جستجوی مقالات مرتبط با کلیدواژه "2" در نشریات گروه "مکانیک"

This study investigated the effects of atmospheric aging through three summer months on the mechanical properties of polyester reinforced with different mass rates of alfa fibers (Stipa Tenacissima). For this purpose, three-point bending tests were performed on pure polyester and polyester /alfa fiber composite specimens. A finite element model of flexural testing was developed to analyze the mechanical behavior of the Alfa/polyester composite. The test results showed that the alfa coarse fibers with 30 wt % were capable of enhancing the mechanical properties of the polyester/alfa composite.

The present study investigates the mechanical behaviors of hybrid fiber-reinforced polyester composites in developing a new strengthened material. The experiments were planned as per the design of experiments, the selected input parameters were fiber length (mm), NaOH treatment (%), and fiber weight (%) and the output parameters were tensile, flexural, and impact strength conditions. A Non-Linear Regression Modelling (NLRM) and Fuzzy logic model have been designed to predict and analyze the mechanical properties in unknown test conditions. Every input factor was categorized into three linguistic descriptors, while each output factor was classified into three linguistic categories. A triangular membership function was employed to define all these variables. The effectiveness of the nonlinear regression analysis and fuzzy logic model was evaluated through confirmatory experiments. The model predicted the mechanical results with an error of 7.19%, 5.38%, and 2.33% respectively. The proposed approach can significantly simplify real-life multi-response optimization problems, thereby reducing fabrication costs and enhancing composite fabrication efficiency.

Experimental and numerical studies are implemented in this work to investigate the modal characteristics of three-layered viscoelastic sandwich beams and plates with a natural rubber core and distinct isotropic face layers. In this study, the material of face layers in both beams and plates is varied with uniform face thickness by keeping the core constant to maintain the constant volume. Through the use of the Impact Hammer Modal Testing technique, experimental modal analysis is carried out with SAMURAI and ME' Scope software. The beams and plates are subjected to numerical analysis using ANSYS 19.2 Mechanical APDL Software, a finite element analysis (FEA) tool to evaluate the modal characteristics. The modal characteristics including natural frequencies and mode shapes of both beams and plates are evaluated under various boundary conditions, such as Clamped-Free (C–F), Simply-Supported (S–S), Clamped–Simply Supported (C–S), and Clamped-Clamped (C–C) for beams. Other plate boundary conditions that are taken into consideration for plates in this inquiry include C-F-F-F (Cantilever), S-S-S-S (All edges simply-supported), C-F-C-F (opposite edges clamped and other edges free), and C-C-C-C (All edges clamped). Ultimately, an excellent agreement is established when the outcomes of the experimental modal analysis are compared to those from ANSYS. The research also investigates how varying face layer material densities and end conditions affect natural frequencies at constant volume.

The aerospace and automotive engineering industries are seeing a growing need for materials that are both lightweight and very durable. This increased demand has prompted the development of innovative metal matrix composites based on aluminum. The current study aimed at developing and characterization Al7020 metal matrix composites by reinforcing micro boron carbide particles, Al7020/B4C MMCs are fabricated by stir casting method by varying the boron carbide particles in wt.% (0, 2, 4, 6, and 8wt. %). Lastly, the prepared samples were subjected to tensile, compression, hardness, and fracture toughness tests to evaluate the impact of B4C particles on density, mechanical, and microstructural parameters. By incorporating B4C particles into the Al7020 alloy, the experimental results demonstrated that metal matrix composites exhibited enhanced ultimate tensile strength, yield strength, hardness, and compression strength. In addition, the lowest density, highest toughness, and superior micrograph were observed in Al7020/B4C MMCs with 8 wt. % reinforcement of B4C particles with a minor decrease in elongation.

The novelty and main contributions of this research are to investigate simultaneously static bending, free vibration, and buckling responses of a sandwich beam composed of a five-layer beam using sinusoidal shear deformation theory (SSDT). In this work, five layers of a sandwich beam including a honeycomb core, carbon nanotubes reinforced composite (Matrix and Resin) (CNTRC) at the top and bottom of the core, and also, shape memory alloy (SMA) in the form of nanoscale particles with matrix in top and bottom of CNTRC are derived. In this study, the governing equations of equilibrium are obtained using the principle of minimum potential energy for deflection and buckling analyses, while Hamilton's principle is employed to obtain the governing equations of motion. Then, based on Navier's type method for simply supported boundary conditions, the deflection, critical buckling load, and the natural frequency for a sandwich beam composed of five layers are obtained. To validate the results, they are compared with existing literature, and there is a good agreement between them. Also, the effects of the thickness of the core, volume fraction of carbon nanotubes, and volume fraction of SMA are analyzed. The results reveal that changing the volume fraction from 0 to 0.01 results in a 30% decrease in deflection. It is concluded that with an enhancement in thickness ratio, the heat flux decreases due to the increase in the thickness of the core, while the thickness of face sheets decreases because the conductivity coefficient for CNT is higher than the core. Moreover, increasing temperature softens the material, leading to a decrease in the critical buckling load.

Grewia Optiva fiber-based polymer composites were prepared with the addition of Marble dust (MD) in varying percentages by hand-layup technique. To understand the behavior of the material, a detailed physical, mechanical, and thermo-mechanical analysis of the samples was conducted. The findings reveal that the addition of MD to 10 wt. % helps in enhancing the interfacial bonding between the fiber and epoxy. Due to the high void fraction and poor surface interaction, further addition of MD restricts beneficial changes in the composite. The thermo-mechanical analysis (DMA) illustrates that adding marble dust powder results in a decrease in chain mobility, hence enhancing the storage modulus of all samples. Due to its maximum elastic and low viscous regions, the GM-2 (MD 10 wt. %) specimen exhibits the lowest level of energy dissipation. The research also focuses on the sliding wear behavior of the material, and a Taguchi design approach is also used for parametric analysis of wear response. In conclusion, the Grewia Optiva fiber polymer composite with (GM-2) 10 wt.% marble dust shows the best mechanical, thermo-mechanical, and sliding wear results due to its superior interfacial bonding and can be found suitable for fabrication of portable cabins.

Because of the relatively high specific mechanical properties of LY556 epoxy resin, is often used as an important matrix for structural composites in high-performance applications. In the current study, an atomistic simulation based on molecular dynamics was performed to characterize the mechanical properties of LY556 epoxy (EP) nanocomposites reinforced with graphene oxide (GO) nanoparticles. The stiffness matrix and elastic properties such as Young’s modulus, shear modulus, and Poisson’s ratio for the pure EP and EP/GO nanocomposites were estimated using the constant-strain method. Three distribution methods including ultrasonic with a probe, mechanical mixing with an ultrasonic cleaner, and a high-shear turbo mixer with an ultrasonic cleaner were employed. The role of the distribution method on the tensile behavior of epoxy reinforced with varying percentages of GO nanoparticles (0.3 and 0.5 wt. %) was investigated. In addition, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were employed to investigate the quality of GO distribution in nanocomposites. In the M3 method (the optimal method) the tensile strength of the EP/GO nanocomposite was increased about 15% (76 MPa) at 0.3 wt% and 22% (80 MPa) at 0.5 wt%. Moreover, the toughness of the EP/GO nanocomposite was improved by around 34% (1.37 J.m-3) and 50% (1.53 J.m-3) at 0.3 and 0.5 wt% respectively.

The objective of the current study is to improve the strength and drainage capabilities of compressible clayey soil through the utilization of waste-to-energy plant ash. Numerous experiments, including consistency limits tests, compaction tests, unconfined compressive strength, California bearing ratio tests, and permeability tests, have been carried out in the laboratory on various combinations of highly compressible clayey soil and waste-to-energy plant ash or Municipal solid waste incinerated ash. The trial testing results show that adding waste to energy plant ash mix with the soil sample improves the strength properties of clayey soil, reducing the issue of ash dumping as well as developing a healthy environment. According to the test results, the falling head permeability test shows an improvement of permeability from 6.2×10-6 to 5.85×10-5 cm/sec for soil and soil with 20% MSWI ash mixed proportion respectively. Moreover, the mix produced by adding incineration plant ash may effectively be used as a sub-grade material, achieving cost-effective benefits. The findings showed that adding an adequate amount of bottom ash (20%) and soil sample (80%) made the soil more effective as a subgrade material by decreasing the value of differential free swell and consistency limitations of the soil and the value of UCS increased by more than 146 % and the soaked CBR values increased by 118% was noticed. The leaching test showed that when up to 20% of the ash is combined with the soil, the concentration of heavy metals lies within acceptable limits.

Developing customized drilling processes that minimize damage and improve overall performance in natural fiber composites relies on a thorough understanding of their drilling performance and potential damages. This study explores the variations in delamination and thrust force in a redmud-filled polyester composite reinforced with coconut sheath fibers. Employing a Taguchi factorial design, the experiment investigates the impact of drilling parameters, including drill diameter, spindle speed, and feed rate. The ANOVA analysis is employed to validate the experimental results. The findings indicate that increased feed rates and spindle speeds contribute to elevated thrust forces and delamination, influenced by the composite's inherent brittleness due to the addition of red mud. Among the drilling parameters, feed rate exerts the most significant influence on thrust force (ca. 30%), while the point angle has the greatest impact on delamination (ca. 60%). The analysis of drilled hole surfaces reveals matrix cracks, fiber extraction, and matrix smearing, underscoring the importance of optimizing drilling parameters, selecting appropriate tools, and implementing effective cooling methods to improve the overall surface finish and quality of drilled fiber composites. The research has the potential to aid in the development of strategies to minimize damages and enhance overall surface quality; ultimately, it contributes to advancing knowledge in materials science and engineering, with applications in the manufacturing and utilization of natural fiber composites across diverse industries.

The automotive industries have been compelled to build lighter, more fuel-efficient vehicles because of rising fuel costs and environmental laws. When the overall vehicle weight is reduced by adopting lightweight metals like aluminum-based composites, the fuel consumption also gets reduced. Aluminum-based composites are broadly used in the automotive and air transport industry due to their remarkable mechanical and tribological characteristics. The importance of composites made of aluminum used in automobile applications, as well as their damping characteristics, are discussed in this article. Due to the need for mechanical stability and performance in engineering applications, vibrations are unacceptable. Damping capability refers to the ability of materials to manage mechanical vibrations at the time of cyclic stress. To reduce mechanical vibrations in today's environment, materials with superior mechanical and damping capabilities are needed. Composites are a better alternative because they have better mechanical properties and damping capacity. The literature delves into the different aspects that influence aluminum-based composites and the need for damping studies in automotive applications. Finally, the research progress of aluminum-based composites towards damping characteristics has been reported by the Scientometric approach using VOSviewer. The Scopus engine search found 1329 documents relevant to Damping & vibration studies. Subsequently, a statistical analysis was conducted exclusively for the 628 research documents spanning the years 2010 to 2022.

This study focuses on the mechanical characterization and application of the various Multiple Attribute Decision Making (MADM) approaches for the selection of composites fabricated using two natural fibers, kenaf, and sawdust. Mechanical characterization involves testing the physical properties of these materials, such as tensile strength, flexural strength, and impact strength along with density and water absorption, to determine their mechanical behavior and suitability for various applications. The MADM approaches namely VIKOR and PSI are used to evaluate the mechanical properties of kenaf and sawdust reinforced composites for different applications based on multiple criteria or attributes. The study analyzes the trade-offs between different attributes to identify the optimal composite configuration for a given application. MADM technique offers a helpful framework for assessing the mechanical attributes of fiber-reinforced composites thereby determining their possible uses in a variety of sectors. However, it is essential to use the MADM approach in conjunction with other methods of material characterization and testing to ensure that the final decision is based on a comprehensive understanding of the material's properties and performance. The outcomes of this feasibility study will benefit researchers, manufacturers, and decision-makers involved in the selection and development of composite materials. It can assist in optimizing the material selection process, promoting sustainable and environmentally friendly choices, and enhancing the overall performance and cost-effectiveness of composite materials in various applications.

The article incisively analyzes the impact of piezoelectricity on Love wave transmission in an inhomogeneous bi-layered structure consisting of smoothly embedded thin piezoelectric material bonded to a semi-infinite fiber-reinforced medium. By applying the variable-separable method, a general form of dispersion equations, analyzing the Love waves’ characteristics in electrically open and shorted cases of the piezoelectric material has been derived. The crux of the study lies in the fact that the presence of the prestresses in the upper layer and lower half-space along with elastic, piezoelectric, and permittivity coefficients lead the derived frequency relation to merge with the classical form of equations of the Love waves. The procured dispersion relation substantiates that the depth of the upper layer prestresses, and piezoelectricity coefficients play a guiding role in the transmission of Love waves. The numerical discussions and findings carry wider applications and may imply guidance of additive manufacturing of varied composite multi-materials for pre-stressed and microstructural configurations with partial and global dispersion properties

This study proposes a numerical investigation for assessing the primary design parameters influencing the efficiency of a Darrieus type vertical axis wind turbine. The methodology consists in the numerical solution of the continuity and momentum equations utilizing the Unsteady Reynolds Averaged Navier-Stokes (URANS) approach. The turbulence closure model is the SST k-ω, and the Finite Volume Method is applied to solve the three-dimensional geometries. The findings confirm that variations in solidity and aspect ratio of twisted blade turbines, in comparison to straight blade configurations, exert a similar influence on the torque coefficient, surpassing the impact of blade torsion angle variations. Results corroborated previous findings of literature about the fluctuations in the torque coefficient (Cm) being smoothed in 55% when helical blades are used in comparison with straight configuration. However, the increase in blade torsion angle corresponded to a decrease in the torque coefficient, with maximum difference of 37% when solidity (σ) is σ = 0.75 and the ratio between height and radius of the turbine is H/R = 1.5. Results also demonstrated that the increase in the solidity from σ = 0.4 to 0.8 reduced the effect of the ratio H/R on the Cm. The increase of σ allowed a gain in Cm of nearly 60%. For constant σ and tip speed ratio (λ), the increase of H/R from 2.5 to 7.5 led to an increase of 79% in Cm. In general, results supplied a guideline on the influence of λ, twisted angle, σ, and H/R on the performance of helical Darrieus turbines.

This study aims to explore the natural convection, magnetohydrodynamics and ternary nanofluids containing Fe3O4, Cu and TiO2 in water-ethylene glycol within a hexagonal cavity containing a square obstacle. The Finite element method is utilized through the COMSOL Multiphysics 6.1 software. By utilizing visual representations, the influence of key variables on flow patterns, temperature distribution, and local Nusselt number is effectively illustrated. Simulations were carried out with Rayleigh number ranging from 103 to 105, heat source and absorption coefficients ranging from -5 to 15, and Hartmann numbers of 0, 70 and 90. The Prandtl number for ethylene glycol is 29.86. The findings of this research confirm that the proper incorporation of nanoparticles significantly enhances the heat transfer properties of base fluids.

Nowadays, there has been a notable surge in the utilization of piezoelectric materials at the micro and nano scales, manifesting across various branches of science through the development of diverse microstructures. On the other hand, given the deployment of microstructures in environments subject to temperature fluctuations or in close proximity to heat sources, it is imperative to thoroughly examine the thermal impacts at a micro scale, particularly concerning piezoelectric materials. This paper delves into the investigation of wave propagation within a micro-scale piezoelectric layer experiencing thermal shock. This study represents the exploration of thermo-electro-elastic wave propagation within the micro dimension. For the first time, it incorporates size-dependent modeling (non-classic continuous theory) along with the application of Lord Shulman's theory to analyze the behavior of the piezoelectric layer. In the modeling process, Maxwell's three equations governing energy, motion, and electrostatics were extracted, subsequently coupled together, and finally, they were reformulated into a dimensionless form. The differential quadrature method was employed to solve the equations, and the coupled equations were resolved. Houbolt's method is employed for solving the equations in the time domain. Ultimately, the findings concerning a micro-scale piezoelectric layer under thermal shock are presented. The findings highlight the significance of size effects at the micro scale, emphasizing the necessity of considering them in analyses and applications.

The motivation of the current work is the flow over a slender surface, which includes the manufacture of optical fibers, polymer sheets, photoelectric devices, wire coatings, solar cells, and fiber sheets. In order to enhance the results of the wire coating process, it is necessary to carefully examine the mass and thermal heat transmission rates. The novelty of this study is the ability to forecast complex thermal issues in the tri-hybrid Sutterby nanofluid flow, considering the effects of electro-hydromagnetic and multi-slip circumstances. The study examines the impact of nonlinear thermal radiation, electric field, and slips in velocity, temperature, and solutal properties on the steady flow confined to two-dimensions Au-TiO2-GO/SA in the field of electro-magneto-hydrodynamics.  Employing similarity transformations, the regulatory boundary layer equations are converted to nonlinear ODEs. Following that, the resulting equations are solved using the homotopy perturbation method. Numerical simulations are performed for several physical parameter values, and the influences of numerous distributions are examined. It is observed that the thermal distribution exhibits a decreasing trend as the values of the mixed convection flow, electric field, temperature jump, and velocity slip parameters are boosted. Moreover, the Sherwood number is declining by m, De, δ1, δ2, and δ3 and rising due to the enhancement of E1, γ1, and γ3.

A model of freshwater ice behavior under impact compression is suggested. To obtain the parameters (mechanical properties of ice at high-speed loading) of the model the Kolsky method is used. The necessary parameter data are obtained at a strain rate of 1.4×103 s-1. A new procedural approach and an experimental data filtering algorithm are proposed. In addition, a phenomenological model of ice is offered, which makes it possible to obtain a relationship between the measured force and the parameters of the material. The verification of the model is performed according to the results of experiments in which forces are obtained in the study of the destruction of ice samples for high strain rates. It is shown that the analytical force model describes the experimental data well.

This paper outlines the conceptual and numerical design process of a comminution equipment centered on particle breakdown through impact. The process is divided into four stages, starting with the generation of device concepts achieved by developing a needs matrix for an optimal machine. Subsequently, in the second stage, various equipment shape proposals were introduced and tested, with the selection of an optimal proposal determined through performance comparisons. For comparison purposes, simulations utilizing the discrete element method (DEM) were conducted, considering analyses of accumulated power from collisions and particle breakage. Once the optimized prototype was identified, a breakage simulation was conducted to measure the device's reduction ratio. In the third stage, the machine elements of the device were calculated. Finally, in the fourth stage, a series of simulations utilizing the finite element method (FEM) were carried out to perform structural and modal analyses of the final design. The evaluated variables identified in the simulations played a crucial role in optimizing the design, ultimately resulting in a device with a reduction ratio of 1:19.8 for limestone.

This article presents a numerical study encompassing the mechanical behavior prediction during the roll bending process applied to four distinct profiles of extruded 6061-T6 aluminum, considering different radii of curvature. The numerical simulations were conducted using the ANSYS® software, based on the finite element method, adopting the three-dimensional SOLID187 finite element. The employed computational model was developed and validated by Moreira et al. [1]. The obtained results demonstrate consistent patterns regarding stresses and displacements for the different radii of curvature. As the radius of curvature decreases, the von Mises stress tends to increase, approaching the material's strength limit. This phenomenon is critical for identifying points of maximum stress and ensuring adequate safety margins to prevent structural failures. Displacements along the profiles were also monitored, providing relevant information about its evolution at different radii of curvature and allowing curve fitting for these displacements in each profile investigated. Therefore, these consistent patterns observed can help to determine the direct influence of curvature on resulting defects, contributing to an in-depth understanding of the mechanical behavior of these profiles.

We discuss methodological aspects of assessment of the service life of structures and devices used in new technologies, paying a particular attention to non-stationary thermomechanical loading of “dangerous” zones of the systems under investigation. As result, using the approach of modern mechanics of the degradable continuum, we develop a model describing the associated processes of viscoplastic deformation and damage accumulation and adapted it to description of thermal fatigue. The presented model describes the main effects of inelastic deformation and damage accumulation processes in polycrystalline structural alloys for arbitrary complex deformation trajectories. A combined form of the kinetic equations for damage accumulation in the areas of interaction between low-cycle fatigue and long-term strength has been proposed, which makes it possible to properly describe the nonlinear nature of the damage accumulation.