【摘要】：在工程結(jié)構(gòu)和機(jī)械設(shè)備中,疲勞破壞現(xiàn)象遍及每一個(gè)運(yùn)動的零部件,隨著服役時(shí)間的延長,會在表面產(chǎn)生微裂紋,最終發(fā)展成導(dǎo)致結(jié)構(gòu)破壞的宏觀裂紋。然而裂紋修復(fù)方法很多,但都不盡如人意。本文提出一種新的思路用于裂紋的修復(fù),即攪拌摩擦裂紋修復(fù)。針對2A12鋁合金表面裂紋實(shí)施攪拌摩擦修復(fù),通過理論分析和試驗(yàn)觀測相結(jié)合的方法得出了攪拌摩擦裂紋修復(fù)工藝區(qū)間,并研究了疲勞壽命和裂紋擴(kuò)展行為。首先,通過修復(fù)工藝試驗(yàn)確立合理的工藝區(qū)間。將修復(fù)后平板制成疲勞試樣和裂紋擴(kuò)展試樣進(jìn)行力學(xué)性能測試;利用OM(光學(xué)顯微鏡)、SEM(掃面電鏡)對修復(fù)區(qū)進(jìn)行金相分析、斷口形貌觀察。通過疲勞試驗(yàn)機(jī)測得不同工藝參數(shù)修復(fù)試樣的疲勞壽命和裂紋擴(kuò)展速率。結(jié)果表明:試樣在ν=70-110mm/min、ω=700-1100rpm范圍內(nèi)可以獲得較好的修復(fù)效果,其中參數(shù)S1100-V110疲勞壽命最低達(dá)44800,參數(shù)S700-V110壽命最高可達(dá)632713,預(yù)制裂紋試樣壽命僅有5147。其次,將最優(yōu)工藝參數(shù)進(jìn)行裂紋修復(fù)后進(jìn)行熱處理,對比修復(fù)試樣與修后熱處理試樣的力學(xué)性能。進(jìn)行疲勞壽命試驗(yàn)和裂紋擴(kuò)展試驗(yàn),結(jié)果表明修復(fù)件壽命達(dá)到632713,熱處理后疲勞壽命提升至853356,修復(fù)件與修后熱處理件疲勞壽命分別達(dá)到母材的36.98%和49.89%。斷口觀察發(fā)現(xiàn),未經(jīng)過熱處理的試樣,穩(wěn)定擴(kuò)展階段由于攪拌摩擦打碎的晶粒而無法形成明顯的疲勞條帶,但在經(jīng)過熱處理以后晶粒、第二相、夾雜重新固溶于母材,修復(fù)區(qū)在穩(wěn)定擴(kuò)展階段有大量疲勞條帶出現(xiàn),瞬斷區(qū)韌窩也比未經(jīng)熱處理試樣要大。最后,研究了裂紋修復(fù)位置對于疲勞壽命的影響。將裂紋置于攪拌頭的前進(jìn)側(cè),返回側(cè)和中間分別進(jìn)行修復(fù),試驗(yàn)結(jié)果:位于前進(jìn)側(cè)時(shí)的疲勞壽命達(dá)14928,位于返回側(cè)時(shí)的疲勞壽命達(dá)到153927,裂紋位于返回側(cè)試樣的疲勞壽命是前進(jìn)側(cè)試樣疲勞壽命的10.31倍,而裂紋位于中間時(shí),修復(fù)試樣疲勞壽命為632713,是返回側(cè)修復(fù)試樣的4.11倍。斷口分析:看出裂紋位于前進(jìn)側(cè)修復(fù)區(qū)分為上下兩層,由于沒有受到攪拌頭的直接作用,晶粒沒有被充分打碎再結(jié)晶,形成絮流狀材料,而亞表面充分打碎再結(jié)晶,于是形成雙層修復(fù)區(qū),裂紋位于返回側(cè)和中間試樣斷口相似。
[Abstract]:In engineering structures and mechanical equipment, fatigue failure occurs all over every moving part. With the extension of service time, micro-cracks will appear on the surface and eventually develop into macroscopic cracks that lead to structural failure. However, there are a lot of crack repair methods, but they are not satisfactory. In this paper, a new idea is proposed for crack repair, that is, friction stir crack repair. Friction stir repair for surface crack of 2A12 aluminum alloy was carried out. By means of theoretical analysis and experimental observation, the process interval of friction stir crack repair was obtained, and the fatigue life and crack propagation behavior were studied. First of all, through the repair process test to establish a reasonable process interval. The mechanical properties of fatigue specimen and crack propagating specimen were tested, and the fracture morphology was observed by means of OM (optical microscope) SEM (scanning electron microscope). Fatigue life and crack growth rate of different process parameters were measured by fatigue testing machine. The results show that the sample can be repaired in the range of S1100-V110 70-110mm / min, 蠅 -700-1100rpm. The fatigue life of parameter S1100-V110 is the lowest 44800, the maximum of parameter S700-V110 is 632713, and the life of precast crack specimen is only 5147. Secondly, the optimum process parameters were heat treated after crack repair, and the mechanical properties of the repaired specimen were compared with that of the repaired sample. The fatigue life test and crack growth test showed that the life of the repaired part reached 632713, the fatigue life of the repaired part increased to 853356 after heat treatment, and the fatigue life of the repaired part and the heat-treated part reached 36.98% and 49.89% of the base metal respectively. The fracture surface observation shows that in the stable extension stage of the sample without heat treatment, the obvious fatigue band can not be formed due to the grain broken by friction stir, but after the heat treatment, the grain, the second phase, the inclusion are dissolved again in the base metal, A large number of fatigue bands appeared in the repair zone during the stable growth stage, and the dimples in the transient fracture zone were larger than those in the untreated specimens. Finally, the effect of crack repair location on fatigue life is studied. The crack is placed on the front side of the mixing head, and the return side and the middle side are repaired separately. The results show that the fatigue life at the forward side is 14928, the fatigue life on the return side is 153927, the fatigue life of the specimen on the return side is 10.31 times that on the forward side, and the crack is in the middle. The fatigue life of the repaired specimen is 632713, 4.11 times longer than that of the return side. Fracture analysis: it can be seen that the crack repair at the forward side is divided into two layers. Due to the direct action of the agitator, the grain is not sufficiently smashed and recrystallized to form the floc flow material, while the sub-surface sufficiently shatters the recrystallization. A double layer repair zone is formed, and the crack is similar to the fracture surface of the intermediate specimen at the return side.
【學(xué)位授予單位】：沈陽航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.21;TG453.9

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 曹景竹;王祝堂;;鋁合金在航空航天器中的應(yīng)用(1)[J];輕合金加工技術(shù);2013年02期

2 王國慶;趙剛;郝云飛;陳雪峰;趙衍華;;2219鋁合金攪拌摩擦焊縫匙孔形缺陷修補(bǔ)技術(shù)[J];宇航材料工藝;2012年03期

3 王快社;林兆霞;周龍海;孔亮;王文;;攪拌摩擦加工鑄態(tài)鋁鐵合金的顯微組織[J];中國有色金屬學(xué)報(bào);2012年05期

4 王磊;朱建軍;張偉;王詠;馮杏梅;馮展鷹;;一種雷達(dá)冷板泄漏的摩擦修復(fù)方法[J];電子機(jī)械工程;2012年01期

5 劉會杰;張會杰;;Repair welding process of friction stir welding groove defect[J];Transactions of Nonferrous Metals Society of China;2009年03期

6 師小紅;徐章遂;康健;;基于斷裂力學(xué)的疲勞裂紋擴(kuò)展速率公式研究[J];機(jī)械設(shè)計(jì)與制造;2007年10期

7 晁小練;楊祖培;杜宗罡;康超;楊莉莉;;自修復(fù)技術(shù)及自修復(fù)復(fù)合材料[J];塑料科技;2006年01期

8 徐崇義,李念奎;2×××系鋁合金強(qiáng)韌化的研究與發(fā)展[J];輕合金加工技術(shù);2005年08期

9 楊守杰;戴圣龍;;航空鋁合金的發(fā)展回顧與展望[J];材料導(dǎo)報(bào);2005年02期

10 王大勇,馮吉才,狄歐,劉會杰;鋁合金攪拌摩擦焊接頭焊核區(qū)等軸再結(jié)晶組織的形成機(jī)制[J];焊接學(xué)報(bào);2003年04期

，

本文編號：2165507