Image based displacement measuring technique for in-plane loading

Abstract

Displacement/ strain measurement plays a significant role in understanding structural and material behaviour. In the local context, commonly used contact based systems have a major limitation when it comes to measuring deformation of a surface. A measuring probe can record the displacement/ strain only at a single location and hence require a larger number of pre-defined measuring points in order to calculate the deformation of the surface. Furthermore, the comparative stiffness between the measuring probe and the object under consideration has to be significantly larger. A non-contact optic based system is an ideal candidate for overcoming the problems encountered in such systems. This research attempts to utilize image processing techniques in order to develop a low cost non-contact based deformation measuring technique to measure the in-plane deformation of an object. A set of pre-defined measuring points (targets) were marked on a timber block and a series of images with a commonly available camera was taken while applying a load in the mid-span. The images were then processed using the image processing tools available in MATLAB software to track the motion of predefined targets. The calculated displacements were validated against the physical measurements taken during the bending test.