1,721,050 research outputs found
Numerical analysis of tube expansion process for heat exchangers production
No full textThis work analyses two different aspects of the mechanical process of tubes expansion used for the production of heat exchangers. In particular, the influences on the expansion process due to mandrel geometry and geometrical errors in tubes, caused by production tolerances, were studied and analyzed using finite element (FE) models. A 2D axisymmetric model was used to study the influence of mandrel geometry, whereas a 3D solid model was adopted to investigate the influence of geometrical errors in tubes. Experimental tests were carried out on actual materials in order to set up and validate the FE models. Force required for expansion, and variation in tube dimensions due to expansion were investigated and a good agreement was found between experimental and FE results. Additionally, the obtained results showed that the fillet radius is the most important geometrical factor of the mandrel in order to reduce the expansion force. A great influence of the tube geometrical errors was observed on the tube expansion process, which can compromise the performance of the heat exchanger. Finally, it is worth mentioning that the present study provides useful information that might be used to improve tubes expansion processes in general and heat exchangers production in particular
Some recent results of the Politecnico di Torino research in the field of vehicle passive safety
No full textSVILUPPO DI UNA METODOLOGIA DI SIMULAZIONE DEL PROCESSO DI FORMATURA DEI TUBI PER I FASCI TUBIERI FORZATI NELLE PIASTRE FRONTALI
No full textIl fissaggio dei tubi sui pacchi alettati con cui sono realizzati i grandi scambiatori di calore può essere realizzato mediante un processo meccanico denominato mandrinatura, in cui una ogiva opportunamente sagomata viene spinta all’interno del tubo. L’obiettivo di questo lavoro è lo studio e la messa a punto di un modello agli elementi finiti in grado di simulare al meglio il processo di espansione. Il lavoro è suddiviso in una prima parte sperimentale, in cui vengono caratterizzati i materiali impiegati ed il processo di espansione, ed una seconda parte numerica in cui viene sviluppato il modello sulla base dei dati sperimentali raccolti. Il modello sviluppato permette di valutare l’influenza dei parametri che governano il processo
Experimental investigation of the structural behaviour of hybrid metal/composite thin walled box beams
No full textInvestigation on the energy absorption capability of composite crash-box with recyclable thermoplastic material
No full textNowadays the key points in the automotive design are the pollutant emissions and the safety. For these reasons, on one side, in the car design the tendency is to use innovative lightweight materials in order to reduce the weight of the vehicle and consequently the fuel consumption and the gas emissions. On the other side, to reach high level of safety, these materials have to be able to absorb high amount of energy in case of impact. For these reasons, in the last decades, the use of composites as design material for impact attenuators in automotive design is increased significantly. The ever-wider use of composite materials for automotive applications involves the need to predict their behaviour under various load conditions which they are subjected, for example with the use of finite element codes. Moreover, more recently, the strong emphasis on recyclability from the end-of-life vehicle directive seems to affect significantly the choice of materials in the design phase. In this overview, the use of thermoplastic composite based components for vehicle structure is investigated in this work. In particular a thermoplastic fibres combined with a thermoplastic matrix is considered. An experimental test campaign, in order to define the mechanical properties of this new material is carried out. Starting from the information obtained in the first experimental tests, the energy absorption capacity of impact attenuators made as thin wall tubes of circular cross section is investigated. The crushing sensitivity of these structures to the wall thickness and to the resistant section is studied. The experimental results and the failure mechanisms obtained in the tests are presented and discussed in the pape
Numerical study of a hybrid wire-net bonnet for pedestrian safety
No full textIn the automotive field the attention of public opinion is focused on the safety of vulnerable road users (VRU) pedestrians and cyclists. At the same time the reduction of pollutant emissions is very important. To improve these two aspects of the automotive design, the use of non-conventional materials and innovative design solutions is increasingly important. In this perspective a new wire net design for the inner structure of a bonnet is proposed and developed in this work. The influence of the main design parameters (thicknesses, materials) is investigated
Mechanical properties and impact behavior of a microcellular structural foam
No full textStructural foams are a relatively new class of materials with peculiar characteristics that make them very attractive in some energy absorption applications. They are currently used for packaging to protect goods from damage during transportation in the case of accidental impacts. Structural foams, in fact, have sufficient mechanical strength even with reduced weight: the balance between the two antagonist requirements demonstrates that these materials are profitable. Structural foams are generally made of microcellular materials, obtained by polymers where voids at the microscopic level are created. Although the processing technologies and some of the material properties, including mechanical, are well known, very little is established for what concerns dynamic impact properties, for the design of energy absorbing components made of microcellular foams. The paper reports a number of experimental results, in different loading conditions and loading speed, which will be a basis for the structural modeling
Mechanical properties and impact behavior of a microcellular structural foam
Full text linkStructural foams are a relatively new class of materials with peculiar characteristics that make them very attractive in some energy absorption applications. They are currently used for packaging to protect goods from damage during transportation in the case of accidental impacts. Structural foams, in fact, have sufficient mechanical strength even with reduced weight: the balance between the two antagonist requirements demonstrates that these materials are profitable. Structural foams are generally made of microcellular materials, obtained by polymers where voids at the microscopic level are created. Although the processing technologies and some of the material properties, including mechanical, are well known, very little is established for what concerns dynamic impact properties, for the design of energy absorbing components made of microcellular foams. The paper reports a number of experimental results, in different loading conditions and loading speed, which will be a basis for the structural modeling
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