Anisotropic ductile fracture Part I: experiments

Deformation and fracture are investigated at room temperature in steel through tension and compression tests. Round smooth bars and cylinders are used to characterize the deformation behavior while round notched bars are used to explore stress state and specimen orientation effects on fracture. The microstructure is characterized to infer initial average values of porosity, void aspect ratio and void spacing ratio, all three playing a key role in the fracture process. Interrupted tests are used to determine the spatial distribution of those variables after crack extension thus providing a basis for comparison at the micro-scale with theoretical predictions. All damage stages are found to be inherently anisotropic, including void nucleation and crack propagation. An important finding of this investigation is that, in quantitative modeling of ductile fracture, any void growth model should be supplemented by a physically motivated void coalescence model. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.