If no elastic deformation
In the case of the steel wire (Fig. 5.7(c)), the development of plastic strain depends on the yield stress level. This is described as strainhardening behaviour. Steel may therefore be described as a strainhardening elasto-plastic material. In the case of soils the linear range is usually very small or completely absent and in the context of plasticity theory they may most appropriately be described as strain-hardening plastic materials.