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Photoelasticity: theoretical aspects
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This wiki is dedicated to the use of photoelasticity in a general manner. Before going more into detail about [how to make](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/method-make) photoelastic samples, [how to image](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/method-image) them and even [how to get quantitative information](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/method-analyze) from photoelasticity, it is important to begin by some physical explanations about this phenomenon. The goal is not here to go deep into details. For those who would like more information, we suggest you to read the excellent [wikipedia page](https://en.wikipedia.org/wiki/Photoelasticity) about photoelasticity or this very nice [lecture by W. Wang](http://depts.washington.edu/mictech/optics/me557/photoelasticity.pdf).
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This wiki is dedicated to the use of photoelasticity in a general manner. Before going more into detail about [how to make](/method-make) photoelastic samples, [how to image](/method-image) them and even [how to get quantitative information](/method-analyze) from photoelasticity, it is important to begin by some physical explanations about this phenomenon. The goal is not here to go deep into details. For those who would like more information, we suggest you to read the excellent [wikipedia page](https://en.wikipedia.org/wiki/Photoelasticity) about photoelasticity or this very nice [lecture by W. Wang](http://depts.washington.edu/mictech/optics/me557/photoelasticity.pdf).
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The photoelastic phenomenon is based on birefringence properties of some transparent materials. In a birefringent material, the speed of light, and consequently the index of refraction depends on wave polarization. In other cases, such as glass and polymeric materials, birefringence arises only when the material is subject to anisotropic stress. In other words, the refractive indexes depend on the eigenvalues of local stress tensor. This phenomenon is called photoelasticity and has been utilized in experimental science for several decade.
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... | ... | @@ -25,6 +25,6 @@ $`I=I_0 sin^2(\frac{\alpha}{2})=sin^2(\frac{\pi C d}{\lambda}(\sigma_1-\sigma_2) |
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This equation relates internal stress and intensity for a single wavelength. In most of the cases, both the light and camera channels cover a wide range of wavelengths. Stress calculation is less noisy using narrow range of wavelength and single channel from the camera. However, it is still possible to retrieve stresses using white light.
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The last equation makes it possible to invert the mechanical problem and to get the full stress field (even if there is non-uniqueness of the solution). This is not a trivial problem but in this wiki we show [how to do](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/inverse-analysis) it in the specific case of loaded discs. Other more [qualitative possibilities](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/method-analyze) exists to have an estimation of the stress field.
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The last equation makes it possible to invert the mechanical problem and to get the full stress field (even if there is non-uniqueness of the solution). This is not a trivial problem but in this wiki we show [how to do](/inverse-analysis) it in the specific case of loaded discs. Other more [qualitative possibilities](/method-analyze) exists to have an estimation of the stress field.
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[<go back to home](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/home) |
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[<go back to home](/home) |
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