礦用液壓支架設計【掩護式】【正四連桿】【7張CAD圖紙】
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河南理工大學萬方科技學院本科畢業(yè)設計(論文)中期檢查表指導教師: 楊志波 職稱: 副教授 所在系部(單位): 機械與動力工程學院 教研室(研究室): 機械教研室 題 目 礦用液壓支架的設計學生姓名林超專業(yè)班級 07機制2班 學號0720150088一、選題質量1, 該選題為礦用液壓支架設計,符合專業(yè)培養(yǎng)目標,能夠體現(xiàn)綜合訓練的要求,可以對 我們大學四年所學知識進行一次全面的練習。2, 這將對我們以后深造學習和工作起到十分有效的幫助,也能達到一個綜合訓練的效果,又加強了實際的動手動腦能力。3, 題目的難易程度很適中,對我們既是一個挑戰(zhàn)也是一個很好的鍛煉提高過程。4, 題目的工作量:要求完成3張以上的A0圖紙,5060頁的說明書一份。5, 選題不但能緊密的結合生產(chǎn)和實踐,而且在我們所學課程的范圍之內(nèi),對我們 以后不管是科研還是從事實際的工作都有很大的幫助。二、開題報告完成情況在老師指導和同學們的幫助之下,我順利的開始本次畢業(yè)設計。我在自己經(jīng)過一些查閱資料的前提下,慢慢地理出頭緒,摸索出了設計思路。 由于我們這次是礦用液壓支架的設計,以前接觸這方面的知識較少,所以在剛開始不是很順利,甚至感到有些無從下手,但是經(jīng)過和指導老師的提導、與本組同學的商量、在工廠實習觀看實物之后, 我逐漸找到設計的切入點,順利的完成了開題報告。并有了一定的成果和進行了一些前期的工作,并使本次設計有了一個良好的開始。在查閱了一些資料后,已經(jīng)進行了計算設計,正在整理說明書,并進行初步繪制草圖.我將繼續(xù)努力,認真完成這次畢業(yè)設計。 三、階段性成果 1通過對液壓傳動原理的學習,在加上老師的仔細講解,我收集了大量的資料和文獻,為設計的順利完成打下了堅實的基礎。 2. 在老師的指導和同學的幫助下找到了設計的基本方法,開始了一些基本的原理的設計計算,并取得了一定成果。 3. 完成了開題報告。 4對整個設計有了一個總體的方案,并進行了前期的一些工作和設計.四、存在主要問題 由于在液壓傳動原理及機械原理的理解不夠深入,實際經(jīng)驗不足,而且這方面參考資料有限,所以隨著設計的逐漸進行中我遇到了許多新的和更加復雜的問題,這些問題使我充分認識到了自己在以前學習中的不足和自己與一些同學在專業(yè)知識方面的差距,所以我要以本次設計為契機加強自己在學習上薄弱環(huán)節(jié),爭取使我的畢業(yè)設計能夠取得好的成績,也能夠使我所學的知識能夠在以后的工作中發(fā)揮更大的作用。五、指導教師對學生在畢業(yè)實習中,勞動、學習紀律及畢業(yè)設計(論文)進展等方面的評語指導教師: (簽名) 年 月 日河南理工大學萬方科技學院本科畢業(yè)設計(論文)開題報告題目名稱礦用液壓支架學生姓名林超 專業(yè)班級07機制2班學號0720150088一、 本課題的研究目的和意義通過本次畢業(yè)設計,培養(yǎng)學生綜合運用液壓傳動、機械設計、工程理學等課程中所學理論知識的能力;強調(diào)設計的獨創(chuàng)性和實用性,培養(yǎng)和提高設計者獨立分析問題和解決實際問題的能力,為今后適應工作崗位和創(chuàng)造性地開展工作打下堅實基礎。采用綜合機械化采煤方法是大幅度增加煤炭產(chǎn)量,提高經(jīng)濟效益的必由之路。為了滿足對煤炭日益增長的需要,必須大量生產(chǎn)綜合機械化采煤設備,迅速增加綜合機械化采煤工作面(簡稱綜采工作面)。而每個綜采工作面平均需要安裝150臺液壓支架,可見對液壓支架的需要量時很大的。由于不同采煤工作面的頂?shù)装鍡l件,煤層厚度、煤層傾角、煤層的物理機械性質等的不同,對液壓支架的要求也不同,為了有效的支護和控制頂板,必須設計出不同類型和不同結構尺寸的液壓支架。因此,液壓支架的設計工作是很重要的。由于液壓支架的類型很多,因此其設計工作量是很大的,由此可見,研制和開發(fā)新型液壓支架是必不可少的一個環(huán)節(jié)。在過去的半個多世紀中,煤礦井下開采支護設備的設計和使用發(fā)生了巨大變化。其中,最引人矚目的是世界范圍內(nèi)廣泛采用液壓支架作為長臂開采支護工程的主要設備。從采煤設備的發(fā)展過程來看,采用液壓支架管理頂板是當代采煤技術史上一次重要的變革,也是煤礦現(xiàn)代化的主要標志。液壓支架作為綜合機械化采煤的關鍵設備之一,其重量約占綜合采煤設備總重量的80%90%,其費用約占綜合采煤設備總費用的60%70%。因此,為了降低成本提高采煤的經(jīng)濟效益,世界各主要產(chǎn)煤大國都一直在積極地開展液壓支架的研究。河南理工大學萬方科技學院本科畢業(yè)論文摘 要本論文主要闡述了一般掩護式液壓支架的設計過程。設計內(nèi)容包括:選架型、總體設計、主要零部件的設計、主要零部件的校核和液壓系統(tǒng)的設計。由于該煤層厚度適中,選用掩護式液壓支架。煤層厚度介于之間,煤層厚度變化較大,選用調(diào)高范圍大且抗水平推力強且?guī)ёo幫裝置的掩護式支架。支架采用正四連桿機構,以改善支架受力狀況。頂梁、掩護梁、底座均做成箱體結構;立柱采用雙伸縮作用液壓缸,以增加工作行程來滿足支架調(diào)高范圍的需要。推移千斤頂采用框架結構,以減少推溜力和增大移架力。為了提高移架速度,確保對頂板的及時支護,采用錐閥液壓系統(tǒng)。關鍵詞:液壓支架 液壓 四連桿機構 采煤 支架選型 推溜 移架- III -河南理工大學萬方科技學院本科畢業(yè)論文AbstractThe article mainly elaborated the general shield type hydraulic pressure support design process. The design content includes: Chooses, the system design, the main spare part design, the main spare part examination and the hydraulic system design.Because this coal bed thickness is moderate, selects the shield type hydraulic pressure support. Coal bed thickness is situated between between the 2.53.8 rice, coal bed thickness change bigger, selects adjusts the high scope big also the anti- horizontal thrust is strong also the belt protects helps the equipment the shield type support. The support uses the four link motion gear, improves the support stress condition. The top-beam, caving shield, the foundation makes the packed in a box body structure; The column uses the double expansion and contraction function hydraulic cylinder, increases the power stroke to satisfy the support to adjust the high scope the need. Passes the hoisting jack to use the portal frame construction, reduces pushes slides the strength and increases moves a strength. In order to enhance moves a speed, guarantees is prompt to the roof support, uses the mushroom valve hydraulic system.Key word: The hydraulic pressure support , hydraulic pressure , four-link mechanism , mining coal, support shaping push forwards the conveyer, advancing the powered support.河南理工大學萬方科技學院本科畢業(yè)論文目 錄1 概述11.1 液壓支架的組成和分類11.1.1液壓支架的組成11.1.2液壓支架的分類21.2液壓支架的工作原理21.3 液壓支架的支護方式51.4支架選型的基本參數(shù)61.4.1 對液壓支架的基本要求62 液壓支架的總體設計2.1 液壓支架的選型2.2 液壓支架參數(shù)的確定2.2.1 支護強度和工作阻力2.2.2 初撐力2.2.3 移架力與推溜力2.2.4 支架調(diào)高范圍2.2.5 中心距和寬度的確定2.2.6 底座寬度2.3 采煤機、液壓支架和輸送機的配套2.3.1 采煤機、液壓支架和輸送機的配套2.3.2 其他附屬設備的配套2.4 四連桿機構設計2.4.1 四連桿機構的作用2.4.2 用優(yōu)選設計法設計四連桿機構2.5 頂梁長度的確定2.6立柱及柱窩位置的確定2.7平衡千斤頂位置的確定2.7.1 平衡千斤頂安裝位置的確定原則2.7.2 平衡千斤頂在頂梁上位置的確定2.8其它千斤頂技術參數(shù)的確定2.8.1 推移千斤頂技術參數(shù)2.8.2 側推千斤頂技術參數(shù)2.8.3 前梁千斤頂技術參數(shù)2.8.4 護幫板千斤頂?shù)募夹g參數(shù)3 液壓支架受力分析和計算3.1 受力分析計算3.2 支護強度計算3.3 底座比壓的計算4 液壓支架的主要部件的設計4.1 前梁4.2 主頂梁4.3 掩護梁4.4 前、后連桿4.5 底座4.6 立柱4.7 千斤頂4.7.1 推移千斤頂5 主要零、部件的強度校核5.1校核的基本要求5.2前梁強度校核5.2.1 前梁受力情況5.2.2 前梁強度計算5.3 主頂梁強度校核5.3.1 主頂梁受力情況5.3.2 主頂梁強度計算5.4 掩護梁強度校核5.4.1 掩護梁受力情況5.4.2 掩護梁強度計算5.5 底座強度校核5.5.1 底座受力情況5.5.2 底座強度校核5.6 立柱強度的校核5.6.1 立柱穩(wěn)定性校核6 液壓系統(tǒng)6.1 液壓支架的液壓系統(tǒng)的簡介6.1.1 液壓支架傳動系統(tǒng)的基本要求6.1.2 液壓支架的液壓傳動特點致 謝參考文獻IV河南理工大學萬方科技學院本科畢業(yè)論文1 概述1.1 液壓支架的組成和分類1.1.1液壓支架的組成液壓支架是綜采工作面支護設備,它的主要作用是支護采場頂板,維護安全作業(yè)空間,推移工作面采運設備。液壓支架的種類很多,但其基本功能是相同的。液壓支架按其結構特點和與圍巖的作用關系“般分為三大類,即支撐式、掩護式(圖1-2)和支撐掩護式(圖1-3) 根據(jù)支架各部件的功能和作用,其組成可分為4個部分:(1) 承載結構件,如頂梁、掩護梁、底座、連桿、尾梁等。其主要功能是承受和傳遞頂板和垮落巖石的載荷。(2) 液壓油缸,包括立柱和各類千斤頂。其主要功能是實現(xiàn)支架的各種動作,產(chǎn)生液壓動力。 (3) 控制元部件,包括液壓系統(tǒng)操縱閥、單向閥、安全閥等各類閥,以及管路、液壓、電控元件等。其主要功能是操作控制支架各液壓油缸動作及保證所需的工作特性。圖1-2 掩護式液壓支架結構 圖1-3 支撐掩護式液壓支架結構 (4) 輔助裝置,如推移裝置、護幫(或挑梁)裝置、伸縮梁(或插板)裝置、活動側護板、防倒防滑裝置、連接件等。這些裝置是為實現(xiàn)支架的某些動作或功能所必需的裝置。1.1.2液壓支架的分類按液壓支架在采煤工作面的安置位置來劃分,有端頭液壓支架和中間液壓支架。端頭液壓支架簡稱端頭支架,專門安裝在每個采煤工作面的兩端。中間液壓支架是安裝在除工作面端頭以外的采煤工作面所有位置的支架。中間液壓支架按其結構形式來劃分,可分為三種基本類型,即:支撐式、掩護式和支撐掩護式。1.2液壓支架的工作原理液壓支架在工作過程中必須具備升、降、推、移四個基本動作,這些動作是利用泵站供給的高壓乳化液通過工作性質不同的幾個液壓缸來實現(xiàn)完成的。如圖1-5示1. 升柱當需要支架上升支護頂板時。高壓乳化液進入立柱的活塞腔,另一腔回液,推動活塞上升,使與活塞桿相連接的頂梁接觸頂板。2. 降柱當需要降柱時,高壓液進入立柱的活塞桿腔,另一腔回液,迫使活塞桿下降,于是頂梁脫離頂板。圖1-5 液壓支架工作原理-頂梁 -立柱 -底座 -推移千斤頂 -安全閥 -液控單向閥 、-操縱閥 -輸送機 -乳化液泵 -主供液管 -主回液管3. 支架和輸送機前移支架和運輸機的前移,都是由底座上的推移千斤頂來完成的。當需要支架前移時,先降柱卸載,然后高壓液進入推移千斤頂?shù)幕钊麠U腔,另一腔回液,以輸送機為支點,缸體前移,把整個支架拉向煤壁;當需要推運輸機時,支架支撐頂板后,高壓液進入推移千斤頂?shù)幕钊?,另一腔回液,以支架為支點,是活塞桿伸出,把運輸機推向煤壁。支架的支撐力與時間曲線,稱為支架的工作特性曲線,如圖1-6所示:支架立柱工作時,其支撐力隨時間的變化過程可分為三個階段-初撐階段; -增阻階段; -恒阻階段;-初撐力;-工作阻力(1)初撐階段支架在升柱時,高壓液進入立柱下腔,立柱升起使頂梁接觸頂板,立柱下腔壓力增加,當增加到泵站工作壓力時,泵站自動卸載,支架的夜控單向閥關閉,立柱下腔壓力達到初撐力,此階段為初撐階段,此時支架對頂板的支撐力為初撐力。支撐式支架的初撐力為 (1.1) 圖1-6 支架的工作特性曲線式中 -支架立柱的缸徑,;-泵站的工作壓力,;-支架立柱的數(shù)量。 由上式可知,支架初撐力的大小取決于泵站的工作壓力,立柱缸徑和立柱的數(shù)量。合理的初撐力是防止直接頂過早的因下沉而離層、減緩頂板下沉速度、增加其穩(wěn)定性和保證安全生產(chǎn)的關鍵。一般采用提高泵站工作壓力的辦法來提高初撐力,以免立柱的缸徑過大。(2)承載增阻階段支架初撐后,隨頂板下沉,立柱下腔壓力增加,直到增加到支架的安全閥調(diào)正壓力,立柱下腔壓力達到工作阻力。此階段為增阻階段。(3)恒阻階段隨著頂板壓力繼續(xù)增加,使立柱下腔壓力超過支架的安全閥壓力調(diào)正值時,安全閥打開而溢流,立柱下縮,使頂板壓力減小,立柱下腔壓力降低,當?shù)陀诎踩y壓力調(diào)整之后,安全閥停止溢流,這樣在安全閥調(diào)整壓力的限制下,壓力曲線隨時間呈波浪形變化,此階段為恒阻階段。此時支架對頂板的支撐力稱為工作阻力,它是由支架安全閥的調(diào)定壓力決定的。支撐式支架的工作組力為 (1.2)式中 -支架安全閥的調(diào)定壓力 ;支架的工作阻力標志著支架的最大承載能力。對于掩護式和支撐掩護式支架,其初撐力和工作阻力的計算還要考慮到立柱傾角的影響因素。支架的工作阻力是支架的一個重要參數(shù),它表示支架支撐力的大小。但是,由于支架的頂梁長短和間距大小不同,所以并不能完全反映支架對頂板的支撐能力。因此,常用單位支護面積頂板上所受支架工作阻力值的大小,即支護強度來表示支架的支護性能。即 (1.3) 式中 支架的支護面積,。1.3 液壓支架的支護方式綜采工作面的主要生產(chǎn)工序有采煤、移架和推溜。 3個工序的不同組合順序,可形成液壓支架的3種支護方式,從而決定工作面“三機”的不同配套關系。1 即時支護般循環(huán)方式為:割煤一移架一推溜,工作面“三機”的配套關系。即時支護的特點是,頂板暴露時間短,梁端距較小。適用于各種頂板條件,是目前應用最廣泛的支護方式。2 滯后支護一般循環(huán)方式為:割煤一推溜一移架。滯后支護的特點是,支護滯后時間較長,梁端距大,支架頂梁較短??捎糜诜€(wěn)定、完整的頂板。3 復合支護般循環(huán)方式為:割煤一支架伸出伸縮梁一推溜一收伸縮梁一移架。復合支護的特點是:支護滯后時間短,但增加了反復支撐次數(shù)??蛇m用于各種頂板條件,但支架操作次數(shù)增加,不能適應高產(chǎn)高效要求,目前應用較少。1.4支架選型的基本參數(shù)1.4.1 對液壓支架的基本要求1. 為了滿足采煤工藝及地質條件的要求,液壓支架要有足夠的初撐力和工作阻力,以便有效地控制頂板,保證合理的下沉量。2. 液壓支架要有足夠的推溜力和移架力。推溜力一般為左右;移架力按煤層厚度而定,薄煤層一般為,中厚煤層一般為,厚煤層一般為。3. 防矸性能要好。4. 排矸性能要好。5. 要求液壓支架能保證采煤工作面有足夠的通風斷面,從而保證人員呼吸、稀釋有害氣體等安全方面的要求。6. 為了操作和生產(chǎn)的需要,要有足夠寬的人行道。7. 調(diào)高范圍要大,照明和通訊方便。8. 支架的穩(wěn)定性要好,底座最大比壓要小于規(guī)定值。9. 要求支架有足夠的剛度,能夠承受一定得不均勻載荷和沖擊載荷。10. 滿足強度條件下,盡可能的減輕支架重量。11. 要易于拆卸,結構要簡單。12. 液壓元件要可靠。山東科技大學學士學位論文 液壓支架的總體設計河南理工大學萬方科技學院本科畢業(yè)論文2 液壓支架的總體設計2.1 液壓支架的選型正確選擇液壓支架的架型,對于提高綜采工作面的產(chǎn)量和效率,充分發(fā)揮綜采設計的效能,實現(xiàn)高產(chǎn)高效,是一個很重要的因素。在具體選擇架型時,首先要考慮煤層的頂板條件。表2-1是根據(jù)國內(nèi)外液壓支架的使用經(jīng)驗,提出了各種頂板條件下適用的架型,它是選擇支架的主要依據(jù).由于給定參數(shù)中頂?shù)装嫘再|:老頂I級、直接頂2級,底板平整,無影響支架通過的斷層,初步選擇為掩護式支架。1 煤層厚度煤層厚度不但直接影響到支架的高度和工作阻力,而且還影響到支架的穩(wěn)定性。當煤層厚度大于(軟煤層下限,硬煤層上限)時,應選用抗水平推力強且?guī)ёo幫裝置的掩護式或支撐掩護式支架。當煤層厚度變化較大時,應選用調(diào)高范圍大的支架。因此本次設計應選用抗水平推力強且?guī)ёo幫裝置的掩護式支架。2 煤層傾角煤層傾角主要影響支架的穩(wěn)定性、傾角大時易發(fā)生傾倒下滑等現(xiàn)象。當煤層傾角大于時,應設防滑和調(diào)架裝置,當傾角超過時,應同時具有防滑防倒裝置。給定煤層傾角,不用設置防滑和調(diào)架裝置。3 底板性質底板承受支架的全部載荷,對支架的底座影響較大,底板的軟硬和平整性,基本上決定了支架地做的結構和支撐面積。選型時,要驗算底座對底板的接觸比壓,其值要小于底板允許比壓(對于砂巖底板,允許比壓為,軟底板為左右)4 瓦斯涌出量 對于瓦斯涌出量大的工作面,支架的通風斷面應滿足通風的要求,選型時要進行驗算。表2-1老頂級別IIIIIIIV直接頂級別12312312344支架類型掩護式掩護式支撐式掩護式掩護式或支撐掩護式掩護式支撐掩護式支撐掩護式支撐或支撐掩護式支撐或支撐掩護式支撐式采高小于2.5m時支撐掩護式采高大于2.5m時支架支護強度采高12340.2940.343(0.245)0.441(0.343)0.539(0.441)1.30.2941.30.343(0.245)1.30.441(0.343)1.30.539(0.441)1.60.2941.60.3431.60.4411.60.53920.29420.34320.44120.539應結合深孔爆破,軟化頂板等措施處理采空區(qū)單體支柱支護強度采高123.0.1470.2450.3431.30.1471.30.2451.30.3431.60.1471.60.2451.60.343按采空區(qū)處理方法確定注:括號內(nèi)的數(shù)字是掩護式支架的支護強度。表中所列支護強度在選用時,可根據(jù)本礦情況允許有5%的波動范圍。表中1.3、1.6、2分別為II、III、IV級老頂?shù)姆旨壴鰤合禂?shù);IV級老頂只給出最低值2,選用時可根據(jù)本礦實際確定適宜值。2.2 液壓支架參數(shù)的確定2.2.1 支護強度和工作阻力支護強度取決于頂板性質和煤層厚度。支護強度可根據(jù)下列公式估算: (2.1)式中K作用與支架上的頂板巖石系數(shù),一般取。頂板條件好、周起來壓不明顯時取下限,否則取上限;H采高,頂板巖石密度,一般為放頂煤支架的支護強度一般為支架工作阻力P應滿足頂板支護強度的要求,即支架工作阻力由支護強度和支護面積所決定。 (2.2)式中 F支架的支護面積,可按下式計算2.2.2 初撐力初撐力的大小是相對與支架的工作阻力而言,并與頂板的性質有關。較大的初撐力可以使支架較快地達到工作阻力,防止頂板過早的離層,增加頂板的穩(wěn)定性。對于不穩(wěn)定和中等穩(wěn)定頂板,為了維護機道上方的頂板,應取較高的初撐力,約為工作阻力的80%;對于穩(wěn)定頂板,初撐力不宜過大,一般不低于工作阻力的60%,對于周期來壓強烈的頂板,為了避免大面積的垮落對工作面的動載威脅,應取較高的初撐力,約為工作阻力的75%。2.2.3 移架力與推溜力移架力與支架結構、噸位、支撐高度、頂板狀況是否帶壓移架等因素有關。一般薄煤層支架的一架力為;中等厚度煤層支架為;厚煤層為。推溜力一般為.2.2.4 支架調(diào)高范圍支架最大結構高度 (2.5)支架最小結構高度 (2.6)式中 、煤層最大、最小采高偽頂冒落的最大厚度,一般取頂板周期來壓時的最大下沉量、移架使支架的下降量和頂梁上、底座下的浮矸、煤層厚度之和,一般取確定支架的最低高度時還應考慮到井下的允許運輸高度。支架的伸縮比 (2.7)值的大小反映了支架對煤層厚度變化的適應能力,其值越大,說明支架適應煤層厚度變化的能力越強,采用單伸縮立柱,值一般為1.6左右。若進一步提高伸縮比,需采用帶機械加長桿的立柱或雙伸縮立柱,其值一般為2.5左右。薄煤層厚度可達。由于又考慮到煤層厚度較高,初選雙伸縮立柱。2.2.5 中心距和寬度的確定 支架中心距一般等于工作面一節(jié)溜槽長度。目前國內(nèi)外液壓支架中心距大部分采用.大采高支架為提高穩(wěn)定性中心距可采用,輕型支架為適應中小煤礦工作面快速搬家的要求,中心距可采用。因此設計中預取1.5m。2.2.6 底座寬度 底座是將頂板壓力傳遞到底板和穩(wěn)固支架的部件。在設計支架的底座長度時,應考慮如下諸方面:支架對底板的接觸比壓要?。恢Ъ軆?nèi)部應有足夠的空間用于安裝立柱、液壓控制裝置、推移裝置和其他輔助裝置;使于人員操作和行走,保證支架的穩(wěn)定性等。通常,掩護式支架的底座長度取3.5倍的移架步距一個移架步距為,即左右;支撐掩護式支架的底座長度取4倍的移架步距,即左右。 2.3 采煤機、液壓支架和輸送機的配套2.3.1 采煤機、液壓支架和輸送機的配套綜采工作面采煤機、液壓支架和輸送機之間在性能參數(shù)、結構參數(shù)、空間尺寸及相互連接等方面,有著嚴格的配套要求,以保證綜采工作面的最大生產(chǎn)能力和安全生產(chǎn)的要求。(1)生產(chǎn)能力的配套(2)性能配套(3)幾何關系的配套2.3.2 其他附屬設備的配套煤層傾角大于時,采用鏈牽引的采煤機應設置防滑裝置;當傾角大于時應安裝防滑絞車,輸送機應設置防滑錨固裝置,支架也應有防倒防滑和調(diào)架裝置;而對于大采高工作面設備,煤層傾角大于時,即應設防滑裝置。落煤塊度過大時,工作面轉載機上應設置破碎裝置。本設計采用配套 液壓支架 北京煤機廠 采煤機 刮板運輸機: 2.4 四連桿機構設計2.4.1 四連桿機構的作用四連桿機構是掩護式支架和支撐掩護式支架的最重要部件之一。其作用概括起來主要有兩個:其一是當支架由高到低變化時,借助四連桿機構使支架頂梁前端點的運動軌跡呈近似雙紐線,從而使支架頂梁前端點與煤壁間距離的變化大大減小,提高了管理頂板的性能;其二是使支架能承受較大的水平力。 為了掌握四連桿機構的設計方法,必須正確理解四連桿機構的作用。下面通過四連桿機構動作過程的幾何特征進一步闡述其作用。這些特征是四連桿動作過程的必然結果。1.支架高度在最大和最小范圍內(nèi)變化時,頂梁端點運動軌跡的最大寬度,最好為以下;2.支架在最高位置時和最低位置時,頂梁與掩護梁的夾角和后連桿與底平面的夾角,應滿足如下要求:支架在最高位置時,;支架在最低位置時,為有利于矸石下滑,防止矸石停留在掩護梁上,根據(jù)物理學摩擦理論可知,要求,如果剛和矸石的摩擦系數(shù),則,為了安全可靠,最低工作位置應使為宜。而角主要考慮后連桿底部距底板要有一定距離,防止支架后部冒落巖石卡住后連桿,使支架不能下降。一般取,在特殊情況下需要角度較小時,可提高后連桿下鉸點的高度;3.掩護梁與頂梁鉸點和瞬心中心間的只限于水平線夾角,滿足。原因是角直接影響支架承受附加力的數(shù)值大小。4.應取頂梁前端點運動軌跡雙紐線向前凸的一段為支架工作段,如圖22所示的h段。圖22所示其原因為當頂板來壓時,立柱讓壓下縮,使頂梁有向前移的趨勢,可防止巖石向后移動,又可以使作用在頂梁上的摩擦力指向采空區(qū)。同時底板防止底座向后移,使整個支架產(chǎn)生順時針轉動的趨勢,從而增加了頂梁前端的支護力,防止頂梁前端上方頂板冒落,并且使底座前端比壓減小,防止啃底,有利移架。水平力的合力也相應減小,所以減輕了掩護梁的外負荷。2.4.2 用優(yōu)選設計法設計四連桿機構目標函數(shù)的確定:令支架由高到低時,頂梁前端運動軌跡近似呈斜線;這樣比用直線作為目標函數(shù)的雙紐線的上半部分要長。四連桿機構的設計通過程序來計算和驗證,程序編制如下所示:Private Sub Command1_Click()Dim h1, h2 As Double 支架最高,最低計算高度Dim p1 As Double 支架在最高位置時,頂梁與掩護梁夾角Dim q1 As Double 支架在最高位置時,后連桿與底座平面夾角Dim i As Double 后連桿與掩護梁的比值Dim i1 As Double 前后連桿上鉸點之距與掩護梁的比值Dim g As Double 掩護梁長度Dim a As Double 后連桿長度Dim b As Double 前后連桿上鉸點之距Dim f As Double 前連桿上鉸點至掩護梁上鉸點之距Dim b1, b2, b3 As DoubleDim c As Double 前連桿長度Dim d As Double 前連桿下鉸點高度Dim e As Double 前后連趕下鉸點在底座上的投影距離Dim a1, q2, o1, l As DoubleDim s As Doubleh1 = Val(Text1.Text)h2 = Val(Text2.Text)For p1 = 0.91 To 1.08 Step 0.034For q1 = 1.31 To 1.48 Step 0.034For i = 0.61 To 0.82 Step 0.042For i1 = 0.22 To 0.3 Step 0.02g = h1 / (Sin(p1) + i * Sin(q1)a = i * gb = i1 * gf = g - be1 = g * Cos(p1) - a * Cos(q1)X1 = f * Cos(p1)Y1 = h1 - f * Sin(p1)q2 = 0.436p2 = Atn(Sqr(Abs(g * g - (e1 + a * Cos(q2) 2) / (e1 + a * Cos(q2)X2 = f * Cos(p2)Y2 = b * Sin(p2) + a * Sin(q2)p3 = 3.14 / 2 - Atn(a / g) - Atn(e1 / Sqr(g * g + a * a - e1 * e1)q3 = 3.14 / 2 - p3x3 = f * Cos(p3)y3 = b * Sin(p3) + a * Sin(q3)m = x3 * x3 - X1 * X1 + y3 * y3 - Y1 * Y1n = X2 * X2 - x3 * x3 + Y2 * Y2 - y3 * y3t = 2 * (x3 - X1) * (Y2 - y3) - (y3 - Y1) * (X2 - x3)xc = (m * (Y2 - y3) - n * (y3 - Y1) / tyc = (n * (x3 - X1) - m * (X2 - x3) / tc = Sqr(X1 - xc) 2 + (Y1 - yc) 2)o = c / aIf o 0.9 And o 1.2 Then d = yc e = e1 - xc x4 = e1 + a * Cos(q1) y4 = a * Sin(q1) x5 = e1 y5 = 0 k1 = (Y1 - yc) / (X1 - xc) c1 = Atn(k1) k2 = (y4 - y5) / (x4 - x5) x6 = (k1 * X1 - Y1 - k2 * x4 + y4) / (k1 - k2) y6 = k1 * (x6 - X1) + Y1 l = x6 s = h1 - y6 u = s / l If u 0 And d h1 / 5 And e 45.2前梁強度校核5.2.1 前梁受力情況假定前梁千斤頂缸體內(nèi)徑先按下表標準取為125表5-2506380100110125140(145)200(210)220(230)250則前梁千斤頂?shù)闹瘟椋?(5.2)圖5-1前梁前端受一集中載荷P,其受力圖如上圖所示:前端集中載荷為:在斷面A-A處的彎矩為:前梁做成變斷面箱形結構,A-A斷面如下圖所示:圖5-2 A-A斷面5.2.2 前梁強度計算(1) 形心位置各板件的計算數(shù)據(jù)如下表所示:表5-3件號12345數(shù)量面積形心位置慣性矩11380.511.62169340112317.51027419.5422044891024結構件的形心位置為: (5.3) (2) 慣性矩 (5.4)=+=53790(3) 彎曲應力 (5.5)=(4) 安全系數(shù)鋼板材料選取16Mn, (5.6)5.3 主頂梁強度校核 5.3.1 主頂梁受力情況假設前梁失去作用,主頂梁受一集中載荷,其受力圖如下圖所示:由上面求出為3279.3KN,距離鉸接點1661mm,最大彎矩為圖5-3 主頂梁受力情況圖主頂梁做成等斷面箱式結構,在最大彎矩處的斷面如下圖所示:圖5-45.3.2 主頂梁強度計算(1)形心位置各板件計算數(shù)據(jù)如下表所示:結構件的形心位置為: (5.7)=表5-4件號123456789數(shù)量1139.20.829.7273.62.431.4227.811.91404.8452.211.95268218.8111107.4237.121.25447.7235.221.25166225.921.23804130.411.2914.5(2) 慣性矩 (5.8) (3) 彎曲應力 (5.9)(4) 安全系數(shù) 鋼板材料選取16Mn, 5.4 掩護梁強度校核5.4.1 掩護梁受力情況由前面已經(jīng)求出在掩護梁上前后連桿的銷軸處受力為2725.9KN和2096.89KN,其受力圖如下圖所示:圖5-5 掩護梁受力圖最大彎矩發(fā)生在前連桿處,其值為:最大彎矩處的斷面表示如下圖所示:圖5-65.4.2 掩護梁強度計算(1) 形心位置各板件記算數(shù)據(jù)如下表所示:表5-5件號12345數(shù)量1114215615017518390.64.414.8142717.2673.52960.1249.414.2結構件的形心位置: (5.10)ORIGINAL ARTICLE An integrated computer-aided decision support system for die stresses and dimensional accuracy of precision forging dies Necip Fazil Yilmaz therefore, steady state conditions are not achieved due to the continuously changing pressure distribution. But in general it is assumed that steady state stress conditions are present and there is a uniform internal pressure along the whole length of the die 23, 24. These assumptions permit calculations based on the theory of thick-walled hollow cylinders to be carried out. The upper bound elemental technique (UBET) incorpo- rates the advantages of both the upper bound theorem and the finite element method to provide more accurate predictions of important parameters such as strain rates, die load, and die cavity filling when compared to the other methods. UBET is perfect for initial stages of the optimization algorithms, where it is necessary to reach near-optimum solutions as quickly as possible. The stresses in dies arise mainly from the high level of internal pressure during forging. However, the pressure is not constant over the whole length of the die. Since it is concentrated in the portion of the die that is in contact with the deforming workpiece, the pressure will vary during forging and the length of the pressurised region will also change. The dimension of the forging is different from the die because of several factors: The die insert is shrink fitted into the outer ring causing an extraction of the die cavity (U e ). In hot forging, the die may be heated prior to forging and further heated by the hot billet during forging. This causes the die insert to expand (U t ). Contraction occurs during cooling from forging tem- perature to room temperature (U c ). In electrodischarge machining of the die components, spark gap occurs between electrode and workpiece. This decreases the die cavity size (G). As seen in Fig. 1, if the radius of the workpiece is assumed to be equal to the original die radius R 0 ; thus, the final radius of the die R 4 will be: R 4 R 0 U e U t C0U c C0G 3 Calculation formulae 3.1 Calculation of the elastic die expansion (U e ) In order to calculate the changes in workpiece dimensions due to elastic deflection of the die, the elasticplastic deformation of the workpiece has to be considered. Assuming that the workpiece is stressed uniformly by the die and always remains cylindrical at the maximum forging R0 R1 R2 R3 R4 Ue Ut Uc G Fig. 1 Half section of a cylindrical forging of die insert 25 876 Int J Adv Manuf Technol (2009) 40:875886 load, the die deflection is elastic and uniform along its axis. Ignoring the friction on workpiecedie interfaces, work- piece dimensions change when the punch load is applied and removed. Also, changes in workpiece dimensions occur during ejection 25. In order to calculate the amount of expansion of the die under radial pressure, an initially stress-free duplex cylinder is considered. By applying the punch load on the workpiece, two modes of deformation will occur. First, the workpiece will deform elastically and when the punch pressure becomes equal to the yield stress of the workpiece material, plastic deformation starts and simple compression continues until the workpiece touches the die wall. For continuity across the interface, the hoop (tangential) strains for insert and shrink ring must be equal at this point, q1 q2 . q1 P i 1C0 nb 2 a 2 C16C17 b 2 a 2 C01 1C0u d1 E d1 P i 1C0n b 2 a 2 C01 1u d1 E d1 1 q2 nP i c 2 b 2 C01 1C0u d2 E d2 nP i c 2 b 2 C16C17 c 2 b 2 C01 1u d2 E d2 2 The subscripts 1 and 2 refer to die insert and shrink ring, respectively. When the maximum load is exerted on the workpiece, the radial stress will be greater than its yield strength. After reaching such a condition, if the punch load is removed, the die will compress the workpiece plastically until the radial stress on the workpiece is reduced to twice its shear yield stress (S y ). By using Trescas yield criterion, the total amount of radial expansion of the workpiece (U)at the end of this stage can be calculated by: U a aa 2 1C0u d1 b 2 1u d1 C02n2S y C02ab 2 P p E d1 b 2 C0a 2 3 At the end of the forging process, the punch pressure is zero and the radial stress (2S y ) is still acting on the workpiece. On ejection, its radius will expand elastically and the amount of recovery (s) can be calculated by assuming a cylindrical state of stress (s r s q ) and by placing z =0, such that: s 1C0u w E w 2S y a 4 where E w and w are the Youngs modulus and Poissons ratio of the workpiece material, respectively. The total b a Ti Tp Fig. 2 Temperature distribution along the die radius in hot forging Die Ring a z b c a b c Fig. 4 Die insert and shrink ring dimensions a b 0 () 0 (+) r () To - Tp=0 Ti - Tp= Fig. 3 Radial and tangential stress distributions due to outward temperature Int J Adv Manuf Technol (2009) 40:875886 877 change in the workpiece dimensions due to elastic die expansion is given by: U e aa 2 1C0u d1 b 2 1u d1 C02n2S y C02ab 2 P p E d1 b 2 C0a 2 1C0u w E w 2S y a 5 3.2 Calculation of the thermal die expansion (U t ) In hot forging, dies are preheated to prevent cracking of the die components and to reduce the cooling rate of the workpiece. Some heat is transferred from the workpiece during forging which further heats the die. The combination of these two sources of heat causes the die to expand. The temperature distribution along the radius of the die with a preheat temperature of T p and bore diameter of T i is given in Fig. 2. The preheat temperature is assumed constant throughout the die, but the heat transferred from the workpiece produces an outward heat flow with radial temperature gradient. Assuming uniform preheating, the die wall will expand freely. The magnitude of the radial expansion (U tp ) at any radius can be determined as: U tp ra d T p C0T r C0C1 6 where T r is room temperature, T p is preheat temperature, and d is the coefficient of thermal expansion of the die material. The temperature increase on the inner surface of the die and stress distributions are shown in Fig. 3. Thus, the radial displacement at any radius r due to thermal stresses can be found with: U ts C0 d T 3 bC0a C0 1 d a 2 b 2 ab 1 r 2 d C01r 2 1C0 d b 3 C0a 3 b 2 C0a 2 C20C21 7 Total die expansion (U t ) due to temperature will then be: U t U tp U ts 8 Top Frame Die Geometry Forging Load Geometry Die Assembly Material Parent Frame Fig. 5 General frame structure Friction Flow Stress FORGING LOAD Contour Frame Remove Frame Region Frame DATABASE Lubrication Good Average Poor Dry INFERENCE ENGINE Fig. 6 Framework for forging load frame 878 Int J Adv Manuf Technol (2009) 40:875886 3.3 Calculation of the thermal product contraction (U c ) Theamountofshrinkageafterhotformingoperationsdepends on the working temperature and coefficient of thermal expansion of the forged material. Assuming that shrinkage takes place radially, and the finish forging temperature is uniform, the amount of radial contraction at any radius is: U c ra w T f C0T r C0C1 9 where T f is the forging temperature, w is the coefficient of thermal expansion of the workpiece, and r is the radius of the workpiece before contraction. In order to achieve close dimensional tolerances on forgings, die dimensions should be closely controlled. From the foregoing it is apparent that knowledge of the magnitude of the above factors should be obtained before appropriate die and electrode dimensions are determined. Using the above analysis, the parameters affecting forging dimensions were calculated and for a given condition the profileofthe die was determined. A program hasbeenwritten to perform these calculations and to create the corrected forging product dimension for die. Die insert and shrink ring dimensions (Fig. 4) are then given in Eqs. 1017. b a Q 1 10 c a Q 11 z b:S y E 1 K 1 C0Q 2 1 C18C19 12 Q Q 1 :Q 2 13 Q 1 1 2 1 1 K 1 C18C19 C0PP s 14 Q 2 Q 1 : K 1 p 15 PP P i S ydie 16 K 1 S ydie S yring 17 Fig. 9 Friction calibration curve in terms of m 27 Table 1 Aluminum ring test data Lubricated Dry (ground) Dry (rough) D o1 (mm) 30 30 30 D o2 (mm) 37.7 38.5 38 D i1 (mm) 15.2 15.2 15.2 D i2 (mm) 14.8 13.5 11.2 H1 (mm) 10 10 10 H2 (mm) 5.65 5.35 5.3 % H 43.5 46.5 47 % D 2.63 11.18 26.3 Load (ton) 25 30 35 m 0.25 0.4 0.6 0 5 10 15 20 051015 DH P(TON) Fig. 7 Disc forging for aluminium ALUMINIUM 0 50 100 150 200 0,00 0,10 0,20 0,30 0,40 STRAIN (DH) STRESS(MPa) Fig. 8 Stressstrain curve for aluminium Int J Adv Manuf Technol (2009) 40:875886 879 where a is the die insert inner radius, b is the die insert outer radius, c is the shrink ring outer radius, z is the interference, and P i is the inner pressure. 4 General structure of the system A general structure for building up an inference and control engine for the decision-support expert system as well as an algorithm for finding a compromise solution for the die stress and dimensional accuracy of the product is achieved. By using an intelligent, knowledge-based object-oriented system, high precision manufacture of product has been put into perspective. Knowledge representation in this work was structured in the network representation. Parent frames (geometry, forging load, diegeometry,dieassembly, material) are connected to the top frame. Each parent frame also has child frames. General frame structure is shown in Fig. 5. Parent frames are used to describe the general class of objects. In a database, the data definition of a record specifies how the data is stored so that the database can search and sort through the data. To actually enter the values into the system, child frames and instances are formed to represent the specific objects. Prediction of forging load has vital importance for the dimensional a b c 40 17.5 30 31.1 Fig. 10 U-shaped product with different sizes of specimen 880 Int J Adv Manuf Technol (2009) 40:875886 accuracy and die life. This frame has six child frames and it is defined as one of the main frames of the developed system (Fig. 6). Contour frame This is the child frame of forging load parent frame. This frame takes its knowledge from the geometry parent frame. In order to determine the forging load, the contour frame is the first frame that is to be fired. The entities are searched to find the inclined lines and arcs. During this process, related rules are fired so that the entities found are inclined line or arc. Remove frame This is the child frame of forging load parent frame. In this frame, removed entities are stored in the database. There are two instances. One of them contains the knowledge about inclined lines and the other contains arcs. Region frame This frame is the child frame of forging load parent frame. The geometry decomposition is made by the knowledge taken from this frame. Vertical and horizontal lines are drawn from the corners to the corresponding line. In this way, rectangular regions are obtained. The knowl- edge about the regions are stored in the database. Friction frame One side of the region contacts one of the material, die, or punch. Therefore, each side must be checked and friction factor must be determined. This frame is used for the determination of sides, whether it contacts the material, die, or punch. c 20 50 a b 40 12.5 30 22.2 Fig. 11 T-shaped product with different sizes of specimen Int J Adv Manuf Technol (2009) 40:875886 881 Lubrication frame This frame takes its knowledge from friction frame and adds its own knowledge. This frame has four slots: good lubrication, average lubrication, poor lubrication, and no lubrication (dry). These slots are required from the user. The entered values are used for the determination of friction factor for each side of the region and therefore for all forging products. Flow stress frame Deformation characteristics of each material are different from the other materials. The flow stress value changes for all deformation conditions. Therefore, this property of the material must be in hand. 5 Experimentation In the experiments a hydraulic press which has a capacity of 600 kN was used. A graphitewater based lubricant was used as a lubricant. Great care was taken to ensure that all the working surfaces were completely and evenly lubricat- ed. As a die insert material, AISI A10 air hardening medium alloy cold worked tool steel was used. The tool set comprised essentially a container, punch, ejector, and bolster. U-shaped, T-shaped, and taper shaped aluminium prod- ucts were forged. Experiments were carried out at room temperature. Three different sizes of cylindrical aluminium billets were used. Products which have a dimension of 40 mm in outside diameter and 20 mm in height were obtained from stock bars and hollow bars. 5.1 Disc forging A disc forging compression test was carried out to determine the stress-strain curveforaluminium.To thisaim,incremental compression was performed and after each loading, reduction of area and corresponding load were calculated and recorded. 40 12 30 22.3 25 32.1 a b c Fig. 12 Taper shaped product with different sizes of specimen 882 Int J Adv Manuf Technol (2009) 40:875886 A reduction in height versus load graphic is shown in Fig. 7, and a stressstrain curve is shown in Fig. 8. In order to determine the friction factor (m), the ring compression test has been carried out. A flat ring specimen is plastically compressed between two platens. Increasing friction results in an inward flow of the material and decreasing friction results in an outward flow of the material. For a given percentage of high reduction during compression test, the corresponding measurement of the internal diameter of the test specimen provides a quantita- tive knowledge of the magnitude of the prevailing friction coefficient at the die and workpiece interface 26, 27. From this perspective, ring compression test data for aluminum are presented in Table 1.%H and %D values Fig. 13 a Die stress calculation screen. b Corrected die dimensions Int J Adv Manuf Technol (2009) 40:875886 883 are obtained by the following equations and friction coefficient m is found from Fig. 9. %H H 1 C0H 2 H 1 *100 %D D i1 C0D i2 D i1 *100 5.2 U-shaped forging Inprecisionforgingoftheproducts,completefillingofthedie is regarded as the most important criterion for improving the dimensional accuracy of the forged part. The volume of the preform should be carefully controlled, otherwise underfilling or overloading of the tools may occur. It can generally be said that metal does not flow easily through the corners. Complete filling can be satisfactorily achieved by using appropriate initial billet geometry. Figure 10 shows the dimensions of the U-shaped forging produced from three different sizes of billets by keeping their volume constant. The first one was forged from solid cylindrical bar and the product was obtained with 26 tons of load. The second one (Fig. 10b) was subjected to 55 tons of load, but the inner side of the specimen could not be filled. In the third one (Fig. 10c) both upsetting and extrusion type metal deformation exists. In this case the product is obtained with 40 tons of load. 5.3 T-shaped forging T-shaped forging is shown in Fig. 11. Forging of this product was approached with three different sizes of specimens by keeping their volume constant. Figure 11 shows the dimensions of the T-shaped forging produced from three different sizes of billets. Although 55 tons of load was applied, Fig. 11a shows that the T-shaped product could not be obtained and the die cavity could not be filled completely. But the second one was subjected to 40 tons of load and the die cavity was almost filled. The third specimen has the same diameter in the smaller part of the shape and 26 tons of load was enough to obtain this product. 5.4 Taper-shaped forging Taper shaped forging is shown in Fig. 12. This product used different sizes of specimens while keeping their volume constant. Figure 12 shows the dimensions of the taper shaped forging produced from three different sizes of billets. Figure 12a shows that taper shaped product could not be obtained by 55 tons of load since the preform is completely subjected to the extrusion mode of deformation. But in the second trial 30 mm diameter of billet was used and the product was obtained with 35 tons of load (Fig. 12b). In this forging, the top of the taper could not be formed Fig. 14 Print screen of Excel sheet Table 2 Corrected die geometry dimensions (mm) U shape T shape Taper shape U e 0.03563 0.03563 0.04667 Final workpiece radius 19.96437 19.96437 19.95333 Final die radius 20.03563 20.03563 20.04667 b 28.78528 28.78528 27.66765 c 41.42962 41.42962 38.27494 z 0.02978 0.02978 0.02642 w1 9.98815 10.0456 7.51274 w2 10.0456 9.98815 7.5110 884 Int J Adv Manuf Technol (2009) 40:875886 completely. The third specimen, having a diameter of 25 mm, was subjected to 24 tons of load and the required product was obtained in almost its desired dimensions. These experiments show that the product can be obtained in different forging loads depending on the initial billet geometry due to the fin formation, upsetting or extrusion mode of deformation, and friction effect. 5.5 Dimensional accuracy analysis Since the die for precision forging experiences very high radial pressure during the process, it considerably deforms in the radial direction. Therefore this radial deformation of the die becomes an important factor influencing the dimensional accuracy of the product. In order to obtain a product with accurate dimension, it is essential to evaluate the elastic deformation (U e ) of the die and the product. Using the above analysis, the parameters affecting forging dimensions,i.e.elasticdieexpansion(U e ), were calculated by using Eq. 5 and for a given condition the dimension of the die was determined. The stress calculation screen and the corrected die dimensions for U-shaped forging, as an example, are shown in Figs. 13a and b, respectively. The results and calculations obtained were also verified in the Excel sheet shown in Fig. 14. According to the die stress and dimensional accuracy calculations, U-shaped, T-shaped, and taper-shaped die cavities are tabulated in Table 2 and the resulting forged profiles are given in Fig. 15. The die design considerations for taper-shaped products are shown in Fig. 16. The punch is shown as a single unit and detail of the punch is not given. The punch forms the top surface of a cavity and is attached to the moving ram of a forging machine. The ejector is used to remove the product from the die without imposing deformation. The ejector is also used to give the shape to the bottom side of the product. The die insert forms the inner side of the die (die cavity). Since the die insert is subjected to forging load, friction load, and temperature,itsmaterialmustbechosensothatitisrobustin all required conditions. In order to increase the resistance against internal pressure, it is usual to make an insert shrink fitted into one or more shrink rings. The compressive stress imposed by the shrink ring has a cumulative effect at the bore of the die insert. Therefore, resultant tensile stress on the bore, caused by the forging loads transmitted through the forging part, can be substantially reduced. Actual Forging Product Profile Corrected Die Dimensions Fig. 15 U-, T-, and taper-shaped die cavities and the resulting product profiles 1 2 3 4 5 6 7 8 9 10 1. Punch 2. Product 3. Die 4. Shrink ring 5. Bolt 6. Die clamp ring 7. Bolster 8. Ejector 9. Ejector seat 10. Ejector rod Fig. 16 General assembly of die shape Int J Adv Manuf Technol (2009) 40:875886 885 6 Conclusion Computer-aided determination of forging design holds great importance for preserving the gradually disappearing know- how for the forging industry. The developed decision support system has wide applicability since the forging shapes, which are partly presented in this work, represent a large proportion of the total industrial parts. It is assumed that i
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