基于材料微观缺陷的滚压形变强化对材料疲劳性能影响研究

发布时间：2018-05-14 02:35

本文选题：微孔洞 + 表面滚压强化　；参考：《燕山大学》2015年硕士论文

【摘要】：金属材料的疲劳裂纹极易在其表面及接近表面附近区域内微孔缺陷处萌生,而表面滚压强化技术是改善材料表面状态,提高材料疲劳寿命的有效方法之一。滚压强化作用可以通过影响微孔洞周围材料表面残余应力和其形状变化而对材料疲劳性能产生作用。本文从这两个角度出发,以铸造铝合金为研究对象,利用计算机有限元仿真技术,分析不同滚压参数下的微孔洞周围的应力分布,得到影响材料疲劳寿命的关键滚压参数。建立二维滚压弹塑性有限元分析模型,通过分析滚压工具和工件的相对变形量,确定三维滚压有限元模型的分析类型,然后以此为依据,建立三维滚压刚塑性有限元分析模型,通过设置确定的滚压参数,分析不同相对位置的微孔周围残余应力的分布,得到表面滚压强化作用对材料表面残余应力的影响,然后通过研究不同滚压参数下的微孔洞周围残余应力分布,确定了影响微孔周围残余应力分布的关键滚压参数,同时得到了经三维滚压模型滚压后微孔形状发生改变的工件。建立微孔形状发生改变后工件的弹性有限元分析模型,通过对确定滚压参数下的材料施加较小名义外载荷,分析不同相对位置的变形微孔周围应力集中系数分布,得到微孔在不同相对位置时周围应力集中系数分布规律,然后通过分析不同滚压参数对形状变化后的微孔周围应力集中系数分布的影响,确定各个滚压参数对变形微孔周围应力集中系数的分布规律。最后根据微孔周围应力集中系数分布的结果,得到不同滚压参数下微孔周围最大应力集中系数的分布;建立滚压前工件弹性有限元分析模型,得到微孔形状未发生改变时的微孔周围最大应力集中系数分布,然后将滚压前后的微孔周围最大应力集中系数进行比较,最后确定滚压强化作用对微孔周围应力集中程度的影响及影响最大应力集中系数的关键滚压参数与其相对最佳值。
[Abstract]:The fatigue crack of metal materials is easy to sprout at the micropore defects on the surface and near the surface. The surface rolling strengthening technique is one of the effective methods to improve the surface state of materials and improve the fatigue life of materials. Rolling strengthening can affect the fatigue properties of the materials by influencing the surface residual stress and the shape change of the materials around the microvoids. In this paper, the stress distribution around the microvoids under different rolling parameters is analyzed by using the computer finite element simulation technique, and the key rolling parameters affecting the fatigue life of the materials are obtained by taking the casting aluminum alloy as the research object from these two angles. A two-dimensional rolling elastoplastic finite element analysis model is established. By analyzing the relative deformation of rolling tools and workpieces, the analysis types of 3D rolling finite element model are determined. Based on this model, a three-dimensional rolling rigid-plastic finite element analysis model is established. By setting certain rolling parameters, the distribution of residual stress around microholes with different relative positions is analyzed, and the effect of surface rolling strengthening on surface residual stress of materials is obtained. Then by studying the distribution of residual stress around the microhole under different rolling parameters, the key rolling parameters affecting the distribution of residual stress around the micropore are determined, and the workpiece which changes the shape of the micropore after rolling with the three-dimensional rolling model is obtained. The elastic finite element analysis model of the workpiece after the change of the micropore shape is established. The stress concentration factor distribution around the deformed microhole at different relative positions is analyzed by applying a smaller nominal external load to the material under certain rolling parameters. The distribution of stress concentration factors around micropores at different relative positions is obtained, and the influence of different rolling parameters on the stress concentration factor distribution around micropores is analyzed. The distribution of stress concentration factors around deformation microholes is determined by rolling parameters. Finally, according to the results of stress concentration factor distribution around micropore, the distribution of maximum stress concentration factor around microhole under different rolling parameters is obtained, and the elastic finite element analysis model of workpiece before rolling is established. The distribution of the maximum stress concentration factor around the micropore is obtained when the shape of the micropore remains unchanged, and then the maximum stress concentration factor around the micropore before and after rolling is compared. Finally, the influence of rolling hardening on the stress concentration around the microhole and the relative optimum value of the key rolling parameters affecting the maximum stress concentration factor are determined.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG306;TG146.21

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