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An important capability of PIP testing is that it allows detailed study of anisotropy (detectable via a lack of radial symmetry in the indent profile) and inhomogeneity (on a scale of a few mm or above). The technique was used in this study to clarify that a particular (additively manufactured) material was isotropic everywhere, but that its stress-strain curve changed significantly with increased distance from the original growth plate. PIP has unrivalled potential for study of AM products.

This work concerns use of the PIP procedure to obtain stress-strain relationships for a series of incremental near-surface layers in a steel that had been hardened by diffusional penetration of carbon (to a depth of about 1 mm). This was done via serial sectioning, with several layers about 200 µm in thickness being tested. Residual stresses were also measured and taken into account. No other testing technique allows such characterization to be carried out.

This paper is focussed on how PIP testing can satisfy the important technological requirement for non-destructive testing of pipes in situ ("in the ditch"), so as to obtain yield stress and UTS values that would be obtained by the "industry standard" (destructive) procedure of flattening a section and tensile testing it in the hoop direction. A number of different pipes are examined in the study. The reliability and practicality of the PIP procedure is clearly demonstrated.