Crash Energy Absorption Research Articles

Optimal Design and Experimental Investigations of Aluminium Extrusion Profiles for Lightweight of Car Bumper

The present study aimed at developing an aluminium car bumper unit to replace the steel ones by using optimization based on experimental and FEM simulation results. The topology optimization method and response surface methodology (RSM) were applied in order to achieve an optimized design for the cross section of the crossbeam and the crash box, respectively. The three-points bending test and crash test for bumper unit were simulated to evaluate the optimization processes. The 6061 and 6063 aluminium alloy bumper unit has a weight reduction of 67% compared to the steel ones. The new extrusion dies were manufactured to produce profiles for the crossbeam and the crash box, respectively. Then the optimized extrusion profiles of crossbeam and crash box were verified by experimental studies. The performance tests were arranged to validate the experimental product. The mechanical properties of extruded aluminium crossbeam and crash box can satisfy the design requirements of products. The results indicate that the new designed unit can change the whole design of automotive parts for crash energy absorption, and definitely contribute to drastic weight reduction of steel parts.

Influence of the Cross Section Shape on Energy Absorbing Component of Bumper Subjected to Low Speed Crash

Energy absorbing component of bumper equipped at the front end of a car, is one of the most important automotive parts for crash energy absorption. It usually was made a mental thin walled tube. In the paper, automobile energy absorbing component at low-velocity impact was studied by using Finite Element Method. The FE model of the tube was builded by comparing the five cross section shape . Results show that the impact peak load and maximum energy absorption have certain effect to energy-absorbing component with different the cross section shape.

충돌에너지 흡수효율 최대화를 위한 자동차 사이드 멤버 최적 설계에 관한 연구

In this study, the design optimization of the automotive side member is performed to maximize the crash energy absorption efficiency per unit weight. Design parameters which seriously influence on the frontal crash performance are selected through the sensitivity analysis using the Plackett-Burman design method. And also the design variables, which are determined from the sensitivity analysis, are optimized by two methods. One is conventional approximate optimization method which uses the statistical design of experiments (DOE) and response surface method (RSM). The other is a methodology derived from previous work by the authors, which is called sequential design of experiments (SDOE), to reduce a trial and error procedure and to find an appropriate condition for using micro-genetic algorithm. The proposed optimization technique shows that the automotive side member structure can be designed considering the frontal crash performance.

Dynamic and quasi-static bending behaviour of thin-walled aluminium tubes filled with aluminium foam

This paper aims to evaluate the potential use of closed-cell aluminium alloy integral-skin foams as stiffening elements for aluminium alloy thin-walled structures that are main basic components in the concept and design of automotive body parts. Foam specimens were prepared using the powder metallurgical route, inserted into empty thin-walled tubes and subjected to quasi-static and dynamic bending loading conditions. The effect of introducing foam into tubes was evaluated using the infrared thermography during the three-point bending tests. The foam-filled tubes, empty tubes and foams are compared in terms of the maximum load carrying capacity, crash energy absorption, specific energy absorption and deformation modes. Results showed that the foam filling leads due to interaction between the tube wall and foam filler, causing an increased bending response of the filled tubes which exceeds the sum of the bending response for the individual components. Their deformation mode is a combination between the modes of the individual components.

Reduced numerical model to investigate the dynamic behaviour of honeycombs under mixed shear–compression loading

Cellular materials such as aluminium honeycombs combine lightweight with an efficient crash energy absorption capability. They have a major role in a wide range of transport applications to reduce gas emission by the design of lighter structures but remaining safe in accident case. Many investigations on the honeycomb behaviour have been performed, under uni-axial compression loading and more recently under mixed shear–compression loading. The influence of the in-plane orientation has not been however considered. The objective is to develop a reduced numerical model able to investigate, with a reduced cost of calculations, the dynamic behaviour of honeycomb under mixed shear–compression loading and taking into account of the in-plane orientation angle. Reduced model based on the periodicity procedure is developed and its validity range is evaluated. The numerical results show that in terms of pressure–crush curve and collapse mechanisms, the reduced model is consistent with a complete FE model composed of 39 cells with a CPU-time gain efficiency about 97.17%. The reduced model is valid from a loading angle ψ=0° to a loading angle ψlimit contained between ψ=30° and ψ=45°. The reduced model allows investigating in depth the influence of the in-plane orientation and the loading angles on the crush behaviour with minimum time calculations in accord with the validity range.

Dynamic testing and modelling of composite fuselage frames and fasteners for aircraft crash simulations

In crash simulations of composite aircraft fuselage sections, frame breaking, skin bending and failure of mechanically fastened joints can typically be identified as major contributors to crash energy absorption. In order to generate a database for model validations, corresponding static and dynamic tests have been performed on coupon and structural element level to characterise the rate-dependent failure behaviour and energy absorption. Skin-bending, frame-bending and joint-failure tests under pull-out, bearing and peeling loads were performed on 977-2/HTS carbon fibre/epoxy specimens. On the one hand, effects of loading rate on the frame-bending behaviour could be observed. On the other hand, fastener failure did not appear to be depending on loading rate for the test speeds up to 10 m/s involved in this study. Adequate modelling methods in Abaqus/Explicit were derived and validated, and finally applied to a global aircraft crash simulation model.

Safety Enhancement of Water‐filled Road Safety Barrier using Interaction of Composite Materials

Road safety barriers are used to redirect traffic at roadside work-zones. When filled with water, these barriers are able to withstand low to moderate impact speeds up to 50kmh-1. Despite this feature, there are challenges when using portable water-filled barriers (PWFBs) such as large lateral displacements as well as tearing and breakage during impact, especially at higher speeds. In this study, the authors explore the use of composite action to enhance the crashworthiness of PWFBs and enable their use at higher speeds. Initially, we investigated the energy absorption capability of water in PWFB. Then, we considered the composite action of a PWFB with the introduction of a steel frame to evaluate its impact on performance. Findings of the study show that the initial height of impact must be lower than the free surface level of water in a PWFB for the water to provide significant crash energy absorption. In general, impact of a road barrier that is 80% filled is a good estimation. Furthermore, the addition of a composite structure greatly reduces the probability of tearing by decreasing the strain and impact energy transferred to the shell container. This allows the water to remain longer in the barrier to absorb energy via inertial displacement and sloshing response. Information from this research will aid in the design of next generation roadside safety structures aimed to increase safety on modern roadways.

Design of thin wall structures for energy absorption applications: Enhancement of crashworthiness due to axial and oblique impact forces

This paper describes a computationally aided design process of a thin wall structure subject to dynamic compression in both axial and oblique directions. Several different cross sectional shapes of thin walled structures subjected to direct and oblique loads were compared initially to obtain the cross section that fulfills the performance criteria. The selection was based on multi-criteria decision making (MCDM) process. The performance parameters used are the absorbed crash energy, crush force efficiency, ease of manufacture and cost. Once the cross section was selected, the design was further enhanced for better crash performances by investigating the effect of foam filling, increasing the wall thickness and by introducing a trigger mechanism. The outcome of the design process was very encouraging as the new design was able to improve the crash performance by an average of 10%.

Front Rail Crashworthiness Design for Front Oblique Impact Using a Magic Cube Approach

The front rail, as one main energy absorption component of vehicle front structures, should present steady progressive collapse along its axis and avoid bending collapse during the front oblique impact, but when the angle of loading direction is larger than some critical angle, it will appear bending collapse causing reduced capability of crash energy absorption. This paper is concerned with crashworthiness design of the front rail on a vehicle chassis frame structure considering uncertain crash directions. The objective is to improve the crash direction adaptability of the front rail, without deteriorating the vehicle's crashworthiness performance. Magic Cube (MQ) approach, a systematic design approach, is conducted to analyze the design problem. By applying Space Decomposition of MQ, an equivalent model of the vehicle chassis frame is generated, which simplifies the design problem. Based on this model, a two-layered front rail is proposed using a multi-step multi-domain topology optimization method and a response surface method. Numerical simulations are carried out with Altair/Hypermesh and LS-DYNA to compare the crashworthiness performances of the original front rail and the proposed two-layered design. The result shows that the two-layered front rail, with a reduced weight by 17%, can absorb 46% more energy in the 30 degree front impact than the original design, meanwhile, the proposed design eliminates the bending collapse on its rear end when the angle of loading direction reaches the critical angle. The energy absorption capability and the direction uncertainty adaptability of the front rail are significantly improved. Language: en

Post curing effect of poly epoxy on visco‐elastic and mechanical properties of different sandwich structures

AbstractPoly epoxy is a high performance room temperature cured epoxy system which provides excellent physical and mechanical properties. However, the effects of post curing of this resin system on the properties of different sandwich structures are unknown. This study aims to evaluate the effect of post curing (at 70°C for 2 hr) on the edgewise compressive and flexural strengths of a sandwich structure, constructed with Styrofoam and honeycomb as core materials and a plain weave carbon fabric as face sheet. Tested factors evaluated from edgewise compressive tests were as follows: peak load, compressive strength, and crash energy absorption of sandwich structures while core shear stress and bending stress of sandwich structures were determined and compared with flexural tests. It was observed that post curing affects significantly on the bending and compressive strengths of the sandwich structures. However, the data obtained for crash energy absorption suggested that the effect of post curing on the core shear strength and the total deflection was statistically insignificant. The matrix polymer was also inspected using dynamic‐mechanical thermal analysis to assess the changes in glass transition temperature and degree of conversion due to post cure. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Influence of Material on Automotive Crash-Box Crashworthiness Subjected to Low Velocity Impact

Crash-box equipped at the front end of a car, is one of the most important automotive parts for crash energy absorption. In case of frontal crash accident, it is expected to be collapsed with absorbing crash energy prior to other body parts so that the damage of the main cabin frame is minimized and passengers may be saved. Crash-box usually was made a mental thin walled tube. In the paper, automobile crash-box at low-velocity impact was studied by using Finite Element Method. The FE model of the tube was validated by comparing the experimental results and FE model results. Results show that on average the difference of these was within 10％.The good correlation of results obtained show that the numerical analyses are reliable. Crash-box of carbon steel and aluminum alloy materials are compared, it indicates that the peak impact force and maximum energy absorption have certain effect to energy-absorbing component with different materials.

Optimum Design on the Crash Energy Absorbing Ability of Reverse Spiral Cylindrical Thin-walled Structure

In order to make the front side member of the car to absorb more energy during frontal crash,thus achieve the purpose of the improvement of the car’s passive safety performance,the reverse spiral cylindrical structure of origami engineering is applied to the structure design of front side member,by using the numerical simulation and optimization design method,to research and development a new type of highly efficient energy absorbing structure.The corresponding finite element model is established,according to the different design parameters of the reverse spiral cylindrical structure,then using LS-DYNA software for the crash simulation,and take the reverse spiral origami structure of different cross-section parameter,rotation angle and the number of segments as design variables,the maximization of energy absorbing as the objective function,response surface method is used for optimization calculation.During the crash,the optimal structure’s crushing wrinkles appear in the folds of the structure,avoiding the slender thin-walled structure instability phenomenon effectively,which is a kind of efficient energy absorption’s deformation mode.Meanwhile,endergonic process smoothly and keep the good energy absorption properties in the entire process of crash,the optimization results that the optimal structure is capable of energy absorption more than that of rectangular cross sectional structure that is used generally.

Development of Buffer Stopper Using Progressive Compression Process for Crash Energy Absorption of a Railway Vehicle

A railway buffer stopper is a crash energy absorbing device which is installed at the end of rail lines in order to prevent derailment. To stop a train which cannot otherwise stop at the rail end due to some kind of trouble, this device should be installed in a railway station or depot where the rail line finishes. Friction type buffer stoppers have been installed at railway stations in most European countries. These devices can absorb the crash energy of the train by using the friction between a friction element and the rail when the train crashes into the buffer stopper. This paper proposes a new concept for the buffer stopper which can replace the friction type buffer stopper. More economical and effective buffer stopper can be suggested by using a progressive compression process. When the train crashes into the new type buffer stopper, a metal strip installed at the rail is progressively compressed and absorbs the kinetic energy of the train through its own plastic deformation. The feasibility of the buffer stopper using the progressive compression process is first investigated using numerical analysis and then the design and concept for the new system are suggested by a parametric study. The design of the progressive compression type has been verified by a series of experiments.

Finite element investigation of the influence of material properties on the crushing characteristics of in-plane loaded composite sandwich panels

In the present paper, the explicit finite element code LS-DYNA3D was used to investigate the influence of selected material properties in the crash energy absorption characteristics of composite sandwich panels subjected to in-plane compressive loading. The first step in this investigation was to simulate as accurate as possible representative tests corresponding to the collapse modes that occurred in a series of static edgewise compression tests performed in the National Technical University of Athens (NTUA) using various types of composite sandwich panels. These sandwich panels were candidate materials for use in the new type of composite front-end bumper of a transportation vehicle. Subsequent to the precise reproduction of the collapse modes, a step-by-step approach was followed in order to examine the influence of selected faceplate and foam core material properties on the crash energy absorption characteristics of the in-plane loaded sandwich panels. More specifically, several series of finite element models were created, by altering the value of only one material parameter per time of the initial FEA models used for the simulation of the sandwich panels collapse modes. The results from the processing of these series of FEA models were used to create figures that graphically depict the influence of the material properties on the energy characteristics. More over the simulation results were analysed in order to express by means of simple linear or polynomial functions the dependence of the crash energy absorption characteristics on the sandwich material parameters. The findings of this series of investigations were recorded aiming to be used as reference to the design of composite sandwich panels in various crashworthiness applications.

외연적 유한요소기법을 활용한 리저널급 항공기 동체 내추락 특성 분석

The impact energy absorbing is a very important characteristic of an aircraft to enhance the survivability of occupants when an aircraft is under the survivable accident such as an emergency landing condition. The impact energy is generally transmitted into the occupant and absorbed through a landing gear, a subfloor (lower structure of fuselage), and a seat. The characteristic of crash energy absorbing of a subfloor depends on the type of an aircraft, a shape of structure, and an applied material. Therefore, the study of crashworthiness characteristics of a subfloor structure is very important work to improve the safety of an aircraft. In this study, a finite element model of a narrow body fuselage section for the 80~90 seats regional aircraft was developed and crash simulation was executed using an explicit finite element analysis. Through survey of the impact energy distribution of each structural part of a fuselage and floor-level acceleration response, the crashworthiness characteristics and performance was evaluated.

Crash Energy Absorption of Braided Composite Tubes and its Application in Vehicle Passive Safety

Braided composite tubular structures are of interest as viable energy absorbing components to improve vehicle passive safety. Unfortunately, there are many difficulties in predicting the crash response of braided composite tubes. In this study, a progressive failure model for braided composite materials, which had been implemented as a user material model in ABAQUS/Explicit, was used to simulate the axial crash response of braided composite tubes. It was shown that the model adequately captured the failure characteristics (such as matrix cracking, fiber fracturing and delamination) and energy absorption of braided composite tubes under axial compression. In addition, the simulation results show that braided composites have higher energy absorption performance compared to traditional metals.

Analysis of Crushing Response of Composite Crashworthy Structures

The paper describes quasi-static and dynamic tests to characterise the energy absorption properties of polymer composite crash energy absorbing segment elements under axial loads. Detailed computer tomography scans of failed specimens are used to identify local compression crush failure mechanisms at the crush front. The varied crushing morphology between the compression strain rates identified in this paper is observed to be due to the differences in the response modes and mechanical properties of the strain dependent epoxy matrix. The importance of understanding the role of strain rate effects in composite crash energy absorbing structures is highlighted in this paper.

Crash and structural analyses of an aluminium railroad passenger car

Crashworthiness, strength and vibrational features of a railroad passenger car, which is originally made of steel members and then converted to an aluminium design, are studied. The finite element (FE) method is utilised for the static analysis in compliance with various scenarios defined in UIC CODE OR 577, modal analysis and simulation of the crash into a rigid wall. Firstly, a full-length, detailed passenger car model made of steel is used in FE analyses and the model is verified for the steel car body by comparisons with strain measurements and experimental evaluation of natural frequencies. The agreement between test measurements and FE results indicates that the FE model of the railroad car accurately represents the original structure. Following, effects of material change on the structural behaviour can be accurately judged based on the outcomes of the analyses. It is observed that the stress values and natural frequencies of the aluminium structure are almost equal to those of the original steel structure. Moreover, the crash energy absorption characteristics are within the acceptable tolerances for both cases. The final aluminium design is found to be about one-third of the weight of the initial steel structure while it preserves stiffness values within acceptable limits. In addition, an equivalent spring-mass system is developed to model the crash of both steel and aluminium passenger cars, which can be used for occupant safety investigations in future.

A study to maximize the crash energy absorption efficiency within the limits of crash space

The design of an engine room is important to protect the passenger from a crash impact by improving the absorption of the crash impact energy. The side member in the engine room absorbs most of the crash impact energy when the vehicle experiences a frontal crash. The side member is of two types: hat and ‘U.’ Analysis of the extent of energy absorption and the mechanism of the side member are necessary through a collapse mode in various load conditions. In this study, the design of experiments was used for evaluating the characteristics of the absorption of crash energy by side members through design variables. First, crash analysis was performed by experiment number extracted from the design of the experiment. Then, using the results of crash analysis, multiple regressions were conducted and sensitivity analysis performed for each design variable. Finally, the optimum design was developed for maximizing the absorption energy per unit weight considering various boundary conditions. In the present study, as a basic step for modeling the fatigue behavior of an extruded Al alloy cylinder, the fatigue crack growth data of the alloy was collected in two orientations. Microstructural analysis revealed that the material had recrystallized grains and clusters of constituent particles aligned in the direction of extrusion. Fatigue life of the samples revealed a shorter fatigue life representing a higher fatigue crack growth rate in the transverse direction.

Advanced composite sandwich structure design for energy absorption applications: Blast protection and crashworthiness

This paper describes an experimental investigation on the response of composite sandwich structures with tubular inserts to quasi-static compression. The performance parameters, namely the peak load, absorbed crash energy, specific energy absorption; average crushing load and crush force efficiency were evaluated. The composite sandwich specimens were fabricated from glass fiber, polystyrene foam and epoxy resin. The primary mode of failure observed was progressive crushing with the composites exhibiting high energy absorption capabilities and high crushes force efficiency. The mechanism of progressive crushing of the sandwich structures and its relation to the energy absorption capabilities was deliberated. Furthermore, a statistical analysis was performed to investigate the effects of the design variables and also to determine if there were interactions between these variables. Such information is vital in the design of polymer composite sandwich structures as energy absorbers.