1,721,011 research outputs found
Behaviour of an Impact Attenuator for Formula SAE Car under Dynamic Loading
No full textDuring the design of a Formula SAE car is necessary to take into account also its behaviour under dynamic loadings, such as frontal impact against a rigid wall, in order to make a safe car in case of an accident. In particular the racing car must have structural devices able to absorb most of the kinetic energy with their progressive crushing minimizing forces and decelerations transferred to the pilot. So the purpose of this study is the design of an impact attenuator for a Formula SAE car and the investigation, through both a numerical and experimental approach, of its dynamic behaviour under frontal impact conditions. The crash-box is obtained by the combination of sandwich panels and aluminium sheets. Firstly experimental tests and numerical analysis on sandwich structures were carried out in order to better understand their behaviour and model them properly. Afterwards a total 3D numerical model was built with the finite element code ANSYS and solved with the non-linear dynamic software LS-DYNA. In order to obtain the best configuration of crash-box in terms of maximum absorbed energy, minimum deceleration and weight saving an optimization process has been done varying some geometrical parameters. Finally a crash-test was done on the real impact attenuator in order to compare the experimental results with the numerical ones. The obtained results show that the crash-box designed and built is able to absorb the total impact energy with progressive and plastic deformation and contain the average deceleration under a 20 g value
Investigation of the most efficient solution for a specific vehicle impact attenuator in CFRP material
No full textNowadays each manufacturers of racing cars must pass specific crash tests controlled by
legislation, before seeing their vehicles in the market and in motor racing. In order to ensure
the driver’s safety in case of high-speed crashes, special impact structures must be designed
to absorb the race car’s kinetic energy and limit the decelerations acting on the human body.
This target is achieved thanks to the synergy between the numerical and experimental
analysis. Investigated in this work is the best solution, in terms of energy absorption, for a
specific frontal impact attenuator in CFRP material with sandwich structure. In particular,
given the geometry reported by the manufacturer, it has been necessary to find the right
combination of material and lamination varying the stacking sequence and its disposition.
Analyses have been conducted by the joining of numerical models, performed using LSDYNA,
with experimental tests, through an instrumented drop tower equipment
Attenuators
No full textAn impact attenuator is a device used to protect a vehicle from damage during a collision, thus preventing the risk of injury to the driver and passengers. Attenuators are used both on public roads and on racetracks as well as built into the vehicles themselves. Nowadays, with an increasing number of injuries that occur during car races due to higher speeds on the tracks, and lower acceptance of injuries, the driver's safety has become a major area of research. The designer must be able to design and build structures able to dissipate the greatest amount of kinetic energy with progressive and controlled crushing, in order to avoid high deceleration peaks dangerous to humans. Given the complexity of the dynamic phenomenon and the use of new materials, such as fiber-reinforced polymer materials, time, and cost of development tend to grow. The use of software dedicated to the finite element (FE) modeling, and optimization can help to reduce cost significantly. The simulated results, however, cannot be used directly without thorough validation with experimental results. The purpose of this article is to present some crashworthiness analysis conducted on frontal impact attenuators, made of conventional, and composite materials, from a numerical and experimental point of view. The results of the FE analysis, obtained using the solver LS-DYNA, proved to be in good agreement with the experimental data, confirming the quality of the numerical simulation
Mathematical design of electric vehicle impact attenuators: Metallic vs composite material
No full textElectric vehicle energy consumption may be minimized redesigning specific car parts in order to not compromise
crashworthiness aspects. Although more challenging compared with metallic counterparts
because of their microstructural heterogeneity and behavioral sophistication, composite materials seem
to be the best solution due to high specific strength and energy absorption. Differently from traditional
shape, electric vehicle may be equipped with frontal impact attenuator whose geometry is very similar to
the square frusta adopted for racing cars. The paper aims at developing an analytical procedure in order
to capture the energy absorption capability of square impact attenuators with a square frusta geometry.
Both metallic and composite materials are analysed in order to save the body weight. An energetic
approach is addressed taking into account the energy contributions responsible for the absorption during
crushing. Comparing the metallic and the composite model introduced, the best configuration of an electric
vehicle specific frontal impact attenuator able to absorb a fixed impact energy is obtained
Energy absorbed by composite conical structures in axial crushing
No full textRecently crashworthiness trend is the use of thin-walled composite impact attenuators in specific vehicle zones, ensuring kinetic energy absorption. The present paper addresses the composite conical structures design using an analytical approach for predicting energy dissipation in a controlled way. A balance of internal energies involved in the absorption and external force yields the average crush load and the total displacement through a numerical method. Comparison between theory and experiments shows the efficiency of the proposed relatively simple model for predicting energy absorption of axially collapsing composite shells
Mathematical and numerical approach for a crashworthy problem
No full textVehicle crashworthiness has been improving in recent years with attention mainly directed towards reducing the impact of the crash on the passengers. An optimal way to achieve this target is by exclusive use of specific impact attenuators, such as strategically placed tubular elements. Many of the mechanical devices are designed to absorb impact energy under axial crushing, bending and/or combined loading. An important requirement is that these structural members must be able to dissipate large amount of energy by controlled collapse in the event of a collision. Generally, the total energy dissipated depends on the governing deformation phenomena of all or part of the structural components of simple geometry, such as thin-walled tubes, cones, frames and sections. The energy absorbing capacity differs from one component to the next in a manner which depends on the mode of deformation involved and the material used.
During the last decades the attention given to crash energy management has been centred on composite structures. The use of fibre-reinforced plastic composite materials in automotive structures may result in many potential economic and functional benefits due to their improved properties respect to metal ones, ranging from weight reduction to increased strength and durability features.
Although significant experimental work on the collapse of fibre-reinforced composite shells has been carried out, studies on the theoretical modelling of the crushing process are quite limited since the complex and brittle fracture mechanisms of composite materials. Most of the studies have been directed towards the axial crush analysis, because it represents more or less the most efficient design.
In the present paper, a mathematical approach on the failure mechanisms, pertaining to the stable mode of collapse (Mode I) of thin-walled composite circular tubes subjected to axial loading, was investigated. The analysis was conducted from an energetic point of view; it is therefore necessary to identify the main energy contributions and then equate the total internal energy to the work done by the external load. The average crush load can be obtained minimizing the force contribution, function of several variables, on a domain using a numerical approach. Comparison between theory and experiments concerning crushing loads and total displacements was analysed, showing how the proposed analytical model is efficient for predicting the energy absorption capability of axially collapsing composite shells
Design Solutions to Improve CFRP Crash-Box Impact Efficiency for Racing Applications
No full textThis research work involves the examination of the front crash structure of a Formula Ford car used to protect the driver in the event of a frontal impact. At the moment every manufacturer has a different method of producing their crash structures. The choice of the material to use is increasingly often dictated by weight and aerodynamic needs as well as structural performance. Recently it is preferable to make such structures in composite materials, thanks to their undoubted advantages such as high strength to weight ratio, the high level of energy absorption and the possibility to reproduce each complex geometry
Lightweight design and crash analysis of composites
No full textThe chapter cover some description about energy absorption of specific impact attenuator made of composite material with a thin-walled structure
Progressive crushing of a fiber reinforced composite crash-box for a racing car
No full textBecause of their superior mechanical properties in combination with a relative low density Fiber Reinforced Composites (FRC) are of great potential in the area of lightweight transportation systems. The present paper describes an experimental and numerical investigation on a frontal energy absorbers for a SR2 prototype, made of a FRC structure. The crash-box is a structure that has the only function to absorb the total kinetic energy during the impact in a controlled mode, so that all the damage is contained in it. Besides, the crash-box does not require a post-crush integrity, but must absorb energy without high peak load, to avoid high deceleration to the pilot. The present research program included some crash tests, in the conditions related to a frontal impact at the velocity of 12 m/s, in order to acquire information on the dynamic behavior of the mentioned structure. A finite element model is then developed using the non-linear explicit dynamic code LS-DYNA. The numerical simulation results accurately predict the deformation and the average deceleration recorded in the tests
Theoretical analysis on the collapse mechanisms of thin-walled composite tubes.
No full textThin walled tubes are often used as impact absorbing elements in automobiles and other transport vehicles. Round cylindrical and conical shells made of composite material prove to be popular energy absorber as they provide reasonably constant operating force, which is the primary characteristics of an ideal absorber. Based on experimental observations, a theoretical procedure is established to predict the post collapse load-compression characteristics of the composite shells. Analytical expressions were obtained to predict the average crush load and the crush length in a crush cycle for the composite conical shells as well as for the cylindrical tubes. The results so obtained were compared with the experimental values available from the literature
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