十噸位橋式起重機大車運行機構(gòu)設(shè)計
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畢 業(yè) 設(shè) 計論 文 任 務(wù) 書一、 題目及專題:1、題目 十噸位橋式起重機大車運行機構(gòu)設(shè)計 、專題 二、課題來源及選題依據(jù)本次課程設(shè)計的課題來源于正常的生產(chǎn)實踐需求。 選題的相關(guān)數(shù)據(jù)參數(shù): 起重機的起重量Q=10T, 橋架跨度L=22.5m, 大車運行速度Vdc=43.8m/min,工作類型為中級,機構(gòu)運行持續(xù)率為JC%=25, 起重機的估計重量G=168KN,小車的重量為Gxc=40KN,橋架采用箱形結(jié)構(gòu)。 3、 本設(shè)計(論文或其他)應(yīng)達到的要求:1. 了解橋式起重機的大車運行機構(gòu)的相關(guān)知識和工作原理。 2. 完成3張A0圖紙(折合)。 3. 撰寫設(shè)計說明書,內(nèi)容包括:課題的目的、意義、國內(nèi)外動態(tài);研究的主要內(nèi)容;總體方案的擬定和主要參數(shù)的設(shè)計計算;傳動方案的確定及設(shè)計計算,主要工作部件的設(shè)計;主要零件分析計算和校核;參考文獻。文字在30頁左右,條理清楚,計算有據(jù),格式按無錫太湖學(xué)院學(xué)士學(xué)位論文(設(shè)計)規(guī)范化要求。 四、接受任務(wù)學(xué)生: 五、開始及完成日期: 自2012年11月12日 至2013年5月25日六、設(shè)計(論文)指導(dǎo)(或顧問):指導(dǎo)教師簽名 簽名 簽名教研室主任 學(xué)科組組長 簽名 系主任 簽名2012年 11 月 12 日編號畢業(yè)設(shè)計(論文)題目:十噸位橋式起重機大車運行機構(gòu)設(shè)計 2013年5月 25日本科畢業(yè)設(shè)計(論文)誠 信 承 諾 書本人鄭重聲明:所呈交的畢業(yè)設(shè)計(論文) 十噸位橋式起重機大車運行機構(gòu)設(shè)計 是本人在導(dǎo)師的指導(dǎo)下獨立進行研究所取得的成果,其內(nèi)容除了在畢業(yè)設(shè)計(論文)中特別加以標(biāo)注引用,表示致謝的內(nèi)容外,本畢業(yè)設(shè)計(論文)不包含任何其他個人、集體已發(fā)表或撰寫的成果作品。 作者姓名: 2013 年 5 月 25 日畢 業(yè) 設(shè) 計論 文 任 務(wù) 書一、 題目及專題:1、題目 十噸位橋式起重機大車運行機構(gòu)設(shè)計 、專題 二、課題來源及選題依據(jù)本次課程設(shè)計的課題來源于正常的生產(chǎn)實踐需求。 選題的相關(guān)數(shù)據(jù)參數(shù): 起重機的起重量Q=10T, 橋架跨度L=22.5m, 大車運行速度Vdc=43.8m/min,工作類型為中級,機構(gòu)運行持續(xù)率為JC%=25, 起重機的估計重量G=168KN,小車的重量為Gxc=40KN,橋架采用箱形結(jié)構(gòu)。 3、 本設(shè)計(論文或其他)應(yīng)達到的要求:1. 了解橋式起重機的大車運行機構(gòu)的相關(guān)知識和工作原理。 2. 完成3張A0圖紙(折合)。 3. 撰寫設(shè)計說明書,內(nèi)容包括:課題的目的、意義、國內(nèi)外動態(tài);研究的主要內(nèi)容;總體方案的擬定和主要參數(shù)的設(shè)計計算;傳動方案的確定及設(shè)計計算,主要工作部件的設(shè)計;主要零件分析計算和校核;參考文獻。文字在30頁左右,條理清楚,計算有據(jù),格式按無錫太湖學(xué)院學(xué)士學(xué)位論文(設(shè)計)規(guī)范化要求。 四、接受任務(wù)學(xué)生: 五、開始及完成日期: 自2012年11月12日 至2013年5月25日六、設(shè)計(論文)指導(dǎo)(或顧問):指導(dǎo)教師簽名 簽名 簽名教研室主任 學(xué)科組組長 簽名 系主任 簽名2012年 11 月 12 日摘 要橋式起重機是一種工作性能比較穩(wěn)定,工作效率比較高的起重機。隨著我國制造業(yè)的發(fā)展,橋式起重機越來越多的應(yīng)用到工業(yè)生產(chǎn)當(dāng)中。在工廠中搬運重物,機床上下件,裝運工作吊裝零部件,流水在線的定點工作等都要用到起重機。在查閱相關(guān)文獻的基礎(chǔ)上,綜述了橋式起重機的開發(fā)和研究成果,重點對橋式起重機大車運行機構(gòu)、端梁、主梁、焊縫及連接進行設(shè)計并進行強度核算,主要是進行端梁的抗震性設(shè)計及強度計算和支承處的接觸應(yīng)力分析計計算過程。設(shè)計包括電動機,減速器,聯(lián)軸器,軸承的選擇和校核。設(shè)計中參考了許多相關(guān)數(shù)據(jù), 運用多種途徑, 利用現(xiàn)有的條件來完成設(shè)計。本次設(shè)計通過反復(fù)考慮多種設(shè)計方案, 認真思考, 反復(fù)核算, 力求設(shè)計合理;通過采取計算機輔助設(shè)計方法以及參考他人的經(jīng)驗, 力求有所創(chuàng)新;通過計算機輔助設(shè)計方法, 繪圖和設(shè)計計算都充分發(fā)揮計算機的強大輔助功能, 力求設(shè)計高效。關(guān)鍵詞:橋式起重機,大車運行機構(gòu),主梁,端梁,焊縫 AbstractBridge crane is a kind of performance is stability, the working efficiency is relatively high crane. Along with the development of Chinas manufacturing industry,bridge crane is applied to industrial production more and more . Carrying heavy loads in factories , machine tool fluctuation pieces, shipping work on the assembly line for hoisting parts, the designated work with a crane.On the basis of literature review, summarized the bridge crane development and research results, focusing on bridge crane during operation organization, main beam,end beam weld and connection for design and the strength calculation; Mainly for the girders extent design and strength calculation and the support of contact stress analysis program in calculation. Design including motor, reducer, coupling, bearing choosing and checking. The design refer to many related information, reference to apply a variety of ways, make the existing conditions to complete design. By considering various design scheme repeatedly, thinking deeply,strive to design reasonable; By taking computer aided design method and reference the experience of others,strive to make innovation; Through computer aided design method, graphics and design calculations give fullplay to the powerful auxiliary function, computer to design efficient.Key words: bridge crane; during operation organization; main beam; end beam;weld目 錄摘 要IVAbstractV目 錄VI1 緒論1 1.1 起重機背景及其理論1 1.2 實際意義1 1.3 研究現(xiàn)狀及存在問題1 1.4 起重機國內(nèi)與國外發(fā)展動向2 1.4.1 國內(nèi)橋式起重機發(fā)展動向2 1.4.2 國外起重機的發(fā)展動向2 1.5 橋式起重機設(shè)計的主要內(nèi)容3 2 大車運行機構(gòu)的設(shè)計5 2.1 設(shè)計的基本原則和要求5 2.1.1 機構(gòu)傳動方案5 2.1.2 大車運行機構(gòu)具體布置的主要問題:5 2.2 大車運行機構(gòu)的計算6 2.2.1 確定機構(gòu)的傳動方案6 2.2.2 選擇車輪與軌道,并驗算其強度6 2.2.3 運行阻力計算8 2.2.4 選擇電動機9 2.2.5 驗算電動機的發(fā)熱功率條件9 2.2.6 減速器的選擇10 2.2.7 驗算運行速度和實際所需功率10 2.2.8 驗算起動時間10 2.2.9 起動工況下校核減速器功率11 2.2.10 驗算啟動不打滑條件11 2.2.11 選擇制動器13 2.2.12 選擇聯(lián)軸器14 2.2.13 浮動軸的驗算14 2.2.14 緩沖器的選擇153 端梁的設(shè)計17 3.1 端梁的尺寸的確定17 3.1.1端梁的截面尺寸17 3.1.2 端梁總體的尺寸17 3.2 端梁的計算17 3.3 主要焊縫的計算20 3.3.1 端梁端部上翼緣焊縫20 3.3.2 下蓋板翼緣焊縫的剪應(yīng)力驗算214 端梁接頭的設(shè)計22 4.1 腹板和下蓋板螺栓受力計算22 4.2 計算螺栓和焊縫的強度24 4.2.1 螺栓的強度校核24 4.2.2 焊縫的強度校核245 焊接工藝設(shè)計266 結(jié)論與展望30致 謝31參考文獻32V十噸位橋式起重機大車運行機構(gòu)設(shè)計1 緒論1.1 起重機背景及其理論橋式起重機是架設(shè)在高架軌道上運行的一種橋架型起重機,又稱為天車。橋式起重機的橋架沿著鋪設(shè)在兩側(cè)的高架軌道縱向運行,起重小車沿著鋪設(shè)在橋架上的軌道橫向運行,構(gòu)成覆蓋一定面積的工作區(qū)域,這樣可以充分利用橋架下面的空間吊運、裝卸貨物,不受地面設(shè)施、貨物的阻礙。橋式起重機廣泛地應(yīng)用在室內(nèi)外倉庫、廠房、機場、港口和露天貨物場所等處。二十世紀以來,隨著鋼鐵、機械制造業(yè)和鐵路、港口、航空運輸及交通業(yè)的的發(fā)展,大大的促進了起重運輸機械行業(yè)的發(fā)展。對起重運輸機械的性能也提出了更高的要求?,F(xiàn)代起重運輸機械擔(dān)當(dāng)著繁重的貨物搬運任務(wù),是工廠、港口、貨運鐵路等工作部門實現(xiàn)貨物搬運、裝卸現(xiàn)代化、機械化的關(guān)鍵。因而起重機的金屬結(jié)構(gòu)都用質(zhì)量可靠的鋼材制造,并用焊接代替鉚接,不但簡化機構(gòu),縮短了制造時間,而且大大地減輕了自身的重量,焊接結(jié)構(gòu)是現(xiàn)代金屬結(jié)構(gòu)的特征。我國是應(yīng)用起重機械最早的國家之一,我們的祖先采用杠桿搬運石料建造城墻,就是利用起重設(shè)備節(jié)省人力、裝卸貨物的例子。幾千年的封建統(tǒng)治和近代革命戰(zhàn)爭的影響,我國工業(yè)基礎(chǔ)薄弱,自行設(shè)計制造的起重機械很少,絕大多數(shù)起重運輸機械需要依靠進口。新中國成立以來,隨著冶金、鋼鐵工業(yè)的發(fā)展,起重運輸機械也獲得了很好的發(fā)展,全國剛解放就建立了全國最大的大連起重機械廠,1949 年10月,在該廠試制成功我國第一臺起重量為50 噸,跨度為22.5m 的橋式起重機。為培養(yǎng)起重運輸機械專業(yè)的人才,多所高等工業(yè)學(xué)校,創(chuàng)辦了起重運輸機械專業(yè)。到目前為止,我國通用門式起重機和工程起重機已擺脫了仿制進口,完全有能力設(shè)計制造各種大型先進的起重設(shè)備。無論從結(jié)構(gòu)形式,還是性能指針都達到世界領(lǐng)先水平。1.2 實際意義我國起重運輸機械行業(yè)從新中國成立后開始建立并逐步發(fā)展壯大,并已形成了各種類型的產(chǎn)品范圍和龐大的企業(yè)群體,服務(wù)于國家經(jīng)濟各個行業(yè)。改革開房以來,隨著我國經(jīng)濟的快速發(fā)展,我國的起重運輸機械制造業(yè)也取得了長足的進步。目前起重機械銷售應(yīng)用市場的前景非常廣闊,2011年度起重運輸機械行業(yè)銷售額達到2730億元,“十一五”期間平均每年超過15%,20112年度市場依然保持著持續(xù)增長的態(tài)勢。 70年代以來,起重機的類型、規(guī)格、性能和技術(shù)水平都獲得了極大的發(fā)展,除了滿足國內(nèi)經(jīng)濟建設(shè)對起重機日益增長的需要外,還向國外出口各種類型的高性能、高水平的起重機。由此可見,起重機的設(shè)計制造,也能從一個方面反映出一個國家的工業(yè)現(xiàn)代化水平。1.3 研究現(xiàn)狀及存在問題上個世紀70年代以來,隨著生產(chǎn)力和科學(xué)技術(shù)的發(fā)展,起重機械無論在類型及質(zhì)量上都得到了極其迅速的發(fā)展。隨著國民經(jīng)濟的快速發(fā)展,特別是國家加大基礎(chǔ)工程建設(shè)的結(jié)構(gòu)部件和機械設(shè)備的重量也越來越大,特別是大型水電站、石油、化工、港口、冶金、航天以及公用民用高層建筑的安裝作業(yè)的迫切需要,極大的促進了起重機、特別是大型起重機的發(fā)展,起重機的設(shè)計制造技術(shù)得到了迅速發(fā)展。隨著起重機的使用頻率、起重量的增大,對其安全性能、經(jīng)濟性能、效率以及耐久性能等問題,也越來越引起人們的重視,并對設(shè)計理念、方法及手段的探討也日趨深入。由于在起重機設(shè)計中采取常規(guī)設(shè)計方法時,許多構(gòu)件存在不合理性,進而影響整個設(shè)備性能。隨著計算機技術(shù)的應(yīng)用,在很大范圍內(nèi)解決了起重機的設(shè)計中遇到的一些問題,尤其是有限元分析方法與計算機技術(shù)的結(jié)合,為起重機結(jié)構(gòu)的準(zhǔn)確分析提供了強力的有效手段,在實際工程已日益普及,且今后的結(jié)構(gòu)分析從孤立的單個構(gòu)件轉(zhuǎn)變到整體結(jié)構(gòu)系統(tǒng)的整體空間分析。1.4 起重機國內(nèi)與國外發(fā)展動向起重機作為一種古老的機械,時至今日,在其承載方式、驅(qū)動裝置、取物機構(gòu)、控制方法及安全等方面上都有了完善的發(fā)展,其設(shè)計理念、制造工藝、檢測方法等都日趨規(guī)范、完善,已經(jīng)成為安全可靠的機械。隨著生產(chǎn)力發(fā)展,起重機的種類、形式也需要相應(yīng)地發(fā)展和創(chuàng)新,性能也需要不斷加強與完善。隨著現(xiàn)代化設(shè)計方法的建立,以及計算機輔助設(shè)計等現(xiàn)代設(shè)計手段的廣泛應(yīng)用,起重機設(shè)計理念和方法得到了進一步的發(fā)展,其它技術(shù)領(lǐng)域和相鄰工業(yè)部門不斷取得的新科技成果在起重機上不斷的滲透、推廣應(yīng)用等,使得起重機的各方面都不斷地發(fā)得到展。因此,起重機向現(xiàn)代化、智能化、數(shù)字化、更安全可靠方便的方向不斷發(fā)展。1.4.1 國內(nèi)橋式起重機發(fā)展動向加入世貿(mào)組織后,雖然國內(nèi)市場(特別是配件)將受到較大沖擊,但同時也給我們帶來了大量的新技術(shù),使國內(nèi)主要起重機械生產(chǎn)企業(yè)更深刻認識到差距,更深刻地了解國產(chǎn)起重機械存在的致命問題,引導(dǎo)主要起重機械設(shè)備生產(chǎn)企業(yè)的進行進一步的技術(shù)創(chuàng)新。隨著機械起重產(chǎn)品十多年來隨著技術(shù)的引進、消化、吸收,有了長足的進步,產(chǎn)品性能、可靠性、外觀都有較大幅度的改善和提升,但同國外同類型產(chǎn)品比較來看,仍然存在較大差距,就工程起重機而言,今后的發(fā)展主要表現(xiàn)在如下幾個方面:(1)整機性能,隨著先進技術(shù)和新型材料的應(yīng)用,同種型號的產(chǎn)品,整機重量將要比現(xiàn)在輕15%左右。隨著結(jié)構(gòu)分析應(yīng)用和先進設(shè)備的使用,使得起重機的結(jié)構(gòu)形式更加合理(2)高性能、高可靠性的配件,零部件選擇范圍大、適應(yīng)性能好,使得起重機性能得到充分發(fā)揮(3)智能數(shù)字控制顯示系統(tǒng)的推廣應(yīng)用和電液比例控制系統(tǒng)的廣泛應(yīng)用(4)完善操作方法,使得起重機更方便、舒適、安全(5)向吊重量大、起升高度、幅度更大的大噸位方向發(fā)展。1.4.2 國外起重機的發(fā)展動向(1)重點產(chǎn)品大型化,高速化和專用化。由于工業(yè)生產(chǎn)規(guī)模不斷擴大,生產(chǎn)效率日益提高,以及產(chǎn)品生產(chǎn)過程中物料將卸搬運費用所占比例逐漸增加,促使大型或高速起重機的需求量不斷增長,起重量越來越大,工作速度越來越高,并對能耗和可靠性提出更嚴格的要求。目前世界上最大的履帶起重機起重量3000t,最大的橋式起重機起升重量200t,集裝箱岸連裝卸橋小車的最大運行速度已達350m/min,堆垛起重機級最大運行速度240m/min,垃圾處理用起重機的起升速度達100m/min。(2)系列產(chǎn)品模塊化、組合化和標(biāo)準(zhǔn)化用模塊化設(shè)計代替?zhèn)鹘y(tǒng)的整機設(shè)計方法,將起重機上功能基本相同的構(gòu)件、部件和零件制成有多種用途的標(biāo)準(zhǔn)件,有相同連接方法和可互換的標(biāo)準(zhǔn)模塊,通過不同模塊的相互組合,形成不同功能和規(guī)格的起重機。(3)通用產(chǎn)品小型化、輕型化和多樣化絕大部分的起重機是在通用的場合使用,工作重量不是很重。這類起重機生產(chǎn)批量大、用途廣,考慮到綜合效益,要求起重機重量降低高度,簡化結(jié)構(gòu),減小自重和輪壓,使得整體建筑物高度下降,建筑結(jié)構(gòu)輕型化,降低造價,降低成本。(4)產(chǎn)品性能自動化、智能化和數(shù)字化起重機的更新和發(fā)展,在很大程度上取決于電氣傳動控制系統(tǒng)的發(fā)展。將機械技術(shù)和電子技術(shù)相結(jié)合,將先進的計算機技術(shù)、電子技術(shù)、電力技術(shù)、光纜技術(shù)、液壓技術(shù)、模糊控制技術(shù)等技術(shù)應(yīng)用到機械的驅(qū)動和控制系統(tǒng),實現(xiàn)起重機的自動化和智能化。大型高效起重機新一代電氣控制裝置已發(fā)展為全電子數(shù)字化控制系統(tǒng)。(5)產(chǎn)品組合成套化、集成化和柔性化在起重機單機自動化的基礎(chǔ)上,通過計算機把各種起重運輸機械組成一個物料搬運集成系統(tǒng),通過中央控制室的控制,與生產(chǎn)設(shè)備有機結(jié)合,與生產(chǎn)系統(tǒng)協(xié)調(diào)配合。(6)產(chǎn)品構(gòu)造新型化、美觀化和實用化結(jié)構(gòu)方面采用薄壁型材和異形鋼、減少結(jié)構(gòu)的拼接焊縫,提高抗疲勞性能。采用各種高強度低合金鋼新材料,提高承載能力,改善受力條件,減輕自重和增加外形美觀。1.5 橋式起重機設(shè)計的主要內(nèi)容 大車運行機構(gòu)的設(shè)計: 了解設(shè)計的基本原則和要求,確定機構(gòu)傳動方案, 解決大車運行機構(gòu)具體布置的主要問題, 計算大車運行機構(gòu)的相關(guān)計算, 通過計算結(jié)果選擇車輪與軌道,驗算校核其強度。 選擇電動機,驗算電動機的發(fā)熱功率條件 選擇合適的減速器 驗算運行速度和實際所需功率 驗算起動時間,并驗算啟動不打滑條件 選擇制動器、聯(lián)軸器 驗算浮動軸 選擇緩沖器 端梁的設(shè)計: 焊縫的計算,選擇合適的焊接方法, 端梁端部上翼緣焊縫, 驗算下蓋板翼緣焊縫的剪應(yīng)力, 設(shè)計端梁接頭 計算腹板和下蓋板螺栓受力 計算校核螺栓和焊縫的強度 設(shè)計焊接工藝 2 大車運行機構(gòu)的設(shè)計2.1 設(shè)計的基本原則和要求大車運行機構(gòu)的設(shè)計通常和橋架的設(shè)計一起考慮,兩者的設(shè)計工作要交叉進行,一般的設(shè)計步驟:1)確定橋架結(jié)構(gòu)的形式和大車運行機構(gòu)的傳方式2)布置橋架的結(jié)構(gòu)尺寸3)安排大車運行機構(gòu)的具體位置和尺寸4)綜合考慮二者的關(guān)系和完成部分的設(shè)計 對大車運行機構(gòu)設(shè)計的基本要求是:1)機構(gòu)要緊湊,重量要輕2)和橋架配合要合適,這樣橋架設(shè)計容易,機構(gòu)好布置3)盡量減輕主梁的扭轉(zhuǎn)載荷,不影響橋架剛度4)維修檢修方便,機構(gòu)布置合理2.1.1 機構(gòu)傳動方案大車機構(gòu)傳動方案,基本分為兩類:主要分為集中驅(qū)動和分別驅(qū)動。集中驅(qū)動又分為高速和低速兩種。高速集中驅(qū)動的大車運行機構(gòu),由電動機通過制動輪與聯(lián)軸器、傳動軸直接連接,減速器安裝在主梁走臺的兩端。采用這種運行機構(gòu)傳動方案的傳動軸轉(zhuǎn)速較高,傳遞轉(zhuǎn)矩小,而傳動軸和軸系零件尺寸也較小、傳動機構(gòu)的重量輕。低速集中驅(qū)動的大車運行機構(gòu),由電機通過制動輪直接與減速器聯(lián)接,減速器安裝在主梁走臺的中間。采用這種傳動方案傳動軸轉(zhuǎn)速低,比較安全,但傳動軸轉(zhuǎn)矩大,因而一些零件的尺寸較大,使得整個機構(gòu)較重。 分別驅(qū)動是在橋式起重機上裝兩套相同,但互不相連的驅(qū)動裝置。其特點是省去了傳動軸而使運行機構(gòu)自重減輕,由于分組性能好,使得安裝和維護保養(yǎng)都很方便。 分別傳動和集中傳動,橋式起重機常用的跨度(10.5-32M)范圍均可用分別傳動的方案本設(shè)計采用分別傳動的方案。2.1.2 大車運行機構(gòu)具體布置的主要問題:(1)聯(lián)軸器的選擇(2)軸承位置的安排(3)軸長度的確定這三著是互相聯(lián)系的。在具體布置大車運行機構(gòu)的零部件時應(yīng)該注意以幾點: (1)因為大車運行機構(gòu)要安裝在起重機橋架上,橋架的運行速度很高,而且受載之后向下?lián)锨?,機構(gòu)零部件在橋架上的安裝可能不十分準(zhǔn)確,所以如果單從保持機構(gòu)的運動性能和補償安裝的不準(zhǔn)確性著眼,凡是靠近電動機、減速器和車輪的軸,最好都用浮動軸。 (2)為了減少主梁的扭轉(zhuǎn)載荷,應(yīng)該使機構(gòu)零件盡量靠近主梁而遠離走臺欄桿;盡量靠近端梁,使端梁能直接支撐一部分零部件的重量。 (3)對于分別傳動的大車運行機構(gòu)應(yīng)該參考現(xiàn)有的資料,在浮動軸有足夠的長度的條件下,使安裝運行機構(gòu)的平臺減小,占用橋架的一個節(jié)間到兩個節(jié)間的長度,總之考慮到橋架的設(shè)計和制造方便。(4)制動器要安裝在靠近電動機,使浮動軸可以在運行機構(gòu)制動時發(fā)揮吸收沖擊動能的作用。2.2 大車運行機構(gòu)的計算已知數(shù)據(jù):起重機的起重量Q=10T,橋架跨度L=22.5m,大車運行速度Vdc=43.8m/min,工作類型為中級,機構(gòu)運行持續(xù)率為JC%=25,起重機的估計重量G=168KN,小車的重量為Gxc=40KN,橋架采用箱形結(jié)構(gòu)。計算過程如下:2.2.1 確定機構(gòu)的傳動方案本起重機采用分別傳動的方案如圖2.11電動機 2制動器 3高速浮動軸 4聯(lián)軸器 5減速器 6聯(lián)軸器 7低速浮動軸 8聯(lián)軸器 9車輪圖2.1 大車運行機構(gòu)2.2.2 選擇車輪與軌道,并驗算其強度按照如圖所示的重量分布,計算大車的最大輪壓和最小輪壓:滿載時的最大輪壓:Pmax = (2.1)= =95.6KN 空載時最大輪壓:Pmax= = =50.2KN 空載時最小輪壓:Pmin = (2.2) = =33.8KN式中的e為主鉤中心線離端梁的中心線的最小距離e=1.5m載荷率:Q/G=100/168=0.595由1表19-6選擇車輪:當(dāng)運行速度為Vdc=30-60m/min,Q/G=0.595時工作類型為中級時,車輪直徑Dc=500mm,軌道為P38的許用輪壓為150KN,故可用。(1)疲勞強度的計算疲勞強度計算時的等效載荷:Qd=2Q=0.6*100000=60000N 式中2等效系數(shù),由1表4-8查得2=0.6車論的計算輪壓:Pj= KCI r Pd (2.3)=1.050.8977450 =72380N式中:Pd車輪的等效輪壓Pd = = =77450Nr載荷變化系數(shù),查1表19-2,當(dāng)Qd/G=0.357時,r=0.89,Kc1沖擊系數(shù),查1表19-1。第一種載荷當(dāng)運行速度為V=1.5m/s時,Kc1=1.05根據(jù)點接觸情況計算疲勞接觸應(yīng)力: sj=4000 (2.4) =4000 =13555Kg/cm2sj =135550N/cm2式中r軌頂弧形半徑,由3附錄22查得r=300mm,對于車輪材料ZG55II,當(dāng)HB320時,sjd =160000-200000N/cm2,因此滿足疲勞強度計算。(2)強度校核最大輪壓的計算:Pjmax=KcIIPmax (2.5)=1.195600=105160N式中KcII沖擊系數(shù),由3表2-7第II類載荷KcII=1.1按點接觸情況進行強度校核的接觸應(yīng)力:4jmax= (2.6)=15353Kg/cm2jmax =153530N/cm2車輪采用ZG55II,查1表19-3得,HB320時, j=240000-300000N/cm2,jmax j。故強度足夠。2.2.3 運行阻力計算摩擦總阻力距Mm=(Q+G)(K+*d/2) (2.7)由1表19-4 Dc=500mm車輪的軸承型號為:22220K, 軸承內(nèi)徑和外徑的平均值為:(100+180)/2=140mm。由1中表9-2到表9-4查得:滾動摩擦系數(shù)K=0.0006m,軸承摩擦系數(shù)=0.02,附加阻力系數(shù)=1.5,代入上式中:當(dāng)滿載時的運行阻力矩:Mm(Q=Q)= Mm(Q=Q)=b(Q+G)( k +m) =1.5(100000+168000)(0.0006+0.020.14/2) =804Nm 運行摩擦阻力:Pm(Q=Q)= (2.8) =3216N空載時:Mm(Q=0)=G(K+d/2) =1.5168000(0.0006+0.020.14/2) =504NP m(Q=0) = Mm(Q=0)/(Dc/2) =5042/0.5 =2016N2.2.4 選擇電動機電動機靜功率:Nj=PjVdc/(60m ) (2.9)=321643.8/60/0.95/2=2.54KW式中Pj=Pm(Q=Q)(P m(Q=0)=2016N)滿載運行時的靜阻力,m=2驅(qū)動電動機的臺數(shù)初選電動機功率:N=Kd*Nj=1.3*2.54=3.3KW式中Kd電動機功率增大系數(shù),由1表9-6查得Kd=1.3,查2表31-27選用電動機YR160M-8;Ne=4KW,n1=705r/min,(GD2)=0.567kg/m2,電動機的重量Gd=160kg2.2.5 驗算電動機的發(fā)熱功率條件等效功率:Nx=K25rNj (2.10) =0.751.32.54 =2.48KW式中K25工作類型系數(shù),由1表8-16查得當(dāng)JC%=25時,K25=0.75,r由1按照起重機工作場所得tq/tg=0.25,由1圖8-37估得r=1.3由此可知:NxNe,故初選電動機發(fā)熱條件通過。選擇電動機:YR160M-82.2.6 減速器的選擇車輪的轉(zhuǎn)數(shù):nc=Vdc/(Dc) (2.11)=43.8/3.14/0.5=57.3rpm機構(gòu)傳動比:i。=n1/nc=705/57.3=12.3查2表19-11,選用兩臺ZLZ-160-12.5-IV減速器i=12.5;N=9.1KW,當(dāng)輸入轉(zhuǎn)速為750rpm,可見NjN中級。(電動機發(fā)熱條件通過,減速器:ZLZ-160-12.5-IV )2.2.7 驗算運行速度和實際所需功率實際運行的速度:Vdc=Vdc i。/ i。 (2.12) =43.812.3/12.5=42.43m/min誤差:=(Vdc- V dc)/ Vdc (2.13)=(43.8-42.43)/43.8100%=6%15%合適實際所需的電動機功率:N j=NjV dc/ Vdc (2.14)=2.5442.43/43.8=2.49KW由于NjN,故所選減速器功率合適。2.2.10 驗算啟動不打滑條件由于起重機室內(nèi)使用,故坡度阻力及風(fēng)阻力不考慮在內(nèi).以下按三種情況計算.(1)兩臺電動機空載時同時驅(qū)動:n=nz (2.18)式中 p1=33.8+50.2=84KN主動輪輪壓p2= p1=84KN從動輪輪壓 f=0.2粘著系數(shù)(室內(nèi)工作)nz防止打滑的安全系數(shù).nz1.051.2n = =2.97nnz,故兩臺電動機空載啟動不會打滑(2)事故狀態(tài)當(dāng)只有一個驅(qū)動裝置工作,而無載小車位于工作著的驅(qū)動裝置這一邊時,則n=nz式中p1=50.2KN主動輪輪壓 p2=2+=233.8+50.2=117.8KN從動輪輪壓一臺電動機工作時空載啟動時間= =13.47 sn= =2.94nnz,故不打滑.(3)事故狀態(tài)當(dāng)只有一個驅(qū)動裝置工作,而無載小車遠離工作著的驅(qū)動裝置這一邊時,則n=nz式中P1=33.8KN主動輪輪壓P2 =2=33.8+2*50.2=134.2KN從動輪輪壓= 13.47 S 與第(2)種工況相同n=1.89 故也不會打滑結(jié)論:根據(jù)上述不打滑驗算結(jié)果可知,三種工況均不會打滑2.2.11 選擇制動器由1中所述,取制動時間tz=5s按空載計算動力矩,令Q=0,得:Mz= (2.19)式中= =-19.2NmPp=0.002G=1680000.002=336NPmin=G=1344NM=2制動器臺數(shù).兩套驅(qū)動裝置工作Mz=41.2 Nm現(xiàn)選用兩臺YWZ-200/25的制動器,查1表18-10其制動力矩M=200 Nm,為避免打滑,使用時將其制動力矩調(diào)制3.5 Nm以下。2.2.12 選擇聯(lián)軸器根據(jù)傳動方案,每套機構(gòu)的高速軸和低速軸都采用浮動軸.(1)機構(gòu)高速軸上的計算扭矩:=110.61.4=154.8 Nm (2.20)式中MI連軸器的等效力矩. MI=255.3=110.6 Nm等效系數(shù) 取=2查2表2-7Mel=9.75*=55.3 Nm由2表33-20查的:電動機Y160M1-8,軸端為圓柱形,d1=48mm,L=110mm;由219-5查得ZLZ-160-12.5-iv的減速器,高速軸端為d=32mm,l=58mm,故在靠電機端從由表2選聯(lián)軸器ZLL2(浮動軸端d=40mm;MI=630Nm,(Gd2ZL=0.063Kgm,重量G=12.6Kg) ;在靠近減速器端,由2選用兩個聯(lián)軸器ZLD,在靠近減速器端浮動軸端直徑為d=32mm;MI=630 Nm, (Gd2)L=0.015Kgm, 重量G=8.6Kg. 高速軸上轉(zhuǎn)動零件的飛輪矩之和為: (Gd2)ZL+(Gd2)L=0.063+0.015=0.078 Kgm與原估算的基本相符,故不需要再算。(2)低速軸的計算扭矩: =154.815.750.95=2316.2 Nm2.2.13 浮動軸的驗算(1)疲勞強度的計算低速浮動軸的等效力矩:MI=1Meli=1.455.312.50.95=919.4Nm式中1等效系數(shù),由2表2-7查得1=1.4由上節(jié)已取得浮動軸端直徑D=40mm,故其扭轉(zhuǎn)應(yīng)力為: N/cm2 (2.21)由于浮動軸載荷變化為循環(huán)(因為浮動軸在運行過程中正反轉(zhuǎn)矩相同),所以許用扭轉(zhuǎn)應(yīng)力為: (2.22) =4910 N/cm2式中,材料用45號鋼,取sb=60000 N/cm2; ss=30000N/cm2,則t-1=0.22sb=0.2260000=13200N/cm2;ts=0.6ss=0.630000=18000N/cm2K=KxKm=1.61.2=1.92考慮零件的幾何形狀表面狀況的應(yīng)力集中系數(shù)Kx=1.6,Km=1.2,nI=1.4安全系數(shù),由2表2-21查得tnt-1k 故疲勞強度驗算通過。(2)靜強度的計算計算強度扭矩:Mmax=2MelI (2.23) =2.555.312.50.95=1641.7 Nm式中2動力系數(shù),查2表2-5的2=2.5扭轉(zhuǎn)應(yīng)力:t=3800N/cm2許用扭轉(zhuǎn)剪應(yīng)力:N/cm2ttII,故強度驗算通過。高速軸所受扭矩雖比低速軸小,但強度還是足夠,故高速軸驗算省去。2.2.14 緩沖器的選擇(1)碰撞時起重機的動能 W動= (2.24) G帶載起重機的重量G=168000+1000000.1 =178000N V0碰撞時的瞬時速度,V0=(0.30.7)Vdx g重力加速度取10m/s2則W動= =5006.25 N m(1)緩沖行程內(nèi)由運行阻力和制動力消耗的功 W阻=(P摩+P制)S 式中P摩運行阻力,其最小值為Pmin=Gf0min=1780000.008=1424N f0min最小摩擦阻力系數(shù)可取f0min=0.008 P制制動器的制動力矩換算到車輪踏面上的力,亦可按最大制動減速度計算 P制 =178000.5=9790N =0.55 m /s2 S緩沖行程取S=140 mm因此W阻=(1424+9790)0.14=1569.96Nm(3)緩沖器的緩沖容量一個緩沖器要吸收的能量也就是緩沖器應(yīng)該具有的緩沖容量為: (2.25)=5006.25-1569.96 =3436.29Nm式中 n緩沖器的個數(shù) 取n=1由1表22-3選擇彈簧緩沖器彈簧D=120mm,d=30mm3 端梁的設(shè)計3.1 端梁的尺寸的確定3.1.1端梁的截面尺寸(1)端梁截面尺寸的確定:上蓋板d1=10mm,中部下蓋板d1=10 mm頭部下蓋板d2=12mm按照1表19-4直徑為500mm的車輪組尺寸,確定端梁蓋板寬度和腹板的高度時,首先應(yīng)該配置好支承車輪的截面,其次再確定端梁中間截面的尺寸。配置的結(jié)果,車輪輪緣距上蓋板底面為25mm;車輪兩側(cè)面距離支承處兩下蓋板內(nèi)邊為10 mm,因此車輪與端梁不容易相碰撞;并且端梁中部下蓋板與軌道便的距離為55 mm。如圖示3.1圖3.1 端梁的截面尺寸3.1.2 端梁總體的尺寸大車輪距的確定:K=()L=()22.5=2.063.3m取K=3300 端梁的高度 H0=(0.40.6)H 主取H0=500確定端梁的總長度L=41003.2 端梁的計算(1)計算載荷的確定設(shè)兩根主梁對端梁的作用力Q(G+P)max相等,則端梁的最大支反力:RA= (3.1)式中 K大車輪距,K=330cm Lxc小車輪距,Lxc=200cm a2傳動側(cè)車輪軸線至主梁中心線的距離,取a2=70 cm =114237N 因此RA= =117699N (2)端梁垂直最大彎矩端梁在主梁支反力作用下產(chǎn)生的最大彎矩為: Mzmax=RAa1=11769960=7.06106N a1導(dǎo)電側(cè)車輪軸線至主梁中心線的距離,a1=60 cm。(3)端梁的水平最大彎矩端梁因車輪在側(cè)向載荷下產(chǎn)生的最大水平彎矩: =Sa1 (3.2)式中:S車輪側(cè)向載荷,S=lP; l側(cè)壓系數(shù),查得,l=0.08; P車輪輪壓,即端梁的支反力P=RA因此: =lRAa1=0.0811769960=564954Ncm端梁因小車在起動、制動慣性載荷作用下而產(chǎn)生的最大水平彎矩: =a1 (3.3)式中小車的慣性載荷:= P1=37000/7=5290N 因此: =327018Ncm 比較和兩值可知,應(yīng)該取其中較大值進行強度計算。(4)端梁的強度驗算端梁中間截面對水平重心線X-X的截面模數(shù): (3.4) =2380.8端梁中間截面對水平重心線X-X的慣性矩: (3.5) =2380.8 =59520 端梁中間截面對垂直重心線Y-Y的截面模數(shù): (3.6) =1154.4 端梁中間截面對水平重心線X-X的半面積矩: (3.7) =1325.6 端梁中間截面的最大彎曲應(yīng)力: (3.8) =2965+489=3454N/cm2端梁中間截面的剪應(yīng)力: (3.9) =2120 N/cm2 端梁支承截面對水平重心線X-X的慣性矩、截面模數(shù)及面積矩的計算如下: 首先求水平重心線的位置水平重心線距上蓋板中線的距離: C1= =5.74 cm水平重心線距腹板中線的距離: C2=5.74-0.5-0.512.7 =-1.11 cm 水平重心線距下蓋板中線的距離: C3=(12.7+0.5+0.6)-5.74 =8.06cm端梁支承截面對水平重心線X-X的慣性矩: =4013+4015.742+212.730.6+212.70.61.112+2111.23+2111.28.062=3297cm4端梁支承截面對水平重心線X-X的最小截面模數(shù): = (3.10) =3297 =406.1 cm3 端梁支承截面水平重心線X-X下部半面積矩: =2111.28.06+(8.06-0.6)0.6(8.06-0.6)/2 =229.5 cm3 端梁支承截面附近的彎矩: =RAd=11769914=1647786Ncm 端梁支承截面的彎曲應(yīng)力: (3.11) =4057.6N/cm2 端梁支承截面的剪應(yīng)力: (3.12) =6827.4 N/cm2 端梁支承截面的合成應(yīng)力: (3.13) =12501.5 N/cm2 端梁材料的許用應(yīng)力: sdII=(0.800.85) sII =(0.800.85)16000=1280013600 N/cm2 tdII=(0.800.85) tII = (0.800.85)9500 =76008070 N/cm2 驗算強度結(jié)果,所有計算應(yīng)力均小于材料的許用應(yīng)力,故端梁的強度滿足要求。3.3 主要焊縫的計算3.3.1 端梁端部上翼緣焊縫端梁支承截面上蓋板對水平重心線X-X的截面積矩:=4015.74=229.6 cm3端梁上蓋板翼緣焊縫的剪應(yīng)力: =4878.8 N/cm2 式中n1上蓋板翼緣焊縫數(shù); Hf焊肉的高度,取hf=0.6 cm3.3.2 下蓋板翼緣焊縫的剪應(yīng)力驗算端梁支承截面下蓋板對水平重心線X-X的面積矩:=2121.28.06=232.128 cm3端梁下蓋板翼緣焊縫的剪應(yīng)力: =4929.8 N/cm2由1表查得t=9500 N/cm2,因此焊縫計算應(yīng)力滿足要求。4 端梁接頭的設(shè)計端梁的安裝接頭設(shè)計在端梁的中部,根據(jù)端梁輪距K大小,則端梁有一個安裝接頭。端梁的街頭的上蓋板和腹板焊有角鋼做的連接法蘭,下蓋板的接頭用連接板和受剪切的螺栓連接。頂部的角鋼是頂緊的,其連接螺栓基本不受力。同時在下蓋板與連接板鉆孔是應(yīng)該同時鉆孔。如下圖為接頭的安裝圖 圖4.1 接頭安裝圖4.2 接頭安裝下蓋板與連接板的連接采用M18的螺栓,而角鋼與腹板和上蓋板的連接采用M16的螺栓。4.1 腹板和下蓋板螺栓受力計算(1)腹板最下一排螺栓受力最大,每個螺栓所受的拉力為:N拉= (4.1)=12500N(2)下腹板每個螺栓所受的剪力相等,其值為: N剪= (4.2) = =7200N式中 n0 下蓋板一端總受剪面數(shù);n0=12 N剪下蓋板一個螺栓受剪面所受的剪力: 編號題目:十噸位橋式起重機大車運行機構(gòu)設(shè)計 信機 系 機械工程及自動化 專業(yè)2013年5月25日目 錄一、畢業(yè)設(shè)計(論文)開題報告二、畢業(yè)設(shè)計(論文)外文資料翻譯及原文三、學(xué)生“畢業(yè)論文(論文)計劃、進度、檢查及落實表”四、實習(xí)鑒定表畢業(yè)設(shè)計(論文)開題報告題目:十噸位橋式起重機大車運行機構(gòu)設(shè)計 2012年11月25日 課題來源生產(chǎn)實踐需求科學(xué)依據(jù)(包括課題的科學(xué)意義;國內(nèi)外研究概況、水平和發(fā)展趨勢;應(yīng)用前景等)1 課題的科學(xué)意義橋式起重機廣泛地應(yīng)用在室內(nèi)外倉庫、廠房、碼頭和露天貯料場等處。二十世紀以來,由于鋼鐵、機械制造業(yè)和鐵路、港口及交通運輸業(yè)的的發(fā)展,促進了起重運輸機械的發(fā)展。對起重運輸機械的性能也提出了更高的要求。現(xiàn)代起重運輸機械擔(dān)當(dāng)著繁重的物料搬運任務(wù),是工廠、鐵路、港口及其他部門實現(xiàn)物料搬運機械化的關(guān)鍵。2 國內(nèi)外研究概況、水平和發(fā)展趨勢 起重機作為一種古老的機械,時至今日,在其承載結(jié)構(gòu)、驅(qū)動機構(gòu)、取物裝置、控制系統(tǒng)及安全裝置等各方面都有了很大的發(fā)展,其設(shè)計理論、制造工藝、檢測手段等都逐漸趨于完善和規(guī)范化,并已經(jīng)成為一種較完善的機械。但由于生產(chǎn)發(fā)展提出新的使用要求,起重機的種類、形式也需要相應(yīng)地發(fā)展和創(chuàng)新,性能也需要不斷變化與究善。由于現(xiàn)代化設(shè)計方法的建立和計算機輔助設(shè)計等現(xiàn)代設(shè)計手段的應(yīng)用,使起重機設(shè)計思維觀念和方法有了進一步的更新,其它技術(shù)領(lǐng)域和相鄰工業(yè)部門不斷取得的新科技成果在起重機上的滲透、推廣應(yīng)用等,更使起重機的各方面不斷地豐富更新。因此,起重機面向現(xiàn)代化、智慧化、更安全可靠方便的方向發(fā)展。3 應(yīng)用現(xiàn)狀及其前景加入世貿(mào)組織后,雖然國內(nèi)市場(特別是配套件)將受到較大沖擊,但同時也給我們帶來新技術(shù)的應(yīng)用,使國內(nèi)主機和配套件企業(yè)更清晰認識到差距,更多地了解國產(chǎn)產(chǎn)品存在的致命問題,必將引導(dǎo)主機和配套件企業(yè)的技術(shù)創(chuàng)新和技術(shù)進步。隨著工程機械產(chǎn)品近十年來隨著技術(shù)的引進、消化、吸收,有了長足的進步,產(chǎn)品性能、可靠性、外觀都有較大幅度的提高,但同國外工程機械比較來看,還存在較大差距,就工程起重機而言,今后的發(fā)展主要表現(xiàn)在如下幾個方面:(1)整機性能,由于先進技術(shù)和新材料的應(yīng)用,同種型號的產(chǎn)品,整機重量要輕20%左右。隨著結(jié)構(gòu)分析應(yīng)用和先進設(shè)備的使用,結(jié)構(gòu)形式更加合理(2)高性能、高可靠性的配套件,選擇余地大、適應(yīng)性好,性能得到充分發(fā)揮(3)電液比例控制系統(tǒng)和智能控制顯示系統(tǒng)的推廣應(yīng)用(4)操作更方便、舒適、安全、保護裝置更加完善(5)向吊重量大、起升高度、幅度更大的大噸位方向發(fā)展。研究內(nèi)容十噸位橋式起重機大車運行機構(gòu)設(shè)計 確定機構(gòu)傳動方案 選擇電動機,并驗算電動機的發(fā)熱功率條件 選擇減速器,制動器,聯(lián)軸器 端梁的設(shè)計 運用CAD繪制裝配圖零件圖撰寫畢業(yè)設(shè)計論文 擬采取的研究方法、技術(shù)路線、實驗方案及可行性分析 去實習(xí)工廠實地研究學(xué)習(xí),查閱橋式起重機的相關(guān)資料,分析總結(jié)。按照機械設(shè)計的相關(guān)要求按步驟進行設(shè)計和驗算。明確設(shè)計要求,調(diào)查研究,收集設(shè)計資料,繪出零件圖,裝配圖。按照步驟,實驗方案可行。 研究計劃及預(yù)期成果研究計劃:2012年11月12日-2012年12月2日:教師下達畢業(yè)設(shè)計任務(wù),學(xué)生初步閱讀資料,完成畢業(yè)設(shè)計開題報告。2013年1月21日-2013年3月1日:指導(dǎo)畢業(yè)實習(xí)。2013年3月4日-2013年3月15日:確定總設(shè)計方案。2013年3月18日-2013年3月22日:總體設(shè)計(包括參數(shù)計算及結(jié)構(gòu)分析計算)。2013年3月25日-2013年4月5日:總體設(shè)計(完成參數(shù)計算及結(jié)構(gòu)分析計算后繪制草圖;裝配圖)。2013年4月8日-2013年4月26日:零件設(shè)計。2013年4月29日-2013年5月25日:畢業(yè)論文說明書撰寫和修改工作。預(yù)期成果:認識了解橋式起重機的相關(guān)知識了解和工作方式。設(shè)計出10噸位橋式起重機的大車部分。完成畢業(yè)設(shè)計論文和CAD制圖。特色或創(chuàng)新之處對橋式起重機進行全面的了解,分析設(shè)計橋式起重機的大車機構(gòu)已具備的條件和尚需解決的問題我已學(xué)習(xí)機械數(shù)控專業(yè)三年之久,掌握了一些這專業(yè)的部分知識,老師也給了一些參照資料,可以進行這方面的研究。尚需解決的問題:(1)車輪的計算及車輪的設(shè)計對各部件之間連接方法和傳動方式的選擇。(2)進給部件的強度剛度校核需要對進給部件的強度和剛度有保證,滿足工作時的受力要求,需要進行校核計算。指導(dǎo)教師意見 指導(dǎo)教師簽名:年 月 日教研室(學(xué)科組、研究所)意見 教研室主任簽名: 年 月 日系意見 主管領(lǐng)導(dǎo)簽名: 年 月 日外文資料翻譯及原文英文原文:Fatigue life prediction of the metalwork of a travelling gantrycraneAbstractIntrinsic fatigue curves are applied to a fatigue life prediction problem of the metalwork of a traveling gantry crane. A crane, used in the forest industry, was studied in working conditions at a log yard, an strain measurements were made. For the calculations of the number of loading cycles, the rain flow cycle counting technique is used. The operations of a sample of such cranes were observed for a year for the average number of operation cycles to be obtained. The fatigue failure analysis has shown that failures some elements are systematic in nature and cannot be explained by random causes.卯1999 Elsevier Science Ltd. All rights reserved.Key words: Cranes; Fatigue assessment; Strain gauging1. Introduction Fatigue failures of elements of the metalwork of traveling gantry cranes LT62B are observed frequently in operation. Failures as fatigue cracks initiate and propagate in welded joints of the crane bridge and supports in three-four years. Such cranes are used in the forest industry at log yards for transferring full-length and sawn logs to road trains, having a load-fitting capacity of 32 tons. More than 1000 cranes of this type work at the enterprises of the Russian forest industry. The problem was stated to find the weakest elements limiting the cranes fives, predict their fatigue behavior, and give recommendations to the manufacturers for enhancing the fives of the cranes.2. Analysis of the crane operation For the analysis, a traveling gantry crane LT62B installed at log yard in the Yekaterinburg region was chosen. The crane serves two saw mills, creates a log store, and transfers logs to or out of road trains. A road passes along the log store. The saw mills are installed so that the reception sites are under the crane span. A schematic view of the crane is shown in Fig. 1.1350-6307/99/$一see front matter 1999 Elsevier Science Ltd. All rights reserved.PII: S 1 3 5 0一6307(98) 00041一7A series of assumptions may be made after examining the work of cranes:if the monthly removal of logs from the forest exceeds the processing rate, i.e. there is a creation of a log store, the crane expects work, being above the centre of a formed pile with the grab lowered on the pile stack;when processing exceeds the log removal from the forest, the crane expects work above an operational pile close to the saw mill with the grab lowered on the pile;the store of logs varies; the height of the piles is considered to be a maximum;the store variation takes place from the side opposite to the saw mill;the total volume of a processed load is on the average k=1.4 times more than the total volume of removal because of additional transfers. 2.1. Removal intensityIt is known that the removal intensity for one year is irregular and cannot be considered as a stationary process. The study of the character of non-stationary flow of road trains at 23 enterprises Sverdlesprom for five years has shown that the monthly removal intensity even for one enterprise essentially varies from year to year. This is explained by the complex of various systematic and random effects which exert an influence on removal: weather conditions, conditions of roads and lorry fleet, etc. All wood brought to the log store should, however, be processed within one year.Therefore, the less possibility of removing wood in the season between spring and autumn, the more intensively the wood removal should be performed in winter. While in winter the removal intensity exceeds the processing considerably, in summer, in most cases, the more full-length logs are processed than are taken out.From the analysis of 118 realizations of removal values observed for one year, it is possible to evaluate the relative removal intensity g(t) as percentages of the annual load turnover. The removal data fisted in Table 1 is considered as expected values for any crane, which can be applied to the estimation of fatigue life, and, particularly, for an inspected crane with which strain measurement was carried out (see later). It would be possible for each crane to take advantage of its load turnover per one month, but to establish these data without special statistical investigation is difficult. Besides, to solve the problem of life prediction a knowledge of future loads is required, which we take as expected values on cranes with similar operation conditions.The distribution of removal value Q(t) per month performed by the relative intensity q(t) is written aswhere Q is the annual load turnover of a log store, A is the maximal designed store of logs in percent of Q. Substituting the value Q, which for the inspected crane equals 400,000 m3 per year, and A=10%, the volumes of loads transferred by the crane are obtained, which are listed in Table 2, with the total volume being 560,000 m3 for one year using K,. 2.2. Number of loading blocksThe set of operations such as clamping, hoisting, transferring, lowering, and getting rid of a load can be considered as one operation cycle (loading block) of the crane. As a result to investigations, the operation time of a cycle can be modeled by the normal variable with mean equal to 11.5 min and standard deviation to 1.5 min. unfortunately, this characteristic cannot be simply used for the definition of the number of operation cycles for any work period as the local processing is extremely irregular. Using a total operation time of the crane and evaluations of cycle durations, it is easy to make large errors and increase the number of cycles compared with the real one. Therefore, it is preferred to act as follows.The volume of a unit load can be modeled by a random variable with a distribution function(t) having mean22 m3 and standard deviation 6;一3 m3, with the nominal volume of one pack being 25 m3. Then, knowing the total volume of a processed load for a month or year, it is possible to determine distribution parameters of the number of operation cycles for these periods to take advantage of the methods of renewal theory 1.According to these methods, a random renewal process as shown in Fig. 2 is considered, where the random volume of loads forms a flow of renewals: In renewal theory, realizations of random:,having a distribution function F(t), are understoodas moments of recovery of failed units or request receipts. The value of a processed load:,afterth operation is adopted here as the renewal moment. Let F(t)=Pt. The function F(t) is defined recurrently, Let v(t) be the number of operation cycles for a transferred volume t. In practice, the total volume of a transferred load t is essentially greater than a unit load, and it is useful therefore totake advantage of asymptotic properties of the renewal process. As follows from an appropriatelimit renewal theorem, the random number of cycles v required to transfer the large volume t hasthe normal distribution asymptotically with mean and variance.without dependence on the form of the distribution function月t) of a unit load (the restriction isimposed only on nonlattice of the distribution). Equation (4) using Table 2 for each averaged operation month,function of number of load cycles with parameters m,. and 6,., which normal distribution in Table 3. Figure 3 shows the average numbers of cycles with 95 % confidence intervals. The values of these parametersfor a year are accordingly 12,719 and 420 cycles.3. Strain measurementsIn order to reveal the most loaded elements of the metalwork and to determine a range of stresses, static strain measurements were carried out beforehand. Vertical loading was applied by hoisting measured loads, and skew loading was formed with a tractor winch equipped with a dynamometer. The allocation schemes of the bonded strain gauges are shown in Figs 4 and 5. As was expected, the largest tension stresses in the bridge take place in the bottom chord of the truss (gauge 11-45 MPa). The top chord of the truss is subjected to the largest compression stresses.The local bending stresses caused by the pressure of wheels of the crane trolleys are added to the stresses of the bridge and the load weights. These stresses result in the bottom chord of the I一beambeing less compressed than the top one (gauge 17-75 and 10-20 MPa). The other elements of the bridge are less loaded with stresses not exceeding the absolute value 45 MPa. The elements connecting the support with the bridge of the crane are loaded also irregularly. The largest compression stresses take place in the carrying angles of the interior panel; the maximum stresses reach h0 MPa (gauges 8 and 9). The largest tension stresses in the diaphragms and angles of the exterior panel reach 45 MPa (causes 1 and hl.The elements of the crane bridge are subjected, in genera maximum stresses and respond weakly to skew loads. The suhand, are subjected mainly to skew loads.1, to vertical loads pports of the crane gmmg rise to on the other The loading of the metalwork of such a crane, transferring full-length logs, differs from that ofa crane used for general purposes. At first, it involves the load compliance of log packs because ofprogressive detachment from the base. Therefore, the loading increases rather slowly and smoothly.The second characteristic property is the low probability of hoisting with picking up. This is conditioned by the presence of the grab, which means that the fall of the rope from the spreader block is not permitted; the load should always be balanced. The possibility of slack being sufficient to accelerate an electric drive to nominal revolutions is therefore minimal. Thus, the forest traveling gantry cranes are subjected to smaller dynamic stresses than in analogous cranes for general purposes with the same hoisting speed. Usually, when acceleration is smooth, the detachment of a load from the base occurs in 3.5-4.5 s after switching on an electric drive. Significant oscillations of the metalwork are not observed in this case, and stresses smoothly reach maximum values. When a high acceleration with the greatest possible clearance in the joint between spreader andgrab takes place, the tension of the ropes happens 1 s after switching the electric drive on, theclearance in the joint taking up. The revolutions of the electric motors reach the nominal value inO.r0.7 s. The detachment of a load from the base, from the moment of switching electric motorson to the moment of full pull in the ropes takes 3-3.5 s, the tensions in ropes increasing smoothlyto maximum. The stresses in the metalwork of the bridge and supports grow up to maximumvalues in 1-2 s and oscillate about an average within 3.5%.When a rigid load is lifted, the accelerated velocity of loading in the rope hanger and metalworkis practically the same as in case of fast hoisting of a log pack. The metalwork oscillations are characterized by two harmonic processes with periods 0.6 and 2 s, which have been obtained from spectral analysis. The worst case of loading ensues from summation of loading amplitudes so that the maximum excess of dynamic loading above static can be 13-14%.Braking a load, when it is lowered, induces significant oscillation of stress in the metalwork, which can be r7% of static loading. Moving over rail joints of 3 mm height misalignment induces only insignificant stresses. In operation, there are possible cases when loads originating from various types of loading combine. The greatest load is the case when the maximum loads from braking of a load when lowering coincide with braking of the trolley with poorly adjusted brakes.4. Fatigue loading analysisStrain measurement at test points, disposed as shown in Figs 4 and 5, was carried out during the work of the crane and a representative number of stress oscillograms was obtained. Since a common operation cycle duration of the crane has a sufficient scatter with average value 11.5min, to reduce these oscillograms uniformly a filtration was implemented to these signals, and all repeated values, i.e. while the construction was not subjected to dynamic loading and only static loading occurred, were rejected. Three characteristic stress oscillograms (gauge 11) are shown inFig. 6 where the interior sequence of loading for an operation cycle is visible. At first, stressesincrease to maximum values when a load is hoisted. After that a load is transferred to the necessary location and stresses oscillate due to the irregular crane movement on rails and over rail joints resulting mostly in skew loads. The lowering of the load causes the decrease of loading and forms half of a basic loading cycle. 4.1. Analysis of loading process amplitudes Two terms now should be separated: loading cycle and loading block. The first denotes one distinct oscillation of stresses (closed loop), and the second is for the set of loading cycles during an operation cycle. The rain flow cycle counting method given in Ref. 2 was taken advantage of to carry out the fatigue hysteretic loop analysis for the three weakest elements: (1) angle of the bottom chord(gauge 11), (2) I-beam of the top chord (gauge 17), (3) angle of the support (gauge 8). Statistical evaluation of sample cycle amplitudes by means of the Waybill distribution for these elements has given estimated parameters fisted in Table 4. It should be noted that the histograms of cycle amplitude with nonzero averages were reduced afterwards to equivalent histograms with zero averages. 4.2. Numbers of loading cycles During the rain flow cycle counting procedure, the calculation of number of loading cycles for the loading block was also carried out. While processing the oscillograms of one type, a sample number of loading cycles for one block is obtained consisting of integers with minimum and maximum observed values: 24 and 46. The random number of loading cycles vibe can be describedby the Poisson distribution with parameter =34.Average numbers of loading blocks via months were obtained earlier, so it is possible to find the appropriate characteristics not only for loading blocks per month, but also for the total number of loading cycles per month or year if the central limit theorem is taken advantage of. Firstly, it is known from probability theory that the addition of k independent Poisson variables gives also a random variable with the Poisson distribution with parameter k,. On the other hand, the Poisson distribution can be well approximated by the normal distribution with average, and variation ,. Secondly, the central limit theorem, roughly speaking, states that the distribution of a large number of terms, independent of the initial distribution asymptotically tends to normal. If the initial distribution of each independent term has a normal distribution, then the average and standard deviation of the total number of loading cycles for one year are equal to 423,096 and 650 accordingly. The values of k are taken as constant averages from Table 3.5. Stress concentration factors and element enduranceThe elements of the crane are jointed by semi-automatic gas welding without preliminary edge preparation and consequent machining. For the inspected elements 1 and 3 having circumferential and edge welds of angles with gusset plates, the effective stress concentration factor for fatigue is given by calculation methods 3, kf=2.r2.9, coinciding with estimates given in the current Russian norm for fatigue of welded elements 4, kf=2.9.The elements of the crane metalwork are made of alloyed steel 09G2S having an endurance limit of 120 MPa and a yield strength of 350 MPa. Then the average values of the endurance limits of the inspected elements 1 and 3 are ES一l=41 MPa. The variation coefficient is taken as 0.1, and the corresponding standard deviation is 6S-、一4.1 MPa.The inspected element 2 is an I-beam pierced by holes for attaching rails to the top flange. The rather large local stresses caused by local bending also promote fatigue damage accumulation. According to tables from 4, the effective stress concentration factor is accepted as kf=1.8, which gives an average value of the endurance limit as ES一l=h7 Map. Using the same variation coiffing dent th e stand arid d emit ion is =6.7 MPa. An average S-N curve, recommended in 4, has the form:with the inflexion point No=5106 and the slope m=4.5 for elements 1 and 3 and m=5.5 for element 2. The possible values of the element endurance limits presented above overlap the ranges of load amplitude with nonzero probability, which means that these elements are subjected to fatigue damage accumulation. Then it is possible to conclude that fatigue calculations for the elements are necessary as well as fatigue fife prediction.6. Life predictionThe study has that some elements of the metalwork are subject to fatigue damage accumulation.To predict fives we shall take advantage of intrinsic fatigue curves, which are detailed in 5and 6.Following the theory of intrinsic fatigue curves, we get lognormal life distribution densities for the inspected elements. The fife averages and standard deviations are fisted in Table 5. The lognormal fife distribution densities are shown in Fig. 7. It is seen from this table that the least
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