編號(hào)： 畢業(yè)設(shè)計(jì)(論文)外文翻譯（譯文）學(xué) 院專 業(yè)學(xué)生姓名學(xué) 號(hào)指導(dǎo)教師單位姓 名職 稱高架起重機(jī)橋架的建模與有限元分析C. Alkin, C. E. Imrak, H. Kocabas摘 要該論文以 35 噸級(jí)，13 米跨度橋式起重機(jī)的兩個(gè)箱式梁為研究對(duì)象進(jìn)行設(shè)計(jì)研究。在該論文中，提出了常規(guī)設(shè)計(jì)計(jì)算 f E.M 規(guī)則和 DIN 標(biāo)準(zhǔn)進(jìn)行了驗(yàn)證應(yīng)力和撓度水平。起重機(jī)設(shè)計(jì)同時(shí)使用立方體和平面。有限元網(wǎng)格劃分使用四個(gè)節(jié)點(diǎn),用正四面體與四邊形單元組成實(shí)體殼模型,再分別通過有限元分析進(jìn)行比較，在正常計(jì)算下，結(jié)合已有的起重機(jī)性能，二次殼單元有限元分析是最接近實(shí)際結(jié)果的。研究結(jié)果表明，該高架起重機(jī)的設(shè)計(jì)是可行的。關(guān)鍵詞：高架起重機(jī)，有限元分析法，建模，箱式梁。注釋兩個(gè)側(cè)板間的距離b下模版的寬度k導(dǎo)軌的靜負(fù)載AF裝載后負(fù)載y主梁末端高度0h側(cè)板高度2滾輪間距AL起重梁跨度k相鄰支撐結(jié)構(gòu)間距p平臺(tái)重量q維護(hù)平臺(tái)重量k均勻分布的橋架單元質(zhì)量p上下夾板的厚度1t側(cè)板厚度2左側(cè)板中心到起重機(jī)重心距離x導(dǎo)軌中心到起重機(jī)重心距離4導(dǎo)軌中心到中軸距離1y上板到起重機(jī)重心距離3上板到中軸距離5X 軸上的主要阻力1xWY 軸上的主要阻力y放大系數(shù)c?Ψ 動(dòng)態(tài)系數(shù)1 引言起重機(jī)是讓超重貨物在建筑里輕松移動(dòng)的最好方式之一。高架起重機(jī)是物料運(yùn)輸系統(tǒng)中運(yùn)送重物最重要的部分。起重機(jī)的主要任務(wù)就是載重后從一個(gè)位置移動(dòng)到另一個(gè)位置。因此經(jīng)常被用與汽車工廠和船塢[1，2]。根據(jù)它們的主要用途有許多設(shè)計(jì)特征上的變化，例如：起重機(jī)的運(yùn)動(dòng)部件結(jié)構(gòu)，工作載荷，起重機(jī)的位置，幾何特征和環(huán)境條件。這些部分使起重機(jī)的設(shè)計(jì)規(guī)程高度標(biāo)準(zhǔn)化，大部分的時(shí)間花費(fèi)在對(duì)現(xiàn)有的設(shè)計(jì)標(biāo)準(zhǔn)的執(zhí)行和說明[3]。有很多關(guān)于結(jié)構(gòu)和受力組成的研究，在靜態(tài)和動(dòng)態(tài)負(fù)載的起重機(jī)上安全進(jìn)行[5-16]。Demirsoy 已經(jīng)進(jìn)行了的關(guān)于橋的結(jié)構(gòu)建模和有限元分析，研究其位移和應(yīng)力測試值[17]。建模技術(shù)來源于公路橋結(jié)構(gòu)，同時(shí)提供研究分析的有限元模型[18]。在該研究中，力和位移用 F.E.M90 軟件分析。橋式起重機(jī)模型不同點(diǎn)的加載和有限元分析方法的應(yīng)用由 Celiktas 完成[19]。她為高架起重機(jī)提供了有限元分析的結(jié)果。DIN 標(biāo)準(zhǔn)和 F.E.M（歐洲聯(lián)合會(huì)）算法提供了被廣泛接受的設(shè)計(jì)與驗(yàn)證方法和公式。DIN 標(biāo)準(zhǔn)第 44 和 185 條收集了關(guān)于起重機(jī)設(shè)計(jì)的標(biāo)準(zhǔn)。DIN 標(biāo)準(zhǔn)廣泛規(guī)定了設(shè)計(jì)參數(shù)的標(biāo)準(zhǔn)值。F.E.M 算法主要收集了起重機(jī)設(shè)計(jì)的規(guī)則指引。它包含了關(guān)于如何選擇不同載荷方式下的起重機(jī)元件。在這項(xiàng)研究中，計(jì)算部分套用 F.E.M 算法和 DIN 標(biāo)準(zhǔn)，用于橋式起重機(jī)的箱梁。箱梁的計(jì)算使用 CESAN 有限公司的標(biāo)準(zhǔn)橋接器。橋式起重機(jī)的模型產(chǎn)生了同等規(guī)模的計(jì)算結(jié)果。使用有限元分析法執(zhí)行靜態(tài)分析。在開始解決方案之前，臨界情況已經(jīng)應(yīng)用到實(shí)踐。2 雙箱式梁高架起重機(jī)雙箱式梁高架起重機(jī)不僅僅只是提升重物，還要攜帶重物在其范圍內(nèi)移動(dòng)。在雙重梁高架起重機(jī)橋架上建造有可移動(dòng)吊運(yùn)車，橋架在導(dǎo)軌上運(yùn)動(dòng)，吊運(yùn)車在橋架上升高或降低貨物，橋架在導(dǎo)軌上運(yùn)送貨物。因此，執(zhí)行了三個(gè)垂直正交的運(yùn)動(dòng)。如圖一，貨物用鋼索固定在橋架上[21，22]。雙箱梁同時(shí)受到水平和垂直方向的吊車重量，工作負(fù)載（吊鉤）和動(dòng)力載荷。關(guān)于雙箱梁的制造，吊運(yùn)車需要在梁之間或上面運(yùn)行。圖 2 說明了合適的建造要求和梁的結(jié)構(gòu)標(biāo)準(zhǔn)。圖 1：高架起重機(jī)的總視圖圖 2：箱形主梁的制造要求。3 高架起重機(jī)的有限元分析及應(yīng)用在數(shù)字技術(shù)之中，有限元分析法被廣泛使用得益與有很多實(shí)用和易于操作的商業(yè)軟件。有限元分析法可以分析任何幾何學(xué)，解決力學(xué)和位移問題[23]。有限元分析法幾乎解決了研究中的全部或部分的有限元節(jié)點(diǎn)問題。該近似解明確表達(dá)了每個(gè)基礎(chǔ)元素和之后整體裝配獲得的剛性矩陣，位移量和力矢量問題。在該論文中的有限元模型是用 Cosmos Works 和 MSC 商業(yè)版完成的。用 Patran（有限元分析軟件）和四面體單元與四邊形殼單元為該高架起重機(jī)橋架建模。四面體單元是最簡單的三維空間單元，應(yīng)用于固體應(yīng)力問題分析如支架的應(yīng)力分析。該單元有四個(gè)節(jié)點(diǎn)，每個(gè)節(jié)點(diǎn)都有三個(gè)移動(dòng)副和能在 x，y，z 軸上旋轉(zhuǎn)的自由度。關(guān)于殼單元的定義，是指允許在平面和曲面上都能擁有長度的單元。它的寬度只能用于 3D 仿真。四面體殼單元因?yàn)檠b配彎曲元件而獲得了一定的自由度。這充分表明殼單元的偏差必須在預(yù)先定義的殼厚度內(nèi)，否則整個(gè)系統(tǒng)會(huì)在一個(gè)過大的偏差內(nèi)運(yùn)行。典型的四面體單元和四邊形殼單元與它們的坐標(biāo)系在圖 3 中說明[24]。選擇的四面體單元每個(gè)節(jié)點(diǎn)有六個(gè)自由度：x，y，z 方向上的平移和繞 x，y，z 軸自由旋轉(zhuǎn)。用正四面體殼單元為高架起重機(jī)梁建模，r 和 s 表示固有坐標(biāo)系，δ 是單元體的厚度。該體系沒有任何水平力。軸向位移和總體的旋轉(zhuǎn)整體來看都近似為零。此外節(jié)點(diǎn)的橫向唯一整體來看也為零。對(duì)系統(tǒng)起作用的外力大部分來自于起重機(jī)的主梁質(zhì)量（分布載荷）和作用在吊車滑輪沿起重機(jī)的力（有效載荷）。吊車滑輪上的力是因?yàn)榈踯嚨馁|(zhì)量，來自提升負(fù)載物和在起重機(jī)上移動(dòng)。四節(jié)點(diǎn)四面體單元四節(jié)點(diǎn)二次殼單元圖 3：為高架起重機(jī)梁建模的單元體4 高架橋起重機(jī)立體有限元模型有限元分析法是一種可以用于為工程學(xué)內(nèi)各種問題提供解決辦法的計(jì)算方案。穩(wěn)定的，瞬時(shí)的，線性的，非線性的應(yīng)力分析問題,熱傳遞，流量問題也可以用有限元方法解決。有限元分析法的基本步驟如下：預(yù)處理，解決方案，后處理。真實(shí)的起重機(jī)數(shù)據(jù)從 CESAN 有限公司收集來，一個(gè)土耳其公司引進(jìn)了該高架起重機(jī)的大量生產(chǎn)。首先，起重機(jī)橋架是模擬成面。橋架幾何體是適合于此方法的，長和薄的部分也同樣被模擬成面。隨后，一個(gè)網(wǎng)格建立成功。在研究中，使用二次單元模式。立體建模是為了計(jì)算起重機(jī)橋架，該立體模型展示在圖 4 中[20]。起重機(jī)橋架立體模型 起重機(jī)橋架的框架視圖圖 4：起重機(jī)橋架模型5 高架起重機(jī)的數(shù)值算例研究對(duì)象為 13T 級(jí)高架起重機(jī)其總長 13 米總重 22.5 噸。該起重機(jī)結(jié)構(gòu)見圖 1。該高架起重機(jī)組成部分包括兩個(gè)大梁和兩個(gè)連接它們的底座，一個(gè)可在軸向移動(dòng)的起重機(jī)空中吊運(yùn)車和滑輪驅(qū)動(dòng)裝置安裝在其中一個(gè)大梁上。起重機(jī)支撐在兩條軌道上，軌道梁安裝在建筑中。為了計(jì)算結(jié)構(gòu)的受力，使用有限元分析法 1.001。橋架分析的設(shè)計(jì)理念來自 F.E.M和 DIN 標(biāo)準(zhǔn)被列在表 1 中。表 1：橋架屬性值裝卸量 : =35 ton吊車重量 : =3 ton橋長度 : =13 m吊車兩輪間距 : =2m吊車速率 : =20 m/min.起重機(jī)速率 : =15 m/min.起吊速率 : =2.7 m/min總使用壽命 : U4用有限元分析法先計(jì)算最大和最小應(yīng)力然后計(jì)算剪切應(yīng)力。使用有限元分析法考慮主梁，我們得到了壓力值。我們由于固有重量而得到了靜態(tài)負(fù)載，負(fù)載來自于工作載荷乘以動(dòng)態(tài)系數(shù)，是水平方向上最不利的兩個(gè)因素，不包括緩沖力。最大的應(yīng)力來自于橋身固有重量的壓力和吊車的固有重量，提升載荷的力，慣力和吊車收縮力。最小應(yīng)力包括橋身固有重量和吊車固有重量的力。最大和最小應(yīng)力的標(biāo)準(zhǔn)來自 F.E.M 規(guī)則[20]如下和動(dòng)態(tài)系數(shù) ψ 的意義是來自于工作負(fù)載的載荷。放大系數(shù)的意義依賴應(yīng)用級(jí)別組，其中維護(hù)臺(tái)的重量為零。[25]。假設(shè)主負(fù)載（372780 N）作用于導(dǎo)軌的中點(diǎn)，而且每個(gè)主梁平均分擔(dān)總負(fù)載。這個(gè)負(fù)載通過系統(tǒng)中兩個(gè)吊車輪的接觸點(diǎn)求得，因此每個(gè)點(diǎn)的作用力是 93195 N。系統(tǒng)總負(fù)載的求解，最大應(yīng)力值等于（1）143.90 N/mm2 精確到兩位小數(shù)點(diǎn)，最小應(yīng)力值等于（2）47.33 N/mm2 精確到兩位小數(shù)點(diǎn)。根據(jù)圖 5，切變的許用應(yīng)力包括剪應(yīng)力和車輪力，定義如下:[20]最大剪應(yīng)力值等于 24.82 N/mm2 精確到兩位小數(shù)點(diǎn)（5）。帶入等式（1）-（3）工作級(jí)別 : Q3設(shè)備組 : A5裝載型號(hào) : H (main load)動(dòng)態(tài)系數(shù) :ψ=1.15放大系數(shù) := 1.11可得到等效應(yīng)力。等效應(yīng)力值為 150.18 N/mm2 精確到兩位小數(shù)點(diǎn)。圖 5：箱形梁中的慣力和阻力6 四面體單元的梁模型結(jié)果為高架橋起重機(jī)梁用四面體單元建模，用 Cosmoswork 軟件進(jìn)行有限元分析，用SolidWork 2003 為梁生成立體模型。彈性模量（ E）為 2.1x105 N/mm2 ，泊松比（）為 0.3 進(jìn)行有限元分析。側(cè)板的最大應(yīng)力值為 12.07 N/mm2 精確到兩位小數(shù)點(diǎn)，底板的最大應(yīng)力值為 15.08 N/mm2 精確到兩位小數(shù)點(diǎn)，如圖 6[20]。高架橋起重機(jī)模型的位移量來自于 CosmosWorks，在圖 7 中說明。梁的最大位移值大概為 2.2 mm。圖 6：高架起重機(jī)梁的四面體單元受力情況圖 7：高架起重機(jī)梁的四面體單元位移量7 四節(jié)點(diǎn)二次殼單元的梁模型結(jié)果為高架橋起重機(jī)梁用四節(jié)點(diǎn)二次殼單元建模，用 MSC Patran 軟件進(jìn)行有限元分析，早期系數(shù)（E）為 2.1x10 N/mm2 ，泊松比（）為 0.3 進(jìn)行有限元分析。側(cè)板的最大應(yīng)力值為 35.40 N/mm2 精確到兩位小數(shù)點(diǎn)，底板的最大應(yīng)力值為 49.30 N/mm2 精確到兩位小數(shù)點(diǎn)如圖 8[20]。高架橋起重機(jī)梁模型的位移量獲得自 MSC Patran 如圖 9。梁的最大位移量約為3.89mm。根據(jù)式（1）最大應(yīng)力值計(jì)算得 143.90 N/mm2 精確到兩位小數(shù)點(diǎn)。起重機(jī)的安全系數(shù)設(shè)計(jì)為 2 到 3。考慮到四面體單元的安全系數(shù)，側(cè)板的最大應(yīng)力在 24.14 到 36.21 N/mm2 之間精確到兩位小數(shù)點(diǎn)。底板的最大應(yīng)力值在 30.16 到 45.24 N/mm2 之間精確到兩位小數(shù)點(diǎn)?？紤]到四節(jié)點(diǎn)二次殼單元的安全系數(shù)，其側(cè)板的最大應(yīng)力在 70.8 到 106.2 N/mm2 之間精確到兩位小數(shù)點(diǎn)。底板的最大應(yīng)力值在 98.60 到 147.90 N/mm2 之間精確到兩位小數(shù)點(diǎn)。根據(jù) F.E.M 規(guī)則梁的允許位移為 13mm。通過四面體單元有限元模型獲得的值在4.40 到 6.60 之間，安全系數(shù)已考慮。通過四節(jié)點(diǎn)二次殼單元有限元模型獲得的值在7.78 到 11.67mm 之間，安全系數(shù)已考慮。圖 8：高架起重機(jī)梁二次殼單元的受力值圖 9：高架起重機(jī)四節(jié)點(diǎn)二次殼單元的位移量8 結(jié)論在該研究中，不像其他論文照搬原有理論，高架箱型梁的殼單元有限元模型已被驗(yàn)證。為了展示出殼單元的用處，給出了一個(gè)高架起重機(jī)橋架的實(shí)例。根據(jù) F.E.M 算法和有限元分析法計(jì)算得，四面體單元的最大應(yīng)力值是 143.90 N/mm2 和 45.24 N/mm2，四節(jié)點(diǎn)二次殼單元的最大應(yīng)力值為 147.9 N/mm2。等效應(yīng)力為 150.18 N/mm2 精確到兩位小數(shù)點(diǎn)。通過 MSC Patran 考慮到安全系數(shù)，應(yīng)力值應(yīng)該在 97-145.5N/mm2之間變化。高架起重機(jī)箱式梁的長厚比高于 20.因此，為了展示高架起重機(jī)橋架分析的精確度，用四節(jié)點(diǎn)二次殼單元代替四面體單元進(jìn)行有限元分析。數(shù)控機(jī)床的改造1 數(shù)控系統(tǒng)發(fā)展簡史及趨勢1946 年誕生了世界上第一臺(tái)電子計(jì)算機(jī)，這表明人類創(chuàng)造了可增強(qiáng)和部分代替腦力勞動(dòng)的工具。它與人類在農(nóng)業(yè)、工業(yè)社會(huì)中創(chuàng)造的那些只是增強(qiáng)體力勞動(dòng)的工具相比，起了質(zhì)的飛躍，為人類進(jìn)入信息社會(huì)奠定了基礎(chǔ)。6 年后，即在 1952 年，計(jì)算機(jī)技術(shù)應(yīng)用到了機(jī)床上，在美國誕生了第一臺(tái)數(shù)控機(jī)床。從此，傳統(tǒng)機(jī)床產(chǎn)生了質(zhì)的變化。近半個(gè)世紀(jì)以來，數(shù)控系統(tǒng)經(jīng)歷了兩個(gè)階段和六代的發(fā)展。1.1 數(shù)控（NC）階段（1952～1970 年）早期計(jì)算機(jī)的運(yùn)算速度低，對(duì)當(dāng)時(shí)的科學(xué)計(jì)算和數(shù)據(jù)處理影響還不大，但不能適應(yīng)機(jī)床實(shí)時(shí)控制的要求。人們不得不采用數(shù)字邏輯電路“搭“成一臺(tái)機(jī)床專用計(jì)算機(jī)作為數(shù)控系統(tǒng)，被稱為硬件連接數(shù)控（HARD-WIRED NC） ，簡稱為數(shù)控（NC） 。隨著元器件的發(fā)展，這個(gè)階段歷經(jīng)了三代，即 1952 年的第一代--電子管；1959 年的第二代--晶體管；1965 年的第三代--小規(guī)模集成電路。1.2 計(jì)算機(jī)數(shù)控（CNC）階段（1970 年～現(xiàn)在）到 1970 年，通用小型計(jì)算機(jī)業(yè)已出現(xiàn)并成批生產(chǎn)。于是將它移植過來作為數(shù)控系統(tǒng)的核心部件，從此進(jìn)入了計(jì)算機(jī)數(shù)控（CNC）階段（把計(jì)算機(jī)前面應(yīng)有的“通用“兩個(gè)字省略了） 。到 1971 年，美國 INTEL 公司在世界上第一次將計(jì)算機(jī)的兩個(gè)最核心的部件--運(yùn)算器和控制器，采用大規(guī)模集成電路技術(shù)集成在一塊芯片上，稱之為微處理器（MICROPROCESSOR） ，又可稱為中央處理單元（簡稱 CPU） 。到 1974 年微處理器被應(yīng)用于數(shù)控系統(tǒng)。這是因?yàn)樾⌒陀?jì)算機(jī)功能太強(qiáng)，控制一臺(tái)機(jī)床能力有富裕（故當(dāng)時(shí)曾用于控制多臺(tái)機(jī)床，稱之為群控） ，不如采用微處理器經(jīng)濟(jì)合理。而且當(dāng)時(shí)的小型機(jī)可靠性也不理想。早期的微處理器速度和功能雖還不夠高，但可以通過多處理器結(jié)構(gòu)來解決。由于微處理器是通用計(jì)算機(jī)的核心部件，故仍稱為計(jì)算機(jī)數(shù)控。到了 1990 年，PC 機(jī)（個(gè)人計(jì)算機(jī)，國內(nèi)習(xí)慣稱微機(jī)）的性能已發(fā)展到很高的階段，可以滿足作為數(shù)控系統(tǒng)核心部件的要求。數(shù)控系統(tǒng)從此進(jìn)入了基于 PC 的階段。總之，計(jì)算機(jī)數(shù)控階段也經(jīng)歷了三代。即 1970 年的第四代--小型計(jì)算機(jī)；1974 年的第五代--微處理器和 1990 年的第六代--基于 PC（國外稱為 PC-BASED） 。還要指出的是，雖然國外早已改稱為計(jì)算機(jī)數(shù)控（即 CNC）了，而我國仍習(xí)慣稱數(shù)控（NC） 。所以我們?nèi)粘Ｖv的“數(shù)控“，實(shí)質(zhì)上已是指“計(jì)算機(jī)數(shù)控“了。1.3 數(shù)控未來發(fā)展的趨勢1.3.1繼續(xù)向開放式、基于 PC的第六代方向發(fā)展基于 PC 所具有的開放性、低成本、高可靠性、軟硬件資源豐富等特點(diǎn)，更多的數(shù)控系統(tǒng)生產(chǎn)廠家會(huì)走上這條道路。至少采用 PC 機(jī)作為它的前端機(jī)，來處理人機(jī)界面、編程、聯(lián)網(wǎng)通信等問題，由原有的系統(tǒng)承擔(dān)數(shù)控的任務(wù)。PC 機(jī)所具有的友好的人機(jī)界面，將普及到所有的數(shù)控系統(tǒng)。遠(yuǎn)程通訊，遠(yuǎn)程診斷和維修將更加普遍。1.3.2向高速化和高精度化發(fā)展這是適應(yīng)機(jī)床向高速和高精度方向發(fā)展的需要。1.3.3向智能化方向發(fā)展隨著人工智能在計(jì)算機(jī)領(lǐng)域的不斷滲透和發(fā)展，數(shù)控系統(tǒng)的智能化程度將不斷提高。（1）應(yīng)用自適應(yīng)控制技術(shù)數(shù)控系統(tǒng)能檢測過程中一些重要信息，并自動(dòng)調(diào)整系統(tǒng)的有關(guān)參數(shù)，達(dá)到改進(jìn)系統(tǒng)運(yùn)行狀態(tài)的目的。（2）引入專家系統(tǒng)指導(dǎo)加工將熟練工人和專家的經(jīng)驗(yàn)，加工的一般規(guī)律和特殊規(guī)律存入系統(tǒng)中，以工藝參數(shù)數(shù)據(jù)庫為支撐，建立具有人工智能的專家系統(tǒng)。（3）引入故障診斷專家系統(tǒng)（4）智能化數(shù)字伺服驅(qū)動(dòng)裝置可以通過自動(dòng)識(shí)別負(fù)載，而自動(dòng)調(diào)整參數(shù)，使驅(qū)動(dòng)系統(tǒng)獲得最佳的運(yùn)行。2 機(jī)床數(shù)控化改造的必要性2.1 微觀看改造的必要性從微觀上看，數(shù)控機(jī)床比傳統(tǒng)機(jī)床有以下突出的優(yōu)越性，而且這些優(yōu)越性均來自數(shù)控系統(tǒng)所包含的計(jì)算機(jī)的威力。2.1.1 可以加工出傳統(tǒng)機(jī)床加工不出來的曲線、曲面等復(fù)雜的零件。由于計(jì)算機(jī)有高超的運(yùn)算能力，可以瞬時(shí)準(zhǔn)確地計(jì)算出每個(gè)坐標(biāo)軸瞬時(shí)應(yīng)該運(yùn)動(dòng)的運(yùn)動(dòng)量，因此可以復(fù)合成復(fù)雜的曲線或曲面。2.1.2可以實(shí)現(xiàn)加工的自動(dòng)化，而且是柔性自動(dòng)化，從而效率可比傳統(tǒng)機(jī)床提高 3～7倍。由于計(jì)算機(jī)有記憶和存儲(chǔ)能力，可以將輸入的程序記住和存儲(chǔ)下來，然后按程序規(guī)定的順序自動(dòng)去執(zhí)行，從而實(shí)現(xiàn)自動(dòng)化。數(shù)控機(jī)床只要更換一個(gè)程序，就可實(shí)現(xiàn)另一工件加工的自動(dòng)化，從而使單件和小批生產(chǎn)得以自動(dòng)化，故被稱為實(shí)現(xiàn)了“柔性自動(dòng)化“。2.1.3加工零件的精度高，尺寸分散度小，使裝配容易，不再需要“修配“。2.1.4可實(shí)現(xiàn)多工序的集中，減少零件 在機(jī)床間的頻繁搬運(yùn)。2.1.5擁有自動(dòng)報(bào)警、自動(dòng)監(jiān)控、自動(dòng)補(bǔ)償?shù)榷喾N自律功能，因而可實(shí)現(xiàn)長時(shí)間無人看管加工。2.1.6由以上五條派生的好處。如：降低了工人的勞動(dòng)強(qiáng)度，節(jié)省了勞動(dòng)力（一個(gè)人可以看管多臺(tái)機(jī)床） ，減少了工裝，縮短了新產(chǎn)品試制周期和生產(chǎn)周期，可對(duì)市場需求作出快速反應(yīng)等等。以上這些優(yōu)越性是前人想象不到的，是一個(gè)極為重大的突破。此外，機(jī)床數(shù)控化還是推行 FMC（柔性制造單元） 、FMS（柔性制造系統(tǒng)）以及 CIMS（計(jì)算機(jī)集成制造系統(tǒng)）等企業(yè)信息化改造的基礎(chǔ)。數(shù)控技術(shù)已經(jīng)成為制造業(yè)自動(dòng)化的核心技術(shù)和基礎(chǔ)技術(shù)。2.2 宏觀看改造的必要性從宏觀上看，工業(yè)發(fā)達(dá)國家的軍、民機(jī)械工業(yè)，在 70 年代末、80 年代初已開始大規(guī)模應(yīng)用數(shù)控機(jī)床。其本質(zhì)是，采用信息技術(shù)對(duì)傳統(tǒng)產(chǎn)業(yè)（包括軍、民機(jī)械工業(yè)）進(jìn)行技術(shù)改造。除在制造過程中采用數(shù)控機(jī)床、FMC、FMS 外，還包括在產(chǎn)品開發(fā)中推行CAD、CAE、CAM、虛擬制造以及在生產(chǎn)管理中推行 MIS（管理信息系統(tǒng)） 、CIMS 等等。以及在其生產(chǎn)的產(chǎn)品中增加信息技術(shù)，包括人工智能等的含量。由于采用信息技術(shù)對(duì)國外軍、民機(jī)械工業(yè)進(jìn)行深入改造（稱之為信息化） ，最終使得他們的產(chǎn)品在國際軍品和民品的市場上競爭力大為增強(qiáng)。而我們在信息技術(shù)改造傳統(tǒng)產(chǎn)業(yè)方面比發(fā)達(dá)國家約落后 20 年。如我國機(jī)床擁有量中，數(shù)控機(jī)床的比重（數(shù)控化率）到 1995 年只有1.9％，而日本在 1994 年已達(dá) 20.8％，因此每年都有大量機(jī)電產(chǎn)品進(jìn)口。這也就從宏觀上說明了機(jī)床數(shù)控化改造的必要性。3 機(jī)床與生產(chǎn)線數(shù)控化改造的市場3.1 機(jī)床數(shù)控化改造的市場我國目前機(jī)床總量 380 余萬臺(tái)，而其中數(shù)控機(jī)床總數(shù)只有 11.34 萬臺(tái)，即我國機(jī)床數(shù)控化率不到 3％。近 10 年來，我國數(shù)控機(jī)床年產(chǎn)量約為 0.6～0.8 萬臺(tái)，年產(chǎn)值約為 18 億元。機(jī)床的年產(chǎn)量數(shù)控化率為 6％。我國機(jī)床役齡 10 年以上的占 60％以上；10 年以下的機(jī)床中，自動(dòng)/半自動(dòng)機(jī)床不到 20％，F(xiàn)MC/FMS 等自動(dòng)化生產(chǎn)線更屈指可數(shù)（美國和日本自動(dòng)和半自動(dòng)機(jī)床占 60％以上） ?？梢娢覀兊拇蠖鄶?shù)制造行業(yè)和企業(yè)的生產(chǎn)、加工裝備絕大數(shù)是傳統(tǒng)的機(jī)床，而且半數(shù)以上是役齡在 10 年以上的舊機(jī)床。用這種裝備加工出來的產(chǎn)品普遍存在質(zhì)量差、品種少、檔次低、成本高、供貨期長，從而在國際、國內(nèi)市場上缺乏競爭力，直接影響一個(gè)企業(yè)的產(chǎn)品、市場、效益，影響企業(yè)的生存和發(fā)展。所以必須大力提高機(jī)床的數(shù)控化率。3.2 進(jìn)口設(shè)備和生產(chǎn)線的數(shù)控化改造市場我國自改革開放以來，很多企業(yè)從國外引進(jìn)技術(shù)、設(shè)備和生產(chǎn)線進(jìn)行技術(shù)改造。據(jù)不完全統(tǒng)計(jì)，從 1979～1988 年 10 年間，全國引進(jìn)技術(shù)改造項(xiàng)目就有 18446 項(xiàng)，大約 165.8 億美元。這些項(xiàng)目中，大部分項(xiàng)目為我國的經(jīng)濟(jì)建設(shè)發(fā)揮了應(yīng)有的作用。但是有的引進(jìn)項(xiàng)目由于種種原因，設(shè)備或生產(chǎn)線不能正常運(yùn)轉(zhuǎn)，甚至癱瘓，使企業(yè)的效益受到影響，嚴(yán)重的使企業(yè)陷入困境。一些設(shè)備、生產(chǎn)線從國外引進(jìn)以后，有的消化吸收不好，備件不全，維護(hù)不當(dāng)，結(jié)果運(yùn)轉(zhuǎn)不良；有的引進(jìn)時(shí)只注意引進(jìn)設(shè)備、儀器、生產(chǎn)線，忽視軟件、工藝、管理等，造成項(xiàng)目不完整，設(shè)備潛力不能發(fā)揮；有的甚至不能啟動(dòng)運(yùn)行，沒有發(fā)揮應(yīng)有的作用；有的生產(chǎn)線的產(chǎn)品銷路很好，但是因?yàn)樵O(shè)備故障不能達(dá)產(chǎn)達(dá)標(biāo)；有的因?yàn)槟芎母?、產(chǎn)品合格率低而造成虧損；有的已引進(jìn)較長時(shí)間，需要進(jìn)行技術(shù)更新。種種原因使有的設(shè)備不僅沒有創(chuàng)造財(cái)富，反而消耗著財(cái)富。這些不能使用的設(shè)備、生產(chǎn)線是個(gè)包袱，也是一批很大的存量資產(chǎn)，修好了就是財(cái)富。只要找出主要的技術(shù)難點(diǎn)，解決關(guān)鍵技術(shù)問題，就可以最小的投資盤活最大的存量資產(chǎn)，爭取到最大的經(jīng)濟(jì)效益和社會(huì)效益。這也是一個(gè)極大的改造市場。4 數(shù)控化改造的內(nèi)容及優(yōu)缺4.1 國外改造業(yè)的興起在美國、日本和德國等發(fā)達(dá)國家，它們的機(jī)床改造作為新的經(jīng)濟(jì)增長行業(yè)，生意盎然，正處在黃金時(shí)代。由于機(jī)床以及技術(shù)的不斷進(jìn)步，機(jī)床改造是個(gè)“永恒“的課題。我國的機(jī)床改造業(yè)，也從老的行業(yè)進(jìn)入到以數(shù)控技術(shù)為主的新的行業(yè)。在美國、日本、德國，用數(shù)控技術(shù)改造機(jī)床和生產(chǎn)線具有廣闊的市場，已形成了機(jī)床和生產(chǎn)線數(shù)控改造的新的行業(yè)。在美國，機(jī)床改造業(yè)稱為機(jī)床再生（Remanufacturing）業(yè)。從事再生業(yè)的著名公司有：Bertsche 工程公司、ayton 機(jī)床公司、Devlieg-Bullavd（得寶）服務(wù)集團(tuán)、US 設(shè)備公司等。美國得寶公司已在中國開辦公司。在日本，機(jī)床改造業(yè)稱為機(jī)床改裝（Retrofitting）業(yè)。從事改裝業(yè)的著名公司有：大隈工程集團(tuán)、崗三機(jī)械公司、千代田工機(jī)公司、野崎工程公司、濱田工程公司、山本工程公司等。4.2 數(shù)控化改造的內(nèi)容機(jī)床與生產(chǎn)線的數(shù)控化改造主要內(nèi)容有以下幾點(diǎn)：其一是恢復(fù)原功能，對(duì)機(jī)床、生產(chǎn)線存在的故障部分進(jìn)行診斷并恢復(fù)；其二是 NC化，在普通機(jī)床上加數(shù)顯裝置，或加數(shù)控系統(tǒng)，改造成 NC 機(jī)床、CNC 機(jī)床；其三是翻新，為提高精度、效率和自動(dòng)化程度，對(duì)機(jī)械、電氣部分進(jìn)行翻新，對(duì)機(jī)械部分重新裝配加工，恢復(fù)原精度；對(duì)其不滿足生產(chǎn)要求的 CNC 系統(tǒng)以最新 CNC 進(jìn)行更新；其四是技術(shù)更新或技術(shù)創(chuàng)新，為提高性能或檔次，或?yàn)榱耸褂眯鹿に?、新技術(shù)，在原有基礎(chǔ)上進(jìn)行較大規(guī)模的技術(shù)更新或技術(shù)創(chuàng)新，較大幅度地提高水平和檔次的更新改造。4.3 數(shù)控化改造的優(yōu)缺4.3.1 減少投資額、交貨期短同購置新機(jī)床相比，一般可以節(jié)省 60％～80％的費(fèi)用，改造費(fèi)用低。特別是大型、特殊機(jī)床尤其明顯。一般大型機(jī)床改造，只花新機(jī)床購置費(fèi)用的 1/3，交貨期短。但有些特殊情況，如高速主軸、托盤自動(dòng)交換裝置的制作與安裝過于費(fèi)工、費(fèi)錢，往往改造成本提高 2～3 倍，與購置新機(jī)床相比，只能節(jié)省投資 50％左右。4.3.2 機(jī)械性能穩(wěn)定可靠，結(jié)構(gòu)受限所利用的床身、立柱等基礎(chǔ)件都是重而堅(jiān)固的鑄造構(gòu)件，而不是那種焊接構(gòu)件，改造后的機(jī)床性能高、質(zhì)量好，可以作為新設(shè)備繼續(xù)使用多年。但是受到原來機(jī)械結(jié)構(gòu)的限制，不宜做突破性的改造。4.3.3 熟悉了解設(shè)備、便于操作維修購買新設(shè)備時(shí)，不了解新設(shè)備是否能滿足其加工要求。改造則不然，可以精確地計(jì)算出機(jī)床的加工能力；另外，由于多年使用，操作者對(duì)機(jī)床的特性早已了解，在操作使用和維修方面培訓(xùn)時(shí)間短，見效快。改造的機(jī)床一安裝好，就可以實(shí)現(xiàn)全負(fù)荷運(yùn)轉(zhuǎn)。4.3.4 可充分利用現(xiàn)有的條件可以充分利用現(xiàn)有地基，不必像購入新設(shè)備時(shí)那樣需重新構(gòu)筑地基。4.3.5 可以采用最新的控制技術(shù)可根據(jù)技術(shù)革新的發(fā)展速度，及時(shí)地提高生產(chǎn)設(shè)備的自動(dòng)化水平和效率，提高設(shè)備質(zhì)量和檔次，將舊機(jī)床改成當(dāng)今水平的機(jī)床。5 數(shù)控系統(tǒng)的選擇數(shù)控系統(tǒng)主要有三種類型，改造時(shí)，應(yīng)根據(jù)具體情況進(jìn)行選擇。5.1 步進(jìn)電機(jī)拖動(dòng)的開環(huán)系統(tǒng)該系統(tǒng)的伺服驅(qū)動(dòng)裝置主要是步進(jìn)電機(jī)、功率步進(jìn)電機(jī)、電液脈沖馬達(dá)等。由數(shù)控系統(tǒng)送出的進(jìn)給指令脈沖，經(jīng)驅(qū)動(dòng)電路控制和功率放大后，使步進(jìn)電機(jī)轉(zhuǎn)動(dòng)，通過齒輪副與滾珠絲杠副驅(qū)動(dòng)執(zhí)行部件。只要控制指令脈沖的數(shù)量、頻率以及通電順序，便可控制執(zhí)行部件運(yùn)動(dòng)的位移量、速度和運(yùn)動(dòng)方向。這種系統(tǒng)不需要將所測得的實(shí)際位置和速度反饋到輸入端，故稱之為開環(huán)系統(tǒng)，該系統(tǒng)的位移精度主要決定于步進(jìn)電機(jī)的角位移精度，齒輪絲杠等傳動(dòng)元件的節(jié)距精度，所以系統(tǒng)的位移精度較低。該系統(tǒng)結(jié)構(gòu)簡單，調(diào)試維修方便，工作可靠，成本低，易改裝成功。5.2 異步電動(dòng)機(jī)或直流電機(jī)拖動(dòng)，光柵測量反饋的閉環(huán)數(shù)控系統(tǒng)該系統(tǒng)與開環(huán)系統(tǒng)的區(qū)別是：由光柵、感應(yīng)同步器等位置檢測裝置測得的實(shí)際位置反饋信號(hào)，隨時(shí)與給定值進(jìn)行比較，將兩者的差值放大和變換，驅(qū)動(dòng)執(zhí)行機(jī)構(gòu)，以給定的速度向著消除偏差的方向運(yùn)動(dòng)，直到給定位置與反饋的實(shí)際位置的差值等于零為止。閉環(huán)進(jìn)給系統(tǒng)在結(jié)構(gòu)上比開環(huán)進(jìn)給系統(tǒng)復(fù)雜，成本也高，對(duì)環(huán)境室溫要求嚴(yán)。設(shè)計(jì)和調(diào)試都比開環(huán)系統(tǒng)難。但是可以獲得比開環(huán)進(jìn)給系統(tǒng)更高的精度，更快的速度，驅(qū)動(dòng)功率更大的特性指標(biāo)。可根據(jù)產(chǎn)品技術(shù)要求，決定是否采用這種系統(tǒng)。5.3 交/直流伺服電機(jī)拖動(dòng)，編碼器反饋的半閉環(huán)數(shù)控系統(tǒng)半閉環(huán)系統(tǒng)檢測元件安裝在中間傳動(dòng)件上，間接測量執(zhí)行部件的位置。它只能補(bǔ)償系統(tǒng)環(huán)路內(nèi)部部分元件的誤差，因此，它的精度比閉環(huán)系統(tǒng)的精度低，但是它的結(jié)構(gòu)與調(diào)試都較閉環(huán)系統(tǒng)簡單。在將角位移檢測元件與速度檢測元件和伺服電機(jī)作成一個(gè)整體時(shí)則無需考慮位置檢測裝置的安裝問題。當(dāng)前生產(chǎn)數(shù)控系統(tǒng)的公司廠家比較多，國外著名公司的如德國 SIEMENS 公司、日本 FANUC 公司；國內(nèi)公司如中國珠峰公司、北京航天機(jī)床數(shù)控系統(tǒng)集團(tuán)公司、華中數(shù)控公司和沈陽高檔數(shù)控國家工程研究中心。選擇數(shù)控系統(tǒng)時(shí)主要是根據(jù)數(shù)控改造后機(jī)床要達(dá)到的各種精度、驅(qū)動(dòng)電機(jī)的功率和用戶的要求。6 數(shù)控改造中主要機(jī)械部件改裝探討一臺(tái)新的數(shù)控機(jī)床，在設(shè)計(jì)上要達(dá)到：有高的靜動(dòng)態(tài)剛度；運(yùn)動(dòng)副之間的摩擦系數(shù)小，傳動(dòng)無間隙；功率大；便于操作和維修。機(jī)床數(shù)控改造時(shí)應(yīng)盡量達(dá)到上述要求。不能認(rèn)為將數(shù)控裝置與普通機(jī)床連接在一起就達(dá)到了數(shù)控機(jī)床的要求，還應(yīng)對(duì)主要部件進(jìn)行相應(yīng)的改造使其達(dá)到一定的設(shè)計(jì)要求，才能獲得預(yù)期的改造目的。6.1 滑動(dòng)導(dǎo)軌副對(duì)數(shù)控車床來說，導(dǎo)軌除應(yīng)具有普通車床導(dǎo)向精度和工藝性外，還要有良好的耐摩擦、磨損特性，并減少因摩擦阻力而致死區(qū)。同時(shí)要有足夠的剛度，以減少導(dǎo)軌變形對(duì)加工精度的影響，要有合理的導(dǎo)軌防護(hù)和潤滑。6.2 齒輪副一般機(jī)床的齒輪主要集中在主軸箱和變速箱中。為了保證傳動(dòng)精度，數(shù)控機(jī)床上使用的齒輪精度等級(jí)都比普通機(jī)床高。在結(jié)構(gòu)上要能達(dá)到無間隙傳動(dòng)，因而改造時(shí)，機(jī)床主要齒輪必須滿足數(shù)控機(jī)床的要求，以保證機(jī)床加工精度。6.3 滑動(dòng)絲杠與滾珠絲杠絲杠傳動(dòng)直接關(guān)系到傳動(dòng)鏈精度。絲杠的選用主要取決于加工件的精度要求和拖動(dòng)扭矩要求。被加工件精度要求不高時(shí)可采用滑動(dòng)絲杠，但應(yīng)檢查原絲杠磨損情況，如螺距誤差及螺距累計(jì)誤差以及相配螺母間隙。一般情況滑動(dòng)絲杠應(yīng)不低于 6 級(jí)，螺母間隙過大則更換螺母。采用滑動(dòng)絲杠相對(duì)滾珠絲杠價(jià)格較低，但難以滿足精度較高的零件加工。滾珠絲杠摩擦損失小，效率高，其傳動(dòng)效率可在 90%以上；精度高，壽命長；啟動(dòng)力矩和運(yùn)動(dòng)時(shí)力矩相接近，可以降低電機(jī)啟動(dòng)力矩。因此可滿足較高精度零件加工要求。6.4 安全防護(hù)效率必須以安全為前提。在機(jī)床改造中要根據(jù)實(shí)際情況采取相應(yīng)的措施，切不可忽視。滾珠絲杠副是精密元件，工作時(shí)要嚴(yán)防灰塵特別是切屑及硬砂粒進(jìn)入滾道。在縱向絲杠上也可加整體鐵板防護(hù)罩。大拖板與滑動(dòng)導(dǎo)軌接觸的兩端面要密封好，絕對(duì)防止硬質(zhì)顆粒狀的異物進(jìn)入滑動(dòng)面損傷導(dǎo)軌。7 機(jī)床數(shù)控改造主要步驟7.1 改造方案的確定改造的可行性分析通過以后，就可以針對(duì)某臺(tái)或某幾臺(tái)機(jī)床的現(xiàn)況確定改造方案，一般包括：7.1.1機(jī)械修理與電氣改造相結(jié)合一般來說，需進(jìn)行電氣改造的機(jī)床，都需進(jìn)行機(jī)械修理。要確定修理的要求、范圍、內(nèi)容；也要確定因電氣改造而需進(jìn)行機(jī)械結(jié)構(gòu)改造的要求、內(nèi)容；還要確定電氣改造與機(jī)械修理、改造之間的交錯(cuò)時(shí)間要求。機(jī)械性能的完好是電氣改造成功的基礎(chǔ)。7.1.2先易后難、先局部后全局原系統(tǒng)的拆除必須對(duì)照原圖紙，仔細(xì)進(jìn)行，及時(shí)在圖紙上作出標(biāo)記，防止遺漏或過拆(局部改造情況下)。在拆的過程中也會(huì)發(fā)現(xiàn)一些新系統(tǒng)設(shè)計(jì)中的欠缺之處，應(yīng)及時(shí)補(bǔ)充與修正，拆下的系統(tǒng)及零件應(yīng)分門別類，妥善保管，以備萬一改造不成功或局部失敗時(shí)恢復(fù)使用。還有一定使用價(jià)值的，可作其他機(jī)床備件用。切忌大手大腳，亂扔亂放。7.2 合理安排新系統(tǒng)位置及布線根據(jù)新系統(tǒng)設(shè)計(jì)圖紙，合理進(jìn)行新系統(tǒng)配置，包括箱體固定、面板安放、線路走向和固定、調(diào)整元器件位置、密封及必要裝飾等。連線工作必須分工明確，有人復(fù)查檢驗(yàn)，以確保連線工藝規(guī)范、線徑合適、正確無誤、可靠美觀。7.3 調(diào)試調(diào)試必須按事先確定的步驟和要求進(jìn)行。調(diào)試人員應(yīng)頭腦冷靜，隨時(shí)記錄，以便發(fā)現(xiàn)和解決問題。調(diào)試中首先試安全保護(hù)系統(tǒng)靈敏度，防止人身、設(shè)備事故發(fā)生。調(diào)試現(xiàn)場必須清理干凈，無多余物品；各運(yùn)動(dòng)坐標(biāo)拖板處于全行程中心位置；能空載試驗(yàn)的，先空載后加載；能模擬試驗(yàn)的，先模擬后實(shí)動(dòng)；能手動(dòng)的，先手動(dòng)后自動(dòng)。7.4 驗(yàn)收及后期工作驗(yàn)收工作應(yīng)聘請(qǐng)有關(guān)的人員共同參加，并按已制定的驗(yàn)收標(biāo)準(zhǔn)進(jìn)行。改造的后期工作也很重要，它有利于項(xiàng)目技術(shù)水平的提高和使設(shè)備盡早投產(chǎn)。驗(yàn)收及后期工作包括：7.4.1機(jī)床機(jī)械性能驗(yàn)收經(jīng)過機(jī)械修理和改造以及全面保養(yǎng)，機(jī)床的各項(xiàng)機(jī)械性能應(yīng)達(dá)到要求，幾何精度應(yīng)在規(guī)定的范圍內(nèi)。7.4.2電氣控制功能和控制精度驗(yàn)收電氣控制的各項(xiàng)功能必須達(dá)到動(dòng)作正常，靈敏可靠。控制精度應(yīng)用系統(tǒng)本身的功能(如步進(jìn)尺寸等)與標(biāo)準(zhǔn)計(jì)量器具(如激光干涉儀、坐標(biāo)測量儀等)對(duì)照檢查，達(dá)到精度范圍之內(nèi)。同時(shí)還應(yīng)與改造前機(jī)床的各項(xiàng)功能和精度作出對(duì)比，獲得量化的指標(biāo)差。7.4.3試件切削驗(yàn)收可以參照國內(nèi)外有關(guān)數(shù)控機(jī)床切削試件標(biāo)準(zhǔn)，在有資格的操作工、編程人員配合下進(jìn)行試切削。試件切削可驗(yàn)收機(jī)床剛度、切削力、噪聲、運(yùn)動(dòng)軌跡、關(guān)聯(lián)動(dòng)作等，一般不宜采用產(chǎn)品零件作試件使用。7.4.4圖紙、資料驗(yàn)收機(jī)床改造完后，應(yīng)及時(shí)將圖紙(包括原理圖、配置圖、接線圖、梯形圖等)、資料(包括各類說明書)、改造檔案(包括改造前、后的各種記錄)匯總、整理、移交入檔。保持資料的完整、有效、連續(xù)，這對(duì)該設(shè)備的今后穩(wěn)定運(yùn)行是十分重要的。7.4.5總結(jié)、提高每次改造結(jié)束后應(yīng)及時(shí)總結(jié)，既有利于提高技術(shù)人員的業(yè)務(wù)水平，也有利于整個(gè)企業(yè)的技術(shù)進(jìn)步。編號(hào)： 畢業(yè)設(shè)計(jì)(論文)外文翻譯（原文）學(xué) 院：專 業(yè)：學(xué)生姓名：學(xué) 號(hào)：指導(dǎo)教師單位：姓 名：職 稱：年 3 月 09 日0Solid Modeling and Finite Element Analysis of an Overhead Crane BridgeC. Alkin, C. E. Imrak, H. KocabasAbstractThe design of an overhead crane bridge with a double box girder has been investigated and a case study of a crane with 35 ton capacity and 13 m span length has been conducted. In the initial phase of the case study, conventional design calculations proposed by F. E.M Rules and DIN standards were performed to verify the stress and deflection levels. The crane design was modeled using both solids and surfaces. Finite element meshes with 4-node tetrahedral and 4-node quadrilateral shell elements were generated from the solid and shell models, respectively. After a comparison of the finite element analyses, the conventional calculations and performance of the existing crane, the analysis with quadratic shell elements was found to give the most realistic results. As a result of this study, a design optimization method for an overhead crane is proposed.Keywords: overhead crane, finite element method, solid modeling, box girder.Notationb distance between two side platesbk width of lower plateFAA static load due to the trolleyFY load due to the working loadh0 height of the girder endh2 height of the side platesLA distance between trolley wheelsLK span of crane girderLP distance between two adjacent supportsq weight of one meter platformqK weight of one meter maintenance platformqP uniformly distributed mass units of bridget1 thickness of the upper and lower platest2 thickness of the side platesx2 distance between center of gravity and the midpoint of the left side platex4 distance between center of gravity and the midpoint of the raily1 distance between neutral axis and the midpoint of the raily3 distance between center of gravity and the midpoint of the top platey5 distance between neutral axis and the midpoint of the top plateWX1 moment of resistance on x-axis1WY1 moment of resistance on y-axisamplifying coefficientC?dynamic coefficient?1 IntroductionCranes are the best way of providing a heavy lifting facility covering virtually the whole area of a building. An overhead crane is the most important materials handling system for heavy goods. The primary task of the overhead crane is to handle and transfer heavy payloads from one position to another. Thus they are used in areas such as automobile plants and shipyards [1, 2]. Their design features vary widely according to their major operational specifications, such as: type of motion of the crane structure, weight and type of the load, location of the crane, geometric features and environmental conditions. Since the crane design procedures are highly standardized with these components, most effort and time are spent on interpreting and implementing the available design standards [3]. There are many published studies on structural and component stresses, safety under static loading and dynamic behavior of cranes [5–16]. Solid modeling of bridge structures and finite element analysis to find the displacements and stress values has been investigated by Demirsoy [17].Solid modeling techniques applied for road bridge structures, and an analysis of these structures using the finite element method are provided in [18]. In this study, stress and displacements were found using FEM90 software. Solid modeling of a crane bridge, the loading at different points on the bridge and then application of the finite element method have been studied by Celiktas [19]. She presented the results of finite element methods for an overhead crane.DIN-Taschenbuch and F. E. M. (Federation Européenne de la Manutention) Rules offer design methods and empirical approaches and equations that are based on previous design experience and widely accepted design procedures. DIN--Taschenbuch 44 and 185 are a collection of standards related to crane design. DIN norms generally state standard values of design parameters. F. E. M Rules are mainly an accepted collection of rules to guide crane designers. It includes criteria for deciding on the external loads to select crane components [3, 20].In this study, the calculations apply the F. E. M. rules and DIN standards, which are used for box girder crane bridges. The calculation of the box girder uses the CESAN Inc. standard bridge tables. Then a solid model of the crane bridge is generated with the same dimensions as in the calculation results. Then static analysis is performed, using the Finite Element Method. Before starting the solution, the 2boundary conditions are applied as in practice.2 Overhead cranes with a double box girderOverhead travelling cranes with a double box girder not only hoist loads but also carry them horizontally. A double beam overhead crane is built of a trolley travelling on bridges, and bridges travelling on rails. The trolley hoists or lowers the loads and carries them on the bridge structure. The bridges carry the loads on a rail. As a result, three perpendicular movements are performed. The system is depicted in Fig. 1, where the payload of the mass is attached to the bridge with wire ropes [21, 22]. The double box girders are subjected to vertical and horizontal loads by the weight of the crane, the working (hook) load and the dynamic loads. With a double box girder construction, the trolley runs above or between the girders. The acceptable construction requirements and values for a box girder bridge structure are shown in Fig.2.Fig. 1: Overall view of an overhead craneFig. 2: Construction requirements for a box girder bridge33 Application of FEM to an overhead craneAmong numerical techniques, the finite element method is widely used due to the availability of many user-friendly commercial softwares. The finite element method can analyse any geometry, and solves both stresses and displacements [23]. FEM approximates the solution of the entire domain under study as an assemblage of discrete finite elements interconnected at nodal points on the element boundaries. The approximate solution is formulated over each element matrix and thereafter assembled to obtain the stiffness matrix, and displacement and force vectors of the entire domain. In this study finite element modeling is carried out by means of the Cosmos Works and MSC commercial package. Patran and 4-node tetrahedral elements and 4-node quadrilateral shell elements have been used for modeling the overhead crane bridge.The four-node tetrahedral element is the simplest three--dimensional element used in the analysis of solid mechanics problems such as bracket stress analysis. This element has four nodes, with each node having three translational and three rotational degrees of freedom on the x, y, and z-axes. A shell element may be defined, which allows in the plane or curved surface of the element and posses both length. Itwidth and may only be used in 3-D simulations. The four--node shell element is obtained by assembling the bending element to the appropriate degrees of freedom. This is sufficient as long as the shell element deflection is within the predefined ratio 4of shell thickness, otherwise the system works as a large deflection.A typical four-node tetrahedral element and four-node quadratic shell element, and their coordinate systems are illustrated in Fig. 3 [24]. The four-node tetrahedral element chosen has six degrees of freedom at each node: translation in the nodal x, y, and z directions and rotations about the nodal x, y, and z directions. For the four-node quadratic shell element used to model the overhead crane girder, r and s denote the natural coordinates and δ is the thickness of the element.This system does not have any horizontal force. The axial displacements and rotations of the first and last faces are equal to zero. In addition, the transverse displacement is zero at the first and last face nodes.The external forces acting on the system are the mass of the main girder of the crane (distributed load) and the forces acting on the wheels of the trolley along the crane (active load). The forces acting on the trolley wheels are caused by the mass of the trolley, an the lifting load which will be moved on the crane.4-node tetrahedral element54-node quadratic shell elementFig. 3: Elements used to model an overhead crane girder4 Solid and finite element modeling of an overhead crane bridgeThe finite element method is a numerical procedure that can be applied to obtain solutions to a variety of problems in engineering. Steady, transient, linear or nonlinear problems in stress analysis, heat transfer, fluid flow and electrome chanism problems may be analysed with finite element methods. The basic steps in the finite element method are defined as follows: preprocessing phase, solution phase, and post processing phase. Real crane data was gathered from CESAN Inc., a Turkish company involved in mass production of overhead cranes. First, the crane bridge is modeled as a surface. Bridge geometry is suitable for this, and long and thin parts should also be modeled as a surface. Later, a mesh is created. In this study, a quadratic element type is used. Solid modeling is generated for the calculated crane bridge and the solid model is shown in Fig. 4 [20].Solid model of a crane bridge Wireframe view of a crane bridge6Fig. 4: Models of an overhead crane bridge5 Numerical example of an overhead craneA 35-ton-capacity overhead crane of overall length 13 m and total weight 22.5 tons was selected as a study object. The configuration of the overhead crane is shown in Fig. 1.The overhead crane consists of two girders, two saddles to connect them, and a trolley moving in the longitudinal direction of the overhead crane and wheels. The driving unit is installed in one of the two girders. The overhead crane is supported by two rails and the runway girders installed in building.In order to calculate the stress in the structure, the rules of F. E. M 1.001 are applied. The design values used in the bridge analysis from the F. E.M and DIN standards are given in Table 1.Table 1: Bridge property valuesFirst the maximum and minimum stresses and then the shear stress are calculated using the F. E. M. rules. Using the finite element method for the considered girder, we obtain the stress valnes. We obtain the static loads due to the dead weight, the loads due to the working load multiplied by the dynamic coefficient, and the two most Handling Capacity : =35 tonTrolley Weight : =3 tonBridge Length : =13 mDistance between wheels of trolley: =2mTrolley Velocity : =20 m/min.Crane Velocity : =15 m/min.Hoisting Velocit : =2.7 m/minTotal duration of use : U4Load spectrum class : Q3Appliance group : A5Loading type : H (main load)Dynamic coefficient :ψ=1.15Amplifying coefficient := 1.117unfavourable horizontal effects, excluding the buffer forces.The maximum stress consists of the stress on the bridge dead weights, the stress on the trolley dead weight, the stress from the hoisting load, stress from the inertia forces and the stress of the trolley contraction. The minimum stress includes the stress on the bridge dead weights and the stress on the trolley dead weight. The maximum and minimum stresses for the given values according to the F. E.M. rules [20] are written in standard form asand,,The value of the dynamic coefficient ψ is applied to the loading arising from the working load. The value of the amplifying coefficient depends the group classification of the application, and the weight of one meter maintenance platform is zero in this work. [25].It is assumed that the total load (372780 N) is effected on the midpoint of the rail and each girder shares this total load equally. This load is applied via the contact points of the two trolley wheels in this system. Therefore the value of the acting force on each point is 93195 N. Applying the total load in the system, the value of the maximum stress according to Eq. (1) is 143.90 N/mm2 to two decimal places, and the value of the minimum stress according to Eq. (2) is 47.33 N/mm2 to two decimal places.According to Fig. 5, the permissible stress in shear consists of the shear stresses of the wheel forces, and is defined as [20]8The value of the maximum shear stress is 24.82 N/mm2 to two decimal places from Eq. (5). Substituting Eq. (1)–(3) the equivalent stress is given by. The value of the equivalent stress is 150.18 N/mm2 to two decimal places.Fig. 5: Inertia and moment of resistance in a box girder6 Results from a girder model with a four-node tetrahedral elementTo model the overhead crane girder with a four-node tethrahedral element, Cosmosworks software was used for finite element analysis using the girder solid model generated by means of SolidWorks 2003. Young’s Modulus (E) is 2.1×105 N/mm2 and the Poisson Ratio () is 0.3 for finite element analysis. The value of the maximum stress of the side plate is 12.07 N/mm2 to two decimal places and the value of the maximum stress of the bottom plate is 15.08N/mm2 to two decimal places from Fig. 6 [20].The displacement of the modelled overhead crane girder was obtained from CosmosWorks, and is illustrated in Fig. 7. The value of maximum displacement of the girder is about 2.2 mm.9Fig. 6: Stress values of an overhead crane girder with a four-node tetrahedral elementFig. 7: Displacements of an overhead crane girder with a four-node tetrahedral element7 Results from a girder model with a four-node quadratic shell elementTo model the overhead crane girder with a four-node quadratic shell element, MSC Patran software was used for the finite element analysis. Young’s Modulus (E) is 2.1×10 N/mm2 and the Poisson Ratio (_St) is 0.3 for finite element analysis. The value of the maximum stress of the side plate is 35.40 N/mm2 to two decimal places, 10and the value of the maximum stress of the bottom plate is 49.30 N/mm2 to two decimal places, from Fig. 8 [20].The displacement of the modelled overhead crane girder was obtained from MSC Patran, and is illustrated in Fig. 9.The value of maximum displacement of the girder is about 3.89 mm. The value of the maximum stress according to Eq. (1) is calculated as 143.90 N/mm2 to two decimal places. The safety factor should be considered between 2 and 3 for overhead crane girder design. The maximum stress value of the side plate is between 24.14 and 36.21 N/mm2 to two decimal places, and the maximum stress value of the bottom plate is between 30.16 and 45.24 N/mm2 to two decimal places for a four-node tetrahedral element, taking into account the safety factor.The maximum stress value of the side plate is between 70.8 and 106.2 N/mm2 to two decimal places and the maximum stress value of the bottom plate is between 98.6 and 147.9 N/mm2 to two decimal places for a four-node quadratic shell element, taking into account the safety factor. The permissible displacement of the girder is 13 mm according to F. E.M. rules. The maximum displacement obtained from the finite element model with a four-node tetrahedral element is between 4.40 and 6.60 mm, taking into account the safety factor. The maximum displacement obtained from the finite element model with a four-node quadratic shell element is between 7.78 and 11.67 mm, taking into account the safety factor.11Fig. 8: Stress values of an overhead crane girder with a quadratic shell elementFig. 9: Displacements of an overhead crane girder with a four-node quadratic shell element8 ConclusionIn this study, unlike the other studies carried out previously, shell elements in 12finite element modeling of an overhead box girder have been examined. In order to show the use of shell elements, one illustrative overhead crane bridge example is given. The maximum stress value is 143.90 N/mm2 and 45.24 N/mm2 for a four-node tetrahedral element and 147.9 N/mm2 for a four-node quadratic shell element using both calculations according to the F. E. M. Rules and finite element analysis. The value of the equivalent stress is 150.18 N/mm2 to two decimal places. Taking into account the safety factor, the stress value varies between 97–145.5N/mm2, which is obtained from MSC Patran.The ratio of length to thickness of the element used in modelling the overhead crane box girder is higher than 20. Therefore, in order to show the accuracy of the analysis of the overhead crane bridges, a four-node quadratic shell element is used instead of the four-node tetrahedral element for finite element analysis.AcknowledgmentIt is pleasure to acknowledge much stimulating correspondence with Dr. Haydar Livatyali and gratefully to acknowledge the support of CESAN Inc., which provided the design data.Machine tool numerical control reforms1 CNC systems and the development trend of history1946 birth of the world's first electronic computer, which shows that human beings created to enhance and replace some of the mental work tools. It and human agriculture, industrial society in the creation of those who merely increase compared to manual tools, from a qualitative leap for mankind's entry into the information society laid the foundation. Six years later, in 1952, computer technology applied to the machine in the United States was born first CNC machine tools. Since then, the traditional machine produced a qualitative change. Nearly half a century since the CNC system has experienced two phases and six generations of development.1.1 Numerical Control (NC) phase (1952 to 1970)13Early computer's computational speed low and the prevailing scientific computing and data processing is not affected, but can not meet the requirements of real-time control machine. People have to use digital logic circuit “tied“ into a single machine as a dedicated computer numerical control system, known as the hardware connection NC (HARD-WIRED NC), called the Numerical Control (NC). With the development of components of this phase after three generations, that is, in 1952 the first generation - tube; 1959 of the second generation - transistor; 1965 of the third generation - small-scale integrated circuits.1.2 Computer Numerical Control (CNC) phase (1970 to present)To 1970, GM has been a small computer and mass-produced. So it transplant system as the core component of NC, have entered a Computer Numerical Control (CNC) stage(in front of the computer should be “universal“ word omitted). To 1971, the United States INTEL company in the world will be the first time the two most core computer components - computing and controller, a large-scale integrated circuit technology integration in a chip, called the microprocessor (MICROPROCESSOR) , also known as the central processing unit (CPU).1974 microprocessor to be used in CNC system. This is because the function of the computer is too small to control a machine tool capacity affluent (the time has been used to control more than one machine, called Group Control), as a reasonable economic use of the microprocessor. Minicomputer reliability and then not ideal. Early microprocessor speed and functionality while still not high enough, but can be adopted to solve the multi-processor architecture. As microprocessor core is a general computer components, it is still known as the CNC.By 1990, PC machines (personal computers, domestic habits that computer) performance has been developed to a high stage, as a CNC system to meet the requirements of the core components. NC system based on PC has now entered the stage.In short, CNC has also experienced a stage three generations. That is, in 1970's fourth generation - small computer; 1974 of the fifth generation - microprocessors and the sixth-generation 1990 - Based on the PC (called PC-BASED abroad).Also pointed out that, although the foreign computer has been renamed NC (CNC), but China still customary said Numerical Control (NC). Therefore, we stress the day-to-day “NC“, in essence, is that “computer numerically controlled.“141.3 the trend of future development of NC1.3.1continue to open, the sixth generation of