Abstract
A cross-line phase-type specimen grating was interrogated by moiré interferometry techniques to produce full-field fringe patterns of three displacement components:U x ,U y , andU 45. ForU 45, sensitivity was 1/1700 mm/fringe (1/43,000 in./fr). Closely packed fringes with much information content were obtained. Fringe patterns of strain components⎵ x ,⎵ y and⎵ 45 were produced by mechanical shearing (or optical differentiation) of the displacement patterns; a shearing distance of only 0.6 mm (0.025 in.) was used. The rosette method yields complete strain information from these three components of normal strain—which were derived from three direct derivatives of displacement. Consequently, the need for cross-derivatives of displacement, which are highly sensitive to accidental rigid-body rotations, is circumvented.
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Abbreviations
- f,f 1,f 2 :
-
frequency of grating
- g 1,g 2,g 3 :
-
pitch of grating
- N x ,N y ,N 45 :
-
fringe order of contour of displacement component
- N′ x ,N′ y ,N′ 45 :
-
fringe order of contour of normal strain
- U x ,U y ,U 45 :
-
displacement component
- x, y :
-
orthogonal coordinates
- x, y, 45:
-
subscripts denoting direction of parent quantity
- X 45 :
-
coordinate lying 45 deg fromx-axis
- α:
-
angle of incidence (Fig. 2)
- γ xy :
-
shear strain
- δ x , δ y , δ45 :
-
translation distance for mechanical shearing
- Δ:
-
change of
- ε x ,ε y ,ε 45 :
-
normal strain component
- λ:
-
wavelength of coherent light
References
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Weissman, E.M., Post, D. Full-field displacement and strain rosettes by moiré interferometry. Experimental Mechanics 22, 324–328 (1982). https://doi.org/10.1007/BF02328534
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DOI: https://doi.org/10.1007/BF02328534