bluuebunny/crossref_metadata_2025 huggingface dataset:
Aromatase Inhibitor–Induced Carpal Tunnel Syndrome: Results From the ATAC Trial
Authors: Sestak Ivana , Sapunar Francisco , Cuzick Jack
Published: September 2009

Purpose

Carpal tunnel syndrome (CTS) is a condition in which the median nerve is compressed, leading to pain and muscle weakness in the fingers and hand. Aromatase inhibitors lead to profound estrogen suppression and may be expected to increase the risk of CTS in postmenopausal women receiving adjuvant therapy for early breast cancer.

Patients and Methods

The current analyses were based on the 100-month median follow-up data in postmenopausal women in the two monotherapy arms (anastrozole, n = 3,092; tamoxifen, n = 3,094). Here, we investigate the natural history of patients who presented with CTS during adjuvant treatment for breast cancer and the relative importance of a range of known risk factors for CTS.

Results

After 100 months of follow-up, 80 cases (2.6%) of CTS were reported in the anastrozole arm, compared with 23 cases (0.7%) in the tamoxifen arm (P < .0001). The majority of CTS cases were reported as mild to moderate intensity and occurred early. None of the women stopped treatment medication as a result of CTS. CTS was significantly increased for women who used prior hormone replacement therapy (P = .007) or received prior chemotherapy (P = .01). Those who were 60 years of age or older at entry were at lower risk of CTS compared with their counterparts (P = .002).

Conclusion

Although the use of anastrozole is associated with a greater incidence of CTS, it is rare, and most cases were of mild to moderate intensity and short duration. CTS has little impact on the overall risk-to-benefit ratio for the use of anastrozole in postmenopausal women with early breast cancer.
2009 National Practice Benchmark: Report on 2008 Data
Authors: Towle Elaine L. , Barr Thomas R.
Published: September 2009

Many oncology practices have responded to rising supply costs and decreasing reimbursements by examining their operational processes and working to reduce costs and enhance practice efficiency.
The future of engineering tribology in concentrated contacts
Authors: Evans H P , Snidle R W
Published: September 2009

This article attempts to anticipate likely trends and developments in the field of engineering tribology. It is, of course, a personal view and the authors have chosen to focus on the field of concentrated contacts operating in elastohydrodynamic lubrication (EHL), where they are tempted to make the kind of predictions required with at least a modicum of confidence. The main thrust of the argument presented is that engineering tribology will develop considerably, and move towards modelling failure of the EHL mechanism rather than simply explaining its successful operation.
Effectiveness of vaginal hysterectomy for benign conditions in semi-urban hospital: report from Maroua-Cameroon
Authors: Tebeu P M , Fomulu J N , Nana Njotang P , Petignat P , Tcheliebou J M , Kouam L , Doh A S
Published: September 2009

We assessed the effectiveness of vaginal hysterectomy for benign uterine conditions in Northern Cameroon. This is a case series study of 29 elective vaginal hysterectomies carried out between February 2005 and June 2007 in Maroua, Cameroon. Hysterocele was found as the only or associated indication in 17 (58.6%) patients, symptomatic uterine fibroids in 4 (13.8%) and other indications in 8 (27.6%) patients. The mean duration of the operation was 132 minutes and the mean blood loss at surgery was 150 ml. Twenty-five of the 28 (89.3%) women had less than seven days of hospitalisation. There was a negative correlation (r = −0.45, P = 0.015) between duration of the surgery and the order of operation. One urinary tract and one wound infection were observed. Two patients had conversion to laparotomy. This study has shown that vaginal hysterectomy is a safe and feasible method of hysterectomy in a semi-urban hospital.
Prevalence of anaemia in the postpartum period: a study of a North Indian village
Authors: Somdatta Patra , Reddaiah V P , Singh Bir
Published: September 2009

Anaemia is a common public health problem but there is a paucity of studies regarding anaemia in the postpartum period. The objective of this study was to investigate the prevalence of anaemia in the postpartum period and factors associated with it. This prospective community-based study was carried out in a village of Haryana, India. Blood samples were collected for haemoglobin estimation at the end of six weeks postpartum. A total of 211 women were recruited and 168 women were included in the final analysis. It was found that 70% of the study participants were anaemic (Hb < 11 g/dL). Only 37% of the population had consumed ≥90 iron folic acid (IFA) tablets. The mean haemoglobin level of women who had consumed ≥90 IFA tablets in the antepartum period was higher (10.43 g/dL) than those who consumed <90 IFA (9.9 g/dL). Multicentric studies are recommended to get the true picture for the whole country.
Co-existence of TB and adult haematological cancers in Benin City, Nigeria
Authors: Omoti Caroline Edijana , Olu-Eddo Adesuwa Noma , Nwannadi Alexander Ikenna
Published: September 2009

Tuberculosis is an ancient human scourge that continues to be an important public health problem worldwide. As impaired immunity is closely associated with the pathogenesis of TB, an increase in the incidence of the disease among patients with cancer is anticipated. A total of 20 cases of haematological cancers co-existing with TB in a tertiary hospital in an African setting between January 2005 and September 2008 were analysed. Clinico-pathologic profiles, types of TB infection and outcome were noted. The incidence of TB in patients with haematological malignancies was 3.4%. Lymphoma and leukaemia were the most common malignancies associated with TB. With the high incidence of such cases we recommend the exclusion of an active disease prior to the initiation of cancer therapy. Chemoprophylaxis might be indicated in TB endemic areas.
Adenomyosis and uterine rupture during labour in a primigravida: an unusual obstetric emergency in Nigeria
Authors: Dim Cyril C , Agu Polycarp U , Dim Ngozi R , Ikeme Arthur C
Published: September 2009

The primigravid uterus is believed to be immune to rupture during labour. This may not be true for those who have had prior adenomyomectomy, hence this report. The patient was a 28-year-old nullipara who became pregnant 11 months after an adenomyomectomy. Twelve hours after vaginal delivery at term, she developed haemoperitoneum of unclear cause. Emergency laparotomy and subsequent histology showed a fundal complete uterine rupture through the adenomyomectomy site, which was repaired. It is concluded that adenomyomectomy predisposes a pregnant uterus to rupture during labour. Therefore, such women should be offered elective caesarean delivery at term.
Ileosigmoid knotting- a rare variant of bowel volvulus
Authors: Alvi A Rehman , Bibi Shahida , Effendi Shahrukh , Khan Salma
Published: September 2009

Two patients with acute intestinal obstruction underwent exploratory laparotomy after adequate fluid resuscitation and radiological imaging. A preoperative diagnosis of sigmoid volvulus and an operative diagnosis of ileosigmoid knotting or compound volvulus were established.
Hepatic cystic echinococcosis: clinical characteristics and outcomes in Pakistan
Authors: Mumtaz Khalid , Kamani Lubna , Chawla Tabish , Hamid Saeed , Jafri Wasim
Published: September 2009

Hepatic cystic echinococcosis (HCE) is an emerging disease in central Asia, particularly in Pakistan, due to the migration of infected people. Medical records of patients with HCE admitted between 1995 and 2006 to a tertiary care hospital were reviewed. A total of 106 patients were admitted with a mean age of 34±17 years; 60 (56.6%) were men, 72 (67.9%) were residing in rural areas of Pakistan and 21 (19.8%) were Afghan refugees. Twenty-seven (25.4%) had extra hepatic cysts and liver cysts. All patients received albendazole. Percutaneous aspiration, instillation and reaspirarion was done in 14 (13.2%) patients and 71 (66.9%) underwent surgery. Three (2.8%) died and 14 (13.2%) had morbidity. This is one of the largest series of HCE reported from Pakistan. HCE is mostly prevalent in rural areas and among Afghan refugees with low mortality and recurrence, but with significant morbidity.
A comparative trial of three therapeutic regimens: ciprofloxacin-rifampin, ciprofloxacin-doxycycline and doxycycline-rifampin in the treatment of brucellosis
Authors: Keramat Fariba , Ranjbar Mitra , Mamani Mojgan , Hashemi Seyyed Hamid , Zeraati Fatemeh
Published: September 2009

This study was designed to compare the efficacy of ciprofloxacin plus rifampin (CR) and ciprofloxacin plus doxycycline (CD) versus doxycycline plus rifampin (DR) in the treatment of brucellosis. A total of 178 patients with brucellosis who were referred to the Sina Hospital, Hamedan, Iran, were included. The responses to therapy were observed in 166 cases (93.7%) – 59 were in the DR group, 59 in the CR group and 48 in the CD group. No significant differences in the therapeutic responses were observed ( P = 0.09). Relapse was observed in 11.7% (DR 7.7%, CR 8.3% and CD 17.5%) after a six-month follow-up. No significant differences were also observed in relapse rates among the three groups ( P = 0.35). We concluded that DR is still the first choice regimen and CR or CD may be used as alternatives for treatment of brucellosis in adults.
Altered consciousness in Ugandan hospital admissions
Authors: Rwebembera Joselyn , Wilson Tony
Published: September 2009

An awareness of diseases causing altered mental status (AMS) in particular localities could greatly facilitate patient management. This cross-sectional study evaluated 100 consecutive patients with AMS admitted to a hospital in Uganda. Patients were assessed by the Confusion Assessment Method. History, examination, available laboratory tests and patients' response to treatment were used to identify aetiologies. Our study included 58 males and 42 females: 82% were 16–50 years old and 38% were HIV-infected. The most common cause of AMS was infection (51.3%), with cerebral malaria and meningitis predominating. The aetiology was unidentified in 12%. The in-hospital mortality rate was 44%, with HIV infection being positively associated.

As infections and metabolic derangements, the most common causes of AMS in our setting, are mostly treatable with a relatively favourable outcome, critical evaluation, early intervention and improved investigative capacity would greatly improve patient outcome.
Testing the Validity of a Demand Model: An Operations Perspective
Authors: Besbes Omar , Phillips Robert , Zeevi Assaf
Published: September 2009

The fields of statistics and econometrics have developed powerful methods for testing the validity (specification) of a model based on its fit to underlying data. Unlike statisticians, managers are typically more interested in the performance of a decision rather than the statistical validity of the underlying model. We propose a framework and a statistical test that incorporate decision performance into a measure of statistical validity. Under general conditions on the objective function, asymptotic behavior of our test admits a sharp and simple characterization. We develop our approach in a revenue management setting and apply the test to a data set used to optimize prices for consumer loans. We show that traditional model-based goodness-of-fit tests may consistently reject simple parametric models of consumer response (e.g., the ubiquitous logit model), while at the same time these models may “pass” the proposed performance-based test. Such situations arise when decisions derived from a postulated (and possibly incorrect) model generate results that cannot be distinguished statistically from the best achievable performance—i.e., when demand relationships are fully known.
Transshipment of Inventories: Dual Allocations vs. Transshipment Prices
Authors: Huang Xiao , Sošić Greys
Published: September 2009

We study a newsvendor game with transshipments, in which n retailers face a stochastic demand for an identical product. Before the demand is realized, each retailer independently orders her initial inventory. After the demand is realized, the retailers select an optimal transshipment pattern and ship residual inventories to meet residual demands. Unsold inventories are salvaged at the end of the period. We compare two methods for distribution of residual profit—transshipment prices (TPs) and dual allocations (DAs)—that were previously analyzed in literature. TPs are selected before the demand is known, and DAs, which are obtained by calculating the dual prices for the transshipment problem, are calculated after observing the true demand. We first study the conditions for the existence of the Nash equilibria under DA and then compare the performance of the two methods and show that neither allocation method dominates the other. Our analysis suggests that DAs may yield higher efficiency among “more asymmetric” retailers, whereas TPs work better with retailers that are “more alike,” but the difference in profits does not seem significant. We also link expected dual prices to TPs and use those results to develop heuristics for TPs with more than two symmetric retailers. For general instances with more than two asymmetric retailers, we propose a TP agreement that uses a neutral central depot to coordinate the transshipments (TPND). Although DAs in general outperform TPND in our numerical simulations, its ease of implementation makes TPND an attractive alternative to DAs when the efficiency losses are not significant (e.g., high critical fractiles or lower demand variances).
The Assessment of Specimens Procured by Endoscopic Ampullectomy
Authors: Bellizzi Andrew M. , Kahaleh Michel , Stelow Edward B.
Published: September 2009

Endoscopic ampullectomy (EA) is increasingly used in the management of ampullary neoplasia. Although studies on the safety and efficacy of this procedure exist, no study has specifically addressed the histopathologic features of the specimens. We review our experience with 45 EA specimens assessed for the following: diagnosis, high-grade dysplasia (HGD), submucosal ampullary gland/ductule involvement, specimen integrity, and margin status. Familial adenomatous polyposis (FAP) status and the endoscopist’s impression of completeness of removal were also ascertained. Previous biopsy diagnoses were compared with ampullectomy diagnoses, and histologic and clinical features were correlated with disease persistence. The histologic features of the ampullectomy specimens were as follows: diagnosis (no diagnostic abnormality, 3; reactive, 8; adenoma, 26; adenocarcinoma, 7; other, 1); HGD, 1; submucosal ampullary gland/ductule involvement, 20; specimen integrity (intact, 22; fragmented, 23); and margin status (positive, 20; negative, 2; could not be assessed, 12). Five patients had FAP, and EA was deemed complete in 21 (47%). The diagnostic agreement between preampullectomy biopsy and ampullectomy was 64%. Of the patients, 33 (73%) had documented persistent disease. None of the histologic or clinical features had a statistically significant relationship with disease persistence.
Failure from Large Grains in Polycrystalline Ceramics: Transitions in Fracture Toughness
Authors: Freiman S
Published: September 2009

This paper addresses issues of fracture for materials in which large grains, exist in a matrix of much smaller grains. Polycrystalline ZnS and ZnSe, used for optical components, frequently fall into this category. For material microstructures of this character failure can occur from flaws contained within the isolated large grains so that the governing fracture toughness is that of a single crystal of the material, rather than that of the polycrystalline matrix. I point out that there are currently limitations and uncertainties associated with the most popular experimental procedure available to determine the fracture toughness for small crystals. As an alternative to testing, I discuss the state of our ability to predict fracture toughness based solely on knowledge of lattice parameters and elastic properties. The historical background and examples of such a prediction technique are demonstrated. Second, the role of microstructure in governing the transition from single crystal to polycrystalline values of toughness is shown. I postulate that mixed mode fracture mechanics expressions can be used to explain the transition in fracture toughness.
Environmental and Thermal Effects on the Toughness of TiCN-Based Materials
Authors: Guicciardi S , Melandri C , Monteverde F , Bellosi A , de Portu G
Published: September 2009

Titanium carbonitrides (TiCN) are very hard materials with increasing technological importance. They are mainly applied in composites with various metal carbides and/or metallic binders for cutting tools. In these applications, high temperatures are usually involved and, sometimes, chemical reactions. Being composed of a metallic-binder phase, in which a hard ceramic phase is dispersed, the performance of these materials can be largely affected by temperature and environment. In this work, nearly fully-dense TiCN based cermets have been produced starting from the following composition (wt%): TiC0.5N0.5+15.3(WC-5%Co)+6.2Ni+2.1Co. Some of the mechanical properties have been routinely measured, such as hardness, Young modulus, fracture toughness and flexural strength. The main effort has been devoted to the study of the effects of temperature and environment on the fracture toughness. Chevron notch tests have been carried out at room temperature, 600 °C, 800 °C and 1 000 °C in static air, flowing air and flowing nitrogen atmosphere. The influence of the interaction between temperature, environment and microstructure on the fracture behavior has been analyzed.
Evaluation of Constant Head Infiltration Test Analysis Methods for Field Estimation of Saturated Hydraulic Conductivity of Compacted Clay Liners
Authors: Cazaux D
Published: September 2009

Field infiltration tests are commonly used to assess the hydraulic conductivity of low permeability materials such as natural clay barriers and compacted clay liners. The soils used for compacted clay liners are always partially saturated and require very long testing times to reach steady-state flow conditions. Consequently, because they are less time consuming, laboratory tests are usually preferred for construction quality control. Nevertheless, it is well-known that field tests are more representative of the clay liner because of the scale effect. This is why, since the 1980s, the main issues associated with field procedures have been studied and several methods proposed for testing low-permeability materials within short time periods. The proposed methods are based on early-time flow analysis in unsaturated conditions and have been applied to various compacted soils under field and laboratory conditions. To evaluate these methods, we carried out a comprehensive testing program using a hydraulic field infiltrometer method (sealed single-ring infiltrometer) and a laboratory rigid-wall permeameter method that reproduces surface field test conditions. The laboratory tests were continued until saturated hydraulic conductivity was obtained so that this value could be compared against the hydraulic conductivity estimated from early-time analysis on the same specimen. The obtained results show the influence of (a) the initial moisture content, (b) the sorptivity and hydraulic head on the early-time infiltration rate, and (c) the final estimated hydraulic conductivity. A comparison of analysis methods shows the limitations of some and tries to explain the reasons for such inadequacies in the description of early-time unsaturated flows. Nevertheless, the conclusions of our study show that conventional early-time analyses give a good estimation of saturated hydraulic conductivity within a short time period compatible with construction quality-control procedures.
Electrokinetic Removal of Phenanthrene from Kaolin Using Different Surfactants and Cosolvents
Authors: Reddy KR , Saichek RE
Published: September 2009

In this study, an experimental program was conducted to determine electrokinetic remedial efficiency of PAHs in low permeability soils. Kaolin was selected as a representative low permeability soil, and phenanthrene was selected as a representative PAH. Several surfactants/cosolvents were evaluated to enhance desorption/solubilization of PAHs in soils, and bench-scale electrokinetic experiments were performed to investigate the enhanced removal of PAHs using surfactants/cosolvents. Electric current, cumulative electroosmotic flow, and cumulative contaminant mass removal were measured during the application of electric potential, and pH and residual contaminant concentration in the soil were measured after electrokinetic treatment. The results showed that the extent of contaminant desorption/solubilzation as well as the amount of electroosmotic flow both affected PAH removal efficiency. Furthermore, significantly different results were obtained due to the chemical and electrical characteristics of the surfactants/cosolvents. Generally, electroosmotic flow behaved according to Helmholz-Smoluchowski (H-S) theory and advective transport of the contaminant occurred from the anode towards the cathode. Electrokinetic treatment caused slightly acidic conditions throughout the soil because of the electrolysis reaction at the anode and the electroosmotic flow towards the cathode. Although contaminant mass removal was low in all the tests, the results showed significant PAH migration towards the cathode. Reaction kinetics or a change in solution and/or surface chemistry under electric potential, however, seems to have caused sorption or precipitation of the contaminant to the soil and hindered complete PAH removal from the soil. Thus, further evaluation needs to be performed to determine the cause of low contaminant removal, but enhanced electrokinetic remediation appears to be a promising technique for the removal of PAHs from low permeability soils.
Tabbed Versus Untabbed Fiber-Reinforced Composite Compression Specimens
Authors: Adams DF
Published: September 2009

The development of suitable specimen configurations and loading methods for the compression testing of high strength composite materials has received considerable attention during the past decade, and especially during the past five years. Both experimental and analytical investigations of very specific aspects of specimen and test fixture configurations have been performed. Many seemingly conflicting results have been presented, leading to considerable confusion within the composite materials testing community. However, a definite conclusion appears to now be emerging, viz., the use of tabs on compression test specimens has a detrimental influence on measured strength. This has been qualitatively suspected for some time since analytical studies and detailed finite element analyses consistently predict induced stress concentrations at the tab ends of the specimen gage section. Numerous approaches have been followed to minimize these stress concentrations, of course including the total elimination of tabs. Key analytical and experimental results, taken from the extensive published literature as well as from the author's own recent work, are presented and compared, to demonstrate the consistent trends that actually do exist in the seemingly scattered and confusing published literature. Finally, options currently available for the successful compression testing of high strength composite materials are presented.
Finite Element Analysis of Unidirectional Composite Compression Test Specimens: A Parametric Study
Authors: Joyce PJ , Violette MG , Moon TJ
Published: September 2009

This research undertakes a comprehensive parametric study of the ASTM D 6641 Combined Loading Compression (CLC) test fixture from Wyoming Test Fixtures (WTF) using numerical analysis to evaluate various test parameters associated with compression testing of unidirectional test specimens. A two-dimensional finite element analysis of the D 6641 CLC fixture was used to identify loading conditions and tabbing configurations that minimized the peak axial, shear, and through-thickness stress concentrations in the test specimen. Combined shear and end loading appears to offer a good compromise between reducing the tab tip stress concentrations inherent in shear loading, and avoiding premature failure by end brooming associated with end loading. Thin, tapered tabs made of compliant materials were found to have the smallest stress concentrations at the tab tip. Specimens with these tab configurations should yield higher measured compressive strengths since premature failure at the tab tip is less likely to occur. Partial debonding of the tab tip was found to increase the stress concentration compared to the fully-bonded case, but to move its location away from the gage section of the specimen. Tab tip debonding should be avoided for compressive strength testing.
Qualification Using a Nested Experimental Design
Authors: Ruffner D , Jouin P
Published: September 2009

The general aviation approach was taken in these material qualifications, where it is assumed that a large portion of composite material property batch-to-batch variability can be reproduced in the laboratory through independent layup and cure of panels, termed a process lot. A nested experimental design was used to quantify the actual sources of variability for hot/wet tension and compression strengths, and dry and wet glass transition temperatures. Two large crossplied panels, each representing a process lot, were independently made from each of three qualification batches. Two subpanels, each representing a machine lot, were cut from each process lot panel, then independently machined into coupons, moisture conditioned, and tested. With these three nested experimental levels the batch-to-batch variability can be partitioned into true batch variability, laminate fabrication, coupon test, and within sample variability. Results indicate that true batch variability was a relatively minor contributor to material property variability as a whole.
A Comparison of Quasi-Static Indentation Testing to Low Velocity Impact Testing
Authors: Nettles AT , Douglas MJ
Published: September 2009

The need for a static test method for modeling low-velocity foreign object impact events to composites would prove to be very beneficial to researchers because much more data can be obtained from a static test than from an impact test. In order to examine if this is feasible, a series of static indentation and low velocity impact tests were carried out and compared. Square specimens of many sizes and thickness were utilized to cover the array of types of low velocity impact events. Laminates with a π/4 stacking sequence were employed because this is by far the most common type of engineering laminate. Three distinct flexural rigidities under two different boundary conditions were tested in order to obtain damage due to large deflections, contact stresses and to examine if the static indentation-impact comparisons are valid under the spectrum of damage modes that can be experienced. Comparisons between static indentation and low velocity impact tests were based on the maximum applied transverse load. The dependent parameters examined included dent depth, back surface crack length, delamination area and to a limited extent, load-deflection behavior. Results from this particular study showed that no distinct differences could be seen between the static indentation tests and the low velocity impact tests.
Detection and Characterization of Imperfections in Composite Pressure Vessels
Authors: Walker JL , Russell SS , Lansing MD
Published: September 2009

Interpreting the information given in a thermogram can be a difficult task under ideal circumstances and extremely challenging in a real world setting. The work discussed in this paper illustrates how the microstructure of several commonly found defects in composite structures relate to their thermographie image counterpart. Two test cases are studied herein, including a large graphite/epoxy RP-1 fuel tank and a graphite composite cryogenic fuel feedline. The structures used in this study were designed to serve as manufacturing proof of concept specimens and to undergo hydroburst testing to verify manufacturing practices and structural design. Prior to hydrostatic testing the structures underwent 100% thermographic evaluation to ensure that no manufacturing or handling damage was present. Due to a large inclusion found in the feedline, it was pulled from service and dissected without performing the hydroproof. The thermographie indications found in the RP-1 tank were below critical limits so it underwent a complete hydroproof loading series and finally a hydroburst. Following the hydroburst samples were cut from the tank in regions where thermography had located damage before the test. These regions were re-evaluated thermographically and then were cross-sectioned and photomicrographed.
Damage Resistance and Damage Tolerance of Pultruded Composite Sheet Materials
Authors: Prabhakaran R , Saha M , Douglas M , Nettles AT
Published: September 2009

The damage resistance of pultruded composites to quasi-static transverse indentation is characterized, and the damage tolerance of transversely indented composites under subsequent compression is assessed. Two specimen thicknesses are investigated. In each case four specimens are transversely indented to failure. Five load levels are selected and sets of five specimens are loaded up to each of these load levels and then unloaded. Extensive data are gathered: load-central displacement, back surface crack length, damage area obtained from X-radiography, optical photomicrographs obtained for specimens sectioned in different orientations, etc. This information is analyzed to develop the damage initiation and progression in pultruded composites. Open hole compression tests are performed on specimens of the two thicknesses, with seven hole sizes. The specimens damaged at five load levels, during transverse indentation, are tested in compression (simulating compression after impact). From the measured compressive strengths, the concept of an ‘equivalent hole diameter’ for damaged specimens is explored. The strain distributions are also compared.
Principles for Recovering Micro-Stress in Multi-Level Analysis
Authors: Wang Y , Sun C , Sun X , Pagano NJ
Published: September 2009

Multi-level stress analysis is widely used to recover the micro-stress of the stress concentration area in composite structures. One common approach is firstly to consider the composite material as a homogeneous material. Effective properties are employed to predict the effective stress and effective displacement fields (or called the macroscopic stress and macroscopic displacement fields). Then, a local domain, which includes the area of interest (normally the stress concentration area), is selected for local microscopic stress analysis, in which the effective stress and/or effective displacement along the local domain boundary are used as boundary conditions. Thus a question arises: can the micro-stress field in the area of interest found from multi-level stress analysis match that from full-field micro-stress analysis? In this paper, two principles and a “local domain test”, which is based upon the two principles, are established for multi-level stress analysis. It is shown that micro-stress in the area of interest will be recovered accurately with multi-level analysis if the selected local domain passes the “local domain test.” These two principles and the “local domain test” elevate multi-level stress analysis into a more powerful tool.
Measurement of CTE at Reduced Temperature for Stressed Specimens
Authors: Zhu H , Li W-Y , Tseng AA , Phelon P
Published: September 2009

The coefficient of thermal expansion (CTE) is one of the critical parameters in determining material behaviors. This article presents a study for developing a new method in measuring CTE at reduced temperature. The machine used in the measurement is a micro mechanical tester. Measured specimens are stressed, and at least one characteristic dimension of specimens is in the order of mm, sub mm or microns. CTE values are determined based on their relation with the measured magnitude of stress jump resulting from the change in temperature. Their comparison with the CTE values reported by other sources is also presented. It is interesting to notice that CTE values measured by the method may vary depending on the level of applied stresses for the same amount of temperature change. Advantages of this method with respect to high sensitivity, easy operation, short testing time and others are also discussed.
Buckling and Fracture Behavior of Tapered Composite Panels Containing Ply Drops
Authors: Parida BK , Vijayaraju K , Mangalgiri PD
Published: September 2009

In typical applications like in the top skin of the wing or in control surfaces of an airframe, laminated composites are often found to be buckling-critical. Under excessive compression loading composite panels may undergo buckling and failure mechanisms would generally involve delamination or fiber breakage. Tapered composite panels with ply drops, when employed in wing skin, are expected to be more prone to the above mode of failure. This is one important area of concern to the designers of composite structures and both analysis and experimental verification of the buckling behavior is recommended as a part of design validation effort. However, data from such analysis are scarce in open literature. In this paper, results of a study on buckling and fracture behavior of laminated Carbon Fiber Composite (CFC) panels containing ply drops are presented. CFC panels of varying thickness with normal and inclined ply drop were tested under compression loading until buckling and ultimate failure. Nearly simply supported boundary conditions at the ends and along the edges were simulated with the help of specially designed test fixtures. Tests were conducted both under room temperature and hot-wet (100°C ± 3 °C and ⩾ 85% RH) environmental conditions. Back-to-back strain gage output and out-of-plane deformation data were recorded and analyzed to determine the critical buckling loads and corresponding mode shapes. Finite element analysis using MSC NASTRAN was also made in order to predict critical buckling loads and corresponding mode shapes. These results were compared with those obtained from experiments and the agreement was found to be good in most cases. It was also found that under hot-wet conditions, both critical buckling loads and failure loads were lower compared to the room temperature values.
Validation of a Miniature Tensile Strength Measurement System
Authors: Roebuck B , Lord JD , Orkney LP
Published: September 2009

Miniature strength test systems are of use for several reasons. For example, many advanced materials are often in limited supply and the use of small testpieces can accelerate the production of useful data. Also, small sections can be taken from working components and tested to assess material degradation without affecting performance. An important criteria for choice of testpiece size is such that the microstructure within the testpiece is representative of the structure as a whole. However, strain measurement becomes more of a challenge as the testpiece size diminishes. Typically extensometers are used on gauge lengths of 10–25 mm, thus smaller testpieces present some problems in the use of conventional extensometers. Because of these difficulties an alternative method of strain measurement, based on changes in resistance, was used in the current work.

A miniature test system, the ETMT (ElectroThermoMechanical Test), developed at the National Physical Laboratory, was used to measure the stress/strain characteristics, particularly at elevated temperatures, of two material types, paniculate reinforced aluminium alloy composites and a Ni-based superalloy, Nimonic 901. The testpiece dimensions were typically 30 × 2 × 1 mm, with a grip separation of 16–20 mm. Elevated temperatures were achieved using a DC heating current. Strain was measured using changes in electrical resistance of a central gauge length of the testpiece, about 2–3 mm in length. Because the strain measurement method was nonstandard the stress/strain data were compared with measurements made from conventional tensile tests using rectangular dogbone testpieces, with a 6 × 3 mm gauge length cross section.

The comparison between the ETMT results and those obtained from elevated temperature conventional tests showed that the effects of deformation rate were very important. Thus the use of miniature testpieces can be a cost effective and rapid technique for obtaining material property data, but it is important to report values for all the parameters that can effect the measurement of strength.
Environmentally Friendly Bearing Steel With Reduced Hardening Distortion
Authors: Lund TB , Ölund LJP
Published: September 2009

Environmental issues are becoming increasingly important as the costs of waste disposal increase and global climate effects of petroleum product usage become more evident. A major problem in the manufacturing of bearing components today is the distortion generated in the heat treatment quenching operation. The quenching is difficult to control and is a polluting fire and health risk due to the quenching media used. The hardening distortion causes excessive grinding, and large efforts have been made to reduce distortion and the excessive grinding costs caused by this. Major efforts have been made to develop gas quenching, but as the standard steels used for component manufacturing today have very limited hardenability, only a minor share of the component range can be effectively gas quenched.

By utilizing modern tools for material development, a family of low-alloyed steel has been designed which combine environmental friendliness, minimum hardening distortion and improved product performance for industrial components. The steels also have been designed in such a way that standard, high volume production routes can be utilized, and -with the advances in hard machining — in many cases can be used to design new and very cost efficient ways of component production with a minimal environmental impact.

This paper presents a concept where components can be martensitically hardened in a simple air cooling, even directly on cooling from a hot forming operation. These steels significantly reduce hardening distortion, improve working environment and are environmentally friendly. They also offer the potential to change component production routes drastically and as well provide high performance components for large volume production.
Statistical Prediction of the Maximum Inclusion Size in Bearing Steels
Authors: Shi G , Atkinson HV , Sellars CM , Anderson CW , Yates JR
Published: September 2009

Large and brittle oxide inclusions may initiate fatigue failure in bearing steels. The size of the maximum inclusion in a large volume must be predicted by statistical analysis because only small samples can directly be analysed and there are limitations on non-destructive testing methods. A new method based on the Generalized Pareto distribution (GPD) was recently proposed by the Sheffield group. This allows data on inclusion sizes in small samples to be used to predict the maximum inclusion size in a large volume of steel. The method has advantages over other statistics of extremes methods. The number of sources of failure and the failure rate of practical bearings can be estimated from the predictions of the GPD and the stress distribution in the bearing. Here the GPD method is compared with the Statistics of extreme values (SEV) method developed by Murakami and co-workers. The application of predictions from the GPD in the safe design of bearings will be illustrated.
Higher Macro-Cleanliness of Bearing Steels Needs More Accurate Measuring-Methods
Authors: Thiery D , Delhaes C
Published: September 2009

Increasing requirements of trendsetter-industry (automotive and railway) on the performance of bearings demand also an improvement of the applied materials. That means principally to reduce macroscopic, non-metallic inclusions. Therefore, steel works need new targets to optimize metallurgical and casting techniques.

For this reason, ultrasonic examination methods are more and more applied to test bigger volumes instead of plains. Especially the immersion ultrasonic testing allows to detect smaller inhomogenities.

To get optimal testing conditions, SAARSTAHL AG and FhG-IZfP made pretests.

Then, the german steel industry in the VDEh made a circle examination to optimize and standardize the test conditions. The reproducible limit size of detectable defects seems to be an equivalent flat bottom hole of 300 to 400 μm for the chosen conditions.

All results of the circle examination were used to prepare detailed prescriptions for a test in form of a german standard (SEP 1927), presented in this paper.
Estimation of Rolling Bearing Life under Contaminated Lubrication
Authors: Tanaka H , Tsushima N
Published: September 2009

The failure mode assumption of Lundberg-Palmgren's bearing life theory is that cracks initiate below the rolling contact surface. Therefore, modification is required to predict surface originated flaking life under contaminated lubrication. A new life estimation method, which can also be applied to surface originated flaking, is described. This method comprises the calculation of a volume element life, which is related to the local stress below the contact area, and then calculating the total life of the contact stressed region. The theoretical result was compared with experimental endurance test results, and both results showed that the lower the bearing load, the greater the life was reduced from the basic rating life. Additional groups of bearing test lives, gathered from references, were also analyzed and the same trend was observed. From these results, an appropriate diagram for the life modification factor is obtained against P/C ( P : equivalent bearing load, C : basic dynamic capacity ) under various contaminated lubrication conditions.
Rolling Contact Fatigue Tests to Investigate Surface Initiated Damage and Tolerance to Surface Dents
Authors: Girodin D , Ville F , Guers R , Dudragne G
Published: September 2009

The improvement in steel cleanliness has resulted in a large reduction of subsurface damage initiated on inclusions. As a consequence surface initiated failure related to lubricant contamination has become the main cause of damage in most commercial applications. Debris contaminants can produce dents on the raceways, which generate stress concentrations, leading to failure.

This paper describes experimental procedures developed to study the surface initiated damage mechanisms using two types of pre-damaging processes to simulate debris contaminant effects. - dents printed on the raceway using a diamond indenter, - natural dents obtained using a lubricant contaminated by fine hard particles

Three-dimensional surface topography was used to characterise dent morphology and to compare the influence of materials. The test results show that the pre-denting method using hard powder is more efficient to reproduce surface morphology and damage mechanisms observed under practical operating conditions.
A Comparison of the Mechanical and Physical Properties of Contemporary and New Alloys for Aerospace Bearing Applications
Authors: Ragen MA , Anthony DL , Spitzer RF
Published: September 2009

This paper presents the results of several contributing sources in establishing the mechanical and physical properties of various new candidate alloys for aerospace bearing applications. The alloys evaluated included the high Nitrogen steels Cronidur 30 and XD15NW, the carburizing stainless steels Pyrowear 675 and CSS-42L, and the nitrided steel 32CDV13. The properties evaluated included hot hardness, recovery hardness, fracture toughness, corrosion resistance, abrasive wear resistance, and structural (rotating beam) fatigue strength. Elemental testing was performed independently of the material suppliers to evaluate these properties for the candidate alloys.

This paper is not intended to promote any one alloy as the best solution to all bearing needs, but rather to provide a data base to assist in the selection of the optimum solution to a specific bearing application. The test results obtained confirmed that each candidate material has unique strengths and weaknesses. For example, Cronidur 30 and XD15NW demonstrated very good corrosion resistance, but do not have good fracture toughness or wear resistance. Conversely, Pyrowear 675 and CSS-42L have very good fracture toughness, but are more susceptible to corrosion problems. The 32CDV13 nitrided steel also had very good fracture toughness and relatively good wear resistance, but demonstrated poor corrosion resistance.
Microstructural Stability and Bearing Performance
Authors: Voskamp AP
Published: September 2009

Predicting rolling performance and dimensional stability of rolling bearings under all combinations of load and temperature becomes a real challenge in the material science discipline, even knowing the differences in bearing performance for different steel alloys and applied heat treatments. The consistently maintained high level of steel cleanliness in present day bearing manufacturing, based on modern steel making technology, is not the only decisive parameter minimizing the probability for spalling fatigue. A second highly important factor is the micro-plastic behavior of the steel under conditions of repetitive cyclic stressing. The steel's elastic response, acquired during running-in, will deteriorate after some time, increasing the probability for crack initiation at and around weak points in the steel matrix and crack propagation away from there leading to fatigue failure. Aspects of shakedown and materials decay are thus related to the probability for bearing failure to occur in combination with steel cleanliness. The ability to maintain an elastic response during cyclic stressing is determined on one hand by the combined effects of applied stress level, running temperature and number of revolutions, and on the other by the selected steel alloy, the applied heat treatment and the work hardening response during running-in. Examples are discussed of observed microstructural stability and superb bearing performance under extreme conditions.
A Physically Based Endurance Limit Model for Through Hardened and Surface Hardened Bearing Steels
Authors: Vincent A , Fougères R , Lormand G , Dudragne G , Girodin D
Published: September 2009

A physically based model for calculating the load rating of rolling bearings for an infinite life is presented. The proposed model is based on the fact that, for bearings operating under EHD conditions, material fatigue can not occur as long as the maximal local shear stress built up in the subsurface region does not exceed the micro-yield shear stress of the steel matrix. The calculation of the local shear stress can account for the presence of, on the one hand, hoop stresses or residual stresses and, on the other hand, on the steel inhomogeneities (nonmetallic inclusions, carbides) that act as stress raisers. The model is applied to investigate the influence of material parameters and operating conditions for various through hardened steels and surface hardened steels (carburized or nitrided).