Unsteady stress field measurement during droplet impact on soft materials using photoelastic tomography

We successfully visualized unsteady stress fields in a soft material during droplet impact using the proposed method with a high-speed polarization camera. Photoelasticity was developed to visualize stress fields in hard materials that can not highly deform, such as residual stresses in glass. We have recently shown that the stress-optic law, which is the relationship between the stress in the material and the measured optical parameter, can apply to even a soft material that is as soft as 1/1000000 of glass, such as a gel (Yokoyama et al., Opt. Lasers Eng., 2023). In this study, we developed an algorithm for photoelastic tomography to reconstruct the axisymmetric stress field from the measured photoelastic parameters, combining tensor tomography and linear interpolation. The accuracy and calculation time of the reconstruction were compared between the proposed method and conventional methods, and the results showed that the proposed method achieved high accuracy in stress reconstruction and reduced calculation time.