【作者】 郑建毅；

【导师】 何闻；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 针对传统时效技术消除残余应力的局限性,本论文提出了一种采用电脉冲时效技术消除材料内部残余应力的方法,并对其理论及若干关键技术问题进行了研究。第一章阐述了论文的研究意义和研究内容。首先,分析了残余应力的产生模型和分类方法,指出了残余应力的危害及消除残余应力的重要意义；其次,评述了残余应力的消除技术和测量方法的国内外研究现状；再次,分析了电脉冲处理技术的国内外研究现状；最后,提出了一种采用电脉冲时效技术消除残余应力的新方法,并概括了论文的主要研究内容。第二章研究了基于电致位错动力学的电脉冲法消除残余应力的微观机理。首先,通过分析位错的基本组态模型以及位错对残余应力的影响,计算了受阻位错塞积群开通所需克服的微观阻力,并推导了材料强化的流变应力；其次,计算了高能电脉冲对位错产生作用的瞬时热压应力和电子风力等作用力；最后,从电致位错动力学出发,提出了电脉冲法消除残余应力的微观作用条件。第三章研究了小孔法中校准系数的有限元数值标定技术和逐层钻孔构建非均匀残余应力的测量技术。首先,用有限元数值分析的方法模拟力学拉伸实验的校准过程,在ANSYS中构造试件和应变花粘合的三维模型,分析了试件贴片平面的边长、试样的厚度、钻孔直径和钻孔深度对校准系数α和b的影响规律；其次,采用逐层钻孔的小孔法测量构建非均匀的残余应力,用分层加载的方法标定出分步逐层钻孔所需的校准系数矩阵αni和bni，建立了一种实用的五步逐层钻孔的应力测试技术；最后,用直接钻孔的小孔法和五步逐层钻孔测量技术,实验对比测试Cr12MoV淬火件的残余应力。第四章研制了适用于电脉冲法消除残余应力的电脉冲发生装置。首先,建立了电容放电回路的RLC等效电路模型,分析了脉冲电流的产生条件以及回路中各参数对脉冲电流特性的影响；其次,采用单片机开发了用于控制充放电开关自动工作的主控单元,并组建了电脉冲发生装置；最后,对该电脉冲发生装置产生的脉冲电流进行了测试分析。第五章对电脉冲法消除残余应力进行了实验研究。首先,利用研制成功的电脉冲发生装置组建了实验系统,以小孔法定量测试技术为评定标准,实验研究了电流峰值Im、脉冲宽度τ、脉冲重复频率f和电脉冲时效次数p等四个电参数对电脉冲时效效果的作用规律；然后,结合金相分析和显微硬度测试等手段,研究了电脉冲法对试样的微细观组织形态的影响；最后,研究了电脉冲时效过程中试样的温升情况和脉冲电流的变化。第六章研究了基于电参数法的电脉冲时效的定量评价技术。基于多元函数逼近模型,建立了同时考虑电流峰值Im、脉冲宽度τ、脉冲重复频率f和电脉冲时效次数p的效果定量评价模型X(Im,τ,f,p)；然后,从构建的评价模型出发,研究了各电参数单独或复合作用下残余应力的消除效果。第七章总结了本论文的研究成果,并展望了今后需进一步开展的研究工作。更多还原

【Abstract】 Considering the limitation of traditional residual stress relief technologies, a method based on electropulsing stress relief was presented in this dissertation, and its theory and several key technologies were investigated.In chapter 1, the research significance and contents of this dissertation were presented. First, the generating model and categorizing method of residual stress were analyzed, and the hazard of residual stress and the significance of eliminating residual stress were pointed out. Secondly, the present research status of residual stress relief technologies and measurement methods at home and abroad was reviewed, as well as the electropulsing treatment technology. Finally, a new method was advanced which used electropulsing treatment to remove residual stress, and the primary contents of this dissertation were generalized.In chapter 2, the microscopic mechanism of the electropulsing stress relief method was researched based on electro-dislocation dynamics. First, the microscopic resistance force to actuate baffled dislocation was calculated by analyzing the basic configuration of dislocation and its influence on residual stress; in addition, the flow stress of material strengthening was derived. Secondly, the instantaneous thermocompression stress and the electron wind force of high-energy electropulse which drove dislocation were obtained. Finally, the microscopic acting condition of electropulsing stress relief method was established based on electro-dislocation dynamics.In chapter 3, the finite element numerical calibration technique for the calibration constants in the hole-drilling method and the measurement technique of the incremental hole-drilling method for constructing non-uniform residual stress were researched. First, the calibration process of mechanical tensile test was simulated with the finite element numerical analysis technique; and an agglutinate 3-D model of a workpiece and a strain rosette was built up in ANSYS; furthermore, the influence parameters on the calibration constants a and-b was analyzed, including the specimen’s pasting-plane side length, the workpiece thickness, the hole diameter and the drilling depth. Secondly, the incremental hole-drilling method was used to measure non-uniform residual stress, and the calibration constants matrix ani, and-bni were calculated by a dividing-layer loading method; moreover, a practical measurement technology of five-step incremental hole-drilling method was established. Finally, the residual stress in Cr12MoV quenching specimens was measured contrastively by the direct hole-drilling method and five-step incremental hole-drilling technology.In chapter 4, an electrical pulse generating device was developed for electropulsing stress relief method. First, the RLC equivalent circuit of the capacitor discharge loop was established, and the generating condition of pulse current was analyzed, as well as the influence of each circuit parameter on characteristic of the pulse current. Secondly, the master control unit was developed based on MCU which controlled the charge and discharge switches for automatic operation, then the electrical pulse generating device was built up. Finally, the pulse current produced by the electrical pulse generating device was tested.In chapter 5, experiments were carried out to study the electropulsing stress relief method. First, the experimental system was constructed with the developed electrical pulse generating device, and the hole-drilling method was used as quantitative evaluation standard; furthermore, experiments were carried out to study the influence of four electrical parameters on residual stress relief effect, including the peak of pulse current Im, the pulse widthτ, the pulse recurrence frequency f and the electropulsing stress relieving times p. Secondly, based on the metallographic analysis and microhardness testing techniques, the impact of the electropulsing method on the micro structure configuration of the specimen was investigated. Finally, the temperature rise of the specimen and the change of pulse current were investigated during the process of electropulsing stress relief.In chapter 6, the quantitative evaluation technique of electropulsing stress relief method was investigated based on electrical-parameter rule. Based on the multivariate function approximation model, the quantitative evaluation model X(Im,τ,f,p) was established considering the current peak Im, the pulse widthτ, the pulse recurrence frequency f, and the electropulsing stress relieving times p. According to the constructed evaluation model, the impact of each electrical parameter or their combination on the residual stress relieving effect was investigated. In chapter 7, the achivements of this dissertation were summarized, and future research work for further study was prospected.更多还原