The small ball punch test at FZJ

Abstract

The next generation of nuclear power reactors and neutron sources, together with the test devices for the fusion program, will pose an unprecedented severity of the environment for structural components near the irradiation sources. Therefore there is a need for material development and testing in the anticipated conditions and a number of institutions are involved in the process. A strong constraint in the volume of material available for testing, due to the high irradiation dose needed to meet proper conditions and the number of necessary samples, has driven the development of a number of tests to extract engineering properties from miniaturised specimens [G.E. Lucas, Metall. Trans. A 21 (1990) 1105, P. Jung, A. Hishinuma, G.E. Lucas, H. Ullmaier, J. Nucl. Mater. 232 (1996) 186]. The small ball punch (BP) test is a mechanical test for miniaturised samples. Although it is not yet a standard test, specimens discs dimensions of 3 mm diameter and 250 μm thickness are routinely used. The BP test finds application in the determination of elastoplastic and fracture properties of materials, such as the tensile strength, yield strength, fracture energy and ductile to brittle transition temperature (DBTT). Here a BP test apparatus developed at the Forschungszentrum Jülich with the contribution of the INFM is presented and its performance discussed.