H. Kurishita

K. Yabuki

S. Jitsukawa

T. Muroga

T. Nagasaka

T. Yamamoto

National Institute for Fusion Science (NIFS-Repository)

I . f R d d gage section of 0.5 mm by 1.2 mm by 5 mm. The §7. Fracture Toughness Eva uatlon 0 e uce crack length, ao, from the notched side to the Activation Materials with Miniaturized h pre-crack front was controlled to be 0.5W and t e Specimen Kurishita, H. (IMR, Tohoku Univ.), Yamamoto, T (IMR, Tohoku Univ.), Yabuki, K. (IMR, Tohoku Univ.), Nagasaka, T, Muroga, T, Jitsukawa, S. (JAERI) side grooves to be O.4B. A temperature control bath, bend test fixtures with different spans and a clip gage (or displacement gage) were specially designed to perform the fracture toughness test at and below room temperature for the miniaturized bend specimens. The clip gage was seated on an attachable knife edge with 1 mm thick that had been cemented on the notched side. The fracture toughness tests were conducted at room temperature and 77K at cross-head speeds of 0.013 and 13 mm s ol. In order to evaluate the degradation of fracture For the test for JIC, a program for unloading toughness of thin wall structures made of reduced compliance method with single bend specimen was activation materials due to heavy irradiations developed. Tensile tests were also conducted at with intense neutron sources such as IFMIF, it is room temperature and 77K at initial strain rates of necessary to develop technologies to measure the lxl0-3 and 1 x 10 s- 1. For FEM analysis, two fracture toughness for sub-sized or miniaturized dimensional plane strain analysis with 1274 8-node specimens of several millimeter thickness under elements was used assuming that the crack-tip needed test conditions. For this purpose a project radius is 1 J.-Lm. entitled "Fracture toughness evaluation of reduced It is found that the COD test is applicable in a activation materials by miniaturized specimens" wide test temperature and strain rate range for any was initiated in 2000 as one of KEP. In 2000, we types of bend specimens mentioned above. installed a fatigue test machine and used it to Application of FEM analysis to the data obtained establish how to introduce a well-defined crack that from the specimen of 5 mmB by 5 mmw by 25 mmL meets the requirements for the fracture toughness and 3.3 mmB by 5 mmw x 25 mmL reproduces well testing of differently sized miniature bend the measured load -clip gage displacement curves at specimens of reduced activation ferritic steels such room temperature and 77K providing that assumed as JLF-l, F82H and JFMS. values of equivalent thickness are chosen. The In this study, the tests for the determination of assumed values agree well with the thickness for fracture toughness using parameters of K, J and plane-strain fracture to occur, which is easily CTOD were conducted under different test determined from fracture surface examination by conditions to examine the applicability of each SEM. This success of FEM analysis for fracture parameter to miniaturized bend specimens for the toughness test results on miniaturized bend opening mode (Mode I) of loading. Tensile tests specimen is very important because it may allow us with miniaturized sheet specimens were also to solve the difficult problem of size effect of fracture conducted under different test conditions. FEM toughness of structure materials. analysis was made to estimate the stress and strain The effect of strain rate on fracture toughness of field around pre-crack tip until the crack starts to JLF-l is not significant, but the effect of test advance under applied load. Efforts to develop a temperature is significant. According to JIC test program required for use of fracture reconstruction result on the specimen of 7 mmB by 10 mmw by 45 methods to analyze the sequence of events leading mmL, at room temperature JLF-l has a high fracture to crack initiation and propagation were made. toughness value, approximately 200-230 kJ/m2. Four types of bend specimens and one type of However, at 77K JLF-l exhibits significant tensile specimen were prepared from reduced embrittlement and gives KIC values that are as low activation ferritic steel, JLF-1. The bend specimen as 13 ~ 16 MPam 112 regardless of specimen size and is single edge-notched and fatigue cracked beam satisfy the criterion ofB, W-a > 2.5(KIC/ (J ys)2. loaded in three-point bending with a support spa~, S, We have almost developed a new program for equal to four times the width and has the following fracture and reconstruction methods to be used in dimensions (the thickness, B, width, W, and lengt~ this project, which is based on the program of L): 7 mmB by 10 mm W by 45 mmL, 5 mmB by 5 mr:: assemble.c originally developed for UNIX by K. by 25 mmL, 3.3 mmB by 5 mm W x 25 mmL, 3.3 mm . x Edsinger. 3.3 mm W x 18.3 mmL. The dimensions for tenSIle L . h specimen are 0.5 mmB by 4 mm W by 16 mm . WIt a 393 

Fracture Toughness Evaluation of Reduced Activation Materials with Miniaturized Specimen

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Fracture Toughness Evaluation of Reduced Activation Materials with Miniaturized Specimen

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