Two holographic blind-hole methods for measuring residual stresses

The relationship between the displacements and stresses relieved from blind-hole drilling is introduced via an easily understandable concept in this paper. Combining this concept with holographic interferometry, two holographic blind-hole methods for measuring residual stresses are established. The first is a new technique which requires measuring three out-of plane displacements; and the second is a modification of another technique which requires measuring two out-of plane displacements. Each of the two methods needs only one interference fringe pattern and is demonstrated by using it to measure a known residual stress in an aluminum specimen.