ABSTRACT

Fatigue crack growth tests were carried out on 2024-T3 aluminium alloy centre crack tension (CCT) specimens. The width, length and thickness of the specimens were 90, 300, 6 mm, respectively. These specimens were machined according to ASTM E 647 recommendation (Roberta 1985). The fatigue tests were conducted with computer controlled electro hydraulic machine (Instron 8501) under load control with the program MAX using a sinusoidal waveform with a frequency of 5 Hz. The crack length was monitored with a travelling microscope (Fatigue Technology Inc.). Periodic and single tensile overload fatigue tests were performed by superimposing I, 2, 3, 4 and 5 overloads on constant amplitude cycles (after every 1000) with R=O.l at the same overload ratio of 1.7. For observing overload effect on the fatigue crack growth, fatigue fracture surfaces were examined visually and in a SEM (CamScan S4).