Research Of Impact Response Of Thin Circular Plate Of Pseudo-elastic TiNi Alloy

Phase transformation materials with unique mechanical performance can greatly affect the mechanical response of structures. It is one of the major research fields of solid mechanics. TiNi alloy is one of phase transformation materials, which has been explored and applied long before, and the application spans a wide variety of industrial sectors such as aerospace, machinery, electronics, biomedical and so on. However, it is rare to study the mechanical property of the phase transformation structures, especially the response under impact loading. This paper selects plate, the basis structure component, as the object to investigate the quasi-static and dynamic mechanical behavior of phase transformation plate under the conditions of fixed support with experiment and numerical methods. The formation and development of phase transformation in complex stress state is studied, which provides solid basis for theory and applications of phase transformation structural component.The quasi static mechanical behavior of thin circular plate under concentrating force with fixed support is studied through the experimental and numerical methods. As a result, such data as loading-displacement curve, full-field out-of-plane displacement, and local strain are derived through the approach of shadow Moire and foil gauge. The loading-displacement curve demonstrates the characters of non-linear, non-residual deformation, indicating that the sample has undergone the Martensitic transformation. According to the strain measurement, the transformation is limited to the small part of the loaded center, while the circumferential deformation is greater than the radial deformation and the deformation of the dragging end is greater than that of the compressing end. It is revealed through finite-element simulation the nature of the transformation range, transformation hinge area, and the asymmetric distribution principle of martensite phase contents on the surface of the two sides of the transformation area.The quasi static mechanical behavior of thin circular plate under uniform load with fixed support is studied through the experimental and numerical methods. The results show that phase transformation occurs at the edge of the plate of loading side firstly, and the transformation range(PTR) and the distribution principle of martensite phase would be increasing with load increasing. When the load exceeds3.2Pc, phase transformation occurs at the center of plate and extends outwards rapidly as the load increases. The radius of the phase transformation range at the center of the plate in the free end expands to67.5mm and the load side is still in the austenite elastic state as the load is5Pc.The experimental investigation of Pseudo-elastic TiNi alloy thin circular plate with the conditions of fixed supports under transversal impact loading was conducted by using a revised Hopkinson bar apparatus and compared to A3steel plate. As a result, the nature of dynamic mechanical response of the structure in spatio-temporal evolution two scales is derived, including the propagation of flexural wave in the plate, evolution of transformation area and full-field out-of-plane displacement. The results indicates that the entire impact response of TiNi plate under fixed support can be divided into three stages:the early wave motion stage, the dynamic structural response stage and the free vibration stage. It is found that phase transformation occurred and then phase transformation hinge(PTH) formed near the center of the impact point. The phase transformation range and the PTH are recoverable and bear most of the deformation and energy absorption. The PTR and the PTH are capable of recovery and their strain increases upon impact in a fluctuant manner, but the asymmetry between the tension and compression side is remarkable. TiNi alloy thin circular plate is under impact by the bullets of different lengths while the kinetic energy is almost in the same situation. For long bullet, the response time is longer, the radius of THR at the center is slightly larger and the difference of the maximum deflection of the center of the plate is not obviously.Numerical simulation researches are conducted on the dynamic mechanical response of thin circular TiNi plate under the step or rectangular pulse load using finite element analysis software LS-DYNA, and the evolution process of PTH, deformation behavior under high load short pulse are discussed. There are different patterns, such as hinge zone at the boundary, phase transformation hinge ring in the middle of the plate and continuous hinge zone may form under step load. Under the rectangular pulse load with the same impulse, the higher amplitude of the load do more work by external force, so the deflection of the center of the plates and the range of phase transformation zone and the PTH become larger, while the duration of phase transformation is longer. From the perspective of energy dissipation, the dissipation of energy is more than45%of the total energy before the plate comes back to the position of equilibrium at the first time. Subsequently, the energy dissipated in each period and the ratio of the total energy decreased systematically, and about98%of the total energy would be consumed due to phase transformation eventually.