Fracture maps with pressure as a variable

Diagrams can be constructed in stress space which show lines or surfaces describing failure by each of several mechanisms. A change of failure mode takes place where the lines or surfaces intersect. The overall failure is described by the inner envelope of the fracture lines or surfaces. The diagrams shown are based on the simplest possible treatment of the mechanisms. In each example, the equations were fitted to experimental data at one or more points to determine the constants sigma exp o sub f , A, n, sigma sub i , C, etc. The model then gives the pressure dependence of the fracture mechanism. The examples with 1045 steel, cast iron, and Cu are not intended, at this stage, to be a precise description; they are merely intended to illustrate the method. As the understanding and modelling of the mechanisms improves, it will be possible to construct more detailed and more accurate maps. 26 ref.--AA