The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of c...The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of curl interface underground or “v” figure complex model, it is difficult to realize. So it is important to forward the complex geoelectricity model. This paper takes two Maxwell’s vorticity equations as departure point, makes use of the principles of Yee’s space grid model theory and the basic principle finite difference time domain method, and deduces a GPR forward system of equation of two dimensional spaces. The Mur super absorbed boundary condition is adopted to solve the super strong reflection on the interceptive boundary when there is the forward simulation. And a self-made program is used to process forward simulation to two typical geoelectricity model.展开更多
In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the pr...In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those of experiment. The results of numerical simulations, such as the strain history and distribution, the stress state and distribution, sheet thickness distribution, etc, were discussed in details, and the influences of process parameters on these results were also analyzed. The simulated results of the radial strain and the thickness distribution are in good agreement with experimental results. The simulations reveal that the deformation is localized around the tool and constantly remains close to a plane strain state. With decreasing depth step, increasing tool diameter and wall inclination angle, the axial stress reduces, leading to less thinning and more homogeneous plastic strain and thickness distribution. During ISF, the plastic strain increases stepwise under the action of the tool. Each increase in plastic strain is accompanied by hydrostatic pressure, which explains why obtainable deformation using ISF exceeds the forming limits of conventional sheet forming.展开更多
Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separ...Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separation of hydrogen in the winding process, this article analyzed the reasons for above phenomena, established a numerical simulation model of winding process of above tube, using elastic-plastic Finite Element method analyzed the max. tensile stress and max. compression stress and their locations, thereby provides a theory base for the control of working forming course of thin wall spiral tube.展开更多
In this paper, the internal fluid motion of a jet system is described by the Navier Stokes mechanics equations. For the simulation of the motion, the penalty function finite element method is used, and the velocity ve...In this paper, the internal fluid motion of a jet system is described by the Navier Stokes mechanics equations. For the simulation of the motion, the penalty function finite element method is used, and the velocity vectors and stream function curves are obtained. Using the Prandtl theory, this paper derives the free jet velocity and the jet bunch width in a half-space, the latter of which is amended by experiment. The results obtained in this paper are applied to micro-type high pressure water jet cleaner and the ejector of rocket engine.展开更多
The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electr...The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical,thermal and mechanical process in the interior ballistic cycle.In this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching process.Especially,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid armature.The results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric current.By the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.展开更多
Design of forming dies and whole process of simulation of cold rolling involutes spline can be realized by using of CAD software of PRO-E and CAE software of DEFORM-3D. Software DEFORM-3D provides an automatic and opt...Design of forming dies and whole process of simulation of cold rolling involutes spline can be realized by using of CAD software of PRO-E and CAE software of DEFORM-3D. Software DEFORM-3D provides an automatic and optimized remeshing function, especially for the large deformation. In order to use this function sufficiently, simulation of cold rolling involutes spline can be implemented indirectly. The relationship between die and workpiece, forming force and characteristic of deformation in the forming process of cold rolling involutes spline are analyzed and researched. Meanwhile, reliable proofs for the design of dies and deforming equipment are provided.展开更多
Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and ...Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.展开更多
A new general optimal principle of designing explicit finite difference method was obtained. Several applied cases were put forward to explain the uses of the principle. The validity of the principal was tested by a n...A new general optimal principle of designing explicit finite difference method was obtained. Several applied cases were put forward to explain the uses of the principle. The validity of the principal was tested by a numeric example.展开更多
文摘The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of curl interface underground or “v” figure complex model, it is difficult to realize. So it is important to forward the complex geoelectricity model. This paper takes two Maxwell’s vorticity equations as departure point, makes use of the principles of Yee’s space grid model theory and the basic principle finite difference time domain method, and deduces a GPR forward system of equation of two dimensional spaces. The Mur super absorbed boundary condition is adopted to solve the super strong reflection on the interceptive boundary when there is the forward simulation. And a self-made program is used to process forward simulation to two typical geoelectricity model.
基金Project(50175034) supported by the National Natural Science Foundation of China
文摘In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those of experiment. The results of numerical simulations, such as the strain history and distribution, the stress state and distribution, sheet thickness distribution, etc, were discussed in details, and the influences of process parameters on these results were also analyzed. The simulated results of the radial strain and the thickness distribution are in good agreement with experimental results. The simulations reveal that the deformation is localized around the tool and constantly remains close to a plane strain state. With decreasing depth step, increasing tool diameter and wall inclination angle, the axial stress reduces, leading to less thinning and more homogeneous plastic strain and thickness distribution. During ISF, the plastic strain increases stepwise under the action of the tool. Each increase in plastic strain is accompanied by hydrostatic pressure, which explains why obtainable deformation using ISF exceeds the forming limits of conventional sheet forming.
文摘Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separation of hydrogen in the winding process, this article analyzed the reasons for above phenomena, established a numerical simulation model of winding process of above tube, using elastic-plastic Finite Element method analyzed the max. tensile stress and max. compression stress and their locations, thereby provides a theory base for the control of working forming course of thin wall spiral tube.
文摘In this paper, the internal fluid motion of a jet system is described by the Navier Stokes mechanics equations. For the simulation of the motion, the penalty function finite element method is used, and the velocity vectors and stream function curves are obtained. Using the Prandtl theory, this paper derives the free jet velocity and the jet bunch width in a half-space, the latter of which is amended by experiment. The results obtained in this paper are applied to micro-type high pressure water jet cleaner and the ejector of rocket engine.
文摘The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical,thermal and mechanical process in the interior ballistic cycle.In this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching process.Especially,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid armature.The results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric current.By the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.
文摘Design of forming dies and whole process of simulation of cold rolling involutes spline can be realized by using of CAD software of PRO-E and CAE software of DEFORM-3D. Software DEFORM-3D provides an automatic and optimized remeshing function, especially for the large deformation. In order to use this function sufficiently, simulation of cold rolling involutes spline can be implemented indirectly. The relationship between die and workpiece, forming force and characteristic of deformation in the forming process of cold rolling involutes spline are analyzed and researched. Meanwhile, reliable proofs for the design of dies and deforming equipment are provided.
文摘Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.
文摘A new general optimal principle of designing explicit finite difference method was obtained. Several applied cases were put forward to explain the uses of the principle. The validity of the principal was tested by a numeric example.
