DYNAMIC STRESS-STRAIN RELATIONS FOR ANNEALED 2S ALUMINUM UNDER COMPRESSION IMPACT - AND APPENDIX

Two methods of securing a dynamic stress-strain curve are considered: namely, from the measurement of impact stress as a function of maximum plastic strain and impact stress as a function of the impact velocity. The results show that the behavior of annealed 2S Al under condition of impact loading into the plastic strain range can be represented to a good approximation by a single dynamic stress-status relation. This dynamic stress-strain relation lies above the static stress-strain curve. The excess of dynamic stress over the static values increases progressively with strain, reaching about 20% of the static stress at a strain of 4.5%. However, the 2 dynamic relations are not coincident which indicates that the behavior of the material cannot be described by a single dynamic stress-strain relation. A detailed analysis of the experimental measurements by means of the von Karman theory of propagation of plastic strains in long rods indicates that the behavior of the material near the impact surface may be described by a family of stress-strain relations. Each member of this family of curves corresponds to a given impact stress, and the curves are arranged consecutively in order of increasing impact stress. All of these curves lie within a narrow region in the stress-strain plane.