Effect of Specimen Size and Material Condition on the Charpy Impact Properties of 9Cr-1Mo-V-Nb Steel

Abstract

The degradation of fracture resistance of ferritic steels subjected to neutron irradiation can be qualitatively evaluated by examining the shift in the ductile-to-brittle transition temperature and the drop in the upper-shelf energy as determined in the Charpy impact test. That is an empirical test, however, and its usefulness is derived primarily from either correlation to more quantitative measures of fracture toughness or comparison with other Charpy test results for different materials or conditions of interest. Any departures from the standard testing procedures, including specimen dimensions, will yield results which will vary in some degree from those of a standard test. In examining the effects of neutron irradiation on the fracture resistance of the high-chromium ferritic steels which are candidates for the first wall of magnetic fusion reactors, it is necessary to severely limit the size of the test specimens to be fit within high-flux test reactors. Impact specimens with cross sections as small as ⅓ by ⅓ cm are employed. To evaluate the effectiveness of small specimens in measuring the relative shift in transition temperature and drop in upper-shelf energy, compared with a standard Charpy specimen, a study of the impact properties of 9Cr-1Mo-V-Nb steel in both the normalized and tempered and the quenched-only condition was conducted. Full-size and various subsize Charpy V-notch specimens of two orientations were examined in both material conditions. Comparing the test results of the tempered with the embrittled 9-Cr-1Mo-V-Nb steel showed that larger transition temperature shifts and smaller fractional drops of upper shelf were measured with the small specimens relative to the standard-size specimens. Attempts were made to improve the correspondence of data by fracture area and volume normalization. No improvement in the shift or shelf drop was obtained. However, a fair agreement for the higher energy tests of absolute energy was obtained with fracture volume normalization.

Empirical Correlation of Specimen Size Effects in Charpy Impact Properties of 11Cr-0.5Mo-2W, V, Nb Ferritic-Martensitic Stainless Steel

“…notch depth and notch root radius, give no significant effect on the USE. Figures 4(b) and 4(c) show the normalized USE by ðBbÞ 3=2 and Bb 2 , according to the proposal by Corwin et al 9) and Lucas et al, 15) respectively. This power law type of equation was introduced to convert from the nominal fracture area to the effective fracture volume where the Charpy impact energy should be absorbed by the plastic deformation process.…”

“…[7][8][9][10][11][12][13][14][15][16][17] Corwin et al 9) empirically used a normalization factor of USE as ðBbÞ 3=2 , and Lucas et al 15) used as Bb 2 , where B is the specimen thickness and b is the ligament size. It is well known that small specimen test technology is required in Charpy impact testing, because the available irradiation volume is very limited in the reactor and future accelerator-based intense neutron sources.…”

The Production of Calibration Specimens for Impact Testing of Subsize Charpy Specimens

“…In order to verify the performance of the testing system, the calibration of the impact tester was checked with full-size specimens supplied by AMMRC. The anvils and tup were then changed to allow subsize specimens to be tested [1]. Fifty low-energy and fifty-one high-energy half-size specimens were tested, with twenty-five each of the third-size high-and low-energy specimens.…”

“…As a result, subsize specimen testing is a significant fraction of the impact testing conducted at ORNL. The use of these sm_ll specimens necessitates changes in the test system to accommodate the reduced specimen dimensions [1]. As a result, changes in the calibration procedures for the test machine are necessary.…”

Influence of specimen dimensions on ductile-to-brittle transition temperature in Charpy impact test

“…A review of the literature shows the efforts to correlate results for standard Charpy with different width [1,2] and standard Charpy with sub-size Charpy [3][4][5][6][7][8][9][10][11][12][13][14]. Small specimen method is also used in another mechanical testing techniques [15,16,17] to minimalize the size of tested material.…”