Analysis of dynamic bending test using ultra high speed DIC and the virtual fields method

Abstract

Full-field deformation response of a copper bar impacted in a three point bending setup is studied. Ultra-high speed photography (frame rate: 5×106 fps) in conjunction with digital image correlation is utilized to study the in-plane deformation kinematics of the impacted specimen over 25.4μs duration after the impact. Distributions of temporal derivatives, i.e. strain rate, velocity and acceleration, over the area of interest are computed using the in-plane displacement and strain fields measured from image correlation. Complex deformation patterns resulting from wave propagation and inertial loading are studied and discussed. Having deformed the specimen well into the plastic regime, the idea initially proposed by Pierron et al. (2011) is extended to identify visco-plastic constitutive response of the examined material by incorporating an analysis based on the method of virtual fields. Accordingly, a strain rate sensitive constitutive model for the copper specimen is identified by reconstructing the inertia and the impact forces using full-field acceleration and reaction force measurements, respectively.