本文選題：7N01鋁合金 + 角焊縫��； 參考：《哈爾濱工業(yè)大學(xué)》2017年碩士論文

【摘要】：我國的高速列車研發(fā)及生產(chǎn)正處于快速發(fā)展的階段,Al-Zn-Mg系合金中的7N01鋁合金在滿足輕量化制造要求的同時由于其優(yōu)秀的力學(xué)性能廣泛應(yīng)用在高速列車車體底架的枕梁、抗蛇形運動減震器等關(guān)鍵部位。由于輕量化及抗形變等性能的要求,在進行焊接時通常只能采取含角焊縫的焊接接頭實現(xiàn)連接,復(fù)雜的多維應(yīng)力載荷和接頭結(jié)構(gòu)使得接頭成為車體底架聯(lián)系的關(guān)鍵和薄弱部位。本研究中通過對7N01鋁合金搭接、T型、十字(聯(lián)系焊縫)、十字(工作焊縫)接頭及其厚板性能的綜合性能探究,為高速列車的高質(zhì)量制造提供了科學(xué)性依據(jù)。為了探究含角焊縫的焊接接頭在多向承載的服役過程中的性能,對四種接頭進行對比性多角度的靜力學(xué)性能及組織分析,得到了接頭間抗拉強度、彎曲性能、接頭內(nèi)各局部區(qū)域顯微性能的對比性結(jié)果。從微觀組織角度分析了宏觀性能方面的差異,對角焊縫接頭靜載性能進行了綜合性總結(jié)。針對高速列車中焊接結(jié)構(gòu)的主要破壞形式即疲勞失效行為,為了探究不同類型角焊縫接頭之間疲勞性能的差異,對四種接頭進行了不同最高應(yīng)力等級的疲勞性能實驗,計算得到了各接頭的疲勞性能并進行對比,對產(chǎn)生疲勞斷裂的試件進行宏觀及掃描電鏡微觀形貌觀察分析,分析了疲勞由源區(qū)到擴展區(qū)直至發(fā)生瞬斷的破壞過程。結(jié)合疲勞性能實驗中四種接頭出現(xiàn)的對比性疲勞強度結(jié)果以及疲勞試件均斷裂于焊趾而非焊根這一規(guī)律性現(xiàn)象。基于缺口應(yīng)力法,利用有限元模擬軟件Abaqus/CAE對四種接頭具體模型進行擬合,模擬缺口局部位置的應(yīng)力分布狀態(tài),計算出對應(yīng)區(qū)域的缺口應(yīng)力強度因子,通過相關(guān)理論轉(zhuǎn)化為平均能應(yīng)變能密度并進行對比,得到各接頭局部平均應(yīng)變能密度即應(yīng)力分布與其疲勞極限值成反比,基于缺口應(yīng)力法建立平均應(yīng)變能密度與疲勞壽命之間的關(guān)系。作為焊接母材的厚板鋁合金為軋制過程而來,由于焊接熱過程的應(yīng)力及低熔物質(zhì)聚集的影響,在焊接加工過程中可能會產(chǎn)生液化裂紋等危險破壞。為了探究這一失效形式的傾向性,進行了Z向窗口試驗,放大了角焊縫對厚板鋁合金的拘束作用,通過掃描電鏡線掃描對層間液化位置的低熔點物質(zhì)元素含量分布進行分析,結(jié)合高溫延性理論得出垂直于鋁合金軋制方向為其高溫承載危險取向。
[Abstract]:The development and production of high speed train in China is in the stage of rapid development. The 7N01 aluminum alloy in Al-Zn-Mg series alloy can meet the requirements of lightweight manufacturing, and its excellent mechanical properties are widely used in the sleeper beam of the frame of high-speed train body because of its excellent mechanical properties. Anti-snake motion shock absorber and other key parts. Due to the requirement of lightweight and anti-deformation, welding joints with fillet welds can only be welded. The complex multi-dimensional stress load and joint structure make the joint become the key and weak part of the frame connection. In this study, the comprehensive properties of 7N01 aluminum alloy lap T type, cross (joint weld), cross (working weld) joints and their thick plates were investigated, which provided scientific basis for high quality manufacture of high speed trains. In order to investigate the performance of welded joints with fillet welds in the service process of multi-direction bearing, the static properties and microstructure of four kinds of joints were analyzed at different angles, and the tensile strength and bending properties of the joints were obtained. Comparative results of the microscopic properties of the local areas in the joints. The differences in macroscopic properties were analyzed from the point of view of microstructure, and the static load properties of fillet weld joints were summarized. In view of the fatigue failure behavior of welded structure in high-speed train, in order to explore the difference of fatigue performance among different types of fillet weld joints, four kinds of joints with different highest stress levels were tested. The fatigue properties of the joints were calculated and compared. The microscopic morphology of the specimens with fatigue fracture was observed and analyzed, and the failure process from the source region to the spreading region to the transient fracture was analyzed. In combination with the comparative fatigue strength results of the four joints in the fatigue performance test and the regularity that the fatigue specimens are broken at the weld toe instead of the weld root. Based on the notch stress method, four specific models of joints are fitted by finite element simulation software Abaqus/CAE, and the stress distribution of the local position of the notch is simulated, and the notch stress intensity factor in the corresponding region is calculated. The local average strain energy density of the joints is inversely proportional to the fatigue limit value of the joints, which is transformed into the average strain energy density by the relevant theory and compared with the local average strain energy density of the joints. The relationship between average strain energy density and fatigue life is established based on notch stress method. The thick plate aluminum alloy, which is the base metal of welding, comes from rolling process. Because of the stress of welding heat process and the effect of low melting material accumulation, liquefaction crack and other dangerous damage may occur in welding process. In order to explore the tendency of this failure form, the Z-direction window test was carried out to amplify the restraint effect of the fillet weld on the thick plate aluminum alloy, and the distribution of the low melting point material elements in the liquefaction position between the layers was analyzed by scanning electron microscope (SEM) line scanning. Combined with the theory of high temperature ductility, it is concluded that the direction perpendicular to the rolling direction of aluminum alloy is the dangerous orientation of high temperature bearing capacity.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG407

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