【作者】 徐银丽；

【导师】 詹梅；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2006， 硕士

【摘要】 异型薄壁壳体是广泛应用于航空、航天、兵器等领域的一类重要的零件,了解和掌握异型薄壁壳体强力旋压成形机理及规律是研究和发展该技术迫切需要解决的关键性问题。为此,本文基于弹塑性显式有限元平台ABAQUS/Explicit,研究建立了该过程的三维有限元分析模型,并分析了异型薄壁壳体强力旋压成形机理及工艺参数对其成形过程的影响规律。主要研究内容和结果如下: 建立了既符合实际又兼顾计算精度和效率的异型薄壁壳体强力旋压的三维弹塑性动态显式有限元模型,解决了建模过程中有关旋轮定位、旋轮运动轨迹的确定、连续变壁厚坯料壁厚的定义等关键问题,并通过理论评估和试验验证验证了其可靠性。该模型的建立,为深入揭示异型薄壁壳体强力旋压成形机理及工艺参数对其成形过程的影响规律奠定了基础。 基于上述模型,研究获得了异型薄壁壳体强力旋压成形过程中的应力应变及壁厚的分布和变化特征:随着成形过程的进行,应力应变极值逐渐增大;应力最大值出现在旋轮与坯料接触处(即成形区),应变最大值在成形初期出现在旋轮与坯料接触处,随着成形过程的进行,转移到旋轮后方;靠近口部的部位壁厚剧烈减薄,而工件的其余部位的壁厚较合理。研究发现异型薄壁壳体强力旋压后期锥体部位易于出现的过量减薄是由于累积减薄量过大而使旋轮前方出现金属堆积所致,因此提出通过控制坯料的局部厚度或旋轮与芯模间的间隙来控制金属堆积所带来的局部减薄的方法。 进而研究揭示了旋轮安装角、旋轮圆角半径、摩擦系数、旋轮进给比对异型薄壁壳体强力旋压成形过程中应力应变和壁厚的影响规律。结果表明:减小旋轮圆角半径、增大摩擦系数、增大旋轮安装角、减小进给率均可使塑性变形及工件壁厚分布更均匀,从而减弱甚至消除金属堆积。这些结果可为异型薄壁壳体强力旋压成形过程成形参数的确定和优化设计提供理论依据。更多还原

【Abstract】 The thin-walled abnormal shells are a kind of very important parts, widely used in aerospace and military industry. Research on the deformation mechanism and deformation laws of the thin-walled abnormal shell power spinning is a key problem urgently to be solved for the research and development of thin-walled abnormal shell spinning. So, in this dissertation, a 3D Elasto-plastic dynamic explicit FEM model of power spinning of thin-walled abnormal shell is established under the ABAQUS/Explicit software environment, then the deformation mechanism and the influencing laws of forming parameters on the process are investigated. A brief introduction to the project and its main results are as follows:At the first, a 3D Elasto-plastic dynamic explicit FEM model of power spinning of thin-walled abnormal shell has been developed. Both computation accuracy and efficiency are taken in account, and some key technologies during the establishing process of the model have been solved, including the determination of initial position of roller and roller path, and the definition of blank thickness which is variable etc. The model has been validated by theoretical evaluation and experimentation comparison. The establishment of the model lays a foundation for the research on the deformation mechanism and the influencing laws of forming parameters on the process.Then, based on the model established above, the distribution and variation features of the stress and strain, the wall thickness during the process of power spinning of the thin-walled abnormal shell have been obtained. In the forming process, the biggest Mises stress and equivalent plastic strain become bigger and bigger;The biggest Mises stress of the blank lies in the place contacting with roller all the time, and the biggest equivalent plastic strain lies in the place contacting with roller in the beginning, then with the forming process, transfers to the behind of the roller;the wall thickness near the part peristome reduces acutely, but for the rest ofthe part, reasonable wall thickness can be obtained. It is found that, at final stage of the process it is easy for an excessive reduction of wall thickness to appear, which is resulting from the metal accumulation appearing at the front of roller due to the cumulative excessive reduction of wall thickness. Thus a method by controlling the local blank thickness or the clearance between roller and mandrel to control the local excessive thickness reduction caused by metal accumulation is proposed.Finally, the influence laws of some important parameters, including radii of roller roundness, roller installation angle, friction coefficient between roller and blank and;feed rate of roller, on the change of the stress and strain, the wall thickness in the power spinning process of the thin-walled abnormal shell have been revealed. The results show that: the decrease of roller roundness radii or roller feed rate, or the increase of friction coefficient between roller and blank or roller installation angle, will make the plastic deformation and the wall thickness distribution more homogeneous, weaken and even eliminate the metal accumulation in front of the roller. These results may provide a guide for the determination and optimization of parameters of power spinning process of thin-walled abnormal shell.更多还原