Fatigue Resistance Design Method for Aluminum Alloy Micro Engine Impeller

Rotor components of micro and miniaturized engines are characterized by low cost and high rotational speed. However, low cost often conflicts with high reliability, and high rotational speed often restricts high reliability, resulting in lower overall reliability for small engines compared with conventional ones. To address the fatigue failure issue of aluminum alloy impellers in micro and miniaturized engines, this study proposes a corresponding fatigue-resistant design method. First, stress distribution of the impeller under centrifugal load is calculated through numerical simulation to identify the critical areas and their stress values. Then, stress values of the critical areas are substituted into the Kitagawa-Takahashi model to calculate the maximum critical flaw size for fatigue crack propagation. Finally, characterization analysis is conducted on the impeller to obtain the maximum flaw size of the component, which is then compared with the calculated critical flaw size to assess service safety of the impeller. Based on the aforementioned fatigue-resistant design method, it was found that the flaw size of a certain impeller exceeded the calculated critical flaw size, leading to fatigue cracking. Therefore, fatigue-resistant design of the impeller in micro and miniaturized engines can be achieved by adjusting the structural geometry to reduce the working stress or optimizing the material process to decrease the flaw size, ensuring that the critical flaw size for crack propagation is larger than the actual detected flaw size.