Creating a strain map

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kmmorales kmmorales
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Creating a strain map

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Hello,

I am trying to quantify the deformation taking place on a layer of sand in a rectangular bin when it is compressed and extended. To do this, I need the vector field and total strain. For the vector field, I am getting vectors not pointed in the right direction. For strain, I am only getting the result of each iteration, from photo 1-2, 2-3, etc. Is there any way to get the cumulative vector field and strain map? Also, would you advise us to remove camera distortions on Photoshop before uploading them to PIVlab?

My goal would be to produce diagrams like the ones below:



Any advice would be very helpful! Thank you!

Best,
Kimi







William William
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Re: Creating a strain map

Dear Kimi, could you upload two image software your dataset? So I could see how the raw images look like and test the analysis.

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kmmorales kmmorales
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Re: Creating a strain map

Hello William,

Thanks for the prompt response! I am a bit confused. What do you mean by "two image software"?

There are 720 photos I am trying to analyze (one photo taken every 2 minutes for 24 hours). Over time, the sand gets deformed into folds. Below is the initial image and the final image of one experiment. The silver wall to the left in the second image is what moved over time to compress the sand.





William William
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Re: Creating a strain map

Hi Kimi,
"could you upload two image software your dataset?" should have meant "two images of your dataset", but my phone decided to write something else...
You can undistort your image before or after the analysis, or undistort your dataset after the analysis; I think there shouldn't be a big difference.
If you want to have the cumulative displacement over the full photo range, then you need to use Matlabs "cumsum" command I think.
You need to export your results from PIVlab (File, Save, MAT-file), then reload that data and use the cumsum command.
I don't know how to calculate "total strain", but you need to perform these operations manually in Matlab.

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.