WorldWideScience

Sample records for fatigue fracture behaviour

  1. Influence of Aging Conditions on Fatigue Fracture Behaviour of 6063 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Rafiq Ahmed Siddiqui

    2001-12-01

    Full Text Available Aluminum - Magnesium - Silicon (Al-Mg-Si 6063 alloy was heat-treated using under aged, peak aged and overage temperatures. The numbers of cycles required to cause the fatigue fracture, at constant stress, was considered as criteria for the fatigue resistance. Moreover, the fractured surface of the alloy at different aging conditions was evaluated by optical microscopy and the Scanning Electron Microscopy (SEM. The SEM micrographs confirmed the cleavage surfaces with well-defined fatigue striations. It has been observed that the various aging time and temperature of the 6063 Al-alloy, produces different modes of fractures. The most suitable age hardening time and temperature was found to be between 4 to 5 hours and to occur at 460 K. The increase in fatigue fracture property of the alloy due to aging could be attributed to a vacancy assisted diffusion mechanism or due to pinning of dislocations movement by the precipitates produced during aging. However, the decrease in the fatigue resistance, for the over aged alloys, might be due to the coalescence of precipitates into larger grains.

  2. Critical fatigue behaviour in brittle glasses

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The dynamic fatigue fracture behaviour in different glasses under various sub-threshold loading conditions are analysed here employing an anomalous diffusion model. Critical dynamical behaviour in the time-to-fracture and the growth of the micro-crack sizes, similar to that observed in such materials in the case.

  3. Fatigue and insufficiency fractures

    International Nuclear Information System (INIS)

    Lodwick, G.S.; Rosenthal, D.I.; Kattapuram, S.V.; Hudson, T.M.

    1987-01-01

    The incidence of stress fracture is increasing. In our younger society this is due largely to a preocupation with physical conditioning, but in our elderly population it is due to improved recognition and better methods of detection and diagnosis. Stress fracture of the elderly is an insufficiency fracture which occurs in the spine, the pelvis, the sacrum and other bones afflicted with disorders which cause osteopenia. Stress fracture is frequently misdiagnosed as a malignant lesion of bone resulting in biopsy. Scintiscanning provides the greatest frequency of detection, while computed tomography often provides the definitive diagnosis. With increased interest and experience a better insight into the disease has been achieved, and what was once thought of as a simple manifestation of mechanical stress is now known to be an orderly, complex pattern of physiological changes in bone which conform to a model by Frost. The diffuse nature of these changes can be recognized by scintigraphy, radiography and magnetic resonance imaging. 27 refs.; 8 figs

  4. Fracture and Fatigue: Some New Insights

    Indian Academy of Sciences (India)

    Fracture and Fatigue: Some New Insights. FOREWORD. It is over nine decades since fracture mechanics found its importance in the design of mechanical, aerospace and civil engineering structures. Its application started in naval structures during the early part of 20th century. The theory of fracture mechanics was initially ...

  5. Fatigue behaviour of cast iron with globular graphite

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, P.; Pusch, G.; Krodel, L. [Institut fuer Werkstofftechnik, TU Bergakademie Freiberg, Gustav-Zeuner-Strasse 5, 09599 Freiberg (Germany)

    2004-07-01

    Cast iron with bainitic matrix and globular graphite, so called austempered ductile iron (ADI), allows the substitution of heat-treatable steels. The use of ADI in safety-relevant components requires knowledge of the fracture and fatigue behaviour. Cyclic stress strain behaviour and fatigue life at total strain control and random loading have been investigated at ADI (EN-GJS-1000-5) and pearlitic cast iron (EN-GJS-600-3). In addition fracture mechanic tests at cyclic loading at various stress ratios were carried out. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  6. High speed rails. Fatigue behaviour

    International Nuclear Information System (INIS)

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

    2005-01-01

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

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

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr

    2007-01-01

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

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

    Science.gov (United States)

    2011-08-01

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

  9. Fatigue fracture modes of a stainless steel

    International Nuclear Information System (INIS)

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

    1977-01-01

    The influence of strain hardening and martensite phase transformation on the fatigue fracture regions (pulsative tension) of a Stainless Steel type AISI 316 was investigated. This lead to the conclusion that the greater austenite strain hardening level only favours the occurrence of a brittle fracture. Also, in as much as the static induced martensite is concerned, a direct influence on the failure process was not observed, whereas, apparently, the one transformed under cyclic loading has no contribution to the rupture mechanisms. (author) [pt

  10. High temperature fatigue behaviour of intermetallics

    Indian Academy of Sciences (India)

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

    brittle to ductile transition temperature, mean stress and environment on fatigue behaviour of same γ-TiAl alloys are discussed. Keywords. Nickel aluminides; titanium aluminides; low cycle fatigue; micro- alloying. 1. Introduction. Ordered intermetallic alloys have undergone extensive development over the past two decades.

  11. TORSIONAL DEFORMATION AND FATIGUE BEHAVIOUR OF 6061 ALUMINIUM ALLOY

    Directory of Open Access Journals (Sweden)

    marini marno

    2012-02-01

    Full Text Available Torsional deformation and fatigue behaviour of both solid and thin-walled tubular specimens were made from as-received and heat treated 6061 aluminium alloy were studied. 6061 aluminium alloy have been widely used as a candidate material in automobile, aerospace, aircraft and structural application because of their superior mechanical properties such as high strength to weight ratio, good ductility and others. The differences in cyclic deformation and fatigue behaviours between round and solid specimens where a stress gradient exist, and thin-walled tubular specimens where a uniform stress state is commonly assumed, are also discussed. Von Mises and Tresca criteria has been used to predict the monotonic and cyclic deformation curve and compared to the torsional data obtained from the experiment. The S-N curve was used to present and evaluate the fatigue life of the specimens. Through fractographic analysis, failure criteria of fracture surfaces were observed and discussed. 

  12. Mechanical Behaviour of Materials Volume II Fracture Mechanics and Damage

    CERN Document Server

    François, Dominique; Zaoui, André

    2013-01-01

    Designing new structural materials, extending lifetimes and guarding against fracture in service are among the preoccupations of engineers, and to deal with these they need to have command of the mechanics of material behaviour. This ought to reflect in the training of students. In this respect, the first volume of this work deals with elastic, elastoplastic, elastoviscoplastic and viscoelastic behaviours; this second volume continues with fracture mechanics and damage, and with contact mechanics, friction and wear. As in Volume I, the treatment links the active mechanisms on the microscopic scale and the laws of macroscopic behaviour. Chapter I is an introduction to the various damage phenomena. Chapter II gives the essential of fracture mechanics. Chapter III is devoted to brittle fracture, chapter IV to ductile fracture and chapter V to the brittle-ductile transition. Chapter VI is a survey of fatigue damage. Chapter VII is devoted to hydogen embrittlement and to environment assisted cracking, chapter VIII...

  13. Study on fracture behaviour of Hybrid Aluminium Composite

    OpenAIRE

    Niranjan D. B.; Shiva Shankar G. S.; Shankar Latha B.

    2018-01-01

    This work makes an attempt to study of fracture behaviour of hybrid Composite reinforced with hard ceramic Boron carbide as primary phase and secondary phase as soft solid lubricant Molybdenum Disulphide with base matrix Al2219 by two stage stir casting method is incorporated. Compact tension type specimen was utilized for test and dimensions are conformity to ASTM E-647.Fatigue crack growth and fracture toughness test conducted as per ASTM Standard E-399 and E-1820. This study discloses that...

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

    DEFF Research Database (Denmark)

    Lassen, Tom

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

  15. Deformation and fracture of high-temperature resistant alloys subject to combined creep and fatigue stressing at temperatures above 800deg C

    International Nuclear Information System (INIS)

    Meurer, H.P.; Schuster, H.; Bhanu Sankara Rao, K.

    1989-01-01

    The fatigue behaviour of a NiCr 23 Co 12 Mo alloy (INCONEL 617) has been investigated under HTR operating conditions (up to 950deg C) and in ambient air. The paper discusses especially the material's deformation behaviour, the relaxation behaviour during the holding tests, and the fracture behaviour (fatigue life). (MM) [de

  16. Fatigue behaviour of metals. 2. ed.; Ermuedungsverhalten metallischer Werkstoffe

    Energy Technology Data Exchange (ETDEWEB)

    Christ, H.J. [Siegen Univ. (Gesamthochschule) (Germany). Inst. fuer Werkstofftechnik

    2009-07-01

    The book presents an outline of the fatigue characteristics of metals. Interested students, engineers, scientists and users are provided with a basic understanding of the possible processes, from which they will get a feeling for the processes going on inside materials under fatigue stress which is indispensable for developing and testing modern constructional materials. Subjects: Introduction and outline - Material fatigue and microstructure - Cyclic stress-strain behaviour - Cracking - Electron microscopy - Fundamentals of fracture mechanics - Fatigue crack growth - Cyclic strength of steels - Thermomechanical fatigue - Operating strength of components - Fatigue of welded constructions. [German] In dem vorliegenden Buch wird ein Ueberblick ueber die Ermuedung metallischer Werkstoffe gegeben. Interessierten Studenten, Ingenieuren, Wissenschaftlern und Anwendern wird ein Grundverstaendnis fuer die moeglichen Prozesse vermittelt, aus dem sich ein Gefuehl fuer die Vorgaenge im Werkstoff bei zyklischer Beanspruchung entwickelt - unabdingbar fuer Entwicklung und Pruefung moderner Kontruktionswerkstoffe. Es enthaelt folgende Themen: Einfuehrung und Ueberblick - Materialermuedung und Mikrostruktur - Zyklisches Spannungs-Dehnungsverhalten - Rissbildung - Elektronenmikroskopische Untersuchungen - Grundlagen der Bruchmechanik - Ermuedungsrisswachstum - Schwingfestigkeit von Staehlen - Thermomechanisches Ermuedungsverhalten - Betriebsfestigkeit von Bauteilen - Ermuedung von Schweisskonstruktionen.

  17. Fatigue and fracture of fibre metal laminates

    CERN Document Server

    Alderliesten, René

    2017-01-01

    This book contributes to the field of hybrid technology, describing the current state of knowledge concerning the hybrid material concept of laminated metallic and composite sheets for primary aeronautical structural applications. It is the only book to date on fatigue and fracture of fibre metal laminates (FMLs). The first section of the book provides a general background of the FML technology, highlighting the major FML types developed and studied over the past decades in conjunction with an overview of industrial developments based on filed patents. In turn, the second section discusses the mechanical response to quasi-static loading, together with the fracture phenomena during quasi-static and cyclic loading. To consider the durability aspects related to strength justification and certification of primary aircraft structures, the third section discusses thermal aspects related to FMLs and their mechanical response to various environmental and acoustic conditions.

  18. Improvements of fatigue behaviour in 2014 Al alloy by solution heat treating and age-hardening

    International Nuclear Information System (INIS)

    Sadeler, R.; Totik, Y.; Gavgali, M.; Kaymaz, I.

    2004-01-01

    In order to understand the fundamental fatigue behaviour of 2014 Al alloy, rotating bending fatigue tests have been carried out using materials with an as-received and four different microstructure feature produced by solution heat treating at 410, 450, 480 and 510 deg. C for 2 h, then quenching in cold water (at 15 deg. C), followed by aging at 190 deg. C for 7 h. Scanning electron microscopy and X-ray diffraction were carried out to characterize the structure properties resulting from different heat treatments. The fatigue test results showed that the solution temperature have very strong influence on fatigue strength. The fatigue strength at 10 7 cycles of Al alloy made by aging after solution treating temperature of 510 deg. C was improved by approximately 43%, compared with as cast alloy. In addition, the fractured fatigue specimens were examined using a scanning electron microscopy in order to clarify fracture initiation points

  19. 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

  20. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

    Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations. The fati......Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

  1. Application of fracture mechanics to fatigue in pressure vessels

    International Nuclear Information System (INIS)

    Ghavami, K.

    1982-01-01

    The methods of application of fracture mechanics to predict fatigue crack propagation in welded structures and pressure vessels are described with the following objectives: i) To identify the effect of different variables such as crack tip plasticity, free surface, finite plate thickness, stress concentration and type of the structure, on the magnitude of stress intensity factor K in Welded joint. ii) To demonstrate the use of fracture mechanics for analysing fatigue crack propagation data. iii) To show how a law of fatigue crack propagation based on fracure mechanics, may be used to predict fatigue behavior of welded structures such as pressure vessel. (Author) [pt

  2. Intermetallic alloys: Deformation, mechanical and fracture behaviour

    International Nuclear Information System (INIS)

    Dogan, B.

    1988-01-01

    The state of the art in intermetallic alloys development with particular emphasis on deformation, mechanical and fracture behaviour is documented. This review paper is prepared to lay the ground stones for a future work on mechanical property characterization and fracture behaviour of intermetallic alloys at GKSS. (orig.)

  3. Fatigue fracture of the sacrum in an adolescent

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, Scott P.; Daffner, Richard H.; Sciulli, Robert L. [Department of Diagnostic Radiology, Allegheny General Hospital, 320 E. North Ave., 15212-4772, Pittsburgh, PA (United States); Schneck-Jacob, Stephanie L. [Department of Orthopaedic Surgery, Allegheny General Hospital, 320 E. North Ave., 15212-4772, Pittsburgh, PA (United States)

    2004-08-01

    There are relatively few reports of sacral stress fractures in children. In adolescents, sacral stress fractures have been reported in patients involved in vigorous athletic activity. Recognition of these fractures is important to avoid unnecessary biopsy if the findings are confused with tumor or infection. We report a sacral fatigue fracture in a 15-year-old without a history of athletic participation or trauma. (orig.)

  4. Evaluation of hot hardness, creep, fatigue and fracture properties of zirconia ceramics by an indentation technique

    International Nuclear Information System (INIS)

    Kutty, T.R.G.; Ganguly, C.; Upadhyaya, D.D.

    1996-01-01

    Zirconia ceramics have wide range engineering applications at room and elevated temperatures. For understanding the mechanical behaviour, the indentation technique was adapted for quick evaluation of hot hardness, creep, fatigue and fracture properties. A Vicker's diamond indentor with 10 N load was employed for hot hardness and creep measurement up to 1300 deg. The fatigue data were evaluated at room temperature by repeated indentation with a constant load (10-2500N) at the same location for a dwell time of 5s until it resulted in the formation of a lateral chip on the sample surface. Thus, the number of cycles for chip formation at a specific indentation load was obtained. The fracture toughness was evaluated at room temperature with a load of 300N using a Vicker's diamond indentor. The results of hot hardness, creep, fatigue, and fracture data ol 3Y-TZP and Mg-PSZ are discussed along with their microstructural features. (authors)

  5. Behaviour of several fatigue prone bridge details

    Science.gov (United States)

    Kubiš, Petr; Ryjáček, Pavel

    2017-09-01

    Three fatigue welded bridge joints analysed in this work are the alternative details of the bottom flange connection. This construction detail is mainly used for the erection connection for steel and composite bridges. If applied in the place, where live load is significant, the fatigue becomes the main design criterion. The detail category is thus very important factor. The aim of this paper is to analyse the possibilities of the improving the behaviour of this detail, by various methods. First solution is to modify the shape of the cope hole to the elliptic shape. Second option is to use the “Olemutz” fully welded detail. This detail is often used in bridge designing despite there is no exact information about the fatigue category, and doubts of the performance exists. “Olemutz” is a long web plate slit that is filled by the double bevel weld after the execution of the bottom flange weld. The last detail is the elliptic cope hole filled by the plate-cap welded into an empty hole. The geometry is the same, as in the first case. The conclusion of the numerical analysis and the pilot fatigue experiments is discussed with several practical recommendations for designing.

  6. Detecting Gear Tooth Fatigue Cracks in Advance of Complete Fracture

    Science.gov (United States)

    Zakrajsek, James J.; Lewicki, David G.

    1996-01-01

    Results of using vibration-based methods to detect gear tooth fatigue cracks are presented. An experimental test rig was used to fail a number of spur gear specimens through bending fatigue. The gear tooth fatigue crack in each test was initiated through a small notch in the fillet area of a tooth on the gear. The primary purpose of these tests was to verify analytical predictions of fatigue crack propagation direction and rate as a function of gear rim thickness. The vibration signal from a total of three tests was monitored and recorded for gear fault detection research. The damage consisted of complete rim fracture on the two thin rim gears and single tooth fracture on the standard full rim test gear. Vibration-based fault detection methods were applied to the vibration signal both on-line and after the tests were completed. The objectives of this effort were to identify methods capable of detecting the fatigue crack and to determine how far in advance of total failure positive detection was given. Results show that the fault detection methods failed to respond to the fatigue crack prior to complete rim fracture in the thin rim gear tests. In the standard full rim gear test all of the methods responded to the fatigue crack in advance of tooth fracture; however, only three of the methods responded to the fatigue crack in the early stages of crack propagation.

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

    Science.gov (United States)

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

    2017-08-25

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

  8. Fatigue-stress relaxation behaviour of alloy 800: Microstructure and modeling

    International Nuclear Information System (INIS)

    Dumaz, P.; Terriez, J.M.; Regnard, C.; Robert, G.

    1985-01-01

    This paper deals with the results found by completing a study work aimed at giving due consideration to the variables controlling the microstructure variation in modeling the alloy 800 fatigue-stress relaxation behaviour along with their effect on the fracturing process. The related push-pull cycles were performed in forced strain condition and the relaxing operation was carried out with the material exhibiting its maximum tension strained condition. Microstructure investigations and behaviour modeling are presented. (orig./RF)

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

    Directory of Open Access Journals (Sweden)

    JING Hong-yang

    2017-05-01

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

  10. 2014 New Trends in Fatigue and Fracture Conference

    CERN Document Server

    Milovic, Ljubica

    2017-01-01

    This book is a compilation of selected papers from the 2014 New Trends in Fatigue and Fracture (NT2F14) Conference, which was held in Belgrade, Serbia. This prestigious conference brought together delegates from around the globe to discuss how to characterize, predict and analyze the fatigue and fracture of engineering materials, components, and structures using theoretical, experimental, numerical and practical approaches. It highlights some important new trends in fracture mechanics presented at the conference, such as: • two-parameter fracture mechanics, arising from the coupling of fracture toughness and stress constraints • high-performance steel for gas and oil transportation and production (pressure vessels and boilers) • safety and reliability of welded joints This book includes 12 contributions from well-known international scientists and a special tribute dedicated to the scientific contributions of Stojan Sedmark, who passed away in 2014.

  11. 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)

  12. Sacral fatigue fractures in children with sacral spina bifida occulta.

    Science.gov (United States)

    Hama, Shingo; Takata, Yoichiro; Sakai, Toshinori; Higashino, Kosaku; Abe, Mitsunobu; Nagamachi, Akihiro; Sairyo, Koichi

    2016-05-01

    In this report, we present two cases of 9-year-old children with spina bifida occulta (SBO) of the sacrum, who were diagnosed with sacral fatigue fractures. In both patients, MRI showed a linear signal void and high signal in sacral ala on the short tau inversion recovery sequence. Sacral SBO at the same level of the sacral fracture was observed in each patient on computed tomography images. These lesions healed with rest. This is the first literature reporting cases with sacral stress fractures who had SBO at the same level of fracture.

  13. Observation of fracture behavior of 3-D printed specimens under rolling contact fatigue in water

    Directory of Open Access Journals (Sweden)

    Mizobe Koshiro

    2017-01-01

    Full Text Available Polymer bearing was widely used in the corrosive conditions because of its high corrosion durability. The polymer bearing had been formed using molding and machining until the new 3-D printing method was developed. In this study, we performed the rolling contact fatigue tests of the 3-D printed specimens in water and observed the fracture behaviour of the specimens. We found that the surface cracks are related to both the rolling direction and the lamination directions.

  14. Cyclic Fracture Toughness of Railway Axle and Mechanisms of its Fatigue Fracture

    Directory of Open Access Journals (Sweden)

    Sorochak Andriy

    2015-06-01

    Full Text Available The main regularities in fatigue fracture of the railway axle material - the OSL steel - are found in this paper. Micromechanisms of fatigue crack propagation are described and systematized, and a physical-mechanical interpretation of the relief morphology at different stages of crack propagation is proposed for fatigue cracks in specimens cut out of the surface, internal and central layers of the axle.

  15. Roughness analysis of local fatigue fracture surface

    Czech Academy of Sciences Publication Activity Database

    Major, Štěpán; Hubálovský, Š.

    2013-01-01

    Roč. 7, č. 2 (2013), s. 65-72 ISSN 1998-4448 Institutional support: RVO:68378297 Keywords : bending - torsion * biaxial loading * fatigue * fractography Subject RIV: JJ - Other Materials http://www.naun.org/cms.action?id=2828

  16. Fracture and Fatigue: Some New Insights

    Indian Academy of Sciences (India)

    It is over nine decades since fracture mechanics found its importance in the design of mechanical, aerospace and civil engineering structures. Its application started in naval structures during the early part of 20th century. The theory of fracture mechanics was initially found ideal to explain the failure of brittle materials like ...

  17. Creep fracture and creep-fatigue fracture in ceramics and ceramic composites

    International Nuclear Information System (INIS)

    Suresh, S.

    1993-01-01

    This paper summarizes recent advances in the areas of subcritical crack growth in ceramics subjected to static and cyclic loads at elevated temperatures. Attention is devoted to the specific role of pre-existing and in-situ-formed glass films in influencing creep fracture and creep-fatigue fracture. Experimental results on the effects of cyclic frequency and load ratio, along with detailed transmission electron microscopy of crack-tip and crack-wake damage are highlighted. Some general conclusions are drawn about the dependence of high-temperature damage tolerance on interfacial glass films and about the susceptibility of ceramic materials to cyclic fatigue fracture

  18. Micro- and macroapproaches in fracture mechanics for interpreting brittle fracture and fatigue crack growth

    International Nuclear Information System (INIS)

    Ekobori, T.; Konosu, S.; Ekobori, A.

    1980-01-01

    Classified are models of the crack growth mechanism, and in the framework of the fracture mechanics suggested are combined micro- and macroapproaches to interpreting the criterion of the brittle fracture and fatigue crack growth as fracture typical examples, when temporal processes are important or unimportant. Under the brittle fracture conditions the crack propagation criterion is shown to be brought with the high accuracy to a form analogous to one of the crack propagation in a linear fracture mechanics although it is expressed with micro- and macrostructures. Obtained is a good agreement between theoretical and experimental data

  19. Influence of thermomechanical aging on fatigue behaviour of 2014 ...

    Indian Academy of Sciences (India)

    The fatigue behaviour of 2014 Al-alloy has been studied in various thermomechanically aged conditions. It is observed that fatigue properties can be improved by a thermomechanical treatment, which would reduce the concentrations of dispersoids, provide a relatively uniform deformation structure and produce fine ...

  20. Fatigue behaviour of window and rods

    International Nuclear Information System (INIS)

    Bergeron, J.; Brochard, J.; Cheron, Ch.; Gabriel, F.

    1999-01-01

    The current CEA project pertains to feasibility studies of an internal source of neutrons used for irradiations of various natures. An external source generates the necessary protons thanks to a particle accelerator that delivers a high energy proton beam: 600 MeV, 40 mA. The target is composed of rod assemblies and the spallation material is lead contained in aluminium cladding cooled by low pressured tepid water. The interface between the accelerator and the target named 'window' must both ensure tightness between the accelerator and the target and maintain a differential pressure while being as thin as possible to avoid a too great dissipation of the incident beam. In this respect, the interface is made of Inconel of low thickness in order to be as transparent as possible of the proton beam whose average power density is about of 10 μA.cm -2 , and is cooled by forced convection water of the target. An analysis of nominal and incidental situations of the facility operating mode has been conducted, especially in order to evaluate the consequences of abrupt and frequent shutdown or tripping of the accelerator on the thermomechanical behaviour of the spallation rods and the window, as well as in terms of thermal fatigue. (author)

  1. Fracture strength of all-ceramic restorations after fatigue loading

    Science.gov (United States)

    Baladhandayutham, Balasudha

    Fracture strength of monolithic and bilayered LAVA and e. max lower molar crowns after load cycling was measured and compared. The study included three groups (n = 8) from LAVA zirconia and three groups from e. max lithium disilicate to compare influences of different layers, thicknesses and manufacturing techniques. Prefabricated anatomically designed crowns were cemented to dies made from Z 100 composite resin using Rely X Luting Plus resin modified glass ionomer cement. Cemented crowns were stored at 37° C for 24 hours then cyclic loaded to test fatigue properties. The crowns were loaded to 200,000 cycles at 25N at a rate of 40 cycles / minute to simulate oral function. Subsequently, fracture properties for each group were measured using an Instron Universal Testing machine. Microscopic evaluation of the surface of fatigued samples did not reveal micro-cracks at the end of 50,000 cycles but minor wear facets were observed at the site of contact from the steatite ball antagonist. Crowns from LAVA bilayered groups showed step by step fractures while crowns from all other groups fractured as a single event as observed by the high speed camera. Zirconia bilayered crowns showed the highest loads to fracture while lithium disilicate monolithic crowns showed the lowest, within the limitations of the study. The study also showed that monolithic zirconia crowns of 0.6mm thickness resulted in relatively high magnitude for forces at fracture.

  2. Fatigue behaviour of synthetic nodular cast irons

    Directory of Open Access Journals (Sweden)

    A. Vaško

    2015-01-01

    Full Text Available The paper shows the influence of charge composition on microstructure, fatigue properties and failure micromechanisms of nodular cast irons. The additive of metallurgical silicon carbide (SiC in analysed specimens increases the content of ferrite in the matrix, decreases the size of graphite and increases the average count of graphitic nodules per unit of area. Consequently, the mechanical and fatigue properties of nodular cast iron are improved. The best fatigue properties (fatigue strength were reached in the melt which was created by 60 % of steel scrap and 40 % of pig iron in the basic charge with SiC additive.

  3. Committee III.2 Fatigue and Fracture

    DEFF Research Database (Denmark)

    Brennan, F. P.; Branner, Kim; den Besten, J.H.

    2015-01-01

    Concern for crack initiation and growth under cyclic loading as well as unstable crack propagation and tearing in ship and offshore structures. Due attention shall be paid to practical application and statistical description of fracture control methods in design, fabrication and service. Consider...

  4. Study on fracture behaviour of Hybrid Aluminium Composite

    Directory of Open Access Journals (Sweden)

    Niranjan D. B.

    2018-01-01

    Full Text Available This work makes an attempt to study of fracture behaviour of hybrid Composite reinforced with hard ceramic Boron carbide as primary phase and secondary phase as soft solid lubricant Molybdenum Disulphide with base matrix Al2219 by two stage stir casting method is incorporated. Compact tension type specimen was utilized for test and dimensions are conformity to ASTM E-647.Fatigue crack growth and fracture toughness test conducted as per ASTM Standard E-399 and E-1820. This study discloses that reinforcing the hard ceramic Boron Carbide of constant 3wt% and soft solid lubricant Molybdenum Disulphide with increasing wt% of 3%, 4%, 5% to Al2219, results increase in energy required to open the crack front to create two new crack surfaces during mode-I type failure and also significantly variation of fracture toughness. Surface of fractured specimens were study under scanning electron microscope and observes that pulled regions tiny dimples results in balance between ductility and strength of prepared hybrid composite.

  5. Fatigue behaviour of GMAW welded aluminium alloy AA7020

    OpenAIRE

    Bloem, Carlos; Salvador Moya, Mª Dolores; Amigó, Vicente; Vicente-Escuder, Ángel

    2009-01-01

    [EN] The aim of this investigation is to evaluate the influence on fatigue behaviour of the finishing of the bulge in a welded aluminium zinc magnesium alloy AA7020. It was determined that total or partial elimination of the bulge has very little influence on its behaviour, giving a very similar result on both cases, where one is better than the other by only 3%. Bloem, C.; Salvador Moya, MD.; Amigó, V.; Vicente-Escuder, Á. (2009). Fatigue behaviour of GMAW welded aluminium alloy AA7020. W...

  6. Sacral fatigue fractures in children with sacral spina bifida occulta

    OpenAIRE

    Hama, Shingo; Takata, Yoichiro; Sakai, Toshinori; Higashino, Kousaku; Abe, Mitsunobu; Nagamachi, Akihiro; Sairyo, Koichi

    2016-01-01

    In this report, we present two cases of 9-year-old children with spina bifida occulta (SBO) of the sacrum, who were diagnosed with sacral fatigue fractures. In both patients, MRI showed a linear signal void and high signal in sacral ala on the short tau inversion recovery sequence. Sacral SBO at the same level of the sacral fracture was observed in each patient on computed tomography images. These lesions healed with rest. This is the first literature reporting cases with sacral stress fractu...

  7. Metallurgical aspects of fatigue fractured surfaces of al grain refined by some rare earth materials

    International Nuclear Information System (INIS)

    Zaid, A.I.O.

    2005-01-01

    Aluminum and aluminum alloys are widely used materials in the automobile and air craft industries due to their high strength-to-weight ratio, in addition to some other attractive characteristics e.g. corrosion resistance and high electrical and thermal conductivities. Aluminum and its alloys are normally grain refined by Ti or Ti+B to enhance their surface quality and improve their mechanical strength. Although the effect of addition of these grain refiners on the microstructure mechanical behaviour has been investigated and reported, little work has been published on the effect of the refiners on the fatigue life of aluminum and its alloys. In this paper, the effect of addition of some rare earth materials, namely Vanadium and Zirconium on the fatigue life of commercially pure aluminum grain refined by Ti or Ti+B is reported and discussed. Furthermore, metallurgical aspects of these elements on the fatigue fractured surfaces are also discussed using scanning electron microscopy, SEM. Finally, photoscans of the fractured surfaces at different fatigue stresses are presented and discussed. (author)

  8. Polymer behaviour and fracture models in dynamic

    Directory of Open Access Journals (Sweden)

    Bourel B.

    2012-08-01

    Full Text Available A phenomenological small strain model is developed to capture the elastoviscoplastic behaviour of a 20% filled polypropylene. The constitutive model is based on a multiplicative viscoplastic law. The hydrostatic pressure dependency is considered by using the Drucker Prager yield surface. A phenomenological damage model characterised directly by experimental investigation is used to capture the yield degradation during the deformation in tension. The volume variation due to the cavitation phenomenon is captured by using non-associated viscoplasticity. Some experimental tests at different speed loadings are carried out for the parameters identification of the constitutive model. Furthermore, a fracture model which depends on the stress triaxiality and the strain rate is developed in order to model the complete behaviour of the material studied until fracture.

  9. Study of fatigue behaviour of 7475 aluminium alloy

    Indian Academy of Sciences (India)

    Unknown

    controlled toughness alloy developed for applications that require a combination of high strength, superior fracture toughness and resistance to fatigue crack propagation both in air and aggressive environment. The 7475 alu- minium alloy is basically a modified version of 7075 alloy. Properties in 7075 alloy are improved by ...

  10. Fatigue behaviour and crack growth rate of cryorolled Al 7075 alloy

    International Nuclear Information System (INIS)

    Das, Prosenjit; Jayaganthan, R.; Chowdhury, T.; Singh, I.V.

    2011-01-01

    Highlights: → High cycle fatigue of cryorolled Al 7075 alloy has been investigated. → Cryorolled Al alloy showed significant enhancement in fatigue strength. → FCGR resistance of the ufg Al alloy is higher at higher values of applied stress. - Abstract: The effects of cryorolling (CR) on high cycle fatigue (HCF) and fatigue crack growth rate behaviour of Al 7075 alloy have been investigated in the present work. The Al 7075 alloy was rolled for different thickness reductions (40% and 70%) at cryogenic (liquid nitrogen) temperature and its tensile strength, fatigue life, and fatigue crack growth mechanism were studied by using tensile testing, constant amplitude stress controlled fatigue testing, and fatigue crack growth rate testing using load shedding (decreasing ΔK) technique. The microstructural characterization of the alloy was carried out by using Field emission scanning electron microscopy (FESEM). The cryorolled Al alloy after 70% thickness reduction exhibits ultrafine grain (ufg) structure as observed from its FESEM micrographs. The cryorolled Al 7075 alloys showed improved mechanical properties (Y.S, U.T.S, Impact energy and Fracture toughness are 430 Mpa, 530 Mpa, 21 J, 24 Mpa m 1/2 for 40CR alloy) as compared to the bulk 7075 Al alloy. It is due to suppression of dynamic recovery and accumulation of higher dislocations density in the cryorolled Al alloys. The cryorolled Al alloy investigated under HCF regime of intermediate to low plastic strain amplitudes has shown the significant enhancement in fatigue strength as compared to the coarse grained (CG) bulk alloy due to effective grain refinement. Fatigue crack growth (FCGR) resistance of the ufg Al alloy has been found be higher, especially at higher values of applied stress intensity factor ΔK The reasons behind such crack growth retardation is due to diffused crack branching mechanism, interaction between a propagating crack and the increased amount of grain boundaries (GB), and steps developed

  11. Fatigue Behaviour of CFRP Strengthened Out-of-Plane Gusset Welded Joints with Double Cracks

    Directory of Open Access Journals (Sweden)

    Qian-Qian Yu

    2015-09-01

    Full Text Available This paper investigates the fatigue behaviour of out-of-plane gusset welded joints strengthened with carbon fibre reinforced polymer (CFRP laminates. Two notches were introduced at the weld toes adjacent to longitudinal plate ends to simulate the initial damage. Variables including the stress range, single- or double-sided strengthening and modulus of CFRP materials were considered. It was found that both cracks propagated under fatigue loading. All the specimens fractured along one predefined notch when the fatigue crack reached a certain length while the other crack also grew to some extent. Test results showed that the addition of composite materials significantly prolonged the fatigue life of specimens by as much as 1.28 to 8.17 times. Double-sided bond and ultra-high modulus CFRP materials led to a better strengthening efficiency. Thereafter, a series of numerical analyses were performed to study the stress intensity factor (SIF and crack opening displacement (COD. Local debonding around the crack tip at the adhesive-steel interface was taken into consideration. Finally, the fatigue life of all the specimens was evaluated based on the linear elastic fracture mechanism (LEFM theory and the predicted results agreed well with the experimental data.

  12. Crack tip fields and mixed mode fracture behaviour of progressively drawn pearlitic steel

    Directory of Open Access Journals (Sweden)

    J. Toribio

    2015-07-01

    Full Text Available This paper deals with the influence of the cold drawing process on the fracture behaviour of pearlitic steels. To this end, fracture tests under axial loading were performed on steel wires with different drawing degree (from a hot rolled bar to a commercial prestressing steel wire, transversely pre-cracked by fatigue, analyzing in detail the changes in fracture micromechanisms. The deflection angles of the fracture path were measured by longitudinal metallographic sections and the characteristic parameters of the loaddisplacement plot were related to different fracture events. Results allowed a calculation of critical stress intensity factors for different fracture angles and drawing degrees, thus evaluating the strength anisotropy and obtaining a sort of directional toughness.

  13. Fatigue and creep-fatigue behaviour of high-temperature alloys for HTR-application

    International Nuclear Information System (INIS)

    Meurer, H.-P.; Breitling, H.; Grosser, E.D.

    1981-01-01

    The development of High Temperature Gas Cooled Reactors requires the evaluation of the fatigue behaviour of those alloys which have been taken into account for possible use as structural materials. Comparative fatigue tests of six wrought alloys at 850 0 C revealed differences especially at low strain ranges. The influence of the coolant gas on Incoloy 800 H and Inconel 617 resulted in an increased fatigue life and for Incoloy 800 H in changes of the deformation behaviour. Hold times introduced at maximum tensile strain reduced fatigue life considerably. The hold time data have been evaluated following the rules of ASME Code Case N 47 and design curves for inelastic and elastic analysis are suggested. (Auth.)

  14. Fatigue Fracture Analysis and Development of Fundamentals of Predictive NDE of Adhesive Composite Joints

    National Research Council Canada - National Science Library

    Dzenis, Y. A

    2005-01-01

    The objective of this research was a systematic fatigue fracture analysis and development of fundamentals of predictive nondestructive evaluation of adhesive composite joints for aerospace structural applications...

  15. The Fatigue Behaviour of Multiplanar Tubular Joints

    NARCIS (Netherlands)

    Romeijn, A.

    1994-01-01

    Circular hollow sections are frequently used in structures subjected to fatigue loading such as bridges, offshore structures and cranes. These sections are generally connected by direct welding of the sections to each other. For the design of these welded connections, information is required on the

  16. Fatigue behaviour of ultrafine-grained copper

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Svoboda, Milan; Bokůvka, O.

    2005-01-01

    Roč. 12, č. 3 (2005), s. 2-6 ISSN 1335-0803. [Degradácia konštrukčných materiálov 2005. Terchová - Biely Potok, 05.09.2005-07.09.2005] Institutional research plan: CEZ:AV0Z20410507 Keywords : Fatigue * Ultra fine grained metals * equal chanel angular pressing Subject RIV: JG - Metallurgy

  17. Impact fatigue behaviour of carbon fibre-reinforced vinylester resin

    Indian Academy of Sciences (India)

    Two types of unidirectional carbon fibre, one of high strength (DHMS) and another of medium strength (VLMS) reinforced vinylester resin composites have been examined for their impact fatigue behaviour over 104 impact cycles for the first time. The study was conducted using a pendulum type repeated impact apparatus ...

  18. Effect of cyclic fatigue on the fracture toughness of Polyoxymethylene

    Science.gov (United States)

    Ramoa, B.; Berer, M.; Schwaiger, M.; Pinter, G.

    2017-05-01

    Polymers are used in a wide range of applications and their properties are dependent upon the morphological development during processing and the specimen configuration which in turn define the mechanical properties. In this context fatigue and monotonic testing are part of the standard procedure to assess relevant mechanical and material parameters to ensure a better part design. The present work addresses the performance issues of a real component made of Polyoxymethylene (POM) which is subjected to cyclic loads from intermediate levels to high peak values inside a damping mechanism. For this linear elastic fracture mechanics concepts were used to characterize the behavior of a POM homopolymer resin used in this application. Injection molded compact tension specimens, with sharp and blunt notches, were tested under a combination of cyclic and monotonic loads and the fracture surfaces were examined. The critical stress intensity factor obtained by monotonic tests was evaluated as a function of the cycle number, where an increase after the first 1000 cycles followed by a continuous decrease with higher numbers of cycles was observed. A variation of approximately 50% and 70% were obtained along the duration of the tests for the sharp and blunt notch specimens, respectively. In light of the obtained results, a discussion is presented considering the dynamic specimen compliance and the structural features observed on the fracture surfaces in combination with the fracture mechanical response.

  19. How does cognitive behaviour therapy reduce fatigue in patients with chronic fatigue syndrome? The role of physical activity.

    NARCIS (Netherlands)

    Wiborg, J.F.; Knoop, H.; Stulemeijer, M.; Prins, J.B.; Bleijenberg, G.

    2010-01-01

    BACKGROUND: Cognitive behaviour therapy (CBT) is known to reduce fatigue severity in chronic fatigue syndrome (CFS). How this change in symptomatology is accomplished is not yet understood. The purpose of the present study was to determine whether the effect of CBT on fatigue is mediated by an

  20. An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

    DEFF Research Database (Denmark)

    Ibsø, Jan Behrend; Agerskov, Henning

    1996-01-01

    test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...

  1. An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

    DEFF Research Database (Denmark)

    Ibsø, Jan Behrend; Agerskov, Henning

    1996-01-01

    Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate...

  2. Fatigue behaviour of 6061 aluminium alloy and its composite

    OpenAIRE

    Hwa, Ping

    2001-01-01

    Fatigue behaviour of an artificial aged powder metallurgy 6061 aluminium alloy, and a composite made of this alloy with 15% volume fraction of SiCp was investigated. The alloy was subjected to T6 heat treatment, as was the composite material chosen (which incorporated SiC particles of average size 30pm). An extensive experimental programme was carried out in which fatigue lives were determined using load-controlled axial loading of unnotched cylindrical samples, at stress ratios of-1 and 0.1....

  3. 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

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

    International Nuclear Information System (INIS)

    Jahed, Hamid; Farshi, Behrooz; Hosseini, Mohammad

    2006-01-01

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

  5. Viscoelastic behaviour and static fatigue strength of glass/epoxy composites. Influence of hydrothermal ageing

    International Nuclear Information System (INIS)

    Chateauminois, Antoine

    1991-01-01

    As ageing strength of composites appears to be one of the main criteria of their durability, this research thesis addresses the hydrothermal ageing of unidirectional glass/epoxy composites used for load-bearing structures. After having presented the used materials (epoxy matrix, reinforcement, composite elaboration), the author present the experimental techniques: viscoelastic analysis, three-point bend static fatigue test, coupled gravimetry and calorimetry, and thermogravimetry. In the next parts, the author reports the study of water sorption processes (bibliographical study, experimental study of water sorption kinetics, experimental study of interfacial diffusion within the composite), the study of plasticizing phenomena (methodology of study of plasticizing phenomena, study of the modifications of the linear viscoelastic behaviour in the glass transition region and at room temperature, relationship between plasticizing and fatigue mechanical properties by fracture studies), and the study of irreversible degradation and damage mechanisms

  6. Fatigue behaviour and crack growth rate of cryorolled Al 7075 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Das, Prosenjit [Central Mechanical Engineering Research Institute (CSIR), Durgapur 713209 (India); Department of Metallurgical and Materials Engineering, IIT Roorkee, Roorkee 247667 (India); Jayaganthan, R., E-mail: rjayafmt@iitr.ernet.in [Department of Metallurgical and Materials Engineering, IIT Roorkee, Roorkee 247667 (India); Chowdhury, T. [School of Material Science and Engineering, Bengal Engineering and Science University, Shibpur (India); Singh, I.V. [Department of Mechanical and Industrial Engineering, IIT Roorkee, Roorkee 247667 (India)

    2011-09-15

    Highlights: {yields} High cycle fatigue of cryorolled Al 7075 alloy has been investigated. {yields} Cryorolled Al alloy showed significant enhancement in fatigue strength. {yields} FCGR resistance of the ufg Al alloy is higher at higher values of applied stress. - Abstract: The effects of cryorolling (CR) on high cycle fatigue (HCF) and fatigue crack growth rate behaviour of Al 7075 alloy have been investigated in the present work. The Al 7075 alloy was rolled for different thickness reductions (40% and 70%) at cryogenic (liquid nitrogen) temperature and its tensile strength, fatigue life, and fatigue crack growth mechanism were studied by using tensile testing, constant amplitude stress controlled fatigue testing, and fatigue crack growth rate testing using load shedding (decreasing {Delta}K) technique. The microstructural characterization of the alloy was carried out by using Field emission scanning electron microscopy (FESEM). The cryorolled Al alloy after 70% thickness reduction exhibits ultrafine grain (ufg) structure as observed from its FESEM micrographs. The cryorolled Al 7075 alloys showed improved mechanical properties (Y.S, U.T.S, Impact energy and Fracture toughness are 430 Mpa, 530 Mpa, 21 J, 24 Mpa m{sup 1/2} for 40CR alloy) as compared to the bulk 7075 Al alloy. It is due to suppression of dynamic recovery and accumulation of higher dislocations density in the cryorolled Al alloys. The cryorolled Al alloy investigated under HCF regime of intermediate to low plastic strain amplitudes has shown the significant enhancement in fatigue strength as compared to the coarse grained (CG) bulk alloy due to effective grain refinement. Fatigue crack growth (FCGR) resistance of the ufg Al alloy has been found be higher, especially at higher values of applied stress intensity factor {Delta}K The reasons behind such crack growth retardation is due to diffused crack branching mechanism, interaction between a propagating crack and the increased amount of grain

  7. Fracture behaviour and cleavage initiation in hypoeutectoid pearlitic steel

    Czech Academy of Sciences Publication Activity Database

    Holzmann, Miloslav; Jurášek, L.; Dlouhý, Ivo

    2007-01-01

    Roč. 148, č. 1 (2007), s. 13-28 ISSN 0376-9429 R&D Projects: GA AV ČR IAA200410502; GA AV ČR 1QS200410502 Institutional research plan: CEZ:AV0Z20410507 Keywords : cleavage fracture * fracture initiation * pearlitic steel Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.003, year: 2007 http://www.springerlink.com/content/2h8167l167436165/fulltext.pdf

  8. Fatigue and Fracture Characterization of Aircraft Aluminum Alloys Damaged by Prior Corrosion

    National Research Council Canada - National Science Library

    Baldwin, J

    2002-01-01

    At the time of the initiation of this project, there was no comprehensive data describing corrosion's effect on the fatigue and fracture behavior of aluminum alloys typically found in aging aircraft...

  9. Micromechanisms of Fracture and Fatigue-Crack Growth in Bulk Metallic Glass Alloys

    National Research Council Canada - National Science Library

    Gilbert, Christopher

    1998-01-01

    .../s), has permitted novel measurements of important mechanical properties. These include, fatigue crack growth and fracture toughness behavior, representing the conditions governing the subcritical and critical propagation of cracks...

  10. Metal Matrix Composites: Fatigue and Fracture Testing. (Latest citations from the Aerospace Database)

    Science.gov (United States)

    1996-01-01

    The bibliography contains citations concerning techniques and results of testing metal matrix composites for fatigue and fracture. Methods include non-destructive testing techniques, and static and cyclic techniques for assessing compression, tensile, bending, and impact characteristics.

  11. Fracture and fatigue behavior of WC-Co and WC-CoNi cemented carbides

    OpenAIRE

    Tarragó Cifre, Jose María; Roa Rovira, Joan Josep; Valle, Vladimir; Marsahll, J. M.; Llanes Pitarch, Luis Miguel

    2015-01-01

    The fracture and fatigue characteristics of several cemented carbide grades are investigated as a function of their microstructure. In doing so, the influence of binder chemical nature and content (Co and 76 wt.% Co-24 wt.% Ni), as well as carbide grain size on hardness, flexural strength, fracture toughness and fatigue crack growth (FCG) behavior is evaluated. Mechanical testing is combined with a detailed inspection of crack-microstructure interaction, by means of scanning electron microsco...

  12. Fracture toughness behaviour using small CCT specimen of Zr-2.5Nb pressure tube materials

    International Nuclear Information System (INIS)

    Oh, Dong Joon; Kim, Young Suk; Ahn, Sang Bok; Im, Kyung Soo; Kwon, Sang Chul; Cheong, Yong Mu

    2001-03-01

    Fracture toughness of Zr-2.5Nb pressure tube is the essential data to estimate the CCL(critical crack length) for the concept of LBB(Leak-Before-Break) in PHWR. Zr-2.5Nb pressure tubes could be degraded due to the absorption of hydrogen from coolant and the irradiation. To investigate the fracture toughness behaviour such as J-resistance curves, dJ/da, and CCL of some Zr-alloys (CANDU-double, -quad, CW-E125, TMT-E125, E-635), the transverse tensile test and the fracture toughness test of small CCT (Curved Compact Tension) specimen with 17 mm width were carried out with the variation of testing temperature at different testing condition. To define the fracture mechanism of degradation, the fractographic comparison of fracture surface was performed using the stereoscope and SEM. In addition, the effect of non-uniformed pre-fatigue crack was also studied. In conclusion, CANDU double-melted was less tougher than CANDU quad-melted and the hydrogen embrittlement was found at room temperature. Finally, while the effect of non-uniformed pre-fatigue crack was considerable at room temperature, this effect was disappeared at 250-300 .deg. C

  13. Fatigue damage and fracture behavior of tungsten fiber reinforced Zr-based metallic glassy composite

    International Nuclear Information System (INIS)

    Zhang, H.; Zhang, Z.F.; Wang, Z.G.; Qiu, K.Q.; Zhang, H.F.; Zang, Q.S.; Hu, Z.Q.

    2006-01-01

    The fatigue life, damage and fracture behavior of tungsten fiber reinforced metallic glass Zr 41.25 Ti 13.75 Ni 10 Cu 12.5 Be 22.5 composites are investigated under cyclic push-pull loading. It is found that the fatigue life of the composite increases with increasing the volume fraction of tungsten fibers. Similar to crystalline metals, the regions of crack initiation, propagation and overload fracture can be discerned on the fracture surface of the specimen. Fatigue crack normally initiates in the metallic glass matrix at the outer surface of the composite specimen and propagates predominantly in the matrix. Different crack front profile around the tungsten fibers and fiber pullout demonstrate that fatigue crack may propagate around the fiber, leading to bridging of the crack faces by the unbroken fiber and hence improved fatigue crack-growth resistance. Locally decreased effective stiffness in the region where fiber distribution is sparse may provide preferential crack path in the composite. A proposed model was exercised to elucidate different tungsten fiber fracture morphologies in the fatigue crack propagation and overload fracture regions in the light of Poisson's ratio effect during fatigue loading

  14. Fatigue fracture of a cemented Omnifit CoCr femoral stem: implant and failure analysis

    Directory of Open Access Journals (Sweden)

    Noah Bonnheim, MS

    2017-12-01

    Full Text Available A cemented, cast CoCr alloy, Omnifit Plus femoral stem was retrieved following mid-stem fracture after 24 years in vivo. The patient was an active 55-year-old male with a high body mass index (31.3 and no traumatic incidents before stem fracture. Fractographic and fatigue-based failure analyses were performed to illuminate the etiology of fracture and retrospectively predict the device lifetime. The fracture surfaces show evidence of a coarse grain microstructure, intergranular fracture, and regions of porosity. The failure analysis suggests that stems with similar metallurgical characteristics, biomechanical environments, and in vivo durations may be abutting their functioning lifetimes, raising the possibility of an increased revision burden. Keywords: Fatigue fracture, Total hip arthroplasty, Stem fracture

  15. Microstructure evolution and fracture behaviour for electron beam ...

    Indian Academy of Sciences (India)

    The effect of microstructural characteristics on fracture behaviour mechanism for electron beam welding of Ti–6Al–4V was investigated. The results indicated that the welded microstructure composed of coarse needle + phases presenting disordered and multidirectional short needle morphology to make fracture ...

  16. Fracture behaviour of bread crust: Effect of bread cooling conditions

    NARCIS (Netherlands)

    Primo Martin, C.; Beukelaer, de H.J.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    The effect of air and vacuum cooling on the fracture behaviour and accompanying sound emission, moisture content and crispness of bread crust were investigated. Vacuum cooling resulted in rapid evaporative cooling of products that contained high moisture content. Fracture experiments showed a clear

  17. Strengthening in and fracture behaviour of CNT and carbon ...

    Indian Academy of Sciences (India)

    Advanced materials such as continuous fibre-reinforced polymer matrix composites offer significant enhancements in strength and fracture resistance properties as compared with their bulk, monolithic counterparts. In the present work, mode-I (tensile) fracture behaviour of the neat epoxy (without nano- or hybrid ...

  18. Fracture behaviour of zirconia FPDs substructures.

    Science.gov (United States)

    Kou, W; Sjögren, G

    2010-04-01

    The purpose of this study was to evaluate the occurrence of superficial flaws after machining and to identify fracture initiation and propagation in three-unit heat-treated machined fixed partial dentures (FPDs) substructures made of hot isostatic pressed (HIPed) yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) after loaded to fracture. Four three-unit HIPed Y-TZP-based FPDs substructures were examined. To evaluate the occurrence of superficial flaws after machining, the surfaces were studied utilizing a fluorescent penetrant method. After static loading to fracture, characteristic fracture features on both mating halves of the fractured specimens were studied using a stereomicroscope and a scanning electron microscope. Grinding grooves were clearly visible on the surfaces of the machined FPDs substructures, but no other flaws could be seen with the fluorescent penetrant method. After loading to fracture, the characteristic fracture features of arrest lines, compression curl, fracture mirror, fracture origin, hackle and twist hackle were detected. These findings indicated that the decisive fracture was initiated at the gingival embrasure of the pontic in association with a grinding groove. Thus, in three-unit heat-treated machined HIPed Y-TZP FPDs substructures, with the shape studied in this study, the gingival embrasure of the pontic seems to be a weak area providing a location for tensile stresses when they are occlusally loaded. In this area, fracture initiation may be located to a grinding groove.

  19. The fracture behavior of an Al-Mg-Si alloy during cyclic fatigue

    International Nuclear Information System (INIS)

    Azzam, Diya; Menzemer, Craig C.; Srivatsan, T.S.

    2010-01-01

    In this paper, is presented and discussed the cyclic fracture behavior of the Al-Mg-Si alloy 6063 that is a candidate used in luminaire light poles. The light poles were subject to fatigue deformation. Test sections were taken from the failed region of the light pole and carefully examined in a scanning electron microscope with the objective of rationalizing the macroscopic fracture mode and intrinsic micromechanisms governing fracture under cyclic loading. The fatigue fracture surface of the alloy revealed distinct regions of early microscopic crack growth, stable crack growth and unstable crack growth and overload. An array of fine striations was found covering the regions of early and stable crack growth. Both macroscopic and fine microscopic cracks were found in the region of unstable crack growth. Very few microscopic voids and shallow dimples were evident on the fatigue fracture surface indicative of the limited ductility of the alloy under cyclic loading conditions.

  20. Deep gold mine fracture zone behaviour

    CSIR Research Space (South Africa)

    Napier, JAL

    1998-12-01

    Full Text Available dimensional section through the samples using the standard DIGS displacement discontinuity program has proved that the numerical techniques are able to capture the nucleation from flaws and the effect of larger scale stress re-distributions by grain... boundaries. The coalescence of the fractures depends on a complicated process whereby tensile stresses produced ahead of growing fractures initiate other fractures and lead to a localized failure surface on a larger scale. In certain cases, the compressive...

  1. An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

    DEFF Research Database (Denmark)

    Ibsø, Jan Behrend; Agerskov, Henning

    1996-01-01

    test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...... of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied....... determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination...

  2. Cognitive behaviour therapy for chronic fatigue syndrome in adults.

    Science.gov (United States)

    Price, Jonathan R; Mitchell, Edward; Tidy, Elizabeth; Hunot, Vivien

    2008-07-16

    Chronic fatigue syndrome (CFS) is a common, debilitating and serious health problem. Cognitive behaviour therapy (CBT) may help to alleviate the symptoms of CFS. To examine the effectiveness and acceptability of CBT for CFS, alone and in combination with other interventions, compared with usual care and other interventions. CCDANCTR-Studies and CCDANCTR-References were searched on 28/3/2008. We conducted supplementary searches of other bibliographic databases. We searched reference lists of retrieved articles and contacted trial authors and experts in the field for information on ongoing/completed trials. Randomised controlled trials involving adults with a primary diagnosis of CFS, assigned to a CBT condition compared with usual care or another intervention, alone or in combination. Data on patients, interventions and outcomes were extracted by two review authors independently, and risk of bias was assessed for each study. The primary outcome was reduction in fatigue severity, based on a continuous measure of symptom reduction, using the standardised mean difference (SMD), or a dichotomous measure of clinical response, using odds ratios (OR), with 95% confidence intervals (CI). Fifteen studies (1043 CFS participants) were included in the review. When comparing CBT with usual care (six studies, 373 participants), the difference in fatigue mean scores at post-treatment was highly significant in favour of CBT (SMD -0.39, 95% CI -0.60 to -0.19), with 40% of CBT participants (four studies, 371 participants) showing clinical response in contrast with 26% in usual care (OR 0.47, 95% CI 0.29 to 0.76). Findings at follow-up were inconsistent. For CBT versus other psychological therapies, comprising relaxation, counselling and education/support (four studies, 313 participants), the difference in fatigue mean scores at post-treatment favoured CBT (SMD -0.43, 95% CI -0.65 to -0.20). Findings at follow-up were heterogeneous and inconsistent. Only two studies compared CBT

  3. Fatigue behaviour analysis for the durability prequalification of strengthening mortars

    International Nuclear Information System (INIS)

    Bocca, P; Grazzini, A; Masera, D

    2011-01-01

    An innovative laboratory procedure used as a preliminary design stage for the pre-qualification of strengthening mortars applied to historical masonry buildings is described. In the analysis of the behaviour of masonry structures and their constituent materials, increasing importance has been assumed by the study of the long-term evolution of deformation and mechanical characteristics, which may be affected by both loading and environmental conditions. Through static and fatigue tests on mixed specimens historical brick-reinforced mortar it has been possible to investigate the durability of strengthening materials, in order to select, from a range of alternatives, the most suitable for the historical masonry. Cyclic fatigue stress has been applied to accelerate the static creep and to forecast the corresponding creep behaviour of the historical brick-strengthening mortar system under static long-time loading. This methodology has proved useful in avoiding the errors associated with materials that are not mechanically compatible and guarantees the durability of strengthening work. The experimental procedure has been used effectively in the biggest restoration building site in Europe, the Royal Palace of Venaria, and it is in progress of carrying out at the Special Natural Reserve of the Sacro Monte di Varallo, in Piedmont (Italy).

  4. Cyclic fatigue and fracture characteristics of ground and twisted nickel-titanium rotary files.

    Science.gov (United States)

    Kim, Hyeon-Cheol; Yum, Jiwan; Hur, Bock; Cheung, Gary Shun-Pan

    2010-01-01

    The purposes of this study were to compare the fatigue resistance of traditional, ground nickel-titanium rotary instruments with the Twisted File and to examine the fracture characteristics of the fatigued fragment. Size #25, 0.06 tapered, TF (SybronEndo), RaCe (FKG Dentaire), Helix (DiaDent), and ProTaper F1 (Dentsply Maillefer) were examined with scanning electron microscope for surface characteristics before subjected to a cyclic (rotational bending) fatigue test. The time until fracture was recorded to calculate the number of revolutions for each instrument. The data were compared for differences by using analysis of variance and post hoc Scheffé test. The fragments were examined with scanning electron microscope both in lateral view and fractographically. TF showed a significantly higher resistance to cyclic fatigue than other nickel-titanium files that were manufactured with a grinding process (P machining grooves seemed to have a higher risk of fatigue.

  5. Fracture Strength After Fatigue Loading of Lithium Disilicate Pressed Zirconia Crowns.

    Science.gov (United States)

    Kim, So-Yeun; Choi, Jae-Won; Ju, Sung-Won; Ahn, Jin-Soo; Yoon, Mi-Jung; Huh, Jung-Bo

    2016-01-01

    The aim of this study was to evaluate the fracture resistance of fatigued lithium disilicate pressed zirconia crowns versus other ceramic crowns. Lithium disilicate pressed zirconia, fluorapatite pressed zirconia, monolithic lithium disilicate, and monolithic zirconia crowns were fabricated. Cyclic and static loadings were applied to the mesiobuccal cusp tip after thermocycling and fracture strengths were recorded. Fatigued lithium disilicate pressed zirconia crowns were found to have a fracture resistance of 9,117.81 ± 727.04 N, compared with 9,240.61 ± 887.21 N for monolithic zirconia crowns, 3,030.18 ± 1,505.83 N for fluorapatite pressed zirconia crowns, and 4,173.94 ± 877.46 N for monolithic lithium disilicate crowns (P = .001). This in vitro study shows that fatigued lithium disilicate pressed zirconia and monolithic zirconia crowns have better fracture resistance than fluorapatite pressed zirconia and monolithic lithium disilicate crowns.

  6. Implicit fracture modelling in FLAC3D: Assessing the behaviour of fractured shales, carbonates and other fractured rock types

    NARCIS (Netherlands)

    Osinga, S.; Pizzocolo, F.; Veer, E.F. van der; Heege, J.H. ter

    2016-01-01

    Fractured rocks play an important role in many types of petroleum and geo-energy operations. From fractured limestone reservoirs to unconventionals, understanding the geomechanical behaviour and the dynamically coupled (dual) permeability system is paramount for optimal development of these systems.

  7. Fracture behaviour of hybrid glass matrix composites: thermal ageing effects

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Chlup, Zdeněk; Boccaccini, D. N.; Atiq, S.; Boccaccini, A. R.

    2003-01-01

    Roč. 34, č. 12 (2003), s. 177-1185 ISSN 1359-835X R&D Projects: GA AV ČR IAA2041003; GA MŠk ME 491 Institutional research plan: CEZ:AV0Z2041904 Keywords : glass matrix * hybrid composites * fracture toughness Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.131, year: 2003 http://www.sciencedirect.com

  8. Behaviour of Ti-doped CFCs under thermal fatigue tests

    Energy Technology Data Exchange (ETDEWEB)

    Centeno, A. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Pintsuk, G.; Linke, J. [Forschungszentrum Juelich GmbH, EURATOM Association, 52425 Juelich (Germany); Gualco, C. [Ansaldo Energia, I-16152 Genoa (Italy); Blanco, C., E-mail: clara@incar.csic.es [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Santamaria, R.; Granda, M.; Menendez, R. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain)

    2011-01-15

    In spite of the remarkable progress in the design of in-vessel components for the divertor of the first International Thermonuclear Experimental Reactor (ITER), a great effort is still put into the development of manufacturing technologies for carbon armour with improved properties. Newly developed 3D titanium-doped carbon fibre reinforced composites and their corresponding undoped counterparts were brazed to a CuCrZr heat sink to produce actively cooled flat tile mock-ups. By exposing the mock-ups to thermal fatigue tests in an electron beam test facility, the material behaviour and the brazing between the individual constituents in the mock-up was qualified. The mock-ups with titanium-doped CFCs exhibited a significantly improved thermal fatigue resistance compared with those undoped materials. The comparison of these mock-ups with those produced using pristine NB31, one of the reference materials as plasma facing material for ITER, showed almost identical results, indicating the high potential of Ti-doped CFCs due to their improved thermal shock resistance.

  9. Characterisation of Fracture Behaviour of Starch Gels Using Conventional Fracture Mechanics and Wire Cutting Tests

    Science.gov (United States)

    Gamonpilas, C.; Charalambides, M. N.; Williams, J. G.; Dooling, P. J.; Gibbon, S. R.

    2008-07-01

    The fracture behaviour of starch gels is investigated through experimental tests and finite element simulations. Both conventional fracture and wire cutting experiments were performed. The results from these two tests were consistent with the fracture toughness increasing with loading rate. In the FE analysis, a non-linear elastic constitutive relationship was used to model the starch gels and frictionless condition was assumed between the wire-starch gel contact interface. A failure criterion based on critical fracture strain was assumed. Predictions of the steady-state cutting force at various wire diameters were found to be in good agreement with the wire cutting data.

  10. Analysis of Fracture Behaviour of Multilayer Pipes

    Czech Academy of Sciences Publication Activity Database

    Nezbedová, E.; Knésl, Zdeněk; Vlach, B.

    2007-01-01

    Roč. 36, č. 5 (2007), s. 207-212 ISSN 1465-8011. [Plastic Pipes /13./. Washington, D. C., 02.10.2006-05.10.2006] R&D Projects: GA ČR GA106/07/1284 Institutional research plan: CEZ:AV0Z20410507 Keywords : multi-layer pipes Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.431, year: 2007

  11. Fracture behaviour of brittle (glass) matrix composites

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Chlup, Zdeněk; Boccaccini, A. R.

    2005-01-01

    Roč. 482, - (2005), s. 115-122 ISSN 0255-5476. [International Conference on Materials Structure and Micromechanics of Fracture /4./. Brno, 23.06.2004-25.06.2004] R&D Projects: GA AV ČR(CZ) IAA2041003; GA ČR(CZ) GA101/02/0683 Institutional research plan: CEZ:AV0Z2041904 Keywords : Ceramic matrix composite s * fracture toughness * toughening effects Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.399, year: 2005

  12. Mode II Interlaminar Fracture Toughness and Fatigue Characterization of a Graphite Epoxy Composite Material

    Science.gov (United States)

    O'Brien, T. Kevin; Johnston, William M.; Toland, Gregory J.

    2010-01-01

    Mode II interlaminar fracture toughness and delamination onset and growth characterization data were generated for IM7/8552 graphite epoxy composite materials from two suppliers for use in fracture mechanics analyses. Both the fracture toughness testing and the fatigue testing were conducted using the End-notched Flexure (ENF) test. The ENF test for mode II fracture toughness is currently under review by ASTM as a potential standard test method. This current draft ASTM protocol was used as a guide to conduct the tests on the IM7/8552 material. This report summarizes the test approach, methods, procedures and results of this characterization effort.

  13. Analysis of fatigue, fatique-crack propagation, and fracture data. [design of metallic aerospace structural components

    Science.gov (United States)

    Jaske, C. E.; Feddersen, C. E.; Davies, K. B.; Rice, R. C.

    1973-01-01

    Analytical methods have been developed for consolidation of fatigue, fatigue-crack propagation, and fracture data for use in design of metallic aerospace structural components. To evaluate these methods, a comprehensive file of data on 2024 and 7075 aluminums, Ti-6A1-4V, and 300M and D6Ac steels was established. Data were obtained from both published literature and unpublished reports furnished by aerospace companies. Fatigue and fatigue-crack-propagation analyses were restricted to information obtained from constant-amplitude load or strain cycling of specimens in air at room temperature. Fracture toughness data were from tests of center-cracked tension panels, part-through crack specimens, and compact-tension specimens.

  14. Probabilistic Fatigue Life Prediction of Bridge Cables Based on Multiscaling and Mesoscopic Fracture Mechanics

    Directory of Open Access Journals (Sweden)

    Zhongxiang Liu

    2016-04-01

    Full Text Available Fatigue fracture of bridge stay-cables is usually a multiscale process as the crack grows from micro-scale to macro-scale. Such a process, however, is highly uncertain. In order to make a rational prediction of the residual life of bridge cables, a probabilistic fatigue approach is proposed, based on a comprehensive vehicle load model, finite element analysis and multiscaling and mesoscopic fracture mechanics. Uncertainties in both material properties and external loads are considered. The proposed method is demonstrated through the fatigue life prediction of cables of the Runyang Cable-Stayed Bridge in China, and it is found that cables along the bridge spans may have significantly different fatigue lives, and due to the variability, some of them may have shorter lives than those as expected from the design.

  15. 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.

  16. Fatigue fracture of cutter blade made of high-speed steel

    Directory of Open Access Journals (Sweden)

    Beata Letkowska

    2015-04-01

    Full Text Available The quality of the surface of cyclically loaded components is very important. Many observations confirm that the root cause of the micro cracks (causing the fatigue fracture are primarily a surface's defects appearing during production process. These surface defects can be also caused by engraving processes used to perform identification marks. This paper presents the failure analysis of broken blade of the cutter Ku 500VX. The blade was subject of standard metallographic examination, hardness measurements, fractography analysis and metallographic studies using stereoscopic, light and scanning electron microscopes. The damage of the blade was caused by changes of the structure (formation of the brittle micro dendritic structure that occurred during manual electric engraving process when the material was heated till its melting point. As a result the stresses occurred in surface what provided to micro cracking and to propagate the fatigue fracture. The origin of this fatigue fracture was in the place where the inscription was made.

  17. Fatigue and pain limit independent mobility and physiotherapy after hip fracture surgery

    DEFF Research Database (Denmark)

    Münter, Kristine H.; Clemmesen, Christopher G.; Foss, Nicolai B.

    2017-01-01

    ; pain, motor blockade, dizziness, fatigue, nausea, acute cognitive dysfunction and “other limitations”, for not achieving a full Cumulated Ambulation Score or inability to complete planned physiotherapy sessions were noted by the physiotherapist on each of the three first postoperative days. This period...... was chosen, because of its importance on how well the patients had regained their pre-fracture functional level. Results: Fatigue and hip fracture-related pain were the most frequent reasons for patients not achieving an independent basic mobility level (> 85%) or not fully completing their planned...... physiotherapy (> 42%) on all three days. At hospital discharge (median day 10), only 54% of the patients had regained their pre-fracture basic mobility level. Conclusion: Based on the patient’s perception, fatigue and pain are the most frequent limitations in not achieving independent basic mobility...

  18. Crack growth and fracture behaviour of stress corrosion cracks of turbine generator steels

    International Nuclear Information System (INIS)

    Berger; Vahle.

    1989-01-01

    The object of this investigation was the quantifying of the behaviour of cracks which were induced during service under corrosive media. To investigate the influence of stress corrosion crack configurations on stress intensity factor, six different test materials from 2 and 3.5% NiCrMoV and 2% Cr/1% Ni steels were chosen. The stress corrosion cracks were induced at wedge loaded compact tension specimens in a corrosive media in the laboratory. Fracture mechanics tests as well as fatigue crack growth tests were performed at these specimens. All stress corrosion cracks have an intercrystalline path and a crack length longer than 1 mm; they are multiple and have branched cracks tips. The fracture mechanics tests at these stress corrosion cracks induced in the laboratory and during service of components show that their stress intensity factor is 30 to 70% smaller than the stress intensity factor calculated for single straight cracks too. Theoretical calculations arrived to the same results. Crack initiation and growth behaviour under cyclic loading starting from these stress corrosion cracks results in that the load or the stress intensity range ΔK has to be increased three times larger than the ΔK-threshold value to induce crack initiation. The crack growth velocity influenced by multiple crack tips and multiple growing cracks from these crack tips is much lower than the crack growth velocity of a normal fatigue crack (one crack tip). (orig./MM) With 32 figs

  19. Fracture strength of implant abutments after fatigue testing: A systematic review and a meta-analysis.

    Science.gov (United States)

    Coray, Rafaela; Zeltner, Marco; Özcan, Mutlu

    2016-09-01

    The use of implants and their respective suprastructures to replace missing teeth has become a common therapeutic option in dentistry. Prior to their clinical application, all implant components have to demonstrate suitable durability in laboratory studies. Fatigue tests utilising cyclic loading typically simulate masticatory function in vitro. The objectives of this systematic review were to assess the loading conditions used for fatigue testing of implant abutments and to compare the fracture strength of different types of implant abutment and abutment-connection types after cyclic loading. Original scientific papers published in MEDLINE (PubMed) and Embase database in English between 01/01/1970 and 12/31/2014 on cyclic loading on implant abutments were included in this systematic review. The following MeSH terms, search terms and their combinations were used: "in vitro" or "ex vivo" or experimental or laboratory, "dental implants", "implants, experimental", "dental prosthesis, implant-supported", "fatigue", "dental abutments", "cyclic loading", "cyclic fatigue", "mechanical fatigue", "fatigue resistance", "bending moments", and "fracture". Two reviewers performed screening and data abstraction. Only the studies that reported, static fracture values before and after fatigue cycling of implant abutments, were included that allowed comparison of aging effect through cyclic loading. Data (N) were analyzed using a weighted linear regression analysis (α=0.05). The selection process resulted in the final sample of 7 studies. In general, loading conditions of the fatigue tests revealed heterogeneity in the sample but a meta-analysis could be performed for the following parameters: a) abutment material, b) implant-abutment connection, and (c) number of fatigue cycles. Mean fracture strength of titanium (508.9±334.6N) and for zirconia abutments (698.6±452.6N) did not show significant difference after cyclic loading (p>0.05). Internal implant-abutment connections

  20. Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material

    Directory of Open Access Journals (Sweden)

    M. Drobne

    2014-10-01

    Full Text Available Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material is presented in this paper. The research is done on a hot strip mill working roll where High Chromium Steel is used for roll’s shell material. To obtain corresponding parameters, a rectangular single edge notched bend specimens – SENB, according to standard BS 7448, were used. The fatigue crack growth analysis was done on a resonant testing machine with use of special crack gauges, while for fracture mechanics parameters the electro–mechanical testing machine was used.

  1. Failure by fracture and fatigue in 'NANO' and 'BIO'materials

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, R.O.; Muhlstein, C.L.; Nalla, R.K.

    2003-12-19

    The behavior of nanostructured materials/small-volumestructures and biologi-cal/bio-implantable materials, so-called "nano"and "bio" materials, is currently much in vogue in materials science. Oneaspect of this field, which to date has received only limited attention,is their fracture and fatigue properties. In this paper, we examine twotopics in this area, namely the premature fatigue failure ofsilicon-based micron-scale structures for microelectromechanical systems(MEMS), and the fracture properties of mineralized tissue, specificallyhuman bone.

  2. Evaluation of the Fatigue Strength of Sintered Steel Based on Fracture Mechanics

    OpenAIRE

    加藤, 正名; 井上, 克己; 鄧, 鋼; 佐藤, 寿樹; 亀子, 峰雄

    1996-01-01

    This paper deals with an evaluation of the fatigue strength of sintered steel based on linear fracture mechanics. The fatigue crack growth is measured with bend test specimens of Fe-Cu-Cr sintered steel of various densities. From this result, the fatigue strengths of the specimens with initial length of crack a at the life N are calculated, and they are shown as N-S-A curves. A model, which has an initial crack at the surface but is homogeneous and has no internal flaws, is introduced to anal...

  3. 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)

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  5. Microstructure evolution and fracture behaviour for electron beam ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The effect of microstructural characteristics on fracture behaviour mechanism for electron beam welding of Ti–6Al–4V was investigated. The results indicated that the welded microstructure composed of coarse needle α + β phases presenting disordered and multidirectional short needle morphology to make frac-.

  6. Fracture, Longevity (Fatigue), Dynamics, and Aeroelasticity of Composite Structures.

    Science.gov (United States)

    1984-12-31

    previous year examining the fracture behavior of a woven fabric .’." graphite/epoxy prepreg (Hercules A370-5H/3501-6) was more aggresively pursued this...tensile fracture, nonlinear stress- strain behavior , failure by delamination, sensitivity to notches under tensile loading, compressive failure...2.2 Fracture of Unnotched Tensile Coupons 10 2.3 Nonlinear Stress-Strain Behavior of 20 Graphite/Epoxy Laminates 2.4 Comparison of Tapered and Straight

  7. MR imaging findings of fatigue fractures of lower extremity in young soldiers

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Jong Hyun; Moon, Sung Hee; Kim, Young Bok; Park, Yang Hee [National Police Hospital, Seoul (Korea, Republic of); Park, Jin Kyoon [Chonnam National Medical School, Kwangju (Korea, Republic of)

    1999-04-01

    To evaluate the MR imaging findings of fatigue fractures of the lower extremity in young soldiers. In 22 cases of fatigue fractures of the lower extremity in young soldiers proven by clinical findings and radiological follow up, the MRI findings were retrospectively evalvated. All patients were male and aged between 19 and 21 years. As seen on MRI, the bone marrow edema, intramedullary low signal intensity band, cortical fracture line, periosteal reaction, surrounding soft tissue edema, and enhancement pattern were analyzed and the site of involvement was determined in the axial plane. The locations of fatigue fractures of the lower extremity were the tibia (n=12), fibula (n=8), femur (n=1) and second metatarsus (n=1). All occurred in diaphyses: the junction of the proximal and middle (n=10), middle (n=9), proximal (n=2), and distal shaft (n=1). The sites of involvement were the posteromedial (n=6) and medial side (n=6) of the tibia, and the entire portion of the fibula(n=5) in the axial plane. MRI findings were bone marrow edema in 20 cases, intramedullary low signal intensity band in 14 (which were continuous with the cortex or cortical fracture line), cortical fracture line in 13, and periosteal reaction and surrounding soft tissue edema in all. On gadolinium-enhanced images, enhancement was seen in the bone marrow in 19 cases, in the subperiosteal region in 18, and in the surrounding soft tissue in 22. In fatigue fractures of the lower extremity in young soldiers, the main locations were the tibia and fibula, and characteristic MR imaging findings were intramedullary low signal intensity bands, which were continuous with the cortex or cortical fracture line and often accompanied by bone marrow edema, periosteal reaction, and surrounding soft tissue edema.

  8. Fatigue behaviour of uni-directional flax fibre/epoxy composites

    DEFF Research Database (Denmark)

    Ueki, Yosuke; Lilholt, Hans; Madsen, Bo

    2015-01-01

    A study related to the fatigue behaviour of natural fibre-reinforced composites was conducted to expand their range of product applications. A uni-directional flax-epoxy composite was fabricated and several conditions of tension-tension fatigue tests were performed. During fatigue testing......, the composite showed an increase of stiffness, a typical observation for natural fibre-reinforced composites, and this was found to be accompanied by accumulation of residual strain. A clear linear relationship was found between the stiffening effect and the residual strain. In addition, it was revealed...... that the fatigue behaviour was clearly influenced by the frequency of cyclic loading. Lower frequencies induced more significant stiffening and shorter fatigue life. These results suggest that fatigue damaging is progressing simultaneously with the stiffening effect in natural fibre-reinforced composites...

  9. Testing the Fracture Behaviour of Chocolate

    Science.gov (United States)

    Parsons, L. B.; Goodall, R.

    2011-01-01

    In teaching the materials science aspects of physics, mechanical behaviour is important due to its relevance to many practical applications. This article presents a method for experimentally examining the toughness of chocolate, including a design for a simple test rig, and a number of experiments that can be performed in the classroom. Typical…

  10. Fracture mechanics of ceramics. Vol. 8. Microstructure, methods, design, and fatigue

    International Nuclear Information System (INIS)

    Bradt, R.C.; Evans, A.G.; Hasselman, D.P.H.; Lange, F.F.

    1986-01-01

    This paper presents information on the following topics: fracture mechanics and microstructures; non-lubricated sliding wear of Al 2 O 3 , PSZ and SiC; mixed-mode fracture of ceramics; some fracture properties of alumina-containing electrical porcelains; transformation toughening in the Al 2 O 3 -Cr 2 O 3 /ZrO 2 -HfO 2 system; strength toughness relationships for transformation toughened ceramics; tensile strength and notch sensitivity of Mg-PSZ; fracture mechanisms in lead zirconate titanate ceramics; loading-unloading techniques for determining fracture parameters of brittle materials utilizing four-point bend, chevron-notched specimens; application of the potential drop technique to the fracture mechanics of ceramics; ceramics-to-metal bonding from a fracture mechanics perspective; observed changes in fracture strength following laser irradiation and ion beam mixing of Ni overlayers on sintered alpha-SiC; crack growth in single-crystal silicon; a fracture mechanics and non-destructive evaluation investigation of the subcritical-fracture process in rock; slow crack growth in sintered silicon nitride; uniaxial tensile fatigue testing of sintered silicon carbide under cyclic temperature change; and effect of surface corrosion on glass fracture

  11. High strength fibre reinforced concrete : Static and fatigue behaviour in bending

    NARCIS (Netherlands)

    Lappa, E.S.

    2007-01-01

    Recently, a number of high strength and ultra high strength steel fibre concretes have been developed. Since these materials seem very suitable for structures that might be prone to fatigue failure, such as bridge decks, the understanding of the static and fatigue bending behaviour is vital. In

  12. Fatigue and fracture behavior of coiled pipes; Comportamento a fratura e fadiga de tubos bobinados

    Energy Technology Data Exchange (ETDEWEB)

    Pope, Alexandre M.; Silva, Renato M.C. [PETROBRAS, Rio de Janeiro, RJ (Brazil); Frainer, Vitor J; Tarnowski, Gabriel A.; Strohaecker, Telmo R. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil)

    2005-07-01

    The possibility of applying coiled pipes in dynamic situations, such as risers, was investigated through full scale fatigue and fracture tests. A total of sixteen X-65 pipe specimens 41/2'' Od x 0.3'' x 13', containing a bias weld at the mid length, were fatigue tested in a resonance rig at 27 Hz. Six specimens were tested in the as fabricated condition while the ten others were previously subjected to five plastic deformation cycles, simulating reeling operations.. Tests were run until a crack propagated through thickness or 10{sup 7} cycles were achieved. Two cracked specimens were fracture tested in tension. All tests were carried out at room temperature. Test results showed that the fatigue lives were above the Bs-7608 mean class 'B' curves independently whether the specimen were plastically deformed or not. Post fatigue inspection and fractographic examination revealed that fatigue cracks propagate mostly from pits or surface scratches rather than from the bias weld. The two full size tensile specimens failed by ductile fracture at 80% of the material measured strength. (author)

  13. Fatigue and fracture resistance of zirconia crowns prepared with different finish line designs

    NARCIS (Netherlands)

    Aboushelib, M.N.

    2012-01-01

    Purpose: The aim of this study was to evaluate the effect of finish line design on the fatigue, fracture resistance, and failure type of veneered zirconia restorations. Materials and Methods: A CAD/CAM system (Cercon) was used to prepare zirconia frameworks (0.5 mm thick) for a maxillary central

  14. Probabilistic model for fatigue crack growth and fracture of welded joints in civil engineering structures

    NARCIS (Netherlands)

    Maljaars, J.; Steenbergen, H.M.G.M.; Vrouwenvelder, A.C.W.M.

    2012-01-01

    This paper presents a probabilistic assessment model for linear elastic fracture mechanics (LEFM). The model allows the determination of the failure probability of a structure subjected to fatigue loading. The distributions of the random variables for civil engineering structures are provided, and

  15. Fracture strength and fatigue resistance of dental resin-based composites

    NARCIS (Netherlands)

    Keulemans, F.; Palav, P.; Aboushelib, M.M.N.; van Dalen, A.; Kleverlaan, C.J.; Feilzer, A.J.

    2009-01-01

    Objectives: The aim of this study was to evaluate in vitro the influence of fiber-reinforcement on the fracture strength and fatigue resistance of resin-based composites. Methods: One hundred rectangular bar-shaped specimens (2 mm × 2 mm × 25 mm) made of resin-based composite were prepared in a

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-15

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

  17. Crack and fracture behaviour in tough ductile materials

    International Nuclear Information System (INIS)

    Venter, R.D.; Hoeppner, D.W.

    1985-10-01

    The report describes various approaches and developments pertaining to the understanding of crack and fracture behaviour in tough ductile materials. The fundamental elastic fracture mechanics concepts based on the concepts of energy, stress field, and displacement are introduced and their interrelationships demonstrated. The extension of these concepts to include elasto-plastic fracture mechanics considerations is reviewed in the context of the preferred options available for the development of appropriate design methodologies. The recommendations of the authors are directed towards the continued development of the J-integral concept. This energy-based concept, in its fundamental form, has a sound theoretical basis and as such offers the possibility of incorporating elasto-plastic fracture mechanics considerations in the crack and fracture behaviour of tough ductile materials. It must however be emphasized that the concise defintion of J becomes increasingly suspect as the crack length increases. J is not a material property, as is J IC , but emerges as a useful empirical parameter which is dependent upon the particular geometry and the loading imposed on the structure. It is proposed that 'lowest bound' J-resistance curves and the associated J-T curves be experimentally developed and employed in the design process. Improvements to these 'lowest bounds' can be developed through extensive analysis of the twin J-CTOA criteria and validation of this approach through near full scale tests

  18. Correlating Scatter in Fatigue Life with Fracture Mechanisms in Forged Ti-6242Si Alloy

    Science.gov (United States)

    Sinha, V.; Pilchak, A. L.; Jha, S. K.; Porter, W. J.; John, R.; Larsen, J. M.

    2018-04-01

    Unlike the quasi-static mechanical properties, such as strength and ductility, fatigue life can vary significantly (by an order of magnitude or more) for nominally identical material and test conditions in many materials, including Ti-alloys. This makes life prediction and management more challenging for components that are subjected to cyclic loading in service. The differences in fracture mechanisms can cause the scatter in fatigue life. In this study, the fatigue fracture mechanisms were investigated in a forged near- α titanium alloy, Ti-6Al-2Sn-4Zr-2Mo-0.1Si, which had been tested under a condition that resulted in life variations by more than an order of magnitude. The crack-initiation and small crack growth processes, including their contributions to fatigue life variability, were elucidated via quantitative characterization of fatigue fracture surfaces. Combining the results from quantitative tilt fractography and electron backscatter diffraction, crystallography of crack-initiating and neighboring facets on the fracture surface was determined. Cracks initiated on the surface for both the shortest and the longest life specimens. The facet plane in the crack-initiating grain was aligned with the basal plane of a primary α grain for both the specimens. The facet planes in grains neighboring the crack-initiating grain were also closely aligned with the basal plane for the shortest life specimen, whereas the facet planes in the neighboring grains were significantly misoriented from the basal plane for the longest life specimen. The difference in the extent of cracking along the basal plane can explain the difference in fatigue life of specimens at the opposite ends of scatter band.

  19. Talar body fatigue stress fractures: three cases observed in elite female gymnasts

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, F. [National Institute of Sports Medicine of the Italian Olympic Committee, Rome (Italy); Dragoni, S. [National Institute of Sports Medicine of the Italian Olympic Committee, Rome (Italy); Istituto Nazionale di Medicina dello Sport, Rome (Italy)

    2005-07-01

    To introduce and emphasize the clinical and radiological findings of three talar body fatigue stress fractures in competitive athletes. Clinical and radiographic skeletal records of 24,562 athletes taken between 1962 and 2002 were retrospectively reviewed. Among these, 6851 files related to acute foot and ankle injuries or chronic post-traumatic sequelae were found. There were 925 (3.76%) stress fatigue fractures selected from the whole collection. Among these there were three cases (0.32%) of talar body stress fractures diagnosed in elite female gymnasts 15 - 17 years old. The negative first radiograph become positive 4-6 weeks later. Scintigraphy was positive at an early stage and consistent for the diagnosis. CT and MRI gave positive results 1-2 weeks after the beginning of symptoms which were always greatly diagnostic. The sports medicine literature lacks reports of talar body fatigue stress fractures. The poor initial sensitivity of radiography makes it problematic to establish an early diagnosis. A wise combination of scintigraphy, CT and MRI has therefore to be relied upon. Familiarity with this rare location for a stress fracture may prevent delayed diagnosis and long-lasting damage, both of which are important factors in competitive athletes. (orig.)

  20. Talar body fatigue stress fractures: three cases observed in elite female gymnasts

    International Nuclear Information System (INIS)

    Rossi, F.; Dragoni, S.

    2005-01-01

    To introduce and emphasize the clinical and radiological findings of three talar body fatigue stress fractures in competitive athletes. Clinical and radiographic skeletal records of 24,562 athletes taken between 1962 and 2002 were retrospectively reviewed. Among these, 6851 files related to acute foot and ankle injuries or chronic post-traumatic sequelae were found. There were 925 (3.76%) stress fatigue fractures selected from the whole collection. Among these there were three cases (0.32%) of talar body stress fractures diagnosed in elite female gymnasts 15 - 17 years old. The negative first radiograph become positive 4-6 weeks later. Scintigraphy was positive at an early stage and consistent for the diagnosis. CT and MRI gave positive results 1-2 weeks after the beginning of symptoms which were always greatly diagnostic. The sports medicine literature lacks reports of talar body fatigue stress fractures. The poor initial sensitivity of radiography makes it problematic to establish an early diagnosis. A wise combination of scintigraphy, CT and MRI has therefore to be relied upon. Familiarity with this rare location for a stress fracture may prevent delayed diagnosis and long-lasting damage, both of which are important factors in competitive athletes. (orig.)

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

    International Nuclear Information System (INIS)

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

    2004-01-01

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

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

    Science.gov (United States)

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

    2004-06-01

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

  3. 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

    The fatique 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 Risø witha flux of approx2.5 x 1017 n/m2s (E> 1 Me...... microscope. The present investigations demonstrated that the fatigue life decreases with increasingtemperature 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...

  4. Effect of zirconia addition on the fatigue behaviour of fine grained alumina

    International Nuclear Information System (INIS)

    Basu, D.; Sarkar, B.K.

    2001-01-01

    The fatigue behaviour of fine grained Al 2 O 3 and ZrO 2 toughened Al 2 O 3 (ZTA) compositions with 15 vol% ZrO 2 (3 mol% Y 2 O 3 stabilized: 3Y-TZP) have been investigated by using three different techniques. Primarily 4-point bending load was employed to generate tension-tension fatigue data under both static and cyclic conditions. The results clearly showed that the materials were susceptible to both the static and cyclic fatigue and the time to failure under cyclic loading was considerably shorter than the equivalent static loads. The repeated indentations at the same spot with varying loads showed a typical fatigue behaviour. In addition, both the materials were subjected to the repeated impact cycles at varying subcritical loads simulating impact fatigue. In all the cases typical fatigue curves were obtained having a progressive endurance at subcritical loads having an endurance limit. The fatigue behaviour of Al 2 O 3 was much improved by the addition of 15 vol% 3Y -TZP, having micro-plasticity contributing towards the cyclic fatigue phenomena of these materials. (author)

  5. Fatigue pre-cracking and fracture toughness in polycrystalline tungsten and molybdenum

    Science.gov (United States)

    Taguchi, Katsuya; Nakadate, Kazuhito; Matsuo, Satoru; Tokunaga, Kazutoshi; Kurishita, Hiroaki

    2018-01-01

    Fatigue pre-cracking performance and fracture toughness in polycrystalline tungsten (W) and molybdenum (Mo) have been investigated in relation to grain boundary (GB) configuration with respect to the crack advance direction. Sub-sized, single edge notched bend (SENB) specimens with three different orientations, R-L (ASTM notation) for a forged Mo rod and L-S and T-S for a rolled W plate, were pre-cracked in two steps: fully uniaxial compression fatigue loading to provoke crack initiation and its stable growth from the notch root, and subsequent 3-point bend (3PB) fatigue loading to extend the crack. The latter step intends to minimize the influence of the residual tensile stresses generated during compression fatigue by moving the crack tip away from the plastic zone. It is shown that fatigue pre-cracking performance, especially pre-crack extension behavior, is significantly affected by the specimen orientation. The R-L orientation, giving the easiest cracking path, permitted crack extension completely beyond the plastic zone, while the L-S and T-S orientations with the thickness cracking direction of the rolled plate sustained the crack lengths around or possibly within the plastic zone size due to difficulty in crack advance through an aligned grain structure. Room temperature fracture toughness tests revealed that the 3PB fatigued specimens exhibited appreciably higher fracture toughness by about 30% for R-L, 40% for L-S and 60% for T-S than the specimens of each orientation pre-cracked by compression fatigue only. This indicates that 3PB fatigue provides the crack tip front out of the residual tensile stress zone by crack extension or leads to reduction in the residual stresses at the crack tip front. Strong dependence of fracture toughness on GB configuration was evident. The obtained fracture toughness values are compared with those in the literature and its strong GB configuration dependence is discussed in connection with the appearance of pop-in.

  6. Sensitization to Corrosion as Initiator of Fatigue Fracture in Compressor Blades

    Directory of Open Access Journals (Sweden)

    Vladimír CIHAL

    2011-06-01

    Full Text Available Certain failures of stainless steels interpreted purely in terms of fracture mechanisms may in fact be closely associated with previous damage caused by localized corrosion. The closeness of the link between fatigue and corrosion is documented by the case history of compressor blades made of grade 14Cr17Ni2 (X14CrNi17-2 stainless steel. Fatigue fracturing observed in areas near the blade root tended to follow intergranular pathways, indicating that some additional mechanism other than fatigue might be involved. This suspicion was confirmed by electrochemical potentiokinetic reactivation (EPR measurements in situ, which revealed sensitization to intergranular corrosion. It has been found that at the transition between the blade root and the blade proper the surfaces had been ground and polished too vigorously, heating the subcutaneous layers to within the danger zone of 400-600°C. Preferential integranular attack in these locations was the initiation mechanism that provoked a subsequent failure of the blades by fatigue fracture.

  7. Kinetic Theory of Fracture Strength in Prediction of Fatigue Lifetime of Epoxy/Carbon Fiber Composites

    Directory of Open Access Journals (Sweden)

    Morteza Molaee

    2016-11-01

    Full Text Available Extensive use of polymer composite materials in many industries has created needs for theoretical modeling tools and the ability to predict the behavior of these materials, namely their fatigue life. Fatigue life is a complex course and depends on material properties, environmental and operational conditions and some other parameters. This work presents an analytical method, based on kinetic logics which are able to predict the lifetime fracture strength and fatigue behavior analysis of carbon fiber-reinforced epoxy composites. The kinetic strength analyzes the mechanical behavior of material based on its molecular properties. Ring-shaped composite samples were used for empirical study of the model. The rings were obtained from the pipes fabricated by the filament winding method. Samples were subjected to cyclic fatigue testing under different strain conditions and evaluated the changes in the structure of composites by FTIR analysis and TGA. The data obtained from the FTIR tests were evaluated in order to propose a theoretical model. The results obtained in this investigation showed that the kinetic models can be as an alternative to the classical mechanical models which usually require expensive testing procedures along with complex calculation tasks. The kinetic model presented here can be used only for the composite samples fabricated according to the procedure described in this study, because they fracture in the transverse direction caused by failure of the matrix. Therefore, prediction of the fatigue lifetime using the developed models only needs to achieve the bond energy and activated volume by performing a few simple tests.

  8. Experimental Study on Fatigue Behaviour of BFRP-Concrete Bond Interfaces under Bending Load

    Directory of Open Access Journals (Sweden)

    Jianhe Xie

    2018-01-01

    Full Text Available Basalt fiber reinforced polymer (BFRP composites are increasingly being used to retrofit concrete structures by external bonding. For such strengthened members, the BFRP-concrete interface plays the crucial role of transferring stresses. This study aims to investigate the fatigue behaviour of the interface under bending load. A series of tests were conducted on BFRP-concrete bonded joint, including static, fatigue, and postfatigue loading. The fatigue failure modes, the development of deflection, the evolution of BFRP strains, and the propagation of interfacial cracks were analysed. In addition, the debonding-induced fatigue life of BFRP-concrete bonded joints was studied. Finally, a new model of fatigue life was proposed by defining the effective fatigue bond stress. The results showed that the fatigue experience has a significant effect on the BFRP strength especially near the root of concrete transverse crack and on the bond performance of the adhesive near the interface crack tip. There are two main fatigue failure modes: BFRP rupture and BFRP debonding. The fatigue damage development of the bond interface has three stages: rapid, stable, and unstable growth. The proposed model for the debonding-induced fatigue life is more conservative for the BFRP-concrete bonded joints under pure shear load than for those under bending load.

  9. Influence of dental restorations and mastication loadings on dentine fatigue behaviour: Image-based modelling approach.

    Science.gov (United States)

    Vukicevic, Arso M; Zelic, Ksenija; Jovicic, Gordana; Djuric, Marija; Filipovic, Nenad

    2015-05-01

    The aim of this study was to use Finite Element Analysis (FEA) to estimate the influence of various mastication loads and different tooth treatments (composite restoration and endodontic treatment) on dentine fatigue. The analysis of fatigue behaviour of human dentine in intact and composite restored teeth with root-canal-treatment using FEA and fatigue theory was performed. Dentine fatigue behaviour was analysed in three virtual models: intact, composite-restored and endodontically-treated tooth. Volumetric change during the polymerization of composite was modelled by thermal expansion in a heat transfer analysis. Low and high shrinkage stresses were obtained by varying the linear shrinkage of composite. Mastication forces were applied occlusally with the load of 100, 150 and 200N. Assuming one million cycles, Fatigue Failure Index (FFI) was determined using Goodman's criterion while residual fatigue lifetime assessment was performed using Paris-power law. The analysis of the Goodman diagram gave both maximal allowed crack size and maximal number of cycles for the given stress ratio. The size of cracks was measured on virtual models. For the given conditions, fatigue-failure is not likely to happen neither in the intact tooth nor in treated teeth with low shrinkage stress. In the cases of high shrinkage stress, crack length was much larger than the maximal allowed crack and failure occurred with 150 and 200N loads. The maximal allowed crack size was slightly lower in the tooth with root canal treatment which induced somewhat higher FFI than in the case of tooth with only composite restoration. Main factors that lead to dentine fatigue are levels of occlusal load and polymerization stress. However, root canal treatment has small influence on dentine fatigue. The methodology proposed in this study provides a new insight into the fatigue behaviour of teeth after dental treatments. Furthermore, it estimates maximal allowed crack size and maximal number of cycles for a

  10. Fatigue behavior of Ilizarov frame versus tibial interlocking nail in a comminuted tibial fracture model: a biomechanical study

    Directory of Open Access Journals (Sweden)

    Stahel Philip F

    2006-12-01

    Full Text Available Abstract Background Treatment options for comminuted tibial shaft fractures include plating, intramedullary nailing, and external fixation. No biomechanical comparison between an interlocking tibia nail with external fixation by an Ilizarov frame has been reported to date. In the present study, we compared the fatigue behaviour of Ilizarov frames to interlocking intramedullary nails in a comminuted tibial fracture model under a combined loading of axial compression, bending and torsion. Our goal was to determine the biomechanical characteristics, stability and durability for each device over a clinically relevant three month testing period. The study hypothesis was that differences in the mechanical properties may account for differing clinical results and provide information applicable to clinical decision making for comminuted tibia shaft fractures. Methods In this biomechanical study, 12 composite tibial bone models with a comminuted fracture and a 25 mm diaphyseal gap were investigated. Of these, six models were stabilized with a 180-mm four-ring Ilizarov frame, and six models were minimally reamed and stabilized with a 10 mm statically locked Russell-Taylor Delta™ tibial nail. After measuring the pre-fatigue axial compression bending and torsion stiffness, each model was loaded under a sinusoidal cyclic combined loading of axial compression (2.8/28 lbf; 12.46/124.6 N and torque (1.7/17 lbf-in; 0.19/1.92 Nm at a frequency of 3 Hz. The test was performed until failure (implant breakage or ≥ 5° angulations and/or 2 cm shortening occurred or until 252,000 cycles were completed, which corresponds to approximately three months testing period. Results In all 12 models, both the Ilizarov frame and the interlocking tibia nail were able to maintain fracture stability of the tibial defect and to complete the full 252,000 cycles during the entire study period of three months. A significantly higher stiffness to axial compression and torsion was

  11. The effect of advanced ultrasonic forging on fatigue fracture mechanisms of welded Ti-6A1-4V alloy

    Science.gov (United States)

    Smirnova, A.; Pochivalov, Yu.; Panin, V.; Panin, S.; Eremin, A.; Gorbunov, A.

    2017-12-01

    The current study is devoted to application of advanced postwelding ultrasonic forging to joints formed by laser welding of Ti-6A1-4V alloy in order to enhance their mechanical properties and fatigue durability. Low cycle fatigue tests were performed via digital image correlation technique used to obtain strain fields and in situ characterization of deformation, crack growth and fracture. Fracture surfaces were studied by SEM analysis accompanied with calculation of fracture patterns percentage. The fatigue tests demonstrate the high increase in the number of cycles until fracture (from 17 000 to 32 000 cycles) which could be explained by high ductility of welded material after treatment. This leads to lower fatigue crack growth rate due to higher energy dissipation. The obtained effect is attributable only for small cracks on micro-/mesoscales and fails to play a significant role for macro cracks.

  12. A comparison of the fracture resistance of three machinable ceramics after thermal and mechanical fatigue.

    Science.gov (United States)

    Yang, Rui; Arola, Dwayne; Han, Zhihui; Zhang, Xiuyin

    2014-10-01

    Mechanical and thermal fatigue may affect ceramic restorations in the oral environment. The purpose of this study was to determine the influence of thermal and mechanical cycling on the fracture load and fracture patterns of 3 machinable ceramics. Seventy-two human third molar teeth were prepared for bonding ceramic specimens of Sirona CEREC Blocs, IPS e.maxCAD, or inCoris ZI meso blocks. The 24 specimens of each ceramic were divided into 4 groups (n=6), which underwent no preloading (control), thermocycling (5°C-55°C, 2000 cycles), mechanical cycling (10(5) cycles, 100 N), and thermocycling (5°C-55°C, 2000 cycles) plus mechanical cycling (10(5) cycles, 100 N). The specimens were subsequently loaded to failure, and both stereomicroscopy and scanning electron microscopy were used to investigate the fracture patterns. The data were analyzed with 2-way ANOVA and the Fisher exact probability test (α=.05). Mechanical and thermal cycling had a significant influence on the critical load to failure of the 3 ceramics. No significant difference was found between mechanical cycling for 10(5) times and thermocycling for 2000 times within the same ceramic. The specimens of inCoris ZI experienced significantly higher fracture loads for all the groups. The fracture patterns of the 3 machinable ceramics showed that failure mainly occurred at the cement-dentin interface. The effects of combined thermal and mechanical cycling on the fracture load of ceramics were more significant than any individual mode of cyclic fatigue. Overall, the inCoris ZI resisted thermal and mechanical fatigue better than the Sirona CEREC and IPS e.maxCAD. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  13. Fatigue crack Behaviour in a High Strength Tool Steel

    DEFF Research Database (Denmark)

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

    2002-01-01

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

  14. Fatigue behaviour of X70 steel in crude oil

    Czech Academy of Sciences Publication Activity Database

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

    2015-01-01

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

  15. Low cycle fatigue behaviour of ODS steels for nuclear application

    Czech Academy of Sciences Publication Activity Database

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

    2011-01-01

    Roč. 465, - (2011), s. 556-559 ISSN 1013-9826 R&D Projects: GA ČR GA106/09/1954; GA ČR GA101/09/0867 Institutional research plan: CEZ:AV0Z20410507 Keywords : Generation IV nuclear reactors * fusion energy * ODS steels * low cycle fatigue * cyclic softening Subject RIV: JL - Materials Fatigue, Friction Mechanics

  16. Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone.

    Science.gov (United States)

    Whitton, R Christopher; Trope, Gareth D; Ghasem-Zadeh, Ali; Anderson, Garry A; Parkin, Timothy D H; Mackie, Eleanor J; Seeman, Ego

    2010-10-01

    Bone modelling and remodelling reduce the risk of fatigue fractures; the former by adapting bone to its loading circumstances, the latter by replacing fatigued bone. Remodelling transiently increases porosity because of the normal delay in onset of the formation phase of the remodelling sequence. Protracted intense loading suppresses remodelling leaving modelling as the only means of maintaining bone strength. We therefore hypothesized that race horses with fatigue fractures of the distal third metacarpal bone (MC3) will have reduced porosity associated with suppressed remodelling while continued adaptive modelling will result in higher volume fraction (BV/TV) at this site. Using high resolution peripheral quantitative computed tomography (HR-pQCT), we measured the distal aspect of the MC3 obtained at postmortem from 13 thoroughbred race horses with condylar fractures of the MC3 (cases), 8 horses without fractures (training controls), 14 horses with a fracture at another site (fractured controls) and 9 horses resting from training (resting controls). Porosity of the subchondral bone of MC3 was lower in cases than resting controls (12±1.4% vs. 18±1.6%, P=0.017) although areas of focal porosity were observed adjacent to fractures in 6/13 horses. BV/TV of the distal metacarpal epiphysis tended to be higher in horses with condylar fractures (0.79±0.015) than training controls (0.74±0.019, P=0.070), but also higher in controls with a fracture elsewhere (0.79±0.014) than the training controls (0.74±0.019, P=0.040). BV/TV was higher in horses over three years of age than those aged two or three years (0.79±0.01 vs. 0.74±0.01, P=0.016). All metacarpal condylar fractures occurred within focal areas of high BV/TV. We infer that intense training in equine athletes suppresses remodelling of third metacarpal subchondral bone limiting damage repair while modelling increases regional bone volume in an attempt to minimise local stresses but may fail to offset bone

  17. Fatigue stress fractures of the pubic ramus in the army: imaging features with radiographic, scintigraphic and MR imaging findings

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Woo; Lee, Chang Hyun [The Armed Forces Capital Hospital, Seongnam (Korea, Republic of)

    2005-03-15

    Although fatigue fractures are not unusual in athletes and military personnel those of the pubic ramus are rare. We report three cases of fatigue fractures of the inferior pubic rami in two male recruits and one female military cadet. On the initial radiograph, most of the lesions were subtle and easy to overlook. However, bone scintigraphy provided more distinct images that allowed easy and early detection of lesion, and MR imaging presented more diagnostic information, which allowed a precise diagnosis.

  18. Fatigue Behaviour of Composite T-Joints in Wind Turbine Blade Applications

    Science.gov (United States)

    Wang, Y.; Soutis, C.

    2017-04-01

    This paper presents a study of fatigue performance of composite T-joints used in wind-turbine blades. A T-joint with various fibre reinforcement architectures were selected to investigate its fatigue behaviour. The 3D angle interlock T-joint was found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue performance while the increasing rate in life performance is changed with the number of fatigue cycles. A finite element (FE) model was developed that can determine the stress distribution and the initiation and propagation of a delamination crack. The location for through-thickness reinforcement is very important to improve fatigue performance of composite T-joints. Fatigue performance is significantly improved for the web with through-thickness reinforcement while fatigue performance is decreased if the through-thickness reinforcement is applied to the flange-skin regions. The interlaminar veil significantly increases the ultimate strength under static load but fatigue performance at high stress cycles is increased but not significantly.

  19. Effect of zirconia addition on the fatigue behaviour of fine grained ...

    Indian Academy of Sciences (India)

    The fatigue behaviour of fine grained Al2O3 and ZrO2 toughened Al2O3 (ZTA) compositions with 15 vol% ZrO2 (3 mol% Y2O3 stabilized: 3Y-TZP) have been investigated by using three different techniques. Primarily 4-point bending load was employed to generate tension–tension fatigue data under both static and cyclic ...

  20. Nanoscale fatigue and fracture toughness measurements of multilayered thin film structures for digital micromirror devices

    Science.gov (United States)

    Wei, Guohua; Bhushan, Bharat; Jacobs, S. Joshua

    2004-07-01

    The digital micromirror device (DMD), which lies at the heart of Digital Light Processing™ projection display technology by Texas Instruments, Dallas, Texas, comprises a surface-micromachined array of mirrors on a base CMOS substrate. The nanomechanical properties of the thin-film structures used are important to the performance of the DMD. In this article, the nanoscale fatigue and fracture toughness of the single and multilayered thin film structures which are of interest in DMDs, i.e., TiN/Si, SiO2/Si, Al alloy/Si, TiN/Al alloy/Si, and SiO2/TiN/Al alloy/Si, were measured using nanoindentation techniques. The multilayered thin film structures with hard films on soft interlayer exhibit shorter fatigue life and higher ductility than the corresponding top hard films. The hardness plays an important role in determining the indentation fatigue life. Longer fatigue life is associated with higher hardness. The fracture toughness of TiN/Si and SiO2/Si was measured using the strain energy release method. .

  1. A study of fatigue and fracture response of cantilevered luminaire structures made from aluminum alloy 6063

    Energy Technology Data Exchange (ETDEWEB)

    Menzemer, Craig C. [Department of Civil Engineering, University of Akron, Akron, OH 443265 (United States); Azzam, Diya [Department of Civil Engineering, University of Akron, Akron, OH 443265 (United States); California Department of Transportation (Caltrans), Bridge Structure Design (Branch, 10) Los Angeles Projects, 1801 30th Street, Sacramento, CA 95816 (United States); Srivatsan, T.S., E-mail: TSrivatsan@uakron.edu [Division of Materials Science and Engineering, Department of Mechanical Engineering, University of Akron, Akron, OH 44325-3903 (United States)

    2010-07-15

    In the experimental results elegantly and exhaustively elaborated upon in this paper the local stresses, obtained from finite element analysis, was used to develop estimates of the stress intensity factor (SIF). In combination with crack growth data, the fatigue lives of both the through-plate and an integrally stiffened socket connection were estimated using software developed by the U.S. Air Force (and referred to as AFGROW). The fatigue life estimates correlated well with the test results provided the crack growth rate data was obtained under conditions of minimal closure at higher stress ratios (of the order R = 0.7). In an attempt to establish the fatigue lives in the high cycle regime, the measured residual stresses had to be included in the analysis. For identical stress ranges, the 25 mm thick through-plate socket connection exhibited noticeably lower fatigue lives when compared to the integrally stiffened shoe-base structure. Scanning electron microscopy observations revealed pockets of well-defined striations consistent with stable growth of the crack through the microstructure prior to the onset of unstable crack growth culminating in catastrophic fracture. In the slow growth region, the fracture surface revealed pockets of shallow, well-defined striations that were uniformly spaced indicative of the occurrence of localized microplastic deformation.

  2. Reliability Analysis of Fatigue Fracture of Wind Turbine Drivetrain Components

    DEFF Research Database (Denmark)

    Berzonskis, Arvydas; Sørensen, John Dalsgaard

    2016-01-01

    in the volume of the casted ductile iron main shaft, on the reliability of the component. The probabilistic reliability analysis conducted is based on fracture mechanics models. Additionally, the utilization of the probabilistic reliability for operation and maintenance planning and quality control is discussed....... of operation and maintenance. The manufacturing of casted drivetrain components, like the main shaft of the wind turbine, commonly result in many smaller defects through the volume of the component with sizes that depend on the manufacturing method. This paper considers the effect of the initial defect present...

  3. Behaviour under fatigue of AISI 304-L stainless steel welded joints

    International Nuclear Information System (INIS)

    Scal, M.W.; Joia, C.J.B.M.; Sousa e Silva, A.S. de

    1979-01-01

    The fatigue behaviour at room temperature of AISI-304-L stainless steel welded joints obtained by two distinct welding methods was studied. The results obtained were compared to those characteristic of the base metal. The welded joint fatigue samples were rectified in order to eliminate the effect of the welded seam geometry. It was concluded that the mechanisms of fatigue crack start in this case is commanded by the austenitic matrix, there being no influence of the delta ferrite rate and distribution present at the melted zone. (Author) [pt

  4. Effect of core thickness differences on post-fatigue indentation fracture resistance of veneered zirconia crowns.

    Science.gov (United States)

    Alhasanyah, Abdulrahman; Vaidyanathan, Tritala K; Flinton, Robert J

    2013-07-01

    Despite the excellent esthetics of veneered zirconia crowns, the incidence of chipping and fracture of veneer porcelain on zirconia crowns has been recognized to be higher than in metal ceramic crowns. The objective of this investigation was to study the effect of selected variations in core thickness on the post-fatigue fracture resistance of veneer porcelain on zirconia crowns. Zirconia crowns for veneering were prepared with three thickness designs of (a) uniform 0.6-mm thick core (group A), (b) extra-thick 1.7 mm occlusal core support (group B), and (c) uniform 1.2-mm thick core (group C). The copings were virtually designed and milled by the CAD/CAM technique. Metal ceramic copings (group D) with the same design as in group C were used as controls. A sample size of N = 20 was used for each group. The copings were veneered with compatible porcelain and fatigue tested under a sinusoidal loading regimen. Loading was done with a 200 N maximum force amplitude under Hertzian axial loading conditions at the center of the crowns using a spherical tungsten carbide indenter. After 100,000 fatigue cycles, the crowns were axially loaded to fracture and maximum load levels before fracture was recorded. One-way ANOVA (P crowns. Extra-thick occlusal core support for porcelain veneer may significantly reduce the veneer chipping and fracture of zirconia crowns. This is suggested as an important consideration in the design of copings for zirconia crowns. © 2013 by the American College of Prosthodontists.

  5. Thermal fatigue behaviour of controlled surface flaws in alumina

    Energy Technology Data Exchange (ETDEWEB)

    Saadaoui, M. [Maghrebian Information Processing Society (MIPS), Rabat (Morocco); Olagnon, C.; Fantozzi, G. [G.E.M.P.P.M., INSA de Lyon, Villeurbanne (France)

    1997-12-31

    Indented rectangular specimens were thermally cycled at an applied temperature difference {Delta}T, and the plot of the critical cycle number versus the initial crack size allowed the determination of a thermal fatigue domain in the V-K{sub 1} diagram (crack growth rate versus the stress intensity factor). Comparison with subcritical crack growth (SCG) laws obtained under isothermal mechanical loading reveals cyclic fatigue effects and shows that life time prediction cannot be done simply from the mechanical results. (orig.) 5 refs.

  6. MR semiology of stress fractures; Semiologie IRM des fractures de fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Boyer, B.; Cordoliani, Y.S.; Naudinat, E.; Sylvestre, A.; Pharaboz, C. [Hopital des Armees Begin, 94 - Saint-Mande (France)

    1995-12-01

    Nuclear Magnetic Resonance imaging can contribute to stress fractures diagnosis when it makes obvious the fracture line which signal is variable in function of site lesion. The importance of inflammatory reactions must not call the diagnosis in question again. 5 figs., 8 refs.

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

    Directory of Open Access Journals (Sweden)

    Fatima Majid

    2016-10-01

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

  8. A discrete element model for damage and fracture of geomaterials under fatigue loading

    Science.gov (United States)

    Gao, Xiaofeng; Koval, Georg; Chazallon, Cyrille

    2017-06-01

    Failure processes in geomaterials (concrete, asphalt concrete, masonry, etc.) under fatigue loading (repeated moving loads, cycles of temperature, etc.) are responsible for most of the dysfunctions in pavements, brick structures, etc. In the beginning of the lifetime of a structure, the material presents only inner defects (micro cracks, voids, etc.). Due to the effect of the cyclic loading, these small defects tend to grow in size and quantity which damage the material, reducing its stiffness. With a relatively high number of cycles, these growing micro cracks become large cracks, which characterizes the fracture behavior. From a theoretical point of view, both mechanisms are treated differently. Fracture is usually described locally, with the propagation of cracks defined by the energy release rate at the crack tip; damage is usually associated to non-local approaches. In the present work, damage and fracture mechanics are combined in a local discrete element approach.

  9. Bilateral fatigue fractures of the distal fibulae caused by a change of running shoes.

    Science.gov (United States)

    Burgess, I; Ryan, M D

    1985-09-30

    A 26-year-old man sustained bilateral, symmetrical fatigue fractures of his distal fibulae while running in a 14-km road race. He had trained repeatedly over the course without developing any symptoms, but on the day of the race he lost one of his regular running shoes. He competed instead in old, borrowed tennis shoes. After running over a distance of 2 km, he felt pain about 4 cm above the distal end of both fibulae. Two weeks later, radiographs showed bilateral fractures. The change of footwear was the only identifiable factor in the causation of these fractures. Analysis by compression-loading showed that his usual running shoes absorbed twice as much energy and deformed five times as much as those used in the race.

  10. Impact fatigue behaviour of carbon fibre-reinforced vinylester resin ...

    Indian Academy of Sciences (India)

    Unknown

    A special swinging pendulum type impact fatigue tester. (Sarkar and Glinn 1971; Maity and Sarkar 1995) based on the principles of Charpy Impact Tester was designed and fabricated in the laboratory (figure 1). It consists of a horizontal shaft to which was attached a rotating circular disc. The circular disc was rotated by a ...

  11. An Investigation on the Wear Resistance and Fatigue Behaviour of Ti-6Al-4V Notched Members Coated with Hydroxyapatite Coatings

    Directory of Open Access Journals (Sweden)

    Reza H Oskouei

    2016-02-01

    Full Text Available In this study, surface properties of Ti-6Al-4V alloy coated with hydroxyapatite coatings were investigated. Wear resistance and fatigue behaviour of samples with coating thicknesses of 10 and 50 µm as well as uncoated samples were examined. Wear experiments demonstrated that the friction factor of the uncoated titanium decreased from 0.31 to 0.06, through a fluctuating trend, after 50 cycles of wear tests. However, the friction factor of both the coated samples (10 and 50 µm gradually decreased from 0.20 to 0.12 after 50 cycles. At the end of the 50th cycle, the penetration depth of the 10 and 50 µm coated samples were 7.69 and 6.06 µm, respectively. Fatigue tests showed that hydroxyapatite coatings could improve fatigue life of a notched Ti-6Al-4V member in both low and high cycle fatigue zones. It was understood, from fractography of the fracture surfaces, that the fatigue zone of the uncoated specimens was generally smaller in comparison with that of the coated specimens. No significant difference was observed between the fatigue life of coated specimens with 10 and 50 µm thicknesses.

  12. Fatigue hydraulic fracturing by cyclic reservoir treatment enhances permeability and reduces induced seismicity

    Science.gov (United States)

    Zang, Arno; Yoon, Jeoung Seok; Stephansson, Ove; Heidbach, Oliver

    2013-11-01

    The occurrence of induced seismic events during hydraulic fracturing of reservoirs to enhance permeability is an unavoidable process. Due to the increased public concern with respect to the risks imposed by induced seismicity, however, the development of a soft stimulation method is needed creating higher permeability with less induced seismicity. We use a discrete element model of naturally fractured rock with pore fluid flow algorithm in order to analyse two scenarios of high-pressure fluid injection (hydraulic fracturing) at depth and associated induced seismicity. The ratio of pumped-in energy to released seismic energy is in agreement with field data. Our results suggest that cyclic reservoir treatment is a safer alternative to conventional hydraulic fracture stimulation as both, the total number of induced events as well as the occurrence of larger magnitude events are lowered. This work is motivated by results of laboratory triaxial indenter tests on granite rock samples where continuous loading leads to a wide fracture process zone while cyclic treatment with frequent starting and stopping of loading fatigues the rock, resulting in smaller damage volume and more persistent fracture growth.

  13. 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

  14. 3-D analysis of fatigue crack behaviour in a shot peened steam turbine blade material

    International Nuclear Information System (INIS)

    He, B.Y.; Katsamenis, O.L.; Mellor, B.G.; Reed, P.A.S.

    2015-01-01

    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

  15. Study of Relation between Shot Peening Parameters and Fatigue Fracture Surface Character of an AW 7075 Aluminium Alloy

    Directory of Open Access Journals (Sweden)

    Libor Trško

    2018-02-01

    Full Text Available Shot peening is a well-known surface treatment method used for fatigue life improvement of cyclically loaded structural components. Since three main variables are considered in the peening process (peening intensity, coverage and peening media type, there is no direct way to choose the best combination of treatment parameters for the best performance, thus it has to be based on experience and laboratory tests. When shot peening is performed with inadequate parameters, or the peening process is not stable in time (decrease of the peening pressure, deterioration of the peening media and so on, it can result in significant degradation of the treated component fatigue properties, what is commonly called as the “overpeening” effect. When a premature fatigue fracture occurs in operation, the fracture surface analysis is usually the most important method of revealing the damage mechanism. This work is aimed at the study of the relation between the shot peening parameters and the fatigue fracture surface character on an AW 7075 aluminium alloy with an objective of identifying marks of overpeening and investigating the fatigue crack initiation mechanism. After performing the tests, it was observed that shot peening with optimized parameters creates a surface layer that is able to change the mechanism of the fatigue crack propagation and improve fatigue strength. On the other hand, using extensive peening parameters decrease the fatigue strength due to the creation of surface cracks and surface layer delamination.

  16. Analysis of fatigue crack propagation behaviour in SiC particulate Al2O3 whisker reinforced hybrid MMC

    International Nuclear Information System (INIS)

    Iqbal, AKM Asif; Arai, Yoshio

    2016-01-01

    The fatigue crack propagation behaviour of a cast hybrid metal matrix composite (MMC) was investigated and compared with the crack propagation behaviour of MMC with Al 2 O 3 and Al alloy in this article. Three dimensional (3D) surface analysis is carried out to analyze the crack propagation mechanism. All three materials clearly show near threshold and stable crack growth regions, but the rapid crack growth region is not clearly understood. The crack propagation resistance is found higher in hybrid MMC than that of MMC with Al 2 O 3 whisker and the Al alloy in the low ΔK region. The crack propagation in the hybrid MMC in the near-threshold region is directed by the debonding of reinforcement-matrix followed by void nucleation in the Al alloy matrix. Besides, the crack propagation in the stable- or midcrack-growth region is controlled by the debonding of particle-matrix and whisker-matrix interface caused by the cycle-by-cycle crack growth along the interface. The transgranular fracture of the reinforcement and void formation are also observed. Due to presence of large volume of inclusions and the microstructural inhomogeneity, the area of striation formation is reduced in the hybrid MMC, caused the unstable fracture. (paper)

  17. Fatigue behaviour of high performance concretes for wind turbines; Ermuedungsverhalten von Hochleistungsbetonen in Windenergieanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Lohaus, Ludger; Oneschkow, Nadja; Elsmeier, Kerstin; Huemme, Julian [Hannover Univ. (Germany). Inst. fuer Baustoffe

    2012-08-15

    New developments in the wind energy sector will lead to wind turbines with enormous capacities. As a result, the loads of the supporting structures are also increasing. For some time now, high performance concretes with self-compacting properties have been used in wind turbines for structural connections. Furthermore, slender foundations and prestressed concrete supporting structures made out of high-strength concrete are under development. In future, fatigue design of these high performance concretes is to be done according to the new fib-Model Code 2010. This code includes a new fatigue design model which enables a safe and economic fatigue design, even for high strength concrete. Extensive research with regard to the fatigue behaviour of different types of high performance concrete has been carried out at the Institute of Building Materials Science, Leibniz Universitaet Hannover. As part of these research activities, the influences of steel fibre reinforcement on the fatigue behaviour of high performance concretes are being investigated. In this paper, interim results of these investigations are presented and the potential for the practical applications of high performance concrete is discussed. The results of the conducted investigations are presented in comparison with the new fatigue design model of the fib-Model Code 2010. (orig.)

  18. The effect of cold work on the fatigue behaviour of α-zirconium at elevated temperatures

    International Nuclear Information System (INIS)

    Snowden, K.U.; Stathiers, P.A.

    1981-01-01

    Controlled amounts of cold work (CW) are commonly used in the fabrication of zirconium alloy reactor components. It is important, therefore, to determine the effects of CW on the mechanical properties of zirconium and its alloys to assess the likely influence on a component's service behaviour. A report is presented on the effects of CW on the fatigue behaviour of crystal bar zirconium to temperatures up to 700 0 C. (author)

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

    International Nuclear Information System (INIS)

    Kosteas, D.

    1979-01-01

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

  20. Fatigue behaviour of post weld heat treated electron beam welded AA2219 aluminium alloy joints

    International Nuclear Information System (INIS)

    Malarvizhi, S.; Raghukandan, K.; Viswanathan, N.

    2008-01-01

    This paper reports the effect of post weld heat treatment on fatigue behaviour of electron beam welded AA2219 aluminium alloy. An attempt has been made to enhance the fatigue strength of the electron beam welded joints through post weld heat treatment methods such as solution treatment, artificial aging, solution treatment and artificial aging. Electron beam welding machine with 100 kV capacity has been used to fabricate the square butt joints. Servo hydraulic controlled fatigue testing machine with a capacity of 100 kN has been used to evaluate the fatigue life of the welded joints. Of the three post weld heat treated joints, the solution treated and aged joints are enduring higher number of cycles under the action of cyclic loads

  1. Effect of Humidity on The Fatigue Behaviour of Adhesively Bonded Aluminium Joints

    Directory of Open Access Journals (Sweden)

    M. Costa

    Full Text Available Abstract The present work focuses on the effects of water degradation on the fatigue behaviour of adhesive joints bonded with aluminium adherends. The objective of this study is to measure the influence that humidity has on the fatigue crack growth velocity of two distinct adhesives characterized using the Paris Law, using double cantilever beam (DCB specimens in unaged and various aged conditions loaded in mode I in order to understand the influence that water content has on the Paris Law constants. It was found that the slope of the Paris Law curve is not heavily changed with the presence of water, but a shift in the curves does occur, generally resulting in a crack initiating at a lower threshold than in the unaged adhesive. Based on this behaviour, it can be concluded that an increase in water content reduces the fatigue joint strength and lifespan of adhesive joints bonded with the studied adhesives.

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

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Bokůvka, O.

    2008-01-01

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

  3. Fretting Fatigue Behaviour of Pin-Loaded Thermoset Carbon-Fibre-Reinforced Polymer (CFRP Straps

    Directory of Open Access Journals (Sweden)

    Fabio Baschnagel

    2016-04-01

    Full Text Available This paper focuses on the fretting fatigue behaviour of pin-loaded carbon-fibre-reinforced polymer (CFRP straps studied as models for rigging systems in sailing yachts, for suspenders of arch bridges and for pendent cables in cranes. Eight straps were subjected to an ultimate tensile strength test. In total, 26 straps were subjected to a fretting fatigue test, of which ten did not fail. An S–N curve was generated for a load ratio R of 0.1 and a frequency f of 10 Hz, showing a fatigue limit stress of the straps around the matrix fatigue limit, corresponding to 46% of the straps’ ultimate tensile strength (σUTS. The fatigue limit was defined as 3 million load cycles (N = 3 × 106, but tests were even conducted up to N = 11.09 × 106. Catastrophic failure of the straps was initiated in their vertex areas. Investigations on the residual strength and stiffness properties of straps tested around the fatigue limit stress (for N ≥ 1 × 106 showed little influence of the fatigue loading on these properties. Quasi-static finite element analyses (FEA were conducted. The results obtained from the FEA are in good agreement with the experiments and demonstrate a fibre parallel stress concentration in the vertex area of factor 1.3, under the realistic assumption of a coefficient of friction (cof between pin and strap of 0.5.

  4. The effect of microstructure and geometry on the fatigue behaviour of bundle assembly welds

    International Nuclear Information System (INIS)

    Surette, B.A.; Gabbani, M.

    1997-01-01

    Cracking of end plates, in the Darlington NGS, was attributed to high-cycle fatigue resulting from flow-induced vibrations. Because the cracks were predominantly associated with the bundle assembly welds and with certain element positions, a program was initiated to study whether the microstructure and geometry of the weld zone affected the fatigue behaviour of the assembly welds. Assembly weld samples were subjected to different heat treatments, resulting in different microstructures of the weld zone. Results of fatigue testing suggest that heat treatment of the welds (i.e., microstructure) had little effect on the fatigue life. Assembly welds were also produced with different weld notch geometries, and compared with samples having notches produced by machining (instead of welding). The results of these tests showed that geometry of the weld had a significant effect on fatigue life. However, the geometry of the weld notch required to significantly improve fatigue life is not achievable using the current assembly welding process. A small improvement in fatigue life of welded samples appears possible by increasing the weld diameter. (author)

  5. Influence of thermomechanical fatigue loading on the fracture resistance of all-ceramic posterior crowns.

    Science.gov (United States)

    Senyilmaz, Dilek Pinar; Canay, Senay; Heydecke, Guido; Strub, Joerg Rudolf

    2010-06-01

    This study evaluated the fracture resistance and the survival rate of different all-ceramic crowns in-vitro after thermomechanical fatigue loading in comparison to porcelain-fused-to-metal posterior crowns. Sixteen crowns for human mandibular first molars were made of each of the following: Cercon, IPS-Empress 2 In-Ceram Zirconia, Procera AllZircon and porcelain-fused-to-metal. Half of the specimens of each group was thermocycled and dynamically loaded using a chewing simulator All samples were thereafter tested for the maximum fracture resistance. The survival rates after 1-2 million cycles in the artificial mouth were 100% in all the tested crown systems. The chewing simulation and thermocycling did not significantly decrease the fracture strength of the ceramic crowns (P>0.005). The median fracture load of Cercon, Procera AllZircon, In-Ceram Zirconia and PFM was significantly higher than IPS-Empress 2 both for loaded and non loaded groups (PZirconia and PFM was not significant (P>0.005). All-ceramic systems showed fracture load values similar to those of porcelain-fused-to-metal molar crowns and therefore may be considered for use in clinical studies.

  6. Study of fatigue behaviour of 7475 aluminium alloy

    Indian Academy of Sciences (India)

    Unknown

    highly stressed region. The greatest potential of commer- cial exploitation is offered by the medium strength. Al–Zn–Mg alloys such as 7075, 7050, etc. The applica- tions of these alloys remained restricted due to their low toughness and environmental sensitive fracture in service, particularly under cyclic loading condition ...

  7. Very high cycle fatigue behaviour of as-extruded AZ31, AZ80, and ZK60 magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Novy, Frantisek; Skorik, Viktor [Zilina Univ. (Slovakia). Dept. of Materials Engineering; Janecek, Milos [Charles Univ., Prague (Czech Republic). Dept. of Physics of Materials; Mueller, Julia; Wagner, Lothar [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). Inst. of Materials Science and Technology

    2009-03-15

    The very high cycle fatigue properties of extruded AZ31, AZ80, and ZK60 magnesium alloys were investigated. Fatigue tests were performed at ultrasonic cyclic frequency and at a load ratio of R = -1 at ambient temperature using smooth electropolished specimens. Fatigue failures were observed at lifetimes above 10{sup 9} cycles. The fatigue life was found to increase with decreasing stress amplitude. The fracture surfaces and fracture profiles of selected specimens cycled until failure were examined. The purpose of the study was to determine the role of the microstructure on the fatigue crack nucleation and growth. Furthermore, the fatigue properties were discussed on the basis of microstructure and the presence of inclusions which are known as crack initiation sites. In AZ31 and AZ80 alloys only surface-induced fatigue cracks were observed. On the other hand, in the ZK60 alloy both surface- and interior-induced fatigue cracks were observed. Both mechanisms operate in the ZK60 also at a lifetime of around 10{sup 1}0 cycles. Interior-induced fatigue cracks were accompanied by clear fish-eye marks on the fracture surfaces of the ZK60 alloy. (orig.)

  8. The Fracture Mechanical Markov Chain Fatigue Model Compared with Empirical Data

    DEFF Research Database (Denmark)

    Gansted, L.; Brincker, Rune; Hansen, Lars Pilegaard

    The applicability of the FMF-model (Fracture Mechanical Markov Chain Fatigue Model) introduced in Gansted, L., R. Brincker and L. Pilegaard Hansen (1991) is tested by simulations and compared with empirical data. Two sets of data have been used, the Virkler data (aluminium alloy) and data...... established at the Laboratory of Structural Engineering at Aalborg University, the AUC-data, (mild steel). The model, which is based on the assumption, that the crack propagation process can be described by a discrete Space Markov theory, is applicable to constant as well as random loading. It is shown...

  9. Effect of stress ratio on the fatigue behaviour of glass/epoxy composite

    Science.gov (United States)

    Syayuthi, A. R. A.; Majid, M. S. Abdul; Ridzuan, M. J. M.; Basaruddin, K. S.; Peng, T. L.

    2017-10-01

    The effect of stress ratio on the fatigue behaviour of the GFRE composite has been investigated. The glass fibre reinforced epoxy (GFRE) composite plates were fabricated using vacuum infusion method. Static tensile was performed in accordance with the ASTM D5766 standard, and the cyclic test was conducted according to ASTM D3479 with three different stress ratio, R = 0, 0.5, -1. Static tensile tests were carried out to determine the ultimate strength of this composite. Subsequently, fatigue tests loads ranging from 30% to 90% of the ultimate load were applied to each specimen. The S–N curve of different stress ratio loading of fibreglass/epoxy composites was then established. The results show that the number of cycles to failure increases as the loading is decreased. The specimens for fatigue tests loads 30% at R = 0 and -1 recorded the highest number of cycles at 2 million cycles. The results obtained from this test indicated a significant life reduction for R = -1 compared with the tension-tension loading, with the life reduction for R = -1 being greatest. The fatigue behaviour of the GFRE composite materials is not only influenced by the percentage of fatigue tests load but with different of stress ratio.

  10. Effect of torsional loading on compressive fatigue behaviour of trabecular bone.

    Science.gov (United States)

    Fatihhi, S J; Rabiatul, A A R; Harun, M N; Kadir, Mohammed Rafiq Abdul; Kamarul, T; Syahrom, Ardiyansyah

    2016-02-01

    The present study reports the effects of combined torsional and compressive cyclic loading on trabecular bone in order to mimic true physiological conditions and thereby provides improved data that represents clinical and real life conditions. However, only compressive behaviour is evaluated in most previous studies of bone mechanics. From the monotonic evaluation, it is observed that lower stress is needed for the onset of microcrack in the sample under torsional loading, compared to the stress needed in compression. Trabecular bone samples were subjected to a combination of torsion and compression fatigue at different stress levels during which they were compared to compressive axial fatigue. The stress levels were determined by considering the monotonic strength at 25-50% for both compressive and shear stresses. Significant decrease in fatigue lifetime is observed in between samples of pure compression fatigue and those with superpositioned torsional loading (ptorsional stress level. In this case, the failure of the sample is said to be 'torsional dominant'. Fatigue behaviour of bovine trabecular bone begins with plastic deformation, followed by strain accumulation and modulus reduction. As the strain rate increases, more energy dissipates and the sample finally failed. Further, the analysis of fractograph revealed something on the trabeculae by bending in sample with superpositioned torsional loading. In conclusion, torsional loading decreases the quality of the trabecular properties in terms of stiffness, life and structural integrity. It is hoped that results from this study will improve the understanding of the behaviour of trabecular bone under combined fatigue and help to develop future assessments of trabecular failure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Fatigue and heat transfer behaviour of shot penned aluminium alloy for automobile applications

    Energy Technology Data Exchange (ETDEWEB)

    Nadkarni, V.S.; Sharma, M.C. [M.A.C.T., Bhopal (India). Dept. of Mech. Eng.

    2000-07-01

    In the present investigation glass beads and zirconium oxide shots were used as media to shot peening aluminium alloy specimens. Fatigue and boiling heat transfer behaviour of this alloy after shot peening was studied. Out of 0.2N and 0.4N peening intensities, 0.4N gave higher improvement on fatigue strength and boiling heat transfer. Fatigue of butt welded aluminium joints were also studied. Shot peening with zirconium oxide shots at 0.4N intensity was found to be more advantageous than glass beads. Welding reduces 19.4% fatigue strength compared to virgin samples, but shot peening could improve fatigue strength by 12% compared to welded samples. Effect of corrosive (3N Nacl) environment on fatigue strength was also studied. Zir shots were found to be economical. The commercial application of shot peening in automobiles to enhance boiling heat transfer was also studied. The heat transfer media then used was the coolant commonly used in car radiators. That was 95% ethylene glycol with some inhibitor to prevent corrosion. This was a mixture of water and glycol in 3:1 ratio. The optimum surface roughness was 6.2 {mu}m which gave optimum heat transfer at 90% improvement in boiling heat transfer compared to unpeened samples. (orig.)

  12. Effect of residual stress and surface roughness on the fatigue behaviour of aluminium matrix composites

    International Nuclear Information System (INIS)

    Smaga, M; Eifler, D

    2010-01-01

    In this investigation the fatigue properties of specimens manufactured with different turning parameters were investigated in stress-controlled constant amplitude tests at ambient temperature. The change of feed rate and depth of cut lead to a change in the near surface microstructure. Hence the fatigue properties were influenced significantly due to different surface roughness and surface residual stress resulting from the unequal turning processes. The cyclic deformation behaviour of AMC225xe is characterised by pronounced initial cyclic hardening. Continuous load increase tests allow a reliable estimation of the endurance limit of AMC225xe with one single specimen on the basis of cyclic deformation, temperature and electrical resistance data.

  13. Fatigue behaviour of 316 L stainless steel pipes containing flaws

    International Nuclear Information System (INIS)

    Bethmont, M.; Cheissoux, J.L.; Lebey, J.

    1981-01-01

    The main objective is to demonstrate that crack growth laws based on CT specimen testing are valid for piping products with realistic flaws under pressure and bending loads. The study is broken down into two phases: - crack growth experiments for various notch shapes in reduced scale piping (1/4) of reactor coolant piping at room temperature and at 285 0 C. - a numerical analysis to determine the K 1 stress intensity factor for tested notch shapes. Tests were carried out on piping with longitudinal and circumferential notches inside and outside. Fatigue crack growth rates are assessed through micrographic exams. The K 1 stress intensity factor was computed by finite element methods or the use of weight functions. (orig./GL)

  14. Creep-fatigue behaviour of the titanium alloy IMI 834 at 600 C

    International Nuclear Information System (INIS)

    Nowack, H.; Kordisch, T.

    1998-01-01

    In the present study the creep-fatigue behaviour of the titanium alloy IMI 834 at 600 C was investigated. A comparison of the crack initiation life behaviour and of the crack propagation as caused by different types of complex creep-fatigue cycles (with hold times into tension and/or into compression direction and with different loading rates into tension and/or into compression direction) showed, that a slow increase of the loadings into tension reduced the life and increased the crack velocity more than hold times at the maximum load. Furthermore, there existed environmental influences. On the basis of the experimental investigations the prediction capability of convenient crack initiation life prediction methods was evaluated. It turned out that the prediction capability of the strain range partitioning method could be improved if it was frequency modified. The prediction capability of the frequency modification method could also be improved, if mean stresses in the cycles were explicitely accounted for. In the short and long crack stage the propagation behaviour could be correlated well if the effective cyclic J-integral was used. This is of importance for damage tolerance considerations. Because the strains and the stresses at the crack tip are most important for the crack propagation behaviour, they were analysed on the basis of the finite element method. It was found that the strains and stresses differed for different types of creep-fatigue cycles. (orig.)

  15. Low cycle fatigue and creep fatigue behaviour of a 316L stainless steel

    International Nuclear Information System (INIS)

    Simon, S.; Fuentes, M.

    1993-01-01

    Application of deformation maps to the formation of damage under low cycle conditions has allowed a better understanding of the principles underlying empiric life prediction methods. This approach has proved to be particularly useful in the formulation of a modified version of the strain range partitioning method where the criterion proposed to divide the inelastic strain into its plastic and creep components has been substanciated by the introduction of a critical strain rate that marks the transition from a matrix deformation dominated regime to a grain boundary one. Development of this approach requires detailed and consistent material data. To this aim the low cycle mechanical response and structural stability through cycling of a 316L stainless steel has been investigated. Low cylce test, including hold periods at maximum tensile strain, were also conducted at 600 and 625 C. Use of the acquired data has been made to construct cyclic stress - strain and stress -relaxation curves of the material. Also its basic fatigue/fatigue equation has been obtained. (orig.) [de

  16. Standard guide for evaluating data acquisition systems used in cyclic fatigue and fracture mechanics testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1998-01-01

    1.1 This guide covers how to understand and minimize the errors associated with data acquisition in fatigue and fracture mechanics testing equipment. This guide is not intended to be used instead of certified traceable calibration or verification of data acquisition systems when such certification is required. It does not cover static load verification, for which the user is referred to the current revision of Practices E 4, or static extensometer verification, for which the user is referred to the current revision of Practice E 83. The user is also referred to Practice E 467. 1.2 The output of the fatigue and fracture mechanics data acquisition systems described in this guide is essentially a stream of digital data. Such digital data may be considered to be divided into two types- Basic Data, which are a sequence of digital samples of an equivalent analog waveform representing the output of transducers connected to the specimen under test, and Derived Data, which are digital values obtained from the Basic D...

  17. Relationship between microstructural evolution and low cycle fatigue behaviour at 5500C of alloy 800 grade 2

    International Nuclear Information System (INIS)

    Van Duysen, J.C.

    1989-01-01

    In this study, deformation modes and precipitations have been characterized in test pieces made of alloy 800, grade 2 (hyper-hardened state and age-conditioned for 3000 h at 550 0 C, used for steam generator tubes of the Super Phenix Reactor, after continuous fatigue and fatigue-relaxation tests in the oligocyclic range. This microstructural study has provided an interpretation of the fatigue behaviour of the material [fr

  18. Effects of the Electron Beam Welding Process on the Microstructure, Tensile, Fatigue and Fracture Properties of Nickel Alloy Nimonic 80A

    Science.gov (United States)

    Zhang, H.; Huang, Chongxiang; Guan, Zhongwei; Li, Jiukai; Liu, Yongjie; Chen, Ronghua; Wang, Qingyuan

    2018-01-01

    The purpose of this study was to evaluate rotary bending high-cycle fatigue properties and crack growth of Nimonic 80A-based metal and electron beam-welded joints. All the tests were performed at room temperature. Fracture surfaces under high-cycle fatigue and fatigue crack growth were observed by scanning electron microscopy. Microstructure, hardness and tensile properties were also evaluated in order to understand the effects on the fatigue results obtained. It was found that the tensile properties, hardness and high-cycle fatigue properties of the welded joint are lower than the base metal. The fracture surface of the high-cycle fatigue shows that fatigue crack initiated from the surface under the high stress amplitude and from the subsurface under the low stress amplitude. The effect of the welding process on the statistical fatigue data was studied with a special focus on probabilistic life prediction and probabilistic lifetime limits. The fatigue crack growth rate versus stress intensity factor range data were obtained from the fatigue crack growth tests. From the results, it was evident that the fatigue crack growth rates of the welded are higher than the base metal. The mechanisms and fracture modes of fatigue crack growth of welded specimens were found to be related to the stress intensity factor range ΔK. In addition, the effective fatigue crack propagation thresholds and mismatch of welded joints were described and discussed.

  19. Fatigue crack behaviour: comparing three-point bend test and wedge splitting test data on vibrated concrete using Paris' law

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Thienpont, T.; De Corte, W.

    2017-01-01

    Roč. 11, č. 39 (2017), s. 110-117 ISSN 1971-8993 R&D Projects: GA MŠk LM2015069 Institutional support: RVO:68081723 Keywords : Fatigue crack behaviour * Tree-point bending test * Wedge splitting test * Self-compacting concrete Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  20. Cognitive behavioural therapy for reducing fatigue in post-polio syndrome and in facioscapulohumeral dystrophy: A comparison

    NARCIS (Netherlands)

    Koopman, F.S.; Brehm, M.A.; Beelen, A.; Voet, N.; Bleijenberg, G.; Geurts, A.C.; Nollet, F.

    2017-01-01

    BACKGROUND: Cognitive behavioural therapy does not reduce fatigue in post-polio syndrome, but is effective in facioscapulohumeral dystrophy. This difference in efficacy might be explained by a different role of cognitions in these conditions. OBJECTIVE: To compare fatigue-related cognitions between

  1. Cognitive behavioural therapy for reducing fatigue in post-polio syndrome and in facioscapulohumeral dystrophy: A comparison

    NARCIS (Netherlands)

    Koopman, Fieke S.; Brehm, Merel A.; Beelen, Anita; Voet, Nicole; Bleijenberg, Gijs; Geurts, Alexander; Nollet, Frans

    2017-01-01

    Cognitive behavioural therapy does not reduce fatigue in post-polio syndrome, but is effective in facioscapulohumeral dystrophy. This difference in efficacy might be explained by a different role of cognitions in these conditions. To compare fatigue-related cognitions between patients with

  2. Tensile and fatigue behaviour of self-piercing rivets of CFRP to aluminium for automotive application

    Science.gov (United States)

    Kang, J.; Rao, H.; Zhang, R.; Avery, K.; Su, X.

    2016-07-01

    In this study, the tensile and fatigue behaviour of self-piercing rivets (SPRs) in carbon fibre reinforced plastic (CFRP) to aluminium 6111 T82 alloys were evaluated. An average maximum lap-shear tensile load capacity of 3858 N was achieved, which is comparable to metal-to-metal SPR lap-shear joints. The CFRP-Al SPRs failed in lap-shear tension due to pull-out of the rivet head from the CFRP upper sheet. The CFRP-Al SPR lap- shear specimens exhibited superior fatigue life compared to previously studied aluminium-to- aluminium SPR lap-shear joints. The SPR lap-shear joints under fatigue loads failed predominantly due to kinked crack growth along the width of the bottom aluminium sheet. The fatigue cracks initiated in the plastically deformed region of the aluminium sheet close to the rivet shank in the rivet-sheet interlock region. Scatter in fatigue life and failure modes was observed in SPR lap-shear specimens tested close to maximum tensile load.

  3. High speed rails. Fatigue behaviour; Carriles para alta velocidad. Comportamiento en fatiga

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-01

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

  4. 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

  5. Analysis of Fatigue and Wear Behaviour in Ultrafine Grained Connecting Rods

    Directory of Open Access Journals (Sweden)

    Rodrigo Luri

    2017-07-01

    Full Text Available Over the last few years there has been an increasing interest in the study and development of processes that make it possible to obtain ultra-fine grained materials. Although there exists a large number of published works related to the improvement of the mechanical properties in these materials, there are only a few studies that analyse their in-service behaviour (fatigue and wear. In order to bridge the gap, in this present work, the fatigue and wear results obtained for connecting rods manufactured by using two different aluminium alloys (AA5754 and AA5083 previously deformed by severe plastic deformation (SPD, using Equal Channel Angular Pressing (ECAP, in order to obtain the ultrafine grain size in the processed materials are shown. For both aluminium alloys, two initial states were studied: annealed and ECAPed. The connecting rods were manufactured from the previously processed materials by using isothermal forging. Fatigue and wear experiments were carried out in order to characterize the in-service behaviour of the components. A comparative study of the results was made for both initial states of the materials. Furthermore, Finite Element Modelling (FEM simulations were used in order to compare experimental results with those obtained from simulations. In addition, dimensional wear coefficients were found for each of the aluminium alloys and initial deformation states. This research work aims to progress the knowledge of the behaviour of components manufactured from ultrafine grain materials.

  6. Microstructural effects on constitutive and fatigue fracture behavior of TinSilverCopper solder

    Science.gov (United States)

    Tucker, Jonathon P.

    As microelectronic package construction becomes more diverse and complex, the need for accurate, geometry-independent material constitutive and failure models increases. Evaluations of packages based on accelerated environmental tests (such as accelerated thermal cycling or power cycling) only provide package-dependent reliability information. In addition, extrapolations of such test data to life predictions under field conditions are often empirical. Besides geometry, accelerated environmental test data must account for microstructural factors such as alloy composition or isothermal aging condition, resulting in expensive experimental variation. In this work, displacement-controlled, creep, and fatigue lap shear tests are conducted on specially designed SnAgCu test specimens with microstructures representative to those found in commercial microelectronic packages. The data are used to develop constitutive and fatigue fracture material models capable of describing deformation and fracture behavior for the relevant temperature and strain rate ranges. Furthermore, insight is provided into the microstructural variation of solder joints and the subsequent effect on material behavior. These models are appropriate for application to packages of any geometrical construction. The first focus of the thesis is on Pb-mixed SnAgCu solder alloys. During the transition from Pb-containing solders to Pb-free solders, joints composed of a mixture of SnPb and SnAgCu often result from either mixed assemblies or rework. Three alloys of 1, 5 and 20 weight percent Pb were selected so as to represent reasonable ranges of Pb contamination expected from different 63Sn37Pb components mixed with Sn3.0Ag0.5Cu. Displacement-controlled (constant strain rate) and creep tests were performed at temperatures of 25°C, 75°C, and 125°C using a double lap shear test setup that ensures a nearly homogeneous state of plastic strain at the joint interface. Rate-dependent constitutive models for Pb

  7. A study of microstructure, quasi-static response, fatigue, deformation and fracture behavior of high strength alloy steels

    Science.gov (United States)

    Kannan, Manigandan

    The history of steel dates back to the 17th century and has been instrumental in the betterment of every aspect of our lives ever since, from the pin that holds the paper together to the Automobile that takes us to our destination steel touches everyone every day. Path breaking improvements in manufacturing techniques, access to advanced machinery and understanding of factors like heat treatment, corrosion resistance have aided in the advancement in the properties of steel in the last few years. In this dissertation document, the results of a study aimed at the influence of alloy chemistry, processing and influence of the quasi static and fatigue behavior of seven alloy steels is discussed. The microstructure of the as-received steel was examined and characterized for the nature and morphology of the grains and the presence of other intrinsic features in the microstructure. The tensile, cyclic fatigue and bending fatigue tests were done on a fully automated closed-loop servo-hydraulic test machine at room temperature. The failed samples of high strength steels were examined in a scanning electron microscope for understanding the fracture behavior, especially the nature of loading be it quasi static, cyclic fatigue or bending fatigue . The quasi static and cyclic fatigue fracture behavior of the steels examined coupled with various factors contributing to failure are briefly discussed in light of the conjoint and mutually interactive influences of intrinsic microstructural effects, nature of loading, and stress (load)-deformation-microstructural interactions.

  8. Fracture Mechanics

    International Nuclear Information System (INIS)

    Jang, Dong Il; Jeong, Gyeong Seop; Han, Min Gu

    1992-08-01

    This book introduces basic theory and analytical solution of fracture mechanics, linear fracture mechanics, non-linear fracture mechanics, dynamic fracture mechanics, environmental fracture and fatigue fracture, application on design fracture mechanics, application on analysis of structural safety, engineering approach method on fracture mechanics, stochastic fracture mechanics, numerical analysis code and fracture toughness test and fracture toughness data. It gives descriptions of fracture mechanics to theory and analysis from application of engineering.

  9. The fracture behaviour and its predicion based on the local approach

    Czech Academy of Sciences Publication Activity Database

    Kozák, Vladislav; Dlouhý, Ivo; Holzmann, Miloslav

    č. 212 (2002), s. 67-73 ISSN 0029-5493 R&D Projects: GA ČR GA101/00/0170 Institutional research plan: CEZ:AV0Z2041904 Keywords : container for spent nuclear fuel * fracture toughness -charpy pre cracked specimen Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.386, year: 2002

  10. Fatigue Fracture of the Calcaneus: From Early Diagnosis to Treatment: A Case Report of a Triathlon Athlete.

    Science.gov (United States)

    Serrano, Simão; Figueiredo, Pedro; Páscoa Pinheiro, João

    2016-06-01

    Stress fractures are frequently underdiagnosed and undertreated despite being common in sports. Early diagnosis is crucial; therefore, a high index of clinical suspicion is required. Complementary examinations are essential for diagnosis and follow-up. The authors report a clinical case of a young adult triathlon athlete referring mechanical pain in the rear left foot, with 2 weeks' progression. An earlier increase in daily training intensity was recorded. Complementary examinations confirmed a calcaneal fatigue fracture. Immobilization and no weight bearing were introduced for an initial period of 4 weeks, and the rehabilitation process was started. Progressive weight bearing was introduced between fourth and eighth weeks. Sports activity started at the 12th week. Boundaries to sports activity were eliminated by the 24th week, without pain or functional limitation. Repetitive overload to the heel and intense axial weight bearing in association to repetitive concentric/eccentric gastrocnemius contraction are related to calcaneal stress fracture, the second most common stress fracture in the foot. Calcaneal stress fractures can be adequately treated with activity modification, without casting or surgical intervention. When in the presence of bilateral stress fractures, metabolic and nutritional issues must be considered. The case report highlights the importance of sports medicine examination for detecting intrinsic and extrinsic fatigue fracture risk factors.

  11. The mechanical behaviour of hydraulic fractured, possibly saturated materials

    NARCIS (Netherlands)

    Visser, J.H.M.; Mier, J.G.M. van

    1998-01-01

    The influence of a fluid pressure load on the extensile fracturing of mortar and sandstone has been investigated. A fluid pressure in the (initiating) fracture stimulates both fracture initiation and propagation and may be as effective as a directly applied uniaxial tensile stress. The efficiency of

  12. Cognitive behavioural therapy for reducing fatigue in post-polio syndrome and in facioscapulohumeral dystrophy: A comparison.

    Science.gov (United States)

    Koopman, Fieke S; Brehm, Merel A; Beelen, Anita; Voet, Nicole; Bleijenberg, Gijs; Geurts, Alexander; Nollet, Frans

    2017-07-07

    Cognitive behavioural therapy does not reduce fatigue in post-polio syndrome, but is effective in facioscapulohumeral dystrophy. This difference in efficacy might be explained by a different role of cognitions in these conditions. To compare fatigue-related cognitions between patients with post-polio syndrome and facio-scapulohumeral dystrophy. Patients with post-polio syndrome (n = 21) and facioscapulohumeral dystrophy (n = 24) allocated to a cognitive behavioural therapy intervention in 2 identical trials. Assessed cognitions included: sense of control over fatigue; catastrophizing; acceptance; focusing on fatigue; and perceived social support. Group differences in cognitions (independent t-tests or Mann-Whitney U tests) and group differences in the association of cognitions with fatigue (linear regression models) were studied. No differences in cognitions were found between the 2 groups (p > 0.18). Furthermore, there were no cognition-by-group interaction effects, except for "perceived social support", for which a different association with fatigue was found between the 2 groups (p = 0.01). However, univariate models revealed no associations per group. Fatigue-related cognitions in severely fatigued patients with post-polio syndrome are not clearly different from that in facioscapulohumeral dystrophy. Thus, the lack of efficacy of cognitive behavioural therapy in post-polio syndrome cannot be attributed to unique cognitive characteristics of this population.

  13. Cognitive behavioural therapy for reducing fatigue in post-polio syndrome and in facioscapulohumeral dystrophy: A comparison

    Directory of Open Access Journals (Sweden)

    Fieke S. Koopman

    2017-06-01

    Full Text Available Background: Cognitive behavioural therapy does not reduce fatigue in post-polio syndrome, but is effective in facioscapulohumeral dystrophy. This difference in efficacy might be explained by a different role of cognitions in these conditions. Objective: To compare fatigue-related cognitions between patients with post-polio syndrome and facio-scapulohumeral dystrophy. Subjects: Patients with post-polio syndrome (n = 21 and facioscapulohumeral dystrophy (n = 24 allocated to a cognitive behavioural therapy intervention in 2 identical trials. Methods: Assessed cognitions included: sense of control over fatigue; catastrophizing; acceptance; focusing on fatigue; and perceived social support. Group differences in cognitions (independent t-tests or Mann–Whitney U tests and group differences in the association of cognitions with fatigue (linear regression models were studied. Results: No differences in cognitions were found between the 2 groups (p > 0.18. Furthermore, there were no cognition-by-group interaction effects, except for “perceived social support”, for which a different association with fatigue was found between the 2 groups (p = 0.01. However, univariate models revealed no associations per group. Conclusion: Fatigue-related cognitions in severely fatigued patients with post-polio syndrome are not clearly different from that in facioscapulohumeral dystrophy. Thus, the lack of efficacy of cognitive behavioural therapy in post-polio syndrome cannot be attributed to unique cognitive characteristics of this population.

  14. Influence of Cooling Holes Distribution on High Cycle Fatigue Fracture Behavior of DD6 Single Crystal Superalloy

    Directory of Open Access Journals (Sweden)

    HU Chun-yan

    2017-04-01

    Full Text Available The modeling air-cooled turbine blades specimens of DD6 single crystal superalloy with different distributions of cooling film holes were used to study the high cycle fatigue properties at room temperature. The SEM fracture observation was carried out. The results indicate that the cooling holes have significant effects on the high fatigue life of DD6 single crystal superalloy. The average life of non-hole specimens is four times of that of the three-row holes specimens under the same testing conditions. However, the distribution of cooling film holes has relatively less influence on fatigue life. The fracture of the specimens with non-hole is linear source by SEM analysis, but the cracks are found around the cooling film holes and the fracture of the specimens with single row to three rows is a typical multi-source rupture, and cracks all initiate from near film holes. According to fracture and crystallography theoretical conjecture, the cracks propagate along the {001} slip plane for non-hole, single-row holes and the middle location of the multi-row holes specimens. However, the cracks around the holes grow along the {111} slip plane for upper and lower holes of the specimens with multi-row holes. In addition, the distribution of stress field along cooling holes of four different specimens was analysed by FEM method. The results show that the fracture location and morphology of specimens are consistent well with numerical simulation analysis.

  15. Fatigue behaviour FEM modeling of deep groove ball bearing mounted in automotive alternator submitted to variable loading

    Directory of Open Access Journals (Sweden)

    Azianou Ayao. E.

    2014-06-01

    Full Text Available Ball bearings subsurface materials are subjected to rolling contact fatigue with multiaxial stress state during loading cycle. The complex operating conditions of automotive bearings are different from classic operating conditions their fatigue crack initiation predicted by standards can be seen underestimated. This work presents a numerical approach of ball bearings to evaluate its fatigue behaviour in order to predict the life. A preliminary study has been done to evaluate the load distribution in the bearings. The results are integrated in a numerical dynamic model to study the bearing material rolling fatigue behaviour in constant and variable loading cases. By using fatigue criteria and damage laws, the analysis of stress state in bearing material leads to life prediction or the number of cycles before crack initiations. These results are compared to current standard methods used for ball bearing life prediction.

  16. Cognitive behaviour therapy for chronic fatigue syndrome: Differences in treatment outcome between a tertiary treatment centre in the United Kingdom and the Netherlands

    NARCIS (Netherlands)

    Worm-Smeitink, M.; Nikolaus, S.; Goldsmith, K.; Wiborg, J.; Ali, S.; Knoop, H.; Chalder, T.

    2016-01-01

    Cognitive behaviour therapy (CBT) reduces fatigue and disability in chronic fatigue syndrome (CFS). However, outcomes vary between studies, possibly because of differences in patient characteristics, treatment protocols, diagnostic criteria and outcome measures. The objective was to compare outcomes

  17. Effects of mechanical heterogeneity on the tensile and fatigue behaviours in a laser-arc hybrid welded aluminium alloy joint

    International Nuclear Information System (INIS)

    He, Chao; Huang, Chongxiang; Liu, Yongjie; Li, Jiukai; Wang, Qingyuan

    2015-01-01

    Highlights: • Full field strain evolution was characterized using DIC method in fatigue test. • The differences of fatigue failure mechanism between HAZ and FZ were discussed. • Porosity in FZ significantly influenced high cycle fatigue behaviours of the weld. - Abstract: The effects of mechanical heterogeneity on the tensile and high cycle fatigue (10 4 –10 7 cycles) properties were investigated for laser-arc hybrid welded aluminium alloy joints. Tensile–tensile cyclic loading with a stress ratio of 0.1 was applied in a direction perpendicular to the weld direction for up to 10 7 cycles. The local mechanical properties in the tensile test and the accumulated plastic strain in the fatigue test throughout the weld’s different regions were characterized using a digital image correlation technique. The tensile results indicated heterogeneous tensile properties throughout the different regions of the aluminium welded joint, and the heat affected zone was the weakest region in which the strain localized. In the fatigue test, the accumulated plastic strain evolutions in different subzones of the weld were analyzed, and slip bands could be clearly observed in the heat affected zone. A transition of fatigue failure locations from the heat affected zone caused by accumulated plastic strain to the fusion zone induced by fatigue crack at pores could be observed under different cyclic stress levels. The welding porosity in the fusion zone significantly influences the high cycle fatigue behaviour

  18. Stress fracture healing: fatigue loading of the rat ulna induces upregulation in expression of osteogenic and angiogenic genes that mimic the intramembranous portion of fracture repair.

    Science.gov (United States)

    Wohl, Gregory R; Towler, Dwight A; Silva, Matthew J

    2009-02-01

    Woven bone is formed in response to fatigue-induced stress fractures and is associated with increased local angiogenesis. The molecular mechanisms that regulate this woven bone formation are unknown. Our objective was to measure the temporal and spatial expression of osteo- and angiogenic genes in woven bone formation in response to increasing levels of fatigue-induced damage. We used the rat forelimb compression model to produce four discrete levels of fatigue damage in the right ulna of 115 male Fischer rats. Rats were killed at 0 (1 h), 1, 3 and 7 days after loading. Using qRT-PCR, we quantified gene expression associated with osteogenesis (BMP2, Msx2, Runx2, Osx, BSP, Osc), cell proliferation (Hist4), and angiogenesis (VEGF, PECAM-1) from the central half of the ulna. The spatial distribution of BMP2, BSP and PCNA was assessed by immunohistochemistry or in situ hybridization in transverse histological sections 1, 4, and 7 mm distal to the ulnar mid-diaphysis. One hour after loading, BMP2 was significantly upregulated in neurovascular structures in the medial ulnar periosteum. Expression of angiogenic markers (VEGF, PECAM-1) increased significantly between Day 0 and 1 and, as with BMP2 expression, remained upregulated through Day 7. While Osx and BSP were upregulated on Day 1, the other osteogenic genes (Msx2, Runx2, Osx, BSP and Osc) were induced on Day 3 in association with the initiation of periosteal woven bone formation and continued through Day 7. The magnitude of osteogenic gene expression, particularly matrix genes (BSP, Osc) was significantly proportional the level of fatigue damage. The woven bone response to fatigue injury is remarkably similar to the "intramembranous" portion of fracture repair - rapid formation of periosteal woven bone characterized by early BMP2 expression, cell proliferation, and upregulation of osteogenic genes. We speculate that woven bone repair of fatigue damage may be an abbreviated fracture response without the requirement

  19. Influence of microstructural parameters on the deformation and failure behaviour of the ODS alloy PM 2000 under creep and creep-fatigue loading

    International Nuclear Information System (INIS)

    Bothe, K.; Kussmaul, K.; Maile, K.

    1999-01-01

    The influence of grain size, manufacturing type and specimen direction (anisotropy) with respect to deformation and failure behaviour under creep, fatigue and creep-fatigue load was investigated. Thus, a basis for the correlation between microstructure and mechanical behaviour has been established. The specific damage and failure behaviour could be explained by means of the different microstructures observed. (orig.)

  20. Fatigue-creep of martensitic steels containing 9-12% Cr: behaviour and damage

    International Nuclear Information System (INIS)

    Fournier, B.

    2007-09-01

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

  1. Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Gheorghe Hutiu

    2018-02-01

    fatigue fracture of metals, and we demonstrate that OCT is able to replace SEM for such investigations as well.

  2. Behaviour of E-glass fibre reinforced vinylester resin composites ...

    Indian Academy of Sciences (India)

    Unknown

    (S–N) behaviour, having a progressive endurance below the threshold single cycle impact fracture stress with decreasing applied stress has been demonstrated. Fractographic analysis revealed fracture by primary debonding having fibre breakage ... fatigue life and stiffness reduction during fatigue loading. (Talreja 1985 ...

  3. Fatigue processes in thermoplastic fibres; Les mecanismes de fatigue dans les fibres thermoplastiques

    Energy Technology Data Exchange (ETDEWEB)

    Herrera Ramirez, J.M.

    2004-09-15

    The present study examines and compares the behaviour of the two types of PA66 fibres and two types of PET fibres under fatigue loading up to failure, and the correlation between the fibres (nano)structures and their structural heterogeneities, with fatigue lifetimes. Several techniques have been used to analyze the materials, such as scanning electron microscopy (SEM), microanalysis (EDS), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and micro-Raman spectroscopy. A meticulous analysis by scanning electron microscopy of the fracture morphology of fibres broken in tension and in fatigue, as well as a study of the fatigue life, were undertaken. The fatigue process occurs when the cyclic load amplitude is sufficiently large, however a condition for fatigue failure is that the minimum load each cycle must be lower than a threshold stress level. Failure under fatigue conditions leads to distinctive fracture morphologies which are very different from those seen after tensile or creep failure and this allows easy identification of the fatigue process. The fibres have been analyzed in the as received state and after fatigue failure in order to observe the microstructural changes resulting from the fatigue loading. The results will be compared with those obtained for fibres loaded under conditions where the fatigue process was hindered. The role of the microstructure of the fibres in determining fatigue will be discussed in this work and the possibility of improving their resistance to fatigue or eliminating the fatigue process will be discussed. (author)

  4. Corrosion fatigue behaviour of aluminium 5083-H111 welded using gas metal arc welding method

    CSIR Research Space (South Africa)

    Mutombo, K

    2011-12-01

    Full Text Available to the requirements of ASTM standards G31 [24] and G46 [25]. The 3.5% NaCl simulated sea water was prepared by dissolving 3.5 ? 0.1 parts by weight of Corrosion Fatigue Behaviour of Aluminium 5083-H111 Welded Using Gas Metal Arc Welding Method 193 NaCl in 96..., dissolve in some chemical solutions, such as strong acids or alkaline solutions. Damage to this passive layer in chloride-containing environments (such as sea water or NaCl solutions), may result in localised corrosive attack such as pitting corrosion...

  5. Creep-fatigue behaviour of aluminum alloy-based metal matrix composite

    International Nuclear Information System (INIS)

    Barbera, Daniele; Chen, Haofeng; Liu, Yinghua

    2016-01-01

    Metal Matrix Composite (MMC) represents a valuable option as structural material for different type of structures and components. Despite this they struggle to become widely adopted due to expensive manufacturing process and complex microstructural behaviour. When subjected to cyclic load conditions the structural response of MMC is not trivial, and becomes even more difficult when high temperature load is involved. Different failure mechanisms would happen and they are originated by the different material properties between the fibre and surrounding matrix. Among all, the mismatch of thermal expansion coefficient is recognized to be the dominant one. The significantly differing coefficients of thermal expansion between ceramic and metal give rise to micro thermal stresses, which enhance the initiation of matrix micro cracks. Their performance under varying load and high temperature is complex, and hence it is difficult to have a clear understanding of the structural responses, especially when fatigue and creep damages become the main failures of MMCs. To improve current understanding of the relationship between creep fatigue interaction of MMCs, the history of thermal and mechanical loading, and the creep dwell period, a highly accurate but robust direct simulation technique on the basis of the Linear Matching Method (LMM) framework has been proposed in this paper, and been applied to model the fatigue and creep behaviour of MMCs. A homogenised FE model is considered in all analyses, which consist of continuous silicon carbide fibres embedded in a square 2024T3 aluminium alloy matrix array. Various factors that affect creep and fatigue behaviours of composites are analysed and discussed, including effects of the applied load level, dwell period and temperature on the MMC's performance. The effects of reversed plasticity on stress relaxation and creep deformation of MMC are investigated, and the behaviours of cyclically enhanced creep and elastic follow-up are

  6. Effect of Process Parameters on Fatigue and Fracture Behavior of Al-Cu-Mg Alloy after Creep Aging

    Directory of Open Access Journals (Sweden)

    Lihua Zhan

    2018-04-01

    Full Text Available A set of creep aging tests at different aging temperatures and stress levels were carried out for Al-Cu-Mg alloy, and the effects of creep aging on strength and fatigue fracture behavior were studied through tensile tests and fatigue crack propagation tests. The microstructures were further analyzed by using scanning electron microscopy (SEM and transmission electron microscopy (TEM. The results show that temperature and stress can obviously affect the creep behavior, mechanical properties, and fatigue life of Al-Cu-Mg alloy. As the aging temperature increases, the fatigue life of alloy first increases, and then decreases. The microstructure also displays a transition from the Guinier-Preston-Bagaryatsky (GPB zones to the precipitation of S phase in the grain interior. However, the precipitation phases grow up and become coarse at excessive temperatures. Increasing stress can narrow the precipitation-free zone (PFZ at the grain boundary and improve the fatigue life, but overhigh stress can produce the opposite result. In summary, the fatigue life of Al-Cu-Mg alloy can be improved by fine-dispersive precipitation phases and a narrow PFZ in a suitable creep aging process.

  7. Low cycle fatigue behaviour of alloy 800H at 600 C - effect of grain size and γ'-precipitate dispersion

    International Nuclear Information System (INIS)

    Nilsson, J.-O.; Thorvaldsson, T.

    1985-01-01

    High strain fatigue properties of Alloy 800H have been investigated at 600 C in strain control. The behaviour of solution heat treated material was compared with that of material aged at 550 and 600 C. It was found that both aging treatments extended the fatigue life significantly, the longest fatigue life being observed for fine-grained material aged at 550 C. The results are explicable in terms of partially reversible plastic flow occurring when the γ' particles are by-passed by shearing. (author)

  8. Effect of prior corrosion state on the fatigue small cracking behaviour of 6151-T6 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li Xudong [Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084 (China); Naval Aeronautical Engineering Academy Qingdao Branch, Qingdao 266000 (China); Wang Xishu, E-mail: xshwang@tsinghua.edu.cn [Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084 (China); Ren Huaihui; Chen Yinlong [Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084 (China); Mu Zhitao [Naval Aeronautical Engineering Academy Qingdao Branch, Qingdao 266000 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Relationship of corrosion pit and fatigue crack is established based on SEM. Black-Right-Pointing-Pointer An equivalent relationship between accelerated and natural corrosion is build up. Black-Right-Pointing-Pointer Prior corrosion damage is crucial to the subsequent fatigue cracking behaviour. Black-Right-Pointing-Pointer The prior corrosion fatigue crack growth rate is expressed by the term of k{sigma}{sub max}{sup n}a. Black-Right-Pointing-Pointer Corrosion states such as SC15, are defined based on corrosion spectrum. - Abstract: The purpose of this paper was to estimate the reliable effect of prior corrosion state on fatigue micro crack initiation and early stage propagation behaviour of aluminum alloy based on scanning electron microscopy (SEM) in situ observation. Results indicated that multi-cracks initiation occurred almost at the corrosion pits and the early stage of fatigue micro crack propagation behaviour can be described by K{sub I}/K{sub II}-mixed mode. The importance of crack-face interaction via crack-face corrosion pits interlocking/bridging was emphasised in the mixed mode. The fatigue crack growth rate in the corrosion states can be empirically expressed by the term of k{sigma}{sub max}{sup n}a.

  9. Effect of prior corrosion state on the fatigue small cracking behaviour of 6151-T6 aluminum alloy

    International Nuclear Information System (INIS)

    Li Xudong; Wang Xishu; Ren Huaihui; Chen Yinlong; Mu Zhitao

    2012-01-01

    Highlights: ► Relationship of corrosion pit and fatigue crack is established based on SEM. ► An equivalent relationship between accelerated and natural corrosion is build up. ► Prior corrosion damage is crucial to the subsequent fatigue cracking behaviour. ► The prior corrosion fatigue crack growth rate is expressed by the term of kσ max n a. ► Corrosion states such as SC15, are defined based on corrosion spectrum. - Abstract: The purpose of this paper was to estimate the reliable effect of prior corrosion state on fatigue micro crack initiation and early stage propagation behaviour of aluminum alloy based on scanning electron microscopy (SEM) in situ observation. Results indicated that multi-cracks initiation occurred almost at the corrosion pits and the early stage of fatigue micro crack propagation behaviour can be described by K I /K II -mixed mode. The importance of crack-face interaction via crack-face corrosion pits interlocking/bridging was emphasised in the mixed mode. The fatigue crack growth rate in the corrosion states can be empirically expressed by the term of kσ max n a.

  10. Correlation of nodular austempered ductile iron (ADI) microstructural parameters and fatigue properties using an approach based on fracture mechanics

    International Nuclear Information System (INIS)

    Dias, Jose Felipe; Fonseca, Vinicius Rizzuti; Godefroid, Leonardo Barbosa; Ribeiro, Gabriel de Oliveira

    2010-01-01

    An investigation has been accomplished to check the effect of temperature and austempering time on austempered ductile iron (ADI) properties by means of fracture toughness (K C ) and fatigue threshold (∆K th ) tests. The correlation of ADI microstructural parameters and ADI two mechanical parameters: KC and Kth, is evaluated. Three sets of samples have ben extracted from ADI casting Y blocks produced in industrial conditions.and austenitized at 900°C for 1.5 hour. The austempering process has been performed in the following ways: the first set was austenitized at 300 deg C for 4 hours, the second set at 360°C for 1.5 hour and the third at 360°C for 0.6 hour. These distinct austempering processes have been adopted in order to obtain distinct microstructures containing austenite with two different carbon rates and two ferritic cell sizes. The materials have been characterized by means of optical and electronic microscopy, X-ray diffraction and mechanical tests. All materials have presented equivalent fatigue crack propagation rates, fracture toughness in the range between 94 and 128 MPa·m 1/2 and ∆K th in the range between 5,7 and 6,4 MPa·m 1/2 . The experimental results have confirmed the effect of microstructural properties (austenitic volumetric rate, austenitic carbon rate, ferritic cell size, total matrix carbon content) on fracture toughness (K C ) and fatigue threshold (∆K th ). Further, it was found that following parameters: fracture toughness (K C ), fatigue threshold ((∆K th ) and impact strength are correlated with the total matrix carbon content and ferritic cell size. (author)

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

    Directory of Open Access Journals (Sweden)

    Norio Maruyama, Sachiko Hiromoto, Eiji Akiyama and Morihiko Nakamura

    2013-01-01

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

  12. Fracture behaviour of alumina and zirconia thin layered laminate

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Hadraba, Hynek; Slabáková, L.; Drdlík, D.; Dlouhý, Ivo

    2012-01-01

    Roč. 32, č. 9 (2012), s. 2057-2061 ISSN 0955-2219 R&D Projects: GA ČR GD106/09/H035 Institutional research plan: CEZ:AV0Z20410507 Institutional support: RVO:68081723 Keywords : Ceramics * Laminates * Crack propagation Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.360, year: 2012

  13. A new method for the experimental study of fatigue behaviour of thermoplastic materials

    Directory of Open Access Journals (Sweden)

    M. Sanità

    2008-10-01

    Full Text Available Nowadays most industrial realities undergo a strong push to improve cost-effectiveness, productivity and quality of manufactured products. In particular we focussed our attention in the area of design of plastic structural components, including both optimization of existing structures and design of new ones. In this case, but the following considerations have a more general value, these needs could be translated into demanding requirements of cost-effectiveness, weight reduction, reduced time-to-market with guarantee reliability. From a material perspective this means demanding mechanical performances, attention to safety margins and need of a better control of key design parameters. To obtain these results, we need to develop a new approach and effective tools in the design of plastic materials and components aimed at tailoring part behaviour to endurance and performance requirements.The target of the project is to find effective tools for predicting life endurance and damage evolution of plastic materials and components under mechanical/thermal service loading, in order to support the development of new material formulations and the design and optimization of structural components. In a particular way, we focussed our work in the characterization and modellization of materials durability and damage mechanisms.One of the main problems related to materials durability is due to fatigue failure. Fatigue process is a progressive weakening of a component with increasing time under load such that loads to be supported satisfactorily for short duration produce failure after long durations [1, 2, 3]. Fatigue failure should not be thought only as the breaking of the specimen into two separated pieces, but as a progressive material damage accumulation [2]. Material damage during fatigue loading manifests as progressive reduction of stiffness and as creep [5].As standard fatigue testing are expensive in terms of money and time, it is essential to develop

  14. Effect of aging time and aging temperature on fatigue and fracture behavior of 6063 aluminum alloy under seawater influence

    International Nuclear Information System (INIS)

    Siddiqui, R.A.; Abdul-Wahab, S.A.; Pervez, T.

    2008-01-01

    This paper describes experimentally the effect of seawater corrosion, aging time, and aging temperature on the fatigue resistance property of 6063 aluminum alloy. The 6063 aluminum alloy that was used for the study was heat treated and soaked in seawater for different intervals of time between 2 and 30 weeks. It was found that the maximum fatigue resistance property in the 6063 aluminum alloy was observed when aged between 7 and 9 h and heat treated at temperatures between 160 o C and 200 o C. Generally at constant load, the results indicated that the number of cycles to fail the 6063 aluminum alloy decreased with increasing the soaking time in seawater. Moreover, fracture surfaces were considered and studied under a scanning electron microscope (SEM). The results showed that the brittle fracture pattern tended to occur with the increase in aging time and temperature. The fatigue striations were observed very clearly at low and peak aging temperature. The increase in the fatigue resistance property with aging time was linked with the vacancies assisted diffusion mechanism and also by the hindering of dislocation movement by impure atoms

  15. A new methodology for automating acoustic emission detection of metallic fatigue fractures in highly demanding aerospace environments: An overview

    Science.gov (United States)

    Holford, Karen M.; Eaton, Mark J.; Hensman, James J.; Pullin, Rhys; Evans, Sam L.; Dervilis, Nikolaos; Worden, Keith

    2017-04-01

    The acoustic emission (AE) phenomenon has many attributes that make it desirable as a structural health monitoring or non-destructive testing technique, including the capability to continuously and globally monitor large structures using a sparse sensor array and with no dependency on defect size. However, AE monitoring is yet to fulfil its true potential, due mainly to limitations in location accuracy and signal characterisation that often arise in complex structures with high levels of background noise. Furthermore, the technique has been criticised for a lack of quantitative results and the large amount of operator interpretation required during data analysis. This paper begins by introducing the challenges faced in developing an AE based structural health monitoring system and then gives a review of previous progress made in addresing these challenges. Subsequently an overview of a novel methodology for automatic detection of fatigue fractures in complex geometries and noisy environments is presented, which combines a number of signal processing techniques to address the current limitations of AE monitoring. The technique was developed for monitoring metallic landing gear components during pre-flight certification testing and results are presented from a full-scale steel landing gear component undergoing fatigue loading. Fracture onset was successfully identify automatically at 49,000 fatigue cycles prior to final failure (validated by the use of dye penetrant inspection) and the fracture position was located to within 10 mm of the actual location.

  16. A computer-controlled automated test system for fatigue and fracture testing

    International Nuclear Information System (INIS)

    Nanstad, R.K.; Alexander, D.J.; Swain, R.L.; Hutton, J.T.; Thomas, D.L.

    1989-01-01

    A computer-controlled system consisting of a servohydraulic test machine, an in-house designed test controller, and a desktop computer has been developed for performing automated fracture toughness and fatigue crack growth testing both in the laboratory and in hot cells for remote testing of irradiated specimens. Both unloading compliance and dc-potential drop can be used to monitor crack growth. The test controller includes a dc-current supply programmer, a function generator for driving the servohydraulic test machine to required test outputs, five measurement channels (each consisting of low-pass filter, track/hold amplifier, and 16-bit analog-to-digital converter), and digital logic for various control and data multiplexing functions. The test controller connects to the computer via a 16-bit wide photo-isolated bidirectional bus. The computer, a Hewlett-Packard series 200/300, inputs specimen and test parameters from the operator, configures the test controller, stores test data from the test controller in memory, does preliminary analysis during the test, and records sensor calibrations, specimen and test parameters, and test data on flexible diskette for later recall and analysis with measured initial and final crack length information. During the test, the operator can change test parameters as necessary. 24 refs., 6 figs

  17. Insights on the fractal-fracture behaviour relationship

    Directory of Open Access Journals (Sweden)

    Rodrigues José de Anchieta

    1998-01-01

    Full Text Available The fractals theory has been increasingly applied in the field of materials science and engineering. Models of fractal lines and surfaces have been generated to describe the microstructural features of materials. Special interest is placed upon a description of the fracture surface based on a fractal geometry in order to understand the crack path in materials. Several papers have demonstrated the relationship between the fractal dimension of a fracture surface and the values of roughness and fracture toughness. In this work an extension of the theory of fractals for ceramic materials is proposed, to which the crack deflection toughening mechanism is thought to be related. In order to accomplish this objective, a review describing the concept of fractals and its relationship with the fracture toughness is presented. In the following part, a correlation between fractal dimension, total energy of fracture and the average resistance to crack propagation is proposed; all these parameters being dependent on the history and on the complexity of crack propagation path.

  18. Fracture Behaviour of Nickel-Titanium Laser Welded Joints

    Science.gov (United States)

    Maletta, C.; Falvo, A.; Furgiuele, F.; Barbieri, G.; Brandizzi, M.

    2009-08-01

    In this study, the effects of Nd:YAG laser welding on the fracture behavior of Ni-rich nickel-titanium sheets are analyzed by experimental investigations. The welding was carried out in open air conditions by using a special shielding/clamping system to avoid the chemical contamination of the molten zone and the formation of hot cracks. Mechanical tests of standard dog bone-shaped and single edge crack specimens were carried out to measure the stress-strain response and the fracture resistance of both the base and the welded materials. Furthermore, scanning electron microscopy observations of the fracture surfaces were carried out in order to better understand the failure mechanisms. Finally, systematic comparative studies between base and laser-welded materials were carried out.

  19. Microstructure, mechanical behaviour and fracture of pure tungsten wire after different heat treatments

    DEFF Research Database (Denmark)

    Zhao, P.; Riesch, J.; Höschen, T.

    2017-01-01

    treatments in terms of microstructure, mechanical behaviour and fracture mode. Recrystallization is already observed at a relatively low temperature of 1273 K due to the large driving force caused by a high dislocation density. Annealing for 30 min at 1900 K also leads to recrystallization, but causes......-edge-necking of individual grains on the fracture surface. While the wire recrystallized at 1900 K displays large, almost equiaxed grains with low aspect ratios as well as distinct brittle properties. Therefore, it is suggested that a high aspect ratio of the grains is important for the ductile behaviour of tungsten wire...

  20. Post-fatigue fracture resistance of metal core crowns: press-on metal ceramic versus a conventional veneering system.

    Science.gov (United States)

    Solá-Ruiz, M Fernanda; Agustín-Panadero, Rubén; Campos-Estellés, Carlos; Labaig-Rueda, Carlos

    2015-04-01

    The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems - press-on metal (PoM) ceramic versus a conventional veneering system - subjected to static compressive loading. Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope. Fracture resistance values showed statistically significant differences (Student's t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern. Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope.

  1. Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

    Science.gov (United States)

    Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

    2017-12-01

    The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

  2. Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading

    Science.gov (United States)

    Duman, M. S.; Kaplan, E.; Cuvalcı, O.

    2018-01-01

    The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.

  3. Influence of interface properties on fracture behaviour of concrete

    Indian Academy of Sciences (India)

    Hardened concrete is a three-phase composite consisting of cement paste, aggregate and interface between cement paste and aggregate. The interface in concrete plays a key role on the overall performance of concrete. The interface properties such as deformation, strength, fracture energy, stress intensity and its ...

  4. Ductile Fracture Behaviour of Hot Isostatically Pressed Inconel 690 Superalloy

    Science.gov (United States)

    Cooper, A. J.; Brayshaw, W. J.; Sherry, A. H.

    2018-01-01

    Herein we assess the differences in Charpy impact behavior between Hot Isostatically Pressed and forged Inconel 690 alloy over the temperature range of 300 °C to - 196 °C. The impact toughness of forged 690 exhibited a relatively small temperature dependence, with a maximum difference of ca. 40 J measured between 300 °C and - 196 °C, whereas the HIP'd alloy exhibited a difference of approximately double that of the forged alloy over the same temperature range. We have conducted Charpy impact testing, tensile testing, and metallographic analyses on the as-received materials as well as fractography of the failed Charpy specimens in order to understand the mechanisms that cause the observed differences in material fracture properties. The work supports a recent series of studies which assess differences in fundamental fracture behavior between Hot Isostatically Pressed and forged austenitic stainless steel materials of equivalent grades, and the results obtained in this study are compared to those of the previous stainless steel investigations to paint a more general picture of the comparisons between HIP vs forged material fracture behavior. Inconel 690 was selected in this study since previous studies were unable to completely omit the effects of strain-induced martensitic transformation at the tip of the Chary V-notch from the fracture mechanism; Inconel 690 is unable to undergo strain-induced martensitic transformation due to the alloy's high nickel content, thereby providing a sister study with the omission of any martensitic transformation effects on ductile fracture behavior.

  5. Incomplete longitudinal fractures and fatigue injury of the proximopalmar medial aspect of the third metacarpal bone in 55 horses.

    Science.gov (United States)

    Morgan, R; Dyson, S

    2012-01-01

    Previous descriptions of incomplete longitudinal fractures and fatigue injury of the proximopalmar aspect of the third metacarpal bone (McIII) have focused on diagnostic imaging findings, especially in racehorses. To document the case details, clinical features, response to diagnostic analgesia, diagnostic imaging findings and follow-up data in a large group of horses with an incomplete longitudinal fracture or fatigue injury of the proximopalmar medial aspect of the McIII. Horses were included in the study if pain was localised to the proximopalmar aspect of the metacarpal region, with radiological evidence of an incomplete longitudinal fracture or generalised increased radiopacity in the proximopalmar medial aspect of the McIII, or focal increased radiopharmaceutical uptake (IRU) in the proximopalmar aspect of the McIII. Age, breed, gender, height, bodyweight, work discipline, work history, duration of lameness, clinical signs and responses to diagnostic analgesia were recorded. Radiographic and scintigraphic images were assessed subjectively and objectively. There were 55 horses representing a broad spectrum of ages and work disciplines, 73% of which had radiological abnormalities. The majority had no localising clinical signs, although 73% of horses with radiological abnormalities showed a characteristic pattern of lameness. Lameness was generally worse in straight lines than in circles. Increased radiopharmaceutical uptake ranged from mild to intense in the lame limb; 14% of nonlame limbs had mild IRU. Of horses for which long-term follow-up was available, 98% returned to full athletic function. Incomplete longitudinal fractures and fatigue injury of the proximopalmar medial aspect of the McIII may occur in horses of many types and sports disciplines, and are not confined to immature performance horses. They should be considered an important differential diagnosis for proximal metacarpal region pain. © 2011 EVJ Ltd.

  6. 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

  7. The Investigation of Knitted Materials Bonded Seams Behaviour upon Cyclical Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Gita BUSILIENĖ

    2017-08-01

    Full Text Available In this research uniaxial tension behaviour of PES knitted materials with bonded seams is analysed. The objects of the investigation were two types of knitted materials, having the same fibre composition (93 % PES, 7 % EL, but different in knitting pattern, i. e. plain single jersey and rib 1 × 1. Bonded overlap seams were formed by changing the orientation of knitted materials strips, i. e. parallel/parallel, parallel/bias, parallel/perpendicular, bias/bias and bias/perpendicular. The strips of each knitted material were joined by two types of thermoplastic polyurethane (PU films different in thickness (75 mm and 150 mm. Mechanical characteristics of bonded seams were defined in longitudinal direction. During uniaxial tension such parameters as maximal force Fmax (N and maximal elongation ɛmax (% were recorded from typical tension diagrams. The changes of tested specimens strength and deformation were compared before and after cyclical fatigue tension the conditions of which were 50 cycles up to tension force F equal 24.5 N. The results have shown that changes before and after cyclical fatigue tension are mostly determined by the structure of knitted materials, the orientation of knitted materials strips in bonded seam, but not effected by thermoplastic polyurethane film. These results are opposite compared to the results of biaxial tension of the same type of specimens, which have shown that changes before and after cyclical fatigue punching are mostly determined by the type of thermoplastic film, but not effected by the orientation of knitted materials strips in bonded seams. DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16065

  8. The effect of anodic oxide coating on the fatigue behaviour of AA6082 with an ultrafine-grained microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, L.; Haendel, M.; Halle, T.; Nickel, D.; Alisch, G.; Lampke, T. [Technische Universitaet Chemnitz, Institut fuer Werkstoffwissenschaft und Werkstofftechnik, Chemnitz (Germany); Hockauf, K.

    2011-07-15

    In this work, the high-cycle fatigue behaviour of the precipitation hardening aluminium wrought alloy AA6082 was investigated for a conventionally-grained and an ultrafine-grained substrate condition, with each a hard and a soft electrolytic anodic oxide (EAO) coating. The investigations were focused on the susceptibility of the coatings to anodising- and fatigue-induced cracking of the coatings and its impact on the fatigue life. For both substrate materials, the fatigue strength of the coated specimens was significantly reduced compared to the uncoated materials. Considering the resistance to crack initiation in the coating, the soft-anodised coatings were found to be superior compared to the hard-anodised ones. Moreover, the coatings on the ultrafine-grained substrate showed an enhanced resistance to anodising-induced as well as fatigue-induced cracking. However, it is supposed that the lower resistance to crack transition from the coating into the substrate is one of the most important factors which strongly limits the fatigue life of the EAO-coated specimens. This might be the reason why the fatigue strength of the ultrafine-grained substrates is relatively low, despite their higher resistance to crack initiation. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. The elastic plastic behaviour of a 1/2% Cr Mo V steam turbine steel during high strain thermal fatigue

    International Nuclear Information System (INIS)

    Murphy, M.C.; Batte, A.D.; Stringer, M.B.

    1979-01-01

    High strain fatigue problem in steam turbine. Cyclic stress strain hysteresis loops and stress relaxation behaviour in 16 h dwell period tests. Variation of stress and strain during tests under nominally strain controlled conditions. Definition of test conditions and of criteria for crack initiation and failure. Comparison of reverse bend and push pull failure data. (orig.) 891 RW/orig. 892 RKD [de

  10. Cyclic fatigue behaviour of fibre reinforced rubber-toughened nylon composite materials

    Science.gov (United States)

    Pinot, L.; Gomina, M.; Jernot, J.-P.; Moreau, R.; Nakache, E.

    2005-03-01

    The effects of the amount of rubber, the concentration of fibres and the state of the fibre/matrix interface upon the mechanical behaviour of glass fibre/rubber-toughened nylon ternary blends are checked. First, monotonic tensile tests were carried out on different intermediate materials and then on the ternary blends to derive the stress-strain curves and document the damage mechanisms. Cyclic fatigue tests were implemented on tensile specimens and the results were analysed in terms of the reduction of the Young's modulus, the increase of the hysteresis energy rate in the stress-strain diagram and the temperature rise. These findings were correlated to fractographic observations to assess the role of the different constituents.

  11. 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

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

    Directory of Open Access Journals (Sweden)

    G.M. Domínguez Almaraz

    2010-06-01

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

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

    Directory of Open Access Journals (Sweden)

    B. Piekarski

    2007-12-01

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

  14. Microstructure and fracture behaviour of Ti3Al/TC4 dissimilar ...

    Indian Academy of Sciences (India)

    Microstructure; dissimilar materials joint; electron beam welding; fracture behaviour. 1. Introduction. Joining dissimilar materials became a focus because the composite structure can exploit the special advantages of two different materials. Titanium alloy TC4 (Ti–6Al–4V) and. Ti3Al-based alloy are widely used in aerospace ...

  15. Post-cracking Behaviour and Fracture Energy of Synthetic Fibre Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Marta KOSIOR-KAZBERUK

    2016-11-01

    Full Text Available The paper reports the results of experimental programme focused on the effect of various synthetic fibres on fracture properties and ductility of concrete. The fracture energy was assessed on beams with initial notches in three-point bend test. The incorporation of synthetic fibres had a slight effect on mechanical properties of concrete but, at the same time, it had a significant influence on the fracture energy by modification of post-cracking behaviour of concrete. It was found that the modern synthetic fibres might be able to impart significant toughness and ductility to concrete. However, the beneficial effect of fibres depends on their length and flexibility. The analysis of load-deflection curves obtained made it possible to fit the simple function, describing the post-peak behaviour of fibre reinforced concrete, which can be useful for the calculation of GF value.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13246

  16. Obtention and evaluation of the fatigue behaviour of aluminium matrix composites subjected to different mechanical surface treatments

    International Nuclear Information System (INIS)

    Jesus Filho, Edson Souza de

    2000-01-01

    The objective of this work was the evaluation of the fatigue behaviour of aluminium metal matrix composites (MMC) obtained by powder metallurgy. The testing variables were the volumetric fraction of reinforcements and the type of mechanical surface treatment used. Initially, the composite materials were obtained from aluminium AA 1100 matrix, reinforced with silicon carbide (SiC) particles in the volumetric fraction of 5, 10 and 15%. An amount of control material (unreinforced) was produced for comparison purposes. The obtained materials were physically, mechanically and microstructurally characterised. The results showed a homogeneous distribution of the reinforcement particles and an improvement of the ultimate tensile strength of the composites with relation to the control material. However, some defects such as porosity and streaks of pure aluminium were detected. In a second stage, the fatigue tests of the composites were accomplished. The types of surface treatments used in the fabrication of the fatigue test specimens were machining and shot peening. For machining the variables were feed rate and tool type. The shot peened materials did not present a significant fatigue life improvement when compared to the control material. The coarse machined materials presented the worst fatigue life and the machining marks worked as strong stress concentrators. The material reinforced with 5% of SiC, differently of those reinforced with 10 and 15% showed inferior fatigue life when compared to the control material, probably because of a lower yielding strength, or lower reinforcement volumetric fraction. The material machined with hard metal (MD) did not present differences of fatigue life with relation to the machined with PCD, probably due to the class of the hard metal used. The material reinforced with 5% of SiC and shot peened, presented fatigue results with the largest standard deviations. The materials reinforced with 5% of SiC presented the smallest fatigue

  17. Effect of fatigue on fracture toughness and phase transformation of Y-TZP ceramics by X-ray diffraction and Raman spectroscopy.

    Science.gov (United States)

    Nemli, Seçil Karakoca; Yilmaz, Handan; Aydin, Cemal; Bal, Bilge Turhan; Tıraş, Tülay

    2012-02-01

    The aim of this study was to evaluate the effect of fatigue on fracture toughness and phase transformation of yttria-stabilized zirconia polycrystal materials (Cercon and Lava). The specimens were tested for indentation fracture toughness either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load). X-ray diffraction (XRD) analysis was used to examine the phase composition of specimens. The indentation images were analyzed using Raman spectroscopy at indentation center (p1), indentation corner (p2), points on crack 100 μm (p3), and 200 μm (p4) away from the corner and a point ∼80 μm away from the crack (p5). Fracture toughness results were statistically analyzed by two-way analysis of variance (ANOVA); XRD and Raman spectroscopy results were analyzed by three-way ANOVA. Fracture toughness of Cercon control (CC) and fatigue (CF) groups were 6.8 and 6.9 MPa√m, respectively, with no significant difference (p > 0.01). Fracture toughness of Lava fatigue (LF; 7.3 MPa√m) was significantly higher than Lava control (LC; p toughness of Cercon and Lava, the second being significant. Phase transformation was also detected after fatigue, which is higher in Lava. Analysis of indentations showed that transformation was highest was at the corner, second at center. Copyright © 2011 Wiley Periodicals, Inc.

  18. Influence of interface properties on fracture behaviour of concrete

    Indian Academy of Sciences (India)

    An attempt has been made in this paper to study the interface and its influence on the behaviour of concrete using sandwich, and direct rock-mortar compact specimens under mode I and mode II loading effects. 3. Research significance. The stress–strain response in high strength concrete has been observed to be linear up ...

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

    Czech Academy of Sciences Publication Activity Database

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

    2010-01-01

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

  20. Fatigue behaviour of core-spun yarns containing filament by means of cyclic dynamic loading

    Science.gov (United States)

    Esin, S.; Osman, B.

    2017-10-01

    The behaviour of yarns under dynamic loading is important that leads to understand the growth characteristics which is exposed to repetitive loadings during usage of fabric made from these yarns. Fabric growth is undesirable property that originated from low resilience characteristics of fabric. In this study, the effects of the filament fineness and yarn linear density on fatigue behaviour of rigid-core spun yarns were determined. Cotton covered yarns containing different filament fineness of polyester (PET) draw textured yarns (DTY) (100d/36f, 100d/96f, 100d/144f, 100d/192f and 100d/333f) and yarn linear densities (37 tex, 30 tex, 25 tex and 21 tex) were manufactured by using a modified ring spinning system at the same spinning parameters. Repetitive loads were applied for 25 cycles at levels between 0.1 and 3 N. Dynamic modulus and dynamic strain of yarn samples were analyzed statistically. Results showed that filament fineness and yarn linear density have significance effect on dynamic modulus and dynamic strain after cyclic loading.

  1. On the fatigue behaviour of the magnesium casting alloy G-MgAl9Zn1 (AZ91)

    International Nuclear Information System (INIS)

    Potzies, C.

    2001-01-01

    The aim of the present thesis was the study of the fatigue behaviour of the new, highly-pure magnesium sand-casting alloy G-MgAl9Zn1 (AZ91) in hardened state. Beside the determination of statistically confirmed Woehler diagrams the influence of the microlunkers typical for magnesium alloys should be explained. A further topic of this thesis formed the studies on the microstructural fatigue processes before and during the rupture initiation. Furthermore the corrosive influence of desalinated water was studied

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

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, B

    2007-09-15

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

  3. Proceedings of the 1985 pressure vessels and piping conference. Volume PVP-98-8. Fracture, fatigue and advanced mechanics

    International Nuclear Information System (INIS)

    Short, W.E.; Zamrik, S.Y.

    1985-01-01

    State-of-the-art engineering practices in pressure vessel and piping technology are the result of continual efforts in the evaluation of problems which have been experienced and the development of appropriate design and analysis methods for those applications. The resulting advances in technology benefit industry with properly engineered, safe, cost-effective pressure vessels and piping systems. To this end, advanced study continues in specialized areas of mechanical engineering such as fracture mechanics, experimental stress analysis, high pressure applications and related material considerations, as well as advanced techniques for evaluation of commonly encountered design problems. This volume is comprised of current technical papers on various aspects of fracture, fatigue and advanced mechanics as related to the design and analysis of pressure vessels and piping

  4. Comparison of the fracture resistances of glass fiber mesh- and metal mesh-reinforced maxillary complete denture under dynamic fatigue loading

    Science.gov (United States)

    2017-01-01

    PURPOSE The aim of this study was to investigate the effect of reinforcing materials on the fracture resistances of glass fiber mesh- and Cr–Co metal mesh-reinforced maxillary complete dentures under fatigue loading. MATERIALS AND METHODS Glass fiber mesh- and Cr–Co mesh-reinforced maxillary complete dentures were fabricated using silicone molds and acrylic resin. A control group was prepared with no reinforcement (n = 15 per group). After fatigue loading was applied using a chewing simulator, fracture resistance was measured by a universal testing machine. The fracture patterns were analyzed and the fractured surfaces were observed by scanning electron microscopy. RESULTS After cyclic loading, none of the dentures showed cracks or fractures. During fracture resistance testing, all unreinforced dentures experienced complete fracture. The mesh-reinforced dentures primarily showed posterior framework fracture. Deformation of the all-metal framework caused the metal mesh-reinforced denture to exhibit the highest fracture resistance, followed by the glass fiber mesh-reinforced denture (Pdenture primarily maintained its original shape with unbroken fibers. River line pattern of the control group, dimples and interdendritic fractures of the metal mesh group, and radial fracture lines of the glass fiber group were observed on the fractured surfaces. CONCLUSION The glass fiber mesh-reinforced denture exhibits a fracture resistance higher than that of the unreinforced denture, but lower than that of the metal mesh-reinforced denture because of the deformation of the metal mesh. The glass fiber mesh-reinforced denture maintains its shape even after fracture, indicating the possibility of easier repair. PMID:28243388

  5. Impact Deformation and Fracture Behaviour of Cobalt-Based Haynes 188 Superalloy

    OpenAIRE

    Woei-Shyan Lee; Hao-Chien Kao

    2014-01-01

    The impact deformation and fracture behaviour of cobalt-based Haynes 188 superalloy are investigated by means of a split Hopkinson pressure bar. Impact tests are performed at strain rates ranging from 1×103 s-1 to 5×103 s-1 and temperatures between 25°C and 800°C. The experimental results indicate that the flow response and fracture characteristics of cobalt-based Haynes 188 superalloy are significantly dependent on the strain rate and temperature. The flow stress, work hardening rate and str...

  6. Effect of Abutment Preparation and Fatigue Loading in a Moist Environment on the Fracture Resistance of the One-Piece Zirconia Dental Implant.

    Science.gov (United States)

    Kamel, Mohamed; Vaidyanathan, Tritala K; Flinton, Robert

    One-piece zirconia dental implants have been widely used in Europe for many years. This in vitro study was done to evaluate the effect of abutment preparation and fatigue (cyclic) loading in a moist environment on the fracture resistance of the one-piece zirconia dental implant. Twenty-four Cera Root zirconium oxide dental implants, divided into three groups of eight, were used in this study: group 1 (control group): implants with no preparation, tested in a dry environment; group 2: implants with no preparation, tested in a moist environment (simulating clinical conditions); and group 3: implants after abutment preparation tested in a moist environment. All implants received IPS e.max porcelain crowns. All samples were subjected to nearly 1 million cycles of sinusoidal fatigue loading (-10 N to -200 N) in a universal testing machine. The postfatigue samples were loaded to fracture. Significant differences (α = .05) in mean fracture loads were statistically analyzed. There was no catastrophic failure of any of the implants during the fatigue tests. The mean (SD) of the fracture loads in postfatigue load-to-failure tests were: group 1: 1,202.9 (62.6); group 2: 1,164.6 (73.8); and group 3: 953.5 (103). Analysis of variance (ANOVA) and post hoc Tukey-Kramer contrast revealed a statistically significant difference (P fracture load of group 3 and those of groups 1 and 2, but no significant difference (P > .05) between groups 1 and 2. While there was a statistically significant adverse effect of abutment preparation and fatigue loading in a moist environment on the postfatigue implant failure load, the load-to-fracture mean of surface-prepared implants after fatigue tests was nevertheless significantly higher than the mean fracture load of the crowns (P < .05) as well as the minimum load-bearing requirement (300 N) for anterior restorations. Abutment preparation in a one-piece zirconia implant is therefore considered clinically safe and acceptable.

  7. Os peroneum friction syndrome complicated by sesamoid fatigue fracture: a new radiological diagnosis? Case report and literature review.

    Science.gov (United States)

    Bashir, Waseem A; Lewis, Steve; Cullen, Nicholas; Connell, David A

    2009-02-01

    Injuries to the peroneal tendons are relatively common worldwide but tendon rupture without significant trauma is uncommon. Ankle mechanics can be seriously affected by disruption of one or both of the peroneal tendons although complete rupture can also remain asymptomatic. Accessory ossicles are sesamoid bones and are common findings in routine radiology of the foot and ankle. Although in the vast majority these "os" are normal variants of anatomy, they can lead to painful syndromes and suffer fractures and even undergo degenerative changes in response to overuse and trauma. Although similar syndromes have been discussed in the surgical literature, there is a lack of literature describing the use of modern imaging in the accurate diagnosis and its subsequent assistance towards appropriate management of os peroneum friction syndrome complicated by sesamoid fatigue syndrome. This article presents the plain film, sonographic and magnetic resonance imaging findings in a case of os peroneum friction syndrome complicated by a sesamoid fatigue fracture as well as reviewing the pertinent literature.

  8. Os peroneum friction syndrome complicated by sesamoid fatigue fracture: a new radiological diagnosis? Case report and literature review

    International Nuclear Information System (INIS)

    Bashir, Waseem A.; Connell, David A.; Lewis, Steve; Cullen, Nicholas

    2009-01-01

    Injuries to the peroneal tendons are relatively common worldwide but tendon rupture without significant trauma is uncommon. Ankle mechanics can be seriously affected by disruption of one or both of the peroneal tendons although complete rupture can also remain asymptomatic. Accessory ossicles are sesamoid bones and are common findings in routine radiology of the foot and ankle. Although in the vast majority these ''os'' are normal variants of anatomy, they can lead to painful syndromes and suffer fractures and even undergo degenerative changes in response to overuse and trauma. Although similar syndromes have been discussed in the surgical literature, there is a lack of literature describing the use of modern imaging in the accurate diagnosis and its subsequent assistance towards appropriate management of os peroneum friction syndrome complicated by sesamoid fatigue syndrome. This article presents the plain film, sonographic and magnetic resonance imaging findings in a case of os peroneum friction syndrome complicated by a sesamoid fatigue fracture as well as reviewing the pertinent literature. (orig.)

  9. Os peroneum friction syndrome complicated by sesamoid fatigue fracture: a new radiological diagnosis? Case report and literature review

    Energy Technology Data Exchange (ETDEWEB)

    Bashir, Waseem A.; Connell, David A. [Royal National Orthopaedic Hospital NHS Trust, Department of Radiology, London, Middlesex (United Kingdom); Lewis, Steve [Craven Cottage, Fulham Football Club, London (United Kingdom); Cullen, Nicholas [The Royal National Orthopaedic Hospital NHS Trust, Department of Orthopaedics, London, Middlesex (United Kingdom)

    2009-02-15

    Injuries to the peroneal tendons are relatively common worldwide but tendon rupture without significant trauma is uncommon. Ankle mechanics can be seriously affected by disruption of one or both of the peroneal tendons although complete rupture can also remain asymptomatic. Accessory ossicles are sesamoid bones and are common findings in routine radiology of the foot and ankle. Although in the vast majority these ''os'' are normal variants of anatomy, they can lead to painful syndromes and suffer fractures and even undergo degenerative changes in response to overuse and trauma. Although similar syndromes have been discussed in the surgical literature, there is a lack of literature describing the use of modern imaging in the accurate diagnosis and its subsequent assistance towards appropriate management of os peroneum friction syndrome complicated by sesamoid fatigue syndrome. This article presents the plain film, sonographic and magnetic resonance imaging findings in a case of os peroneum friction syndrome complicated by a sesamoid fatigue fracture as well as reviewing the pertinent literature. (orig.)

  10. High strain rate fracture behaviour of fused silica

    International Nuclear Information System (INIS)

    Ruggiero, A; Iannitti, G; Testa, G; Bonora, N; Limido, J; Lacome, J L; Olovsson, L; Ferraro, M

    2014-01-01

    Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the strain rate related effects become significant and should be accounted for in the constitutive modelling. In this study, the Johnson-Holmquist (J-H) model parameters have been identified by inverse calibration technique, on selected validation test configurations, according to the procedure described hereafter. Numerical simulations were performed with LS-DYNA and IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. In order to overcome numerical drawbacks associated with element erosion, a modified version of the J-H model is proposed.

  11. Strength, Fatigue, and Fracture Toughness of Ti-6Al-4V Liner from a Composite Over-Wrapped Pressure Vessel

    Science.gov (United States)

    Salem, Jonathan A.; Lerch, Brad; Thesken, John C.; Sutter, Jim; Russell, Richard

    2008-01-01

    It was demonstrated by way of experiment that Composite Over-wrapped Pressure Vessel (COPV) Ti-6Al-4V liner material can sustain the expected service loads and cycles. The experiments were performed as part of investigations on the residual life of COPV tanks being used in Space Shuttle Orbiters. Measured properties included tensile strength, compressive strength, reversed loading cycles to simulate liner proof strains, and cyclic fatigue loading to demonstrate the ability to sustain 1000 cycles after liner buckling. The liner material came from a salvaged 40 in. Columbia (orbiter 102) tank (SN029), and tensile strength measurements were made on both boss-transition (thick) and membrane regions (thin). The average measured yield strength was 131 ksi in the boss-transition and membrane regions, in good agreement with measurements made on 1970 s vintage forged plate stock. However, Young s modulus was 17.4+/-0.3 Msi, somewhat higher than typical handbook values (approx.16 Msi). The fracture toughness, as estimated from a failed fatigue specimen, was 74 ksi/sq in, in reasonable agreement with standardized measurements made on 1970 s vintage forged plate stock. Low cycle fatigue of a buckled test specimen implied that as-imprinted liners can sustain over 4000 load cycles.

  12. Fractographic analysis of fatigue damage in 7000 aluminium alloys.

    Science.gov (United States)

    Cvijović, Z; Vratnica, M; Gerić, K

    2008-12-01

    In this paper, an attempt is made to correlate the fatigue damage in 7000 aluminium alloys with different impurity contents to the microstructural features and to explain their interdependence through fractographic observations. The Paris constants of these alloys in the form of hot-forged plates subjected to the overaged T73 temper are evaluated and differences in the fatigue crack growth rate described by striation spacing measurements. Scanning electron microscopy analysis of fatigue fracture surfaces revealed that the type and morphological parameters of coarse intermetallic particles play a critical role in fatigue crack growth behaviour. The elemental distribution determined by means of energy-dispersive spectroscopy analysis showed that the fractured particles accelerating the crack advances are larger particles of Fe-rich phases. The fatigue crack growth rate increases considerably with increasing amounts of these particles. The smaller eta, S and Mg(2)Si particles contribute beneficially to fatigue life.

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

    Science.gov (United States)

    2014-01-01

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

  14. Thermo-mechanical fatigue behaviour of the near-{gamma}-titanium aluminide alloy TNB-V5 under uniaxial and multiaxial loading

    Energy Technology Data Exchange (ETDEWEB)

    Brookes, Stephen Peter

    2009-12-19

    -strain history. The effects of TMF on the microstructure were also investigated. For all types of tests intergranular fracture is predominant. Failure is strongly influenced by environmental conditions. This study compares TMF results of TiAl with previous TMF investigations on the nickel-based alloys IN 738 and Nimonic 90. IN 738 shows similar TMF behaviour to {gamma}-TiAl in that uniaxial IP loading has the longest fatigue lifetimes. Nimonic 90 shows the opposite behaviour to both of these alloys. A lifetime model developed for this near-{gamma}-TiAl alloy, successfully describes all temperaturestrain TMF loading conditions over the test temperature range, with the use of a single loading parameter. The loading parameter is based on the plastic work per cycle, and is not only dependant on the mean tensile stress but also on the maximum principal stress. The loading parameter responds to various strain-temperature-paths differently. It describes the lifetime relation between uniaxial IP and OP loading, axial and torsional loading and the hold period effect. (orig.)

  15. Two Parameter Fracture Mechanics: Fatigue Crack Behavior under Mixed Mode Conditions

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Knésl, Zdeněk

    2008-01-01

    Roč. 75, č. 3-4 (2008), s. 857-865 ISSN 0013-7944. [Crack Paths 2006. Parma, 14.09.2006-16.09.2006] R&D Projects: GA ČR GP101/04/P001 Institutional research plan: CEZ:AV0Z20410507 Keywords : Constraint * Mixed-mode loading * Fatigue crack * Crack growth * Crack path Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.713, year: 2008

  16. In-vitro fatigue and fracture testing of CAD/CAM-materials in implant-supported molar crowns.

    Science.gov (United States)

    Preis, Verena; Hahnel, Sebastian; Behr, Michael; Bein, Laila; Rosentritt, Martin

    2017-04-01

    To investigate the fatigue and fracture resistance of different CAD/CAM-materials as implant- or tooth-supported molar crowns with respect to the clinical procedure (screwed/bonded restoration). 168 crowns were fabricated from different CAD/CAM-materials (n=8/material): ZLS (zirconia-reinforced lithium silicate ceramic; Suprinity, Vita-Zahnfabrik), COB (composite; Brilliant Crios, Coltene), COL (composite; Lava Ultimate, 3M Espe), PMV/PPV (polyether ether ketone (PEEK)+milled composite veneer/composite paste veneer; BioHPP+HIPC veneer/Crealign veneer, Bredent), COH (composite; Block HC, Shofu), and ZIR (zirconia; IPS e.max ZirCAD, Ivoclar-Vivadent) as reference. Three groups were designed simulating the following clinical procedures: (a) chairside procedure ([CHAIR] implant crown bonded to abutment), (b) labside procedure ([LAB] abutment and implant crown bonded in laboratory, screwed chairside), and (c) reference ([TOOTH] crowns bonded on human teeth). Combined thermal cycling and mechanical loading (TCML) were performed simulating a 5-year clinical situation. Fracture force was determined and failures were documented. Data were statistically analyzed (Kolmogorov-Smirnov-test, one-way-ANOVA; post-hoc-Bonferroni, α=0.05). All crowns of group LAB-PPV showed cracks after TCML. The other groups survived fatigue testing without failures. Fracture forces varied between 921.3N (PPV) and 4817.8N (ZIR) [CHAIR], 978.0N (COH) and 5081.4N (ZIR) [LAB], 746.7N (PPV) and 3313.5N (ZIR) [TOOTH]. Significantly (pcrowns provided no significant (p>0.05) differences between the individual groups. Different ceramic and resin-based materials partly performed differently in implant or tooth situations. Individual resin-based materials (PPV, COB, COH) were weakened by inserting a screw channel. Most CAD/CAM-materials may be clinically applied in implant-supported crowns without restrictions. ​. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights

  17. Determination of the fatigue behaviour of thin hard coatings using the impact test and a FEM simulation

    Energy Technology Data Exchange (ETDEWEB)

    Bouzakis, K.D. [Aristoteles Univ., Thessaloniki (Greece). Dept. of Mech. Eng.; Vidakis, N. [Aristoteles Univ., Thessaloniki (Greece). Dept. of Mech. Eng.; Leyendecker, T. [CemeCon, 52068 Aachen (Germany); Lemmer, O. [CemeCon, 52068 Aachen (Germany); Fuss, H.G. [CemeCon, 52068 Aachen (Germany); Erkens, G. [CemeCon, 52068 Aachen (Germany)

    1996-12-15

    The impact test, in combination with a finite element method (FEM) simulation, is used to determine stress values that characterise the fatigue behaviour of thin hard coatings, such as TiAlN, TiAlCN, CrN, MoN, etc. The successive impacts of a cemented carbide ball onto a coated probe induce high contact loads, which can vary in amplitude and cause plastic deformation in the substrate. In the present paper FEM calculations are used in order to determine the critical stress values, which lead to coating fatigue failure. The parametric FEM simulation developed considers elastic behaviour for the coating and elastic plastic behaviour for the substrate. The results of the FEM calculations are correlated to experimental data, as well as to SEM observations of the imprints and to microspectrum analyses within the contact region. Herewith, critical values for various stress components, which are responsible for distinctive fatigue failure modes of the coating-substrate compounds can be obtained. (orig.)

  18. DEM Modelling of Granule Rearrangement and Fracture Behaviours During a Closed-Die Compaction.

    Science.gov (United States)

    Furukawa, Ryoichi; Kadota, Kazunori; Noguchi, Tetsuro; Shimosaka, Atsuko; Shirakawa, Yoshiyuki

    2017-08-01

    The closed-die compaction behaviour of D-mannitol granules has been simulated by the discrete element method (DEM) to investigate the granule rearrangement and fracture behaviour during compaction which affects the compactibility of the tablet. The D-mannitol granules produced in a fluidized bed were modelled as agglomerates of primary particles connected by linear spring bonds. The validity of the model granule used in the DEM simulation was demonstrated by comparing to the experimental results of a uniaxial compression test. During uniaxial compression, the numerical results of the force-displacement curve corresponded reasonably well to the experimental data. The closed-die compaction of the modelled granules was carried out to investigate the rearrangement and fracture behaviours of the granule at different upper platen velocities. The forces during closed-die compaction calculated by DEM fluctuated in the low-pressure region due to the rearrangement of granules. A Heckel analysis showed that the force fluctuation occurred at the initial bending region of the Heckel plot, which represents the granule rearrangement and fracture. Furthermore, the upper platen velocity affected the trend of compaction forces, which can lead to compaction failure due to capping. These results could contribute to designing the appropriate granules during closed-die compaction.

  19. In vitro fatigue and fracture resistance of one- and two-piece CAD/CAM zirconia implant abutments.

    Science.gov (United States)

    Gehrke, Peter; Johannson, Dirk; Fischer, Carsten; Stawarczyk, Bogna; Beuer, Florian

    2015-01-01

    All-ceramic abutments are employed increasingly often in implant dentistry for esthetic reasons. In vitro stress testing is required to evaluate the suitability of these constructions, especially in load-bearing posterior regions. The purpose of the study was to assess and compare the fatigue and fracture resistance of one- and two-piece computer-aided design/computer-assisted manufacture (CAD/CAM) zirconia implant abutments with an internal-hex connection and prefabricated commercially available zirconia stock abutments. Twenty-one abutment-crown specimens were prepared for three test groups. Control group 1 (SZ) included specimens with unprepared stock zirconia abutments, test group 2 (OP) included one-piece CAD/CAM zirconia abutments, and test group 3 (TP) included two-piece CAD/CAM zirconia abutments. All 21 specimens underwent thermocycling and fatigue testing. Finally, all specimens were tested for fracture resistance with a universal testing machine. The maximum load was applied to the tapered occlusal area of each crown at a 30-degree angle and a crosshead speed of 0.5 mm/min until the implant-abutment connection failed. Kolmogorov-Smirnov, Shapiro-Wilk, and post-hoc Scheffé tests were used for statistical analysis. All abutments in groups SZ and OP fractured into two or more pieces after fracture resistance testing. None of the TP abutments displayed apparent disintegration, but failure was evidenced by bending of the retention screw. OP abutments (232.1 ± 29.8 N) and SZ abutments (251.8 ± 23.2 N) showed lower fracture loads than the TP abutments (291.4 ± 27.8 N). However, only the difference between the OP and TP groups was statistically significant. Further load-displacement analyses corroborated the higher mechanical stability of the TP abutments. Superior resistance was achieved for two-piece hybrid CAD/CAM zirconia abutments. These abutments might be clinically beneficial in high-load areas, such as premolar and molar regions.

  20. Protocol for a randomised controlled trial for Reducing Arthritis Fatigue by clinical Teams (RAFT) using cognitive-behavioural approaches.

    Science.gov (United States)

    Hewlett, S; Ambler, N; Almeida, C; Blair, P S; Choy, E; Dures, E; Hammond, A; Hollingworth, W; Kirwan, J; Plummer, Z; Rooke, C; Thorn, J; Tomkinson, K; Pollock, J

    2015-08-06

    Rheumatoid arthritis (RA) fatigue is distressing, leading to unmanageable physical and cognitive exhaustion impacting on health, leisure and work. Group cognitive-behavioural (CB) therapy delivered by a clinical psychologist demonstrated large improvements in fatigue impact. However, few rheumatology teams include a clinical psychologist, therefore, this study aims to examine whether conventional rheumatology teams can reproduce similar results, potentially widening intervention availability. This is a multicentre, randomised, controlled trial of a group CB intervention for RA fatigue self-management, delivered by local rheumatology clinical teams. 7 centres will each recruit 4 consecutive cohorts of 10-16 patients with RA (fatigue severity ≥ 6/10). After consenting, patients will have baseline assessments, then usual care (fatigue self-management booklet, discussed for 5-6 min), then be randomised into control (no action) or intervention arms. The intervention, Reducing Arthritis Fatigue by clinical Teams (RAFT) will be cofacilitated by two local rheumatology clinicians (eg, nurse/occupational therapist), who will have had brief training in CB approaches, a RAFT manual and materials, and delivered an observed practice course. Groups of 5-8 patients will attend 6 × 2 h sessions (weeks 1-6) and a 1 hr consolidation session (week 14) addressing different self-management topics and behaviours. The primary outcome is fatigue impact (26 weeks); secondary outcomes are fatigue severity, coping and multidimensional impact, quality of life, clinical and mood status (to week 104). Statistical and health economic analyses will follow a predetermined plan to establish whether the intervention is clinically and cost-effective. Effects of teaching CB skills to clinicians will be evaluated qualitatively. Approval was given by an NHS Research Ethics Committee, and participants will provide written informed consent. The copyrighted RAFT package will be freely available. Findings

  1. Fracture behaviour of a self-healing microcapsule-loaded epoxy system

    Directory of Open Access Journals (Sweden)

    2011-03-01

    Full Text Available The effect of temperature on the fracture behaviour of a microcapsule-loaded epoxy matrix was investigated. Microencapsulated epoxy and mercaptan-derivative healing agents were incorporated into an epoxy matrix to produce a polymer composite capable of self-healing. Maximum fracture loads were measured using the double-torsion method. Thermal aging at 55 and 110°C for 17 hours [hrs] was applied to heal the pre-cracked samples. The addition of microcapsules appeared to increase significantly the load carrying capacity of the epoxy after healing. Once healed, the composites achieved as much as 93–171% of its virgin maximum fracture load at 18, 55 and 110°C. The fracture behavior of the microcapsule- loaded epoxy matrix was influenced by the healing temperature. The high self-healing efficiency may be attributed to the result of the subsurface micro-crack pinning or deviation, and to a stronger microencapsulated epoxy and mercaptanderivative binder than that of the bulk epoxy. The results show that the healing temperature has a significant effect on recovery of load transferring capability after fracture.

  2. An overview of fatigue

    International Nuclear Information System (INIS)

    Mc Evily, A.J.

    1987-01-01

    Four topics are briefly discussed in this paper: fatigue crack initiation and growth in a nickel-base superalloy single crystal, the environment effect on near-threshold fatigue crack growth behaviour, the role of crack closure in load-interaction effects in fatigue crack growth, and the nature of creep-fatigue interactions, if any, during fatigue crack growth. (Author)

  3. Fracture and fatigue of high strength filaments. Final report, September 25, 1974--August 30, 1975

    International Nuclear Information System (INIS)

    Holt, N.L.; Finnie, I.

    1975-01-01

    The history of high strength filamentary materials is traced and it is seen that their use has been widespread. It is shown that today's demands upon these materials require a better understanding of their behavior than is presently available. Current theories for both the static and fatigue strength of filamentary materials are reviewed. An analysis of static strength tests on short filaments is presented that explains seemingly anomalous test behavior which has been reported in the literature. The proposed approach is supported by experiments and computer analysis. A new machine for the fatigue testing of filaments or wires was designed and is described in detail. Results are presented for fatigue tests on tungsten wire, graphite filaments and glass filaments. Graphite filaments showed an unexpected deterioration in strength after very many cycles (10 8 ). An explanation of this effect is offered and supported by scanning electron microscope observations. The work concludes with some suggestions for further research

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

    International Nuclear Information System (INIS)

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

    1985-06-01

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

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

    International Nuclear Information System (INIS)

    Wong, F.M.G.

    1990-06-01

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

  6. Fatigue surviving, fracture resistance, shear stress and finite element analysis of glass fiber posts with different diameters.

    Science.gov (United States)

    Wandscher, Vinícius Felipe; Bergoli, César Dalmolin; de Oliveira, Ariele Freitas; Kaizer, Osvaldo Bazzan; Souto Borges, Alexandre Luiz; Limberguer, Inácio da Fontoura; Valandro, Luiz Felipe

    2015-03-01

    This study evaluated the shear stress presented in glass fiber posts with parallel fiber (0°) and different coronal diameters under fatigue, fracture resistance and FEA. 160 glass-fiber posts (N=160) with eight different coronal diameters were used (DT=double tapered, number of the post=coronal diameter and W=Wider - fiber post with coronal diameter wider than the conventional): DT1.4; DT1.8W; DT1.6; DT2W; DT1.8; DT2.2W; DT2; DT2.2. Eighty posts were submitted to mechanical cycling (3×10(6) cycles; inclination: 45°; load: 50N; frequency: 4Hz; temperature: 37°C) to assess the surviving under intermittent loading and other eighty posts were submitted to fracture resistance testing (resistance [N] and shear-stress [MPa] values were obtained). The eight posts types were 3D modeled (Rhinoceros 4.0) and the shear-stress (MPa) evaluated using FEA (Ansys 13.0). One-way ANOVA showed statistically differences to fracture resistance (DT2.2W and DT2.2 showed higher values) and shear stress values (DT1.4 showed lower values). Only the DT1.4 fiber posts failed after mechanical cycling. FEA showed similar values of shear stress between the groups and these values were similar to those obtained by shear stress testing. The failure analysis showed that 95% of specimens failed by shear. Posts with parallel fiber (0°) may suffer fractures when an oblique shear load is applied on the structure; except the thinner group, greater coronal diameters promoted the same shear stresses. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Cognitive Behavioural Therapy for Chronic Fatigue Syndrome in a 15 year-old girl; A case-report

    Directory of Open Access Journals (Sweden)

    Vahdet GORMEZ

    2015-08-01

    Full Text Available Abstract: Chronic Fatigue Syndrome (CFS is a relatively common clinical condition that can cause sufferers to experience significant disability and distress, which may be further exacerbated by a lack of understanding from others, including health professionals. Cognitive behaviour therapy (CBT has been widely researched and reported to be an evidence-based effective treatment approach for CSF. Cognitive-behavioural theory of CFS aims to describe how certain cognitions and behaviours could account for the symptoms, distress, and disability that maintain the illness. In this case study, a successful application of CBT in a 15-year-old young person with a twelve-month-history of disabling CFS is presented. We argue that for a clinical success, a non-judgemental approach to address the parental role in maintenance of the sick role is necessary. [JCBPR 2015; 4(2.000: 97-103

  8. The Fracture of Plasma-Treated Polyurethane Surface under Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Ilya A. Morozov

    2018-02-01

    Full Text Available Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading. The influence of the strain amplitude and the plasma treatment regime on damage character is discussed. Surface defects are studied in unloaded and stretched states of the material. As a result of fatigue loading, transverse cracks (with closed overlapping edges as well as with open edges deeply propagating into the polymer and longitudinal folds which are break and bend inward, appear on the surface. Hard edges of cracks cut the soft polymer which is squeezed from the bulk to the surface. The observed damages are related to the high stiffness of the modified surface and its transition to the polymer substrate.

  9. The bridge crane mechanism shaft reliability calculating in case of the fatigue fracture parameters correlation

    Directory of Open Access Journals (Sweden)

    Krutitskiy M.N.

    2016-03-01

    Full Text Available The method of statistical tests examines the impact of the correlation of the parameters of fatigue-such as the durability of the shaft mechanism of an overhead traveling crane for General use is under consideration in this article. It is be-lieved that the normal and shear stresses together affect the overall durability of the shaft. There may be a correlation between endurance limits and coefficients of block similarity of loading. To calculate resource used corrected linear theory of fatigue damage accumulation. Parameters on the reliability are computed after building the function, the reli-ability function directly or through private functions the reliability function for each type of stress.

  10. Fracture mechanical investigations about crack resistance behaviour in non-transforming ceramics in particular aluminum oxide

    International Nuclear Information System (INIS)

    Baer, K.K.O.; Kleist, G.; Nickel, H.

    1991-03-01

    The aim of this work is the clearification of R-curve behaviour of non-transforming ceramics, in particular aluminum oxide exhibiting incrystalline fracture. Investigations of crack growth in controlled bending experiments were performed using 3-Pt- and 4-Pt-bending samples of differing sizes under inert conditions. The fracture experiments were realized using several loading techniques, for example constant and varying displacement rates, load rupture (P = 0) and relaxation tests (v = 0). In addition unloading and reloading experiments were performed to investigate hysteresis curves and residual displacements in accordance with R-curve behaviour. During the crack-growth experiments, the crack extension was measured in situ using a high resolution immersion microscope. With this technique, the fracture processes near the crack tip (crack activity zone) was observed as well. The crack resistance as a function of crack extension (R-curve) was determined using differing calculation methods. All of the methods used resulted in approximately identical R-curves, within the statistical error band. The crack resistance at initiation R 0 was 20 N/m. The crack resistance increased during approximately 3 mm of growth to a maximum of 90 N/m. A decrease in the crack resistance was determined for large a/W (crack length normalized with sample height) values, independant of the calculation methods. The R-curve behaviour was interpreted as due to a functional resistance behind the observed crack tip, which arises from a volume dilatation in the crack activity zone while the crack proceeds. (orig.) [de

  11. Fatigue crack propagation behaviour of a TiAl-based alloy

    International Nuclear Information System (INIS)

    Henaff, G.; Mabru, C.; Petit, J.

    1996-01-01

    In the present study the fatigue crack propagation resistance of a nearly fully lamellar quaternary TiAl based is investigated at room-temperature. The fatigue crack growth rates material are shown to be highly sensitive on the applied stress intensity factor amplitude. A special attention is also paid to the influence of extrinsic factors. Thus crack-closure is proved to strongly influence the propagation. As regards environmental effects, ambient air induces fatigue crack growth rates two orders of magnitude higher than those measured in vacuum. The role of moisture in this deleterious effect is discussed. (orig.)

  12. Chronic fatigue syndrome: comparing outcomes in White British and Black and minority ethnic patients after cognitive-behavioural therapy.

    Science.gov (United States)

    Ingman, Tom; Ali, Sheila; Bhui, Kamaldeep; Chalder, Trudie

    2016-09-01

    Cognitive-behavioural therapy (CBT) is one of the most promising treatments for chronic fatigue syndrome (CFS). It is unclear whether CBT is effective for Black and minority ethnic (BME) groups. To assess the effectiveness of CBT in BME patients compared with White British patients presenting to a specialist CFS service. Data from 67 (19.0%) BME participants and 285 (81.0%) White British participants referred to a specialist CFS service in the UK were collected at baseline and after CBT treatment. Pairwise comparisons revealed that both BME participants and White British participants significantly improved on measures of fatigue severity (P<0.001), physical functioning (P<0.001) and work/social adjustment (P<0.001). Independent samples t-tests showed that BME participants improved despite exhibiting significantly higher baseline damage beliefs (P = 0.009), catastrophising (P = 0.024), all-or-nothing behaviour (P = 0.036) and avoidance/resting behaviour (P = 0.001), compared with White British participants. To our knowledge, this study is the first to indicate that CBT is effective for treating CFS in a group of patients from diverse BME backgrounds. © The Royal College of Psychiatrists 2016.

  13. Some Micromechanical Aspects of Damage and Fracture

    Directory of Open Access Journals (Sweden)

    P. Brož

    2000-01-01

    Full Text Available The failure mode is described by means of elasto-plastic fracture mechanics and the main aspects of fatigue crack behaviour are itemized. The crux of the matter is the presentation of the pplicability limits of the three substantially different fatigue fracture mechanics equations based on fatigue crack propagation development. In the course of this, the microstructural effects,  predominantly crystallographic identification, grain dimension, and second phase structures are considered. For some sorts of FCC polycrystalline metals, the fatigue life and micro-damage heterogeneity are investigated, especially the stage of early plastic fatigue damage initiation while emphasizing slip theory and the localization homogenization technique. An internal damage variable ds is applied to illustrate of the micro-damage of each slip system.

  14. Behaviour of E-glass fibre reinforced vinylester resin composites ...

    Indian Academy of Sciences (India)

    A well-defined impact fatigue (S–N) behaviour, having a progressive endurance below the threshold single cycle impact fracture stress with decreasing applied stress has been demonstrated. Fractographic analysis revealed fracture by primary debonding having fibre breakage and pullout at the tensile zone, but a shear ...

  15. Fatigue Behaviour of Fastening Joints of Sheet Materials and Finite Element Analysis

    Directory of Open Access Journals (Sweden)

    Xiaocong He

    2013-01-01

    Full Text Available Some fastening techniques such as self-piercing riveting, mechanical clinching, and structural adhesive bonding are efficient joining methods which are suitable for joining advanced lightweight sheet materials that are hard to weld. The recent literature relating to fatigue behavior of such fastening joints and finite element analysis is reviewed in this paper. The recent development in fatigue behavior analysis of the fastening joints is described with particular reference to some major factors that influence the fatigue behavior of the fastening joints: failure mechanism, environmental effects, and hybrid joining techniques. The main methods used in finite element analysis of fatigue behavior of the fastening joints of sheet materials are discussed and illustrated with brief case studies from the literature.

  16. Effect of hydrogen on fatigue behaviour of Ti-6Al-4V

    International Nuclear Information System (INIS)

    Tasleem, M.; Haq, A.U.; Evans, W.J.; Bache, M.R.

    1995-01-01

    The fatigue behavior of hydrogen-charged titanium alloy (Ti-6Al-4V) has been studied. It is noted that hydrogen-charging to 100 ppm results in a marked decrease in the fatigue response of notched specimens. Furthermore, there is a significant increase in hardness even through the alloy microstructure is unaltered. It is argued that the hydrogen atoms act as a strengthened agent thereby restricting stress redistribution at the root of the notch and causing early crack initiation. (author)

  17. Gigacycle fatigue behaviour of austenitic stainless steels used for mercury target vessels

    International Nuclear Information System (INIS)

    Naoe, Takashi; Xiong, Zhihong; Futakawa, Masatoshi

    2016-01-01

    A mercury enclosure vessel for the pulsed spallation neutron source manufactured from a type 316L austenitic stainless steel, a so-called target vessel, suffers the cyclic loading caused by the proton beam induced pressure waves. A design criteria of the JSNS target vessel which is defined based on the irradiation damage is 2500 h at 1 MW with a repetition rate of 25 Hz, that is, the target vessel suffers approximately 10 9 cyclic loading while in operation. Furthermore, strain rate of the beam window of the target vessel reaches 50 s −1 at the maximum, which is much higher than that of the conventional fatigue. Gigacycle fatigue strength up to 10 9 cycles for solution annealed 316L (SA) and cold-worked 316L (CW) were investigated through the ultrasonic fatigue tests. Fatigue tests were performed under room temperature and 250 °C which is the maximum temperature evaluated at the beam window in order to investigate the effect of temperature on fatigue strength of SA and CW 316L. The results showed that the fatigue strength at 250 °C is clearly reduced in comparison with room temperature, regardless of cold work level. In addition, residual strength and microhardness of the fatigue tested specimen were measured to investigate the change in mechanical properties by cyclic loading. Cyclic hardening was observed in both the SA and CW 316L, and cyclic softening was observed in the initial stage of cyclic loading in CW 316L. Furthermore, abrupt temperature rising just before fatigue failure was observed regardless of testing conditions.

  18. Structural Reliability of Ceramics at High Temperature: Mechanisms of Fracture and Fatigue Crack Growth

    Energy Technology Data Exchange (ETDEWEB)

    Reinhold H. Dauskardt

    2005-08-01

    Final report of our DOE funded research program. Aim of the research program was to provide a fundamental basis from which the mechanical reliability of layered structures may be understood, and to provide guidelines for the development of technologically relevant layered material structures with optimum resistance to fracture and subcritical debonding. Progress in the program to achieve these goals is described.

  19. Fatigue crack growth behaviour of 21/4Cr1Mo steel tube at elevated temperature

    International Nuclear Information System (INIS)

    Bulloch, J.H.; Buchanan, L.W.

    1987-01-01

    The fatigue crack growth characteristics of 21/4Cr1Mo steel tube have been examined at 588 0 C over the frequency range 0.02-20 Hz and dwell time range 10-960 min. All tests were conducted under load control in laboratory air at an R-ratio of 0.5. The elevated temperature fatigue crack growth characteristics were adequately described in terms of the stress intensity range ΔKAPPA. The continuous cyclic test data exhibited a significant effect of frequency that agreed well with predicted effects using a simple mathematical model of the high temperature fatigue process. With the dwell time range of 10-100 min there was a significant dwell time effect on the critical ΔKAPPA level for creep-fatigue interactive growth. At dwell times > 100 min the dwell time effect saturates. When creep-fatigue interactive growth occurs, growth rates reside above the maximum for continuum-controlled fatigue crack growth, and exhibit a da/dN varies as ΔKAPPA 10 dependence; failure is then intergranular in nature. (author)

  20. Influence of the structure on the mechanical properties, the tenacity and the fatigue behaviour of the T-A6V titanium alloy

    International Nuclear Information System (INIS)

    Laziou, J.C.

    1976-01-01

    The propagation rate of fatigue cracks is an essential aspect in spacecraft safety. The 'Fissad' machine manufactured by the Company Aubert and Duval (France), which stems from the conventional 'Manlab's' machine, enables fatigue tests on Charpy V test specimens (10x10X55 mm) to be made. The advantage of such tests carried out on reduced size test specimens is a simple as well as a cheap way of plotting the fatigue-initiation curve and also the follow-up of the propagation rate. The results are compared of conventional fatigue tests under constant load with those obtained by means of the 'Fissad' machine, which stresses the test specimen under a constant distortion. With the T-A6V titanium alloy, the effect of forging conditions (β or α + β) and thermal treatments on the tensile conventional mechanical characteristics, the intensity factor of critical strain (Ksub(1C) and the fatigue behaviour has been investigated. (Auth.)

  1. Measuring relationships between self-compassion, compassion fatigue, burnout and well-being in student counsellors and student cognitive behavioural psychotherapists: a quantitative survey.

    OpenAIRE

    Beaumont, Elaine.; Durkin, Mark.; Hollins Martin, Caroline J.; Carson, Jerome.

    2016-01-01

    Background: Prolonged deficiency in self-care strategies puts counsellors and psychotherapists at risk of burnout and compassion fatigue. Aim: To measure associations between self-compassion, compassion fatigue, wellbeing and burnout in student counsellors and student cognitive behavioural psychotherapists. Method: A quantitative survey using four validated data collection instruments: (1) Professional Quality of Life Scale; (2) Self-Compassion Scale; (3) short Warwick and Edinburgh Mental We...

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

    Directory of Open Access Journals (Sweden)

    G. Magudeeswaran

    2014-03-01

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

  3. Early fatigue fractures in the IS-1 connector leg of a small-diameter ICD lead: value of returned product analysis for improving device safety.

    Science.gov (United States)

    Hauser, Robert G; Kallinen Retel, Linda M

    2013-10-01

    Conductor fractures may affect the performance of implantable cardioverter-defibrillator leads. During routine surveillance of returned product analyses (RPAs) in the Food and Drug Administration's Manufacturers and User Facility Device Experience database, we found a number of conductor fractures in small diameter implantable cardioverter-defibrillator leads manufactured by St Jude Medical, Inc (SJM, Sylmar, CA). To determine the location and cause of these fractures and to catalog their clinical signs and consequences. We searched the FDA's Manufacturers and User Facility Device Experience database on April 11, 2013. SJM provided information and data it collected independently. Our search found 59 leads with fractures in the IS-1 leg. Most fractures were in leads implanted in 2008-2009; no fractures were found in leads implanted after 2010. Outer coil conductor fractures accounted for the majority (51 of 59, 86%). Oversensing and noise were common signs, and 81% of the patients received inappropriate shocks. SJM's RPAs found that the fractures were due to inadequate strain relief and redesigned the IS-1 leg by shortening the crimp bore. Younger age and subpectoral implants appeared to be associated with these fractures. SJM stated the incidence is low (0.040%) and has not seen further fractures of this type in leads with the modified crimp. SJM's small diameter leads that were manufactured before 2011 are prone to early outer coil fatigue fractures in the IS-1 leg. The failure mechanism appears to have been mitigated by a design change. RPA is important for improving device safety. © 2013 Heart Rhythm Society. All rights reserved.

  4. Analysis of the binder yield energy test as an indicator of fatigue behaviour of asphalt mixes

    Science.gov (United States)

    O'Connell, Johan; Mturi, Georges A. J.; Komba, Julius; Du Plessis, Louw

    2017-09-01

    Empirical binder testing has increasingly failed to predict pavement performance in South Africa, with fatigue cracking being one of the major forms of premature pavement distress. In response, it has become a national aspiration to incorporate a performance related fatigue test into the binder specifications for South Africa. The Binder Yield Energy Test (BYET) was the first in a series of tests analysed for its potential to predict the fatigue performance of the binder. The test is performed with the dynamic shear rheometer, giving two key parameters, namely, yield energy and shear strain at maximum shear stress (γτmax). The objective of the investigation was to perform a rudimentary evaluation of the BYET; followed by a more in-depth investigation should the initial BYET results prove promising. The paper discusses the results generated from the BYET under eight different conditions, using six different binders. The results are then correlated with four point bending beam fatigue test results obtained from asphalt mix samples that were manufactured from the same binders. Final results indicate that the BYET is not ideal as an indicator of fatigue performance.

  5. The effect of the changing microstructure on the fatigue behaviour during cyclic rolling contact loading

    International Nuclear Information System (INIS)

    Voskamp, A.P.; Mittemeijer, E.J.

    1997-01-01

    During rolling contact fatigue of the inner rings of ball bearings three stages of material response can be distinguished, in terms of the volume that is plastically deformed upon overrolling. After a first stage of material strengthening during which a decrease occurs for the volume that is deformed plastically, an effectively stationary, second stage is entered which is eventually succeeded by a third stage exhibiting a pronounced increase of the volume that is deformed plastically upon overrolling, which leads to failure. It is suggested that carbon diffusion induced by local temperature peaks occurring at the moment of overrolling is the key mechanism leading to fatigue damage. The amount of decomposed retained austenite is a useful, practical parameter to assess fatigue life. It is shown that published ideas about the role of certain components of residual stress in enhancing fatigue life are not correct and that the so-called Palmgren-Miner rule, as applied in practice, and the risk volume defined by Lundberg and Palmgren are inappropriate for assessing fatigue life. (orig.)

  6. Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4?mm locking compression plate

    OpenAIRE

    Chao, Peini; Conrad, Bryan P; Lewis, Daniel D; Horodyski, MaryBeth; Pozzi, Antonio

    2013-01-01

    Background There are several factors that can affect the fatigue life of a bone plate, including the mechanical properties of the plate and the complexity of the fracture. The position of the screws can influence construct stiffness, plate strain and cyclic fatigue of the implants. Studies have not investigated these variables in implants utilized for long bone fracture fixation in dogs and cats. The purpose of the present study was to evaluate the effect of plate working length on construct ...

  7. Load limit of mini-implants with reduced abutment height based on fatigue fracture resistance: experimental and finite element study.

    Science.gov (United States)

    Toyoshima, Yusuke; Wakabayashi, Noriyuki

    2015-01-01

    The primary objective of this study was to investigate the fracture resistance of experimental mini-implants with a reduced abutment height. The secondary objective was to assess the effects of implant diameter and bone level on the load limit, using finite element simulations. Two Ti-6A1-4V 1.8-mm-diameter implants were subjected to monotonic bending testing and fatigue tests incorporating 5 x 10(6) cycles (ISO 14801): a commercially available implant (c18), and an experimental implant with a reduced abutment height (e18). The load limit was estimated using the finite element models based on the maximum stress at failure in the experiments. For simulations, implants with increased diameters of 2.1 and 2.4 mm were also modeled, and the load limit was estimated for all models in a bone model. In the bending test, e18 revealed a higher mean load at yield stress than c18, and this was attributed to the reduced height of the former. An endurance limit of 140 N was detected for both c18 and e18 in the fatigue test, while the load limit of e18 was higher than that of c18. The estimated load limit increased as the implant diameter or the bone level increased, with the highest value of 510 N observed at a diameter of 2.4 mm. A higher load limit was evident in the experimental mini-implant with a reduced abutment height. The simulations indicated that the load limit increased with increased implant diameter and higher bone levels.

  8. Failure behaviour of the superalloy MAR-M247 LC under LCF, HCF and combined LCF/HCF loading

    Energy Technology Data Exchange (ETDEWEB)

    Gelmedin, Domnin; Lang, Karl-Heinz [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (DE). Inst. fuer Angewandte Materialien (IAM-WK)

    2012-01-15

    Materials for turbine blades experience in service a combined loading of low and high cycle fatigue at high temperatures. In order to understand the failure behaviour under these loading conditions, systematic investigations were carried out. Low cycle fatigue, high cycle fatigue and combined low and high cycle fatigue tests were realised on MAR-M247 LC at 650 C in an air environment under total strain control. Surface damage and fracture surfaces were analysed. Under combined low and high cycle fatigue, the lifetime is reduced if the low cycle fatigue leads to a degradation of the high cycle fatigue strength caused by crack initiation and crack growth. By analysing the fracture surface, the crack growth rate under combined cycle fatigue loading could be determined and it was significantly higher than under pure low cycle fatigue loading. The accelerated crack growth mainly causes the lifetime reduction. (orig.)

  9. Fatigue behaviour of fiberglass wind turbine blade material under variable amplitude loading

    Energy Technology Data Exchange (ETDEWEB)

    Delft, D.R.V. Van; Winkel, G.D. de [Delft Univ. of Technology, STEVIN Lab., Delft (Netherlands); Joosse, P.A. [Stork Product Engineering b.v., Amsterdam (Netherlands)

    1996-09-01

    In the work presented here fatigue tests with the WISPER and WISPERX load sequence have been carried out and analysed. The test programme includes tests at low stress levels which results in fatigue lives of 50 millions of cycles. The results are compared with constant amplitude tests in the very high cycle range, carried out in a previous programme. The results are also compared with ECN results in the lower cycle range (on identical specimens). It appeared, that the difference between the fatigue life of the specimens tested with the WISPER and the WISPERX load sequence is larger than can be expected from the theoretical damage rates. Moreover, the slope of the S-N data differs from theoretical values obtained by using commonly applied design rules. (au)

  10. Advanced methods of fatigue assessment

    CERN Document Server

    Radaj, Dieter

    2013-01-01

    The book in hand presents advanced methods of brittle fracture and fatigue assessment. The Neuber concept of fictitious notch rounding is enhanced with regard to theory and application. The stress intensity factor concept for cracks is extended to pointed and rounded corner notches as well as to locally elastic-plastic material behaviour. The averaged strain energy density within a circular sector volume around the notch tip is shown to be suitable for strength-assessments. Finally, the various implications of cyclic plasticity on fatigue crack growth are explained with emphasis being laid on the DJ-integral approach.   This book continues the expositions of the authors’ well known reference work in German language ‘Ermüdungsfestigkeit – Grundlagen für Ingenieure’ (Fatigue strength – fundamentals for engineers).

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

    Science.gov (United States)

    Cerfontaine, B.; Collin, F.

    2018-02-01

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

  12. Stable interstitial layer to alleviate fatigue fracture of high nickel cathode for lithium-ion batteries

    Science.gov (United States)

    Yang, Chengkai; Shao, Ruiwen; Mi, Yingying; Shen, Lanyao; Zhao, Binglu; wang, Qian; Wu, Kai; Lui, Wen; Gao, Peng; Zhou, Henghui

    2018-02-01

    High nickel cathodes can deliver higher capacity with lower cost than conventional LiCoO2, however, the irreversible structural and morphology degradation with long-term cycling hinder their further application. In this paper, LiNi0.815Co0.15Al0.035O2 agglomerates are treated by LiNi0.333Co0.333Mn0.333O2 coating to get a stable interstitial layer without capacity loss. The interstitial layer is about 10 nm in thickness and has a layered (R-3m) structure, which can improve the chemical and mechanical stability of cathode materials with capacity retention of 88.5% after 200 cycles. The structural analysis and in-situ compression test proves that the morphology degradation is a fatigue process within long-term electrochemical reaction, and the coated sample has an excellent elastic recovery capacity thus leading to long cycle life.

  13. Mixed-Mode Fracture and Fatigue Analysis of Cracked 3D Complex Structures using a 3D SGBEM-FEM Alternating Method

    Science.gov (United States)

    Bhavanam, Sharada

    The aim of this thesis is to numerically evaluate the mixed-mode Stress Intensity Factors (SIFs) of complex 3D structural geometries with arbitrary 3D cracks using the Symmetric Galerkin Boundary Element Method-Finite Element Method (SGBEM-FEM) Alternating Method. Various structural geometries with different loading scenarios and crack configurations were examined in this thesis to understand the behavior and trends of the mixed-mode SIFs as well as the fatigue life for these complex structural geometries. Although some 3D structures have empirical and numerical solutions that are readily available in the open literature, some do not; therefore this thesis presents the results of fracture and fatigue analyses of these 3D complex structures using the SGBEM-FEM Alternating Method to serve as reference for future studies. Furthermore, there are advantages of using the SGBEM-FEM Alternating Method compared to traditional FEM methods. For example, the fatigue-crack-growth and fatigue life can be better estimated for a structure because different fatigue models (i.e. Walker, Paris, and NASGRO) can be used within the same framework of the SGBEM-FEM Alternating Method. The FEM (un-cracked structure)/BEM(crack model) meshes are modeled independently, which speeds up the computation process and reduces the cost of human labor. A simple coarse mesh can be used for all fracture and fatigue analyses of complex structures. In this thesis, simple coarse meshes were used for 3D complex structures, which were below 5000 elements as compared to traditional FEM, which require meshes where the elements range on the order of ˜250,000 to ˜106 and sometimes even more than that.

  14. Fracture mechanics characterization of crack growth under creep and fatigue conditions

    International Nuclear Information System (INIS)

    Hollstein, T.; Kienzler, R.

    1987-01-01

    Based on theoretical considerations and experimental evidence, several concepts have been investigated to correlate crack growth under high-temperature conditions with material parameters of fracture mechanics, e.g., stress-intensity factor K, and line integrals J and C * . It could be shown for different materials that these parameters describe the behavior of cracks independent of geometry and loading conditions within certain limits of validity. The laboratory results then can be transferred to real structures for (residual) lifetime predictions or safety analyses (Incoloy 800H, Thermon 4972, 9% chromium steel). With 45 refs., 3 tabs., 56 figs [de

  15. The fatigue behaviour of the breathing webs of steel bridge girders

    Czech Academy of Sciences Publication Activity Database

    Škaloud, Miroslav; Zörnerová, Marie

    2005-01-01

    Roč. 11, č. 4 (2005), s. 323-336 ISSN 1392-3730 R&D Projects: GA ČR(CZ) GA103/05/2059 Institutional research plan: CEZ:AV0Z20710524 Keywords : repeated loads * fatigue crack * S-N curves Subject RIV: JM - Building Engineering

  16. Overview of fatigue behaviour of ultrafine-grained copper produced by severe plastic deformation

    Czech Academy of Sciences Publication Activity Database

    Lukáš, Petr; Kunz, Ludvík; Svoboda, Milan

    2008-01-01

    Roč. 567-568, - (2008), s. 9-16 ISSN 0255-5476. [MSMF /5./. Brno, 27.06.2007-29.06.2007] Institutional research plan: CEZ:AV0Z20410507 Keywords : Fatigue strength * Ultrafine-grained copper Subject RIV: BM - Solid Matter Physics ; Magnetism

  17. Thermo-mechanical fatigue behaviour and life prediction of C-1023 ...

    African Journals Online (AJOL)

    user

    Nickel based superalloys are used for manufacturing turbine blades and vanes components due to their ability to withstand high stress levels at high temperatures. The complex thermo-mechanical fatigue loadings that those components suffer (as a result of start ups and shutdowns) make life assessment a complex task.

  18. Fatigue behaviour of fine-grained alumina hip-joint heads under ...

    Indian Academy of Sciences (India)

    In prosthetic applications, the reliability of implant materials over a period of thirty years is absolutely essential. Calculation of the lifetimes of alumina ceramic heads is generally made on the basis of experimental fatigue and slow crack growth tests using finite element analysis. This investigation is aimed at understanding ...

  19. Polypropylene-rubber blends 4: the effect of the rubber particle size on the fracture behaviour at low and high test speed

    NARCIS (Netherlands)

    van der Wal, A.; Wal, A.; Verheul, A.J.J.; Gaymans, R.J.

    1999-01-01

    The effect of the rubber particle size and rubber content on the fracture behaviour of polypropylene–EPR blends was studied at low and high test speeds. The particle size was varied by changing the molecular weight of the EPR phase, and ranged from about 0.5 to around 4.0 μm. The fracture behaviour

  20. The role of behavioural modification and exercise in the management of cancer-related fatigue to reduce its impact during and after cancer treatment.

    Science.gov (United States)

    Minton, Ollie; Jo, Foster; Jane, Maher

    2015-05-01

    Fatigue is a symptom that can occur during treatment as an acute side effect but can also result in persistent fatigue as a long-term side effect or late effect. We undertook a narrative review of the current literature and discuss the current evidence of assessment of fatigue and we specifically focus on the role of promoting behavioural change and focused rehabilitation to minimise these long-term effects and update the literature relating to this area from 2012 to date. We suggest there are behavioural change models that can be scaled up to enable patients to manage long-term fatigue using exercise. However, from this updated review there are limitations to the current infrastructure and evidence base that will impact on the ability to do this. We continually need to raise awareness amongst health professionals to continue to suggest modifications to impact on fatigue at all stages of cancer treatment and into survivorship and late effects. These can range from simple brief interventions suggested in the clinic to full scale rehabilitation programmes if the correct infrastructure is available. Whichever approach is adopted we suggest exercise will be the mainstay of the treatment of fatigue in this group.

  1. Study of the fatigue behaviour and damage of a aged duplex stainless steel; Etude du comportement et de l'endommagement en fatigue d'un acier inoxydable austeno-ferritique moule vieilli

    Energy Technology Data Exchange (ETDEWEB)

    Le Roux, J.Ch

    2000-07-01

    Cast duplex stainless steels are commonly used in components of pressurized water reactors primary circuit. When submitted to in-service temperatures embrittlement occurs because of the nucleation and growth of a harder phase in the ferrite by spinodal composition. Macrostructure of this steel (ferritic primary grain size is about 4-5 mm) and embrittlement of ferrite due to aging lead to a very high scattering of mechanical properties for monotonous loadings. We showed that, in spite of this macrostructure, the cyclic behaviour of aged duplex stainless steels fits usual Manson-Coffin law while initial hardening is followed by softening, in part because of the demodulation of the composition. The fatigue crack propagation rate of material follows a Paris law. While crack initiation mainly appears next to the millimetric cast defects, fatigue crack propagation remains a continuous mechanism. Ferritic and austenitic elements break successively (ferrite first breaks by cleavage, then austenite breaks by ductile fatigue). In spite of the fact that the aged ferrite is embrittled, cleavage microcracks, for load levels examined, seldom appear in ferrite at the crack tip and on both sides of the main crack. Effects of cast defects and crystallographic ferrite orientation were also studied. Propagation fatigue crack behaviour was modeled assuming that the crack tip material behaves as if it was submitted to low cycle fatigue loadings. If we consider a homogeneous material, results are in good agreement with experiments. (authors)

  2. Fatigue crack growth behaviour of the aluminium-lithium alloy 2090

    International Nuclear Information System (INIS)

    Tabrett, C.P.; McKeighan, P.C.; Smith, D.J.

    1993-01-01

    The fatigue crack growth (FCG) behavior of the aluminum lithium (Al-Li) alloy 2090-T84 has been investigated from a series of constant amplitude FCG tests. The influence of in plane orientation (L-T, T-L+45) and sheet thickness (1.6 and 6 mm) on the FCG rates for the rolled product has been examined. In general, the T-L orientation possess superior FCG resistance for both thicknesses and the 6 mm thick sheet material showed improved FCG resistance when compared to the 1.6 mm thick material for all orientations. It is believed this trend is related to the greater roughness and larger asperities found on the fatigue crack surfaces for the 6 mm thick material. Closure corrected FCG data suggests that much of the difference between the L-T and T-L orientation for the 6 mm thick sheet arise from variations in crack closure levels. (author)

  3. Neutron diffraction study of fatigue behaviour of a low-carbon stainless steel

    International Nuclear Information System (INIS)

    Taran, Yu.V.; Mikula, P.; Lukas, P.; Neov, D.; Vrana, M.

    1999-01-01

    Complete text of publication follows. Samples from a low-carbon austenite stainless steel (0.04 wt.% C) with some content of martensite produced by plastic deformation during low- (0.1 Hz) and high- (5 Hz) cycle fatigue were studied by high resolution neutron diffraction. Mean-square microstrain 2 > 1/2 have been deduced from the broadening of diffraction profiles. Practically no evolution of microstrain on the fatigue degree was observed in the austenitic and induced martensitic phases of the low-cycling samples as well as the martensitic phase of the high-cycling samples. The appreciable jump of 2 > 1/2 was found in the austenitic phase of the high-cycling samples after 5 x 10 5 cycles. The interpretation of this phenomenon is in a progress. (author)

  4. Effect of pulsed current welding on fatigue behaviour of high strength aluminium alloy joints

    International Nuclear Information System (INIS)

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

    2008-01-01

    High strength aluminium alloys (Al-Zn-Mg-Cu alloys) have gathered wide acceptance in the fabrication of light weight structures requiring high strength-to weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding processes of high strength aluminium alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass welded joints. Single V butt joint configuration has been prepared for joining the plates. The filler metal used for joining the plates is AA 5356 (Al-5Mg (wt%)) grade aluminium alloy. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW) and (iv) pulsed current GMAW (PCGMAW) processes. Argon (99.99% pure) has been used as the shielding gas. Fatigue properties of the welded joints have been evaluated by conducting fatigue test using rotary bending fatigue testing machine. Current pulsing leads to relatively finer and more equi-axed grain structure in gas tungsten arc (GTA) and gas metal arc (GMA) welds. In contrast, conventional continuous current welding resulted in predominantly columnar grain structures. Grain refinement is accompanied by an increase in fatigue life and endurance limit

  5. High temperature fatigue behaviour of TZM molybdenum alloy under mechanical and thermomechanical cyclic loads

    Science.gov (United States)

    Shi, H. J.; Niu, L. S.; Korn, C.; Pluvinage, G.

    2000-02-01

    High temperature isothermal mechanical fatigue and in-phase thermomechanical fatigue (TMF) tests in load control were carried out on a molybdenum-based alloy, one of the best known of the refractory alloys, TZM. The stress-strain response and the cyclic life of the material were measured during the tests. The fatigue lives obtained in the in-phase TMF tests are lower than those obtained in the isothermal mechanical tests at the same load amplitude. It appears that an additional damage is produced by the reaction of mechanical stress cycles and temperature cycles in TMF situation. Ratcheting phenomenon occurred during the tests with an increasing creep rate and it was dependent on temperature and load amplitude. A model of lifetime prediction, based on the Woehler-Miner law, was discussed. Damage coefficients that are functions of the maximum temperature and the variation of temperature are introduced in the model so as to evaluate TMF lives in load control. With this method the lifetime prediction gives results corresponding well to experimental data.

  6. High temperature fatigue behaviour of TZM molybdenum alloy under mechanical and thermomechanical cyclic loads

    International Nuclear Information System (INIS)

    Shi, H.J.; Niu, L.S.; Korn, C.; Pluvinage, G.

    2000-01-01

    High temperature isothermal mechanical fatigue and in-phase thermomechanical fatigue (TMF) tests in load control were carried out on a molybdenum-based alloy, one of the best known of the refractory alloys, TZM. The stress-strain response and the cyclic life of the material were measured during the tests. The fatigue lives obtained in the in-phase TMF tests are lower than those obtained in the isothermal mechanical tests at the same load amplitude. It appears that an additional damage is produced by the reaction of mechanical stress cycles and temperature cycles in TMF situation. Ratcheting phenomenon occurred during the tests with an increasing creep rate and it was dependent on temperature and load amplitude. A model of lifetime prediction, based on the Woehler-Miner law, was discussed. Damage coefficients that are functions of the maximum temperature and the variation of temperature are introduced in the model so as to evaluate TMF lives in load control. With this method the lifetime prediction gives results corresponding well to experimental data

  7. 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.

  8. Time and temperature dependence on flexural state creep and fatigue fracture behaviors of unidirectional CFRP laminates; Ichihoko CFRP sekisoban no mage ni yoru seiteki, creep oyobi hiro no hakai kyodo no jikan oyobi ondo izonsei

    Energy Technology Data Exchange (ETDEWEB)

    Miyano, Y.; Nakata, M.; Ishiguro, T. [Kanazawa Inst. of Tech., Ishikawa (Japan); Yamamoto, T. [Fukuoka Univ. (Japan)

    1998-07-15

    The time and temperature dependencies of static, creep, and fatigue fracture behavior of unidirectional CERP are investigated by 3-point bending tests in the direction parallel to fibers. The effects of time and temperature on the fracture behavior are investigated by the observation of fractured surface. The fracture behavior evaluated by the strength, deformation, and fractured surface varies markedly by the rate of loading and temperature irrespective of the forms of static, creep, and fatigue load. Regardless of the loading forms of static, creep, and fatigue, the same time-temperature equivalent law holds good between the time dependence and temperature dependence of the fracture behavior as that of dynamic behavior of the matrix resins. As a result, long-term behaviors of static, creep, and fatigue can be estimated by using the time-temperature equivalent law, and they can be compared and evaluated on the same time and temperature axes if each of the static test, creep test, and fatigue test are performed by varying the temperature. 9 refs., 13 figs., 1 tab.

  9. Cyclic deformation and precipitation behaviour of NiCr22Co12Mo9 during thermal fatigue

    International Nuclear Information System (INIS)

    Pan, Y.; Lang, K.H.; Loehe, D.; Macherauch, E.

    1993-01-01

    Specimens of the nickel-base superalloy NiCr22C12Mo9 (corresponding to Inconel 617) are thermally fatigued with a constant minimum temperature T min =473 K and maximum temperatures T max =873, 1123, 1323, and 1473 K. Cryclic hardening is observed in test with T max ≤1323 K, whereas cyclic softening occurs in tests with T max =1473 K. Coherent and incoherent γ'-precipitates develop during cycling with T max =873 K. In experiments with T max ≤1323 K the major secondary precipitates are found to be M 23 C 6 carbides. In tests with T max =1323 K, carbide bands are produced in former twin areas. Almost no carbides are observed after thermal cycling with T max =1473 K. The thermal cyclic deformation behaviour of the material is discussed taking into account the occurring precipitation features and other microstructural changes. A model to explain the development of carbide bands is suggested. (orig.)

  10. Fracture Behaviours in Compression-loaded Triangular Corrugated Core Sandwich Panels

    Directory of Open Access Journals (Sweden)

    Zaid N.Z.M.

    2016-01-01

    Full Text Available The failure modes occurring in sandwich panels based on the corrugations of aluminium alloy, carbon fibre-reinforced plastic (CFRP and glass fibre-reinforced plastic (GFRP are analysed in this work. The fracture behaviour of these sandwich panels under compressive stresses is determined through a series of uniform lateral compression performed on samples with different cell wall thicknesses. Compression test on the corrugated-core sandwich panels were conducted using an Instron series 4505 testing machine. The post-failure examinations of the corrugated-core in different cell wall thickness were conducted using optical microscope. Load-displacement graphs of aluminium alloy, GFRP and CFRP specimens were plotted to show progressive damage development with five unit cells. Four modes of failure were described in the results: buckling, hinges, delamination and debonding. Each of these failure modes may dominate under different cell wall thickness or loading condition, and they may act in combination. The results indicate that thicker composites corrugated-core panels tend can recover more stress and retain more stiffness. This analysis provides a valuable insight into the mechanical behaviour of corrugated-core sandwich panels for use in lightweight engineering applications.

  11. Fracture behaviour of the 14Cr ODS steel exposed to helium and liquid lead

    Science.gov (United States)

    Hojna, Anna; Di Gabriele, Fosca; Hadraba, Hynek; Husak, Roman; Kubena, Ivo; Rozumova, Lucia; Bublikova, Petra; Kalivodova, Jana; Matejicek, Jiri

    2017-07-01

    This work describes the fracture behaviour of the 14Cr ODS steel produced by mechanical alloying process, after high temperature exposures. Small specimens were exposed to helium gas in a furnace at 720 °C for 500 h. Another set of specimens was exposed to flowing liquid lead in the COLONRI II loop at 650 °C for 1000 h. All specimens were tested for the impact and tensile behaviour. The impact test results are compared to other sets of specimens in the as received state and after isothermal annealing at 650 °C for 1000 h. The impact curves of the exposed materials showed positive shifts on the transition temperature. While the upper shelf value did not change in the Pb exposed ODS steel, it significantly increased in the He exposed one. The differences are discussed in terms of surface and subsurface microscopy observation. The embrittlement can be explained as the effect of a slight change in the grain boundary and size distribution combined with the depletion of sub-surface region from alloying elements forming oxide scale on the surface.

  12. Cognitive behavioural therapy versus multidisciplinary rehabilitation treatment for patients with chronic fatigue syndrome: study protocol for a randomised controlled trial (FatiGo

    Directory of Open Access Journals (Sweden)

    Vos-Vromans Desirée CWM

    2012-05-01

    Full Text Available Abstract Background Patients with chronic fatigue syndrome experience extreme fatigue, which often leads to substantial limitations of occupational, educational, social and personal activities. Currently, there is no consensus regarding the treatment. Patients try many different therapies to overcome their fatigue. Although there is no consensus, cognitive behavioural therapy is seen as one of the most effective treatments. Little is known about multidisciplinary rehabilitation treatment, a combination of cognitive behavioural therapy with principles of mindfulness, gradual increase of activities, body awareness therapy and pacing. The difference in effectiveness and cost-effectiveness between multidisciplinary rehabilitation treatment and cognitive behavioural therapy is as yet unknown. The FatiGo (Fatigue-Go trial aims to compare the effects of both treatment approaches in outpatient rehabilitation on fatigue severity and quality of life in patients with chronic fatigue syndrome. Methods One hundred twenty patients who meet the criteria of chronic fatigue syndrome, fulfil the inclusion criteria and sign the informed consent form will be recruited. Both treatments take 6 months to complete. The outcome will be assessed at 6 and 12 months after the start of treatment. Two weeks after the start of treatment, expectancy and credibility will be measured, and patients will be asked to write down their personal goals and score their current performance on these goals on a visual analogue scale. At 6 and 14 weeks after the start of treatment, the primary outcome and three potential mediators—self-efficacy, causal attributions and present-centred attention-awareness—will be measured. Primary outcomes are fatigue severity and quality of life. Secondary outcomes are physical activity, psychological symptoms, self-efficacy, causal attributions, impact of disease on emotional and physical functioning, present-centred attention-awareness, life

  13. Adaptive Pacing, Cognitive Behaviour Therapy, Graded Exercise, and Specialist Medical Care for Chronic Fatigue Syndrome: A Cost-Effectiveness Analysis

    Science.gov (United States)

    McCrone, Paul; Sharpe, Michael; Chalder, Trudie; Knapp, Martin; Johnson, Anthony L.; Goldsmith, Kimberley A.; White, Peter D.

    2012-01-01

    Background The PACE trial compared the effectiveness of adding adaptive pacing therapy (APT), cognitive behaviour therapy (CBT), or graded exercise therapy (GET), to specialist medical care (SMC) for patients with chronic fatigue syndrome. This paper reports the relative cost-effectiveness of these treatments in terms of quality adjusted life years (QALYs) and improvements in fatigue and physical function. Methods Resource use was measured and costs calculated. Healthcare and societal costs (healthcare plus lost production and unpaid informal care) were combined with QALYs gained, and changes in fatigue and disability; incremental cost-effectiveness ratios (ICERs) were computed. Results SMC patients had significantly lower healthcare costs than those receiving APT, CBT and GET. If society is willing to value a QALY at £30,000 there is a 62.7% likelihood that CBT is the most cost-effective therapy, a 26.8% likelihood that GET is most cost effective, 2.6% that APT is most cost-effective and 7.9% that SMC alone is most cost-effective. Compared to SMC alone, the incremental healthcare cost per QALY was £18,374 for CBT, £23,615 for GET and £55,235 for APT. From a societal perspective CBT has a 59.5% likelihood of being the most cost-effective, GET 34.8%, APT 0.2% and SMC alone 5.5%. CBT and GET dominated SMC, while APT had a cost per QALY of £127,047. ICERs using reductions in fatigue and disability as outcomes largely mirrored these findings. Conclusions Comparing the four treatments using a health care perspective, CBT had the greatest probability of being the most cost-effective followed by GET. APT had a lower probability of being the most cost-effective option than SMC alone. The relative cost-effectiveness was even greater from a societal perspective as additional cost savings due to reduced need for informal care were likely. PMID:22870204

  14. Adaptive pacing, cognitive behaviour therapy, graded exercise, and specialist medical care for chronic fatigue syndrome: a cost-effectiveness analysis.

    Directory of Open Access Journals (Sweden)

    Paul McCrone

    Full Text Available The PACE trial compared the effectiveness of adding adaptive pacing therapy (APT, cognitive behaviour therapy (CBT, or graded exercise therapy (GET, to specialist medical care (SMC for patients with chronic fatigue syndrome. This paper reports the relative cost-effectiveness of these treatments in terms of quality adjusted life years (QALYs and improvements in fatigue and physical function.Resource use was measured and costs calculated. Healthcare and societal costs (healthcare plus lost production and unpaid informal care were combined with QALYs gained, and changes in fatigue and disability; incremental cost-effectiveness ratios (ICERs were computed.SMC patients had significantly lower healthcare costs than those receiving APT, CBT and GET. If society is willing to value a QALY at £30,000 there is a 62.7% likelihood that CBT is the most cost-effective therapy, a 26.8% likelihood that GET is most cost effective, 2.6% that APT is most cost-effective and 7.9% that SMC alone is most cost-effective. Compared to SMC alone, the incremental healthcare cost per QALY was £18,374 for CBT, £23,615 for GET and £55,235 for APT. From a societal perspective CBT has a 59.5% likelihood of being the most cost-effective, GET 34.8%, APT 0.2% and SMC alone 5.5%. CBT and GET dominated SMC, while APT had a cost per QALY of £127,047. ICERs using reductions in fatigue and disability as outcomes largely mirrored these findings.Comparing the four treatments using a health care perspective, CBT had the greatest probability of being the most cost-effective followed by GET. APT had a lower probability of being the most cost-effective option than SMC alone. The relative cost-effectiveness was even greater from a societal perspective as additional cost savings due to reduced need for informal care were likely.

  15. Ratcheting fatigue behaviour of Al-7075 T6 alloy: Influence of stress parameters

    Science.gov (United States)

    Amarnath, Lala; Bhattacharjee, Antara; Dutta, K.

    2016-02-01

    The use of aluminium and aluminium based alloys are increasing rapidly on account of its high formability, good thermal and electrical conductivity, high strength and lightness. Aluminium alloys are extensively used in aerospace, automobile, marine and space research industries and are also put into structural applications where chances of fatigue damage cannot be ruled out. In the current work, it is intended to study the ratcheting fatigue behavior of 7075-T6 aluminium alloy at room temperature. This Al alloy is potentially used in aviation, marine and automotive components as well as in bicycle parts, rock mounting equipment and parts of ammunition where there is every chance of failure of the parts due to deformation caused by ratcheting. Ratcheting is the process of accruement of plastic stain produced when a component is subjected to asymmetric cyclic loading under the influence of low cycle fatigue. To accomplish the requirements of the projected research, stress-controlled cyclic loading experiments were done using a ±250 kN servo-hydraulic universal testing machine (Instron: 8800R). The effect of stress parameters such as mean stress and stress amplitude were investigated on the ratcheting behavior of the selected aluminium alloy. It was observed that, ratcheting strain increased with increase in the value of stress amplitude at any constant mean stress while a saturation in strain accumulation attained in the investigated material after around 10-20 cycles, under all test conditions. The analyses of hysteresis loop generated during cyclic loading indicate that the material exhibits cyclic hardening in the initial fifty cycles which gets softened in further loading up to about 70-80 cycles and finally attains a steady state. The increase in the ratcheting strain value with stress parameters happens owing to increased deformation domain during cycling. The cyclic hardening accompanied by softening is correlated with characteristic precipitation features of

  16. Ratcheting fatigue behaviour of Al-7075 T6 alloy: Influence of stress parameters

    International Nuclear Information System (INIS)

    Amarnath, Lala; Bhattacharjee, Antara; Dutta, K.

    2016-01-01

    The use of aluminium and aluminium based alloys are increasing rapidly on account of its high formability, good thermal and electrical conductivity, high strength and lightness. Aluminium alloys are extensively used in aerospace, automobile, marine and space research industries and are also put into structural applications where chances of fatigue damage cannot be ruled out. In the current work, it is intended to study the ratcheting fatigue behavior of 7075-T6 aluminium alloy at room temperature. This Al alloy is potentially used in aviation, marine and automotive components as well as in bicycle parts, rock mounting equipment and parts of ammunition where there is every chance of failure of the parts due to deformation caused by ratcheting. Ratcheting is the process of accruement of plastic stain produced when a component is subjected to asymmetric cyclic loading under the influence of low cycle fatigue. To accomplish the requirements of the projected research, stress-controlled cyclic loading experiments were done using a ±250 kN servo-hydraulic universal testing machine (Instron: 8800R). The effect of stress parameters such as mean stress and stress amplitude were investigated on the ratcheting behavior of the selected aluminium alloy. It was observed that, ratcheting strain increased with increase in the value of stress amplitude at any constant mean stress while a saturation in strain accumulation attained in the investigated material after around 10-20 cycles, under all test conditions. The analyses of hysteresis loop generated during cyclic loading indicate that the material exhibits cyclic hardening in the initial fifty cycles which gets softened in further loading up to about 70-80 cycles and finally attains a steady state. The increase in the ratcheting strain value with stress parameters happens owing to increased deformation domain during cycling. The cyclic hardening accompanied by softening is correlated with characteristic precipitation features of

  17. Effect of aerobic exercise training and cognitive behavioural therapy on reduction of chronic fatigue in patients with facioscapulohumeral dystrophy: protocol of the FACTS-2-FSHD trial

    Directory of Open Access Journals (Sweden)

    van Engelen Baziel GM

    2010-06-01

    Full Text Available Abstract Background In facioscapulohumeral dystrophy (FSHD muscle function is impaired and declines over time. Currently there is no effective treatment available to slow down this decline. We have previously reported that loss of muscle strength contributes to chronic fatigue through a decreased level of physical activity, while fatigue and physical inactivity both determine loss of societal participation. To decrease chronic fatigue, two distinctly different therapeutic approaches can be proposed: aerobic exercise training (AET to improve physical capacity and cognitive behavioural therapy (CBT to stimulate an active life-style yet avoiding excessive physical strain. The primary aim of the FACTS-2-FSHD (acronym for Fitness And Cognitive behavioural TherapieS/for Fatigue and ACTivitieS in FSHD trial is to study the effect of AET and CBT on the reduction of chronic fatigue as assessed with the Checklist Individual Strength subscale fatigue (CIS-fatigue in patients with FSHD. Additionally, possible working mechanisms and the effects on various secondary outcome measures at all levels of the International Classification of Functioning, Disability and Health (ICF are evaluated. Methods/Design A multi-centre, assessor-blinded, randomized controlled trial is conducted. A sample of 75 FSHD patients with severe chronic fatigue (CIS-fatigue ≥ 35 will be recruited and randomized to one of three groups: (1 AET + usual care, (2 CBT + usual care or (3 usual care alone, which consists of no therapy at all or occasional (conventional physical therapy. After an intervention period of 16 weeks and a follow-up of 3 months, the third (control group will as yet be randomized to either AET or CBT (approximately 7 months after inclusion. Outcomes will be assessed at baseline, immediately post intervention and at 3 and 6 months follow up. Discussion The FACTS-2-FSHD study is the first theory-based randomized clinical trial which evaluates the effect and the

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

    Directory of Open Access Journals (Sweden)

    B. Vargas-Arista

    2013-01-01

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

  19. Corrigendum to 'On the influence of microstructure on the fracture behaviour of hot extruded ferritic ODS steels' [J. Nucl. Mater. 497 (2017) 60-75

    Science.gov (United States)

    Das, A.; Viehrig, H. W.; Altstadt, E.; Heintze, C.; Hoffmann, J.

    2018-02-01

    ODS steels are known to show inferior fracture properties as compared to ferritic martensitic non-ODS steels. Hot extruded 13Cr ODS steel however, showed excellent fracture toughness at a temperature range from room temperature to 400 °C. In this work, the factors which resulted in superior and anisotropic fracture behaviour were investigated by comparing different orientations of two hot extruded materials using scanning electron, electron backscatter and transmission electron microscopy. Fracture behaviour of the two materials was compared using unloading compliance fracture toughness tests. Anisotropic fracture toughness was predominantly influenced by grain morphology. Superior fracture toughness in 13Cr ODS-KIT was predominantly influenced by factors such as smaller void inducing particle size and higher sub-micron particle-matrix interfacial strength.

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

    International Nuclear Information System (INIS)

    Rementeria, Rosalia; Morales-Rivas, Lucia; Kuntz, Matthias; Garcia-Mateo, Carlos; Kerscher, Eberhard; Sourmail, Thomas; Caballero, Francisca G.

    2015-01-01

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

  1. Does the heterogeneity of chronic fatigue syndrome moderate the response to cognitive behaviour therapy? An exploratory study.

    Science.gov (United States)

    Cella, Matteo; Chalder, Trudie; White, Peter D

    2011-01-01

    Chronic fatigue syndrome (CFS) is a heterogeneous condition. A few studies have shown that some independent factors predict outcomes after cognitive behaviour therapy (CBT). Two recent systematic reviews suggest that heterogeneity may moderate treatment outcomes. However, no study has explored whether subgroups of CFS predict response to treatment. We used both latent class analysis (LCA) and latent class regression (LCR) to clarify the relationship between subgroups of CFS patients (n = 236), diagnosed using the Oxford diagnostic criteria, and the response to CBT. We measured symptoms, demographics, mood, and cognitive and behavioural responses to illness to define subgroups. We found 5 latent classes by LCA, which did not differ in the direction of their response to CBT, with all classes showing improvement. In contrast, an exploratory LCR identified 4 latent classes, 1 of which predicted a poor response to CBT, whereas the other 3 predicted a good outcome, accounting for more than 70% of the patients. The negative outcome class was defined by weight fluctuations and physical shakiness, anxiety, pain and being focused on symptoms. CBT should be offered to all classes of patients with CFS, when defined by these measures. It may be possible to predict a minority group with a negative outcome, but this exploratory work needs replication. Copyright © 2011 S. Karger AG, Basel.

  2. 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.)

  3. Systematic investigation of the fatigue performance of a friction stir welded low alloy steel

    International Nuclear Information System (INIS)

    Toumpis, Athanasios; Galloway, Alexander; Molter, Lars; Polezhayeva, Helena

    2015-01-01

    Highlights: • The fatigue behaviour of a friction stir welded low alloy steel has been assessed. • The welds’ fatigue lives outperform the International Institute of Welding’s recommendations for fusion welds. • The slow weld exhibits the best fatigue performance of the investigated welds. • Fracture surface analysis shows that minor embedded flaws do not offer crack initiation sites. • Process-related surface breaking flaws have a significant effect on the fatigue life. - Abstract: A comprehensive fatigue performance assessment of friction stir welded DH36 steel has been undertaken to address the relevant knowledge gap for this process on low alloy steel. A detailed set of experimental procedures specific to friction stir welding has been put forward, and the consequent study extensively examined the weld microstructure and hardness in support of the tensile and fatigue testing. The effect of varying welding parameters was also investigated. Microstructural observations have been correlated to the weldments’ fatigue behaviour. The typical fatigue performance of friction stir welded steel plates has been established, exhibiting fatigue lives well above the weld detail class of the International Institute of Welding even for tests at 90% of yield strength, irrespective of minor instances of surface breaking flaws which have been identified. An understanding of the manner in which these flaws impact on the fatigue performance has been established, concluding that surface breaking irregularities such as these produced by the tool shoulder’s features on the weld top surface can be the dominant factor for crack initiation under fatigue loading

  4. Viscoelastic behaviour and fracture toughness of linear-low-density polyethylene reinforced with synthetic boehmite alumina nanoparticles

    Directory of Open Access Journals (Sweden)

    D. Pedrazzoli

    2013-08-01

    Full Text Available Aim of the present study is to investigate how synthetic boehmite alumina (BA nanoparticles modify the viscoleastic and fracture behaviour of linear low-density polyethylene. Nanocomposites containing up to 8 wt% of untreated and octyl silane-functionalized BA nanoparticles, were prepared by melt compounding and hot pressing. The BA nanoparticles were finely and unformly dispersed within the matrix according to scanning electron microscopy inspection. The results of quasi-static tensile tests indicated that nanoparticles can provide a remarkable stiffening effect at a rather low filler content. Short term creep tests showed that creep stability was significatively improved by nanofiller incorporation. Concurrently, both storage and loss moduli were enhanced in all nanocomposites, showing better result for surface treated nanoparticles. The plane-stress fracture toughness, evaluated by the essential work of fracture approach, manifested a dramatic increase (up to 64% with the BA content, with no significant differences among the various types of BA nanoparticles.

  5. Hot deformation behaviour and fracture of 10CrMoWNb ferritic–martensitic steel

    International Nuclear Information System (INIS)

    Churyumov, A.Yu.; Khomutov, M.G.; Solonin, A.N.; Pozdniakov, A.V.; Churyumova, T.A.; Minyaylo, B.F.

    2015-01-01

    Highlights: • The optimal temperature range for hot deformation of 10CrMoWNb steel was established. • A constitutive Arrhenius-type model of 10CrMoWNb steel was obtained. • The Nb 7 B 4 C 4 phase was identified as a reason of the hot fracture of the steel. - Abstract: High-Cr ferritic–martensitic steels are important materials for use in nuclear reactors. This study describes a development activity for this category of steels involving the investigation of the hot deformation behaviour and microstructure evolution during hot deformation of 10CrMoWNb steel. Hot compression and tension tests were performed in the temperature range of 900–1350 °C by using a Gleeble 3800 thermomechanical simulator. The results indicate that the flow stress and ultimate tensile strength increase with a decrease of the deformation temperature and an increase of the strain rate. Based on the experimental true strain-true stress data, the modified Arrhenius-type constitutive model was established for a form of 10CrMoWNb ferritic–martensitic steel. The hot plasticity properties of the 10CrMoWNb steel increase with temperature up to 1275 °C due to dynamic recrystallisation processes in the austenite phase. The reduction of area decreases when the temperature is higher than 1300 °C and is zero at 1350 °C for all strain rates because of the liquid phase appearance in the structure of the steel

  6. On modeling the large strain fracture behaviour of soft viscous foods

    Science.gov (United States)

    Skamniotis, C. G.; Elliott, M.; Charalambides, M. N.

    2017-12-01

    Mastication is responsible for food breakdown with the aid of saliva in order to form a cohesive viscous mass, known as the bolus. This influences the rate at which the ingested food nutrients are later absorbed into the body, which needs to be controlled to aid in epidemic health problems such as obesity, diabetes, and dyspepsia. The aim of our work is to understand and improve food oral breakdown efficiency in both human and pet foods through developing multi-scale models of oral and gastric processing. The latter has been a challenging task and the available technology may be still immature, as foods usually exhibit a complex viscous, compliant, and tough mechanical behaviour. These are all addressed here through establishing a novel material model calibrated through experiments on starch-based food. It includes a new criterion for the onset of material stiffness degradation, a law for the evolution of degradation governed by the true material's fracture toughness, and a constitutive stress-strain response, all three being a function of the stress state, i.e., compression, shear, and tension. The material model is used in a finite element analysis which reproduces accurately the food separation patterns under a large strain indentation test, which resembles the boundary conditions applied in chewing. The results lend weight to the new methodology as a powerful tool in understanding how different food structures breakdown and in optimising these structures via parametric analyses to satisfy specific chewing and digestion attributes.

  7. Unified viscoplasticity modelling and its application to fatigue-creep behaviour of gas turbine rotor

    OpenAIRE

    Benaarbia, A.; Rae, Y.; Sun, Wei

    2018-01-01

    This paper presents an elasto-visco-plastic finite element modelling framework including the associated UMAT codes to investigate the high temperature behaviour of gas turbine rotor steels. The model used in the FE study is an improved and unified multi-axial Chaboche-Lemaitre model which takes into account non-linear kinematic and isotropic hardening. The computational methodology is a three-dimensional framework following an implicit formulation and based on a radial return mapping algorith...

  8. An individualized exercise programme with and without behavioural change enhancement strategies for managing fatigue among frail older people: a quasi-experimental pilot study.

    Science.gov (United States)

    Liu, Justina Y-W; Lai, Claudia Ky; Siu, Parco M; Kwong, Enid; Tse, Mimi My

    2017-04-01

    To evaluate the feasibility and preliminary effects of an individualized exercise programme with and without behavioural change enhancement strategies for frail older people with fatigue. A three-arm, single-blinded, quasi-experimental pilot study. Community health centres. A total of 79 frail older people with fatigue, mean age 79.32 years (±7.72). The combined group received a 16-week combined intervention consisting of exercise training and a behavioural change enhancement programme. The exercise group received exercise training and health talks, whereas the control group received only health talks. Feasibility was assessed through the participants' recruitment, retention, attendance and adherence, feedback, and reports of adverse events. The preliminary effects were assessed by the participants' level of fatigue, physical endurance, self-efficacy, and self-perceived compliance with exercise. Feasibility was achievable with high recruitment (87.2%) and low overall attrition (7.1%) rates. A similar reduction in fatigue was identified in all groups, but a trend of greater improvement in physical endurance was observed in the combined group than in the other two groups. The combined group also had a significantly better attendance rate [F(2,76) = 5.64, p change, when the participants are establishing the habit of exercising daily.

  9. Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes.

    Science.gov (United States)

    Jian, Yu-Tao; Tang, Tian-Yu; Swain, Michael V; Wang, Xiao-Dong; Zhao, Ke

    2016-12-01

    The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05. As grit size of the diamond disc increased, zirconia surface roughness decreased (pzirconia surface after fracture for all groups. Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength. Copyright © 2016. Published by Elsevier Ltd.

  10. Fatigue and creep crack growth behaviour at high temperatures for weld metals of Alloy 800 and Alloy 617

    International Nuclear Information System (INIS)

    Roedig, M.; Choudhary, B.K.

    1993-01-01

    High temperature fatigue crack growth (FCG) and creep crack growth (CCG) experiments have been conducted in air on weld metal, heat affected zone (HAZ) and base metal of the austenitic Alloy 800 and the nickel base Alloy 617. Tests were performed on specimens machined from pipes, in the temperature range 550-900 deg. C. The crack propagation mode was examined. At all temperatures and for both materials, FCG of base metal was found to be the highest, whereas the weld metal exhibited the lowest FCG rate. The FCG rate in the HAZ was found to lie in between of those observed for base and weld metal. The crack propagation mode remained transgranular in base metal and transdendritic in weld metal at all temperatures. CCG behaviour could be described using the energy rate integral C*. Base metal and weld metal exhibited similar CCG rate at same C*. The crack propagation mode under CCG condition was found to be intergranular in base metal and HAZ and interdendritic in the weld metal. (author)

  11. Fracture strength and probability of survival of narrow and extra-narrow dental implants after fatigue testing: In vitro and in silico analysis.

    Science.gov (United States)

    Bordin, Dimorvan; Bergamo, Edmara T P; Fardin, Vinicius P; Coelho, Paulo G; Bonfante, Estevam A

    2017-07-01

    To assess the probability of survival (reliability) and failure modes of narrow implants with different diameters. For fatigue testing, 42 implants with the same macrogeometry and internal conical connection were divided, according to diameter, as follows: narrow (Ø3.3×10mm) and extra-narrow (Ø2.9×10mm) (21 per group). Identical abutments were torqued to the implants and standardized maxillary incisor crowns were cemented and subjected to step-stress accelerated life testing (SSALT) in water. The use-level probability Weibull curves, and reliability for a mission of 50,000 and 100,000 cycles at 50N, 100, 150 and 180N were calculated. For the finite element analysis (FEA), two virtual models, simulating the samples tested in fatigue, were constructed. Loading at 50N and 100N were applied 30° off-axis at the crown. The von-Mises stress was calculated for implant and abutment. The beta (β) values were: 0.67 for narrow and 1.32 for extra-narrow implants, indicating that failure rates did not increase with fatigue in the former, but more likely were associated with damage accumulation and wear-out failures in the latter. Both groups showed high reliability (up to 97.5%) at 50 and 100N. A decreased reliability was observed for both groups at 150 and 180N (ranging from 0 to 82.3%), but no significant difference was observed between groups. Failure predominantly involved abutment fracture for both groups. FEA at 50N-load, Ø3.3mm showed higher von-Mises stress for abutment (7.75%) and implant (2%) when compared to the Ø2.9mm. There was no significant difference between narrow and extra-narrow implants regarding probability of survival. The failure mode was similar for both groups, restricted to abutment fracture. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Are bi-axial proximal sesamoid bone fractures in the British Thoroughbred racehorse a bone fatigue related fracture? A histological study.

    Science.gov (United States)

    Kristoffersen, M; Hetzel, U; Parkin, T D H; Singer, E R

    2010-01-01

    To investigate whether microfractures and alterations in the trabecular bone area are associated with catastrophic bi-axial proximal sesamoid bone fractures (PSBF). Proximal sesamoid bones (PSB) from 10 racehorses with PSBF and from 10 control racehorses without musculoskeletal injury were examined using the bulk basic fuchsin method. Bone histomorphometric and microfracture analysis was performed, and cases and controls compared using two-sample t-test, paired t-test, and Mann-Whitney U test. There was no significant difference in the microfracture density and the trabecular bone area between bones from case and control horses, and between fractured and non-fractured bones in case horses. Microfracture density was low in the areas of the PSB examined. Microfracture density was not significantly different between groups, indicating that propagation of micro-cracks is an unlikely predisposing pathologic alteration in PSBF in British racehorses. There was no significant difference in the bone surface area between groups, which one would expect if modelling, adaptation and an increase in bone density were associated with PSBF fracture in the case horses. Therefore, PSBF in the British racehorse does not appear to be associated with microfractures of the trabecular bone of the PSB. The PSB fractures might represent an acute monotonic fracture; however, the aetiology of the fractures remains unknown with additional research required.

  13. Investigations on the lifetime behaviour of a P23 pipe under fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Friedmann, V.; Hartrott, P. von [Fraunhofer IWM, Freiburg (Germany)

    2008-07-01

    The performance of girth welds on new P23 low chromium steel pipes under cyclic loading at 450 C was investigated. The loading conditions were chosen to be representative for bore crack initiation and growth observed in main steam lines fabricated of 0.5Cr0.5Mo0.25V (CrMoV) steel. The microstructure of the base material and weldments was analysed. A lifetime model, initially set up for the prediction of thermo-cyclic loading, is used to predict the isothermal component behaviour. It is based on a Chaboche-type deformation model and the DTMF crack growth model. The failure mechanism of two component tests was compared to the model assumptions and the component lifetimes and failure locations are compared to the model predictions. (orig.)

  14. A randomised controlled trial testing the feasibility and efficacy of a physical activity behavioural change intervention in managing fatigue with gynaecological cancer survivors.

    Science.gov (United States)

    Donnelly, C M; Blaney, J M; Lowe-Strong, A; Rankin, J P; Campbell, A; McCrum-Gardner, E; Gracey, J H

    2011-09-01

    To determine the feasibility and efficacy of a physical activity behavioural change intervention in managing cancer-related fatigue among gynaecological cancer survivors during and post anti-cancer treatments. A two arm, single blind, randomised controlled trial was conducted within the Northern Ireland regional Cancer Centre. Thirty three sedentary gynaecological cancer survivors (stage I-III; ≤3 years post diagnosis), experiencing cancer-related fatigue (mild-severe) took part. Participants were randomly assigned to a behavioural change, moderate intensity physical activity intervention (n=16) or a Contact Control group (n=17). The primary outcome was fatigue (Multidimensional Fatigue Symptom Inventory-Short Form and Functional Assessment in Chronic Illness Therapy-Fatigue subscale). Secondary outcomes included quality of life, physical functioning, positive and negative affect, depression, body composition, sleep dysfunction and self-reported physical activity. Feasibility was assessed based on the recruitment rate, programme and physical activity adherence and participants' programme evaluation, including optional focus groups (n=16). Twenty five percent of eligible women took part (33/134). Participants were 8.7 (SD=9.1) months post diagnosis, with a mean age of 53 (SD=10.3) years. The majority of the sample had a diagnosis of ovarian (n=12) or endometrial cancer (n=11). Significant differences favouring the intervention group were observed for fatigue at 12 weeks and 6 months follow-up (12 week: mean difference=-11.06; 95% confidence interval (CI)=-21.89 to -0.23; effect size (d)=0.13; p=0.046; 6 month: mean difference=-19.48; 95% CI=-19.67 to -19.15; effect size (d)=0.20; p=0.01). A mean of 10 calls (SD=1.2 calls) were delivered to the Physical Activity Group, and 10 (SD=1.6 calls) to the CC group. The intervention was positively perceived based on exit questionnaire and focus group findings. A physical activity behavioural change intervention for

  15. Fear of movement and avoidance behaviour toward physical activity in chronic-fatigue syndrome and fibromyalgia: state of the art and implications for clinical practice.

    Science.gov (United States)

    Nijs, Jo; Roussel, Nathalie; Van Oosterwijck, Jessica; De Kooning, Margot; Ickmans, Kelly; Struyf, Filip; Meeus, Mira; Lundberg, Mari

    2013-08-01

    Severe exacerbation of symptoms following physical activity is characteristic for chronic-fatigue syndrome (CFS) and fibromyalgia (FM). These exacerbations make it understandable for people with CFS and FM to develop fear of performing body movement or physical activity and consequently avoidance behaviour toward physical activity. The aims of this article were to review what measures are available for measuring fear of movement and avoidance behaviour, the prevalence fear of movement and avoidance behaviour toward physical activity and the therapeutic options with fear of movement and avoidance behaviour toward physical activity in patients with CFS and FM. The review revealed that fear of movement and avoidance behaviour toward physical activity is highly prevalent in both the CFS and FM population, and it is related to various clinical characteristics of CFS and FM, including symptom severity and self-reported quality of life and disability. It appears to be crucial for treatment (success) to identify CFS and FM patients displaying fear of movement and avoidance behaviour toward physical activity. Individually tailored cognitive behavioural therapy plus exercise training, depending on the patient's classification as avoiding or persisting, appears to be the most promising strategy for treating fear of movement and avoidance behaviour toward physical activity in patients with CFS and FM.

  16. Direct Numerical Simulation of Fracture Behaviour for Random Short Wood Fibres Reinforced Composites, Comparison with Digital Image Correlation Experiments

    Directory of Open Access Journals (Sweden)

    Brillaud J.

    2010-06-01

    Full Text Available The work is to predict fracture behaviour of bio-composites from the tensile properties of its components. In this work, we have realized a direct numerical simulation of fracture behaviour for random short spruce fibers reinforced composites. For calculations, wood fibers have been considered as linear elastic bodies, polypropylene matrix as an elastic-plastic material. Then, numerical results have been compared with experimental results that have been obtained by digital image correlation. This comparison indicates that random fiber FE model of random short spruce fibers reinforced composites can be able to fairly reflect the influence of random fibers microstructure in the composite on its fracture behavior. The calculation of both random fiber and homogeneous FE model and their comparison with experiments show that the average values of J-integral in a region in the front of the crack tip from both numerical FE models are in good agreement with the average J value of DIC experiment in the same region when the numerical and experimental CT specimens of the short spruce fiber reinforced composite are subjected to the same extension at their loading point.

  17. 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

  18. Fatigue Crack Growth and Fracture Behavior of As-Cast Ti-43.5Al-4Nb-1Mo-0.1B (TNM) Compared to Ti-48Al-2Nb-2Cr (4822) (Postprint)

    Science.gov (United States)

    2017-11-22

    duplex microstructures exhibit low fracture toughness and creep resistance but moderate ten- sile ductility at ambient temperatures. This inverse...Mercer, Mechanisms of fatigue crack growth in Ti- 48Al at ambient and elevated temperature, Scr. Metall. Mater. 33 (7) (1995) 1169–1176. [9] J.J. Kruzic

  19. Creep-fatigue deformation behaviour of OFHC-copper and CuCrZr alloy with different heat treatments and with and without neutron irradiation

    International Nuclear Information System (INIS)

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

    2005-08-01

    The creep-fatigue interaction behaviour of a precipitation hardened CuCrZr alloy was investigated at 295 and 573 K. To determine the effect of irradiation a number of fatigue specimens were irradiated at 333 and 573 K to a dose level in the range of 0.2 - 0.3 dpa and were tested at room temperature and 573 K, respectively. The creep-fatigue deformation behaviour of OFHC-copper was also investigated but only in the unirradiated condition and at room temperature. The creep-fatigue interaction was simulated by applying a certain holdtime on both tension and compression sides of the cyclic loading with a frequency of 0.5 Hz. Holdtimes of up to 1000 seconds were used. Creep-fatigue experiments were carried out using strain, load and extension controlled modes of cyclic loading. In addition, a number of 'interrupted' creep-fatigue tests were performed on the prime aged CuCuZr specimens in the strain controlled mode with a strain amplitude of 0.5% and a holdtime of 10 seconds. The lifetimes in terms of the number of cycles to failure were determined at different strain and load amplitudes at each holdtime. Post-deformation microstructures was investigated using a transmission electron microscopy. The main results of these investigations are presented and their implications are briefly discussed in the present report. The central conclusion emerging from the present work is that the application of holdtime generally reduces the number of cycles to failure. The largest reduction was found to be in the case of OFHC-copper. Surprisingly, the magnitude of this reduction is found to be larger at lower levels of strain or stress amplitudes, particularly when the level of the stress amplitude is below the monotonic yield strength of the material. The reduction in the yield strength due to overaging heat treatments causes a substantial decrease in the number of cycles to failure at all holdtimes investigated. The increase in the yield strength due to neutron irradiation at 333 K

  20. The influence of environment and frequency on near threshold and spectrum loading fatigue behaviour of SA508 RPV steel

    International Nuclear Information System (INIS)

    Achilles, R.D.; Bulloch, J.H.

    1987-01-01

    Since the discovery of an environmentally assisted fatigue crack growth phenomenon in Light Water Reactor (LWR) environments, numerous studies including Bamford (1980) and Kondo et al (1972), have been conducted over the past fifteen years. The present paper describes a series of fatigue tests in pure argon and a Pressurised Water Reactor (PWR) environment which have a number of differing loading sequences. (orig.)

  1. The influence of environment and frequency on near threshold and spectrum loading fatigue behaviour of SA508 RPV steel

    International Nuclear Information System (INIS)

    Achilles, R.D.; Bulloch, J.H.

    1987-01-01

    Since the discovery of an environmentally assisted fatigue crack growth phenomenon in Light Water Reactor (LWR) environments, numerous studies have been conducted over the past fifteen years. The present paper describes a series of fatigue tests in pure argon and a Pressurised Water Reactor (PWR) environment which have a number of differing loading sequences

  2. Final report on in-reactor creep-fatigue deformation behaviour of a CuCrZr alloy: COFAT 1

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Tähtinen, S.; Moilanen, P.

    CrZr(HT1) alloy exposed concurrently to flux of neutrons and creep-fatigue cyclic loading directly in a fission reactor. Special experimental facilities were designed and fabricated for this purpose. A number of in-reactor creep-fatigue experiments were successfully carried out in the BR-2 reactor at Mol...

  3. Fatigue behaviour of cast nickel based superalloy inconel 792-5A at 700 °C

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Obrtlík, Karel; Polák, Jaroslav; Kruml, Tomáš

    2006-01-01

    Roč. 40, č. 5 (2006), s. 175-178 ISSN 1580-2949 R&D Projects: GA AV ČR 1QS200410502; GA ČR(CZ) GP106/05/P521 Institutional research plan: CEZ:AV0Z20410507 Keywords : high temperature fatigue * superalloy * slip markings-bands Subject RIV: JL - Materials Fatigue, Friction Mechanics

  4. 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.

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

    Science.gov (United States)

    Senthilkumar, R.; Arunkumar, N.; Manzoor Hussian, M.

    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.

  6. Creep, Fatigue and Fracture Behavior of Environmental Barrier Coating and SiC-SiC Ceramic Matrix Composite Systems: The Role of Environment Effects

    Science.gov (United States)

    Zhu, Dongming; Ghosn, Louis J.

    2015-01-01

    Advanced environmental barrier coating (EBC) systems for low emission SiCSiC CMC combustors and turbine airfoils have been developed to meet next generation engine emission and performance goals. This presentation will highlight the developments of NASAs current EBC system technologies for SiC-SiC ceramic matrix composite combustors and turbine airfoils, their performance evaluation and modeling progress towards improving the engine SiCSiC component temperature capability and long-term durability. Our emphasis has also been placed on the fundamental aspects of the EBC-CMC creep and fatigue behaviors, and their interactions with turbine engine oxidizing and moisture environments. The EBC-CMC environmental degradation and failure modes, under various simulated engine testing environments, in particular involving high heat flux, high pressure, high velocity combustion conditions, will be discussed aiming at quantifying the protective coating functions, performance and durability, and in conjunction with damage mechanics and fracture mechanics approaches.

  7. Behaviour and fatigue damage study of cast aluminium alloys; Etude du comportement et de l'endommagement en fatigue d'alliages d'aluminium de fonderie

    Energy Technology Data Exchange (ETDEWEB)

    Barlas, B.

    2004-02-15

    This study is aimed at determining the influence of chemical composition and heat treatment of cast aluminium alloys Al-Si-Cu-Mg on mechanical behaviour and fatigue life of structures. The industrial frame of this study concerns cylinder-heads of high efficiency diesel engines, for Renault and Montupet companies. The experimental means involved in this work are as well microscopic (TEM, microhardness, image analysis), mechanical (LCF and aniso-thermal tests, macro-hardness) and numerical (simulation of the stability of the hardening phases, behaviour and damage model identification, cylinder-head life time calculation). The link between micro and macro approaches is provided by the means of an internal microscopic variable representing thermal aging through coarsening of the precipitates and implemented into the macroscopic model. (author)

  8. Effect of iron content on the microstructure and the fatigue behaviour of GK-AlSi12CuMgNi

    International Nuclear Information System (INIS)

    Bischofberger, U.; Exner, H.E.; Neite, G.

    1990-01-01

    During recycling, iron can be accumulated in aluminium alloys. The limits at which an enlarged iron content in cast aluminium-silicon alloys of type GK-AlSi12CuMgNi can become detrimental for high cycle fatigue at room temperature, 150 degC and 250 degC and the reasons for these limits are evaluated. The mechanisms by which iron containing micro-structural features (large primary platelets of β-Al 5 FeSi) contribute to crack initiation are discussed on the basis of scanning electron fractography. These mechanisms are shown to be different for low and high temperatures involving oxide inclusions at room temperature and 150 degC and favourably oriented precipitation-free zones in the surrounding Al matrix at 250 degC. Due to the fact that crack initiation at β-Al 5 FeSi is a rare event, fatigue fracture becomes a statistical function of sample size which explains the excessive scatter of fatigue data when small samples are tested

  9. Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4 mm locking compression plate.

    Science.gov (United States)

    Chao, Peini; Conrad, Bryan P; Lewis, Daniel D; Horodyski, MaryBeth; Pozzi, Antonio

    2013-06-24

    There are several factors that can affect the fatigue life of a bone plate, including the mechanical properties of the plate and the complexity of the fracture. The position of the screws can influence construct stiffness, plate strain and cyclic fatigue of the implants. Studies have not investigated these variables in implants utilized for long bone fracture fixation in dogs and cats. The purpose of the present study was to evaluate the effect of plate working length on construct stiffness, gap motion and resistance to cyclic fatigue of dog femora with a simulated fracture gap stabilized using a 12-hole 2.4 mm locking compression plates (LCP). Femora were plated with 12-hole 2.4 mm LCP using 2 screws per fracture segment (long working length group) or with 12-hole 2.4 mm LCP using 5 screws per fracture segment (a short working length group). Construct stiffness did not differ significantly between stabilization techniques. Implant failure did not occur in any of the plated femora during cycling. Mean ± SD yield load at failure in the short plate working length group was significantly higher than in the long plate working length group. In a femoral fracture gap model stabilized with a 2.4 mm LCP applied in contact with the bone, plate working length had no effect on stiffness, gap motion and resistance to fatigue. The short plate working length constructs failed at higher loads; however, yield loads for both the short and long plate working length constructs were within physiologic range.

  10. The Variable Angle Hip Fracture Nail Relative to the Gamma 3: A Finite Element Analysis Illustrating the Same Stiffness and Fatigue Characteristics

    Directory of Open Access Journals (Sweden)

    Amir Matityahu

    2013-01-01

    Full Text Available Ten percent of the 250,000 proximal femur fractures that occur in the United States each year are malreduced into a varus position after treatment. Currently, there is no cephalomedullary nail available that allows the physician to dynamically change the lag-screw-to-nail angle. The Variable Angle Nail (VAN was designed to allow movement of the lag screw relative to the shaft of the nail. This study compared the characteristics of the VAN to the Gamma 3 nail via finite element analysis (FEA in stiffness and fatigue. The results of the FEA model with the same loading parameters showed the Gamma 3 and the VAN with lag-screw-to-nail angle of 120° to have essentially the same stiffness values ranging from 350 to 382 N/mm. The VAN with lag-screw-to-nail angles of 120°, 130°, and 140° should be able to withstand more than 1,000,000 cycles from 1,400 N to 1,500 N loading of the tip of the lag screw. The Gamma 3 should be able to last more than 1,000,000 cycles at 1,400 N. In summary, the VAN is superior or equivalent in stiffness and fatigue when compared to the Gamma 3 using FEA.

  11. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds

    International Nuclear Information System (INIS)

    Le Corre, V.

    2006-09-01

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests on CT specimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  12. Fracture and Fatigue Resistance of Cemented versus Fused CAD-on Veneers over Customized Zirconia Implant Abutments.

    Science.gov (United States)

    Nossair, Shereen Ahmed; Aboushelib, Moustafa N; Morsi, Tarek Salah

    2015-01-05

    To evaluate the fracture mechanics of cemented versus fused CAD-on veneers on customized zirconia implant abutments. Forty-five identical customized CAD/CAM zirconia implant abutments (0.5 mm thick) were prepared and seated on short titanium implant abutments (Ti base). A second scan was made to fabricate 45 CAD-on veneers (IPS Empress CAD, A2). Fifteen CAD-on veneers were cemented on the zirconia abutments (Panavia F2.0). Another 15 were fused to the zirconia abutments using low-fusing glass, while manually layered veneers served as control (n = 15). The restorations were subjected to artificial aging (3.2 million cycles between 5 and 10 kg in a water bath at 37°C) before being axially loaded to failure. Fractured specimens were examined using scanning electron microscopy to detect fracture origin, location, and size of critical crack. Stress at failure was calculated using fractography principles (alpha = 0.05). Cemented CAD-on restorations demonstrated significantly higher (F = 72, p CAD-on and manually layered restorations. Fractographic analysis of fractured specimens indicated that cemented CAD-on veneers failed due to radial cracks originating from the veneer/resin interface. Branching of the critical crack was observed in the bulk of the veneer. Fused CAD-on veneers demonstrated cohesive fracture originating at the thickest part of the veneer ceramic, while manually layered veneers failed due to interfacial fracture at the zirconia/veneer interface. Within the limitations of this study, cemented CAD-on veneers on customized zirconia implant abutments demonstrated higher fracture than fused and manually layered veneers. © 2014 by the American College of Prosthodontists.

  13. Effect of precipitation condition, prestrain and temperature on the fatigue behaviour of wrought nickel-based superalloys in the VHCF range

    Energy Technology Data Exchange (ETDEWEB)

    Stoecker, Christian, E-mail: christian.stoecker@uni-siegen.de [Fakultaet 4, Institut fuer Werkstofftechnik, Universitaet Siegen, Paul-Bonatz-Strasse 9-11, Siegen 57068 (Germany); Zimmermann, Martina; Christ, Hans-Juergen [Fakultaet 4, Institut fuer Werkstofftechnik, Universitaet Siegen, Paul-Bonatz-Strasse 9-11, Siegen 57068 (Germany)

    2011-08-15

    The influence of a monotonic predeformation at room temperature on the very high cycle fatigue (VHCF) behaviour was studied in polycrystalline nickel-based superalloys (Nimonic 75 and Nimonic 80A) in three characteristic precipitation conditions (precipitation-free, peak-aged and overaged) after various degrees of predeformation. Isothermal fatigue tests were executed at temperatures up to 800 deg. C. In the intermediate temperature range (400-600 deg. C) the effect of predeformation becomes weaker with increasing temperature. This can be partially explained by the beginning of recovery. However, additional effects not related to the strain-hardened microstructure play a role, such as the formation of oxide layers and the decrease in notch sensitivity. The latter effect is important because of the surface roughening resulting from prestraining. Even for the overaged condition, 4% predeformation led to a higher VHCF fatigue resistance at 600 deg. C, due to the relatively stable recovered dislocation arrangement. Isothermal cyclic deformation at 800 deg. C revealed a pronounced decrease in cyclic lifetime for all precipitation conditions with or without a mechanical prehistory. Transmission electron microscopy was carried out in order to characterize the influence of the microstructure, the resulting dislocation slip behaviour and the relevant dislocation/particle interaction mechanisms on the VHCF behaviour. Furthermore, scanning electron microscopy observations revealed that all precipitation conditions show, independent of their predeformation condition, a transition from transgranular (room temperature to 600 deg. C) to intergranular (600-800 deg. C) microfatigue crack formation in the emerging oxide layers at the surface after VHCF tests.

  14. Effect of precipitation condition, prestrain and temperature on the fatigue behaviour of wrought nickel-based superalloys in the VHCF range

    International Nuclear Information System (INIS)

    Stoecker, Christian; Zimmermann, Martina; Christ, Hans-Juergen

    2011-01-01

    The influence of a monotonic predeformation at room temperature on the very high cycle fatigue (VHCF) behaviour was studied in polycrystalline nickel-based superalloys (Nimonic 75 and Nimonic 80A) in three characteristic precipitation conditions (precipitation-free, peak-aged and overaged) after various degrees of predeformation. Isothermal fatigue tests were executed at temperatures up to 800 deg. C. In the intermediate temperature range (400-600 deg. C) the effect of predeformation becomes weaker with increasing temperature. This can be partially explained by the beginning of recovery. However, additional effects not related to the strain-hardened microstructure play a role, such as the formation of oxide layers and the decrease in notch sensitivity. The latter effect is important because of the surface roughening resulting from prestraining. Even for the overaged condition, 4% predeformation led to a higher VHCF fatigue resistance at 600 deg. C, due to the relatively stable recovered dislocation arrangement. Isothermal cyclic deformation at 800 deg. C revealed a pronounced decrease in cyclic lifetime for all precipitation conditions with or without a mechanical prehistory. Transmission electron microscopy was carried out in order to characterize the influence of the microstructure, the resulting dislocation slip behaviour and the relevant dislocation/particle interaction mechanisms on the VHCF behaviour. Furthermore, scanning electron microscopy observations revealed that all precipitation conditions show, independent of their predeformation condition, a transition from transgranular (room temperature to 600 deg. C) to intergranular (600-800 deg. C) microfatigue crack formation in the emerging oxide layers at the surface after VHCF tests.

  15. Associations between stress, fatigue, sleep disturbances and dental students' oral health-related behaviours: changes throughout academic year

    OpenAIRE

    Rovas, Adomas; Staniulytė, Agnė; Pūrienė, Alina

    2017-01-01

    Background. Stress, fatigue and sleep disturbances are common among university students and they have an impact on their personal health. The prevalence as well as the influence of these factors on oral health-related behaviors are likely to vary during the academic year. Objectives. The objective of this study was to evaluate the prevalence of symptoms related to stress, fatigue and sleep disturbances among dental students during the academic year and to investigate whether these sympto...

  16. Fracture and Fatigue of Diffusion, Explosive, and Roll Bonded Al/Al and Ti/Al Laminates

    Science.gov (United States)

    1977-05-13

    received laminate panel. This was con- sidered equivalent to Ti-6AI-4V sheet in the mill annealed state given a I hr soak at 524°C (975°F). Condition B- this...Strength-Steel Laminar Composites," Trans. ASM 60, 384 (1967). 5. E. A’. Almond , N. J. Petch, A. E. Wraith, and E. S. Wright, "The Fracture of...Pressurlzed Laminated Cylinders", J. Iron Steel Inst. M2,7 1319 (1969). 6. E. A. Almond , J. D. Embury, and E. S. Wright, "Fracture in Laminated Materials

  17. Influence of non-metallic second phases on fatigue behaviour of high strength steel components; Efecto de segundas fases no metalicas sobre el comportamiento a fatiga de componentes de acero con elevadas solicitaciones

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, L.; Elvira, R.; Garcia de Andoin, A.; Pizarro, R.; Bertrand, C.

    2005-07-01

    To assess the real effect of the inclusion type on fatigue life of ultra clean high strength steels mechanical components made of 100Cr6 steel were fatigue tested and fracture surfaces analysed to determine the origin of fatigue cracks.Two heats proceedings from different steelmaking routes were taken for the tests. The material were forged into ring shape components which were fatigue tested under compression-compression loads. Failures were analysed by SFEM (Scanning field Emission Microscopy), proving that most of failures at high loads were originated by manganese sulphides of small size (10-70 micros), while less than 40% of all fatigue cracks due to inclusions were caused by titanium carbonitrides and hard oxides. It has been demonstrated that once number and size of hard inclusions have been reduced, the hazardous effect of oxides and carbonitrides on the fatigue life decreases also. However, softer inclusions as manganese sulphides, currently considered as less hazardous, play a more relevant role as direct cause of fatigue failure and they should be taken into account in a deeper way in order to balance both machinability and fatigue life requirements in high strength steel components. (Author) 11 refs.

  18. Short Fatigue Crack Growth Micromechanisms in a Cast Aluminium Piston Alloy

    Science.gov (United States)

    Mbuya, T. O.; Crump, J.; Sinclair, I.; Soady, K. A.; Thomson, R. C.; Reed, P. A. S.

    The short fatigue crack growth behaviour of a model cast aluminium piston alloy has been investigated. This has been achieved using a combination of fatigue crack replication methods at various intervals during fatigue testing and post-mortem analysis of fracture surfaces and crack profiles. Crack-microstructure interactions have been clearly delineated using a combination of optical microscopy (OM), scanning electron microscopy (SEM) and three dimensional (3D) X-ray microtomography (SRCT). Results show that intermetallic particles play a significant role in determining the crack path and growth rate of short fatigue cracks. It is observed that the growth of short cracks is often retarded or even arrested at intermetallic particles and grain boundaries. Crack deflection at intermetallics and grain boundaries is also frequently observed. These results have been compared with the long crack growth behaviour of the alloy

  19. Constraint Effects at Brittle Fracture Initiation in a Cast Ferritic Steel

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Chlup, Zdeněk; Kozák, Vladislav

    č. 71 (2004), s. 873-883 ISSN 0013-7944 R&D Projects: GA AV ČR IAA2041003 Institutional research plan: CEZ:AV0Z2041904 Keywords : Cast ferritic steel * transition behaviour * fracture toughness Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.299, year: 2004 www.sciencedirect.com

  20. Modified Disk-Shaped Compact Tension Test for Measuring Concrete Fracture Properties

    Czech Academy of Sciences Publication Activity Database

    Cifuentes, H.; Lozano, M.; Holušová, Táňa; Medina, F.; Seitl, Stanislav; Fernández-Canteli, A.

    2017-01-01

    Roč. 11, č. 2 (2017), s. 215-228 ISSN 1976-0485 R&D Projects: GA ČR(CZ) GA16-18702S Institutional support: RVO:68081723 Keywords : Concrete * Fracture behaviour * Experimental techniques Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 2.031, year: 2016

  1. Role of pyrolysis conditions on fracture behaviour of fibre reinforced Composites

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Černý, Martin; Strachota, Adam; Dlouhý, Ivo

    2011-01-01

    Roč. 465, - (2011), s. 455-458 ISSN 1013-9826 R&D Projects: GA ČR GA106/09/1101 Institutional research plan: CEZ:AV0Z20410507; CEZ:AV0Z40500505; CEZ:AV0Z30460519 Keywords : CMCs * fracture toughness * heat treatment Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  2. Fracture behaviour and impact testing of materials on isotactic polypropylene base

    Czech Academy of Sciences Publication Activity Database

    Elíšek, P.; Raab, Miroslav; Mollíková, E.

    2001-01-01

    Roč. 8, č. 3 (2001), s. 41-46 ISSN 1335-0803 R&D Projects: GA AV ČR KSK4050111 Institutional research plan: CEZ:AV0Z4050913 Keywords : fracture toughness * isotactic propylene * beta nucleant Subject RIV: CD - Macromolecular Chemistry

  3. Exercise therapy and cognitive behavioural therapy to improve fatigue, daily activity performance and quality of life in postpoliomyelitis syndrome: the protocol of the FACTS-2-PPS trial.

    Science.gov (United States)

    Koopman, Fieke S; Beelen, Anita; Gerrits, Karin H; Bleijenberg, Gijs; Abma, Tineke A; de Visser, Marianne; Nollet, Frans

    2010-01-18

    Postpoliomyelitis Syndrome (PPS) is a complex of late onset neuromuscular symptoms with new or increased muscle weakness and muscle fatigability as key symptoms. Main clinical complaints are severe fatigue, deterioration in functional abilities and health related quality of life. Rehabilitation management is the mainstay of treatment. Two different therapeutic interventions may be prescribed (1) exercise therapy or (2) cognitive behavioural therapy (CBT). However, the evidence on the effectiveness of both interventions is limited. The primary aim of the FACTS-2-PPS trial is to study the efficacy of exercise therapy and CBT for reducing fatigue and improving activities and quality of life in patients with PPS. Additionally, the working mechanisms, patients' and therapists' expectations of and experiences with both interventions and cost-effectiveness will be evaluated. A multi-centre, single-blinded, randomized controlled trial will be conducted. A sample of 81 severely fatigued patients with PPS will be recruited from 3 different university hospitals and their affiliate rehabilitation centres. Patients will be randomized to one of three groups i.e. (1) exercise therapy + usual care, (2) CBT + usual care, (3) usual care. At baseline, immediately post-intervention and at 3- and 6-months follow-up, fatigue, activities, quality of life and secondary outcomes will be assessed. Costs will be based on a cost questionnaire, and statistical analyses on GEE (generalized estimated equations). Analysis will also consider mechanisms of change during therapy. A responsive evaluation will be conducted to monitor the implementation process and to investigate the perspectives of patients and therapists on both interventions. A major strength of the FACTS-2-PPS study is the use of a mixed methods design in which a responsive and economic evaluation runs parallel to the trial. The results of this study will generate new evidence for the rehabilitation treatment of persons with PPS

  4. Fatigue crack growth rate behaviour of friction-stir aluminium alloy AA2024-T3 welds under transient thermal tensioning

    International Nuclear Information System (INIS)

    Ilman, M.N.; Kusmono,; Iswanto, P.T.

    2013-01-01

    Highlights: • FSW enables unweldable aircraft material AA2024-T3 to be welded without cracking. • FSW applied to aircraft structure is required to have superior fatigue resistance. • Transient thermal tensioning (TTT) is being developed for stress relieving in FSW. • The fatigue crack growth rates of FSW joints under TTT are studied. - Abstract: Friction stir welding (FSW) has become a serious candidate technology to join metallic fuselage panels for the next generation of civil aircrafts. However, residual stress introduced during welding which subsequently affects fatigue performance is still a major problem that needs to be paid attention. The present investigation aims to improve fatigue crack growth resistance of friction stir aluminium alloy AA2024-T3 welds using transient thermal tensioning (TTT) treatment. In this investigation, aluminium alloy AA2024-T3 plates were joined using FSW process with and without TTT. The welding parameters used including tool rotation speed (Rt) and the plate travelling speed (v) were 1450 rpm and 30 mm/min respectively. The TTT treatments were carried out by heating both sides of friction stir weld line using moving electric heaters ahead of, beside and behind the tool at a heating temperature of 200 °C. Subsequently, a sequence of tests was carried out including microstructural examination, hardness measurement, tensile test and fatigue crack growth rate (FCGR) test in combination with fractography using scanning electron microscopy (SEM). The FCGR test was carried out using a constant amplitude fatigue experiment with stress ratio (R) of 0.1 and frequency (f) of 11 Hz whereas specimens used were centre-crack tension (CCT) type with the initial crack located at the weld nugget. Results of this investigation showed that at low ΔK, typically below 9 MPa m 0.5 , the friction stir welds under TTT treatments lowered fatigue crack growth rate (da/dN) and the lowest (da/dN) was achieved as the heaters were located ahead of

  5. FRACTURE BEHAVIOUR OF P/M Cr-V LEDEBURITIC STEEL WITH DIFFERENT SURFACE ROUGHNESS

    Directory of Open Access Journals (Sweden)

    Peter Jurči

    2011-07-01

    Full Text Available The samples made from the Vanadis 6 PM ledeburitic tool steel were surface machined to different quality and heat treated by standard regime of the processing. Three point bending tests were carried out on processed samples. It was found that the flexural strength decreased with decreasing surface quality. The lowering of flexural strength has been accompanied with the decrease of the plastic component of plastic straining preceeding to fracture initiation (work of fracture of the material. It indicates that the surface roughness leads to the crack initiation before a larger plastic deformation of the material can be developed. Based on the results it can be suggested that to prevent the cracking of tools in the practice it is essential to make a surface machining (grinding, lapping, polishing to as high quality as possible.

  6. Cyclic plasticity and fatigue of metals

    International Nuclear Information System (INIS)

    Mughrabi, H.

    1993-01-01

    This report is a survey of the cyclic deformation and fatigue behaviour of selected engineering steels and alloys. Emphasis is placed on the important roles of the cyclic slip mode and the stability of the microstructure during cyclic stressing and on the conditions of fatigue testing with respect to the failure mechanisms and fatigue life. The examples presented include low-temperature fatigue, high-temperature fatigue in the presence of dynamic strain ageing and thermomechanical fatigue. (orig.)

  7. Fracture behaviour of WC-Co hardmetals with WC partially substituted by titanium carbide

    Science.gov (United States)

    Szutkowska, M.; Boniecki, M.; Cygan, S.; Kalinka, A.; Grilli, M. L.; Balos, S.

    2018-03-01

    The addition of various amounts of TiC0.9 phase in the range from 5wt.% to 20wt.% substituting WC phase was applied in WC-Co hardmetals with 9.5 wt.% bonding cobalt phase. The hardmetals were consolidated using Hot Isostatic Pressing (HIP) method at temperature of 1573K and pressure of 1500 atm. The plain strain fracture toughness has been determined from 3PB test on a precracking single edge notched beam (SENB) specimen. The indentation fracture toughness with Vickers cracks for comparison was also measured, which changed from 12 to 9.0 MPa·m1/2. The amount of the TiC0.9 phase affected the mechanical and physical properties: Vickers hardness from 12.5 to 14.0 GPa, Young’s modulus from 550 to 460 GPa, density from 13.1 to 9.6 g/cm3, friction coefficient from 0.24 to 0.45, fracture toughness from 16.8 to 11.0 MPa·m1/2. Scanning electron microscopy (SEM), X-ray and electron diffraction phase analysis were used to examine the WC-Co hardmetal with addition of the TiC0.9 phase. For comparison, physical and mechanical properties of the WC-Co hardmetals before modification were tested.

  8. Buckling and fracture behaviour of cracked thin plates under shear loading

    International Nuclear Information System (INIS)

    Brighenti, Roberto; Carpinteri, Andrea

    2011-01-01

    Thin-walled structural components are widely used in several engineering applications such as in aerospace, naval, nuclear power plant, pressure vessel, mechanical and civil fields. Since they are frequently characterised by a high slenderness, the safety assessment of such structural components requires to carefully consider the buckling collapse which can heavily limit their allowable bearing capacity. For very thin plates, buckling collapse can occur under compression, shear, or even under tension. In the present paper, the buckling and fracture collapse mechanisms in an elastic rectangular thin-plate with a central straight crack under shear loading are analysed. Different boundary conditions, crack length and orientation are considered. Through a parametric finite elements (FE) numerical analysis, the crack sensitivity of the collapse load of such a structural component is examined. The obtained results are discussed, and some interesting and useful conclusions are drawn. The collapse mechanism occurring earlier (buckling or fracture) is found by varying the fracture toughness of the material, and some failure-type maps depending on the geometrical parameters of the crack are determined.

  9. Understanding the nano- and macromechanical behaviour, the failure and fatigue mechanisms of advanced and natural polymer fibres by Raman/IR microspectrometry

    Science.gov (United States)

    Colomban, Philippe

    2013-03-01

    The coupled mechanical and Raman/infrared (IR) analysis of the (nano)structure and texture of synthetic and natural polymer fibres (polyamides (PA66), polyethylene terephthalate (PET), polypropylene (PP), poly(paraphenylene benzobisoxazole) (PBO), keratin/hair, Bombyx mori, Gonometa rufobrunea/postica Antheraea/Tussah silkworms and Nephila Madagascarensis spider silks) is applied so as to differentiate between crystalline and amorphous macromolecules. Bonding is very similar in the two cases but a broader distribution of conformations is observed for the amorphous macromolecules. These conclusions are then used to discuss the modifications induced by the application of a tensile or compressive stress, including the effects of fatigue. Detailed attention is paid to water and the inter-chain coupling for which the importance of hydrogen bonding is reconsidered. The significant role of the ‘amorphous’ bonds/domains in the process of fracture/fatigue is shown. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2012, 30 October-2 November 2012, Ha Long, Vietnam.

  10. Final report on in-reactor creep-fatigue deformation behaviour of a CuCrZr alloy: COFAT 2

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Johansen, Bjørn Sejr; Tähtinen, S.

    facilities for this purpose, in-reactor creep-fatigue tests have been performed at strain amplitudes of 0.25 and 0.35 % with a holdtime of 10s in the BR-2 reactor at Mol (Belgium). These tests were performed at the ambient temperatures of 326K and 323K. For comparison purposes corresponding out...

  11. The Effects of Exercise Education Intervention on the Exercise Behaviour, Depression, and Fatigue Status of Chronic Kidney Disease Patients

    Science.gov (United States)

    Kao, Yu-Hsiu; Huang, Yi-Ching; Chen, Pei-Ying; Wang, Kuo-Ming

    2012-01-01

    Purpose: The purpose of this paper is to investigate the effects of an exercise education intervention on exercise behavior, depression and fatigue status of chronic kidney disease (CKD) patients. Design/methodology/approach: This was a pilot study using an exercise education program as an intervention for CKD patients. The authors used the…

  12. Experimental Investigation of the Fracture Behaviour of Reinforced Ultra High Strength Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, J. P.; Henriksen, M. S.; Aarup, B.

    In the last fifteen years new types of cement based materials have been developed in Denmark at the Aalborg Portland Cement Factory. These types of new materials are characterized by very high strength even when mixed at room temperature and using conventional mixing techniques. In this paper...... the structural behaviour of a very high strength cement based material with and without steel fibres is investigated. A simple structural geometry has been tested, namely a beam subjected to three point bending. The results shows that the increase of ductility of the material also gives a more ductile behaviour...

  13. Surface characterization and influence of anodizing process on fatigue life of Al 7050 alloy

    International Nuclear Information System (INIS)

    Shahzad, Majid; Chaussumier, Michel; Chieragatti, Remy; Mabru, Catherine; Rezai-Aria, Farhad

    2011-01-01

    Highlights: → We studied the effect of surface treatments on fatigue behaviour of 7050 alloy. → Dissolution of constituent particles in pickling solution result in pits formation. → Decrease is fatigue life caused by anodization is small. → Multi-site cracks initiation has been observed for pickled and anodized specimens. -- Abstract: The present study investigates the influence of anodizing process on fatigue life of aluminium alloy 7050-T7451 by performing axial fatigue tests at stress ratio 'R' of 0.1. Effects of pre-treatments like degreasing and pickling employed prior to anodizing on fatigue life were studied. The post-exposure surface observations were made by scanning electron microscope (SEM) to characterize the effect of each treatment before fatigue testing. The surface observations have revealed that degreasing did not change the surface topography while pickling solution resulted in the formation of pits at the surface. Energy dispersive spectroscopy (EDS) was used to identify those constituent particles which were responsible for the pits formation. These pits are of primary concern with respect to accelerated fatigue crack initiation and subsequent anodic coating formation. The fatigue test results have shown that pickling process was detrimental in reducing the fatigue life significantly while less decrease has been observed for anodized specimens. Analyses of fracture surfaces of pickled specimens have revealed that the process completely changed the crack initiation mechanisms as compared to non-treated specimens and the crack initiation started at the pits. For most of the anodized specimens, fatigue cracks still initiated at the pits with very few cracks initiated from anodic coating. The decrease in fatigue life for pickled and anodized specimens as compared to bare condition has been attributed to decrease in initiation period and multi-site crack initiations. Multi-site crack initiation has resulted in rougher fractured surfaces for

  14. Polypropylene-rubber blends b 3: the effect of test speed on the fracture behaviour

    NARCIS (Netherlands)

    van der Wal, A.; Wal, A.; Gaymans, R.J.

    1999-01-01

    Polypropylene–EPDM blends were prepared on a twin screw extruder with a rubber content 0–40 vol%. On these materials the yield strength and the notched tensile behaviour was studied as function of test speed (10−4–10 m/s). With an infrared temperature camera the heat development in the notched

  15. Fatigue data compilation and evaluation of fatigue on design

    International Nuclear Information System (INIS)

    Nyilas, A.

    1985-05-01

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

  16. MICRO-CRACK BEHAVIOUR IN POLYMER MATRIX OF PARTICULATE COMPOSITE: INFLUENCE OF NON-LINEAR MATRIX

    Czech Academy of Sciences Publication Activity Database

    Majer, Z.; Náhlík, Luboš

    2012-01-01

    Roč. 106, SUPPL. 3 (2012), S472-S473 ISSN 0009-2770 Institutional support: RVO:68081723 Keywords : polymer matrix composite * fracture behaviour * non-linear matrix * micro-crack Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 0.453, year: 2012

  17. Structural changes, Evolution of damage parameters and crack crack propagation behaviour in welded plastic pipes

    Czech Academy of Sciences Publication Activity Database

    Lach, R.; Hutař, Pavel; Veselý, P.; Nezbedová, E.; Knésl, Zdeněk; Grellmann, W.

    2011-01-01

    Roč. 465, - (2011), s. 427-430 ISSN 1013-9826 R&D Projects: GA ČR GC101/09/J027 Institutional research plan: CEZ:AV0Z20410507 Keywords : plastic pipes * welded joints * microhardness * laser extensometry * fracture behaviour Subject RIV: JL - Materials Fatigue, Friction Mechanics

  18. EFAM GTP 02 - the GKSS test procedure for determining the fracture behaviour of materials

    International Nuclear Information System (INIS)

    Schwalbe, K.H.; Heerens, J.; Zerbst, U.; Kocak, M.

    2002-01-01

    This document describes a unified fracture mechanics test method in procedural form for quasi-static testing of materials. It is based on the ESIS Procedures P1 and P2 and introduces additional features, such as middle cracked tension specimens, shallow cracks, the δ 5 crack tip opening displacement, the crack tip opening angle, the rate of dissipated energy, testing of weldments, and guidance for statistical treatment of scatter. Special validity criteria are given for tests on specimens with low constraint. This document represents an updated version of EFAM GTP 94. (orig.) [de

  19. Fracture behaviour of teeth with conventional and mini-invasive access cavity designs

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Žižka, R.; Kania, J.; Přibyl, M.

    2017-01-01

    Roč. 37, č. 14 (2017), s. 4423-4429 ISSN 0955-2219. [FAC 2016 - International Conference on Fractography of Advanced Ceramics /5./. Smolenice, 09.10.2016-12.10.2016] R&D Projects: GA ČR GA14-11234S; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : endodontically treated premolars * in-vitro * maxillary premolars * stress-distribution * cusp coverage * resistance * composite * resin * restorations * scaffolds * Fracture resistance * Cavity * Tooth * Compressive test * Fractography Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 3.411, year: 2016

  20. Behaviour of generators retaining rings. Evaluation of material properties for fracture mechanics analyses

    International Nuclear Information System (INIS)

    Bethmont, M.; Masson, S.H.; Vaillant, F.

    1985-01-01

    Retaining rings of the first alternators of the French PWR program have been damaged by corrosion in humid medium. This led to the change of steel quality, 18 Mn 18 Cr instead of 18Mn 5Cr. This paper presents the results of tests concerning the fracture and tensile properties of these two steels. The temperature influence (between the ambient temperature and 300 0 C) and the hardening process influence have been studied. Crack propagation induced by stress corrosion has been measured at 80 0 C in aerated and desaerated water, and in an aerated solution of acidified sodium at pH3 [fr

  1. Fracture behaviour of the 14Cr ODS steel exposed to helium and liquid lead

    Czech Academy of Sciences Publication Activity Database

    Hojná, A.; Di Gabriele, F.; Hadraba, Hynek; Husák, Roman; Kuběna, Ivo; Rozumová, L.; Bublíková, P.; Kalivodová, J.; Matějíček, Jiří

    2017-01-01

    Roč. 490, JUL (2017), s. 143-154 ISSN 0022-3115 R&D Projects: GA ČR(CZ) GA14-25246S; GA ČR(CZ) GA14-12837S; GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 ; RVO:61389021 Keywords : Impact fracture * Microanalysis * Nanostructured steel * Oxidation * Thermal ageing Subject RIV: JG - Metallurgy; JG - Metallurgy (UFP-V) OBOR OECD: Materials engineering ; Materials engineering (UFP-V); Materials engineering (UFM-A) Impact factor: 2.048, year: 2016

  2. Modelling the effect of oxide fuel fracturing on the mechanical behaviour of fuel rods

    International Nuclear Information System (INIS)

    Helfer, T.; Garcia, P.; Ricaud, J.M.; Plancq, D.; Sidoroff, F.; Bernard, L.

    2005-01-01

    Computing stress and strain fields in fuel pellets is essential to modelling the in-pile behaviour of PWR fuel rods, especially under pellet-cladding interaction conditions. Fuel cracking occurs immediately after reactor start-up and is effective in relaxing stresses in the pellet. It is therefore important that the brittle behaviour of oxide fuels be modelled. A first attempt to take into account fuel cracking involved describing radial and axial fuel cracks in the pellet through a phenomenological modification of Hooke's law. A description of the model is given along with its two-dimensional extension applied to axisymmetrical fuel pellet simulations. The first results pertaining to this model are discussed. Another approach to modelling the damage to pellets induced by cracking involves the use of so-called cohesive models. These models describe the progressive loss of cohesion of the material in the damaged area ahead of the crack tip. A short review of these models is presented. (authors)

  3. Model for fracture mechanics based prediction of the fatigue strength of engineering alloys containing microscopical initial defects

    Directory of Open Access Journals (Sweden)

    Zerbst Uwe

    2014-06-01

    Full Text Available Recently two of the authors of the present paper proposed a model for fracture mechanics based prediction of the S-N characteristics of metallic components with large microstructural defects and supported this by a validation excercise on an aluminium alloy AL5380 H321. Within this presentation the authors extend the study using a number of data sets from the literature. Despite of necessary assumptions for the compensation of partially missing input information the results are fairly reasonable, with the exception of high loading levels where the analyses of two of the data sets yield non-conservative results. The authors propose multiple crack initiation as the potential root of the problem and discuss methods for extending the model for taking into account crack initiation.

  4. Mechanical properties and fracture behaviour of ODS Steel Friction Stir Welds at variable temperatures

    OpenAIRE

    Dawson, Huw; Serrano, Marta; Hernandez, Roberto; Cater, Steve; Jimenez-Melero, Enrique

    2017-01-01

    We have assessed the microstructure and the temperature-dependent mechanical behaviour of five bead-on-plate friction stir welds of Oxide Dispersion Strengthened (ODS) steel, produced using systematic changes to the tool rotation and traverse speed. Friction stir welding can potentially retain the fine dispersion of nanoparticles, and therefore also the high-temperature strength and radiation damage resistance of these materials. Tensile testing was carried out on the MA956 base material at a...

  5. 3D atomistic simulation of fatigue behaviour of cracked single crystal of bcc iron loaded in mode III

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Pokluda, J.; Machová, Anna; Hora, Petr

    2011-01-01

    Roč. 33, č. 12 (2011), s. 1564-1573 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional research plan: CEZ:AV0Z20760514 Keywords : fatigue * mode III * bcc iron * molecular dynamic simulations Subject RIV: JG - Metallurgy Impact factor: 1.546, year: 2011 http://www.sciencedirect.com/science/article/pii/S0142112311001708

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

    Science.gov (United States)

    Krewerth, D; Weidner, A; Biermann, H

    2013-12-01

    The present paper illustrates the application of infrared thermal measurements for the investigation of crack initiation point and crack propagation in the high-cycle and the very high-cycle fatigue range of cast AlSi7Mg alloy (A356). The influence of casting defects, their location, size and amount was studied both by fractography and thermography. Besides internal and surface fatigue crack initiation as a further crack initiation type multiple fatigue crack initiation was observed via in situ thermography which can be well correlated with the results from fractography obtained by SEM investigations. In addition, crack propagation was studied by the development of the temperature measured via thermography. Moreover, the frequency influence on high-cycle fatigue behaviour was investigated. The presented results demonstrate well that the combination of fractography and thermography can give a significant contribution to the knowledge of crack initiation and propagation in the VHCF regime. Copyright © 2013 Elsevier B.V. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-07-01

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

  8. Low and high cycle fatigue behaviour of steel-X6CRNI1811 (Type 304 SS) in air and flowing sodium

    International Nuclear Information System (INIS)

    Huthmann, H.; Jenner, G.

    Strain controlled LCF-tests were performed on X6CrNi1811 steel (Type 304 SS) in air and flowing sodium in a non-isothermal sodium loop. The results measured at 550 deg. C in an upstream position of the sodium loop show an increase in fatigue life in the strain range from about 1.5% to 0.4% for the base material in the as-received condition while the welded joints remain unaffected by the environment. The LCF-behaviour of base material specimens tested at 500 deg. C in a downstream position after a prior pre-exposure to sodium (4058 h, 500 deg. C) is also improved in comparison to parallel specimens tested in air with comparable thermal aging. Load controlled HCF-tests performed on X6CrNi1811 steel at 550 deg. C show a significant increase in fatigue life in the low cycle region (Nsub(f) 6 cycles) and a higher endurance limit for the base material in sodium but no influence of the environment is indicated for the welded joints. (author)

  9. Thermal/moisture-related stresses and fracture behaviour in solid wood members during forced drying

    DEFF Research Database (Denmark)

    Larsen, Finn

    with a drying history that was generated, to verify a model that was used to simulate disc samples of the same type. The stresses were analyzed so as to clarify whether and when critical stress stateswere encountered during the drying process. The reversibility of the mechano-sorptive strains, i...... of wood without injury to the timber itself. When solid wood products are dried from a green condition down to an average moisture content level close to the service life conditions of the final product, significant moisture-induced stresses and related fracturing can occur. The drying stresses arise......, in particular the stress and cracking that takeplace during kiln-drying. Both experimental and numerical work was carried out so as to obtain knowledge regarding stress, strain, mechano-sorption and crackbehaviours in wood during drying.The investigations aimed also at revealing how drying damagecan best...

  10. Environmental Barrier Coating Fracture, Fatigue and High-Heat-Flux Durability Modeling and Stochastic Progressive Damage Simulation

    Science.gov (United States)

    Zhu, Dongming; Nemeth, Noel N.

    2017-01-01

    Advanced environmental barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to protect emerging light-weight SiC/SiC ceramic matrix composite (CMC) engine components, further raising engine operating temperatures and performance. Because the environmental barrier coating systems are critical to the performance, reliability and durability of these hot-section ceramic engine components, a prime-reliant coating system along with established life design methodology are required for the hot-section ceramic component insertion into engine service. In this paper, we have first summarized some observations of high temperature, high-heat-flux environmental degradation and failure mechanisms of environmental barrier coating systems in laboratory simulated engine environment tests. In particular, the coating surface cracking morphologies and associated subsequent delamination mechanisms under the engine level high-heat-flux, combustion steam, and mechanical creep and fatigue loading conditions will be discussed. The EBC compostion and archtechture improvements based on advanced high heat flux environmental testing, and the modeling advances based on the integrated Finite Element Analysis Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program will also be highlighted. The stochastic progressive damage simulation successfully predicts mud flat damage pattern in EBCs on coated 3-D specimens, and a 2-D model of through-the-thickness cross-section. A 2-parameter Weibull distribution was assumed in characterizing the coating layer stochastic strength response and the formation of damage was therefore modeled. The damage initiation and coalescence into progressively smaller mudflat crack cells was demonstrated. A coating life prediction framework may be realized by examining the surface crack initiation and delamination propagation in conjunction with environmental

  11. [Growth behaviour after fractures of the proximal radius: differences to the rest of the skeleton].

    Science.gov (United States)

    Hell, A K; von Laer, L

    2014-12-01

    Fractures of the proximal end of the radius in the growth phase have three characteristics: the head of the radius articulates with two joint partners and is therefore indispensable for an undisturbed function of the elbow. The blood supply of the proximal end of the radius is via periosteal vessels in the sense of a terminal circulation which makes it extremely vulnerable. Severe trauma caused either by accidents or treatment, can result in partial or complete necrosis with deformity of the head and neck region of the radius. Radioulnar synostosis and chronic epiphysiolysis are irreversible complications which can occur after excessive physiotherapy. Despite a low potency growth plate, in young patients the proximal end of the radius shows an enormous spontaneous correction of dislocations. Side to side shifts, however, will not be remodeled. Therapy should be as atraumatic as possible. Due to the blood supply situation, with the appropriate indications the spontaneous correction and a brief period of immobilization without physiotherapy should be integrated into the therapy concept. If an operation is necessary, repeated traumatic repositioning maneuvers should be avoided and in case of doubt closed or careful open repositioning can be achieved with intramedullary nailing. In order to take the special characteristics of the proximal radius into consideration, the vulnerability and correction potential must be weighed up against each other. Therapy must be as atraumatic as possible. The spontaneous correction potential should be integrated into the primary therapy without overestimating this potential with respect to the extent and age of the patient.

  12. Characterisation of the fatigue properties of cast irons used in the water industry and the effect on pipe strength and performance

    International Nuclear Information System (INIS)

    Mohebbi, H; Jesson, D A; Mulheron, M J; Smith, P A

    2009-01-01

    As part of an on going programme to characterise the residual properties and understand the failure mechanisms of in-service grey cast iron water pipes, the fatigue crack propagation behaviour of grey cast iron samples has been studied. Specimens were sourced from three ex-service pipes. For each pipe the microstructure and composition were characterised and the fracture toughness was determined. The fatigue behaviour was investigated in terms of the crack growth rate (da/dN) as a function of the applied stress intensity factor range. Clear differences in the fatigue behaviour of the samples from different pipes were observed. The result from these investigations, which indicate that microstructural differences play a role in mechanical behaviour, will support the development of asset management tools for use in the water industry.

  13. The AREVA integrated and sustainable concept of fatigue design, monitoring and re-assessment

    International Nuclear Information System (INIS)

    Begholz, Steffen; Rudolph, Juergen

    2008-01-01

    Prevention of fatigue damage of components is an important topic with respect to safety and availability of a nuclear power plant. The issue of fatigue monitoring should be of primary interest throughout service life. Based on the changing general framework, i.e. planning of new plants with a projected lifetime of 60 years and the lifetime extension of existing plants AREVA is focussing R and D activities on improved detection methods. Primary objective is the realistic determination of the actual usage level of reactor components. The fatigue monitoring is supposed to enhance cost optimization and minimize inspection frequency. Fatigue monitoring should be implemented at the beginning of start-up period since the high loads during this phase introduce a significant contribution to the usage level. AREVA recommends the use of the FAMOS (fatigue monitoring system) for the assessment of the realistic transient loads and the data processing with respect to fatigue evaluation. Every 10 years the actual usage levels should be evaluated in detail according to the standards, based on measured load data. The fatigue evaluation is usually performed using finite element analyses taking into account the transient temperature loads at the component, dependent on the component demands based on elastic or elasto-plastic material behaviour. Potential problematic areas can be identified reliably. Direct measurement of fatigue damage, refined analysis concepts (short crack fracture mechanics, and ratcheting simulation) are supposed to support the concept [de

  14. Family-focused cognitive behaviour therapy versus psycho-education for adolescents with chronic fatigue syndrome: long-term follow-up of an RCT.

    Science.gov (United States)

    Lloyd, Samantha; Chalder, Trudie; Rimes, Katharine A

    2012-11-01

    The aim of this study was to investigate the long term efficacy of family-focused cognitive behaviour therapy (CBT) compared with psycho-education in improving school attendance and other secondary outcomes in adolescents with chronic fatigue syndrome (CFS). A 24 month follow-up of a randomised controlled trial was carried out. Participants received either 13 one-hour sessions of family-focused CBT or four one-hour sessions of psycho-education. Forty-four participants took part in the follow-up study. The proportion of participants reporting at least 70% school attendance (the primary outcome) at 24 months was 90% in CBT group and 84% in psycho-education group; the difference between the groups was not statistically significant (OR = 1.29, p = 0.80). The proportion of adolescents who had recovered in the family-focused CBT group was 79% compared with 64% in the psycho-education, according to a definition including fatigue and school attendance. This difference was not statistically significant (Fisher's exact test, p = 0.34). Family-focused CBT was associated with significantly better emotional and behavioural adjustment at 24 month follow-up compared to psycho-education, as reported by both adolescents (F = 6.49, p = 0.02) and parents (F = 4.52, P = 0.04). Impairment significantly decreased in both groups between six and 24 month follow-ups, with no significant group difference in improvement over this period. Gains previously observed for other secondary outcomes at six month follow-up were maintained at 24 month follow-up with no further significant improvement or group differences in improvement. In conclusion, gains achieved by adolescents with CFS who had undertaken family-focused CBT and psycho-education generally continued or were maintained at two-year follow-up. The exception was that family-focused CBT was associated with maintained improvements in emotional and behavioural difficulties whereas psycho-education was associated with

  15. Effect of laser-arc hybrid welding on fracture and corrosion behaviour of AA6061-T6 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Daquan, E-mail: zhdq@sh163.net [Department of Environmental Engineering, Shanghai University of Electric Power, Shanghai 200090 (China); Jin Xin; Gao Lixin [Department of Environmental Engineering, Shanghai University of Electric Power, Shanghai 200090 (China); Joo, Hyung Goun [Stress Analysis and Failure Design Laboratory, School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Kang Yong, E-mail: KYL2813@yonsei.ac.kr [Stress Analysis and Failure Design Laboratory, School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2011-03-15

    Research highlights: {yields} A dendritic cellular structure was formed in the weld fusion zone (WFZ) and caused alloying element segregation. {yields} The precipitation of intermetallic phases and the formation of galvanic corrosion couplings contribute to the improving pitting susceptibility in the WFZ. {yields} The intergranular corrosion nucleates on pit walls and spreads from them. - Abstract: The welding condition of the hybrid laser-gas metal arc (GMA) welding for AA6061-T6 alloy was optimized by tensile test. Formability performance was checked by the bend test. Fractographic analysis indicates a large number of fine ductile type voids in the fracture surface. The microstructure measurements exhibit a dendritic cellular structure in the weld fusion zone (WFZ) and a partially melted zone adjacent to the fusion boundaries. The corrosion behaviour of the weldment and the base alloy were investigated by weight-loss test in nitric acid solution. The WFZ suffers more severe pitting than the rest regions in the weldment. It shows that corrosion cracking is owing to the precipitation of intermetallic phases and the formation of galvanic corrosion couplings in the weldment of AA6061-T6 alloy.

  16. Experimental investigation on the fracture behaviour of black shale by acoustic emission monitoring and CT image analysis during uniaxial compression

    Science.gov (United States)

    Wang, Y.; Li, C. H.; Hu, Y. Z.

    2018-04-01

    Plenty of mechanical experiments have been done to investigate the deformation and failure characteristics of shale; however, the anisotropic failure mechanism has not been well studied. Here, laboratory Uniaxial Compressive Strength tests on cylindrical shale samples obtained by drilling at different inclinations to bedding plane were performed. The failure behaviours of the shale samples were studied by real-time acoustic emission (AE) monitoring and post-test X-ray computer tomography (CT) analysis. The experimental results suggest that the pronounced bedding planes of shale have a great influence on the mechanical properties and AE patterns. The AE counts and AE cumulative energy release curves clearly demonstrate different morphology, and the `U'-shaped curve relationship between the AE counts, AE cumulative energy release and bedding inclination was first documented. The post-test CT image analysis shows the crack patterns via 2-D image reconstructions, an index of stimulated fracture density is defined to represent the anisotropic failure mode of shale. What is more, the most striking finding is that the AE monitoring results are in good agreement with the CT analysis. The structural difference in the shale sample is the controlling factor resulting in the anisotropy of AE patterns. The pronounced bedding structure in the shale formation results in an anisotropy of elasticity, strength and AE information from which the changes in strength dominate the entire failure pattern of the shale samples.

  17. FATIGUE OF DENTAL CERAMICS

    Science.gov (United States)

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-01-01

    Objectives Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. Data/sources The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Conclusions Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically-assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Clinical significance Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. PMID:24135295

  18. Mechanical properties and fracture behaviour of ODS steel friction stir welds at variable temperatures

    International Nuclear Information System (INIS)

    Dawson, H.; Serrano, M.; Hernandez, R.; Cater, S.; Jimenez-Melero, E.

    2017-01-01

    We have assessed the microstructure and the temperature-dependent mechanical behaviour of five bead-on-plate friction stir welds of Oxide Dispersion Strengthened (ODS) steel, produced using systematic changes to the tool rotation and traverse speed. Friction stir welding can potentially retain the fine dispersion of nanoparticles, and therefore also the high-temperature strength and radiation damage resistance of these materials. Tensile testing was carried out on the MA956 base material at a range of temperatures, from room temperature up to 750 °C. The mechanical properties of the welds were investigated via tensile testing at room temperature and at 500 °C, together with micro-hardness testing. The welds exhibited similar strength and ductility to the base material at both testing temperatures as welding caused a partial loss of particle strengthening, alongside an increase in grain boundary strengthening due to a greatly refined grain size in the stir zones. The micro-hardness data revealed a trend of increasing hardness with increasing tool traverse speed or decreasing rotation speed. This was attributed to the smaller grain size and lower nanoparticle number density in the welds created with these parameters. At 500 °C, the yield stress and ultimate tensile stress of the base material and the welds decreased, due to a progressive reduction in both the Orowan-type particle strengthening and the grain boundary strengthening.

  19. Effects of particle fracturing and moisture content on fire behaviour in masticated fuelbeds burned in a laboratory

    Science.gov (United States)

    Jesse K. Kreye; J. Morgan Varner; Eric E. Knapp

    2011-01-01

    Mechanical mastication is a fuels treatment that converts shrubs and small trees into dense fuelbeds composed of fractured woody particles. Although compaction is thought to reduce fireline intensity, the added particle surface area due to fracturing could also influence fire behavior. We evaluated effects of particle fracturing and moisture content (ranging from 2.5...

  20. Fatigue and Corrosion in Metals

    CERN Document Server

    Milella, Pietro Paolo

    2013-01-01

    This textbook, suitable for students, researchers and engineers, gathers the experience of more than 20 years of teaching fracture mechanics, fatigue and corrosion to professional engineers and running experimental tests and verifications to solve practical problems in engineering applications. As such, it is a comprehensive blend of fundamental knowledge and technical tools to address the issues of fatigue and corrosion. The book initiates with a systematic description of fatigue from a phenomenological point of view, since the early signs of submicroscopic damage in few surface grains and continues describing, step by step, how these precursors develop to become mechanically small cracks and, eventually, macrocracks whose growth is governed by fracture mechanics. But fracture mechanics is also introduced to analyze stress corrosion and corrosion assisted fatigue in a rather advanced fashion. The author dedicates a particular attention to corrosion starting with an electrochemical treatment that mechanical e...

  1. Fatigue behavior of ADI: Some specific features

    Energy Technology Data Exchange (ETDEWEB)

    Svejcar, J.; Vechet, S.; Pokluda, J. [Technical Univ. of Brno (Czech Republic). Faculty of Mechanical Engineering

    1997-12-31

    The paper summarizes the results of fatigue tests on austempered ductile iron. Attention is mainly focused on the effect of graphite on crack propagation and on some irregularities exhibited by ADI and other ductile irons, e.g., some specific features of fatigue fracture (especially the occurrence of fatigue striations on intergranular facets), decrease of fatigue limit with increasing UTS, and anomalous dependence of loading cycle amplitude on mean cycle stress.

  2. Fracture mechanics

    CERN Document Server

    Perez, Nestor

    2017-01-01

    The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing. Explains computational and engineering approaches for solving crack-related problems using straightforward mathematics that facilitate comprehension of the physical meaning of crack growth processes; Expands computational understandin...

  3. Cognitive behavioural therapy versus multidisciplinary rehabilitation treatment for patients with chronic fatigue syndrome: study protocol for a randomised controlled trial (FatiGo)

    NARCIS (Netherlands)

    Vos-Vromans, D.C.; Smeets, R.J.P.; Rijnders, L.J.; Gorrissen, R.R.; Pont, M.; Koke, A.J.; Hitters, M.W.; Evers, S.M.; Knottnerus, A.J.

    2012-01-01

    ABSTRACT: BACKGROUND: Patients with chronic fatigue syndrome experience extreme fatigue, which often leads to substantial limitations of occupational, educational, social and personal activities. Currently, there is no consensus regarding the treatment. Patients try many different therapies to

  4. Significant other behavioural responses and patient chronic fatigue syndrome symptom fluctuations in the context of daily life: An experience sampling study.

    Science.gov (United States)

    Band, Rebecca; Barrowclough, Christine; Emsley, Richard; Machin, Matthew; Wearden, Alison J

    2016-09-01

    Significant other responses to patients' symptoms are important for patient illness outcomes in chronic fatigue syndrome (CFS/ME); negative responses have been associated with increased patient depression, whilst increased disability and fatigue have been associated with solicitous significant other responses. The current study aimed to examine the relationship between significant other responses and patient outcomes within the context of daily life. Experience Sampling Methodology (ESM). Twenty-three patients with CFS/ME and their significant others were recruited from specialist CFS/ME services. Sixty momentary assessments, delivered using individual San Francisco Android Smartphones, were conducted over a period of 6 days. All participants reported on affect, dyadic contact, and significant other responses to the patient. Patients reported on symptom severity, disability, and activity management strategies. Negative significant other responses were associated with increased patient symptom severity and distress reported at the same momentary assessment; there was evidence of a potentially mediating role of concurrent distress on symptom severity. Patient-perceived solicitous responses were associated with reduced patient activity and disability reported at the same momentary assessment. Lagged analyses indicate that momentary associations between significant other responses and patient outcomes are largely transitory; significant other responses were not associated with any of the patient outcomes at the subsequent assessment. The results indicate that significant other responses are important influences on the day-to-day experience of CFS/ME. Further research examining patient outcomes in association with specific significant other behavioural responses is warranted and future interventions that target such significant other behaviours may be beneficial. Statement of contribution What is already known on this subject? The existing literature has identified

  5. Driver education: Enhancing knowledge of sleep, fatigue and risky behaviour to improve decision making in young drivers.

    Science.gov (United States)

    Alvaro, Pasquale K; Burnett, Nicole M; Kennedy, Gerard A; Min, William Yu Xun; McMahon, Marcus; Barnes, Maree; Jackson, Melinda; Howard, Mark E

    2018-03-01

    This study assessed the impact of an education program on knowledge of sleepiness and driving behaviour in young adult drivers and their performance and behaviour during simulated night driving. Thirty-four participants (18-26 years old) were randomized to receive either a four-week education program about sleep and driving or a control condition. A series of questionnaires were administered to assess knowledge of factors affecting sleep and driving before and after the four-week education program. Participants also completed a two hour driving simulator task at 1am after 17 h of extended wakefulness to assess the impact on driving behaviour. There was an increase in circadian rhythm knowledge in the intervention group following the education program. Self-reported risky behaviour increased in the control group with no changes in other aspects of sleep knowledge. There were no significant differences in proportion of intervention and control participants who had microsleeps (p ≤ .096), stopped driving due to sleepiness (p = .107), recorded objective episodes of drowsiness (p = .455), and crashed (p = .761), although there was a trend towards more control participants having microsleeps and stopping driving. Those in the intervention group reported higher subjective sleepiness at the end of the drive [M = 6.25, SD = 3.83, t(31) = 2.15, p = .05] and were more likely to indicate that they would stop driving [M = 3.08, SD = 1.16, t(31) = 2.24, p = .04]. The education program improved some aspects of driver knowledge about sleep and safety. The results also suggested that the education program lead to an increased awareness of sleepiness. Education about sleep and driving could reduce the risk of drowsy driving and associated road trauma in young drivers, but requires evaluation in a broader sample with assessment of real world driving outcomes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    1999-01-01

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

  7. 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)

  8. Isothermal Low Cycle Fatigue of Uncoated and Coated Nickel-Base Superalloys

    International Nuclear Information System (INIS)

    Stekovic, Svjetlana

    2004-01-01

    High strength nickel-base superalloys have been used in turbine blades for many years because of their superior performance at high temperatures. However, the superalloys have limited oxidation and corrosion resistance and to solve this problem, protective coatings are deposited on the surface of the superalloys. The positive effect of coatings is based on protecting the surface zone in contact with hot gas atmosphere with elements like aluminium, chromium, which form a thermodynamically stable oxide layer that acts as a diffusion barrier to slow down the reaction between the substrate material and the aggressive environment. There are also other degradation mechanisms that affect nickel-base superalloys such as aging of microstructure, fatigue and creep. Long-term aging in metallic coating results in the changes of mechanical properties due to the significant interdiffusion of the main alloying elements between substrate and coatings. However, application of the coatings has mechanical side effects, the significance of which is not yet fully investigated. This work covers a study on the fatigue behaviour of a polycrystalline, IN792. and two single crystal nickel-base superalloys, CMSX-4 and SCB, coated with three different coatings. an overlay coating AMDRY997, a platinum aluminide modified diffusion coating RT22 and an innovative coating with an interdiffusion harrier of NiW called IC1, under low cycle fatigue loading conditions. Both low cycle fatigue properties, cyclic strain and stress response and fracture behaviour of the uncoated, coated and long-term aged coated specimens are presented. The main conclusions are that at 500 deg C the presence of the coatings have, in most cases, reduced the fatigue lives of the nickel-base substrates while at 900 deg C the coatings do improve the fatigue lives of the superalloys except RT22 coated on some superalloys and under certain test conditions. The reduction of the fatigue life at 500 deg C can be related to early

  9. Structural dynamics and fracture mechanics calculations of the behaviour of a DN 425 test piping system subjected to transient loading by water hammer

    International Nuclear Information System (INIS)

    Kussmaul, K.; Kobes, E.; Diem, H.; Schrammel, D.; Brosi, S.

    1994-01-01

    Within the scope of the German HDR safety programme, several tests were carried out to investigate transient pipe loading initiated by a simulated double-ended guillotine break event, and subsequent closure of a feedwater check valve (water hammer, blow-down). Numerical analyses by means of finite element programmes were performed in parallel to the experiments. Using water hammer tests of a DN 425 piping system with predamaged components, the procedure of such analyses will be demonstrated. The results are presented, beginning with structural dynamic calculations of the undamaged piping; followed by coupling of structural dynamics and fracture mechanics computations with simple flaw elements (line spring); and finishing with costly three-dimensional fracture mechanics analyses. A good description of the real piping behaviour can be made by the numerical methods, even in the case of high plastification processes. ((orig.))

  10. Contribution to the characterization of 222-radon concentrations variability in water to the understanding of an aquifer behaviour in fractured medium: example of the Ploemeur site, Morbihan

    International Nuclear Information System (INIS)

    Le Druillennec, Th.

    2007-06-01

    Heterogeneous fractured aquifers which developed in crystalline rocks, such as schist or granite, supply 20% of tap water production of Brittany. These fractured media present a large range of permeability. In these aquifers, fluid flow and transport of elements dissolved in water are strongly related on the geometry of the fractured network. Increasing the knowledge of the hydrogeological behaviour of the aquifer is fundamental for the management and the protection of the groundwater resources. Radon-222 is a radioactive noble gas produced from radium-226 further to the radioactive decay of uranium-238; it occurs naturally in ground waters and derives primarily from U-rich rocks and minerals that have been in contact with water. Radon-222 concentrations in waters are liable to provide significant and relevant information on both the geometry of a fracture network and the flow distribution. Furthermore, radon may also be used as a tracer in the aquifer of water exchanges between zones of variable permeability. Three main results were obtained in this study: 1. An accurate characterisation of the radon concentrations in water was carried out in the Ploemeur aquifer (Brittany, France). These results highlight the variability in the spatial and vertical distributions of 222 Rn activity in groundwater together with a wide range of concentrations extending from 0 to 1 500 Bq.L -1 . 2. The influence of fracture aperture on radon content in groundwater has been demonstrated with the modelling of radon concentration. Indeed, the satisfactory results obtained with a simple crack model highlight that the geometry of the fracture network controls the radon activity in groundwater. 3. Thus, the results of pumping tests performed in the boreholes improved our understanding of the system. After the pumping test, an increase of the radon content in groundwater occurred and evidenced a contribution of a radon-rich water to supply the flow rate that seems to come from the low

  11. High strain fatigue behaviour of a high-temperature, low-alloyed forging steel subject to a servicelike loading history

    International Nuclear Information System (INIS)

    Kloos, K.H.; Granacher, J.; Rieth, P.

    1979-01-01

    A test plan was developed for selected cases of service-like long-time high strain load of a heated surface of massive components, which includes service-like anisothermic high strain tests with pressure-strain in the start-up phase and pull-strain in the shutdown phase, comparable isothermal tests at the highest cycle temperature, and finally tests with 'packaged' high strain and creep strain periods, which should enable long-time-tests with only short use of the large-scale high-strain-test-technique. The tests started on the melts of the high-temperature steel 28 Cr Mo NiV 4 9 have reached a longest tests time of nearly 1000 at a maximum temperature of 525 0 C. On the basis of there results, the carrying-out of 'packaged' long-time high strain tests with short creep strain periods seem to be a good way of determining the long-time high-strain behaviour of this steel under service-like strain cycles. (orig./RW) 891 RW/orig.- 892 RKD [de

  12. The Influence of Corrosion Attack on Grey Cast Iron Brittle‑Fracture Behaviour and Its Impact on the Material Life Cycle

    Directory of Open Access Journals (Sweden)

    Jiří Švarc

    2017-01-01

    Full Text Available The paper is concerned with brittle‑fracture behaviour of grey cast iron attacked by corrosion and its impact on the life cycle of a spare part made of grey cast iron. In a corrosion chamber, outdoor climatic conditions (temperature and relative air humidity were simulated in which degradation processes, induced by material corrosion, degrading mechanical properties of a material and possibly leading to irreversible damage of a machine component, occur in the material of maintenance vehicles that are out of operation for the period of one year. The corrosion degradation of grey cast iron, which the spare parts constituting functional parts of an engine are made of grey cast iron, is described with regard to brittle‑fracture behaviour of the material. For the description of corrosion impact on grey cast iron, an instrumented impact test was employed. A corrosion degradation effect on grey cast iron was identified based on measured values of total energy, macro plastic deformation limit, initiation force of unstable crack propagation and force exerted on unstable crack arrest. In the first part of the experiment, a corrosion test of the material concerned was simulated in a condensation chamber; in the second part of the experiment, research results are provided for the measured quantities describing the material brittle‑fracture behaviour; this part is supplemented with a table of results and figures showing the changes in the values of the measured quantities in relation to test temperatures. In the discussion part, the influence of corrosion on the values of unstable crack initiation and arrest forces is interpreted. In the conclusion, an overview of the most significant research findings concerning the impact of corrosion on the life cycle of grey cast iron material is provided.

  13. Caffeine, fatigue, and cognition

    NARCIS (Netherlands)

    Lorist, M.M.; Tops, M.

    2003-01-01

    Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support

  14. Fatigue of reinforcing bars during hydro-demolition

    Science.gov (United States)

    Hyland, C. W. K.; Ouwejan, A.

    2017-05-01

    Reinforcing steel fractured during hydro-demolition of a reinforced concrete pier head due to low cycle flexural fatigue from vibration caused by impact of the high pressure water jet on the exposed length of the bars. Research into the fatigue performance of steel reinforcing steel tends to focus on the high cycle axial performance in reinforced concrete members and re-bending behaviour. However with the increasing use of hydro-demolition of concrete structures as part of remediation works care is required to ensure the steel reinforcement exposed to the high pressure jet of water is not going to suffer relatively low cycle flexural damage that may compromise the designed performance of the completed reinforced concrete structure. This paper describes the failure assessment, fatigue analysis, and metallographic examination that was undertaken. It was found that the rib to flank transition radius on the reinforcement steel was small enough to cause a significant stress concentration effect and was the location of fatigue crack growth. A relatively simple analysis using the maximum unrestrained cantilevered bar length and force exerted by the water jet was used to calculate the maximum expected bending moment. This was compared to the bending capacity at initiation of yielding at the rib flank transition accounting for stress concentration effects. This showed that the observed cyclic reversing ductile crack growth and fracture of the H25 bars was consistent with the loading applied. A method is proposed based on these observations to assess suitable limits for unrestrained bar lengths or maximum working offset of the water jet from the point of bar restraint when undertaking hydro-demolition work. The fatigue critical performance requirements of AS/NZS4671 500E bars are also therefore compared with those of BS4449:2005 and PN EN/ISO 15630-1:2011 for comparable 500C bars

  15. Fracture behaviour of mullite fibre reinforced-mullite matrix composites under quasi-static and ballistic impact loading

    Czech Academy of Sciences Publication Activity Database

    Boccaccini, A. R.; Atiq, S.; Boccaccini, D. N.; Dlouhý, Ivo; Kaya, C.

    č. 65 (2005), s. 325-333 ISSN 0266-3538 R&D Projects: GA AV ČR IAA2041003 Keywords : ceramic matrix composites * mullite matrix * toughness Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.184, year: 2005

  16. Physiological and neurophysiological determinants of postcancer fatigue: design of a randomized controlled trial

    NARCIS (Netherlands)

    Prinsen, Hetty; Bleijenberg, Gijs; Zwarts, Machiel J.; Hopman, Maria T. E.; Heerschap, Arend; van Laarhoven, Hanneke W. M.

    2012-01-01

    Background: Postcancer fatigue is a frequently occurring, severe, and invalidating problem, impairing quality of life. Although it is possible to effectively treat postcancer fatigue with cognitive behaviour therapy, the nature of the underlying (neuro) physiology of postcancer fatigue remains

  17. Caffeine, fatigue, and cognition.

    Science.gov (United States)

    Lorist, Monicque M; Tops, Mattie

    2003-10-01

    Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support the general belief that caffeine acts as a stimulant. Studies using ERP measures indicate that caffeine has an effect on attention, which is independent of specific stimulus characteristics. Behavioural effects on response related processes turned out to be mainly related to more peripheral motor processes. Recent insights in adenosine and dopamine physiology and functionality and their relationships with fatigue point to a possible modulation by caffeine of mechanisms involved in the regulation of behavioural energy expenditure.

  18. Physical fracture properties (fracture surfaces as information sources; crackgrowth and fracture mechanisms; exemples of cracks)

    International Nuclear Information System (INIS)

    Meny, Lucienne.

    1979-06-01

    Fracture surfaces are considered as a useful source of informations: an introduction to fractography is presented; the fracture surface may be observed through X ray microanalysis, and other physical methods such as Auger electron spectroscopy or secundary ion emission. The mechanisms of macroscopic and microscopic crackgrowth and fracture are described, in the case of unstable fracture (cleavage, ductile with shear, intergranular brittleness) and of progressive crack propagation (creep, fatigue). Exemples of cracks are presented in the last chapter [fr

  19. Influence of directional coarsening on the isothermal high-temperature fatigue behaviour of the monocrystalline nickel-base superalloys CMSX-6 and CMSX-4

    International Nuclear Information System (INIS)

    Ott, M.; Tetzlaff, U.; Mughrabi, H.

    1999-01-01

    The influence of the γ/γ'-morphology, namely cuboidal γ'-particles in a γ-matrix, a plate-like γ/γ'-morphology perpendicular to the stress axis and a plate-like γ/γ'-morphology parallel to the stress axis, on the high-temperature fatigue properties of two monocrystalline [001]-orientated nickel-base superalloys was investigated. Both alloys show that material with a γ/γ'-raft structure parallel to the stress axis exhibits a longer fatigue life compared to material with cuboidal γ'-particles, whereas the fatigue life of material with γ/γ'-rafts perpendicular to the stress axis is reduced compared to material with cuboidal γ'-particles. These results are a consequence of the different modes of fatigue crack propagation observed in the three cases. (orig.)

  20. Nose fracture

    Science.gov (United States)

    Fracture of the nose; Broken nose; Nasal fracture; Nasal bone fracture; Nasal septal fracture ... A fractured nose is the most common fracture of the face. It most ... occurs with other fractures of the face. Nose injuries and neck ...

  1. Fatigue crack growth detect, assess, avoid

    CERN Document Server

    Richard, Hans Albert

    2016-01-01

    This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.

  2. Fatigue Life Prediction in Journal Bearing

    Directory of Open Access Journals (Sweden)

    Irsyadi Yani

    2017-03-01

    Full Text Available Failure of fatigue is damaged materials where caused frequent load. Fatigue owing to some factors, which is Stress concentration on fatigue, Stress life, Effect size and surface, and Change properties of surface. The fatigue failure of a material is dependent on the interaction of a large stress with a critical flow. In essence, fatigue is controlled by the weakest link of the material, with the probability of a weak link increasing with material volume. This phenomenon is evident in the fatigue test results of a material using specimens of varying diameters. From this research we can get effect of concentration stress on strength fatigue with S-N method. On this method only count fatigue life or endurance limit from Journal bearing housing. By Finite Element Analysis, it is not so easy to determine fatigue life. When we find the first yield point, it means this point is in the highest stress state. Then we can refer S-N curve. In this paper, the effect of bearing and housing elasticity on the stress field, which could result in surface fatigue in journal bearing, has been investigated. This condition is proved with occurred slip lines on surface of specimen. These slip lines are caused on some thousands stress cycles. Additional crack is happened immediately and finally long enough crack. So that formed unstable crack that caused fracture of brittleness or fracture of toughness because section of specimen cannot keep

  3. Mean Stress Effect on the Axial Fatigue Strength of DIN 34CrNiMo6 Quenched and Tempered Steel

    Directory of Open Access Journals (Sweden)

    Luis Pallarés-Santasmartas

    2018-03-01

    Full Text Available The present study consists of a theoretical and experimental investigation of the effect of axial mean stresses on the high cycle fatigue behaviour of DIN 34CrNiMo6 high strength steel in quenched and tempered conditions. The axial S-N curves under 4 different stresses ratios were obtained. Experimental results show that increasing the value of the tension mean stresses gradually reduces the axial stress amplitude the material can withstand without failure. Moreover, the compressive mean stresses show a beneficial effect in terms of the axial fatigue strength, resulting in a non-symmetrical Haigh diagram. A historic review of the axial mean stress effect is presented, showing the shape of the Haigh diagrams for ductile metals and presenting the most-known empirical and physical theories. The results for this steel are compared with the physical theories of Findley based on the critical plane; the Froustey’s and Marin’s methods, based on energetic theories; and the Crossland invariants method based on the Gough’s theory of fatigue damage. Taking into account the experimental results, a physical fatigue function based on energetic considerations is proposed. Its application to the fatigue case with mean stresses can be interpreted in terms of a balance of elastic energies of distortion and volume change. Macro-analyses of specimen fracture appearance were conducted in order to obtain the fracture characteristics for different mean stress values.

  4. Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko

    Science.gov (United States)

    Höfner, S.; Vincent, J.-B.; Blum, J.; Davidsson, B. J. R.; Sierks, H.; El-Maarry, M. R.; Deller, J.; Hofmann, M.; Hu, X.; Pajola, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger, A.-T.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marqués, P.; Güttler, C.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Moissl-Fraund, R.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.; Zitzmann, S.

    2017-12-01

    Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain. Aims: Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods. Methods: We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain. Results: Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P. Conclusions: At 3.5 AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50 W / m2 and trigger dust activity that can be related mainly to H2O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue.

  5. Forecasts on service life by fracture mechanics methods

    International Nuclear Information System (INIS)

    Munz, D.

    1985-01-01

    The service life of many component parts can frequently be divided into the stages up to the formation of a crack and of crack propagation. This holds good of fatigue crack, stress corrosion crack, and also in many cases of creep. But often the crack propagation stage is the only one of interest for service life forecasts if cracks must be reckoned with already on putting parts into service. Cracks in welding constructions are typical examples. Crack- and -fracture mechanics deal with the laws underlying crack propagation and provide quantitative information on crack propagation behaviour. (orig./DG) [de

  6. Fracture behaviour of Cu-Al-Ni shape memory alloys obtained by powder metallurgy; Comportamiento a fractura de aleaciones pulvimetalurgicas de Cu-Al-Ni con efecto memoria de forma

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, P. P.; Perez-Saez, R. B.; Recarte, V.; San Juan, J.M.; Ruano, O. A.; No, M. L.

    2001-07-01

    Polycrystalline Cu-Al-Ni shape memory alloys have been scarcely employed for technological applications due to their high brittleness. The development of a new elaboration technique based on powder metallurgy has recently overcome this problem, through the improvement of the ductility of the produced alloys without affecting its shape memory properties. The fracture behaviour of an alloy obtained using the elaboration technique has been studied by means of Scanning Electron Microscopy and mechanical testing. The results show a ductile fracture with a maximum strain close to 13%, which is the best fracture behaviour obtained for Cu-Al-Ni polycrystals. The microstructure of such alloys ha been studied by means of Transmission Electron Microscopy, showing a poligonyzed structure in which martensite plated passing through the subboundaries easily. (Author) 19 refs.

  7. Seafarer fatigue

    DEFF Research Database (Denmark)

    Jepsen, Jørgen Riis; Zhao, Zhiwei; van Leeuwen, Wessel M. A.

    2015-01-01

    Background: The consequences of fatigue for the health and safety of seafarers has caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This review gives an overview of the key issues relating...... to seafarer fatigue. Materials and methods: A literature study was conducted aiming to collect publications that address risk factors for fatigue, short-term and long-term consequences for health and safety, and options for fatigue mitigation at sea. Due to the limited number of publications that deals...

  8. Crack growth and high cycle fatigue behaviour of an aa6060 aluminium alloy after ecap combined with a subsequent heat treatment; Rissfortschritts- und Ermuedungsverhalten der Aluminiumlegierung EN AW-6060 nach ECAP und nachgelagerter Waermebehandlung

    Energy Technology Data Exchange (ETDEWEB)

    Hockauf, K.; Meyer, L.W.; Halle, T.; Hockauf, M. [Lehrstuhl Werkstoffe des Maschinenbaus, TU Chemnitz, 09107 Chemnitz (Germany)

    2009-07-15

    Crack growth properties of the Al-Mg-Si alloy AA6060 as well as the high cycle fatigue behaviour have been investigated after equal-channel angular pressing (ECAP). In our study, experiments have been conducted on different stages of microstructural breakdown and strain hardening of the material as they were present after different numbers of ECAP passes. A bimodal condition, obtained after two pressings, and a homogeneously ultrafine-grained condition after eight repetitive pressings have been investigated. Furthermore, optimized conditions with an enhanced ductility, produced by ECAP processing combined with a following short-time aging treatment were included into the study. Crack growth experiments have been conducted in the near-threshold regime and the region of stable crack growth, covering a range of load ratios from R = 0.1 up to 0.7. It was found that the lowered fatigue threshold {delta}K{sub th} of the as-extruded material can be enhanced by the combination of ECAP and short-time aging, owing to the increased ductility and strain hardening capability of this material. By means of SEM investigations and tensile tests, the crack growth properties of the different conditions were related to microstructural and mechanical features. In fatigue tests, load reversals up to failure and the fatigue limit for an as-extruded condition and an optimized condition after two ECAP-passes have been compared to the coarse grained initial condition and a remarkable increase in fatigue strength was noted. (Abstract Copyright [2009], Wiley Periodicals, Inc.) [German] An der warmaushaertenden Aluminiumlegierung EN AW-6060 wurden Untersuchungen zum Rissfortschritt und zur Ermuedung nach hochgradig plastischer Verformung durch ECAP (Equal-Channel Angular Pressing) durchgefuehrt. Es wurden Zustaende in unterschiedlichen Stadien der Mikrostrukturfeinung und Verformungsverfestigung untersucht: ein bimodaler Zustand nach zwei sowie ein homogen ultrafeinkoerniger Zustand nach acht

  9. Effect of fibre arrangement on the multiaxial fatigue of fibrous composites: a micromechanical computational model

    Directory of Open Access Journals (Sweden)

    Roberto Brighenti

    2015-10-01

    Full Text Available Structural components made of fibre-reinforced materials are frequently used in engineering applications. Fibre-reinforced composites are multiphase materials, and complex mechanical phenomena take place at limit conditions but also during normal service situations, especially under fatigue loading, causing a progressive deterioration and damage. Under repeated loading, the degradation mainly occurs in the matrix material and at the fibre-matrix interface, and such a degradation has to be quantified for design structural assessment purposes. To this end, damage mechanics and fracture mechanics theories can be suitably applied to examine such a problem. Damage concepts can be applied to the matrix mechanical characteristics and, by adopting a 3-D mixed mode fracture description of the fibre-matrix detachment, fatigue fracture mechanics concepts can be used to determine the progressive fibre debonding responsible for the loss of load bearing capacity of the reinforcing phase. In the present paper, a micromechanical model is used to evaluate the unixial or multiaxial fatigue behaviour of structures with equi-oriented or randomly distributed fibres. The spatial fibre arrangement is taken into account through a statistical description of their orientation angles for which a Gaussian-like distribution is assumed, whereas the mechanical effect of the fibres on the composite is accounted for by a homogenization approach aimed at obtaining the macroscopic elastic constants of the material. The composite material behaves as an isotropic one for randomly distributed fibres, while it is transversally isotropic for unidirectional fibres. The fibre arrangement in the structural component influences the fatigue life with respect to the biaxiality ratio for multiaxial constant amplitude fatigue loading. One representative parametric example is discussed.

  10. Improved Fatigue Performance of Threaded Drillstring Connections by Cold Rolling

    Energy Technology Data Exchange (ETDEWEB)

    Kristoffersen, Steinar

    2002-01-01

    The research work presented in this thesis is concerned with analytical, numerical and experimental studies of the effect of cold rolling on the fatigue behaviour of threaded drillstring connections. A comprehensive literature study is made of the various effects on the fatigue behaviour of residual stresses introduced by mechanical deformation of notched components. Some of the effects studied are cyclic hardening behaviour after prestraining, cyclic creep, fatigue initiation in prestrained materials, short cracks and crack growth models including crack closure. Residual stresses were introduced in the surface of a smooth pipe by a rolling device to simulate a cold rolling process and verify the calculated residual stresses by measurements. Strain hardening and contact algorithm of the two bodies were incorporated in the FE analyses. Two significant errors were found in the commercial software package for residual stress evaluation, Restran v. 3.3.2a also called SINT, when using the Schajer method. The Schajer algorithm is the only hole-drilling algorithm without theoretical shortcomings, and is recommended when measuring large residual stress gradients in the depth direction. Using the Schajer method solved by in-house Matlab-routines good agreement between measured residual stress gradients and residual stress gradients from FE analyses was found. Full scale fatigue tests were performed on pipes cut from used drillstrings with notches of similar geometry as threads used in drillstring connections. The simulated threads consisted of four full depth helix notches with runouts at the surface. The pipe threads were cold rolled and fatigue tested in a full-scale four-point rotating bending fatigue testing rig. The test results showed that cold rolling had an effect on the crack initiation period. A major part of the fatigue life was with cracks observed at the notch root, but due to the increased fatigue crack propagation resistance the final fracture initiated at

  11. Influence of dynamical ion mixing of crystalline aluminium and nickel coatings on the fatigue behaviour of a 316L-type stainless steel

    International Nuclear Information System (INIS)

    Villechaise, P.; Mendez, J.; Violan, P.; Riviere, J.P.

    1991-01-01

    New techniques of dynamical ion mixing have been applied to the improvement of fatigue resistance of metallic materials. Such techniques involve a deposition method combined with simultaneous ion implantation. In this way, well adherent cyrstalline coatings of pure Al and Ni, 0.5 μm thick, have been deposited on a 316L-type austenitic stainless steel substrate. It has been shown that such coatings lead to a substantial increase in the fatigue lifetime of the stainless steel at room temperature, which is associated with important modifications in surface damage processes. (orig.)

  12. High strain rate and quasi-static tensile behaviour of Ti-6Al-4V after cyclic damage

    Directory of Open Access Journals (Sweden)

    Verleysen P.

    2012-08-01

    Full Text Available It is common that energy absorbing structural elements are subjected to a number of loading cycles before a crash event. Several studies have shown that previous fatigue can significantly influence the tensile properties of some materials, and hence the behaviour of structural elements made of them. However, when the capacity of absorbing energy of engineering materials is determined, fresh material without any fatigue damage is most often used. This study investigates the effect of fatigue damage on the dynamic tensile properties of Ti-6Al-4V in thin-sheet form. Results are completed with tests at quasi-static strain rates and observations of the fracture surfaces, and compared with results obtained from other alloys and steel grades. The experiments show that the dynamic properties of Ti-6Al-4V are not affected by a number of fatigue loading cycles high enough to significantly reduce the energy absorbing capabilities of EDM machined samples.

  13. Fatigue Strength of Titanium Risers - Defect Sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Babalola, Olusegun Tunde

    2001-07-01

    This study is centred on assessment of the fatigue strength of titanium fusion welds for deep-water riser's applications. Deep-water risers are subjected to significant fatigue loading. Relevant fatigue data for titanium fusion welds are very scarce. Hence there is a need for fatigue data and life prediction models for such weldments. The study has covered three topics: Fatigue testing, Fractography and defect assessment, and Fracture Mechanics modelling of fatigue crack growth. Two series of welded grade of titanium consisting of 14 specimens in each series were fatigue tested under constant amplitude loading. Prior to fatigue testing, strain gauge measurements of some specimens was conducted to enable the definition of stress range in the fatigue assessment procedure. The results were compared with finite solid element analysis and related to fatigue stresses in a riser pipe wall. Distribution and geometry of internal and surface defects both in the as-welded and in the post-weld machined conditions were assessed using fractography. This served as a tool to determine the fatigue initiation point in the welds. Fracture mechanics was applied to model fatigue strength of titanium welds with initiation from weld defects. Two different stress intensity factor formulations for embedded eccentrically placed cracks were used for analysis of elliptical cracks with the major axis parallel and close to one of the free surfaces. The methods were combined to give a satisfactory model for crack growth analysis. The model analyses crack growth of elliptical and semi-elliptical cracks in two directions, with updating of the crack geometry. Fatigue strength assessment was conducted using two crack growth models, the Paris-Erdogan relation with no threshold and the Donahue et al. relation with an implied threshold. The model was validated against experimental data, with a discussion on the choice of crack growth model. (author)

  14. Crack modelling: A novel technique for the prediction of fatigue failure in the presence of stress concentrations

    Science.gov (United States)

    Taylor, D.

    1997-07-01

    Finite element (FE) analysis and other computational methods have developed rapidly in recent years, allowing accurate predictions of elastic stresses in components of complex geometry. However, the prediction of fatigue failure in these components is still a non-trivial problem; one reason for this is the difficulty of assessing stress concentrations and regions of high stress-gradient. This paper describes a new technique, called "crack modelling", which addresses the problem through a modification of linear-elastic fracture mechanics (LEFM). LEFM is designed to deal with cracks in nominally elastic stress fields, using elastic analysis to derive a characteristic stress intensity, K or, for cyclic loading, a range Δ K. This methodology is modified in two ways. Firstly it is shown that LEFM can be extended to predict the fatigue behaviour of bodies containing notches of standard geometry, instead of cracks. Secondly, FE analysis is used in conjunction with a modelling exercise in order to extend the method to include bodies of arbitrary shape subjected to any set of loads. The method was first tested using standard notch geometries (blunt and sharp notches in beams), where accurate predictions of fatigue limit could be achieved. It was then applied to an industrial problem, giving a prediction of high-cycle fatigue behaviour for an automotive crankshaft. The method requires only simple mechanical-property data (the material fatigue limit and stress-intensity threshold) and uses only linear-elastic FE modelling. It allows fracture mechanics theory to be used without the need to specifically model the presence of a crack and uses far-field elastic stresses to infer behaviour in the region of a stress concentration.

  15. Elastic characteristics and fracture behaviour of materials in the system Al2O3+TiC at elevated temperatures

    International Nuclear Information System (INIS)

    Grellner, W.

    1978-01-01

    In the region between room temperature and 1400 0 C the elastic constants, fracture values and flow-stress values of different compositions of the Al 2 O 3 +TiC system were determined. It was found that: 1. The elasticity modulus and shear modulus increase linearly with the TiC content. 2. Up to approximately 1050 0 C the elastic constants decrease linearly with increasing temperature. 3. Additions of dispersed TiC lead to a uniform grain size distribution. 4. In the low temperature region the faults leading to cracks are about 50 times as large as the average grain size; this suggests the effect of thermal stresses on the occurrence of microcracks. 5. At temperatures above 900 0 C TiC deforms macroscopically. In the case of a high proportion of the 2nd phase the latter contributes, as a plastic substance, to stress reduction and thus to an increase of fracture stress in comparison to the single-phase material. (orig.) [de

  16. Dynamic strain ageing in C-Mn steels and associated welds. 2. effect on fracture toughness behaviour

    International Nuclear Information System (INIS)

    Wagner, D.; Moreno, J.C.; Prioul, C.; Frund, J.M.; Houssin, B.

    2001-01-01

    C-Mn steels and associated welds are susceptible to Dynamic Strain Ageing (DSA). In this case, fracture toughness shows a minimum when the temperature increases from 20 to 300 deg C. After a literature review, the results of J-R tearing resistance tests, characterized by crack initiation resistance J 0,2 and tearing modulus dJ/da relative to a base metal (A48 French standard steel) and Manual Metal Arc deposited metals are presented and discussed. The decrease of both crack initiation resistance J 0,2 and tearing modulus dJ/da is related to the DSA sensitivity of the material. A simplified engineering method based on the evolution of the Ultimate Tensile Strength versus temperature and a method of J 0,2 determination according to a local approach model of ductile fracture are proposed to predict the maximal drop in tearing resistance exhibited by the materials around 200 deg C as a function of ageing sensitivity of the product. (authors)

  17. Fatigue crack growth behaviour of semi-elliptical surface cracks for an API 5L X65 gas pipeline under tension

    Science.gov (United States)

    Shaari, M. S.; Akramin, M. R. M.; Ariffin, A. K.; Abdullah, S.; Kikuchi, M.

    2018-02-01

    The paper is presenting the fatigue crack growth (FCG) behavior of semi-elliptical surface cracks for API X65 gas pipeline using S-version FEM. A method known as global-local overlay technique was used in this study to predict the fatigue behavior that involve of two separate meshes each specifically for global (geometry) and local (crack). The pre-post program was used to model the global geometry (coarser mesh) known as FAST including the material and boundary conditions. Hence, the local crack (finer mesh) will be defined the exact location and the mesh control accordingly. The local mesh was overlaid along with the global before the numerical computation taken place to solve the engineering problem. The stress intensity factors were computed using the virtual crack closure-integral method (VCCM). The most important results is the behavior of the fatigue crack growth, which contains the crack depth (a), crack length (c) and stress intensity factors (SIF). The correlation between the fatigue crack growth and the SIF shows a good growth for the crack depth (a) and dissimilar for the crack length (c) where stunned behavior was resulted. The S-version FEM will benefiting the user due to the overlay technique where it will shorten the computation process.

  18. 3D atomistic studies of fatigue behaviour of edge crack (0 0 1) in bcc iron loaded in mode i and II

    Czech Academy of Sciences Publication Activity Database

    Machová, Anna; Pokluda, J.; Uhnáková, Alena; Hora, Petr

    2014-01-01

    Roč. 66, September (2014), s. 11-19 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional support: RVO:61388998 Keywords : fatigue crack growth * bcc iron * 3D atomistic simulations * molecular dynamics Subject RIV: JQ - Machines ; Tools Impact factor: 2.275, year: 2014 www.elsevier.com/locate/ijfatigue

  19. Bridging the gap between metallurgy and fatigue reliability of hydraulic turbine runners

    International Nuclear Information System (INIS)

    Thibault, D; Gagnon, M; Godin, S

    2014-01-01

    The failure of hydraulic turbine runners is a very rare event. Hence, in order to assess the reliability of these components, one cannot rely on statistical models based on the number of failures in a given population. However, as there is a limited number of degradation mechanisms involved, it is possible to use physically-based reliability models. Such models are more complicated but have the advantage of being able to account for physical parameters in the prediction of the evolution of runner degradation. They can therefore propose solutions to help improve reliability. With the use of such models, the effect of materials properties on runner reliability can easily be illustrated. This paper will present a brief review of the Kitagawa-Takahashi diagram that links the damage tolerance approach, based on fracture mechanics, to the stress or strain-life approaches. This diagram is at the centre of the reliability model used in this study. Using simplified response spectra obtained from on-site runner stress measurements, the paper will show how fatigue reliability is impacted by materials fatigue properties, namely fatigue crack propagation behaviour and fatigue limit obtained on S-N curves. It will also present a review of the most important microstructural features of 13%Cr- 4%Ni stainless steels used for runner manufacturing and will review how they influence fatigue properties in an effort to bridge the gap between metallurgy and turbine runners reliability

  20. Correlation of nodular austempered ductile iron (ADI) microstructural parameters and fatigue properties using an approach based on fracture mechanics; Correlacao entre parametros microestruturais do ferro fundido nodular austemperado (ADI) com suas propriedades a fadiga utilizando uma abordagem baseada na mecanica de fratura

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Jose Felipe [Universidade de Itauna (UIT), MG (Brazil). Faculdade de Engenharia; Fonseca, Vinicius Rizzuti; Godefroid, Leonardo Barbosa [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Escola de Minas; Ribeiro, Gabriel de Oliveira [Universidade Federal de Minas Gerais (UFMG), MG (Brazil). Departamento de Engenharia de Estruturas

    2010-07-01

    An investigation has been accomplished to check the effect of temperature and austempering time on austempered ductile iron (ADI) properties by means of fracture toughness (K{sub C}) and fatigue threshold (∆K{sub th}) tests. The correlation of ADI microstructural parameters and ADI two mechanical parameters: KC and Kth, is evaluated. Three sets of samples have ben extracted from ADI casting Y blocks produced in industrial conditions.and austenitized at 900°C for 1.5 hour. The austempering process has been performed in the following ways: the first set was austenitized at 300 deg C for 4 hours, the second set at 360°C for 1.5 hour and the third at 360°C for 0.6 hour. These distinct austempering processes have been adopted in order to obtain distinct microstructures containing austenite with two different carbon rates and two ferritic cell sizes. The materials have been characterized by means of optical and electronic microscopy, X-ray diffraction and mechanical tests. All materials have presented equivalent fatigue crack propagation rates, fracture toughness in the range between 94 and 128 MPa·m{sup 1/2} and ∆K{sub th} in the range between 5,7 and 6,4 MPa·m{sup 1/2}. The experimental results have confirmed the effect of microstructural properties (austenitic volumetric rate, austenitic carbon rate, ferritic cell size, total matrix carbon content) on fracture toughness (K{sub C}) and fatigue threshold (∆K{sub th}). Further, it was found that following parameters: fracture toughness (K{sub C}), fatigue threshold ((∆K{sub th}) and impact strength are correlated with the total matrix carbon content and ferritic cell size. (author)

  1. Proceedings of the Air Force Conference on Fatigue and Fracture of Aircraft Structures and Materials Held at Miami Beach, Florida on 15-18 December 1969

    Science.gov (United States)

    1970-12-01

    70 in.. ethanol, 12 ml. distilled water, 10 ml. butyl- The results of all fatigue tests are presented in terms cellosolve, 7.8 ml. perchloric acid...I.- 4w w 40 A 94 we z WK U.-h - 0 L z In4Iný- 4 -0- 3W3 -z C s OQ~ IW ýa. 4-0-w4w4h- Omw WSM m i%0, W WS W4 9 x 0 zoo I- CW aLW W Wh- P-.4 & X W W t a6...recommendations for critical compo- and cyclic exposure. The only difference between E and nents. F is that group E specimens are dampened with distilled

  2. Mechanical behaviour of ferritic ODS steels - Temperature dependancy and history

    Czech Academy of Sciences Publication Activity Database

    Fournier, B.; Steckmeyer, A.; Rouffié, A.-L.; Malaplate, J.; Garnier, J.; Ratti, M.; Wident, P.; Ziolek, L.; Tournie, I.; Rabeau, V.; Gentzbittel, J.M.; Kruml, Tomáš; Kuběna, Ivo

    2012-01-01

    Roč. 430, 1-3 (2012), s. 142-149 ISSN 0022-3115 Institutional support: RVO:68081723 Keywords : ODS steels * fatigue * fracture mechanics Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.211, year: 2012

  3. Comparison between the Eurocode for fatigue of steel structures, en 1993-1-9, and the Eurocode for fatigue of aluminium structures, en 1999-1-3

    NARCIS (Netherlands)

    Maljaars, J.; Lukić, M.; Soetens, F.

    2013-01-01

    The fatigue behaviour of aluminium shows not only many similarities, but also some differences with the fatigue behaviour of steel. There exist separate Eurocodes for the fatigue design of steel and of aluminium structures, EN1993-1-9 and EN1999-1-3, respectively. The latter standard was developed

  4. Fatigue crack propagation and delamination growth in Glare

    NARCIS (Netherlands)

    Alderliesten, R.C.

    2005-01-01

    Fibre Metal Laminate Glare consists of thin aluminium layers bonded together with pre-impregnated glass fibre layers and shows an excellent fatigue crack growth behaviour compared to monolithic aluminium. The fibres are insensitive to the occurring fatigue loads and remain intact while the fatigue

  5. Changing doctors' behaviours: an educational program to disseminate a new clinical pathway for the hospital management of hip fractures in elderly patients in the Lazio Region, Italy.

    Science.gov (United States)

    Ciaschi, Alma; Caprara, Andrea; Gillespie, Francesca; Furnari, Giacomo; Mamede, Sílvia

    2011-08-01

    Concerns with patient safety have increased interest in approaches to improving doctors' performance, yet dissemination of clinical guidelines and conventional continuing medical education have often failed. This study investigated the effects of an educational program based on reflection upon experience on the quality of care for patients with hip fracture in Lazio, Italy. Five hospitals participated. The study consisted of the development of a clinical pathway, a preparatory phase and the educational intervention itself, which comprised a course followed by monthly audits with reflection on practice, guided by analysis of patients' charts. Data on the quality of care for patients with hip fracture were collected from the routine information system for the period before and after the intervention. There was a significant increase in the proportion of patients who underwent surgery within 48 hours of admission (from 7% in 2006 to 26.4% in 2007) and a significant reduction in the average length of hospital stay (from 18.8 to 16.4 days). Some process indicators of quality of care were high after the intervention, though non-recommended practices were still routinely used (e.g. urinary catheterization in 72.2% of patients). There were differences in the changes when comparing hospitals. An educational intervention that combined the dissemination of a clinical pathway with external auditing geared to reflection upon practice was effective in promoting changes in doctors' behaviours. The persistence of non-recommended practices and the variation among hospitals indicate that multiple factors influence performance and affect the effectiveness of interventions. © 2010 Blackwell Publishing Ltd.

  6. Influence of hydrogen on the behaviour of metals - Mechanical and kinetic properties of fatigue cracking of steady (ZXNCTD-26-15) and unsteady (Z2CN-18-10) austenitic stainless steels. Role of heat treatments and of cathodic hydrogen

    International Nuclear Information System (INIS)

    Huwarts, Pascale; Habashi, Mahmoud

    1984-01-01

    In a context which is characterized by an increased demand in high resistance stainless steels, austenitic stainless steels with structural hardening have been notably studied. These are ductile materials in over-hardened state, therefore machinable, and can be hardened by ageing heat treatment after machining. The author reports the study of the tensile and resilience mechanical behaviour, and of the kinetic fatigue cracking of three austenitic stainless steels in presence of hydrogen. One of them is unsteady and belongs to the 300 family, whereas the two others are grades of a steady steel with structural hardening (26 pc Ni - 15 pc Cr). The author more particularly focused on the influence of thermal treatments and of phase transformation on hydrogen-induced embrittlement of these steels. After a bibliographical study on austenitic stainless steels and on their behaviour with respect to hydrogen, the author reports a detailed analysis of the studied steels. He reports tests and their results, and discusses the role of microstructure in the mechanical behaviour of these steels in presence and in absence of cathodic hydrogen [fr

  7. Advances in fatigue lifetime predictive techniques; Proceedings of the Symposium, San Francisco, CA, Apr. 24, 1990

    International Nuclear Information System (INIS)

    Mitchell, M.R.; Landgraf, R.W.

    1992-01-01

    Recent progress in the development of methods to predict fatigue performance of materials and structures is reviewed. Attention is given to general approaches to fatigue mechanics, elevated temperature phenomena, spectrum loading, the multiaxial behavior, and applications. Particular attention is given to a fracture-mechanics-based model for cumulative damage assessment, thermo-mechanical fatigue life prediction methods, a probabilistic fracture mechanics approach for structural reliability assessment of space flight systems, a multiaxial fatigue life estimation technique, plasticity and fatigue damage modeling of severely loaded tubing, damage evaluation in composite materials using thermographic stress analysis, and fatigue lifetime monitoring in power plants

  8. Physiological and neurophysiological determinants of postcancer fatigue: design of a randomized controlled trial

    OpenAIRE

    Prinsen Hetty; Bleijenberg Gijs; Zwarts Machiel J; Hopman Maria T E; Heerschap Arend; van Laarhoven Hanneke W M

    2012-01-01

    Abstract Background Postcancer fatigue is a frequently occurring, severe, and invalidating problem, impairing quality of life. Although it is possible to effectively treat postcancer fatigue with cognitive behaviour therapy, the nature of the underlying (neuro)physiology of postcancer fatigue remains unclear. Physiological aspects of fatigue include peripheral fatigue, originating in muscle or the neuromuscular junction; central fatigue, originating in nerves, spinal cord, and brain; and phys...

  9. Experimental investigation of short fatigue crack behaviour in the age-hardened aluminium alloy 6082 and approaches to crystal-plastic simulation with the purpose of fatigue life prediction

    International Nuclear Information System (INIS)

    Gaudig, W.; Kraemer, D.; Roos, E.

    2000-01-01

    Cyclic loading tests with various block sequences were carried out. Short blocks yielded shortest life times. The initiation of microcracks and crack growth was examined. Strain controlled cyclic tests were also carried out to be evaluated for theoretical fitting. Crystal plasticity and the resulting polycrystalline behaviour were modelled and programmed in form of finite element subroutines. Test calculations showed satisfactory results. (orig.)

  10. Fatigue of Dental Implants: Facts and Fallacies

    Directory of Open Access Journals (Sweden)

    Keren Shemtov-Yona

    2016-05-01

    Full Text Available Dental implants experience rare yet problematic mechanical failures such as fracture that are caused, most often, by (time-dependent metal fatigue. This paper surveys basic evidence about fatigue failure, its identification and the implant’s fatigue performance during service. We first discuss the concept of dental implant fatigue, starting with a review of basic concepts related to this failure mechanism. The identification of fatigue failures using scanning electron microscopy follows, to show that this stage is fairly well defined. We reiterate that fatigue failure is related to the implant design and its surface condition, together with the widely varying service conditions. The latter are shown to vary to an extent that precludes devising average or representative conditions. The statistical nature of the fatigue test results is emphasized throughout the survey to illustrate the complexity in evaluating the fatigue behavior of dental implants from a design perspective. Today’s fatigue testing of dental implants is limited to ISO 14801 standard requirements, which ensures certification but does not provide any insight for design purposes due to its limited requirements. We introduce and discuss the random spectrum loading procedure as an alternative to evaluate the implant’s performance under more realistic conditions. The concept is illustrated by random fatigue testing in 0.9% saline solution.

  11. Fatigue Reliability under Random Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    We consider the problem of estimating the probability of survival (non-failure) and the probability of safe operation (strength greater than a limiting value) of structures subjected to random loads. These probabilities are formulated in terms of the probability distributions of the loads and the...... propagation stage. The consequences of this behaviour on the fatigue reliability are discussed....

  12. Fatigue-damage evolution and damage-induced reduction of critical current of a Nb3Al superconducting composite

    International Nuclear Information System (INIS)

    Ochiai, S; Sekino, F; Sawada, T; Ohno, H; Hojo, M; Tanaka, M; Okuda, H; Koganeya, M; Hayashi, K; Yamada, Y; Ayai, N; Watanabe, K

    2003-01-01

    We have studied the fatigue-damage mechanism of a Nb 3 Al superconducting composite at room temperature, and the influences of the fatigue damages introduced at room temperature on the critical current at 4.2 K and the residual strength at room temperature. The main (largest) fatigue crack arose first in the clad copper and then extended into the inner core with an increasing number of stress cycles. The cracking of the Nb 3 Al filaments in the core region occurred at a late stage (around 60-90% of the fatigue life). Once the fracture of the core occurred, it extended very quickly, resulting in a quick reduction in critical current and the residual strength with increasing stress cycles. Such a behaviour was accounted for by the crack growth calculated from the S-N curves (the relation of the maximum stress to the number of stress cycles at failure) combined with the Paris law. The size and distribution of the subcracks along the specimen length, and therefore the reduction in critical current of the region apart from the main crack, were dependent on the maximum stress level. The large subcracks causing fracture of the Nb 3 Al filaments were formed when the maximum stress was around 300-460 MPa, resulting in large reduction in critical current, but not when the maximum stress was outside such a stress range

  13. A Review of the As-Built SLM Ti-6Al-4V Mechanical Properties towards Achieving Fatigue Resistant Designs

    Directory of Open Access Journals (Sweden)

    Dylan Agius

    2018-01-01

    Full Text Available Ti-6Al-4V has been widely used in both the biomedical and aerospace industry, due to its high strength, corrosion resistance, high fracture toughness and light weight. Additive manufacturing (AM is an attractive method of Ti-6Al-4V parts’ fabrication, as it provides a low waste alternative for complex geometries. With continued progress being made in SLM technology, the influence of build layers, grain boundaries and defects can be combined to improve further the design process and allow the fabrication of components with improved static and fatigue strength in critical loading directions. To initiate this possibility, the mechanical properties, including monotonic, low and high cycle fatigue and fracture mechanical behaviour, of machined as-built SLM Ti-6Al-4V, have been critically reviewed in order to inform the research community. The corresponding crystallographic phases, defects and layer orientations have been analysed to determine the influence of these features on the mechanical behaviour. This review paper intends to enhance our understanding of how these features can be manipulated and utilised to improve the fatigue resistance of components fabricated from Ti-6Al-4V using the SLM technology.

  14. 3D/4D analyses of damage and fracture behaviours in structural materials via synchrotron X-ray tomography.

    Science.gov (United States)

    Toda, Hiroyuki

    2014-11-01

    X-ray microtomography has been utilized for the in-situ observation of various structural metals under external loading. Recent advances in X-ray microtomography provide remarkable tools to image the interior of materials. In-situ X-ray microtomography provides a unique possibility to access the 3D character of internal microstructure and its time evolution behaviours non-destructively, thereby enabling advanced techniques for measuring local strain distribution. Local strain mapping is readily enabled by processing such high-resolution tomographic images either by the particle tracking technique or the digital image correlation technique [1]. Procedures for tracking microstructural features which have been developed by the authors [2], have been applied to analyse localised deformation and damage evolution in a material [3]. Typically several tens of thousands of microstructural features, such as particles and pores, are tracked in a tomographic specimen (0.2 - 0.3 mm(3) in volume). When a sufficient number of microstructural features is dispersed in 3D space, the Delaunay tessellation algorithm is used to obtain local strain distribution. With these techniques, 3D strain fields can be measured with reasonable accuracy. Even local crack driving forces, such as local variations in the stress intensity factor, crack tip opening displacement and J integral along a crack front line, can be measured from discrete crack tip displacement fields [4]. In the present presentation, complicated crack initiation and growth behaviour and the extensive formation of micro cracks ahead of a crack tip are introduced as examples.A novel experimental method has recently been developed by amalgamating a pencil beam X-Ray diffraction (XRD) technique with the microstructural tracking technique [5]. The technique provides information about individual grain orientations and 1-micron-level grain morphologies in 3D together with high-density local strain mapping. The application of this

  15. [Auditory fatigue].

    Science.gov (United States)

    Sanjuán Juaristi, Julio; Sanjuán Martínez-Conde, Mar

    2015-01-01

    Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. Using a 60dB pure tone acoustic stimulation, we obtained a microphonic response at 20dB. We then caused fatigue with 100dB of the same frequency, reaching a loss of approximately 11dB after 15minutes; after that, the deterioration slowed and did not exceed 15dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100dB and over an hour of overstimulation. No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials. Copyright © 2013 Elsevier España, S.L.U. y Sociedad Española de Otorrinolaringología y Patología Cérvico-Facial. All rights reserved.

  16. Design of a medical non-linear drilling device: the influence of twist and wear on the fatigue behaviour of NiTi wires subjected to bending rotation

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, M.; Frenzel, J.; Eggeler, G. [Lehrstuhl Werkstoffwissenschaften, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Richter, J.; Groenemeyer, D. [Institut fuer Mikrotherapie, Universitaet Witten/ Herdecke (Germany)

    2004-05-01

    This paper considers fundamental and experimental aspects associated with the engineering design of a medical, non-linear drilling device which exploits shape memory pseudoelasticity of NiTi wires. For this application it is important that the NiTi wires have a good fatigue resistance. This is why the present authors have previously determined the influence of various parameters on cyclic life, crack growth and stress state of pseudoelastic wires subjected to bending rotation fatigue. The actual drilling device has to withstand twist in addition to bending rotation because the free rotation is constrained by friction between the drill head and the bone material. In addition, friction between the wire and a NiTi guiding tube results in wear and this may well promote fatigue crack nucleation. In this paper, we explain the function of the medical drill. We then report results on the effect of the additional parameters (1) twist and (2) wear on the fatigue life of thin pseudoelastic NiTi wires. We finally discuss the implications of our experimental results for the design process of the medical drilling device. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [German] Dieser Artikel behandelt Voruntersuchungen fuer die Entwicklung eines medizinischen nicht-linearen Bohrsystems. Aus materialwissenschaftlicher Sicht spielt die Ermuedung der mechanischen Komponenten aus NiTi eine wichtige Rolle. Die Autoren haben in bisherigen Studien den Einfluss verschiedener Parameter auf Lebensdauer, Risswachstum und Spannungszustand in pseudoelastischen Draehten waehrend Umlaufbiegung ermittelt. Der Draht im eigentlichen Bohrsystem wird jedoch nicht ausschliesslich durch reine Umlaufbiegung, sondern zusaetzlich durch eine Verdrillung aufgrund der Reibung zwischen Bohrkopf und Knochengewebe, belastet. Ausserdem bewirkt die Reibung zwischen dem Draht und einem Fuehrungsrohr aus NiTi Verschleiss; diese Materialschaedigung stellt einen weiteren Mechanismus zur Risseinleitung dar. In

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

    Czech Academy of Sciences Publication Activity Database

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

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

  18. In situ observation by the high-voltage electron microscope of dynamic dislocation behaviour in the processes of tensile deformation and fatigue

    International Nuclear Information System (INIS)

    Imura, T.; Yukawa, N.; Saka, H.; Nohara, A.; Ishikawa, I.; Kamino, T.

    1975-01-01

    To investigate the dynamic properties of dislocations, a new direct method was developed by using a high-voltage electron microscope (HVEM). The motion of edge and screw dislocations was observed in thick foil specimens of Fe, Fe-3%Si, 18-8 stainless steel, and A1 being stretched at various temperatures with a new straining device in HVEM operated at 500 to 1000 kV. The dislocation motions were recorded continuously on video tape with the aid of an image intensifier, and the corresponding stress-strain curve of the specimen under observation was also recorded simultaneously. Newly developed tensile testing devices and a fatigue stage are introduced, all of which can be mounted on a goniometer stage and are equipped with high-sensitivity strain gauges. The velocity of dislocations as a function of applied stress, the types of dislocation sources and mechanism of dislocation multiplication, the dynamic crossing-over of dislocations, the information on the elemental dislocation mechanisms of yielding, work hardening, crack propagation, and fatigue are obtained. The effects of specimen thickness and high-energy electron bombardment on the dislocation motion are discussed to testify to the validity of the result obtained. (author)

  19. Strain controlled fatigue testing of the metastable {beta}-titanium alloy Ti-6.8Mo-4.5Fe-1.5Al (Timetal LCB)

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Bernd [BAM Federal Institute for Materials Research and Testing, Division 5.2, Unter den Eichen 87, 12205 Berlin (Germany); Skrotzki, Birgit, E-mail: birgit.skrotzki@bam.de [BAM Federal Institute for Materials Research and Testing, Division 5.2, Unter den Eichen 87, 12205 Berlin (Germany)

    2011-07-15

    Highlights: {yields} Strain controlled fatigue tests on the {beta}-alloy Ti-6.8Mo-4.5Fe-1.5Al. {yields} Characterization of deformed microstructure by TEM. {yields} Deformation induced precipitation takes place in solution treated condition. {yields} Deformation of aged state is characterized by subgrain formation in secondary {alpha}-phase. - Abstract: The present work covers the mechanical behaviour of Timetal LCB under fatigue loading and utilizes transmission electron microscopy (TEM) to study the associated microstructural evolution. Fatigue specimens were taken out of LCB wire made for automotive suspension spring manufacturing in a solution treated as well as an additionally aged state. Uniaxial fatigue tests were carried out in total strain control with R = 0.1. Solution treated specimens tested at 3% and 4% maximum total strain showed a saturating force response, which differed from all other total strain controlled tests, and a distinct fracture behaviour. In addition, an increase of the dynamic Young's modulus is observed under these test conditions and in this material state. These findings are interpreted as a deformation induced precipitation of nanosize {alpha}- or {omega}-phase. In the aged state, the {alpha}-phase carries the major part of deformation work, noticeable by distinct {alpha}-substructures in fatigued specimen states.

  20. Strain controlled fatigue testing of the metastable β-titanium alloy Ti-6.8Mo-4.5Fe-1.5Al (Timetal LCB)

    International Nuclear Information System (INIS)

    Koch, Bernd; Skrotzki, Birgit

    2011-01-01

    Highlights: → Strain controlled fatigue tests on the β-alloy Ti-6.8Mo-4.5Fe-1.5Al. → Characterization of deformed microstructure by TEM. → Deformation induced precipitation takes place in solution treated condition. → Deformation of aged state is characterized by subgrain formation in secondary α-phase. - Abstract: The present work covers the mechanical behaviour of Timetal LCB under fatigue loading and utilizes transmission electron microscopy (TEM) to study the associated microstructural evolution. Fatigue specimens were taken out of LCB wire made for automotive suspension spring manufacturing in a solution treated as well as an additionally aged state. Uniaxial fatigue tests were carried out in total strain control with R = 0.1. Solution treated specimens tested at 3% and 4% maximum total strain showed a saturating force response, which differed from all other total strain controlled tests, and a distinct fracture behaviour. In addition, an increase of the dynamic Young's modulus is observed under these test conditions and in this material state. These findings are interpreted as a deformation induced precipitation of nanosize α- or ω-phase. In the aged state, the α-phase carries the major part of deformation work, noticeable by distinct α-substructures in fatigued specimen states.

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

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-10-01

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

  2. Crack initiation and propagation on the polymeric material ABS (Acrylonitrile Butadiene Styrene, under ultrasonic fatigue testing

    Directory of Open Access Journals (Sweden)

    G. M. Domínguez Almaraz

    2015-10-01

    Full Text Available Crack initiation and propagation have been investigated on the polymeric material ABS (Acrylonitrile Butadiene Styrene, under ultrasonic fatigue testing. Three controlled actions were implemented in order to carry out fatigue tests at very high frequency on this material of low thermal conductivity, they are: a The applying load was low to limit heat dissipation at the specimen neck section, b The dimensions of testing specimen were small (but fitting the resonance condition, in order to restraint the temperature gradient at the specimen narrow section, c Temperature at the specimen neck section was restrained by immersion in water or oil during ultrasonic fatigue testing. Experimental results are discussed on the basis of thermo-mechanical behaviour: the tail phenomenon at the initial stage of fatigue, initial shear yielding deformation, crazed development on the later stage, plastic strain on the fracture surface and the transition from low to high crack growth rate. In addition, a numerical analysis is developed to evaluate the J integral of energy dissipation and the stress intensity factor K, with the crack length

  3. Comparison of mechanical fatigue with thermal fatigue in ceramics

    International Nuclear Information System (INIS)

    Wilson, B.A.; Case, E.D.

    1993-01-01

    Thermal fatigue studies have shown a saturation of damage accumulation with cycling. Similar damage saturation has been observed for mechanical fatigue. This study compares damage saturation behavior for mechanical fatigue with thermal fatigue in ceramics. Studies of thermal fatigue of ceramics show that the accumulation of thermal shock cycling damage depends on the magnitude of the thermal shock, ΔΤ (where ΔΤ is the temperature change of the specimen from the initial temperature to the temperature of the quenching medium). Three distinct regimes of damage accumulation exist depending on the magnitude of ΔΤ. For the first regime where the thermal shock cycling is below ΔΤ c , a critical thermal shock value, there is no thermal damage detected. In the second regime where ΔΤ is higher than ΔΤ c but lower than ΔΤ 1 , the accumulating microcrack damage initially induces a rapid change in material property P. As the number of cycles increases a steady state value of properties is reached. For the third regime ΔΤ is higher than ΔΤ 1 and rapid crack growth results in fracture of the specimen. Each regime depends on ΔΤ since, for a given specimen and quenching medium, the maximum thermal shock stress is proportional to ΔΤ. So characterization of each regime by ΔΤ is indicative of the maximum stress applied by the thermal shock

  4. The Effect of Shot Peening on the Improvement of Fatigue Strength and Characteristics Fatigue Crack of the Aluminum Alloys

    International Nuclear Information System (INIS)

    Jeon, Hyun Bae; Lim, Man Bae; Park, Won Jo

    2007-01-01

    The purpose of this study is to investigate the effect of shot peening on the fatigue strength and fatigue life of two kinds of aluminum alloys. The fatigue strength behavior of aluminum alloys were estimated by the stress ratio and shot velocities. The fatigue life and strength increased with increasing the test shot velocity. However, at the shot velocity range between 50m/s and 70m/s, the compressive residual stress phenomena were observed in test conditions of different shot velocity. The optimal shot velocity is acquired by considering the peak values of the compressive residual stress, dislocations, brittle striation, slip, and fisheye on the fracture surface of test specimen. It was observed from the SEM observation on the deformed specimen that the brittle striation, fisheye were showed in the intergranular fracture structure boundaries at the this velocities. Therefore, fatigue strength and fatigue life would be considered that shot velocity has close relationship with the compressive residual stress

  5. Correlations between the post-HIP treatment, resulting microstructure and fatigue behaviour of prealloyed Ti6Al4V powder compacts

    International Nuclear Information System (INIS)

    Wirth, G.; Grundhoff, K.J.; Smarsly, W.

    1985-01-01

    Prealloyed Ti6Al4V powders, hot isostatically pressed in the (alpha + beta) temperature range, always possess a mixed microstructure of lenticular and equiaxed parts. Numerous treatments have been used to improve microstructural homogeneity, especially to achieve fine equiaxed grains well known to possess good HCF properties. In this contribution, four different conditions of HIP compacts from ultraclean PREP powder were investigated together with PSV powder compacted by combined die forging (CDF). The HIP compacts had pure equiaxed and lenticular, a mixture of both (as HIP) as well as a swaged + beta annealed microstructure. The best HCF fatigue strength was correlated to the last condition instead of the expected equiaxed microstructure. CDF resulted in a homogeneous equiaxed microstructure which thus could be achieved by a one-step compaction process directly from untreated powder. 12 references

  6. Optimal Inspection Planning for Fatigue Damage of Offshore Structures

    DEFF Research Database (Denmark)

    Madsen, H.O.; Sørensen, John Dalsgaard; Olesen, R.

    1990-01-01

    A formulation of optimal design, inspection and maintenance against damage caused by fatigue crack growth is formulated. A stochastic model for fatigue crack growth based on linear elastic fracture mechanics Is applied. Failure is defined by crack growth beyond a critical crack size. The failure...

  7. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2009-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...

  8. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2008-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...

  9. Fatigue crack layer propagation in silicon-iron

    Science.gov (United States)

    Birol, Y.; Welsch, G.; Chudnovsky, A.

    1986-01-01

    Fatigue crack propagation in metal is almost always accompanied by plastic deformation unless conditions strongly favor brittle fracture. The analysis of the plastic zone is crucial to the understanding of crack propagation behavior as it governs the crack growth kinetics. This research was undertaken to study the fatigue crack propagation in a silicon iron alloy. Kinetic and plasticity aspects of fatigue crack propagation in the alloy were obtained, including the characterization of damage evolution.

  10. Fatigue (PDQ)

    Science.gov (United States)

    ... can lessen the patient's quality of life and self-esteem . Getting help with fatigue may prevent some of ... National Institutes of Health FOLLOW US Facebook Twitter Instagram YouTube Google+ LinkedIn GovDelivery RSS CONTACT INFORMATION Contact ...

  11. Analyses of fractured implant fixture after prolonged implantation

    Science.gov (United States)

    Choe, Han-Cheol; Lee, June-Kyu; Chung, Chae-Heon

    2004-07-01

    Although fortunately rare, fracture of implants causes significant problems for both clinicians and patients. The major cause of a fractured implant may be corrosion fatigue fracture. To investigate how to increase the fatigue life and corrosion resistance of dental implants, the surface morphology of six Steri-Oss fractured implants was analyzed. The period of implantation after loading in patient jaws varied between 23 months and 37 months. The topography and surface chemical composition were studied with electron probe micro-analysis (point mapping, energy dispersive x-ray spectroscopy) and field emission scanning electron microscopy. All samples were fractured at the screw root and the crest formed a keen-edged shape. The five samples were fractured at the first thread of the fixture and one sample at the third thread of fixture. The fatigue cracks were mainly nucleated and grown at scratches occurring for the screw root and crest formation and the cervix portion of the implant having a small curvature. The pits were nucleated in the vicinity of inclusions such as SiO2 and corrosion fatigue cracking was predominantly propagated. Corrosion products were found on the opposite side of the starting point of corrosion fatigue crack. From observations of fatigue striations, it is possible to predict the life time of fractured implants and estimate the cleavage fracture and dimple fracture of implants. In this study, analysis of fractured surfaces revealed the characteristics of the implant materials, problems of design, fatigue life, and manufacturing process. In order to protect against corrosion fatigue fractures and prolong the fatigue life of dental implants, we must consider the implant design, implant manufacturing, and surface treatment of the implant materials.

  12. 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)

  13. Oxidation and fatigue behaviour of {gamma}-TiAl coated with HIPIMS CrAlYN/CrN nanoscale multilayer coatings and EB-PVD thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Braun, Reinhold; Schulz, Uwe [DLR - German Aerospace Center, Koeln (Germany). Inst. of Materials Research; Leyens, Christoph [DLR - German Aerospace Center, Koeln (Germany). Inst. of Materials Research; Technische Univ. Dresden (Germany). Inst. of Materials Science; Hovsepian, Papken E.; Ehiasarian, Arutiun P. [Sheffield Hallam Univ. (United Kingdom). Nanotechnology Centre for PVD Research

    2010-05-15

    CrAlYN/CrN nanoscale multilayer coatings were deposited on {gamma}-TiAl substrate material using high power impulse magnetron sputtering technology. The nitride coating provided effective oxidation protection to {gamma}-TiAl at 850 C for exposure time periods exceeding 2000 cycles of 1 h dwell time at high temperature in air. High oxidation resistance was also observed at 900 C. After exposure to air at 850 C for 300 h, coated tension specimens exhibited a reduction in fatigue strength of about 70 MPa compared to the bare {gamma}-TiAl alloy. Zirconia topcoats produced by electron-beam physical vapour deposition were well adherent to the CrAlYN/CrN coating with an oxy-nitride overcoat. When thermally cycled at 900 C, the lifetime of this thermal barrier coating system on {gamma}-TiAl exceeded 1000 1 h cycles. Below cracks in the nitride coating, the substrate was oxidised and protrusions of an outer oxide scale with columnar structure formed. (orig.)

  14. Fatigue of coated and laser hardened steels

    International Nuclear Information System (INIS)

    La Cruz, P. de.

    1990-01-01

    In the present work the effect of ion nitriding, laser hardening and hot dip galvanizing upon the fatigue limit and notch sensitivity of a B-Mn Swedish steel SS 2131 have been investigated. The fatigue tests were performed in plane reverse bending fatigue (R=1). The quenched and tempered condition was taken as the reference condition. The microstructure, microhardness, fracture surface and coating appearance of the fatigue surface treated specimens were studied. Residual stress and retained austenite measurements were also carried out. It was found that ion nitriding improves the fatigue limit by 53 % for smooth specimens and by 115 % for notched specimens. Laser hardening improves the fatigue limit by 18 % and 56 % for smooth and notched specimen respectively. Hot dip galvanizing gives a slight deterioration of the fatigue limit (9 % and 10 % for smooth and notched specimen respectively). Ion nitriding and laser hardening decrease the value of the notch sensitivity factor q by 78 % and 65 % respectively. Hot dip galvanizing does not modify it. A simple schematic model based on a residual stress distribution, has been used to explain the different effects. It seems that the presence of the higher compressive residual stresses and the higher uniformity of the microstructure may be the causes of the better fatigue performance of ion nitrided specimens. (119 refs.) (author)

  15. Fatigue Reliability Analysis of a Mono-Tower Platform

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Brincker, Rune

    1991-01-01

    In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed...... through linear-elastic fracture mechanics (LEFM). In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability, as well as systems reliability, is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters...... is investigated. The systems reliability index, estimated by using the fatigue elements with the fatigue strength expressed through SN relations, is found to be smaller than the systems reliability index estimated by using LEFM. It is shown that the systems reliability index is very sensitive to variations...

  16. Influence of joint line remnant on crack paths under static and fatigue loadings in friction stir welded Al-Mg-Sc alloy

    Directory of Open Access Journals (Sweden)

    Y. Besel

    2016-01-01

    Full Text Available The influence of the joint line remnant (JLR on tensile and fatigue fracture behaviour has been investigated in a friction stir welded Al-Mg-Sc alloy. JLR is one of the microstructural features formed in friction stir welds depending on welding conditions and alloy systems. It is attributed to initial oxide layer on butting surfaces to be welded. In this study, two different tool travel speeds were used. JLR was formed in both welds but its spatial distribution was different depending on the tool travel speeds. Under the tensile test, the weld with the higher heat input fractured partially along JLR, since strong microstructural inhomogeneity existed in the vicinity of JLR in this weld and JLR had weak bonding. Resultantly, the mechanical properties of this weld were deteriorated compared with the other weld. Fatigue crack initiation was not affected by the existence of JLR in all welds. But the crack propagated preferentially along JLR in the weld of the higher heat input, when it initiated on the retreating side. Consequently, such crack propagation behaviour along JLR could bring about shorter fatigue lives in larger components in which crack growth phase is dominant.

  17. 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.)

  18. Mesoscopic scale thermal fatigue damage

    International Nuclear Information System (INIS)

    Robertson, C.; Fissolo, A.; Fivel, M.

    2001-01-01

    In an attempt to better understand damage accumulation mechanisms in thermal fatigue, dislocation substructures forming in 316L steel during one specific test were examined and simulated. Hence, thin foils taken out of massive, tested specimens were first observed in transmission electron microscopy (TEM). These observations help in determining one initial dislocation configuration to be implemented in a 3-D model combining 3D discrete dislocation dynamics simulation (DDD) and finite element method computations (FEM). It was found that the simulated mechanical behaviour of the DDD microstructure is compatible with FEM and experimental data. The numerically generated dislocation microstructure is similar to ladder-like dislocation arrangements as found in many fatigued f.c.c. materials. Distinct mechanical behaviour for the two active slip systems was shown and deformation mechanisms were proposed. (authors)

  19. Physiological and neurophysiological determinants of postcancer fatigue: design of a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Prinsen Hetty

    2012-06-01

    Full Text Available Abstract Background Postcancer fatigue is a frequently occurring, severe, and invalidating problem, impairing quality of life. Although it is possible to effectively treat postcancer fatigue with cognitive behaviour therapy, the nature of the underlying (neurophysiology of postcancer fatigue remains unclear. Physiological aspects of fatigue include peripheral fatigue, originating in muscle or the neuromuscular junction; central fatigue, originating in nerves, spinal cord, and brain; and physical deconditioning, resulting from a decreased cardiopulmonary function. Studies on physiological aspects of postcancer fatigue mainly concentrate on deconditioning. Peripheral and central fatigue and brain morphology and function have been studied for patients with fatigue in the context of chronic fatigue syndrome and neuromuscular diseases and show several characteristic differences with healthy controls. Methods/design Fifty seven severely fatigued and 21 non-fatigued cancer survivors will be recruited from the Radboud University Nijmegen Medical Centre. Participants should have completed treatment of a malignant, solid tumour minimal one year earlier and should have no evidence of disease recurrence. Severely fatigued patients are randomly assigned to either the intervention condition (cognitive behaviour therapy or the waiting list condition (start cognitive behaviour therapy after 6 months. All participants are assessed at baseline and the severely fatigued patients also after 6 months follow-up (at the end of cognitive behaviour therapy or waiting list. Primary outcome measures are fatigue severity, central and peripheral fatigue, brain morphology and function, and physical condition and activity. Discussion This study will be the first randomized controlled trial that characterizes (neurophysiological factors of fatigue in disease-free cancer survivors and evaluates to which extent these factors can be influenced by cognitive behaviour therapy

  20. Side Effects: Fatigue

    Science.gov (United States)

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  1. Fatigue in Aluminum Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2014-01-01

    Fatigue damage accumulation in aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test...... is normally used in the design against fatigue in aluminum bridges, may give results which are unconservative. The validity of the results obtained from Miner’s rule will depend on the distribution of the load history in tension and compression....

  2. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds; Etude de la competition dechirure ductile/rupture fragile: application de la tenue mecanique des tubes en acier C-Mn et de leurs joints soudes

    Energy Technology Data Exchange (ETDEWEB)

    Le Corre, V

    2006-09-15

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests onspecimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  3. Tank Structural Fatigue Fracture in Hydrocarbon Transportation

    Directory of Open Access Journals (Sweden)

    Pimnev Alexey

    2016-01-01

    Full Text Available The article touches upon the reasons of cracks formation in a vertical steel tank wall used in oil transportation. Here are given the comparative research results of chemical composition and mechanical properties of steel, used in manufacture of the flat product: tensile strength, yield strength, impact strength and hardness.

  4. 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

  5. Simplified elastoplastic fatigue analysis

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  6. 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.

  7. Fatigue Assessment of Nickel-Titanium Peripheral Stents: Comparison of Multi-Axial Fatigue Models

    Science.gov (United States)

    Allegretti, Dario; Berti, Francesca; Migliavacca, Francesco; Pennati, Giancarlo; Petrini, Lorenza

    2018-02-01

    Peripheral Nickel-Titanium (NiTi) stents exploit super-elasticity to treat femoropopliteal artery atherosclerosis. The stent is subject to cyclic loads, which may lead to fatigue fracture and treatment failure. The complexity of the loading conditions and device geometry, coupled with the nonlinear material behavior, may induce multi-axial and non-proportional deformation. Finite element analysis can assess the fatigue risk, by comparing the device state of stress with the material fatigue limit. The most suitable fatigue model is not fully understood for NiTi devices, due to its complex thermo-mechanical behavior. This paper assesses the fatigue behavior of NiTi stents through computational models and experimental validation. Four different strain-based models are considered: the von Mises criterion and three critical plane models (Fatemi-Socie, Brown-Miller, and Smith-Watson-Topper models). Two stents, made of the same material with different cell geometries are manufactured, and their fatigue behavior is experimentally characterized. The comparison between experimental and numerical results highlights an overestimation of the failure risk by the von Mises criterion. On the contrary, the selected critical plane models, even if based on different damage mechanisms, give a better fatigue life estimation. Further investigations on crack propagation mechanisms of NiTi stents are required to properly select the most reliable fatigue model.

  8. Three-point bending fatigue behavior of WC–Co cemented carbides

    International Nuclear Information System (INIS)

    Li, Anhai; Zhao, Jun; Wang, Dong; Gao, Xinliang; Tang, Hongwei

    2013-01-01

    Highlights: ► Mechanical fatigue tests were conducted on a specific designed jig. ► Three-point bending fatigue behavior of WC–Co cemented carbides was studied. ► Fatigue mechanisms of WC–Co cemented carbides with different WC grain sizes and Co binder contents were revealed. -- Abstract: WC–Co cemented carbides with different WC grain sizes and Co binder contents were sintered and fabricated. The three-point bending specimens with a single edge notch were prepared for tests. In the experiments, the mechanical properties of materials were investigated under static and cyclic loads (20 Hz) in air at room temperature. The fatigue behaviors of the materials under the same applied loading conditions are presented and discussed. Optical microscope and scanning electron microscopy were used to investigate the micro-mechanisms of damage during fatigue, and the results were used to correlate with the mechanical fatigue behavior of WC–Co cemented carbides. Experimental results indicated that the fatigue fracture surfaces exhibited more fracture origins and diversification of crack propagation paths than the static strength fracture surfaces. The fatigue fracture typically originates from inhomogeneities or defects such as micropores or aggregates of WC grains near the notch tip. Moreover, due to the diversity and complexity of the fatigue mechanisms, together with the evolution of the crack tip and the ductile deformation zone, the fatigue properties of WC–Co cemented carbides were largely relevant with the combination of transverse rupture strength and fracture toughness, rather than only one of them. Transverse rupture strength dominated the fatigue behavior of carbides with low Co content, whilst the fatigue behavior of carbides with high Co content was determined by fracture toughness.

  9. Influence of pyrolysis temperature on fracture response in SiOC based composites reinforced by basalt woven fabric

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Černý, Martin; Strachota, Adam; Sucharda, Zbyněk; Halasová, Martina; Dlouhý, Ivo

    2014-01-01

    Roč. 34, č. 14 (2014), s. 3389-3398 ISSN 0955-2219 R&D Projects: GA ČR GAP107/12/2445; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 ; RVO:67985891 ; RVO:61389013 Keywords : Fracture behaviour * CMCs * Pyrolysis * Basalt fibre * Polysiloxane Subject RIV: JL - Materials Fatigue, Friction Mechanics; JI - Composite Materials (USMH-B); JH - Ceramics, Fire-Resistant Materials and Glass (UMCH-V) Impact factor: 2.947, year: 2014

  10. FATIGUE CRACK PROPAGATION THROUGH AUSTEMPERED DUCTILE IRON MICROSTRUCTURE

    Directory of Open Access Journals (Sweden)

    Lukáš Bubenko

    2010-10-01

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

  11. Bending Fatigue of Carburized Steel at Very Long Lives

    Science.gov (United States)

    Nelson, D. V.; Long, Z.

    2016-01-01

    The bending fatigue behavior of two carburized steels is investigated for lives between approximately 105 and 108 cycles. Cracks are observed to start at sub-surface inclusions and develop features on fracture surfaces resembling "fish eyes" in appearance. This type of sub-surface cracking tends to govern fatigue strength at long lives. Previous studies of "fish eye" fatigue in carburized steel have been relatively few and have mainly considered failures originating at depths beneath a carburized case, where compressive residual stresses are minimal and hardness values approach those in the core. This study provides fatigue data for cracks originating within cases at various depths where compressive residual stresses are substantial and hardness is much higher than in the core. Fatigue strength is predicted by a simple model, accounting for the influence of residual stresses and hardness values at the different depths at which cracks started. Predictions of fatigue strength are compared with data generated in this study.

  12. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

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

    1997-01-01

    on welded plate test specimens have been carried through. The materials that have been used are either conventional structural steel with a yield stress of ~ 400-410 MPa or high-strength steel with a yield stress of ~ 810-840 MPa.The fatigue tests have been carried out using load histories, which correspond...... to one week's traffic loading, determined by means of strain gage measurements on the orthotropic steel deck structure of the Farø Bridges in Denmark.The test series which have been carried through show a significant difference between constant amplitude and variable amplitude fatigue test results. Both...... the fatigue test results and the fracture mechanics analysis indicate that the linear fatigue damage accumulation formula, which is normally used in the design against fatigue in steel bridges, may give results, which are unconservative. The validity of the results obtained from the linear fatigue damage...

  13. Periostin deficiency increases bone damage and impairs injury response to fatigue loading in adult mice.

    Directory of Open Access Journals (Sweden)

    Nicolas Bonnet

    Full Text Available Bone damage removal and callus formation in response to fatigue loading are essential to prevent fractures. Periostin (Postn is a matricellular protein that mediates adaptive response of cortical bone to loading. Whether and how periostin influences damage and the injury response to fatigue remains unknown. We investigated the skeletal response of Postn(-/- and Postn(+/+ mice after fatigue stimulus by axial compression of their tibia. In Postn(+/+ mice, cracks number and surface (CsNb, CsS increased 1h after fatigue, with a decrease in strength compared to non-fatigued tibia. At 15 days, CsNb had started to decline, while CtTV and CtBV increased in fatigued vs non-fatigued tibia, reflecting a woven bone response that was present in 75% of the fatigued bones. Cortical porosity and remodelling also prominently increased in the fatigued tibia of Postn(+/+ mice. At 30 days, paralleling a continuous removal of cortical damage, strength of the fatigued tibia was similar to the non-fatigue tibia. In Postn(-/- mice, cracks were detectable even in the absence of fatigue, while the amount of collagen crosslinks and tissue hardness was decreased compared to Postn(+/+. Fatigue significantly increased CsNb and CsS in Postn(-/-, but was not associated with changes in CtTV and CtBV, as only 16% of the fatigued bones formed some woven bone. Cortical porosity and remodelling did not increase either after fatigue in Postn(-/-, and the level of damage remained high even after 30 days. As a result, strength remained compromised in Postn(-/- mice. Contrary to Postn(+/+, which osteocytic lacunae showed a change in the degree of anisotropy (DA after fatigue, Postn(-/- showed no DA change. Hence periostin appears to influence bone materials properties, damage accumulation and repair, including local modeling/remodeling processes in response to fatigue. These observations suggest that the level of periostin expression could influence the propensity to fatigue fractures.

  14. Experimental and numerical approach on fracture behaviour of four inches diameter carbon-manganese cracked welded pipes in four point bending

    International Nuclear Information System (INIS)

    Semete, P.; Faidy, C.; Lautier, J.L.

    2001-01-01

    EDF has conducted a research programme to demonstrate the fracture resistance of carbon-manganese welded pipes. The main task of this programme consisted of testing three four inches diameter (114.3 mm O.D.) thin welded pipes (8.56 mm thick) which are representative of those of the sites. The three pipes were loaded under four point bending at a quasi-static rate at -20 C till their maximum bending moment was reached. This paper presents the experimental results, finite element calculations and their comparison with the simplified fracture assessment method of the RSE-M Code. (author)

  15. Ultrasonic fatigue of a high strength steel

    Science.gov (United States)

    Koster, M.; Wagner, G.; Eifler, D.

    2010-07-01

    At the Institute of Materials Science and Engineering at the University of Kaiserslautern an ultrasonic testing system for the fatigue assessment of metallic materials in the very high cycle fatigue (VHCF) regime was developed. The ultrasonic testing system allows to control the test and to measure detailed fatigue data. The achieved results can be used to describe the cyclic deformation behaviour of wheel steels at ultrasonic frequencies. In load increase tests (LIT), the critical stress amplitude can be determined, which leads to a defined change of process parameters like generator power, dissipated energy and specimen temperature. With SEM investigations it was proved that the change of the process parameters correlates with irreversible changes in the microstructure. It can be shown that the stress amplitude, leading to first irreversible changes in the microstructure, strongly depends on the depth position within the original wheel rim. New and basic results on the fatigue mechanisms of high strength steels in the VHCF-regime can be achieved.

  16. Mechanical Behaviour of Stainless Steels under Dynamic Loading: An Investigation with Thermal Methods

    Directory of Open Access Journals (Sweden)

    Rosa De Finis

    2016-11-01

    Full Text Available Stainless steels are the most exploited materials due to their high mechanical strength and versatility in producing different alloys. Although there is great interest in these materials, mechanical characterisation, in particular fatigue characterisation, requires the application of several standardised procedures involving expensive and time-consuming experimental campaigns. As a matter of fact, the use of Standard Test Methods does not rely on a physical approach, since they are based on a statistical evaluation of the fatigue limit with a fixed probabilistic confidence. In this regard, Infra-Red thermography, the well-known, non-destructive technique, allows for the development of an approach based on evaluation of dissipative sources. In this work, an approach based on a simple analysis of a single thermographic sequence has been presented, which is capable of providing two indices of the damage processes occurring in material: the phase shift of thermoelastic signal φ and the amplitude of thermal signal at twice the loading frequency, S2. These thermal indices can provide synergetic information about the mechanical (fatigue and fracture behaviour of austenitic AISI 316L and martensitic X4 Cr Ni Mo 16-5-1; since they are related to different thermal effects that produce damage phenomena. In particular, the use of φ and S2 allows for estimation of the fatigue limit of stainless steels at loading ratio R = 0.5 in agreement with the applied Standard methods. Within Fracture Mechanics tests, both indices demonstrate the capacity to localize the plastic zone and determine the position of the crack tip. Finally, it will be shown that the value of the thermoelastic phase signal can be correlated with the mechanical behaviour of the specific material (austenitic or martensitic.

  17. Hip Fracture

    Science.gov (United States)

    ... hip fractures in people of all ages. In older adults, a hip fracture is most often a result of a fall from a standing height. In people with very weak bones, a hip fracture can occur simply by standing on the leg and twisting. Risk factors The rate of hip fractures increases substantially with ...

  18. Micrographic and microfractographic characteristics of the T-A6V titanium alloy under fatigue and stress corrosion

    International Nuclear Information System (INIS)

    Laziou, J.C.

    1976-01-01

    In a previous article the author studied the influence of the structure on the mechanical properties, tenacity and fatigue behaviour of the T-A6V titanium alloy. The four stages of a crack propagation have been observed: (i) The initial stage or initiation, characterized by the forming of slipband, on the one hand, and of extrusions-intrusions, on the other hand, which are generative of micro-cracks. The α-β interfaces are also initiation sites. (ii) Stage 1, characterized by its fracture of fragile aspect. (iii) Stage II, characterized by the presence of fatigue striations. (iv) The ultimate stage or rapid propagation of the crack. The behaviour of the different structure of the T-A6V and the effect of the forging field (β or α+β) has also been studied from the standpoint of resistance to crack propagation in a corrosive environment. These tests have confirmed that satisfactory behaviour of an acicular structure with regard to the stress-corrosion. It is confirmed that a stress-corrosion crack propagates by cleavage in the α-phase according to a plane approximately oriented by 13 to 14 0 in relation to the base plane (0001)sub(α). (Auth.)

  19. Experimental Investigation and Finite Element Analysis on Fatigue Behavior of Aluminum Alloy 7050 Single-Lap Joints

    Science.gov (United States)

    Zhou, Bing; Cui, Hao; Liu, Haibo; Li, Yang; Liu, Gaofeng; Li, Shujun; Zhang, Shangzhou

    2018-03-01

    The fatigue behavior of single-lap four-riveted aluminum alloy 7050 joints was investigated by using high-frequency fatigue test and scanning electron microscope (SEM). Stress distributions obtained by finite element (FE) analysis help explain the fatigue performance. The fatigue test results showed that the fatigue lives of the joints depend on cold expansion and applied cyclic loads. FE analysis and fractography indicated that the improved fatigue lives can be attributed to the reduction in maximum stress and evolution of fatigue damage at the critical location. The beneficial effects of strengthening techniques result in tearing ridges or lamellar structure on fracture surface, decrease in fatigue striations spacing, delay of fatigue crack initiation, crack deflection in fatigue crack propagation and plasticity-induced crack closure.

  20. Alloy 800: Low cycle fatigue curves as the basis for design against fatigue of HTR-components

    International Nuclear Information System (INIS)

    Diehl, H.; Blume-Firla, I.; Mergler, W.

    1988-01-01

    For a reliable fatigue analysis, one requires secure characteristics of the alternating strain behaviour, which were provided by a scatter band evaluation from low cycle fatigue experiments on materials of the alloy 800 type. This evaluation takes into account the latest state of the experiments in the context of the prototype nuclear process heat plant project (PNP) and beyond this all the information available from the literature. There is a special question regarding the low cycle fatigue behaviour in the HTR helium atmosphere. (orig./DG) [de