1,721,039 research outputs found
Automotive composite components design and test: a vibration reduction oriented approach
No full textVehicle manufacturers initially relied on horsepower and speed performances as "standout qualities" to sell their products, but as time progressed, it became increasingly clear that customers were very much concerned about their comfort and safety while driving vehicles. In the late seventies, requirements for driver and passenger comfort were increased significantly, since-then, a large amount of effort has been invested into the vehicle improvement of noise and vibration reduction nevertheless enhancing the safety. Nowadays NVH performance is considered as a critical factor in the purchase decisions of many buyers. This work focusses on the development of a composite automotive door but, the methodology and materials applied could be extended for other panels, as there are several kinds in a typical vehicle whatever class or purpose it has. In the last years, furthermore, lightweight design imposed different design methodologies and materials like fiber reinforced plastics are becoming more and more used in the construction of vehicles for structural and non-structural parts. Reinforced plastics could perform higher performance and higher tailorable possibilities compared to conventional metallic materials, more and more composites are targeted toward structural applications involving combined dynamic, mechanical, thermal and hygral loading. Composite materials are principally preferred in such applications because of their advanced elastic properties and tailoring capability to individual design requirements. They also have the potential for incorporating significant and tailorable passive damping into the candidate structure. At the beginning, tests on two different viscoelastic materials are performed in order to identify mechanical characteristics necessary to provide valid data for numerical analysis of structures. ‘Oberst Beam Method' is the standard test method for measuring dynamic properties of materials (ASTM E756 - 05). Mechanical characteristics of damping materials have been determined for different temperatures (SAE J1637), frequencies and at different stage of aging (ISO 60068). Besides, low-velocity impact tests have been executed (ASTM 7136). After having post-processed the experimental data, the best material has been chosen. For each test, for each material and specimens topology a significant number of specimen has been tested for statistical purpose. ASTM 756 tests have been replicated virtually and to compare the results FRF Receptance, eigenfrequencies have been matched. Excellent correlation between simulation and experiment has been found. To evaluate the FEM virtual capabilities to reproduce and simulate the dynamic response of a real component and to validate correlation methodology, a first modal analysis has been carried out on a real automotive component. An innovative composite leaf spring is subjected to a free-free frequency response test, in which a series of accelerometers measures the response of the component to an excitation imposed by an electromechanical shaker. Moreover, LIPEZ methodology permitted to post-process data logged and to evaluate the characteristic vibrating modes of the structure. While the real component has been experimentally tested, FEM numerical simulation is reproduced. In the end, eigenfrequencies, eigenmodes (MAC) of experimental and virtual tests have been compared; excellent mode shape correlation has been found-out, errors on eigenfrequencies lower than 5%. Last part of this dissertation is focussed on the design, testing, and development of a damped door by means of interlaminar materials. The activity has been performed in two stages: undamped door testing and correlation with FEM and then manufacturing, testing and correlation of the damped solution. LIPEZ modal extraction algorithm has been used to extract modal parameters for the two artifacts, as well. The undamped door has been tested, real and virtual receptance, eigenfrequencies, eigenmodes computed and correlated. Damped material patches have been dimensioned and positioned considering a trade-off between added mass, costs and vibro-reduction capabilities. Modal analysis executed on the door have demonstrated that high damping capabilities have been achieved with limited drawbacks on weight increase (+5%) and inappreciable cost augmentation. In view of the scopes of the work, the results are deemed satisfactory
Method for Increasing the Humidity in Polymer ElectrolyteMembrane Fuel Cell
Full text linkThe water content within the polymer electrolyte membrane is essential to have good proton conduction and high efficiency of a fuel cell system. In this paper a new technique to increase the fuel cell efficiency acting on the internal humidity will be presented. In order to understand the potentialities and the limitations of such technique, the method was studied in a theoretical approach and then applied on a proton exchange membrane fuel cell (1kW PEMFC) that supplies the energy for the traction of a prototype vehicle, which took part in the last Shell Eco-marathon competition. Finally has been verified that the membrane water content is related to the hydrogen consumption and for some applications (e.g., military single-use equipment), the ‘‘filling'' method could be advantageous over humidified system and non-humidified systems. To ensure the proper success of the procedure it is also applied the differential method to fault detectio
Genetic testing for paediatric neurological disorders
No full textPaediatric neurological disorders encompass a large group of clinically heterogeneous diseases, of which some are known to have a genetic cause. Over the past few years, advances in nosological classifications and in strategies for molecular testing have substantially improved the diagnosis, genetic counselling, and clinical management of many patients, and have facilitated the possibility of prenatal diagnoses for future pregnancies. However, the increasing availability of genetic tests for paediatric neurological disorders is raising important questions with regard to the appropriateness, choice of protocols, interpretation of results, and ethical and social concerns of these services. In this Review, we discuss these topics and how these concerns affect genetic counselling
Different methods to evaluate SEA in GFRP laminated plates
No full textAbstract The necessity of weight reduction in vehicle has brought nowadays, new and innovative materials that are able to replace traditional materials. For these reasons, the R&D world, especially composite materials for automotive applications, became important for that components which must ensure both lightness and high mechanical property. The research presented in this paper is based on drop-weight impact tests of GFRP (Glass Fiber Reinforced Plastics) laminated plate (Epoxy resin matrix reinforced with E-Glass Twill woven) at LVI (Low Velocity Impact). The tests have been carried out at different impact velocity (1.5 m/s and 6 m/s) to understand the strain rate effects. The Specific Energy Absorption, or SEA, has been evaluated after the test
Design and optimisation of XAM 2.0 plug-in powertrain
No full textAfter the European Union Legislation set mandatory emission and consumption standards for 2020, an upgrade for personal mobility in cities has become a priority in the automotive sector. Electrification of the existing traditional car platforms while facing problems like weight repartition, battery cost and the weight to maintain the same performances is not feasible in a short period. In this paper, a case study of developing a hybrid powertrain is presented with systematic designing phase, system dimensioning and selection of the different subsystems for XAM 2.0, an innovative prototype city vehicle designed at the Politecnico di Torino. Thanks to these solutions, XAM 2.0 won the first prize for the ‘Best Range Extender Prototype’ at the Brighton-London Future Car Challenge 2012, running with different OEMs and car-makers
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