The Energy Absorption And Optimization Design Of Thin-walled Square Tubes With Cutouts Under Axial Impact Loading

Thin-walled metallic tubular structure perform particularly well under axial impact because of their excellent energy absorption capacity during large plastic deformation and stable and repeatable deformation mechanisms. So they have been widely used to the collision dissipative systems of many engineering fields such as vehicle armors, storage and transportation, aeronautical and so on. It can predict or control the deformation model by means of introducing initial defect on the wall of the square tubes. The paper studied thin-walled square tubes with cutouts and the tubes have the same thickness and graded thickness. Numerical simulation of these tubes under axial impact have been carried out to discuss the energy absorption capacity and deformation process. Studied the impact of the size of the cutouts, the length and width of the cutouts on the energy absorption capacity and deformation process. Multi-objective optimization of the thin-walled square tubes with same thickness has been carried out. The main work are as follows:The effects of different length and width on the energy absorption properties are studied based on some crashworthiness parameters. The simulation results show that, deformation modes of square tubes can be classified into three stages, the elastic deformation stage, the elastic-plastic deformation stage and the densification stage. These tubes are produced four folds, it just depends on the geometric dimension of the tubes. The initial peak load mainly depends on the length of the cutouts, with the increase of the length, the initial peak load reduced. The mean crushing force reduced with the increase of length and width, the influence of the length on the mean crushing force is less than width. With the increase of cutouts area, the absorption of energy gradually and SEA reduced. The CFE increased with the increase of length and reduced with the increase of width. The multi-objective optimization are carried out based on the surrogate model technique which with the length and width as design variables and the initial peak load, mean crushing force,total energy and SEA as objective function. And the Pareto optimal solutions are obtained. When the preferences of each target are determined, the size of cutouts of the square tube is determined.The numerical simulation has been carried out about square tubes with different cutouts,and the six models have the same area but different length and width. The results show that, different sizes have a great influence on the deformation process and force-displacement curve. The deformation are irregular both the ratio of length and width are big and small. The initial peak load mainly depends on the length of the cutouts, there is a liner relationship between initial peak load and the change of length. The linear proportional constant is about 1.33. With the increase of the ratio of length and width, the CFE and STE increases and similar to a linear relationship.The finite element model of square tubes with graded thickness is established and the deformation mode and energy absorption properties are simulated. The results show that, the graded thickness square tubes deform as a extensional modes and the stress distribution is homogeneous. However, the deformation modes of cutout tubes are more complicated, the deformation mode is extensional with the small area. When the area of cutouts is large, the deformation is irregular, and the stress distribution is heterogeneous. Compared with the uniform square tubes, the mass, initial peak load, mean crushing force, SEA and CFE all reduce.