铸态7075铝合金筒形件强力热反旋基于扩径的成形极限研究

发布时间：2018-03-18 01:02

本文选题：铸态7075铝合金　切入点：强力热反旋　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：铸态7075铝合金所具有的低密度、高比强、耐高压、耐腐蚀等优点,已成为近年来研究较多的难成形材料之一。筒形件强力热反旋成形,不仅可以有效地减小零件的设计壁厚、减轻重量、提高疲劳性能,而且可消除铸造缺陷、细化晶粒提高塑性,已成为铸态7075铝合金筒形件成形的最有效的方法之一。然而,铸态7075铝合金筒形件在强力旋压过程中经常出现的扩径,是旋压中的重要缺陷之一,严重影响旋压件成形质量和成形精度的提高。因此,本文基于ABAQUS有限元仿真平台建立并优化了相关有限元模型,研究了工艺参数对筒形件扩径度的影响规律,并获得了筒形件各道次强力热反旋过程的最优工艺参数和基于扩径的成形极限。本文主要研究内容与研究结果如下:(1)基于ABAQUS/Explicit平台,解决了有限元建模过程中的关键技术(如旋轮参数的选择,高温条件下铸态7075铝合金材料本构的建立,接触条件、加载条件和网格划分的建立),建立了符合实际且稳定的铸态7075铝合金多道次强力热反旋有限元模型,并通过实验验证了所建立模型的可靠性。(2)基于所建立的有限元模型,研究了工艺参数(旋轮进给速度、各道次减薄量、芯模温度、芯模转速、芯模与筒形件间摩擦和旋轮与筒形件间摩擦)对筒形件扩径度的影响规律,结果表明:随着旋轮进给速度的增大,前三道次的扩径度随之增大,第四道次的扩径度先减小后增大;随着各道次减薄量的增加,扩径度都基本表现出增长的趋势;各道次的扩径度随着芯模温度的升高都呈现先减小后增大的趋势;随着芯模转速的增加,第一道次和第四道次的扩径度随之先减小后逐渐增大,第二道次和第三道次的扩径度变化并不明显;随着芯模与筒形件间摩擦系数的增大,第一道次和第二道次的扩径度呈现先减小后逐渐增大的趋势,而第三道次和第四道次的扩径度出现增大的趋势;旋轮与筒形件间摩擦的增大对各道次扩径度影响较小。基于上述研究,得到各工艺因素的最佳取值范围。(3)采用有限元模拟、正交试验与响应面法建立了工艺参数与扩径耦合关系模型,从而得出各个道次基于扩径的最优工艺参数值为:第一道次旋压成形过程的最优工艺参数为减薄量为2.522mm,芯模温度为276.3℃,旋轮进给速度为0.521mm/s;第二道次旋压成形过程的最优工艺参数为减薄量为1.757mm,芯模温度为214.8℃,旋轮进给速度为0.726mm/s;第三道次旋压成形过程的最优工艺参数芯模与筒形件间摩擦系数为0.079,芯模温度为138.7℃,减薄量为1.478 mm;第四道次旋压成形过程的最优工艺参数为芯模转速为3.864r/s,芯模温度为108.3℃,芯模与筒形件间摩擦系数为0.061。(4)基于上述耦合关系模型,建立了各道次基于扩径的成形极限预测模型,并研究了扩径度影响显著因素对扩径成形极限的影响规律:第一道次的成形极限随着旋轮进给速度的增大,呈现先增大后减小的趋势;第二道次的成形极限随着旋轮进给速度的增大先减小后增大,随芯模温度的增大而增大;第三道次的成形极限随着芯模温度的增大而减小,随芯模与筒形件间摩擦系数的增大而增大;第四道次的成形极限随着芯模温度的增大而增大,随芯模与筒形件间摩擦系数的增大而增大。基于上述研究,建立了筒形件强力热反旋过程基于扩径的成形极限图。
[Abstract]:Low density cast 7075 Aluminum Alloy with the high specific strength, high pressure resistance, corrosion resistance and other advantages, has become more difficult to form the research in recent years. One of the material cylinder hot power backward spinning process, the design of wall not only can effectively reduce the thickness of parts, reduce weight, improve the fatigue performance, but also can eliminate the casting defects, grain refinement and plasticity, has become one of the 7075 Aluminum Alloy cast cylinder forming the most effective method. However, the as cast 7075 Aluminum Alloy cylindrical parts often appear in the spinning process of expanding, is one of the most important defects in spinning, spinning forming quality and serious influence improving the forming accuracy. Therefore, this paper ABAQUS finite element simulation platform was established and optimized based on finite element model, studied the influence of process parameters on the expanding of a cylinder, and the optimal tube pass strong thermal reverse rotation process The process parameters and the forming limit based on expanding. The main research contents and results are as follows: (1) based on the ABAQUS/Explicit platform, to solve the key technology of the finite element modeling process (such as roller parameters, under the condition of high temperature cast 7075 Aluminum Alloy material constitutive model established, contact conditions, loading conditions and the grid, the establishment) practical and stable cast 7075 Aluminum Alloy multipass hot power spinning finite element model is established, and tested the reliability of the model. (2) based on the established finite element model, the effects of process parameters (feed speed, each time thickness, core temperature, rotational speed of mandrel, the mandrel and the cylinder friction between the roller and the cylinder friction) influences, expanding a degree of cylinder showed that with the increase of feed speed, the first three times the diameter increasing, Fourth times the diameter of the first decreases and then increases with the increase of each pass; thinning ratio, expanding degree basically showed a growth trend; each pass is expanding with the increase of core temperature will increase firstly and then decrease with the increase of rotational speed of mould; the first line and fourth times the diameter decreases and then increases gradually along with the degree of change in diameter, second times and third times the expansion is not obvious; with the increase of friction coefficient between the mandrel and the cylinder, the first and the second times of the diameter of first decreases gradually increasing trend. The third pass and fourth passes of the expanding degree appeared increasing trend; the roller and the cylinder friction between the increase of the expansion of small size effect. Based on the above research, the optimal range of various process factors. (3) by using the finite element simulation, orthogonal test and response surface method the establishment of the industry The parameters and expanding coupling model, so that each pass the optimal process parameters of expanding based on Value: first pass spinning forming process parameters for optimal thinning quantity is 2.522mm, core temperature is 276.3 DEG C, the roller feed speed is 0.521mm/s; the optimum process parameters of second pass spinning forming process for the reduction of 1.757mm, mold temperature is 214.8 DEG C, the roller feed rate is 0.726mm/s; third pass spinning forming process of friction coefficient of the optimal process parameters of the mandrel and tube is 0.079, mold temperature 138.7 C, reduction of 1.478 mm; fourth pass spinning the optimal process parameters for the mandrel speed is 3.864r/s, core temperature is 108.3 DEG C, the mandrel and the cylinder friction coefficient between 0.061. (4) model based on the coupling relationship, establishes each pass based on expanding the forming limit prediction model, and study the expansion Influence of significant factors influence on the diameter of the expanding limit: the first forming limit with the increase of feed speed, first increased and then decreased; second times with the increase of the forming limit of roller feed rate decreases first and then increases, increases with increasing core temperature; the forming limit of third times decreased with increasing core temperature, coefficient increased with the increase of the mandrel and the cylinder friction; forming limit fourth times increases with the increase of core temperature, with the mandrel and the cylinder friction coefficient increase increases. Based on the above research a tube, hot power backward spinning process of forming limit diagram based on expanding.

【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG306

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