Publications
| Title | | Authors |
|---|---|
| Investigation of the drop weight tear test « back |
N Torvella |
| 16th Joint Technical Meeting, Canberra, Australia, April 2007 | |
| DWTT performance is one of the key acceptance criteria for gas pipes. According to the DWT testing standard EN 10274 arrowhead shaped areas on the fracture surface have to be evaluated as totally brittle. The influence of steel type, manufacturing parameters, and microstructure on the tendency to have arrowhead-like areas has been investigated. Arrowhead areas were found in the upper transition temperature range of every steel type investigated. No correlation was found between any manufacturing parameter and the tendency to arrowhead areas. The correlation between fracture surface shear area percentage and absorbed energy has also been investigated in a large number of different pipe steels. Large differences between the absorbed energies of the steels can exist, even in the case of fully ductile fracture. In co-operation with five EPRG member companies Rautaruukki Oyj arranged a DWTT Round Robin test with one pipe material. The shear area percentages, percentages of arrowhead area, and absorbed energies of one specific pipe material were determined at all participating laboratories. The conclusion of the test results was that the scatter in the shear area percentages and absorbed energies were very different in different laboratories, in the worst cases the correlations were non-existent. The best correlation was obtained with a pendulum type testing machine where the energy is measured accurately by a mechanical pointer. | |
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