CrossCourt4’s HR Processing Package has Cross Correlation (XCF) and Remapping functions to prepare conventional EBSD data
Materials Library
CrossCourt4’s Materials’ Library has a large selection of elastic constants available to match with the material phase(s) of the data under analysis; these elastic constants are needed to evaluate the full strain tensor and further calculate the stress tensor. The software will try automatically to match the relevant elastic constants with the material phase described in the source EBSD file but you can also select the appropriate set of constants manually from the library ; in addition, CrossCourt4 allows you to enter and edit your own elastic constants’ values and include them in the Materials’ Library.
Pre-Processing Data Filters
There are times when areas of the imported EBSD data are below an acceptable level of reliability; this shortfall is indicated by map results such as the confidence level, image quality, or KAM. In these cases, you can identify and then remove or isolate these features from the data set before processing using CrossCourt4’s set of filter functions which includes a Threshold Filter, Grain Filter, Pixel Filter and Area Filter.
Reference Determination
Identifying the “zero strain” reference EBSD pattern is key to the preparation steps for cross correlation. CrossCourt4’s Reference Determination feature makes it easy to identify these pattern locations by providing automated tools based on the KAM, Confidence Index, or Pattern Quality data. It is also possible for you to identify the reference pattern manually and mix and match auto and manually selected references.
Pattern ROI
The Pattern ROI feature automatically sets up and align Regions of Interest (ROI’s) over selected EBSD patterns. CrossCourt4 then divides the EBSD pattern into multiple regions, some overlapping to pass into the Cross Correlation process. This process determines the pattern’s average shift within each ROI in relation to identically placed ROIs in a reference pattern. Using multiple regions allows better statistical sampling.
FFT Filter
The Fast Fourier Transform (FFT) is especially adapted by CrossCourt4 for use with EBSD patterns. The FFT is used to filter an image’s low and high frequency information and enhance the signal passed to the XCF function. The higher frequency components relay information regarding a pattern’s sharp changes and the low frequency components relay information regarding long range contrast changes.
Cross Correlation Function
Cross Correlation is central to the HREBSD method. The Cross Correlation Function or XCF is a well-established mathematical technique used in many fields from signal processing to astronomy. In HREBSD, XCF provides a comparative measure of the distortion between a test pattern and a reference pattern. XCF is performed over numerous Regions of Interest (ROI) common to both patterns and these results are then used to calculate a material’s stress/strain state.
Remapping
The Remapping Function enables improved measurement of elastic strain in plastically deformed samples. The Remapping Function works by discriminating large lattice rotations from the elastic strains which is exhibited in plastically deformed metals. Remapping is a method where the EBSD patterns are back rotated to ‘remove’ the rotations and leave only the elastic stress and strains.
1D Line Data Extraction
You can extract Line data (1D) from any 2D map displayed within the CrossCourt application; this includes the raw EBSD data maps or data maps, for example strain and stress, resulting from the Cross Correlation Function. A 1D dataset is generated by extracting and interpolating data along the line and this is stored as a CrossCourt project file. The project file can be uploaded into CrossCourt and managed just like a 2D dataset, using the HR Analysis package’s cross-sectional line chart, to view and analyse shifts, elastic, plastic and GND results.