Metallic thin-walled round tubes are widely used as energy absorption elements. However, lateral splash of the round tubes under impact loadings reduces the energy absorption efficiency and may cause secondary damages. Therefore, it is necessary to a
ssemble and fasten round tubes together by boundary constraints and/or fasteners between tubes, which increases the time and labor cost and affects the mechanical performance of round tubes. In an effort to break through this limitation, a novel self-locked energy-absorbing system has been proposed in this paper. The proposed system is made up of thin-walled tubes with dumbbell-shaped cross section, which are specially designed to interlock with each other and thus provide lateral constraint under impact loadings. Both finite element simulations and impact experiment demonstrated that without boundary constraints or fasteners between tubes, the proposed self-locked energy-absorbing system can still effectively attenuate impact loads while the round tube systems fail to carry load due to the lateral splashing of tubes. Furthermore, the optimal geometric design for a single dumbbell-shaped tube and the optimal stacking arrangement for the system are discussed, and a general guideline on the structural design of the proposed self-locked energy absorbing system is provided.
The configuration of graphene (GE) sheet conforming to the spherical surface substrate is studied through theoretical model and molecular simulations. Two basic configurations are observed: fully conformation and wrinkling. The final configuration of
the adsorbed GE results from the competition between two energy terms: the adhesion energy between GE and substrate, the strain energy stored in the GE due to the deformations. Here, we derive theoretical solutions by accounting for two energy terms, and predict the final morphology of GE on the spherical surface (a special kind of nano-developable curved surface) substrate with using the phase diagram. A critical cone angle of the absorbed GE for an arbitrary spherical surface substrate is obtained. Fully conformation of GE is observed when the cone angle of absorbed GE is below the critical value, otherwise wrinkles appear. Molecular simulations are implemented to verify the theoretical model with results agree well with theoretical predictions. Results from our present work can offer a guide for designing new functional graphene electronical devices (such as nanoswithes) and fabricating high quality nanostructured coating (Fig. 13).
