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Abstract
Along with the development of the construction industry, construction machinery as a modern industrial and civil buildings and the construction of the production process indispensable equipment. Building production and the construction process mechanization and automation, reducing the construction site with the labor intensity, improve labor productivity and lower production cost of construction for the development of the construction industry has laid a solid foundation. As construction machinery for the construction industry to provide the necessary technical equipment, So as the construction industry to measure productivity levels are an important sign, and to ensure project quality, lower construction costs, enhance economic efficiency, social benefits and speeding up the pace of construction provides an important tool. Therefore, the design of construction machinery and research is of great significance.
In this paper, the bar straight for the design of a more systematic study Straightening of reinforced plane were classified and comprehensive presentation; Straightening of reinforced machine control system outlined; Straightening of reinforced the working principle for the analysis of the system; Straightening of reinforced machine power calculation and allocation, Analysis, structural design, the design of the key parts and choice of detail. In light of the actual production of the needs of the overall product structure and properties of the optimal design, reached a relatively sound design requirements, the final straight of reinforcing bars for the overall test.
The design of reinforced Straightening motor-driven machine for cutting scissors bar helicopters, Straightening for the diameter of 14 mm disk or drawing a round of reinforced steel bars. As required length automatically and directly cut, the transfer process will be reinforced direct oxidation of the surface skin, remove rust and dirt. Make full use of its good mobility, small size, simple operation, high efficiency, improving the speed, Construction quality assurance at the same time, reducing manual and materials costs, reduce labor intensity and improved labor productivity.
Keywords : reinforcement bar straightening machine; Architecture; Machinery; Construction
本科生實(shí)習(xí)報(bào)告書(shū)
教學(xué)單位 機(jī)械工程學(xué)院
專(zhuān) 業(yè)
班 級(jí)
學(xué)生姓名
學(xué) 號(hào)
指導(dǎo)教師
學(xué)生實(shí)習(xí)報(bào)告：要求對(duì)實(shí)習(xí)的主要內(nèi)容、本人學(xué)習(xí)與工作的表現(xiàn)、收獲與體會(huì)、以及存在的問(wèn)題等方面進(jìn)行總結(jié)。
在畢業(yè)設(shè)計(jì)前期，為了充實(shí)設(shè)計(jì)知識(shí)，了解設(shè)計(jì)內(nèi)容，我去了阜新北方建設(shè)集團(tuán)進(jìn)行為期四周的的生產(chǎn)實(shí)習(xí)。生產(chǎn)實(shí)習(xí)是每一個(gè)大學(xué)畢業(yè)生必須擁有的一段經(jīng)歷，它使我們?cè)趯?shí)踐中了解社會(huì)，讓我們學(xué)到了很多在課堂上學(xué)不到的知識(shí),使我們開(kāi)拓了視野，增長(zhǎng)了見(jiàn)識(shí)，為我們以后進(jìn)一步走向社會(huì)打下了堅(jiān)實(shí)的基礎(chǔ)。同時(shí)，通過(guò)親身體驗(yàn)社會(huì)實(shí)踐，鍛煉自己的才干，培養(yǎng)自己的韌性，更為重要的是檢驗(yàn)一下自己所學(xué)的知識(shí)能否被社會(huì)所用，自己的能力能否被社會(huì)所承認(rèn)。并且找出自己的不足和差距所在。實(shí)習(xí)對(duì)于我們將要走入社會(huì)的學(xué)生來(lái)說(shuō)是一次熟悉社會(huì),了解社會(huì)的好機(jī)會(huì)。實(shí)習(xí)是我們了解社會(huì)的第一站。
作為一個(gè)施工企業(yè)，在接受工程任務(wù)后，必須高質(zhì)量、高速度、高效率、低成本地來(lái)完成建筑工程的施工，為國(guó)家提供積累，同時(shí)促進(jìn)企業(yè)自身的發(fā)展。在這里，先進(jìn)的施工機(jī)械是完成這一任務(wù)的重要保證。
一 實(shí)習(xí)內(nèi)容
1 建筑機(jī)械的類(lèi)型
1）沙石機(jī)械 2）混凝土機(jī)械 3）混凝土制品機(jī)械 4）起重運(yùn)輸機(jī)械 5）裝修機(jī)械 6）鋼筋及預(yù)應(yīng)力機(jī)械 7）木工機(jī)械 8）空氣壓縮機(jī)與水泵 9）壓實(shí)機(jī)械 10）樁工機(jī)械 11）土方機(jī)械 12）路面機(jī)械 13）拆除機(jī)械。
2 建筑機(jī)械的產(chǎn)品型號(hào)
例如：
（1） 挖掘機(jī)WY25：表示整機(jī)質(zhì)量等級(jí)為25t的履帶式液壓?jiǎn)味吠诰驒C(jī)
（2） 塔式起重機(jī)QTZ80：表示額定重力矩為800kN·m的上回轉(zhuǎn)自升式塔式起重機(jī)
（3） 混凝土攪拌機(jī)JZC350：表示出料容量為350L的齒圈錐形反轉(zhuǎn)出料混凝土攪拌機(jī)
（4） 鋼筋調(diào)直切斷機(jī)GTG 6/12：表示調(diào)直切斷鋼筋公稱(chēng)直徑為6—12㎜的固定式鋼筋調(diào)直切斷機(jī)
3 鋼筋機(jī)械的類(lèi)型
1）鋼筋強(qiáng)化機(jī)械 2）鋼筋切斷機(jī)械 3）鋼筋調(diào)直機(jī)械 4）鋼筋彎曲機(jī)械 5）鋼筋鐓頭機(jī)械 6）鋼筋連接機(jī)械。
4鋼筋調(diào)直機(jī)的分類(lèi)：
鋼筋調(diào)直機(jī)按調(diào)直原理分為孔模式和斜棍式兩種；按切斷機(jī)構(gòu)分為下切剪刀式和旋轉(zhuǎn)剪刀式；而下切剪刀式按切斷控制裝置的不同可分為機(jī)械控制式與光電控制式.
二收獲與體會(huì)
現(xiàn)代科技時(shí)代飛速發(fā)展中，高技術(shù)產(chǎn)品的種類(lèi)越來(lái)越多，生產(chǎn)工藝以及生產(chǎn)流程也各不相同。但不論是何種產(chǎn)品，從原料加工到制成產(chǎn)品都是遵循一定的生產(chǎn)原理，通過(guò)一些主要設(shè)備及工藝流程來(lái)完成的。因此，在專(zhuān)業(yè)實(shí)習(xí)過(guò)程中，我們首先要了解其生產(chǎn)原理，弄清生產(chǎn)的工藝流程和主要設(shè)備的構(gòu)造及操作。其次，在專(zhuān)業(yè)人員指導(dǎo)下，通過(guò)實(shí)習(xí)過(guò)程見(jiàn)習(xí)產(chǎn)品的設(shè)計(jì)、生產(chǎn)及開(kāi)發(fā)等環(huán)節(jié)，初步培養(yǎng)我們的知識(shí)運(yùn)用能力。實(shí)習(xí)期間，我利用此次難得的機(jī)會(huì)，努力工作，嚴(yán)格要求自己，虛心向領(lǐng)導(dǎo)學(xué)習(xí)，利用空余時(shí)間認(rèn)真學(xué)習(xí)一些課本內(nèi)容以外的相關(guān)知識(shí)，掌握了一些基本的專(zhuān)業(yè)技能，從而進(jìn)一步鞏固自己所學(xué)到的知識(shí)，為以后真正走上工作崗位打下基礎(chǔ)。這次實(shí)習(xí)中，我們的各個(gè)方面都有了進(jìn)步，相信這次實(shí)習(xí)給我們帶來(lái)的經(jīng)歷一定可以為我們將來(lái)的學(xué)習(xí)和生活提供很大的幫助!我會(huì)不斷的理解和體會(huì)實(shí)習(xí)中所學(xué)到的知識(shí)，在未來(lái)的工作中我將把我所學(xué)到的理論知識(shí)和實(shí)踐經(jīng)驗(yàn)不斷的應(yīng)用到實(shí)際工作來(lái)，充分展示自我的個(gè)人價(jià)值和人生價(jià)值。為實(shí)現(xiàn)自我的理想和光明的前程努力。
指
導(dǎo)
教
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意
見(jiàn)
成績(jī)?cè)u(píng)定： 指導(dǎo)教師簽字：
年 月 日
實(shí)習(xí)單位意見(jiàn)
負(fù)責(zé)人簽字：
（單位蓋章）
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注：實(shí)習(xí)結(jié)束時(shí)，由實(shí)習(xí)學(xué)生填寫(xiě)本表后，交指導(dǎo)教師和實(shí)習(xí)單位簽署意見(jiàn)，最后交所在教學(xué)單位歸檔保管。
本科畢業(yè)設(shè)計(jì)（論文）開(kāi) 題 報(bào) 告
題 目 鋼筋調(diào)直機(jī)設(shè)計(jì)
指 導(dǎo) 教 師
院（系、部）
專(zhuān) 業(yè) 班 級(jí)
學(xué) 號(hào)
姓 名
日 期
教務(wù)處印制
4
一、選題的目的、意義和研究現(xiàn)狀
伴隨著建筑業(yè)的發(fā)展，建筑機(jī)械成為現(xiàn)代工業(yè)與民用建筑施工與生產(chǎn)過(guò)程中不可缺少的設(shè)備。建筑生產(chǎn)與施工過(guò)程實(shí)現(xiàn)機(jī)械化、自動(dòng)化、降低施工現(xiàn)場(chǎng)人員的勞動(dòng)強(qiáng)度、提高勞動(dòng)生產(chǎn)率以及降低生產(chǎn)施工成本，為建筑業(yè)的發(fā)展奠定了堅(jiān)實(shí)的基礎(chǔ)。由于建筑機(jī)械能夠?yàn)榻ㄖI(yè)提供必要的技術(shù)設(shè)備，因此成為衡量建筑業(yè)生產(chǎn)力水平的一個(gè)重要標(biāo)志，并且為確保工程質(zhì)量、降低工程造價(jià)、提高經(jīng)濟(jì)效益、社會(huì)效益與加快工程建設(shè)速度提供了重要的手段。所以，提高建筑機(jī)械的管理、使用、維護(hù)與維修能力，對(duì)加快建筑生產(chǎn)與施工速度，具有十分重要的意義。
在建筑物中，鋼筋混凝土與預(yù)應(yīng)力鋼筋混凝土機(jī)構(gòu)得到廣泛的應(yīng)用，而鋼筋作為結(jié)構(gòu)中的骨架起著級(jí)其重要的作用。因此，鋼筋加工機(jī)械成為建設(shè)施工工程中不可缺少的重要設(shè)備。而鋼筋調(diào)直機(jī)作為一種重要的鋼筋加工機(jī)械，是其中使用較多的一種設(shè)備。為了更快速、更有效的調(diào)直出高質(zhì)量的鋼筋，設(shè)計(jì)一種自動(dòng)化程度高、加工質(zhì)量好、結(jié)構(gòu)簡(jiǎn)單，調(diào)節(jié)方便，加工品種多，工作效率高，適用于建筑、水利、橋梁等施工行業(yè)的鋼筋調(diào)直機(jī)，既能提高生產(chǎn)效率和鋼筋調(diào)直質(zhì)量，又能簡(jiǎn)化操作程序，而且可以減輕工人的勞動(dòng)強(qiáng)度。
鋼筋調(diào)直是鋼筋加工中的一項(xiàng)重要工序，通常，鋼筋調(diào)直機(jī)用于調(diào)直φ14㎜以下的盤(pán)圓鋼筋和冷拔鋼筋，并且根據(jù)需要的長(zhǎng)度進(jìn)行自動(dòng)調(diào)直，在調(diào)直過(guò)程中將鋼筋表面的氧化皮、鐵銹和污物除掉。鋼筋調(diào)直機(jī)又分為孔模式和斜輥式兩種。而孔模式是現(xiàn)今應(yīng)用較多的一種方式。本次設(shè)計(jì)的建筑鋼筋調(diào)直機(jī)為GT4-8型鋼筋調(diào)直機(jī)，采用切刀斷料式的調(diào)直剪切方法，這種調(diào)直機(jī)結(jié)構(gòu)簡(jiǎn)單，造型獨(dú)特，噪聲較低，功率損失少，效率較高，鋼筋調(diào)直準(zhǔn)確，調(diào)直范圍大，操作安全可靠，特別是減輕了工人的勞動(dòng)強(qiáng)度。綜上所述，此鋼筋調(diào)直機(jī)制造難度小，精度易控制，成本也較低，能夠很好的完成鋼筋調(diào)直工作。
二、研究方案及預(yù)期結(jié)果
GT4-8型鋼筋調(diào)直機(jī)為切刀斷料式，主要由調(diào)直筒、傳動(dòng)箱、切斷機(jī)構(gòu)、承受架、及機(jī)座等組成，能夠調(diào)直切斷直徑為4—8㎜的鋼筋，鋼筋抗拉強(qiáng)度650MPa，切斷長(zhǎng)度為300-6000㎜，切斷長(zhǎng)度誤差≤3，牽引速度為40m/min，調(diào)直筒轉(zhuǎn)速為2800r/min，送料、牽引輥直徑為90㎜，調(diào)直、牽引與切斷電機(jī)型號(hào)為JO2-42-4型，調(diào)直、牽引與切斷功率為5.5KW，外形尺寸長(zhǎng)×寬×高為7250㎜×600㎜×1220㎜，整機(jī)重量為1000Kg。
調(diào)直過(guò)程：鋼筋經(jīng)導(dǎo)向筒進(jìn)入調(diào)直筒，調(diào)直筒內(nèi)裝有五個(gè)不在同一中心線上的調(diào)直塊，鋼筋在每個(gè)調(diào)直塊的中孔中穿過(guò)，由上、下?tīng)恳唺A緊后向前送進(jìn)，穿過(guò)切斷機(jī)構(gòu)到受料槽中，調(diào)直筒以高速旋轉(zhuǎn)，調(diào)直塊反復(fù)的連續(xù)彎曲鋼筋，將鋼筋調(diào)直，同時(shí)清除鋼筋表面的污物。
傳動(dòng)系統(tǒng)：電動(dòng)機(jī)通過(guò)三角膠帶傳動(dòng)裝置帶動(dòng)調(diào)直筒旋轉(zhuǎn)而進(jìn)行調(diào)直工作。經(jīng)電動(dòng)機(jī)上的另一膠帶輪以及一對(duì)錐齒輪帶動(dòng)偏心軸，再經(jīng)二級(jí)齒輪減速，驅(qū)動(dòng)上下壓輥等速反向旋轉(zhuǎn)，從而實(shí)現(xiàn)鋼筋牽引運(yùn)動(dòng)。又經(jīng)過(guò)偏心軸和雙滑塊機(jī)構(gòu)，帶動(dòng)錘頭上下運(yùn)動(dòng)，當(dāng)上切刀進(jìn)入錘頭下面時(shí)即受到錘頭敲擊，完成鋼筋切斷。
切斷機(jī)構(gòu)主要由曲柄輪、連桿、錘頭、定長(zhǎng)拉桿、復(fù)位彈簧、刀臺(tái)座、上切刀、下切刀、上切刀架組成。
電器線路主要由熔斷器、交流接觸器、熱繼電器、常開(kāi)按鈕、電動(dòng)機(jī)、轉(zhuǎn)換開(kāi)關(guān)等組成。
三、研究進(jìn)度
第5 ~6周 調(diào)研收集資料；
第7 周 擬訂設(shè)計(jì)方案；
第8~11周 對(duì)鋼筋調(diào)直機(jī)總體設(shè)計(jì)；
第12周 對(duì)傳動(dòng)系統(tǒng)和電器線路進(jìn)行設(shè)計(jì)；
第13周 對(duì)調(diào)直機(jī)機(jī)構(gòu)和牽引剪切機(jī)構(gòu)進(jìn)行設(shè)計(jì)；
第14~15周 整理圖紙、編寫(xiě)設(shè)計(jì)說(shuō)明書(shū)；
第16周 進(jìn)行論文的檢查并準(zhǔn)備答辯
四、主要參考文獻(xiàn)
[1] 田奇 馬志奇 童占榮 王進(jìn)．鋼筋及預(yù)應(yīng)力機(jī)械應(yīng)用技術(shù)．中國(guó)建材工業(yè)出版社. ．
2004，5
[2] 田奇 建筑機(jī)械使用與維護(hù) 中國(guó)建材工業(yè)出版社 2003.8
[3] 孟憲源．現(xiàn)代機(jī)構(gòu)手冊(cè)[M]．第1版．北京：機(jī)械工業(yè)出版社．1994，6
[4] 徐灝．機(jī)械設(shè)計(jì)手冊(cè)（1）[M] ．第2版．北京：機(jī)械工業(yè)出版社．2000
[5] 徐灝．機(jī)械設(shè)計(jì)手冊(cè)（2）[M] ．第2版．北京：機(jī)械工業(yè)出版社．2000
[6] 徐灝．機(jī)械設(shè)計(jì)手 冊(cè)（3）[M] ．第2版．北京：機(jī)械工業(yè)出版社．2000
[7] 王宗林．CHC5/14鋼筋矯直切斷機(jī)．北京．建筑機(jī)械．2003
[8] 何斌 宋銘奇．中小型建筑機(jī)械手冊(cè)．長(zhǎng)沙．湖南科學(xué)技術(shù)出版社．1986
[9] 《建筑機(jī)械使用手冊(cè)》編寫(xiě)組．建筑機(jī)械使用手冊(cè)．北京．中國(guó)建筑工業(yè)出版社．1990
[10] ]Zhou Youqiang,Shu Xiaolong.Anglysis of the contact tooth number and load sharing of the small teeth difference[C]. Tokyo: International Symposium on Design and Synthesis.1996.
[11] Shu Xiaolong.Determination of load sharing factor for plametary gearing with small tooth number difference[J].Mechanism and Machine Throry,1995,30(2).
五、指導(dǎo)教師意見(jiàn)
指導(dǎo)教師簽字：
摘要
伴隨著建筑業(yè)的發(fā)展，建筑機(jī)械成為現(xiàn)代工業(yè)與民用建筑施工與生產(chǎn)過(guò)程中不可缺少的設(shè)備。建筑生產(chǎn)與施工過(guò)程實(shí)現(xiàn)機(jī)械化、自動(dòng)化、降低施工現(xiàn)場(chǎng)人員的勞動(dòng)強(qiáng)度、提高勞動(dòng)生產(chǎn)率以及降低生產(chǎn)施工成本，為建筑業(yè)的發(fā)展奠定了堅(jiān)實(shí)的基礎(chǔ)。由于建筑機(jī)械能夠?yàn)榻ㄖI(yè)提供必要的技術(shù)設(shè)備，因此成為衡量建筑業(yè)生產(chǎn)力水平的一個(gè)重要標(biāo)志，并且為確保工程質(zhì)量、降低工程造價(jià)、提高經(jīng)濟(jì)效益、社會(huì)效益與加快工程建設(shè)速度提供了重要的手段。因此，對(duì)建筑機(jī)械的設(shè)計(jì)和研究具有十分重要的意義。
本文對(duì)鋼筋調(diào)直機(jī)的設(shè)計(jì)進(jìn)行了比較系統(tǒng)的研究，對(duì)鋼筋調(diào)直機(jī)進(jìn)行了分類(lèi)和綜合的介紹；對(duì)鋼筋調(diào)直機(jī)的控制系統(tǒng)進(jìn)行了概述；對(duì)鋼筋調(diào)直機(jī)的工作原理進(jìn)行了系統(tǒng)的分析；對(duì)鋼筋調(diào)直機(jī)的功率計(jì)算與分配、受力分析、結(jié)構(gòu)設(shè)計(jì)、主要零部件設(shè)計(jì)與選擇等進(jìn)行了詳細(xì)的介紹。結(jié)合實(shí)際生產(chǎn)的需要，對(duì)產(chǎn)品總體結(jié)構(gòu)和工作性能進(jìn)行了優(yōu)化設(shè)計(jì)，達(dá)到了比較完善的設(shè)計(jì)要求，最后對(duì)鋼筋調(diào)直機(jī)進(jìn)行了總體調(diào)試。
本次設(shè)計(jì)的鋼筋調(diào)直機(jī)為電機(jī)驅(qū)動(dòng)下切剪刀式鋼筋調(diào)直機(jī)，用于調(diào)直直徑為14mm以下的盤(pán)圓鋼筋或冷拔鋼筋。并且根據(jù)需要長(zhǎng)度進(jìn)行自動(dòng)調(diào)直和切斷，調(diào)直過(guò)程中將鋼筋表面氧化皮、鐵銹和污物除掉。充分發(fā)揮了其良好的機(jī)動(dòng)性，體積小，操作簡(jiǎn)單，效率高等特點(diǎn)，在提高施工速度，保證施工質(zhì)量的同時(shí)，降低了人工與材料的成本，減輕了勞動(dòng)強(qiáng)度，提高了勞動(dòng)生產(chǎn)率。
關(guān)鍵詞：鋼筋調(diào)直機(jī)；建筑；機(jī)械；施工
Abstract
Along with the development of the construction industry, construction machinery as a modern industrial and civil buildings and the construction of the production process indispensable equipment. Building production and the construction process mechanization and automation, reducing the construction site with the labor intensity, improve labor productivity and lower production cost of construction for the development of the construction industry has laid a solid foundation. As construction machinery for the construction industry to provide the necessary technical equipment, So as the construction industry to measure productivity levels are an important sign, and to ensure project quality, lower construction costs, enhance economic efficiency, social benefits and speeding up the pace of construction provides an important tool. Therefore, the design of construction machinery and research is of great significance.
In this paper, the bar straight for the design of a more systematic study Straightening of reinforced plane were classified and comprehensive presentation; Straightening of reinforced machine control system outlined; Straightening of reinforced the working principle for the analysis of the system; Straightening of reinforced machine power calculation and allocation, Analysis, structural design, the design of the key parts and choice of detail. In light of the actual production of the needs of the overall product structure and properties of the optimal design, reached a relatively sound design requirements, the final straight of reinforcing bars for the overall test.
The design of reinforced Straightening motor-driven machine for cutting scissors bar helicopters, Straightening for the diameter of 14 mm disk or drawing a round of reinforced steel bars. As required length automatically and directly cut, the transfer process will be reinforced direct oxidation of the surface skin, remove rust and dirt. Make full use of its good mobility, small size, simple operation, high efficiency, improving the speed, Construction quality assurance at the same time, reducing manual and materials costs, reduce labor intensity and improved labor productivity.
Keywords : reinforcement bar straightening machine; Architecture; Machinery; Construction
目錄
前言 1
1 鋼筋調(diào)直機(jī)的設(shè)計(jì) 2
1.1 鋼筋調(diào)直機(jī)的分類(lèi) 2
1.2 鋼筋調(diào)直機(jī)調(diào)直剪切原理 2
1.3 鋼筋調(diào)直機(jī)的主要技術(shù)性能 3
1.4 鋼筋調(diào)直機(jī)工作原理與基本構(gòu)造 3
2 主要計(jì)算 8
2.1 生產(chǎn)率和功率計(jì)算 8
2.1.1 生產(chǎn)率計(jì)算 8
2.1.2 功率計(jì)算，選擇電動(dòng)機(jī) 8
2.2 第一組皮帶傳動(dòng)機(jī)構(gòu)的設(shè)計(jì) 12
2.2.1 確定設(shè)計(jì)功率 12
2.2.2 初選帶的型號(hào) 12
2.2.3 確定帶輪的基準(zhǔn)直徑和 12
2.2.4 確定中心距a和帶的基準(zhǔn)長(zhǎng)度 13
2.2.5 驗(yàn)算小輪包角 13
2.2.6 計(jì)算帶的根數(shù) 13
2.2.7 計(jì)算帶作用在軸上的載荷Q 14
2.3 第二組皮帶傳動(dòng)機(jī)構(gòu)的設(shè)計(jì) 14
2.3.1 確定設(shè)計(jì)功率 14
2.3.2 初選帶的型號(hào) 14
2.3.3 確定帶輪的基準(zhǔn)直徑和 15
2.3.4 確定中心距a和帶的基準(zhǔn)長(zhǎng)度 15
2.3.5 驗(yàn)算小輪包角 15
2.3.6 計(jì)算帶的根數(shù) 15
2.3.7 計(jì)算帶作用在軸上的載荷Q 16
2.3.8 主動(dòng)帶輪設(shè)計(jì) 16
3 直齒輪設(shè)計(jì) 18
3.1 確定齒輪傳動(dòng)精度等級(jí) 18
3.1.1 計(jì)算許用應(yīng)力 19
3.1.2 按齒面接觸疲勞強(qiáng)度確定中心距 19
3.1.3 驗(yàn)算齒面接觸疲勞強(qiáng)度 20
3.1.4 驗(yàn)算齒根彎曲疲勞強(qiáng)度 21
3.1.5 齒輪主要參數(shù)和幾何尺寸 21
4 錐齒輪的設(shè)計(jì) 24
5 軸的設(shè)計(jì)與強(qiáng)度校核 29
5.1 Ⅰ軸的設(shè)計(jì)與強(qiáng)度校核 29
5.1.1 軸的結(jié)構(gòu)設(shè)計(jì) 29
5.1.2 求出齒輪受力 29
5.2 Ⅱ軸的設(shè)計(jì)與強(qiáng)度校核 31
5.2.1 軸的結(jié)構(gòu)設(shè)計(jì) 31
5.2.2 求出齒輪受力 32
6 主要零件的規(guī)格及加工要求 36
6.1 調(diào)直筒及調(diào)直塊 36
6.2.齒輪 36
6.3.調(diào)直機(jī)的各傳動(dòng)軸均安裝滾動(dòng)軸承 36
6.4 傳送壓輥的選用和調(diào)整 37
6.5 定長(zhǎng)機(jī)構(gòu)的選擇與調(diào)整 37
7 結(jié)論 38
致謝 39
參考文獻(xiàn) 40
附錄A 譯文 41
附錄B 外文文獻(xiàn) 47
附錄A 譯文
降低商用飛機(jī)的直接維護(hù)費(fèi)用的方法
Haiqiao Wu
Yi Liu
Yunliang Ding和
Jia Liu
[作者]
Haiqiao Wu，Yi Liu，Yunliang Ding和Jia Liu都是在中華人民共和國(guó)南京大學(xué)航空宇航工程學(xué)院從事航空學(xué)和行于學(xué)的學(xué)者。
[關(guān)鍵詞]
直接費(fèi)用，商用飛機(jī)，維護(hù)費(fèi)用，專(zhuān)家，鑒定測(cè)試
[摘要]
商用飛機(jī)的直接維護(hù)費(fèi)用（DMC）對(duì)飛機(jī)費(fèi)用的所有權(quán)起一個(gè)重要作用。我們的研究目標(biāo)是發(fā)現(xiàn)一些減少DMC的方法。本論文首先指出設(shè)計(jì)和果實(shí)診斷是影響DMC的主要因素，對(duì)于特定的航空公司這一因素，可忽略不計(jì)。一項(xiàng)R&M設(shè)計(jì)的新觀念——為了要減少DMC，本論文討論了自由操作時(shí)期和過(guò)失診斷專(zhuān)家系統(tǒng)的維護(hù)。
[電子的通路路徑]
本文的翡翠研究寄存器可以從以下網(wǎng)站得到：
www.emeraldinsight.com/researchregister
現(xiàn)在的議題和本文的完整文件可以從以下網(wǎng)站
www.emeraldinsight.com/0002-2667.htm
降低商用飛機(jī)的直接維護(hù)費(fèi)用的方法
[介紹]
商用飛機(jī)的維護(hù)活動(dòng)是飛機(jī)耐飛性能的一個(gè)必要組成部分。飛機(jī)維護(hù)是令飛機(jī)回復(fù)到可使用狀態(tài)下的一個(gè)上木。它包括維護(hù)、修理、徹底檢查、檢驗(yàn)和狀態(tài)測(cè)定。它可以分為兩種類(lèi)型。
修正的維護(hù)。這些活動(dòng)，即由提供對(duì)于某一已知的或疑似的故障及（或）缺陷的方案，來(lái)是失敗的結(jié)果回復(fù)到一種令人滿意的情況。修正的維護(hù)大體上可分為過(guò)失確認(rèn)、過(guò)失隔離、拆卸、替換、重新裝配、對(duì)準(zhǔn)或者調(diào)整，以及測(cè)試。這一種維護(hù)的類(lèi)型即是不預(yù)定的維護(hù)，而且受益于診斷的使用以減輕在維護(hù)資源方面的負(fù)擔(dān)。
預(yù)防的維護(hù)。這些活動(dòng)，即由系統(tǒng)檢驗(yàn)、探測(cè)、疲勞項(xiàng)目的替換、調(diào)整、口徑測(cè)定，以及清潔等，來(lái)使之保持在可使用狀態(tài)。在飛機(jī)和儀器的整個(gè)壽命中，它以一種規(guī)定的形式實(shí)行。因此，它也被成做預(yù)定的維護(hù)。
維護(hù)通常的目標(biāo)是，在一家航空公司需要維修飛機(jī)時(shí)，能夠以最低的費(fèi)用提供一套完整的維護(hù)服務(wù)。現(xiàn)在商用飛機(jī)的維護(hù)費(fèi)用對(duì)飛機(jī)費(fèi)用的所有權(quán)起一個(gè)重要作用。維護(hù)費(fèi)用一般占與飛機(jī)操作相關(guān)費(fèi)用的10%-20%（Maple,2001）。
直接的維護(hù)費(fèi)用（DMC）被定義為，用于維護(hù)一個(gè)飛機(jī)或相關(guān)儀器所需的勞動(dòng)力費(fèi)用和材料費(fèi)用（ATA，國(guó)際航空運(yùn)輸協(xié)會(huì)和ICCAIA，1992）。DMC不包括勞動(dòng)和物質(zhì)的開(kāi)支，如行政、監(jiān)督、使用工具工作、測(cè)試儀器、設(shè)備、記錄及保存等活動(dòng)的費(fèi)用（Knotts,1999）。航空公司通常會(huì)尋求維護(hù)費(fèi)用的保證，如果DMC超過(guò)約定的指定水平，飛機(jī)制造者將招致財(cái)政上的處罰。
我們的研究目標(biāo)是找出一些為商用飛機(jī)減少DMC的方法。本論文首先分析了影響DMC的主要因素，然后討論了可以減少DMC的一些方法。
[DMC的主要影響因素]
依照定義，DMC的公式是：
DMC=（+）LR+MC,
其中，是指飛機(jī)維護(hù)人員在飛機(jī)上的工作時(shí)間；是指飛機(jī)維護(hù)人員不在飛機(jī)上的凌夷部分工作時(shí)間；LR是指勞動(dòng)費(fèi)用；MC是指材料的費(fèi)用。影響DMC的因素可以依下列各項(xiàng)分類(lèi)。
[設(shè)計(jì)因素]
可靠性和可維護(hù)性（R&M）是飛機(jī)的固有價(jià)值。它只能由設(shè)計(jì)決定。雖然像經(jīng)過(guò)高度訓(xùn)練的人和一個(gè)應(yīng)答的補(bǔ)給系統(tǒng)這樣的其他因素，也能使時(shí)間限定在一個(gè)絕對(duì)的最小量中，但是只有國(guó)有的R&M才能決定這一最小量。即使改良訓(xùn)練或技術(shù)支持也不能夠有效的彌補(bǔ)因一架拙劣設(shè)計(jì)（根據(jù)R&M）的商用飛機(jī)在可用性方面所造成的損失。將支持飛機(jī)飛行的費(fèi)用減少到最小，最大限度的提高籍由最好設(shè)計(jì)所生產(chǎn)出的產(chǎn)品的可用性，使之可靠并且可維護(hù)。對(duì)于商用飛機(jī)整個(gè)壽命期所花費(fèi)用來(lái)說(shuō)，大概有70%-80%的費(fèi)用是由設(shè)計(jì)階段來(lái)決定的。
[過(guò)失診斷效率]
系統(tǒng)和技術(shù)的復(fù)雜性逐漸增加加大了即使、有效的過(guò)失診斷的困難。由此成為系統(tǒng)可維護(hù)性的問(wèn)題因素。而且，從減少時(shí)間周期和費(fèi)用方面來(lái)看，無(wú)效的過(guò)失診斷可能會(huì)很貴。因?yàn)椤皼](méi)有發(fā)現(xiàn)錯(cuò)誤（NFF）”的情形會(huì)對(duì)維護(hù)費(fèi)用產(chǎn)生很大的影響?，F(xiàn)代系統(tǒng)的設(shè)計(jì)經(jīng)歷了40%或者更高的儀器錯(cuò)誤消除率。這些錯(cuò)誤是有歧義的、勞動(dòng)密集型的測(cè)試程序所造成的。航空電子學(xué)和電氣科學(xué)方面的不可預(yù)定維護(hù)費(fèi)用占民用飛機(jī)DMC的18%，40%與儀器錯(cuò)誤消除相關(guān)的被歸類(lèi)為NFF。在1992年，一項(xiàng)對(duì)部件轉(zhuǎn)移的審計(jì)突出了英國(guó)空中航線的機(jī)群每平均有8000項(xiàng)被轉(zhuǎn)移走?？v觀所有的工作室，其所有部件中的14%，被發(fā)現(xiàn)有NFF。一臺(tái)航空電子學(xué)儀器平均會(huì)產(chǎn)生出30%的NFF。在財(cái)政上來(lái)看，若是考慮到直接和間接費(fèi)用，那么 這就等于是每年在NFF上的開(kāi)支總共就需要兩千萬(wàn)英鎊（Knotts,1999）。
[與組織相關(guān)的可變因素]
這些可變因素跟一家特定的航空公司有關(guān)。他們包括飛機(jī)機(jī)群的規(guī)模和共通性，飛機(jī)的齡和使用率，維修標(biāo)準(zhǔn)和計(jì)劃，檢查間隔的頻率，承做轉(zhuǎn)包工作的水平，會(huì)計(jì)方法，通貨波動(dòng)，地方勞動(dòng)力費(fèi)用，消耗品的可循環(huán)率，以及材料價(jià)格（Maple,2001）。
[環(huán)境因素]
這些因素依賴(lài)于操作員的位置。舉例來(lái)說(shuō)，它是沙漠的環(huán)境或者海洋性氣候。再舉例來(lái)說(shuō)，由于沙和鹽的腐蝕，將會(huì)對(duì)引擎的維護(hù)儀器產(chǎn)生重要影響。
在本論文中，我們忽略了某一特定的航空公司這一因素，再討論了設(shè)計(jì)和過(guò)失診斷的影響。
[一項(xiàng)關(guān)于R&M在自由操作期間的維護(hù)的新觀念]
在傳統(tǒng)方式下，R&M設(shè)計(jì)的探討是建立在失敗基礎(chǔ)上的。這種探討認(rèn)為，在儀器設(shè)備的整個(gè)壽命期間，偶然的失敗是不可避免的，并且這種失敗將導(dǎo)致許多不可預(yù)定的維護(hù)工作在日常工作中產(chǎn)生。由于不可預(yù)定的維護(hù)是不能被計(jì)劃出來(lái)的，所以，從維護(hù)費(fèi)用方面來(lái)說(shuō)，不可預(yù)定的維護(hù)可能是做昂貴的。最近的研究表明，給大型的商用噴氣式飛機(jī)每一年每一架飛機(jī)的不可預(yù)定維護(hù)費(fèi)用在一百萬(wàn)英鎊左右（Kumar et al.,1999a）。為了減少費(fèi)用，一個(gè)以維護(hù)的自由操作時(shí)期（MFOP）為基礎(chǔ)的新方法已經(jīng)發(fā)展起來(lái)了。MFOP被定義為，儀器設(shè)備在沒(méi)有任何維護(hù)措施，也沒(méi)有因系統(tǒng)錯(cuò)誤或限制導(dǎo)致的操作員的約束行為就能夠執(zhí)行現(xiàn)已指定的任務(wù)。這個(gè)操作的時(shí)間段就是MFOP。（Hockley,1998）。
在MFOP的時(shí)期，籍由設(shè)計(jì)，任何的維護(hù)的必要性應(yīng)該是保持在一個(gè)最小量。并且，儀器設(shè)備僅僅允許執(zhí)行如飛行服務(wù)這樣的在計(jì)劃內(nèi)的最低限度維護(hù)。一個(gè)MFOP之后，緊接著就是一個(gè)維護(hù)恢復(fù)時(shí)期（MRP）。
MRP被定義為是一段被限定了的時(shí)間。在此期間，需要完成適當(dāng)?shù)陌才藕驼_的維護(hù)，使系統(tǒng)回復(fù)到滿負(fù)荷狀態(tài)，這樣才能夠完成接下來(lái)的MFOP。由于它們必須包括不同的維護(hù)活動(dòng)，所以不是所有的MRP將會(huì)是相同的期間，因?yàn)榭商鎿Q的單位（LRU）個(gè)體排成一行，比如那些使用壽命期滿的，需要做一些徹底檢查，而且不用維護(hù)或正確的檢驗(yàn)。另外，我們會(huì)做出正確的維護(hù)來(lái)是那些錯(cuò)誤的系統(tǒng)回復(fù)到滿負(fù)荷狀態(tài)（Hockley,1998）。
MFOP是一個(gè)擔(dān)保時(shí)期的延長(zhǎng)。操作員正在考慮在系統(tǒng)的整個(gè)使用壽命期間擴(kuò)充這一概念。產(chǎn)品供應(yīng)商或者制造商需要作出如下保證，即在指定的一段操作時(shí)間內(nèi)，因?yàn)橛蓄A(yù)先社頂?shù)馁|(zhì)量保證登記，不可預(yù)定的維護(hù)工作是不需要的。這個(gè)質(zhì)量由自由操作時(shí)期的存留能力時(shí)間（MFOPS）按比例來(lái)決定（Kumar et al.,1999b）。
MFOPS被定義為某一項(xiàng)目在MFOP的期間存留下來(lái)的可能性。
對(duì)于商用飛機(jī)的MFOP，當(dāng)考慮到R&M的設(shè)計(jì)時(shí)，會(huì)有兩種減少DMC的方法。
飛機(jī)的固有可靠性可以得到句到的改變。更高的可靠性可以減低錯(cuò)誤的次數(shù)，因此，飛機(jī)可靠性是有工時(shí)和必需的物質(zhì)決定的，DMC就會(huì)相應(yīng)減低。
完成飛機(jī)的MFOPS，這就意味著任意的失敗應(yīng)該在MFOP期間被根除。傳統(tǒng)的文化認(rèn)為，錯(cuò)誤不僅是不可避免的，而且，從某種角度來(lái)看，它是可以接受的，這應(yīng)該放棄。一種細(xì)節(jié)詳細(xì)的知識(shí)環(huán)境和使用經(jīng)驗(yàn)，以及對(duì)于為什么失敗的非常機(jī)制下的理解，會(huì)被灌輸給發(fā)展程序員。許多技術(shù)或者解決辦法都以一條更積極的方式設(shè)計(jì)其可靠性，不給失敗予任何機(jī)會(huì)。這些技術(shù)可以有一種緩慢的設(shè)計(jì)變化過(guò)程，即選擇不同的成分，生成一個(gè)改進(jìn)的程序，或者，可以有一種更快速的設(shè)計(jì)變化過(guò)程。
完成最適宜的維護(hù)計(jì)劃。很明顯，飛機(jī)所有的系統(tǒng)在某一時(shí)間都需要做一些維護(hù)工作，而且，這些工作是在MRP計(jì)劃中的。MFOP延期事實(shí)上是對(duì)MRP所有正確的 維護(hù)，因此，不可預(yù)定的維護(hù)部分其實(shí)被轉(zhuǎn)化成了更多的計(jì)劃中的維護(hù)，它是建立在有更高可靠性的儀器上的，這才能產(chǎn)生更高的可靠性能。MRP的價(jià)值與效率的關(guān)系及其平衡的設(shè)置建立并支持最好的整個(gè)MFOP系統(tǒng)。其實(shí)際價(jià)值可以在設(shè)計(jì)期間的系統(tǒng)工程學(xué)中的經(jīng)貿(mào)學(xué)和方法學(xué)來(lái)體現(xiàn)。這些能減少維護(hù)計(jì)劃中一定量的百分比。而后勤支援可能被集中到一個(gè)特定的飛機(jī)操作地點(diǎn)。緊急事故處理資源可能會(huì)重新分配到幾頂?shù)墓ぷ髦?。這樣，MFOP就能為操作者帶來(lái)靈活性。此時(shí)，操作者可以在一定范圍內(nèi)執(zhí)行組織和正確的維護(hù)工作。然后，DMC就會(huì)下降，這是因?yàn)橛糜趫?bào)廢飛機(jī)的勞動(dòng)力和材料減少了。舉例來(lái)說(shuō)，如今一架飛機(jī)在整天壽命期中的直線型維護(hù)占所有維護(hù)勞動(dòng)力的50%（Maple,2001），由MFOP設(shè)計(jì)出的飛機(jī)常規(guī)工作將會(huì)減少到最小量。
[過(guò)失診斷]
過(guò)失診斷的進(jìn)程一般可氛圍感應(yīng)信號(hào)、提取特征以及連續(xù)的診斷論證。當(dāng)對(duì)現(xiàn)代的商用飛機(jī)診斷失敗時(shí)，大部分感應(yīng)信號(hào)和提取的特征程序由于感應(yīng)器、動(dòng)力學(xué)實(shí)驗(yàn)和信號(hào)檢測(cè)這些技術(shù)的發(fā)展，可以是自動(dòng)完成的。這樣，診斷論證（即，怎樣找出錯(cuò)誤的根源）就成為了決定過(guò)失診斷的效率的主要因素。
根據(jù)過(guò)失診斷的觀念，飛機(jī)是一個(gè)復(fù)雜的系統(tǒng)。它的結(jié)構(gòu)是多樣的階層建筑結(jié)構(gòu)，它包含有許多次級(jí)系統(tǒng)，比如飛機(jī)主結(jié)構(gòu)、引擎、自動(dòng)飛行系統(tǒng)、起落架、聯(lián)絡(luò)系統(tǒng)、液壓和飛行系統(tǒng)。每個(gè)次級(jí)系統(tǒng)是由更低級(jí)別的次級(jí)系統(tǒng)或者次級(jí)單元構(gòu)成的。并且，這些次級(jí)系統(tǒng)或次級(jí)單元之間通常是有聯(lián)系的。由于飛機(jī)結(jié)構(gòu)和功能的復(fù)雜性和多相性，飛機(jī)結(jié)構(gòu)水平之間的聯(lián)系是難以定義的。次級(jí)系統(tǒng)或次級(jí)單元的輸入和輸出之間的數(shù)量關(guān)系往往是無(wú)法測(cè)知或不正確的。
很多技術(shù)領(lǐng)域中，先進(jìn)的技術(shù)如機(jī)械化、電氣化、計(jì)算機(jī)和自動(dòng)機(jī)械控制，以及電子學(xué)都適用于現(xiàn)代的飛機(jī)。越來(lái)越多的電機(jī)械儀器已經(jīng)用于飛機(jī)。這些儀器的機(jī)械和電子部分已經(jīng)不僅整合了飛機(jī)的控制，還整合了飛機(jī)的功能和結(jié)構(gòu)。飛機(jī)的過(guò)失診斷囊括了各種學(xué)科的知識(shí)。
我們從以上的議題中總結(jié)出了商用飛機(jī)的診斷論證的困難性，而且很多時(shí)候，這需要有專(zhuān)家的參與。然而，我們需要的專(zhuān)家因?yàn)檎{(diào)換、疾病，以及雇傭關(guān)系的改變等原因，經(jīng)常是不到位的。除此之外，很多技術(shù)領(lǐng)域已經(jīng)應(yīng)用于大型商用飛機(jī)，而且一個(gè)專(zhuān)家不再可能蚩尤所有現(xiàn)有的系統(tǒng)知識(shí)。發(fā)展一個(gè)包涵系統(tǒng)知識(shí)、專(zhuān)長(zhǎng)和經(jīng)驗(yàn)的過(guò)失診斷專(zhuān)家系統(tǒng)被視為一個(gè)定位困難的方法。這樣不僅可以帶來(lái)比人工更正確，更一致的結(jié)果，而且在某種程度上，它可以代替一個(gè)專(zhuān)家，使很多使用者可以輕易獲得寶貴的專(zhuān)長(zhǎng)，尤其適用于相對(duì)不熟練的職工和新來(lái)者。
大部分的NFF將會(huì)被專(zhuān)家系統(tǒng)避免，如此一種有成本效益和及時(shí)的過(guò)失診斷將會(huì)幫助減少DMC。
[結(jié)論]
MFOP的觀念已經(jīng)作為面向未來(lái)所作出的一個(gè)大步驟被航空宇航工業(yè)認(rèn)同。一些在較早時(shí)間所提出的關(guān)頂已應(yīng)用于A340-600（Cini和Griffith,1999）。過(guò)失診斷專(zhuān)家系統(tǒng)已經(jīng)應(yīng)用于波音777的中央計(jì)算機(jī)維護(hù)系統(tǒng)。毫無(wú)疑問(wèn)，它們能極大地減少DMC。
附錄B 外文文獻(xiàn)
Methods to reduce direct
maintenance costs for
commercial aircraft
Haiqiao Wu
Yi Liu
Yunliang Ding and
Jia Liu
The authors
Haiqiao Wu, Yi Liu, Yunliang Ding and Jia Liu are all in the College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, People’s Republic of China
Keywords
Direct costs, Commercial aircraft, Maintenance costs, Experts, Diagnostic testing
Abstract
Direct maintenance costs (DMC) of commercial aircraft make a significant contribution to an aircraft’s cost of ownership. The aim of our research is to find out some methods to reduce DMC. The paper first points out that design and fault diagnosis are the key factors to influence DMC, disregarding factors unique to a particular airline. A new concept of R&M design-maintenance free operating period and fault diagnosis expert system are discussed in this paper, in order to reduce DMC.
Electronic access
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www.emeraldinsight.com/0002-2667.htm
Introduction
Commercial aircraft maintenance activities form an essential part of airworthiness. Aircraft maintenance is actions that can restore an item to a serviceable condition, and consist of servicing, repair, modification, overhaul, inspection and determination of condition. It can be classified into two types.
Corrective maintenance. All actions performed as a result of failure to restore an item to a satisfactory condition by providing correction of a known or suspect malfunction and/or defect. Corrective maintenance in general consists of fault verification, fault isolation, disassembly, replacement, reassembly, alignment/adjustment, and test. This type of maintenance is known as unscheduled maintenance, and benefit from the use of diagnostics to ease the burden on the maintenance resource.
Preventive maintenance. All actions performed at defined intervals to retain an item in a serviceable condition by systematic inspection, detection, replacement of wear out item, adjustment, calibration, cleaning etc. It is carried out at prescribed points in an aircraft and equipment’s life. It is also termed as scheduled maintenance.
The common goal of maintenance is to provide a fully serviceable aircraft when it is required by an airline at minimum cost. For the present, maintenance costs of commercial aircraft make a significant contribution to an aircraft’s cost of ownership. Maintenance costs typically account for 10-20 per cent of aircraft-related operating costs (Maple, 2001).
Direct maintenance costs (DMC) is defined as the labor and material costs directly expended in performing maintenance of an aircraft or related equipment (ATA, IATA and ICCAIA, 1992). DMC do not include the labor and material expenditures, which contribute to activities such as administration, supervision, tooling , test equipment, facilities, record keeping etc. (Knotts, 1999). Airlines usually seek maintenance cost guarantees, where the aircraft manufacturer incurs financial penalties if DMC exceed agreed specified levels.
The aim of our research is to find our some methods to reduce DMC for commercial aircraft. In the continuation, the paper first analyzes the key factors that influence DMC, then discusses some methods that could reduce DMC, and finally draws a conclusion.
Key influence factors of DMCs
According to the definition, the formula for DMC is
DMC = ( +) LR + MC
Where is maintenance man hours off aircraft, LR is labor rate, and MC is material costs.
The factors, which effect on DMC, can be categorized as follows.
Design factor
Reliability and maintainability (R&M) is an inherent property of aircraft. It can be achieved only by design. Although other factors, such as highly trained people and a responsive supply system, can help keep down time to an absolute minimum, it is the inherent R&M that determines this minimum. Improving training or support cannot effectively compensate for the effect on availability of a poorly designed (in terms of R&M) commercial aircraft. Minimizing the cost to support an aircraft and maximizing the availability of that aircraft are best done by designing the product to be reliable and maintainable. R&M design has become an essential art of the development process of modern commercial aircraft life costs are determined during the design stage.
Fault diagnosis efficiency
The increasing complexity of systems and technology adds to the difficulty of effective and timely fault diagnosis, thus contributing to the problems of system maintainability. Moreover, ineffective fault diagnosis can be expensive in terms of down time and cost, with “no fault found (NFF)” situations contributing significantly to maintenance costs. Current system designs experience a 40 per cent, or higher, equipment false removal rate as a result of ambiguous and labor intensive test procedures. Avionics and electrical unscheduled maintenance accounts for 18 per cent of a civil aircraft’s DMC, 40 per cent of related equipment removals are classified as NFF. In 1992, an audit of component removals highlighted an average of 8,000 items removed from British Airways’ fleet per month. A total of 14 per cent of components, across all workshops, were found to have NFF. Certain avionics equipment experienced 30 per cent NFF. Financially, considering direct and indirect costs, this equated to an annual NFF expenditure totaling $20 million (Knotts, 1999).
Organization-related variables
These variables are relative to a specific airline. They include fleet size and commonality, aircraft age and utilization, maintain standard and plan, frequency of check intervals level of subcontracting, accounting method, currency fluctuations over time, local labor rates, and material prices (Maple, 2001).
Environmental factors
These factors depend on the location of the operator. For example, it is a desert environment or a maritime climate. For example, corrosion due to sand salt will have a significant influence to engine maintenance equipment.
Disregarding factors unique to a particular airline, impacts of design and fault diagnosis are discussed in this paper.
A new concept of R&M design- maintenance free operating period
The traditional approach pf R&M design, which is based on the meantime between failures (MTBF), acknowledge that random failures are inevitable throughout the equipment’ life, and leads to much unscheduled maintenance to be performed in routine of airline. The unscheduled maintenance tends to be most expensive in terms of maintenance costs because it is unplanned. Recent studies show that the cost of unscheduled maintenance for large commercial jet aircraft is in the range of 1 million pounds per aircraft per year (Kumar et al.,1999a). in order to reduce the costs, a new method based on maintenance free operating period (MEOP) has been developed.
MFOP is defined as a period of operation during which the equipment must be able to carry out all its assigned missions without any maintenance action and without the operator being restricted in any way duo to system faults or limitations (Hockley, 1998).
During MFOP, the necessity for any maintenance should be, by design, kept to a minimum. And the equipment is allowed to carry out only some planned minimal maintenance, such an flight servicing. A maintenance recovery period (MRP) follows immediately after a MFOP.
MRP is defined as the down time during which appropriate scheduled or corrective maintenance is done to recover the system to its fully serviceable state so that it is capable of achieving the next MEOP. Not all MRPs will be of the same duration because they need to encompass different maintenance activities for individual line replaceable unit (LRU), such as those that are life-expired, those that require some overhaul and prevent maintenance or just inspection to be done to restore the full capability of those faulty systems (Hockley, 1998).
MEOP is an extension of warranty period. The operators are considering extending this concept throughout the life of the system. The contractor/manufacture will be expected to guarantee that no unscheduled maintenance activities will be required during each defined period operation with the predefined level of confidence. The confidence is scaled by maintenance free operating period survivability (MFOPS) (Kumar et al., 1999b).
MFOPS is defined as the probability that the item will survive for the duration of the MEOP.
There are two ways to reduce DMC when conducting R&M design with MEOP for commercial aircraft.
Inherent reliability of aircraft can be improved greatly. Higher reliability and therefore, the man-hours and material necessary to fix them, so DMC will be brought down.
To achieve MFOPs of aircraft, it means that random failure should be eradicated during MEOP. The traditional culture, which believes that not only failures are unavoidable but also that are acceptable in a way, should be discarded. A detailed knowledge of the environment and usage to be experienced, together with a more thorough understanding of the very mechanisms of why things fail, will be fed into development programmers. Many technique or solutions will be applied to design for reliability in a more proactive way, so that failure mechanism is not given the opportunity to occur. The techniques could range from a change in physical design, selecting a different component, an improved build process, or a more radical design change.
To achieve an optimum maintenance plan. Obviously, the overall system of aircraft will need some maintenance actions at some point, but there will be performed during the planned MRPs. The MEOP defers virtually all corrective maintenance to MRP, so the “unscheduled” element of maintenance is exchanged for more scheduled maintenance, based on the general improvement of reliability associated with more inherently reliable equipment. A more practical, cost-effective and balanced set of MRPs that build-up and support the best overall system MFOP, can be achieved by means of trade-off and methodology for system engineering during design. This reduce some of the uncertainty present in maintenance planning. Contingency resources could be re-allocated to scheduled work and logistic support could be concentrated in one particular location of aircraft operations. In this way, the MFOP provides the operator with flexibility in where and when it carries out its preventive and corrective maintenance to an extent. Then DMC will be reduced, because of decrease of labor and materials to cope with unserviceable aircraft. For example, line maintenance accounts for 50 per cent of all maintenance labor over the course of an aircraft’s lift cycle today (Maple, 2001), the routine work of an aircraft designed by MFOP will be decreased to minimum.
Fault diagnosis
The process of fault diagnosis can be generally divided into sense signal, feature extraction and diagnostic reasoning in sequence. When diagnosing failures of modern commercial aircraft, most of the procedure of sense signal and feature extraction can be accomplished automatically, due to the technology development of sensor, dynamic test and signal analysis. Then diagnostic reasoning (how to find out the source of failure) is a key factor to contribute to the efficiency of fault diagnosis.
In terms of the concept of fault diagnosis, aircraft is a complicated system. Its structure is a multiple hierarchical architecture, which is comprised of many subsystems, for example, aircraft structure, engine, auto flight system, landing gear, communications system, hydraulic power and navigation system. Each subsystem is formed by subsystem or subunits are lower level. And the subsystems of subunits are usually interactive with each other. Connections between the levels of aircraft structure are usually difficult to define duo to the multiplicity and heterogeneity the structures and functions of aircraft. The quantitative relationships between the input and output of subsystem or unit usually are unavailable or inexact.
Advanced technology of much technosphere has been applied to modern aircraft synthetically, such as machinery, electrics, computer, automatic control and electronics. More and more electromechanical equipments have been used in aircraft. The mechanical and electric components of these equipments have been integrated in the manner not only of control, but also of function and structure. Multidisciplinary knowledge is required to diagnose the fault of aircraft.
Above issues result in the difficulties of diagnostic reasoning for commercial aircraft, and it always needs the expert’s participation. However, the required expert is not often available due to shift, sickness, change of employment and so on. In addition, much technosphere has been utilized in large commercial aircraft, and an expert is unlike to possess all the exiting system knowledge. To develop a fault diagnosis expert system, which could capture system knowledge, expertise and experience, is seen as a way to address the difficulty. It would not only produce more accurate and consistent results than its human counterpart, but also take the place of an expert in a manner and make precious expertise available to many users, in particular to less skilled staff and newcomer.
Most of NFF will be avoided by expert system, thus a cost-effective and timely fault diagnosis will help to reduce DMC.
Conculsion
The concept of MFOP has been acknowledged by aerospace industry as large step for future reliability specifications. Some of the ideas described in the earlier sections are being developed for A340-600 (Cini and Griffith, 1999). Fault diagnosis expert system has been encompassed in central maintenance computer system of Boeing 777. there is no doubt that they can reduce DMC greatly.
References
Cini, P.F. and Griffith, P. (1999), “Designing for MFOP: towards the autonomous aircraft”, journal of Quality in Maintenance Engineering, Vol. 5 No. 4, pp. 296-308.
Hockley, C.J. (1988), “Design for success”, Proc. Instn. Engrs., Part G Vol. 212, pp.371-8.
Knots, R.M.H. (1999), “Civil aircraft maintenance and support fault diagnosis from a business perspective”, Journal of Quality in Maintenance Engineering, Vol. 5 No.4, pp. 335-47.
Kumar, U.D., Crocker, J. and Knezevic, J. (1999a), “Evolutionary maintenance for aircraft engines”, Proceedings Annual Reliability and Maintainability Symposium, pp. 62-8.
Kumar, U.D., Knezevic, J. and Crocker, J. (1999b), “Maintenance free operating period - an alternative measure to MTBF and failure rate for specifying reliability”, Reliability Engineering and System Safety, Vol. 64, pp. 127-31.
Maple, M. (2001), “Understanding maintenance costs for new and existing aircraft”, Airline Fleet and Asset Management, No. 5, pp. 56-62
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