Dynamic Behavior Of Energy Absorption Unit Of Circular Tubes

Thin-walled tubes and their different structures filled with foam are frequently used as energyabsorption units. They are widely used in energy absorption devices of automobiles, aerospacevehicles, rail transportations and other vehicles because of their light weight, good capability ofenergy-absorbing, long compression stroke and stable deformation modes. It has become a hottopic to judge the energy absorption capability of thin-walled tubes and the effects of their differentstructures and as well as to improve their energy-absorbing behavior. It is necessary to study thedynamic properties of thin-walled tubes, and.the following studies are included in this paper:1) Based on the concept of energy absorption efficiency, we proposed unified evaluation ofenergy absorption capacity. The specific energy(SEA), main load(Pm) and effective stroke ratioare redefined. The response of thin-walled tubes is theoretically analyzed and the range of densityof foam-filled tubes to increase the energy absorption capacity is simulated.2) The experimental studies of thin-walled circular tubes under axial compression have beenperformed by using Drop Hammer. Two types tubes, which are made of soft steel and aluminumrespectively, are adopted in the tests. Experimental results show that SEA and Pm under quasi-static state are lower than under dynamic results. In particular,3.5petal of fold under quasi-staticaxial compression is increased to4.5petal of fold under dynamic loading. Through analysis, it isfound that the rate dependent behavior of soft steel tube is more sensitive than that of aluminumtube. And in the dynamic experiments, the strain rate of the tube is proportional to the impactvelocity v.3) The energy absorption capability in foam-filled tube, sandwich tube, double tube isinvestigated based on the experiment. The study finds that the sandwich tube had higher SAE valuethan empty tube about20%, also higher than that of foam-filled tube. The paper specificallyanalyses the mechanism of sandwich tube with higher energy absorption ability. It found that themain cause is the neatly diamond deformation mode of outside tube, which originally deformed inEuler buckling mode, becoming to an excellent energy absorption member. Consequently, throughreasonable design a low density thin-walled tube, which acts as an outside tube to the main energy-absorbing member, it can largely improve the energy absorption ability of the whole structure.4) The dynamic responses of thin-walled circular tubes under axial compression have beenstudied. It shows that the inertia has negligible influence on dynamic properties of the tube whilethe incensement of strain-rate enhances SEA and Pm of thin-walled circular tubes. Based on dimensionless analysis of Pm under different strain-rates, it shows that the experimental results arein good agreement with the theoretical ones obtained by former researchers. The result shows thatthe deformation mode of the tubes under impact is different from the quasi-static ones, and thedynamic behavior of thin-walled circular tubes under impact with higher speeds needs furtherstudy.