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Formability Study for Stamping Aluminum Alloy Sheets
No full text近年來，由於消費者對於空間舒適與多功能要求提升，導致代步工具之體積重量不斷增加。然而面對能源危機與日漸惡化的生存環境，減少溫室氣體的排放已成為重要課題，以至於部品輕量化已是各大板金廠發展的目標，而由於鋁合金的比重約為鋼的三分之一，使得許多鋼板逐漸被鋁合金所取代，甚至歐美先進國家皆陸續推出全鋁合金汽車以及遊艇。
鋁合金板件雖然擁有重量輕及耐腐蝕特性，但其成形性較傳統鋼板為差，在沖壓過程中除了容易產生破裂（crack）問題外，鋁合金因較低的彈性係數（elastic modulus）而產生的回彈（springback）缺陷，更使得尺寸精度上的變異難以克服。也因此過去鋼板的設計概念無法直接套用於鋁合金的模具設計，造成板金廠開發時程與成本的耗費。
在沖壓成形上，鋁板大都選用成形性相對較佳的5000與6000系列材料，本論文亦是選用A5083-O與鋁A6181-T4板材作為研究素材，藉以探討不同降伏準則（yield criteria）與硬化準則（hardening rule）對鋁合金板材沖壓成形CAE分析準確性的影響。並經由實際實驗取得材料參數，應用於V型彎曲及U形帽狀（U-hat）引伸成形之CAE模擬分析上，再將板件進行成形實驗，以比對模擬分析結果，提供適於鋁合金板件成形分析之材料模型。
複雜載具方面，本論文選用實際開發之引擎蓋板，探討傳統鋼板與鋁合金板件之成形差異，經由製程參數與模具修正條件的改善，整理各參數對成品拉伸之影響。引擎蓋板選用了A6181-T4材料，由於
經過T4熱處理後的機械性質會隨著時間而有所改變，因此本研究經由實驗取得各時效時間之材料參數，將時效實驗結果應用於CAE模擬分析，並進行實際開模驗證，以比對鋁合金沖壓成形之分析模式。
本研究採用所上述鋁合金板件成形分析模式，進行鋁合金遊艇外板沖壓成形之技術建立。由於遊艇外板屬大面積且局部深抽型特徵，成形時容易產生破裂與皺褶同時存在之缺陷問題，因此目前遊艇外板的製造仍有賴於焊接製程。遊艇外板材料係選用具耐腐蝕性的A5083-O，再針對遊艇外板之成品部份進行特徵歸納及成形性分析，將其難以克服之特徵造型，給予較佳化之餘肉造型（addendums）設計與製程參數，以改善鋁合金遊艇板件之沖壓成形技術問題。In recent year, customers had raising demands for the coziness of spaces and multi-functions, which makes the sizes and weights of vehicles increased. However, when facing the energy crisis and the deteriorating living environment, it is essential to decrease the emission of greenhouse gases. To produce light-weighted parts then becomes the goal of most sheet metal factories. In European and American countries, some factories have even launched aluminum alloy automotives and aluminum alloy yachts one after another.
The weight of aluminum alloy is approximately one-third of steel; as a result, aluminum alloy has gradually substituted for steel. Aluminum alloy bears its own advantages of light-weight and better corrosion resistance, but its formability is inferior to that of steel. In the stamping process, except that aluminum alloy would crack easily, the low elastic modulus makes the aluminum alloy easier to produce a significant springback defect, which would lead to variation of accuracy hard to grapple with. As a result, the design concept of stamping conventional steel sheets cannot be completely applied to the die design of aluminum alloy, which causes the tooling maker to spend more time and money to develop a set of stamping dies. And thus, the computer-aided engineering (CAE)technology becomes even more necessary in helping the die design.
It is well known that the material model including the yield criterion and the hardening rule plays an important role in the CAE analysis for predicting the springback. In the present study, the tension-compression reversal tests were conducted to obtain the stress-strain relations and the Bauschinger effect exhibited in the A5083-O and A6181-T4 sheets. The test results were fitted into different yield criteria and work hardening rules used in different finite element software. The finite element simulations were then preformed for V-bending and U-hat drawing of A5083-O and A6181-T4 sheets, and the results of springback and side-wall curl were compared with those obtained from experiments. It can be concluded from the comparison that the material model which includes the Bauschinger effect renders a more consistent results with the experimental data.
The formability of stamping an engine hood with A6181-T4 was also examined in the present study. The aging phenomenon of A6181-T4 was first observed from aging tests and the test results were included in the subsequent finite element simulations. In order to investigate the difference of forming characteristics between conventional steel and A6181-T4 in the stamping process of an engine hood, the effects of material properties, such as n-value, r-value and yield stress, on the different forming modes were systematically analyzed by the finite element simulations.
In addition, the stamping process of the outer panels of a yacht with A5083-O sheets was developed in the present study to replace the current welding process. Due to the V-shaped deep drawing, the defects of wrinkling and fracture are apt to occurring in the stamping process. In order to avoid the presence of these defects, the deformation mechanism in the stamping process of the yacht outer panels were characterized by the finite element simulations. An optimum die face shape with a proper addendum design was then developed according to the finite element analysis, and an actual stamping die set is scheduled to be manufactured following the suggested die design
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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