An elasto-polycrystalline plastic finite element method is developed to simulate the deformation behavior and corresponding crystallographic textureevolution of sheet metals in stamping processes. A rate-independent crystalplasticity model and a degenerated shell element are introduced into the explicitfinite element formulation. A successive integration method by which the shear rates on the slip systems can be calculated without prior determination of active/non-active state of the slip systems, as generally done in rate-dependent models, is employed to calculate the plastic strain rate of a crystal during the de for mation.Represent ative crystal orientations are extracted from the orientation distribution function (ODF) data and assigned to the integration points of elements according to the distributional characteristic of crystal orientations. The macroscopic stress of a polycrystalline aggregate is evaluated by avolume-averaged response of the representative crystals. Two drawing processes are simulated, one with a cylindrical punch and the other with a square punch. Good agreements between the calculated results and experimental ones are obtained.

As an important sheet metal forming process, stretch flanging is widely applied in automobile industry. The formability of sheet metal during stretch flanging depends on appropriate process parameters. In this paper, an elastic-plastic large deformation FEM program is developed based on Mindlin shell element model. A quasi-flow corner theory of elastic-plastic finite deformation and a normally anisotropic yield criterion are introduced. Then the stretch flanging of a V-shaped sheet metal part is simulated and the effects of geometry and material on flanging are unveiled according to the calculated results. Meanwhile, a mathematical model for axisymmetric case (flanging tube) is developed based on the total strain theory and membrane assumption. Compared with material parameters, geometrical parameters exert greater effects on the formability and the flange angle is the most influential parameter affecting the free edge strain. The analytical model is easy to use, but it gives reasonable results only when the flange angle or initial flange length is small.

A rate independent crystal plasticity model is developed to analyze the plastic deformation of hexagonal close packed (HCP) materials by incorporating the crystallography of deformation twinning in plasticity model. The "successive integration method" is used to identify active slip/twinning systems and determine plastic strain. This model is implemented in the commercial finite element code ABAQUS/Explicit to simulate the deformation process of the magnesium alloy sheet. For the determination of model parameters, simulated stress-strain curves for uniaxial tension are adjusted to the measured curves. Then the stamping process of a cylindrical cup is simulated with the developed model, and the effect of initial crystal orientation on final cup earing is discussed.

Warm forming of magnesium alloy sheet has attracted more and more attention in recent years. The formability of magnesium alloy sheet at elevated temperature depends on appropriate processes, and the fabrication of high-performance sheet. In this research, an AZ31 magnesium alloy sheet with excellent performances is fabricated by the cross-rolling and the uniform annealing treatments. The uniaxial tensile tests are conducted using a Gleeble 3500 thermal-mechanical simulator, and the mechanical properties of AZ31 magnesium alloy sheet are analyzed. Finally, some limiting drawing ratio (LDR) experiments are performed. The experiments show that the LDR can reach 2.0 at the forming temperature of 150 1C and the drawing velocity of 15 mm/s. A warm deep drawing process is also simulated by the finite element method. The influences of drawing temperature and blank holder force on the formability are numerically investigated. The simulation demonstrated that variable blank holder force technology can improve the LDR from 3.0 to 3.5, and decrease the wall thinning ratio from 15.21% to 12.35%.

The superplastie forming potential of two fine-grained 5083 aluminum alloys were studied under biaxial tension using apneumatic bulge test. Experiments were performed at temperatures ranging from 475 to 525℃ with three different strain pathsranging from equi-biaxial to approaching plane strain. The shape of the forming limited diagram(FLD) is found to be significantlydifferent from FLDs commonly used in room temperature stamping. The effects of temperature on final thickness distribution, domeheight and cavitation were investigated for the case of equi-biaxial stretching. Increasing temperature in free bulge forming canimprove the thickness distribution of final parts but have no significant effect on dome height. The results indicate that determinationof forming limits in SPF cannot be represented with a simple FLD and additional metrics such as external thinning and internalcavitation needed to determine the SPF potential of a material.

Cage roll forming is an advanced roll-forming technique to manufacture electric resistancewelded (ERW) round pipes. In the cage roll-forming process, many small rolls are arranged along the outer surface of the deformable strip to bend the strip edge in a more smooth way. Furthermore, these small rolls can be used for forming pipes of different sizes. Therefore, cage roll forming can reduce roll change time and improve forming quality, as compared with the conventional step roll forming. However, very fewstudies can be found about cage roll forming, due to its complexity, and the industrial practice depends greatly on experience rather than science-based design today. In this work, the whole cage roll-forming process is simulated with the explicit elastic-plastic finite element method, and the strip deformation during the cage roll-forming process has been investigated in detail. Through the simulation, the "non-bending area" phenomenon is found, and the ranges of the non-bending area at different forming stands are obtained. In addition, the longitudinal strain at the inside edge and center are predicted, and by comparison, it can be known that the deformation of the strip edge is usually larger and edge buckling is most likely to occur at the entry sides of No.1-No.3 fin-pass stands. Finally, the circumferential length, opening distance and the profiles of the deformed strip are measured on the cage roll-forming mill. There is a good agreement between the experimental and simulated results.

The properties of fiber reinforced metal matrix composites (MMCs) are anisotropic. These properties can be more appropriately evaluated in polar coordinate. In this paper, the elastic-plastic mechanics model of MMCs is presented based on the combination of macroscopic and meso-scopic analysis in polar coordinate. The influence of micro-parameters such as matrix materials, the fibers and fiber volume fraction of Al/Mg metal matrix composites (MMCs) on the tensile properties of MMCs is also investigated numerically by the representative volume element (RVE) and the numerical results are compared with the experimental data. The results show that the model built in polar coordinate is suitable to the real constructs of MMCs; the fiber plays a major role of load supporting during MMCs stretched. And there is little distinction of the value of maximum stress of MMCs between tests and the numerical analysis.

Inner grooved copper tubes have attracted more and more attention in recent years. In mass production of tube-fin heat exchanger plates in ACR (air conditioning and refrigeration) industry, mechanical expansion is a key forming process which joins the fins to the tubes. During the process, the spiral grooves inside the tube with thermally efficient geometries are deformed and the tube-fin joints are influenced by the groove layer. In this paper, tube expansion forming process is studied and effect of the groove shape on forming quality is analyzed. Experiments are performed with tubes of different groove types. FE (finite element) model of the forming process is developed. Influences of the key geometry parameters, such as groove height ratio, apex and helix angle, on strength of the grooves as well as tube wall thinning are investigated. Sections of the tube-fin joints are observed and the die geometry on the joining status is examined. The results indicate that helix angle has significant effect on groove height reduction while groove height ratio is the main factor influencing the deformation resistant force; outer diameter and radius of the front part of the expanding die influence the tube-fin joining status.

将率相关晶体塑性本构理论引入Mindlin曲壳单元模型与动力显式有限元法，采用切线系数法计算剪切应变率，根据晶体取向正态分布规律在单元积分点处分配晶体取向，按各晶体取向体积分数的加权平均计算多晶体应力，开发晶体塑性动力显式有限元程序，实现板材冲压成形过程模拟和晶体取向演化预示。以主要初始织构为铜织构和S织构的轧制铝板为对象，对方盒件冲压成形过程及织构演化进行数值模拟，计算结果与试验结果呈现出较好的一致性。通过晶体弹塑性有限元法不仅可以预示板材宏观成形构形变化，而且能够预测板材织构的演化情况。模拟结果显示在方盒件冲压成形过程中，铜织构和S织构为不稳定取向，变形后逐渐转到其他取向。