Failure investigation of blade and disk in first stage compressor

A matched blade tenon and disk mortise of the first stage compressor in an aeroengine fractured simultaneously, Apparently, both had fatigue features on the fracture surfaces. Macro observations showed the cracking sites were roughly at the central region of the matched tenon and mortise. Contact su rfaces examination revealed there were important marks, showing abnormal co ntact of the tenon and mortise in service. Material qualities were inspecte d and the stresses in the tenon and in the mortise were calculated under no rmal conditions. These demonstrate that the failures were not due to the in sufficiency of failure resistance but the deviation from expected condition s. Conclusively, the bad contact of the tenon and the mortise is responsibl e for the failures. Field non-destructive inspection was performed on other aeroengines of the same type, and some cracks, which were very similar to those in the fractured tenon and mortise, were found. Further investigation revealed that the design shortcoming resulted in over-compensation of cent rifugal bend moment and bad contact condition. (C) 2000 Elsevier Science Lt d. All rights reserved.