Energy absorption characteristic of a novel topology-optimized self-locking structure

Purpose Metal thin-walled tubes are commonly employed in energy absorption devices due to their lightweight and exceptional energy absorption capabilities. However, traditional circular tube stack energy absorption systems are susceptible to transverse spalling under impact loads, leading to a degradation in energy absorption performance. Furthermore, the kinetic energy of ejected fragments can cause secondary injuries, limiting the system’s applicability. As a result, designing energy absorption structures with self-locking mechanisms and enhanced performance has become a major focus in the field of safety protection. The paper aims to discuss this issue. Design/methodology/approach This study investigates the energy absorption characteristics of a self-locking structure, formed by layer-by-layer stacking of dumbbell-shaped thin-walled tubes, under in-plane impact loading. Addressing gaps in previous research on self-locking structures, the study explores the effects of the self-locking mechanism, geometric parameters, and performance enhancement strategies. Numerical simulations were conducted to analyze the impact of different geometric parameters of the single dumbbell-shaped tube on the structural dynamic response. Additionally, a novel section configuration with internal ribs was proposed through topology optimization to improve the crashworthiness of the original self-locking structure. Finally, a gradient design of the structure’s wall thickness and its dynamic response under different impact velocities were examined. Findings The results show that increasing tube wall thickness, reducing tube diameter, and incorporating internal reinforcements significantly enhance the structure’s energy absorption capacity. Moreover, the transverse width plays a critical role in the contact behavior between tubes; more contact points lead to better energy absorption performance. Material optimization within the tubes further improves energy absorption, with the reinforced self-locking structure achieving a 508.3% increase in specific energy absorption compared to conventional hollow structures. Finally, the gradient wall thickness design effectively controls the collapse force and enhances energy absorption efficiency at various impact velocities. Originality/value This study provides a guide for a promising method for designing of self-locking structures, which can be recommended as an underlying candidate for passive safety protection applications.