STRAIN HARDENING PROPERTIES OF HIGH STRENGTH SHEET MATERIALS.

Measurements were made of the principle strain in the width and thickness dimensions on sheet specimens, thereby developing more basic plastic flow and fracture properties of these sheet materials. The deformational properties of high strength steels appear quite heterogeneous, which is probably due to their low strain hardening properties. Shear band formation, which results from a neck in the thickness direction, was prevalent in the high strength steels but not in the titanium alloys. With the exception of the AM 355 alloy, the steel showed only slight anisotropy with the ratio of width to thickness strains being somewhat smaller than one. However, the titanium alloys showed a high degree of anisotropy with width to thickness strains ranging from about 7.2 to 0.2. The strength parameters generally increase with decreasing temperature until brittle fracture occurs. The ductility decreases gradually and then abruptly when brittle fracture ensues with decreasing test temperature. The fracture properties seem to be related to the strain hardening properties indirectly. For the titanium alloys, the fracture ductility seems to be directly related to the strain hardening properties.