Local stress evaluation of rapid crack propagation in finite element analyses

The objective of this research is to perform the verification of finite element analyses with a nodal force release technique to simulate rapid crack propagation based on the local fracture stress criterion, and to propose a method suitable for the accurate evaluation of local stress. The verification of the accuracy and stability of local stress evaluation was first performed by generation phase analyses. The verification was first conducted for conventional methods, but there were large errors caused by violent vibration in local stress fields. Even though the nodal force release paths were optimized, the vibration in the local stress fields could not be sufficiently suppressed. Two types of artificial damping, the viscous term of the time integration method and Rayleigh damping, were then applied to the rapid crack propagation analyses. The results showed that only stiffness damping in Rayleigh damping could suppress the vibration and an appropriate degree of damping provided stably accurate local stress for all the crack velocities. This proposed method was then applied to the application phase analyses based on the local fracture stress criterion and successfully duplicated the exact solution of the crack velocity history.