Mobility and Vehicle Mechanics

19-38

Authors: Giovanni Belingardi, Brunetto Martorana

Vehicle weight reduction (and in turn reduction of fuel consumption, noxious gas and greenhouse gas emissions), manufacturing costs and riding comfort are pushing toward relevant growth the amount of polymeric materials employed in modern cars. At the same time the main performance of the car (and in particular safety and NVH comfort) should be maintained. In order to pursue this trend, it is important to carry out research and innovation on new polymer-based materials, with a high structural performance to weight ratio to replace standard materials, such as mild steel, for structural components. The base costs of composite materials are still relatively too high, therefore research activities are needed to reduce manufacturing costs of composite components. On the other hand the use of composites offer advantages not only in terms of lightweight but also in terms of parts integration, TTM reduction, etc. Innovative components can take advantage from new materials but need for proper design rules and proper manufacturing technologies. Cycle times and production volumes are key factors. The production value chain and the research have to work in order to overtake some technological limits (joining technologies, recyclability, repairing, safety, costs, …) for a wider employment of lightweight materials. This paper is presenting some recent results in the design of vehicle components with composite materials and is also presenting some recent achievements in the use of thermoplastic adhesives, nanomodified by ferromagnetic particles, sensitive to the electromagnetic field finalized to speed up both the manufacturing and the dismounting processes.

55-62

Authors: THE MECHANICAL BEHAVIOUR OF MATERIAL IN AUTOMOTIVE ENGINEERING REINFORCED BY STRONG FIBRES

Laminate is made from layers mutually bonded to form multilayered composite. Composite materials consist two or more constituents such as fibres and matrix. Matrix bond fibres together, gives shape of composite, have role in transfer loads to fibre. Usually fibres are 60-70% of composite volume and they are made of carbon, glass, aramid (such as kevlar) or metal. In the present paper we study wave propagation bulk waves. The properties of these waves are determined by the dependence between the propagation direction and constitutive properties of media. Here we study slowness surfaces, as indicators of dynamical behavior, in order to obtain information about wave propagation in arbitrary directions. The surfaces associated with wave front surfaces are slowness surfaces, with slowness defined by the inverse of the wave front speeds. Constitutive equations are developed for material which is made of unidirectionally reinforced thin sheets, which form model of material. Degrees of wave surfaces deviations depend on the degrees of anisotropy, and may give valuable information about dynamic deformations. The materials used in the present analysis are fibre reinforced materials with two families of continuous elastic and mechanically equivalent fibres, having axes of symmetry along bisectors of the fibre directions and along the normal to the plane tangent to fibres.

17-31

Authors: Slobodan Mišanović

The problem of air pollution, acid rain and the formation of ''greenhouse effect'', as a result of emissions a carbon dioxide (CO2), from vehicles are found in the developed countries of the EU several decades. This problem was got primary importance. EU has chosen a strategy of increase number the vehicles with lower emissions of carbon dioxide (CO2). Introduction of city buses with hybrid (diesel-electric) engines in a growing number of EU cities, are first stage in the implementation of the EU strategy which has defined (Transport policy- White Paper 2011) where is the ultimate goal that of the 2050 year, the cities in the EU will be used only vehicles with zero emissions (CO2). Defined strategy for the EU to promote an ecological clean the bus subsystem of public transport, have accelerated all manufacturers of buses in the European market, to produce buses with hybrid power, which allowed that companies for public transport, are used tender procedures for procurement of hybrid buses pursuant to Directive EC/2009/33. In this paper, is presented experiences in operation of hybrid buses in the some EU cities, which have this type of buses in regular service.

43-55

Authors: Milan Milovanović Miroslav Demić Saša Jovanović

The development of the carrying construction of one producer is an endless process. In addition to the analysis of carrying construction behaviour, it is necessary to take into account the influence of additionally installed drive units onto the carrying construction behaviour. In this paper, the influence of subframe on carrying construction behaviour, is shown. With the aim of presenting the results, behaviour of carrying construction in conditions of quasi-static test has been shown, as well as in conditions of simulation of front impact test.

15-26

Authors: Dejanu Marcel, Dascalu Traian, Popa Dinel, Pârlac Sebastian, Salamu Gabriela

The experimental bench has in its composure a laser equipment, a high speed recording video equipment, a measuring system for recording pressure variations and a static enclosure in which experiments are conducted. The recording of images was done using the shadow graph technique, a source of light with xenon and a 3000 frames/s high speed camera with a resolution of 512x512 pixels. There were recorded and analyzed the next phenomenon: the variation of the flame front depending on the initial pressure, the variation of the pressure from inside the chamber depending on the initial pressure and also the shape and the way of how the flame front is propagated. The results are presented under the form of images and diagrams.

35-50

Authors: Adrian Clenci, Adrian Biziiac, Pierre Podevin, Rodica Niculescu

Reducing fuel consumption is a prime objective in the automotive industry in order to meet legal and customer demands due to the increasing price of oil. Variable valve actuation offers many opportunities for improving the spark ignition engine’s performance in areas such as fuel economy and pollutant emissions. This study presents a variable intake valve lift (ViVL) mechanism, used to enhance fuel economy in the area of idle operation and low part loads, which are the ones most frequently encountered in a vehicle’s operation time. Currently, this mechanism is self-regulated thanks to a hydro-mechanical system and allows a continuous intake valve lift variation during engine operation. Our studies revealed that the ability to control valve lift does indeed offer the ability to control intake air mass but also has the added benefit that it improves the fuel-air mixing process and controls air motion. This is particularly important at idle and low part loads when low lifts are to be used for improving the fuel economy or for achieving the required power. The paper focuses on the experimental results obtained when approaching idle operation with different configurations of the intake valve timing system. Results indicating the potential of the ViVL system for fuel economy improvement, as well as results regarding the in-cylinder pressure evolution are presented in this paper. Last but not least, the paper also presents a so-called Sleep&Start strategy, which can be seen as an alternative to the Stop&Start micro-hybridization solution. In other words, once a ViVL system has been installed on an engine, it should be used in every possible way in order to obtain a high benefits/cost ratio.

19-29

Authors: ejanu Marcel , Popa Dinel, Dascălu Traian, Tabacu Ion, Pârlac Sebastian

The experimental bench has in its composure a laser equipment, a high speed recording video equipment, a measuring system for recording pressure variations and a static enclosure in which experiments are conducted. The recording of images was done using the shadowgraph technique, a source of light with xenon and a 3000 frames/s high speed camera with a resolution of 512x512 pixels. There were recorded and analyzed the next phenomenon: the variation of the flame front depending on the initial pressure, the variation of the pressure from inside the chamber depending on the initial pressure and also the shape and the way of how the flame front is propagated. The results are presented under the form of images and diagrams.

43-63

Authors: Dobrivoje Ninković, Dragan Taranović, Saša Milojević, Radivoje Pešić

Thermodynamic performance (delivery rate and power intake) and reliability of reciprocating compressors are dependent upon the valves. Since the valves open and close automatically, there is a high degree of coupling between the gas flow through the valve and the sealing element dynamics; a mismatch between the two leads inevitably to degradation of the compressor performance and/or short valve life. The latter is due to impact forces between the sealing element and other parts of the valve assembly. Therefore, matching the valves to the compressor application at hand is a complex task that calls for the use of the corresponding simulation models. Surveyed in the paper are mathematical models for the prediction of the valve performance, consisting of the sub models describing compressible gas flow through the valves, sealing element dynamics, and the interaction of the latter with the flow. Flow models based on the discharge coefficient are intrinsically not able to predict the critical flow regime with sufficient accuracy, requiring thus experimental data that are not always available. It is also suggested that other loss calculation approaches, such as the stagnation pressure loss model, should be investigated as possible alternatives to the discharge coefficient concept.

27-40

Authors: Saeed Abu Alyazeed Albatlan

In particular, a commercial vehicle may meet critical braking conditions when the vehicle is partially or fully loaded, and when the road is wet or slippery. Under these conditions, the vehicle can spin out, the tractor can jackknife or the trailer can swing out. The air brake system has many design variables; there must be intense research on a method on how to prevent dynamic instability and how to maximize vehicle deceleration. So; some of the commercial vehicles are provided with the combination valve. The behavior of this valve is important to improve the braking performance. In this study, mathematical models and a computer simulation program is used to evaluate the valve and vehicle braking performance characteristics. The measurements performed on the valve using the test rig concord with mathematical model.

69-89

Authors: Miroslav Demić, Jovanka Lukić, Živorad Milić

Investigations of a human body behavior exposed to whole body vibration of vehicles are important in design phase of vehicles. Results make possible to model human vehicle oscillatory system and vehicle parameter optimization from ride comfort aspects. Experimental results of investigations of motor vehicles users vibratory loads (passengers and duty) depending on operational conditions (road surface, vehicle speed). Obtained results were base for further investigation of human body behavior exposed to whole body vibrations in laboratory conditions.