Local strength in an S460M welded joint

The practical question: where does the joint start to yield?

Testing a welded joint is not only about the load carried by the whole specimen. Development work may require knowing which region starts to deform permanently and how neighbouring regions respond as loading continues. This means considering mechanical properties together with their measurement locations.

In a narrow heat-affected zone, extracting a suitable tensile specimen is an additional challenge. A local indentation offers another approach: the material is loaded at a selected position and its plastic response is evaluated using a material model.

What was investigated in S460M?

Four S460M welding variants were compared. An Imprintec Type A indenter produced three rows of 20 indents at 0.5 mm spacing. The residual indentation shapes were measured optically in 3D and evaluated using inverse FE analysis. Complementary testing included hardness measurements and tensile comparisons on weld and base metal. See the original paper and method clarification.

What did the local evaluation show?

PC-GMAW-F, gas metal arc welding with pulsed current in forced mode, produced more uniform local comparative strengths. Hardness and strength were also related. The variants additionally differed in joint preparation. Findings in Section 3.2 of the paper.

For practical assessment, this suggests comparing the distribution of properties. An average strength alone does not reveal whether substantial local differences exist. More uniform properties are not a universal measure of quality either: the preferred distribution depends on the design and loading conditions.

How should the properties be interpreted?

• Comparative yield strength Rⁱ_p0.2: a value derived from indentation evaluation for comparison with the 0.2% proof strength from a tensile test.
• Comparative tensile strength Rⁱ_m: a model-derived value for comparison with ultimate tensile strength.
• Local flow curve: the relationship between stress and increasing plastic, or permanent, strain.

The combination of mechanical indentation testing, optical 3D measurement of the residual indentation shapes and a material model is described in DIN SPEC 4864. The term “comparative” makes clear that these values are obtained through a different route from tensile testing.

Where does hardness testing add useful information?

A hardness profile is useful for assessing hardening or softening across a weld. Conversion to tensile strength, however, requires an applicable relationship for the material and its condition. ISO 18265 addresses the limits of such conversions.

Understanding how a region responds during further plastic deformation requires more information than a hardness number. Our page on weld hardness testing explains hardness profiles and when local indentation evaluation can add useful information.

What does this mean for your own test programme?

For test planning, we draw three practical questions from the example:

1. Process comparison: at which equivalent locations should two welding variants be compared?
2. Local transition: does the task require a hardness profile, strength values or the development of plastic deformation?
3. Simulation: which weld regions need separate material data, and which strain range is relevant?

Results should therefore always be linked to their measurement locations. A curve without a location on the specimen does not yet establish which part of the welded joint it describes.

Which limitations need to be considered?

For narrow zones, the mechanically affected test volume matters. The stated grid spacing does not demonstrate a spatial resolution of 0.5 mm. Zone width, microstructure, surface condition and distance from transitions must therefore be considered before selecting a measurement plan.

Evaluation requires a suitable material model. A local plastic flow curve does not establish elongation at fracture, freedom from cracks or fatigue life. ASTM E3499-25 also describes limitations of indentation plastometry. Required acceptance or qualification tests need to be planned separately.

Your welded joint as the next application

Tell us the material, welding process, specimen dimensions and the question you need answered. A photograph or sketch helps identify the relevant regions. We can then discuss which local test fits the task.

Our service: local weld testing and stress-strain curves

Publication and data source

The identification of the Imprintec Type A indenter used in the study is based on an additional clarification by co-author Peter Zok.

A. Zavdoveev, P. Zok, V. Pozniakov and co-authors: Effect of Pulse Current GMAW on the Yield Stress of the S460M TMCP Steel Welded Joints. Metals and Materials International 29, 795–806 (2023), first published online on 26 July 2022. DOI: 10.1007/s12540-022-01261-1.

Peter Zok is a co-author of the original paper. This article places selected published findings in the context of test planning. Experimental conditions and original figures are available in the full text provided by a co-author. Practical recommendations on this page are our interpretation.