Residual stress measurement using indentation and a radial in-plane ESPI interferometer

A radial in-plane electronic speckle pattern interferometer (ESPI) has been developed by the authors' group. This interferometer is used in this paper to measure residual stresses in combination with the indentation method. A semiempirical mathematical model is developed to quantify the residual stresses. Several tests were made in a specimen with different levels of residual stresses imposed by a mechanical loading. Empirical constants were computed from those tests and are used in combination with the developed model to predict the residual stresses levels. The radial displacement field around a controlled indentation print is measured, processed and fitted to a mathematical model to predict residual stresses. Series of tests were designed and executed. Different indentation tip geometry and different loading conditions were involved. This paper presents the measurement principle, implementation details and results of the performance evaluation. The tests presented here are not complete since they are restricted to only one material, oneaxis stress state, two indentation tip geometry and only one indentation force, but they are sufficient to encourage further development.