Papers by Author: Yan Jin Guan

Abstract: As the needs of profiled rings continuously increase, studies about profiled ring rolling processes is becoming a hot problem. This paper established a FE model of hot ring rolling process of inner L-shaped ring based on ABAQUS/Explicit software. The reasonable value range of mandrel feed rate is determined at first. Then the deformation characteristics of rings are analyzed and compared in L-shaped ring rolling process under four different ring blank dimensions. Finally, for realizing a steady rolling process and obtaining good dimensions properties of rolled ring, an appropriate ring blank dimension is given.

Abstract: A FE model of radial conical ring rolling process with a closed die structure on the top and bottom part of driven roll (RCRRCDS) process was set up based on ABAQUS/Explicit software. The effect of the initial temperature of conical ring blank on equivalent plastic strain (PEEQ) and temperature distribution of rolled ring, average rolling force and average rolling moment was investigated. The results indicated that with the increase of the initial temperature of ring blank, the PEEQ distribution of rolled ring becomes uniform at first and then less uniform; the temperature distribution gradually becomes homogeneous; and both average rolling force and average rolling moment decrease. When the initial temperature of ring blank is 925°C, the PEEQ distribution of rolled ring is most uniform; the temperature distribution of rolled ring is relatively uniform; the average rolling force and average rolling moment are relatively smaller.

Abstract: The windage yaw of suspension string under dynamic wind was analyzed with the method of finite element (FEM). By using finite element software ABAQUS, the windage yaw angle of suspension string under gust and pulsating wind for 500kV high voltage transmission line was also computed and compared with the result calculated by traditional statics method, it clearly shows that the windage yaw angles of suspended under those two kinds of dynamic winds are larger than those determined by existing design discipline of high voltage transmission line, which may be one of the reasons for flashover caused by windage yaw happening frequently.

Abstract: Improvement of materials properties induced by constrained groove pressing (CGP) depends largely on deformation homogeneity. Utilizing commercial software DEFORM-3D, a finite element model of multi-pass CGP was established. The distribution and homogeneity evolution of equivalent strain ware analyzed in detail. Based on Taguchi optimization method, the influence of processing parameters (such as groove width, groove angle, friction coefficient and deformation rate) on strain homogeneity was studied numerically and systematically. Within a certain range, the optimum parameter combination is obtained by means of signal to noise ratio analysis. The inhomogeneity factor of the optimum model decreases by about 50 %. The average accumulative equivalent strain is almost twice that of the initial model. Analysis of variance shows that groove angle and groove width are the two most important parameters and effect of friction between dies and sample should not be neglected.

Abstract: Laser bending process of tubes is a new flexible forming process without rigid tools and external forces. The tube is formed by internal thermal stress induced by laser irradiation. The process simulation of laser bending of tubes is realized numerically. When the other parameters remain invariable, the laser bending angle augments with the increase of the laser power. The laser bending angle decreases with the increase of the scanning velocity. Meanwhile, the bending angle varies with the diameter of the laser spot. The angle begins to decrease when the laser spot diameter get to an optimum value. The bending angle enlarges if the scanning wrap angle augments. The bending angle is largest when the scanning wrap angle is 180°. When the scanning wrap angle is over 180°, the bending angle decreases with the increase of the scanning wrap angle. The relationship between the number of scans and the bending angle is about in direct ratio. The bending angle induced by the first irradiated time is the largest.

Abstract: A fully transient method for the simulation of the coupled plastic part and mold temperature in the filling stage of Rapid Heat Cycle Molding process was presented. Unlike the constant temperature boundary conditions in conventional injection molding simulation methods, the mold temperature was assumed to be variable in the filling process. The mold temperature in the heating process was first simulated. In the filling process, the flow equations were solved only on the cavity domain, while the energy equations were solved in a coupled manner for the cavity and mold domain at the matrix level. The temperature evolution in a two-dimensional filling process with heated mold was simulated. Numerical results showed that the proposed coupled simulation method provides reliable temperature estimations in mold filling process.

Abstract: Rapid electrical heating cycle injection molding technology can be used to produce polymer parts with no weld mark, flow mark and other surface defects on the parts surface. Recently, it has been gradually found wide use in plastic injection industry. In this paper, a structure of the rapid electrical heating cycle injection mold and its working processes were presented. As the production efficiency and the part’s quality are seriously affected by the temperature of the mold cavity surface and its distribution uniformity, the heat transfer process of the mold was analyzed by using 3D finite element simulation. The transient temperature values on different places of the cavity surface were obtained. The results provided theoretical guidelines for the engineers to evaluate the layout of the heating rods in the mold.

Abstract: Combining element free Galerkin method with rigid/visco-plastic flow theory, the paper establishes the three-dimensional rigid/visco-plastic element free Galerkin method, and introduces it to analyze three-dimensional bulk metal forming processes. The velocity field is approximated by MLS method. Employing the incomplete generalized variation principle, stiffness matrix equation and solution formulas are derived. And STL format discrete triangular patches are used to describe the mould cavity. An analysis program for simulating three-dimensional bulk metal forming processes is developed. The program is capable of simulating three-dimensional unsteady bulk metal forming processes with severe deformation and arbitrarily shaped dies. A numerical example is analyzed. Numerical results such as material flow patterns and distributions of the effective stress are obtained. The effectiveness and validity of the proposed method and techniques are demonstrated by comparing with results obtained by using commercial finite element software.

Abstract: There are many factors, such as the laser and geometrical parameters, which influence greatly on the laser bending process. So it is of great importance to determine these variables properly. Considering the relationship of material properties and temperature, a 3-D thermal-mechanical finite element analysis model for laser micro-bending of stainless steel foil is developed based on the software MSC.Marc, and the laser micro-bending process of 0.1mm thick stainless steel foil is implemented. The finite element method simulation process is integrated with the optimization software package iSIGHT through secondary development. The objective function is to realize the maximum bending angle after single laser scan, and laser power, beam diameter and scanning velocity are regarded as the design variables. The forming process is optimized by using genetic algorithm. The optimal result shows the bending angle can be got to the maximum 1.0332°when the laser power, beam diameter and scanning velocity are 32W, 0.17mm and 132mm/s respectively. The experiment results are in good agreement with optimal results.

Abstract: The meshless methods effectively deal with large material distortion simulation. Based on the rigid (visco)plastic material model, the element-free Galerkin method (EFGM) is introduced to simulate the metal forming processes. Aiming at the volume locking and pressure oscillation during EFGM analysis, a volumetric strain rate mapping method is proposed based on pressure projection method. The releasing algorithm is established by modifying the volumetric strain rate in the functional equation. The volumetric strain rate calculated according to velocity field is mapped onto a lower-order space to reduce the number of independent discrete constrain equations. The numerical example shows that the releasing algorithm can effectively eliminate the volumetric locking and pressure oscillation without the expense of employing large support size in the rigid-plastic meshless method.