Simple Application of Opensource PIV Technique for Measuring Displacements and Strains

Abstract

Strain measurements obtained from images can be useful in the study of constitutive equations or cracks stress concentration among other open problems. Many techniques have been used to calculate the deformation between to images, but they generally require complex or expensive
software applications. In this work an open source code for Particle Image Velocimetry under MATLAB© (MATPIV) was employed to measure strains around 10% in uniaxial deformation. A regular pattern was drawn on the surface of a tensile specimen which was observed and deformed
simultaneously inside the chamber of a Scanning Electronic Microscope. A posteriori analysis of the images using the code MATPIV allowed computing the strains of an inhomogeneous welded material. These values were compared with direct measurements of the deformed pattern and good agreement
was obtained. Moreover, small cracked fracture specimens were also analyzed, but difficulties aroused due to large displacements and rotations. However, a displacement field was calculated by measuring directly the position a regular grid. Then, the strain field under the large deformation model was obtained with a simple numerical scheme.