Application of Digital Image Correlation in Space and Frequency Domains to Deformation Analysis of Polymer Film

Abstract

Using speckle patterns formed by an expanded and collimated He-Ne laser beam, we apply DIC (Digital Image Correlation) methods to estimate the deformation of LLDPE (linear low-density polyethylene) film. The laser beam was transmitted through the film specimen while a tensile machine applied a load to the specimen vertically. The transmitted laser light was projected on a screen, and the resultant image was captured by a digital camera. The captured image was analyzed both in space and frequency domains. For the space-domain analysis, the random speckle pattern was used to register the local displacement due to the deformation. For the frequency-domain analysis, the diffraction-like pattern, due to the horizontally-running, periodic groove-like structure of the film was used to characterize the overall deformation along vertical columns of analysis. It has been found that when the deformation is small and uniform, the conventional space domain analysis is applicable to the entire film specimen. However, once the deformation loses the spatial uniformity, the space-domain analysis falls short if applied to the entire specimen. The application of DIC to local (windowed) regions is still useful but time consuming. In the non-uniform situation, the frequency-domain analysis is found capable of revealing average deformation along each column of analysis.

Experimental Study on the Effect of Gradient Interface on the Mechanical Properties of Cu/WCP Functionally Gradient Materials Using Digital Image Correlation Technique

“…Digital image correlation (DIC) [ 16 , 17 ] is a non-contact optical technique that is capable of measuring full-field two-dimensional or three-dimensional surface deformations. Over the years, with the rapid advancement in computer vision technology, and with the availability of cheaper and more powerful digital image acquisition devices, DIC has gained increasing popularity among researchers in different fields [ 18 , 19 ]. Ahmed et al [ 20 ] used DIC to investigate the fracture parameters and crack tip deformation field in continuous functionally graded (FG) glass-filled epoxy composite.…”

Mechanics and Analysis of Advanced Materials and Structures

“…Kopfler et al [10] use optical speckles for another purpose. They utilized the randomness of the speckle pattern to uniquely identify local areas of a transparent specimen (polyethylene films) and analyzed nonuniform deformation under tensile loading.…”