Strainrange partitioning behavior of the nickel-base superalloys, Rene' 80 and in 100

A study was made to assess the ability of the method of Strainrange Partitioning (SRP) to both correlate and predict high-temperature, low cycle fatigue lives of nickel base superalloys for gas turbine applications. The partitioned strainrange versus life relationships for uncoated Rene' 80 and cast IN 100 were also determined from the ductility normalized-Strainrange Partitioning equations. These were used to predict the cyclic lives of the baseline tests. The life predictability of the method was verified for cast IN 100 by applying the baseline results to the cyclic life prediction of a series of complex strain cycling tests with multiple hold periods at constant strain. It was concluded that the method of SRP can correlate and predict the cyclic lives of laboratory specimens of the nickel base superalloys evaluated in this program

The strainrange partitioning behavior of an advanced gas turbine disk alloy, AF2-1DA

The low-cycle, creep-fatigue characteristics of the advanced gas turbine disk alloy, AF2-1DA have been determined at 1400 F and are presented in terms of the method of strainrange partitioning (SRP). The mean stresses which develop in the PC and CP type SRP cycles at the lowest inelastic strainrange were observed to influence the cyclic lives to a greater extent than the creep effects and hence interfered with a conventional interpretation of the results by SRP. A procedure is proposed for dealing with the mean stress effects on life which is compatible with SRP

Separation of the strain components for use in strainrange partitioning

Two methods are presented for separating the inelastic strain components of a complex hysteresis loop so that strainrange partitioning formulas can be applied to accurately determine cyclic life at elevated temperatures. These methods are required only if lower bounds established by strainrange partitioning concepts have been deemed inadequate in the establishment of expected lifetime. In one method, rapid loading and unloading is applied in the tensile and compressive half to isolate the plastic strain. In the second method, the creep is measured at a discrete number of points along the hysteresis loop by combining load-control tests into the general pattern of strain cycling under arbitrary temperature. Both methods are shown to give good results

Evaluation of structural analysis methods for life prediction

The utility of advanced constitutive models and structural analysis methods are evaluated for predicting the cyclic life of an air-cooled turbine blade for a gas turbine aircraft engine. Structural analysis methods of various levels of sophistication were exercised to obtain the cyclic stress-strain response at the critical airfoil location. Calculated strain ranges and mean stresses from the stress-strain cycles were used to predict crack initiation lives by using the total strain version of the strain range partitioning life prediction method. The major results are given and discussed

Preliminary study of thermomechanical fatigue of polycrystalline MAR-M 200

Thermomechanical fatigue (TMF) experiments were conducted on polycrystalline MAR-M 200 over a cyclic temperature range of 500 to 1000 C. Inelastic strain ranges of 0.03 to 0.2 percent were imposed on the specimens. The TMF lives were found to be significantly shorter than isothermal low-cycle-fatigue (LCF) life at the maximum cycle temperature, and in-phase cycling was more damaging than out-of-phase cycling. Extensive crack tip oxidation appeared to play a role in promoting the severity of in-phase cycling. Carbide particle - matrix interface cracking was also observed after in-phase TMF cycling. The applicability of various life prediction models to the TMF results obtained was assessed. It was concluded that current life prediction models based on isothermal data as input must be modified to be applicable to the TMF results

Thermomechanical and bithermal fatigue behavior of cast B1900 + Hf and wrought Haynes 188

High temperature thermomechanical and bithermal fatigue behavior was investigated for two superalloys: cast nickel-base B1900+Hf and wrought cobalt-base Haynes 188. Experimental results were generated to support development of an advanced thermal fatigue life prediction method. Strain controlled thermomechanical and load-controlled, strain-limited, bithermal fatigue tests were used to determine the fatigue crack initiation and cyclic stress-strain response characteristics of superalloys. Bithermal temperatures of 483 and 871 C were used for B1900+Hf, and 316 and 760 C for Haynes 188. Thermomechanical fatigue tests were conducted by using maximum and minimum temperatures corresponding to those for the bithermal experiments. Lives cover the range from about 10 to 3000 cycles to failure. Isothermal fatigue results obtained previously are also discussed

The role of lipid and carbohydrate digestive enzyme inhibitors in the management of obesity: a review of current and emerging therapeutic agents

Obesity is a global epidemic associated with significant morbidity and mortality in adults and ill health in children. A proven successful approach in weight management has been the disruption of nutrient digestion, with orlistat having been used to treat obesity for the last 10 years. Although orlistat-induced weight loss remains modest, it produces meaningful reductions in risk factors for obesity-related conditions such as diabetes and cardiovascular disease. Moreover, this lipase inhibitor is free of the serious side effects that have dogged appetite-suppressing drugs. This success had driven investigation into new generation nutraceuticals, supplements and pharmaceutical agents that inhibit the breakdown of complex carbohydrates and fats within the gut. This review focuses on agents purported to inhibit intestinal enzymes responsible for macronutrient digestion. Except for some synthetic products, the majority of agents reviewed are either botanical extracts or bacterial products. Currently, carbohydrate digestion inhibitors are under development to improve glycemic control and these may also induce some weight loss. However, colonic fermentation induced side effects, such as excess gas production, remain an issue for these compounds. The α-glucosidase inhibitor acarbose, and the α-amylase inhibitor phaseolamine, have been used in humans with some promising results relating to weight loss. Nonetheless, few of these agents have made it into clinical studies and without any clinical proof of concept or proven efficacy it is unlikely any will enter the market soon

Missing children: risks, repeats and responses

Investigating reports of missing children is a major source of demand for the police in the UK. Repeat disappearances are common, can indicate underlying vulnerabilities and have been linked with various forms of exploitation and abuse. Inspired by research on repeat victimisation, this paper examines the prevalence and temporal patterns of repeat missing episodes by children, as well as the characteristics of those involved. Using data on all missing children incidents recorded by one UK police service in 2015 (n = 3352), we find that: (a) 75% of missing incidents involving children were repeats, i.e. attributed to children who had already been reported missing in 2015; (b) a small proportion of repeatedly missing children (n = 59; 4%) accounted for almost a third of all missing children incidents (n = 952, 28%); (c) over half of all first repeat disappearances occurred within four weeks of an initial police recorded missing episode; and (d) children recorded as missing ten times or more over the one year study period were significantly more likely than those recorded missing once to be teenagers, in the care system or to have drug and/or alcohol dependencies. We conclude by discussing the implications of our findings for future research and the prevention of repeat disappearances by childre

Progress on reducing acrylamide levels in potato crisps in Europe, 2002 to 2019

European Snacks Association (ESA) data on acrylamide in potato crisps from 2002 to 2019 (99704 observations) were analysed. Acrylamide levels have plateaued since 2011, although the lowest mean so far was attained in 2018 at 353 ± 2.7 ng g-1: a 54% reduction since 2002. The 85th, 90th and 95th quantiles did show evidence of continued downward progress, the 90th quantile being lower than the 750 ng g-1 European Benchmark Level from 2017 to 2019. A smaller dataset from the European Food Safety Authority (2124 observations) for 2011-2018, was also analysed. The yearly means were higher than those of the ESA data, but showed a fall in average acrylamide from 715 ± 40.5 ng g-1 in 2015 to 505 ±28.5 ng g-1 in 2018, as well as steep falls in the 85th, 90th and 95th quantiles. Nevertheless, even the 85th quantile remained above the 750 ng g-1 Benchmark Level. The ESA data showed a reduction in the proportion of samples with acrylamide exceeding 750 ng g-1, from over 40 % in 2002 to 7.75 % in 2019. Seasonality was evident, with highest acrylamide levels from November to May. Crisp type had little effect except that thicker types had a higher proportion of samples containing >750 ng g-1 acrylamide. Analysis of the region of origin in Europe of the final product revealed improvements in the east and north. Geographical factors combined with seasonality continued to be problematic but was also an aspect in which progress was most evident. The findings show that improvements have been made in reducing the number of samples with very high levels of acrylamide, but do not suggest that mean acrylamide levels could be reduced substantially below where they have been since 2011, or that levels could be kept consistently below the current Benchmark Level