摘要
Modifications were made on the traditional split Hopkinson pressure bar （SHPB） system to conduct dynamic shear tests. The shear response of Ti-6A1-4V was acquired at a shear strain rate of 104 s-1 by using this modified apparatus. The geometry as well as the clamping mode of the double-notch specimen was optimized by commercial FEM software ABAQUS, and the feasibility of the experiment set-up was validated. A shear stress calibration coeff^cient of γT = 1.03 and a shear strain calibration coefficient of γT- = 0.50 were obtained.We have employed high- speed photography to record the deformation process, especially the initiation and propagation of adiabatic shear band （ASB）, during the dynamic shear test. The frames show that the time duration from ASB initiation to its completion is less than 2 μs, from which we can estimate that the propagation speed of ASB within Ti-6A1-4V is more than 1250 m/s under such loading conditions. The temperature rise within ASB is also estimated to be △T2 ≈ 1460 ℃ based on energy balance. Such high temperature has led to softening of the material within the ASBs, and has intensified the shear localization and finally resulted in fracture of the material.
Modifications were made on the traditional split Hopkinson pressure bar （SHPB） system to conduct dynamic shear tests. The shear response of Ti-6A1-4V was acquired at a shear strain rate of 104 s-1 by using this modified apparatus. The geometry as well as the clamping mode of the double-notch specimen was optimized by commercial FEM software ABAQUS, and the feasibility of the experiment set-up was validated. A shear stress calibration coeff^cient of γT = 1.03 and a shear strain calibration coefficient of γT- = 0.50 were obtained.We have employed high- speed photography to record the deformation process, especially the initiation and propagation of adiabatic shear band （ASB）, during the dynamic shear test. The frames show that the time duration from ASB initiation to its completion is less than 2 μs, from which we can estimate that the propagation speed of ASB within Ti-6A1-4V is more than 1250 m/s under such loading conditions. The temperature rise within ASB is also estimated to be △T2 ≈ 1460 ℃ based on energy balance. Such high temperature has led to softening of the material within the ASBs, and has intensified the shear localization and finally resulted in fracture of the material.
基金
Project supported by National Natural Science Foundation of China (Nos. 11102166 and 10932008)
the 111 project(No. B07050)
the Basic Research Foundation of NPU (No. JC201201)
