Influence of Cracks on Vibration Characteristics of High-Temperature Alloy Blades

The vibration characteristics of aero-engine turbine blades are critical to their operational safety and reliability. To address the issue of cracks caused by superalloy turbine blades in service, a three-dimensional model of blades with cracks at different positions and penetration depths was constructed based on the finite element method. The natural frequency and mode shape of the first ten modes of the blades were computed, and the frequency response characteristics of intact and cracked blades under base excitation were further compared and analyzed. The results indicate that a crack reduces local stiffness, leading to an overall decrease in natural frequencies; this effect is mode-dependent. Cracks closer to the blade root cause a more significant frequency reduction, with the first and fourth order modes being the most sensitive to crack location. As the crack depth increases and the effective load-bearing section diminishes, the frequency drops more substantially. When the crack depth exceeds approximately 10% of the blade width, the fourth order natural frequency decreases by more than 5%. Frequency response analysis reveals that the vibration energy distribution at the interface is uneven, and the vibration amplitude on the upper interface of the crack is about 30 times greater than that on the lower interface during the first order resonance, which significantly exacerbates local stress concentration and potentially accelerates crack propagation. This study elucidates the influence of crack location and depth on blade vibration characteristics, providing a valuable reference for vibration-based monitoring, crack fault diagnosis, and safety assessment of aero-engine blades.