A Study on Experimental Determination of Mixed-Mode Sif’s Using Digital Photoelasticity and DIC

Veerkar, V V and M, Ramji (2012) A Study on Experimental Determination of Mixed-Mode Sif’s Using Digital Photoelasticity and DIC. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Several experimental techniques can be used for the estimation of mixed-mode SIF’s. Out of these, digital photoelasticity and digital image correlation (DIC) have evolved as the most preferred techniques for the evaluation of fracture parameters. The present study attempts to evaluate SIF’s for different specimen configurations using digital photoelasticity and DIC. For photoelastic determination of SIF’s, an over-deterministic nonlinear least square approach has been used. Isochromatic fringe order has been evaluated over the entire model domain by using ten-step method. Using the techniques of digital image processing, data required for evaluation of SIF’s has been collected in an automated manner. The methodology has been applied for the extraction of SIF’s for two different specimen configurations, single edge notched (SEN) panel and interacting parallel edge cracked panel. The experimental results have been compared with analytical and finite element (FE) estimates. For the estimation of mixed-mode SIF’s using DIC, required displacement data has been obtained using 3D-DIC. Using this data as an input, over-deterministic nonlinear least square approach has been implemented in modified form for reliable and better convergence of solution. For this purpose, MATLAB program has been written. In order to ensure the sufficiency of number of parameters, displacement field has been reconstructed theoretically to compare it with the experimentally obtained displacement distribution. The presented methodology has been used to extract mixed-mode SIF’s for various specimen configurations. The experimentally obtained results are compared with the analytical solutions available in the literature.

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