【摘要】：多點成形是一種新型的板材柔性成形技術,目前已經廣泛應用于航空航天、船體外板、汽車覆蓋件、建筑外觀等制造領域。隨著板材加工技術的不斷發(fā)展,人們對產品的個性化要求也越來越高,因此本文提出柔性拉邊多點對壓成形技術。它是利用多點模具對金屬板材進行對壓成形,采用四周拉邊的方式,由離散夾鉗夾緊板材,并對板材施加垂直板材方向的正壓力和平行板材方向的拉邊力,保證夾鉗與板材始終不發(fā)生脫離現(xiàn)象,從而成形出復雜曲面件的一種板材加工方法。與其他沖壓技術相比,該技術不僅可以成形出質量更好、形狀更加復雜的曲面件,還可以通過調整上、下基本體群的模具型面實現(xiàn)板材的快速成形。本文詳細介紹了柔性拉邊多點成形工藝的研究背景、基本原理及設備結構。以球形件和馬鞍件為例,利用ABAQUS有限元分析軟件建立了板材柔性拉邊多點對壓成形有限元模型,并對不同的工藝參數(shù)進行了一系列的數(shù)值模擬分析。具體研究內容如下:1.以球形件和馬鞍件為例,建立了剛性壓邊、柔性壓邊和柔性拉邊三種多點對壓成形工藝的有限元模型,并對其數(shù)值模擬結果進行了詳細的對比分析。結果表明:剛性壓邊多點成形得到的成形件的直壁區(qū)出現(xiàn)應力集中現(xiàn)象,容易出現(xiàn)拉裂缺陷;柔性壓邊多點成形得到的成形件邊緣區(qū)處的柔性壓邊圈與工件曲面變化趨勢一致,但其應力應變不均勻,邊角處容易出現(xiàn)起皺缺陷;柔性拉邊多點成形得到的成形件邊緣區(qū)處的離散夾鉗排列方式與板材變形趨勢一致,應力應變分布均勻,不易出現(xiàn)拉裂和起皺缺陷,成形效果最好。2.研究了夾鉗數(shù)量、拉邊力、材料參數(shù)及摩擦系數(shù)對柔性拉邊多點成形結果的影響。結果表明:離散夾鉗的數(shù)量越多,成形件應力應變越均勻,工件的質量越好;在一定范圍內,拉邊力越大,板材受力時材料流動性越好,成形件變形越均勻;與2024鋁板相比,屈服強度較大的08AL鋼板容易得到質量較好的成形件;摩擦系數(shù)越小,彈性墊和金屬板材之間的接觸阻力越小,板材變形時內部金屬流動性更好,成形效果也更好。3.研究了彈性墊厚度對柔性拉邊多點成形結果的影響。結果表明:彈性墊厚度越大,成形后工件的表面接觸應力越小,分布越均勻,壓痕缺陷逐漸消失,但是其精度會隨之下降。
[Abstract]:Multi-point forming is a new type of sheet metal flexible forming technology, which has been widely used in aerospace, hull outer plate, automobile panel, building appearance and other manufacturing fields. With the development of sheet metal processing technology, the individuation requirement of products is becoming more and more high, so this paper puts forward the flexible edge drawing multi-point pressing forming technology. It uses multi-point die to press the sheet metal, uses the way of drawing the edge around, clamps the plate by the discrete clamp, and exerts the positive pressure in the vertical direction of the plate and the pull force in the direction of the parallel plate. It is ensured that the clamping clamp and the sheet metal do not break away from each other at all times, thus forming a kind of sheet metal processing method for complex curved surface parts. Compared with other stamping technologies, this technology can not only produce better quality and more complicated curved surface, but also realize rapid forming of sheet metal by adjusting the top and bottom basic body groups' die surfaces. In this paper, the research background, basic principle and equipment structure of flexible edge drawing multipoint forming process are introduced in detail. Taking spherical parts and saddle parts as examples, the finite element model of multi-point compression forming for flexible edge drawing of sheet metal was established by using ABAQUS finite element analysis software, and a series of numerical simulation analysis for different technological parameters were carried out. The specific research contents are as follows: 1. Taking spherical parts and saddle parts as examples, the finite element models of rigid blank holder, flexible blank holder and flexible edge drawing are established, and the numerical simulation results are compared and analyzed in detail. The results show that the stress concentration in the straight wall of the forming parts obtained by multi-point forming with rigid blank holder is obvious, and the tensile cracks are easy to appear. The change trend of the flexible edge holder is the same as that of the workpiece surface, but the stress and strain are not uniform, and the wrinkle defect is easy to appear at the edge corner. The discrete clamp arrangement at the edge of the forming part obtained by flexible drawing multi-point forming is consistent with the deformation trend of the sheet metal, the stress and strain distribution is uniform, the defects of tensile crack and wrinkle are not easy to appear, and the forming effect is the best. 2. The effects of the number of clamps, drawing force, material parameters and friction coefficient on the multi-point forming results of flexible edge drawing were studied. The results show that the more the number of discrete clamps, the more uniform the stress and strain of the forming parts, the better the quality of the workpiece, the greater the drawing force, the better the material fluidity and the more uniform the deformation of the forming parts. Compared with 2024 aluminum sheet, the 08AL sheet with higher yield strength is easy to obtain the forming parts with better quality. The smaller the friction coefficient, the smaller the contact resistance between the elastic pad and the sheet metal, the better the metal fluidity and the better forming effect when the sheet is deformed. The effect of the thickness of elastic pad on the results of flexible edge drawing multipoint forming was studied. The results show that the greater the thickness of the elastic pad, the smaller the surface contact stress, the more uniform the distribution, and the less the indentation defect is, but the lower the precision is.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG306

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