Axial Flow Fan Resonance Related Fracture - Motion Amplification
A carbon fiber axial flow fan ferrule base fracture was caused by resonance at twice the blade pitch frequency, amplified by structural resonance. This highlights the need for proper modal analysis, vibration monitoring, and material consideration in design.
Resonance fracture in the base of the ferrule of an axial flow fan.
Recently we faced a critical case of fracture in the base that supports the ferrule of a fan made of carbon fiber.
The Motion Magnification analysis (filter at 2x of the blade pitch, with a magnification of 60x), together with the traditional vibration measurement and an impact test test with an instrumented modal hammer, showed that the excitation frequency coincided with the 2x of the blade pitch, amplified by the phenomenon of a structural resonance of the ferrule. This condition caused a magnification of the vibration that ended up compromising the integrity of the concrete of the base, an uncommon situation but of high operational impact.
These types of failures highlight the importance of:
• Proper modal analysis during design
• Vibration monitoring in the field
• Consideration of materials or redesign of the rigidity for the manufacture of the ferrule.
Resonance is unforgiving, and when aligned with structural components, even the most robust materials can fail.
Have you had to analyze similar failures? How do you handle early MRI detection in large industrial ventilators?
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