Journal of Computational Applied Mechanics
Volume:53 Issue: 1, Mar 2022

In this study, dynamic analysis of functionally graded carbon nanotube reinforced composite (FGCNT) beam resting on viscoelastic foundation is investigated. Four different types of carbon nanotubes (CNTs) distribution including uniform (UD-CNT), and three types of functionally graded distribution of CNTs through the thickness of beam are considered. The Kelvin–Voigt viscoelastic model and higher-order shear deformation beam theory (HOBT) have been used. The rule of mixture is used to describe the effective material properties of the nanocomposite beams. The equations of motion are derived by using Lagrange’s equations, and solved by using finite element and Newmark methods. The effects of volume fraction and distribution of CNTs, stiffness and damping of viscoelastic foundation, slenderness ratio and different boundary conditions on transverse displacement and stresses of beam are investigated. The results show that by using viscoelastic foundation the amount of normal and shear stress have decreased considerably, and by increasing the stiffness coefficient of foundation, transverse displacement of beam reduces and the frequency of vibration increases as well, meanwhile by increasing the damping coefficient of foundation, amplitude of vibration decreases considerably. The model is verified and compared with previously published works and it shows good agreement.

This paper presents a nonlocal strain gradient theory for capturing size effects in buckling analysis of Euler-Bernoulli nanobeams made of three-dimensional functionally graded materials. The material properties vary according to any function. These models can degenerate to the classical models if the material length-scale parameters is assumed to be zero. The Hamilton's principle applied to drive the governing equation and boundary conditions. Generalized differential quadrature method used to solve the governing equation. The effects of some parameters, such as small-scale parameters and constant material parameters are studied.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important hospital pathogens that cause of severe morbidity and mortality worldwide. Coagulase gene (Coa) is a pathogenicity factor of this bacterium which found in all pathogenic strains. The aim of this study was to evaluate the antibacterial effect of hydroalcoholic extract of Satureja mutica, zinc oxide nanoparticle and zinc complex alone and simultaneously on inhibiting the growth of clinical and standard of coagulase gene expression isolates of MRSA. Minimum Inhibitory Concentration (MIC), cell viability and zone of inhibition were determained by microdilution method. MTT assay and disk diffusion method were performed against MRSA strains that possess coa gene respectively. In addition, the changes in expression of this gene were investigated by RT-PCR in MIC concentration. Hydroalcoholic extract of Satureja mutica, zinc oxide nanoparticle, and copper nano-complex showed antibacterial and inhibitory effects on MRSA growth. Additionally, a significant inhibitory effect was seen on coagulase gene expression in presence of hydroalcoholic extract of Satureja mutica. Frurthermore, the MIC for clinical and standard MRSA were determined as 1500 and 3000 µg/ml for the Satureja mutica extract, 20 and 40 µg/ml for the zinc oxide nanoparticle, and 20 and 40 µg/ml for the Zinc complex respectively. After performing RT-PCR, the results of electrophoresis showed that Satureja mutica extract in MIC induced an inhibitory effect on coagulase gene expression. Using Satureja mutica extract with nanoparticles in MIC concentration showed a synergistic effect in coa gene expression. However, no effect was observed on housekeeping arcC gene. Zinc oxide nanoparticles also have inhibitory effects on the growth of bacteria but no inhibitory effect was observed on expression coa gene.

In order to investigate and improve the destructive effects of maneuvers that the flying body has during a flight in space, it is necessary to know the forces acting on the flying body. In this paper, an analysis of the composite sandwich structure of a launch vehicle fairing is considered. This study explores carbon-fiber-reinforced skins with different cores used to deploy satellites and can be used as a space habitat. In order to calculate the effective forces on sandwich skins, finite element method (FEM) was used to determine three-dimensional stress and strain. Three types of structural models with honeycomb and solid core under dynamic loads were compared and evaluated. Models were compared in three category of stress distribution, strain and weight. The honeycomb core pattern helps reduce the structure's weight up to half of the structure compared to a solid core. The effect of mesh size sensitivity applied on simulations. The results showed that the amount of stress and strain were the same in all models and only differed in dispersion. However, the composite sandwich structure with aluminum core showed more strength against the applied forces.

Due to the high latent heat value, using microencapsulated PCMs increases the heat transfer coefficient in the heat sinks in mini electronic devices, chilled celling, … . In this paper, convective heat transfer by mixed PCM particles in a fluid as slurry, has been studied by the Eulerian-Lagrangian two-phase method. In this method, the fluid phase is studied by the Eulerian and the particle phase is studied using the Lagrangian view. In this paper, the base fluid is water and the particles made of encapsulated micro-size paraffin wax which has covered by a thin layer of Fe3O4. The fluid phase is solved by a control volume method (SIMPLE) and the velocities of the particle phase are solved by the 4th order of the Runge-Kutta method. Due to high Biot number for particles, the lumped temperature assumption for particles is not valid and the transient one dimensional conduction equation has been solved. In this paper details of solving the energy equation inside the particles has been presented. The results include the local and mean Nusselt numbers for different Reynolds numbers including 200, 350 and 500, wide range of the volume fraction from 0-5% for PCM particle with 10 micro-meter diameter, inside the mini annular tube with inner diameter of 1 mm and outer diameter of 3 mm. The results show for  and Re=200, 500, the Nusselt number increases by 10 and 12.5%, while the pressure loss increases by 2 and 5.5% respectively. The maximum performance coefficient is 1.078 and occurs for Re=200 at .

In this research, vibration frequency analysis of a microbeam under a temperature pulse is investigated. In view of the modified couple stress theory and generalized Lord-Shulman (LS) hyperbolic heat conduction model with a single relaxation time, the thermoelastic coupled equations for clamped microbeams have been determined. The analytical terminologies for temperature, deflection, axial displacement, dilatation, flexure moment, couple stress, and axial stress in the microbeam have been acquired utilizing Laplace transform technique. Furthermore, examinations have been displayed in graphs to figure the effect of particular boundaries, for example, the couple stress and pulse of temperature on every one of the thoughts about factors. The couple stress parameter significantly affects all the field distributions. The higher temperature pulses show many disagreements between the results of the present couple stress model and the classical LS one. Alternate estimations of thermal relaxation time have been utilized to the curves anticipated by two unique theories of thermoelasticity that gotten as exceptional instances of the current LS model. Numerical inferences explain that evaluation of deflection anticipated by brand new theory is lower than that of classical LS one.

Dynamics of beams made of axially grading material has been analyzed in present work. Shear deformation and rotational inertia of the rectangular cross-sectional beam have been considered using Timoshenko-Ehrenfest beam model. Material properties of the beam have been assumed as a power-law function. Solution of the vibration problem of the axially functionally graded Timoshenko-Ehrenfest beam has been carried out with Ritz formulation. Present model has been validated with the previous literature works. Effects of power-law index parameter and grading material properties on the dynamics of axially functionally graded Timoshenko-Ehrenfest beam have been investigated. Transverse deflection and slope of the beam have been depicted in various cases. Present study can give useful results for designing of axially graded structural elements.

Machining hardened steels is a common requirement in various industries. This includes gearing and spline cutting on hardened steel parts at high speeds. Traditionally, gearing tools were made of high-speed steels, which made them suitable only for gearing at low cutting speeds with coolant. However, hard gearing using disk cutters with interchangeable carbide inserts is a new and flexible method for machining various types of splines and gears without special equipment. In this research, a disk cutter with four carbide cutting inserts is designed and manufactured. Experimental analysis is performed to assess the applicability of the developed cutter in machining splines on hardened steel axle shafts. Workpieces made of DIN 60SiMn5 steel with a hardness of 46 HRC and AISI 1552 steel with a hardness of 61 HRC are machined using two types of carbide inserts in wet and dry cutting conditions. Results show achieved surface roughness values in the range of 0.161 μm < Ra < 0.376 μm, which is an indication of a very good surface quality. Also, ANOVA methods are used to assess the impact of input parameters on machined surface roughness and cutting tool wear. The analysis shows that surface roughness is most affected by insert type, while use of coolant is the most effective parameter on tool wear. This research also proves applicability of dry milling as a sustainable and environmentally friendly method for spline cutting on hardened steels.

This paper presents a systematic formulation of the hyperbolic shear deformation theory for bending problems of thick beams; and the Fourier series method for solving the resulting system of coupled differential equations and ultimately finding the displacements and stress fields. Hyperbolic sine and cosine functions are used in formulating the displacement field components such that transverse shear stress free conditions are achieved at the top and bottom surfaces of the beam, thus obviating the shear correction factors of the first order shear deformation theories. The vanishing of the first variation of the total potential energy functional is used to obtain the system of coupled differential equations for the domain and the boundary conditions. The domain equations are solved using Fourier series method for simply supported ends for linearly distributed and uniformly distributed loads. The solutions are found as infinite series with good convergence. Solutions obtained for the axial and transverse displacements, and normal and shear stresses at critical points on the beam agree remarkably well with previous solutions, and for normal stresses, the errors of the present method are less than 0.5% for aspect ratio of 4 and less than 1.9% for aspect ratio of 10.

Raman spectroscopy is an important method for identifying molecules and has many uses in determining the chemical and structural properties of different materials. Despite the structure of the intelligently enhanced substrates used in laboratory research, the development of a simple, flexible, and cost-effective substrate is also important for enhancing the application of surface-enhanced Raman spectroscopy (SERS) in practical analysis. Recently, paper has been considered for the fabrication of flexible SERS substrates. Compared to other SERS substrates, paper substrates have the unique advantage of strong mechanical properties, various components, and adjustable pore size. These features give many advantages to paper-based substrates for SERS analysis in practice, such as low-cost and straightforward substrate preparation, high efficiency, separation, and detection methods. Therefore, paper-based substrates in SERS analysis have been promising in applications such as environmental monitoring, food safety with high sensitivity and efficiency, etc. This review presents a summary of the research related to paper involving SERS analysis. First, a brief introduction to understanding its background is provided, followed by a brief history of the paper-based substrates. Then, the preparation of the paper-based substrate and the role of the paper are summarized, and the applications of paper-based SERS substrate in the analysis are presented. Then, in a separate section, several studies reported in the field of microfluidic paper-based SERS platforms are reviewed. Finally, the challenges and perspectives of this issue are discussed.