Theories of Brittle Failure

Abstract

There have been many different approaches to developing a theory of brittle failure that will predict the macroscopic fracture stress. Very broadly, the approaches fall into two groups. The first group is comprised of the empirical attempts to state criteria of failure that are consistent with observed failure conditions in particular types of experiments but whose applicability is intended to extend to more general states of stress. The Coulomb and Mohr criteria are theories of failure in this sense. Although such theories may be discussed in physical terms, such as limits on stresses on certain planes or limits on strain energy, they say very little about the physical mechanisms of failure and are generally best regarded as purely empirical expressions. Their main function is to provide a basis for calculating failure conditions in practical situations.