Open Access

ARTICLE

The Theory of Critical Distances: a History and a New Definition

by ,

1 Mechanical Engineering Dept., Trinity College Dublin, Ireland

Structural Durability & Health Monitoring 2006, 2(1), 1-10. https://doi.org/10.3970/sdhm.2006.002.001

Abstract

Current theories of fracture recognize the importance of material length scales, i.e. parameters having the dimensions of length which are included, either explicitly or implicitly, in many methods of fracture prediction. This paper is a review of the development of one particular approach, which we have called the Theory of Critical Distances (TCD). The history of this approach -- which is presented here for the first time - is a story of parallel developments in the areas of fatigue and brittle fracture and in different material fields: metals, polymers, ceramics and composites. A particular milestone in the development of the TCD was the incorporation of fracture mechanics concepts which allowed the critical distance parameter, L, to be calculated as a function of other mechanical properties. Over the last decade the theory has been rediscovered and extended by several workers, precipitating another phase of rapid development. This review concludes by proposing a precise definition for the TCD, which includes four related methods of analysis, and by suggesting some directions for future research.

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