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Measurement of Residual Stresses with Optical Techniques
Author(s) -
Ribeiro J.,
Monteiro J.,
Vaz M.,
Lopes H.,
Piloto P.
Publication year - 2009
Publication title -
strain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.477
H-Index - 47
eISSN - 1475-1305
pISSN - 0039-2103
DOI - 10.1111/j.1475-1305.2008.00421.x
Subject(s) - electronic speckle pattern interferometry , hole drilling method , optics , residual stress , strain gauge , calibration , materials science , grating , interferometry , moiré pattern , speckle pattern , finite element method , structural engineering , engineering , physics , composite material , quantum mechanics
The goal of this work was the development of other experimental techniques to measure residual stresses, as an alternative to the hole‐drilling method with strain gauges. The proposed experimental techniques are based on the use of Moiré interferometry and in‐plane electronic speckle pattern interferometry (ESPI). Both are field techniques allowing the assessment of in‐plane displacements without contact and high resolution. Grating replication techniques were developed to record high‐quality diffraction gratings onto the specimen's surfaces. An optical set‐up of laser interferometry was developed to generate the master grating (virtual). An in‐plane ESPI set‐up was also designed and implemented to measure displacements in one direction. The stress relaxation was promoted by the blind hole‐drilling and the obtained fringe patterns (Moiré and speckle) were video‐recorded. Image processing techniques were applied to assess the in‐plane strain field. A finite‐element code ( ansys ®) was used to simulate the stress relaxation process, whose values were compared with the experimental data, and to calculate the hole‐drilling calibration constants.