The strain gage ring-coring method is a semi-destructive method able to measure residual stresses with some specific key-feature that make it popular and commonly used in some typical applications.
Compared to the hole drilling method, the ring-coring method offers a higher depth of investigation that can reach 5mm far from the surface. On the other hand, the surface accuracy is lower than hole-drilling. Regarding the ratio of destruction of the specimen, the ring-coring has a higher level of damaging compared to the hole-drilling.
All the typical features of the method above can define its typical fields of application. The ring-coring method is generally used in all the applications in which the analysis of the surface or the low-depth residual stresses are not enough or not so significant for an accurate study of the residual stress field. This is the typical condition of huge parts realized for forging or casting: in these workpieces the surface can be altered by surface processes and a simple surface or low-depth residual stress analysis can be not enough for understanding the stress level after the production process.
As a consequence, forged parts and components realized in high strength steels for the production of compressor or turbine parts are generally inspected using the ring-coring method: in addition, several technical specifications have been drawn up for the testing and the analysis of residual stress. Some of them are an excerpt or an evolution of the KWU method.
The ring-coring method has found several applications in different types of analysis and it offers an affordable compromise between cost and total depth of analysis.
The MTS3000-RingCore system can be used both for laboratory and on field measurements: the limited dimensions of the mechanical device guarantee a simple positioning even in the most complicated testing conditions. The presence of magnetic feet allows also a strong and precise fixing in magnetic materials. In case of non-magnetic materials (aluminum alloys or stainless steels) a dedicated rapid glue can be used to block the device in the correct position.
Last but not least, the specific shape of the mechanical device allows to perform measurements also inside holes and pipes: the presence of a camera and 2 laser beams guarantees the positioning and the centering of the drilling tool concentric with the strain gage rosette.