Endurance test for steel: the DWTT test

Resistance to dynamic stress is of crucial importance. The DWTT test focuses on this property and provides important findings.

What is a DWTT test?

The Drop Weight Tear Test (DWTT) was developed at the Battelle Institute in the early 1960s. This is why the DWTT test is also known colloquially as the Battelle test. Sometimes the procedure is also referred to as the BDWTT test.

The aim of this mechanical material test is to prevent brittle fracture and ensure crack arrest in pipelines (seamless or welded).

What DWTT standards are there?

• API RP 5L3: “Recommended practice for conducting drop weight crack tests on line pipe”
• ASTM E436: “Standard Test Method for Drop-Weight Tests on Ferritic Steel”
• EN 10274: Metallic materials – Drop weight test

How is the DWTT test carried out?

The DWTT (Drop Weight Tear Test) is a technological toughness test in which a defined weight is dropped vertically onto a steel sample from a specified height in order to break it. In contrast to the notched bar impact test, this is carried out with so-called large drop weight testers (from 20,000 J), which often have a considerable height (approx. 3 – 12 meters). The specimen, mounted in a similar way to a three-point bending machine, has a cold-pressed notch against which the weight strikes. The energy settings – weight and notch height – are adjusted so that the sample breaks and the fracture surface can be visually assessed. The result of the DWTT test is the appearance of the fracture surfaces, whereby the proportions of the deformation (ductile) and brittle (crystalline) fracture surfaces are determined visually. In addition, similar to the notched bar impact test, the impact energy consumed at a certain temperature can be evaluated.

For which steel grades is the DWTT test used?

The DWTT test is not a typical mechanical material test for sheet metal, but is mainly used for pipes. This applies in particular to steels intended for line pipe according to API5L such as X60, X65, X70 or according to DIN EN ISO 3183 such as L415, L450 and L485, as well as for steels according to M-630 material data sheets and element data sheets for pipelines.

What are the areas of application for DWTT-tested steels?

Steels that pass the DWTT test are often used in transportation systems for liquid crude oil and natural gas as well as in the petrochemical industry.