| 引用本文: | 翟傲霜,黄啸,王欣,许春玲,商宏飞.基于位错密度理论的喷丸强化诱导7050铝合金组织细化数值模拟[J].中国表面工程,2023,36(2):114~124 |
| ZHAI Aoshuang,HUANG Xiao,WANG Xin,XU Chunling,SHANG Hongfei.Numerical Simulation of Surface Grain Refinement of 7050 Aluminum Alloy Induced by Shot Peening Based on Dislocation Density Theory[J].China Surface Engineering,2023,36(2):114~124 |
|
| 摘要: |
| 7050 铝合金喷丸过程中微观组织演变机理及纳米化结构与工艺参数的关系还没有得到广泛研究。基于位错密度理论对喷丸强化诱导 7050 铝合金表层晶粒细化进行研究。利用有限元方法模拟 7050 铝合金受单个和多个喷丸冲击过程，建立将喷丸强化的有限元模型与累积塑性应变引起的位错密度演化模型相结合的混合数值模型，并利用遗传算法得到混合模型的数值参数，用以预测喷丸强化层的位错密度和晶粒尺寸梯度分布，为研究喷丸强化 7050 铝合金的组织结构强化机理提供依据。 建立喷丸尺寸、速度和覆盖率等工艺参数与强化层内晶粒细化结构的物理联系和数量关系。结果表明，从单个喷丸冲击到大量随机喷丸冲击过程都会在强化层内产生显著的晶粒细化；强化层内位错密度增加、晶粒细化的程度以及强化影响深度随着喷丸覆盖率、速度、尺寸的增加而增加；较高的喷丸覆盖率和强度可生成纳米级晶粒结构表面层。综合运用 JC 本构有限元模拟、四阶五级 RKF 算法解方程、遗传算法优化调参、概率约束方法控制随机喷丸以及 VUMAT 子程序定义本构关系，实现 7050 铝合金喷丸强化微宏观联系的定量研究，可为设计 7050 铝合金喷丸工艺参数获得所需纳米结构提供理论依据。 |
| 关键词: 喷丸强化 位错密度 晶粒细化 有限元 遗传算法 |
| DOI：10.11933/j.issn.1007-9289.20220526001 |
| 分类号:O733;O242;TG146;TG668 |
| 基金项目:国家科技重大专项(J2019-VII-0015-0155)、国家自然科学基金(51705533)和中央高校基本科研业务费(2021YQJD23)资助项目 |
|
| Numerical Simulation of Surface Grain Refinement of 7050 Aluminum Alloy Induced by Shot Peening Based on Dislocation Density Theory |
|
ZHAI Aoshuang1, HUANG Xiao1, WANG Xin2, XU Chunling2, SHANG Hongfei3
|
|
1.School of Mechanical Electronic & Information Engineering, China University of Mining & Technology,Beijing 100083 , China;2.AECC Beijing Institute of Aeronautical Materials, Beijing 100095 , China;3.State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 , China
|
| Abstract: |
| Microstructure evolution of 7050 aluminum alloy occurs during shot peening, allowing the surface grain to be refined to the nanometer level. However, the microstructural evolution mechanism of 7050 aluminum alloy and the relationship between its nanostructure and the shot-peening process parameters have not been widely studied. Therefore, based on dislocation density theory, the grain refinement of the 7050 aluminum alloy surface layer induced via shot peening was studied. First, the process of 7050 aluminum alloy impacted by single- and multiple-shot peening was simulated using the finite element method. A mixed numerical model was established, which combined the finite element model of shot-peening strengthening with the dislocation density evolution model caused by the cumulative plastic strain. Moreover, the flow stress of the target was obtained from the dislocation density evolution and Johnson–Cook (JC) constitutive relationships. The genetic algorithm was used to adjust the flow stress of the target to be as consistent as possible so as to obtain the numerical parameters of the mixed model. Second, to simulate the shot-peening process of 7050 aluminum alloy more realistically, a three-dimensional finite element model based on probabilistic control of multiple-shot peening random impact target locations was established to consider the interaction between shots. Then, the dislocation density evolution constitutive model is embedded into the shot-peening finite element model to predict the gradient distribution of dislocation density and grain size in the shot-peening strengthened layer. This provides a basis for the study of the microstructure strengthening mechanism of shot-peening strengthened 7050 aluminum alloy. The grain size and dislocation density in the strengthened layer induced by single-shot peening, multiple-shot peening with a regular arrangement, and multiple-shot peening with a random distribution were simulated and calculated. The physical and quantitative relationships between the process parameters, such as shot-peening size, speed, and coverage, and the grain refinement structure in the strengthened layer were established. Additionally, the dynamic mechanical behavior (e.g., stress and strain rate) and microstructure (e.g., dislocation density and grain size) of the target during shot peening were studied. High strain rate plastic deformation of the target will occur owing to the projectile impact, which will lead to the evolution of the microstructure of the target. From a single shot-peening impact to multiple random shot-peening impact processes, grain refinement and dislocation density will significantly increase in the strengthened layer. However, lower shot-peening strength and coverage will not produce uniform nanostructures. The increase of dislocation density, degree of grain refinement, and depth of strengthening effect in the strengthened layer increase with the increase of shot-peening coverage, speed and size. Additionally, the grain refinement effect will be improved by the impact of adjacent projectiles and repeated impact of projectiles. Higher shot-peening coverage and strength will generate a surface layer with nano grain structure. The following methods are comprehensively used to establish a multi-scale 3D finite element model of shot-peening strengthened 7050 aluminum alloy and obtain the optimized material parameters of 7050 aluminum alloy in dislocation density theory: JC constitutive model for finite element simulation, four- and five-level Runge-Kutta-Fehlberg algorithm for solving the equations, genetic algorithm for optimizing the parameter adjustment, probabilistic constraint method for controlling the random shot peening, and VUMAT subroutine for defining the constitutive relations. The model takes the shot-peening process parameters as input and outputs of the stress and strain. The processes for strain rate, dislocation density, and grain size changes enabled the quantitative study of the micro–macro relationship of 7050 aluminum alloy shot-peening strengthening. This provides a theoretical basis for the design of 7050 aluminum alloy shot-peening process parameters to obtain the required nanostructures. |
| Key words: shot peening dislocation density grain refinement finite element method genetic algorithm |
