bluuebunny/crossref_metadata_2025 huggingface dataset:
β2‐Microglobulin amyloidosis
Authors: ARGILÉS ÀNgel
Published: April 2007

Summary: β2‐microglobulin amyloidosis is a new type of amyloidosis mainly observed in dialysis patients, whose frequency increases with the elapsed time of dialysis treatment. Its high incidence and its disabling characteristics bring it to the front among the complications observed in chronic renal failure patients. the pathophysiology of β2‐microglobulin amyloidosis is not known. However, great progress has been achieved with recent work identifying a variety of substances that are contained in amyloid deposits and which have known metabolic activities likely to participate in amyloid fibril formation. Among them, three deserve special mention: (i) the advanced glycation end products (particularly the AGEP‐β2‐microglobulin), which result from the non‐enzymatic glycation of proteins, known to be altered in chronic renal failure; (ii) the reactive oxygen species (ROS) which are released by the cells related to the amyloid deposits (macrophages and endothelial cells) and may participate in tissue damage and fibril precipitation; and (iii) α2‐macroglobulin, amyloid P component and other anti‐proteases which modify the processing of amyloid fibrils and may also interact with macrophages and enhance amyloid fibril formation. Unfortunately, there is no treatment curing or preventing β2‐microglobulin amyloidosis that we can presently offer to dialysis patients. the use of high flux membranes seems to delay its appearance and there is agreement in that renal transplantation clearly stops progression of this type of amyloidosis.
The application of microwave techniques in multiple immunostaining and in situ hybridization
Authors: LAN HUI Y , MU WEI , NIKOLIC‐PATERSON DAVID J , ATKINS ROBERT C
Published: April 2007

Summary: We describe simple, rapid, reliable and sensitive microwave‐based methods for both multiple immunostaining and in situ hybridization. This technique involves treating sections with a 10 min period of microwave oven heating. the ability of microwave oven heating to retrieve cytoplasmic and nuclear antigens, block antibody cross‐reactivity and inactivate peroxidase and alkaline phosphatase enzymes has resulted in the development of a simple and generally applicable method of multiple immunostaining in which two or more antigens can be detected within the same section using primary antibodies raised in the same species combined with a sensitive three layer staining protocol involving peroxidase anti‐peroxidase (PAP) and alkaline phosphatase anti‐alkaline phosphatase (APAAP) complexes. the application of microwave oven heating as a pretreatment of cryostat sections prior to in situ hybridization using digoxigenin‐labelled cRNA and cDNA probes resulted in improved probe access to target nucleic acid sequences, stronger hybridization signals, reduced hybridization times, maintenance of excellent tissue morphology and outstanding reliability. Thus, the application of microwave oven heating has overcome many of the difficulties associated with current protocols used in these two techniques. These new methodologies have general applicability and will be of significant benefit to both research scientists and clinical pathologists alike.
Pirfenidone prevents the progression of irreversible glomerular sclerotic lesions in rats
Authors: SHIMIZU Fujio , FUKAGAWA Masafumi , YAMAUCHI Shitotomo , TANIYAMA Masayoshi , KOMEMUSHI Sadao , MARGOLIN Solomon B , KUROKAWA Kiyoshi
Published: April 2007

Summary: Pirfenidone (PFD) is a new drug which has been shown to prevent or even reverse the extracellular matrix accumulation in several organs. to examine the effect of PFD on the progressive glomerulosclerosis, we treated model rats with irreversible chronic renal disease per orally with 500 mg/kg bodyweight of PFD per day. the model rats were made by intravenous injection of anti‐Thy‐1 monoclonal antibody 1‐22‐3 at 1 h following unilateral nephrectomy, which results in chronic progressive glomerulosclerosis. Twenty‐four hours later, 32 female Wistar rats were divided into two groups and were fed standard chow with (PFD group: P) or without PFD (control group: C). All rats were sacrificed on day 42. No significant difference in the bodyweight or the amount of chow intake was observed between the two groups. the remnant kidney was significantly (P<0.05) heavier in C (2.11 ± 0.15 g) than in P (1.70 ± 0.13 g). This finding, together with light microscopic findings, showed that PFD administration resulted in the prevention of renal hypertrophy. On day 42, proteinuria in P (124.3 ± 31.9 mg/day) was significantly lower than in C (214.6 ± 8.1 mg/day), and P maintained significantly better renal function than C as judged by serum urea nitrogen and creatinine levels. Mean matrix score was less in P (178 ± 17) than in C (225 ± 22). Crescent formation was observed in 17% of glomeruli in P and in 35% in C. Tubulointerstitial lesions were also less severe in P. Furthermore, inflammation and sclerosis indices detected by immunohistochemistry (e.g. ED‐1, OX8, TGF‐beta α‐smooth muscle actin, collagen type I, were less in P). These data suggest that PFD may be a promising agent for the prevention of progressive and irreversible glomerulosclerosis.
Enhancement of chronic cyclosporine nephrotoxicity by sodium depletion in an experimental mouse model
Authors: ANDOH Takeshi F , LAM Tri T , LINDSLEY Jessie , ALPERS Chaiues E , BENNETI William M
Published: April 2007

Summary: The major adverse reaction to cyclosporine A (CsA) is chronic nephrotoxicity. to elucidate the pathogenesis of CsA nephrotoxicity and the potential role of the renin‐angiotensin system (RAS) in mediating this toxicity, a reliable mouse model would enable us to take advantage of various probes, and gene knockout animals available in this species, but not in the rat, would be extremely useful. Using the manoeuvre of sodium depletion and activation of RAS, an experimental model in the mouse has been developed to reproduce structural and functional characteristics of chronic CsA nephrotoxicity in humans. Mice were treated with CsA subcutaneously at dosages of 10 mg/kg per day and 30 mg/kg per day or olive oil as a placebo on a low sodium diet (LS) (0.01% sodium) for 28 days. Comparisons were made with mice treated with CsA at 100 mg/kg per day on a normal sodium diet (NS; 0.4% sodium) for 56 days. Cyclosporine A treatment induced significant increases in serum creatinine and blood urea nitrogen (BUN) and a decrease in creatinine clearance in mice on LS (P<0.05 vs placebo). Sodium‐depleted animals on CsA 30mg/kg per day treatment developed significant histological lesions in the kidneys consisting of tubulointerstitial fibrosis, arteriolopathy, nephrocalcinosis, and tubular injury after 28 days (P<0.001 vs placebo). By contrast, CsA treatment in mice on NS did not induce functional and structural abnormalities in the kidneys even up to 56 days at a higher dose. This mouse model can be useful to gain further insights into the pathogenetic mechanisms of chronic CsA nephropathy.
The mesangial response to injury: Mechanisms of progression and repair
Authors: JOHNSON Richard J , SHANKLAND Stuart J , HUGO Christian , PICHLER Raimund H , NANGAKU Masaomi , McCLARRINON Molly , OPHASCHAROENSUK Vuddhidej , ZACHEM Charles , KUAN Chia JEN , THOMAS Susan E , MEEK Richard , COUSER William G
Published: April 2007

Summary: Mesangial injury accompanies many glomerular diseases and diabetic nephropathy. Whereas in some diseases the injury resolves, in other cases it may progress to sclerosis. We have studied mesangial injury in the Thy 1 model in rats. In this model, the injection of anti‐Thy 1 antibody results in complement‐mediated killing of <95% of the mesangial cells by 24h. Subsequently there is a migration of mesangial cell ‘precursors’ from the hilus which proliferate inside the glomerulus to reconstitute the mesangium. Mesangial cell proliferation is dependent on several growth factors, including platelet‐derived growth factor (PDGF), basic fibroblast growth factor (bFGF) and endothelin‐1, and is accompanied by a phenotypic change of the mesangial cell to a myofibroblast. A transforming growth factor (TGF)‐β mediated matrix expansion also occurs. Both the proliferation and matrix expansion subsequently resolve, and the hypercellularity returns to normal by apoptosis. However, if repeated doses of anti‐Thy 1 antibody are administered, resolution does not occur and progressive mesangial sclerosis develops. This appears to be mediated by both a lack of proliferation and excess apoptosis, which lead to hypocellularity, and to continued TGF‐β expression. Understanding how to prevent these changes could have potential therapeutic impact.
EFFECT OF STRESS‐STRAIN BEHAVIOR ON LOW‐CYCLE FATIGUE OF α‐β TITANIUM ALLOYS
Authors: KRAFFT J. M.
Published: April 2007

Abstract—

Tensile specimens of Ti‐6A1‐4V with four levels of interstitial oxygen content and a Ti‐8Al‐1Mo‐1V alloy with different heat treatments to alter grain size and/or microstructural character are subjected to slow strain‐controlled cyclic deformation leading to rupture in the 5‐500 cycle range. Indication of crack initiation as well as rupture life are compared, relative to the plastic excursion strain. On this basis, the effects of grain size and oxygen content are not clearly discriminated. Yet, some of the materials exhibit markedly superior performance. This improvement seems to be related to a characteristic evolution in the shape of the cyclic stress‐strain curve. Here, relative to a full convex hysteresis loop of early cycles, the later cycles exhibit a reduced stress level, or cyclic softening, in the first half of the excursion, followed by a resurgence of strength to initial stress levels in the latter portion. The enhanced strain hardening rate enabling this terminal strength restoration is thought to stabilize the deformation, reducing the amount of stress‐relaxation‐induced tensile strain. Taking such strain as an increment of damage in a cumulative cyclic creep strain criterion provides a correlation between the evolving shape of the cyclic stress‐strain curve and the low cycle fatigue endurance. Results indicate the absolute increase in the terminal plastic strain hardening rate to be a constant of a material, independent of the cyclic strain excursion.
FATIGUE CRACK PROPAGATION BEHAVIOUR OF SHORT CRACKS; THE EFFECT OF MICROSTRUCTURE
Authors: TAYLOR D. , KNOTT J. F.
Published: April 2007

Abstract—

–Fatigue cracks shorter than some critical length tend to propagate anomalously quickly. This paper examines the concept of a ‘critical length’, identifying three regimes of behaviour for different crack lengths. Some published work is examined, covering a wide range of different materials. It is concluded that there is an approximate correlation between the critical length for short crack behaviour and the scale of the microstructure. LEFM is difficult, if not impossible, to apply to cracks shorter than this critical length because the material surrounding a crack cannot be assumed to approximate to a homogeneous continuum. Suggestions are made for a fatigue design philosophy which incorporates short crack behaviour.
FRACTOGRAPHIC ANALYSIS IN THE UNDERSTANDING OF CORROSION FATIGUE MECHANISMS
Authors: McMINN A.
Published: April 2007

Abstract—

Fractographic analyses have been used to explain the cyclic crack growth behaviour of A533‐B, Ducol W30, a C‐Mn steel and type 304 stainless steel in simulated light water reactor environments at ambient temperature. Fractographic observations have offered an explanation for anomalous crack growth behaviour and have also indicated where micro structural or environmental variables dominate in producing certain fracture modes and crack growth rates. An understanding of the operative corrosion fatigue mechanisms has been formulated through these fractographic analyses. Environmental crack growth in the ferritic steels has been described by a model involving both anodic dissolution and hydrogen embrittlement. Conditions where only one of these mechanisms would dominate have been identified and limits to their effect postulated. A crystallographic mode of failure observed in the austenitic type 304 stainless steel has also been explained by a selective dissolution process.
A CRITICAL REVIEW OF CRACK TIP STRESS INTENSITY FACTORS FOR SEMI‐ELLIPTIC CRACKS*
Authors: SCOTT P. M. , THORPE T. W.
Published: April 2007

Several crack tip stress intensity factor solutions have been published for semi‐elliptic, surface breaking cracks in plates subjected to tension or bending forces. These solutions do not agree with each other particularly well and the basis for choosing which one is the best has not been established. In this paper, the development of fatigue crack shape is used as a diagnostic tool to test the accuracy of these theoretical stress intensity solutions in predictive fatigue crack growth calculations. Those solutions giving the best engineering estimate of crack tip stress intensity factors are identified. Single equations are also given for each loading case at the deepest point or surface intersection point of semi‐elliptic cracks in order to facilitate calculations on programmable calculators. A rational basis for calculating the progress of a crack which snaps through the thickness and continues to propagate in a stable way by fatigue is suggested.
STRESS‐RATIO EFFECT OF FATIGUE CRACK PROPAGATION IN A BIAXIAL STRESS FIELD
Authors: HOSHIDE T. , TANAK.A K. , YAMADA A.
Published: April 2007

Fatigue crack propagation tests were conducted under conditions of equibiaxial, uniaxial and shear loading by using a cruciform specimen in a servo hydraulic testing machine. The effect of non‐singular stress cycling on the fatigue crack propagation rate was examined based on the observation of crack opening behavior. The crack propagation rate was significantly influenced by the non‐singular stress parallel to the crack when it was correlated to the stress intensity range. The crack closure behavior was greatly affected by the non‐singular stress. The crack propagation rate was uniquely correlated to the effective range of the stress intensity factor except for the case of completely reversed shear loading where significant plasticity was detected. The crack opening displacement range was concluded to be a parameter controlling the crack propagation rate for all the stress conditions examined in the present experiments. Some discussion is made on the effect of material anisotropy on fatigue crack propagation in a biaxial stress field.
FATIGUE LIFE CALCULATION AND TESTING OF FULL‐SCALE WELDED I‐BEAMS
Authors: GLINKA G. , KRZYŻEKI A.
Published: April 2007

Abstract —Fatigue tests under four‐point bending were carried out on low alloy steel welded I‐beams under constant and variable amplitude loading. Four different types of stiffeners welded to flanges and webs were analysed. Particular attention was paid to the effect of configuration at the stiffener‐ends. It was shown that the stiffener‐ends were the most critical points. Fatigue cracks initiated and propagated in both tension and compression flanges. The fatigue life to crack initiation was calculated on the basis of the local stress‐strain analysis. Both theoretically and experimentally estimated stress concentration factors were used for calculation. The predicted fatigue lives were compared with the respective values obtained in experiments.
THE HYSTERESIS LOOP 1. A STATISTICAL THEORY
Authors: POLÁK J. , KLESNIL M.
Published: April 2007

Abstract— Starting from a knowledge of inhomogeneous dislocation structures observed in cyclically strained metals, a model for cyclic straining is developed. A distribution of volumes with different internal critical flow stresses is assumed characterized by a probability density function. A generalization which includes a thermally activated component of the flow stress is derived assuming that the saturated microscopic effective stress, μes, is equal in all volumes. The relations to obtain the probability density function from experimental data are derived. The theory yields the macroscopic internal stress, σe and the macroscopic effective stress, σe, along the hysteresis loop. Experimental observations on cyclically strained metals can be explained using this statistical theory.
THE HYSTERESIS LOOP 2. AN ANALYSIS OF THE LOOP SHAPE
Authors: POLÁK J. , KLESNIL M. , HELEŠIC J.
Published: April 2007

Abstract— Hysteresis loops of a low carbon steel measured at various temperatures and plastic strain amplitudes are analysed using the statistical theory of the hysteresis loop. It is shown that the parameters of the statistical theory characterizing the saturated hysteresis loop, i.e. the probability density function and effective saturated stress, can be obtained from experiments. The probability density function is influenced mainly by strain amplitude; the effective saturated stress mainly by temperature.
THE EFFECT OF HYDROGEN ON FATIGUE AND DISLOCATION BEHAVIOR OF AN α/β TITANIUM ALLOY
Authors: MOODY N. R. , GERBERICH W. W.
Published: April 2007

Abstract— Fatigue thresholds and crack growth rates were studied in the experimental alloy, Ti—5Al—4Mo, as a function of temperature, grain size and hydrogen concentration. Deformation is confined to planar slip bands along which fracture occurred at low hydrogen concentrations. Hydrogen accelerated crack growth rates at various combinations of temperature, grain size and hydrogen with a corresponding change in fracture from “cleavage’ to interface phase fracture. In addition, hydrogen was found to promote interface phase formation. It is proposed that stress‐assisted hydrogen accumulation increases the interface phase hydrogen concentration which reduces the interface phase fracture stress. This process depends on the local stress and β‐phase hydrogen concentrations, temperature and the time under load. At 340 K, hydrogen had a relatively small effect on crack growth due to a change in slip behavior with increased hydrogen concentration.
ON THE CALIBRATION, OPTIMIZATION AND USE OF d.c. ELECTRICAL POTENTIAL METHODS FOR MONITORING MODE III CRACK GROWTH IN TORSIONALLY‐LOADED SAMPLES
Authors: RITTER M. A. , RITCHIE R. O.
Published: April 2007

Abstract—The use of d.c. electrical potential methods is described for the monitoring of Mode III (anti‐plane shear) fatigue cracks in circumferentially‐notched cylindrical specimens subjected to cyclic torsion. Calibration of potential change with crack depth and optimization of current input and potential measurement probe locations are achieved using simple finite element procedures, and are verified experimentally. The use of the method for Mode III crack growth studies is described in the light of crack face electrical shorting problems associated with torsional crack closure.
MIXED‐MODE FRACTURE MECHANISMS NEAR THE FATIGUE THRESHOLD OF AISI 316 STAINLESS STEEL
Authors: Hua Gao , de los Rios E. R. , Miller K. J.
Published: April 2007

Abstract— Near threshold, mixed mode (I and II), fatigue crack growth occurs mainly by two mechanisms, coplanar (or shear) mode and branch (or tensile) mode. For a constant ratio of ΔKI/ΔKII the shear mode growth shows a self‐arrest character and it would only start again when ΔKI and ΔKII are increased. Both shear crack growth and the early stages of tensile crack growth, are of a crystallographic nature; the fatigue crack proceeds along slip planes or grain boundaries. The appearance of the fracture surfaces suggest that the mechanism of crack extension is by developing slip band microcracks which join up to form a macrocrack. This process is thought to be assisted by the nature of the plastic deformation within the reversed plastic zone where high back stresses are set up by dislocation pile‐ups against grain boundaries. The interaction of the crack tip stress field with that of the dislocation pile‐ups leads to the formation of slip band microcracks and subsequent crack extension. The change from shear mode to tensile mode growth probably occurs when the maximum tensile stress and the microcrack density in the maximum tensile plane direction attain critical values.
SPECIMEN SIZE DEPENDENCE OF LOW FREQUENCY FATIGUE TESTS IN HIGH‐PRESSURE HYDROGEN
Authors: Roebuck B.
Published: April 2007

Abstract— Fatigue data required for estimates of cracked component lifetimes are conventionally obtained by cyclic loading of specimens manufactured to a specific geometry. Crack growth in the specimen results in an increase in the stress intensity factor range and crack growth curves are calculated from the variation of crack length with time. An environmental fatigue study of the effect of high pressure hydrogen on the low cycle fatigue of a medium strength steel has shown that, due to effects of elapsed time in the environment and effects of specimen size, in certain circumstances this procedure may not yield geometry‐independent results which can be applied with confidence to cracked components. It is concluded that to obtain useful crack growth data in cases where fracture is influenced by diffusion or other strongly time dependent processes might require a modified approach to fracture mechanics testing procedures.
EFFECT OF SIDE‐GROOVES ON FATIGUE CRACK RETARDATION
Authors: Hess J. P. , Grandt A. F. , Dumanis A.
Published: April 2007

Abstract— This paper describes results of an experimental program conducted to determine the influence of deep side‐grooves on fatigue crack retardation. The results indicate that side‐grooves significantly reduce the delay in fatigue crack growth caused by single peak overloads. It is suggested that the decreased retardation is due to simulation of plane strain conditions in the “thin” test sections by the stress field at the root of the side‐groove.
THE EFFECT OF WATER VAPOR ON FATIGUE CRACK TIP MECHANICS IN 7075‐T651 ALUMINUM ALLOY
Authors: Davidson D. L. , Lankford J.
Published: April 2007

Abstract— Strains very near a growing fatigue crack have been computed from measured material displacements, both for a very dry environment and for humid air. Significant differences in crack tip strains arid crack tip opening displacements occur in these environments, with crack tip deformation in water vapor evidencing less plasticity than the dry environment. These quantitative results are incorporated into a previously developed mathematical model which is based, in part, on dynamic observations of intermittent crack growth. Fractography is shown to support the concepts of intermittent crack advance and decreased crack tip plasticity due to environmental water vapor.
THE EFFECT OF CONCRETE BOND ON THE STRESS INTENSITY FACTORS FOR AN EDGE CRACK IN A REINFORCING BAR
Authors: Daoud Osama E. K. , Lovegrove J. M.
Published: April 2007

Abstract— The stress intensity factors at the tip of an edge crack in a round bar embedded in the tension zone of a concrete beam are found for several conditions of bond failure between the steel reinforcing bar and the concrete. A two‐dimensional finite element technique is modified to represent the third dimension, the steel‐concrete interface and debonding. The integrated form of the Paris crack growth law is used with the calculated stress intensity factors to compute the propagating fatigue lives for embedded bar and bar in air. The results indicate that embedded bars appear to have shorter fatigue propagation lives than bars in air if the crack initiators are less than 0.05 of the bar diameter, while for deeper crack initiators, the opposite is true. It has also been shown that the propagating fatigue life of the bar increases with the degree of bond.
SEGMENTED FITTING OF FATIGUE CRACK GROWTH DATA
Authors: Shaw W. J. D. , Le May I.
Published: April 2007

Abstract— Segmented fitting of fatigue crack growth rate data is shown to give a more accurate prediction of fatigue life with less statistical scatter than by a single fitting using the straight line of a Paris‐type plot. Changes in the slope of the log (da/dN) vs log ΔK data are seen to correlate well with changes in the mode and mechanism of fracture.
THE EFFECT OF ENVIRONMENT ON THE GROWTH OF SMALL FATIGUE CRACKS
Authors: LANKFORD J.
Published: April 2007

Abstract— The growth of “large” and “small” cracks in 7075–T6 aluminum is characterized in moist air and dry nitrogen. It is found that in both environments, the small cracks grow faster than large ones, but unlike large cracks, which grow much faster in air than in nitrogen, the small cracks extend in each environment at about the same average rate. The absence of environmental effect is found to be only apparent, a change to an inherently slower mode of growth in air offsetting the crack‐accelerating influence of moisture. Subsurface grain boundaries apparently retard microcrack growth in both environments. Possible rationales for the rapid growth of small cracks are discussed.
FATIGUE DAMAGE IN 1045 STEEL UNDER CONSTANT AMPLITUDE BIAXIAL LOADING
Authors: Hua C. T. , Socie D. F.
Published: April 2007

The progressive nature of fatigue damage under multiaxial stress states has been investigated. Experiments were performed on thin‐wall tubular specimens of 1045 steel in tension, torsion and combined tension‐torsion loading. Two equivalent strain amplitudes, one in the high cycle fatigue (HCF) region and one in low cycle fatigue (LCF) region were employed in this study. Four recently proposed damage theories were evaluated. Crack depth was used as a damage parameter in comparing damage curves under different loading modes.

Different types of crack systems were observed in the HCF and LCF regions. The damage curve obtained in tension loading can be used to evaluate the damage behavior under combined tension—torsion loading. The results of torsion loading show that torsional damage behavior is different from the above two loading modes.
A NOTE ON THE INFLUENCE OF REST PERIODS ON THE FATIGUE ENDURANCE OF A TITANIUM ALLOY
Authors: Brown R. , Smith G. C.
Published: April 2007

S‐N curves have been determined for continuous cycling and for interrupted cycling using commercial purity titanium, and also a Ti‐6Al‐4V alloy in four different states of heat treatment. The incorporation of rest periods during the fatigue tests resulted in increased lives to fracture to an extent which appeared to be independent of specimen composition or microstructure, and hence primarily a function of the titanium itself. Failures from internal crack origins were found at longer lives from some specimens for both continuous and interrupted tests. It is suggested that the observed effects are due to localised hardening and strain ageing as a consequence of oxygen and/or nitrogen pick‐up from the testing environment, and also as a result of oxygen and/or nitrogen present in the starting material.
SHORT CRACK BEHAVIOUR IN NODULAR CAST IRON
Authors: Clement P. , Angeli J. P. , Pineau A.
Published: April 2007

Fatigue crack growth rates have been determined on standard specimens containing long cracks (∼5–10mm) and on specimens containing two‐dimensional short cracks (∼0.10–0.50mm). Large differences have been observed indicating that at a given stress intensity factor short cracks propagate much faster than long cracks. Mouth opening displacement measurements for both specimen geometries have shown that the crack closure effect is largely responsible for the observed effect. These results are used to rationalize the behaviour of short cracks initiated from natural sites which were either graphite nodules or microshrinkage pores. The three‐dimensional aspect of these natural small cracks is analysed and discussed in detail.
FATIGUE UNDER CYCLIC COMPRESSIVE LOAD
Authors: Chu Wu‐Yang , Hsiao Chi‐Mei , Liu Tian‐Hua
Published: April 2007

For ultra‐high strength steels and aluminium alloys, a fatigue crack could initiate from a notch tip under cyclic compressive load. The threshold value for fatigue crack initiation under compressive load can be as great as four times that under tensile load. The crack grew at a decreasing rate until eventually it stopped growing altogether under cyclic compressive load with a maximum length of 0.2‐0.5 mm. If the minimum compressive load was near zero, i.e. compression to zero load cycling, the threshold value was near that under tensile loading and the compressive fatigue crack could continue to grow; however, the crack growth rate under compression to zero load fatigue was 10–100 times less than that under the tensile fatigue loading.
INTERPRETATION OF FATIGUE CRACK GROWTH IN ALUMINIUM ALLOYS UNDER PROGRAMMED BLOCK LOADING
Authors: Gabra M. , Bathias C.
Published: April 2007

The effect of cycle ratio R on the crack propagation rate for two aluminium alloys is analysed. Fatigue crack growth under programmed block loading is presented, linear damage accumulation is established for some flight simulation tests. Aspects covered include microscopic and fractographic observations. The incidence of crack closure is examined and the concept of equivalent constant amplitude is applied. The agreement between predictions and test results is very promising.
EFFECTS OF PRE‐MOULDED WOVEN CFRP PATCHES ON FATIGUE CRACK GROWTH AND RESIDUAL STRENGTH IN 7475‐T761 ALUMINIUM ALLOY SHEET
Authors: Kemp R. M. J. , Murphy D. J. , Butt R. I. , Wilson R. N. , Phillips L. N.
Published: April 2007

Fatigue crack propagation tests have been made on 150 mm wide panels of 1.6 mm thick 7475‐T761 clad aluminium alloy sheet with and without adhesively bonded patches of pre‐formed carbon fibre reinforced plastic (CFRP). The test frequency was 10 Hz, the minimum stress: maximum stress ratio, R, was 0.1 and the peak applied fatigue stress was 60 MPa.

The tests were undertaken to assess the possibility of preventing the growth of fatigue cracks, or reducing their rate of growth, by the application of CFRP patches to one face only of pre‐cracked aluminium alloy sheet. The variables examined included the type of patch and adhesive; the size, shape and thickness of the patch; and the effect of chamfering the edges of the patch and the removal of the cladding prior to patching.

Results indicated that correctly designed and bonded CFRP patches substantially decreased the subsequent crack growth rate. The size and thickness of the patch had significant effects upon the reduction of fatigue crack growth rate whereas the shape of the patch, chamfering and the removal of the cladding prior to patching had little influence.
FATIGUE CRACK GROWTH RATE BEHAVIOUR OF STAINLESS STEEL CLADDINGS IN AIR AND UNDER VACUUM AT 300°C
Authors: Pedron J. P. , Diboine A. , Pineau A.
Published: April 2007

CT type specimens containing two layers of 309L and 308L cladding stainless steels welded to A508 carbon steel and 316 stainless steel were specially devised to test the influence of R ratio and environment on the crack propagation rate behaviour of cladding materials at 300°C. Large effects are shown. The crack growth rate under vacuum can be smaller by more than one order of magnitude as compared to air. Large differences are also shown on the fracture surfaces, where it is observed than vacuum promotes the formation of large crystallographic {111} facets. The effect of environment is briefly discussed on the basis of existing gas adsorption models.
THE EFFECTS OF MEAN STRESS AND STRESS CONCENTRATION ON FATIGUE UNDER COMBINED BENDING AND TWISTING
Authors: McDiarmid D. L.
Published: April 2007

The Gough test data on fatigue under combined bending and twisting with superimposed mean bending and torsion stresses with and without stress raisers has been re‐investigated in terms of the stresses acting on the plane of maximum range of shear stress. It has been shown that the allowable amplitude of shear stress on this plane can be predicted from an equation of the form

τa= [t ‐ c1 (Kt×σa)1.5−c2σ2m]/Kt

where σa and σm are the normal stress amplitude and mean normal stress respectively on the plane of maximum range of shear stress, c1 and c2 are defined material constants and Kt is the theoretical stress concentration factor.
MODELLING FOR FATIGUE CRACK GROWTH PREDICTION IN AIRCRAFT
Authors: Finney J. M.
Published: April 2007

Fatigue crack growth models, having application to Mirage III0 aircraft, have been calibrated with test data. Of the four crack growth retardation models examined—Wheeler, Willenborg, modified Willenborg and Crack Closure—the Wheeler and modified Willenborg models are the most satisfactory but both require calibration by test. Even so, crack growth is not accurately predicted when the specimen geometry and the test sequence are varied from those used in calibrating the models.

Apart from the crack growth models, the main sources of inaccuracy in predicting crack growth are the inadequacy of the growth rate basic data, incorrect assumptions of crack shape and uncertainty in stress history. Thus, crack growth life may not be confidently predicted to better than a factor of two on actual life and, in some cases, the factor may be as high as ten.
FATIGUE LIFE BEHAVIOR OF MONOCRYSTALLINE COPPER IN 0.1 M PERCHLORIC ACID
Authors: Yan Benda , Farrington GregoryC. , Laird Campbell
Published: April 2007

We have studied the fatigue lives of single crystals of copper in 0.1 M HClO4under different polarization potentials. Perchloric acid was chosen for the aqueous environment because it allows us to control the corrosion reactions rigorously. Persistent slip band (PSB) behaviour and crack nucleation were studied during life, and fracture surfaces after failure.

Different behavior was observed depending on strain amplitude. At 2 × 10‐3 plastic shear strain amplitude, anodic potential was observed to decrease life, whereas cathodic potenlial was found to be less damaging than laboratory air. Crack nucleation and propagation occurred along the primary slip plane for both conditions. The reduction of fatigue life under anodic potential is explained by enhanced localized strain at the PSB's and preferential dissolution within them.

However, for a strain amplitude of 4 × 10‐3, cracks nucleated and propagated along the secondary slip system. We observed crack nucleation to be associated with deformation‐induced stress concentrations, and the aqueous solution showed no aggressive effect under either anodic or cathodic potential.
FATIGUE OF POLYCRYSTALLINE COPPER AT CONSTANT AND VARIABLE PLASTIC STRAIN AMPLITUDES
Authors: Kuokkala V.‐T. , Kettunen P.
Published: April 2007

Fatigue behavior of polycrystalline copper of two different grain sizes was studied using constant and randomly varying plastic strain amplitude tests. The different regimes in the ess‐curves of large‐grained samples (d˜ 2.0 mm) were found to be reflected also in the measured fatigue lives in both test modes. The variable amplitude fatigue lives of the small‐grained samples (d˜ 0.03 mm) seemed to follow the Coffin–Manson linear law. The damage accumulation rate in variable amplitude tests was found to be lower than in the corresponding constant amplitude tests, e.g. when expressed as cumulative plastic strains to failure. The fatigue life predictions based on the Palmgren–Miner rule, rain‐flow analysis and the constant amplitude life data measured in this work were also conservative.
FATIGUE DAMAGE IN 1045 STEEL UNDER VARIABLE AMPLITUDE BIAXIAL LOADING
Authors: Hua C. T. , Socie D. F.
Published: April 2007

Abstract—During constant amplitude loading, two different types of crack systems have been reported In the high cycle fatigue (HCF) region, cracks nucleate on a small number of maxium shear strain amplitude planes One of these cracks becomes a dominant crack and leads to failure of the specimen In the low cycle fatigue (LCF) region, equally developed microcracks are observed over the entire gage section and grow during the majority of the life. The failure is due to a linking in which the microcracks join up during the last few cycles of the fatigue life.

To investigate the interaction of these two types of crack systems in biaxial fatigue, experiments were performed on thin‐wall tubular specimens in tension, torsion and combined tension‐torsion loading The test program included step loading and block loading in which two equivalent strain amplitudes were employed. One of the equivalent strain amplitudes is in the HCF region and the other was in the LCF region

Fatigue lives were predicted from constant amplitude damage curves when a single crack system dominated the fatigue process Two competitive crack systems were sometimes developed on the maximum shear strain amplitude planes in a single specimen under block loading This resulted in a conservative prediction of the fatigue life.
THE INFLUENCE OF MICROSTRUCTURE ON THE GROWTH OF SMALL FATIGUE CRACKS
Authors: Lankford J.
Published: April 2007

Abstract—Recent experimental work on the growth of small fatigue cracks is surveyed and critically analyzed. It is shown that microcracks grow at anomalous rapid rates relative to large ones only when certain criteria, involving crack size, plastic zone size, and micro‐structural element size, are met. Retardation and arrest of microcracks is found to correlate with microstructural element size, hence with crystallographic influence.
FATIGUE MICROCRACKS IN A LOW CARBON STEEL
Authors: Suh C. M. , Yuuki R. , Kitagawa H.
Published: April 2007

Abstract— The behaviour of a low carbon steel has been studied, in particular the initiation, growth and coalescence of fatigue microcracks on the surfaces of smooth specimens via surface replicas and photomicrographs. From the study, quantitative information on the initiation period, growth and coalescence of cracks, statistical distributions of crack length and crack depth, density of cracks, distribution pattern and characteristics of the major crack, were obtained. Knowledge of these parameters is critical for non‐destructive inspection during service life and the application of fracture mechanics to life assessment.
ON FATIGUE CRACK SIZE DISTRIBUTIONS IN COPPER SINGLE CRYSTALS
Authors: Bao‐Tong Ma , Laird Campbell
Published: April 2007

Measurements of crack depths by newly developed sectioning techniques raise questions about the validity of the optical microscopy technique used by Cheng and Laird for measuring crack size distributions. Accordingly, these measurements have been repeated using an improved technique. The cracks have thus been found deeper than reported earlier. This result suggests that random‐walk mechanisms for crack nucleation apply to the earliest stages of fatigue life. Moreover, it is found that the crack size distribution matches the distribution of local strains in persistent slip bands, suggesting that Stage I crack propagation kinetics are controlled by the local plastic strain.
FATIGUE AT LOW GROWTH RATES IN A MARAGING STEEL
Authors: Clark Graham
Published: April 2007

This paper describes an experimental investigation of fatigue‐crack growth in an ultra‐high strength maraging steel, with particular attention to the relationship between crack growth rate and microstructural element size. The occurrence of intergranular fracture is shown to be unrelated to any grain size‐plastic zone size equivalence, while inflections in the growth rate vs ΔK relationship are discussed in terms of the interaction between the plastic zone and other microstructural dimensions. The incidence of intergranular fracture and crack surface oxide is shown to decrease with decreasing test frequency.
FATIGUE LIFE PREDICTION FOR GAUSSIAN RANDOM LOADS AT THE DESIGN STAGE
Authors: TUNNA J. M.
Published: April 2007

Fatigue life prediction under variable amplitude loading normally involves a two stage process of cycle counting and damage summation. This paper shows that for certain classes of strain history, predictions can be made directly from a knowledge only of the power spectral density of the strain history and conventional fatigue strength data.
CYCLIC STRESS‐STRAIN RESPONSE OF 2 1/4Cr‐1 Mo STEEL AT ELEVATED TEMPERATURES
Authors: Polák J. , Klesnil M. , Helešic J.
Published: April 2007

The temperature dependence of the cyclic stress‐strain response of 2 1/4 Cr‐1 Mo steel has been studied in the temperature range 20–550°C. Fatigue hardening‐softening curves and cyclic stress‐strain curves were obtained. A more detailed analysis was based on the statistical theory of the hysteresis loop and the concept of internal and effective stresses. A stress‐dip procedure allowed the separation of the contribution of internal and effective stresses both in dependence on temperature and during fatigue life in high temperature cyclic straining. The high effective stress contributes to the fatigue resistance of the steel. In high temperature fatigue both the internal and the effective stress decrease with cyclic straining.
AN EGF EXERCISE IN PREDICTING DUCTILE INSTABILITY: PHASE 2, CRACKED PRESSURE VESSEL
Authors: Milne I. , Knee N.
Published: April 2007

This report discusses the results of a collaborative European Group on Fracture exercise to predict the pressure‐crack size relationships of an experimental cracked pressure vessel which was undergoing tests for the CEGB. The details of the test and background mechanical properties data had been circulated to interested parties with a request for predictions to be returned prior to the vessel test results being published. The results of this exercise are described here, analysed in detail and compared with the test results.

Collectively, eighteen individuals provided thirty eight different estimates of the vessel behaviour. The procedures used included R6 and variants of it, crack tip opening displacement approaches, engineering J design curve approaches, simple plastic collapse criteria and the GE J estimation scheme.

Analysis of the predictions showed that:

(1) in the prediction of maximum pressures, the plastic limit pressure was important;

(2) in the prediction of initiation pressures the initiation toughness dominated;

(3) the detailed form of the resistance curve had little influence on either the crack growth predictions or the maximum pressure predictions.

(4) all forms of failure assessment diagram based upon the R6 axes were capable of producing accurate predictions.

(5) where a poor model was used to represent the cracked section the results were unsatisfactory.
THE EFFECTS OF SUB‐CRITICAL CRACK GROWTH ON THE FRACTURE BEHAVIOUR OF CRACKED FERRITIC STEELS AFTER WARM PRESTRESSING
Authors: Chell G. G.
Published: April 2007

The effects of sub‐critical crack extension on the fracture properties of ferritic steels after they have been subjected to warm prestressing are investigated. The crack growth is assumed to occur at the temperature of the final loading, after the warm prestressing and the subsequent unloading. Predictions of the fracture behaviour are made using continuum mechanics and a fracture criterion based on a modified J‐integral. The results of these calculations are consistent with those of a micromechanistic model of cleavage fracture from a sharp crack. Both the theories predict that the beneficial elevation in fracture load produced by warm prestressing is maintained after sub‐critical crack growth provided the latter is not greater than the compressive yielded zone formed on unloading.
A STUDY OF SHORT CRACK GROWTH IN TORSIONAL LOW CYCLE FATIGUE FOR A MEDIUM CARBON STEEL
Authors: Carbonell E. Perez , Brown M. W.
Published: April 2007

A study of short crack growth for a medium carbon steel in low cycle torsional fatigue has been carried out in order to measure crack length and derive growth laws. Comparison with a previous analysis of uniaxial tests in low cycle fatigue for the same material provides a tentative basis for formulating an equivalent stress approach to describe uniquely the propagation of short cracks under multiaxial stress.
A GENERALIZED CONCEPT OF A FATIGUE THRESHOLD
Authors: Castro D. E. , Marci G. , Munz D.
Published: April 2007

Abstract— The conditions for non‐propagating LEFM type fatigue cracks were investigated on an Inconel, 617 Alloy in the range of Kmax between 10 and 50 MPa m1/2 under four different types of fatigue loading conditions. In all tests, Kmax was held constant during the fatigue cycling prior to determining the non‐propagation condition. It was found that with decreasing range of applied K the fatigue tolerance range ΔKeff, th increases. Furthermore, there is slight increase of ΔKeff,th with decreasing Kmax of approximately 20–30% when Kmax is decreased from 50 to 10 MPa m1/2. The results of the four types of tests are considered in respect to the damage in the near‐region of the crack front, i.e. increasing Kmax increases the damage zone and therefore decreases the fatigue tolerance range ΔKeff,th.
A SINGLE EXPRESSION FORMULA FOR INVERTING STRAIN‐LIFE AND STRESS‐STRAIN RELATIONSHIPS
Authors: Manson S. S. , Muralidharan U.
Published: April 2007

Starting with the basic fatigue life formula

Δε/ΔεT= (Nf/NT)b+ (Nf/NT)c

an inversion formula is derived in the form

N
f/NT= [(Δε/ΔεT)z/b+ (Δε/ΔεT)z/c]1/z

where z is a function of strain range and the ratio c/b. The inversion formula is valid over the entire life range of engineering interest for all materials examined. Conformity between the two equations is extremely close, suitable for all engineering problems. The approach used to invert the life relation is also suitable for the inversion of other formulas involving the sum of two power‐law terms.
A STUDY OF FATIGUE FRACTURE SURFACES OF A CAST NICKEL‐BASE SUPERALLOY
Authors: Weicheng Yu , Jincai Yuan , Zhongguang Wang
Published: April 2007

Morphological features of fatigue fracture surfaces of a cast nickel‐base super‐alloy were investigated over the range of crack growth rates, 10‐10 ‐10‐6m/cycle. The cleavage facet growth in stage I and the transition of crack propagation from state I to stage II were studied by a combined study of surface crack growth rate and fracture surface examinations. A correlation between fatigue crack growth and the fracture surface appearance plus microstructural aspects has been established. It is suggested that fatigue‐induced vacancies might play a significant part in cleavage facet growth at lower crack growth rates.
FATIGUE ANALYSIS OF A RAIL SUBJECTED TO CONTROLLED SERVICE CONDITIONS
Authors: Rice R. C. , Rungta R.
Published: April 2007

Abstract— A fatigue analysis was conducted on a rail that was placed in the Facility for Accelerated Service Testing (FAST) after a detail fracture was detected in service. The initial detail crack produced in service was grown to failure under controlled FAST conditions simulating service. Knowledge of the FAST wheel/rail load history for this rail made it an ideal candidate for quantitative fatigue crack growth analysis.

The investigation revealed that undulations in the detail fracture surface were caused by changes in the direction of traffic. The angle of the facture surface, with respect to the running surface of the rail, was measured for each direction change. These results showed that the angles did not change significantly as the depth of the crack increased, relative to the running surface.

The change in the direction of traffic and the associated change in the angle of the detail fracture provided benchmarks on the surface that were used to estimate the crack growth rate between each train reversal. The results showed that the rate of detail crack growth remained relatively constant from its initial size, until it broke out on the gage side of the rail. After gage‐side break out, the crack growth rate increased until failure of the rail occurred.

This paper provides documentation on the process of detail fracture development in this specific rail. A discussion is also included which addresses the question of why detail fractures develop, and what the probable driving forces are for their growth.