A calculation model of stress field in laser additive manufacturing of walnut shell composite powder(walnut shell/Co-PES powder)was established.The DFLUX subroutine was used to implement the moveable application of a ...A calculation model of stress field in laser additive manufacturing of walnut shell composite powder(walnut shell/Co-PES powder)was established.The DFLUX subroutine was used to implement the moveable application of a double ellipsoid heat source by considering the mechanical properties varying with temperature.The stress field was simulated by the sequential coupling method,and the experimental results were in good accordance with the simulation results.In addition,the distribution and variation of stress and strain field were obtained in the process of laser additive manufacturing of walnut shell composite powder.The displacement of laser additive manufacturing walnut shell composite parts gradually decreased with increasing preheating temperature,decreasing laser power and increasing scanning speed.During the cooling process,the displacement of laser additive manufacturing of walnut shell composite parts gradually increased with the increasing preheating temperature,decreasing scanning speed and increasing laser power.展开更多
To fit in with the strict geometrical integrity and ensure dimensionally consistent fabrication of the welded aerospace structures. the low stress no distortion(LSND)welding, a technique for thin materials, was poinee...To fit in with the strict geometrical integrity and ensure dimensionally consistent fabrication of the welded aerospace structures. the low stress no distortion(LSND)welding, a technique for thin materials, was poineered and developed to provide an ininprocess active control of welding distortion. Satisfactory distortion free results were achieved in both welding of jet engine cases of heat-resistance alloys and rocket fuel tanks of aluminuim alloys, and there need no. reworking operations for post-weld distortion correction. Based on the 'static' method a newly developed method for dvnamic in-process control is also discussed in this paper. Both methods provide quanutiative in-process control of incompatible strains in weld zone and low stress no distortion welding results.展开更多
In order to ensure the safety and stability of the soft rock roadway under high stress, based on the characteristics of the surrounding rock deformation and failure, this paper presented the support technology‘‘coup...In order to ensure the safety and stability of the soft rock roadway under high stress, based on the characteristics of the surrounding rock deformation and failure, this paper presented the support technology‘‘coupling support of double yielding shell'', then gave the design method of inner and outer shells and analyzed the principle and requirements of the support technology by taking the -850 m east belt roadway of Qujiang coal mine as the background. The field application results show that the support technology can control the soft rock roadway deformation better under high stress. The displacement between roadway sides was 851 mm, the displacement of the roof was 430 mm, and the displacement of the floor was 510 mm.展开更多
A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers.The condition for existence of bi-s...A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers.The condition for existence of bi-stability of the shell structural system is presented and analytical expressions for corresponding rolled-up radii of the stable shell are given based on the principle of minimum strain energy.The resulting solution indicates that the shell system may have two stable configurations besides its initial state under a combined action of the actuating electric field and initial stresses characterized by the bending moment.If the piezoelectric layer materials act as only sensor materials without the actuating electric field,initial stresses may produce the bi-stable states,but one corresponding to its initial state.For the shell without initial stresses,the magnitude in the actuating electric field determines the number of the stable states,one or two stable configurations besides the initial state.The theoretical prediction for the bi-stable states is verified by finite element method(FEM) simulation by using the ABAQUS code.展开更多
This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more importa...This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more important and interesting aspects of the research,judged from a personal viewpoint,are discussed.They can be crudely classified into four categories:(1) shells subjected to non-uniform loads;(2) shells on discrete supports;(3) shells with intended cutouts/holes;and (4) shells with non-uniform settlements.展开更多
As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary ...As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary forming technology, and the upper and lower rolls have different radii and speeds. To quickly predict the three-dimensional stresses and eliminate fishtail defect, an improved strip layer method is developed, in which the asymmetry of the upper and lower rolls, non-uniform deformation and stress, as well as the asymmetrical spread on the end surface are considered. The deformation zone is divided into a certain number of layers and strips along the thickness and width, respectively. The transverse displacement model is constructed by polynomial function, in order to increase the computation speed greatly. From the metal plastic mechanics principle, the three-dimensional stress models are established. The genetic algorithm is used for optimization calculation in an industrial experiment example. The results show that the rolling pressure, the normal stresses, the upper and lower friction stress distributions are not similar with those of a general plate rolling. There are two relative maximum values in rolling pressure distribution. The upper and lower longitudinal friction stresses change direction nearby the upper and lower neutral points, respectively. The fishtail profile of spread on the end surface is predicted satisfactorily. The reduction could be helpful to eliminate fishtail defect. The large cylindrical shell rolling example illustrates the calculation results acquired rapidly are good agreements with the finite element simulation and experimental values of previous study. A highly effective and reliable three-dimensional simulation method is proposed for large cylindrical shell rolling and other asymmetrical rolling.展开更多
In order to explore the influence of different caving thicknesses on the MSS distributionand evolving characteristics of surrounding rocks in unsymmetrical disposal andfully mechanized top-coal caving (FMTC),based on ...In order to explore the influence of different caving thicknesses on the MSS distributionand evolving characteristics of surrounding rocks in unsymmetrical disposal andfully mechanized top-coal caving (FMTC),based on unsymmetrical disposal characteristics,the analyses of numerical simulation,material simulation and in-situ observation weresynthetically applied according to the geological and technical conditions of the 1151(3)working face in Xieqiao Mine.The results show that the stress peak value of the MSS-baseand the ratio of MSS-body height to caving thickness are nonlinear and inverselyproportional to the caving thickness.The MSS-base width,the MSS-body height,theMSS-base distance to working face wall and the rise distance of MSS-base beside coalpillar are nonlinear and directly proportional to the caving thickness.The characteristics ofMSS distribution and its evolving rules of surrounding rocks and the integrated cavingthickness effects are obtained.The investigations will provide lots of theoretic referencesto the surrounding rocks' stability control of the working face and roadway,roadway layout,gas extraction and exploitation,and efficiency of caving,etc.展开更多
-This paper adopts approximate formulas for residual stresses caused by cold bending for plates with stress-strain curve form a = K n. A typical distribution of the longitudinal residual stress due to welding is also ...-This paper adopts approximate formulas for residual stresses caused by cold bending for plates with stress-strain curve form a = K n. A typical distribution of the longitudinal residual stress due to welding is also assumed. The effects of residual stress due to cold bending and welding on plastic buckling of axially compressed cylindrical shells are studied by the finite element method.展开更多
Simplified equations are derived for the analysis of stress concentration for shear-deformable shallow shells with a small hole. General solutions of the equations are obtained, in terms of series, for shallow spheric...Simplified equations are derived for the analysis of stress concentration for shear-deformable shallow shells with a small hole. General solutions of the equations are obtained, in terms of series, for shallow spherical shells and shallow circular cylindrical shells with a small circular hole. Approximate explicit solutions and numerical results are obtianed for the stress concentration factors of shallow circular cylindrical shells with a small hole on which uniform pressure is acting.展开更多
In this paper, based on the theory of thick shells including effects of transverse shear deformations, a complex variables analytic method to solve stress concentrations in circular cylindrical shells with a small cut...In this paper, based on the theory of thick shells including effects of transverse shear deformations, a complex variables analytic method to solve stress concentrations in circular cylindrical shells with a small cutout is established A general solution and expression satisfying the boundary conditions on the edge of arbitrary cutouts are obtained. The stress problem can be reduced to the solution of an infinite algebraic equation series, and can be normalized by means of this method. Numerical results for stress concentration factors of the shell with a small circular and elliptic cutout are presented.展开更多
In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic e...In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic equation series. The solution can be normal and effective by means of this method. Numerical results for stress concentrations in the shell with a circular, elliptic cutout are graphically presented.展开更多
The dispersion relation of torsional wave in a dissipative,incompressible cylindrical shell of infinite length incorporating initial stresses effects is investigated.The governing equation and closed form solutions ar...The dispersion relation of torsional wave in a dissipative,incompressible cylindrical shell of infinite length incorporating initial stresses effects is investigated.The governing equation and closed form solutions are derived with the aid of Biot’s principle.Phase velocity and damping of torsional wave are obtained analytically and the influences of dissipation and initial stresses are studied in details.We proposed a new method for obtaining the phase and damping velocities of torsional wave in a complex form.Numerical results analyzing the torsional wave propagation incorporating initial stress effects are analyzed and presented in graphs.The analytical and numerical solutions reveal that,the dissipation as well as the initial stresses have notable impacts on the phase velocity of torsional wave in a pre-stressed dissipative cylindrical shell.The numerical results reveal that,the initial stresses and dissipation,considerably,effect the phase velocity of the torsional wave.It has been observed that,any change in dissipation parameter(δ)produces a substantial change in damping velocity of torsional wave.In addition,it can be seen that,the phase velocity increases as the initial stress parameter increases.Finally,the result of numerical simulation illustrated the influence of dissipation and initial stresses on damping and phase velocities of torsional wave propagation.The conclusion made shown the consistency with the Biot’s incremental deformation theory,and the effective on model such as engineering mechanics and displacement of particles.展开更多
This paper studies electromagnetoelastic static investigation of a sandwich doubly curved microshell subjected to multi-field loading based on a new thickness stretching included refined higher order shear/normal defo...This paper studies electromagnetoelastic static investigation of a sandwich doubly curved microshell subjected to multi-field loading based on a new thickness stretching included refined higher order shear/normal deformable model.Modified-couple-stress-theory(MCST)is used for accounting small-scaledependency.The numerical results are derived using an analytical method.The effect of small scale parameter in micro scale,initial electric and magnetic potentials and foundation parameters is studied on the electromagnetoelastic bending results.It is confirmed an enhancing in stiffness of small scale shell with an increase in micro length scale parameter.展开更多
The thermal stress in a magnetic core–shell nanoparticle during a thermal process is an important parameter to be known and controlled in the magnetization process of the core–shell system. In this paper we analyze ...The thermal stress in a magnetic core–shell nanoparticle during a thermal process is an important parameter to be known and controlled in the magnetization process of the core–shell system. In this paper we analyze the stress that appears in a core–shell nanoparticle subjected to a cooling process. The external surface temperature of the system, considered in equilibrium at room temperature, is instantly reduced to a target temperature. The thermal evolution of the system in time and the induced stress are studied using an analytical model based on a time-dependent heat conduction equation and a differential displacement equation in the formalism of elastic displacements. The source of internal stress is the difference in contraction between core and shell materials due to the temperature change. The thermal stress decreases in time and is minimized when the system reaches the thermal equilibrium. The radial and azimuthal stress components depend on system geometry, material properties, and initial and final temperatures. The magnitude of the stress changes the magnetic state of the core–shell system. For some materials, the values of the thermal stresses are larger than their specific elastic limits and the materials begin to deform plastically in the cooling process. The presence of the induced anisotropy due to the plastic deformation modifies the magnetic domain structure and the magnetic behavior of the system.展开更多
Stress analysis of cylindrical grid-stiffened composite shells was conducted under transverse loading,pure bending,torsion and axial compression under clamped-free boundary condition.Electrical strain gauges were empl...Stress analysis of cylindrical grid-stiffened composite shells was conducted under transverse loading,pure bending,torsion and axial compression under clamped-free boundary condition.Electrical strain gauges were employed to measure the strains in transverse loading case to validate the finite element analysis which was conducted using ANSYS software.Good agreement was obtained between the two methods.It was observed that stiffening the composite shell with helical ribs decreased the average equivalent Von Mises stress on the shell.The reduction of the stress seemed to be higher in the intersection of two ribs.It was also seen that the stress reduction ratio was higher when the structure was under bending compared to torsion and axial compression.The reduction ratio was approximately 75% in pure bending in the intersection point of the ribs,while it was approximately 25% in torsion.Therefore,it is concluded that the presence of the ribs is more effective under bending.Failure analysis was done using Tsai-Wu criterion.The ribs were observed to result in maximum and minimum increase in the failure load of the structure under transverse bending and torsional loading,respectively.展开更多
The effect of temperature loading on the stress of a flexspline is investigated. Based on the geometric and mechanical characteristics of the harmonic gear flexspline, a circular thin shell model is presented in this ...The effect of temperature loading on the stress of a flexspline is investigated. Based on the geometric and mechanical characteristics of the harmonic gear flexspline, a circular thin shell model is presented in this paper. The theoretical solution for the flexspline under different displacement loads and different temperature fields is derived. Meanwhile, an impact factor formula, which reflects the effect of the temperatures of the inner and outer surfaces of the flexspline on the stress of the flexspline, is presented. Finally, numerical calculations by the finite element method (FEM) are adopted to verify the corresponding conclusions.展开更多
In order to propose high effective simulation using finite element method (FEM) for predicting deformation and residual stress generated by one pass butt welding, a series of numerical analyses were carried out. By id...In order to propose high effective simulation using finite element method (FEM) for predicting deformation and residual stress generated by one pass butt welding, a series of numerical analyses were carried out. By idealizing the movement of heat source (the instantaneous heat input method), the tendency of welding out-of-plane deformation and the residual stress distribution could be predicted. The computing time was around 9% of that by the precise model with considering the movement of heat source. On the other hand, applicability of two dimensional shell elements instead of generally used three dimensional solid elements was examined. The heat input model with considering the temperature distribution in the thickness direction was proposed for the simulation by using the shell elements. It was confirmed that the welding out-of-plane deformation and residual stress could be predicted with high accuracy by the model with shell elements and the distributed heat input methods. The computing time was around 8% of that by the precise model with solid elements.展开更多
基金Supported by the Scientific Research Start-Up Fund Project of Northeast Petroleum University(2019KQ67 and 2021KQ09)the Guiding Innovation Fund Project of Northeast Petroleum University(2021YDL-13)+1 种基金National Natural Science Foundation of China(52075090)Supported by the National Key R&D Program of China(2017YFD0601004).
文摘A calculation model of stress field in laser additive manufacturing of walnut shell composite powder(walnut shell/Co-PES powder)was established.The DFLUX subroutine was used to implement the moveable application of a double ellipsoid heat source by considering the mechanical properties varying with temperature.The stress field was simulated by the sequential coupling method,and the experimental results were in good accordance with the simulation results.In addition,the distribution and variation of stress and strain field were obtained in the process of laser additive manufacturing of walnut shell composite powder.The displacement of laser additive manufacturing walnut shell composite parts gradually decreased with increasing preheating temperature,decreasing laser power and increasing scanning speed.During the cooling process,the displacement of laser additive manufacturing of walnut shell composite parts gradually increased with the increasing preheating temperature,decreasing scanning speed and increasing laser power.
文摘To fit in with the strict geometrical integrity and ensure dimensionally consistent fabrication of the welded aerospace structures. the low stress no distortion(LSND)welding, a technique for thin materials, was poineered and developed to provide an ininprocess active control of welding distortion. Satisfactory distortion free results were achieved in both welding of jet engine cases of heat-resistance alloys and rocket fuel tanks of aluminuim alloys, and there need no. reworking operations for post-weld distortion correction. Based on the 'static' method a newly developed method for dvnamic in-process control is also discussed in this paper. Both methods provide quanutiative in-process control of incompatible strains in weld zone and low stress no distortion welding results.
基金supported by the National Natural Science Foundation for Youth (No. 51304200)the China Postdoctoral Science Foundation Project (No. 2013M540477)
文摘In order to ensure the safety and stability of the soft rock roadway under high stress, based on the characteristics of the surrounding rock deformation and failure, this paper presented the support technology‘‘coupling support of double yielding shell'', then gave the design method of inner and outer shells and analyzed the principle and requirements of the support technology by taking the -850 m east belt roadway of Qujiang coal mine as the background. The field application results show that the support technology can control the soft rock roadway deformation better under high stress. The displacement between roadway sides was 851 mm, the displacement of the roof was 430 mm, and the displacement of the floor was 510 mm.
文摘A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers.The condition for existence of bi-stability of the shell structural system is presented and analytical expressions for corresponding rolled-up radii of the stable shell are given based on the principle of minimum strain energy.The resulting solution indicates that the shell system may have two stable configurations besides its initial state under a combined action of the actuating electric field and initial stresses characterized by the bending moment.If the piezoelectric layer materials act as only sensor materials without the actuating electric field,initial stresses may produce the bi-stable states,but one corresponding to its initial state.For the shell without initial stresses,the magnitude in the actuating electric field determines the number of the stable states,one or two stable configurations besides the initial state.The theoretical prediction for the bi-stable states is verified by finite element method(FEM) simulation by using the ABAQUS code.
文摘This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more important and interesting aspects of the research,judged from a personal viewpoint,are discussed.They can be crudely classified into four categories:(1) shells subjected to non-uniform loads;(2) shells on discrete supports;(3) shells with intended cutouts/holes;and (4) shells with non-uniform settlements.
基金Supported by National Science and Technology Major Project of China(Grant No.2011ZX04002-101)National Science and Technology Support Plan of China(Grant No.2011BAF15B02)National Natural Science Foundation of China(Grant No.51305388)
文摘As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary forming technology, and the upper and lower rolls have different radii and speeds. To quickly predict the three-dimensional stresses and eliminate fishtail defect, an improved strip layer method is developed, in which the asymmetry of the upper and lower rolls, non-uniform deformation and stress, as well as the asymmetrical spread on the end surface are considered. The deformation zone is divided into a certain number of layers and strips along the thickness and width, respectively. The transverse displacement model is constructed by polynomial function, in order to increase the computation speed greatly. From the metal plastic mechanics principle, the three-dimensional stress models are established. The genetic algorithm is used for optimization calculation in an industrial experiment example. The results show that the rolling pressure, the normal stresses, the upper and lower friction stress distributions are not similar with those of a general plate rolling. There are two relative maximum values in rolling pressure distribution. The upper and lower longitudinal friction stresses change direction nearby the upper and lower neutral points, respectively. The fishtail profile of spread on the end surface is predicted satisfactorily. The reduction could be helpful to eliminate fishtail defect. The large cylindrical shell rolling example illustrates the calculation results acquired rapidly are good agreements with the finite element simulation and experimental values of previous study. A highly effective and reliable three-dimensional simulation method is proposed for large cylindrical shell rolling and other asymmetrical rolling.
基金Supported by National Basic Research Program(973)(2005cb221503)National Natural Science Foundation of China(50674003)Science and Technological Fund of Anhui Province for Outstanding Youth(08040106839)
文摘In order to explore the influence of different caving thicknesses on the MSS distributionand evolving characteristics of surrounding rocks in unsymmetrical disposal andfully mechanized top-coal caving (FMTC),based on unsymmetrical disposal characteristics,the analyses of numerical simulation,material simulation and in-situ observation weresynthetically applied according to the geological and technical conditions of the 1151(3)working face in Xieqiao Mine.The results show that the stress peak value of the MSS-baseand the ratio of MSS-body height to caving thickness are nonlinear and inverselyproportional to the caving thickness.The MSS-base width,the MSS-body height,theMSS-base distance to working face wall and the rise distance of MSS-base beside coalpillar are nonlinear and directly proportional to the caving thickness.The characteristics ofMSS distribution and its evolving rules of surrounding rocks and the integrated cavingthickness effects are obtained.The investigations will provide lots of theoretic referencesto the surrounding rocks' stability control of the working face and roadway,roadway layout,gas extraction and exploitation,and efficiency of caving,etc.
文摘-This paper adopts approximate formulas for residual stresses caused by cold bending for plates with stress-strain curve form a = K n. A typical distribution of the longitudinal residual stress due to welding is also assumed. The effects of residual stress due to cold bending and welding on plastic buckling of axially compressed cylindrical shells are studied by the finite element method.
文摘Simplified equations are derived for the analysis of stress concentration for shear-deformable shallow shells with a small hole. General solutions of the equations are obtained, in terms of series, for shallow spherical shells and shallow circular cylindrical shells with a small circular hole. Approximate explicit solutions and numerical results are obtianed for the stress concentration factors of shallow circular cylindrical shells with a small hole on which uniform pressure is acting.
文摘In this paper, based on the theory of thick shells including effects of transverse shear deformations, a complex variables analytic method to solve stress concentrations in circular cylindrical shells with a small cutout is established A general solution and expression satisfying the boundary conditions on the edge of arbitrary cutouts are obtained. The stress problem can be reduced to the solution of an infinite algebraic equation series, and can be normalized by means of this method. Numerical results for stress concentration factors of the shell with a small circular and elliptic cutout are presented.
文摘In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic equation series. The solution can be normal and effective by means of this method. Numerical results for stress concentrations in the shell with a circular, elliptic cutout are graphically presented.
基金The authors thank Taif university researchers for supporting project number(TURSP-2020/16),Taif University,Taif,Saudi Arabia.The first author would like to acknowledge the supports provided by the Deanship of Scientific Research of Prince Sattam bin Abdulaziz University during this research work.
文摘The dispersion relation of torsional wave in a dissipative,incompressible cylindrical shell of infinite length incorporating initial stresses effects is investigated.The governing equation and closed form solutions are derived with the aid of Biot’s principle.Phase velocity and damping of torsional wave are obtained analytically and the influences of dissipation and initial stresses are studied in details.We proposed a new method for obtaining the phase and damping velocities of torsional wave in a complex form.Numerical results analyzing the torsional wave propagation incorporating initial stress effects are analyzed and presented in graphs.The analytical and numerical solutions reveal that,the dissipation as well as the initial stresses have notable impacts on the phase velocity of torsional wave in a pre-stressed dissipative cylindrical shell.The numerical results reveal that,the initial stresses and dissipation,considerably,effect the phase velocity of the torsional wave.It has been observed that,any change in dissipation parameter(δ)produces a substantial change in damping velocity of torsional wave.In addition,it can be seen that,the phase velocity increases as the initial stress parameter increases.Finally,the result of numerical simulation illustrated the influence of dissipation and initial stresses on damping and phase velocities of torsional wave propagation.The conclusion made shown the consistency with the Biot’s incremental deformation theory,and the effective on model such as engineering mechanics and displacement of particles.
基金the Programs for Science and Technology Development of Henan province(No.202102210020)Basic research plan of key scientific research projects of Henan universities(No.20B430011).
文摘This paper studies electromagnetoelastic static investigation of a sandwich doubly curved microshell subjected to multi-field loading based on a new thickness stretching included refined higher order shear/normal deformable model.Modified-couple-stress-theory(MCST)is used for accounting small-scaledependency.The numerical results are derived using an analytical method.The effect of small scale parameter in micro scale,initial electric and magnetic potentials and foundation parameters is studied on the electromagnetoelastic bending results.It is confirmed an enhancing in stiffness of small scale shell with an increase in micro length scale parameter.
基金Project supported by Romanian CNCS–UEFISCDI project IDEI-EXOTIC(Grant No.185/25.10.2011)
文摘The thermal stress in a magnetic core–shell nanoparticle during a thermal process is an important parameter to be known and controlled in the magnetization process of the core–shell system. In this paper we analyze the stress that appears in a core–shell nanoparticle subjected to a cooling process. The external surface temperature of the system, considered in equilibrium at room temperature, is instantly reduced to a target temperature. The thermal evolution of the system in time and the induced stress are studied using an analytical model based on a time-dependent heat conduction equation and a differential displacement equation in the formalism of elastic displacements. The source of internal stress is the difference in contraction between core and shell materials due to the temperature change. The thermal stress decreases in time and is minimized when the system reaches the thermal equilibrium. The radial and azimuthal stress components depend on system geometry, material properties, and initial and final temperatures. The magnitude of the stress changes the magnetic state of the core–shell system. For some materials, the values of the thermal stresses are larger than their specific elastic limits and the materials begin to deform plastically in the cooling process. The presence of the induced anisotropy due to the plastic deformation modifies the magnetic domain structure and the magnetic behavior of the system.
文摘Stress analysis of cylindrical grid-stiffened composite shells was conducted under transverse loading,pure bending,torsion and axial compression under clamped-free boundary condition.Electrical strain gauges were employed to measure the strains in transverse loading case to validate the finite element analysis which was conducted using ANSYS software.Good agreement was obtained between the two methods.It was observed that stiffening the composite shell with helical ribs decreased the average equivalent Von Mises stress on the shell.The reduction of the stress seemed to be higher in the intersection of two ribs.It was also seen that the stress reduction ratio was higher when the structure was under bending compared to torsion and axial compression.The reduction ratio was approximately 75% in pure bending in the intersection point of the ribs,while it was approximately 25% in torsion.Therefore,it is concluded that the presence of the ribs is more effective under bending.Failure analysis was done using Tsai-Wu criterion.The ribs were observed to result in maximum and minimum increase in the failure load of the structure under transverse bending and torsional loading,respectively.
基金Project supported by the National Natural Science Foundation of China(Nos.10972128 and11142004)the Shanghai Leading Academic Discipline Project(No.S30106)
文摘The effect of temperature loading on the stress of a flexspline is investigated. Based on the geometric and mechanical characteristics of the harmonic gear flexspline, a circular thin shell model is presented in this paper. The theoretical solution for the flexspline under different displacement loads and different temperature fields is derived. Meanwhile, an impact factor formula, which reflects the effect of the temperatures of the inner and outer surfaces of the flexspline on the stress of the flexspline, is presented. Finally, numerical calculations by the finite element method (FEM) are adopted to verify the corresponding conclusions.
文摘In order to propose high effective simulation using finite element method (FEM) for predicting deformation and residual stress generated by one pass butt welding, a series of numerical analyses were carried out. By idealizing the movement of heat source (the instantaneous heat input method), the tendency of welding out-of-plane deformation and the residual stress distribution could be predicted. The computing time was around 9% of that by the precise model with considering the movement of heat source. On the other hand, applicability of two dimensional shell elements instead of generally used three dimensional solid elements was examined. The heat input model with considering the temperature distribution in the thickness direction was proposed for the simulation by using the shell elements. It was confirmed that the welding out-of-plane deformation and residual stress could be predicted with high accuracy by the model with shell elements and the distributed heat input methods. The computing time was around 8% of that by the precise model with solid elements.