本文選題：攪拌摩擦焊 + 數(shù)值模擬　； 參考：《南京航空航天大學》2017年碩士論文

【摘要】：本文通過數(shù)值模擬與實驗研究相結合的方法,研究了6061-T6鋁合金對接攪拌摩擦焊的溫度場與流場,對6061-T6鋁合金與T2紫銅異種材料進行攪拌摩擦焊對接,探索了溫度場對焊接接頭組織及性能的影響。研究過程首先是建立了攪拌摩擦焊的二維模型,其中除了包含最基本的質(zhì)量和動量連續(xù)方程模型,還有熱量方程模型,能夠?qū)附拥哪Σ廉a(chǎn)熱和塑形變形產(chǎn)熱、焊接過程中的熱傳導、板材與空氣間的熱交換進行求解。模型對攪拌針周圍網(wǎng)格進行非結構性劃分,采用了自適應網(wǎng)格(動網(wǎng)格),能夠通過不斷地消除和生成網(wǎng)格,使攪拌針壁面實現(xiàn)像實驗中一樣的水平運動。模型耦合了歐拉多相流模型,將實驗中的鋁定義為第一相,鋅和銅分別定義為第二相進行雙相求解。通過設置邊界條件和編譯用戶自定義功能,將材料的包括粘度、散熱系數(shù)在內(nèi)的各種物理參數(shù)均耦合到了模型中,以獲得更加精確的實驗結果。在6061-T6鋁合金的焊接過程中,在焊縫前進側(cè)中間高度上加入小的鋅塊,以求獲得實驗的示蹤效果,并在模型中也有所體現(xiàn)。通過熱電偶的溫度記錄與模型的計算可知,在焊接過程中鋅發(fā)生了熔化,并對溫度場造成一定的影響,但這有限的溫度影響并不影響焊縫流動行為的觀察研究。通過結合分析焊縫攪拌針附近的節(jié)點運動矢量圖和跡線圖,可以得出攪拌針附近材料的三條基本運動軌跡,分別是攪拌針周圍順時針渦流、焊縫后退側(cè)右前方逆時針渦流和攪拌針后端順時針渦流。這些渦流的存在,使得焊縫中的材料混合更加充分,焊縫力學性能更加均勻。在6061-T6鋁合金與T2紫銅的對接實驗過程中,實驗記錄了焊接過程中的溫度變化,但用模擬得到的溫度云圖更能反映攪拌針周圍的溫度場變化。銅一側(cè)產(chǎn)熱較少,熱傳導快,熱容也相對較低,使得遠離焊縫處銅相對鋁一側(cè)的溫度較高,而在焊縫中心能量無法聚集,使得銅一側(cè)流動性降低。通過給銅一側(cè)設置外加熱源,增加該側(cè)的焊縫中心溫度,提升了焊縫材料的流動性。當焊縫流動性較差時,焊接的熱加工過程易生成鋁銅的中間相化合物,并堆積在銅一側(cè)的熱機影響區(qū)附近,使得該區(qū)域硬度值上升,而抗拉強度急劇降低。流動性較好時,只生成少量的中間相,并且大部分中間相流動到焊縫中去,減少了銅一側(cè)中間相的堆積,提升抗拉強度。
[Abstract]:In this paper, the temperature field and flow field of 6061-T6 aluminum alloy butt friction stir welding are studied by means of numerical simulation and experimental study. Friction stir welding of 6061-T6 aluminum alloy and T2 copper dissimilar material is carried out. The effect of temperature field on the microstructure and properties of welded joints was investigated. First of all, the two-dimensional model of friction stir welding is established, which includes not only the most basic mass and momentum continuum model, but also the heat equation model, which can generate heat for friction and plastic deformation of welding. Heat conduction during welding, heat exchange between plate and air is solved. The model uses adaptive mesh (moving mesh) to divide the meshes around the needle into non-structural ones. It can eliminate and generate the mesh continuously and make the wall of the agitated needle achieve the same horizontal motion as in the experiment. The Euler multiphase flow model is coupled. Aluminum is defined as the first phase in the experiment, and zinc and copper are defined as the second phase for two-phase solution. By setting boundary conditions and compiling user-defined functions, various physical parameters, including viscosity and heat dissipation coefficient, are coupled to the model to obtain more accurate experimental results. In the welding process of 6061-T6 aluminum alloy, a small zinc block was added to the middle height of the forward side of the weld in order to obtain the experimental tracer effect, which was also reflected in the model. Through the temperature record of the thermocouple and the calculation of the model, it can be seen that zinc melts in the welding process and has a certain effect on the temperature field, but this limited temperature effect does not affect the observation and study of the flow behavior of the weld. By analyzing the joint motion vector diagram and trace chart, three basic motion trajectories of the material near the needle can be obtained, one is clockwise swirl around the needle, and the other is the clockwise eddy current around the needle. Weld receding side right front counterclockwise eddy current and mixing needle back end clockwise eddy current. Due to the existence of these eddies, the materials in the weld are more fully mixed and the mechanical properties of the weld are more uniform. During the docking experiment between 6061-T6 aluminum alloy and T2 copper, the temperature change in welding process was recorded, but the temperature cloud diagram obtained by simulation could reflect the temperature field around the stirring needle more effectively. The heat production on the copper side is less, the heat conduction is fast, and the heat capacity is relatively low, which makes the temperature of copper far away from the weld seam higher than that of the aluminum side, while the energy in the center of the weld cannot be accumulated, which makes the fluidity of the copper side decrease. By setting the additional heat source on the copper side, the center temperature of the weld seam is increased and the fluidity of the weld material is enhanced. When the fluidity of weld is poor, the mesophase compound of aluminum and copper is easily formed in the hot working process of welding, and it accumulates near the influence zone of heat engine on the side of copper, which makes the hardness value of this area increase and the tensile strength decrease sharply. When the fluidity is good, only a small amount of mesophase is generated, and most of the mesophase flows into the weld, which reduces the accumulation of mesophase on the copper side and enhances the tensile strength.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG453.9

【參考文獻】

相關期刊論文 前8條

1 吳小偉;沈以赴;李博;周冠男;姚磊;胡偉葉;;鋁—銅攪拌摩擦焊搭接焊縫共晶組織形成與抑制[J];焊接學報;2014年01期

2 孫飛龍;李曉剛;盧琳;萬紅霞;杜翠薇;劉智勇;;銅合金在中國南海深海環(huán)境下的腐蝕行為研究[J];金屬學報;2013年10期

3 張新明;劉勝膽;;航空鋁合金及其材料加工[J];中國材料進展;2013年01期

4 馬鳴圖;游江海;路洪洲;王志文;;鋁合金汽車板性能及其應用[J];中國工程科學;2010年09期

5 張滿;;鋁/銅異種材料焊接的研究現(xiàn)狀[J];熱加工工藝;2009年09期

6 佟建華;李煉;鄧冬;萬發(fā)榮;;6061-T6鋁合金薄板的攪拌摩擦焊接[J];北京科技大學學報;2008年09期

7 肖代紅;黃伯云;宋e，

本文編號：2067405