Crack Tip Plasticity
All brittle fractures are accompanied by some extent of plastic deformation.
- Plastic deformation will occur in regions near the
crack tip where the stresses exceed the yield stress.
- This plastic deformation results in relaxation of
stresses in the plastic zone
- Assume plasticity is contained in front of the crack
tip
- stresses and displacements in crack tip region are controlled
by the K-controlled zone surrounding the crack.
Need to estimate the size of the plastic zone
- must be small in comparison to all pertinent length
dimensions (crack size, etc.)