A linear least squares approach for evaluation of crack tip stress field parameters using DIC

• A new algorithm involving linear least square technique is proposed for the extraction of crack tip location and crack tip stress field parameter.
• The proposed method has been used to extract mixed-mode SIF׳s involving multi-parameter displacement field equation.
• An open source 2D DIC software Ncorr is used for the crack tip displacement field extraction.
• The reconstructed and experimental crack tip displacement fields are superposed over each other and are found to be in coherence.

In the present work, an experimental study is carried out to estimate the mixed-mode stress intensity factors (SIF) for different cracked specimen configurations using digital image correlation (DIC) technique. For the estimation of mixed-mode SIF׳s using DIC, a new algorithm is proposed for the extraction of crack tip location and coefficients in the multi-parameter displacement field equations. From those estimated coefficients, SIF could be extracted. The required displacement data surrounding the crack tip has been obtained using 2D-DIC technique. An open source 2D DIC software Ncorr is used for the displacement field extraction. The presented methodology has been used to extract mixed-mode SIF׳s for specimen configurations like single edge notch (SEN) specimen and centre slant crack (CSC) specimens made out of Al 2014-T6 alloy. The experimental results have been compared with the analytical values and they are found to be in good agreement, thereby confirming the accuracy of the algorithm being proposed.