Fatigue Crack Propagation Under Variable Amplitude Loading in Steels Used in Francis Turbine Runners

RÉSUMÉ Les turbines hydrauliques sont soumises à de très grands nombres de cycles à faible amplitude de contrainte et à haute fréquence. Ces petits cycles sont générés par des phénomènes hydrauliques et sont superposés à une contrainte statique de tension. Aussi, dépendant des conditions de fonctionnement, il est possible d’avoir superposé aux petits cycles un plus faible nombre de grands cycles à forte amplitude de contrainte et basse fréquence. On a ainsi en pratique une superposition de petits cycles, de grands cycles et d’une contrainte statique de tension durant les 70 ans de durée de vie de la turbine. Les turbines hydrauliques qui sont fabriquées à partir des aciers AISI 415, ASTM A516, et AISI 304L (notés 415, A516, et 304L pour simplification) sont soumises à de telles contraintes cycliques et statique. Ces contraintes ont pour effet de favoriser la propagation des défauts existants dans les roues des turbines et peuvent mener à leur rupture. Pour éviter la propagation des fissures, les petits cycles doivent induire un ΔK qui est en dessous du seuil de fatigue. Néanmoins, les grands cycles peuvent contribuer à propager ces fissures. Ainsi, pour prédire la vitesse de propagation des fissures dans de telles conditions de cycles superposés, on a recours à la sommation linéaire de dommage (SLD). Il a été observé que les grands cycles superposés aux petits cycles peuvent induire une diminution du seuil de fatigue des petits cycles. Différentes procédures ont été proposées dans la littérature pour mesurer les seuils associés au petits cycles seuls et avec superposition des grands cycles. Cependant, la plupart des procédures ne minimise pas la fermeture induite lors de la mesure du seuil conduisant ainsi à une surestimation de leur valeur. La présente étude propose de nouvelles procédures d’essais pour réduire la fermeture lors de la mesure du seuil de fatigue pour les aciers mentionnés précédemment. De plus, différentes études ont démontré que les fissures peuvent se propager plus rapidement sous l’effet des grands cycles que ce que prédit la SLD. Nous vérifierons ainsi la précision de la prédiction LDS par rapport aux mesures de propagation. Dans une première étude, la propagation des fissures par l’interaction de petits et de grands cycles est caractérisée dans les trois aciers. Les cycles de base sont entrecoupés par les grands cycles. Les vitesses de propagation des fissures par les cycles de base et les grands cycles de sous-charges sont additionnées dans la SLD pour évaluer la vitesse de propagation de fissure.----------ABSTRACT Hydraulic turbine runners are subjected to a very large number of cycles with small stress amplitudes at high frequencies. These cycles are generated by hydraulic phenomena and are superimposed to a tensile static stress. Depending on the operating conditions, much lower number of large cycles are generated with large stress amplitudes at low frequencies. As a summary, the whole stress spectrum consists of small cycles superimposed to a tensile static stress that is intercut with large cycles during the 70 years design life of turbine runners. Turbine runners, which are fabricated from AISI 415, ASTM A516, and AISI 304L steels (i.e. called 415, A516 and 304L for simplicity), are subjected to the aforementioned stress cycles. The imposed stress spectrum propagates the existing defects or cracks in turbine runners and may lead to their failure. In order to avoid crack propagation, the small cycles should induce a ΔK that is lower than the fatigue threshold. Nonetheless, the crack can grow due to large cycles. As a result, linear damage summation (LDS) is employed to predict the crack growth. The large cycles superimposed to small cycles can also induce a decrease in fatigue threshold of the small cycles. Different test procedures have been proposed to measure the fatigue threshold of small cycles and the ones superimposed to large cycles; however, most of them do not minimize the crack closure while reaching the fatigue threshold leading to an overestimation of fatigue thresholds. In this study new test procedures are proposed in order to minimize crack closure while reaching the fatigue thresholds in turbine runner steels. Different studies have shown that crack can grow faster than the LDS prediction due to the interaction between large cycles. Therefore, we verify the precision of LDS prediction compared to the measured crack growth rates. In this first study, crack growth due to the interaction between two large cycles is investigated in the three aforementioned turbine runner steels. Baseline cycles are periodically intercut by an underload cycle. This variable amplitude loading is hereafter called periodic underloads. Crack growth rates of baseline cycles and underload cycles are summated in LDS to predict crack growth under periodic underloads. Crack growth measured under periodic underloads is then compared to LDS prediction. A ratio between the measured and predicted crack growth, that is greater than unity, is defined as an acceleration factor

Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In an era of shifting global agendas and expanded emphasis on non-communicable diseases and injuries along with communicable diseases, sound evidence on trends by cause at the national level is essential. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic scientific assessment of published, publicly available, and contributed data on incidence, prevalence, and mortality for a mutually exclusive and collectively exhaustive list of diseases and injuries. Methods: GBD estimates incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) due to 369 diseases and injuries, for two sexes, and for 204 countries and territories. Input data were extracted from censuses, household surveys, civil registration and vital statistics, disease registries, health service use, air pollution monitors, satellite imaging, disease notifications, and other sources. Cause-specific death rates and cause fractions were calculated using the Cause of Death Ensemble model and spatiotemporal Gaussian process regression. Cause-specific deaths were adjusted to match the total all-cause deaths calculated as part of the GBD population, fertility, and mortality estimates. Deaths were multiplied by standard life expectancy at each age to calculate YLLs. A Bayesian meta-regression modelling tool, DisMod-MR 2.1, was used to ensure consistency between incidence, prevalence, remission, excess mortality, and cause-specific mortality for most causes. Prevalence estimates were multiplied by disability weights for mutually exclusive sequelae of diseases and injuries to calculate YLDs. We considered results in the context of the Socio-demographic Index (SDI), a composite indicator of income per capita, years of schooling, and fertility rate in females younger than 25 years. Uncertainty intervals (UIs) were generated for every metric using the 25th and 975th ordered 1000 draw values of the posterior distribution. Findings: Global health has steadily improved over the past 30 years as measured by age-standardised DALY rates. After taking into account population growth and ageing, the absolute number of DALYs has remained stable. Since 2010, the pace of decline in global age-standardised DALY rates has accelerated in age groups younger than 50 years compared with the 1990–2010 time period, with the greatest annualised rate of decline occurring in the 0–9-year age group. Six infectious diseases were among the top ten causes of DALYs in children younger than 10 years in 2019: lower respiratory infections (ranked second), diarrhoeal diseases (third), malaria (fifth), meningitis (sixth), whooping cough (ninth), and sexually transmitted infections (which, in this age group, is fully accounted for by congenital syphilis; ranked tenth). In adolescents aged 10–24 years, three injury causes were among the top causes of DALYs: road injuries (ranked first), self-harm (third), and interpersonal violence (fifth). Five of the causes that were in the top ten for ages 10–24 years were also in the top ten in the 25–49-year age group: road injuries (ranked first), HIV/AIDS (second), low back pain (fourth), headache disorders (fifth), and depressive disorders (sixth). In 2019, ischaemic heart disease and stroke were the top-ranked causes of DALYs in both the 50–74-year and 75-years-and-older age groups. Since 1990, there has been a marked shift towards a greater proportion of burden due to YLDs from non-communicable diseases and injuries. In 2019, there were 11 countries where non-communicable disease and injury YLDs constituted more than half of all disease burden. Decreases in age-standardised DALY rates have accelerated over the past decade in countries at the lower end of the SDI range, while improvements have started to stagnate or even reverse in countries with higher SDI. Interpretation: As disability becomes an increasingly large component of disease burden and a larger component of health expenditure, greater research and developm nt investment is needed to identify new, more effective intervention strategies. With a rapidly ageing global population, the demands on health services to deal with disabling outcomes, which increase with age, will require policy makers to anticipate these changes. The mix of universal and more geographically specific influences on health reinforces the need for regular reporting on population health in detail and by underlying cause to help decision makers to identify success stories of disease control to emulate, as well as opportunities to improve. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Investigation of thickness and thermal treatments on the deep drawing process for the aluminum plate

Effective parameters on deep drawing include punch diameter, mold diameter, punch speed, power of preservative sheet, friction, traction and depth. In this work, the effect of precipitation hardening in 2618Al alloys was studied. In 2618 alloy the LDR values vary with the condition of heat treatment and the best condition at the value of 1.33 was obtained. Comparison of LDR in different conditions had shown that precipitation hardening cause decrement in limiting drawing ratio and consequently is detrimental to drawing ability. In 2618 alloy at SA and SW conditions, the LDR was decreased. In this paper, the effect of temperature on earing in 2618 Al alloy was also discussed. Results show that at the temperature at 350oC the amount of earing is least

A Surrogate Approach to Reveal Microstructural Mechanisms Controlling the 3D Short Crack Growth in a Ti-6Al-4V Alloy

Microstructural features and short crack growth behavior were characterized and linked in a Ti-6Al-4V by employing X-ray micro-tomography combined with EBSD serial sectioning. Statistical analysis was used to rank the contributing features to the crack behavior. Afterwards, by creating surrogate models, the microstructural mechanism controlling the short crack behavior were revealed. Short crack preferably grows inside the predominant α phase above the average microstructural fraction. A high number of grains in contact with cracked α grains elongated in the loading direction may impose a constraint on the crack opening resulting in low crack growth rates. As the crack front becomes larger, the increase in the shear stress field away from the cracked grain leads to crack bifurcations, resulting in a decrease in crack driving forces with low crack growth rates. This leads to a preferable growth in α+β phase and along the interface above the average microstructural fractions

3D short fatigue crack closure behavior in Ti-6Al-4V alloy investigated using in-situ high resolution synchrotron X-ray tomography

In-situ synchrotron X-ray microtomography has been employed to investigate the three-dimensional (3D) closure behavior of short fatigue crack in Ti-6Al-4V alloy. At a spatial resolution level of 1 µm, tomography datasets were taken at two short crack fronts to observe the time evolution behavior of closure (sometimes called 4D imaging). Owing to the high spatial resolution level, the complex 3D crack morphology consisting of deflections, facet paths and crack branching/overlap caused by the 3D variation in the microstructural features were readily observed together with the occurrence of crack closure. This study separated the contributions of near-tip and behind-tip crack closure and observed their behavior with crack growth. It was deduced that the evolution of behind-tip closure with increase in crack length predominantly affects the overall closure behavior in the short crack regime. Crack front closure behavior variation was found to be attributable to the existence of different crack path morphologies which showed varied degree of fracture surface roughness due to Mode II and Mode III displacements. The relationship between closure, crack tip opening displacement range (∆CTOD) and crack growth rate are also discussed

The global, regional, and national burden of colorectal cancer and its attributable risk factors in 195 countries and territories, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017

Safiri S, Sepanlou SG, Ikuta KS, et al. The global, regional, and national burden of colorectal cancer and its attributable risk factors in 195 countries and territories, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. LANCET GASTROENTEROLOGY & HEPATOLOGY. 2019;4(12):913-933.Background Data about the global, regional, and country-specific variations in the levels and trends of colorectal cancer are required to understand the impact of this disease and the trends in its burden to help policy makers allocate resources. Here we provide a status report on the incidence, mortality, and disability caused by colorectal cancer in 195 countries and territories between 1990 and 2017. Methods Vital registration, sample vital registration, verbal autopsy, and cancer registry data were used to generate incidence, death, and disability-adjusted life-year (DALY) estimates of colorectal cancer at the global, regional, and national levels. We also determined the association between development levels and colorectal cancer age-standardised DALY rates, and calculated DALYs attributable to risk factors that had evidence of causation with colorectal cancer. All of the estimates are reported as counts and age-standardised rates per 100 000 person-years, with some estimates also presented by sex and 5-year age groups. Findings In 2017, there were 1.8 million (95% UI 1.8-1.9) incident cases of colorectal cancer globally, with an age-standardised incidence rate of 23.2 (22.7-23.7) per 100 000 person-years that increased by 9.5% (4.5-13.5) between 1990 and 2017. Globally, colorectal cancer accounted for 896 000 (876 300-915 700) deaths in 2017, with an age-standardised death rate of 11.5 (11.3-11.8) per 100 000 person-years, which decreased between 1990 and 2017 (-13.5% [-18.4 to -10.0]). Colorectal cancer was also responsible for 19.0 million (18.5-19.5) DALYs globally in 2017, with an age-standardised rate of 235.7 (229.7-242.0) DALYs per 100 000 person-years, which decreased between 1990 and 2017 (-14.5% [-20.4 to -10.3]). Slovakia, the Netherlands, and New Zealand had the highest age-standardised incidence rates in 2017. Greenland, Hungary, and Slovakia had the highest age-standardised death rates in 2017. Numbers of incident cases and deaths were higher among males than females up to the ages of 80-84 years, with the highest rates observed in the oldest age group (>= 95 years) for both sexes in 2017. There was a non-linear association between the Socio-demographic Index and the Healthcare Access and Quality Index and age-standardised DALY rates. In 2017, the three largest contributors to DALYs at the global level, for both sexes, were diet low in calcium (20.5% [12.9-28.9]), alcohol use (15.2% [12.1-18.3]), and diet low in milk (14.3% [5.1-24.8]). Interpretation There is substantial global variation in the burden of colorectal cancer. Although the overall colorectal cancer age-standardised death rate has been decreasing at the global level, the increasing age-standardised incidence rate in most countries poses a major public health challenge across the world. The results of this study could be useful for policy makers to carry out cost-effective interventions and to reduce exposure to modifiable risk factors, particularly in countries with high incidence or increasing burden. Copyright (C) 2019 The Author(s). Published by Elsevier Ltd

Mapping routine measles vaccination in low- and middle-income countries

The safe, highly effective measles vaccine has been recommended globally since 1974, yet in 2017 there were more than 17 million cases of measles and 83,400 deaths in children under 5 years old, and more than 99% of both occurred in low- and middle-income countries (LMICs)1–4. Globally comparable, annual, local estimates of routine first-dose measles-containing vaccine (MCV1) coverage are critical for understanding geographically precise immunity patterns, progress towards the targets of the Global Vaccine Action Plan (GVAP), and high-risk areas amid disruptions to vaccination programmes caused by coronavirus disease 2019 (COVID-19)5–8. Here we generated annual estimates of routine childhood MCV1 coverage at 5 × 5-km2 pixel and second administrative levels from 2000 to 2019 in 101 LMICs, quantified geographical inequality and assessed vaccination status by geographical remoteness. After widespread MCV1 gains from 2000 to 2010, coverage regressed in more than half of the districts between 2010 and 2019, leaving many LMICs far from the GVAP goal of 80% coverage in all districts by 2019. MCV1 coverage was lower in rural than in urban locations, although a larger proportion of unvaccinated children overall lived in urban locations; strategies to provide essential vaccination services should address both geographical contexts. These results provide a tool for decision-makers to strengthen routine MCV1 immunization programmes and provide equitable disease protection for all children