Composite Overwrapped Pressure Vessels (COPV) Stress Rupture Test

One of the major concerns for the aging Space Shuttle fleet is the stress rupture life of composite overwrapped pressure vessels (COPVs). Stress rupture life of a COPV has been defined as the minimum time during which the composite maintains structural integrity considering the combined effects of stress levels and time. To assist in the evaluation of the aging COPVs in the Orbiter fleet an analytical reliability model was developed. The actual data used to construct this model was from testing of COPVs constructed of similar, but not exactly same materials and pressure cycles as used on Orbiter vessels. Since no actual Orbiter COPV stress rupture data exists the Space Shuttle Program decided to run a stress rupture test to compare to model predictions. Due to availability of spares, the testing was unfortunately limited to one 40" vessel. The stress rupture test was performed at maximum operating pressure at an elevated temperature to accelerate aging. The test was performed in two phases. The first phase, 130 F, a moderately accelerated test designed to achieve the midpoint of the model predicted point reliability. The more aggressive second phase, performed at 160 F was designed to determine if the test article will exceed the 95% confidence interval of the model. This paper will discuss the results of this test, it's implications and possible follow-on testing

Composite Overwrapped Pressure Vessels (COPV) Stress Rupture Test: Part 2

One of the major concerns for the aging Space Shuttle fleet is the stress rupture life of composite overwrapped pressure vessels (COPVs). Stress rupture life of a COPY has been defined as the minimum time during which the composite maintains structural integrity considering the combined effects of stress levels and time. To assist in the evaluation of the aging COPVs in the Orbiter fleet an analytical reliability model was developed. The actual data used to construct this model was from testing of COPVs constructed of similar, but not exactly same materials and pressure cycles as used on Orbiter vessels. Since no actual Orbiter COPV stress rupture data exists the Space Shuttle Program decided to run a stress rupture test to compare to model predictions. Due to availability of spares, the testing was unfortunately limited to one 40" vessel. The stress rupture test was performed at maximum operating pressure at an elevated temperature to accelerate aging. The test was performed in two phases. The first phase, 130 F, a moderately accelerated test designed to achieve the midpoint of the model predicted point reliability. A more aggressive second phase, performed at 160 F, was designed to determine if the test article will exceed the 95% confidence interval ofthe model. In phase 3, the vessel pressure was increased to above maximum operating pressure while maintaining the phase 2 temperature. After reaching enough effectives hours to reach the 99.99% confidence level of the model phase 4 testing began when the temperature was increased to greater than 170 F. The vessel was maintained at phase 4 conditions until it failed after over 3 million effect hours. This paper will discuss the results of this test, it's implications and possible follow-on testing

Education and its Effects on Income and Mortality of Men aged Sixty-five and over in Great Britain

We explore the effects of income and, additionally education on the income, selfreported health and survival of people aged sixty-five and over in Great Britain in order to identify benefits resulting from education which are omitted in the conventional analysis with its focus on labour income excluding employer contributions. We find, for men, that income at the age of sixty-five is significantly influenced by educational attainment and has a significant effect on survival. Even after controlling for circumstances at age sixty-five or when first observed, we identify benefits discounted to age sixty-five of £115,000 for men with higher education qualifications as compared to those with minimal qualifications

Efficacy and safety of once-daily fluticasone furoate 50 mcg in adults with persistent asthma: a 12-week randomized trial

Abstract Background Fluticasone furoate (FF) is a novel, once-daily inhaled corticosteroid (ICS) that has been shown to improve lung function vs. placebo in asthma patients. This study evaluated the efficacy and safety of FF 50 mcg compared with placebo in asthma patients uncontrolled by non-ICS therapy. Methods This 12-week, multicentre, randomized, double-blind, placebo-controlled, parallel-group, phase III study randomized 248 patients (aged ≥12 years) to once-daily FF 50 mcg administered via the ELLIPTA™a dry powder inhaler or placebo. The primary endpoint was change from baseline in pre-dose evening trough forced expiratory volume in one second (FEV1). Secondary endpoints were change from baseline in percentage of rescue-free 24-h periods (powered), evening and morning peak expiratory flow, symptom-free 24-h periods and withdrawals due to lack of efficacy. Other endpoints included Asthma Control Test™, Asthma Quality of Life Questionnaire and ELLIPTA ease of use questions. Safety was assessed throughout the study. Results There was a significant difference in evening trough FEV1 between FF 50 mcg and placebo (treatment difference: 120 mL; p = 0.012). There was also a significant difference in rescue-free 24-h periods (11.6%; p = 0.004) vs. placebo. There were numerically greater improvements with FF vs. placebo for all remaining secondary endpoints. The incidence of adverse events was lower with FF (31%) than with placebo (38%); few were treatment-related (FF 50 mcg: n = 1, <1%; placebo: n = 4, 3%). Conclusion FF 50 mcg once daily significantly improved FEV1 and percentage of rescue-free 24-h periods experienced over 12 weeks vs. placebo, and was well tolerated. Trial registration www.clinicaltrials.gov , registration number: NCT0143607

A Novel Approach to Rotorcraft Damage Tolerance

Damage-tolerance methodology is positioned to replace safe-life methodologies for designing rotorcraft structures. The argument for implementing a damage-tolerance method comes from the fundamental fact that rotorcraft structures typically fail by fatigue cracking. Therefore, if technology permits prediction of fatigue-crack growth in structures, a damage-tolerance method should deliver the most accurate prediction of component life. Implementing damage-tolerance (DT) into high-cycle-fatigue (HCF) components will require a shift from traditional DT methods that rely on detecting an initial flaw with nondestructive inspection (NDI) methods. The rapid accumulation of cycles in a HCF component will result in a design based on a traditional DT method that is either impractical because of frequent inspections, or because the design will be too heavy to operate efficiently. Furthermore, once a HCF component develops a detectable propagating crack, the remaining fatigue life is short, sometimes less than one flight hour, which does not leave sufficient time for inspection. Therefore, designing a HCF component will require basing the life analysis on an initial flaw that is undetectable with current NDI technology

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Damage-tolerance methodology is positioned to replace safe-life methodologies for designing rotorcraft structures. The argument for implementing a damage-tolerance method comes from the fundamental fact that rotorcraft structures typically fail by fatigue cracking. Therefore, if technology permits prediction of fatigue-crack growth in structures, a damage-tolerance method should deliver the most accurate prediction of component life. Implementing damage-tolerance (DT) into high-cycle-fatigue (HCF) components will require a shift from traditional DT methods that rely on detecting an initial flaw with nondestructive inspection (NDI) methods. The rapid accumulation of cycles in a HCF component will result in a design based on a traditional DT method that is either impractical because of frequent inspections, or because the design will be too heavy to operate efficiently. Furthermore, once a HCF component develops a detectable propagating crack, the remaining fatigue life is short, sometimes less than one flight hour, which does not leave sufficient time for inspection. Therefore, designing a HCF component will require basing the life analysis on an initial flaw that is undetectable with current NDI technology