Design Of Energy Absorber Research Articles

Axial crushing behavior and energy absorption efficiency of corrugated tubes

This paper presents the effect of corrugations on the crushing behavior, energy absorption, and failure mode of circular aluminum tubes. Experimental investigations were carried out on five geometrical types of corrugated and simple tubes, with corrugations different in size and direction, subjected to axial compressive loading. In order to produce corrugations, an innovative solution is introduced. The results show that tubes with corrugations have a uniform load–displacement curve without an initial peak load. Moreover, introducing corrugations makes the failure mode more predictable and controllable. The latter is highly promising and of foremost interest to designers, as it is essential for reliable design of energy absorbers in practice. The experimental results show the significant effect of the presented corrugated tubes on improving the crashworthiness characteristics, controllability and collapse modes of circular tubes under axial loading.

Crashworthiness analysis on alternative square honeycomb structure under axial loading

Hexagonal metal honeycomb is widely used in energy absorption field for its special construction. However, many other metal honeycomb structures also show good energy absorption characteristics. Currently, most of the researches focus on hexagonal honeycomb, while few are performed into different honeycomb structures. Therefore, a new alternative square honeycomb is developed to expand the non-hexagonal metal honeycomb applications in the energy absorption fields with the aim of designing low mass and low volume energy absorbers. The finite element model of alternative square honeycomb is built to analyze its specific energy absorption property. As the diversity of honeycomb structure, the parameterized metal honeycomb finite element analysis program is conducted based on PCL language. That program can automatically create finite element model. Numerical results show that with the same foil thickness and cell length of metal honeycomb, the alternative square has better specific energy absorption than hexagonal honeycomb. Using response surface method, the mathematical formulas of honeycomb crashworthiness properties are obtained and optimization is done to get the maximum specific energy absorption property honeycomb. Optimal results demonstrate that to absorb same energy, alternative square honeycomb can save 10% volume of buffer structure than hexagonal honeycomb can do. This research is significant in providing technical support in the extended application of different honeycomb used as crashworthiness structures, and is absolutely essential in low volume and low mass energy absorber design.

Global stability of an aluminum foam stand-alone energy absorber

Aluminum alloy foam is the commonly used material in energy absorber design due to its excellent ability to dissipate energy in relation to density. This paper investigates the behavior of standalone absorber made of ALPORAS aluminum foam. The limiting parameters in the aforementioned application are the stability of absorber column and the risk of global buckling. Specimens with different slenderness ratio were crushed in order to find the transition point between local collapse of the cell walls and global buckling of the entire column. The ability of the aluminum foam energy absorber to work even after partial global buckling was presented.

Establishment and Application of an Equivalent Impact Model of Coupler in Front of Subway Locomotive

Coupler’s energy absorption part is made up of elastic buffer and crushing tube. Elastic buffer is used to absorb impact energy produced from locomotive’s normal running process while the crushing tube is used to absorb the ones produced from accidental impact process. It is one of key problems to solve in locomotive’s impact simulation process that to establish and manage the coupler’s equivalent model. The article simulates coupler’s absorbing of energy in impact process at two operating conditions. According to the relative energy absorption design standards, the article evaluates the correctness of the established coupler’s equivalent model. The simulation result indicates that the established coupler’s equivalent model satisfies the design requests.

Effect of Slot Geometry on the Impact Response of Square Column

Thin-walled square columns are generally used as impact energy absorber due to their versatile application, high energy absorption capacity and long stroke. However, the main drawback of existing square column is the high initial peak force. In this paper, a single slotted square column was proposed to reduce the initial peak force. Parametric study of the slot geometry on the impact response of square column was carried out. Non-linear finite element code Abaqus/Explicit was employed to evaluate the response of a single slotted square column subjected to impact in the axial direction. The study found that the slot geometry has a prominent effect on the impact response. However, the size of the slot which affects the structural stiffness of the column is not directly proportional to the reduction in initial peak force. It can be seen that a specific slot size is most effective in reducing the initial peak force at a particular impact speed. Overall, it can be deduced that a slot may enhance the impact performance of a standard square column and therefore could be incorporated in the design of energy absorber when designing for occupant and critical goods safety.

Damage Tolerance of Rail Vehicle Energy Absorbers

Despite significant progress in the design of rail vehicles to ensure a high level of passive safety the effects of quality of manufacturing and assembly parameters on the local and global structural behavior in the event of a collision have not been adequately addressed. The present paper deals with one of these aspects, namely the attachment of impact energy absorbers at the front end of rail vehicles, since the functional requirements of these devices are particularly stringent in terms of their reliability and functionality throughout the life of the vehicle. In this work the merits of a welded and a bolted energy absorber design are investigated, the latter offering the advantage of ease of through life maintenance and replacement, ensuring that defects such as general corrosion or cracks that could have affected their performance are easily identified and replacements made and also introduce the prospect of retrofitting energy absorbing devices to older rail vehicles to improve crashworthiness. FEA modelling to simulate the dynamic response of welded and bolted joints has been carried out using the LS-DYNA code. For the welded joints the influence of welding defects such as lack of fusion, weld under matching, and weld cracking on the performance of the energy absorbers has been investigated. The numerical model, validated on the basis of results from impact tests, was subsequently used to investigate the behaviour of the absorption system in collision scenarios as prescribed by EN 15227:2008.

Dynamic Crushing of Hexagonal Honeycombs under In-Plane Loading

The in-plane dynamic crushing of hexagonal honeycombs was numerically studied by means of explicit dynamic finite element method using ANSYS/LS-DYNA. Under the assumption that the edge length and thickness were the same, the metal honeycomb models filled with convex and concave cells were established. And then the effects of expanding angle and impact velocity on the plateau stress and the energy absorption capacities of hexagonal honeycombs were discussed in detail. Numerical results show that the energy absorption capacities of convex hexagonal honeycombs are stronger than the concave ones. These results will provide some useful guides for the dynamic energy absorption design of cellular materials.

Core Design for Energy Absorption in Sandwich Composites

To achieve high energy absorption under edgewise compression loading, sandwich composites must experience a progressive failure that includes compression failure of the facesheets. This investigation focused on sandwich core design for energy absorption through the use of failure mode maps. Predictive models for global buckling, facesheet wrinkling, and facesheet compression failure were used to construct failure mode maps as a function of sandwich core thickness and density. Predicted failure loads and initial failure modes were found to be in good agreement with results from edgewise compression testing. Sandwich configurations experiencing facesheet compression failure as the initial failure mode were found to produce the highest energy absorption. These results suggest that sandwich composites may be designed for enhanced energy absorption through the proper selection of core materials and geometries.

Optimization of thin conical frusta for impact energy absorption

Experimental and numerical investigations were carried out to optimize thin-walled conical shells for their use in design for energy absorption. Geometrical parameters, such as bottom diameter, height, and semi-apical angle were considered to obtain the design space. The numerical analysis and impact experiments were designed using design of experiments (DOE). A three-level, second-order Box–Bhenken technique was used to select the design points from the design space. Various set of numerical simulations were carried out using LS-DYNA. To investigate the influence of flow stress of the material on the energy absorption, numerical simulations were carried out using frusta made of aluminium, zinc, and mild steel. From the numerical results, mathematical models were created using response surface methodology (RSM). With the help of impact experiments carried out on specimens made of zinc on a drop mass test rig, a mathematical model has been developed using RSM. The mathematical models developed using experimental data and the numerical data were used as objective functions for optimization of the design. The non-dominated sorting genetic algorithm code NSGA II was used to optimize the design. The mathematical models were also used to predict the energy absorbed and deformation. The influence of various design parameters on energy absorption has been analysed and is discussed.

Optimum design for energy absorption of bitubal hexagonal columns with honeycomb core

This paper is concerned with the maximisation problem of the crushing energy absorption of bitubal hexagonal aluminium columns with honeycomb core under dynamic axial crushing. The honeycomb core is made up of 18 internal cell walls with the same thickness. The mass of the whole crush element and the outer dimension of the section are kept constant, while the side length of inner profile and the thickness of the inner and outer wall are used as design variables. The nonlinear explicit finite element code LS-DYNA is adopted to simulate the axial crushing behaviour of bitubal columns and the response surface method is applied to obtain the optimum design in the design space. The results show that the specific energy absorption of bitubal hexagonal columns with honeycomb core can be significantly improved by optimisation and allow us to present useful proposals for the crashworthy design of similar structures.

Conceptual design of a polymer composite automotive bumper energy absorber

In this paper, a study of conceptual design of fibre reinforced epoxy composite bumper absorber is presented. This study describes the use of the composite in energy absorption in car bumper as a pedestrian energy absorber. The systematic exploitation of proven ideas or of experience was used to generate the ideas and the most suitable idea was followed as a guide for conceptual design. The absorber was analyzed experimentally and the data from these experiments were used to decide on the number of energy absorber to be used in the design. Final design of the composite energy absorber in elliptical shape with two slots at both ends was considered. The method of fixing the energy absorber to the fascia and bumper was also studied.

Dynamic simulation and energy absorption of tapered tubes under impact loading

This paper investigates the energy absorption response of straight and tapered rectangular tubes under axial impact loading using dynamic finite element techniques. The parameters in the study are the number of tapers, taper angle, wall thickness, impact velocity and impact duration. The results show that tubes with three tapered sides have the highest energy absorption capacity, followed by straight tubes and tubes with four tapered sides. Impact velocity has less effect on the absorbed energy for tapered tubes compared with straight tubes. Furthermore, the amplification of absorbed energy with increasing velocity can be controlled using the number of tapered sides. Finally, it was found that tapered tubes have a higher crush force efficiency than straight tubes. Overall, the results highlight the advantages of using tapered tubes for impact energy absorbers such as in crashworthiness applications. The research findings can be used to quantify energy absorption in the design of energy absorbers for impact applications.

Applications of regional strain energy in compliant structure design for energy absorption

Topology optimization of regional strain energy is studied in this paper. Unlike the conventional mean compliance formulation, this paper considers two main functions of structure: rigidity and compliance. For normal usages, rigidity is chosen as the design objective. For compliant design, a portion of the structure absorbs energy, while another part maintains the structural integrity. Therefore, we implemented a regional strain energy formulation for topology optimization. Sensitivity to regional strain energy is derived from the adjoint method. Numerical results from the proposed formulation are presented.

Asymptotic investigation of vehicle shock absorber with reversing shell of revolution

An energy absorber, which contains an elastic thin shell of revolution, is considered. An asymptotic method is suggested for the investigation of non-linear behaviour of the structure. An analytical solution, which is valuable for sthe design of energy absorber, has been obtained. The influence of the geometrical and stiffness parameters of the structure on the force-displacement characteristics, stresses and absorption energy are studied.

Optimum design for energy absorption of square aluminium columns with aluminium foam filler

The performance in axial compression of square aluminium columns with aluminium foam filler has been assessed based upon existing design formulas for average crush force, maximum force and effective crushing distance. Using an optimisation algorithm, the combination of (1) foam density, (2) column wall thickness, (3) column width, (4) column material strength and (5) total component length giving the component of minimum mass was determined for specific cases. It was found that optimum foam filled columns compared to the traditionally designed non-filled columns showed smaller cross section dimensions in addition to less weight. As a consequence, mass-, length- and volume reductions are possible by utilising foam filler.

Composite vehicle structural crashworthiness - A status of design methodology and numerical simulation techniques

Composite vehicle crash resistance requires system design aspects. In aircraft this includes the airframe, the landing gear, seats and restraint systems, and overhead mass retention. However, design aspects will be focused in more detail on the airframe and airframe substructures, i.e. sub-floor beams, structural intersections, sub-floor sections and frames. The use of high performance composite materials needs specific design philosophy and concepts due to the brittle nature but high energy absorption (EA) capability of composites. Verified design concepts and evaluation of highly efficient EA and load bearing composite airframe components comprising impact conditions on rigid surface, soft soil, and water will be demonstrated. Also, for other vehicles - cars and trains - the use of composite materials in EA management systems is of interest due to the high weight saving potential and efficient EA design capability of composite structures. Analytical methods and predictive simulation tools will be described for evaluating the crash response of vehicles, in particular of aircraft structures. Attention is given to an explicit Finite Element (FE) code (PAM-CRASH) which is suited for more detailed local analysis of a substructure or structural element and to a hybrid code (KRASH), which is appropriate for global crash analysis of a complete vehicle structure. The simulation tools are briefly discussed and examples of crash simulations on aircraft structures and substructures are given. Correlation with crash data and simulation results are made.

Development of a Flared Energy-Absorbing Terminal for W-Beam Guardrails

A new flared W-beam guardrail terminal that incorporates energy-absorbing technology has been developed and successfully crash tested to meet the criteria presented in NCHRP Report 350. The terminal, designated FLEAT-350, incorporates an impact head designed to dissipate impact energy by producing a series of plastic hinges in the W-beam as the impact head is pushed down the guardrail. The energy-absorption mechanism allows the flared terminal to absorb large amounts of kinetic energy before the vehicle is allowed to gate through the system. Most components of the new terminal are similar to those incorporated in the SKT-350 terminal. The terminal system is 11.4 m (37.5 ft) long and incorporates a straight flare with a final end offset of between 0.76 m (2.5 ft) and 1.2 m (4 ft). The terminal uses two breakaway posts in foundation tubes and five rough-cut controlled-release terminal posts of 150 by 200 mm (6 by 8 in.). The energy-absorbing design minimizes problems associated with vehicles that penetrate the terminal and strike slopes, ditches, or other hazards behind the guardrail while still traveling at a high rate of speed. Furthermore the new design has fewer components and is less sensitive to post location and installation details than some other flared systems.

Deformation and energy absorption of polymer foams as a function of 2‐D indenter and absorber geometries

AbstractTwo‐dimensional indenters (flat plate and cylinder) were used to compress rectangular and trapezoidal foam energy absorbers as a function of polymer, foam density, and thickness. An increased deformation volume formed when the indenter contact area was less than the foam absorber area, resulting in both increased energy absorption and stress transmitted to the indenter (i.e., “load spreading”). The deformation volume was trapezoidal, not prismatic, and was characterized by the indenter geometry, dimensions, and foam thickness. Conservative energy absorber design can be achieved by using “energy absorption diagrams” that account for the indenter (i.e., product) and absorber geometry and degree of load spreading.

Design of a metal skinning energy absorber for the U.S. capitol subway system

The design of a metal skinning emergency overshoot stopping device for the U.S. Capitol Subway System is discussed. The kinetic energy of the vehicle is dissipated by pulling a round rod through a circular cutting tool. The design procedure used in the selection of critical components is reviewed and a systematic method for their selection is shown. Photographs of the final design hardware are shown. A subway collision test was conducted and the results of the test are shown to agree well with predictions.