M. Bayat

Aalborg University · Department of Civil Engineering

Ratcheting analysis for cantilever beams subjected to the thermomechanical loads is presented using the finite element method. The cantilever beam is constrained along the vertical direction, and plane stress conditions are assumed according to the bilinear isotropic hardening model. Two points are considered to obtain areas of ratcheting by using...

This study aims to obtain Bree's diagram for a Functionally Graded (FG) beam under cyclic thermal and constant mechanical loadings. For this purpose, the mapping algorithm is employed to specify the borders of ratcheting, shakedown, and elastic. Also, two parameters are considered to obtain Bree's diagram, and the iteration method is utilized to pr...

The thermoelastic analysis of axisymmetric bending of rotating functionally graded material (FGM) disks, with and without imperfection, is presented. Material properties are assumed to be temperature dependent and graded in the thickness direction following a grading index power-law distribution. Theories of von Karman and first-order shear deforma...

A thermo-elastic contact problem of functionally graded materials (FGMs) rotating brake disk with different pure brake pad areas under temperature dependent material properties is solved by Finite Element Method (FEM). The properties of brake disk change gradually from metal to ceramic by power-law distribution along the radial direction from the i...

A typical viable technique to decrease the seismic response of liquid storage tanks is to isolate them at the base. Base-isolation systems are an efficient and feasible solution to reduce the vulnerability of structures in high seismic risk zones. Nevertheless, when liquid storage tanks are under long-period shaking, the base-isolation systems coul...

In collaboration with international journals

The well-known - curve method provides soil-structure interaction that does not account for the pore pressure effect for dynamic analysis of offshore wind turbines (OWTs). In order to avoid overly conservative designs, reliable estimates of the dynamic response should be taken into account. The turbine is introduced using a simplified model to asse...

The well-known p-y curve method provides soil-structure interaction that is independent of the load rate. In this paper an improved p-y curve method is proposed by considering the influence of the excitation frequency. For this purpose, a two-dimensional finite-element program is developed for analysis of a segment of an offshore monopile foundatio...

Large offshore wind turbines are founded on jacket structures. In this study, an elastic full-space jacket structure foundation in an elastic and viscoelastic medium is investigated by using boundary integral equations. The jacket structure foundation is modeled as a hollow, long circular cylinder when the dynamic vertical excitation is applied. Th...

Offshore wind turbine foundations are affected by cyclic loads due to oscillatory kinematic loads, such as those from wind, waves, and earthquakes. Monopiles are often used as a foundation concept for offshore windmill turbines. In this study, coupled dynamic equations with the formulation for low-frequency load are considered for an offshore wind...

The mechanical responses of an offshore monopile foundation mounted in over-consolidated clay are calculated by employing a stochastic approach where a nonlinear p-y curve is incorporated with a finite element scheme. The random field theory is applied to represent a spatial variation for undrained shear strength of clay. Normal and Sobol sampling...

In this study, the authors present a coupled fluid-structures-seabed interaction analysis of a monopile type of wind turbine foundations in liquefiable soils. A two dimensional analysis is performed with a nonlinear stiffness degradation model incorporated in the finite difference program Fast Lagrangian Analysis of Continua (FLAC), which captured...

In this paper, the magneto-thermo-mechanical response of a functionally graded magneto-elastic material (FGMM) annular variable-thickness rotating disk is investigated. The material properties namely material stiffness, heat conduction coefficient, thermal expansion coefficient, mass density and magnetic permeability are assumed to vary continuousl...

The fatigue life of offshore wind turbines strongly depends on the dynamic behaviour of the structures including the underlying soil. To diminish dynamic amplification and avoid resonance, the eigenfrequency related to the lowest eigenmode of the wind turbine should not coalesce with excitation frequencies related to strong wind, wave and ice loadi...

This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM) comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjuste...

In this work, functionally graded femoral prostheses (FGFPs) with different geometrical configurations are studied using three-dimensional finite element analysis. The FGFP consists of stainless steel–hydroxyapatite (SS 316L-HA) and titanium alloy–hydroxyapatite (Ti-HA) with various volume fraction gradient exponents n = 0.0, 0.1, 0.5, and 1.0. Thi...

This study focused on developing a 3D finite element model of functionally graded femoral prostheses to decrease stress shielding and to improve total hip replacement performance. The mechanical properties of the modeled functionally graded femoral prostheses were adjusted in the sagittal and transverse planes by changing the volume fraction gradie...

OBJECTIVE: This study provides an experimental and finite element analysis of knee-joint structure during extended-knee landing based on the extracted impact force, and it numerically identifies the contact pressure, stress distribution and possibility of bone-to-bone contact when a subject lands from a safe height. METHODS: The impact time and loa...

In this paper, finite element contact analysis of a functionally graded (FG) brake disk in contact with a pad, subjected to rotation, contact pressure, and frictional heat, is presented. The material properties vary through the thickness according to a power-law characterized by a grading index, n. The contact surfaces are full-ceramic with full-me...

In this study a stochastic approach is conducted to obtain the horizontal and rotational stiffness of an offshore monopile foundation. A nonlinear stochastic p-y curve is integrated into a finite element scheme for calculation of the monopile response in over-consolidated clay having spatial undrained shear strength. The random field is applied to...

This paper presents elastic solutions of a disk made of functionally graded material (FGM) with variable thickness subjected to rotating load. The material properties are represented by combination of two sigmoid FGM (S-FGM) namely aluminum–ceramic–aluminum and the disk's different thickness profiles are assumed to be represented by power law distr...

A thermoelastic simulation of functionally graded (FG) brake discs is performed using finite element (FE) ANSYS. The material properties of two types of FG brake discs are assumed to vary in both radial and thickness directions according to a power law distribution. The brake discs are in contact with one hollow pure pad disc. Dry contact friction...

Second-order shear deformation theory (SSDT) is employed to analyze vibration of temperature-dependent solar functionally graded plates (SFGP’s). Power law material properties and linear steady-state thermal loads are assumed to be graded along the thickness. Two different types of SFGP’s such as ZrO2/Ti-6Al-4V and Si3N4/SUS304 are considered. Unif...

A multilayered titanium (Ti)-hydroxyapatite (HA) functionally graded material was produced via pressureless sintering at 1100°C. The initial and final porosities were determined via shrinkage measurements. The final porosity verification was carried out by the Archimedes method. The experimental porosity measurements were compared with two proposed...

This paper demonstrates the functionally graded metal-ceramic composite fabricated via pressure-less sintering. The pure metallic and ceramic components are Titanium (Ti) and Hydroxyapatite (HA), which were located at the ends of a cylindrical specimen. FG samples are prepared with mixing ratios of 100:0, 75:25, 50:50, 25:75, 0:100. The cylindrical...

This research has been conducted to approach second-order shear deformation theory (SSDT) to analysis vibration characteristics of Functionally Graded Plates (FGP’s). Material properties in FGP's were assumed to be temperature dependent and graded along the thickness using a simple power law distribution in term of the volume fractions of the const...

Functionally graded metal-ceramic composite was fabricated by pressure-less sintering. The pure metallic component (Ti) and the pure ceramic component (HA) were located at the ends of a cylindrical specimen. Titanium and-Hydroxyapatite were utilized as a metallic and ceramic layer. The target sample thickness was 6 mm with radius cylindrical 20 mm....

In this paper, a semi-analytical investigation intended to determine the axisymmetric elastic response of functionally graded (FG) disks. The material properties of the disk are assumed to be graded continuously along the radial direction. An exponential function and the Mori-Tanaka scheme are used for estimating the effective material properties....

Tubular structure with various Cee-shaped cross sections is numerically investigated in order to find the centre of gravity (COG) under axial crush by using program code of ANSYS/LS-DYNA. A subroutine is developed using this code to obtain the COG of deformed shape, during and after crush deformation. The effect of wall thickness of the structure o...

Natural frequency of functionally graded (F.G.) rectangular plate is carried out by using second-order shear deformation theory (SSDT). The material properties of functionally graded rectangular plates, except the Poisson's ratio, are assumed to vary continuously through the thickness of the plate in accordance with the exponential law distribution...

A glass-like (viscoelastic) functionally graded cylinder is studied by using finite element method to investigate the mechanical responses. A subroutine is developed by using ANSYS parametric design language (APDL) to simulate two nonlinearities, which are the variation of material properties with respect to time and position. The cylinder is made...

The present work studies the crack behavior along the surface of the friction stir welded (FSW) joint of 2024-T351 aluminum alloy. The surface engineering of shot peening and skimming are used to enhance the fracture characteristics of the joint. Then multiple crack initiation is detected within FSW zones by scanning electron microscopy, while plas...

In this study a subroutine was developed and added in the pre-processing module of the frame work of commercial package of ANSYS to distribute the extra masses according to specific assigned centre of gravity (COG). The work further calculate the first bending and torsional natural frequencies of the simplified body in white (BIW) model of automoti...

The work presents a summary of previous studies on fatigue crack propagation within various Aluminum alloys. The effective characteristics on crack growth are first highlighted and the influence of surface engineering such as polishing, shot peening and skimming to enhance the failure resistance are discussed. Several different existing developed m...

Mechanical respond of the tibiofemoral joint in impact with a rigid plate is the aim of current study. A circular plate with initial velocity hit the tibiofemoral joint. All components all considered as linear elastic material. Cartilages were perfectly attached to the femur and tibia; and while menisci were allowed to move vertically. Circular pla...

Full extension landing present great amount of stress, deflection, and energy, which damps by a contribution of bones, muscle, and ground reaction force (GRF). This study focused on analyzing the bone components deflection and energy absorption in full extension landing by dynamic finite element analysis (FEA). The impact load and time were derived...

Assessment of the stress distribution in the tibiofemoral joint during standing on both legs was the aim of the present work. The finite element method was employed to perform the current study. A compressive load of half of body weight (250N) was applied to the femur head. The cartilages perfectly attached to femur and tibia; and while the femur a...

In this paper, the transient and contact analysis of functionally graded (FG) brake disk is presented. The analysis was carried out using ANSYS parametric design language (APDL). The FG brake disk is made of metal–ceramic material. The material properties vary in radial direction with the values from full-metal at the inner radius to that of full-c...

Exact elastic solutions for axisymmetric variable-thickness hollow rotating discs with heat source made of functionally graded (FG) materials under free—free and fixed—free boundary conditions are presented. Material properties and disc thickness profiles are assumed to be represented by specified power law distributions. The effect of the heat sou...

Objective: To analyse thermo-mechanical stress in endodontically treated teeth restored with Multilayered Structured Dental Posts (MSDPs) under cold and hot conditions using Finite Element Analysis (FEM). Methods: Three MSDPs of multilayer design of xTi-yHA composition added to a zirconia layer (model A), an alumina layer (model B) and a titanium l...

Objective: To analyse thermo-mechanical stress in endodontically treated teeth restored with Multilayered Structured Dental Posts (MSDPs) under cold and hot conditions using Finite Element Analysis (FEM). Methods: Three MSDPs of multilayer design of xTi-yHA composition added to a zirconia layer (model A), an alumina layer (model B) and a titanium l...

Second-order shear deformation theory (SSDT) is applied to evaluate the displacement and stress fields of a solar functionally graded plate (SFGP) due to mechanical loadings. The material properties are graded by a simple power law between Full-ceramic and Full-metal at upper and lower surfaces, respectively. Navier's method is applied to find anal...

A finite element analysis of thermo-elastic contact problem of rotating functionally graded (FG) brake and pad disks is presented. Plane 13 element is applied for brake and pad disks while Conta 172 and Targe 169 is applied for contact line. Two types of disks are considered to compare the thermal and structural behaviors in FG and pure material br...

An analysis of thermoelastic contact problem of functionally graded (FG) rotating brake disk with heat source due to contact friction is presented. Finite element method (FEM) is used. The material properties of disk are assumed to be represented by power-law distributions in the radial direction. The inner and outer surfaces considered are metal a...

This paper focuses on design of high-performance MEMS LC-tank circuit for use in CMOS voltage controlled oscillators (VCO) operating at 2.4 GHz. The high-Q air suspended inductor has been designed by inductance of 2.87 nH using MEMS technology to reduce the resistive loss and the substrate loss. A MEMS two-gap tunable capacitor has been designed. T...

A general approach for free vibration of functionally graded materials (FGMs) plates based on second-order shear deformation theory (SSDT) is presented. Material properties are assumed to be graded in the thickness direction by power law distribution in term of the volume fractions of the constituents. The equilibrium equations are derived by energ...

The theoretical formulation for bending analysis of functionally graded (FG) rotating disks based on first order shear deformation theory (FSDT) is presented. The material properties of the disk are assumed to be graded in the radial direction by a power law distribution of volume fractions of the constituents. New set of equilibrium equations with...

A thermo elastic analysis is presented for axisymmetric rotating disks made of functionally graded material (FGM) with variable thickness. Material properties are assumed to be temperature-dependent and graded in the radial direction according to a grading index power law distribution. The temperature field considered is assumed to be uniformly dis...

Rotating disks have many applications in the aerospace industry such as gas turbines and gears. These disks normally work under thermo mechanical loads. Minimizing the weight of such components can help reduce the overall payload in aerospace industry. For this purpose, a rotating functionally graded (FG) disk with variable thickness under a steady...

A theoretical solution for thermoelastic analysis of functionally graded (FG) rotating disk with variable thickness based on first-order shear deformation theory (FSDT) is presented. Material properties and disk thickness profile are assumed to be represented by power law distributions. A semi analytical solution for displacement field is given und...

This paper presents the full design, operational principle, structure and frequency response simulation of one-port Surface Acoustic Wave (SAW) Resonator using Micro Wave Office (MWO) and MATLAB used for passive wireless sensing of various measurands. Since SAW Resonators are widely used in radio frequency sensing application, the development and e...

Silicon integrated circuit spiral inductors and transformers are finding wide ranging applications in RF circuits. This paper presents implementation and characterization of spiral inductor using MEMS technology on silicon substrate for use in design of voltage controlled oscillator (VCO). MEMS inductors have been realized from the CMOS-compatible...

Elastic solutions for axisymmetric rotating disks made of functionally graded material with variable thickness are presented. The material properties and disk thickness profile are assumed to be represented by two power-law distributions. In the case of hollow disk, based on the form of the power-law distribution for the mechanical properties of th...

This paper presents the elastic solutions of the gear wheels made of functionally graded material (FGM) with variable thickness subjected to rotating loads. The material properties and wheel thickness profile are assumed to be represented by two power law distributions. Solid and hollow wheels are considered and the solutions for the stresses and d...

A functionally graded (FG) rotating disk with axisymmetric bending and steady-state thermal loading is studied. The material properties of the disk are assumed to be graded in the direction of the thickness by a power law distribution of volume fractions of the constituents. First-order shear deformation Mindlin plate and von Karman theories are em...

In a recent study [I], an ordinary differential equation model has been given for one-prey (mussel) and one-predator (sea star) of a benthic community, representing their spatially-structured dynamics. We generalize this model in this paper and extend its scope to the dynamics of three species (one-prey, two-predators) of benthic community namely:...