bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of complementary therapies in pregnancy: The perceptions of obstetricians and midwives in South Australia
Authors: Gaffney Lauren , Smith Caroline A.
Published: January 2004

Objective  To examine South Australian obstetricians and midwives attitude's towards the use of complementary and alternative medicines (CAM) during pregnancy, to examine their referral patterns and their views on the usefulness and safety of these therapies during pregnancy.

Design  All members of the South Australian branch of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists and a 50% sample of midwives belonging to the South Australian Branch of The Australian College of Midwives, were sent a postal self‐completion questionnaire.

Results  A response rate of 78% was obtained. Only 14% of doctors considered CAM was a threat to public health. Over 90% of midwives and obstetricians thought they should have some knowledge about CAM. A greater proportion of obstetricians (72%) held a view there needs to be an evidence base for CAM compared with 26% of midwives. The majority of obstetricians (68%) and midwives (78%) had formally referred a patient for use of one of the complementary therapies. Over 70% of obstetricians and midwives considered massage, acupuncture, vitamins, yoga, meditation and hypnosis to be useful and safe to use during pregnancy.

Conclusion  The majority of clinician's held positive views towards CAM and considered some complementary therapies to be useful and safe for use during pregnancy. Limited evidence exists on the safety and efficacy of these therapies and attention needs to be given to undertaking high quality randomised controlled trials.
Simplified colposuspension: A 15‐year follow‐up
Authors: Ladwig Denise , Miljkovic‐Petkovic Ljiljana , Hewson Alan D.
Published: January 2004

Aim:  Retrospective analysis of long‐term results of a simplified ‘Burch type’ colposuspension.

Methods:  A retrospective chart review, with follow‐up through postal questionnaires sent in September 2000, of all 374 patients who had a simplified colposuspension between 1985 and 1998, with additional total abdominal hysterectomy in 103 patients. Outcome measures were patient satisfaction, complications and recovery.

Results:  The mean period of follow‐up was 9.2 years. Response rate to the questionnaire was 85% with 51.5% of patients very satisfied with the surgery, 17.4% moderately satisfied and 12.6% having some symptomatic relief. Complications developed in 31.3% but few were serious. Average hospitalisation was 5.8 days. The mean time to establishment of normal voiding was 58.5 h. The average length of catheterisation was 49.9 h, with only seven patients requiring prolonged catheterisation. Seventy‐four patients required additional surgery for de novo, persistent or recurring symptoms.

Conclusions:  The present study provides evidence that a simplified Burch type colposuspension provides a satisfactory cure rate on long‐term follow‐up and is associated with earlier resumption of normal voiding. Transurethral drainage remains a simple and effective method of bladder management after colposuspension. The present study also confirms that many patients do need further pelvic floor surgery for later development of deficiencies in the pelvic floor.
Long‐term success of endometrial resection: In everyday clinical practice, personal audit is more important than the knowledge of how the majority of surgeons perform
Authors: Maouris Panos , Jamieson Rosalind
Published: January 2004

Results of a personal audit of the long‐term success of endometrial resection are used for comparison with other published data to demonstrate the importance of personal audit.
Value of single and paired serum human chorionic gonadotropin measurements in predicting outcome of in vitro fertilisation pregnancy
Authors: Alahakoon Thushari Indika , Crittenden Jenny , Illingworth Peter
Published: January 2004

Objectives:  To assess whether paired human chorionic gonadotropin (hCG) measurements in early pregnancy are more effective than a single measurement, in predicting the outcome for an in vitro fertilisation pregnancy.

Design:  Retrospective analysis.

Setting:  Westmead Fertility Centre, Westmead Hospital, Sydney, Australia.

Materials and methods:  Serial hCG measurements in 143 patients at Westmead Fertility Centre, from August 1997 to April 2000, were studied retrospectively. The predictive value of single hCG measurements relative to the published assay reference ranges were evaluated. The predictive value of serial hCG levels in predicting pregnancy outcome was assessed separately. Normal daily rate of rise (ROR) of hCG was defined as the mean ROR for ongoing pregnancies ± 1 SD. Abnormal daily ROR was defined as a daily increase in hCG less than the mean ROR for ongoing pregnancies − 1 SD.

Main outcome measures:  Viability of the pregnancy at 20 weeks’ gestation.

Results:  An initial hCG measurement below the 5th centile reference limit for gestation has 85% (confidence interval (CI) 75–92%) positive predictive value for non‐viability, with a sensitivity of 40% (CI 33–48). Serial testing of borderline samples for ROR did not improve positive predictive value (70%: CI 50–86%) or sensitivity (30%: CI 20–43%) in identifying non‐ongoing pregnancies.

Conclusions:  In assisted reproductive technologies pregnancies, comparison of a single hCG value with appropriate reference ranges enables approximately 40% of non‐viable pregnancies to be identified with a high positive predictive value. Repeated measurements did not contribute further to the predictive value.
Survey of the management of preterm labour in Australia and New Zealand in 2002
Authors: Cook Colleen‐M. , Peek Michael J.
Published: January 2004

Aim:  To determine current attitudes and practices regarding the suppression of preterm labour among obstetricians in Australia and New Zealand.

Methods:  A questionnaire mailed to all Diplomates, Members and Fellows of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists in April 2002.

Results:  A total of 813 surveys were returned – 33% (470/1412) of Fellows and Members and 11% (322/2806) of Diplomates. The response rate for Australia was 18.9% (759 of 4019) compared to 27.1% (54 of 199) from New Zealand. Routine suppression of preterm labour was attempted by 79% of respondents, primarily to prolong pregnancy for steroid administration (83%) and/or transfer (74%). The gestation for initiation of suppression ranged from 20 to 37 weeks. Tocolysis was discontinued at 32.9 ± 2.7 weeks (mean ± SD), range 24–38 weeks. The first choice drug for tocolysis was the β‐adrenergic group (73%), followed by nifedipine (21%). Maintenance tocolysis was used by 34%. Respondents were asked the percentage of women in whom suppression was attempted that achieved: (i) steroid cover – median 80% (range 10–100); (ii) prolongation of pregnancy ≥7 days – 50% (0–100); and (iii) prolongation of pregnancy to term – 10% (0–100).

Conclusion:  Most respondents attempted to suppress preterm labour for steroid administration and/or transfer. However, a wide range of opinions and uncertainty was evident as to the effectiveness of tocolytic therapy in clinical management, the most appropriate drug and drug side‐effects.
The Ligation of Coronary Arteries with Electrocardiographic Study*
Authors: Smith Fred M.
Published: January 2004

This article is based on a study of sixty‐six dogs in which known myocardial lesions had been produced by the ligation of definite branches of the coronary arteries of the heart. While the experiments were made with the primary object of determining the change in the electrocardiograms brought about by these ligations, other results, anatomic and pathologic, are deemed worthy of brief mention.
Beat‐to‐Beat QT Dynamics in Healthy Subjects
Authors: Jensen Berit T. , Larroude Charlotte E. , Rasmussen Lars P. , Holstein‐Rathlou Niels‐Henrik , Hojgaard Michael V. , Agner Erik , Kanters Jørgen K.
Published: January 2004

Background: Measures of QT dynamics express repolarization abnormalities that carry prognostic information, but the reproducibility of beat‐to‐beat QT dynamics has never been established. The QT interval is prolonged at night, but how the circadian rhythm and heart rate influence the dynamic QT measurements is still unsettled. The aims of the present study were: (1) to describe the reproducibility of beat‐to‐beat QT dynamics with respect to intrasubject, between‐subject, and between‐observer variability and (2) to describe the normal range, circadian variation, and heart rate dependence of QT dynamics.

Methods: Ambulatory Holter recordings were performed three times on 20 healthy volunteers and were analyzed by two experienced cardiologists. Slope and intercept of the QT/RR regression, the variability of QT and R‐R intervals expressed as the standard deviation, and the relation between QT and RR variability expressed as a variability ratio were measured among other QT dynamics.

Results: The reproducibility of all QT dynamics was good. All QT dynamics showed circadian variation when calculated on an hourly basis. The day/night variation in slope could be explained by the differences in heart rate, whereas the day/night variation in intercept was heart rate independent.

Conclusion: The present study shows that reliable automatic QT measurements could be performed, encouraging further evaluation of the clinical value of QT dynamics in risk stratification of cardiac patients.
Structural, Functional and Autonomic Changes in the Cardiovascular System in Growth Hormone Deficient Patients
Authors: Erdoğan Doğan , Tükek Tufan , Aral Ferihan , Oflaz Hüseyin , Özaydin Mehmet , Kocaman Orhan , Akkaya Vakur , Gören Taner , Molvalilar Senay
Published: January 2004

Background: Growth hormone deficiency (GHD) is known to cause higher rates of cardiovascular mortality. The purpose of the study was to analyze the structural and functional changes in the heart and investigate their relation to autonomic function as assessed with heart rate variability (HRV).

Methods: Eleven untreated GHD patients (mean age 50.4 ± 10.7 years, M/F: 3/8) and 15 age‐ and sex‐matched healthy persons (mean age 45.3 ± 10.4 years, M/F: 5/10) were compared. Both groups were examined with echocardiography, HRV, and exercise testing and findings were analyzed.

Results: The groups were similar in height, weight, body mass index, body surface area, systolic and diastolic blood pressure, heart rate. The GHD patients had lower exercise duration and metabolic equivalent (MET) compared to controls (7.94 ± 1.26 vs. 9.8 ± 1.9 min, P < 0.001, for MET 8.85 ± 0.86 vs. 10.7 ± 2.23, P = 0.03). On echocardiography, GHD patients had lower interventricular septum diastolic diameter (9 ± 0.89 vs. 10.7 ± 0.88 mm, P < 0.001) and posterior wall thickness (8.4 ± 0.93 vs. 9.8 ± 0.91 mm, P = 0.002), and lower left ventricle mass index (90.9 ± 20 vs. 112 ± 8 g/m2, P = 0.01). Left ventricular ejection fraction was lower in the GHD patients (57.4 ± 5.12% vs. 65.5 ± 4.1%, P < 0.001). Time and frequency domain heart rate variability parameters, SDNN, SDANN, VLF, LF ve LF/HF were lower in GHD patients compared to controls. There was a significant correlation between left ventricle diastolic diameter and LF (r = 0.62, P = 0.02).

Conclusion: GHD seemed to cause decreased left ventricle mass and decreases in the sympathetic components of HRV that may have a bearing on the increased cardiovascular risk seen in these patients.
The Relationship between Plasma Endothelin‐1, Nitric Oxide Levels, and Heart Rate Variability in Patients with Coronary Slow Flow
Authors: Pekdemir Hasan , Cicek Dilek , Camsari Ahmet , Akkus M. Necdet , Cin V. Gokhan , Doven Oben , Parmaksiz H. Tuncay , Katircibasi M. Tuna , Ozcan I. Turkay
Published: January 2004

Background: Coronary slow flow (CSF) is characterized by delayed opacification of coronary arteries in the absence of epicardial occlusive disease. In this study, we aimed to determine endothelin‐1 (ET‐1), nitric oxide (NOx) levels and time domain heart rate variability (HRV) parameters in patients with CSF and relationship among these parameters.

Methods: Thirty‐three patients with CSF detected in the coronary angiography (17 females; mean age 55 ± 7) and 19 patients with normal coronary flow (10 females; mean age 54 ± 11) as a control group were enrolled in the study. Patients were divided into two groups according to exercise testing as if positive (group A, n = 8) or negative (group B, n = 25).

Results: Plasma ET‐1 levels were higher in the group A patients (28.7 ± 17.4 pg/ml) than that of group B (15.9 ± 10.6 pg/ml) and control group (6.0 ± 5.7 pg/ml); and higher in group B patients than that of control group (P < 0.05). Although groups A and B did not differ according to plasma NOx levels (23.4 ± 13.5 μmol/L vs. 32.8 ± 22.7 μmol/L, P > 0.05), NOx levels in group A were lower than the control group (23.4 ± 13.5 μmol/L versus 42.5 ± 15.9 μmol/L, P < 0.05). Time domain HRV parameters were decreased in all patient groups. This was more prominent in group A. Additionally, HRV parameters were negatively correlated with ET‐1 and TIMI frame counts. TIMI frame count was also significantly correlated with ET‐1 and NOx levels (r = 0.61, P < 0.0001, r =−0.30, P < 0.05). Upon intravascular ultrasonography investigation, the common finding was longitudinally extended massive calcification throughout the epicardial arteries. Mean intimal thickness was 0.50 ± 0.13 mm (group A; 0.58 ± 0.11 mm, group B 0.47 ± 0.12 mm, P = 0.029).

Conclusions: The present study demonstrated that in patients with CSF, both increased plasma ET‐1, decreased plasma NOx and diffuse atherosclerosis may cause the decrease in HRV by effecting myocardial blood flow.
Increased P Wave Dispersion and Maximum P Wave Duration after Hemodialysis
Authors: Tezcan Ugur K. , Amasyali Basri , Can Ilknur , Aytemir Kudret , Köse Sedat , Yavuz Izzet , Kursaklioglu Hurkan , Işik Ersoy , Demirtaş Ertan , Oto Ali
Published: January 2004

Background: Atrial fibrillation is a frequent arrhythmia in patients undergoing hemodialysis. The consequences of hemodialysis on P wave durations and P wave dispersion have not been fully understood. The objective of this study was to study the effect of dialysis on P wave maximum (Pmax), P wave minimum (Pmin), and P wave dispersion (Pd).

Methods: We studied Pmax, Pmin, and Pd in 32 patients (17 men and 15 women, mean age 54 ± 18 years) with chronic renal failure undergoing hemodialysis. The difference between maximum and minimum P wave duration was calculated and defined as P wave dispersion (Pd= Pmax− Pmin).

Results: There was a significant increase in Pmax at the end of dialysis compared to the beginning (98 ± 13 ms vs. 125 ± 12 ms, P < 0.001). Pmin did not show any significant change (71 ± 11 ms vs. 73 ± 10 ms, P = 0.42). Pd was significantly increased at the end of dialysis (27 ± 9 ms vs. 52 ± 11 ms, P < 0.001). There was a negative correlation between serum potassium, magnesium, phosphate, blood urea nitrogen, and creatinin at the end of dialysis and Pmax and Pd, respectively (P < 0.05). A weak positive correlation was found between serum calcium, bicarbonate at the end of dialysis and Pmax and Pd (P < 0.05).

Conclusion: Hemodialysis ends with significant increase in P wave maximum duration and P wave dispersion, which might be responsible for the increased occurrence of atrial fibrillation in these groups of patients.
High correlation between the bacterial species in denture plaque and pharyngeal microflora
Authors: Sumi Yasunori , Kagami Hideaki , Ohtsuka Yoshiaki , Kakinoki Yasuaki , Haruguchi Yuuji , Miyamoto Hiroshi
Published: January 2004

Objectives: The morbidity and mortality of the dependent elderly that result from aspiration pneumonia are recognized as a major geriatric health problem. Most cases of bacterial pneumonia are initiated following colonization or superinfection of the pharynx by pathogenic bacteria, followed by aspiration of pharyngeal contents. A recent study revealed that bacteria, that commonly cause respiratory infection, colonized the dentures of dependent elderly. This suggests that denture plaque may function as a reservoir of potential respiratory pathogens to facilitate colonization on the pharynx. The purpose of this study was to determine the possible correlation between denture and pharyngeal microflora. Study Design: The denture and pharyngeal bacterial flora of 50 dependent elderly were examined, and the microorganisms identified by culturing. The agreement between the bacterial species in denture plaque and pharyngeal microflora was investigated using the Kappa method. Results: The microorganism species on the dentures and pharyngeal mucosa of the subjects had an agreement rate of 68.5%. The agreement rate for each of the bacterial species of the dentures and pharynx was also demonstrated to be high.

Conclusions: Dentures should be considered an important reservoir of organisations which could colonise the pharynx, and the importance of controlling denture plaque for the prevention of aspiration pneumonia cannot be overemphasized.
Validation of a Sinhalese translation of the Oral Health Impact Profile‐14 for use with older adults
Authors: Ekanayake L. , Perera I.
Published: January 2004

Objective: To test the psychometric properties of a Sinhalese translation of the OHIP‐14 scale for use among older adults in Sri Lanka. Design: A cross‐sectional survey. The English version of the OHIP‐14 was translated in to Sinhalese, pre‐tested and subsequently administered to the subjects by a trained interviewer. Setting: Moratuwa — a densely populated urban area in the Western province of Sri Lanka. Subjects: 585 individuals aged 60 years and above. Main outcome measures: Reliability of the translated scale was assessed in terms of internal consistency using Cronbach's alpha. Construct validity was evaluated by examining the associations between perceived oral health status, perceived need for dental care and the OHIP scores. Results: Cronbach's alpha of the translated scale was 0.93. Corrected item‐total correlation coefficients ranged from 0.53–0.80. The highly significant associations between perceived oral health status, perceived need for dental care and the OHIP scores support the construct validity of the translated scale. Conclusion: The Sinhalese translation of the OHIP‐14 is a valid and reliable instrument to measure oral health related quality of life in older adults of Sri Lanka.
The influence of age and denture wear on the size of edentulous structures
Authors: Pietrokovski J , Harfin J , Levy F
Published: January 2004

Objectives: This study was designed to evaluate the influence of age and denture use on the size of arches and residual ridges in edentulous patients. Design: At two nursing homes, maxillary and mandibular stone casts of 302 fully edentulous patients were utilized to measure the size of the arches and residual ridges, according to age and use of complete dentures. Age cohorts were divided into three groups; 60–69, 70–79, and 80–89 years old. Two hundred and forty‐nine denture wearers used complete dentures for at least 2 years before examinations. Fifty‐three non‐denture users had never worn removable prostheses. Chi‐square analysis (p<0.05) was used to establish the possible relations between the linear values and the size indexes of the ridges and arches and the two examined parameters: age and denture wear. Results: Young old patients possessed edentulous structures that were not significantly larger than elderly old patients in both the maxilla and the mandible. Non‐denture users had significantly bigger arches and ridges in both edentulous jaws than denture users. Conclusions: Young old, non‐denture users tended to have bigger residual edentulous tissues compared to elderly old patients who used complete dentures.
An Information-Theoretic Entropy Metric for Assessing Multi-Objective Optimization Solution Set Quality
Authors: Farhang-Mehr Ali , Azarm Shapour
Published: January 2004

An entropy-based metric is presented that can be used for assessing the quality of a solution set as obtained from multi-objective optimization techniques. This metric quantifies the “goodness” of a set of solutions in terms of distribution quality over the Pareto frontier. The metric can be used to compare the performance of different multi-objective optimization techniques. In particular, the metric can be used in analysis of multi-objective evolutionary algorithms, wherein the capabilities of such techniques to produce and maintain diversity among different solution points are desired to be compared on a quantitative basis. An engineering test example, the multi-objective design optimization of a speed-reducer, is provided to demonstrate an application of the proposed entropy metric.
Kinematic Analysis of the Ball Screw Mechanism Considering Variable Contact Angles and Elastic Deformations
Authors: Wei Chin Chung , Lin Jen Fin
Published: January 2004

The theoretical analyses developed by Lin et al. 6 for the kinematics of the ball screw mechanism have been partly adapted for the present study. In order to better understand the sliding behavior arising at two contact areas, the analyses of a ball bearing, while accounting for elastic deformation, are modified through coordinate transformations prior to their applications to the analyses for the ball screw mechanism. The influence of differing the parameters such as friction coefficient, normal force acting on the ball, and contact angle on a ball-screw’s mechanism at two contact areas are evaluated. The results of the ball-screw’s mechanical efficiency achieved by the present model are displayed to compare with those evaluated based on the model of Lin et al. Substantial differences exist in the results evaluated by these two models, especially those created at high screw rotational speeds.
Identification of Compliant Pseudo-Rigid-Body Four-Link Mechanism Configurations Resulting in Bistable Behavior
Authors: Jensen Brian D. , Howell Larry L.
Published: January 2004

Bistable mechanisms, which have two stable equilibria within their range of motion, are important parts of a wide variety of systems, such as closures, valves, switches, and clasps. Compliant bistable mechanisms present design challenges because the mechanism’s energy storage and motion characteristics are strongly coupled and must be considered simultaneously. This paper studies compliant bistable mechanisms which may be modeled as four-link mechanisms with a torsional spring at one joint. Theory is developed to predict compliant and rigid-body mechanism configurations which guarantee bistable behavior. With this knowledge, designers can largely uncouple the motion and energy storage requirements of a bistable mechanism design problem. Examples demonstrate the power of the theory in bistable mechanism design.
Performance Analysis for Design of a High-Precision Electronic Opto-Mechanical System for Vehicle Delineation Detection on Highway
Authors: Wang Zhaoqing , Chen Bo , Cheng Harry H. , Shaw Ben , Palen Joe
Published: January 2004

We have developed a laser photodiode array based detection system that can non-intrusively detect delineations of vehicles on the highway. The U.S. Patent Office has recently approved a patent for this detection system. The system is built with low-cost off-the-shelf opto-mechanical components. The error sources from a system design point of view will be analyzed in this paper. Our study indicates that the frequency of pulsed laser diodes, computer-sampling rates, deviations in the angle of laser light and imperfectly matched detection points for sensor pairs are the main sources of error in the detection system.
Design Formulas for Permanent-Magnet Bearings
Authors: Paden Brad , Groom Nelson , Antaki James F.
Published: January 2004

As the energy densities in permanent magnet materials increases, permanent magnet (PM) bearings are becoming increasingly attractive machine elements for applications ranging from turbo machinery to energy storage flywheels. Desirable qualities include high speed, low wear, energy savings, and freedom from lubricants that can degrade or contaminate other system components. In this paper we develop analytical expressions for stiffness and peak load in stacked-structure radial magnetic bearings that extend the seminal work of Backers, and Yonnet and co-workers. In addition to the derivation of simple design rules, the axial peak force and negative axial stiffness are calculated.
Optimized Bearing Ellipses of Hypoid Gears1
Authors: Achtmann J. , Ba¨r G.
Published: January 2004

For given machine tool settings of a universal hypoid gear generator, the tooth contact patterns are computed for the coast and drive side of a hypoid gear drive. Each contact pattern is replaced by a determined tooth-bearing ellipse. The position, shape, and inclination of each bearing ellipse is calculated. By the help of these data, an influence function is designed that describes the influence of supplemental kinematic flank correction motions (modified motions) on the gear-tooth contact. Examples show the influence of helical motion and modified roll. An evaluation function permits the calculation of modified motions which improve the tooth contact either at coast and drive side simultaneously, or only at one of the sides. For a given pair of start-bearing ellipses at coast and drive side, and for given importance weights to the sides, we describe how modified motions can be computed that best fit a given target pair of bearing ellipses.
Investigation of Fracture in Transparent Glass Fiber Reinforced Polymer Composites Using Photoelasticity
Authors: Khanna Sanjeev K. , Ellingsen Marius D. , Winter Robb M.
Published: January 2004

Fiber-reinforced plastic composite materials are being widely used in a variety of load bearing and high-performance structures. Reliable use and optimum design requires accurate methods for predicting their fracture behavior, among other things. Fiber reinforced plastic composites are generally opaque and hence experimental fracture mechanics studies utilize surface measurements or post-fracture analysis. Hence quality transparent glass cloth reinforced polyester composites have been fabricated and transmission photoelasticity used to investigate quasi-static Mode-I fracture. The isochromatic fringe patterns obtained were analyzed using orthotropic photoelasticity to determine Mode-I stress intensity factors. Opening mode stress field equations in conjunction with an orthotropic stress-optic law were utilized to regenerate the isochromatic fringe patterns. Good agreement was found between the regenerated fringe patterns and the experimentally obtained patterns
Interfacial Structure and Micro and Nano-Mechanical Behavior of Laser-Welded 6061 Aluminum Alloy Blank
Authors: Wu N. Q. , Xia Cedrix , Li Ming , Perrusquia N. , Mao Scott X.
Published: January 2004

1 mm thick tailor-welded blank of 6061 alloy has been fabricated by Nd:YAG laser welding. The microstructure and the failure mechanism of the welded blank are investigated using optical microscope, atomic force microscope, energy dispersive spectroscopy, microindentation, and nanomechanical tester. The dendrite structure exists at the fusion zone. The partially melted zone is found near the fusion line. The tensile tests show that the welded alloy exhibits lower strength and ductility than the base alloy, and failure occurs at the partially melted zone during tensile testing. Combined nanoindentation with in-situ AFM imaging reveal that the hardness at the partially melted zone is distributed inhomogeneously on the microscopic scale. The hardness at the area adjacent to the grain boundary is lower than that at the center of grain. This is responsible for the failure upon tensile loading, and attributed to the loss of strength and ductility of the welded blank on a macroscopic scale.
Modeling of Fatigue Crack Propagation
Authors: Jiang Yanyao , Feng Miaolin
Published: January 2004

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.
Finite Element Evaluation of the Remaining Mechanical Strength of Deteriorated Cast Iron Pipes
Authors: Seica Michael V. , Packer Jeffrey A.
Published: January 2004

The problem of deteriorating water pipes, resulting in leaks and breaks, affects municipalities worldwide. Corrosion appears to be a leading factor affecting pipe strength and service life. While techniques to evaluate the corrosion damage of in-service pipes are being developed successfully, “affordable” methods to estimate the remaining strength of such pipes are presently not available. A three-dimensional finite element strength evaluation method, as presented herein, is able to predict the strength of corrosion-deteriorated cast iron water pipes subjected to specific loading conditions. It can be used by engineers to identify those pipe sections which require attention.
Transverse-Isotropic Elastic and Viscoelastic Solids
Authors: Freed Alan D.
Published: January 2004

A set of invariants are presented for transverse-isotropic materials whose gradients produce strain fields, instead of deformation fields as is typically the case. Finite-strain theories for elastic and K-BKZ-type viscoelastic solids are derived. Shear-free and simple shearing deformations are employed to illustrate the constitutive theory.
Size Effect on Flexural Strength of Fiber-Composite Laminates
Authors: Bazˇant Zdeneˇk P. , Zhou Yong , Nova´k Drahomı´r , Daniel Isaac M.
Published: January 2004

The size effect on the flexural strength (or modulus of rupture) of fiber-polymer laminate beams failing at fracture initiation is analyzed. A generalized energetic-statistical size effect law recently developed on the basis of a probabilistic nonlocal theory is introduced. This law represents asymptotic matching of three limits: (1) the power-law size effect of the classical Weibull theory, approached for infinite structure size; (2) the deterministic-energetic size effect law based on the deterministic nonlocal theory, approached for vanishing structure size; and (3) approach to the same law at any structure size when the Weibull modulus tends to infinity. The limited test data that exist are used to verify this formula and examine the closeness of fit. The results show that the new energetic-statistical size effect theory can match the existing flexural strength data better than the classical statistical Weibull theory, and that the optimum size effect fits with Weibull theory are incompatible with a realistic coefficient of variation of scatter in strength tests of various types of laminates. As for the energetic-statistical theory, its support remains entirely theoretical because the existing test data do not reveal any improvement of fit over its special case, the purely energetic theory—probably because the size range of the data is not broad enough or the scatter is too high, or both.
Observations of the Constitutive Response and Characterization of Filled Natural Rubber Under Monotonic and Cyclic Multiaxial Stress States
Authors: Mars W. V. , Fatemi A.
Published: January 2004

This work explores the monotonic and cyclic behaviors of filled, natural rubber. Results of stress-strain experiments conducted under stress states of simple, planar, and equibiaxial tension are presented. The ability of hyperelastic models to capture the observed response, as well as recent developments in constitutive modeling of filled rubber such as the consequences of the Mullins effect, are discussed. Monotonic and cyclic multiaxial experiments were also conducted using a short, thin-walled, cylindrical specimen subjected to a wide range of combined axial and twist displacements. Experiments included pure axial tension, pure torsion, combined loading in which the axial and torsion displacements varied proportionally, and combined loading in which the axial and torsion displacements varied non-proportionally (phase between axial and torsion channels of ϕ=0 deg, 90 deg, 180 deg). Results from these tests are presented and discussed, including evolution of stress-strain behavior with load cycles, and the effects of a short period of initial overloading on the subsequent evolution of the stress-strain response.
Effect of Bond Thickness on the Fracture Toughness of Adhesive Joints
Authors: Lee Deok-Bo , Ikeda Toru , Miyazaki Noriyuki , Choi Nak-Sam
Published: January 2004

The effect of bond thickness on the fracture toughness of adhesive joints was investigated from a microstructural perspective, using compact tension (CT) adhesive-joint specimens with different bond thicknesses. The adhesive material was a rubber-modified epoxy resin with 12.5 wt% carboxy-terminated butadiene acrylonitrile (CTBN) elastomer. The shapes of the rubber particles dispersed in adhesive layers of damaged and undamaged specimens were observed with an optical microscope. The damage was distributed along the interfaces between the adhesive layer and the two adherends. The results show that the primary causes of variations in the fracture toughness of an adhesive joint with the bond thickness are not only a damage zone around a crack tip but also the combination of a damage zone around a crack tip and additional damage zones along the interfaces.
Introduction of Compressive Residual Stress Using a Cavitating Jet in Air
Authors: Soyama Hitoshi
Published: January 2004

Cavitation impact from a cavitation jet, which is formed from bubbles induced by a high-speed water jet in water, can be used for surface modification in a similar manner to shot peening. A cavitating jet is normally produced by injecting a high-speed water jet into a water-filled chamber. It is possible to make a cavitating jet in air by injecting a high-speed water jet into a concentric low-speed water jet that surrounds the high-speed jet. In order to demonstrate this, a high-speed water jet with a concentric low-speed water jet was impacted onto an aluminum specimen to observe the pattern of erosion. The mass loss of the specimen was weighed to measure the capability of the jet, since a more powerful jet produces a larger mass loss. It was shown that the combination of high- and concentric low-speed water jets produced a typical erosion pattern such as that obtained using a cavitating jet in a water-filled chamber. When the injection pressure of the concentric low-speed water jet was optimized, the capability of the cavitating jet in air was much greater than that of a cavitating jet in a water-filled chamber. It was demonstrated that an optimized cavitating jet in air introduced more compressive residual stress in the surface of tool steel alloy than that from a cavitating jet in a water-filled chamber. In addition, this stress was larger than that induced by shot peening. The peened surface was also less rough compared with shot peening.
A Non-Incremental Nonlinear Finite Element Solution for Cable Problems
Authors: Sugiyama Hiroyuki , Mikkola Aki M. , Shabana Ahmed A.
Published: January 2004

In this investigation, a nonlinear finite element method for the large deformation and rotation of cable problems is presented. This method is based on finite element absolute nodal coordinate formulation that guarantees the continuity of all displacement gradients and leads to a constant mass matrix. The classical cable theory is first reviewed and the assumptions used in this linear theory are defined in order to demonstrate the basic differences between the linear theory and the nonlinear finite element formulation proposed in this paper for cable applications. The elastic cable forces in the absolute nodal coordinate formulation are obtained using a general continuum mechanics approach that accounts for the effect of all geometric nonlinearities. It is shown in this investigation that the use of the general continuum mechanics approach leads to a simpler and more efficient formulation as compared to the use of the assumptions of the linear theory that employs a local finite element coordinate system. The results obtained using the absolute nodal coordinate formulation show a good agreement with the results obtained using the classical cable theory when linear cable problems are considered. In particular it is shown that the use of perturbation methods to linearize the finite element equations of motion leads to modal characteristics results that are in a good agreement with the linear theory. The results of this investigation obtained using explicit numerical integration also show the potential of the proposed finite element formulation in the nonlinear analysis of cables that experience large rotations and deformations. The generalization of the procedure presented in this paper to three-dimensional cable problems is demonstrated and the computer implementation in multibody algorithms is discussed.
Stick-Slip Vibration Between Two Large Concentric Circular Discs in Rotational Contact With Multiple Point Loads
Authors: Baleri M. , Sassani F. , Ko P. L.
Published: January 2004

This paper presents a study of the stick-slip frictional phenomenon when large contact areas subjected to uneven contact loads, such as the rotating platform of excavators and large robotic manipulators, are involved. The objective of the investigation is to a gain better understanding of the phenomenon from experimental observations and to develop a mathematical representation that can be used for modeling, simulation and design purposes. A dynamic integral-model has been proposed and simulations have been carried out. The effects of various system parameters on the behavior of the system have been studied experimentally and analytically. The simulation results using the proposed integral-model are in good agreement with the experimental results. The latter also show that stick-slip vibrations can be influenced by the loading conditions.
Modeling Variation Propagation of Multi-Station Assembly Systems With Compliant Parts
Authors: Camelio Jaime , Hu S. Jack , Ceglarek Dariusz
Published: January 2004

Products made of compliant sheet metals are widely used in automotive, aerospace, appliance and electronics industries. One of the most important challenges for the assembly process with compliant parts is dimensional quality, which affects product functionality and performance. This paper develops a methodology to evaluate the dimensional variation propagation in a multi-station compliant assembly system based on linear mechanics and a state space representation. Three sources of variation: part variation, fixture variation and welding gun variation are analyzed. The proposed method is illustrated through a case study on an automotive body assembly process.
Kinematic Synthesis of Adjustable RSSR-SS Mechanisms for Multi-Phase Finite and Multiply Separated Positions
Authors: Russell Kevin , Sodhi Raj S.
Published: January 2004

This paper presents a new technique for synthesizing RSSR-SS mechanisms to achieve phases of rigid body positions, velocities and accelerations using the same hardware. This work considers two-phase fixed pivot adjustment problems with fixed crank and follower lengths. By specifying the R-S link joint axes, the constant length condition becomes the only design constraint for these links. The prescribed finite and multiply separated positions are then incorporated in the link constraint equations with respect to the prescribed coordinate frame for each link and the RSSR-SS mechanism joint variables and driving link parameters are calculated.
Error Analysis for the In-Situ Fabrication of Mechanisms
Authors: Rajagopalan Sanjay , Cutkosky Mark
Published: January 2004

Fabrication techniques like Solid Freeform Fabrication (SFF), or Layered Manufacturing, enable the manufacture of completely pre-assembled mechanisms (i.e. those that require no explicit component assembly after fabrication). We refer to this manner of building assemblies as in-situ fabrication. An interesting issue that arises in this domain is the estimation of errors in the performance of such mechanisms as a consequence of manufacturing variability. Assumptions of parametric independence and stack-up made in conventional error analysis for mechanisms do not hold for this method of fabrication. In this paper we formulate a general technique for investigating the kinematic performance of mechanisms fabricated in-situ. The technique presented admits deterministic and stochastic error estimation of planar and spatial linkages with ideal joints. The method is illustrated with a planar example. Errors due to joint clearances, form errors, or other effects like link flexibility and driver-error, are not considered in the analysis—but are part of ongoing research.
On the Design of Spring-Actuated Mechanism for 69KV SF6 Gas Insulated Circuit Breaker
Authors: Chen Fu-Chen
Published: January 2004

This paper studies the design of a spring-actuated mechanism of 69KV SF6 Gas insulated circuit breakers. The creative mechanism design method is first used to synthesize all the feasible mechanisms that satisfy the requirements for the circuit breaker. The kinematics of the mechanism are then analyzed using the vector-loop method. Subsequently, the equations of motion are derived with the Lagrange equation and solved by the Runge-Kutta method. The duration of individual operation, and hence the total duration to complete the full cycle of the mechanism has also been calculated. The times taken for the closing and opening operations were found to be 0.116 and 0.076 sec, respectively, comparable with the experiments.
Elastic Plastic Finite Element Analysis of Bolted Joint During Tightening Process
Authors: Fukuoka Toshimichi , Takaki Tomohiro
Published: January 2004

Mechanical behavior of bolted joints during the tightening process with torque control is analyzed by FEM as elastic plastic contact problems. Three-dimensional analysis was conducted employing two-dimensional model with each node having three degrees of freedom that attains high computation efficiency. Such important factors as development of plastic zones, variations of load distributions along engaged threads, the relationships between axial bolt stress and nut rotation angle were analyzed in order to provide an effective guideline when tightening critical structures with high bolt preloads. It was also shown that the proposed numerical method can be applied to evaluate the tightening process by “plastic region tightening” used extensively in recent years. The validity of the numerical method is demonstrated by comparing the calculated bolt elongation with that obtained from experiment.
A Comparison of Two Self-Consistent Models to Predict the Cyclic Behavior of Polycrystals
Authors: Abdul-Latif A.
Published: January 2004

Being of particular interest in this work, the effect of the interaction law on the predicted non-linear overall and local behaviors of FCC polycrystals of two well-established self-consistent models is examined under uni, bi, and triaxial cyclic loading conditions. The principal difference between these models is related to their interaction laws. Comparisons between the predictions of the models are performed at the overall and local levels simultaneously. Some experimental cyclic results of two states of Waspaloy and 316L stainless steel are employed in calibrating the parameters of both models. The effects of loading complexity, aggregate type and the kinematic hardening on the polycrystal responses are investigated for each model. It is recognized that the connection between the aggregate constitution and the form of the loading paths play also an important role notably on the local responses of polycrystals.
Procedure for the Determination of True Stress-Strain Curves From Tensile Tests With Rectangular Cross-Section Specimens
Authors: Scheider I. , Brocks W. , Cornec A.
Published: January 2004

The problem of determining true stress-strain curves from flat tensile specimens beyond the onset of necking has been investigated based on finite element analyses under consideration of experimental accessible data using digital image correlation (DIC). The displacement field on the specimen surface is determined by in-situ deformation field measurement. A three-dimensional finite element study with different stress-strain-curves has been carried out to develop a formula, with which it is possible to calculate the true stress subject to the strain in the necking region. The method has been used to evaluate the true stress-strain curve with a so-called micro flat tensile specimen, which is normally used to determine the material properties in the material gradient around thin weldments.
Through-Thickness Residual Stress Distribution After the Cold Expansion of Fastener Holes and Its Effect on Fracturing
Authors: O¨zdemir A. Tamer , Edwards Lyndon
Published: January 2004

Many analytical and experimental techniques utilize two-dimensional analysis approach to determine residual strains and stresses at cold expanded holes. In the present work, a recently developed technique of hole drilling was used to sketch stress patterns in three-dimension at a particular orientation of split-sleeve cold expanded holes. At this orientation, similarities were obtained in between the present results and the stress distributions measured by Fourier series expansion, neutron diffraction methods and prediction of a recent finite element analysis. It is clear that after cold expansion there are significant variations in residual hoop stresses at different sections through the thickness of the plate. However, finish reaming and de-burring around the hole redistributes residual stresses such that hoop stresses adjacent to the hole along its entire length becomes more compressive and almost uniform. Finally a correlation between stress pattern and crack profile, displaying the through-thickness effect was shown.
Temporal and seasonal variation in the occurrence of chemical incidents: Table 1
Authors: Olowokure B , Saunders P J , Dyer J A , Kibble A J
Published: January 2004

Aims:To determine whether there were temporal or seasonal patterns in the occurrence of chemical incidents reported to the West Midlands Chemical Incident Surveillance System, UK.

Methods:A retrospective analysis of reports maintained on a computerised database was carried out for information received from January 1997 to December 2001.

Results:Annual numbers of events increased significantly from 77 (7.5%) in 1997 to 282 (27.4%) in 2001. Compared to the average of other seasons, proportionately more incidents occurred in the summer (29.3%). Compared with the average of other days, incidents were more likely to occur on Thursdays (17.1%) and least likely on Saturdays (8.9%). When grouped together on a six hourly basis incidents were most frequent between 12 00 and 17 59 (31.1%) and least frequent between 00 00 and 05 59 (21.2%).

Conclusions:The surveillance system shows that chemical incidents do not occur randomly but have marked temporal and seasonal variation. These results have implications for service provision, training, and the development of preventive strategies.