An operational test and degradation analysis of a hydraulic fluid based on synthetic esters was performed in three types of work machines. To enhance its performance, ZDDP anti-wear agents were added. Hydraulic fluids are susceptible to degradation by oxidation; therefore, to ensure the long service life of the equipment, it is essential to monitor their current condition through laboratory analyses during machine operation. Emission spectrometry was used to determine the presence of contaminants and the concentration of additive substances in the oil. Pollution was assessed by cleanliness code analysis according to ISO 4406-2021, alongside Total Acid Number (TAN) analysis and LNF analysis of wear and contamination in lubricants. The combination of cleanliness code analysis and LNF analysis of particle type and origin allows for monitoring not only the count but also the origin of contaminating metallic particles, which increases the probability of correct diagnostics and successful detection and resolution of wear problems. All three machines were still operational at the end of the test interval, meaning the tested hydraulic fluid is a suitable alternative to mineral variants. However, in all three pieces of equipment, it is necessary to replace the hydraulic fluid and flush the system before further operation. Furthermore, we recommend replacing the filter elements and inspecting the internal spaces of rotating parts with an increased potential for wear. From the oil’s perspective, it is advisable to add more anti-wear additives (ZDDP), which are depleted the fastest.

The research problem is oriented to shortening the development time of products for the automotive and engineering industry and to improving their output properties, such as weight reduction by implementation of advanced design methods (DfAMs). The intention of the study is to achieve positive properties in components and to shorten the development phase when applying DfAM methods, specifically the use of topological optimization (TO). In development of the design methodology using TO, the procedure and results were addressed and consulted with a specific manufacturer in the industry who provided the necessary materials for the research. The methodology was formed based on the partial results and their analysis for selecting the right solutions, such as the analysis of traditional procedures, strength checks, meshes, boundary conditions, etc. The procedure and design were focused and limited to additive manufacturing, specifically SLM. The results agreed with the research aim, and a significant reduction in times was achieved over traditional design methods. There was also a reduction in masses. The research concludes with an evaluation of the results together with those of the manufacturer, and a statement of the benefits, particularly for the scientific discipline and practice. It was concluded that, by implementing the given design methods, it is possible to significantly reduce the financial costs with proper application, simplify the operation of design software and create the possibility of use in training workplaces. With further research and extension of the applicability of the given methodology, substantial positive factors for development can be assumed. However, it should not be forgotten that the use of DfAM methods is greatly influenced by advances in additive manufacturing.

The solved research problem is oriented to the implementation of advanced methods of component design and their sophisticated use in the ever-advancing additive manufacturing. Based on the stated objectives, the research was divided into several parts. Initially, the methods and principles of design in additive manufacturing were evaluated and investigated, from which the intent was subsequently defined and the DfAM method in the component design and development process was determined. The given design method, namely topology optimization (TO), was applied to multiple development and production cycles of additive manufacturing parts to validate the research conclusions. In this paper, the procedure for a specific part or component assembly is shown. By evaluating the developed design procedure using the TO method included in the design process, the conclusions are positive in terms of both time savings and properties of the designed part such as strength and weight parameters. The given findings need to be further developed by implementing on specific product lines for increasing the efficiency of the developed design methodology.

Hydraulic oils and lubricants are predominantly made of petroleum-based materials, which can be harmful to the environment if leaked into the environment. Plant-based oils, represent an environmentally acceptable alternative to mineral and synthetic hydraulic oils, however, they tend to degrade faster in operation. Therefore, monitoring their properties is essential to protect hydraulic equipment from damage caused by oxidation, moisture-related effects or corrosion. The electrical parameters of plant-based biodegradable hydraulic oil MOL Biohyd 46 were measured over a 150-hour operational interval. A university-developed parallel testing device designed for determination of the life expectancy of hydraulic transducers was used in cooperation with HYDAC HLB 1400 sensor. Results were supplemented with laboratory analyses performed by an accredited laboratory of Slovnaft company. Conductivity and dielectric constant increased rapidly throughout the entire test indicating chemical changes in the oil. This observation was confirmed by Total acid number (TAN) test, which showed an exponential increase over time. Early signs of degradation are crucial for protecting hydraulic components from negative effects of degraded fluid like compromised lubricating function or metallic surface protection, and on-line monitoring of electrical parameters poses a solution. Dielectric constant was found as more precise value to indirectly assess increase in TAN with correlations 0.81-0.95 for various temperatures, while electrical conductivity remains as a good supplementary measurement with correlations 0.8-0.88 with TAN results.

This paper presents an experimental investigation into the flow characteristics and volumetric efficiency (η_vol) of a fixed-displacement external gear pump (GHD 17R) operating under coupled hydraulic parameters. Measurements were performed on a single-circuit hydraulic test rig within rotational speeds of 500–2500 min^-1, operating pressures of 2–10 MPa, and fluid temperatures of 30–60 °C using a biodegradable synthetic ester-based hydraulic fluid (48 mm²·s^-1 at 40 °C). To handle flow fluctuations caused by structural vibrations around 1250 and 1750 min^-1, a 15% trimmed mean statistical filter was successfully implemented. Experimental 3D flow and efficiency maps were constructed using Matlab. To determine the driving factors behind pump performance variation, a sensitivity analysis based on absolute, normalized, and relative significance was proposed and compared against a three-way analysis of variance (ANOVA) effect size model (η² and partial η²). The relative sensitivity approach identified rotational speed as the dominant parameter for direct hydraulic flow, contributing 95.80%, whereas pressure and temperature contributed 1.88% and 2.32%, respectively. In contrast, when focusing on volumetric efficiency, the proportional impact of speed was removed, revealing a balanced distribution of losses: rotational speed contributed 54.73%, temperature 26.08%, and pressure 19.19%. The three-way ANOVA confirmed that all factors and their interactions had a statistically significant effect (p < 0.05). The minor discrepancies between relative sensitivity and ANOVA effect size (η² = 10.24% for pressure vs. 3.98% for temperature) were attributed to coupled parameter interactions, which are successfully uncoupled by ANOVA. The findings demonstrate that a concurrent evaluation of both actual flow and volumetric efficiency maps provides critical information for advanced diagnostic, control, and optimization tasks in modern fluid power systems using eco-friendly fluids.

This paper presents an experimental investigation into the flow characteristics and volumetric efficiency (η_vol) of a fixed-displacement external gear pump (GHD 17R) operating under coupled hydraulic parameters using an eco-friendly synthetic ester-based hydraulic fluid (48 mm²·s⁻¹ at 40 °C). Measurements were performed on a laboratory single-circuit hydraulic test rig across a rotational speed range of 500–2500 min⁻¹, operating pressure range of 2–10 MPa, and fluid temperature range of 30–60 °C. To eliminate flow fluctuations caused by structural vibrations at 1250 and 1750 min⁻¹, a 15% trimmed mean statistical filter was successfully implemented. A comparative sensitivity analysis—evaluating absolute, normalized, and relative significance—was developed and compared against a three-way analysis of variance (ANOVA) effect size model (η² and partial η²). The relative sensitivity approach identified rotational speed as the dominant parameter for direct hydraulic flow, accounting for 95.80% of total variation. Conversely, when evaluating volumetric efficiency, the proportional impact of speed was removed, revealing a balanced distribution of internal losses: rotational speed contributed 54.73%, fluid temperature 26.08%, and pressure 19.19%. The three-way ANOVA confirmed that all primary parameters and their cross-interactions had a statistically significant effect (p < 0.05). The findings scientifically demonstrate that temperature-induced viscosity collapse exhibits a stronger relative dynamic sensitivity on volumetric losses than pressure fluctuations within standard operating envelopes. The constructed multi-dimensional flow and efficiency maps provide practical input for advanced diagnostic tools, real-time thermal condition monitoring, predictive maintenance, and energy-optimized control schemes in modern fluid power systems using eco-friendly lubricants.