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 Jc critical crack tip opening displacement δc, essential work of fracture Wee, and essential work of fracture and initiation weinit 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 Jc values. Fair agreement was also found between Jc and weinit. The essential work of fracture We was ∼20% lower than Jc. This discrepancy is attributed to inaccuracy in the detection of cracking initiation. The Shih factor derived from the measured Jc and δc values closely corresponds with the plane stress prediction.