The Experts below are selected from a list of 732612 Experts worldwide ranked by ideXlab platform
Veljkovic M. - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional fatigue crack propagation simulation using extended finite element methods for steel grades S355 and S690 considering mean Stress Effects
'Elsevier BV', 2021Co-Authors: Xin H., Correia, José A.f.o., Veljkovic M.Abstract:The assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean Stress Effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean Stress Effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean Stress Effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.
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Three-dimensional fatigue crack propagation simulation using extended finite element methods for steel grades S355 and S690 considering mean Stress Effects
'Elsevier BV', 2021Co-Authors: Xin H., Correia, José A.f.o., Veljkovic M.Abstract:The assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean Stress Effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean Stress Effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean Stress Effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.Concrete StructuresSteel & Composite Structure
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Residual Stress Effects on fatigue crack growth rate of mild steel S355 exposed to air and seawater environments
'Elsevier BV', 2020Co-Authors: Xin H., Veljkovic M.Abstract:In this paper, the parameters of fatigue crack growth rate for Q355J2 steel exposed to air and seawater were presented using the “Paris' law” based on the Stress intensity factor (SIF), J-integral, crack tip opening displacement (CTOD) and crack tip opening angle (CTOA). The residual Stress of a compact tension specimen is analysed by modelling of the welding process based on subsequently thermal mechanical Stress analysis. Effect of the residual Stresses on the fatigue crack growth rate is investigated by considering the numerically predicted residual Stress distribution due to welding. The fatigue crack growth rate based on the parent material considering residual Stress Effects is compared with welds and the heat affected zone (HAZ).Steel & Composite Structure
Xin H. - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional fatigue crack propagation simulation using extended finite element methods for steel grades S355 and S690 considering mean Stress Effects
'Elsevier BV', 2021Co-Authors: Xin H., Correia, José A.f.o., Veljkovic M.Abstract:The assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean Stress Effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean Stress Effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean Stress Effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.
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Three-dimensional fatigue crack propagation simulation using extended finite element methods for steel grades S355 and S690 considering mean Stress Effects
'Elsevier BV', 2021Co-Authors: Xin H., Correia, José A.f.o., Veljkovic M.Abstract:The assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean Stress Effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean Stress Effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean Stress Effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.Concrete StructuresSteel & Composite Structure
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Residual Stress Effects on fatigue crack growth rate of mild steel S355 exposed to air and seawater environments
'Elsevier BV', 2020Co-Authors: Xin H., Veljkovic M.Abstract:In this paper, the parameters of fatigue crack growth rate for Q355J2 steel exposed to air and seawater were presented using the “Paris' law” based on the Stress intensity factor (SIF), J-integral, crack tip opening displacement (CTOD) and crack tip opening angle (CTOA). The residual Stress of a compact tension specimen is analysed by modelling of the welding process based on subsequently thermal mechanical Stress analysis. Effect of the residual Stresses on the fatigue crack growth rate is investigated by considering the numerically predicted residual Stress distribution due to welding. The fatigue crack growth rate based on the parent material considering residual Stress Effects is compared with welds and the heat affected zone (HAZ).Steel & Composite Structure
S Sahmani - One of the best experts on this subject based on the ideXlab platform.
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surface Stress Effects on the nonlinear postbuckling characteristics of geometrically imperfect cylindrical nanoshells subjected to axial compression
International Journal of Engineering Science, 2016Co-Authors: S Sahmani, M Bahrami, M M AghdamAbstract:Abstract For structures at nanoscale, the surface Effects can be important due to the high ratio of surface area to volume. In the current investigation, the nonlinear axial postbuckling behavior of geometrically imperfect cylindrical nanoshells is studied including surface Stress Effects. For this purpose, Gurtin–Murdoch continuum elasticity theory in conjunction with von Karman–Donnell-type geometric nonlinearity is implemented into the classical shell theory. By the developed size-dependent shell model, the surface Effects which include surface elasticity and residual surface Stress are taken into account. In order to satisfy balance conditions on the surfaces of nanoshell, a linear variation through the thickness is considered for the normal Stress component of the bulk. Based on the variational approach using virtual work's principle, the non-classical governing differential equations are derived. In order to solve the nonlinear problem, a boundary layer theory is employed which contains simultaneously the nonlinear prebuckling deformations, initial geometric imperfections and large deflections corresponding to the postbuckling domain. Subsequently, a two-stepped singular perturbation methodology is utilized to predict the nonlinear critical buckling loads as well as the postbuckling equilibrium paths. It is observed that by taking surface Stress Effects into account, the both critical buckling load and critical end-shortening of a cylindrical nanoshell made of Silicon increase.
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on the postbuckling behavior of geometrically imperfect cylindrical nanoshells subjected to radial compression including surface Stress Effects
Composite Structures, 2015Co-Authors: S Sahmani, M M Aghdam, M BahramiAbstract:Abstract The main objective of the present study is to investigate the effect of surface Stress on the nonlinear buckling and postbuckling behavior of cylindrical nanoshells with initial geometric imperfection subjected to radial compressive load. Gurtin–Murdoch elasticity theory is implemented into the classical shell theory to develop a size-dependent shell model which is capable to capture surface Stress Effects efficiently. In order to satisfy balance conditions on the surfaces of nanoshell, a linear variation through the thickness is considered for the normal Stress component of the bulk. The principle of virtual work is put to use in order to formulate the non-classical governing differential equations. Afterwards, a boundary layer theory is employed including the nonlinear prebuckling deformations, initial geometric imperfection and large postbuckling deflections. Finally, a two-stepped singular perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of imperfect nanoshells corresponding to both lateral and hydrostatic pressure loading cases. It is found that for the positive and negative values of surface elastic constants, the both critical buckling load and critical end-shortening of nanoshell increase and decrease, respectively.
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nonlinear buckling and postbuckling behavior of cylindrical nanoshells subjected to combined axial and radial compressions incorporating surface Stress Effects
Composites Part B-engineering, 2015Co-Authors: S Sahmani, M M Aghdam, M BahramiAbstract:Abstract In the present study, the Gurtin-Murdoch elasticity theory, as a theory capable of capturing size Effects, is implemented to predict the nonlinear buckling and postbuckling response of cylindrical nanoshells under combined axial and radial compressive loads in the presence of surface Stress Effects. For this purpose, a size-dependent shell mode containing geometric nonlinearity is proposed within the framework of the classical shell theory. Because it is necessary to satisfy balance conditions on the surfaces of nanoshell, it is assumed that the normal Stress component of the bulk varies linearly through the shell thickness. On the basis of a variational formulation using the principle of virtual work, the non-classical governing differential equations are derived. Subsequently, a boundary layer theory is employed including the nonlinear prebuckling deformations and the large deflections in the postbuckling regime. Then a two-stepped perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of nanoshells corresponding to the axial dominated and radial dominated loading cases. It is revealed that in the radial dominated loading case, a positive value of surface elastic constants leads to increase the critical buckling load but decrease the critical end-shortening of nanoshell. However, in the axial dominated loading case, surface elastic constants with positive sign causes to increase the both critical buckling load and critical end-shortening of nanoshell.
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bending behavior and buckling of nanobeams including surface Stress Effects corresponding to different beam theories
International Journal of Engineering Science, 2011Co-Authors: R Ansari, S SahmaniAbstract:Abstract A new frontier of research in the area of computational nanomechanics is to study the behavior of structures at very small length scales. As the dimensions of a structure approach the nanoscale, the classical continuum theories may fail to accurately predict the mechanical behavior of nanostructures. Among these nanostructures, nanobeams are attracting more and more attention due to their great potential engineering applications. One of the most important factors that influence the behavior of such submicron-sized structures is surface Stress effect because of their high surface to volume ratio. In this paper, a non-classical solution is proposed to analyze bending and buckling responses of nanobeams including surface Stress Effects. Explicit formulas are proposed relevant to each type of beam theory to evaluate the surface Stress Effects on the displacement profile and critical buckling load of the nanobeams. Numerical results are presented to demonstrate the difference between the behaviors of the nanobeam predicted by the classical and non-classical solutions which depends on the magnitudes of the surface elastic constants.
M Bahrami - One of the best experts on this subject based on the ideXlab platform.
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surface Stress Effects on the nonlinear postbuckling characteristics of geometrically imperfect cylindrical nanoshells subjected to axial compression
International Journal of Engineering Science, 2016Co-Authors: S Sahmani, M Bahrami, M M AghdamAbstract:Abstract For structures at nanoscale, the surface Effects can be important due to the high ratio of surface area to volume. In the current investigation, the nonlinear axial postbuckling behavior of geometrically imperfect cylindrical nanoshells is studied including surface Stress Effects. For this purpose, Gurtin–Murdoch continuum elasticity theory in conjunction with von Karman–Donnell-type geometric nonlinearity is implemented into the classical shell theory. By the developed size-dependent shell model, the surface Effects which include surface elasticity and residual surface Stress are taken into account. In order to satisfy balance conditions on the surfaces of nanoshell, a linear variation through the thickness is considered for the normal Stress component of the bulk. Based on the variational approach using virtual work's principle, the non-classical governing differential equations are derived. In order to solve the nonlinear problem, a boundary layer theory is employed which contains simultaneously the nonlinear prebuckling deformations, initial geometric imperfections and large deflections corresponding to the postbuckling domain. Subsequently, a two-stepped singular perturbation methodology is utilized to predict the nonlinear critical buckling loads as well as the postbuckling equilibrium paths. It is observed that by taking surface Stress Effects into account, the both critical buckling load and critical end-shortening of a cylindrical nanoshell made of Silicon increase.
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on the postbuckling behavior of geometrically imperfect cylindrical nanoshells subjected to radial compression including surface Stress Effects
Composite Structures, 2015Co-Authors: S Sahmani, M M Aghdam, M BahramiAbstract:Abstract The main objective of the present study is to investigate the effect of surface Stress on the nonlinear buckling and postbuckling behavior of cylindrical nanoshells with initial geometric imperfection subjected to radial compressive load. Gurtin–Murdoch elasticity theory is implemented into the classical shell theory to develop a size-dependent shell model which is capable to capture surface Stress Effects efficiently. In order to satisfy balance conditions on the surfaces of nanoshell, a linear variation through the thickness is considered for the normal Stress component of the bulk. The principle of virtual work is put to use in order to formulate the non-classical governing differential equations. Afterwards, a boundary layer theory is employed including the nonlinear prebuckling deformations, initial geometric imperfection and large postbuckling deflections. Finally, a two-stepped singular perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of imperfect nanoshells corresponding to both lateral and hydrostatic pressure loading cases. It is found that for the positive and negative values of surface elastic constants, the both critical buckling load and critical end-shortening of nanoshell increase and decrease, respectively.
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nonlinear buckling and postbuckling behavior of cylindrical nanoshells subjected to combined axial and radial compressions incorporating surface Stress Effects
Composites Part B-engineering, 2015Co-Authors: S Sahmani, M M Aghdam, M BahramiAbstract:Abstract In the present study, the Gurtin-Murdoch elasticity theory, as a theory capable of capturing size Effects, is implemented to predict the nonlinear buckling and postbuckling response of cylindrical nanoshells under combined axial and radial compressive loads in the presence of surface Stress Effects. For this purpose, a size-dependent shell mode containing geometric nonlinearity is proposed within the framework of the classical shell theory. Because it is necessary to satisfy balance conditions on the surfaces of nanoshell, it is assumed that the normal Stress component of the bulk varies linearly through the shell thickness. On the basis of a variational formulation using the principle of virtual work, the non-classical governing differential equations are derived. Subsequently, a boundary layer theory is employed including the nonlinear prebuckling deformations and the large deflections in the postbuckling regime. Then a two-stepped perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of nanoshells corresponding to the axial dominated and radial dominated loading cases. It is revealed that in the radial dominated loading case, a positive value of surface elastic constants leads to increase the critical buckling load but decrease the critical end-shortening of nanoshell. However, in the axial dominated loading case, surface elastic constants with positive sign causes to increase the both critical buckling load and critical end-shortening of nanoshell.
M M Aghdam - One of the best experts on this subject based on the ideXlab platform.
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surface Stress Effects on the nonlinear postbuckling characteristics of geometrically imperfect cylindrical nanoshells subjected to axial compression
International Journal of Engineering Science, 2016Co-Authors: S Sahmani, M Bahrami, M M AghdamAbstract:Abstract For structures at nanoscale, the surface Effects can be important due to the high ratio of surface area to volume. In the current investigation, the nonlinear axial postbuckling behavior of geometrically imperfect cylindrical nanoshells is studied including surface Stress Effects. For this purpose, Gurtin–Murdoch continuum elasticity theory in conjunction with von Karman–Donnell-type geometric nonlinearity is implemented into the classical shell theory. By the developed size-dependent shell model, the surface Effects which include surface elasticity and residual surface Stress are taken into account. In order to satisfy balance conditions on the surfaces of nanoshell, a linear variation through the thickness is considered for the normal Stress component of the bulk. Based on the variational approach using virtual work's principle, the non-classical governing differential equations are derived. In order to solve the nonlinear problem, a boundary layer theory is employed which contains simultaneously the nonlinear prebuckling deformations, initial geometric imperfections and large deflections corresponding to the postbuckling domain. Subsequently, a two-stepped singular perturbation methodology is utilized to predict the nonlinear critical buckling loads as well as the postbuckling equilibrium paths. It is observed that by taking surface Stress Effects into account, the both critical buckling load and critical end-shortening of a cylindrical nanoshell made of Silicon increase.
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on the postbuckling behavior of geometrically imperfect cylindrical nanoshells subjected to radial compression including surface Stress Effects
Composite Structures, 2015Co-Authors: S Sahmani, M M Aghdam, M BahramiAbstract:Abstract The main objective of the present study is to investigate the effect of surface Stress on the nonlinear buckling and postbuckling behavior of cylindrical nanoshells with initial geometric imperfection subjected to radial compressive load. Gurtin–Murdoch elasticity theory is implemented into the classical shell theory to develop a size-dependent shell model which is capable to capture surface Stress Effects efficiently. In order to satisfy balance conditions on the surfaces of nanoshell, a linear variation through the thickness is considered for the normal Stress component of the bulk. The principle of virtual work is put to use in order to formulate the non-classical governing differential equations. Afterwards, a boundary layer theory is employed including the nonlinear prebuckling deformations, initial geometric imperfection and large postbuckling deflections. Finally, a two-stepped singular perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of imperfect nanoshells corresponding to both lateral and hydrostatic pressure loading cases. It is found that for the positive and negative values of surface elastic constants, the both critical buckling load and critical end-shortening of nanoshell increase and decrease, respectively.
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nonlinear buckling and postbuckling behavior of cylindrical nanoshells subjected to combined axial and radial compressions incorporating surface Stress Effects
Composites Part B-engineering, 2015Co-Authors: S Sahmani, M M Aghdam, M BahramiAbstract:Abstract In the present study, the Gurtin-Murdoch elasticity theory, as a theory capable of capturing size Effects, is implemented to predict the nonlinear buckling and postbuckling response of cylindrical nanoshells under combined axial and radial compressive loads in the presence of surface Stress Effects. For this purpose, a size-dependent shell mode containing geometric nonlinearity is proposed within the framework of the classical shell theory. Because it is necessary to satisfy balance conditions on the surfaces of nanoshell, it is assumed that the normal Stress component of the bulk varies linearly through the shell thickness. On the basis of a variational formulation using the principle of virtual work, the non-classical governing differential equations are derived. Subsequently, a boundary layer theory is employed including the nonlinear prebuckling deformations and the large deflections in the postbuckling regime. Then a two-stepped perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of nanoshells corresponding to the axial dominated and radial dominated loading cases. It is revealed that in the radial dominated loading case, a positive value of surface elastic constants leads to increase the critical buckling load but decrease the critical end-shortening of nanoshell. However, in the axial dominated loading case, surface elastic constants with positive sign causes to increase the both critical buckling load and critical end-shortening of nanoshell.
