Comparison of methods for fracture toughness testing of thin low carbon steel plates

Abstract

The fracture toughness of double edge notched tension (DENT) specimens of a low carbon steel sheet was evaluated using experimental and numerical methods. The concepts of critical J integral J_c critical crack tip opening displacement δ_c, essential work of fracture We_e, and essential work of fracture and initiation we^init were compared. The numerical methods were based on finite strain, three-dimensional finite element simulations of the tensile straining of the DENT specimens. Good agreement was found between numerical and experimental J_c values. Fair agreement was also found between J_c and we^init. The essential work of fracture W_e was ∼20% lower than J_c. This discrepancy is attributed to inaccuracy in the detection of cracking initiation. The Shih factor derived from the measured J_c and δ_c values closely corresponds with the plane stress prediction.