Measurement of the residual stresses around a cold expanded hole in an EN8 steel plate using the contour method

Cold expansion is now a commonly accepted process for enhancing the fatigue endurance of structures containing fastener holes. However, precise knowledge of the residual stress profile around a cold-expanded fastener hole is clearly required if the fatigue life of such structures is to be accurately predicted. There have been many experimental studies of the residual stress distribution surrounding cold expanded holes. Hence, the determination of residual stress fields surrounding a split-sleeve cold-expanded hole in an En8 steel plate is ideal system on which to explore the effectiveness of a newly developed method of characterizing residual stress distribution, the Contour Method. In this paper, the two-dimensional residual hoop stress map obtained from the Contour Method is compared with the results form a three-dimensional finite element simulation. The Contour Method was found to be experimentally demanding but careful application of technique provided good agreement between the two methods showing that the Contour Method has the potential to be a powerful alternative to current residual stress measurement techniques.