Applicability Of Modified Ritchie-Knott-Rice Failure Criterion To Predict The Onset Of Cleavage Fracture For The Test Specimen With Residual Stress Introduced To The Crack Tip

In this work, applicability of the modified Ritchie-Knott-Rice (RKR) failure criterion (which predicts the onset of cleavage fracture when the crack opening stress measured at four times the crack-tip opening displacement σ22d exceeds a critical value σ22c) is demonstrated for the test specimen with residual stress. This was done by comparing the results of the fracture toughness test and elastic-plastic finite element analysis results. 0.45 % carbon steel JIS S45C, whose tensile to yield stress ratio was equal to 1.5 was chosen as material for the test. SE(B) specimen of width 46 x thickness 23 mm, which complies the ASTM E1921 was used for the test. The residual stress was introduced to the crack-tip by mechanical pre-loading. The results showed that though scatter of the fracture toughness Jc was large, scatter of the critical value σ22c was very small. Thus, the modified RKR failure criterion has been shown to be applicable to the S45C SE(B) specimens of thickness 23 mm with residual stress by mechanical pre-loading. In addition, the J corresponding to the load that σ22d first reaches σ22c seemed to predict the lower bound toughness for the material and the specified specimen configuration.