The crack of engine-block made of cast iron often occurs suddenly in engine-block fatigue test, and the crack is not easy to be diagnosed. In order to overcome the above difficulties, the strain which is the response of output in the engine-block fatigue test was used to diagnose the occurrence of fatigue crack. The strain gauge was sticked on the bottom of crankcase to acquire the real-time strain signals,and the signals were modeled by time series analysis. Euclid distance, Mahalanobis distance and the variance of residual were calculated respectively to find the symptom of fatigue crack in the engine-block fatigue test. The result shows that the amplitude of strain has subtle difference between undamaged block and damaged block in time field, but the variance of residual has the instantaneous mutation at the same time, so it can be used to diagnose the fatigue crack occurrence.%针对灰铸铁材料发动机机体疲劳试验中裂纹的出现表现为瞬间突发性,以及疲劳裂纹的出现不易识别的问题,采用实测应变信号作为系统的输出响应研究机体疲劳裂纹的诊断方法,对机体疲劳试验过程中曲轴箱底部应变信号进行了实时记录,并且采用经典时序方法对所测应变信号进行建模,计算各个时间段时序模型的欧几里得(Euclid)距离、马氏(Mahalanobis)距离及模型残差的方差.分析结果表明:疲劳裂纹出现瞬间,应变时域信号幅值表现为不易察觉的微小变化,但是时序模型残差的方差却出现瞬间突变,因此,残差的方差对裂纹出现瞬间具有敏感特性.
展开▼
