【作者】 彭本栋；

【导师】 张建；

【作者基本信息】 天津理工大学 ， 材料学， 2008， 硕士

【摘要】 基于保护环境和节约能源方面的考虑,降低车身质量已成为汽车制造业的一个基本发展目标。目前汽车车身轻量化的最重要的方法就是采用新材料以及新的成形方法。由于铝合金板具有密度小,比强度高,耐锈蚀等优点,能满足汽车轻量化的特殊要求,已成为汽车轻量化技术中替代钢板的主要材料。同时在新的成形方法中,拼焊板技术可以优化工件结构,减少材料消耗,对于汽车轻量化起着重要作用,在汽车制造中得到了广泛应用。本文对等厚拼焊镀锌板SGCC的单向拉伸性能进行了研究。针对焊缝处于拉伸试样的不同方位进行了试验,并与母材SGCC的拉伸性能进行了比较,分析了不同焊缝方位对拼焊板拉伸性能的影响。研究表明:当焊缝平行于拉伸方向时,材料在变形过程中容易失稳,同时与母材相比,其断后伸长率较低,板材的拉伸变形能力较差;当焊缝垂直于拉伸方向时,材料在变形过程中不容易失稳,且形状稳定不容易回弹。通过对拼焊镀锌板SGCC拉伸试样断口的测试,分析了拼焊板拉伸试样的断裂机制。研究表明:当焊缝垂直于拉伸方向时,焊缝的断口形貌与母材基本一致,但是其韧窝呈现出不同于母材韧窝的方向性;当焊缝平行于拉伸方向时,焊缝的断口形貌为韧性断裂与解理断裂的混合断裂。通过杯突试验对拼焊镀锌板SGCC的胀形性能进行了测试,并与母材进行了比较,研究了焊缝的移动规律及焊缝对杯突值的影响。试验表明:拼焊镀锌板SGCC的杯突值要低于母材的杯突值;拼焊镀锌板焊缝两侧的材料变形一致,焊缝没有发生偏移;焊缝基本上没有发生变形,仍保持直线型,焊缝的加强筋作用明显。本文还对6061铝合金板的单向拉伸性能、成形性能进行了研究,研究表明:6061铝合金板材具有一定的成形性能,这种板材在单向拉伸过程中受到了双向非均匀应力,容易产生应力集中,但是在胀形过程中为双向应力均匀扩展,成形性能较好;6061铝合金板材在拉伸过程中的强化段会产生锯齿形屈服,导致试件表面上形成类似滑移带的形变花纹而损害产品的外观,所以采用该材料作汽车表面件时,必须避免产生锯齿形屈服;在铝合金板材塑性变形过程中随着变形量逐渐加大时,硬度相应地增加,这一现象可以用位错增殖机理来解释。本文分析了铝合金板材冲压成形过程中有限元模拟的关键技术;利用Dynaform软件分析了铝合金覆盖件在成形过程中的厚度变化、应力和应变分布情况;通过铝合金冲压件的数值模拟结果和实物冲压结果进一步说明了铝合金汽车覆盖件数值模拟的有效性和可行性,也为铝合金板的冲压成形工艺设计提供了科学依据。更多还原

【Abstract】 Based on the consideration of environmental protection and energy conservation, lowering the auto body weight becomes the basic development goals of automotive industry. Nowadays the main methods of light weighting of automotive are the adoption of new materials and forming methods. As aluminum alloy sheets with small density, high strength, corrosion resistance, etc., which meet the specific requirements of lightweight of automobile, it has become the main alternative to steel materials in the technology of lightweight of automobile. And TWB (Tailor Weld Blank) technology can optimize the structure of the workpieces and reduce material consumption, so the TWB technology plays an important role in lightweight of automobile, it has been widely used in automotive industry.In this paper the tensile properties of TWB for SGCC galvanized sheet with same thickness jointed were researched. The tensile tests were carried out with different locations of weld lines in the specimens. Compared with the tensile properties of original materials, the influence of weld line location on formability of the TWB was studied. The research results were shown that when the weld line was paralleled to tensile axis, the deformation of the TWB was uneven, the plastic deformation was poor. Compared with its of original materials, elongation after fracture was poorer. when the weld line was perpendicular to tensile axial, the forming process of the TWB was stable, the shape of materials after drawing was not easy to be rebounded, the plastic deformation of the blank was very good.By the fracture surface scanning test, the research results were shown that the fracture surface was the same as those of welding materials SGCC, but the directions of dimples were different, when the weld line was perpendicular to tensile axial. the fracture was ductile fracture and cleavage fracture, when the weld line was paralleled to tensile axial.The cupping tests were carried out to test the bulging formability of the TWB, which compared with base material, eventually the phenomenon of weld movement during the cup test was discussed. The research results were shown that cupping test value (IE) of the TWB was smaller than that of the base materials, material deformation on both sides of the weld line was same, the weld line didn’t move, the weld line didn’t deform and was still straight line, the weld line had apparent effect as the rebar.In this paper tensile properties and forming properties of 6061 aluminum alloy sheet were investigated. The research results were shown that 6061 aluminum alloy had certain forming capability. When this sheet was subjected to non-uniform biaxial stress in unilateral stretching, this sheet easily occurred stress concentration and brittle rupture, but when this sheet was subjected to biaxial stress and spread even in cup drawing, it appeared excellent formability. When 6061 aluminum alloy is to be processed, it should be avoided to appear bidirectional non-uniform stress. Because 6061 aluminum alloy appeared fluctuation load in strain hardening stage of stretching, it easily brought on tracery that come on surface as a result of slip band, it would damage product appearance. So when 6061 aluminum alloy were made on automotive panel, fluctuation of load must be augmented to avoid.Grain size gradually decreased along with deformation increase in the process of plastic deformation of aluminum alloy sheet, accordingly microhardness will be increased as a result of dislocation multiplication.The key technologies of finite element simulation of 6061 aluminum alloy were used to analyze sheet stress, plastic strain, thick variety analyzed, and the wrinkling and cracking prone areas. Therefore, the effective reference can be provided for the forming process of 6xxx based Alloy auto panel.更多还原