1060铝合金多点—柔性模圆柱面弯曲成形回弹规律研究

发布时间：2019-01-18 21:39

【摘要】：多点-柔性模成形是一种新型的模具可重构技术,结合了多点成形和软模成形的优点,改善了板材成形的表面质量并显著减小了回弹,柔性下模的使用简化了模具结构和操作流程,降低了生产周期和成本。对其成形过程中板材变形特点和变形规律的研究可为改善板材成形精度,提高多点成形技术的经济性提供有益参考,为模具可重构技术的拓展和应用提供一定的理论基础。本文选用圆柱面为研究对象,采用数值模拟和实验研究相结合的方法,探讨了多点-柔性模成形中聚氨酯和板材的变形过程和特点,以此为依据研究了板材弯曲变形规律,揭示了多点-柔性模成形中回弹减小机理,获得了板材回弹及成形轮廓几何信息的理论计算方法,并采用1060铝合金板材的实验结果进行验证。结果表明:边部优先成形中压头支反力随着到对称中心距离的增大而逐渐增大,心部优先成形与之相反;板材弯矩随着附加应力的增大和反复弯曲作用的增强而减小,从而导致回弹减小;反复弯曲作用下板材成形后的截面轮廓由曲率半径不等的圆弧相切而成,且优先成形区域的回弹更小。多点-柔性模成形中板材在不同成形方式、不同变形顺序下的受力和变形特点不同,采用单一变量法,系统地研究了在无预加载成形和预加载成形两种成形方式下及边部优先成形和心部优先成形两种变形顺序下,不同因素对回弹的影响规律。采用回弹位移和回弹曲率两种方法表征板材回弹大小,结合理论分析和数值模拟结果,从应力应变分布、弯矩分布、支反力变化及聚氨酯流动速度变化等方面分析了板材变形特点,揭示了多点-柔性模成形抑制回弹的机理。结果表明:同无预加载成形方式相比较,预加载成形时板材回弹更小,回弹减小了53.25%;无预加载成形和预加载成形中不同因素对回弹的影响规律一致,随着板材屈服强度和弹性模量比值的减小,目标曲率半径及聚氨酯硬度的减小,板材回弹减小;随着预加载量、板材厚度及聚氨酯厚度的增大,板材成形精度提高;采用厚板及流动性较好的聚氨酯柔性模成形时,板材回弹较小;无预加载成形和预加载成形时,回弹位移预修正总量随着到对称中心距离的增大分别沿抛物线和四次多项式曲线变化,两次回弹位移预修正后,板材回弹位移平均值分别减小了93.40%和97.85%,验证了回弹位移预修正在提高板材成形精度方面的优越性。
[Abstract]:Multi-point flexible die forming is a new kind of reconfigurable die technology, which combines the advantages of multi-point forming and soft die forming, improves the surface quality of sheet metal forming and significantly reduces springback. The use of flexible lower die simplifies die structure and operation flow and reduces production cycle and cost. The study on the deformation characteristics and rules of sheet metal in the forming process can provide a useful reference for improving the forming accuracy and the economy of multi-point forming technology, and provide a certain theoretical basis for the expansion and application of the reconfigurable die technology. In this paper, the deformation process and characteristics of polyurethane and sheet metal in multi-point flexible die forming are discussed by using the method of numerical simulation and experimental study, and the bending deformation law of sheet metal is studied based on the cylindrical surface. The mechanism of springback reduction in multi-point flexible die forming is revealed. The theoretical calculation method of springback and geometric information of forming profile is obtained, and the experimental results of 1060 aluminum alloy sheet are used to verify it. The results show that the reaction force of the head support increases with the distance from the center to the center of the center, but the center of the center is the opposite. The bending moment of the plate decreases with the increase of the additional stress and the reinforcement of the repeated bending action, which leads to the reduction of the springback. The section profile of sheet metal formed after repeated bending is tangent by circular arc with different curvature radius, and the springback of priority forming region is smaller. In multi-point flexible die forming, the stress and deformation characteristics of sheet metal under different forming modes and different deformation sequences are different. The single variable method is used. The effects of different factors on springback are studied systematically under the two kinds of forming modes without preloading and preloading, and the deformation sequence of edge preforming and center preforming. Springback displacement and springback curvature are used to characterize the springback size of the plate. Combined with theoretical analysis and numerical simulation results, the stress-strain distribution and bending moment distribution are analyzed. The deformation characteristics of sheet metal were analyzed in terms of the change of support reaction force and the change of polyurethane flow velocity, and the mechanism of restraining springback by multi-point flexible die forming was revealed. The results show that the springback of the sheet metal is smaller and the springback decreases by 53.2525 when compared with the non-preloading forming method. The effect of different factors on springback is the same as that in non-preloading forming and preloading forming. With the decrease of yield strength and elastic modulus ratio, the radius of curvature and the hardness of polyurethane, the springback of sheet metal decreases. With the increase of preloading, the thickness of sheet and the thickness of polyurethane, the forming precision of sheet is improved, and the springback of sheet is smaller when the thick plate and flexible polyurethane die with good fluidity are used. When there is no preloading and preloading, the total amount of springback displacement precorrection changes along parabola and quartic polynomial curves with the increase of the distance from the center to the symmetric center, and after the pre-correction of the twice springback displacement, The average springback displacement is reduced by 93.40% and 97.85% respectively, which proves the superiority of pre-correction of springback displacement in improving the forming accuracy of sheet metal.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG306

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