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揚州大學廣陵學院
本科生畢業(yè)設計
畢業(yè)設計題目 激光測量機縱軸傳動機構(gòu)設計
學 生 姓 名 朱明智
專 業(yè) 機械設計制造及其自動化
班 級 機械81001
指 導 教 師 張軍
完 成 日 期 2014 年 6 月 4 日
廣陵學院畢業(yè)設計(論文)開題報告
學 生 姓名: 朱明智 學號: 100007150
專 業(yè): 機械設計制造及其自動化
設計(論文)題目: 激光測量機縱軸傳動機構(gòu)設計
指導 老 師: 張 軍
2014年 4 月 8 日
畢業(yè)設計(論文)開題報告
1、結(jié)合畢業(yè)設計(論文)課題情況,根據(jù)所查閱的文獻資料,每人撰寫2000字左右的文獻綜述:
文 獻 綜 述
1.測量機的簡況與基本構(gòu)成
測量機的測量原理是將被測零件放入其容許的測量空間以獲得被測幾何型面上各測點的坐標尺寸。根據(jù)這些點的空間坐標值進行計算, 求出被測零件的幾何形狀位置尺寸及其不確定度。
世界上第一臺測量機是在1959年由英國制造的?,F(xiàn)在,國內(nèi)外的應用已相當普遍。目前, 世界上生產(chǎn)測量機的廠商已超過50家, 品種規(guī)格已達300種以上。全世界擁有2萬臺以上, 我國也擁有400臺以上。
現(xiàn)代測量機用于:
(1)對三維復雜零件的尺寸、形狀和相互位置進行高準確度測量;
(2)實物模型數(shù)字化,例如對飛機機翼的實驗模型、汽車外型實驗模型的測量;
(3)在線質(zhì)量控制。
可以看出,測量機的萬能性強,自動化程度高。它是現(xiàn)代化工業(yè)生產(chǎn)、科學研究必不可少的精密測量儀器。
測量機是以精密機械為基礎, 綜合應用光學、電子技術、計算機技術等先進技術的測量儀器。稱它為坐標測量系統(tǒng)更名符其實。它包括:1)測量機;2)數(shù)據(jù)處理及控制系統(tǒng);3)測頭和4)軟件等四部分。
2.激光測量機的工作原理
隨著我國工業(yè)的發(fā)展, 人們越來越關注產(chǎn)品質(zhì)量, 而保證產(chǎn)品質(zhì)量的關鍵環(huán)節(jié)是檢驗。為解決生產(chǎn)中箱體零件的檢測而研制的通用激光測量儀,可對零件的高度、寬度、長度、厚度、距離、位移和各種有關的行位、誤差進行高速的、非接觸式檢測。該儀器具有體積小、功能多等優(yōu)點。 既可作為獨立的光電檢測儀,也可作為激光測頭與其他系統(tǒng)相結(jié)合成為具有柔性的多功能測量機。該項目屬于國防科工委“八五”重點項目先進制造技術中關鍵技術——激光測量技術的研究。
儀器的基本工作原理是利用光學系統(tǒng)將被測頭的空間位置成像于PSD ( 光電位置傳感器) 上, 通過光、物、像之間的三角關系, 獲得像點在PSD 上的位置, 經(jīng)PSD, 將光信號轉(zhuǎn)換成電信號, 再通過信號處理實現(xiàn)空間位置測量。這種測量方法又稱光三角測量法。
3.激光測量機系統(tǒng)結(jié)構(gòu)及測量過程
激光非接觸式三坐標測量系統(tǒng)主要由:三維掃描機構(gòu)、激光非接觸測量頭及對準裝置、控制系統(tǒng)和數(shù)據(jù)處理系統(tǒng)等四部分組成。它實質(zhì)上是由一個水平X軸、一個垂直Y軸、一個回轉(zhuǎn)工作臺加上CCD激光測量頭等構(gòu)成的特別適合回轉(zhuǎn)體高速非接觸測量的三坐標機。
系統(tǒng)工作過程為:主控程序先完成系統(tǒng)的初始化,然后把被測量部件放在轉(zhuǎn)臺上,在測量過程中轉(zhuǎn)臺一直勻速旋轉(zhuǎn)。測量從最底圈開始,一圈一圈測量。當測量一圈時,主控程序啟動控制模塊控制橫梁和滑動臂沿水平及垂直方向運動,使得測量點在測量頭的測量范圍內(nèi),然后轉(zhuǎn)頭旋轉(zhuǎn),使得測量頭對準被測部件。轉(zhuǎn)頭運動完畢后,運動控制模塊通知主控程序運動結(jié)束,然后由主控程序啟動數(shù)據(jù)采集模塊。數(shù)據(jù)采集模塊在高精度定時線程的控制下進行數(shù)據(jù)采集。當測量完一圈后,數(shù)據(jù)采集模塊暫停,同時通知主控程序完成一圈數(shù)據(jù)采集。這時候主控制程序再啟動運動控制模塊 來調(diào)整測量頭的位置,準備測量下一圈。這樣一直測量到最后一圈,然后系統(tǒng)復位。數(shù)據(jù)利用串行化技術存儲,以供數(shù)據(jù)處理程序處理。
4.機械傳動機構(gòu)的種類
通常來說,用于步進、伺服電機驅(qū)動的機械傳動機構(gòu),一般有以下幾類:
機構(gòu)
特點
滾珠絲杠(直接連接)
用于距離較短的高精度定位。
電機和滾珠絲杠只用聯(lián)軸節(jié)連接,沒有間隙。
滾珠絲杠(減速)
選擇減速比,可加大向機械系統(tǒng)傳遞的轉(zhuǎn)矩。
由于產(chǎn)生齒輪側(cè)隙,需要采取補償措施。
齒條和小齒輪
用于距離較長的(臺車驅(qū)動等)定位。
小齒輪轉(zhuǎn)動一圈包含了π值,因此需要修正。
同步皮帶(傳送帶)
與鏈條比較,形態(tài)上的自由度變大。
主要用于輕載。
皮帶輪轉(zhuǎn)動一圈的移動量中包含π值,因此需要修正。
鏈條驅(qū)動
多用于輸送線上。必須考慮鏈條本身的伸長并采取相應的措施。在減速比比較大的狀態(tài)下使用,機械系統(tǒng)的移動速度小。
進料輥
將板帶上的材料夾入輥間送出。
由于未嚴密確定輥子直徑,在尺寸長的物件上將產(chǎn)生誤差,需進行π補償。
如果急劇加速,將產(chǎn)生打滑,送出量不足。
轉(zhuǎn)盤分度
轉(zhuǎn)盤的慣性矩大,需要設定足夠的減速比。
轉(zhuǎn)盤的轉(zhuǎn)速低,多使用蝸輪蝸桿。
主軸驅(qū)動
在卷繞線材時,由于慣性矩大,需要設定夠的減速比。
在等圓周速度控制中,必須把周邊機械考慮進來研究。
5.滾珠絲杠副
當今世界中,能代表機械的、有各種運動機構(gòu)的裝置,可以說無一不是具有某種形式的運動傳導機構(gòu)。滾珠絲杠副是將回轉(zhuǎn)運動轉(zhuǎn)化為直線運動,或?qū)⒅本€運動轉(zhuǎn)化為回轉(zhuǎn)運動的最合理的產(chǎn)品。
滾珠絲杠傳動系統(tǒng)是一個以滾珠作為滾動媒介的滾動螺旋傳動的體系。以傳動形式分為兩種:
(1)將回轉(zhuǎn)運動轉(zhuǎn)化成直線運動。
(2)將直線運動轉(zhuǎn)化成回轉(zhuǎn)運動。
滾珠絲杠副特性有:
(1)傳動效率高?
滾珠絲杠傳動系統(tǒng)的傳動效率高達90%~98%,為傳統(tǒng)的滑動絲杠系統(tǒng)的2~4倍,所以能以較小的扭矩得到較大的推力,亦可由直線運動轉(zhuǎn)為旋轉(zhuǎn)運動(運動可逆)。??
(2)運動平穩(wěn)?
滾珠絲杠傳動系統(tǒng)為點接觸滾動運動,工作中摩擦阻力小、靈敏度高、啟動時無顫動、低速時無爬行現(xiàn)象,因此可精密地控制微量進給。
(3)高精度?
滾珠絲杠傳動系統(tǒng)運動中溫升較小,并可預緊消除軸向間隙和對絲杠進行預拉伸以補償熱伸長,因此可以獲得較高的定位精度和重復定位精度。
(4)高耐用性?
鋼球滾動接觸處均經(jīng)硬化(HRC58~63)處理,并經(jīng)精密磨削,循環(huán)體系過程純屬滾動,相對對磨損甚微,故具有較高的使用壽命和精度保持性。
(5)同步性好?
由于運動平穩(wěn)、反應靈敏、無阻滯、無滑移,用幾套相同的滾珠絲杠傳動系統(tǒng)同時傳動幾個相同的部件或裝置,可以獲得很好的同步效果。
(6)高可靠性?
與其它傳動機械,液壓傳動相比,滾珠絲杠傳動系統(tǒng)故障率很低,維修保養(yǎng)也較簡單,只需進行一般的潤滑和防塵。在特殊場合可在無潤滑狀態(tài)下工作。
(7)無背隙與高剛性?
滾珠絲杠傳動系統(tǒng)采用歌德式溝槽形狀、使鋼珠與溝槽達到最佳接觸以便輕易運轉(zhuǎn)。若加入適當?shù)念A緊力,消除軸向間隙,可使?jié)L珠有更佳的剛性,減少滾珠和螺母、絲杠間的彈性變形,達到更高的精度。
參考文獻
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2、本課題要研究或解決的問題和擬采用的研究手段(途徑):
1.研究的問題
本課題面向三座標激光測量機的傳動機構(gòu),要求按照設計參數(shù)完成縱軸的傳動機構(gòu)設計,并對設計機構(gòu)校核。完成縱軸傳動機構(gòu)的二維裝配圖,設計完成關鍵零件的零件圖,建立零件的三維模型。
2.研究手段
數(shù)控工作臺是一個由許多環(huán)節(jié)構(gòu)成的復雜的動力學系統(tǒng),動力學建模是對動力學系統(tǒng)進行分析、仿真、修改、控制和優(yōu)化的基礎。關于建模方法,Leonard-Cristian Pop 等提出建模的整個過程包括:基于物理模型確定力學模型,基于力學模型確定數(shù)學模型;得到模型的部件參數(shù)有兩種方法:一種方法采用系統(tǒng)固有頻率方程求解,另一種方法是得到系統(tǒng)的傳遞函數(shù);通常用有限數(shù)量自由度( DOF) 機械模型對其機械結(jié)構(gòu)進行建模,模型的自由度數(shù)越少越好,盡管有限的自由度數(shù)會影響結(jié)果的精度,但是只要精度在可接受范圍內(nèi)。關于模型的尺度,U.C.Gu等研究了承受移動質(zhì)量的高速主軸的動態(tài)響應,用 Timoshenko 梁理論把滾珠絲杠作為一個高速旋轉(zhuǎn)軸來建模,把螺母作為一個移動的集中質(zhì)量來建模。R.Whalley等用混合的、分布-集總參數(shù)的方法建立機床x 軸驅(qū)動系統(tǒng)模型。關于數(shù)控工作臺模型,王軍平等運用集中參數(shù)法建立了機械系統(tǒng)進給機構(gòu)的非線性動力學模型。C Pislaru 等提出了基于傳遞線建模技術的一臺測試裝置的建模和仿真,強調(diào)了非線性( Coulomb摩擦力和粘性摩擦力、間隙) 的建模和在滾珠絲杠螺母直線運動時作用在其上的軸向力和扭轉(zhuǎn)力矩。
滾珠絲杠驅(qū)動的數(shù)控工作臺的物理模型如圖 1所示。可以看出: 它是由驅(qū)動電機、電機支承、聯(lián)軸器、前端軸承、前端軸承座、滾珠絲杠、滾珠螺母、后端軸承、后端軸承座、導軌和工作臺等組成,是一個復雜的動力學系統(tǒng)。
傳動部分主要利用步進電機2作為動力源輸出轉(zhuǎn)矩,電機輸出軸通過聯(lián)軸器 3 與滾珠絲杠 5 相聯(lián)接,最后通過滾珠螺母帶動工作臺 X 向或 Y 向運動,X 向工作臺機構(gòu),(Y 向圖中未示,結(jié)構(gòu)與此類似),如圖2所示。
換向機構(gòu)采用滾珠絲杠,固定方式為一端固定,一段有隙,其優(yōu)點在于壓桿穩(wěn)定和臨界轉(zhuǎn)校高,而且絲杠有熱膨脹的余地。支承形式采用角接觸球軸承一對,背靠背組合的形式。滾動直線導軌副是在滑塊與導軌之間放入適當?shù)匿撝椋够瑝K與導軌之間的滑動摩擦變?yōu)闈L動摩擦大大降低二者之間的摩擦阻力,有助于提高數(shù)控系統(tǒng)的相應度與靈敏度。因此在x、y向用滾動導軌副。
滾珠絲杠副的選用:
1. 滾珠絲杠副的導程 Ph的確定
2. 精度選擇
3. 滾珠絲杠副的載荷及轉(zhuǎn)速計算
4. 依據(jù)當量轉(zhuǎn)速 nm及當量載荷 Fm確定預期額定動載荷 Cam
5. 初步確定滾珠絲杠公稱直徑 D0及規(guī)格型號
6. 精度校核
7. 壓桿 (拉) 穩(wěn)定性校核
8. 極限轉(zhuǎn)速及 DN 值校核
9. 最大靜負載校核
10. 強度校核
畢業(yè)設計(論文)開題報告
指導教師意見:
1、對“文獻綜述”的評語:
2、對本課題的深度、廣度及工作量的意見和對設計(論文)結(jié)果
的預測:
指導老師:
年 月 日
所在專業(yè)審查意見:
負責人:
年 月 日
9
September 11th Testimony
MSC.Software Corp has provided simulation software tools MSC.Dytran and MSC.Marc to a US Congressional Committee to simulate and understand the collapse of the World Trade Center buildings.
On March 6, 2002, Dr. Abolhassan Astaneh-Asl, PhD., professor of Civil and Environmental engineering at the University of California, Berkeley, testified before the Committee on Science of the U.S. House of Representatives regarding his investigation of the WTC collapsed structures. His testimony included a series of simulations, developed in conjunction with MSC.Software using MSC.Dytran, of a 747 jetliner crashing into a steel structure.
"The tragic events of September 11th prompted us all to ask what we could do to help," said Frank Perna, chairman and chief executive officer of MSC.Software. "MSC.Software has a long history of working with researchers and governmental entities around the world to recreate complex engineering problems, including those dealing with forensics, in the hope of preventing tragedies like the World Trade Center collapse in the future. We are proud to have played a small part in the efforts up to this point and hope more governmental agencies will take up our offer to provide our software and services free of charge to any government entity investigating the attacks."
"Understanding how and why the World Trade Center buildings collapsed will help us prevent this type of building collapse in the future", said Dr. Astaneh-Asl, "To simulate the very complex issues and non-linearities involved in analysing the impact of an airplane and the ensuing fire you need the most powerful and advanced software, such as MSC.Software's simulation tools. The contributions of MSC.Software to our research program have been invaluable. We will continue to use these tools in our investigation to gain insight to what might have caused the collapse and to learn valuable lessons that can be applied in the future to prevent such catastrophic collapses."
The images accompanying this article show an analysis of the performance of a generic steel high-rise structure subjected to the impact of a 747 jetliner and the ensuing fire. The example demonstrates the power of advanced technology developed in aerospace and mechanical engineering that can be brought to bear on such a problem. Professor Astaneh has suggested during the investigation (which is still ongoing, with a fuller report due out in September this year) that a possible cause of the collapse was the buckling of the exterior columns of the WTC towers after being subjected to intense heat. He also investigated fracturing of the steel columns and the break up of the plane that occurred during the dynamic impact.
MSC.Dytran helps engineers predict how structures respond to real-world, high-speed events such as crashes. Typical applications include airbag deployment and occupant interaction in vehicle crashes, sheet metal forming, bird strikes on aircraft, explosive containment within aircraft structures, ship collision and grounding, projectile impact and penetration, drop tests, sheet metal forging and fluid-sloshing effects on structures. MSC.Marc is a nonlinear analysis tool for advanced engineering simulation. It can be used to simulate temperature effects such as during fires.?
Professor Astaneh's investigation, whilst focusing on the events surrounding the tragic collapse of the WTC due to terrorist activity, was put into sharper focus by more recent events in Milan, where a small aircraft crashed accidentally into the Pirelli building in the center of the city. Being able to forecast the damage that would be caused by deliberate, accidental or environmental events on high-rise buildings enables civil engineers to mitigate the potentially catastrophic results by modifying designs. Whilst not wishing to pre-empt the final results of the investigation it would appear that although considerable damage from such an action could not have been avoided, the eventual collapse of the building was entirely unforeseen.?
A comparison was also made about the efforts made, 30 or 40 years ago, by the National Science Foundation, funded by Congress, regarding the hazards of other 'extreme events' such as earthquakes and their effect on buildings and the subsequent loss of life. Research and engineering communities have been able to develop more efficient and economical technologies to mitigate seismic hazards. Professor Astaneh has been the Principal Investigator in conducting research on damage and collapse of several major buildings and bridges in the aftermath of earthquakes. The approach taken in earthquake engineering can equally be applied to investigation of damage due to terrorist attacks, as well as to minimising the consequences of such attacks. He argues that similar efforts are needed to counter the equally devastating effects of terrorism against the built environment.
Other comparisons with earthquake studies were made by committee member Dr W Gene Corley, the Senior Vice president of CTL Engineering, representing the American Society of Civil Engineers. ASCE has been involved in five recent studies, in El Salvador, India, Seattle and Peru, and, in 1995, examined the Murrah Federal Office Building collapse in Oklahoma City.?
Among the important points made, he stated that one of the main difficulties was in establishing, as accurately as possible, the physical attributes of the buildings prior to the collapse. Doing this, he said, was a monumental task. The construction of the building was documented by literally thousands of engineering drawings. In addition, there were numerous changes to them over their lives. Such data has to be used to construct detailed computer models of the structures. Besides the hard work involved in scouring libraries and other data repositories for the information, ACSE ran briefings for the investigation team using the principal designers to explain how the buildings were constructed.
A principal cause of the collapse of the Twin Towers has been attributed to Progressive Collapse. Dr Corley explained that the likelihood of such an occurrence is dependent upon two inter-related though separate behaviours - the event or load to which the subject is subjected, and the strength or redundancy of the structure. At present there is no rational technical basis to specify either the initiating event or to evaluate the effectiveness of alternative mitigating strategies, and there is a need to develop engineering-based tools to guide the profession in the future.
Dr Corley added, also, that while events like September are rare, fires in buildings are not rare. To improve the performance of structures in a fire environment will also require the development of new tools and design methods through collaboration between fire engineering and structural engineering communities for application to both new and existing buildings.
Further testimony by Dr. Arden L Bement Jr, of the National Institute of Standards and Technology (NIST), discussed progressive collapse as well, regarding it as the spread of failure by a chain reaction that is disproportionate to the triggering event - responsible, besides the WTC, for the large number of deaths in the bombing of the Federal Building in Oklahama City.?
He admitted that the United States has not yet developed standards and practices to assess and reduce this vulnerability. He also stated that the problem for modern buildings is their smaller margin of safety - and the reserve capacity to accommodate abnormal loads - due to increased efficiency in the use of building materials and refinements in analysis techniques. Professor Astaneh's, and others, testimony before the Committee on Science as well as a video of the entire hearing can be found atwww.house.gov/science/welcome.htm. CU?http://www.msc.software.com/
9月11日 聲明
MSC軟件公司通過仿真軟件工具MSC.DYTRAN和MSC.MARC向美國國會委員會模擬,了解世界貿(mào)易中心大樓倒塌的情況。
2002年3月6日,ASL Abolhassan Astaneh博士(加州大學伯克利分校土木與環(huán)境工程教授),在美國國會眾議院科學委員會,發(fā)表關于世貿(mào)中心的調(diào)查倒塌。他的證詞,包括一系列使用MSC.Dytran MSC.Software公司開發(fā)的軟件來模擬波音747客機撞擊成鋼結(jié)構(gòu)模擬。
“MSC.Software公司董事長兼首席執(zhí)行官弗蘭克說:“9月11日發(fā)生的悲慘事件,促使我們?nèi)ピ儐栕约何覀兛梢宰鲂┦裁磥韼椭恕SC.Software公司有著一段和與世界各地的研究人員和政府機構(gòu)的一起工作,研究復雜的工程問題的歷史,其中包括處理與取證,防止像在未來類似世界貿(mào)易中心倒塌的悲劇的發(fā)生。我們很榮幸能在努力防止此類事件發(fā)生起到小小的作用,并希望更多的政府機構(gòu)將采用我們提供的免費軟件和服務來調(diào)查攻擊任何政府實體的事件?!?
“分析了解世界貿(mào)易中心大廈為什么倒塌,將有助于我們防止這種類型的建筑在未來的崩潰”,Astaneh-Asl博士說,“為了模擬非常復雜飛機的沖擊以及隨后火災的問題,你需要最強大和最先進的軟件,比如MSC.Software公司提供的仿真工具。對于我們的研究方案MSC.Software公司的貢獻是非常重要的。我們將繼續(xù)使用這些工具,并通過我們調(diào)查,了解崩潰的誘因,學習寶貴的經(jīng)驗,以便在未來防止這種災難的發(fā)生?!?
本文附帶的圖片為一個通用鋼鐵高層建筑受到波音747客機的撞擊以及隨后的火災影響而發(fā)生的變化,演示了航空航天機械工程的先進技術在帶來這類問題上所能承受的能力。Astaneh教授在調(diào)查期間(今年九月將進行更全面的報告目前調(diào)查工作還在進行中)發(fā)表崩潰的原因可能是因為世貿(mào)中心雙塔的外部受強烈的熱而彎曲,他還研究了斷裂的鋼柱和飛機解體過程中發(fā)生動態(tài)影響。
MSC.Dytran幫助工程師預測結(jié)構(gòu)在已知情況下發(fā)生的變化如崩潰以及如何應對。典型的應用如在車輛碰撞時安全氣囊和乘員的相互作用,金屬板材成形,飛機上的鳥擊,飛機結(jié)構(gòu)內(nèi)爆炸的遏制,船舶碰撞和擱淺,彈丸的影響力和滲透力,跌落試驗,板材鍛造和結(jié)構(gòu)上的液體晃動的影響。MSC.Marc是一個先進的工程模擬的非線性分析工具。它還可以用來模擬溫度的影響比如用在火災。
Astaneh教授在調(diào)查由于恐怖活動而造成在世貿(mào)中心悲劇倒塌事件的周邊因素,同時更加關注在米蘭一架小型飛機墜毀到城市中心Pirelli building的事件。能夠預測將由高層建筑上的意外或環(huán)境事件造成的損害,使民間的工程師通過修改設計以減輕可能帶來的災難性的結(jié)果。雖然不希望搶先調(diào)查的最終結(jié)果會出現(xiàn),但是相當大的破壞,已經(jīng)不能避免的,建設的最終崩潰也是完全不可預見的。
一個比較,30年或40年前由美國國會資助的,通過國家科學基金會的努力取得了有關的危害如地震及其對建筑物的影響和隨后的生命損失等研究成果。其后研究和工程社區(qū)已經(jīng)開發(fā)出更有效和經(jīng)濟的技術,以減輕地震災害。Astaneh教授已經(jīng)在幾個主要研究建筑物和橋梁在地震后的破壞和崩潰的團隊擔任首席研究員。地震工程所采取的方法同樣可以用于調(diào)查恐怖襲擊造成的損害,以及減少這類攻擊的后果。他認為對抗同樣由于恐怖主義而造成對建筑以及環(huán)境毀滅性的打擊需要類似的努力。
煤制油工程的高級副總裁,美國土木工程師學會代表委員博士W Gene Corley也就地震與ASCE五個最近的研究在西雅圖和秘魯,薩爾瓦多,印度,以及1995年在審查默拉聯(lián)邦辦公室在俄克拉何馬城的建筑物倒塌等進行了比較。
在重要幾點中,他指出,建立以及可能準確描述崩潰前建筑物的物理屬性變化是主要困難之一。他說建立以及可能準確描述崩潰前建筑物的物理屬性變化是一項艱巨的任務。建筑物的結(jié)構(gòu)是由數(shù)千個工程圖紙描述的。此外,在建筑物生命周期內(nèi)還有許多變化。利用這些數(shù)據(jù)來構(gòu)造詳細的計算機模型結(jié)構(gòu)。除了淘圖書館和其他數(shù)據(jù)信息庫所涉及的辛勤工作,ACSE的跑簡報調(diào)查隊還要找主要設計師來了解如何建造此建筑物。
雙塔倒塌的主要根源是由于其慢慢倒塌。科利博士解釋說,這種情況發(fā)生的可能是因為兩個相互獨立又相互依賴的事件或主題受到的負荷,結(jié)構(gòu)強度或冗余。目前還沒有合理的技術基礎去描述開始發(fā)生的事件又或去評估緩解戰(zhàn)略的成效,所以有必要開發(fā)以工程為基礎的工具來指導今后的工作。
科利博士補充,而像九月的事件是罕見的,但建筑物中火災并不少見。需要新的工具和設計方法以及通過與消防工程和應用新的和現(xiàn)有的建筑結(jié)構(gòu)工程社區(qū)之間的協(xié)作來改善火災環(huán)境中的結(jié)構(gòu)顯示。
國家標準與技術研究院(NIST)的Dr. Arden L Bement Jr提出的證據(jù),進一步證明連續(xù)倒塌以及,關于失敗的蔓延是不相稱的觸發(fā)事件 - 負責連鎖反應,除了世貿(mào)中心,為大量的Oklahama市聯(lián)邦大樓爆炸案的死亡。
他承認,美國尚未制定標準和慣例,以評估和減少此漏洞。他還指出,現(xiàn)代建筑的問題在于安全余量較小儲備能力也較低難以適應由于頻繁使用建筑材料和分析技術的改進以增加效率而造成的異常負載。Dr.Astaneh以及其他人的在聽證會發(fā)表的調(diào)查以及整個聽證會視頻委員會的證詞都可以在www.house.gov/science/welcome.htm以及http://www.msc.software.com/找到。
Solid Views
Version 16 of Cimmetry's Autovue enables user to view solid models over the web and provides a faster and more secure method of transferring model data from servers to clients.
Autovue is one of the most popular visualisation and collaboration tools available. Cimmetry's latest version, AutoVue 16, introduces numerous enhancements - the two most significant using Java to enable designers to download and work on solid models directly over the web, and producing 3D metafiles to speed up the transferral of solid model data to clients, reducing the size of files to the minimum required to view the model.
The new version supports a number of new formats, including EAI/HP DirectModel .JT format and Microstation, and enhances existing support for the major Solid Modelling applications. AutoVue 16 also introduces visualisation for the electronics industry, supporting EDA formats, and there are considerable enhancements to markup, including a Markup Navigation Tree. This enables users to navigate through the markups of collaborators, shown in a list of entities in a markup file, making sure that none are overlooked.
AutoVue SolidModel for Java Cimmetry uses the web's own language, Java, to provide a native, thin-client, 3D visualisation solution, with which design engineers can view and collaborate on 3D CAD designs directly within their web browsers. This simple, out-of-the-box solution relies on straightforward administration of access on the server, no admin for the client, and transparent visualisation of metafile copies of original documents, reducing security issues to a minimum.
Similar to AutoVue's Windows based product, users have access to native 3D CAD assemblies, parts and 2D drafts from all major software suppliers, and can single-click through entire assemblies and family trees, explode assemblies into component parts, manipulate 3D views, view multiple rendering modes and cross-section assemblies. Autovue 16 enables users to switch between 3D assemblies and corresponding draft views, and produce precise measurements of distances, angles, arcs and mass properties.?
Cimmetrys believe that, writing the software in Java 1.1, provides users with a complete 3D visualisation solution on the most widely known platform available - and does not require the thin-client user to have to download Java upgrades before he begins to use the software. Besides being the simplest method of collaborating through web browsers, the software is also integrated with EDM/PDM and supply chain solutions via Cimmetry's Document Management API (DMAPI).
Server Based Metafile?Rendering?
Autovue's SolidModel solution can also be used to optimise performance levels and speed up data delivery. Using Metafiles, it can reduce the amount of data being transferred between the server and the client by a significant amount. After the initial viewing session, when the model is delivered to the client, a 3D Metafile, from 5 to 15% the size of the original solid model file, is generated by Autovue (3D CMF) for subsequent streaming of data. The CMF Metafile, transferring data to and from the server in a continuous stream, has two methods of transmission - to accommodate fast and slow connections. As it is used to gradually build up 3D models on the client's screen, it can be interrupted in full flow - essential, should the client decide to change the view he requires.?
When bandwidth is not an issue, the algorithm cycles through parts in an assembly and requests data from the server via the CMF in 'chunks' - usually about 10% of the original file size, until the full 3D model of the part being viewed reaches full resolution on the screen. Initial views are in coarse resolution, which is improved as more data is received. If the CMF is about 10% of the original model size, and the chunks are 10% of that, only 1% of the original data needs to be transmitted for the client to see the initial view of the complete assembly, and only 0.01% to see the initial view of the first part (given a model with an average of 100 parts).?
The second method is more complex, and looks at the view parameters to compute the level of detail required on a part-by-part basis, only transferring enough data to accurately visually represent the assembly. If a part is completely off the screen, it doesn't need to be updated, and the data will not be sent. If the user zooms in on a part, a higher level of detail will be required. AutoVue uses a number of algorithms to achieve such a high level of interactivity, but the advantage is that only the amount of data needed to view a model is transferred, making considerable savings on the bandwidth and memory required.
Cimmetry say that Version 16 of AutoVue constitutes a significant enhancement over earlier releases, enabling them to offer, now, powerful visualisation and collaboration solutions for both Windows and Java platforms.
http://www.cimmetry.com/
可靠的意見
Cimmetry的AutoVue 16版使用戶在網(wǎng)上查看實體模型,并提供了從服務器到客戶端傳輸模型數(shù)據(jù)的速度更快,更安全的方法。
AutoVue的是最流行的可視化和協(xié)作工具之一。 AutoVue 16,Cimmetry公司的最新版本介紹了許多增強功能 - 兩種具有重大意義是設計師能使用Java下載和直接在網(wǎng)絡中的建立實體模型,并制作三維圖元文件加快了堅實的模型數(shù)據(jù)到客戶端傳輸,減少了文件查看模型所需的最低要求。
新版本支持一些新的格式,包括EAI/HP DirectModel.JT格式和Microstation格式,并提高對現(xiàn)有的主要固體建模應用的支持。 AutoVue 16還引入了電子行業(yè)的可視化,支持的EDA格式,并有增強標記的功能,包括標記導航樹。這使用戶能夠瀏覽通過合作者的標記,對照標記文件中的實體名單,確定沒有東西被忽略。
Cimmetry公司的AutoVue Solid java模型使用自己的網(wǎng)上語言,提供本機,客戶機,三維可視化解決方案,設計工程師可以在瀏覽器中查看和協(xié)作三維CAD設計。這個簡單的創(chuàng)新解決方案依賴于直接訪問服務器上,沒有為客戶的管理,透明的可視化圖元文件拷貝原始文件的安全問題減少到最低限度,管理。
相似的對于Windows AutoVue基于產(chǎn)品,用戶訪問原始的3D CAD組件,部件和所有主要的軟件供應商的2D草稿,并可以通過整個集會和家庭樹單,點擊,爆炸制成零部件裝配,操縱3D視圖,查看多個渲染模??式和橫截面組件。 AutoVue 16使用戶之間能夠交換3D組件和相應的草案的意見,并產(chǎn)生精確的測量距離,角度,弧和質(zhì)量特性。
Cimmetrys相信,在Java 1.1編寫的軟件,為用戶在最廣為人知的平臺上提供一個完整的三維可視化解決方案 - 不需要受客戶機的限制,就開始使用該軟件下載進行Java升級。除了最簡單通過網(wǎng)頁瀏覽器的的方法的合作合作,這個軟件也能夠通過EDM/PDM 得到協(xié)調(diào)和通過Cimmetry的DMAP理論提供鏈的解決方法。
基于服務器的Metafile渲染
AutoVue的SolidModel解決方案也可以用于優(yōu)化性能水平,加快數(shù)據(jù)傳輸。使用圖元文件,它可以減少相當數(shù)量的服務器和客戶端之間傳輸?shù)臄?shù)據(jù)量。初始觀看會議后,當模型被傳遞到客戶端,一個三維圖元文件只有原來的實體模型文件的大小的5%到15%,之后由AutoVue(3D CMF)后續(xù)生成。 CMF的圖元文件,連續(xù)傳輸有兩種方法 - 適應快速和慢速連接。當它用來逐步建立客戶端的屏幕上的三維模型,用戶可以在全流中斷以防客戶決定改變他的看法。
當帶寬是不是一個問題,在裝配零件和通過CMF的“塊”的服務器請求數(shù)據(jù)通過算法周期 - 通常大約10%的原始文件的大小,直到正在觀看的部分達到全三維模型全分辨率的屏幕上。原來的觀點是一種比較粗糙的解決方法,但是它隨著更多的數(shù)據(jù)被提供而得到改進。如果CMF大約是原始模型尺寸的10%,并且大塊只是它的10%,那么只需要將原始數(shù)據(jù)的1%傳遞給客戶以看到整個集成的最初觀點,另外只有0.01%用于看到第一部分的最初觀點(特定的一個模型平均100部分)。第二方法更復雜的,觀視圖參數(shù)計算細致的程度要求在一個part-by-part基礎,只有傳輸足夠的數(shù)據(jù)才能準確表現(xiàn)。如果數(shù)據(jù)完全不在屏幕上顯示,它不需要進行更新,數(shù)據(jù)也不會被發(fā)送。如果用戶縮放一部分,那么一個需要提供更高的細節(jié)水平。 AutoVue的算法可以實現(xiàn)這樣一個高層次的互動,只需要傳輸少量模型的數(shù)據(jù)量,需要的帶寬和內(nèi)存大大減少。
Cimmetry公司說AutoVue的16版本,相對于早期版本的有著顯著增強,為Windows和Java的平臺提供強大的可視化和協(xié)作解決方案。
http://www.cimmetry.com/