We know that total strain is the symmetric part of the displacement gradient. Total strain can be represented by the sum of the elastic and plastic (eigen) strains. Let consider a dislocation in an arbitrary solid. Suppose we computed the displacement filed, therefore the total strain can be obtained immediately. What are the criteria for the decomposition of the total strain into elastic and plastic parts?

 Maybe in classical continuum it is relatively easy to decompose the total strsain into elastic and plastic parts since the singular terms can be regarded as the plastic parts as deWit (1973) mentioned. However in some generalized theories of continuum mechanics that is not true. For example suppose a dislocation is located in an infinite medium. Consideting this case within strain gradient elasticity, it is well-known that the plastic strain exists everywhere as well as it is not singular. For more complicated problems what are the criteria for the decomposition?