超声波光整强化表层组织变形机理及力学性能研究

发布时间：2018-05-02 23:49

本文选题：超声波光整 + 表层组织　；参考：《济南大学》2015年硕士论文

【摘要】：超声波光整强化是一种新兴的表面处理技术,该技术通过高频振动的加工头在工件表面施加滚动挤压复合作用,使工件表层组织产生强烈塑性变形,实现表层晶粒细化,在表层一定厚度内预置残余压应力,提高零件的疲劳寿命,提高表层显微硬度,改善耐磨性能和抗腐蚀性等。目前该技术处于推广试用阶段,在基础强化理论和工程实际应用方面所做的工作较少,本文选用典型材料为研究对象,利用正交试验的方法,将关键工艺参数即工作频率、振幅和压力作为实验因素,系统分析加工过程中工件表层组织的变形机理,从组织变形的角度分析该技术的强化原理,此外通过检测的手段得出该技术对于不同类型材料的工件表面力学特征值影响规律。本文利用L9(34)正交表设计实验,以40Cr、GCr15和工业纯铁为实验材料,研究关键工艺参数工作频率、振幅和压力对于工件表面粗糙度的影响规律。利用SEM和超景深显微镜等手段对加工前后工件表面三维形貌和表层微观组织进行观察,找出不同材料工件表面流变层分布情况,发现加工后工件表层晶粒沿轴向拉伸,呈扁平状,表层组织变形程度沿轴向有波动,分析加工过程中工件表层组织的变形机理。借助盲孔法残余应力检测仪对不同材料加工前后工件表面残余应力进行检测,得到超声波光整强化技术可以有效地将工件表面初始时的残余拉应力转变成有利的残余压应力。提出一种多次钻孔的逐层应力释放方法,根据每层的应力应变检测值变化趋势,分析残余应力在厚度方向上的分布情况。利用显微硬度计对加工后工件表面硬化层进行检测,对比得到加工后工件表面硬化情况。在测试过程中,通过减少试样厚度方向位移增加切向位移的方法,实现了在有限厚度方向上的显微硬度值测量,分析表面硬化层内部显微硬度值的分布情况,根据测试需要设计了一种可调角度的显微硬度测试载物台。
[Abstract]:Ultrasonic finishing strengthening is a new technology of surface treatment. The technology exerts rolling extrusion compound action on the surface of workpiece through high frequency vibration machining head, which makes the surface structure of workpiece produce strong plastic deformation and realize the grain refinement of surface layer. The residual compressive stress is preset in a certain thickness of the surface layer to increase the fatigue life of the parts, to improve the microhardness of the surface layer, to improve the wear resistance and corrosion resistance, and so on. At present, the technology is in the stage of popularization and trial, and less work has been done in the field of foundation strengthening theory and practical engineering application. In this paper, typical materials are chosen as the research object, and the key technological parameters, namely the working frequency, are used in the orthogonal test. The amplitude and pressure are used as experimental factors to systematically analyze the deformation mechanism of the surface structure of the workpiece during the machining process, and the strengthening principle of the technique is analyzed from the point of view of the microstructure deformation. In addition, the influence of this technique on the mechanical eigenvalues of workpiece surface of different types of materials is obtained by means of testing. In this paper, an experiment is designed by using L9 / 34) orthogonal table. Using 40CrGCr15 and industrial pure iron as experimental materials, the effects of working frequency, amplitude and pressure on the surface roughness of workpiece are studied. The surface morphology and microstructure of workpiece before and after processing were observed by means of SEM and hyperfield microscope. The distribution of rheological layer on workpiece surface of different materials was found, and the grain of workpiece surface was stretched along axial direction after processing. The deformation degree of the surface structure fluctuates along the axial direction, and the deformation mechanism of the surface structure of the workpiece is analyzed. The residual stress of workpiece surface before and after processing with blind hole method was measured by means of the blind hole method, and the ultrasonic finishing strengthening technique was obtained, which can effectively transform the residual tensile stress of the workpiece surface into favorable residual compressive stress at the beginning of the workpiece surface. In this paper, a method of stress release from multiple boreholes is proposed, and the distribution of residual stress in thickness direction is analyzed according to the change trend of stress and strain detection value in each layer. The workpiece surface hardening layer was tested by microhardness tester, and the workpiece surface hardening was compared. In the testing process, by reducing the thickness direction displacement of the specimen and increasing the tangential displacement, the microhardness value in the finite thickness direction is measured, and the distribution of the microhardness value in the surface hardening layer is analyzed. According to the need of testing, a microhardness testing platform with adjustable angle is designed.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG66

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