Now at: Department of Civil and Materials Engineering, University of Malaga, C/Dr Ortiz Ramos s/n, 29071 Malaga, Spain
Overload effects on fatigue crack-tip fields under plane stress conditions: surface and bulk analysis
Article first published online: 14 MAR 2012
© 2012 Wiley Publishing Ltd.
Fatigue & Fracture of Engineering Materials & Structures
Volume 36, Issue 1, pages 75–84, January 2013
How to Cite
LOPEZ-CRESPO, P., WITHERS, P. J., YUSOF, F., DAI, H., STEUWER, A., KELLEHER, J. F. and BUSLAPS, T. (2013), Overload effects on fatigue crack-tip fields under plane stress conditions: surface and bulk analysis. Fatigue & Fracture of Engineering Materials & Structures, 36: 75–84. doi: 10.1111/j.1460-2695.2012.01670.x
- Issue published online: 11 DEC 2012
- Article first published online: 14 MAR 2012
- Received in final form 15 January 2012
- overload effect;
- synchrotron X-ray diffraction
The surface crack opening displacements are characterised by digital image correlation for a (thin) plane stress 316 stainless steel compact tension sample subjected to an overload event. This supports a traditional plasticity-induced closure interpretation showing a knee in the closure response prior to overload, an absence of closure in the accelerated growth regime followed by accentuated closure in the retardation regime. By contrast, measurement of the mid-thickness elastic strain field behind and ahead of the crack made by synchrotron X-ray diffraction shows no evidence of significant crack face contact stresses behind the crack tip on approaching minimum loading. Rather the changes during loading and overloading can mostly be explained by a simple elastic plastic analysis using a value of the yield stress intermediate between the initial yield stress and the UTS. This shows very significant compressive reverse plastic strains ahead of the crack that start to form early during unloading. At the moment it is not clear whether this difference is because of the increasing stress intensity applied as the crack grows, or for some other reason, such as prevention of the crack faces closing mid-thickness due to the reverse plastic zone.