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    مهندسی مکانیک

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Transient elastodynamic behavior of cylindrical tubes under moving pressures and different boundary conditions

Hamed Ramezani, Majid Mirzaei
Journal PapersApplied Mathematical Modelling , Volume 77 , 2020 January 1, {Pages 934-949 }

Abstract

A complete set of analytical solutions for the transient elastodynamic response of thick cylindrical shells with finite length to single and successive moving pressures are presented over a wide range of load speeds. The formulation of the problem is based on the first-order shear deformation theory and the solutions are obtained using the mode-summation method. The effects of reflected waves at different types of boundary condition (simply-supported, clamped-clamped, and clamped-free) are also considered in the solution procedures. The results of the analytical solutions are validated through comparisons with the experimental results from the literature and a series of finite element simulations. The very good agreement between the analyti

Determination of fracture properties of cortical bone using arc-shaped specimen

Fereshteh Alizadeh Fard, Majid Mirzaei
Journal PapersIranian Journal of Biomedical Engineering , Volume 14 , Issue 2, 2020 June 21, {Pages 131-140 }

Abstract

Regarding the application of testing and analysis of bone fractures in both medical and engineering fields, finding proper specimens for measuring fracture properties is important. In this study, the experimental and numerical fracture analyses of bovine cortical bone were performed for 4 anatomical regions using arc-shaped specimens. The tensile fracture tests for arc-shaped specimens were performed at ambient temperature. In practice, the stress intensity factor was calculated using standard analytical formula for arc-shaped specimens and also the related finite element (FE) models. In order to validate the FE models, the stress and strain analyses results were compared with the results obtained from digital image correlation (DIC) metho

Effect of Microstructure on the Mechanical Properties and Fracture Toughness of API X65 Pipeline Steel in the Presence of Hydrogen

Meysam Ranjbar, Reza Miresmaeili, Mohammad Reza Naimi-Jamal, Majid Mirzaei
Journal PapersMetals and Materials International , 2020 October 16, {Pages 17-Jan }

Abstract

This study investigated the influence of microstructure on the mechanical properties and fracture toughness of API X65 pipeline steel in the presence of hydrogen. In this study, electrochemical method was used for hydrogen charging and indentation technique was applied to obtain the fracture toughness. The results showed that in the presence of hydrogen, elongation (EL%), reduction of area (RA), ductile fracture percentage, and fracture toughness of all microstructures decreased. The microstructure of martensite (M)+ bainite (B)+ ferrite (F), had the highest hydrogen trapping and uptake (C app) as 8.58? 10–6 mol cm− 3 and the lowest apparent hydrogen diffusivity (D app) as 5.68? 10− 10 m 2 s− 1; thus, the maximum decrements of 33% i

Investigations of Transient Thermal Response of Pulse Detonation Engine Tube under Sequential Operation

MJ Torkaman Asadi, M Mirzaei
Journal PapersJournal of Solid and Fluid Mechanics , Volume 9 , Issue 1, 2019 March 21, {Pages 153-171 }

Abstract

The practical and prolonged implementation of pulse detonation engines implies the control of temperature in detonation tubes. The nature of the detonation itself, plus the rapid repetition of different processes within the working cycle, are accompanied by variations of speed, temperature and pressure and create a heating environment which is different from conventional engines and difficult to specify and control. In this paper the various processes of the working cycle are studied and a template is proposed for the loading and thermal boundary conditions. In continuation, the analytical and thermal models have been developed based on the described assumptions and the thermal responses have been obtained for sequential loadings. The sever

Linear and nonlinear analyses of femoral fractures: Computational/experimental study

Majid Mirzaei, Fatemeh Alavi, Farzaneh Allaveisi, Vahid Naeini, Pegah Amiri
Journal PapersJournal of biomechanics , Volume 79 , 2018 October 5, {Pages 155-163 }

Abstract

This paper describes two new methods for computational fracture analysis of human femur using Quantitative Computed Tomography (QCT) voxel-based finite element (FE) simulation. The paper also reports comprehensive mechanical testing for validation of the methods and evaluation of the required material properties. The analyses and tests were carried out on 15 human femurs under 11 different stance-type loading orientations. Several classical forms of subcapital, transcervical, basicervical, and intertrochanteric fractures plus a specific type of subtrochanteric fracture were created and analyzed. A new procedure was developed for prediction of the strengths and the fracture initiation patterns using a FE-based linear scheme. The predicted an

An applied method for fatigue life assessment of engineering components using rigid-insert crack closure model

Mahmoud Shariati, Majid Mirzaei, Reza Masoudi Nejad
Journal PapersEngineering Fracture Mechanics , Volume 204 , 2018 December 1, {Pages 421-433 }

Abstract

The purpose of this paper is to provide a new method for analyzing and evaluating the fatigue crack closure load and estimating the life of engineering components using RICC (Rigid-Insert Crack Closure Model), non-destructive replica technique, and a new sample. For this purpose, first, the method of solving the RICC model has been changed from linear approximation to nonlinear state and therefore, a significant improvement in the accuracy of the model results has been achieved. Then, using the model, a new formulation for the influence line in the points of sample is obtained, which has a significant accuracy. The formulation of the RICC model results in a set of equations that can help to determine the closure load and the characteristics

Experimental determination and numerical implementation of ductile damage parameters of Al 2024-O

E Salimpour
Journal Papers , , {Pages }

Abstract

On the role of stress waves in dynamic rupture of cylindrical tubes

M Mirzaei, S Tavakoli, M Najafi
Journal PapersFatigue & Fracture of Engineering Materials & Structures , Volume 40 , Issue 12, 2017 December , {Pages 2008-2018 }

Abstract

A systematic experimental/computational study was performed to investigate the role of stress waves in ductile fracture of cylindrical tubes. The stress waves were created by high‐speed moving load, which was produced by detonation of explosive cord inside two intact and two pre‐flawed steel tubes. Several distinct phenomena like cyclic crack growths in Modes I and III, crack flap bulging and crack curving/branching were observed and simulated by finite element (FE) method. The FE models were composed of 3D brick elements equipped with interface cohesive elements. The analysis results showed that the crack growths in Modes I and III were governed by the detonation‐induced stress waves. The crack speeds were obtained based on the incr

Pull-in instability of double clamped microbeams under dispersion forces in the presence of thermal and residual stress effects using nonlocal elasticity theory

Fateme Tavakolian, Amin Farrokhabadi, Majid Mirzaei
Journal PapersMicrosystem Technologies , Volume 23 , Issue 4, 2017 April 1, {Pages 839-848 }

Abstract

The present study deals with the consideration of the small-scale effects on the pull-in instability of micro-switches subjected to electrostatic and intermolecular forces in the presence of thermal and residual stress effects. Using Eringen’s nonlocal elasticity theory along with the nonlocal Euler–Bernoulli beam model, the equilibrium equation is derived in the presence of thermal and residual stress effects using virtual displacement principle. The static governing equation, which is extremely nonlinear due to the intermolecular and electrostatic attraction forces plus thermal and residual effects, is solved numerically by Galerkin method. The accuracy of the solution is verified by comparing the obtained results with

Effect of temperature on the fracture mechanism of wood–plastic composites in situ

Fatemeh Alavi, Amir Hossein Behravesh, Majid Mirzaei
Journal PapersJournal of Thermoplastic Composite Materials , Volume 29 , Issue 1, 2016 January , {Pages 15-Mar }

Abstract

An experimental study was carried out to investigate the effect of temperature on the mechanical properties and the fracture mechanism of wood–plastic composites (WPCs) under tension. The specimens were prepared via injection molding of various weight fractions of pine wood particles and high-density polyethylene (with and without coupling agent, maleic anhydride-grafted polyethylene (MAPE)). The deformation and fracture behaviors of the samples at different temperatures were studied using a portable microscope setup during the test. The results indicated the significant effect of the test temperature on the fracture mechanism of WPC specimens. At room temperature, the dominant fracture mechanism for the samples without MAPE was debonding

On fracture analysis of exploded pressure vessels and pipes

Majid Mirzaei, Saharnaz Tavakoli
Journal PapersModares Mechanical Engineering , Volume 16 , Issue 5, 2016 July 15, {Pages 297-302 }

Abstract

The main scope of this paper is the analysis of the specifications of deflagration-induced and detonation-induced deformation and fracture behaviors of cylindrical tubes. The main characteristics of deformation and fracture behaviors were studied through experimentations on steel pipes and failure analysis of a compressed natural gas (CNG) cylinder. The paper also reports the results of transient-dynamic elasto-plastic finite element (FE) analyses of the combustion-induced deformation and fracture behaviors of the pipe and the CNG cylinder. The FE models were composed of 3D brick elements equipped with interface cohesive elements for crack growth analysis. Very good agreements were found between the simulation results and the observed defor

Effects of high-dose gamma irradiation on tensile properties of human cortical bone: Comparison of different radioprotective treatment methods

Farzaneh Allaveisi, Majid Mirzaei
Journal PapersJournal of the mechanical behavior of biomedical materials , Volume 61 , 2016 August 1, {Pages 475-483 }

Abstract

There are growing interests in the radioprotective methods that can reduce the damaging effects of ionizing radiation on sterilized bone allografts. The aim of this study was to investigate the effects of 50?kGy (single dose, and fractionated) gamma irradiation, in presence and absence of l-Cysteine (LC) free radical scavenger, on tensile properties of human femoral cortical bone. A total of 48 standard tensile test specimens was prepared from diaphysis of femurs of three male cadavers (age: 52, 52, and 54 years). The specimens were assigned to six groups (n=8) according to different irradiation schemes, i.e.; Control (Non-irradiated), LC-treated control, a single dose of 50?kGy (sole irradiation), a single dose of 50?kGy in presence of LC,

EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF FRACTURE LOAD AND PATTERN OF HUMAN FEMUR USING COHESIVE ZONE MODEL

FATEMEH ALAVI, MAJID MIRZAEI
Journal Papers , Volume 15 , Issue 10, 2016 January 1, {Pages 192-200 }

Abstract

Fracture of femur is considered as one of the most significant causes of disability and death, especially among the elderly. Therefore, there is a global effort towards noninvasive assessment of the femoral fractures. This study was aimed at investigation of the mechanical behavior of human femur subjected to various loading orientations, under the two categories of high-stiffness (HS) and low-stiffness (LS) loading conditions. The experimental and computational analysis of deformation and fracture patterns were carried out using the QCT images and finite element analysis. The predictions of the force and fracture pattern of the HS and LS specimens were performed using linear and nonlinear finite element analyses, respectively. Also, the co

Experimental and Computational Analysis of Fracture Load and Pattern of Femur using Cohesive Zone Model

FS Alavi, M Mirzaei
Journal Papers , , {Pages }

Abstract

On vibrational behavior of pulse detonation engine tubes

M Mirzaei, MJ Torkaman Asadi, R Akbari
Journal PapersAerospace Science and Technology , Volume 47 , 2015 December 1, {Pages 177-190 }

Abstract

This paper presents a set of analytic solutions for the transient elastodynamic response of orthotropic cylindrical tubes to sequential moving pressures with specific profiles. The general form of the presented formulations and the solution methods are applicable to a number of theoretical and practical problems. However, the final solutions are tailored for sequential gaseous detonations, with direct application in the stress analysis of pulse detonation engines (PDE). The PDE generates trust by high cycling of gaseous detonations and is regarded as a promising candidate for providing very efficient propulsion systems for aviation and electric power generation. The presented analytic solutions are validated with the available experimental

Mixed-mode cohesive zone modeling and damage prediction of irregular-shaped interfaces in wood–plastic composites

Fatemeh Alavi, Amir Hossein Behravesh, Majid Mirzaei
Journal PapersComposite Interfaces , Volume 22 , Issue 7, 2015 September 2, {Pages 651-662 }

Abstract

Debonding is the dominant fracture mechanism in wood–plastic composites, and the direction of wood fibrils significantly affects the normal and tangential wood–plastic interfacial properties. This study was aimed at simulation of the mixed-mode damage initiation and growth in wood–plastic interfaces using the cohesive zone model. The wood–plastic interfacial properties in longitudinal and transverse directions were determined. The opening and sliding displacements across the wood–plastic interfaces were measured by means of digital image correlation techniques, and the force-displacement diagrams were obtained from the experimental data. The Nelder–Mead algorithm was employed to identify the wood–plastic cohesive parameters th

QCT-based failure analysis of proximal femurs under various loading orientations

Majid Mirzaei, Maziyar Keshavarzian, Fatemeh Alavi, Pegah Amiri, Saeid Samiezadeh
Journal PapersMedical & biological engineering & computing , Volume 53 , Issue 6, 2015 June 1, {Pages 477-486 }

Abstract

In this paper, the variations of the failure strength and pattern of human proximal femur with loading orientation were analysed using a novel quantitative computed tomography (QCT)-based linear finite element (FE) method. The QCT images of 4 fresh-frozen femurs were directly converted into voxel-based finite element models for the analyses of the failure loads and patterns. A new geometrical reference system was used for the alignment of the mechanical loads on the femoral head. A new method was used for recognition and assortment of the high-risk elements using a strain energy-based measure. The FE results were validated with the experimental results of the same specimens and the results of similar case studies reported in

Failure Prediction of Proximal Femur using quantitative computed tomography based finite element method

Pegah Amiri Motlagh, Majid Mirzaei, Vahid Naeini
Journal PapersModares Mechanical Engineering , Volume 15 , Issue 5, 2015 July 15, {Pages 153-158 }

Abstract

Quantitative computed tomography (QCT)-based finite element analysis is a commonly accepted approach for prediction of mechanical behavior of bones. The objective of this research is to suggest linear criterion in order to accelerate and increase the precision of predicting of failure load in femoral bone. Accordingly, ten fresh frozen femora were QCT scanned and performed to use in this study. The specimens were loaded under eight different orientations. Finite element model for these samples were generated from QCT images, and related mechanical properties were calculated for each single voxel based on the value of density. In addition, the models were analyzed by linear finite element method. Risk factor that defines as the strain energy

Experimental and Computational Analysis of Fracture Load and Pattern of Femur using Cohesive Zone Model

Fatemeh Sadat Alavi, Majid Mirzaei
Journal PapersModares Mechanical Engineering , Volume 15 , Issue 10, 2015 December 15, {Pages 192-200 }

Abstract

Fracture of femur is considered as one of the most significant causes of disability and death, especially among the elderly. Therefore, there is a global effort towards noninvasive assessment of the femoral fractures. This study was aimed at the investigation of the mechanical behavior of human femur subjected to various loading orientations, under the two categories of high-stiffness (HS) and low-stiffness (LS) loading conditions. The experimental and computational analysis of deformation and fracture patterns were carried out using the QCT images and finite element analysis. The predictions of the force and fracture pattern of the HS and LS specimens were performed using linear and nonlinear finite element analyses, respectively. Also, th

Experimental and numerical analysis of dynamic rupture of steel pipes under internal high-speed moving pressures

Majid Mirzaei, Mahdi Najafi, Hosein Niasari
Journal PapersInternational Journal of Impact Engineering , Volume 85 , 2015 January , {Pages 27-36 }

Abstract

This paper reports the experimentation and finite element analysis (FEA) of dynamic ductile rupture of steel pipes subjected to high-speed internal moving pressures. The experimentation included the detonations of tiny explosive cords inside small segments of ordinary gas pipes. A number of specific features of the detonation-driven fracture of cylindrical tubes such as; formation of special fracture surface markings due to cyclic crack growth, flap bulging, and crack curving/branching adjacent to the bulged area were identified. In the analysis part, the overall transient dynamic response of the pipe to detonation loading, the detonation-driven crack growth, the cyclic bulging of the crack flaps, and the resultant crack branching were simu

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