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Fatigue Damage of Rivet Joints in the Condition of Stable Cyclic Load

Hutsaylyuk V., Śnieżek L., Hlado V.

Fatigue of Aircraft Structures

2009

Iss. 1

63--73

The article is devoted, to the attempt of working out of a method for determination of period of exploitation for riveting connections with microdefects on the initial stage and propagation of crack to the moment of appearances to the surface. The tested material used aluminum alloy 2024-T3. Experimental researches are realized on flat specimens from an aluminum alloy 2024-T3 with the row of openings for riveting: without riveting (initial state), with a removal of riveting, and also the specimens connected by riveting at stable amplitude loading (tension, σ=100 MPpa) at the coefficients of asymmetry of cycle of R: 0,15;0,3 and 0,5. An origin of local damages in the sheets, and also in riveting connections was controlled by the use of vortex-current defectoscope BD 3-71 with a sensor of a converting type PN-12 MDF 01. Researches of mechanisms of fracture and fatigue were realized with the use of electron scanning microscope of REM of 106I. As a result of these research, information was received about the mechanisms of failure, defined a form and a size of initial damage in appearance in a crack, which can be used as a quality parameter for determination of transitional period of exploitation with microdefects. On the basis of the collected experimental results, statistical description of sizes of local damages was made.

Analiza rozwoju małych pęknięć zmęczeniowych od otworu oraz mikromechanizm pękania platerowanej blachy stopu aluminium 2024-T3

Kocańda D., Hutsaylyuk V., Hlado V.

Biuletyn Wojskowej Akademii Technicznej

2007

Vol. 56, nr 4

37-53

Zbadano powstawanie i rozwój małych pęknięć zmęczeniowych propagujących od otworu w obustronnie platerowanej blasze lotniczego stopu aluminium 2024-T3 przy stałoamplitudowym jednostronnym zginaniu (R=0,1). Badania początkowego okresu rozwoju pęknięć przeprowadzone za pomocą mikroskopu SEM pozwoliły ustalić miejsce inicjacji pęknięcia i mikromechanizm pękania blachy aluminiowej. Rozwój pęknięć na powierzchni próbek wyciętych z blachy rejestrowano metodą replik. Wykazano duży rozrzut prędkości pękania w przedziale rozwoju małych powierzchniowych pęknięć, który w blachach o grubości 3 mm sięga do 0,5 mm.

The paper deals with mechanism of small crack initiation and growth from a central hole for 2024-T3 Alclad aluminium alloy sheet under cyclic constant amplitude bending (R=0,1). It was established for 3-mm-thick sheet that surface short cracks do not exceed the length of 0,5 mm. Fatigue lifetime that corresponds to this crack length covers 20-25% of total lives of the specimens. The range of crack length was estimated for mechanistically small crack too. The microfacture analysis, made by using SEM microscope, revelated that in cladded sheet the crack source is located beneath a thin Alclad layer at the border with the matrix material. The quasi-cleavage mechanism of cracking was found in the spot of crack initiation as well as in the vicinity of the crack source and in the Alclad layer. This microfracture analysis revealed a complex shape of a crack head in a thin sheet as well.