The critical resolved shear stress and work hardening

6 The critical resolved shear stress and work hardening 

Through the associated strain field, a dislocation is able to interact with other dislocations and also with point defects such as vacancies and impurities. The c.r.s.s. can be affected by the presence of these defects so that the c.r.s.s. is, to some extent. 

Once plastic deformation has started in a specimen an increase in stress is needed to produce further deformation. In microscopic terms this means that as deformation proceeds, the movement of dislocations on their slip planes becomes progressively more difficult. This hardening of the material may arise from elastic interactions between dislocations, through their strain fields, it may arise from dislocation reactions that produce segments that cannot sUp and it may also arise from interactions with other defects such as vacancies, impurities and grain boundaries. 

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