Residual stress assessment using optical techniques

• Author(s): Ribeiro, J.E. ; Monteiro, J. ; Vaz, M.A.P. ; Lopes, H. ; Piloto, P.A.G.
• Date: 2006
• Persistent ID: http://hdl.handle.net/10198/4346
• Origin: Biblioteca Digital do IPB
• Subject(s): Residual stress; Optical techniques; Moiré interferometry; ESPI
• Document Type: Article
• Language: English

Description

The goal of this work is the development of different experimental techniques to measure residual stresses as alternative to the hole-drilling method with strain gages. The proposed experimental techniques are based on the use of Moiré Interferometry and in-plane Digital Speckle Pattern Interferometry (ESPI). They are field techniques that allow measure in-plane displacements without contact and with high resolution. Grating replication techniques are developed to record high quality diffraction gratings onto the specimen’s surfaces .It is also, developed an optical assembly of laser interferometry used to generate the master grating (virtual). It was designed and implemented an in-plane interferometer to measure displacements in one direction. It was also developed a drilling equipment to provoke the stress relaxation in the specimens. During residual stresses measurements the obtained fringe patterns (Moiré and speckle) are video recorded. Image processing techniques are used to assess the in-plane strain field. A finite elements code (ANSYS®) is used to simulate the process of relaxation of stresses whose values will be compared with the experimental ones and to calculate the hole-drilling calibration constants.