Journal of Solid Mechanics
Volume:14 Issue: 4, Autumn 2022

In this study, the effects of impact angle and impactor geometry were investigated on the impact behavior of aluminum honeycombs experimentally and numerically. The high-velocity impact tests were carried out using a gas-gun test machine with flat, spherical and conical-head impactors and impact angles of 0°, 15° and 30° at different incident velocities ranging from 55.8 to 150.5 m/s. The numerical models were developed in LS-Dyna finite element code and well validated against the experimental results. The results showed that the impact behavior of honeycombs is considerably dependent on the impactor head geometry and the impact angle. The honeycomb panel impacted by the conical projectile experienced the highest absorbed energy and ballistic limit velocity. Moreover, it was found out that increasing the impact angle increased the absorbed energy and ballistic limit velocity of honeycombs. Furthermore, different impactor head geometries resulted in different failure mechanisms in the course of impact loading.

This study deals with the free vibration of the sandwich plate made of two smart magnetostrictive face sheets and an electro-rheological fluid core. Electro-rheological fluids are polymer-based material that changes its viscosity under the applied electric field. A feedback control system follows the magnetization effect on the vibration characteristics of the sandwich plate when subjected to the magnetic field. It is assumed that there is no slip between layers, so the stress-strain relations of each layer are separately considered. Energy method is utilized in order to derive the five coupled equations of motion. These equations are solved by differential quadrature method (DQM). Results of this study show the rheology response of fluid in presence of electric field where the core gets hard and the dimensionless frequency increases. Also, the significant effect of thickness and aspect ratios and velocity feedback gain are discussed in detail. Such intelligent structures can replace in many of the systems used in automotive, aerospace and building industries as the detector, warning, and vibration absorber etc.

Regarding the necessity of designing high Q-resonators in micro electromechanical systems, this paper investigates the viscoelastic behavior of a rectangular micro-plate subjected to electrical actuation. Equations governing the vibrations of the homogeneous plate were obtained on the basis of classical plate theory (Kirchhoff's model). The Kelvin–Voigt model was also employed to consider the viscoelastic properties. The Galerkin decomposition method was used for decomposition of the governing differential equations. Additionally, the effects of various parameters were investigated on the Q-factor. Furthermore, a Finite Element simulation is carried out using COMSOL Multiphysics. The verification of the proposed model was conducted by comparing the obtained results with those from previous studies which revealed the validity of the proposed approach and the accuracy of the assumptions made The suggested design approach proposed in this this study is expected to design high Q-factor micro resonators and may be used to improve the performance of many MEMS devices.

Composite structures are increasingly being used in various engineering structures such as automotive, aerospace, and civil  structures due to their superior properties, namely, high strength-to-weight ratio, impact resistance, and durability. For the purpose of accessibility to other components and possibility of installation, aerospace structures encounters geometrical discontinuities which can lead to a complex structural analysis due to non-isotropic behavior. This paper aims to study the frequency response behavior of a composite lattice conical structure considering the effect of geometric discontinuity stiffened by a circular ring. The lattice structures are made of glass fiber reinforced polymers (GFRP) fabricated using filament winding method and cured in an autoclave. Numerical analysis and experimental modal testing was performed to obtain frequency response of the structures considering geometrical discontinuities. The results showed that the natural frequency values of structures with cutout in free-free boundary conditions are lower than those without cutout. Furthermore, comparing the mode shapes of structures indicated that these shapes were similar to each other and only some slight differences in discontinuity area were observed in some modes. Finally, the highest difference of numerical analysis results in structures with or without cutout was 2.61% while the highest difference of experimental analysis results in the structures was 3.73%. The greatest difference in the numerical and experimental analysis results is pertinent to the second mode in the structure without cutout is 15.64% and in the structure with cutout is 12.48%.

Plane strain upsetting of round cross-section billets between the flat and V-shaped dies has been studied in this paper. A deformation model has been proposed and the geometry of the deformed billet cross-section is determined for a given displacement of the top flat die. To analyze the process, the slab method of analysis has been applied and for a given process conditions, the required forming load has been estimated. The process under consideration has been performed also with the finite-element method to predict the forming load and the material flow. The calculated forming load and the deformed billet cross-section geometry compare well with the FE simulations data. The effects of friction factor and the angle of the V-shaped bottom die on the forming load have been investigated. The theoretical results have been indicated that as the bottom die angle decreases the forming load decreases and the forming load is not influenced by friction in case of small bottom die angles.

In this article, a biomechanical model is presented for dynamic instability behavior of aorta arteries with atherosclerosis conveying pulsating blood including pharmaceutical nanoparticles. Utilizing Mindlin theory of cylindrical shell, the aorta artery is simulated mathematically. The atherosclerosis is assumed symmetric with lipid tissue. The pharmaceutical nanoparticles are subjected to magnetic field for attract to the lipid tissue in artery. Applying energy method and numerical method of differential quadrature (DQ), the final equations are solved for obtaining the dynamic instability region (DIR). The DIR is curve of dynamic blood velocity with respect to artery frequency. The influences of various variables of magnetic field, magnetic nanoparticle’s volume percent, tissue, lipid’s height and length upon dynamic behavior of aorta artery are investigated. Based on the results, the existence of magnetic nanoparticle in the blood enhances the artery frequency and consequently can lead to better heart performance and reduce the risk of heart attack.

Design multiphase heterogeneous structures in order to provide multifunctional properties has many applications in the field of material design. In this research, a new method for construction multiscale heterogeneous microstructure is presented. Using statistical correlation function, specifically, two-point correlation functions, bicontinuous two-phase structure is constructed that has solid and void phases. In order to construction the heterogeneous media, an exponentially decreasing sine function is used as autocovariance function. Then based on Schwartz P minimal surface the porous media structure, is divided into two parts; porous solid phase and void phase. From the point of view of continuity, the phases are investigated and it is observed both phases of the constructed microstructure are connected throughout the media. Using this method it is possible to construct bicontinuous multiscale microstructures that are solid and void phase in coarse scale and the solid phase can be constructed as void and solid phase in fine scale.

A composite grid sandwich panel consists of a core with a composite grid structure and two faces on both sides of the core. This study investigated low-velocity impact in grid sandwich panels with grid cores experimentally and numerically by constructing and performing experimental tests using Abaqus finite element software. In the experimental part, three sandwich panels with grid cores were made for the low- velocity impact test. In the numerical part, three-dimensional elements were used, and damage was solved via programming in the Fortran language in Abaqus software. The results showed that the use of foam in the core of these structures reduced deflection due to impact despite a slight increase in the final weight of the structures.