mohammad mashayekhi - Academia.edu (original) (raw)

Papers by mohammad mashayekhi

Research paper thumbnail of An Experimental and Numerical Study of Ductile Fracture of Copper/Stainless Steel Clad Sheet in Deep Drawing Process

Iranian Journal of Science and Technology-Transactions of Mechanical Engineering, 2015

This work is an attempt towards employing ductile damage criterion and finite elementsimulations ... more This work is an attempt towards employing ductile damage criterion and finite elementsimulations for prediction of fracture initiation and evolution in deep drawing of copper/stainlesssteel clad sheets. The material mechanical properties and ductile damage parameters weredetermined through standard and notched tensile tests. The effect of some important processparameters on damage evolution were examined through numerical modeling and the acceptablerange of variations for each parameter were introduced in order to prevent tearing of the blankduring the process. The numerical predictions of deformation and fracture behavior were in a goodagreement with experimental observations.

Research paper thumbnail of An experimental and numerical investigation of energy absorption of sportswear in seam area

Fashion and Textiles

This study aims to investigate the energy absorption of seam areas in sportswear. Weft knitted fa... more This study aims to investigate the energy absorption of seam areas in sportswear. Weft knitted fabrics with two structures of plain and rib were fabricated by polyester/Lycra and viscose/ Lycra yarns. Fabrics were stitched in two stitch classes. Moreover, two types of seams were considered. A pull-out test was carried out on all samples to determine the energy absorption values. Furthermore, a finite element model was applied to predict the energy absorption of each structure. The unit cell of each sample was created in ABAQUS software and the tensile load was applied to the stitch yarn. The unit cells of the fabric and the stitched section were modeled in the meso-scale and then elastic and viscoelastic properties of the yarns were assigned to the model. The energy absorption of the sample with rib pattern, lapped seam, and 607 stitch class was more than other samples. Also, the numerical and experimental results showed a high correlation with each other in samples with 304 stitch ...

Research paper thumbnail of Investigation on the Ultrasonic Tube Hydroforming in the Bulging Process Using Finite Element Method

Applied and Computational Mechanics, 2017

In ultrasonic tube hydroforming, the tube is hydro formed while the ultrasonic vibration is appli... more In ultrasonic tube hydroforming, the tube is hydro formed while the ultrasonic vibration is applied to the die. Prior studies provide experimental proof that ultrasonic tube hydroforming reduces corner radius, improves lubrication and uniform thickness. Use of ultrasonic vibration can decrease friction at the tube-die interface. Few attempts have been made to analyze the wire drawing while the ultrasonic vibrations were also applied during the processes. A detailed analysis and understanding of the mechanism of improvement is not possible with conventional experimental observation because the ultrasonic vibration processing phenomenon occurs at high speed. Therefore, we attempt to understand the processing mechanism of ultrasonic tube hydroforming using the finite element method (FEM).ABAQUS was used for the FEM. Forming force and formability in tube hydroforming analyzed. From these studies, we quantitatively clarified the mechanism of improved formability characteristics, such as ...

Research paper thumbnail of Investigating the Ultrasonic Assistance in the Tube Hydroforming Process

Applied and Computational Mechanics, 2017

The purpose of introducing ultrasonic vibrations in the tube hydroforming process is to create mo... more The purpose of introducing ultrasonic vibrations in the tube hydroforming process is to create more formability by obtaining a lower corner radius, improve thickness distribution of the wall and provide good tribological conditions at the tube and the die interface. Vibrations imposed on the die create alternating gaps which improve the formability in the tube hydroforming process in the presence of ultrasonic vibrations. Therefore, we attempted to understand the processing mechanism of the ultrasonic tube hydroforming in the square die using the finite element method. Abaqus software was used in these simulations and the die was considered as a deformable element.

Research paper thumbnail of Estimating High Cycle Fatigue Lifetime using Chaboche-Lemaitre Damage Model

Journal of Computational Methods In Engineering, 2016

This article predicts lifetime of high cycle fatigue loading using Chaboche-Lemaitre damage model... more This article predicts lifetime of high cycle fatigue loading using Chaboche-Lemaitre damage model. The Chaboche-Lemaitre damage model takes into account mean stress effect as well as compressive stresses effect, making crack to close. In the this paper, a numerical algorithm is offered to integrate this model implicitly and the obtained algorithm is implemented as a user material subroutine of the ABAQUS finite element software. To reduce computation time, Jump-in-Cycles procedure is used based on fatigue loading simulation. To verify the proposed algorithm, a V-notched specimen is chosen under a fatigue loading with different stress ratios, and its lifetime is compared with experiments. Next, an aviation industry part, main rotor spindle of an aircraft blades, subjected to a variable fatigue loading is analysed.

Research paper thumbnail of ‫ﭘﯿﺶ‬ ‫در‬ ‫ﻣﺤﺪود‬ ‫ﺳﻠﻮل‬ ‫روش‬ ‫ﮐﺎرﺑﺮد‬ ‫در‬ ‫ﺑﺎ‬ ‫ﻧﺮم‬ ‫آﺳﯿﺐ‬ ‫ﺑﯿﻨﯽ‬ ‫ﻧﻈﺮ‬ ‫ﺑﺴﺘﻪ‬ ‫اﺛﺮ‬ ‫ﮔﺮﻓﺘﻦ‬ ‫ﺗﺮك‬ ‫ﺷﺪن‬ ‫ﻫﺎ‬ ‫اﻣﯿﺮ‬ ‫اﺻﻔﻬﺎﻧﯽ‬ ‫ﺣﺪادﮔﺮ‬ ‫ﺣﺴﯿﻦ‬ ‫ﻣﺸﺎﯾﺨﯽ‬ ‫ﻣﺤﻤﺪ‬ ، 2 * ، ‫ﭘﺮوﯾﺰﯾﺎن‬ ‫ﺟﻤﺸﯿﺪ‬ Using the finite cell method to predict ductile damage with crack closure effect

‫ﻣﺠﻠﻪ‬ ،‫ﻣﺪرس‬ ‫ﻣﮑﺎﻧﯿﮏ‬ ‫ﻣﻬﻨﺪﺳﯽ‬ ‫ﻓﻮق‬ ‫اﺳﻔﻨﺪ‬ ‫اﻟﻌﺎده‬ 1393 ‫دوره‬ ، 14 ، ‫ﺷﻤﺎره‬ 13 ، ‫ص‬ ‫ص‬ 1... more ‫ﻣﺠﻠﻪ‬ ،‫ﻣﺪرس‬ ‫ﻣﮑﺎﻧﯿﮏ‬ ‫ﻣﻬﻨﺪﺳﯽ‬ ‫ﻓﻮق‬ ‫اﺳﻔﻨﺪ‬ ‫اﻟﻌﺎده‬ 1393 ‫دوره‬ ، 14 ، ‫ﺷﻤﺎره‬ 13 ، ‫ص‬ ‫ص‬ 107-118 ‫ﭘﮋوﻫﺸﯽ‬ ‫ﻋﻠﻤﯽ‬ ‫ﻣﺎﻫﻨﺎﻣﻪ‬ ‫ﻣﻬﻨﺪﺳﯽ‬ ‫ﻣﮑﺎﻧﯿﮏ‬ ‫ﻣﺪرس‬ mme.modares.ac.ir ‫ﻧﻤﺎﯾﯿﺪ‬ ‫اﺳﺘﻔﺎده‬ ‫ذﯾﻞ‬ ‫ﻋﺒﺎرت‬ ‫از‬ ‫ﻣﻘﺎﻟﻪ‬ ‫اﯾﻦ‬ ‫ﺑﻪ‬ ‫ارﺟﺎع‬ ‫ﺑﺮاي‬ : Please cite this article using: A. H. Hadadgar Esfahani, M. Mashayekhi, J. Parvizian, Using the finite cell method to predict ductile damage with crack closure effect, Modares ABSTRACT Original Research Paper In this paper, the Finite Cell Method (FCM) is used to predict the ductile damage and crack evolution in ductile materials under small strains and nonlinear isotropic hardening conditions. In the first step, a fully coupled elastic-plastic-damage model based on modified Lemaitre ductile damage model was developed and implemented into FCM implicit codes. Also, the effect of micro-crack closure, which may dramatically decrease the rate of damage growth under compression, was incorporated and its computational implementation discussed. Th...

Research paper thumbnail of Safe Designing Of Jet Trainer Aircraft Tailplane on Impact with Runway in Anomalistic Takeoff (Persian Language)

Research paper thumbnail of Prediction of All-Steel CNG Cylinder Fracture Under Impact Using a Damage Mechanics Approach

In this paper, a damage mechanics approach is used to investigate the e ect of crash and damage c... more In this paper, a damage mechanics approach is used to investigate the e ect of crash and damage caused by impact in a steel cylinder lled by Compressed Natural Gas (CNG). The Canadian Standard Association (CSA) for CNG cylinders is used as a damage detection criterion, and the cylinders' capability of reuse. The Johnson-Cook damage model is used to compute cylinder failures. Simulations are carried out in di erent impact directions, and the e ect of cylinder internal pressure, collision velocity and fall height are analyzed. Also, failure due to collisions in various situations is studied and discussed. Investigations for cases including crash and drop tests showed that the maximum damage in a cylinder is created in the case of normal impact and, by changing impact direction from normal to the side, the amount of damage will be decreased. Also, by eliminating failed elements and comparing the damage depth caused by collision using the CSA standard, it was observed that in most cases of normal accidents and drop tests, damaged cylinders lose their ability for reuse. However, in the case of side impact, the cylinder remains intact or can be reused after repair.

Research paper thumbnail of Biodegradation evaluation of poly (lactic acid) for stent application: Role of mechanical tension and temperature

Journal of Applied Polymer Science

Research paper thumbnail of Multiscale Finite Element Modeling of the Viscoelastic Behavior of Sportswear Under Periodic Load

Clothing and Textiles Research Journal

The aim of this study was to investigate the influence of different stitch factors on the mechani... more The aim of this study was to investigate the influence of different stitch factors on the mechanical behavior of the seam section of sportswear under periodic load. Multiscale finite element (FE) modeling was then utilized to predict the mechanical behavior of the samples under periodic tensile load. The unit cells of the fabric and the stitched section were modeled in the mesoscale. Elastic and viscoelastic properties of the yarns were assigned to the model. In order to obtain the mechanical properties of the sample, periodic boundary conditions were applied to the unit cell. Elastic and viscoelastic properties calculated from the mesoscale were then used for the macromodel. FE results had a good agreement with the experimental ones in predicting the mechanical behavior of the seam section under the periodic tensile load. By using Taguchi method, the optimum sample was found.

Research paper thumbnail of Using the Equivalent Fiber Approach in Two-Scale Modeling of the Elastic Behavior of Carbon Nanotube/Epoxy Nanocomposite

Nanomaterials

In this study, the mechanical behavior of epoxy/carbon nanotubes (CNTs) nanocomposite is predicat... more In this study, the mechanical behavior of epoxy/carbon nanotubes (CNTs) nanocomposite is predicated by a two-scale modeling approach. At the nanoscale, a CNT, the interface between the CNT and the matrix and a layer of the matrix around the CNT are modeled and the elastic behavior of the equivalent fiber (EF) has been identified. The CNT/epoxy interface behavior is modeled by the Park–Paulino–Roesler (PPR) potential. At the microscale, the EFs are embedded in the matrix with the extracted elastic properties from the nanoscale model. The random pattern has been used for the dispersing of EFs in the representative volume element (RVE). The effect of CNTs agglomeration in the epoxy matrix has also been investigated at the micro level. The Young’s modulus of the nanocomposite was extracted from simulation of the RVE. CNT/epoxy nanocomposites at four different volume fractions were manufactured and the modeling results were validated by tensile tests. The results of the numerical models ...

Research paper thumbnail of Continuum damage mechanics application in low-cycle thermal fatigue

International Journal of Damage Mechanics

In this article, a fatigue model for low-cycle thermal fatigue formulated in a continuum damage m... more In this article, a fatigue model for low-cycle thermal fatigue formulated in a continuum damage mechanics framework is presented. The model is based on a unified damage law presented by Lemaitre for low-cycle fatigue, which has been extended to low-cycle thermal fatigue. The temperature dependencies of material parameters are considered in the damage evolution integration to take the non-isothermal condition of loading into account. This model considers the stress triaxiality and non-linearity of damage evolution, and it is developed to a fatigue damage accumulation rule in which the load sequence effect is also included. The stabilized structural response under thermomechanical loading motivates the use of uncoupled analysis approach making the model a fast tool suitable for design purposes in the costly and time-consuming field of thermomechanical fatigue life assessment. To demonstrate the capability and ease of use of this model for real industrial applications, the low-cycle th...

Research paper thumbnail of A micro-structural model for prediction of void initiation in superplastic forming

International Journal of Damage Mechanics, 2013

ABSTRACT Superplastic forming has been used to produce complex parts without local thinning. Cavi... more ABSTRACT Superplastic forming has been used to produce complex parts without local thinning. Cavitations that occur during this procedure can reduce the quality of products. In this paper, a model is proposed to predict void initiation in superplastic forming based on the study of dominant micro-mechanisms. For this purpose, a constitutive model is proposed that considers micro mechanisms of superplastic forming including: grain interior deformation, grain boundary sliding and grain boundary diffusion. The possibility of void initiation around a second phase particle is evaluated by calculating relative velocity between two adjacent grains and mass transportation around the particle due to diffusion. The proposed model is calibrated for an Aluminum alloy at 500oC and 550oC. Then the model is used to predict void numbers in various strains and strain rates at these temperatures. Model predictions are in excellent agreement with experimental data. It is shown that grain boundary sliding has a significant role in void initiation of superplastic materials.

Research paper thumbnail of Cohesive zone and level set method for simulation of high cycle fatigue delamination in composite materials

Composite Structures, 2017

Research paper thumbnail of A Cohesive Zone Approach for Fatigue-Driven Delamination Analysis in Composite Materials

Applied Composite Materials, 2016

Research paper thumbnail of Evaluation of Fracture in a Three Stage Forging Process Using Continuum Damage Mechanics

AIP Conference Proceedings, 2007

In forging process, formability is limited by ductile fracture. In many cases forgeability is det... more In forging process, formability is limited by ductile fracture. In many cases forgeability is determined by the occurrence of ductile fracture and therefore limitations are set by the appearance of surface or internal cracks within regions that are highly strained due to extensive material flow. In this paper, the continuum damage mechanics framework for ductile materials developed by Lemaitre has been utilized numerically. A constitutive elastic-plastic-damage model has been implemented inside the finite element code ABAQUS. In forming process, crack closure effects have a strong influence on damage evolution. Therefore, it is necessary to split the tensile and compression stresses in damage evolution and deal with them separately. A modified version of Lemaitre model has been implemented and utilized through the study. The prediction of the surface cracks in forging is analyzed numerically. The results could correctly predict the location of surface cracks in the forging process.

Research paper thumbnail of Determining the Critical Region and Reusability of CNG All-Steel Cylinders in Collision (Persian Language)

In this paper damage mechanics approach has been applied to investigate the effect of impact and ... more In this paper damage mechanics approach has been applied to investigate the effect of impact and damage caused by that in under pressure CNG All-steel cylinders by using ABAQUS\Explicit. The CSA standard in CNG cylinders is used as a damage detection criterion and cylinders ability to reuse. Simulation of cylinder failures caused by collision has been done by using Johnson-Cook damage model. Accomplished simulations are carried out in different impact directions, and effect of cylinder internal pressure and collision velocity are analyzed. These investigations for different cases show that the maximum damage created in case of vertical impact and by changing direction from vertical to horizontal resultant damage will be decreased. The results show that in collision process the cylinder's rear wall and the front hemisphere of cylinder have more damaged and are the critical areas in the horizontal and vertical collisions, respectively. For a specific impact direction in lower cylinder internal pressure and higher collision velocity damage will be more. The resulted diagrams indicate that damaged area of the cylinders predominately are under compression and endure large plastic deformation.for equations, tables and references are also presented.

Research paper thumbnail of A two-scale damage model for high cycle fatigue delamination in laminated composites

Composites Science and Technology, 2015

In this paper a model for predicting fatigue delamination growth in laminated composites under hi... more In this paper a model for predicting fatigue delamination growth in laminated composites under high cycle fatigue is proposed. The model uses the cohesive zone approach and a two-scale continuum damage mechanics model. The behavior of the interface material is considered quasi-brittle at the macro scale while plastic deformations are allowed at the scale of micro-defects. The validity of the proposed model is investigated through several standard tests using experimental data from literature. Good agreement between the numerical and experimental results is observed. The model is also capable of simulating fatigue under variable amplitude loading. This feature of model is shown through several sample simulations.

Research paper thumbnail of Prediction of All-Steel CNG Cylinders Fracture in Impact by Using Damage Mechanic Approach (Persian Language)

Research paper thumbnail of Determining the Critical Region and Reusability of CNG All-Steel Cylinders in Collision

In this paper damage mechanics approach has been applied to investigate the effect of impact and ... more In this paper damage mechanics approach has been applied to investigate the effect of impact and damage caused by that in under pressure CNG All-steel cylinders by using ABAQUS\Explicit. The CSA standard in CNG cylinders is used as a damage detection criterion and cylinders ability to reuse. Simulation of cylinder failures caused by collision has been done by using Johnson-Cook damage model. Accomplished simulations are carried out in different impact directions, and effect of cylinder internal pressure and collision velocity are analyzed. These investigations for different cases show that the maximum damage created in case of vertical impact and by changing direction from vertical to horizontal resultant damage will be decreased. The results show that in collision process the cylinder’s rear wall and the front hemisphere of cylinder have more damaged and are the critical areas in the horizontal and vertical collisions, respectively. For a specific impact direction in lower cylinder...

Research paper thumbnail of An Experimental and Numerical Study of Ductile Fracture of Copper/Stainless Steel Clad Sheet in Deep Drawing Process

Iranian Journal of Science and Technology-Transactions of Mechanical Engineering, 2015

This work is an attempt towards employing ductile damage criterion and finite elementsimulations ... more This work is an attempt towards employing ductile damage criterion and finite elementsimulations for prediction of fracture initiation and evolution in deep drawing of copper/stainlesssteel clad sheets. The material mechanical properties and ductile damage parameters weredetermined through standard and notched tensile tests. The effect of some important processparameters on damage evolution were examined through numerical modeling and the acceptablerange of variations for each parameter were introduced in order to prevent tearing of the blankduring the process. The numerical predictions of deformation and fracture behavior were in a goodagreement with experimental observations.

Research paper thumbnail of An experimental and numerical investigation of energy absorption of sportswear in seam area

Fashion and Textiles

This study aims to investigate the energy absorption of seam areas in sportswear. Weft knitted fa... more This study aims to investigate the energy absorption of seam areas in sportswear. Weft knitted fabrics with two structures of plain and rib were fabricated by polyester/Lycra and viscose/ Lycra yarns. Fabrics were stitched in two stitch classes. Moreover, two types of seams were considered. A pull-out test was carried out on all samples to determine the energy absorption values. Furthermore, a finite element model was applied to predict the energy absorption of each structure. The unit cell of each sample was created in ABAQUS software and the tensile load was applied to the stitch yarn. The unit cells of the fabric and the stitched section were modeled in the meso-scale and then elastic and viscoelastic properties of the yarns were assigned to the model. The energy absorption of the sample with rib pattern, lapped seam, and 607 stitch class was more than other samples. Also, the numerical and experimental results showed a high correlation with each other in samples with 304 stitch ...

Research paper thumbnail of Investigation on the Ultrasonic Tube Hydroforming in the Bulging Process Using Finite Element Method

Applied and Computational Mechanics, 2017

In ultrasonic tube hydroforming, the tube is hydro formed while the ultrasonic vibration is appli... more In ultrasonic tube hydroforming, the tube is hydro formed while the ultrasonic vibration is applied to the die. Prior studies provide experimental proof that ultrasonic tube hydroforming reduces corner radius, improves lubrication and uniform thickness. Use of ultrasonic vibration can decrease friction at the tube-die interface. Few attempts have been made to analyze the wire drawing while the ultrasonic vibrations were also applied during the processes. A detailed analysis and understanding of the mechanism of improvement is not possible with conventional experimental observation because the ultrasonic vibration processing phenomenon occurs at high speed. Therefore, we attempt to understand the processing mechanism of ultrasonic tube hydroforming using the finite element method (FEM).ABAQUS was used for the FEM. Forming force and formability in tube hydroforming analyzed. From these studies, we quantitatively clarified the mechanism of improved formability characteristics, such as ...

Research paper thumbnail of Investigating the Ultrasonic Assistance in the Tube Hydroforming Process

Applied and Computational Mechanics, 2017

The purpose of introducing ultrasonic vibrations in the tube hydroforming process is to create mo... more The purpose of introducing ultrasonic vibrations in the tube hydroforming process is to create more formability by obtaining a lower corner radius, improve thickness distribution of the wall and provide good tribological conditions at the tube and the die interface. Vibrations imposed on the die create alternating gaps which improve the formability in the tube hydroforming process in the presence of ultrasonic vibrations. Therefore, we attempted to understand the processing mechanism of the ultrasonic tube hydroforming in the square die using the finite element method. Abaqus software was used in these simulations and the die was considered as a deformable element.

Research paper thumbnail of Estimating High Cycle Fatigue Lifetime using Chaboche-Lemaitre Damage Model

Journal of Computational Methods In Engineering, 2016

This article predicts lifetime of high cycle fatigue loading using Chaboche-Lemaitre damage model... more This article predicts lifetime of high cycle fatigue loading using Chaboche-Lemaitre damage model. The Chaboche-Lemaitre damage model takes into account mean stress effect as well as compressive stresses effect, making crack to close. In the this paper, a numerical algorithm is offered to integrate this model implicitly and the obtained algorithm is implemented as a user material subroutine of the ABAQUS finite element software. To reduce computation time, Jump-in-Cycles procedure is used based on fatigue loading simulation. To verify the proposed algorithm, a V-notched specimen is chosen under a fatigue loading with different stress ratios, and its lifetime is compared with experiments. Next, an aviation industry part, main rotor spindle of an aircraft blades, subjected to a variable fatigue loading is analysed.

Research paper thumbnail of ‫ﭘﯿﺶ‬ ‫در‬ ‫ﻣﺤﺪود‬ ‫ﺳﻠﻮل‬ ‫روش‬ ‫ﮐﺎرﺑﺮد‬ ‫در‬ ‫ﺑﺎ‬ ‫ﻧﺮم‬ ‫آﺳﯿﺐ‬ ‫ﺑﯿﻨﯽ‬ ‫ﻧﻈﺮ‬ ‫ﺑﺴﺘﻪ‬ ‫اﺛﺮ‬ ‫ﮔﺮﻓﺘﻦ‬ ‫ﺗﺮك‬ ‫ﺷﺪن‬ ‫ﻫﺎ‬ ‫اﻣﯿﺮ‬ ‫اﺻﻔﻬﺎﻧﯽ‬ ‫ﺣﺪادﮔﺮ‬ ‫ﺣﺴﯿﻦ‬ ‫ﻣﺸﺎﯾﺨﯽ‬ ‫ﻣﺤﻤﺪ‬ ، 2 * ، ‫ﭘﺮوﯾﺰﯾﺎن‬ ‫ﺟﻤﺸﯿﺪ‬ Using the finite cell method to predict ductile damage with crack closure effect

‫ﻣﺠﻠﻪ‬ ،‫ﻣﺪرس‬ ‫ﻣﮑﺎﻧﯿﮏ‬ ‫ﻣﻬﻨﺪﺳﯽ‬ ‫ﻓﻮق‬ ‫اﺳﻔﻨﺪ‬ ‫اﻟﻌﺎده‬ 1393 ‫دوره‬ ، 14 ، ‫ﺷﻤﺎره‬ 13 ، ‫ص‬ ‫ص‬ 1... more ‫ﻣﺠﻠﻪ‬ ،‫ﻣﺪرس‬ ‫ﻣﮑﺎﻧﯿﮏ‬ ‫ﻣﻬﻨﺪﺳﯽ‬ ‫ﻓﻮق‬ ‫اﺳﻔﻨﺪ‬ ‫اﻟﻌﺎده‬ 1393 ‫دوره‬ ، 14 ، ‫ﺷﻤﺎره‬ 13 ، ‫ص‬ ‫ص‬ 107-118 ‫ﭘﮋوﻫﺸﯽ‬ ‫ﻋﻠﻤﯽ‬ ‫ﻣﺎﻫﻨﺎﻣﻪ‬ ‫ﻣﻬﻨﺪﺳﯽ‬ ‫ﻣﮑﺎﻧﯿﮏ‬ ‫ﻣﺪرس‬ mme.modares.ac.ir ‫ﻧﻤﺎﯾﯿﺪ‬ ‫اﺳﺘﻔﺎده‬ ‫ذﯾﻞ‬ ‫ﻋﺒﺎرت‬ ‫از‬ ‫ﻣﻘﺎﻟﻪ‬ ‫اﯾﻦ‬ ‫ﺑﻪ‬ ‫ارﺟﺎع‬ ‫ﺑﺮاي‬ : Please cite this article using: A. H. Hadadgar Esfahani, M. Mashayekhi, J. Parvizian, Using the finite cell method to predict ductile damage with crack closure effect, Modares ABSTRACT Original Research Paper In this paper, the Finite Cell Method (FCM) is used to predict the ductile damage and crack evolution in ductile materials under small strains and nonlinear isotropic hardening conditions. In the first step, a fully coupled elastic-plastic-damage model based on modified Lemaitre ductile damage model was developed and implemented into FCM implicit codes. Also, the effect of micro-crack closure, which may dramatically decrease the rate of damage growth under compression, was incorporated and its computational implementation discussed. Th...

Research paper thumbnail of Safe Designing Of Jet Trainer Aircraft Tailplane on Impact with Runway in Anomalistic Takeoff (Persian Language)

Research paper thumbnail of Prediction of All-Steel CNG Cylinder Fracture Under Impact Using a Damage Mechanics Approach

In this paper, a damage mechanics approach is used to investigate the e ect of crash and damage c... more In this paper, a damage mechanics approach is used to investigate the e ect of crash and damage caused by impact in a steel cylinder lled by Compressed Natural Gas (CNG). The Canadian Standard Association (CSA) for CNG cylinders is used as a damage detection criterion, and the cylinders' capability of reuse. The Johnson-Cook damage model is used to compute cylinder failures. Simulations are carried out in di erent impact directions, and the e ect of cylinder internal pressure, collision velocity and fall height are analyzed. Also, failure due to collisions in various situations is studied and discussed. Investigations for cases including crash and drop tests showed that the maximum damage in a cylinder is created in the case of normal impact and, by changing impact direction from normal to the side, the amount of damage will be decreased. Also, by eliminating failed elements and comparing the damage depth caused by collision using the CSA standard, it was observed that in most cases of normal accidents and drop tests, damaged cylinders lose their ability for reuse. However, in the case of side impact, the cylinder remains intact or can be reused after repair.

Research paper thumbnail of Biodegradation evaluation of poly (lactic acid) for stent application: Role of mechanical tension and temperature

Journal of Applied Polymer Science

Research paper thumbnail of Multiscale Finite Element Modeling of the Viscoelastic Behavior of Sportswear Under Periodic Load

Clothing and Textiles Research Journal

The aim of this study was to investigate the influence of different stitch factors on the mechani... more The aim of this study was to investigate the influence of different stitch factors on the mechanical behavior of the seam section of sportswear under periodic load. Multiscale finite element (FE) modeling was then utilized to predict the mechanical behavior of the samples under periodic tensile load. The unit cells of the fabric and the stitched section were modeled in the mesoscale. Elastic and viscoelastic properties of the yarns were assigned to the model. In order to obtain the mechanical properties of the sample, periodic boundary conditions were applied to the unit cell. Elastic and viscoelastic properties calculated from the mesoscale were then used for the macromodel. FE results had a good agreement with the experimental ones in predicting the mechanical behavior of the seam section under the periodic tensile load. By using Taguchi method, the optimum sample was found.

Research paper thumbnail of Using the Equivalent Fiber Approach in Two-Scale Modeling of the Elastic Behavior of Carbon Nanotube/Epoxy Nanocomposite

Nanomaterials

In this study, the mechanical behavior of epoxy/carbon nanotubes (CNTs) nanocomposite is predicat... more In this study, the mechanical behavior of epoxy/carbon nanotubes (CNTs) nanocomposite is predicated by a two-scale modeling approach. At the nanoscale, a CNT, the interface between the CNT and the matrix and a layer of the matrix around the CNT are modeled and the elastic behavior of the equivalent fiber (EF) has been identified. The CNT/epoxy interface behavior is modeled by the Park–Paulino–Roesler (PPR) potential. At the microscale, the EFs are embedded in the matrix with the extracted elastic properties from the nanoscale model. The random pattern has been used for the dispersing of EFs in the representative volume element (RVE). The effect of CNTs agglomeration in the epoxy matrix has also been investigated at the micro level. The Young’s modulus of the nanocomposite was extracted from simulation of the RVE. CNT/epoxy nanocomposites at four different volume fractions were manufactured and the modeling results were validated by tensile tests. The results of the numerical models ...

Research paper thumbnail of Continuum damage mechanics application in low-cycle thermal fatigue

International Journal of Damage Mechanics

In this article, a fatigue model for low-cycle thermal fatigue formulated in a continuum damage m... more In this article, a fatigue model for low-cycle thermal fatigue formulated in a continuum damage mechanics framework is presented. The model is based on a unified damage law presented by Lemaitre for low-cycle fatigue, which has been extended to low-cycle thermal fatigue. The temperature dependencies of material parameters are considered in the damage evolution integration to take the non-isothermal condition of loading into account. This model considers the stress triaxiality and non-linearity of damage evolution, and it is developed to a fatigue damage accumulation rule in which the load sequence effect is also included. The stabilized structural response under thermomechanical loading motivates the use of uncoupled analysis approach making the model a fast tool suitable for design purposes in the costly and time-consuming field of thermomechanical fatigue life assessment. To demonstrate the capability and ease of use of this model for real industrial applications, the low-cycle th...

Research paper thumbnail of A micro-structural model for prediction of void initiation in superplastic forming

International Journal of Damage Mechanics, 2013

ABSTRACT Superplastic forming has been used to produce complex parts without local thinning. Cavi... more ABSTRACT Superplastic forming has been used to produce complex parts without local thinning. Cavitations that occur during this procedure can reduce the quality of products. In this paper, a model is proposed to predict void initiation in superplastic forming based on the study of dominant micro-mechanisms. For this purpose, a constitutive model is proposed that considers micro mechanisms of superplastic forming including: grain interior deformation, grain boundary sliding and grain boundary diffusion. The possibility of void initiation around a second phase particle is evaluated by calculating relative velocity between two adjacent grains and mass transportation around the particle due to diffusion. The proposed model is calibrated for an Aluminum alloy at 500oC and 550oC. Then the model is used to predict void numbers in various strains and strain rates at these temperatures. Model predictions are in excellent agreement with experimental data. It is shown that grain boundary sliding has a significant role in void initiation of superplastic materials.

Research paper thumbnail of Cohesive zone and level set method for simulation of high cycle fatigue delamination in composite materials

Composite Structures, 2017

Research paper thumbnail of A Cohesive Zone Approach for Fatigue-Driven Delamination Analysis in Composite Materials

Applied Composite Materials, 2016

Research paper thumbnail of Evaluation of Fracture in a Three Stage Forging Process Using Continuum Damage Mechanics

AIP Conference Proceedings, 2007

In forging process, formability is limited by ductile fracture. In many cases forgeability is det... more In forging process, formability is limited by ductile fracture. In many cases forgeability is determined by the occurrence of ductile fracture and therefore limitations are set by the appearance of surface or internal cracks within regions that are highly strained due to extensive material flow. In this paper, the continuum damage mechanics framework for ductile materials developed by Lemaitre has been utilized numerically. A constitutive elastic-plastic-damage model has been implemented inside the finite element code ABAQUS. In forming process, crack closure effects have a strong influence on damage evolution. Therefore, it is necessary to split the tensile and compression stresses in damage evolution and deal with them separately. A modified version of Lemaitre model has been implemented and utilized through the study. The prediction of the surface cracks in forging is analyzed numerically. The results could correctly predict the location of surface cracks in the forging process.

Research paper thumbnail of Determining the Critical Region and Reusability of CNG All-Steel Cylinders in Collision (Persian Language)

In this paper damage mechanics approach has been applied to investigate the effect of impact and ... more In this paper damage mechanics approach has been applied to investigate the effect of impact and damage caused by that in under pressure CNG All-steel cylinders by using ABAQUS\Explicit. The CSA standard in CNG cylinders is used as a damage detection criterion and cylinders ability to reuse. Simulation of cylinder failures caused by collision has been done by using Johnson-Cook damage model. Accomplished simulations are carried out in different impact directions, and effect of cylinder internal pressure and collision velocity are analyzed. These investigations for different cases show that the maximum damage created in case of vertical impact and by changing direction from vertical to horizontal resultant damage will be decreased. The results show that in collision process the cylinder's rear wall and the front hemisphere of cylinder have more damaged and are the critical areas in the horizontal and vertical collisions, respectively. For a specific impact direction in lower cylinder internal pressure and higher collision velocity damage will be more. The resulted diagrams indicate that damaged area of the cylinders predominately are under compression and endure large plastic deformation.for equations, tables and references are also presented.

Research paper thumbnail of A two-scale damage model for high cycle fatigue delamination in laminated composites

Composites Science and Technology, 2015

In this paper a model for predicting fatigue delamination growth in laminated composites under hi... more In this paper a model for predicting fatigue delamination growth in laminated composites under high cycle fatigue is proposed. The model uses the cohesive zone approach and a two-scale continuum damage mechanics model. The behavior of the interface material is considered quasi-brittle at the macro scale while plastic deformations are allowed at the scale of micro-defects. The validity of the proposed model is investigated through several standard tests using experimental data from literature. Good agreement between the numerical and experimental results is observed. The model is also capable of simulating fatigue under variable amplitude loading. This feature of model is shown through several sample simulations.

Research paper thumbnail of Prediction of All-Steel CNG Cylinders Fracture in Impact by Using Damage Mechanic Approach (Persian Language)

Research paper thumbnail of Determining the Critical Region and Reusability of CNG All-Steel Cylinders in Collision

In this paper damage mechanics approach has been applied to investigate the effect of impact and ... more In this paper damage mechanics approach has been applied to investigate the effect of impact and damage caused by that in under pressure CNG All-steel cylinders by using ABAQUS\Explicit. The CSA standard in CNG cylinders is used as a damage detection criterion and cylinders ability to reuse. Simulation of cylinder failures caused by collision has been done by using Johnson-Cook damage model. Accomplished simulations are carried out in different impact directions, and effect of cylinder internal pressure and collision velocity are analyzed. These investigations for different cases show that the maximum damage created in case of vertical impact and by changing direction from vertical to horizontal resultant damage will be decreased. The results show that in collision process the cylinder’s rear wall and the front hemisphere of cylinder have more damaged and are the critical areas in the horizontal and vertical collisions, respectively. For a specific impact direction in lower cylinder...