Residual stress measurement using indentation and a radial electronic speckle pattern interferometer — recent progress

Abstract

A new kind of electronic speckle pattern interferometer (ESPI) was developed by the authors' group using conical mirrors to measure the radial in-plane displacement component. True radial in-plane sensitivity is achieved by double illumination. This device is used in the present work to measure residual stresses in combination with the indentation method. A semi-empirical mathematical model is developed to quantify the residual stresses. Several tests were made on a specimen with different levels of stress imposed by mechanical loading. Empirical constants were computed from these tests and are used in combination with the developed model to predict the residual stress levels. The tests presented here are preliminary as they are restricted to only one material, a uniaxial stress state, one geometry of the indentation tip, and only one value of indentation force. In these conditions the results are very encouraging, a typical measurement error of about 5 per cent being found for the principal residual stress.