bluuebunny/crossref_metadata_2025_split huggingface dataset:
BEHAVIOUR OF FIBRE‐REINFORCED CONCRETES WITH REFERENCE TO FRACTURE RESISTANCE
Authors: Lai Sergio 
Published: April 2007

AbstractThis paper examines the effect of beam size, fibre volume fraction and various fibres on the flexural behaviour of concretes, and their fracture resistance. The ratio of flexural strength to tensile strength is used as a measure of brittleness; a low value indicating a more brittle material.Two flexural toughness indices are used which provide a basis for analysing load–deflection curves. The relation between these structural indices and the material fracture resistance is assessed by adopting parameters which involve flexural and tensile strengths alone and fibre length to reflect fracture resistance.
A RANDOMIZED ENDURANCE LIMIT IN FATIGUE DAMAGE ACCUMULATION MODELS
Authors: Kopnov V. A. 
Published: April 2007

AbstractThe use of random parameters for describing S‐N curves requires special caution. A Peculiar Fatigue Curves (PFC) method based on a linear damage accumulation rule is proposed for modelling the fatigue damage accumulation process. The fatigue properties of a component are presented in the PFC form by randomizing its endurance limit which facilitates a simple technique to predict fatigue life and residual life distributions. Possible usages of the models and their restrictions are illustrated for some common load histories of a component. Particular attention is paid to the stochastic relations between random variables having in some cases improper distributions. The problem of experimental testing of the models is also discussed.
THE USE OF A FAILURE ASSESSMENT DIAGRAM FOR INITIATION AND PROPAGATION OF DEFECTS AT HIGH TEMPERATURES
Authors: Ainsworth R. A. 
Published: April 2007

AbstractThe use of a failure assessment diagram, of the type in the R 6 defect assessment procedure, is investigated for creep crack growth under steady loading. While a detailed approach based on C* remains attractive for appreciable creep crack growth, it is shown that a simplified approach can be formulated for limited crack extension. A failure assessment diagram is derived based on the option 2 curve of R 6 using isochronous stress‐strain data. The inclusion of elastic strains in the isochronous data covers stress redistribution effects.Equations are given which enable a toughness, Kmat, for assessments at temperatures in the creep range to be evaluated from creep crack incubation and growth data presented in terms of C*. The toughness, Kmat, replaces the fracture toughness used in low temperature R 6 assessments. Thermal stresses can be included in assessments by evaluating the stress intensity factor for the combined thermal and mechanical loading. A formula is given which enables the effect of thermal stresses to be reduced when creep strains are sufficient to relax out part or all of the thermal stress.
COMPARISONS OF THEORETICAL AND FINITE ELEMENT STRESS ANALYSIS SOLUTIONS FOR A BIMATERIAL STRIP AND PLATE SUBJECTED TO THERMAL LOADING
Authors: Kfouri A. P. , Wong H. D. 
Published: April 2007

Abstract— A study is made on a bimaterial beam of length 2L and height 2h, composed of a lower half‐beam made from material A and an upper half‐beam made from material B, under thermal loading. The geometrically identical half‐beams are bonded together at the interface. Materials A and B have similar elastic properties, i.e., Young's modulus E(=207 GPa) and Poisson's ratio v(=0.3) are the same for both materials but the coefficients of linear thermal expansion are αA for material A and αB for material B, where αA > αB.A theoretical solution based on simple beam theory is derived for the stress‐strain‐displacement fields at a temperature T1 > T0 where T0 corresponds to an initial stress‐free state, when the beam is held at the centre only to prevent rigid‐body motion. The main purpose of the investigation is to compare the results of the theoretical solution with those obtained from elastic, plane‐stress, finite element analyses, using two different meshes. The case when the ends of the beam are held down is also examined.Finally the analogous axisymmetric problem of a bimaterial circular plate comprising a lower and an upper half‐plate bonded together, is investigated and a theoretical solution of the biharmonic equation, using Legendre polynomials, is derived. The results from the theoretical solutions are compared with the results from an axisymmetric finite element analysis and also from a simulation plane‐stress analysis using E1 as the effective modulus of elasticity, where E1=E/(1 –v). Some interesting features and oddities arising from these investigations are discussed.
A SIMPLE RELIABILITY MODEL FOR THE FATIGUE FAILURE OF REPAIRABLE OFFSHORE STRUCTURES
Authors: Connolly Mark P. , Hudak Stephen J. 
Published: April 2007

AbstractA simple reliability model for fatigue failure of tubular welded joints used in the construction of offshore oil and gas platforms is proposed. The stress‐life data obtained from large‐scale fatigue tests conducted on tubular joints is used as the starting point in the analysis and is combined with a fracture mechanics model to estimate the distribution of initial defect sizes. This initial defect distribution is hypothetical but it agrees well with other initial defect distributions quoted in the literature and when used with the fracture mechanics model results in failure probabilities identical to those obtained from the stress‐life data. This calculated distribution of initial defect sizes is modified as a result of crack growth under cyclic loading and the probability of failure as a function of fatigue cycles is calculated. The failure probability is modified by inspection, and repair and the results illustrate the trade‐off between inspection sensitivity and inspection interval for any desired reliability.
ASPECTS OF HIGH‐TEMPERATURE LOW‐CYCLE THERMOMECHANICAL FATIGUE OF A SINGLE CRYSTAL NICKEL‐BASE SUPERALLOY
Authors: Kraft S. , Zauter R. , Mughrabi H. 
Published: April 2007

AbstractHigh‐temperature thermomechanical fatigue (TMF) tests were performed on monocrystalline specimens of the γ′‐precipitate‐strengthened nickel‐base superalloy CMSX‐6. The specimens had axial orientations near [001]. In‐phase, out‐of‐phase, clockwise‐diamond and counter‐clockwise‐diamond TMF tests were conducted in total strain control in symmetric push‐pull. The temperature interval extended from 873 to 1373 K, the total strain amplitude was 0.5% with a cycle time of 300 s. The stress response, the plastic strain amplitudes and the fatigue lives were measured. In addition, fatigue‐induced micro‐structural changes were investigated.The shapes of the hysteresis loops and the mechanical TMF behaviour varied markedly with the shape of the strain‐temperature cycles. The TMF life of the alloy was found to correlate with the stress amplitude in the tensile half‐cycle. The evolution of the microstructure shows the formation of dislocation networks around the precipitates and in particular, severe changes in the size and the morphology of the γ'‐precipitate structure. These changes vary with the strain‐temperature cycle shape. Failure occurred exclusively by fatigue (and not creep) in the form of localized shear.
RATCHETTING IN PRESSURISED PIPES
Authors: Rider R. J. , Harvey S. J. , Charles I. D. 
Published: April 2007

Abstract— The plastic deformation of thin‐walled cylinders has been experimentally examined for the loading conditions of ±1% axial strain with hoop stresses of approximately 0, 1/4, 1/2 and 3/4 of the initial uniaxial yield stress.Two materials similar to those used in the pipework of PWR nuclear plant in the U.K. have been tested, namely 304S11 stainless steel and En6 low‐carbon steel. The results of the tests were to be compared with the allowable stresses and deformations specified in the ASME Boiler and Pressure Vessel Code, Section III. The code specifies that a prescribed combination of primary stresses must not exceed 1.5Sm, where Sm is a stress value defined for each material.The results indicate that the limit of 1.5Sm is excessively low for both materials and that in particular, the stainless steel could tolerate 5Sm. Although the En6 steel is more prone to ratchetting than the stainless steel, the results suggest that it too could tolerate a higher primary stress than the code allows. Both materials are shown to satisfy the proposed ASME ratchet strain limit of 5% hoop strain after 10 cycles of ±1% axial strain range, for any value of internal pressure.
NON‐PROPAGATION CONDITIONS (ΔKth) AND FATIGUE CRACK PROPAGATION THRESHOLD (δKT)
Authors: Marci G. 
Published: April 2007

Abstract— Fatigue crack propagation threshold values have been determined with two experimental methods, it., the constant R method and the constant Kmax method. Three materials, namely A17075‐T7351 and Ti6A14V STA in the LT‐ and TL‐orientations, and a Ti‐turbine disk material (IMI 685) in the CR‐orientation, were investigated.The paper is divided into 3 parts. In the first part the test conditions, the experimental results and the conclusions drawn from the experimental results are presented, namely that the three different functional dependencies of ΔKth on R cannot be reconciled with present continuum mechanics concepts. In the second part, some facts used in conjunction with the da/dN–ΔKeff methodology are applied to the non‐propagation condition ΔKth. Parameters such as KOp, the threshold ΔKT, and a parameter “KLL” are investigated by numerical modelling of their individual influence on the ΔKth versus R curves. This modelling work shows that the individual ΔKth versus R curves are primarily dependent on the Kop behavior of the respective material. Further, it is shown that the threshold ΔKT is a constant value, independent of any particular cyclic loading condition. In the third part of the paper, the ΔKeff concept is applied to the experimental results obtained in the first part. Using either experimentally or semi‐empirically determined Kop functions and the measured ΔKT values, the ΔKth versus R curves of the three materials investigated were accurately reconstructed. It follows that the ΔKth versus R curves of the individual materials are the natural consequence of the driving force for fatigue crack propagation, namely ΔKeff
A BIAXIAL CYCLIC PLASTIC ANALYSIS FOR CYLINDRICAL SPECIMENS
Authors: YANG W. , BROWN M. W. , MILLER K. J. 
Published: April 2007

AbstractThe cylindrical specimen is a common configuration adopted for biaxial fatigue testing. A rigorous yet practical analysis is presented here under the framework of incremental plasticity. The cyclic stress‐strain curve is obtained from four different plasticity models, and correlated with twenty‐six in‐phase biaxial tests on En15R steel. Stabilized hysteresis loops can also be derived based on the cyclic stress‐strain curve under a J2‐kinematic hardening formulation with special consideration of the rounding transition at the instant of yielding. A correlation for the hysteretic strain hardening exponent N is required for materials that exhibit non‐Masing behaviour; i.e. do not allow a full description of hysteresis loops from knowledge of the cyclic stress‐strain curve. The solution is further generalized to out‐of‐phase loading, where the rotation of the active stress state around the yield surface is illustrated. This compares favourably with ten out‐of‐phase tests on En15R steel.
SHEAR LIPS ON FATIGUE FRACTURES OF ALUMINIUM ALLOY SHEETS SUBJECTED TO BIAXIAL CYCLIC LOADS AT VARIOUS R‐RATIOS
Authors: SHANYAVSKY A. A. , KORONOV M. Z. 
Published: April 2007

AbstractAn analysis is made of shear lip measurements as observed on fatigue crack surfaces of an aluminium alloy sheet material. It is shown that, for biaxial cyclic loads at stress ratios 1 and various R‐ratios, shear lips were controlled by an equivalent intensity factor Ke=K1F(λ,R).For crack growth in air the shear lip width ts was approximately proportional to K2e at ts < t*s= 2.5 × 10−4 m and K4E, at ts > t*s where t*s is the critical value of the shear lip dimension. The initiation of shear lips and the orientation of crack growth for different parameters of the loading cycle are briefly considered in the discussion.
A VARIABLE Kf‐NEUBERS RULE FOR PREDICTING FATIGUE CRACK INITIATION LIFE
Authors: NIE H. , WU F. M. , LIU J. F. 
Published: April 2007

AbstractAs is well known, the fatigue strength reduction factor due to a notch (Kf) in the modified Neuber's rule should not be considered a constant since it varies with different stress levels. In this paper, the definition and the variation of Kf are discussed on the basis of theoretical and experimental analyses, leading to the presentation of a variable Kf‐Neuber's rule. Comparing the results of experimental stress analyses and the fatigue life tests of specimens, the variable Kf‐Neuber's rule gives good predictions and is applied to the life prediction of an aircraft component.
A MICRO AND MACRO APPROACH TO THE ENERGY DISSIPATION RATE MODEL OF STABLE DUCTILE CRACK GROWTH
Authors: TURNER C. E. , KOLEDNIE O. 
Published: April 2007

Abstract—The equations for the energy dissipation rate, D per unit area of crack growth, for plasticity and fracture combined, are presented for equilibrium crack extension in a real elastic‐plastic material. These relationships are a necessary condition for stable growth. The term D is identical to G for lefm and to the rate at which work is done for the rigid‐plastic limit. Crack growth is seen at both micro‐ and macro‐levels as a two stage process of damage accumulation in a process zone followed by actual separation as a micro‐instability at the crack tip. Some examples of the behaviour of ductile metals are cited in support at both micro‐ and macro‐level. For the fully plastic case, D reduces strongly with growth. Relationships with conventional rising R‐curves are stated for contained and uncontained yield.
CLASSIFICATION OF THE FATIGUE DOMAIN AND PREDICTION OF DAMAGE WITH CRACK EXTENSION PARAMETERS
Authors: Weiss M. P. 
Published: April 2007

AbstractThe whole fatigue domain has been divided into six Werent zones, each governed by a separate fatigue regime. Some of these regimes coincide with a known classification of fatigue, and others are new regimes, where new prediction methods have been introduced. The proposed predictions are to be considered as practical curve fitting relations for special cases, but those cases can also be fairly general and useful for design purposes. The proposed fatigue diagram can be used as a basis for a quantified explanation of several known fatigue phenomena.
THE INFLUENCE OF MACHINING DEFECTS AND INCLUSIONS ON THE FATIGUE PROPERTIES OF A HARDENED SPRING STEEL
Authors: Bergengren Y. , And M. Larson , Melander A. 
Published: April 2007

Abstract In hardened steel with high tensile strengths the fatigue strength is often limited by defects, either surface defects or interior defects. In this work the influence of different surface conditions on the fatigue strength of a hardened spring steel has been studied. The fatigue limit of hour‐glass shaped specimens with turned, ground or polished surface was found using load‐controlled testing combined with the stair‐case method.A model based on a statistical treatment of the machining defects (surface) and the inclusions (interior) combined with fracture mechanics has been used to predict the fatigue limit. It was intended to consider the total effect of surface defects and interior defects. The model also makes it possible to predict the failure mode, i.e. surface‐defect initiated failures or inclusion‐initiated failures.
PREDICTION OF FATIGUE LIFE BASED ON LEVEL CROSSINGS AND A STATE VARIABLE
Authors: Holm S. , Josefson B. L. , DeMaré J. , Svensson T. 
Published: April 2007

Abstract The differences between the cycle count approach and the level crossing approach are discussed from the general fatigue life estimation assumptions as formulated by Holm and de Maré. It is concluded that the differences are related to the interpretation of the assumption of order independence, i.e. the neglecting of sequential effects.A revised level crossing model is proposed where damage accumulation depends on the level crossing and the stress history condensed in a state variable. In order to formulate a mean fatigue life the stationarity and ergodicity conditions on the involved processes are outlined.In this revised model sequential effects can be taken into account and in an example the state variable is chosen as the opening stress of a fatigue loaded crack. The dynamics of the opening stress is described by a simple two parameter auto‐regressive model. The entering parameters are estimated from published experimental results and the model is applied to different variable amplitude results from the literature. Calculated results for fatigue life are promising compared to experimental results.
SOME COMMENTS ON A CURRENT MODEL FOR SCATTER OF FRACTURE TOUGHNESS IN CARBON STEELS
Authors: Mimura H. 
Published: April 2007

Abstract The present paper proposes possible mechanisms to explain the following experimental facts reported in the literature.

Fracture toughness has little dependence on plate thickness in the low temperature range.
In some steels, crack initiation sites are much closer to the crack tip than predicted in the transition temperature range by current theory.

The former was attributed to little difference between fracture toughness at crack initiation and that of crack arrest in the low temperature range, and the latter was explained by accounting for the plastic strain effect on crack initiation.
CRACK PROPAGATION AND FRACTURE IN CONTACTING BODIES
Authors: Orringer O. 
Published: April 2007

AbstractWhen a body subject to contact loads develops a crack, the origin, orientation, and tendency to propagate or not depend on fabrication details and maintenance history as well as the service environment. Research over the past twenty years has led to better characterization of crack behavior in some contacting bodies (railroad rail and wheels). Computational methods in solid mechanics provide the basis for quantitative results, but true understanding also requires application of materials science principles. The two disciplines are being brought to bear in combination; quantitative assessments of potential manufacturing improvements and prediction of effects on performance in service are now within reach.
EFFECTS OF ENVIRONMENT AND HEAT TREATMENT ON THE TENSILE AND FATIGUE PROPERTIES OF Ti‐24 at%A1‐11 at%Nb
Authors: Fox T. R. , Knorr D. B. , Stoloff N. S. 
Published: April 2007

AbstractThe α2+β alloy Ti‐24 at%A1‐11 at%Nb was evaluated for mechanical properties in the as‐received, mill annealed condition (nearly equiaxed) and in the β annealed condition (basketweave). The as‐received condition had a moderately strong basal transverse α2 texture which gave a higher yield strength, higher elastic modulus, and higher fatigue crack growth rate (FCGR) for loading in the transverse direction at room temperature. The β annealed material was stronger and more isotropic in both texture and properties. The fatigue crack growth rate is higher at 732°C in argon than at room temperature. A hydrogen environment results in a FCGR at 732°C comparable to or less than the FCGR in argon at 732°C for the as‐received and β annealed conditions respectively. Although the hydrogen in solution at levels as high as several thousand ppm does not embrittle at elevated temperature, embrittlement is found after cooling to room temperature.
DYNAMIC CRACK PROPAGATION AND CRACK ARREST INVESTIGATED WITH A NEW SPECIMEN GEOMETRY: PART I: EXPERIMENTAL AND NUMERICAL CALCULATIONS
Authors: Iung T. , Pineau A. 
Published: April 2007

AbstractA new test specimen geometry was advised to investigate unstable crack propagation and crack arrest. This geometry is a cracked ring which is subjected to a compressive load applied to its poles while the crack is located on the equatorial plane at the outer surface of the specimen. The main interest of this geometry lies in the variation of the stress intensity factor, K, with crack length which follows a bell‐shaped curve numerically determined. The increasing part of the curve enables us to study unstable propagation and the decreasing one ensures crack arrest. This experiment has two major advantages in comparison with other specimen geometries; the boundary conditions are well controlled during the propagation, and the loading conditions of the crack are therefore precisely known. The round shape of the ring reduces wave reflection effects from free boundary surfaces. It is therefore shown that a static analysis can then be used to investigate crack arrest behaviour.
CYCLIC FATIGUE OF ZIRCONIA
Authors: Schmitt R. , Fett T. , Munz D. 
Published: April 2007

AbstractTwo partially‐stabilized zirconia materials, Mg‐PSZ and Y‐PSZ, were investigated in static and cyclic fatigue tests. The crack growth rates were determined as a function of the stress intensity factor (static tests) and the stress intensity factor range (cyclic tests). For all R‐ratios investigated the crack‐growth relations are sufficiently described by power laws. An influence of frequency is obvious. Finally, the crack growth behaviour of natural flaws is compared with that of macroscopic cracks
THE INFLUENCE OF HYDROGEN ON THE FATIGUE BEHAVIOUR OF THE BETA‐TITANIUM ALLOY Ti‐3Al‐8V‐6Cr‐4Mo‐4Zr
Authors: Christ H.‐J. , Alvarez A.‐M. , Birnbaum H. K. , Robertson I. M. 
Published: April 2007

AbstractIn order to characterize the influence of hydrogen on the mechanical properties of β‐titanium alloys, monotonic tensile and strain‐controlled fatigue tests were performed on samples of the metastable alloy Ti‐3Al‐8V‐6Cr‐4Mo‐4Zr in uncharged (0.5 at.% hydrogen) and hydrogen‐charged (3‐4 at.% hydrogen) conditions. The hydrogen was introduced into the material during the last 8 h of an ageing treatment (28 h at 482°C) from the gas phase, whereas the reference (uncharged) specimens were annealed completely in vacuum. The results of the mechanical tests indicate that hydrogen slightly increases the strength of the alloy in monotonic as well as in cyclic loading. Under tensile loading the fracture strain decreases as a result of hydrogen. Under cyclic loading both charged and uncharged conditions show initial softening followed by a saturation state. The cyclic lifetime at a constant total strain amplitude, however, is not reduced by the hydrogen charging. The effect of hydrogen on the mechanical behaviour can be interpreted and understood on the basis of microstructural observations that reveal a hydrogen‐induced change in the precipitation state. This indirect influence of hydrogen on the microstructure, which leads to a reduction of the mean size of the α‐precipitates, in combination with a slight decrease on the volume fraction of the α‐phase, seems to dominate over any direct intrinsic hydrogen effect
DEVELOPMENT OF SEMI‐ELLIPTIC FATIGUE CRACKS IN AK6 ALUMINIUM ALLOY UNDER BIAXIAL LOADING
Authors: Shanyavskii A. A. 
Published: April 2007

AbstractFatigue mechanisms are investigated in AK6 aluminum alloy under biaxial loading. The development of a semi‐elliptic crack under conditions of biaxial compression‐tension is connected with the emergence of spherical particles. A mechanism of rotational instability is suggested, connecting the processes of particle formation with a specific mechanism of material failure. A similarity is revealed in the formation of fatigue striations within the studied ratio λ of biaxial loads from –0.9 to +0.9. As λ increases, the crack‐growth rate also increases. It is suggested that this be allowed for when introducing a correction to the mode I stress‐intensity factor.