Application of aluminium hybrid composites in automotive industry

Pooštravanje konstrukcijskih zahtjeva s aspekta povećanja radnog vijeka i smanjenja mase, a samim tim i cijene konstrukcije, iniciralo je razvoj i primjenu novih materijala s osnovom od lakih metala. Kompoziti s metalnom matricom nalaze sve veću primjenu pri izradi košuljica cilindara motora, klipova, kočionih diskova i doboša, kardanskih vratila kao i drugih dijelova u automobilskoj i avio industriji. Posebno mjesto, od svih metalnih materijala, zauzimaju kompoziti na osnovi legure aluminija zbog niza dobrih svojstava. Poboljšanje mehaničkih, a posebice triboloških karakteristika hibridnih kompozita moguće je uporabom određenih ojačivača, najčešće SiC, Al2O3 i grafita, u odgovarajućem masenom ili volumenskom udjelu. Novodobiveni hibridni kompoziti s aluminijskom osnovom imaju znatno povećanu otpornost na habanje, povećanu specifičnu krutost i povećanu otpornost na zamor. Povećanjem količine proizvedenih dijelova od aluminijskih kompozitnih materijala dolazi do smanjenja cijene ovih dijelova, što dodatno povećava područje njihove primjene. U radu su prikazani primjeri primjene aluminijskih hibridnih kompozita s osvrtom i težištem na automobilskoj industriji.Strict requirements that are put on mechanical constructions from the aspect of increase of exploitation periods and reduction of their weights, therefore of their prices as well, implicate developments and applications of new composite materials with matrices of lightweight metals. Composite materials with metal matrices are used for engine cylinders, pistons, disc and drum brakes, Cardan shafts and for other elements in automotive and aviation industry. The most important type of metallic materials is composite materials with matrices of aluminium alloys due to a set of their beneficial properties. Improvement of mechanical, especially tribological properties of hybrid composites were provided by the use of certain reinforce materials such as SiC, Al2O3 and graphite in defined weight or volumetric share. New developed hybrid composites with aluminium matrices have significantly higher resistance to wear, higher specific stiffness and higher resistance to fatigue. By the increase of quantities of produced elements made of hybrid composites, decrease of their prices is induced that even further enlarge their applications. The applications of aluminium hybrid composites are considered from the aspect and with the focus on automotive industry

Biomimetics design for tribological applications

Biomimetics, biomimicry and bionics are synonyms for the scientific discipline of creating new structures inspired by nature. Biomimetics systematically analyses the evolutionary processes of living organisms, their structural relationships, the characteristics of natural materials and it studies how this knowledge can be used to create the optimal products and new sustainable materials. In the past decade, the biomimetics has received an incentive for the development by the technology modernization, and above all, by making it possible to study the micro-and nanolevels of biological structures. On the other hand, the miniaturization of technological devices has increased the need to understand the tribological phenomena on micro-and nanolevel, where is a huge potential for technological innovation. The integration of advanced research methods made it possible to discover new aspects in the structure and properties of biological materials and transfer that knowledge into new concepts or products. State-of-the-art of biomimetics progress is discussed, as well as, its goals and the potential to simultaneously achieve the financial and ecological contribution by realization of bio-inspired concepts. An overview of biomimetic researches is also provided, with special emphasis on the possibility of their tribological applications. The characteristic examples have been presented and those examples show how the structural and mechanical properties of the material were used as the basis for developing new creative solutions to solve the problem of friction in engineering applications

Biomimetics design for tribological applications

Biomimetics, biomimicry and bionics are synonyms for the scientific discipline of creating new structures inspired by nature. Biomimetics systematically analyses the evolutionary processes of living organisms, their structural relationships, the characteristics of natural materials and it studies how this knowledge can be used to create the optimal products and new sustainable materials. In the past decade, the biomimetics has received an incentive for the development by the technology modernization, and above all, by making it possible to study the micro-and nanolevels of biological structures. On the other hand, the miniaturization of technological devices has increased the need to understand the tribological phenomena on micro-and nanolevel, where is a huge potential for technological innovation. The integration of advanced research methods made it possible to discover new aspects in the structure and properties of biological materials and transfer that knowledge into new concepts or products. State-of-the-art of biomimetics progress is discussed, as well as, its goals and the potential to simultaneously achieve the financial and ecological contribution by realization of bio-inspired concepts. An overview of biomimetic researches is also provided, with special emphasis on the possibility of their tribological applications. The characteristic examples have been presented and those examples show how the structural and mechanical properties of the material were used as the basis for developing new creative solutions to solve the problem of friction in engineering applications

Oblikovanje krstaste osovine sa aspekta nosivosti

To ensure the quality of mechanical parts it is necessary to fulfill the basic constructional requirements that are related to the form, function, material and manufacturing procedure. Form of mechanical parts is the result of adjusting all of those requirements, and the task of constructor is the development of forms with the aim of finding the best solution. This paper describes the procedure to determine the effect of geometry changes to stress level in cross shaft Cardan joint. The task of the Cardan joint is mechanical transmission of power and motion between shafts that are changing the position of axis in the process of exploitation and are placed by a certain angle. Cross shaft is one of the most important parts of the Cardan joint. In most cases the size and lifetime depend on the Cardan joint from the cross shaft. The critical stress at the cross shaft was calculated by analytic method and tested by numerical simulation. It is shown how small changes in geometry of cross shaft can lead to a significant reduction in critical stress. By the means of iterative correction of form and repetition of the numerical calculation of stress, favorable ration between the geometry of cross shaft and extreme values of stress has been obtained

Analysis of impact of shaft speed and external load on the radial ball bearing lubrication regimes

Potrebno je odgovarajuće podmazivanje kotrljajućeg ležaja kako bi se smanjilo trenje između površina u međusobnom kontaktu i njihovo habanje. Mazivo bi trebalo da u potpunosti odvoji kotrljajuće elemente od staza. U radu su analizirane vrednosti koje utiču na efikasnost i režime podmazivanja, nakon čega se uvodi koeficijent režima podmazivanja. Ovaj koeficijent omogućava da se na jednostavan i brz način odabere optimalna kombinacija kotrljajućeg ležaja i maziva na osnovu poznate brzine osovine, spoljašnjeg opterećenja i radne temperature kotrljajućeg ležaja. Za pojedine ležajeve sa radijalnim kontaktom i određena maziva prikazana je zavisnost režima podmazivanja od brzine osovine i kontaktnog opterećenja.Appropriate lubrication of the rolling bearing is needed to lower the friction between the surfaces in mutual contact and their wear. A lubricant should completely separate the rolling elements from the raceways. The values that affect the efficiency and regimes of lubrication are analyzed in the paper, after which it is introduced a lubrication regime coefficient. This coefficient makes it possible to choose in a simple and fast manner an optimum combination of rolling bearing and lubricant based on the known shaft speed, external load, and rolling bearing operating temperature. For certain bearings with radial contact and certain lubricants, the lubrication regime dependence on the shaft speed and contact load is shown

Correlation between Emission and Combustion Characteristics with the Compression Ratio and Fuel Injection Timing in Tribologically Optimized Diesel Engine

Diesel engines are economical thanks to their combustion process characteristics, which is why they have a high noise emission level as well as exhaust emissions of nitrogen oxide and particulate matters. By continuously changing the value of compression ratio, it is possible to control the power and emissions. Implementation of variable compression ratio has many benefits, such as being able to work with different types of fuel. In this way, it is possible to optimize the combustion process for operation with minimum fuel consumption and emission generation, so that diesel engines can be applied to the framework of future hybrid vehicle concepts, and so forth. As far as the crucial objective of the manuscript is concerned, experimental diesel engine investigation was performed on a roller test-bench by using zero-dimensional computer model (specifically AVL IndiCom Indicate Software). Engine indication was executed with the factory compression ratio value and with three lower values. During our examination, the change in the compression ratio value was achieved by changing the volume of a combustion chamber at a piston-bowl. The results of laboratory research on the experimental engine are presented in the paper when discussing a series of specific parameters (characteristics), such as compression ratio, fuel injection timing, engine speed, as well as load influence on combustion process and exhaust emissions

IMPACT TOUGHNESS OF HIGH-STRENGTH LOW-ALLOY STEEL WELDED JOINTS

Impact toughness of samples with three different relative positions of V-notch and multipass V- butt welded joint at high-strength low-alloy steel S690 are considered in this paper. The aim of this paper is to analyze the influence of material degradation due to welding to impact toughness of samples made of considered steel. Impact toughness was analyzed by experimental approach objected to including as many influential factors as it is possible. The main objective of impact toughness testing is to evaluate the influence of welding to overall load capacity and stability of welded mechanical construction made of high-strength low-alloy steels. Fully understanding of transformation processes provoked by welding of high-strength low-alloy steels and impact toughness testing as resulting property of those processes are crucial to perform integrity, safety and reliability analysis. This paper pointed out the necessity of analyzing the welded constructions on different dimension levels. Further investigations in this area have to be a continued through more quantitative analysis of welded joints which will, established precise analytical model of zones of welded joints, and furthermore, in involvement with adequate software, a complete evaluation of the experimentally obtained results. As experimentally obtained results of impact toughness that correlate to microstructure and microhardness distribution implicated that development of those steels must be followed with improving weld processes and development, adjusting and modification of the design

Wear of A356/Al2O3 nanocomposites and optimisation of material and operating parameters

The aim of this study was optimization of wear of nanocomposites with A356 alloy as a matrix. Different percentages of Al2O3 particles (0.2, 0.3 and 0.5 wt. %), with two average size (25 and 100 nm), were dispersed in the A356 matrix and fabricated by compocasting process. The tribological tests were conducted by the orthogonal L24 matrix. By application of the RSM method, a mathematical model was developed that best describes wear dependence on the observed factors and it was found that all considered factors have a significant impact on the wear of nanocomposite

Solving the Problem of Friction and Wear in Auxiliary Devices of Internal Combustion Engines on the Example of Reciprocating Air Compressor for Vehicles

Using vehicles and other mobile systems to transport passengers and goods, approximately 25% of Europe\u27s greenhouse gases are generated. At the same time, many research papers, published by researchers and students, promote the use of electric vehicles as zero-emission vehicles. Given that, more broadly, the emission of electric vehicles is higher, especially in countries where electricity is obtained by burning coal, the use of internal-combustion engines is still dominant. There are other reasons for using an internal-combustion engine, such as already developed pumping station infrastructure, which is not the case when recharging electric vehicles. Improvements in engine design contribute to meet the regulations relating to the fuel consumption and toxic gas emissions. This refers to the use of alternative fuels, improving the combustion process, and increasing efficiency (efficiency coefficient) by reducing losses. The research is focused on the problem of friction and wear in internal combustion engines and reciprocating air compressors, as auxiliary devices on engines. For that purpose, construction of the reciprocating air compressor in motor vehicles was redesigned. The paper presents the characteristic test results of material used to strengthen liner of the aluminum cylinder. Specifically, a method for testing the performance characteristics of a single-cylinder reciprocating compressor inside of an experimental installation for compressed air supply has also been proposed

Cross shaft design from the aspect of capacity

A cross shaft is one of the most important parts of the Cardan joint. In most cases, the size and lifetime of the Cardan joint depend on the cross shaft. To ensure the quality of mechanical parts, it is necessary to fulfill the basic constructional requirements related to the form, function, material and manufacturing procedure. The form of mechanical parts is the result of adjusting all of these requirements, and the task of a constructor is to develop forms with the aim of finding the best solution. This paper describes the procedure of determining the effect of geometry changes on the stress level in the cross shaft of the Cardan joint. The task of the Cardan joint is mechanical transmission of power and motion between shafts that change the position of their axes in the process of exploitation or are placed at a certain angle. The critical stress at the cross shaft was calculated by the analytical method and tested by a numerical solution. It is shown how small changes in the geometry of the cross shaft can lead to a significant reduction of critical stress. The most favorable ratio between the geometry of the cross shaft and the extreme stress values has been obtained by the means of the iterative correction of the form and the repetition of the numerical stress calculation