Kmax effects on the near-threshold fatigue crack growth of powder-metallurgy aluminum alloys

Fatigue crack growth (FCG) research conducted in the near-threshold regime has identified a room-temperature creep crack growth damage mechanism for a fine-grain powder-metallurgy aluminum alloy (8009). At very low Delta K, an abrupt acceleration in room-temperature FCG rate occurs at high stress ratio and is exacerbated by increased levels of K-max (K-max >= 0.4K(Ic)). Detailed crack-surface analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near-threshold and K-max influenced accelerated crack growth is time and temperature dependent. (C) 2009 Published by Elsevier Ltd.