bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytokine, chemokine and growth factor expression in the pathogenesis of progressive renal damage
Authors: SCHENA F Paolo , GRANDALIANO Giuseppe , MONTINARO Vincenzo , RANIERI Elena , MONNO Raffaella , GESUALDO Loreto
Published: April 2007

Summary: Chronic renal diseases are untreatable conditions characterized by a final phase of progressive impairment of renal function, leading to end‐stage renal failure (ESRF). Once the primary injury has damaged a part of the nephron, the remainder undergo a number of adaptative changes leading to glomerulosclerosis, interstitial fibrosis and, consequently, end‐stage kidney disease. Glomerular lesions, mainly represented by mesangial cell proliferation, mononuclear cell infiltration and extracellular matrix deposition, have always been considered as the key factors in the progression of renal damage. However, in this context, it is now clear that the degree of tubulointerstitial damage is a better prognostic marker than the extent of glomerular lesions. Tubulointerstitial involvement is characterized by monocyte and neutrophil infiltration, tubular atrophy, proliferation of interstitial fibroblasts, that acquire a myofibroblast‐like phenotype and, finally, extracellular matrix deposition. the pathogenesis of these histological changes is largely unknown, but there is an increasing body of evidence suggesting the possible involvement of some soluble factors produced and released locally, such as cytokines, chemokines and growth factors. Aiming to elucidate the pathogenetic mechanisms underlying glomerular and tubulointerstitial damage in progressive renal diseases, we investigated the renal gene and protein expression of some of these soluble factors. On the basis of the histopathological lesions, we decided to focus our attention on monocyte chemotactic peptide‐1 (MCP‐1), a specific chemotactic and activating factor for monocytes, on complement C3, a powerful activator of neutrophils, on epidermal growth factor (EGF), the physiological modulator of tubular cell growth, on platelet‐derived growth factor (PDGF), the most powerful mitogenic and activating peptide for mesenchymal cells and on transforming growth factor‐β (TGF‐β), the main regulator of extracellular matrix synthesis and degradation.
In situ hybridization analysis in IgA nephropathy
Authors: MIYAZAKI Masanobu
Published: April 2007

Summary: In situ hybridization provides much information on gene expression in renal biopsy specimens and is useful for detecting intrarenal cells producing molecules that are also present in the circulation. These molecules may deposit in the glomeruli. In situ hybridization is also useful for detecting cells producing cytokine that may be secreted immediately from such cells. Finally, in situ hybridization is useful for detecting extracellular matrix producing cells. Semiquantitative in situ hybridization is useful for assessing the retained RNA in the tissue and comparing the expression of specific mRNA in different tissues. This method may be useful in predicting the clinical outcome at the time of renal biopsy. In conclusion, in situ hybridization allows for the evaluation of cell function in human renal biopsy specimens. It not only provides information related to cell morphology, but also provides an estimation of functionality of human renal biopsy specimens.
Histological classification of IgA nephropathy: Grading and staging
Authors: SHIGEMATSU Hidekazu
Published: April 2007

Summary: More than 30% of IgA nephropathy cases progress to end‐stage renal failure within 20 years. Histologically this disease is made up of at least three types of tissue damage: (i) minimal inflammation including deposition of IgA containing substances with minor matricial increase; (ii) acute lesions characterized by matricial damage with inflammatory cell accumulation; and intrinsic cell proliferation; and (iii) chronic lesion, mainly composed of postinflammatory sclerosis. Progression is accelerated by the frequency of acute lesions, resulting in the increased glomerular sclerosis. the histologic grading and staging (G‐S system) aims to enhance our understanding of IgA nephropathy. the histological grade (G) is estimated by the extent of acute glomerular and tubulointerstitial lesions, while the stage (S) is evaluated by the increase of extracellular matrices of the glomeruli and interstitial fibrosis. the evaluation of the G and S is expressed semiquantitatively for more helpful use in the clinical side.
Treatment of IgA nephropathy: an overview
Authors: D'AMICO Giuseppe
Published: April 2007

Summary: The results of proposed approaches to the treatment of IgA nephropathy are discussed, stressing the difficulty of their correct evaluation due to the variable evolution of the disease. There is no convincing evidence that supports a beneficial effect for many of the therapeutical remedies with the following exceptions: (i) steroids are effective in the rare patients with selective proteinuria in the nephrotic range and very mild lesions by light microscopy (minimal change nephropathy with IgA mesangial deposits). the use of steroids is useful, in association with cyclophosphamide, even in patients with morphological features of intraglomerular capillaritis (segmental necrotizing lesions) and/or extracapillary proliferation in more than 25% of glomeruli (independently of the presence of diffuse circumferential crescents and a rapidly progressive course). A controlled trial that is underway will attempt to establish whether steroids can be effective in retarding deterioration of renal function in other subgroups of patients at risk of progression; (ii) fish‐oil, administered orally (12 g/day for 2 years), is beneficial in patients at risk of progression (marked proteinuria, moderately impaired renal function, arterial hypertension and morphological features of active disease); and (iii) long‐term administration of angiotensin converting enzyme (ACE)‐inhibitors, even in the absence of arterial hypertension, seem to slow the progression and reduce the protein loss in the same group of patients at risk.
FATIGUE THRESHOLDS AND DUCTILE‐BRITTLE TRANSITIONS IN Ti‐30Mo
Authors: JATAVALLABHULA K. , GERBERICH W. W.
Published: April 2007

Abstract—

Substantial effects of hydrogen are found on the DBTT and cleavage fracture stress in both cathodically and gas phase charged samples of a BCC Ti alloy. Fatigue thresholds when plotted as a function of temperature exhibit a peak and this peak shifts towards higher temperatures when the hydrogen level is increased. An elastic calculation of static threshold stress intensities using experimentally observed fracture stress parameters show a similar trend to fatigue threshold stress intensities.
INTRINSIC MATERIAL SCATTER IN FATIGUE CRACK PROPAGATION
Authors: SHAW W. J. D. , MAY I. LE
Published: April 2007

The statistical nature of fatigue crack growth rate has been examined for G41400 steel exposed to different heat treatments and for different loading and environmental conditions. Techniques for determining the intrinsic value of the crack propagation rate are discussed. The intrinsic scatter due to the material has been evaluated and considered in terms of its effect on fatigue life prediction, both normal and log normal distributions of fatigue crack growth data being considered. It appears that the intrinsic material scatter in crack propagation rate is closely related to the scatter in total life.
A METHOD OF CREEP DAMAGE SUMMATION BASED ON ACCUMULATED STRAIN FOR THE ASSESSMENT OF CREEP‐FATIGUE ENDURANCE
Authors: Hales R.
Published: April 2007

Abstract— A method of combining long term creep data with relatively short term mechanical behaviour to provide an estimate of creep‐fatigue endurance is presented. It is proposed that the creep‐fatigue effect in high temperature cyclic deformation is governed by a difference in strain rate around the cycle and the associated variation in ductility with strain rate.
THE EFFECT OF MODE III LOADING ON FATIGUE CRACK GROWTH IN A ROTATING SHAFT
Authors: Akhurst K. N. , Lindley T. C. , Nix K. J.
Published: April 2007

Abstract— Four particularly pronounced beachmarks have been identified on the fracture surface of a cracked rotor. A correlation has been made between these beachmarks and events in the operational record. Fatigue crack growth calculations have been performed for a chordally cracked shaft subject to alternating self‐weight bend stresses. The shaft dimensions and loading used correspond to the position of the crack in the rotor and growth rates were calculated over a range of crack depths spanning the positions of the major beachmarks. The results of the calculations agree with the beachmark correlation if allowance is made for the effect of the torsional loading of the shaft.
INFLUENCE OF AN OVERLOAD ON THE FATIGUE CRACK GROWTH IN STEELS
Authors: ROBIN C. , LOUAH M. , PLUVINAGE G.
Published: April 2007

Abstract— This study is concerned with the influence of a single‐peak overload and the overload ratio on the subsequent rate of growth of a fatigue crack in steels. Retardation increases with increasing overload ratio.

The crack opening load was also measured during all tests. It is shown that the Elber's crack closure concept is not able to explain the effect of overloads. The importance of the material yield stress was evaluated by testing steels of different strength. It seems that the residual stress state induced by the overload is the major factor causing retardation. Two models are analyzed.
ON THE RELATION BETWEEN STABLE CRACK GROWTH AND FATIGUE
Authors: KAISER S.
Published: April 2007

Abstract— Fatigue crack growth in the intermediate range can be described by the Paris law of linear elastic fracture mechanics. However, if gross plastic deformation is involved, the crack growth rate is often underestimated by LEFM. In the present study the increased crack growth rate due to plastic deformation is determined by using the J–R curve. This model was found to give very good results over a wide range of high crack growth rates for three different geometries of two different steels. A way to predict instability under controlled cyclic load is discussed and is proved to work well in practice. Instability under displacement control is also discussed.
A STUDY OF SHORT FATIGUE CRACK GROWTH BEHAVIOUR IN TITANIUM ALLOY IMI 685
Authors: BROWN C. W. , HICKS M. A.
Published: April 2007

Abstract— The fatigue growth of short cracks in coarse grained IMI 685, having an aligned a microstructure, has been monitored using a two stage replication technique. Crack growth rates are presented in terms of the failure mechanism and compared with standard data obtained from through cracked, compact tension specimens. The maximum difference, of up to four orders of magnitude, between long and short crack growth rates is associated with separation along specific crystallographic planes resulting in a cleavage‐like fracture appearance. The rate of short crack growth is also shown to be dependent on applied stress and a dwell at maximum load during the fatigue cycle.
ANISOTROPIC YIELD SURFACES IN CYCLIC PLASTICITY
Authors: HARVEY S. J. , ADKIN P. , JEANS P. J.
Published: April 2007

Abstract— An anisotropic form of the Von Mises yield criteria is presented which includes linear terms and therefore enables Bauschinger effects to be considered when constructing yield or loading surfaces.

The coefficients representing the state of anisotropy are expressed in terms of the uni‐axial and shear yield stress of the material. It is suggested that this form of the yield or loading surface can be used to determine the plastic strains for a range of multi‐axial and cyclic plasticity problems and results are presented for the particular case of a tube subjected to cyclic plastic torsion with an axial stress.
THE EFFECT OF CRACK LENGTH ON FATIGUE THRESHOLD
Authors: Taylor D.
Published: April 2007

This paper puts forward a new method for analysing the behaviour of very short fatigue cracks. A probability function is introduced into the definition of the growth threshold, which rationalises the scatter in experimental data produced using an aluminium bronze alloy. This probability function can be visualised in terms of the microstructure of the material.

It is shown that, in this material as in mild steels, fatigue crack initiation is not the critical stage. Initiation occurs relatively easily, but the cracks so formed may grow to only a few grain diameters in length before being arrested; thus it is the behaviour of cracks of this length which is critical in determining the fatigue strength of the material.

These observations, when combined with the probability functions, allow estimation of the probability of failure of a component or structure in service with greater confidence than the methods used at present.
SMALL FATIGUE CRACK GROWTH BEHAVIOUR UNDER TWO STRESS LEVEL MULTIPLE LOADING
Authors: Tokaji Keiro , Ando Zenji
Published: April 2007

Small fatigue crack growth behaviour in a low alloy steel was investigated under two stress step multiple loading in which the secondary stress was below the fatigue limit. Crack growth rates were presented in terms of a stress intensity factor and compared with data obtained under constant amplitude loading. In the higher ΔK region, crack growth rates increased monotonously with increasing ΔK even though the stress level was below the fatigue limit, and tended to be lower than those for constant amplitude loading. In the lower ΔK region, cracks showed a complicated behaviour, that is, an initial high growth rate was observed followed by an arrest or a drop to a minimum value and then a gradual increase. The average crack growth rates per cycle at both primary and secondary stresses in each block were approximately consistent with the da/dn‐ΔK relation for constant amplitude loading. A suggestion for the prediction of crack growth life is given.
ANALYSIS OF THE LOW‐CYCLE FATIGUE BEHAVIOUR OF TWO Ni‐Cr‐BASE ALLOYS
Authors: Day M. F. , Thomas G. B.
Published: April 2007

The low‐cycle fatigue performance of the Ni‐Cr‐base alloys IN597 and IN738 has been examined with particular reference to the creep‐fatigue interaction. Results are reported showing a systematic effect on life of IN597 of the level of tensile stress during tests involving cycles with dwell periods. For both alloys the simple life fraction rule correlates the data in a fairly satisfactory manner but some method of stress compensation is necessary for the strain range partitioning (SRP) method. Certain limitations of the SRP method in dealing with results from highly creep resistant alloys are discussed.
ENVIRONMENTAL SENSITIVITY OF SMALL CRACK GROWTH IN 7075 ALUMINIUM ALLOY
Authors: Zeghloul A. , Petit J.
Published: April 2007

Fatigue propagation tests on artificial short cracks (initial length ˜ 0.15 mm) were performed in vacuum and in nitrogen containing small traces of water vapour (˜ 3 ppm) on a high strength aluminium alloy type 7075 in two aged conditions (T651 and T7351) at a load ratio of 0.1 and a frequency of 35 Hz. A predominant influence of environment was determined for short crack growth. This behaviour has been discussed in terms of crack growth rate versus the effective stress intensity factor range relationship previously determined for long cracks. The results obtained suggest the absence of closure at the early stage of short crack growth with an enhanced environmental influence as compared to long crack behaviour at the same load ratio. As the crack grows the effect of closure increases progressively and the short crack effect disappears after a crack growth of the order of 1 mm.
THE GROWTH OF SMALL FATIGUE CRACKS IN A LOW CARBON STEEL; THE EFFECT OF MICROSTRUCTURE AND LIMITATIONS OF LINEAR ELASTIC FRACTURE MECHANICS
Authors: Tokaji Keiro , Ogawa Takeshi , Harada Yukio
Published: April 2007

The growth characteristics of small fatigue cracks were studied under rotary bending in a low carbon steel prepared with two ferrite grain sizes of 24 and 84 μm, and were compared with the growth characteristics of large through cracks in fracture mechanics type specimens. The effect of microstructure on crack growth rates and the interaction in growth behaviour between two neighboring small cracks were examined experimentally, and also the critical crack lengths above which linear elastic fracture mechanics (LEFM) is applicable were evaluated for small crack growth and for fatigue crack thresholds. It is found that small cracks grow much faster than large ones and also show growth rate perturbations due to grain boundaries. It is indicated that the critical crack lengths for fatigue crack thresholds are significantly shorter than those for small crack growth.
COMPARISON OF SHORT AND LONG FATIGUE CRACK GROWTH IN 7075‐T6 ALUMINUM
Authors: Bu R. , Stephens R. I.
Published: April 2007

The fatigue crack growth rates of physically‐short cracks (0.5 ≤a≤ 1.0 mm), intermediate cracks (1 < a≤ 2 mm) and long cracks (7 < a < 25 mm) were compared using SEN type tensile specimens in 7075‐T6 aluminum alloy with load ratios, R, of 0.05, − 1 and 0.5 under constant amplitude testing at room temperature. It was found that the short cracks grew much faster than long cracks based on applied δK with da/dN≤ 10−7 m/cycle. Even the intermediate cracks grew faster than the long cracks below 10−7 m/cycle. The transition crack lengths where similitude with δK existed was between 1 and 2 mm. Mean stress effects were similar for R= 0.05 and − t, but R= 0.5 caused increased crack growth rates. The above differences are partially attributed to crack closure effects. Based upon plastic zone sizes, LEFM was justifiable with all the experiments.
MICROSTRUCTURAL STUDY OF CYCLIC STRAIN HARDENING BEHAVIOUR IN BIAXIAL STRESS STATES AT ELEVATED TEMPERATURE
Authors: Nishino Seiichi , Hamada Naomi , Sakane Masao , Ohnami Masateru , Matsumura Naomi , Tokizane Masaharu
Published: April 2007

This paper describes the cyclic strain hardening behaviour and dislocation structures of material in biaxial low cycle fatigue at elevated temperatures. In this study, push‐pull, reversed torsion and combined push‐pull/reversed torsion tests were carried out using a type 304 stainless steel in air. While there was no significant difference between the cyclic stress amplitudes in the push‐pull and reversed torsion tests on a von Mises' base, combination tests exhibited a 40% increase in stress amplitude. Most of the dislocations in the first two types of test adopted ladder or maze structures, while in the later case cells were found. Changing the loading mode at a certain cycle, for example, from push‐pull to reversed torsion, revealed that stress amplitude depended mainly on the concurrent applied strain mode and furthermore, that the strain mode before the interchange had little or no effect on the stress amplitude after the interchange. Tests were also performed in order to examine how prestrained material hardened in the three different loading modes, with the following results: prestrained material in push‐pull or in reversed torsion exhibited an anisotropic stress response, while the material in the combined tests exhibited an isotropic response. These cyclic responses are discussed in connection with the dislocation structure.
CRACK PROPAGATION STUDIES ON Al 7475 ON THE BASIS OF CONSTANT AMPLITUDE AND SELECTIVE VARIABLE AMPLITUDE LOADING HISTORIES
Authors: Zhang S. , Marissen R. , Schulte K. , Trautmann K. K. , Nowack H. , Schijve J.
Published: April 2007

Abstract— Fatigue crack propagation behaviour under variable amplitude loading is significantly influenced by load history induced sequence effects. Because the understanding of the causes of such sequence effects is still rather limited, crack propagation predictions become difficult. In the present investigation an exploratory test program with simple variable amplitude load sequences was performed, which was designed to improve the general understanding of sequence effects and to offer a basis both for an evaluation of existing crack propagation prediction models and for the development of improved methods.

The investigations were performed on center cracked 8 mm thick Al 7475‐T7351 specimens. In the first part of the study constant amplitude tests were performed over a wide range of R‐ratios. The test results and the transition of the fracture mode during tests could be represented on the basis of the effective ΔK‐value.

In the second part of the paper tests with simple systematically varied sequences of high loads, low loads and underloads were performed and the crack propagation behaviour was measured. In order to obtain detailed information on the crack propagation increments per cycle, fractographic analyses were also performed. It was found that also under variable amplitude loading the crack propagation approximately followed the effective ΔK‐values, except in one case.

A linear (non‐interaction) prediction model could not describe the observed crack propagation behaviour. The results of the application of a model assuming a constant crack opening level are also given. Finally, some general viewpoints regarding further developments of models are outlined.
THE INFLUENCE OF SPECIMEN GEOMETRY ON NEAR THRESHOLD FATIGUE CRACK GROWTH
Authors: Vecchio R. S. , Crompton J. S. , Hertzberg R. W.
Published: April 2007

Abstract— The near threshold fatigue behavior of a nickel base superalloy and a wrought 2024 aluminum alloy is examined as a function of specimen geometry. Experimental results revealed that for a given value of ΔK in Region I, crack growth rates were observed to increase as the specimen loading became more symmetric with respect to the load line. Compact tension type specimens exhibited lower crack growth rates than the more symmetrically loaded center cracked tension specimens. Consideration of the observed discrepancies is given in terms of the near field crack tip stress distribution and deformation behavior of the material affecting crack advance.
WEIGHTED AVERAGED STRESS INTENSITY FACTORS OF CIRCULAR‐FRONTED CRACKS IN CYLINDRICAL BARS
Authors: CASPERS M. , Mattheck C.
Published: April 2007

Stress intensity factors are calculated in weighted average at the surface and the deepest point of a circular‐fronted surface crack in a cylindrical bar by use of the weight function method. A wide range of various crack shapes are studied, from a nearly straight‐fronted edge crack to a semi‐circular crack front. Use of the weight function method requires that the crack opening displacement field of a reference load has to be known. It was obtained by 3‐D finite element analysis. Results are presented for the cracked cylinder subjected to a constant stress (tension) and a linear stress distribution acting perpendicular to the crack faces and they are compared with values found by other investigators.
A STATISTICAL MODEL OF INTERMITTENT SHORT FATIGUE CRACK GROWTH
Authors: Cox B. N. , Pardee W. J. , Morris W. L.
Published: April 2007

The stochastic nature of the growth of short surface fatigue cracks under uniform cyclic loading can be attributed to their interaction with a stochastic microstructure. In this paper, a computational scheme is proposed to describe the statistical effects of the temporary arrest of short cracks by grain boundaries, and the modification of rates of propagation across grains by various effects of grain boundary constraint. The fact that a crack tip may be in one of two states, either temporarily arrested at a grain boundary or actively propagating, is treated explicitly by considering probability densities evolving in complementary state spaces corresponding to each case. The evolution of the densities during fatigue is described by conservation equations, which are solved numerically. It is shown how engineering quantities, such as the time to initiation of a macroscopic crack, can be derived from the calculated densities. The explicitness with which the characteristics of short crack growth are treated greatly enhances the potential accuracy of predictions based on this approach.

The theory is constructed to allow considerable flexibility in the microstructure‐related mechanisms assumed to control growth rates in any given material. However, as it is stated here, the theory is restricted to Mode I (tensile opening) transgranular crack growth under constant amplitude cyclic loading. Examples are given of the various effects that can be treated, as well as those that would require modification of the structure of the computational procedure. The theory is illustrated by an application to data for Al 2219‐T851.
FATIGUE UNDER OUT‐OF‐PHASE BENDING AND TORSION
Authors: McDiarmid D. L.
Published: April 2007

Test data on fatigue under out‐of‐phase bending and torsion has been reanalysed. For the materials tested failure has been found to be consistent with the plane of maximum range of maximum range of maximum principal stress, as for the in‐phase case. The critical shear planes are assumed to be those associated with this principal stress plane. A multiaxial fatigue damage parameter based on the maximum range of shear stress on the critical shear plane allowing for the effect of the range of normal stress occurring on this plane has been used to develop a proposed set of design curves for in‐phase bending and torsion which are conservative for the long life out‐of‐phase case.
A FATIGUE CRACK PROPAGATION MODEL FOR APPLICATION TO SERVICE LOADS
Authors: Ono H. , Tsunenari T.
Published: April 2007

Abstract— The authors previously proposed a simulation model for fatigue crack propagation for varying load ranges by considering retardation behaviour due to high level loads and showed that the model could estimate crack propagation lives under quasi‐random loading. However as the model was somewhat simplified, it was predicted that some problems would occur when estimating lives under actual random loads.

In this study the model was modified by considering the interaction effect of retardation and acceleration processes of crack propagation based on the test results of two and three level load programs. The model was verified by executing random load crack propagation tests.
FATIGUE CRACK PROPAGATION AND CRACK CLOSURE BEHAVIOR IN POLYCARBONATE AND FIBRE REINFORCED POLYCARBONATE
Authors: Murakami R. , Noguchi S. , Akizono K. , Ferguson W. G.
Published: April 2007

Abstract— Fatigue crack propagation was investigated in polycarbonate and glass fibre reinforced polycarbonate and the effect of stress ratio and glass fibre content determined. The addition of glass fibre increases the tensile strength, but does not always contribute to an increase in fatigue crack propagation resistance. For polycarbonate the effect of stress ratio can be partly explained by using crack closure concepts as other researchers have suggested, but for glass fibre reinforced polycarbonate this was not possible. Fractography revealed a void growth process, which occurred by decohesion at the interface of the glass fibres and the base material, which was dependent on the maximum stress intensity factor. The process of linking the voids and the main crack growth behavior depended on the stress intensity factor range, ΔK. A proposed crack propagation model can explain the effect of stress ratio on crack propagation in fibre reinforced polycarbonate.
FATIGUE CRACK TIP STRAINS IN 7075‐T6 ALUMINUM ALLOY
Authors: Nicoletto Gianni
Published: April 2007

Abstract— The plastic enclave surrounding a fatigue crack in a 7075‐T6 aluminum alloy specimen is studied using moiré interferometry. Two distinct plastic zones are identified from inspection of moiré interferometric fringe patterns. The sizes and shapes of the monotonic and the cyclic plastic zones are correlated with previous theoretical and experimental results. Live load strain distributions in the plastic enclave are computed from high sensitivity (0.417 micron per fringe) full‐field in‐plane displacement contour maps. Comparison with theoretical and experimental strain distributions are included.
A REVIEW OF FATIGUE CRACK GROWTH CHARACTERISATION BY LINEAR ELASTIC FRACTURE MECHANICS (LEFM). PART II—ADVISORY DOCUMENTS AND APPLICATIONS WITHIN NATIONAL STANDARDS
Authors: Allen R. J. , Booth G. S. , Jutla T.
Published: April 2007

Abstract— This paper presents a review of the application of LEFM to the characterisation of fatigue crack growth. This part covers national standards and other documents of comparable status that (a) offer explicit advice on the use of fatigue crack growth data, and (b) in which crack growth considerations are implicit. Documents falling into the first category were noted to have many features in common, differences occurring only in areas where the current understanding of the subject is far from complete (e.g. variable amplitude loading, long life, etc.). Documents implicitly addressing fatigue crack growth comprise three distinct groups: (i) those which aim to simplify fracture mechanics analyses for the user, (ii) those in which fracture mechanics has influenced design criteria, and (iii) those which aim to provide inspection and/or acceptance criteria. As with the “explicit documents”, a degree of commonality was observed within each group of “implicit documents”, the exception being the military aircraft specifications of the U.K. and the U.S.A.
THE AIR FATIGUE AND CORROSION FATIGUE OF A 13% Cr TURBINE BLADE STEEL
Authors: Congleton J. , Wilks T. P.
Published: April 2007

Abstract— Reasons for data scatter from fatigue tests on a high strength 13% Cr steel are discussed and data is presented for corrosion fatigue of this steel in a condensing steam environment. Rotating bend tests were performed at 50 and 3 Hz and tension‐tension fatigue tests at 0.016 Hz and R=0.1. Some specimens were periodically inspected to identify sites of fatigue crack initiation. The role of inclusions in initiating fatigue cracks was investigated and it was found that the population of larger inclusions in the steel matched that at fatigue crack initiation sites. Comparison of fatigue lives from polished and abraded specimens indicated that there is little point in producing highly polished surfaces for this steel to try and improve fatigue life unless the inclusion content can be reduced in size and number. Corrosion fatigue data is presented indicating the magnitude of the reduction of fatigue life caused by condensing pure steam and condensing chlorinated steam.
THE GROWTH OF MICROSTRUCTURALLY SMALL FATIGUE CRACKS IN A FERRITIC‐PEARLITIC STEEL
Authors: Tokaji Keiro , Ogawa Takeshi , Osako Shuji
Published: April 2007

Abstract— The growth behaviour of microstructurally small fatigue cracks was investigated with smooth specimens of a ferritic‐pearlitic steel, S45C. under rotating bending. The effects of microstructure, particularly the role of pearlite structure, on crack growth were evaluated based on detailed microscopic observations. In the region smaller than a certain crack length. small cracks tended to grow preferentially in the ferrite structure, and the crack growth rates decreased markedly at ferrite‐pearlite boundaries when small cracks grew into the pearlite from the ferrite. The above region of crack length, i.e. the length of microstructurally small cracks, depended on stress level, increasing with decreasing stress level. The growth mechanism is also discussed in terms of the results obtained from fractogrdphy.
CREEP, FATIGUE AND CREEP‐FATIGUE CRACK GROWTH RATES IN PARENT AND SIMULATED HAZ TYPE 321 STAINLESS STEEL
Authors: Gladwin D. N. , Miller D. A. , Neate G. J. , Priest R. H.
Published: April 2007

Abstract— Crack growth rate data are presented from a range of fully reversed displacement‐controlled fatigue and creep‐Fatigue tests and from static load‐controlled creep crack growth tests on aged 321 stainless steel (parent and simulated HAZ) at 650 ° C. In the creep fatigue tests, constant displacement tensile hold periods of 12–192 h were used. Crack growth rates comprised both cyclic and dwell period contributions. Cyclic growth contributions are described by a Paris‐type law and give faster crack growth rates than those associated with pure fatigue tests. Dwell period contributions are described by the C* parameter. The total cyclic crack growth rates are given by summing the cyclic and dwell period contributions. Estimates of C* using a reference stress approach together with the appropriate stress relaxation creep data are shown to correlate well with experimentally measured C* values. Crack growth rates during static load‐controlled tests correlate well with C*. Good agreement is obtained between crack growth rates during the static tests and those produced during the hold period of the creep‐fatigue tests.
A DUCTILITY EXHAUSTION EVALUATION OF SOME LONG TERM CREEP/FATIGUE TESTS ON AUSTENITIC STEEL
Authors: Wood D. S. , Wynn J. , Austin C. , Green J. G.
Published: April 2007

Abstract— A limited number of long term creep/fatigue tests performed on two batches of Type 316 steel and one batch of associated 17Cr8Ni2Mo weld metal are reported. Test durations range from 5000 to 32,000 h and temperatures from 5.50 to 625 ° C. Subsequent metallographic examination shows the failures to be wholly or predominantly intergranular. The results are analysed using a ductility exhaustion approach and it is shown that the endurances obtained are within a factor of two of predicted values. The results confirm that the design approach to creep/fatigue currently being developed in the U.K. and based on ductility exhaustion is likely to be satisfactory.
THE PROGRESSION OF BENDING FATIGUE IN MONEL K500
Authors: Price C. E. , Henderson G. W.
Published: April 2007

Abstract—A comparison was made at room temperature of the fatigue sequence in Monel K 500 (N05500), both between the different states of solution heat treated, aged, and overaged, and with nickel that had been studied previously. The test mode was reversed bending and monitoring was by Nomarski interference contrast microscopy, in conjunction with sequential microhardness measurements. It was found that variations in Monel between the heat treated states were minor in comparison to differences with nickel. In Monel, the fatigue resistance was relatively poor because of ready intergranular, as well as transgranular, cracking. To achieve a significant life, the stress level had to be kept well below the yield strength, low enough to delay the onset of visible slip, for cracking would follow promptly. This meant that, in contrast to nickel, stress levels high enough to invoke strain hardening and obvious secondary slip led to exceedingly short lives. Also, inclusions mattered, slip occurring preferentially in their vicinity.
CRACK GROWTH BEHAVIOUR IN A THERMAL FATIGUE TEST. EXPERIMENTS AND CALCULATIONS
Authors: Burlet H. , Vasseur S. , Besson J. , Pineau A.
Published: April 2007

Abstract— This study is concerned with the results of experiments in which thermal cycles have been repeatedly applied through the wall thickness of axisymmetrically cracked tubular specimens. The investigated material is a Cr–Mo steel used for the moulds when fabricating centrifugally cast iron pipes. Crack growth rates have been measured by using the interrupted tests technique. A methodology is proposed to model the crack growth rates under such thermal fatigue loadings. The elastic and plastic stress‐strain fields are calculated on the uncracked specimen by means of a finite element code. Special attention was paid to reach a mechanical steady state regime. Fatigue crack growth rates data were obtained, both under isothermal and anisothermal conditions, on CT and SEN specimens. The latter specimens were tested under large‐scale yielding in order to obtain the data appropriate to the cyclic stress‐strain field calculated in the thermal fatigue specimens. An effective stress intensity factor, which takes into account both plastic strains and crack closure effect, was used to correlate the results of isothermal tests on CT and SEN specimens and to calculate the thermal fatigue crack growth rates in tubular specimens. It is shown that the use of the effective stress intensity factor gives a satisfactory agreement between the observed and the calculated crack growth rates.
FRACTURE TOUGHNESS OF BAINITIC NODULAR CAST IRON
Authors: Doong Ji‐Liang , Chen Chun‐Sheng
Published: April 2007

Abstract— The fracture toughness of bainitic ductile iron transformed at various austempering temperatures and austempering times was evaluated by using compact tension specimens and compared with the fracture toughness of bulleye casting structure. Using Scanning Electron Microscopy, the mechanism of the fracture mode can be understood by observing the fracture surface. An X‐ray diffractometer was used to determine the volume fraction of retained austenite. From the results of fracture toughness properties, it can be concluded that the most suitable austempering temperature of the material used in the present study is from 300 to 350°C.
THE EFFECT OF FINAL FRICTION COEFFICIENT ON FRETTING FATIGUE WAVEFORMS
Authors: Rooke D. P. , Courtney T. J.
Published: April 2007

Abstract— The waveforms of the frictional forces and the relationship between the frictional forces and the applied forces are derived for a fretting fatigue model in which the coefficient of friction is not constant. This study is a continuation of a previous one in which it was assumed that the coefficient of friction was a constant. In this new model it is assumed that the coefficient of friction between the rubbing surfaces is initially zero and slowly increases to a constant value during the early cycles of the fatigue life. The consequences of this change are examined and the results from the two models compared. It is observed that the two models give different frictional forces if the deformation of the surfaces is elastic, but are identical when non‐linear macroslip occurs on both loading and unloading.
THE USE OF SPATE TO MEASURE RESIDUAL STRESSES AND FATIGUE CRACK GROWTH
Authors: Leaity G. P. , Smith† R. A.
Published: April 2007

Abstract— —SPATE was used to monitor thermoemissions during fatigue crack propagation tests conducted on centre‐cracked tension (CCT) specimens at different mean stress levels, and on CCT specimens containing compressive residual stresses. The results obtained showed the SPATE stress intensity factor (SIF) predictions to correlate with the applied SIF range rather than the effective SIF range, thus demonstrating that SPATE was unable to account for the effects of mean stress and residual stress on fatigue crack growth. Further, although SPATE can be used to predict fatigue crack growth rates faster than 10–8m/cycle, in the region of low growth rates slower than this, the prediction of growth rates became impractical. Even at maximum resolution and scan time, the technique was unable to detect the changes in thermoemission caused by such small and slow crack tip advances.
THE EFFECT OF SPECIMEN SIZE ON THE J R‐CURVE BEHAVIOUR OF A TITANIUM ALLOY
Authors: Gordon J. R. , Jones R. L.
Published: April 2007

Abstract— —This paper presents preliminary results from a large experimental programme to study geometry and size effects in J R‐curves, The results presented were obtained from unloading compliance R‐curve tests performed at room temperature on different sized single‐edge‐notch‐bend specimens made from Ti‐3Al–2V alloy. The crack growth resistance was measured in terms of the standard fracture resistance J (i.e. not corrected for crack growth), J corrected for crack growth, and the J modified parameter proposed by Ernst. It was found that the best agreement was exhibited by the R‐curves based on the standard fracture resistance J, which displayed reasonable size independence up to, and in many cases beyond crack growths corresponding to 50% of the initial uncracked ligament.
INITIATION AND PROPAGATION OF SHORT FATIGUE CRACKS IN A WELD METAL
Authors: Youshi Hong , Yonghua Lu , Zhemin Zheng
Published: April 2007

Abstract— Fatigue tests were performed using a purpose designed triangular shaped specimen to investigate the initiation and propagation of short fatigue cracks in a weld metal. It was observed that short fatigue cracks evolved from slip bands and were predominantly within ferrite grains. As the test progressed, the short crack density increased with minor changes in crack length. The growth of short cracks, in the early stage resulted mainly from coalescence with other existing cracks. The mechanism of short crack behaviour is discussed.
EXPERIMENTAL CHARACTERISATION OF DYNAMIC TENSILE AND FRACTURE TOUGHNESS PROPERTIES
Authors: Jones R. L. , Davies P. C.
Published: April 2007

Abstract— —An experimental procedure for obtaining material tensile and fracture toughness properties at rates applicable to shock loading is reported. A variant of the key curve approach to determine dynamic J‐R curves is described and results are presented for a nickel aluminium bronze alloy for actuator loading rates in the range 0.75–7500 mm/s.
CORROSION FATIGUE OF STEEL IN VARIOUS AQUEOUS ENVIRONMENTS
Authors: Ragab A. , Alawi H. , Sorein K.
Published: April 2007

Abstract—Corrosion fatigue of three steels namely: AISI 1018, AISI 4340 and 17–7 PH stainless steel are investigated in various environments. Testing mediums chosen are natural seawater, polluted sea water from an industrial site, drinking tap water produced by desalination process, 4% sodium chloride tap water solution and a laboratory air environment. Results obtained for the three steels are consistent in pointing out that pollutants in seawater do not contribute to an acceleration of corrosion fatigue. The aggressiveness of drinking water is attributed to its chemical instability, low alkalinity and bicarbonate content.
APPLICATION OF FRACTURE MECHANICS TECHNIQUES TO THE ENVIRONMENTALLY ASSISTED CRACKING OF ALUMINIUM 2024
Authors: Dietzel W. , Schwalbe K.‐H. , Wu D.
Published: April 2007

Abstract— Stress corrosion cracking of 2024 T351 aluminium alloy in an aqueous 3.5% sodium chloride solution was investigated using three fracture mechanics based testing techniques: constant load, constant displacement, and constant displacement rate. In spite of their different loading characteristics, all three test methods yielded approximately the same Klscc value. Crack growth rates in the plateau region, as measured from bolt loaded DCB specimens and from CT specimens tested at low constant displacement rates are similar. The tests at constant displacement rate not only provide results in a much shorter time, but produce additional information in terms of crack growth resistance curves as a function of the displacement rate. Linear elastic as well as elastic‐plastic fracture mechanics test evaluation procedures are applied and discussed in view of an assessment of criteria for the accelerated evaluation of SCC parameters such as Klscc, Jlscc, and δlscc.
HYDRODYNAMIC PRESSURE EFFECTS OF VISCOUS FLUID FLOW IN A FATIGUE CRACK
Authors: Davis F. H. , Ellison E. G.
Published: April 2007

Abstract— The influence of hydrodynamic pressure on fatigue crack growth rates has been investigated. It was shown that the effects were small but beneficial, effectively reducing the stress intensity range. A theoretical model has been developed which successfully predicted the trends and approximate magnitudes of reductions in fatigue crack growth rates for a range of test conditions.
A UNIAXIAL CYCLIC PLASTICITY MODEL INCLUDING TRANSIENT MATERIAL BEHAVIOUR
Authors: Skallerud B. , Larsen P. K.
Published: April 2007

Abstract— A phenomenological uniaxial material model, which is a one‐dimensional equivalent to a two‐surface multiaxial plasticity model, is presented. The model takes into account the transient effects cyclic hardening/softening and mean stress relaxation by means of exponential relationships that are functions of number of reversals. The parameters describing these relationships are obtained from the strain‐life curve and the cyclic stress‐strain curve. The hysteresis loops are assumed to be bounded by two parallel, straight lines in tension and compression, i.e. bounding lines. The stress‐strain curve approaches these lines with increasing strain through a nonlinearly decreasing plastic modulus. The transient effects are simulated by increasing/decreasing the distance between the lines for cycling hardening/softening at each stress or strain reversal. A positive mean stress yields translation downwards of the bounding lines if the material is subjected to strain control, and translation in the opposite direction if the mean stress is negative. Dynamic creep is simulated when the material is subjected to stress control and mean stress. The test data was obtained from an experimental programme on St52–3N, which is a normalized structural steel. The specimens were loaded in strain or stress control. The comparison between tests and simulations shows that the model described simulates the cyclic transient material behaviour quite well. The main inaccuracy is due to using parallel bounding lines, as the tests show that these lines are not completely parallel for the present steel material.
THE SIZE EFFECT OF MICROSTRUCTURAL IMPLICATIONS OF THE WEAKEST LINK MODEL
Authors: Brückner‐Foit A. , Ehl W. , Munz D. , Trolldenier B.
Published: April 2007

Abstract— CT specimens made of a reactor pressure vessel steel were loaded at—40°C until final failure occurred by cleavage fracture. The samples of Jlcl values obtained in these tests are analysed using the weakest link model. The size effect observed with specimens of different thicknesses is compared with the predictions of the weakest link model. A formula is derived for the distribution of the locations of fracture origins which have been determined for almost all specimens with a scanning electron microscope. The distribution of the size of the “weak spots” is calculated from the distribution of the fracture origins using two different models for the stress field ahead of the crack tip. These fractographic results and the Jlcl data confirm the basic ideas of the weakest link model. The deviations observed between the quantitative predictions of the weakest link model and the data can partly be explained by the change in the stress state ahead of the crack tip caused by a change in the specimen thickness.
STRESS INTENSITY FACTORS FOR CORNER CRACKS AT A SEMI‐CIRCULAR NOTCH UNDER STRESS GRADIENTS
Authors: Zhao W. , Wu X. R.
Published: April 2007

Abstract— A weight function method, recently developed by the authors, is applied to calculate stress intensity factors for corner cracks emanating from a semi‐circular notch under crack face polynomial pressure loading. A wide range of configuration parameters are considered. These results, combined with superposition principle, allow determination of stress intensity factors under general loading conditions. The approach is demonstrated by obtaining stress intensity factors for the load cases of remote tension and shot‐peening residual stresses at the notch.
A THERMOELASTICITY THEORY FOR DAMAGE IN ANISOTROPIC MATERIALS
Authors: Zhang Daqing , Sandor Bela I.
Published: April 2007

A thermoelasticity theory for damage in anisotropic materials is developed. This theory can be applied to evaluate the damage parameter D, the normalized effective mess density ρe/ρ, and the effective modulus Ee quantitatively in some metals and composites by incorporating the thermographic stress analysis method (TSA; also, SPATE method). The effective moduli due to fatigue damage and static loads in a glass fiber/epoxy laminate obtained by the TSA method are compared with the values measured by an extensometer. The correlation between the measurements using the two methods is very good.