Band 66, Heft 8

An improved white shark optimizer (MWSO) algorithm has been proposed. The algorithm adopts an improved tent chaotic mapping strategy to enhance the diversity of the initial population of white sharks, introduces the balance pool strategy of the EO algorithm to improve the convergence speed and accuracy of the algorithm, applies adaptive t-distribution dynamic selection probability perturbation to the global optimal solution, and adjusts the exploration and development ability of the algorithm at different iteration periods. MWSO, WSO, and seven excellent metaheuristic algorithms are tested and compared on 23 classic test functions and the CEC2017 test suite, and two non-parametric tests, a Wilcoxon rank sum test with a significance level of 0.05 and Friedman test, are conducted. The statistical results indicate that the proposed MWSO is significantly superior to other algorithms. In addition, nine algorithms are applied for the first time to optimize the structural parameters of the oil sealing edge of oil pads in response to the issue of the bearing capacity of hydrostatic bearings. This not only further verified the superiority of MWSO, but also provided new ideas for the optimization of hydrostatic bearings.

The purpose of this work was to examine how the microstructure and oxidation characteristics of Monel 400 Alloy were affected by the low-temperature aluminizing method. Monel 400 alloy was subjected to a low-temperature aluminizing procedure for 2 and 4 h at 600, 650, and 700 °C. Pure aluminum powder was used as the source of aluminum deposition to prepare the packs for the process. The activator and inert filler utilized were ammonium chloride (NH 4 Cl) and Al 2 O 3 powder, respectively. The coating surfaces were characterized using energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM), as well as X-ray diffraction (XRD) analysis. It was discovered that the through-thickness variance in the layer microstructure varied between 4 and 30 µm, and that it increased with greater process temperatures and times. The coating layer hardness grew to 800 HV after the deposition process, whereas the matrix hardness remained at 200 HVN. Furthermore, the sample that was coated at 600 °C for 4 h was exposed to oxidation at 750–800 and 850 °C. It was found that the oxidation kinetics were 176 kJ/mol.

Considering the emerging importance of a sustainable green environment today, this study contributed to realizing resource sustainability by expanding the use of natural materials in the brake pad sector. Brake pads used in vehicle applications were developed using natural components, and their effects on brake performance properties were observed in brake pad samples containing four different amounts of natural components with additive rates of 0 %, 4 %, 8 %, and 12 %. Tests were conducted on the pad tester to determine the samples’ friction coefficient and wear rates. Hardness measurements were made with a Shore D measuring device. Average and maximum disc roughness were measured to determine the effect of brake pads on the brake disc. Microscopic analyses were performed with a scanning electron microscope. The results showed that using tamarind seed powder in the pad content created a synergy with alumina, brass powder, and graphite as friction modifiers, and the friction coefficient increased slightly. Considering the emerging importance of a sustainable green environment today, it has been determined that using natural materials contributes to realizing resource sustainability by expanding its application in the brake pad sector and positively affecting the brake system disc roughness.

In this study, brake linings with Cu (copper)-based and Cu-10Sn (bronze)-based matrix structures have been developed and produced by the powder metallurgy method using sinter metal technology for use in high-speed trains. The developed linings were compared with commercial high-speed train linings. Firstly, the mixing process was carried out in a Turbulo 3V three-dimensional mixer for 4.5 h at 50 rpm. The pressing process was performed at room temperature, under the pressure of 350–450 MPa, and the sintering temperature for Cu-based linings was 1,000 °C, while for Cu-10Sn-based linings, it was 800 °C. After the pressing and sintering processes, lining sample density calculations were conducted, and hardness tests were carried out in the Rockwell L scale. Shear strength tests, friction coefficient, and wear tests were conducted according to SAE J 661 standards. It was observed that sinter metal brake linings with Cu and Cu-10Sn main matrix structures showed similar properties and met the technical requirements. It was determined that the developed production prescriptions are promising for industrial production and patent studies.

An AlCoCrFeNi high-entropy alloy coating containing 20 % mass fraction of TiC was prepared using the laser cladding method. The effect of heat treatment on the coating’s microstructure was analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM). It was observed that following high-temperature heat treatment, the phase transition of AlCoCrFeNi–20%TiC shifted from BCC to FCC at 750 °C. Through microhardness and wear resistance tests, the increased diffusion of carbon post-heat treatment led to a higher precipitation of TiC-reinforced phases, resulting in exceptional wear resistance with a notable 128.3 % enhancement.

Wing ribs, which play a critical role in aviation, are an important design element, especially for unmanned aerial vehicles. Aircraft wing ribs are structural elements that generally extend from the wing root to the tip, used to maintain the shape of the wing, provide aerodynamic stability and add durability to the wing surface. In this study, the wing root rib of the MQ-1B Predator unmanned aerial vehicle were modeled with cavities with different geometric structures and its mechanical behavior were examined. Wing rib structures were created from circular, elliptical, slot and beam geometry gaps. The hybrid structure was created by considering the combined use of Carbon–Kevlar–Aramid. In the hybrid structure, the thickness of each fiber layer was taken into account as 0.25 mm and the wing rib consisted of six layers. The effects of different fiber angles in hybrid composite structures were also examined. As a result of the analyses, equivalent stress (von-Mises stress) and total deformation results were examined.

This research examines the incorporation of spent coffee grounds (SCGs) into composite materials utilizing a three-part system composed of modified castor oil, polyester resin, and SCGs. The objective is to assess the mechanical, microstructural, and thermal characteristics of the resultant composites. The composite specimens underwent a thorough preparation and were tested through a battery of procedures comprising tensile testing, shore D hardness testing, SEM, FT-IR, and thermal conductivity measurements. Tensile testing revealed higher mechanical resilience, reinforcing the desirable properties of SCGs. The 5 % SCG-reinforced sample exhibited the highest tensile strength value, with a 41.85 % increase observed in comparison to the pure sample. The results of shore D hardness tests demonstrated that there was no significant change in material hardness up to 3 % additive content. However, a decrease in hardness was observed at higher additive rates. At a 7 % additive rate, there was a 2.82 % decrease in material hardness. Furthermore, the application of scanning electron microscopy (SEM) analysis has revealed the microstructural features of the composite matrix, which have highlighted the distribution of SCGs within it. The successful implementation of SCGs has also been verified by means of Fourier transform infrared (FT-IR) analysis. Finally, based on thermal conductivity measurements, it has been determined that SCGs are suitable for thermal insulation purposes. This study represents a significant contribution to the field of sustainable materials science, emphasising the potential benefits of SCGs in improving the effectiveness of composite materials.

Multistage fluid activities play an important role in the interaction between jadeitite and symplectite coronas; therefore, we studied the compositional zoning and evolution of representative Myanmar jadeitite. Under the influence of multistage Ca-, Na-, and Si-rich fluid activity, some minerals in Myanmar jadeitite formed symplectite coronas with concentric rings and multilayer metasomatic reaction rim structures. Additionally, the concentrations of Cr and Fe decrease from the core to the peripheral jadeite minerals, whereas the concentration of Si markedly increases. There is almost no Si or Ca in the chromite core, and the concentrations of Si and Ca increase sharply in rims composed of uvarovite. Due to Cr diffusion, the edge of the jadeite adjacent to kosmochlor is Cr-rich and Al-poor. The different element concentrations indicate that the uvarovite formed from the presence of a chromite and jadeite interaction, Si in the kosmochlor after metasomatism or an external Ca-rich fluid. One possible explanation for the formation of kosmochlor is the interaction between chromite and a Na- and Si-rich fluid. Also, Ca-rich fluid could have first interacted with chromite and formed uvarovite; subsequently, a Na-rich fluid could have entered and become saturated with kosmochlor, leading to the formation of kosmochlor surrounding the uvarovite.

In this study, the influence of the addition of Nb in varying amounts (0.5, 1, 1.5, and 2 wt.%) to Cu–14Al–4Ni shape memory alloy on the microstructure and wear behavior of the alloy was investigated. Cu–Al–Ni-xNb alloys were produced from elemental powders using the mechanical alloying (MA) method. The microstructures of the produced samples were examined using SEM + EDS and XRD, and density and hardness measurements were performed. For the wear tests of Cu–14Al–4Ni and alloys containing different amounts of Nb, a pin-on-disk type wear testing device was used with three different loads (10 N, 20 N, and 30 N) and five different sliding distances (400 m, 800 m, 1,200 m, 1,600 m, and 2000 m). As a result of the conducted research, it was determined that an increase in the Nb content resulted in a decrease in the average grain size and a more homogeneous grain size distribution. The highest hardness and density values were measured in the alloy with 2 wt.% Nb addition. In the wear tests, it was observed that the friction coefficients decreased with increasing load, and the lowest wear rate was achieved in the alloy with 2 wt.% Nb addition.

This paper introduces a novel approach, the Modified Electric Eel Foraging Optimization (EELFO) algorithm, which integrates artificial neural networks (ANNs) with metaheuristic algorithms for solving multidisciplinary design problems efficiently. Inspired by the foraging behavior of electric eels, the algorithm incorporates four key phases: interactions, resting, hunting, and migrating. Mathematical formulations for each phase are provided, enabling the algorithm to explore and exploit solution spaces effectively. The algorithm’s performance is evaluated on various real-world optimization problems, including weight optimization of engineering components, economic optimization of pressure handling vessels, and cost optimization of welded beams. Comparative analyses demonstrate the superiority of the MEELFO algorithm in achieving optimal solutions with minimal deviations and computational effort compared to existing metaheuristic methods.

Structures that are very difficult to produce with classical manufacturing methods have become easily produced with the development of additive manufacturing (AM) technique. AM technique allows creating special infill patterns with gaps in the internal structures of the products to be produced. These special infill patterns ensure that the product has maximum rigidity and strength while also providing minimum mass. For this reason, it is important to investigate the effects of infill patterns produced by AM technique on the mechanical properties of the product. In this study, the compression characteristics of compression test samples produced in five different infill patterns (octet, grid, cubic, quarter cubic, gyroid) using the AM method were experimentally investigated in three different axes. Test samples were produced from PLA material with a 3-dimensional (3D) printer in accordance with the ASTM C365-16 standard. Compression tests were repeated three times at a compression speed of 0.5 mm/min, with five different infill patterns and three different axes for each parameter. According to the results obtained, the octet infill pattern provided the best compressive strength in all three axes. It has been determined that the infill pattern or load axis change greatly affects the compression performance of the product.

In this study, pure and hBN-doped ZnO nanoparticles were synthesized by sol–gel method. ZnO–hBN nanoparticles were mixed with pure aluminum powders and samples were prepared using powder metallurgy processing parameters. It was observed that Al, ZnO, and hBN nanocomposite particles formed homogeneously. With the addition of ZnO–hBN, significant changes occurred in hardness, wear, and friction coefficient values compared to pure Al samples. The highest hardness value in the samples is mesh. It was obtained as 105 HB in 10 wt.% hBN added sample. In the wear tests, it is seen that the wear resistance is seven times higher in the 1 wt.% hBN added sample compared to the pure Al sample, while the friction coefficient decreases with the increase of the hBN additive.

This study proposes a novel human-inspired metaheuristic search algorithm called marathon runner algorithm. This method mimics competitive behaviors observed in real marathon runners through mathematical modeling. Unlike classical elitist algorithms that prioritize position of the best agent, the marathon runner algorithm introduces a novel concept called vision point. This point considers the quality of the entire population, not just the leader. By guiding the population towards vision point, the risk of getting trapped in local optima is reduced. A two-part evaluation was conducted to thoroughly assess the search capabilities of the marathon runner algorithm. First, it is tested against a set of unconstrained benchmark mathematical functions and the algorithm’s quantitative attributes, such as complexity, accuracy, stability, diversity, sensitivity, and convergence rate are analyzed. Subsequently, the algorithm was applied to mechanical and structural optimization problems with both continuous and discrete variables. This application demonstrated the effectiveness of the algorithm in solving practical engineering challenges with constraints. The outcomes are compared with those obtained by six other well-established techniques. The obtained results indicate that the marathon runner algorithm yields promising and competitive solutions for both mathematical, mechanical, and structural problems.

The material behavior under cyclic loading is more complex than under monotonic loading and the usage of the sophisticated constitutive models is required to accurately define the elastoplastic behaviors of the advanced high-strength steels and aluminum alloys. These models involve the numerous material parameters that are determined from cyclic tests and accurate calibration of the variables has a great influence on the description of the material response. Therefore, the development of a precise and robust identification method is needed to obtain reliable results. In this study, a systematic methodology depending upon the firefly algorithm (FA) with variable step size has been developed and Yoshida–Uemori combined hardening model parameters of a dual-phase steel (DP980) and an aluminum alloy (AA6XXX-T4) are determined. The identified parameters are verified based on comparisons between the finite element simulations of the cyclic uniaxial tension-compression tests and experimental data and also the search performance of the variable FA is evaluated by comparing it with the standard FA. It is seen from these comparisons that variable FA can easily find and rapidly converge to the global optimum solutions.

In this study, a response surface based approach is introduced to determine the physical parameters of the tip mass of a beam – tip mass system, such as mass, mass moment of inertia and coordinates of the centre of gravity with respect to the beam end point. To this end, first, a difference function was formulated based on the differences between the peak frequencies and peak amplitudes of the experimental and analytical frequency response functions. Later, observation points were established in the design space using orthogonal arrays, and a response surface was developed using the difference function values at these points. Next, the tip mass parameters were determined by minimizing the response surface with genetic algorithm and particle swarm optimization as well as fmincon, a gradient-based solver of the Matlab program. For comparison purposes, those parameters were obtained by also direct minimization of the difference function with the same algorithms. It was concluded that the tip mass parameters were successfully determined within reasonable error limits by the response surface method with less computational burden. Finally, the effect of design space width on the response surface quality is demonstrated numerically.

The rapid depletion of natural resources and the increase of environmental problems due to production-related waste necessitate sustainable waste management. In particular, reintroducing by-products and waste generated by agricultural activities into the economy is critical to reduce environmental pollution, solve the storage problem, and promote sustainability. Agricultural wastes such as fiber, husks, cobs, stalks, straw, dust, and particles are recyclable and can be innovatively reused in various sectors. One of the innovative fields where sustainable agricultural waste management can be implemented is the development of biocomposites. One of the most important steps in the production of biocomposites reinforced with agricultural waste is processing the waste biomass and making it usable as a reinforcing element. This study investigated the production of powder reinforcements for biocomposite material from the biomass of walnut shells using a ring mill. The walnut shells, mechanically reduced in size, were first dried at 100 °C for 3 h and ground at four different grinding times (10, 20, 30, and 40 min). Afterward, the waste walnut shell powders were subjected to sieve analysis and precise weight measurements. Then, the waste walnut shell powders, which were dried at 100 °C for 3 h and ground for 40 min, were subjected to a second drying process at 100 °C (60, 180, and 300 min) and ground again for 40 min. Then, the resulting waste walnut shell powders were subjected to sieve analysis, precision weight measurements, and microscopic, and SEM analyses to determine the characterization of the powders.

In this work, to promote the cathodic and barrier performance of zinc-rich cycloaliphatic epoxy resin (ZRER) coatings containing 90 wt.% zinc dust particles, cerium oxide nanoparticles were used. The effect of CeO 2 content 0–5 wt.% and the anticorrosion behavior of nanocomposite coatings were investigated by different techniques, including open circuit potential, electrochemical impedance spectroscopy, and salt spray tests. Results revealed that ZRER coatings containing 2 wt.% CeO 2 nanoparticles had boosted sacrificial anode and barrier protection during immersion in a 3.5 wt.% NaCl solution. The addition of 2 wt.% CeO 2 into the coating system significantly reduced corrosion products and blisters while increasing resistances from 72,443 Ω cm 2 to 426,579 Ω cm 2 compared with the control ZRER sample after 120 days immersion. This high-performance anticorrosion behavior of the nanocomposite coatings is mostly due to the CeO 2 nanoparticles, which have the capability to moderate the zinc dissolution rate in addition to improving the barrier by filling porosity and creating tortuous paths.