Title: Micro-fracture maps in progressively drawn pearlitic steels under triaxial stress states

Authors: J. Toribio, F.J. Ayaso

Addresses: Department of Materials Engineering, University of Salamanca E.P.S., Campus Viriato, Avda. Requejo 33, 49022 Zamora, Spain. ' Department of Materials Engineering, University of Salamanca E.P.S., Campus Viriato, Avda. Requejo 33, 49022 Zamora, Spain

Abstract: In this paper, the fracture performance of axisymmetric notched samples taken from prestressing steels with different levels of cold drawing is studied. Fractographic analysis of the samples by means of scanning electron microscope (SEM) revealed the microscopic topographies after failure and allowed the assembly of micro-fracture maps (MFM) covering the whole fracture surface and containing relevant information on the micromechanisms of fracture in the material. With regard to the influence of the stress triaxiality (constraint), the behaviour is more ductile in the case of blunt notches than in the case of sharp notches. In the matter of the influence of the cold drawing degree, the fracture behaviour becomes more ductile as the strain hardening level of the steel increases, so that cleavage is predominant in the fracture area of slightly drawn steels, whereas the presence of micro-void coalescence (MVC) increases with the degree of cold drawing and becomes predominant in the case of the most heavily drawn steels in which cleavage can hardly be detected as an extended region.

Keywords: pearlitic steel; cold drawing; triaxial stress states; notched samples; microfracture maps; MFM; topological schemes of fracture; TSF; prestressing steels; strain hardening; micro-void coalescence.

DOI: 10.1504/IJMATEI.2009.024027

International Journal of Materials Engineering Innovation, 2009 Vol.1 No.1, pp.61 - 73

Published online: 24 Mar 2009 *

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