Stress Corrosion Cracking of Tunnel Ventilation Fan Blades: A Case Study

Installations in road tunnels, such as jet fans, are exposed to a harsh environment. After two failures of rotor blades, made of aluminum cast, a failure analysis was initiated. The main goal of this study was to determine the causes, e.g., overloading, material defect, corrosion, and design deficie...

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Bibliographic Details
Published in:Metals (Basel ) 2022-12, Vol.12 (12), p.2065
Main Authors: Michel, Silvain, Tuchschmid, Martin, Sauder, Martin, Frey, Simon
Format: Article
Language:English
Subjects:
Aluminum
aluminum cast alloy
Aluminum castings
Analysis
Brittleness
Case studies
Corrosion
Corrosion and anti-corrosives
Corrosion effects
Corrosion fatigue
Corrosion products
Corrosion resistance
Damage
Design
Design defects
Electrical installations
Failure analysis
Fan blades
Fatigue strength
Fracture mechanics
Humidity
Hydrogen embrittlement
Hypotheses
Laboratories
Outdoor air quality
Roads & highways
Rotor blades
static fracture
Stress corrosion cracking
Tunnels
Ventilation
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Summary:Installations in road tunnels, such as jet fans, are exposed to a harsh environment. After two failures of rotor blades, made of aluminum cast, a failure analysis was initiated. The main goal of this study was to determine the causes, e.g., overloading, material defect, corrosion, and design deficiencies, and to define actions to avoid such events in the future. The fractographical analysis showed corrosion attack and a cleavage type of fracture. These findings pointed to two damage mechanisms acting in both cases: stress corrosion cracking due to hydrogen embrittlement, causing a brittle static failure. The failure analysis did not lead to a full understanding of the damage mechanisms: Service loads were far too low to explain the high stresses needed for a brittle static failure. A wedging effect of corrosion products in the gap between the blade and the mounting was proposed as the cause of high static stresses in the fractured cross section. Alternative materials as well as different corrosion surface protections were evaluated with respect to corrosion and corrosion fatigue resistance. Finally, an appropriate surface protection was proposed as the solution for inhibiting corrosion and therefore the risk of the reproduction of such failures.
ISSN:2075-4701
2075-4701
DOI:10.3390/met12122065