Failure of plastic structures under intense dynamic loading: modes, criteria and thresholds

This paper surveys the failure modes, criteria and thresholds of plastic structural members (beams, rings, plates and thin shells, etc.) subjected to intense dynamic loads, such as impulsive velocities or impact. Besides the three basic failure modes identified by Menkes and Opat [7] for impulsively loaded beams, namely, large inelastic deformation (Mode I), tensile tearing (Mode II) and transverse shear failure at the supports (Mode III), more complicated failure behaviours observed in the cases of complex structural members and/or dynamic loading conditions are summarized and discussed. All the failure criteria used in the relevant theoretical analyses including elementary failure criterion, energy density criterion and quasi-static equivalent energy criterion, etc., are commented upon. The threshold impulsive velocities for the onset of Mode III failure of fully clamped beams predicted from various approaches are compared with each other, as well as with the relevant experimental results. Particular attention is paid to structural members with macro imperfections (for example, containing cracks or notches), where failure which usually originate from the imperfections are fracture-dominant so that local fracture criteria, such as the J-integral criterion, should be incorporated into the global structural failure description. In addition, some most recent results of the authors’ studies are briefly presented.