【摘要】：激光點(diǎn)焊—膠接復(fù)合技術(shù)憑借著自身良好的結(jié)構(gòu)適應(yīng)性,以及接頭優(yōu)良的綜合力學(xué)性能,在航空、航天和汽車等領(lǐng)域具有很大的應(yīng)用前景。但是,由于膠粘劑的氣化溫度較低,在激光的熱作用下會(huì)產(chǎn)生大量氣體沖擊熔池,使復(fù)合連接過程存在著較大的不穩(wěn)定性。目前,通常會(huì)采用一些輔助措施的方式控制膠粘劑氣化。另外,目前對于點(diǎn)焊—膠接復(fù)合接頭力學(xué)性能以及應(yīng)力分布的研究,無法很好地揭示復(fù)合接頭的斷裂機(jī)制。本文以此為研究目標(biāo),以低碳鋼Q195,和三種不同的膠粘劑J-11、AD-1301和Terokal-5089為試驗(yàn)材料,提出了利用組合脈沖的激光點(diǎn)焊—膠接復(fù)合連接的工藝,并對工藝和所獲復(fù)合接頭斷裂行為進(jìn)行了系統(tǒng)的研究。首先,研究組合脈沖激光對于膠層氣體的控制。試驗(yàn)結(jié)果表明,利用低功率長時(shí)間的預(yù)氣化脈沖,在保證金屬上板未熔透的前提下,使焊接區(qū)域下方的膠層氣化,并在焊接區(qū)域形成足夠大的“無膠區(qū)域”,達(dá)成無膠焊接的目的。通過系統(tǒng)的工藝試驗(yàn),證明了利用預(yù)氣化脈沖控制膠層氣化的可行性,成功地解決了激光點(diǎn)焊—膠接復(fù)合連接工藝過程中膠層氣化對熔池的沖擊問題。并且提出了實(shí)現(xiàn)膠層預(yù)氣化過程的三個(gè)判定條件:1、預(yù)氣化過程中上板金屬不能熔透;2、膠層達(dá)到受力平衡狀態(tài)時(shí),膠層氣體壓力不足以沖擊熔池;3、膠層達(dá)到受力平衡狀態(tài)時(shí),所形成的無膠區(qū)域尺寸大于點(diǎn)焊熔合面尺寸。并以此建立預(yù)氣化脈沖的工藝模型,優(yōu)化預(yù)氣化脈沖的工藝參數(shù)以及確定本工藝條件下膠粘劑粘度的最大值。進(jìn)一步,開展對于激光點(diǎn)焊—膠接復(fù)合接頭斷裂機(jī)制的研究,解釋復(fù)合接頭力學(xué)性能變化的原因,獲得復(fù)合接頭力學(xué)性能的主要控制因素。通過對膠接接頭、激光點(diǎn)焊接頭和激光點(diǎn)焊—膠接復(fù)合接頭的靜載和動(dòng)載力學(xué)性能進(jìn)行測試,證明激光點(diǎn)焊—膠接復(fù)合接頭具有優(yōu)秀的綜合力學(xué)性能。在靜載試驗(yàn)中,相比于點(diǎn)焊接頭,拉剪載荷提高140%,剝離載荷提高17%,抗彎載荷提高33%,相比于膠接接頭,拉剪載荷提高12%,剝離載荷提高336%,抗彎載荷提高47%;在動(dòng)載力學(xué)性能測試中,激光點(diǎn)焊—膠接復(fù)合接頭所表現(xiàn)出的性能與膠接接頭較為接近,明顯優(yōu)于激光點(diǎn)焊接頭,且疲勞斷口表明,復(fù)合接頭的疲勞性能主要依賴膠接部分。在拉剪力學(xué)性能測試的基礎(chǔ)上,建立了激光點(diǎn)焊—膠接復(fù)合接頭拉剪過程的動(dòng)態(tài)斷裂有限元計(jì)算模型。分析了復(fù)合接頭的拉剪斷裂過程,證明復(fù)合接頭兩個(gè)膠接端面是受力的關(guān)鍵位置。并且解釋了復(fù)合接頭承載能力提高的原因:焊點(diǎn)的加入,焊點(diǎn)的存在提高了接頭的彈性模量,降低了承載過程中搭接界面的相對位移,增強(qiáng)了連接界面的抗裂能力,從而提高復(fù)合接頭的承載能力。利用斷裂模型,計(jì)算分析了膠層彈性模量、膠接斷裂位移、膠接斷裂強(qiáng)度等特性對復(fù)合接頭拉剪性能的影響。證明了影響激光點(diǎn)焊—膠接復(fù)合接頭性能的主要因素是膠層的膠接斷裂強(qiáng)度。分析了焊點(diǎn)排布方式對復(fù)合接頭斷裂過程的影響,證明焊點(diǎn)可以阻礙裂紋在復(fù)合接頭膠接界面內(nèi)的擴(kuò)展,當(dāng)與受力方向串行排列時(shí),可以使復(fù)合接頭內(nèi)的膠層開裂過程產(chǎn)生遞次斷裂的現(xiàn)象。
[Abstract]:The laser spot-welding glue-bonding composite technology has a great application prospect in the fields of aviation, space and automobile by virtue of good structural adaptability and excellent comprehensive mechanical property of the joint. However, because the gasification temperature of the adhesive is low, a large amount of gas is generated to impact the molten pool under the action of the laser, so that the composite connection process has great instability. Currently, some of the auxiliary measures are used to control the gasification of the adhesive. In addition, the fracture mechanism of the composite joint can not be well disclosed for the study of the mechanical properties and the stress distribution of the spot-welded composite joint. In this paper, using the low-carbon steel Q195 and three different adhesives, J-11, AD-1301 and Tekal-5089 as the test materials, the technology of using the combined pulse to spot-weld the composite joint was put forward, and the fracture behavior of the composite joint was studied. First, the control of the combined pulse laser on the gas of the glue layer is studied. The test results show that the glue layer under the welding area is gasified under the premise of ensuring that the upper plate of the metal is not fused, and a sufficient 鈥渘on-adhesive area鈥，

本文編號：2314669