[en] The methods applicable to determining fracture mechanics characteristics of the threshold toughness, published in various recommendations and draft standards, are compared and evaluated. The methods are put to the test and comparatively analysed using compact tensile specimens (CT), standardized three-point bending specimens (TPB), and TPB specimens with short cracks. It is shown that only the physical crack initiation value J_i yields results that can be applied for comparative evaluations. (orig./CB)

[en] The aim of this work is to show the validity in the employment of small test tubes (1/2 T) in order to determine the fracture thoughness in ferritic steels that experience the beginning of cracking by cleavage, to elastic instability, and/or elasto-plastic. It was calculated the change of fracture thoughness in the ductile brittle transition region like function of the temperature employing statistic methods for steel to the annealed carbon of the type AISI4140. The testings were carried out within an interval of temperatures, where the cracking by cleavage and/or pop-in occurs. The thoughness curve of the cracking in the transition region was determined, in small test tubes 1/2 T, and in standard test tubes, 1T. It was calculated the beginning of instability of the integral J, J_IC, and was converted to its equivalent in K_JC units based in the ASTM Standard rev. 6-12-95 (ref. 6). (Author)

[en] The tribological couple of the titanium alloy Ti6Al4V and ultrahigh molecular weight polyethylene (UHMWPE) is used for hip and knee joint prostheses. It is known that surface treatment of the titanium alloy Ti6Al4V by ion implantation of various elements can improve the wear behavior of such prostheses. The results of tribological tests, performed in Ringer solution with a ring-on-disc tester, show that oxygen in the implanted near surface region has a pronounced influence on the wear performance. Oxygen can be introduced into the surface by different mechanisms: either by direct implantation of oxygen ions or by indiffusion during the implantation of other elements like nitrogen or carbon at higher temperatures. The influence of the oxygen content in the near surface region of implanted and nonimplanted Ti6Al4V on the tribological performance is discussed in detail. (orig.)

[en] Low speed tribological properties of stainless steel, ceramics and hard metals were investigated in air at room temperature and in nitrogen atmosphere at high temperature for the consideration of sliding type support structure in intermediate heat exchanger of fast reactor. The following results are obtained. (1) In low speed friction measurements in air at room temperature, friction coefficients of ceramics and hard metals were smaller than that of stainless steel. Surface roughness of the specimens increased the friction force and silicon carbide showed the smallest friction coefficient among the specimens with mirror polished surface. (2) From the results of friction measurements at various sliding speeds in air at room temperature, friction coefficients of ceramics and hard metals were always stable and lower than that of stainless steel. Among ceramics, PSZ showed the smallest friction and silicon carbide showed the most stable friction at any sliding speeds. (3) Friction coefficients of silicon carbide and silicon nitride in nitrogen atmosphere at high temperature showed low values as measured at room temperature. On the contrary, friction coefficient of stainless steel measured in nitrogen atmosphere at high temperature were higher than that measured at room temperature, over 1. (4) In the reciprocal sliding tests in nitrogen atmosphere at high temperature, friction coefficient of stainless steel were over 1. On the contrary, the friction coefficients of ceramics were less than 1 instead of chipping during the slidings. (author)

[en] The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the code specify fatigue design curves for structural materials. While effects of reactor coolant environments are not explicitly addressed by the design curves, test data indicate that the Code fatigue curves may not always be adequate in coolant environments. This report summarizes work performed by Argonne National Laboratory on fatigue of carbon and low-alloy steels in light water reactor (LWR) environments. The existing fatigue S-N data have been evaluated to establish the effects of various material and loading variables such as steel type, dissolved oxygen level, strain range, strain rate, temperature, orientation, and sulfur content on the fatigue life of these steels. Statistical models have been developed for estimating the fatigue S-N curves as a function of material, loading, and environmental variables. The results have been used to estimate the probability of fatigue cracking of reactor components. The different methods for incorporating the effects of LWR coolant environments on the ASME Code fatigue design curves are presented

[en] The pumped storage power plant at Markersbach is equipped with 6 pump turbine sets of a total output of 1050 MW. In the course of an in-service inspection, ultrasonic examination detected cracks in a segment of 120 and with assessed depths of 20-40 mm at a ball pivot gate valve (750 mm in diameter), so that activities were performed for comprehensive clarification of the causes and elaboration of a safety analysis based on fracture mechanics concepts. Examination of the fracture surfaces and materials parameters was done by the Institut fuer Werkstofftechnik of Bergakademie Freiberg. The tasks performed are: (1) Examination of fracture mechanisms using SEM; (2) determination of crack growth curves under cyclic loads with R=0.1; (3) determination of crack growth curves under static loads at 0 C; and (4) determination of the crack arrest toughness data K_Ia. (orig./CB)

[en] A state-of-the art is surveyed on the liquid metal reactor core materials HT9. The purpose of this report is to give an insight for choosing and developing the materials to be applied to the KAERI prototype liquid metal reactor which is planned for the year of 2010. In-core stability of cladding materials is important to the extension of fuel burnup. Austenitic stainless steel (AISI 316) has been used as core material in the early LMR due to the good mechanical properties at high temperatures, but it has been found to show a poor swelling resistance. So many efforts have been made to solve this problem that HT9 have been developed. HT9 is 12Cr-1MoVW steel. The microstructure of HT9 consisted of tempered martensite with dispersed carbide. HT9 has superior irradiation swelling resistance as other BCC metals, and good sodium compatibility. HT9 has also a good irradiation creep properties below 500 dg C, but irradiation creep properties are degraded above 500 dg C. Researches are currently in progress to modify the HT9 in order to improve the irradiation creep properties above 500 dg C. New design studies for decreasing the core temperature below 500 dg C are needed to use HT9 as a core material. On the contrary, decrease of the thermal efficiency may occur due to lower-down of the operation temperature. (author). 51 refs., 6 tabs., 19 figs

[en] The effect of boron on the mechanism of strain transfer across grain boundaries in Ni₃Al has been investigated by dynamic recording of events occurring during in-situ straining in the transmission electron microscope. Boundaries in both doped and undoped material can act as effective barriers to dislocation motion, large numbers of dislocations being incorporated into the boundary without any plastic strain occurring in the adjacent grain. In the undoped material, the grain-boundary strain is relieved by the sudden failure of the grain boundary. In the doped material the strain is relieved by the sudden generation and emission of large numbers of dislocations from the grain boundary. This effect may be understood by boron either increasing the grain-boundary cohesion or reducing the stress required to operate grain-boundary dislocation sources, rather than easing the passage of slip dislocations through the grain boundary

[en] In order to intensify power supply facility in quality, study for practical use of Tank Type Fast Breeder Reactor (FBR) have been carried out. It is necessary to understand crack propagation behaviour initiated from defects, particularly it is important to understand crack propagation characteristics under long period and thermal fatigue condition. In this report we carried out strain controlled iso-thermal and thermal fatigue crack propagation test with due regard to strain condition and temperature alternation in actual components using 304 stainless steel and discussed about crack propagation characteristics under creep fatigue interaction condition. As a result it became clear that crack propagation characteristics under thermal fatigue condition was also divided into cycle dependent type and time dependent type, and both types of crack propagation characteristics under thermal fatigue condition agree with them under iso-thermal fatigue condition. (author)

[en] Effect of phase transformations during the W-Zr-C alloy quenching and ageing on strain hardening has been studied. Mechanical properties were determined on tensile testing at a deformation rate ε=2.2x10^-3 s^-1. Electron-microscopic were carried on objects made of a working part of extended specimens. Temperature ranges of dynamic strain ageing (DSA) in quenched state have been revealed. DSA effect on hardening parameters obtained during the loading curve processing in coordinates Δσ-VE, where E is real strain is shown