Measurement of stress intensity factors by digital camera

This paper developed a least-squares method to evaluate the mixed-mode stress intensity factors (SIFs) of the isotropic material using the computer images from the digital-camera experiment. This experiment measures the crack opening displacement (COD) and then evaluates SIFs by using the least-squares method. The attractions of this method include: (1) specimen preparation and experiment procedures are not complicated and (2) the isolation of the micro-vibration is not necessary in the experiment. Both finite element simulations and laboratory experiments were applied to validate the current least-squares method with acceptable accuracy, if the even terms of the Irwin's equation are removed.