【摘要】：搭接接頭是攪拌摩擦焊(FSW)中常見的接頭形式,在交通運(yùn)輸業(yè)應(yīng)用廣泛。為了改善搭接接頭性能,本文從優(yōu)化攪拌頭形貌的角度出發(fā),設(shè)計(jì)并制作了八種攪拌頭,可分成兩類:變螺紋攪拌頭、變針長攪拌頭。本文以2024-T4鋁合金為研究對(duì)象,對(duì)攪拌頭形貌影響FSW搭接接頭的橫截面形貌與拉剪性能的規(guī)律進(jìn)行詳細(xì)討論�；谧兟菁y攪拌頭的試驗(yàn)結(jié)果發(fā)現(xiàn):全螺紋攪拌頭(F-pin)將材料堆積至攪拌針尖端;尖端半螺紋攪拌頭(T-pin)除了將材料堆積至攪拌針尖端外,螺紋的起始端對(duì)周圍材料有向下的作用力;根部半螺紋攪拌頭(B-pin)在螺紋的末端及攪拌針尖端堆積材料;正反螺紋攪拌頭(R-pin)的材料堆積區(qū)主要位于焊核區(qū)中部。拉剪試驗(yàn)結(jié)果表明:當(dāng)前進(jìn)側(cè)受力時(shí),在不同轉(zhuǎn)速下T-pin均可獲得最高的斷裂載荷值;當(dāng)后退側(cè)受力時(shí),T-pin所得接頭的斷裂載荷值均比B-pin與R-pin高�；谧冡橀L攪拌頭的試驗(yàn)結(jié)果表明:當(dāng)針長為3mm時(shí),前進(jìn)側(cè)的hook缺陷幾乎呈水平分布,而后退側(cè)包鋁層向焊核中心延伸較多;當(dāng)針長增加至4mm時(shí),形成了明顯向上彎曲的hook缺陷與cold lap缺陷;當(dāng)針長為5mm時(shí),hook缺陷和cold lap缺陷的高度有所減少,且cold lap缺陷向焊核區(qū)延伸的距離減小。拉剪試驗(yàn)結(jié)果表明:相同轉(zhuǎn)速下針長由3mm增加至5mm后,斷裂載荷先減小后增加;當(dāng)針長為3mm時(shí),接頭斷裂載荷值最高,前進(jìn)側(cè)與后退側(cè)受力模式分別達(dá)到20825N與25665N。為了消除hook缺陷,本文采用了針長為2mm的攪拌頭,以不扎透上板的方式成功地實(shí)現(xiàn)了搭接接頭的有效連接,其斷裂載荷為12185N。
[Abstract]:Lap joint is a common joint form in friction stir welding (FSW), and is widely used in transportation industry. In order to improve the performance of the lap joint, eight kinds of mixing heads are designed and manufactured from the point of view of optimizing the shape of the mixing heads. They can be divided into two types: variable thread mixing head and variable needle length mixing head. In this paper, taking 2024-T4 aluminum alloy as an object of study, the effects of mixing head morphology on cross section morphology and tensile shear properties of FSW lap joints are discussed in detail. Based on the experimental results of the variable thread mixing head, it is found that the full thread mixing head (F-pin) accumulates the material to the tip of the mixing needle, and the tip half thread stirring head (T-pin) accumulates the material to the tip of the needle. The starting end of the thread has downward force on the surrounding material, the root half threaded stirring head (B-pin) accumulates at the end of the thread and the tip of the stirring needle, and the material accumulation area of the positive and inverse thread stirring head (R-pin) is mainly located in the middle of the nuke zone. The results of tensile and shear tests show that T-pin can obtain the highest fracture load value at different rotational speeds and the fracture load value of T-pin joint is higher than that of B-pin and R-pin when the back side is loaded. The experimental results based on the variable-pin length mixing head show that when the needle length is 3mm, the hook defects on the forward side are almost horizontally distributed, while the aluminum coating on the receding side extends more to the core of the weld, and when the pin length is increased to 4mm, The hook defects and cold lap defects with obvious upward bending are formed, and the height of hooks and cold lap defects decreases when the pin length is 5mm, and the distance from cold lap defects to the nugget zone decreases. The results of tensile shear test show that when the pin length increases from 3mm to 5mm at the same rotational speed, the fracture load decreases first and then increases, and when the pin length is 3mm, the fracture load of the joint is the highest, and the stress modes of the forward and backward sides reach 20825N and 25665N, respectively. In order to eliminate the defect of hook, a mixing head with the length of 2mm is adopted in this paper, and the effective connection of the lap joint is successfully realized in the way of not penetrating the upper plate. The fracture load of the lap joint is 12185N.
【學(xué)位授予單位】：沈陽航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG453.9

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本文編號(hào)：2145537