Materials Testing

Stress concentration factors (SCFs) play a critical role in the structural integrity of circular plates subjected to internal and external compressive loading. This study uses Artificial Neural Networks (ANNs) and the Finite Element Method (FEM) to examine SCFs of circular plates with different circular hole configurations. The stress distribution and stacking patterns were thoroughly examined using FEM. Then, using geometrical and loading parameters, an ANN model was created that can predict SCFs. The FEM-generated data sets were used to train and validate the ANN model, which showed that it could generalize to various hole configurations and pressure levels. A comparison of the FEM and ANN findings revealed a strong connection, confirming the suggested ANN model’s dependability. The study’s conclusions offer valuable information for perforated plate design and optimization, offering a computationally effective substitute for traditional numerical methods.

Fatigue damage is the major factor in the failure of components. During the fatigue loading, the local plastic strain deformation forms persistent slip bands (PSBs) and emerges on the surface as persistent slip markings (PSMs). The PSM can develop roughness and be observed on the surface as extrusions and intrusions, while the intrusions are possible sites of crack initiation. Thus, surface roughness development is a reasonable way to inspect fatigue damage. Many techniques were utilized to inspect and monitor the cracks and fatigue damage progress to protect the components and to predict the remaining lifetime. Most of these techniques consume a lot of measuring time. In this study, a scattered light sensor from Optosurf will be performed to measure and determine the roughness evolution during cyclic loading of a high-strength steel 115CrV3. As a result, the profile and areal measurement from a confocal microscope and the measured Aq values are suitable to illustrate severe surface changes before failure. Moreover, the Aq values using a scattered light sensor are comparable with the results using a confocal microscope (Nanofocus).

Traditional brake pads often contain metal-based components, leading to environmental pollution, high wear rates, and noise issues. This study explores an aloe vera fiber–reinforced polyester composite with chitosan for automotive brake pad applications. Developing sustainable, lightweight, and wear-resistant alternatives is essential. The composite exhibits low void content (3.13 %) and water absorption (2.41 %), ensuring moisture resistance. Its density (1.51 g·cm −3 ) indicates a well-structured material with minimal defects. Mechanical properties include hardness (86.2), impact energy (4.2 J), tensile strength (94.6 MPa), flexural strength (154.68 MPa), and shear strength (146.94 MPa), making it suitable for high-friction applications. Tribological analysis shows wear decreases with sliding distance due to a protective layer formation. Friction is mainly influenced by applied load, followed by velocity and distance. Taguchi optimization identifies ideal conditions for minimal wear (20  N , 1,500 m, 2 m·s −1 ) and friction (40  N , 500 m, 2 m·s −1 ). ANOVA confirms sliding distance as the main wear factor, while load affects friction most. SEM analysis shows debris, delamination, and crack. These findings highlight the composite’s potential as a sustainable, wear-resistant alternative for automotive brake pads, offering enhanced durability and reduced environmental impact.

This study investigated the effect of austenitization time on the mechanical properties of 5Cr–0.5Mo steel. As-received steel specimens were subjected to water quenching heat treatment with five austenitization durations (1, 2, 4, 6, and 8 h) to produce different grain sizes with a consistent microstructure. The microstructural characteristics and hardness of the resulting specimens were then analyzed. Subsequently, normalizing heat treatment was applied to three specimens austenitized for 1, 4, and 8 h to evaluate their metallographic characteristics and mechanical properties through microhardness and tensile tests. Mechanical properties, including yield strength, ultimate tensile strength, percentage of area reduction, and elongation at break, were quantified through tensile testing. Area reduction and elongation were found to decrease by approximately 50 % as austenitization (grain size increased) progressed. Additionally, yield strength and ultimate tensile strength increased by approximately 300 % and 150 %, respectively, relative to the as-received specimen after normalizing heat treatment following 1 h of austenitization. The yield strengths of normalized specimens demonstrated minimal variations across different austenitization times.

Zn-induced liquid metal embrittlement (LME) cracks tend to be formed in hot-dip galvanizing (GI) medium-Mn advanced high-strength steel (AHSS) in the process of resistance spot welding (RSW). In the present study, the LME susceptibility of the medium-Mn AHSS with GI coating was systematically evaluated in accordance with the criterion of “Auto/Steel Partnership (A/SP)”. The samples were welded at 16 groups of distinct welding current levels from 7.0 kA to 14.5 kA in 0.5 kA increments. Some severe LME cracks were evident in the cross sections of the RSW joints even below expulsion, and more pronounced and serious LME cracks appeared at or above expulsion. It was discovered that the tendency for LME crack formation tended to worsen as the welding current increased. The maximum LME crack lengths of Type A, B, C, and D among all groups were approximately 1,285.0 μm, 980.5 μm, 1,397.0 μm, and 131.9 μm, respectively. Results revealed that the medium-Mn AHSS with GI coating displayed high LME susceptibility, which consequently failed to satisfy the necessary criterion for RSW application in the automotive industry. Moreover, the elevated Mn content was deemed as a critical factor leading to the high LME susceptibility of medium-Mn AHSS with GI coating.

In this study, laser remelting was applied using Nd:Yag laser beam to plasma sprayed coatings that include Al 2 O 3 -43 % of TiO 2 for the first experiment series, 2.15 % of TiO 2 , 4.36 % of SiO 2 in Cr 2 O 3 for the second experiment series, and 4.31 % of TiO 2 , 2.15 % of SiO 2 in Cr 2 O 3 for the third experiment series. Wear tests and microstructural analyses were conducted to reveal characterization of the laser remelted specimens. According to the results, the fusion zone exhibited the highest hardest in the microstructure due to quick solidification inducing martensitic transformation in the microstructure. The pearlitic and ferritic structure were transformed into tempered martensite and bainite in heat affected zone, gradually increasing the micro-hardness. While the coefficient of friction in the first series of specimens was measured as 0.23, it was 0.31 for the second and third series of specimens. Although friction coefficient was higher than that of first series, the lowest weight loss was observed in the specimen that laser remelted at 350A plasma spray current level.

In this study, contrary to the conventional approach, severe plastic deformation (SPD) was applied at room temperature and under low strain, revealing notable results. AA6013, an aluminum alloy widely used for its high strength-to-weight ratio, was subjected to multi-directional forging (MDF), an SPD technique. Despite the low deformation rates in the MDF process, cold deformation led to significant microstructural refinement, enhancing mechanical properties. Following four cycles, improvements in the material’s mechanical properties were assessed through compression and hardness tests. At the same time, microstructural evolution was analyzed using optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The effects of pre-SPD heat treatment and the SPD process on microstructural evolution were examined at both micro and nano scales, with a particular focus on grain and crystal structures. The results demonstrated that SPD not only reduced grain and crystal sizes but also rendered them more uniform, leading to consistent improvements in mechanical properties. Furthermore, the MDF process, applied up to four cycles, was numerically modeled, and the results were compared with experimental findings.

In this study, AA7075-T6 aluminum alloy substrates were coated with WC-Co by the high velocity oxy-fuel (HVOF) method. The coatings were applied in two and four layers to surfaces with three different roughnesses. The effects of WC-Co coating applied to the AA7075 aluminum surface on the hardness and corrosion properties of the alloy were examined. The corrosion properties of uncoated and WC-Co coated aluminum alloy samples were determined in salt water environment by potentiodynamic corrosion tests. Additionally, microstructure and XRD examinations of the samples were performed. The surface hardness of WC-Co coated samples increased by up to 140 %. According to the results of corrosion tests, it was determined that the WC-Co coating applied to the surface of AA7075 aluminum alloy improved its corrosion resistance by reducing the corrosion rate of the alloy. The best corrosion resistance was obtained in four layers of coating on the sample with the smallest surface roughness.

A connecting rod should be designed with high reliability, being sufficiently strong to remain rigid under mechanical loads, yet lightweight enough to reduce the inertia forces, which are produced when the rod and piston stop, reverse directions, and accelerate again at the end of each stroke. In this study, a traditionally designed steel-forged connecting rod is used as a baseline. The concept of Function Graded Materials (FGM) is introduced as an alternative to conventional steel. A three-dimensional model of the connecting rod is constructed and analyzed by finite element method (FEM) with the ANSYS software package to evaluate the stresses distribution over the entire rod. In addition, transient and force analyses are performed, and the results are validated through computer simulations. It is well established that improvements in connecting rod design directly enhance engine performance by increasing reliability, service life, efficiency, fuel economy, and reducing noise, size, weight, and vibration. This study investigates the impact of functionally graded materials on connecting rod performance and aims to optimize the design to reduce maximum von Mises stress in critical regions. The analysis is conducted using FEA software, with comprehensive modeling and simulation results presented in detail. To achieve optimization, three material compositions (aluminum–steel, aluminum–titanium, and titanium–steel) are evaluated. The most effective composition is identified based on performance. Theoretical analysis suggests that manufacturing an FGM-based connecting rod using a bulk layering process is feasible. From a stress standpoint, the aluminum–titanium composite provides the best performance, showing a 49.4 % stress reduction compared to the steel connecting rod. However, due to its higher cost, the aluminum–steel composite offers a more balanced solution, achieving a 44 % stress reduction while being more cost-effective.

Integrating maintenance considerations into aircraft design is essential for ensuring both operational efficiency and reliability. One of the key factors in aircraft selection and facilitating maintenance is the accessibility of critical components. This study focuses on the design and enhancement of design-based maintenance access panels during the early stages of conceptual design. The primary goal is to develop a methodology for identifying optimal locations for access panels, thereby minimizing the need for modifications during later design phases. The approach considers various factors, including Mean Time Between Failures (MTBF), maintenance intervals, and accessibility. The research encompasses several phases, such as evaluating maintenance needs, establishing a product lifecycle framework, and implementing Digital Mock-Up (DMU) activities based on Computer Aided Design (CAD) data and product development processes. This methodology fosters collaboration between design and maintenance teams, employing iterative techniques to develop access panels based on advanced DMU and CAD models. The findings of this research underscore the importance of a collaborative approach, the necessity of integrating maintenance considerations early in the design process, and the advantages of using design-based tools to optimize access panel design. Adopting this methodology helps aircraft manufacturers improve maintainability, reduce maintenance costs, and boost efficiency.

This paper is dedicated to enhancing the crash performance of a PA6 GF30 multicell crash box used for the crashworthiness and safety of the battery pack system used in electric vehicles. In this paper, a new hybrid optimization algorithm (HSFOA) combining the starfish optimization algorithm, dynamic oppositional-based learning, and a piecewise chaotic map is proposed, and a novel PA6 GF30 composite multicell crash box is developed to protect the electric vehicle battery pack. The performance of HSFOA is validated by applying it to piston rod design, car collision study, welded beam design, and truss structure optimization. After validation, the HSFOA is used to optimize a multicell energy absorber to evaluate its effectiveness in enhancing energy dissipation during collisions of electric vehicle battery pack. The developed crash box design, via finite element analysis and hybrid starfish optimization method, is manufactured by 3D printing and subjected to dynamic impact tests to validate crash performance. The results revealed that the developed design exhibited the highest crash performances, which are comparable to each other. Additionally, the PA6-Gf30 material for the developed multicell crash box, and HSFOA perform well in terms of efficiency, convergence, and stability in polymer-based electric vehicle battery pack design.

This study investigates the cure kinetics characteristics of a carbon fiber/epoxy prepreg used in the aerospace industry. Understanding the curing behavior of prepreg during the autoclave process is critical for optimizing high-performance composite manufacturing. DSC data obtained at different heating rates (2, 4 and 10 °C min −1 ) were analyzed to provide a comprehensive kinetic profile by determining the enthalpy and exothermic peak temperature for experimental model. Additionally, based on the T-β extrapolation curve, the optimum cure temperatures; T i (gel), T p (cure) and T f (post) were calculated 139.42, 196.32 and 256.35 °C, respectively. Kinetic parameters for kinetic model, including activation energy E a , pre-exponential factor A and reaction order n  ​​were calculated by Kissinger, Ozawa and Crane methods. These were integrated into the nth-order reaction model, a model-fitting approach, to derive the kinetic equation for the prepreg and to analyze the relationship between the degree of cure and temperature based on the kinetic model. Consequently, the suitability of the nth-order reaction model was evaluated by comparing it with the experimental model to determine the suitable heating rate and curing temperature range. This study presents a practical example of the autoclave curing mechanism and behavior of carbon fiber/epoxy prepreg used in unmanned aerial vehicle manufacturing.

The use of agricultural wastes containing natural fibres in the materials industry within the framework of environmental approaches offers various opportunities such as efficient use of resources, waste management, carbon footprint reduction and sustainability. Biocomposite materials reinforced with agricultural wastes are one of the important approaches for sustainable waste management. In the study, mechanical, thermal and microstructural properties of biocomposite materials produced by mixing bioresin and waste walnut, hazelnut and rice husk powders were investigated. Thus, these wastes were ground with a ring mill and pulverized in the range of −77/+45 μm. Biocomposite materials were produced by mixing 5 % by weight micropowders with epoxy resin. Tensile, three-point bending, izod impact and hardness tests were performed to determine the mechanical properties of the biocomposite materials. In addition, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM) analysis were performed on the biocomposite materials. The highest tensile strength was obtained in 5 % walnut powder-reinforced biocomposite material. All biocomposite materials had higher modulus of elasticity and lower elongation than the base material. After the base material, the highest flexural strength was obtained in the biocomposite material reinforced with 5 % rice husk powder. All reinforcing elements negatively affected the izod impact strength of the biocomposite materials. The base material and all biocomposites lost mass between approximately 200–600 °C.