Design Of Vehicle Morphing Skin Based On Multistable Dimples

With the increasing production and sales of automobiles,improving the dynamic quality and fuel efficiency has been the key problem to be solved to fulfill the requirements of energy conservation.The automobile morphing technology developed in recent years can be used to adjust the windward area and reduce the air resistance coefficient,thus improving the fuel economy,power performance and wind noise performance of automobiles.The main difficulty lies in how to design and control deformation of the morphing structure to meet the changing requirements.In this paper,considering the aerodynamic demand of automobile body skin,a multistable morphing skin with dimple array is proposed,and the snap-through procedure of dimple array is analyzed considering both material nonlinearity and geometric nonlinearity by using finite element method.Then,a principle experiment platform is built to verify the accuracy of the analyzing model.Through parameter optimization,a multistable dimple with specific force-displacement characteristic is designed,and also,the deformation process of the morphing skin with multiple dimples is studied.The main work includes:(1)A bistable dimple structure design method with specific mechanical characteristics is proposed,and a nonlinear dimple analysis model based on Mooney-Rivlin hyperelastic material constitutive property is established.The snap-through process and the relationship between the geometry dimension and the threshold force,the steady-state point location,the steady-state number and the zero-stiffness region are simulated.The static property control method based on size optimization is obtained and the validity of the analytical model is verified by experiments.(2)According to the steady state snap-through analysis model,the dynamic properties of the bistable dimple are investigated,and the influence relationship of geometric dimension and natural vibration frequency of dimpe is analyzed.The method for adjusting the natural vibration frequency of the dimple through parameters is proposed.(3)The design method of morphing skin with array dimples is presented,and the influence of multicell deformation mode on the deformation of the whole skin structure is studied based on the thin shell finite element theory.The influence of snap-through sequence,arrangement of different dimples and skin boundary shape on the whole skin deformation is analyzed,and the method to regulate the body skin deformation configuration is obtained.