bluuebunny/crossref_metadata_2025_split huggingface dataset:
SHORT CRACKS AT BIAXIALLY STRESSED NOTCHES: A FINE‐MESH ELASTIC‐PLASTIC FINITE ELEMENT ANALYSIS
Authors: Seed G. M. , Miller K. J. 
Published: April 2007

AbstractAn elastic‐plastic fracture mechanics study on the effects of biaxial stress fields is presented relating to various centre and edge notches containing short cracks under plane strain. The elastic stress intensity factor and the non‐singular elastic T‐stress term are determined by finite element analyses. Comparisons of these results with small scale yielding plastic zone size predictions are given for a wide range of applied stress intensity factors, revealing an improved correlation when considering the T‐stress effect. The influence of positive biaxial stress‐induced crack closure on the stress intensity factor is also discussed.
MODELLING SMALL FATIGUE CRACKS INTERACTING WITH GRAIN BOUNDARIES
Authors: Sun Zuyu , de, los Rios E. R. , Miller K. J. 
Published: April 2007

AbstractA theoretical model which describes the microstructural aspects of short fatigue cracks is further developed to quantify the strength of microstructural barriers. The effectiveness of a barrier to decelerate or arrest short fatigue cracks in single phase materials depends on the relative orientation of the grains ahead of the barrier. A method of calculating the progression of orientation factors of the grains traversed by a fatigue crack is presented. Introducing the orientation factor into the crack growth equation allows the model to be used in the prediction of crack growth rate and of fatigue life. Comparison with experimental results, obtained with an A1‐Li alloy, establishes the accuracy of the predictions. The sequence of grain orientation factors ahead of the crack is also used to predict the stress boundary conditions for short fatigue crack propagation in the form of a Kitagawa‐Takahashi diagram which is compared with the experimental results due to Lukas.
A FULLY AUTOMATED SYSTEM FOR MONITORING SHORT CRACK GROWTH
Authors: Hussey I. W. , Roche J. , Grabowski L. 
Published: April 2007

AbstractThis paper describes a fully automatic short crack monitoring system used to study the growth of short cracks in Waspaloy at ambient temperature. Freely initiated fatigue cracks as small as 34 μ were detected using this system. Frequent monitoring enabled crack growth to be recorded over 2000 cycle increments. Several methods of data presentation were reviewed, the most appropriate being a linear plot of growth rate vs crack length.
FATIGUE CRACK GROWTH BEHAVIOUR IN MOLTEN‐METAL PROCESSED Sic PARTICLE‐REINFORCED ALUMINIUM ALLOYS
Authors: Kumai Shinji , King Julia E. , Knott John F. 
Published: April 2007

AbstractFatigue crack initiation and subsequent short crack growth behaviour of 2014‐5wt%SiC aluminium alloy composites has been examined in 4‐point bend loading using smooth bar specimens. The growth rates of long fatigue cracks have also been measured at different stress ratios using pre‐cracked specimens. The distributions of Sic particles and of coarse constituent particles in the matrix (which arise as a result of the molten‐metal processing and relatively slow cooling rate) have been investigated. Preferential crack initiation sites were found to be Sic‐matrix interfaces, Sic particles associated with constituent particles and the coarse constituent particles themselves. For microstructurally short cracks the dispersed SiC particles also act as temporary crack arresters. In the long crack growth tests, higher fatigue crack growth rates were obtained than for monolithic alloys. This effect is attributed to the contribution of void formation, due to the decohesion of Sic particles, to the fatigue crack growth process in the composite. Above crack depths of about 200 μm “short” crack growth rates were in good agreement with the long crack data, showing a Paris exponent, m= 4 in both cases. For the long crack and short crack growth tests little effect of specimen orientation and grain size was observed on fatigue crack growth rates, but, specimen orientation affected the toughness. No effect of stress ratio in the range R=0.2‐0.5 was seen for long crack data in the Paris region.
A BRITTLE FRACTURE KNOWLEDGE BASE AND ITS PRACTICAL APPLICATIONS
Authors: Dohnal M. , Vystrcil J. , Kvapilik M. , Vykutil J. , Dohnalova J. 
Published: April 2007

AbstractConventional experimental/knowledge records (usually tables, graphs and/or equations) are not suitable for an efficient uncertainty‐reasoning because of the poor knowledge‐acquisition methods used to develop them. A fuzzy knowledge base is a suitable framework for acquisition of vague, sparse and inconsistent knowledge. A revitalization of valuable records and re‐used literature knowledge items is a retrospective application of knowledge engineering algorithms. This is an ad hoc process and a general theoretical background does not exist. Therefore this paper presents a detailed description of a case study (49 variables, 4000 statements).A query as an element of a man‐machine dialogue is presented. No a priori knowledge of fuzzy mathematics is needed.
FRACTURE BEHAVIOUR OF AXISYMMETRIC BARS UNDER HIGH TRIAXIAL STRESS AND LARGE STRAIN CYCLIC LOADING
Authors: Du M. L. , Li G. C. , Zhang Y. Z. , Fang W. D. 
Published: April 2007

AbstractAxisymmetric notched bars with notch roots of large and small radius were tested under large strain cyclic loading. The main attention is focused on the fracture behaviour of steels having cycles to failure within the range 1‐100. Our study shows that a gradual transition from a static ductile nature to one of fatigue cleavage can be observed and characterized by the Coffin‐Manson formula in a generalized form. Both the triaxial tensile stress within the central region of specimens and static damage caused by the first increasing load have effects on the final failure event. A generalized cyclic strain range parameter δε is proposed as a measure of the numerous factors affecting behaviour. Fractographs are presented to illustrate the behaviour reported in the paper.
PREDICTION OF CREEP CRACK GROWTH INCUBATION PERIODS
Authors: Austin T. S. P. , Webster G. A. 
Published: April 2007

AbstractAn incubation period is often observed prior to the onset of creep crack growth. This paper presents a procedure for estimating its duration from a knowledge only of the stress rupture properties and creep ductility of a material. Comparisons are made with experimental data on type 316L stainless steel at 600°C and a 1% CrMoV low alloy steel at 550°C. It is shown that good agreement is achieved when allowance for a build up of damage in a process zone at the crack tip during the early stages of cracking is incorporated into the analysis.
EFFECTS OF SMALL PRESTRAIN ON THE FATIGUE BEHAVIOUR OF SPHEROIDAL PEARLITE STEEL
Authors: Nagase Yasuo , Kanri Toshifumi 
Published: April 2007

AbstractIn order to clarify the effect of a small prestrain on the fatigue strength of a carbon steel, the fatigue behaviour of plain specimens of a eutectoid steel with spheroidal pearlite, previously subjected to a tensile prestrain, is investigated and compared with that of annealed and strain‐aged specimens. It is found that a small prestrain of a few percent does not decrease the fatigue limit nor the crack initiation or propagation lives. Fatigue slip initiation, however, is accelerated by the small prestrain. It is also observed that cyclic strain ageing does not occur. From these results, it is inferred that dislocations are unpinned by the small prestrain and this causes fatigue slip to occur more readily, but the fatigue behaviour following slip initiation is not affected because the spheroidal cementite particles act as obstacles to further slip deformation and Stage I crack propagation.
FATIGUE BEHAVIOUR OF THREE VARIANTS OF THE ROLLER BEARING STEEL SAE 52100
Authors: Christ H.‐J. , Sommer C. , Mughrabi H. , Voskamp A. P. , Beswick J. M. , Hengerer F. 
Published: April 2007

AbstractStress‐controlled, low‐cycle, push‐pull fatigue tests were performed on three variants of the bearing steel SAE 52100 with slightly different compositions and heat treatments. The experiments demonstrated differences in the cyclic plastic behaviour of differently hardened steels (bainitically‐hardened and martensitically‐hardened, respectively), whereas the two martensitic variants, which differ in composition, behaved very similarly. Bainitically‐hardened SAE 52100 steel exhibited initial hardening followed by cyclic softening above a stress amplitude level of 1200 MPa. In contrast, the martensitically‐hardened variants showed a pronounced cyclic hardening. The deformation behaviour of the martensitically‐hardened bearing steel in a monotonic tensile test and during the first cycles can be well understood on the basis of the transformation of retained austenite. This process leads to an onset of plastic deformation at lower stresses compared to the bainitically‐hardened bearing steel. As a result of the subsequent cyclic hardening of the martensitic variants, the CSS curves are almost identical for the differently hardened conditions under investigation. Additional tests under pulsating compression documented that a high negative mean stress enhances the cyclic plasticity.
THE EFFECTS OF FREQUENCY AND R‐RATIO ON FATIGUE CRACK GROWTH BEHAVIOUR IN Al‐Li‐Cu‐Mg ALLOY (8090) PLATE
Authors: Kemp R. M. J. , Wilson R. N. , Gregson P. J. 
Published: April 2007

Abstract— The effects of frequency and R‐ratio on the fatigue crack growth rate of the Al‐Li‐Cu‐Mg alloy 8090 have been assessed in air. Compact tension test pieces (B= 25 mm) were tested at constant Pmax using a triangular waveform (CA) and the crack length was monitored by a four‐wire pulsed potential drop technique. Crack closure measurements were made during the test by a front face compliance technique.The crack growth rate was found to be dominated by the high level of crack closure and the fatigue fracture morphology. Two fracture types were identified; a highly deviated “shear” fracture mode which was in competition with a macroscopically flat “tensile” fracture mode. The tensile fracture mode was predominant at low test frequency, high R‐ratio and short crack lengths whereas the shear mode was predominant at high frequency, low R‐ratio and long crack lengths. The transition from tensile to shear mode was primarily controlled by the effective stress intensity factor range, ΔKeff.The effect of loading variables on the transition was explained in terms of the diffusion distance of hydrogen relative to the effective cyclic plastic zone diameter. Test piece thickness had a secondary effect on the transition and this was explained in terms of gas transport considerations.
PREDICTION OF THE FIRST SPINNING CYLINDER TEST USING DUCTILE DAMAGE THEORY
Authors: Bilby B. A. , Howard I. C. , Li Z. H. 
Published: April 2007

AbstractUsing the standard Rousselier ductile damage theory, a prediction is made of crack growth in the First Spinning Cylinder Test carried out by AEA Technology, Risley. Only data from small‐scale mechanical tests and metallography have been used. The prediction has been “blind” in the sense that, although we were aware of the observed high J‐R ‐curve (hitherto defying detailed interpretation by any of the standard fracture mechanics techniques), we restrained ourselves from any attempt to use the detailed results of the test itself in making the prediction. Indeed, we were in some confusion about the reported J‐R‐curves until a final meeting when our predictions were discussed with the experimental workers. Furthermore, crack growth versus rotation speed was predicted before sight of the experimental results.Originally, reasonable estimates of the size scale determining the averaging involved in the damage theory gave predictions of crack growth versus rotation speed which agreed very well with the cylinder test, except near initiation, where the apparent increase in initiation toughness was not predicted. These predictions involved the parameter J only through the use of the compact tension specimen results in fitting the damage theory parameters and were quite independent of any complications which might arise from the use of J when centrifugal or body forces are present. The J‐R ‐curve predictions were not quite so good, but were still well above the small specimen results. Again, there was discrepancy near initiation.Subsequently, we have learned that metallography which we were led to believe applied to a section perpendicular to the line of the mean crack front in fact referred to a section parallel to the mean crack plane. A rough correction using limited additional data improves our “blind” prediction slightly, but other limitations of the available small‐scale data mean that, had some suggestions in the literature been adopted, a result more in accord with that expected from the small‐scale tests might well have been obtained. It is concluded that further development of the modelling and the associated large‐ and small‐scale testing is required. Some comments on this further development and the potential of the method as a predictive engineering tool for the transfer of results from specimens to structures are made.
THE EFFECT OF ARTIFICIAL FATIGUE‐CRACK CLOSURE ON FATIGUE‐CRACK GROWTH
Authors: Ur‐Rehman A. , Thomason P. F. 
Published: April 2007

AbstractAn investigation of the effects of artificial fatigue‐crack closure on the subsequent growth of fatigue cracks, at constant range of stress‐intensity factor, was carried out for the following closure materials: (i) electroplated nickel; (ii) electroless nickel; (iii) ethylcyanoacrylate (ECA) adhesive; (iv) low‐melting point (LMP) solder. It was observed that (a) the wedge thickness and area of crack surface covered by the artificial‐closure material and (b) the distance of the tip of the closure wedge from the crack tip (i.e. the penetration of the closure material towards the crack tip) were the main parameters controlling the reduction in the subsequent growth rate of the fatigue crack. The results suggest that if the crack thickness (opening) is completely filled with a dense wedge of artificial‐closure material, the wedge becomes effectively rigid and the precise mechanical properties of the closure material will have only a secondary influence on subsequent fatigue‐crack growth in comparison to (a) and (b) above. This follows from the fact that the closure material is effectively a very thin strip compressed between the rough (high friction) sides of a crack. A rigid‐wedge and elastic‐crack model was found to successfully predict the changes in fatigue‐crack growth rate following artificial crack‐closure and gave a lower bound to the measured growth rates.
CHARACTERIZATION OF DUCTILE TEARING RESISTANCE BY ENERGY DISSIPATION RATE
Authors: Memhard D. , Brocks W. , Fricke S. 
Published: April 2007

AbstractThe J integral, which is widely used in elastic‐plastic fracture mechanics, is not the true driving force any more if the crack is propagating. This leads to some inconsistencies when ductile tearing resistance is characterized in terms of J, especially for large crack extensions. Instead, Turner has proposed the energy dissipation rate as a physically more meaningful quantity. His concept is discussed and more evidence is given that will provide a better understanding of ductile tearing. It is shown how this quantity can be determined by measuring the heat production ahead of a fast running crack, or calculated in a finite element analysis, or re‐evaluated from J‐R test records of bend and tensile specimens. The energy dissipation rate is decreasing with crack extension in gross plasticity and approaches a stationary state. From these relations, the shapes of the cumulative J‐R curves can be derived for different specimen geometries.
A STUDY OF SUPERIMPOSED FRACTURE MODES I, II AND III ON PMMA
Authors: Davenport J. C. W. , Smith D. J. 
Published: April 2007

AbstractA test apparatus has been developed to study the fracture behaviour of engineering materials subjected to superimposed tensile and shear (Mode I and II) loads using a single edge notch specimen. Stress intensity factors were calculated using finite element analysis. Test results for PMMA are reported. Results from circumferentially notched round bar specimens, subjected to combined tension and torsion (Mode I and III) loading are also reported. The Mode I/II results are consistent with the mixed mode fracture response of a wide range of brittle materials, although there is some evidence of non‐linear behaviour. The fracture behaviour for superimposed Modes I and III indicates the strong influence of non‐linear deformation which causes the mixed mode toughness to be dependent on the sequence and type of loading.
EFFECT OF AN ELASTIC‐PLASTIC SHOCK WAVE PART B: ON THE FATIGUE CRACK GROWTH RATE OF WELDED JOINTS
Authors: Liangshan Chen , Huaining Chen , Zhongyao Si , Shenyu Tan , Guangyuan Chui 
Published: April 2007

AbstractFatigue crack growth behavior in welded joints subjected to elastic‐plastic shock waves was investigated using three‐point‐bend specimens. The results indicate that the fatigue crack growth rate is reduced in the affected region of elastic or plastic waves. The travel of a plastic stress wave reaches 10 to 13 mm depth, but the hardness in this region is not increased although the lattice distortion is high. The crack path morphologies were observed, and reasons for a decrease in crack growth rate are presented.
COMPARISON OF FATIGUE LIFE PREDICTIONS IN WELDED JOINTS USING 2D AND 3D K SOLUTIONS
Authors: Ferreira J. M. , Branco C. M. 
Published: April 2007

AbstractThe paper presents the results of fatigue life predictions in non‐loaded carrying tee and cruciform joints and also longitudinal seams of tubes, obtained with 2D and 3D stress intensity factor solutions. The 2D computational method uses the standard Bueckner weight function solution to obtain the 2D values of the stress magnifying factor MK. In the 3D approach a modified 3D weight function solution was used in conjunction with the Raju and Newman base stress intensity formulation.Comparison of results is shown between the 2D and 3D fatigue life predictions and experimental results of fatigue strength obtained by the authors. Results are also given showing the influence of crack aspect ratio, thickness and the ratio of tube radius to tube thickness.
EXPERIMENTAL DETERMINATION OF STRESS INTENSITY FACTORS FOR CRACKS IN TURBINE DISCS
Authors: Nurse A. D. , Patterson E. A. 
Published: April 2007

AbstractStage‐II fatigue crack growth paths in firtree fixtures have been predicted using a photoelastic technique. Initiation was assumed to occur at the edge of contact on the load‐bearing flanks and, subsequently, the cracks were extended in the direction of the maximum circumferential stress. After a short initial length, in which propagation was perpendicular to the contact surface, the direction of crack growth was, in a broad sense, equivalent to the hoop direction in the disc. Stress intensity factors were found for the majority of the crack path using data taken from the isochromatic fringe patterns. It was concluded that the most catastrophic failure was likely to occur from the innermost land of the firtree and that the width of the firtree had little influence on the stress intensity factors.
A MULTIAXIAL FATIGUE DAMAGE MODEL FOR ORTHOTROPIC MATERIALS UNDER PROPORTIONAL LOADING
Authors: Lin Hong , Nayeb‐Hashemi H. , Pelloux R. M. 
Published: April 2007

AbstractA new multiaxial fatigue damage model for orthotropic materials is proposed based on the strain vector. Six material constants are included in the model. These material constants represent the dependence of fatigue resistance on material orientation, and they can be obtained by conducting strain‐controlled uniaxial fatigue tests along the three principal orthotropic directions of an orthotropic material. The model can also be transformed in new coordinate systems to predict the fatigue lives of new material orientations. Biaxial low‐cycle fatigue tests are conducted to verify the model. The prediction of the model agrees with the experimental results reasonably well.
A MECHANISTIC‐BASED THERMOMECHANICAL FATIGUE LIFE PREDICTION MODEL FOR METAL MATRIX COMPOSITES
Authors: Neu R. W. 
Published: April 2007

AbstractThe framework for developing a mechanistic‐based life prediction model for metal matrix composites is described. For a composite consisting of unidirectional silicon carbide fibers in a titanium aluminide matrix, SCS‐6/Ti‐24A1‐1INb (at%) [0]8, three dominant damage mechanisms were identified: (1) matrix fatigue damage, (2) surface‐initiated environmental damage, and (3) fiber‐dominated damage. Damage expressions were developed for each mechanism along with a method for determining the constants. The damage is summed to obtain the total life. The model is capable of making predictions for a wide range of histories, including isothermal fatigue at different frequencies and stress‐ratios, thermomechanical fatigue (TMF) under in‐phase and out‐of‐phase cycling conditions, thermal cycling at constant stress, and stress holds at either maximum or minimum stress. Considering the wide range of cyclic conditions, the predictions compare favorably with experiments. In addition, the controlling damage mechanism for each history is predicted.
SIZE, THICKNESS AND GEOMETRY EFFECTS ON TRANSITION FRACTURE
Authors: Landes J. D. , Heerens J. , Schwalbe K.‐H. , Petrovski B. 
Published: April 2007

Abstract— Transition fracture toughness was studied to look at the effect of size, thickness and geometry. Size effects were studied on six sets of data collected from the literature in which proportionally sized compact specimens of various steels were tested. Thickness effects were studied on tests of compact specimens of constant thickness and varying planar dimensions. Tests were conducted on a pressure vessel steel at a constant thickness of 20 mm where planar dimensions were increased so that thickness constraint was decreased. Geometry effects were studied on tests from a center cracked tension specimen geometry. Initially all of the data from the tests were included in the study; none were eliminated due to a size or other validity requirement. Then two validity requirements, the KIc and the Anderson‐Dodds size requirements, were imposed to study their effect on the data.The results showed that a smaller specimen size does not necessarily result in higher toughness. Rather, the smallest size often gave the lowest values of toughness. Loss of thickness constraint tended to increase toughness but not very much; it may not increase at all at the lower temperatures. The center cracked tension geometry appeared to have a lower constraint. These specimens showed an increase in toughness which is similar to that observed on a compact specimen for a change of temperature from −90°C to −60°C. Imposing a size validity requirement eliminated much of the fracture toughness data in the transition and influenced the distribution of data. Validity size criteria should be avoided if possible, especially for a scientific study.
ESTIMATION OF LOWER BOUND FRACTURE RESISTANCE OF PRESSURE VESSEL STEEL IN THE TRANSITION REGIME
Authors: Zerbst U. , Heerens J. , Schwalbe K.‐H. 
Published: April 2007

Abstract— An empirical investigation of different procedures was carried out for determining a lower bound fracture toughness on the basis of small specimen test data in the ductile‐to‐brittle transition range. The procedures have been applied to various data sets in order to study the practicability and behaviour of the different procedures.It has been shown that these procedures produce estimates which fall into the lower tail regime of the scatter band of fracture toughness. Within the range of the data sets investigated these estimated lower bounds do not significantly depend on the specimen size, side grooving of the specimens and the magnitude of the data set used for the estimation. Nevertheless, the estimated lower bound values themselves are different depending on the method used for the estimation.