1,720,955 research outputs found
Examination of the tool wear on machining of steel of the bearing rings
Full text linkPrilikom izrade prstenova kotrljajućih ležajeva najčešće se primjenjuju čelici kvalitete 100Cr6, 80CrMn4 ili 100CrMnS6-4. Sama izrada prstenova provodi se na različitim tokarilicama uz primjenu različitih oblika i kvaliteta reznih pločica. Kako se radi o velikoserijskoj ili masovnoj proizvodnji prstenova kotrljajućih ležajeva tako je i potrošnja reznih pločica također velika. Iz tog razloga važno je odabirom kvalitetnih pločica utjecati na troškove izrade prstenova kotrljajućih ležajeva. Kako danas na tržištu imamo različite proizvođače reznih pločica različitih kvaliteta (sastava osnovnog materijala, prevučene različitim slojevima) potrebno je prateći trošenje i analizom reznih pločica, zaključiti o kvaliteti istih. U ovom radu provedena su ispitivanja na istrošenim reznim pločicama koje su napravljene od tvrdog metala i prevučene funkcionalnim prevlakama. Primjenom kalotestera izmjerena je debljina prevlake. Utiskivanjem i analizom otiska Rockwell C indentorom utvrđena je adhezivnost prevlake. Nanoindentacijom je određena tvrdoća osnovnog materijala i prevlake, dok je Palmqvistovom metodom određena lomna žilavost osnovnog materijala. Metalografskim ispitivanjem poprečnog presjeka provjerena je mikrostruktura osnovnog materijala te su dobiveni rezultati stavljeni u kontekst trajnosti reznog alata.In the manufacturing of rolling bearings rings, materials like 100Cr6, 80CrMn4 or 100CrMnS6-4 are most commonly used. Bearing rings are generally manufactured using machining techniques like turning, in which cutting tools with different geometry and quality are applied. This industry being high volume production, uses large quantities of aforementioned cutting tools. By using cutting tools of different quality, it is possible to cut down on production costs in manufacturing of rolling bearing rings. In this research, coated cemented carbide cutting tools were tested using different analytical methods. Thickness of functional coatings was measured using calotest. Coating adherence to the substrate was analysed by Rockwell C indentation. Nano-hardness was tested using the instrumented method for hardness testing, while the fracture toughness of substrate was determined by Palmqvist method. Microstrucutre in cross section was metallographicly analysed, and all of the results were interpreted trough the longevity of cutting tools in real life application
Analiza trošenja dijamantnih reznih alata pomoću karakterizacije dijamantnih čestica
No full textThis thesis highlights an approach in research and development of diamond materials for use in insert tools. ‘Diamond insert tools’ may be used on different construction jobs for the specific purposes of sawing, coring or grinding on concretes (heterogeneous) and masonry materials like brick and limestone (homogeneous). A diamond insert tool comprises a steel base (such as a saw blade centre, core bit barrel or cup wheel) and cutting elements. These cutting elements are in most cases metal-matrix composite segments with embedded diamond particles, as carriers of extreme hardness and therefore needed abrasive properties. The two principal performance characteristics of an insert tools are cutting speed and lifetime. These characteristics are commonly inverse hence, obtaining a simultaneous increase in cutting speeds and lifetime is proven to be quite challenging.
By performing diamond characterisation using the state-of-the-art techniques, the obtained characteristics will be assessed and used to detect the correlation with the insert tools behaviour. Optical microscopy, in conjunction with advanced imaging techniques, will provide insight into the better understanding of diamond wear state of the insert’s active surface throughout its life cycle. These results, influenced by varying geometries of the inserts and in relation with operational parameters like torque, cutting speeds, and feed rates, ensure that the evolution of diamonds’ state and its active failure modes are fully understood. These findings will enable better comprehension of diamond tools behaviour and performance in real-life application.U ovom diplomskom radu istaknut je pristup istraživanja i razvoja dijamantnih materijala za upotrebu u reznim alatima. "Dijamantni rezni alati" mogu se koristiti u različitim građevinskim primjenama kao što su piljenje, jezgreno brušenje ili bušenje na zidanim materijalima poput opeke, vapnenca (homogeni materijal) i betona (heterogeni materijal).
Dijamantni alat sastoji se od čelične osnove (kao što je jezgra pile, cijev za jezgru ili kotača) i reznog elementa (neke vrste dijamanta). Ti su rezni elementi u većini slučajeva kompoziti sa metalnom matricom odnosno segmenti s ugrađenim česticama dijamanata kao nosača iznimne tvrdoće, a time i visokih abrazivnih svojstava. Dvije glavne karakteristike dijamantnih alata su brzina rezanja i vijek trajanja. Te su karakteristike obično recipročne, a dokazano je da je istodobno povećavanje brzine rezanja i vijeka trajanja alata poprilično izazovno.
Provođenjem karakterizacije dijamanata koristeći najsuvremenije tehnike, dobivene karakteristike ocjenjivat će se dovoditi u kontekst ponašanja alata u eksploataciji. Optička mikroskopija, u kombinaciji s naprednim tehnikama snimanja, pruža uvid u bolje razumijevanje stanja trošenja dijamanta aktivne površine umetka tijekom njegovog životnog ciklusa. Ovi rezultati, pod utjecajem različitih arhitektura segmenata i u odnosu na radne parametre poput zakretnog momenta, brzine rezanja i posmaka, osiguravaju potpuno razumijevanje evolucije stanja dijamanata i njihovih procesa degradacije. Ovi će rezultati omogućiti bolje razumijevanje ponašanja i performansi dijamantnih alata u stvarnoj primjeni
Ispitivanje trošenja alata kod obrade čelika za izradu prstenova kotrljajućih ležaja
Full text linkPrilikom izrade prstenova kotrljajućih ležajeva najčešće se primjenjuju čelici kvalitete 100Cr6, 80CrMn4 ili 100CrMnS6-4. Sama izrada prstenova provodi se na različitim tokarilicama uz primjenu različitih oblika i kvaliteta reznih pločica. Kako se radi o velikoserijskoj ili masovnoj
proizvodnji prstenova kotrljajućih ležajeva tako je i potrošnja reznih pločica također velika. Iz tog razloga važno je odabirom kvalitetnih pločica utjecati na troškove izrade prstenova kotrljajućih ležajeva. Kako danas na tržištu imamo različite proizvođače reznih pločica različitih kvaliteta (sastava osnovnog materijala, prevučene različitim slojevima) potrebno je prateći trošenje i analizom reznih pločica, zaključiti o kvaliteti istih.
U ovom radu provedena su ispitivanja na istrošenim reznim pločicama koje su napravljene od tvrdog metala i prevučene funkcionalnim prevlakama. Primjenom kalotestera izmjerena je
debljina prevlake. Utiskivanjem i analizom otiska Rockwell C indentorom utvrđena je adhezivnost prevlake. Nanoindentacijom je određena tvrdoća osnovnog materijala i prevlake, dok je Palmqvistovom metodom određena lomna žilavost osnovnog materijala. Metalografskim ispitivanjem poprečnog presjeka provjerena je mikrostruktura osnovnog materijala te su dobiveni rezultati stavljeni u kontekst trajnosti reznog alata
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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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