Benchmarking Phase Unwrapping Algorithms in Digital Photoelasticity

This study benchmarks five phase unwrapping algorithms—Goldstein’s branch-cut, Flynn’s minimum discontinuity, quality-guided, least-squares, and CPULSI—for digital photoelastic stress field reconstruction using a 3D-printed diametrically compressed disk with a known analytical solution. Quantitative evaluation under loads of 700 N and 1500 N reveals that all algorithms perform well under low-gradient conditions (correlation coefficients > 0.95), but path-following methods degrade significantly under high gradients: Goldstein’s algorithm fails with a Pearson correlation of −0.4127. The least-squares and CPULSI algorithms maintain robust performance, ranking highest in composite evaluation. The composite robustness ranking is as follows: least-squares ≈ CPULSI > Flynn’s > quality-guided > Goldstein’s branch-cut. These findings provide quantitative engineering guidance for algorithm selection in photoelastic stress concentration analysis. The main contribution of this work is not the proposal of a new unwrapping algorithm, but the establishment of a unified experimental–theoretical benchmark for evaluating representative phase unwrapping algorithms in digital photoelastic stress field reconstruction.