bluuebunny/crossref_metadata_2025 huggingface dataset:
DUPLICATE GALLBLADDER DIAGNOSED WITH ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY AND TREATED WITH LAPAROSCOPIC CHOLECYSTECTOMY
Authors: Ohtani Yasuo , Tobita Kosuke , Dowaki Shoichi , Sugio Yoshinori , Kashiwagi Hiroyuki , Tucker Adam , Makuuchi Hiroyasu
Published: March 2003

A 44‐year‐old man was admitted to hospital because of sudden severe postprandial right epigastric pain. Abdominal echography showed multiple calculi in the gallbladder and evidence of a probable septum at the neck. Based on the results, tentative diagnoses were made of gallbladder calculosis with associated gallbladder curvature or malformation, and gallbladder adenomyomatosis. Preoperative endoscopic retrograde cholangiopancreatography (ERCP) revealed a duplicate gallbladder consisting of two cystic ducts with two connected gallbladders. Laparoscopic cholecystectomy (Lap‐C) was performed. Inflammation of the Calot's triangle was mild. The two cystic ducts with one common bile duct were identified, and the cystic ducts separated by individual clipping. Duplicate gallbladder, a malformation of the gallbladder, has been reported to occur at an incidence of 0.02%. To date, a total of 60 cases have been reported in Japan, and recent cases have been treated with Lap‐C. In the present case, the surgery could be safely performed because the bifurcation of the cystic ducts could be identified by preoperative ERCP.
Mechanisms involved in hydroxycamptothecin‐induced apoptosis of gastric cancer cells
Authors: TU Shui Ping , JIANG Shi Hu , TAN Ji Hong , ZHONG Jie , QIAO Min Min , JIANG Xiao Hua , ZHANG Yong Ping , YUAN Yao Zong , WU Yun Lin , WU Yu Xin
Published: March 2003

OBJECTIVE: Hydroxycamptothecin (HCPT) is a unique antitumor drug that acts
directly on topoisomerase I and inhibits its activity. However, the mechanism of
HCPT‐induced apoptosis is unclear. In the present study, the mechanism of HCPT‐induced
apoptosis in gastric cancer cells was investigated by detecting the expression of
p53, c‐myc, bcl‐2, bcl‐xl and bcl‐xs genes in gastric cancer cells.

METHODS: Apoptosis of gastric cancer cells (SGC‐7901, MKN‐45) was determined
by terminal deoxyribonucleotidyl transferase‐mediated dUTP– digoxigenin nick‐end
labeling (TUNEL) and flow cytometry. The mRNA and protein levels of the p53,
c‐myc, bcl‐2, bcl‐xl and bcl‐xs genes were tested by reverse transcription–polymerase chain reaction analysis and immunocytochemical stain, respectively.

RESULTS: Hydroxycamptothecin may induce apoptosis in different differentiated
gastric cancer cells. The effect of HCPT‐induced apoptosis on gastric cancer cells
was dependent on the dose of HCPT used and the time of exposure to HCPT. Both SGC‐7901
and MKN‐45 cells manifested some morphological features of apoptosis after 12 h exposure
to HCPT, including cell shrinkage, nuclear condensation, DNA fragmentation and formation
of apoptotic bodies. Some typical subdiploid peaks before the G0/G1
phase were observed. The apoptotic rates induced by 10 μg/mL HCPT in SGC‐7901
and MKN‐45 cells were 21.88 and 12.34%, respectively. The mRNA and protein
levels of p53 and bcl‐2 were downregulated after treatment with HCPT in SGC‐7901 cells. However, the c‐myc, bcl‐xl and bcl‐xs protein levels were unchanged in SGC‐7901 cells. In MKN‐45 cells, the mRNA and protein levels of p53 increased after treatment with HCPT, whereas the protein levels of bcl‐2, c‐myc, bcl‐xl and bcl‐xs remained unchanged.

CONCLUSIONS: Our results indicate that HCPT‐induced apoptosis in gastric
cancer cells may be regulated through modulation of the expression of p53
and bcl‐2 genes.
Autofluorescence imaging analysis of gastric cancer
Authors: XIAO Shu Dong , ZHONG Liang , LUO Hong Yu , CHEN Xiao Yu , SHI Yao
Published: March 2003

AIMS: To investigate the characteristics of gastric cancer in autofluorescence images.

METHODS: A double‐channel laser scanning confocal microscope with an argon ion laser (excitation wavelength 488 nm) and helium−neon laser (excitation wavelength 543 nm) were used to detect autofluorescence from 16 gastric cancer tissue specimens and corresponding normal gastric tissue.

RESULTS: Autofluorescence from normal gastric tissue produced a green‐colored image. The intensity of red color increased obviously in all gastric cancer tissues (100%) after illumination and the tissues produced a reddish‐brown‐colored image.

CONCLUSIONS: A reddish‐brown image is characteristic of autofluorescence in gastric cancer detected by an argon ion laser and helium−neon laser with a double‐channel laser scanning confocal microscope. Autofluorescence imaging analysis is useful in the diagnosis of gastric cancer.
Diabetes hyperglycemia and recovery from stroke
Authors: Gray Christopher S , O'Connell Janice E , Lloyd Hilary
Published: March 2003

Strokeis a major cause of death and severe disability in older people. Despite the burden of disease, there is still no safe, simple and proven medical therapy for the treatment of acute stroke. Advances in acute stroke treatment have been either consistently disappointing (neuroprotective therapy) or fraught with controversy regarding risk/benefit (thrombolysis), and attention is once again being directed towards physiological variables that may influence outcome. Both insulin‐dependent and non‐insulin‐dependent diabetes mellitus are major risk factors for stroke. Diabetes mellitus has also been shown to be associated with increased mortality and reduced functional outcome after stroke. Hyperglycemia is a frequent finding following stroke and may reflect the metabolic stress of the acute event, so‐called stress hyperglycemia, and/or underlying impaired glucose metabolism. Several large clinical studies have now demonstrated a positive association between a raised blood glucose and poor outcome from stroke; greater mortality and reduced functional recovery. What is not clear is to what extent hyperglycemia is a ‘normal’ physiological response to stroke or whether hyperglycemia per se increases cerebral damage in the acute phase. There are many potential mechanisms by which hyperglycemia can exert a harmful effect upon cerebral tissue and it is probable that an important relationship exists, not only between glucose and stroke outcome, but also between insulin and neuroprotection. It remains to be determined whether lowering and maintaining ‘normal’ glucose levels in the immediate aftermath of stroke, combined with the administration of insulin as an acute treatment, can modify this outcome.
Head injury‐related road crash mortality in rural Western Australia
Authors: Stella Julian , Sprivulis Peter , Cooke Clive
Published: March 2003

Background:  The aim of the present paper was to assess the incidence of, and identify factors associated with road crash (RC)‐related fatal head injuries in rural and metropolitan Western Australia.

Methods:  Examination of demographics, driving behaviour and RC characteristics for RC fatalities involving a head injury (Abbreviated Injury Scale (AIS) ≥ 2) between 1 January 1998 and 31 December 1999 was carried out using the State Coronial ­Database.

Results:  There were 328 deaths. The median age was 28 years and 74.1% of cases were male. Seventy per cent died at the scene. Of scene survivors, 89% were transferred to a metropolitan hospital before dying. Sixty per cent of total RC and 65% of at‐scene deaths occurred in rural areas. Single‐vehicle crashes comprised 45% of total crashes, of which 72.8% occurred in rural locations. Poor driver behaviour was identified in 53% of deaths. Ethanol was implicated in 29.8% of deaths, other intoxicating drugs were implicated in 19.2%, speeding was implicated in 19.5%, and lack of safety restraints/devices was implicated in 22%. Poor driver behaviour was identified in 72% of single‐vehicle deaths, compared with 38% of multivehicle crashes (P < 0.001). Rural people comprised 61% of rural crash victims. Ninety‐one per cent of rural victims died in rural crashes. The incidence of RC death associated with head injury in the rural population is 13.4 deaths/100 000 per year, more than double that for the metropolitan population (6.4 deaths/100 000 per year; P < 0.001).

Conclusion:  The rural population of Western Australia is overrepresented in head injury‐related RC deaths. Single‐vehicle crashes where unsafe driving behaviour is implicated comprise a large proportion of these. Strategies to reduce unsafe driving practices aimed at rural drivers are necessary.
Do patients assess rectal bleeding accurately?
Authors: Simpson Richard R. , Kennedy Michael L. , Chew Simon B. , Lubowski David Z.
Published: March 2003

Background:  The accuracy of a patient’s assessment of the volume of blood passed per rectum is unknown. The aim of the present study was to compare subjective estimations with known amounts of blood.

Methods:  Thirty subjects (10 patients, 10 nurses and 10 doctors) made a visual estimation of four volumes of blood (0.25 mL, 10 mL, 50 mL, 200 mL), each placed in a standardized way into a toilet bowl. Subjects gave their estimations in mL, and also by drawing a line on a cup at the level to which they estimated that the amount of blood would fill the cup. Statistical analysis was carried out using Student’s t‐test. Multiple comparisons were analysed by anova.

Results:  There was no significant difference between the groups in their estimations of each of the four volumes. Each group made a statistically significant overestimation for the 0.25 mL, 10 mL and 50 mL volumes with cup marking, as well as with estimation in mL (except for patients with the 50 mL volume, where there was a non‐significant overestimation). For the 200 mL volume, patients and doctors made statistically significant underestimations with cup marking, but for nurses the underestimation did not reach sig­nificance. For the 200 mL volume estimations in mL, both nurses and doctors made underestimations that were not significant.

Conclusions:  Small to moderate amounts of blood in the toilet bowl are subjectively significantly overestimated, whereas larger volumes tend to be underestimated. This may have implications for the management of patients presenting with rectal bleeding.
Minimally invasive parathyroidectomy using the ‘focused’ lateral approach. II. Surgical technique
Authors: Agarwal Gaurav , Barraclough Bruce H. , Reeve Tom S. , Delbridge Leigh W.
Published: March 2003

Background: This paper describes the technique of minimally invasive parathyroidectomy. The technique is based on a thorough understanding of the anatomy of the fascial planes in neck, the surgical pathology and embryology of parathyroid glands and precise anatomical interpretation of preoperative localization studies.

Methods: Tissue trauma is minimized by using a 2.0 cm incision placed directly over the abnormal parathyroid gland and by removing the adenoma, without compromising the basic endocrine surgical principles of identification and preservation of recurrent laryngeal nerve, avoidance of any capsular breech, and ligation of the vascular pedicle.

Results/Conclusions: With proper patient selection, this technique results in a failure rate of less than 4% and ensures that the incidence of complications, such as recurrent laryngeal nerve injury, remains comparable with that of standard open parathyroidectomy.
When exactly can carpal tunnel syndrome be considered work‐related?
Authors: Falkiner Sonja , Myers Stuart
Published: March 2003

Background: Carpal tunnel syndrome (CTS), compression of the median nerve at the wrist, is the most frequently encountered peripheral entrapment neuropathy. Whilst rates of all other work‐related conditions have declined, the number of work‐related musculoskeletal disorders (which include CTS) has not changed for the past 9 years in the USA. Median days off work are also highest for CTS: 27 compared to 20 for fractures and 18 for amputations. This results in enormous Workers Compensation and other costs to the community. Awareness of CTS as a disorder associated with repeated trauma at work is now so widespread amongst workers that many have diagnosed themselves before being medically assessed, often by means of the Internet. Surprisingly, however, a definite causal relationship has not yet been established for most occupations. Although the quality of research in this area is generally poor, CTS research studies are being used as the basis for acceptance of Workers Compensation claims, substantial expensive ergonomic workplace change and even workplace closures. The fact that the incidence of work‐related musculoskeletal disorders has not changed despite these latter measures would suggest that a causal relationship is not proven and that some resources are being misdirected in CTS prevention and treatment.

Method: A literature review of 64 articles on CTS was conducted. This included those articles most frequently cited as demonstrating the relationship between CTS and work.

Results: Primary risk factors in the development of CTS are: being a woman of menopausal age, obesity or lack of fitness, diabetes or having a family history of diabetes, osteoarthritis of the carpometacarpal joint of the thumb, smoking, and lifetime alcohol intake. In most cases, work acts as the ‘last straw’ in CTS causation.

Conclusion: Except in the case of work that involves very cold temperatures (possibly in conjunction with load and repetition) such as butchery, work is less likely than demographic and disease‐related variables to cause CTS. To label other types of work as having caused CTS, therefore, would result in inappropriate allocation of resources. It would also relieve individuals of the responsibility of addressing correctable lifestyle factors and treatable illnesses such as obesity, diabetes, smoking and increased alcohol intake which may have contributed to their CTS more that their work. This results in both avoidable long‐term health effects and ongoing costs to the community.
Electromagnetic motion analysis in the assessment of surgical skill: Relationship between time and movement
Authors: Mackay Sean , Datta Vivek , Mandalia Mirren , Bassett Paul , Darzi Ara
Published: March 2003

Introduction:  Electromagnetic motion analysis is a promising method of assessing surgical skill in a skills‐laboratory setting. There is a very strong correlation between movement and time data, and this study was conducted to determine whether this relationship is fixed, or whether it can vary.

Methods
:
 After a pilot study, four subjects were recruited. Each performed 30 trials of a simple standardized suturing task, alternating between ‘normal’, ‘precise’, and ‘fast’ strategies. The number of movements, and time to complete each task were recorded.

Results:  Comparing the ‘fast’ to ‘normal’ strategies, there was a significant decrease in total number of movements per trial (P < 0.001), and time taken (P < 0.001). Regression analysis was performed to examine the relationship between the time taken and the number of movements, and revealed significant differences between both the fast (P
= 0.006), and precise (P = 0.002) strategies, when compared to the normal strategy.

Discussion:  This study confirms that the relationship between time and movements is not fixed, but varies with the operative strategy adopted for this simple suturing task.
Relationship between elevated preoperative troponin T and adverse outcomes following cardiac surgery
Authors: Lyon William J. , Baker Robert A. , Andrew Marie J. , Tirimacco Rosy , White Graham H. , Knight John L.
Published: March 2003

Background:  The prognostic value of troponin T (TnT) has been demonstrated in patients following a myocardial infarction. There are limited data regarding the prognostic utility of preoperative TnT in patients undergoing cardiac surgery. The aim of the present study was to determine if elevated preoperative TnT is a predictor of more complex recovery outcomes in the cardiac surgical setting.

Methods:  A single preoperative TnT measurement was assessed in 696 patients undergoing isolated coronary artery bypass graft surgery. Elevated preoperative TnT levels were classified as ≥0.2 ng/mL. Preoperative, intraoperative, intensive care and postoperative events were prospectively recorded for all patients, and retrospectively reviewed for the present study.

Results:  Elevated preoperative TnT levels were detected in 10% (71/696) of patients. Compared to patients with normal TnT levels, elevated preoperative TnT increased the risk of mortality at 30 days (7%vs 1%, P = 0.004, odds ratio (OR) = 6.7) and 2 years (14%vs 3%, P < 0.001, OR = 5.0), and resulted in prolonged intensive care unit (ICU) stays (P < 0.001) and longer postoperative hospitalization (P < 0.001). Elevated preoperative TnT was also associated with an increased need for perioperative and postoperative cardiovascular support, early ischaemic change and postoperative congestive cardiac failure. In multivariate analyses preoperative TnT was a significant independent predictor of 30‐day and 2‐year mortality, and duration of ICU stay.

Conclusions:  Elevated preoperative TnT highlights a subgroup of cardiac surgical patients who are more likely to have a post­operative course with increased morbidity and mortality.
FATIGUE DESIGN OF SPOT‐WELDED AUSTENITIC AND DUPLEX STAINLESS SHEET STEELS
Authors: Linder J , Melander A , Larsson M , Bergengren Y
Published: March 2003

The fatigue strength of spot‐welded stainless sheet steels has been investigated. The main part of the fatigue tests was performed on a cold rolled austenitic stainless sheet steel (AISI304) in air at ambient temperature. For comparison, a duplex stainless steel (SAF2304) of similar yield strength as AISI304 was also incorporated into the test programme. Since the fatigue strength of spot‐welded joints depends on the mode of loading, both shear‐loaded and peel‐loaded joints were tested. The fatigue strength of the spot‐welded stainless steels was found to decrease with decreasing sheet thickness. Furthermore, the fatigue strength for peel‐loaded joints is lower than that of shear‐loaded joint for sheets of equal thickness.

The local loading conditions at the weld edge have been analysed in terms of finite element calculations and fracture mechanics. A design parameter derived from a fracture mechanics analysis was defined for spot‐welded stainless sheet steels. It was shown to predict the fatigue life of the present steels and joint configurations in a satisfactory way.
A THEORETICAL MODEL FOR PREDICTING FATIGUE CRACK GROWTH RATES IN FIBRE‐REINFORCED METAL LAMINATES
Authors: Guo YJ , Wu XR
Published: March 2003

This paper is concerned with the development and application of an analytical model for predicting fatigue crack growth in fibre‐reinforced metal laminates (FRMLs). An analytical model for the distribution of bridging traction is first introduced. Based upon observations of the delamination shapes in FRMLs under fatigue loading and a model for characterizing delamination growth in FRMLs, a model for predicting crack growth rates in CCT specimens of FRMLs is developed. The model is applied to two GLARE laminates (2/1, 3/2 lay‐ups) under various cyclic stress levels and stress ratios. The predicted crack growth rates are compared with experimental data. The predicted crack growth rates agree well with the experimental results.
THE COALESCENCE OF VOIDS IN PRESTRAINED NOTCHED ROUND COPPER BARS
Authors: Pardoen  , Delannay
Published: March 2003

Notched round copper bars are prestrained to various extents, recrystallized, and finally strained until fracture. Void nucleation and growth during prestraining cause a decrease in the macroscopic void coalescence strain. Modelling of this experiment requires a proper account of the changes in void sizes and their interdistances during prestraining. Modelling based on the Gurson–Leblond–Perrin model for void growth and the Thomason model for void coalescence is proposed. Comparison with experimental results allows a demonstration of the validity of the Thomason model and the inadequacy of models based on a critical porosity value. Porosity at coalescence is found to depend on the initial void volume fraction, the flow properties and the stress state.
THE APPLICABILITY OF NEURAL NETWORKS IN MODELLING THE GROWTH OF SHORT FATIGUE CRACKS
Authors: Seed GM , Murphy GS
Published: March 2003

This paper examines the use of a neural network to model the chaotic behaviour of the growth of short fatigue cracks which are characterized by a decreasing crack growth rate with increasing crack length. Fatigue crack growth is modelled in terms of the Hobson short fatigue crack growth law. The neural network is exclusively trained and tested on Hobson’s experimental data of short fatigue cracks propagating in a 0.4% carbon steel. The empirical constants d, α and C of Hobson’s growth law are determined from the neural network predictions and are found to be within the following approximate ranges 63 < d < 400 (μm), −0.27 < α < 0.08 and 1 × 10−4 < C < 509 × 10−4 with no proportional relationship observed between the constant C and the applied cyclic stress. It is shown that neural networks are a viable computational tool for modelling the chaotic behaviour of short fatigue crack growth.
EFFECTS OF TEMPERATURE, CYCLIC FREQUENCY AND ENVIRONMENT ON FIBRE DEGRADATION AND FATIGUE CRACK GROWTH RESISTANCE IN A FIBRE‐REINFORCED TITANIUM METAL‐MATRIX COMPOSITE UNDER DISPLACEMENT‐RANGE LOADING
Authors: Shimojo M , Bowen P
Published: March 2003

The fatigue crack growth resistance of a [0/90°]2s cross‐ply SCS6 fibre‐reinforced Ti–6Al–4V alloy metal‐matrix composite has been assessed under displacement range control (i.e. under load shedding conditions with crack extension) to investigate potential fibre degradation and the process of crack extension at room temperature, and at 450°C, in air and in vacuum. Attention is focused on initial conditions that will promote crack arrest at room temperature. Under the test conditions employed here, regions of crack growth can occur where the applied nominal stress intensity factor range (ΔK) is relatively constant. This ‘constant’ΔK range is the result of a fortuitous balance between the particular test‐piece geometry, loading conditions utilized, matrix crack growth and the rate of fibre fracture. It allows the influence of environment, cyclic frequency and temperature on fatigue crack growth resistance to be analysed more easily than for tests carried out under load control.

The crack growth rate remained almost constant but with some steep local retardations in growth rate in the constant ΔK region at a temperature of 450°C, while crack arrest occurred at room temperature for the same initial ΔK. The average crack propagation rate in this ‘constant ΔK region’ at a temperature of 450°C in air was much greater than that at a temperature of 450°C in vacuum. This indicates that environment plays an important role in the process of fibre degradation. The effect of cyclic frequency is saturated at a frequency of less than 1 Hz. The process of crack growth at various frequencies is also discussed.
The significance of fractography for investigations of fatigue crack growth under variable‐amplitude loading
Authors: Schijve
Published: March 2003

Fatigue crack growth tests were carried out on 2024‐T3 and 7075‐T6 centrally cracked specimens. Variable‐amplitude (VA) load spectra were used with periodic overload (OL) cycles added to constant‐amplitude (CA) cycles. The fatigue fracture surfaces were examined in the SEM to obtain more detailed information on crack growth contributions of different load cycles. The striation patterns could be related to the load histories. SEM observations were related with (i) delayed retardation, (ii) the effect of 10 or a single OL on retardation, (iii) crack growth during the OL cycles, and (iv) crack growth arrest after a high peak load. Fractographs exhibited local scatter of crack growth rates and sometimes a rather tortuous 3D geometry of the crack front. Indications of structurally sensitive crack growth under VA loading were obtained. Fractography appears to be indispensable for the evaluation of fatigue crack growth prediction models in view of similarities and dissimilarities between crack growth under VA and CA loading.
Stepwise S‐N curve and fish‐eye failure in gigacycle fatigue
Authors: Nishijima  , Kanazawa
Published: March 2003

Fatigue failure is normally initiated at the surface of a material. For some materials, failure can be initiated both at the surface and the interior. This twofold materials behaviour in fatigue is represented by a stepwise shape in the S–N curve. An internal failure mode is especially important for fatigue life in the gigacycle range, as this mode is predominant at low stress ranges.

Materials with a hardened surface fail from the surface only at high stresses, and at low stresses from the inside, forming a fish‐eye facet on the fracture surface. Exactly the same behaviour can be observed for materials without a hard surface, even at elevated temperatures. This paper displays some of the results obtained at NRIM and discusses possible interpretations.
Fatigue strength of crack‐healed Si3N4/SiC composite ceramics
Authors: Ando K. , Chu M. C. , Yao F. , Sato S.
Published: March 2003

Si3 N4 /SiC composite ceramics were sintered and subjected to three‐point bending on specimens made according to the appropriate JIS standard. A semi‐circular surface crack of 110 μm in diameter was made on each specimen. By using three kinds of specimen (smooth, cracked and crack healed), crack‐healing behaviour, cyclic and static fatigue strengths were determined systematically at room temperature and 1000 °C. The main conclusions are as follows: (i) Si3 N4 /SiC composite ceramics have the ability to heal after cracking; (ii) crack‐healed specimens showed similar cyclic and static fatigue strengths as smooth specimens, this being caused by crack healing; (iii) crack‐healed zones had a sufficient fatigue strength and most fractures occurred outside the pre‐cracked zone in those crack‐healed specimens.
Circumferential inner fatigue crack growth and penetration behaviour in pipe subjected to a bending moment
Authors: Yoo  , Ando
Published: March 2003

Surface defects in most pipe components under cyclic stress tend to be origins of fatigue crack growth, which may cause serious failure of the whole structure. An analysis of crack growth and penetration behaviour from these defects may therefore be one of the most important subjects on the reliability of the LBB (leak before break) design philosophy. However, studies on fatigue crack growth and COD (crack opening displacement) behaviour in a complex through‐wall crack are relatively rare. To that purpose, a series of fatigue tests has been carried out at room temperature on carbon steel pipe which has an inner surface crack. Before crack penetration, leak‐life, fatigue crack growth behaviour, e.g. aspect ratios and da/dN versus ΔK were evaluated successfully by using a proposed plate model. After crack penetration, a new formula to evaluate K is proposed. For the complex crack created after through‐wall penetration, fatigue life and fatigue crack growth behaviour were evaluated quantitatively by using the new formula and the model proposed in this study.
On the transverse shear modulus of negative Poisson’s ratio honeycomb structures
Authors: Scarpa F. , Tomlin P. J.
Published: March 2003

The transverse shear modulus of in‐plane negative Poisson’s ratio honeycombs is determined using numerical simulations. General honeycombs have theoretical upper and lower bounds of transverse shear moduli. The actual transverse shear modulus is an intermediate value, depending on the relative density and the gauge thickness ratio. The difference between upper and lower bounds is particularly significant for negative Poisson’s ratio honeycombs. Finite element simulations confirm the theoretical trend, and show gauge ratio dependence different from that envisaged in the literature for conventional honeycombs. A modified approximate formula is thus proposed to predict the actual transverse shear modulus for honeycombs having in‐plane negative Poisson’s ratio values.
Interior fatigue fracture of gear teeth
Authors: Mackaldener  , Olsson
Published: March 2003

A new type of gear tooth fatigue failure is presented and analysed. It is initiated in the interior of the tooth and is given the self‐explanatory name tooth interior fatigue fracture (TIFF).

A fractographic examination of TIFF is presented. The fracture surface of TIFF has characteristic features that distinguish it from other gear failures.

A hypothesis for TIFF initiation is presented. The crack‐initiating stresses in the interior of the gear tooth are: (i) a residual tensile stress due to case hardening; and (ii) alternating stresses due to idler usage of the gear.

A finite element analysis is used to compute the stress state history of engaging gear teeth throughout the load cycle. The critical plane fatigue criterion of McDiarmid is employed. The analysis shows that the risk of fatigue initiation is high in the root of the tooth and in a large region in the interior of the tooth. These findings agree with test results where both modes of failure occurred.
The effect of pitting corrosion on fatigue life
Authors: Dolley  , Lee  , Wei
Published: March 2003

Fatigue testing of pre‐pitted 2024‐T3 aluminium alloy specimens is performed in laboratory air at 22 °C and 40% RH to characterize the effect of pitting corrosion on fatigue life. Specimens, pre‐corroded in a 0.5 M NaCl solution from 48 to 384 h, have fatigue lives that are reduced by more than one order of magnitude after 384 h pre‐corrosion as compared to those of uncorroded specimens. The reduction in fatigue life is interpreted in terms of the influence of the time of exposure to the corrosive environment or pit size. The crack‐nucleating pit sizes, ranging from 20 to 70 μm, are determined from post‐fracture examinations by scanning electron microscopy. Fatigue lives are estimated using a fracture mechanics approach and are shown to be in good agreement with the actual data. A probabilistic analysis shows that the distribution of fatigue life is strongly correlated to the distribution in nucleating pit size.
Technical note A study on stress, reflection and double shot peening to inrease compressive residual stress
Authors: Ishigami H. , Matsui K. , Jin Y. , Ando K.
Published: March 2003

The technique of shot peening is commonly used to increase the fatigue limit of a steel. However, there are many practical difficulties in applying it to very high HV steel and complicated components. To overcome these problems, the authors proposed two new methods: stress double shot peening and stress reflection double shot peening. Both techniques were applied to quench and tempered steel (QT steel) and induction‐heated steel (IH steel). The main results were as follows: (a) by double shot peening, the compressive residual stress near the sample surface was increased considerably; (b) by stress shot peening, the maximum compressive residual stress (σmax ) and the surface compressive residual stress (σs ) were greatly increased; (c) by stress double shot peening, very high compressive residual stresses (σmax = −1710 MPa and σs = −1320 MPa) were successfully introduced into a hard steel (HV = 700); (d) in the new method (stress reflection double shot peening), very high compressive residual stresses (σmax = −1760 MPa and σs = −1460 MPa) were successfully introduced into a hard steel (HV = 700).
On the mechanism of fatigue failure in the superlong life regime (N>107 cycles). Part II: influence of hydrogen trapped by inclusions
Authors: Murakami Y. , Nomoto T. , Ueda T. , Murakami Y.
Published: March 2003

High cycle fatigue fracture surfaces of specimens in which failure was initiated at a subsurface inclusion were investigated by atomic force microscopy and by scanning electron microscopy. The surface roughness Ra increased with radial distance from the fracture origin (inclusion) under constant amplitude tension–compression fatigue, and the approximate relationship: Ra ≅ CΔK 2I holds. At the border of a fish‐eye there is a stretched zone. Dimple patterns and intergranular fracture morphologies are present outside the border of the fish‐eye. The height of the stretch zone is approximately a constant value around the periphery of the fish‐eye. If we assume that a fatigue crack grows cycle‐by‐cycle from the edge of the optically dark area (ODA) outside the inclusion at the fracture origin to the border of the fish‐eye, we can correlate the crack growth rate da/dN, stress intensity factor range ΔKI and Ra for SCM435 steel by the equation

and by da/dN proportional to the parameter Ra .

Integrating the crack growth rate equation, the crack propagation period Np2 consumed from the edge of the ODA to the border of the fish‐eye can be estimated for the specimens which failed at Nf > 107. Values of Np2 were estimated to be ∼1.0 × 106 for the specimens which failed at Nf ≅ 5 × 108. It follows that the fatigue life in the regime of Nf >107 is mostly spent in crack initiation and discrete crack growth inside the ODA.
A review of multiaxial fatigue of weldments: experimental results, design code and critical plane approaches
Authors: Bäckström M. , Marquis G.
Published: March 2003

A survey of biaxial (bending or tension and torsion) constant amplitude fatigue of welded connections is presented. Re‐analysis of 233 experimental results from eight different studies has been performed based on hot spot stresses and three potential damage parameters: maximum principal stress range; maximum shear stress range; and a modified critical plane model for welds. Of the three methods, the critical plane model was most successful in resolving the data to a single S–N line. The design curve for all toe failures based on the critical plane model was FAT 97 with a slope of 3. By excluding butt welds and including only fillet welds that failed at the weld toe, the design curve was increased to FAT 114 with a slope of 3. However, observed scatter was 70–100% larger than that observed in uniaxial loaded specimens analysed using the hot spot approach.
ANN based prediction model for fatigue crack growth in DP steel
Authors: Haque M. E. , Sudhakar K. V.
Published: March 2003

An artificial neural network (ANN)‐based model was developed to analyse high‐cycle fatigue crack growth rates (da/dN ) as a function of stress intensity ranges (ΔK ) for dual phase (DP) steel. The training data consisted of da/dN at ΔK ranges between 5 and 16 MPa √ for DP steel with martensite contents in the range 32 to 76%. The ANN back‐propagation model with Gaussian activation function exhibited excellent agreement with the experimental results. The fatigue crack growth rate predictions were made to demonstrate its practical significance in a given real‐life situation. Because of the wide range of data points used during training of the model, it will provide a useful predictor for fatigue crack growth in DP steels.
Fracture of a ductile layer constrained by stiff substrates
Authors: Choi S.‐H. , Song B.‐G. , Kang K.‐J. , Fleck N. A.
Published: March 2003

A combined experimental and theoretical analysis of the fracture behaviour of brass/solder/brass sandwich specimens is conducted. First, the theories of interfacial fracture initiation for a ductile layer sandwiched between elastic substrates are reviewed. The fracture behaviours are then reported of brass/solder/brass sandwich specimens under various mode mixities. Additionally, the effects of solder layer thickness h and specimen lateral thickness t are presented. The effects of mode mix and plastic constraint on the failure mechanism and toughness are analysed.
Influence of stress state on high temperature fatigue crack growth in Inconel 718
Authors: Antunes F. V. , Ferreira J. M. , Branco C. M. , Byrne J.
Published: March 2003

The influence of stress state on fatigue crack growth in nickel‐base superalloys at high temperature is considered, based on studies in corner crack specimens of Inconel 718 at 600 °C. At high frequency and low R, cycle‐dependent trans‐granular crack growth occurs along the whole crack front, and growth rates are similar at the surface and within the interior of specimens, maintaining the original quarter‐circular shape. For conditions of low frequency and high R, increased crack growth rate per cycle is observed with the crack tunnelling ahead at the centre. A time‐dependent intergranular crack propagation mode occurs in the plane strain interior, attributed to an oxidation mechanism, whereas near the surfaces under plane stress, a trans‐granular cyclic plasticity mechanism is observed. It is proposed that in addition to frequency and R, that stress state influences the competition between the mechanisms controlling crack growth and the transition between them: plane strain in the interior favouring an oxidation‐controlled intergranular cracking mechanism as compared with the plane stress surfaces where cyclic plasticity dominates. An FEM study suggests that this influence of stress state is not associated with variation of ΔK along the crack front.
A three‐dimensional progressive damage model for bolted joints in composite laminates subjected to tensile loading
Authors: Tserpes K. I. , Papanikos P. , Kermanidis TH.
Published: March 2003

A three‐dimensional progressive damage model was developed to simulate the damage accumulation and predict the residual strength and final failure mode of bolted composite joints under in‐plane tensile loading. The parametric study included stress analysis, failure analysis and material property degradation. Stress analysis of the three‐dimensional geometry was performed numerically using the finite element code ANSYS with special attention given to the detailed modelling of the area around the bolt in order to account for all damage modes. Failure analysis and degradation of material properties were implemented using a set of stress‐based Hashin‐type failure criteria and a set of appropriate degradation rules, respectively. In order to validate the finite element model, a comparison of stress distributions with results from analytical models found in the literature was carried out and good agreement was obtained. A parametric study was performed to examine the effect of bolt position and friction upon damage accumulation and residual strength.
Cyclic crystal plasticity analyses of stationary, microstructurally small surface cracks in ductile single phase polycrystals
Authors: BENNETT V. P. , McDOWELL D. L.
Published: March 2003

ABSTRACT This paper explores the effects of microstructural heterogeneity on the cyclic crack tip opening and sliding displacements for stationary, microstructurally small transgranular surface cracks in a single phase metallic polycrystal using planar double slip crystal plasticity computations. Crack tip displacements are examined under plane strain conditions for stationary cracks of different lengths relative to grain size as a function of the applied nominal strain amplitude for tension‐compression and cyclic shear. Nominal strain amplitudes range from well below to slightly above the nominal cyclic yield strength for each type of loading condition. Results indicate the complex nature of the crack tip sliding and opening displacements as functions of nominal strain amplitude and orientation of the nearest neighbour grains, the influence of the free surface in promoting the cyclic opening displacement even for cracks in the first surface grain, the rather restricted limits of applicability of linear elastic fracture mechanics, and very interesting crack tip plasticity effects which include crack tip displacement ratcheting or progressive accumulation, even for completely reversed, proportional applied loading. Results are compared for cases with and without crack face friction.
Fatigue crack propagation behaviour derived from S–N data in very high cycle regime
Authors: TANAKA K , AKINIWA Y
Published: March 2003

ABSTRACT The crack propagation law was derived from the S–N data in the very high cycle fatigue of a bearing steel. The propagation rate, da/dN (m/cycle), of surface cracks was estimated to be a power function of the stress intensity range, ΔK (MPa√m) with the coefficient Cs = 5.87 × 10−13 and the exponent ms = 4.78. The threshold stress intensity range was 2.6 MPa√m. The crack propagation from internal inclusions was divided into Stages I and II. For Stage I, the coefficient of the power law was C0 = 3.44 × 10−21 and the exponent m0 = 14.2. The transition from Stage I to II took place at ΔK = 4.0 MPa√m. For Stage II, the coefficient was Ci = 2.08 × 10−14 and the exponent mi = 4.78. The specimen size and loading mode did not influence the surface fatigue life, while the internal fatigue life was shortened in larger specimens and under tension–compression loading. For ground specimens, the surface fatigue life was raised by the compressive residual stress, while reduced by the surface roughness introduced by grinding. For shot‐peened specimens, fatigue fracture did not take place from the surface because of a high surface compressive residual stress. The internal fatigue life was reduced by the tensile residual stress existing in the interior of the specimens.
Step loading for very high cycle fatigue
Authors: NICHOLAS T.
Published: March 2003

ABSTRACT The conventional method for determining fatigue strength at high cycle counts is to either extrapolate S–N data from lower cycle counts or to generate S–N data in the high cycle count regime using special high frequency test machines. In the process of generating S–N data, runout tests often occur where no failure is obtained within the allotted time for a test. Such data points are normally indicated on an S–N plot with an arrow, but no information is available as to whether failure would ever occur. As an alternative, and as a method for getting a data point for every test, a step‐loading method may be employed. In this paper, some of the unique test equipment being applied to the study of high cycle fatigue in our laboratory are reviewed. Data are presented on the long‐life fatigue behaviour of Ti‐6Al‐4V which validate both the step‐loading methodology and indicate the trend of fatigue strength as a function of cycle number in the very high cycle fatigue regime. The absence of coaxing is demonstrated by comparing S–N data with step‐loading data. Applicability of high frequency testing to the determination of fatigue crack growth thresholds is also demonstrated.
Very high‐cycle fatigue behaviour of shot‐peened high‐carbon–chromium bearing steel
Authors: SHIOZAWA K. , LU L.
Published: March 2003

Effect of shot‐peening on fatigue behaviour in the gigacycle regime was investigated in order to clarify the duplex S–N curve characteristics. Cantilever‐type rotary bending fatigue tests were performed in laboratory air at room temperature by using hourglass‐shaped specimens of high‐carbon–chromium bearing steel, JIS SUJ2. Fatigue crack initiation site changed from the surface of untreated specimen to the subsurface of the specimen because of hardening and compressive residual stress with shot‐peening in the region of high‐stress amplitude. On the other hand, no difference in fatigue life controlled by the subsurface crack initiation between untreated specimen and shot‐peening one was observed in high‐cycle region. It was suggested that the S–N curve corresponding to the internal fracture mode is inherent in the material, as compared with the S–N curve of surface fracture mode, which is affected by surface conditions, environmental conditions and so on. Subsurface crack initiation and propagation behaviour were discussed under the detailed measurement of crack initiation area and shape of the fish‐eye fracture surface.
Mechanism of fatigue failure in ultralong life regime
Authors: MURAKAMI Y. , YOKOYAMA N. N. , NAGATA J.
Published: March 2003

ABSTRACT The fatigue fracture surfaces of specimens of heat treated hard steels which failed in the regime of N = 105 to 5 × 108 cycles, were investigated by optical microscopy and SEM. Specimens having a longer fatigue life had a particular morphology beside the inclusion at the fracture origin. The particular morphology looked optically dark and in the previous paper it was named the Optically Dark Area, ODA. The roughness inside ODA is larger than outside ODA. The relative size of the ODA to the size of the inclusion at the fracture origin increases with increase in fatigue life. Thus, the ODA is considered to have a crucial role in the mechanism of ultra long life fatigue failure. Direct evidences of existence of hydrogen at the inclusion at fracture origin are presented. It is presumed that the ODA is made by the cyclic stress coupled with the hydrogen which is trapped by the inclusion at the fracture origin. To verify the influence of hydrogen, specimens containing different levels of hydrogen were prepared by different heat treatments. The results obtained by fatigue tests of these specimens suggest that the hydrogen trapped by inclusions is a crucial factor which causes the ultra long fatigue failure of high strength steels. Aspects of the double S–N curve are also discussed in terms of experimental methods, specimen size and statistical distribution of inclusions sizes.
Modelling of fatigue damage progression and life of CFRP laminates
Authors: PAPANIKOS P. , TSERPES K. I. , PANTELAKIS SP.
Published: March 2003

A progressive fatigue damage model has been developed for predicting damage accumulation and life of carbon fibre‐reinforced plastics (CFRP) laminates with arbitrary geometry and stacking sequence subjected to constant amplitude cyclic loading. The model comprises the components of stress analysis, fatigue failure analysis and fatigue material property degradation. Stress analysis of the composite laminate was performed by creating a three‐dimensional finite element model in the ANSYS FE code. Fatigue failure analysis was performed by using a set of Hashin‐type failure criteria and the Ye‐delamination criterion. Two types of material property degradations on the basis of element stiffness and strength were applied: a sudden degradation because of sudden failure detected by the fatigue failure criteria and a gradual degradation because of the nature of cyclic loading, which is driven by the increased number of cycles. The gradual degradation of the composite material was modelled by using functions relating the residual stiffness and residual strength of the laminate to the number of cycles. All model components have been programmed in the ANSYS FE code in order to create a user‐friendly macro‐routine. The model has been applied in two different quasi‐isotropic CFRP laminates subjected to tension–compression (T–C) fatigue and the predictions of fatigue life and damage accumulation as a function of the number of cycles were compared with experimental data available in the literature. A very good agreement was obtained.