## 4 Structural Crashworthiness
### Influence of Thin-Walled Outer Tube Thickness  
When subjected to impact, the anti-climb energy-absorbing device can undergo an orderly plastic deformation designed to absorb the initial kinetic energy, reduce the impact on the vehicle structure, and enhance the vehicle's safety. To investigate the effects of the thin-walled tube thickness on the energy absorption characteristics and collision force, the thickness \(t2\) of the thin-walled outer tube is set to 2, 3, 4, 5, and 6 mm, respectively, to obtain the crashworthiness performance of the anti-climb energy-absorbing device under different thin-walled tube thicknesses. The collision force-displacement curves and energy absorption-displacement curves for different outer tube wall thicknesses are depicted in Figure 5.  
From Figure 5a, it can be observed that the variation in the thickness of the thin-walled tube has a significant impact on the initial peak force. The same pattern of influence is observed for the peak force at the second wave crest. For the thin-walled tube with a thickness of 2 mm, the second wave crest differs from those of other thickness parameters, as it begins to decline after only a slight increase. This indicates that changes in the thickness parameter of the thin-walled tube have a considerable effect on the peak force of the anti-climb energy-absorbing device. By reducing the thickness of the thin-walled tube, it is possible to decrease the magnitude of the initial and second wave crest peak forces, thereby reducing the impact force of the collision. At the same time, with the 2 mm thin-walled tube, the displacement difference in the valley peak force between the anti-climb energy-absorbing device and other thicknesses is significant, reaching 59.4 mm. This suggests that reducing the thickness of the thin-walled tube can increase the valley peak force at the front end. The discovery of this phenomenon is of great significance for effectively reducing the impact peak force and can provide a reference for the orderly crushing design of anti-climb energy-absorbing devices.  
From Figure 5b, it is evident that the thickness of the thin-walled tube significantly enhances the energy absorption capacity of the anti-climb energy-absorbing device. When the crushing displacement reaches 538 mm, the device with a 2 mm thin-walled tube absorbs 138 kJ of energy during the collision impact, while the device with a 6 mm thick tube absorbs up to 353 kJ, an increase of 215 kJ, which is a 156% increase compared to the previous value. It also represents a 116% increase compared to the energy absorption of the 5 mm thickness, indicating a significant enhancement effect. In conjunction with Figure 6, it can be seen that although increasing the thickness of the thin-walled tube can significantly improve energy absorption, the peak force also increases accordingly. Therefore, in the design of the anti-climb energy-absorbing device, it is necessary to consider increasing energy absorption while minimizing the impact of the peak force. A possible solution could involve the use of multiple longitudinally arranged induction grooves to reduce the peak force, thus meeting the design requirements of the anti-climb energy-absorbing device.  
Figure 5: (a) Collision force–displacement curves for different outer tube wall thicknesses; (b) Influence of thin-walled tube thickness on energy absorption.  
Figure 6: (a) Variation in collision force with displacement across different thicknesses of thin-walled inner tubes; (b) Variation in energy absorption with displacement across different thicknesses of thin-walled inner tubes.