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Bilyalı dövme işleminin tane boyutuna etkisinin deneysel incelenmesi
No full textShot peening is a type of mechanical surface treatment and applied to enhance mechanical properties against fatigue and stress corrosion cracking failures. Shot peening process can be applied both cold or warm. Shot peening process enhances not only hardness but also strength of materials. This process expose material surface and just below the surface, compressive residual stress. This study, covers formation of ultrafined grain structure of metal surfaces or just below and alteration of mechanical properties due to severe plastic deformation with extra ordinary shot peening conditions. For AISI 1017 mild steel and commercially pure titanium hardness values were measured by nanoindentation tests and observed to be greatly increased from cross-section to surface. Furthermore, existence of ultrafined grain structures on surface and just below the surface is proved with optical and SEM (Scanning Electron Microscope) images.Bilyalı dövme, metallerin yorulma ve gerilmeli korozyona karşı mukavemetlerini arttırmak amacı ile uygulanan bir mekanik yüzey işlemidir. Bilyalı dövme işlemi metallerde hem sertlik artışına hem de yüzeyde ve yüzeyin altında basma kalıntı gerilmesine sebep olan soğuk veya ılık olarak uygulanabilen bir işlemdir. Bu çalışma, yüksek dövme şiddetleri uygulanarak bilyalı dövülen metalik malzemelerin aşırı plastik deformasyon sonucu yüzeyde ve yüzeyin hemen altında ince taneli yapıların varlığını ve bu bölgenin mekanik özelliklerinin değişimini kapsamaktadır. AISI 1017 çelik ve ticari saflıkta titanyum malzemeleri yüksek şiddette bilyalı dövülerek yüzeylerinden itibaren nanoindentasyon metodu ile sertlik ölçümleri yapılmış ve iç kısımlardan yüzeye doğru sertlik değerlerinde büyük oranda artış olduğu gözlemlenmiştir. Bununla birlikte metallerin enine kesitinden alınan optik mikroskop (OM) ve taramalı elektron mikroskobu (SEM) görüntülerinde yüzeyde ve yüzeyin hemen altındaki bölgelerde aşırı plastik deformasyonun ve buna bağlı olarak da ince taneli yapıların varlığına rastlanılmıştır
Yivsiz setsiz av ve spor tüfeklerinde kaliteyi artırmak amacıyla kritik parçalarda iyileştirme çalışmaları
No full textBu çalışmada, ülkemizdeki bir tüfek fabrikasında üretilen yarı otomatik tüfeklerdeki kilit parçasında meydana gelen hasar incelenmiştir. Hasar sebebini belirleyebilmek için kırık yüzeyi ve parça geometrisi ele alınmıştır. Parça üzerindeki gerilme dağılımı ANSYS Workbench 11.0 programı ile analiz edilmiştir. Kilit parçasında meydana gelen hasarın yanlış malzeme seçimi, yanlış ısıl işlem ve parça geometrisinde yapılan hatalardan kaynaklandığı anlaşılmıştır. En uygun malzeme ve ısıl işlem şartlarını belirlemek için AISI4140 ve AISI4340 çelikleri aday malzemeler olarak kullanılmış ve ısıl işleme tabi tutulmuştur. Isıl işlemler sonucu değişen mekanik özellikleri belirlemek için numunelere çekme, Charpy çentik darbe ve üç nokta eğme deneyleri uygulanmış ve sertik ölçümleri yapılmıştır. Mekanik özellikler ve kırık yüzeyi incelemeleri en uygun malzemenin seçiminde kullanılmıştır. Sonuç olarak en uygun malzemenin AISI4340 çeliği olduğu ve en uygun ısıl işlem şartının kilit parçası için yağda sertleştirme sonrası yapılan 450 ºC'deki temperleme olduğu sonucuna varılmıştır.ANSYS analizi sonucunda ise kilit parçasında kritik bölgelerde oluşan aşırı gerilmelerin plastik deformasyona yol açtığı belirlenmiştir.In this work, we mainly focused on occurrences of locking block failure in the semi-automatic shotgun bolts at a shotgun factory in our country. The fracture surface and locking block geometry examined in order to determine failure reasons. The stress distribution of the locking block was performed using ANSYS Workbench 11.0. It was discovered that the reasons for fracture of locking block are; incorrect material selection, incorrect heat treatment, and dimensional geometry problems. For defining best material and heat treatment conditions, AISI4140 and AISI4340 steels used and heat-treated. Tensile, Charpy notched-impact and hardness testing were used to fully characterize the material properties. Mechanical test results and fractured surface analysis were turned to account to decide for proper material. It is concluded that the most convenient material for locking block is AISI4340 steel and optimum heat treatment parameters for this steel is oil quenching and tempering at 450 ºC.ANSYS Workbench analysis revealed that over loading has caused the plastic deformation in the critical zones of the part
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
EFFECT OF HEAT AND MECHANICAL SURFACE TREATMENTS ON THE FATIGUE PROPERTIES OF SAE 8620 STEEL
No full textIn this study, the fatigue properties of SAE 8620 case hardened steel was investigated. Carburizing, shot peening and their combinations were applied to SAE 8620 steel fatigue specimens. Different fabrication parameters of carburizing were applied. Shot peening was also applied to carburized and noncarburized specimens. Hardness and residual stress distribution of mechanical and heat-treated fatigue specimens were determined. Rotating bending fatigue tests were performed using treated test specimens. Plotted S-N curves, for treated at different conditions and different ways, were compared to curves for drawn specimens. The maximum increase in fatigue limit is determined for double quenched and shot peened specimens as 72%
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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