A primary relationship between critical strain energy density and fracture toughness of mild steel

This paper presents a novel and simplified method for determining the initial fracture toughness of mild steel under the mode-I loading conditions. This method is proposed based on an established correlation between critical strain energy density and fracture toughness. A Digital Image Correlation (DIC)-based fracture toughness test is conducted on four different grades of mild steel to validate the proposed method. A comparative analysis of the results demonstrates a high level of agreement between the initial fracture toughness values obtained from the proposed method and the DIC-based tests, with a deviation of less than 5%. Furthermore, the test results show that the relationship between critical strain energy density and fracture toughness remains constant, regardless of the initial crack length ratio. The significance of this new method lies in its ability to obtain the fracture toughness from tensile tests only, offering a much-simplified approach for determining the initial fracture toughness of mild steel while maintaining an acceptable level of accuracy.