Data base of impact stress-strain relations of high strength titanium alloys

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The stress-strain relations of high strength beta titanium alloy(Ti-15V-3Cr-3Sn-3Al) at high strain rate are focused in the present study, and are systematically investigated to frame the relevant data base in terms of the aging conditions, temperature, and strain rate, since the material is very promising for high velocity transportation vehicles in near future.To clarify the temperature and strain rate dependence of stress-strain relations in the wide strain range, the quasi-static compression test, the strain rate change test, and the impact test were first carried out for the un-aged and the aged materials. Since the temperature and strain rate effect on the strength is well understood in connection with the thermally activated deformation process, we can apply the concept to predict the stress strain relation at high strain rate by taking account of adiabatic heating effect during deformation. The experimental results were well understood. Impact tensile stress-strain relations fo … More r three kinds of age-hardened specimens were fully obtained using a newly developed split Hopkinson bar type impact testing apparatus. Besides the data base for impact strength of the materials, followings are also summarized. (1)Impact strength both in the tension and the compression test was always higher than the static value independent of temperature and aging treatments, except the case of the brittle fracture occurred in the elastic deformation range at very low temperatures. (2) Work softening phenomenon was observed much more significantly on the impact stress-strain relations at lower temperatures. (3) The elongation and the reduction of area both increased in the impact test independent of temperature and aging conditions. (4) Temperature and strain rate dependence of the flow stress was almost independent of aging treatment, and consequently, the impact stress-strain relations can be uniquely predicted only depending the athermal component of stress to the strain relation which would be respectively evaluated in the static test at appropriately high temperatures. Less