A 3D measurement procedure for internal local crack driving forces via synchrotron X-ray microtomography

Synchrotron X-ray microtomography has been utilized for the in situ observation of fatigue crack opening/closure during load cycles. High-resolution phase contrast imaging technique has enabled the reconstruction of clear crack images together with the details of microstructural features. Physical displacements of micro-pores in a crack-tip stress field are used to obtain local mixed-mode crack driving forces along a crack front, and its feasibility is confirmed. Complicated crack closure behaviour are observed due to the combined effects of local modes II and III displacements. The technique used provides a highly effective way of assessing local crack driving forces together with supplementary ways of verifying and interpreting it by visualising and quantifying various forms of crack-tip shielding behaviour. The proposed technique is clearly advantageous compared to the limited procedures available in the current literature, where detailed internal information can only be achieved for limited types of material.

[1]  I. Sinclair,et al.  Assessment of the fatigue crack closure phenomenon in damage-tolerant aluminium alloy by in-situ high-resolution synchrotron X-ray microtomography , 2003 .

[2]  Faculdade de Engenharia,et al.  Recent Advances in Experimental Mechanics , 1994 .

[3]  Angus J. Wilkinson,et al.  A crystallographic mechanism for fatigue crack propagation through grain boundaries , 2000 .

[4]  T. Kinoshita.  Stress singularity near the crack-tip in silicon carbide : Investigation by atomic force microscopy , 1998 .

[5]  O. Sbaizero,et al.  Raman Microprobe Evaluation of Bridging Stresses in Highly Anisotropic Silicon Nitride , 2004 .

[6]  Yuh J. Chao,et al.  Quantification of constraint on elastic–plastic 3D crack front by the J–A2 three-term solution , 2001 .

[7]  Peter Cloetens,et al.  Characterization of internal damage in a MMCp using X-ray synchrotron phase contrast microtomography , 1999 .

[8]  Stavros Syngellakis,et al.  Numerical modelling of combined roughness and plasticity induced crack closure effects in fatigue , 2000 .

[9]  J. Schijve,et al.  FATIGUE CRACK CLOSURE MEASUREMENT OF 2024-T3 SHEET SPECIMEN , 1994 .

[10]  J. Knott.  Mechanics of Fracture , 1983 .

[11]  Peter Cloetens,et al.  Study of the interaction of a short fatigue crack with grain boundaries in a cast Al alloy using X-ray microtomography , 2003 .

[12]  Paul C. Paris,et al.  An evaluation of ΔKeff estimation procedures on 6061-T6 and 2024-T3 aluminum alloys , 1999 .

[13]  Bhushan Lal Karihaloo,et al.  Approximate Green's functions for singular and higher order terms of an edge crack in a finite plate , 2002 .

[14]  Albert S. Kobayashi,et al.  Handbook on experimental mechanics , 1987 .

[15]  Nadarajah Narendran,et al.  Application of fiber optic sensors to fracture mechanics problems , 1991 .

[16]  J C Froment,et al.  Positron Emission Tomography Metabolic Data Corrected for Cortical Atrophy Using Magnetic Resonance Imaging , 1996, Alzheimer disease and associated disorders.

[17]  J. Llorca,et al.  ROUGHNESS-INDUCED FATIGUE CRACK CLOSURE: A NUMERICAL STUDY , 1992 .

[18]  Guk-Rwang Won.  American Society for Testing and Materials , 1987 .

[19]  K. Sassen.  The Polarization Lidar Technique for Cloud Research: A Review and Current Assessment , 1991 .

[20]  Gabor T. Herman,et al.  Image reconstruction from projections : the fundamentals of computerized tomography , 1980 .

[21]  S. Hudak,et al.  The crack-tip mechanics and growth rates of small fatigue cracks in ASTROLOY , 1995 .