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

In plastic injection and plastic welding processes, the inability to accurately classify machine downtimes, the lack of visibility regarding performance discrepancies between shifts, and the reliance on largely manual methods for operator tracking hinder the sustainable improvement of Overall Equipment Effectiveness (OEE). Furthermore, the retention of pro- duction and energy consumption data in isolated systems complicates integrated performance evaluation.
In this study, the HBS MES system, developed by the in-house engineering team of Pleksan A.S. and fully integrated with HBS ERP, is examined within the scope of a field application aimed at real-time production tracking, performance analysis, and energy consumption reporting in plastic injection lines. As of 2025, HBS MES is actively used in its V1 version across three different plastic manufacturing enterprises; this paper exemplifies a facility predominantly focused on plastic injection.
The paper presents the system architecture, data collection logic, modeling of production and downtime events, the approach to calculating OEE and its sub-metrics, and user interface components in detail. As a result of the implementation in the studied facility, an improvement of approximately 25% in production quantities was reported, particularly during night shifts, and the mechanisms underlying this improvement are discussed. The findings demonstrate that MES solutions integrated with machine-embedded data collection modules can provide measurable productivity gains even in small and medium-sized enterprises.

At the start of exploitation of any hydrocarbon or geothermal water reservoir, production of reservoir fluids is driven by natural energy in the form of reservoir pressure. Therefore, the primary task for production engineers is to maintain this reservoir pressure for as long as possible, ensuring long-term economic production. Unfortunately, sooner or later it becomes necessary to introduce mechanical methods of fluid lifting. Today, there are numerous solutions on the market for mechanical lifting of reservoir fluids (progressing cavity pumps-PCP, electric submersible pumps-ESP), and one of the oldest mechanical methods for producing reservoir fluids is the sucker rod pump. In the Republic of Croatia, sucker rod pumps are among the most commonly used mechanical methods for lifting reservoir fluids. Although Croatian production engineers have significant experience working with sucker rod pumps, operational problems are common and are accompanied by additional expenses related to workover operations. This paper presents an analysis of workover operations over a tenyear period (from 2011 to 2022) in an oil and gas field in the Republic of Croatia. Based on the collected data, an analysis was conducted to determine the volume of fluid not produced during equipment maintenance and repair, the waiting time for repairs, the duration of equipment maintenance as well as the cost-effectiveness of the repairs. Special attention is given to the analysis of the causes of problems in using sucker rod pumps and the identification of problematic wells.

This study presents a machine learning framework for predicting the mechanical properties of 2xxx series Al-Cu alloys (2024, 2219, 2524) across 11 temper conditions. Monte Carlo augmentation generated 8,800 synthetic samples from compositional specification ranges of a literature-mined dataset. Three regression models, Random Forest, Gradient Boosting, and SVR-RBF were evaluated via 5-fold cross-validation (CV) to predict ultimate tensile strength (UTS), yield strength (YS), and elongation. All models achieved coefficient of determination R² > 0.991, with Mean Absolute Error MAE ≤ 7.4 MPa for UTS, ≤ 5.4 MPa for YS, and ≤ 0.51% for elongation. Feature importance analysis revealed that temper condition encoding dominated predictions (>75% importance), while individual compositional features contributed <5% each. The high predictive accuracy reflects the effectiveness of the augmentation scheme in capturing withingroup property–composition–temper relationships, though generalization to unseen alloy–temper conditions remains to be validated. The results illustrate the potential of combining corpus-mined data with Monte Carlo augmentation for rapid alloy property screening.

This study investigates the electrochemical performance of Sacrificial Anode Cathodic Protection (SACP) systems for offshore steel structures using Finite Element Analysis (FEA). Two structural substrates, S235JR carbon steel and S550QL high-strength steel, were modelled in a 3 wt.% NaCl electrolyte. A comparative analysis was performed between two sacrificial anode materials: a conventional Al- 5Mg alloy and a quaternary Al-6Zn-0.2In-1Mg-0.03Ti alloy. The simulations evaluate the influence of anode placement errors by comparing an ideal symmetric distribution (90°) with a clustered configuration (10°). The results show that geometric clustering significantly alters the potential distribution along the structure. For S235JR steel, the clustered configuration produces localized underprotection with potentials reaching −0.78 V (vs. Ag/AgCl). In contrast, for S550QL steel, the same configuration results in localized over-polarization (≈ −0.96 V), thereby increasing the risk of hydrogen-induced stress cracking (HISC). The study demonstrates that improper anode placement may compromise cathodic protection efficiency even when high-performance anode alloys are used. These findings highlight the importance of accurate anode distribution and support the use of numerical simulations in digital twin approaches for offshore corrosion management.

This study presents a theoretical investigation of the densification kinetics of titanium powder during electro-pulse consolidation. A mathematical model was developed to analyze the influence of electrical current parameters in different sintering regimes – direct current (DC), alternating current (AC), pulsed current, and their superposition – on the thermophysical processes governing sintering.
The heating rates and the evolution of relative density were calculated for different applied pressing pressures. The results show that the superposition of currents is the most energy-efficient regime. This regime enables the material to reach a relative density above 99% within a minimal processing time. The effect is attributed to the combined action of intense Joule heating and the electroplastic effect.

Growing energy and environmental challenges highlight the need for a transition to sustainable supply chains. This paper presents a methodology for assessing a hydrogen supply chain based on steam reforming of biogas (SMR), as a low-carbon alternative to conventional natural gas. The framework covers the entire life cycle, from feedstock to end use. The proposed framework supports strategic planning and provides a basis for future modeling, optimization, and assessment of environmental and socio-economic benefits.

The hydrogen embrittlement susceptibility of P460NL1 pressure-vessel steel was assessed by slow strain rate testing (SSRT) with in situ electrochemical hydrogen charging. An electrochemical cell integrated with a tensile testing machine was used to generate hydrogen in a 3.5 wt.% NaCl solution containing 1 g/L thiourea. Cathodic charging was applied at a constant current of −20 mA (approximately −1.4 V). SSRT was performed at a strain rate of 10⁻ ⁵ s⁻ ¹ in accordance with ASTM G129-21. Tensile specimens extracted from the base material and welded joints were tested in air and under hydrogen-charging conditions. The methodology enabled controlled hydrogen introduction during deformation of tensile probes and allowed comparison of hydrogen-assisted cracking susceptibility between base metal and welded material. Tested brocken tensile probes were subjected to determination of dissolved hydrogen. Tensile probes were first tested in the air and after that in prepared solution.
To analyse hydrogen embritlement of investigated steel hydrogen embritlement index was determined through determination of fracture elongation and reduction of Area (RA) of the brocken specimen. Light and SEM microscopy was used to analyse possible location of the present defects in material i.e. hot rolled steel. Types of non-metallic inclusions were determined too.

Rolling element bearing fault detection is of significant importance due to the widespread use of bearings across numerous industrial applications. In this study, vibration measurements using an accelerometer and a laser displacement sensor are carried out on a laboratory bearing test rig under different operating conditions, including a healthy state and bearings with localized inner- and outer-ring faults. Measurements are conducted at a constant rotational speed of 1700 rpm and the acquired signals are analysed to extract characteristic features associated with potential bearing faults. The results demonstrate that the applied methodology enables indicative bearing fault detection using both measurement approaches.

The intensification methods for carburizing and nitrocarburizing investigated in this study include the use of biochar, preliminary oxidation, and plastic deformation. The possibility of combining oxidation and plastic deformation was also examined.

Casing string is critical component in wellbore construction, defining wellbore diameter and providing structural integrity throughout drilling and production operations. Traditionally, steel casings are generally used due to their mechanical strength; however, problems connected with corrosion, particularly in environments containing hydrogen sulfide or saline formation water, presents significant operational and financial challenges. This paper explores the use of fiber-reinforced plastic (FRP) casing as a corrosion-resistant alternative, focusing on glass fiber-reinforced epoxy composites, especially concerning cementing operation. FRP casing properties depend on the fiber–matrix composition, fiber type, and manufacturing quality, which affect tensile and compressive strength, thermal stability, and resistance to environmental degradation. Laboratory and field studies, including pilot projects in Argentina, Oman, Brunei, and Kuwait, evaluated casing handling, rig down speed, anchoring, and cement bonding. Special attention was given to cementation procedures, fluid formulations for mud cake removal, and ultrasonic methods for assessing casing-to-cement bonding, adapted for the acoustic characteristics of FRP materials. Results indicate that while steel casings exhibit superior cement bonding, FRP casings can achieve adequate structural performance when mechanical stresses during handling and installation are carefully controlled and proper chemical compatibility between fluids and cement is ensured. Field data show that FRP casings can be deployed with only minor reductions in installation speed for smaller diameters and that optimized handling and cementation practices are crucial for operational success. These data demonstrate that FRP casings offer a technically feasible and economically advantageous alternative for wells in highly corrosive environments. However, their successful implementation requires tailored operational procedures, including modified handling equipment, optimized fluid systems, and specialized evaluation methods. Further field studies are needed to develop comprehensive guidelines for widespread adoption.

Corn stalk was used as a biosorbent for the adsorption of copper ions from synthetic solutions. To examine the mechanism of the adsorption process and identify the potential rate-determining step, the following kinetic models were used in this study: the pseudo-first order kinetic model, the pseudo-second order kinetic model, the Elovich kinetic model, and the interparticle diffusion model. Kinetic studies show that copper ions adsorption followed the pseudo-second order kinetic model. The maximum adsorption capacity was 5.5 mg g⁻¹. The results indicate that corn stalk can be successfully used as a biosorbent for the adsorption of copper ions from synthetic solutions.

In this paper, the inherent strain method is employed for the purpose of predicting welding residual stresses in large shell structures. Such structures include roof structures in the construction industry and deck sections in the shipbuilding industry. The study focuses on the numerical aspect of the inherent strain method, with the objective of investigating the most appropriate technique for transferring analytically calculated inherent strains into the elastic finite element model of the structure. The approach under consideration takes into account the thermally induced stresses, to the extent that they are considered to be significant for the structures and their behaviour in question, with the objective of determining the field of welding residual stresses over the entire structure (macro-scaled). The work proposes theoretical parameters for the alignment of finite element meshes within the weld seam domain. The discussion in the conclusion encompasses the general application capabilities, limitations, and challenges for further development