A fatigue striation spacing analysis was made from measurements on AVT Al-alloy specimens tested in air under combined cyclic tension and static-rotation loads at various alpha-angles of rotation, and stress ratios, R. Fractographic analyses have shown similarities in terms of striation spacing formation in the investigated range of alpha-angles and R ratios. The similarity in the fatigue fracture mechanisms attested to the possibility of characterizing the striation spacing formation by a unified kinetic diagramm via a Ke = KIF(alpha,R) approach for different alpha-angles and R ratios. The function F(alpha,R) was determined and it can be used to calculate the tensile stress equivalent according to values of sigmai measurements taken from components broken in tests or in service. It was a longeron of the rotor-blade of helicopters manufactured from AVT Al-alloy broken in service and tested cyclically that were investigated fractographically. An analysis of the formation of striations and their spacing has shown similarities with the investigated longerons fatigued in tests and in service. The crack growth life versus number of flights and stress equivalent was calculated according to values of the sigmai measurements. It was shown that a fatigue crack will not nucleate in longerons in service if the depth of defects on the external surface have a size less than 0.3 mm. The stress for tested longerons is near to the calculated equivalent for longerons failed in service.
Quantitative fractographic analyses of fatigue crack growth in longerons of in-service helicopter rotor-blades
Quantitative fraktographische Analysen des Ermüdungsrißwachstums in Längsträgern von in-service Hubschrauber-Rotorblättern
Fatigue and Fracture of Engineering Materials and Structures ; 19 , 9 ; 1129-1141
1996
13 Seiten, 10 Bilder, 6 Tabellen, 18 Quellen
Aufsatz (Zeitschrift)
Englisch
Engineering Index Backfile | 1955
Europäisches Patentamt | 2020
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