Residual stress measured in a hardened (carburized and quenched) steel ring

Paper on these measurements and some nice FEM predictions:

M. B. Prime, V. C. Prantil, P. Rangaswamy and F. P. Garcia, "Residual Stress Measurement and Prediction in a Hardened Steel Ring," Materials Science Forum, Vols. 347-349, pp. 223-228, 2000. preprint (pdf) (LA-UR-99-5103)
The finte element model described in this paper includes phase transormation kinetics and transformation induced plasticity (TRIP).

The Specimen: The specimen was a carburized low alloy 0.2% carbon steel ring Approximate Dimensions: 2.25" Outer Diameter (57mm) 1.4" Inner Diameter (35mm) 0.8" Height (20mm) At the left of the specimen in the photo you can just make out some of the wire used for the EDM cut

Ring specimen after EDM cut.

The raw data - measured strains

Great Sensitivity! - Look how big the strain readings are

The results - residual stress

• This is Hoop residual stress in the first mm or so of depth
• See paper (pdf) for information on finite element model and surface x-ray measurements
• The residual stress is given as a 4th order polynomial from the least squares fit used to reduce the data
• How well does this fit the strain data? See below

Fit to the strain data

• The solid lines are the strains predicted analytically by the residual stress distribution shown above
• The symbols are the actual data
• The ± 1 microstrain fit error corresponds well with how well you can measure strain
• The compliances were calculated using the solution for a slot of finite width, reference # 20