Load capacity evaluated from fracture initiation and onset of rapid propagation for cast iron by digital image correlation

• The crack initiation load can be determinated based on analytical results of the strain-rate obtained by DIC.
• Strain fields of the area above the pre-notch obtained by DIC were applied to detect crack patterns.
• The load capacity was evaluated from fracture initiation and onset of propagation by DIC and double-K fracture criterion.

Digital image correlation was used to measure the fracture process of the castiron in this research. The crack opening displacements, crack mouth opening displacements and neutral layer positions were obtained by correlation calculating. The initial crack load was determined by analyzing results of the strain-rate of the area around the tip of the pre-notch. The predicted fracture initiation and crack propagation patterns are consistent with the observed cracking behavior. The load capacity was evaluated by the method combined digital image correlation with the double-K fracture criterion and the simplified double-K fracture model. It indicates that the data determined by the combined method well agree with those of the experiment and better than those from the simplified double-K model.