Influence of the radius of curvature of crack-tip on the mixed mode stress intensity factor by infrared hybrid method

The seven kinds of mixed-mode loading of the CNS specimen were carried out using the thermography and servopulser, and the data of the sum of the principal stresses were obtained. After estimating the nodal forces from the sum of the principal stresses by an inverse problem, the error included in the experiment field was modified by the intelligent hybrid method. The stress intensity factor was evaluated by the virtual crack extension method and the displacement extrapolation, and the validity was discussed as comparing with the 3-dimensional finite element analysis. The relative error to the stress intensity factor obtained by the 3-dimensional finite element analysis increases as a load application angle increases. The stress distribution obtained from the infrared thermography differed from the finite element method greatly, and it became clear that the influence of thermal conduction cannot be disregarded. Therefore, thermal-conduction inverse problem analysis is needed to estimate a true stress field.