Overview of the effects of process parameters on the accuracy in residual stress measurements by using HD and ESPI

Several researches have been recently carried out about the feasibility of adopting optical methods, such as Electronic Speckle Pattern Interferometry (ESPI), in combination with hole-drilling. Using this kind of approach instead of adopting strain gage rosette, as usual, can be advantageous in view of the fact that costs and time of the measurement can be reduced. However it should be taken into account that several parameters involved in the whole measurement process can significantly determine the final accuracy of the measurement. In this paper an overview of the effects of some of those parameters is presented: errors on the knowledge of some of geometrical paramters, direction of the sensitivity vector of the system with respect to the principal stress direction, drilling rotation speed.