基于小裂纹理论的铸造钛合金ZTC4疲劳寿命预测  

Fatigue Life Prediction of Cast Titanium Alloy ZTC4 Based on the Small Crack Theory

作　　者：童第华[1] 吴学仁[1] 刘建中[1] 胡本润[1] 陈勃[1] 

机构地区：[1]北京航空材料研究院,北京100095

出　　处：《材料工程》2015年第6期60-65,共6页Journal of Materials Engineering

基　　金：国家自然科学基金青年基金项目(11402249)

摘　　要：铸造钛合金ZTC4在飞机和航空发动机上应用日益广泛。深入研究ZTC4疲劳全寿命预测方法,旨在为航空构件的损伤容限设计和寿命预测探索新的途径。本文以宏观和微观结合的手段,采用板材试样的高周疲劳试验、中心裂纹试样的长裂纹扩展试验和扫描电子显微镜(SEM)的断口分析等三种试验,研究了ZTC4在室温恒幅载荷条件下的疲劳断口特征和裂纹扩展行为;对引起疲劳失效的主要原因-材料初始缺陷(夹杂或气孔)进行了定量表征;基于Newman裂纹闭合模型建立了ZTC4长裂纹的(da/d N)-ΔKeff基线数据;通过对平板内埋椭圆裂纹的断裂力学分析,从基于微观结构和断口分析统计确定的初始缺陷尺寸出发,对ZTC4在恒幅载荷条件下两种应力比的疲劳全寿命进行了预测和实验验证,得到了具有较好学术意义和工程应用价值的研究结果。The casting titanium alloy ZTC4 is widely used in aircraft and aircraft engine.Through indepth investigation of the total fatigue life prediction methods for ZTC4,the present thesis aims at exploring new ways for damage tolerance design and life prediction of aero＇s key components.By a combination of macro-and microscopic analysis methods,ZTC4 was studied systematically under constant-amplitude loading with three types of tests,i.e.high-cycle fatigue test of plane specimens,long crack growth test of center crack tensile （CCT） specimens and direct SEM observation.The main causes of fatigue failure,namely material＇s initial defects （inclusions or pores）,were quantitatively characterized.The baseline long crack growth data of ZTC4,（da/dN）-Keff,was generated based on the Newman crack closure model.By fracture mechanics analysis of embedded elliptical cracks,and starting from the initial flaw sizes determined from statistical analysis of the material＇s microstructure and fractographic observation of fracture surfaces,total fatigue life of ZTC4 under constant-amplitude loading for two stress ratios was predicted and experimentally verified.The good research results withboth academic significance and engineering application value are obtained.

关 键 词：铸造钛合金 小裂纹 疲劳寿命预测 裂纹闭合 

分 类 号：O346.2[理学—固体力学]