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Dynamic finite element modeling of the fracture behavior of pressure vessel materials under impact loading was conducted to study the effects of ligament size and tensile properties on the crack extension (USEe) and propagation (USEpr) energies. The sum of USEe and USEpr is the total energy absorbed, USEp, in complete fracture of the specimen. ASTM standard (full size) and subsize precracked Charpy specimens with varying ligament sizes (b) were investigated for five materials with a wide range of ductility. It was found that for all materials studied the dependence of USEp on ligament size for half and third size specimens was similar, but quite different from that for full size specimens. USEp varied as b2 for half and third size specimens. For full size specimens, it varied as b2.5 for low ductility and as b3.5 for high ductility materials. It was further found that the ratio, r, of crack extension and propagation energies decreased sharply with b for both low and high ductility materials if the ligament sizes were less than half the width. For larger ligament sizes, the value of r was close to 1 for all materials and specimen sizes. The crack extension energy did not show any systematic pattern in its variation as a function of material ductility or specimen constraint. USEpr, however, did show a systematic variation with ligament size. For the highest ductility material, the full size USEpr. behaved as b3.5 whereas USEpr,. for the half and third size specimens behaved approximately as b2.5. For the lowest ductility material, USEpr for all three sizes behaved approximately as b2.
Ferritic steel, A533B, embrittlement, pressure vessel steel, neutron irradiation, finite element modeling, impact, upper shelf energy
Design Engineer, Westinghouse-CNFD, Columbia, SC
Chairman and Professor, Nuclear Engineering, Univ. of Missouri, Rolla, MO
Senior Scientist, Pacific Northwest Laboratory, Richland, WA