Ring Core

The ring-core technique is a mechanical measurement method used to determine principal residual stresses incrementally with depth.

This technique can be used on metals, ceramics, and polymers. Materials that can’t be tested by X-ray diffraction, such as coarse grain or amorphous materials, can be tested with the ring-core method.

How Does It Work?

The technique is based on linear elastic theory and consists of machining a circular groove containing a strain gage. The change in strain resulting from relieving the stressed material is recorded at varying core depths.


It’s technique is similar to the hole-drill method but has a higher sensitivity than the hole drilling method and can measure larger residual stresses up to the yield strength of the material.

The core that is machined using the ring-core method is larger in size compared to the hole introduced with the hole-drill method.

Other features include:

  • Measures residual stresses in all directions in the plane of the part surface
  • Maximum measurement depth of 0.25 in. (6 mm)
Principal Stress Distribution with Ring Core
Residual Stress in a Stainless Steel Bowl chart

How are Lambda’s services superior?

Lambda is a recognized leader in the field of residual stress measurement, with extensive experience
testing all types of materials, including metallics, ceramics, and polymers of nearly any shape and size.

  • We can test components in our laboratory or in the field
  • All residual stress measurements are performed by our certified residual stress engineers and technicians
  • Lambda does not subcontract residual stress testing to a third party

Questions about the ring-core technique or other residual stress measurement needs?

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