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管材彎曲工藝研究新進(jìn)展
[摘要] 管材成形由于容易滿足塑性成形產(chǎn)品輕量化、強(qiáng)韌化和低耗高效、精確制造等方面的要求,在航空航天、汽車工業(yè)等許多行業(yè)中得到廣泛的應(yīng)用。管材彎曲成形工藝的研究是其中備受關(guān)注并得到迅速發(fā)展的重要領(lǐng)域之一。介紹了幾種新的彎管工藝,闡述了國內(nèi)外彎管工藝的最新研究進(jìn)展和發(fā)展趨勢。
[關(guān)鍵詞] 管材;彎曲;彎管工藝
管材塑性加工是以管材作毛坯,通過塑性加工手段,制造管材零件的加工技術(shù)[1]。管材塑性加工由于容易滿足塑性成形產(chǎn)品輕量化、強(qiáng)韌化和低耗高效、精確制造等方面的要求,已成為先進(jìn)塑性加工技術(shù)面向21世紀(jì)研究與發(fā)展的一個(gè)重要方向[2]。在航空航天、汽車、石油化工、輕工及交通運(yùn)輸?shù)裙I(yè)部門中,廣泛地采用管材制造零件。例如在汽車工業(yè)中,采用中空鋁型材作車身結(jié)構(gòu)和保險(xiǎn)杠,在保持與鋼鐵制件具有同等的抗沖擊強(qiáng)度條件下,能減輕30%～40%車體質(zhì)量,對(duì)汽車的輕量化具有十分重要的意義;當(dāng)汽車發(fā)生碰撞等意外事故時(shí),管材結(jié)構(gòu)還可以吸收因碰撞帶來的沖擊能,保護(hù)乘客的安全[3]。管塑性彎曲成形是管塑性成形技術(shù)的重要組成部分。用管材制造的彎曲零件,無論是平面彎曲件,還是空間彎曲件,除大量應(yīng)用于氣體、液體的輸送管路外,在金屬結(jié)構(gòu)中的應(yīng)用也十分廣泛。因此管材彎曲成形工藝是備受關(guān)注并得到迅速發(fā)展的重要領(lǐng)域,開展這方面的研究工作,具有十分重要的意義。文中介紹了管材彎曲的幾種新工藝,以及國內(nèi)外研究進(jìn)展和發(fā)展趨勢。
1、基于成形方式的管材彎曲工藝分類
實(shí)踐中有許多不同的彎管工藝,從不同的角度出發(fā)可以有多種不同的分類。工程中通常按彎曲時(shí)加熱與否可分為冷彎和熱彎,根據(jù)彎曲時(shí)有無填充物可分為有芯彎管和無芯彎管。文獻(xiàn)[4]根據(jù)不同的成形方式。無模彎曲成形是指管材彎曲變形區(qū)不直接受到模具的作用,最終的形狀由工具和工件的相對(duì)運(yùn)動(dòng)決定,屬于高度靈活的柔性加工手段。有模彎曲成形是指通過剛性模具直接作用于彎曲變形區(qū)而進(jìn)行的管材彎曲,要求此剛性模具作用部分尺寸可以補(bǔ)償制件卸載后發(fā)生的彎曲回彈,屬于可重復(fù)性高而且快速的加工手段。
2、管材彎曲的幾種新工藝
2.1熱應(yīng)力彎曲
熱應(yīng)力彎曲是一種利用工件內(nèi)部溫度分布不均勻所產(chǎn)生的熱應(yīng)力來驅(qū)動(dòng)工件變形的成形方法。這種方法不需外力作用,因而也不需要專門加工模具,便于現(xiàn)場操作,是一種柔性加工手段,近年來對(duì)這種成形方法的研究逐漸增多。加熱熱源可采用火焰或激光,加熱方式包括局部加熱及加熱爐內(nèi)整體加熱;冷卻方式包括空冷、噴水冷卻及浸水冷卻。具體工藝取決于實(shí)際工況和工件特征。
激光成形是對(duì)局部材料采用激光加熱,通過不對(duì)稱的加熱和冷卻,一個(gè)楔形區(qū)域上產(chǎn)生了壓縮變形。通過在ｘ軸方向不同區(qū)域的反復(fù)激光照射加熱,可以最終確定管材的形狀。因?yàn)闅堄鄳?yīng)力對(duì)制件質(zhì)量有影響,所以在工藝設(shè)計(jì)時(shí)需要考慮工件的殘余應(yīng)力分布。這種方法由于可以方便地控制激光功率大小和作用軌跡,因此易于成形空間彎曲件。它不僅可以適用于簡單的矩形截面管材,而且可以彎曲復(fù)雜截面的管材。但是在彎制多型腔型材時(shí)有一些限制,且加工時(shí)間長,生產(chǎn)效率低
文獻(xiàn)[5]提出的管的熱應(yīng)力彎曲方案是:先將管件在加熱爐中均勻加熱到某一溫度,然后以一定速度水平浸入水中,直至管件完全冷卻。管件最終凹向后入水一側(cè),其彎曲規(guī)律如下:內(nèi)外弧的彎曲程度無明顯差別;管件截面扁化,其中沿彎曲半徑方向的截面尺寸大于垂直彎曲平面方向的截面尺寸,即同壓彎法彎管所造成的截面變化趨勢相反;管件彎曲程度及截面變化程度隨加熱溫度的提高而增大;長度直徑比值較大的管件,其彎曲效果較好。
2.2 基于工具運(yùn)動(dòng)控制的無模彎曲
如圖1所示可以通過控制管端夾具軌跡來實(shí)現(xiàn)無模彎曲。管端夾具的運(yùn)動(dòng)產(chǎn)生的彎曲力矩使得管材在局部區(qū)域產(chǎn)生彎曲塑性變形并發(fā)生
圖1基于管端夾具運(yùn)動(dòng)控制的無模彎曲
轉(zhuǎn)移。因此可以實(shí)現(xiàn)軸向多曲率半徑工件的無模彎曲。通過對(duì)軌跡的微分方程進(jìn)行數(shù)值求解,可以得到用于彎曲成形設(shè)備上的不同的控制程序。文獻(xiàn)[6]使用這種方法成形得到Ｓ型的零件。
另一種通過控制工具運(yùn)動(dòng)實(shí)現(xiàn)無模彎曲的方法。管材通過一個(gè)導(dǎo)向圓柱軸向送料,在離出口一定距離處有一個(gè)移動(dòng)模,其用球軸承作為支撐點(diǎn),并且可以在垂直于軸向的平面內(nèi)移動(dòng)。根據(jù)移動(dòng)模的位置和偏轉(zhuǎn)方向的不同,管材會(huì)產(chǎn)生相應(yīng)的彎曲。通過軸向的進(jìn)給運(yùn)動(dòng),可以使管材在包括端部的整個(gè)長度上進(jìn)行彎曲。
這種彎曲設(shè)備的基本原理是ＭＯＳ彎曲原理,它可以用來方便地實(shí)現(xiàn)管材的空間彎曲,但卻必須為各種截面的管材定制不同的模具。圖2展示了利用這種成形工藝得到的彎曲管材。
2.3疊加法彎曲
疊加法的原理3所示當(dāng)金屬材料在塑性區(qū)域內(nèi)變形時(shí),可以利用一個(gè)相對(duì)于成形力Ｆ來說很小的側(cè)向作用Ｆｚ,實(shí)現(xiàn)彎曲。在具體實(shí)現(xiàn)過疊加法原理程中,這個(gè)很小的作用力可以通過一個(gè)偏轉(zhuǎn)輪施加,其產(chǎn)生了一個(gè)很小的力矩,影響金
屬的流動(dòng),從而實(shí)現(xiàn)了可控制曲率的彎曲加工。由于零件本身是按彎曲要求生產(chǎn)的,因此可以避免產(chǎn)生諸的截面變形、破裂或起皺問題。
疊加法最直接的應(yīng)用就是管材的擠壓生產(chǎn)。實(shí)際直型材在擠壓過程中由于在擠壓模中存在不理想的摩擦條件,因而產(chǎn)生了非常小的摩擦力Ｆμ,引起輕微彎曲現(xiàn)象;反過來說,如果在擠壓過程中有效控制這個(gè)力,利用其使擠壓金屬的流動(dòng)速度產(chǎn)生速度梯度,從而實(shí)現(xiàn)制件彎曲。另外通過改變摩擦力作用長度也同樣可以產(chǎn)生類似的效果。該工藝的優(yōu)點(diǎn)是可以比較靈活地控制偏轉(zhuǎn)輪而不必改變擠壓模具的設(shè)計(jì),甚至復(fù)雜的多型腔橫截面的型材也可以通過這個(gè)方法彎曲。目前開展的大多是平面內(nèi)常曲率彎曲的研究[8],對(duì)于空間變曲率彎曲從理論的角度上來說是可行的,但是由于需要對(duì)偏轉(zhuǎn)輪的實(shí)時(shí)控制,因此設(shè)備方面還需要進(jìn)行重大改進(jìn)。另一個(gè)類似的彎曲工藝把疊加法原理運(yùn)用到擴(kuò)管設(shè)備中。
2.4數(shù)控機(jī)床繞彎
繞彎是指將管材夾緊在彎曲模上,隨彎曲模一起轉(zhuǎn)動(dòng),當(dāng)管材被拉過壓塊時(shí),壓塊即將管材繞彎在彎曲管上,屬于成形模彎曲工藝。傳統(tǒng)繞彎工藝多是手工繞彎,效率低,質(zhì)量難以保證。隨著數(shù)控機(jī)床業(yè)的發(fā)展,采用先進(jìn)的數(shù)控彎管機(jī)床實(shí)現(xiàn)繞彎工藝,可以大大地提高生產(chǎn)效率,保證產(chǎn)品的質(zhì)量。由于可以方便地調(diào)節(jié)工藝參數(shù),因此數(shù)控彎管機(jī)可以既準(zhǔn)確又穩(wěn)定地完成彎曲、送進(jìn)、轉(zhuǎn)角等動(dòng)作,保證了管制件的彎曲準(zhǔn)確度。數(shù)控彎管機(jī)可以自動(dòng)連續(xù)地成形不同曲率半徑的空間彎曲件。結(jié)合相應(yīng)的數(shù)據(jù)庫軟件系統(tǒng),控制程序還可以預(yù)先修正彎曲回彈量。但是該工藝的模具結(jié)構(gòu)（見圖4）比較復(fù)雜,制件質(zhì)量對(duì)工藝參數(shù)敏感,要求有充分的前期準(zhǔn)備和試制工作。尤其是對(duì)于彎制薄壁管制件的情況,如果工藝參數(shù)選擇不當(dāng),則很容易出現(xiàn)起皺現(xiàn)象導(dǎo)致零件甚至是模具的報(bào)廢。如何高效準(zhǔn)確地獲取這些工藝參數(shù),充分保證彎管產(chǎn)品質(zhì)量,是數(shù)控繞彎工藝的研究熱點(diǎn)。
3、管材彎曲研究進(jìn)展
上述介紹的新彎管工藝多數(shù)屬于柔性加工手段,拓展了管料彎曲加工的工藝方法范圍。實(shí)際生產(chǎn)中彎管工藝往往易產(chǎn)生如圖5所示的質(zhì)量缺陷。
(1) 在彎曲變形區(qū)外側(cè)壁會(huì)產(chǎn)生壁厚變薄;
(2) 在彎曲變形區(qū)內(nèi)側(cè)壁會(huì)產(chǎn)生壁厚增大起皺;
(3) 橫截面形狀畸變;
(4) 回彈問題。
為了解決上述質(zhì)量缺陷,目前國內(nèi)外學(xué)者對(duì)管材彎曲的研究,主要集中于兩個(gè)方面:通過理論解析和試驗(yàn)研究的方法對(duì)彎管的機(jī)理進(jìn)行研究;通過數(shù)值模擬的方法對(duì)彎管質(zhì)量缺陷進(jìn)行研究并改進(jìn)工藝。
在試驗(yàn)研究方面:通過實(shí)驗(yàn)研究,分析了牛角芯棒熱推彎管成形過程瞬時(shí)應(yīng)力、應(yīng)變狀態(tài)及其演化過程,闡明了彎管成形時(shí)的受力、變形特點(diǎn),揭示了彎管成形過程所遵循的力學(xué)原理及其分析求解方法,為牛角芯棒熱推彎管成形理論研究奠定了基礎(chǔ)。根據(jù)彎管加工理論、實(shí)驗(yàn)研究和大量實(shí)踐,總結(jié)出了對(duì)管材彎曲加工成形精度有重要影響的回彈、伸長和成形半徑等參數(shù)的確定方法,并可用智能彎管測量儀測取上述數(shù)據(jù),以用于指導(dǎo)生產(chǎn)。文獻(xiàn)[7]采用能量原理分析截面變扁率和材料性質(zhì)及工藝參數(shù)之間的關(guān)系,理論和實(shí)驗(yàn)結(jié)果吻合得較好。提出的Ｔｕｂｅｍｏｄ系統(tǒng)建立了系列數(shù)控彎管機(jī)床的幾何、運(yùn)動(dòng)、變形、調(diào)試及干涉測試的總體仿真模型和完整的模具庫及導(dǎo)管庫。該系統(tǒng)采用數(shù)控指令驅(qū)動(dòng),能直接從彎管數(shù)據(jù)庫中讀?。危贸绦?進(jìn)行裝夾、彎曲、回彈等數(shù)控彎管全過程的三維動(dòng)態(tài)顯示,并可進(jìn)行干涉檢測處理。對(duì)中頻感應(yīng)局部加熱彎管在不同鋼管材料及規(guī)格、不同彎曲半徑及彎曲角度等工藝參數(shù)時(shí)的加載和卸載的力能參數(shù)、應(yīng)力應(yīng)變進(jìn)行了理論分析和實(shí)驗(yàn)研究。
在數(shù)值模擬方面:提出了中頻感應(yīng)局部加熱彎制大直徑鋼管的回彈理論,計(jì)算結(jié)果與有限元模擬結(jié)果以及實(shí)際彎制的鋼管彎頭實(shí)測的回彈量吻合良好。文獻(xiàn)[8]對(duì)管材彎曲時(shí)的截面變形作了研究和數(shù)值模擬,研究表明截面的變形會(huì)明顯地減小彎曲力,因此在有限元模擬時(shí),會(huì)嚴(yán)重地影響力和截面變形的計(jì)算結(jié)果。文獻(xiàn)[9]采用商用有限元軟件ＭＡＲＣ對(duì)矩形截面管材彎曲作了數(shù)值模擬,在起皺、外側(cè)塌陷、截面變形等方面模擬結(jié)果和實(shí)際情況相符合。在全面分析無模彎曲成形工藝過程的基礎(chǔ)上,對(duì)該種工藝過程的復(fù)雜邊界條件作了合理的處理,建立了無模彎管有限元分析模型,開發(fā)了可用于管材彎曲分析的三維剛塑性有限元程序,可預(yù)報(bào)管材(型材)彎曲后斷面畸變的情況,有重要的實(shí)用價(jià)值。此外,對(duì)于管材加工中的起皺現(xiàn)象,雖然涉及因素多、研究難度大,但是由于對(duì)精確成形的日益迫切的要求,也引起了國內(nèi)外學(xué)者的關(guān)注,發(fā)表了一些對(duì)管材起皺機(jī)理的分析和數(shù)值模擬方面的研究報(bào)道:文獻(xiàn)對(duì)管材縮口及軸向壓縮過程用分叉理論和彈塑性有限元法進(jìn)行了起皺的預(yù)測,分析了單元尺寸、模具尺寸和材料性能對(duì)分叉點(diǎn)的影響;對(duì)中空矩形鋁管的彎曲起皺進(jìn)行了預(yù)測,對(duì)低剛度和高剛度兩種材料的皺曲波形進(jìn)行了描述,并采用能量法分別計(jì)算了兩種材料起皺的臨界應(yīng)力值;在分析討論國內(nèi)外關(guān)于板材起皺研究的基礎(chǔ)上,提出了采用最小能量法預(yù)測薄壁管彎曲成形過程中失穩(wěn)起皺的新思路;采用商用有限元軟件ＰＡＭ ＳＴＡＭＰ模擬了數(shù)控彎管過程,研究發(fā)現(xiàn)管材和防皺塊之間的間隙是影響起皺的重要因素,同時(shí)隨著彎曲半徑的減小,截面畸變率和壁厚減薄率將會(huì)變大。
隨著計(jì)算機(jī)技術(shù)的發(fā)展和有限元軟件算法的改進(jìn)完善,采用數(shù)值模擬的方法對(duì)實(shí)際生產(chǎn)進(jìn)行模擬是一種被證明是行之有效并且具有很大潛力的途徑。采用計(jì)算機(jī)進(jìn)行模擬仿真,可以大大地減少試驗(yàn)的工作量,減少時(shí)間和人力物力消耗,并且可以方便地改變工藝參數(shù),以系統(tǒng)探索工藝參數(shù)對(duì)成形的作用和影響。管材彎曲的研究工作方法,也越來越多的由解析試驗(yàn)方法向數(shù)值模擬方法轉(zhuǎn)變。
但是,由于管材彎曲建模的復(fù)雜性,不能簡單地用軸對(duì)稱或平面模型描述。研究人員在進(jìn)行解析和數(shù)值建模時(shí),為了降低三維計(jì)算工作量,通常都提出了一些假設(shè)前提,這使得研究結(jié)果和實(shí)際生產(chǎn)出現(xiàn)不小的差距。目前對(duì)普通壁厚管料彎曲的模擬的研究比較完善,但是對(duì)于薄壁管易壓縮失穩(wěn)出現(xiàn)起皺的情況,還是不能準(zhǔn)確判斷和正確處理,因此這方面的研究也是管料彎曲研究領(lǐng)域的熱點(diǎn)。對(duì)于彎曲回彈問題,試驗(yàn)方法取得一定進(jìn)展,建立了一些基礎(chǔ)參數(shù)數(shù)據(jù)庫,但是試驗(yàn)工作量非常大,如何用數(shù)值模擬方法研究回彈問題,依然是一個(gè)難點(diǎn),有待進(jìn)一步發(fā)展。
4、結(jié) 語
(1) 管塑性加工由于容易滿足塑性成形產(chǎn)品輕量化、強(qiáng)韌化和低耗高效、精確制造等方面的要求,在航空航天等許多行業(yè)中得到了廣泛的應(yīng)用,因此管材彎曲工藝備受關(guān)注并得到了迅速發(fā)展。
(2) 基于成形方式的分類是管材彎曲的一種新的分類方法。熱應(yīng)力法和基于工具運(yùn)動(dòng)控制的無模彎曲可以實(shí)現(xiàn)柔性制造;重疊法具有避免產(chǎn)生截面變形等缺陷的特點(diǎn),可以直接生產(chǎn)彎管制件;數(shù)控繞彎可以進(jìn)行高效批量化生產(chǎn),符合現(xiàn)代化生產(chǎn)的需要。
(3) 國內(nèi)外對(duì)于彎管的研究工作,主要集中于試驗(yàn)研究和數(shù)值模擬兩個(gè)方面。數(shù)值模擬方法被證明是一種行之有效并且具有潛力的研究方法,對(duì)彎管質(zhì)量缺陷的研究工作越來越多地采用了有限元模擬方法。對(duì)管料彎曲建模、薄壁管彎曲起皺和彎曲回彈的研究正成為國內(nèi)外研究關(guān)注的熱點(diǎn)。氣體的壓力作用下噴射到冷卻板上,合金凝固后可獲得具有細(xì)小等軸晶粒組織的坯料。該坯料可用于半固態(tài)成形加工用的坯料。這一方法在制備大過共晶鋁硅合金等特殊材料的坯料方面有一定的優(yōu)勢,但成本較高。
(4) 控制結(jié)晶過程及晶粒細(xì)化法。該方法是通過對(duì)合金液體加入晶粒細(xì)化劑或控制冷卻速度等,以使合金凝固后的固相晶粒不為枝晶狀而為非枝晶狀(近似等軸晶)。由于這種方法在幾種坯料生產(chǎn)方法中成本最低,因而具有較大的發(fā)展前途。
1.2 半固態(tài)成形用設(shè)備(壓力機(jī))
目前歐洲、美國及日本等國已生產(chǎn)出專門用于半固態(tài)加工的成套設(shè)備(壓力機(jī)),也可以在現(xiàn)有壓鑄機(jī)或鍛壓設(shè)備的基礎(chǔ)上改造。
半固態(tài)加工時(shí)溫度的控制
半固態(tài)加工的溫度是該加工工藝的主要參數(shù)之一。這是因?yàn)樵摐囟葲Q定了液相和固相的比例,它對(duì)零件加工時(shí)所采用的壓力以及獲得零件的強(qiáng)度、健全性都有重要的影響。目前多采用熱電偶、超聲波等方法測控。
半固態(tài)加工用的模具
半固態(tài)加工用模具的設(shè)計(jì)可參考?jí)鸿T模、沖壓模等的設(shè)計(jì),但必須考慮半固態(tài)加工的實(shí)際條件。和壓鑄相比,半固態(tài)坯料的溫度低,流動(dòng)時(shí)間短,呈層流狀;和沖壓相比,半固態(tài)坯料的流動(dòng)性遠(yuǎn)高于固態(tài)且成形壓力低。有研究表明,半固態(tài)加工所用的沖壓力僅為傳統(tǒng)鍛壓方法的1/5左右。由于沖壓力的降低,對(duì)模具材料的要求也降低,可以用非金屬材料(如陶瓷、石墨等)制作模具。
在發(fā)達(dá)國家,半固態(tài)加工的模具設(shè)計(jì)多采用計(jì)算機(jī)模擬設(shè)計(jì)。
已用于半固態(tài)成形的鋁合金
最早用于半固態(tài)成形的為亞共晶鑄造鋁合金(Ａ356,Ａ357)。這兩種合金在發(fā)達(dá)國家采用半固態(tài)成形已實(shí)現(xiàn)工業(yè)化生產(chǎn)。后來,他們又開發(fā)了過共晶成分的Ａ390鋁硅合金。這種合金中的初晶硅相,在電磁攪拌生產(chǎn)坯料的方法中,被細(xì)化并均勻地分布在合金中,提高了合金的強(qiáng)度和耐磨性。有關(guān)鍛鋁合金用于半固態(tài)成形加工的技術(shù)正處于研究開發(fā)階段。
鋁合金半固態(tài)成形技術(shù)的發(fā)展趨勢
鋁合金的半固態(tài)成形加工主要用于汽車工業(yè)中零件的生產(chǎn)。而汽車工業(yè)持續(xù)要求降低車體重量和減少環(huán)境污染,這就要求半固態(tài)成形技術(shù)能提供高強(qiáng)度的鋁合金以替代鋼和鑄鐵制零件等。因此,半固態(tài)成形加工技術(shù)有廣闊的應(yīng)用前景。半固態(tài)成形加工技術(shù)今后應(yīng)在低成本制備半固態(tài)加工用坯料、成形設(shè)備研制、成形模具設(shè)計(jì)及成形過程計(jì)算機(jī)模擬以及開發(fā)適合于半固態(tài)加工用的新型鋁合金材料方面進(jìn)行深入研究。
附錄B
State of the Art of the Bending Process and Research of Tube
Abstract: With the characteristic of high efficiency,forming precision and strength/weight ratio product and low consumption,tube froming processes find an wide application in modern industries such as aero-space and automobile.Tube bending process is one of the most important tube forming processes are introduced,as well as advancement and trend of relative research report.
Key word: tube ; bending ;bending process
Pipe plastic property process is acting as Mao Pi with pipe ,and by means of the plastic property process measure,manufactures the pipe spare parts process technology.Pipe plastic property is processed meeting the light quantification of produce that the plastic property takes shape thanks to easily、High efficiency of powerful with consumes slowly 、Accurately manufactures and so on the respect demand has become the significant orientation [2] to the 21 centuries research and development of well-developed plastic property process technology.Aviation spaceflight is living 、Motor vehicle 、Mineral oil chemical industry 、Widely adopt the pipe spare parts in the industry department such as light industry and communications and transportation and so on.In for instance being living the auto industry empty the mould material in adopting acting as bodywork composition and the bumper ,and is living to maintain having below the same resisted shock intensity term,and be able to eases 30% against the iron and steel finished piece 40%The automobile body quality have the fully significant sense to the light quantification of motor vehicle;When the motor vehicle happen to run into and so on when the unforeseen mishap,the pipe composition still may suck up the shock capacity brought as a result of ruing into,and safeguards the security [3] of passenger.It is the significant component part ruing the plastic property forming technique that tube plastic property crookedly takes shape.In the way of the crooked spare parts of pipe,no matter is crooked on plane , nevertheless crooked in room,except for the greats quantity are used to gas 、Outside the liquid pipeline route,the application that is living in the metal structure is also fully wide-ranging .The crooked forming technology of pipe this respect research work,and have the fully significant sense hence being accepting the significant territory that the concern obtain the swift development in every possible way.Introduced some kinds of fresh technology that pipe is crooked in the script,along with the home and abroad is researched to make progress and development tendency.
1 .Based on , forming means crooked technology of pipe is classified
That to possess much in the practice distinct flexed runs technology,may possess much kinds of classifications difference through the distinct angle departs .During usually according to crooked heat whether or not to be divided into cold bend and temperature flexing in the project,and having or not the filler may be divided into processing the rush pith to flex the tube to flex the tube during on the basis of crooked with not is not the rush pith.The literature [4] is on the basis of the forming means of difference.Not is not the standard crookedly to take shape is the crooked deformation district of pipe directly is not subjected to the pattern action, ultimate form shape is through means and the work relative movement resolution ,and pertains to highly the agile flexible process measure.It is crooked by means of the stiff pattern direct action to crooked deformation district but pipe that is underway to possess the standard crookedly to take shape,and requires this stiff part of dimensions of pattern action may compensation finished piece down load what afterwards happen the crooked time pellet,and pertains to the tall but also fast process measure of repeatability.
2 .Crooked some kinds of fresh technology of pipe
2.1 Warmhearted stress is crooked
One kind of temperature of use work inside that the warmhearted stress is crooked is distributes,and the uniform warmhearted stress coming into being comes drive work the person who becomes deformed the forming means.This kind of means does not require the function of outside force,and as a result also not needing the special process pattern,is convenient for the operation at field,and is one kind of flexible process measure,and grows in number one by one to this kind of forming means research in the past few years.Heating the heat source may adopt flame either laser,and heats that the means consists of that the part is heated the heating furnace the entirety to heat;The cooling means consists of that it is cool to empty 、Spouting the water-cooling yet reaches the cooling reted.Concrete technology is decided by actual operational mode and the work feature.
It is adopting laser to heat to the part stuff that the laser takes shape,by means of not symmetrical heating and cooling,the wedge form comes into being on the area compresses the deformation,By means of be living.Reversal laser in distinct areas of shaft orientation illuminates to be heated,and may finally fix pipe form shape.For remains' stress possess the effect to the finished piece quality,the necessaries are consider that work remains' stress distributes when being living the technological design.This kind of means is since may dominate conveniently laser service rate size and the action locus,hence being easy to crooked in forming room.It not merely may be applicable to easy rectangle section pipe,but also may crooked complex section pipe.Yet is living to flex possess some limits when manufacturing the many types of cavity mould material,and process time elder , the production efficiency is later drop.
Tube that the literature [5] the is propose crooked scheme of warmhearted stress is:Shall Guan be living in the heating furnace evenly to heat earlier, afterwards with the specified velocity level macerate in the water,and becomes cool completely till Guan up some temperature.Guan finally hollowly enter the water side backward,and such crooked regular pattern is as follows:The crooked degree of inside and outside arc does not there is not the obvious disparity;In immediate future of Guan section in it is more than crooked plane orientation of the uprightness section dimensions along the bending radius orientation section dimensions,with is getting near flexed that the law flexed the section that the tube created to change tendency contrary;Guan crooked degree and section changing the degree and broad with heating the temperature raise;Guan of length diameter ratio,such crooked effect is better.
2.2 Baseded on , the means movement control nil standard is crooked
May by means of control Guan no standard crooked clamping apparatus locus achieving.Crooked moment that Guan clamping apparatus movement is come into being causes that is living pipe,and the crooked plastic deformation of part area coming into being is complicated by to bear to transfer.Hence the nil standard that may achieve the axial much curvatures radius work is crooked.By means of carries on the numeric value resolution to the locus differential equation,difference that may obtain is used on the crooked forming installation control procedure.The literature [6] employs this kind of means to take shape and obtains S Spare parts of mould.
Another kind does not there is not the means that the standard is crooked by means of do means movement achieving.The stuff is send by means of the direction cylinder axial by the pipe,and being living to part from to export surely to possess the standard removing away from the part,such is in the way of the ball bearing as the centre of resistance,moreover may be living that the uprightness in is removed the axial plane inner place.The pipe be able to come into being relevant crooked to the difference on the basis of the place to remove the standard with the yawing orientation.What it is by means of the axial moves forward to the movement,and may cause pipe be living to consist of the entire length of butt to make progress line bend.The fundamental rule of this kind of crooked installation is MOS It is crooked that it may be used for conveniently achieving pipe room,yet have to act as the different sections pipe customization differences patterns to the crooked rule.Opening up before one's eyes utilizes this kind of crooked pipe that forming technology obtain.
2.3 The superimpose law is crooked
When the metal material is living when becoming deformed inner place the plastic property area,may utilize one relatively with takes shape force Very little cross acting force,Achieve crookedlyBeing living concrete realization passing through superimpose law rule Cheng Zhong,this very little acting force may be bring to bear on by means of the yawing wheel,such come into being one very little moment,effect metal going from place to place,thereby yet achieved the crooked process of control curvature.May avert coming into being that various sections become deformed since the fact that the spare parts in itself are according to crooked demand manufacture、Split either creases the problem.
The most immediate application of superimpose law is a pipe press manufacture.The actual upright mould material is living in the press process thanks to being living that the press is the not ideal rub term in the standard,as a result coming into being very much little friction,The crooked appearance is aroused lightly;Saying the other way round , in the press process effectively this force in case being living,such causes going from place to place velocity the metal come into being the velocity gradient to the use,thereby the realization finished piece is crooked.Besides also may come into being equally analogous effect by means of revising friction action length.That the technology strong point is may comparatively agile dominate the yawing wheel but need not revise the press pattern design,and it is crooked that the mould material in even to the extent that complex tranverse section of many types of cavity also may pass this means.The crooked research [ 8 ] of constantly curvature that the politically progressive at the moment is for the most part inner place the plane changes into curvature as to the room crookedly being supposed to on theory angle,yet thanks to the fact that the necessaries adjust the yawing wheel real-time control,hence still need to importantly improve the installation.Another analogous crooked technology is utilized the superimpose law rule up enlarged ruing installation.
2.4 The APT coils to be flex
Coiling to flex is by on the taut crooked standard being living of pipe clip ,adapts to the crooked standard turning in company,serves as pipe has been to be getting near cake hour,is getting near cake soon pipe to coil to flex being living on the crooked tube,and pertains to the crooked technology of forming block.That the handwork coils to flex is coil to flex technology to be mostly that to the tradition,and the effectiveness is later drop,and the quality is difficult to,In the wake of the APT trade development,adopt the well-developed digital control to flex the ruing machine tool achieving to coil flexing technology,and may lift the production efficiency,quality of guaranty produce enormously.Since may regulate conveniently the technology parameter , hence the digital control flexed Guan Ji may be not only accurately but also steadies completed crookedly 、Send 、The crooked degree of accuracy of tube finished piece in the movements such as street corner and so on.Crooked in the room that Guan Ji may continuously take shape the distinct curvatures radius is voluntarily flex in the digital control.Uniting the relevant data bank software system,the control procedure still may be amend crooked time pellet and measure beforehand.Yet that the technology pattern composition is comparatively more complex,it is susceptible that the finished piece quality adjust technology parameter,the demand possess sufficiently earlier days get ready and the development work.Especially manufactures the thin wall tube finished piece situation as to flexing,in case the technology parameter selection is unsuitably,has arise the appearance creased to cause the spare parts even to the extent that is reporting something as worthless of pattern piece easily.How the high efficiency is accurately gained these technology parameters,sufficiently to flex ruing the produce quality,is the digital control coils flexed the technology research heat。
3.The crooked research of pipe makes progress
Above-mentioned introduction fresh flexed to run the technology majority pertaining to the flexible process measure,and spread crooked process of the Guan Liao technology means limit.Flex in the actual manufacture quality fault runs technology frequently easily to come into being.
(1) The breastwork being living outside the crooked deformation district side wall be able t to come into being is thick and changes into slight;
(2) The breastwork being living inner place the crooked deformation district side wall be able t to come into being thickly broadens creasing;
(3) The section form shape distortion;
(4) Go back to play the problem.
In order to resolve the above-mentioned quality faul,at the moment a learned man in home and abroad adjust the research that pipe is crooked,and main lumping is to two respects:The means is researched to mechanism flexing the tube by means of what theory analysis and equipment were researched;The means by means of the numeric value imitation adjust to flex to run the quality fault and researches modification technology.
The equipment research respect is living:Research by means of the test,and analysis the strong temperature of ox horn rush pith pushing to flex the tube and takes shape the instantaneous stress of process 、The condition meet an emergency reaches such evolution process , and accepting force when flexing