bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue behaviour of a box‐welded joint under biaxial cyclic loads
Authors: Takahashi I. , Ushijima M. , Takada A. , Akiyama S. , Maenaka H. 
Published: March 2003

Multiaxial fatigue behaviour of box‐welded (wrap‐around) joints in a JIS SM400B steel (12‐mm‐thick plate) was examined using a biaxial fatigue test facility. For the specimen, two stiffeners were attached to a main plate by a CO2semi‐automatic welding procedure. Residual stress measurements and finite element (FE) analyses were also performed. Fatigue tests were performed under both uniaxial and biaxial (mainly out‐of‐phase) cyclic loads, and both results were compared and examined.It was found that fatigue cracks in the biaxial fatigue test specimens were initiated at the boxing‐weld toes and propagated almost in the direction of the lateral loads. This is considered to be due to the dominant direction of tensile residual stresses from welding and the stress concentration in the vicinity of the boxing‐weld toe.From the relation between the strain range near a weld toe, Δε5 , and the fatigue lives, it was found that crack initiation life,Nc , was almost equivalent in the biaxial and uniaxial fatigue tests, while the failure life,Nf , was slightly longer in the biaxial tests. However, when the fatigue lives are put in order using the stress range near a weld toe, Δσ5 , the crack initiation life,Nc , in the out‐of‐phase biaxial tests (phase difference ofπ) is ~30% lower than in the in‐phase biaxial and uniaxial tests, while the failure life,Nf , was almost equivalent in the biaxial and uniaxial tests. From these results, it is concluded that an increase in Δσ5(lowering of the minimum value ofσ5 ), induced by the out‐of‐phase lateral loads, leads to an increase in fatigue damage where the high tensile welding residual stresses exist in the vicinity of the boxing‐weld toe.Finally, a simple life estimation for the biaxial fatigue tests was made using FE analyses and the results of the uniaxial fatigue tests, proving that the effects of the lateral loads should be taken into consideration.
Response of notched carbon/PEEK and carbon/epoxy laminates subjected to tension fatigue loading
Authors: Aymerich F. , Found M. S. 
Published: March 2003

In this study a comparison is made between the tensile static and fatigue behaviours of quasi‐isotropic carbon/PEEK and carbon/epoxy notched laminates, selected as separate representatives of both tough and brittle matrix composites. Damage progression was monitored by various non‐destructive (ultrasonic scanning and x‐radiography) and destructive (deply and microscopic examinations) techniques, and by continuously measuring the change in stiffness, in order to identify the effect of damage on mechanical properties.The experimental observations indicated that fatigue damage in carbon/epoxy laminates consists of a combination of matrix cracks, longitudinal splitting and delaminations which attenuate the stress concentration and suppress fibre fracture at the notch; as a consequence, fatigue failure can be reached only after very high numbers of cycles while tensile residual strengths continuously increase over the range of lives investigated (103–106cycles). Due to the superior matrix toughness and the high fibre‐matrix adhesion, the nature of fatigue damage in carbon/PEEK laminates strongly depends on the stress level. At high stresses the absence of early splitting and delaminations promotes the propagation of fibre fracture therefore resulting in poor fatigue performances and significant strength reductions; while at low stress levels damage modes are matrix controlled and this again translates into very long fatigue lives. These results indicate a strong influence of the major damage mechanisms typical of the two material systems on the behaviour of the laminates, with the nature, more than the amount, of damage appearing as the controlling parameter of the material response up to failure.
Restraint of fatigue crack growth by wedge effects of fine particles
Authors: Takahashi I. , Takahashi C. , Kotani N. 
Published: March 2003

This paper presents some experimental results which demonstrate restraint of fatigue crack growth in an Al–Mg alloy by wedge effects of fine particles.Fatigue test specimens were machined from a JIS A5083P‐O Al–Mg alloy plate of 5 mm thickness and an EDM starter notch was introduced to each specimen. Three kinds of fine particles were prepared as the materials to be wedged into the fatigue cracks, i.e. magnetic particles and two kinds of alumina particles having different mean particle sizes of 47.3 μm and 15.2 μm. Particles of each kind were suspended in an oil to form a paste, which was applied on the specimen surface covering the notch zone prior to the fatigue tests. In order to make some fracture mechanics approaches, in situ observations of fatigue cracks were performed for the two cases using a CCD microscope, with a magnification of ×1000. The crack length and the crack opening displacement (COD) at the notch root, δ, were measured.First it was ensured by control tests that the wedge effect of the oil itself was negligible. Then it was found that the large size alumina particles were not effective in restraining crack growth because the paste was difficult to make due to the large particle size and the particles could not enter the cracks properly.However, both of the magnetic particles and the small size alumina particles effectively restrained crack growth, especially the latter which produced 143–350% increase in the lifetime to failure.From the in situ observations, in the case of the small size alumina particles, a pronounced retardation of crack growth was observed immediately after the crack length exceeded 0.4 mm, and this is considered to be due to the range of COD value, δmax − δmin , being strongly affected by the wedge effects of the particles. The crack retardation effect continues almost through the entire lifetime if the alumina paste is re‐applied at specified intervals, while the effect is apparently lost after the crack length exceeds ∼2 mm when such re‐painting is not continued.After the fatigue tests, some macro‐ and microfractographic analyses were performed using a CCD microscope, a SEM and an EPMA (electron probe microanalyser), in order to examine the mechanism of fatigue crack restraint by the wedge effects of the fine particles. From those analyses, it was reasoned that the fine particles that entered a fatigue crack are subjected to cyclic pressures between the crack faces and then form a kind of wedge which causes significant levels of crack closure that restrain crack growth.
Fatigue of casting flaws at a notch root under an SAE service load history
Authors: Dabayeh A. A. , Topper T. H. 
Published: March 2003

Smooth and notched specimens of a 319 cast aluminium alloy were fatigue tested under a Society of Automotive Engineers service load history in the as‐cast and hipped conditions. The hipping process, which includes subjecting the cast material to a high pressure at high temperature and then slowly cooling down to eliminate internal flaws, decreased the flaw size and improved the fatigue life of cast Al 319 smooth specimens. A 0.6‐mm‐diameter hole was drilled at the notch root of notched specimens to simulate a natural flaw at the notch root. Specimens with two different notch sizes were tested. Circular edge notches reduced the fatigue strength and a 0.6‐mm‐diameter drilled hole at the notch root resulted in a further reduction.The fatigue lives of smooth specimens, notched specimens and notched specimens with a flaw at the notch root subjected to the service load history were predicted using the strain‐life approach, an effective strain‐life approach and a strain‐based intensity factor crack growth model. In crack growth modelling of the fatigue life of smooth cast aluminium specimens the flaw was modelled as a circular edge notch having the same diameter as the flaw. However, in the case of a flaw at a notch root the flaw was modelled as a three‐dimensional cavity subjected to the notch stress field and the crack length was predicted in the longitudinal and transverse directions of the specimen cross‐section. The strain‐life approach was unconservative for all specimen geometries studied. The effective strain‐life approach gave good predictions for smooth and blunt notched specimens but gave very conservative predictions for the specimens with flaws in the notch roots. The crack growth calculations gave accurate predictions for all the specimen geometries.
A rolling contact fatigue crack driven by squeeze fluid film
Authors: BOGDAÑSKI S. 
Published: March 2003

ABSTRACT A new model of surface breaking rolling contact fatigue (RCF) crack driven by a coupled action of a squeeze oil film built up in the crack interior and a pressure exerted at the external contact interface was developed. The model can be applied to the ‘nominally dry’ contact couples with an occasional presence of liquid in the crack interior (wheel/rail contact) as well as to the elastohydrodynamic lubrication (EHL) conditions. In the first case, the contact load is a result of solid/solid interaction and can be determined by solving the FE contact problem, but the liquid contained in the crack interior forms a thin film between the crack faces changing their interaction into the type of liquid/solid. This liquid is being periodically squeezed under contact load and acts as a ‘squeeze film’ known from the lubrication theory. In the second case, the liquid (lubricating oil) is permanently present in the contact area and consequently in the vicinity of the crack mouth. This creates conditions for filling the crack with oil. Similarly as in the first case, the ‘squeeze oil film’ is built between the crack faces. The contact load in this case results from a liquid/solid interaction and can be approximated by the pressure and traction distributions obtained from the numerical solution of the elastohydrodynamic contact problem. In both cases the model can be used to determine the Linear Elastic Fracture Mechanics (LEFM) crack tip stress intensity histories during cyclic loading and consequently to predict the crack growth rate and direction.An example of applying the model to the EHL case is given to explain the mechanisms and phenomena leading to the crack front loading. The cycle of rolling a roller over the crack was numerically simulated to obtain the mixed mode (I and II) SIF histories. In the analysis, the EHD pressure and traction were determined through the full solution of the EHD line contact problem accounting for the presence of a crack, whilst the pressure in the crack was found with the use of the wedge shaped squeeze oil film (SOF) model. Possible effects of the mode I and mode II stress intensity cycles on crack growth rate and direction are discussed. The solution indicates high pressure in the neighbourhood of the crack tip, exerted on the crack faces by the squeeze oil film. This leads to the ranges of the mode I and mode II SIF variations, which are larger than for the ‘dry’ and ‘fluid entrapment’ models, and can be an explanation for the crack growth rate observed in practice
Effects of mean stress and crack closure on fatigue life of spot welds
Authors: HENRYSSON H.‐F. 
Published: March 2003

ABSTRACTThe effects of mean stress and crack closure on fatigue life of spot welds were investigated. A review showed that several of the previously proposed mean stress corrections give similar results. Fatigue tests on shear and peel loaded specimens were carried out, and the results agreed with the corrections reviewed. The present study shows that crack closure explains the mean stress effects observed. The crack opening force for spot welds was obtained, both experimentally from F–N curves with different load ratios and analytically from the available mean stress corrections. This was verified with detailed finite element simulations. Finally, the experiments and simulations indicate that the use of linear damage accumulation in fatigue life prediction of spot welds can be non‐conservative.
Evidence that the fungus cultured by leaf‐cutting ants does not metabolize cellulose
Authors: Abril Adriana B. , Bucher Enrique H. 
Published: March 2003

AbstractLeaf‐cutting ants are a very specialized group of ants that cultivate fungus gardens in their nests, from which they obtain food. The current opinion is that the fungus cultivated by leaf‐cutting ants digests cellulose. Here we reassess the cellulose‐degrading capability of the fungus by using two complementary approaches tested in four Attini species (genera Atta and Acromyrmex): (1) ability of fungus to grow in cellulose; and (2) lignin/cellulose ratio in the refuse material dumped outside the nest, as an indicator of cellulose consumption. We found that (1) the fungus did not grow in cellulose, and (2) the lignin/cellulose ratio was much lower in the ants' refuse than in material digested by cellulose‐digesting organisms, such as brown‐rot fungus, termites, and ruminant mammals. This evidence strongly suggests the inability of the fungus to degrade cellulose. Therefore, the fungus–ant symbiosis and the ecological role of leaf‐cutting ants need to be reconsidered.
Complex networks: two ways to be robust?
Authors: Melián Carlos J. , Bascompte Jordi 
Published: March 2003

AbstractRecent studies of biological networks have focused on the distribution of the number of links per node. However, the connectivity distribution does not uncover all the complexity of their topology. Here, we analyse the relation between the connectivity of a species and the average connectivity of its nearest neighbours in three of the most resolved community food webs. We compare the pattern arising with the one recently reported for protein networks and for a simple null model of a random network. Whereas two highly connected nodes are unlikely to be connected between each other in protein networks, the reverse happens in food webs. We discuss this difference in organization in relation to the robustness of biological networks to different types of perturbation.
β‐Glucose 1‐phosphate‐interconverting enzymes in maltose‐ and trehalose‐fermenting lactic acid bacteria
Authors: Andersson Ulrika , Rådström Peter 
Published: March 2003

SummaryMaltose and trehalose catabolic pathways are linked through their common enzyme, β‐phosphoglucomutase, and metabolite, β‐glucose 1‐phosphate, in Lactococcus lactis. Maltose is degraded by the concerted action of maltose phosphorylase and β‐phosphoglucomutase, whereas trehalose is assimilated by a novel pathway, including the recently discovered enzyme, trehalose 6‐phosphate phosphorylase, and β‐phosphoglucomutase. In the present study, 40 strains of lactic acid bacteria were investigated for utilization of metabolic reactions involving β‐glucose 1‐phosphate. All genera of the low G+C content lactic acid bacteria belonging to the clostridial subbranch of Gram‐positive bacteria were represented in the study. The strains, which fermented maltose or trehalose, were investigated for β‐phosphoglucomutase, maltose phosphorylase and trehalose 6‐phosphate phosphorylase activity, as indications of maltose and trehalose catabolic pathways involving β‐glucose 1‐phosphate interconversions. Eighty per cent of all strains fermented maltose and, of these strains, 63% were shown to use a maltose phosphorylase/β‐ phosphoglucomutase pathway. One‐third of the strains fermenting trehalose were found to harbour trehalose 6‐phosphate phosphorylase activity, and these were also shown to possess β‐phosphoglucomutase activity. Mainly L. lactis and Enterococcus faecalis strains were found to harbour the novel trehalose 6‐phosphate phosphorylase/β‐phosphoglucomutase pathway. As lower β‐glucose 1‐phosphate interconverting enzyme activities were observed in the majority of glucose‐cultivated lactic acid bacteria, glucose was suggested to repress the synthesis of these enzymes in most strains. Thus, metabolic reactions involving the β‐anomer of glucose 1‐phosphate are frequently found in both maltose‐ and trehalose‐utilizing lactic acid bacteria.
Microenvironments and microbial community structure in sediments
Authors: Tankéré S. P. C. , Bourne D. G. , Muller F. L. L. , Torsvik V. 
Published: March 2003

SummaryThe aim of this study was to explore the potential of a combined chemical and microbiological approach as part of a study of organic carbon oxidation processes in sediments. An assessment of microbiological diversity using molecular techniques was carried out in combination with high resolution chemical measurements at the sediment–water interface of a coastal lagoon affected by eutrophication in autumn 2000. There was a 0.2 mm overlap between the O2 and H2S profiles. pH showed a maximum just above the sediment–water interface coinciding with an oxygen maximum, suggesting photosynthetic activity, and a minimum coinciding with the O2–H2S interface. The redox potential was high in bottom water and surface sediment, reflecting the presence of oxygen and oxides, and reached low values after a step‐wise decrease at −18 mm. Reduction of Fe occurred within the biofilm at the O2–H2S interface and was mostly due to reduction by H2S. The elevated concentrations of dissolved Mn in the oxic water may have been caused either by in situ production within organic aggregates or lateral water flow from sites nearby at which Mn2+ diffuses out of the sediment. Sequences related to sulphur chemolitotrophs were retrieved from the biofilm samples, which is consistent with the small overlap between O2 and H2S observed in this biofilm. Although the resolution of techniques used was different, sequencing results were consistent with chemical data in delineating the same horizons according to redox, pH or ecological properties.
Endoluminal stenting for relief of colonic obstruction is safe and effective
Authors: Cole  , Boorman  , Osman  , Sathananthan  , Parker  
Published: March 2003

ObjectiveThe aim of this study was to investigate the outcome of endoluminal stenting in the management of patients presenting with acute large bowel obstruction.Patients and methodsTwenty‐eight consecutive patients presenting to one consultant surgeon with large bowel obstruction were considered for the procedure.ResultsTwenty‐four patients were successfully treated using this modality, which is to date the largest series in the UK. We discuss the complications encountered in detail and discuss the cost effectiveness of this procedure.ConclusionEndoluminal stenting is safe and effective, and cost effective for palliation. We advocate a multicentre randomized prospective trial of best practice emergency surgery vs endoluminal stenting and subsequent elective surgery for large bowel obstruction.
Rectal excision with coloanal anastomosis for superficial distal third rectal cancer: Survival and local recurrence
Authors: Gamagami R. A. , Liagre A. , Istvan G. , Muhammad S. , Moossa A. R. , Lazorthes F. 
Published: March 2003

ObjectiveAppropriate surgical treatment of distal third rectal cancer limited to bowel wall (i.e. T1 or T2) in medically operable patients is controversial. Transanal excision can deprive some patients of accurate pathological staging, prognosis and cure. In contrast abdominoperineal resection has considerable practical and psychosocial problems largely related to a permanent colostomy. We hypothesize that superficial distal rectal tumours can be effectively treated with rectal excision and coloanal anastomosis.Subjects and methodsProspective oncological study of 80 patients with distal third superficial rectal carcinomas treated by complete rectal excision with coloananl anastomosis from December 1977 to January 1993 was carried out. The resected specimens were examined for depth of spread and number of histologically positive nodes. The actuarial local recurrence and survival rates for superficial node‐negative and node‐positive tumours were analysed independently.ResultsSeventy‐eight patients had complete postoperative assessment. Thirty‐one percent had received low‐dose preoperative neo‐adjuvant radiotherapy (3500 rads). Mean follow‐up time in all patients was 70 months on average. The lymph node involvement rate for T1 and T2 tumours was 12.5 and 15.6%, respectively. The local recurrence rates for patients with (T1/T2) N0 and (T1/T2) N1 were 1.5 and 16.7%, respectively, and the five year actuarial survival rates were 96.6 and 90%, respectively. The overall local recurrence was 3.8% with five‐year actuarial survival of 95.8%.ConclusionsLymph node involvement in superficial tumours is not rare. Rectal excision with coloanal anastomosis results in a high cure rate especially for node‐positive superficial tumours. This treatment strategy avoids the psychological trauma of colostomy following abdominoperineal resection and the potential risk of undertreatment by local excision.
The results of total mesorectal excision for rectal carcinoma in a district general hospital before the era of surgical specialization
Authors: Saha S. , Booth M. I. , Dehn T. C. B. 
Published: March 2003

ObjectiveTo evaluate the results of rectal cancer surgery performed by a gastrointestinal surgeon in a district general hospital prior to the introduction of specialization, and to compare these to the targets set by the Royal College of Surgeons for specialist units.MethodsData collection in 73 consecutive patients (prospective in 53) undergoing elective excisional surgery (sphincter conserving in 77%) for rectal cancer. While adjuvant radio/chemotherapy and pathological assessment evolved over the study period, a standardized surgical technique (total mesorectal excision) was used in all patients.ResultsObserved (and recommended) outcome measures were operative mortality 4.1% (<5), anastomotic leak 6.2% (<8), wound infection 2.7% (< 10), pelvic recurrence after curative resection 9.6% (< 10). Temporary defunctioning stomas were used in 32/48 (66.7%) of patients. Other complications, currently without recommended outcomes, were erectile dysfunction (13%), stoma related (7.1%) urinary retention (4.1%), urinary incontinence (2.7%) and benign anastomotic stricture (2.7%).ConclusionAll treatment outcome criteria were met. Trained gastrointestinal surgeons outside the setting of a specialist unit can achieve good results with acceptable complication rates.