Abstract
In order to clarify the fatigue failure mechanism of an alumina short fiber reinforced aluminum alloy (FRM), a series of fatigue crack growth tests were carried out under several stress ratio conditions on the center cracked tension (CCT) and compact tension (CT) specimens. The crack growth rate was observed for CCT specimens and the crack opening displacement was measured by using a clip gauge attached at the crack mouth of CT specimens. Aluminum alloy, A6061-T6 was also used as a reference material.
The comparison of fatigue crack growth rate curves determined on A6061-T6 and the FRM specimens indicated that FRM had low fatigue crack growth resistance in comparison with A6061-T6 alloy in the high crack growth rate region. And it was revealed that both the crack opening ratio and crack opening displacement of FRM were suppressed under a high stress ratio of R=0.7, due to the bridging effect of alumina short fibers. The fatigue crack growth rate of FRM was not governed only by the effective stress intensity factor range, ΔKeff, contrary to the case of monolithic metallic materials. A detailed evaluation indicated that the fatigue crack growth rate of the FRM could be expressed by using both Kmax and ΔKeff as follows:
da/dN=C{(Kmax)α(ΔKeff)1-α}m
