In situ observation of ductile fracture using X-ray tomography technique

Abstract

Fast microtomography combined with local crack driving force analysis has been employed to analyze crack-tip stress/strain singularities in an aluminum alloy. The application of fast microtomography has made it possible to observe real crack initiation and propagation behaviors without intermediate unloading. The details of a crack and its local propagation behaviors are readily observed with this technique along with evidence of microstructure/crack interactions. After a preliminary investigation of the achieved spatial resolution, we show that conventional stationary and growing crack singularities can be quantitatively validated by deriving the local crack opening displacement. This is to our knowledge the first three-dimensional validation of conventional fracture mechanics during a real time continuous experiment that has been mainly developed via surface observations so far. We also reveal that there is a spatial transition from a stationary crack singularity to a growing crack singularity in addition to the well-known temporal transition that occurs with the onset of crack propagation. Local crack propagation behaviors are also discussed on the basis of this validation. To separate the effects of complex crack geometry from those of microstructure, we also perform an image-based numerical simulation.

In situ laminography study of three-dimensional individual void shape evolution at crack initiation and comparison with Gurson–Tvergaard–Needleman-type simulations

“…Aiming at investigating microscopic mechanisms of fracture, X-ray computed tomography (CT) has been used to observe in situ the 3-D damage evolution in ductile engineering materials [15][16][17][18]. However, a drawback of CT is that the shape of specimens is limited to small matchstick-like ones with cross-sections of the order of 1 Â 1 mm 2 due to the fact that a large variation in X-ray transmission while rotating specimens should be avoided for better reconstruction of a 3-D image from 2-D projections.…”

Quantitative X-ray tomography

“…The finite element tools also have the advantage 21 Particle tracking (PT) can be used to quantify some fracture mechanics parameters and their evolution during a fast in situ tensile fracture test. 310 a Virtual tomographic slices representing typical crack-tip morphology and its evolution at various steps to failure. The images are acquired using fast tomography during a continuous tensile test for a precracked AA.…”

Quantification and characterisation of porosity in selectively laser melted Al–Si10–Mg using X-ray computed tomography

“…2D and 3D analysis approaches each have their merits when applied in different circumstances. The interested reader is directed to the works of Landron et al [49][50], Gupta et al [51], Weck et al [52] and Toda et al [53], which detail some applications of 3D metal porosity analysis.…”