High strain rate mechanical properties of this material are required for the structural design of ship components for advanced naval applications. Taylor cylinder specimens were machined from pure titanium plate stock proposed for use in ship building. Since the specimens were machined from plate stock, it was assumed that the processing of the plate induced anisotropic behavior. To assure that all the effects would be captured by the tests, specimens were machined in the rolling direction, transverse direction, and 45° to the rolling direction in the plane of the plate. Indeed, distinct differences were observed in the rolling and transverse directions. Specimens in the 45° direction also showed the unsymmetrical deformation field that is associated with anisotropy. There was modest anisotropy in the thickness direction. However, the analysis of the data from the tests required corrections to accommodate this effect.
Data from these tests can be reduced using two distinct methods; a one-dimensional theory and a finite element analysis with a conventional constitutive model adjusting the free parameters until the specimen geometry is matched. While the second method usually produces excellent results, we will employ a one-dimensional analysis that was proposed several years ago by one of the authors in this paper. In order to effectively apply such a theory, very low scale specimens, in this case 0.164-inch diameter, are required. The use of such low diameter specimens demands accurate measurement of the specimen profile. The recovered specimens were measured with a laser micrometer and the results were used to find estimates of quasi-static compressive stress and compressive stress at strain rates exceeding 104/sec.
Some scatter in the data from these tests was observed. This was mostly due to some variations in the initial specimen diameter. Pure titanium presents a machining challenge for conventional equipment, when a tolerance of a thousandth of an inch is required. The scatter in Taylor cylinder data can be mitigated by conducting a large number of tests. However, in this case, many of the specimens that did not meet the criteria for success were discarded. Nevertheless, the results are very convincing.
Size effect on the high strain rate micro/meso-tensile behaviors of pure titanium foil
