bluuebunny/crossref_metadata_2025_split huggingface dataset:
ON FATIGUE CRACK GROWTH AND STABLE TEARING
Authors: Neale B. K. , Priddle E. K. 
Published: April 2007

Abstract— An experimental and analytical investigation has been performed to examine the effect of concurrent fatigue cycling and stable tearing on the crack growth fracture resistance of EN3A steel at 360°C. The steel was tested in the as‐received and hardened conditions, hardening being achieved by pre‐cracking at a load comparable to the elastic limit of the test specimens. For each condition of the steel, resistance curves are obtained both with and without concurrent fatigue cycling.A significant increase in the crack growth rates occurred as a result of concurrent fatigue cycling. The rates are in reasonably close agreement with the values predicted from the sum of the fatigue crack growth and stable tearing components. The J‐estimation formula of Ainsworth is used to demonstrate that there is no interaction between stable tearing and fatigue in the tests for the steel in the as‐received condition.
FATIGUE CRACK GROWTH AND CLOSURE BEHAVIOUR THROUGH A COMPRESSIVE RESIDUAL STRESS FIELD
Authors: Kang Ki J. , Song Ji H. , Earmme Youn Y. 
Published: April 2007

AbstractBehaviour of fatigue crack growth and closure through a compressive residual stress field is investigated by performing fatigue crack growth tests on welded SEN specimens of a structural steel (JIS SM50A). Depending on the type of the initial residual stress in the region of crack growth, the growth and closure of the crack show different behaviour. In particular, in the transition region from a compressive residual stress field to a tensile residual stress field, the fatigue crack growth rates cannot be described by the effective stress intensity factor range ΔKeff, based on the measured crack opening stress intensity factor Kop. Also it is found that the R'‐method using the data of da/dN vs ΔK for residual stress‐free specimens, with the effective stress ratio R'[=(Kmax+Kr)/(Kmin+Kr)], gives non‐conservative predictions of the growth rates in the transition region. Observations of crack closure behaviour in this study indicates that partial opening of the crack occurs and this plays an important role in crack growth through a compressive residual stress field. Based on the concept of a partial opening point (defined and measured in this work), fatigue crack growth behaviour can be better explained.
GEOMETRY INDEPENDENT R‐CURVES IN A TITANIUM ALLOY USING A NORMALISED AXIS FOR CRACK GROWTH
Authors: John S. J. , Turner C. E. 
Published: April 2007

AbstractData from a study of the effect of geometric variation on J‐R curves for a titanium alloy in three‐point bending are presented up to large amounts of growth. Four series are reported, various widths, various a/W ratios, various thicknesses and various absolute sizes, all failing in the limit load regime by stable tearing. Analysis is made in terms of Jm‐R curves, adjusted to a common initiation toughness, J1, to clarify the effects of geometry. Strong trends are then found with absolute size over a four fold range and with width over a two fold range; a weaker trend with a/W over a four fold range but practically none with thickness over a nine fold range. Many of these trends are different from those reported for other more ductile materials but consistent in some cases with those reported for another high strength material, HY130. All the deep notch cases (14 tests) reduce to a single group when plotted as Jm against a normalised abscissa, Δa/bo, with a very slight trend to a higher curve for the thinner pieces.
NUCLEATION AND SHORT CRACK GROWTH IN FATIGUED POLYCRYSTALLINE COPPER
Authors: Polák J. , Liškutían P. 
Published: April 2007

AbstractSurface evolution in polycrystalline copper specimens with a shallow notch has been studied in interrupted constant strain amplitude cyclic loading. The inhomogeneous strain distribution close to stress amplitude saturation leads to the formation of extrusions and intrusions along persistent slip bands within the grain and also in suitably oriented grain boundaries. Numerous primary cracks within a grain or at a grain boundary are nucleated. Some cracks can grow further either by linking with existing cracks or by nucleation of new elementary cracks ahead of the crack tip. Crack growth rates of individual cracks fluctuate considerably but for each strain amplitude, which results in a saturated plastic strain amplitude, a crack growth rate of an equivalent crack can be established. This crack growth rate was found to depend strongly on the plastic strain amplitude in agreement with the Manson‐Coffin law.
STRESS INTENSITY FACTOR EXPRESSIONS FOR REGULAR CRACK ARRAYS IN PRESSURISED CYLINDERS
Authors: Pook L. P. 
Published: April 2007

AbstractArrays of radial cracks are sometimes observed at the bore of pressurised cylinders. The stress intensity factors of closely spaced regular arrays of edge cracks depends primarily on the crack spacing and are approximately proportional to the square root of crack spacing for crack length to spacing ratios down to 0.16. A stress intensity factor expression for this range of spacing ratios and of engineering accuracy has been developed for a large regular array of radial cracks at the bore of a pressurised cylinde. For smaller spacing ratios the stress intensity factor depends on crack length than crack spacing and a complementary expression has been developed.
STATIC AND CYCLIC LOADING OF NOTCHED 304 STAINLESS STEEL BARS AT 650°C
Authors: Wu Kuang‐Hsi , Leckie Frederick A. 
Published: April 2007

AbstractCircular‐notched and sharp‐notched specimens made from 304 stainless steel have been tested at 650°C. The notched specimens are subjected to both constant and cyclic loading. The cyclic loading consists of a ramp increase in load followed by constant load and ramp unloading. The cycle times are 1 min and 10 min. It is found for the circular‐notched specimen that failure is dictated by the time on load and is independent of the number of cycles. Metallographic observations support the test results with fatigue damage being apparent only in the sharp‐notched specimens subjected to short‐time cyclic loading. Otherwise damage has the character of intergranular creep rupture.
LIFETIME PREDICTION ON Cr‐Mo‐V AND 316L STEELS UNDER THERMAL AND MECHANICAL CYCLING
Authors: Degallaix Gearard , Korn Christophe , Pluvinage Guy 
Published: April 2007

AbstractThe thermal‐mechanical fatigue resistance of a Cr‐Mo‐V steel and a 316L steel under combined complex mechanical strain and temperature cycling has been evaluated. The applicability to thermal‐mechanical lifetime prediction of several isothermal fatigue damage concepts is investigated. From a designer viewpoint, some predictions are well acceptable, in particular with the Degallaix thermal activation model for which a recent development is reported.
ESTIMATIONS OF STRESS INTENSITY FACTORS FOR SMALL CRACKS AT NOTCHES
Authors: Kujawski D. 
Published: April 2007

AbstractThis paper presents a simple method for determining the stress intensity factors for small notch‐emanating cracks. The proposed method is based on similarities between elastic notch‐tip stress fields described by two parameters; the stress concentration factor K1, and the notch‐tip radius ρ. The method developed here is rather general, and can be used for a variety of central and edge notches with through‐thickness of semi‐elliptical cracks. The predicted values are in good agreement with the available numerical data.
FINITE ELEMENT ELASTIC‐PLASTIC‐CREEP AND CYCLIC LIFE ANALYSIS OF A COWL LIP
Authors: Arya V. K. , Melis M. E. , Halford G. R. 
Published: April 2007

AbstractResults are presented of elastic, elastic‐plastic and elastic‐plastic‐creep analyses of an actively cooled cowl lip. A cowl lip is part of the leading edge of an engine inlet of proposed hypersonic aircraft and is subject to severe thermal loadings and gradients during flight. Values of stresses calculated by elastic analysis are well above the yield strength of the cowl lip material. Such values are highly unrealistic, and thus elastic stress analyses are inappropriate. The inelastic (elastic‐plastic and elastic‐plastic‐creep) analyses produce more reasonable and acceptable stress and strain distributions in the component. Finally, using the results from these analyses, predictions are made for the cyclic crack initiation life of a cowl lip. A comparison of predicted cyclic lives shows the cyclic life prediction from the elastic‐plastic‐creep analysis to be the lowest and, hence, most realistic.
LOW CYCLE FATIGUE DAMAGE ACCUMULATION IN ARMCO‐IRON
Authors: Vašek A. , Polak J. 
Published: April 2007

AbstractA study has been performed relating to fatigue damage accumulation in Armco‐iron with a mean ferrite grain size of 40 μ. Two constant strain amplitudes, εa= 1 × 10−3 (Nf= 250,000 cycles) and εa= 6 × 10−3 (Nf= 3050 cycles) were employed to derive base data for cumulative fatigue loading where unit blocks of low (1000 cycles) and high (10 cycles) strains were mixed until failure occurred. Observations in a scanning electron microscope permitted a periodic evaluation of surface damage to be recorded. Two regimes of damage were noted. During the early crack initiation phase, crack density increased and crack growth rate was constant. During the later phase, or crack propagation stage, new cracks did not nucleate, the smallest cracks arrested, crack density decreased, and the largest cracks grew in an exponential manner, which included linkage with smaller cracks. A damage accumulation model is presented which permits a prediction of fatigue lifetime under variable amplitude loading.
THE EFFECT OF MEAN SHEAR STRESS ON TORSIONAL FATIGUE BEHAVIOUR
Authors: Wang C. H. , Miller K. J. 
Published: April 2007

AbstractTorsional tests under different mean shear stresses were conducted at room temperature using a 1.99% NiCrMo steel. A technique was developed to control both the mean and the alternating shear stresses. It is shown that the mean shear stress plays a fundamental role in promoting stage I, mode II short crack growth. The effect of mean shear stress on the plastic deformation at stage II crack tips is discussed, which illustrates the mean shear effect on the transition between stage I and stage II crack growth. The polarity of mean shear stress is found to have no effect on the fatigue crack growth rate and the fatigue lifetime of an isotropic material. A model is proposed to account for the effect of mean shear stress on the fatigue lifetime under torsional loading.
THE FATIGUE PERFORMANCE OF MACHINED SURFACES
Authors: Taylor D. , Clancy O. M. 
Published: April 2007

AbstractIt is well known that surface condition has a strong effect on fatigue life, and that most surfaces produced by conventional manufacturing operations such as machining and forging have poorer fatigue behaviour than polished surfaces commonly used for laboratory specimens. As yet, there are no reliable quantitative models to predict the behaviour of such surfaces; the problem is a multi‐parameter one, involving surface roughness, surface microstructure and residual stress. High‐cycle fatigue data was obtained for En19 steel, using four types of machined surface, produced by: polishing, grinding, milling and shaping. Residual stress was eliminated by heat treatment. Fatigue limit data were plotted as a function of roughness parameters using Kitagawa‐type diagrams, and compared to simple notch‐based and crack‐based models. It was found that, whilst both theories tended to be overly conservative, fracture mechanics approaches are useful for relatively low roughness, when the surfaces can be modelled as a series of short cracks. For higher roughness a notch‐based approach is appropriate.
SIMPLE MODELS FOR PREDICTING STRESS INTENSITY FACTORS FOR TUBULAR JOINTS
Authors: Haswell J. 
Published: April 2007

AbstractOffshore structures are subjected to onerous environmental conditions. These conditions can cause cracking at tubular joints in these jacket structures and increasingly fracture mechanics is being applied to assess the cracks.There are a variety of fracture mechanics approaches to assessing cracks in tubular joints, all of which predict similar trends but give a wide variation of stress intensity factors. This variation is caused by the different models and inconsistent input parameters used.This paper presents a finite element study of a cracked tubular joint using several different structural models and consistent input parameters. The analysis includes both simple representations of a tubular joint, e.g. a plate model, and a full‐scale analysis on the joint. A comparison of the full‐scale analysis and the simple representations allow conclusions to be drawn on the applicability of simplifications to the problem and also allows errors to be quantified.
RECENT STUDIES INITIATED BY THE NAFEMS FRACTURE MECHANICS WORKING GROUP
Authors: Remzi E. M. 
Published: April 2007

AbstractThe U.K. National Agency for Finite Element Methods and Standards (NAFEMS) is a government agency funded by the Department of Trade and Industry. The task of the Agency is to evaluate the standards used in developing FE programs in order to improve the general level of user competence in industry. The Agency has established Working Groups to consider various aspects of FE techniques. The responsibility of the Working Groups is to identify the analytical work required to investigate specific techniques and applications, and to ensure the execution of the work. One Working Group is concerned with finite element fracture mechanics and its activities are described in detail in this paper. Various categories of benchmark specifications were identified by the Working Group along with the need to provide educational input, guidance documents and a general interest in current developments and user requirements.
OXIDATION‐ASSISTED FATIGUE CRACK GROWTH BEHAVIOR IN ALLOY 718‐PART II. APPLICATIONS
Authors: Zheng D. , Ghonem H. 
Published: April 2007

AbstractIn previous work by the authors, a quantitative model based on a two‐stage oxidation mechanism was developed to describe the oxidation‐assisted crack growth behavior in alloy 718. This model is used here to predict the crack growth rate in this alloy at 650°C for two different loading conditions: one is a continuous cycle with a hold time duration of 300 s imposed at minimum load, the other is a continuous cycle without a hold time duration. The results obtained from applying the model to these loading profiles were then compared with those obtained experimentally. Good agreement was observed between the two data sets. Details of the model calculations are discussed, and suggestions to further extend the model capabilities are made in this paper.
THE EFFECT OF HARDNESS ON THE FRETTING FATIGUE OF ALLOY STEELS
Authors: Husheng Gao , Haicheng Gu , Huijiu Zhou 
Published: April 2007

AbstractThe fretting fatigue behaviour of several alloy steels is reported in this paper. Fretting fatigue experiments were conducted on flat fretting junctions in axial tension at a stress ratio of 0.1. In all cases the same materials were fretted against each other. The fretting fatigue strength at a slip amplitude of 45 μ is rather insensitive to the hardness of the materials. The fretting fatigue strength at the slip amplitude of 10 μ increases with increase in hardness. As the slip amplitude increases the fretting fatigue life of 3SCrMo steel decreases, the depth of wear scars increases and the wear damage becomes more severe. The reason for similarity of fretting fatigue to the fatigue of notched specimens is that the effect of wear scars is similar to that of notches.
ESTIMATION OF SERVICE LOADING FROM THE WIDTH AND HEIGHT OF FATIGUE STRIATIONS OF 2017‐T4 A1 ALLOY
Authors: Murakami Yukitaka , Shiraishi Nobuhiko , Furukawa Katsuaki 
Published: April 2007

AbstractA case‐study method is proposed to determine service loading from fracture surface striations. Although it is well known that striation spacing relates to the crack growth rate, it is considered impossible to determine maximum and minimum loads under service loading conditions, and which define the stress ratioR, from an analysis of the striation spacing. This paper presents a new method of determining the maximum and minimum loads which is based on the experimental fact that the relative height of a striationHto striation spacingsis strongly influenced by the stress ratio. The results of fatigue tests on 2017‐T4 A1 alloy showed a definite correlation between these parameters. The difficulty of measuring striation height was overcome by taking the measurements in a scanning electron microscope after sectioning the specimens at a large inclined angle. Striations under a stress ratioR=−1 are compressed and flat, and the ratioH/sis small. With increasingR, the value ofH/sbecomes large. Therefore a standard laboratory test that determines the relationship betweensand ΔK, and also betweenH/sandRenables one to estimate service loadings from fatigue fracture surfaces.
SCATTER CHARACTERISTICS OF FATIGUE LIFE AND THE BEHAVIOUR OF SMALL CRACKS
Authors: Goto M. 
Published: April 2007

AbstractUsually, there is large scatter in fatigue data and this should be evaluated quantitatively when fatigue data are applied to the design of machines and structures. Consequently it is important to clarify the physical basis of scatter in fatigue life. In this present study, rotary bending fatigue tests were performed on an annealed 0.21% carbon steel. At least sixteen smooth specimens were fatigued at each of three stress ranges and successive observations of the surface were studied for all the specimens using the plastic replica method. By examining the initiation and propagation behaviour of cracks the physical basis of scatter in fatigue life is analysed and discussed. To estimate the scatter characteristics quantitatively, the distributions of crack initiation life, propagation life, fatigue life and crack length were individually studied by assuming a Weibull distribution for each set of data.
CRACK NUCLEATION AND PROPAGATION IN BLADE STEEL MATERIAL
Authors: Gabetta G. , Torri L. 
Published: April 2007

AbstractStress corrosion cracking and corrosion fatigue of 12 Cr steel in sodium chloride solution has been investigated. Tests have been performed in air at room temperature and in aqueous solution with 22% NaCl at 80°C. The influence of corrosion pits on crack nucleation has been investigated. On fracture surfaces tested in environment (22% NaCl solution), crack initiation was observed in correspondence with corrosion pits; in this case fatigue life can be described using a fracture mechanics approach. The ΔK value for crack nucleation from a pit in rotating bending fatigue tests is very low in air (about 3 MPa√m). The results of slow strain rate tests on smooth specimens show that there is a threshold stress intensity, KISCC, of about 15 MPa√m and a plateau in stress corrosion crack growth rate of about 10‐5mm/s.
INFLUENCE OF MICROSTRUCTURE ON THE FRACTURE TOUGHNESS AND FRACTURE TOPOGRAPHY OF A DUPLEX STAINLESS STEEL
Authors: Erauzkin E. , Irisarri A. M. 
Published: April 2007

AbstractThe effect of heat treatment on the fracture toughness and fracture topography of a duplex stainless steel has been studied. Samples treated above 1050˚C exhibit just a slight decrease in toughness in good agreement with the metallographic and fractographic analyses. However, in those coupons annealed between 675 and 900˚C a marked loss of toughness was detected. This embrittlement is maximum in samples treated at 825˚C and has been associated with sigma phase precipitation clearly seen in the metallographic examination. Elongated splits of brittle walls are present in their fracture surfaces. Specimens treated at lower temperatures for short times show a certain decrease in toughness. The almost featureless surfaces of the fissures present in these samples suggest a delamination along the austeniteferrite interfaces. Longer exposure times produce a greater loss of toughness and fracture morphologies similar to those in 825˚C treated specimens. Treatment at 475˚C produces an embrittlement attributed to alpha‐prime phase.
DELTA‐K‐EFFECTIVE: WHICH FORMULA?
Authors: Finney J. M. , Deirmendjian G. 
Published: April 2007

AbstractSeveral equations are examined which were developed to eliminate the R‐effect in fatigue crack growth rate by using the concept of a δKeff. Their performance was objectively rated by using a limited set of growth rate data with the result that an early equation by Schijve proved the best. However, relatively small variations in growth rates markedly affected the order of rating the equations, and none of them appear to include the variables necessary to cope with a wide range of R‐values and growth rates. The usefulness of an effective δK in predicting fatigue crack growth is thus brought into question.
FATIGUE CRACK INITIATION AND PROPAGATION IN A LOW‐CARBON STEEL OF TWO DIFFERENT GRAIN SIZES
Authors: Kage M. , Miller K. J. , Smith R. A. 
Published: April 2007

AbstractRotary bending fatigue tests were carried out using both plain and notched specimens of a low‐carbon steel with two different grain sizes (15 and 50 μm). The process of early crack development was observed by the replication method. The effect of grain size on crack development was studied.The main conclusions were as follows. (1) Fatigue resistance, in terms of the relative positions of the S‐N curves, increases with decreasing grain size. This phenomenon is related to the number of cycles to propagate a crack to failure and the condition for the non‐propagation of a fatigue crack. (2) The size of a non‐propagating crack, which initiates below the fatigue limit, tends to become larger as grain size increases. (3) The difference in fatigue behaviour between small (15μm) and large (50μm) grain sized specimens is due both to a decrease in crack propagation rate and a smaller non‐propagating crack limit in the finer grained material.
A MODEL FOR PREDICTING CRACK GROWTH RATE FOR MIXED MODE FRACTURE UNDER BIAXIAL LOADS
Authors: Shlyannikov V. N. , Braude N. Z. 
Published: April 2007

AbstractA model for predicting the crack growth rate of an initially angled crack under biaxial loads of arbitrary direction is suggested. The model is based on a combination of both the Manson–Coffin equation for low cycle fatigue and the Paris equation for fatigue crack propagation. The model takes into consideration the change in material plastic properties in the region around the crack tip due to the stress state, together with the initial orientation of the crack and also its trajectory of growth. Predictions of crack growth rate for any mixed mode fracture is based on the results of uniaxial tension experiments.
FATIGUE LIMIT MODEL FOR HARDENED STEELS
Authors: Gustavsson A. I. , Melander A. 
Published: April 2007

AbstractA fracture mechanics‐based model is developed for the fatigue limit of hardened steels. In such steels, non‐metallic inclusions are known to initiate fatigue cracks. In this work, these inclusions are modelled as spherical voids and, as the fatigue process continues, fatigue cracks are thought to develop from these sites.The growth or arrest of these cracks is analysed in terms of the effective stress intensity range and the corresponding effective threshold for crack propagation. Elasto‐plastic crack closure is evaluated by finite element calculations. The fatigue limit of a sample is defined in terms of crack arrest at all inclusions. Simple equations of the model are presented and compared to experimental data from the literature as well as to an earlier model by Murakami.