Vol.12, No3, 2012, pp. 159–163
UDC 620.17

Hole drilling (HDM) is the most widespread method for measuring the residual stress profile. HDM is based on the principle that a hole in the material causes stress relaxation; stress field around the hole changes so that the released strain can be measured in order to calculate initial residual stress. Recently, the use of optical methods, as measurement tool for the strain field generated around the drilled hole, has been investigated in place of the traditional strain gauge rosette technique. Optical methods have the advantage that guarantees very high sensitivity, provides much more significant statistics, eliminates error due to hole eccentricity, and reduces the cost in a single test. The accuracy of the final results depends, among other factors, on the proper choice of the area of analysis. Deformations detected by ESPI are in fact analysed within an annulus determined by two parameters, that is to say, the internal and the external radius. The choice of these parameters affects the final results in terms of measured residual stress. Results of this analysis are the object of this paper.

Keywords: residual stress, ESPI, integral method