Experimental Mechanics

, Volume 43, Issue 4, pp 396–402

Digital speckle correlation for strain measurement by image analysis

  • D. Amodio
  • G. B. Broggiato
  • F. Campana
  • G. M. Newaz
Article

Abstract

This paper is concerned with small strain measurement utilizing the numerical processing of digital images. The proposed method has its theoretical basis in digital signal analysis and, from a methodological point of view, it can be considered as an extension to digital images of the wellknown white light speckle photography technique. That conventional method is based on the analysis of photographic plates that are exposed twice (before and after the specimen deformation) with the image of a random speckle pattern that has been previously printed on the test piece surface. The digital speckle correlation advantages consist of requiring a very simple specimen preparation and, mainly, of allowing the strain field computation just by numerical elaboration of the acquired images.

In this paper, the theoretical basis of the technique and some valuable improvements to the known analogous methodologies are presented. Finally, test results for an application of digital speckle correlation are shown and advantages and disadvantages of the technique are elaborated. In addition, further developments in this area are discussed.

Key Words

Speckle methods speckle photography speckle correlation strain analysis image processing 

Nomenclature

g, p, q

real mono- or two-dimensional signals in the space domain

G, P, Q

complex spectrum ofg, p andq

c, C

cross-correlation function and its transform

j

imaginary unit

M, N

sub-image dimensions

m, n

row and column index in the space domain

h, k

row and column index in the frequency domain

sh, sk

non-integer shifting values

u, d

suffixes referring to the undeformed and deformed images

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Copyright information

© Society for Experimental Mechanics 2003

Authors and Affiliations

  • D. Amodio
    • 1
  • G. B. Broggiato
    • 2
  • F. Campana
    • 2
  • G. M. Newaz
    • 3
  1. 1.Department of MechanicsUniversity of Ancona, via Brecce BiancheAncomaItaly
  2. 2.Department of Mechanics and AeronauticsUniversity of Rome “La Sapienza”RomeItaly
  3. 3.Department of Mechanical EngineeringWayne State UniversityDetroitUSA

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