ELASTOPLASTIC BUCKLING OF COMPRESSION MEMBERS AS A COUPLED INSTABILITY

In the paper the author shows that plastic deformations can be considered as a bifurcational instability of the atomic lattice. Thus, the plastic buckling of a compression bar is examined like a coupled instability between the general buckling by flexural and the local buckling by plastic deformations. The modified Hunt-Burgan model is studied and an interaction relationship between the elastic buckling load and the plastic collapse load is determined. Although this relationship is obtained in an elastic field, the form corresponds to the Ayrton-Perry relationship for plastic buckling, used by Maquoi and Rondal for the analytical expressions of the ECCS buckling curves. However, one can see that the general imperfections corresponding to Eulerian buckling and local imperfection due to residual stresses have different effects, in opposition to Maquoi-Rondal relationships. A new relationship for the simple plastic buckling and coupled plastic buckling are proposed.