Determination of Stress Intensity Factors for an Interfacial Crack in a Bi-Material by Digital Photoelasticity

Abstract

The main sources of error in the determination of stress intensity factors (SIFs) for an interface crack in a bi-material by conventional photoelasticity are the measurement of the positional co-ordinates of the data point and the fringe order. In the present work, use of two digital photoelasticity methods for collecting these data is discussed. SIFs are evaluated using constant radius method and a least squares approach based on the singular stress field equation. The need for developing a multi-parameter stress field solution for evaluating SIF is highlighted.

Evaluation of stress field parameters for an interface crack in a bimaterial by digital photoelasticity

“…The best solution is obtained when the convergence error is less than 0.05 [14]. Using the parameters thus obtained, the program recalculates 1 ÿ 2 values, and hence the fringe order at every point in the data field, which is used to reconstruct the stress field for comparison.…”

“…The stress field expressions for the bottom half-plane can be obtained simply by changing e "p to e ÿ"p , e ÿ"p to e "p , and w to 1=w. It was verified numerically in reference [14] that, when " ¼ 0, equation ( 8) reduces to the multi-parameter equations of Atluri and Kobayashi [15] for the homogeneous problem. When equation ( 8) is transformed into polar coordinates, the first term of the equation (n ¼ 0) is the same as equation ( 1) [14].…”

“…Appendix 2 gives the simplified stress field equations based on Rice's work. The details of the simplification can be found in reference [14]. Although, in 1993, Deng [9] reported another form of multi-parameter stress field equations for an interface crack in a homogeneous bimaterial, the paper has remained obscure for researchers dealing with the interface crack of homogeneous materials for a long time.…”

New Initiatives on Comparison of Whole‐field Experimental and Numerical Results

“…Comparison of Figure 5B,F shows that the artificial crack has indeed behaved very much like a natural crack. The specimen is deemed valid and is then used to establish the need for multi‐parameter solution for evaluating SIF by photoelasticity [14, 15].…”

Calculation of stress intensity factors for an interfacial notch of a bi-material joint using photoelasticity

“…Hence, calculating the SIFs is the first step for investigating fracture behaviour of interface notched specimens. Although there are some experimental investigations for stress analysis of interface cracks (Ravichandran & Ramesh, 2004, 2005, the experimental evaluation of stress field for a bi-material and simple notches has rarely been investigated (Ayatollahi et al, 2011(Ayatollahi et al, , 2013. Mirsayar and Samaei (2013) recently have investigated the effects of combination of materials on the shape and size of the Photoelastic fringe patterns near the interface notch tip.…”