Studies on fatigue crack growth for airframe structural integrity applications

Sunder, R. (1995) Studies on fatigue crack growth for airframe structural integrity applications Sadhana (Academy Proceedings in Engineering Sciences), 20 (1). pp. 247-285. ISSN 0256-2499

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A review is made of efforts at the National Aerospace Laboratories in the development of fatigue crack growth prediction technology for airframe applications. The research was focused on extension of rainflow techniques for crack growth analysis and development of accelerated crack growth calculation methods for spectrum loading. Fatigue crack closure forms a crucial element of modelling and fractographic techniques were developed for its study. These, combined with binary coded event registration enabled crack growth and closure mapping for part-through cracks in metallic materials. Experimental research on short cracks at notches led to discovery of the hysteretic nature of crack closure, which explains well-known history-sensitive local mean stress effects in notch root fatigue. Optical fractography of failures obtained under simulated service conditions revealed that short cracks do not exhibit any more scatter than long cracks at comparable growth rates. The nature of multi-site crack initiation and growth of small cracks at notches was investigated and the effort extended to lug joints that are widely used in airframe applications. Results from this work suggest the possibility of modelling crack growth from a size smaller than 50 microns through to failure, thereby accounting for a major fraction of total life.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Fatigue Crack Growth; Rainflow Technique; Airframe Structural Integrity; Fractographic Techniques
ID Code:51382
Deposited On:28 Jul 2011 11:50
Last Modified:18 May 2016 05:21

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