Habib Ahmadi

• University of Shahrood

In this study, the primary resonance of a hyperelastic thin-walled cylindrical shell subjected to external excitation is examined. The incompressible Moony–Rivlin model, nonlinear Donnell’s shell theory, and Hamilton principle are employed to extract the fundamental equations in three directions. The Galerkin approach is employed to reduce the gove...

In this work, for the first time, the mixed local/nonlocal elasticity theory is employed for the free axisymmetric vibration of an annular single-layer graphene sheet. According to the insufficiency of pure Eringen's nonlocal elasticity, recently researchers have been fascinated by the two-phase elasticity theory to study nanostructures. Some of th...

In this paper, the control algorithm for longitudinal control of a passenger car that is moving on the highway and urban traffic is provided. Longitudinal dynamic equation including resisting forces acting on the vehicle presented and structural and non-structural uncertainties in the model are investigated. To control the speed of vehicles on the...

In this paper, free vibration analysis of rotating stiffened truncated conical shells with functionally graded materials (FGM) in a thermal environment is presented based on the higher-order shear deformation theory (HSDT). Assuming Coriolis acceleration and the centrifugal force, the governing equations of stiffened rotating FGM truncated conical...

When the magnitude of the lateral elastic deformation of a pipe over its length is more prominent than in a linear situation, it is necessary to use nonlinear terms to reduce the gap between the mathematical model and the real system. Also, the importance of nonlinear terms is more considerable when a pipe conveying fluid is studied. Since the pass...

In the presented paper, a novel mechanical design is suggested to utilize in the variable impedance actuators called VSAPLM. This mechanism is proposed for a knee rehabilitation portable exoskeleton and functions based on a lever mechanism with an adjustable pivot. To improve the mechanism efficiency, both actuation and stiffness transmission syste...

In this paper, the nonlinear vibration and resonance analyses of a rectangular hyperelastic membrane embedded within a nonlinear Winkler–Pasternak elastic medium subjected to a uniformly distributed hydrostatic pressure are investigated. The material of the membrane is incompressible, homogeneous, isotropic, and hyperelastic. The constitutive law o...

In this study, the nonlinear vibration of a curved carbon nanotube conveying fluid is analyzed. The nanotube is assumed to be covered by a piezoelectric layer and the Euler–Bernoulli beam theory is employed to establish the governing equations of motion. The influence of carbon nanotube curvature on structural modeling and fluid velocity vector is...

In this paper, one of the most efficient passive absorbers, called nonlinear energy sink (NES), is analytically studied. A two-degree-of-freedom system is considered which consists of a linear oscillator (LO) with a base excitation and an NES, called grounded NES (GNES), which is connected to the ground with a nonlinear spring. In this study, we pr...

In this study, an analytical method is presented to investigate the nonlinear buckling analysis of functionally graded porous (FGP) shallow spherical shells exposed to external excitation in a thermal environment resting on elastic foundations. The elastic foundations of the FGP shell are consist of a two-term Winkler-Pasternak’s model. Using the c...

In this work, an analytical method is presented to analyze the nonlinear static and dynamic buckling of imperfect stiffened double-layer functionally graded porous (FGP) shallow shells subjected to external pressure. The shallow spherical shell consists of two layers, where upper layer of shell is nonporous functionally graded (FG) material and the...

In this paper, a semi-analytical method is presented for nonlinear vibration analysis of rotating stiffened truncated conical shells with functionally graded materials (FGM) in the thermal environment subjected to harmonic excitation. Considering Coriolis acceleration and the centrifugal force, the governing equations of stiffened rotating FGM trun...

In this study, the unified formulation of a full geometrically nonlinear refined plate theory in a total Lagrangian approach is developed to study the post-buckling and large-deflection analysis of sandwich functionally graded (FG) plate with FG porous (FGP) core. The plate has three layers so that the upper and lower layers are FG and the middle l...

The nonlinear vibration behavior of the spiral stiffened multilayer functionally graded (SSMFG) cylindrical shells with initial imperfection exposed to axial parametric and external excitation in the thermal environment is presented in this paper using a semi-analytical method. The distribution of temperature and material constitutive of the stiffe...

In this work, nonlinear forced vibrations of truncated conical shells are presented using a semi-analytical method. The material properties are varied along the thickness direction as a power law distribution. The functionally graded truncated conical shells are exposed to external harmonic load and placed in the thermal environment and have an ini...

In this study, the nonlinear vibration control of functionally graded laminated piezoelectric cylindrical shells under simultaneous parametric axial and radial external excitations is presented. The partial differential equations of shells are derived based on Hamilton’s principle, first-order shear deformation theory (FSDT), and nonlinear von Karm...

In this article, the semianalytical method based on the Galerkin technique and fourth-order Runge-Kutta method is utilized to investigate the static and dynamic postbuckling analysis of internal/external spiral stiffened functionally graded (ISSFG/ESSFG) cylindrical shells, respectively. The simply supported SSFG shell subjected to an axial compres...

This study investigates the non-linear vibrations of stiffened imperfect functionally graded double-curved shallow shells, as rested on nonlinear elastic foundations. The shells are exposed to external harmonic excitation and are placed in the thermal situations. The modeling of shells is derived according to the classical shell theory and the non-...

In this article, analytical and semi-analytical methods are used to analyze the nonlinear static and dynamic hygrothermal postbuckling response of sandwich cylindrical panels with functionally graded carbon nanotube-reinforced composite (FG-CNTRC) core. The sandwich cylindrical panels with an FG-CNTRC core are resting on generalized nonlinear visco...

This paper investigates the nonlinear free vibration and nonlinear dynamic hygrothermal buckling behavior of imperfect functionally graded carbon nanotube-reinforced composite (FG-CNTRC) cylindrical panels under hygrothermal environment. The nonlinear temperature distribution is assumed along the thickness direction. The structure is resting on a g...

In this paper, semi-analytical and analytical methods for the nonlinear static and dynamic buckling analyses of imperfect functionally graded porous (FGP) cylindrical shells subjected to axial compression are presented. The structure is embedded within a generalized nonlinear elastic foundation, treated as a two-parameter Winkler–Pasternak foundati...

In this study, active vibration control of an FGM truncated conical shell, subjected to the harmonic excitation, is investigated via a semi-analytical method. The governing equations of truncated conical shells in conjunction with piezoelectric layers are derived using Donnell shell theory and von Karman's non-linearity. Then, the dynamic equation...

This paper is devoted to superharmonic and subharmonic behavior investigation of imperfect functionally graded (FG) cylindrical shells with external FG spiral stiffeners under large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation, which is composed of a two-parameter Winkler–Pasternak foundati...

In this paper, a semi-analytical method for the free vibration behavior of spiral stiffened multilayer functionally graded (SSMFG) cylindrical shells under the thermal environment is investigated. The distribution of linear and uniform temperature along the direction of thickness is assumed. The structure is embedded within a generalized nonlinear...

In this article, a semi-analytical and analytical method for the nonlinear static and dynamic thermal buckling behavior of imperfect multilayer FG cylindrical shells with an FG porous core in the thermal environment is investigated. The structure is embedded within a generalized nonlinear elastic foundation which is composed of a two-parameter Wink...

In this paper, the non-linear vibration and resonances analysis of truncated FGM conical shells are investigated under harmonic excitation. Utilizing von Karman–Donnell and the large deformation theory, the governing equations of the truncated FGM conical shell are extracted. The material properties of the truncated FGM conical shell changes along...

This paper presents the nonlinear vibration of multilayer FG cylindrical shells reinforced by spiral FG stiffeners surrounded by damping and elastic foundation in thermal environment. The primary, superharmonic and subharmonic resonances of spiral stiffened multilayer FG cylindrical shell are analyzed. It is assumed that the material properties are...

In this paper, an analytical method is used to study the nonlinear primary resonance of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal stiffeners. The SSFG cylindrical shell is surrounded by linear and nonlinear elastic foundation and the effect of structural damping on the system response is also considered....

An analytical approach for the nonlinear vibration analysis of imperfect functionally graded carbon nanotube-reinforced composite (FG-CNTRC) cylindrical panels is presented. The FG-CNTRC cylindrical panel is subjected to external pressure in the thermal environment. The nonlinear temperature distribution in the thickness direction is assumed. The c...

This paper investigates the analytical and semi-analytical approaches for the nonlinear dynamic and static hygrothermal buckling analysis of imperfect functionally graded porous (FGP) cylindrical shells under hygrothermal loading. Effect of the von Kármán strain-displacement kinematic nonlinearity is included in the constitutive laws of the shell....

This paper presents the superharmonic and subharmonic resonances of spiral stiffened functionally graded (SSFG) cylindrical shells under harmonic excitation. The stiffeners are considered to be externally or internally added to the shell. Also, it is assumed that the material properties of the stiffeners are continuously graded in the thickness dir...

In this paper, a Tuned Bistable Nonlinear Energy Sink (TBNES) considering local and global potentials is implemented to decrease the vibrations of the host structural system. The structural system consists of two coupled linear symmetric oscillators and the nonlinear energy sink consists of a mass-spring-damper which is connected to the ground by m...

This paper studies a nonlinear primary resonance of spiral stiffened functionally graded (SSFG) cylindrical shell with viscos damping force. The cylindrical shell is subjected to the harmonic excitation. The material properties of the shell and stiffeners are assumed to be continuously graded in the thickness direction. The FG cylindrical shell wit...

In this paper, an analytical method is used to study the nonlinear static and dynamic thermal buckling analysis of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells. The SSFG cylindrical shell is surrounded by a linear and nonlinear elastic foundation. The proposed linear model is based on the two-parameter elastic foundation...

Functional electrical stimulation (FES) is the most commonly used system for restoring function after spinal cord injury (SCI). In this study, we used a model consists of a joint, two links with one degree of freedom, and two muscles as flexor and extensor of the joint, which simulated in MATLAB using SimMechanics and Simulink Toolboxes. The muscle...

Performance increasing of robot-aided training in stroke elbow rehabilitation is the goal of this paper. Therapist holds on the arm of patient and guides the center of mass along a desired trajectory. In robotic rehabilitation, when the arm of patient is rotated within the desired boundaries, (s)he should ideally not feel the robot. The robot needs...

To document the epidemiology and risk factors of acute carbon monoxide (CO) poisoning in the west of Iran and specify potentially presentable characteristics. Observational study. Imam Khomeini Hospital of Kermanshah, Iran, from July 2006 to March 2008. This study was conducted using the records of 143 cases of CO poisoning referred to the only cen...

The overall goal of this study has been to advance the understanding of the role of family background variables, school, and peer influence in the explanation of juvenile delinquency, particularly in relation to different language groups. The assumptions which inform the basic theoretical perspective of this study have been developed from three maj...