Experimental evaluation of the strain intensity factor at the inclusion tip using digital photoelasticity

• Published in: Optics and lasers in engineering 2020-03, Vol.126, p.105855, Article 105855
• Main Authors: Jobin, T.M., Khaderi, S.N., Ramji, M.
• Format: Article
• Language: English
• Subjects: Digital photoelasticity; Least squares; Multi-parameter stress field equations; Rigid line inclusion; Strain intensity factor
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2019.105855

•Multi-parameter stress field equations for a rigid line inclusion is derived.•Digital photoelasticity is used to obtain the whole-field isoclinic and isochromatic contours around the inclusion tip.•Inclusion parallel and inclined to the loading direction is studied.•An over-deterministic linear least squares approach is used to obtain the strain intensity factor for both the inclusion configurations.•The experimentally determined strain intensity factors agrees well with the analytical estimates. Digital photoelasticity is used for the experimental evaluation of the strain intensity factor for a rigid line inclusion embedded in an elastic matrix. The multi-parameter stress field equations are derived using the Airy’s stress function approach. The ten-step phase shifting technique (PST) is used to obtain the whole field isochromatic and isoclinic data, and the adaptive quality-guided phase unwrapping (AQGPU) algorithm is used for unwrapping the phase map. An over-deterministic linear least squares approach is used to solve the multi-parameter stress field equations in an optimization framework to obtain the inclusion tip parameters and the actual inclusion tip location. The relations for strain intensity factor and stress intensity factor (SIF) with the parameters is presented. Photoelastic experiments are performed on two inclusion configurations where inclusion is kept along and inclined to the direction of loading. The obtained strain intensity factor is compared with the analytical solution, and a good match is observed.