In this study the fracture analysis was performed to investigate the damage mechanisms of the turbine disc. To solve this problem, a geometrically complicated FE model with some nonlinearities as contact and elastic-plastic material was created. This study explains the reasons for catastrophic failure of the turbine disc. The analysis performed for several conditions has indicated a few critical regions of the turbine, with operational and excessive rotational speed. The first critical area is located on the corner of the 3rd lower slot of the dovetail-rim region of the disc, where the maximum stress was observed. Fracture of the disc in this zone can occur in the speed range of 14,500-16,000 rpm due to excessive stresses. Damage of the turbine wheel is possible also at lower speed, when the volume of the disc will contain a preliminary fatigue crack. However, accurate estimation of the maximum permissible speed as a function of crack size is possible only with a fracture mechanics analysis. The second dangerous area of the disc is also its middle zone, which can yield at 20,000 rpm. Fracture of the turbine in this zone is very dangerous because the engine casing can be punctured by the larger fragments of the disc. However, the probability of this failure is very small because the speed of 20,000 rpm can only be obtained after disconnection of turbine and compressor. Recommendations: (a) Increase the radius of the lower slot of the serration fitting. (b) Change the dimensional tolerance of the dovetail-rim area of the turbine to unload the critical zone of the 3rd lower slot of the disc.
Failure analysis of turbine disc of an aero engine
Schadensanalyse eines Turbinenrades von einem Flugzeugmotor
Engineering Failure Analysis ; 13 , 1 ; 9-17
2006
9 Seiten, 10 Bilder, 12 Quellen
Article (Journal)
English
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