Keywords: indentation, mechanical properties, steel, weld, plastometer, rail.

This paper relates to the application of a novel technology to measurement of the mechanical properties of sections of rail steel, and of welds between them. The outcome of this type of test – ie the stress-strain relationship of the material – is much more informative than the numbers obtained by hardness testing, which should be regarded as no better than semi-quantitative indicators of the resistance of the metal to plastic deformation. Stress-strain curves, on the other hand, can be used in fully quantitative modelling of how the rail will respond to further periods in service – particularly since the testing can be carried out at a series of depths. Although this type of testing is thus much more informative than hardness testing, it can be carried out in a similarly quick and convenient way. Results presented here, and also large amounts of other work published over the past few years, have confirmed a high level of consistency between PIP-derived curves and those obtained via conventional uniaxial testing. It has also been shown that variations in the properties across the width of a flash butt weld can be picked up with a spatial resolution of the order of a millimetre. An ongoing project is aimed at the development of a portable version of the PIP facility, which will be suitable for application to rails.

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