Failure analysis of gearbox mounting bolt

Sujata, M and Madan, M and Venkataswamy, MA and Bhaumik, SK (2007) Failure analysis of gearbox mounting bolt. Project Report. National Aerospace Laboratories, Bangalore, India.

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Two mounting bolts pertaining to different accessory gearboxes were sent to the laboratory for analyzing the cause of failure. Investigation revealed that both the bolts have failed by fatigue; one under bending and the other under reverse bending. The fatigue cracks have initiated at the thread root in both the cases. No metallurgical and/or mechanical abnormalities were found responsible for the fatigue crack initiation and the fatigue was found to be stress related. Analysis showed that in one bolt, the fatigue crack initiation was accelerated due to bending stress resulting from the assembly stresses. In the other bolt, the reverse bending fatigue occurred during service due to high length to diameter ratio of the bolts. It appears that such failures in the present accessory gearbox mounting scheme is unavoidable. A detailed analysis of the failures has been presented in this report with a few recommendations for a possible improvement in the fatigue life of the mounting bolts.

Item Type: Monograph (Project Report)
Uncontrolled Keywords: Aircraft;Accessory gearbox;Bolts;Bending fatigue
Subjects: AERONAUTICS > Aeronautics (General)
CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
Depositing User: Ms. Alphones Mary
Date Deposited: 25 Jul 2011 05:11
Last Modified: 25 Jul 2011 05:11

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