Trans Motauto World
Vol. 11 (2026), Issue 1

Table of Contents

  • TRANSPORT TECHNICS. INVESTIGATION OF ELEMENTS. RELIABILITY

    • Using laser surface microtexturing to improve tribological properties of surfaces

      pg(s) 3-7

      Tribological properties of functional surfaces are a key factor influencing the durability, reliability and efficiency of mechanical systems. One of the progressive approaches to surface modification is laser surface microtexturing, which allows for the precise creation of controlled microstructures capable of modifying contact conditions and lubricant retention at tribological interfaces. This article focuses on the application of laser-induced surface microtexturing to improve the tribological performance of hard nanocomposite coatings nACRo³ and nACRo⁴. The experimental part of the research is dedicated to the preparation of microtextures on the substrate surface using a pulsed laser system, followed by the deposition of nanocomposite coatings nACRo³ and nACRo⁴. The created microstructures are characterized in terms of their geometry, distribution and influence on the contact properties of the coated surfaces. The wettability of the microtextured surfaces was evaluated based on the measurement of the contact angle. Optimizing surface microtexture is an effective way to increase wettability and potentially improve lubrication conditions during technological processes of forming or tribological loading of materials.
      Keywords: laser surface texturing, tribology, nanocomposite coating, wettability, contact angle, PVD coating, tool steel, die casting

    • Application possibilities of ultrasonic testing for quality control of resistance spot welds in the automotive industry

      pg(s) 8-12

      This study investigates the application possibilities of ultrasonic testing for quality control of resistance spot welds used in the automotive industry. Experimental resistance spot welds were produced on galvanized DP600 and H420LAD steel sheets using different welding current values. The weld quality was evaluated by metallographic analysis, EDX surface analysis and several ultrasonic testing approaches, including automatic C-scan evaluation and manual A-scan interpretation. The obtained ultrasonic results were correlated with metallographic observations and macrostructural characteristics of welded joints to assess the sensitivity of ultrasonic methods for detecting weld imperfections and evaluating weld nugget formation. The results confirmed that welding current significantly influences weld geometry, weld nugget formation and the occurrence of internal defects. Among the samples investigated, the most acceptable weld quality was achieved at a welding current of 7.6 kA for both investigated steel grades. The study also demonstrated the potential of advanced ultrasonic testing methods for rapid and reliable non-destructive inspection of resistance spot welds in automotive manufacturing.

    • Comparative thermo-mechanical severity assessment of automotive brake discs under repeated braking cycles

      pg(s) 13-16

      This paper presents a comparative finite element assessment of the thermo-mechanical severity of automotive brake discs for Mercedes-Benz A180, E220 and E350 under intensive and repeated braking cycles. Transient thermal and structural simulations were evaluated for 27 cases covering high-speed, interurban and urban braking profiles. Gray cast iron EN-GJL-250/G3000 was used as the disc material, while heat flux, convection and radiation were considered as thermal boundary conditions. Maximum temperature, heat flux, total elastic deformation and von Mises stress were normalised and combined through several severity-index scenarios. The results show that the repeated 120-0-120-0 km/h braking cycle is the governing condition for all vehicles. A180 reached the highest raw temperature, stress and deformation, while the equal-weight severity indices confirmed the same critical braking profile within each vehicle group. All cases remained below the selected thermal and mechanical limits.

    • Implementation of Composite Materials into the Design of an Experimental Vehicle for the Shell Eco-Marathon Competition

      pg(s) 17-20

      The current optimization of materials in the automotive industry is primarily driven by the objective of progressively reducing vehicle curb weight, which serves as a critical instrument for lowering greenhouse gas emissions and enhancing energy efficiency. Empirical data demonstrate a direct correlation between weight reduction and fuel consumption: a 10% decrease in vehicle mass generates an approximate 7% reduction in fuel consumption. Composite materials, defined as heterogeneous systems consisting of at least two components—a continuous matrix (binder) and a discontinuous reinforcement (fibers, particles, or layers)—enable a synergistic effect of mechanical properties that are unattainable with monolithic metallic materials. In structural applications, polymer matrices (including both thermosets and thermoplastics) predominate in combination with high-strength carbon, aramid, or glass fiber reinforcements. These material systems exhibit extreme specific strength, a high modulus of elasticity, fatigue resistance, and anisotropic properties that allow for the directional optimization of stiffness. For components requiring maximum dimensional stability and self-supporting (monocoque) capabilities, sandwich configurations are utilized, typically integrating an aramid honeycomb core between high-performance composite face sheets. The qualitative parameters of the resulting components are directly dependent on the chosen manufacturing technology and the fiber-to-resin ratio. The Vacuum Infusion (VI) method represents a highly efficient process in which a vacuum-sealed mold ensures the uniform saturation of dry reinforcement with liquid resin. This procedure minimizes porosity, achieves a high fiber volume fraction—reaching up to 70% in advanced systems—and guarantees high production reproducibility and surface quality without the need for secondary machining. Despite their technical superiority, the primary limiting factors for widespread implementation remain the high economic cost of raw materials and the complexity of manufacturing cycles. Prospective development is focused on streamlining processes for mass production, implementing sustainable bio-fibers as reinforcing components, and addressing the challenges of recyclability and component replacement at the end of the life cycle. Advanced composite structures thus form the essential material foundation for the next generation of ultra-lightweight and safe transport vehicles.

    • Operation guidelines for proper arrangement of pumps in the marine steam propulsion system

      pg(s) 21-25

      : In this paper are investigated and presented the most influential operating parameters and the guidelines for proper arrangement of pumps in the condensing/feedwater heating system. The observed system operates in marine steam propulsion power plant. In the analyzed system operates three pumps: Condensate Pump (CP), Auxiliary Pump (AP) and FeedWater Pump (FWP). Considering all observed pumps, FWP is the dominant mechanical power consumer because it operates with the highest pressure difference and with the highest fluid mass flow rate. Used mechanical power and losses (energy and exergy) of all observed pumps are directly proportional to fluid mass flow rate through the pump – higher fluid mass flow rate through the pump will result with higher mechanical power used by pump and with higher losses (both energy and exergy) and vice versa. Energy and exergy efficiencies of the observed pumps have reverse proportional trends. The most influencing factor related to the pump efficiency (both energy and exergy) is the pump inlet pressure. Pump inlet pressure is directly proportional to the pump exergy efficiency, but simultaneously pump inlet pressure is reverse proportional to pump energy efficiency.

    • Mesh-Converged Modal Profile Assessment of Functionally Graded Spur Gears

      pg(s) 25-27

      This study presents a mesh-converged finite element assessment of functionally graded spur gears. Two gear models are studied: a fully graded gear and a half-metal/half-graded gear. The material properties vary gradually from aluminum alloy to zirconia according to power-law distribution. The modal analysis is carried out in ANSYS using SOLID187 elements and the Block Lanczos method. A mesh-convergence study is performed, and a 0.25 mm mesh is adopted for the results. The study compares the natural frequencies and normalized mode-shape profiles of the two models. The results show how the material layout influences the vibration behavior of the gear.

  • TRANSPORT. SAFETY AND ECOLOGY. LOGISTICS AND MANAGEMENT

    • Traffic safety in Serbia and automotive industry today

      pg(s) 28-29

      According to a new study by the most influential European consumer association BEUC, new mid-size electric vehicles will generally be cheaper to run than their petrol equivalents as early as 2026, while in 2025 “Sandero” became the best-selling car in Europe. Small city electric cars are forecast to be cheaper only from 2026. However, the EU is abandoning its plan to make all cars electric by 2035. “Ford” is radically reducing investments in electric vehicles – weak demand in the US is also cited.
      Chinese Technology giant Xiaomi is testing a factory of the future where humanoid robots are helping to assemble electric cars at a factory in Beijing. In November 2025, Peugeot changes the rules – the beginning of a new era for drivers – the square steering wheel!
      It is interesting that the Chinese company Changan is entering the market of Serbia and the Western Balkans by launching the Deepal So5 and So7 models. These are electric SUV models, and in our city of Belgrade, test drives of these cars are already being scheduled.
      In 2026 production of the “Grande Panda” with a gasoline engine has begun in Kragujevac.
      In February 2026, the most urban electric car for 2025 was announced, and it was the Byd Dolphin Surf. It was also promoted in Belgrade, Serbia. Serbia was also the first country in Europe to sign an agreement with the American manufacturer of flying taxis, Archer Aviation. The first demonstration flights are expected in 2027, during the specialized exhibition EXPO.
      Unfortunately, on our roads in Serbıa we had the black month of March 2026. In the first 12 days of the third month, 19 people died in traffic accidents, most of them young people. Since the beginning of the year, 120 people have lost their lives in traffic accidents. (The Traffic Safety Agency).
      How to prevent traffic tragedies in our country? Caution is essential for all road users. Smart radars should contribute to compliance with regulations. Recently, stationary radars were installed at a total of 30 “black spots”. It is expected that they will significantly improve traffic safety.

    • Technical validity of motorcycles and mopeds as a factor of road safety in the Republic of Croatia

      pg(s) 30-34

      This paper examines the technical validity of motorcycles and mopeds registered in the Republic of Croatia as a factor of road safety, analysing data from the Centre for Vehicles of Croatia (CVH) for the period 2023–2025. The study focuses on three dimensions: the age structure of the registered L category vehicle fleet, aggregate periodic technical inspection (PTI) defect data for all L category vehicles in 2025, and disaggregated inspection outcomes for L1 (mopeds) and L3 (motorcycles) subcategories. Results indicate that the Croatian PTW fleet is structurally aged, with over 57% of vehicles exceeding ten years of age in 2025. The overall PTI failure rate stands at 8,28%, with mopeds recording a substantially higher rate of 10,79% compared to 6,73% for motorcycles. The most prevalent defect categories are lighting and signalling devices (32,64%) and tires and suspension (25,15%). The findings highlight the need for strengthened PTI enforcement and targeted public awareness campaigns.

    • Determining the use indicators of the wagon vehicle and improving the efficiency of the transportation process

      pg(s) 35-41

      The primary function of the Azerbaijan Railways wagon fleet is to ensure the transportation process is continuously supplied with serviceable and operational wagons. Given the continuous growth in transit freight volumes along international transport routes passing through our country, Azerbaijan Railways CJSC successfully continues to modernize and expand its wagon fleet to ensure the efficient and safe transportation of goods. To this end, studying the wagon fleet structure, analyzing optimal wagon fleet utilization indicators, and determining the required number of wagon fleets are currently considered pressing issues. Accordingly, determining the structure of wagons within and outside the railway wagon fleet is of particular importance. Accounting for freight wagon fleets is crucial for regulating, standardizing, and utilizing the wagon fleet for its intended purpose in managing rail transport to meet the needs of the national economy for freight and passenger transportation. The operating freight car fleet includes both local cars operated by Azerbaijan Railways CJSC and transit freight cars from abroad located on the tracks of industrial enterprises. Efficient use of the freight car fleet is an important factor influencing the operational performance, cost structure, and service reliability of rail transport systems. This study develops a comprehensive methodological framework for determining the efficiency of the freight car fleet and proposes an integrated performance assessment model. Key performance indicators, including car turnaround time, technical availability, load factor, downtime rate, and daily productivity, are analytically formalized. An integrated performance function is proposed for assessing overall operational efficiency. The results demonstrate that reducing turnaround time, minimizing downtime, increasing technical availability, and implementing digital fleet management systems significantly improve the efficiency of rail freight transportation. The proposed model can be applied to comparative analysis, strategic planning, and optimization of rail crew work at railway enterprises

  • VEHICLE ENGINES. APPLICATION OF FUELS TYPES. EFFICIENCY

    • Prospects for the use of liquefied gas in marine diesel engines

      pg(s) 41-44

      the paper discusses the preparation of a fuel mixture consisting of liquefied gas and diesel fuel in marine diesel engines through the implementation of the gas–diesel process, where diesel fuel is used as pilot fuel. This approach reduces the ignition delay period compared to conventional liquid fuels, shortens combustion duration, and extends the flammability limits of the working mixture. Improved mixture formation leads to an increase in combustion rate and more complete combustion during the active combustion phase, causing the engine cycle to approach the Otto cycle. As a result, the environmental and performance characteristics of the diesel engine are significantly improved compared to conventional diesel and standard gas–diesel engines. The paper also analyzes the dependence of ignition delay on combustion parameters and fuel injection timing.

    • Piston secondary dynamics and their effect on blow-by, friction and power loss.

      pg(s) 45-49

      In this paper the effect of the piston secondary dynamics was investigated. The piston secondary dynamics comprises the rotation around the pin axis and the translation of the piston body between the two sides of the liner. The most prominent situation of this motion arises on diesel engines. For this purpose ©Ricardo RINGPACK simulation suite was used to simulate the behavior of the piston and rings of a turbodiesel engine. In particular, three aspects of the work of the engine were analysed: Gas blow-by, friction and power losses of the pack. In order to detect the magnitude of the secondary dynamics of the piston, the engine was simulated in two conditions, with and without the secondary motions of the piston. According to results, the rings of a piston without the secondary motion, maintain a more stable position in relation with the piston groove and are more able to prevent gas flows. Furthermore, the secondary motions elimination seems to decrease the friction between components and thus to slightly improve the power loss of the assembly, although at a smaller magnitude with respect to the blow-by gasses.