Original paper(Vol.45 No.1 pp.64)

Fatigue crack growth behavior of alumina short fiber reinforced aluminum alloy at room and higher temperatures

Tanaka Tsuneshichi; Nakayama Hideaki; Yamamoto Shigeru; Kobayashi Yukiyoshi

Abstract:In order to clarify the fatigue crack growth mechanism of an alumina short fiber reinforced aluminum alloy (FRM), fatigue crack growth tests were carried out at several stress ratios on the center cracked tension (CCT) specimens at room and elevated temperatures. Aluminum alloy, A6061-T6 was also used as a reference material. Comparison of fatigue crack growth rate curves determined for A6061-T6 and FRM specimens indicated that the effect of temperature on the crack growth rate curves was much smaller for FRM than that for A6061, and the crack growth property of FRM was superior to A6061 in the region of low crack growth rate including the threshold, when the comparison was made on K_max and DK. By estimating the values of DK_eff, it was shown that the fatigue crack growth rates of A6061 and FRM at each temperature were governed by DK_eff and K_max^aDK_eff^(1-a), respectively. Moreover, the detailed evaluation indicated that the fatigue crack growth rates of A6061 and FRM at different stress ratios and temperatures could be expressed by introducing new parameters, excepting in the threshold region, as follows:
da/dN =C₁{U_R(1-R) /U_R=0.1 K_max(E s_0.2)^-1/2} ^m1 for A6061
da/dN =C₂ {{U_R(1 -R)/U_R=0.1} ^(1-a)K_max(Es_0.2)^-1/2}^m2 for FRM
where R is the stress ratio, U_R is the crack opening ratio at stress ratio R, U_R=0.1 is the value of U at R =0.1, E and s_0.2 are Young's modulus and 0.2% proof stress at each temperature, and C₁, C₂, m₁ and m₂ are material constants.

Key Words:alumina short fiber reinforced aluminum alloy, aluminum alloy A6061-T6, room and higher temperature, new fracture mechanical parameters