Study On The Performance Of Thin-walled Structures With Graded Features Under Impact Loads

Accidental collision events often cause significant threats to human life and property security and therefore relevant researches on the energy absorption behavior of materials and structures is of great importance to the society. Lightweight thin-walled structures possess good performance under the impact loading. In order to further improve the performance of structures and materials under impact loading, the introduction of gradient variables to thin-walled structures became a research focus in this field in recent years. From the perspective of design, introducing gradient variables expands the design domain of the structure, and it will definitely be able to obtain better performance than that of uniform structures. With this in mind, relevant studies were carried out in this dissertation.(1) Under axial quasi-static loading, the energy absorption efficiency of circular tapered tubes with graded thickness in the longitudinal direction and square tubes with graded thickness in the cross-section plane are experimentally investigated and compared with tubes with uniform thickness. The introduction of gradient was validated to show a remarkable effect on improving the energy absorption performance of the thin-walled structures.(2) Based on optimization design method, the distribution of radius and thickness for axially loaded thin-walled circular tubes was investigated. Results show that graded wall thickness can imporve the performance of thin-walled circular tube under the axial loads. A circular straight tube is superior to that of a circular tapered tube with the same mass under the same load condition, and the anti-impact performance tends to be better with the decreasing of the outer radius of circular straight tube.(3) The optimization design of thin-walled circular tapered or straight tube under the oblique impacts was conducted. The radius and the thickness were employed as design variables and different constraints were adopted in the design. Results indicate that the performance of a circular tapered tube is superior to that of a circular straight tube under the oblique impact, and the performance of the circular tapered tube with graded thickness distribution can be more superior to that of the one with uniform thickness(4) The responses of thin-walled square tubes under transverse loads were investigated and the wall thickness in the cross-section was optimized. Research results showed that the performance of square tube under the lateral impact can be improved by introducing proper thickness distribution in the cross-section. When the mass is kept constant, the performance of the squared tube tends to be better with more material distributed in the two vertical walls parallel to the loading direction and the wall proximal to the impact load.