Comparaison des énergies dépensées en flambage plastique

The comparison of energy levels is a classical problem in elastic buckling. In plastic buckling, this comparison can also be done through the notion of energy expense, which is an extension of the potential energy of conservative systems to dissipative systems. The difference of the energy expenses associated with the fundamental and the bifurcated branches just after bifurcation is discussed here in standard plasticity. The principal difficulty concerns bifurcation points satisfying the conditions of tangent modulus and total loading. In this particular situation, bifurcation may occur with or without elastic unloading. It is established in all cases that, as in elastic bifurcation with increasing load, the difference of energy expenses is of order 3 with respect to the modal component and that bifurcated branch has a lower energy expense under a certain condition of symmetry.