As discussed in the last chapter, a given load or stress acting on a body results in deformations that for ideal solids are adequately measured by strains. In such solids, the application of a time-independent load on a body results in an instantaneous, time-independent strain. For an ideally elastic material, on removing the load the body reverts to its original unloaded state, the strains dropping to zero. However, in a plastic material, unloading can result in a residual strain called plastic strain.