Small Punch Specimens Research Articles

Small-punch and TEM-disc testing techniques and their application to characterization of radiation damage

The present paper summarizes the development of miniaturized small-punch (SP) and TEM-disc (TD) testing techniques and shows their applicability in characterizing the mechanical properties of irradiated materials. The yield strength, ductility and fracture toughness,Jlc, were empirically estimated by analysing the deformation and fracture behaviour observed in the miniaturized specimen tests. The ductile-brittle transition temperature (DBTT) was determined from the variation of the SP or TD fracture energy with temperature. A linear correlation between the DBTT obtained from the SP and Charpy V-notched specimen tests has been theoretically and experimentally established. The problems of cracking detection and data scattering often observed in the SP or TD specimen tests are discussed in terms of heterogeneous embrittlement behaviour of materials. It has been demonstrated that these miniaturized testing techniques are capable of evaluating hardening, DBTT shifts andJlc decreases caused by neutron irradiation.

Estimation of mechanical properties of irradiated nuclear pressure vessel steel by use of subsized CT specimen and small punch specimen

This paper reports on the 2-1/4 Cr-1M{sub 0} steel that has been selected as the material for the reactor pressure vessel (RPV) of a multipurpose experimental high temperature gas cooled reactor designed by JAERI. The 2-1/4 Cr-1M{sub 0} steel has successful records for high temperature pressure vessels in the petrochemical industries and the ASME Code Case authorizes the use of the steel in these pressure vessels. However, the steel has not been used to nuclear reactor pressure vessels so far. Since the material in the so-called belt line region of the nuclear pressure vessels undergo changes in toughness and strength due to neutron irradiation, it is quite urgent to collect the fracture toughness and strength data of the irradiated steel for the evaluation of the structural intergravity of the reactor pressure vessel of high radiation resistance. In order to study irradiation damage of 2-1/4 Cr-1M{sub 0} steel, small specimens are required because of the severe limitations on specimen size in irradiated-material testing facilities (e.g. the limited space available for testing in nuclear reactors and the narrow damage zone produced by charged particle accelerators). In order to obtain more information about fracture properties of the 2-1/4 Cr- 1M{sub 0} steel frommore » specimens, a subsized compact tensile (CT) specimen, a small punch (SP) specimen and tensile specimen of the irradiated 2-1/4 Cr-1M{sub 0} steel were used to provide radiation effects on fracture toughness, yield strength and ultimate strength. The small punch test, which has been developed recently provides information of the yield and ultimate strength as well as fracture toughness. This report describes the behavior of the neutron irradiation embrittlement of the nuclear reactor pressure vessel steel 2-1/4 Cr-1M{sub 0} by use of new testing approach - subsized specimen techniques.« less

Small punch testing method for the development of functionally gradient materials.

This paper discusses the use of a small punch (SP) testing method to determine the elastic modulus and fracture strength of the material. Numerical analyses using the FEM were carried out to calibrate a SP specimen. Three loading modes were analysed to examine the punch tip effect on the deformation and fracture behaviour. Several ceramics and ceramics/metal composites were tested using the SP method, and their mechanical properties were determined using the results of FEM analyses. It is shown that the SP method provides a reliable means for measuring the elastic modulus. Furthermore, it is demonstrated that the fracture strength determined by the SP method shows a good correlation with the bending strength obtained from the three-point bend specimen which is commonly used for the determination of the fracture strength of ceramics.