Phase transformation dynamic buckling behaviors of pseudo-elastic TiNi shells under axial impact

A series of quasi-static axial compression tests were conducted on pseudo-elastic TiNi shells by an MTS 809 material testing system to observe their dynamic progressive buckling responses. And numerical simulations were carried out to analyze phase transformation dynamic buckling behaviors of the pseudo-elastic shape-memory alloy shells under short pulse loading. It is indicated that TiNi shells have different buckling modes under different load levels. The buckling of shells begins with the formation of axisymmetric rings under high load speeds and produces a stress plateau. With the gradual increase of martensite fraction, ring phase transformation buckling travels gradually through the whole shell and the nominal stress increases slowly. When the nominal stress exceeds a certain threshold, the axisymmetric ring buckling mode transforms into a nonsymmetrical massive buckling mode and the nominal stress decreases dramatically. The calculation sample with the impact velocity of 40 m/s and the random defect of 10% is in agreement with the experiments by Nemat-Nasser S, et al. The results show that phase transformation energy dissipation is the main mechanism of TiNi shells absorbing impact energy and TiNi shells are suitable for reusable efficient energy dissipation mechanism. And the corresponding perfect diameter-thickness ratio of TiNi shells was proposed.