Ramon Miralbes

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.

Design of motorcycle rider protection systems using numerical techniques

The goal of this paper is the development of a design methodology, based on the use of finite elements numerical tools and dummies in order to study the damages and injuries that appear during a motorcyclist collision against a motorcyclist protection system (MPS). According to the existing regulation, a Hybrid III dummy FEM model has been used as a starting point and some modifications have been included. For instance a new finite element helmet model has been developed and later added to the dummy model. Moreover, some structural elements affecting the simulation results such as the connecting bolts or the ground have been adequately modeled. Finally there have been analyzed diverse types of current motorcyclists protection systems, for which it has been made a comparative numerical-experiment analysis to validate the numerical results and the methodology used.

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.

Simulation of Suspensions, Torsion Bars, and Fifth Wheel for Semitrailers Using Finite Elements

The objective of this paper is the simulation of some different types of elements for semitrailers, like the suspension, both mechanical with springs and pneumatic with a spring anddiapresses; other parts like the wheels, the torsion bars, the fifth wheel and the suspension of the tractor unit have also been simulated. Then, the numerical simplified FE model of these elements that allows simulating the real behavior of the suspension to apply adequately the boundary conditions of a heavy vehicle has been obtained for a structural simulation using numerical tools with a good accuracy of the local and global behavior of the vehicle.

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.

Comparative Analysis of Two Numerical Methods of Rollover Simulation of a Semitrailer for Hydrogen Transport

Nowadays, the use of the Finite Element Method [1] by means of simulation computer tools has made possible a substantial step forward in the field of calculation and optimization of vehicle structures. More specifically, these modern calculation tools are achieving great cost reductions corresponding to the experimental tests necessary to verify the appropriate performance of a vehicle in impact cases. On the other hand, great efforts will have to be done to develop correct numerical models for calculation. Once these numerical models have been validated with experimental tests, elimination of experimental costs compensates for these calculation efforts. A greater flexibility in decision making with respect to design and optimization alternatives will be achieved as well. The objective of this paper is to obtain an appropriate test simulation methodology for a specific vehicle and a specific impact case: There have been carried out the simulations of two different rollover test typologies in order to verify an adequate and safe behaviour of a semitrailer designed for hydrogen transport. After results of these two simulations are obtained, they will be compared in order to set which is the most restrictive and therefore the most appropriate. A lightened configuration has been also considered so as to carry out a sensibility analysis of material and thickness of some structural parts over numerical results in both test typologies in order to verify these simulations.Copyright

New Concept of Rollover Resistant Semitrailer for Hydrogen Transport

In this paper a new concept of semitrailer for hydrogen carriers is presented. It has been developed by means of numerical calculations carried out with the finite elements method. This new design of semitrailer incorporates several new functions. The first one is to achieve a rollover resistant vehicle. It has to be taken into account the absence of a specific regulation in Europe for this type of vehicles, so former vehicles were not enough rollover resistant. Nevertheless, in this development process it has been taken into account the European rollover regulation concerning large passenger vehicles “Regulation n° 66 of Geneva”, applied in this case to a vehicle having a much higher mass and a higher centre of gravity than a bus. Therefore a higher kinetic energy will be obtained in case of rollover. The second characteristic inherent to this new design of semitrailer is its lightness. It has achieved a mass reduction of 8500 kg in comparison with former designs, by means of lightening the structure, in charge of supporting the hydrogen cylinders, as well as making lighter these hydrogen cylinders themselves. Numerical models developed have been calculated by explicit integration of the dynamic balance equation. Very complex finite element models have been developed in order to include all geometric details. In these models, the elastic-plastic curves of involved materials have been included as well as its variation due to the strain rate influence. There have also been taken into account non-linear effects from contacts and from large strains that take place.Copyright

Study of the influence of impact velocity and angle of impact against a motorcyclists´ protection systems design and neural damage sustained using numerical methods

ABSTRACT MPS (Motorcyclists´ protection systems) play an essential role in the reduction of fatalities and morbidity involved in motorbike and moped accidents, since they offer protection from impact against road elements such as guardrail posts and nearby elements such as traffic signs, trees, etc. For the standardisation of such elements, different regulations have been developed which, by means of experimental tests, allow the simulation of those accidents through tests at a specific velocity and angle. Nevertheless, there is the possibility that, under different angles and velocity, those systems fail to be safe. To assess this, a series of accidents involving diverse angles and velocities have been studied through virtual tests by using numerical models and the finite elements method with a view to obtaining data on head acceleration and neural damage sustained in the event of collision against MPS. In addition, the accidentology for this type of vehicles has been studied in order to break accidents down according to impact angle and velocity impact range as well as age category and gender of those sustaining injuries. To that aim, homologated commercial MPS have been analysed in order to get the variation of the main biomechanical indexes depending on the impact angle and velocity; the results thus obtained have allowed us to determine the real security level of the MPS studied. This information has been extrapolated to determine the level of security provided by MPS. Finally some modifications in the homologation regulations to improve safety of MPS have been suggested.

Motorcyclist Protection Systems: Analysis of the Crash Test Tolerances of the European Technical Specification and the Spanish Standard

One of the most frequent and harmful kinds of motorcycle accidents is an impact against the post of the roadside barrier, so designers have developed some motorcyclist protection system (MPS) to reduce it. Some countries have developed a standard testing procedure, like the Spanish UNE-135900-2008 standard, identical to the CENs recently approved Technical Specification (TS 1317-8). These standards specify the test procedure to obtain the behaviour of the MPS, but experimental tests have shown some dispersion of results for identical tests of the same barrier. There are some theories to explain this but the most reasonable is the influence of tolerances of some of the test variables in the final result like impact height, impact velocity, yaw angle, and mass. To analyze these theories, numerical analysis that can measure the independent influence of each parameter in the results has been used, using a correlated numerical model, a common and experimentally tested barrier, and an MPS. So, the results of this paper show how some parameters of impact significantly influence the behaviour of the system, changing impact severity, potential damage, and injuries. Therefore, the test tolerances do not guarantee repeatability and can accept systems too harmful for the same test conditions, so it will be necessary to reduce limit deviations of some impact variables.