and fracture behavior of these forged steels. Fully reversed strain controlled LCF testing at room temperature and at 350 °C has been carried out at a constant strain rate, and for different axial strain amplitude levels. LCF material behavior has been studied from cyclic stress-strain responses and the strain-life relationships. Fracture behavior of the steel has been studied based on tests carried out for crack growth rate and fracture toughness (J-R curve). Further, responses of fatigue crack growth rate tests have been compared with the rate evaluated from fatigue precracking carried out for fracture toughness (J-R) tests. Fractography of the samples have been carried out to reveal dominant damage mechanisms in crack propagation and fracture. The fatigue and fracture properties of indigenously developed low alloy steel 20MnMoNi55 (modified) steels are comparable with similar class of steels. (author)

  17. Estimate of thermal fatigue lifetime for the INCONEL 625lCF plate while exposed to concentrated solar radiation

    Directory of Open Access Journals (Sweden)

    Rojas-Morín, A.

    2011-04-01

    Full Text Available A system for testing the thermal cycling of materials and components has been developed and installed at the DISTAL-I parabolic dish facility located at the Plataforma Solar de Almería (PSA in Spain. This system allows us to perform abrupt heating/cooling tests by exposing central solar receiver materials to concentrated solar radiation. These tests are performed to simulate both the normal and critical operational conditions of the central solar receiver. The thermal fatigue life for the INCONEL 625LCF® plate when subjected to concentrated solar radiation has been estimated with this system. We have also developed a numerical model that evaluates the thermal behavior of the plate material; additionally, the model yields the tensile-compressive stresses on the plate, which allow the estimation of the Stress-Life (S-N fatigue curves. These curves show that the lifetime of the plate is within the High Cycle Fatigue (HCF region at the operational temperatures of both 650 °C and 900 °C.

    En el concentrador solar de disco parabólico DISTAL-I, situado en la Plataforma Solar de Almería (PSA, en España, se ha instalado un sistema para pruebas de ciclado térmico de materiales. Este sistema permite realizar pruebas abruptas de calentamiento y enfriamiento, en materiales para receptores solares de torre central, al exponerlos a radiación solar concentrada. Estas pruebas se realizan para simular las condiciones de operación de un receptor solar, las condiciones críticas y las condiciones normales. Con este sistema se ha estimado el tiempo de vida bajo fatiga térmica, en una placa de INCONEL 626LCF®, cuando es sometida a radiación solar concentrada. Asimismo, hemos desarrollado un modelo numérico que evalúa el desarrollo térmico en el material de la placa: adicionalmente, el modelo obtiene los esfuerzos de tensión-compresión en la placa, los cuales permiten la estimaciónde las curvas de fatiga vidaesfuerzo (S-N. Estas curvas

  18. Influence of weld discontinuities on strain controlled fatigue behavior of 308 stainless steel weld metal

    International Nuclear Information System (INIS)

    Bhanu Sankara Rao, K.; Valsan, M.; Sandhya, R.; Mannan, S.L.; Rodriguez, P.

    1994-01-01

    Detailed investigations have been performed for assessing the importance of weld discontinuities in strain controlled low cycle fatigue (LCF) behavior of 308 stainless steel (SS) welds. The LCF behavior of 308 SS welds containing defects was compared with that of type 304 SS base material and 308 SS sound weld metal. Weld pads were prepared by shielded metal arc welding process. Porosity and slag inclusions were introduced deliberately into the weld metal by grossly exaggerating the conditions normally causing such defects. Total axial strain controlled LCF tests have been conducted in air at 823 K on type 304 SS base and 308 SS sound weld metal employing strain amplitudes in the range from ±0.25 to ±0.8 percent. A single strain amplitude of ±0.25 percent was used for all the tests conducted on weld samples containing defects. The results indicated that the base material undergoes cyclic hardening whereas sound and defective welds experience cyclic softening. Base metal showed higher fatigue life than sound weld metal at all strain amplitudes. The presence of porosity and slag inclusions in the weld metal led to significant reduction in life. Porosity on the specimen surface has been found to be particularly harmful and caused a reduction in life by a factor of seven relative to sound weld metal

  19. Cyclic deformation and fatigue behaviors of Hadfield manganese steel

    Energy Technology Data Exchange (ETDEWEB)

    Kang, J. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, F.C., E-mail: zfc@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Long, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Lv, B. [School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2014-01-03

    The cyclic deformation characteristics and fatigue behaviors of Hadfield manganese steel have been investigated by means of its ability to memorize strain and stress history. Detailed studies were performed on the strain-controlled low cycle fatigue (LCF) and stress-controlled high cycle fatigue (HCF). Initial cyclic hardening to saturation or peak stress followed by softening to fracture occurred in LCF. Internal stress made the dominant contribution to the fatigue crack propagation until failure. Effective stress evolution revealed the existence of C–Mn clusters with short-range ordering in Hadfield manganese steel and demonstrated that the interaction between C atoms in the C–Mn cluster and dislocation was essential for its cyclic hardening. The developing/developed dislocation cells and stacking faults were the main cyclic deformation microstructures on the fractured sample surface in LCF and HCF, which manifested that fatigue failure behavior of Hadfield manganese steel was induced by plastic deformation during strain-controlled or stress-controlled testing.

  20. Development and Manufacturing Technology of Prototype Monoblock Low Pressure Rotor Shaft by 650ton Large Ingot

    Energy Technology Data Exchange (ETDEWEB)

    Song, Duk-Yong; Kim, Dong-Soo; Kim, Jungyeup; Lee, Jongwook; Ko, Seokhee [Doosan Heavy Industries and Construction, Changwon(Korea, Republic of)

    2016-10-15

    In order to establish the manufacturing technology for monoblock LP rotor shaft, DHI has produced the prototype monoblock LP rotor shaft with a maximum diameter of φ 2,800 mm using 650 ton ingot and investigated the mechanical properties and the internal quality of the ingot. As a result, the quality and mechanical properties required the large rotor shaft for nuclear power plant met a target. These results indicate that DHI can be contributed to increasing demands with high efficiency and capacity at the nuclear power plant. Additionally, some tests such as high cycle fatigue (HCF), low cycle fatigue (LCF), fracture toughness (K1C/J1C) and dynamic crack propagation velocity (da/dN) are in progress.

  1. The Effect of Material Variability on Fatigue Behaviors of Low Alloy Steels in 310 .deg. C Deoxygenated Water

    International Nuclear Information System (INIS)

    Jang, Hun; Jang, Changheui; Kim, Insup; Cho, Hyunchul

    2008-01-01

    As environmental fatigue damage is one of the main crack initiation mechanisms in nuclear power plants (NPPs), it is most important factor to assess the integrity and safety of NPPs. So, based on extensive researches, argon nation laboratory (ANL) suggested the statistical model to predict fatigue life of low alloy steels (LASs) which are widely used as structural material in NPPs. Also, we reported the environmental fatigue behaviors of SA508 Gr.1a LAS. However, from comparison between our experimental fatigue data and ANL's statistical model, our fatigue life data showed poor agreement with the ANL's statistical model. In this regard, the additional low cycle fatigue (LCF) tests were performed in 310 .deg. C deoxygenated water, and compared with ANL's statistical model to evaluate reliability of the data. And then, the effect of material variability on the fatigue life of LASs was investigated through microstructure analysis

  2. Nondestructive testing for microstructural characterization in 9Cr-1Mo ferritic steel towards assessment of fabrication quality and in-service degradation

    Energy Technology Data Exchange (ETDEWEB)

    Jayakumar, T.; Rao, K.B.S.; Raj, Baldev [Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    1999-07-01

    The paper discusses the usefulness of non destructive testing for microstructural characterization in 9Cr-1Mo ferritic steel. Ultrasonic velocity and attenuation measurements and spectral analysis have been used in a complementary way for characterizing Ac{sub 1} and Ac{sub 3} temperatures, amount of martensite and ferrite, dissolution of V{sub 4}C{sub 3} and NbC and formation of {delta}-ferrite. The microstructural degradation occurring due to thermal ageing and creep has also been studied by ultrasonic velocity measurements. Magnetic Barkhausen noise technique has been used for estimating the extent of various regions in heat affected zone (HAZ) of 9Cr-1Mo ferritic steel weldment. The same technique has been used for the assessment of low cycle fatigue damage in 9Cr-1Mo steel. The study establishes that non destructive methods can be used for the assessment of fabrication quality and in service degradation of the components. (author)

  3. Design study of ITER-like divertor target for DEMO

    International Nuclear Information System (INIS)

    Crescenzi, Fabio; Bachmann, C.; Richou, M.; Roccella, S.; Visca, E.; You, J.-H.

    2015-01-01

    Highlights: • ‘DEMO’ is a near-term Power Plant Conceptual Study (PPCS). • The ITER-like design concept represents a promising solution also for DEMO plasma facing units. • The optimization of PFUs aims to enhance the thermo-mechanical behaviour of the component. • The optimized geometry was evaluated by ITER SDC-IC criteria and in terms of low cycle fatigue (LCF). - Abstract: A near-term water-cooled target solution has to be evaluated together with the required technologies and its power exhaust limit under ‘DEMO’ conditions. The ITER-like design concept based on the mono-block technology using W as armour material and the CuCrZr-IG as structural material with an interlayer of pure copper represents a promising solution also for DEMO. This work reports the design study of an “optimized” ITER-like Water Cooled Divertor able to withstand a heat flux of 10 MW m"−"2, as requested for DEMO operating conditions. The optimization of plasma facing unit (PFU) aims to enhance the thermo-mechanical behaviour of the component by varying some geometrical parameters (monoblock size, interlayer thickness and, tube diameter and thickness). The optimization was performed by means of the multi-variable optimization algorithms using the FEM code ANSYS. The coolant hydraulic conditions (inlet pressure, temperature and velocity) were fixed for simplicity. This study is based on elastic analysis and 3 dimensional modelling. The resulting optimized geometry was evaluated on the basis of the ITER SDC-IC criteria and in terms of low cycle fatigue (LCF). The margin to the critical heat flux (CHF) was also estimated. Further design study (taking into account the effect of neutron radiation on the material properties) together with mock-up fabrication and high-heat-flux (HHF) tests are foreseen in next work programmes.

  4. Design study of ITER-like divertor target for DEMO

    Energy Technology Data Exchange (ETDEWEB)

    Crescenzi, Fabio, E-mail: fabio.crescenzi@enea.it [ENEA, Unità Tecnica Fusione, ENEA C. R. Frascati, via E. Fermi 45, 00044 Frascati (Roma) (Italy); Bachmann, C. [EFDA, Power Plant Physics and Technology, Boltzmannstraße 2, 85748 Garching (Germany); Richou, M. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Roccella, S.; Visca, E. [ENEA, Unità Tecnica Fusione, ENEA C. R. Frascati, via E. Fermi 45, 00044 Frascati (Roma) (Italy); You, J.-H. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)

    2015-10-15

    Highlights: • ‘DEMO’ is a near-term Power Plant Conceptual Study (PPCS). • The ITER-like design concept represents a promising solution also for DEMO plasma facing units. • The optimization of PFUs aims to enhance the thermo-mechanical behaviour of the component. • The optimized geometry was evaluated by ITER SDC-IC criteria and in terms of low cycle fatigue (LCF). - Abstract: A near-term water-cooled target solution has to be evaluated together with the required technologies and its power exhaust limit under ‘DEMO’ conditions. The ITER-like design concept based on the mono-block technology using W as armour material and the CuCrZr-IG as structural material with an interlayer of pure copper represents a promising solution also for DEMO. This work reports the design study of an “optimized” ITER-like Water Cooled Divertor able to withstand a heat flux of 10 MW m{sup −2}, as requested for DEMO operating conditions. The optimization of plasma facing unit (PFU) aims to enhance the thermo-mechanical behaviour of the component by varying some geometrical parameters (monoblock size, interlayer thickness and, tube diameter and thickness). The optimization was performed by means of the multi-variable optimization algorithms using the FEM code ANSYS. The coolant hydraulic conditions (inlet pressure, temperature and velocity) were fixed for simplicity. This study is based on elastic analysis and 3 dimensional modelling. The resulting optimized geometry was evaluated on the basis of the ITER SDC-IC criteria and in terms of low cycle fatigue (LCF). The margin to the critical heat flux (CHF) was also estimated. Further design study (taking into account the effect of neutron radiation on the material properties) together with mock-up fabrication and high-heat-flux (HHF) tests are foreseen in next work programmes.

  5. Influence of Localized Plasticity on IASCC Sensitivity of Austenitic Stainless Steels under PWR Primary Water

    Science.gov (United States)

    Cissé, Sarata; Tanguy, Benoit; Laffont, Lydia; Lafont, Marie-Christine; Guerre, Catherine; Andrieu, Eric

    The sensibility of precipitation-strengthened A286 austenitic stainless steel to Stress Corrosion Cracking (SCC) is studied by means of Slow Strain Rate Tests (SSRT). First, alloy cold working by Low Cycle Fatigue (LCF) is investigated. Fatigue tests under plastic strain control are performed at different strain levels (Δ ɛp/2=0.2%, 0.5% and 0.8%) in order to establish correlation between stress softening and deformation microstructure resulting from LCF tests. Deformed microstructures have been identified through TEM investigations. Three states of cyclic behaviour for precipitation-strengthened A286 have been identified: hardening, cyclic softening and finally saturation of softening. It is shown that the A286 alloy cyclic softening is due to microstructural features such as defects — free deformation bands resulting from dislocations motion along family plans , that swept defects or γ' precipitates and lead to deformation localization. In order to quantify effects of plastic localized deformation on intergranular stress corrosion cracking (IGSCC) of the A286 alloy in PWR primary water, slow strain rate tests are conducted. For each cycling conditions, two specimens at a similar stress level are tested: the first containing free precipitate deformation bands, the other not significant of a localized deformation state. SSRT tests are still in progress.

  6. Present status of mechanical testing technology at the Research Hot Laboratory

    International Nuclear Information System (INIS)

    Kizaki, M.; Tobita, T.; Koya, T.; Kikuchi, T.

    1993-01-01

    Mechanical tests of irradiated metallic materials at the Research Hot Laboratory(RHL) have been carried out for 30 years to support material research in JAERI and to evaluate the irradiation integrity of pressure vessel steel in commercial power plant. Two tensile testing machines and one Charpy impact testing machine are available for the examinations. One of the tensile testing machines has 1000 kgf load capacity under the vacuum of ∼ 10 -7 torr at the temperature of 1300degC max.. The other one has 10 tonf load capacity, and is utilized for the multi-purpose tests such as tensile and compressive tests in air atmosphere at the temperature between -160 and 900degC. Examinations cover tensile test, bending test, J ic fracture toughness test, low cycle fatigue test and so on. Charpy impact testing machine with notched-bar specimen is instrumented with 30 kgf-m capacity in the temperature range of -140 - 240 degC. To support these mechanical tests in RHL, special jigs, devices and instruments have been developed. (author)

  7. Toward a better understanding of strain incompatibilities at grain boundaries in the analysis of fatigue crack initiation at low temperature in the UdimetTM 720 Li superalloy

    Directory of Open Access Journals (Sweden)

    Larrouy Baptiste

    2014-01-01

    Full Text Available Low cycle fatigue properties of polycrystalline γ-γ′ Ni-based superalloys are dependent on many factors such as temperature, environment, grain size and distribution of the strengthening phases. Under LCF conditions at intermediate temperatures, an intergranular crack initiation could be observed. In this paper we propose to analyze the local conditions favouring such an intergranular cracking mode considering the high strength C&W UdimetTM720 Li alloy, widely used for manufacturing high pressure turbine disk for aeroengine applications. Tensile and fatigue tests were performed in air in the 20–465 ∘C range of temperature on micro-samples in order to focus on plasticity and damage processes developed near grain boundaries. A special attention was paid on the slip transfer between neighbouring grains taking into account their local crystallographic orientations. In some specific crystallographic configurations, small zones were detected at the tip of slip bands presenting an intense elastic/plastic activity. Although they are limited in size, they are associated to local crystalline rotations. High levels of local strain/stress were also evaluated in these volumes using an EBSD pattern cross correlation technique. The development of such specific zones was investigated at different stages of the tensile and LCF behaviour and was identified as leading to micro-cracks initiation for both solicitation modes.

  8. Modeling the influence of high dose irradiation on the deformation and damage behavior of RAFM steels under low cycle fatigue conditions

    Energy Technology Data Exchange (ETDEWEB)

    Aktaa, J. [Forschungszentrum Karlsruhe GmbH, Institute for Materials Research II, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)], E-mail: aktaa@imf.fzk.de; Petersen, C. [Forschungszentrum Karlsruhe GmbH, Institute for Materials Research II, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2009-06-01

    A viscoplastic deformation damage model developed for RAFM steels in the reference un-irradiated state was modified taking into account the irradiation influence. The modification mainly consisted in adding an irradiation hardening variable with an appropriate evolution equation including irradiation dose driven terms as well as inelastic deformation and thermal recovery terms. With this approach, the majority of the material and temperature dependent model parameters are no longer dependent on the irradiation dose and only few parameters need to be determined by applying the model to RAFM steels in the irradiated state. The modified model was then applied to describe the behavior of EUROFER 97 observed in the post irradiation examinations of the irradiation programs ARBOR 1, ARBOR 2 and SPICE. The application results will be presented and discussed in addition.

  9. Mechanical testing and development of the helical field coil joint for the Advanced Toroidal Facility

    International Nuclear Information System (INIS)

    Nelson, B.E.; Bryan, W.E.; Goranson, P.L.; Warwick, J.E.

    1985-01-01

    The helical field (HF) coil set for the Advanced Toroidal Facility (ATF) is an M = 12, l = 2, constant-ratio torsatron winding consisting of 2 coils, each with 14 turns of heavy copper conductor. The coils are divided into 24 identical segments to facilitate fabrication and minimize the assembly schedule. The segments are connected across through-bolted lap joints that must carry up to 124,000 A per turn for 5 s or 62,500 A steady-state. In addition, the joints must carry the high magnetic and thermal loads induced in the conductor and still fit within the basic 140- by 30-mm copper envelope. Extensive testing and development were undertaken to verify and refine the basic joint design. Tests included assembly force and clamping force for various types of misalignment; joint resistance as a function of clamping force; clamp bolt relaxation due to thermal cycling; fatigue testing of full-size, multiturn joint prototypes; and low-cycle fatigue and tensile tests of annealed CDA102 copper. The required performance parameters and actual test results, as well as the final joint configuration, are presented. 2 refs., 9 figs., 4 tabs

  10. Test report on experimental stress analysis of a 24 inch diameter tee (ORNL T-13)

    International Nuclear Information System (INIS)

    Henley, D.R.

    1975-03-01

    The experimental stress analysis and low cycle fatigue test of one 24 in. x 24 in. x 10 in. schedule 160 carbon steel, ANSI B16.9 tee performed by Combustion Engineering, Inc. are described. The tee was instrumented with 230 rectangular strain gage rosettes. Elastic data was obtained for 12 loading conditions consisting of internal pressure and orthogonal pure moments and orthogonal direct forces applied individually to the free branch and run ends of the tee. One of the run ends of the tee was ''built in'' throughout the test. All loads were applied through pipe extensions welded to the tee. The tee was tested to failure in a low cycle pressure fatigue test with a cyclic internal pressure between 100 psi and 7000 psi. A through-the-wall fatigue crack occurred at 15,084 cycles. Significant test results are summarized and compared with design values tabulated in the ASME Boiler and Pressure Vessel Code, Section III, 1971. (U.S.)

  11. Bending test in epoxy composites reinforced with continuous and aligned PALF fibers

    Directory of Open Access Journals (Sweden)

    Gabriel Oliveira Glória

    2017-10-01

    Full Text Available Sustainable actions aiming to prevent increasing worldwide pollution are motivating the substitution of environmentally friendly materials for conventional synthetic ones. A typical example is the use of natural lignocellulosic fiber (LCF as reinforcement of polymer composites that have traditionally been reinforced with glass fiber. Both scientific research and engineering applications support the use of numerous LCFs composites. The pineapple fiber (PALF, extracted from the leaves of Ananas comosus, is considered a LCF with potential for composite reinforcement. However, specific mechanical properties and microstructural characterization are still necessary for this purpose. Therefore, the objective of this short work is to evaluate the flexural properties, by means of three points, bend tests, of epoxy composites incorporated with up to 30 vol% of PALF. Results reveal that continuous and aligned fibers significantly increase the flexural strength. Scanning electron microscopy disclosed the fracture mechanism responsible for this reinforcement. Keywords: Pineapple fibers, PALF, Flexural properties, Bending test, Epoxy composites, Fracture mechanism

  12. Effect of test temperature on tensile and fatigue properties of nickel-base heat-resistant alloys

    International Nuclear Information System (INIS)

    Tsuji, Hirokazu; Nakajima, Hajime

    1987-01-01

    A series of tensile and strain controlled low-cycle fatigue tests were conducted at temperatures ranging from RT to 900 0 C on a nickel-base heat-resistant alloy, Hastelloy XR-II, which is one of the candidate alloys for applications in the process heating high-temperature gas-cooled reactor (HTGR). Fatigue tests at room temperature and all tensile tests were conducted in air, while fatigue tests at and above 400 0 C were conducted in the simulated HTGR helium environment. In those tests the effect of test temperature on tensile and fatigue properties was investigated. The ductility minimum point was observed near 600 0 C, while tensile and fatigue strengths decreased with increasing test temperature. The fatigue lives estimated with the method proposed by Manson were compatible with the experimental results under the given conditions. For the specimens fatigued at and above 700 0 C, the percentage of the intergranular fracture mode gradually increased with increasing test temperature. (orig.)

  13. Experimental stress analysis and fatigue tests of five 12-in. NPS ANSI Standard B16.9 tees

    International Nuclear Information System (INIS)

    Moore, S.E.; Grigory, S.C.; Weed, R.A.

    1984-04-01

    The tees, designated as ORNL tees T-4, T-6, T-7, T-8, and T-15, were tested under subcontract at Southwest Research Institute, and the data were analyzed at ORNL. Experimental stress analyses were conducted for 13 individual loadings on each tee, including internal pressure and 3 mutually perpendicular force and moment loads on the branch and on the run. Each test model was instrumented with approx. 220, 1/16-in. three-gage, 45 0 strain rosettes on the body of the tee, and approx. 10, 1/16-in. two-gage, strain rosettes on the pipe extensions. Dial indicators, mounted on a special nonflexible holding frame, were used to measure deflections and rotations of the pipe extensions. Normalized maximum stress intensities for each loading condition on each tee are summarized in the text. Complete sets of strain-gage data, normalized stresses, and displacement measurements for each tee are given on microfiche in the appendixes. Following completion of the strain-gage tests, each tee was tested to failure in a fully reversed displacement-controlled low-cycle fatigue test with an alternating transverse load applied to the branch pipe. The load was directed out of plane for T-4, T-6, T-8, and T-15; and in plane for T-7. A constant internal pressure equal to the nominal design pressure was maintained during the fatigue tests. Failure data from the fatigue tests are summarized in the text

  14. Influence of dynamic sodium environment on the creep-fatigue behaviour of Modified 9Cr-1Mo ferritic-martensitic steel

    International Nuclear Information System (INIS)

    Kannan, R.; Ganesan, V.; Mariappan, K.; Sukumaran, G.; Sandhya, R.; Mathew, M.D.; Bhanu Sankara Rao, K.

    2011-01-01

    Highlights: → The effects of dynamic sodium on the CFI behaviour of Mod. 9Cr-1Mo steel has investigated. → The cyclic stress response of Mod. 9Cr-1Mo steel under flowing sodium environment is similar to that of air environment. → The creep-fatigue endurance of the alloy is found to decrease with introduction of hold time and with increase in the duration of hold time and the factor of life increase in sodium compared to air environment is reduced with increase in hold time. → In contrast to air environment, tensile holds were found to be more damaging than compression hold in sodium environment. → Design rules based on air environment can be safely applied for the components operating in sodium environment. - Abstract: The use of liquid sodium as a heat transfer medium for sodium-cooled fast reactors (SFRs) necessitates a clear understanding of the effects of dynamic sodium on low cycle fatigue (LCF), creep and creep-fatigue interaction (CFI) behaviour of reactor structural materials. Mod. 9Cr-1Mo ferritic steel is the material of current interest for the steam generator components of sodium cooled fast reactors. The steam generator has a design life of 30-40 years. The effects of dynamic sodium on the LCF and CFI behaviour of Mod. 9Cr-1Mo steel have been investigated at 823 and 873 K. The CFI life of the steel showed marginal increase under flowing sodium environment when compared to air environment. Hence, the design rules for creep-fatigue interaction based on air tests can be safely applied for components operating in sodium environment. This paper attempts to explain the observed LCF and CFI results based on the detailed metallography and fractography conducted on the failed samples.

  15. Experimental stress analysis and fatigue tests of five 24-in. NPS ANSI Standard B16.9 tees

    International Nuclear Information System (INIS)

    Moore, S.E.; Hayes, J.K.; Weed, R.A.

    1985-03-01

    Experimental stress analyses and low-cycle fatigue tests of five 24-in. nominal pipe size American National Standards Institute (ANSI) Standard B16.9 forged tees are documented in this report. The tees, designated as Oak Ridge National Laboratory tees T10, T11, T12, T13, and T16, were tested under subcontract at Combustion Engineering, Inc. in Chattanooga, Tennessee. Experimental stress analyses were conducted for 12 individual loadings on each tee. Each test model was instrumented with approx. 225, 1/8-in. three-gage, 45 0 strain rosettes on the inside and outside surfaces; and 6 linear variable differential transformers mounted on special nonflexible holding frames for measuring deflections and rotations of the pipe extensions. Following completion of the strain-gate tests, each tee was fatigue tested to failure with either a fully reversed displacement controlled in-plane bending moment on the branch or a cyclic internal pressure that ranged from a value slightly above zero to about 90% of the nominal yield pressure of the pipe extensions

  16. Experimental stress analysis and fatigue tests of five 24-in. NPS ANSI Standard B16. 9 tees. [PWR; BWR

    Energy Technology Data Exchange (ETDEWEB)

    Moore, S.E.; Hayes, J.K.; Weed, R.A.

    1985-03-01

    Experimental stress analyses and low-cycle fatigue tests of five 24-in. nominal pipe size American National Standards Institute (ANSI) Standard B16.9 forged tees are documented in this report. The tees, designated as Oak Ridge National Laboratory tees T10, T11, T12, T13, and T16, were tested under subcontract at Combustion Engineering, Inc. in Chattanooga, Tennessee. Experimental stress analyses were conducted for 12 individual loadings on each tee. Each test model was instrumented with approx. 225, 1/8-in. three-gage, 45/sup 0/ strain rosettes on the inside and outside surfaces; and 6 linear variable differential transformers mounted on special nonflexible holding frames for measuring deflections and rotations of the pipe extensions. Following completion of the strain-gate tests, each tee was fatigue tested to failure with either a fully reversed displacement controlled in-plane bending moment on the branch or a cyclic internal pressure that ranged from a value slightly above zero to about 90% of the nominal yield pressure of the pipe extensions.

  17. Characterisation and modelling of the microstructural and mechanical evolution of a steam turbine rotor steel

    International Nuclear Information System (INIS)

    Mayer, T.

    2012-01-01

    This dissertation deals with the effective mechanical analysis of steam turbine parts which is not only required for the reliable and safe use of newly built steam turbines, but also for the remaining life assessment of components that have been exposed to service duty over long periods of time. This Thesis aims to develop a physically motivated evolutionary constitutive model for a low-alloy bainitic 2CrMoNiWV (23CrMoNiWV8-8) steam turbine rotor steels. A comprehensive experimental characterisation is performed concerning the mechanical and microstructural evolution of 2CrMoNiWV as subjected to low cycle fatigue (LCF) deformation at elevated temperatures, at different strain rates and for various strain amplitudes. This cyclic plastic deformation causes the rearrangement of dislocations in the microstructure of the steels used for such rotor applications. Symmetric, strain controlled LCF experiments have been carried out in the Laboratory of the High Temperature Integrity Group at the Swiss Federal Laboratories for Materials Science and Technology EMPA. These include mechanical tests in the temperature range between 20 °C to 600 °C at strain rates of 0.001%/s to 1.0%/s and strain amplitudes of ±0.25% to ±1.0%. The LCF experiments reported on comprehensively characterise the temperature, strain rate and strain amplitude dependent cyclic elastic-plastic behaviour of 2CrMoNiWV. Both complete single-specimen endurance tests and interrupted multi-specimen tests have been performed. On the basis of this experimental evidence, an evolutionary formulation of the model is further developed that excellently reproduces the strain amplitude dependent mechanical evolution of 2CrMoNiWV when subjected to LCF loading at different constant strain amplitudes but equal temperature and strain rate. The simulation of benchmark experiments introducing increasing or decreasing strain amplitude steps into the LCF deformation history provide promising results. A further important

  18. Characterisation and modelling of the microstructural and mechanical evolution of a steam turbine rotor steel

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, T.

    2012-07-01

    This dissertation deals with the effective mechanical analysis of steam turbine parts which is not only required for the reliable and safe use of newly built steam turbines, but also for the remaining life assessment of components that have been exposed to service duty over long periods of time. This Thesis aims to develop a physically motivated evolutionary constitutive model for a low-alloy bainitic 2CrMoNiWV (23CrMoNiWV8-8) steam turbine rotor steels. A comprehensive experimental characterisation is performed concerning the mechanical and microstructural evolution of 2CrMoNiWV as subjected to low cycle fatigue (LCF) deformation at elevated temperatures, at different strain rates and for various strain amplitudes. This cyclic plastic deformation causes the rearrangement of dislocations in the microstructure of the steels used for such rotor applications. Symmetric, strain controlled LCF experiments have been carried out in the Laboratory of the High Temperature Integrity Group at the Swiss Federal Laboratories for Materials Science and Technology EMPA. These include mechanical tests in the temperature range between 20 °C to 600 °C at strain rates of 0.001%/s to 1.0%/s and strain amplitudes of ±0.25% to ±1.0%. The LCF experiments reported on comprehensively characterise the temperature, strain rate and strain amplitude dependent cyclic elastic-plastic behaviour of 2CrMoNiWV. Both complete single-specimen endurance tests and interrupted multi-specimen tests have been performed. On the basis of this experimental evidence, an evolutionary formulation of the model is further developed that excellently reproduces the strain amplitude dependent mechanical evolution of 2CrMoNiWV when subjected to LCF loading at different constant strain amplitudes but equal temperature and strain rate. The simulation of benchmark experiments introducing increasing or decreasing strain amplitude steps into the LCF deformation history provide promising results. A further important

  19. The LCF behaviour of SS AISI 304 in the temperature range between 450 deg. C and 850 deg. C in connection with life time predictions

    International Nuclear Information System (INIS)

    Bocek, M.; Petersen, C.; Schmitt, R.

    The lifetime in high amplitude strain cycling with tensional hold periods is analysed presuming that creep failure damage is life determining. The life fraction rule (LFR) is used to calculate the lifetime consumpted during the dwell period in strain controlled tests as well as during tensional hold time stress cycles. It follows from the present investigation that stress relaxation occurring during the strain hold periods has a dominant influence upon the lifetime. The damage in stress relaxation is calculated by means of the LFR and the results are compared to experiments conducted on Zircaloy-4 (T=600 deg. C) and the austenitic stainless steel Type AISI 304 (T=650 deg. C). From the very good agreement between both it is concluded that under the loading conditions considered, creep failure damage is the main life determining damage contribution. To investigate the contributions of creep and fatigue to failure damage stress controlled experiments were conducted on AISI 304 at 550 deg. C and 850 deg. C. Whereas at the lower temperature (T 0.6 Tsub(s)) the lifetime increased with decreasing R. Therefrom it is concluded that in the case considered for T>0.6 Tsub(s) fatigue damage is not lifetime determining. (author)

  20. Acoustic events during fatigue test of structural steels

    Energy Technology Data Exchange (ETDEWEB)

    Por, Gabor; Fekete, Balazs; Csicso, Gabor; Trampus, Peter [College of Dunaujvaros (Hungary)

    2014-11-01

    Acoustic emission sensors were applied recording noises during low cycle fatigue tests in steel materials. The test specimens were machined from the base metal (15H2MFA) and the anticorrosive cladding metal (08H18N10T) of the VVER-440/V-213 (Russian designed PWR) reactor pressure vessel. During the first period, the measurements were carried out with isothermal condition at 260 C on GLEEBLE 3800 servo-hydraulic thermal-mechanical simulator. The tests were run under uniaxial tension-compression loading with total strain control. The programmed waveform was triangular for all the fatigue tests with the frequency of 0.08 Hz. The cyclic loading was started from the compressed side. It was observed that besides rare acoustic emission events regular 10 msec Acoustic Barkhausen Noise (ABN) burst were recorded due to 50Hz AC current drive for heating and maintaining the constant temperature. The amplitude of MABN was higher under pressure than during relaxing and drawing-out by a factor of 2-5. We have carried out also thermo-mechanical fatigue experiment with the same strain-controlled mechanical cycle and simultaneous thermal cycle between 150 C and 270 C. The total number of cycles was terminated, when the force level necessary for the original elongation had been reduced to 75% of its original value. Visual examination showed always some at least surface cracks after stopping the fatigue test. ABN events registered during the beginning cycle exhibited different spectra from the middle and especially from the last cycles before the end of the test, where also double ABN bursts could be recorded. At the end of the test explicit AE events could be found by a new technique. The most interesting result is the possibility to use ABN for testing reactor materials, which could have practical application for fatigue testing.

  1. Present status of the disk pressure tests for hydrogen embrittlement

    International Nuclear Information System (INIS)

    Fidelle, J.P.

    1985-05-01

    The Disk Pressure Tests (DPT) have been developed considerably theoretically and experimentally for Internal Hydrogen Embrittlement (IHE) e.g. Co, Ti, U alloys, for Environment Embrittlement due to H 2 , hydrogenated media such as water vapor, alcohol, machining fluids or liquid NH 3 . The range has been expanded considerably for pressure up to 300 MPa and temperature (-160 0 C to 1000 0 C). Very low strain rate -longer than a month- tests have been able to evidence embrittlement of FFC alloys where H diffusivity is low. Conversely for very oxidation - sensitive metals (e.g. Nb and Ta) effects may appear only at somewhat high rates. The relationship between dynamic (increasing stress) tests, static (delayed failure) and low-cycle fatigue tests has been determined. In a number of instances, including SCC, other techniques and even fracture mechanics have been compared to the DPT and proved at best equivalent and several times, less sensitive than a well conducted DPT. At extreme they could not reproduce the field service phenomenon whereas the DPT did and could also be applied satisfactorily to low yield stress materials. The main rupture aspects have been analyzed mechanically and organized in a rational and comprehensive chart based on 12,000 + tests over 150 + materials in different conditions. From the tests on a large number of metal systems, a theory of HE has been derived which accounts for the behavior of metals and alloys either embrittled and or hydrited. Finally comparison of HGE tests and service behavior of a large variety of materials and industrial equipments has made possible to specify acceptance criteria for industrial service

  2. Present status of the disk pressure tests for hydrogen embrittlements

    International Nuclear Information System (INIS)

    Fidelle, J.P.

    1988-01-01

    The Disk Pressure Tests (DPT) have been developed considerably. Theoretically: a finite elements mechanical analysis shows the build up of a triaxial stress state already at the beginning of the test, which, with other reasons accounts for the very high sensitivity. Experimentally: for Internal Hydrogen Embrittlement (IHE) e.g. Co, Ti, U alloys, for environment embrittlement due to H 2 hydrogenated media such as water vapor, alcohol, machining fluids or liquid NH 3 . The range has been expanded considerably: up to 300 MPa and up to 1000 0 C. Very low strain rate - longer than a month - tests have been able to evidence HGE; of FCC alloys where H diffusivity is low for very oxidation -sensitive metals such as Nb and Ta, effects may appear only at somewhat high rates. The relationship between dynamic tests, static and low-cycle fatigue tests has been determined. In a number of instances, including SCC, other techniques and even fracture mechanics have been compared to the DPT and proved at best equivalent and several times, less sensitive than a well conducted DPT. At extreme they could not reproduce the field service phenomenon whereas the DPT did and could also be applied satisfactorily to low yield stress materials. The main rupture aspects have been analysed mechanically and organized in a rational and comprehensive chart based on 12,000 + tests over 15O + materials in different conditions. Comparison of HGE tests and service behaviour of a large variety of materials and industrial equipments has made possible to specify acceptance criteria for industrial service, which, provided the shape of the stress strain curves is not significantly affected, can be expanded to IHE, HE by other fluids than H 2 , 36 refs

  3. Characterization of a 14Cr ODS steel by means of small punch and uniaxial testing with regard to creep and fatigue at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bruchhausen, M., E-mail: matthias.bruchhausen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Turba, K. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Lund University, Division of Materials Engineering, P.O. Box 118, SE-221 00 Lund (Sweden); Haan, F. de; Hähner, P.; Austin, T. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Carlan, Y. de [CEA, DEN, Service de Recherches Métallurgiques Appliquées, 91191 Gif-sur-Yvette (France)

    2014-01-15

    A 14Cr ODS steel was characterized at elevated temperatures with regard to its behavior in small punch and uniaxial creep tests and in low cycle fatigue tests. A comparison of small punch and uniaxial creep tests at 650 °C revealed a strong anisotropy of the material when strained parallel and perpendicular to the extrusion direction with rupture times being several orders of magnitude lower for the perpendicular direction. The stress-rupture and Larson–Miller plots show a very large scatter of the creep data. This scatter is strongly reduced when rupture time is plotted against minimum deflection rate or minimum creep rate (Monkman–Grant plot). Fatigue tests have been carried out at 650 °C and 750 °C. The alloy is cyclically very stable with practically no hardening/softening. Results from the tests at both temperatures can be described by a common power law. An increase in the test temperature has little influence on the fatigue ductility exponent. For a given total strain level, the fatigue life of the alloy is reduced with increasing temperature.

  4. Advanced Gear Alloys for Ultra High Strength Applications

    Science.gov (United States)

    Shen, Tony; Krantz, Timothy; Sebastian, Jason

    2011-01-01

    Single tooth bending fatigue (STBF) test data of UHS Ferrium C61 and C64 alloys are presented in comparison with historical test data of conventional gear steels (9310 and Pyrowear 53) with comparable statistical analysis methods. Pitting and scoring tests of C61 and C64 are works in progress. Boeing statistical analysis of STBF test data for the four gear steels (C61, C64, 9310 and Pyrowear 53) indicates that the UHS grades exhibit increases in fatigue strength in the low cycle fatigue (LCF) regime. In the high cycle fatigue (HCF) regime, the UHS steels exhibit better mean fatigue strength endurance limit behavior (particularly as compared to Pyrowear 53). However, due to considerable scatter in the UHS test data, the anticipated overall benefits of the UHS grades in bending fatigue have not been fully demonstrated. Based on all the test data and on Boeing s analysis, C61 has been selected by Boeing as the gear steel for the final ERDS demonstrator test gearboxes. In terms of potential follow-up work, detailed physics-based, micromechanical analysis and modeling of the fatigue data would allow for a better understanding of the causes of the experimental scatter, and of the transition from high-stress LCF (surface-dominated) to low-stress HCF (subsurface-dominated) fatigue failure. Additional STBF test data and failure analysis work, particularly in the HCF regime and around the endurance limit stress, could allow for better statistical confidence and could reduce the observed effects of experimental test scatter. Finally, the need for further optimization of the residual compressive stress profiles of the UHS steels (resulting from carburization and peening) is noted, particularly for the case of the higher hardness C64 material.

  5. Effects of Control Mode and R-Ratio on the Fatigue Behavior of a Metal Matrix Composite

    Science.gov (United States)

    2005-01-01

    Composite Because of their high specific stiffness and strength at elevated temperatures, continuously reinforced metal matrix composites (MMC's) are under consideration for a future generation of aeropropulsion systems. Since components in aeropropulsion systems experience substantial cyclic thermal and mechanical loads, the fatigue behavior of MMC's is of great interest. Almost without exception, previous investigations of the fatigue behavior of MMC's have been conducted in a tension-tension, load-controlled mode. This has been due to the fact that available material is typically less than 2.5-mm thick and, therefore, unable to withstand high compressive loads without buckling. Since one possible use of MMC's is in aircraft skins, this type of testing mode may be appropriate. However, unlike aircraft skins, most engine components are thick. In addition, the transient thermal gradients experienced in an aircraft engine will impose tension-compression loading on engine components, requiring designers to understand how the MMC will behave under fully reversed loading conditions. The increased thickness of the MMC may also affect the fatigue life. Traditionally, low-cycle fatigue (LCF) tests on MMC's have been performed in load control. For monolithic alloys, low-cycle fatigue tests are more typically performed in strain control. Two reasons justify this choice: (1) the critical volume from which cracks initiate and grow is generally small and elastically constrained by the larger surrounding volume of material, and (2) load-controlled, low-cycle fatigue tests of monolithics invariably lead to unconstrained ratcheting and localized necking--an undesired material response because the failure mechanism is far more severe than, and unrelated to, the fatigue mechanism being studied. It is unknown if this is the proper approach to composite testing. However, there is a lack of strain-controlled data on which to base any decisions. Consequently, this study addresses the

  6. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

    Science.gov (United States)

    Avery, Katherine R.

    Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

  7. Creep-fatigue of High Temperature Materials for VHTR: Effect of Cyclic Loading and Environment

    Energy Technology Data Exchange (ETDEWEB)

    Celine Cabet; L. Carroll; R. Wright; R. Madland

    2011-05-01

    Alloy 617 is the one of the leading candidate materials for Intermediate Heat eXchangers (IHX) of a Very High Temperature Reactor (VHTR). System start-ups and shut-downs as well as power transients will produce low cycle fatigue (LCF) loadings of components. Furthermore, the anticipated IHX operating temperature, up to 950°C, is in the range of creep so that creep-fatigue interaction, which can significantly increase the fatigue crack growth, may be one of the primary IHX damage modes. To address the needs for Alloy 617 codification and licensing, a significant creep-fatigue testing program is underway at Idaho National Laboratory. Strain controlled LCF tests including hold times up to 1800s at maximum tensile strain were conducted at total strain range of 0.3% and 0.6% in air at 950°C. Creep-fatigue testing was also performed in a simulated VHTR impure helium coolant for selected experimental conditions. The creep-fatigue tests resulted in failure times up to 1000 hrs. Fatigue resistance was significantly decreased when a hold time was added at peak stress and when the total strain was increased. The fracture mode also changed from transgranular to intergranular with introduction of a tensile hold. Changes in the microstructure were methodically characterized. A combined effect of temperature, cyclic and static loading and environment was evidenced in the targeted operating conditions of the IHX. This paper This paper reviews the data previously published by Carroll and co-workers in references 10 and 11 focusing on the role of inelastic strain accumulation and of oxidation in the initiation and propagation of surface fatigue cracks.

  8. Thermomechanical fatigue in single crystal superalloys

    Directory of Open Access Journals (Sweden)

    Moverare Johan J.

    2014-01-01

    Full Text Available Thermomechanical fatigue (TMF is a mechanism of deformation which is growing in importance due to the efficiency of modern cooling systems and the manner in which turbines and associated turbomachinery are now being operated. Unfortunately, at the present time, relatively little research has been carried out particularly on TMF of single crystal (SX superalloys, probably because the testing is significantly more challenging than the more standard creep and low cycle fatigue (LCF cases; the scarcity and relative expense of the material are additional factors. In this paper, the authors summarise their experiences on the TMF testing of SX superalloys, built up over several years. Emphasis is placed upon describing: (i the nature of the testing method, the challenges involved in ensuring that an given testing methodology is representative of engine conditions (ii the behaviour of a typical Re-containing second generation alloy such as CMSX-4, and its differing performance in out-of-phase/in-phase loading and crystallographic orientation and (iii the differences in behaviour displayed by the Re-containing alloys and new Re-free variants such as STAL15. It is demonstrated that the Re-containing superalloys are prone to different degradation mechanisms involving for example microtwinning, TCP precipitation and recrystallisation. The performance of STAL15 is not too inferior to alloys such as CMSX-4, suggesting that creep resistance itself does not correlate strongly with resistance to TMF. The implications for alloy design efforts are discussed.

  9. Environmental Fatigue Behaviors of CF8M Stainless Steel in 310 .deg. C Deoxygenated Water - Effects of Hydrogen and Microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Hun; Cho, Pyungyeon; Jang, Changheui [KAIST, Daejeon (Korea, Republic of); Kim, Tae Soon [Korea Hydro and Nuclear Power Corporation, Seoul (Korea, Republic of)

    2014-01-15

    The effects of environment and microstructure on low cycle fatigue (LCF) behaviors of CF8M stainless steels containing 11% of ferrites were investigated in a 310 .deg. C deoxygenated water environment. The reduction of LCF life of CF8M in a 310 .deg. C deoxygenated water was smaller than 316LN stainless steels. Based on the microstructure and fatigue surface analyses, it was confirmed that the hydrogen induced cracking contributed to the reduction in LCF life for CF8M as well as for 316LN. However, many secondary cracks were found on the boundaries of ferrite phases in CF8M, which effectively reduced the stress concentration at the crack tip. Because of the reduced stress concentration, the accelerated fatigue crack growth by hydrogen induced cracking was less significant, which resulted in the smaller environmental effects for CF8M than 316LN in a 310 .deg. C deoxygenated water.

  10. 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.

  11. Prediction of three-dimensional crack propagation paths taking high cycle fatigue into account

    Directory of Open Access Journals (Sweden)

    Guido Dhondt

    2016-01-01

    Full Text Available Engine components are usually subject to complex loading patterns such as mixed-mode Low Cycle Fatigue Loading due to maneuvering. In practice, this LCF Loading has to be superimposed by High Cyclic Fatigue Loading caused by vibrations. The changes brought along by HCF are twofold: first, the vibrational cycles which are superposed on the LCF mission increase the maximum loading of the mission and may alter the principal stress planes. Secondly, the HCF cycles themselves have to be evaluated on their own, assuring that no crack propagation occurs. Indeed, the vibrational frequency is usually so high that propagation leads to immediate failure. In the present paper it is explained how these two effects can be taken care of in a standard LCF crack propagation procedure. The method is illustrated by applying the Finite Element based crack propagation software CRACKTRACER3D on an engine blade.

  12. Effectiveness of Shot Peening In Suppressing Fatigue Cracking At Non-Metallic Inclusions In Udimet(Registered Trademark)720

    Science.gov (United States)

    Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, T.; Bonacuse, P. J.

    2006-01-01

    The fatigue lives of modern powder metallurgy disk alloys can be reduced over an order of magnitude by cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens with and without shot peened test sections at 427 C and 650 C. The low cycle fatigue lives and failure initiation sites varied as functions of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with the introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. These inclusions reduced fatigue life by up to 100X, when compared to lives of material without inclusions residing at specimen surface. Large inclusions produced the greatest reductions in life for tests at low strain ranges and high strain ratios. Shot peening improved life in many cases by reducing the most severe effects of inclusions.

  13. Magnetic properties of cyclically deformed austenite

    Energy Technology Data Exchange (ETDEWEB)

    Das, Arpan, E-mail: dasarpan1@yahoo.co.in

    2014-06-01

    In meta-stable austenitic stainless steels, low cycle fatigue deformation is accompanied by a partial stress/strain-induced solid state phase transformation of paramagnetic γ(fcc) austenite phase to ferromagnetic α{sup /}(bcc) martensite. The measured characteristic of magnetic properties, which are the saturation magnetization, susceptibility, coercivity, retentivity, and the area under the magnetic hysteresis loop are sensitive to the total strain amplitude imposed and the corresponding material behaviour. The morphologies and nucleation characteristics of deformation induced martensites (i.e., ϵ(hcp), α{sup /}(bcc)) have been investigated through analytical transmission electron microscope. It has been observed that deformation induced martensites can nucleate at a number of sites (i.e., shear band intersections, isolated shear bands, shear band–grain boundary intersection, grain boundary triple points, etc.) through multiple transformation sequences: γ(fcc)→ϵ(hcp), γ(fcc)→ϵ(hcp)→α{sup /}(bcc), γ(fcc)→ deformation twin →α{sup /}(bcc) and γ(fcc)→α{sup /}(bcc). - Highlights: • LCF tests were done at various strain amplitudes of 304LNSS. • Quantification of martensite was done through ferritecope. • Magnetic properties were characterised through VSM. • Correlation of magnetic properties with the cyclic plastic response was done. • TEM was done to investigate the transformation micro-mechanisms.

  14. ISOTHERMAL AND THERMOMECHANICAL FATIGUE OF A NICKEL-BASE SUPERALLOY

    Directory of Open Access Journals (Sweden)

    Carlos Carvalho Engler-Pinto Júnior

    2014-06-01

    Full Text Available Thermal gradients arising during transient regimes of start-up and shutdown operations produce a complex thermal and mechanical fatigue loading which limits the life of turbine blades and other engine components operating at high temperatures. More accurate and reliable assessment under non-isothermal fatigue becomes therefore mandatory. This paper investigates the nickel base superalloy CM 247LC-DS under isothermal low cycle fatigue (LCF and thermomechanical fatigue (TMF. Test temperatures range from 600°C to 1,000°C. The behavior of the alloy is strongly affected by the temperature variation, especially in the 800°C-1,000°C range. The Ramberg-Osgood equation fits very well the observed isothermal behavior for the whole temperature range. The simplified non-isothermal stress-strain model based on linear plasticity proposed to represent the thermo-mechanical fatigue behavior was able to reproduce the observed behavior for both in-phase and out-of-phase TMF cycling.

  15. Effect of alumina-silica-zirconia eutectic ceramic thermal barrier coating on the low cycle fatigue behaviour of cast polycrystalline nickel-based superalloy at 900 °C

    Czech Academy of Sciences Publication Activity Database

    Obrtlík, Karel; Čelko, L.; Chráska, Tomáš; Šulák, Ivo; Gejdoš, P.

    2017-01-01

    Roč. 318, MAY (2017), s. 374-381 ISSN 0257-8972. [RIPT - International Meeting on Thermal Spraying /7./. Limoges, 09.12.2015-12.12.2015] R&D Projects: GA ČR(CZ) GA15-20991S Institutional support: RVO:68081723 ; RVO:61389021 Keywords : Thermal barrier coating * Nickel-based superalloy * Plasma spraying * High temperature fatigue * Fatigue life * Cyclic stress-strain curve Subject RIV: JL - Materials Fatigue, Friction Mechanics; JL - Materials Fatigue, Friction Mechanics (UFP-V) OBOR OECD: Audio engineering, reliability analysis; Audio engineering, reliability analysis (UFM-A); Audio engineering, reliability analysis (UFP-V) Impact factor: 2.589, year: 2016

  16. Test

    DEFF Research Database (Denmark)

    Bendixen, Carsten

    2014-01-01

    Bidrag med en kortfattet, introducerende, perspektiverende og begrebsafklarende fremstilling af begrebet test i det pædagogiske univers.......Bidrag med en kortfattet, introducerende, perspektiverende og begrebsafklarende fremstilling af begrebet test i det pædagogiske univers....

  17. Fatigue crack propagation under elastic plastic medium at elevated temperature

    International Nuclear Information System (INIS)

    Asada, Y.; Yuuki, R.; Sakon, T.; Sunamoto, D.; Tokimasa, K.; Makino, Y.; Kitagawa, M; Shingai, K.

    1980-01-01

    The purposes of the present study are to establish the testing method to obtain compatible data on the low cycle fatigue crack propagation at elevated temperature, and to investigate the parameter controlling the crack propagation rate. In the present study, the preliminary experiments have been carried out on low cycle fatigue crack propagation behaviour in type 304 stainless steel in air at 550 0 C, using two types of specimen with a through thickness notch. Both strain controlled and stress controlled fatigue tests have been done under a fully reversed strain or stress cycling. The data obtained are correlated with some fracture mechanics parameters and are discussed with the appropriate parameter for evaluating the low cycle fatigue crack propagation behaviour at elevated temperature. (author)

  18. Effects of the Heterogeneity in the Electron Beam Welded Joint on Mechanical Properties of Ti6Al4V Alloy

    Science.gov (United States)

    Liu, Jing; Gao, Xiao-Long; Zhang, Lin-Jie; Zhang, Jian-Xun

    2015-01-01

    The aim of this investigation was to evaluate the effect of microstructure heterogeneity on the tensile and low cycle fatigue properties of electron beam welded (EBW) Ti6Al4V sheets. To achieve this goal, the tensile and low cycle fatigue property in the EBW joints and base metal (BM) specimens is compared. During the tensile testing, digital image correlation technology was used to measure the plastic strain field evolution within the specimens. The experimental results showed that the tensile ductility and low cycle fatigue strength of EBW joints are lower than that of BM specimens, mainly because of the effect of microstructure heterogeneity of the welded joint. Moreover, the EBW joints exhibit the cyclic hardening behavior during low fatigue process, while BM specimens exhibit the cyclic softening behavior. Compared with the BM specimens with uniform microstructure, the heterogeneity of microstructure in the EBW joint is found to decrease the mechanical properties of welded joint.

  19. Coupling of experimental measurements to study the influence of microscopic defects on the fatigue damage in A319 Al-Si alloy

    Directory of Open Access Journals (Sweden)

    Wang Long

    2014-06-01

    Full Text Available An experimental protocol based on the coupling of kinematic field measurements on the surface and in volume at the microstructure scale has been set up in order to study the influence of the casting microstructure upon the initiation and propagation of cracks in low cycle fatigue. Preliminary applications of this protocol on tensile tests were successful as it allowed tracking the development and localization of plastic deformation and identifying the initiation sites of microcracks during tests in relation with the observed surface and volume microstructures. Application of the proposed protocol to low cycle fatigue is an on-going work.

  20. LCF data for aging of Cu NPs in soil

    Data.gov (United States)

    U.S. Environmental Protection Agency — Linear combination fitting data for Cu NPs in five soils as a function of aging time. This dataset is associated with the following publication: Sekine, R., E....

  1. A method for determination of complete mechanical characteristics of heterogeneous-structured materials

    Directory of Open Access Journals (Sweden)

    M. Maj

    2009-07-01

    Full Text Available The article outlines the possibilities to evaluate by a modified low-cycle fatigue test the quality of materials characterised by different structures and the resulting mechanical properties. The method was described by computer program (MLCF, adjusted to the operating parameters of a versatile testing machine.

  2. Microstructural and mechanical characterization of the ferritic martensitic steel eurofer'97 after simulated service conditions

    International Nuclear Information System (INIS)

    Fernandez, P.; Lancha, A. M.; Lapena, J.

    2002-01-01

    This report details the metallurgical characterization of the Eurofer'97 steel thermally aged in the range of temperatures from 400 degree centigrade to 600 degree centigrade up to 10000 H, microstructural studies and mechanical testing (hardness, tensile, Charpy and low cycle fatigue test) have been carried out

  3. 3-D analysis of fatigue crack behaviour in a shot peened steam turbine blade material

    Energy Technology Data Exchange (ETDEWEB)

    He, B.Y., E-mail: Binyan.he@soton.ac.uk [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Katsamenis, O.L. [muVIS X-ray Imaging Centre, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Mellor, B.G.; Reed, P.A.S. [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-08-26

    Serial mechanical sectioning and high resolution X-ray tomography have been used to study the three-dimensional morphology of small fatigue cracks growing in a 12 Cr tempered martensitic steam turbine blade material. A range of surface conditions has been studied, namely polished and shot peened (with varying levels of intensity). In the polished (unpeened) condition, inclusions (alumina and manganese sulphide) played an important role in initiating and controlling early fatigue crack behaviour. When fatigue cracks initiated from an alumina stringer, the crack morphology was normally dominated by single stringers, which were always in the centre of the fatigue crack, indicating its primary role in initiation. Manganese sulphide inclusion groups however seemed to dominate and affect the crack path along both the surface and depth crack growth directions. The more intensely shot peened condition did not however evidence inclusion or stringer affected fatigue crack initiation or growth behaviour; sub-surface crack coalescence being clearly observed by both serial sectioning and computed tomography (CT) imaging techniques at a depth of about 150–180 μm. These sub-surface crack coalescences can be linked to both the extent of the compressive residual stress as well as the depth of the plastic deformation arising from the intense shot peening process. Shot peening appears to provide a different defect population that initiates fatigue cracks and competes with the underlying metallurgical defect populations. The most beneficial shot peening process would in this case appear to “deactivate” the original metallurgical defect population and substitute a known defect distribution from the shot peening process from which fatigue cracks grow rather slowly in the strain hardened surface layer which also contains compressive residual stresses. A benefit to fatigue life in bending, even under Low Cycle Fatigue (LCF) conditions, has been observed in these tests if a

  4. Thermal fatigue. Materials modelling

    International Nuclear Information System (INIS)

    Siegele, D.; Fingerhuth, J.; Mrovec, M.

    2012-01-01

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

  5. Rotordynamic Analysis and Feasibility Study of a Disk Spin Test Facility for Rotor Health Monitoring

    Science.gov (United States)

    Sawicki, Jerzy T.

    2005-01-01

    Recently, National Aeronautics and Space Administration (NASA) initiated a program to achieve the significant improvement in aviation safety. One of the technical challenges is the design and development of accelerated experiments that mimic critical damage cases encountered in engine components. The Nondestructive Evaluation (NDE) Group at the NASA Glenn Research Center (GRC) is currently addressing the goal concerning propulsion health management and the development of propulsion system specific technologies intended to detect potential failures prior to catastrophe. For this goal the unique disk spin simulation system was assembled at NASA GRC, which allows testing of rotors with the spinning speeds up to 10K RPM, and at the elevated temperature environment reaching 540 C (1000 F). It is anticipated that the facility can be employed for detection of Low Cycle Fatigue disk cracking and further High Cycle Fatigue blade vibration. The controlled crack growth studies at room and elevated temperatures can be conducted on the turbine wheels, and various NDE techniques can be integrated and assessed as in-situ damage monitoring tools. Critical rotating parts in advanced gas turbine engines such as turbine disks frequently operate at high temperature and stress for long periods of time. The integrity of these parts must be proven by non-destructive evaluation (NDE) during various machining steps ranging from forging blank to finished shape, and also during the systematic overhaul inspections. Conventional NDE methods, however, have unacceptable limits. Some of these techniques are time-consuming and inconvenient for service aircraft testing. Almost all of these techniques require that the vicinity of the damage is known in advance. These experimental techniques can provide only local information and no indication of the structural strength at a component and/or system level. The shortcomings of currently available NDE methods lead to the requirement of new damage

  6. Functional and hypoglycemic properties of nopal cladodes (O. ficus-indica) at different maturity stages using in vitro and in vivo tests.

    Science.gov (United States)

    Nuñez-López, María A; Paredes-López, Octavio; Reynoso-Camacho, Rosalía

    2013-11-20

    Nopal (Opuntia ficus-indica) cladodes are recommended for their therapeutic properties; their maturity stage may affect their biological properties. Cladodes of three maturity stages, from the same crop and location, were dehydrated and evaluated for some of their physicochemical and nutritional characteristics and antidiabetic properties. The flours of small and medium cladodes (SCF and MCF, respectively) had higher contents of dietary fiber, water absorption, swelling, and viscosity compared to those of the large cladode flour (LCF). Streptozotocin-induced diabetic rats, treated with MCF and SCF (doses of 50 mg/kg body weight), showed reduction of postprandial blood glucose on 46.0 and 23.6%, respectively (p < 0.05), in relation to the control; and LCF had no significant effect. In vitro, glucose diffusion tests showed similar ranking by the two former samples, whereas the latter was close to the control. Cladode maturity stages showed different fiber content and produced suspensions with differences in viscosity, which may affect in vitro and in vivo glucose responses.

  7. Fatigue and creep-fatigue in sodium of 316 L stainless-steel

    International Nuclear Information System (INIS)

    Ardellier, A.

    1981-03-01

    The present paper describes test-facility developed to perform low-cycle fatigue and creep-fatigue interaction in sodium on stainless steel - 316 L . Fatigue life in sodium and in air are compared. A beneficial effect in sodium is noted

  8. Testing Testing Testing.

    Science.gov (United States)

    Deville, Craig; O'Neill, Thomas; Wright, Benjamin D.; Woodcock, Richard W.; Munoz-Sandoval, Ana; Gershon, Richard C.; Bergstrom, Betty

    1998-01-01

    Articles in this special section consider (1) flow in test taking (Craig Deville); (2) testwiseness (Thomas O'Neill); (3) test length (Benjamin Wright); (4) cross-language test equating (Richard W. Woodcock and Ana Munoz-Sandoval); (5) computer-assisted testing and testwiseness (Richard Gershon and Betty Bergstrom); and (6) Web-enhanced testing…

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

    International Nuclear Information System (INIS)

    Gagnon, M; Tahan, S A; Bocher, P; Thibault, D

    2012-01-01

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

  10. Fatigue damage in coarse-grained lean duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Strubbia, R., E-mail: strubbia@ifir-conicet.gov.ar; Hereñú, S.; Marinelli, M.C.; Alvarez-Armas, I.

    2016-04-06

    The present investigation is focused on assessing the effect of a thermal treatment for grain coarsening on the low cycle fatigue damage evolution in two types of Lean Duplex Stainless Steels (LDSSs). The dislocation structure developed during cycling is observed by transmission electron microscopy (TEM). Additionally, a detailed analysis of short crack initiated and grown during low cycle fatigue (LCF) is performed by means of optical and scanning electron (SEM) microscopy in combination with automated electron back-scattered diffraction (EBSD) technique. Though in both coarse-grained LDSSs the short cracks nucleate in the ferrite phase, in each steels its origin is different. The embrittlement caused by the Cr{sub 2}N precipitation and the plastic activity sustained by each phase can explain this difference. The propagation behavior of the short cracks present two alternative growing mechanisms: the crack grows along a favorable slip plane with high Schmid Factor (SF) or the crack alternates between two slip systems. In both cases, the crack follows the path with the smallest tilt angle (β) at a grain boundary.

  11. Non-destructive Determination of Martensitic Content by Means of Magnetic Methods

    Energy Technology Data Exchange (ETDEWEB)

    Niffenegger, M.; Bauer, R.; Kalkhof, D

    2003-07-01

    The detection of material degradation in a pre-cracked stage would be very advantageous. Therefore the main objective of the EC 5th Framework Programme 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 low cycle fatigue (LCF) and neutron irradiation of metastable austenitic and ferritic low-alloy steel. Within work package WP6 and WP7 several project partners tested aged or irradiated samples, using various advanced measuring techniques, such as acoustic, magnetic and thermoelectric ones. 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. Based on results from former investigations, main attention was paid to the content of martensitic phase as an indicator for fatigue. Since most NDT-methods are considered as indirect methods for the detection of martensite, neutron diffraction was applied as a reference method for a quantitative determination of martensite. The material characterization performed at PSI and INSA de Lyon is published in the PSI Bericht Nr. 03-17, July 2003, (ISSN 1019-0643). The present report only describes the magnetic methods applied at PSI for the detection of material degradation and summarises the results obtained in WP3 of the CRETE project. The report is issued simultaneously as a PSI report and the CRETE work package WP3 report. At PSI the following magnetic methods were applied to LCF specimens: (1) Ferromaster for measuring the magnetic permeability, (2) Eddy current impedance measuring by means of a Giant Magneto Resistance sensor (GMR), (3) Remanence field measurements using high sensitive Fluxgate and SQUID sensors. With these methods three sets of fatigue specimens, made from different metastable

  12. Influence of localized plasticity on Stress Corrosion Cracking of austenitic stainless steel. Application to IASCC of internals reactor core vessels

    International Nuclear Information System (INIS)

    Cisse, Sarata

    2012-01-01

    The surface conditions of the 316L screw connecting vessel internals of the primary circuit of PWR (pressurized water reactor) corresponds to a grinding condition. These screws are affected by the IASCC (Irradiation Assisted Stress Corrosion Cracking). Initiation of cracking depends on the surface condition but also on the external oxidation and interactions of oxide layer with the deformation bands. The first objective of this study is to point the influence of surface condition on the growth kinetic of oxide layer, and the surface reactivity of 304, 316 stainless steel grade exposed to PWR primary water at 340 C. The second objective is to determine influence of strain localization on the SCC of austenitic stainless steels in PWR primary water. Indeed, the microstructure of irradiated 304, 316 grades correspond to a localized deformation in deformation bands free of radiation defects. In order to reproduce that microstructure without conducting irradiations, low cycle fatigue tests at controlled stain amplitude are implemented for the model material of the study (A286 austenitic stainless steel hardened by the precipitation of phase γ'Ni3(Ti, Al)). During the mechanical cycling (after the first hardening cycles), the precipitates are dissolved in slip bands leading to the localization of the deformation. Once the right experimental conditions in low cycle fatigue obtained (for localized microstructure), interactions oxidation / deformation bands are studied by oxidizing pre deformed samples containing deformation bands and non deformed samples. The tensile tests at a slow strain rate of 8 x 10 -8 /s are also carried out on pre deformed samples and undeformed samples. The results showed that surface treatment induces microstructural modifications of the metal just under the oxide layer, leading to slower growth kinetics of the oxide layer. However, surface treatment accelerates development of oxides penetrations in metal under the oxide layer. As example, for

  13. Non-destructive detection of fatigue in austenitic steel X6CrNiNb1810 in the HCF and VHCF range. Final report; Zerstoerungsfreie Detektion der Ermuedung von austenitischem Stahl X6CrNiNb1810 im HCF- und VHCF-Bereich. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Seiler, Georg; Boller, Christian [Univ. des Saarlandes, Saarbruecken (Germany). Lehrstuhl fuer Zerstoerungsfreie Pruefung und Qualitaetsmanagement

    2014-12-31

    In addition to load cycles in the Low Cycle Fatigue (LCF)-regime due to start up and shut down procedures of power plants, in some components additional high-frequency loadings in the High Cycle Fatigue (HCF)- and Very High Cycle Fatigue (VHCF)-regime occur. These loadings are induced e.g. by stresses due to thermal cyclic fluctuations and fluid dynamic processes. Therefore it is necessary to characterize experimentally the cyclic deformation behavior of metastable austenitic steels at operating temperature particularly in the HCF- and VHCF-regime and to develop a nondestructive method to detect fatigue processes. This joint research project was conducted in cooperation between the Institute of Materials Science and Engineering (WKK) of the University of Kaiserslautern and the Chair of Non-Destructive Testing and Quality Assurance of Saarland University (LZfPQ). WKK was focused on experimental investigations of the cyclic deformation behavior of metastable austenitic steel in the HCF- and VHCF-range, taking into account cyclic hardening and softening processes and in particular to consider fatigue-induced changes in microstructure. The samples were taken from a real pressurized water reactor component (surgeline). LZfPQ has focused on the development and application of a testing concept based on electromagnetic ultrasonic measurements. Within this subproject, electromagnetic acoustic transducers (EMATs) for in situ Operation in WKK's fatigue testing equipment have been developed and assembled. Single-step fatigue tests at elevated temperature (300 C) were conducted both with total-stress and strain control. During the test, the fatigue specimens were characterized by EMAT ultrasound in transmission mode. Different sensor types and wavemodes were used. The transmission signal was evaluated in terms of time of flight and amplitude. Both measured values are seen to behave in a characteristic manner depending on the test duration and the mechanical measured value

  14. Shear strength of a thermal barrier coating parallel to the bond coat

    International Nuclear Information System (INIS)

    Cruse, T.A.; Dommarco, R.C.; Bastias, P.C.

    1998-01-01

    The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard Iosipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material

  15. Post irradiation examination of RAF/M steels after fast reactor irradiation up to 33 dpa and < 340 C (ARBOR1). RAFM steels. Metallurgical and mechanical characterisation. Final report for TW2-TTMS-001b, D9

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, C. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). EURATOM, Inst. fuer Materialforschung, Programm Kernfusion

    2010-07-01

    In an energy generating fusion reactor structural materials will be exposed to very high dpa-levels of about 100 dpa. Due to this fact and because fast reactor irradiation facilities in Europe are not available anymore, a reactor irradiation at the State Scientific Center of the Russian Federation with its Research Institute of Atomic Reactors (SSC RIAR), Dimitrovgrad, had been performed in the fast reactor BOR 60 with an instrumented test rig. This test rig contained tensile, impact and Low Cycle Fatigue type specimens used at FZK since many years. Samples of actual Reduced Activation Ferritic/Martensitic (RAF/M) -steels (e.g. EUROFER 97) had been irradiated in this reactor at a lower temperature (< 340 C) up to a damage of 33 dpa. This irradiation campaign was called ARBOR 1. Starting in 2003 one half of these irradiated samples were post irradiation examined (PIE) by tensile testing, low cycle fatigue testing and impact testing under the ISTC Partner Contract 2781p in the hot cells of SSC RIAR. In the post irradiation instrumented impact tests a significant increase in the Ductile to Brittle Transition Temperature as an effect of irradiation has been detected. During tensile testing the strength values are increasing and the strain values reduced due to substantial irradiation hardening. The hardening rate is decreasing with increasing damage level, but it does not show saturation. The low cycle fatigue behaviour of all examined RAF/M - steels show at total strain amplitudes below 1 % an increase of number of cycles to failure, due to irradiation hardening. From these post irradiation experiments, like tensile, low cycle fatigue and impact tests, radiation induced design data, e.g. for verification of design codes, can be generated.

  16. Fatigue behavior of austenitic steels. Subproject. Mechanism oriented investigation of the fatigue behavior of austenitic steel X6CrNiNb1810 in the HCF and VHCF regime. Final report; Ermuedungsverhalten Austenit. Teilprojekt. Mechanismenorientierte Untersuchung des Ermuedungsverhaltens des austenitischen Stahles X6CrNiNb1810 im HCF- und VHCF-Bereich. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Sorich, A.; Smaga, M.; Eifler, D.

    2015-01-23

    In addition to load cycles in the Low Cycle Fatigue (LCF)-regime due to start up and shut down procedures of power plants, in some components additional high-frequency loadings in the High Cycle Fatigue (HCF)- and Very High Cycle Fatigue (VHCF)-regime occur. These loadings are induced e.g. by stresses due to thermal cyclic fluctuations and fluid dynamic processes. Therefore it is necessary to characterize experimentally the cyclic deformation behavior of metastable austenitic steels at operating temperature particularly in the HCF- and VHCF-regime and to develop a nondestructive method to detect fatigue processes. This joint research project was conducted in cooperation between the Institute of Materials Science and Engineering (WKK) of the University of Kaiserslautern and the Fraunhofer-Institute for Non-Destructive Testing (IZFP) in Saarbruecken. WKK was focused on experimental investigations to characterize the cyclic deformation behavior of the metastable austenitic steel in the HCF- and VHCF-range, taking into account cyclic hardening and softening processes and in particular to consider fatigue-induced changes in microstructure. The IZFP has focused on the development and application of a testing concept based on electromagnetic ultrasonic measurements. The isothermal cyclic deformation behavior of the metastable austenitic steel X6CrNiNb1810 (1.4550, AISI 347) at 300 C in the HCF-range is characterized by cyclic softening until specimen failure. At strain amplitudes of 0.10 % ≤ ε{sub a,t} ≤ 0.15 % and the stress amplitude σ{sub a} = 160 MPa cyclic softening is followed by cyclic hardening, which results in a significant increase in life time, up to the limiting number of cycles, which was defined at N{sub I} = 10{sup 7} in HCF-regime. The cyclic hardening is determined by a transformation induced phase formation from face-centered cubic (fcc) austenite to body-centered cubic (bcc) α{sup '}-martensite and/or in hexagonal (hcp) ε-martensite. In

  17. Fatigue behaviour and crack growth of ferritic steel under environmental conditions

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  18. Fatigue and creep-fatigue in sodium of 316 1 stainless steel

    International Nuclear Information System (INIS)

    Ardellier, A.

    1982-01-01

    Equipment and results obtained on type 316 L stainless stee1 at 450 0 C and 600 0 C with low-cycle fatique and creep fatigue tests are described. Comparison with runs in air on type 316 L stainless steel shows a better low-cycle fatigue behavior in a sodium environment. This beneficial effect can be attributed to the low oxygen content which limits the surface oxidazation

  19. Boiler-turbine life extension

    Energy Technology Data Exchange (ETDEWEB)

    Natzkov, S. [TOTEMA, Ltd., Sofia (Bulgaria); Nikolov, M. [CERB, Sofia (Bulgaria)

    1995-12-01

    The design life of the main power equipment-boilers and turbines is about 105 working hours. The possibilities for life extension are after normatively regulated control tests. The diagnostics and methodology for Boilers and Turbines Elements Remaining Life Assessment using up to date computer programs, destructive and nondestructive control of metal of key elements of units equipment, metal creep and low cycle fatigue calculations. As well as data for most common damages and some technical decisions for elements life extension are presented.

  20. フェライト型球状黒鉛鋳鉄の低サイクル疲労寿命に及ぼす黒鉛粒数の影響

    OpenAIRE

    原田, 昭治; 秋庭, 義明; 植田, 隆浩; 矢野, 満

    1994-01-01

    This paper deals with the effect of nodule count on the low-cycle fatigue life of ferritic ductile cast iron. Stress amplitude-controlled fatigue tests are conducted on ferritic ductile cast iron with different nodule count, i. e. high nodule count (HNC), and low nodule count (LNC) with same chemical composition and heat treatment. The difference of nodule count yields difference of fatigue mechanism in HNC and LNC. The fatigue life of both materials satisfies the Manson-Coffin relationship a...

  1. Material fatigue in high pressure piping

    Energy Technology Data Exchange (ETDEWEB)

    Brunne, W.C. [Pro Novum, Research and Technological Services, Ltd, Katowice, (Poland)

    1998-12-31

    The present paper describes a type of damage to four-way cross pieces on live steam and reheated steam pipelines. The results of metallographic examination and strength tests are presented. The occurring mechanisms of material degradation, i.e. low-cycle fatigue and hydrogen corrosion are discussed. The both mechanisms result in the corrosion fatigue of the material causing the failure of cross pieces. A new design of cross piece was proposed. (orig.) 5 refs.

  2. Annual report for the steering committee of the association Euratom-Belgian State for fusion 1994

    International Nuclear Information System (INIS)

    Moons, F.

    1994-09-01

    The work performed in 1994 at SCK/CEN in the field of technology for thermonuclear fusion is reported. It mainly embraces: (1) neutron irradiation effects on beryllium, (2) corrosion experiments on copper and molybdenum, (3) radiation hardening of opto-electronic components, (4) environmental tolerance and testing optical fibres assessment, (5) electrolytic recovery of elemental tritium from highly tritiated water, (6) in pile AISI 316L low cycle fatigue

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-09-15

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

  4. Effect of welding structure and δ-ferrite on fatigue properties for TIG welded austenitic stainless steels at cryogenic temperatures

    Science.gov (United States)

    Yuri, Tetsumi; Ogata, Toshio; Saito, Masahiro; Hirayama, Yoshiaki

    2000-04-01

    High-cycle and low-cycle fatigue properties of base and weld metals for SUS304L and SUS316L and the effects of welding structure and δ-ferrite on fatigue properties were investigated at cryogenic temperatures in order to evaluate the long-life reliability of the structural materials to be used in liquid hydrogen supertankers and storage tanks and to develop a welding process for these applications. The S-N curves of the base and weld metals shifted towards higher levels, i.e., the longer life side, with decreasing test temperatures. High-cycle fatigue tests demonstrated the ratios of fatigue strength at 10 6 cycles to tensile strength of the weld metals to be 0.35-0.7, falling below those of base metals with decreasing test temperatures. Fatigue crack initiation sites in SUS304L weld metals were mostly at blowholes with diameters of 200-700 μm, and those of SUS316L weld metals were at weld pass interface boundaries. Low-cycle fatigue tests revealed the fatigue lives of the weld metals to be somewhat lower than those of the base metals. Although δ-ferrite reduces the toughness of austenitic stainless steels at cryogenic temperatures, the effects of δ-ferrite on high-cycle and low-cycle fatigue properties are not clear or significant.

  5. Modeling of the influence of coarsening on viscoplastic behavior of a 319 foundry aluminum alloy

    International Nuclear Information System (INIS)

    Martinez, R.; Russier, V.; Couzinié, J.P.; Guillot, I.; Cailletaud, G.

    2013-01-01

    Both metallurgical and mechanical behaviors of a 319 foundry aluminum alloy have been modeled by means of a multiscale approach. The nano-scale, represented by the coarsening of Al 2 Cu precipitates, has been modeled according to the Lifshitz–Slyozov–Wagner (LSW) law in a range of temperature going from 23 °C to 300 °C up to 1000 h aging time. Results were then compared to transmission electron microscope (TEM) observations and are in good agreement with the experimental measurements. The model allows us to know the critical radius, the volume fraction and the number of particles per μm 3 in a α-phase representative volume element (RVE). The increase in yield stress generated by the interaction of dislocations with precipitates, lattice and solid solution, is modeled on the microscale. The yield stress becomes thus a function of the precipitation state, and is time/temperature dependent. These two models were then combined into a mechanical macroscale model in order to represent the Low Cycle Fatigue (LCF) behavior of the material. An elasto-viscoplastic law has been used and all the material parameters were experimentally determined with LCF stress/strain loops for the first cycle and for the mechanical steady state. The simulation results are in good agreement with the experiments.

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

    Science.gov (United States)

    Fekete, Balazs; Trampus, Peter

    2015-09-01

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

  7. Precipitate microstructure evolution in exposed IN738LC superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Strunz, Pavel, E-mail: strunz@ujf.cas.cz [Nuclear Physics Institute ASCR, CZ-25068 Řež near Prague (Czech Republic); Petrenec, Martin [Institute of Physics of Materials of the AS CR, Brno (Czech Republic); Gasser, Urs [Laboratory for Neutron Scattering, PSI, CH-5232 Villigen (Switzerland); Tobiáš, Jiří; Polák, Jaroslav [Institute of Physics of Materials of the AS CR, Brno (Czech Republic); Šaroun, Jan [Nuclear Physics Institute ASCR, CZ-25068 Řež near Prague (Czech Republic)

    2014-03-15

    Highlights: • Evolution of γ′-phase morphology in IN738LC Ni-base superalloy was examined by SANS. • In situ tests at high temperatures revealed trimodal precipitate distribution. • Formation, dissolution and (slow) kinetics of small γ′ precipitates was determined. • Equilibrium volume fraction of γ′ phase is significantly higher than 45%. • The small γ′ precipitates arise regardless the application of the mechanical load. -- Abstract: Nickel base superalloy IN738LC has been studied after low-cycle fatigue by Small Angle Neutron Scattering (SANS). Samples subjected to high-temperature low-cycle fatigue were annealed at various temperatures to change the size and the distribution of precipitates. Ex and in situ SANS and TEM studies were performed. It was found that additional precipitates are formed either during slow cooling from high temperatures or after reheating above 570 °C. Their size and distribution were evaluated. The precipitates arise regardless the application of the mechanical load. Nevertheless, these small precipitates influence low-cycle fatigue resistance. From the SANS data, it can be also deduced that the equilibrium volume fraction of γ′-precipitates at temperatures from room temperature to 825 °C is significantly higher than 45%. The kinetics of formation of small and medium-size γ′ precipitates at 700 and 800 °C was determined as well.

  8. Effect of chemistry modifications and heat treatments on the mechanical properties of DS Mar-M200 superalloy

    International Nuclear Information System (INIS)

    Yunrong, Z.; Yuping, W.; Jizhou, X.; Caron, P.; Khan, T.

    1988-01-01

    This paper discusses how Hf and Zr can promote the formation of eutectic (γ + γ), MC 2 , and Ni 5 M phases. In the alloy with equal atomic percent Zr and Hf, the solubility of Zr in eutectic γ is lower than that of Hf, and Zr content in Ni 5 M is much higher than Hf. This distribution of Zr is beneficial to the formation of Ni 5 M and lowers the strengthening efficiency of Zr. A pretreatment of 1130 degrees C/3hr efficiently eliminates Ni 5 M and, as a consequence, increases the incipient melting temperature of the alloy. The precipitation treatment of 1100 degrees C/4hr leads to cuboidal γ precipitation of about 0.5 μm size and causes the Hf-containing alloy to have a much higher creep strength than the Hf-free alloy in the temperature range of 760 to 1050 degrees C. The Hf-containing alloy showed greater LCF (low cycle fatigue) life in comparison to the Hf-free alloy. A similar tendency was found when Zr was either partially or totally substituted for Hf. A higher rate of solidification facilitates enhanced LCF life due to a finer structure and more perfect orientation. Surface slip analysis showed that intersection of two sets of slip in adjacent grains occurred in the Hf-free and HF-containing alloys, but cracking at the columnar grain boundary easily took place in the Hf-free alloy. The number of surface cracks of LCF specimens and their length per unit area are much higher in the Mar-M200 alloy. Mc cracking preferentially occurs at long rod-shaped carbides perpendicular to the stress axis, and then propagates through the interdendritic region. The Hf-containing alloy cracks along the crystallographic planes by separation of slip bands

  9. Toward enhanced hydrogen generation from water using oxygen permeating LCF membranes

    KAUST Repository

    Wu, Xiao-Yu; Chang, Le; Uddi, Mruthunjaya; Kirchen, Patrick; Ghoniem, Ahmed F.

    2015-01-01

    and flow rates on the feed and sweep sides on the water thermolysis rate and oxygen flux. A single step reaction mechanism is proposed for surface reactions, and three-resistance permeation models are derived. Results show that water thermolysis

  10. Linear Combination Fitting (LCF)-XANES analysis of As speciation in selected mine-impacted materials

    Data.gov (United States)

    U.S. Environmental Protection Agency — This table provides sample identification labels and classification of sample type (tailings, calcinated, grey slime). For each sample, total arsenic and iron...

  11. Fabrication of porous bioceramics for bone tissue applications using luffa cylindrical fibres (LCF as template

    Directory of Open Access Journals (Sweden)

    Mazen Alshaaer

    2017-03-01

    Full Text Available Three-dimensionally ordered macroporous biomaterials containing hydroxyapatite were synthesized using natural luffa cylindrical fibres (with diameter of 100–400 µm as templates. The preliminary evaluation of this novel method for production of porous bioceramics showed promising potential applications in bone tissue engineering. The produced bioceramics were subjected to microstructural, physical, mechanical, and in vitro characterisation. Mercury intrusion porosimetry, supported by SEM analysis, showed the presence of bimodal porosity (smaller pores with diameters of 10 to 30 µm and cylindrical macropores with diameters from 100 to 400 µm and 60% of the interconnected porosity. These porous calcium phosphate ceramics proved to be bioactive and exhibited mechanical properties comparable to those of natural spongy bones with compressive strength up to 3 MPa and elastic modulus in compression around 0.05 GPa. In vitro characterization of the porous ceramics showed cells attaching to the apatite crystals that make up the scaffold matrix. Cell adhesion resulted in elongated and highly stretched cells within the macropores with focal adhesion points on the scaffolds. Moreover, the cells adhered to the calcium phosphate cement (CPC and developed cytoplasmic extensions as shown by SEM imagery. Their proliferation in the scaffolds in culture demonstrates that the scaffold architecture is suitable for Mesenchymal stem cells seeding and growth.

  12. Secondary Hardening Behavior in Super Duplex Stainless Steels during LCF in Dynamic Strain Ageing Regime

    OpenAIRE

    Chai, Guocai; Andersson, Marcus

    2013-01-01

    Cyclic deformation behaviors in five modified duplex stainless steel S32705 grades have been studied at 20 °C, 200 °C, 250° and 350 °C. The influence of temperature and nitrogen concentration on the occurrence of the second hardening phenomenon, in the stress response curve was focused. An increase in nitrogen concentration can have a positive effect on dynamic strain ageing by increasing the first hardening and also the second hardening behavior during cyclic deformation. Furthermore, an inc...

  13. Crack behaviour of ferritic pressure vessels steels in oxygenated high temperature water under transient loadings. Crack corrosion phase 2. Crack development and fatigue. Final report; Rissverhalten ferritischer Druckbehaelterstaehle in sauerstoffhaltigem Hochtemperaturwasser bei transienten Vorgaengen. Risskorrosion Phase 2. Rissentstehung und Ermuedung. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Weissenberg, Thomas

    2014-03-15

    Using the example of the ferritic steels 22NiMoCr3-7 and 15MnNi6-3 representative for Nuclear Power Plants experimental data for the evaluation of the influence of the light water reactor (LWR) coolant environment and postulated chloride contaminations on crack development and fatigue have been determined in order to verify and extend the basis for a reliable estimation of the residual service life of reactor components. The aim of the research project was the investigation of the environmental effects at low strain rate conditions and the determination of the fatigue life under cyclic loading at uniaxial and multiaxial stress state. The quasi-static tensile tests (Constant Extension Rate Test, CERT) were performed using 3 low strain rates, each differing by about one order of magnitude (2.5.10{sup -3}, 3.1.10{sup -4} and 2.3.10{sup -5} %/s). The low cycle fatigue (LCF) experiments were conducted applying alternating tensile-compression loading with strain amplitudes of 0.3, 0.5 and 0.9 % at strain rates of 0.1 and 0.01 %/s (tests in air primarily 0.1 %/s). The cyclic notched tensile tests were carried out with a nominal axial strain in the notch root of 0.5 % at a strain rate of 0.1 %/s. The experiments in each case were performed in air, high purity water and chloride containing water at a testing temperature of 240 C, the oxygen content of the liquid medium was set to 0.4 ppm (simulated boiling water reactor coolant). In the CERT experiments chloride contents of 30, 50 and 100 ppb were applied, in the LCF tests the chloride content was 50 ppb which can be regarded as an upper realistic limit for a postulated chloride contamination of the reactor coolant. All experiments in liquid environment were preceded by a pre-autoclaving phase of at least 100 h in order to allow the formation of a stable oxide layer (magnetite). The testing material 22NiMoCr3-7 was available in form of an original reactor pressure vessel shell primarily designated for the German nuclear

  14. Crack behaviour of ferritic pressure vessels steels in oxygenated high temperature water under transient loadings. Crack corrosion phase 2. Crack development and fatigue. Final report

    International Nuclear Information System (INIS)

    Weissenberg, Thomas

    2014-03-01

    Using the example of the ferritic steels 22NiMoCr3-7 and 15MnNi6-3 representative for Nuclear Power Plants experimental data for the evaluation of the influence of the light water reactor (LWR) coolant environment and postulated chloride contaminations on crack development and fatigue have been determined in order to verify and extend the basis for a reliable estimation of the residual service life of reactor components. The aim of the research project was the investigation of the environmental effects at low strain rate conditions and the determination of the fatigue life under cyclic loading at uniaxial and multiaxial stress state. The quasi-static tensile tests (Constant Extension Rate Test, CERT) were performed using 3 low strain rates, each differing by about one order of magnitude (2.5.10 -3 , 3.1.10 -4 and 2.3.10 -5 %/s). The low cycle fatigue (LCF) experiments were conducted applying alternating tensile-compression loading with strain amplitudes of 0.3, 0.5 and 0.9 % at strain rates of 0.1 and 0.01 %/s (tests in air primarily 0.1 %/s). The cyclic notched tensile tests were carried out with a nominal axial strain in the notch root of 0.5 % at a strain rate of 0.1 %/s. The experiments in each case were performed in air, high purity water and chloride containing water at a testing temperature of 240 C, the oxygen content of the liquid medium was set to 0.4 ppm (simulated boiling water reactor coolant). In the CERT experiments chloride contents of 30, 50 and 100 ppb were applied, in the LCF tests the chloride content was 50 ppb which can be regarded as an upper realistic limit for a postulated chloride contamination of the reactor coolant. All experiments in liquid environment were preceded by a pre-autoclaving phase of at least 100 h in order to allow the formation of a stable oxide layer (magnetite). The testing material 22NiMoCr3-7 was available in form of an original reactor pressure vessel shell primarily designated for the German nuclear power plant

  15. Pre- and postirradiation properties of brazed joints of AISI 316L stainless steel

    International Nuclear Information System (INIS)

    Brossa, M.; Franconi, E.; Guerreschi, U.; Pierazzi, L.; Poggi, P.; Rustia, V.

    1994-01-01

    An extensive test campaign has been performed to verify the reliability and the endurance of brazed joints between AISI 316L parts for structural applications in the nuclear field. The tests, conducted for comparison with three different high melting temperature alloys, included tensile tests (normal and shear), fatigue tests (fatigue crack propagation, low cycle fatigue, 4-point bending fatigue) and impact tests; besides, tensile tests have been performed with both unirradiated and irradiated specimens. Generally, the tests demonstrated satisfactory mechanical properties of the joints and revealed occasionally strong differences in the behaviour of the different brazing alloys, thus providing important design indications. ((orig.))

  16. Experimental stress analysis for four 24-in. ANSI standard B16.9 tees

    International Nuclear Information System (INIS)

    Hayes, J.K.; Moore, S.E.

    1976-01-01

    The experimental stress analysis and low cycle fatigue tests of four tees tested by Combustion Engineering, Inc. (E-E) under subcontract to Union Carbide Nuclear Division are described. These tests are part of the ORNL Design Criteria for Piping and Nozzles Program which is being conducted for the development of design criteria for nuclear power plant service piping components. The test assemblies were fabricated at C-E from commercially obtained ANSI B16.9 tees and matching diameter steel pipes welded to the tees, with suitable and closures and fixtures for applying the loads

  17. Test Architecture, Test Retrofit

    Science.gov (United States)

    Fulcher, Glenn; Davidson, Fred

    2009-01-01

    Just like buildings, tests are designed and built for specific purposes, people, and uses. However, both buildings and tests grow and change over time as the needs of their users change. Sometimes, they are also both used for purposes other than those intended in the original designs. This paper explores architecture as a metaphor for language…

  18. Mechanical Performance versus Corrosion Damage Indicators for Corroded Steel Reinforcing Bars

    Directory of Open Access Journals (Sweden)

    Silvia Caprili

    2015-01-01

    Full Text Available The experimental results of a testing campaign including tensile and low-cycle fatigue tests on different reinforcing steel bar types in the as-delivered and corroded condition are presented. Experimental data were statistically analyzed adopting ANOVA technique; Performance Indicators (PIs, describing the mechanical performance characteristics of reinforcements, and Corrosion Damage Indicators (CDIs, describing the detrimental effects of corrosion phenomena, were determined and correlated in order to evaluate the influence of corrosion on the behaviour of reinforcing steels, providing useful information for designers in addition to what is presented in current standards.

  19. Optimal design of base isolation and energy dissipation system for nuclear power plant structures

    International Nuclear Information System (INIS)

    Zhou Fulin

    1991-01-01

    This paper suggests the method of optimal design of base isolation and energy dissipation system for earthquake resistant nuclear power plant structures. This method is based on dynamic analysis, shaking table tests for a 1/4 scale model, and a great number of low cycle fatigue failure tests for energy dissipating elements. A set of calculation formulas for optimal design of structures with base isolation and energy dissipation system were introduced, which are able to be used in engineering design for earthquake resistant nuclear power plant structures or other kinds of structures. (author)

  20. Description of the sodium loop ML-3

    International Nuclear Information System (INIS)

    Torre, de la M.; Melches, I; Lapena, J.; Martinez, T.A.; Miguel, de D.; Duran, F.

    1979-01-01

    The sodium loop ML-3 is described. The main objective of this facility is to obtain mechanical property data for LMFBR materials in creep and low cycle fatigue testing in flowing sodium. ML-3 includes 10 test stations for creep and two for fatigue. It is possible to operate simultaneously at three different temperature levels. The maximum operating temperature is 650 deg C at flow velocities up to 5 m/s. The ML-3 loop has been located in a manner that permits the fill/dump tank cover gas and security systems to be shared with an earlier circuit, the ML-1. (author)

  1. Testing Significance Testing

    Directory of Open Access Journals (Sweden)

    Joachim I. Krueger

    2018-04-01

    Full Text Available The practice of Significance Testing (ST remains widespread in psychological science despite continual criticism of its flaws and abuses. Using simulation experiments, we address four concerns about ST and for two of these we compare ST’s performance with prominent alternatives. We find the following: First, the 'p' values delivered by ST predict the posterior probability of the tested hypothesis well under many research conditions. Second, low 'p' values support inductive inferences because they are most likely to occur when the tested hypothesis is false. Third, 'p' values track likelihood ratios without raising the uncertainties of relative inference. Fourth, 'p' values predict the replicability of research findings better than confidence intervals do. Given these results, we conclude that 'p' values may be used judiciously as a heuristic tool for inductive inference. Yet, 'p' values cannot bear the full burden of inference. We encourage researchers to be flexible in their selection and use of statistical methods.

  2. Understanding and modelling of the aniso-thermal cyclic mechanical behaviour of the AISI 316LN austenitic stainless steel

    International Nuclear Information System (INIS)

    Gentet, D.

    2009-11-01

    The main subject of this report consists in proposing a mechanical model of the viscoplastic behaviour of an austenitic stainless steel under isothermal and aniso-thermal low cycle fatigue loadings at high temperatures (550-900 K). In this domain, numerous phenomena linked to dynamic strain ageing (DSA) and to dipolar dislocation structure formation may appear. Isothermal and aniso-thermal low cycle fatigue tension-compression tests were performed in order to verify some aspects about the effect of temperature on the mechanical behaviour. The study of the hysteresis loops and the observation of dislocation structures carried on transmission electron microscopy establish two different DSA mechanisms during isothermal tests. The effect of temperature history is shown for for particular temperature sequences. It is demonstrated that the stress amplitude increase when the sample is submitted to cycles at 'high temperature' is linked to the second mechanism of DSA. It comes from the increase of short range interaction between dislocations (chromium segregation), but it is also the consequence of the lack of dipolar structure annihilation at low temperature. From the experimental analysis of DSA mechanisms and dipolar restoration, a macroscopic aniso-thermal model is developed using physical internal variables (densities of dislocations). The equations of a polycrystalline model are rewritten with the aim of getting a simple multi-scale approach which can be used on finite elements analysis software. Between 550 and 873 K, the simulation results are in good accordance with the macroscopic and microscopic observations of low cycle fatigue, relaxation, and 2D-ratchetting tests. (author)

  3. Impurity levels and fatigue lives of pseudoelastic NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Rahim, M.; Frenzel, J.; Frotscher, M.; Pfetzing-Micklich, J.; Steegmüller, R.; Wohlschlögel, M.; Mughrabi, H.; Eggeler, G.

    2013-01-01

    In the present work we show how different oxygen (O) and carbon (C) levels affect fatigue lives of pseudoelastic NiTi shape memory alloys. We compare three alloys, one with an ultrahigh purity and two which contain the maximum accepted levels of C and O. We use bending rotation fatigue (up to cycle numbers >10 8 ) and scanning electron microscopy (for investigating microstructural details of crack initiation and growth) to study fatigue behavior. High cycle fatigue (HCF) life is governed by the number of cycles required for crack initiation. In the low cycle fatigue (LCF) regime, the high-purity alloy outperforms the materials with higher number densities of carbides and oxides. In the HCF regime, on the other hand, the high-purity and C-containing alloys show higher fatigue lives than the alloy with oxide particles. There is high experimental scatter in the HCF regime where fatigue cracks preferentially nucleate at particle/void assemblies (PVAs) which form during processing. Cyclic crack growth follows the Paris law and does not depend on impurity levels. The results presented in the present work contribute to a better understanding of structural fatigue of pseudoelastic NiTi shape memory alloys

  4. Microstructure and mechanical properties of lost foam cast 356 alloys

    Directory of Open Access Journals (Sweden)

    Qi-gui Wang

    2015-05-01

    Full Text Available Microstructure and mechanical properties of lost foam cast aluminum alloys have been investigated in both primary A356 (0.13% Fe and secondary 356 (0.47%. As expected, secondary 356 shows much higher content of Fe-rich intermetallic phases, and in particular the porosity in comparison with primary A356. The average area percent and size (length of Fe-rich intermetallics change from about 0.5% and 6 祄 in A356 to 2% and 25 祄 in 356 alloy. The average area percent and maximum size of porosity also increase from about 0.4% and 420 祄 to 1.4% and 600 祄, respectively. As a result, tensile ductility decreases about 60% and ultimate tensile strength declines about 8%. Lower fatigue strength was also experienced in the secondary 356 alloy. Low cycle fatigue (LCF strength decreased from 187 MPa in A356 to 159 MPa in 356 and high cycle fatigue (HCF strength also declined slightly from 68 MPa to 64 MPa.

  5. Influence of pores on crack initiation in monotonic tensile and cyclic loadings in lost foam casting A319 alloy by using 3D in-situ analysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Long, E-mail: longwang_calt@163.com [Univ. Lille, CNRS, Centrale Lille, Arts et Metiers Paris tech, FRE 3723 – LML – Laboratoire de Mecanique de Lille, F-59000 Lille (France); Limodin, Nathalie; El Bartali, Ahmed; Witz, Jean-François; Seghir, Rian [Univ. Lille, CNRS, Centrale Lille, Arts et Metiers Paris tech, FRE 3723 – LML – Laboratoire de Mecanique de Lille, F-59000 Lille (France); Buffiere, Jean-Yves [Laboratoire Matériaux, Ingénierie et Sciences (MATEIS), CNRS UMR5510, INSA-Lyon, 20 Av. Albert Einstein, 69621 Villeurbanne (France); Charkaluk, Eric [Univ. Lille, CNRS, Centrale Lille, Arts et Metiers Paris tech, FRE 3723 – LML – Laboratoire de Mecanique de Lille, F-59000 Lille (France)

    2016-09-15

    Lost Foam Casting (LFC) process is replacing the conventional gravity Die Casting (DC) process in automotive industry for the purpose of geometry optimization, cost reduction and consumption control. However, due to lower cooling rate, LFC produces in a coarser microstructure that reduces fatigue life. In order to study the influence of the casting microstructure of LFC Al-Si alloy on damage micromechanisms under monotonic tensile loading and Low Cycle Fatigue (LCF) at room temperature, an experimental protocol based on the three dimensional (3D) in-situ analysis has been set up and validated. This paper focuses on the influence of pores on crack initiation in monotonic and cyclic tensile loadings. X-ray Computed Tomography (CT) allowed the microstructure of material being characterized in 3D and damage evolution being followed in-situ also in 3D. Experimental and numerical mechanical fields were obtained by using Digital Volume Correlation (DVC) technique and Finite Element Method (FEM) simulation respectively. Pores were shown to have an important influence on strain localization as large pores generate enough strain localization zones for crack initiation both in monotonic tensile and cyclic loadings.

  6. Influence of pores on crack initiation in monotonic tensile and cyclic loadings in lost foam casting A319 alloy by using 3D in-situ analysis

    International Nuclear Information System (INIS)

    Wang, Long; Limodin, Nathalie; El Bartali, Ahmed; Witz, Jean-François; Seghir, Rian; Buffiere, Jean-Yves; Charkaluk, Eric

    2016-01-01

    Lost Foam Casting (LFC) process is replacing the conventional gravity Die Casting (DC) process in automotive industry for the purpose of geometry optimization, cost reduction and consumption control. However, due to lower cooling rate, LFC produces in a coarser microstructure that reduces fatigue life. In order to study the influence of the casting microstructure of LFC Al-Si alloy on damage micromechanisms under monotonic tensile loading and Low Cycle Fatigue (LCF) at room temperature, an experimental protocol based on the three dimensional (3D) in-situ analysis has been set up and validated. This paper focuses on the influence of pores on crack initiation in monotonic and cyclic tensile loadings. X-ray Computed Tomography (CT) allowed the microstructure of material being characterized in 3D and damage evolution being followed in-situ also in 3D. Experimental and numerical mechanical fields were obtained by using Digital Volume Correlation (DVC) technique and Finite Element Method (FEM) simulation respectively. Pores were shown to have an important influence on strain localization as large pores generate enough strain localization zones for crack initiation both in monotonic tensile and cyclic loadings.

  7. Creep-fatigue damage in austenitic stainless steels

    International Nuclear Information System (INIS)

    Rezgui, Brahim.

    1980-06-01

    This is a study of hold time effects on the low cycle fatigue (L.C.F.) properties of 316L austenitic stainless steel at 600 0 C in air. Results obtained for different plastic strain levels indicate that a tension hold time at peak strain lead to a reduction in fatigue life. The importance of this effect depend on the length of hold period, and also on the strain amplitude. No saturation had been observed. Metallographic and microstructural analysis of failed specimens indicates mechanisms by which failure is produced. For continuous cycling the fractures occurs by the initiation and the propagation of a trans-granular crack. Creep damage in the bulk of material is formed during periods of tensile stress relaxation; it causes a change in the failure mode which became intergranular. It is the interaction between this creep-damage and fatigue cracks which is partly responsable for the reduction in the fatigue life. Predictions based upon linear cumulative damage method indicate that virgin material properties may be irrelevant in creep-fatigue interactions [fr

  8. Seismic testing

    International Nuclear Information System (INIS)

    Sollogoub, Pierre

    2001-01-01

    This lecture deals with: qualification methods for seismic testing; objectives of seismic testing; seismic testing standards including examples; main content of standard; testing means; and some important elements of seismic testing

  9. Schirmer test

    Science.gov (United States)

    Tear test; Tearing test; Dry eye test; Basal secretion test; Sjögren - Schirmer; Schirmer's test ... used when the eye doctor suspects you have dry eye. Symptoms include dryness of the eyes or excessive ...

  10. Pinworm test

    Science.gov (United States)

    Oxyuriasis test; Enterobiasis test; Tape test ... diagnose this infection is to do a tape test. The best time to do this is in ... lay their eggs at night. Steps for the test are: Firmly press the sticky side of a ...

  11. 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.

  12. A proposal of predictive methods of crack propagation life and remaining life of structural metal under creep-fatigue interacted conditions by use of X-ray profile analysis

    International Nuclear Information System (INIS)

    Ohnami, M.; Sakane, M.; Nishino, S.

    1987-01-01

    The following two series of studies are described: One is crack propagation life prediction in high-temperature low-cycle fatigue tests under triangular and trapezoidal strain or stress waves for austenitic stainless steel by X-ray fractography. Another is remaining life prediction of the steel under creep-fatigue interacted conditions by applying the concept of the remaining life diagram and X-ray profile analysis. Particle size and microstrain obtained by X-ray profile analysis were effective nondestructive parameters for estimating crack propagation life and remaining life in creep-fatigue interaction

  13. Fatigue damage evaluation of austenitic stainless steel using nonlinear ultrasonic waves in low cycle regime

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jianfeng; Xuan, Fu-Zhen, E-mail: fzxuan@ecust.edu.cn [MOE Key Laboratory of Pressurized System and Safety, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2014-05-28

    The interrupted low cycle fatigue test of austenitic stainless steel was conducted and the dislocation structure and fatigue damage was evaluated subsequently by using both transmission electron microscope and nonlinear ultrasonic wave techniques. A “mountain shape” correlation between the nonlinear acoustic parameter and the fatigue life fraction was achieved. This was ascribed to the generation and evolution of planar dislocation structure and nonplanar dislocation structure such as veins, walls, and cells. The “mountain shape” correlation was interpreted successfully by the combined contribution of dislocation monopole and dipole with an internal-stress dependent term of acoustic nonlinearity.

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

    DEFF Research Database (Denmark)

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

    1999-01-01

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

  15. Case Study of Local Damage Indicators for a 2-Bay, 6-Storey RC-Frame subject to Earthquakes

    DEFF Research Database (Denmark)

    Skjærbæk, P. S.; Nielsen, Søren R. K.; Kirkegaard, Poul Henning

    1997-01-01

    A simulation study of a 2-bay, 6storey model test RC-frame(scale 1:5) subject to earthquakes is considered in this paper. Based on measured (simulated) storey accelerations and ground surface accelerations several indices for the storey damage, including interstorey drift, flexural damage ratios......, normalized cumulative dissipated energy, Park and Ang's indicator, a low-cycle fatigue damage index and a recently proposed local softening damage index estimated from time-varying eigenfrequencies are used to evaluate the damage state of the structure after the earthquake. Storey displacements are obtained...

  16. Case Study of Local Damage Indicators for a 2-Bay, 6-Storey RC-Frame subject to Earthquakes

    DEFF Research Database (Denmark)

    Skjærbæk, P. S.; Nielsen, Søren R. K.; Kirkegaard, Poul Henning

    A simulation study of a 2-bay, 6storey model test RC-frame(scale 1:5) subject to earthquakes is considered in this paper. Based on measured (simulated) storey accelerations and ground surface accelerations several indices for the storey damage, including interstorey drift, flexural damage ratios......, normalized cumulative dissipated energy, Park and Ang's indicator, a low-cycle fatigue damage index and a recently proposed local softening damage index estimated from time-varying eigenfrequencies are used to evaluate the damage state of the structure after the earthquake. Storey displacements are obtained...

  17. Electrostimulated recovery of welded joint durability: experiment and model

    International Nuclear Information System (INIS)

    Semakin, E.V.; Chirakadze, D.Z.; Tsellermaer, V.Ya.; Gromov, V.E.; Sosnin, O.V.

    1997-01-01

    The possibility to increase the durability of welded joints operating under conditions of low cycle fatigue is shown to be brought about using electric current pulses. Experimental method of recovery of operational capability is demonstrated on welded joints of tool steels R6M5 and 40Kh/ The onset of critical stage of fatigue in the welded joint was determined by ultrasonic testing. Then the specimens were treated with 20 Hz electric pulses with amplitude of 250 MA/M 2 for 100 μs. Such treatment resulted in an increase of time to fracture. The phenomenological model of the process is proposed

  18. Roughness Influence On Macro- And Micro-Tribology Of Multi-Layered Hard Coatings On Carbon Fibre Polymer Composite

    Directory of Open Access Journals (Sweden)

    Lackner J.M.

    2015-09-01

    Full Text Available Goal of this work is the investigation of roughness influences on the abrasive wear behaviour of magnetron sputtered multi-layered, low-friction coatings on carbon-fibre reinforced polymers (CFRP. Higher coating roughness at similar CFRP quality was realized by higher deposition rates, leading to increased heat flux to the substrates during deposition. Thermal expansion of the epoxy matrix on the micro scale results in a wavy, wrinkled surface topography. Both in scratch and reciprocal sliding testing against alumina, the friction coefficients are lower for the smooth coatings, but their wear rate is higher due to low-cycle fatigue caused abrasion.

  19. Experimental study on uniaxial ratcheting deformation and failure behavior of 304 stainless steel

    International Nuclear Information System (INIS)

    Yang Xianjie; Gao Qing; Cai Lixun; Liu Yujie

    2004-01-01

    In the paper, the tests of cyclic strain ratcheting and low cycle fatigue for 304 stainless steel under uniaxial cyclic straining were carried out to systematically explore the deformation and failure behavior of the material. The experimental study shows that the cyclic strain ratcheting deformation behavior of the material is different from either the uniaxial monotonic tensile one or the cyclic deformation one under the symmetrical cyclic straining with the same strain amplitude, and the strain ratcheting deformation and failure behaviors depend on both the plastic strain amplitude and the strain increment at the cyclic maximum strain. Some significant results were observed

  20. Thermal-buckling analysis of an LMFBR overflow vessel

    International Nuclear Information System (INIS)

    Severud, L.K.

    1983-01-01

    During a reactor scram, cold sodium flows into the hot overflow vessel. The effect on the vessel is a compressive thermal stress in a zone just above the sodium level. This condition must be sufficiently controlled to preclude thermal buckling. Also, under repeated scrams, the vessel should not suffer thermal stress low cycle fatigue. To evaluate the closeness to buckling and satisfaction of ASMA Code limits, a combination of simple approximations, detailed elastic shell buckling analyses, and correlations to results of thermal buckling tests were employed. This paper describes the analysis methods, special considerations, and evaluations accomplished for this FFTF vessel to assure satisfaction of ASME buckling design criteria, rules, and limits

  1. Thermomechanical Fatigue Behavior of a Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate Glass-Ceramic Matrix Composite.

    Science.gov (United States)

    1992-08-01

    Testing of Coated Monocrystalline Superalloys," in Low Cycle Fatigue. ASTM STP 942, Solomon, H.D., Hafford, G.R., Kaisand, L.R., and Keis, B.N. , eds...HOTOL) project is considering the use of CMCs on lower aeroshell panels , air intake leading edges, and the nose cone where temperatures may climb to...Works (Corning, NY). The composite was supplied in 16-ply, unidirectionally reinforced (10116) panels , measuring 152.4 cm x 152.4 cm (6 in x 6 in

  2. Mechanical properties of austenitic stainless steels in sodium

    International Nuclear Information System (INIS)

    Lloyd, G.J.

    1978-03-01

    A detailed review of the mechanical properties of austenitic stainless steels in liquid sodium is presented. Consideration has been given to the influence of the of the impurities in reactor sodium and metallurgical variables upon the stress rupture life, the low cycle fatigue and combined creep/fatigue resistance, elastic-plastic crack propagation rates, the high cycle fatigue life, tensile properties and fracture toughness. The effects of exposure to contaminated sodium prior to testing are also discussed. Examples of the success of mechanistic interpretations of materials behaviour in sodium are given and additionally, the extent to which mechanical properties in sodium may be predicted with the use of appropriate data. (author)

  3. Cyclic plastic material behavior leading to crack initiation in stainless steel under complex fatigue loading conditions

    International Nuclear Information System (INIS)

    Facheris, G.

    2014-01-01

    The improvement of the reliability and of the safety in the design of components belonging to the primary cooling circuit of a light water nuclear reactor is nowadays one of the most important research topics in nuclear industry. One of the most important damage mechanisms leading the crack initiation in this class of components is the low cycle fatigue (LCF) driven by thermal strain fluctuations caused by the complex thermo-mechanical loading conditions typical for the primary circuit (e.g. operating thermal transients, thermal stratification, turbulent mixing of cold and hot water flows, etc.). The cyclic application of the resulting plastic deformation to the steel grades commonly used for the fabrication of piping parts (e.g. austenitic stainless steels) is associated with a continuous evolution of the mechanical response of the material. As an additional complication, the cyclic behavior of stainless steels is influenced by temperature, strain amplitude and cyclic accumulation of inelastic strain (i.e. ratcheting). The accurate prediction of the structural response of components belonging to the primary cooling circuit requires the development of a reliable constitutive model that must be characterized by a reduced complexity to allow its application in an industrial context. In this framework, the main goal of the current dissertation is to formulate, calibrate and implement in a commercial Finite Element code, a constitutive model that is suitable for the stainless stain grade 316L subjected to complex loading conditions. As a first task, a characterization of the mechanical behavior of 316L subjected to uniaxial and multiaxial strain-controlled conditions (including LCF and ratcheting) is carried out performing several tests in the laboratories of the Paul Scherrer Institute (PSI, Villigen, Switzerland) and of Politecnico di Milano (Italy). The uniaxial experiments demonstrate that, prescribing a strain-controlled ratcheting path, a harder material response

  4. Cyclic plastic material behavior leading to crack initiation in stainless steel under complex fatigue loading conditions

    Energy Technology Data Exchange (ETDEWEB)

    Facheris, G.

    2014-07-01

    The improvement of the reliability and of the safety in the design of components belonging to the primary cooling circuit of a light water nuclear reactor is nowadays one of the most important research topics in nuclear industry. One of the most important damage mechanisms leading the crack initiation in this class of components is the low cycle fatigue (LCF) driven by thermal strain fluctuations caused by the complex thermo-mechanical loading conditions typical for the primary circuit (e.g. operating thermal transients, thermal stratification, turbulent mixing of cold and hot water flows, etc.). The cyclic application of the resulting plastic deformation to the steel grades commonly used for the fabrication of piping parts (e.g. austenitic stainless steels) is associated with a continuous evolution of the mechanical response of the material. As an additional complication, the cyclic behavior of stainless steels is influenced by temperature, strain amplitude and cyclic accumulation of inelastic strain (i.e. ratcheting). The accurate prediction of the structural response of components belonging to the primary cooling circuit requires the development of a reliable constitutive model that must be characterized by a reduced complexity to allow its application in an industrial context. In this framework, the main goal of the current dissertation is to formulate, calibrate and implement in a commercial Finite Element code, a constitutive model that is suitable for the stainless stain grade 316L subjected to complex loading conditions. As a first task, a characterization of the mechanical behavior of 316L subjected to uniaxial and multiaxial strain-controlled conditions (including LCF and ratcheting) is carried out performing several tests in the laboratories of the Paul Scherrer Institute (PSI, Villigen, Switzerland) and of Politecnico di Milano (Italy). The uniaxial experiments demonstrate that, prescribing a strain-controlled ratcheting path, a harder material response

  5. Ultrasonic Testing

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeong Jun; Kuk, Jeong Han

    2002-02-15

    This book introduces ultrasonic testing, which tells of outline of ultrasonic testing, principle of ultrasonic testing, prosperities of ultrasonic waves, radiographic test and ultrasonic test, basic theory on ultrasonic testing, mode conversion, transmission and diffraction, ultrasonic flaw detection and probe, standard test piece and reference test piece, like KS(JIS) ASME and ASTM, classification and properties of ultrasonic testing, straight beam method, angle beam method, ASME SEC.V.Art.5 ASTMA 388 and KS B 0817 Korean industrial standard.

  6. Development of IN-RAFM steel and fabrication technologies for Indian TBM

    Energy Technology Data Exchange (ETDEWEB)

    Albert, S.K., E-mail: shaju@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603 102 (India); Laha, K.; Bhaduri, A.K.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603 102 (India); Rajendrakumar, E. [TBM Division, Institute of Plasma Research, Bhat, Gandhinagar 382428 (India)

    2016-11-01

    Highlights: • India specific RAFM steel IN-RAFM has been produced in commercial scale and physical property data for the same have been generated. • Mechanical properties of the commercial heats are comparable to that of the laboratory heats. • IN-RAFM steel filler wires has been produced indigenously. • Process parameters have been optimized so that toughness of the fusion zone of the EB and laser welds is comparable to that of the base metal even at sub-zero temperatures. • Fabrication of the mock ups of different components of Indian TBM has been initiated. - Abstract: India has indigenously developed its own Indian Reduced Activation Ferritic Martensitic Steel (IN-RAFM steel) which, it is proposed to use for fabrication of Indian TBM to be installed in ITER. With an objective of qualifying this material for use in ITER, extensive testing of this material to generate the necessary data required to offer this material for Particular Material Appraisal of ITER has been undertaken. Accordingly, data generation on creep, fatigue and physical properties of this steel is in progress. Physical properties like thermal diffusivity, heat capacity and thermal expansion coefficient for this steel at various temperatures have been measured and thermal conductivity estimated from the measured physical properties. Values obtained for these physical properties are comparable with those reported for other RAFM steels. Results of creep tests that are in progress also indicate that creep is comparable to that of other RAFM steels. Low cycle fatigue (LCF) behaviour of this steel has been studied in air with total strain control in the strain amplitude range of ±0.25–1% and temperatures range of 300–873 K at a constant strain rate of 3 × 10{sup −3} s{sup −1}. Results confirm that fatigue life of IN-RAFM steel is at par with that of the European Union grade Eurofer 97 RAFM steel. During production of IN-RAFM steel plates of different thicknesses, it is observed

  7. Trichomonas Testing

    Science.gov (United States)

    ... Genetic Tests for Targeted Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy ... With some NAATs, samples collected for testing of gonorrhea and chlamydial infections can also be used to ...

  8. Coombs test

    Science.gov (United States)

    Direct antiglobulin test; Indirect antiglobulin test; Anemia - hemolytic ... No special preparation is necessary for this test. ... There are 2 types of the Coombs test: Direct Indirect The direct ... that are stuck to the surface of red blood cells. Many diseases ...

  9. Ham test

    Science.gov (United States)

    Acid hemolysin test; Paroxysmal nocturnal hemoglobinuria - Ham test; PNH - Ham test ... BJ. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures . 6th ed. Philadelphia, PA: Elsevier ...

  10. Magnesium Test

    Science.gov (United States)

    ... PF4 Antibody Hepatitis A Testing Hepatitis B Testing Hepatitis C Testing HER2/neu Herpes Testing High-sensitivity C-reactive Protein (hs-CRP) Histamine Histone Antibody HIV Antibody and HIV Antigen (p24) HIV Antiretroviral Drug Resistance Testing, Genotypic HIV Viral Load HLA Testing HLA- ...

  11. Lipase Test

    Science.gov (United States)

    ... PF4 Antibody Hepatitis A Testing Hepatitis B Testing Hepatitis C Testing HER2/neu Herpes Testing High-sensitivity C-reactive Protein (hs-CRP) Histamine Histone Antibody HIV Antibody and HIV Antigen (p24) HIV Antiretroviral Drug Resistance Testing, Genotypic HIV Viral Load HLA Testing HLA- ...

  12. Rubella Test

    Science.gov (United States)

    ... PF4 Antibody Hepatitis A Testing Hepatitis B Testing Hepatitis C Testing HER2/neu Herpes Testing High-sensitivity C-reactive Protein (hs-CRP) Histamine Histone Antibody HIV Antibody and HIV Antigen (p24) HIV Antiretroviral Drug Resistance Testing, Genotypic HIV Viral Load HLA Testing HLA- ...

  13. Mono Test

    Science.gov (United States)

    ... PF4 Antibody Hepatitis A Testing Hepatitis B Testing Hepatitis C Testing HER2/neu Herpes Testing High-sensitivity C-reactive Protein (hs-CRP) Histamine Histone Antibody HIV Antibody and HIV Antigen (p24) HIV Antiretroviral Drug Resistance Testing, Genotypic HIV Viral Load HLA Testing HLA- ...

  14. AMA Test

    Science.gov (United States)

    ... PF4 Antibody Hepatitis A Testing Hepatitis B Testing Hepatitis C Testing HER2/neu Herpes Testing High-sensitivity C-reactive Protein (hs-CRP) Histamine Histone Antibody HIV Antibody and HIV Antigen (p24) HIV Antiretroviral Drug Resistance Testing, Genotypic HIV Viral Load HLA Testing HLA- ...

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

    International Nuclear Information System (INIS)

    Shahram Shahrooi; Ibrahim Henk Metselaar; Zainul Huda; Ghezavati, H.R.

    2009-01-01

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

  16. Neuropathy Tests

    Science.gov (United States)

    ... LD) Lactoferrin Lactose Tolerance Tests LDL Cholesterol LDL Particle Testing (LDL-P) Lead Legionella Testing Leptin Levetiracetam Lipase ... tests, such as computed tomography (CT) scans or magnetic resonance imaging ... suspected, additional testing may be performed to evaluate heart rate, blood ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-01

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

  18. European concerted action COST 50 - materials for gas turbines

    Energy Technology Data Exchange (ETDEWEB)

    Bressers, J.; Cat, R. de; Fenske, E.

    1984-01-01

    A combined approach which would yield differential information regarding both crack initiation and crack growth from a single test specimen has been adopted to study the low cycle fatigue behaviour of PM Astrology over a range of testing conditions (temperature, strain-rate, plastic strain-amplitude) which span the range from cycle dependent to time dependent low cycle fatigue. It appears that both crack initiation and crack growth depend in a non-systematic manner on the testing parameters, which results from the simultaneous action of several time dependent processes. These time-dependent processes cause Tomkins' crack growth model to fail to correctly predict the number of cycles spent in crack growth at the high-temperature, low strain-rate end of the test parameter spectrum. At the other end of the test parameter spectrum the match with the experimental data is fortuitious since the laws governing the crack growth behaviour for crack sizes below and beyond approximately 200 ..mu..m (short crack growth behaviour and higher order dependence of the crack growth rate on the crack depth, respectively) deviate from the crack growth law which is at the basis of Tomkins' model. The experimental crack increment data are used to compute fracture mechanics lives. It is suggested that these fracture mechanics lives are appropriate lower bound estimates of the life of PM Astrology containing defects such as inclusions.

  19. Pharmacogenomic Testing

    Science.gov (United States)

    ... your family Plan for the future Insurance and financial planning Transition for children Emergency preparedness Testing & Services Testing ... Support Genetic Disease Information Find a Support Group Financial Planning Who Should I Tell? Genetic Testing & Counseling Compensation ...

  20. Predictive Testing

    Science.gov (United States)

    ... your family Plan for the future Insurance and financial planning Transition for children Emergency preparedness Testing & Services Testing ... Support Genetic Disease Information Find a Support Group Financial Planning Who Should I Tell? Genetic Testing & Counseling Compensation ...

  1. Syphilis Test

    Science.gov (United States)

    ... Genetic Tests for Targeted Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy ... treated for another sexually transmitted disease , such as gonorrhea Is pregnant, during the first prenatal visit and ...

  2. Effect of variable load on crack initiation microalloyed steel S 690-QL

    Directory of Open Access Journals (Sweden)

    M. Burzić

    2015-01-01

    Full Text Available The accumulation of damage in the form of initiation and growth of micro-cracks is the first stage of destruction that ends when the merger microcracks form macro cracks. Cracks formed in the cycle number N =104 - 105 are the result of low cycle fatigue. From the need to evaluate low cycle fatigue life was carried out to investigate the low cycle fatigue microalloyed high-strength steel S690QL in the heat-treated.

  3. Randomization tests

    CERN Document Server

    Edgington, Eugene

    2007-01-01

    Statistical Tests That Do Not Require Random Sampling Randomization Tests Numerical Examples Randomization Tests and Nonrandom Samples The Prevalence of Nonrandom Samples in Experiments The Irrelevance of Random Samples for the Typical Experiment Generalizing from Nonrandom Samples Intelligibility Respect for the Validity of Randomization Tests Versatility Practicality Precursors of Randomization Tests Other Applications of Permutation Tests Questions and Exercises Notes References Randomized Experiments Unique Benefits of Experiments Experimentation without Mani

  4. Test chamber

    NARCIS (Netherlands)

    Leferink, Frank Bernardus Johannes

    2009-01-01

    A test chamber for measuring electromagnetic radiation emitted by an apparatus to be tested or for exposing an apparatus to be tested to an electromagnetic radiation field. The test chamber includes a reverberation chamber made of a conductive tent fabric. To create a statistically uniform field in

  5. Statistical evaluation of low cycle loading curves parameters for structural materials by mechanical characteristics

    International Nuclear Information System (INIS)

    Daunys, Mykolas; Sniuolis, Raimondas

    2006-01-01

    About 300 welded joint materials that are used in nuclear power energy were tested under monotonous tension and low cycle loading in Kaunas University of Technology together with St. Peterburg Central Research Institute of Structural Materials in 1970-2000. The main mechanical, low cycle loading and fracture characteristics of base metals, weld metals and some heat-affected zones of welded joints metals were determined during these experiments. Analytical dependences of low cycle fatigue parameters on mechanical characteristics of structural materials were proposed on the basis of a large number of experimental data, obtained by the same methods and testing equipment. When these dependences are used, expensive low cycle fatigue tests may be omitted and it is possible to compute low cycle loading curves parameters and lifetime for structural materials according to the main mechanical characteristics given in technical manuals. Dependences of low cycle loading curves parameters on mechanical characteristics for several groups of structural materials used in Russian nuclear power energy are obtained by statistical methods and proposed in this paper

  6. Three-dimensional stress and strain around real shape Si particles in cast aluminum alloy under cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Teranishi, Masaki [Department of Nuclear Power & Energy Safety Engineering, University of Fukui (Japan); Kuwazuru, Osamu, E-mail: kuwa@u-fukui.ac.jp [Department of Nuclear Power & Energy Safety Engineering, University of Fukui (Japan); Gennai, Shota [Department of Nuclear Power & Energy Safety Engineering, University of Fukui (Japan); Kobayashi, Masakazu [Department of Mechanical Engineering, Toyohashi University of Technology (Japan); Toda, Hiroyuki [Department of Mechanical Engineering, Kyushu University (Japan)

    2016-12-15

    The crack initiation mechanism of cast Al-Si-Mg alloy under low-cycle fatigue was addressed by using the synchrotron X-ray computed tomography (CT) and the image-based finite element analysis. The fatigue test and its in situ CT observation were conducted to visualize the crack initiation behavior. In the low-cycle fatigue, the cracking generally started with the voiding by the fracture of silicon particles, and the coalescence of these voids formed the crack. To elucidate the mechanism of silicon particle fracture, the finite element elastic-plastic analyses were performed with regard to twelve silicon particles including the fractured and intact particles detected by the chronological CT observation. By using the image-based modeling technique, the interested particle was embedded in the finite element model along with the surrounding particles as they were in the specimen. The material properties of silicon phase and aluminum matrix were identified by the nanoindentation tests. Ten cycles of loading by the uniform stress which was equivalent to the load in the fatigue test was applied to the finite element model, and the stress, strain and their cyclic response around the silicon particles were simulated. The morphology analysis was also carried out for the interested particles, and the geometrical parameters affecting the particle fracture were examined. By comparing the results of fractured and intact particles, we found that there were some geometrical conditions for the fracture of silicon particles, and a certain magnitude of hydrostatic stress was required to break the particles.

  7. Tensile testing

    CERN Document Server

    2004-01-01

    A complete guide to the uniaxial tensile test, the cornerstone test for determining the mechanical properties of materials: Learn ways to predict material behavior through tensile testing. Learn how to test metals, alloys, composites, ceramics, and plastics to determine strength, ductility and elastic/plastic deformation. A must for laboratory managers, technicians, materials and design engineers, and students involved with uniaxial tensile testing. Tensile Testing , Second Edition begins with an introduction and overview of the test, with clear explanations of how materials properties are determined from test results. Subsequent sections illustrate how knowledge gained through tensile tests, such as tension properties to predict the behavior (including strength, ductility, elastic or plastic deformation, tensile and yield strengths) have resulted in improvements in materals applications. The Second Edition is completely revised and updated. It includes expanded coverage throughout the volume on a variety of ...

  8. Test quality

    International Nuclear Information System (INIS)

    Hartley, R.S.; Keller, A.E.

    1992-01-01

    Inservice testing of safety-related components at nuclear power plants is performed under the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (the Code). Subsections IWP and IWV of Section 11 of the Code state test method and frequency requirements for pumps and valves, respectively. Tests vary greatly in quality and frequency. This paper explores the concept of test quality and its relationship with operational readiness and preventive maintenance. This paper also considers the frequencies of component testing. Test quality is related to a test's ability to detect degradation that can cause component failure. The quality of the test depends on several factors, including specific parameters measured, system or component conditions, and instrument accuracy. The quality of some currently required tests for check valves, motor-operated valves, and pumps is also discussed. Suggestions are made to improve test quality by measuring different parameters, testing valves under load, and testing positive displacement pumps at high pressure and centrifugal pumps at high flow rate conditions. These suggestions can help to improve the level of assurance of component operational readiness gained from testing

  9. Test quality

    International Nuclear Information System (INIS)

    Hartley, R.S.; Keller, A.E.

    1992-01-01

    This document discusses inservice testing of safety-related components at nuclear power plants which is performed under the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (the Code). Subsections IWP and IWV of Section XI of the Code state test method and frequency requirements for pumps and valves respectively. Tests vary greatly in quality and frequency. This paper explores the concept of test quality and its relationship with operational readiness and preventive maintenance. This paper also considers the frequencies of component testing. Test quality is related to a test's ability to detect degradation that can cause component failure. The quality of the test depends on several factors, including specific parameters measured, system or component conditions, and instrument accuracy. The quality of some currently required tests for check valves, motor-operated valves, and pumps is also discussed. Suggestions are made to improve test quality by measuring different parameters, testing valves under load, and testing positive displacement pumps at high pressure and centrifugal pumps at high flow rate conditions. These suggestions can help to improve the level of assurance of component operational readiness gained from testing

  10. High Temperature Mechanical Constitutive Modeling of a High-Nb TiAl Alloy

    Directory of Open Access Journals (Sweden)

    DONG Chengli

    2018-02-01

    Full Text Available Uniaxial tensile, low cycle fatigue, fatigue-creep interaction and creep experiments of a novel high-Nb TiAl alloy (i.e. Ti-45Al-8Nb-0.2W-0.2B-0.02Y (atom fraction/% were conducted at 750℃ to obtain its tested data and curves. Based on Chaboche visco-plasticity unified constitutive model, Ohno-Wang modified non-linear kinematic hardening was introduced in Chaboche constitutive model to describe the cyclic hardening/softening, and Kachanov damage was coupled in Chaboche constitutive model to characterize the accelerated creep stage. The differential equations of the constitutive model discretized by explicit Euler method were compiled in to ABAQUS/UMAT to simulate the mechanical behavior of high-Nb TiAl alloy at different test conditions. The results show that Chaboche visco-plasticity unified constitutive model considering both Ohno-Wang modified non-linear kinematic hardening and Kachanov damage is able to simulate the uniaxial tensile, low cycle fatigue, fatigue-creep interaction and creep behavior of high-Nb TiAl alloy and has high accuracy.

  11. Low-cyclic fatigue behavior of modified 9Cr–1Mo steel at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Guguloth, Krishna; Sivaprasad, S. [CSIR-National Metallurgical laboratory, Material Science and Technology Division, Jamshedpur 831007 (India); Chakrabarti, D. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Tarafder, S. [CSIR-National Metallurgical laboratory, Material Science and Technology Division, Jamshedpur 831007 (India)

    2014-05-01

    The low-cycle fatigue behavior of indigenously developed modified 9Cr–1Mo steel has been evaluated using a constant strain rate (1×10{sup −3} s{sup −1}) at ambient temperature (25 °C) and at elevated temperatures (500–600 °C) over the strain amplitudes varying between ±0.7% and ±1.2%. Cyclic stress response showed a gradual softening regime that ended in a stress plateau until complete failure of the specimens. The estimated fatigue life decreased with the increase in test temperature. The effect of temperature on fatigue life was more pronounced at lower strain amplitudes. The cyclic deformation behavior at different temperatures has been analyzed from hysteresis loop and also in view of the changes taking place in dislocation structure and dislocation–precipitation interaction. Evaluation of low-cycle fatigue properties of modified 9Cr–1Mo steel over a range of test temperature can help in designing components for in-core applications in fast breeder reactors and in super heaters for nuclear power plants.

  12. Improvement of high temperature fatigue lifetime in AZ91 magnesium alloy by heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Mokhtarishirazabad, Mehdi [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Azadi, Mohammad, E-mail: m_azadi@ip-co.com [Fatigue and Wear Workgroup, Irankhodro Powertrain Company (IPCO), Tehran (Iran, Islamic Republic of); Hossein Farrahi, Gholam [School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Winter, Gerhard; Eichlseder, Wilfred [Chair of Mechanical Engineering, University of Leoben, Leoben (Austria)

    2013-12-20

    In the present paper, an improvement in high temperature fatigue properties of the AZ91 magnesium alloy with rare earth elements has been obtained by a typical heat treatment, denoted by T6. For this objective, out-of-phase thermo-mechanical fatigue, room temperature and high temperature low cycle fatigue tests are performed to compare lifetimes. Several rare earth elements are initially added to the AZ91 alloy during a gravity casting process in permanent molds. Also, the type of the heat treatment is examined. Results of specimens with only the solution (the T4 heat treatment) and the solution with the ageing process (the T6 heat treatment) are compared under isothermal fatigue loadings. Microstructural investigations are carried out, before and after fatigue experiments to demonstrate the heat treatment effect. Results showed that both low cycle fatigue and thermo-mechanical fatigue of the alloy at high temperatures increases tremendously after the T6 heat treatment. This behavior attributes to the variation of the ductility, which was a result of microstructural changes during the heat treatment and the varying temperature in fatigue tests.

  13. Improvement of high temperature fatigue lifetime in AZ91 magnesium alloy by heat treatment

    International Nuclear Information System (INIS)

    Mokhtarishirazabad, Mehdi; Azadi, Mohammad; Hossein Farrahi, Gholam; Winter, Gerhard; Eichlseder, Wilfred

    2013-01-01

    In the present paper, an improvement in high temperature fatigue properties of the AZ91 magnesium alloy with rare earth elements has been obtained by a typical heat treatment, denoted by T6. For this objective, out-of-phase thermo-mechanical fatigue, room temperature and high temperature low cycle fatigue tests are performed to compare lifetimes. Several rare earth elements are initially added to the AZ91 alloy during a gravity casting process in permanent molds. Also, the type of the heat treatment is examined. Results of specimens with only the solution (the T4 heat treatment) and the solution with the ageing process (the T6 heat treatment) are compared under isothermal fatigue loadings. Microstructural investigations are carried out, before and after fatigue experiments to demonstrate the heat treatment effect. Results showed that both low cycle fatigue and thermo-mechanical fatigue of the alloy at high temperatures increases tremendously after the T6 heat treatment. This behavior attributes to the variation of the ductility, which was a result of microstructural changes during the heat treatment and the varying temperature in fatigue tests

  14. Effects of thermally induced porosity on an as-HIP powder metallurgy superalloy

    Science.gov (United States)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1980-01-01

    The effect of thermally induced porosity on the mechanical properties of an as-hot-isostatically pressed and heat-treated pressing made from low carbon Astroloy is examined. Tensile, stress-rupture, creep, and low cycle fatigue tests were performed and the results were compared with industrial acceptance criteria. It is shown that the porous pressing has a porosity gradient from the rim to the bore with the bore having 1-1/2% greater porosity. Mechanical properties of the test ring below acceptance level are tensile reduction in area at room temperature and 538 C and time for 0.1% creep at 704 C. It is also found that the strength, ductility, and rupture life of the rim are slightly inferior to those of the rim of the sound pressings, while those of the bore are generally below the acceptable level. At strain ranges typical of commercial aircraft engines, the low cycle fatigue life of the rim of the porous pressings is slightly lower than that of the sound pressings.

  15. Randomization tests

    National Research Council Canada - National Science Library

    Edgington, Eugene S

    1980-01-01

    .... This book provides all the necessary theory and practical guidelines, such as instructions for writing computer programs, to permit experimenters to transform any statistical test into a distribution-free test...

  16. Laboratory Tests

    Science.gov (United States)

    ... Medical Devices Radiation-Emitting Products Vaccines, Blood & Biologics Animal & ... What are lab tests? Laboratory tests are medical devices that are intended for use on samples of blood, urine, or other tissues ...

  17. Triglycerides Test

    Science.gov (United States)

    ... K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2 nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Triglycerides; 491–2 p. Lab Tests ...

  18. Lactate Test

    Science.gov (United States)

    ... Plasma Free Metanephrines Platelet Count Platelet Function Tests Pleural Fluid Analysis PML-RARA Porphyrin Tests Potassium Prealbumin ... ency/article/000391.htm . (2002 January, Updated). Lactate (Liquid) Reagent Set. Pointe Scientific, Inc. [On-line Reagent ...

  19. Electrolytes Test

    Science.gov (United States)

    ... Plasma Free Metanephrines Platelet Count Platelet Function Tests Pleural Fluid Analysis PML-RARA Porphyrin Tests Potassium Prealbumin ... of potassium is found in the plasma , the liquid portion of the blood. Monitoring potassium is important ...

  20. Ferritin Test

    Science.gov (United States)

    ... normal" values. By comparing your test results with reference values, you and your healthcare provider can see if ... along with other iron tests , when a routine complete blood count (CBC) shows that a person's hemoglobin and hematocrit ...

  1. Cholesterol Test

    Science.gov (United States)

    ... artery disease. Other names for a cholesterol test: Lipid profile, Lipid panel What is it used for? If you ... Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998-2017.Cholesterol Test: Overview; 2016 Jan 12 [ ...

  2. Gonorrhea Test

    Science.gov (United States)

    ... Links Patient Resources For Health Professionals Subscribe Search Gonorrhea Testing Send Us Your Feedback Choose Topic At ... Sources Ask Us Also Known As GC Test Gonorrhea NAAT or NAT Neisseria gonorrhoeae Nucleic Acid Amplification ...

  3. Susceptibility Testing

    Science.gov (United States)

    ... Marker Bicarbonate (Total CO2) Bilirubin Blood Culture Blood Gases Blood Ketones Blood Smear Blood Typing Blood Urea ... hours depending on the method used. There are commercial tests available that offer rapid susceptibility testing and ...

  4. Nationale test

    DEFF Research Database (Denmark)

    2009-01-01

    Professor Sven Erik Nordenbo og centerleder Niels Egelund, begge DPU, i samtale om nationale test.......Professor Sven Erik Nordenbo og centerleder Niels Egelund, begge DPU, i samtale om nationale test....

  5. Nationale Test

    DEFF Research Database (Denmark)

    2009-01-01

    Hvad er egentlig formålet med de nationale test? Bliver eleverne klogere af at blive testet? Og er der en sammenhæng mellem bandekrig og nationale test? Fysisk medie: dpu.dk/tv......Hvad er egentlig formålet med de nationale test? Bliver eleverne klogere af at blive testet? Og er der en sammenhæng mellem bandekrig og nationale test? Fysisk medie: dpu.dk/tv...

  6. VDRL test

    Science.gov (United States)

    ... confirmed with another blood test to make the diagnosis of syphilis. Normal value ranges may vary slightly among different ... broken) Alternative Names Venereal disease research ... laboratory test (VDRL) – serum. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures . 6th ed. St Louis, MO: Elsevier Saunders; ...

  7. Drug Testing

    Science.gov (United States)

    ... testing, substance abuse testing, toxicology screen, tox screen, sports doping tests What is it used for? Drug screening is used to find out whether or not a person has taken a certain drug or drugs. It ... Sports organizations. Professional and collegiate athletes usually need to ...

  8. HIV Testing

    Science.gov (United States)

    ... Abroad Treatment Basic Statistics Get Tested Find an HIV testing site near you. Enter ZIP code or city Follow HIV/AIDS CDC HIV CDC HIV/AIDS See RSS | ... All Collapse All Should I get tested for HIV? CDC recommends that everyone between the ages of ...

  9. Nondestructive Testing

    Energy Technology Data Exchange (ETDEWEB)

    Berger, Harold [Argonne National Laboratory

    1969-01-01

    A nondestructive test is an examination of an object in any manner which will not impair the future usefulness of the object. This booklet discusses a few basic methods of nondestructive testing, and some of their characteristics. In addition, it discusses possible future methods for nondestructive testing by taking a quick look at some of the methods now under study.

  10. Fatigue life assessment based on crack growth behavior in reduced activation ferritic/martensitic steel

    International Nuclear Information System (INIS)

    Nogami, Shuhei; Sato, Yuki; Hasegawa, Akira

    2010-01-01

    Crack growth behavior under low cycle fatigue in reduced activation ferritic/martensitic steel, F82H IEA-heat (Fe-8Cr-2W-0.2V-0.02Ta), was investigated to improve the fatigue life assessment method of fusion reactor structural material. Low cycle fatigue test was carried out at room temperature in air at a total strain range of 0.4-1.5% using an hourglass-type miniature fatigue specimen. The relationship between the surface crack length and life fraction was described using one equation independent of the total strain range. Therefore, the fatigue life and residual life could be estimated using the surface crack length. Moreover, the microcrack initiation life could be estimated using the total strain range if there was a one-to-one correspondence between the total strain range and number of cycles to failure. The crack growth rate could be estimated using the total strain range and surface crack length by introducing the concept of the normalized crack growth rate. (author)

  11. FAA Fluorescent Penetrant Laboratory Inspections

    Energy Technology Data Exchange (ETDEWEB)

    WINDES,CONNOR L.; MOORE,DAVID G.

    2000-08-02

    The Federal Aviation Administration Airworthiness Assurance NDI Validation Center currently assesses the capability of various non-destructive inspection (NDI) methods used for analyzing aircraft components. The focus of one such exercise is to evaluate the sensitivity of fluorescent liquid penetrant inspection. A baseline procedure using the water-washable fluorescent penetrant method defines a foundation for comparing the brightness of low cycle fatigue cracks in titanium test panels. The analysis of deviations in the baseline procedure will determine an acceptable range of operation for the steps in the inspection process. The data also gives insight into the depth of each crack and which step(s) of the inspection process most affect penetrant sensitivities. A set of six low cycle fatigue cracks produced in 6.35-mm thick Ti-6Al-4V specimens was used to conduct the experiments to produce sensitivity data. The results will document the consistency of the crack readings and compare previous experiments to find the best parameters for water-washable penetrant.

  12. Fatigue micro-crack initiation behavior and effect of irradiation damage on it in austenitic stainless steel

    International Nuclear Information System (INIS)

    Nakai, Ryosuke; Sato, Yuki; Nogami, Shuhei; Hasegawa, Akira

    2012-01-01

    The effect of irradiation on slip band formation and growth and micro-crack initiation behavior under low cycle fatigue in SUS316L austenitic stainless steel was investigated using accelerator-based proton irradiation and a low cycle fatigue test at room temperature in air. The micro-crack initiation was observed at slip band, grain boundary, twin boundary, and triple junction regardless of the total strain range and the proton irradiation. In unirradiated specimens, the micro-crack initiation life dropped by 75-90% due to the increase of the plastic strain range. Under the condition the plastic strain range was 0.4%, the micro-crack initiation was observed mainly at the grain boundary. On the other hand, under the condition the plastic strain range was 1.0%, the number fractions of the micro-crack initiation in slip band and twin boundary were increased. In proton-irradiated specimens, the micro-crack initiation life decreased by 50-80% and the micro-crack initiation was observed mainly at slip band and twin boundary. (author)

  13. Ultrasonic testing

    Energy Technology Data Exchange (ETDEWEB)

    Song, Sung Jin [Sungkwunkwan Univ., Seoul (Korea, Republic of); Jeong, Hyun Jo [Wonkwang Univ., Iksan (Korea, Republic of)

    2004-02-15

    For the proper performance of ultrasonic testing of steel welded joints, and anisotropic material it is necessary to have sound understanding on the underlying physics. To provide such an understanding, it is beneficial to have simulation tools for ultrasonic testing. In order to address such a need, we develop effective approaches to simulate angle beam ultrasonic testing with a personal computer. The simulation is performed using ultrasonic measurement models based on the computationally efficient multi-Gaussian beams. This reach will describe the developed ultrasonic testing models together with the experimental verification of their accuracy.

  14. Thermo-mechanical lifetime assessment of components for 700 °C steam turbine applications

    International Nuclear Information System (INIS)

    Ehrhardt, F.

    2014-01-01

    In order to increase thermal efficiency, steam turbine technology has been oriented to cover steam inlet temperatures above 700 °C and steam pressures exceeding 350 bar. These temperature levels require the use of nickel and cobalt based alloys. Nickel-based alloys were identified as being suitable for forgeable high-pressure steam turbine rotor materials, including welding procedures for joints between nickel-based alloys and alloyed ferritic steels. Expensive nickel-based alloys should be replaced with conventional heat-resistant steels in applications operating below ∼500-550°C. Since a welded rotor design is favoured, dissimilar metal weldments are required. The research work presented is aimed at the development of thermo-mechanical lifetime assessment methodologies for 700°C steam turbine components. The first main objective was the development of advanced creep-fatigue (CF) lifetime assessment methodologies for the evaluation of Alloy 617 steam turbine rotor features at maximum application temperatures. For the characterisation of the material behaviour under static loading conditions, creep rupture experiments for both medium temperatures and target application temperature have been conducted in order to investigate the influence of ageing treatment on Alloy 617. A creep deformation equation was developed on the basis of a modified Graham-Walles law. Continuous Low Cycle Fatigue (LCF) experiments have been performed. A plasticity model of Chaboche type has been developed. Cyclic/hold experiments have been conducted on Alloy 617. A modification on the creep law was introduced for the description of the material’s decreased creep resistance under combined CF loading. A very promising approach considering plastic and creep-dissipated energy was developed. The effectiveness of this energy exhaustion method was verified with the calculation of endurance curves for continuous cycling LCF and cyclic/hold conditions over a broad range of temperatures, strain

  15. Thermo-mechanical lifetime assessment of components for 700 °C steam turbine applications

    Energy Technology Data Exchange (ETDEWEB)

    Ehrhardt, F.

    2014-07-01

    In order to increase thermal efficiency, steam turbine technology has been oriented to cover steam inlet temperatures above 700 °C and steam pressures exceeding 350 bar. These temperature levels require the use of nickel and cobalt based alloys. Nickel-based alloys were identified as being suitable for forgeable high-pressure steam turbine rotor materials, including welding procedures for joints between nickel-based alloys and alloyed ferritic steels. Expensive nickel-based alloys should be replaced with conventional heat-resistant steels in applications operating below ∼500-550°C. Since a welded rotor design is favoured, dissimilar metal weldments are required. The research work presented is aimed at the development of thermo-mechanical lifetime assessment methodologies for 700°C steam turbine components. The first main objective was the development of advanced creep-fatigue (CF) lifetime assessment methodologies for the evaluation of Alloy 617 steam turbine rotor features at maximum application temperatures. For the characterisation of the material behaviour under static loading conditions, creep rupture experiments for both medium temperatures and target application temperature have been conducted in order to investigate the influence of ageing treatment on Alloy 617. A creep deformation equation was developed on the basis of a modified Graham-Walles law. Continuous Low Cycle Fatigue (LCF) experiments have been performed. A plasticity model of Chaboche type has been developed. Cyclic/hold experiments have been conducted on Alloy 617. A modification on the creep law was introduced for the description of the material’s decreased creep resistance under combined CF loading. A very promising approach considering plastic and creep-dissipated energy was developed. The effectiveness of this energy exhaustion method was verified with the calculation of endurance curves for continuous cycling LCF and cyclic/hold conditions over a broad range of temperatures, strain

  16. Troponins Test

    Science.gov (United States)

    ... lab's website in order to provide you with background information about the test(s) you had performed. You will need to return ... C, Banfi G, Guidi GC. Influence of a half-marathon run on NT-proBNP and troponin ... MedlinePlus Medical Encyclopedia [On-line information]. Available online ...

  17. Insulin Test

    Science.gov (United States)

    ... hours before blood is collected, but occasionally a health practitioner may do testing when fasting is not possible, such as when a glucose tolerance test (see Glucose ) is done. In some cases, the health practitioner may request that a person fast longer ...

  18. Genetic Testing

    Science.gov (United States)

    ... is often the only way to determine if symptoms could possibly be related to celiac disease. For a person who faces this situation, a negative gene test would indicate that symptoms are not the result of celiac disease. A positive gene test, however, does not diagnose ...

  19. Potassium test

    Science.gov (United States)

    ... hyperkalemia ) may be due to: Addison disease (rare) Blood transfusion Certain medicines Crushed tissue injury Hyperkalemic periodic paralysis ... released. This may cause a falsely high result. Alternative Names Hypokalemia test; K+ Images Blood test References Mount DB. Disorders of potassium balance. ...

  20. Nationale test

    DEFF Research Database (Denmark)

    Bundsgaard, Jeppe; Puck, Morten Rasmus

    Nationale test skubber undervisning i en forkert retning. Det er lærerne og skolelederne enige om. Men særligt skolelederne ser også muligheder for at bruge testen til at få viden om elevernes faglige kompetencer og om undervisningen. Det kommer til udtryk i rapporten Nationale test: Danske lærere...

  1. Oedometer Tests

    DEFF Research Database (Denmark)

    Thorsen, Grete

    1996-01-01

    The paper describes the results of oedometer tests carried out with samples from Eemian fresh-water deposits and the methods used to determine the preconsolidation pressure from the test results. The influence of creep in the material on the apparent preconsolidation pressure is estimated from...

  2. TORCH Test

    Science.gov (United States)

    ... Parietal Cell Antibody Partial Thromboplastin Time (PTT, aPTT) Parvovirus B19 Pericardial Fluid Analysis Peritoneal Fluid Analysis Pertussis Tests ... enterovirus, Epstein-Barr virus , varicella-zoster virus , and parvovirus B19 . How is the sample collected for testing? A ...

  3. Automating Test Activities: Test Cases Creation, Test Execution, and Test Reporting with Multiple Test Automation Tools

    OpenAIRE

    Loke Mun Sei

    2015-01-01

    Software testing has become a mandatory process in assuring the software product quality. Hence, test management is needed in order to manage the test activities conducted in the software test life cycle. This paper discusses on the challenges faced in the software test life cycle, and how the test processes and test activities, mainly on test cases creation, test execution, and test reporting is being managed and automated using several test automation tools, i.e. Jira, ...

  4. Trypsinogen test

    Science.gov (United States)

    ... care provider about the meaning of your specific test results. What Abnormal Results ... vary in size, so it may be harder to get a blood sample from one person than another. Other risks associated with having ...

  5. Just testing

    International Nuclear Information System (INIS)

    Robinson, D.

    1985-01-01

    In the 1950s, most of the men who witnessed Britain's nuclear tests at Christmas Island in the Pacific were national servicemen, aged 19 or 20. Some revelled in sun and swimming, some were bored, some were too busy to be bored. How many of the twenty thousand servicemen involved in the tests suspected that they might be exposed to radiation that would reveal itself a generation later in blood and bone cancers, sterility, cataracts, or deformities in their children. The Ministry of Defence insists nobody was in danger. This book tells a different story, in the words of the servicemen, and of their medical reports, about secrets which are no longer Official. It is important not only to the victims of a government's extraordinary reluctance to face up to the tragic consequences of a programme of nuclear tests on Christmas Island and in Australia, but to anyone concerned with the damage that nuclear testing is still doing in the world today. (author)

  6. Test Ship

    Data.gov (United States)

    Federal Laboratory Consortium — The U. S. Navy dedicated the decommissioned Spruance Class destroyer ex-PAUL F. FOSTER (EDD 964), Test Ship, primarily for at sea demonstration of short range weapon...

  7. Injection Tests

    CERN Document Server

    Kain, V

    2009-01-01

    The success of the start-up of the LHC on 10th of September was in part due to the preparation without beam and injection tests in 2008. The injection tests allowed debugging and improvement in appropriate portions to allow safe, efficient and state-of-the-art commissioning later on. The usefulness of such an approach for a successful start-up becomes obvious when looking at the problems we encountered before and during the injection tests and could solve during this period. The outline of the preparation and highlights of the different injection tests will be presented and the excellent performance of many tools discussed. A list of shortcomings will follow, leading to some planning for the preparation of the run in 2009.

  8. Fungal Tests

    Science.gov (United States)

    ... Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1569, 1570, 1532, 1616. Forbes, B. et. al. (© 2007). Bailey & Scott's Diagnostic Microbiology, Twelfth Edition: Mosby Elsevier Press, St. Louis, Missouri. ...

  9. PTH Test

    Science.gov (United States)

    ... Gregory C. Sephel PhD FACB MT(ASCP). Lab Tests Online adjunct board member. Director Clinical Pathology, VA TN Valley Healthcare System; Associate Professor Pathology, Microbiology, Immunology, Vanderbilt University School of Medicine. Sources Used ...

  10. Phosphorus Test

    Science.gov (United States)

    ... be seen with increased intake of the mineral, hypocalcemia , and with kidney dysfunction. Someone with a mild ... usually detected because of the relationship with and effect on calcium levels . Calcium is routinely tested as ...

  11. Procalcitonin Test

    Science.gov (United States)

    ... normal" values. By comparing your test results with reference values, you and your healthcare provider can see if ... g., blood culture , urine culture ), lactate , blood gases , complete blood count (CBC) , and cerebrospinal fluid (CSF) analysis . When is ...

  12. RSV Test

    Science.gov (United States)

    ... Sex Hormone Binding Globulin (SHBG) Shiga toxin-producing Escherichia coli Sickle Cell Tests Sirolimus Smooth Muscle Antibody (SMA) ... University Medical Center, LAB Letter [On-line newsletter]. PDF available for download at http://www.stanfordhospital.com/ ...

  13. Prenatal Tests

    Science.gov (United States)

    ... tests are considered routine — that is, almost all pregnant women receiving prenatal care get them. They include things like checking urine (pee) levels for protein, sugar, or signs of infection. Other non-routine ...

  14. Progesterone Test

    Science.gov (United States)

    ... replacement therapy, or help diagnose the cause of abnormal uterine bleeding When To Get Tested? At specific times during ... receiving progesterone replacement therapy; when a woman has abnormal uterine bleeding Sample Required? A blood sample drawn from a ...

  15. Testosterone Test

    Science.gov (United States)

    ... Testing Triglycerides Troponin Tryptase Tumor Markers Uric Acid Urinalysis Urine Albumin and Albumin/Creatinine Ratio Urine Culture ... 2010) 2536–259. Centers for Disease Control Hormone Standardization website(HoST). Available online at http://www.cdc. ...

  16. Pertussis Tests

    Science.gov (United States)

    ... of Conditions Not Listed? Not Listed? Acidosis and Alkalosis Adrenal Insufficiency and Addison Disease Alcoholism Allergies Alzheimer ... tested? Pertussis, commonly called whooping cough, is a respiratory infection caused by the bacteria Bordetella pertussis . These ...

  17. Tests computarizados

    Directory of Open Access Journals (Sweden)

    R. Fernando Prialé Z.

    1983-12-01

    Full Text Available En primer lugar, se considera el impacto de las microcomputadoras en la actualidad, viéndolo como un hecho social destinado a traer profundos cambios: nos orientamos hacia una cultura informática cuyo signo es la posibilidad de tratar grandes cantidades de información. En segundo lugar; se analiza brevemente la importancia de los tests en el desarrollo de la psicología. Finalmente, se discute la posibilidad de aplicar la informática a la psicometría con el ejemplo del test de BARSIT.   The impact of microcomputers is discussed as a cultural fact that will bring profound changes in the near future: a society with an ubiquous capacity for treating big amounts of information. The importance of tests for the development of psychology is then analysed. Finaly, the possibility of applying microcomputers to psychometry is discussed trough a concrete example: The BARSIT test.

  18. VMA Test

    Science.gov (United States)

    ... spasms and rapid eye movements referred to as "dancing eyes, dancing feet." The VMA test may also be ordered ... a pheochromocytoma or neuroblastoma? People with a family history of multiple endocrine neoplasia (MEN2), a genetic condition ...

  19. Neuropsychological testing.

    Science.gov (United States)

    Zucchella, Chiara; Federico, Angela; Martini, Alice; Tinazzi, Michele; Bartolo, Michelangelo; Tamburin, Stefano

    2018-06-01

    Neuropsychological testing is a key diagnostic tool for assessing people with dementia and mild cognitive impairment, but can also help in other neurological conditions such as Parkinson's disease, stroke, multiple sclerosis, traumatic brain injury and epilepsy. While cognitive screening tests offer gross information, detailed neuropsychological evaluation can provide data on different cognitive domains (visuospatial function, memory, attention, executive function, language and praxis) as well as neuropsychiatric and behavioural features. We should regard neuropsychological testing as an extension of the neurological examination applied to higher order cortical function, since each cognitive domain has an anatomical substrate. Ideally, neurologists should discuss the indications and results of neuropsychological assessment with a clinical neuropsychologist. This paper summarises the rationale, indications, main features, most common tests and pitfalls in neuropsychological evaluation. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  20. Testing theories

    International Nuclear Information System (INIS)

    Casten, R F

    2015-01-01

    This paper discusses some simple issues that arise in testing models, with a focus on models for low energy nuclear structure. By way of simplified examples, we illustrate some dangers in blind statistical assessments, pointing out especially the need to include theoretical uncertainties, the danger of over-weighting precise or physically redundant experimental results, the need to assess competing theories with independent and physically sensitive observables, and the value of statistical tests properly evaluated. (paper)