7055铝合金厚板淬火残余应力的测量与数值模拟

发布时间：2018-03-18 13:10

  本文选题：7055铝合金　切入点：淬火残余应力　出处：《北京有色金属研究总院》2016年硕士论文　论文类型：学位论文

【摘要】：7055铝合金属于可热处理强化的Al-Zn-Mg-Cu系变形铝合金,具有超高强度和良好的综合性能,其厚板产品被国际上广泛应用于航空航天等领域重要结构件的制造。7055铝合金厚板在航空用户使用过程中存在着因残余应力偏大导致结构件机加工过程中易出现变形超差甚至开裂的问题。淬火残余应力是厚板中残余应力存在的源头,本文针对7055铝合金厚板淬火残余应力分布规律开展测量与数值模拟研究,可为其工业化生产工艺的优化制定提供实验基础,研究工作具有实用价值和理论意义。对比研究了X射线衍射法和钻孔法测量表征7055铝合金厚板表面淬火残余应力的可靠性。与X射线衍射法相比,钻孔法测量结果的稳定性较好,适于7055铝合金厚板表面残余应力的测量。采用裂纹柔度法测量分析了7055铝合金厚板内部淬火残余应力的分布规律。淬火残余应力沿厚度方向轧向分应力和横向分应力的分布规律相似,均表现出表面为压应力状态,心部为拉应力状态;表面应力的轧向分应力最大值为-110MPa,横向分应力最大值为-140MPa,心部应力的轧向分应力最大值为130MPa,横向分应力最大值为115MPa。采用钻孔法系统测量评价了7055铝合金厚板在不同淬火条件(淬火介质种类、温度和浓度)下表面淬火残余应力的变化规律。淬火介质(20℃)的冷却能力顺序为:15%PAG10%PAG5%PAG水10%NaCl;随水温或PAG浓度的升高,厚板表面淬火残余应力水平降低;水温从20℃升至80℃时,厚板表面淬火残余应力轧向分应力值从-187.1MPa降低到-88.0MPa,横向分应力值从-225.7MPa降低到-45.3MPa,表面淬火残余应力水平降低达50%以上;与5%PAG溶液相比,淬火介质PAG浓度升至15%时,厚板表面淬火残余应力轧向分应力降低比例达52.2%,横向分应力降低比例达47.2%。结合厚板峰时效态性能对比发现,经10%NaCl水溶液淬火处理后,厚板具有最高的强度性能,但淬火残余应力处于最高水平;经15%PAG水溶液淬火处理后,厚板淬火残余应力水平显著降低,但强度性能较前者降低了22.9MPa。通过测定7055铝合金厚板物性参数等,利用建立的有限元模型,数值模拟研究了7055铝合金厚板淬火残余应力的分布规律,经淬火处理后,7055铝合金厚板表面淬火残余应力为压应力,心部淬火残余应力为拉应力,经实测结果进行验证,表明与数值模拟预测结果基本吻合。并研究了厚板尺寸对淬火残余应力水平的影响,随着厚板厚度的增加,淬火残余应力水平呈明显增大趋势,当板厚增至80mm以后,淬火残余应力的增速有所减缓。
[Abstract]:7055 aluminum alloy belongs to the heat treatment strengthened Al-Zn-Mg-Cu system deformed aluminum alloy, it has super high strength and good comprehensive properties. Its thick plate products are widely used in the manufacture of important structural parts in aerospace and other fields. 7055 aluminum alloy thick plate is easy to change in machining process because of the large residual stress in the course of aeronautical users' use. Quenching residual stress is the source of residual stress in thick plate. In this paper, the measurement and numerical simulation are carried out on the distribution of quenching residual stress in 7055 aluminum alloy thick plate, which can provide the experimental basis for the optimization of industrial production process. The research work is of practical value and theoretical significance. The reliability of X-ray diffraction method and borehole method for measuring surface quenching residual stress of 7055 aluminum alloy thick plate is compared with that of X-ray diffraction method. The stability of the results measured by drilling method is good. It is suitable for measuring the surface residual stress of 7055 aluminum alloy thick plate. The distribution of quenching residual stress in 7055 aluminum alloy thick plate is measured and analyzed by crack flexibility method. The distribution of stress is similar. The surface is in the state of compressive stress and the center is in the state of tensile stress. The maximum of surface stress is -110MPa, the maximum of transverse stress is -140MPa, the maximum of center stress is 130MPa, and the maximum of transverse stress is 115MPa. Same quenching conditions (type of quenchant, The order of cooling capacity of quenching medium is: 1: 15 PAG10PAG5PAG5PAG water 10NaCl1; with the increase of water temperature or PAG concentration, the surface quenching residual stress level of thick plate decreases; when water temperature rises from 20 鈩，

本文编号：1629714