中文摘要：

以航空器APU压气机第一级叶轮损伤为研究对象，详细分析了APU压气机第一级叶轮断口的形貌、化学成分、金相组织。研究结果表明，APU第一级叶轮叶片掉块和裂纹均属于疲劳断裂，疲劳导致叶片掉块和开裂。叶片疲劳可能与叶盆根部表面存在显微缺陷有关，显微缺陷可能是由于叶轮工作中微小颗粒随气流在叶盆表面冲蚀的结果，它们的存在加重了局部应力的集中，形成了疲劳的起源。叶片前缘损伤部位通过能谱分析未发现外来元素，但不排除外来物击伤叶片前缘的可能性。该分析结果将有助于飞行事故的调查并得出正确的失效分析结论。

英文摘要：

The fractograph, chemical composition and microstructure of the failedstage 1 APU wheel of civil aviation aircraft are analyzed by SEM and energy spectrum. The results show that fatigue results in the breaks and cracks of blades of the stage 1 APU wheel. The fatigue of blades may be caused by the microscopical defects located at the surface of root of blade basin. The microscopical defects may he the result of erosion of the tiny grains in the airflow. The increase of local stress caused by these defects forms the origins of fatigue. There are no extra elements at the damage position of blade leading edge of two APU wheels by the analysis of X-ray energy spectrum. However the possibility of attack by extra objects cannot be eliminated. There are no abnormity of the chemical composition and microstructure in the APU wheel. The results are very helpful for aircraft accident investigation to find out the right failure analysis results.