International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

With the development of the world, innovative technologies are increasingly used for the purpose of faster, higher quality and cheaper production of machine parts and household materials. Advantages and disadvantages of conventional and innovative production of metal and polymer products are presented, as well as the possibility of replacing metal parts with plastic ones. The mechanical parameters of different types of materials produced through traditional and innovative production are compared. The comparative analysis shows that both conventional and modern 3D manufacturing have their place in modern industry, taking into account all factors and applications.

Laser welding has become a highly effective technique for joining of metal sheets, offering precision and minimal thermal distortion. The quality of the welds, however, is significantly influenced by the proper selection and control of process parameters. This study focuses on the optimization of key parameters like laser power, welding speed, wire feed rate, and beam oscillation through experimental welding trials.
The practical part of the research involved welding thin sheets with LW-2000W device at various parameter settings, followed by visual inspection and metallographic analysis of the final welds. The findings provide insights into how parameter optimization can enhance consistency and overall process reliability, offering valuable guidelines for industrial applications where high precision is required.

The paper addresses the problem of designing 3D models of gears, how well the resulting involute profile corresponds to the real one. Very often are used 3d models of gears to produce various gears through 3d prototyping. Some of the most used CAD systems (Solid Works, Solid Edge or Autodesk Inventor) are used to design the 3D models. The comparative analysis made shows the accuracy of modelling the involute profile of the 3D models from different CAD systems compared to the real profile, what are the deviations and how suitable it is to use them for 3D prototyping of gears. Solutions are presented to obtain realistic gear tooth profiles.

The European Union’s REPowerEU strategy places green hydrogen at the center of its plan to eliminate fossil fuels and accelerate the green transition. The strategy targets 20 million tonnes (MTPA) of green hydrogen per year by 2030: 10 MTPA to be produced domestically and 10 MTPA imported. Achieving this requires scaling electrolysis capacity from the current 0.3 GW to 120 GW, a remarkably ambitious, if not unrealistic, target. Current green hydrogen production costs range from 100 to 200 €/MWh, several times higher than natural gas prices, which fluctuate between 20 and 40 €/MWh. In contrast, blue hydrogen, which is produced through natural gas reforming combined with carbon capture and storage (CCS), generally costs between 50 and 100 €/MWh. To bridge the cost gap between hydrogen and fossil fuels, the EU established the Hydrogen Bank with €3 billion to kick-start the market through competitive funding mechanisms. The REPowerEU hydrogen targets have drawn criticism due to limited availability of renewable electricity, underdeveloped infrastructure, and the slow pace of electrolysis deployment. Concerns also focus on the inefficiency of hydrogen use in sectors such as passenger transport, short sea shipping, residential and commercial heating, where direct electrification is significantly more effective. Nonetheless, the EU is advancing regulatory frameworks, developing over 40 Hydrogen Valley Projects, and establishing international import corridors to support market growth. This paper examines REPowerEU’s hydrogen ambitions, balancing its potential as a key decarbonization tool against economic, technical, and logistical challenges that may hinder its realization.

The study reports on a series of numerical simulations conducted to assess how tube diameter affects charging (melting) and discharging (solidification) performance in a shell-and-tube latent thermal energy storage (LTES) with longitudinal fins. In the investigated LTES, water flows through the tubes and serves as the heat transfer fluid (HTF), while paraffin is used as the phase change material (PCM) and fills the shell side. Employing an experimentally validated mathematical model and numerical procedure, LTES charging and discharging performances were investigated for three tube diameters: 28/24, 38/34 and 48/44 mm. LTES performance for different tube diameters was assessed by comparing melting and solidification times, as well as stored and released thermal energies in 8, 9 and 10 h of charging and 12, 13 and 14 h of discharging for each configuration. Results show that larger tube diameters accelerate melting and solidification processes due to increased conductive surface area, but also decrease LTES energy storing capacity as the amount of the PCM reduces as a result of increased tube diameter. The results indicate that tube diameter greatly influences LTES thermal performance and must be chosen carefully for the LTES to be effective.

The present manuscript describes some of the results obtained as part of a research contract investigating the effects of gamma irradiation on leather and library materials. Six samples of books and magazines, produced in Germany, the USA, and the former USSR between 1896 and 1962, were selected. All paper materials showed visible signs of biodeterioration and environmental damage. The samples were gamma-irradiated with a dose of 20 kGy using BULGAMMA radiation facility, based on the JS-850 60Co gamma irradiator at Sopharma AD, Bulgaria. The applied dose rate was 0.47 kGy/h. The effects of gamma irradiation were studied using thermogravimetric analysis. The results showed a 13% reduction in residual mass at 700 °C in the 1962 Soviet Union Newsletter, accompanied by a 3.6% decrease in the temperature (Tmax) at maximum weight loss rate. An 8.7% increase in residual mass at 700 °C was observed in the 1952 Reference Journal, and a 6.6% increase was measured in a German monograph from 1923. The study revealed that the effects of gamma radiation on paper structure depend on both the degree of prior damage and the type and composition of the paper.

The paper presents an analysis of the results of measurements of electromagnetic radiation from a base station installed on the roof of a site located in an area with a higher degree of urbanization, an extended center of the capital of Bulgaria, Sofia. Using mobile measuring equipment Narda AMB-8057-03, the dynamics of electromagnetic radiation in the frequency range from 100 kHz to 7 GHz was monitored over a period of eight days (weekdays and weekends). The obtained values for the levels of electromagnetic fields comply with the current national legislation and European standards. They are ≤ 10 μW/cm2. However, there remains a need for monitoring, tracking and control of the emitting EMF sources, because the susceptibility of an individual person is individual and the possible health effects are different, which in some cases manifests itself as “hypersensitivity” to electromagnetic radiation.

In order to enhance the efficiency of oscillation damping, the viscoelastic element in a Duffing-type system is divided into parts, with discrete commutation occurring four times per period between them. It has been demonstrated that the enhancement of oscillation energy dissipation is achieved through mass transfer between the parts. The influence on the equivalent coefficients of the solution parameters has been analyzed. 3D surfaces of the dissipated energy and equivalent coefficients have been constructed as functions of amplitude, mass ratio of the parts, and tension. It has been shown that discrete commutation allows for obtaining a hyperbolic type of frequency dependence of the aperiodicity coefficient, reaching values of 0,4..0,6 in the resonance zone.

A novel two-stage approach for obtaining wear-resistant multifunctional powder composites based on metal powders with highmodulus Ti–TiC system fillers is proposed. The method combines high-voltage electric discharge (HVED) treatment and spark plasma sintering (SPS), offering a promising alternative to conventional techniques for producing Al–Ti–C system composites. This approach enables the development of a unified route for material synthesis using high-energy-density processing. HVED treatment prevents oxidation of metal particles, reduces contamination by tool materials, and initiates the synthesis of additional dispersed strengthening phases. For example, HVED treatment of titanium powder in a hydrocarbon liquid promotes the in situ formation of titanium carbide (TiC) particles.
The present work investigates the influence of adding Ti–TiC powder—synthesized via HVED in ethanol under reverse polarity mode with a specific energy input of 20 MJ/kg—on the structure, phase composition, and properties of Al–Ti–C metal matrix composites (MMCs). It was shown that the addition of 2 wt% of Ti–TiC powder synthesized via HVED in ethanol to aluminum powder results in an MMC with an electrical resistivity of 0.5 Ω·mm²/m and a hardness of 31 HRB. However, the heat resistance of this composite is 2.5 times lower than that of consolidated pure aluminum powder. Increasing the Ti–TiC content to 10 wt% leads to the formation of a wear-resistant Al–Ti–C composite, whose structure includes Al, Ti, TiC, the intermetallic compound Al₃ Ti, MAX phases Ti₂ AlC and Ti₃ AlC₂ , and free carbon. For the MMC sample with the addition of 10% Ti–TiC, the mass gain per cycle during the heat resistance test is 0.23%/cycle, whereas for samples made from consolidated Al powder it is 0.18%/cycle, indicating that their heat resistance is approximately the same. The wear resistance of this composite is more than three times higher than that of the consolidated base aluminum powder, with wear rates of 0.003 g/km and 0.010 g/km, respectively. This material also demonstrates a hardness of 43 HRB and relatively low electrical resistivity at the level of 0.3 Ω·mm²/m.

Manual laser welding has become one of the progressive technologies in recent years for processing of metallic materials, showing particular advantages in the welding of different metals. By the high energy concentration and precise focus of the laser beam, it is possible to produce joints with minimal heat-affected zones, significantly reducing the risk of deformation, cracking and other types of defects. This technology enables high-quality and aesthetically welds without the need of post-processing, while also increasing productivity and process repeatability.
This article examines the main principles, parameters and modes of laser beam welding itself, analyzes practical parameters of device LW-2000W, designed for manual laser welding. The final section summarizes practical part focusing on welding of sheet metals at different values of parameters such as power, welding speed, wire feed and beam oscillation.

In this article, hardness Shore D of 3D printed ABS samples were investigated. The experimental results were analytical and statistically processed.

Recent researches have shown that Nano-coating materials play a vital role in improving the performance of the PV cell operation, enhancing the life span and reducing its surface temperature. In addition to that, the Nano-coating can achieve many benefits such as making a smoother surface, stronger and less adhesive of externous on the surface of PV panel. In this work, the effect of nanomaterials coating using Titanium dioxide, silicon dioxide and Nano fluid Titanium dioxide on performance and temperature of PV cell when coated by these Nano particles separately with different thicknesses (0.5μm, 50μm,100μm and 300μm). To achieve these objectives ANSYS software technology (version.1) was used. The results showed that there is a significant effect specifically when using TiO2 Nano fluid. The maximum improvements were when using Nano coating TiO2 and SiO2 which are (0.62%) and (0.135%), respectively, at thickness 300μm and ambient temperature16 ͦ C in case without externous particles. But the minimum improvement was with TiO2 and SiO2 of coating thickness 0.5μm which are (0.0937%) and (0.0937%), respectively, at ambient temperature 23 ͦ C in presence of dust. The results of TiO2 Nano fluid with concentration and flow rate which are (5%and 0.01 kg/s), respectively, showed that the maximum improvement was (39.88%) in case without externous particles at ambient temperature 23 ͦ C, but the minimum improvement was (37.84%) in case with dust at ambient temperature 16 ͦ C.