On image gradients in digital image correlation

J. Neggers, B. Blaysat, J.P.M. Hoefnagels, M.G.D. Geers

Research output: Contribution to journalArticleAcademicpeer-review

42 Citations (Scopus)
585 Downloads (Pure)

Abstract

In digital image correlation (DIC), the unknown displacement field is typically identified by minimizing the linearized form of the brightness conservation equation, while the minimization scheme also involves a linearization, yielding a two-step linearization with four implicit assumptions. These assumptions become apparent by minimizing the non-linear brightness conservation equation in a consistent mathematical setting, yielding a one-step linearization allowing a thorough study of the DIC tangent operator. Through this analysis, eight different image gradient operators are defined, and the impact of these alternative image gradients on the accuracy, efficiency, and initial guess robustness is discussed on the basis of a number of academic examples and representative test cases. The main conclusion is that for most cases, the image gradient most common in literature is recommended, except for cases with: (1) large rotations; (2) initial guess instabilities; and (3) costly iterations due to other reasons (e.g., integrated DIC), where a large deformation corrected mixed gradient is recommended instead.

Original languageEnglish
Pages (from-to)243-260
Number of pages18
JournalInternational Journal for Numerical Methods in Engineering
Volume105
Issue number4
DOIs
Publication statusPublished - 27 Jan 2016

Keywords

  • Brightness conservation
  • Digital image correlation
  • Displacement fields
  • Strain measurement

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