Partial crack closure under block loading

• Main Author: Borrego, L. P.
• Publication Date: 2008
• Other Authors: Ferreira, J. M., Costa, J. M.
• Format: Article
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: https://hdl.handle.net/10316/4171; https://doi.org/10.1016/j.ijfatigue.2008.02.004
• topic: Aluminium alloy; Fatigue crack growth; Block loading; Crack closure; Partial crack closure

Fatigue crack propagation tests under high-low and low-high block loading sequences have been performed in aluminium alloy specimens. The tests were carried out at constant [Delta]K conditions. Two stress ratios were analysed: R = 0.05 and R = 0.4. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. The observed transient post load step behaviour is discussed in terms of the load change magnitude, [Delta]K baseline levels and stress ratio. The crack closure level was obtained and compared with the crack growth transients. A good agreement between experimental and predicted crack growth rates is obtained when the partial crack closure effect is properly taken into account. Therefore, plasticity-induced crack closure plays an important role on the load interaction effects observed in aluminium alloys.