本研究主要使用的材料為Al-Mg系5083鋁合金，為一固溶強化材，具有強度佳、加工易、耐蝕能力強等優點，常被應用於汽車側構骨架之鈑材。但接合時，如使用傳統的電阻點銲進行鋁合金的接合，會因為鋁合金的高電熱傳導性而造成耗電量大、電極壽命降低的問題，故傳統電阻點銲不適用於接合鋁合金，因此可改用摩擦攪拌點銲(FSSW)來進行鋁合金的接合。
本研究探討進行FSSW時，攪拌頭進給深度、摩擦攪拌轉速、摩擦點銲時間對於銲點的拉剪破斷負荷(TSFL)和點銲組織特徵的影響，並且利用相對於5083材合金成分較少的5052材來做為對照。最後，應用韋伯可靠度解析對所得到的實驗數據進行可靠度的分析。
實驗結果顯示，當點銲時間增加時TSFL隨之上升，增加的趨勢會漸趨減緩；隨攪拌轉速上升，TSFL會先陡升再緩降，存在一最適宜的轉速可以讓TSFL達到最高值，進給深度2.5mm時最適宜轉速為2000rpm，進給深度提高至3.5mm則增為3000rpm；進給深度的增加可以大幅的提高TSFL，明顯減少達到預定的TSFL值所需的點銲時間，但進給深度的範圍亦有上限，如過高除了TSFL會略降之外還會造成試片彎曲變形的情形；合金成分較高的5083材本身強度優於5052材，經由摩擦攪拌點銲後所得的TSFL也較高。
研究中定義了五個特徵值，皆與TSFL值呈高度的正相關。當同時考慮測量的效率和相關性大小時則以有效接合長度「Lbond」為最佳的特徵值，相關係數也高達0.959。
韋伯可靠度解析的結果，本研究所有實驗參數韋伯模數m值皆大於1，屬於磨耗破壞型。當攪拌轉速在最適宜轉速以上，並且有足夠的點銲時間時，韋伯模數m值皆可達3以上，呈常態分布。進給深度的提高雖能大幅提高TSFL但對可靠度並無明顯助益；足夠的點銲時間可以使可靠度上升；適宜的轉速下可靠度亦較佳。而綜合所有結果，本研究最佳參數為進給深度3.5mm、攪拌轉速3000rpm、點銲時間10s，點銲耗時短，且可靠度和TSFL皆高。

Al-Mg series aluminum alloy 5083 is the major material in this study. It is a solid-solution strengthening material. Because of its high mechanical strength, easier manufacturing and good corrosion resistance, it has been used in inner panels of side carcass of automobile body. However, traditional resistance spot welding is not suitable for aluminum alloy joining due to higher electric and thermal conductivities of aluminum alloy. It will lead to higher energy consumption and electrode life reduction. Therefore, friction stir spot welding(FSSW) is take the place of resistance spot welding in aluminum alloy joining.
In this research, by changing the pin plunge depth, rotation speed and welding time, we will discuss the effect in tensile shear failure load (TSFL) and microstructure characteristic. And then, we will use 5052, an aluminum alloy which’s composition is lower, to compare with 5083 alloy to understand the effect of composition. Finally, we analyze the reliability of experiment data by using Welbull reliability analysis.
The result of tensile test shows that the TSFL increases with increasing welding time, but the increasing tendency decrease with increasing welding time. When rotation speed increases, TSFL will increases sharply in the beginning and decreases slightly thereafter. TSFL will be a maximum at a most suitable rotation speed. As pin plunge depth is 2.5mm, the most suitable rotation speed is 2000rpm. And as pin plunge depth is 3.5mm, the most suitable rotation speed is 3000rpm. Increasing pin plunge depth will promote TSFL largely and reduce time of welding for predetermined TSFL. But the depth is also limited. And the mechanical strength of lower composition alloy 5052 is lower than 5083 no matter before welding or after welding.
There are five microstructure characteristic value is defined for this research. Their correlation coefficient with TSFL are all larger than 0.94. However, as we also consider to the measure efficiency, “Lbond” is the best microstructure characteristic value. And its correlation coefficient is 0.959.
The results of Weibull analysis show that the Weibull moduli of all the experiment parameters are wear-out failure modes. And the Weibull modili are higher than 3 when rotation speed is higher than the most suitable rotation speed and welding time is plentiful. It means that they are normal distribution. Higher pin plunge depth lead TSFL higher but has no contribution to enhance reliability. And plentiful welding time make TSFL and reliability be higher. Concluding above all the conditons, 3.5 mm pin plunge depth and 3000rpm rotation speed with 10s welding time is the best condition in this study.

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