A Novel Technique for Extracting Stretch Zone Features from Fractographs

The crack tip blunting process leaves an imprint in the form of stretch zone on fracture surfaces during the event of ductile fracture. A schematic representation of the stretch zone in a fractured specimen and a corresponding fractographs is shown in Fig. 1. A typical stretch zone has two components, stretch zone width (SZW) and stretch zone depth (SZD). The SZW is basically the virtual crack extension Δa and SZD is half of the CTOD,. Stretch zones can be easily identified, when observed under the SEM, since they have visually identifiable boundaries in between the fatigue precracked region and the ductile fracture region