本文關(guān)鍵詞：高速列車用7XXX系高強(qiáng)鋁合金焊接接頭的疲勞行為研究　出處：《上海工程技術(shù)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： A7N01鋁合金 焊接接頭 棘輪效應(yīng) 疲勞裂紋 滑移帶 循環(huán)軟化

【摘要】：A7N01高強(qiáng)鋁合金為典型的7×××系高強(qiáng)鋁合金,由于具有良好的性能,被廣泛應(yīng)用于高速列車的車身中,其疲勞行為的研究對(duì)高速列車的安全運(yùn)行具有重要意義,通過(guò)對(duì)A7N01鋁合金焊接接頭及其各個(gè)區(qū)域進(jìn)行疲勞試驗(yàn),對(duì)焊接接頭顯微硬度和顯微組織以及疲勞后斷口表面和試樣表面疲勞損傷形貌進(jìn)行觀察分析,得出了以下幾點(diǎn):A7N01鋁合金焊接接頭在單軸低周疲勞作用下產(chǎn)生了棘輪效應(yīng),結(jié)果表明,在循環(huán)初期,棘輪效應(yīng)顯著,特別是在第一循環(huán)內(nèi),材料發(fā)生明顯的較大的塑性變形;在循環(huán)中期,棘輪應(yīng)變速率減慢,棘輪應(yīng)變較小,但棘輪應(yīng)變?nèi)允俏⒘鸭y增長(zhǎng)的驅(qū)動(dòng)力;在循環(huán)后期,材料內(nèi)部空洞長(zhǎng)大、裂紋擴(kuò)展速度增加,材料內(nèi)部的應(yīng)力集中更加明顯,導(dǎo)致材料的承載能力降低,最終導(dǎo)致了試樣的疲勞失效。A7N01鋁合金焊接接頭在疲勞過(guò)程中主要為循環(huán)軟化為主,應(yīng)力大小不同,軟化階段占整個(gè)疲勞過(guò)程的比例不同,應(yīng)力越小,達(dá)到循環(huán)穩(wěn)定階段所需的時(shí)間越長(zhǎng),當(dāng)應(yīng)力小于一定值時(shí),整個(gè)階段都處于循環(huán)軟化狀態(tài),當(dāng)應(yīng)力大到一定程度時(shí),沒(méi)有循環(huán)軟化階段,反而在循環(huán)初始階段表現(xiàn)出循環(huán)硬化現(xiàn)象。焊接接頭的疲勞塑性變形主要發(fā)生在焊縫部位,焊縫的疲勞損傷主要以滑移帶開裂為主,而熱影響區(qū)疲勞損傷主要為含F(xiàn)e、Si較多的粗大硬質(zhì)化合物在疲勞作用下與基體分離或化合物破碎產(chǎn)生疲勞裂紋。當(dāng)應(yīng)力較大時(shí),焊縫部位變形明顯,很容易導(dǎo)致滑移開裂,熔合線部位應(yīng)力也較為集中,熱影響區(qū)硬質(zhì)相與基體更容易擠壓分離,所以各個(gè)區(qū)域可能為疲勞試樣失效位置;當(dāng)應(yīng)力較小時(shí),由于焊縫塑性相對(duì)較好,熱影響區(qū)硬質(zhì)相在疲勞過(guò)程中對(duì)試樣的破壞作用相對(duì)較大,試樣一般在熱影響區(qū)斷裂。由于受熱循環(huán)作用的影響,熱影響區(qū)內(nèi)粗大化合物粒子里Fe、Si元素的含量為母材的3倍,使粒子更硬更脆,所以熱影響區(qū)的疲勞性能遠(yuǎn)不及母材的疲勞性能。
[Abstract]:A7N01 high strength aluminum alloy is a typical 7 脳 脳 脳 series high strength aluminum alloy. Because of its good performance, A7N01 is widely used in the body of high-speed train. The study of fatigue behavior is of great significance for the safe operation of high-speed trains. The fatigue tests of A7N01 aluminum alloy welded joints and its various regions are carried out. The microhardness and microstructure of welded joints and the fatigue damage morphology of fracture surface and specimen surface after fatigue were observed and analyzed. The following points have been obtained: the ratchet effect of the welded joints of the aluminum alloy at the following points is produced under uniaxial low cycle fatigue. The results show that the ratchet effect is significant at the initial stage of the cycle, especially in the first cycle. Obvious plastic deformation occurs in the material; In the middle of cycle, ratchet strain rate slows down, ratchet strain is smaller, but ratchet strain is still the driving force of microcrack growth. In the later stage of the cycle, the cavity grows, the crack growth speed increases, and the stress concentration inside the material becomes more obvious, which results in the decrease of the loading capacity of the material. Finally, the fatigue failure of the specimen. A7N01 aluminum alloy welded joints in the fatigue process is mainly cyclic softening, the stress size is different, softening phase accounts for different proportion of the whole fatigue process, the smaller the stress. When the stress is less than a certain value, the whole stage is in the state of cyclic softening, and when the stress is large enough, there is no cycle softening stage. The fatigue plastic deformation of welded joints mainly occurs in the weld, and the fatigue damage of weld is mainly caused by slip band cracking. However, the fatigue damage in the heat-affected zone is mainly caused by the fatigue crack of coarse hard compound containing more Fe-Si under fatigue action. When the stress is high, the deformation of weld is obvious. It is easy to lead to slip and crack, and the stress in the fusion line is also concentrated. The hard phase and matrix are more easily separated by extrusion in the heat affected zone, so each region may be the failure position of fatigue specimen. When the stress is small, due to the relatively good plasticity of the weld, the hard phase in the heat-affected zone has a relatively large failure effect on the specimen during the fatigue process, and the specimen is generally fractured in the heat-affected zone, which is affected by the effect of thermal cycling. The content of Fe ~ (2 +) Si in the coarse compound particles in the heat affected zone is 3 times of that of the base metal, which makes the particles harder and more brittle, so the fatigue performance of the heat affected zone is far less than that of the base metal.
【學(xué)位授予單位】：上海工程技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG407

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 王柏齡;全鋁車身的研究及發(fā)展[J];汽車工業(yè)研究;2000年06期

2 ;Ageing Effect on Hardness and Microstructure of Al-Zn-Mg Alloys[J];Journal of Materials Science & Technology;2000年03期

3 關(guān)紹康,姚波,王迎新;汽車鋁合金車身板材的研究現(xiàn)狀及發(fā)展趨勢(shì)[J];機(jī)械工程材料;2001年05期

4 ;Fatigue crack initiation for Al-Zn-Mg alloy welded joint[J];Acta Metallurgica Sinica(English Letters);2012年03期

5 鄧波;鐘毅;起華榮;張家濤;;7NO1鋁合金高速反向擠壓實(shí)驗(yàn)研究[J];云南冶金;2006年04期

6 王希靖;張忠科;李晶;達(dá)朝炳;;Plastic flow pattern and its effect in friction stir welding of A2024 and A1060[J];Transactions of Nonferrous Metals Society of China;2006年S3期

7 蹇海根;姜鋒;文康;蔣龍;黃宏鋒;韋莉莉;;Fatigue fracture of high-strength Al-Zn-Mg-Cu alloy[J];Transactions of Nonferrous Metals Society of China;2009年05期

8 嚴(yán)軍;高明;曾曉雁;;激光-MIG復(fù)合焊接2A12鋁合金工藝和接頭性能[J];中國(guó)有色金屬學(xué)報(bào);2009年12期

9 張紅霞;吳廣賀;閆志峰;裴飛飛;李晉永;王文先;李永蓮;;5A06鋁合金及其焊接接頭的疲勞斷裂行為[J];中國(guó)有色金屬學(xué)報(bào);2013年02期

10 何振波;彭勇宜;尹志民;雷學(xué)鋒;;Al-Mg-Mn-Sc-Zr合金板材攪拌摩擦焊和氬弧焊焊接接頭的對(duì)比(英文)[J];Transactions of Nonferrous Metals Society of China;2011年08期

相關(guān)會(huì)議論文 前1條

1 丁俊;康國(guó)政;劉宇杰;郭嚴(yán);;35CrMo鋼單軸棘輪-疲勞交互作用實(shí)驗(yàn)研究[A];中國(guó)力學(xué)學(xué)會(huì)學(xué)術(shù)大會(huì)'2009論文摘要集[C];2009年

相關(guān)碩士學(xué)位論文 前1條

1 李超;16MnR鋼單軸棘輪效應(yīng)實(shí)驗(yàn)及預(yù)測(cè)[D];天津大學(xué);2009年

，

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