Plastic deformation and crack growth behavior

Abstract

Even though the theory of plasticity has been used extensively to describe the permanent deformation of solids, some of the hidden restrictions imposed by the underlying assumptions are subtle and can be unwittingly overlooked in application. Generally speaking, the theory can be divided into two ranges. In situations where the plastic strains dominate the global behavior of the structure, the theory has been successful, as in the case of limit analysis. The same cannot be said for the application of plasticity to regions near holes or defects where the local strain rates can differ appreciably from those at distances away. Ordinary plasticity does not account for any change in material properties with load or strain rate history because the same constitutive relation is generally applied to all elements in a solid body. No provisions are made for the elevation of strain rates in elements next to the defects or cracks. Unless certain modifications are made, plasticity will not give a realistic prediction of crack growth behavior, a problem that has attracted the attention of many past investigations in fracture mechanics.