數(shù)值模擬和實(shí)驗(yàn)的調(diào)整曲率 micro-cantilevers 使用 water-confined激光產(chǎn)生等離子體外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯,數(shù)值模擬和實(shí)驗(yàn)的調(diào)整曲率,micro-cantilevers,使用,water-confined激光產(chǎn)生等離子體外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯,數(shù)值,模擬,實(shí)驗(yàn),調(diào)整,曲率,micro,cantilevers 附錄一： 數(shù)值模擬和實(shí)驗(yàn)的調(diào)整曲率 micro-cantilevers 使用 water-confined 激光產(chǎn)生等離子體 摘要： 本文描述了一個(gè)精確的和非接觸式調(diào)整技術(shù)使用 water-confined lasergenerated 等離子體調(diào)整離散曲率(micro-mechanical 懸臂)。一系列的激光沖擊微調(diào)實(shí)驗(yàn)進(jìn)行 0.4 毫米厚鋁樣品使用脈沖Nd:YAG 激光操作 1064 納米波長(zhǎng)的驗(yàn)證技術(shù)可行性。系統(tǒng)研究的術(shù)語(yǔ)進(jìn)行了各種因素對(duì)調(diào)整結(jié)果的影響,包括激光能量、激光焦點(diǎn)位置,激光沖擊次數(shù)和限制制度配置。研究結(jié)果表明,可以獲得不同的彎曲角度和彎曲方向通過(guò)改變激光加工參數(shù)。調(diào)整過(guò)程,沒(méi)有限制制度配置也可以生成合適的彎曲變形。但是,在更大的能量的情況下,最終的表面會(huì)消融的跡象,因此導(dǎo)致表面質(zhì)量變差。分析過(guò)程包括通過(guò)ANSYS / LS-DYNA 執(zhí)行動(dòng)態(tài)分析和靜態(tài)分析介紹了由ANSYS 實(shí)現(xiàn)模擬激光沖擊微調(diào)來(lái)預(yù)測(cè)最后的彎曲變形。預(yù)測(cè)彎曲的概要文件是與現(xiàn)有的實(shí)驗(yàn)數(shù)據(jù),顯示有限元分析可以預(yù)測(cè)最后的曲率micro-cantilevers 正常。 介紹： MEMS 制造的需求增加導(dǎo)致生產(chǎn)技術(shù)的新需求[1 - 3],特別是離散的調(diào)整,比如 micro-mechanical 懸臂,廣泛用作極度敏感的物理、化學(xué)和生物傳感器[4 - 7],需要高精度定位、高重現(xiàn)性和低生產(chǎn)成本。滿足這些需求仍然是一個(gè)最新的最關(guān)鍵的任務(wù)。自傳統(tǒng)的機(jī)械調(diào)整技術(shù)未能滿足要求平淡無(wú)味的精度和耗時(shí)的機(jī)械力量或動(dòng)態(tài)影響部隊(duì)[8]。需要一個(gè)精確的和無(wú)接觸充電成為調(diào)整技術(shù)來(lái)控制一些 micro-mechanical 懸臂的彎曲角度。基于激光 micro-adjustment 提供了實(shí)現(xiàn)這一目標(biāo)的潛力。 激光熱成形,稱為非接觸式技術(shù)利用激光熱效應(yīng)塑造融化樣品沒(méi)有工具或外部力量, 是一個(gè)例子[9]。這項(xiàng)技術(shù)被認(rèn)為是溫度場(chǎng)和變形場(chǎng)之間的相互作用過(guò)程產(chǎn)生的殘余應(yīng)變懸臂材料表面的溫度梯度[10]。當(dāng)激光照射目標(biāo)表面,工件表面加熱并產(chǎn)生一個(gè)不均勻的溫度場(chǎng)在厚度方向。生成的熱應(yīng)力是用來(lái)實(shí)現(xiàn)塑性變形等彎曲變形(11、12)。通過(guò)改變激光加工參數(shù),得到不同的彎曲角度和彎曲方向調(diào)整的離散曲率。應(yīng)用激光熱成形的調(diào)整懸架預(yù)加載磁記錄頭堆棧組件被辛格等人企圖。 [13] 。丈許,[7] 使用這種技術(shù)來(lái)調(diào)整硅micro-cantilever 的曲率。最近,格里菲思等。[9]調(diào)查熱激光 micro-adjustment 使用微微秒脈沖持續(xù)時(shí)間。以前的工作表明,有三種常見的形成機(jī)制,即溫度梯度機(jī)理(電報(bào)),失穩(wěn)機(jī)制(博雅)和破壞機(jī)制(嗯)(14 - 16)。沈徹底調(diào)查機(jī)制激光微調(diào)。在他們的工作中,提出了耦合的電報(bào),嗯來(lái)說(shuō)明兩個(gè)橋接致動(dòng)器的熱機(jī)械行為。 然而,熱形成機(jī)制是由激光誘導(dǎo)溫度場(chǎng)是影響工件的幾何形狀,激光功率、激光光束直徑、掃描速度、掃描路徑等。它使彎曲方向不確定,成為一個(gè)難以控制的過(guò)程形成復(fù)雜的形狀和精度高曲率修正[18]。此外,熱效應(yīng)將導(dǎo)致不良的微觀結(jié)構(gòu)變化包括再結(jié)晶和相變過(guò)程中[19]。也,可以融化或燃燒表面,甚至導(dǎo)致小裂紋表面上[20]。因此,很難維護(hù)材料激光熱成形彎曲懸臂的屬性。 他的論文描述了一個(gè)精確的和非接觸式調(diào)整技術(shù)使用 water-confined 激光產(chǎn)生等離子體。laser-shock-waves 薄金屬板上的應(yīng)用受到越來(lái)越多的關(guān)注(21、22)。它被認(rèn)為是一個(gè)純機(jī)械成形方法通過(guò)激光誘導(dǎo)沖擊波修改目標(biāo)曲率。激光熱成形的優(yōu)點(diǎn),如非接觸、 tool-free 和效率高。此外,其非熱能的過(guò)程可以保持甚至提高他們的物質(zhì)屬性誘導(dǎo)殘余應(yīng)力在目標(biāo)表面,這是可取的,因?yàn)樗侵匾脑诠I(yè)的目標(biāo)以防止腐蝕和疲勞產(chǎn)生裂縫[20]。lasershock-wave 誘導(dǎo)薄金屬板彎曲趨勢(shì)類似傳統(tǒng)噴丸成形研究科普和舒爾茨[24]。因此, 激光沖擊微調(diào)實(shí)現(xiàn)很簡(jiǎn)單,但非常有用的高精度曲率調(diào)整。因此它有潛力制造和微電子行業(yè)廣泛應(yīng)用。Ocan?適用性的研究小組研究了激光 micro-bending 薄金屬條通過(guò) ns 脈沖激光器[25]。 在本文,water-confined 激光產(chǎn)生等離子體用于調(diào)整 micro-cantilever 的曲率。一系列的激光沖擊微調(diào)實(shí)驗(yàn)是為了研究激光能量的影響,激光焦點(diǎn)位置,激光沖擊次數(shù)和限制制度配置調(diào)整結(jié)果。此外,激光沖擊的實(shí)際可行性的微調(diào) micro-cantilevers 也通過(guò)有限元模擬研究。激光能量對(duì)彎曲變形的影響進(jìn)行實(shí)驗(yàn),以及實(shí)驗(yàn)獲得的數(shù)據(jù)被用來(lái)驗(yàn)證相應(yīng)的仿真模型。預(yù)計(jì)最終工件曲率進(jìn)行了分析并與實(shí)驗(yàn)結(jié)果。 2 調(diào)整機(jī)制 如在圖 1 中,激光沖擊的典型應(yīng)用程序調(diào)整過(guò)程是在政權(quán)下進(jìn)行配置。目標(biāo)表面首先是局部涂保護(hù)涂層,然后由一個(gè)透明的覆蓋(例如水)。當(dāng)一個(gè)高能聚焦和脈沖激光輻照到工件表面,涂層是瞬間蒸發(fā)成高溫高壓等離子體。這傷口從工件表面等離子體膨脹,反過(guò)來(lái),對(duì)工件表面施加機(jī)械壓力,這將引起工件的壓縮波。保護(hù)涂層作為犧牲材料避免的熱效應(yīng)加熱表面,透明疊加延遲熱膨脹和限制等離子體對(duì)目標(biāo)材料的表面,從而產(chǎn)生更高的壓力[26]。如圖 2 所示, 樣品在 cantilevers-shape 免費(fèi)和固定。當(dāng)激光束照射在樣品的自由端(如圖 2 所示(一個(gè))),向下沖擊加載將傳授下行慣性震驚地區(qū)和彎曲變形是剛剛開始產(chǎn)生震驚地區(qū)激光沖擊微調(diào)過(guò)程中由于激光沖擊的持續(xù)時(shí)間很短。在激光沖擊停止時(shí),繼續(xù)向下運(yùn)動(dòng),由于慣性的作用,使震驚地區(qū)可塑性變形。,當(dāng)?shù)氐乃苄宰冃蔚男袆?dòng)區(qū)沖擊壓力將導(dǎo)致最后可塑性變形和產(chǎn)生彎曲變形。形成行為可以比較一些高能量的形成過(guò)程。所以我們可以控制形成程度調(diào)整激光能量[18]。 3 調(diào)整實(shí)驗(yàn) 3.1. 實(shí)驗(yàn)儀器和準(zhǔn)備 實(shí)驗(yàn)中,一個(gè)短脈沖 Nd-YAG 激光與高斯分布梁。是經(jīng)營(yíng) 10 赫茲和重復(fù)頻率的脈沖持續(xù)時(shí)間約 8 ns。選擇的波長(zhǎng) 1064 nm 使激光束傳播不再通過(guò)水梁的較低的吸收能量。激光脈沖進(jìn)行的交互區(qū)域通過(guò)反射鏡和聚焦透鏡(f?100 毫米),如圖 1 所示。為了得到理想的光斑大小, 工件放置遠(yuǎn)離焦點(diǎn)在適當(dāng)?shù)木嚯x。 圖 3 顯示了試樣的形狀和大小。樣品是削減從商業(yè) cantilever-shape 提供鋁(1060 99.6% 純度)表作為目標(biāo)。采用無(wú)水酒精清潔表面的工件,以及工件的平面度和平滑應(yīng)該保證了波蘭。為了提高材料對(duì)激光的吸收率在彎曲過(guò)程中,樣品通常應(yīng)該涂上黑漆。和水用作透明疊加把生成的等離子體。確保樣本空間的位置,一個(gè)特殊的夾具設(shè)計(jì)工件。一些關(guān)鍵實(shí)驗(yàn)條件和試樣參數(shù)總結(jié)在表 1。 B 結(jié)束位移的非接觸式圖像測(cè)量系統(tǒng)的測(cè)量標(biāo)本立體顯微鏡(Axio 凸輪 ERc5s)精度高和操作簡(jiǎn)單。執(zhí)行所有測(cè)量在長(zhǎng)度方向上表面的邊緣。彎曲位移計(jì)算,認(rèn)為基于測(cè)量數(shù)據(jù)之外的自由端激光沖擊。此外,為了獲得形成深度和表面的激光沖擊地區(qū)的三維形態(tài),測(cè)量系統(tǒng)的真彩色材料共焦顯微鏡顯微鏡與掃描階段(700 年 Axio CSM) Parameters Value Laser energy E (mJ) 675, 1020, 1550 , 1900 Beam diameter ^D (mm) 1.6 Specimen length. L (mm) 18, 16, 14 Specimen width. W ( mm ) 4.6 Specimen thickness, t ( mm ) 0.4 3.2 實(shí)驗(yàn)結(jié)果 圖 4 顯示了燒蝕的保護(hù)涂層(黑漆)在樣品表面,當(dāng)脈沖能量 1900 mJ。它可以發(fā)現(xiàn),激光沖擊微調(diào)后的保護(hù)涂層完好,揭示,輕微的燒蝕的狀態(tài)不會(huì)對(duì)工件質(zhì)量產(chǎn)生不利的影響。 圖 5(a)和(b)顯示了測(cè)量三維表面微形貌的樣品在激光焦點(diǎn)位置 a .它可以發(fā)現(xiàn)光滑的火山口形成和沒(méi)有融化的跡象,燃燒,或消融觀察,也就是說(shuō),非熱能的形成過(guò)程?？梢钥吹?樣品產(chǎn)生塑性變形,工件在 micron-level 具有很高的空間分辨率。黑漆可以保護(hù)工件的熱影響,這樣純粹的機(jī)械效應(yīng)引起的。圖 5(c)顯示樣品的表面輪廓曲線表面隕石坑。有趣的是,變形深度可達(dá) 50 毫米,表明除了彎曲變形,激光能量也可以用于形成 micro-crater 例舉增加抗疲勞強(qiáng)度的激光沖擊微調(diào)過(guò)程中工件。 3.2.1 激光能量的影響 為了確定脈沖能量對(duì)彎曲變形的影響,與厚度 0.4 毫米的鋁標(biāo)本應(yīng)用不同脈沖能量。圖6(a)、(b)、(c)和(d)顯示了最終的形狀的樣品輻照后不同的激光脈沖能量(675 mJ,1020 年喬丹,675 mJ,1900 mJ)。圖 7 顯示彎曲位移之間的關(guān)系和脈沖能量的標(biāo)本。從實(shí)驗(yàn)結(jié)果,可以獲得不同的向下彎曲位移通過(guò)改變激光能量。可以發(fā)現(xiàn),向下彎曲位移增加激光能量從 675 mJ - 1900 mJ。在調(diào)整過(guò)程中,當(dāng)激光束輻照在工件自由的一面,激光誘導(dǎo)沖擊波在工件表面施加機(jī)械壓力和傳授的下行慣性震驚地區(qū)。向下彎曲位移的增加會(huì)提高脈沖能量。高脈沖能量能產(chǎn)生更大的下行慣性在當(dāng)前條件下,樣品免費(fèi)的一面向下運(yùn)動(dòng)期間將繼續(xù)放松,發(fā)揮更大的彎曲位移。因此,可以推斷,我們可以通過(guò)調(diào)整控制彎曲程度的激光能量、激光沖擊和技術(shù)調(diào)整可以申請(qǐng)調(diào)整曲率和形狀的目標(biāo)。 43 河海大學(xué)文天學(xué)院本科畢業(yè)設(shè)計(jì)（論文） 3.2.2 激光焦點(diǎn)位置的影響 如圖 3 所示,三個(gè)激光焦點(diǎn)位置如下:不同工件自由端(圖 3);樣品中間位置(標(biāo)志著圖 3 B); 結(jié)位置在圖 3(C)。圖 8 顯示了三種不同的焦點(diǎn)位置之間的關(guān)系(A、B 和 C)和彎曲位移相同激光能量(1900 mJ)。如圖 8 所示,激光焦點(diǎn)位置在該地區(qū),彎曲位移幾乎達(dá)到了 1800 毫米。然而, 彎曲位移震驚在焦點(diǎn)位置C 減少 77.08 毫米。它可以發(fā)現(xiàn)彎曲位移降低逐漸從 A 到C 彎曲變形的趨勢(shì)的原因之一可能是解釋如下:當(dāng)激光接點(diǎn)位置附近的樣本,彎曲位移減少由于彎矩與XL(增加)。 3.2.3 激光沖擊次數(shù)的影響 為了描述沖擊次彎曲變形的影響,鋁標(biāo)本與厚度 0.4 毫米(單一沖擊能量是 1900 mJ)是應(yīng)用不同的沖擊,和彎曲位移確定。如圖 9 所示(一個(gè)),實(shí)驗(yàn)中使用的三種不同沖擊時(shí)間(1 次,2 次和 3 次)在該地區(qū)的a .它可以發(fā)現(xiàn)彎曲位移與沖擊時(shí)間逐漸增加。通過(guò)激光沖擊次數(shù)的增加,彎曲位移增加向下彎曲。圖 9(b)顯示沖擊次彎曲位移的影響在該地區(qū)的 C,不同于在該地區(qū)的一個(gè)趨勢(shì),彎曲方向該地區(qū)是受沖擊影響的次震驚 C .它可以發(fā)現(xiàn)明顯的彎曲位移是不同凹凸的沖擊時(shí)間從 1 到 5 次。通過(guò)改變沖擊,彎曲位移減少起初向下彎曲,然后變成消極向上彎曲。因此,它是可能的特殊厚度的樣品得到所需的彎曲方向和位移通過(guò)改變沖擊時(shí)間。 4 4 河海大學(xué)文天學(xué)院本科畢業(yè)設(shè)計(jì)（論文） 3.2.4 在政權(quán)配置的影響下 常見的激光沖擊配置使用水約束生成等離子體增強(qiáng)的壓力,和保護(hù)涂層(黑漆),避免表面的燒蝕和融化。工業(yè)應(yīng)用激光過(guò)程大多是依賴這涂層的使用或不被認(rèn)為是一個(gè)關(guān)鍵問(wèn)題。為了描述樣本的行為沒(méi)有保護(hù)層,鋁標(biāo)本與 0.4 毫米厚度應(yīng)用不同脈沖能量。圖 10 顯示彎曲位移之間的關(guān)系和脈沖能量的標(biāo)本沒(méi)有保護(hù)涂層。根據(jù)實(shí)驗(yàn)結(jié)果,可以獲得不同的向下彎曲位移通過(guò)改變激光能量?？梢园l(fā)現(xiàn),向下彎曲位移增加激光能量從 675 mJ - 1900 mJ。與實(shí)驗(yàn)結(jié) 果相比圖 7 所示,當(dāng)震驚與相同的激光能量在焦點(diǎn)位置,裸試樣的彎曲位移小于樣品的保護(hù)涂層?？磥?lái),激光沖擊微調(diào)沒(méi)有保護(hù)涂層也可以應(yīng)用,以及缺乏涂料是一個(gè)負(fù)擔(dān)得起的配置生成合適的彎曲變形,因此授權(quán)更多的靈活性在一個(gè)工業(yè)過(guò)程配置。 然而,在圖 11 中所示(一)-(d),工件表面生成的傷口隕石坑。隨著激光能量的增加,表面燒蝕的程度更加嚴(yán)重。的重大不利影響工件表面質(zhì)量的消融。在缺乏保護(hù)涂層作為犧牲材料避免熱效應(yīng)加熱表面,激光脈沖似乎會(huì)融化或燃燒表面,甚至導(dǎo)致小表面裂縫。因此,根據(jù)現(xiàn)有的結(jié)果,它可以意味著調(diào)整處理涂層會(huì)比沒(méi)有更合適的涂層。 此外,另一個(gè)案例中還應(yīng)該考慮。在這種情況下,樣品沒(méi)有保護(hù)涂層(黑漆)和透明疊加(水) 覆蓋應(yīng)用不同脈沖能量和沖擊時(shí)間。樣品的彎曲位移調(diào)整后不會(huì)被探測(cè)脈沖的能量從 675 mJ - 1900 mJ。當(dāng)三個(gè)激光脈沖在自由端應(yīng)用示例(沖擊地區(qū)),一個(gè)小彎曲位移(向下彎曲位移:375.29 毫米)可以觀察到,伴隨著顯著的消融在工件的表面。這是不可取的,因?yàn)榭偀g工件表面有表面質(zhì)量差,很難保持材料屬性的目標(biāo)。 4 數(shù)值模擬 整個(gè)模擬激光沖擊的調(diào)整是在兩個(gè)模塊:完成 ANSYS / LS-DYNA 和 ANSYS。ANSYS / LS-DYNA 顯式動(dòng)態(tài)分析程序,用于模擬激波的傳播和獲取材料的動(dòng)態(tài)響應(yīng)。采用 ANSYS 通用程序,來(lái)確定樣品的產(chǎn)生的彎曲變形。LS-DYNA 使用的顯式的解決方法提供了快速的短期解決 45 河海大學(xué)文天學(xué)院本科畢業(yè)設(shè)計(jì)（論文） 方案,高速非線性問(wèn)題。當(dāng)樣品材料的動(dòng)態(tài)應(yīng)力狀態(tài)大致穩(wěn)定,所有瞬態(tài)壓力將導(dǎo)入到有限元分析軟件代碼來(lái)執(zhí)行靜態(tài)分析獲取最后的彎曲變形或靜力平衡的殘余應(yīng)力場(chǎng)。因此,我們可以模型結(jié)構(gòu)和獲得顯式動(dòng)態(tài)解決方案通過(guò) LS-DYNA 和審查標(biāo)準(zhǔn) ANSYS 完成靜態(tài)分析后的結(jié)果。結(jié)合策略利用的最佳功能的代碼來(lái)執(zhí)行顯式和隱式分析。 河海大學(xué)文天學(xué)院本科畢業(yè)設(shè)計(jì)（論文） 4.1 控制方程 4.1.1 顯示有限元算法 分析材料的沖擊壓力的反應(yīng)顯式有限元的意思,基于虛功原理、動(dòng)力學(xué)方程在時(shí)間 t[27] 可以表示如下: r 質(zhì)量密度,u_和u€是節(jié)點(diǎn)的速度和加速度,分別u 阻尼系數(shù),杜是虛擬位移,f 我的體力密度、TG 是邊界上的邊界力應(yīng)用G,ij 是柯西應(yīng)力張量,和 D ij?(jtduj 酒后駕車,我)/ 2 是應(yīng)變率張量。 使用標(biāo)準(zhǔn)的有限元程序,Eq。(1)將離散。聚合后,動(dòng)態(tài)平衡方程可以更新如下(27) Mis 的對(duì)角線質(zhì)量矩陣、U€和 U_節(jié)點(diǎn)加速度和速度矢量,分別 C 是對(duì)角阻尼矩陣,弗林特是內(nèi)部元素力向量,Fext 占外部負(fù)載和身體力量。推進(jìn)時(shí)間 tnt1,中心差分時(shí)間集成通常使用如下(27): 中心差分格式是條件穩(wěn)定的,需要時(shí)間步長(zhǎng)不能超過(guò)臨界值。穩(wěn)定臨界值可以定義使用元素長(zhǎng)度勒,和材料的波速 Cd[27]: 4.1.2 隱式有限元算法 根據(jù)虛功原理、平衡方程的隱式算法可以表示如下[28]: 55 年代和 e 應(yīng)力和應(yīng)變張量,分別f 和 TG 身體力密度和邊界力,分別,杜是虛擬位移。使用標(biāo)準(zhǔn)的有限元程序,Eq。(8)將離散。聚合后,一組非線性方程組可以得到如下,要求線性化的牛頓迭代方法[28] K?R OBTDB 做切線剛度矩陣,一般幾何矩陣 B,D 應(yīng)力-應(yīng)變矩陣,杜元素節(jié)點(diǎn)的位移增量, 弗林特?ROBTs 牛頓迭代恢復(fù)力向量和 Fext 等于零的身體力量和外部負(fù)載釋放彈性能量的問(wèn)題。 執(zhí)行靜態(tài)分析之后,一個(gè)穩(wěn)定的殘余應(yīng)力分布和回彈變形場(chǎng)將獲得。假設(shè) Uressurand Ustasur 表面節(jié)點(diǎn)位移模型的動(dòng)態(tài)分析和靜態(tài)分析,分別。然后表面變形模型可以計(jì)算如下[28]: Uressur 是每個(gè)節(jié)點(diǎn)的位移激光沖擊后產(chǎn)生的表面微量調(diào)整。 4.2 的 water-confined 激光產(chǎn)生等離子體加載 根據(jù)水在政權(quán)(WCR)配置研究 Berthe et al .(29),如果目標(biāo)之前一直覆蓋著一層水,沖擊波持續(xù)約 2 倍時(shí)間比激光脈沖持續(xù)時(shí)間由于延遲冷卻階段的等離子體(雖然激光關(guān)閉)。 摘要加載時(shí)間作為 16 ns,即激光脈沖持續(xù)時(shí)間的兩倍。圖 12 給出了計(jì)算激光產(chǎn)生的沖擊壓力。其中 Pmax 是峰值壓力,t0 激光脈沖持續(xù)時(shí)間。 有用的一維模型,提出 Berthe et al .(29),開發(fā)的預(yù)測(cè)在燒蝕模式激光感應(yīng)的壓力。它描述了三個(gè)不同的階段發(fā)生這些限制等離子體(激光加熱、絕熱冷卻和最終擴(kuò)張),并允許估計(jì)在等離子體內(nèi)部的壓力。根據(jù)Berthe et al .,工作壓力脈沖相對(duì)統(tǒng)一整個(gè)表面的激光點(diǎn),也就是說(shuō), 現(xiàn)貨半徑內(nèi),壓力大約是常數(shù)。這個(gè)最大壓力 WCR 激光產(chǎn)生的等離子體是由以下方程: 其中一個(gè)是一小部分的內(nèi)部能源致力于熱能,0 是入射功率密度,和 Z 是減少?zèng)_擊阻抗之間的目標(biāo)和定義的封閉水以下關(guān)系: 4.3 本構(gòu)模型 激光沖擊過(guò)程中微量調(diào)整,目標(biāo)材料受到的沖擊壓力幾 GPa 交互時(shí)間短。材料模型模擬必須考慮材料的行為依賴高應(yīng)變率的模擬高速過(guò)程。此外,吸水層(黑漆)可以保護(hù)目標(biāo)從熱影響,幾乎純粹的機(jī)械效應(yīng)引起的。因此,Johnson-Cook 污點(diǎn)敏感采用塑性模型本構(gòu)方程的顯式模型考慮 highstrain-rate 對(duì)金屬流動(dòng)行為的影響。?馮?米塞斯屈服應(yīng)力,根據(jù) Johnson-Cook 模型可以表示如下(30)： 在 A、B、C 和n 被認(rèn)為是材料常數(shù),e 是等效塑性應(yīng)變,和e_and e_0 是應(yīng)變速率和應(yīng)變率在準(zhǔn)靜態(tài)加載下,分別。以下所需材料的材料特性有限元分析仿真結(jié)果如表 2 所示[31]。 4.4 結(jié)果 激光沖擊微調(diào)是基于一個(gè)傳播的過(guò)程,應(yīng)力波的反射和交互?？偰芰繌耐獠繅毫γ}沖的工作主要是轉(zhuǎn)化為動(dòng)能和內(nèi)部的能量。隨著時(shí)間的增加,動(dòng)能逐漸轉(zhuǎn)化為內(nèi)能,從而導(dǎo)致減少的動(dòng)能、內(nèi)能的增加,如圖 13 所示。動(dòng)能、內(nèi)能和總能量振動(dòng)略,1.2 毫秒后趨于穩(wěn)定。 圖 14 顯示了典型的變形階段 Z-displacement 分布的輪廓。在調(diào)整過(guò)程中,當(dāng)一個(gè)高能聚焦和脈沖激光輻照到工件表面,激光誘導(dǎo)沖擊波在工件表面施加機(jī)械壓力和傳授的下行慣性沖擊壓力的行動(dòng)區(qū),如圖 14 所示(一個(gè))。激光沖擊后停止,這繼續(xù)向下運(yùn)動(dòng)由于慣性的影響。它使震驚區(qū)和塑性變形引起產(chǎn)生彎曲變形,如圖 14 所示(b)和(c)。最后,圖 14(d)所示,最大變形發(fā)生在 1.2 毫秒。 如上所述,緊隨其后的是靜態(tài)分析動(dòng)態(tài)分析。在 1.2 毫秒的壓力動(dòng)態(tài)分析結(jié)果讀入 ANSYS 代碼執(zhí)行靜態(tài)分析獲得殘余應(yīng)力場(chǎng)和回彈變形。圖 15 描述彎曲位移歷史節(jié)點(diǎn) 204 年自由的 模型和預(yù)測(cè)模型變形的輪廓。如圖 15 所示(一個(gè)),自由端彎曲位移的節(jié)點(diǎn)增加的時(shí)間和最后達(dá)到穩(wěn)定狀態(tài)。圖 15(b)顯示了最終的彎曲變形狀態(tài)通過(guò)靜態(tài)分析釋放彈性應(yīng)變。仿真結(jié)果表明,向下彎曲位移的自由邊約 1650 嗯和實(shí)驗(yàn)值是 1766.19 毫米(圖 6 所示(d))。模擬方法產(chǎn)生一個(gè)好的協(xié)議但有點(diǎn)低估了結(jié)果。 圖 16 顯示了 micro-crater 概要文件之間的對(duì)比實(shí)驗(yàn)和數(shù)值結(jié)果。根據(jù)結(jié)果,micro-crater 通過(guò)實(shí)驗(yàn)的變形深度可以達(dá)到深達(dá) 53.109 毫米,而僅通過(guò)仿真獲得的深度達(dá)到 49.3 毫米。此 外,從圖 16 中,可以發(fā)現(xiàn),實(shí)驗(yàn)結(jié)果顯然不是對(duì)稱的。激光脈沖的負(fù)載是不完美在這個(gè)實(shí)驗(yàn)中, 所以 micro-crater 不是軸對(duì)稱變形的。結(jié)果表明,仿真與實(shí)驗(yàn)結(jié)果有很好的一致性,但仍存在一些錯(cuò)誤。 重要的是要突出彎曲的比較資料和位移模型和實(shí)驗(yàn)。模擬和實(shí)驗(yàn)完成當(dāng)激光脈沖的能量是 675 mJ,1020 年喬丹,1550 mJ,分別和 1900 年喬丹。圖 17 顯示了彎曲的概要文件的比較實(shí)驗(yàn)和數(shù)值結(jié)果之間具有不同的能量。雖然實(shí)驗(yàn)數(shù)據(jù)是有限的,由于限制能量的調(diào)整,彎曲的現(xiàn)有結(jié)果概要文件可以暗示有限元分析可以正確預(yù)測(cè)最后 micro-cantilevers 曲率。從圖 18,它可以清楚地發(fā)現(xiàn),激光能量向下彎曲位移產(chǎn)生重大的影響,向下彎曲位移與激光能量增加。結(jié)果表明,仿真與實(shí)驗(yàn)結(jié)果有很好的一致性,但仍然存在一些錯(cuò)誤。 5 結(jié)論 激光沖擊微調(diào)調(diào)整是一個(gè)精確的和非接觸式技術(shù)使用 laser-shock-waves 調(diào)整離散曲率(micro-mechanical 懸臂)。系統(tǒng)研究的術(shù)語(yǔ)進(jìn)行了各種因素對(duì)調(diào)整結(jié)果的影響,包括激光能量、激光焦點(diǎn)位置,激光沖擊次數(shù)和限制制度配置。根據(jù)實(shí)驗(yàn)結(jié)果,可以發(fā)現(xiàn)不同的彎曲角度和彎曲方向可以通過(guò)改變激光加工參數(shù)。調(diào)整過(guò)程,沒(méi)有限制制度配置也可以生成合適的彎曲變形授權(quán)更多的靈活性。但是,在更大的能量的情況下,最終的表面會(huì)消融的跡象,因此導(dǎo)致表面質(zhì)量變差。此外,實(shí)驗(yàn)研究了激光能量對(duì)變形的影響,與實(shí)驗(yàn)獲得的數(shù)據(jù)被用來(lái)驗(yàn)證相應(yīng)的仿真模型。結(jié)果表明,有限元分析可以預(yù)測(cè)最后的曲率 micro-cantilevers 正常。此外,從結(jié)果,激光能量的一部分用于形成micro-crater 震驚表面增加疲勞可取的,因?yàn)樗梢约訌?qiáng)懸臂梁的彎曲強(qiáng)度與彎矩。 總之,通過(guò)調(diào)整激光加工參數(shù)從激光能量激光焦點(diǎn)位置,所需的彎曲角度和彎曲方向可以獲得。這種技術(shù)很容易實(shí)現(xiàn),但非常有用的應(yīng)用程序涉及調(diào)整懸臂的化學(xué)和生物傳感。然而, 很多需要進(jìn)一步建模和實(shí)驗(yàn)工作,才能采用工業(yè)使用。 應(yīng)答 這項(xiàng)工作得到了國(guó)家自然科學(xué)基金（51175235 號(hào)）、江蘇省自然科學(xué)基金（BK2012712） 的優(yōu)先自助的學(xué)術(shù)計(jì)劃。 附錄二： Optics and Lasers in Engineering 51 (2013) 460–471 Numerical simulation and experimentation of adjusting the curvatures of micro-cantilevers using the water-confined laser-generated plasma Chunxing Gu 1, Zongbao Shen 1,23, Huixia Liu, Pin Li, Mengmeng Lu, Yinxin Zhao, Xiao Wang School of Mechanical Engineering, Jiangsu University, Xuefu Road, Zhengjiang 212013, China 1 . Introduction The increasing demands in MEMS fabrication are leading to new requirements in production technology [1–3], especially adjustment of the micro-components, such as micro-mechanical cantilevers, which is widely used as extremely sensitive physical, chemical, and biological sensors [4–7], require high accuracy in positioning, high reproducibility and low production costs. Meeting these demands is still an up-to-date key assignment in micro-manufacturing. Since the traditional mechanical adjustment technologies failed to meet the requirement for their unideal accuracy and time consuming by mechanical forces or dynamic impact forces [8]. There is a need for a precise and contact-free adjustment technology to control the bending angles of some micro-mechanical cantilevers. Laser based microadjustment offers the potential to achieve this. Laser thermal forming, known as a non-contact technique utilizing laser-induced thermal effect to shape melt sample without tooling or external forces, is an example of this [9]. The technique is regarded as the interaction process between 2 Corresponding author. Tel.: t86 0511 8879 7998. E -mail address: szb@ujs.edu.cn (Z. Shen). 1 Chunxing Gu and Zongbao Shen contributed equally to this work. 3 -8166/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.optlaseng.2012.11.002 a r t i c l e i n f o  Laser shock adjustment Curvature adjustment Numerical simulation a b s t r a c t This paper describes a precise and non-contact adjustment technique using the water-confined Article history: Received 10 September 2012 Received in revised form 15 October 2012 Accepted 13 November 2012 Available online 21 December 2012 lasergenerated plasma to adjust the curvature of micro-components (micro-mechanical cantilevers). A series of laser shock micro-adjustment experiments were conducted on 0.4 mm-thick Al samples using pulsed Nd:YAG lasers operating at 1064 nm wavelengths to verify the technical feasibility. Systematic study was carried out in the term of effects of various factors on the adjusting results, including laser energies, laser focus positions, laser shock times and confined regime configuration. The research results have shown that the different bending angles and bending directions can be obtained by changing the laser processing parameters. And, for the adjustment process, the absence of confined regime configuration could also generate suitable bending deformation. But, in the case of larger energy, the final surfaces would have the sign of ablation, hence resulting in poor surface quality. An analysis procedure including dynamic analysis performed by ANSYS/LS-DYNA and static analysis performed by ANSYS is presented in detail to attain the simulation of laser shock micro-adjustment to predict the final bending deformation. The predicted bending profiles is well correlated with the available experimental data, showing the finite element analysis can Keywords: Laser-generated plasma predict the final curvatures of the micro-cantilevers properly.  & 2012 Elsevier Ltd. All rights reserved. temperature field and deformation field which produces a residual strain at the surface of the cantilever material by the temperature gradient [10]. When laser beam irradiates the target surface, the workpiece surface is heated and produces a nonuniform temperature field in the thickness direction. The generated thermal stress is used to achieve plastic deformation such as the bending deformation [11,12]. By changing the laser processing parameters, different bending angles and bending directions are obtained to adjust curvature of the micro-components. Application of the laser thermal forming to the adjust the suspension preload of magnetic recording head stack assemblies was attempted by Singh et al. [13]. Zhangs and Xu [7] used this technique to adjust the curvature of the silicon micro-cantilever. Recently, Griffiths et al. [9] investigated the thermal laser microadjustment using picosecond pulse durations. The previous works show that there are three common forming mechanisms, namely temperature gradient mechanism (TGM), buckling mechanism (BM) and upsetting mechanism (UM) [14–16]. Shen [17] thoroughly investigated the mechanism of laser micro-adjustment. In their work, a coupled TGM and UM were presented to illustrate the thermal mechanical behaviors of two-bridge actuators. However, the thermal forming mechanisms are determined by the laser induced temperature field which is influenced by the geometry of workpiece, laser power, laser beam diameter, scanning velocity, scanning path, etc. It makes the bending direction uncertain and become a hard-to-control process for forming complex shapes and high precision curvature modification [18]. In addition, the thermal effect will result in undesirable microstructure change including recrystallization and phase transformation during the process [19]. Also, it may melt or burn the surface and even result in small cracks on the surface [20]. Therefore, it is hard for laser thermal forming to maintain material properties of bended cantilevers. This paper describes a precise and non-contact adjustment technique using the water-confined laser-generated plasma. The application of laser-shock-waves on thin sheet metal has received more and more attentions [21,22]. It is regarded as a purely mechanical forming method achieved through the laser induced shock waves to modify the target curvature. It has the advantages of laser thermal forming, such as noncontact, tool-free and high efficiency. In addition, its non-thermal process makes it possible to maintain material properties or even improve them by inducing residual stress over the target surface, which is desirable because it is important in industry for shaped target to keep corrosion and fatigue from generating cracks [20–23]. The lasershock-wave induced thin sheet metal bending trends are similar to traditional shot peen forming studied by Kopp and Schulz [24]. Therefore, laser shock micro-adjustment is simple to implement, yet very useful for high-precision curvature adjustment. As such it has potential for widespread application in both the manufacturing and microelectronics industry. Ocan?a’s research groups have studied the suitability of laser micro-bending of thin metal strips by means of ns pulsed lasers [25]. In the present paper, the water-confined laser-generated plasma is used to adjust the curvature of micro-cantilever. A series of laser shock micro-adjustment experiments were conducted in order to investigate the influences of laser energies, laser focus positions, laser shock times and confined regime configuration on the adjusting results. In addition, the practical feasibility of laser shock micro-adjustment of micro-cantilevers was also studied by means of FEM simulations.  The effect of laser energies on the bending deformations was investigated experimentally, and experimental data obtained were then used to validate the corresponding simulation model. The predicted final curvatures of the workpiece were analyzed and compared with the experimental results. 2. Adjustment mechanism As illustrated in Fig. 1, the typical application of laser shock adjustment process is carried out under a confined regime configuration. The target surface is first locally coated with a protective coating and then covered by a transparent overlay (such as water). When a high-energy focused and pulsed laser beam is irradiated onto workpiece surface, the coating is instantaneously vaporized into a high-temperature and high-pressure Fig. 1. The layout of experiment. Fig. 2. Schematic of laser shock micro-adjustment: (a) laser shock loading; (b) generation of bending deformation due to the effect of inertia imparted by shock loading; and (c) final bending deformation occur along with the disappearance of inertia. Fig. 3. Schematic of workpiece (material: Al; dimension: the width W, the length L, the thickness t; focus position: A, B, C). 56 plasma. This ablated plasma expands from the work piece surface and, in turn, exerts mechanical pressure on the workpiece surface, which would induce compressive waves in the workpiece. The protective coating acts as the sacrificial material to avoid the thermal effect from heating the surface, the transparent overlay delays the thermal expansion and confines plasma against the surface of target material, thus generating higher pressure [26]. As shown in Fig. 2, the sample was made in cantilevers-shape with a free side and a fixed side. When the laser beam is irradiating at the free side of the sample (as shown in Fig. 2(a)), the downward shock loading would impart a downward inertia to the shocked region, and the bending deformation is just beginning to generate over the shocked region during laser shock micro-adjustment process because the duration of laser shock is short. When the laser shock is stopped, this downward movement continues due to the effect of inertia to make the shocked region plastically deformed. And, the local plastic deformation in the action zone of the shock pressure would lead to plastically deforming and generating bending deformation finally. The forming behavior can be compared to that of some high energy rate forming process. So we can control the forming degree by adjustment of the laser energy [18]. 3. Adjustment experiment 3.1. Experiment instruments and preparation For experiments, a short pulse Nd-YAG laser with Gaussian distribution beam is used. It is operated at the repetition frequency of 10 Hz and the pulse duration about 8 ns. The wavelength of 1064 nm is selected to enable the laser beam to propagate longer through water with lower absorption of beam energy. The laser pulse is conducted to the interaction area by means of a reflecting mirror and focusing lens (f?100 mm), as shown in Fig. 1. In order to get the desired spot size, the work piece is placed away from the focus at the right distance. Fig. 3 shows the shape and size of specimen. The sample which was cut to cantilever-shape from commercially supplied Aluminum (1060 of 99.6% purity) sheets is used as the target. Anhydrous alcohol was adopted to clean the surface of work piece, and Table 1 The detailed experimental conditions and specimen parameters. Parameters Value Laser energy E (mJ) 675, 1020, 1550 , 1900 Beam