Luis Castejon

INTERCITY BUS ROLLOVER SIMULATION

Bus accidents involving rollover are of such violence that is not usually seen in other kinds of accidents. In order to provide buses with a minimal rollover-resistant superstructure, the Regulation No. 66 of Geneve was issued. Calculations made by means of the finite element method, as well as a subroutine application that has been created for this purpose, are presented in this paper. These calculations have been made for an intercity bus structure that is actually working in real life. This technique has been checked by means of the realisation of the test explained in the above-mentioned Geneve regulation, with a module of the superstructure of the bus, and the subsequent numerical simulation. A high degree of theoretical and experimental correlation is obtained, which confirms its validity. Once the method was assessed, a complete vehicle rollover test simulation was carried out, with and without the application of an energy absorber on each of its upper lateral edges, which is able to absorb 30% of the energy released in the impact. The results obtained in the complete rollover simulation prove the efficacy of the use of the energy absorber, and it is inferred that the structure of the bus is able to pass the required regulations.

Numerical Analysis of Three-Dimensional Braided Composite by Means of Geometrical Modeling Based on Machine Emulation.

Three dimensional braided composite materials exhibit better performance in terms of structural integrity, through-thickness strength and impact resistance, than laminated composites. Other advantages regarding production are the ability to produce composite structures with intricate geometries close to the near-net-shape, and also with continuous changes in its cross-section. These properties are a consequence of the internal geometry of the 3D braided composites, in which yarns are interlaced following specific patterns programmed on a braiding machine. In this article, the operation of a typical rotary braiding machine is emulated in order to automatically obtain the geometry of a braiding unit cell. Once the geometrical description is obtained, a finite element model has been developed in order to carry out virtual testing of 3D composite materials. An AS4/epoxy braided material system has been virtually tested and a theory-experimental correlation has been performed for the longitudinal modulus and yield strength compression, using a failure criterion based on constituents and interface failures.

Composite Bus Rollover Simulation and Testing

The present paper shows a simulation technique for the rollover test, based on the Geneva Regulation number 66, of complete steel or composite buses, which required a previous validation. A new concept of lightweight bus wholly made of composites is shown, owing to its outstanding advantages in the transportation, such as weight saving. This bus structure is able to meet the stiffness and strength requirements, which must be overcome by metallic buses. The rollover of the composite bus is studied by means of the developed simulation technique. A prototype of the composite bus was built and tested.

Development of an innovative concept of light semi-trailer by means of FEM and testing

A new light semi-trailer concept has been developed using numerical and experimental methods. In order to achieve this objective different types of light materials, such as high strength steels, aluminum alloys and sandwich compound materials, have been studied. The different semi-trailer models have been studied by means of a numerical model simulation based on F.E.M. (Finite Element Method) and subjected to whole loads and various boundary conditions. In testing whole strain values from critical points located in the semi-trailer have been obtained in order to correlate the numerical and the experimental results. Finally, some of the initial semi-trailer parts and areas were optimized by means of numerical methods. Results obtained in the numerical simulations were applied to the analyzed structure in order to design a second generation of semi-trailer structure in which weight is decreased.

Advances in the Crash Simulation of Vehicle Frontal Crash Structures Made of Braided Composite Materials

In this paper, new advances in simulation of composite materials under crash loads are applied to the analysis of a car frontal crash structure. Experimental results are used to calibrate constitutive material models and simulation procedures to obtain more accurate representation of material behavior under crash loading. These advanced computational techniques are then applied to crash simulations of components. The front longitudinal beam studied herein is analyzed for 2 load cases: frontal and lateral crash. Qualitative results on specific energy absorption, as well as the absolute energy absorbed by the structure, are especially relevant. Results of simulations of the structure in carbon and glass fibers are presented and compared, focusing on the absolute energy absorbed and specific energy absorption of the structure.

Structural design and optimization using neural networks and genetic algorithms of a tanker vehicle

The aim of this article is to introduce a structural optimization tool based on the combination of neural networks and genetic algorithms, applied to optimize a cryogenic tanker vehicle. To use this tool, it is necessary to introduce an equation that defines the aspects that are going to be optimized (weight, resistance, rigidity, etc.) of a part of the vehicle (the parking zone). Sometimes, this equation is difficult or impossible to model mathematically and then the neuronal networks allow approaching this equation from some particular solutions of the equation and then we will be able to find the solution at any point in the search space on the basis of a set of values of different solutions to the equation. For the tanker vehicle, the neuronal network is used to know the maximum Von Mises stress that is impossible to model mathematically. The genetic algorithms are used to optimize the equation and allow knowing the optimal design of the vehicle tanker. The symbiosis of both techniques are very useful because it will enable us to find the solution to the equation at any point of the search space on the basis of a discrete set of solutions, following which we will be able to optimize the equation in the search space. This allows us to optimize an equation about which the only knowledge we have is a finite set of solutions in the search space. At the end with a Pareto multi-objective set, the effectiveness of the methodology has been verified, and with an extensometrical analysis, the numerical results have been correlated too.

Aerodynamic analysis of some boat tails for heavy vehicles

The aim of this paper is the aerodynamic study of the use of boat tails to reduce the aerodynamic drag coefficient in heavy vehicles. There are some improvements and some patents that improve the aerodynamic efficiency of the vehicle and the fuel consumption, but there are no experimental or numerical analyses of this benefit. This paper analyses some of these improvements using numerical tools and comparing the results with the results of the vehicle without them. To make the numerical analysis, the CFD methodology, using FLUENT, has been used since it allows simulating some geometries and modifications of the geometry.

Behaviour of Rear Underrun Protection System on Car-to-tank Vehicle Impact Used for Fuel Transportation

The European legislation for rear underrun protection systems on heavy vehicles, Commission Directive 2006/20/EC, specifies a series of criteria that must be fulfilled so that these devices can be homologated. The different models of devices used as rear underrun impact protection in tank vehicles for fuel transportation are an example of these criteria. Basically, the homologation tests based on this regulation consist in the quasi-static application of a load series at different points of the structure. In analysing the guidelines of Commission Directive 2006/20/EC, a number of questions about their validity may be raised with respect to, for instance, how efficient a homologated system of these characteristics is in real collision. The aim of this paper is to compare the behaviour of a rear underrun impact protection system, incorporated into a tank vehicle, to the behaviour of the same device when a car hits it at different collision speeds.

Validation of the Finite Element Method Applied to Isotactic Polypropylene Homopolymers

The main aim of the present article is to validate results obtained using numerical techniques on an isotactic polypropylene homopolymer. With this in mind, results obtained by the finite element method (FEM) are compared with numerical results obtained using a free-fall tower. This comparison validates the FEM calculations, as differences between empirically and numerically obtained results are never greater than 9.84%.

Response analyses of a two-phase cryogenic tank to longitudinal and lateral accelerations

The aim of this article is to present a methodology for calculating vehicle tankers by analysing the way baffle shape contributes to the movement of the fluid. This methodology could be used to optimise the geometry of these parts analysing different geometries. Four different lateral types of baffles used by different cryogenic tank manufacturers have been examined. Both the movement of the fluid and the forces transmitted by the latter to the tank during emergency braking manoeuvres are analysed and the principal conclusion is that the contribution of the geometry is very important. Besides, a longitudinal baffle meant to reduce the tendency of the tank to overturn while diminishing the moment generated by the load has been designed. The longitudinal baffle has been optimised, modifying the height and depending on the level of filling of the tanker the rollover moment can be reduced.