Accession Number : ADP001607

Title :   Fracture Mechanics Analysis of Short Cracks at Loaded Holes,


Personal Author(s) : Rooke,D. P.

Report Date : APR 1983

Pagination or Media Count : 6

Abstract : In a predominantly tensile field the time for a fatigue crack to grow a critical length is dominated by the time spent when the crack is short. Cracks frequently start in the vicinity of a stress concentrator such as a hole, and the stress intensity factor which controls crack growth-rate is largely determined by the local stress field. If the hole is loaded on its perimeter, the stress intensity factor for short cracks is strongly dependent on the actual distribution of load on the perimeter. In a cracked pin-loaded lug load is, in general, transmitted from the pin to the lug by both normal and shear forces; the shear forces arise from the friction (fretting) between the pin and the lug. It is shown, by using a Green's function technique, that the presence of friction increases the stress intensity factor and hence increases the rate of growth of fatigue cracks which reduces the fatigue lifetime. The magnitude of these effects depends on the coefficient of friction and how it varies round the hole.

Descriptors :   *Airframes, *Cracking(Fracturing), *Structural mechanics, Fracture(Mechanics), Fatigue(Mechanics), Crack propagation, Growth(General), Sizes(Dimensions), Defects(Materials), Measurement, Loads(Forces), Holes(Openings), Mathematical analysis

Distribution Statement : APPROVED FOR PUBLIC RELEASE