Notch Effects and the Critical Alternating Stress Required to Propagate a Crack in an Aluminium Alloy Subject to Fatigue Loading

Abstract

Fatigue tests at zero mean load have been carried out on aluminium alloy (BS.L65) specimens containing edge cracks of various lengths. It was found that the relationship between the crack length l (inches) and the critical alternating propagation stress σ (ton/in2) was given by σ3 l = 0·2. A similar type of relationship (i.e., σ3 l = 5·5) was obtained previously for mild steel (2). Fatigue tests have also been carried out on notched specimens and the occurrence of non-propagating cracks discussed in terms of the above relationship.