A consistent full-field integrated DIC framework for HR-EBSD

Abstract

A general, transparent, finite-strain Integrated Digital Image Correlation (IDIC) framework for high angular resolution EBSD (HR-EBSD) is proposed, and implemented through a rigorous derivation of the optimization scheme starting from the fundamental brightness conservation equation in combination with a clear geometric model of the Electron BackScatter Pattern (EBSP) formation. This results in a direct one-step correlation of the full field-of-view of EBSPs, which is validated here on dynamically simulated patterns. Strain and rotation component errors are, on average, (well) below 10 for small (E=0.05%) and medium (E=0.2%) strain, and below 3×10 for large strain (E=1%), all for large rotations up to 10° and 2% image noise. High robustness against poor initial guesses (1° misorientation and zero strain) and typical convergence in 5 iterations is consistently observed for, respectively, image noise up to 20% and 5%. This high accuracy and robustness rivals, when comparing validation on dynamically simulated patterns, the most accurate HR-EBSD algorithms currently available which combine sophisticated filtering and remapping strategies with an indirect two-step correlation approach of local subset ROIs. The proposed general IDIC/HR-EBSD framework lays the foundation for future extensions towards more accurate EBSP formation models or even absolute HR-EBSD.

Pattern matching analysis of electron backscatter diffraction patterns for pattern centre, crystal orientation and absolute elastic strain determination – accuracy and precision assessment

“…During the review process of this paper, a novel approach for absolute strain/stress analysis within HR-EBSD analysis without using a simulated reference pattern was demonstrated in the papers [43,44], exploiting crystal symmetry and plane-stress condition. It is claimed that the strain determination error is less than 10 -4 .…”

Estimation of elastic strain by integrated image correlation on electron diffraction patterns

“…Very recently, Vermeij and Hoefnagels have proposed an Integrated DIC (IDIC) framework dedicated to HR-EBSD [19]. In this approach, the physical relationship between the distortion of EBSD patterns and the elastic strain for the studied crystal was considered as exact, and only the corresponding few degrees of freedom describing the elastic strains are considered for registering EBSD patterns.…”

“…The present work also proposes an IDIC framework, very similar in spirit to that of Vermeij and Hoefnagels [19], although developed independently [20]. Section 2 details the IDIC data processing for HR-EBSD.…”

Novel remapping approach for HR-EBSD based on demons registration

“…A recent study by Tanaka et al [9] has utilized a differential evolution method to optimize measured Euler angles and pattern center of the experimental reference pattern, which demonstrates promising sensitivity for dynamical simulation based 'absolute' HR-EBSD. In addition, full-field integrated DIC method developed by Vermeij et al [10] also tries to answer the question of solving 'absolute' residual deformation without the need of a zero-strain reference pattern using only dynamically simulated patterns.…”

“…Recently, new global image cross-correlation based techniques have been proposed to simultaneously improve the strain and rotation sensitivity of HR-EBSD [10,18,19], inspired by the studies on matching the whole region of interest [20][21][22][23][24]. In this work, we propose a new remapping method based on an image registration method (i.e.…”