Study On The Dynamic Behavior Of Polycrystalline Titanium At Elevated Temperature

The present research is financially supported by the National Natural Science Foundation of China (NO. 10172080 and No. 10472110)Research on the dynamic behavior of metallic materials at elevated temperatures is one of the principal directions in the solid mechanics and material science. An understanding of tensile deformation behavior of metals over a wide range of strain rates and temperatures is very important in the design of structures. However, due to the experimental technique difficulties, few reports on tensile behavior of metals at high strain rates and elevated temperatures are available so far. In the present work, a new heating technique was proposed in a self-designed Split Hopkinson Tensile Bar (SHTB) and a high temperature and high strain-rate tensile testing system was established, which is suitable for measuring the dynamic response of metals over a wide temperature range of 298K-1073K. A thorough calibration on the testing system showed that a nearly homogeneous temperature field in the specimen (the temperature deviation <3%) can be rapidly (in 30 seconds) created, and the temperature rise in the bars of SHTB can be controlled to meet the requirement of one-dimensional experimental principle.Tensile impact load-unload experimental technique was improved by using specially designed input/output wave filter fixtures to absorb the secondary loading waves in the input/output bars. As a result, the amplitude of the secondary input/output waves can be reduced to a value of 1/4 and 1/6 of their corresponding initial waves, respectively. Owing to this improvement, a more reliable load-unload curve was obtained and the tensile impact recovery experimental technique was updated.Tensile experiments on the CP-Ti were carried out in a temperature range of 298K-973K and a strain rate range of 10^-3s^-1-1400s^-1. The testing results indicate that: 1) The density of deformation twinning decreases rapidly with increasing temperature, which leads to a noticeable difference of strain-hardening rate at room temperature...