What is the DWT test?
The drop weight test (DWT) was developed at the Naval Research Laboratory in 1952. The DWT test is also colloquially known as the Pellini test. Like the DWT and CTOD test, it is a test of fracture mechanics. In this test, the NDT temperature is determined as the crack arrest temperature (nil-ductility-transition). This is the temperature at which the material becomes tough enough to stop a stably propagating crack. Below this NDT temperature, the material cannot be used, so the NDT temperature is a design criterion for corresponding components (fracture mechanical strength verification).
How is the DWT test conducted?
A weld seam is applied to a rectangular specimen (in the centre in the longitudinal direction with a brittle weld bead). The tests are carried out at different temperatures, for example, with a temperature difference of 5°C from specimen to specimen. The specimen is placed on an abutment and subjected to a falling weight of 4 to 4000 kg, which falls on the specimen from a great height. When the weight hits, the specimens bend and a crack runs from the weld bead into the base material. The temperature of the specimen at which the crack runs through, for example, is the NDT (nil-ductility-transition) temperature.
For which steel grades is the DWT test used?
The DWT test was part of the approval programme for shipbuilding steels or offshore steels such as EH36, NV36, F36, FH36 or NVF36, but also steels according to EN 10225 Weldable structural steels for fixed offshore structures – Technical delivery conditions Part 1 Sheet metal 355G10+N/M (1. 8813+N/M), S460G2+M (1.8857+M), S355NLO (1.8808), S355MLO (1.8811) and .Today it is largely replaced by the CTOD test.
What are the application areas of DWT tested steels?
For example, transport systems of liquid crude oil and natural gas. Natural gas and oil pipes and their accessories. Ships, drilling rigs or other offshore constructions.
