Investigation of fatigue fracture of generator-rotor fan blades
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Mahmood Sameezadeh
Abstract
The failure of a rotating axial flow fan of a 123 MW electric power generator unit is analyzed. The fan was mounted on the generator-rotor at the turbine end. Initial investigations showed that three fan blades had fractured just about 11 h after resuming operation following the last overhaul, causing extensive damage to the unit. The failure of the blades was investigated using fractographic and microstructural characterization techniques as well as mechanical evaluations. Based on fractographic observations high cycle fatigue was identified as the failure mechanism. Formation of multiple primary cracks which coalesced during crack growth to form shallow and semi-elliptical crack geometry was indicative of the influence of additional bending stresses, probably resulting from excessive vibrations. Using fracture mechanics principles, the magnitude of the maximum stress at the time of final fracture of the first broken blade was estimated to be more than 3 times higher than the design operating stress. Furthermore, crack growth lifetime of the blades was evaluated using FRANC3D software. It was found that an operating period of just about one hour was required for small initial cracks to propagate to final failure under the action of excessive bending stresses.
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© 2009, Carl Hanser Verlag, München
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Articles in the same Issue
- Contents
- Contents
- Editorial
- Multiscale materials simulation: the maturing of a scientific concept
- Feature
- Atomistic modelling of materials with bond-order potentials
- Interstitial impurities at grain boundaries in metals: insight from atomistic calculations
- Multiscale modeling of polymers at interfaces
- Coupling atomistic accuracy with continuum effectivity for predictive simulations in materials research – the Quasicontinuum Method
- Basic
- Relative effects of Mo and B on ferrite and bainite kinetics in strong steels
- Experimental study of phase relations in the ZrO2–La2O3–Y2O3 system
- Surface tension of liquid Al–Cu binary alloys
- Microstructure of Ti-6Al-4V specimens produced by shaped metal deposition
- A mesoscopic grain boundary sliding controlled flow model for superplasticity in intermetallics
- Molten salt synthesis and phase evolution of Ba(Cd1/3Nb2/3)O3
- Applied
- Microstructure and properties of violin strings made of metastable austenitic steel
- Transformation of reverted austenite in a maraging steel under external loading: an in-situ X-ray diffraction study using high-energy synchrotron radiation
- Effect of heat treatment on the strain hardening behaviour of an Al–Zn–Mg alloy
- Ball milling as a possible means to produce zinc based coatings
- Size difference effects on the bulk, and surface properties of Bi–Zn, Cu–Pb, K–Pb and K–Tl liquid alloys
- Microstructure and mechanical properties of NiAl–Cr(Mo)–Hf/Ho near-eutectic alloy prepared by suction casting
- Investigation of fatigue fracture of generator-rotor fan blades
- Notifications
- Personal
