Local Strain Measurement in a Strip Cast Automotive Aluminum Alloy Sheet

Local strain measurement based on digital image correlation at both macroscopic and microscopic scales is presented. A speckle pattern was used for the macroscopic strain mapping to reveal the inhomogeneous deformation processes occurring during tensile deformation of a strip cast automotive aluminum sheet. Moreover, a novel microscopic strain mapping technique based on scanning electron microscopic (SEM) topography image correlation was introduced for strain mapping down to the grain level. The SEM images taken from an in-situ tensile sample of the same material within a field emission SEM chamber are used to demonstrate the validity of the method. The results clearly reveal the evolution of local strain of order of one as well as the formation of shear band in the material.