How to use i3D^® Testing Technology compared with tensile testing

What was compared on S355?

In the underlying practical example, structural steel S355 was first characterised by conventional tensile testing. Three local points were then tested using i3D^® Testing Technology. Each point creates a defined residual imprint and an indentation-derived local plastic stress–strain curve.

The two tests are not identical. Tensile testing provides a global result for a standardised specimen; i3D provides a local result for the material zone that was actually tested. The useful comparison is therefore between corresponding strength values and their technical agreement.

What results were obtained in the S355 example?

The published comparison reports the following values:

In this particular test, both local i3D comparison values were close to the tensile-test reference. The example illustrates a practical workflow; it is not a universal accuracy claim across all materials, geometries and surface conditions.

Download the original data and test reports

These two original documents support the reference values compared above. The tensile-test report gives R_p0.2 = 310 MPa and R_m = 520 MPa. The Imprintec report documents 13 i3D measurement points and the overall mean used in the comparison: R^I_p0.2 = 287 MPa and R^I_m = 494 MPa.

Acknowledgement: We thank Element Materials Technology for providing the tensile-test data that made the direct comparison with the local i3D results possible.

Documentation date: 17 October 2025. The results apply to the tested sample and do not replace a task-specific assessment of material condition, test location and measurement uncertainty.

How to use i3D Testing Technology in five steps

1. Define the reference and target: decide whether yield strength, tensile strength, local scatter or a plastic stress–strain curve is required.
2. Select the test zone: document points on the base material, component, weld, heat-affected zone or gradient.
3. Create controlled imprints: match force, indenter, surface and point spacing to the material and geometry.
4. Evaluate the imprint in 3D: capture topography and pile-up and reconstruct the local material response through inverse modelling.
5. Compare with the reference: interpret R^I_p0.2, R^I_m and curve shape together with material state, location and tensile data.

When should i3D be used, and when is tensile testing still required?

How should the values be interpreted?

R^I_p0.2 and R^I_m are local indentation-derived comparison values. Their meaning depends on material state, surface preparation, grain size, accessibility, indenter, load and the representativeness of the selected point. A comparison should therefore include repeat measurements, uncertainty and the actual engineering question rather than relying on a percentage alone.

The broader validation page with 704 comparison measurements provides a statistical context. The indentation plastometry method page explains the underlying workflow.

Prepare your own comparison measurement

A useful request includes material and condition, component geometry, accessible test zone, target properties, available tensile references and the intended number of measurement points.