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Brittleness, fracture energy and size effect in theory and in reality
Abstract It is natural that, with the recent fast development of fracture mechanics, the meanings of some standard expressions such as brittleness, fracture energy and size effect need to be revised in order to avoid serious misunderstandings and ambiguities. The paper aims at answering such ticklish questions as the following. Can Griffith's criterion for quasi-static crack propagation, which is valid in linear-elastic fracture mechanics, be applied to the non-linear stress softening theory called the fictitious crack model? What is in fact the mutual relationship of the two theories? How can brittleness be distinctly defined? What is a brittle material and what does quasi-brittle mean? Is the fracture toughness a measure of toughness or rather a measure of strength? Is the fracture energy a material parameter and can a material parameter be ‘measured’ directly or must a theory always be used for interpreting results from experiments? What is the fundamental idea of damage mechanics? What does size effect mean? Is a size-effect law the same as a model law derived from dimensional analysis? What is in fact the relation of a model law to the theory (known or unknown) to which the model law is connected? Giving replies to such questions it is essential to distinguish between theory and reality and not to mix two or more theories, unless the mutual relations of the theories involved are taken into account.
Brittleness, fracture energy and size effect in theory and in reality
Abstract It is natural that, with the recent fast development of fracture mechanics, the meanings of some standard expressions such as brittleness, fracture energy and size effect need to be revised in order to avoid serious misunderstandings and ambiguities. The paper aims at answering such ticklish questions as the following. Can Griffith's criterion for quasi-static crack propagation, which is valid in linear-elastic fracture mechanics, be applied to the non-linear stress softening theory called the fictitious crack model? What is in fact the mutual relationship of the two theories? How can brittleness be distinctly defined? What is a brittle material and what does quasi-brittle mean? Is the fracture toughness a measure of toughness or rather a measure of strength? Is the fracture energy a material parameter and can a material parameter be ‘measured’ directly or must a theory always be used for interpreting results from experiments? What is the fundamental idea of damage mechanics? What does size effect mean? Is a size-effect law the same as a model law derived from dimensional analysis? What is in fact the relation of a model law to the theory (known or unknown) to which the model law is connected? Giving replies to such questions it is essential to distinguish between theory and reality and not to mix two or more theories, unless the mutual relations of the theories involved are taken into account.
Brittleness, fracture energy and size effect in theory and in reality
Harder, N. A. (Autor:in)
1992
Aufsatz (Zeitschrift)
Englisch
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