Volume 67, Issue 5

Applying a coating to substrates is widespread across various industrial domains, aimed at tailoring base material properties for specific applications. The three-point bending test has emerged as a critical tool for evaluating the mechanical characteristics of coating/substrate systems, ensuring integrity and safe operation under high contact loads and harsh environments. This paper reviews the literature pertaining to the assessment of coated specimens by the three-point bending test. Interesting insights are reported on describing test process, coating/substrate configurations, and important techniques used in combination for an easier and clearer understanding of the obtained results. Specifically, this paper comprehensively discusses and reviews the various outstanding goals that could be achieved by subjecting the coated specimen to the three-point bending test. The mechanical properties that could be acquired from this test are exhaustively enumerated, along with an explanation of the methodology. Finally, the different methods to assess the coating/substrate integrity are summarized. These insights aim to provide guidelines for gaining benefits and using them effectively for studying other coating/substrate assemblies.

The Strenx 700MC steel is one of the HSLA steels used in the manufacturing of transportation, crane, and mining vehicles and machines due to its cold-forming abilities, strength, abrasion resistance, and weldability. The AISI304 austenitic stainless steel is also widely used in industry because of its strength, resistance to corrosion, and good weldability. In industrial applications, there is a demand for welding dissimilar steels, as well as the requirement for Strenx 700MC-AISI304 steel welded joints. Although conventional fusion welding methods are widely used in the joining of similar and dissimilar steels, MAG welding is the most widely used method in the industry due to easy adaptation to automation. The basic problem of dissimilar steels weldment is that the superior mechanical properties and corrosion resistance of the base metal of the joint are partially lost due to weld thermal cycling. For this purpose, the gas metal arc weldability of Strenx 700MC-AISI304 dissimilar steels is investigated. The mechanical properties of the weldment were determined by tensile test and hardness measurement, and their formability was detected by bending test. Additionally, the microstructure of the weldment and the fracture surfaces of the test samples were examined. Results confirm that the Strenx 700MC-AISI304 couple has been successfully joined by the GMAW method using austenitic stainless filler metal and that the strength and formability of the joint are within the acceptable range.

Wire and arc additive manufacturing (WAAM) represents an additive manufacturing process utilizing an electric arc to liquefy wire feedstock, enabling the precise deposition of material layers to construct intricate structures. The advantages of high product quality and fast production make the WAAM method stand out. This study delves into the critical role of process parameter optimization in WAAM, focusing on the application of 5554 aluminum wire as a suitable material. Through analysis of samples produced with parameters including robot speed, wire feeding speed, and dwell time between layers, the study aims to elucidate their impact on final product characteristics. By assessing different values for each parameter and employing six distinct parameter sets in sample manufacturing, the research facilitates comprehensive comparative analysis. Mechanical testing of the produced samples reveals a significant correlation between heat input during aluminum alloy production and resulting hardness values, underscoring the pivotal role of temperature control in process. The highest properties were at the wire feed speed 7.5 m min −1 , robot speed 0.5 m min −1 and dwell time between layers 30 s. These findings not only highlight the importance of meticulous parameter selection in WAAM but also contribute valuable insights for optimizing production processes and enhancing material properties.

In this study, coating deposition processes were carried out by the TIG welding technique using Magmaweld FCO-540 flux-cored wire and ferroboron (FeB) additive to improve the surface properties and service life of micro-alloyed 38MnVS6 steel. Microstructure determination, chemical composition analyses, hardness measurement, and wear tests characterized the coatings obtained. End of the characterization processes, it was determined that there were complex carbide structures consisting of various alloying elements in the coating microstructures and these structures transform into carbides and boro-carbides and borides morphology depending on the increasing amount of ferroboron. Similarly, thanks to the use of flux-cored wire and increasing rates of FeB, the amount of alloying elements in the coatings increased and this increase caused the hardness values from 59 to 65 HRC. Besides, reductions in wear losses were determined inversely proportional to the hardness results, depending on the flux-cored wire and the increased FeB amounts. However, due to the presence of macro-size cracks in #4 and #5 samples with the highest hardness values, it has been determined that the usability of these coatings in practice is limited and there is no obstacle to the use of other coatings.

In this study, the effects of infill ratio, layer thickness, nozzle temperature, and raster angle on the flexural strength of polylactic acid material were investigated through microstructural analysis. A total of 10 different sample groups were produced, changing the parameters of the filling ratio (20, 40, 60, 80 %), layer thickness (0.15, 0.20, 0.25, 0.30 mm), nozzle temperature (210, 220, 230 °C), and raster angle (±45°, 0/90°). Three-point bending tests were conducted using the Shimadzu bending machine, and the results were used to calculate maximum bending stress, modulus of elasticity, and strain values. The results showed that the values of maximum bending stress and modulus of elasticity vary significantly with changes in layer thickness, filling ratio, nozzle temperature, and raster angle. The Scanning Electron Microscopy (SEM) images were obtained from the longitudinal cross-section of the samples in the failure area. The obtained images were used to identify the gaps between beads, voids, porosity, filament rapture, pull-out breakage, elongation, and necking patterns on the samples. The variations in flexural properties were verified by using SEM micrographs in the failure area.

Welding is a joining technique that still maintains its importance in today’s transportation, civil and industrial structure designs. Fatigue life of welded structures is generally estimated by considering the stress field near the weld. However, even for the same loading conditions, the stress gradient near the weld toe will vary from one specimen to another due to imperfections. This in turn causes large scatters in the S–N curves of fatigue life estimation methods. A successful fatigue life estimation is considered to have a reduced scatter of the corresponding S–N curve under variable geometry and loading conditions. In this study, an improvement of hot-spot stress method using optimization techniques is presented. The modified hot-spot stress method is then used to estimate the fatigue life of welded structures with different thicknesses and loading conditions. The results show that the proposed method will noticeably reduce the scatter in SN curves.

This study examines the role of water as a blowing agent in generating porous polyurethane foams used as synthetic cancellous bone surrogates in biomechanical osteosynthesis testing. Polyurethane foams, typically used to replicate bone structures, often fail to fully mimic the intricate morphology and mechanical properties of natural bone, especially in open-cell, cancellous structures. By varying water content, with and without a cell-stabilizing agent, foams with distinct morphological and mechanical characteristics were produced. Morphometric analysis and mechanical compression testing were conducted on foams with water content ranging from 0.25 to 3 wt.%. Results indicate that decreasing water content yields denser, mechanically stiffer foams, whereas the stabilizer consistently enhanced cellular stability and uniformity. Quantitative analysis, including bone volume to total volume ratio, trabecular thickness, and connectivity density, demonstrated that specific water-stabilizer combinations align more closely with human trabecular bone. These findings suggest that optimized water-based foaming in polyurethane can improve synthetic bone models’ biomechanical fidelity, offering valuable implications for testing orthopedic implants.

Neck injuries can range from mild discomfort to severe disability. Despite the abundance of biomechanical models of the cervical spine in the literature, their capabilities for modal and frequency response analysis are limited. A comprehensive head-cervical spine model was developed to address this gap, enabling frequency domain analysis. A multi-body dynamics (MBD) model with 20 degrees-of-freedom (DoFs) was created using ADAMS software’s frequency response analysis capabilities. This model incorporates elements, including vertebrae, ligaments, and muscles. The validation was performed using OpenSim and existing experimental findings. The model was then employed to conduct a Design of Experiments (DoE) study, where key design factors of a conceptual neck support system were varied. Two vibration objective functions were selected to evaluate the parametric designs. The first function identifies the maximum value of the head’s acceleration, while the second measures overall vibration within the frequency range of interest. In a case study, the model’s capabilities were demonstrated, identifying key design parameters for the neck support system. The methodology has the potential to make significant contributions across multiple industries. Applications range from designing anti-vibration devices to reduce fatigue in the automotive and aerospace sectors to enhancing rehabilitation systems in healthcare, ultimately improving patient exercise effectiveness.

In this study novel natural fibers were extracted from Rumex obtusifolius L. Extracted fibers were dried for further analysis. The chemical composition was analyzed, revealing the following fiber contents: cellulose at 63.52 ± 1.51 %, hemicellulose at 27.15 ± 0.72 %, and lignin at 9.35 ± 0.57 %. Thermal behavior of the fibers was investigated by using thermogravimetric and derivative thermogravimetric analyses (TG and DTG) and it was found that fibers were thermally stable up to 237.55 °C (T onset ) and maximum degradation temperature (T max ) was determined as 354.67 °C. Fiber diameter was varied in range of 226–539 µm and density was measured as 1.12 ± 0.74 g cm −3 . The crystalline structure of the fibers was examined through X-ray diffraction (XRD) analysis, and the crystallinity index (CI) and crystallite size (CS) were determined based on the corresponding diffraction patterns. CI and CS values were determined as 69.81 % and 3.08 nm, respectively. The mechanical properties of the fibers were evaluated using a single fiber tensile testing method. The measured values for tensile strength, elastic modulus, and strain at break were 192.81 ± 43.33 MPa, 14.56 ± 3.27 GPa, and 1.45 ± 0.43 %, respectively. Result showed that the R. obtusifolius L. fibers are suitable for composite applications as reinforcement material.

In this study, dissimilar alloys were joined by friction welding using different speeds. The microstructure characteristics in the joints were inspected by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), elemental mapping, X-ray diffraction (XRD), and electron backscattering diffraction (EBSD) analysis. The FW was well-suited for joining various steels and alloys. At high rotational speeds and a set pressure, corona bonding initiated at the outer edge of the friction interface and propagated toward the center. In the IPF map, the color of each grain corresponded to its crystallographic orientation, as illustrated by the stereographic triangle: red indicated the {001} orientation, blue represented the {111} orientation, and green denoted the {101} orientation.

Atmospheric pressure plasma (APP) applications have started to come to the fore today because of their fast and stable applicability to material surfaces and many advantages compared to plasma applications made under vacuum. With APP, it is possible to improve the surface energies, adhesion behavior and surface mechanical properties of materials. However, the changes obtained are not permanent since the surface tends to return to its untreated original state after plasma treatment. In this study, the wettability of APP treated metal surfaces, aging behavior and storage conditions that can delay the return of the surface to its untreated initial state were investigated. While one type of material (H300LAD), two different plasma treatments (cold and hot) and three different plasma treatment numbers (1, 2 and 3 times) were determined as test parameters; two different ambient conditions such as air and water (for 1, 10 and 60 min) were chosen as the storage conditions that can delay the return of the plasma treated surfaces to their original state. In addition, the effects of temperature on the aging time were investigated for two different temperature values (−20 °C and 30 °C). The effects of the applied plasma type, plasma treatment number, the storage conditions in which the samples were kept and the temperature on the aging behavior were evaluated and the conditions that could delay the aging time were investigated. The results showed that aging is greatly affected by the type of plasma applied to the surfaces, the storage conditions in which the samples were kept and the temperature.

In applications requiring high corrosion resistance, it is crucial to utilize dissimilar welding techniques that incorporate structural steels in critical areas to reduce costs, rather than constructing the entire structure from high-cost stainless steels. Ferritic steels are often preferred due to their higher strength compared to stainless steels. In this study, Gas Metal Arc Welding (GMAW) was performed on 12 mm thick S355 structural steel and AISI 304 austenitic stainless steel using SG307 austenitic filler metal. Following welding operations with three different heat inputs, macrostructural assessments were carried out according to the EN ISO5817:2023(E) standard on the welds deemed successful based on nondestructive tests. Microstructural characterization, microhardness tests, tensile test, and impact tests (performed by notching different regions of the weld joint) were also conducted. The results demonstrated that undesirable changes in mechanical properties due to microstructural transformations in the welding of carbon steels with austenitic stainless steels can be mitigated with the correct parameters and proper filler metal selection. Thus, the mechanical properties required to ensure the expected performance of the welded structure were successfully achieved. Results revealed that the dissimilar joint efficiency with respect to yield strength of ferritic steel was calculated as 103.77 % and 175.42 % for austenitic AISI 304 steel. The impact toughness test results for the heat-affected zone (HAZ) of S355 steel showed satisfactory levels. Although the dissimilar weld metal region exhibited lower toughness values, they remained above 100 J.

This paper introduces an improved optimization algorithm based on migration patterns of greylag geese, known for their efficient flying formations. The Modified Greylag Goose Optimization Algorithm (MGGOA) is modified by augmenting the levy flight mechanism and artificial neural network (ANN) strategies. The algorithm is detailed, presenting mathematical formulations for both phases. Subsequently, the paper applies the MGGOA to various engineering optimization problems, including heat exchanger design, car side impact design, spring design optimization, disc clutch brake optimization, and structural optimization of an automobile component. Statistical comparisons with benchmark algorithms demonstrate the efficacy of MGGOA in finding optimal solutions for these design engineering problems.

The present study examines the machinability performance of AA 7075 alloy under dry, air, and MQL-assisted machining conditions with cryogenically treated drills. The machinability performance of the AA 7075 alloy was evaluated in terms of surface roughness, cutting temperature, tool wear, deviation from diameter and circularity. Drilling tests were created using the Taguchi Taguchi L18 index. The cutting tool, cutting environments (dry, air and MQL), cutting speed, and feed rate were selected as drilling parameters. The data obtained from the drilling experiments were subjected to statistical analysis using the following techniques: signal-to-noise ratio (SNR), variance (ANOVA), and regression. The outcomes of this study show that cryogenic treatment increases the microhardness of tungsten carbide drills and positively affects machinability performance characteristics. It was also determined that surface roughness, cutting temperature, deviation from diameter and circularity values were approximately 99.81 %, 27 %, 38 %, and 40 % lower in air-assisted machining conditions and approximately 33.62 %, 30 %, 42 %, and 50 % lower in MQL-assisted machining conditions, respectively, compared to dry-machining condition. Moreover, SEM examination shows that the dominant wear mode for the cutting tools is built-up chipping (BUE) and negligible tool chipping occurs.

A connecting rod must be designed with high reliability, ensuring sufficient strength to remain rigid under loading while being lightweight to minimize inertia forces. These forces arise when the rod and piston decelerate, reverse direction, and accelerate at the end of each stroke. In this study, a numerical shape optimization procedure was implemented in conjunction with a three-dimensional finite element model to optimize the geometry and volume of a stainless-steel connecting rod. The objective was to minimize the maximum von Mises stress under both tensile and compressive loading conditions while simultaneously reducing the rod’s volume. The results indicate that modifying the connecting rod’s shape – specifically by increasing the outer radii of the crankpin and piston-pin ends and incorporating a hollow tapered slot in the shank section – significantly enhances performance. This optimized design reduces maximum von Mises stress by approximately 6 % under tensile loading and 45 % under compressive loading. Additionally, the new design decreases the connecting rod’s volume by 10.5 %, leading to a reduction in overall weight. Consequently, this weight reduction lowers fuel consumption costs and decreases the manufacturing cost of the connecting rod. Ultimately, this optimization process contributes to lighter engine components, reducing inertia forces, lowering overall engine weight, enhancing efficiency, and promoting energy savings.