bluuebunny/crossref_metadata_2025_split huggingface dataset:
RESIDUAL STRESS FIELDS DURING FATIGUE CRACK GROWTH
Authors: Sun Wei , Sehitoglu Huseyin 
Published: April 2007

AbstractThis study outlines the distinction between (1) residual stresses at an ideal crack tip, undergoing reversed deformation in the absence of crack closure, and (2) additional residual stresses generated due to plasticity induced closure upon fatigue crack growth. Residual stresses resulting from reversed deformation in plane strain were higher compared to the plane stress case, while residual stresses generated behind the crack tip were more significant in plane stress compared to plane strain. The origin of these residual stresses was studied for two specimen geometries over a wide range of loading conditions. We define a new crack tip parameter, Stt as the applied stress level that corresponds to the development of tensile stresses immediately ahead of crack tips. The Stt levels were significantly higher for a fatigue crack than for an ideal crack. We attribute the difference in Stt levels between these two cases to plasticity induced closure. The results demonstrate the importance of the Stt parameter, since the stresses ahead of crack tips could remain compressive even when the crack surfaces are open. Moreover, the study emphasizes the need, when describing fatigue crack growth, to incorporate both the closure concept and residual stress field ahead of a crack tip.
LEAK‐BEFORE‐BREAK CONDITIONS OF PLATES AND PIPES UNDER HIGH FATIGUE STRESSES
Authors: Nam Ki Woo , Ando Kotoji , Yuzuru Sakai , Ogura Nobukazu 
Published: April 2007

AbstractThe leak‐before‐break(LBB) behaviour of a structural component under high fatigue stress, low‐cycle fatigue conditions is an important problem in nuclear power plants, liquid nitrogen gas tankers and chemical plants. This paper is an experimental study to clarify the crack shape at penetration, crack opening behaviour after penetration and the LBB condition for plate specimens and pipe specimens. The fatigue load which realizes the LBB condition, PFLBB' is based on a net‐stress criterion. It is found that PFLBB is dependent only on the initial crack length a0. Furthermore, it is shown that the crack opening displacement V at the centre of a penetrated crack can be derived using the gross stress, σG' and the front surface crack length, as' together with the back surface crack length, ab.
OVERLOAD RETARDATION OF FATIGUE CRACK GROWTH IN A 9%Cr 1%Mo STEEL AT ELEVATED TEMPERATURES
Authors: Cotterill P. J. , Knott J. F. 
Published: April 2007

AbstractThis paper describes an investigation into the effects of a single‐peak tensile overload on fatigue crack propagation in a 9%Cr 1 %Mo steel. Overloads were applied during cycling at a constant stress intensity range (ΔK), and any consequent transients in growth rate were recorded. The severity of retardation rises as the magnitude of the applied overload is increased. The effect of temperature is complex, but a 525˚C retardation is significantly less marked than at 25 or 225˚C. Signs of crack face contact are seen on post‐overload fracture surfaces, but there is little crack branching. The dominant cause of overload retardation in this steel appears to be plasticity‐induced closure. At 525˚C, post‐overload dwell periods significantly reduce the severity of retardations. This is not observed at lower temperatures, indicating that the residual clamping stresses that lead to closure are gradually relieved at 525˚C.
CRACK FACE INTERACTIONS AND NEAR‐THRESHOLD FATIGUE CRACK GROWTH
Authors: Tschegg E. K. , Stanzl S. E. , Mayer H. R. , Czegley M. 
Published: April 2007

AbstractRough fracture surfaces usually influence substantially the fatigue growth properties of materials in the regime of low growth rates. Friction, abrasion, interlocking of fracture surface asperites and fretting debris reduce the applied load amplitude to a smaller effective value at the crack tip (“sliding crack closure”, or “crack surface interaction” or “crack surface interference”). The influence of these phenomena on the fatigue crack growth properties of structural steel is discussed and compared for the two kinds of mixed mode loading employed in this work. Mixed mode loading was performed by (A): cyclic mode III + superimposed static mode I and (B): cyclic mode I + superimposed static mode III loading. Such loading cases frequently occur in rotating load‐transmission devices.Several differences are typical for these two mixed‐mode loading cases. A superimposed static mode I load increases the crack propagation rate under cyclic mode III loading whereas cyclic mode I fatigue crack propagation is retarded when a static mode III load is superimposed. Increase of the R ‐ratio (of the cyclic mode III load) leads to an insignificant increase of fracture surface interaction and subsequently to a small decrease of the crack growth rate for cyclic mode III loading, whereas higher R ‐values during cyclic mode I+ superimposed static mode III loading lead to a significant reduction of the crack growth rates.
A CRACK CLOSURE MODEL FOR PREDICTING THE THRESHOLD STRESSES OF NOTCHES
Authors: Ting Jason C. , Jr Frederick V. Lawrence, 
Published: April 2007

AbstractA model is proposed to estimate the threshold stress range of a notched component. The model considers the variation of crack closure with crack length in the presence of a notch. The threshold stress range was found from the condition that the minimum value of effective threshold stress intensity range of a crack emanating from a notch equals the effective threshold stress intensity range of a “long” crack. The effects of notch depth, of notch acuity, of notch and specimen type, of load ratio, and of material properties on the threshold stresses were considered. Experimental data reported in the literature were used to assess the validity of the model. It was found that the model correctly predicts the behavior of cracks in notched components.
FATIGUE BEHAVIOUR OF FIBRE ALUMINIUM LAMINATES WITH DIFFERENT RESIDUAL STRESSES
Authors: Danmei Liu , Wei Qu , Weifeng Yang , Mei Yao , Reiping Zhang , Yuebo Xia 
Published: April 2007

AbstractIn this study two kinds of fibre aluminium laminates (aramid aluminium laminates, ARALL and glass aluminium laminates, GLARE) with different residual stresses in the aluminium layers were prepared. Fatigue crack propagation tests were performed. It is found that the residual stress condition plays an important role in the fatigue behaviour of fibre aluminium laminates. With a decrease of the tensile residual stress in the aluminium layers, the fatigue crack growth rate of the laminates is greatly reduced, and the shape of the curves of fatigue crack propagation rate as a function of the stress intensity factor changed. Compared to GLARE, the ARALL is more sensitive to the residual stress condition. The fatigue properties of non‐prestressed GLARE are better than those of ARALL. The influence of the residual stress is discussed in detail.
THE EFFECTS OF CRACK DEPTH ON THE J‐INTEGRAL AND CTOD FRACTURE TOUGHNESS FOR WELDED BEND SPECIMENS
Authors: Shi Y. W. , Han Z. X. 
Published: April 2007

AbstractThis work deals with the influence of crack depth on the fracture toughness at initiation of crack growth and the constraint factor in relationship between the J‐integral and the crack tip opening displacement (CTOD). A series of tests were performed on high strength low alloyed HT80 steel welds, and the critical J‐integral and CTOD were determined using the load versus load point displacement record from three‐point bend specimens with 0.05 < a/W < 0.5. It was found that the fracture toughness for shallow cracks at the onset of crack growth was larger than that for deep cracks for the steel welds tested, but it is felt that there is no fixed relationship between these values in the welds tested. The constraint factor is also a function of crack depth, and values of the factor increase from 0.5 to 1.5 when a/W increases from about 0.05 to 0.5. The factors are not very sensitive to the crack tip materials (HAZ or weld metal) in the welds tested.
EFFECT OF AN ELASTIC‐PLASTIC SHOCK WAVE PART A: ON THE FATIGUE STRENGTH OF WELDED JOINTS
Authors: Liangshan Chen , Huaining Chen , Zhongyao Si , Shenyu Tan , Guangyuan Chui 
Published: April 2007

AbstractFatigue data for welded joints subjected to an explosion treatment (ET) were obtained using rotary bending fatigue specimens. The fatigue fracture surfaces were observed by SEM and the dislocation morphologies by TEM. Mechanical properties have been quantitively studied by considering elastic and plastic shock wave characteristics. The test results indicate that the fatigue strength of welded joints subjected to ET is apparently improved due to the action of elastic or plastic stress waves while the ductility of the welded joints, i.e., reduction in area, is greatly increased.
THE PROBLEM OF SCATTER OF FRACTURE TOUGHNESS DATA
Authors: Troshchenko V. T. , Yasniy P. V. , Pokrovsky V. V. , Podkolzin V. Yu. 
Published: April 2007

AbstractThe authors studied the influence of the conditions for growing an initial fatigue crack on the scatter of fracture toughness data determined under static loading. It was found that the values of static fracture toughness for cyclically softening steels at temperatures below the brittle‐to‐ductile transition are essentially dependent on the degree of the material fatigue damage in the vicinity of the crack tip during the final stage of crack initiation. A method is proposed for evaluating the fracture toughness under static loading which makes it possible to take into account the material damage in the vicinity of the crack tip.
A STUDY OF RETARDING FATIGUE CRACK GROWTH USING AN ARTIFICIAL WEDGE
Authors: Yanyan Wang , Mingxu Zho , Daqing Feng 
Published: April 2007

AbstractBased on the analysis of an artificial wedge, a model for an equivalent crack opening load for three point bend specimens is presented. It has been verified by experiments that the crack growth force calculated from the above model, and the relationship between the calculated ΔKeff and da/dN are almost the same as those of cracked specimens without a wedge. Therefore this model can be applied to estimate retardation or crack arrest behaviour.
MODELING THE LONG‐LIFE FATIGUE BEHAVIOR OF A CAST ALUMINUM ALLOY
Authors: Ting Jason C. , Lawrence Frederick V. 
Published: April 2007

As‐cast specimens and smooth specimens of a AA 319 cast aluminum alloy containing casting porosity were fatigue tested with special attention given to the long‐life region (N 1.25 × 108 cycles). Fatigue cracks were observed to initiate from the near‐surface casting pores or from discontinuities resulting from the as‐cast surface texture. The observed fatigue lives were strongly dependent on the size (√area) of these casting defects.The effect of casting defects on the fatigue life was modeled assuming the fatigue life to be the sum of the crack nucleation and the crack propagation life (including both the growth of short and long cracks). The crack growth behavior of (mechanically) short cracks was considered in detail by a developed crack‐closure‐at‐a‐notch (CCN) model. The CCN model predicted the fatigue lives for both as‐cast and machine‐notched specimens. Extension of the CCN model to reliability‐based design was attempted using the measured size distribution of the fatigue‐initiating casting pores.
NOTCH ROOT CRACK CLOSURE UNDER CYCLIC INELASTICITY
Authors: Sunder R. 
Published: April 2007

AbstractAluminium alloy sheet coupons with a central hole were tested in fatigue under specially designed programmed load sequences. Electron microscopy of the fatigue fracture surfaces showed striation mode fatigue crack extension up to more than a millimeter before onset of rapid failure. Crack opening stress was determined from striation patterns. Under variable amplitude loading and conditions of notch root cyclic inelasticity, crack opening stress exhibits noticeable hysteresis. The hysteresis is attributed to a difference between crack closure and opening stresses. A linear model of this phenomenon appears to describe observed behaviour.
REPAIR EFFICIENCY IN FATIGUE‐CRACKED ALUMINIUM COMPONENTS REINFORCED WITH BORON/EPOXY PATCHES
Authors: Baker A. A. 
Published: April 2007

AbstractThis paper describes studies on fatigue crack propagation in cracked aluminium alloy (2024 T3) panels repaired with boron/epoxy patches, adhesively bonded with either an epoxy‐nitrile film adhesive or an acrylic adhesive. Studies were undertaken to assess the effect on patching efficiency of (a) disbonding of the patch system and (b) test temperature. A simple model is proposed for estimating the reduction of patching efficiency due to cyclic disbonding of the reinforcement. In the elevated‐temperature tests it was found, unexpectedly, that patching efficiency in panels patched using the film adhesive was unaffected by temperatures up to 100°C.
SCATTER IN SMALL CRACK PROPAGATION AND FATIGUE BEHAVIOUR IN CARBON STEELS
Authors: Goto M. 
Published: April 2007

AbstractIn order to investigate the physical basis of scatter in fatigue behaviour, rotatory bending of smooth fatigue specimens was carried out using two steels with different microstructures (ferrite/pearlite and tempered martensite). Fifteen or sixteen specimens were fatigued at each stress, and the initiation and propagation behaviour of a crack which led to the final fracture were examined for all the specimens. The emphasis was to investigate the scatter characteristics of fatigue behaviour based on the scatter of small crack propagation data. The data were analysed by assuming the Weibull distribution, and a statistical investigation of the physical basis of scatter was performed, i.e. the distributions for fatigue life, crack propagation life and growth rate of small cracks were established and the relation between the scatter in those distributions was studied.
FATIGUE CRACK GROWTH BEHAVIOUR AND FRACTURE RESISTANCE IN CERAMICS
Authors: Ogawa T. , Ochi T. , Tokaji K. 
Published: April 2007

AbstractFatigue crack growth and the fracture resistance curve (R‐curve) were investigated in a polycrystalline alumina (AD90) and a silicon carbide whisker‐reinforced alumina composite (Al2O3‐SiCw) at room temperature in air using a combined loading technique for stabilizing crack growth, and a surface film technique for monitoring crack length. Fatigue crack growth was evaluated successfully with those experimental techniques. Load shedding tests were performed until the crack became dormant, in order to determine the threshold stress intensity factor Kth. Subsequently, the specimens were used for quasi‐static crack growth tests under a monotonic loading condition. The R‐curves were determined in this experiment; however, fracture resistance did not increase markedly with crack growth. Detailed observations of the crack growth behaviour revealed that the flat R‐curve was attributed to the shielding effect of the fatigue crack tip wake. Thus, the fatigue precrack introduced by the load shedding test was not regarded as an ideal crack for determining the R‐curve. Fractographic observations were performed to investigate the mechanistic difference between fatigue and quasi‐static crack growth. It was found that the cyclic loading produced fretting damage in the wake region and it reduced the shielding effect of the fatigue cracks. Based on the experimental results, the relationship between the fatigue crack growth and the R‐curve is discussed as is the significance of Kth as a material parameter.
FATIGUE CRACK GROWTH IN SEVERAL CERAMIC MATERIALS
Authors: Mutoh Y. , Takahashi M. , Takeuchi M. 
Published: April 2007

AbstractFatigue crack growth tests of five ceramic materials were carried out in order to investigate the general characteristics of cyclic and static fatigue crack growth in ceramics. A cyclic effect was found in Si3N4, Al2O3and TiB2, where the main fracture mechanism was intergranular separation, and stress shielding due to grain bridging occurred near the crack tip. On the other hand, no cyclic effect was observed in Sic and ZrO2, where the main fracture mechanism was transgranular fracture. The fatigue crack growth curves reduced to a unique curve by using the parameterKup/E, regardless of the kind of ceramics studied.
PREDICTION OF THE LIFETIME DISTRIBUTION OF HIGH‐STRENGTH COMPONENTS SUBJECTED TO FATIGUE LOADING
Authors: Brückner‐Foit A. , Jäckels H. , Quadfasel U. 
Published: April 2007

AbstractA probabilistic model is developed for predicting the lifetime distribution of a high‐strength component subjected to low cycle fatigue loading. The damage process considered consists of two consecutive stages. First, cracks are initiated from microstructural inhomogeneities such as non‐metallic inclusions. These cracks will then extend stably until final failure occurs or the component is removed from service. The probabilistic model is used to determine the maximum tolerable inclusion size for a model turbine disc. This quantity is defined as the size of the initial defect for which the number of load cycles to failure at a given reliability level exceeds the design life of the component. This maximum tolerable inclusion size is compared with the results of a deterministic lifetime analysis.
FORMULATION OF A STOCHASTIC MODEL OF FATIGUE CRACK GROWTH
Authors: Doliński K. 
Published: April 2007

AbstractBased on a global/local energy balance a deterministic model of fatigue crack growth under constant amplitude loading is derived. The energy terms resulting from the continuous plasticity and localized fracture around the crack tip are determined for small scale yielding leading to the fatigue crack growth equation involving the stress intensity factor and its amplitude. Four material parameters which should be identified from experimental data have a physical interpretation; these are eventually assumed to be random variables and model the statistical scatter of the crack growth versus N curves observed in experiments. A Gaussian white noise random field is additionally assumed to describe the stochastic material non‐homogeneity within a specimen. Its effect on the crack growth is derived and results in a positive non‐stationary random function depending on the crack length. Statistical parameters of the random fields are identified. Verification of the model by comparison with experimental results is undertaken in a subsequent paper.
MODELING THE INFLUENCE OF INITIAL MATERIAL INHOMOGENEITIES ON THE FATIGUE LIFE OF NOTCHED COMPONENTS
Authors: Grandt A. F. , Scheumann T. D. , Todd R. E. , Hinkle A. J. 
Published: April 2007

AbstractThis paper summarizes a fracture mechanics analysis developed to study the effect of initial size and spatial distribution of inherent material inhomogeneities on fatigue life. Calculations were performed for a set of experiments conducted previously to determine the influence of microporosity size and frequency on the fatigue life of notched 7050‐T7451 aluminum specimens. The favorable comparison between the numerical and experimental results indicates the analysis method could be used to predict the benefits to fatigue life obtained by reducing the size and distribution of initial inhomogeneities such as those due to microporosity.
THE EFFECTS OF A MARINE ENVIRONMENT ON THE CORROSION FATIGUE CRACK PROPAGATION RATE OF PURE TITANIUM AND ITS WELD METAL
Authors: Murakami Ri‐ichi , Ferguson W. G. 
Published: April 2007

AbstractThe effects of stress ratio and microstructure on fatigue crack growth rate in air and natural seawater were investigated for pure titanium and its weld metal. The corrosion fatigue characterization of pure titanium was also studied under a cathodic potential in natural seawater. In air, the fatigue crack growth rates of pure titanium and its weld metal increased with increasing stress ratio. In natural seawater, the effect of stress ratio was similar to that in air. However, the crack growth rates were greater for pure titanium than for the weld metal. These results indicate that the corrosion action is sensitive to the microstructure in front of the crack tip. When the crack growth rate for the weld metal was plotted using the effective stress intensity factor range, the crack growth rate in natural seawater was coincident with that in air, regardless of stress ratio. For the base metal, there is a significant difference in the crack growth rate between natural seawater and air.
THE ROLE OF CAVITY GROWTH MECHANISMS IN DETERMINING CREEP‐RUPTURE UNDER MULTIAXIAL STRESSES
Authors: Hales R 
Published: April 2007

Abstract— The effect of stress state on the time and strain to failure has been considered in terms of currently accepted models of cavity growth. It is shown that the increasing contributions of compressive stress cause changes in cavity growth mechanisms which lead to increases in ductility. A tensile component of stress is necessary to provide the driving force for cavity growth by diffusion of vacancies and hence only strains in the presence of a tensile stress can lead to creep‐dominated failure in creep‐fatigue.Equivalent stress functions for isochronous stress rupture have been derived in terms of the cavity growth models and their corresponding relationships for calculating damage in terms of strain fractions developed. It is shown that it is difficult to discriminate between the various models on the basis of available experimental data. However, the analysis allows data to be assessed within the framework of physically based mechanisms and suggests methods which lead to conservative lower bound estimates of endurance.It is concluded that the shape of the isochronous creep rupture locus depends on the controlling process of cavity growth and that a detailed analysis of uniaxial creep ductility is necessary to obtain a complete description of the multiaxial behaviour. In many instances such an analysis will prove more valuable than simply performing creep tests over a limited range of stress states. Increasing contribution of principal stress to the failure process leads to a greater value for the equivalent stress in the presence of a compressive component compared with the von Mises equivalent value. However, the equivalent stress is reduced in the tensile quadrant of bi‐axial stress. Hence the degree of conservatism arising from using the von Mises equivalent stress will vary with stress and may become slightly non‐conservative. The relationship between equivalent stress functions for application in a time fraction assessment of creep and the calculation of creep damage by a strain fraction method has been demonstrated. Finally, guidance is given on how a limited data base of uniaxial rupture properties can be used to obtain a conservative estimate of behaviour under multiaxial loading.
ELEVATED TEMPERATURE FATIGUE IN Ni3Al‐BASED ALLOYS
Authors: GORDON D. E. , Unni C. K. , STOLOFF N. S. 
Published: April 2007

Abstract—Both high‐cycle and low‐cycle fatigue properties of hot‐extruded powders of a Ni3Al‐based alloy, IC218, have been evaluated. High cycle fatigue measurements were performed under stress controlled conditions at temperatures ranging from 25°C to 850°C. Tests were made in both laboratory air and vacuum environments. Low cycle fatigue tests were conducted under total strain control in a laboratory air environment at 650°C. In high cycle fatigue, high ratios of the fatigue limit (Δσ at 106 cycles) to monotonic yield strength (σys), of approximately Δσ/σys∼1, were obtained in the powder extruded IC218 alloy for temperatures ranging from 25°C to 650°C. In low cycle fatigue, a substantial decrease in fatigue life occurred at 650°C, compared to results obtained previously at 25°C. High cycle fatigue performance at low stress/strain amplitudes is better than expected when compared to precipitation strengthened superalloys. The improved performance is explained in terms of the cyclic hardening behavior of the alloy.