Issue 41

P. Lopez-Crespo et alii, Frattura ed Integrità Strutturale, 41 (2017) 203-210; DOI: 10.3221/IGF-ESIS.41.28 203 Focused on Crack Tip Fields Mid-thickness studies of the stress intensity factor in the bulk of bainitic steel P. Lopez-Crespo, J. Vazquez-Peralta Department of Civil and Materials Engineering, University of Malaga, C/Dr Ortiz Ramos s/n, 29071 Malaga, Spain plopezcrespo@uma.es C. Simpson School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK T. Buslaps European Synchrotron Radiation Facility (ESRF), 6 rue J Horowitz, 38000 Grenoble, France P. J. Withers School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK Research Complex at Harwell, Didcot, Oxfordshire, OX11 0FA, UK. A BSTRACT . The current work aims at estimating the stress intensity factor deep inside the bulk from elastic strain data measured by synchrotron X-ray diffraction. Key features affecting the evaluation of the stress intensity factor are the number of terms in the analytical model describing the crack tip field, the extension and position of the area of interest of the experimental data, the effect of the experimental data collected within the plastic zone and the number of elastic strain data points used. Here a parametric study of these features is presented in terms of their influence for the stress intensity factor determination. It was found that 3 or 4 terms in Williams’ expansion is often sufficient; the data should be collected from across the full range of angles around the crack tip; and the number of points/number of terms should be greater than 40. K EYWORDS . Stress intensity factor; Bainitic steel; Williams’ expansion; X-ray diffraction. Citation: P. Lopez-Crespo, J. Vazquez- Peralta, C. Simpson, T. Buslaps, P. J. Withers, Mid-thickness studies of the stress intensity factor in the bulk of bainitic steel , Frattura ed Integrità Strutturale, 41 (2017) 203-210. Received: 28.02.2017 Accepted: 15.04.2017 Published: 01.07.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he experimental characterisation of crack tip fields is normally done using surface techniques such as photo- elasticity [1], Moiré interferometry [2], thermo-elastic stress analysis [3], electronic speckle pattern interferometry [4] or digital image correlation [5,6]. For thin components, the surface behaviour is normally representative of the T