A small punch test device developed for low temperature tests with initial acceptance results

The correct knowledge of the mechanical properties of irradiated structural materials is an inherent need in the design and maintenance of nuclear facilities due to the high responsibility inherent to the components and involved risks. Handling samples of such materials is risky as they are radioactive and their masses are great. That is true even for the Charpy specimen (10mm x 10mm x 55mm). So, it is of strong interest the use of small specimens like the ones for the Small Punch Test (SPT) as presented in the ASTM standard E3205/2020. The test consists basically of pressing a small sphere or semi-sphere against a (circular) plate of the investigated material until it ruptures. The applied force (F) and the displacement of the sphere (d) are recorded while the plate deforms. From the analysis of the F x d curve, which has certain characteristics, and from the analysis of the fracture surface of the ruptured sheet, and the shape of the macroscopic fracture itself, it is possible to obtain several mechanical properties of the tested material, such as, for example, the yield stress, tensile strength besides fracture properties of the material such as its toughness (for this specific see, for instance. This technique is a very new one and can be considered still under development but is very promising. In the Brazilian Multipurpose Reactor (RMB) project there is the prevision of a hot cell laboratory to characterize the degradation of irradiated structural components used in a nuclear reactor compared with the virgin material. Recently at IPEN, a Research Institute at São Paulo City, Brazil, started an interdisciplinary project aiming the development of a small punch test (SPT) device for tests at room temperature and another one to be used at Low temperatures. The project has the main following goals: (i) design and manufacture of two mechanical devices to perform SPT tests at ambient as well as subzero temperatures; (ii) Carrying out SPT tests on standardized nuclear materials (ferritic and stainless steel), not irradiated, for later correlation with conventional mechanical tests; (iii) Develop numerical simulations using the finite element method to correlate them with experimental results and determine the parameters used to obtain the respective mechanical properties. (author)