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  本文關鍵詞：擠壓成形7A04合金輪圈軸向和周向力學性能研究　出處：《中北大學》2017年碩士論文　論文類型：學位論文

  更多相關文章： 7A04合金輪圈 拉伸 沖擊 疲勞 斷口形貌

【摘要】：在能源和環(huán)保的雙重要求下,輕量化已成為交通運輸車輛節(jié)能減排的重要手段之一。為此人們通過擠壓成形開發(fā)了重型車輛用鋁合金輪輞,并取得良好效果。為改善擠壓鋁合金輪輞組織,進一步提高其性能,本文借助拉伸試驗、沖擊試驗、疲勞試驗和SEM等方法分別對輪圈軸向和周向的力學性能進行分析,并從輪圈擠壓后的組織來分析引起各向異性的原因,為改進鋁合金輪輞成形工藝提供了參考依據(jù)。主要結(jié)論如下:(1)擠壓成形7A04合金輪圈軸向與周向的拉伸性能相差不大,屈服強度和抗拉強度基本相同。但由于輪圈表面組織中被拉長的晶粒及第二相粒子沿軸向分布,更多的抑制了周向的變形,使其延伸率和斷面收縮率都低于軸向,因此軸向的塑韌性比周向好。(2)輪圈軸向與周向(兩個方向上缺口都在輪圈表面)的沖擊性能也相差不大,這是由于本試驗中沖擊功主要為裂紋擴展功,缺口都在輪圈表面時,軸向與周向的裂紋擴展路徑基本相同,而輪圈表面組織結(jié)構(gòu)對其影響較小,故軸向沖擊功比周向僅大約2%;由于擠壓后的輪圈組織沿厚度方向逐層堆積,缺口在輪圈表面的試樣比缺口在輪圈側(cè)切面的試樣在沖擊斷裂過程中所消耗的能量大,沖擊功高約17.6%,且斷面也更曲折。(3)輪圈軸向與周向的疲勞性能存在差異:周向S-N曲線為S12.658N=6.639×1036,軸向S-N曲線為S12.987N=7.640×1037。軸向的疲勞性能優(yōu)于周向,其中高應力時兩個方向上疲勞壽命相差偏小,低應力時相差偏大。這是由于輪圈表面上晶粒與第二相沿軸向分布,使得周向上裂紋更容易擴展,而軸向裂紋擴展時需切斷纖維組織,有明顯的扭曲現(xiàn)象,不易擴展,且軸向疲勞裂紋形核粒子較大,微裂紋孕育成核階段壽命較高;另外在周向解理臺階上分布有脆性疲勞條帶,具有更明顯的脆性斷裂特征,且相同應力下周向的疲勞條帶間距要大于軸向,應力越小差值越大,故周向的裂紋擴展速率比軸向快,且低應力下相差較多。
[Abstract]:With the requirement of both energy and environmental protection, lightweight has become one of the important means of energy saving and emission reduction of transportation vehicles. So people through the extrusion is developed with Aluminum Alloy rim heavy vehicle, and achieved good results. Aluminum Alloy extrusion and rim organization to improve, improve its performance by means of tensile test, impact test analysis of fatigue test and SEM method respectively on the mechanical properties of the axial and circumferential rim, and extruded from the rim to analyze the cause of anisotropy, in order to improve the Aluminum Alloy forming process provides the reference. The main conclusions are as follows: (1) the tensile properties of 7A04 alloy rim of the axial and circumferential direction difference little extrusion, yield strength and tensile strength are basically the same. But the organization is in the rim surface grain and second phase particles elongated along the axial direction, more circumferential suppression The deformation, the elongation and contraction rates are lower than the axial, so the axial ductility than week for the better. (2) the axial and circumferential rim (two direction of the gap in the rim surface) the impact performance is less, this is due to the impact of the experiment work mainly for crack propagation work the gap in the rim surface, axial and circumferential crack propagation path is basically the same, but the organization structure has little influence on the wheel surface, so the axial impact power ratio is only about 2% weeks to the rim after extrusion; microstructure along the thickness direction of each layer accumulation, notch on the specimen surface than the gap in the circle of wheel rim the side section consumed during impact fracture energy, the impact is too high about 17.6%, and the section is more tortuous. (3) the fatigue performance of axial and circumferential rim difference: circumferential S-N curve for the S12.658N=6.639 * 1036, axial S-N curve was S12.987N=7.640 * 1037. axial fatigue properties than circumferential, including high stress in two directions is the fatigue life of small, low stress is too large. This is because the rim on the surface of grains and second phase axial distribution, makes the circumferential cracks propagate more easily, and the axial crack extension need to cut off the fibrous tissue there are obvious distortions, and not easy to expand, and the axial fatigue crack nucleation for larger particles, the micro crack develops into a higher stage in the life of nuclear; circumferential cleavage steps on the distribution of brittle fatigue striations, brittle fracture has more obvious characteristics, and the same stress next week to the fatigue striation spacing to greater than the axial stress, the smaller the difference is large, so the circumferential crack growth rate is faster than the axial, and low stress are different.

【學位授予單位】：中北大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.21;TG379

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本文編號：1432693