Title: Elastic-Plastic material response at noches and fatigue cracks by a coherent optics method

Authors: Gianni Nicoletto

Addresses: Dipartmento di Ingengneria delle Construzoni Meccaniche, Nucleari, Aeronautiche e di Metallurgia, Universita di Bologna, 2, 40136 Bologna, Italy.

Abstract: Elastic-Plastic material response near notch roots and fatigue cracks has been studied by moire interferometry, which is a coherent optics technique for high sensitivity full-field in-plane displacement measurement. Different materials, namley a NiCrMov steel, an as-cast aluminium alloy and precipitation-strengthened aluminium alloy, were studied. The evolution of residual deformations at blunt and sharp notches under monotomic loading conditions was determined. Non-linear finite-element companion calculations were performed for correlation purposes. Inhomogeneous plastic response, apparently due to the material microstructure, was observed and discussed. The presence of cyclic plastic zone at a fatigue crack tip, as well the localized strain distributions, have been investigated. Experimentally determined stress-intensity factors have been found to differ from linear elastic fracture mechanics predictions.

Keywords: mechanics of materials; fatigue cracks; fracture mechanics; notches; stress intensity factors; strain concentration factors; material plasticity; NiCrMov steel; aluminium alloys; coherent optics; Moire interferometry; elastic-plastic response; residual deformation.

DOI: 10.1504/IJMPT.1987.036785

International Journal of Materials and Product Technology, 1987 Vol.2 No.3/4, pp.338 - 355

Published online: 07 Nov 2010 *

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