Crack propagation in fine grained graphites


XCT visualization of the crack as it propagates with increasing load in SNG742 and T220 in 30 degree configuration

Stable crack growth in two fine grained advanced graphites for advanced nuclear reactor systems has been studied to show the feasibility of small specimen tests that may ultimately be used to investigate fracture toughness of irradiated graphites.

Xiaochao Jin, with colleagues from Professor T James Marrow's research group, the State Key Laboratory for Strength and Vibration of Mechanical Structures at Jiaotong University, the Space Structures Research Centre at Guizhou University and the Department of Materials at Loughborough University, investigated how cracks propagated from a central notch, inclined at 0o or 30o to the loading axis, as the tests were observed in situ by X-ray computed microtomography.  

The three-dimensional (3D) displacement fields were measured by digital volume correlation.  The crack shape, tip location and crack opening displacements were determined by 3D phase congruency edge detection of full field displacements.  Linear elastic 3D finite element simulations calculated the J-integral and mode I, mode II and mode III stress intensity factors (SIFs) acting on the crack tip, using the full field displacements as boundary conditions, to find the critical condition for crack growth.

You can read the full paper 'Crack propagation in fine grained graphites under mode I and mixed-mode loading, as observed in situ by microtomography' in Carbon - volume 193 (30 June 2022).