Ferritic steels are noted for various special characteristics, including low nickel content and specific magnetic properties, making them suitable for a wide range of applications. When they are used for such items as tanks or containers it becomes necessary to investigate their tendency to brittle fracture and crack arrest behavior and this is done by means of drop weight tests as described by W.S. Pellini.
In the Pellini drop weight test, rectangular flexure specimens are loaded with a free-falling mass in such a way that a brittle fracture is caused on the tension side of the specimen within a prescribed total deflection. This brittle fracture is caused by a notched welding bead laid on this side – the so-called crack starter. The prescribed flexure is limited via suitable stops.
It is necessary to determine whether the brittle fracture caused by the artificial crack-starter spreads as far as one of the two side faces of the specimen or is arrested beforehand. If the fracture reaches one of the side faces, the specimen is regarded as fractured.
The highest temperature at which the specimen breaks, when at a stated higher temperature two further specimens of the same material do not break, is described as the NDT temperature and represents a characteristic value for the crack arrest behaviour of the material under test conditions. The NDT (nil ductility transition) temperature is used to describe the transition temperature for crack arrest as determined in the drop weight test named after W.S. Pellini and described in Stahl-Eisen-Prüfblatt 1325 and in ASTM E 208.
Zwick has expanded its metals testing program to include two standardized Pellini drop weight testers rated at 550j (Type P550) and 1630j (TypeP1630).
The 550 joule drop weight tester is used for Pellini drop weight tests on metallic materials with specimen dimensions to P2, P3 and P4. The drop height is infinitely adjustable up to a maximum of 1000 mm and tooling for the various specimens can be changed quickly and easily.
In accordance with the Standard the prescribed drop energies are obtained by the simple use of weights, the drop energy being calculated automatically.
In common with Zwick high-energy drop weight testers, the Pellini testers feature a particularly ingenious safety arrangement which prevents access to the test area during test mode. In line with Zwick’s modular design policy, the proven control system used for the high-energy drop weight testers is also employed with the Pellini testers.
In the Pellini drop weight test, rectangular flexure specimens are loaded with a free-falling mass in such a way that a brittle fracture is caused on the tension side of the specimen within a prescribed total deflection. This brittle fracture is caused by a notched welding bead laid on this side – the so-called crack starter. The prescribed flexure is limited via suitable stops.
It is necessary to determine whether the brittle fracture caused by the artificial crack-starter spreads as far as one of the two side faces of the specimen or is arrested beforehand. If the fracture reaches one of the side faces, the specimen is regarded as fractured.
The highest temperature at which the specimen breaks, when at a stated higher temperature two further specimens of the same material do not break, is described as the NDT temperature and represents a characteristic value for the crack arrest behaviour of the material under test conditions. The NDT (nil ductility transition) temperature is used to describe the transition temperature for crack arrest as determined in the drop weight test named after W.S. Pellini and described in Stahl-Eisen-Prüfblatt 1325 and in ASTM E 208.
Zwick has expanded its metals testing program to include two standardized Pellini drop weight testers rated at 550j (Type P550) and 1630j (TypeP1630).
The 550 joule drop weight tester is used for Pellini drop weight tests on metallic materials with specimen dimensions to P2, P3 and P4. The drop height is infinitely adjustable up to a maximum of 1000 mm and tooling for the various specimens can be changed quickly and easily.
In accordance with the Standard the prescribed drop energies are obtained by the simple use of weights, the drop energy being calculated automatically.
In common with Zwick high-energy drop weight testers, the Pellini testers feature a particularly ingenious safety arrangement which prevents access to the test area during test mode. In line with Zwick’s modular design policy, the proven control system used for the high-energy drop weight testers is also employed with the Pellini testers.
