Papers by Keyword: Energy Absorption

Abstract: Due to their exceptional mechanical properties,xerogels attract increasing attention forstructural applications. In this study, the mechanical behavior of two types of polymeric xerogelsis investigated. The excellent energy-absorbing capability of those xerogelsis demonstrated by their stress-strain relations with respect to their microstructure determined withscanning electron microscopy (SEM). A pilot study on the effects of xerogellayers in an FRP system for concrete confinementis conducted.Test results clearly indicatedthat the proposed multi-layer systemcan significantly increase the ductility of confined concrete.

Abstract: Current crash structures in cars are still using the buckling of metallic structures to absorb the kinetic energy in case of an impact. The disadvantage of this technology is that changes within the static structural behaviour, like e.g. the stiffness or eigenfrequencies, will cause changes in the crash behaviour, even if this is not desired. This correlation between static and dynamic behaviour causes many development loops to adjust the crash behaviour, e.g. through optimizing trigger geometries which lower the initial crash forces. The German Aerospace Center (DLR) - Institute of Vehicle Concepts has developed a novel method to offer an efficient way of absorbing energy by peeling the outer skin of load bearing structures, like the crash boxes and the longitudinal rails. This technology provides an adjustable force level without changing the static behaviour of the front structure itself. This property offers the opportunity to create adaptable crash behaviour with only smallest changes within the peeling depth. Furthermore, it is possible to generate close to ideal force-deflection curves, which offers the potential to achieve high specific energy absorption. The DLR will show results of static and dynamic testing of crash tubes and of a vehicle front structure equipped with this mechanism. In addition the implementation of the methodology into the dynamic simulation with LS-Dyna will be shown. Benefits and limitations of this novel energy absorption method will be discussed.

Abstract: Reduction tube using a die is a kind of deformation tubes which are used on railway train as energy absorbers. In this paper, axial compression behavior and energy absorption characteristics of reduction tubes using a die under impact load are investigated. No-linear finite element software LS-DYNA is used to conduct the numerical study. Results for the expansion tube using a die (another kind of deformation tube) and the reduction tube using a die are compared. Assuming two different structures with the same material and sectional area, an analysis shows that the energy absorption of reduction tube is better than the expansion tube. Hence, the reduction tubes using a die are investigated using a series of numerical analysis. The relationship between displacement and load, average load are obtained. The influences of impact mass and impact velocity are discussed.

Abstract: A metal hollow sphere (MHS) sheet structure is developed and its mechanical property is investigated. We performed piercings for steel MHS and placed them on a piece of tungsten wire to make an MHS thread. MHS sheets with two kinds of construction have been developed using the thread; plain weave construction and reverse stitching construction. Their tensile property is investigated through tensile test, where advanced specific tensile strength and plateau tensile behaviour are found. Its mechanism is investigated using video and the properties compared with conventional MHS clusters. A block cluster is made from the sheet and compression property is researched by observing their breaking behaviour. The sheet is introduced into a pure aluminium tube and energy absorption through side compression is evaluated.

Abstract: This paper treats the design and analysis of an energy absorbing system. Experimental tests were conducted on a prototype, and these tests were used to validate a finite element model of the system. The model was then used to analyze the response of the system under dynamic impact loading. The response was compared with that of a similar system consisting of straight circular tubes, empty and foam-filled conical tubes. Three types of such supplementary devices were included in the energy absorbing system to examine the crush behavior and energy absorption capacity when subjected to axial and oblique impact loadings. The findings were used to develop design guidelines and recommendations for the implementation of tapered tubes in energy absorbing systems. To this end, the system was conceptual in form such that it could be adopted for a variety of applications. Nevertheless, for convenience, the approach in this study is to treat the system as a demonstrator car bumper system used to absorb impact energy during minor frontal collisions.

Abstract: The purposes of this study are to investigate the effect on variation of the specimens tube length and annealing temperature on the amount of energy absorption of Aluminium tubes (AA 6061) towards inversion collapse mode. The tests were performed on the Aluminium tubes using compression test according to ASTM E8 standard procedure. In this study, a quasi-static inversion tests were conducted in order to obtain the energy absorbed during inversion stages. It was found that the energy absorbed by Aluminium tubes were increased by increasing the tube length but decreased with annealing temperature.

Abstract: Sandwich panels with a V-type corrugated core are developed to investigate their crushing performance under lateral load based on the numerical method. The validity and feasibility of the calculation method is qualified by comparing numerical results with experiment results. Based on that, finite element software is applied to analyze the effects of structural parameters on the crushing performance of sandwich structure. Then inspecific energy increases as the core thickness and inclination angle are increased, but it will induce as the core height is raised. Additionally, the average crushing strength is increased with the increasing thickness, but it will decrease as the core height and inclination angle are raised. The results of this research may help the practical design and optimization of sandwich panel with corrugated core.

Abstract: Foam-filled enclosures are very common in structural crashworthiness to increase energy absorption. However, very less research has been targeted on potential use of natural/recycled material reinforced foam-filled tubes. Therefore, an experimental investigation was performed to quantify energy absorption capacity of polyurethane (PU) composite foam-filled circular steel tubes under quasi-static axial loading. The thickness of the tubes was varied from 1.9, 2.9 and 3.6 mm. The tubes were filled with PU composite foam. The PU composite foam was processed with addition of kenaf plant fiber and recycled rubber particles that were refined at 80 mesh particulates into PU system. The density of PU resin was varied from 100, 200 and 300 kgm^-3. The PU composite foam-filled tubes were crushed axially at constant speed in a universal testing machine and their energy absorption was characterized from the resulting load-deflection data. Results indicate that PU composite foam-filled tubes exhibited better energy absorption capacity than those PU foam-filled tubes and its respective empty tubes. Interaction effect between the tube and the foam and incorporation of filler into PU system led to an increase in mean crushing load compared to that of the unfilled PU foam or tube itself. Relatively, progressively collapse modes were observed for all tested tubes. Findings suggested that composite foam-filled tubes could be used as crashworthy member.

Abstract: In this study, numerical simulation of tubes of various cross section under axial compression is carried out using LS-DYNA. The effect of varying configurations of tube cross-section shape on the deformation response, collapse mode and energy absorption characteristics of tubes under quasi-static axial compression have been studied. The validation of the finite element tube model was made by comparison with the experimental results of the square tube subjected to quasi-static axial compression. Tabulated results are presented and plots have been included for the specific energy absorption for different cross sections. The study provides an insight on ways to increasing energy absorption of light weight aluminium tubes.

Abstract: Thin-walled tubes are generally used as impact energy absorber in various application due to their ease of fabrication and installation, high energy absorption capacity and long stroke. However, the main drawback of plain tube is the high initial peak force. A concentric plunger in the form of tapered block is proposed to overcome this shortcoming while at the same time, improving the impact performance. Static and dynamic axial crushing were performed to determine the initial peak force (IPF), crush force efficiency (CFE) and specific energy absorption (SEA) for the concentric plunger with various taper angles. It was found that the concentric plunger affected the tube impact response. Comparison with plain circular tube was carried out and it was found that the concentric plunger improved the impact response of the tube especially in term of initial peak force.