Volume 66, Issue 6

In this study, the microstructure and electrochemical corrosion behavior of the UNS S32205 alloy were investigated. Firstly, the phase diagram of the studied samples was determined by Thermo-Calc 2022 software, and the solution treatment temperature was designated. The studied samples were cooled by various cooling rates following the solution treatment at 1050 °C for 30 min. The samples were characterized by optical microscope, scanning electron microscope, and XRD analysis. Also, electrochemical corrosion behavior was investigated by potentiodynamic polarization, cyclic potentiodynamic polarization and electrochemical impedance spectroscopy analyses. Microstructural examinations revealed that decreasing cooling rate causes the precipitation of the sigma phase, and the ratio of the sigma phase was increased up to 29 % by the decreasing cooling rate. Furthermore, it was determined that precipitation of the sigma phase reduces the E pit values, and the sample with the highest amount of sigma exhibits the lowest corrosion resistance. On the other hand, presence of the sigma changed the electrochemical impedance spectroscopy behavior of the UNS S32205 and double-layered model fit the results.

The high specific properties and environmental durability of synthetic fibers make them a popular choice for reinforcing lightweight composites. Unfortunately, they are often limited by their poor biodegradability and high cost. Nevertheless, natural fibers are critical in industrial applications due to their environmental and economic benefits. This study investigated the tensile and flexural behavior of natural hybrid jute/ramie and jute/flax composites with different stacking sequences. A quasi-static punch shear test was also performed to understand their deformation behavior. Jute, ramie, and flax composites have also been fabricated for comparison. Tensile and flexural tests showed a positive hybrid effect in some samples, whereas flax–jute hybrid composites in two different stacking sequences exhibited a synergistic effect. While a maximum improvement of 37.99 % was achieved in the tensile test, this rate was 64.81 % in the flexural test with these hybrid composites. According to punch shear experiments, punch geometry and stacking sequence considerably impact punch shear strength, energy absorption capacity, and deformation.

This work propose a new experimental methodology to optimize the gaseous nitriding process of 33CrMoV12-9 steel grade, widely used in the mechanical industry for the fabrication of gears, pinions, and bearings. Several nitriding experiments were conducted at a temperature of 520 °C in the interval between 4 and 55 h using both constant and variable nitriding potential K N . The obtained results allowed us to determine the optimal conditions and to propose a sequenced cycle consisting of three steps. Multiple characterizations using X-ray diffraction (XRD), optical microscopy (OM), Vickers microhardness testing (HV), and electron probe microanalysis (EPMA) indicate a surface hardness of 810 HV0.5, nitrogen diffusion depth of approximately 0.7 mm. finally, a metallurgical structure devoid of complex networks of nitrides and carbonitrides. The validation results confirmed the effectiveness of the proposed methodology, thereby paving the way for improving the nitriding process in the mechanical industry. This work represents a significant contribution to the optimization of thermochemical treatments for materials used in demanding environments.

Additive manufacturing (AM) has come to the fore in recent years among manufacturing techniques. This technique, which has different advantages than traditional ones such as casting, forging and machining, is expected to be widely used in producing machine parts like gears in the coming years. Therefore, experimental data on AM parameters for lightweight metal gears are important for industrial production. In this study, a wear test was applied to AlSi10Mg and Ti6Al4V gears under operational conditions, and the wear behaviour of conventionally and additively manufactured gears was compared. The amount of abrasion elements was determined by analysing the oil in the gearbox. In addition, gear surfaces were analysed using scanning electron microscopy and an energy-dispersive spectrometer before and after wear. Thus, the wear behaviour of gears produced by conventional and AM under service conditions was demonstrated comparatively.

For the first time, bronze/SiC/mica hybrid composite has been manufactured using powder metallurgy method. Mixture – process variable design has been applied to design of experiments and optimization of the composite composition, as well as the production process variables (compaction pressure and sintering temperature) to attain superior corrosion resistance. This involved mixing different compositions of bronze, SiC, and mica powders, which were subsequently subjected to varied pressures and temperatures during the pressing and sintering stages, all in accordance with the experimental design plan. The microstructure, chemical composition, and elemental distribution of the samples were examined using scanning electron microscope equipped by energy dispersive X-ray analyzer, and an optical microscope. In order to study the corrosion resistance, potentiodynamic polarization test and electrochemical impedance spectroscopy were performed in 3.5 wt.% NaCl solution. The results revealed that co-incorporation of SiC and mica particles in Cu–10Sn bronze matrix increases the corrosion resistance, with a synergistic effect between these particles. The result of optimization process showed that the highest corrosion resistance could be achieved for the composite with the composition of Cu–10Sn/9.85SiC/0.67mica. This outcome was subsequently validated through experimental procedures.

In recent years, additive manufacturing (AM) technologies have been used in many industries, such as automotive, defense, space, and aviation. Depending on the development of this technology, the effect of the relationship between many parameters, such as raster angles, production speed, and melting temperature used during the production of materials, has been an important issue in the mechanical properties of materials. In this study, the effects of ±45° and 0–90° raster angles used during the production of 15 % short carbon fiber reinforced polyethylenetereflatate (CF15PET) and 30 % short glass fiber reinforced polypropylene (GF30PP) materials on the mechanical properties of the materials were investigated. As a result of the study, it was determined that different raster angles affect the mechanical properties of both materials.

Epoxy resin-based composites find extensive applications across various industries due to their unique mechanical properties. They are commonly used in gas and petrochemical industries for pipes and fittings in transmission lines. The primary objective of this study is to investigate changes in the mechanical properties of epoxy resin-based composites under different environmental moisture conditions. To achieve this, epoxy resin with varying weight percentages of graphite additive (0, 5, 10, 15, and 25 wt%) was used. The water absorption characteristics of the specimens were assessed by immersing samples in potable water (PW), distilled water (DW), a 10 vol% alkaline solution (NaCl), and a 10 vol% acidic solution (HCl), following ASTM standards. Both dry and wet samples were examined for various mechanical strengths. The results indicate that, for all weight percentages of graphite additive, water absorption follows the increasing order: NaCl < PW < DW < HCl, as compared to the blank resin case. In terms of mechanical testing, increasing the weight percentage of graphite additive resulted in a 24 % decrease in Barcol hardness and a 39 % decrease in impact strength, while the hot deflection temperature (HDT) increased for 5 wt% and showed no significant effects for the other cases.

The aim of this work is to study the effect of chitosan on mechanical and thermal properties of aloe vera fiber reinforced composites. In this work, we have fabricated the five different composites namely pure polyester composite (SP), pure aloe vera fiber composite (S0), 1 wt.% of chitosan filled aloe vera fiber composite (S1), 3 wt.% of chitosan filled aloe vera fiber composite (S3), and 5 wt.% of chitosan filled aloe vera fiber composite (S5) through simple hand layup method and investigated the mechanical and thermal properties. From the results, it is concluded that, 3 wt.% of chitosan filled aloe vera fiber reinforced composite was performed well in all the testing and it is suitable for various engineering applications such as automobile, aeronautical and marine. SEM analysis shows good adhesion behavior between fiber and matrix with the addition of chitosan. Further, 3 wt.% of chitosan can be added in natural fiber based polymer composites to enhance mechanical properties of the composites.

Nowadays, the need for new technologies is increasing, especially to find solutions to the inadequacies in the production of complex structures. The additive manufacturing methods developed facilitate the production of complex parts and move the technology forward with factors such as cost and efficiency. With the optimization of new parts designed by additive manufacturing methods, it is possible to obtain the optimum product even in the most complex structures. At the end of the production process, the final product with the desired properties is obtained as a result of part size tolerance precision and optimizations. In this study, lattice optimization is applied to a passenger aircraft bracket. It is aimed to reduce the weight and, at the same time, increase the efficiency of the part by optimizing it with lattice structures. For this purpose, the Altair Inspire program was used, and the variation of mass, displacement, safety coefficient, and stress values of the part according to different lattice structures were investigated.

The self-piercing riveting (SPR) experiences problems of poor forming qualities and mechanical properties during joining aviation alloy sheet materials. To address this issue, a novel combined process nominated ultrasonic self-piercing riveting (USPR) is carried out to join a 5A06 aluminium alloy and a TA1 titanium alloy sheets. The forming qualities, mechanical properties, failure modes, and mechanisms of USPR and SPR joints are comprehensively investigated. The results showed that the mechanical properties of the USPR joints were enhanced due to the welding formation of a solid phase between the specimen sheets and the degree of solid phase. The investigation showed that the welding was mainly affected by the material of the upper sheet. However, the welding also increased the brittleness of the rivet to some extent. The failure modes of the joints are affected by the welding process. The results determined that APL, AFD, and AEA of USAA joints were improved by 25.6 %, 31.3 %, and 88.8 %, respectively. The performance of the USPR joints with 5A06 aluminum alloy as the upper sheet is improved more than 88.8 % after the welding process. The combined method can be advantageous and supportive for automotive and spacecraft applications.

A statics finite element (FE) model as well as a dynamics FE model for Sendzimir mill have been established. It is in order to solve the bilateral wave defect caused by loose edge rolling during the cold rolling process with SUS430 stainless steel strip. The profile and flatness control effects are quantitatively analyzed by adjusting various roll contour configurations such as work roll crown, the second intermediate idler roll crown, the first intermediate roll taper depth and taper length. The coupling relationship between strip edge-drop and flatness under different roll contour configurations has been studied to analyze their effects on flatness defect control. The first intermediate roll taper depth is the most effective way to control edge wave. The first intermediate roll taper depth has been adjusted from 0.4 mm to 0.6 mm in the industrial production line. The overall profile has been improved by 21.5 %. The deviation of residual stress at strip edges has been reduced by 32.9 %. An excellent flatness defect control result has been achieved for the industrial production of SUS430 stainless steel. The present work is responsible for providing a theoretical basis and practical experience for the flatness defect control technology of a Sendzimir mill.

In precision casting, many model materials can be used to make complex, accurately sized molds. Model material is an important key for successful production. Wax models are widely used in model manufacturing because they allow economical production. In the wax injection method, some undesirable situations occur during the production of the model such as shrinkage, collapse, warpage, weld marks, surface defects, air marks, and burr formation that the manufacturer does not want. In this study, it is aimed to examine the effect of temperature and pressure parameters on shrinkage of the wax model in injection molding. The study was carried out at wax temperatures of 65 °C, 70 °C, and 75 °C and injection pressures of 0.1 MPa, 0.15 MPa, 0.2 MPa, and 0.25 MPa. In the experiments, the flow of the parts was observed during the filling of the plexiglass mold, and the shrinkage ratio of the obtained wax model was determined and evaluated. It is assigned that some of factors which affect quality of the final product produced by investment casting method are product shrinkage and surface quality of wax model.

Carbon nanotubes (CNTs) have garnered significant attention due to their extraordinary mechanical and other physical characteristics. This study demonstrates that incorporating a small number of carbon nanotubes, ranging from 0.1 to 0.9 wt.%, into a polymer, can effectively enhance its mechanical properties. In comparison to the pure polymer, the addition of −0.3 % carbon nanotubes resulted in a notable 24.1 % increase in tensile strength, a 4.4 % increase in compressive strength, a significant 319.5 % increase in the fatigue life cycle at 0.1 % carbon nanotubes, and a remarkable 43.0 % increase in fracture toughness at 0.3 wt.% carbon nanotubes.

This research work aims for developing the water jet erosion (WJE) prediction equation and analyzing the optimum water jet erosion parameters such as impingement angle (degree), water jet velocity (m s −1 ), stand-off distance (mm), and erodent discharge rate (g min −1 ) for minimizing the water jet erosion of 35CrMo steel coated with WC10Ni5Cr coating. The optimized high velocity oxy fuel (HVOF) process parameters were employed for developing the coating of WC10Ni5Cr on 35CrMo steel. The WJE prediction equations were checked for its validity employing analysis of variance (ANOVA). The water jet erosion was measured as the loss of mass (g) after water jet erosion testing for noncoated and coated 35CrMo steel substrates. From the results it was analyzed that the noncoated and coated 35CrMo steel substrates when subjected to the impingement angle of 60°, water jet velocity of 15 m s −1 , stand-off distance of 40 mm, and erodent discharge rate of 1500 g min −1 displayed lower mass loss of 0.0177 g and 0.0079 g. The coated 35CrMo steel substrate showed 55.36 % decrement in erosion compared to noncoated 35CrMo steel substrate. These findings support the employability of WC10Ni5Cr HVOF coating for 35CrMo steel to improve its water jet erosion resistance in engineering applications.