COMPARISON OF METHODS FOR FRACTURE-TOUGHNESS TESTING OF THIN LOW-CARBON STEEL PLATES

The fracture toughness of double edge notched tension (DENT) specimens of a low carbon steel sheet was evaluated using experimental and nume rical methods. The concepts of critical J integral J(c) critical crack tip opening displacement delta(c), essential work of fracture w(e), a nd essential work of fracture and initiation w(e)(init) were compared. The numerical methods were based an finite strain, three-dimensional finite element simulations of the tensile straining of the DENT specim ens. Good agreement was found between numerical and experimental J(c) values. Fair agreement was also found between J(c), and w(e)(init). Th e essential work of fracture w(e), was similar to 20% lower than J(c). This discrepancy is attributed to inaccuracy in the detection of clac king initiation. The Shih factor derived from the measured J(c) and de lta(c) values closely corresponds with the plane stress prediction. MS T/3935.