喷丸残余应力及粗糙度对2024铝合金疲劳寿命影响的仿真与实验研究

发布时间：2018-05-25 07:28

本文选题：2024铝合金 + 喷丸强化　；参考：《山东大学》2017年硕士论文

【摘要】：喷丸作为一种表面强化工艺,可有效提升材料的抗疲劳性能。通常认为疲劳性能的强化是由于喷丸引入的残余应力,但喷丸在引入残余应力的同时还会改变材料表面形貌而增加粗糙度,这对材料的疲劳性能存在负面影响,而粗糙度与残余应力存在着一定的相关性。因此,喷丸所引入的残余应力,所增加的粗糙度,两者的相关性以及对疲劳寿命的影响都需要得到足够关注。本文针对2024铝合金,结合实验研究与数值仿真研究各自的优点,开展喷丸及相关实验研究,然后建立相应的ABAQUS有限元数值模型来模拟实验过程,通过实验与仿真结果的对照,在验证数值模型的正确性和有效性后,利用数值仿真进行参数影响的研究,主要研究内容如下:(1)对2024铝合金试件进行喷丸处理,实验测量喷丸后的粗糙度特征值Ra,通过ABAQUS/Explicit建立多丸粒数值模型模拟喷丸过程,基于所提出的Ra离散化计算式,通过对节点位移进行统计分析得到Ra模拟值,通过实验与模拟结果的对照,验证仿真方法的正确性及有效性,最后利用该数值模型进行喷丸参数对粗糙度影响的研究。(2)对喷丸处理后的试件进行剥层残余应力测量,得到喷丸残余应力沿深度分布的曲线,同时通过多丸粒数值模型得到相应的仿真残余应力曲线,通过两者结果的比较研究来检验仿真方法,通过数值模型进行喷丸参数对残余应力的影响研究。最后将不同参数下粗糙度与残余应力的结果进行线性拟合及相关性分析,建立喷丸残余应力特征值与相应粗糙度的相关关系。(3)利用2024铝合金的三弯试样,通过疲劳试验机分别对喷丸与未喷丸的试件进行三弯疲劳实验,得出喷丸对疲劳寿命影响的实验结果。通过ABAQUS建立试件的二维平面应力模型,利用扩展有限元法模拟循环载荷下裂纹的萌生与扩展,对比实验结果验证该扩展有限元数值模型的正确性。最后利用该模型研究不同载荷工况下残余应力对疲劳寿命的影响效果。
[Abstract]:As a surface strengthening process, shot peening can effectively improve the fatigue resistance of the material. It is generally believed that the strengthening of the fatigue properties is due to the residual stress introduced by the shot peening, but the surface morphology of the material will be changed and the roughness is increased while the residual stress is introduced, which has a negative effect on the fatigue property of the material, and the roughness and residual strength. The residual stress has a certain correlation. Therefore, the residual stress introduced by the shot peening, the increased roughness, the correlation between the two and the fatigue life need to be paid enough attention. In this paper, 2024 aluminum alloy, combining the advantages of experimental and numerical simulation research and numerical simulation, to carry out the shot peening and related experimental research, and then build up. The corresponding ABAQUS finite element numerical model is established to simulate the experimental process. The main research contents are as follows: (1) the shot peening treatment of 2024 aluminum alloy specimens is carried out, and the roughness of the shot peening is measured by the experiment. The eigenvalue Ra is used to simulate the shot peening process by the multi pellet numerical model of ABAQUS/Explicit. Based on the proposed Ra discrete calculation formula, the Ra simulation value is obtained by statistical analysis of the node displacements. The correctness and effectiveness of the simulation method are verified by the comparison between the experiment and the simulation results. Finally, the shot blasting parameters are carried out by the numerical model. Study on the influence of roughness. (2) measure the residual stress of the peeling layer after shot peening, get the curve of the residual stress along the depth distribution, and get the corresponding simulation residual stress curve through the multi pellet numerical model, and test the simulation method through the comparison study of the two results, and carry out the shot peening parameter through the numerical model. The effect of number on residual stress is studied. Finally, the results of roughness and residual stress under different parameters are linear fitting and correlation analysis, and the correlation between the characteristic values of residual stress of shot peening and the corresponding roughness is established. (3) using three bending specimens of 2024 aluminum alloy, the specimens of shot peening and unpeening are three respectively through fatigue testing machine. The experimental results of the effect of shot peening on fatigue life are obtained. A two-dimensional plane stress model of the specimen is established by ABAQUS. The propagation of crack initiation and propagation under cyclic loading is simulated by the extended finite element method, and the correctness of the extended finite element model is verified by comparison with the experimental results. Finally, the model is used to study the different load conditions. The effect of the residual stress on the fatigue life.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG668

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