Vibration analysis of sandwich beams with variable cross section on variable Winkler elastic foundation

In this study, free vibration behavior of a multilayered symmetric sandwich beam made of functionally graded materials (FGMs) with variable cross section resting on variable Winkler elastic foundation are investigated. The elasticity and density of the functionally graded (FG) sandwich beam vary through the thickness according to the power law. This law is related to mixture rules and laminate theory. In order to provide this, a 50-layered beam is considered. Each layer is isotropic and homogeneous, although the volume fractions of the constituents of each layer are different. Furthermore, the width of the beam varies exponentially along the length of the beam, and also the beam is resting on an elastic foundation whose coefficient is variable along the length of the beam. The natural frequencies are computed for conventional boundary conditions of the FG sandwich beam using a theoretical procedure. The effects of material, geometric, elastic foundation indexes and slenderness ratio on natural frequencies and mode shapes of the beam are also computed and discussed. Finally, the results obtained are compared with a finite-element-based commercial program, ANSYS®, and found to be consistent with each other

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

Elastic properties and buckling load evaluation of ceramic particles filled glass/epoxy composites

In the current investigation, the effects of the various ceramic particles on elastic properties and load carrying capabilities of filled E-glass/epoxy composite plates are determined experimentally and numerically. The composite plates are filled with 0% (unfilled), 5%, 10% and 15% particle weight fractions (based on the weight of composite), such as silicon carbide (SiC), which has two particle sizes, aluminum oxide (Al2O3) and boron carbide (B4C). The results indicate that the load carrying capability of composites are significantly influenced by particle weight fractions, different particle sizes and different ceramic particles (fillers). Accordingly, the load carrying capabilities of composites filled with 10 wt% ceramic particles are found higher for small particle sizes. Moreover, the addition of 10 wt% boron carbide (B4C) particles to composites increases the critical buckling load value of composite up to 42%. © 2013 Elsevier Ltd. All rights reserved

Influences of multiple holes on thermal stresses in a thermoplastic composite disc

157-168The aim of this investigation is to observe the influence of multiple holes on thermal stresses in a thermoplastic composite hollow disc. For this purpose, a thermoplastic composite disc is reinforced by steel fibers as curvilinear for radial direction, and thermal loads are carried out for uniform distribution at various temperatures. The solution is completed in two parts that are elastic and elastic-plastic analysis. Additionally, residual stresses are calculated using these analysis results. Finite element method (FEM) is utilized for calculation of thermal stresses. Therefore, the thermal stress analysis is performed using ANSYS® finite element software. Due to the fact that composite disc have different thermal expansions in radial and tangential directions, thermal stresses are taken place in disc by the applied uniform thermal loadings. The magnitude of the tangential stress components both elastic and elastic-plastic solutions is higher than that of the radial stress components, except edges of multiple holes. The present study concludes that magnitudes and distributions of thermal and residual stresses on the composite disc are considerably affected by increasing the uniform temperature loadings and existence of multiple hole

Elasto-plastic thermal stress analysis in a thermoplastic composite disc under uniform temperature using FEM

The aim of this study was to investigate elasto-plastic thermal stresses in a thermoplastic composite disc that is reinforced by steel fibers, curvilinearly. Finite element method (FEM) was used to calculate the thermal stress distribution in the model of composite disc. The solution was performed by ANSYS software code. In order to evaluate the effects of uniform temperature, different values of it were carried out on the model of composite disc, uniformly. Radial and tangential stresses were calculated under a uniform temperature distribution which was selected from 60 C to 120 C. Because of the composite disc having different thermal expansions in radial and tangential directions, thermal stresses were produced in it by the applied uniform temperature values. The magnitude of the tangential stress component for elastic and elasto-plastic solutions was higher than the radial stress component. The radial stress components were obtained as compressive on the inner and outer surfaces. Besides the tangential stress components were calculated as compressive and tensile on the inner and outer surfaces, respectively. The absolute values of it were the highest on the inner surface both radial and tangential directions. The residual stress components also were calculated using elastic and elasto-plastic solution results. The obtained results showed that the positions of the improved thermal stresses and residual stresses were considerably affected increasing uniform temperature value. © Association for Scientific Research

Elasto-Plastic Thermal Stress Analysis in a Thermoplastic Composite Disc under Uniform Temperature Using FEM

The aim of this study was to investigate elasto-plastic thermal stresses in a thermoplastic composite disc that is reinforced by steel fibers, curvilinearly. Finite element method (FEM) was used to calculate the thermal stress distribution in the model of composite disc. The solution was performed by ANSYS software code. In order to evaluate the effects of uniform temperature, different values of it were carried out on the model of composite disc, uniformly. Radial and tangential stresses were calculated under a uniform temperature distribution which was selected from 60 C to 120 C. Because of the composite disc having different thermal expansions in radial and tangential directions, thermal stresses were produced in it by the applied uniform temperature values. The magnitude of the tangential stress component for elastic and elasto-plastic solutions was higher than the radial stress component. The radial stress components were obtained as compressive on the inner and outer surfaces. Besides the tangential stress components were calculated as compressive and tensile on the inner and outer surfaces, respectively. The absolute values of it were the highest on the inner surface both radial and tangential directions. The residual stress components also were calculated using elastic and elasto-plastic solution results. The obtained results showed that the positions of the improved thermal stresses and residual stresses were considerably affected increasing uniform temperature value

Elasto-Plastic Thermal Stress Analysis in a Thermoplastic Composite Disc under Uniform Temperature Using FEM

The aim of this study was to investigate elasto-plastic thermal stresses in a thermoplastic composite disc that is reinforced by steel fibers, curvilinearly. Finite element method (FEM) was used to calculate the thermal stress distribution in the model of composite disc. The solution was performed by ANSYS software code. In order to evaluate the effects of uniform temperature, different values of it were carried out on the model of composite disc, uniformly. Radial and tangential stresses were calculated under a uniform temperature distribution which was selected from 60 C to 120 C. Because of the composite disc having different thermal expansions in radial and tangential directions, thermal stresses were produced in it by the applied uniform temperature values. The magnitude of the tangential stress component for elastic and elasto-plastic solutions was higher than the radial stress component. The radial stress components were obtained as compressive on the inner and outer surfaces. Besides the tangential stress components were calculated as compressive and tensile on the inner and outer surfaces, respectively. The absolute values of it were the highest on the inner surface both radial and tangential directions. The residual stress components also were calculated using elastic and elasto-plastic solution results. The obtained results showed that the positions of the improved thermal stresses and residual stresses were considerably affected increasing uniform temperature value. © Association for Scientific Research

Influences of multiple holes on thermal stresses in a thermoplastic composite disc

Şen, Faruk (Aksaray, Yazar)The aim of this investigation is to observe the influence of multiple holes on thermal stresses in a thermoplastic composite hollow disc. For this purpose, a thermoplastic composite disc is reinforced by steel fibers as curvilinear for radial direction, and thermal loads are carried out for uniform distribution at various temperatures. The solution is completed in two parts that are elastic and elastic-plastic analysis. Additionally, residual stresses are calculated using these analysis results. Finite element method (FEM) is utilized for calculation of thermal stresses. Therefore, the thermal stress analysis is performed using ANSYS® finite element software. Due to the fact that composite disc have different thermal expansions in radial and tangential directions, thermal stresses are taken place in disc by the applied uniform thermal loadings. The magnitude of the tangential stress components both elastic and elastic-plastic solutions is higher than that of the radial stress components, except edges of multiple holes. The present study concludes that magnitudes and distributions of thermal and residual stresses on the composite disc are considerably affected by increasing the uniform temperature loadings and existence of multiple hole

Darbe Yükü Altındaki Hibrit Kompozit Plakalara Sıcaklığın Etkisi

Bu çalışmada, karbon-cam elyaf/epoksi (hibrit) kompozitlerin sıcaklık ve artan darbe enerjisi altındaki darbe davranışları incelenmiştir. Bununla ilgili olarak iki tip tabaka dizilim açısına sahip, 8 tabakalı hibrit kompozit numunelere -20, 0, 20 ve 40 oC sıcaklıklarında, numunelerde delinme meydana gelene kadar darbe enerjisi uygulanmıştır. Hibrit kompozitlerin saplanma ve delinme sınır değerlerinin belirlenmesinde, darbe enerjisi ve absorbe edilen enerji arasındaki ilişkiyi göstermede kullanılan enerji profili diyagramı kullanılmıştır. Bunun yanı sıra, maksimum temas kuvveti (Fmax), toplam çökme (d) ve maksimum temas süresi (t) gibi önemli darbe karakteristiklerinin sıcaklık geçişlerindeki değişimleri de sunulmuştur. Sonuç olarak, cam ve karbon fiberlerin -20 oC'de, diğer sıcaklıklara göre daha çok gevrekleştiği görülmüştür. Buna göre her iki tip hibrit kompozit için -20 oC'de meydana gelen delinme sınırı diğer sıcaklıklara göre en yüksek değerde bulunmuştur

Temperature Effects on Hybrid Composite Plates Under Impact Loads

In this work, impact responses of carbon-glass fiber/epoxy (hybrid) composites were investigated under various temperatures and increasing impact energies. The increasing impact energies were applied to the specimens at various temperatures as -20, 0, 20 and 40 oC until perforation took place of specimens. Those specimens are composed by two types of fiber orientation with eight laminates hybrid composites. An Energy profiling diagram, used for showing the relationship between impact and absorbed energy, has been used to obtain penetration and perforation thresholds of hybrid composites. Beside those, temperature effects on impact characteristics such as maximum contact force (Fmax), total deflection (d) and maximum contact duration (t) were also presented in figures. Finally, glass and carbon fibers exhibited more brittle characteristics at -20 oC according to other temperatures. So, perforation threshold of each hybrid composites at -20 oC was found higher than other temperatures. Keywords : Hybrid composit