Approximate Energy-Based Methods
Building on the results of Section 2.1, let us now review the techniques that provide approximate solutions for Q in a number of cases. The presentation is not intended to be exhaustive. Its purpose is twofold: to give at least a minimum of insight on how to obtain the energy release rate, and to provide a number of simple equations for Q which can be used in solving typical fracture problems.
The section covers first the simplified approaches to truly linear problems, relying only on simple mechanics of materials. After that, a certain geometrically nonlinear case is briefly analyzed: the extension of a surface delamination crack due to buckling under compression.