Fatigue crack paths

Abstract

The determination of fatigue crack paths is a matter of concern to engineers, industry experts and research scientists. In September 2003, fatigue and fracture delegates from 21 countries all over the world gathered in Parma, Italy for the International Conference on Fatigue Crack Paths. The conference was chaired by Professor Andrea Carpinteri (University of Parma, Italy) and Professor Les P. Pook (University College London, UK), and sponsored by the European Structural Integrity Society (ESIS), the University of Parma, together with various industries, organizations and institutions. As is well known, most engineering structures and components contain cracks or flaws and, therefore, crack growth must be considered both in design and in the analysis of failures. The complete solution of a fatigue crack growth problem includes the determination of the path taken by the crack. The path taken by a fatigue crack in a critical component or structure can determine whether fatigue failure is catastrophic or not. Knowledge of potential crack paths is also needed for the selection of appropriate non-destructive testing procedures. It is often assumed that the crack path is known either from theoretical considerations or from the results of laboratory tests but, at the present state of the art, the factors controlling the path taken by a crack are not completely understood. In general, crack paths are difficult to predict and, in practice, crack paths in structures are often determined by large-scale structural tests. Agreement between theoretically predicted and experimentally determined fatigue crack paths is sometimes poor. After the conference, the ESIS Technical Committee TC3 on Fatigue of Engineering Materials and Structures, chaired by Andrea Carpinteri and Les P. Pook, proposed to the editors of the FFEMS International Journal the publication of this special issue. It contains 26 selected papers from the conference arranged in four groups. The five papers in the first group are primarily theoretical and provide the applied mechanics framework needed for the study of fatigue crack paths. The remaining papers describe observed crack paths in a number of situations, with observations carried out at a wide range of scales. The nine papers in the second group are a combination of theory and experiment, while the 10 papers in the third group are primarily experimental. The final group of two papers is on welded joints. Taken together, the papers show that there has been significant progress in the understanding of fatigue crack path behaviour, and in the application of this knowledge to practical engineering problems. The papers have been revised and extended by the authors and subjected to the normal FFEMS review process. We would like to thank the many anonymous reviewers who assisted us. This special issue would not have been possible without their efforts. The next international conference on Crack Paths will be held in Parma, on 14–16 September 2006, where the delegates will exchange recent information and discuss how to promote research and development in this field early in the 21st century.