Table of Contents


    • Simulation of the hobbing process of enveloping wormwheels for the calculation of contact pattern and contact lines

      pg(s) 3-6

      The contact pattern and contact line calculation is an essential part of the design of worm gears. The existing calculation algorithms are based on the law of gearing. For this reason, cases like meshing interferences can only be analysed to a limited extent. The simulation of the hobbing process of enveloping wormwheels, introduced here, makes it possible to generate any wheel flank precisely. For the contact pattern calculation, one wheel flank is generated from the cutter geometry and one from the worm geometry. These two generated flanks are brought into contact. For each flank coordinate, the distance to the opposite flank is obtained. The graphical
      application of this distance over the wheel coordinates results in a contour diagram that is known as the contact pattern. The contact linecalculation of worm gears also shows on which part of the flanks power is transmitted at a certain rotational position. For this calculation, the wheel flank generated from the cutter is brought into contact with the worm flank at any angular positions.

    • The vehicle that can move on an accidental field

      pg(s) 7-10

      The designed vehicle can move on rough terrain (with multiple bumps); also (the vehicle) can climb a sloping terrain (with a relatively large angle).
      The movement (of the vehicle) is not continuous; contact with the ground (tread) takes place periodically, simulating the steps taken by a moving man; this movement is obtained by generating a hypocycloid.
      The vehicle will move with the help of four wheels; they (wheels) will lift and move the vehicle when they come in contact wi th the road (ground).

    • Determination of the quality of welds produced by robotic welding

      pg(s) 11-14

      The paper focuses on the evaluation of the quality of fillet welds produced robotically by the method of impulse synergic welding MAG. This welding technology is used in the automotive industry in the production of rear seat backs for passenger cars. In the process of automated production, the speed of the process, accuracy, and quality of the made joints are important. Several factors affect the accuracy and quality of welded joints. The paper presents the results of research where the influence of filleting of fillet welds on their quality was confirmed. Visual and capillary methods were used to determine the quality of welds, metallographic analysis for evaluation depth of weld root penetration, strength properties of welds were evaluated by static tensile test. Statistical ANOVA methods were used to process the obtained values. Experimental work confirmed that the depth of welding of the weld root into the base material has the greatest influence on the final quality of fillet welds. It is this parameter that results in the elimination of the weld and thus the entire produ ct.

    • Research on loading-transport machine parts in order to determine the causes of defects

      pg(s) 15-18

      Possible defects in the system: piston-cooling jacket occur for various reasons. This system work in severe conditions: heat load; variable gas pressure and mechanical friction, which requires high strength, good wear resistance with limited lubrication and overall high resistance to abrasion, corrosion and other wear.The operation of the cylinder-piston group with insufficient or poor quality oil is the most common cause of overheating or engine blockage. Seizing of one or more pistons leads to major engine repairs or even scrappin g. Damaged fuel injectors, inaccurate injection or ignition timing can also cause the mechanism to melt or puncture. Therefore, it is essential to identify the exact causes of defects in the system and look for ways to prevent them.
      Studied details were functioned under the identical conditions of good lubrication and no overheating. The reason, apart from the ones mentioned above, which led to their destruction, has been established.


    • Influencing factors on the speed of vehicles in the school and kindergarten zones on the territory of Novi Sad

      pg(s) 19-21

      Pedestrians, in addition to cyclists, represent the most vulnerable road users. Children from an early age participate in tra ffic as pedestrians, so the need to increase their level of safety is understandable. The speed limit in a school and kindergarten zones, by installing different types of calming measures, is one of the measures applied to protect children in traffic. It often happens that despite the speed limit and placement of speed humps on the roads, drivers do not respect the speed of movement and move at a much higher speed than allowed. Within this work, the speed of vehicles in the zones of some schools and kindergartens in the area of Novi Sad was measured. Based on the obtained results, factors that have an impact on the regime of vehicle movement in the investigated areas have been identified.

    • Use of innovative methods in the management of tourist transport infrastructure

      pg(s) 22-24

      In many countries in the world, including Georgia, tourism has become one of the leading sectors of the country’s economy and a source of raising public finance. Tourism is recognized as one of the priority areas for the development of the Georgian economy and contributes to the socio-economic development of the country. In particular, it is important to explore the existing tourism transport infrastructure and introduce the innovative technologies in its management. The paper describes some innovative methods whose use will contribute to the development of tourism in Georgia and will significantly increase the attraction of visitors.

    • Decade of road markings and traffic signs quality testing in Croatia

      pg(s) 25-29

      With more than 1.35 million fatalities worldwide each year, road crashes are among the world’s most significant public health and injury prevention problems. In the last decade, with the new technological breakthroughs, a significant effort has been devoted to improving different safety systems related to infrastructure and vehicles. Road marking and road signs represent main road elements whose main task is to provide timely and necessary information to the drivers related to the upcoming situation. In other words, they warn and inform drivers about the conditions and construction characteristics of the road, guide road users through the traffic network and regulate traffic in a safe way. Therefore, continuous monitoring and testing of their quality is of great importance for road safety in general. The a im of this paper is to present Croatian experience regarding the quality testing of road markings and signs in last decade. Overall, the analysis confirmed that systematic control of road markings and signs will positively affect their quality and optimize maintenance activities

    • The impact of COV – 19 pandemic on use of public transport in selected city in Slovakia

      pg(s) 30-34

      The aim of the article was to analyze the impact of lockdowns carried out during the Covid-19 pandemic in Slovakia in the years 2020 and 2021 on changes in public transport utilization in a selected locality. The sample city was the city of Košice in Slovakia and the sample contained data about the number of transported persons by public transport in this city during single days in the years 2018, 2019, 2020, 2021.
      We created weekly time series from line graphs compiled for separate years. Subsequently, we analyzed the dynamics of individual time series using calculations of absolute and relative increments, basic indices, growth coefficients, absolute increment and total growth coefficient, and we modeled trends in time analysis and exponential adjustment for the observed years. We compared the years before the pandemic (2018, 2019) with the years most affected by the Corona crisis (2020, 2021). We evaluated the obtained data in the context of the timeline of ongoing lockdowns.


    • Development of an 1D simulation model to optimize performance and emissions of large gas engines

      pg(s) 35-38

      The main subject of this paper is the development of a multicylinder engine model for the prediction and optimization of engine performance based on one-dimensional (1D) simulation. 1D simulation is widely used to preoptimize engine geometry and operating parameters to achieve performance targets and comply with operational and emission constraints. Due to the short calculation times, 1D simulation allows the evaluation of a larger number of variants. As new engine concepts are developed, many operating parameters are first defined and optimized with a 1D multicylinder engine model. This model illustrates the full complexity of the engine with its geometry, turbocharging and combustion parameters. In this paper the design of experiments (DoE) method is used in connection with 1D simulation to determine the optimal engine configuration as well as parameters related to the combustion process, i.e., valve timing, compression ratio, ignition timing, excess air ratio. This approach enables the determination of the maximum engine efficiency while taking the boundary conditions and the constraints of nitrogen oxide emissions (NOx) and knock into account. The method also enables the reduction of the cylinder-to-cylinder deviations by improving the gas dynamics and the fuel metering in the main combustion chamber and in the prechamber, which is especially important for the multicylinder engine. The simulation results are validated with experimental investigations on a single cylinder research engine.

    • Methane number influence on the dual fuel four stroke marine engine performance at high load range

      pg(s) 39-41

      In the present publication it is considered the technology and the features of the operation of the newly introduced in the marine industry wide spreading dual fuel four stroke engines. There are analysed the significant differences between the conventional Diesel engines and the dual fuel Otto engines in their operation process. The influence of the gas fuel quality in the case of the dual fuel engines is in the main concern underlined. Simulation based experiment is carried out for data attaining, related to the performance of the dual fuel engines influenced by the fuel quality on high load range. The acquired data is analysed, and evaluation of the engine derating outcome is performed. On the base of the results are stated conclusions and recommendations to be followed by the engineering crew members dealing with such kind of engines on board LNG fuelled ships.