Linear least squares approach for evaluating crack tip fracture parameters using isochromatic and isoclinic data from digital photoelasticity

Digital photoelasticity for calculating coefficients of the Williams series expansion in plate with two collinear cracks under mixed mode loading

“…With the advent of digital image processing techniques in photomechanics, digital photoelasticity has become very popular [1][2][3][4][5][6][7][8][9]. The development of the computer-aided analysis of the experimental data obtained from photoelastic experiment caused rapid growth of the photoelasticity experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], especially in fracture mechanics for analysis of the crack tip fields and crack tip parameters. In the past two decades crack-tip mechanics has been studied increasingly using full-field techniques, namely DIC [15] and photoelasticity [1][2][3][4][5][6][7][8].…”

“…Note that the coefficients of higher-order terms in the Williams series expansions were computed by different approaches in numerous studies [11][12][13][14][15].…”

“…In [11] the digital photoelasticity technique is used to estimate the crack tip fracture parameters for different crack configurations. Conventionally, only isochromatic data surrounding the crack tip is used for SIF estimation, but with the advent of digital photoelasticity, pixel-wise availability of both isoclinic and isochromatic data could be exploited for SIF estimation in a novel way.…”

“…The efficiency and accuracy of the DIC technique in determining the coefficients of higher order terms in the Williams expansion were demonstrated for the CT specimen. As it is noted in [11] the accuracy of SIF estimate could be improved by improving the accuracy of the isoclinic parameter estimate using the white light photoelasticity thereby eliminating the isochromatic-isoclinic interaction noise. An advanced experimental technique for determination of the stress intensity factor (SIF) and the T-stress is developed in [18] and carefully verified.…”

Photoelastic Analysis of Cracked Thick Walled Cylinders

“…A similar overdeterministic algorithm based on photoelastic data was proposed by Stepanova et al [14] to assess the complete Williams series coefficients of the linear elastic stress field in the vicinity of the crack tip for a wide class of experimental specimens subject to mixed mode loading: edge cracked semi-circular disk specimen, plates with two collinear cracks under tensile loading, pure shear loading and mixed mode loading. Patil et al [15] proposed a linear least square approach to estimate the mixed-mode crack tip fracture parameters by solving the multi-parameter stress field equation. The stress intensity factor was extracted from the estimated fracture parameters, calculated using isochromatic and isoclinic data around the crack tip obtained by the ten-step phase shifting technique.…”