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Welcome

Welcome to the CHESS_RealTimeDIC wiki! CHESS_RealTimeDIC is a MATLAB real time digital image correlation software used for monitoring in-situ mechanical loading high energy x-ray diffraction (HEXD) experiments at the Cornell High Energy Synchrotron Source (CHESS).

Structure

ContinuousUpdate.m: Helper function used to continuously read and process DIC data to update stress-strain plot.

CPcorr.m: Helper function that is a custom version for MATLAB function 'cpcorr.m' for use with DIC software.

FindPeak.m: Helper function that is a custom version of the MATLAB function 'findpeak.m', created specifically to work with custom function 'CPcorr.m' in DIC software.

FitStrain.m: Helper function that fits a polynomial to the displacement calculations in order to calculate macroscopic strain.

GenerateGrid.m: Helper function used to create or load existing grid of control points in a region of interest.

GetImageDataType.m: Helper function used to gather image data type into structure.

OpenDicParFile.m: Helper function used to locate and open dic.par experiment file.

ProcessCorrelations.m: Helper function used select and define processing modes for the correlation.

ProcessDicParFile.m: Helper function used to process dic.par experiment file.

RealTimeDIC.m: Main function used to set-up processing controls and continuously read, process, and plot DIC data in real time during mechanical loading experiment.

SelectFirstImage.m: Helper function used to locate and open first DIC image file.

Usage

To used this package, import repository into a MATLAB friendly environment and run RealTimeDIC.m. The program will iterate through each section of which a description for each is given below.

%% user input paramters

Section allows users to define input parameters to control portions of the DIC processing. Commented descriptions for each parameter are given in the file.

%% select the dic.par file for current sample, contains image index, force, and screw position

Section allows users to locate and process dic.par experiment file. A GUI directory is used to navigate and select the file. The file is processed after selection.

%% select the reference image

Section allows users to locate and process first DIC image from experiment. A GUI directory is used to navigate and select the file. The file is processed after selection.

%% generate grid from the first reference image

Section allows users to define a grid of control points and size of region of interest for DIC processing. A MATLAB GUI was created to service "drawing" the region of interest and UI controls are available for adjusting the size of the correlation areas. Users can save grid patterns for re-loading in future processings.

%% calculate stress and strain

Section allows users to process DIC measurements previously collected before the RealTimeDIC.m script was ran. Whatever DIC images have been measured and read into the dic.par file will be process sequentially before any continuous updating.

%% intial plotting

Section allows users to plot the macroscopic stress-strain curve from the previously collected data.

%% process the rest of the images in a while loop --> built-in while loop in "Continuous Update"

Section allows users to automatically and continuously search for, read, process, and update any new DIC measurement collected and recorded into the dic.par file. A MATLAB GUI was create to service controlling certain aspects of the real time DIC process like:

• Reprocess Image: Allows users to reprocess the previous image. Useful for trying to re-gain correlation.
• Reset Estimate: Allows users to reset the displacement estimate for processing DIC images. Useful for trying to re-gain correlation.
• Cycling Options: WORK IN PROGRESS
• Correlation Area Controls: A set of UI control sliders that allows users to control the size of the correlation regions in real time. Useful for trying to re-gain correlation.

Future Work

A full set of instructions along with demonstration videos will be published soon.

%% Save stress and strain values