Direct measurement procedure for three-dimensional local crack driving force using synchrotron X-ray microtomography

Abstract

X-ray microtomography has been utilized for the observation of ductile fractures in an aluminum alloy with an Al/Al-Si dual phase structure. A procedure for analyzing a series of tomographic images is proposed for extracting the variation in the local crack-tip opening displacement (CTOD), and its feasibility is confirmed. Complicated crack growth behavior and the formation of uncracked ligaments ahead of a crack tip are observed in the alloy owing to the marked difference in local fracture toughness between the two phases. The proposed technique has provided a quantitative interpretation for such phenomena. It is clarified that a conventional measurement significantly overestimates the CTOD level. The transition behavior in CTOD has been revealed over a certain distance across an interface between the two phases, suggesting the existence of scaling effects that influence the microstructure/fracture relationship. Overall the current method could offer a highly effective way of assessing 3-D local fracture behavior.

W-Concentration 3D Mapping in SKH51 Steel by Dual-Energy K-Absorption Edge Subtraction Imaging

“…The average W-concentration in whole specimen was consistent with the chemical composition in the SKH51 steel. The maximum W-concentration at measureable minimum volume, (0.5 μm) 3 , also agreed with the concentration that was obtained by SEM-EDS. It was not easy to assess W-concentration on a carbide particle by means of segmentation based on a linear absorption coefficient.…”

“…[1][2][3][4][5][6][7] X-ray computed tomography (CT) is one of measurement technique to visualize an inner structure, which utilizes a difference of X-ray absorption of matter. Linear absorption coefficients in X-ray are different depending on a chemical element.…”

Four-Dimensional Annihilation Behaviors of Micro Pores during Surface Cold Working

“…The experimental setup and the microtomography conditions have already been reported elsewhere. 4,9,12) The high-resolution detector consisted of a 4000Â2624 pixel cooled-CCD camera (used in the 2Â2 binning mode), an Lu 2 SiO 5 :Ce scintillator, and a 20Â optical lens. The experiment employed 20 keV X-rays monochromatized by a double-crystal monochromator using the Si (111) surface.…”

“…This technique is excellent in that it allows not only the four-dimensional (i.e., three-dimensional time evolution) observation of the inside of a material but also the highdensity mapping of internal mechanical quantities by tracing the physical displacement of dispersion particles. [11][12][13] 2. Experimental Method…”

Fatigue crack growth in SiC particle reinforced Al alloy matrix composites at high and low R-ratios by in situ X-ray synchrotron tomography

“…3D visualization and quantification of heterogeneous microstructures has been successfully performed in Sn-rich alloys [20], powder metallurgy steels [21], metal matrix composites [22][23][24][25] and aluminum and copper alloys [26][27][28].…”