MECHANICAL PROPERTIES ANALYSIS OF A NEW ENERGY ABSORBING STRUCTURE WITH NEGATIVE STIFFNESS

As a kind of mechanical metamaterial with wide application prospect, negative stiffness structures show significant advantages in energy absorption, vibration attentuation, and noise reduction . However, their engineering applications are severely limited attributed to the low specific energy absorption efficiency and non-autonomous spring-back of negative stiffness structures with the speciality of multi-stability. In order to solve this problem, by means of cell configuration design, a new kind of three-dimensional negative stiffness structure with the characteristic of autonomous spring-back is proposed in this paper. For this negative stiffness cells in series, the self rebound of curved beams during the loading and unloading process is used to realize the cyclic loading and multiple reuse of the structure.The multi-stability is restrained by adding a groove of certain depth. The buckling mode is selected via the adjustment of side wall thickness. The difference between critical loads of negative stiffness is thus enlarged, accordingly, the energy absorption efficiency is significantly improved. Then in order to achieve high energy absorption under complex load environments, the gradient design of structure size is carried out, and a gradient negative stiffness structure is proposed. The energy absorption efficiency of gradient negative stiffness structure and uniform negative stiffness structure under different load cinditons is compared by finite element simulations. Analytical and numerical results reveal that for the newly developed negative stiffness structure, not only the feature of autonomous spring-back is achieved, but also the energy absorption ability is improved. Moreover, different critical load maximums for negative stiffness are obtained for the gradient structure due to different microstructure sizes, which makes it to exhibit better energy absorption efficiency on the basis of realizing autonomous spring-back under various impact load environments. The new energy-absorption structure proposed in this paper provides technical support for engineering applications such as vibration attenuation and structure reorganization.