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dicengine / dice

Digital Image Correlation Engine (DICe): a stereo DIC application that runs on Mac, Windows, and Linux
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about vsg #251

Open wztneedahelp opened 2 years ago

wztneedahelp commented 2 years ago

Hello,Mr Turner,I'm sorry to distrub you. In your VIRTUAL STRAIN GAUGE,you discussed the solution of VSG in 2 dimensions.But in stereo analysis,after finding out the fitted plane,for example,we can get the local coordinates(xl,yl,zl). To calculate VSG, should we use (XL, YL, ZL) or (XL, YL)? image image

dicengine commented 2 years ago

Sorry for the delayed response...I thought I had replied to this post already.

Yes, that's correct. In stereo the distance between the neighboring subsets used to calculate the VSG strain is determined in reference to the subset's MODEL_COORDINATES in 3d. If you are using a best fit plane, these coordinates are the local coordinates to the best fit plane.

In reference to your question about how the VSG strain gauge does a linear regression of the displacement field to get the strain, it's done separably in x and y so the z distance doesn't enter the equation. Whether or not this is the best way to do it is probably a good question, but that's how it's done in DICe. To see specifically what I mean you can look at the initialize_neighborhood() method in DICe_PostProcessor.cpp.