Band 67, Heft 1

In this study, the effect of multi-walled carbon nanotube concentration on the electrical resistance change characteristics of multi-walled carbon nanotube filled glass/epoxy composites under low-cycle fatigue loading was experimentally investigated. For this purpose, multi-walled carbon nanotube concentrations of 0.2, 0.3, and 0.4 wt.% within composites were utilized to ensure electrical conductivity. The rectangular specimens for fatigue tests were manufactured by vacuum bagging method. The fatigue tests were conducted in a load-controlled manner with an ultimate strength ratio of 0.6 and at a stress ratio of 0.1. The results showed that the alteration in electrical resistance within the composites experiences a sharp and exponential rise when the concentrations of multi-walled carbon nanotube reach 0.2 and 0.3 wt.%, whereas the rate of this increase in electrical resistance is more gradual at 0.4 wt.%. multi-walled carbon nanotube concentration. The electrical resistance change curves of multi-walled carbon nanotube filled composites at various fatigue life levels were determined for statistical analysis using the Weibull distribution method. Finally, the average stiffness loss and the average residual fatigue life were determined at the electrical resistance changes corresponding to 95, 80, and 50 % Weibull reliabilities at various fatigue life levels and various multi-walled carbon nanotube concentrations.

Coating of metal or nonmetallic materials made conductive can be achieved by electrodeposition method. Metals with low conductivity and cost, such as copper or steel, can be coated with materials with higher hardness, corrosion, and wear resistance, such as nickel and boron, and can meet the relevant requirements according to their usage areas. In this study, the impact of trimethylamine borane complex (TMAB) and zirconium carbide (ZrC) contents added to the bath concentrate in the Ni–B/ZrC composite coating applied on copper on the surface properties of electroplating was investigated. Electroplated specimens were examined with regard to mechanical, morphological, and corrosion resistance. The highest microhardness value was obtained in the coatings obtained with 6 g L −1 TMAB and 4 g L −1 ZrC bath concentration, and this value was found to be 1,020.4 H V. When examined in terms of coating morphology, it was seen that as the amount of TMAB increased, the ZrC content decreased over time. In the nanocomposite coating with 4 g L −1 ZrC concentration, which showed the best corrosion performance, the corrosion current decreased by 70 % compared to the Ni–B alloy.

This study presents the effects of pulse duration and frequency in laser surface texturing on the surface roughness and microstructure of CoCr28Mo alloy for biomedical applications. Texturing of the alloy surface was performed using 20 W fiber laser marking equipment. The pulse duration ranged from 50 to 300 ns and the frequency from 100 to 200 kHz. Higher frequencies generally correlated with reduced surface roughness, whereas pulse duration exhibited fluctuation. Statistical analyses confirmed the significance of both parameters and their interaction in affecting the surface roughness of the alloy. Optimal conditions with a pulse duration of 200–300 ns and a frequency of 200 kHz suggest potential for achieving a surface roughness less than 2 µm. The lowest surface roughness value of 0.81 ± 0.04 µm was achieved at a frequency of 200 kHz and a pulse duration of 300 ns. After removing the metal from the surface using this frequency and pulse duration during laser texturing, metal residues accumulated on the textured surface in spherical and layered forms, significantly affecting the surface roughness. This study emphasizes the complex relationship between laser surface-texturing processing parameters and surface properties, providing a promising approach for achieving the highly desirable surface roughness for biomedical applications.

In order to coat the surface of AISI 1040 steel using the TIG coating process, SiC and B4C are added to NiCrBAl powder at various rates. The microstructure and wear characteristics are then analyzed. Thus, it is intended to increase the AISI 1040 steel’s resistance to elements like abrasion and friction while lowering maintenance expenses. The ratio of B4C to SiC reinforcing powder affected the produced coating layer’s microstructure analyses and wear tests were carried out. Therefore, it has been found that the hard carbide phases and boron carbides generated in the coating layer have a favorable impact on wear, lowering weight losses and friction coefficients.

Magnesium (Mg) and aluminum (Al) alloys are considered to be among the lightest structural metals. Using these materials in a design can considerably decrease weight, which brings many benefits like reducing fuel consumption and increasing the performance of an aircraft or a ground vehicle. However, these alloys are too difficult to be joined via fusion welding techniques. In this context, welding AZ91 Mg alloy to ENAW7075-T651 Al alloy by the solid-state welding method of friction stir spot welding was investigated comprehensively. These alloys were welded by utilizing a tool with a triangle pin and various tool rotational speeds (1,000, 1,400, and 1,800 rpm) and welding times (3 and 6 s). Macro and microstructure of the welds and their hardness, tensile strength, and tension-compression fatigue life were determined. Generally, an improvement in the mechanical properties of the weld was observed by increasing the welding time due to the expansion of the joining area. The welding with the best mechanical properties was obtained at 1,400 rpm, and the worst at 1,800 rpm. All the welds failed from the weld area during the tensile and fatigue tests and exhibited a brittle fracture mode due to the formation of intermetallic compounds in the welds.

Arc welding is one of the most commonly applied methods in the welded manufacturing industry. The pulse MIG/MAG welding method (GMAW-P) was developed to prevent problems that may occur in the weld bead due to high heat input to the base metal during the feeding of the weld metal in MIG/MAG welding applications. The synergistic controlled welding machines have been developed that facilitate the selection of welding parameters and provide simultaneous feeding of pulsed welding wire by adjusting the variables to the most appropriate values relative to each other. Weld bead geometry is greatly influenced by welding process parameter, i.e., welding speed, welding current, shielding gas flow rate, voltage, arc travel speed, type of shielding gas, etc. In this study, steel welding samples in T-joint shape were produced with synergistic controlled GMAW-P. The effect of welding parameters on weld bead geometry was investigated. As a result of this study, it was determined that increases in weld wire feed speed, arc voltage, and welding current increased weld depths of penetration and weld bead thickness.

Aluminum-based composites exhibit significant potential in automotive engineering, especially in engine components, with potential to improve efficiency and lifespan. The potential and usability of developing high-performance aluminum-based hybrid composites with silicon carbide and tungsten disulfide for automotive applications were investigated in the present study. This study investigates a novel aluminum-based hybrid composite, incorporating 10 wt.% SiC and varying WS 2 concentrations (0–12 wt.%). WS 2 addition reduces friction, enhancing engine efficiency and lifespan. The structural and morphological features with mechanical behavior of the hybrid composites manufactured via powder metallurgy were examined. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis reveals the phase identification with topographical features. Microstructural analysis reveals uniform SiC distribution and WS 2 clustering at aluminum grain boundaries. Microhardness increases from 52.86 ± 1.264 HV to 71.12 ± 2.175 HV with increase in WS 2 (1–9 wt.%). Wear decreases from 70.56 to 8.48 μm, indicating better lubrication. After 120 h, corrosion rates drop from 0.041 to 0.013 mm a −1 with WS 2 (up to 9 wt.%). The research findings suggest that with addition of WS 2 and SiC improves corrosion resistance and hardness, minimizing wear.

Sandwich structures may be exposed to different impact loads depending on their areas of use. In this study, low-speed impact tests were implemented on balsa core sandwich composite materials and impact behaviors were examined. Balsa woods of 4, 6, 8, and 10 mm in thickness were used as core elements. Eight- and 12-layered glass fiber-reinforced composite materials with different orientation arrangements were used for the sandwich structures’ top and bottom surfaces. The fiber orientation angles of the glass fiber materials were determined as [0°] 2s and [0°/90°] s . The balsa core sandwich composite materials were produced using the vacuum infusion method. The prepared samples were tested at impact energy of 15, 30, 45, and 60 J. At the end of these tests, the effects of impact energy, core thickness, increase in number of outer surface layers, and change in orientation angle on contact force, displacement, and absorbed energy values were analyzed. The outer surfaces of the damaged samples and the damage patterns that occurred in the balsa wood were examined after the tests.

The advanced material properties and high quality of composite products are largely dependent on the production methods. In the current search, it was examined how the mechanical properties of flax, jute, and basalt fiber-reinforced composites were affected by three different production methods and hybridization processes. The materials were produced by hand lay-up, vacuum bagging, and vacuum-assisted resin transfer molding methods. While the physical and mechanical properties of specimens were determined by hardness, tensile, and water absorption tests, the fiber behavior of the composites was investigated by micrograph analysis. Tensile test data gave better results for homogeneous samples by 1.4–16.4 % for the samples produced with the use of vacuum-assisted resin transfer technique in comparison to the samples manufactured by the vacuum bagging technique, and by 7.3–22.5 % in comparison to the samples fabricated by the hand lay-up technique. Compared to the other two methods, 7.3–35.3 % better tensile strength results were obtained when using the VARTM technique in hybrid samples. Moreover, the hardness value measurement of the samples also supports the tensile strength data. However, the water absorption analysis results display that samples produced by hand lay-up absorb less water than samples produced by the other two production methods.

Copper and titanium plates were used in the studies. Explosive welding (EW) processes were carried out using different explosive rates. The resulting composite plates were heat treated at different temperatures. Various tests were then carried out on samples with and nonheat treatment. In the SEM studies, it was observed that a flat interface shape was formed in the joints where the lowest explosive rate (R = 2.5) was used, but as the explosive rate increased, the interface shape became wavy. It was also found that a thickening diffusion layer formed as the heat treatment temperature increased. As a result of XRD and EDS analyses, it was found that Cu 4 Ti, CuTi 2 , CuTi, CuTi 3 , Cu 3 Ti 2 , and Cu 4 Ti 3 intermetallic phases could be formed because of the high explosive rate and heat treatment applications. Increasing the amount of explosives increased the tensile-shear strength. However, the heat treatment applied reduced the strength values. No defects were detected in the bending tests performed on all heat-treated and nonheat-treated samples.

In this study, the effect of thermomechanical treatments applied to strontium-modified A360 alloy on the microstructure and mechanical properties of the alloy was investigated. Optical microscopy, XRD, and SEM were employed to examine the microstructural properties, while tensile and hardness tests were conducted on the samples to evaluate the mechanical properties. It was observed that the strength values increased as the deformation amount increased, and subsequently, optimum conditions (tensile strength and ductility) were determined after the subsequent aging treatment. Following cold deformation, dendritic structure shifted towards the direction of deformation along with the eutectic silicon structure. After aging, it was found that the dendritic structure transformed into equiaxed grains at certain temperature. The highest tensile strength of 383 MPa was achieved in the sample with a deformation amount of 70 %. In this case, the ductility value was 2.85 %. Subsequently, the optimum conditions after aging were determined as 160 °C & 4 h, resulting in a tensile strength of 341 MPa and ductility of 3.62 %.

TBF1050 and DP1000 sheets in different thicknesses were laser welded in butt configuration. The welds were performed both similar and dissimilar. Welding speed was changed between 40 and 120 mm/min. Characterization of the welds was carried out by means of microstructure, microhardness, tensile properties and fractography. The grain structure in heat affected zone (HAZ) on DP1000 side was a relatively coarser than that on TBF1050 side. The highest hardness was obtained in fusion zone. The presence of TBF1050 steel in the joint increased the hardness of the fusion zone. On both steel sides, the hardness in a narrow zone between the tempered zone and the base metal decreased below the hardness of the base metals (softening zone). The softening zone hardness on TBF1050 side was relatively higher than that on DP1000 side. The tensile strengths of each laser welded joint, except for DP1000 similar joint, were all higher than 1,000 MPa. When the fractures occurred on the TBF1050 side, the tensile strength was higher. Whether the TBF1050 steel sheet was galvanized or not did not cause any significant effect on the microstructure and the mechanical properties of the joints. The joint fractured from HAZ had a completely brittle fracture behavior.

Thanks to machine learning algorithms, the performance of composites with high energy absorption capacity can be predicted with high accuracy rates with a small number of data. The aim of this study is to experimentally and numerically determine the crushing performances of glass/epoxy composite pipe structures under compressive force and to predict their compression behavior with the help of different machine learning algorithms. In the study, the crushing performances of composite pipes (peak force (PF), peak force displacement (PFD), mean crushing force (MCF), specific energy absorption (SEA), and total inner energy (TIE)) were determined for different specimen thicknesses, specimen lengths, mesh sizes, numbers of integration points, diameters ( D ), and compression directions (axial and radial). Additionally, the maximum strength values of composite pipes under force were estimated with the help of Linear Regression (LR), K-Nearest Neighbors (KNN), and Artificial Neural Networks (ANN) machine learning algorithms. The data taken from the ANN algorithm were found to be more reliable in estimating the PF and TIE values, with an accuracy rate of 92 %. When determining the MCF value, it was found that the data obtained from the LR algorithm was more reliable than other algorithms, with an accuracy rate of 80 %.

In today’s competitive environment, the lightweighting of vehicle components is under intense study. While some of these studies focus on material modification, a very important part of these studies focuses on lightweighting the same material. The most widely used techniques in light-weight studies are topology, topography, size, shape optimization, and metaheuristic algorithms. This work introduces a novel hybrid generalized normal distribution optimization (GNDO) simulated annealing algorithm (GNDO-SA) adapted to optimize a vehicle component made of aluminum material. The focus is on shape optimization, which aims to minimize the weight of the vehicle component while ensuring that stress constraints are met. A combination of latin hypercube sampling (LHS) and artificial neural network is used to generate the mathematical equations governing mathematical equations for the objective/constraint used in the optimization. These findings highlight the effectiveness and superiority of the GNDO-SA method for optimization problems.

Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This concept is illustrated in this work focusing test machines used in rotary testing procedures. Drive element pairs, which serve as component test objects, are primarily exposed to wear stress. These stressed element pairs are consequently integral parts of a tribological system. The underlying principles of power amplification and power feedback are explained from the perspectives of drive technology, systematic design, methodical design, and mechatronics.