bluuebunny/crossref_metadata_2025 huggingface dataset:
IN SITU SCANNING ELECTRON MICROSCOPE OBSERVATIONS OF FATIGUE IN MAGNESIA‐PARTIALLY‐STABILIZED ZIRCONIA
Authors: Møller C. V. , Healy J. C. , Mai Y.‐W.
Published: April 2007

Abstract— The response of magnesia‐partially‐stabilized zirconia to cyclic loading was investigated using a purpose‐built loading stage, designed to operate in the vacuum chamber of a scanning electron microscope. Crack tip/microstructural interactions, along with fatigue crack growth rates were studied and recorded photographically and via a video cassette recorder. For the experimental conditions examined, crack bridging, deflection and closure are discussed as possible mechanisms of fatigue crack growth resistance.
STATIC AND DYNAMIC FRACTURE TOUGHNESS OF AN Al‐Li 8090 ALLOY PLATE
Authors: Prasad N. Eswara , Kamat S. V. , Malakondaiah G. , Kutumbarao V. V.
Published: April 2007

Abstract— The static and dynamic fracture toughness of an Al‐Li 8090 alloy plate was evaluated as a function of notch orientation. Static fracture toughness is marginally lower than the dynamic fracture toughness in all the three notch orientations that were studied. The fracture mechanism remains unchanged and the degree of in‐plane anisotropy is significant, but more or less similar under static and dynamic conditions.
AN ENGINEERING FRACTURE PARAMETER FOR NON‐J‐CONTROLLED CRACK GROWTH
Authors: Wang B. , Yang W. , Hwang K.‐C.
Published: April 2007

Abstract— An engineering fracture parameter (CTOA) is studied under non‐J‐controlled growth. Based on the asymptotic solution of the crack tip field and the concept of the J̃1 integral, an analytical relation linking the crack tip opening angle (CTOA) and the J̃1 integral is established. A numerical investigation of the process of crack growth is carried out by the finite element method. The whole field solution, fracture parameters and indeterminate parameters are determined by FE analysis. An experimental investigation on a ductile structural steel has also been conducted and the crack resistance curve (CTOA)R is obtained. The numerical and experimental results validate the theoretical analysis and show that they are consistent. It can be concluded that CTOA is always constant during steady crack propagation.
THEORETICAL AND EXPERIMENTAL STUDIES OF FRETTING‐INITIATED FATIGUE FAILURE OF AEROENGINE COMPRESSOR DISCS
Authors: Papanikos P. , Meguid S. A.
Published: April 2007

Abstract— A finite element analysis and fatigue crack growth studies are made of dovetail joints in aeroengine compressor discs. Three aspects are examined: the first deals with the finite element stress analysis of the critical geometrical features and interface conditions of different dovetail configurations, thus enabling an assessment to be made of the critically loaded regions in the disc. The second deals with the prediction of the direction of potential fatigue cracks, which were allowed to initiate in the finite element model at the regions where fretting damage is most likely to occur, using an incremental crack tracking criterion. The third is concerned with the verification of the above modelling techniques with fatigue tests on a uniaxial back‐to‐back arrangement, which attempts to simulate the stress fields of a rotating disc.
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.
USE OF THE DISTRIBUTED DISLOCATIONS METHOD TO DETERMINE THE T‐STRESS
Authors: Seed G. M. , Nowell D.
Published: April 2007

Abstract— This paper demonstrates a method to determine the elastic T‐stress for a semi‐infinite half‐plane containing a surface‐breaking crack which is loaded by an arbitrarily distributed far‐field tension. The method consists of representing the crack by a continuous distribution of edge dislocations and forming singular integral equations to determine the equilibrium dislocation distributions. By numerically solving the integral equations, stress intensity factors and T‐stresses are obtained for the example case of a crack which is normal and inclined to the free‐surface of a half‐plane and loaded by a uniform far‐field tension.
STATISTICAL INVESTIGATION OF THE BEHAVIOUR OF SMALL CRACKS AND FATIGUE LIFE IN CARBON STEELS WITH DIFFERENT FERRITE GRAIN SIZES
Authors: Goto M.
Published: April 2007

Abstract— In order to study the relation between the scatter characteristics of small crack growth behaviour and fatigue life, rotatory bending fatigue tests of smooth specimens were carried out using 0.21% carbon steels of different ferrite grain sizes. Fifteen to eighteen specimens were fatigued at each stress amplitude, and the initiation and propagation behaviour of the cracks which led to the final fractures were examined for all the specimens. The physical basis of scatter in fatigue life was investigated, based on the successive observation of fatigue damage on the surface using the plastic replica technique, followed by an analysis of the data assuming a Weibull distribution. A statistical investigation of the physical basis of scatter in relation to the ferrite grain size was performed, i.e. the distributions for crack initiation life, crack propagation life, fatigue life and growth rate of small cracks. Finally, the fluctuation of crack growth rate was studied in relation to the application of a crack growth law for microstructurally small cracks.
ELEVATED TEMPERATURE LOW‐CYCLE FATIGUE BEHAVIOR OF HK40 ALLOY
Authors: Konosu S.
Published: April 2007

Abstract— By conducting creep tests and creep‐fatigue tests at temperatures of 800°C, 900°C, and 1000°C, on centrifugal cast HK40 alloy (which is used for example for the steam reformer tubes of fuel cell plants) and varying the strain rate during the loading and unloading process, the influence of strain history on the life of the material has been clarified. Furthermore, the data obtained from these tests were subjected to analyses by means of life evaluation methods utilizing the life fraction rule, strain range partitioning method, and damage rate approach, and comparative studies were conducted on each life evaluation method. As a result, problematic points concerning the application of the life fraction rule, strain range partitioning method, and damage rate approach have been clarified and data which would be useful in establishing design guidelines for structures to be used under conditions such as involves the interaction of creep and fatigue have been obtained.
FATIGUE TESTING WITH A DISCRETE‐TIME STOCHASTIC PROCESS
Authors: Svensson T.
Published: April 2007

Abstract— A computer program that creates time histories for use in fatigue tests in servo‐hydraulic machines is presented. The time histories can be tailored from certain user specifications, namely the irregularity factor and the level‐crossing spectrum. The program is based on the theory of stochastic time series, and the formulae needed for the program are derived in the paper. Problems of optimality are treated both with respect to fulfilment of the specifications and with respect to machine performance. Examples from two fatigue‐testing projects, where the program has been applied, are presented.
BASIC DIAGRAMS OF CYCLIC CRACK GROWTH RESISTANCE OF TITANIUM ALLOYS
Authors: Panasyuk V. V. , Ratych L. V. , Petranyuk I. Ya.
Published: April 2007

Abstract— Basic diagrams of the cyclic crack growth resistance of two of the most investigated titanium alloys, namely Ti‐6A1–4V and Ti‐6A1–6V‐2Sn, are presented. Diagrams are plotted for, in‐air, distilled water and 3.5% NaCl solution, which are necessary for lifetime calculations of structural elements made of these metals. The dependency of cyclic crack growth resistance on the yield strength is established. It is shown that cyclic crack growth resistance of titanium alloys in corrosive environments is determined not only by the stress‐strain state but also by the electrochemical conditions at the corrosion fatigue crack tip, which for aqueous environments can be characterized integrally by the hydrogen index of the environment and the electrode potential of the metal. Therefore, cyclic corrosion crack growth resistance testing should be performed under constant electrochemical conditions at the corrosion fatigue crack tip or these conditions should be taken into account. A new method of plotting the basic cyclic corrosion crack growth resistance diagrams of titanium alloys is considered.
FATIGUE CRACK GROWTH IN DUCTILE MATERIALS UNDER CYCLIC COMPRESSIVE LOADING
Authors: Hermann R.
Published: April 2007

Abstract— Mode I fatigue crack growth has been studied in notched specimens of 7017‐T651 aluminium alloy subjected to fully compressive cyclic loads. The specimens were first subjected to a deliberate compressive preload which causes plastic deformation at the notch tip. On unloading, this region developed a residual tensile stress field and on subsequent compressive cyclic loading in laboratory air, a fatigue crack was nucleated at the notch and grew at a diminishing rate until it stopped. The final crack length increased with an increase in the value of the initial compressive preload and with an increase in the negative value of the applied cyclic mean load. To gain a better understanding of crack growth in residual stress fields, the magnitude and extent of residual stress induced from compressive preloads have been analysed. This was achieved when extending the notch by cutting while recording the change in the back face strain. From residual strain models it was found that the fatigue crack growth was confined to a region of tensile cyclic stress within the residual stress field. The effective stress intensity range was investigated at selected mean loads and amplitudes, for correlating purposes, using both the compliance technique and by invoking the crack growth rate behaviour of the alloy. Finally, a brief discussion of the fracture morphology of cracks subjected to cyclic compression is presented.
DYNAMIC FATIGUE AND COMPUTER SIMULATION OF THE BEHAVIOUR OF Y2O3‐ZrO2 CERAMICS
Authors: Wang J. , Jin Z. , Ling W. , Wang X.
Published: April 2007

Abstract— There is a critical stress rate Kc for each of the three ZrO2 ceramics tested. Fracture is controlled by the materials polycrystal fracture toughness, Kcp, if the stress rate is less than Kc. Otherwise, fracture is controlled by the single crystal fracture toughness, Kcs. The crack growth parameters determined by dynamic fatigue experiments can only represent macrocrack growth behaviour although the fracture of specimens in experiments originates from small surface flaws.
FATIGUE CRACK GROWTH IN RESIDUAL STRESS FIELDS: EXPERIMENTAL RESULTS AND MODELLING
Authors: Beghini M. , Bertini L. , Vitale E.
Published: April 2007

Abstract— The paper discusses the results of fatigue crack growth rate tests conducted in the presence of residual stresses. Three different residual stress distributions, obtained by laser welds, were employed in order to characterize the crack propagation behaviour under different conditions, producing either an increase or a reduction of the stress intensity factor due to external loads. Test results are analysed by means of a non‐linear numerical model (based on the weight function method) and a knowledge of the fatigue crack growth properties of the base material, free from residual stresses. The results of the analysis are discussed with reference to experimental trends, in order to clarify the predictive capabilities of the method and aspects needing further investigation.
A SHEAR STRESS BASED CRITICAL‐PLANE CRITERION OF MULTIAXIAL FATIGUE FAILURE FOR DESIGN AND LIFE PREDICTION
Authors: McDiarmid D. L.
Published: April 2007

Abstract— The use of a previously presented general criterion of failure for high cycle multiaxial fatigue, τa/tA,B+σn.max/2σT= 1, is extended to cases where the shear and normal stress on the critical plane are non‐proportional and also to give life predictions in the range of 104 to 106 cycles. The criterion takes account of whether case A cracks, growing along the surface, or case B cracks, growing in from the surface, occur.
FATIGUE STRENGTH AND FRACTURE MECHANISMS OF CERAMIC‐ SPRAYED STEEL IN AIR AND A CORROSIVE ENVIRONMENT
Authors: HWANG J. U. , OGAWA T. , TOKAJI K.
Published: April 2007

Abstract— In order to investigate the fatigue strength and fracture mechanism of ceramic‐sprayed steel, rotary bending fatigue tests were conducted at room temperature in air and 3% NaCl solution using specimens of a medium carbon steel (S45C) with sprayed coating layers of Ni‐5% A1 (under‐coating) and chromia (top‐coating). The results obtained are discussed based on observations of fatigue cracks and experimental data on specimens subjected to individual treatments during the ceramic spraying process. It was found that at a very early stage of fatigue life, cracks were initiated at the interface between under‐ and top‐coating layers, and grew rapidly into the ceramic‐sprayed layer. However, these cracks did not propagate continuously into the substrate, and the final failure was led by the growth of a crack newly initiated at the surface of the substrate steel. Thus, the fatigue strength of the ceramic‐sprayed steel in air could be evaluated due to the property of the substrate. The corrosion fatigue strength of ceramic‐ sprayed steel was improved when compared to that of the substrate steel. However, the coating layer contained many pores, through which NaCl solution was supplied from the specimen surface to the substrate. Corrosion pits were formed at the interface between the under‐coating and the substrate. Subsequently, cracks initiated from the pits and grew into the substrate. Tests were also conducted on specimens whose pores were closed by a shielding treatment. In this case, NaCl solution was supplied to the substrate by cracks initiated in the top‐coating layer. The shielding treatment was effective at low stress levels where fatigue life was more than 107 cycles, while it had little effect on improving corrosion fatigue strength at higher stress levels because of the many cracks initiated in the top‐coating layer.
FATIGUE LIFE AND PENETRATION BEHAVIOUR OF A SURFACE‐CRACKED PLATE UNDER COMBINED TENSION AND BENDING
Authors: Nam K. W. , Ando K. , Ogura N. , Matu1 K.
Published: April 2007

Abstract— The present study is to investigate the fatigue crack propagation behaviour of surface cracks subjected to combined tension and bending stress. An estimation of fatigue crack growth behaviour employed the Newman‐Raju formula before penetration, and a K solution, proposed by the authors, after penetration. Crack length aL at penetration increases with an increase in bending stress. The calculated fatigue crack shape was in good agreement with the experimental shape. It was also found that the crack growth behaviour and the crack shape after penetration can be satisfactorily evaluated using the K solution proposed by the authors.
COMPLEX STRESS INTENSITY FACTORS FOR A CRACK IN A BIMATERIAL BRAZILIAN TEST SPECIMEN
Authors: Fiala Z.
Published: April 2007

Abstract— The stress field in front of a crack tip lying in a plane bimaterial interface is always of a complex nature. The stress intensity factor characterising its asymptotic variation is therefore a complex number and its assessment from a numerical calculation requires the separation of the particular loading modes by an appropriate method. A suitable method is provided by the combination of curve integrals and an auxiliary singular field, enabling this separation by means of simple post‐processing. This method can also be applied to the separation of load modes in front of the crack tip in a homogeneous specimen exposed to a mixed‐mode load.
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.
INTERACTIVE EFFECT OF TWO COPLANAR CRACKS ON PLASTIC YIELDING AND COALESCENCE
Authors: XIN X. J. , RIOS E. R. DE LOS
Published: April 2007

Abstract—

A theoretical study of the conditions for coalescence of two fatigue cracks in a multi‐crack system is presented. As both cracks grow, the near‐side plastic zone sizes of the interacting cracks increase more rapidly than the off‐side zone sizes which results in higher overall crack propagation rates for an interacting crack growth system than the simple addition of individual crack growth rates. The use of a single crack growth model to predict failure in the presence of two or more cracks may therefore underestimate the interaction between cracks and lead to un‐conservative predictions. Some of the theoretical predictions were confirmed by published results of experimental measurements of crack interaction distances in multi‐crack systems.
PLASTIC HINGE MODEL: A GENERALIZATION TO A TWO‐DIMENSIONAL SITUATION
Authors: Manzione P. N. , Perez‐Ipiña J. E.
Published: April 2007

Abstract— Several experimental techniques used in fracture toughness tests are based on the “Plastic hinge” model that permits different fracture mechanics parameters to be determined. This model is only valid under the following conditions: small displacements, small stable crack growth, and small distances between knife edges and the apparent centre of rotation. A generalized model for a two‐dimensional situation is presented which permits a better representation of the phenomena that occur in a test involving crack growth and large displacements. The use of a two‐dimensional factor, that corrects the measured displacements by converting them into ones that would be measured under a one‐dimensional hypothesis, is proposed. In this way the same methodology used for CTOD determination, may again be used.
ELASTIC‐PLASTIC STRESS ANALYSIS OF COLD EXPANDED FASTENER HOLES
Authors: Ball D. L.
Published: April 2007

A closed form solution technique first presented by Hsu and Fonnan for the radial expansion of a fastener hole is extended to include elastic‐plastic unloading and therefore the creation of a reverse yielded zone. In addition, the dependence of interface pressure upon interference with an elastic insert is established. Numerous parametric studies are presented to demonstrate the effect of significant model variables and selected example calculations are compared with experimental results.
NOTCH SENSITIVITY OF ALUMINUM‐LITHIUM ALLOYS IN FATIGUE
Authors: Bian J.‐C. , Tokaji K. , Ogawa T.
Published: April 2007

In order to evaluate the notch fatigue strength and notch sensitivity of aluminum‐lithium, 2090 and 8090, alloys, rotary bending fatigue tests have been carried out using circumferentially notched specimens with different stress concentration factors. The results were compared with those of traditional aluminum, 2024T4 and 7075‐T6511, alloys. It was found that 2090 and 8090 alloys showed superior notch fatigue strength in comparison to the conventional aluminum alloys. The notch sensitivities to the crack initiation limit of the aluminum‐lithium alloys were lower than those of 7075‐T6511, while they were nearly equal to those of 2024T4 for blunt notches. The notch sensitivities to the crack propagation limit were also lower in aluminum‐lithium alloys, in particular the 8090 alloy, than in the conventional aluminum alloys. It was suggested that the decreased notch sensitivities of the aluminum‐lithium alloys were attributed to both the crack propagation mode and the excellent propagation resistance related to their microstructures.
A STATISTICAL MULTI‐SITE FATIGUE DAMAGE ANALYSIS MODEL
Authors: Wang G. s.
Published: April 2007

A statistical model has been developed to evaluate fatigue damage at multi‐sites in complex joints based on coupon test data and fracture mechanics methods. The model is similar to the USAF model, but modified by introducing a failure criterion and a probability of fatal crack occurrence to account for the multiple site damage phenomenon. The involvement of NDI techniques has been included in the model which can be used to evaluate the structural reliability, the detectability of fatigue damage (cracks), and the risk of failure based on NDI results taken from samples. A practical example is provided for rivet fasteners and bolted fasteners. It is shown that the model can he used even if it is based on conventional S‐N coupon experiments should further fractographic inspections be made for cracks on the broken surfaces of specimens.
DAMAGE MECHANICS APPROACH TO REMOVE THE CONSTRAINT DEPENDENCE OF ELASTIC–PLASTIC FRACTURE TOUGHNESS
Authors: Wang T.‐J. , Kuang Z.‐B.
Published: April 2007

It is now generally agreed that the applicability of a one‐parameter J‐based ductile fracture approach is limited to so‐called high constraint crack geometries, and that the elastic‐plastic fracture toughness J1c, is not a material constant but strongly specimen geometry constraint‐dependent. In this paper, the constraint effect on elastic‐plastic fracture toughness is investigated by use of a continuum damage mechanics approach. Based on a new local damage theory for ductile fracture(proposed by the author) which has a clear physical meaning and can describe both deformation and constraint effects on ductile fracture, a relationship is described between the conventional elastic‐plastic fracture toughness, J1c, and crack tip constraint, characterized by crack tip stress triaxiality T. Then, a new parameter Jdc (and associated criterion, Jd=Jdc) for ductile fracture is proposed. Experiments show that toughness variation with specimen geometry constraint changes can effectively be removed by use of the constraint correction procedure proposed in this paper, and that the new parameter Jdc is a material constant independent of specimen geometry (constraint). This parameter can serve as a new parameter to differentiate the elastic‐plastic fracture toughness of engineering materials, which provides a new approach for fracture assessments of structures. It is not necessary to determine which laboratory specimen matches the structural constraint; rather, any specimen geometry can be tested to measure the size‐independent fracture toughness Jdc. The potential advantage is clear and the results are very encouraging.
STRESS INTENSITY FACTORS FOR CIRCUMFERENTIAL SURFACE CRACKS IN PIPES
Authors: Bergman M.
Published: April 2007

Abstract Stress intensity factors for circumferential surface cracks in pipes have been derived using the finite element method. Both cracks located at the in‐ and outside of the pipes have been analysed. The derived solutions cover a wide range of geometry and load configurations and are presented in a tabular form that defines influence functions for the stress intensity factor along the whole crack front. The solutions show good agreements in comparisons to other published solutions.
A FATIGUE LIFE MODEL FOR GENERAL ROLLING CONTACT WITH APPLICATION TO WHEEL/RAIL DAMAGE
Authors: Ekberg A. , Bjarnehed H. , Lundbéan R.
Published: April 2007

Abstract A high cycle fatigue model for the prediction of component lifetime in elastic rolling contacts is developed and applied. Varying magnitudes and positions of the contact loads are described by use of discretized statistical distributions. Longitudinal and lateral adhesion are included. The Hertzian contact pressures are analytically found, and the corresponding subsurface stresses are calculated using a numerical integration scheme starting from the exact point force solutions of Boussinesq and Cerruti. Triaxial fatigue with rotating directions of principal stresses is studied using the Dang Van fatigue initiation criterion, together with the Palmgren‐Miner damage accumulation law. The full model has been implemented in a computer code. A wheel/rail contact problem is treated and the results are compared to previous numerical and experimental data.
FRACTOGRAPHIC ANALYSES OF FATIGUE CRACK GROWTH IN D16T ALLOY SUBJECTED TO BIAXIAL CYCLIC LOADS AT VARIOUS R‐RATIOS
Authors: Shanyavsky A. A. , Orlov E. F. , Koronov M. Z.
Published: April 2007

Abstract Fractographic peculiarities of fatigue crack development are studied in cruciform specimens of D16T aluminium alloy under biaxial tension and tension‐compression. In the range of the biaxial load ratios λ from ‐ 1 to +1.5, and in the range of R‐ratios 0.05 to 0.8, fatigue striation formation took place over a crack growth rate near to 4×10−8 m/cycle. The striation spacing and the crack growth rate decrease as the ratios λ and R increase. The ratio between the increment of crack growth, da/dN, and the striation spacing, δ, is approximately 1:1 when da/dN is greater than 4×10‐−8 m/cycle. The relationship between the number of cycles from the beginning of a test up to the growth rate of 2.14×10−7 m/cycle (Nd), and the crack growth period, Np, from when the crack initiates up to the instant when that growth rate is reached, was determined for different λ and R‐ratios. The value of Nd increases as the stress ratio, λ, is increased.

Cycle loading parameters must be taken into account in order to describe the crack growth period when using a unified method involving an equivalent stress intensity factor Ke, =K1,F(λ, Rs). The values of F(λ, R) for the growth rate (F(λ, R)s) and for the striation spacing (F(λ, Rs) were determined and compared.

The fatigue crack growth period, Ntp, applicable to the stage of fatigue striation formation, (predicted by using both of the F(λ, R) values) is correlated with the experimental data and the error is of the order of 15%.
THE BLUNTING LINE IN ELASTIC‐PLASTIC FRACTURE
Authors: Landes J. D.
Published: April 2007

AbstractThe blunting line evaluation procedure used in the ESIS standard fracture toughness test method “Procedure for Determining the Fracture Behaviour of Materials” is re‐evaluated to see if a simpler format can be developed. An equation based on the ultimate tensile strength was found to represent the blunting line in a simple manner. This equation is in error at most ±5% from the analytical representation and is as accurate as the graphical procedure used to determine the blunting line. It is recommended that this equation be used for fracture toughness test standards which use the ESIS blunting line. A comparison of the ESIS blunting line and the ASTM blunting line is made using someJ‐Rcurve data generated with an elastic unloading compliance test procedure. These data do not favor one line over the other. Microscopic evaluation of the blunting line reported in the literature using the stretch zone width measured on the fracture surface suggests that the ESIS blunting line better represents the physical blunting process.
A FATIGUE‐CRACK‐GROWTH‐BASED ANALYSIS OF TWO‐STEP CORROSION FATIGUE TESTS
Authors: Ishihara S. , McEvily A. J. , Shiozawa K.
Published: April 2007

AbstractA method for the analysis of two‐step fatigue level sequences is proposed and compared with experimental results. Two‐step loading tests of the aluminum alloy 2017‐T4 in 3% sodium chloride solution have been carried out in conjunction with a replica technique used to monitor the growth of fatigue cracks. Fatigue cracks were nucleated at corrosion pits 10–15 μm in size, and crack growth rather than crack initiation was found to take up the major portion of the fatigue lifetime in these tests. The results could therefore be analyzed on the basis of the following constitutive relation for fatigue crack growth. da/dN=A(ΔKeff‐ΔKeffth)2

This analysis was simplified since the influence of transients in the crack growth rate induced upon change in load level was found to be minimal. The approach provides a rational basis for dealing with load‐sequence effects.
THE EFFECT OF GRAIN SIZE ON THE FATIGUE OF COMMERCIALLY PURE ALUMINIUM
Authors: Turnbull A. , De Los Rios E. R.
Published: April 2007

Abstract— Fully reversed uniaxial fatigue tests were performed on polished hour‐glass specimens of commercially pure aluminium with three different grain sizes, in order to examine the effect of grain size on fatigue. The growth of surface cracks was monitored by a plastic replication method. An improvement in fatigue strength was observed, as the polycrystal grain size was refined. The endurance limit stress was shown to depend on the inverse square root of the grain size as described empirically by a type of Hall‐Petch relation. The effect of refining grain size on fatigue crack growth is to increase the number of microstructural barriers to the advancing crack and to reduce the slip length ahead of the crack tip, and thereby lower the crack growth rate. Multiple crack initiation and growth is a feature of the fatigue of aluminium, while the grain size influences the specific detail of crack coalescence. Crack path deviation is greatest in the coarse grained microstructure and crack surface roughness is more pronounced. SEM fractography reveals that crack initiation and early crack growth takes place along crystallographic slip planes, and that fatigue striations, characteristic of stage II cracking, extend to the very edge of the specimen section, suggesting extensive crack tip blunting.
AGEING EFFECTS ON FATIGUE CRACK CLOSURE OF AN Al–Li–Zr ALLOY IN Na2SO4, SOLUTION
Authors: Chun Y.‐G. , Pyun S‐I.
Published: April 2007

Abstract— Fatigue of an Al–Li–Zr alloy has been studied as a function of ageing stage by measuring crack closure in Na2SO4 solution with an unloading elastic compliance technique and comparing results in dry air and oxygenated solution. Anodic behaviour of peak‐aged and overaged alloy specimens in the Na2SO4 solution has been investigated by potentiodynamic polarisation and potentiostatic current transient experiments. The Na2SO4 solution increased the intrinsic fatigue crack propagation (FCP) rate for the overaged specimen in dry air compared to that for the peak‐aged sample. The Na2SO4 solution inhibited the development of crack closure for the peak‐aged specimen in dry air, but aided it in the overaged condition. The result of the environmental crack closure study is discussed in terms of the more enhanced through‐thickness tortuosity of the overaged specimen in the Na2SO4 solution when compared to that of the peak‐aged specimen. The oxygen dissolved in the Na2SO4 solution slightly increased the environmental intrinsic FCP rate, which seems to be due to the reduced repassivation rate as compared to that in the N2‐purged solution. The anodic dissolution rate from the bare surface of the overaged specimen in the Na2SO4 solution was higher than that from the peak‐aged sample. The difference between environmental FCP rates and crack closures for the peak‐aged and overaged specimens is discussed in terms of environment‐assisted crack‐tip damage processes involving anodic dissolution.
FRACTURE BEHAVIOUR OF Al12wt.%Si0.35wt.%Mg(0–0.02)wt.%Sr CASTING ALLOYS UNDER FATIGUE TESTING
Authors: Lee F. T. , Major J. F. , Samuel F. H.
Published: April 2007

Abstract— A systematic study of the fatigue crack growth characteristics and mechanisms in Al–Si–Mg and A356 casting alloys was carried out. Compact tension specimens, prepared from modified and unmodified alloys were tested at different stress ratios and stress intensity factor range values, and a study of the mechanistic role of the silicon particles in influencing the fracture behaviour during fatigue crack propagation was made, employing both optical and scanning electron microscopy. The results indicated that the fatigue crack growth behaviour of the alloys is affected by the stress ratio, stress intensity level and the size, shape and distribution of the eutectic silicon particles. The particle characteristics also determine the fracture mode of the alloy. Fracture Characteristics observed include decohesion of the silicon particles from the aluminum matrix; silicon particle cleavage/cracking; and striations in the aluminum phase, particularly at high stress ratios.
EFFECT OF SENSITIZING HEAT TREATMENT ON FATIGUE CRACK GROWTH PROPERTIES AT LIQUID HELIUM TEMPERATURE
Authors: Konosu S. , Kishiro T. , Ivano O. , Nunoya Y. , Nakajima H. , Tsuji H.
Published: April 2007

Abstract Many cases exist where material supporting superconducting magnets at liquid helium temperature (4.2 K) are subjected to repeated applications of thermal and electromagnetic stresses. Additionally, since welding cannot be avoided, it is highly desirable that the materials used for supporting superconducting magnets possess excellent strength and toughness in addition to superior mechanical properties after heat treatment. In the current research, an austenitic stainless steel was subjected to a sensitizing heat treatment whose effects, at 4.2 K, on the tensile and the fatigue crack growth properties were clarified. Tensile ductility of the sensitized material was markedly reduced to about one‐half that of the solution treated material because of an intergranular form of fracturing in such material. Fatigue crack growth rate of the sensitized material was faster than that of the solution treated material because of the tendency for cracks to develop intergranularly.
EFFECT OF OVERSTRESSING ON FATIGUE BEHAVIOUR OF AUSTEMPERED DUCTILE IRON
Authors: Rao P. Prasad , Padmaprabha
Published: April 2007

Abstract Studies have been conducted on the effect of overstressing in rotary bending fatigue on the fatigue properties of an annealed and austempered ductile iron containing 1.5 Ni–0.3 Mo. For various R ratios S–N curves were determined and the fatigue limit estimated. It was found that the fatigue limit was a function of the level of overstressing and cycle ratio. In the case of austempered samples a beneficial effect of overstressing was observed at a certain level of overstressing. This was related to the work hardening behaviour of the austenite phase. In annealed samples, a reduction in the fatigue limit was observed at all levels of overstressing.
A PROCEDURE FOR DETERMINING THE FRACTURE BEHAVIOUR OF MATERIALS—THE UNIFIED FRACTURE MECHANICS TEST METHOD EFAM GTP 94
Authors: Schwalbe K.‐H. , Neale B.
Published: April 2007

Abstract— A unified fracture mechanics test method for quasi‐static testing of materials is described. It builds on the ESIS Procedures P1 and P2 and introduces additional aspects, such as the δ5 crack tip opening displacement, non‐standard CT and SENB specimen configurations, centre cracked tensile specimens, testing of weldments, and guidance for statistical treatment of scattered data.
AN ANALYTICAL PROCEDURE FOR PREDICTING OPENING LOADS OF CRACKS AT NOTCHES
Authors: Savaidis G. , Dankert M. , Seeger T.
Published: April 2007

Abstract—An analytical procedure for the prediction of opening load levels for cracks growing from notches is presented, and estimates are made using experimental crack opening load data. The procedure is based on McClung's original procedure for estimating the local elastic‐plastic stress—strain situation at the point of a hypothetical crack tip in a notched but uncracked body. A crack opening stress value for a crack in an urmotched body under the same stress—strain condition is then predicted. The corresponding opening load level for the crack stress‐strain configuration in the notched but uncracked body is then predicted with a simple backward calculation. For the evaluation of the elastic‐plastic stress distribution, simple analytical relationships, such as Neuber's rule, are used. Estimation of the crack opening stress level is performed using various crack opening stress formulae reported in the literature for cracks in unnotched specimens under a uniform stress distribution. The accuracy of all the investigated crack opening stress formulae within the scope of the presented procedure is checked, and discussed in detail using experimental data sets for opening load levels of comer cracks and through‐thickness cracks in notched specimens of FeE460 and A15086. The predicted results using Newman's crack opening stress formulae, simply modified in respect to the definition of the flow stress, have been identified to be qualitatively and quantitatively consistent with the trends observed in experimental crack opening data.
AN EXPERIMENTAL INVESTIGATION INTO THE OPERATIONAL SAFETY OF A WELDED PENSTOCK BY A FRACTURE MECHANICS APPROACH
Authors: Sedmak S. , Sedmak A.
Published: April 2007

Abstract—Three different fracture mechanics approaches were applied to two full‐scale penstock model tests. The two models were produced, using a Sumiten 80P HSLA steel (minimum yield strength 700 MPa and minimum ultimate tensile strength 800 MPa), in the form of pressure vessels. The first experiment was a burst test performed on a pre‐cracked model to determine crack arrest properties. The second experiment was a hydro‐pressure test on a model with no cracks and this enabled a post‐yield experimental analysis of the undermatched weld metal, when cracks did not initiate. Crack driving forces, obtained numerically, and J‐R curves, obtained by the J‐integral direct measurement on tensile panels, were used to predict the residual strength. The overall behaviour of a welded penstock under load was analysed on the basis of the results of these three approaches, allowing an evaluation of the significance of cracks.
A STUDY OF FATIGUE AND CREEP BEHAVIOUR OF FOUR HIGH TEMPERATURE SOLDERS
Authors: Liang J. , Gollhardt N. , Lee P. S. , Schroeder S. A. , Morris W. L.
Published: April 2007

Creep and cyclic deformation behavior of two lead‐free high temperature solder alloys, 95Sn‐5Ag and 99Sn‐1.0Cu, a high lead alloy 97.SPb‐1.SAg‐1.0Sn, and an Ag‐modified eutectic alloy 62.SSn‐36.1Pb‐1.4Ag, were studied. Room temperature and high (100°C and 150°C) temperature fatigue tests (with cyclic strain amplitude up to 6.0%) for the four solders were conducted, with the fatigue lives ranging from a few cycles to more than 100,000 cycles. It is shown that among the alloys studied, 62.SSn‐36.1Pb‐1.4Ag (the modified Sn‐Pb eutectic alloy) has the lowest fatigue resistance in term of low cycle fatigue life (strain controlled). The high lead alloy, 97.SPb‐1.5Ag‐1.0Sn, has the highest strain fatigue resistance in the large strain region (Δ > 2.0%). Temperature has a significant effect on alloys 95Sn‐5Ag and 99Sn‐1.0Cu, but has a negligible effect on the Ag modified Sn‐Pb eutectic alloy 62.5Sn‐36.1Pb‐1.4Ag and 97.5Pb‐1.5Ag‐1.0Sn. Creep studies show that these alloys generally have a very significant primary creep regime (up to 20%); thus, any realistic constitutive relation has to take such a primary creep phase into consideration. Cyclic deformation of alloy 95Sn‐SAg was simulated by using a constitutive relation built upon a 2‐cell model, which covers both primary and secondary creep. This model provides a good estimate of the peak stresses (the minimum stress and the maximum stress in each cycle); it agrees with experimental results when the applied cyclic strain is small and/or the applied strain rate is very low.
STATIC AND CYCLIC FRETTING FATIGUE BEHAVIOUR OF SILICON NITRIDE
Authors: Okane M. , Mutoh Y. , Kishi Y. , Suzuki S.
Published: April 2007

A cyclic fretting fatigue test machine was constructed. The piezoelectric bimorphs were used as actuators for cyclic loading and fretting motion at the resonance frequency of the system. Fretting fatigue tests under static and cyclic loading conditions were carried out using HIP‐sintered silicon nitride. From the experimental results, it was found that fretting fatigue strengths under the two test conditions were identical and hence the effect of cyclic loading on fretting fatigue strength of silicon nitride was almost negligible. A fretting crack initiated in a very early stage of the fatigue life at the position of the maximum frictional stress in the contact area. Fretting fatigue life prediction based on fracture mechanics was also carried out. The predicted lives were in good agreement with the experimental results.
ON A POSSIBLE MECHANICAL QUANTIFICATION OF FATIGUE DAMAGE
Authors: Galtier A. , Seguret J.
Published: April 2007

Abstract— Criteria exist in the field of multiaxial fatigue for predicting the cyclic lifetime for a high number of cycles. They can predict the fracture of a part, but they are not able to calculate the damage level introduced. Since such theories are often used in Research and Development departments, we have based this present study on these criteria. Experiments were made on more than 1000 specimens that now allow us to propose a general procedure for the use of multiaxial criteria after pre‐cycling, i.e. for non‐virgin materials. We also suggest the introduction of a threshold, which depends on the damage level, to filter out small cycles.
BIAXIAL HIGH CYCLE FATIGUE TESTS ON A GAS TRANSMISSION PIPELINE STEEL
Authors: Batisse R. , Fant‐Jaeckels H. Di , Curie F. , Virely J. M.
Published: April 2007

Abstract— Gas transmission pipes are sometimes subject to external damage due to interference by excavators. Optimized grinding of gouges may offer a solution in repairing pipes. Since pipelines may be subjected to internal pressure variations, the Dang Van criterion has been used to size the allowable grinding depth. The criterion's boundary has been determined from uniaxial fatigue testing and extrapolated to the higher hydrostatic pressure which occurs in practice. The aim of this paper is to check by means of biaxial fatigue tests on specimens, that this extrapolation ensures a lifetime of 105 cycles for the ground pipes. The state of stresses in the central area of the biaxial specimen was calculated from an elastic finite element simulation. The test machine had independent motions of the two perpendicular axes of loading. The fatigue testing was limited to 105 cycles and was carried out at a hydrostatic pressure of 200 MPa. The results validated the extrapolation technique for the Dang Van criterion.
A TEST METHOD FOR MODE II FATIGUE CRACK GROWTH RELATING TO A MODEL FOR ROLLING CONTACT FATIGUE
Authors: Otsuka A. , Sugawara H. , Shomura M.
Published: April 2007

Abstract— From fractographic observations of specimens that have failed due to rolling contact fatigue, it has been concluded that the first stage of damage is the formation of mode II fatigue cracks parallel to the contact surface due to the cyclic shear stress component of the contact stress. Although these initial subsurface cracks, in both metals and ceramics, are produced in a direction parallel to the cyclic shear stress, cracks eventually grow in a direction close to the plane of the maximum tensile stress if we apply a simple mode II loading to them. The difference between crack growth in simple mode II loading and crack growth due to rolling contact fatigue is, we suppose, whether or not there is a superimposed compressive stress. Based on this hypothesis, we developed an apparatus to obtain the intrinsic characteristics of mode II fatigue crack growth, and developed a simplified model of subsurface crack growth due to rolling contact fatigue.

Some results in terms of da/dN versus ΔKII relations have been obtained using this apparatus on specimens of steel and aluminum alloys. Fractographs of the mode II fatigue fracture surfaces of the various materials are also provided.
FATIGUE DAMAGE IN TWO‐STEP LOADING OF 316L STEEL II. SHORT CRACK GROWTH
Authors: Vašek A. , Polák J. , Obrtlíak K.
Published: April 2007

Abstract— The evolution of the surface crack distribution in single‐step and two‐step plastic strain amplitude controlled cycling was studied. The frequency of crack occurrence and total crack density were evaluated together with crack growth rates of the largest cracks. The crack density increases, reaches a maximum, and then decreases during fatigue life. The maximum value of crack density partitions the whole life into a “crack generation period” and a “crack propagation period”. In the first period the crack growth rate is approximately constant and is determined by the applied plastic strain amplitude. The crack growth rate increases with crack length in the second period, but is basically determined by the crack growth rate in the “crack generation” period. Hence the crack growth rate in the “crack generation” period is the life determining factor.
FATIGUE STRENGTH OF BUTT‐WELDED JOINTS UNDER CONSTANT MAXIMUM STRESS AND RANDOM MINIMUM STRESS CONDITIONS
Authors: Ohta A. , Maeda Y. , Suzuki N.
Published: April 2007

Abstract— The fatigue strength of steel welded joints has been obtained by tests in which the maximum applied stress, σmax, was kept constant and equal to the yield strength, σy, (which is equivalent to the tensile residual stress that exists in real welded structures) while the minimum stress was changed randomly. The equivalent range of applied stress, calculated by neglecting the stress cycles for which amplitudes were below the fatigue limit that was determined from constant amplitude tests, can be a useful design parameter. This is confirmed because Miner's rule applies for all the σmax=σy tests reported here and which simulate the actual stress condition of welded structures and gives the lowest S‐N curve.