【作者】 张志建；

【导师】 姚枚； 杨庆祥；

【作者基本信息】 燕山大学 ， 材料学， 2003， 硕士

【摘要】 本文采用40Cr、35CrMo、20CrMnTi钢及LD7铝合金四种材料，加工成光滑和缺口疲劳试样以及齿轮、压气机转子叶片等疲劳零件，研究了喷丸及渗碳后喷丸对其疲劳强度的影响。为了阐明喷丸对缺口件的影响，还对不喷丸缺口件表象疲劳极限进行了研究。本文的试验内容包括：试样的热处理、试样喷丸强化、金相组织分析、表面残余应力场测定、表面粗糙度测定、显微硬度测定、表象疲劳极限测定、断口分析以及有限元计算等工作。本文跳出学科分工的局限性，在“疲劳源形成的微细观过程理论”及材料“内部/表面疲劳极限”的概念指导下，从综合的角度对喷丸件表象疲劳极限及喷丸工艺优化问题进行分析。对光滑喷丸试样表象疲劳极限的研究，提出了喷丸残余压应力场深度为奥氏体晶粒平均直径10-15倍的喷丸工艺优化准则以及计算优化喷丸件表象疲劳极限的方法。本文还将上述结论应用于铝合金叶片的优化喷丸过程，取得了良好的效果。在分析缺口试样的弯曲疲劳极限时，提出了“细观屈服区临界尺寸”xW的概念，xW是为了满足疲劳裂缝萌生的力学、协调性和概率条件而必须在缺口顶端附近形成的细观屈服区域的大小。在本研究中，xW约为原始奥氏体晶粒大小的11倍。文章还提出了计算缺口件表象疲劳极限的方法。分析了20CrMnTi钢光滑小试样及齿轮经渗碳和渗碳后喷丸表象疲劳极限的变化规律，探讨了根据小试样疲劳极限确定复杂零件（如齿轮）疲劳极限载荷的方法，以及表面强化工艺优化的问题。更多还原

【Abstract】 In this paper, the influence of shot peening with or without carburization on fatigue strength of smooth and notched specimens and some machine parts, such as gears and blades of compressor rotor, which were made from 40Cr, 35CrMo, 20CrMnTi steel and LD7 aluminum alloy, were studied. Apparent fatigue limits of un-peened notched specimens were also studied. Following experiments are included in this paper: heat treatment of specimens, shot peening, analysis of micro-structures, measurement of surface residual stress fields, measurement of surface roughness, measurement of microhardness, measurement of apparent fatigue limit, analysis of fatigue fracture surfaces and finite element calculation.According to a "micro-meso-process theory of fatigue source initiation" and a concept of ’internal/surface fatigue limit’, apparent fatigue limits of shot-peened specimens and optimization of shot peening were discussed.Through a study on apparent fatigue limits of smooth shot-peened specimens, a criterion of shot peening technology optimization was proposed, and a method to calculate the apparent fatigue limits of optimized peened specimens was also proposed. The conclusions above were applied in the shot peening optimization process of aluminum alloy blades, and good effects were achieved.During analyzing fatigue limits of notched specimens, a concept of “dimension of a critical meso-yielding region” xW was proposed. In this work, xW is about 11 times of the original austenite grains. A method to predict apparent fatigue limits of notched specimen was also suggested.The apparent fatigue limit changing rules of carburized and carburized then shot peened smooth specimens and gears were analyzed, and then a calculation method of critical fatigue load of complex machine parts, such as gears, according to the fatigue limit determined with small specimens, as well as a judgment for optimization of surface hardening technology, was discussed.更多还原