bluuebunny/crossref_metadata_2025 huggingface dataset:
Rectal cancer in Victoria in 1994: Patterns of reported management
Authors: Farmer K. Chip , Penfold Campbell , Millar Jeremy L. , Zalcberg John , McLeish John A. , Thomas Robert J. S. , Lade Stephen , Thursfield Vicky J. , Giles Graham G.
Published: March 2003

Background: A retrospective survey of medical practitioners was conducted to describe the management of patients newly diagnosed with rectal cancer in 1994, prior to the publication of best practice guidelines.

Methods: A sample of 908 patients with rectal cancer diagnosed between 1 January and 31 December 1994 was identified from the Victorian Cancer Registry. Questionnaires were then sent to the treating doctor(s) for completion. The topics covered by the questionnaires included: reported management by method of diagnosis; staging investigations; and treatment by surgery, chemotherapy and radiotherapy.

Results: Seven hundred and twenty‐six (80%) of 908 eligible patients were surveyed. Surgery was the primary treatment in 681 (93.8%) with curative intent in 483 (70.9%) of these cases. One‐ third (163; 33.7%) of curative cases were pathologically staged as Dukes’ C. Almost all patients (96%) were symptomatic, and three‐quarters were referred by general practitioners to 166 surgeons. One‐third (221; 32.5%) underwent liver computed tomography or ultrasound, and only three cases had transrectal ultrasound. Restorative anterior resection was the most common surgical procedure (431; 63.3%) with 160 (23.5%) and 34 (5.0%) patients being managed with abdominoperineal resections and local excision, respectively. Chemotherapy and radiotherapy were administered as part of the initial management to 216 (31.7%) and 171 (25.1%) patients, respectively. In five of the 171 cases, radiotherapy was given preoperatively.

Conclusions: There was considerable variation in preoperative assessment. Staging was less complete than expected by today’s standards. The diversity of surgical techniques observed may reflect both the lack of clinical trials and disparity in surgical training and experience. Referral to stomal therapists, and medical and radiation oncologists was lower than would now be expected, as was the use and timing of adjuvant therapies. These findings will be useful as a baseline for comparison with subsequent surveys conducted since the introduction of evidence‐based guidelines.
Survival from colorectal cancer in Victoria: 10‐year follow up of the 1987 management survey
Authors: McLeish John A. , Thursfield Vicky J. , Giles Graham G.
Published: March 2003

Background: In 1987, the Victorian Cancer Registry identified a population‐based sample of patients who underwent surgery for colorectal cancer for an audit of management following resection. Over 10 years have passed since this survey, and data on the survival of these patients (incorporating various prognostic indicators collected at the time of the survey) are now discussed in the present report.

Methods: Relative survival analysis was conducted for each prognostic indicator separately and then combined in a multivariate model.

Results: Relative survival at 5 years for patients undergoing curative resections was 76% compared with 7% for those whose treatment was considered palliative. Survival at 10 years was little changed (73% and 7% respectively). Survival did not differ significantly by sex or age irrespective of treatment intention. In the curative group, only stage was a significant predictor of survival. Multivariate analysis was performed only for the curative group. Adjusting for all variables simultaneously, stage was the only ­significant predictor of survival. Patients with Dukes’ stage C disease were at a significantly greater risk (OR 5.5 (1.7−17.6)) than those with Dukes’ A. Neither tumour site, sex, age, surgeon activity level nor adjuvant therapies made a significant contribution to the model.
Isolated dissection of a non‐aneurysmal popliteal artery
Authors: Krishna Govind , G. Bourchier Russell , MacCormick D. E. M. , A. Hill Andrew
Published: March 2003

Two cases of isolated dissection of a non‐aneurysmal, non‐atherosclerotic popliteal artery are reported. Isolated dissection of the popliteal artery is a distinct entity that may have far reaching effects on patient's mobility if not adequately treated. This lesion can be seen in non‐aneurysmal, non‐atherosclerotic vessels and in patients with no predisposing medical causes. It requires a high degree of suspicion for diagnosis because of its rarity. Surgical treatment is the best option and results in a good outcome.
Wound healing and growth factor expression in T lymphocyte deficiency
Authors: Chircop Matthew P. , Yu Yan , Berney Christopher R. , Yang Jia‐Lin , Crowe Philip J. , Walsh William R.
Published: March 2003

Background:  There are many clinical situations in which immune suppression or deficiency occurs. This may lead to healing impairment. The aim of the present study was to characterize the effect of T lymphocyte deficiency on wound healing, and on ­platelet‐derived growth factor (PDGF), bFGF (basic fibroblast growth factor) and insulin‐like growth factor‐1 (IGF‐1) expression, using an animal model.

Methods:  Nude and normal 10−12‐week‐old male BALB/c mice were given standard dermal incisions and killed at 1, 2, 4 or 6 weeks postinjury. The pelts were harvested and the wounds cut (perpendicularly) into strips for analysis. Strips from each animal were tested mechanically or processed for histological assessment and immunohistochemical detection of PDGF, bFGF and IGF‐1 and colour video image analysis. The data were assessed by analysis of variance (anova).

Results:  The interaction between species and time resulted in statistically significant differences in mechanical properties. Wound peak load was higher in nude mice at weeks 1 and 2 postinjury, but lower in nude mice at week 6 postinjury. Colour video image analysis demonstrated that the expression of bFGF and IGF‐1 was greater in nude mice at week 1 postinjury (P < 0.05).

Conclusions:  The mechanical data suggest that the overall effect of the T lymphocyte system on wound healing is initially inhibitory and later stimulatory. This may be associated with corresponding differences in wound growth factor expression.
Why not use a small incision to treat large hydroceles?
Authors: Chalasani Venu , Woo Henry H.
Published: March 2003

Background:  Operative treatment of large hydroceles generally requires a large incision.

Methods:  A technique is described which permits a traditional Jaboulay's or Lord's repair to be done through a 3 cm incision.

Results:  Twenty patients with large hydroceles were operated on from June 2000 to November 2001 using this technique and to date, only one patient has had a recurrence. There has been no occurrence of either scrotal wound infection or haematoma ­formation.

Conclusions:  A hydrocele repair of the surgeon's choice can be done safely through a 3 cm incision.
Use of octreotide and lanreotide in the treatment of symptomatic non‐resectable carcinoid tumours
Authors: Rohaizak Muhammad , Farndon John Richard
Published: March 2003

Background:  Carcinoid tumours are rare neoplasms that secrete hormones and biogenic amines, most commonly serotonin. Octreotide and long acting lanreotide are found to be useful in the management of carcinoid syndrome by its interaction with somatostatin receptor, found on the carcinoid tumour. The aim of this study is to look at the efficacy of octreotide and long acting lanreotide in the treatment of symptomatic non‐resectable carcinoid tumours.

Method:  The effects of octreotide and long‐acting lanreotide were studied in 10 patients with symptomatic non‐resectable carcinoid tumours.

Results:  Symptom improvement occurred in nine of 10 patients. Three patients responded only to octreotide, three patients responded to both octreotide and long‐acting lanreotide and three patients only responded to long‐acting lanreotide. Slight reductions in 24‐h urine 5‐hydroxyindoleacetic acid levels occurred in three of six patients but no patients were found to have objective tumour regression on computed tomography scan.

Conclusions:  Octreotide and long‐acting lanreotide are useful palliative treatments for the control of symptoms in patients with non‐resectable carcinoid tumours but there is no evidence of tumour stasis.
A technique for wound closure that minimizes sepsis after stoma closure
Authors: Sutton Christopher Derek , Williams Nigel , Marshall Leslie‐Jayne , Lloyd Geraint , Thomas William Michael
Published: March 2003

Background:  The aim of the present study was to assess the incidence of wound sepsis following closure of ileostomies and colostomies in our institution.

Methods:  Circumferential subcuticular wound approximation was used in 51 patients in our institution. Evidence of wound sepsis (assessed by the presence of cellulitis, induration and or purulent discharge) was documented both in the postoperative period and in outpatient follow‐up.

Results:  A wound infection rate of 0% was achieved, both in the immediate postoperative period and upon 6‐week follow‐up.

Conclusions:  Circumferential subcuticular wound approximation is, therefore, a safe and efficacious technique for dealing with the skin woundafter stomal closure, virtually abolishing wound sepsis.
Thyroid cancer: The Kuala Lumpur experience
Authors: Abdullah Muhammad
Published: March 2003

Background:  There have been few detailed studies on thyroid cancer (TC) in Malaysia, a multiethnic country with three major races − Malays, Chinese and Indians.

Methods:  The paper retrospectively audits the records of 107 consecutive cases with histologically proven thyroid cancer between 1995 and 2000 presenting to University Hospital, Kuala Lumpur. The demographic distribution, histological variants, mode of presentation, sensitivity of fine needle aspiration cytology and the modalities of treatment are examined in the present paper.

Results:  Of a total of 107 cases of TC, 74 were papillary, 23 follicular, one Hurthle Cell, seven medullary and two anaplastic. There were 91 women and 16 men; the corresponding median age of presentation being 34.0 and 40.0 years. The median age at presentation of TC was 36 years in the Malay population, 37 in the Chinese population and 33 in the Indian population. Fifty‐six per cent of follicular cancer incidence was in the Malay population alone, the remaining in the other populations. Solitary thyroid nodule was seen in 75 patients, generalized enlargement in 20 and no goiter in 11. Local symptoms were reported in <10% of patients. Preoperative FNAC had a sensitivity of 72.26%. Of 98 patients with well‐differentiated TC (WDTC), total thyroidectomy was employed in 92. Surgery alone was used in 48 cases and combined with radioactive iodine ablation in the remaining 50.

Conclusion:  All histological variants of TC are represented in the study. Well‐differentiated TC forms the bulk with papillary cancer having the largest percentage. Follicular cancer is more common in the Malay population. Total thyroidectomy in WDTC, although controversial, remains the mainstay of surgical treatment in Malaysia.
Fasciotomy for chronic compartment syndrome in the lower limb
Authors: Cook Steven , Bruce Greg
Published: March 2003

Background:  The aim of this study was to determine the success of fasciotomy of lower limb compartments with elevated intra­compartment pressure.

Methods:  The present report is a retrospective cohort study at No. 3 Combat Support Hospital involving a survey and case note review of patients who had undergone fasciotomy for compartment syndrome at least 6 months earlier (December 1997−December2000).

Results:  Fourteen patients met the inclusion criteria. Eleven reported success with complete resolution of symptoms and return to military fitness levels. Two reported no change and significant residual symptoms. One reported worse symptoms and one required re‐operation with a successful result.

Conclusion:  Surgical decompression is the accepted treatment of compartment syndrome as proven by pressure manometry, after failure of conservative treatment.
Does laparoscopic fenestration provide long‐term alleviation for symptomatic cystic disease of the liver?
Authors: Tan Y. M. , Ooi London Lucien , Soo K. C. , Mack P.O. P.
Published: March 2003

Background:  The use of laparoscopic technique for management of symptomatic liver cysts is documented to be a feasible and safe procedure with good short‐term symptomatic relief. However, it cannot be recommended as the standard of care as long‐term results are scarce. The present study was initiated to review the long‐term results of this approach in the management of symptomatic liver cysts.

Methods:  A retrospective review of all patients with symptomatic liver cysts that were treated by laparoscopic fenestration in our department over an 8‐year period from 1993 to 2001. The clinical and radiographical data were analysed at follow‐up to assess the ­outcome.

Results:  Eleven patients were treated using a laparoscopic approach;10 patients with solitary cysts and one with adult polycystic liver disease. All patients achieved short‐term alleviation of symptoms and an uneventful postoperative course. The mean hospital stay was 3 days. Long‐term follow up was available for 9 patients with a mean of 44 months. Histologically, one of the patients was diagnosed with a biliary cystadenoma and she had a symptomatic recurrence and a liver resection at 20 months. In the other seven patients, there was no clinical recurrence but a radiographical recurrence of 28.5%. The patient with adult polycystic liver disease had two symptomatic recurrences: at 26 months where he underwent a repeat laparoscopic fenestration and at 43 monthswhere he underwent an open fenestration.

Conclusion:  The present study confirms that with adequate patient selection, long‐term alleviation of symptoms can be achieved with the laparoscopic approach for solitary simple liver cysts but not for polycystic liver disease or cystic tumours of the liver.
Recurrent laryngeal nerve in thyroid surgery: A critical appraisal
Authors: Hisham Abdullah N. , Lukman Mohd R.
Published: March 2003

Background:  Identification and preservation of the recurrent laryngeal nerve (RLN) is of major concern in surgery of the thyroid gland. The purpose of this study was to review the surgical anatomy of the nerve and to describe its relationship to other important structures.

Methods:  A total of 325 patients were accrued in this prospective non‐randomized study from January 1999 to December 2000. All patients who had total, subtotal and hemithyroidectomies were included in this study. Each side of the thyroid gland was considered as a separate unit in the analysis of the results.

Results:  Two hundred and seventy‐six patients had thyroidectomies as their primary operation, while 49 patients had them as a reoperative procedure. There were 276 women and 46 men (6:1 female to male ratio) with a mean age of 43.1 years (range: 10−84 years). The total number of dissections was 502. The RLN was clearly identified in 491 (97.8%) dissections: single trunk in 323 dissections (65.8%), two extralaryngeal branches in 164 dissections (33.4%), and three extralaryngeal branches in three dissections (0.6%). One non‐recurrent laryngeal nerve was encountered (0.2%) in the series. The proximity of the RLN to the inferior thyroid artery (ITA) was noted in 444 (90.4%) dissections: 372 (83.8%) nerves were described to be posterior and intertwined between the branches of the ITA, and in 72 (16.2%) RLNs, they were observed to be anterior to the ITA. The close association of RLN to an enlarged tubercle of Zuckerkandl was documented in 381 dissections (73.7%). A total of 231 RLNs (60.8%) was seen in the tracheoesophageal groove, 18 (4.9%) nerves were observed to be lateral to the trachea, and in 109 (28.3%), they were posterior in location. Of concern in 23 (6.0%) dissections the RLN was on the anterior surface of the thyroid gland, which is at highest risk of injury before curving down to pass behind the tubercle of Zuckerkandl. It appears that the anterior course of the RLN was seen more often in the reoperative procedures to the thyroid gland (20%).

Conclusions:  Although various methods of localizing the RLN have been described, surgeons should be aware of the variations and have a thorough knowledge of normal anatomy in order to achieve a high standard of care. This will ensure the integrity and safety of the RLN in thyroid surgery. The anatomical variation may be minor in degree, but is of great importance as it may affect the outcome of the surgery and the patient's quality of life.
Vascular closure staples reduce intimal hyperplasia in prosthesis implantation
Authors: Hawthorne Wayne J. , Ao Peng Y. , Fletcher John P.
Published: March 2003

Background:  Vascular surgery, like the various other surgical specialities, has seen an increasing demand toward faster and more minimally invasive procedures. One such need is to create a reliable vascular anastomosis that is faster, easier and less damaging to the tissue. The vascular closure staples (VCS*) device provides such characteristics but, to date, no studies have investigated its effectiveness in reducing intimal hyperplasia when used for vascular prosthesis implantation. The present study evaluated its effectiveness compared with suturing of a graft in vascular prosthesis implantation.

Methods:  Twelve female Merino sheep underwent gelatin sealed Dacron patch graft implantation into the left and right common carotid artery. Grafts were randomly allocated so that one carotid artery and graft was anastomosed using sutures and the other with VCS*. The two techniques were compared for operation time, clip/suture numbers and blood loss during the implantation procedure. After a 4‐week period, the sheep were killed and the grafts were harvested for intimal hyperplasia (IH) assessment.

Results:  There was a significant reduction in the amount of IH seen in the VCS* group (mean ± SD: 0.278 ± 0.079 mm2/mm) when compared with the sutured group (0.575 ± 0.331 mm2/mm) (P < 0.05). There was also significant reduction in anastomosis time (mean ± SD: 14 ± 4.4 min) and fewer points of contact (23 ± 1.4) using the VCS* compared with suturing (22 ± 3.2 min, P < 0.01; 27 ± 3.3, P < 0.05, respectively).

Conclusions:  In this model, the VCS* shows several distinct advantages over suturing with significant time saving at operation and, most importantly, the reduction of IH seen at 1 month.
Cutaneous innervation in man before and after lumbar sympathectomy: evidence for interruption of both sensory and vasomotor nerve fibres
Authors: Coventry Brendon J. , Walsh John A.
Published: March 2003

Background:  Rest pain and severe ischaemia in patients who are unable to be offered (further) surgery to revascularize the lower limb is still problematic. Lumbar sympathectomy has been used for many years but the mechanisms by which this works are not absolutely clear. Both sensory and vasomotor fibres travel in the lumbar sympathetic chain and the effects of lumbar sympathectomy on these nerve types have been investigated in the present paper.

Methods:  Immunohistochemical methods were used to detect neuropeptides contained in sensory and vasomotor nerves in the lower limb skin of (i) patients having amputations for peripheral vascular disease (PVD) after previous (chemical or surgical) sympathectomy; (ii) patients having amputations for PVD without previous (chemical or surgical) sympathectomy; and in control normal skin. The three groups are compared and the results are discussed.

Results:  Normal and PVD controls had intact sensory and vasomotor nerves around dermal cutaneous blood vessels, but these were completely or virtually completely lost after lumbar sympathectomy, by either chemical or surgical means.

Conclusions:  Lumbar sympathectomy severs both vasomotor and sensory fibres, suggesting that relief of rest pain may be explained not only by increased cutaneous and muscle blood flow, but also by nociceptive sensory denervation.
CONDITIONS FOR ADAPTATION OF DAMAGED ELASTIC–PLASTIC BODIES TO CYCLIC LOADING
Authors: Druyanov  , Roman
Published: March 2003

Conditions for adaptation of isotropically damaged elastic–plastic bodies with isotropic strain hardening are investigated in the framework of the energy‐based coupled elastic–plastic damage model by Ju. The yield function is assumed to be a homogeneous function of the first order in the stress tensor components. Due to this assumption, the notion of effective yield stress can be introduced. The loading program is supposed to be prescribed. Features of the stress path at the post‐adaptation stage are considered, which lead to new necessary shakedown conditions expressed by a set of inequalities, and, in turn, to a problem of mathematical programming whose solution yields lower estimates for the damage and strain‐hardening parameters. In the event, if the calculated value of the damage parameter is greater than its critical value, an adaptation to a given loading program is impossible. This condition is also necessary for adaptation in the case if only bounds for applied loads are prescribed. A correction of the constitutive material model is proposed which possibly could be good for ductile damage. The derived shakedown condition is not only necessary, but also sufficient for the plastic adaptation. The developed method is expounded in an example.
AN ANALYTICAL STUDY OF VOID GROWTH IN VISCOPLASTIC SOLIDS
Authors: Mohan  , Brust
Published: March 2003

Detailed numerical analyses are conducted to examine the effect of material elasticity and non‐linear shape changes on void growth in viscoplastic solids. Numerical simulations are carried out under constant stress as well as cyclic loading conditions. The material response is assumed to be elastic‐non‐linear viscous (power law creep). Analyses of void growth are conducted assuming creep‐controlled mechanism. The role of finite geometry changes in understanding cavity growth under balanced strain‐controlled cyclic loading is also explored. The results indicate that while elastic accommodation does not influence void growth, non‐linear shape changes of the voids significantly affect their growth characteristics. It is also shown that while grain boundary voids can grow under balanced strain cyclic loading when the accompanying shape changes are accounted for, they can either shrink or grow under load‐controlled cycling depending on the loading frequency.
CREEP BEHAVIOUR OF FULL‐SIZE WELDED JOINTS: DEFECT ACCEPTANCE CRITERIA
Authors: Allais  , Dessalas  , Forgeron  , François  , Huthmann  , Escaravage  , Poette  , Sassoulas
Published: March 2003

In order to explore the creep crack growth behaviour in welds of real components, creep tests were performed at 600 °C on large specimens made of 316L(N) stainless steel plates. Manual Metal Arc (MMA) welds were investigated. The overall deformation of the specimens, and in many instances the local deformations of the welds, were recorded. The evolutions of the defects were followed by potential drop techniques. The experimental results were compared with two‐dimensional finite element computations, based on the creep behaviour of the base and weld metals, determined with small standard specimens. The time to creep crack growth initiation was correlated with theC* parameter determined from the load–displacement rate. The times to initiation of creep crack growth were compared with evaluations using the RCC‐MR code and R5 rules, as well as other methods, in particular those derived by finite elements analysis
A BOUNDARY ELEMENT MODEL OF PLASTICITY‐INDUCED FATIGUE CRACK CLOSURE
Authors: Nowell
Published: March 2003

This paper describes a plane stress boundary element model of plasticity‐induced fatigue crack closure. A simple Dugdale‐type strip yield zone is used and quadratic programming techniques are employed to establish crack shape, stress and plastic deformation. The technique is extremely effective and the model can be readily implemented on a personal computer. Predictions of crack closure behaviour are produced for cracks growing under constant amplitude loading, and also following an overload or overload/underload cycle. These results are compared with an empirical R‐ratio correction due to Walker and with experimental measurements taken from the literature. The model is found to give good predictions of crack behaviour under constant amplitude loading. Predictions for crack closure levels following an overload cycle give qualitative agreement with experimental results; the differences observed may well be due to the different definition of crack closure in the experiments.
HIGH‐TEMPERATURE LOW‐CYCLE FATIGUE AND CREEP BEHAVIOUR OF NICKEL‐BASED SUPERALLOYS WITH HEAT‐RESISTANT COATINGS
Authors: Okrajni J , Cie M , Swad L
Published: March 2003

The problems associated with nickel‐based superalloys with heat‐resisting coatings, as used in aerospace, have been addressed in this paper. The influence of the heat‐resisting coating technology on both the fatigue and creep behaviour of the alloys has been shown. Low‐cycle fatigue and creep tests have been performed. Lifetime conditions have been determined in relation to low‐cycle fatigue, isothermal creep and creep at cyclically variable temperatures, as a function of the chemical composition of the coating, parameters of the thermal treatment and thickness of the coating. Possible processes and mechanisms of fracture are discussed.
BIMODAL CONCEPT OF HIGH‐CYCLE FATIGUE LIFE PREDICTION FOR CONSTANT AND VARIABLE AMPLITUDE FATIGUE
Authors: Perovic
Published: March 2003

A bimodal concept for the prediction of the high‐cycle fatigue life of structural details subjected to constant‐ or variable‐amplitude loading is considered in this paper. The total fatigue life was separated into two phases: crack initiation and crack propagation. The portion of life spent in crack initiation was estimated by using S–N data obtained on smooth specimens. A fracture mechanics concept was used to calculate the portion of life spent in crack propagation, and the S–N curve, including the fatigue limit of a structural detail, was determined by using material properties and the geometry of the detail. The bimodal concept was applied to a welded stiffener and the results are compared with experimental data reported in the literature.
FATIGUE CRACK GROWTH BEHAVIOUR OF SM45C STEEL UNDER MIXED‐MODE I AND II LOADING
Authors: You BR , Lee SB
Published: March 2003

The practical applications of studies related to constant amplitude mode I loading are somewhat limited in situations where more than one mode exists. So, criteria, rules and laws for these situations have to be validated with experiments. This paper extends previous results by the authors for mixed‐mode I and II fatigue loading. An effective stress intensity factor range which considers crack closure and crack surface interference is described for the analysis of a crack under mixed‐mode I and II fatigue loadings, and this factor is assessed from experimental results.
SURFACE FLAWS IN CYLINDRICAL SHAFTS UNDER ROTARY BENDING
Authors: Carpinteri A , Brighenti R , Spagnoli A
Published: March 2003

The propagation of a surface flaw in a cylindrical shaft subjected to rotary bending is analysed using a two‐parameter theoretical model. The stress‐intensity factor distribution along the crack front is numerically determined for any position of the flaw with respect to the bending moment axis. The crack front is assumed to present an elliptical‐arc shape with aspect ratio α = a/b (a, b = ellipse semi‐axes), whereas the relative depth ξ of the deepest point on the front is equal to the ratio between the maximum crack depth, a, and the bar diameter, D. The results for rotary bending are compared to those for reversed cyclic bending.
EFFECTS OF MICROSTRUCTURE ON RESISTANCE TO SHEAR LOCALIZATION FOR A CLASS OF METAL MATRIX COMPOSITES
Authors: Zhou
Published: March 2003

The development of shear bands in a class of materials with inhomogeneous and composite microstructures is analysed using dynamic finite element calculations. The analysis is based on experimental studies of the deformation localization and constitutive behaviour of tungsten composites having two‐phase microstructures consisting of hard tungsten grains and a soft alloy metal matrix. The calculations concern the effects of variations in microstructures on the resistance of the materials to shear banding. Specifically, three variations from the currently used microstructure are considered: (1) the alteration of the matrix phase to one that has a lower thermal conductivity; (2) the introduction of an interfacial layer between the grains and the matrix which limits microscopic heat exchange between the phases by having a low thermal conductivity; and (3) the modification of the matrix to one having a lower strength at high temperatures, but otherwise the same thermal and mechanical properties as the nickel–iron–tungsten matrix currently used in many tungsten composites. Numerical results show that the introduction of the low‐conductivity interfacial layer significantly enhances the formation of shear bands and reduces the overall flow stress of the composite throughout the deformation. On the other hand, accelerated thermal softening of the matrix phase at high temperatures expedites localization in later stages of deformation while allowing the material to maintain a strong stress–strain response in the early part of the deformation. The results point out possible directions for the improvement of advanced composites in applications where the localization of deformation plays an important role.
INTERACTIONS BETWEEN TIME AND CYCLIC DEFORMATION PROCESSES IN A NIMONIC ALLOY
Authors: Rees DWA
Published: March 2003

Interactive creep–fatigue behaviour of a nickel‐base superalloy (IN 597) has been examined at 850 °C under various strain‐limited, cyclic torsional loading conditions. In one test, forward creep deformation was reversed by creep under equal magnitude stress levels and strain limits. In other tests, forward creep strain was reversed by fast monotonic plasticity with and without a subsequent period of relaxation. These cycles were repeated within each test until fracture. This paper examines empirically the influence of a number of test variables upon cyclic creep curves, and demonstrates the usefulness of predictions based upon continuous low cycle fatigue and simple creep data when used in conjunction with a mechanical equation of state. A cyclic equilibrium condition was not achieved from these tests. Instead, a progressive softening occurred giving reductions to the amount of creep strain, creep time interval and reversed peak stress with each new cycle. Such reductions are expressed from derived formulae that embrace the range of inelastic strain, cycle number, creep dwell stress, reversed peak stress, and times expended in creep and relaxation.

Observations made on accumulated creep strain reveal the contribution to a creep–fatigue fracture from cyclic creep. This has led to a modified form of the linear damage rule which can provide conservative life predictions for components operating in service under similar cyclic conditions.
THE INFLUENCE OF COMPRESSIVE LOADS ON FATIGUE CRACK PROPAGATION IN METALS
Authors: Lang M , Huang X
Published: March 2003

An experimental study on Al alloy 7475‐T7351 was conducted to determine the influence of compressive loads on fatigue crack propagation. The investigation was based on the determination of the crack propagation stress intensity factor, KPR , under three different basic loading sequences involving compressive loads. The data of the entire experimental program collapse onto a single ‘master curve’ which describes KPRas a function of Kmaxand the unloading ratio UR. Load interaction effects are mainly due to the changes of the residual compressive stress state in front of the crack tip, while crack closure plays a minor part. The results give an improved understanding of fatigue crack propagation.
CONSIDERING ENVIRONMENTAL CONDITIONS IN THE DESIGN OF BONDED STRUCTURES: A FRACTURE MECHANICS APPROACH
Authors: Johnson  , Butkus
Published: March 2003

The continued airworthiness of ageing aircraft and long‐term durability of new airframes depends, in part, on the integrity of adhesive bonds used for repairs and joining structural components. Additionally, the advent of composite materials and advanced repair techniques incorporating composites has increased the number of adhesively bonded joints specified for use in aerospace structures. Traditionally, adhesive bonds have been analysed and designed using a dependable and rigorous stress‐based approach. However, the need to address the effect of bondline flaws and to understand the fatigue characteristics of bonded joints has led to the adoption of a discipline already common in the design of metallic components—fracture mechanics. To understand the durability of bonded structures, however, it is further necessary to examine the effect of environmental exposure on the performance of the adhesive bondline. Familiarity with the stress‐based and fracture mechanics analytical approaches, as well as an understanding of environmentally induced trends in bond performance is paramount to quality design. This paper will briefly discuss the attributes of the two main forms of bonded joint analysis, and will broadly outline a design approach that uses fracture mechanics and accounts for environmental effects. Experiments discussed in this paper were performed specifically to use fracture mechanics in assessing the environmental effects on a toughened epoxy adhesive. Results indicate that the Mode I fracture toughness and fatigue crack growth threshold of this adhesive are significantly reduced upon exposure to a high temperature, high humidity aircraft service environment. These results will be used to illustrate the philosophical arguments supporting the design approach.
Analysis of ductile to cleavage transition in part‐through cracks using a cell model incorporating statistics
Authors: Gao  , Faleskog  , Fong Shih
Published: March 2003

This paper describes an approach to study ductile/cleavage transition in ferritic steels using the methodology of a cell model for ductile tearing incorporating weakest link statistics. The model takes into account the constraint effects and puts no restriction on the extent of plastic deformation or amount of ductile tearing preceding cleavage failure. The parameters associated with the statistical model are calibrated using experimental cleavage fracture toughness data, and the effect of threshold stress on predicted cleavage fracture probability is investigated. The issue of two approaches to compute Weibull stress, the ‘history approach’ and the ‘current approach’, is also addressed. The numerical approach is finally applied to surface‐cracked thick plates subject to different histories of bending and tension, and a new parameter, ψ, is introduced to predict the location of cleavage initiation.
Micromechanical simulations of microstructure‐sensitive Stage I fatigue crack growth
Authors: Doquet
Published: March 2003

Simulations of dislocation dynamics at the tip of a Stage I crack are performed, taking into account the influence of the normal stress on the friction of the crack flanks and on the condition for dislocation emission at the crack tip. The interactions of the emitted dislocations with microstructural obstacles are analysed. The repeated decelerations and sometimes arrests that characterize Stage I crack growth are properly described by the model, and the differences in Stage I kinetics observed in reversed torsion and push–pull are analysed in terms of crack tip–grain boundary interactions.
Acoustic emission from surface fatigue cracks in SS41 steel
Authors: Nam
Published: March 2003

Crack penetration behaviour by fatigue crack propagation and the measurements of acoustic emission (AE) before and after crack penetration were examined using SS41 steel plate. The experimental crack shape of the SU type which has an out‐of‐plane degree of freedom was in good agreement with the calculated shape. But this was not so for the S type which has a restriction to out‐of‐plane freedom. The crack propagation behaviour on the front surface appears not to change markedly after penetration. However, crack growth on the back surface appears to accelerate. As a crack propagates, substantial acoustic emission occurred just prior to penetration. Then it decreased and the crack penetrated. Intense AE emanation has been attributed to a transition from a plane strain condition to a plane stress condition.
From a local stress approach to fracture mechanics: a comprehensive evaluation of the fatigue strength of welded joints
Authors: Atzori B. , Lazzarin P. , Tovo R.
Published: March 2003

This paper investigates the possibility of unifying different criteria concerned with the fatigue strength of welded joints. In particular, it compares estimates based on local stress fields due to geometry (evaluated without any crack‐like defect) and residual life predictions in the presence of a crack, according to LEFM. Fatigue strength results already reported in the literature for transverse non‐load‐carrying fillet welds are used as an experimental database. Nominal stress ranges were largely scattered, due to large variations of joint geometrical parameters. The scatter band greatly reduces as soon as a 0.3‐mm virtual crack is introduced at the weld toe, and the behaviour of the joints is given in terms of ΔKIversus total life fatigue. Such calculations, not different from residual life predictions, are easily performed by using the local stress distributions determined near the weld toes in the absence of crack‐like defects. More precisely, the analytical expressions forKIare based on a simple combination of the notch stress intensity factorsK1NandK2Nfor opening and sliding modes. Then, fatigue strength predictions, as accurate as those based on fracture mechanics, are performed by the local stress analysis in a simpler way.
Fracture control assessment in the base metal and welded joint of a pipeline steel
Authors: Costa  , Bastian
Published: March 2003

The present study evaluates the fracture behaviour of a pipe steel and compares the real scale pipeline assessment methodology (pipeline methodology) with the Guidance on Methods for Assessing the Acceptability of Flaws in Welded Structures (PD 6493). It is shown that the base metal is the toughest region and that the heat‐affected zone is the least tough zone, that both assessment methods do not give the same result for the base metal, and that plasticity at the crack tip can toughen the welded joint.
An ultimate crack resistance concept
Authors: Morozov
Published: March 2003

A two‐parameter fracture criterion is discussed in terms of an ultimate crack resistance concept. The difference is found between the failure assessment diagram and the ultimate crack resistance. The concept of an ultimate crack resistance provides one with the ability to estimate crack resistance behaviour in cases of brittle, ductile and intermediate fracture states with the customary use of stress intensity factors.
Thermal failure under conditions of restrained deformation
Authors: Shesterikov  , Yumasheva  , Yumashev  , Lebedev
Published: March 2003

The time behaviour of solids during unsteady temperature conditions is considered. The conditions for the initiation of failure of a solid are formulated in the form of conditions for the attainment of the threshold values of stress and strain fields. The evolution of a cracked region through the body is considered. It is shown that the destruction process is divided into two stages in some cases. At the first stage, when a threshold value is achieved at some point or region of the body, a jump‐like extension of the region occurs until a state of equilibrium within the region is attained. This jump‐like destruction can be considered as an instability process. Various examples are presented relating to the destruction of brittle solids. The influences of plasticity and time‐dependent characteristics is considered.
Stress intensity factors for tunnelling corner cracks under mode I loading
Authors: Antunes  , Ferreira  , Branco  , Byrne
Published: March 2003

Stress intensity factors (SIFs) presented in the literature for corner cracks are limited to ideal quarter‐circular and quarter‐elliptical crack shapes. This paper presents SIF solutions for corner cracks that exhibit tunnelling, extending the range of corner crack shapes illustrated in the literature. Solutions were developed in a parametric form, obtained by empirically fitting polynomials to numerical values of SIF obtained from the FEM. A parameter was defined to quantify the extent of tunnelling. It was observed that crack shape has a significant effect on the SIF, so the consideration of equivalent quarter‐circular cracks can produce inaccurate results when significant tunnelling occurs. SIF solutions for quarter‐circular cracks are also presented and compared with those quoted in the literature.
Stress intensity factors for surface flaws in toughened glasses
Authors: Hand
Published: March 2003

An approximate method of deriving stress intensity factors as a function of angle for semicircular surface flaws is outlined. The method can be applied to a wide range of load distributions including non‐polynomial distributions. The method is used to calculate stress intensity factors for thermally and chemically tempered glasses. The stress intensity factor equations developed are also used to calculate equivalent flaw sizes for some toughened glasses subjected to bending loads.
Direct adjustment procedure for weight functions of graded materials
Authors: Fett  , Munz  , Yang
Published: March 2003

The weight function procedure simplifies the determination of stress intensity factors. If the weight function is known for a crack in a component of homogeneous material, the stress intensity factor can be obtained by multiplying this function by the stress distribution and integrating it over the crack length. In the case of graded materials, weight functions are seldom available in the literature. The main point of this paper is to demonstrate whether or not the approximate direct adjustment procedure for the derivation of weight functions is also valid in the case of graded materials. In this study it has been found that the procedure is applicable and no changes are necessary compared with the procedure for homogeneous materials.
A crack tip blunting analysis in the ductile‐to‐brittle transition of a structural steel
Authors: Tosal  , Rodríguez  , Belzunce  , Betegón
Published: March 2003

The J‐integral versus crack growth resistance curves ( J–R curves) of an AE‐460 structural steel were evaluated at different temperatures in the ductile‐to‐brittle transition region. This curve as well as the critical JI value at the initiation of crack growth was found to be independent of temperature, being dependent only on the stress triaxiality state of the specimen.

The blunting expressions described in the ASTM and ESIS standards were evaluated using fractographic techniques. The ESIS blunting line fits the linear regression of the experimental results very well, while the blunting line predicted by the ASTM standard is clearly located below the experimental points.
A model for fatigue crack growth, part II: modelling*
Authors: Lang
Published: March 2003

A fatigue crack growth prediction model for metals is presented. It is based on experimental evidence obtained on the aluminium alloy Al 7475‐T7351, which is presented in Part I of this paper. This part of the paper generalises the results from Part I and develops a new fatigue crack growth prediction model for variable amplitude loading. The central parameter of this model is the crack propagation stress intensity factor,KPR . The general description of the relatively simple loading sequences in Part I of this paper in terms ofKPRleads to a scheme that is denoted as the ‘Fatigue Crack Growth Map.’ This map defines all possible crack growth conditions and is the heart of the crack growth prediction method. It is shown that any arbitrary loading spectrum consists only of three different types of load cycles, Type I, II and III. This paper elaborates on the specific conditions that lead to a specific type of cycle and explains the determination of the correspondingKPRvalue. The model determinesKPRcycle by cycle throughout a loading spectrum.KPRdetermines the driving force, ΔKeff , for the following cycle. The model requires the knowledge of the yield strength and the intrinsic threshold value, ΔKT , for the material, as well as five different functions that also depend on the material. Phenomenologically, the model accounts for residual compressive stresses ahead of the crack front, theintrinsicresponse of the material and crack closure, which is anextrinsiceffect. A few variable amplitude loading sequences are presented to compare predictions ofKPRwith experiments. The results are in encouraging agreement.
The validation of some methods of notch fatigue analysis
Authors: Taylor  , Wang
Published: March 2003

This paper is concerned with the testing and validation of certain methods of notch analysis which the authors have developed theoretically in earlier publications. These methods were developed for use with finite element (FE) analysis in order to predict the fatigue limits of components containing stress concentrations. In the present work we tested and compared these methods using data from standard notches taken from the literature, covering a range of notch geometries, loading types,R‐ratios and materials: a total of 47 different data sets were analysed. The greatest predictive success was achieved with critical‐distance methods known as the point, line and area methods: 94% of these predictions fell within 20% of the experimental fatigue limits. This was a significant improvement on previous methods of this kind, e.g. that of Klesnil and Lucas [(1980)Fatigue of Metallic Materials, Elsevier Science]. Methods based on the Smith and Miller [(1978)Int. J. Mech. Sci.20, 201–206] concept of crack‐like notches were successful in 42% of cases; they experienced difficulties dealing with very small notches, and could be improved by using an ElHaddad‐type correction factor, giving 87% success. An approach known as ‘crack modelling’ allowed the Smith and Miller method to be used with non‐standard stress concentrations, where notch geometry is ill defined; this modification, with the same short‐crack correction, had 68% success. It was concluded that the critical‐distance approach is more accurate and can be more easily used to analyse components of complex shape, however, the crack modelling approach is sometimes preferable because it can be used with less mesh refinement.