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

Reasoning with linguistic preferences using NPN logic

Negative-positive-neutral logic provides an alternative framework for fuzzy cognitive maps development and decision analysis. This paper reviews basic notion of NPN logic and NPN relations and proposes adaptive approach to causality weights assessment. It employs linguistic models of causality weights activated by measurement-based fuzzy cognitive maps' concepts values. These models allow for quasi-dynamical adaptation to the change of concepts values, providing deeper understanding of possible side effects. Since in the real-world environments almost every decision has its consequences, presenting very valuable portion of information upon which we also make our decisions, the knowledge about the side effects enables more reliable decision analysis and directs actions of decision maker

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

Surface texturing for tribological applications: a review

Surface texturing is one of the surface modification techniques which deliberately change the texture of the surface, in order to improve, among other things, its tribological performance. This is obtained through different patterns, which can be on micro or nano scale, created on the contact surfaces. The performance of a textured surface depends on the shape, geometry and pattern of the surface texture and the operating condition of the components in contact. There is a number of various techniques for surface texturing, among which laser surface texturing is most often used. The different surface texture shapes, different textured area ratios and patterns, different lubrication regimes with different contact geometries and materials have been subject of theoretical and experimental research for many years. This paper reviews the state-of-the-art of researches that consider various surface texturing for tribological application, as well as its effect on performance enhancement. Conclusions of this paper may provide guidance for optimal design of surface textures in practical engineering applications

Surface texturing for tribological applications: a review

Surface texturing is one of the surface modification techniques which deliberately change the texture of the surface, in order to improve, among other things, its tribological performance. This is obtained through different patterns, which can be on micro or nano scale, created on the contact surfaces. The performance of a textured surface depends on the shape, geometry and pattern of the surface texture and the operating condition of the components in contact. There is a number of various techniques for surface texturing, among which laser surface texturing is most often used. The different surface texture shapes, different textured area ratios and patterns, different lubrication regimes with different contact geometries and materials have been subject of theoretical and experimental research for many years. This paper reviews the state-of-the-art of researches that consider various surface texturing for tribological application, as well as its effect on performance enhancement. Conclusions of this paper may provide guidance for optimal design of surface textures in practical engineering applications

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

The influence of temperature on mechanical properties of the base material (BM) and welded joint (WJ) made of steel S690QL

This paper presents the analysis of the influence of temperature on mechanic properties of the base material and welded joints made of high strength steel. The joints were welded on S690QL high strength steel plates using the Metal Active Gas (MAG) Welding and two filler materials of different properties. Since the steel S690QL belongs to a group of steels with high strength, the aim of this paper is to determine the temperature at which strength starts to decrease. Experimental tensile testings of the welded joints were performed at five different temperatures in the range from 20 to 550 °C

The influence of temperature on mechanical properties of the base material (BM) and welded joint (WJ) made of steel S690QL

This paper presents the analysis of the influence of temperature on mechanic properties of the base material and welded joints made of high strength steel. The joints were welded on S690QL high strength steel plates using the Metal Active Gas (MAG) Welding and two filler materials of different properties. Since the steel S690QL belongs to a group of steels with high strength, the aim of this paper is to determine the temperature at which strength starts to decrease. Experimental tensile testings of the welded joints were performed at five different temperatures in the range from 20 to 550 °C