In-plane deformation monitoring of a cylindriscal specimen using a simple approximate method combined with two-dimensional digital image correlation.

Abstract

This paper presents a quick-to-implement and simple approximate method that uses a single camera system to measure the relatively small surface deformation of a cylindrical specimen in the context of triaxial tests in geotechnical engineering. Digital images of a speckled cylindrical specimen before and after loading were obtained from only one perspective view. For each acquired image, there are geometric distortions and speckle losses, which are mainly caused by both perspective projection and column shape. Based on particular prior knowledge, we attempted to back-project the raw perspective images onto a cylindrical curved surface to reconstruct the speckle feature scene. These back-projected images were subsequently analyzed by the two-dimensional digital image correlation method to reveal the surface deformation information of the region of interest on the surface of the test specimen. Finally, a test case and a finite element study were, respectively, given to validate the effectiveness of the method. This feasibility study demonstrates the potential of extending this method to handle a wide range of regular cylindrical specimens with a relatively small deformation which are analyzed without taking out-of-plane motion into consideration.