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喷丸强化论文:基于光滑粒子流体动力学(SPH)法的喷丸强化数值模拟研究

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喷丸强化论文:基于光滑粒子流体动力学(SPH) 喷丸强化论文:基于光滑粒子流体动力学(SPH)法的喷丸 强化数值模拟研究

【中文摘要】喷丸强化是一种提高工件疲劳寿命的表面强化工 艺。通过弹丸高速撞击金属表面,在表面形成均匀的残余压应力层, 抵消工件表面承受的破坏性拉应力,减缓裂纹的扩展速度,延长零件 疲劳寿命。然而喷丸表面强化过程机理复杂,各工艺参数选择和搭配 对喷丸效果的影响很大,且难以用精确的数学模型描述。目前国内外 的研究大多集中于实验领域,数值模拟多采用有限元法(Finite Element Method,简称 FEM)模拟单个弹丸或者几个弹丸对工件的冲击 作用,不能反映实际喷丸时大量弹丸重复打击工件和弹丸间相互作用 的影响。为克服有限元法在喷丸强化仿真模拟中的缺陷,本文首次采 用光滑粒子流体动力学(Smoothed Particle Hydrodynamics,简称 SPH) 耦合有限元法(FEM)模拟喷丸强化过程,并对此方法做了系统的研究, 通过仿真结果与实验数据的对比分析,验证了仿真模型及结果的正确 性,为喷丸强化的仿真研究和工艺参数优化设计提供了强有力的工 具。SPH 算法是无网格算法的一种,因其自身公式构造不会受粒子分 布的随意性的影响,具有良好的自适应性,又因为其典型的 Lagrange 性,方便追踪其粒子运动轨迹,使得 SPH 粒子更具灵活性。 现已广泛应 用于具有大变形的流体动力学问题。SPH 耦合 FEM 建模,其中金属工 件采用 Lagrange 网格建模; 弹丸采用 SPH 粒子建模,通过状态方程考 虑了空气和弹丸的混合作用,提出了弹丸流空气混合材料模型。SPH

和 FEM 的耦合作用通过接触算法实现,以模拟弹丸对工件的冲击强化 过程。通过仿真结果与实验结果的对比,分别分析了弹丸大小、弹丸 打击次数、覆盖率、弹丸速度等参数对金属工件残余压应力分布的影 响,并从能量角度,讨论了初始速度与能量利用率的关系。 揭示了喷丸 强化各工艺参数对喷丸效果的影响,并总结规律取得了一系列的研究 成果。为进一步研究喷丸强化机理,本文还从微观针对单个弹丸打击 状况进行了建模仿真。通过对打击次数、弹丸大小、打击速度等相关 参数的实验与仿真对比,再一次验证了耦合建模所得参数影响规律的 正确性,并对所得喷丸强化规律做出补充,从而对喷丸强化作用机理 有了更深刻的理解。 本文通过对喷丸强化整体过程及单个弹丸冲击的 微观过程的模拟仿真分析,深入探讨了喷丸强化各工艺参数对工件表 面残余压应力分布的影响,并通过实验对比验证了模型的正确性,所 得规律为优化工艺参数提供了参考。 【英文摘要】Shot peening is a surface treating process which can effectively enhance the fatigue life of workpieces. A large compressive residual stress is formed in subsurface of the work pieces by impinging the surface of the metallic components with thousands of shots at high velocities that can ensure a good fatigue resistance to stress corrosion. However shot peening is a complex process involving modeling for a mass of discrete shots and the disciplines of dynamic plasticity. The choices of the process parameters and its arrangements have

a great effect on the compressive residual stress values and its distribution. Obviously, it is also difficult to describe this process using analytical mathematical model. In order to predict the shot peening process, numerical simulations were used and existing simulation models were all based on finite element method (FEM) to investigate the relationships between the compressive residual stress and the shot peening parameters. Most existing FEM models used only a single shot or several shots (less than 9) to simulate the shot peening process, thus the effect of a mass of shots repeat impacting and the influence among adjacent shots are ignored.To overcome above defects caused by FEM, a coupled method of smoothed particle hydrodynamic (SPH) and FEM is adopted to build the numerical model to simulate the whole shot peening process. The simulation results agree well with the existing experimental data. The study will not only provide a new powerful tool for the simulation of shot peening process, but also be benefit to optimize the operating parameters.SPH method is one of mesh-free methods. Because of its Lagrange property and remarkable self-adaptability, it is easy to trace the track. To overcome these defects of FEM models, SPH coupled FEM modeling is presented, in which the shots are modeled by SPH

particles and the target material is modeled by finite elements. The mixture model of shots and air is established by SPH particles and state equation. Contact algorithm is used to simulate the interaction of shots impinging target. Utilizing this model, the relationships between compressive residual stress and peening frequencies, coverage, velocities and energy utilization are analyzed. Finally, some conclusions are educed.For further research, the micro-model of single shot is established. Through the comparison of results between experiment and simulation, the validity of influence law gotten by SPH coupled FEM model is confirmed and some supplement conclusions are presented.It will be benefit to understand the shot peening mechanism and optimize the operating parameters. 【关键词】喷丸强化 SPH/FEM 耦合 弹丸流材料模型 残余压应 力 有限元 【英文关键词】Shot peening Material model of shots Finite element 【目录】基于光滑粒子流体动力学(SPH)法的喷丸强化数值模 拟研究 13-23 摘要 9-11 ABSTRACT 11-12 第 1 章 绪论 1.1.1 喷丸强化发展 1.1.3 Coupled SPH/FEM Compressed residual stress

1.1 喷丸强化概述 13-18

背景及应用 13-14

1.1.2 喷丸强化原理 14-15

喷丸设备及参数 15-18 18-21

1.2 国内外喷丸强化数值模拟现状 第 2 章 有限

1.3 课题的研究意义和内容 21-23

元及 SPH 理论 23-35 23-25 应用 25-26

2.1 基于网格的有限元理论 2.2.1 SPH 方法的发展背景及 2.3 SPH

2.2 SPH 论 25-29

2.2.2 SPH 方法的基本理论 26-29 2.4 ANSYS/LS-Dyna 软件介绍

与 FEM 耦合 29-31 31-33

2.5 本章小结 33-35

第 3 章 SPH 耦合 FEM 法数

值仿真模型 35-41 35-37 38-40

3.1 金属工件材料的本构方程 3.3 模型描述 第 4 章 工艺参数对强化效

3.2 喷丸材料模式 37-38 3.4 本章小结 40-41

果影响分析 41-51 43-46

4.1 打击次数与残余压应力分布关系 4.3

4.2 覆盖率与残余压应力分布关系 46-47

打击速度与残余压应力分布关系 47 率的关系 47-48

4.4 打击速度与能量利用 第 5 章 单丸粒 5.1 仿真模型建模 5.2.1 弹丸塑性对残

4.5 本章小结 48-51

FEM 法数值仿真模型及结果分析 51-61 51-53 5.2 数值结果分析 53-59 53-57

余压应力分布的影响 布的影响 57-58 58 58-59 总结 61-63

5.2.2 弹丸速度对残余压应力分

5.2.3 弹丸大小对残余压应力分布的影响

5.2.4 撞击次数对残余压应力分布的影响 5.3 本章小结 59-61 展望 63-65 总结与展望 61-65 参考文献 65-71 致谢 73-74 攻读硕 学位论文评

士学位期间发表的论文 71-73

阅及答辩情况表 74




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