Residual stress measurements with laser speckle correlation interferometry and local heat treating

Abstract

A new experimental technique has been devised to measure residual stresses in ductile materials with a combination of laser speckle pattern interferometry and spot heating. The speckle pattern interferometer measures in-plane deformations while the heating provides for very localized stress relief. The residual stresses are determined by the amount of strain that is measured subsequent to the heating and cool-down of the region being interrogated. A simple lumped-parameter model is presented to provide a description of the method. This description is followed by presentation of the results of finite-element analyses and experimental results with uniaxial test specimens. Excellent agreement between the experiments and the computer analyses was obtained.