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內(nèi)容摘要:該設(shè)計(jì)主要對雙梁橋式起重機(jī)主起升機(jī)構(gòu)、副起升機(jī)構(gòu)、小車運(yùn)行機(jī)構(gòu)、主端梁、大車運(yùn)行機(jī)構(gòu)進(jìn)行了設(shè)計(jì)。
主副起升機(jī)構(gòu)的計(jì)算包括鋼絲繩的選擇、卷筒的計(jì)算、電動機(jī)、減速器的選擇等,小車運(yùn)行機(jī)構(gòu)的設(shè)計(jì)主要有電動機(jī)、減速器、最大輪壓最小輪壓的計(jì)算,主梁和端梁的設(shè)計(jì)包括主端梁截面幾何性質(zhì)的確定,載荷的計(jì)算,主端梁強(qiáng)度的校核,主梁強(qiáng)度的校核等。
關(guān) 鍵 詞:橋式起重機(jī) 機(jī)構(gòu) 主端梁
Abstract: The main design of double beam bridge crane hoisting mechanism, deputy Lord lifting mechanism, the car running institutions, Lord girders during operation, the organization design.
The Lord vice lifting mechanism of the calculation of the selection of wire rope, including the calculation of drum, motor, gear reducer choice and so on, the car running design of the mechanism are the main motor, gear reducer, maximum wheel pressure calculation of minimum wheel pressure, main girder and the design of the girders including the main girders section determination of geometrical properties, and the load calculation, the main girders of strength, check the main girder strength check, etc.
Key words: Bridge crane Mechanism Main girders
1.緒 論
1.1 國內(nèi)外橋式起重機(jī)現(xiàn)狀與發(fā)展前景
橋式起重機(jī)是橫架于車間、倉庫和料場上空進(jìn)行物料吊運(yùn)的起重設(shè)備。由于它的兩端坐落在高大的水泥柱或者金屬支架上,形狀似橋。橋式起重機(jī)的橋架沿鋪設(shè)在兩側(cè)高架上的軌道縱向運(yùn)行,可以充分利用橋架下面的空間吊運(yùn)物料,不受地面設(shè)備的阻礙。它是使用范圍最廣、數(shù)量最多的一種起重機(jī)械。
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1.1.1 國內(nèi)起重機(jī)現(xiàn)狀
經(jīng)過幾十年的發(fā)展,我國橋式起重機(jī)行業(yè)已經(jīng)形成了一定的規(guī)模,市場競爭也越發(fā)激烈。橋式起重機(jī)行業(yè)在國內(nèi)需求旺盛和出口快速增長的帶動下,依然保持高速發(fā)展,產(chǎn)品幾近供不應(yīng)求。
盡管我國起重機(jī)行業(yè)發(fā)展迅速,但是國內(nèi)起重機(jī)仍缺乏競爭力。從技術(shù)實(shí)力看,與歐美日等發(fā)達(dá)地區(qū)相比,中國的技術(shù)實(shí)力還有一定差距。目前,國內(nèi)大型起重機(jī)尚不具備大量生產(chǎn)能力。從產(chǎn)品結(jié)構(gòu)看,由于技術(shù)能力所限,中國起重機(jī)在產(chǎn)品結(jié)構(gòu)上也不完善,難以同國外匹敵。
同時(shí)我國起重行業(yè)目前存在幾個(gè)突出問題,歸納如下:
(1)整體技術(shù)含量偏低,突出表現(xiàn)在產(chǎn)品的品種規(guī)格少,性能、可靠性等指標(biāo)低于發(fā)達(dá)國家同類產(chǎn)品的水平。
(2)知名品牌寥寥無幾,能打入國際市場并享有一定聲譽(yù)的知名品牌幾乎沒有。
(3)產(chǎn)品低價(jià)惡性競爭嚴(yán)重,企業(yè)合理利潤難保,已嚴(yán)重制約企業(yè)生產(chǎn)技術(shù)的持續(xù)發(fā)展。
1.1.2國外起重機(jī)發(fā)展前景
隨著國際合作的增加,國際起重機(jī)行業(yè)發(fā)展迅速。到目前為止,國際主要知名起重機(jī)制造廠商有德國的DEMAG起重機(jī),芬蘭的Kone起重機(jī),美國CM集團(tuán)等。上述企業(yè)在起重機(jī)行業(yè)內(nèi)較為知名。
橋式起重機(jī)的更新和發(fā)展,在很大程度上取決于電氣傳動與控制的改進(jìn)。將機(jī)械技術(shù)和電子技術(shù)相結(jié)合,將先進(jìn)的計(jì)算機(jī)技術(shù)、微電子技術(shù)、電力電子技術(shù)、光纜技術(shù)、液壓技術(shù)、模糊控制技術(shù)應(yīng)用到機(jī)械的驅(qū)動和控制系統(tǒng),實(shí)現(xiàn)起重機(jī)的自動化和智能化。大型高效橋式起重機(jī)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)。主要由全數(shù)字化控制驅(qū)動裝置、可編程序控制器、故障診斷及數(shù)據(jù)管理系統(tǒng)、數(shù)字化操縱給定檢測等設(shè)備組成。變壓變頻調(diào)速、射頻數(shù)據(jù)通訊、故障自診監(jiān)控、吊具防搖的模糊控制、激光查找起吊物重心、近場感應(yīng)防碰撞技術(shù)、現(xiàn)場總線、載波通訊及控制、無接觸供電及三維條形碼技術(shù)等將廣泛得到應(yīng)用。使起重機(jī)具有更高的柔性,以適合多批次少批量的柔性生產(chǎn)模式,提高單機(jī)綜合自動化水平。重點(diǎn)開發(fā)以微處理機(jī)為核心的高性能電氣傳動裝置,使起重機(jī)具有優(yōu)良的調(diào)速和靜動特性,可進(jìn)行操作的自動控制、自動顯示與記錄,起重機(jī)運(yùn)行的自動保護(hù)與自動檢測,特殊場合的遠(yuǎn)距離遙控等,以適應(yīng)自動化生產(chǎn)的需要。
隨著現(xiàn)代科學(xué)技術(shù)的發(fā)展,各種新技術(shù)、新材料、新結(jié)構(gòu)、新工藝在橋式起重機(jī)上得到廣泛的應(yīng)用。所有這些因素都有里地促進(jìn)了橋式起重機(jī)的發(fā)展。根據(jù)國內(nèi)外現(xiàn)有橋式起重機(jī)產(chǎn)品和技術(shù)資料的分析,近年來橋式起重機(jī)的發(fā)展趨勢主要體現(xiàn)在以下幾個(gè)方面:
(1)重點(diǎn)產(chǎn)品大型化,高速化和專用化;
(2)系列產(chǎn)品模塊化、組合化和標(biāo)準(zhǔn)化;
(3)通用產(chǎn)品小型化、輕型化和多樣化;
(4)產(chǎn)品性能自動化、智能化和數(shù)字化;
(5)產(chǎn)品組合成套化、集成化和柔性化。
1.2 本設(shè)計(jì)的主要內(nèi)容、目標(biāo)和方法
主要內(nèi)容:了解橋式起重機(jī)的發(fā)展和應(yīng)用現(xiàn)狀,設(shè)計(jì)一臺滿足要求的室內(nèi)32/5t雙梁橋式起重機(jī),并用AutoCAD繪圖軟件繪制出要求的圖紙。由于橋式起重機(jī)基本上是采用電力驅(qū)動,且電動機(jī)容量的選擇與各機(jī)構(gòu)的尺寸布置和運(yùn)轉(zhuǎn)的經(jīng)濟(jì)性有密切關(guān)系,因此,進(jìn)行傳動系統(tǒng)設(shè)計(jì)之初,先對動力系統(tǒng)進(jìn)行計(jì)算、選擇及校驗(yàn)。橋式起重機(jī)傳動系統(tǒng)設(shè)計(jì)主要包括起升機(jī)構(gòu)傳動系統(tǒng)設(shè)計(jì)、小車運(yùn)行機(jī)構(gòu)傳動系統(tǒng)設(shè)計(jì)、大車運(yùn)行機(jī)構(gòu)設(shè)計(jì)。在設(shè)計(jì)中,先是確定傳動設(shè)計(jì)方案,再根據(jù)動力傳動方向進(jìn)行設(shè)計(jì)和計(jì)算。在這三個(gè)傳動系統(tǒng),起升機(jī)構(gòu)傳動系統(tǒng)是最重要也是最關(guān)鍵的。對起重機(jī)金屬結(jié)構(gòu)時(shí),采用經(jīng)濟(jì)梁法設(shè)計(jì)出起重機(jī)主梁最優(yōu)截面,并校核截面幾何尺寸。
本設(shè)計(jì)采用規(guī)范的設(shè)計(jì)計(jì)算對橋式起重機(jī)各機(jī)構(gòu)進(jìn)行了分析。首先,通過查閱相關(guān)書籍和資料,學(xué)習(xí)橋式起重機(jī)的相關(guān)知識,了解橋式起重機(jī)的發(fā)展和應(yīng)用現(xiàn)狀,掌握橋式起重機(jī)金屬結(jié)構(gòu)的設(shè)計(jì)方法,學(xué)習(xí)并掌握AutoCAD軟件的使用,掌握一般的繪圖方法和計(jì)算分析步驟;其次,根據(jù)現(xiàn)今國內(nèi)外生產(chǎn)橋式起重機(jī)采用的各種結(jié)構(gòu)類型,結(jié)合課本知識和參考文獻(xiàn)信息,設(shè)計(jì)符合使用要求的結(jié)構(gòu);橋式起重機(jī)的受力情況,計(jì)算橋式起重機(jī)的自重載荷、起升載荷、水平慣性載荷,并對橋式起重機(jī)的抗傾覆穩(wěn)定性進(jìn)行校核。
2. 型式及主要技術(shù)參數(shù)
2.1 型式及構(gòu)造特點(diǎn)
箱形雙梁結(jié)構(gòu)具有加工零件少、工藝性好、通用性好及機(jī)構(gòu)安裝檢修方便等一系列優(yōu)點(diǎn),因而在生產(chǎn)中得到廣泛采用。我國在5噸到80噸的中、小起重量系列產(chǎn)品中主要采用了這種形式,但這種結(jié)構(gòu)型式也存在一些缺點(diǎn);自重大、易下?lián)?。它的主要組成部分有小車(主、副起升機(jī)構(gòu)、小車運(yùn)行機(jī)構(gòu)和小車架)。橋架(主梁和端架)、大車運(yùn)行機(jī)構(gòu)和電氣設(shè)備等。
2.2主要技術(shù)參數(shù)
起重量:主鉤=32 t,副鉤=5 t
跨度:L=19.5 m
起升高度:主鉤=12 m,副鉤=14 m;
工作級別:主起升機(jī)構(gòu): M5
副起升機(jī)構(gòu): M5
大車: M5
小車: M5
工作速度:主起升速度:V=7.5 m/min
副起升速度:V=19.5 m/min
小車運(yùn)行速度:V=38.5 m/min
大車運(yùn)行速度:V=74.5 m/min
小車軌距:2.5 m
大車走輪:4只,其中一半為驅(qū)動輪
3. 起重小車的計(jì)算
32/5噸雙梁橋式起重機(jī)小車采用四個(gè)走輪支承的起重小車。它主要由主、副起升機(jī)構(gòu)、小一運(yùn)行機(jī)構(gòu)和小車架所組成。
3.1主起升機(jī)構(gòu)的計(jì)算
3.1.1主要參數(shù)與機(jī)構(gòu)的布置簡圖
主起升機(jī)構(gòu)傳動簡圖如下:
1——電動機(jī):2——聯(lián)軸器:3——傳動軸:4——制動器:5——減速器:6——卷筒
圖3-1 主起升機(jī)構(gòu)傳動簡圖
已知: 起重量:Q=32000kg;
工作級別:M5
最大起升高度:12 m
起升速度:7.5 m/min
3.1.2鋼絲繩的選擇
根據(jù)起重機(jī)的額定起重量,選擇雙聯(lián)起升機(jī)構(gòu)滑輪倍率為4,鋼絲繩纏繞方式如圖所示。
圖3-2 主起升機(jī)構(gòu)鋼絲繩的纏繞方式
(1) 鋼絲繩所受最大靜拉力;
(公斤)
式中:
Q——額定起重量 Q=32 t;
G——吊鉤組重量,G=700kg(起重量的2%~4%,這里取700kg);
M——滑輪組倍率,m=4;
——滑輪組效率,=0.87;
。
(2) 鋼絲繩的選擇:
所選擇鋼絲繩的破斷拉力應(yīng)滿足:
;
而;
——鋼絲繩安全系數(shù),對于中級工作類型=5;
由上式可得:
根據(jù)上式計(jì)算查鋼絲繩產(chǎn)品目錄可選用:
鋼絲繩選用破斷拉力1670的纖維芯鋼絲繩。
查所提供的參考資料取得鋼絲繩直徑為12mm。
3.1.2 卷筒的計(jì)算
已知主起升機(jī)構(gòu)卷筒的直徑為650mm;
卷筒長度和厚度的計(jì)算:
卷筒半邊繩槽部分的長度:
式中 為最大起升高度,已知大小為22m;
n為鋼絲繩的安全系數(shù);
選取鋼絲繩的安全系數(shù)為n=5;
t為繩槽節(jié)距,+(2~4)=24~26, 取t=25mm;
為卷筒的計(jì)算直徑,已給出大小為650mm;
卷筒長度,取長度為2000mm,其壁厚可按經(jīng)驗(yàn)公式確定mm,取厚度為24mm。
卷筒轉(zhuǎn)速
3.1.3根據(jù)靜功率初選電動機(jī)
起升機(jī)構(gòu)靜功率計(jì)算:
式中——起升機(jī)構(gòu)的總效率:
初選電動機(jī)功率;
查電機(jī)產(chǎn)品目錄,選280s-10。在工作級別為M5時(shí),功率N=52千瓦,轉(zhuǎn)速n=970轉(zhuǎn)/分。
3.1.4減速器的選擇
(1) 起升機(jī)構(gòu)總的傳動比:
根據(jù)傳動比i=40,電動機(jī)功率N=45kw,電動機(jī)轉(zhuǎn)速n=581轉(zhuǎn)/分;
可選用電機(jī)ZQH65-II-3CA型減速器,傳動比i=4,輸入減速器功率為26kw。
(2) 驗(yàn)算減速器的最大扭矩及最大徑向載荷:
低速軸上最大扭矩的驗(yàn)算:
式中 為電動機(jī)的額定扭矩,;
i 為傳動比,i=40;
為電動機(jī)至減速器被動軸的傳動效率,;
為電動機(jī)最大轉(zhuǎn)矩倍數(shù),;
減速器低速軸上的最大短暫容許扭矩,=6250;
滿足要求
最大徑向載荷的驗(yàn)算:
式中 為卷筒上鋼絲繩的最大拉力,大小為4170kg;
為卷筒重量,查大起起重廠資料,查得;
為低速軸端的最大容許徑向載荷,查所提供的資料得;
滿足要求
3.1.5制動器的選擇
制動器裝在高速軸上,其制動力矩應(yīng)滿足式:
式中 K制——制動安全系數(shù),對M5級工作類型取1.75;
M制靜——滿載時(shí)制動軸上之靜力矩;
式中——機(jī)構(gòu)總效率值為0.85;
;
;
根據(jù)以上計(jì)算,從制動器目錄選用制動器。
3.2副起升機(jī)構(gòu)的計(jì)算
3.2.1主要參數(shù)與機(jī)構(gòu)的布置簡圖
已知:
起重量:Q=5000kg
工作級別:M5
最大起升高度:14m
起升速度:19.5m
機(jī)構(gòu)布置與主起升機(jī)構(gòu)類似。
3.1.2鋼絲繩的選擇
根據(jù)起重機(jī)的額定起重量,選擇雙聯(lián)起升機(jī)構(gòu)滑輪倍率為2,鋼絲繩纏繞方式如圖所示。
圖3-3 主起升機(jī)構(gòu)鋼絲繩的纏繞方式
鋼絲繩所受最大靜拉力;
式中 Q——額定起重量,Q=5000公斤;
G鉤——吊鉤組重量,G鉤=100公斤(起重量的2%~4%,這里取100公斤);
M——滑輪組倍率,m=2;
——滑輪組效率,=0.99;
所選擇鋼絲繩的破斷拉力應(yīng)滿足:
;而
——鋼絲繩安全系數(shù),對于中級工作類型=5
由上式可得:
根據(jù)上式計(jì)算查鋼絲繩產(chǎn)品目錄可選用:
鋼絲繩619WFC破斷拉力1670的纖維芯鋼絲繩,從而確定鋼絲繩直徑為13mm。
3.1.3滑輪、卷筒的計(jì)算
(1) 滑輪、卷筒最小直徑的確定:
為了確保鋼絲繩具有一定的使用壽命,滑輪、卷筒的直徑應(yīng)滿足:
式中 e為系數(shù),對工作級別為M5的橋式起重機(jī),取e=25;
所以,取卷筒和滑輪直徑為400mm。
(2) 卷筒長度和厚度的計(jì)算:
卷筒長度,取長度為1500mm,卷筒材料采用HT20-40,其壁厚可按經(jīng)驗(yàn)公式確定mm,取厚度為18mm。
(3) 卷筒轉(zhuǎn)速:
3.1.4根據(jù)靜功率初選電動機(jī)
起升機(jī)構(gòu)靜功率計(jì)算;
式中——起升機(jī)構(gòu)的總效率;
初選電動機(jī)功率;
查電機(jī)產(chǎn)品目錄,選在工作級別為M5時(shí),功率N=17千瓦,轉(zhuǎn)速n=955轉(zhuǎn)/分。
3.1.5減速器的選擇
起升機(jī)構(gòu)總的傳動比:
根據(jù)傳動比i=22.99,電動機(jī)功率N=16千瓦,電動機(jī)轉(zhuǎn)速n=710轉(zhuǎn)/分。
可選用電機(jī)ZQ-500-IV-4CA型減速器,傳動比i=23.34,輸入減速器功率為21千瓦,轉(zhuǎn)速n=750轉(zhuǎn)/分。
驗(yàn)算減速器的最大扭矩及最大徑向力
最大扭矩的驗(yàn)算
式中 為電動機(jī)的額定扭矩,=21.97;
i為傳動比,i=23.34;
為電動機(jī)至減速器被動軸的效率,大小為0.94;
為電動機(jī)的最大轉(zhuǎn)矩倍數(shù),大小為3.92;
查ZQ系列減速器軸端容許扭矩;
滿足要求
最大徑向力的驗(yàn)算:
卷筒上鋼絲繩最大拉力,為1288kg;
卷筒重量,;
;
查減速器低速軸端容許載荷表得;
滿足要求
3.1.6制動器的選擇
制動器裝在高速軸上,其制動力矩應(yīng)滿足式:
式中——制動安全系數(shù),對中級工作類型取1.75;
——滿載時(shí)制動軸上之靜力矩;
式中——機(jī)構(gòu)總效率值為0.917;
根據(jù)以上計(jì)算,從制動器目錄選用制動器。
4. 小車運(yùn)行機(jī)構(gòu)的計(jì)算
4.1主要參數(shù)和機(jī)構(gòu)布置簡圖
起重量在5號到50噸范圍內(nèi)的雙梁橋式起重機(jī)的小車,一般采用四個(gè)車輪支承的四車,其中兩個(gè)車輪為主動車輪。主動輪由小車運(yùn)行機(jī)構(gòu)集中驅(qū)動。
主要參數(shù)
起重量:=32t =5t
工作級別:M5
小車運(yùn)行速度:38.5m/min
車輪數(shù):4個(gè)
驅(qū)動形式:集中驅(qū)動
4.2 輪壓的計(jì)算
參考同類型規(guī)格相近的起重機(jī),估計(jì)小車總重為7.5噸,近似認(rèn)為由四個(gè)車輪平均承受。吊鉤位于小車軌道的縱向?qū)ΨQ軸線上,根據(jù)小車架布置圖偏離主、從動輪之間的中心線為80mm。
根據(jù)起重小車架的平衡方程式,可分別示出主動輪和從動輪的輪壓。
主動輪:
式中P1——主動輪輪壓;
Kt——小車輪矩,為2400毫米。
4.3電動機(jī)的選擇
4.3.1運(yùn)行阻力的計(jì)算
(1)小車滿載運(yùn)行時(shí)的最大摩擦阻力
式中(Q+G)——額定起重量量加吊鉤重量,(Q+G)=32500kg;
——小車 自重,=7500kg;
K——滾動摩擦系數(shù),K=0.05cm;
U——軸承摩擦系數(shù)取0.015;
——附加摩擦阻力系數(shù)取1.5;
——車輪直徑為9cm;
(空載運(yùn)行時(shí)為81公斤)
(2) 小車滿載運(yùn)行時(shí)的最大坡度阻力:
式中 ——坡度阻力系數(shù)取0.002;
=(32500+7500)0.002=80kg
(空載運(yùn)行時(shí)=16公斤)
(3) 小車滿載運(yùn)行時(shí)的最大靜阻力:
(=81+16=97公斤)
4.3.2選擇電動機(jī),確定減速器
(1) 滿載運(yùn)行時(shí)電動機(jī)的靜功率:
式中 ——小車滿載運(yùn)行時(shí)的靜阻力;=480kg
——小車運(yùn)行速度,=32.5m/min;
——小車運(yùn)行機(jī)構(gòu)傳動效率,=0.9;
m——電動機(jī)個(gè)數(shù),m=1;
(2) 選擇電動機(jī)
式中 ——電動機(jī)起動為克服慣性的功率增大系數(shù),查《起重設(shè)計(jì)手冊》表9-6,?。?.4;
kw
查電動機(jī)產(chǎn)品目錄選擇21-6型電動機(jī),功率N=5kw,轉(zhuǎn)速925轉(zhuǎn)/分,轉(zhuǎn)子飛輪矩公斤,最大扭矩倍數(shù)。
(3) 確定減速器
減速器的傳動比:
式中——小車運(yùn)行速度,=38.5米/分;
n——電動機(jī)轉(zhuǎn)速,n=925轉(zhuǎn)/分;
D——小車車輪直徑取0.35米;
起時(shí)的慣性力:
式中——小車滿載起動時(shí)的平均加速度,取0.1米/。
根據(jù)起動時(shí)期的輸入功率、減速比、輸入轉(zhuǎn)速及工作類型查產(chǎn)品目錄,先取立式減速器ZSC-400,i=22.4,N=2.8千瓦(n=1000轉(zhuǎn)/分)。
4.2.3車輪計(jì)算
根據(jù)輪壓、小車運(yùn)行速度、工作類型選車輪直徑D=350mm,車輪的計(jì)算輪壓:
(1) 疲勞計(jì)算時(shí)的等效起長載荷由下式確定:
式中——等效靜載荷系數(shù)查表得0.6;
——起升載荷重量值為32500kg ;
=0.632500=19500kg
根據(jù)等效起升載荷確定車輪的等效輪壓,然后再由下式確定車輪的計(jì)算輪壓。
式中——根據(jù)等效起升載荷計(jì)算的最大輪壓,作為疲勞計(jì)算時(shí)的計(jì)算輪壓。
——等效沖擊系數(shù),查得值為1;
——載荷變化系數(shù),根據(jù);
查起重設(shè)計(jì)實(shí)例,表2-8得=0.8;
(2) 強(qiáng)度校核時(shí)的最大計(jì)算輪壓:
式中 為動力系數(shù),取為1.47;
為滿載小車最大輪壓,=8854kg;
=kg
5. 主梁的設(shè)計(jì)
5.1主梁設(shè)計(jì)的說明
在計(jì)算箱形雙梁橋式起重機(jī)的主梁時(shí),為保證起重機(jī)安全、正常的工作,主梁應(yīng)滿足強(qiáng)度、剛度和穩(wěn)定性的要求。強(qiáng)度和穩(wěn)定性要求是指主梁在載荷的作用下產(chǎn)生的內(nèi)力不應(yīng)超過主梁材料許用的承載能力,剛度要求是指主梁在載荷作用下產(chǎn)生的變形量不應(yīng)超過許用的變形值。
5.2 主梁斷面幾何特性
根據(jù)參考資料選出主梁斷面見圖5-1
圖5-1 主梁斷面圖
斷面面積:
F=55×(1.4+1.4)+2×0.6×115=292
慣性矩:
水平慣性矩:
垂直慣性矩:
斷面模數(shù):
5.3 主梁載荷的計(jì)算
箱形雙梁橋架的自重載荷和起升載荷。
5.3.1自重載荷及其最大彎矩的計(jì)算
自重載荷有均布載荷和集中載荷兩種。作用在主梁上的均布載荷有主梁、走臺、軌道、欄桿等重量,作用在主梁上的集中載荷有操縱室、大車運(yùn)行機(jī)構(gòu)以及布置在走臺上的電氣設(shè)備等的重量。
主梁均布載荷為:
算式中為一根主梁的重量,大小為5298kg;
為傳動側(cè)走臺的重量,大小為1273kg;
為主梁軌道的重量,大小為595kg;
為一側(cè)欄桿的重量,大小為147kg;
為主梁上的一些其他小物件,如接線盒等,大小為176kg,L為跨度,大小為19.5m。
計(jì)算式所需的各個(gè)部件的重量,由參考文獻(xiàn)和設(shè)計(jì)手冊中差得,最后應(yīng)按實(shí)際結(jié)構(gòu)的重量進(jìn)行校核修改,具體數(shù)據(jù)大小參考了大連起重機(jī)器廠73年系列產(chǎn)品的主梁數(shù)據(jù)。
均布載荷產(chǎn)生的最大彎矩(在跨中):
固定集中載荷的跨中產(chǎn)生的彎矩:
式中大車運(yùn)行機(jī)構(gòu)的重量,大小為440kg;
為操縱室的重量,大小為1100kg;
為布置在走臺上的電氣設(shè)備的重量,大小為194kg;
=2.588
固定載荷上主梁上的最大彎矩:
5.3.2起升載荷及其最大彎矩的計(jì)算
小車在橋架主梁的軌道上運(yùn)行時(shí),作用于鋼軌上的小車輪壓以P表示,由于起升機(jī)構(gòu)起動或制動時(shí)產(chǎn)生垂直慣性力,所以計(jì)算式應(yīng)考慮動力系數(shù)。
小車靜輪壓:
小車計(jì)算輪壓:
式中 為小車自重引起的輪壓;
為負(fù)載引起的輪壓;
為動力系數(shù),根據(jù)起重機(jī)的工作級別來確定,起重機(jī)的工作級別為M5,參考設(shè)計(jì)手冊,取。
小車靜輪壓:
靜載最大彎矩:
計(jì)算最大彎矩:
式中 小車輪距為2.8m
起重機(jī)跨度為L=19.5m
5.3.3水平慣性載荷
水平慣性載荷是在小車及橋架的運(yùn)行機(jī)構(gòu)起動或制動時(shí)產(chǎn)生的這種慣性力,通過制動車輪的粘著力,傳遞到主梁上。
當(dāng)小車制動時(shí),水平慣性力。由于是縱向作用,所以在箱形結(jié)構(gòu)主梁計(jì)算中一般不考慮,只在端梁計(jì)算中考慮。
當(dāng)橋架制動時(shí),橫向作用于主梁軸線的水平慣性載荷根據(jù)主動車輪數(shù)決定。
在計(jì)算中,一般不單獨(dú)計(jì)算,而對主梁取水平慣性力引起彎矩等于垂直載荷引起的彎矩的0.1倍,端梁計(jì)算中去0.15倍。
由水平慣性力產(chǎn)生的主梁最大彎曲力矩為。
5.4 載荷組合及主梁應(yīng)力的計(jì)算
5.4.1 跨中主梁法向應(yīng)力
第一類載荷組合:
第二類載荷組合:
第三類載荷組合:
為第一、第二類許用應(yīng)力;
為第三類許用應(yīng)力。
5.4.2 跨端主梁腹板的剪應(yīng)力
式中:在固定載荷及活動載荷的作用下,主端跨端的最大剪力。
其中: ;
;
為小車位于跨端極限位置,所以去=0。
滿足要求
5.5 剛度的計(jì)算
5.5.1主梁的靜剛度
對兩個(gè)輪壓力:
式中 為小車的實(shí)際靜輪壓,不計(jì)動力系數(shù),分別取7.3t和6.7t;
L為起重機(jī)的跨度,大小為1950cm;
E為彈性模數(shù),大小為;
為主梁跨中毛截面對中心軸的慣性矩,大小為558751;
滿足要求
5.5.2 主梁的動剛度
按空載時(shí)的自振周期:
式中 T為自振周期,單位為秒;
M為大車及小車的換算質(zhì)量:
其中 q為橋架結(jié)構(gòu)單位長度的重量;
為小車的重量;
為橋架結(jié)構(gòu)的慣性矩;
所以滿足要求
6. 端梁計(jì)算
箱形結(jié)構(gòu)橋架的端梁一般亦采用箱形斷面:
圖6-1 端梁斷截面尺寸
6.1中間斷面系數(shù)
圖中符號 d——下蓋板螺釘孔直徑,d=21mm;
n——下蓋板斷面螺釘孔數(shù),n=5;
D——腹板工藝孔直徑,D=150mm。
下蓋板凈斷面面積
對x-x軸凈斷面慣性矩:
對x-x軸凈斷面系數(shù):
對y-y軸凈斷面慣性矩:
對y-y軸凈斷面系數(shù):
6.2端部支承處斷面系數(shù)
斷面上部對x-x軸的靜矩:
斷面上蓋板對x-x軸的靜矩:
斷面下蓋板對x-x軸的靜矩:
7. 大車運(yùn)行機(jī)構(gòu)的計(jì)算
雙梁橋式起重機(jī)的橋架,起重量在5至50噸范圍內(nèi)一般均由四個(gè)車輪支承,其中兩個(gè)車輪為主動車輪,主動動車輪由大車運(yùn)行機(jī)構(gòu)分別驅(qū)動。
1——電動機(jī); 2——制動器; 3——傳動軸; 4——高速軸齒輪聯(lián)軸器;
5——減速器; 6——低速軸齒輪聯(lián)軸器; 7——車輪
圖7-1 大車運(yùn)行機(jī)構(gòu)簡圖
7.1主要參數(shù)
起重量:Q=32/5噸
跨度:L=19.5米
工作級別: M5
大車運(yùn)行速度: V=70.6米/分
大車輪距 B=4.7米
車輪數(shù) 4個(gè)
驅(qū)動形式 分別驅(qū)動
計(jì)算重量 小車重=7.5噸;吊具重G=0.7噸;
起重機(jī)總重量(包括小車)=32.5噸
7.2輪壓計(jì)算
參考同類型規(guī)格相近的起重機(jī),可挖認(rèn)為主鉤中心線至端梁兩端主、從車輪中心線距離相等,主鉤中心線離端梁中心線最小距離(極限尺寸)=1.5米。
7.2.1大車最大輪壓(滿載)
式中 ——起重機(jī)總重,32500公斤;
——小車自重,=7500公斤;
——起升載荷,=32500公斤;
L——橋架跨度,L=19.5米;
——吊鉤中心線至端梁中心線的最小距離,=1.5米。
7.2.2大車最小輪壓(滿載)
7.2.3大車最大輪壓(空載)
7.2.4大車最小輪壓(空載)
7.3電動機(jī)的選擇
7.3.1運(yùn)行阻力的計(jì)算
——起重機(jī)運(yùn)行靜阻力;
——起重機(jī)運(yùn)行摩擦阻力;
——起重機(jī)在有坡度的軌道上運(yùn)行時(shí)須克服的由起重機(jī)重量分力引起的阻力。
(1) 起重機(jī)滿載運(yùn)行時(shí)的最大摩擦阻力:
——起重機(jī)總重,=32.5t;
——起升載荷重量,=32.5t;
K——滾動摩擦系數(shù),K=0.09cm;
——軸承摩擦系數(shù),=0.02;
——附加摩擦阻力系數(shù),=1.5;
——車輪直徑,=70cm;
d——軸承內(nèi)徑,d=12cm。
(2) 起重機(jī)滿載運(yùn)行時(shí)最大坡度阻力:
式中——坡度阻力系數(shù),=0.001;
(3) 起重機(jī)滿載運(yùn)行時(shí)最大靜阻力:
(4) 起重機(jī)空載運(yùn)行時(shí)最小摩擦阻力:
——吊具重量,=0.7t;
(5) 起重機(jī)空載運(yùn)行時(shí)坡度阻力:
(6) 起重機(jī)空載運(yùn)行時(shí)靜阻力:
7.3.2確定電動機(jī)、確定減速器
(1) 滿載運(yùn)行時(shí)電動機(jī)的靜功率:
P——起重機(jī)滿載運(yùn)行時(shí)的靜阻力,P=530kg;
——大車運(yùn)行速度,=74.6m/min;
——大車運(yùn)行機(jī)構(gòu)傳動效率,=0.87;
m——電動機(jī)個(gè)數(shù),m=2。
(2) 選電動機(jī)
式中——電動機(jī)起動時(shí)為克服慣性的功率增大系數(shù);
當(dāng),?。?;
N=23.96=7.92kw
查電動機(jī)產(chǎn)品目錄選擇22-6型電動機(jī),功率N=7.5kw,轉(zhuǎn)速n=930轉(zhuǎn)/分,轉(zhuǎn)子飛輪矩,最大扭矩倍數(shù)=3。
(3) 確定減速器
減速器的傳動比:
其中——大車運(yùn)行速度,=74.6m/min;
——電動機(jī)轉(zhuǎn)速,=930n/min;
——大車車輪直徑,=0.8m;
n/min
起動時(shí)的慣性力:
起動時(shí)期減速器輸入功率:
根據(jù)起動進(jìn)的輸入功率、減速比、輸入轉(zhuǎn)速及工作產(chǎn)品目錄選型,i=23.05,N=9kw。
整車電機(jī)有主起升電機(jī)、副起升電機(jī)、小車運(yùn)行電機(jī)、大車運(yùn)行電機(jī)。
參考文獻(xiàn)
[1] 揚(yáng)長骙.起重機(jī)械.北京:機(jī)械工業(yè)出版社,1982:84~86.
[2] 石殿均.工程起重機(jī)械.北京:水利電力出版社,1987:23~34.
[3] 徐格寧等.起重機(jī)設(shè)計(jì)規(guī)范2008.北京: 中國標(biāo)準(zhǔn)出版社,2008:43~47.
[4] 陳道南,盛漢中.GB-T14405-93通用橋式起重機(jī).北京:中國標(biāo)準(zhǔn)出版社,1994:24~43.
[5] 張質(zhì)文等.起重機(jī)設(shè)計(jì)手冊.北京: 中國鐵道工業(yè)出版社,1998:23~35.
[6] 濮良貴.機(jī)械設(shè)計(jì).北京: 高等教育出版社,2001:65~86.
[7] 成大先.機(jī)械設(shè)計(jì)手冊第4卷.北京:機(jī)械工業(yè)出版社,2004:45~67.
[8]倪慶興,王煥勇.起重機(jī)械.上海:上海交通大學(xué)出版社,1990:56~76.
[9]徐格寧.機(jī)械裝備金屬結(jié)構(gòu)設(shè)計(jì)(第2版).北京:機(jī)械工業(yè)出版社,2009:271~282.
[10]林貴瑜,史勇.關(guān)于起重機(jī)發(fā)展的幾個(gè)技術(shù)問題.建設(shè)機(jī)械技術(shù)與管理, 2006:32~75.
致 謝
40
新鄉(xiāng)學(xué)院畢業(yè)論文(設(shè)計(jì))任務(wù)書
題目名稱 32/5t雙梁橋式起重機(jī)設(shè)計(jì)
學(xué)生姓名
所學(xué)專業(yè)
班級
指導(dǎo)教師姓名
所學(xué)專業(yè)
職稱
完成期限
一、論文(設(shè)計(jì))主要內(nèi)容及主要技術(shù)指標(biāo)
設(shè)計(jì)參數(shù):
主起升 32t 高度 12米 速度 7.5m/min 卷筒直徑 650mm工作級別 M5起升倍率 4;副起升5t高度14米 卷筒直徑 400mm速度 19.5m/min 工作級別 M5起升倍率 2。車輪直徑:大車800mm 小車400mm。
主要技術(shù)指標(biāo)
(2)合理選擇部件。
(3)對關(guān)鍵部件的結(jié)構(gòu)設(shè)計(jì)。
(3)最后進(jìn)行載荷的校驗(yàn)及分析。
二、畢業(yè)論文(設(shè)計(jì))的基本要求
1. 開題報(bào)告一份。
2. 中期檢查表一份。
3. 畢業(yè)設(shè)計(jì)(論文)一份:有400字左右的中英文摘要,正文后有10篇以上的參考文獻(xiàn),主要是期刊、雜志,少量是教材。正文中要引用5篇以上文獻(xiàn),并注明出處。論文總字?jǐn)?shù)在6000字以上。
4. 有1500字左右漢字的與本課題有關(guān)的外文翻譯資料。
5. 畢業(yè)設(shè)計(jì)總字?jǐn)?shù)在5000字以上。
6. 確定各個(gè)零件進(jìn)行結(jié)構(gòu)參數(shù)設(shè)計(jì)校核。
三、2012年畢業(yè)論文(設(shè)計(jì))進(jìn)度安排
12.3.14~12.3.24 開題,開題報(bào)告
12.3.25~12.4. 1 課題構(gòu)思,查找資料
12.4. 2~12.5.14 論文準(zhǔn)備,修正
12.5.15~12.6 答辯準(zhǔn)備及答辯
評閱設(shè)計(jì)報(bào)告,畢業(yè)設(shè)計(jì)答辯資格審查。畢業(yè)設(shè)計(jì)答辯,學(xué)生修改整理設(shè)計(jì)報(bào)告
Mechanical engineering
1.The porfile of mechanical engineering
Engingeering is a branch of mechanical engineerig,it studies mechanical and power generation especially power and movement.
2.The history of mechanical engineering
18th century later periods,the steam engine invention has provided a main power fountainhead for the industrial revolution,enormously impelled each kind of mechznical biting.Thus,an important branch of a new Engineering – separated from the civil engineering tools and machines on the branch-developed together with Birmingham and the establishment of the Associantion of Mechanical Engineers in 1847 had been officially recognized.The mechanical engineering already mainly used in by trial and error method mechanic application technological development into professional engineer the scientific method of which in the research,the design and the realm of production used .From the most broad perspective,the demend continuously to enhance the efficiencey of mechanical engineers improve the quality of
work,and asked him to accept the history of the high degree of education and training.Machine operation to stress not only economic but also infrastructure costs to an absolute minimun.
3.The field of mechanical engineering
The commodity machinery development in the develop country,in the high level material life very great degree is decided each kind of which can realize in the mechanical engineering.Mechanical engineers unceasingly will invent the machine next life to produce the commodity,unceasingly will develop the accuracy and the complexity more and more high machine tools produces the machine.The main clues of the mechanical development is:In order to enhance the excellent in quality and reasonable in price produce to increase the precision as well as to reduce the production cost.This three requirements promoted the complex control system development.The most successful machine manufacture is its machine and the control system close fusion,whether such control system is essentially mechanical or electronic.The modernized car engin production transmission line(conveyer belt)is a series of complex productions craft mechanization
very good example.The people are in the process of development in order to enable further automation of the production machinery ,the use of a computer to store and handle large volumes of data,the data is a multifunctional machine tools necessary for the production of spare parts.One of the objectives is to fully automated production workshop,three rotation,but only one officer per day to operate.The development of production for mechanical machinery must have adequate power supply.Steam engine first provided the heat to generate power using practical methods in the old human,wind and hydropower,an increase of engin .New mechanical engineering industry is one of the challenges faced by the initial increase thermal effciency and power,which is as big steam turbine and the development of joint steam boilers basically achieved.20th century,turbine generators to provide impetus has been sustained and rapid growth,while thermal efficiency is steady growth,and large power plants per kW capital consumption is also declining.Finally,mechanical engineers have nuclear energy.This requires the application of nuclear energy particularly high reliability and security,
which requires solving many new problems.Large power plants and the nuclear power plant control systems have become highly complex electroonics,fluid,electricity,water and mechanical parts networks All in all areas related to the mechanical engineers.Small internal combustion engine,both to the type (petrol and diesel machines)or rotary-type(gas turbines and Mong Kerr machine),as well as their broad application in the field of transport should also due to mechanical enginerrs.Throughout the transport,both in the air and space,or in the terrestrial and marine,mechanial engineers created a variety of equipment and power devices to their increasing cooperation with electrical engineers,especially in the development of appropration control systems.Mechanical engineers in the development of military weapons technology and civil war ,needs a similar,though its purpose is to enhance rather than destroy their productivity.However.War needs a lot of resources to make the area of techonlogy,many have a far-reaching development in peacetime efficiency.Jet aircraft and nuclear reactors are well known examples.
The Biological engineering,mechanical engineering biotechnology is a relatively new and different areas,it provides for the replacement of the machine or increase the body functions as well as for medical equipment.Artficial limbs have been developed and have such a strong movement and touch response function of the human body.In the development of artificial organ transplant is rapid,complex cardiac machines and similar equipment to enable increasingly complex surgery,and injuries and ill patients life functions can be sustained.Some enviromental control mechanical engineers through the initial efforts to drainage or irrigation pumping to the land and to mine and ventilation to control the human environment.Modern refrigeration and air-conditioning plant commonaly used reverse heat engine,where the heat from the engine from cold places to more external heat.Many mechanical engineering products,as well as other leading technology development city have side effects on the environment,producing noise,water and air pollution caused,destroyed land and landscape.Improve productivity and diver too fast in the commodity,that the renewable natural
forces keep pace.For mechanical engineers and others,environmental control is rapidly developing area,which includes a possible development and production of small quantities of pollutants machine sequnce,and the development of new equipment and teachnology has been to reduce and eliminate pollution.
4.The role of mechanical engineering
There are four generic mechanical engineers in common to the above all domains function.The 1st function is the understanding and the research mechanical science foundation.It includes the power and movement of the relationship dynamics For example,in the vibration and movement of the relationship;Automatic control;Study of the various forms of heart,energy,power relations between the thermodynamic;Fluidflows; Heat transfer; Lubricant; And material properties.The 2nd function will be conducts the research,the desing and the development,this function in turn attempts to carry on the essential change to satisfy current and the future needs.This not only calls for a clear understanding of mechanical science,and have to break
down into basic elements of a complex system capacity.But also the need for synthetic and innovative inventions.The 3rd function is produces the product and the power,include plan,operation and maintenance.Its goal lies in the maintenance either enhances the enterprise or the organization longer-tern and survivabilaty prestige at the same time,produces the greatest value by the least investments and the consumption.The 4th function is mechanical engineer’s coordinated function,including the management,the consultation,as well as carries on the market marking in certain situation.
In all these function,one kind unceasingly to use the science for a long time the method,but is not traditional or the intuition method tendency,this is a mechanical engineering skill aspect which unceasingly grows.These new rationalization means typical names include:The operations research,the engineering economics,the logical law problem analysis(is called PABLA) However,creativity is not rationalization.As in other areas,in mechanical engineering,
to take unexpected and important way to bring about a new capacity,still has a personal,marked characteristice.
5.The design of mechanical engineering
The design of mechanical is the design has the mechanical property the thing or the system,such as:the instrument and the measuring appliance in very many situations,the machine design must use the knowledge of discipline the and so on mathematics,materials science and mechanics.
Mechanical engineering desgin includeing all mechanical desgin,but it was a study,because it also includes all the branches of mechsnical engineering,such as thermodynamics all hydrodynamics in the basic disciplines needed,in the mechanical engineering design of the initial stude or mechanical design.Design stages.The entire desgin process from start to finish,in the process,a demand that is designed for it and decided to do the start.After a lot of repetition,the final meet this demand by the end of the design procees and the plan.Design considerations.Sometimes in a system is to decide which parts needs intensity parts of geometric shapes
and size an important factor in this context that we must consider that the intensity is an important factor in the design.When we use expression design considerations,we design parts that may affect the entire system design features.In the circumstances specified in the design,usually for a series of such functions must be taken into account.Howeever,to correct purposes,we should recognize that,in many cases the design of important design considerations are not calculated or test can determine the components or systems.Especially students,wheen in need to make important decisions in the design and conduct of any operation that can not be the case,they are often confused.These are not special,they occur every day,imagine,for example,a medical laboratory in the mechanical design,from marketing perspective,people have high expectations from the strength and relevance of impression.Thick,and heavy parts installed together:to produce a solid impression machines.And sometimes machinery and spare parts from the design style is the point and not the other point of view.Our purpose is to make those you do not be misled to believe that every design decision will need
reasonable mathematical methods.
Manufacturing refers to the raw meterials into finished products in the enterprise.Create three distinct phases.They are:input,processing exprot.The first phase includes the production of all products in line with market needs essential.First there must be the demand for the product,the necessary materials,while also needs such as energy,time,human knowledge and technology resourcess .
Finall,the need for funds to obtain all the other resources. Lose one stage after the second phase of the resources of the processes to be distributed.Processing of raw materials into finished products of these processes.To complete the design,based on the design,and then develop plans.Plan implemented through various production processes.Management of resources and processes to ensure efficiency and productivity.For example,we must carefully manage resources to ensure proper use of funds.Finally,people are talking about the product market was cast.Stage is the final stage of exporting finished or stage.Once finished just purchased,it must be delivered to the users.According to product performance,installation and may have to conduct further debugging in addition,some products,especially those very complex products User training is necessary.
6.The processes of materials and maunfacturing
Here said engineering materials into two main categories:metals and non-ferrous,high-performance alloys and power metals.Non-metallic futher divided into plastice,synthetic rubber,composite materials and ceramics.It said the production proccess is divided into several major process,includingshape,forging,casting/ founding,heat treatment,fixed/connections ,measurement/ quality control and materal cutting.These processes can be further divide into each other’s craft.Various stages of the development of the manufacturing industry Over the years,the manufacturing process has four distinct stages of development, despite the overlap.These stages are:The first phase is artisanal,the second Phase is mechanization.The third phase is automation the forth Phase is integrated.
When mankind initial processing of raw materials into finished products will be,they use manual processes.Each with their hands and what are the tools manuslly produced.This is totally integrated production take shape.A person needs indentification,collection materials,the design of a product to meet that demand,the production of such products and use it.From beginning to end,everything is focused on doing the work of the human mind.later in the industrial revolution introduced mechanized production process,people began to use machines to complete the work accomplished previously manual. This led to the specialization.Specialization in turn reduce the manufacture of integrated factors.In this stage of development,manufacturing workers can see their production as a whole represent a specific piece of the part of the production process.One can not say that their work is how to cope with the entire production process,or how they were loaded onto a production of parts finished.Development of manufacting processes is the next phase of the selection process automation.This is a computer-controlled machinery and processes.At this stage,automation island began to emerge in the workshop lane.Each island represents a clear production process or a group of processes.Although these automated isolated island within the island did raise the productivity of indivdual processes,but the overall productivity are often not change.This is because the island is not caught in other automated production process middle,but not synchronous with them .The ultimate result is the efficient working fast parked through automated processes,but is part of the stagnation in wages down,causing bottlenecks.To better understand this problem,you can imagine the traffic in the peak driving a red light from the red Service Department to the next scene. Occasionally you will find a lot less cars,more than being slow-moving vehicles,but the results can be found by the next red light Brance.In short you real effect was to accelerate the speed of a red Department obstruction offset.If you and other drivers can change your speed and red light simultaneously.Will advance faster.Then,all cars will be consistent,sommth operation,the final everyone forward faster.In the workshop where the demand for stable synchronization of streamlined production,and promoted integration of manufacturing development.This is a still evolving technology.Fully integrated in the circumstances,is a computer-controllrd machinery and processing.integrated is completed through computer.For example in the preceding paragraph simulation problems,the computer will allow all road vehicles compatible with the change in red.So that everyone can steady traffic.
Scientific analysis of movement,timing and mechanics of the disciplines is that it is composed of two pater:statics and dynamics.Statics analyzed static system that is in the system,the time is not taken into account,research and analysis over time and dynamics of the system change.Dynameics from the two componets.
Euler in 1775 will be the first time two different branches: Rigid body movement studies can conveniently divided into two parts:geometric and mechanics.The first part is without taking into account the reasons for the downward movement study rigid body from a designated location to another point of the movement,and must use the formula to reflect the actual,the formula would determine the rigid body every point position. Therefore,this study only on the geometry and,more specifically,on the entities from excision.Obviously,the first part of the school and was part of a mechanical separation from the principles of dynamics to study movement,which is more than the two parts together into a lot easier.Dynamics of the two parts are subsequently divided into two separate disciplines,kinematic and dynamics,a study of movement and the movement strength.Therefore,the primary issue is the design of mechanical systems understand its kinematic.Kinematic studies movement,rather than a study of its impact.In a more precise kinematic studies position,displacement,rotation, speed,velocity and acceleration of disciplines,for esample,or planets orbiting research campaing is a paradigm.
In the above quotation content should be pay attention that the content of the Euler dynamics into kinematic and rigid body dynamics is based on the assumption that they are based on research.In this very important basis to allow for the treatment of two separate disciplines.For soft body,soft body shape and even their own soft objects in the campaign depends on the role of power in their possession.In such cases,should also study the power and movement,and therefore to a large extent the analysis of the increased complexity.Fortunately, despite the real machine parts may be involved are more or less the design of machines,usually with heavy material designed to bend down to the lowest parts.Therefore,when the kinematic analysis of the performance of machines,it is often assumed that bend is negligible,spare parts are hard,but when the load is known,in the end analysis engine,re-engineering parts to confirm this assnmption.
機(jī)械工程
1.機(jī)械工程簡介
機(jī)械工程是工程學(xué)的一個(gè)分支,它研究機(jī)械和動力的產(chǎn),尤其是力和動力。
2.機(jī)械工程的歷史
18世紀(jì)后期,蒸汽機(jī)的發(fā)明為工業(yè)革命提供了一個(gè)主要的能量, 它極大地推動了各種機(jī)械的發(fā)展。這樣, 一個(gè)新的工程學(xué)的重要分支—從民用工程學(xué)中分離出來的關(guān)于工具和機(jī)器的分支就發(fā)展了起來,并隨著在1847年英國伯明翰機(jī)械工程師協(xié)會的建立得到了正式承認(rèn)。 機(jī)械工程已經(jīng)由一門主要用于技工應(yīng)用的技術(shù)發(fā)展成為專業(yè)工程師在研究、 設(shè)計(jì)和生產(chǎn)領(lǐng)域中使用的科學(xué)方法。 從最廣義的角度講,增進(jìn)效率的需求不斷地促使機(jī)械工程師提高工作質(zhì)量, 并要求他接受中高程度的教育和訓(xùn)練。 不僅機(jī)器運(yùn)轉(zhuǎn)要講求經(jīng)濟(jì), 而且基建費(fèi)也要降到最低。
3.機(jī)械工程的領(lǐng)域
商品機(jī)械的發(fā)展在發(fā)達(dá)國家中, 高水平的物質(zhì)生活很大程度上取決于機(jī)械工程中得以實(shí)現(xiàn)的各種機(jī)械。 機(jī)械工程師們不斷地發(fā)明機(jī)器來生產(chǎn)商品, 不斷的開發(fā)精確性和復(fù)雜性越來越高的機(jī)械工具來生產(chǎn)機(jī)器。機(jī)械發(fā)展的主要線索是: 為提高生產(chǎn)率而增加機(jī)器的運(yùn)轉(zhuǎn)速度、 為獲得物美價(jià)廉的產(chǎn)品而提高精度以及降低生產(chǎn)成本。 這3個(gè)要求促進(jìn)了復(fù)雜的控制系統(tǒng)的發(fā)展。 最成功的機(jī)械制造是其機(jī)器的機(jī)械設(shè)計(jì)能與控制系統(tǒng)緊密融合, 不論這種控制系統(tǒng)從本質(zhì) 上是機(jī)械的還是電子的。 現(xiàn)代化的汽車發(fā)動機(jī)生產(chǎn)傳送線(傳動帶) 就是一系列復(fù)雜的生產(chǎn)工藝機(jī)械化的很好例子。 人們正在著手開發(fā)以使機(jī)械生產(chǎn)進(jìn)一步自動化, 利用計(jì)算機(jī)來存儲和處理大量數(shù)據(jù), 這些數(shù)據(jù)是少量多功能機(jī)床生產(chǎn)多種零件所必須的。 其中一個(gè)目標(biāo)就是使批量生產(chǎn)車間完全自動化,三班輪換, 但每天只需一班人員來操作。 動力機(jī)械的發(fā)展生產(chǎn)機(jī)械必須先有充足的動力供應(yīng)。 蒸汽機(jī)最先提供了用熱能來產(chǎn)生動力的實(shí)際可行的方法, 在舊有的人力、風(fēng)力和水力之外增加了動力源。 新的機(jī)械工程業(yè)面臨的最初挑戰(zhàn)之一就是增加熱效率和動力, 這一點(diǎn)隨著蒸汽渦輪機(jī)和大的聯(lián)合蒸汽鍋爐的發(fā)展而基本實(shí)現(xiàn)了。20世紀(jì), 渦輪機(jī)為發(fā)電機(jī)提供的動力得到了持續(xù)快速的增長,同時(shí)熱效率也在穩(wěn)定增長, 而且大電站每千瓦的資本消耗也在下降。最后, 機(jī)械工程師們獲得了核能源。 這種核能源的應(yīng)用需要有特別高的可靠性和安全性, 這就需要解決許多全新的問題。 大型電廠和整個(gè)核電站的控制系統(tǒng)已變成高度復(fù)雜的電子、流體、電、 水力和機(jī)械零件的網(wǎng)絡(luò)這一切都涉及到機(jī)械工程師的所有學(xué)術(shù)領(lǐng)域。 小型的內(nèi)燃機(jī), 不論是往復(fù)式(汽油機(jī)和柴油機(jī))還是旋轉(zhuǎn)式(燃?xì)廨啓C(jī)和旺克爾機(jī)) , 以及它們在運(yùn)輸領(lǐng)域的廣泛應(yīng)用也都要?dú)w功于機(jī)械工程師們。 在整個(gè)運(yùn)輸業(yè),不論是在空中和太空, 還是在陸地和海洋,機(jī)械工程師創(chuàng)造了各種設(shè)備和動力裝置,他們越來越多的與電氣工程師合作,尤其是在開發(fā)適合的控制系統(tǒng)方面。 軍用武器的開發(fā)機(jī)械工程師應(yīng)用于戰(zhàn)爭的技術(shù)與民用中需要的類似, 盡管其目的是增強(qiáng)毀壞力而不是提高生產(chǎn)率。然而,戰(zhàn)爭的需要使得大量的資源用于技術(shù)領(lǐng)域, 很多發(fā)展在和平時(shí)期有著深遠(yuǎn)的效益。噴氣式飛機(jī)和核反應(yīng)堆就是眾所周知的例子。
生物工程是機(jī)械工程中的一個(gè)相對新的領(lǐng)域,它用來替換或增加人體功能的機(jī)器和進(jìn)行醫(yī)療的設(shè)備。 人造肢體已被開發(fā)出來, 并且具有諸如有力的運(yùn)動和觸摸反應(yīng)等人體功能。 在人工器官移植手術(shù)方面的發(fā)展史迅速的, 復(fù)雜的心肺機(jī)器和類似的設(shè)備使越來越復(fù)雜的手術(shù)得以進(jìn)行, 并使受重傷和重病病人的生命功能得以持續(xù)。 環(huán)境控制機(jī)械工程師的一些最初的努力是要通過抽水來排澇或灌溉土地以及給礦井通風(fēng)來控制人類的環(huán)境。 現(xiàn)代的制冷和空調(diào)廠普遍采用反向的熱引擎, 在這些地方動力吧熱從冷的地方抽出送到更熱的外部。 很多機(jī)械工程的產(chǎn)品以及其他領(lǐng)域的技術(shù)發(fā)展對環(huán)境有副作用, 產(chǎn)生了噪音, 引起了水和空氣的污染,破壞了土地和風(fēng)景。 商品和動力的生產(chǎn)率提高太快, 以至于自然力的再生跟不上步伐。 對于機(jī)械工程師和他人來說, 環(huán)境控制是一個(gè)快速發(fā)展的領(lǐng)域,它包括開發(fā)盡可能產(chǎn)生少量污染物的機(jī)器和生產(chǎn)上序, 以及開發(fā)新的設(shè)備和技術(shù)來減少和消除已造成的污染。
4.機(jī)械工程的作用
機(jī)械工程師有四個(gè)上述所有領(lǐng)域的作用。第1個(gè)作用是理解和研究機(jī)械科學(xué)的基礎(chǔ)。它包括涉及力和運(yùn)動的關(guān)系的動力學(xué)。 比如在在震動中的力和運(yùn)動的關(guān)系;自動控制;研究各種形式的熱、能量、動力之間關(guān)系的熱力學(xué);流體流動;熱傳遞; 潤滑; 和材料特性。 第2個(gè)作用是依次地進(jìn)行研究、設(shè)計(jì)和開發(fā)、 該作用試圖進(jìn)行必要的改變以滿足當(dāng)前和將來的需要。 這一工作不僅要求對機(jī)械科學(xué)有
一個(gè)清楚的了解,并且有把復(fù)雜系統(tǒng)分解成基本因素的能力。 而且還需要有創(chuàng)新性來進(jìn)行人工合成和發(fā)明。 第3個(gè)作用是生產(chǎn)產(chǎn)品和動力, 包括計(jì)劃、運(yùn)作和維護(hù)。 其目的在于維護(hù)或提高企業(yè)或機(jī)構(gòu)的較長期的和生存能力聲譽(yù)的同時(shí), 以最少的投資和消耗生產(chǎn)出最大的價(jià)值。 第4個(gè)作用是機(jī)械工程師的協(xié)調(diào)作用,包括管理、咨詢、以及在某些情況下進(jìn)行市場營銷。
在所有這些作用中, 體現(xiàn)出一種長期不斷地使用科學(xué)的方法, 而不是傳統(tǒng)的或直覺的方法, 這是不斷成長的機(jī)械工程專門技術(shù)的一個(gè)方面。 這些新的合理化方法的典型名稱有:運(yùn)籌學(xué)、工程經(jīng)濟(jì)學(xué)、邏輯法問題分析(簡稱PABLA)。然而,創(chuàng)造性是無法合理化的。正如在其他領(lǐng)域一樣, 在機(jī)械工程中,能夠采取重要的出人意料的并能開創(chuàng)出新方法的能力,仍然具有個(gè)人的、即興的特點(diǎn)。
5.機(jī)械工程設(shè)計(jì)
機(jī)械設(shè)計(jì)是設(shè)計(jì)具有機(jī)械性質(zhì)的事物或系統(tǒng), 如:各種機(jī)器、產(chǎn)品、結(jié)構(gòu)、器械和儀表在很多情況下, 機(jī)械設(shè)計(jì)要用到數(shù)學(xué)、材料科學(xué)和工程力學(xué)等學(xué)科的知識。
機(jī)械工程設(shè)計(jì)包括所有的機(jī)械設(shè)計(jì), 但它研究得更廣,因?yàn)樗舶ㄋ袡C(jī)械工程的分支科學(xué), 如熱力學(xué)和流體力學(xué)除了所需的基本學(xué)科外, 在機(jī)械工程設(shè)計(jì)中最初學(xué)習(xí)的還是機(jī)械設(shè)計(jì)。 設(shè)計(jì)的各個(gè)階段設(shè)計(jì)的整個(gè)過程從開始到結(jié)束,在這一過程中, 設(shè)計(jì)是以認(rèn)定一個(gè)需求并決定去為它做些什么而開始的。經(jīng)過很多重復(fù)之后,最后提出滿足這一要求的計(jì)劃而結(jié)束這一設(shè)計(jì)過程。 設(shè)計(jì)中考慮的因素。 有時(shí)在某個(gè)系統(tǒng)中零件所需的強(qiáng)度是決定這零件的幾何形狀和尺寸大小的重要因素在這種情況下, 我們說強(qiáng)度就是設(shè)計(jì)中要考慮的重要因素。 當(dāng)我們使用設(shè)計(jì)考慮因素這一表達(dá)方式時(shí), 我們是指影響零件設(shè)計(jì)或許整個(gè)系統(tǒng)設(shè)計(jì)的一些性能