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Fatigue striation morphology

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Presentation on theme: "Fatigue striation morphology"— Presentation transcript:

1 Fatigue striation morphology
(a) Ductile specimens – high stresses (b) Ductile specimens – high stresses common also for small cracks (c) Specimens cycled at lower stresses (d) Specimens cycled at lower stresses (Source: Campbell Laird “The influence of Metallurgical Structure on the Mechanisms of Fatigue Crack Propagation”, Fatigue Crack Propagation, ASTM STP 415, ASTM, 1967, p. 131)

2 Stage II crack - Crack tip plastic blunting and fatigue striation formation
Zero load small tensile load Maximum tensile load Small compressive load Maximum compressive load Small tensile load (Source: Campbell Laird “The influence of Metallurgical Structure on the Mechanisms of Fatigue Crack Propagation”, Fatigue Crack Propagation, ASTM STP 415, ASTM, 1967, p. 131)

3 Crack tip profile in a copper single crystal cycled in tension-compression with a stress axis parallel to [001] (x250) (Source: Campbell Laird “The influence of Metallurgical Structure on the Mechanisms of Fatigue Crack Propagation”, Fatigue Crack Propagation, ASTM STP 415, ASTM, 1967, p. 131)

4 Changes occurring at the crack tip during a fatigue cycle
Compression Maximum tension Crack tip in an annealed nickel specimen after 360 cycles at a strain range of (N = 465) (x850) Crack in a fully compressed aluminum specimen cycled at 0.02 (x350)

5 Fracture surface of a cold-worked copper specimen cycled at high strain showing striations and inter-striations (x4500) (Source: Campbell Laird “The influence of Metallurgical Structure on the Mechanisms of Fatigue Crack Propagation”, Fatigue Crack Propagation, ASTM STP 415, ASTM, 1967, p. 131)

6 Stage I FCG – plastic blunting
(a) Zero stress (b) Maximum stress (c) Compressive stress (Source: Campbell Laird “The influence of Metallurgical Structure on the Mechanisms of Fatigue Crack Propagation”, Fatigue Crack Propagation, ASTM STP 415, ASTM, 1967, p. 131)


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