Failure analysis of cracked NLG brackets

Kannan, CR and Madan, M and Sujata, M and Raghavendra, K and Bhaumik, SK (2011) Failure analysis of cracked NLG brackets. Project Report. National Aerospace Laboratories, Bangalore, India.

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Two cracked NLG brackets; one in finished condition and the other in semi-finished condition, were sent to the laboratory for analysis. Cracks were noticed in the components during dye penetrant inspection. It was established that the cracks were resulted during heat treatment of the semi-finished components. Hence, study was undertaken to establish first whether or not there were any problems in the material or in heat treatment procedure. Microstructural and fractographic examination confirmed that there were no abnormalities in the material. Based on the microstructural study, the possibility of overheating during heat treatment was also ruled out. However, analysis of the failure, in general, indicated that most probably, the cracking of the NLG brackets occurred due to differential stresses that got developed in different sections of the components during quenching process. Because of the shape, varying thickness and extra material left in the component after semi-finishing operation, some of the fillet regions were found to be vulnerable for crack generation during quenching operation. Analysis also shows that such heat treatment cracking in the NLG brackets in its present form is probably unavoidable. In view of this, it is recommended that suitable modification be made in the design so that the fabrication problems encountered currently can be avoided.

Item Type: Monograph (Project Report)
Uncontrolled Keywords: Aircraft;NLG brackets;Fabrication;Quench cracks;Design
Subjects: AERONAUTICS > Aeronautics (General)
CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
Depositing User: Users 11 not found.
Date Deposited: 12 Jul 2011 08:41
Last Modified: 12 Jul 2011 08:41

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