Use of Profilometry-Based Indentation Plastometry to Study the Effects of Pipe Wall Flattening on Tensile Stress–Strain Curves of Steels |
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Authors: | Marcus Warwick Harika Vaka Chizhou Fang Jimmy Campbell James Dean Trevor William Clyne |
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Affiliation: | 204 Science Park, Milton Road, Cambridge, CB4 0GZ UK |
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Abstract: | Herein, the flattening and subsequent tensile testing (in the hoop direction) of steel pipes used for transmission of oil and gas are concerned. A particular focus is on the use of a novel indentation plastometry test (PIP), applied to the outer free surface of an as-received pipe. This allows a stress–strain curve to be obtained from a relatively small volume (a disk of diameter about 1 mm and thickness around 100–200 μm). Whole section and reduced section tensile testing, of as-received and flattened samples are carried out. Four different pipes are studied. While there are some variations between them, there is a general trend for near-surface regions of the pipe to be a little harder than the interior, and for flattened pipes to be a little harder than unflattened ones, although these are not dramatic or well-defined effects. PIP testing also confirms that these pipes exhibit little or no anisotropy. It is in general concluded that PIP-derived stress–strain curves for testing of the outside of a pipe are likely to be quite close to those obtained by tensile testing of the whole section in the hoop direction, after flattening. |
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Keywords: | finite-element method modeling indentation plastometry pipelines tensile testing |
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