Effect of Subcritical Crack Growth on Fracture Toughness and Work‐of‐Fracture Tests Using Chevron‐Notched Specimens

A correlation between the plane strain stress intensity factor K I , load, and crack extension has been analyzed for constant displacement and constant loading rate experiments, using chevron‐notched, four‐point‐bend specimens. It is assumed that at the beginning of the experiment the chevron triangle tip is not ideally sharp. As loading continues, the crack initially moves with velocity v t at K I equal to a threshold value K t . Maximum crack velocity is reached at K I = K IC , the fracture toughness. Depending on the type of material tested, a specific displacement or loading rate must be used to correlate the maximum load with K Ic . An error in K IC calculation is estimated if different displacement rates are applied. Repeated loading‐unloading work‐of‐fracture (WOF) experiments generate values related to the resistance of the material to fracture initiation, K t , only when the crack length approaches 100% of the specimen width. Values related to material's fracture toughness, K IC are not generated in WOF tests.