Synchrotron 3D characterization of arrested fatigue cracks initiated from small tilted notches in steel
Journal Title: Frattura ed Integrità Strutturale - Year 2015, Vol 9, Issue 33
Abstract
High resolution synchrotron X-ray tomography has been used to obtain 3D images of arrested cracks initiated at small artificial defects located on the surface of cylindrical steel specimens subjected to mode I fatigue loading. These defects consist in small semi-circular slits tilted at 0°, 30° or 60° with respect to the plane normal to the loading axis; all of them had the same defect size, area = 188 μm, where the area denotes the area of the domain defined by projecting the defect on a plane normal to the loading axis. Arrested cracks initiated from the notch were observed for all tilt angles at the surface of samples cycled at the fatigue limit (stress amplitude at which the specimen does not fail after 1×107 cycles). High resolution synchrotron X-ray tomography has been used to obtain 3D images of those small defects and non-propagating cracks (NPC). Despite the fact that steel is a highly attenuating material for X rays, high resolution 3D images of the cracks and of the initiating defects were obtained (0.65 m voxel size). The values of surface crack length measured by tomography are the same as those obtained by optical microscope measurements. The area values present the same tendency as the surface length of NPC, i.e. larger non-propagating cracks areas were observed in the softer steel. In the extreme case of 60º tilted defect, the crack fronts appear much more discontinuous with several cracks propagating in mode I until arrest.
Authors and Affiliations
P. Lorenzino, J. Buffiere, S. Okazaki, H. Matsunaga, Y. Murakami
Keywords
Related Articles
- EP ID EP122215
- DOI 10.3221/IGF-ESIS.33.27
- Views 53
- Downloads 0
Electro-mechanical coupled design of self-powered sensing systems and performances comparison through experiments
Recent advances in low-power sensors and electronic components open to innovative strategies in structural monitoring and real-time data processing, in particular for industrial and vehicular fields. Dedicated devi...
Fatigue characterization of a crankshaft steel: Use and interaction of new models
The peculiar geometrical shape and working conditions of crankshafts make fatigue becoming responsible for most of the failure cases in such components. Therefore, improvement of crankshaft performance requires e...
Fatigue life assessment of thin-walled welded joints under non-proportional load-time histories by the shear stress rate integral approach
Fatigue life tests under constant and variable amplitude loadings were performed on the tube-tube thin-walled welded specimens made of magnesium (AZ31 and AZ61) alloys. The tests included pure axial, pure torsiona...
Fatigue life prediction of casing welded pipes by using the extended finite element method
The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. B...
Numerical modelling of reinforced concrete beams with fracture-plastic material
This paper describes the use of models of fracture-plastic materials for reinforced concrete in numerical modelling of beams made from reinforced concrete. The purpose of the paper is to use of a model of concret...