小型飼草揉搓機的設(shè)計【含CAD圖紙、說明書】

小型飼草揉搓機的設(shè)計【含CAD圖紙、說明書】,含CAD圖紙、說明書,小型,飼草,揉搓,設(shè)計,cad,圖紙,說明書,仿單 畢業(yè)設(shè)計任務(wù)書 畢業(yè)設(shè)計(論文)題目 小型飼草揉搓機設(shè)計 學(xué)生姓名 專業(yè)班級 學(xué) 號 指導(dǎo)教師 教 研 室 機械設(shè)計教研室 業(yè)設(shè)計任務(wù)、目的、要求： 1、畢業(yè)設(shè)計任務(wù) 復(fù)習(xí)、鞏固機械制造工藝學(xué)、機械制造裝備設(shè)計等系列課程的基本理論；完成竹筷拋光機的研究及設(shè)計（中批量生產(chǎn)），畫出裝配圖和全部零件圖。 2、目的 本次設(shè)計主要任務(wù)是設(shè)計出一種小型飼草揉搓機，它要實現(xiàn)各類秸稈和飼草揉搓成適合家畜喂養(yǎng)大小。在設(shè)計中要充分考慮實際操作性，以及電動機的轉(zhuǎn)速，提高生產(chǎn)率。 通過完成畢業(yè)設(shè)計，全面復(fù)習(xí)、鞏固機械制造工藝學(xué)、機械制造裝備設(shè)計以及相關(guān)課程的基本知識，并運用所學(xué)知識解決機械加工中的工藝、工藝裝備等實際設(shè)計問題，提高分析問題、解決問題的能力。掌握各種手冊、文獻資料在工藝工裝設(shè)計的運用方法。通過文獻檢索、英文翻譯，提高運用計算機和英語的能力，提高學(xué)生的綜合實質(zhì)。 3、具體要求 （1）、完成開題的前期準(zhǔn)備工作，撰寫開題報告1份； （2）、完成規(guī)定的英文文獻[1]翻譯工作，譯文質(zhì)量達到要求。 （3）、完成小型飼草揉搓機的設(shè)計； （4）、畫出小型飼草揉搓機的裝配圖和全部零件圖； （5）、總結(jié)課題成果，撰寫畢業(yè)設(shè)計計算說明書，文本質(zhì)量符合規(guī)范。 （6）、圖紙工作量應(yīng)不少于3張A0幅面，設(shè)計說明書不少于1.5萬字。 （7）、翻譯英文資料一份，數(shù)量不少于12000字符： 指定資料為： [1] Application, Design, and Manufacturing of Conical Involute Gears for Power Transmissions 主要參考文獻與資料： [1] Altinttas,Y.,and Weck,M.,2004,“Chatter Stability in Metal Cutting and Grinding.”CIRP Ann.,53(2) [2] 中國農(nóng)業(yè)機械化科學(xué)研究院編.農(nóng)業(yè)機械設(shè)計手冊[M].北京：中國工業(yè)出版社，1971 [3] 孟憲源，姜琪. 機構(gòu)構(gòu)型與應(yīng)用[M] 北京: 機械工業(yè)出版社，2004.1 [4] 馮炳饒.模具設(shè)計與制造簡明手冊[M] . 上海：上?？萍汲霭嫔?，1998 [5] 李洪. 機械加工工藝手冊[M] . 北京: 北京出版社，1994 [6] 成大仙 《機械設(shè)計手冊》（第1、2、3卷）[M].北京：化學(xué)工業(yè)出版社,2002 [7] 周鳳云主編 《工程材料及運用》（第二版）武漢：華中科技大學(xué)出版社，2002.11 [8] 謝家瀛主編 《機械制造技術(shù)概論》 北京: 機械工業(yè)出版社，2001.7 [9] 孫靖民，梁迎春主編 《機械優(yōu)化設(shè)計》（第四版） 北京：機械工業(yè)出版社，2006.12 [10] 東北重型機械學(xué)院等 . 機床夾具設(shè)計手冊，第二版[M] . 上海：上?？茖W(xué)技術(shù)出版社，1998 [11] 艾新，肖詩綱 . 切削用量手冊[M] . 北京：機械工業(yè)出版社，1985 [12] 濮良貴，紀(jì)名剛主編.機械設(shè)計[M].北京：高等教育出版社，2005 [13] 一機部農(nóng)機研究院編.收獲機械通用件圖冊.北京:技術(shù)標(biāo)準(zhǔn)出版社，1979 [14] 史美堂.金屬材料及熱處理知識.北京：機械工業(yè)出版社, 2005.3 [15] 哈爾濱工業(yè)大學(xué)理論力學(xué)教研室.理論力學(xué)(第6版). 北京：高等教育出版社，2002.8 [16] 校園網(wǎng)維普中文期刊數(shù)據(jù)庫：查閱中文期刊中與本課題有關(guān)的機械制造工藝、機構(gòu)及工裝設(shè)計文獻10篇以上。重點查閱期刊為：機械工藝師，機械制造，機械工程師。 [17] Lubrication Engineering 1997-05,“Friction, Wear and Lubrication of Hybrid Bearing” Wang Zongying Wu Yuhou Shi Weijia 畢業(yè)設(shè)計進度安排： 1、畢業(yè)設(shè)計開題：2012年12月25日前 2、畢業(yè)分散實習(xí)、調(diào)研。(2013年1月8日至2013年2月12日)寒假期間要求學(xué)生進行畢業(yè)實習(xí)與調(diào)研，并結(jié)合畢業(yè)設(shè)計課題寫出調(diào)研報告?！? 3、中期檢查：2013年5月5日前　 4、畢業(yè)設(shè)計結(jié)題、資格審查：2013年上學(xué)期第13周5月7日至11日。 5、預(yù)定答辯時間：2013年上學(xué)期第14周，5月12日至5月20日 課 題 申 報 與 審 查 指導(dǎo)教師（簽名）： 年 月 日 教研室主任（簽名）： 年 月 日 系主任（簽名）： 年 月 日 本科生畢業(yè)設(shè)計開題報告書 題 目: 小型飼草揉搓機的設(shè)計 學(xué)生姓名: 學(xué) 號: 專業(yè)班級: 指導(dǎo)老師: 論文（設(shè)計）題目 小型飼草揉搓機的設(shè)計 課題來源、目的、意義及相關(guān)研究動態(tài)： 由于我國農(nóng)村基本以家庭為單位進行農(nóng)耕養(yǎng)植，家畜飼草以各類農(nóng)作物秸稈為主，各類秸稈須經(jīng)過切碎揉成較柔軟的散碎飼料，才一能完全被牛、羊、豬等牲畜采食消化。以前多以原始手工為主進行加工，不僅勞動強度大、工作環(huán)境惡劣、危險性大、效率低，而且作業(yè)質(zhì)量差。目前雖有部分粉碎機面市，但真正適合農(nóng)民家庭需求的中小型飼草加工機械仍很少，不少養(yǎng)畜戶仍采用原始的手工操作方式切碎秸稈后即直接飼喂，一方面牲畜的適口性差，另一方面秸稈中的營養(yǎng)物質(zhì)因基葉表面角質(zhì)層和硅細胞的嚴(yán)密覆蓋及細胞木質(zhì)素的阻礙而使牲畜難于吸收 本設(shè)計擬針對上述現(xiàn)狀設(shè)計一種適合農(nóng)村家庭使用的飼草揉搓機，動力采用小型（小于8KW）電動機，功能要求能將目前農(nóng)村常見的各類秸稈和飼草揉搓成適合家畜喂養(yǎng)大小且有較高的采食率和消化率。 國內(nèi)外概況和發(fā)展趨勢： 國外許多國家和地區(qū)非常重視秸稈資源的開發(fā)和利用，因此，在秸稈加工設(shè)備和工藝等的研究和應(yīng)用方面起步較早，研究深入，應(yīng)用面廣，成效很高。并且絕大多數(shù)國家和地區(qū)一直注重于研制、發(fā)展和推廣與應(yīng)用自動化程度高、通用性好的大型秸稈加工機具，大幅度提高了生產(chǎn)效率和秸稈的加工質(zhì)量與利用程度。英國在二十世紀(jì)80年代初，就開始利用收獲機械對秸稈進行粉碎等加工。近年來,丹麥多農(nóng)TAARUP) 機械廠生產(chǎn)的多農(nóng)805型飼草加工機械采用55kW以上的拖拉機動力輸出軸驅(qū)動。丹麥皮里士登( PRESIDENT) 有限公司生產(chǎn)的皮里士登100型錘式粉碎機配套動力為5～ 110kW, 生產(chǎn)率達4～5t/ h。國外于20世紀(jì)80年代初研制出一種帶有圓錐或圓柱形桷式料斗的桷式粉碎機。其核心部件是錘片式粉碎裝置。目前, 美、英、加拿大和澳大利亞等國10余家公司生產(chǎn)的此類產(chǎn)品已達數(shù)十種型號, 如“機械手( Farmhand) ”公司的 F890、F900、XG40、F903等,“W1H1O”公司的P12-42型粉碎機。西歐一些公司還相當(dāng)重視生產(chǎn)小型粗飼料粉碎機型。其特點是體積小、質(zhì)量輕、動力消耗少。意大利塞科(Seko) 公司生產(chǎn)的小型桷式粗飼料粉碎機的粉碎刀片沿螺旋線分布, 機具振動小、粉碎均勻。英國艾里溫(Alvan Blanch) 公司生產(chǎn)的38MKⅡ型草捆粉碎機, 粉碎轉(zhuǎn)子只有6 個鉸鏈錘片, 結(jié)構(gòu)簡單, 生產(chǎn)率達2t/ h。美國萬國公司于上世紀(jì)60年代初首次在聯(lián)合收割機上采用切碎機對秸稈進行切碎，其后研制了與 90KW 拖拉機配套的60型秸稈切碎揉碎機。美國JONHAN DEER公司研制生產(chǎn)出立軸式飼草揉碎機配套功率50kw,生產(chǎn)率可達4t/h 以上。 隨著我國畜牧業(yè)由“耗糧型”向“節(jié)約型”的戰(zhàn)略轉(zhuǎn)移以及農(nóng)區(qū)畜牧業(yè)“秸稈過腹還田”工程的推進，秸稈加工也得到了長足的發(fā)展和廣泛的應(yīng)用。我國從 1955 年開始研制錘片式飼料粉碎機，1958 年開始推廣。由于各地自己選型、設(shè)計、制造而沒有標(biāo)準(zhǔn)，1977 年農(nóng)機部制訂了有關(guān)錘片式飼料粉碎機的一般技術(shù)條件和錘片標(biāo)準(zhǔn)。經(jīng)過系列化設(shè)計和標(biāo)準(zhǔn)制訂及實施，我國飼料粉碎機的性能、質(zhì)量和三化程度有了很大提高。 針對農(nóng)作物秸稈利用率和破碎率低等特點，20世紀(jì)80年代后期開始，為適應(yīng)玉米秸稈養(yǎng)牛發(fā)展的需要，我國北方一些省、市、自治區(qū)開發(fā)研制了秸稈飼草揉碎機。這種機械是在錘片式飼料粉碎機基礎(chǔ)上發(fā)展起來的，用齒板代替篩片，在高速旋轉(zhuǎn)的錘片和齒板作用下，將秸桿揉搓成細絲。1989年，黑龍江省畜牧機械化研究所研制的9RC—40型粗飼料揉碎機通過了省級鑒定。隨后在90年代初期和中期，遼寧省農(nóng)機研究所研制的9RF—40型揉搓粉碎機， 吉林省農(nóng)機研究所研制的9RF—40型揉碎機均已通過鑒定。一些工廠企業(yè)也開發(fā)生產(chǎn)了飼料揉碎機械。如河北南農(nóng)縣大地農(nóng)機制造有限公司，生產(chǎn)了玉皇牌多功能秸稈揉碎機。該機高生產(chǎn)能力，低能耗低價位，使用壽命長，可把各類秸稈物料揉成綿軟的絲條狀飼料，在國內(nèi)處于領(lǐng)先地位。北京嘉亮林海農(nóng)牧機械有限責(zé)任公司，生產(chǎn)了9RC—40I型飼料揉碎機，該系列產(chǎn)品適用于中小型牧場和飼養(yǎng)專業(yè)戶使用。還有江西省紅星機械廠生產(chǎn)的93FC—50型揉碎機，山西省大同農(nóng)牧機械廠生產(chǎn)的9RS—40型揉碎機等。近年來，隨著畜牧業(yè)的發(fā)展，越來越多的揉碎機大量涌入市場，揉搓機型號也隨之增多，但是還很難滿足飼料加工業(yè)的發(fā)展需求。 已有工作基礎(chǔ)和解決的主要問題： （1）已有工作基礎(chǔ) 為了搞好本次設(shè)計，我做了大量的工作，如到常德市農(nóng)業(yè)科學(xué)技術(shù)研究所、 常德市聯(lián)嘉機械有限公司、常德農(nóng)機大市場進行調(diào)研和實地考察，在那里我們更進一步的了解到揉搓機的基本原理及工作過程，理論聯(lián)系實踐，使我們看到了許多以前沒有考慮到的問題，這些問題可能是我所設(shè)計的揉搓機能否運用到實際生產(chǎn)中的關(guān)鍵。 我們還到圖書館及網(wǎng)上找到大量的關(guān)于揉搓機的書籍和資料，根據(jù)相關(guān)的資料及實地調(diào)研使我了解到揉搓機大體由軸、皮帶輪、箱體、軸承、軸承座、機架、動力裝置組成，并對其進行實例分析，使我了解揉搓機的工作原理。 在此基礎(chǔ)上，大學(xué)四年我們還學(xué)到很多與此相關(guān)的課程，如：《機械設(shè)計》,《機械制造工藝學(xué)》，《畫法幾何與工程制圖》,《機械原理》,《機械工程材料》，《理論力學(xué)》等相關(guān)課程。這些也為畢業(yè)設(shè)計打下了一定的基礎(chǔ)。 (2)解決的主要問題 參考其他實例分析及設(shè)計，我認為此次揉搓機的設(shè)計主要要考慮以下問題： 1、 揉搓機動力裝置的選擇與使用，根據(jù)電源（交流和直流）、工作條件（溫度、環(huán)境、空間尺寸等）和載荷特點（性質(zhì)、大小、啟動性能和過載情況）來選擇電動機類型和結(jié)構(gòu)形式； 2、 根據(jù)揉搓機的功率選擇電動機的容量，進而確定電動機的轉(zhuǎn)速； 3、 計算總傳動比合理分配各級傳動比，計算傳動裝置的運動和功力參數(shù)，為設(shè)計各級傳動件提供條件； 4、 揉搓機傳動裝置帶傳動的選型，根據(jù)比較平帶傳動、V帶傳動、多楔帶傳動、圓帶傳動、同步帶傳動的優(yōu)缺點選擇最合適的帶傳動裝置； 5、 主要零部件的選型與設(shè)計計算； 6、 機架的設(shè)計； 課題的主要內(nèi)容（觀點）、創(chuàng)新之處： 本次課題，我設(shè)計的揉搓機在滿足普通揉搓機的功能的基礎(chǔ)上準(zhǔn)備做一些改進，設(shè)計一種工作效率更高，操作更簡單，成本低的揉搓機。廣泛的適用于揉搓生產(chǎn)中的揉搓機工序。 運用機械優(yōu)化設(shè)計方法對揉搓機各個部件進行優(yōu)化設(shè)計，以降低制造成本，從而降低揉搓機的價格。 改進的揉搓機，將由原來垂直主軸方向變成平行主軸，這樣秸稈被具有一定間隔、高速旋轉(zhuǎn)錘片的沖擊作用打成短段狀。段狀秸稈在離心慣性作用下，被甩向機體內(nèi)壁，同時又受到螺旋狀氣流的作用，隨氣流產(chǎn)生了螺旋線運動，由此又受到安裝在機體內(nèi)的齒條橫向阻礙而形成的揉搓作用，而被破碎成粗絲狀。特別是當(dāng)秸稈段運動到齒條頂部時，齒條與旋轉(zhuǎn)的錘片對秸稈段產(chǎn)生了更強的揉搓作用，使粗段被揉搓成細絲段。在錘片以及氣流的共同作用下產(chǎn)生軸向運動，經(jīng)過揉碎段部分流向機器的拋送室，然后由風(fēng)扇葉片和氣流產(chǎn)生的拋送作用將秸稈拋送出機外。 研究方法、設(shè)計方案或論文撰寫提綱： 本次設(shè)計，我所設(shè)計的為小型飼草揉搓機。在開始設(shè)計之前，我明確了設(shè)計任務(wù)、收集和整理有關(guān)資料，并作必要的分析。參考有關(guān)的資料及以往的飼草揉搓機的設(shè)計，我認為要做好本次設(shè)計，需明確以下幾個問題： 一、明確任務(wù)書的要求 (1)明確小型飼草揉搓機的設(shè)計要求。因為我所設(shè)計的飼草揉搓機要求粉碎效果好，工作效率高，體積小。因此在設(shè)計時，主要考慮粉碎效果，尺寸方面的要求。 (2)明確零件的生產(chǎn)批量。本次所設(shè)計的飼草揉搓機機屬于中批量生產(chǎn)，在保證零件質(zhì)量的前提下，應(yīng)盡量降低生產(chǎn)成本。 (3)確定飼草揉搓機的體積和重量。此次設(shè)計的為小型飼草揉搓機、體積較小、重量較輕，選用普通機床加工即可。 (4)分析飼草揉搓機的尺寸要求及材料要求。 二、要確定飼草揉搓機結(jié)構(gòu)方案時，又要注意以下幾個問題： (1)確定帶傳動裝置； (2)確定電動機的功率及轉(zhuǎn)速； (3)確定錘片的薄厚及數(shù)量； （4）確定V帶的基準(zhǔn)長度和傳動中心距； 三、飼草揉搓機的有關(guān)計算 （1）計算選擇電動機的容量； （2）計算總傳動比分配各傳動比； （3）計算傳動裝置的運動和動力參數(shù)； （4）計算帶輪功率； （5）驗算主動輪上的包角。 四、設(shè)備的選擇及校核 根據(jù)設(shè)計簡單原則選擇成形設(shè)備，根據(jù)錘片末端線速度確定驅(qū)動功率，對于軸類零件及軸承必須予以校核。 五、繪制揉搓機總裝配圖和零件圖 (1)總裝配圖； (2)軸零件圖； (3)帶輪零件圖； 完成期限和預(yù)期進度： 畢業(yè)設(shè)計開題報告階段：（2013年1.25之前） 其中包括：完成開題報告、畢業(yè)設(shè)計文件資料的準(zhǔn)備。 畢業(yè)分散實習(xí)與畢業(yè)設(shè)計調(diào)研階段：（2013.2.20～2013.3.25） 完成畢業(yè)實習(xí)；完成英文文獻翻譯；完成畢業(yè)設(shè)計資料查找。 中期檢查：（2013.4.5之前） 畢業(yè)設(shè)計結(jié)題、資格審查階段：（2013.5.7～5.11） 其中包括：寫出論文、繪制、打印圖紙、完成所有畢業(yè)設(shè)計文件資料。 ⑤預(yù)定答辯時間：2013年5月12日～5月20日。 主要參考資料： [1]于海燕，劉向陽.秸稈飼料加工機械現(xiàn)狀及進展[J].糧油加工與機械，2003，(6）: 53. [2]劉偉峰，楊明韶，王睿.利用揉碎加工技術(shù)開發(fā)秸稈飼料[J].內(nèi)蒙古農(nóng)業(yè)大學(xué)學(xué)報(自然科學(xué)版), 2003,24(2) [3]吳宗澤，羅圣國.機械設(shè)計課程設(shè)計手冊[M].北京：高等教育出版社，2006.05 [4]張祖立，程玉來，陶棟材.機械設(shè)計基礎(chǔ)[M].中國農(nóng)業(yè)大學(xué)出版社，2004.06 [5]成大先.機械設(shè)計手冊[M].化學(xué)工業(yè)出版社，2004.9 [6]劉剛，趙滿全，王文明，劉偉峰，李林.揉碎機軸向喂入性實驗研究[D].2009. [7]李林，楊明韶，王春光等.9R-40型揉碎機的研制與試驗[J].內(nèi)蒙古農(nóng)牧學(xué)院學(xué)報， 1997，18(3):73 [8]李林，趙滿全，劉偉峰，張三強，催紅梅.揉碎機工作機理的分析與研究[D].2008 [9]哈爾濱工業(yè)大學(xué)理論力學(xué)教研室．理論力學(xué)第七版[M]. 北京：高等教育出版社，2009.7 [10]孫學(xué)強.機械制造基礎(chǔ)[M]. 北京：機械工業(yè)出版社，2008.2 [11]胡鳳蘭.互換性與技術(shù)測量基礎(chǔ)第二版[M].北京：高等教育出版社，2010.5 [12]劉鴻文.材料力學(xué)第四版[M]. 北京：高等教育出版社，2004.1 [13]中國農(nóng)業(yè)機械化科學(xué)研究院.農(nóng)業(yè)機械設(shè)計手冊[M].北京：中國農(nóng)業(yè)科學(xué)技術(shù)出版社， 2007.10.1 [14]張淑娟，全臘珍.畫法幾何與機械制圖[M].北京：中國農(nóng)業(yè)出版社，2007.8 [15]王森華，李行.我國粗飼料加工機械的發(fā)展概述[J].糧油加工與機械，2000.9 [16]劉剛.秸稈揉碎機喂入裝置設(shè)計及性能試驗研究[D].2009.5 [17]韓魯佳，閻巧娟，劉向陽等.中國農(nóng)作物秸稈資源及其利用現(xiàn)狀[J] .農(nóng)業(yè)工程學(xué)報，2002， 18（3）：87-91 [18]高國章，西慶祥，何占松等.國內(nèi)外粗飼料加工技術(shù)及其機具的發(fā)展水平與趨勢[J].農(nóng)機化研 究，1996，2（1）：48-51 [18]李國清．揉碎物料拋送裝置理論分析與試驗研究[D]. 2009.6 [19]王亞波，王金平，胡景媛. 9RS-60 型秸稈揉絲機的研制[J]. 農(nóng)機化研究，2006，6 （6）:125-126 [20]李繼光.錘片式飼料揉搓機的應(yīng)用竅門[J].南方農(nóng)機，2004（3）:35 [21]李向蘭. 9RC-400 型飼草揉搓機的設(shè)計研究[J]. 山西農(nóng)業(yè)大學(xué)學(xué)報 2004（3）:267-269 [22]徐志瑩，陳波. 9RC-430 型揉碎機的結(jié)構(gòu)設(shè)計與參數(shù)選擇[J].農(nóng)業(yè)機械化與電氣化，2006 [23]M.J.ODogherty．A Review of Research on Forage Chopping．Journal of Agriculture Engineering Research．1982，27：267～289 [24]Berentsen O J．Energy requirement for grass chopping．Norway Institute Agriculture Engineering Research，1973，22～65 指導(dǎo)教師意見： 簽名： 年 月 日 開 題 報 告 會 紀(jì) 要 時 間 地 點 與 會 人 員 姓 名 職務(wù) （職稱） 姓 名 職務(wù) （職稱） 姓 名 職務(wù) （職稱） 會議記錄摘要： 會議主持人： 記 錄 人： 年 月 日 教研室意見 教研室主任簽名： 年 月 日 Efficiency enhancement in sheet metal forming analysis with a mesh regularization method J.H. Yoon, H. Huh? D epartment of Mechanical Engineering, Korea Advanced Institute of Science and Technology Science Town, Daejeon 305-701, South Korea Abstract This paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS (non-uniform rational B-spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The state variables calculated from its original mesh geometry are mapped into the new mesh geometry for the next stage or incremental step of a forming analysis. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method. 1. Introduction Numerical simulation of sheet metal forming processes enjoys its prosperity with a burst of development of the computers and the related numerical techniques. The numerical analysis has extended its capabilities for sheet metal forming of complicated geometry models and multi-stage forming. In the case of a complicated geometry model, however, severe local deformation occurs to induce the increase of the computing time and deteriorate the convergence of the analysis. Distortion and severe deformation of the mesh geometry has an effect on the quality of forming analysis results especially in the case of multi-stage forming analysis when the mesh geometry formed by the forming analysis at the first stage is used for the forming analysis at the next stage. This ill behavior of the distorted mesh can be avoided by the reconstruction of the mesh system such as the total or the adaptive remeshing techniques. The adaptive remeshing technique is known to be an efficient method to reduce distortion of element during the simulation, but it still needs tremendous computing and puts restrictions among subdivided elements. ? Effective methods to construct a mesh system have been proposed by many researchers. Typical methods could be r-method [1] in which nodal points are properly rearranged without the change of the total degrees of freedom of the mesh system, h-method [2] in which the number of meshes is increased with elements of the same degrees of freedom, and p-method [3] in which the total degrees of freedom of the mesh system is increased to enhance the accuracy of solutions. Sluiter and Hansen [4] and Talbert and Parkinson [5] constructed the analysis domain as a continuous loop and created elements in sub-loops divided from the main loop. Lo [6] constructed triangular elements in the whole domain and then constructed rectangular elements by combining adjacent triangular elements. In this paper, a mesh regularization method is newly proposed in order to enhance the efficiency of finite element analyses of sheet metal forming. The mesh regularization method automatically finds out distorted elements with searching criteria proposed and composes patches to be modified. Each patch is then extended to three-dimensional surfaces in order to obtain the information of the continuous coordinates on the three-dimensional surface. The surface enclosing each patch is described as a three-dimensional free surface with the use of NURBS (non-uniform rational B-spline). On the basis of the constructed surface, each node is properly arranged to compose regular elements close to a square. The state variables calculated from its original mesh geometry are mapped into the new mesh geometry for the forming analysis at the next stage. Numerical results confirm the efficiency of the proposed method and the accuracy of the result. It is also noted that the present method is effective in the crash analyses of sheet metal members obtained from the forming simulation. 2. Regularization of the distorted element The regularization procedure to modify distorted elements is introduced in order to enhance the efficiency of analysis for the next finite element calculation. The distorted elements are selected with appropriate searching criteria and allocated to several patches for regularization. The patches are extended to three-dimensional surfaces with the use of NURBS for full information of the continuous coordinates on the three-dimensional surface. On obtaining the new coordinates of each node, the distorted elements are regularized to a regular element that is close to a square. 2.1. The criterion of mesh distortion Distorted meshes are selected with the two geometrical criteria: one is the inner angle; and the other is the aspect ratio of the element side, 2.1.1. Inner angle The inner angle of a quadrilateral element should be close to the right angle for good results from finite element calculation. Zhu et al. [7] defined the reasonable element when the four inner angles are formed with the angle of 90?±45?while Lo and Lee [8] proposed the inner angle of 90?±52.5?as the same criterion. The criterion of mesh distortion for the inner angle is determined by constituting Eq. (1). A mesh is regarded as distorted when Eq. (1) is less than π/3 or (δθi)max in Eq. (3) [9] is greater than π/6. The criterion is rather strict in order to avoid the geometrical limitation in case of applying the regularization method in confined regions: 2.1.2. Aspect ratio of the element The ideal aspect ratio of the element side should be unity when the four sides of an element have the same length. The aspect ratio is defined as Eq. (4) and then the distortion is defined when it is less than 5 that could be much less for a strict criterion: max{r12,r23,r34,r41} min{r12,r23,r34,r41} (4) where rijis the length of each element side. 2.2. Domain construction 2.2.1. Construction of the patch Distorted elements selected by the criteria of mesh distortion are distributed in various regions according to the complexity of the shape of formed geometry. These elements are allocated to patches constructed for the efficiency of the algorithm. The shape of patches is made up for rectangular shapes including all distorted elements for expanding the region of regularization and applying to NURBS surface explained in next section. This procedure is shown in Fig. 1. When holes and edges are located between distorted elements, the regions are filled up to make patches a rectangular shape. The patch is then mapped to a three-dimensional free surface by using NURBS surface. The procedure is important to obtain entire information of the continuous coordinates on the three-dimensional surface. NURBS surface can describe the complex shape quickly by using less data points and does not change the entire domain data due to the local change. Fig. 1. Process for construction of a patch . 2.2.2. NURBS surface NURBS surface is generally expressed by Eq. (5) as the p-order in the u-direction and the q-order in the v-direction [10]: nm j=0Ni,p(u)Nj,q(v)wi,jPi,j i=0 S(u,v)=(5) nm j=0Ni,p(u)Nj,q(v)wi,j i=0 where Pi,jis the control points as the u-, v-direction, wi,jthe weight factor and Nu,p(u), Nj,q(u) the basis function that are expressed by Eq. (6): 1if ui≤u≤ui+1,Ni,0 = 0 otherwise,u?uiui+p+1 ?u Ni,p(u)=Ni,p(u)+Ni+1,p?1(u)ui+p?uiui+p+1 ?ui+1 (6) In order to map the nodes from the patches onto the constructed surface, a number of points are created for their coordinates on the NURBS surface. The location of each moving node by applying a regularization method is determined such that the location of a point has the minimum distance between nodes on NURBS surface. The information on the coordinates of the nodal points to be moved is stored to construct a new mesh system. 2.3. Regularization procedure The regularization method is carried out with the unit of a patch that forms a rectangular shape. Finite elements to be regularized is selected by the order of Fig. 2. Each selected element is divided by two triangular elements and then the divided element is made of a right triangular element by relocating the vertex on the circle having the diameter from x1 to x2 as shown in Eq. (7) and Fig. 3. When the procedure terminates, the same procedure is repeated in the opposite direction: The final location of a node relocated by using the regularization method is substituted for the location of a point on NURBS surface. After the regularization procedure is finished, a simple soothing procedure is carried out by Eq. (8) for the rough region generated during the procedure. where PN is the coordinate of a new node, Aithe areas of adjacent elements and Cithe centroid of the adjacent elements. Fig. 3. Regularization scheme by moving nodes 2.4. Level of distortion As a distortion factor, level of distortion (LD) is newly proposed. LD can be used to evaluate the degree of improvement in the element quality: where LD has the value between 0 and 1; when LD =1, the element is an ideal element of a square and when LD =0, the quadrilateral element becomes a triangular element. θiare the four inner angles of an element, so A is the factor for the inner angle. B is the factor for the aspect ratio of element sides and is defined by the hyperbolic tangent function in order to make LD less sensitive to the change of B. For example, when the reasonable aspect ratio of the element side is 1:4, the value of B can be adjusted by applyingα=0.25 andβ=0.6 such that the slope of the function B is changed abruptly around the value of B=0.25. Consequently, the value of LD decreases rapidly when the aspect ratio Bis less than 0.25 while the value of LD increases slowly when the Bis greater than 0.25. This scheme can regulate the inner angle and the aspect ratio to have the equal effect on the LD. 2.5. Mapping of the state variables When the regularized mesh system is used for the next calculation of the forming analysis or the structural analysis, mapping of the state variables is needed for more accurate analysis considering the previous forming history. The mapping procedure is to map the calculated state variables in the original mesh system onto the regularized mesh system. As shown in Fig. 4, a sphere is constructed surrounding a new node such that the state variables of nodes in the sphere have an effect on the state variables of the new node. The state variables of the new node are determined from the state variables of the neighboring nodes in the sphere by imposing the weighting factor inversely proportional to the distance between the two nodes as shown in Eq. (12) where Vjis the state variable calculated on the original mesh system, and rjthe distance between the new node and the neighboring nodes. 3. Numerical examples 3.1. Forming analysis of an oil pan While oil pans are usually fabricated with a two-stage process in the press shop, the present analysis is carried out with a single-stage process as shown in Fig. 5 that describes the punch and die set. The regularization method can be applied to the finite element mesh system whenever neededfor enhancement of the computation efficiency. of In this example for demonstration, the method is applied to the analysis of oil pan forming at two forming intervals for regularization of distorted meshes as directed in Fig. 6. Fig. 7 explains the procedure of the regularization method. Fig. 7(a) shows the deformed shape at the punch stroke of 60% and three parts of mesh distortion by the forming procedure. It indicates that the number of patches to be constructed is 3. Distorted meshes are selected according to the two geometrical criteria for mesh distortion. And then the patches of a rectangular shape are formed to include all distorted elements as shown in Fig. 7(b). Finally, the elements in the patches are regularized as shown in Fig. 7(c). In order to evaluate the degree of improvement in the element quality after applying the regularization method, the value of LD for the regularized mesh system is compared the one for the original mesh system. The LD values for the regularized mesh system have uniform distribution throughout the elements while those for the original mesh system have wide variation as shown in Fig. 8. It means that the quality of the regularized mesh system is enhanced with the same level distortion. Consequently, explicit finite element computation with the regularized mesh system can be preceded with a larger incremental time step as shown in Fig. 9. In this analysis of oil pan forming, the computing time with the regularized mesh system is reduced about 12% even after two times of regularization. The amount of reduction in the computing time can be increased with more frequent regularization. 3.2. Crash analysis of a front side member The crash analysis is usually carried out without considering the forming effect and adopts the mesh system apart form the forming analysis. In case that the forming effect is considered to improve the accuracy and reliability of the analysis results, the mesh system for the forming analysis could be directly used in the crash analysis for the efficiency of the analysis. The mesh system after the forming analysis,however, has too many distorted meshes due to severe deformation and distortion be used directly in the crash analysis without remeshing. One remedy is to construct a new mesh system and the other is to modify the mesh system after the forming analysis. The latter can be very efficient if the remeshing process is successfully carried out. For an efficient remeshing process, the regularization method can be applied to transform distorted meshes into a near square. In this example, a part of the front side member, named ‘front reinforcement’, in Fig. 10 is selected for the crash analysis. The irregular finite elements in the local distorted region of the member after forming analysis are modified to a regular element using the regularization method as shown in Fig. 11 and then the regularized mesh system is used in the crash analysis. The analysis condition is depicted in Fig. 12. The crash analysis with the regularized mesh system could be carried out with a lager time step as shown in Fig. 13 without sacrificing the accuracy of the analysis result. The computing time for the crash analysis was reduced by 40% of the time with the original mesh system. The analysis result was encouraging in both the computing time and the accuracy of the computation result and proved that the regularized mesh system could be used effectively to enhance the efficiency of the numerical analysis. 4. Conclusion A mesh regularization method is newly proposed in order to enhance the efficiency of finite element analyses of sheet metal forming. Meshes in the sheet metal forming analysis are distorted so severely that the subsequent analysis would be difficult or produce poor results. This can be avoided by the present method with the minimum effort of remeshing. Mesh regularization can be carried out during the incremental analysis or for the next stage in multi-stage forming. It is also proved that the analysis efficiency is greatly improved when mesh regularization is carried out for the crash analysis of formed members obtained from the sheet metal forming simulation. 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