Extension to the blind hole drilling technique for residual stress determination with airabrasive hole forming

Abstract

For an austenitic clad ferritic steel plate it was necessary to determine the residual stress state between the austenitic surface and a region below the austenitic/ferritic interface.The thickness of claddings was 6 mm and to determine the stress variation between the surface and 8 mm an incremental analysis is required. Any material removal en masse in conjunction with small hole residual stress measurements would have resulted in a stress redistribution and hence a distortion in the stress field being measured. In conjunction with strain change measurements on the other face the sensitivity would not have been sufficient. These two options assume that a thin layer of material over relatively large areas can be removed by a non‐stress inducing technique.A blind hole residual stress measurement using a 13 mm diameter hole 13 mm deep will facilitate accurate incremental analysis to a depth of 8 mm.The end mill method of hole forming cannot be used with stainless steels because of the random damage effect which is induced in the readings. The airabrasive method which induces no damage effect was used.The standard airabrasive method of hole forming produces a 2 mm diameter and a 2 mm deep hole.The modification of the standard airabrasive system is discussed which enables 13 mm diameter and 13 mm deep holes to be formed.A deviation from the standard hole/gauge layout geometry has been investigated due to non‐availability of suitable standard rosettes, and a significant increase in sensitivity has been obtained.The incremental stress results for the austenitic layer and the austenitic/ferritic interface are discussed using the results from 1.6 mm, 3.2 mm and 13 mm diameter/deep holes.