Before revision: The Willenborg model Crack growth equations Threshold equation To predict the crack growth rate at the near threshold region, the following relation has been used Tayyip –Erdoğan equation To predict the crack growth rate in the intermediate regime, the Paris–Erdoğan equation is used Forman equation In 1967, Forman proposed the following relation to account for the increased growth rates due to stress ratio and when approaching the fracture toughness McEvily–Groeger equation McEvily and Groeger proposed the following power-law relationship which considers the effects of both high and low values of .
After revision: The Willenborg model Crack growth equations Threshold equation To predict the crack growth rate at the near threshold region, the following relation has been used Paris –Erdoğan equation To predict the crack growth rate in the intermediate regime, the Paris–Erdoğan equation is used Forman equation In 1967, Forman proposed the following relation to account for the increased growth rates due to stress ratio and when approaching the fracture toughness McEvily–Groeger equation McEvily and Groeger proposed the following power-law relationship which considers the effects of both high and low values of .