Axial compression tests were conducted on short rhombic tubes of different cross-sectional shapes. The deformation modes of the rhombic short tubes were obtained. To induce a finite element model with deformation modes consistent with the actual working conditions, buckling modes are introduced into the model as the initial imperfections of the structure. However, the buckling modes resulting from finite element buckling analyses often do not meet the needs of actual crushing modes. A coefficient superposition method of solution is proposed to derive modal characteristics consistent with the actual deformation modes by linear superposition of the buckling modes. Through the study of three aspects of theory, test, and simulation, and the comparison and verification of this method with the simulation results of related literature, the results show that the indexes derived from this method are closer to the actual circumstances and are more expandable, which provides a reference for the project.

The corner element is the most basic constitutive element of multi-cellular thin-walled structures; however, scenarios for using relevant theories are limited. To improve this situation, this research investigated the effect of boundary conditions on the compression performance of corner elements with different angles. The deformation laws of corner elements were also explored. The approach was based on experiments and the finite element method. The result shows the outwardly extending plates on both sides yield first, the central twisted wire region then destabilizes and exits the working state, and the plate enters the post-buckling phase. A more relaxed boundary and larger angle can make it easier for the corner elements to trigger the symmetric deformation mode. Moreover, a mechanical model for simplified computation is proposed to predict the initial peak crushing force. The research can provide a reference for studying the compression performance of energy-absorbing elements in engineering.