Hill Engineering Blog

Ring core

At Hill Engineering we work with residual stress on a daily basis. Ring Core is one of the techniques that we use for residual stress measurement. Ring Core is capable of measuring residual stress over depths spanning the near-surface to bulk regions, and can be applied to quantify the average residual stress over the depth of a drilled core. Ring Core is portable, and can be applied under a variety of circumstances, including in the field. Hill Engineering uses Ring Core measurements to support process development and quality control. Ring Core measurements can be performed in our laboratory or at your site, to your specifications.

In the Ring Core method, an annular groove is incrementally extended into a body containing residual stress (see figure below). The strain released with each incremental groove depth is measured using a strain gage rosette placed on the surface of the part. The measured strains are used to calculate the residual stress that was initially in the part through an elastic inverse solution, which is based on a finite element analysis.

The Ring Core method is useful for many different residual stress measurement applications. At Hill Engineering, we perform Ring Core measurements to quantify the residual stress over intermediate depths (up to approximately 0.250 inches from the surface). Ring Core is also used for applications requiring in-field measurements with portable equipment. Ring Core is useful when multiple residual stress components are desired.

At Hill Engineering, we are experts in Ring Core and other residual stress measurement methods. Hill Engineering is a global leader in improving the performance of materials. We are a trusted partner to engineers seeking solutions in design, manufacturing, operations, and sustainment; delivering expertise in residual stress measurement, mechanical design, material testing, structural integrity, and service life extension. If you have any questions about the Ring Core method please contact us for more information.

Photograph of a Ring Core residual stress measurement on an aluminum alloy 7085-T7452 die forging