Abstract: The dynamic behaviors of Ti-5553 alloy under high strain rate are investigated by Taylor bar impact test and numerical simulation. Ti-5553 alloy achieves equal-axis microstructure and duplex microstructure with different mechanical properties after it is processed through two kinds of heat treatment processes. By means of numerical simulation with ANSYS/LS-DYNA software， the influences of yield stress σ_s and failure strain ε_f on the processing parameters and impact results，such as kinematic energy，velocity and acceleration， are studied on the base of Taylor bar impact tests. The yield stress is set to 1 170 ~1 400 MPa and the failure strain is set to 0.1~0.8. The experimental and numerical simulation results demonstrate that the value of yield stress has little influence on kinetic energy，velocity and acceleration during the Taylor impacting test. The higher the yield stress is，the lower the final strain of projectile is. The changing rates of energy，velocity and acceleration improve slightly. For Ti-5553 alloy with the equal-axis microstructure， the changing rates of energy，velocity and acceleration increase with strain rate for ε_f<0.7，and the projectile has no spring back. For ε_f ≥0.7，the curves of processing parameters coincide with each other and the projectiles spring back. When failure strains are defined as 0.75 and 0.35 for the equal-axis and duplex microstructure alloys, respectively，the numerical simulation results are in good accordance with the actual Taylor experimental results.

Key words: solid mechanics, Ti-5553 alloy, Taylor bar, yield stress, failure strain