脉冲电流法调控碳钢残余应力的机理及相关实验研究

发布时间：2018-06-02 03:09

本文选题：残余应力 + 脉冲电流　；参考：《浙江大学》2016年博士论文

【摘要】：本文结合国家自然科学基金项目"消除残余应力的电击法及其应用基础研究"和航空科学基金项目"高精度加速度计稳定化处理关键技术研究",对脉冲电流法调控碳钢残余应力的机理和相关实验进行了研究。第一章阐述了论文的研究背景、意义和内容。首先,分析了残余应力的产生、分类、测量方法,以及对工件性能的影响,指出了调控残余应力的重要意义;其次,评述了残余应力调控技术和脉冲电流在材料处理中应用的研究现状;然后,重点分析了脉冲电流法调控残余应力的国内外研究现状,指出了现有研究中存在的不足;最后,提出了本文的研究内容。第二章研究了基于多尺度力学理论的残余应力松弛机理。首先,建立了残余应力松弛的连续介质力学模型,确定了宏观弹塑性变形与残余应力松弛的关系;然后,分别推导出了晶体切应变速率与位错滑移和位错密度之间的关系,以及晶粒弹塑性变形与残余应力松弛之间的关系,解决了由微观到宏观的力学尺度转换问题;最后,基于位错牛顿力学模型、热动力学模型和位错密度演化规律,讨论了位错与残余应力的相互作用。第三章研究了脉冲电流对碳钢微观结构动态行为的作用机制。首先,建立了碳原子的电子拖拽力模型,分析了脉冲电流对淬火碳钢试样碳原子扩散、偏聚行为的影响规律;然后,建立了位错的电子拖拽力模型,分析了电子拖拽力、Joule热效应、微观结构对位错动态行为的作用机制;最后,建立了脉冲电流对碳钢马氏体晶界作用的力学模型,讨论了脉冲电流影响马氏体形貌的机制,分析了脉冲电流法通过对微观结构动态行为的作用调控残余应力的机理。第四章研究了趋肤效应对脉冲电流调控碳钢残余应力的影响。首先,根据Maxwell方程组,推导出了衰减振荡脉冲电流通过矩形截面试样时电场强度、电流密度的解析表达式;然后,分析了趋肤效应对碳原子和位错受到的电子拖拽力的影响规律,讨论了趋肤效应对残余应力的影响。第五章实验研究了脉冲电流法调控残余应力的机理。首先,完善了脉冲电流法调控金属试样残余应力的实验系统;然后,实验研究了脉冲电流对淬火45钢试样力学性能的影响规律,主要包括残余应力、拉伸性能、表面硬度;最后,实验研究了脉冲电流对淬火45钢试样显微组织形态的作用规律,主要包括碳原子分析、位错密度、马氏体微观形貌。通过对脉冲电流对淬火45钢试样力学性能和显微组织形态影响的研究,验证了脉冲电流法调控残余应力机理的正确性。第六章总结了本文的研究成果,并展望了今后需要进一步展开的研究工作。
[Abstract]:In this paper, the pulse current method is adjusted according to the project of the National Natural Science Foundation of China, "Electric shock method for eliminating residual stress and its application basic research" and the project "key technology of high precision accelerometer stabilization treatment", which is a project of aviation science foundation. The mechanism and experiment of residual stress of carbon steel were studied. The first chapter describes the research background, significance and content of the thesis. Firstly, the generation, classification, measurement method and effect on the performance of the workpiece are analyzed, and the significance of controlling the residual stress is pointed out. The research status of residual stress regulation technology and pulse current application in material treatment is reviewed. Then, the research status of pulse current method in controlling residual stress at home and abroad is analyzed, and the shortcomings of existing research are pointed out. The research content of this paper is put forward. In chapter 2, the mechanism of residual stress relaxation based on multi-scale mechanics is studied. Firstly, the continuum mechanics model of residual stress relaxation is established, and the relationship between macroscopic elastic-plastic deformation and residual stress relaxation is determined, and the relationship between crystal shear strain rate and dislocation slip and dislocation density is derived respectively. And the relationship between grain elastic-plastic deformation and residual stress relaxation solves the problem of mechanical scale conversion from microcosmic to macroscopic. Finally, based on dislocation Newtonian mechanics model, thermodynamics model and dislocation density evolution law, The interaction between dislocation and residual stress is discussed. In chapter 3, the mechanism of pulse current acting on microstructure dynamic behavior of carbon steel is studied. Firstly, the electronic drag force model of carbon atom is established, and the influence of pulse current on the diffusion and segregation behavior of carbon atom in quenched carbon steel sample is analyzed, and then the electronic drag force model of dislocation is established. The mechanism of the effect of electron tug force Joule thermal effect and microstructure on the dynamic behavior of dislocation is analyzed. Finally, a mechanical model of the effect of pulse current on martensite grain boundary of carbon steel is established, and the mechanism of pulse current affecting the morphology of martensite is discussed. The mechanism of controlling residual stress by pulse current method is analyzed. In chapter 4, the effect of skin effect on residual stress of carbon steel regulated by pulse current is studied. Firstly, according to the Maxwell equations, the analytical expressions of the electric field intensity and current density of the attenuated oscillating pulse current passing through the rectangular cross section sample are derived. The effect of skin effect on the electronic drag force of carbon atoms and dislocations is analyzed, and the effect of skin effect on residual stress is discussed. In chapter 5, the mechanism of residual stress regulation by pulse current method is studied experimentally. Firstly, the experimental system of controlling residual stress of metal specimen by pulse current method is improved, and then the influence of pulse current on mechanical properties of quenched 45 steel specimen is studied, including residual stress, tensile property and surface hardness. Finally, the effect of pulse current on microstructure of quenched 45 steel was studied, including carbon atom analysis, dislocation density and martensite morphology. The effect of pulse current on mechanical properties and microstructure of quenched 45 steel samples was studied and the correctness of residual stress control mechanism by pulse current method was verified. The sixth chapter summarizes the research results of this paper and looks forward to further research work in the future.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG142.1

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