Multi-objective optimization of crashworthiness for double-layer thin-walled tube composite anti-climb energy-absorbing device in subway vehicles

To enhance the crashworthiness of subway vehicles, this study presents a novel hybrid anti-climb energy-absorbing device. It integrates inner and outer double-layer thin-walled square tubes with honeycomb structures for synergistic energy absorption. To analyze the energy absorption characteristics of the anti-climb energy-absorbing device, collision simulations were conducted by mounting the device on the front end of a test trolley. Based on Optimal Latin hypercube sampling (OLHS), a Kriging surrogate model characterizing energy absorption (EA) and peak crushing force (PCF) was developed for the parameters of aluminum honeycomb average crushing stress (c), partition thickness (t₁), thin-walled outer tube thickness (t₂), and thin-walled inner tube thickness (t₃). The main effects of parameters on EA and PCF were analyzed, and the results indicated that t₂ exerted the most significant influence on the energy absorption characteristics. Multi-objective optimization via the Non-dominated Sorting Genetic Algorithm II (NSGA-II algorithm) was implemented for different vertical offset conditions (h = 0 mm and 40 mm), simultaneously maximizing EA while minimizing PCF. The optimal solution is identified at c = 3.9 MPa, t₁ = 4 mm, t₂ = 2.9 mm, and t₃ = 2.4 mm, with the surrogate model’s prediction errors relative to finite element simulation results below 10%. Collision simulations of 6-car subway vehicles demonstrated that key collision indicators all met the requirements of the EN15227 standard, verifying that the device exhibits excellent energy absorption and anti-climb performance, and providing critical references for its optimized design and application in subway vehicles.