Abstract
A distinction is made between the theoretical mechanical behaviour of cubic crystals in [100] loading (i.e. transverse stresses are zero) and [1001 deformation (i.e. transverse stretches are zero). In the former, a primary loading path passes through thee zeros (the unstressed f.c.c., b.c.c. and b.c.t. states); in the latter, three corresponding states of hydrostatic loading are reached (one of which is unstressed). Detailed computations are made of the mechanical behaviour in both [100] loading and deformation for lattice models of Cu and Ni. In Cu, the elastic instability associated with the invariant eigenstate C22 = C23 occurs in tensile [100] loading at about 20% of the maximum theoretical stress, thus lowering the estimate of the ‘theoretical tensile strength’ of Cu to within the range of experimentally based estimates. The stress and energy barriers for f.c.c. → b.c.c. and b.c.c. → f.c.c. transitions are computed (within the framework of the lattice models) along a path of [100] loading.
