bluuebunny/crossref_metadata_2025_split huggingface dataset:
A MODEL FOR THE FATIGUE LIMIT AND SHORT CRACK BEHAVIOUR RELATED TO SURFACE STRAIN REDISTRIBUTION
Authors: Abdel‐Raouf H. , Topper T. H. , Plumtree A. 
Published: April 2007

AbstractA model based on surface strain redistribution and the reduced closure stress of short cracks is shown to successfully predict the fatigue limit and short crack growth behaviour for aluminium alloy 2024‐T351. Using this approach, the length of non‐propagating cracks can be anticipated. The local stress intensity range may be resolved into two components (first the linear elastic fracture mechanics component and the second is due to surface strain concentration). Consequently, the local stress intensity range of aluminium alloy 2024‐T351 is a maximum at a depth of approximately half a grain diameter and a minimum at a depth slightly in excess of three grain diameters. The reduced closure stress for short cracks coupled with the increased applied stress intensity caused by surface strain redistribution accounts for the variation of the effective stress intensity parameter as a function of crack depth. This parameter is a maximum for the smallest possible crack (3 μm) and decreases as crack length increases.
A THREE‐DIMENSIONAL FINITE ELEMENT ANALYSIS FOR A CRYSTALLOGRAPHIC CRACK NEAR THE INTERFACE OF AN INCOMPATIBLE BICRYSTAL
Authors: Li Chingshen 
Published: April 2007

AbstractOn the basis of modelling bicrystal deformation, using three‐dimensional, anisotropic finite elements, the problem of a crystallographic crack approaching the interface in a [111] tilt bicrystals of 90˚ misfit angle under shear loads is solved. The influence of thickness direction material heterogeneity across the interface on the distribution of the stresses, strains and crack sliding displacements along the crack front near the interface has been revealed. As the crack approaches the interface, those mechanical parameters are considerably changed by the heterogeneity across the interface. Remarkable variations in the stresses and strains along the crack front have also been identified and are referred to the different constraint across the thickness. The maximum stress may shift from the crack tip to the interface ahead of it, where, as suggested by numerical results and previous experimental observation, a new fracture process core may be activated. The interface‐induced crack shielding or antishielding under mode II and III loading is analyzed and discussed.
FATIGUE STRENGTH OF NON‐LOAD‐CARRYING FILLET WELDED JOINTS: EFFECTS OF WELD RESIDUAL STRESSES AND STRESS CONCENTRATION
Authors: Takahashi Ichihiko , Yoshii Tokuharu , Iidaka Hiroo , Fujii Eisuke , Matsuoka Kazuyoshi 
Published: April 2007

AbstractThe fatigue strength of non‐load‐carrying fillet welded joints of KE36(TMCP) steel was studied. Both residual stress measurements and fatigue tests were carried out, with the plate thickness, the plate width and the heat input being varied. Specimens given a Post Weld Heat Treatment (PWHT) were also prepared.The plate width had no effect on the fatigue strength, because it hardly affected the transverse residual stresses at the weld toe. However, the heat input influenced the transverse residual stress distribution, and a significant difference in fatigue strength due to the heat input was observed, especially when N≥ 106 cycles. It was also found that PWHT removed almost all the residual stresses at the weld toe, improving the fatigue strength drastically.In this study, the values of stress concentration factor K2 were estimated by Machida's method and it was concluded that the thickness effect resulted from a combination of both stress concentration and residual stresses with the contribution of the latter being particularly significant for N≥ 106 cycles.
FATIGUE PROPERTIES OF C/Al METAL‐MATRIX COMPOSITES WITH DIFFERENT INTERFACIAL BONDS
Authors: Chen Rong , Wu Renjie , Zhang Guoding 
Published: April 2007

AbstractThe fatigue properties of four kinds of composite wires with different interface bonds, together with the effects of a notch in the surface of the composite wires, have been studied. Fatigue endurance (S‐N) curves of these materials revealed that no definitive fatigue limit was obvious. The C/Al composites with weak interfacial bonds were insensitive to the notch, but the notch was an important source of cracks which propagated rapidly when the interface bonding was strong. Although initial cracks would occur very early in the fatigue life, their propagation were arrested by the internal structure of the composite wires with suitable interface bonds.
FATIGUE BEHAVIOUR OF STEEL CASTINGS CONTAINING NEAR‐SURFACE DEFECTS
Authors: Heuler P. , Berger C. , Motz J. 
Published: April 2007

AbstractManufacturing defects in the near‐surface region of 2¼% Cr 1% Mo castings were investigated in a joint research programme. After ultrasonic testing and X‐ray inspection, large push‐pull specimens (cross section 1000 mm2) were taken from castings in regions with indications of defects and tested under fully reversed loading in the elastic and elastic plastic region up to predetermined levels of defect growth. The defects are micropores, pin holes, slag and oxide layers or inclusions, hot tears and small micro cracks in welds.The initiation of crack growth was analysed by two methods, namely (a) the local strain concept with idealization of defects as three‐dimensional elliptical notches and (b) by the fracture mechanics concept with idealization of defects as two‐dimensional elliptical cracks. The main results can be summarized as follows:1. The local strain concept describes the crack initiation potential of the defects more accurately than the fracture mechanics concept.2. Interpretation of casting defects as cracks produces very conservative estimates in many cases.3. Analytical evaluation of crack growth behaviour using the fracture mechanics approach for defects experiencing crack growth of at least 1 mm is much more accurate than when defects having a smaller extent of crack growth are included in the analysis.Additional evaluations of crack growth behaviour of hot tears by fracture mechanics show that crack growth starting from open and partially closed hot tears must be subjected to a larger number of cycles than normal fatigue cracks of sound material. Partially closed hot tears in the vicinity of the crack front additionally delay crack propagation.
COMPARISON OF A STOCHASTIC MODEL OF FATIGUE CRACK GROWTH WITH EXPERIMENTS
Authors: Doliński K. 
Published: April 2007

AbstractA stochastic model of fatigue crack growth under constant amplitude loading, derived from a global/local energy balance, is compared with experiment data. Four random variables and a Gaussian white noise random field were assumed to model, respectively the statistical scatter of the crack length versus N curves and their stochastic fluctuations reflecting the effect of stochastic material non‐homogeneity within a specimen. The statistical analysis of the so called Virkler and Ghonem‐Dore data sets is extensively used to identify the probabilistic characteristics of the random variables and random field and to verify the stochastic model. Based on the importance sampling integration technique the fatigue lifetime probability distributions are effectively calculated. The influence of the particular assumptions accounting for the random material properties is investigated and the quality of the model prediction is verified by comparison with empirical statistical characteristics of the lifetime.
LIMIT LOAD AND J‐ESTIMATES FOR IDEALISED PROBLEMS OF DEEPLY CRACKED WELDED JOINTS IN PLANE‐STRAIN BENDING AND TENSION
Authors: Joch J. , Ainsworth R. A. , Hyde T. H. 
Published: April 2007

AbstractUsing simple assumed deformation fields, approximate solutions have been obtained for tension and bending specimens containing welds for both limit loads and for fully plastic proportionality coefficients between the singular field amplitude J and the strain energy. The solutions allow for the degree of over or undermatch in the material tensile properties of the weld metal relative to the parent steel, and for the size of the weld region relative to the remaining ligament ahead of the crack.Detailed finite‐element analyses have been performed for particular values of under/over‐match and size of weld region. These refine the approximate analytical solutions for the particular cases examined, and show broad agreement with the trends predicted by the analytical models.The results have been used to provide guidance for testing weldments using standard, bend‐type geometries. For small‐specimen testing, cracks should be sufficiently deep for the remaining ligament ahead of a centrally located crack to be less than the total width of the weld. For large specimens, the weld region should be less than 20% of the size of the remaining ligament. If these guidelines are followed then standard relationships may be used to derive J from the area under the load‐displacement curve.Common advice that the tensile properties of the weaker material in a weldment should be used in J‐estimation techniques has been shown to be appropriate in many cases. However, the advice is likely to be overconservative when plastic deformation is predominantly in the weld even for overmatched weld properties, or predominantly in base metal even for undermatched weld properties. The results in the paper enable such cases to be identified.
A FRACTURE AND SEVERITY ANALYSIS OF COMPOSITE CERAMICS
Authors: Chu M. C. , Ando K. 
Published: April 2007

AbstractCeramic composite crucibles failed when they were operated under extreme conditions of temperature and heating rate. To analyze the failure causes, fracture stress and fracture toughness values were ascertained and previously reported. Moreover, a new failure criterion for ceramics was proposed based on the existence of a crack‐tip process zone. A probabilistic failure assessment curve was proposed to evaluate quantitatively the reliability of ceramics.By using the above data and theories, a fracture and severity analysis for crucibles has been completed. Some manufacturing techniques are proposed to improve reliability during service.
FLEXURAL FATIGUE CHARACTERISTICS OF FRP SANDWICH BEAMS
Authors: Shenoi R. A. , Aksu S. , Allen H. G. 
Published: April 2007

The flexural fatigue characteristics of FRP sandwich beams are investigated. The skins of the beams are made from hybrid glass‐aramid fibres set in epoxy resin and the core material is made from linear PVC foam. The beams under investigation have practical applications in marine operations.The applied load is uniformly distributed throughout the length of the beam which is simply supported.From both static and fatigue tests, it is revealed that the failure occurred in the core due to excessive shear, in turn, resulting in large deflections. An empirical expression is derived to postulate a failure criterion.
FATIGUE GROWTH OF PHYSICALLY SMALL INCLINED CRACKS
Authors: Kujawski D. , Ellyin F. 
Published: April 2007

AbstractThe growth of physically small, self initiated, inclined corner and through‐the‐width cracks is investigated in a carbon steel under tension fatigue (R= 0.05). A preliminary procedure involving crack initiation under far‐field cyclic compression is used. This precracking method is adopted to minimize the effect of residual damage at the tip of the crack grown (and arrested) under cyclic compression. Thus, the subsequent tensile fatigue crack propagates through a region with no (or very small) residual stress or damage. Experiments indicate that the early growth rate of the inclined corner cracks is discontinuous with a few decelerations. During the intermittent propagation period the corner cracks only extend into the thickness (depth) of the specimen and do not propagate along the width direction. However, after reaching a certain aspect ratio, the inclined flaws grow in a steady (continuous) manner in both the thickness and width directions. Through‐the‐width cracks, both inclined and perpendicular to loading direction, do not show the discontinuous growth pattern typical of the inclined corner cracks, but exhibit only one minimum in the crack growth rate behaviour.
THE EFFECT OF SPECIMEN SIZE ON THE BEHAVIOUR OF PENETRATING FATIGUE CRACKS
Authors: Nam K. W. , Ando K. , Ogura N. 
Published: April 2007

AbstractFatigue life and penetration behaviour of cracks in HT80 steel plates were examined experimentally at room temperature for both large and small specimens containing a surface crack. Application of stress intensity factor solutions from small specimens, as proposed by the present authors, to large specimens was investigated. Crack growth behaviour, crack shape and crack opening displacement after penetration can be satisfactorily determined using the K solutions proposed by the authors.
THE DEVELOPMENT OF STRESSES AND THEIR DISTRIBUTION IN TWO‐PHASE ALLOYS DURING CYCLIC LOADING
Authors: Zhonghua Li , Yimin Li , Jinghua Luo 
Published: April 2007

AbstractA finite element program calculates the cyclic behaviour of the individual component phases of a multiphase material using a master curve observed in uniaxial cyclic stress tests. The fatigue behaviour of the two‐phase alloys was characterized by visualizing the evolution of the phase stress (denoted by an average effective stress and an hydrostatic stress) during cyclic loading. The evolution procedure shows a unique fatigue behaviour of the in situ component phases, which differs from that observed in uniaxial or multiaxial fatigue tests of the single phase material. The fatigue damage on a microstructural scale was identified by the distributions of the plastic strain accumulated during cyclic loading and the stress triaxility in the component phases.
SIZE EFFECTS AND A MEAN‐STRENGTH CRITERION FOR CERAMICS
Authors: Bao Y. , Jin Z. 
Published: April 2007

AbstractOn the basis of a large amount of research on the fracture behaviour of ceramics, a new failure criterion is advanced. It is pointed out that the rupture of structural ceramics is governed by the mean stress in a specific zone, rather than by the peak stress value. The size of the process zone was derived as a material constant, and reflects the relation between the toughness and the strength of the material. The results show that the critical maximum stress varies with the stress gradient: the steeper the stress gradient, the higher the critical peak stress. Different experiments concerning the size effect have been carried out and the reason for size effects has been explained by a mean strength theory.
A PROBABILISTIC MODEL FOR PREDICTION OF LCF SURFACE CRACK INITIATION IN PM ALLOYS
Authors: de Bussac A. , Lautridou JC. 
Published: April 2007

AbstractThe Low Cycle Fatigue (LCF) life of PM Ni‐base superalloys is commonly reduced by surface crack initiation at ceramic inclusions. For this reason, a probabilistic model has been developed that predicts the size of surface crack initiation sites from the inclusion size distribution. For the experimental correlation of the model two sets of alloys were examined: a “standard” (i.e. as‐received) alloy, and a second material of identical composition to which a known distribution of ceramic inclusions was incorporated (or seeded). Model predictions were found to be in excellent agreement with the results obtained from the seeded materials in which the defect size distribution is larger and better characterized, and were satisfactory for the unseeded material in which two types of surface defects (pores and ceramic inclusions) initiate LCF cracks. The results of these experiments were employed in LCF simulations of both test specimens and full scale components. These indicated that differences exist between the site preference for LCF crack initiation in small test specimens and large scale components due to a scale effect. Such results demonstrate the utility of seeding experiments for generation of LCF test data used in component design.
STRETCH ZONE GEOMETRICAL MEASUREMENT, A PARTICULAR WAY TO MEASURE FRACTURE TOUGHNESS
Authors: Pluvinage G. , Lanvin A. 
Published: April 2007

AbstractStretch zone geometry (height and length) has been measured using five methods (Transmission Electron Microscopy, Retrodiffused Electron Microscopy, Nickel Plating, Roughness Measurement, Ondulation Method). Experimental investigations show that the major difficulty of these measurements is the great scatter of experimental results. However, it is seen that Transmission Electron Microscopy and Nickel Plating give sufficiently accurate results. By using these different methods, we have found a linear relationship between stretch zone geometry and the classical fracture toughness parameterJIC.Rolling direction, grain size, loading rate, yield stress and the material texture are the influential parameters determining the stretch zone geometry.
THE EFFECT OF MICROSTRUCTURE AND FRACTURE SURFACE ROUGHNESS ON FATIGUE CRACK PROPAGATION IN A Ti‐6A1‐4V ALLOY
Authors: Ogawa Takeshi , Tokaji Keiro , Ohya Kohji 
Published: April 2007

AbstractCharacteristics of fatigue crack propagation (FCP) have been studied on materials with three different microstructures of a Ti‐6A1‐4V alloy, prepared with different heat treatments. The effect of microstructure on the FCP behaviour was attributed to the development of crack tip shielding, primarily resulting from the role of crack path morphology in inducing crack closure and crack deflection. Roughness‐induced crack closure played an important role on the near‐threshold FCP behaviour at a stress ratio of 0.05, but the FCP data plotted in terms of the effective stress intensity factor range, δKeff (allowing for crack closure), still exhibited the effect of microstructure. Fractographic examinations were performed, using a scanning electron microscope (SEM) with the aid of image processing, which enabled a three‐dimensional reconstruction of the fracture surface using a stereo pair of SEM micrographs. Fracture surface roughness was evaluated quantitatively by the ratio of the real area of the reconstructed fracture surface to its projected area. As fracture surface roughness was taken into account in evaluating the FCP data in addition to crack closure, the effect of microstructure disappeared, indicating that the intrinsic FCP resistance was the same in all the materials. Thus, it was concluded that fracture surface roughness was a dominating parameter in controlling the FCP of the Ti‐6A1‐4V alloy.
FATIGUE LIFE ENHANCEMENT OF BUTT WELDS USING A THERMO‐MECHANICAL TECHNIQUE
Authors: Lam Y. C. , Cole G. K. 
Published: April 2007

AbstractPrevious investigations have shown that the introduction of a compressive residual stress at critical locations enhances the fatigue life of welds. In the present study a combination of heat and applied stress is used to induce a compressive residual stress at critical locations such as the weld toe. The theory of the technique is discussed and an experimental study is carried out to investigate the effect of the technique on the fatigue behaviour of transverse butt welded specimens made from C‐Mn steel.
“EFFECT OF LOADING MODE ON THE CYCLIC RESPONSE AND THE ASSOCIATED SUBSTRUCTURE OF POLYCRYSTALLINE COPPER IN THE HIGH‐CYCLE REGIME”
Authors: Llanes L. , Laird C. 
Published: April 2007

AbstractStudies on the influence of loading mode on the cyclic response of small‐grained polycrystalline copper and the associated dislocation structures have been carried out in the high‐cycle regime. It is found that the saturation behaviour under constant load control, for two sets of specimens, with and without initial ramp‐loading, exhibits strong differences in the “intermediate” range of stress amplitudes, i.e., between 70 and 98 MPa. Within this range the ramp‐loading mode promotes a gradual substructure evolution which leads to localization of slip in primary systems and formation of persistent slip bands (PSBs), whereas conventional loading leads to the formation of elongated cells and multiple sets of wall structures (e.g., labyrinth structure), both intimately associated with multiple slip conditions. At low stress amplitudes observed differences in the plastic strain amplitudes obtained at saturation, as an effect of different loading modes, are relatively small and related to equally small differences in the uniformity and homogeneity, from grain to grain, of the dislocation structures associated with that stage. At high stress amplitudes equiaxed cell structures are promoted under both loading modes, the deformation is homogenized, and the cyclic response as a function of loading mode shows no differences.
STRESS RESPONSE UNDER THERMAL‐MECHANICAL STRAIN CYCLING FOR A 1 CrMoV FERRITIC STEEL AND TWO 316 STAINLESS STEELS
Authors: Ellison E. G. , Al‐Zamily A. 
Published: April 2007

Abstract— Isothermal and thermal‐mechanical strain fatigue tests were conducted in air on representative service alloys; a 1 CrMoV steel, and two batches of 316 stainless steel. Data was obtained for thermal‐mechanical in‐phase and out‐of‐phase cycles, and also for isothermal tests at the maximum, minimum, and mid‐temperature of the thermal‐mechanical cycle. Dwell periods were also incorporated in the cycle to assess their effects.A comparative evaluation has been made on the basis of the materials' cyclic stress response. In general, the results have shown that the thermal‐mechanical strain cycling tests cause a large increase in stress range over those tested under isothermal conditions at maximum temperature. In addition, mean stress and strain offsets were developed in continuous cycle thermal‐mechanical tests, whereas negligible offsets occurred in isothermal tests.It appears that the response of the materials could not always simply be explained by reference to the temperature change itself.