CRACK CLOSURE ANALYSIS AFTER PEAK OVERLOADS

L.P. Borrego  J.M. Ferreira  J.M. Costa      

Anales de la Mecánica de la Fractura, nº 18 . 2001 . Pág. -
Ver (.pdf): 7014IMP

Resumen: Fatigue crack propagation tests with single tensile peak overloads have been performed in 6082-T6 aluminium alloy at several baseline ?K levels, ranging from 4 to 10 MPa m1/2, and at stress ratios of 0.05 and 0.25. The tests were carried out at constant ?K conditions, using MT specimens in a servohydraulic machine at a frequency of 20 Hz. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. The observed transient post overload behaviour is discussed in terms of overload ratio and baseline ?K level. The crack closure parameter U was obtained and compared with the crack growth transients. Plasticity induced closure seems to be the main mechanism determining the transient crack growth behaviour following overloads on 6082-T6 alloy. Predictions based on crack closure measurements show good correlation with the observed crack growth rates for all the postoverload transients when discontinuous closure is accounted for.

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Department of Mechanical Engineering, ISEC/IPC, 3030 Coimbra, Portugal
Department of Mechanical Engineering/FCT, University of Coimbra Polo II, Pinhal de Marrocos, 3030 Coimbra, Portugal
Department of Mechanical Engineering/FCT, University of Coimbra Polo II, Pinhal de Marrocos, 3030 Coimbra, Portugal