Mechanical properties of open-cell rhombic dodecahedron titanium alloy lattice structure manufactured using electron beam melting under dynamic loading

The compressive behavior of Ti-6Al-4 V lattice structures with rhombic dodecahedron unit cells is investigated at four different strain rates. Quasi-static compressive experiments are conducted by an electronic universal testing machine with a strain rate of 10⁻³/s, while Split Hopkinson pressure bar(SHPB) tests are used for achieving higher deformation rates about 1000/s. The loading processes are recorded by a digital and high speed camera respectively for all tests in order to determine the failure modes at different strain rates. The nominal stress-strain relationship is curved afterwards. The results show that the peak stress exhibits certain dependence on the loading rate for the structures with smaller unit cells. The deformation modes are found to be unchanged in quasi-static and SHPB experiments. All specimens are deformed with a shear band along 45°plane firstly. Finite element(FE) model is established based on the specimen with 5 mm unit cell size by 3D reconstruction from X-ray tomography to take the surface quality of struts into account. Afterwards, numerical analysis is conducted by LS-DYNA to simulate the specimens impacted at different velocities. The FE results which can be employed to make some useful predictions are partly consistent with the experimental data. Then the crushing behavior of Ti-6Al-4 V lattice structure is analyzed by the rigid-power-law hardening(R-PLH) model, and the critical velocities for deformation mode transition are predicted.