The constitutive behaviour of rocksalt is explained from micro mechanical concepts. Rocksalt plasticity (or primary creep) can be well explained by a dislocation glide mechanism, where gliding becomes increasingly hindered by dislocations (in fact dislocation pairs or dipoles), disturbing the glide paths. Such dipoles are both the main source for hardening, as well as the main source for time dependent behaviour. From such a description a deformation model can be derived that relates strain rates to stresses, strains and the temperature. The resulting creep curve bears great similarity with the Lemaitre and the Menzel-Schreiner deformation law. However, different from these curve fitting laws, primary creep here is based on proper micro-mechanical considerations and moreover can cope with the transient effects as occurring when load or strain rate increments are suddenly changed.

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