Significance of the Drop-Weight Tear Test and Charpy V-Notch Impact Test Results

Abstract

The results of extensive research on piping and pressure vessels of plain carbon and low-alloy materials is providing an understanding of the significance of impact test results in terms of the full-scale fracture initiation and propagation characteristics. The impact tests employed in the research work were the Charpy V-notch impact test and the drop-weight tear test (DWTT). The impact tests have been correlated with full-size cylindrical vessel tests in which the initiation and propagation characteristics have been determined under controlled conditions. The results of the research indicate that, for the materials studied, the impact test fracture appearances relate to the structural fracture appearance with certain limitations. Specifically, the DWTT when conducted on material of the same thickness as the structure will predict directly the fracture propagation transition temperature. The Charpy V-notch test fracture appearance can be correlated to the structural fracture propagation transition temperature but is offset generally on the temperature scale because of the difference in thickness between the Charpy specimen and the structure. Correlations have been attempted between Charpy or DWTT energies and the fracture initiation characteristics determined from full-scale cylindrical vessel experiments. These correlations to date between the plane stress-stress intensity factor Kc and the plateau impact energies have exhibited considerable scatter, and no consistent trends are indicated. Also, correlations were attempted between the impact energies and the fracture propagation behavior, but no consistent relationship was found.