摘要
主起落架完成3倍目标寿命疲劳试验后,进行分解检查时发现上转轴的一个孔边缘及孔内壁出现了裂纹,该上转轴共经历了4倍目标寿命疲劳试验,材料为30CrMnSiNi2A超高强度钢。通过外观检查、残余应力测试、断口宏微观观察、能谱分析、金相检验、硬度测试和化学成分分析等方法,对上转轴的开裂原因进行了分析。采用疲劳断口定量分析方法反推上转轴的裂纹萌生寿命,并给出疲劳裂纹扩展速率与裂纹长度之间的关系曲线。结果表明:该上转轴裂纹的性质为高周疲劳开裂,其裂纹萌生于2倍目标寿命+5个加载谱块之前;上转轴开裂原因与轴孔安装过紧进而承受较大载荷谱应力、源区侧表面损伤和残余应力共同作用有关。通过加强装配过程控制、提高表面处理,上转轴已完成安全寿命试验(即7倍目标寿命)。
A rotating shaft was found to have some cracks at a hole edge and the hole inwall during overhauling after the main undercarriage had completed 3 times the target life in fatigue testing.The rotating shaft in the main undercarriage completed 4 times the target life in fatigue testing altogether.The material of the rotating shaft is 30CrMnSiNi2A super-strength steel.In order to find out the failure mode and cause,a number of testing was performed,including appearance inspection,residual stress testing,fracture surface observation,energy spectrum analysis,microstructure examination,hardness testing and chemical composition analysis.The relationship between fatigue crack propagation rate and crack length was given by the fatigue fractography quantitative analysis.The results indicate that the fracture of the rotating shaft was caused by high cycle fatigue cracking,and the cracks initialized before 2 times the target life and 5 loading spectrums.The initiation of the cracks was mainly related to the large load spectrum stress,damage of the source region side and residual stress.On the basis of the analysis above,the assembly process and surface treatment were improved.As a result,the rotating shaft is now able to stand security life testing （with 7 times of target life）.
出处
《航空学报》
EI
CAS
CSCD
北大核心
2014年第2期461-468,共8页
Acta Aeronautica et Astronautica Sinica
关键词
主起落架
上转轴
疲劳开裂
断口定量分析
磨损痕迹
安装应力
main undercarriage
rotating shaft
fatigue cracking
fractography quantitative analysis
wear trace
assembly stress
