Our Work

TrueSlot® – near surface residual stress measurement

TrueSlot® is an innovative technique for measuring near-surface residual stress that is more reliable than conventional techniques.

TrueSlot® is a residual stress measurement technique for generating a profile of residual stress versus depth from the material surface. The stress computation is similar to slitting but offers more sensitivity near the surface due to the proximity of the strain gage.

Additionally, TrueSlot® is globally less invasive than slitting because the volume of removed material is localized to the surface and does not typically extend through most of the specimen thickness.

A solid model block with a long but thin slot cut out of the top.
A model of a completed TrueSlot® method measurement.

The physical application of TrueSlot® is like hole drilling, however instead of a shallow hole being milled into the body of a specimen containing residual stress, the material removed is a shallow slot. The strain released with each incremental slot depth is measured near the slot using a strain gage.

TrueSlot® is useful for

  • Production quality control applications
  • Applications requiring in-field measurements with portable equipment
  • Near-surface residual stress determination
  • Parts with large or complex geometry
  • Applications with challenging measurement access
  • Applications requiring rapid turn time

TrueSlot® was found to have better repeatability when compared with conventional x-ray diffraction.

A plot with depth and repeatability as the axis and two lines of data, one red, the other black. For most depths, the red line is higher than the black, signifying that XRD is less repeatable than slotting.
Results from the method repeatability study which found TrueSlot® to be a more repeatable measurement method than XRD

You can read about our repeatability study here.

TrueSlot® measurements are performed using our DARTTM system for automated residual stress measurement.

Case studies

TrueSlot® – near surface residual stress measurement ExpressRS® – expedited residual stress results Strain Gaging Services Residual Stress DART – automated residual stress measurement Mechanical stress relief of aluminum alloys Rapid Forge Design Aluminum forging quench modeling Machining distortion modeling with multi-step models including residual stress BAMpF®

Technical Publications

Measurement-driven, model-based estimation of residual stress and its effect on fatigue crack growth. Part 2: fatigue crack growth testing and modeling Measurement-driven, model-based estimation of residual stress and its effects on fatigue crack growth. Part 1: validation of an eigenstrain model Near Surface Residual Stress Measurement Using Slotting Measurement Layout for Residual Stress Mapping Using Slitting Precision of Hole-Drilling Residual Stress Depth Profile Measurements and an Updated Uncertainty Estimator An Uncertainty Estimator for Slitting Method Residual Stress Measurements Including the Influence of Regularization Validation of a Contour Method Single-Measurement Uncertainty Estimator Repeatability of Contour Method Residual Stress Measurements for a Range of Materials, Processes, and Geometries PSR Biaxial Residual Stress Mapping Validation The Contour Method (book chapter)