Through examination of fatigue crack growth in 3D synchrotron computed tomography, and displacement fields computation with digital volume correlation, the effects of a single tensile overload on crack behaviour and growth are investigated. The experimental procedure of this study consisted in subjecting a corner-notched AlSi dog-bone type samples to cyclic tensile loading in-situ at a synchrotron X-ray tomography beamline. During the loading sequence, 3D reconstructed scans of the samples were regularly acquired. When nominal crack growth is achieved, single overloads in the loading sequence were applied. Characteristic periods of crack retardation after overloads have been observed, with crack growth recovery occurring preferentially in the bulk of the sample, rather than close to the free surfaces.
Extracting crack opening displacement maps from displacement fields allows the crack closure phenomenon to be studied qualitatively and quantitatively by trying to link areas affected by crack closure to the plastic zones created by the overload.
In order to quantify crack growth behaviour, crack growth rates and stress intensity factor ranges are computed. The systematic study of these parameters is expected to yield quantitative insight into the retardation phenomenon.
|Wednesday 29th November
S06-1 Damage tolerance and fatigue life
83 - 3D study of fatigue crack growth with overload effects in AlSi alloy through synchrotron X-ray tomography and digital volume correlation