本文選題：微孔洞 + 表面滾壓強化��； 參考：《燕山大學》2015年碩士論文

【摘要】：金屬材料的疲勞裂紋極易在其表面及接近表面附近區(qū)域內微孔缺陷處萌生,而表面滾壓強化技術是改善材料表面狀態(tài),提高材料疲勞壽命的有效方法之一。滾壓強化作用可以通過影響微孔洞周圍材料表面殘余應力和其形狀變化而對材料疲勞性能產生作用。本文從這兩個角度出發(fā),以鑄造鋁合金為研究對象,利用計算機有限元仿真技術,分析不同滾壓參數(shù)下的微孔洞周圍的應力分布,得到影響材料疲勞壽命的關鍵滾壓參數(shù)。建立二維滾壓彈塑性有限元分析模型,通過分析滾壓工具和工件的相對變形量,確定三維滾壓有限元模型的分析類型,然后以此為依據(jù),建立三維滾壓剛塑性有限元分析模型,通過設置確定的滾壓參數(shù),分析不同相對位置的微孔周圍殘余應力的分布,得到表面滾壓強化作用對材料表面殘余應力的影響,然后通過研究不同滾壓參數(shù)下的微孔洞周圍殘余應力分布,確定了影響微孔周圍殘余應力分布的關鍵滾壓參數(shù),同時得到了經三維滾壓模型滾壓后微孔形狀發(fā)生改變的工件。建立微孔形狀發(fā)生改變后工件的彈性有限元分析模型,通過對確定滾壓參數(shù)下的材料施加較小名義外載荷,分析不同相對位置的變形微孔周圍應力集中系數(shù)分布,得到微孔在不同相對位置時周圍應力集中系數(shù)分布規(guī)律,然后通過分析不同滾壓參數(shù)對形狀變化后的微孔周圍應力集中系數(shù)分布的影響,確定各個滾壓參數(shù)對變形微孔周圍應力集中系數(shù)的分布規(guī)律。最后根據(jù)微孔周圍應力集中系數(shù)分布的結果,得到不同滾壓參數(shù)下微孔周圍最大應力集中系數(shù)的分布;建立滾壓前工件彈性有限元分析模型,得到微孔形狀未發(fā)生改變時的微孔周圍最大應力集中系數(shù)分布,然后將滾壓前后的微孔周圍最大應力集中系數(shù)進行比較,最后確定滾壓強化作用對微孔周圍應力集中程度的影響及影響最大應力集中系數(shù)的關鍵滾壓參數(shù)與其相對最佳值。
[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.
【學位授予單位】：燕山大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG306;TG146.21

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