An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback.In the optimization model,a mathematical formulation of stress dif...An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback.In the optimization model,a mathematical formulation of stress difference was developed as an indicator of the degree of springback instead of implicit springback analysis.Explicit finite element method(FEM)was used to analyze the forming process and to provide the stress distribution for calculating the amount of the stress indicator.In addition,multi-island genetic algorithm(MGA)was employed to seek the optimal loading condition.A case study was performed to demonstrate the potential of the suggested method.The results show that the optimization design of process parameters effectively reduces the amount of springback and improves the part shape accuracy.It provides a guideline for controlling springback in stretch forming of aircraft skin.展开更多
A process design approach for multi-stage stretch forming was proposed by combining the strain distribution method and finite element method(FEM)to determine the minimum stage number and deformation amount of each sta...A process design approach for multi-stage stretch forming was proposed by combining the strain distribution method and finite element method(FEM)to determine the minimum stage number and deformation amount of each stage.The strain distribution method was used to calculate the deformation amount of each stage and evaluate the formability through a safety criterion.FE simulation was taken as an analysis tool to reveal the deformation behaviour,to predict the strain contour and to determine the process parameters at each stage.To evaluate the effect of heat treatment after pre-strain on occurrence of deformation defects during the subsequent deformation,a multi-stage uniaxial tension test for 2B06 aluminium alloy sheet was carried out.A case study demonstrates that the approach has high reliability and good practicability.展开更多
The aim of this paper is two-dimensional magnetohydrodynamic viscous fluid bounded by infinite sheets to examine the Dufour and Soret effects on the （MHD） steady flow of an electrically conducting An incompressible...The aim of this paper is two-dimensional magnetohydrodynamic viscous fluid bounded by infinite sheets to examine the Dufour and Soret effects on the （MHD） steady flow of an electrically conducting An incompressible viscous fluid fills the porous space. The mathematical analysis is performed in the presence of viscous dissipation, Joule heating, and a first-order chemical reaction. With suitable transformations, the governing partial differential equations through momentum, energy, and concentration laws are transformed into ordinary differential equations. The resulting equations are solved by the homotopy analysis method （HAM）. The convergence of the series solutions is ensured. The effects of the emerging parameters, the skin friction coefficient, the Nusselt number, and the Sherwood number are analyzed on the dimensionless velocities, temperature, and concentration fields.展开更多
This investigation examines the time dependent magnetohydrodynamic （MHD） flow problem of a micropolar fluid between two radially stretching sheets. Both strong and weak concentrations of microelements are taken into...This investigation examines the time dependent magnetohydrodynamic （MHD） flow problem of a micropolar fluid between two radially stretching sheets. Both strong and weak concentrations of microelements are taken into account. Suitable transformations are employed for the conversion of partial differential equations into ordinary differential equations. Solutions to the resulting problems are developed with a homotopy analysis method （HAM）. The angular velocity, skin friction coefficient, and wall couple stress coefficient are illustrated for various parameters.展开更多
In this paper, the heat transfer effect on the steady boundary layer flow of a Casson fluid past a stretching surface in the presence of slip conditions was analyzed. The stretching surface is maintained at a constant...In this paper, the heat transfer effect on the steady boundary layer flow of a Casson fluid past a stretching surface in the presence of slip conditions was analyzed. The stretching surface is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller-box finite difference scheme. The resulting equations are solved numerically by using the Kellerbox finite-difference method, and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for non-Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that both velocity and temperature decrease with an increase of the Casson fluid parameter.展开更多
In general,for the majority of men,the amount of exercise is relatively large,so the dress requirements for the men＇ s trousers gradually have new requirements.It pays more attention to comfort and personality.The th...In general,for the majority of men,the amount of exercise is relatively large,so the dress requirements for the men＇ s trousers gradually have new requirements.It pays more attention to comfort and personality.The theoretical basis of the clothing loose amount and structural design are both the shape change cased by skin stretch of human body under various movement conditions,the human body has different postures,which will generate different skin stretch data.The combination of static body type and dynamic movements of human body determines clothing structure design,different body movements,different degree of movements and changes in skin stretch all have a direct impact on the form of clothing attached to the human body.展开更多
基金Project(50905008)supported by the National Natural Science Foundation of ChinaProject(2007AA041905)supported by the National High-tech Research and Development Program of ChinaProject(YWF-10-01-B08)supported by the Fundamental Research Funds for the Central Universities,China
文摘An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback.In the optimization model,a mathematical formulation of stress difference was developed as an indicator of the degree of springback instead of implicit springback analysis.Explicit finite element method(FEM)was used to analyze the forming process and to provide the stress distribution for calculating the amount of the stress indicator.In addition,multi-island genetic algorithm(MGA)was employed to seek the optimal loading condition.A case study was performed to demonstrate the potential of the suggested method.The results show that the optimization design of process parameters effectively reduces the amount of springback and improves the part shape accuracy.It provides a guideline for controlling springback in stretch forming of aircraft skin.
基金Project(2006AA04Z143) supported by the National High-tech Research and Development Program of ChinaProject(2006BAF04B00) supported by the National Key Technologies R&D Program of ChinaProject(2007ZE51055) supported by the Aviation Science Foundation of China
文摘A process design approach for multi-stage stretch forming was proposed by combining the strain distribution method and finite element method(FEM)to determine the minimum stage number and deformation amount of each stage.The strain distribution method was used to calculate the deformation amount of each stage and evaluate the formability through a safety criterion.FE simulation was taken as an analysis tool to reveal the deformation behaviour,to predict the strain contour and to determine the process parameters at each stage.To evaluate the effect of heat treatment after pre-strain on occurrence of deformation defects during the subsequent deformation,a multi-stage uniaxial tension test for 2B06 aluminium alloy sheet was carried out.A case study demonstrates that the approach has high reliability and good practicability.
基金Project supported by the Deanship of Scientific Research (DSR) of King Abdulaziz University of Saudi Arabia (No. HiCi/40-3/1432H)
文摘The aim of this paper is two-dimensional magnetohydrodynamic viscous fluid bounded by infinite sheets to examine the Dufour and Soret effects on the （MHD） steady flow of an electrically conducting An incompressible viscous fluid fills the porous space. The mathematical analysis is performed in the presence of viscous dissipation, Joule heating, and a first-order chemical reaction. With suitable transformations, the governing partial differential equations through momentum, energy, and concentration laws are transformed into ordinary differential equations. The resulting equations are solved by the homotopy analysis method （HAM）. The convergence of the series solutions is ensured. The effects of the emerging parameters, the skin friction coefficient, the Nusselt number, and the Sherwood number are analyzed on the dimensionless velocities, temperature, and concentration fields.
文摘This investigation examines the time dependent magnetohydrodynamic （MHD） flow problem of a micropolar fluid between two radially stretching sheets. Both strong and weak concentrations of microelements are taken into account. Suitable transformations are employed for the conversion of partial differential equations into ordinary differential equations. Solutions to the resulting problems are developed with a homotopy analysis method （HAM）. The angular velocity, skin friction coefficient, and wall couple stress coefficient are illustrated for various parameters.
文摘In this paper, the heat transfer effect on the steady boundary layer flow of a Casson fluid past a stretching surface in the presence of slip conditions was analyzed. The stretching surface is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller-box finite difference scheme. The resulting equations are solved numerically by using the Kellerbox finite-difference method, and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for non-Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that both velocity and temperature decrease with an increase of the Casson fluid parameter.
文摘In general,for the majority of men,the amount of exercise is relatively large,so the dress requirements for the men＇ s trousers gradually have new requirements.It pays more attention to comfort and personality.The theoretical basis of the clothing loose amount and structural design are both the shape change cased by skin stretch of human body under various movement conditions,the human body has different postures,which will generate different skin stretch data.The combination of static body type and dynamic movements of human body determines clothing structure design,different body movements,different degree of movements and changes in skin stretch all have a direct impact on the form of clothing attached to the human body.
