Multiple parameter measurement of mixed-mode stress intensity factors using the photoelastic method

Precise calculation of the stress intensity factors at crack tips is of great significance in accurate analysis of a structure's crack initiation and fracture mode. In this research, a three-dimensional printing technique was adopted to manufacture a non-residual stress plate model, where high-precision printed pre-cracks avoid the occurrence of residual stress compared to traditional manufacturing processes. By comprehensively considering the singular and non-singular stresses at the near-crack-tip region, three constant stresses controlled by the far field were adopted. Multiple parameters of the photoelastic method combined with the least-squares method were applied to analyze the stress intensity factors of mode I and mixed modes in three-point bending tests under different loads, and a theoretical solution comparison was conducted. Results show that compared with the theoretical solution, the average calculation error for the mode I stress intensity factor is 6.1% and those for I-Ⅱ mixed modes are 6.4% and 5.5%, respectively. This slight calculation error verifies the reliability and accuracy of the multiple-parameter method and provides a reference for further precise calculations of the stress intensity factors using the photoelastic method.