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譯文標(biāo)題
基于工程數(shù)據(jù)庫的起重機(jī)結(jié)構(gòu)計算機(jī)輔助設(shè)計
原文標(biāo)題
CAD/CAM OF CRANE’S STRUCTURE BASED ON ENGINEERING DATABASE
作 者
Chonghua Wang
譯 名
王重華
國 籍
中國
原文出處
Department of Mechanical Engineering Shanghai Maritime University P.R.China e-mail spmtc@shmtu.edu.cn
譯文：
基于工程數(shù)據(jù)庫的起重機(jī)結(jié)構(gòu)計算機(jī)輔助設(shè)計
摘要根據(jù)大型復(fù)雜結(jié)構(gòu)機(jī)械CAD/CAM專業(yè)，根據(jù)起重機(jī)的結(jié)構(gòu)工程數(shù)據(jù)庫的CAD / CAM系統(tǒng)是本文提出的?；谧皂斚蛳碌膶哟谓Y(jié)構(gòu)，特征技術(shù)，裝配約束關(guān)系，自下而上的裝配工藝和向下到頂部尺寸約束關(guān)系，建立了一個三維參數(shù)化模型族的計算機(jī)輔助設(shè)計平臺，允許生成可行的配置的起重機(jī)結(jié)構(gòu)。一個總結(jié)的GUI和ANSYS的APDL圖案的背景知識，起重機(jī)的有限元模型是基于組合模式的建立。實(shí)現(xiàn)了有限元模型的同步更新和分析。在系統(tǒng)中構(gòu)建了2種工程數(shù)據(jù)庫。一個是參數(shù)化的數(shù)據(jù)庫，包含了各種參數(shù)化的零件和部件，常用于起重機(jī)結(jié)構(gòu)。另一種是針對每一個單獨(dú)的起重機(jī)而設(shè)計的，其中包括用于起重機(jī)結(jié)構(gòu)的所有部件和部件，其中參數(shù)化的變量被確定的值所代替。以后可以用來創(chuàng)建BOM，建立有限元模型，安排零件在數(shù)控切割鋼板，焊接和制造工藝裝置設(shè)計。微軟SQL服務(wù)器選擇構(gòu)建數(shù)據(jù)庫和CAD／CAM集成是使用MS VC++ 6和Pro/TOOLKIT實(shí)現(xiàn)。
關(guān)鍵詞計算機(jī)輔助設(shè)計/凸輪，結(jié)構(gòu)，起重機(jī)，工程數(shù)據(jù)庫，三維設(shè)計
1。在過去的幾十年里，國際貿(mào)易迅速增長，這依賴于世界物流的運(yùn)輸鏈。深水港的能力，迅速處理和分發(fā)大量的集裝箱和貨物，這是在
在物流鏈中不斷發(fā)揮關(guān)鍵作用?，F(xiàn)在世界上幾乎所有的港口都在忙著擴(kuò)張。港口起重機(jī)在最近幾年迅速增長。港口起重機(jī)是非常大的，復(fù)雜的機(jī)器，越來越大，更自動化，更高的速度，以滿足巨大的船舶和大量的負(fù)載和卸載。與一般的機(jī)器相比，它具有一個獨(dú)特的組成部分，它是一個巨大且復(fù)雜的結(jié)構(gòu)。起重機(jī)結(jié)構(gòu)的計算機(jī)輔助設(shè)計/凸輪機(jī)構(gòu)的特點(diǎn)是：起重機(jī)的結(jié)構(gòu)型式和設(shè)計參數(shù)，滿足各種不同的自然、環(huán)境和運(yùn)行條件的設(shè)計參數(shù)。結(jié)構(gòu)由幾個部件組成。每一個部件都是由焊接而成的。雖然很多零件都是矩形板，但它們的厚度可以隨構(gòu)件的變化而不斷變化，以減輕重量，同時保持足夠的強(qiáng)度。此外，有大量的結(jié)構(gòu)細(xì)節(jié)，讓組件支持外部負(fù)載。因此，該組件是非常復(fù)雜的。C）的結(jié)構(gòu)設(shè)計應(yīng)符合強(qiáng)度、穩(wěn)定性等要求，補(bǔ)償?shù)臉?biāo)準(zhǔn)和規(guī)范，累積損傷和振動頻率等。因此有必要對結(jié)構(gòu)進(jìn)行有限元分析。由于結(jié)構(gòu)非常大，復(fù)雜，任何有限元軟件包的商業(yè)計算機(jī)輔助設(shè)計軟件是不夠的，以處理復(fù)雜結(jié)構(gòu)的起重機(jī)。起重機(jī)結(jié)構(gòu)凸輪的技術(shù)比較簡單。特別是數(shù)控切割和自動焊接在大多數(shù)工廠都有廣泛的應(yīng)用。本文提出了起重機(jī)結(jié)構(gòu)的計算機(jī)輔助設(shè)計/計算機(jī)輔助設(shè)計。它主要是基于程序的計算機(jī)與參數(shù)化三維建模技術(shù)、有限元分析、工程數(shù)據(jù)庫技術(shù)、Pro/E、ANSYS、MS Visual C++和微軟SQL Server。該系統(tǒng)包括建立起重機(jī)械三維參數(shù)化模型族的計算機(jī)輔助設(shè)計平臺，建立有限元模型，二次開發(fā)的三維參數(shù)化模型，同步更新和有限元分析，參數(shù)化和若干模型的構(gòu)造和收集信息，組件和起重機(jī)的應(yīng)用和供應(yīng)平臺。
2。為了支持起重機(jī)設(shè)計的計算機(jī)輔助設(shè)計平臺，設(shè)計了起重機(jī)的三維參數(shù)化模型，為每個家庭成員提供了一種可行的起重機(jī)、部件和部件的配置，然后將它們縮放到期望的尺寸。港口集裝箱起重機(jī)計算機(jī)輔助設(shè)計模型平臺的框架，為港口集裝箱起重機(jī)提供支持功能：
2.1。分解成零部件和零部件的基礎(chǔ)上的自頂向下的層次結(jié)構(gòu)的產(chǎn)品結(jié)構(gòu)，能夠方便的設(shè)計任務(wù)的開發(fā)團(tuán)隊的成員，一個起重機(jī)的設(shè)計必須以某種方式結(jié)構(gòu)化。著名的層次結(jié)構(gòu)的產(chǎn)品結(jié)構(gòu)是用于此。起重機(jī)由若干部件組成。每個組件可以包含若干子或一部分。第一種類型的組件被稱為復(fù)合組件（在下面的文本，我們只稱之為組件），第二類是一個單一的組件（我們稱之為下面的一部分）。該產(chǎn)品結(jié)構(gòu)以這種方式持續(xù)下去，直到所有的組件在層次結(jié)構(gòu)中的最低水平。因此，產(chǎn)品是結(jié)構(gòu)化的自上而下的方式，創(chuàng)造盡可能多的層次，如所需的設(shè)計師。圖1顯示了一個簡化的集裝箱起重機(jī)的層次結(jié)構(gòu)。
2.2。構(gòu)建了基于特征技術(shù)特征技術(shù)的CAD軟件平臺如Pro/Engineer提供的三維零件模型、SolidWorks等包括：a）草案的特點(diǎn)，基本幾何特征繪制截面拉伸，旋轉(zhuǎn)或掃描；b）附件的功能被添加到基本特征包括孔、圓角、塌角等。根據(jù)上述特征技術(shù)，生成集裝箱起重機(jī)零件的三維模型。
2.3。指定組件的空間約束關(guān)系，以創(chuàng)建產(chǎn)品種類的組件和組件之間的空間關(guān)系，在產(chǎn)品族中的代表使用裝配約束關(guān)系。在計算機(jī)輔助設(shè)計軟件的裝配模塊中，如支持/工程、裝配等約束關(guān)系，如匹配、對準(zhǔn)、插入和切向等。在這里，根據(jù)起重機(jī)的層次結(jié)構(gòu)，零部件和組件之間的關(guān)系是建立使用裝配約束提供的專業(yè)/工程師。圖2表示門戶框架中的組件之間的裝配約束關(guān)系。
2.4。為了使零件、零部件和起重機(jī)的設(shè)計參數(shù)發(fā)生改變時，為了使零件、部件和起重機(jī)的新的三維模型發(fā)生改變，從而建立起到頂部尺寸約束關(guān)系，從而建立零件或部件的設(shè)計參數(shù)。設(shè)計參數(shù)由設(shè)計人員根據(jù)零件或部件的結(jié)構(gòu)設(shè)計。尺寸變量，這是自動生成時，三維模型的零件或組件，控制真正的幾何尺寸和拓?fù)潢P(guān)系的一部分或一個組件。因此，為了使設(shè)計參數(shù)發(fā)生變化時，零件、部件或吊車的精確的新模型得到改變，應(yīng)準(zhǔn)確構(gòu)造設(shè)計參數(shù)和尺寸變量之間的關(guān)系。商業(yè)計算機(jī)輔助設(shè)計軟件，如專業(yè)/工程師提供的功能，建立設(shè)計參數(shù)和設(shè)計參數(shù)和尺寸變量之間的關(guān)系。必須指出的是，每一部分都將被用來組成一個組件。所有的引用而不是對部分實(shí)體將失效，必須重新開業(yè)。因此，重要的是要設(shè)置所有的參數(shù)的模型的一部分。
2.5。部件或產(chǎn)品的裝配約束關(guān)系的基礎(chǔ)上，根據(jù)起重機(jī)的層次結(jié)構(gòu)模型自下而上的方式產(chǎn)生的，一個設(shè)計師能盡快的任務(wù)已經(jīng)分配給他開始建立零件三維模型。另一方面，三維建模組件設(shè)計器所獲分配只能在其子組件和零件已創(chuàng)建啟動。因此，實(shí)際的建?；顒邮亲韵露系倪^程，從層次結(jié)構(gòu)的產(chǎn)品結(jié)構(gòu)的葉子開始。根據(jù)起重機(jī)的層次結(jié)構(gòu)和組件和零件之間的裝配約束關(guān)系，生成了零件的三維模型。對零件模型的參數(shù)進(jìn)行評估，并在組裝前進(jìn)行修改一個組件。如果有必要修改部分后，它已被組裝，應(yīng)刪除部分和一個新的模型的部分進(jìn)行評估，以適當(dāng)?shù)膬r值和被組裝。所有的設(shè)計參數(shù)必須在部件或組件的模型上設(shè)置。無設(shè)計參數(shù)是在系統(tǒng)中的起重機(jī)裝配模型上設(shè)置，以避免在任何參數(shù)發(fā)生改變后，在整個起重機(jī)模型再生故障。圖3顯示了基于組件和零件之間的約束關(guān)系的繁榮的三維裝配模型。圖4和圖5基于裝配約束關(guān)系的子組件和零件之間不同的門戶框架顯示3D模型。
3。有限元分析中的有限元分析模型的生成，數(shù)學(xué)模型應(yīng)盡可能準(zhǔn)確地模擬真實(shí)物體、載荷和約束條件，得到可靠的結(jié)果。在整個起重機(jī)結(jié)構(gòu)上，應(yīng)進(jìn)行有限元分析。由于結(jié)構(gòu)非常大，復(fù)雜，任何有限元軟件包的商業(yè)計算機(jī)輔助設(shè)計軟件是不夠的，以滿足任務(wù)。ANSYS是選中是因為其強(qiáng)大的分析功能。同樣的道理，在ANSYS中不能采用板單元。Beam188單元的建立起重機(jī)有限元模型。在ANSYS中，兩種建模模式提供了建立有限元模型，即人機(jī)交互模式也叫GUI模式和命令流輸入模式也被稱為APDL模式。雙模式也有優(yōu)點(diǎn)和缺點(diǎn)，這是在參考文獻(xiàn)中描述。一個總結(jié)的GUI和ANSYS的APDL圖案的背景知識，起重機(jī)的有限元模型是基于組合模式的建立。首先，對起重機(jī)有限元模型可以通過ANSYS的GUI模式構(gòu)建。第二，CAE分析起重機(jī)進(jìn)行相應(yīng)的日志文件也產(chǎn)生。日志文件可以通過使用ANSYS APDL參數(shù)化設(shè)計語言所提供的一些變化后，已在部分修訂，組件或起重機(jī)。
該起重機(jī)包括生成模型的APDL，載荷和約束的施加，建立了有限元求解、后處理。生成的模型由參數(shù)定義、節(jié)點(diǎn)/單元/節(jié)建立有限元分析模型等新的起重機(jī)是通過運(yùn)行APDL文件構(gòu)造。實(shí)現(xiàn)了有限元模型的同步更新和分析。參見圖6和7的有限元模型和應(yīng)力分析圖的起重機(jī)結(jié)構(gòu)。
4。數(shù)據(jù)庫系統(tǒng)是為了管理起重機(jī)的設(shè)計與制造的所有信息，實(shí)現(xiàn)數(shù)據(jù)共享，由計算機(jī)輔助設(shè)計/凸輪集成系統(tǒng)的各個模塊共享，使程序獨(dú)立于數(shù)據(jù)，保證數(shù)據(jù)的完整性和安全性，必須采用數(shù)據(jù)庫系統(tǒng)。在流行的數(shù)據(jù)庫管理系統(tǒng)微機(jī)如FoxPro、Visual Foxpro、SQL Server等，微軟SQL Server 2000是最后的選擇。
4.1。為了GDB和深發(fā)展加快設(shè)計，提高設(shè)計質(zhì)量，減少重復(fù)工作，兩種數(shù)據(jù)庫是系統(tǒng)設(shè)計。一個被稱為通用數(shù)據(jù)庫（GDB）。其他特殊的數(shù)據(jù)庫（SDB）個人起重機(jī)。GDB是一個參數(shù)化的數(shù)據(jù)庫，包括各種參數(shù)化零件和常用的起重機(jī)結(jié)構(gòu)組成。部件和組件被存儲在多個分支和層次，作為一個樹結(jié)構(gòu)。雖然有可能是大量的矩形板的一個組成部分，例如，在繁榮，在梁，…只有一個參數(shù)化的矩形板在每一個分支，以減少冗余。GDB可以被所有設(shè)計師的公司參觀。
當(dāng)一個設(shè)計師給設(shè)計的一個組成部分，他可以先搜索gdb的相應(yīng)部門利用現(xiàn)有的參數(shù)化零部件和組件的三維模型構(gòu)建。同時，信息的零件和部件的使用記錄在SDB。他可以修改在GDB的零部件如果他們稍有不同，從什么是需要的。他甚至可以創(chuàng)建一個新的參數(shù)化零件和組件并將它們保存到GDB的機(jī)關(guān)批準(zhǔn)。
SDB是專為每一個個體的起重機(jī)和包含所有零部件用于起重機(jī)結(jié)構(gòu)。它們也存儲在一個樹結(jié)構(gòu)中。不同于GDB，每一部分都有相應(yīng)的記錄，在深發(fā)展。參數(shù)化變量被確定值替換。隨著這些，代碼，名稱，存儲位置，位置，材料，重量，重心，制造等參數(shù)的參數(shù)。一些數(shù)據(jù)，例如重量的一部分，計算的一部分已被縮放。
SDB可以用來創(chuàng)建BOM，建立有限元模型，安排零件在數(shù)控切割鋼板，焊接和制造工藝裝置設(shè)計。
4.2。數(shù)據(jù)庫結(jié)構(gòu)與數(shù)據(jù)庫的使用，一些一般性的問題將被解決：數(shù)據(jù)完整性：在一個文件系統(tǒng)中，設(shè)計師誰保存的文件的變化，然后刪除由設(shè)計師誰保存的文件之后。但同時，采用數(shù)據(jù)庫的交易機(jī)制，在同一時間，一個計算機(jī)輔助設(shè)計模型不能同時進(jìn)行修改。直接關(guān)系：模型的數(shù)據(jù)實(shí)體的直接關(guān)系，三維模型之間的技術(shù)依賴關(guān)系可以很容易地發(fā)現(xiàn)。直接關(guān)系給設(shè)計者一個提示，在模型的改變之后，模型也必須改變。中心數(shù)據(jù)管理：數(shù)據(jù)中心庫提供備份和版本控制的幾個優(yōu)點(diǎn)。數(shù)據(jù)聚類：數(shù)據(jù)的聚類速度的數(shù)據(jù)訪問，因為每個設(shè)計師可以得到所需的信息，在他的本地PC。這是非常重要的分布式和協(xié)同設(shè)計項目。我們已經(jīng)使用了實(shí)體關(guān)系（二）模型，這是一個流行的高層次的概念數(shù)據(jù)模型，設(shè)計數(shù)據(jù)庫。這種模式及其變化經(jīng)常被用于數(shù)據(jù)庫應(yīng)用程序的概念設(shè)計，和許多數(shù)據(jù)庫設(shè)計工具采用其概念。二型模型描述數(shù)據(jù)的實(shí)體，關(guān)系和屬性。二型代表是一個實(shí)體，它是現(xiàn)實(shí)世界中的一個獨(dú)立存在的基本對象。每個實(shí)體都有屬性，即描述它的特定屬性。一個特定的實(shí)體將有一個值的每個屬性。描述每個實(shí)體的屬性值成為存儲在數(shù)據(jù)庫中的數(shù)據(jù)的一個重要部分。一個關(guān)系型R在n個實(shí)體類型E1，E2…恩定義的關(guān)聯(lián)或關(guān)系集從這些類型的實(shí)體之間的。實(shí)體類型和實(shí)體集的關(guān)系類型及其對應(yīng)關(guān)系設(shè)置統(tǒng)稱同名的R.
根據(jù)起重機(jī)的層次結(jié)構(gòu)，數(shù)據(jù)庫具有實(shí)體。每一部分，組件和起重機(jī)可以被表示為一個實(shí)體，它具有設(shè)計參數(shù)描述的屬性。在起重機(jī)產(chǎn)品零部件之間的空間關(guān)系表示為關(guān)系集R的數(shù)據(jù)庫采用微軟SQL Server和組件對象模型（COM）。
5。CAD／CAM集成的基于Visual C++和SQL Server數(shù)據(jù)庫管理系統(tǒng)作為管理工程數(shù)據(jù)庫和Pro/ENGINEER用于建立三維模型，采用Visual C++作為
編程語言構(gòu)建計算機(jī)輔助設(shè)計/凸輪的整體系統(tǒng)。第一個原因是Visual C++是一個可以訪問SQL數(shù)據(jù)庫語言。其次，當(dāng)我們設(shè)置GDB必須訪問數(shù)據(jù)庫以及訪問的三維模型，利用Pro/TOOLKIT，這是第二利用Pro/ENGINEER提供的軟件包。當(dāng)我們處理的是深發(fā)展，我們也需要訪問數(shù)據(jù)庫和參數(shù)化模型的同時，做一些修改。Visual C++是強(qiáng)大的編譯程序能訪問Pro/Engineer和SQL Server 2000的同時，實(shí)現(xiàn)它們之間的數(shù)據(jù)通信。第三、Visual C++是一種面向?qū)ο蟮木幊誊浖性S多優(yōu)點(diǎn)。
6。本文介紹了基于工程數(shù)據(jù)庫的集裝箱起重機(jī)結(jié)構(gòu)計算機(jī)輔助設(shè)計/凸輪一體化系統(tǒng)的設(shè)計。基于自上而下的層次化的產(chǎn)品結(jié)構(gòu)、特征技術(shù)、裝配約束關(guān)系，利用Pro/ENGINEER提供的自底向上的裝配工藝和尺寸關(guān)系到頂部，一個三維參數(shù)化模型的CAD平臺的建立是為了讓家庭的起重機(jī)的可行的配置生成。一個總結(jié)的GUI和ANSYS軟件APDL圖案的背景知識，基于復(fù)合模式建立了該橋的有限元模型。實(shí)現(xiàn)了有限元模型的同步更新和分析。利用微軟SQL Server 2000，兩種數(shù)據(jù)庫是系統(tǒng)與CAD/CAM集成系統(tǒng)的各個模塊進(jìn)行設(shè)計。數(shù)據(jù)共享整個系統(tǒng)。以Visual C++的幫助下，實(shí)現(xiàn)了CAD／CAM的集成開發(fā)方法。該系統(tǒng)可以大大提高港口集裝箱起重機(jī)結(jié)構(gòu)設(shè)計效率和開發(fā)凸輪機(jī)械結(jié)構(gòu)復(fù)雜的大型結(jié)構(gòu)的應(yīng)用提供一個平臺。
致謝本文受上海市重點(diǎn)學(xué)科建設(shè)項目，資助號：T0601。
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原文：
LathesCAD/CAM OF CRANE’S STRUCTURE BASED ON ENGINEERING DATABASE
ABSTRACT According to the specialties of CAD/CAM for largescale complex structures of machinery, a CAD/CAM system based on engineering database for crane’s structures is proposed in this paper. Based on the top-down hierarchical product structure, feature technology, assembly constraint relationship, bottom-up assembly process and down-to-top dimension constraint relationship, a CAD platform of 3D parametric model family is built to allow generation of feasible configurations of crane structures. With a sum up of background knowledge of GUI and APDL patterns of ANSYS, the finite element model of the crane is set up based on composite pattern. Synchronous updating and analysis of FEA model are realized. Two kinds of engineering databases are constructed in the system. One is a parameterized database and contains all kinds of parameterized parts and components common used in crane structures. Another is designed for every individual crane and contains all parts and components used in crane structure, where parameterized variables are replaced by definite values. The later can be used to create BOM, to build FEM model, to arrange parts in the steel sheet for numerical control cutting and to design technological apparatus for welding and manufacture. Microsoft SQL Server is selected to construct the databases and the CAD/CAM integration is achieved using MS VC++6.0 and Pro/TOOLKIT.
KEYWORDS CAD/CAM, Structure, Crane, Engineering database, 3D design
1. INTRODUCTION The international trades which increase rapidly in the last few decades rely on the transportation chains of world logistics. The abilities of the deepwater ports to swiftly handle and distribute the large quantity of containers and goods which are surging in
continuously play a key role in the logistics chains. Almost all ports in the world are busy expanding nowadays. The port cranes increase rapidly all over the world in the recent years. The port cranes are very large and complex machines and becoming larger, more automatic and with higher speeds to meet the huge ships and the great quantity of load and unload. Comparing with normal machines, it has a unique component that is the huge and complicated structure. The characters of CAD/CAM for crane’s structure are: a) Crane’s structure has various types and a lot of design parameters to meet the different natural, environmental and operating conditions of every harbor. b) The structure is consisted of several components. Every component is formed by welding numerous parts. Although a lot of parts are rectangle plates, their thickness may vary continually along the component to reduce the weight while keeping enough strength. In addition, there are lots of construct details to let the component support external loads. So the components are very complicated. c) The design of the structure should conform to the requirements about strength, stability, bucking, cumulative damage and vibration frequency etc. of the Standards and Specifications. So it is necessary to do finite element analysis on the structure. As the structure is very large and complex, any FEA package of commercial CAD software is insufficient to handle the complex structures of crane. d) The techniques of CAM for crane structure are comparatively simple. Especially numerical control cutting and automatic welding are widely used in most factories. An integrated CAD/CAM for the crane’s structure is proposed in this paper. It is mainly based on the technologies of parametric 3D modeling, finite element analysis, engineering database technique, Pro/ENGINEER, ANSYS, MS Visual C++ and Microsoft SQL Server. The system includes building CAD platform of 3D parametric model family for crane, setting up FEA model, the second exploiting of 3D parametric model, the synchronous updating and analysis of FEA, construction and collection information of parametric and certain models of parts, components and cranes and supply a platform to develop the application of CAM.
2. CAD PLATFORM OF 3D PARAMETRIC MODEL FAMILY FOR CRANE In order to support the designing of crane family, CAD representations for product platform is developed to allow generation of feasible configurations of cranes, components and parts for each family member and then scaling them to the desired size. The framework of CAD model platform for port container crane has to provide support functions listed as follows:
2.1. Decompose crane into components and parts based on top-down hierarchical product structure To be able to facilitate design tasks to the members of a development team, a crane to be designed has to be structured in some way. The well-known hierarchical product structure is used for this. A crane consists of a number of components. Each component can either consist of a number of subcomponents or be a part. The first type of component is called a compound component (in following text, we only call it as component), the second type a single component (we call it as part below). The product structuring continues recursively in this way, until all components at the lowest level in the hierarchy are parts. So the product is structured in a top-down way, creating as many levels as desired by the designers. Figure 1 shows a simplified hierarchical product structure of a container crane. 2.2. Construct 3D part model based on feature technology Feature technology provided by CAD software platform such as Pro/ENGINEER, Solidworks etc. includes: a)Draft features which are fundamental geometry characters produced by drawing cross sections and stretching, rotating or scanning them; b)Attachment features which are added to the fundamental characters include hole, round corner, collapse corner and so on. According to the feature technology describes above, the 3D models of the parts of the container crane are generated.
2.3. Specify spatial constraint relationships of components to create product variety The spatial relationships among the components and parts in the product family are represented using assembly constraint relationship. In the assembly module of CAD software such as Pro/ENGINEER, constraint relationships in assembling, for example, matching, aligning, inserting and tangential etc. are provided. Here, based on the hierarchical structure of crane, relationships among parts and components are built using the assembly constraints provide by Pro/ENGINEER. Figure 2 represents the assembly constraint relationships among the parts of portal frame.
2.4. Establishment of down to top size constraint relationship In order to regenerate the new 3D model of parts, components and crane when the values of design parameters are changed, a down to top size constraint relationships between size variables and design parameters in a part or component should be built. Design parameters are established by designers according to the structure of part or component. Size variables, which are generated automatically when 3D models of parts or components are built, control the real geometrical size and topological relationship of a part or a component. Therefore, in order to regenerated the accurate new model of a part, a component or crane when the values of design parameters are changed, the relationship between design parameters and size variables should be constructed accurately. Commercial CAD software such as Pro/ENGINEER has provided function to set up design parameters and build relationships between design parameters and size variables. It must be pointed out that every part would be used to compose a component. All the references which are not on the entity of the part would be invalidated then and must be setting up again. So it is important to setting all the references of parameters on the model of the part.
2.5. Generation of component or product assembly model based on constraint relationships in bottomup way Based on the hierarchical structure of the crane, a designer can start building 3D model of a part as soon as the task has been assigned to him. On the other hand, 3D modeling of a component by a designer to whom it was assigned can only start just after its subcomponents and parts have been created. So the actual modeling activity is bottom-up process, starting at the leaves of the hierarchical product structure. According to the hierarchical product structure of the crane and assembly constraint relationships among components and parts, 3D models of a component desired are generated. The parameters on the model of a part should be evaluated and can be modified before it is assembled to a component. If it is necessary to amend the part after it has been assembled, the part should be deleted and a new model of the part is evaluated to the proper values and to be assembled. All design parameters must be setting on the models for parts or components. No design parameter is setting on the assembling model of the crane in the system to avoid failure in regenerating the model of whole crane after any parameter has changed. Figure 3 shows the 3D assembly model of the boom based on constraint relationships among subcomponents and parts. Figure 4 and 5 show 3D models of different portal frames based on assembly constraint relationships among subcomponents and parts.
3. GENERATION OF FEA MODEL FOR THE CRANE In finite element analysis, the mathematical model shall simulate the real object, loads and constraints as accurately as possible to get the reliable results. The FEA should usually be carried out on the whole crane structure. As the structures are very large and complex, any FEA package of commercial CAD software is insufficient to fulfill the task. The ANSYS is selected because of its powerful structural analysis functions. As the same reason, the plate elements in ANSYS could not be adopted. The beam188 elements are used to build the FEA model of the crane. In ANSYS, two modeling patterns are provided to build the FEA model, i.e. the human-machine interactive pattern also called GUI pattern and the command stream flow input pattern also known as APDL pattern. Two patterns have also advantages and shortcomings which are described in reference literature. With a sum up of background knowledge of GUI and APDL patterns of ANSYS, the FEA model of the crane is built based on composite pattern. First, FEA model of the crane can be built through ANSYS GUI pattern. Second, CAE analyses of the crane are carried out and corresponding log file is also generated. The log file can be amended by using parametric design language APDL provide by ANSYS after some changes have been made on the parts, components or crane. The APDL of the crane including generation of model, imposing of load and constraint, finite unit solution and post treatment is built. Generation of model consists of parameter definition, node/unit/section establishment etc. A new FEA model of the crane is constructed by running the APDL file. Synchronous updating and analysis of FEA model are realized. See Figure 6 and 7 for the FEA model and stress analysis chart of a crane structure.
4. DATABASE SYSTEM In order to manage all the information about design and manufacture of crane, achieve the data to be shared by every module of CAD/CAM integration system, keep the programs independent from the data and guarantee the data integrality and security, the database system must be used. Among the popular database management systems for microcomputer such as FoxPro, Visual FoxPro, SQL Server and so on, Microsoft SQL Server 2000 is final selected.
4.1. GDB and SDB In order to speed up design, improve design quality and reduce repeat work, two kinds of databases are designed in the system. One is called general database (GDB). The others are special databases (SDB) for individual cranes. The GDB is a parameterized database and contains all kinds of parameterized parts and components common used in crane structures. The parts and components are stored in many branches and levels as a tree structure. Although there may be lots of rectangular plates in a component, for example, in the boom, in the girder,…. There is only one parameterized rectangular plate in every branch to reduce redundancy. The GDB can be visited by all designers of the company. As soon as a designer is assigned to design a component, he can first search the corresponding branch of GDB to make use of the exis