Inversion of speckle interferometer fringes for hole-drilling residual stress determinations

Speckle interferometric fringe patterns record stress-relief displacements induced by the drilling of blind-holes into prestressed objects. The quantitative determination of residual stress states from such stress patterns is difficult because of the ambiguity in the order of the observed fringes. I...

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Bibliographic Details
Published in:Experimental mechanics 2000-06, Vol.40 (2), p.129-137
Main Authors: SCHMITT, D. R, HUNT, R. W
Format: Article
Language:English
Subjects:
Applied sciences
Computational techniques
Cutting
Exact sciences and technology
Finite-element and galerkin methods
Mathematical methods in physics
Metals. Metallurgy
Other machining methods
Physics
Production techniques
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Summary:Speckle interferometric fringe patterns record stress-relief displacements induced by the drilling of blind-holes into prestressed objects. The quantitative determination of residual stress states from such stress patterns is difficult because of the ambiguity in the order of the observed fringes. In this paper, fringe patterns were forward-modeled from a large ensemble of calculated biaxial stress-relief displacement fields. Inversion of these noise-free fringe patterns reproduced the biaxial stresses with negligible error. Analysis of more realistic fringe patterns that include speckle noise gave stress magnitude errors that diminished rapidly with the number of selected points to better than 3 percent for 100 points. Sensitivity of the optical method is influenced by a number of factors, but the ensemble of model fringe patterns studied indicates that the stress magnitudes (normalized with respect to the material's Young's modulus) from 3 x 10 exp -4 to 10 exp -2 can be determined accurately with visible laser radiation. The method is amenable to automation and can easily be extended to study near surface gradients in the residual stresses or applied to other optical recording techniques, such as moire and phase-shifting interferometry. (Author)
ISSN:0014-4851
1741-2765
DOI:10.1007/BF02325038