Study On Energy Absorption Properties Of Thin-walled Metal Tubes Filled With Aluminum Foam Under Axial Load

As a typical energy absorption structure, thin-walled metal tubes filled withaluminum foam have been widely used to the collision dissipative systems ofmany engineering fields such as machinery, civil and aerospace because of theirgood mechanical properties and energy absorption characteristics. Themechanical properties of this structure subjected to quasi-static axialcompression and impact load have always been a hot topic of academia. Thethin-walled aluminum alloy tubes and thin-walled circular tubes filled withaluminum foam were studied in this paper. Their energy absorptioncharacteristics under quasi-static axial compression and impact load werestudied systematically through experimental research and numerical simulation.The main conclusions are shown as follows:The influences of the geometric parameters of tubes, include thickness,height, diameter and the foam density on energy absorption properties of tubesand foam-filled tubes under quasi-static axial compression were discussed bythe analyzation of some crashworthiness parameters, such as the specific energyabsorption (SEA), the compression efficiency (CFE), the average force and thepeak force. The results showed that: The deformation modes of the aluminum alloy tubes and tubes filled with aluminum foam subjected to axial compressioncan be classified into three stages: the initial elastic stage, the stable progressbuckling stage and the densification stage. The thickness and the diameter of thetubes have a significant effect on energy absorption properties of the structures,while the effect of height is not evident. But the increase of the height canimprove the total energy absorption of the tubes. Aluminum foam filler reducesthe fluctuation of the axial load during compression and improves the crushingforce, total energy absorption, the specific energy absorption and thecompression force efficiency of the tubes. But the degree of the improvementchanges when the geometric parameters of the tubes are different. Thealuminum foam filler with the same density can play a more obvious advantagein tubes with thinner thickness and larger diameter. The higher the density ofaluminum foam, the greater the crushing force and total energy absorption offoam-filled tube. Because the foam filler increases the total mass of thefoam-filled tube at the same time, the SEA of the foam-filled tube has nosignificant increase compared with the empty tube before it s densificationstage.The finite element models of the metal circular tubes and foam-filled tubessubjected to axial impact load were established using finite element softwareABAQUS. By comparing with the results of the experiments, the feasibility ofnumerical simulation was validated. On this basis the influences of tubesthickness, impact velocity and foam density on the initial peak force, averageforce and energy absorption efficiency of the structures were researched. Theresearch showed that the initial peak force, average force and energy absorptionof circular tubes and foam-filled tubes under axial impact load increase with theincrease of the tubes thickness. The average force, the initial peak force andthe CFE of the foam-filled tubes are greater than corresponding empty tubeswhen subjected to axial impact load, but the degree of the increase changes when the thickness of the tubes is different. The thinner the thickness offoam-filled tubes, the larger the percentage of the improvement of their energyabsorption evaluation indexes when compared with empty tubes. Aluminumfoam filler can effectively improve the anti-deformability and the energyabsorption capability of the structure. The higher the density of aluminum foamfiller, the more the total energy absorption of the structure. The axial impactload, total energy absorption and the SEA of circular tubes increase with theincreases of impact velocity, the impact load and energy absorption offoam-filled tubes also increase slightly, but the increase rate is not obvious. Thisshows that the energy absorption efficiency of the structures is improved withthe improvement of impact velocity, but the effect of impact velocity on emptytubes is greater than that on foam-filled tubes.