Integrated Photoelasticity in a Soft Material: Phase Retardation, Azimuthal Angle, and Stress-Optic Coefficient
15 Pages Posted: 25 Jul 2022
Integrated photoelasticity is investigated for a soft material subjected to a three-dimensional stress state with large deformation. Our measurement target is designed based on the three-dimensional Hertzian contact problem, i.e., a solid sphere is pressed against a gelatin gel (Young’s modulus is about 4.2 kPa) with varying applied forces from zero to the maximum force that deforms the gel up to approximately 4.5 mm. The resulting photoelastic parameters (phase retardation and azimuthal angle) in the gel are measured using a polarization camera. The measured retardation and azimuth are compared with the analytical prediction based on Hertzian contact theory. Remarkably, experimental and analytical results of the photoelastic parameters show a reasonable agreement not only in the retardation but also in the azimuth that is related to the direction of principal stresses and but rarely validated in previous studies, is essential for reconstructing three-dimensional stress fields in soft materials. In addition, the stress-optic coefficient of the gelatin gel used is measured to be 3.12×10 -8 1/Pa. Such findings proved that integrated photoelasticity is useful for measuring the three-dimensional stress field in soft materials, which is of importance in biomedical engineering and cell printing applications.
Keywords: Integrated photoelasticity, Soft material, Gelatin, Azimuthal angle, Stress-optic coefficient
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