Surface-Energy Determinations by Cleavage

Abstract

An analysis is made of the strain‐energy distribution in a slotted double‐cantilever cleavage specimen. In this type of specimen the crack is medially constrained by a pair of longitudinal slots, so that surface energies can be determined in nonmonocrystalline samples. The analysis treats the arms of the crack as end‐loaded cantilever beams, and the post crack‐tip region as a pair of elastically supported beams. The web produced by slotting is assumed to act as an elastic foundation for the remaining beam‐like portions of the post crack‐tip region. An expression for the specific surface energy of the material is then derived from conservation of energy at the instant the crack begins to propagate. Linear elastic behavior of the material is assumed and shearing strains are neglected. Extension of the analysis to conventional (unslotted) specimens in which medial constraint of the crack is obtained through a preferred direction of cleavage, is discussed semiquantitatively in terms of an effective foundation modulus.