RF/analog Performance Assessment of High Frequency, Low Power In 0.3 Al 0.7As/InAs/InSb/In0.3 Al0.7 As HEMT Under High Temperature Effect

M. Khaouani,H. Bencherif,A. Hamdoune,A. Belarbi,Z. Kourdi 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.4

In this paper, we performed a Pseudo-morphic High Electron Mobility Transistors (pHEMT) In0.3 Al0.7 As/InAs/InSb/In0.3 Al0.7 using Silvaco-TCAD. RF and analog electrical characteristics are assessed under high temperature eff ect. The impact of the temperature is evaluated referring to a device at room temperature. In particular, the threshold voltage ( V th ), transconductance ( g m ), and I on / I off ratio are calculated in the temperature range of 300 K to 700 K. The primary device exhibits a drain current of 950 mA, a threshold voltage of −1.75 V, a high value of transconductance g m of 650 mS/mm, I on / I off ratio of 1 × 10 6 , a transition frequency ( f t ) of 790 GHz, and a maximum frequency ( f max ) of 1.4 THZ. The achieved results show that increasing temperature act to decrease current, reduce g m , and I on / I off ratio. In more detail high temperature causes a phonon scattering mechanism happening that determine in turn a reduced drain current and shift positively the threshold voltage resulting in hindering the device DC/AC capability.

A numerical method for buckling analysis of built-up columns with stay plates

Djafour, M.,Megnounif, A.,Kerdal, D.,Belarbi, A. Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.26 No.4

A new numerical model based on the spline finite strip method is presented here for the analysis of buckling of built-up columns with and without end stay plates. The channels are modelled with spline finite strips while the connecting elements are represented by a 3D beam finite element, for which the stiffness matrix is modified in order to ensure complete compatibility with the strips. This numerical model has the advantage to give all possible failure modes of built-up columns for different boundary conditions. The end stay plates are also taken into account in this method. To validate the model a comparative study was carried out. First, a general procedure was chosen and adopted. For each numerical analysis, the lowest buckling loads and modes were calculated. The basic or "pure" buckling modes were identified and their critical loads were compared with solutions obtained using analytical methods and/or other numerical methods. The results showed that the proposed numerical model can be used in practice to study the elastic buckling of built-up columns. This model is considered accurate and efficient for the local buckling of short columns and global buckling for slender columns.

Strength buckling predictions of cold-formed steel built-up columns

A. Belarbi,A. Megnounif,M. Djafour,D. Kerdal 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.4

The aim of this paper is to propose a design procedure for predicting the buckling strength of built-up, cold-formed steel columns based on the two well known methods; the effective width method and the Direct Strength Method. Several design approaches, based on different elastic buckling solutions, were considered in this investigation. Traditional hand methods, without interaction effects between the different modes, and a new numerical spline finite strip method were used to predict the buckling stresses. All of the proposed methods were compared with experimental data on plain and lipped, built-up columns. Results have shown that the effective width approaches are more accurate than the Direct Strength Method. However, both methods can be investigated using more experimental data to assess a practical design method for built-up columns.

Shear correction factors of a new exponential functionally graded porous beams

Mohammed Sid Ahmed Houari,Aicha Bessaim,Tarek Merzouki,Ahmed Amine Daikh,Aman Garg,Abdelouahed Tounsi,Mohamed A. Eltaher,Mohamed-Ouejdi Belarbi 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.1

This article introduces a novel analytical model for examining the impact of porosity on shear correction factors (SCFs) in functionally graded porous beams (FGPB). The study employs uneven and logarithmic-uneven modified porositydependent power-law functions, which are distributed throughout the thickness of the FGP beams. Additionally, a modified exponential-power law function is used to estimate the effective mechanical properties of functionally graded porous beams. The correction factor plays a crucial role in this analysis as it appears as a coefficient in the expression for the transverse shear stress resultant. It compensates for the assumption that the shear strain is uniform across the depth of the cross-section. By applying the energy equivalence principle, a general expression for static SCFs in FGPBs is derived. The resulting expression aligns with the findings obtained from Reissner’s analysis, particularly when transitioning from the two-dimensional case (plate) to the onedimensional case (beam). The article presents a convenient algebraic form of the solution and provides new case studies to demonstrate the practicality of the proposed formulation. Numerical results are also presented to illustrate the influence of porosity distribution on SCFs for different types of FGPBs. Furthermore, the article validates the numerical consistency of the mechanical property changes in FG beams without porosity and the SCF by comparing them with available results.

Multiscale bending and free vibration analyses of functionally graded graphene platelet/ fiber composite beams

A. Garg,T. Mukhopadhyay,H.D. Chalak,M.O. Belarbi,L. Li,R. Sahoo 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.5

In the present work, bending and free vibration analyses of multilayered functionally graded (FG) graphene platelet (GPL) and fiber-reinforced hybrid composite beams are carried out using the parabolic function based shear deformation theory. Parabolic variation of transverse shear stress across the thickness of beam and transverse shear stress-free conditions at top and bottom surfaces of the beam are considered, and the proposed formulation incorporates a transverse displacement field. The present theory works only with four unknowns and is computationally efficient. Hamilton’s principle has been employed for deriving the governing equations. Analytical solutions are obtained for both the bending and free vibration problems in the present work considering different variations of GPLs and fibers distribution, namely, FG-X, FG-U, FG-Λ, and FG-O for beams having simply-supported boundary condition. First, the matrix is assumed to be strengthened using GPLs, and then the fibers are embedded. Multiscale modeling for material properties of functionally graded graphene platelet/fiber hybrid composites (FGGPL/FHRC) is performed using Halpin-Tsai micromechanical model. The study reveals that the distributions of GPLs and fibers have significant impacts on the stresses, deflections, and natural frequencies of the beam. The number of layers and shape factors widely affect the behavior of FG-GPL-FHRC beams. The multilayered FG-GPL-FHRC beams turn out to be a good approximation to the FG beams without exhibiting the stress-channeling effects.

Strength buckling predictions of cold-formed steel built-up columns

Megnounif, A.,Djafour, M.,Belarbi, A.,Kerdal, D. Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.4

The aim of this paper is to propose a design procedure for predicting the buckling strength of built-up, cold-formed steel columns based on the two well known methods; the effective width method and the Direct Strength Method. Several design approaches, based on different elastic buckling solutions, were considered in this investigation. Traditional hand methods, without interaction effects between the different modes, and a new numerical spline finite strip method were used to predict the buckling stresses. All of the proposed methods were compared with experimental data on plain and lipped, built-up columns. Results have shown that the effective width approaches are more accurate than the Direct Strength Method. However, both methods can be investigated using more experimental data to assess a practical design method for built-up columns.

Bending of axially functionally graded carbon nanotubes reinforced composite nanobeams

Ahmed Drai,Ahmed Amine Daikh,Mohamed Oujedi Belarbi,Mohammed Sid Ahmed Houari,Benoumer Aour,Amin Hamdi,Mohamed A. Eltaher Techno-Press 2023 Advances in nano research Vol.14 No.3

This work presents a modified analytical model for the bending behavior of axially functionally graded (AFG) carbon nanotubes reinforced composite (CNTRC) nanobeams. New higher order shear deformation beam theory is exploited to satisfy parabolic variation of shear through thickness direction and zero shears at the bottom and top surfaces.A Modified continuum nonlocal strain gradient theoryis employed to include the microstructure and the geometrical nano-size length scales. The extended rule of the mixture and the molecular dynamics simulations are exploited to evaluate the equivalent mechanical properties of FG-CNTRC beams. Carbon nanotubes reinforcements are distributed axially through the beam length direction with a new power graded function with two parameters. The equilibrium equations are derived with associated nonclassical boundary conditions, and Navier's procedure are used to solve the obtained differential equation and get the response of nanobeam under uniform, linear, or sinusoidal mechanical loadings. Numerical results are carried out to investigate the impact of inhomogeneity parameters, geometrical parameters, loadings type, nonlocal and length scale parameters on deflections and stresses of the AFG CNTRC nanobeams. The proposed model can be used in the design and analysis of MEMS and NEMS systems fabricated from carbon nanotubes reinforced composite nanobeam.

Static bending response of axially randomly oriented functionally graded carbon nanotubes reinforced composite nanobeams

Ahmed Amine Daikh,Ahmed Drai,Mohamed Ouejdi Belarbi,Mohammed Sid Ahmed Houari,Benoumer Aour,Mohamed A. Eltaher,Norhan A. Mohamed Techno-Press 2024 Advances in nano research Vol.16 No.3

In this work, an analytical model employing a new higher-order shear deformation beam theory is utilized to investigate the bending behavior of axially randomly oriented functionally graded carbon nanotubes reinforced composite nanobeams. A modified continuum nonlocal strain gradient theory is employed to incorporate both microstructural effects and geometric nano-scale length scales. The extended rule of mixture, along with molecular dynamics simulations, is used to assess the equivalent mechanical properties of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) beams. Carbon nanotube reinforcements are randomly distributed axially along the length of the beam. The equilibrium equations, accompanied by nonclassical boundary conditions, are formulated, and Navier's procedure is used to solve the resulting differential equation, yielding the response of the nanobeam under various mechanical loadings, including uniform, linear, and sinusoidal loads. Numerical analysis is conducted to examine the influence of inhomogeneity parameters, geometric parameters, types of loading, as well as nonlocal and length scale parameters on the deflections and stresses of axially functionally graded carbon nanotubes reinforced composite (AFG CNTRC) nanobeams. The results indicate that, in contrast to the nonlocal parameter, the beam stiffness is increased by both the CNTs volume fraction and the length-scale parameter. The presented model is applicable for designing and analyzing microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) constructed from carbon nanotubes reinforced composite nanobeams.

Free vibration analysis of power-law and sigmoidal sandwich FG plates using refined zigzag theory

Aman Garg,Simmi Gupta,Hanuman D. Chalak,Mohamed-Ouejdi Belarbi,Abdelouahed Tounsi,Li Li,A.M. Zenkour Techno-Press 2023 Advances in materials research Vol.12 No.1

Free vibration analysis of power law and sigmoidal sandwich plates made up of functionally graded materials (FGMs) has been carried out using finite element based higher-order zigzag theory. The present model satisfies all-important conditions such as transverse shear stress-free conditions at the plate's top and bottom surface along with continuity condition for transverse stresses at the interface. A Nine-noded C0 finite element having eleven degrees of freedom per node is used during the study. The present model is free from the requirement of any penalty function or post-processing technique and hence is computationally efficient. The present model's effectiveness is demonstrated by comparing the present results with available results in the literature. Several new results have been proposed in the present work, which will serve as a benchmark for future works. It has been observed that the material variation law, power-law exponent, skew angle, and boundary condition of the plate widely determines the free vibration behavior of sandwich functionally graded (FG) plate.