This paper presents tribological research of an abaca fiber-reinforced epoxy composite material, analyzing fiber orientation and its effect on the tribological performances of the composite. The extremely low viscosity epoxy resin reinforced with NaOH-treated long abaca fibers is investigated under the different operating conditions. The unidirectional abaca fibers reinforced the epoxy resin and formed composite specimens with fibers in three directions, parallel (P-O), anti-parallel (AP-O) and normal (N-O), while keeping the sliding direction. The specimens were fabricated using fiber volume fractions of 10 vol%, 20 vol% and 30 vol% using the vacuum infusion technique. The block-on-disc (BOD) apparatus has been used to exhibit the tribological tests. Normal loads of 35 N and 45 N have been used for testing purposes. The experimental results indicated that the presence of abaca fiber significantly improved the wear characteristics of the matrix. An increased coefficient of friction was observed in samples with anti-parallel-oriented fibers at an applied load of 35 N. The conducted research shows that the use of abaca fibers as fillers could improve the tribological characteristics of the epoxy resin-based composite material.

The structural, mechanical and tribological properties of ZA-27/SiC nanocomposites were investigated at micro/nanoscale. The nanocomposites with different volume fractions of nano-sized SiC particles were produced using the compocasting technique. The microstructure of nanocomposites was characterized with formation of SiC nano agglomerates, which were relatively uniformly distributed. The increase in SiC content contributed to the uniformity of their distribution. Also, the phenomenon of particle segregation in the form of particle-rich clusters, as well as particle-porosity clusters, was identified. The density level of composites decreased with the increase of the SiC content. The porosity followed a reverse trend. The tendency for formation of local particle-porosity clusters was the highest in ZA-27/1% SiC nanocomposite, causing the highest level of porosity. Increasing percentage of SiC content was followed by the increase in micro/nanohardness of the composites. The results of micro/nanoscale tribotests revealed that the reinforcing with SiC nanoparticles significantly improved wear and friction behavior of ZA-27 matrix alloy. The rate of improvement increased with the increase of SiC nanoparticle content, load, and sliding speed. The highest degree of changes corresponded to the change of the SiC nanoparticle content from 0 to 1 wt%. The further decrease of wear with SiC content (from 1 to 5 wt%) was almost linear. The different tribological behavior of tested ZA-27 matrix and ZA-27/SiC nanocomposites was influenced by differences of intensity of adhesion resulted in transferred layers of matrix material onto worn surfaces of Al₂O₃ ball counterpart. The intensity of adhesion significantly decreased with the increase of SiC nanoparticle content.

Applying new technologies to reduce friction and wear in vehicles and equipment can minimize mechanical losses. This reduces power loss in internal combustion engines and reduces fuel consumption and emissions. Consumption of fuel energy...

To improve solar collector efficiency, a variety of designs and materials have been introduced into production practice. Studies describing solar collector specifics, therefore, are particularly valuable to the scientific community as they contribute to the overall body of knowledge and constant improvement the in the scientific field. In that regard, the study presented in this paper analyses the thermal performance of the fixed flat-plate collector with an Sn-Al2O3 selective absorber. The fixed flat-plate collector design utilizes gravity water flow in an open loop system. A two-month study was conducted to perform the analysis. The experiment was based on measurements of water flow in the fixed flat-plate col-lector, the water temperature at the fixed flat-plate collector inlet and outlet, and solar radiation intensity on a horizontal surface. Results for three randomly selected measurement days have shown that fixed flat-plate collector can achieve relatively satisfactory values for average daily specific heat power, thermal efficiency, and inlet-outlet water temperature gradient, respectively: June 29 (381.78 W/m2, 60.67%, and 9.06?C), June 30 (364.33 W/m2, 59.43%, and 7.46?C), and July 15 (373.06 W/m2, 59.85%, and 8.69?C). Apart from the relatively good measurement results, this type of solar collector does not require circulating pumps for operation, which brings a double advantage: energy saving and energy production.

FSW is a solid-state joining process. It is widely used for joining hard alloys like steel, titanium, and aluminium which are very difficult to join by fusion welding. FSW joint quality is mainly influenced by shoulder and pin geometry, its diameter, tool material, tool rotation speed, and linear traveling speed. The paper presents a brief overview of the tools used during the FSW procedure. The influence of the tool pin on the material flow and mixture was analysed in detail. In addition, the primary and secondary material flow and how it is affected by the shape and dimensions of the tool pin are also discussed.

This paper investigates the possibility of the application of different optimization techniques in the design and production planning phase in the metal additive manufacturing process, specifically laser powder bed fusion (L-PBF) additive technology. This technology has a significant market share and belongs to the group of mature additive technology for the production of end-use metal parts. In the application of this technology, there is a space for additional cost/time reduction by simultaneously optimizing topology structure and part orientations. Simultaneous optimization reduces the production time and, indirectly, the cost of parts production, which is the goal of effective process planning. The novelty in this paper is the comparison of the part orientation solutions defined by the software algorithm and the experienced operator, where the optimal result was selected from the aspect of time and production costs. A feature recognition method together with symmetry operations in the part orientation process were also examined. A framework for the optimal additive manufacturing planning process has been proposed. This framework consists of design and production planning phases, within which there are several other activities: the redesign of the part, topological optimization, the creation of alternative build orientations (ABOs), and, as a final step, the selection of the optimal build orientation (OBO) using the multi-criteria decision method (MCDM). The results obtained after the MCDM hybrid method application clearly indicated that simultaneous topology optimization and part orientation has significant influence on the cost and time of the additive manufacturing process. The paper also proposed a further research direction that should take into consideration the mechanical as well as geometric, dimensioning and tolerances (GDT) characteristics of the part during the process of ABOs and OBO, as well as the uses of symmetry in these fields.