Integrated Photoelasticity in a Soft Material: Phase Retardation, Azimuthal Angle, and Stress-Optic Coefficient
Integrated Photoelasticity in a Soft Material: Phase Retardation, Azimuthal Angle, and Stress-Optic Coefficient
复制标题
软材料中的集成光弹性：相位延迟、方位角和应力光学系数
DOI：
10.1016/j.optlaseng.2022.107335
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发表时间：
2022
影响因子：
4.6
通讯作者：
Y.,
中科院分区：
文献类型：
--
作者：
Yokoyama;Y.;Mitchell;B. R.;Nassiri;A.;Kinsey;B. L.;Korkolis;Y. P.;Tagawa;Y.,
本文研究了软材料在三维大变形应力状态下的积分光弹性问题。我们的测量目标是基于轴对称应力场（赫兹接触问题）设计的。在实验中，一个固体球压在明胶凝胶（杨氏模量约为4.2千帕）与不同的施加力从零到最大的力，使凝胶变形高达约4.5毫米。对于软材料，二维光弹性，如传统的做法，是很难被使用。这是因为高度可变形材料的二维切片，如本研究中使用的明胶，不允许稳定的实验。这需要具有足够厚度的三维体以实现稳定性，其中需要集成的光弹性。利用偏振照相机测量了受应力凝胶的光弹性参数（相位延迟和方位角）。测量的相位延迟和方位角进行了比较，基于赫兹接触问题的分析预测。值得注意的是，光弹性参数的实验和分析结果显示出合理的协议，不仅在相位延迟，但也在方位角，这是有关的二次主应力的方向。这对于软材料三维应力场的重建具有重要意义。此外，所用明胶凝胶的应力-光学系数经测量为3.12× 10− 8 1/Pa。这些发现证明，综合光弹性的好处是测量软材料中的三维应力场，这在生物医学工程和细胞打印应用中至关重要。
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 axisymmetric stress field (Hertzian contact problem). In the experiment, 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. For soft materials, two-dimensional photoelasticity, as conventionally practiced, is difficult to be used. This is because two-dimensional slices of highly deformable materials, such as the gelatin used in this study, do not allow stable experiments. This requires a three-dimensional body with sufficient thickness for stability, where integrated photoelasticity is demanded. The stressed gel’s photoelastic parameters (phase retardation and azimuthal angle) are measured using a polarization camera. The measured phase retardation and azimuthal angle are compared with the analytical prediction based on Hertzian contact problem. Remarkably, experimental and analytical results of the photoelastic parameters show a reasonable agreement not only in the phase retardation but also in the azimuthal angle that is related to the direction of secondary principal stresses. Never before validated in previous studies, which is crucial 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 benefits measure the three-dimensional stress field in soft materials, which is essential in biomedical engineering and cell printing applications.