Micro-scale deformation measurement using the digital image correlation technique and scanning electron microscope imaging

Abstract

This paper presents a study of micro-scale deformation of materials utilizing scanning electron microscopy (SEM) images and the digital image correlation (DIC) technique. A loading stage was integrated into the SEM imaging system. During the experiment, a series of SEM images of the specimen were acquired in situ. The DIC technique was then applied to these SEM images to calculate the displacement and strain field at the area of interest. Additional surface preparation may be needed in order to have an effective pattern for DIC analysis. Two applications are presented in the paper. Using small tensile specimens, the mechanical properties of electrodeposited nickel-based LIGA (an acronym from German words for lithography, electroplating, and moulding) specimens were characterized. In this case, the natural microstructural feature of the specimen surface was used directly as the pattern for DIC analysis. This method was also applied to study the strain concentration around the crack tip during the ductile fracture test of Al 6061-T651. In contrast to the previous case, the DIC patterns were generated by sputtering a thin layer of gold film on to the specimen surface through the copper mesh grid.