Applied Mechanics and Materials Vol. 925

Abstract: The determination of glucose concentrations in the blood and urine were important to monitor the health of human being. This study was carried out to study the effect GO thicknesses in enhancing the sensitivity of the Au/GO sensor for detection of glucose with various concentration. The partial unclad SMF was fabricated by using low-cost mechanical etching technique. The cladding thickness was successfully reduced from 125μm to 124μm by using this technique. To enhance the strength of evanescent field, Au nanoparticles were deposited on top of unclad fiber via drop casting method. To excite surface plasmon polaritons. GO with various layers from one to five layers were coated on the Au coated partial unclad SMF. The optimum sensitivity of the Au/GO SMF was resulted as three layers of GO with laser excitation under infrared range, λ=1310nm was employed. In conclusion, the effect of GO thicknesses mainly influenced the performance of the proposed sensor, in which the best thickness of GO to enhance the evanescent field and the excitation of SPP is three layers.

Abstract: Recently, demand for this Anodic Alumina Oxide (AAO) has been raised throughout the year due to its unique and special properties that will bring many benefits to the nanotechnology industry. AAO is the self-organized porous alumina produced by anodizing aluminum and can also be seen as nanotube arrays with honeycomb-like structures. Throughout these centuries, many research has been done in order to study the optimum parameter to produce high-quality AAO. This paper is specifically to investigate the effect of anodization voltage on the structural formation of AAO by using anodization of the aluminum process. A porous alumina template was prepared by using a difference voltage range of 20 V – 30 V in 0.3 M of oxalic acid; a copper wire was used as the cathode electrode and an aluminum template was used as an anode. It is observed that after the anodization process, there is a significant increase in current density at every voltage increment, as well as an increase in the size of the nanopores in AAO. The morphology and phase composition were characterized by using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier Transform Infrared Spectroscopy (FTIR).

Abstract: This study investigates the mechanical behavior of single and multi-wall carbon nanotubes (SWCNT/MWCNT) during torsional loading using the molecular dynamics (MD) simulation technique. The open-source software Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is utilized to conduct MD simulations to gain valuable insights into the response of pristine and defective carbon nanotubes. The torsional behavior of armchair SWCNTs with chiralities (5,5); (7,7); (10,10); (12,12) and (15,15) and zigzag SWCNTs (12,0); (17,0) and (22,0) is explored to understand the effect of chirality on the torsional properties. Furthermore, the impact of the aspect ratio is examined by varying the diameter of SWCNTs while keeping the length constant. The findings reveal a notable decrease in shear modulus with increasing tube diameter, providing a crucial understanding of the torsional behavior concerning SWCNT geometry. To assess the effect of vacancy defects, 1%, 2%, and 4% vacancy defects are introduced on (10,10) armchair SWCNTs, and their torsional response is analyzed. The predictions highlight a significant reduction in shear modulus by 25% for SWCNTs with the rising concentration of vacancy defects from 1% to 4%. Overall, this study contributes to a deeper comprehension of the mechanical properties of carbon nanotubes under torsional loading, paving the way for potential applications in nanotechnology and nanocomposite design.

Abstract: Beams find extensive applications in Nanoelectromechanical systems (NEMS) and Microelectromechanical systems (MEMS). The mechanical characteristics of these microstructures are significantly influenced by both their inherent microstructure and the forces acting at the micro/nano scales. Classical continuum theories fall short in capturing these small-scale effects due to the absence of a length scale parameter in their constitutive relations. To address this limitation, the existing literature primarily relies on the stress gradient nonlocal approach, which, however, has been found flawed and its universal applicability questioned in various scenarios. Therefore, the authors have endeavored to emphasize the strain gradient nonlocal approach, which has been relatively less explored. In this study, carbon nanotubes are modeled using the isotropic Timoshenko beam theory. To introduce the small-scale size effect into the model, the second-order negative strain gradient theory (NSGT) is employed. The Euler-Lagrange differential equations of motion and their corresponding boundary conditions are derived through Hamilton's principle. Analytical solutions are developed for static bending under uniformly distributed transverse load and free vibration problems using Navier's approach. Mathematical results are presented to validate the proposed solutions. Both analyses reveal that the nonlocal effect implemented in this study stiffens the structures, resulting in reduced static deflection and increased natural frequencies. It is noteworthy that beams with dimensions comparable to microstructural length scales exhibit a significant nonlocal effect, which diminishes as the structure's size increases. Additionally, the response obtained using the Timoshenko beam model is softer in comparison to the Euler-Bernoulli model due to the consideration of shear deformation.

Abstract: Heusler alloys are intermetallic compounds formed in two combinations: Full-Heusler (X₂YZ) and Half-Heusler (XYZ). X and Y can be any transition element, and Z belongs to the main group. This shows that there can be a huge variation in the combinations, leading to various properties and applications. We aimed at predicting the combination leading to shape memory properties using machine learning tools and then synthesizing the same. The predictions are done by training the tool with input data. We employed the lattice strain, valence electron concentration ratio, mechanical stress, difference in entropy, and saturation magnetization as input features. The correlation between the martensitic and austenitic temperature was evaluated in terms of regression metrics. The random forest and decision tree modeling were executed. Test scores were obtained using frequency ordering, PCA, linear regression, and correlation matrix to forecast magnetically controlled shape memory effect. The silhouette score matched the transition temperature at which the material showed shape memory behavior. Additionally, from 70% of the training data, a combination of Iron (Fe), Nickel (Ni), and Aluminum (Al) as Full Heusler alloys stimulated the algorithms in gaining the accuracy of predictive modeling by minimizing the error. Through DFT-based bandgap and density of states calculations, the Fe₂NiAl Heusler compound is hypothesized to behave as a half-metallic ferromagnet by considering the atomic number, the number of valence electrons, and the local magnetic moment. The experimental validation will be done along with magnetization studies, magneto-transport, and magneto-caloric measurements.

Abstract: Aluminum alloy sheets are widely considered for manufacturing lightweight thin-walled structural components in the automotive and aerospace industries. However, the poor formability of the material at room temperature is still a technical challenge. Warm forming evolved as a promising technology where the sheet metal is deformed at elevated temperatures below the recrystallization temperature. Numerical modeling is vital in the modern scenario to better understand formability and to improve the designing of tooling for complex sheet components during warm forming. Hence, it is imperative to understand the accuracy of material models on formability predictions at elevated temperatures. This work presents the effect of three yield criteria, namely, von Mises, Hill-48, and Barlat-89, on the formability predictions of AA6082-O sheet at elevated temperature, say, 200 °C. Analytical necking-based Marciniak-Kuczynski forming limit diagrams (MK-FLD) at the elevated temperature were predicted by incorporating these yield models. The accuracy of predicted MK-FLDs was validated with experimental data. Furthermore, finite element (FE) modeling of limiting dome height (LDH) tests was performed using sample sizes that developed deformation modes towards biaxial, plane strain, and uniaxial modes. The effect of different yield models on the forming behavior was studied in terms of part depths and major surface strain distributions. The compatibility of yield criteria on accuracy in prediction was assessed by overlapping with the experimental data. It was demonstrated that Barlat-89 was best suited compared to Hill48 and von Mises yield models.

Abstract: This study investigates the Mg-6.5Zn-7.24Sn-1.22Ca alloy, focusing on its microstructural evolution, corrosion resistance, and mechanical performance under varying thermal and mechanical treatments. The alloy was cast under an argon environment, homogenized at 400°C for 18 hours, and hot rolled at 400°C with a 15% thickness reduction. Microstructural analysis through XRD, SEM-EDS, and optical microscopy revealed grain refinement, phase redistribution, and reduced porosity after rolling. Corrosion behavior in 3.5% NaCl solution, assessed via electrochemical techniques and weight loss measurements, indicated superior corrosion resistance in the homogenized condition due to reduced micro-galvanic coupling. Rolling, however, increased corrosion susceptibility due to strain-induced defects. High-temperature ( 200°C- 350°C ) tensile tests at strain rates of 10-4 and 5×10-4 s-1 demonstrated that tensile strength decreases with temperature, driven by dynamic recrystallization and grain boundary sliding. Strain rate variations revealed increased tensile strength at higher rates due to enhanced dislocation density and strain hardening. These findings highlight the interplay between processing conditions, strain rates, and alloy performance, offering insights for optimizing magnesium alloys for advanced engineering applications.

Abstract: The combination of cement and natural fibers, as well as Luffa fibers, represents a revolutionary breakthrough in sustainable building materials. By combining these elements, this innovation has metamorphosed the mechanical properties of the fibers, significantly improving their ability to bond with cement. This synergy offers a major breakthrough in the creation of composites that are both robust and environmentally friendly, opening the way to a multitude of potential applications in the industrial and construction sectors. The Luffa fibers were subjected to extensive tensile tests to evaluate their strength and elasticity after a sodium hydroxide (NaOH) treatment procedure, while the composite material was subjected to three-point bending tests to analyze its mechanical properties under varying loads. At the same time, the density of the composite was accurately determined, and in-depth studies were carried out to assess its water absorption rate, which is critical for construction applications. In addition, detailed mathematical modeling was performed using advanced methods such as Hirsch, ROM and IROM. Alkali treatment substantially increased the tensile strength and Young’s modulus of Luffa fibers respectively from 23.80^{± 2.1} MPa to 67.01^{± 2.8} MPa with an increasement by 142%, and 3.65^±0.4 GPa to 11.39^{± 0.9} GPa with an increasement by 152%. Cement composites showed a peak flexural strength of 1.42 MPa at 1.04%. The significant improvement in the mechanical properties of Luffa fibers achieved through alkali treatment, coupled with their inherent biodegradability, positions them as a promising sustainable reinforcement material for the construction industry.

Abstract: To enhance the interfacial bonding capacity between basalt fiber and cementitious matrix, and to maximize the efficacy of basalt fiber in augmenting toughness, fracture resistance, and flexural strength within the cementitious matrix, the basalt fiber underwent treatment using a solution of γ-amino propyl triethoxy silane (KH550). Employing a single-fiber electron tensile testing instrument, the fracture strength and fracture elongation of basalt fibers were examined under various treatment conditions, leading to the determination of the optimal treatment concentration and immersion time. Subsequently, the scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) were employed to investigate the surface morphology and elemental composition of the self-assembled molecular coating on the basalt fibers. Lastly, the UTM universal testing machine was utilized to subject concrete beams to loading, while the XTDIC digital speckle correlation full-field strain measurement system was employed to analyze strain conditions and crack propagation throughout the loading process. The experiments indicate that the KH550 system solution can spontaneously generate a fish-scale-like coating on the basalt fibers, thereby enhancing the interconnection between basalt fibers and cementitious materials, optimizing the role of basalt fibers in enhancing toughness and flexural resistance within cementitious materials, and retarding the initiation and development of concrete cracks.