Mechanics of Advanced and Smart Materials journal
Year:2024 | Volume:4 | Issue:1|Papers Count:8

In this research, free vibration of tapered sandwich beam with variable thickness is investigated. The core is made of porous aluminum foam, which is included by two composite skins reinforced with carbon nanotubes. In order to derive the equations of motion, first the constitutive equations of the core and skins are expressed. Then the kinetic and strain energies of the beam are calculated. Formerly, with the aid of applying Hamilton's principle, the equations of motion of the beam, which are of the type of partial differential equations, and also the equations of the boundary conditions are derived. Next, using the differential quadrature method, the equations of motion and boundary conditions are discretized in the form of algebraic equations and rewritten in the form of the standard eigenvalue equation. By solving the eigenvalue problem, the natural frequency is evaluated. In order to validation of modeling and solution method, the present results are compared with those available in the literature. Finally, the effect of porosity distribution, porosity coefficient, core thickness and beam length on the natural frequency is investigated.

In this study, an analytical solution has been developed to examine the mechanical behavior of an incompressible functionally graded hyperelastic cylinder subjected to simultaneous extension and torsion. The recently proposed exp-exp strain energy density is employed to predict the behavior of hyperelastic material, and its related material parameters are assumed to vary along the radial direction in an exponential fashion. Finite element analysis is conducted by preparing a user-defined UHYPER subroutine in ABAQUS to evaluate the proposed analytical solutions. FEM results and those of the analytical solution are in good agreement for various stretches and twists and reveal that the form of stress distributions and the maximum stress depend on the exponential power in the material variation function. In contrast to axial stretch, the effect of twist on the distribution of longitudinal stress is more complicated, and for large twists, two extrema in the stress distribution plot are observed, which move toward the center and outer surface of the cylinder on further twisting. Moreover, the longitudinal stress controls the variation of von-Mises and strain energy density throughout the radial direction. Additionally, considering an axial stretch, a point is identified where the axial force arising from torsion is compressive for stretches below this value, and it brings about the cylinder to elongate under twisting. However, this part of the total axial force varies from a tension state to a compression one for larger stretches, i.e., by increasing the twist, the cylinder first tends to shorten and then elongates on further twisting.

In the present study, the natural frequencies of rectangular plates made of multi-directional functionally graded materials on an elastic substrate was investigated for the first time. The mechanical properties of the material in the examined plate can be changed in all three coordinate directions according to a power law function. Equations of motion are written according to the three-dimensional theory of elasticity and then discretized using the method of Generalized Differential Quadratics. By comparing the results of several examples in the published articles, the validity of the method and the solution was examined, indicating the high accuracy of the method used. The influence of a change in direction on the mechanical properties is examined using several examples and the results are examined. In addition, the effects of plate thickness, plate dimension ratio and the effects of elastic foundation parameters for different boundary conditions were investigated and presented in the form of diagrams. The results show that the direction of change in material properties can have a significant effect on the natural frequency of the plate.

Optimization of composite shafts subjected to torsional loading has been investigated in the previous studies by considering the constant value of load and so, minimization of shaft mass was defined as the objective function (OF). In the current study, maximization of the torque to mass (T/m) ratio was considered as OF. To do so, the Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) methods were utilized. The number of layers, thickness and angle of each ply as well as the applied torque were considered as the input variables. Moreover, preventing of failure in composite shaft, based on Tsai-Wu failure theory developed in Abaqus finite element software, was defined as the constraint of optimization problem. Also, in order to investigate the effect of OF type, in addition to the T/m, the mass was also defined as OF in a separate optimization problem. The results revealed that despite PSO, GA had suitable convergence in the optimization. Moreover, in spite of the type of OF, using a composite shaft compared to the steel one, had at least 80% mass reduction. Furthermore, although the predicted composite shaft via T/m OF has more mass compared to that predicted via m OF, it can tolerate torsional loading up to 8.5 times more. This point can increase the load carrying capacity of composite shaft.

Nanomanipulation and displacement of nanoparticles has found wide applications in various sciences today.One of the basic tools for performing the Nanomanipulation process is the atomic force microscope.Today the atomic force microscope has found various applications, including surface imaging, manipulation and movement of particles, extracting the properties of materials and textures.The manipulation of nanoparticles usually involves two phases.The first phase includes the extraction of the critical force and the critical time before the start of the particle movement.The second phase also includes the investigation of particles during movement during Nano manipulation and displacement.Due to the fact that in micro/Nano dimensions,surface forces are more effective than volume forces,so it is very important to choose the appropriate contact model in modeling and simulating the Nano manipulation process.Various parameters affect contact models on the micro/Nano scale.In this research, the effect of different parameters on Hertz, JKR and DMT contact models has been investigated.For this purpose, in order to investigate the effect of different input parameters, the statistical method of sensitivity analysis called E-fast, which is one of the fast methods,has been used.The input parameters examined in this research include tip radius,volume of the particle,elastic modulus of the tip,elastic modulus of the particle,Poisson's coefficient of the tip and Poisson's coefficient of the particle, as well as penetration depth and force, which are explained as output parameters.The obtained results show that the volume of the target particles and the tip radius have a great influence on the force and depth of penetration in the contact models

Tube flow forming is one of the most cost-effective production methods for creating simple cylindrical tubes with external and internal protrusions, with or without flanges. The dimensional accuracy of tubes produced by this method is higher than that of other methods, making it widely used in the aerospace industry. In this study, the flow forming process of three-roller high-strength steel was investigated through finite element analysis and compared with experimental results. The forming process was investigated for various mandrel rotation speeds and feed rates. By comparing the experimental results, the effects of each parameter on the surface quality (roughness), geometric quality and accuracy of the manufactured product (out-of-roundness, diametral increase) were studied. The results showed that the surface roughness of the final product increases with the increase in the feed rate. Increasing the feed rate also leads to a reduction in out-of-roundness and thus improves the geometric quality of the final product. Increasing the mandrel rotation speed results in a reduction in the surface roughness. Increasing the rotation speed also result in an increase in the out-of-roundness of the product.

The bone drilling process is a crucial and widely used machining technique in the field of surgery and medical engineering. It is particularly prominent in orthopedic surgery, fracture treatment, bone sampling, and dentistry. The most important complication that may occur in bone removal surgery is the increase in temperature from the permissible range and causing thermal necrosis in the bone tissue. In general, if the temperature of the bone piercing process exceeds 47°C, thermal necrosis occurs. In case of thermal necrosis, bone fixation is not done well. In recent years, researchers did not achieve acceptable results in this field due to the lack of efficient optimization methods and the failure to consider all parameters affecting the bone drilling process. Also, it was not possible to achieve the best effective parameters to prevent thermal necrosis. Therefore, in this article, in order to prevent this issue, along with the precise design of the experiments, a relatively accurate method has been presented as a solution to control the temperature and axial force in order to optimize the effective parameters on the bone drilling process and improve the bone drilling process. In this article, the Taguchi optimization method is used for this purpose, and this method performs the optimization process with high accuracy in a shorter period of time compared to other optimization methods.

Thin-walled structures due to their lightness, good energy absorption capacity and high energy to weight absorption ratio are one of the most efficient energy absorption systems in various industries such as automotive, rail and military industries to protect the lives of passengers and pedestrians. Also they are considered in case of accidents or when protecting devices. The purpose of this project is to investigate the response of hierarchical square thin-walled structures that made of ABS polymer and made by a 3D printer under lateral impact. At first, different models are presented in separate categories. Then, due to the hierarchically of the samples, in the simulations, the effect of parameters such as the shape of the houses, the number of houses, the thickness of the walls and etc. are examined and the best samples are made for experimental tests. Then, in order to validate the samples, after making them by a 3D printer, they were subjected to lateral impact by a drop-weight impact test machine and the obtained results were compared with the simulation results. According to the results, it has been observed that 1HR16 is the best sample in energy absorption rate, mean crushing force and crush force efficiency. Also, by increasing the number of houses in each sample, all energy absorption parameters are improved. generally, rectangular-house specimens have better impact resistance.