... | ... | @@ -7,7 +7,7 @@ In the [previous section](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Ma |
|
|
Using transmission photoelasticity method:
|
|
|
------------------------------------------
|
|
|
|
|
|
In the most favourable case you have optically access to both sides of the sample and you can then have light going through it from a polarised source to a crossed polarised camera. In this case you can use [the transmission photoelasticity method](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity). This section presents the method and answers basic questions like:
|
|
|
In the most favourable case you have optically access to both sides of the sample and you can then have light going through it from a polarised source to a cross polarised camera. In this case you can use [the transmission photoelasticity method](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity). This section presents the method and answers basic questions like:
|
|
|
* Should I use a circular or a linear polarizer?
|
|
|
* Should I add a quater-wave plate?
|
|
|
* How to orient the whole thing and check that I did it properly?
|
... | ... | @@ -20,24 +20,21 @@ This is the most simple case so even if you do not use this method, we strongly |
|
|
Using reflection photoelasticity method:
|
|
|
----------------------------------------
|
|
|
|
|
|
When the sample is optically accessible from one side only because au the loading mechanism for example, the [transmission method](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity) cannot be used anymore. In this case the sample must be both lit and image from the same side. This means the other side, whether it is the back of the particle or the or anything on the non accessible side, must be reflective. So the light is reflected on the back of the sample and go trough it two times. More details about this method are given [here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/reflection-photoelasticity).
|
|
|
When the sample is optically accessible from one side only because au the loading mechanism for example, the [transmission method](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/transmission-photoelasticity) cannot be used anymore. In this case the sample must be both lit and imaged from the same side. This means the other side, whether it is the back of the particle or anything on the non accessible side, must be reflective. So the light is reflected on the back of the sample and go trough it two times before being caught by the camera. More details about this method are given [here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/reflection-photoelasticity).
|
|
|
|
|
|
|
|
|
Using different wavelengths:
|
|
|
----------------------------
|
|
|
|
|
|
To make photoelastic measurements only monochromatic light is enough even if polychromatic light can permit to get more beautiful picture. This mean that the sample can be light and imaged with polarized light of a given wavelength. So other wavelengths can be used for other purpose like detecting the sample geometry, position and orientation. In the figure below extracted from [this article](https://aip.scitation.org/doi/abs/10.1063/1.4983049), for example red light is used to localized the particles while green one is used to measure the photoelastic response. More detail about how to use different wavelengths when imaging photoelastic samples are given [here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/wavelength-imaging)
|
|
|
To make photoelastic measurements only monochromatic light is enough even if polychromatic light can permit to get more beautiful picture. This means that the sample can be lit and imaged with polarized light of a given wavelength. So other wavelengths can be used for other purposes like detecting the sample geometry, position and orientation. For example, in the figure below extracted from [this article](https://aip.scitation.org/doi/abs/10.1063/1.4983049), red light is used to localized the particles while green one is used to measure the photoelastic response. More details about how to use different wavelengths when imaging photoelastic samples are given [here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/wavelength-imaging).
|
|
|
|
|
|
![Capture_du_2019-01-09_13-05-39.rotated](uploads/b0439f1ea9f2fad899f679d5b2a50d0f/Capture_du_2019-01-09_13-05-39.rotated.png)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Using terahertz photoelasticity method:
|
|
|
---------------------------------------
|
|
|
[here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/terahertz)
|
|
|
|
|
|
One of the main drawback of optical photoelasticimetry is that it is only doable for quasi-2D transparent materials. However, very recently, it has been shown that photoelasticimetry can also be performed using polarised teraHertz waves. These waves can go through optically non-transparent material and could permit to image stresses in 3D. [In this section](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/terahertz) we give the main principles of this method and how to implement it. Still, this is a cutting edge method much more complicated to use than any other presented in this wiki.
|
|
|
|
|
|
![Capture_du_2019-01-09_13-10-53](uploads/04b04f314a1659bc20bafccd689bccfc/Capture_du_2019-01-09_13-10-53.png)
|
|
|
|
... | ... | |