Ring coring

The ring coring method is a variant of the hole drilling method where a relatively stress-free island of material is created by machining away a ring around it. The relaxed strains or defamations on the surface of the stress-free island are then recorded using strain gauge rosettes or optical methods such as Digital Image correlations (DIC).  Numerically determined influence functions are then used to calculate residual stresses from the measured relaxed strains.