Abstract. The present study defines criteria for evaluation of intermodal passenger and freight transportationintegrated railway and road transport (motorail trains and Ro-La trains). This type of transportation improves the efficiency of distribution in the supply chain. Two variants of criteria are studied in the paper -main and extended. The main criteria are divided into four groups: environmental, economic, technological and social. Eleven factors have been examined in the extended criteria: environmental, operating costs, transportation fares, infrastructure charges, duration of transportation, transportation from door to door, duration of transshipment operations, comfort, safety, reliability and stability. The method of multi-criteria analysis Decision Making Trial and the Evaluation Laboratory (DEMATEL) method have been applied to analyze the importance and the relations among the criteria. The summarized results of both variants are similar. They show that the economic criteria have the greatest impact. Operating costs are the key factor among the extended variant of criteria. Other criteria of great importance are also duration of transportation and transport from door to door. The defined criteria can be applied for the evaluation, comparison and selection the transportation with different modes of transport.
The paper presents a study of the vibrational behaviour of a car suspension in the frequency range from 50 to 200 Hz. The vehicle has a torsion spring suspension. The aim of the study is to provide a numerical approach, which evaluates the impact of the tyre vibration characteristics and the elastic properties of suspension elements on the vibrational behaviour of the “tyre-suspension-body” system. The object of the study are the elements of the suspension – stub-axle, upper and lower suspension arms, strut rod, torsion bar and others. The suspension is equipped with pneumatic tyres with different vibration characteristics. Laboratory experiments are done. The tyre contact patch is disturbed by harmonic force. The accelerations of the wheel axle and specific points of the suspension are obtained. A numerical model of the system is created by using the Finite Element Method available in SolidWorks Simulation software. The model allows to determinate the accelerations at different points of the suspension. The results of the experimental and theoretical studies are compared. The values obtained in the two studies are similar.
Abstract. This study presents a methodology for selection the route of a truck moving between two points by taking into account multiple factors relevant to transport. The evaluation criteria have been selected so that they take account into the infrastructure road conditions, geographic characteristics of the road, roadside conditions and the weather conditions, on the one hand, and fuel consumption, on the other hand. The study examines four main sets of criteria with fifteenth sub-criteria. As sub-criteria related to the main criteria we have selected the condition of the road surface, the longitudinal and transverse unevenness of the road, inclines on the road, number of turns, restaurants and petrol stations, and others. The methods of Analytic Hierarchy Process (AHP) and Cost/Benefits have been applied. The AHP method has been used to determine the weights of the criteria and sub-criteria, and the priorities of alternative routes. The Cost/Benefits method has been applied for the selection of the best route of a truck among the alternatives under study. The methodology has been tried out on two variants taking into account the meteorological conditions. The results show that the criterions of the infrastructure road conditions are of great importance. Sub-criteria of great importance are the condition of the road surface, longitudinal and transverse lumpiness of the road, sections of the road under repair, category of road, availability of places to take a rest and parking lots.The decision approach proposed in this paper was tested for a route selection among alternatives for the road network in Bulgaria. The proposed model can help transport managers enhance the effectiveness of the movement of vehicles.Keywords: AHP method, truck, transportation, route selection. IntroductionTransport processes in automotive companies require the choice of a route, according to the condition of the roads for carriage the goods according to the season. It is necessary for managers of transport companies to take decisions in any situation. These decisions are often made intuitively, on the basis of their experience. To choose the route of the truck between two points it is necessary to adopt a complex approach, which will assess the objective criteria.The multi-criteria decision-making approach Analytic Hierarchy Process (AHP) has been applied for best routes prioritization and selection. In [1; 2] the authors have studied the problem of multiplecriteria selection of the transportation mode of cargo. The four main criteria characterizing the efficiency of freight transportation and the transportation system, such as the cost for cargo delivery, time of delivery, reliability of cargo transportation and ecological impact, have been defined by the authors. For route selection they have used the AHP method. In [3] the authors examine criteria such as costs, time, risk of freight damage, risk of infrastructure and equipment, risk of other factors for multimodal routes selection. In [4] the AHP method is used to choose the best...
This article presents the results of experimental study of the influence of tire vertical load and tire internal pressure on tire cornering stiffness. The results have been obtained with a mobile tire tester which was developed at department “CEAET” at TU-SOFIA. The information about the dates of size load, index speed, index group, wearing out is obtained from Goodyear website, www.goodyear.eu. The study process concerns three main areas: (i) the choice of the experimental methodology; (ii) calculation and analysis of the data; (iii) discussion and conclusion. The obtained results give the possibility to determinate the role of tire on vehicle handling and stability.
I n t h i s work t h e v i b r a t o r y behaviour o f t h e f r o n t suspension o f a c a r i s i n v e s t i g a t e d . I n t h e system o f t h e suspension a pneumatic t y r e i s a l s o included, as a v i b r o a c t i v e element i n t h e considered frequency range 50 -200 Hz. A plane mathematical model o f t h e considered system has been made, which i s described by d i f f e r e n t i a l equations. An account has been g i v e n o f t h e i n f l u e n c e o f t h e e l a s t i c and damping p r o p e r t i e s o f t h e rubber v i b r o i s o l a t o r s , t h e e l a s t i c p r o p e r t i e s o f t h e l i n k s and t h e geometry o f t h e suspension. I n a u n i t y t h e behaviour o f t h e separate elements as s o l i d bodies and such w i t h d i s t r i b u t e d masses i s studied. A p e r i o d i c d i s t u r b i n g power i n t h e c o n t a c t area between t h e t y r e and t h e road i s included. By making t h e system o f t h e d i f f e r e n t i a l equations l i n e a r a system o f non-homogeneous equations i s obtained.
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