This article investigates nonlinear free vibrations of porous functionally graded (FG) annular spherical shell segments surrounded by elastic medium and reinforced by circumferential stiffeners. Porous FG material contains distributed even and un-even porosities and is modeled based on refined power–law function. The governing equations of stiffened porous annular spherical shell segments have been

In this paper, the nonlocal strain gradient theory and a new quasi 3D plate theory are employed to investigate the wave propagation in functionally graded (FG) porous graphene platelets (GPLs)-reinforced nanoplates on elastic foundations subjected to in-plane mechanical load and magnetic field. The present theory takes into account the shear deformation as well as the thickness stretching effect. The

The application of oil-bearing joint that is widely used in various mechanical equipment can effectively improve the dynamic characteristics of integrated machineries. A fractal contact model of oil-bearing joint considering the effect of asperity interaction is proposed in this article. The equivalent stiffness and damping of oil-bearing joint are divided into a solid contact portion and a liquid

In this work, a parameterized model of 3-RRR planar parallel manipulator is proposed, aiming to optimize the overall performance with optimum shapes and sizes of the base and mobile platforms. In the model, the inverse and direct kinematics are addressed, upon which the global kinematic performance in terms of dexterity index is calculated and analyzed. A shape and dimensional optimization is accomplished

The main aim of this study is to analyze the fuel saving possibilities of optimized gear shifting strategies in a vehicle with a flex-fuel engine powered by both ethanol and gasoline when submitted to a real-world driving cycle. A computational model is implemented and, for each fuel option, an optimization problem is solved aiming at minimization of fuel consumption and traveling time. The standard

Crawler crane designers continually extend the height of the machines. Models that reach over 500 feet high are commercially available. Of course, as the crane height increases, so do the hazards associated with tip-over accidents. Destabilizing tip-over moments are generated by the boom and the suspended payload when they extend beyond the base of support. Stabilizing moments are generated by the

Airships are inherently sensitive to random atmospheric disturbances that could potentially make their data gathering and observation missions a formidable task. In this context robust closed loop feedback controllers are important. The present study is therefore focused on optimal feedback controller design of an indigenous domestically designed airship (DA) for added robustness against atmospheric

The present article aims to clarify the effect of the nanoflow on the nonlinear dynamic instability of graphene sheets under parametric excitation. To achieve this aim, the graphene layer is added to a visco-Pasternak foundation then, the resulting nanostructure is subjected to the nanoflow and a parametric axial force, simultaneously. The nonlocal elasticity and the nonlinear von Karman theories and

The present article is devoted to the cyclic responses of functionally graded (FG) pipe incorporating continuum damage mechanics parameters under thermomechanical loadings. The thermal, mechanical, the coefficients of Chaboche nonlinear kinematic hardening model, and damage parameters are considered to be varied continuously in the radial direction with power-law function, instead of being constant

The use of piezoelectric nano-fillers in a non-piezoelectric matrix is a very attractive proposition for developing smart nanocomposite materials with desired electro-mechanical properties. The eco-friendly nanowires (NWs) of zinc oxide (ZnO) and gallium nitride (GaN) are the two candidates used to introduce smart piezoelectric nanocomposite materials. Specifically, in this first effort, we examined

As the main contribution, a nonlocal strain gradient theory (NSGT) is developed in conjugation with the generalized differential quadrature method (GDQM) to analyze the free vibration of a transversely graded nanoshell subjected to magnetic and thermal loads derived by using the first-order shear deformation theory (FSDT) and Hamilton’s principle. Comparisons with other common methods have shown the

Nowadays there is an increasing demand to develop light weight defense vehicles, fighter aircrafts and warships in order to enhance their mobility and fuel economy. It can be achieved by using the light weight structures made up of Aluminum and Magnesium plates which will reduce the weight, increase the payload carrying capacity and efficiency of the vehicles. In the present work, experimental ballistic

This article deals with the investigation of free vibration and buckling behaviors of carbon nanotube (CNT)-reinforced cross-ply laminated composite plates. The plate kinematics is assumed to follow a first-order shear deformation theory (FSDT). After the coupled equations of motion and buckling are derived, the method of discrete singular convolution (DSC) is used for the numerical solution of the

In this article, free vibration and dynamic transient response of a multilayer polymer nanocomposite beam resting on elastic foundation reinforced by graphene platelets (GPLs) non-uniformly distributed through the thickness direction in thermal environment is investigated. Theoretical formulations are derived based on Hamilton’s principle, Timoshenko beam theory relationships. The effective Young’s

The geometric nonlinear response of spherical shells made of sandwich functionally graded material (SFGM) under uniform external pressure incorporating the effects of transverse shear deformations is considered. The equilibrium and compatibility nonlinear differential equations can be solved by using the modified interaction method. All of the equations are developed based on the first-order shear

The seismic performance of an improved column-to-column connection in the precast concrete frame is studied in this article, including five precast specimens and one cast-in-place specimen. The traditional reinforced concrete tenon connection of precast concrete frame columns is replaced by the concrete-filled steel tubular tenon. The welding or cold extrusion sleeve connection of the column longitudinal

This paper provides a method to study the effect of porosity and the thermal relaxation time in a poro-thermo-elastic medium using finite element method. One-dimensional application for a poro-elastic half-space is considered. Due to the complex basic equation, the finite element method has been adopted to solve this problem. The Laplace transformation technique is applied to the domain of time and

In this work, a new attempt has been made using machine learning algorithms for assessing failure mode of austempered ductile iron perforated plates. This aims at providing some insights into these problems by comparing the performance of machine learning models which are part of artificial intelligence. The ballistic performance could be assessed by k-nearest neighbors (KNN), support vector machine

Modeling of viscoelastic behavior can be useful to accurate study of micro-shell vibration. In this study, influence of viscoelastic coefficient and material length scale parameter on frequency of a cylindrical micro-shell with/without conveying fluid are investigated. Considering trapezoidal shape factor via Kirchhoff-Love’s hypotheses and modified couple stress theory (MCST), governing equations

This paper presents the design, mathematical development and experimental validation of a new vibration-driven locomotion module for capsule robots. The proposed system consists of a mass moving inside a body mass. A nonlinear elastic spring is used to connect the two masses, providing the ability to enhance the resonant characteristics. Being excited by a half-sine electromagnetic force, the internal

This is the first research on the pre-thermal buckling and vibration analysis of imperfect graphene nanoplatelets reinforced composite (GPLRC) doubly curved open cylindrical micropanel in the framework of numerical based two dimensional-generalized differential quadrature method (2D-GDQM). Additionally, the small-scale effects are analyzed based on nonlocal strain gradient theory (NSGT). The stresses

In this paper, the large amplitude vibration of moderately thick three-phase multi-scale composite doubly curved shells is investigated. The epoxy resin is enriched by carbon nanotubes (CNTs) and the E-glass fibers are embedded in the reinforcement matrix. The effective materials properties are predicted by combination of Halpin-Tsai relation and micromechanics approach. The von Kármán geometric nonlinearities

In this paper, the dynamics of a viscoelastic pipe conveying fluid attached to a nonlinear energy sink (NES) subjected to a sinusoidal flow is studied, aiming at performance improvement of such fluid-interaction systems. The NES has an essentially nonlinear cubic stiffness and a nonlinear cubic damping. Complexification-averaging and fourth-order Runge-Kutta methods are applied to solve the equations

Strength and durability investigations of parallel-mechanism (PM) and robotic systems, used as integral part in modern manufacturing, are necessary at the virtual design stage. Nonetheless, because of the limitations of existing finite element (FE) approaches, flexible-link geometries are often simplified or distorted when converting solid models to FE analysis meshes. This article introduces and demonstrates

The variation of modal responses due to the change in shapes (square/rectangular) and sizes of the cutout impregnated composite panels (Glass/Epoxy) are predicted numerically using higher-order finite element formulation. The degree of accuracy of the proposed model is verified by comparing the modal values with the experimentally recorded data for the validation purpose, including the experimental

The main shaft device (MSD) is a key component of the mine hoisting system. During lifting, vibration of the system will cause dynamic tension of wire rope at both ends, resulting in the complex stress state at the critical location of the MSD and thus considerably decreasing its service life. This study is aimed at investigating time-dependent reliability of the MSD based on fatigue damage accumulation

In manufacturing firms, welding technology plays a supreme role in joining purposes. The joining of dissimilar metals is complex in several conventional type welding. Friction stir spot welding (FSSW) is a solid-state welding technique and it is a derivative of conventional friction stir welding (FSW) to join the metals. The recent demands of advanced engineering materials such as aluminum alloys and

A finite element approach for modal analysis of square FGM plates is developed by the ABACUS software coupled with FORTRAN. The Material properties are assumed to be changed continuously from one surface to another through its thickness direction according to the simple power-law distribution. The analysis was performed on relatively thin square FGM plates with various combinations of simply supported

During the topology optimization process, the stiffness matrix of the structure changes continuously. Suppose we have a structure whose stiffness matrix is in a special form such as block tridiagonal matrix at the beginning of topology optimization process. The question now arises: How this special property can be used in the topology optimization process in an efficient manner? To find the answer

In this task, a numerical study is utilized to determine the residual stress of the flash butt joint in the UIC60 rail. To accurately predict critical locations of tensile residual stress, the influence of phase transformation is considered in the simulation. To reduce the possibility of failure in the welded rail, the most effective parameters of the flash butt welding during and after the process

In this article, static response of functionally graded saturated porous rotating truncated cone is investigated for the first time. Three different patterns are considered for porosity distribution along with the thickness of the cone, which are symmetric nonlinear, nonlinear asymmetric and uniform distributions. The relationship between stress and strain is based on the Biot constitutive law instead

Effects of adding graphene nanoplatelets (GNPs) on the elastic properties of short SiC fiber-reinforced aluminum (Al)-based hybrid nanocomposites are evaluated using a micromechanical approach. Agglomeration and size of GNPs and formation of Al/GNP Al4C3 interphase are evaluated. Influences of alignment, aspect ratio and volume fraction of SiC on the Al-based hybrid nanocomposite properties are studied

In this article, the vibration analysis of a double-walled carbon nanotube (DWCNT) conveying viscous flow with the aid of modified strain gradient theory has been investigated. The visco-Pasternak model is used to simulate the elastic medium. The force caused by viscous fluid is calculated by modified Navier–Stokes relation. The Gurtin-Murdoch surface elasticity theory has the capability to capture

The present paper investigates the reflection coefficient of thermoelastic plane waves at the free surface of an elastic half-space influenced by initial stress and temperature-dependent properties in the presence of thermal loading bounded by the three-phase-lag (3PHL) thermoelastic model. It revealed three plane waves, i.e. (thermal wave (T-wave), P-wave, and SV-wave). It provided the numerical solution

In this article, vibration characteristics of three different types of Single-Walled Carbon Nanotubes (SWCNTs) such as armchair, chiral, and zigzag carbon nanotubes have been investigated considering the effects of surface energy and surface residual stresses. The nanotubes are embedded in the elastic substrate of the Winkler type and are also exposed to low and high-temperature environments. A new

In this article, the influence of angular acceleration on the mechanical response of an exponentially graded piezoelectric material (EGPM) rotating annular plate with variable thickness placed in a magnetic field is studied. As a result of angular acceleration, the Lorentz force exists in both radial and circumferential directions. Using the separation of variable method, three coupled governing partial

The aim of this work is to provide a method for dynamics and trajectory control simulation for underwater vehicle motions which is based on quasi-velocity decomposition of the inertia matrix. In terms of the transformed equations of motion a tracking control algorithm (containing an adaptive term) for an underwater vehicle is given. In the algorithm dynamics of the vehicle is included into the control

In this paper the forced axial vibration of a nanobeam by deploying the nonlocal strain gradient theory exposed to a distributed moving force, is investigated. The assumed nanobeam in this paper is under the axial constant distributed load. The governing equations of the vibration of the nanobeam are obtained via the classic beam theory and the Hamilton principle. The determined partial differential

In the present study, based on 12-unknown higher order shear deformation theory (HSDT), buckling and vibration analysis of FG-CNTRC rectangular plate are investigated for various types of temperature distribution and boundary conditions. Implementing Hamilton’s principle, the equations of motion are derived and solved by adopting the Navier solution for the simply supported boundary conditions and

The transient response of a slant-cracked rotor system during shut-down has been analyzed while it is decelerating through the critical speed. Vibration response has been simulated by using finite element method (FEM) for flexural vibrations. An unbalance force and a harmonically-varying torque is applied on the rotor system. Subharmonic frequency components at an interval frequency corresponding to

In this study, we investigate the dynamic scaling laws of geometrically similitude models and systems for predicting their vibration characteristics accurately. A determination method of scaling laws based on least square method for calculating weighted powers of scaling factors is proposed for the first time. Taking geometric parameters as input (design) parameters and vibration characteristics parameters

This article deals with the thermal vibration analysis of the graphene-oxide powder-reinforced (GOPR) nanocomposite plates, once the plate is embedded on the viscoelastic substrate. The structure is subjected to thermal loadings with various temperature rises such as sinusoidal temperature rise (STR), linear temperature rise (LTR), and uniform temperature rise (UTR). Damping behavior of the GOPR nanocomposite

This paper presents the free vibration analysis of a composite laminated square plate with complicated cutout. The problem formulation is based on the higher order shear deformation plate theory HDST C0 coupled with a curved quadrilateral p-element. The elements of the stiffness and mass matrices are calculated analytically. The curved edges are accurately represented using the blending function method

Since the two-directional functionally graded (2D-FG) materials can satisfy the new requirements raised based on the elimination of the stress concentration, delamination and cracking problems accompanying with the low cost and lightweight on the structures without sacrificing the stiffness and strength, the structural analyses of these structures become more important than ever. Moreover, the usage

In the present study, free vibration of sandwich flexoelectric plates resting on Pasternak foundation is investigated. The top and bottom layers are under applied voltage based on flexoelectricity considerations and core is a nanocomposite plate where reinforced by carbon nanotubes. Based on first-order shear deformation theory, flexoelectricity considerations and Hamilton’s principle, the governing

The optimal design of the stress state in elastic plate structures with openings is a problem of great significance in engineering practice. Achieving proper shape of hole can reduce stress concentration around the boundaries remarkably. The optimal shape of a single hole in an infinite plate under uniform stresses has been obtained by complex variable method based on different optimal criteria. The

The vibration and stability of hybrid functionally graded (FG) composite plates subject to an arbitrary initially stress in thermal environments is investigated. The plate is reinforced by single walled carbon nanotubes (CNTs). Various profiles of CNTs distributions and volume fractions of hybrid nanocomposite plates are considered. Based on the perturbation method, the governing equations for the

Based on the non-linear dual phase lag model, the present investigation treats with mathematical models of bioheat transfer to study the transient phenomena in a spherical tissue due to the effect of laser heat source. Caused by the nonlinear basic equations, the finite element method is adopted to get the solutions of this problem. To verify the accuracy of the numerical solutions, the numerical results

This paper constitutes a first attempt to explore the influence of porosity on bending static analysis of functionally graded (FG) beams using a refined mixed finite element beam model. The material properties of functionally graded porous beams are estimated using a modified power law distribution with two different types of porosity namely even and uneven distributions. The potential of the proposed

Due to the remarkable progress in the field of the manufacturing process, smart composites have become the desired target for high-tech engineering applications. Accordingly, for the first time, thermal buckling, critical voltage and vibration response of a thermally affected graphene nanoplatelet reinforced composite (GPLRC) microdisk in the thermal environment are explored with the aid of generalized

In this paper a numerical solution is presented for free vibration analysis of sandwich cylindrical panels made of a saturated functionally graded porous (FG-porous) core and two similar homogenous face sheets. The panel is modeled based on the third order shear deformation theory (TSDT) and stress-strain relations are considered based on the linear poroelasticity theory of Biot. Natural frequencies

With the developing construction technologies, the formwork systems used in the manufacturing of the structures have also changed and developed significantly. Especially in the production of high-rise buildings, a special sliding formwork system that is quick-installation, resistant to external loads, can be used more than once, are widely used and preferred. Timber and composite timber materials are

Metal-polymer composites are one of the considered materials as a potential representative substitute for metals that have superior properties compared to monometallic materials. In this study, forming limit diagram of the AA5754/ polyethylene / AA5754 sandwich composites was investigated experimentally and numerically. After validating the model, the effect of variation in thickness of the core layer

Parallel robots are preferred over serial robots owing to their enhanced accuracy and rigidity which comes from their higher stiffness. However, there are applications both in industry and in healthcare where higher accuracy is required alongside high compliance (reduced stiffness). Accuracy and compliance being conflicting to each other are difficult to achieve simultaneously. To address this issue

This study proposes a computationally efficient approach about the dynamic response of a homogeneous, transversely isotropic, thermoelastic micro-beam resonator subjected to time-dependent thermal loading. Due to the shortcomings of power law distributions in fractional derivatives, the usage of some other forms of derivatives with few other kernel functions are proposed. With this motivation, the

This article deals with introducing a closed-form solution for considering the vibration of macro-micro-nano plates and shells made of unit material with functionally graded porosity (FGP). Classic continuum theory beside modified nonlocal strain gradient theory are used at macro and micro/nano scales, respectively. The governing equations are obtained in the frame work of third order plate and shell

Some serious errors exist in the above paper. Communicated by Nickolay Banichuk.

This article aims to investigate the forced and free dynamic torsional vibrations of single-walled carbon nanotube (SWCNT) embedded in a viscoelastic medium under a harmonic external torque. Eringen’s nonlocal elasticity is established. It takes the effect of the small size into the formulation due to dealing with nanostructures. The governing equation and corresponding boundary condition are derived

Current investigation deals with the forced vibration response of a composite laminated plate which is reinforced with graphene platelets (GPLs). The weight fraction of GPLs in each layer may be different which results in a piecewise functionally graded (FG) media. The elastic properties of the composite media are obtained using the Halpin-Tsai approach. The motion equations of the plate are established

Drilling trials were conducted on E glass woven composites and machine learning models were employed for correlating drilling variables namely point angle, feed rate and spindle speed with response measures. The thrust force, surface roughness (Ra) and burr height were considered as performance characteristics in this study. Using self-organizing map (SOM) method, Neighboring weight distances in SOM