On the growth of cracks from etch pits and the scatter associated with them under a miniTWIST spectrum. (April 2018)

• Record Type: Journal Article
• Authors: Tamboli, D.; Barter, S.; Jones, R.
• Is Part Of: International journal of fatigue. Volume 109(2018)
• Page Start: 10
• Page End: 16
• Publication Date: 2018-04
• Subjects: Aircraft sustainment -- Etch pits -- Fatigue crack growth -- Lead cracks -- Fatigue variability; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2017.12.002
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: Presents the growth of cracks growing from pits under a civil transport aircraft spectrum. Quantitative Fractography is performed with the aid of markerbands. Results show that crack growth is exponential in nature, similar to that observed under combat aircraft spectra. The growth of cracks under miniTWIST spectrum can be captured well by the Hartman-Schijve equation. Abstract: This paper examines the growth of cracks from small naturally occurring discontinuities in AA7050-T7451 coupons tested under a miniTWIST load spectrum. A markerband is inserted in the spectrum to aid in Quantitative Fractography. The resulting crack growth curve is reasonably exponential in nature, which indicates that crack growth under combat aircraft spectra and civil aircraft transport spectra is similar. It is also shown that the Hartman-Schijve crack growth equation can be used to compute the crack growth histories and account for the scatter seen in the various tests by allowing for small changes in the value of ΔKthr .