SEDL / STP / STP833-EB / STP32576S

Effect of Specimen Dimensions on Critical J-Value at the Onset of Crack Extension

De Roo, P
Institut de Recherches de la Sidérurgie Française (IRSID), Saint Germain en Laye,

Marandet, B
Institut de Recherches de la Sidérurgie Française (IRSID), Saint Germain en Laye,

Phelippeau, G
Institut de Recherches de la Sidérurgie Française (IRSID), Saint Germain en Laye,

Rousselier, G
Electricité de France (EDF) Les Renardières, Moret Sur Loing,

Pages: 16    Published: Jan 1984

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Abstract

This paper presents the experimental results of a test program designed to evaluate the effect of specimen dimensions on the critical J transition curve. These tests were conducted, along with K^Ic measurements, on four quenched-and-tempered medium strength steels with 15 to 200 mm thick specimens. In the cleavage fracture domain, J^c yielded toughness values that overestimated K^Ic, especially with the smallest specimens. Although ASTM E 813 requirements were met, the cleavage to ductile tearing transition temperature increased with increasing the J-specimen size. The level of the ductile plateau was found to be strongly dependent on the uncracked ligament length. It is pointed out that J^Ic measurements may overestimate the plane-strain fracture toughness, the ASTM E 813 size requirements being not restrictive enough.