【摘要】：鋁合金板料因其質(zhì)量輕、密度低、耐腐蝕、比強度高等特點,使其在汽車白車身中得到廣泛應用。汽車白車身的制造精度影響到裝配精度、車輛NVH、駕駛體驗以及車輛的壽命。而沖壓工藝作為汽車白車身制造的重要工藝之一,其工藝參數(shù)的制定將顯著影響鋁合金成形的性能。本文考慮到鋁合金板料具有應變率敏感性的力學特性,提出壓邊力—沖壓速度成形窗口的概念。利用壓邊力—沖壓速度成形窗口對鋁合金板料成形中的壓邊力和沖壓速度的合理范圍進行限制,從而避免起皺與破裂。此外,在壓邊力—沖壓速度成形窗口中構(gòu)建最佳回彈控制壓邊力—沖壓速度加載曲線,以此抑制材料的回彈問題。首先,本文從壓邊力成形窗口的概念出發(fā),引申出壓邊力—沖壓速度成形窗口的概念,并提出壓邊力—沖壓速度成形窗口的基本形式和構(gòu)建方法。其次,進行必要的材料力學測試實驗和摩擦性能測試實驗。通過不同應變率下的單向拉伸試驗,研究應變率對力學性能的影響,并建立相應的真實應力—應變本構(gòu)模型。進行剛模脹形實驗,分析成形極限曲線和最大拉深深度與沖壓速度關系。在不同的正向載荷和滑動速率的作用下進行銷盤摩擦實驗,觀察不同工藝條件下的表面摩擦質(zhì)量,分析摩擦系數(shù)和摩擦表面質(zhì)量的變化規(guī)律。再者,建立盒形件拉深的有限元模型,從而構(gòu)建壓邊力—沖壓速度成形窗口。通過MATLAB樣條函數(shù)內(nèi)插法,將不同沖壓速度下的臨界起皺壓邊力成形曲線和臨界破裂壓邊力成形曲線,分別擬合為臨界起皺壓邊力—沖壓速度成形曲面和臨界破裂壓邊力—沖壓速度成形曲面。并且,將該兩種臨界條件下的成形曲面合并為壓邊力—沖壓速度成形窗口。最后,從單向拉伸試驗的回彈現(xiàn)象出發(fā),分析回彈的一般性規(guī)律;并在安全裕度控制下的壓邊力—沖壓速度成形窗口內(nèi),設計最佳回彈控制壓邊力—沖壓速度成形曲線,以此抑制鋁合金板料的回彈量。
[Abstract]:Aluminum alloy sheet is widely used in automobile body because of its light weight, low density, corrosion resistance and high specific strength. The manufacturing accuracy of the car's white body affects assembly accuracy, vehicle NVH, driving experience, and vehicle life. The stamping process is one of the most important processes in automobile white body manufacturing, and the formulation of its process parameters will significantly affect the forming properties of aluminum alloy. In this paper, considering the mechanical properties of aluminum alloy sheet with strain rate sensitivity, the concept of blank holder force-stamping speed forming window is put forward. In order to avoid wrinkling and cracking, the reasonable range of blank holder force and stamping speed in aluminum alloy sheet forming is limited by using blank holding force and stamping speed forming window. In addition, the best springback control beam-pressing speed loading curve is constructed in the blank holding force-stamping speed forming window to suppress the springback problem of materials. Firstly, from the concept of blank holding force forming window, this paper generalizes the concept of blank holder force stamping speed forming window, and puts forward the basic form and construction method of blank holder force stamping speed forming window. Secondly, the necessary material mechanics test and friction performance test are carried out. The effect of strain rate on mechanical properties was studied by uniaxial tensile test at different strain rates, and the corresponding true stress-strain constitutive model was established. The forming limit curve and the relationship between the maximum drawing depth and the stamping speed were analyzed by the bulging experiment of the rigid die. The friction experiments were carried out under different positive loads and sliding rates to observe the surface friction quality under different technological conditions and to analyze the variation of friction coefficient and friction surface quality. Furthermore, the finite element model of box drawing is established to construct the blank holder-stamping speed forming window. By means of MATLAB spline function interpolation, the critical wrinkle blank holder forming curve and the critical fracture blank holder forming curve at different stamping speeds are obtained. The surface is fitted as critical wrinkling beam-pressing speed forming surface and critical fracture beam-pressing speed forming surface respectively. Furthermore, the forming surface under these two critical conditions is combined into a blank holder-stamping speed forming window. Finally, from the springback phenomenon of uniaxial tensile test, the general law of springback is analyzed, and the optimum springback control beam-blank-pressing velocity forming curve is designed in the blank-holder forming window controlled by safety margin. In this way, the springback of aluminum alloy sheet is restrained.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG389

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本文編號：2196269