Key Engineering Materials Vol. 1017

Abstract: Gear wear is the main factor affecting their performance and service life. In addition to the accuracy of production, the quality of the material from which the gears are made also depends on the degree of wear. The article compares the material properties of gears of JAWA motorcycle transmissions. In addition to the original gears, produced at that time in Czechoslovakia, the market also offers gears that are produced today, originally from the Czech Republic and Taiwan. Since the only comparable indicator is their price difference, the question arose whether the new variants can compete with the original part in terms of quality of workmanship. For this finding, the gears were subjected to wear tests and determination of the hardness of the material with the devices intended for this. In this way, valuable data will be obtained that will contribute to a better understanding of the performance and lifetime of these components. The quality of workmanship as well as the price are factors that should always be considered before the final selection of the item.

Abstract: The article deals with the creation of a mathematical model that can be applied in the testing of various materials. These are testing cases where the measurement and subsequent evaluation of the value of the coefficient of friction in various tribological measurements is considered. The mathematical model considers the static and dynamic coefficient of friction. It started with the creation of a simpler mathematical model, which was subsequently modified to a more sophisticated one, considering the real situation, which is closer to the real case. With the mathematical model created in this way, various simulations were performed and evaluated for cases of (constant) permanent load, but also repetitive (periodic) load. In another case, an improvement of the mathematical model was carried out, which represented the addition of an option that allows considering the degradation of the investigated material. Degradation of the material represents only part of the surface of the material, which during testing is exposed to contact with another material with a higher hardness than the tested material.

Abstract: The study focuses on analyzing the interior surfaces of the component responsible for directing projectiles during discharge. This investigation involves a detailed assessment of the chamber's internal condition, aiming to uncover any signs of wear, erosion, or deformation that could impact performance and safety of use. In the study, results from surface analysis of cut fragments taken from eight selected locations of the examined object were utilized. The samples were scanned using the ATOS Compact Scan 5M portable 3D scanner. Subsequently, a geometric model of the sample’s surface was created using CAD software and compared with the scan data through ATOS Professional software. The resulting surface maps enabled the evaluation of the scale of erosion on the sample surfaces and facilitated the analysis of the destructive mechanisms occurring during the object’s operation. Surface roughness measurements were conducted on 2x2 mm areas of the samples using a Hommel-Etamic T8000RC stationary profilometer. According to ISO 25178, three-dimensional surface maps were obtained, allowing for a detailed description of surfaces condition and the mechanisms occurring at the analyzed areas . The evaluation employs advanced imaging SEM, EDS and measurement techniques to ensure a comprehensive understanding of the structural integrity and functional state of this crucial element in the armament assembly.

Abstract: Various steels with suitable properties can be used as barrel steel. Most of the steels intended for the production of barrels are low or medium alloy steels. Barrel steels are significantly stressed by high pressures and temperatures during firing. During the shot, various forms of wear occur in the barrels, mostly abrasive, adhesive, and erosive wear. One of the most widely used steels for greater traction, from which barrels are made, is 34CrNiMo6. This steel is normally used for larger calibers, such as artillery, or for more stressed small-caliber weapons. This steel and its derivatives are the most widely used steels for the production of highly stressed barrels. We subjected the 34CrNiMo6 steel to tribological tests. In this article, we evaluated the coefficient of friction between 34CrNiMo6 steel and a G40 bearing ball. All measurements were performed on a UMT TriboLab universal tribo-meter (TA Instruments, New Castle, Delaware, USA) in dry conditions. The main goal of the experiments was to analyze the friction properties and wear of steel for the production of stressed 34CrNiMo6 barrels in contact with a G40 bearing ball with a diameter of 6.35 mm. In this evaluation of measurements, the authors of the article focused mainly on the influence of the peripheral speed on the change in wear and the coefficient of friction for two types of surfaces.

Abstract: Aluminum, steel, and cast iron pistons all function in the automotive market, each possessing specific properties. The most common type of piston is aluminum, but in recent years, there has been a noticeable increase in the production of steel pistons. One of the manufacturing processes used in the production of steel pistons is manganese phosphating. The coating obtained through this process provides corrosion resistance and enhances the sliding properties of the working surfaces, thereby extending the lifespan of the internal combustion engine piston. When conducting a tribological analysis of the surface created in the chemical process, it is essential to pay particular attention to the grain size and the thickness of the coating to ensure that the pistons have the appropriate properties. The analysis was carried out using both micro and macroscopic examination. A grain growth analysis was conducted over time, and a comparative analysis was performed to evaluate the impact of operating time in an internal combustion engine on the working surface of the piston. The grain size affects the amount of oil carried during operation. These grains tend to wear down during operation, losing their properties, and the degree of change occurring on the surface was described using a piston with a mileage of approximately 100,000 kilometers as an example.

Abstract: This paper addresses the study of hydraulic oil degradation, the increase in the number of wear metals, and contaminants in the monitored oil sample during 6 months of operation of an agricultural tractor. In a closed hydraulic circuit, the oil undergoes gradual degradation due to operational influences, which is caused not only by contamination from external impurities but also by the mixing of operational fluids from other attachment devices. Chemical analysis, water content measurements, and ferography were conducted on a sample of HARVELLA TX 10W40 hydraulic oil, which was compared with a sample of new, uncontaminated oil. The condition of operational fluids affects the proper functioning and lifespan of hydraulic circuit components and is one of the diagnostic indicators of their wear. During the operation of the equipment, the mixing of hydraulic oil from the main device and attachment devices occurs, resulting in changes to the operational properties of the fluid. The study compared the state and contamination of the mixed fluid in the tractor's internal hydraulic circuit with the hydraulic fluid applied by the manufacturer in new equipment. The measurement results indicated that during the experiment, no significant contamination of the oil occurred from pollutant elements present in the external environment, and the physicochemical properties of the monitored fluid were not significantly reduced.

Abstract: The synthesis of epoxidized waste cooking oil (EWCO) from used oil and the potential of using EWCO as a plasticizer to replace glycerol in xyloglucan-chitosan film were studied. The epoxidation reaction generated an epoxy group, which was induced to break off and form OH groups, potentially used as EWCO plasticizers (EWCOP). The determination of EWCOP by analyzing the chemical structure using FT-IR, where peaks were observed at 3496 cm^-1 and 827 cm^-1, indicating the opening of the epoxy group. According to the physical properties test, EWCOP has a total acid number of 9.91 mg KOH/g, a flash point below 50 °C, and a viscosity of 0.79 cST at 40 °C. A xyloglucan-chitosan film was prepared using a concentration ratio of xyloglucan to chitosan of 4:1, mixed with a solution of glycerol and EWCOP as the plasticizer at ratios of 7:0, 5:2, 3:4, and 0:7, representing 35% of the total weight of solids. The tensile strength of the xyloglucan-chitosan film increases with a decrease in the glycerol : EWCOP ratio, offering hope for the potential of EWCOP in future applications. Conversely, an increase in the glycerol : EWCOP ratio reduces the elongation of the xyloglucan-chitosan film. The water vapor transfer rate and T_g in the xyloglucan-chitosan film are lowest when the glycerol : EWCOP ratio is 3:4 and 0:7, respectively. The results showed that using EWCOP as plasticizers to replace glycerol significantly enhanced many aspects of synthesized xyloglucan-chitosan film properties, demonstrating the potential of this research to make a substantial impact in the field.

Abstract: Petroleum-based plastic is a critical issue for the global environment, especially packaging, due to high demand and short-term usage duration. Replacing petroleum-based packaging with bio-based packaging has been extensively severe, resulting in many research articles about biopolymer film preparation and characterization. One of the main bottlenecks of scaling up biopolymer film production from lab to industrial scale is needing more techno-economic analysis. In this work, tamarind seed, a main waste from the tamarind pulp processing industry, was selected as a raw material to produce tamarind kernel powder (TKP) edible film, followed by our previous work. For a project lifetime of 15 years with one metric ton (MT)/year of tamarind seed feed, 244.8 MT TKP film production, making revenues of 6,119 $/year with 2.62 years payback time and 38.12% ROI. Sensitivity analysis was studied in terms of selling price and amount of production. Results revealed that the selling price was more significant than film production. The TKP film production on a large scale is an attractive and profitable project, increasing the possibility of petroleum-based food packaging.

Abstract: This study evaluated the adsorption of Zn²⁺ from simulated mining wastewater using unmodified sugarcane bagasse-derived biochar (U-SCBB) and NaClO-modified sugarcane bagasse-derived biochar (SH-SCBB). The effectiveness of NaClO modification in enhancing the biochar's adsorption capacity was a key focus of this research. Results indicated that both U-SCBB and SH-SCBB exhibited significant Zn²⁺adsorption capabilities, with SH-SCBB showing superior performance. Specifically, SH-SCBB achieved the highest Zn²⁺ removal efficiency at pH 5 and adsorbent dosage of 0.9 g. Adsorption behavior and maximum Zn²⁺ removal were modeled using various isotherms, including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Flory-Huggins (F-H), and Temkin. It was determined that the SH-SCBB was best described by the D-R isotherm with a coefficient of determination or R² equivalent to 0.96. Kinetic data were analyzed with Pseudo-First Order (PFO), Pseudo-Second Order (PSO), Elovich, and Intra-Particle Diffusion (IPD) models, and it was found to pattern out a PSO model with an R² of 0.99, suggesting a physisorption process with an equilibrium time of 75 minutes. Optimal adsorption considering statistical significance was at pH 5 with 0.7 g of SH-SCBB, underscoring its potential as a cost-effective and environmentally sustainable adsorbent for Zn²⁺removal in mining wastewater treatment.