RAQUEL DE MORAES LOBO

RAQUEL DE MORAES LOBO

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Correlations of mechanical properties by SPT and conventional tensile test for stainless steel 316L
2024 - LOBO, RAQUEL de M.; MIRANDA, CARLOS A. de J.; FALOPPA, ALTAIR A.; LIMA, JOSE R. de; MATTAR NETO, MIGUEL; CAJA, FERNANDO
The Small Punch Test (SPT) method is an “almost non-destructive”[1] method by uses miniaturized samples to obtain mechanical properties of materials. It was development by nuclear industry to analyses mechanical behavior of irradiated materials principally by small volume of the samples, which facilitates their storage and handling. Its applications are spreading across several areas of materials engineering, for use in situations where conventional methods do not apply. SPT consists of pressing a sphere, with a diameter equal to 2.5 mm, in a miniaturized sample of circular geometry (diameter d = 8 mm and thickness about 0.5 mm)[2], which has fixed edges, tested in conventional mechanical testing machines with the aid of a device developed for their achievement. In this work, mechanical properties of stainless steel (316 L) were abstained by two different methods: conventional tensile test and the small punch test (SPT), for comparing the results and allow the evaluation of the method. The SPT results depends on graph interpretations and discussions take place at now. Correlations of results guide us in choosing the most appropriated method for interpreting the force x displacement graph from SPT.
A Small Punch Test device developed for low temperature tests with initial acceptance results
2024 - MIRANDA, C.A.J.; FALOPPA, A.A.; LIMA, J.R. de; LOBO, R.M.; CAJA, F.S.; MATTAR NETO, M.
Correlations of mechanical properties by SPT (Small Punch Test) and conventional tensile test for Al 6061 – T6
2023 - LOBO, RAQUEL de M.; CASTAGNET, MARIANO; MIRANDA, CARLOS A. de J.; FALOPPA, ALTAIR A.; LIMA, JOSE R. de; MATTAR NETO, MIGUEL; PEREIRA, LETICIA dos S.; ANDRADE, ARNALDO H.P. de
The Small Punch Test (SPT) was development by nuclear industries to analyses mechanical properties of irradiated materials principally by small volume of the samples. This technique intend to evaluate the materials behavior during the time life of nuclear reactors, where yours properties changed by irradiation intensity and exposition time. It is considered an almost ¨non-destructive” method [2] due to small sample volume and its applications are spreading for use in situations where conventional methods do not apply. SPT consists of pressing a sphere, with a diameter equal to 2.5 mm, in a miniaturized sample of circular geometry (diameter d = 8 mm and thickness about 0.5 mm)[1], which has fixed edges, tested in conventional mechanical testing machines with the aid of a device developed for their achievement. In this work, mechanical properties of aluminum (Al 6061-T6) were abstained by two different methods: conventional tensile test and the small punch test (SPT). The SPT results depends on graph interpretations and discussions take place at now. Correlations of results guide us in choosing the most appropriated method for interpreting the force x displacement graph from SPT.
The use of miniaturized samples to determine mechanical properties of materials
2022 - LOBO, RAQUEL de M.; CASTAGNET, MARIANO; MIRANDA, CARLOS A. de J.; LIMA, JOSE R. de; FALOPPA, ALTAIR A.; MATTAR NETO, MIGUEL; PEREIRA, LETICIA dos S.; ANDRADE, ARNALDO H.P. de
The caracterization of irradiated materials through the SPT (Small Punch Test) technique uses miniaturized samples, with 8 mm in diameter and 0.5 mm in thickness, which has fixed edges, pressed by a sphere that has a diameter d=2.5 mm[1], tested in convencional mechanical testing machines, with the aid of a device developed for their achivement. This tecnique developed for nuclear industry can be used where conventional methods do not apply because it is considered an almost “non-destructive” method[2]due to the small sample volume. In this work two different devices were developed to perform tests at room and sub-zero temperature. The SPT tests will be carried out on standardized nuclear materials unirradiated (ferritic and stainless steels) for later correlation with conventional mechanical tests. Several mechanical properties will be obtained such as yield stress, tensile strength and fracture properties of the materials such as its toughness.
Small punch tests with a recently developed device in IPEN
2021 - MIRANDA, C.A.J.; ANDRADE, A.H.P. de; CASTAGNET, M.; LOBO, R.M.; FALOPPA, A.A.; MATTAR NETO, M.; LIMA, J.R.; PEREIRA, L.S.
Small punch test devices in development at IPEN aiming to perform tests in RMB hot cells
2021 - MIRANDA, C.A.J.; LIMA, J.R.; FALOPPA, A.A.; ANDRADE, A.H.P. de; MATTAR NETO, M.; CASTAGNET, M.; LOBO, R.M.; PEREIRA, L.S.
Numerical analysis of the small punch test for different theoretical materials
2021 - PEREIRA, L.S.; MATTAR NETO, M.; MIRANDA, C.A.J.; LIMA, J.R.; FALOPPA, A.A.; ANDRADE, A.H.P. de; CASTAGNET, M.; LOBO, R.M.
Monitoring of the ductile to brittle transition temperature of reactor pressure vessel steels by means of small specimens
2019 - ANDRADE, ARNALDO H.P. de; MIRANDA, CARLOS A.J.; LOBO, RAQUEL de M.
Neutron irradiation in nuclear power plants (NPPs) lead to microstructural changes in structural materials which induce a shift of the ductile to brittle transition temperature (DBTT) towards higher temperatures. Monitoring of the DBTT in NPP components receives therefore considerable attention. Small specimen testing techniques are developed for characterizing structural components with a limited amount of materials. One of the most used of these miniature testing is the small punch test (SPT) which is based on disc or square shaped specimens. SPTs may be performed from room to cryogenic temperatures, plotting the absorbed energy until rupture, against the test temperature. A ductile region (high energy) and a brittle region (low energy) with a transition between both zones are usually reported. The transition temperature thus obtained, DBTTSPT, is also related through empirical expressions to the transition temperature obtained in CVN tests, DBTTCVN, or in fracture toughness testing. Linear expressions such as DBTTSPT = α DBTTCVN have been used where α is a material characteristic constant. In all cases, the DBTTSPT temperature is much lower than that obtained in the CVN tests. In this paper, we present a short review of the literature on the determination of the DBTT for nuclear reactors pressure vessels steels by those two techniques analyzing the reason for the difference in their value as mentioned before. In dealing with irradiated materials, is a high priority to limit the exposure of the professional to irradiation. Therefore, the use of miniature specimens receives significant attention in the nuclear community. The high cost of irradiation experiments is a further incentive for using small specimen testing techniques.
Recent advances on charpy specimen reconstitution techniques
2017 - ANDRADE, ARNALDO H.P.; LOBO, RAQUEL M.; MIRANDA, CARLOS A.J.
Charpy specimen reconstitution is widely used around the world as a tool to enhance or supplement surveillance programs of nuclear reactor pressure vessels. The reconstitution technique consists in the incorporation of a small piece from a previously tested specimen into a compound specimen, allowing to increase the number of tests. This is especially important if the available materials is restricted and fracture mechanics parameter have to be determined. The reconstitution technique must fulfill some demands, among them tests results like the original standard specimens and the loaded material of the insert must not be influenced by the welding and machining procedure. It is known that reconstitution of Charpy specimens may affect the impact energy in a consequence of the constraint of plastic deformation by the hardened weldment and HAZ. This paper reviews some recent advances of the reconstitution technique and its applications.